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2f6b4cdd3e3fd1826894bbe2f94f7557d994b161 | wikidoc | PLA2G4A | PLA2G4A
Cytosolic phospholipase A2 is an enzyme that in humans is encoded by the PLA2G4A gene.
# Function
This gene encodes a member of the cytosolic phospholipase A2 group IV family. The enzyme catalyzes the hydrolysis of membrane phospholipids to release arachidonic acid which is subsequently metabolized into eicosanoids. Eicosanoids, including prostaglandins and leukotrienes, are lipid-based cellular hormones that regulate hemodynamics, inflammatory responses, and other intracellular pathways. The hydrolysis reaction also produces lysophospholipids that are converted into platelet-activating factor. The enzyme is activated by increased intracellular Ca2+ levels and phosphorylation, resulting in its translocation from the cytosol and nucleus to perinuclear membrane vesicles.
# Interactions
PLA2G4A has been shown to interact with HTATIP.
# Clinical significance
Mutations in this gene have been associated with multifocal stenosing ulceration of the small intestine. | PLA2G4A
Cytosolic phospholipase A2 is an enzyme that in humans is encoded by the PLA2G4A gene.[1][2]
# Function
This gene encodes a member of the cytosolic phospholipase A2 group IV family. The enzyme catalyzes the hydrolysis of membrane phospholipids to release arachidonic acid which is subsequently metabolized into eicosanoids. Eicosanoids, including prostaglandins and leukotrienes, are lipid-based cellular hormones that regulate hemodynamics, inflammatory responses, and other intracellular pathways. The hydrolysis reaction also produces lysophospholipids that are converted into platelet-activating factor. The enzyme is activated by increased intracellular Ca2+ levels and phosphorylation, resulting in its translocation from the cytosol and nucleus to perinuclear membrane vesicles.[2]
# Interactions
PLA2G4A has been shown to interact with HTATIP.[3]
# Clinical significance
Mutations in this gene have been associated with multifocal stenosing ulceration of the small intestine.[4] | https://www.wikidoc.org/index.php/PLA2G4A | |
3c02ef24569b0e67a287a688943bab4e55890502 | wikidoc | PLEKHG5 | PLEKHG5
Pleckstrin homology domain containing, family G member 5 (PLEKHG5) is a protein that in humans is encoded by the PLEKHG5 gene. Multiple transcript variants encoding different isoforms have been found for this gene.
# Function
This gene encodes a protein that activates the nuclear factor kappa B (NFKB1) signaling pathway.
# Clinical significance
Mutations in the PLEKHG5 gene are associated with distal spinal muscular atrophy type 4. | PLEKHG5
Pleckstrin homology domain containing, family G member 5 (PLEKHG5) is a protein that in humans is encoded by the PLEKHG5 gene.[1] Multiple transcript variants encoding different isoforms have been found for this gene.
# Function
This gene encodes a protein that activates the nuclear factor kappa B (NFKB1) signaling pathway.[1]
# Clinical significance
Mutations in the PLEKHG5 gene are associated with distal spinal muscular atrophy type 4. | https://www.wikidoc.org/index.php/PLEKHG5 | |
c1fe0876f69f2a88e06b83270cfc4a42548ee4a7 | wikidoc | PLEKHM2 | PLEKHM2
Pleckstrin homology domain-containing family M member 2 is a protein that in humans is encoded by the PLEKHM2 gene.
# Model organisms
Model organisms have been used in the study of PLEKHM2 function. A conditional knockout mouse line, called Plekhm2tm1a(EUCOMM)Wtsi was generated as part of the International Knockout Mouse Consortium program—a high-throughput mutagenesis project to generate and distribute animal models of disease to interested scientists.
Male and female animals underwent a standardized phenotypic screen to determine the effects of deletion. Twenty six tests were carried out on mutant mice and three significant abnormalities were observed. Male homozygous mutants had increased circulating alkaline phosphatase levels and an increased susceptibility to bacterial infection, while females had an increased leukocyte cell number. | PLEKHM2
Pleckstrin homology domain-containing family M member 2 is a protein that in humans is encoded by the PLEKHM2 gene.[1]
# Model organisms
Model organisms have been used in the study of PLEKHM2 function. A conditional knockout mouse line, called Plekhm2tm1a(EUCOMM)Wtsi[8][9] was generated as part of the International Knockout Mouse Consortium program—a high-throughput mutagenesis project to generate and distribute animal models of disease to interested scientists.[10][11][12]
Male and female animals underwent a standardized phenotypic screen to determine the effects of deletion.[6][13] Twenty six tests were carried out on mutant mice and three significant abnormalities were observed.[6] Male homozygous mutants had increased circulating alkaline phosphatase levels and an increased susceptibility to bacterial infection, while females had an increased leukocyte cell number.[6] | https://www.wikidoc.org/index.php/PLEKHM2 | |
8f165aa11f7cc442008ce1f26cdcef1bf554f91f | wikidoc | PLEKHM3 | PLEKHM3
Pleckstrin Homology domain containing Family M Member 3, or PLEKHM3, is the hypothetical protein that in humans is encoded by the PLEKHM3 gene. PLEKHM3 is also known as DAPR (differentiation associated protein), and Pleckstrin Homology Domain Containing Family M, Member 1-like.
# Gene
PLEKHM3 is a valid, protein coding gene that is located on the minus strand of the q-arm of chromosome 2. Its exact location is 2q33.3. Its genomic mRNA length is 9,807 base pairs.
Its genomic DNA length is 24.3 kilobases. It has 8 exons, 4 common splice forms.
# Protein
PLEKHM3 contains 3 domains. Two domains are highly conserved across mammalian species. The most highly conserved region is the DUF4206 Domain. The third is a domain of unknown function 4206, which is highly conserved across all eukarya. Its molecular weight is 87.2 kilodaltons. Its isoelectric point is 6.81. It is predicted to be localized primarily in the cytosol. PLEKHM3 has orthologs in eukaryotes.
## Function
The function of PLEKHM3 is not characterized in any scientific database. It is thought to be associated with cell differentiation and is expressed at ubiquitously low levels in all cell types. The Pleckstrin Homology domains are involved with phosphate binding. The DUF4206 Domain is cysteine rich and forms with 7 CXXC protein motifs. This motif is responsible for forming disulfide bridges. The DUF4206 domain is conserved in PLEKHM3 homologs as distant as Nile Tilapia.
## Interactions
PLEKHM3 is thought to interact with a protein called GDAP1, which is responsible for differentiation in neuronal cell types and plays a role in the signal transduction pathway. This also supports the predicted role of PLEKHM3 in differentiation. | PLEKHM3
Pleckstrin Homology domain containing Family M Member 3, or PLEKHM3, is the hypothetical protein that in humans is encoded by the PLEKHM3 gene.[1] PLEKHM3 is also known as DAPR (differentiation associated protein), and Pleckstrin Homology Domain Containing Family M, Member 1-like.[2]
# Gene
PLEKHM3 is a valid, protein coding gene that is located on the minus strand of the q-arm of chromosome 2. Its exact location is 2q33.3. Its genomic mRNA length is 9,807 base pairs.
Its genomic DNA length is 24.3 kilobases. It has 8 exons, 4 common splice forms.
# Protein
PLEKHM3 contains 3 domains. Two domains are highly conserved across mammalian species. The most highly conserved region is the DUF4206 Domain. The third is a domain of unknown function 4206, which is highly conserved across all eukarya.[3] Its molecular weight is 87.2 kilodaltons. Its isoelectric point is 6.81. It is predicted to be localized primarily in the cytosol.[4] PLEKHM3 has orthologs in eukaryotes.
## Function
The function of PLEKHM3 is not characterized in any scientific database. It is thought to be associated with cell differentiation and is expressed at ubiquitously low levels in all cell types. The Pleckstrin Homology domains are involved with phosphate binding. The DUF4206 Domain is cysteine rich and forms with 7 CXXC protein motifs. This motif is responsible for forming disulfide bridges. The DUF4206 domain is conserved in PLEKHM3 homologs as distant as Nile Tilapia.
## Interactions
PLEKHM3 is thought to interact with a protein called GDAP1, which is responsible for differentiation in neuronal cell types and plays a role in the signal transduction pathway. This also supports the predicted role of PLEKHM3 in differentiation. | https://www.wikidoc.org/index.php/PLEKHM3 | |
f077107a358076dcff807073b9d51568f6ddc5fc | wikidoc | PLXNA4A | PLXNA4A
Plexin-A4 is a protein that in humans is encoded by the PLXNA4 gene.
# Function
Plexin A4 binds to neuropilin 1 (Nrp1) and neuropilin 2 (Nrp2) and transduces signals from Sema3A, Sema6A, and Sema6B. These Nrp-plexin and semaphorin complexes initiate cascades that regulate diverse processes such as axon pruning and repulsion, dendritic attraction and branching, regulation of cell migration, vascular remodeling, and growth cone collapse. Both upregulation and downregulation of Plexin A4 has been observed following neural injury suggesting a dynamic role for Sema3A and Plexin A4 in neural maintenance and regeneration. Additionally, Sema3A and therefore its receptor, Plexin A4, have been implicated as possible components of fast-fatigable muscle fiber denervation in ALS.
# Structure
Plexin A4 has ~1890 amino acids that include a likely signal sequence, transmembrane domain, and 12 extracellular N-linked glycosylation sites. It also contains domains consistent with other class A plexins including a Sema domain, three "Met-related sequences"/cysteine clusters, three extracellular glycine-proline repeats, intracellular SP domains, and a putative intracellular tyrosine kinase phosphorylation site.
# Tissue distribution
In the adult rat central nervous system (CNS), plexin A4 was present in neurons and fibers throughout the brain and spinal cord, including neocortex, hippocampus, lateral hypothalamus, red nucleus, facial nucleus, and the mesencephalic trigeminal nucleus. Fibers expressed Plexin A4 in the lateral septum, nucleus accumbens, several thalamic nuclei, substantia nigra pars reticulata, zona incerta, pontine reticular formation, as well as in several cranial nerve nuclei. Plexin A4 has been found in dorsal and, to a greater extent, ventral horns of the spinal cord. Both motor neurons and interneurons in the ventral horn express Plexin A4. Motor axons exiting via the ventral roots and the ascending and descending white matter tracts express Plexin A4. In dorsal root ganglia, Plexin A4 is expressed in the neuronal cell bodies as well as the central and peripheral processes of those cells. | PLXNA4A
Plexin-A4 is a protein that in humans is encoded by the PLXNA4 gene.[1]
# Function
Plexin A4 binds to neuropilin 1 (Nrp1) and neuropilin 2 (Nrp2) and transduces signals from Sema3A, Sema6A, and Sema6B.[2] These Nrp-plexin and semaphorin complexes initiate cascades that regulate diverse processes such as axon pruning and repulsion, dendritic attraction and branching, regulation of cell migration, vascular remodeling, and growth cone collapse.[3][4] Both upregulation and downregulation of Plexin A4 has been observed following neural injury suggesting a dynamic role for Sema3A and Plexin A4 in neural maintenance and regeneration.[3][5] Additionally, Sema3A and therefore its receptor, Plexin A4, have been implicated as possible components of fast-fatigable muscle fiber denervation in ALS.[6]
# Structure
Plexin A4 has ~1890 amino acids that include a likely signal sequence, transmembrane domain, and 12 extracellular N-linked glycosylation sites. It also contains domains consistent with other class A plexins including a Sema domain, three "Met-related sequences"/cysteine clusters, three extracellular glycine-proline repeats, intracellular SP domains, and a putative intracellular tyrosine kinase phosphorylation site.[7]
# Tissue distribution
In the adult rat central nervous system (CNS), plexin A4 was present in neurons and fibers throughout the brain and spinal cord, including neocortex, hippocampus, lateral hypothalamus, red nucleus, facial nucleus, and the mesencephalic trigeminal nucleus. Fibers expressed Plexin A4 in the lateral septum, nucleus accumbens, several thalamic nuclei, substantia nigra pars reticulata, zona incerta, pontine reticular formation, as well as in several cranial nerve nuclei.[8] Plexin A4 has been found in dorsal and, to a greater extent, ventral horns of the spinal cord. Both motor neurons and interneurons in the ventral horn express Plexin A4. Motor axons exiting via the ventral roots and the ascending and descending white matter tracts express Plexin A4. In dorsal root ganglia, Plexin A4 is expressed in the neuronal cell bodies as well as the central and peripheral processes of those cells.[3] | https://www.wikidoc.org/index.php/PLXNA4A | |
ead166fdbab064e75d2f743f0594d780830e46d0 | wikidoc | PPP1R1B | PPP1R1B
Protein phosphatase 1 regulatory subunit 1B (PPP1R1B), also known as dopamine- and cAMP-regulated neuronal phosphoprotein (DARPP-32), is a protein that in humans is encoded by the PPP1R1B gene.
# Function
Midbrain dopaminergic neurons play a critical role in multiple brain functions, and abnormal signaling through dopaminergic pathways has been implicated in several major neurologic and psychiatric disorders. One well studied target for the actions of dopamine is DARPP32. In the densely dopamine- and glutamate-innervated rat caudate-putamen, DARPP32 is expressed in medium-sized spiny neurons that also express dopamine D1 receptors. The function of DARPP32 seems to be regulated by receptor stimulation. Both dopaminergic and glutamatergic (NMDA) receptor stimulation regulate the extent of DARPP32 phosphorylation, but in opposite directions. Dopamine D1 receptor stimulation enhances cAMP formation, resulting in the phosphorylation of DARPP32; (this is disputed by more recent research that claims cAMP signaling induces dephosphorylation of DARPP32) phosphorylated DARPP32 is a potent protein phosphatase-1 (PPP1CA) inhibitor. NMDA receptor stimulation elevates intracellular calcium, which leads to activation of calcineurin and dephosphorylation of phospho-DARPP32, thereby reducing the phosphatase-1 inhibitory activity of DARPP32. DARPP-32 is critical for dopamine dependent striatal synaptic plasticity, possibly by serving as a dopamine-dependent gating mechanism for calcium/CaMKII signaling. It has been predicted that DARPP-32, in conjunction with ARPP-21, could also be involved in setting-up of eligibility trace-like temporal window for striatal postsynaptic signaling.
# Clinical significance
## CNS
This gene is also known as DARPP-32, highlighting its role as a dopamine- and cyclic AMP-regulated phosphoprotein. As such PPP1R1B affects dopamine, glutamate and adenosine; and there is some support for a role of the gene in schizophrenia, as well as being involved in the action of drugs including cocaine, amphetamine, nicotine, LSD, caffeine, PCP, ethanol and morphine, and in Parkinson's disease or EPS (Extra-pyramidal symptoms). DARPP-32 levels are decreased in the dorsolateral prefrontal cortex and lymphocytes of both schizophrenia and bipolar disorder patients. This alteration is suggested to be related to the pathology, since antipsychotics do not regulate the expression of DARPP-32.
A considerable proportion of the psychomotor effects of cannabinoids can be accounted for by a signaling cascade in striatal projection neurons involving PKA-dependent phosphorylation of DARPP-32, achieved via modulation of dopamine D2 and adenosine A2A transmission.
PPP1R1B has also been associated with improved transfer of information between the striatum and the prefrontal cortex, suggesting that variants of PPP1R1B can in some circumstances lead to improved and more flexible cognition, while, in the presence of other genetic and environmental factors, it may lead to symptoms of schizophrenia.
## Cancer
There are two protein products encoded by PPP1R1B: DARPP-32 and t-Darpp. t-Darpp is a truncated version of DARPP-32 as it is missing the first 36 amino acids at the N-terminus. Both isoforms are overexpressed in a number of cancers including those derived from gastric, colon, prostate, esophageal, breast, and lung tissues. In Her-2-positive breast cancer cells, t-Darpp overexpression imparts resistance to Trastuzumab (Herceptin), the chemotherapy drug that shuts down the Her-2 signaling pathway.
# Regulation
Brain-derived neurotrophic factor regulates the expression of DARPP-32. The Akt and CDK5/p35 intracelular pathway is suggested to be involved on this regulation. Also, neuronal calcium sensor-1 was suggested to modulate the expression of DARPP-32.
# Discovery
PPP1R1B was discovered by Paul Greengard and his co-workers.
# Interactive pathway map
Click on genes, proteins and metabolites below to link to respective articles.
- ↑ The interactive pathway map can be edited at WikiPathways: "NicotineDopaminergic_WP1602"..mw-parser-output cite.citation{font-style:inherit}.mw-parser-output q{quotes:"\"""\"""'""'"}.mw-parser-output code.cs1-code{color:inherit;background:inherit;border:inherit;padding:inherit}.mw-parser-output .cs1-lock-free a{background:url("")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-limited a,.mw-parser-output .cs1-lock-registration a{background:url("")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-subscription a{background:url("")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration{color:#555}.mw-parser-output .cs1-subscription span,.mw-parser-output .cs1-registration span{border-bottom:1px dotted;cursor:help}.mw-parser-output .cs1-hidden-error{display:none;font-size:100%}.mw-parser-output .cs1-visible-error{display:none;font-size:100%}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration,.mw-parser-output .cs1-format{font-size:95%}.mw-parser-output .cs1-kern-left,.mw-parser-output .cs1-kern-wl-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right,.mw-parser-output .cs1-kern-wl-right{padding-right:0.2em} | PPP1R1B
Protein phosphatase 1 regulatory subunit 1B (PPP1R1B), also known as dopamine- and cAMP-regulated neuronal phosphoprotein (DARPP-32), is a protein that in humans is encoded by the PPP1R1B gene.[1][2]
# Function
Midbrain dopaminergic neurons play a critical role in multiple brain functions, and abnormal signaling through dopaminergic pathways has been implicated in several major neurologic and psychiatric disorders. One well studied target for the actions of dopamine is DARPP32. In the densely dopamine- and glutamate-innervated rat caudate-putamen, DARPP32 is expressed in medium-sized spiny neurons[3] that also express dopamine D1 receptors.[4] The function of DARPP32 seems to be regulated by receptor stimulation. Both dopaminergic and glutamatergic (NMDA) receptor stimulation regulate the extent of DARPP32 phosphorylation, but in opposite directions.[5] Dopamine D1 receptor stimulation enhances cAMP formation, resulting in the phosphorylation of DARPP32;[4] (this is disputed by more recent research that claims cAMP signaling induces dephosphorylation of DARPP32[6]) phosphorylated DARPP32 is a potent protein phosphatase-1 (PPP1CA) inhibitor.[7] NMDA receptor stimulation elevates intracellular calcium, which leads to activation of calcineurin and dephosphorylation of phospho-DARPP32, thereby reducing the phosphatase-1 inhibitory activity of DARPP32.[1][5] DARPP-32 is critical for dopamine dependent striatal synaptic plasticity,[8] possibly by serving as a dopamine-dependent gating mechanism for calcium/CaMKII signaling.[9] It has been predicted that DARPP-32, in conjunction with ARPP-21, could also be involved in setting-up of eligibility trace-like temporal window for striatal postsynaptic signaling.[9]
# Clinical significance
## CNS
This gene is also known as DARPP-32, highlighting its role as a dopamine- and cyclic AMP-regulated phosphoprotein. As such PPP1R1B affects dopamine,[10] glutamate and adenosine; and there is some support for a role of the gene in schizophrenia, as well as being involved in the action of drugs including cocaine, amphetamine, nicotine, LSD, caffeine, PCP, ethanol and morphine,[11] and in Parkinson's disease or EPS (Extra-pyramidal symptoms).[12] DARPP-32 levels are decreased in the dorsolateral prefrontal cortex and lymphocytes of both schizophrenia and bipolar disorder patients.[13][14][15] This alteration is suggested to be related to the pathology, since antipsychotics do not regulate the expression of DARPP-32.[16][17]
A considerable proportion of the psychomotor effects of cannabinoids can be accounted for by a signaling cascade in striatal projection neurons involving PKA-dependent phosphorylation of DARPP-32, achieved via modulation of dopamine D2 and adenosine A2A transmission.[18]
PPP1R1B has also been associated with improved transfer of information between the striatum and the prefrontal cortex, suggesting that variants of PPP1R1B can in some circumstances lead to improved and more flexible cognition, while, in the presence of other genetic and environmental factors, it may lead to symptoms of schizophrenia.[19]
## Cancer
There are two protein products encoded by PPP1R1B: DARPP-32 and t-Darpp. t-Darpp is a truncated version of DARPP-32 as it is missing the first 36 amino acids at the N-terminus.[20] Both isoforms are overexpressed in a number of cancers including those derived from gastric, colon, prostate, esophageal, breast, and lung tissues.[21][22] In Her-2-positive breast cancer cells, t-Darpp overexpression imparts resistance to Trastuzumab (Herceptin), the chemotherapy drug that shuts down the Her-2 signaling pathway.[23][24][25]
# Regulation
Brain-derived neurotrophic factor regulates the expression of DARPP-32.[26] The Akt and CDK5/p35 intracelular pathway is suggested to be involved on this regulation.[27] Also, neuronal calcium sensor-1 was suggested to modulate the expression of DARPP-32.[28]
# Discovery
PPP1R1B was discovered by Paul Greengard and his co-workers.[2]
# Interactive pathway map
Click on genes, proteins and metabolites below to link to respective articles.[§ 1]
- ↑ The interactive pathway map can be edited at WikiPathways: "NicotineDopaminergic_WP1602"..mw-parser-output cite.citation{font-style:inherit}.mw-parser-output q{quotes:"\"""\"""'""'"}.mw-parser-output code.cs1-code{color:inherit;background:inherit;border:inherit;padding:inherit}.mw-parser-output .cs1-lock-free a{background:url("https://upload.wikimedia.org/wikipedia/commons/thumb/6/65/Lock-green.svg/9px-Lock-green.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-limited a,.mw-parser-output .cs1-lock-registration a{background:url("https://upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Lock-gray-alt-2.svg/9px-Lock-gray-alt-2.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-subscription a{background:url("https://upload.wikimedia.org/wikipedia/commons/thumb/a/aa/Lock-red-alt-2.svg/9px-Lock-red-alt-2.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration{color:#555}.mw-parser-output .cs1-subscription span,.mw-parser-output .cs1-registration span{border-bottom:1px dotted;cursor:help}.mw-parser-output .cs1-hidden-error{display:none;font-size:100%}.mw-parser-output .cs1-visible-error{display:none;font-size:100%}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration,.mw-parser-output .cs1-format{font-size:95%}.mw-parser-output .cs1-kern-left,.mw-parser-output .cs1-kern-wl-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right,.mw-parser-output .cs1-kern-wl-right{padding-right:0.2em} | https://www.wikidoc.org/index.php/PPP1R1B | |
a6590c9433b1054eb221034bda13f73438c4a03d | wikidoc | PPP1R9B | PPP1R9B
Neurabin-2 is a protein that in humans is encoded by the PPP1R9B gene.
Spinophilin is a regulatory subunit of protein phosphatase-1 catalytic subunit (PP1; see MIM 176875) and is highly enriched in dendritic spines, specialized protrusions from dendritic shafts that receive most of the excitatory input in the central nervous system (Allen et al., 1997).
# Interactions
PPP1R9B has been shown to interact with PPP1CB, PPP1CA, Dopamine receptor D2, P16, PPP1CC, T-cell lymphoma invasion and metastasis-inducing protein 1 and PPP1R2. | PPP1R9B
Neurabin-2 is a protein that in humans is encoded by the PPP1R9B gene.[1][2]
Spinophilin is a regulatory subunit of protein phosphatase-1 catalytic subunit (PP1; see MIM 176875) and is highly enriched in dendritic spines, specialized protrusions from dendritic shafts that receive most of the excitatory input in the central nervous system (Allen et al., 1997).[supplied by OMIM][2]
# Interactions
PPP1R9B has been shown to interact with PPP1CB,[3] PPP1CA,[3] Dopamine receptor D2,[4] P16,[5] PPP1CC,[3][4] T-cell lymphoma invasion and metastasis-inducing protein 1[6] and PPP1R2.[7] | https://www.wikidoc.org/index.php/PPP1R9B | |
0a13c573c383c728e0740b13bbc33ec5ea61b39a | wikidoc | PPP2R1A | PPP2R1A
Serine/threonine-protein phosphatase 2A 65 kDa regulatory subunit A alpha isoform is an enzyme that in humans is encoded by the PPP2R1A gene. In the plant Arabidopsis thaliana a similar enzyme is encoded by the RCN1 gene (At1g25490).
# Function
This gene encodes a constant regulatory subunit of protein phosphatase 2. Protein phosphatase 2 is one of the four major Ser/Thr phosphatases, and it is implicated in the negative control of cell growth and division. It consists of a common heteromeric core enzyme, which is composed of a catalytic subunit and a constant regulatory subunit, that associates with a variety of regulatory subunits. The constant regulatory subunit A serves as a scaffolding molecule to coordinate the assembly of the catalytic subunit and a variable regulatory B subunit. This gene encodes an alpha isoform of the constant regulatory subunit A.
# Interactions
PPP2R1A has been shown to interact with:
- CTTNBP2NL,
- FAM40A,
- PPP2CB, PPP2CA, PPP4C,
- PPP2R2A,
- PPP2R3B,
- PPP2R5A.
- STK24,
- STRN, and
- STRN3.
# Arabidopsis RCN1
RCN1 At1g25490 is one of three genes in Arabidopsis encoding Phosphoprotein Phosphatase 2A Regulatory Subunit A (PP2Aa). The association of different b subunits with a PP2Aa-PP2ac dimer is believed to determine substrate specificity. | PPP2R1A
Serine/threonine-protein phosphatase 2A 65 kDa regulatory subunit A alpha isoform is an enzyme that in humans is encoded by the PPP2R1A gene.[1] In the plant Arabidopsis thaliana a similar enzyme is encoded by the RCN1 gene (At1g25490).[2]
# Function
This gene encodes a constant regulatory subunit of protein phosphatase 2. Protein phosphatase 2 is one of the four major Ser/Thr phosphatases, and it is implicated in the negative control of cell growth and division. It consists of a common heteromeric core enzyme, which is composed of a catalytic subunit and a constant regulatory subunit, that associates with a variety of regulatory subunits. The constant regulatory subunit A serves as a scaffolding molecule to coordinate the assembly of the catalytic subunit and a variable regulatory B subunit. This gene encodes an alpha isoform of the constant regulatory subunit A.[3]
# Interactions
PPP2R1A has been shown to interact with:
- CTTNBP2NL,[4]
- FAM40A,[4]
- PPP2CB,[4][5] PPP2CA,[4][5] PPP4C,[6]
- PPP2R2A,[4][5]
- PPP2R3B,[4][5]
- PPP2R5A.[4][5]
- STK24,[4][7]
- STRN,[4] and
- STRN3.[4]
# Arabidopsis RCN1
RCN1 At1g25490 is one of three genes in Arabidopsis encoding Phosphoprotein Phosphatase 2A Regulatory Subunit A (PP2Aa). The association of different b subunits with a PP2Aa-PP2ac dimer is believed to determine substrate specificity. | https://www.wikidoc.org/index.php/PPP2R1A | |
74dc3f8958fc2af833e714bce7a5147da8eb1f2a | wikidoc | PPP2R3B | PPP2R3B
Serine/threonine-protein phosphatase 2A regulatory subunit B'' subunit beta is an enzyme that in humans is encoded by the PPP2R3B gene.
# Function
Protein phosphatase 2 (formerly named type 2A) is one of the four major Ser/Thr phosphatases and is implicated in the negative control of cell growth and division. Protein phosphatase 2 holoenzymes are heterotrimeric proteins composed of a structural subunit A, a catalytic subunit C, and a regulatory subunit B. The regulatory subunit is encoded by a diverse set of genes that have been grouped into the B/PR55, B'/PR61, and B''/PR72 families. These different regulatory subunits confer distinct enzymatic specificities and intracellular localizations to the holozenzyme. The product of this gene belongs to the B'' family. The B'' family has been further divided into subfamilies. The product of this gene belongs to the beta subfamily of regulatory subunit B''. Alternative splicing results in multiple transcript variants encoding different isoforms.
# Interactions
PPP2R3B has been shown to interact with PPP2R1B, PPP2R1A, CDC6 and PPP2CA. | PPP2R3B
Serine/threonine-protein phosphatase 2A regulatory subunit B'' subunit beta is an enzyme that in humans is encoded by the PPP2R3B gene.[1][2]
# Function
Protein phosphatase 2 (formerly named type 2A) is one of the four major Ser/Thr phosphatases and is implicated in the negative control of cell growth and division. Protein phosphatase 2 holoenzymes are heterotrimeric proteins composed of a structural subunit A, a catalytic subunit C, and a regulatory subunit B. The regulatory subunit is encoded by a diverse set of genes that have been grouped into the B/PR55, B'/PR61, and B''/PR72 families. These different regulatory subunits confer distinct enzymatic specificities and intracellular localizations to the holozenzyme. The product of this gene belongs to the B'' family. The B'' family has been further divided into subfamilies. The product of this gene belongs to the beta subfamily of regulatory subunit B''. Alternative splicing results in multiple transcript variants encoding different isoforms.[2]
# Interactions
PPP2R3B has been shown to interact with PPP2R1B,[3] PPP2R1A,[3][4] CDC6[5] and PPP2CA.[4][5] | https://www.wikidoc.org/index.php/PPP2R3B | |
6cd8866d963152b44e3d2bcd2bf2598130d25c39 | wikidoc | PPP2R5C | PPP2R5C
Serine/threonine-protein phosphatase 2A 56 kDa regulatory subunit gamma isoform is an enzyme that in humans is encoded by the PPP2R5C gene.
# Function
The product of this gene belongs to the Protein phosphatase 2A regulatory subunit B family. Protein phosphatase 2A is one of the four major Ser/Thr phosphatases, and it is implicated in the negative control of cell growth and division. It consists of a common heteromeric core enzyme, which is composed of a catalytic subunit and a constant regulatory subunit, that associates with a variety of regulatory subunits. The B regulatory subunit might modulate substrate selectivity and catalytic activity. This gene encodes a gamma isoform of the regulatory subunit B56 subfamily. Alternatively spliced transcript variants encoding different isoforms have been identified.
# Interactions
PPP2R5C has been shown to interact with PPP2R1B, PPP2CA and PPP2R5A. | PPP2R5C
Serine/threonine-protein phosphatase 2A 56 kDa regulatory subunit gamma isoform is an enzyme that in humans is encoded by the PPP2R5C gene.[1][2]
# Function
The product of this gene belongs to the Protein phosphatase 2A regulatory subunit B family. Protein phosphatase 2A is one of the four major Ser/Thr phosphatases, and it is implicated in the negative control of cell growth and division. It consists of a common heteromeric core enzyme, which is composed of a catalytic subunit and a constant regulatory subunit, that associates with a variety of regulatory subunits. The B regulatory subunit might modulate substrate selectivity and catalytic activity. This gene encodes a gamma isoform of the regulatory subunit B56 subfamily. Alternatively spliced transcript variants encoding different isoforms have been identified.[2]
# Interactions
PPP2R5C has been shown to interact with PPP2R1B,[3] PPP2CA[3][4][5] and PPP2R5A.[6] | https://www.wikidoc.org/index.php/PPP2R5C | |
07d7b98a1ded91aef045316d656c5575690cf021 | wikidoc | PRKAR1A | PRKAR1A
cAMP-dependent protein kinase type I-alpha regulatory subunit is an enzyme that in humans is encoded by the PRKAR1A gene.
# Function
cAMP is a signaling molecule important for a variety of cellular functions. cAMP exerts its effects by activating the cAMP-dependent protein kinase A (PKA), which transduces the signal through phosphorylation of different target proteins. The inactive holoenzyme of PKA is a tetramer composed of two regulatory and two catalytic subunits. cAMP causes the dissociation of the inactive holoenzyme into a dimer of regulatory subunits bound to four cAMP and two free monomeric catalytic subunits. Four different regulatory subunits and three catalytic subunits of PKA have been identified in humans. The protein encoded by this gene is one of the regulatory subunits. This protein was found to be a tissue-specific extinguisher that down-regulates the expression of seven liver genes in hepatoma x fibroblast hybrids Three alternatively spliced transcript variants encoding the same protein have been observed.
# Clinical significance
Functional null mutations in this gene cause Carney complex (CNC), an autosomal dominant multiple neoplasia syndrome. This gene can fuse to the RET protooncogene by gene rearrangement and form the thyroid tumor-specific chimeric oncogene known as PTC2.
Mutation of PRKAR1A leads to the Carney complex, associating multiple endocrine tumors.
# Interactions
PRKAR1A has been shown to interact with:
- AKAP10,
- AKAP1,
- AKAP4,
- ARFGEF1,
- ARFGEF2,
- Grb2,
- MYO7A,
- PRKAR1B, and
- UBE2M. | PRKAR1A
cAMP-dependent protein kinase type I-alpha regulatory subunit is an enzyme that in humans is encoded by the PRKAR1A gene.[1]
# Function
cAMP is a signaling molecule important for a variety of cellular functions. cAMP exerts its effects by activating the cAMP-dependent protein kinase A (PKA), which transduces the signal through phosphorylation of different target proteins. The inactive holoenzyme of PKA is a tetramer composed of two regulatory and two catalytic subunits. cAMP causes the dissociation of the inactive holoenzyme into a dimer of regulatory subunits bound to four cAMP and two free monomeric catalytic subunits. Four different regulatory subunits and three catalytic subunits of PKA have been identified in humans. The protein encoded by this gene is one of the regulatory subunits. This protein was found to be a tissue-specific extinguisher that down-regulates the expression of seven liver genes in hepatoma x fibroblast hybrids Three alternatively spliced transcript variants encoding the same protein have been observed.[2]
# Clinical significance
Functional null mutations in this gene cause Carney complex (CNC), an autosomal dominant multiple neoplasia syndrome. This gene can fuse to the RET protooncogene by gene rearrangement and form the thyroid tumor-specific chimeric oncogene known as PTC2.[2]
Mutation of PRKAR1A leads to the Carney complex, associating multiple endocrine tumors.[citation needed]
# Interactions
PRKAR1A has been shown to interact with:
- AKAP10,[3][4]
- AKAP1,[5][6]
- AKAP4,[7][8]
- ARFGEF1,[9]
- ARFGEF2,[9]
- Grb2,[10]
- MYO7A,[11]
- PRKAR1B,[5][12] and
- UBE2M.[13] | https://www.wikidoc.org/index.php/PRKAR1A | |
6b1e4f823ef1b1fbaf9e994f4770c3877b6d7c21 | wikidoc | PRKAR2B | PRKAR2B
cAMP-dependent protein kinase type II-beta regulatory subunit is an enzyme that in humans is encoded by the PRKAR2B gene.
# Function
cAMP is a signaling molecule important for a variety of cellular functions. cAMP exerts its effects by activating the cAMP-dependent protein kinase (PKA), which transduces the signal through phosphorylation of different target proteins. The inactive holoenzyme of PKA is a tetramer composed of two regulatory and two catalytic subunits. cAMP causes the dissociation of the inactive holoenzyme into a dimer of regulatory subunits bound to four cAMP and two free monomeric catalytic subunits. Four different regulatory subunits and three catalytic subunits of PKA have been identified in humans. The protein encoded by this gene is one of the regulatory subunits. This subunit can be phosphorylated by the activated catalytic subunit. This subunit has been shown to interact with and suppress the transcriptional activity of the cAMP responsive element binding protein 1 (CREB1) in activated T cells. Knockout studies in mice suggest that this subunit may play an important role in regulating energy balance and adiposity. The studies also suggest that this subunit may mediate the gene induction and cataleptic behavior induced by haloperidol.
# Interactions
PRKAR2B has been shown to interact with AKAP11 in an advanced Stage. | PRKAR2B
cAMP-dependent protein kinase type II-beta regulatory subunit is an enzyme that in humans is encoded by the PRKAR2B gene.[1][2]
# Function
cAMP is a signaling molecule important for a variety of cellular functions. cAMP exerts its effects by activating the cAMP-dependent protein kinase (PKA), which transduces the signal through phosphorylation of different target proteins. The inactive holoenzyme of PKA is a tetramer composed of two regulatory and two catalytic subunits. cAMP causes the dissociation of the inactive holoenzyme into a dimer of regulatory subunits bound to four cAMP and two free monomeric catalytic subunits. Four different regulatory subunits and three catalytic subunits of PKA have been identified in humans. The protein encoded by this gene is one of the regulatory subunits. This subunit can be phosphorylated by the activated catalytic subunit. This subunit has been shown to interact with and suppress the transcriptional activity of the cAMP responsive element binding protein 1 (CREB1) in activated T cells. Knockout studies in mice suggest that this subunit may play an important role in regulating energy balance and adiposity. The studies also suggest that this subunit may mediate the gene induction and cataleptic behavior induced by haloperidol.[2]
# Interactions
PRKAR2B has been shown to interact with AKAP11 in an advanced Stage.[3] | https://www.wikidoc.org/index.php/PRKAR2B | |
eb3cf40f8e353a5c3620cc713134931d00ea43fe | wikidoc | PRO 140 | PRO 140
PRO 140 is a humanized monoclonal antibody targeted against the CCR5 receptor found on T lymphocytes of the human immune system. It is being investigated as a potential therapy in the treatment of HIV infection.
The United States Food and Drug Administration has designated PRO 140 for fast-track approval.
# Development
PRO 140 is being developed by Progenics Pharmaceuticals. In May 2007, they announced results from the phase I clinical trial of the drug. The researchers said the results demonstrated "potent, rapid, prolonged, dose-dependent, highly significant antiviral activity" for PRO 140. Participants in the highest dosing group received 5mg/kg and showed a average viral load decrease of -1.83 log10. On average, reductions of greater than -1 log10 copies/ml were maintained for between two and three weeks, from only a single dose of the drug. The largest individual HIV RNA reductions ranged up to -2.5 log10 among patients receiving both the 2 and 5 mg/kg doses.
# Mechanism of Action
PRO 140 functions as an entry inhibitor. PRO 140 binds to the CCR5 receptor, and interferes with HIV's ability to enter the cell. Unlike other entry inhibitors, PRO 140 is an monoclonal antibody. As such, it must be injected to be effective. However, once inside the body, PRO 140 binds to to CCR5 for >60 days, which may allow for dosing as infrequently as every other week. | PRO 140
PRO 140 is a humanized monoclonal antibody targeted against the CCR5 receptor found on T lymphocytes of the human immune system. It is being investigated as a potential therapy in the treatment of HIV infection.[1]
The United States Food and Drug Administration has designated PRO 140 for fast-track approval.[2]
## Development
PRO 140 is being developed by Progenics Pharmaceuticals. In May 2007, they announced results from the phase I clinical trial of the drug. The researchers said the results demonstrated "potent, rapid, prolonged, dose-dependent, highly significant antiviral activity" for PRO 140. Participants in the highest dosing group received 5mg/kg and showed a average viral load decrease of -1.83 log10. On average, reductions of greater than -1 log10 copies/ml were maintained for between two and three weeks, from only a single dose of the drug.[3] The largest individual HIV RNA reductions ranged up to -2.5 log10 among patients receiving both the 2 and 5 mg/kg doses.[4]
## Mechanism of Action
PRO 140 functions as an entry inhibitor.[5] PRO 140 binds to the CCR5 receptor, and interferes with HIV's ability to enter the cell. Unlike other entry inhibitors, PRO 140 is an monoclonal antibody. As such, it must be injected to be effective. However, once inside the body, PRO 140 binds to to CCR5 for >60 days,[1] which may allow for dosing as infrequently as every other week.[6][7]
# External links
Animation of PRO 140 mechanism | https://www.wikidoc.org/index.php/PRO_140 | |
360afac9135024f38138a888da6878e270ded580 | wikidoc | PRPSAP2 | PRPSAP2
Phosphoribosyl pyrophosphate synthetase-associated protein 2 is a protein that in humans is encoded by the PRPSAP2 gene.
# Function
The enzyme phosphoribosyl pyrophosphate synthetase (PRS) catalyzes the formation of phosphoribosyl pyrophosphate which is a substrate for synthesis of purine and pyrimidine nucleotides, histidine, tryptophan and NAD. PRS exists as a complex with two catalytic subunits and two associated subunits. This gene encodes a non-catalytic associated subunit of PRS.
## Model organisms
Model organisms have been used in the study of PRPSAP2 function. A conditional knockout mouse line, called Prpsap2tm1a(EUCOMM)Wtsi was generated as part of the International Knockout Mouse Consortium program — a high-throughput mutagenesis project to generate and distribute animal models of disease to interested scientists — at the Wellcome Trust Sanger Institute. Male and female animals underwent a standardized phenotypic screen to determine the effects of deletion. Twenty five tests were carried out and two phenotypes were reported. Homozygous mutant males displayed more rearing in an open field test, and mutants of both sex had decreased IgG1 levels. | PRPSAP2
Phosphoribosyl pyrophosphate synthetase-associated protein 2 is a protein that in humans is encoded by the PRPSAP2 gene.[1]
# Function
The enzyme phosphoribosyl pyrophosphate synthetase (PRS) catalyzes the formation of phosphoribosyl pyrophosphate which is a substrate for synthesis of purine and pyrimidine nucleotides, histidine, tryptophan and NAD. PRS exists as a complex with two catalytic subunits and two associated subunits. This gene encodes a non-catalytic associated subunit of PRS.[1]
## Model organisms
Model organisms have been used in the study of PRPSAP2 function. A conditional knockout mouse line, called Prpsap2tm1a(EUCOMM)Wtsi[7][8] was generated as part of the International Knockout Mouse Consortium program — a high-throughput mutagenesis project to generate and distribute animal models of disease to interested scientists — at the Wellcome Trust Sanger Institute.[9][10][11] Male and female animals underwent a standardized phenotypic screen to determine the effects of deletion.[5][12] Twenty five tests were carried out and two phenotypes were reported. Homozygous mutant males displayed more rearing in an open field test, and mutants of both sex had decreased IgG1 levels.[5] | https://www.wikidoc.org/index.php/PRPSAP2 | |
b68245b5988f5998b4451842f556ca06b1af7338 | wikidoc | PSTPIP2 | PSTPIP2
# Introduction
Proline-serine-threonine phosphatase-interacting protein 2 is an enzyme that in humans is encoded by the Pstpip2 gene. This protein, also known as macrophage F-actin-asosiated and tyrosine phosphorylated protein (MAYP) is a member of the Pombe Cdc15 homology (PCH) family of proteins has been shown to coordinate membrane and cytoskeletal dynamics
# Function
Pstpip2 is selectively expressed in macrophages and macrophage precursors, and it is an actin bundling protein which regulates filopodia formation and macrophage motility
# Cytokine expression profile
PSTPIP2 deficiency leads to elevated levels of circulating inflammatory mediators in vivo. In asymptomatic mice, only MIP-1α and IL-6 are elevated, however symptomatic PSTPIP2-deficient mice have elevated levels of circulating IL-6, MIP-1α, TNF-α, CSF-1 and IP-10< and decreased levels of IL-13
# Disease linkage
The missense mutation I228N leads to a macrophage-mediated autoinflammatory disease called Lupo Pstpip2 (Pstpip2Lupo/Lupo ). It is characterized by skin necrosis, inflammation of paws, ears and inflammatory bone resorption. Another mutation in Pstpip2, L98P, was described in chronic multifocal osteomyelitis (cmo) mice. This disease is also autoinflammatory, and causes inflammatory infiltrate of polymorphonuclear leukocytes, macrophages, lymphocytes, plasma cells and osteoclasts. Later the infiltrate is replaced with new bone tissue which lead to tail kinks and hind-foot deformities. The cmo mice also develop ear inflammation in the epidermis, dermis and cartilage.
# Interactions
PSTPIP2 interacts with protein tyrosine phosphatases from the proline-, glutamic acid-, serine- and threonine-rich (PEST) family , SHIP1 and Csk | PSTPIP2
# Introduction
Proline-serine-threonine phosphatase-interacting protein 2 is an enzyme that in humans is encoded by the Pstpip2 gene.[1][2] This protein, also known as macrophage F-actin-asosiated and tyrosine phosphorylated protein (MAYP) is a member of the Pombe Cdc15 homology (PCH) family of proteins has been shown to coordinate membrane and cytoskeletal dynamics [3]
# Function
Pstpip2 is selectively expressed in macrophages and macrophage precursors[4][5], and it is an actin bundling protein which regulates filopodia formation and macrophage motility[6]
# Cytokine expression profile
PSTPIP2 deficiency leads to elevated levels of circulating inflammatory mediators in vivo. In asymptomatic mice, only MIP-1α and IL-6 are elevated, however symptomatic PSTPIP2-deficient mice have elevated levels of circulating IL-6, MIP-1α, TNF-α, CSF-1 and IP-10<[7] and decreased levels of IL-13[8][9]
# Disease linkage
The missense mutation I228N leads to a macrophage-mediated autoinflammatory disease called Lupo Pstpip2 (Pstpip2Lupo/Lupo ). It is characterized by skin necrosis, inflammation of paws, ears and inflammatory bone resorption[5]. Another mutation in Pstpip2, L98P, was described in chronic multifocal osteomyelitis (cmo) mice. This disease is also autoinflammatory, and causes inflammatory infiltrate of polymorphonuclear leukocytes, macrophages, lymphocytes, plasma cells and osteoclasts. Later the infiltrate is replaced with new bone tissue which lead to tail kinks and hind-foot deformities. The cmo mice also develop ear inflammation in the epidermis, dermis and cartilage[10].
# Interactions
PSTPIP2 interacts with protein tyrosine phosphatases from the proline-, glutamic acid-, serine- and threonine-rich (PEST) family [11], SHIP1 and Csk[12] | https://www.wikidoc.org/index.php/PSTPIP2 | |
3d152175d78965632de87c30c84db0f91e5956a1 | wikidoc | PTTG1IP | PTTG1IP
Pituitary tumor-transforming gene 1 protein-interacting protein (PTTG1), also known as PTTG1-binding factor (PBF), is a poorly characterised protein that in humans is encoded by the PTTG1IP gene located within the chromosomal region 21q22.3.
# Structure
The encoded protein is composed of 180 amino acids and has a predicted molecular mass of 22kDa. The peptide sequence shares no significant homology with any other human proteins but is highly conserved across a wide diversity of animal species, suggesting both unique function and evolutionary importance. Initial protein prediction studies suggested that PTTG1IP was a cell surface glycoprotein, however, the recent identification of a nuclear localisation signal (NLS) suggests that it may have a role both in the cytoplasm and as a nuclear protein.
# Function
Although PTTG1IP is ubiquitously expressed in normal human tissues, its exact function remains elusive. It has been shown to directly interact with the human securin and proto-oncogene, PTTG1, thus facilitating its nuclear translocation and the subsequent transcriptional activation of basic fibroblast growth factor (bFGF) by PTTG1.
Further evidence suggests that PTTG1IP may have a direct role in cancer. Initially, PTTG1IP expression was found to be higher in pituitary tumours compared with normal pituitary tissue. In particular, PTTG1IP has been shown to regulate thyroid cell growth, with overexpression resulting in hyperplasia and the formation of lesions within the thyroid gland. PTTG1IP expression has also been independently associated with tumour recurrence and subcutaneous expression results in tumour formation in nude mice.
PTTG1IP is also implicated in breast cancer. Immunohistochemical analysis of tissue samples has revealed that PTTG1IP is strongly expressed in several types and grades of breast cancer. Furthermore, overexpression and secretion of PTTG1IP induces cell invasion, a process that is essential for the formation of metastatic disease.
Furthermore, PTTG1IP has been reported to regulate the expression of the human sodium-iodide symporter (NIS). NIS is expressed by thyroid follicular epithelial cells and is responsible for iodine transport and uptake. The ability of the thyroid to accumulate iodine provides the basis for radioiodine ablation of thyroid tumours and their metastases. Overexpression of PTTG1 or PTTG1IP inhibits NIS mRNA expression and iodide uptake in human and rat thyroid cells. This has important implications for radioiodine ablation therapy and highlights PTTG1IP as a novel target for improving radioiodine uptake by thyroid tumours.
# Interactions
PTTG1IP has been shown to interact with:
- PTTG1,
- MCT8, and
- NIS. | PTTG1IP
Pituitary tumor-transforming gene 1 protein-interacting protein (PTTG1), also known as PTTG1-binding factor (PBF), is a poorly characterised protein that in humans is encoded by the PTTG1IP gene [1][2][3] located within the chromosomal region 21q22.3.[4]
# Structure
The encoded protein is composed of 180 amino acids and has a predicted molecular mass of 22kDa. The peptide sequence shares no significant homology with any other human proteins but is highly conserved across a wide diversity of animal species, suggesting both unique function and evolutionary importance.[4] Initial protein prediction studies suggested that PTTG1IP was a cell surface glycoprotein, however, the recent identification of a nuclear localisation signal (NLS) suggests that it may have a role both in the cytoplasm and as a nuclear protein.[4]
# Function
Although PTTG1IP is ubiquitously expressed in normal human tissues, its exact function remains elusive.[4] It has been shown to directly interact with the human securin and proto-oncogene, PTTG1, thus facilitating its nuclear translocation and the subsequent transcriptional activation of basic fibroblast growth factor (bFGF) by PTTG1.[4]
Further evidence suggests that PTTG1IP may have a direct role in cancer. Initially, PTTG1IP expression was found to be higher in pituitary tumours compared with normal pituitary tissue.[5] In particular, PTTG1IP has been shown to regulate thyroid cell growth, with overexpression resulting in hyperplasia and the formation of lesions within the thyroid gland.[6] PTTG1IP expression has also been independently associated with tumour recurrence [5] and subcutaneous expression results in tumour formation in nude mice.[5]
PTTG1IP is also implicated in breast cancer.[7] Immunohistochemical analysis of tissue samples has revealed that PTTG1IP is strongly expressed in several types and grades of breast cancer.[7] Furthermore, overexpression and secretion of PTTG1IP induces cell invasion,[7] a process that is essential for the formation of metastatic disease.
Furthermore, PTTG1IP has been reported to regulate the expression of the human sodium-iodide symporter (NIS).[8] NIS is expressed by thyroid follicular epithelial cells and is responsible for iodine transport and uptake. The ability of the thyroid to accumulate iodine provides the basis for radioiodine ablation of thyroid tumours and their metastases. Overexpression of PTTG1 or PTTG1IP inhibits NIS mRNA expression and iodide uptake in human and rat thyroid cells.[6][8][9][10] This has important implications for radioiodine ablation therapy and highlights PTTG1IP as a novel target for improving radioiodine uptake by thyroid tumours.
# Interactions
PTTG1IP has been shown to interact with:
- PTTG1,[4]
- MCT8,[11] and
- NIS.[4] | https://www.wikidoc.org/index.php/PTTG1IP | |
f6091d45d9cd681ce352c0c025aa966948c3b2f5 | wikidoc | Panacea | Panacea
In Greek mythology, Panacea (Greek Πανάκεια, Panakeia) was the goddess of healing. She was the daughter of Asclepius, god of medicine, and the granddaughter of Apollo, god of healing (among other things).
Panacea and her five sisters each performed a facet of Apollo's art: Panacea was the goddess of cures, Iaso was the goddess of recuperation, Hygieia was the goddess of disease prevention, Aceso was the goddess of recovery, Meditrina was the goddess of longevity, and Aglaea was the goddess of natural beauty.
Panacea also had four brothers — Podaleirus, one of the two kings of Tricca, who had a flair for diagnostics, and Machaon, the other king of Tricca, who was a master surgeon (these two took part in the Trojan War until Machaon was killed by Penthesilea, queen of the Amazons); Telesphoros, who devoted his life to serving Asclepius; and Aratus, her step-brother, who was a Greek hero and the patron/liberator of Sicyon.
Panacea was said to have a poultice or potion with which she healed the sick. This brought about the concept of the panacea in medicine.
# Etymology
- Panacea is from Greek Panakeia, from panakés, "all healing"; pas (neuter pan), "all" (from Indo-European *kua-nt-, a zero-grade extension of *keu-, "large space; vault; hole") + akos, "cure" (perhaps from Indo-European *yék-, "to heal").
- Hygieia is from Greek hugeia, "health", from Indo-European *su-gwiyes-ya, "living in good condition"; *su-, "well" + *gwei-, "to live".
- Iaso is from Greek iasthai, "to cure; to heal".
# Genealogy
(the primordial serpent Ophion sets alight the edges of Chaos, out of which is born Eurynome)
Ophion + Eurynome
(Ophion coils around Eurynome, the moon, and she flies away as a white bird, laying six silver eggs, one of which will be Gaea)
Gaea
(conceives a child without fertilization)
Uranus + Gaea
Cronus + Rhea
Zeus + Leto
Apollo + Coronis, princess of Epidaurus (or Arsinoe, princess of Messenia)
Asclepius + Epione (or Salus) | Panacea
Template:Otheruses4
Template:Greek myth (other gods)
In Greek mythology, Panacea (Greek Πανάκεια, Panakeia) was the goddess of healing. She was the daughter of Asclepius, god of medicine, and the granddaughter of Apollo, god of healing (among other things).
Panacea and her five sisters each performed a facet of Apollo's art: Panacea was the goddess of cures, Iaso was the goddess of recuperation, Hygieia was the goddess of disease prevention, Aceso was the goddess of recovery, Meditrina was the goddess of longevity, and Aglaea was the goddess of natural beauty.
Panacea also had four brothers — Podaleirus, one of the two kings of Tricca, who had a flair for diagnostics, and Machaon, the other king of Tricca, who was a master surgeon (these two took part in the Trojan War until Machaon was killed by Penthesilea, queen of the Amazons); Telesphoros, who devoted his life to serving Asclepius; and Aratus, her step-brother, who was a Greek hero and the patron/liberator of Sicyon.
Panacea was said to have a poultice or potion with which she healed the sick. This brought about the concept of the panacea in medicine.
# Etymology
- Panacea is from Greek Panakeia, from panakés, "all healing"; pas (neuter pan), "all" (from Indo-European *kua-nt-, a zero-grade extension of *keu-, "large space; vault; hole") + akos, "cure" (perhaps from Indo-European *yék-, "to heal").
- Hygieia is from Greek hugeia, "health", from Indo-European *su-gwiyes-ya, "living in good condition"; *su-, "well" + *gwei-, "to live".
- Iaso is from Greek iasthai, "to cure; to heal".
# Genealogy
(the primordial serpent Ophion sets alight the edges of Chaos, out of which is born Eurynome)
Ophion + Eurynome
(Ophion coils around Eurynome, the moon, and she flies away as a white bird, laying six silver eggs, one of which will be Gaea)
Gaea
(conceives a child without fertilization)
Uranus + Gaea
Cronus + Rhea
Zeus + Leto
Apollo + Coronis, princess of Epidaurus (or Arsinoe, princess of Messenia)
Asclepius + Epione (or Salus) | https://www.wikidoc.org/index.php/Panacea | |
fe6ac37ff9bc01f934dec1daf41ef088b1c5dc23 | wikidoc | Papilla | Papilla
A papilla (plural: papillae) can be:
- A small projection, such as a nipple-like projection on the skin, at the base of a hair or the root of a feather; the base of a new tooth.
- A pimple or blister
- An interdental papilla is the part of the gingiva located between teeth.
- Dental papilla
- Renal papilla
- Lacrimal papilla
- Mammary papilla
- Any of the small projections on the top of the tongue:
vallate papilla (contains taste buds)
fungiform papilla (contains taste buds)
filiform papilla (does not contain taste buds)
foliate papilla (contains taste buds)
- vallate papilla (contains taste buds)
- fungiform papilla (contains taste buds)
- filiform papilla (does not contain taste buds)
- foliate papilla (contains taste buds)
- Alternative name for the Optic disc of the eye.
- Genital papilla, found in fishes. | Papilla
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
A papilla (plural: papillae) can be:
- A small projection, such as a nipple-like projection on the skin, at the base of a hair or the root of a feather; the base of a new tooth.
- A pimple or blister
- An interdental papilla is the part of the gingiva located between teeth.
- Dental papilla
- Renal papilla
- Lacrimal papilla
- Mammary papilla
- Any of the small projections on the top of the tongue:
vallate papilla (contains taste buds)
fungiform papilla (contains taste buds)
filiform papilla (does not contain taste buds)
foliate papilla (contains taste buds)
- vallate papilla (contains taste buds)
- fungiform papilla (contains taste buds)
- filiform papilla (does not contain taste buds)
- foliate papilla (contains taste buds)
- Alternative name for the Optic disc of the eye.[1]
- Genital papilla, found in fishes. | https://www.wikidoc.org/index.php/Papilla | |
1565be554391c233837c1e9ff3c458df8e369c19 | wikidoc | Paprika | Paprika
Paprika is a spice made from the grinding of dried sweet red or green bell peppers (Capsicum annuum). In many European countries, the name paprika also refers to bell peppers themselves. The seasoning is used in many cuisines to add colour and flavour to dishes.
According to the Oxford English Dictionary, the English word comes from the Hungarian "paprika," which means 'pepper' (the red spice or the vegetable). This derives from the Serbian and Croatian "paprena" that means "the one that is hot" and it is derived from Serbian and Croatian noun papar, "pepper", which in turn was borrowed from the Latin "piper", for "pepper."
Paprika is used as an ingredient in a broad variety of dishes throughout the world. Paprika (pimentón in Spain, colorau in Portugal, chiltoma in Nicaragua, but these "paprikas" are not made exclusively from bell peppers, other varieties are used, and there are several hot and sweet "paprikas") is principally used to season and colour rices, stews, and soups, such as goulash. In Spain, Germany, Hungary, Slovakia, Bosnia and Herzegovina, Croatia, Serbia, Romania, Bulgaria, Turkey and Portugal, paprika is also used in the preparation of sausages as an ingredient that is mixed with meats and other spices. Paprika may be smoked for additional flavour.
In Poland, cans with Paprykarz szczeciński are made by many seafood producers, of steamed sea fish, rice, paprika, and onion.
In India, a similar powdered spice comes from a fruit locally called 'deghi mirchi', which is grown widely and takes on a slightly different flavour, depending on local soil and climatic conditions.
The hottest paprikas are not the bright red ones, but rather the palest red and light brown coloured ones.
Types of Hungarian paprika (Hungarian name in parentheses):
- Special Quality (Különleges): The mildest and brightest red of all Hungarian paprikas, with excellent aroma.
- Delicate (Édes csemege): Ranging from light to dark red, a mild paprika with a rich flavour.
- Exquisite Delicate (Csemegepaprika): Similar to Delicate, but more pungent.
- Pungent Exquisite Delicate (Csípős Csemege, Pikáns): An even more pungent Delicate.
- Rose (Rózsa): Pale Red in colour with strong aroma and mild pungency.
- Noble Sweet (Édesnemes): The most commonly exported paprika; bright red and slightly pungent.
- Half-Sweet (Félédes): A blend of mild and pungent paprikas; medium pungency.
- Hot (Erős): Light brown in colour, this is the hottest of all the paprikas.
Hungarian paprika is mainly made in the cities of Kalocsa and Szeged, both areas in the southern part of Hungary.
In Hungarian and some other languages, such as Dutch, German, Polish, Japanese and Korean, the word "paprika" is used for the fruits, the bell pepper or hot pepper too, of which the spices are made.
# Health benefits
Paprika is unusually high in vitamin C. Hungary's 1937 Nobel prize-winning Albert Szent-Györgyi first discovered the vitamin in paprika peppers in 1932.
The capsicum peppers used for paprika contain six to nine times as much vitamin C as tomatoes by weight.
High heat leaches the vitamins from peppers, thus commercially-dried peppers are not as nutritious as those dried naturally in the sun.
As an antibacterial agent and stimulant, paprika can help normalize blood pressure, improve circulation, and increase the production of saliva and stomach acids to aid digestion.
# Origin
Red paprika originated in Southern Mexico, Central America, and the Antilles Islands, where Native Americans used it for healing and seasoning. Christopher Columbus returned from the New World with unknown spices with a never-before-seen present: a paprika plant. At first, the plants were used to decorate baroque gardens of nobility in Europe. The plant also arrived in Turkey via trade routes.
From there it came to Hungary through the Balkans. In the second half of the 16th century, Margit Széchy, a noble lady already had a plant in her garden called the Turkish pepper (at that time also called Indian pepper or heathen pepper). The name ‘paprika’ came from the 18th Century as a diminutive form for the south-slavish name of pepper (papar), then after the Hungarian usage, the word became international and universal.
The first note mentioning red pepper in Szeged dates back to 1748, the word paprika stood in an account book.
In Hungary, paprika was first used as a cure for intermittent fever, it later became a typical spice of Hungarian cooking. | Paprika
Paprika is a spice made from the grinding of dried sweet red or green bell peppers (Capsicum annuum). In many European countries, the name paprika also refers to bell peppers themselves. The seasoning is used in many cuisines to add colour and flavour to dishes.
According to the Oxford English Dictionary, the English word comes from the Hungarian "paprika," which means 'pepper' (the red spice or the vegetable). This derives from the Serbian and Croatian "paprena" that means "the one that is hot" and it is derived from Serbian and Croatian noun papar, "pepper", which in turn was borrowed from the Latin "piper", for "pepper."
Paprika is used as an ingredient in a broad variety of dishes throughout the world. Paprika (pimentón in Spain, colorau in Portugal, chiltoma in Nicaragua, but these "paprikas" are not made exclusively from bell peppers, other varieties are used, and there are several hot and sweet "paprikas") is principally used to season and colour rices, stews, and soups, such as goulash. In Spain, Germany, Hungary, Slovakia, Bosnia and Herzegovina, Croatia, Serbia, Romania, Bulgaria, Turkey and Portugal, paprika is also used in the preparation of sausages as an ingredient that is mixed with meats and other spices. Paprika may be smoked for additional flavour.
In Poland, cans with Paprykarz szczeciński are made by many seafood producers, of steamed sea fish, rice, paprika, and onion.
In India, a similar powdered spice comes from a fruit locally called 'deghi mirchi', which is grown widely and takes on a slightly different flavour, depending on local soil and climatic conditions.
The hottest paprikas are not the bright red ones, but rather the palest red and light brown coloured ones.
Types of Hungarian paprika (Hungarian name in parentheses):
- Special Quality (Különleges): The mildest and brightest red of all Hungarian paprikas, with excellent aroma.
- Delicate (Édes csemege): Ranging from light to dark red, a mild paprika with a rich flavour.
- Exquisite Delicate (Csemegepaprika): Similar to Delicate, but more pungent.
- Pungent Exquisite Delicate (Csípős Csemege, Pikáns): An even more pungent Delicate.
- Rose (Rózsa): Pale Red in colour with strong aroma and mild pungency.
- Noble Sweet (Édesnemes): The most commonly exported paprika; bright red and slightly pungent.
- Half-Sweet (Félédes): A blend of mild and pungent paprikas; medium pungency.
- Hot (Erős): Light brown in colour, this is the hottest of all the paprikas.
Hungarian paprika is mainly made in the cities of Kalocsa and Szeged, both areas in the southern part of Hungary.
In Hungarian and some other languages, such as Dutch, German, Polish, Japanese and Korean, the word "paprika" is used for the fruits, the bell pepper or hot pepper too, of which the spices are made.
# Health benefits
Paprika is unusually high in vitamin C. Hungary's 1937 Nobel prize-winning Albert Szent-Györgyi first discovered the vitamin in paprika peppers in 1932.
The capsicum peppers used for paprika contain six to nine times as much vitamin C as tomatoes by weight.
High heat leaches the vitamins from peppers, thus commercially-dried peppers are not as nutritious as those dried naturally in the sun.
As an antibacterial agent and stimulant, paprika can help normalize blood pressure, improve circulation, and increase the production of saliva and stomach acids to aid digestion.[citation needed]
# Origin
Red paprika originated in Southern Mexico, Central America, and the Antilles Islands, where Native Americans used it for healing and seasoning. Christopher Columbus returned from the New World with unknown spices with a never-before-seen present: a paprika plant. At first, the plants were used to decorate baroque gardens of nobility in Europe. The plant also arrived in Turkey via trade routes.
From there it came to Hungary through the Balkans. In the second half of the 16th century, Margit Széchy, a noble lady already had a plant in her garden called the Turkish pepper (at that time also called Indian pepper or heathen pepper). The name ‘paprika’ came from the 18th Century as a diminutive form for the south-slavish name of pepper (papar), then after the Hungarian usage, the word became international and universal.
The first note mentioning red pepper in Szeged dates back to 1748, the word paprika stood in an account book.
In Hungary, paprika was first used as a cure for intermittent fever, it later became a typical spice of Hungarian cooking.
# External links
- Nutrition Facts and Analysis from NutritionData.com | https://www.wikidoc.org/index.php/Paprika | |
d1ce32c4ab36c1c02081dc92fbc98bcdd2b7935d | wikidoc | Paraben | Paraben
Parabens are a group of chemicals widely used as preservatives in the cosmetic and pharmaceutical industries. Parabens are effective preservatives in many types of formulas. These compounds, and their salts, are used primarily for their bacteriocidal and fungicidal properties. They can be found in shampoos, commercial moisturizers, shaving gels, cleansing gels, personal lubricants, topical/parenteral pharmaceuticals, spray tanning solution and toothpaste. They are also used as food additives.
Their efficacy as preservatives, in combination with their low cost, their long history of safe use—at least to the extent that scientific studies have not proven they are harmful—and the unproven efficacy of natural ingredients like grapefruit seed extract (GSE), probably explains why parabens are so commonplace. They are becoming increasingly controversial, however, and some organizations which adhere to the precautionary principle object to their everyday use.
# Chemistry
Parabens are esters of para-hydroxybenzoic acid, from which the name is derived. Common parabens include methylparaben (E number E218), ethylparaben (E214), propylparaben (E216) and butylparaben. Less common parabens include isobutylparaben, isopropylparaben, benzylparaben and their sodium salts. The general chemical structure of a paraben is shown at top right, where R symbolizes an alkyl group such as methyl, ethyl, propyl or butyl.
# Occurrence
Some parabens are found naturally in plant sources such as methylparaben from the fruit of the blueberry shrub, where it acts as an antimicrobial agent.
# Synthesis
All commercially used parabens are synthetically produced, although some are identical to those found in nature. They are produced by the esterification of para-hydroxybenzoic acid with the appropriate alcohol. para-Hydroxybenzoic acid is in turn produced industrially from a modification of the Kolbe-Schmitt reaction, using potassium phenoxide and carbon dioxide.
# Toxicology
Parabens are considered to be safe because of their low toxicity profile and their long history of safe use; however, a few recent controversial studies have begun to challenge this view. Studies on the acute, subchronic, and chronic effects in rodents indicate that parabens are practically non-toxic. Parabens are rapidly absorbed, metabolized, and excreted. The major metabolites of parabens are p-hydroxybenzoic acid (pHBA), p-hydroxyhippuric acid (M1), p-hydroxybenzoyl glucuronide (M3), and p-carboxyphenylsulfate (M4).
## Allergic reactions
In individuals with normal skin, parabens are, for the most part, non-irritating and non-sensitizing. Parabens can, however, cause skin irritation and contact dermatitis in individuals with paraben allergies, a small percentage of the general population.
## Breast cancer
One controversial scientific study reports that parabens were found in samples of breast tumors. The validity of the conclusions of this study have been debated in the scientific literature. Nevertheless, this study has fueled the belief that parabens in underarm deodorants or other cosmetics migrated into the breast tissue and contributed to the development of the tumors. However, no causal link with cancer has ever been proven and so far there is no scientific evidence to support any link with any form of cancer. A recent review of the available data has concluded "it is biologically implausible that parabens could increase the risk of any estrogen-mediated endpoint, including effects on the male reproductive tract or breast cancer" and that "that worst-case daily exposure to parabens would present substantially less risk relative to exposure to naturally occurring endocrine active chemicals (EACs) in the diet such as the phytoestrogen daidzein." In addition, the American Cancer Society has concluded that there is no good scientific evidence to support a claim that use of cosmetics such as antiperspirants increase an individual's risk of developing breast cancer.
## Estrogenic activity
Animal experiments have shown that parabens have weak estrogenic activity, acting as xenoestrogens. In an in vivo study, the effect of butylparaben was determined to be approximately 100,000 times weaker than estradiol, although this effect was only observed when employing a dose level which was 25,000 times higher than is actually used to preserve products. As the estrogenic effect is dose-related, it may be calculated that the estrogenic effect at normal use concentrations of butylparaben is 100,000 x 25,000, i.e. 2,500,000,000 times weaker than estradiol. In the same study it was shown that the in vivo estrogenic activity of parabens is reduced by about three orders of magnitude compared to in vitro activity probably through the rapid metabolism of the parabens to the non-estrogenic metabolites. In vivo data are accepted as being more relevant than in vitro data.
The estrogenic activity of parabens increase with the length of the alkyl group. It is believed that propylparaben is estrogenic to a certain degree as well, though this is expected to be less than butylparaben by virtue of its less lipophilic nature. Since it can be concluded that the estrogenic activity of butylparaben is negligible under normal use, the same should be concluded for shorter analogs.
Some estrogens are known to drive the growth of tumors; however the estrogenic activity and mutagenic activity of estrogens are not the same with the latter dependent on free radical chemistry and not estrogen receptor activity. Nonetheless, this study has elicited some concern about the use of butylparaben, and to a lesser extent other parabens as well, in cosmetics and antiperspirants. However, there is no evidence that any cosmetics containing parabens pose a health risk, because of the low doses involved and the fact that parabens are unlikely to penetrate into the tissue, remain intact, and to accumulate there.
Nevertheless, the European Scientific Committee on Consumer Products (SCCP) stated in 2006 that the available data on parabens do not enable a decisive response to the question of whether propyl, butyl and isobutyl paraben can be safely used in cosmetic products at individual concentrations up to 0.4%, which is the allowed limit in the EU.
# Paraben controversy
The above mentioned studies have resulted in scientific debate that in turn led to popular controversy largely propagated by mass e-mail. The controversy has led to some concerns (both over its possible carcinogenicity, as well as its estrogenic effect,) being expressed over the continued use of parabens as preservatives, although the scientific community has found no correlation with cancer and mostly agree that any causation is improbable. There has been consensus that any estrogenic effect caused by the doses of parabens received from consumer products are insignificant compared to natural estrogens and other xenoestrogens.
The mainstream cosmetic industry believes that parabens, like most cosmetic ingredients, are safe based on their long term use and safety record and recent scientific studies. Public interest organizations which raise awareness about cosmetic ingredients believe that further research is necessary to determine the safety of parabens (see also precautionary principle). The concerns have led to a significant minority shift from their usage by natural personal care companies seeking alternatives. | Paraben
Parabens are a group of chemicals widely used as preservatives in the cosmetic and pharmaceutical industries. Parabens are effective preservatives in many types of formulas. These compounds, and their salts, are used primarily for their bacteriocidal and fungicidal properties. They can be found in shampoos, commercial moisturizers, shaving gels, cleansing gels, personal lubricants, topical/parenteral pharmaceuticals, spray tanning solution and toothpaste. They are also used as food additives.
Their efficacy as preservatives, in combination with their low cost, their long history of safe use—at least to the extent that scientific studies have not proven they are harmful—and the unproven efficacy of natural ingredients like grapefruit seed extract (GSE),[1] probably explains why parabens are so commonplace. They are becoming increasingly controversial, however, and some organizations which adhere to the precautionary principle object to their everyday use.[2]
# Chemistry
Parabens are esters of para-hydroxybenzoic acid, from which the name is derived. Common parabens include methylparaben (E number E218), ethylparaben (E214), propylparaben (E216) and butylparaben. Less common parabens include isobutylparaben, isopropylparaben, benzylparaben and their sodium salts. The general chemical structure of a paraben is shown at top right, where R symbolizes an alkyl group such as methyl, ethyl, propyl or butyl.
# Occurrence
Some parabens are found naturally in plant sources such as methylparaben from the fruit of the blueberry shrub,[3][4][5] where it acts as an antimicrobial agent.
# Synthesis
All commercially used parabens are synthetically produced, although some are identical to those found in nature. They are produced by the esterification of para-hydroxybenzoic acid with the appropriate alcohol. para-Hydroxybenzoic acid is in turn produced industrially from a modification of the Kolbe-Schmitt reaction, using potassium phenoxide and carbon dioxide.
# Toxicology
Parabens are considered to be safe because of their low toxicity profile and their long history of safe use; however, a few recent controversial studies have begun to challenge this view. Studies on the acute, subchronic, and chronic effects in rodents indicate that parabens are practically non-toxic.[6][7] Parabens are rapidly absorbed, metabolized, and excreted.[6] The major metabolites of parabens are p-hydroxybenzoic acid (pHBA), p-hydroxyhippuric acid (M1), p-hydroxybenzoyl glucuronide (M3), and p-carboxyphenylsulfate (M4).[8]
## Allergic reactions
In individuals with normal skin, parabens are, for the most part, non-irritating and non-sensitizing. Parabens can, however, cause skin irritation and contact dermatitis in individuals with paraben allergies, a small percentage of the general population.[9]
## Breast cancer
One controversial scientific study reports that parabens were found in samples of breast tumors.[10] The validity of the conclusions of this study have been debated in the scientific literature.[11] Nevertheless, this study has fueled the belief that parabens in underarm deodorants or other cosmetics migrated into the breast tissue and contributed to the development of the tumors. However, no causal link with cancer has ever been proven and so far there is no scientific evidence to support any link with any form of cancer. A recent review of the available data[12] has concluded "it is biologically implausible that parabens could increase the risk of any estrogen-mediated endpoint, including effects on the male reproductive tract or breast cancer" and that "that worst-case daily exposure to parabens would present substantially less risk relative to exposure to naturally occurring endocrine active chemicals (EACs) in the diet such as the phytoestrogen daidzein."[13] In addition, the American Cancer Society has concluded that there is no good scientific evidence to support a claim that use of cosmetics such as antiperspirants increase an individual's risk of developing breast cancer.[14]
## Estrogenic activity
Animal experiments have shown that parabens have weak estrogenic activity, acting as xenoestrogens.[15] In an in vivo study, the effect of butylparaben was determined to be approximately 100,000 times weaker than estradiol, although this effect was only observed when employing a dose level which was 25,000 times higher than is actually used to preserve products.[16] As the estrogenic effect is dose-related, it may be calculated that the estrogenic effect at normal use concentrations of butylparaben is 100,000 x 25,000, i.e. 2,500,000,000 times weaker than estradiol. In the same study it was shown that the in vivo estrogenic activity of parabens is reduced by about three orders of magnitude compared to in vitro activity probably through the rapid metabolism of the parabens to the non-estrogenic metabolites. In vivo data are accepted as being more relevant than in vitro data.
The estrogenic activity of parabens increase with the length of the alkyl group. It is believed that propylparaben is estrogenic to a certain degree as well,[17] though this is expected to be less than butylparaben by virtue of its less lipophilic nature. Since it can be concluded that the estrogenic activity of butylparaben is negligible under normal use, the same should be concluded for shorter analogs.
Some estrogens are known to drive the growth of tumors; however the estrogenic activity and mutagenic activity of estrogens are not the same with the latter dependent on free radical chemistry and not estrogen receptor activity.[18] Nonetheless, this study has elicited some concern about the use of butylparaben, and to a lesser extent other parabens as well, in cosmetics and antiperspirants. However, there is no evidence that any cosmetics containing parabens pose a health risk, because of the low doses involved and the fact that parabens are unlikely to penetrate into the tissue, remain intact, and to accumulate there.[6]
Nevertheless, the European Scientific Committee on Consumer Products (SCCP) stated in 2006 that the available data on parabens do not enable a decisive response to the question of whether propyl, butyl and isobutyl paraben can be safely used in cosmetic products at individual concentrations up to 0.4%, which is the allowed limit in the EU.[19]
# Paraben controversy
The above mentioned studies have resulted in scientific debate that in turn led to popular controversy largely propagated by mass e-mail.[20][21] The controversy has led to some concerns (both over its possible carcinogenicity,[22] as well as its estrogenic effect,[23]) being expressed over the continued use of parabens as preservatives, although the scientific community has found no correlation with cancer and mostly agree that any causation is improbable.[11][24][25][26] There has been consensus that any estrogenic effect caused by the doses of parabens received from consumer products are insignificant compared to natural estrogens and other xenoestrogens.[15]
The mainstream cosmetic industry believes that parabens, like most cosmetic ingredients, are safe based on their long term use and safety record and recent scientific studies.[26] Public interest organizations which raise awareness about cosmetic ingredients believe that further research is necessary to determine the safety of parabens (see also precautionary principle).[22] The concerns have led to a significant minority shift from their usage by natural personal care companies seeking alternatives.[27]
# External Links
- Concise Kaia House article on Parabens including recent Dabre Study
- The Most UN-wanted List (lists effects of Parabens on the body) | https://www.wikidoc.org/index.php/Paraben | |
187a28051420918cde45018636d3ad1b63ae664c | wikidoc | Paresis | Paresis
Paresis is a condition typified by partial loss of movement, or impaired movement. When used without qualifiers, it usually refers to the limbs, but it also can be used to describe the muscles of the eyes and also the stomach. Neurologists use the term paresis to describe weakness, and plegia to describe paralysis in which all movement is lost.
# Subtypes
- Monoparesis -- One leg or one arm
- Paraparesis -- Both legs or both arms
- Hemiparesis -- One arm and one leg on either side of the body
- Quadraparesis -- All four limbs
- Gastroparesis -- Impaired stomach emptying
# Associated conditions
- It frequently refers to the impairment of motion in multiple sclerosis.
- It is also used to describe a form of ophthalmoplegia.
- In the past, the term was most commonly used to refer to "General paresis," which was a symptom of untreated syphilis. However, due to improvements in treatment of syphilis, it is now rarely used in this context. | Paresis
Paresis is a condition typified by partial loss of movement, or impaired movement. When used without qualifiers, it usually refers to the limbs, but it also can be used to describe the muscles of the eyes and also the stomach. Neurologists use the term paresis to describe weakness, and plegia to describe paralysis in which all movement is lost.
# Subtypes
- Monoparesis -- One leg or one arm
- Paraparesis -- Both legs or both arms
- Hemiparesis -- One arm and one leg on either side of the body
- Quadraparesis -- All four limbs
- Gastroparesis -- Impaired stomach emptying
# Associated conditions
- It frequently refers to the impairment of motion in multiple sclerosis.
- It is also used to describe a form of ophthalmoplegia.
- In the past, the term was most commonly used to refer to "General paresis," which was a symptom of untreated syphilis. However, due to improvements in treatment of syphilis, it is now rarely used in this context. | https://www.wikidoc.org/index.php/Paresis | |
07a8288e92f44681b14dcfe70a407c891941d2fe | wikidoc | Parsley | Parsley
Parsley (Petroselinum crispum) is a bright green, biennial herb, also used as spice. It is very common in Middle Eastern, European, and American cooking. Parsley is used for its leaf in much the same way as coriander (which is also known as Chinese parsley or cilantro), although it has a milder flavor.
# Varieties
Two forms of parsley are used as herbs: curly leaf and Italian, or flat leaf (P. neapolitanum). Curly leaf parsley is often used as a garnish. Many people think flat leaf parsley has a stronger flavor, and this opinion is backed by chemical analysis which finds much higher levels of essential oil in the flat-leaved cultivars. One of the compounds of the essential oil is apiol.
The use of curly leaf parsley may be favored by some because it cannot be confused with poison hemlock, like flat leaf parsley or chervil.
## Root parsley
Another type of parsley is grown as a root vegetable, as with hamburg root parsley. This type of parsley produces much thicker roots than types cultivated for their leaves. Although little known in Britain and the United States, root parsley is very common in Central and Eastern European cuisine, where it is used in most soups or stews.
Though it looks similar to parsnip it tastes quite different. Parsnips are among the closest relatives of parsley in the umbellifer family of herbs, although the similarity of the names is a coincidence, parsnip meaning "forked turnip". It is not related to real turnips.
# Cultivation
Parsley's germination is notoriously difficult. Tales have been told concerning its lengthy germination, with some suggesting that "germination was slow because the seeds had to travel to hell and back two, three, seven, or nine times (depending on sources) before they could grow." Germination is inconsistent and may require 3-6 weeks.
Furanocoumarins in parsley's seed coat may be responsible for parsley's problematic germination. These compounds may inhibit the germination of other seeds, allowing parsley to compete with nearby plants. However, parsley itself may be affected by the furanocoumarins. Soaking parsley seeds overnight before sowing will shorten the germination period.
Parsley grows well in deep pots, which helps accommodate the long taproot. Parsley grown indoors requires at least five hours of sunlight a day.
## Companion plant
Parsley is widely used as a companion plant in gardens. Like many other umbellifers, it attracts predatory insects, including wasps and predatory flies to gardens, which then tend to protect plants nearby. They are especially useful for protecting tomato plants, for example the wasps that kill tomato hornworms also eat nectar from parsley. While parsley is biennial, not blooming until its second year, even in its first year it is reputed to help cover up the strong scent of the tomato plant, reducing pest attraction.
# Culinary uses
In parts of Europe, and particularly in West Asia, many foods are served with chopped parsley sprinkled on top. The fresh flavor of parsley goes extremely well with fish. Parsley is a key ingredient in several West Asian salads, e.g., tabbouleh which is the national dish of Lebanon. In Southern and Central Europe, parsley is part of bouquet garni, a bundle of fresh herbs used to flavor stocks, soups, and sauces. Additionally, parsley is often used as a garnish. Persillade is mixture of chopped garlic and chopped parsley. Gremolata is a mixture of parsley, garlic, and lemon zest.
# Medicinal uses
- Tea may be used as an enema. Chinese and German herbologists recommend parsley tea to help control high blood pressure, and the Cherokee Native Americans used it as a tonic to strengthen the bladder. It is also often used as an emmenagogue.
- Parsley also appears to increase diuresis by inhibiting the Na+/K+-ATPase pump in the kidney, thereby enhancing sodium and water excretion while increasing potassium reabsorption. It is also valued as an aquaretic.
- When crushed and rubbed on the skin, parsley can reduce itching in mosquito bites.
# Health risks
- Parsley should not be consumed as a drug or supplement by pregnant women. Parsley as an oil, root, leaf, or seed could lead to uterine stimulation and preterm labor.
- Parsley is high (1.70% by mass, ) in oxalic acid, a compound involved in the formation of kidney stones and nutrient deficiencies.
- Parsley oil contains furanocoumarins and psoralens which leads to extreme photosensitivity if used orally. | Parsley
Template:Nutritionalvalue
Parsley (Petroselinum crispum) is a bright green, biennial herb, also used as spice. It is very common in Middle Eastern, European, and American cooking. Parsley is used for its leaf in much the same way as coriander (which is also known as Chinese parsley or cilantro), although it has a milder flavor.
# Varieties
Two forms of parsley are used as herbs: curly leaf and Italian, or flat leaf (P. neapolitanum). Curly leaf parsley is often used as a garnish. Many people think flat leaf parsley has a stronger flavor, and this opinion is backed by chemical analysis which finds much higher levels of essential oil in the flat-leaved cultivars[citation needed]. One of the compounds of the essential oil is apiol.
The use of curly leaf parsley may be favored by some because it cannot be confused with poison hemlock, like flat leaf parsley or chervil.
## Root parsley
Another type of parsley is grown as a root vegetable, as with hamburg root parsley. This type of parsley produces much thicker roots than types cultivated for their leaves. Although little known in Britain and the United States, root parsley is very common in Central and Eastern European cuisine, where it is used in most soups or stews.
Though it looks similar to parsnip it tastes quite different. Parsnips are among the closest relatives of parsley in the umbellifer family of herbs, although the similarity of the names is a coincidence, parsnip meaning "forked turnip". It is not related to real turnips.
# Cultivation
Parsley's germination is notoriously difficult. Tales have been told concerning its lengthy germination, with some suggesting that "germination was slow because the seeds had to travel to hell and back two, three, seven, or nine times (depending on sources) before they could grow."[1] Germination is inconsistent and may require 3-6 weeks.[1]
Furanocoumarins in parsley's seed coat may be responsible for parsley's problematic germination. These compounds may inhibit the germination of other seeds, allowing parsley to compete with nearby plants. However, parsley itself may be affected by the furanocoumarins. Soaking parsley seeds overnight before sowing will shorten the germination period.[1]
Parsley grows well in deep pots, which helps accommodate the long taproot. Parsley grown indoors requires at least five hours of sunlight a day.
## Companion plant
Parsley is widely used as a companion plant in gardens. Like many other umbellifers, it attracts predatory insects, including wasps and predatory flies to gardens, which then tend to protect plants nearby. They are especially useful for protecting tomato plants, for example the wasps that kill tomato hornworms also eat nectar from parsley. While parsley is biennial, not blooming until its second year, even in its first year it is reputed to help cover up the strong scent of the tomato plant, reducing pest attraction.
# Culinary uses
In parts of Europe, and particularly in West Asia, many foods are served with chopped parsley sprinkled on top. The fresh flavor of parsley goes extremely well with fish. Parsley is a key ingredient in several West Asian salads, e.g., tabbouleh which is the national dish of Lebanon. In Southern and Central Europe, parsley is part of bouquet garni, a bundle of fresh herbs used to flavor stocks, soups, and sauces. Additionally, parsley is often used as a garnish. Persillade is mixture of chopped garlic and chopped parsley. Gremolata is a mixture of parsley, garlic, and lemon zest.
# Medicinal uses
- Tea may be used as an enema. Chinese and German herbologists recommend parsley tea to help control high blood pressure, and the Cherokee Native Americans used it as a tonic to strengthen the bladder. It is also often used as an emmenagogue.[citation needed]
- Parsley also appears to increase diuresis by inhibiting the Na+/K+-ATPase pump in the kidney, thereby enhancing sodium and water excretion while increasing potassium reabsorption.[2] It is also valued as an aquaretic.
- When crushed and rubbed on the skin, parsley can reduce itching in mosquito bites.[citation needed]
# Health risks
- Parsley should not be consumed as a drug or supplement by pregnant women. Parsley as an oil, root, leaf, or seed could lead to uterine stimulation and preterm labor.[3]
- Parsley is high (1.70% by mass, [1]) in oxalic acid, a compound involved in the formation of kidney stones and nutrient deficiencies.
- Parsley oil contains furanocoumarins and psoralens which leads to extreme photosensitivity if used orally.[citation needed] | https://www.wikidoc.org/index.php/Parsley | |
02b30e7c8e3e9b8f1eb55de458c1e9595e91b5d6 | wikidoc | Parsnip | Parsnip
The parsnip (Pastinaca sativa) is a root vegetable related to the carrot. Parsnips resemble carrots, but are paler and have a stronger flavor. Like carrots, parsnips are native to Eurasia and have been eaten there since ancient times. Zohary and Hopf note that the archeological evidence for the cultivation of the parsnip is "still rather limited", and that Greek and Roman literary sources are a major source about its early use, but warn "there are some difficulties in distinguishing between parsnip and carrot in classical writings since both vegetables seem to have been sometimes called pastinaca yet each vegetable appears to be well under cultivation in Roman times."
Until the potato arrived from the New World, its place in dishes was occupied by the parsnip. Parsnips can be boiled, roasted or used in stews, soups and casseroles. In some cases, the parsnip is boiled and the solid portions are removed from the soup or stew, leaving behind a more subtle flavor than the whole root and contributing starch to thicken the dish. Roasted parsnip is considered an essential part of Christmas dinner in some parts of the English speaking world and, in the north of England, frequently features alongside roast potatoes in the traditional Sunday Roast.
# Cultivation
Parsnips are not grown in warm climates, since frost is necessary to develop their flavor. The parsnip is a favorite with gardeners in areas with short growing seasons. Sandy, loamy soil is preferred; silty, clay, and rocky soils are unsuitable as they produce short forked roots.
Seeds can be planted in early spring, as soon as the ground can be worked. Harvesting can begin in late fall after the first frost, and continue through winter until the ground freezes over.
More than almost any other vegetable seed, parsnip seed significantly deteriorates in viability if stored for long, so it is advisable to use fresh seed each year.
In Roman times parsnips were believed to be an aphrodisiac.
In the United States, most states have wild parsnip on their list of noxious weeds or invasive species.
Parsnip is used as a food plant by the larvae of some Lepidoptera species, including the Common Swift, Garden Dart, and Ghost Moth.
# Nutritional properties
The parsnip is richer in vitamins and minerals than its close relative the carrot. It is particularly rich in potassium with 600 mg per 100 g. The parsnip is also a good source of dietary fiber. 100 g of parsnip contains 55 calories (230 kJ) energy.
Some people can get an allergic reaction from parsnip, and parsnip leaves may irritate the skin.
# Dangers connected to wild parsnips
When picking wild vegetables, it is easy to mistake poison hemlock (Conium maculatum) for parsnip, with deadly results.
Wild parsnips contain three furocoumarins (psoralen, xanthotoxin, and bergapten). These chemicals are phototoxic, mutagenic, and photo-carcinogenic. Psoralens, which are potent light-activated carcinogens not destroyed by cooking, are found in parsnip roots at concentrations of 40 ppm. Water hemlock is another plant that smells and looks like parsnips. Ivie, et al. report:
"Consumption of moderate quantities of this vegetable by man can result in the intake of appreciable amounts of psoralens. Consumption of 0.1 kg of parsnip root could expose an individual to 4 to 5 mg of total psoralens, an amount that might be expected to cause some physiological effects under certain circumstances..." | Parsnip
The parsnip (Pastinaca sativa) is a root vegetable related to the carrot. Parsnips resemble carrots, but are paler and have a stronger flavor. Like carrots, parsnips are native to Eurasia and have been eaten there since ancient times. Zohary and Hopf note that the archeological evidence for the cultivation of the parsnip is "still rather limited", and that Greek and Roman literary sources are a major source about its early use, but warn "there are some difficulties in distinguishing between parsnip and carrot in classical writings since both vegetables seem to have been sometimes called pastinaca yet each vegetable appears to be well under cultivation in Roman times."[1]
Until the potato arrived from the New World, its place in dishes was occupied by the parsnip. Parsnips can be boiled, roasted or used in stews, soups and casseroles. In some cases, the parsnip is boiled and the solid portions are removed from the soup or stew, leaving behind a more subtle flavor than the whole root and contributing starch to thicken the dish. Roasted parsnip is considered an essential part of Christmas dinner in some parts of the English speaking world and, in the north of England, frequently features alongside roast potatoes in the traditional Sunday Roast.
# Cultivation
Parsnips are not grown in warm climates, since frost is necessary to develop their flavor. The parsnip is a favorite with gardeners in areas with short growing seasons. Sandy, loamy soil is preferred; silty, clay, and rocky soils are unsuitable as they produce short forked roots.
Seeds can be planted in early spring, as soon as the ground can be worked. Harvesting can begin in late fall after the first frost, and continue through winter until the ground freezes over.
More than almost any other vegetable seed, parsnip seed significantly deteriorates in viability if stored for long, so it is advisable to use fresh seed each year.
In Roman times parsnips were believed to be an aphrodisiac.
In the United States, most states have wild parsnip on their list of noxious weeds or invasive species.
Parsnip is used as a food plant by the larvae of some Lepidoptera species, including the Common Swift, Garden Dart, and Ghost Moth.
# Nutritional properties
The parsnip is richer in vitamins and minerals than its close relative the carrot. It is particularly rich in potassium with 600 mg per 100 g. The parsnip is also a good source of dietary fiber. 100 g of parsnip contains 55 calories (230 kJ) energy.
Some people can get an allergic reaction from parsnip, and parsnip leaves may irritate the skin.
# Dangers connected to wild parsnips
Template:Cleanup
When picking wild vegetables, it is easy to mistake poison hemlock (Conium maculatum) for parsnip, with deadly results.
Wild parsnips contain three furocoumarins (psoralen, xanthotoxin, and bergapten). These chemicals are phototoxic, mutagenic, and photo-carcinogenic. Psoralens, which are potent light-activated carcinogens not destroyed by cooking, are found in parsnip roots at concentrations of 40 ppm. Water hemlock is another plant that smells and looks like parsnips. Ivie, et al. report:
"Consumption of moderate quantities of this vegetable by man can result in the intake of appreciable amounts of psoralens. Consumption of 0.1 kg of parsnip root could expose an individual to 4 to 5 mg of total psoralens, an amount that might be expected to cause some physiological effects under certain circumstances..."[2] | https://www.wikidoc.org/index.php/Parsnip | |
0efa749ea5b93c573898bab1e248242ed56e3881 | wikidoc | Patched | Patched
Patched (Ptc) is a conserved 12-pass transmembrane protein receptor that plays an obligate negative regulatory role in the Hedgehog signaling pathway in insects and vertebrates. Patched is an essential gene in embryogenesis for proper segmentation in the fly embryo, mutations in which may be embryonic lethal. Patched functions as the receptor for the Hedgehog protein and controls its spatial distribution, in part via endocytosis of bound Hedgehog protein, which is then targeted for lysosomal degradation.
# Discovery
The original mutations in the ptc gene were discovered in the fruit fly Drosophila melanogaster by 1995 Nobel Laureates Eric F. Wieschaus and Christiane Nusslein-Volhard and colleagues, and the gene was independently cloned in 1989 by Joan Hooper in the laboratory of Matthew P. Scott, and by Philip Ingham and colleagues.
# Role in hedgehog signaling
Patched is part of a negative feedback mechanism for hedgehog signaling that helps shape the spatial gradient of signaling activity across tissues. In the absence of hedgehog, low levels of patched are sufficient to suppress activity of the signal transduction pathway. When hedgehog is present, its cholesterol moiety binds to the sterol-sensing domain in patched, which then inhibits the activity of smoothened. Smoothened is a G protein-coupled receptor, most of which is stored in membrane bound vesicles internally within the cell and which increases at the cell surface when hedgehog is present. Smoothened must be present on the cell membrane in order for the Hedgehog signaling pathway to be activated. Among other genes, the transcription of the patched gene is induced by hedgehog signaling, with the accumulation of the patched protein limiting signaling through the Smoothened protein. Recent work implicates the cilium in intracellular trafficking of hedgehog signaling components in vertebrate cells.
# Role in disease
Mutated patched proteins have been implicated in a number of cancers including basal cell carcinoma, medulloblastoma, and rhabdomyosarcoma. Hereditary mutations in the human patched homolog PTCH1 cause autosomal dominant Gorlin syndrome, which consists of overgrowth and hereditary disposition to cancer including basal cell carcinoma and medulloblastoma. Mice with mutations in mouse PTCH1 similarly develop medulloblastoma. | Patched
Patched (Ptc) is a conserved 12-pass transmembrane protein receptor that plays an obligate negative regulatory role in the Hedgehog signaling pathway in insects and vertebrates. Patched is an essential gene in embryogenesis for proper segmentation in the fly embryo, mutations in which may be embryonic lethal. Patched functions as the receptor for the Hedgehog protein [1] and controls its spatial distribution, in part via endocytosis of bound Hedgehog protein, which is then targeted for lysosomal degradation.[2]
# Discovery
The original mutations in the ptc gene were discovered in the fruit fly Drosophila melanogaster by 1995 Nobel Laureates Eric F. Wieschaus and Christiane Nusslein-Volhard and colleagues, and the gene was independently cloned in 1989 by Joan Hooper in the laboratory of Matthew P. Scott, and by Philip Ingham and colleagues.
# Role in hedgehog signaling
Patched is part of a negative feedback mechanism for hedgehog signaling that helps shape the spatial gradient of signaling activity across tissues. In the absence of hedgehog, low levels of patched are sufficient to suppress activity of the signal transduction pathway. When hedgehog is present, its cholesterol moiety binds to the sterol-sensing domain in patched, which then inhibits the activity of smoothened. Smoothened is a G protein-coupled receptor, most of which is stored in membrane bound vesicles internally within the cell and which increases at the cell surface when hedgehog is present. Smoothened must be present on the cell membrane in order for the Hedgehog signaling pathway to be activated. Among other genes, the transcription of the patched gene is induced by hedgehog signaling, with the accumulation of the patched protein limiting signaling through the Smoothened protein. Recent work implicates the cilium in intracellular trafficking of hedgehog signaling components in vertebrate cells.
# Role in disease
Mutated patched proteins have been implicated in a number of cancers including basal cell carcinoma, medulloblastoma, and rhabdomyosarcoma.[3] Hereditary mutations in the human patched homolog PTCH1 cause autosomal dominant Gorlin syndrome, which consists of overgrowth and hereditary disposition to cancer including basal cell carcinoma and medulloblastoma. Mice with mutations in mouse PTCH1 similarly develop medulloblastoma. | https://www.wikidoc.org/index.php/Patched | |
079f14fe4dd45ccdab9cf6990f35b693b3dbe1c4 | wikidoc | Pendrin | Pendrin
Pendrin, is an anion exchange protein that in humans is encoded by the SLC26A4 gene (solute carrier family 26, member 4).
Pendrin was initially identified as a sodium-independent chloride-iodine exchanger with subsequent studies showing that it also accepts formate and bicarbonate as substrates. Pendrin is similar to the Band 3 transport protein found in red blood cells. Pendrin is the protein which is mutated in Pendred syndrome, which is an autosomal recessive disorder characterized by sensorineural hearing loss, goiter and a partial organification problem detectable by a positive perchlorate test.
Pendrin is responsible for mediating the electroneutral exchange of chloride (Cl−) for bicarbonate (HCO3−) across a plasma membrane in the chloride cells of freshwater fish.
By phylogenetic analysis, pendrin has been found to be a close relative of prestin present on the hair cells or organ of corti in the inner ear. Prestin is primarily an electromechanical transducer but pendrin is an ion transporter.
# Function
Pendrin is an ion exchanger found in many types of cells in the body. High levels of pendrin expression have been identified in the inner ear and thyroid. In the thyroid, pendrin mediates a component of the efflux of iodide across the apical membrane of the thyrocyte, which is critical for the formation of thyroid hormone. The exact function of pendrin in the inner ear remains unclear; however, pendrin may play a role in acid-base balance as a chloride-bicarbonate exchanger, regulate volume homeostasis through its ability to function as a chloride-formate exchanger or indirectly modulate the calcium concentration of the endolymph. Pendrin is also expressed in the kidney, and has been localized to the apical membrane of a population of intercalated cells in the cortical collecting duct where it is involved in bicarbonate secretion.
# Clinical significance
Mutations in this gene are associated with Pendred syndrome, the most common form of syndromic deafness, an autosomal-recessive disease. Pendred syndrome is characterized by thyroid goiter and enlargement of the vestibular aqueduct resulting in deafness; however, despite being expressed in the kidney, individuals with Pendred syndrome do not show any kidney-related acid-base, or volume abnormalities under basal conditions. This is probably the result of other bicarbonate or chloride transporters in the kidney compensating for any loss of pendrin function. Only under extreme situations of salt depletion or metabolic alkalosis, or with inactivation of the sodium-chloride cotransporter, are fluid and electrolyte disorders manifested in these patients. SLC26A4 is highly homologous to the SLC26A3 gene; they have similar genomic structures and this gene is located 3' of the SLC26A3 gene. The encoded protein has homology to sulfate transporters.
Another little-understood role of pendrin is in airway hyperreactivity and inflammation, as during asthma attacks and allergic reactions. Expression of pendrin in the lung increases in response to allergens and high concentrations of IL-13, and overexpression of pendrin results in airway inflammation, hyperreactivity, and increased mucus production. These symptoms could result from pendrin's effects on ion concentration in the airway surface liquid, possibly causing the liquid to be less hydrated. | Pendrin
Pendrin, is an anion exchange protein that in humans is encoded by the SLC26A4 gene (solute carrier family 26, member 4).[1][2]
Pendrin was initially identified as a sodium-independent chloride-iodine exchanger[3] with subsequent studies showing that it also accepts formate and bicarbonate as substrates.[4][5] Pendrin is similar to the Band 3 transport protein found in red blood cells. Pendrin is the protein which is mutated in Pendred syndrome, which is an autosomal recessive disorder characterized by sensorineural hearing loss, goiter and a partial organification problem detectable by a positive perchlorate test.[6]
Pendrin is responsible for mediating the electroneutral exchange of chloride (Cl−) for bicarbonate (HCO3−) across a plasma membrane in the chloride cells of freshwater fish.
By phylogenetic analysis, pendrin has been found to be a close relative of prestin present on the hair cells or organ of corti in the inner ear. Prestin is primarily an electromechanical transducer but pendrin is an ion transporter.
# Function
Pendrin is an ion exchanger found in many types of cells in the body. High levels of pendrin expression have been identified in the inner ear and thyroid. In the thyroid, pendrin mediates a component of the efflux of iodide across the apical membrane of the thyrocyte, which is critical for the formation of thyroid hormone.[7] The exact function of pendrin in the inner ear remains unclear; however, pendrin may play a role in acid-base balance as a chloride-bicarbonate exchanger, regulate volume homeostasis through its ability to function as a chloride-formate exchanger[8][9] or indirectly modulate the calcium concentration of the endolymph.[10] Pendrin is also expressed in the kidney, and has been localized to the apical membrane of a population of intercalated cells in the cortical collecting duct where it is involved in bicarbonate secretion.[11][12]
# Clinical significance
Mutations in this gene are associated with Pendred syndrome, the most common form of syndromic deafness, an autosomal-recessive disease. Pendred syndrome is characterized by thyroid goiter and enlargement of the vestibular aqueduct resulting in deafness; however, despite being expressed in the kidney, individuals with Pendred syndrome do not show any kidney-related acid-base, or volume abnormalities under basal conditions. This is probably the result of other bicarbonate or chloride transporters in the kidney compensating for any loss of pendrin function. Only under extreme situations of salt depletion or metabolic alkalosis, or with inactivation of the sodium-chloride cotransporter, are fluid and electrolyte disorders manifested in these patients.[13] SLC26A4 is highly homologous to the SLC26A3 gene; they have similar genomic structures and this gene is located 3' of the SLC26A3 gene. The encoded protein has homology to sulfate transporters.[1]
Another little-understood role of pendrin is in airway hyperreactivity and inflammation, as during asthma attacks and allergic reactions. Expression of pendrin in the lung increases in response to allergens and high concentrations of IL-13,[14][15] and overexpression of pendrin results in airway inflammation, hyperreactivity, and increased mucus production.[16][17] These symptoms could result from pendrin's effects on ion concentration in the airway surface liquid, possibly causing the liquid to be less hydrated.[18] | https://www.wikidoc.org/index.php/Pendrin | |
ad8922407489a127d1c3fd22d5f83a7f1255a4ef | wikidoc | Perilla | Perilla
Perilla is a genus of annual herb that is a member of the mint family, Lamiaceae. In mild climates the plant reseeds itself. The most common species is Perilla frutescens var. japonica or shiso which is mainly grown in India and East Asia. There are both green-leafed and purple-leafed varieties which are generally recognized as separate species by botanists. The leaves resemble stinging nettle leaves, being slightly rounder in shape. It is also widely known as the Beefsteak plant. In North America, it is increasingly commonly called by its Japanese name, shiso, in addition to being generally referred to as perilla. Its essential oils provide for a strong taste whose intensity might be compared to that of mint or fennel. It is considered rich in minerals and vitamins, has anti-inflammatory properties and is thought to help preserve and sterilize other foods. In Nepal and parts of India, it is called silam. Its seeds are ground with chili and tomatoes to make a savoury dip/side dish.
It is sometimes known as purple mint, Japanese basil, or wild coleus (although it is not a mint, basil or coleus).
# China
Perilla (Template:Zh-tsp) is traditionally used in Chinese medicine and has been shown to stimulate interferon activity and thus, the body's immune system.
# Japan
The Japanese name for perilla is Template:Nihongo. The Japanese call the green type Template:Nihongo, aoba ("green leaf"), ōba (corruption of aoba, often written as 大葉, "big leaf") or aoshiso and often eat it with sashimi (sliced raw fish) or cut into thin strips in salads, spaghetti, and meat and fish dishes. It is also used as a flavorful herb in a variety of dishes, even as a pizza topping (initially it was used in place of basil). The purple type is called Template:Nihongo and is used to make umeboshi (pickled ume), or combined with ume paste in sushi to make umeshiso maki. An inflorescence of shiso is called hojiso. Its young leaves and flower buds are used for pickling in Japan and Taiwan.
# Vietnam
Vietnamese cuisine uses a variety similar to the Japanese hojiso but with greenish bronze on the top face and purple on the opposite face. The leaves are smaller and have a much stronger fragrance than hojiso. In Vietnamese, it is called tía tô, derived from the characters (紫蘇) whose standard pronunciation in Vietnamese is tử tô. It is usually eaten as a garnish in rice vermicelli dishes called bún and a number of stews and simmered dishes.
# Indonesia
In Indonesia, Perilla is known as "Kemangi." The variety is similar to the one used in Thailand. The seeds collected from the flowers are known as "Selasih" and are often added to drinks.
# Korea
The plant's Korean name is deulkkae or tŭlkkae (]). The same word is also used when referring to its seed, which has many uses in Korean cuisine, just as the leaves (kkaennip, ]) do. The literal translations of deulkkae ("wild sesame") and kkaennip ("sesame leaf") are in spite of perilla's not being closely related to sesame, and Korean cookbooks translated to English sometimes use these translations. Cans of pickled kkaennip can be found in Korean shops all over the world, with some ground red pepper between every two leaves in the can. The leaves' essential oils provide for their strong taste. Fresh leaves have an aroma reminiscent of apples and mint and are eaten in salad dishes. The flavor is distinct from Japanese perilla, and the leaf appearance is different as well – larger, rounder, flatter, with a less serrate edge and often, a violet coloring on the reverse side. Perilla oil (deulgireum, ]) is extracted from the seeds; the cake can be used as animal food. Perilla oil has a rich taste and scent slightly resembling dark sesame oil (chamgireum, ]). Perilla seed can be cooked with meals, roasted, crushed to intensify its taste and/or mixed with sesame and salt.
# Chemistry
The essential oil extracted from the leaves of perilla by steam distillation consists of a variety of chemical compounds, which may vary depending on species. The most abundant, comprising about 50–60% of the oil, is perillaldehyde which is most responsible for the aroma and taste of perilla. Other terpenes such as limonene, caryophyllene, and farnesene are common as well.
Of the known chemotypes of perilla, PA (main component: perillaldehyd) is the only one used for culinary purposes. Other chemotypes are PK (perilla ketone), EK (elsholzia ketone), PL (perillene), PP (phenylpropanoids: myristicin, dillapiole, elemicin), C (citral) and a type rich in rosefuran.
Perilla ketone is toxic to some animals. When cattle and horses consume purple mint (of the PK chemotype) while grazing in fields in which it grows, the perilla ketone causes pulmonary edema leading to a condition sometimes called perilla mint toxicosis.
Perilla oil is obtained by pressing the seeds of perilla, which contain 35 to 45 percent oil. In parts of Asia, perilla oil is used as an edible oil that is valued more for its medicinal benefit than its flavor. Perilla oil is a very rich source of the omega-3 fatty acid alpha-linolenic acid. As a drying oil similar to tung oil or linseed oil, perilla oil has been used for paints, varnishes, linoleum, printing ink, lacquers, and for protective waterproof coatings on cloth. Perilla oil can also be used for fuel.
The oxime of perillaldehyde (perillartin) is used as an artificial sweetener in Japan as it is about 2000 times sweeter than sucrose. | Perilla
Perilla is a genus of annual herb that is a member of the mint family, Lamiaceae. In mild climates the plant reseeds itself. The most common species is Perilla frutescens var. japonica or shiso which is mainly grown in India and East Asia. There are both green-leafed and purple-leafed varieties which are generally recognized as separate species by botanists. The leaves resemble stinging nettle leaves, being slightly rounder in shape. It is also widely known as the Beefsteak plant. In North America, it is increasingly commonly called by its Japanese name, shiso, in addition to being generally referred to as perilla. Its essential oils provide for a strong taste whose intensity might be compared to that of mint or fennel. It is considered rich in minerals and vitamins, has anti-inflammatory properties and is thought to help preserve and sterilize other foods. In Nepal and parts of India, it is called silam. Its seeds are ground with chili and tomatoes to make a savoury dip/side dish.
It is sometimes known as purple mint, Japanese basil, or wild coleus (although it is not a mint, basil or coleus).
# China
Perilla (Template:Zh-tsp) is traditionally used in Chinese medicine and has been shown to stimulate interferon activity and thus, the body's immune system.
# Japan
The Japanese name for perilla is Template:Nihongo. The Japanese call the green type Template:Nihongo, aoba ("green leaf"), ōba (corruption of aoba, often written as 大葉, "big leaf") or aoshiso and often eat it with sashimi (sliced raw fish) or cut into thin strips in salads, spaghetti, and meat and fish dishes. It is also used as a flavorful herb in a variety of dishes, even as a pizza topping (initially it was used in place of basil). The purple type is called Template:Nihongo and is used to make umeboshi (pickled ume), or combined with ume paste in sushi to make umeshiso maki. An inflorescence of shiso is called hojiso. Its young leaves and flower buds are used for pickling in Japan and Taiwan.
# Vietnam
Vietnamese cuisine uses a variety similar to the Japanese hojiso but with greenish bronze on the top face and purple on the opposite face. The leaves are smaller and have a much stronger fragrance than hojiso. In Vietnamese, it is called tía tô, derived from the characters (紫蘇) whose standard pronunciation in Vietnamese is tử tô. It is usually eaten as a garnish in rice vermicelli dishes called bún and a number of stews and simmered dishes.
# Indonesia
In Indonesia, Perilla is known as "Kemangi." The variety is similar to the one used in Thailand. The seeds collected from the flowers are known as "Selasih" and are often added to drinks.
# Korea
The plant's Korean name is deulkkae or tŭlkkae ([[Hangul|들깨]]). The same word is also used when referring to its seed, which has many uses in Korean cuisine, just as the leaves (kkaennip, [[Hangul|깻잎]]) do. The literal translations of deulkkae ("wild sesame") and kkaennip ("sesame leaf") are in spite of perilla's not being closely related to sesame, and Korean cookbooks translated to English sometimes use these translations. Cans of pickled kkaennip can be found in Korean shops all over the world, with some ground red pepper between every two leaves in the can. The leaves' essential oils provide for their strong taste. Fresh leaves have an aroma reminiscent of apples and mint and are eaten in salad dishes. The flavor is distinct from Japanese perilla, and the leaf appearance is different as well – larger, rounder, flatter, with a less serrate edge and often, a violet coloring on the reverse side. Perilla oil (deulgireum, [[Hangul|들기름]]) is extracted from the seeds; the cake can be used as animal food. Perilla oil has a rich taste and scent slightly resembling dark sesame oil (chamgireum, [[Hangul|참기름]]). Perilla seed can be cooked with meals, roasted, crushed to intensify its taste and/or mixed with sesame and salt.
# Chemistry
The essential oil extracted from the leaves of perilla by steam distillation consists of a variety of chemical compounds, which may vary depending on species. The most abundant, comprising about 50–60% of the oil, is perillaldehyde which is most responsible for the aroma and taste of perilla. Other terpenes such as limonene, caryophyllene, and farnesene are common as well.
Of the known chemotypes of perilla, PA (main component: perillaldehyd) is the only one used for culinary purposes. Other chemotypes are PK (perilla ketone), EK (elsholzia ketone), PL (perillene), PP (phenylpropanoids: myristicin, dillapiole, elemicin), C (citral) and a type rich in rosefuran.
Perilla ketone is toxic to some animals. When cattle and horses consume purple mint (of the PK chemotype) while grazing in fields in which it grows, the perilla ketone causes pulmonary edema leading to a condition sometimes called perilla mint toxicosis.
Perilla oil is obtained by pressing the seeds of perilla, which contain 35 to 45 percent oil. In parts of Asia, perilla oil is used as an edible oil that is valued more for its medicinal benefit than its flavor. Perilla oil is a very rich source of the omega-3 fatty acid alpha-linolenic acid. As a drying oil similar to tung oil or linseed oil, perilla oil has been used for paints, varnishes, linoleum, printing ink, lacquers, and for protective waterproof coatings on cloth. Perilla oil can also be used for fuel.
The oxime of perillaldehyde (perillartin) is used as an artificial sweetener in Japan as it is about 2000 times sweeter than sucrose. | https://www.wikidoc.org/index.php/Perilla | |
75261d11ae0a635742def915dfa691ba00cc9987 | wikidoc | Phorate | Phorate
# Overview
Phorate is an organophosphate used as an insecticide and acaricide. At normal conditions, it is a pale yellow mobile liquid poorly soluble in water but readily soluble in organic solvents. It is relatively stable and hydrolyses only at very acidic or basic conditions. It is very toxic both for target organisms and for mammalians including human. It inhibits acetylcholinesterase and pseudocholinesterase.
Phorate is most commonly applied in granular form. It is non-biocumulative and has no residual action. But some metabolites may persist in soil. It also damages some seeds.
Phorate is absorbed readily through all ways. Its toxicity is high. Oral LD50 to rats is 1.1 – 3.2 mg/kg, to mice 3.5 – 6.5 mg/kg (technical phorate). Similar values has been found out to birds. | Phorate
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
# Overview
Phorate is an organophosphate used as an insecticide and acaricide. At normal conditions, it is a pale yellow mobile liquid poorly soluble in water but readily soluble in organic solvents. It is relatively stable and hydrolyses only at very acidic or basic conditions. It is very toxic both for target organisms and for mammalians including human. It inhibits acetylcholinesterase and pseudocholinesterase.[1]
Phorate is most commonly applied in granular form. It is non-biocumulative and has no residual action. But some metabolites may persist in soil. It also damages some seeds.[1]
Phorate is absorbed readily through all ways. Its toxicity is high. Oral LD50 to rats is 1.1 – 3.2 mg/kg, to mice 3.5 – 6.5 mg/kg (technical phorate). Similar values has been found out to birds.[1] | https://www.wikidoc.org/index.php/Phorate | |
7f36ff1e9112df745f8c75112d435732d5cb0417 | wikidoc | Pigment | Pigment
A pigment is a material that changes the color of light it reflects as the result of selective color absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which the material itself emits light.
Many materials selectively absorb certain wavelengths of light. Materials that humans have chosen and developed for use as pigments usually have special properties that make them ideal for coloring other materials. A pigment must have a high tinting strength relative to the materials it colors. It must be stable in solid form at ambient temperatures.
For industrial applications, as well as in the arts, permanence and stability are desirable properties. Pigments that are not permanent are called fugitive. Fugitive pigments fade over time, or with exposure to light, while some eventually blacken.
Pigments are used for coloring paint, ink, plastic, fabric, cosmetics, food and other materials. Most pigments used in manufacturing and the visual arts are dry colourants, usually ground into a fine powder. This powder is added to a vehicle (or matrix), a relatively neutral or colorless material that acts as a binder.
A distinction is usually made between a pigment, which is insoluble in the vehicle (resulting in a suspension), and a dye, which either is itself a liquid or is soluble in its vehicle (resulting in a solution). A colorant can be both a pigment and a dye depending on the vehicle it is used in. In some cases, a pigment can be manufactured from a dye by precipitating a soluble dye with a metallic salt. The resulting pigment is called a lake pigment.
# Physical basis
Pigments appear the colors they are because they selectively reflect and absorb certain wavelengths of light. White light is a roughly equal mixture of the entire visible spectrum of light. When this light encounters a pigment, some wavelengths are absorbed by the chemical bonds and substituents of the pigment, and others are reflected. This new reflected light spectrum creates the appearance of a color. Ultramarine reflects blue light, and absorbs other colors. Pigments, unlike fluorescent or phosphorescent substances, can only subtract wavelengths from the source light, never add new ones.
The appearance of pigments is intimately connected to the color of the source light. Sunlight has a high color temperature, and a fairly uniform spectrum, and is considered a standard for white light. Artificial light sources tend to have great peaks in some parts of their spectrum, and deep valleys in others. Viewed under these conditions, pigments will appear different colors.
Color spaces used to represent colors numerically must specify their light source. Lab color measurements, unless otherwise noted, assume that the measurement was taken under a D65 light source, or "Daylight 6500 K", which is roughly the color temperature of sunlight.
Other properties of a color, such as its saturation or lightness, may be determined by the other substances that accompany pigments. Binders and fillers added to pure pigment chemicals also have their own reflection and absorption patterns, which can affect the final spectrum. Likewise, in pigment/binder mixtures, individual rays of light may not encounter pigment molecules, and may be reflected as is. These stray rays of source light contribute to the saturation of the color. Pure pigment allows very little white light to escape, producing a highly saturated color. A small quantity of pigment mixed with a lot of white binder, however, will appear desaturated and pale, due to the high quantity of escaping white light.
# Pigment groups
- Arsenic pigments: Paris Green
- Carbon pigments: Carbon Black, Ivory Black, Vine Black, Lamp Black
- Cadmium pigments: cadmium pigments, Cadmium Green, Cadmium Red, Cadmium Yellow, Cadmium Orange
- Iron oxide pigments: Caput Mortuum, oxide red, Red Ochre, Sanguine, Venetian Red
- Prussian blue
- Chromium pigments: Chrome Green, Chrome Yellow
- Cobalt pigments: Cobalt Blue, Cerulean Blue, Cobalt Violet, Aureolin
- Lead pigments: lead white, Naples yellow, Cremnitz White, red lead
- Copper pigments: Paris Green, Verdigris, Viridian, Egyptian Blue, Han Purple
- Titanium pigments: Titanium White, Titanium Beige, Titanium yellow, Titanium Black
- Ultramarine pigments: Ultramarine, Ultramarine Green Shade, French Ultramarine
- Mercury pigments: Vermilion
- Zinc pigments: Zinc White
- Clay earth pigments (which are also iron oxides): Raw Sienna, Burnt Sienna, Raw Umber, Burnt Umber, Yellow Ochre.
- Lapis lazuli,
- Biological origins: Alizarin, Alizarin Crimson, Gamboge, Indigo, Indian Yellow, Cochineal Red, Tyrian Purple, Rose madder
- Other Organic: Pigment Red 170, Phthalo Green, Phthalo Blue, Quinacridone Magenta.
# Biological pigments
In biology, a pigment is any material in color of plant or animal cells. Many biological structures, such as skin, eyes, fur and hair contain pigments (such as melanin) in specialized cells called chromatophores. Many conditions affect the levels or nature of pigments in plant, animal, some protista, or fungus cells. For instance, Albinism is a disorder affecting the level of melanin production in animals.
Pigment color differs from structural colour in that it is the same for all viewing angles, whereas structural color is the result of selective reflection or iridescence, usually because of multilayer structures. For example, butterfly wings typically contain structural color, although many butterflies have cells that contain pigment as well.
# History
Naturally occurring pigments such as ochres and iron oxides have been used as colorants since prehistoric times. Archaeologists have uncovered evidence that early humans used paint for aesthetic purposes such as body decoration. Pigments and paint grinding equipment believed to be between 350,000 and 400,000 years old have been reported in a cave at Twin Rivers, near Lusaka, Zambia.
Before the Industrial Revolution, the range of color available for art and decorative uses was technically limited. Most of the pigments in use were earth and mineral pigments, or pigments of biological origin. Pigments from unusual sources such as botanical materials, animal waste, insects, and mollusks were harvested and traded over long distances. Some colors were costly or impossible to mix with the range of pigments that were available. Blue and purple came to be associated with royalty because of their expense.
Biological pigments were often difficult to acquire, and the details of their production were kept secret by the manufacturers. Tyrian Purple is a pigment made from the mucus of one of several species of Murex snail. Production of Tyrian Purple for use as a fabric dye began as early as 1200 BCE by the Phoenicians, and was continued by the Greeks and Romans until 1453 CE, with the fall of Constantinople. The pigment was expensive and complex to produce, and items colored with it became associated with power and wealth. Greek historian Theopompus, writing in the 4th century BCE, reported that "purple for dyes fetched its weight in silver at Colophon ."
Mineral pigments were also traded over long distances. The only way to achieve a deep rich blue was by using a semi-precious stone, lapis lazuli, to produce a pigment known as ultramarine, and the best sources of lapis were remote. Flemish painter Jan Van Eyck, working in the 15th century, did not ordinarily include blue in his paintings. To have one's portrait commissioned and painted with ultramarine blue was considered a great luxury. If a patron wanted blue, they were forced to pay extra. When Van Eyck used lapis, he never blended it with other colors. Instead he applied it in pure form, almost as a decorative glaze. The prohibitive price of lapis lazuli forced artists to seek less expensive replacement pigments, both mineral (azurite, smalt) and biological (indigo).
Spain's conquest of a New World empire in the 16th century introduced new pigments and colors to peoples on both sides of the Atlantic. Carmine, a dye and pigment derived from a parasitic insect found in Central and South America, attained great status and value in Europe. Produced from harvested, dried, and crushed cochineal insects, carmine could be used in fabric dye, body paint, or in its solid lake form, almost any kind of paint or cosmetic.
Natives of Peru had been producing cochineal dyes for textiles since at least 700 CE, but Europeans had never seen the color before. When the Spanish invaded the Aztec empire in what is now Mexico, they were quick to exploit the color for new trade opportunities. Carmine became the region's second most valuable export next to silver. Pigments produced from the cochineal insect gave the Catholic cardinals their vibrant robes and the English "Redcoats" their distinctive uniforms. The true source of the pigment, an insect, was kept secret until the 18th century, when biologists discovered the source.
While Carmine was popular in Europe, blue remained an exclusive color, associated with wealth and status. The 17th century Dutch master Johannes Vermeer often made lavish use of lapis lazuli, along with Carmine and Indian Yellow, in his vibrant paintings.
## Development of synthetic pigments
The earliest known pigments were natural minerals. Natural iron oxides give a range of colors and are found in many Paleolithic and Neolithic cave paintings. Two examples include Red Ochre, anhydrous Fe2O3, and the hydrated Yellow Ochre (Fe2O3.H2O). Charcoal, or carbon black, has also been used as a black pigment since prehistoric times.
Two of the first synthetic pigments were white lead (basic lead carbonate, (PbCO3)2Pb(OH)2) and blue frit (Egyptian Blue). White lead is made by combining lead with vinegar (acetic acid, CH3COOH) in the presence of CO2. Blue frit is calcium copper silicate and was made from glass colored with a copper ore, such as malachite. These pigments were used as early as the second millennium BCE.
The Industrial and Scientific Revolutions brought a huge expansion in the range of synthetic pigments, pigments that are manufactured or refined from naturally occurring materials, available both for manufacturing and artistic expression. Because of the expense of Lapis Lazuli, much effort went into finding a less costly blue pigment.
Prussian Blue was the first modern synthetic pigment, discovered by accident in 1704. By the early 19th century, synthetic and metallic blue pigments had been added to the range of blues, including French ultramarine, a synthetic form of lapis lazuli, and the various forms of Cobalt and Cerulean Blue. In the early 20th century, organic chemistry added Phthalo Blue, a synthetic, organic pigment with overwhelming tinting power.
Discoveries in color science created new industries and drove changes in fashion and taste. The discovery in 1856 of mauveine, the first aniline dye, was a forerunner for the development of hundreds of synthetic dyes and pigments. Mauveine was discovered by an 18-year-old chemist named William Henry Perkin, who went on to exploit his discovery in industry and become wealthy. His success attracted a generation of followers, as young scientists went into organic chemistry to pursue riches. Within a few years, chemists had synthesized a substitute for madder in the production of Alizarin Crimson. By the closing decades of the 19th century, textiles, paints, and other commodities in colors such as red, crimson, blue, and purple had become affordable.
Development of chemical pigments and dyes helped bring new industrial prosperity to Germany and other countries in northern Europe, but it brought dissolution and decline elsewhere. In Spain's former New World empire, the production of cochineal colors employed thousands of low-paid workers. The Spanish monopoly on cochineal production had been worth a fortune until the early 1800s, when the Mexican War of Independence and other market changes disrupted production. Organic chemistry delivered the final blow for the cochineal color industry. When chemists created inexpensive substitutes for carmine, an industry and a way of life went into steep decline.
## New sources for historic pigments
Before the Industrial Revolution, many pigments were known by the location where they were produced. Pigments based on minerals and clays often bore the name of the city or region where they were mined. Raw Sienna and Burnt Sienna came from Siena, Italy, while Raw Umber and Burnt Umber came from Umbria. These pigments were among the easiest to synthesize, and chemists created modern colors based on the originals that were more consistent than colors mined from the original ore bodies. But the place names remained.
Historically and culturally, many famous natural pigments have been replaced with synthetic pigments, while retaining historic names. In some cases the original color name has shifted in meaning, as a historic name has been applied to a popular modern color. By convention, a contemporary mixture of pigments that replaces a historical pigment is indicated by calling the resulting color a hue, but manufacturers are not always careful in maintaining this distinction. The following examples illustrate the shifting nature of historic pigment names:
- Indian Yellow was once produced by collecting the urine of cattle that had been fed only mango leaves. Dutch and Flemish painters of the 17th and 18th centuries favored it for its luminescent qualities, and often used it to represent sunlight. In Girl with a Pearl Earring, Vermeer's patron remarks that Vermeer used "cow piss" to paint his wife. Since mango leaves are nutritionally inadequate for cattle, the practice of harvesting Indian Yellow was eventually declared to be inhumane. Modern Indian Yellow Hue is a mixture of synthetic pigments.
- Ultramarine, originally the semi-precious stone lapis lazuli, has been replaced by an inexpensive modern synthetic pigment manufactured from aluminium silicate with sulfur impurities. At the same time, Royal Blue, another name once given to tints produced from lapis lazuli, has evolved to signify a much lighter and brighter color, and is usually mixed from Phthalo Blue and titanium dioxide, or from inexpensive synthetic blue dyes. Since synthetic ultramarine is chemically identical with lapis lazuli, the "hue" designation is not used. French Blue, yet another historic name for ultramarine, was adopted by the textile and apparel industry as a color name in the 1990s, and was applied to a shade of blue that has nothing in common with the historic pigment French ultramarine.
- Vermilion, a toxic mercury compound favored for its deep red-orange color by old master painters such as Titian, has been replaced by convenience mixtures of synthetic, inorganic pigments. Although genuine Vermilion paint can still be purchased for fine arts and art conservation applications, few manufacturers make it, because of legal liability issues. Few artists buy it, because it has been superseded by modern pigments that are both less expensive and less toxic, as well as less reactive with other pigments. As a result, genuine Vermilion is almost unavailable. Modern vermilion colors are properly designated as Vermilion Hue to distinguish them from genuine Vermilion.
# Manufacturing and industrial standards
Before the development of synthetic pigments, and the refinement of techniques for extracting mineral pigments, batches of color were often inconsistent. With the development of a modern color industry, manufacturers and professionals have cooperated to create international standards for identifying, producing, measuring, and testing colors.
First published in 1905, the Munsell Color System became the foundation for a series of color models, providing objective methods for the measurement of color. The Munsell system describes a color in three dimensions, hue, value (lightness), and chroma (color purity), where chroma is the difference from gray at a given hue and value.
By the middle years of the 20th century, standardized methods for pigment chemistry were available, part of an international movement to create such standards in industry. The International Organization for Standardization (ISO) develops technical standards for the manufacture of pigments and dyes. ISO standards define various industrial and chemical properties, and how to test for them. The principal ISO standards that relate to all pigments are as follows:
- ISO-787 General methods of test for pigments and extenders
- ISO-8780 Methods of dispersion for assessment of dispersion characteristics
Other ISO standards pertain to particular classes or categories of pigments, based on their chemical composition, such as ultramarine pigments, titanium dioxide, iron oxide pigments, and so forth.
Many manufacturers of paints, inks, textiles, plastics, and colors have voluntarily adopted the Colour Index International (CII) as a standard for identifying the pigments that they use in manufacturing particular colors. First published in 1925, and now published jointly on the web by the Society of Dyers and Colourists (United Kingdom) and the American Association of Textile Chemists and Colorists (USA), this index is recognized internationally as the authoritative reference on colorants. It encompasses more than 27,000 products under more than 13,000 generic color index names.
In the CII schema, each pigment has a generic index number that identifies it chemically, regardless of proprietary and historic names. For example, Phthalo Blue has been known by a variety of generic and proprietary names since its discovery in the 1930s. In much of Europe, phthalocyanine blue is better known as Helio Blue, or by a proprietary name such as Winsor Blue. An American paint manufacturer, Grumbacher, registered an alternate spelling (Thalo Blue) as a trademark. Colour Index International resolves all these conflicting historic, generic, and proprietary names so that manufacturers and consumers can identify the pigment (or dye) used in a particular color product. In the CII, all Phthalo Blue pigments are designated by a generic colour index number as either PB15 or PB36, short for pigment blue 15 and pigment blue 16. (The two forms of Phthalo Blue, PB15 and PB16, reflect slight variations in molecular structure that produce a slightly more greenish or reddish blue.)
# Scientific and technical issues
Selection of a pigment for a particular application is determined by cost, and by the physical properties and attributes of the pigment itself. For example, a pigment that is used to color glass must have very high heat stability in order to survive the manufacturing process; but, suspended in the glass vehicle, its resistance to alkali or acidic materials is not an issue. In artistic paint, heat stability is less important, while lightfastness and toxicity are greater concerns.
The following are some of the attributes of pigments that determine their suitability for particular manufacturing processes and applications:
- Lightfastness
- Heat stability
- Toxicity
- Tinting strength
- Staining
- Dispersion
- Opacity or transparency
- Resistance to alkalis and acids
- Reactions and interactions between pigments
# Swatches
Pure pigments reflect light in a very specific way that cannot be precisely duplicated by the discrete light emitters in a computer display. However, by making careful measurements of pigments, close approximations can be made. The Munsell Color System provides a good conceptual explanation of what is missing. Munsell devised a system that provides an objective measure of color in three dimensions: hue, value (or lightness), and chroma. Computer displays in general are unable to show the true chroma of many pigments, but the hue and lightness can be reproduced with relative accuracy. However, when the gamma of a computer display deviates from the reference value, the hue is also systematically biased.
The following approximations assume a display device at gamma 2.2, using the sRGB color space. The further a display device deviates from these standards, the less accurate these swatches will be. Swatches are based on the average measurements of several lots of single-pigment watercolor paints, converted from Lab color space to sRGB color space for viewing on a computer display. Different brands and lots of the same pigment may vary in color. Furthermore, pigments have inherently complex reflectance spectra that will render their color appearance greatly different depending on the spectrum of the source illumination; a property called metamerism. Averaged measurements of pigment samples will only yield approximations of their true appearance under a specific source of illumination. Computer display systems use a technique called chromatic adaptation transforms to emulate the correlated color temperature of illumination sources, and cannot perfectly reproduce the intricate spectral combinations originally seen. In many cases the perceived color of a pigment falls outside of the gamut of computer displays and a method called gamut mapping is used to approximate the true appearance. Gamut mapping trades off any one of Lightness, Hue or Saturation accuracy to render the color on screen, depending on the priority chosen in the conversion's ICC rendering intent.
# Notes
- ↑ Kassinger, Ruth G. (2003-02-06). Dyes: From Sea Snails to Synthetics. 21st century. ISBN 0-7613-2112-8..mw-parser-output cite.citation{font-style:inherit}.mw-parser-output q{quotes:"\"""\"""'""'"}.mw-parser-output code.cs1-code{color:inherit;background:inherit;border:inherit;padding:inherit}.mw-parser-output .cs1-lock-free a{background:url("")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-limited a,.mw-parser-output .cs1-lock-registration a{background:url("")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-subscription a{background:url("")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration{color:#555}.mw-parser-output .cs1-subscription span,.mw-parser-output .cs1-registration span{border-bottom:1px dotted;cursor:help}.mw-parser-output .cs1-hidden-error{display:none;font-size:100%}.mw-parser-output .cs1-visible-error{display:none;font-size:100%}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration,.mw-parser-output .cs1-format{font-size:95%}.mw-parser-output .cs1-kern-left,.mw-parser-output .cs1-kern-wl-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right,.mw-parser-output .cs1-kern-wl-right{padding-right:0.2em}
- ↑ Theopompus, cited by Athenaeus in c. 200 BCE; according to Gulick, Charles Barton. (1941). Athenaeus, The Deipnosophists. Cambridge: Harvard University Press.
- ↑ Michel Pastoureau (2001-10-01). Blue: The History of a Color. Princeton University Press. ISBN 0-691-09050-5.
- ↑ Jan Wouters, Noemi Rosario-Chirinos (1992). "Dye Analysis of Pre-Columbian Peruvian Textiles with High-Performance Liquid Chromatography and Diode-Array Detection". Journal of the American Institute for Conservation. 31 (2): 237–255.
- ↑ Amy Butler Greenfield (2005-04-26). A Perfect Red: Empire, Espionage, and the Quest for the Color of Desire. HarperCollins. ISBN 0-06-052275-5.
- ↑ "Pigments Through the Ages" (html). WebExhibits.org. Retrieved 2007-10-18.
- ↑ "Pigments Through the Ages" (html). WebExhibits.org. Retrieved 2007-10-18.
- ↑ Rossotti, Hazel (1983). Colour: Why the World Isn't Grey. Princeton, NJ: Princeton University Press. ISBN 0-691-02386-7.
- ↑ Simon Garfield (2000). Mauve: How One Man Invented a Color That Changed the World. Faber and Faber. ISBN 0-393-02005-3.
- ↑ Octavio Hernández. "Cochineal". Mexico Desconocido Online. Unknown parameter |accessyear= ignored (|access-date= suggested) (help); Unknown parameter |accessmonthday= ignored (help)
- ↑ Jeff Behan. "The bug that changed history". Unknown parameter |accessyear= ignored (|access-date= suggested) (help); Unknown parameter |accessmonthday= ignored (help)
- ↑ "Dictionary of Color Terms". Retrieved 2006-07-20.
- ↑ Chromatic Adaptation | Pigment
Template:Editor help
A pigment is a material that changes the color of light it reflects as the result of selective color absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which the material itself emits light.
Many materials selectively absorb certain wavelengths of light. Materials that humans have chosen and developed for use as pigments usually have special properties that make them ideal for coloring other materials. A pigment must have a high tinting strength relative to the materials it colors. It must be stable in solid form at ambient temperatures.
For industrial applications, as well as in the arts, permanence and stability are desirable properties. Pigments that are not permanent are called fugitive. Fugitive pigments fade over time, or with exposure to light, while some eventually blacken.
Pigments are used for coloring paint, ink, plastic, fabric, cosmetics, food and other materials. Most pigments used in manufacturing and the visual arts are dry colourants, usually ground into a fine powder. This powder is added to a vehicle (or matrix), a relatively neutral or colorless material that acts as a binder.
A distinction is usually made between a pigment, which is insoluble in the vehicle (resulting in a suspension), and a dye, which either is itself a liquid or is soluble in its vehicle (resulting in a solution). A colorant can be both a pigment and a dye depending on the vehicle it is used in. In some cases, a pigment can be manufactured from a dye by precipitating a soluble dye with a metallic salt. The resulting pigment is called a lake pigment.
# Physical basis
Pigments appear the colors they are because they selectively reflect and absorb certain wavelengths of light. White light is a roughly equal mixture of the entire visible spectrum of light. When this light encounters a pigment, some wavelengths are absorbed by the chemical bonds and substituents of the pigment, and others are reflected. This new reflected light spectrum creates the appearance of a color. Ultramarine reflects blue light, and absorbs other colors. Pigments, unlike fluorescent or phosphorescent substances, can only subtract wavelengths from the source light, never add new ones.
The appearance of pigments is intimately connected to the color of the source light. Sunlight has a high color temperature, and a fairly uniform spectrum, and is considered a standard for white light. Artificial light sources tend to have great peaks in some parts of their spectrum, and deep valleys in others. Viewed under these conditions, pigments will appear different colors.
Color spaces used to represent colors numerically must specify their light source. Lab color measurements, unless otherwise noted, assume that the measurement was taken under a D65 light source, or "Daylight 6500 K", which is roughly the color temperature of sunlight.
Other properties of a color, such as its saturation or lightness, may be determined by the other substances that accompany pigments. Binders and fillers added to pure pigment chemicals also have their own reflection and absorption patterns, which can affect the final spectrum. Likewise, in pigment/binder mixtures, individual rays of light may not encounter pigment molecules, and may be reflected as is. These stray rays of source light contribute to the saturation of the color. Pure pigment allows very little white light to escape, producing a highly saturated color. A small quantity of pigment mixed with a lot of white binder, however, will appear desaturated and pale, due to the high quantity of escaping white light.
# Pigment groups
- Arsenic pigments: Paris Green
- Carbon pigments: Carbon Black, Ivory Black, Vine Black, Lamp Black
- Cadmium pigments: cadmium pigments, Cadmium Green, Cadmium Red, Cadmium Yellow, Cadmium Orange
- Iron oxide pigments: Caput Mortuum, oxide red, Red Ochre, Sanguine, Venetian Red
- Prussian blue
- Chromium pigments: Chrome Green, Chrome Yellow
- Cobalt pigments: Cobalt Blue, Cerulean Blue, Cobalt Violet, Aureolin
- Lead pigments: lead white, Naples yellow, Cremnitz White, red lead
- Copper pigments: Paris Green, Verdigris, Viridian, Egyptian Blue, Han Purple
- Titanium pigments: Titanium White, Titanium Beige, Titanium yellow, Titanium Black
- Ultramarine pigments: Ultramarine, Ultramarine Green Shade, French Ultramarine
- Mercury pigments: Vermilion
- Zinc pigments: Zinc White
- Clay earth pigments (which are also iron oxides): Raw Sienna, Burnt Sienna, Raw Umber, Burnt Umber, Yellow Ochre.
- Lapis lazuli,
- Biological origins: Alizarin, Alizarin Crimson, Gamboge, Indigo, Indian Yellow, Cochineal Red, Tyrian Purple, Rose madder
- Other Organic: Pigment Red 170, Phthalo Green, Phthalo Blue, Quinacridone Magenta.
# Biological pigments
In biology, a pigment is any material in color of plant or animal cells. Many biological structures, such as skin, eyes, fur and hair contain pigments (such as melanin) in specialized cells called chromatophores. Many conditions affect the levels or nature of pigments in plant, animal, some protista, or fungus cells. For instance, Albinism is a disorder affecting the level of melanin production in animals.
Pigment color differs from structural colour in that it is the same for all viewing angles, whereas structural color is the result of selective reflection or iridescence, usually because of multilayer structures. For example, butterfly wings typically contain structural color, although many butterflies have cells that contain pigment as well.
# History
Naturally occurring pigments such as ochres and iron oxides have been used as colorants since prehistoric times. Archaeologists have uncovered evidence that early humans used paint for aesthetic purposes such as body decoration. Pigments and paint grinding equipment believed to be between 350,000 and 400,000 years old have been reported in a cave at Twin Rivers, near Lusaka, Zambia.
Before the Industrial Revolution, the range of color available for art and decorative uses was technically limited. Most of the pigments in use were earth and mineral pigments, or pigments of biological origin. Pigments from unusual sources such as botanical materials, animal waste, insects, and mollusks were harvested and traded over long distances. Some colors were costly or impossible to mix with the range of pigments that were available. Blue and purple came to be associated with royalty because of their expense.
Biological pigments were often difficult to acquire, and the details of their production were kept secret by the manufacturers. Tyrian Purple is a pigment made from the mucus of one of several species of Murex snail. Production of Tyrian Purple for use as a fabric dye began as early as 1200 BCE by the Phoenicians, and was continued by the Greeks and Romans until 1453 CE, with the fall of Constantinople.[1] The pigment was expensive and complex to produce, and items colored with it became associated with power and wealth. Greek historian Theopompus, writing in the 4th century BCE, reported that "purple for dyes fetched its weight in silver at Colophon [in Asia Minor]."[2]
Mineral pigments were also traded over long distances. The only way to achieve a deep rich blue was by using a semi-precious stone, lapis lazuli, to produce a pigment known as ultramarine, and the best sources of lapis were remote. Flemish painter Jan Van Eyck, working in the 15th century, did not ordinarily include blue in his paintings. To have one's portrait commissioned and painted with ultramarine blue was considered a great luxury. If a patron wanted blue, they were forced to pay extra. When Van Eyck used lapis, he never blended it with other colors. Instead he applied it in pure form, almost as a decorative glaze.[3] The prohibitive price of lapis lazuli forced artists to seek less expensive replacement pigments, both mineral (azurite, smalt) and biological (indigo).
Spain's conquest of a New World empire in the 16th century introduced new pigments and colors to peoples on both sides of the Atlantic. Carmine, a dye and pigment derived from a parasitic insect found in Central and South America, attained great status and value in Europe. Produced from harvested, dried, and crushed cochineal insects, carmine could be used in fabric dye, body paint, or in its solid lake form, almost any kind of paint or cosmetic.
Natives of Peru had been producing cochineal dyes for textiles since at least 700 CE,[4] but Europeans had never seen the color before. When the Spanish invaded the Aztec empire in what is now Mexico, they were quick to exploit the color for new trade opportunities. Carmine became the region's second most valuable export next to silver. Pigments produced from the cochineal insect gave the Catholic cardinals their vibrant robes and the English "Redcoats" their distinctive uniforms. The true source of the pigment, an insect, was kept secret until the 18th century, when biologists discovered the source.[5]
While Carmine was popular in Europe, blue remained an exclusive color, associated with wealth and status. The 17th century Dutch master Johannes Vermeer often made lavish use of lapis lazuli, along with Carmine and Indian Yellow, in his vibrant paintings.
## Development of synthetic pigments
The earliest known pigments were natural minerals. Natural iron oxides give a range of colors and are found in many Paleolithic and Neolithic cave paintings. Two examples include Red Ochre, anhydrous Fe2O3, and the hydrated Yellow Ochre (Fe2O3.H2O).[6] Charcoal, or carbon black, has also been used as a black pigment since prehistoric times.[7]
Two of the first synthetic pigments were white lead (basic lead carbonate, (PbCO3)2Pb(OH)2) and blue frit (Egyptian Blue). White lead is made by combining lead with vinegar (acetic acid, CH3COOH) in the presence of CO2. Blue frit is calcium copper silicate and was made from glass colored with a copper ore, such as malachite. These pigments were used as early as the second millennium BCE.[8]
The Industrial and Scientific Revolutions brought a huge expansion in the range of synthetic pigments, pigments that are manufactured or refined from naturally occurring materials, available both for manufacturing and artistic expression. Because of the expense of Lapis Lazuli, much effort went into finding a less costly blue pigment.
Prussian Blue was the first modern synthetic pigment, discovered by accident in 1704. By the early 19th century, synthetic and metallic blue pigments had been added to the range of blues, including French ultramarine, a synthetic form of lapis lazuli, and the various forms of Cobalt and Cerulean Blue. In the early 20th century, organic chemistry added Phthalo Blue, a synthetic, organic pigment with overwhelming tinting power.
Discoveries in color science created new industries and drove changes in fashion and taste. The discovery in 1856 of mauveine, the first aniline dye, was a forerunner for the development of hundreds of synthetic dyes and pigments. Mauveine was discovered by an 18-year-old chemist named William Henry Perkin, who went on to exploit his discovery in industry and become wealthy. His success attracted a generation of followers, as young scientists went into organic chemistry to pursue riches. Within a few years, chemists had synthesized a substitute for madder in the production of Alizarin Crimson. By the closing decades of the 19th century, textiles, paints, and other commodities in colors such as red, crimson, blue, and purple had become affordable.[9]
Development of chemical pigments and dyes helped bring new industrial prosperity to Germany and other countries in northern Europe, but it brought dissolution and decline elsewhere. In Spain's former New World empire, the production of cochineal colors employed thousands of low-paid workers. The Spanish monopoly on cochineal production had been worth a fortune until the early 1800s, when the Mexican War of Independence and other market changes disrupted production.[10] Organic chemistry delivered the final blow for the cochineal color industry. When chemists created inexpensive substitutes for carmine, an industry and a way of life went into steep decline.[11]
## New sources for historic pigments
Before the Industrial Revolution, many pigments were known by the location where they were produced. Pigments based on minerals and clays often bore the name of the city or region where they were mined. Raw Sienna and Burnt Sienna came from Siena, Italy, while Raw Umber and Burnt Umber came from Umbria. These pigments were among the easiest to synthesize, and chemists created modern colors based on the originals that were more consistent than colors mined from the original ore bodies. But the place names remained.
Historically and culturally, many famous natural pigments have been replaced with synthetic pigments, while retaining historic names. In some cases the original color name has shifted in meaning, as a historic name has been applied to a popular modern color. By convention, a contemporary mixture of pigments that replaces a historical pigment is indicated by calling the resulting color a hue, but manufacturers are not always careful in maintaining this distinction. The following examples illustrate the shifting nature of historic pigment names:
- Indian Yellow was once produced by collecting the urine of cattle that had been fed only mango leaves. Dutch and Flemish painters of the 17th and 18th centuries favored it for its luminescent qualities, and often used it to represent sunlight. In Girl with a Pearl Earring, Vermeer's patron remarks that Vermeer used "cow piss" to paint his wife. Since mango leaves are nutritionally inadequate for cattle, the practice of harvesting Indian Yellow was eventually declared to be inhumane. Modern Indian Yellow Hue is a mixture of synthetic pigments.
- Ultramarine, originally the semi-precious stone lapis lazuli, has been replaced by an inexpensive modern synthetic pigment manufactured from aluminium silicate with sulfur impurities. At the same time, Royal Blue, another name once given to tints produced from lapis lazuli, has evolved to signify a much lighter and brighter color, and is usually mixed from Phthalo Blue and titanium dioxide, or from inexpensive synthetic blue dyes. Since synthetic ultramarine is chemically identical with lapis lazuli, the "hue" designation is not used. French Blue, yet another historic name for ultramarine, was adopted by the textile and apparel industry as a color name in the 1990s, and was applied to a shade of blue that has nothing in common with the historic pigment French ultramarine.
- Vermilion, a toxic mercury compound favored for its deep red-orange color by old master painters such as Titian, has been replaced by convenience mixtures of synthetic, inorganic pigments. Although genuine Vermilion paint can still be purchased for fine arts and art conservation applications, few manufacturers make it, because of legal liability issues. Few artists buy it, because it has been superseded by modern pigments that are both less expensive and less toxic, as well as less reactive with other pigments. As a result, genuine Vermilion is almost unavailable. Modern vermilion colors are properly designated as Vermilion Hue to distinguish them from genuine Vermilion.
# Manufacturing and industrial standards
Before the development of synthetic pigments, and the refinement of techniques for extracting mineral pigments, batches of color were often inconsistent. With the development of a modern color industry, manufacturers and professionals have cooperated to create international standards for identifying, producing, measuring, and testing colors.
First published in 1905, the Munsell Color System became the foundation for a series of color models, providing objective methods for the measurement of color. The Munsell system describes a color in three dimensions, hue, value (lightness), and chroma (color purity), where chroma is the difference from gray at a given hue and value.
By the middle years of the 20th century, standardized methods for pigment chemistry were available, part of an international movement to create such standards in industry. The International Organization for Standardization (ISO) develops technical standards for the manufacture of pigments and dyes. ISO standards define various industrial and chemical properties, and how to test for them. The principal ISO standards that relate to all pigments are as follows:
- ISO-787 General methods of test for pigments and extenders
- ISO-8780 Methods of dispersion for assessment of dispersion characteristics
Other ISO standards pertain to particular classes or categories of pigments, based on their chemical composition, such as ultramarine pigments, titanium dioxide, iron oxide pigments, and so forth.
Many manufacturers of paints, inks, textiles, plastics, and colors have voluntarily adopted the Colour Index International (CII) as a standard for identifying the pigments that they use in manufacturing particular colors. First published in 1925, and now published jointly on the web by the Society of Dyers and Colourists (United Kingdom) and the American Association of Textile Chemists and Colorists (USA), this index is recognized internationally as the authoritative reference on colorants. It encompasses more than 27,000 products under more than 13,000 generic color index names.
In the CII schema, each pigment has a generic index number that identifies it chemically, regardless of proprietary and historic names. For example, Phthalo Blue has been known by a variety of generic and proprietary names since its discovery in the 1930s. In much of Europe, phthalocyanine blue is better known as Helio Blue, or by a proprietary name such as Winsor Blue. An American paint manufacturer, Grumbacher, registered an alternate spelling (Thalo Blue) as a trademark. Colour Index International resolves all these conflicting historic, generic, and proprietary names so that manufacturers and consumers can identify the pigment (or dye) used in a particular color product. In the CII, all Phthalo Blue pigments are designated by a generic colour index number as either PB15 or PB36, short for pigment blue 15 and pigment blue 16. (The two forms of Phthalo Blue, PB15 and PB16, reflect slight variations in molecular structure that produce a slightly more greenish or reddish blue.)
# Scientific and technical issues
Selection of a pigment for a particular application is determined by cost, and by the physical properties and attributes of the pigment itself. For example, a pigment that is used to color glass must have very high heat stability in order to survive the manufacturing process; but, suspended in the glass vehicle, its resistance to alkali or acidic materials is not an issue. In artistic paint, heat stability is less important, while lightfastness and toxicity are greater concerns.
The following are some of the attributes of pigments that determine their suitability for particular manufacturing processes and applications:
- Lightfastness
- Heat stability
- Toxicity
- Tinting strength
- Staining
- Dispersion
- Opacity or transparency
- Resistance to alkalis and acids
- Reactions and interactions between pigments
# Swatches
Pure pigments reflect light in a very specific way that cannot be precisely duplicated by the discrete light emitters in a computer display. However, by making careful measurements of pigments, close approximations can be made. The Munsell Color System provides a good conceptual explanation of what is missing. Munsell devised a system that provides an objective measure of color in three dimensions: hue, value (or lightness), and chroma. Computer displays in general are unable to show the true chroma of many pigments, but the hue and lightness can be reproduced with relative accuracy. However, when the gamma of a computer display deviates from the reference value, the hue is also systematically biased.
The following approximations assume a display device at gamma 2.2, using the sRGB color space. The further a display device deviates from these standards, the less accurate these swatches will be.[12] Swatches are based on the average measurements of several lots of single-pigment watercolor paints, converted from Lab color space to sRGB color space for viewing on a computer display. Different brands and lots of the same pigment may vary in color. Furthermore, pigments have inherently complex reflectance spectra that will render their color appearance greatly different depending on the spectrum of the source illumination; a property called metamerism. Averaged measurements of pigment samples will only yield approximations of their true appearance under a specific source of illumination. Computer display systems use a technique called chromatic adaptation transforms[13] to emulate the correlated color temperature of illumination sources, and cannot perfectly reproduce the intricate spectral combinations originally seen. In many cases the perceived color of a pigment falls outside of the gamut of computer displays and a method called gamut mapping is used to approximate the true appearance. Gamut mapping trades off any one of Lightness, Hue or Saturation accuracy to render the color on screen, depending on the priority chosen in the conversion's ICC rendering intent.
# Notes
- ↑ Kassinger, Ruth G. (2003-02-06). Dyes: From Sea Snails to Synthetics. 21st century. ISBN 0-7613-2112-8..mw-parser-output cite.citation{font-style:inherit}.mw-parser-output q{quotes:"\"""\"""'""'"}.mw-parser-output code.cs1-code{color:inherit;background:inherit;border:inherit;padding:inherit}.mw-parser-output .cs1-lock-free a{background:url("https://upload.wikimedia.org/wikipedia/commons/thumb/6/65/Lock-green.svg/9px-Lock-green.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-limited a,.mw-parser-output .cs1-lock-registration a{background:url("https://upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Lock-gray-alt-2.svg/9px-Lock-gray-alt-2.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-subscription a{background:url("https://upload.wikimedia.org/wikipedia/commons/thumb/a/aa/Lock-red-alt-2.svg/9px-Lock-red-alt-2.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration{color:#555}.mw-parser-output .cs1-subscription span,.mw-parser-output .cs1-registration span{border-bottom:1px dotted;cursor:help}.mw-parser-output .cs1-hidden-error{display:none;font-size:100%}.mw-parser-output .cs1-visible-error{display:none;font-size:100%}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration,.mw-parser-output .cs1-format{font-size:95%}.mw-parser-output .cs1-kern-left,.mw-parser-output .cs1-kern-wl-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right,.mw-parser-output .cs1-kern-wl-right{padding-right:0.2em}
- ↑ Theopompus, cited by Athenaeus [12.526] in c. 200 BCE; according to Gulick, Charles Barton. (1941). Athenaeus, The Deipnosophists. Cambridge: Harvard University Press.
- ↑ Michel Pastoureau (2001-10-01). Blue: The History of a Color. Princeton University Press. ISBN 0-691-09050-5.
- ↑ Jan Wouters, Noemi Rosario-Chirinos (1992). "Dye Analysis of Pre-Columbian Peruvian Textiles with High-Performance Liquid Chromatography and Diode-Array Detection". Journal of the American Institute for Conservation. 31 (2): 237–255.
- ↑ Amy Butler Greenfield (2005-04-26). A Perfect Red: Empire, Espionage, and the Quest for the Color of Desire. HarperCollins. ISBN 0-06-052275-5.
- ↑ "Pigments Through the Ages" (html). WebExhibits.org. Retrieved 2007-10-18.
- ↑ "Pigments Through the Ages" (html). WebExhibits.org. Retrieved 2007-10-18.
- ↑ Rossotti, Hazel (1983). Colour: Why the World Isn't Grey. Princeton, NJ: Princeton University Press. ISBN 0-691-02386-7.
- ↑ Simon Garfield (2000). Mauve: How One Man Invented a Color That Changed the World. Faber and Faber. ISBN 0-393-02005-3.
- ↑ Octavio Hernández. "Cochineal". Mexico Desconocido Online. Unknown parameter |accessyear= ignored (|access-date= suggested) (help); Unknown parameter |accessmonthday= ignored (help)
- ↑ Jeff Behan. "The bug that changed history". Unknown parameter |accessyear= ignored (|access-date= suggested) (help); Unknown parameter |accessmonthday= ignored (help)
- ↑ "Dictionary of Color Terms". Retrieved 2006-07-20.
- ↑ Chromatic Adaptation | https://www.wikidoc.org/index.php/Pigment | |
886c9b569e712e89a3804ce22d0a92698f44e4d4 | wikidoc | Pilates | Pilates
Please Take Over This Page and Apply to be Editor-In-Chief for this topic:
There can be one or more than one Editor-In-Chief. You may also apply to be an Associate Editor-In-Chief of one of the subtopics below. Please mail us to indicate your interest in serving either as an Editor-In-Chief of the entire topic or as an Associate Editor-In-Chief for a subtopic. Please be sure to attach your CV and or biographical sketch.
The Pilates Method (or simply Pilates), pronounced /Template:IPA/ ("Pih - LAH - Teez"), is a physical fitness system developed in the early 20th century by Joseph Pilates. As of 2005 there are 11 million people who practice the discipline regularly and 14,000 instructors in the United States.
Pilates called his method Contrology, because he believed his method uses the mind to control the muscles. The program focuses on the core postural muscles which help keep the body balanced and which are essential to providing support for the spine. In particular, Pilates exercises teach awareness of breath and alignment of the spine, and aim to strengthen the deep torso muscles.
# History
Pilates was formed by Joseph Pilates during the First World War with the proposal to improve the rehabilitation program for the many returning veterans. Joseph Pilates believed mental and physical health are essential to one another. He recommended a few, precise movements emphasizing control and form to aid injured soldiers in regaining their health by strengthening, stretching,and stabilizing key muscles. Pilates created "The Pilates Principles" to condition the entire body: proper alignment, centering, concentration, control, precision, breathing, and flowing movement.
Joseph Pilates wrote two books concerning the Pilates method: Return to Life through Contrology and Your Health: A Corrective System of Exercising That Revolutionizes the Entire Field of Physical Education.
# Principles
Pilates claimed his method has a philosophical and theoretical foundation. It claims not merely to be a collection of exercises but a method developed and refined over more than eighty years of use and observation. One interpretation of Pilates Principles: Centering, Concentration, Control, Precision, Breathing, and Flowing Movement, is similar to yoga.
## Mind over matter
According to practitioners, the central aim of Pilates is to create a fusion of mind and body, so that without thinking about it the body will move with economy, grace, and balance. The end goal is to produce an attention-free union of mind and body. Practitioners believe in using one's body to the greatest advantage, making the most of its strengths, counteracting its weaknesses, and correcting its imbalances. The method requires that one constantly pay attention to one's body while doing the movements. Paying attention to movement is so vital that it is more important than any other single aspect of the movements.
## Breathing
Joseph Pilates believed in circulating the blood so that it could awaken all the cells in the body and carry away the wastes related to fatigue. For the blood to do its work properly, he maintained, it has to be charged with oxygen and purged of waste gases through proper breathing. Full and thorough inhalation and exhalation are part of every Pilates exercise. Pilates saw forced exhalation as the key to full inhalation. “Squeeze out the lungs as you would wring a wet towel dry,” he is reputed to have said. Breathing, too, should be done with concentration, control, and precision. It should be properly coordinated with movement. Each exercise is accompanied by breathing instructions. Joseph Pilates stated, “Even if you follow no other instructions, learn to breathe correctly.”
## Centering
Pilates called the very large group of muscles in the center of the body – encompassing the abdomen, lower back, hips, and buttocks – the “powerhouse.” All energy for Pilates exercises begins from the powerhouse and flows outward to the extremities. Physical energy exerted from the center coordinates one's movements. Pilates felt that it was important to build a strong powerhouse in order to rely on it in daily living. Modern instructors call the powerhouse the "core".
## Concentration
Pilates demands intense focus. For instance, the inner thighs and pelvic floor may be assessed when doing a standing exercise that tones the triceps. Beginners learn to pay careful attention to their bodies, building on very small, delicate fundamental movements and controlled breathing. In 2006, at the Parkinson Center of the Oregon Health and Science University in Portland, Oregon, the concentration factor of the Pilates method was being studied in providing relief from the degenerative symptoms of Parkinson's disease .
## Control
Joseph Pilates built his method on the idea of muscle control. That meant no sloppy, uncontrolled movements. Every Pilates exercise must be performed with the utmost control, including all body parts, to avoid injury and produce positive results. Pilates emphasizes not intensity or multiple repetitions of a movement, but proper form for safe, effective results.
## Precision
Every movement in the Pilates method has a purpose. Every instruction is vitally important to the success of the whole. To leave out any detail is to forsake the intrinsic value of the exercise. The focus is on doing one precise and perfect movement, rather than many halfhearted ones. Eventually this precision becomes second nature, and carries over into everyday life as grace and economy of movement.
# Precautions
Many exercises are contra-indicated for pregnant women and the use of Pilates in pregnancy should only be undertaken under guidance of a fully trained expert.
# Legal action
In recent years the term "Pilates" worked itself into the mainstream and, following an unsuccessful intellectual property lawsuit, a US federal court ruled the term "Pilates" generic and free for unrestricted use. While this ruling prevented artificial restrictions on the use of the term "Pilates", it also permitted many untrained or under-qualified practitioners to capitalise on the name. Consumers now face extensive and conflicting information about what Pilates really is, how it works, and what credentials they should seek in an instructor. | Pilates
Please Take Over This Page and Apply to be Editor-In-Chief for this topic:
There can be one or more than one Editor-In-Chief. You may also apply to be an Associate Editor-In-Chief of one of the subtopics below. Please mail us [2] to indicate your interest in serving either as an Editor-In-Chief of the entire topic or as an Associate Editor-In-Chief for a subtopic. Please be sure to attach your CV and or biographical sketch.
Template:Globalize/US
The Pilates Method (or simply Pilates), pronounced /Template:IPA/ ("Pih - LAH - Teez"), is a physical fitness system developed in the early 20th century by Joseph Pilates[1]. As of 2005 there are 11 million people who practice the discipline regularly and 14,000 instructors in the United States. [2]
Pilates called his method Contrology, because he believed his method uses the mind to control the muscles.[3] The program focuses on the core postural muscles which help keep the body balanced and which are essential to providing support for the spine. In particular, Pilates exercises teach awareness of breath and alignment of the spine, and aim to strengthen the deep torso muscles.
# History
Pilates was formed by Joseph Pilates during the First World War with the proposal to improve the rehabilitation program for the many returning veterans. Joseph Pilates believed mental and physical health are essential to one another. He recommended a few, precise movements emphasizing control and form to aid injured soldiers in regaining their health by strengthening, stretching,and stabilizing key muscles. Pilates created "The Pilates Principles" to condition the entire body: proper alignment, centering, concentration, control, precision, breathing, and flowing movement.[citation needed]
Joseph Pilates wrote two books concerning the Pilates method: Return to Life through Contrology and Your Health: A Corrective System of Exercising That Revolutionizes the Entire Field of Physical Education.
# Principles
Pilates claimed his method has a philosophical and theoretical foundation. It claims not merely to be a collection of exercises but a method developed and refined over more than eighty years of use and observation. One interpretation of Pilates Principles: Centering, Concentration, Control, Precision, Breathing, and Flowing Movement, is similar to yoga.[citation needed]
## Mind over matter
According to practitioners, the central aim of Pilates is to create a fusion of mind and body, so that without thinking about it the body will move with economy, grace, and balance. The end goal is to produce an attention-free union of mind and body. Practitioners believe in using one's body to the greatest advantage, making the most of its strengths, counteracting its weaknesses, and correcting its imbalances. The method requires that one constantly pay attention to one's body while doing the movements. Paying attention to movement is so vital that it is more important than any other single aspect of the movements.[citation needed]
## Breathing
Joseph Pilates believed in circulating the blood so that it could awaken all the cells in the body and carry away the wastes related to fatigue. For the blood to do its work properly, he maintained, it has to be charged with oxygen and purged of waste gases through proper breathing. Full and thorough inhalation and exhalation are part of every Pilates exercise. Pilates saw forced exhalation as the key to full inhalation. “Squeeze out the lungs as you would wring a wet towel dry,” he is reputed to have said.[citation needed] Breathing, too, should be done with concentration, control, and precision. It should be properly coordinated with movement. Each exercise is accompanied by breathing instructions. Joseph Pilates stated, “Even if you follow no other instructions, learn to breathe correctly.”[citation needed]
## Centering
Pilates called the very large group of muscles in the center of the body – encompassing the abdomen, lower back, hips, and buttocks – the “powerhouse.” All energy for Pilates exercises begins from the powerhouse and flows outward to the extremities. Physical energy exerted from the center coordinates one's movements. Pilates felt that it was important to build a strong powerhouse in order to rely on it in daily living. Modern instructors call the powerhouse the "core".[citation needed]
## Concentration
Pilates demands intense focus. For instance, the inner thighs and pelvic floor may be assessed when doing a standing exercise that tones the triceps. Beginners learn to pay careful attention to their bodies, building on very small, delicate fundamental movements and controlled breathing.[citation needed] In 2006, at the Parkinson Center of the Oregon Health and Science University in Portland, Oregon, the concentration factor of the Pilates method was being studied in providing relief from the degenerative symptoms of Parkinson's disease .[4]
## Control
Joseph Pilates built his method on the idea of muscle control. That meant no sloppy, uncontrolled movements. Every Pilates exercise must be performed with the utmost control, including all body parts, to avoid injury and produce positive results. Pilates emphasizes not intensity or multiple repetitions of a movement, but proper form for safe, effective results.[citation needed]
## Precision
Every movement in the Pilates method has a purpose. Every instruction is vitally important to the success of the whole. To leave out any detail is to forsake the intrinsic value of the exercise. The focus is on doing one precise and perfect movement, rather than many halfhearted ones. Eventually this precision becomes second nature, and carries over into everyday life as grace and economy of movement.[citation needed]
# Precautions
Many exercises are contra-indicated for pregnant women and the use of Pilates in pregnancy should only be undertaken under guidance of a fully trained expert.[5]
# Legal action
In recent years the term "Pilates" worked itself into the mainstream and, following an unsuccessful intellectual property lawsuit, a US federal court ruled the term "Pilates" generic and free for unrestricted use.[6] While this ruling prevented artificial restrictions on the use of the term "Pilates", it also permitted many untrained or under-qualified practitioners to capitalise on the name. Consumers now face extensive and conflicting information about what Pilates really is, how it works, and what credentials they should seek in an instructor.[7] | https://www.wikidoc.org/index.php/Pilates | |
33775bc33bd43ae6e25e72fd578389ae817e5320 | wikidoc | Plasmin | Plasmin
Plasmin is an important enzyme (EC 3.4.21.7) present in blood that degrades many blood plasma proteins, including fibrin clots. The degradation of fibrin is termed fibrinolysis. In humans, the plasmin protein is encoded by the PLG gene.
# Function
Plasmin is a serine protease that acts to dissolve fibrin blood clots. Apart from fibrinolysis, plasmin proteolyses proteins in various other systems: It activates collagenases, some mediators of the complement system, and weakens the wall of the Graafian follicle, leading to ovulation. It cleaves fibrin, fibronectin, thrombospondin, laminin, and von Willebrand factor. Plasmin, like trypsin, belongs to the family of serine proteases.
Plasmin is released as a zymogen called plasminogen (PLG) from the liver into the systemic circulation. Two major glycoforms of plasminogen are present in humans - type I plasminogen contains two glycosylation moieties (N-linked to N289 and O-linked to T346), whereas type II plasminogen contains only a single O-linked sugar (O-linked to T346). Type II plasminogen is preferentially recruited to the cell surface over the type I glycoform. Conversely, type I plasminogen appears more readily recruited to blood clots.
In circulation, plasminogen adopts a closed, activation resistant conformation. Upon binding to clots, or to the cell surface, plasminogen adopts an open form that can be converted into active plasmin by a variety of enzymes, including tissue plasminogen activator (tPA), urokinase plasminogen activator (uPA), kallikrein, and factor XII (Hageman factor). Fibrin is a cofactor for plasminogen activation by tissue plasminogen activator. Urokinase plasminogen activator receptor (uPAR) is a cofactor for plasminogen activation by urokinase plasminogen activator. The conversion of plasminogen to plasmin involves the cleavage of the peptide bond between Arg-561 and Val-562.
Plasmin cleavage produces angiostatin.
# Mechanism of plasminogen activation
Full length plasminogen comprises seven domains. In addition to a C-terminal chymotrypsin-like serine protease domain, plasminogen contains an N-terminal Pan Apple domain (PAp) together with five Kringle domains (KR1-5). The Pan-Apple domain contains important determinants for maintaining plasminogen in the closed form, and the kringle domains are responsible for binding to lysine residues present in receptors and substrates.
The X-ray crystal structure of closed plasminogen reveals that the PAp and SP domains maintain the closed conformation through interactions made throughout the kringle array . Chloride ions further bridge the PAp / KR4 and SP / KR2 interfaces, explaining the physiological role of serum chloride in stabilizing the closed conformer. The structural studies also reveal that differences in glycosylation alter the position of KR3. These data help explain the functional differences between the type I and type II plasminogen glycoforms.
In closed plasminogen, access to the activation bond (R561/V562) targeted for cleavage by tPA and uPA is blocked through the position of the KR3/KR4 linker sequence and the O-linked sugar on T346. The position of KR3 may also hinder access to the activation loop. The Inter-domain interactions also block all kringle ligand-binding sites apart from that of KR-1, suggesting that the latter domain governs pro-enzyme recruitment to targets. Analysis of an intermediate plasminogen structure suggests that plasminogen conformational change to the open form is initiated through KR-5 transiently peeling away from the PAp domain. These movements expose the KR5 lysine-binding site to potential binding partners, and suggest a requirement for spatially distinct lysine residues in eliciting plasminogen recruitment and conformational change respectively.
# Mechanism of plasmin inactivation
Plasmin is inactivated by proteins such as α2-macroglobulin and α2-antiplasmin. The mechanism of plasmin inactivation involves the cleavage of an α2-macroglobulin at the bait region (a segment of the aM that is particularly susceptible to proteolytic cleavage) by plasmin. This initiates a conformational change such that the α2-macroglobulin collapses about the plasmin. In the resulting α2-macroglobulin-plasmin complex, the active site of plasmin is sterically shielded, thus substantially decreasing the plasmin's access to protein substrates. Two additional events occur as a consequence of bait region cleavage, namely (i) a h-cysteinyl-g-glutamyl thiol ester of the α2-macroglobulin becomes highly reactive and (ii) a major conformational change exposes a conserved COOH-terminal receptor binding domain. The exposure of this receptor binding domain allows the α2-macroglobulin protease complex to bind to clearance receptors and be removed from circulation.
# Pathology
Plasmin deficiency may lead to thrombosis, as clots are not adequately degraded. Plasminogen deficiency in mice leads to defective liver repair, defective wound healing, reproductive abnormalities.
In humans, a rare disorder called plasminogen deficiency type I (Online Mendelian Inheritance in Man (OMIM) 217090) is caused by mutations of the PLG gene and is often manifested by ligneous conjunctivitis.
# Interactions
Plasmin has been shown to interact with Thrombospondin 1, Alpha 2-antiplasmin and IGFBP3. Moreover, plasmin induces the generation of bradykinin in mice and humans through high molecular weight kininogen cleavage. | Plasmin
Plasmin is an important enzyme (EC 3.4.21.7) present in blood that degrades many blood plasma proteins, including fibrin clots. The degradation of fibrin is termed fibrinolysis. In humans, the plasmin protein is encoded by the PLG gene.[1]
# Function
Plasmin is a serine protease that acts to dissolve fibrin blood clots. Apart from fibrinolysis, plasmin proteolyses proteins in various other systems: It activates collagenases, some mediators of the complement system, and weakens the wall of the Graafian follicle, leading to ovulation. It cleaves fibrin, fibronectin, thrombospondin, laminin, and von Willebrand factor. Plasmin, like trypsin, belongs to the family of serine proteases.
Plasmin is released as a zymogen called plasminogen (PLG) from the liver into the systemic circulation. Two major glycoforms of plasminogen are present in humans - type I plasminogen contains two glycosylation moieties (N-linked to N289 and O-linked to T346), whereas type II plasminogen contains only a single O-linked sugar (O-linked to T346). Type II plasminogen is preferentially recruited to the cell surface over the type I glycoform. Conversely, type I plasminogen appears more readily recruited to blood clots.
In circulation, plasminogen adopts a closed, activation resistant conformation. Upon binding to clots, or to the cell surface, plasminogen adopts an open form that can be converted into active plasmin by a variety of enzymes, including tissue plasminogen activator (tPA), urokinase plasminogen activator (uPA), kallikrein, and factor XII (Hageman factor). Fibrin is a cofactor for plasminogen activation by tissue plasminogen activator. Urokinase plasminogen activator receptor (uPAR) is a cofactor for plasminogen activation by urokinase plasminogen activator. The conversion of plasminogen to plasmin involves the cleavage of the peptide bond between Arg-561 and Val-562.[1][2][3][4]
Plasmin cleavage produces angiostatin.
# Mechanism of plasminogen activation
Full length plasminogen comprises seven domains. In addition to a C-terminal chymotrypsin-like serine protease domain, plasminogen contains an N-terminal Pan Apple domain (PAp) together with five Kringle domains (KR1-5). The Pan-Apple domain contains important determinants for maintaining plasminogen in the closed form, and the kringle domains are responsible for binding to lysine residues present in receptors and substrates.
The X-ray crystal structure of closed plasminogen reveals that the PAp and SP domains maintain the closed conformation through interactions made throughout the kringle array .[4] Chloride ions further bridge the PAp / KR4 and SP / KR2 interfaces, explaining the physiological role of serum chloride in stabilizing the closed conformer. The structural studies also reveal that differences in glycosylation alter the position of KR3. These data help explain the functional differences between the type I and type II plasminogen glycoforms.
In closed plasminogen, access to the activation bond (R561/V562) targeted for cleavage by tPA and uPA is blocked through the position of the KR3/KR4 linker sequence and the O-linked sugar on T346. The position of KR3 may also hinder access to the activation loop. The Inter-domain interactions also block all kringle ligand-binding sites apart from that of KR-1, suggesting that the latter domain governs pro-enzyme recruitment to targets. Analysis of an intermediate plasminogen structure suggests that plasminogen conformational change to the open form is initiated through KR-5 transiently peeling away from the PAp domain. These movements expose the KR5 lysine-binding site to potential binding partners, and suggest a requirement for spatially distinct lysine residues in eliciting plasminogen recruitment and conformational change respectively.[4]
# Mechanism of plasmin inactivation
Plasmin is inactivated by proteins such as α2-macroglobulin and α2-antiplasmin. The mechanism of plasmin inactivation involves the cleavage of an α2-macroglobulin at the bait region (a segment of the aM that is particularly susceptible to proteolytic cleavage) by plasmin. This initiates a conformational change such that the α2-macroglobulin collapses about the plasmin. In the resulting α2-macroglobulin-plasmin complex, the active site of plasmin is sterically shielded, thus substantially decreasing the plasmin's access to protein substrates. Two additional events occur as a consequence of bait region cleavage, namely (i) a h-cysteinyl-g-glutamyl thiol ester of the α2-macroglobulin becomes highly reactive and (ii) a major conformational change exposes a conserved COOH-terminal receptor binding domain. The exposure of this receptor binding domain allows the α2-macroglobulin protease complex to bind to clearance receptors and be removed from circulation.
# Pathology
Plasmin deficiency may lead to thrombosis, as clots are not adequately degraded. Plasminogen deficiency in mice leads to defective liver repair,[5] defective wound healing, reproductive abnormalities.[citation needed]
In humans, a rare disorder called plasminogen deficiency type I (Online Mendelian Inheritance in Man (OMIM) 217090) is caused by mutations of the PLG gene and is often manifested by ligneous conjunctivitis.
# Interactions
Plasmin has been shown to interact with Thrombospondin 1,[6][7] Alpha 2-antiplasmin[8][9] and IGFBP3.[10] Moreover, plasmin induces the generation of bradykinin in mice and humans through high molecular weight kininogen cleavage.[11] | https://www.wikidoc.org/index.php/Plasmin | |
40738b66b7a8e70bbb98057daae53b9d5185017b | wikidoc | Plastic | Plastic
Please Take Over This Page and Apply to be Editor-In-Chief for this topic:
There can be one or more than one Editor-In-Chief. You may also apply to be an Associate Editor-In-Chief of one of the subtopics below. Please mail us to indicate your interest in serving either as an Editor-In-Chief of the entire topic or as an Associate Editor-In-Chief for a subtopic. Please be sure to attach your CV and or biographical sketch.
Plastics is the general term for a wide range of synthetic or semisynthetic polymerization products. They are composed of organic condensation or addition polymers and may contain other substances to improve performance or reduce costs. There are many natural polymers generally considered to be "plastics". Plastics can be formed into many different types of objects, or films, or fibers. Their name is derived from the malleability, or plasticity, of many of them. The "s" in "plastics" is there to distinguish between the polymer and the way a material deforms. For example, aluminum is a ductile material and can undergo "plastic" deformation when the material undergoes stress from a force and results in a strain of which it will not return. "Plastics" refers to the polymer material. The word derives from the Greek πλαστικός (plastikos), "fit for molding", from πλαστός (plastos) "molded".
# Overview
Plastics can be classified in many ways, but most commonly by their polymer backbone (polyvinyl chloride, polyethylene, polymethyl methacrylate, and other acrylics, silicones, polyurethanes, etc.). Other classifications include thermoplastic, thermoset, elastomer, engineering plastic, addition or condensation or polyaddition (depending on polymerization method used), and glass transition temperature or Tg.
Some plastics are partially crystalline and partially amorphous in molecular structure, giving them both a melting point (the temperature at which the attractive intermolecular forces are overcome) and one or more glass transitions (temperatures above which the extent of localized molecular flexibility is substantially increased). So-called semi-crystalline plastics include polyethylene, polypropylene, poly (vinyl chloride), polyamides (nylons), polyesters and some polyurethanes. Many plastics are completely amorphous, such as polystyrene and its copolymers, poly (methyl methacrylate), and all thermosets.
Plastics are polymers: long chains of atoms bonded to one another. Common thermoplastics range from 20,000 to 500,000 in molecular mass, while thermosets are assumed to have infinite molecular weight. These chains are made up of many repeating molecular units, known as "repeat units", derived from "monomers"; each polymer chain will have several 1000's of repeat units. The vast majority of plastics are composed of polymers of carbon and hydrogen alone or with oxygen, nitrogen, chlorine or sulfur in the backbone. (Some of commercial interest are silicon based.) The backbone is that part of the chain on the main "path" linking a large number of repeat units together. To vary the properties of plastics, both the repeat unit with different molecular groups "hanging" or "pendant" from the backbone, (usually they are "hung" as part of the monomers before linking monomers together to form the polymer chain). This customization by repeat unit's molecular structure has allowed plastics to become such an indispensable part of twenty first-century life by fine tuning the properties of the polymer.
People experimented with plastics based on natural polymers for centuries. In the nineteenth century a plastic material based on chemically modified natural polymers was discovered: Charles Goodyear discovered vulcanization of rubber (1839) and Alexander Parkes, English inventor (1813—1890) created the earliest form of plastic in 1855. He mixed pyroxylin, a partially nitrated form of cellulose (cellulose is the major component of plant cell walls), with alcohol and camphor. This produced a hard but flexible transparent material, which he called "Parkesine." The first plastic based on a synthetic polymer was made from phenol and formaldehyde, with the first viable and cheap synthesis methods invented by Leo Hendrik Baekeland in 1909, the product being known as Bakelite. Subsequently poly (vinyl chloride), polystyrene, polyethylene (polyethene), polypropylene (polypropene), polyamides (nylons), polyesters, acrylics, silicones, polyurethanes were amongst the many varieties of plastics developed and have great commercial success.
The development of plastics has come from the use of natural materials (e.g., chewing gum, shellac) to the use of chemically modified natural materials (e.g., natural rubber, nitrocellulose, collagen) and finally to completely synthetic molecules (e.g., epoxy, polyvinyl chloride, polyethylene).
In 1959, Koppers Company in Pittsburgh, PA had a team that developed the expandable polystyrene (EPS) foam.
## The polystyrene foam cup
On this team was Edward J. Stoves who made the first commercial foam cup. The experimental cups were made of puffed rice glued together to form a cup to show how it would feel and look. The chemistry was then developed to make the cups commercial. Today, the cup is used throughout the world in countries desiring fast food, such as the United States, Japan, Australia, and New Zealand. Freon was never used in the cups, as Stoves said: "We didn't know freon was bad for the ozone, but we knew it was not good for people so the cup never used freon to expand the beads." However, for many years polystyrene foam
The foam cup can be buried, and it is as stable as concrete and brick. No plastic film is required to protect the air and underground water. If it is properly incinerated at high temperatures, the only chemicals generated are water, carbon dioxide, some volatile compounds and carbon soot. If properly burned, one ton of foam cups product 0.2 ounces of ash. Paper cups, when incinerated, produces an average of 200 pounds of ash. Polystyrene burned without enough oxygen or at lower temperatures (as in a campfire or household fireplace) can produce polycyclic aromatic compounds , carbon black and carbon monoxide in addition to styrene monomers. EPS can be recycled to make park benches, flower pots and toys. Paper cups, which often have more oil in them than a foam cup, cannot be recycled if they are coated.
It is relatively easy to make the cups biodegradable. One has only to mix rice flour in the polystyrene. When the micro-organisms eat the rice, they also ingest the polystyrene. But there are three reasons to not make the cups biodegradable: 1. The time frame cannot be set. You don't want the cup disappearing on the grocer's shelf or when you have coffee in it; 2. The products of degradation are not food-grade approved; 3. If people know the material is biodegradable, they throw more cups carelessly away.
Photodegradable is superior but they have to be thrown into sunny places. If you throw the cups under a tree, they will not degrade. Manufacturers of the cups say, "If you can teach people to throw the cups into the sunlight, you can teach them to throw them into the trash."
# Cellulose-based plastics: celluloid and rayon
All Goodyear had done with vulcanization was improve the properties of a natural polymer. The next logical step was to use a natural polymer, cellulose, as the basis for a new material.
Inventors were particularly interested in developing synthetic substitutes for those natural materials that were expensive and in short supply, since that meant a profitable market to exploit. Ivory was a particularly attractive target for a synthetic replacement.
An Englishman from Birmingham named Alexander Parkes developed a "synthetic ivory" named "pyroxlin", which he marketed under the trade name "Parkesine", and which won a bronze medal at the 1862 World's fair in London. Parkesine was made from cellulose treated with nitric acid and a solvent. The output of the process hardened into a hard, ivory-like material that could be molded when heated. However, Parkes was not able to scale up the process reliably, and products made from Parkesine quickly warped and cracked after a short period of use.
Englishmen Daniel Spill and the American John Wesley Hyatt both took up where Parkes left off. Parkes had failed for lack of a proper softener, but they independently discovered that camphor would work well. Spill launched his product as Xylonite in 1869, while Hyatt patented his "Celluloid" in 1870, naming it after cellulose. Rivalry between Spill's British Xylonite Company and Hyatt's American Celluloid Company led to an expensive decade-long court battle, with neither company being awarded rights, as ultimately Parkes was credited with the product's invention. As a result, both companies operated in parallel on both sides of the Atlantic.
Celluloid/Xylonite proved extremely versatile in its field of application, providing a cheap and attractive replacement for ivory, tortoiseshell, and bone, and traditional products such as billiard balls and combs were much easier to fabricate with plastics. Some of the items made with cellulose in the nineteenth century were beautifully designed and implemented. For example, celluloid combs made to tie up the long tresses of hair fashionable at the time are now highly-collectable jewel-like museum pieces. Such pretty trinkets were no longer only for the rich.
Hyatt was something of an industrial genius who understood what could be done with such a shapeable, or "plastic", material, and proceeded to design much of the basic industrial machinery needed to produce good-quality plastic materials in quantity. Some of Hyatt's first products were dental pieces, and sets of false teeth built around celluloid proved cheaper than existing rubber dentures. However, celluloid dentures tended to soften when hot, making tea drinking tricky, and the camphor taste tended to be difficult to suppress.
Celluloid's real breakthrough products were waterproof shirt collars, cuffs, and the false shirtfronts known as "dickies", whose unmanageable nature later became a stock joke in silent-movie comedies. They did not wilt and did not stain easily, and Hyatt sold them by trainloads. Corsets made with celluloid stays also proved popular, since perspiration did not rust the stays, as it would if they had been made of metal.
Celluloid could also be used in entirely new applications. Hyatt figured out how to fabricate the material in a strip format for movie film. By the year 1900, movie film was a major market for celluloid.
However, celluloid still tended to yellow and crack over time, and it had another more dangerous defect: it burned very easily and spectacularly, unsurprising given that mixtures of nitric acid and cellulose are also used to synthesize smokeless powder.
Ping-pong balls, one of the few products still made with celluloid, sizzle and burn if set on fire, and Hyatt liked to tell stories about celluloid billiard balls exploding when struck very hard. These stories might have had a basis in fact, since the billiard balls were often celluloid covered with paints based on another, even more flammable, nitrocellulose product known as "collodion". If the balls had been imperfectly manufactured, the paints might have acted as primer to set the rest of the ball off with a bang.
Cellulose was also used to produce cloth. While the men who developed celluloid were interested in replacing ivory, those who developed the new fibers were interested in replacing another expensive material, silk.
In 1884, a French chemist, the Comte de Chardonnay, introduced a cellulose-based fabric that became known as "Chardonnay silk". It was an attractive cloth, but like celluloid it was very flammable, a property completely unacceptable in clothing. After some ghastly accidents, Chardonnay silk was taken off the market.
In 1894, three British inventors, Charles Cross, Edward Bevan, and Clayton Beadle, patented a new "artificial silk" or "art silk" that was much safer. The three men sold the rights for the new fabric to the French Courtauld company, a major manufacturer of silk, which put it into production in 1905, using cellulose from wood pulp as the "feedstock" material.
Art silk, technically known as Cellulose Acetate, became well known under the trade name "rayon", and was produced in great quantities through the 1930s, when it was supplanted by better artificial fabrics. It still remains in production today, often in blends with other natural and artificial fibers. It is cheap and feels smooth on the skin, though it is weak when wet and creases easily. It could also be produced in a transparent sheet form known as "cellophane". Cellulose Acetate became the standard substrate for movie and camera film, instead of its very flammable predecessor.
# Bakelite (phenolic)
The limitations of cellulose led to the next major advance, known as "phenolic" or "phenol-formaldehyde" plastics. A chemist named Leo Hendrik Baekeland, a Belgian-born American living in New York state, was searching for an insulating shellac to coat wires in electric motors and generators. Baekeland found that mixtures of phenol (C6H5OH) and formaldehyde (HCOH) formed a sticky mass when mixed together and heated, and the mass became extremely hard if allowed to cool. He continued his investigations and found that the material could be mixed with wood flour, asbestos, or slate dust to create "composite" materials with different properties. Most of these compositions were strong and fire resistant. The only problem was that the material tended to foam during synthesis, and the resulting product was of unacceptable quality.
Baekeland built pressure vessels to force out the bubbles and provide a smooth, uniform product. He publicly announced his discovery in 1912, naming it bakelite. It was originally used for electrical and mechanical parts, finally coming into widespread use in consumer goods in the 1920s. When the Bakelite patent expired in 1930, the Catalin Corporation acquired the patent and began manufacturing Catalin plastic using a different process that allowed a wider range of coloring.
Bakelite was the first true plastic. It was a purely synthetic material, not based on any material or even molecule found in nature. It was also the first thermosetting plastic. Conventional thermoplastics can be molded and then melted again, but thermoset plastics form bonds between polymers strands when cured, creating a tangled matrix that cannot be undone without destroying the plastic. Thermoset plastics are tough and temperature resistant.
Bakelite was cheap, strong, and durable. It was molded into thousands of forms, such as radios, telephones, clocks, and billiard balls. The U.S. government even considered making one-cent coins out of it when World War II caused a copper shortage.
Phenolic plastics have been largely replaced by cheaper and less brittle plastics, but they are still used in applications requiring its insulating and heat-resistant properties. For example, some electronic circuit boards are made of sheets of paper or cloth impregnated with phenolic resin.
Phenolic sheets, rods and tubes are produced in a wide variety of grades under various brand names. The most common grades of industrial phenolic are Canvas, Linen and Paper.
# Polystyrene and PVC
After the First World War, improvements in chemical technology led to an explosion in new forms of plastics. Among the earliest examples in the wave of new plastics were "polystyrene" (PS) and "polyvinyl chloride" (PVC), developed by IG Farben of Germany.
Polystyrene is a rigid, brittle, inexpensive plastic that has been used to make plastic model kits and similar knickknacks. It would also be the basis for one of the most popular "foamed" plastics, under the name "styrene foam" or "Styrofoam". Foam plastics can be synthesized in an "open cell" form, in which the foam bubbles are interconnected, as in an absorbent sponge, and "closed cell", in which all the bubbles are distinct, like tiny balloons, as in gas-filled foam insulation and flotation devices. In the late 1950s "High Impact" styrene was introduced, which was not brittle. It finds much current use as the substance of toy figurines and novelties.
PVC has side chains incorporating chlorine atoms, which form strong bonds. PVC in its normal form is stiff, strong, heat and weather resistant, and is now used for making plumbing, gutters, house siding, enclosures for computers and other electronics gear. PVC can also be softened with chemical processing, and in this form it is now used for shrink-wrap, food packaging, and raingear.
# Nylon
The real star of the plastics industry in the 1930s was "polyamide" (PA), far better known by its trade name nylon. Nylon was the first purely synthetic fiber, introduced by Du Pont Corporation at the 1939 World's Fair in New York City.
In 1927, Du Pont had begun a secret development project designated "Fiber66", under the direction of Harvard chemist Wallace Carothers and chemistry department director Elmer Keiser Bolton. Carothers had been hired to perform pure research, and he worked to understand the new materials' molecular structure and physical properties. He took some of the first steps in the molecular design of the materials.
His work led to the discovery of synthetic nylon fiber, which was very strong but also very flexible. The first application was for bristles for toothbrushes. However, Du Pont's real target was silk, particularly silk stockings. Carothers and his team synthesized a number of different polyamides including polyamide6.6 and 4.6, as well as polyesters.
It took Du Pont twelve years and US$27 million to refine nylon, and to synthesize and develop the industrial processes for bulk manufacture. With such a major investment, it was no surprise that Du Pont spared little expense to promote nylon after its introduction, creating a public sensation, or "nylon mania".
Nylon mania came to an abrupt stop at the end of 1941 when the USA entered World War II. The production capacity that had been built up to produce nylon stockings, or just "nylons", for American women was taken over to manufacture vast numbers of parachutes for fliers and paratroopers. After the war ended, Du Pont went back to selling nylon to the public, engaging in another promotional campaign in 1946 that resulted in an even bigger craze, triggering the so called "nylon riots".
Subsequently polyamides 6, 10, 11, and 12 have been developed based on monomers which are ring compounds, e.g. caprolactam.nylon 66 is a material manufactured by condensation polymerisation
Nylons still remain important plastics, and not just for use in fabrics. In its bulk form it is very wear resistant, particularly if oil-impregnated, and so is used to build gears, bearings, bushings, and because of good heat-resistance, increasingly for under-the-hood applications in cars, and other mechanical parts.
# Synthetic rubber
A polymer that was critical to the war effort was "synthetic rubber", which was produced in a variety of forms. Synthetic rubbers are not plastics. Synthetic rubbers are elastic materials.
The first synthetic rubber polymer was obtained by Lebedev in 1910. Practical synthetic rubber grew out of studies published in 1930 written independently by American Wallace Carothers, Russian scientist Lebedev and the German scientist Hermann Staudinger. These studies led in 1931 to one of the first successful synthetic rubbers, known as "neoprene", which was developed at DuPont under the direction of E.K. Bolton. Neoprene is highly resistant to heat and chemicals such as oil and gasoline, and is used in fuel hoses and as an insulating material in machinery.
In 1935, German chemists synthesized the first of a series of synthetic rubbers known as "Buna rubbers". These were "copolymers", meaning that their polymers were made up from not one but two monomers, in alternating sequence. One such Buna rubber, known as "GR-S" (Government Rubber Styrene), is a copolymer of butadiene and styrene, became the basis for U.S. synthetic rubber production during World War II.
Worldwide natural rubber supplies were limited and by mid-1942 most of the rubber-producing regions were under Japanese control. Military trucks needed rubber for tires, and rubber was used in almost every other war machine. The U.S. government launched a major (and largely secret) effort to develop and refine synthetic rubber. A principal scientist involved with the effort was Edward Robbins.
By 1944 a total of 50 factories were manufacturing it, pouring out a volume of the material twice that of the world's natural rubber production before the beginning of the war.
After the war, natural rubber plantations no longer had a stranglehold on rubber supplies, particularly after chemists learned to synthesize isoprene. GR-S remains the primary synthetic rubber for the manufacture of tires.
Synthetic rubber would also play an important part in the space race and nuclear arms race. Solid rockets used during World War II used nitrocellulose explosives for propellants, but it was impractical and dangerous to make such rockets very big.
During the war, California Institute of Technology (Caltech) researchers came up with a new solid fuel, based on asphalt fuel mixed with an oxidizer, such as potassium or ammonium perchlorate, plus aluminium powder, which burns very hot. This new solid fuel burned more slowly and evenly than nitrocellulose explosives, and was much less dangerous to store and use, though it tended to flow slowly out of the rocket in storage and the rockets using it had to be stockpiled nose down.
After the war, the Caltech researchers began to investigate the use of synthetic rubbers instead of asphalt as the fuel in the mixture. By the mid-1950s, large missiles were being built using solid fuels based on synthetic rubber, mixed with ammonium perchlorate and high proportions of aluminium powder. Such solid fuels could be cast into large, uniform blocks that had no cracks or other defects that would cause nonuniform burning. Ultimately, all large military rockets and missiles would use synthetic rubber based solid fuels, and they would also play a significant part in the civilian space effort.
# Plastics explosion: acrylic, polyethylene, etc.
Other plastics emerged in the prewar period, though some would not come into widespread use until after the war.
By 1936, American, British, and German companies were producing polymethyl methacrylate (PMMA), better known as acrylic glass. Although acrylics are now well known for their use in paints and synthetic fibers, such as fake furs, in their bulk form they are actually very hard and more transparent than glass, and are sold as glass replacements under trade names such as Plexiglas and Lucite. Plexiglas was used to build aircraft canopies during the war, and it is also now used as a marble replacement for countertops.
Another important plastic, polyethylene (PE), sometimes known as polythene, was discovered in 1933 by Reginald Gibson and Eric Fawcett at the British industrial giant Imperial Chemical Industries (ICI). This material evolved into two forms, low density polyethylene (LDPE), and high density polyethylene (HDPE).
PEs are cheap, flexible, durable, and chemically resistant. LDPE is used to make films and packaging materials, while HDPE is used for containers, plumbing, and automotive fittings. While PE has low resistance to chemical attack, it was found later that a PE container could be made much more robust by exposing it to fluorine gas, which modified the surface layer of the container into the much tougher polyfluoroethylene.
Polyethylene would lead after the war to an improved material, polypropylene (PP), which was discovered in the early 1950s by Giulio Natta. It is common in modern science and technology that the growth of the general body of knowledge can lead to the same inventions in different places at about the same time, but polypropylene was an extreme case of this phenomenon, being separately invented about nine times. The ensuing litigation was not resolved until 1989.
Polypropylene managed to survive the legal process and two American chemists working for Phillips Petroleum, J. Paul Hogan and Robert Banks, are now generally credited as the "official" inventors of the material. Polypropylene is similar to its ancestor, polyethylene, and shares polyethylene's low cost, but it is much more robust. It is used in everything from plastic bottles to carpets to plastic furniture, and is very heavily used in automobiles.
Polyurethane was invented by Friedrich Bayer & Company in 1937, and would come into use after the war, in blown form for mattresses, furniture padding, and thermal insulation. It is also one of the components (in non-blown form) of the fiber spandex.
In 1939, IG Farben filed a patent for polyepoxide or epoxy. Epoxies are a class of thermoset plastic that form cross-links and cure when a catalyzing agent, or hardener, is added. After the war they would come into wide use for coatings, adhesives, and composite materials.
Composites using epoxy as a matrix include glass-reinforced plastic, where the structural element is glass fiber, and carbon-epoxy composites, in which the structural element is carbon fiber. Fiberglass is now often used to build sport boats, and carbon-epoxy composites are an increasingly important structural element in aircraft, as they are lightweight, strong, and heat resistant.
Two chemists named Rex Whinfield and James Dickson, working at a small English company with the quaint name of the "Calico Printer's Association" in Manchester, developed polyethylene terephthalate (PET or PETE) in 1941, and it would be used for synthetic fibers in the postwar era, with names such as polyester, dacron, and terylene.
PET is less gas-permeable than other low-cost plastics and so is a popular material for making bottles for Coca-Cola and other carbonated drinks, since carbonation tends to attack other plastics, and for acidic drinks such as fruit or vegetable juices. PET is also strong and abrasion resistant, and is used for making mechanical parts, food trays, and other items that have to endure abuse. PET films are used as a base for recording tape.
One of the most impressive plastics used in the war, and a top secret, was polytetrafluoroethylene (PTFE), better known as Teflon, which could be deposited on metal surfaces as a scratch-proof and corrosion-resistant, low-friction protective coating. The polyfluoroethylene surface layer created by exposing a polyethylene container to fluorine gas is very similar to Teflon.
A Du Pont chemist named Roy Plunkett discovered Teflon by accident in 1938. During the war, it was used in gaseous-diffusion processes to refine uranium for the atomic bomb, as the process was highly corrosive. By the early 1960s, Teflon adhesion-resistant frying pans were in demand.
Teflon was later used to synthesize the breathable fabric Gore-Tex, which can be used to manufacture wet weather clothing that is able to "breathe". Its structure allows water vapour molecules to pass, while not permitting water as liquid to enter. Gore-Tex is also used for surgical applications such as garments and implants; Teflon strand is used to make dental floss; and Teflon mixed with fluorine compounds is used to make decoy flares dropped by aircraft to distract heat-seeking missiles.
After the war, the new plastics that had been developed entered the consumer mainstream in a flood. New manufacturing were developed, using various forming, molding, casting, and extrusion processes, to churn out plastic products in vast quantities. American consumers enthusiastically adopted the endless range of colorful, cheap, and durable plastic gimmicks being produced for new suburban home life.
One of the most visible parts of this plastics invasion was Earl Tupper's Tupperware, a complete line of sealable polyethylene food containers that Tupper cleverly promoted through a network of housewives who sold Tupperware as a means of bringing in some money. The Tupperware line of products was well thought out and highly effective, greatly reducing spoilage of foods in storage. Thin-film plastic wrap that could be purchased in rolls also helped keep food fresh.
Another prominent element in 1950s homes was Formica, a plastic laminate that was used to surface furniture and cabinetry. Formica was durable and attractive. It was particularly useful in kitchens, as it did not absorb, and could be easily cleaned of stains from food preparation, such as blood or grease. With Formica, a very attractive and well-built table could be built using low-cost and lightweight plywood with Formica covering, rather than expensive and heavy hardwoods like oak or mahogany.
Composite materials like fiberglass came into use for building boats and, in some cases, cars. Polyurethane foam was used to fill mattresses, and Styrofoam was used to line ice coolers and make float toys.
Plastics continue to be improved. General Electric introduced Lexan, a high-impact polycarbonate plastic, in the 1970s. Du Pont developed Kevlar, an extremely strong synthetic fiber that was best known for its use in ballistic rated clothing and combat helmets. Kevlar was so impressive that its manufacturer, DuPont, deemed it necessary to release an official statement denying alien involvement.
# Negative health effects
Some plastics have been associated with negative health effects.
Polyvinyl chloride (PVC) contains numerous toxic chemicals called adipates and phthalates ("plasticizers"), which are used to soften brittle PVC into a more flexible form. PVC is commonly used to package foods and liquids, ubiquitous in children's toys and teethers, plumbing and building materials, and in everything from cosmetics to shower curtains. Traces of these chemicals can leach out of PVC when it comes into contact with food. The World Health Organization's International Agency for Research on Cancer (IARC) has recognized the chemical used to make PVC, vinyl chloride, as a known human carcinogen. The European Union has banned the use of DEHP (di-2-ethylhexyl phthalate), the most widely used plasticizer in PVC, and in children's toys.
Polystyrene (PS) is one of the toxins the USEPA (United States Environmental Protection Agency) monitors in America's drinking water. Prior to the ban on the use of CFCs in extrusion of polystyrene (and general use, except in life-critical fire suppression systems; see Montreal Protocol), the production of polystyrene contributed to the depletion of the ozone layer; however, non-CFCs are currently used in the extrusion process. Some compounds leaching from polystyrene food containers interfere with hormone functions. It's a possible human carcinogen.
Polycarbonates are a particular group of thermoplastic polymers, whose primary building block is bisphenol A (BPA), a hormone disrupter that releases into food and liquid and acts like estrogen. Research in Environmental Health Perspectives finds that BPA (leached from the lining of tin cans, dental sealants and polycarbonate bottles) can increase body weight of lab animals' offspring, as well as impact hormone levels. A more recent animal study suggests that even low-level exposure to BPA results in insulin resistance, which can lead to inflammation and heart disease.
# The environment
Plastics are durable and degrade very slowly. In some cases, burning plastic can release toxic fumes. Also, the manufacturing of plastics often creates large quantities of chemical pollutants.
By 1995, plastic recycling programs were common in the United States and elsewhere. Thermoplastics can be remelted and reused, and thermoset plastics can be ground up and used as filler, though the purity of the material tends to degrade with each reuse cycle. There are methods by which plastics can be broken back down to a feedstock state.
To assist recycling of disposable items, the Plastic Bottle Institute of the Society of the Plastics Industry devised a now-familiar scheme to mark plastic bottles by plastic type. A plastic container using this scheme is marked with a triangle of three "chasing arrows", which encloses a number giving the plastic type:
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2-HDPE
3-PVC
4-LDPE
5-PP
6-PS
7-Other
- PET (PETE), polyethylene terephthalate: Commonly found on 2-liter soft drink bottles, cooking oil bottles, peanut butter jars.
- HDPE, high-density polyethylene: Commonly found on detergent bottles, milk jugs.
- PVC, polyvinyl chloride: Commonly found on plastic pipes, outdoor furniture, shrink-wrap, water bottles, salad dressing and liquid detergent containers.
- LDPE, low-density polyethylene: Commonly found on dry-cleaning bags, produce bags, trash can liners, food storage containers.
- PP, polypropylene: Commonly found on bottle caps, drinking straws, yogurt containers.
- PS, polystyrene: Commonly found on "packing peanuts", cups, plastic tableware, meat trays, take-away food clamshell containers
- OTHER, other: This plastic category, as its name of "other" implies, is any plastic other than the named #1–#6, Commonly found on certain kinds of food containers, Tupperware, and Nalgene bottles.
Unfortunately, recycling plastics has proven difficult. The biggest problem with plastic recycling is that it is difficult to automate the sorting of plastic waste, and so it is labor intensive. Typically, workers sort the plastic by looking at the resin identification code, though common containers like soda bottles can be sorted from memory. Other recyclable materials, such as metals, are easier to process mechanically. However, new mechanical sorting processes are being utilized to increase plastic recycling capacity and efficiency.
While containers are usually made from a single type and color of plastic, making them relatively easy to sort out, a consumer product like a cellular phone may have many small parts consisting of over a dozen different types and colors of plastics. In a case like this, the resources it would take to separate the plastics far exceed their value and the item is discarded. However, developments are taking place in the field of Active Disassembly, which may result in more consumer product components being re-used or recycled. Recycling certain types of plastics can be unprofitable, as well. For example, polystyrene is rarely recycled because it is usually not cost effective. These unrecyclable wastes can be disposed of in landfills, incinerated or used to produce electricity at waste-to-energy plants.
## Bioplastics and biodegradable plastics
Research has been done on biodegradable plastics that break down with exposure to sunlight (e.g. ultra-violet radiation), water or dampness, bacteria, enzymes, wind abrasion and some instances rodent pest or insect attack are also included as forms of biodegradation or environmental degradation. It is clear some of these modes of degradation will only work if the plastic is exposed at the surface, while other modes will only be effective if certain conditions are found in landfill or composting systems. Starch powder has been mixed with plastic as a filler to allow it to degrade more easily, but it still does not lead to complete breakdown of the plastic. Some researchers have actually genetically engineered bacteria that synthesize a completely biodegradable plastic, but this material, such as Biopol, is expensive at present. The German chemical company BASF makes Ecoflex, a fully biodegradable polyester for food packaging applications.
A potential disadvantage of biodegradable plastics is that the carbon that is locked up in them is released into the atmosphere as a greenhouse gas carbon dioxide when they degrade, though if they are made from natural materials, such as vegetable crop derivatives or animal products, there is no net gain in carbon dioxide emissions, although concern will be for a worse greenhouse gas, methane release. Of course, incinerating non-biodegradable plastics will release carbon dioxide as well, while disposing of it in landfills will release methane when the plastic does eventually break down.
So far, these plastics have proven too costly and limited for general use, and critics have pointed out that the only real problem they address is roadside litter, which is regarded as a secondary issue. When such plastic materials are dumped into landfills, they can become "mummified" and persist for decades even if they are supposed to be biodegradable.
There have been some success stories. The Courtauld concern, the original producer of rayon, came up with a revised process for the material in the mid-1980s to produce "Tencel". Tencel has many superior properties over rayon, but is still produced from "biomass" feedstocks, and its manufacture is extraordinarily clean by the standards of plastic production.
Researchers at the University of Illinois at Urbana have been working on developing biodegradable resins, sheets and films made with zein
(corn protein).Template:PDFlink
Recently, however, a new type of biodegradable resin has made its debut in the United States, called Plastarch Material (PSM). It is heat, water, and oil resistant and sees a 70% degradation in 90 days. Biodegradable plastics based on polylactic acid (once derived from dairy products, now from cereal crops such as maize) have entered the marketplace, for instance as polylactates as disposable sandwich packs.
An alternative to starch-based resins are additives such as Bio-Batch an additive that allows the manufacturers to make PE, PS, PP, PET, and PVC totally biodegradable in landfills where 94.8% of most plastics end up, according to the EPA's latest MSW report located under "Municipal Solid Waste in the United States": 2003 Data Tables.
It is also possible that bacteria will eventually develop the ability to degrade plastics. This has already happened with nylon: two types of nylon eating bacteria, Flavobacteria and Pseudomonas, were found in 1975 to possess enzymes (nylonase) capable of breaking down nylon. While not a solution to the disposal problem, it is likely that bacteria will evolve the ability to use other synthetic plastics as well. In 2008, a 16-year-old boy reportedly isolated two plastic-consuming bacteria.
The latter possibility was in fact the subject of a cautionary novel by Kit Pedler and Gerry Davis (screenwriter), the creators of the Cybermen, re-using the plot of the first episode of their Doomwatch series. The novel, "Mutant 59: The Plastic Eater", written in 1971, is the story of what could happen if a bacterium were to evolve—or be artificially cultured—to eat plastics, and be let loose in a major city.
## Bioplastics
Some plastics can be obtained from biomass, including:
- from pea starch film with trigger biodegradation properties for agricultural applications (TRIGGER).
- from biopetroleum .
# Price, environment, and the future
The biggest threat to the conventional plastics industry is most likely to be environmental concerns, including the release of toxic pollutants, greenhouse gas, litter, biodegradable and non-biodegrable landfill impact as a result of the production and disposal of petroleum and petroleum-based plastics. Of particular concern has been the recent accumulation of enormous quantities of plastic trash in ocean gyres, particularly the North Pacific Gyre, now known informally as the Great Pacific Garbage Patch or the Pacific Trash Vortex.
For decades one of the great appeals of plastics has been their low price. Yet in recent years the cost of plastics has been rising dramatically. A major cause is the sharply rising cost of petroleum, the raw material that is chemically altered to form commercial plastics.
With some observers suggesting that future oil reserves are uncertain, the price of petroleum may increase further. Therefore, alternatives are being sought. Oil shale and tar oil are alternatives for plastic production but are expensive. Scientists are seeking cheaper and better alternatives to petroleum-based plastics, and many candidates are in laboratories all over the world. One promising alternative may be fructose .
# Common plastics and uses
# Special-purpose plastics | Plastic
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Plastics is the general term for a wide range of synthetic or semisynthetic polymerization products. They are composed of organic condensation or addition polymers and may contain other substances to improve performance or reduce costs. There are many natural polymers generally considered to be "plastics". Plastics can be formed into many different types of objects, or films, or fibers. Their name is derived from the malleability, or plasticity, of many of them. The "s" in "plastics" is there to distinguish between the polymer and the way a material deforms. For example, aluminum is a ductile material and can undergo "plastic" deformation when the material undergoes stress from a force and results in a strain of which it will not return. "Plastics" refers to the polymer material.[citation needed] The word derives from the Greek πλαστικός (plastikos), "fit for molding", from πλαστός (plastos) "molded"[1][2].
# Overview
Plastics can be classified in many ways, but most commonly by their polymer backbone (polyvinyl chloride, polyethylene, polymethyl methacrylate, and other acrylics, silicones, polyurethanes, etc.). Other classifications include thermoplastic, thermoset, elastomer, engineering plastic, addition or condensation or polyaddition (depending on polymerization method used), and glass transition temperature or Tg.[3]
Some plastics are partially crystalline and partially amorphous in molecular structure, giving them both a melting point (the temperature at which the attractive intermolecular forces are overcome) and one or more glass transitions (temperatures above which the extent of localized molecular flexibility is substantially increased). So-called semi-crystalline plastics include polyethylene, polypropylene, poly (vinyl chloride), polyamides (nylons), polyesters and some polyurethanes. Many plastics are completely amorphous, such as polystyrene and its copolymers, poly (methyl methacrylate), and all thermosets.
Plastics are polymers: long chains of atoms bonded to one another. Common thermoplastics range from 20,000 to 500,000 in molecular mass, while thermosets are assumed to have infinite molecular weight. These chains are made up of many repeating molecular units, known as "repeat units", derived from "monomers"; each polymer chain will have several 1000's of repeat units. The vast majority of plastics are composed of polymers of carbon and hydrogen alone or with oxygen, nitrogen, chlorine or sulfur in the backbone. (Some of commercial interest are silicon based.) The backbone is that part of the chain on the main "path" linking a large number of repeat units together. To vary the properties of plastics, both the repeat unit with different molecular groups "hanging" or "pendant" from the backbone, (usually they are "hung" as part of the monomers before linking monomers together to form the polymer chain). This customization by repeat unit's molecular structure has allowed plastics to become such an indispensable part of twenty first-century life by fine tuning the properties of the polymer.
People experimented with plastics based on natural polymers for centuries. In the nineteenth century a plastic material based on chemically modified natural polymers was discovered: Charles Goodyear discovered vulcanization of rubber (1839) and Alexander Parkes, English inventor (1813—1890) created the earliest form of plastic in 1855. He mixed pyroxylin, a partially nitrated form of cellulose (cellulose is the major component of plant cell walls), with alcohol and camphor[citation needed]. This produced a hard but flexible transparent material, which he called "Parkesine." The first plastic based on a synthetic polymer was made from phenol and formaldehyde, with the first viable and cheap synthesis methods invented by Leo Hendrik Baekeland in 1909, the product being known as Bakelite. Subsequently poly (vinyl chloride), polystyrene, polyethylene (polyethene), polypropylene (polypropene), polyamides (nylons), polyesters, acrylics, silicones, polyurethanes were amongst the many varieties of plastics developed and have great commercial success.
The development of plastics has come from the use of natural materials (e.g., chewing gum, shellac) to the use of chemically modified natural materials (e.g., natural rubber, nitrocellulose, collagen) and finally to completely synthetic molecules (e.g., epoxy, polyvinyl chloride, polyethylene).
In 1959, Koppers Company in Pittsburgh, PA had a team that developed the expandable polystyrene (EPS) foam.
## The polystyrene foam cup
On this team was Edward J. Stoves who made the first commercial foam cup. The experimental cups were made of puffed rice glued together to form a cup to show how it would feel and look. The chemistry was then developed to make the cups commercial. Today, the cup is used throughout the world in countries desiring fast food, such as the United States, Japan, Australia, and New Zealand. Freon was never used in the cups, as Stoves said[citation needed]: "We didn't know freon was bad for the ozone, but we knew it was not good for people so the cup never used freon to expand the beads." However, for many years polystyrene foam
The foam cup can be buried, and it is as stable as concrete and brick. No plastic film is required to protect the air and underground water. If it is properly incinerated at high temperatures, the only chemicals generated are water, carbon dioxide, some volatile compounds and carbon soot[4]. If properly burned, one ton of foam cups product 0.2 ounces of ash. Paper cups, when incinerated, produces an average of 200 pounds of ash. Polystyrene burned without enough oxygen or at lower temperatures (as in a campfire or household fireplace) can produce polycyclic aromatic compounds , carbon black and carbon monoxide in addition to styrene monomers.[4][5] EPS can be recycled to make park benches, flower pots and toys. Paper cups, which often have more oil in them than a foam cup, cannot be recycled if they are coated.
It is relatively easy to make the cups biodegradable. One has only to mix rice flour in the polystyrene. When the micro-organisms eat the rice, they also ingest the polystyrene. But there are three reasons to not make the cups biodegradable: 1. The time frame cannot be set. You don't want the cup disappearing on the grocer's shelf or when you have coffee in it; 2. The products of degradation are not food-grade approved; 3. If people know the material is biodegradable, they throw more cups carelessly away.
Photodegradable is superior but they have to be thrown into sunny places. If you throw the cups under a tree, they will not degrade. Manufacturers of the cups say[citation needed], "If you can teach people to throw the cups into the sunlight, you can teach them to throw them into the trash."
# Cellulose-based plastics: celluloid and rayon
All Goodyear had done with vulcanization was improve the properties of a natural polymer. The next logical step was to use a natural polymer, cellulose, as the basis for a new material.
Inventors were particularly interested in developing synthetic substitutes for those natural materials that were expensive and in short supply, since that meant a profitable market to exploit. Ivory was a particularly attractive target for a synthetic replacement.
An Englishman from Birmingham named Alexander Parkes developed a "synthetic ivory" named "pyroxlin", which he marketed under the trade name "Parkesine", and which won a bronze medal at the 1862 World's fair in London. Parkesine was made from cellulose treated with nitric acid and a solvent. The output of the process hardened into a hard, ivory-like material that could be molded when heated. However, Parkes was not able to scale up the process reliably, and products made from Parkesine quickly warped and cracked after a short period of use.
Englishmen Daniel Spill and the American John Wesley Hyatt both took up where Parkes left off. Parkes had failed for lack of a proper softener, but they independently discovered that camphor[citation needed] would work well. Spill launched his product as Xylonite in 1869, while Hyatt patented his "Celluloid" in 1870, naming it after cellulose. Rivalry between Spill's British Xylonite Company and Hyatt's American Celluloid Company led to an expensive decade-long court battle, with neither company being awarded rights, as ultimately Parkes was credited with the product's invention. As a result, both companies operated in parallel on both sides of the Atlantic.
Celluloid/Xylonite proved extremely versatile in its field of application, providing a cheap and attractive replacement for ivory, tortoiseshell, and bone, and traditional products such as billiard balls and combs were much easier to fabricate with plastics. Some of the items made with cellulose in the nineteenth century were beautifully designed and implemented. For example, celluloid combs made to tie up the long tresses of hair fashionable at the time are now highly-collectable jewel-like museum pieces. Such pretty trinkets were no longer only for the rich.
Hyatt was something of an industrial genius who understood what could be done with such a shapeable, or "plastic", material, and proceeded to design much of the basic industrial machinery needed to produce good-quality plastic materials in quantity. Some of Hyatt's first products were dental pieces, and sets of false teeth built around celluloid proved cheaper than existing rubber dentures. However, celluloid dentures tended to soften when hot, making tea drinking tricky, and the camphor taste tended to be difficult to suppress.
Celluloid's real breakthrough products were waterproof shirt collars, cuffs, and the false shirtfronts known as "dickies", whose unmanageable nature later became a stock joke in silent-movie comedies. They did not wilt and did not stain easily, and Hyatt sold them by trainloads. Corsets made with celluloid stays also proved popular, since perspiration did not rust the stays, as it would if they had been made of metal.
Celluloid could also be used in entirely new applications. Hyatt figured out how to fabricate the material in a strip format for movie film. By the year 1900, movie film was a major market for celluloid.
However, celluloid still tended to yellow and crack over time, and it had another more dangerous defect: it burned very easily and spectacularly, unsurprising given that mixtures of nitric acid and cellulose are also used to synthesize smokeless powder.
Ping-pong balls, one of the few products still made with celluloid, sizzle and burn if set on fire, and Hyatt liked to tell stories about celluloid billiard balls exploding when struck very hard. These stories might have had a basis in fact, since the billiard balls were often celluloid covered with paints based on another, even more flammable, nitrocellulose product known as "collodion". If the balls had been imperfectly manufactured, the paints might have acted as primer to set the rest of the ball off with a bang.
Cellulose was also used to produce cloth. While the men who developed celluloid were interested in replacing ivory, those who developed the new fibers were interested in replacing another expensive material, silk.
In 1884, a French chemist, the Comte de Chardonnay, introduced a cellulose-based fabric that became known as "Chardonnay silk". It was an attractive cloth, but like celluloid it was very flammable, a property completely unacceptable in clothing. After some ghastly accidents, Chardonnay silk was taken off the market.
In 1894, three British inventors, Charles Cross, Edward Bevan, and Clayton Beadle, patented a new "artificial silk" or "art silk" that was much safer. The three men sold the rights for the new fabric to the French Courtauld company, a major manufacturer of silk, which put it into production in 1905, using cellulose from wood pulp as the "feedstock" material.
Art silk, technically known as Cellulose Acetate, became well known under the trade name "rayon", and was produced in great quantities through the 1930s, when it was supplanted by better artificial fabrics. It still remains in production today, often in blends with other natural and artificial fibers. It is cheap and feels smooth on the skin, though it is weak when wet and creases easily. It could also be produced in a transparent sheet form known as "cellophane". Cellulose Acetate became the standard substrate for movie and camera film, instead of its very flammable predecessor.
# Bakelite (phenolic)
The limitations of cellulose led to the next major advance, known as "phenolic" or "phenol-formaldehyde" plastics. A chemist named Leo Hendrik Baekeland, a Belgian-born American living in New York state, was searching for an insulating shellac to coat wires in electric motors and generators. Baekeland found that mixtures of phenol (C6H5OH) and formaldehyde (HCOH) formed a sticky mass when mixed together and heated, and the mass became extremely hard if allowed to cool. He continued his investigations and found that the material could be mixed with wood flour, asbestos, or slate dust to create "composite" materials with different properties. Most of these compositions were strong and fire resistant. The only problem was that the material tended to foam during synthesis, and the resulting product was of unacceptable quality.
Baekeland built pressure vessels to force out the bubbles and provide a smooth, uniform product. He publicly announced his discovery in 1912, naming it bakelite. It was originally used for electrical and mechanical parts, finally coming into widespread use in consumer goods in the 1920s. When the Bakelite patent expired in 1930, the Catalin Corporation acquired the patent and began manufacturing Catalin plastic using a different process that allowed a wider range of coloring.
Bakelite was the first true plastic. It was a purely synthetic material, not based on any material or even molecule found in nature. It was also the first thermosetting plastic. Conventional thermoplastics can be molded and then melted again, but thermoset plastics form bonds between polymers strands when cured, creating a tangled matrix that cannot be undone without destroying the plastic. Thermoset plastics are tough and temperature resistant.
Bakelite was cheap, strong, and durable. It was molded into thousands of forms, such as radios, telephones, clocks, and billiard balls. The U.S. government even considered making one-cent coins out of it when World War II caused a copper shortage.
Phenolic plastics have been largely replaced by cheaper and less brittle plastics, but they are still used in applications requiring its insulating and heat-resistant properties. For example, some electronic circuit boards are made of sheets of paper or cloth impregnated with phenolic resin.
Phenolic sheets, rods and tubes are produced in a wide variety of grades under various brand names. The most common grades of industrial phenolic are Canvas, Linen and Paper.
# Polystyrene and PVC
After the First World War, improvements in chemical technology led to an explosion in new forms of plastics. Among the earliest examples in the wave of new plastics were "polystyrene" (PS) and "polyvinyl chloride" (PVC), developed by IG Farben of Germany.
Polystyrene is a rigid, brittle, inexpensive plastic that has been used to make plastic model kits and similar knickknacks. It would also be the basis for one of the most popular "foamed" plastics, under the name "styrene foam" or "Styrofoam". Foam plastics can be synthesized in an "open cell" form, in which the foam bubbles are interconnected, as in an absorbent sponge, and "closed cell", in which all the bubbles are distinct, like tiny balloons, as in gas-filled foam insulation and flotation devices. In the late 1950s "High Impact" styrene was introduced, which was not brittle. It finds much current use as the substance of toy figurines and novelties.
PVC has side chains incorporating chlorine atoms, which form strong bonds. PVC in its normal form is stiff, strong, heat and weather resistant, and is now used for making plumbing, gutters, house siding, enclosures for computers and other electronics gear. PVC can also be softened with chemical processing, and in this form it is now used for shrink-wrap, food packaging, and raingear.
# Nylon
The real star of the plastics industry in the 1930s was "polyamide" (PA), far better known by its trade name nylon. Nylon was the first purely synthetic fiber, introduced by Du Pont Corporation at the 1939 World's Fair in New York City.
In 1927, Du Pont had begun a secret development project designated "Fiber66", under the direction of Harvard chemist Wallace Carothers and chemistry department director Elmer Keiser Bolton. Carothers had been hired to perform pure research, and he worked to understand the new materials' molecular structure and physical properties. He took some of the first steps in the molecular design of the materials.
His work led to the discovery of synthetic nylon fiber, which was very strong but also very flexible. The first application was for bristles for toothbrushes. However, Du Pont's real target was silk, particularly silk stockings. Carothers and his team synthesized a number of different polyamides including polyamide6.6 and 4.6, as well as polyesters.
It took Du Pont twelve years and US$27 million to refine nylon, and to synthesize and develop the industrial processes for bulk manufacture. With such a major investment, it was no surprise that Du Pont spared little expense to promote nylon after its introduction, creating a public sensation, or "nylon mania".
Nylon mania came to an abrupt stop at the end of 1941 when the USA entered World War II. The production capacity that had been built up to produce nylon stockings, or just "nylons", for American women was taken over to manufacture vast numbers of parachutes for fliers and paratroopers. After the war ended, Du Pont went back to selling nylon to the public, engaging in another promotional campaign in 1946 that resulted in an even bigger craze, triggering the so called "nylon riots".
Subsequently polyamides 6, 10, 11, and 12 have been developed based on monomers which are ring compounds, e.g. caprolactam.nylon 66 is a material manufactured by condensation polymerisation
Nylons still remain important plastics, and not just for use in fabrics. In its bulk form it is very wear resistant, particularly if oil-impregnated, and so is used to build gears, bearings, bushings, and because of good heat-resistance, increasingly for under-the-hood applications in cars, and other mechanical parts.
# Synthetic rubber
A polymer that was critical to the war effort was "synthetic rubber", which was produced in a variety of forms. Synthetic rubbers are not plastics. Synthetic rubbers are elastic materials.
The first synthetic rubber polymer was obtained by Lebedev in 1910. Practical synthetic rubber grew out of studies published in 1930 written independently by American Wallace Carothers, Russian scientist Lebedev and the German scientist Hermann Staudinger. These studies led in 1931 to one of the first successful synthetic rubbers, known as "neoprene", which was developed at DuPont under the direction of E.K. Bolton. Neoprene is highly resistant to heat and chemicals such as oil and gasoline, and is used in fuel hoses and as an insulating material in machinery.
In 1935, German chemists synthesized the first of a series of synthetic rubbers known as "Buna rubbers". These were "copolymers", meaning that their polymers were made up from not one but two monomers, in alternating sequence. One such Buna rubber, known as "GR-S" (Government Rubber Styrene), is a copolymer of butadiene and styrene, became the basis for U.S. synthetic rubber production during World War II.
Worldwide natural rubber supplies were limited and by mid-1942 most of the rubber-producing regions were under Japanese control. Military trucks needed rubber for tires, and rubber was used in almost every other war machine. The U.S. government launched a major (and largely secret) effort to develop and refine synthetic rubber. A principal scientist involved with the effort was Edward Robbins.
By 1944 a total of 50 factories were manufacturing it, pouring out a volume of the material twice that of the world's natural rubber production before the beginning of the war.
After the war, natural rubber plantations no longer had a stranglehold on rubber supplies, particularly after chemists learned to synthesize isoprene. GR-S remains the primary synthetic rubber for the manufacture of tires.
Synthetic rubber would also play an important part in the space race and nuclear arms race. Solid rockets used during World War II used nitrocellulose explosives for propellants, but it was impractical and dangerous to make such rockets very big.
During the war, California Institute of Technology (Caltech) researchers came up with a new solid fuel, based on asphalt fuel mixed with an oxidizer, such as potassium or ammonium perchlorate, plus aluminium powder, which burns very hot. This new solid fuel burned more slowly and evenly than nitrocellulose explosives, and was much less dangerous to store and use, though it tended to flow slowly out of the rocket in storage and the rockets using it had to be stockpiled nose down.
After the war, the Caltech researchers began to investigate the use of synthetic rubbers instead of asphalt as the fuel in the mixture. By the mid-1950s, large missiles were being built using solid fuels based on synthetic rubber, mixed with ammonium perchlorate and high proportions of aluminium powder. Such solid fuels could be cast into large, uniform blocks that had no cracks or other defects that would cause nonuniform burning. Ultimately, all large military rockets and missiles would use synthetic rubber based solid fuels, and they would also play a significant part in the civilian space effort.
# Plastics explosion: acrylic, polyethylene, etc.
Other plastics emerged in the prewar period, though some would not come into widespread use until after the war.
By 1936, American, British, and German companies were producing polymethyl methacrylate (PMMA), better known as acrylic glass. Although acrylics are now well known for their use in paints and synthetic fibers, such as fake furs, in their bulk form they are actually very hard and more transparent than glass, and are sold as glass replacements under trade names such as Plexiglas and Lucite. Plexiglas was used to build aircraft canopies during the war, and it is also now used as a marble replacement for countertops.
Another important plastic, polyethylene (PE), sometimes known as polythene, was discovered in 1933 by Reginald Gibson and Eric Fawcett at the British industrial giant Imperial Chemical Industries (ICI). This material evolved into two forms, low density polyethylene (LDPE), and high density polyethylene (HDPE).
PEs are cheap, flexible, durable, and chemically resistant. LDPE is used to make films and packaging materials, while HDPE is used for containers, plumbing, and automotive fittings. While PE has low resistance to chemical attack, it was found later that a PE container could be made much more robust by exposing it to fluorine gas, which modified the surface layer of the container into the much tougher polyfluoroethylene.
Polyethylene would lead after the war to an improved material, polypropylene (PP), which was discovered in the early 1950s by Giulio Natta. It is common in modern science and technology that the growth of the general body of knowledge can lead to the same inventions in different places at about the same time, but polypropylene was an extreme case of this phenomenon, being separately invented about nine times. The ensuing litigation was not resolved until 1989.
Polypropylene managed to survive the legal process and two American chemists working for Phillips Petroleum, J. Paul Hogan and Robert Banks, are now generally credited as the "official" inventors of the material. Polypropylene is similar to its ancestor, polyethylene, and shares polyethylene's low cost, but it is much more robust. It is used in everything from plastic bottles to carpets to plastic furniture, and is very heavily used in automobiles.
Polyurethane was invented by Friedrich Bayer & Company in 1937, and would come into use after the war, in blown form for mattresses, furniture padding, and thermal insulation. It is also one of the components (in non-blown form) of the fiber spandex.
In 1939, IG Farben filed a patent for polyepoxide or epoxy. Epoxies are a class of thermoset plastic that form cross-links and cure when a catalyzing agent, or hardener, is added. After the war they would come into wide use for coatings, adhesives, and composite materials.
Composites using epoxy as a matrix include glass-reinforced plastic, where the structural element is glass fiber, and carbon-epoxy composites, in which the structural element is carbon fiber. Fiberglass is now often used to build sport boats, and carbon-epoxy composites are an increasingly important structural element in aircraft, as they are lightweight, strong, and heat resistant.
Two chemists named Rex Whinfield and James Dickson, working at a small English company with the quaint name of the "Calico Printer's Association" in Manchester, developed polyethylene terephthalate (PET or PETE) in 1941, and it would be used for synthetic fibers in the postwar era, with names such as polyester, dacron, and terylene.
PET is less gas-permeable than other low-cost plastics and so is a popular material for making bottles for Coca-Cola and other carbonated drinks, since carbonation tends to attack other plastics, and for acidic drinks such as fruit or vegetable juices. PET is also strong and abrasion resistant, and is used for making mechanical parts, food trays, and other items that have to endure abuse. PET films are used as a base for recording tape.
One of the most impressive plastics used in the war, and a top secret, was polytetrafluoroethylene (PTFE), better known as Teflon, which could be deposited on metal surfaces as a scratch-proof and corrosion-resistant, low-friction protective coating. The polyfluoroethylene surface layer created by exposing a polyethylene container to fluorine gas is very similar to Teflon.
A Du Pont chemist named Roy Plunkett discovered Teflon by accident in 1938. During the war, it was used in gaseous-diffusion processes to refine uranium for the atomic bomb, as the process was highly corrosive. By the early 1960s, Teflon adhesion-resistant frying pans were in demand.
Teflon was later used to synthesize the breathable fabric Gore-Tex, which can be used to manufacture wet weather clothing that is able to "breathe". Its structure allows water vapour molecules to pass, while not permitting water as liquid to enter. Gore-Tex is also used for surgical applications such as garments and implants; Teflon strand is used to make dental floss; and Teflon mixed with fluorine compounds is used to make decoy flares dropped by aircraft to distract heat-seeking missiles.
After the war, the new plastics that had been developed entered the consumer mainstream in a flood. New manufacturing were developed, using various forming, molding, casting, and extrusion processes, to churn out plastic products in vast quantities. American consumers enthusiastically adopted the endless range of colorful, cheap, and durable plastic gimmicks being produced for new suburban home life.
One of the most visible parts of this plastics invasion was Earl Tupper's Tupperware, a complete line of sealable polyethylene food containers that Tupper cleverly promoted through a network of housewives who sold Tupperware as a means of bringing in some money. The Tupperware line of products was well thought out and highly effective, greatly reducing spoilage of foods in storage. Thin-film plastic wrap that could be purchased in rolls also helped keep food fresh.
Another prominent element in 1950s homes was Formica, a plastic laminate that was used to surface furniture and cabinetry. Formica was durable and attractive. It was particularly useful in kitchens, as it did not absorb, and could be easily cleaned of stains from food preparation, such as blood or grease. With Formica, a very attractive and well-built table could be built using low-cost and lightweight plywood with Formica covering, rather than expensive and heavy hardwoods like oak or mahogany.
Composite materials like fiberglass came into use for building boats and, in some cases, cars. Polyurethane foam was used to fill mattresses, and Styrofoam was used to line ice coolers and make float toys.
Plastics continue to be improved. General Electric introduced Lexan, a high-impact polycarbonate plastic, in the 1970s. Du Pont developed Kevlar, an extremely strong synthetic fiber that was best known for its use in ballistic rated clothing and combat helmets. Kevlar was so impressive that its manufacturer, DuPont, deemed it necessary to release an official statement denying alien involvement. [6]
# Negative health effects
Some plastics have been associated with negative health effects.
Polyvinyl chloride (PVC) contains numerous toxic chemicals called adipates and phthalates ("plasticizers"), which are used to soften brittle PVC into a more flexible form. PVC is commonly used to package foods and liquids, ubiquitous in children's toys and teethers, plumbing and building materials, and in everything from cosmetics to shower curtains. Traces of these chemicals can leach out of PVC when it comes into contact with food. The World Health Organization's International Agency for Research on Cancer (IARC) has recognized the chemical used to make PVC, vinyl chloride, as a known human carcinogen[7]. The European Union has banned the use of DEHP (di-2-ethylhexyl phthalate), the most widely used plasticizer in PVC, and in children's toys.
Polystyrene (PS) is one of the toxins the USEPA (United States Environmental Protection Agency) monitors in America's drinking water. Prior to the ban on the use of CFCs in extrusion of polystyrene (and general use, except in life-critical fire suppression systems; see Montreal Protocol), the production of polystyrene contributed to the depletion of the ozone layer; however, non-CFCs are currently used in the extrusion process. Some compounds leaching from polystyrene food containers interfere with hormone functions. It's a possible human carcinogen[7].
Polycarbonates are a particular group of thermoplastic polymers, whose primary building block is bisphenol A (BPA), a hormone disrupter that releases into food and liquid[7] and acts like estrogen. Research in Environmental Health Perspectives finds that BPA (leached from the lining of tin cans, dental sealants and polycarbonate bottles) can increase body weight of lab animals' offspring, as well as impact hormone levels. A more recent animal study suggests that even low-level exposure to BPA results in insulin resistance, which can lead to inflammation and heart disease.
# The environment
Plastics are durable and degrade very slowly. In some cases, burning plastic can release toxic fumes. Also, the manufacturing of plastics often creates large quantities of chemical pollutants.
By 1995, plastic recycling programs were common in the United States and elsewhere. Thermoplastics can be remelted and reused, and thermoset plastics can be ground up and used as filler, though the purity of the material tends to degrade with each reuse cycle. There are methods by which plastics can be broken back down to a feedstock state.
To assist recycling of disposable items, the Plastic Bottle Institute of the Society of the Plastics Industry devised a now-familiar scheme to mark plastic bottles by plastic type. A plastic container using this scheme is marked with a triangle of three "chasing arrows", which encloses a number giving the plastic type:
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2-HDPE
3-PVC
4-LDPE
5-PP
6-PS
7-Other
- PET (PETE), polyethylene terephthalate: Commonly found on 2-liter soft drink bottles, cooking oil bottles, peanut butter jars.
- HDPE, high-density polyethylene: Commonly found on detergent bottles, milk jugs.
- PVC, polyvinyl chloride: Commonly found on plastic pipes, outdoor furniture, shrink-wrap, water bottles, salad dressing and liquid detergent containers.
- LDPE, low-density polyethylene: Commonly found on dry-cleaning bags, produce bags, trash can liners, food storage containers.
- PP, polypropylene: Commonly found on bottle caps, drinking straws, yogurt containers.
- PS, polystyrene: Commonly found on "packing peanuts", cups, plastic tableware, meat trays, take-away food clamshell containers
- OTHER, other: This plastic category, as its name of "other" implies, is any plastic other than the named #1–#6, Commonly found on certain kinds of food containers, Tupperware, and Nalgene bottles.
Unfortunately, recycling plastics has proven difficult. The biggest problem with plastic recycling is that it is difficult to automate the sorting of plastic waste, and so it is labor intensive. Typically, workers sort the plastic by looking at the resin identification code, though common containers like soda bottles can be sorted from memory. Other recyclable materials, such as metals, are easier to process mechanically. However, new mechanical sorting processes are being utilized to increase plastic recycling capacity and efficiency.
While containers are usually made from a single type and color of plastic, making them relatively easy to sort out, a consumer product like a cellular phone may have many small parts consisting of over a dozen different types and colors of plastics. In a case like this, the resources it would take to separate the plastics far exceed their value and the item is discarded. However, developments are taking place in the field of Active Disassembly, which may result in more consumer product components being re-used or recycled. Recycling certain types of plastics can be unprofitable, as well. For example, polystyrene is rarely recycled because it is usually not cost effective. These unrecyclable wastes can be disposed of in landfills, incinerated or used to produce electricity at waste-to-energy plants.
## Bioplastics and biodegradable plastics
Research has been done on biodegradable plastics that break down with exposure to sunlight (e.g. ultra-violet radiation), water or dampness, bacteria, enzymes, wind abrasion and some instances rodent pest or insect attack are also included as forms of biodegradation or environmental degradation. It is clear some of these modes of degradation will only work if the plastic is exposed at the surface, while other modes will only be effective if certain conditions are found in landfill or composting systems. Starch powder has been mixed with plastic as a filler to allow it to degrade more easily, but it still does not lead to complete breakdown of the plastic. Some researchers have actually genetically engineered bacteria that synthesize a completely biodegradable plastic, but this material, such as Biopol, is expensive at present[citation needed]. The German chemical company BASF makes Ecoflex, a fully biodegradable polyester for food packaging applications.
A potential disadvantage of biodegradable plastics is that the carbon that is locked up in them is released into the atmosphere as a greenhouse gas carbon dioxide when they degrade, though if they are made from natural materials, such as vegetable crop derivatives or animal products, there is no net gain in carbon dioxide emissions, although concern will be for a worse greenhouse gas, methane release. Of course, incinerating non-biodegradable plastics will release carbon dioxide as well, while disposing of it in landfills will release methane when the plastic does eventually break down.
So far, these plastics have proven too costly and limited for general use, and critics have pointed out that the only real problem they address is roadside litter, which is regarded as a secondary issue. When such plastic materials are dumped into landfills, they can become "mummified" and persist for decades even if they are supposed to be biodegradable.
There have been some success stories. The Courtauld concern, the original producer of rayon, came up with a revised process for the material in the mid-1980s to produce "Tencel". Tencel has many superior properties over rayon, but is still produced from "biomass" feedstocks, and its manufacture is extraordinarily clean by the standards of plastic production.
Researchers at the University of Illinois at Urbana have been working on developing biodegradable resins, sheets and films made with zein
(corn protein).Template:PDFlink
Recently, however, a new type of biodegradable resin has made its debut in the United States, called Plastarch Material (PSM). It is heat, water, and oil resistant and sees a 70% degradation in 90 days. Biodegradable plastics based on polylactic acid (once derived from dairy products, now from cereal crops such as maize) have entered the marketplace, for instance as polylactates as disposable sandwich packs.
An alternative to starch-based resins are additives such as Bio-Batch an additive that allows the manufacturers to make PE, PS, PP, PET, and PVC totally biodegradable in landfills where 94.8% of most plastics end up, according to the EPA's latest MSW report located under "Municipal Solid Waste in the United States": 2003 Data Tables.
It is also possible that bacteria will eventually develop the ability to degrade plastics. This has already happened with nylon: two types of nylon eating bacteria, Flavobacteria and Pseudomonas, were found in 1975 to possess enzymes (nylonase) capable of breaking down nylon. While not a solution to the disposal problem, it is likely that bacteria will evolve the ability to use other synthetic plastics as well. In 2008, a 16-year-old boy reportedly isolated two plastic-consuming bacteria.[8]
The latter possibility was in fact the subject of a cautionary novel by Kit Pedler and Gerry Davis (screenwriter), the creators of the Cybermen, re-using the plot of the first episode of their Doomwatch series. The novel, "Mutant 59: The Plastic Eater", written in 1971, is the story of what could happen if a bacterium were to evolve—or be artificially cultured—to eat plastics, and be let loose in a major city.
## Bioplastics
Some plastics can be obtained from biomass, including:
- from pea starch film with trigger biodegradation properties for agricultural applications (TRIGGER). [9]
- from biopetroleum [10].
# Price, environment, and the future
The biggest threat to the conventional plastics industry is most likely to be environmental concerns, including the release of toxic pollutants, greenhouse gas, litter, biodegradable and non-biodegrable landfill impact as a result of the production and disposal of petroleum and petroleum-based plastics. Of particular concern has been the recent accumulation of enormous quantities of plastic trash in ocean gyres, particularly the North Pacific Gyre, now known informally as the Great Pacific Garbage Patch or the Pacific Trash Vortex.
For decades one of the great appeals of plastics has been their low price. Yet in recent years the cost of plastics has been rising dramatically. A major cause is the sharply rising cost of petroleum, the raw material that is chemically altered to form commercial plastics.
With some observers suggesting that future oil reserves are uncertain, the price of petroleum may increase further. Therefore, alternatives are being sought. Oil shale and tar oil are alternatives for plastic production but are expensive. Scientists are seeking cheaper and better alternatives to petroleum-based plastics, and many candidates are in laboratories all over the world. One promising alternative may be fructose [11].
# Common plastics and uses
# Special-purpose plastics | https://www.wikidoc.org/index.php/Plastic | |
2cb16d358eefe0c22f0148c21351f546a40fbd36 | wikidoc | Plastid | Plastid
Plastids are major organelles found in plants and algae.
# Plastids in plants
Plastids are responsible for photosynthesis, storage of products like starch and for the synthesis of many classes of molecules such as fatty acids and terpenes which are needed as cellular building blocks and/or for the function of the plant. Depending on their morphology and function, plastids have the ability to differentiate, or redifferentiate, between these and other forms. All plastids are derived from proplastids (formerly "eoplasts", eo-: dawn, early), which are present in the meristematic regions of the plant. Proplastids and young chloroplasts commonly divide, but more mature chloroplasts also have this capacity.
In plants, plastids may differentiate into several forms, depending upon which function they need to play in the cell. Undifferentiated plastids (proplastids) may develop into any of the following plastids:
- Chloroplasts: for photosynthesis; see also etioplasts, the predecessors of chloroplasts
- Chromoplasts: for pigment synthesis and storage
- Leucoplasts: for monoterpene synthesis; leucoplasts sometimes differentiate into more specialized plastids:
Amyloplasts: for starch storage
Statoliths: for detecting gravity
Elaioplasts: for storing fat
Proteinoplasts: for storing and modifying protein
- Amyloplasts: for starch storage
Statoliths: for detecting gravity
- Statoliths: for detecting gravity
- Elaioplasts: for storing fat
- Proteinoplasts: for storing and modifying protein
Each plastid creates multiple copies of the rectangular 75-250 kilo bases plastid genome. The number of genome copies per plastid is flexible, ranging from more than 1000 in rapidly dividing cells, which generally contain few plastids, to 100 or fewer in mature cells, where plastid divisions has given rise to a large number of plastids. The plastid genome contains about 100 genes encoding ribosomal and transfer ribonucleic acids (rRNAs and tRNAs) as well as proteins involved in photosynthesis and plastid gene transcription and translation. However, these proteins only represent a small fraction of the total protein set-up necessary to build and maintain the structure and function of a particular type of plastid. Nuclear genes encode the vast majority of plastid proteins, and the expression of plastid genes and nuclear genes is tightly co-regulated to allow proper development of plastids in relation to cell differentiation.
Plastid DNA exists as large protein-DNA complexes associated with the inner envelope membrane and called 'plastid nucleoids'. Each nucleoid particle may contain more than 10 copies of the plastid DNA. The proplastid contains a single nucleoid located in the centre of the plastid. The developing plastid has many nucleoids, localized at the periphery of the plastid, bound to the inner envelope membrane. During the development of proplastids to chloroplasts, and when plastids convert from one type to another, nucleoids change in morphology, size and location within the organelle. The remodelling of nucleoids is believed to occur by modifications to the composition and abundance of nucleoid proteins.
In plant cells long thin protuberances called stromules sometimes form and extend from the main plastid body into the cytosol and interconnect several plastids. Proteins, and presumably smaller molecules, can move within stromules. Most cultured cells that are relatively large compared to other plant cells have very long and abundant stromules that extend to the cell periphery.
# Plastids in algae
In algae, the term leucoplast (leukoplast) is used for all unpigmented plastids. Their function differ from the leukoplasts in plants. Etioplast, amyloplast and chromoplast are plant-specific and do not occur in algae. Algal plastids may also differ from plant plastids in that they contain pyrenoids.
# Inheritance of plastids
Most plants inherit the plastids from only one parent. Angiosperms generally inherit plastids from the mother, while many gymnosperms inherit plastids from the father. Algae also inherit plastids from only one parent. The plastid DNA of the other parent is thus completely lost.
In normal intraspecific crossings (resulting in normal hybrids of one species), the inheritance of plastid DNA appears to be quite strictly 100% uniparental. In interspecific hybridisations, however, the inheritance of plastids appears to be more erratic. Although plastids inherit mainly maternally in interspecific hybridisations, there are many reports of hybrids of flowering plants that contain plastids of the father.
# Origin of plastids
Plastids are thought to have originated from endosymbiotic cyanobacteria. They developed around 1500 mya and allowed eukaryotes to carry out oxygenic photosynthesis. Due to a split-up into three evolutionary lineages, the plastids are named differently: chloroplasts in green algae and plants, rhodoplasts in red algae and cyanelles in the glaucophytes. The plastids differ by their pigmentation, but also in ultrastructure. The chloroplasts e.g. have lost all phycobilisomes, the light harvesting complexes found in cyanobacteria, red algae and glaucophytes, but - only in plants and in closely related green algae - contain stroma and grana thylakoids. The glaucocystophycean plastid - in contrast to the chloroplasts and the rhodoplasts - is still surrounded by a remains of the cyanobacterial cell wall. All these primary plastids are surrounded by two membranes.
Complex plastids start by secondary endosymbiosis, when a eukaryote engulfs a red or green alga and retains the algal plastid, which is typically surrounded by more than two membranes, and reduced in its metabolic and/or photosynthetic capacity. Algae with complex plastids derived by secondary endosymbiosis of a red alga include the heterokonts, haptophytes, cryptomonads, and most dinoflagellates (= rhodoplasts). Those that endosymbiosed a green alga include the euglenids and chlorarachniophytes (= chloroplasts). The Apicomplexa, a phylum of obligate parasitic protozoa including the causative agents of malaria (Plasmodium spp.), toxoplasmosis (Toxoplasma gondii), and many other human or animal diseases also harbor a complex plastid (although this organelle has been lost in some apicomplexans, such as Cryptosporidium parvum, which causes cryptosporidiosis). The 'apicoplast' is no longer capable of photosynthesis, but is an essential organelle, and a promising target for antiparasitic drug development.
Some dinoflagellates take up algae as food and keep the plastid of the digested alga to profit from the photosynthesis; after a while the plastids are also digested. These captured plastids are known as kleptoplastids.
# Sources
- A Novel View of Chloroplast Structure: contains fluorescence images of chloroplasts and stromules as well as an easy to read chapter.
- Continuous expression in tobacco leaves of a Brassica napus PEND homologue blocks differentiation of plastids and development of palisade cells Wycliffe et al., 2005. The Plant Journal Volume 44 Issue 1 Page 1. PMID: 16167891
- Birky, C. W. 2001. The inheritance of genes in mitochondria and chloroplasts: laws, mechanisms and models. Annual Review of Genetics 35: 125-148. | Plastid
Plastids are major organelles found in plants and algae.
# Plastids in plants
Plastids are responsible for photosynthesis, storage of products like starch and for the synthesis of many classes of molecules such as fatty acids and terpenes which are needed as cellular building blocks and/or for the function of the plant. Depending on their morphology and function, plastids have the ability to differentiate, or redifferentiate, between these and other forms. All plastids are derived from proplastids (formerly "eoplasts", eo-: dawn, early), which are present in the meristematic regions of the plant. Proplastids and young chloroplasts commonly divide, but more mature chloroplasts also have this capacity.
In plants, plastids may differentiate into several forms, depending upon which function they need to play in the cell. Undifferentiated plastids (proplastids) may develop into any of the following plastids:
- Chloroplasts: for photosynthesis; see also etioplasts, the predecessors of chloroplasts
- Chromoplasts: for pigment synthesis and storage
- Leucoplasts: for monoterpene synthesis; leucoplasts sometimes differentiate into more specialized plastids:
Amyloplasts: for starch storage
Statoliths: for detecting gravity
Elaioplasts: for storing fat
Proteinoplasts: for storing and modifying protein
- Amyloplasts: for starch storage
Statoliths: for detecting gravity
- Statoliths: for detecting gravity
- Elaioplasts: for storing fat
- Proteinoplasts: for storing and modifying protein
Each plastid creates multiple copies of the rectangular 75-250 kilo bases plastid genome. The number of genome copies per plastid is flexible, ranging from more than 1000 in rapidly dividing cells, which generally contain few plastids, to 100 or fewer in mature cells, where plastid divisions has given rise to a large number of plastids. The plastid genome contains about 100 genes encoding ribosomal and transfer ribonucleic acids (rRNAs and tRNAs) as well as proteins involved in photosynthesis and plastid gene transcription and translation. However, these proteins only represent a small fraction of the total protein set-up necessary to build and maintain the structure and function of a particular type of plastid. Nuclear genes encode the vast majority of plastid proteins, and the expression of plastid genes and nuclear genes is tightly co-regulated to allow proper development of plastids in relation to cell differentiation.
Plastid DNA exists as large protein-DNA complexes associated with the inner envelope membrane and called 'plastid nucleoids'. Each nucleoid particle may contain more than 10 copies of the plastid DNA. The proplastid contains a single nucleoid located in the centre of the plastid. The developing plastid has many nucleoids, localized at the periphery of the plastid, bound to the inner envelope membrane. During the development of proplastids to chloroplasts, and when plastids convert from one type to another, nucleoids change in morphology, size and location within the organelle. The remodelling of nucleoids is believed to occur by modifications to the composition and abundance of nucleoid proteins.
In plant cells long thin protuberances called stromules sometimes form and extend from the main plastid body into the cytosol and interconnect several plastids. Proteins, and presumably smaller molecules, can move within stromules. Most cultured cells that are relatively large compared to other plant cells have very long and abundant stromules that extend to the cell periphery.
# Plastids in algae
In algae, the term leucoplast (leukoplast) is used for all unpigmented plastids. Their function differ from the leukoplasts in plants. Etioplast, amyloplast and chromoplast are plant-specific and do not occur in algae. Algal plastids may also differ from plant plastids in that they contain pyrenoids.
# Inheritance of plastids
Most plants inherit the plastids from only one parent. Angiosperms generally inherit plastids from the mother, while many gymnosperms inherit plastids from the father. Algae also inherit plastids from only one parent. The plastid DNA of the other parent is thus completely lost.
In normal intraspecific crossings (resulting in normal hybrids of one species), the inheritance of plastid DNA appears to be quite strictly 100% uniparental. In interspecific hybridisations, however, the inheritance of plastids appears to be more erratic. Although plastids inherit mainly maternally in interspecific hybridisations, there are many reports of hybrids of flowering plants that contain plastids of the father.
# Origin of plastids
Plastids are thought to have originated from endosymbiotic cyanobacteria. They developed around 1500 mya and allowed eukaryotes to carry out oxygenic photosynthesis.[1] Due to a split-up into three evolutionary lineages, the plastids are named differently: chloroplasts in green algae and plants, rhodoplasts in red algae and cyanelles in the glaucophytes. The plastids differ by their pigmentation, but also in ultrastructure. The chloroplasts e.g. have lost all phycobilisomes, the light harvesting complexes found in cyanobacteria, red algae and glaucophytes, but - only in plants and in closely related green algae - contain stroma and grana thylakoids. The glaucocystophycean plastid - in contrast to the chloroplasts and the rhodoplasts - is still surrounded by a remains of the cyanobacterial cell wall. All these primary plastids are surrounded by two membranes.
Complex plastids start by secondary endosymbiosis, when a eukaryote engulfs a red or green alga and retains the algal plastid, which is typically surrounded by more than two membranes, and reduced in its metabolic and/or photosynthetic capacity. Algae with complex plastids derived by secondary endosymbiosis of a red alga include the heterokonts, haptophytes, cryptomonads, and most dinoflagellates (= rhodoplasts). Those that endosymbiosed a green alga include the euglenids and chlorarachniophytes (= chloroplasts). The Apicomplexa, a phylum of obligate parasitic protozoa including the causative agents of malaria (Plasmodium spp.), toxoplasmosis (Toxoplasma gondii), and many other human or animal diseases also harbor a complex plastid (although this organelle has been lost in some apicomplexans, such as Cryptosporidium parvum, which causes cryptosporidiosis). The 'apicoplast' is no longer capable of photosynthesis, but is an essential organelle, and a promising target for antiparasitic drug development.
Some dinoflagellates take up algae as food and keep the plastid of the digested alga to profit from the photosynthesis; after a while the plastids are also digested. These captured plastids are known as kleptoplastids.
# Sources
- A Novel View of Chloroplast Structure: contains fluorescence images of chloroplasts and stromules as well as an easy to read chapter.
- Continuous expression in tobacco leaves of a Brassica napus PEND homologue blocks differentiation of plastids and development of palisade cells Wycliffe et al., 2005. The Plant Journal Volume 44 Issue 1 Page 1. PMID: 16167891
- Birky, C. W. 2001. The inheritance of genes in mitochondria and chloroplasts: laws, mechanisms and models. Annual Review of Genetics 35: 125-148. | https://www.wikidoc.org/index.php/Plastid | |
fe07c243ed0ed07c9d858abd8c040434e514fb64 | wikidoc | Plectin | Plectin
Plectin is a giant protein found in nearly all mammalian cells which acts as a link between the three main components of the cytoskeleton: actin microfilaments, microtubules and intermediate filaments. In addition plectin links the cytoskeleton to junctions found in the plasma membrane that structurally connect different cells. By holding these different networks together plectin plays an important role in maintaining the mechanical integrity and viscoelastic properties of tissues.
# Structure
Plectin can exist in cells as several alternatively-spliced isoforms, all around 500 kDa and >4000 amino acids. The structure of plectin is thought to be a dimer consisting of a central coiled coil of alpha helices connecting two large globular domains (one at each terminus). These globular domains are responsible for connecting plectin to its various cytoskeletal targets. The carboxy-terminal domain is made of 6 highly homologous repeating regions. The subdomain between regions five and six of this domain is known to connect to the intermediate filaments cytokeratin and vimentin. At the opposite end of the protein, in the N-terminal domain, a region has been defined as responsible for binding to actin. In 2004, the exact crystal structure of this actin-binding domain (ABD) was determined in mice and shown to be composed of two calponin homology (CH) domains. Plectin is expressed in nearly all mammalian tissues. In cardiac muscle and skeletal muscle, plectin is localized to specialized entities known as Z-discs. Plectin binds several proteins, including vinculin, DES, actin., fodrin, microtubule-associating proteins, nuclear laminin B., SPTAN1, vimentin and ITGB4.
# Function
Studies employing a plectin knockout mouse have shed light on the functions of plectin. Pups died 2–3 days after birth, and these mice exhibited marked skin abnormalities, including degeneration of keratinocytes. Skeletal and cardiac muscle tissues were also significantly affected. Cardiac intercalated discs were disintegrated and sarcomeres were irregularly shapen, and intracellular accumulation of aberrant isolated myofibrillar bundles and Z-disc components was also observed. Expression of vinculin in muscle cells was strikingly down-regulated.
Through the use of gold-immunoelectron microscopy, immunoblotting and immunofluorescence experiments plectin has been found to associate with all three major components of the cytoskeleton. In muscle, plectin binds to the periphery of Z-discs, and along with the intermediate filament protein desmin, may form lateral linkages among neighboring Z-discs. This interaction between plectin and desmin intermediate filaments also appears to facilitate the close association of myofibrils and mitochondria, both at Z-discs and along the remainder the sarcomere. Plectin also functions to link cytoskeleton to intercellular junctions, such as desmosomes and hemidesmosomes, which link intermediate filament networks between cells. Plectin has been revealed to localize to the desmosomes and in vitro studies have shown that it can form bridges between the desmosome protein, desmoplakin and intermediate filaments. In hemidesmosomes plectin has been shown to interact with the integrin β4 subunits of the hemidesmosome plaque and function in a clamp-like manner to link the intermediate filament cytokeratin to the junction.
# Clinical significance
Mutations in PLEC have been associated with epidermolysis bullosa simplex with muscular dystrophy. A missence variant of PLEC has been recently proposed as a cause of atrial fibrillation in some populations. Isolated left ventricular non-compaction accompanying epidermolysis bullosa simplex with muscular dystrophy was also noted.
Plectin has been proposed as a biomarker for pancreatic cancer. Although normally a cytoplasmic protein, plectin is expressed on the cell membrane in pancreatic ductal adenocarcinoma (PDAC) and can therefore be used to target PDAC cells. | Plectin
Plectin is a giant protein found in nearly all mammalian cells which acts as a link between the three main components of the cytoskeleton: actin microfilaments, microtubules and intermediate filaments.[1] In addition plectin links the cytoskeleton to junctions found in the plasma membrane that structurally connect different cells. By holding these different networks together plectin plays an important role in maintaining the mechanical integrity and viscoelastic properties of tissues.[2]
# Structure
Plectin can exist in cells as several alternatively-spliced isoforms, all around 500 kDa and >4000 amino acids.[3][4] The structure of plectin is thought to be a dimer consisting of a central coiled coil of alpha helices connecting two large globular domains (one at each terminus). These globular domains are responsible for connecting plectin to its various cytoskeletal targets. The carboxy-terminal domain is made of 6 highly homologous repeating regions. The subdomain between regions five and six of this domain is known to connect to the intermediate filaments cytokeratin and vimentin. At the opposite end of the protein, in the N-terminal domain, a region has been defined as responsible for binding to actin.[5] In 2004, the exact crystal structure of this actin-binding domain (ABD) was determined in mice and shown to be composed of two calponin homology (CH) domains.[6] Plectin is expressed in nearly all mammalian tissues. In cardiac muscle and skeletal muscle, plectin is localized to specialized entities known as Z-discs.[7] Plectin binds several proteins, including vinculin, DES,[8] actin.,[2][9] fodrin,[2][9] microtubule-associating proteins,[2][9] nuclear laminin B.,[2][9] SPTAN1,[10][11] vimentin[10][11][12] and ITGB4.[2][9]
# Function
Studies employing a plectin knockout mouse have shed light on the functions of plectin. Pups died 2–3 days after birth, and these mice exhibited marked skin abnormalities, including degeneration of keratinocytes. Skeletal and cardiac muscle tissues were also significantly affected. Cardiac intercalated discs were disintegrated and sarcomeres were irregularly shapen, and intracellular accumulation of aberrant isolated myofibrillar bundles and Z-disc components was also observed. Expression of vinculin in muscle cells was strikingly down-regulated.[13]
Through the use of gold-immunoelectron microscopy, immunoblotting and immunofluorescence experiments plectin has been found to associate with all three major components of the cytoskeleton. In muscle, plectin binds to the periphery of Z-discs,[8] and along with the intermediate filament protein desmin, may form lateral linkages among neighboring Z-discs. This interaction between plectin and desmin intermediate filaments also appears to facilitate the close association of myofibrils and mitochondria, both at Z-discs and along the remainder the sarcomere.[14] Plectin also functions to link cytoskeleton to intercellular junctions, such as desmosomes and hemidesmosomes, which link intermediate filament networks between cells. Plectin has been revealed to localize to the desmosomes and in vitro studies have shown that it can form bridges between the desmosome protein, desmoplakin and intermediate filaments.[15] In hemidesmosomes plectin has been shown to interact with the integrin β4 subunits of the hemidesmosome plaque and function in a clamp-like manner to link the intermediate filament cytokeratin to the junction.[16]
# Clinical significance
Mutations in PLEC have been associated with epidermolysis bullosa simplex with muscular dystrophy. A missence variant of PLEC has been recently proposed as a cause of atrial fibrillation in some populations[17]. Isolated left ventricular non-compaction accompanying epidermolysis bullosa simplex with muscular dystrophy was also noted.[18]
Plectin has been proposed as a biomarker for pancreatic cancer.[19][20] Although normally a cytoplasmic protein, plectin is expressed on the cell membrane in pancreatic ductal adenocarcinoma (PDAC) and can therefore be used to target PDAC cells.[19] | https://www.wikidoc.org/index.php/Plectin | |
9a6b57b27ef4d899bb2597e9f60f2821358dadde | wikidoc | Podocin | Podocin
Podocin is a protein component of the filtration slits of podocytes. Glomerular capillary endothelial cells, the glomerular basement membrane and the filtration slits function as the filtration barrier of the kidney glomerulus.
Mutations in the podocin gene NPHS2 can cause nephrotic syndrome, such as focal segmental glomerulosclerosis (FSGS) or minimal change disease (MCD). Symptoms may develop in the first few months of life (congenital nephrotic syndrome) or later in childhood.
# Structure
Podocin is a membrane protein of the band-7-stomatin family, consisting of 383 amino acids. It has a transmembrane domain forming a hairpin structure, with two cytoplasmic ends at the N- and C-terminus, the latter of which interacts with the cytosolic tail of nephrin, with CD2AP serving as an adaptor.
# Function
Podocin is localized on the membranes of podocyte pedicels (foot-like long processes), where it oligomerizes in lipid rafts together with nephrin to form the filtration slits. | Podocin
Podocin is a protein component of the filtration slits of podocytes. Glomerular capillary endothelial cells, the glomerular basement membrane and the filtration slits function as the filtration barrier of the kidney glomerulus.[1]
Mutations in the podocin gene NPHS2 can cause nephrotic syndrome, such as focal segmental glomerulosclerosis (FSGS) or minimal change disease (MCD).[2] Symptoms may develop in the first few months of life (congenital nephrotic syndrome) or later in childhood.[3]
# Structure
Podocin is a membrane protein of the band-7-stomatin family, consisting of 383 amino acids. It has a transmembrane domain forming a hairpin structure, with two cytoplasmic ends at the N- and C-terminus, the latter of which interacts with the cytosolic tail of nephrin, with CD2AP serving as an adaptor.
[4]
# Function
Podocin is localized on the membranes of podocyte pedicels (foot-like long processes), where it oligomerizes in lipid rafts together with nephrin to form the filtration slits.[4] | https://www.wikidoc.org/index.php/Podocin | |
e5735f0132d47ebf1bde16fbb45acf89383f3cf3 | wikidoc | Politor | Politor
Politor is the brand name of the Pioglitazone and Metformin combination preparation (Pioglitazone 15mg and Metformin 500mg tablet and Pioglitazone 15mg and Metformin 850mg tablet) from ACI Pharmaceuticals (Bangladesh). It is also available in Bangladesh under the brand name of Piomet (Silva Pharmaceuticals) and Rezulin (Square Pharmaceuticals). It is marketed in the USA by the originator Takeda Pharmaceuticals North America, Inc. under the brand name of Actoplus Met™.
Politor contains two oral antihyperglycemic agents (pioglitazone hydrochloride and metformin hydrochloride) with different mechanisms of action to improve glycemic control in patients with Diabetes mellitus type 2.
- Pioglitazone is a member of the thiazolidinedione class, decreases insulin resistance in the periphery and in the liver resulting in increased insulin dependent glucose disposal and decreased hepatic glucose output.
- Metformin is a member of the biguanide class, improves glucose tolerance in patients with type 2 diabetes, lowering both basal and postprandial plasma glucose. Metformin decreases hepatic glucose production, decreases intestinal absorption of glucose and improves insulin sensitivity by increasing peripheral glucose uptake and utilization.
Indication
Politor is indicated as an adjunct to diet and exercise:
- To improve glycemic control in patients with type 2 diabetes, or
- For patients who are already treated with a separate combination of pioglitazone and metformin,
- For patients whose diabetes is not adequately controlled with metformin alone, or
- For patients who have initially responded to pioglitazone alone and require additional glycemic control.
# Dosage and administration
Recommended dose
Use of antihyperglycemic agents in the management of type 2 diabetes should be individualized on the basis of effectiveness and tolerability.
Politor should be given with meals; the initial starting dose is either the 15mg/500mg or 15mg/850mg tablet strength once or twice daily, and gradually titrated after assessing adequacy of therapeutic response, while not exceeding the maximum recommended daily dose of pioglitazone 45mg and metformin 2550mg.
Starting dose for patients who initially responded to pioglitazone monotherapy and require additional glycemic control: Based on the usual starting doses of metformin (500mg twice daily or 850mg daily), Politor may be initiated at either the 15mg/500mg twice daily or 15mg/85mg once daily, and gradually titrated after assessing adequacy of therapeutic response.
Starting dose for patients inadequately controlled on metformin monotherapy: Based on the usual starting dose of pioglitazone (15-30mg daily), Politor may be initiated at either the 15mg/500mg or 15mg/850mg once or twice daily, and gradually titrated after assessing adequacy of therapeutic response.
Starting dose for patients switching from combination therapy of pioglitazone plus metformin as separate tablets: Politor may be initiated with either the 15mg/500mg or 15mg/850mg tablet strengths based on the dose of pioglitazone and metformin already being taken.
Use in pregnancy and lactation: Politor(pioglitazone and metformin) should not be used during pregnancy unless the potential benefit justifies the potential risk to the fetus. There are no adequate and well-controlled studies in pregnant women with combination of pioglitazone and metformin or its individual components. It is not known whether pioglitazone and/or metformin are secreted in human milk. Because many drugs are excreted in human milk, Politor should not be administered to a breastfeeding woman.
Precautions
Politor (pioglitazone and metformin) should not be used in patients with type I diabetes or for the treatment of diabetic ketoacidosis and should be used with caution in patients with edema. Serum ALT levels should be evaluated prior to the initiation of therapy with combination of pioglitazone and metformin in all patients and periodically thereafter per the clinical judgment of the health care professional.
Side-effects
The most common side-effects are upper respiratory tract infection, diarrhea, combined edema/peripheral edema and headache, respectively. Most clinical adverse events were similar between groups treated with pioglitazone in combination with metformin and those treated with pioglitazone monotherapy.
Contraindications
Politor (pioglitazone and metformin) is contraindicated in patients with known hypersensitivity to any components of this combination. These combination also contraindicated in renal disease which may also result from conditions, e.g., acute myocardial infarction, septicemia, acute or chronic metabolic acidosis, including diabetic ketoacidosis, with or without coma.
Drug interaction
Politor (pioglitazone and metformin) may interact with furosemide, nifedipine, cationic drugs (e.g., amiloride, digoxin, morphine, procainamide, quinidine, quinine, ranitidine, triamterene, trimethoprim, and vancomycin) and certain drugs tend to produce hyperglycemia and may lead to loss of glycemic control (e.g., thiazides and other diuretics, corticosteroids, phenothiazines, thyroid products, estrogens, oral contraceptives, phenytoin, nicotinic acid, sympathomimetics, calcium channel blocking drugs, and isoniazid). | Politor
Template:Wikify
Politor is the brand name of the Pioglitazone and Metformin combination preparation (Pioglitazone 15mg and Metformin 500mg tablet and Pioglitazone 15mg and Metformin 850mg tablet) from ACI Pharmaceuticals (Bangladesh). It is also available in Bangladesh under the brand name of Piomet (Silva Pharmaceuticals) and Rezulin (Square Pharmaceuticals). It is marketed in the USA by the originator Takeda Pharmaceuticals North America, Inc. under the brand name of Actoplus Met™.
Politor contains two oral antihyperglycemic agents (pioglitazone hydrochloride and metformin hydrochloride) with different mechanisms of action to improve glycemic control in patients with Diabetes mellitus type 2.
- Pioglitazone is a member of the thiazolidinedione class, decreases insulin resistance in the periphery and in the liver resulting in increased insulin dependent glucose disposal and decreased hepatic glucose output.
- Metformin is a member of the biguanide class, improves glucose tolerance in patients with type 2 diabetes, lowering both basal and postprandial plasma glucose. Metformin decreases hepatic glucose production, decreases intestinal absorption of glucose and improves insulin sensitivity by increasing peripheral glucose uptake and utilization.
Indication
Politor is indicated as an adjunct to diet and exercise:
- To improve glycemic control in patients with type 2 diabetes, or
- For patients who are already treated with a separate combination of pioglitazone and metformin,
- For patients whose diabetes is not adequately controlled with metformin alone, or
- For patients who have initially responded to pioglitazone alone and require additional glycemic control.
# Dosage and administration
Recommended dose
Use of antihyperglycemic agents in the management of type 2 diabetes should be individualized on the basis of effectiveness and tolerability.
Politor should be given with meals; the initial starting dose is either the 15mg/500mg or 15mg/850mg tablet strength once or twice daily, and gradually titrated after assessing adequacy of therapeutic response, while not exceeding the maximum recommended daily dose of pioglitazone 45mg and metformin 2550mg.
Starting dose for patients who initially responded to pioglitazone monotherapy and require additional glycemic control: Based on the usual starting doses of metformin (500mg twice daily or 850mg daily), Politor may be initiated at either the 15mg/500mg twice daily or 15mg/85mg once daily, and gradually titrated after assessing adequacy of therapeutic response.
Starting dose for patients inadequately controlled on metformin monotherapy: Based on the usual starting dose of pioglitazone (15-30mg daily), Politor may be initiated at either the 15mg/500mg or 15mg/850mg once or twice daily, and gradually titrated after assessing adequacy of therapeutic response.
Starting dose for patients switching from combination therapy of pioglitazone plus metformin as separate tablets: Politor may be initiated with either the 15mg/500mg or 15mg/850mg tablet strengths based on the dose of pioglitazone and metformin already being taken.
Use in pregnancy and lactation: Politor(pioglitazone and metformin) should not be used during pregnancy unless the potential benefit justifies the potential risk to the fetus. There are no adequate and well-controlled studies in pregnant women with combination of pioglitazone and metformin or its individual components. It is not known whether pioglitazone and/or metformin are secreted in human milk. Because many drugs are excreted in human milk, Politor should not be administered to a breastfeeding woman.
Precautions
Politor (pioglitazone and metformin) should not be used in patients with type I diabetes or for the treatment of diabetic ketoacidosis and should be used with caution in patients with edema. Serum ALT levels should be evaluated prior to the initiation of therapy with combination of pioglitazone and metformin in all patients and periodically thereafter per the clinical judgment of the health care professional.
Side-effects
The most common side-effects are upper respiratory tract infection, diarrhea, combined edema/peripheral edema and headache, respectively. Most clinical adverse events were similar between groups treated with pioglitazone in combination with metformin and those treated with pioglitazone monotherapy.
Contraindications
Politor (pioglitazone and metformin) is contraindicated in patients with known hypersensitivity to any components of this combination. These combination also contraindicated in renal disease which may also result from conditions, e.g., acute myocardial infarction, septicemia, acute or chronic metabolic acidosis, including diabetic ketoacidosis, with or without coma.
Drug interaction
Politor (pioglitazone and metformin) may interact with furosemide, nifedipine, cationic drugs (e.g., amiloride, digoxin, morphine, procainamide, quinidine, quinine, ranitidine, triamterene, trimethoprim, and vancomycin) and certain drugs tend to produce hyperglycemia and may lead to loss of glycemic control (e.g., thiazides and other diuretics, corticosteroids, phenothiazines, thyroid products, estrogens, oral contraceptives, phenytoin, nicotinic acid, sympathomimetics, calcium channel blocking drugs, and isoniazid). | https://www.wikidoc.org/index.php/Politor | |
3b5096727c76a33d5dfbb2bf8ccbf7a13740ba79 | wikidoc | Populus | Populus
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Populus is a genus of between 25–35 species of flowering plants in the family Salicaceae, native to most of the Northern Hemisphere. English names variously applied to different species include poplar, aspen, and cottonwood.
They are medium-sized to large or very large deciduous trees growing to 15–50 m tall, with trunks up to 2.5 m diameter. The bark on young trees is smooth, white to greenish or dark grey, often with conspicuous lenticels; on old trees it remains smooth in some species, but becomes rough and deeply fissured in others. The shoots are stout, with (unlike in the related willows) the terminal bud present. The leaves are spirally arranged, and vary in shape from triangular to circular or (rarely) lobed, and with a long petiole; in species in the sections Populus and Aegiros, the petioles are laterally flattened, so that breezes easily cause the leaves to wobble back and forth, giving the whole tree a "twinkling" appearance in a breeze. Leaf size is very variable even on a single tree, typically with small leaves on side shoots, and very large leaves on strong-growing lead shoots. The leaves often turn bright gold to yellow before they fall during autumn.
The flowers are mostly dioecious (rarely monoecious) and appear in early spring before the leaves. They are borne in long, drooping, sessile or pedunculate catkins produced from buds formed in the axils of the leaves of the previous year. The flowers are each seated in a cup-shaped disk which is borne on the base of a scale which is itself attached to the rachis of the catkin. The scales are obovate, lobed and fringed, membranous, hairy or smooth, usually caducous. The male flowers are without calyx or corolla, and comprise a group of 4–60 stamens inserted on a disk; filaments short, pale yellow; anthers oblong, purple or red, introrse, two-celled; cells opening longitudinally. The female flower also has no calyx or corolla, and comprises a single-celled ovary seated in a cup-shaped disk. The style is short, with 2–4 stigmas, variously lobed, and numerous ovules. Pollination is by wind, with the female catkins lengthening considerably between pollination and maturity. The fruit is a two to four-valved capsule, green to reddish-brown, mature in mid summer, containing numerous minute light brown seeds surrounded by tufts of long, soft, white hairs which aid wind dispersal.
Poplars of the cottonwood section are often wetlands or riparian trees. The aspens are among the most important boreal broadleaf trees.
Poplars and aspens are important food plants for the larvae of a large number of Lepidoptera species - see List of Lepidoptera that feed on poplars.
# Classification
The genus Populus has traditionally been divided into six sections on the basis of leaf and flower characters; this classification is followed below. Recent genetic studies have largely supported this, though showing that the relationships are somewhat more complex, with some reticulate evolution due to past hybridisation and introgression events between the groups; some species (noted below) had differing relationships indicated by their nuclear DNA (paternally inherited) and chloroplast DNA sequences (maternally inherited), a clear indication of likely hybrid origin. Hybridisation continues to be common in the genus, with several hybrids between species in different sections known.
- Populus section Populus - aspens and White Poplar. Circumpolar subarctic and cool temperate, and mountains farther south (White Poplar warm temperate)
Populus tremula - Common Aspen, Trembling Aspen or Eurasian Aspen. Europe, northern Asia. This is the type species of the genus.
Populus adenopoda - Chinese Aspen. Eastern Asia.
Populus alba - White Poplar. Southern Europe to central Asia.
Populus × canescens (P. alba × P. tremula) - Grey Poplar
Populus grandidentata - Bigtooth Aspen. Eastern North America.
Populus sieboldii - Japanese Aspen. Eastern Asia.
Populus tremuloides - Quaking Aspen or Trembling Aspen. North America.
- Populus tremula - Common Aspen, Trembling Aspen or Eurasian Aspen. Europe, northern Asia. This is the type species of the genus.
- Populus adenopoda - Chinese Aspen. Eastern Asia.
- Populus alba - White Poplar. Southern Europe to central Asia.
Populus × canescens (P. alba × P. tremula) - Grey Poplar
- Populus × canescens (P. alba × P. tremula) - Grey Poplar
- Populus grandidentata - Bigtooth Aspen. Eastern North America.
- Populus sieboldii - Japanese Aspen. Eastern Asia.
- Populus tremuloides - Quaking Aspen or Trembling Aspen. North America.
- Populus section Aegiros - black poplars or cottonwoods. North America, Europe, western Asia; temperate
Populus deltoides - Eastern Cottonwood. Eastern North America.
Populus fremontii - Fremont Cottonwood. Western North America.
Populus nigra - Black Poplar. Europe. Placed here by nuclear DNA; cpDNA places in sect. Populus.
Populus × canadensis (P. nigra × P. deltoides) - Hybrid Black Poplar
- Populus deltoides - Eastern Cottonwood. Eastern North America.
- Populus fremontii - Fremont Cottonwood. Western North America.
- Populus nigra - Black Poplar. Europe. Placed here by nuclear DNA; cpDNA places in sect. Populus.
Populus × canadensis (P. nigra × P. deltoides) - Hybrid Black Poplar
- Populus × canadensis (P. nigra × P. deltoides) - Hybrid Black Poplar
- Populus section Tacamahaca - balsam poplars. North America, Asia; cool temperate
Populus angustifolia - Willow-leaved Poplar or Narrowleaf Cottonwood. Central North America.
Populus balsamifera - Ontario Balsam Poplar. Northern North America.
Populus laurifolia - Laurel-leaf Poplar. Central Asia.
Populus maximowiczii - Maximowicz' Poplar. Northeast Asia.
Populus simonii - Simon's Poplar. Northeast Asia.
Populus szechuanica Northeast Asia. Placed here by nuclear DNA; cpDNA places in sect. Aegiros.
Populus trichocarpa - Western Balsam Poplar or Black Cottonwood. Western North America.
Populus tristis - Northeast Asia. Placed here by nuclear DNA; cpDNA places in sect. Aegiros.
- Populus angustifolia - Willow-leaved Poplar or Narrowleaf Cottonwood. Central North America.
- Populus balsamifera - Ontario Balsam Poplar. Northern North America.
- Populus laurifolia - Laurel-leaf Poplar. Central Asia.
- Populus maximowiczii - Maximowicz' Poplar. Northeast Asia.
- Populus simonii - Simon's Poplar. Northeast Asia.
- Populus szechuanica Northeast Asia. Placed here by nuclear DNA; cpDNA places in sect. Aegiros.
- Populus trichocarpa - Western Balsam Poplar or Black Cottonwood. Western North America.
- Populus tristis - Northeast Asia. Placed here by nuclear DNA; cpDNA places in sect. Aegiros.
- Populus section Leucoides - necklace poplars or bigleaf poplars. Eastern North America, eastern Asia; warm temperate
Populus heterophylla - Swamp Cottonwood. Southeastern North America.
Populus lasiocarpa - Chinese Necklace Poplar. Eastern Asia.
Populus wilsonii - Wilson's Poplar. Eastern Asia.
- Populus heterophylla - Swamp Cottonwood. Southeastern North America.
- Populus lasiocarpa - Chinese Necklace Poplar. Eastern Asia.
- Populus wilsonii - Wilson's Poplar. Eastern Asia.
- Populus section Turanga - subtropical poplars. Southwest Asia, east Africa; subtropical to tropical
Populus euphratica - Euphrates Poplar. Southwest Asia.
Populus ilicifolia - Tana River Poplar. East Africa.
- Populus euphratica - Euphrates Poplar. Southwest Asia.
- Populus ilicifolia - Tana River Poplar. East Africa.
- Populus section Abaso - Mexican poplars. Mexico; subtropical to tropical
Populus guzmanantlensis Mexico.
Populus mexicana - Mexico Poplar. Mexico.
- Populus guzmanantlensis Mexico.
- Populus mexicana - Mexico Poplar. Mexico.
In the September 2006 issue of Science, it was announced that Populus trichocarpa was the first tree to have its full DNA code sequenced.
# Cultivation and uses
Many poplars are grown as ornamental trees, with numerous cultivars selected. They have the advantage of growing very big very fast. Trees with fastigiate (erect, columnar) branching are particularly popular, and very widely grown across Europe and southwest Asia in particular. However, like willows, poplars have very vigorous and invasive root systems stretching up to 40 m from the trees; planting close to houses or ceramic water pipes may result in damaged foundations and cracked walls and pipes due to their search for moisture.
Fast-growing hybrid poplars are grown on plantations in many areas for pulpwood and used for the manufacture of paper. The wood is generally white, often with a slightly yellowish cast. It is also sold as inexpensive hardwood timber, used for pallets and cheap plywood; more specialised uses include matches and the boxes in which camembert cheese is sold. Poplar wood is widely used in the snowboard industry for the snowboard "core", because it has exceptional flexibility.
Poplar was the most common wood used in Italy for panel paintings; the Mona Lisa and indeed most famous early renaissance Italian paintings are on poplar.
Due to its tannic acid content, the bark has been used in Europe for tanning leather.
There has been some interest in using poplar as an energy crop for biofuel, particularly in light of its high energy in - energy out ratio, large carbon mitigation potential and fast growth.
Poplar wood also, particularly when seasoned, makes a good hearth for a bow drill. It was picked as the material for the bones of "Buster", the crash test dummy used in the TV show MythBusters, after some experiments revealed that it fractures under approximately the same loads as human bone. Poplar is sometimes used in the bodies of electric guitars and drums.
A folk tradition noted among Michigan miners in the early 20th century asserted that poplar wood was used to make the cross upon which Jesus Christ was crucified. | Populus
Template:Otheruses1
Lua error in Module:Redirect at line 65: could not parse redirect on page "Poplar".
Populus is a genus of between 25–35 species of flowering plants in the family Salicaceae, native to most of the Northern Hemisphere. English names variously applied to different species include poplar, aspen, and cottonwood.
They are medium-sized to large or very large deciduous trees growing to 15–50 m tall, with trunks up to 2.5 m diameter. The bark on young trees is smooth, white to greenish or dark grey, often with conspicuous lenticels; on old trees it remains smooth in some species, but becomes rough and deeply fissured in others. The shoots are stout, with (unlike in the related willows) the terminal bud present. The leaves are spirally arranged, and vary in shape from triangular to circular or (rarely) lobed, and with a long petiole; in species in the sections Populus and Aegiros, the petioles are laterally flattened, so that breezes easily cause the leaves to wobble back and forth, giving the whole tree a "twinkling" appearance in a breeze. Leaf size is very variable even on a single tree, typically with small leaves on side shoots, and very large leaves on strong-growing lead shoots. The leaves often turn bright gold to yellow before they fall during autumn.[1][2]
The flowers are mostly dioecious (rarely monoecious) and appear in early spring before the leaves. They are borne in long, drooping, sessile or pedunculate catkins produced from buds formed in the axils of the leaves of the previous year. The flowers are each seated in a cup-shaped disk which is borne on the base of a scale which is itself attached to the rachis of the catkin. The scales are obovate, lobed and fringed, membranous, hairy or smooth, usually caducous. The male flowers are without calyx or corolla, and comprise a group of 4–60 stamens inserted on a disk; filaments short, pale yellow; anthers oblong, purple or red, introrse, two-celled; cells opening longitudinally. The female flower also has no calyx or corolla, and comprises a single-celled ovary seated in a cup-shaped disk. The style is short, with 2–4 stigmas, variously lobed, and numerous ovules. Pollination is by wind, with the female catkins lengthening considerably between pollination and maturity. The fruit is a two to four-valved capsule, green to reddish-brown, mature in mid summer, containing numerous minute light brown seeds surrounded by tufts of long, soft, white hairs which aid wind dispersal.[1][3]
Poplars of the cottonwood section are often wetlands or riparian trees. The aspens are among the most important boreal broadleaf trees.[1]
Poplars and aspens are important food plants for the larvae of a large number of Lepidoptera species - see List of Lepidoptera that feed on poplars.
# Classification
The genus Populus has traditionally been divided into six sections on the basis of leaf and flower characters;[2][4] this classification is followed below. Recent genetic studies have largely supported this, though showing that the relationships are somewhat more complex, with some reticulate evolution due to past hybridisation and introgression events between the groups; some species (noted below) had differing relationships indicated by their nuclear DNA (paternally inherited) and chloroplast DNA sequences (maternally inherited), a clear indication of likely hybrid origin.[5] Hybridisation continues to be common in the genus, with several hybrids between species in different sections known.[1]
- Populus section Populus - aspens and White Poplar. Circumpolar subarctic and cool temperate, and mountains farther south (White Poplar warm temperate)
Populus tremula - Common Aspen, Trembling Aspen or Eurasian Aspen. Europe, northern Asia. This is the type species of the genus.
Populus adenopoda - Chinese Aspen. Eastern Asia.
Populus alba - White Poplar. Southern Europe to central Asia.
Populus × canescens (P. alba × P. tremula) - Grey Poplar
Populus grandidentata - Bigtooth Aspen. Eastern North America.
Populus sieboldii - Japanese Aspen. Eastern Asia.
Populus tremuloides - Quaking Aspen or Trembling Aspen. North America.
- Populus tremula - Common Aspen, Trembling Aspen or Eurasian Aspen. Europe, northern Asia. This is the type species of the genus.
- Populus adenopoda - Chinese Aspen. Eastern Asia.
- Populus alba - White Poplar. Southern Europe to central Asia.
Populus × canescens (P. alba × P. tremula) - Grey Poplar
- Populus × canescens (P. alba × P. tremula) - Grey Poplar
- Populus grandidentata - Bigtooth Aspen. Eastern North America.
- Populus sieboldii - Japanese Aspen. Eastern Asia.
- Populus tremuloides - Quaking Aspen or Trembling Aspen. North America.
- Populus section Aegiros[6] - black poplars or cottonwoods. North America, Europe, western Asia; temperate
Populus deltoides - Eastern Cottonwood. Eastern North America.
Populus fremontii - Fremont Cottonwood. Western North America.
Populus nigra - Black Poplar. Europe. Placed here by nuclear DNA; cpDNA places in sect. Populus.
Populus × canadensis (P. nigra × P. deltoides) - Hybrid Black Poplar
- Populus deltoides - Eastern Cottonwood. Eastern North America.
- Populus fremontii - Fremont Cottonwood. Western North America.
- Populus nigra - Black Poplar. Europe. Placed here by nuclear DNA; cpDNA places in sect. Populus.
Populus × canadensis (P. nigra × P. deltoides) - Hybrid Black Poplar
- Populus × canadensis (P. nigra × P. deltoides) - Hybrid Black Poplar
- Populus section Tacamahaca - balsam poplars. North America, Asia; cool temperate
Populus angustifolia - Willow-leaved Poplar or Narrowleaf Cottonwood. Central North America.
Populus balsamifera - Ontario Balsam Poplar. Northern North America.
Populus laurifolia - Laurel-leaf Poplar. Central Asia.
Populus maximowiczii - Maximowicz' Poplar. Northeast Asia.
Populus simonii - Simon's Poplar. Northeast Asia.
Populus szechuanica Northeast Asia. Placed here by nuclear DNA; cpDNA places in sect. Aegiros.
Populus trichocarpa - Western Balsam Poplar or Black Cottonwood. Western North America.
Populus tristis - Northeast Asia. Placed here by nuclear DNA; cpDNA places in sect. Aegiros.
- Populus angustifolia - Willow-leaved Poplar or Narrowleaf Cottonwood. Central North America.
- Populus balsamifera - Ontario Balsam Poplar. Northern North America.
- Populus laurifolia - Laurel-leaf Poplar. Central Asia.
- Populus maximowiczii - Maximowicz' Poplar. Northeast Asia.
- Populus simonii - Simon's Poplar. Northeast Asia.
- Populus szechuanica Northeast Asia. Placed here by nuclear DNA; cpDNA places in sect. Aegiros.
- Populus trichocarpa - Western Balsam Poplar or Black Cottonwood. Western North America.
- Populus tristis - Northeast Asia. Placed here by nuclear DNA; cpDNA places in sect. Aegiros.
- Populus section Leucoides - necklace poplars or bigleaf poplars. Eastern North America, eastern Asia; warm temperate
Populus heterophylla - Swamp Cottonwood. Southeastern North America.
Populus lasiocarpa - Chinese Necklace Poplar. Eastern Asia.
Populus wilsonii - Wilson's Poplar. Eastern Asia.
- Populus heterophylla - Swamp Cottonwood. Southeastern North America.
- Populus lasiocarpa - Chinese Necklace Poplar. Eastern Asia.
- Populus wilsonii - Wilson's Poplar. Eastern Asia.
- Populus section Turanga - subtropical poplars. Southwest Asia, east Africa; subtropical to tropical
Populus euphratica - Euphrates Poplar. Southwest Asia.
Populus ilicifolia - Tana River Poplar. East Africa.
- Populus euphratica - Euphrates Poplar. Southwest Asia.
- Populus ilicifolia - Tana River Poplar. East Africa.
- Populus section Abaso - Mexican poplars. Mexico; subtropical to tropical
Populus guzmanantlensis Mexico.
Populus mexicana - Mexico Poplar. Mexico.
- Populus guzmanantlensis Mexico.
- Populus mexicana - Mexico Poplar. Mexico.
In the September 2006 issue of Science, it was announced that Populus trichocarpa was the first tree to have its full DNA code sequenced.[7]
# Cultivation and uses
Many poplars are grown as ornamental trees, with numerous cultivars selected. They have the advantage of growing very big very fast. Trees with fastigiate (erect, columnar) branching are particularly popular, and very widely grown across Europe and southwest Asia in particular. However, like willows, poplars have very vigorous and invasive root systems stretching up to 40 m from the trees; planting close to houses or ceramic water pipes may result in damaged foundations and cracked walls and pipes due to their search for moisture.
Fast-growing hybrid poplars are grown on plantations in many areas for pulpwood and used for the manufacture of paper.[8] The wood is generally white, often with a slightly yellowish cast. It is also sold as inexpensive hardwood timber, used for pallets and cheap plywood; more specialised uses include matches and the boxes in which camembert cheese is sold. Poplar wood is widely used in the snowboard industry for the snowboard "core", because it has exceptional flexibility.
Poplar was the most common wood used in Italy for panel paintings; the Mona Lisa and indeed most famous early renaissance Italian paintings are on poplar.
Due to its tannic acid content, the bark has been used in Europe for tanning leather.[3]
There has been some interest in using poplar as an energy crop for biofuel, particularly in light of its high energy in - energy out ratio, large carbon mitigation potential and fast growth.
Poplar wood also, particularly when seasoned, makes a good hearth for a bow drill. It was picked as the material for the bones of "Buster", the crash test dummy used in the TV show MythBusters, after some experiments revealed that it fractures under approximately the same loads as human bone. Poplar is sometimes used in the bodies of electric guitars and drums.
A folk tradition noted among Michigan miners in the early 20th century asserted that poplar wood was used to make the cross upon which Jesus Christ was crucified.[9] | https://www.wikidoc.org/index.php/Poplar | |
da0326739ae6182d8a0359d0db73ec85065f757d | wikidoc | Prestin | Prestin
Prestin is a protein that is critical to sensitive hearing in mammals. It is encoded by the SLC26A5 (solute carrier anion transporter family 26, member 5) gene.
Prestin is the motor protein of the outer hair cells of the inner ear of the mammalian cochlea. It is highly expressed in the outer hair cells, and is not expressed in the nonmotile inner hair cells. Immunolocalization shows prestin is expressed in the lateral plasma membrane of the outer hair cells, the region where electromotility occurs. The expression pattern correlates with the appearance of outer hair cell electromotility.
# Function
Prestin is essential in auditory processing. It is specifically expressed in the lateral membrane of outer hair cells (OHCs) of the cochlea. There is no significant difference between prestin density in high-frequency and low-frequency regions of the cochlea in fully developed mammals. There is good evidence that prestin has undergone adaptive evolution in mammals associated with acquisition of high frequency hearing in mammals. The prestin protein shows several parallel amino acid replacements in bats and dolphins that have independently evolved ultrasonic hearing and echolocation, and it represents a rare case of convergent evolution at the sequence level.
Prestin (mol. wt. 80 kDa) is a member of a distinct family of anion transporters, SLC26. Members of this family are structurally well conserved and can mediate the electroneutral exchange of chloride and carbonate across the plasma membrane of mammalian cells, two anions found to be essential for outer hair cell motility. Unlike the classical, enzymatically driven motors, this new type of motor is based on direct voltage-to-displacement conversion and acts several orders of magnitude faster than other cellular motor proteins. A targeted gene disruption strategy of prestin showed a >100-fold (or 40 dB) loss of auditory sensitivity.
Prestin is a transmembrane protein that mechanically contracts and elongates leading to electromotility of outer hair cells (OHC). Electromotility is the driving force behind the somatic motor of the cochlear amplifier, which is a mammalian evolution that increases sensitivity to incoming sound wave frequencies and, thus, amplifies the signal. Previous research has suggested that this modulation takes place via an extrinsic voltage-sensor (partial anion transporter model), whereby chloride binds to the intracellular side of prestin and enters a defunct transporter, causing prestin elongation. However, there is new evidence that prestin acts through an intrinsic voltage-sensor (IVS) in which intracellular chloride binds allosterically to prestin to modify shape.
## Intrinsic voltage sensing
In this model of intrinsic voltage-sensing, the movement of ions generates a nonlinear capacitance (NLC). Based upon the generated voltage and the depolarized or hyperpolarized state of the cell, prestin will transition through two distinct steps, representing the three-state model of prestin modulation. Experiments show that with increasing depolarizing stimuli, prestin transitions from an elongated state to an intermediate state to a contracted state, increasing its NLC. Under hyperpolarizing conditions, NLC decreases and prestin transitions back to its elongated state. Of significance, increased membrane tension as characterized by prestin elongation decreases the chloride allosteric binding site affinity for chloride, perhaps playing a role in regulation of prestin modulation. The total estimated displacement of prestin upon modulation from elongated to contracted state is 3–4 nm2. A recent study supports the IVS model showing that mutations of 12 residues that span the intracellular side of prestin’s core membrane resulted in significant decrease in NLC. Eight of the 12 residues were positively charged and are hypothesized to make up the allosteric chloride binding site of prestin.
## Anion transport
Although previously thought to be absent, anion transport has also been shown to be an important aspect of prestin’s ability to drive electromotility of hair cells. This mechanism is independent of prestin’s voltage-sensing capabilities based upon mutagenesis experiments showing that different mutations lead to effects in either anion-uptake or NLC, but not both. It is suggested that prestin contains an intrinsic anion-uptake mechanism based upon research showing concentration dependent formate uptake in Chinese hamster ovary (CHO) cells. These results could not be reproduced in oocytes. Therefore, prestin may require an associated cofactor for anion uptake in oocytes; however, this hypothesis is still under question. Experiments have shown that various anions can compete for prestin uptake including malate, chloride, and alkylsulfonic anions.
# Discovery
Prestin was discovered by Peter Dallos's group in 2000 and named from the musical notation presto.
The prestin molecule was patented by its discoverers in 2003.
# Clinical significance
Mutations in the SLC26A5 gene have been associated with non-syndromic hearing loss.
# Blockers
Electromotile function of mammalian prestin is blocked by the amphiphilic anion salicylate at millimolar concentrations. Application of salicylate blocks prestin function in a dose-dependent and readily reversible manner. | Prestin
Prestin is a protein that is critical to sensitive hearing in mammals. It is encoded by the SLC26A5 (solute carrier anion transporter family 26, member 5) gene.[1][2]
Prestin is the motor protein of the outer hair cells of the inner ear of the mammalian cochlea.[1] It is highly expressed in the outer hair cells, and is not expressed in the nonmotile inner hair cells. Immunolocalization shows prestin is expressed in the lateral plasma membrane of the outer hair cells, the region where electromotility occurs. The expression pattern correlates with the appearance of outer hair cell electromotility.
# Function
Prestin is essential in auditory processing. It is specifically expressed in the lateral membrane of outer hair cells (OHCs) of the cochlea. There is no significant difference between prestin density in high-frequency and low-frequency regions of the cochlea in fully developed mammals.[3] There is good evidence that prestin has undergone adaptive evolution in mammals [4] associated with acquisition of high frequency hearing in mammals.[5] The prestin protein shows several parallel amino acid replacements in bats and dolphins that have independently evolved ultrasonic hearing and echolocation, and it represents a rare case of convergent evolution at the sequence level.[6]
Prestin (mol. wt. 80 kDa) is a member of a distinct family of anion transporters, SLC26. Members of this family are structurally well conserved and can mediate the electroneutral exchange of chloride and carbonate across the plasma membrane of mammalian cells, two anions found to be essential for outer hair cell motility. Unlike the classical, enzymatically driven motors, this new type of motor is based on direct voltage-to-displacement conversion and acts several orders of magnitude faster than other cellular motor proteins. A targeted gene disruption strategy of prestin showed a >100-fold (or 40 dB) loss of auditory sensitivity.[7]
Prestin is a transmembrane protein that mechanically contracts and elongates leading to electromotility of outer hair cells (OHC). Electromotility is the driving force behind the somatic motor of the cochlear amplifier, which is a mammalian evolution that increases sensitivity to incoming sound wave frequencies and, thus, amplifies the signal. Previous research has suggested that this modulation takes place via an extrinsic voltage-sensor (partial anion transporter model), whereby chloride binds to the intracellular side of prestin and enters a defunct transporter, causing prestin elongation.[8] However, there is new evidence that prestin acts through an intrinsic voltage-sensor (IVS) in which intracellular chloride binds allosterically to prestin to modify shape.[9][10]
## Intrinsic voltage sensing
In this model of intrinsic voltage-sensing, the movement of ions generates a nonlinear capacitance (NLC). Based upon the generated voltage and the depolarized or hyperpolarized state of the cell, prestin will transition through two distinct steps, representing the three-state model of prestin modulation.[11] Experiments show that with increasing depolarizing stimuli, prestin transitions from an elongated state to an intermediate state to a contracted state, increasing its NLC. Under hyperpolarizing conditions, NLC decreases and prestin transitions back to its elongated state. Of significance, increased membrane tension as characterized by prestin elongation decreases the chloride allosteric binding site affinity for chloride, perhaps playing a role in regulation of prestin modulation. The total estimated displacement of prestin upon modulation from elongated to contracted state is 3–4 nm2.[11] A recent study supports the IVS model showing that mutations of 12 residues that span the intracellular side of prestin’s core membrane resulted in significant decrease in NLC. Eight of the 12 residues were positively charged and are hypothesized to make up the allosteric chloride binding site of prestin.[9]
## Anion transport
Although previously thought to be absent, anion transport has also been shown to be an important aspect of prestin’s ability to drive electromotility of hair cells.[9][10] This mechanism is independent of prestin’s voltage-sensing capabilities based upon mutagenesis experiments showing that different mutations lead to effects in either anion-uptake or NLC, but not both.[9] It is suggested that prestin contains an intrinsic anion-uptake mechanism based upon research showing concentration dependent [14C]formate uptake in Chinese hamster ovary (CHO) cells. These results could not be reproduced in oocytes. Therefore, prestin may require an associated cofactor for anion uptake in oocytes; however, this hypothesis is still under question. Experiments have shown that various anions can compete for prestin uptake including malate, chloride, and alkylsulfonic anions.[9][12]
# Discovery
Prestin was discovered by Peter Dallos's group in 2000[1] and named from the musical notation presto.
The prestin molecule was patented by its discoverers in 2003.[13]
# Clinical significance
Mutations in the SLC26A5 gene have been associated with non-syndromic hearing loss.[2]
# Blockers
Electromotile function of mammalian prestin is blocked by the amphiphilic anion salicylate at millimolar concentrations. Application of salicylate blocks prestin function in a dose-dependent and readily reversible manner.[8] | https://www.wikidoc.org/index.php/Prestin | |
7f6f85afaaed0d2f30b86a3fc7bc0ff08a264773 | wikidoc | Pro-ana | Pro-ana
# Background
Pro-ana refers to a group or subculture that promotes or supports anorexia as a lifestyle choice rather than an eating disorder. Most pro-ana material is disseminated over the Internet, with web sites, discussion groups, and web rings dedicated to the movement.
The pro-ana viewpoint is controversial because it contradicts the prevailing psychological and medical consensus that treats anorexia nervosa as a mental illness rather than a "lifestyle choice". However, not all pro-ana groups follow this view. They state that pro-ana websites do not promote anorexia, and that anorexia is a real medical disorder. However, these groups may also promote recovery (by the use of support systems) while still supporting their peers to refuse medical or psychological treatment for the disorder.
# Overview
Since pro-ana is a loosely descriptive term rather than an organized social movement, the attitudes taken by self-proclaimed pro-ana individuals are not always comparable, and do not always reflect the definitions given on larger pro-ED (Eating Disorder) sites. The views range from denying anorexia as disease, to admitting that anorexia is a disease but stating that non-recovery from the disorder is a choice that should be respected by doctors and family. Still other pro-ED sites promote the decision to recover and offer support for those not ready to make that decision.
However, though many do claim to support those who are not ready for recovery, this form of support may include inviting members on fasting challenges, or encouraging others to harm themselves by emulating eating disordered behaviors.
# Thinspiration
In pro-ana online communities, pro-ana activity often takes the form of "thinspiration" (often known as "thinspo") pictures: images of slim women, often celebrities, meant to serve as inspiration for continuing to lose weight. Thinspiration pictures can vary in nature from images of naturally slim women to emaciated women with visible bones. Conversely, "reverse thinspiration" images are photographs of overweight or obese people, meant to disgust and therefore motivate further weight loss. Journal entries on pro-ana journals often contain thinspiration pictures, and many pro-ana forums have threads dedicated to sharing thinspiration.
Thinspiration can also take the form of quotes, songs or mantras.
# Criticism and controversy
Despite the pro-ana community's insistence that pro-ana sites give anorexics a place to turn to discuss their illness in a non-judgmental environment, doctors view the pro ana concept as "promot a myth that eating disorders are choices, rather than a physical and mental illness...Patients are supported in their illnesses and encouraged to stay ill by ". A 2006 Stanford study quoted in an issue of Newsweek published on the 18th of December 2006 found that "users of sites were sick longer...96 percent of reported learning new tips for weight loss or purging, and 69 percent said they used them." The Academy for Eating Disorders position statement on pro-anorexia web sites states that "websites that glorify anorexia as a lifestyle choice play directly to the psychology of its victims", expressing concern that sites dedicated to the promotion of anorexia as a desirable "lifestyle choice" "provide support and encouragement to engage in health threatening behaviors, and neglect the serious consequences of starvation." beat (Formally The Eating Disorder Association) states that the real danger of pro-ana sites comes when "a visitor affected by an eating disorder has at last found someone who really understands the way they feel about themselves... can help me avoid eating, avoid going to the doctor, or if I have to go, show me how to load up with water so my weight seems ok, or load my pockets with stones to have the same effect."
Pro-ana has also naturally spawned several grassroots opposition communities, such as the Anti-Ana community, and many satirical communities, such as Pro-Cancer or Pro-Scurvy.
The communities have also gained a response among "anti-pro-ana" LiveJournal users who have started communities such as Ed_ucate, a play on the common shorthand for eating disorder, ED. The purpose of these communities is to inform pro-anas about eating disordered criteria and the health effects of disordered behaviors so that they can make informed decisions and not spread misinformation. They also encourage accurate self-diagnosis using the DSM-IV-TR criteria. One of the effects of this response has been an increase in awareness about ED-NOS because many pro-anas are told that they do not meet the criteria for anorexia. Some communities also encourage members of pro-ana to go into recovery. However on August 7, 2007, at least two people speaking in an official capacity for LiveJournal declared that pro-ana communities on the site "do far more good than harm" and that "it's not illegal to aspire to be thin" in response to a user complaint that pro-ana communities violated LiveJournal's Terms of Service.
Pro-anorexia/ED has become somewhat of an underground crash diet amongst many teenage women who have not been able to properly stick to diets that have been healthy, or do not like the results they have had, thus they seem to believe that emulating eating disordered behaviors will promote more weight loss. This is usually one of the common causes of upset amongst "anti-pro-ana" as, usually, this group of individuals have been diagnosed with the illness medically, and are long term sufferers of the illness. Thus when viewing the pro-anorexia movement, those with anorexia nervosa feel it is a belittlement of a fatal condition; hence the usually angry response that is produced. | Pro-ana
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
# Background
Pro-ana refers to a group or subculture that promotes or supports anorexia as a lifestyle choice rather than an eating disorder. Most pro-ana material is disseminated over the Internet, with web sites, discussion groups, and web rings dedicated to the movement.
The pro-ana viewpoint is controversial because it contradicts the prevailing psychological and medical consensus that treats anorexia nervosa as a mental illness rather than a "lifestyle choice". However, not all pro-ana groups follow this view. They state that pro-ana websites do not promote anorexia, and that anorexia is a real medical disorder. However, these groups may also promote recovery (by the use of support systems) while still supporting their peers to refuse medical or psychological treatment for the disorder.
# Overview
Since pro-ana is a loosely descriptive term rather than an organized social movement, the attitudes taken by self-proclaimed pro-ana individuals are not always comparable, and do not always reflect the definitions given on larger pro-ED (Eating Disorder) sites. The views range from denying anorexia as disease, to admitting that anorexia is a disease but stating that non-recovery from the disorder is a choice that should be respected by doctors and family. Still other pro-ED sites promote the decision to recover and offer support for those not ready to make that decision.
However, though many do claim to support those who are not ready for recovery, this form of support may include inviting members on fasting challenges, or encouraging others to harm themselves by emulating eating disordered behaviors.
# Thinspiration
In pro-ana online communities, pro-ana activity often takes the form of "thinspiration" (often known as "thinspo") pictures: images of slim women, often celebrities, meant to serve as inspiration for continuing to lose weight. Thinspiration pictures can vary in nature from images of naturally slim women to emaciated women with visible bones. Conversely, "reverse thinspiration" images are photographs of overweight or obese people, meant to disgust and therefore motivate further weight loss. Journal entries on pro-ana journals often contain thinspiration pictures, and many pro-ana forums have threads dedicated to sharing thinspiration.
Thinspiration can also take the form of quotes, songs or mantras.
# Criticism and controversy
Despite the pro-ana community's insistence that pro-ana sites give anorexics a place to turn to discuss their illness in a non-judgmental environment, doctors view the pro ana concept as "promot[ing] a myth that eating disorders are choices, rather than a physical and mental illness...Patients are supported in their illnesses and encouraged to stay ill by [pro-ana websites]". [2] A 2006 Stanford study quoted in an issue of Newsweek published on the 18th of December 2006 found that "users of [pro-eating disorder] sites were sick longer...96 percent of [patients] reported learning new tips for weight loss or purging, and 69 percent said they used them." [1] The Academy for Eating Disorders position statement on pro-anorexia web sites states that "websites that glorify anorexia as a lifestyle choice play directly to the psychology of its victims", expressing concern that sites dedicated to the promotion of anorexia as a desirable "lifestyle choice" "provide support and encouragement to engage in health threatening behaviors, and neglect the serious consequences of starvation." [2] beat (Formally The Eating Disorder Association) states that the real danger of pro-ana sites comes when "a visitor affected by an eating disorder has at last found someone who really understands the way they feel about themselves...[The pro-ana community] can help me avoid eating, avoid going to the doctor, or if I have to go, show me how to load up with water so my weight seems ok, or load my pockets with stones to have the same effect." [3]
Pro-ana has also naturally spawned several grassroots opposition communities, such as the Anti-Ana community, and many satirical communities, such as Pro-Cancer [4] or Pro-Scurvy.
The communities have also gained a response among "anti-pro-ana" LiveJournal users who have started communities such as Ed_ucate, a play on the common shorthand for eating disorder, ED. The purpose of these communities is to inform pro-anas about eating disordered criteria and the health effects of disordered behaviors so that they can make informed decisions and not spread misinformation. They also encourage accurate self-diagnosis using the DSM-IV-TR criteria. One of the effects of this response has been an increase in awareness about ED-NOS because many pro-anas are told that they do not meet the criteria for anorexia. Some communities also encourage members of pro-ana to go into recovery. However on August 7, 2007, at least two people speaking in an official capacity for LiveJournal declared that pro-ana communities on the site "do far more good than harm" and that "it's not illegal to aspire to be thin" in response to a user complaint that pro-ana communities violated LiveJournal's Terms of Service[5].
Pro-anorexia/ED has become somewhat of an underground crash diet amongst many teenage women who have not been able to properly stick to diets that have been healthy, or do not like the results they have had, thus they seem to believe that emulating eating disordered behaviors will promote more weight loss. This is usually one of the common causes of upset amongst "anti-pro-ana" as, usually, this group of individuals have been diagnosed with the illness medically, and are long term sufferers of the illness. Thus when viewing the pro-anorexia movement, those with anorexia nervosa feel it is a belittlement of a fatal condition; hence the usually angry response that is produced. | https://www.wikidoc.org/index.php/Pro-ana | |
d42738b84153db83a7129d00da50ee0f2af1e7c8 | wikidoc | Prograf | Prograf
Please Take Over This Page and Apply to be Editor-In-Chief for this topic:
There can be one or more than one Editor-In-Chief. You may also apply to be an Associate Editor-In-Chief of one of the subtopics below. Please mail us to indicate your interest in serving either as an Editor-In-Chief of the entire topic or as an Associate Editor-In-Chief for a subtopic. Please be sure to attach your CV and or biographical sketch.
Tacrolimus (also FK-506 or Fujimycin) is an immunosuppressive drug whose main use is after allogenic organ transplant to reduce the activity of the patient's immune system and so the risk of organ rejection. It is also used in a topical preparation in the treatment of severe atopic dermatitis ("eczema"), severe refractory uveitis after bone marrow transplants, and the skin condition vitiligo. It is a 23-membered macrolide lactone discovered in 1984 from the fermentation broth of a Japanese soil sample that contained the bacteria Streptomyces tsukubaensis.
# History
Tacrolimus was discovered in 1987 by a Japanese team headed by T. Goto, T. Kino and H. Hatanaka; it was among the first macrolide immunosuppressants discovered, preceded by the discovery of rapamycin (sirolimus) on Rapa Nui (Easter Island) in 1975. Like ciclosporin, it was found in a soil fungus, although it is produced by a type of bacteria, Streptomyces tsukubaensis. The name tacrolimus is reportedly derived from 'Tsukuba macrolide immunosuppressant'.
The drug is owned by Astellas Pharma Inc. (Merging of Fujisawa Pharmaceutical Co.,Ltd.
and Yamanouchi Pharmaceutical Co., Ltd as of April 1, 2005) and is sold under the tradenames Prograf®, Advagraf and Protopic®. It is sometimes referred to as FK-506, an early name relating to its action. It was first approved by the Food and Drug Administration (FDA) in 1994 for use in liver transplantation, this has been extended to include kidney, heart, small bowel, pancreas, lung, trachea, skin, cornea, bone marrow, and limb transplants.
# Pharmacology
Tacrolimus is chemically known as a macrolide. It reduces peptidyl-prolyl isomerase activity by binding to the immunophilin FKBP-12 (FK506 binding protein) creating a new complex. This FKBP12-FK506 complex interacts with and inhibits calcineurin thus inhibiting both T-lymphocyte signal transduction and IL-2 transcription. Although this activity is similar to cyclosporin, studies have shown that the incidence of acute rejection is reduced by tacrolimus use over cyclosporin.
# Indications
## Immunosuppresion following transplantation
It has similar immunosuppressive properties to cyclosporin, but is much more potent in equal volumes. Also like cyclosporin it has a wide range of adverse interactions, including that with grapefruit which increases plasma-tacrolimus concentration. Several of the newer class of antifungals, especially of the azole class (fluconazole, posaconazole) also increase drug levels by competing for degradative enzymes. Immunosuppression with tacrolimus was associated with a significantly lower rate of acute rejection compared with cyclosporin-based immunosuppression (30.7% vs 46.4%) in one study.
## Use in treating ulcerative colitis
In recent years, Tacrolimus has been used to suppress the inflammation associated with ulcerative colitis, a form of inflammatory bowel disease. Although almost exclusively used in trial cases only, Tacrolimus has shown to be significantly effective in the suppression of outbreaks of UC.
## Dermatological use
See also: Immunomodulators in the treatment of eczema
As an ointment (Protopic®), tacrolimus is a recent addition in the treatment of eczema, particularly atopic dermatitis. It suppresses inflammation in a similar way to steroids, and is equally as effective as a mid-potency steroid. An important advantage of tacrolimus is that unlike steroids, it does not cause skin thinning (atrophy), or other steroid related side-effects. It may therefore be used continuously on the body (clinical trials of up to one year in length have occurred), and applied to the thinner skin over the face and eyelids.Recently it has also been used to treat segmental vitiligo in children,especially on the face.
The most common adverse events associated with the use of Protopic included the sensation of skin burning, pruritus, flu-like symptoms, and headache. The use of Protopic should be avoided on known or suspected malignant lesions. The use of Protopic on patients with Netherton's syndrome or similar skin diseases is not recommended. Patients should minimize or avoid natural or artificial sunlight exposure. Skin infections should be cleared prior to application, and there may be an increased risk of certain skin infections. Protopic should not be used with occlusive dressings (/)
# Contraindications and Precautions
- breast-feeding
- hepatic disease
- immunosuppression
- infants
- infection
- intravenous administration
- neoplastic disease
- occlusive dressing
- oliguria
- pregnancy
- QT prolongation
- skin cancer
- sunlight (UV) exposure
- grapefruit juice
# Side effects
## From oral and intravenous administration
Side effects can be severe and include blurred vision, liver and kidney problems (it is nephrotoxic), seizures, tremors, hypertension, hypomagnesemia, diabetes mellitus, hyperkalemia, itching, insomnia, confusion, loss of appetite, hyperglycemia, weakness, depression, cramps, and neuropathy, as well as potentially increasing the severity of existing fungal or infectious conditions such as herpes zoster or polyoma viral infections.
## From topical use
A common side effect of tacrolimus ointment, if used over a wide area, is to cause a burning or itching sensation on the first one or two applications. Less common side effects include flu-like symptoms, headache, cough and burning eyes.
## Cancer risks
Tacrolimus and a related drug for eczema (pimecrolimus) were suspected of carrying a cancer risk, though the matter is still a subject of controversy. The FDA issued a health warning in March 2005 for the drug, based on animal models and a small number of patients. Until further human studies yield more conclusive results, the FDA recommends that users be advised of the potential risks. Whereas current practice by UK dermatologists is not to consider this a significant real concern and they are increasingly recommending the use of these new drugs.
Dermatologists agree that the drug should be used as a second-line remedy only after conventional methods of treatment have failed. | Prograf
Please Take Over This Page and Apply to be Editor-In-Chief for this topic:
There can be one or more than one Editor-In-Chief. You may also apply to be an Associate Editor-In-Chief of one of the subtopics below. Please mail us [1] to indicate your interest in serving either as an Editor-In-Chief of the entire topic or as an Associate Editor-In-Chief for a subtopic. Please be sure to attach your CV and or biographical sketch.
Tacrolimus (also FK-506 or Fujimycin) is an immunosuppressive drug whose main use is after allogenic organ transplant to reduce the activity of the patient's immune system and so the risk of organ rejection. It is also used in a topical preparation in the treatment of severe atopic dermatitis ("eczema"), severe refractory uveitis after bone marrow transplants, and the skin condition vitiligo. It is a 23-membered macrolide lactone discovered in 1984 from the fermentation broth of a Japanese soil sample that contained the bacteria Streptomyces tsukubaensis.
# History
Tacrolimus was discovered in 1987 by a Japanese team headed by T. Goto, T. Kino and H. Hatanaka; it was among the first macrolide immunosuppressants discovered, preceded by the discovery of rapamycin (sirolimus) on Rapa Nui (Easter Island) in 1975.[1] Like ciclosporin, it was found in a soil fungus, although it is produced by a type of bacteria, Streptomyces tsukubaensis.[2] The name tacrolimus is reportedly derived from 'Tsukuba macrolide immunosuppressant'.
The drug is owned by Astellas Pharma Inc. (Merging of Fujisawa Pharmaceutical Co.,Ltd.
and Yamanouchi Pharmaceutical Co., Ltd as of April 1, 2005) and is sold under the tradenames Prograf®, Advagraf and Protopic®. It is sometimes referred to as FK-506, an early name relating to its action. It was first approved by the Food and Drug Administration (FDA) in 1994 for use in liver transplantation, this has been extended to include kidney, heart, small bowel, pancreas, lung, trachea, skin, cornea, bone marrow, and limb transplants.
# Pharmacology
Tacrolimus is chemically known as a macrolide. It reduces peptidyl-prolyl isomerase activity by binding to the immunophilin FKBP-12 (FK506 binding protein) creating a new complex. This FKBP12-FK506 complex interacts with and inhibits calcineurin thus inhibiting both T-lymphocyte signal transduction and IL-2 transcription.[3] Although this activity is similar to cyclosporin, studies have shown that the incidence of acute rejection is reduced by tacrolimus use over cyclosporin.[citation needed]
# Indications
## Immunosuppresion following transplantation
It has similar immunosuppressive properties to cyclosporin, but is much more potent in equal volumes. Also like cyclosporin it has a wide range of adverse interactions, including that with grapefruit which increases plasma-tacrolimus concentration. Several of the newer class of antifungals, especially of the azole class (fluconazole, posaconazole) also increase drug levels by competing for degradative enzymes. Immunosuppression with tacrolimus was associated with a significantly lower rate of acute rejection compared with cyclosporin-based immunosuppression (30.7% vs 46.4%) in one study.[4]
## Use in treating ulcerative colitis
In recent years, Tacrolimus has been used to suppress the inflammation associated with ulcerative colitis, a form of inflammatory bowel disease. Although almost exclusively used in trial cases only, Tacrolimus has shown to be significantly effective in the suppression of outbreaks of UC.
## Dermatological use
See also: Immunomodulators in the treatment of eczema
As an ointment (Protopic®), tacrolimus is a recent addition in the treatment of eczema, particularly atopic dermatitis. It suppresses inflammation in a similar way to steroids, and is equally as effective as a mid-potency steroid. An important advantage of tacrolimus is that unlike steroids, it does not cause skin thinning (atrophy), or other steroid related side-effects. It may therefore be used continuously on the body (clinical trials of up to one year in length have occurred), and applied to the thinner skin over the face and eyelids.Recently it has also been used to treat segmental vitiligo in children,especially on the face.[5]
The most common adverse events associated with the use of Protopic included the sensation of skin burning, pruritus, flu-like symptoms, and headache. The use of Protopic should be avoided on known or suspected malignant lesions. The use of Protopic on patients with Netherton's syndrome or similar skin diseases is not recommended. Patients should minimize or avoid natural or artificial sunlight exposure. Skin infections should be cleared prior to application, and there may be an increased risk of certain skin infections. Protopic should not be used with occlusive dressings (http://www.protopic.com/)
# Contraindications and Precautions
- breast-feeding
- hepatic disease
- immunosuppression
- infants
- infection
- intravenous administration
- neoplastic disease
- occlusive dressing
- oliguria
- pregnancy
- QT prolongation
- skin cancer
- sunlight (UV) exposure
- grapefruit juice[6]
# Side effects
## From oral and intravenous administration
Side effects can be severe and include blurred vision, liver and kidney problems (it is nephrotoxic), seizures, tremors, hypertension, hypomagnesemia, diabetes mellitus, hyperkalemia, itching, insomnia, confusion, loss of appetite, hyperglycemia, weakness, depression, cramps, and neuropathy, as well as potentially increasing the severity of existing fungal or infectious conditions such as herpes zoster or polyoma viral infections.
## From topical use
A common side effect of tacrolimus ointment, if used over a wide area, is to cause a burning or itching sensation on the first one or two applications. Less common side effects include flu-like symptoms, headache, cough and burning eyes.[7]
## Cancer risks
Tacrolimus and a related drug for eczema (pimecrolimus) were suspected of carrying a cancer risk, though the matter is still a subject of controversy. The FDA issued a health warning in March 2005 for the drug, based on animal models and a small number of patients. Until further human studies yield more conclusive results, the FDA recommends that users be advised of the potential risks. Whereas current practice by UK dermatologists is not to consider this a significant real concern and they are increasingly recommending the use of these new drugs.[8]
Dermatologists agree that the drug should be used as a second-line remedy only after conventional methods of treatment have failed. | https://www.wikidoc.org/index.php/Prograf | |
c0d0436272408a7c4fa70b81a42d21d703e99bfa | wikidoc | Prolene | Prolene
Please Take Over This Page and Apply to be Editor-In-Chief for this topic:
There can be one or more than one Editor-In-Chief. You may also apply to be an Associate Editor-In-Chief of one of the subtopics below. Please mail us to indicate your interest in serving either as an Editor-In-Chief of the entire topic or as an Associate Editor-In-Chief for a subtopic. Please be sure to attach your CV and or biographical sketch.
Prolene is a synthetic, nonabsorable polypropylene suture. It is indicated for skin closure and general soft tissue approximation and ligation. Its advantages include high tensile strength, minimal tissue reactivity, and slipperiness (allowing easy removal from tissues). Disadvantages include high plasticity, high expense, and difficulty of use compared to standard nylon sutures.
Composed of an isotactic crystalline stereoisomer of polypropylene, Prolene sutures are intended to be durable and long lasting. They are dyed blue, allowing for easy visibility against skin and when operating. It is composed of a single filiment.
A polypropylene mesh is also marketed under the name Prolene by Ethicon. It is used for repairing hernias and other iunjuries to the fascia.
Prolene commonly is used in both human and veterinary medicine for skin closure. In human mdeicine it is used in cardiovascular, ophthalmic and neurological procedures. It is often used in conjunction with the absorbable suture Monocryl. Prolene is manufactured by Ethicon Inc., a subsidiary of Johnson and Johnson. The name Prolene is a trademark of Ethicon Inc.
# See Also
- Monocryl
- Ethicon | Prolene
Please Take Over This Page and Apply to be Editor-In-Chief for this topic:
There can be one or more than one Editor-In-Chief. You may also apply to be an Associate Editor-In-Chief of one of the subtopics below. Please mail us [1] to indicate your interest in serving either as an Editor-In-Chief of the entire topic or as an Associate Editor-In-Chief for a subtopic. Please be sure to attach your CV and or biographical sketch.
Prolene is a synthetic, nonabsorable polypropylene suture. It is indicated for skin closure and general soft tissue approximation and ligation. Its advantages include high tensile strength, minimal tissue reactivity, and slipperiness (allowing easy removal from tissues). Disadvantages include high plasticity, high expense, and difficulty of use compared to standard nylon sutures.
Composed of an isotactic crystalline stereoisomer of polypropylene, Prolene sutures are intended to be durable and long lasting. They are dyed blue, allowing for easy visibility against skin and when operating. It is composed of a single filiment.
A polypropylene mesh is also marketed under the name Prolene by Ethicon. It is used for repairing hernias and other iunjuries to the fascia.
Prolene commonly is used in both human and veterinary medicine for skin closure. In human mdeicine it is used in cardiovascular, ophthalmic and neurological procedures. It is often used in conjunction with the absorbable suture Monocryl. Prolene is manufactured by Ethicon Inc., a subsidiary of Johnson and Johnson. The name Prolene is a trademark of Ethicon Inc.
# See Also
- Monocryl
- Ethicon
# External Links
- Ethicon Product Catalog
Template:SIB
Template:WH
Template:WS | https://www.wikidoc.org/index.php/Prolene | |
87d65b3a17d6d5b99f47a36a02aa642ad7df981a | wikidoc | Proser1 | Proser1
PROSER1 is a protein that in humans is encoded by the PROSER1 gene.
# Nomenclature
PROSER1 has several aliases: C13orf23, KIAA2032, and proline and serine-rich protein 1.
# Gene
## Location
PROSER1 is located on the negative (reverse) strand of chromosome 13 at position 13q13.3. It spans from 39,009,865 base pairs from the pter to 39,038,095 bp from the pter, with a size of 28,231 bases. PROSER1 has a total of 13 exons in its primary unspliced transcript mRNA of 5,185 bp. There are 2 isoforms of PROSER1, both within the 5,000 bp range.
## Gene neighborhood
Genes STOML3 and NHLRC3 neighbor PROSER1 on chromosome 13.
## Tissue distribution
Expressed Sequence Tag mapping of PROSER1 expression shows that it has particularly high expression in lymph, embryonic tissue, thymus, and uterus sites. It has moderate expression in testis, larynx, nerve, blood, and adipose tissue sites.
According to the Human Protein Atlas, PROSER1 has general cytoplasmic expression and is expressed in all RNA tissue categories.
# Homology
## Paralogs
PROSER1 has no paralogs.
## Orthologs
PROSER1 is highly conserved among mammals. It is less highly conserved, though has been found, in fish, birds, and some invertebrates. It is not expressed in bacteria, plants, or fungi. Show below is table of orthologs compiled from NCBI.
# Protein
## General properties
The translated PROSER1 protein is 944 amino acids long. Its predicted molecular weight is 95.7 kdal. PROSER1 has an isoelectric point of 9. It is predicted to be localized to the nucleus.
## Composition
The sequence is rich in proline and serine and not particularly low in any other amino acids.
## Domains
PROSER1 contains one domain of unknown function, DUF 4476, part of pfam14771. The DUF spans from amino acids 26 to 121.
The molecular weight of DUF 4476 is 11.1 kdal.
## Secondary structure
PROSER1 is composed primarily of alpha helices, beta sheets, and coils. The protein is largely coiled. The DUF is composed mainly of alpha helices and coils. It has slightly fewer beta sheets compared to the protein as a whole. | Proser1
PROSER1 is a protein that in humans is encoded by the PROSER1 gene.[1]
# Nomenclature
PROSER1 has several aliases: C13orf23, KIAA2032, and proline and serine-rich protein 1.[2]
[3]
# Gene
## Location
PROSER1 is located on the negative (reverse) strand of chromosome 13 at position 13q13.3. It spans from 39,009,865 base pairs from the pter to 39,038,095 bp from the pter, with a size of 28,231 bases.[4] PROSER1 has a total of 13 exons in its primary unspliced transcript mRNA of 5,185 bp. There are 2 isoforms of PROSER1, both within the 5,000 bp range.[5]
## Gene neighborhood
Genes STOML3 and NHLRC3 neighbor PROSER1 on chromosome 13.[6]
## Tissue distribution
Expressed Sequence Tag mapping of PROSER1 expression shows that it has particularly high expression in lymph, embryonic tissue, thymus, and uterus sites. It has moderate expression in testis, larynx, nerve, blood, and adipose tissue sites.[7]
According to the Human Protein Atlas, PROSER1 has general cytoplasmic expression and is expressed in all RNA tissue categories.[8]
# Homology
## Paralogs
PROSER1 has no paralogs.[9]
## Orthologs
PROSER1 is highly conserved among mammals. It is less highly conserved, though has been found, in fish, birds, and some invertebrates. It is not expressed in bacteria, plants, or fungi.[10] Show below is table of orthologs compiled from NCBI.
# Protein
## General properties
The translated PROSER1 protein is 944 amino acids long. Its predicted molecular weight is 95.7 kdal.[11] PROSER1 has an isoelectric point of 9.[12] It is predicted to be localized to the nucleus.[13]
## Composition
The sequence is rich in proline and serine and not particularly low in any other amino acids.
## Domains
PROSER1 contains one domain of unknown function, DUF 4476, part of pfam14771. The DUF spans from amino acids 26 to 121.[2]
The molecular weight of DUF 4476 is 11.1 kdal.
## Secondary structure
PROSER1 is composed primarily of alpha helices, beta sheets, and coils. The protein is largely coiled. The DUF is composed mainly of alpha helices and coils. It has slightly fewer beta sheets compared to the protein as a whole.[14] | https://www.wikidoc.org/index.php/Proser1 | |
9c0f5701a920e755e2891a9af767a0a00aec33e3 | wikidoc | Proteus | Proteus
# Overview
Proteus is a urease-producing, motile, nitrite-reducing, hydrogen sulfide-producing, catalase-positive, facultatively anaerobic, Gram-negative bacillus. It can be found in soil, water, and fecal matter. It inhabits the intestinal tracts of humans and animals, and is considered an opportunistic pathogen of humans. Transmission to the human host (usually urinary tract) typically occurs via self-contamination.
# Taxonomy
Kingdom: Bacteria; Phylum: Proteobacteria; Class: Gamma proteobacteria; Order: Enterobacteriales; Family: Enterobacteria; Genus: Proteus; Species: Proteus mirabilis
# Genome
- Proteus contains more than 3,658 coding sequences with 7 rRNA loci.
- Total genome length is 4.063 Mb (28.8% GC content).
- Proteus contains a single plasmid that contains 26,298 nucleotides.
# Microbiological Characteristics
- Proteus is a urease-producing, motile, nitrite-reducing, hydrogen sulfide-producing, catalase-positive, facultatively anaerobic, Gram-negative bacillus.
- It grows optimally at 40 °C (104 °F).
- It produces hydrogen sulfide gas, and forms clear films on growth media. It is motile, possessing peritrichous flagella, and is known for its swarming ability. It is commonly found in the intestinal tracts of humans. P. mirabilis is not pathogenic in guinea pigs or chickens.
- Characteristically, Proteus can inhibit the growth of other strains in culture media, resulting in a macroscopically visible line (Dienes line) of reduced bacterial growth where two swarming strains intersect.
- The following table summarizes the microbiological characteristics of Proteus:
# Natural Reservoir
- Proteus can be found in soil, water, and fecal matter.
- It inhabits the intestinal tracts of humans and animals, and is considered an opportunistic pathogen of humans.
# Transmission
- Proteus is usually transmitted to the human host by self-contamination (e.g. fecal material from gastrointestinal tract to genitourinary tract). | Proteus
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
# Overview
Proteus is a urease-producing, motile, nitrite-reducing, hydrogen sulfide-producing, catalase-positive, facultatively anaerobic, Gram-negative bacillus. It can be found in soil, water, and fecal matter. It inhabits the intestinal tracts of humans and animals, and is considered an opportunistic pathogen of humans. Transmission to the human host (usually urinary tract) typically occurs via self-contamination.
# Taxonomy
Kingdom: Bacteria; Phylum: Proteobacteria; Class: Gamma proteobacteria; Order: Enterobacteriales; Family: Enterobacteria; Genus: Proteus; Species: Proteus mirabilis
# Genome
- Proteus contains more than 3,658 coding sequences with 7 rRNA loci.[1]
- Total genome length is 4.063 Mb (28.8% GC content).[1]
- Proteus contains a single plasmid that contains 26,298 nucleotides.[1]
# Microbiological Characteristics
- Proteus is a urease-producing, motile, nitrite-reducing, hydrogen sulfide-producing, catalase-positive, facultatively anaerobic, Gram-negative bacillus.
- It grows optimally at 40 °C (104 °F).
- It produces hydrogen sulfide gas, and forms clear films on growth media. It is motile, possessing peritrichous flagella, and is known for its swarming ability. It is commonly found in the intestinal tracts of humans. P. mirabilis is not pathogenic in guinea pigs or chickens.
- Characteristically, Proteus can inhibit the growth of other strains in culture media, resulting in a macroscopically visible line (Dienes line) of reduced bacterial growth where two swarming strains intersect.
- The following table summarizes the microbiological characteristics of Proteus:
# Natural Reservoir
- Proteus can be found in soil, water, and fecal matter.
- It inhabits the intestinal tracts of humans and animals, and is considered an opportunistic pathogen of humans.
# Transmission
- Proteus is usually transmitted to the human host by self-contamination (e.g. fecal material from gastrointestinal tract to genitourinary tract). | https://www.wikidoc.org/index.php/Proteus | |
36376a530b88b5436eadcc84451fbe33688617c5 | wikidoc | Protist | Protist
Please Take Over This Page and Apply to be Editor-In-Chief for this topic:
There can be one or more than one Editor-In-Chief. You may also apply to be an Associate Editor-In-Chief of one of the subtopics below. Please mail us to indicate your interest in serving either as an Editor-In-Chief of the entire topic or as an Associate Editor-In-Chief for a subtopic. Please be sure to attach your CV and or biographical sketch.
Protists (Template:IPAEng), Greek protiston -a meaning the (most) first of all ones, are a diverse group of organisms, comprising those eukaryotes that cannot be classified in any of the other kingdoms as fungi, animals, or plants. They are usually treated as the kingdom Protista or Protoctista. Protoctists (or protists) are a paraphyletic grade, rather than a natural, (monophyletic) group, and so do not have much in common besides a relatively simple organization -- either they are unicellular, or they are multicellular without highly specialized tissues. The term protista was coined by Ernst Haeckel in 1866.
Protists were traditionally subdivided into several groups based on similarities to the "higher" kingdoms: the one-celled animal-like protozoa, the plant-like protophyta (mostly one-celled algae), and the fungus-like slime molds and water molds. Because these groups often overlap, they have been replaced by phylogenetic-based classifications. However, they are still useful as informal names for describing the morphology and ecology of protists.
At one time, the non-nucleated bacteria were also considered protists under the three-kingdom system of Animalia (comprising the many-celled animals or metazoans), Plantae (which then included fungi as well as green land plants), and Protista (which included everything else, except viruses). However, most current textbooks treat bacteria (and the newly-discovered archaea) as either a separate kingdom or domain.
# Obtaining nutrients
Protists obtain nutrients and digest nutrients in a complex acquirement and assimilation system. Most protists also feed on bacteria. Protists acquire their food material through internal digestion. They extend their cell wall and cell membrane around the food material to form a food vacuole in exocytosis and cytoplasmic metabolic ingestion, also sometimes pinocytosis. The food vacuole is used to paralyze the food material. It contains a grana-like texture that can support the use of toxins to paralyze organisms. The food vacuole extends from the prey to inside the protist's cytoplasm and the food material basically falls through the vacuole through gravity (similar to tropism in plants) and enters the cell.
A protist cell generally has an intestinal tract that is considerably small and is around the Golgi Apparatus. Once the food is into the cell, it can be used by ribosomes in the rough endoplasmic reticulum to be manufactured into proteins.
Nutrition in some different types of protists is variable. In flagellates, for example, filter feeding may sometimes occur where the flagella find the prey. In other multicellular protists, elements like nitrogen and oxygen is acquired by constant beating of the flagella. Protists often occur in hydrophilic conditions and thus have large amounts of oxygen within them, which is necessary for them to conduct respiration and photosynthesis to desirable levels.
# Organization
## Protozoa, the animal-like protists
Protozoa are mostly single-celled, motile protists that feed by phagocytosis, though there are numerous exceptions. They are usually only 0.01–0.5 mm in size, generally too small to be seen without magnification. Protozoa are grouped by method of locomotion into:
## Algae, the plant-like protists
They include many single-celled organisms that are also considered protozoa, such as Euglena, which many believe have acquired chloroplasts through secondary endosymbiosis. Others are non-motile, and some (called seaweeds) are truly multicellular, including members of the following groups:
The green and red algae, along with a small group called the glaucophytes, appear to be close relatives of other plants, and so some authors treat them as Plantae despite their simple organization. Most other types of algae, however, developed separately. They include the haptophytes, cryptomonads, dinoflagellates, euglenids, and chlorarachniophytes, all of which have also been considered protozoans.
Note some protozoa host endosymbiotic algae, as in Paramecium bursaria or radiolarians, that provide them with energy but are not integrated into the cell.
## Fungus-like protists
Various organisms with a protist-level organization were originally treated as fungi, because they produce sporangia. These include chytrids, slime moulds, water moulds, and Labyrinthulomycetes. Of these, the chytrids are now known to be related to other fungi and are usually classified with them. The others are now placed among the heterokonts (which have cellulose rather than chitin walls) and the Amoebozoa (which do not have cell walls).
# The term Protoctista
During the latter 20th century, the terms Protista, protist and protistan were increasingly used by biological scientists and laymen alike. Groups devoted to protistology emerged, while protozoology seemed to fade as an intellectual construct. In more recent years, however, the terms Protoctista, protoctist and protoctistan have been championed by some scholars in microbiology and micropaleontology. For example, the 50-volume Treatise on Invertebrate Paleontology -- eager to fill in the gaps left by vertebrate paleontology -- has moved from its 1953 (and onwards) use of Protista to the 21st-century use of Protoctista. So a Protist-Protoctist debate would seem to be inevitable.
The taxonomic category Protoctista was first coined by an English biologist, John Hogg, in an article entitled On the distinctions between a plant and an animal, and on a fourth kingdom of nature (1860). In this article, Hogg argued that the term Protoctist should be used to include "both the Protophyta ... and Protozoa". Therefore, he said, there should be a "fourth kingdom of nature" in addition to the then-traditional kingdoms of plants, animals and minerals. For nearly a century, however, his ideas were eclipsed by those of Haeckel, the reputed founder of protistology. Herbert F. Copeland resurrected Hogg's label almost a century later in his article, Progress report on basic classification (1947). Arguing that "Protoctista" literally meant "first established beings", Copeland complained that Haeckel's term included anucleated microbes such as bacteria. Copeland's use of the term did not.
In contrast, Copeland's term included nucleated eukaryotes such as brown and red algae -- but not the green algae, which he placed with the other green plants. Copeland further elaborated on his taxonomic proposal in his 1956 book, Classification of Lower Organisms (Palo Alto, California: Pacific Books). For a more recent delineation of the protoctists, see the Handbook of Protoctista (Boston: Jones & Bartlett) by Lynn Margulis, Heather I. McKhann, and Lorraine Olendzenski (1990).
# Phylogenetic classifications
The taxonomy of protists is still changing. Newer classifications attempt to present monophyletic groups based on ultrastructure, biochemistry, and genetics. Because the protists as a whole are paraphyletic, such systems often split up or abandon the kingdom, instead treating the protist groups as separate lines of eukaryotes. The recent scheme by Adl et al. (2005) is an example that does not bother with ranks (phylum, class, etc.).
Some of the main groups of protists, which may be treated as phyla, are listed in the taxobox at right. Most have been established as monophyletic, though for some this is still uncertain; for instance the metamonads, which may be paraphyletic to other excavates, and the Chromista, which may be paraphyletic to the alveolates (see chromalveolates). Various smaller groups of protists also existed; these are listed under the traditional categories, linked to above. | Protist
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Please Take Over This Page and Apply to be Editor-In-Chief for this topic:
There can be one or more than one Editor-In-Chief. You may also apply to be an Associate Editor-In-Chief of one of the subtopics below. Please mail us [2] to indicate your interest in serving either as an Editor-In-Chief of the entire topic or as an Associate Editor-In-Chief for a subtopic. Please be sure to attach your CV and or biographical sketch.
Protists (Template:IPAEng), Greek protiston -a meaning the (most) first of all ones, are a diverse group of organisms, comprising those eukaryotes that cannot be classified in any of the other kingdoms as fungi, animals, or plants. They are usually treated as the kingdom Protista or Protoctista. Protoctists (or protists) are a paraphyletic grade, rather than a natural, (monophyletic) group, and so do not have much in common besides a relatively simple organization -- either they are unicellular, or they are multicellular without highly specialized tissues. The term protista was coined by Ernst Haeckel in 1866.
Protists were traditionally subdivided into several groups based on similarities to the "higher" kingdoms: the one-celled animal-like protozoa, the plant-like protophyta (mostly one-celled algae), and the fungus-like slime molds and water molds. Because these groups often overlap, they have been replaced by phylogenetic-based classifications. However, they are still useful as informal names for describing the morphology and ecology of protists.
At one time, the non-nucleated bacteria were also considered protists under the three-kingdom system of Animalia (comprising the many-celled animals or metazoans), Plantae (which then included fungi as well as green land plants), and Protista (which included everything else, except viruses). However, most current textbooks treat bacteria (and the newly-discovered archaea) as either a separate kingdom or domain.
# Obtaining nutrients
Protists obtain nutrients and digest nutrients in a complex acquirement and assimilation system. Most protists also feed on bacteria. Protists acquire their food material through internal digestion. They extend their cell wall and cell membrane around the food material to form a food vacuole in exocytosis and cytoplasmic metabolic ingestion, also sometimes pinocytosis. The food vacuole is used to paralyze the food material. It contains a grana-like texture that can support the use of toxins to paralyze organisms. The food vacuole extends from the prey to inside the protist's cytoplasm and the food material basically falls through the vacuole through gravity (similar to tropism in plants) and enters the cell.
A protist cell generally has an intestinal tract that is considerably small and is around the Golgi Apparatus. Once the food is into the cell, it can be used by ribosomes in the rough endoplasmic reticulum to be manufactured into proteins.
Nutrition in some different types of protists is variable. In flagellates, for example, filter feeding may sometimes occur where the flagella find the prey. In other multicellular protists, elements like nitrogen and oxygen is acquired by constant beating of the flagella. Protists often occur in hydrophilic conditions and thus have large amounts of oxygen within them, which is necessary for them to conduct respiration and photosynthesis to desirable levels.
# Organization
## Protozoa, the animal-like protists
Protozoa are mostly single-celled, motile protists that feed by phagocytosis, though there are numerous exceptions. They are usually only 0.01–0.5 mm in size, generally too small to be seen without magnification. Protozoa are grouped by method of locomotion into:
## Algae, the plant-like protists
They include many single-celled organisms that are also considered protozoa, such as Euglena, which many believe have acquired chloroplasts through secondary endosymbiosis. Others are non-motile, and some (called seaweeds) are truly multicellular, including members of the following groups:
The green and red algae, along with a small group called the glaucophytes, appear to be close relatives of other plants, and so some authors treat them as Plantae despite their simple organization. Most other types of algae, however, developed separately. They include the haptophytes, cryptomonads, dinoflagellates, euglenids, and chlorarachniophytes, all of which have also been considered protozoans.
Note some protozoa host endosymbiotic algae, as in Paramecium bursaria or radiolarians, that provide them with energy but are not integrated into the cell.
## Fungus-like protists
Various organisms with a protist-level organization were originally treated as fungi, because they produce sporangia. These include chytrids, slime moulds, water moulds, and Labyrinthulomycetes. Of these, the chytrids are now known to be related to other fungi and are usually classified with them. The others are now placed among the heterokonts (which have cellulose rather than chitin walls) and the Amoebozoa (which do not have cell walls).
# The term Protoctista
During the latter 20th century, the terms Protista, protist and protistan were increasingly used by biological scientists and laymen alike. Groups devoted to protistology emerged, while protozoology seemed to fade as an intellectual construct. In more recent years, however, the terms Protoctista, protoctist and protoctistan have been championed by some scholars in microbiology and micropaleontology. For example, the 50-volume Treatise on Invertebrate Paleontology -- eager to fill in the gaps left by vertebrate paleontology -- has moved from its 1953 (and onwards) use of Protista to the 21st-century use of Protoctista. So a Protist-Protoctist debate would seem to be inevitable.
The taxonomic category Protoctista was first coined by an English biologist, John Hogg, in an article entitled On the distinctions between a plant and an animal, and on a fourth kingdom of nature (1860). In this article, Hogg argued that the term Protoctist should be used to include "both the Protophyta ... and Protozoa". Therefore, he said, there should be a "fourth kingdom of nature" in addition to the then-traditional kingdoms of plants, animals and minerals. For nearly a century, however, his ideas were eclipsed by those of Haeckel, the reputed founder of protistology. Herbert F. Copeland resurrected Hogg's label almost a century later in his article, Progress report on basic classification (1947). Arguing that "Protoctista" literally meant "first established beings", Copeland complained that Haeckel's term included anucleated microbes such as bacteria. Copeland's use of the term did not.
In contrast, Copeland's term included nucleated eukaryotes such as brown and red algae -- but not the green algae, which he placed with the other green plants. Copeland further elaborated on his taxonomic proposal in his 1956 book, Classification of Lower Organisms (Palo Alto, California: Pacific Books). For a more recent delineation of the protoctists, see the Handbook of Protoctista (Boston: Jones & Bartlett) by Lynn Margulis, Heather I. McKhann, and Lorraine Olendzenski (1990).
# Phylogenetic classifications
The taxonomy of protists is still changing. Newer classifications[1] attempt to present monophyletic groups based on ultrastructure, biochemistry, and genetics. Because the protists as a whole are paraphyletic, such systems often split up or abandon the kingdom, instead treating the protist groups as separate lines of eukaryotes. The recent scheme by Adl et al. (2005)[2] is an example that does not bother with ranks (phylum, class, etc.).
Some of the main groups of protists, which may be treated as phyla, are listed in the taxobox at right. Most have been established as monophyletic, though for some this is still uncertain; for instance the metamonads, which may be paraphyletic to other excavates, and the Chromista, which may be paraphyletic to the alveolates (see chromalveolates). Various smaller groups of protists also existed; these are listed under the traditional categories, linked to above. | https://www.wikidoc.org/index.php/Protist | |
8957501eea82bdf8abaeabe11e514143f6fb86eb | wikidoc | Psi-DOM | Psi-DOM
Ψ-DOM, or 2,6-dimethoxy-4-methylamphetamine, is a hallucinogenic drug and a structural isomer of the better-known hallucinogen DOM. Ψ-DOM was first reported by Alexander Shulgin in his book PIHKAL.
Ψ-DOM has similar effects to DOM, but is only around 1/3 - 1/2 the potency, with an active dose reported to be between 15-25 milligrams. The effects of Ψ-DOM last for around 6-8 hours.
The activity of Ψ-DOM (and Ψ-2C-T-4) demonstrates that the two methoxy groups on the psychedelic phenethylamines are not strictly limited to the 2,5 positions on the phenyl ring. Indeed any of the 2Cx or DOx series of drugs could alternatively be made as the 2,6 isomer and would still be expected to show similar activity, although slightly less potent. In theory this would vastly expand the range of different hallucinogens that could be derived from this family of drugs. The 2,6 isomer of another similar drug 2C-D-FLY (see 2C-B-FLY) has also been made by David Nichols and found to be active, this might by extension be referred to as Ψ-2C-D-FLY. | Psi-DOM
Ψ-DOM, or 2,6-dimethoxy-4-methylamphetamine, is a hallucinogenic drug and a structural isomer of the better-known hallucinogen DOM. Ψ-DOM was first reported by Alexander Shulgin in his book PIHKAL.
Ψ-DOM has similar effects to DOM, but is only around 1/3 - 1/2 the potency, with an active dose reported to be between 15-25 milligrams. The effects of Ψ-DOM last for around 6-8 hours.
The activity of Ψ-DOM (and Ψ-2C-T-4) demonstrates that the two methoxy groups on the psychedelic phenethylamines are not strictly limited to the 2,5 positions on the phenyl ring. Indeed any of the 2Cx or DOx series of drugs could alternatively be made as the 2,6 isomer and would still be expected to show similar activity, although slightly less potent. In theory this would vastly expand the range of different hallucinogens that could be derived from this family of drugs. The 2,6 isomer of another similar drug 2C-D-FLY (see 2C-B-FLY) has also been made by David Nichols and found to be active,[1] this might by extension be referred to as Ψ-2C-D-FLY. | https://www.wikidoc.org/index.php/Psi-DOM | |
e31cd42bc4b21c5a0dbe4fec51c4b91b0ab65200 | wikidoc | Pterion | Pterion
Please Take Over This Page and Apply to be Editor-In-Chief for this topic:
There can be one or more than one Editor-In-Chief. You may also apply to be an Associate Editor-In-Chief of one of the subtopics below. Please mail us to indicate your interest in serving either as an Editor-In-Chief of the entire topic or as an Associate Editor-In-Chief for a subtopic. Please be sure to attach your CV and or biographical sketch.
# Overview
The point corresponding with the posterior end of the sphenoparietal suture is named the pterion.
# Location
It is situated about 3 cm. behind, and a little above the level of the zygomatic process of the frontal bone.
It marks the junction between four bones:
- the parietal bone
- the temporal bone
- the sphenoid bone
- the frontal bone
# Clinical significance
The pterion is known as the weakest part of the skull.
Clinically, the pterion is relevant because the middle meningeal artery runs beneath it, on the inner side of the skull, which is quite thin at this point.
A blow to the pterion (e.g. in boxing) may rupture the artery causing an extradural haematoma.
# Etymology
The pterion receives its name from the Greek root pteron, meaning "wing".
In Greek mythology, Hermes, messenger of the Gods, was enabled to fly by winged sandals, and wings on his head, which were attached at the pterion. | Pterion
Template:Infobox Anatomy
Please Take Over This Page and Apply to be Editor-In-Chief for this topic:
There can be one or more than one Editor-In-Chief. You may also apply to be an Associate Editor-In-Chief of one of the subtopics below. Please mail us [1] to indicate your interest in serving either as an Editor-In-Chief of the entire topic or as an Associate Editor-In-Chief for a subtopic. Please be sure to attach your CV and or biographical sketch.
# Overview
The point corresponding with the posterior end of the sphenoparietal suture is named the pterion.
# Location
It is situated about 3 cm. behind, and a little above the level of the zygomatic process of the frontal bone.
It marks the junction between four bones:
- the parietal bone
- the temporal bone
- the sphenoid bone
- the frontal bone
# Clinical significance
The pterion is known as the weakest part of the skull.
Clinically, the pterion is relevant because the middle meningeal artery runs beneath it, on the inner side of the skull, which is quite thin at this point.
A blow to the pterion (e.g. in boxing) may rupture the artery causing an extradural haematoma.
# Etymology
The pterion receives its name from the Greek root pteron, meaning "wing".
In Greek mythology, Hermes, messenger of the Gods, was enabled to fly by winged sandals, and wings on his head, which were attached at the pterion.
# External links
- Diagram at shoshinryu.com
- Template:SUNYAnatomyFigs
- Diagram - look for #24 (source here)
- Template:EMedicineDictionary
Template:Gray's
Template:Sutures
Template:SIB
Template:WH
Template:WS | https://www.wikidoc.org/index.php/Pterion | |
9c17b2fdb5e29cd048c998c7aebb610c75938937 | wikidoc | Puffing | Puffing
Puffing is a technique to bring smoke (usually tobacco) into the mouth cavity. One hereby produces a negative pressure, so that the smoke arrives at the mucous membranes and to the taste receptors. In this way, nicotine is absorbed, and the flavors in the tar particles can be tasted.
After the time of moment of effect (from a few seconds at maximum), the smoke is blown out again. With cigars and pipes, one takes a draw every few minutes according to preference. Some smokers may choose to do so less often.
The smoke is mostly not directly inhaled into the lungs, as with tobacco smoking. When puffing, the taste is at the center of attention, which is why many varieties of tobacco are produced with added flavors and aromas such as vanilla.
de:Paffen | Puffing
Puffing is a technique to bring smoke (usually tobacco) into the mouth cavity. One hereby produces a negative pressure, so that the smoke arrives at the mucous membranes and to the taste receptors. In this way, nicotine is absorbed, and the flavors in the tar particles can be tasted.
After the time of moment of effect (from a few seconds at maximum), the smoke is blown out again. With cigars and pipes, one takes a draw every few minutes according to preference. Some smokers may choose to do so less often.
The smoke is mostly not directly inhaled into the lungs, as with tobacco smoking. When puffing, the taste is at the center of attention, which is why many varieties of tobacco are produced with added flavors and aromas such as vanilla.
de:Paffen | https://www.wikidoc.org/index.php/Puffing | |
251eb0deef868e248f89e13f974863ddc415e0d5 | wikidoc | Pumpkin | Pumpkin
Pumpkin is a gourd of the genus Cucurbita and the family Cucurbitaceae . It can refer to either species Cucurbita pepo or Cucurbita mixta, or possibly to a specific variety of either the species Cucurbita maxima or Cucurbita moschata.
# Description
Since some squash share the same botanical classifications as pumpkins, the names are frequently used interchangeably. In general, pumpkins have stems which are firmer, ridgid, pricker, have +/- a 5 degree angle, and squarer in shape than squash stems which are generally softer, more rounded, and more flared where joined to the fruit.
Pumpkins generally weigh 9–18 lbs (4–8 kg) with the largest (of the species c. maxima) capable of reaching over 75 lbs (34 kg) . The pumpkin varies greatly in shape, ranging from oblate through oblong. The rind is smooth and usually lightly ribbed .
Although pumpkins are usually orange or yellow , some fruits are dark green, pale green, orange-yellow, white, red and gray.
Pumpkins are angiosperms, having both male and female flowers, the latter distinguished by the small ovary at the base of the petals.
These bright and colorful flowers have extremely short life spans, and may only open for as short a time as one day. Their orange color is due to containing massive amounts of lutein, alpha- and beta-carotene. These nutrients turn to vitamin A in the body.
# Taxonomy
Pumpkin is a fruit of the species Cucurbita pepo or Cucurbita mixta. It can refer to a specific variety of the species Cucurbita maxima or Cucurbita moschata, which are all of the genus Cucurbita and the family Cucurbitaceae.
In Korea and Japan, the word translating to "pumpkin" is a slang term for an unattractive woman. In the American South and Midwest, however, the term "pumpkin" is sometimes used as an endearment.
# Distribution and Habitation
Although native to the Western hemisphere, pumpkins are cultivated in North America, continental Europe, Australia, New Zealand, India and some other countries. The pumpkin is the state fruit of New Hampshire.
# Ecology
## Cultivation in the US
Pumpkins have historically been pollinated by the native squash bee Peponapis pruinosa, but this bee has declined, probably due to pesticide sensitivity, and today most commercial plantings are pollinated by honeybees. One hive per acre (4,000 m² per hive) is recommended by the United States of America (US) Department of Agriculture. If there are inadequate bees for pollination, gardeners often have to hand pollinate. Inadequately pollinated pumpkins usually start growing but abort before full development. An opportunistic fungus is also sometimes blamed for abortions.
## Giant Pumpkins
Pumpkins are capable of growing extremely large with the proper attention and care. The world record pumpkin weighs 1689 lbs . The 2007 record pumpkin was grown in Rhode Island and weighed at the Topsfield Fair GPC in Topsfield, Massachusetts . The growth of enormous pumpkins being cultivated by hybridizing their seeds.
The largest pumpkins are Cucurbita maxima. They were culminated from the hubbard squash genotype, crossed with kabocha-pumpkin types by enthusiast farmers through intermittent effort since the early 1800s. As such germplasm is commercially provocative, a U.S. legal right was granted for the rounder phenotypes, levying them as constituting a variety, with the appellation "Atlantic Giant." Processually this phenotype graduated back into the public domain, except now it had the name Atlantic Giant on its record (see USDA PVP # 8500204).
# Uses
## Cooking
When ripe, the pumpkin is very versatile. It can be boiled, baked, or roasted. Often, it is made into various kinds of pie which is a traditional staple of the Canadian and American Thanksgiving holiday. Pumpkins that are still small and green may be eaten in the same way as the vegetable marrow/zucchini. Pumpkins can also be eaten mashed or incorporated into soup. If milk is poured into a pumpkin and then the pumpkin is baked, it can be made into a pudding. In the Middle East, pumpkin is used for sweet dishes; a well-known sweet delicacy is called halawa yaqtin. In South Asian countries like India, pumpkin is cooked with butter, sugar, and spices; this dish is called kadu ka halwa. In Australia, pumpkin is often roasted in conjunction with other vegetables. In Japan, small pumpkins are served in savory dishes, including tempura. In Thailand, small pumpkins are steamed with custard inside and served as a dessert. Finally, pumpkin can be used to flavor both alcoholic and nonalcoholic beverages.
## Pumpkin seeds
The hulled or semi-hulled seeds of pumpkins can be roasted and eaten as a snack, similar to the sunflower seed. Pumpkin seeds can be prepared for eating by first separating them from the orange pumpkin flesh, then coating them in a generally salty sauce (Worcestershire sauce, for example), after which the seeds are distributed upon a baking sheet, and then cooked in an oven at a relatively low temperature for a long period of time.
Pumpkin seeds are a good source of iron, zinc, essential fatty acids, potassium, and magnesium. Pumpkin seeds may also promote prostate health since components in pumpkin seed oil appear to interrupt the triggering of prostate cell multiplication by testosterone and DHT. Removing the white hull of the pumpkin seed reveals an edible, green-colored seed inside that is commonly referred to as a pepita in North and South America.
One gram of pumpkin seed protein contains as much tryptophan as a full glass of milk . Multiplying the number of fruiting sections in a field pumpkin (C. pepo variety) by 16 gives roughly the number of seeds in the pumpkin (give or take 10 or so). Guessing the number of seeds in the pumpkin is a game sometimes played by children.
Austria is a well-known producer of pumpkin seed oil.
# Activities involving pumpkins
## Halloween
Using pumpkins as lanterns during Halloween is based on an ancient Celtic custom brought to America by Irish immigrants. All Hallows Even was celebrated on 31 October and marked the New Year of the Celtic calendar year and the Festival of Samhain. On that night hollowed-out turnips, beets and rutabagas with candles inside them were placed on windowsills and porches to welcome home the spirits of deceased ancestors and ward off evil spirits and a restless soul called "Stingy Jack," hence the name "Jack-o-lantern".
On Halloween night, Linus Van Pelt of the comic strip Peanuts waits in a pumpkin patch for "the Great Pumpkin", a fictional pumpkin which had many of Santa Claus's characteristics. It seems, however, to exist only in his imagination.
## Chucking
Pumpkin chucking is a competitive activity in which teams build various mechanical devices designed to throw a pumpkin as far as possible. Catapults, trebuchets, ballistas and air cannons are the most common mechanisms. Some pumpkin chuckers breed and grow special varieties of pumpkin under specialized conditions in order to improve the pumpkin's chances of surviving a throw.
## Pumpkin festivals and competitions
Pumpkin growers often compete to see whose pumpkins are the most massive. Festivals are often dedicated to the pumpkin and these competitions.
Circleville, Ohio, holds a big festival each year, the Circleville Pumpkin Show. Half Moon Bay, California, holds the annual Pumpkin and Arts Festival, drawing over 250,000 visitors each year and including the World Champion Pumpkin Weigh-Off. Farmers from all over the west compete to determine who can grow the greatest gourd . The winning pumpkin regularly tops the scale at more than 1200 pounds. (The world record pumpkin in 2007 was grown by Joe Jutras in Topsfield, Massachusetts.) Morton, Illinois, the self-declared pumpkin capital of the world, has held a Pumpkin Festival since 1966. The town, where Nestlé's pumpkin packing plant is located (and where 90% of canned pumpkins eaten in the US are processed) carved and lit pumpkins in one place, a record which the town held for several years before losing it to Boston, Massachusetts in 2006. A large contributor of pumpkins to the festival is local Keene State College which hosts an event called "Pumpkin Lobotomy" on their main quad. Usually held the day before the festival itself, Pumpkin Lobotomy has the air of a large party, with the school providing pumpkins and carving instruments alike (though some students prefer to use their own) and music provided by college radio station, WKNH. | Pumpkin
Pumpkin is a gourd of the genus Cucurbita and the family Cucurbitaceae [1]. It can refer to either species Cucurbita pepo or Cucurbita mixta, or possibly to a specific variety of either the species Cucurbita maxima or Cucurbita moschata.
# Description
Since some squash share the same botanical classifications as pumpkins, the names are frequently used interchangeably. In general, pumpkins have stems which are firmer, ridgid, pricker, have +/- a 5 degree angle, and squarer in shape than squash stems which are generally softer, more rounded, and more flared where joined to the fruit. [2] [3]
Pumpkins generally weigh 9–18 lbs (4–8 kg) with the largest (of the species c. maxima) capable of reaching over 75 lbs (34 kg) [4]. The pumpkin varies greatly in shape, ranging from oblate through oblong. The rind is smooth and usually lightly ribbed [4].
Although pumpkins are usually orange or yellow [3] , some fruits are dark green, pale green, orange-yellow, white, red and gray.[citation needed]
Pumpkins are angiosperms, having both male and female flowers, the latter distinguished by the small ovary at the base of the petals.
These bright and colorful flowers have extremely short life spans, and may only open for as short a time as one day.[citation needed] Their orange color is due to containing massive amounts of lutein, alpha- and beta-carotene. These nutrients turn to vitamin A in the body.[citation needed]
# Taxonomy
Pumpkin is a fruit of the species Cucurbita pepo or Cucurbita mixta. It can refer to a specific variety of the species Cucurbita maxima or Cucurbita moschata, which are all of the genus Cucurbita and the family Cucurbitaceae. [1]
In Korea and Japan, the word translating to "pumpkin" is a slang term for an unattractive woman. In the American South and Midwest, however, the term "pumpkin" is sometimes used as an endearment.
# Distribution and Habitation
Although native to the Western hemisphere, pumpkins are cultivated in North America, continental Europe, Australia, New Zealand, India and some other countries.[citation needed] The pumpkin is the state fruit of New Hampshire.
# Ecology
## Cultivation in the US
Pumpkins have historically been pollinated by the native squash bee Peponapis pruinosa, but this bee has declined, probably due to pesticide sensitivity, and today most commercial plantings are pollinated by honeybees. One hive per acre (4,000 m² per hive) is recommended by the United States of America (US) Department of Agriculture. If there are inadequate bees for pollination, gardeners often have to hand pollinate. Inadequately pollinated pumpkins usually start growing but abort before full development. An opportunistic fungus is also sometimes blamed for abortions.
## Giant Pumpkins
Pumpkins are capable of growing extremely large with the proper attention and care. The world record pumpkin weighs 1689 lbs [5]. The 2007 record pumpkin was grown in Rhode Island and weighed at the Topsfield Fair GPC in Topsfield, Massachusetts [5]. The growth of enormous pumpkins being cultivated by hybridizing their seeds[citation needed].
The largest pumpkins are Cucurbita maxima. They were culminated from the hubbard squash genotype, crossed with kabocha-pumpkin types by enthusiast farmers through intermittent effort since the early 1800s. As such germplasm is commercially provocative, a U.S. legal right was granted for the rounder phenotypes, levying them as constituting a variety, with the appellation "Atlantic Giant." Processually this phenotype graduated back into the public domain, except now it had the name Atlantic Giant on its record (see USDA PVP # 8500204).
# Uses
## Cooking
Template:Nutritionalvalue
When ripe, the pumpkin is very versatile. It can be boiled, baked, or roasted. Often, it is made into various kinds of pie which is a traditional staple of the Canadian and American Thanksgiving holiday. Pumpkins that are still small and green may be eaten in the same way as the vegetable marrow/zucchini. Pumpkins can also be eaten mashed or incorporated into soup. If milk is poured into a pumpkin and then the pumpkin is baked, it can be made into a pudding[citation needed]. In the Middle East, pumpkin is used for sweet dishes; a well-known sweet delicacy is called halawa yaqtin. In South Asian countries like India, pumpkin is cooked with butter, sugar, and spices; this dish is called kadu ka halwa. In Australia, pumpkin is often roasted in conjunction with other vegetables. In Japan, small pumpkins are served in savory dishes, including tempura. In Thailand, small pumpkins are steamed with custard inside and served as a dessert. Finally, pumpkin can be used to flavor both alcoholic and nonalcoholic beverages.
## Pumpkin seeds
The hulled or semi-hulled seeds of pumpkins can be roasted and eaten as a snack, similar to the sunflower seed. Pumpkin seeds can be prepared for eating by first separating them from the orange pumpkin flesh, then coating them in a generally salty sauce (Worcestershire sauce, for example), after which the seeds are distributed upon a baking sheet, and then cooked in an oven at a relatively low temperature for a long period of time.
Pumpkin seeds are a good source of iron, zinc, essential fatty acids, potassium, and magnesium. Pumpkin seeds may also promote prostate health since components in pumpkin seed oil appear to interrupt the triggering of prostate cell multiplication by testosterone and DHT.[6] Removing the white hull of the pumpkin seed reveals an edible, green-colored seed inside that is commonly referred to as a pepita in North and South America.
One gram of pumpkin seed protein contains as much tryptophan as a full glass of milk [7]. Multiplying the number of fruiting sections in a field pumpkin (C. pepo variety) by 16 gives roughly the number of seeds in the pumpkin (give or take 10 or so). Guessing the number of seeds in the pumpkin is a game sometimes played by children.[citation needed]
Austria is a well-known producer of pumpkin seed oil.
# Activities involving pumpkins
## Halloween
Using pumpkins as lanterns during Halloween is based on an ancient Celtic custom brought to America by Irish immigrants.[citation needed] All Hallows Even was celebrated on 31 October and marked the New Year of the Celtic calendar year and the Festival of Samhain. On that night hollowed-out turnips, beets and rutabagas with candles inside them were placed on windowsills and porches[citation needed] to welcome home the spirits of deceased ancestors and ward off evil spirits and a restless soul called "Stingy Jack," hence the name "Jack-o-lantern".
On Halloween night, Linus Van Pelt of the comic strip Peanuts waits in a pumpkin patch for "the Great Pumpkin", a fictional pumpkin which had many of Santa Claus's characteristics. It seems, however, to exist only in his imagination.
## Chucking
Pumpkin chucking is a competitive activity in which teams build various mechanical devices designed to throw a pumpkin as far as possible. Catapults, trebuchets, ballistas and air cannons are the most common mechanisms. Some pumpkin chuckers breed and grow special varieties of pumpkin under specialized conditions in order to improve the pumpkin's chances of surviving a throw.
## Pumpkin festivals and competitions
Pumpkin growers often compete to see whose pumpkins are the most massive. Festivals are often dedicated to the pumpkin and these competitions.
Circleville, Ohio, holds a big festival each year, the Circleville Pumpkin Show. Half Moon Bay, California, holds the annual Pumpkin and Arts Festival, drawing over 250,000 visitors each year and including the World Champion Pumpkin Weigh-Off.[8] Farmers from all over the west compete to determine who can grow the greatest gourd [9]. The winning pumpkin regularly tops the scale at more than 1200 pounds. (The world record pumpkin in 2007 was grown by Joe Jutras in Topsfield, Massachusetts.[10]) Morton, Illinois, the self-declared pumpkin capital of the world,[11] has held a Pumpkin Festival since 1966. The town, where Nestlé's pumpkin packing plant is located (and where 90% of canned pumpkins eaten in the US are processed) carved and lit pumpkins in one place, a record which the town held for several years before losing it to Boston, Massachusetts in 2006. A large contributor of pumpkins to the festival is local Keene State College which hosts an event called "Pumpkin Lobotomy" on their main quad. Usually held the day before the festival itself, Pumpkin Lobotomy has the air of a large party, with the school providing pumpkins and carving instruments alike (though some students prefer to use their own) and music provided by college radio station, WKNH. | https://www.wikidoc.org/index.php/Pumpkin | |
c5ba6bde45ff6fa31334da188ddcce0db3b2053c | wikidoc | Quinine | Quinine
# Disclaimer
WikiDoc MAKES NO GUARANTEE OF VALIDITY. WikiDoc is not a professional health care provider, nor is it a suitable replacement for a licensed healthcare provider. WikiDoc is intended to be an educational tool, not a tool for any form of healthcare delivery. The educational content on WikiDoc drug pages is based upon the FDA package insert, National Library of Medicine content and practice guidelines / consensus statements. WikiDoc does not promote the administration of any medication or device that is not consistent with its labeling. Please read our full disclaimer here.
# Black Box Warning
# Overview
Quinine is a cinchona alkaloid, antimalarial and anti-Infective Agent, that is FDA approved for the treatment of of uncomplicated Plasmodium falciparum malaria. There is a Black Box Warning for this drug as shown here. Common adverse reactions include cinchonism include headache, vasodilation and sweating, nausea, tinnitus, hearing impairment, vertigo or dizziness, blurred vision, and disturbance in color perception..
# Adult Indications and Dosage
## FDA-Labeled Indications and Dosage (Adult)
- Quinine sulphate is an antimalarial drug indicated only for treatment of uncomplicated Plasmodium falciparum malaria. Quinine sulfate has been shown to be effective in geographical regions where resistance to chloroquine has been documented.
- Quinine sulphate oral capsules are not approved for:
- Treatment of severe or complicated P. falciparum malaria.
- Prevention of malaria.
- Treatment or prevention of nocturnal leg cramps
### Dosing Information
- Treatment of Uncomplicated P. falciparum malaria
- For treatment of uncomplicated P. falciparum malaria in adults: Orally, 648 mg (two capsules) every 8 hours for 7 days.
- Quinine sulphate should be taken with food to minimize gastric upset.
- In patients with acute uncomplicated malaria and severe chronic renal impairment, the following dosage regimen is recommended: one loading dose of 648 mg Quinine sulphate followed 12 hours later by maintenance doses of 324 mg every 12 hours.
- The effects of mild and moderate renal impairment on the safety and pharmacokinetics of quinine sulfate are not known.
- Adjustment of the recommended dose is not required in mild (Child-Pugh A) or moderate (Child-Pugh B) hepatic impairment, but patients should be monitored closely for adverse effects of quinine. Quinine should not be administered in patients with severe (Child-Pugh C) hepatic impairment.
## Off-Label Use and Dosage (Adult)
### Guideline-Supported Use
There is limited information regarding off-label use and dosage for adults.
### Non–Guideline-Supported Use
- Babesiosis
- Malaria, Uncomplicated, Plasmodium vivax
# Pediatric Indications and Dosage
## FDA-Labeled Indications and Dosage (Pediatric)
There is limited information regarding FDA-Labeled Use of Quinine sulphate in pediatric patients.
## Off-Label Use and Dosage (Pediatric)
### Guideline-Supported Use
There is limited information regarding Off-Label Guideline-Supported Use of Quinine sulphate in pediatric patients.
### Non–Guideline-Supported Use
There is limited information regarding Off-Label Non–Guideline-Supported Use of Quinine sulphate in pediatric patients.
# Contraindications
Quinine sulphate is contraindicated in patients with the following:
- One case of a fatal ventricular arrhythmia was reported in an elderly patient with a prolonged QT interval at baseline, who received quinine sulfate intravenously for P. falciparum malaria.
- Hemolysis can occur in patients with G6PD deficiency receiving quinine.
- These include, but are not limited to, the following:
- Thrombocytopenia
- Idiopathic thrombocytopenia purpura (ITP) and Thrombotic thrombocytopenic purpura (TTP)
Hemolytic uremic syndrome (HUS)
- Blackwater fever (acute intravascular hemolysis, hemoglobinuria, and hemoglobinemia)
- Known hypersensitivity to mefloquine or quinidine: cross-sensitivity to quinine has been documented.
- Myasthenia gravis. Quinine has neuromuscular blocking activity, and may exacerbate muscle weakness.
- Optic neuritis. Quinine may exacerbate active optic neuritis
# Warnings
### Use of Quinine for Treatment or Prevention of Nocturnal Leg Cramps:
- Quinine sulphate may cause unpredictable serious and life-threatening hematologic reactions including thrombocytopenia and hemolytic-uremic syndrome/thrombotic thrombocytopenic purpura (HUS/TTP) in addition to hypersensitivity reactions, QT prolongation, serious cardiac arrhythmias including torsades de pointes, and other serious adverse events requiring medical intervention and hospitalization. Chronic renal impairment associated with the development of TTP, and fatalities have also been reported. The risk associated with the use of Quinine sulphate in the absence of evidence of its effectiveness for treatment or prevention of nocturnal leg cramps, outweighs any potential benefit in treating and/or preventing this benign, self-limiting condition.
- Quinine-induced thrombocytopenia is an immune-mediated disorder. Severe cases of thrombocytopenia that are fatal or life threatening have been reported, including cases of HUS/TTP. Chronic renal impairment associated with the development of TTP has also been reported. Thrombocytopenia usually resolves within a week upon discontinuation of quinine. If quinine is not stopped, a patient is at risk for fatal hemorrhage. Upon re-exposure to quinine from any source, a patient with quinine-dependent antibodies could develop thrombocytopenia that is more rapid in onset and more severe than the original episode.
- QT interval prolongation has been a consistent finding in studies which evaluated electrocardiographic changes with oral or parenteral quinine administration, regardless of age, clinical status, or severity of disease. The maximum increase in QT interval has been shown to correspond with peak quinine plasma concentration. Quinine sulfate has been rarely associated with potentially fatal cardiac arrhythmias, including torsades de pointes, and ventricular fibrillation.
- Quinine sulphate has been shown to cause concentration-dependent prolongation of the PR and QRS interval. At particular risk are patients with underlying structural heart disease and preexisting conduction system abnormalities, elderly patients with sick sinus syndrome, patients with atrial fibrillation with slow ventricular response, patients with myocardial ischemia or patients receiving drugs known to prolong the PR interval (e.g. verapamil) or QRS interval (e.g. flecainide or quinidine).
- Quinine sulphate is not recommended for use with other drugs known to cause QT prolongation, including Class IA antiarrhythmic agents (e.g., quinidine, procainamide, disopyramide), and Class III antiarrhythmic agents (e.g., amiodarone, sotalol, dofetilide).
- The use of macrolide antibiotics such as erythromycin should be avoided in patients receiving Quinine sulphate. Fatal torsades de pointes was reported in an elderly patient who received concomitant quinine, erythromycin, and dopamine. Although a causal relationship between a specific drug and the arrhythmia was not established in this case, erythromycin is a CYP3A4 inhibitor and has been shown to increase quinine plasma levels when used concomitantly. A related macrolide antibiotic, troleandomycin, has also been shown to increase quinine exposure in a pharmacokinetic study.
- Quinine may inhibit the metabolism of certain drugs that are CYP3A4 substrates and are known to cause QT prolongation, e.g., astemizole, cisapride, terfenadine, pimozide, halofantrine and quinidine. Torsades de pointes has been reported in patients who received concomitant quinine and astemizole. Therefore, concurrent use of Quinine sulphate with these medications, or drugs with similar properties, should be avoided.
- Concomitant administration of Quinine sulphate with the antimalarial drugs, mefloquine or halofantrine, may result in electrocardiographic abnormalities, including QT prolongation, and increase the risk for torsades de pointes or other serious ventricular arrhythmias. Concurrent use of Quinine sulphate and mefloquine may also increase the risk of seizures.
- Quinine sulphate should also be avoided in patients with known prolongation of QT interval and in patients with clinical conditions known to prolong the QT interval, such as uncorrected hypokalemia, bradycardia, and certain cardiac conditions.
- Treatment failures may result from the concurrent use of rifampin with Quinine sulphate, due to decreased plasma concentrations of quinine, and concomitant use of these medications should be avoided.
- The use of neuromuscular blocking agents should be avoided in patients receiving Quinine sulphate. In one patient who received pancuronium during an operative procedure, subsequent administration of quinine resulted in respiratory depression and apnea. Although there are no clinical reports with succinylcholine or tubocurarine, quinine may also potentiate neuromuscular blockade when used with these drugs.
- Serious hypersensitivity reactions reported with quinine sulfate include anaphylactic shock, anaphylactoid reactions, urticaria, serious skin rashes, including Stevens-Johnson syndrome and toxic epidermal necrolysis, angioedema, facial edema, bronchospasm, and pruritus.
- A number of other serious adverse reactions reported with quinine, including thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS), thrombocytopenia, immune thrombocytopenic purpura (ITP), blackwater fever, disseminated intravascular coagulation, leukopenia, neutropenia, granulomatous hepatitis, and acute interstitial nephritis may also be due to hypersensitivity reactions.
- Quinine sulphate should be discontinued in case of any signs or symptoms of hypersensitivity.
- Quinine sulphate should be used with caution in patients with atrial fibrillation or atrial flutter. A paradoxical increase in ventricular response rate may occur with quinine, similar to that observed with quinidine. If digoxin is used to prevent a rapid ventricular response, serum digoxin levels should be closely monitored, because digoxin levels may be increased with use of quinine.
- Quinine stimulates release of insulin from the pancreas, and patients, especially pregnant women, may experience clinically significant hypoglycemia.
# Adverse Reactions
## Clinical Trials Experience
### Overall
- Quinine can adversely affect almost every body system. The most common adverse events associated with quinine use are a cluster of symptoms called "cinchonism", which occurs to some degree in almost all patients taking quinine. Symptoms of mild cinchonism include headache, vasodilation and sweating, nausea, tinnitus, hearing impairment, vertigo or dizziness, blurred vision, and disturbance in color perception. More severe symptoms of cinchonism are vomiting, diarrhea, abdominal pain, deafness, blindness, and disturbances in cardiac rhythm or conduction. Most symptoms of cinchonism are reversible and resolve with discontinuation of quinine.
- The following ADVERSE REACTIONS have been reported with quinine sulfate. Most of these reactions are thought to be uncommon, but the actual incidence is unknown:
- Fever, chills, sweating, flushing, asthenia, lupus-like syndrome, and hypersensitivity reactions.
- Agranulocytosis, hypoprothrombinemia, thrombocytopenia, disseminated intravascular coagulation, hemolytic anemia; hemolytic uremic syndrome, thrombotic thrombocytopenic purpura, idiopathic thrombocytopenic purpura, petechiae, ecchymosis, hemorrhage, coagulopathy, blackwater fever, leukopenia, neutropenia, pancytopenia, aplastic anemia, and lupus anticoagulant.
- Headache, diplopia, confusion, altered mental status, seizures, coma, disorientation, tremors, restlessness, ataxia, acute dystonic reaction, aphasia, and suicide.
- Cutaneous rashes, including urticarial, papular, or scarlatinal rashes, pruritus, bullous dermatitis, exfoliative dermatitis, erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis, fixed drug eruption, photosensitivity reactions, allergic contact dermatitis, acral necrosis, and cutaneous vasculitis.
- Asthma, dyspnea, pulmonary edema.
- Chest pain, vasodilatation, hypotension, postural hypotension, tachycardia, bradycardia, palpitations, syncope, atrioventricular block, atrial fibrillation, irregular rhythm, unifocal premature ventricular contractions, nodal escape beats, U waves, QT prolongation, ventricular fibrillation, ventricular tachycardia, torsades de pointes, and cardiac arrest.
- Nausea, vomiting, diarrhea, abdominal pain, gastric irritation, and esophagitis.
- Granulomatous hepatitis, hepatitis, jaundice, and abnormal liver function tests.
- Hypoglycemia and anorexia.
- Myalgias and muscle weakness.
- Hemoglobinuria, renal failure, renal impairment, and acute interstitial nephritis.
- Visual disturbances, including blurred vision with scotomata, sudden loss of vision, photophobia, diplopia, night blindness, diminished visual fields, fixed pupillary dilatation, disturbed color vision, optic neuritis, blindness, vertigo, tinnitus, hearing impairment, and deafness.
## Postmarketing Experience
There is limited information regarding Postmarketing Experience of Quinine sulphate in the drug label.
# Drug Interactions
There is limited information regarding Quinine Drug Interactions in the drug label.
# Use in Specific Populations
### Pregnancy
Pregnancy Category (FDA):
There is no FDA guidance on usage of Quinine in women who are pregnant.
Pregnancy Category (AUS):
There is no Australian Drug Evaluation Committee (ADEC) guidance on usage of Quinine in women who are pregnant.
### Labor and Delivery
There is no FDA guidance on use of Quinine during labor and delivery.
### Nursing Mothers
There is no FDA guidance on the use of Quinine in women who are nursing.
### Pediatric Use
There is no FDA guidance on the use of Quinine in pediatric settings.
### Geriatic Use
There is no FDA guidance on the use of Quinine in geriatric settings.
### Gender
There is no FDA guidance on the use of Quinine with respect to specific gender populations.
### Race
There is no FDA guidance on the use of Quinine with respect to specific racial populations.
### Renal Impairment
There is no FDA guidance on the use of Quinine in patients with renal impairment.
### Hepatic Impairment
There is no FDA guidance on the use of Quinine in patients with hepatic impairment.
### Females of Reproductive Potential and Males
There is no FDA guidance on the use of Quinine in women of reproductive potentials and males.
### Immunocompromised Patients
There is no FDA guidance one the use of Quinine in patients who are immunocompromised.
# Administration and Monitoring
### Administration
There is limited information regarding Quinine Administration in the drug label.
### Monitoring
There is limited information regarding Quinine Monitoring in the drug label.
# IV Compatibility
There is limited information regarding the compatibility of Quinine and IV administrations.
# Overdosage
There is limited information regarding Quinine overdosage. If you suspect drug poisoning or overdose, please contact the National Poison Help hotline (1-800-222-1222) immediately.
# Pharmacology
There is limited information regarding Quinine Pharmacology in the drug label.
## Mechanism of Action
There is limited information regarding Quinine Mechanism of Action in the drug label.
## Structure
There is limited information regarding Quinine Structure in the drug label.
## Pharmacodynamics
There is limited information regarding Quinine Pharmacodynamics in the drug label.
## Pharmacokinetics
There is limited information regarding Quinine Pharmacokinetics in the drug label.
## Nonclinical Toxicology
There is limited information regarding Quinine Nonclinical Toxicology in the drug label.
# Clinical Studies
There is limited information regarding Quinine Clinical Studies in the drug label.
# How Supplied
There is limited information regarding Quinine How Supplied in the drug label.
## Storage
There is limited information regarding Quinine Storage in the drug label.
# Images
## Drug Images
## Package and Label Display Panel
# Patient Counseling Information
There is limited information regarding Quinine Patient Counseling Information in the drug label.
# Precautions with Alcohol
Alcohol-Quinine interaction has not been established. Talk to your doctor about the effects of taking alcohol with this medication.
# Brand Names
There is limited information regarding Quinine Brand Names in the drug label.
# Look-Alike Drug Names
There is limited information regarding Quinine Look-Alike Drug Names in the drug label.
# Drug Shortage Status
# Price | Quinine
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Adeel Jamil, M.D. [2]
# Disclaimer
WikiDoc MAKES NO GUARANTEE OF VALIDITY. WikiDoc is not a professional health care provider, nor is it a suitable replacement for a licensed healthcare provider. WikiDoc is intended to be an educational tool, not a tool for any form of healthcare delivery. The educational content on WikiDoc drug pages is based upon the FDA package insert, National Library of Medicine content and practice guidelines / consensus statements. WikiDoc does not promote the administration of any medication or device that is not consistent with its labeling. Please read our full disclaimer here.
# Black Box Warning
# Overview
Quinine is a cinchona alkaloid, antimalarial and anti-Infective Agent, that is FDA approved for the treatment of of uncomplicated Plasmodium falciparum malaria. There is a Black Box Warning for this drug as shown here. Common adverse reactions include cinchonism include headache, vasodilation and sweating, nausea, tinnitus, hearing impairment, vertigo or dizziness, blurred vision, and disturbance in color perception..
# Adult Indications and Dosage
## FDA-Labeled Indications and Dosage (Adult)
- Quinine sulphate is an antimalarial drug indicated only for treatment of uncomplicated Plasmodium falciparum malaria. Quinine sulfate has been shown to be effective in geographical regions where resistance to chloroquine has been documented.
- Quinine sulphate oral capsules are not approved for:
- Treatment of severe or complicated P. falciparum malaria.
- Prevention of malaria.
- Treatment or prevention of nocturnal leg cramps
### Dosing Information
- Treatment of Uncomplicated P. falciparum malaria
- For treatment of uncomplicated P. falciparum malaria in adults: Orally, 648 mg (two capsules) every 8 hours for 7 days.
- Quinine sulphate should be taken with food to minimize gastric upset.
- In patients with acute uncomplicated malaria and severe chronic renal impairment, the following dosage regimen is recommended: one loading dose of 648 mg Quinine sulphate followed 12 hours later by maintenance doses of 324 mg every 12 hours.
- The effects of mild and moderate renal impairment on the safety and pharmacokinetics of quinine sulfate are not known.
- Adjustment of the recommended dose is not required in mild (Child-Pugh A) or moderate (Child-Pugh B) hepatic impairment, but patients should be monitored closely for adverse effects of quinine. Quinine should not be administered in patients with severe (Child-Pugh C) hepatic impairment.
## Off-Label Use and Dosage (Adult)
### Guideline-Supported Use
There is limited information regarding off-label use and dosage for adults.
### Non–Guideline-Supported Use
- Babesiosis
- Malaria, Uncomplicated, Plasmodium vivax
# Pediatric Indications and Dosage
## FDA-Labeled Indications and Dosage (Pediatric)
There is limited information regarding FDA-Labeled Use of Quinine sulphate in pediatric patients.
## Off-Label Use and Dosage (Pediatric)
### Guideline-Supported Use
There is limited information regarding Off-Label Guideline-Supported Use of Quinine sulphate in pediatric patients.
### Non–Guideline-Supported Use
There is limited information regarding Off-Label Non–Guideline-Supported Use of Quinine sulphate in pediatric patients.
# Contraindications
Quinine sulphate is contraindicated in patients with the following:
- One case of a fatal ventricular arrhythmia was reported in an elderly patient with a prolonged QT interval at baseline, who received quinine sulfate intravenously for P. falciparum malaria.
- Hemolysis can occur in patients with G6PD deficiency receiving quinine.
- These include, but are not limited to, the following:
- Thrombocytopenia
- Idiopathic thrombocytopenia purpura (ITP) and Thrombotic thrombocytopenic purpura (TTP)
Hemolytic uremic syndrome (HUS)
- Blackwater fever (acute intravascular hemolysis, hemoglobinuria, and hemoglobinemia)
- Known hypersensitivity to mefloquine or quinidine: cross-sensitivity to quinine has been documented.
- Myasthenia gravis. Quinine has neuromuscular blocking activity, and may exacerbate muscle weakness.
- Optic neuritis. Quinine may exacerbate active optic neuritis
# Warnings
### Use of Quinine for Treatment or Prevention of Nocturnal Leg Cramps:
- Quinine sulphate may cause unpredictable serious and life-threatening hematologic reactions including thrombocytopenia and hemolytic-uremic syndrome/thrombotic thrombocytopenic purpura (HUS/TTP) in addition to hypersensitivity reactions, QT prolongation, serious cardiac arrhythmias including torsades de pointes, and other serious adverse events requiring medical intervention and hospitalization. Chronic renal impairment associated with the development of TTP, and fatalities have also been reported. The risk associated with the use of Quinine sulphate in the absence of evidence of its effectiveness for treatment or prevention of nocturnal leg cramps, outweighs any potential benefit in treating and/or preventing this benign, self-limiting condition.
- Quinine-induced thrombocytopenia is an immune-mediated disorder. Severe cases of thrombocytopenia that are fatal or life threatening have been reported, including cases of HUS/TTP. Chronic renal impairment associated with the development of TTP has also been reported. Thrombocytopenia usually resolves within a week upon discontinuation of quinine. If quinine is not stopped, a patient is at risk for fatal hemorrhage. Upon re-exposure to quinine from any source, a patient with quinine-dependent antibodies could develop thrombocytopenia that is more rapid in onset and more severe than the original episode.
- QT interval prolongation has been a consistent finding in studies which evaluated electrocardiographic changes with oral or parenteral quinine administration, regardless of age, clinical status, or severity of disease. The maximum increase in QT interval has been shown to correspond with peak quinine plasma concentration. Quinine sulfate has been rarely associated with potentially fatal cardiac arrhythmias, including torsades de pointes, and ventricular fibrillation.
- Quinine sulphate has been shown to cause concentration-dependent prolongation of the PR and QRS interval. At particular risk are patients with underlying structural heart disease and preexisting conduction system abnormalities, elderly patients with sick sinus syndrome, patients with atrial fibrillation with slow ventricular response, patients with myocardial ischemia or patients receiving drugs known to prolong the PR interval (e.g. verapamil) or QRS interval (e.g. flecainide or quinidine).
- Quinine sulphate is not recommended for use with other drugs known to cause QT prolongation, including Class IA antiarrhythmic agents (e.g., quinidine, procainamide, disopyramide), and Class III antiarrhythmic agents (e.g., amiodarone, sotalol, dofetilide).
- The use of macrolide antibiotics such as erythromycin should be avoided in patients receiving Quinine sulphate. Fatal torsades de pointes was reported in an elderly patient who received concomitant quinine, erythromycin, and dopamine. Although a causal relationship between a specific drug and the arrhythmia was not established in this case, erythromycin is a CYP3A4 inhibitor and has been shown to increase quinine plasma levels when used concomitantly. A related macrolide antibiotic, troleandomycin, has also been shown to increase quinine exposure in a pharmacokinetic study.
- Quinine may inhibit the metabolism of certain drugs that are CYP3A4 substrates and are known to cause QT prolongation, e.g., astemizole, cisapride, terfenadine, pimozide, halofantrine and quinidine. Torsades de pointes has been reported in patients who received concomitant quinine and astemizole. Therefore, concurrent use of Quinine sulphate with these medications, or drugs with similar properties, should be avoided.
- Concomitant administration of Quinine sulphate with the antimalarial drugs, mefloquine or halofantrine, may result in electrocardiographic abnormalities, including QT prolongation, and increase the risk for torsades de pointes or other serious ventricular arrhythmias. Concurrent use of Quinine sulphate and mefloquine may also increase the risk of seizures.
- Quinine sulphate should also be avoided in patients with known prolongation of QT interval and in patients with clinical conditions known to prolong the QT interval, such as uncorrected hypokalemia, bradycardia, and certain cardiac conditions.
- Treatment failures may result from the concurrent use of rifampin with Quinine sulphate, due to decreased plasma concentrations of quinine, and concomitant use of these medications should be avoided.
- The use of neuromuscular blocking agents should be avoided in patients receiving Quinine sulphate. In one patient who received pancuronium during an operative procedure, subsequent administration of quinine resulted in respiratory depression and apnea. Although there are no clinical reports with succinylcholine or tubocurarine, quinine may also potentiate neuromuscular blockade when used with these drugs.
- Serious hypersensitivity reactions reported with quinine sulfate include anaphylactic shock, anaphylactoid reactions, urticaria, serious skin rashes, including Stevens-Johnson syndrome and toxic epidermal necrolysis, angioedema, facial edema, bronchospasm, and pruritus.
- A number of other serious adverse reactions reported with quinine, including thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS), thrombocytopenia, immune thrombocytopenic purpura (ITP), blackwater fever, disseminated intravascular coagulation, leukopenia, neutropenia, granulomatous hepatitis, and acute interstitial nephritis may also be due to hypersensitivity reactions.
- Quinine sulphate should be discontinued in case of any signs or symptoms of hypersensitivity.
- Quinine sulphate should be used with caution in patients with atrial fibrillation or atrial flutter. A paradoxical increase in ventricular response rate may occur with quinine, similar to that observed with quinidine. If digoxin is used to prevent a rapid ventricular response, serum digoxin levels should be closely monitored, because digoxin levels may be increased with use of quinine.
- Quinine stimulates release of insulin from the pancreas, and patients, especially pregnant women, may experience clinically significant hypoglycemia.
# Adverse Reactions
## Clinical Trials Experience
### Overall
- Quinine can adversely affect almost every body system. The most common adverse events associated with quinine use are a cluster of symptoms called "cinchonism", which occurs to some degree in almost all patients taking quinine. Symptoms of mild cinchonism include headache, vasodilation and sweating, nausea, tinnitus, hearing impairment, vertigo or dizziness, blurred vision, and disturbance in color perception. More severe symptoms of cinchonism are vomiting, diarrhea, abdominal pain, deafness, blindness, and disturbances in cardiac rhythm or conduction. Most symptoms of cinchonism are reversible and resolve with discontinuation of quinine.
- The following ADVERSE REACTIONS have been reported with quinine sulfate. Most of these reactions are thought to be uncommon, but the actual incidence is unknown:
- Fever, chills, sweating, flushing, asthenia, lupus-like syndrome, and hypersensitivity reactions.
- Agranulocytosis, hypoprothrombinemia, thrombocytopenia, disseminated intravascular coagulation, hemolytic anemia; hemolytic uremic syndrome, thrombotic thrombocytopenic purpura, idiopathic thrombocytopenic purpura, petechiae, ecchymosis, hemorrhage, coagulopathy, blackwater fever, leukopenia, neutropenia, pancytopenia, aplastic anemia, and lupus anticoagulant.
- Headache, diplopia, confusion, altered mental status, seizures, coma, disorientation, tremors, restlessness, ataxia, acute dystonic reaction, aphasia, and suicide.
- Cutaneous rashes, including urticarial, papular, or scarlatinal rashes, pruritus, bullous dermatitis, exfoliative dermatitis, erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis, fixed drug eruption, photosensitivity reactions, allergic contact dermatitis, acral necrosis, and cutaneous vasculitis.
- Asthma, dyspnea, pulmonary edema.
- Chest pain, vasodilatation, hypotension, postural hypotension, tachycardia, bradycardia, palpitations, syncope, atrioventricular block, atrial fibrillation, irregular rhythm, unifocal premature ventricular contractions, nodal escape beats, U waves, QT prolongation, ventricular fibrillation, ventricular tachycardia, torsades de pointes, and cardiac arrest.
- Nausea, vomiting, diarrhea, abdominal pain, gastric irritation, and esophagitis.
- Granulomatous hepatitis, hepatitis, jaundice, and abnormal liver function tests.
- Hypoglycemia and anorexia.
- Myalgias and muscle weakness.
- Hemoglobinuria, renal failure, renal impairment, and acute interstitial nephritis.
- Visual disturbances, including blurred vision with scotomata, sudden loss of vision, photophobia, diplopia, night blindness, diminished visual fields, fixed pupillary dilatation, disturbed color vision, optic neuritis, blindness, vertigo, tinnitus, hearing impairment, and deafness.
## Postmarketing Experience
There is limited information regarding Postmarketing Experience of Quinine sulphate in the drug label.
# Drug Interactions
There is limited information regarding Quinine Drug Interactions in the drug label.
# Use in Specific Populations
### Pregnancy
Pregnancy Category (FDA):
There is no FDA guidance on usage of Quinine in women who are pregnant.
Pregnancy Category (AUS):
There is no Australian Drug Evaluation Committee (ADEC) guidance on usage of Quinine in women who are pregnant.
### Labor and Delivery
There is no FDA guidance on use of Quinine during labor and delivery.
### Nursing Mothers
There is no FDA guidance on the use of Quinine in women who are nursing.
### Pediatric Use
There is no FDA guidance on the use of Quinine in pediatric settings.
### Geriatic Use
There is no FDA guidance on the use of Quinine in geriatric settings.
### Gender
There is no FDA guidance on the use of Quinine with respect to specific gender populations.
### Race
There is no FDA guidance on the use of Quinine with respect to specific racial populations.
### Renal Impairment
There is no FDA guidance on the use of Quinine in patients with renal impairment.
### Hepatic Impairment
There is no FDA guidance on the use of Quinine in patients with hepatic impairment.
### Females of Reproductive Potential and Males
There is no FDA guidance on the use of Quinine in women of reproductive potentials and males.
### Immunocompromised Patients
There is no FDA guidance one the use of Quinine in patients who are immunocompromised.
# Administration and Monitoring
### Administration
There is limited information regarding Quinine Administration in the drug label.
### Monitoring
There is limited information regarding Quinine Monitoring in the drug label.
# IV Compatibility
There is limited information regarding the compatibility of Quinine and IV administrations.
# Overdosage
There is limited information regarding Quinine overdosage. If you suspect drug poisoning or overdose, please contact the National Poison Help hotline (1-800-222-1222) immediately.
# Pharmacology
There is limited information regarding Quinine Pharmacology in the drug label.
## Mechanism of Action
There is limited information regarding Quinine Mechanism of Action in the drug label.
## Structure
There is limited information regarding Quinine Structure in the drug label.
## Pharmacodynamics
There is limited information regarding Quinine Pharmacodynamics in the drug label.
## Pharmacokinetics
There is limited information regarding Quinine Pharmacokinetics in the drug label.
## Nonclinical Toxicology
There is limited information regarding Quinine Nonclinical Toxicology in the drug label.
# Clinical Studies
There is limited information regarding Quinine Clinical Studies in the drug label.
# How Supplied
There is limited information regarding Quinine How Supplied in the drug label.
## Storage
There is limited information regarding Quinine Storage in the drug label.
# Images
## Drug Images
## Package and Label Display Panel
# Patient Counseling Information
There is limited information regarding Quinine Patient Counseling Information in the drug label.
# Precautions with Alcohol
Alcohol-Quinine interaction has not been established. Talk to your doctor about the effects of taking alcohol with this medication.
# Brand Names
There is limited information regarding Quinine Brand Names in the drug label.
# Look-Alike Drug Names
There is limited information regarding Quinine Look-Alike Drug Names in the drug label.
# Drug Shortage Status
# Price | https://www.wikidoc.org/index.php/QM-260 | |
c9bd372b34fbcd77a35491d4e028de68fd17d835 | wikidoc | Q cycle | Q cycle
# History
The Q cycle describes a series of reactions first proposed by Peter Mitchell that describe how the sequential oxidation and reduction of the lipophilic electron carrier, ubiquinol-ubiquinone (a.k.a. Coenzyme Q), can result in the net pumping of protons across a lipid bilayer (in the case of mitochondria, the inner mitochondrial membrane). A modified version of Mitchell's original scheme is now accepted as the mechanism by which Complex III pumps protons (i.e. how biochemical generation of ATP is achieved).
# Process
Operation of the modified Q cycle in Complex III results in the oxidation of Cytochrome c, reduction of ubiquinol to ubiquinone, and the transfer of four protons into the intermembrane space, per two-cycle process.
Ubiquinol (QH2) binds to the Qo site of complex III via hydrogen bonding to His181 of the Rieske iron-sulfur protein His181 and Glu272 of Cytochrome b. Ubiquinone (Q), in turn, binds the Qi site of complex III. Ubiquinol is divergently oxidized (gives up one electron each) to the Rieske iron-sulfur '(FeS) protein' and to the bL heme. This oxidation reaction produces a transient semiquinone before complete oxidation to ubiquinone, which then leaves the Qo site of complex III.
Having acquired one electron from ubiquinol, the 'FeS protein' is freed from its electron donor and is able to migrate to the Cytochrome c1 subunit. 'FeS protein' then donates its electron to Cytochrome c1, reducing its bound heme group. The electron is from there transferred to an oxidized molecule of Cytochrome c externally bound to complex III, which then dissociates from the complex. In addition, the reoxidation of the 'FeS protein' releases the proton bound to His181 into the intermembrane space.
The other electron, which was transferred to the bL heme, is used to reduce the bH heme, which in turn transfers the electron to the ubiquinone bound at the Qi site. The attached ubiquinone is thus reduced to a semiquinone radical. The proton taken up by Glu272 is subsequently transferred to a hydrogen-bonded water chain as Glu272 rotates 170° to hydrogen bond a water molecule, in turn hydrogen-bonded to a propionate of the bL heme.
Because the last step leaves a stable semiquinone at the Qi site, the reaction is not yet fully completed. A second Q cycle is necessary, with the second electron transfer from cytochrome bH reducing the semiquinone to ubiquinol. The ultimate products of the Q cycle are four protons entering the intermembrane space, two protons taken up from the matrix and the reduction of two molecules of cytochrome c. The reduced cytochrome c is eventually reoxidized by complex IV. The process is cyclic as the ubiquinone created at the Qi site can be reused by binding to the Qo site of complex III.
# Notes
- ↑ Zhang, Z., Huang, L., Schulmeister, V.M., Chi, Y.I., Kim, K.K., Hung, L.W., Crofts, A.R., Berry, E.A. and Kim, S.H. (1998) Nature 392, 677-684.
- ↑ Crofts, A.R., Hong, S., Ugulava, N., Barquera, B., Gennis, R., Guerrgova-Kuras, M. and Berry, E. (1999) Proc. Natl. Acad. Sci. USA 96, 10021-10026.
- ↑ Palsdottir, H., Gomez-Lojero, Trumpower, B.L. and Hunte, C. (2003) J. Biol. Chem., 31303-31311
# References and Reviews
- Trumpower, B.L. (2002) Biochim. Biophys. Acta 1555, 166-173
- Hunte, C., Palsdottir, H. and Trumpower, B.L. (2003) FEBS Letters 545, 39-46
- Trumpower, B.L. (1990) J. Biol. Chem., 11409-11412
de:Q-Zyklus | Q cycle
# History
The Q cycle describes a series of reactions first proposed by Peter Mitchell that describe how the sequential oxidation and reduction of the lipophilic electron carrier, ubiquinol-ubiquinone (a.k.a. Coenzyme Q), can result in the net pumping of protons across a lipid bilayer (in the case of mitochondria, the inner mitochondrial membrane). A modified version of Mitchell's original scheme is now accepted as the mechanism by which Complex III pumps protons (i.e. how biochemical generation of ATP is achieved).
# Process
Operation of the modified Q cycle in Complex III results in the oxidation of Cytochrome c, reduction of ubiquinol to ubiquinone, and the transfer of four protons into the intermembrane space, per two-cycle process.
Ubiquinol (QH2) binds to the Qo site of complex III via hydrogen bonding to His181 of the Rieske iron-sulfur protein His181 and Glu272 of Cytochrome b. Ubiquinone (Q), in turn, binds the Qi site of complex III. Ubiquinol is divergently oxidized (gives up one electron each) to the Rieske iron-sulfur '(FeS) protein' and to the bL heme. This oxidation reaction produces a transient semiquinone before complete oxidation to ubiquinone, which then leaves the Qo site of complex III.
Having acquired one electron from ubiquinol, the 'FeS protein' is freed from its electron donor and is able to migrate to the Cytochrome c1 subunit. 'FeS protein' then donates its electron to Cytochrome c1, reducing its bound heme group[1][2]. The electron is from there transferred to an oxidized molecule of Cytochrome c externally bound to complex III, which then dissociates from the complex. In addition, the reoxidation of the 'FeS protein' releases the proton bound to His181 into the intermembrane space.
The other electron, which was transferred to the bL heme, is used to reduce the bH heme, which in turn transfers the electron to the ubiquinone bound at the Qi site. The attached ubiquinone is thus reduced to a semiquinone radical. The proton taken up by Glu272 is subsequently transferred to a hydrogen-bonded water chain as Glu272 rotates 170° to hydrogen bond a water molecule, in turn hydrogen-bonded to a propionate of the bL heme[3].
Because the last step leaves a stable semiquinone at the Qi site, the reaction is not yet fully completed. A second Q cycle is necessary, with the second electron transfer from cytochrome bH reducing the semiquinone to ubiquinol. The ultimate products of the Q cycle are four protons entering the intermembrane space, two protons taken up from the matrix and the reduction of two molecules of cytochrome c. The reduced cytochrome c is eventually reoxidized by complex IV. The process is cyclic as the ubiquinone created at the Qi site can be reused by binding to the Qo site of complex III.
# Notes
- ↑ Zhang, Z., Huang, L., Schulmeister, V.M., Chi, Y.I., Kim, K.K., Hung, L.W., Crofts, A.R., Berry, E.A. and Kim, S.H. (1998) Nature 392, 677-684.
- ↑ Crofts, A.R., Hong, S., Ugulava, N., Barquera, B., Gennis, R., Guerrgova-Kuras, M. and Berry, E. (1999) Proc. Natl. Acad. Sci. USA 96, 10021-10026.
- ↑ Palsdottir, H., Gomez-Lojero, Trumpower, B.L. and Hunte, C. (2003) J. Biol. Chem., 31303-31311
# References and Reviews
- Trumpower, B.L. (2002) Biochim. Biophys. Acta 1555, 166-173
- Hunte, C., Palsdottir, H. and Trumpower, B.L. (2003) FEBS Letters 545, 39-46
- Trumpower, B.L. (1990) J. Biol. Chem., 11409-11412
de:Q-Zyklus
Template:WH
Template:WikiDoc Sources | https://www.wikidoc.org/index.php/Q_cycle | |
cbc7ba8c3f0dc46fce534cd20ba4b86cadbeb0ce | wikidoc | Quantum | Quantum
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In physics, a quantum (plural: quanta) is an indivisible entity of a quantity that has the same units as the Planck constant and is related to both energy and momentum of elementary particles of matter (called fermions) and of photons and other bosons. The word comes from the Latin "quantus," for "how much." Behind this, one finds the fundamental notion that a physical property may be "quantized", referred to as "quantization". This means that the magnitude can take on only certain discrete numerical values, rather than any value, at least within a range. There is a related term of quantum number.
A photon is often referred to as a "light quantum." The energy of an electron bound to an atom (at rest) is said to be quantized, which results in the stability of atoms, and of matter in general. But these terms can be a little misleading, because what is quantized is this Planck's constant quantity whose units can be viewed as either energy multiplied by time or momentum multiplied by distance.
Usually referred to as quantum "mechanics," it is regarded by virtually every professional physicist as the most fundamental framework we have for understanding and describing nature at the infinitesimal level, for the very practical reason that it works. It is "in the nature of things", not a more or less arbitrary human preference.
# Development of quantum theory
Quantum theory, the branch of physics which is based on quantization, began in 1900 when Max Planck published his theory explaining the emission spectrum of black bodies. In that paper Planck used the Natural system of units he invented the previous year.
The consequences of the differences between classical and quantum mechanics quickly became obvious. But it was not until 1926, by the work of Werner Heisenberg, Erwin Schrödinger, and others, that quantum mechanics became correctly formulated and understood mathematically. Despite tremendous experimental success, the philosophical interpretations of quantum theory are still widely debated.
Planck was reluctant to accept the new idea of quantization, as were many others. But, with no acceptable alternative, he continued to work with the idea, and found his efforts were well received. Eighteen years later, when he accepted the Nobel Prize in Physics for his contributions, he called it "a few weeks of the most strenuous work" of his life. During those few weeks, he even had to discard much of his own theoretical work from the preceding years. Quantization turned out to be the only way to describe the new and detailed experiments which were just then being performed. He did this practically overnight, openly reporting his change of mind to his scientific colleagues, in the October, November, and December meetings of the German Physical Society, in Berlin, where the black body work was being intensely discussed. In this way, careful experimentalists (including Friedrich Paschen, O.R. Lummer, Ernst Pringsheim, Heinrich Rubens, and F. Kurlbaum), and a reluctant theorist, ushered in a momentous scientific revolution.
## The quantum black-body radiation formula
When a body is heated, it emits radiant heat, a form of electromagnetic radiation in the infrared region of the EM spectrum. All of this was well understood at the time, and of considerable practical importance. When the body becomes red-hot, the red wavelength parts start to become visible. This had been studied over the previous years, as the instruments were being developed. However, most of the heat radiation remains infrared, until the body becomes as hot as the surface of the Sun (about 6000 °C, where most of the light is green in color). This was not achievable in the laboratory at that time. What is more, measuring specific infrared wavelengths was only then becoming feasible, due to newly developed experimental techniques. Until then, most of the electromagnetic spectrum was not measurable, and therefore blackbody emission had not been mapped out in detail.
The quantum black-body radiation formula, being the very first piece of quantum mechanics, appeared Sunday evening October 7, 1900, in a so-called back-of-the-envelope calculation by Planck. It was based on a report by Rubens (visiting with his wife) of the very latest experimental findings in the infrared. Later that evening, Planck sent the formula on a postcard, which Rubens received the following morning. A couple of days later, he informed Planck that it worked perfectly. At first, it was just a fit to the data; only later did it turn out to enforce quantization.
This second step was only possible due to a certain amount of luck (or skill, even though Planck himself called it "a fortuitous guess at an interpolation formula"). It was during the course of polishing the mathematics of his formula that Planck stumbled upon the beginnings of Quantum Theory. Briefly stated, he had two mathematical expressions:
- (i) from the previous work on the red parts of the spectrum, he had x;
- (ii) now, from the new infrared data, he got x².
Combining these as x(a+x), he still has x, approximately, when x is much smaller than a (the red end of the spectrum); but now also x² (again approximately) when x is much larger than a (in the infrared). The formula for the energy E, in a single mode of radiation at frequency λ, and temperature T, can be written
This is (essentially) what is being compared with the experimental measurements. There are two parameters to determine from the data, written in the present form by the symbols used today: h is the new Planck's constant, and k is Boltzmann's constant. Both have now become fundamental in physics, but that was by no means the case at the time. The "elementary quantum of energy" is hλ. But such a unit does not normally exist, and is not required for quantization.
# Beyond electromagnetic radiation
While quantization was first discovered in electromagnetic radiation, it describes a fundamental aspect of energy not just restricted to photons.
## The birthday of quantum mechanics
From the experiments, Planck deduced the numerical values of h and k. Thus he could report, in the German Physical Society meeting on December 14, 1900, where quantization (of energy) was revealed for the first time, values of the Avogadro-Loschmidt number, the number of real molecules in a mole, and the unit of electrical charge, which were more accurate than those known until then. This event has been referred to as "the birth of quantum mechanics". | Quantum
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Template:Nofootnotes
In physics, a quantum (plural: quanta) is an indivisible entity of a quantity that has the same units as the Planck constant and is related to both energy and momentum of elementary particles of matter (called fermions) and of photons and other bosons. The word comes from the Latin "quantus," for "how much." Behind this, one finds the fundamental notion that a physical property may be "quantized", referred to as "quantization". This means that the magnitude can take on only certain discrete numerical values, rather than any value, at least within a range. There is a related term of quantum number.
A photon is often referred to as a "light quantum." The energy of an electron bound to an atom (at rest) is said to be quantized, which results in the stability of atoms, and of matter in general. But these terms can be a little misleading, because what is quantized is this Planck's constant quantity whose units can be viewed as either energy multiplied by time or momentum multiplied by distance.
Usually referred to as quantum "mechanics," it is regarded by virtually every professional physicist as the most fundamental framework we have for understanding and describing nature at the infinitesimal level, for the very practical reason that it works. It is "in the nature of things", not a more or less arbitrary human preference.
# Development of quantum theory
Quantum theory, the branch of physics which is based on quantization, began in 1900 when Max Planck published his theory explaining the emission spectrum of black bodies. In that paper Planck used the Natural system of units he invented the previous year.
The consequences of the differences between classical and quantum mechanics quickly became obvious. But it was not until 1926, by the work of Werner Heisenberg, Erwin Schrödinger, and others, that quantum mechanics became correctly formulated and understood mathematically. Despite tremendous experimental success, the philosophical interpretations of quantum theory are still widely debated.
Planck was reluctant to accept the new idea of quantization, as were many others. But, with no acceptable alternative, he continued to work with the idea, and found his efforts were well received. Eighteen years later, when he accepted the Nobel Prize in Physics for his contributions, he called it "a few weeks of the most strenuous work" of his life. During those few weeks, he even had to discard much of his own theoretical work from the preceding years. Quantization turned out to be the only way to describe the new and detailed experiments which were just then being performed. He did this practically overnight, openly reporting his change of mind to his scientific colleagues, in the October, November, and December meetings of the German Physical Society, in Berlin, where the black body work was being intensely discussed. In this way, careful experimentalists (including Friedrich Paschen, O.R. Lummer, Ernst Pringsheim, Heinrich Rubens, and F. Kurlbaum), and a reluctant theorist, ushered in a momentous scientific revolution.
## The quantum black-body radiation formula
When a body is heated, it emits radiant heat, a form of electromagnetic radiation in the infrared region of the EM spectrum. All of this was well understood at the time, and of considerable practical importance. When the body becomes red-hot, the red wavelength parts start to become visible. This had been studied over the previous years, as the instruments were being developed. However, most of the heat radiation remains infrared, until the body becomes as hot as the surface of the Sun (about 6000 °C, where most of the light is green in color). This was not achievable in the laboratory at that time. What is more, measuring specific infrared wavelengths was only then becoming feasible, due to newly developed experimental techniques. Until then, most of the electromagnetic spectrum was not measurable, and therefore blackbody emission had not been mapped out in detail.
The quantum black-body radiation formula, being the very first piece of quantum mechanics, appeared Sunday evening October 7, 1900, in a so-called back-of-the-envelope calculation by Planck. It was based on a report by Rubens (visiting with his wife) of the very latest experimental findings in the infrared. Later that evening, Planck sent the formula on a postcard, which Rubens received the following morning. A couple of days later, he informed Planck that it worked perfectly. At first, it was just a fit to the data; only later did it turn out to enforce quantization.
This second step was only possible due to a certain amount of luck (or skill, even though Planck himself called it "a fortuitous guess at an interpolation formula"). It was during the course of polishing the mathematics of his formula that Planck stumbled upon the beginnings of Quantum Theory. Briefly stated, he had two mathematical expressions:
- (i) from the previous work on the red parts of the spectrum, he had x;
- (ii) now, from the new infrared data, he got x².
Combining these as x(a+x), he still has x, approximately, when x is much smaller than a (the red end of the spectrum); but now also x² (again approximately) when x is much larger than a (in the infrared). The formula for the energy E, in a single mode of radiation at frequency λ, and temperature T, can be written
This is (essentially) what is being compared with the experimental measurements. There are two parameters to determine from the data, written in the present form by the symbols used today: h is the new Planck's constant, and k is Boltzmann's constant. Both have now become fundamental in physics, but that was by no means the case at the time. The "elementary quantum of energy" is hλ. But such a unit does not normally exist, and is not required for quantization.
# Beyond electromagnetic radiation
While quantization was first discovered in electromagnetic radiation, it describes a fundamental aspect of energy not just restricted to photons.[1]
## The birthday of quantum mechanics
From the experiments, Planck deduced the numerical values of h and k. Thus he could report, in the German Physical Society meeting on December 14, 1900, where quantization (of energy) was revealed for the first time, values of the Avogadro-Loschmidt number, the number of real molecules in a mole, and the unit of electrical charge, which were more accurate than those known until then. This event has been referred to as "the birth of quantum mechanics". | https://www.wikidoc.org/index.php/Quanta | |
382f2c76a7c98353c3ede4b5ca0eef1a7ace13a1 | wikidoc | Quassia | Quassia
# Disclaimer
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NOTE: Most over the counter (OTC) are not reviewed and approved by the FDA. However, they may be marketed if they comply with applicable regulations and policies. FDA has not evaluated whether this product complies.
# Overview
Quassia is a OTC cream that is FDA approved for the treatment of head lice, pubic (crab lice) and body lice. Common adverse reactions include eye irritation, skin or scalp irritation.
# Adult Indications and Dosage
## FDA-Labeled Indications and Dosage (Adult)
### Indications
- treats head lice, pubic (crab lice) and body lice
### Dosage
- Important: Read warnings and full directions. For more information read the enclosed Consumer Information Leaflet.
- For adults and children 6 months and over.
- apply the entire contents of one tube thoroughly to dry hair, starting from behind the ears to the back of the neck, working forward.
- to be effective, all lice and eggs must come in contact with product, ensure hair and scalp are saturated. For long or very thick hair two tubes may be required.
- use the shower cap supplied to keep hair damp, leave on for 4 hours before washing.
- for serious infestation remove shower cap after 4 hours and leave product on overnight.
- wash area thoroughly with warm water and regular shampoo. Towel hair dry and comb out tangles using a regular comb or brush.
- as an option remove any remaining lice or nits with the included nit comb or fingernails.
- if hair dries during combing dampen slightly with water.
## Off-Label Use and Dosage (Adult)
### Guideline-Supported Use
There is limited information regarding Off-Label Guideline-Supported Use of Quassia in adult patients.
### Non–Guideline-Supported Use
There is limited information regarding Off-Label Non–Guideline-Supported Use of Quassia in adult patients.
# Pediatric Indications and Dosage
## FDA-Labeled Indications and Dosage (Pediatric)
### Dosage
- Important: Read warnings and full directions. For more information read the enclosed Consumer Information Leaflet.
- For adults and children 6 months and over.
- apply the entire contents of one tube thoroughly to dry hair, starting from behind the ears to the back of the neck, working forward.
- to be effective, all lice and eggs must come in contact with product, ensure hair and scalp are saturated. For long or very thick hair two tubes may be required.
- use the shower cap supplied to keep hair damp, leave on for 4 hours before washing.
- for serious infestation remove shower cap after 4 hours and leave product on overnight.
- wash area thoroughly with warm water and regular shampoo. Towel hair dry and comb out tangles using a regular comb or brush.
- as an option remove any remaining lice or nits with the included nit comb or fingernails.
- if hair dries during combing dampen slightly with water.
## Off-Label Use and Dosage (Pediatric)
### Guideline-Supported Use
There is limited information regarding Off-Label Guideline-Supported Use of Quassia in pediatric patients.
### Non–Guideline-Supported Use
There is limited information regarding Off-Label Non–Guideline-Supported Use of Quassia in pediatric patients.
# Contraindications
There is limited information regarding Quassia Contraindications in the drug label.
# Warnings
- For external use only.
- near eyes
- inside the nose, mouth or vagina
- on lice in eyebrows or eyelashes
- See a doctor if lice are present in these areas.
- keep tightly closed and protect eyes with a washcloth or towel.
- if product gets into the eyes, flush with water right away.
- eye irritation occurs
- skin or scalp irritation continues or infection occurs
- If swallowed, get medical help or contact a Poison Control Center right away.
# Adverse Reactions
## Clinical Trials Experience
- eye irritation
- skin or scalp irritation
## Postmarketing Experience
There is limited information regarding Postmarketing Experience of Quassia in the drug label.
# Drug Interactions
There is limited information regarding Quassia Drug Interactions in the drug label.
# Use in Specific Populations
### Pregnancy
Pregnancy Category (FDA):
- Pregnancy Category
Pregnancy Category (AUS):
- Australian Drug Evaluation Committee (ADEC) Pregnancy Category
There is no Australian Drug Evaluation Committee (ADEC) guidance on usage of Quassia in women who are pregnant.
### Labor and Delivery
There is no FDA guidance on use of Quassia during labor and delivery.
### Nursing Mothers
There is no FDA guidance on the use of Quassia with respect to nursing mothers.
### Pediatric Use
There is no FDA guidance on the use of Quassia with respect to pediatric patients.
### Geriatic Use
There is no FDA guidance on the use of Quassia with respect to geriatric patients.
### Gender
There is no FDA guidance on the use of Quassia with respect to specific gender populations.
### Race
There is no FDA guidance on the use of Quassia with respect to specific racial populations.
### Renal Impairment
There is no FDA guidance on the use of Quassia in patients with renal impairment.
### Hepatic Impairment
There is no FDA guidance on the use of Quassia in patients with hepatic impairment.
### Females of Reproductive Potential and Males
There is no FDA guidance on the use of Quassia in women of reproductive potentials and males.
### Immunocompromised Patients
There is no FDA guidance one the use of Quassia in patients who are immunocompromised.
# Administration and Monitoring
### Administration
- Topical application
### Monitoring
There is limited information regarding Monitoring of Quassia in the drug label.
# IV Compatibility
There is limited information regarding IV Compatibility of Quassia in the drug label.
# Overdosage
There is limited information regarding Overdose of Quassia in the drug label.
# Pharmacology
## Mechanism of Action
There is limited information regarding Quassia Mechanism of Action in the drug label.
## Structure
- ACTIVE INGREDIENTS
- Quassia amara 2X HPUS (Amargo 200mcg/g)
- INACTIVE INGREDIENTS
- aqua, cetearyl alcohol, dimethicone, fragrance, cetrimonium bromide, citric acid
## Pharmacodynamics
There is limited information regarding Pharmacodynamics of Quassia in the drug label.
## Pharmacokinetics
There is limited information regarding Pharmacokinetics of Quassia in the drug label.
## Nonclinical Toxicology
There is limited information regarding Nonclinical Toxicology of Quassia in the drug label.
# Clinical Studies
There is limited information regarding Clinical Studies of Quassia in the drug label.
# How Supplied
There is limited information regarding Quassia How Supplied in the drug label.
## Storage
- keep carton for important product information
- protect from excessive heat
# Images
## Drug Images
## Package and Label Display Panel
### PACKAGING INFORMATION
Quit Nits®
Caring for your child, naturally
2.03 FL OZ (60mL)
ADVANCE
Kills head lice and eggs with one application
WILD CHILD®
Born, not made.
Ingredients Incl: Aqua, cetearyl alcohol, dimethicone, fragrance, cetrimonium bromide, citric acid, quassia wood jamaican extract.
4 simple steps to help eliminate Head Lice Infestation:
APPLY - Massage cream through dry hair and onto scalp, ensuring all of the hair and the back of the neck is wet with product.
COVER - Use shower cap supplied to keep hair damp and leave on for 4 hours. For serious infestation remove cap and leave treatment on overnight.
WASH - after 4 hours use your regular shampoo to remove the product. Any remaining lice and eggs should be removed with fingernails.
FOLLOW-UP try Quit Nits Every Day Lice Preventative Spray to limit re-infestation.
For external use only. Avoid contact with eyes. If product gets into eyes, rinse well with water. If irritation occurs, discontinue use.
Manufactured for:
Wild Child (US) Pty Ltd
by The Triad Group
Hartland, WI 53029
[email protected]
For batch and expiry date see crimp
### Ingredients and Appearance
# Patient Counseling Information
800-961-4936 or
[email protected]
www.QuitNits.com
# Precautions with Alcohol
- Alcohol-Quassia interaction has not been established. Talk to your doctor about the effects of taking alcohol with this medication.
# Brand Names
- QUIT NITS ADVANCE®
# Look-Alike Drug Names
There is limited information regarding Quassia Look-Alike Drug Names in the drug label.
# Drug Shortage Status
# Price | Quassia
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Rabin Bista, M.B.B.S. [2]
# Disclaimer
WikiDoc MAKES NO GUARANTEE OF VALIDITY. WikiDoc is not a professional health care provider, nor is it a suitable replacement for a licensed healthcare provider. WikiDoc is intended to be an educational tool, not a tool for any form of healthcare delivery. The educational content on WikiDoc drug pages is based upon the FDA package insert, National Library of Medicine content and practice guidelines / consensus statements. WikiDoc does not promote the administration of any medication or device that is not consistent with its labeling. Please read our full disclaimer here.
NOTE: Most over the counter (OTC) are not reviewed and approved by the FDA. However, they may be marketed if they comply with applicable regulations and policies. FDA has not evaluated whether this product complies.
# Overview
Quassia is a OTC cream that is FDA approved for the treatment of head lice, pubic (crab lice) and body lice. Common adverse reactions include eye irritation, skin or scalp irritation.
# Adult Indications and Dosage
## FDA-Labeled Indications and Dosage (Adult)
### Indications
- treats head lice, pubic (crab lice) and body lice
### Dosage
- Important: Read warnings and full directions. For more information read the enclosed Consumer Information Leaflet.
- For adults and children 6 months and over.
- apply the entire contents of one tube thoroughly to dry hair, starting from behind the ears to the back of the neck, working forward.
- to be effective, all lice and eggs must come in contact with product, ensure hair and scalp are saturated. For long or very thick hair two tubes may be required.
- use the shower cap supplied to keep hair damp, leave on for 4 hours before washing.
- for serious infestation remove shower cap after 4 hours and leave product on overnight.
- wash area thoroughly with warm water and regular shampoo. Towel hair dry and comb out tangles using a regular comb or brush.
- as an option remove any remaining lice or nits with the included nit comb or fingernails.
- if hair dries during combing dampen slightly with water.
## Off-Label Use and Dosage (Adult)
### Guideline-Supported Use
There is limited information regarding Off-Label Guideline-Supported Use of Quassia in adult patients.
### Non–Guideline-Supported Use
There is limited information regarding Off-Label Non–Guideline-Supported Use of Quassia in adult patients.
# Pediatric Indications and Dosage
## FDA-Labeled Indications and Dosage (Pediatric)
### Dosage
- Important: Read warnings and full directions. For more information read the enclosed Consumer Information Leaflet.
- For adults and children 6 months and over.
- apply the entire contents of one tube thoroughly to dry hair, starting from behind the ears to the back of the neck, working forward.
- to be effective, all lice and eggs must come in contact with product, ensure hair and scalp are saturated. For long or very thick hair two tubes may be required.
- use the shower cap supplied to keep hair damp, leave on for 4 hours before washing.
- for serious infestation remove shower cap after 4 hours and leave product on overnight.
- wash area thoroughly with warm water and regular shampoo. Towel hair dry and comb out tangles using a regular comb or brush.
- as an option remove any remaining lice or nits with the included nit comb or fingernails.
- if hair dries during combing dampen slightly with water.
## Off-Label Use and Dosage (Pediatric)
### Guideline-Supported Use
There is limited information regarding Off-Label Guideline-Supported Use of Quassia in pediatric patients.
### Non–Guideline-Supported Use
There is limited information regarding Off-Label Non–Guideline-Supported Use of Quassia in pediatric patients.
# Contraindications
There is limited information regarding Quassia Contraindications in the drug label.
# Warnings
- For external use only.
- near eyes
- inside the nose, mouth or vagina
- on lice in eyebrows or eyelashes
- See a doctor if lice are present in these areas.
- keep tightly closed and protect eyes with a washcloth or towel.
- if product gets into the eyes, flush with water right away.
- eye irritation occurs
- skin or scalp irritation continues or infection occurs
- If swallowed, get medical help or contact a Poison Control Center right away.
# Adverse Reactions
## Clinical Trials Experience
- eye irritation
- skin or scalp irritation
## Postmarketing Experience
There is limited information regarding Postmarketing Experience of Quassia in the drug label.
# Drug Interactions
There is limited information regarding Quassia Drug Interactions in the drug label.
# Use in Specific Populations
### Pregnancy
Pregnancy Category (FDA):
- Pregnancy Category
Pregnancy Category (AUS):
- Australian Drug Evaluation Committee (ADEC) Pregnancy Category
There is no Australian Drug Evaluation Committee (ADEC) guidance on usage of Quassia in women who are pregnant.
### Labor and Delivery
There is no FDA guidance on use of Quassia during labor and delivery.
### Nursing Mothers
There is no FDA guidance on the use of Quassia with respect to nursing mothers.
### Pediatric Use
There is no FDA guidance on the use of Quassia with respect to pediatric patients.
### Geriatic Use
There is no FDA guidance on the use of Quassia with respect to geriatric patients.
### Gender
There is no FDA guidance on the use of Quassia with respect to specific gender populations.
### Race
There is no FDA guidance on the use of Quassia with respect to specific racial populations.
### Renal Impairment
There is no FDA guidance on the use of Quassia in patients with renal impairment.
### Hepatic Impairment
There is no FDA guidance on the use of Quassia in patients with hepatic impairment.
### Females of Reproductive Potential and Males
There is no FDA guidance on the use of Quassia in women of reproductive potentials and males.
### Immunocompromised Patients
There is no FDA guidance one the use of Quassia in patients who are immunocompromised.
# Administration and Monitoring
### Administration
- Topical application
### Monitoring
There is limited information regarding Monitoring of Quassia in the drug label.
# IV Compatibility
There is limited information regarding IV Compatibility of Quassia in the drug label.
# Overdosage
There is limited information regarding Overdose of Quassia in the drug label.
# Pharmacology
## Mechanism of Action
There is limited information regarding Quassia Mechanism of Action in the drug label.
## Structure
- ACTIVE INGREDIENTS
- Quassia amara 2X HPUS (Amargo 200mcg/g)
- INACTIVE INGREDIENTS
- aqua, cetearyl alcohol, dimethicone, fragrance, cetrimonium bromide, citric acid
## Pharmacodynamics
There is limited information regarding Pharmacodynamics of Quassia in the drug label.
## Pharmacokinetics
There is limited information regarding Pharmacokinetics of Quassia in the drug label.
## Nonclinical Toxicology
There is limited information regarding Nonclinical Toxicology of Quassia in the drug label.
# Clinical Studies
There is limited information regarding Clinical Studies of Quassia in the drug label.
# How Supplied
There is limited information regarding Quassia How Supplied in the drug label.
## Storage
- keep carton for important product information
- protect from excessive heat
# Images
## Drug Images
## Package and Label Display Panel
### PACKAGING INFORMATION
Quit Nits®
Caring for your child, naturally
2.03 FL OZ (60mL)
ADVANCE
Kills head lice and eggs with one application
WILD CHILD®
Born, not made.
Ingredients Incl: Aqua, cetearyl alcohol, dimethicone, fragrance, cetrimonium bromide, citric acid, quassia wood jamaican extract.
4 simple steps to help eliminate Head Lice Infestation:
APPLY - Massage cream through dry hair and onto scalp, ensuring all of the hair and the back of the neck is wet with product.
COVER - Use shower cap supplied to keep hair damp and leave on for 4 hours. For serious infestation remove cap and leave treatment on overnight.
WASH - after 4 hours use your regular shampoo to remove the product. Any remaining lice and eggs should be removed with fingernails.
FOLLOW-UP try Quit Nits Every Day Lice Preventative Spray to limit re-infestation.
For external use only. Avoid contact with eyes. If product gets into eyes, rinse well with water. If irritation occurs, discontinue use.
Manufactured for:
Wild Child (US) Pty Ltd
by The Triad Group
Hartland, WI 53029
[email protected]
800.961.4936
For batch and expiry date see crimp
### Ingredients and Appearance
# Patient Counseling Information
800-961-4936 or
[email protected]
www.QuitNits.com
# Precautions with Alcohol
- Alcohol-Quassia interaction has not been established. Talk to your doctor about the effects of taking alcohol with this medication.
# Brand Names
- QUIT NITS ADVANCE®[1]
# Look-Alike Drug Names
There is limited information regarding Quassia Look-Alike Drug Names in the drug label.
# Drug Shortage Status
# Price | https://www.wikidoc.org/index.php/Quassia | |
e5516ffbd32ec4e8090bb5180e95f7f096b0201a | wikidoc | RACGAP1 | RACGAP1
Rac GTPase-activating protein 1 is an enzyme that in humans is encoded by the RACGAP1 gene.
# Function
Rho GTPases control a variety of cellular processes. There are 3 subtypes of Rho GTPases in the Ras superfamily of small G proteins: RHO (see MIM 165370), RAC (see RAC1; MIM 602048), and CDC42 (MIM 116952). GTPase-activating proteins (GAPs) bind activated forms of Rho GTPases and stimulate GTP hydrolysis. Through this catalytic function, Rho GAPs negatively regulate Rho-mediated signals. GAPs may also serve as effector molecules and play a role in signaling downstream of Rho and other Ras-like GTPases.
# Interactions
RACGAP1 has been shown to interact with Rnd2 and SLC26A8.
During cytokinesis, RACGAP1 has been shown to interact with KIF23 to form the centralspindlin complex. This complex is essential for the formation of the central spindle. RACGAP1 also interacts with PRC1 to stabilize and maintain the central spindle as anaphase proceeds. | RACGAP1
Rac GTPase-activating protein 1 is an enzyme that in humans is encoded by the RACGAP1 gene.[1]
# Function
Rho GTPases control a variety of cellular processes. There are 3 subtypes of Rho GTPases in the Ras superfamily of small G proteins: RHO (see MIM 165370), RAC (see RAC1; MIM 602048), and CDC42 (MIM 116952). GTPase-activating proteins (GAPs) bind activated forms of Rho GTPases and stimulate GTP hydrolysis. Through this catalytic function, Rho GAPs negatively regulate Rho-mediated signals. GAPs may also serve as effector molecules and play a role in signaling downstream of Rho and other Ras-like GTPases.[supplied by OMIM][2]
# Interactions
RACGAP1 has been shown to interact with Rnd2[3] and SLC26A8.[4]
During cytokinesis, RACGAP1 has been shown to interact with KIF23 to form the centralspindlin complex.[5] This complex is essential for the formation of the central spindle. RACGAP1 also interacts with PRC1 to stabilize and maintain the central spindle as anaphase proceeds.[6] | https://www.wikidoc.org/index.php/RACGAP1 | |
d9d5ff4c7025777f0768ad73ca0b81765f9b47ca | wikidoc | RANGAP1 | RANGAP1
Ran GTPase-activating protein 1 is an enzyme that in humans is encoded by the RANGAP1 gene.
# Function
RanGAP1, is a homodimeric 65-kD polypeptide that specifically induces the GTPase activity of RAN, but not of RAS by over 1,000-fold. RanGAP1 is the immediate antagonist of RCC1, a regulator molecule that keeps RAN in the active, GTP-bound state. The RANGAP1 gene encodes a 587-amino acid polypeptide. The sequence is unrelated to that of GTPase activators for other RAS-related proteins, but is 88% identical to Fug1, the murine homolog of yeast Rna1p. RanGAP1 and RCC1 control RAN-dependent transport between the nucleus and cytoplasm. RanGAP1 is a key regulator of the RAN GTP/GDP cycle.
# Interactions
RanGAP1 is a trafficking protein which helps transport other proteins from the cytoplasm to the nucleus. Small ubiquitin-related modifier needs to be associated with it before it can be localized at the nuclear pore.
RANGAP1 has been shown to interact with:
- Ran, and
- UBE2I. | RANGAP1
Ran GTPase-activating protein 1 is an enzyme that in humans is encoded by the RANGAP1 gene.[1][2]
# Function
RanGAP1, is a homodimeric 65-kD polypeptide that specifically induces the GTPase activity of RAN, but not of RAS by over 1,000-fold. RanGAP1 is the immediate antagonist of RCC1, a regulator molecule that keeps RAN in the active, GTP-bound state. The RANGAP1 gene encodes a 587-amino acid polypeptide. The sequence is unrelated to that of GTPase activators for other RAS-related proteins, but is 88% identical to Fug1, the murine homolog of yeast Rna1p. RanGAP1 and RCC1 control RAN-dependent transport between the nucleus and cytoplasm. RanGAP1 is a key regulator of the RAN GTP/GDP cycle.[2]
# Interactions
RanGAP1 is a trafficking protein which helps transport other proteins from the cytoplasm to the nucleus. Small ubiquitin-related modifier needs to be associated with it before it can be localized at the nuclear pore.[3]
RANGAP1 has been shown to interact with:
- Ran,[4][5][6] and
- UBE2I.[7][8][9] | https://www.wikidoc.org/index.php/RANGAP1 | |
bc8bc253809431ab15e015f4b86224ecc0d91180 | wikidoc | RAPGEF3 | RAPGEF3
Rap guanine nucleotide exchange factor 3 also known as exchange factor directly activated by cAMP 1 (EPAC1) or cAMP-regulated guanine nucleotide exchange factor I (cAMP-GEFI) is a protein that in humans is encoded by the RAPGEF3 gene.
As the name suggests, EPAC proteins (EPAC1 and EPAC2) are a family of intracellular sensors for cAMP, and function as nucleotide exchange factors for the Rap subfamily of RAS-like small GTPases.
# History and discovery
Since the landmark discovery of the prototypic second messenger cAMP in 1957, three families of eukaryotic cAMP receptors have been identified to mediate the intracellular functions of cAMP. While protein kinase A (PKA) or cAMP-dependent protein kinase and cyclic nucleotide regulated ion channel (CNG and HCN) were initially unveiled in 1968 and 1985 respectively; EPAC genes were discovered in 1998 independently by two research groups. Kawasaki et al. identified cAMP-GEFI and cAMP-GEFII as novel genes enriched in brain using a differential display protocol and by screening clones with cAMP-binding motif. De Rooij and colleagues performed a database search for proteins with sequence homology to both GEFs for Ras and Rap1 and to cAMP-binding sites, which led to the identification and subsequent cloning of RAPGEF3 gene. The discovery of EPAC family cAMP sensors suggests that the complexity and possible readouts of cAMP signaling are much more elaborate than previously envisioned. This is due to the fact that the net physiological effects of cAMP entail the integration of EPAC- and PKA-dependent pathways, which may act independently, converge synergistically, or oppose each other in regulating a specific cellular function.
# Gene
Human RAPGEF3 gene is present on chromosome 12 (12q13.11: 47,734,367-47,771,041). Out of the many predicted transcript variants, three that are validated in the NCBI database include transcript variant 1 (6,239 bp), 2 (5,773 bp) and 3 (6,003 bp). While variant 1 encodes for EPAC1a (923 amino acids), both variant 2 and 3 encode EPAC1b (881 amino acids).
# Protein family
In mammals, the EPAC protein family contains two members: EPAC1 (this protein) and EPAC2 (RAPGEF4). They further belong to a more extended family of Rap/Ras-specific GEF proteins that also include C3G (RAPGEF1), PDZ-GEF1 (RAPGEF2), PDZ-GEF2 (RAPGEF6), Repac (RAPGEF5), CalDAG-GEF1 (ARHGEF1), CalDAG-GEF3 (ARHGEF3), PLCε1 (PLCE1) and RasGEF1A, B, C.
# Protein structure and mechanism of activation
EPAC proteins consist of two structural lobes/halves connected by the so-called central “switchboard” region. The N terminal regulatory lobe is responsible for cAMP binding while the C-terminal lobe contains the nucleotide exchange factor activity. At the basal cAMP-free state, EPAC is kept in an auto-inhibitory conformation, in which the N-terminal lobe folds on top of the C-terminal lobe, blocking the active site. Binding of cAMP to EPAC induces a hinge motion between the regulatory and catalytic halves. As a consequence, the regulatory lobe moves away from catalytic lobe, freeing the active site. In addition, cAMP also prompts conformational changes within the regulatory lobe that lead to the exposure of a lipid binding motif, allowing the proper targeting of EPAC1 to the plasma membrane. Entropically favorable changes in protein dynamics have also been implicated in cAMP mediated EPAC activation.
# Tissue distribution and cellular localization
Human and mice EPAC1 mRNA expression is rather ubiquitous. As per Human Protein Atlas documentation, EPAC1 mRNA is detectable in all normal human tissues. Further, medium to high levels of corresponding protein are also measureable in more than 50% of the 80 tissue samples analyzed. In mice, high levels of EPAC1 mRNA are detected in kidney, ovary, skeletal muscle, thyroid and certain areas of the brain.
EPAC1 is a multifunctional protein whose cellular functions are tightly regulated in spatial and temporal manners. EPAC1 is localized to various subcellular locations during different stages of the cell cycle. Through interactions with an array of cellular partners, EPAC1 has been shown to form discrete signalsomes at plasma membrane, nuclear-envelope, and cytoskeleton, where EPAC1 regulates numerous cellular functions.
# Clinical relevance
Studies based on genetically engineered mouse models of EPAC1 have provided valuable insights into understanding the in vivo functions of EPAC1 under both physiological and pathophysiological conditions. Overall, mice deficient of EPAC1 or both EPAC1 and EPAC2 appear relatively normal without major phenotypic defects. These observations are consistent with the fact that cAMP is a major stress response signal not essential for survival. This makes EPAC1 an attractive target for therapeutic intervention as the on-target toxicity of EPAC-based therapeutics will likely be low. Up to data, genetic and pharmacological analyses of EPAC1 in mice have revealed that EPAC1 plays important roles in cardiac stresses and heart failure, leptin resistance and energy homeostasis, chronic pain, infection, cancer metastasis and metabolism.
# Pharmacological agonists and antagonists
There have been significant interests in discovering and developing small modulators specific for EPAC proteins for better understanding the functions of EPAC mediated cAMP signaling, as well as for exploring the therapeutic potential of targeting EPAC proteins. Structure-based design targeting the key difference between the cAMP binding sites of EPAC and PKA led to the identification of a cAMP analogue, 8-pCPT-2’-O-Me-cAMP that is capable of selectively activate EPAC1. Further modifications allowed the development of more membrane permeable and metabolically stable EPAC-specific agonists.
A high throughput screening effort resulted in the discovery of several novel EPAC specific inhibitors (ESIs), among which two ESIs act as EPAC2 selective antagonists with negligible activity towards EPAC1. Another ESI, CE3F4, with modest selectivity for EPAC1 over EPAC2, has also been reported. The discovery of EPAC specific antagonists represents a research milestone that allows the pharmacological manipulation of EPAC activity. In particular, one EPAC antagonist, ESI-09, with excellent activity and minimal toxicity in vivo, has been shown to be a useful pharmacological tool for probing physiological functions of EPAC proteins and for testing therapeutic potential of targeting EPAC in animal disease models.
# Notes | RAPGEF3
Rap guanine nucleotide exchange factor 3 also known as exchange factor directly activated by cAMP 1 (EPAC1) or cAMP-regulated guanine nucleotide exchange factor I (cAMP-GEFI) is a protein that in humans is encoded by the RAPGEF3 gene.[1][2][3]
As the name suggests, EPAC proteins (EPAC1 and EPAC2) are a family of intracellular sensors for cAMP, and function as nucleotide exchange factors for the Rap subfamily of RAS-like small GTPases.
# History and discovery
Since the landmark discovery of the prototypic second messenger cAMP in 1957, three families of eukaryotic cAMP receptors have been identified to mediate the intracellular functions of cAMP. While protein kinase A (PKA) or cAMP-dependent protein kinase and cyclic nucleotide regulated ion channel (CNG and HCN) were initially unveiled in 1968 and 1985 respectively; EPAC genes were discovered in 1998 independently by two research groups. Kawasaki et al. identified cAMP-GEFI and cAMP-GEFII as novel genes enriched in brain using a differential display protocol and by screening clones with cAMP-binding motif.[3] De Rooij and colleagues performed a database search for proteins with sequence homology to both GEFs for Ras and Rap1 and to cAMP-binding sites, which led to the identification and subsequent cloning of RAPGEF3 gene.[2] The discovery of EPAC family cAMP sensors suggests that the complexity and possible readouts of cAMP signaling are much more elaborate than previously envisioned. This is due to the fact that the net physiological effects of cAMP entail the integration of EPAC- and PKA-dependent pathways, which may act independently, converge synergistically, or oppose each other in regulating a specific cellular function.[4][5][6]
# Gene
Human RAPGEF3 gene is present on chromosome 12 (12q13.11: 47,734,367-47,771,041).[7] Out of the many predicted transcript variants, three that are validated in the NCBI database include transcript variant 1 (6,239 bp), 2 (5,773 bp) and 3 (6,003 bp). While variant 1 encodes for EPAC1a (923 amino acids), both variant 2 and 3 encode EPAC1b (881 amino acids).[1]
# Protein family
In mammals, the EPAC protein family contains two members: EPAC1 (this protein) and EPAC2 (RAPGEF4). They further belong to a more extended family of Rap/Ras-specific GEF proteins that also include C3G (RAPGEF1), PDZ-GEF1 (RAPGEF2), PDZ-GEF2 (RAPGEF6), Repac (RAPGEF5), CalDAG-GEF1 (ARHGEF1), CalDAG-GEF3 (ARHGEF3), PLCε1 (PLCE1) and RasGEF1A, B, C.
# Protein structure and mechanism of activation
EPAC proteins consist of two structural lobes/halves connected by the so-called central “switchboard” region.[8] The N terminal regulatory lobe is responsible for cAMP binding while the C-terminal lobe contains the nucleotide exchange factor activity. At the basal cAMP-free state, EPAC is kept in an auto-inhibitory conformation, in which the N-terminal lobe folds on top of the C-terminal lobe, blocking the active site.[9][10] Binding of cAMP to EPAC induces a hinge motion between the regulatory and catalytic halves. As a consequence, the regulatory lobe moves away from catalytic lobe, freeing the active site.[11][12] In addition, cAMP also prompts conformational changes within the regulatory lobe that lead to the exposure of a lipid binding motif, allowing the proper targeting of EPAC1 to the plasma membrane.[13][14] Entropically favorable changes in protein dynamics have also been implicated in cAMP mediated EPAC activation.[15][16]
# Tissue distribution and cellular localization
Human and mice EPAC1 mRNA expression is rather ubiquitous. As per Human Protein Atlas documentation, EPAC1 mRNA is detectable in all normal human tissues. Further, medium to high levels of corresponding protein are also measureable in more than 50% of the 80 tissue samples analyzed.[17] In mice, high levels of EPAC1 mRNA are detected in kidney, ovary, skeletal muscle, thyroid and certain areas of the brain.[3]
EPAC1 is a multifunctional protein whose cellular functions are tightly regulated in spatial and temporal manners. EPAC1 is localized to various subcellular locations during different stages of the cell cycle.[18] Through interactions with an array of cellular partners, EPAC1 has been shown to form discrete signalsomes at plasma membrane,[14][19][20][21] nuclear-envelope,[22][23][24] and cytoskeleton,[25][26][27] where EPAC1 regulates numerous cellular functions.
# Clinical relevance
Studies based on genetically engineered mouse models of EPAC1 have provided valuable insights into understanding the in vivo functions of EPAC1 under both physiological and pathophysiological conditions. Overall, mice deficient of EPAC1 or both EPAC1 and EPAC2 appear relatively normal without major phenotypic defects. These observations are consistent with the fact that cAMP is a major stress response signal not essential for survival. This makes EPAC1 an attractive target for therapeutic intervention as the on-target toxicity of EPAC-based therapeutics will likely be low. Up to data, genetic and pharmacological analyses of EPAC1 in mice have revealed that EPAC1 plays important roles in cardiac stresses and heart failure,[28][29] leptin resistance and energy homeostasis,[30][31][32] chronic pain,[33][34] infection,[35][36] cancer metastasis[37] and metabolism.[38]
# Pharmacological agonists and antagonists
There have been significant interests in discovering and developing small modulators specific for EPAC proteins for better understanding the functions of EPAC mediated cAMP signaling, as well as for exploring the therapeutic potential of targeting EPAC proteins. Structure-based design targeting the key difference between the cAMP binding sites of EPAC and PKA led to the identification of a cAMP analogue, 8-pCPT-2’-O-Me-cAMP that is capable of selectively activate EPAC1.[39][40] Further modifications allowed the development of more membrane permeable and metabolically stable EPAC-specific agonists.[41][42][43][44]
A high throughput screening effort resulted in the discovery of several novel EPAC specific inhibitors (ESIs),[45][46][47] among which two ESIs act as EPAC2 selective antagonists with negligible activity towards EPAC1.[48] Another ESI, CE3F4, with modest selectivity for EPAC1 over EPAC2, has also been reported.[49] The discovery of EPAC specific antagonists represents a research milestone that allows the pharmacological manipulation of EPAC activity. In particular, one EPAC antagonist, ESI-09, with excellent activity and minimal toxicity in vivo, has been shown to be a useful pharmacological tool for probing physiological functions of EPAC proteins and for testing therapeutic potential of targeting EPAC in animal disease models.[35][37][50]
# Notes | https://www.wikidoc.org/index.php/RAPGEF3 | |
89a95295429357420cf797f6430d3a85acf9170b | wikidoc | RAPGEF4 | RAPGEF4
Rap guanine nucleotide exchange factor (GEF) 4 (RAPGEF4), also known as exchange protein directly activated by cAMP 2 (EPAC2) is a protein that in humans is encoded by the RAPGEF4 gene.
Epac2 is a target of cAMP, a major second messenger in various cells. Epac2 is coded by the RAPGEF4 gene, and is expressed mainly in brain, neuroendocrine, and endocrine tissues. Epac2 functions as a guanine nucleotide exchange factor for the Ras-like small GTPase Rap upon cAMP stimulation. Epac2 is involved in a variety of cAMP-mediated cellular functions in endocrine and neuroendocrine cells and neurons.
# Gene and transcripts
Human Epac2 is coded by RAPGEF4 located at chromosome 2q31-q32, and three isoforms (Epac2A, Epac2B, and Epac2C) are generated by alternate promoter usage and differential splicing. Epac2A (called Epac2 originally) is a multi-domain protein with 1,011 amino acids, and is expressed mainly in brain and neuroendocrine and endocrine tissues such as pancreatic islets and neuroendocrine cells. Epac2A is composed of two regions, an amino-terminal regulatory region and a carboxy-terminal catalytic region. The regulatory region contains two cyclic nucleotide-binding domains (cNBD-A and cNBD-B) and a DEP (Dishevelled, Egl-10, and Pleckstrin) domain. The catalytic region, which is responsible for the activation of Rap, consists of a CDC25 homology domain (CDC25-HD), a Ras exchange motif (REM) domain, and a Ras association (RA) domain. Epac2B is devoid of the first cNBD-A domain and Epac2C is devoid of a cNBD-A and a DEP domain. Epac2B and Epac2C are expressed specifically in adrenal gland and liver, respectively.
# Mechanism of action
The crystal structure reveals that the catalytic region of Epac2 interacts with cNBD-B intramolecularly, and in the absence of cAMP is sterically masked by a regulatory region, which thereby inhibits interaction between the catalytic region and Rap1. The crystal structure of the cAMP analog-bound active form of Epac2 in a complex with Rap1B indicates that the binding of cAMP to the cNBD-B domain induces the dynamic conformational changes that allow the regulatory region to rotate away. This conformational change enables access of Rap1 to the catalytic region and allows activation.
# Specific agonists
Several Epac-selective cAMP analogs have been developed to clarify the functional roles of Epacs as well those of the Epac-dependent signaling pathway distinct from the PKA-dependent signaling pathway. The modifications of 8-position in the purine structure and 2’-position in ribose is considered to be crucial to the specificity for Epacs. So far, 8-pCPT-2’-O-Me-cAMP (8-pCPT) and its membrane permeable form 8-pCPT-AM are used for their great specificity toward Epacs. Sulfonylurea drugs (SUs), widely used for the treatment of type 2 diabetes through stimulation of insulin secretion from pancreatic β-cells, have also been shown to specifically activate Epac2.
# Function
In pancreatic β-cells, cAMP signaling, which can be activated by various extracellular stimuli including hormonal and neural inputs primarily through Gs-coupled receptors, is of importance for normal regulation of insulin secretion to maintain glucose homeostasis. Activation of cAMP signaling amplifies insulin secretion by Epac2-dependent as well as PKA-dependent pathways. Epac2-Rap1 signaling is critical to promote exocytosis of insulin-containing vesicles from the readily releasable pool. In Epac2-mediated exocytosis of insulin granules, Epac2 interacts with Rim2, which is a scaffold protein localized in both plasma membrane and insulin granules, and determines the docking and priming states of exocytosis. In addition, piccolo, a possible Ca2+ sensor protein, interacts with the Epac2-Rim2 complex to regulate cAMP-induced insulin secretion. It is suggested that phospholipase C-ε (PLC-ε), one of the effector proteins of Rap, regulates intracellular Ca2+ dynamics by altering the activities of ion channels such as ATP-sensitive potassium channel, ryanodine receptor, and IP3 receptor.
In neurons, Epac is involved in neurotransmitter release in glutamatergic synapses from calyx of Held and in crayfish neuromuscular junction. Epac also has roles in the development of brain by regulation of neurite growth and neuronal differentiation as well as axon regeneration in mammalian tissue. Furthermore, Epac2 may regulate synaptic plasticity, and thus control higher brain functions such as memory and learning.
In heart, Epac1 is expressed predominantly, and is involved in the development of hypertrophic events by chronic cAMP stimulation through β-adrenergic receptors. In contrast, chronic stimulation of Epac2 may be a cause of cardiac arrhythmia through CaMKII-dependent diastolic sarcoplasmic reticulum (SR) Ca2+ release in mice. Epac2 also is involved in GLP-1-stimulated atrial natriuretic peptide (ANP) secretion from heart.
# Clinical implications
As Epac2 is involved in many physiological functions in various cells, defects in the Epac2/Rap1 signaling mechanism could contribute to the development of various pathological states. Studies of Epac2 knockout mice indicate that Epac-mediated signaling is required for potentiation of insulin secretion by incretins (gut hormones released from enteroendocrine cells following meal ingestion) such as glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide, suggesting that Epac2 is a promising target for treatment of diabetes. In fact, incretin-based diabetes therapies are currently used in clinical practice worldwide; development of Epac2-selective agonists might well lead to the discovery of further novel anti-diabetic drugs. An analog of GLP-1 has been shown to exert a blood pressure-lowering effect by stimulation of atrial natriuretic peptide (ANP) secretion through Epac2. In heart, chronic stimulation of β-adrenergic receptor is known to progress to arrhythmia through an Epac2-dependent mechanism. In brain, up-regulation of Epac1 and down-regulation of Epac2 mRNA are observed in patients with Alzheimer’s disease, suggesting roles of Epacs in the disease. An Epac2 rare coding variant is found in patients with autism and could be responsible for the dendritic morphological abnormalities.
Thus, Epac2 is involved in the pathogenesis and pathophysiology of various diseases, and represents a promising therapeutic target. | RAPGEF4
Rap guanine nucleotide exchange factor (GEF) 4 (RAPGEF4), also known as exchange protein directly activated by cAMP 2 (EPAC2) is a protein that in humans is encoded by the RAPGEF4 gene.[1][2][3]
Epac2 is a target of cAMP, a major second messenger in various cells. Epac2 is coded by the RAPGEF4 gene, and is expressed mainly in brain, neuroendocrine, and endocrine tissues.[4] Epac2 functions as a guanine nucleotide exchange factor for the Ras-like small GTPase Rap upon cAMP stimulation.[4][5] Epac2 is involved in a variety of cAMP-mediated cellular functions in endocrine and neuroendocrine cells and neurons.[6][7]
# Gene and transcripts
Human Epac2 is coded by RAPGEF4 located at chromosome 2q31-q32, and three isoforms (Epac2A, Epac2B, and Epac2C) are generated by alternate promoter usage and differential splicing.[4][8][9] Epac2A (called Epac2 originally) is a multi-domain protein with 1,011 amino acids, and is expressed mainly in brain and neuroendocrine and endocrine tissues such as pancreatic islets and neuroendocrine cells.[4] Epac2A is composed of two regions, an amino-terminal regulatory region and a carboxy-terminal catalytic region. The regulatory region contains two cyclic nucleotide-binding domains (cNBD-A and cNBD-B) and a DEP (Dishevelled, Egl-10, and Pleckstrin) domain. The catalytic region, which is responsible for the activation of Rap, consists of a CDC25 homology domain (CDC25-HD), a Ras exchange motif (REM) domain, and a Ras association (RA) domain.[10] Epac2B is devoid of the first cNBD-A domain and Epac2C is devoid of a cNBD-A and a DEP domain. Epac2B and Epac2C are expressed specifically in adrenal gland[8] and liver,[9] respectively.
# Mechanism of action
The crystal structure reveals that the catalytic region of Epac2 interacts with cNBD-B intramolecularly, and in the absence of cAMP is sterically masked by a regulatory region, which thereby inhibits interaction between the catalytic region and Rap1.[11] The crystal structure of the cAMP analog-bound active form of Epac2 in a complex with Rap1B indicates that the binding of cAMP to the cNBD-B domain induces the dynamic conformational changes that allow the regulatory region to rotate away. This conformational change enables access of Rap1 to the catalytic region and allows activation.[11][12]
# Specific agonists
Several Epac-selective cAMP analogs have been developed to clarify the functional roles of Epacs as well those of the Epac-dependent signaling pathway distinct from the PKA-dependent signaling pathway.[13] The modifications of 8-position in the purine structure and 2’-position in ribose is considered to be crucial to the specificity for Epacs. So far, 8-pCPT-2’-O-Me-cAMP (8-pCPT) and its membrane permeable form 8-pCPT-AM are used for their great specificity toward Epacs. Sulfonylurea drugs (SUs), widely used for the treatment of type 2 diabetes through stimulation of insulin secretion from pancreatic β-cells, have also been shown to specifically activate Epac2.[14]
# Function
In pancreatic β-cells, cAMP signaling, which can be activated by various extracellular stimuli including hormonal and neural inputs primarily through Gs-coupled receptors, is of importance for normal regulation of insulin secretion to maintain glucose homeostasis. Activation of cAMP signaling amplifies insulin secretion by Epac2-dependent as well as PKA-dependent pathways.[6] Epac2-Rap1 signaling is critical to promote exocytosis of insulin-containing vesicles from the readily releasable pool.[15] In Epac2-mediated exocytosis of insulin granules, Epac2 interacts with Rim2,[16][17] which is a scaffold protein localized in both plasma membrane and insulin granules, and determines the docking and priming states of exocytosis.[18][19] In addition, piccolo, a possible Ca2+ sensor protein,[20] interacts with the Epac2-Rim2 complex to regulate cAMP-induced insulin secretion.[18] It is suggested that phospholipase C-ε (PLC-ε), one of the effector proteins of Rap, regulates intracellular Ca2+ dynamics by altering the activities of ion channels such as ATP-sensitive potassium channel, ryanodine receptor, and IP3 receptor.[7][21]
In neurons, Epac is involved in neurotransmitter release in glutamatergic synapses from calyx of Held and in crayfish neuromuscular junction.[22][23][24] Epac also has roles in the development of brain by regulation of neurite growth and neuronal differentiation as well as axon regeneration in mammalian tissue.[25][26] Furthermore, Epac2 may regulate synaptic plasticity, and thus control higher brain functions such as memory and learning.[27][28]
In heart, Epac1 is expressed predominantly, and is involved in the development of hypertrophic events by chronic cAMP stimulation through β-adrenergic receptors.[29] In contrast, chronic stimulation of Epac2 may be a cause of cardiac arrhythmia through CaMKII-dependent diastolic sarcoplasmic reticulum (SR) Ca2+ release in mice.[30][31] Epac2 also is involved in GLP-1-stimulated atrial natriuretic peptide (ANP) secretion from heart.[32]
# Clinical implications
As Epac2 is involved in many physiological functions in various cells, defects in the Epac2/Rap1 signaling mechanism could contribute to the development of various pathological states. Studies of Epac2 knockout mice indicate that Epac-mediated signaling is required for potentiation of insulin secretion by incretins (gut hormones released from enteroendocrine cells following meal ingestion) such as glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide,[33][34] suggesting that Epac2 is a promising target for treatment of diabetes. In fact, incretin-based diabetes therapies are currently used in clinical practice worldwide; development of Epac2-selective agonists might well lead to the discovery of further novel anti-diabetic drugs. An analog of GLP-1 has been shown to exert a blood pressure-lowering effect by stimulation of atrial natriuretic peptide (ANP) secretion through Epac2.[32] In heart, chronic stimulation of β-adrenergic receptor is known to progress to arrhythmia through an Epac2-dependent mechanism.[30][31] In brain, up-regulation of Epac1 and down-regulation of Epac2 mRNA are observed in patients with Alzheimer’s disease, suggesting roles of Epacs in the disease.[35] An Epac2 rare coding variant is found in patients with autism and could be responsible for the dendritic morphological abnormalities.[36][37]
Thus, Epac2 is involved in the pathogenesis and pathophysiology of various diseases, and represents a promising therapeutic target. | https://www.wikidoc.org/index.php/RAPGEF4 | |
bd9de5bc5d0ba3669f065b2eb18516bc4db64d5d | wikidoc | RASGRF1 | RASGRF1
Ras protein-specific guanine nucleotide-releasing factor 1 is a protein in humans that is encoded by the RASGRF1 gene.
The protein encoded by this gene is a guanine nucleotide exchange factor (GEF) similar to the Saccharomyces cerevisiae CDC25 gene product. Functional analysis has demonstrated that this protein stimulates the dissociation of GDP from RAS protein.
The studies of the similar gene in mice suggested that the Ras-GEF activity of this protein in the brain can be activated by Ca2+ influx, muscarinic receptors, and G protein beta-gamma subunit. Mouse studies also indicated that the Ras-GEF signaling pathway mediated by this protein may be important for long-term memory. Alternatively spliced transcript variants encoding distinct isoforms have been reported. . | RASGRF1
Ras protein-specific guanine nucleotide-releasing factor 1 is a protein in humans that is encoded by the RASGRF1 gene.
[1]
The protein encoded by this gene is a guanine nucleotide exchange factor (GEF) similar to the Saccharomyces cerevisiae CDC25 gene product. Functional analysis has demonstrated that this protein stimulates the dissociation of GDP from RAS protein.
The studies of the similar gene in mice suggested that the Ras-GEF activity of this protein in the brain can be activated by Ca2+ influx, muscarinic receptors, and G protein beta-gamma subunit. Mouse studies also indicated that the Ras-GEF signaling pathway mediated by this protein may be important for long-term memory. Alternatively spliced transcript variants encoding distinct isoforms have been reported. [provided by RefSeq, Mar 2009]. | https://www.wikidoc.org/index.php/RASGRF1 | |
529c454531290afa403435c2a88144cde7dbea6a | wikidoc | RASGRF2 | RASGRF2
Ras-specific guanine nucleotide-releasing factor 2 is a protein that in humans is encoded by the RASGRF2 gene.
RAS (MIM 190020) GTPases cycle between an inactive GDP-bound state and an active GTP-bound state. Guanine-nucleotide exchange factors (GEFs), such as RASGRFs, stimulate the conversion of the GDP-bound form into the active form.
Variations in this gene has been shown to be linked to the propensity to binge drink by teenagers. | RASGRF2
Ras-specific guanine nucleotide-releasing factor 2 is a protein that in humans is encoded by the RASGRF2 gene.[1]
RAS (MIM 190020) GTPases cycle between an inactive GDP-bound state and an active GTP-bound state. Guanine-nucleotide exchange factors (GEFs), such as RASGRFs, stimulate the conversion of the GDP-bound form into the active form.[supplied by OMIM][1]
Variations in this gene has been shown to be linked to the propensity to binge drink by teenagers.[2] | https://www.wikidoc.org/index.php/RASGRF2 | |
4f2fbcb07b1e0562d078ad28b44e61f1a283bd2f | wikidoc | RASGRP1 | RASGRP1
RAS guanyl-releasing protein 1 is a protein that in humans is encoded by the RASGRP1 gene.
# Function
RAS guanyl nucleotide-releasing protein (RASGRP) is a member of a family of genes characterized by the presence of a Ras superfamily guanine nucleotide exchange factor (GEF) domain. It functions as a diacylglycerol (DAG)-regulated nucleotide exchange factor specifically activating Ras through the exchange of bound GDP for GTP. It activates the Erk/MAP kinase cascade and regulates T-cells and B-cells development, homeostasis and differentiation.
# Gene
Alternatively spliced transcript variants encoding different isoforms have been identified. The corresponding rat gene rbc7, which lacks a 5-prime exon, represents a 5-prime and 3-prime truncated version of a larger normal rat transcript that encodes a predicted 90-kD protein. This shorter transcript has not been found in humans.
# Clinical significance
In November 2016 a 12-year-old patient was hospitalized for repetitive infections. Scientists have assumed that a genetic problem might be the reason. More specifically, the genetic cause is a defect of the RASGRP1 gene which makes it inactive. .
RASGRP1 plays a role in the functions of natural killer cell dyneins. Since dyneins are motor proteins, their function is to circulate the elements inside the cells. Dr. Orange's laboratory studies have established a functional link between the defects of natural killer cells and dyneins, which in combination with Other observations led doctors to try the drug lenalidommide to treat the patient. The drug was able to reverse certain effects of the mutation RASGRP1. | RASGRP1
RAS guanyl-releasing protein 1 is a protein that in humans is encoded by the RASGRP1 gene.[1][2][3]
# Function
RAS guanyl nucleotide-releasing protein (RASGRP) is a member of a family of genes characterized by the presence of a Ras superfamily guanine nucleotide exchange factor (GEF) domain. It functions as a diacylglycerol (DAG)-regulated nucleotide exchange factor specifically activating Ras through the exchange of bound GDP for GTP. It activates the Erk/MAP kinase cascade and regulates T-cells and B-cells development, homeostasis and differentiation.[3]
# Gene
Alternatively spliced transcript variants encoding different isoforms have been identified. The corresponding rat gene rbc7, which lacks a 5-prime exon, represents a 5-prime and 3-prime truncated version of a larger normal rat transcript that encodes a predicted 90-kD protein. This shorter transcript has not been found in humans.[3]
# Clinical significance
In November 2016 a 12-year-old patient was hospitalized for repetitive infections. Scientists have assumed that a genetic problem might be the reason. More specifically, the genetic cause is a defect of the RASGRP1 gene which makes it inactive. .
RASGRP1 plays a role in the functions of natural killer cell dyneins. Since dyneins are motor proteins, their function is to circulate the elements inside the cells. Dr. Orange's laboratory studies have established a functional link between the defects of natural killer cells and dyneins, which in combination with Other observations led doctors to try the drug lenalidommide to treat the patient. The drug was able to reverse certain effects of the mutation RASGRP1. | https://www.wikidoc.org/index.php/RASGRP1 | |
b6e29cf99405b3095a29eb0a9872f75c873c10a8 | wikidoc | RASGRP2 | RASGRP2
RAS guanyl-releasing protein 2 is a protein that in humans is encoded by the RASGRP2 gene.
The protein encoded by this gene is a brain-enriched nucleotide exchanged factor that contains an N-terminal GEF domain, 2 tandem repeats of EF-hand calcium-binding motifs, and a C-terminal diacylglycerol/phorbol ester-binding domain. This protein can activate small GTPases, including RAS and RAP1/RAS3. The nucleotide exchange activity of this protein can be stimulated by calcium and diacylglycerol. Two alternatively spliced transcript variants of this gene, encoding distinct isoforms, have been reported.
# Clinical significance
Mutations in RASGRP2 are associated with severe bleeding . | RASGRP2
RAS guanyl-releasing protein 2 is a protein that in humans is encoded by the RASGRP2 gene.[1][2]
The protein encoded by this gene is a brain-enriched nucleotide exchanged factor that contains an N-terminal GEF domain, 2 tandem repeats of EF-hand calcium-binding motifs, and a C-terminal diacylglycerol/phorbol ester-binding domain. This protein can activate small GTPases, including RAS and RAP1/RAS3. The nucleotide exchange activity of this protein can be stimulated by calcium and diacylglycerol. Two alternatively spliced transcript variants of this gene, encoding distinct isoforms, have been reported.[2]
# Clinical significance
Mutations in RASGRP2 are associated with severe bleeding .[3] | https://www.wikidoc.org/index.php/RASGRP2 | |
e326d19c80cb84cfd9f44d149b973e2562af23fe | wikidoc | RHOBTB3 | RHOBTB3
Rho-related BTB domain-containing protein 3 is a protein that in humans is encoded by the RHOBTB3 gene.
# Function
RHOBTB3 is a member of the evolutionarily conserved RhoBTB subfamily of Rho GTPases. For background information on RHOBTBs, see RHOBTB1 (MIM 607351).
# Model organisms
Model organisms have been used in the study of RHOBTB3 function. A conditional knockout mouse line, called Rhobtb3tm1a(KOMP)Wtsi was generated as part of the International Knockout Mouse Consortium program — a high-throughput mutagenesis project to generate and distribute animal models of disease to interested scientists.
Male and female animals underwent a standardized phenotypic screen to determine the effects of deletion. Twenty three tests were carried out on mutant mice and four significant abnormalities were observed. Homozygote mutant males had a decreased body weight and abnormal tooth morphology; females had decreased forepaw grip strength and both sexes had a decreased body length. | RHOBTB3
Rho-related BTB domain-containing protein 3 is a protein that in humans is encoded by the RHOBTB3 gene.[1][2][3]
# Function
RHOBTB3 is a member of the evolutionarily conserved RhoBTB subfamily of Rho GTPases. For background information on RHOBTBs, see RHOBTB1 (MIM 607351).[supplied by OMIM][3]
# Model organisms
Model organisms have been used in the study of RHOBTB3 function. A conditional knockout mouse line, called Rhobtb3tm1a(KOMP)Wtsi[11][12] was generated as part of the International Knockout Mouse Consortium program — a high-throughput mutagenesis project to generate and distribute animal models of disease to interested scientists.[13][14][15]
Male and female animals underwent a standardized phenotypic screen to determine the effects of deletion.[9][16] Twenty three tests were carried out on mutant mice and four significant abnormalities were observed.[9] Homozygote mutant males had a decreased body weight and abnormal tooth morphology; females had decreased forepaw grip strength and both sexes had a decreased body length.[9] | https://www.wikidoc.org/index.php/RHOBTB3 | |
c492ee927ff47bc629144798bd322179a2dde28c | wikidoc | RNASET2 | RNASET2
Ribonuclease T2 is an enzyme that in humans is encoded by the RNASET2 gene.
This ribonuclease gene is a novel member of the Rh/T2/S-glycoprotein class of extracellular ribonucleases. It is a single copy gene that maps to 6q27, a region associated with human malignancies and chromosomal rearrangement.
RNASET2 has been reported as a tumour associated antigen in anaplastic large cell lymphoma and other lymphomas. | RNASET2
Ribonuclease T2 is an enzyme that in humans is encoded by the RNASET2 gene.[1][2]
This ribonuclease gene is a novel member of the Rh/T2/S-glycoprotein class of extracellular ribonucleases. It is a single copy gene that maps to 6q27, a region associated with human malignancies and chromosomal rearrangement.[2]
RNASET2 has been reported as a tumour associated antigen in anaplastic large cell lymphoma and other lymphomas.[3] | https://www.wikidoc.org/index.php/RNASET2 | |
06c5ff487785fc331b7c5317dbc61f7fe5d36458 | wikidoc | RPS6KA3 | RPS6KA3
Ribosomal protein S6 kinase, 90kDa, polypeptide 3, also known as RPS6KA3, is an enzyme that in humans is encoded by the RPS6KA3 gene.
# Function
This gene encodes a member of the RSK (ribosomal S6 kinase) family of serine/threonine kinases. This kinase contains 2 non-identical kinase catalytic domains and phosphorylates various substrates, including members of the mitogen-activated kinase (MAPK) signalling pathway. The activity of this protein has been implicated in controlling cell growth and differentiation.
# Clinical significance
Mutations in this gene have been associated with Coffin–Lowry syndrome (CLS).
# Interactions
RPS6KA3 has been shown to interact with CREB-binding protein, MAPK1 and PEA15. | RPS6KA3
Ribosomal protein S6 kinase, 90kDa, polypeptide 3, also known as RPS6KA3, is an enzyme that in humans is encoded by the RPS6KA3 gene.[1][2]
# Function
This gene encodes a member of the RSK (ribosomal S6 kinase) family of serine/threonine kinases. This kinase contains 2 non-identical kinase catalytic domains and phosphorylates various substrates, including members of the mitogen-activated kinase (MAPK) signalling pathway. The activity of this protein has been implicated in controlling cell growth and differentiation.[1]
# Clinical significance
Mutations in this gene have been associated with Coffin–Lowry syndrome (CLS).[3]
# Interactions
RPS6KA3 has been shown to interact with CREB-binding protein,[4] MAPK1[5][6] and PEA15.[7] | https://www.wikidoc.org/index.php/RPS6KA3 | |
d5893e77d31c53b40259f6f8835a417f5abee1ec | wikidoc | Ragweed | Ragweed
Ragweeds (Ambrosia), also called bitterweeds and bloodweeds, are a genus of flowering plants from the sunflower family (Asteraceae).
The scientific name of this genus is sometimes claimed to be derived from the Ancient Greek term for the perfumed nourishment of the gods, ambrosia (ἀμβροσία) which would be ironic since the genus is best known for one fact: its pollen produces severe and widespread allergies. However, the generic name is actually cognate with the name of the divine dish, both being derived from ambrotos (άμβροτος), "immortal". In the case of the plants, this aptly refers to their tenaciousness, which makes it hard to rid an area of them if they occur as invasive weeds.
Ragweeds occur in temperate regions of the northern hemisphere and South America. Ragweeds prefer dry, sunny grassy plains, sandy soils, and to grow along river banks, along roadsides, disturbed soils, vacant lots and ruderal sites.
There are c.41 species worldwide. Many are adapted to the arid climates of the desert. Burrobush (A. dumosa) is one of the most arid-adapted perennials in North America. About 10 species occur in the Sonoran Desert.
# Description and Ecology
Ragweeds are annuals, perennials, and shrubs and subshrubs (called bursages), with erect, hispid stems growing in large clumps to a height of usually 75-90 cm. The stems are basally branched. They form a slender taproot or a creeping rhizome. Common Ragweed (A. artemisifolia) is the most widespread of this genus in North America. It attains a height of about a meter. Great Ragweed (Giant Ragweed, "Horseweed"; A. trifida), may grow to four meters (13 feet) or more.
The foliage is grayish to silvery green with bipinnatifid, deeply lobed leaves with winged petioles; in the case of Ambrosia coronopifolia, the leaves are simple. The leaf arrangement is opposite at the base, but becomes alternate higher on the stem.
Ambrosia is a monoecious plant, i.e. it produces separate male and female flower heads on the same plant. The numerous tiny male inflorescences are yellowish-green disc flowers about 3 mm in diameter. They grow in a terminal spike, subtended by joined bracts. The whitish-green single female flowers are inconspicuously situated below the male ones, in the leaf axils. A pappus is lacking.
After wind pollination, the female flowers develops into a prickly, ovoid burr with 9-18 straight spines. It contains one arrowhead-shaped seed, brown when mature, and smaller than a wheat grain. This burr gets dispersed by clinging to the fur or feathers of animals passing by.
The seeds are an important winter food for many bird species. Ragweed plants are used as food by the larvae of a number of Lepidoptera (butterflies and moths); see list of Lepidoptera that feed on ragweeds.
# Ragweed pollen as an allergen
Each plant is reputed to be able to produce about a billion grains of pollen over a season, and the plant is anemophilous (wind-pollinated). It is highly allergenic, generally considered the greatest allergen of all pollens, and the prime cause of hayfever in North America. Common Ragweed (A. artemisiifolia) and Western Ragweed A. psilostachya are considered the most noxious to those prone to hay fever. Ragweeds bloom in the northern hemisphere from about mid-August until cooler weather arrives.
A plant usually produces pollen more copiously in wet years. When the humidity rises above 70 percent, however, the pollen tends to clump and is not so likely to become airborne. Ragweed is a plant of concern in the global warming issue, because tests have shown that higher levels of carbon dioxide will greatly increase pollen production. On dry windy days, the pollen will travel many kilometers.
Goldenrod is frequently blamed for hayfever, but simply happens to have a showy flower that blooms about the same time. Goldenrod is entomophilous, i.e. insect pollinated. Its pollen is heavy and sticky, and cannot become airborne.
Some high mountain and desert areas of North America used to be refuges for severe hay fever sufferers, who would go to such areas for relief during the pollen season, but increased human activity such as building and other disturbances of the soil, irrigation, and gardening, have encouraged ragweed to spread to these areas as well. Today, no area in the United States is ragweed pollen free, and moving can only offer a degree of relief. Ragweeds were accidentally introduced to Europe during World War I; they thrived and have greatly spread since the 1950s. Hungary is currently the most heavily affected country in Europe (and possibly the entire world), especially since the early 1990s, when abandonment of communist-style collective agriculture left vast fields uncultivated, which were promptly invaded by ragweed.
Anecdotal claims are made of honey giving some relief for ragweed pollen allergies, which is noteworthy because honeybees very rarely visit ragweed flowers, and even then only for pollen. However, during ragweed pollen shed, the pollen dusts every surface, and honeybees, being electrostatically charged, will accumulate some ragweed pollen. The pollen is frequently identified as a component of raw honey.
The major allergenic protein has been identified as Amb a 1, a 38 kDa nonglycosylated protein composed of two subunits. Other allergens widespread among pollen - profilin and calcium-binding proteins - are also present.
# Control and eradication
Total eradication of ragweed is considered impossible, owing to the plant's frugality and tremendous seed-producing capability. As of 2005, there is no known safe biological control to be used against ragweed in the open. Mechanical and chemical methods are available and can be used to control its spread, although there is evidence that these are actually no more effective in the long run than leaving the weed alone.
The act of manually uprooting ragweeds, sometimes shown in the media for public awareness purposes, promises more than it can deliver. It is ineffective, and skin contact may cause the onset of full-blown hayfever symptoms in persons with latent ragweed hyper-sensitivity. That being said, ragweed is best uprooted in late spring, before the flowering season and before a strong root system has developed.
Although the scythe and its motorized descendants have a reduced efficiency against ragweed, they remain indispensable tools, especially in populated areas and near delicate plantation, where herbicides use must be limited. Fighting ragweed with the scythe is a continuous process, because it is difficult to cut the plant right at the soil level, and the plant will regrow in two weeks (and often branch into three or four full-sized stems) if more than half an inch of the plant remains above the ground. Areas where ragweed has been reaped should be mowed down every three weeks to prevent regrowth.
It is considered important to control the spread of ragweed in large abandoned or uncultivated areas. Ragweed pollen can remain airborne for days and travel great distances, affecting people hundreds of miles away. One efficient method for large-scale ragweed extermination is chemical spraying. Because ragweed only reacts to some of the more aggressive herbicides, it is highly recommended to consult professionals when deciding on dosage and methodology, especially near urban areas. Some proven effective active ingredients include those that are glyphosate-based (Roundup, Gliphogan, Glialka), sulphosat-based (Medallon) and gluphosinat-ammonia based (Finale14SL). In badly infested areas usually 2 to 6.5 liters of herbicides are dispersed per hectare (approx. 0.2 to 0.7 US gallons per acre).
One favored method of controlling ragweed in the past was cutting it, leaving the cuts in the field, then burning them there once the stalks have dried since standing, live ragweed won't burn. It has become less popular today because the smoke produced is seen as unacceptable pollution, as with the decline in leaf-burning and trash burning. But the method has the added benefit of killing off the stems so the plant does not grow back, which (as noted above) is otherwise almost inevitable.
# Species
- Ambrosia acanthicarpa – Flatspine Burr Ragweed, Annual Bursage
- Ambrosia ambrosioides – Ambrosia Burr Ragweed, Canyon Ragweed, chicura
Ambrosia ambrosioides ssp. septentrionale
- Ambrosia ambrosioides ssp. septentrionale
- Ambrosia artemisiifolia – Common Ragweed, Annual Ragweed, American Wormwood, Blackweed, Carrotweed
- Ambrosia aspera
- Ambrosia bidentata – Camphor Weed, Lanceleaf Ragweed
- Ambrosia canescens – Hairy Ragweed
- Ambrosia carduacea – Baja California Ragweed
- Ambrosia chamissonis – Silver Burr Ragweed, Silver Beachweed, Silver Beach Burr
- Ambrosia cheirnathifolia – Rio Grande Ragweed
- Ambrosia chenopodiifolia – San Diego Burr Ragweed, San Diego Burrsage
- Ambrosia confertiflora – Weakleaf Burr Ragweed
- Ambrosia cordifolia – Tucson Burr Ragweed
- Ambrosia coronopifolia
- Ambrosia deltoidea – Triangle Burr Ragweed, Triangleleaf Bursage, Rabbitbush
- Ambrosia dumosa – Burrobush, Burroweed, White Bursage
- Ambrosia grayi – Woollyleaf Burr Ragweed
- Ambrosia helenae
- Ambrosia hispida – Coastal Ragweed
- Ambrosia ilicfolia – Hollyleaf Burr Ragweed, Hollyleaf Bursage
- Ambrosia intergradiens
- Ambrosia johnstoniorum
- Ambrosia linearis – Streaked Burr Ragweed
- Ambrosia maritima (the type species)
- Ambrosia palustris
- Ambrosia pannosa
- Ambrosia parvifolia
- Ambrosia peruviana – Peruvian Ragweed
- Ambrosia psilostachya – Western Ragweed, Cuman Ragweed, Perennial Ragweed
- Ambrosia pumila – Dwarf Burr Ragweed, San Diego Ambrosia
- Ambrosia sandersonii
- Ambrosia scabra
Ambrosia scabra var. robusta
Ambrosia scabra var. tenuior
- Ambrosia scabra var. robusta
- Ambrosia scabra var. tenuior
- Ambrosia tarapacana
- Ambrosia tenuifolia – Slimleaf Burr Ragweed
- Ambrosia tomentosa – Skeletonleaf Burr Ragweed
- Ambrosia trifida – Great Ragweed, Giant Ragweed, Buffalo Weed
Ambrosia trifida texana – Texan Great Ragweed
- Ambrosia trifida texana – Texan Great Ragweed
- Ambrosia trifolia – Greater Ragweed
- Ambrosia velutina
Ambrosia mexicana is actually the Jerusalem Oak Goosefoot (Chenopodium botrys), an entirely unrelated plant.
# Footnotes
- ↑ Payne (1963)
- ↑ Mainly Common (A. artemisiifolia), Western (A. psilostachya) and Great Ragweed (A. trifida)
- ↑ Wopfner et al. (2005)
- ↑ Jump up to: 4.0 4.1 Lewis (1973) | Ragweed
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Ragweeds (Ambrosia), also called bitterweeds and bloodweeds, are a genus of flowering plants from the sunflower family (Asteraceae).
The scientific name of this genus is sometimes claimed to be derived from the Ancient Greek term for the perfumed nourishment of the gods, ambrosia (ἀμβροσία) which would be ironic since the genus is best known for one fact: its pollen produces severe and widespread allergies. However, the generic name is actually cognate with the name of the divine dish, both being derived from ambrotos (άμβροτος), "immortal". In the case of the plants, this aptly refers to their tenaciousness, which makes it hard to rid an area of them if they occur as invasive weeds.
Ragweeds occur in temperate regions of the northern hemisphere and South America. Ragweeds prefer dry, sunny grassy plains, sandy soils, and to grow along river banks, along roadsides, disturbed soils, vacant lots and ruderal sites.
There are c.41 species worldwide. Many are adapted to the arid climates of the desert. Burrobush (A. dumosa) is one of the most arid-adapted perennials in North America. About 10 species occur in the Sonoran Desert.
# Description and Ecology
Ragweeds are annuals, perennials, and shrubs and subshrubs (called bursages), with erect, hispid stems growing in large clumps to a height of usually 75-90 cm. The stems are basally branched. They form a slender taproot or a creeping rhizome. Common Ragweed (A. artemisifolia) is the most widespread of this genus in North America. It attains a height of about a meter. Great Ragweed (Giant Ragweed, "Horseweed"; A. trifida), may grow to four meters (13 feet) or more.
The foliage is grayish to silvery green with bipinnatifid, deeply lobed leaves with winged petioles; in the case of Ambrosia coronopifolia, the leaves are simple. The leaf arrangement is opposite at the base, but becomes alternate higher on the stem.
Ambrosia is a monoecious plant, i.e. it produces separate male and female flower heads on the same plant. The numerous tiny male inflorescences are yellowish-green disc flowers about 3 mm in diameter. They grow in a terminal spike, subtended by joined bracts. The whitish-green single female flowers are inconspicuously situated below the male ones, in the leaf axils. A pappus is lacking.[1]
After wind pollination, the female flowers develops into a prickly, ovoid burr with 9-18 straight spines. It contains one arrowhead-shaped seed, brown when mature, and smaller than a wheat grain. This burr gets dispersed by clinging to the fur or feathers of animals passing by.
The seeds are an important winter food for many bird species. Ragweed plants are used as food by the larvae of a number of Lepidoptera (butterflies and moths); see list of Lepidoptera that feed on ragweeds.
# Ragweed pollen as an allergen
Each plant is reputed to be able to produce about a billion[verification needed] grains of pollen over a season, and the plant is anemophilous (wind-pollinated). It is highly allergenic, generally considered the greatest allergen of all pollens, and the prime cause of hayfever in North America. Common Ragweed (A. artemisiifolia) and Western Ragweed A. psilostachya are considered the most noxious to those prone to hay fever. Ragweeds bloom in the northern hemisphere from about mid-August until cooler weather arrives.
A plant usually produces pollen more copiously in wet years. When the humidity rises above 70 percent, however, the pollen tends to clump and is not so likely to become airborne. Ragweed is a plant of concern in the global warming issue, because tests have shown that higher levels of carbon dioxide will greatly increase pollen production. On dry windy days, the pollen will travel many kilometers.
Goldenrod is frequently blamed for hayfever, but simply happens to have a showy flower that blooms about the same time. Goldenrod is entomophilous, i.e. insect pollinated. Its pollen is heavy and sticky, and cannot become airborne.
Some high mountain and desert areas of North America used to be refuges for severe hay fever sufferers, who would go to such areas for relief during the pollen season, but increased human activity such as building and other disturbances of the soil, irrigation, and gardening, have encouraged ragweed to spread to these areas as well. Today, no area in the United States is ragweed pollen free, and moving can only offer a degree of relief. Ragweeds[2] were accidentally introduced to Europe during World War I; they thrived and have greatly spread since the 1950s. Hungary is currently the most heavily affected country in Europe (and possibly the entire world), especially since the early 1990s, when abandonment of communist-style collective agriculture left vast fields uncultivated, which were promptly invaded by ragweed.
Anecdotal claims are made of honey giving some relief for ragweed pollen allergies, which is noteworthy because honeybees very rarely visit ragweed flowers, and even then only for pollen. However, during ragweed pollen shed, the pollen dusts every surface, and honeybees, being electrostatically charged, will accumulate some ragweed pollen. The pollen is frequently identified as a component of raw honey.
The major allergenic protein has been identified as Amb a 1, a 38 kDa nonglycosylated protein composed of two subunits. Other allergens widespread among pollen - profilin and calcium-binding proteins - are also present.[3]
# Control and eradication
Total eradication of ragweed is considered impossible, owing to the plant's frugality and tremendous seed-producing capability. As of 2005, there is no known safe biological control to be used against ragweed in the open. Mechanical and chemical methods are available and can be used to control its spread, although there is evidence that these are actually no more effective in the long run than leaving the weed alone.[4]
The act of manually uprooting ragweeds, sometimes shown in the media for public awareness purposes, promises more than it can deliver. It is ineffective, and skin contact may cause the onset of full-blown hayfever symptoms in persons with latent ragweed hyper-sensitivity. That being said, ragweed is best uprooted in late spring, before the flowering season and before a strong root system has developed.
Although the scythe and its motorized descendants have a reduced efficiency against ragweed, they remain indispensable tools, especially in populated areas and near delicate plantation, where herbicides use must be limited. Fighting ragweed with the scythe is a continuous process, because it is difficult to cut the plant right at the soil level, and the plant will regrow in two weeks (and often branch into three or four full-sized stems) if more than half an inch of the plant remains above the ground. Areas where ragweed has been reaped should be mowed down every three weeks to prevent regrowth.
It is considered important to control the spread of ragweed in large abandoned or uncultivated areas. Ragweed pollen can remain airborne for days and travel great distances, affecting people hundreds of miles away. One efficient method for large-scale ragweed extermination is chemical spraying. Because ragweed only reacts to some of the more aggressive herbicides, it is highly recommended to consult professionals when deciding on dosage and methodology, especially near urban areas. Some proven effective active ingredients include those that are glyphosate-based (Roundup, Gliphogan, Glialka), sulphosat-based (Medallon) and gluphosinat-ammonia based (Finale14SL). In badly infested areas usually 2 to 6.5 liters of herbicides are dispersed per hectare (approx. 0.2 to 0.7 US gallons per acre).
One favored method of controlling ragweed in the past was cutting it, leaving the cuts in the field, then burning them there once the stalks have dried[4] since standing, live ragweed won't burn. It has become less popular today because the smoke produced is seen as unacceptable pollution, as with the decline in leaf-burning and trash burning. But the method has the added benefit of killing off the stems so the plant does not grow back, which (as noted above) is otherwise almost inevitable.
# Species
- Ambrosia acanthicarpa – Flatspine Burr Ragweed, Annual Bursage
- Ambrosia ambrosioides – Ambrosia Burr Ragweed, Canyon Ragweed, chicura
Ambrosia ambrosioides ssp. septentrionale
- Ambrosia ambrosioides ssp. septentrionale
- Ambrosia artemisiifolia – Common Ragweed, Annual Ragweed, American Wormwood, Blackweed, Carrotweed
- Ambrosia aspera
- Ambrosia bidentata – Camphor Weed, Lanceleaf Ragweed
- Ambrosia canescens – Hairy Ragweed
- Ambrosia carduacea – Baja California Ragweed
- Ambrosia chamissonis – Silver Burr Ragweed, Silver Beachweed, Silver Beach Burr
- Ambrosia cheirnathifolia – Rio Grande Ragweed
- Ambrosia chenopodiifolia – San Diego Burr Ragweed, San Diego Burrsage
- Ambrosia confertiflora – Weakleaf Burr Ragweed
- Ambrosia cordifolia – Tucson Burr Ragweed
- Ambrosia coronopifolia
- Ambrosia deltoidea – Triangle Burr Ragweed, Triangleleaf Bursage, Rabbitbush
- Ambrosia dumosa – Burrobush, Burroweed, White Bursage
- Ambrosia grayi – Woollyleaf Burr Ragweed
- Ambrosia helenae
- Ambrosia hispida – Coastal Ragweed
- Ambrosia ilicfolia – Hollyleaf Burr Ragweed, Hollyleaf Bursage
- Ambrosia intergradiens
- Ambrosia johnstoniorum
- Ambrosia linearis – Streaked Burr Ragweed
- Ambrosia maritima (the type species)
- Ambrosia palustris
- Ambrosia pannosa
- Ambrosia parvifolia
- Ambrosia peruviana – Peruvian Ragweed
- Ambrosia psilostachya – Western Ragweed, Cuman Ragweed, Perennial Ragweed
- Ambrosia pumila – Dwarf Burr Ragweed, San Diego Ambrosia
- Ambrosia sandersonii
- Ambrosia scabra
Ambrosia scabra var. robusta
Ambrosia scabra var. tenuior
- Ambrosia scabra var. robusta
- Ambrosia scabra var. tenuior
- Ambrosia tarapacana
- Ambrosia tenuifolia – Slimleaf Burr Ragweed
- Ambrosia tomentosa – Skeletonleaf Burr Ragweed
- Ambrosia trifida – Great Ragweed, Giant Ragweed, Buffalo Weed
Ambrosia trifida texana – Texan Great Ragweed
- Ambrosia trifida texana – Texan Great Ragweed
- Ambrosia trifolia – Greater Ragweed
- Ambrosia velutina
Ambrosia mexicana is actually the Jerusalem Oak Goosefoot (Chenopodium botrys), an entirely unrelated plant.
# Footnotes
- ↑ Payne (1963)
- ↑ Mainly Common (A. artemisiifolia), Western (A. psilostachya) and Great Ragweed (A. trifida)
- ↑ Wopfner et al. (2005)
- ↑ Jump up to: 4.0 4.1 Lewis (1973) | https://www.wikidoc.org/index.php/Ragweed | |
5f5598fbcaf89dc999b70ab7636cb36a1bdb1b27 | wikidoc | Ragwort | Ragwort
Ragwort (Senecio jacobaea) is a very common wild flower in the family Asteraceae that is found throughout Europe, usually in dry, open places, and has also been widely distributed as a weed elsewhere.
(For the North American species, see Packera obovata.)
Alternative names include Cushag (Isle of Man), Buachalán Buí (Ireland), Tansy Ragwort, St. James-wort, Ragweed, Stinking Nanny/Ninny/Willy, Staggerwort, Dog Standard, Cankerwort, Stammerwort and Mare's Fart. In the western US it is generally known as "Tansy Ragwort", or even more confusingly "Tansy", though its resemblance to the true tansy is superficial at best. This is a potentially dangerous misuse of names, since the true tansy has been used for culinary purposes.
# Botanical description
The plant is biennial or perennial. The stems are erect, straight, have no or few hairs, and reach a height of 0.3-2.0 metres. The leaves are pinnately lobed and the end lobe is blunt. The many names that include the word "stinking" (and Mare's Fart) arise because of the unpleasant smell of the leaves. The hermaphrodite flower heads are 1.5-2.5 cm diameter, and are borne in dense, flat-topped clusters; the florets are bright yellow. It has a long flowering period lasting from June to November.
Pollination is by a wide range of bees, flies and moths and butterflies. Over a season, one plant may produce 2,000 to 2,500 yellow flowers in 20- to 60-headed, flat-topped corymbs. This number of seeds produced may be as large as 75,000 to 200,000, although in its native range in Eurasia very few of these would grow into new plants and research has shown that most seeds do not travel a great distance from the parent plant.
# Taxonomy
Two subspecies are accepted:
- Senecio jacobaea ssp. jacobaea - the typical plant, with ray florets present.
- Senecio jacobaea ssp. dunensis - the ray florets are missing.
# Distribution
Ragwort can be found along road sides and waste grounds, and grows in all cool and high rainfall areas.
The Ragwort is native to the Eurasian continent. In Europe it is widely spread, from Scandinavia to the Mediterranean. In Britain and Ireland it is listed as a weed. In the USA it has been introduced, and is present mainly in the North West and North East: California, Idaho, Illinois, Maine, Massachusetts, Michigan, Montana, New Jersey, New York, Oregon, Pennsylvania, and Washington.
In South America it grows in Argentina, in Africa in the north, and on the Asian continent in India and Siberia. It is widespread weed in New Zealand and Australia. In many Australian states ragwort has been declared a noxious weed. This status requires landholders to remove it from their property, by law. The same applies to New Zealand where farmers sometimes bring in helicopters to spray their farms if the ragwort is too widespread.
# Biological control
Ragwort is foodplant for the larvae of Cochylis atricapitana, Phycitodes maritima, and Phycitodes saxicolais. Ragwort is best known as the food of caterpillars of the Cinnabar moth Tyria jacobaeae. They absorb alkaloids from the plant and become distasteful to predators , a fact advertised by the black and yellow warning colours. The red and black, day-flying adult moth is also distasteful to many potential predators.
The moth is used as a control for ragwort in countries in which it has been introduced and become a problem, like New Zealand and the western United States. In New Zealand, the ragwort flea beetle (Longitarsus jacobaea) has been introduced to combat the plant.
Ragwort is hostplant for Longitarsus ganglbaueri.
# Poisonous effects
Ragwort contains many different alkaloids, making it poisonous to animals. Pyrrolizidine Alkaloids have been reported by the WHO to be toxic to humans. (EHC 80,section 9.1.4). Alkaloids which have been found in the plant confirmend by the WHO report EHC 80 are -- jacobine, jaconine, jacozine, otosenine, retrorsine, seneciphylline, senecionine, and senkirkine (pp322 Appendix II). Other alkaloids claimed to be present but from an undeclared source are acetylerucifoline, (Z)-erucifoline, (E)-erucifoline, 21-hydroxyintegerrimine, integerrimine, jacoline, riddelline, senecivernine, spartioidine, and usaramine.
Ragwort is of concern to people who keep horses and cattle. In areas of the world where ragwort is a native plant, such as Britain and continental Europe, documented cases of proven poisoning are rare because the result of ragwort poisoning may only become apparent many months after ingestion of the alkaloids. Although horses do not normally eat ragwort due to its bitter taste. The result, if sufficient quantity is consumed, can be irreversible cirrhosis of the liver. Signs that a horse has been poisoned include yellow mucus membranes, depression, and lack of coordination. Animals may also resort to the consumption of ragwort when there is shortage of food. In rare cases they can even become addicted to it. Sheep, in marked contrast, eat small quantities of the plant with relish. The WHO warns however that sheep and goats suffer the same process of liver destruction but at a reduced rate to horses and pigs. They seem to profit slightly from eating it, according to some reports Template:Who the alkaloids kill worms in the sheep's stomach.
The danger of Ragwort is that the toxin can have a cumulative effect. The alkaloid does not actually accumulate in the liver but a breakdown product can damage DNA and progressively kills cells. About 3-7% of the body weight is sometimes claimed as deadly for horses, but an example in the scientific literature exists of a horse surviving being fed over 20% of its body weight. The WHO warns that frequent ingestion of very small doses is just as harmful as ingesting one lethal dose in one meal. The WHO warns that humans using herbal remedies suffering jaundice from ingesting PAs have a high risk of death 18 months to 24 months later. The effect of low doses is lessened by the destruction of the original alkaloids by the action of bacteria in the digestive track before they reach the bloodstream. There is no known antidote or cure to poisoning, but at least one example is known from the scientific literature Template:Whoof a horse making a full recovery once consumption has been stopped.
Honey collected over Ragwort has been found to contain small quantities of jacoline, jacobine, jacozine, senecionine, and seneciphylline. One study completed by MAFF. The MAFF study may be viewed online at *Information Sheet 52
# Control Legislation
## Republic of Ireland
In the Republic of Ireland, The Noxious Weeds (Thistle, Ragwort, and Dock) Order 1937, issued under The Noxious Weeds Act 1936, declares ragwort as a noxious weed, requiring landowners to control its growth.
## United Kingdom
In the United Kingdom, Common Ragwort (Senecio jacobaea) is one of the five plants named as an injurious weed under the provisions of the Weeds Act 1959. The word injurious in this context indicates that it could be harmful to agriculture not that it is dangerous to animals, as all the other injurious weeds listed are non-toxic. Under the terms of this act, a land occupier can be required by the Secretary of State for Environment, Food and Rural Affairs to prevent the spread of the plant. However, the growth of the plant is not made illegal by the act and there is no statutory obligation for control placed upon landowners in general.
A private member's bill, the Ragwort Control Bill, was introduced by John Greenway and was passed by the House of Commons in 2003. The act provides for a code of practice on ragwort but does not place any further legal responsibilities on landowners to control the plant.
# Medicine
From medieval times to the mid 20th century, Ragwort was used against inflammations of the eye, for sore and cancerous ulcers, rheumatism, sciatica and gout, for painful joints.
According to some, it would relieve the pain of bee stings.
All applications should be outward only, never internally, and only under professional supervision.
With the large range of pyrrolizidine alkaloids, which are known to inhibit or reduce cell division, some researchers hope to use them to slow down or arrest the growth of cells in cancer.
# Other usage
In ancient Greece and Rome a supposed aphrodisiac was made from the plant; it was called satyrion.
Also, the leaves can be used to obtain good green dye, as yellow dye is obtained from the flowers, as can be done for brown and orange.
# Literature and Poetry
The Greek physician Dioscorides (c.40-90 CE) recommended the herb. The two "fathers" of herbalism, Gerard and Culpeper, also recommended the herb.
The poet John Clare had a more positive opinion of the plant, as revealed in this poem of 1831:
Josephine Kermode (1852-1937) wrote the following well-known poem about the Cushag.
"The Cushag"
(Vannin Veg Veen is Manx for dear little Isle of Man)
# Cultivation
Ragwort is not cultivated. There are no varieties known.
# Trivia
Ragwort is wrongly called the national flower of the Isle of Man, where it is known as Cushag. The true national flower is the Mugwort ("Bollan Bane" in Manx) | Ragwort
Ragwort (Senecio jacobaea) is a very common wild flower in the family Asteraceae that is found throughout Europe, usually in dry, open places, and has also been widely distributed as a weed elsewhere.
(For the North American species, see Packera obovata.)
Alternative names include Cushag (Isle of Man), Buachalán Buí (Ireland), Tansy Ragwort, St. James-wort, Ragweed, Stinking Nanny/Ninny/Willy, Staggerwort, Dog Standard, Cankerwort, Stammerwort and Mare's Fart. In the western US it is generally known as "Tansy Ragwort", or even more confusingly "Tansy", though its resemblance to the true tansy is superficial at best. This is a potentially dangerous misuse of names, since the true tansy has been used for culinary purposes.
# Botanical description
The plant is biennial or perennial. The stems are erect, straight, have no or few hairs, and reach a height of 0.3-2.0 metres. The leaves are pinnately lobed and the end lobe is blunt. The many names that include the word "stinking" (and Mare's Fart) arise because of the unpleasant smell of the leaves. The hermaphrodite flower heads are 1.5-2.5 cm diameter, and are borne in dense, flat-topped clusters; the florets are bright yellow. It has a long flowering period lasting from June to November.
Pollination is by a wide range of bees, flies and moths and butterflies. Over a season, one plant may produce 2,000 to 2,500 yellow flowers in 20- to 60-headed, flat-topped corymbs. This number of seeds produced may be as large as 75,000 to 200,000, although in its native range in Eurasia very few of these would grow into new plants and research has shown that most seeds do not travel a great distance from the parent plant.
# Taxonomy
Two subspecies are accepted:
- Senecio jacobaea ssp. jacobaea - the typical plant, with ray florets present.
- Senecio jacobaea ssp. dunensis - the ray florets are missing.
# Distribution
Ragwort can be found along road sides and waste grounds, and grows in all cool and high rainfall areas.
The Ragwort is native to the Eurasian continent. In Europe it is widely spread, from Scandinavia to the Mediterranean. In Britain and Ireland it is listed as a weed. In the USA it has been introduced, and is present mainly in the North West and North East: California, Idaho, Illinois, Maine, Massachusetts, Michigan, Montana, New Jersey, New York, Oregon, Pennsylvania, and Washington.
In South America it grows in Argentina, in Africa in the north, and on the Asian continent in India and Siberia. It is widespread weed in New Zealand and Australia. In many Australian states ragwort has been declared a noxious weed. This status requires landholders to remove it from their property, by law. The same applies to New Zealand where farmers sometimes bring in helicopters to spray their farms if the ragwort is too widespread.
# Biological control
Ragwort is foodplant for the larvae of Cochylis atricapitana, Phycitodes maritima, and Phycitodes saxicolais. Ragwort is best known as the food of caterpillars of the Cinnabar moth Tyria jacobaeae. They absorb alkaloids from the plant and become distasteful to predators , a fact advertised by the black and yellow warning colours. The red and black, day-flying adult moth is also distasteful to many potential predators.
The moth is used as a control for ragwort in countries in which it has been introduced and become a problem, like New Zealand and the western United States. In New Zealand, the ragwort flea beetle (Longitarsus jacobaea) has been introduced to combat the plant.
Ragwort is hostplant for Longitarsus ganglbaueri.
# Poisonous effects
Ragwort contains many different alkaloids, making it poisonous to animals. Pyrrolizidine Alkaloids have been reported by the WHO to be toxic to humans. (EHC 80,section 9.1.4). Alkaloids which have been found in the plant confirmend by the WHO report EHC 80 are -- jacobine, jaconine, jacozine, otosenine, retrorsine, seneciphylline, senecionine, and senkirkine (pp322 Appendix II). Other alkaloids claimed to be present but from an undeclared source are acetylerucifoline, (Z)-erucifoline, (E)-erucifoline, 21-hydroxyintegerrimine, integerrimine, jacoline, riddelline, senecivernine, spartioidine, and usaramine.
Ragwort is of concern to people who keep horses and cattle. In areas of the world where ragwort is a native plant, such as Britain and continental Europe, documented cases of proven poisoning are rare because the result of ragwort poisoning may only become apparent many months after ingestion of the alkaloids. Although horses do not normally eat ragwort due to its bitter taste. The result, if sufficient quantity is consumed, can be irreversible cirrhosis of the liver. Signs that a horse has been poisoned include yellow mucus membranes, depression, and lack of coordination. Animals may also resort to the consumption of ragwort when there is shortage of food. In rare cases they can even become addicted to it. Sheep, in marked contrast, eat small quantities of the plant with relish. The WHO warns however that sheep and goats suffer the same process of liver destruction but at a reduced rate to horses and pigs. They seem to profit slightly from eating it, according to some reports Template:Who the alkaloids kill worms in the sheep's stomach.
The danger of Ragwort is that the toxin can have a cumulative effect. The alkaloid does not actually accumulate in the liver but a breakdown product can damage DNA and progressively kills cells. About 3-7% of the body weight is sometimes claimed as deadly for horses, but an example in the scientific literature exists of a horse surviving being fed over 20% of its body weight. The WHO warns that frequent ingestion of very small doses is just as harmful as ingesting one lethal dose in one meal. The WHO warns that humans using herbal remedies suffering jaundice from ingesting PAs have a high risk of death 18 months to 24 months later. The effect of low doses is lessened by the destruction of the original alkaloids by the action of bacteria in the digestive track before they reach the bloodstream. There is no known antidote or cure to poisoning, but at least one example is known from the scientific literature Template:Whoof a horse making a full recovery once consumption has been stopped.
Honey collected over Ragwort has been found to contain small quantities of jacoline, jacobine, jacozine, senecionine, and seneciphylline. One study completed by MAFF. The MAFF study may be viewed online at *Information Sheet 52
# Control Legislation
## Republic of Ireland
In the Republic of Ireland, The Noxious Weeds (Thistle, Ragwort, and Dock) Order 1937, issued under The Noxious Weeds Act 1936, declares ragwort as a noxious weed, requiring landowners to control its growth.
## United Kingdom
In the United Kingdom, Common Ragwort (Senecio jacobaea) is one of the five plants named as an injurious weed under the provisions of the Weeds Act 1959. The word injurious in this context indicates that it could be harmful to agriculture not that it is dangerous to animals, as all the other injurious weeds listed are non-toxic. Under the terms of this act, a land occupier can be required by the Secretary of State for Environment, Food and Rural Affairs to prevent the spread of the plant. However, the growth of the plant is not made illegal by the act and there is no statutory obligation for control placed upon landowners in general.[1]
A private member's bill, the Ragwort Control Bill, was introduced by John Greenway and was passed by the House of Commons in 2003. The act provides for a code of practice on ragwort but does not place any further legal responsibilities on landowners to control the plant.[2]
# Medicine
From medieval times to the mid 20th century, Ragwort was used against inflammations of the eye, for sore and cancerous ulcers, rheumatism, sciatica and gout, for painful joints.
According to some, it would relieve the pain of bee stings.
All applications should be outward only, never internally, and only under professional supervision.
With the large range of pyrrolizidine alkaloids, which are known to inhibit or reduce cell division, some researchers hope to use them to slow down or arrest the growth of cells in cancer.
# Other usage
In ancient Greece and Rome a supposed aphrodisiac was made from the plant; it was called satyrion.
Also, the leaves can be used to obtain good green dye, as yellow dye is obtained from the flowers, as can be done for brown and orange.
# Literature and Poetry
The Greek physician Dioscorides (c.40-90 CE) recommended the herb. The two "fathers" of herbalism, Gerard and Culpeper, also recommended the herb.
The poet John Clare had a more positive opinion of the plant, as revealed in this poem of 1831:
Josephine Kermode (1852-1937) wrote the following well-known poem about the Cushag.
"The Cushag"
(Vannin Veg Veen is Manx for dear little Isle of Man)
# Cultivation
Ragwort is not cultivated. There are no varieties known.
# Trivia
Template:Trivia
Ragwort is wrongly called the national flower of the Isle of Man, where it is known as Cushag. The true national flower is the Mugwort ("Bollan Bane" in Manx)
# External links
- Environmental Health Criteria 80 Pyrrolizidine Alkaloids World Health Organisation review of Health Dangers from Pyrrolizidine Alkaloids -- the full text of the report is available.
- Ragwort myths and facts This website is the English version of a Dutch Ragwort website
- Ragwort Facts.com Information on Ragwort in the UK from a scientific perspective
- Buglife's ragwort pages Information on the importance of Ragwort to wildlife on the Buglife website
- The Merck Veterinary Manual introduction to pyrrolizidine alkaloidosis | https://www.wikidoc.org/index.php/Ragwort | |
cb8209de8f1d192133677c821a9f3460acc9b158 | wikidoc | Reading | Reading
# Overview
Reading is the cognitive process of deriving meaning from written or printed text.
It is a means of language acquisition, of communication, and of sharing information and ideas. Effective readers use decoding skills (to translate printed text into the sounds of language), use morpheme, semantics, syntax and context cues to identify the meaning of unknown words, activate prior knowledge (schemata theory), use comprehension, and demonstrate fluency during reading.
Other types of reading may not be text-based, such as music notation or pictograms. By analogy, in computer science, reading is acquiring of data from some sort of computer storage.
Although reading print text is now an important way for the general population to access information, this has not always been the case. With some exceptions, only a small percentage of the population in many countries were considered literate before the Industrial Revolution.
# Reading skills
## Skill development
Other methods of teaching and learning to read have developed, and become somewhat controversial :
- Phonics involves teaching reading by associating characters or groups of characters with sounds. Sometimes argued to be in competition with whole language methods.
- Whole language methods involve acquiring words or phrases without attention to the characters or groups of characters that compose them. Sometimes argued to be in competition with phonics methods, and that the whole language approach tends to impair learning how to spell.
Learning to read in a second language, especially in adulthood, may be a different process than learning to read a native language in childhood.
There are cases of very young children learning to read without having been taught. Such was the case with Truman Capote who reportedly taught himself to read and write at the age of 5. There are accounts of people who taught themselves to read by comparing street signs or Biblical passages to speech, as well as many mentions of Lincoln teaching himself. The novelist Nicholas Delbanco taught himself to read at age six by studying a book about boats during a transatlantic crossing.
## Methods
There are several types and methods of reading, with differing rates that can be attained for each, for different kinds of material and purposes:
- Subvocalized reading combines sight reading with internal sounding of the words as if spoken. Advocates of speed reading claim it can be a bad habit that slows reading and comprehension. These claims are currently backed only by controversial, sometimes non-existent scientific research.
- Speed reading is a collection of methods for increasing reading speed without an unacceptable reduction in comprehension or retention. It is closely connected to speed learning.
- Proofreading is a kind of reading for the purpose of detecting typographical errors. One can learn to do it rapidly, and professional proofreaders typically acquire the ability to do so at high rates, faster for some kinds of material than for others, while they may largely suspend comprehension while doing so, except when needed to select among several possible words that a suspected typographic error allows.
- Structure-Proposition-Evaluation (SPE) method, popularized by Mortimer Adler in How to Read a Book, mainly for non-fiction treatise, in which one reads a writing in three passes: (1) for the structure of the work, which might be represented by an outline; (2) for the logical propositions made, organized into chains of inference; and (3) for evaluation of the merits of the arguments and conclusions. This method involves suspended judgment of the work or its arguments until they are fully understood.
- Survey-Question-Read-Recite-Review (SQ3R) method, often taught in public schools, which involves reading toward being able to teach what is read, and would be appropriate for instructors preparing to teach material without having to refer to notes during the lecture.
- Multiple Intelligences-based methods, which draw upon the reader's diverse ways of thinking and knowing to enrich his or her appreciation of the text. Reading is fundamentally a linguistic activity: one can basically comprehend a text without resorting to other intelligences, such as the visual (e.g., mentally "seeing" characters or events described), auditory (e.g., reading aloud or mentally "hearing" sounds described), or even the logical intelligence (e.g., considering "what if" scenarios or predicting how the text will unfold based on context clues). However, most readers already use several intelligences while reading, and making a habit of doing so in a more disciplined manner -- i.e., constantly, or after every paragraph -- can result in more vivid, memorable experience.
# Reading assessment
## Reading rate
Rates of reading include reading for memorization (under 100 words per minute (wpm)), reading for learning (100–200 wpm), reading for comprehension (200–400 wpm), and skimming (400–700 wpm). Reading for comprehension is the essence of most people’s daily reading. Skimming is sometimes useful for processing larger quantities of text superficially at a much lower level of comprehension (below 50%).
Advice for the appropriate choice of reading rate includes reading flexibly, slowing down when the concepts are closer together or when the material is unfamiliar, and speeding up when the material is familiar and the material is not concept rich. Speed reading courses and books often encourage the reader to continually speed up; comprehension tests lead the reader to believe their comprehension is constantly improving. However, competence in reading involves the understanding that skimming is dangerous as a default habit.
The table to the left shows how reading rate varies with age
, probably regardless of time period (1965 to 2005) and language (English, French German). The values of Taylor are probably higher because he discarded students who failed the comprehension test.
The test of the french psychologist Pierre Lefavrais ("L'alouette", published in 1967) asked for reading out aloud with a penalty for errors and could therefore not be much faster than 150 wpm.
## Types of reading tests
- Sight word reading: reading words of increasing difficulty until they become unable to read or understand the words presented to them. Difficulty is manipulated by using words that have more letters or syllables, are less common and have more complicated spelling-sound relationships.
- Nonword reading: reading lists of pronounceable nonsense words out loud. The difficulty is increased by using longer words, and also by using words with more complex spelling or sound sequences.
- Reading comprehension: a passage is presented to the reader, which they must read either silently or out loud. Then a series of questions are presented that test the reader's comprehension of this passage.
- Reading fluency: the rate with which individuals can name words.
- Reading accuracy: the ability to correctly name a word on a page.
Some tests incorporate several of the above components at once. For instance, the Nelson-Denny Reading Test scores readers both on the speed with which they can read a passage, and also their ability to accurately answer questions about this passage.
# Effects
## Intelligence
Studies have shown that American children who learn to read by the third grade are less likely to end up in prison, drop out of school, or take drugs. Adults who read literature on a regular basis are nearly three times as likely to attend a performing arts event, almost four times as likely to visit an art museum, more than two-and-a-half times as likely to do volunteer or charity work, and over one-and-a-half times as likely to participate in sporting activities. Literacy rates in the United States are also more highly correlated to weekly earnings than IQ. A graph showing this relationship is shown here. Reading books is generally regarded as being a relaxing past-time, while at the same time requiring the brain to process text so it can be stimulated. Because of this it is sometimes considered to cause at least a temporary increase in one's mental faculties.
## Lighting
Reading requires more lighting than many other activities. Therefore, the possibility of comfortable reading in cafés, restaurants, buses, at bus stops or in parks greatly varies depending on available lighting and time of day. Starting in the 1950s, many offices and classrooms were over-illuminated. Since about 1990, there has been a movement to create reading environments with appropriate lighting levels (approximately 600 to 800 lux). | Reading
# Overview
Reading is the cognitive process of deriving meaning from written or printed text.
It is a means of language acquisition, of communication, and of sharing information and ideas. Effective readers use decoding skills (to translate printed text into the sounds of language), use morpheme, semantics, syntax and context cues to identify the meaning of unknown words, activate prior knowledge (schemata theory), use comprehension, and demonstrate fluency during reading.
Other types of reading may not be text-based, such as music notation or pictograms. By analogy, in computer science, reading is acquiring of data from some sort of computer storage.
Although reading print text is now an important way for the general population to access information, this has not always been the case. With some exceptions, only a small percentage of the population in many countries were considered literate before the Industrial Revolution.
# Reading skills
## Skill development
Other methods of teaching and learning to read have developed, and become somewhat controversial [1]:
- Phonics involves teaching reading by associating characters or groups of characters with sounds. Sometimes argued to be in competition with whole language methods.
- Whole language methods involve acquiring words or phrases without attention to the characters or groups of characters that compose them. Sometimes argued to be in competition with phonics methods, and that the whole language approach tends to impair learning how to spell.
Learning to read in a second language, especially in adulthood, may be a different process than learning to read a native language in childhood.
There are cases of very young children learning to read without having been taught. [2] Such was the case with Truman Capote who reportedly taught himself to read and write at the age of 5. There are accounts of people who taught themselves to read by comparing street signs or Biblical passages to speech, as well as many mentions of Lincoln teaching himself. The novelist Nicholas Delbanco taught himself to read at age six by studying a book about boats during a transatlantic crossing.
## Methods
There are several types and methods of reading, with differing rates that can be attained for each, for different kinds of material and purposes:
- Subvocalized reading combines sight reading with internal sounding of the words as if spoken. Advocates of speed reading claim it can be a bad habit that slows reading and comprehension. These claims are currently backed only by controversial, sometimes non-existent scientific research.
- Speed reading is a collection of methods for increasing reading speed without an unacceptable reduction in comprehension or retention. It is closely connected to speed learning.
- Proofreading is a kind of reading for the purpose of detecting typographical errors. One can learn to do it rapidly, and professional proofreaders typically acquire the ability to do so at high rates, faster for some kinds of material than for others, while they may largely suspend comprehension while doing so, except when needed to select among several possible words that a suspected typographic error allows.
- Structure-Proposition-Evaluation (SPE) method, popularized by Mortimer Adler in How to Read a Book, mainly for non-fiction treatise, in which one reads a writing in three passes: (1) for the structure of the work, which might be represented by an outline; (2) for the logical propositions made, organized into chains of inference; and (3) for evaluation of the merits of the arguments and conclusions. This method involves suspended judgment of the work or its arguments until they are fully understood.
- Survey-Question-Read-Recite-Review (SQ3R) method, often taught in public schools, which involves reading toward being able to teach what is read, and would be appropriate for instructors preparing to teach material without having to refer to notes during the lecture.
- Multiple Intelligences-based methods, which draw upon the reader's diverse ways of thinking and knowing to enrich his or her appreciation of the text. Reading is fundamentally a linguistic activity: one can basically comprehend a text without resorting to other intelligences, such as the visual (e.g., mentally "seeing" characters or events described), auditory (e.g., reading aloud or mentally "hearing" sounds described), or even the logical intelligence (e.g., considering "what if" scenarios or predicting how the text will unfold based on context clues). However, most readers already use several intelligences while reading, and making a habit of doing so in a more disciplined manner -- i.e., constantly, or after every paragraph -- can result in more vivid, memorable experience.
# Reading assessment
## Reading rate
Rates of reading include reading for memorization (under 100 words per minute (wpm)), reading for learning (100–200 wpm), reading for comprehension (200–400 wpm), and skimming (400–700 wpm). Reading for comprehension is the essence of most people’s daily reading. Skimming is sometimes useful for processing larger quantities of text superficially at a much lower level of comprehension (below 50%).
Advice for the appropriate choice of reading rate includes reading flexibly, slowing down when the concepts are closer together or when the material is unfamiliar, and speeding up when the material is familiar and the material is not concept rich. Speed reading courses and books often encourage the reader to continually speed up; comprehension tests lead the reader to believe their comprehension is constantly improving. However, competence in reading involves the understanding that skimming is dangerous as a default habit.
The table to the left shows how reading rate varies with age [4]
, probably regardless of time period (1965 to 2005) and language (English, French German). The values of Taylor are probably higher because he discarded students who failed the comprehension test.
The test of the french psychologist Pierre Lefavrais ("L'alouette", published in 1967) asked for reading out aloud with a penalty for errors and could therefore not be much faster than 150 wpm.
## Types of reading tests
- Sight word reading: reading words of increasing difficulty until they become unable to read or understand the words presented to them. Difficulty is manipulated by using words that have more letters or syllables, are less common and have more complicated spelling-sound relationships.
- Nonword reading: reading lists of pronounceable nonsense words out loud. The difficulty is increased by using longer words, and also by using words with more complex spelling or sound sequences.
- Reading comprehension: a passage is presented to the reader, which they must read either silently or out loud. Then a series of questions are presented that test the reader's comprehension of this passage.
- Reading fluency: the rate with which individuals can name words.
- Reading accuracy: the ability to correctly name a word on a page.
Some tests incorporate several of the above components at once. For instance, the Nelson-Denny Reading Test scores readers both on the speed with which they can read a passage, and also their ability to accurately answer questions about this passage.
# Effects
## Intelligence
Studies have shown that American children who learn to read by the third grade are less likely to end up in prison, drop out of school, or take drugs. Adults who read literature on a regular basis are nearly three times as likely to attend a performing arts event, almost four times as likely to visit an art museum, more than two-and-a-half times as likely to do volunteer or charity work, and over one-and-a-half times as likely to participate in sporting activities.[5] Literacy rates in the United States are also more highly correlated to weekly earnings than IQ. A graph showing this relationship is shown here. Reading books is generally regarded as being a relaxing past-time, while at the same time requiring the brain to process text so it can be stimulated. Because of this it is sometimes considered to cause at least a temporary increase in one's mental faculties.
## Lighting
Reading requires more lighting than many other activities. Therefore, the possibility of comfortable reading in cafés, restaurants, buses, at bus stops or in parks greatly varies depending on available lighting and time of day. Starting in the 1950s, many offices and classrooms were over-illuminated. Since about 1990, there has been a movement to create reading environments with appropriate lighting levels (approximately 600 to 800 lux). | https://www.wikidoc.org/index.php/Reading | |
8850205de1106690a6b43f357487ca9a760bb68d | wikidoc | Recluse | Recluse
# Overview
A recluse is someone in isolation who hides away from the attention of the public, a person who lives in solitude, i.e. seclusion from intercourse with the world. The word is from the Latin recludere, which means "shut up" or "sequester".
A person may become a recluse for many reasons: a celebrity may seek to escape the attentions of his or her fans; a misanthrope may be unable to tolerate human society; a survivalist may be practicing self-sufficiency; and a criminal might hide away from people to avoid detection by police. It can also be due to psychological reasons, such as: apathy, an autism spectrum disorder, a phobia, schizoid personality type, or due to avoidant personality disorder. A recluse can also be considered as a loner.
Some may become a recluse due to a physical deformity that makes their outward appearance unsettling to others. A person may also become a recluse for religious reasons, in which case he or she is usually referred to as a hermit or an anchorite.
Reclusiveness does not necessarily connote geographical isolation. A recluse may live in a crowded city, but infrequently leave the security of his or her home. However, isolated and sparsely populated US states (e.g., Montana, Wyoming, and Alaska) often harbor recluses, who are often seeking complete escape from civilization.
In Japan, an estimated 1.2 million people suffer from psychological problems which cause reclusive behavior. The phenomenon of "Hikikomori" or "social withdrawal" has become a major problem, often blamed on Japan's education system and social pressure to succeed. | Recluse
# Overview
A recluse is someone in isolation who hides away from the attention of the public, a person who lives in solitude, i.e. seclusion from intercourse with the world. The word is from the Latin recludere, which means "shut up" or "sequester".
A person may become a recluse for many reasons: a celebrity may seek to escape the attentions of his or her fans; a misanthrope may be unable to tolerate human society; a survivalist may be practicing self-sufficiency; and a criminal might hide away from people to avoid detection by police. It can also be due to psychological reasons, such as: apathy, an autism spectrum disorder, a phobia, schizoid personality type, or due to avoidant personality disorder. A recluse can also be considered as a loner.
Some may become a recluse due to a physical deformity that makes their outward appearance unsettling to others. A person may also become a recluse for religious reasons, in which case he or she is usually referred to as a hermit or an anchorite.
Reclusiveness does not necessarily connote geographical isolation. A recluse may live in a crowded city, but infrequently leave the security of his or her home. However, isolated and sparsely populated US states (e.g., Montana, Wyoming, and Alaska) often harbor recluses, who are often seeking complete escape from civilization.
In Japan, an estimated 1.2 million people suffer from psychological problems which cause reclusive behavior. The phenomenon of "Hikikomori" or "social withdrawal" has become a major problem, often blamed on Japan's education system and social pressure to succeed. | https://www.wikidoc.org/index.php/Recluse | |
fc9d4283038612539ce8241b59c777a352da9708 | wikidoc | Relaxin | Relaxin
Relaxin is a protein hormone of about 6000 Da first described in 1926 by Frederick Hisaw.
The relaxin-like peptide family belongs in the insulin superfamily and consists of 7 peptides of high structural but low sequence similarity; relaxin-1 (RLN1), 2 (RLN2) and 3 (RLN3), and the insulin-like (INSL) peptides, INSL3, INSL4, INSL5 and INSL6. The functions of relaxin-3, INSL4, INSL5, INSL6 remain uncharacterised.
# Synthesis
In the female, it is produced by the corpus luteum of the ovary, the breast and, during pregnancy, also by the placenta, chorion, and decidua.
In the male, it is produced in the prostate and is present in human semen.
# Structure
Structurally, relaxin is a heterodimer of two peptide chains of 24 and 29 amino acids linked by disulfide bridges, and it appears related to insulin.
Relaxin is produced from its prohormone, "prorelaxin", by splitting off one additional peptide chain reaction.
# Function
## In humans
In females, relaxin is produced mainly by the corpus luteum, in both pregnant and nonpregnant females. Relaxin levels rise to a peak within approximately 14 days of ovulation, and then decline in the absence of pregnancy, resulting in menstruation. Relaxin may be involved in the vital process of decidualisation, working alongside steroid hormones to allow the endometrium to prepare for implantation. During the first trimester of pregnancy, levels rise and additional relaxin is produced by the decidua. Relaxin's peak is reached during the first trimester (14-weeks) and at delivery. Relaxin mediates the hemodynamic changes that occur during pregnancy, such as increased cardiac output, increased renal blood flow, and increased arterial compliance. It also relaxes other pelvic ligaments. It is believed to soften the pubic symphysis.
In males, relaxin enhances motility of sperm in semen.
In the cardiovascular system, relaxin works mainly by activating the nitric oxide pathway. Other mechanisms include activation of NFκB leading to vascular endothelial growth factor (VEGF) and matrix metalloproteinases transcription.
Relaxin has been shown to relax vascular smooth muscle cells and increase nitric oxide production in rat endothelial cells, thus playing a role in regulation of cardiovascular function by dilating systemic resistance arteries. Relaxin increases the rate and force of cardiac contraction in rat models. Via upregulation of VEGF, relaxin plays a key role in blood vessel formation (angiogenesis) during pregnancy, tumour development or ischaemic wounds.
## In other animals
In animals, relaxin widens the pubic bone and facilitates labor; it also softens the cervix (cervical ripening), and relaxes the uterine musculature. Thus, for a long time, relaxin was looked at as a pregnancy hormone. However, its significance may reach much further. Relaxin may affects collagen metabolism, inhibiting collagen synthesis and enhancing its breakdown by increasing matrix metalloproteinases. It also enhances angiogenesis and is a potent renal vasodilator.
In the mouse model Relaxin has been found to promote maturation of cardiomyocytes.
Several animal studies have found relaxin to have a cardioprotective function against ischaemia and reperfusion injury, by reducing cellular damage, via anti-apoptotic and anti-inflammatory effects. Relaxin has been shown to reduce cardiac fibrosis in animal models by inhibiting cardiac fibroblasts secreting collagen and stimulating matrix metalloproteinase.
In the European Rabbit, (Oryctolagus cuniculus), relaxin is associated with squamous differentiation and is expressed in tracheobronchial epithelial cells as opposed to being involved with reproduction.
In horses (Equus caballus), relaxin is also an important hormone involved in pregnancy, however, before pregnancy occurs, relaxin is expressed by ovarian structures during the oestrous cycle. Prior to ovulation, relaxin will be produced by ovarian stromal cells, which will promote secretion of gelatinases and tissue inhibitors of metalloproteinases. These enzymes will then aid the process of ovulation, which will lead to the release of a developed follicle into the fallopian tube. Furthermore, granular and theca cells in the follicles will express relaxin in increasing levels depending on their size. During early pregnancy, the preimplantation conceptus will express relaxin, which will promote angiogenesis in the endometrium by up-regulating VEGF . This will allow the endometrium to prepare for implantation. In horses alone, the embryo in the uterus will express relaxin mRNA at least 8 days after ovulation. Then as the conceptus develops expression will increase, which is likely to promote embryo development.
In addition to relaxin production by the horse embryo, the maternal placenta is the main source of relaxin production, whereas in most animals the main source of relaxin is the corpus luteum. Placental trophoblast cells produce relaxin, however, the size of the placenta does not determine the level of relaxin production. This is seen because different breeds of horses show different relaxin levels. From 80 day of gestation onwards, relaxin levels will increase in the mare's serum with levels peaking in late gestation. Moreover, the pattern of relaxin expression will follow the expression of oestrogen, however, there is not yet a known link between these two hormones. During labour, there is a spike in relaxin 3-4 hours before delivery, which is involved in myometrial relaxation and softening of the pelvic ligaments to aid preparation of the birth canal for the delivery of the horse foetus. Following birth, the levels of relaxin will gradually decrease if the placenta is also delivered, however, if the placenta is retained in the mare then the levels will remain high. In addition, if the mare undergoes an abortion then the relaxin levels will decline as the placenta ceases to function.
# Receptors
Relaxin interacts with the relaxin receptor LGR7 (RXFP1) and LGR8 (RXFP2), which belong to the G protein-coupled receptor superfamily. They contain a heptahelical transmembrane domain and a large glycosylated ectodomain, distantly related to the receptors for the glycoproteohormones, such as the LH-receptor or FSH-receptor.
Relaxin receptors have been found in the heart, smooth muscle, the connective tissue, and central and autonomous nervous system.
# Disorders
Women who have been on relaxin treatment during unrelated clinical trials have experienced heavier bleeding during their menstrural cycle, suggesting that relaxin levels could play a role in abnormal uterine bleeding. However, more research needs to go into this to confirm relaxin as a direct cause.
A lower expression of relaxin has been found amongst women who have endometriosis. The research in this area is limited and more studying of relaxin's contribution could contribute greatly to the understanding of endometriosis.
Specific disorders related to relaxin have not been heavily described, yet a link to scleroderma and fibromyalgia has also been suggested.
## Pregnancy
It is possible that relaxin in the placenta could be a contributing factor to inducing labour in humans and therefore serum relaxin levels during pregnancy have been linked to premature birth.
# Pharmacological targets
A recombinant form of human relaxin-2 has been developed as investigational drug RLX030 (serelaxin).
It is suggested that relaxin could be used as a therapeutic target when it comes to gynaecological disorders.
# Evolution
Relaxin 1 and Relaxin 2 arose from the duplication of a proto-RLN gene between 44.2 and 29.6 million years ago in the last common ancestor of catarrhine primates. The duplication that led to RLN1 and RLN2 is thought to have been a result of positive selection and convergent evolution at the nucleotide level between the relaxin gene in New World monkeys and the RLN1 gene in apes . As a result, Old World monkeys, a group that includes the subfamilies colobines and cercopithecines, have lost the RLN1 paralog, but apes have retained both the RLN1 and the RLN2 genes ; Lawrence and Cords, 2012). | Relaxin
Relaxin is a protein hormone of about 6000 Da[1] first described in 1926 by Frederick Hisaw.[2][3]
The relaxin-like peptide family belongs in the insulin superfamily and consists of 7 peptides of high structural but low sequence similarity; relaxin-1 (RLN1), 2 (RLN2) and 3 (RLN3), and the insulin-like (INSL) peptides, INSL3, INSL4, INSL5 and INSL6. The functions of relaxin-3, INSL4, INSL5, INSL6 remain uncharacterised.[4]
# Synthesis
In the female, it is produced by the corpus luteum of the ovary, the breast and, during pregnancy, also by the placenta, chorion, and decidua.
In the male, it is produced in the prostate and is present in human semen.[5]
# Structure
Structurally, relaxin is a heterodimer of two peptide chains of 24 and 29 amino acids linked by disulfide bridges, and it appears related to insulin.[citation needed]
Relaxin is produced from its prohormone, "prorelaxin", by splitting off one additional peptide chain reaction.[citation needed]
# Function
## In humans
In females, relaxin is produced mainly by the corpus luteum, in both pregnant and nonpregnant females.[1] Relaxin levels rise to a peak within approximately 14 days of ovulation, and then decline in the absence of pregnancy, resulting in menstruation.[citation needed] Relaxin may be involved in the vital process of decidualisation, working alongside steroid hormones to allow the endometrium to prepare for implantation.[6] During the first trimester of pregnancy, levels rise and additional relaxin is produced by the decidua. Relaxin's peak is reached during the first trimester (14-weeks) and at delivery. Relaxin mediates the hemodynamic changes that occur during pregnancy, such as increased cardiac output, increased renal blood flow, and increased arterial compliance.[citation needed] It also relaxes other pelvic ligaments.[7] It is believed to soften the pubic symphysis.[citation needed]
In males, relaxin enhances motility of sperm in semen.[8]
In the cardiovascular system, relaxin works mainly by activating the nitric oxide pathway. Other mechanisms include activation of NFκB leading to vascular endothelial growth factor (VEGF) and matrix metalloproteinases transcription.[9]
Relaxin has been shown to relax vascular smooth muscle cells and increase nitric oxide production in rat endothelial cells, thus playing a role in regulation of cardiovascular function by dilating systemic resistance arteries.[9] Relaxin increases the rate and force of cardiac contraction in rat models.[10] Via upregulation of VEGF, relaxin plays a key role in blood vessel formation (angiogenesis) during pregnancy, tumour development or ischaemic wounds.[10]
## In other animals
In animals, relaxin widens the pubic bone and facilitates labor; it also softens the cervix (cervical ripening), and relaxes the uterine musculature.[citation needed] Thus, for a long time, relaxin was looked at as a pregnancy hormone. However, its significance may reach much further. Relaxin may affects collagen metabolism, inhibiting collagen synthesis and enhancing its breakdown by increasing matrix metalloproteinases.[11] It also enhances angiogenesis and is a potent renal vasodilator.[citation needed]
In the mouse model Relaxin has been found to promote maturation of cardiomyocytes.[10]
Several animal studies have found relaxin to have a cardioprotective function against ischaemia and reperfusion injury, by reducing cellular damage, via anti-apoptotic and anti-inflammatory effects.[citation needed] Relaxin has been shown to reduce cardiac fibrosis in animal models by inhibiting cardiac fibroblasts secreting collagen and stimulating matrix metalloproteinase.[10][9]
In the European Rabbit, (Oryctolagus cuniculus), relaxin is associated with squamous differentiation and is expressed in tracheobronchial epithelial cells as opposed to being involved with reproduction.[12]
In horses (Equus caballus), relaxin is also an important hormone involved in pregnancy, however, before pregnancy occurs, relaxin is expressed by ovarian structures during the oestrous cycle[13]. Prior to ovulation, relaxin will be produced by ovarian stromal cells, which will promote secretion of gelatinases and tissue inhibitors of metalloproteinases. These enzymes will then aid the process of ovulation, which will lead to the release of a developed follicle into the fallopian tube.[13] Furthermore, granular and theca cells in the follicles will express relaxin in increasing levels depending on their size[13]. During early pregnancy, the preimplantation conceptus will express relaxin, which will promote angiogenesis in the endometrium by up-regulating VEGF [13][14]. This will allow the endometrium to prepare for implantation. In horses alone, the embryo in the uterus will express relaxin mRNA at least 8 days after ovulation. Then as the conceptus develops expression will increase, which is likely to promote embryo development.[13]
In addition to relaxin production by the horse embryo, the maternal placenta is the main source of relaxin production, whereas in most animals the main source of relaxin is the corpus luteum[13]. Placental trophoblast cells produce relaxin, however, the size of the placenta does not determine the level of relaxin production. This is seen because different breeds of horses show different relaxin levels[15]. From 80 day of gestation onwards, relaxin levels will increase in the mare's serum with levels peaking in late gestation[15][16]. Moreover, the pattern of relaxin expression will follow the expression of oestrogen, however, there is not yet a known link between these two hormones[16]. During labour, there is a spike in relaxin 3-4 hours before delivery, which is involved in myometrial relaxation and softening of the pelvic ligaments to aid preparation of the birth canal for the delivery of the horse foetus[13][15]. Following birth, the levels of relaxin will gradually decrease if the placenta is also delivered, however, if the placenta is retained in the mare then the levels will remain high[15]. In addition, if the mare undergoes an abortion then the relaxin levels will decline as the placenta ceases to function[15].
# Receptors
Relaxin interacts with the relaxin receptor LGR7 (RXFP1) and LGR8 (RXFP2), which belong to the G protein-coupled receptor superfamily.[17] They contain a heptahelical transmembrane domain and a large glycosylated ectodomain, distantly related to the receptors for the glycoproteohormones, such as the LH-receptor or FSH-receptor.
Relaxin receptors have been found in the heart, smooth muscle, the connective tissue, and central and autonomous nervous system.[citation needed]
# Disorders
Women who have been on relaxin treatment during unrelated clinical trials have experienced heavier bleeding during their menstrural cycle, suggesting that relaxin levels could play a role in abnormal uterine bleeding.[18] However, more research needs to go into this to confirm relaxin as a direct cause.[citation needed]
A lower expression of relaxin has been found amongst women who have endometriosis. The research in this area is limited and more studying of relaxin's contribution could contribute greatly to the understanding of endometriosis.[18]
Specific disorders related to relaxin have not been heavily described, yet a link to scleroderma and fibromyalgia has also been suggested.[19]
## Pregnancy
It is possible that relaxin in the placenta could be a contributing factor to inducing labour in humans and therefore serum relaxin levels during pregnancy have been linked to premature birth.[18]
# Pharmacological targets
A recombinant form of human relaxin-2 has been developed as investigational drug RLX030 (serelaxin).[citation needed]
It is suggested that relaxin could be used as a therapeutic target when it comes to gynaecological disorders.[18]
# Evolution
Relaxin 1 and Relaxin 2 arose from the duplication of a proto-RLN gene between 44.2 and 29.6 million years ago in the last common ancestor of catarrhine primates.[20] The duplication that led to RLN1 and RLN2 is thought to have been a result of positive selection and convergent evolution at the nucleotide level between the relaxin gene in New World monkeys and the RLN1 gene in apes .[20] As a result, Old World monkeys, a group that includes the subfamilies colobines and cercopithecines, have lost the RLN1 paralog, but apes have retained both the RLN1 and the RLN2 genes [20]; Lawrence and Cords, 2012). | https://www.wikidoc.org/index.php/Relaxin | |
3dc7f9eedb3fee6d74e7e433b788a470fbc3a881 | wikidoc | Remorse | Remorse
Remorse is an emotional expression of personal regret - that is, the emotion felt by the injurer after he or she has injured. Remorse is closely allied to guilt and self directed resentment (e.g. - The boy felt much remorse after hitting the old lady. The idea of remorse is used in restorative justice).
One incapable of feeling remorse is often labelled a sociopath (US) or psychopath (UK) - formerly a DSM III condition. Some researchers have lately suggested that this lack is more characteristic of the INTJ personality, a highly rational temperament that relies very little on emotion, but the scientific worth and psychological accuracy of the Myers-Briggs Type Indicator test have been strongly questioned. In general, a person needs to be unable to feel fear, as well as remorse in order to develop psychopathic traits.
"Buyer's remorse" is the concept of regretting a purchase after the fact of buying it.
Regretting one's earlier action or failure to act may be because of remorse or to various other consequences, including being punished for it.
# Expressing remorse
Despite the role apologies play in our lives and the almost daily news reports of the latest celebrity or political apology, there is a surprising dearth of systematic empirical research on the subject of apologies as expressions of remorse.
Two notable exceptions are The Five Languages of Apology by Gary Chapman and Jennifer Thomas, and On Apology by Aaron Lazare. The consensus emerging from these and other studies is quite clear - effective apologies that express remorse typically include the following components: a detailed account of the offense; acknowledgment of the hurt or damage done; acceptance of the responsibility for, and ownership of, the mistake; an explanation that recognizes ones role; a statement or expression of regret, humility or remorse; a request for forgiveness; and an expression of a credible commitment to change or a promise that it won't happen again; and some form of restitution, compensation or token gesture in line with the damage that you caused.
Perhaps the most active research on the relevance of apologies as an expression of remorse appears in the legal and business professions, primarily because of the potential litigation and financial implications.
When an apology is delayed, for instance if a friend has been wronged and the offending party does not apologize, the perception of the offense can compound over time. This is sometimes known as compounding remorse. | Remorse
Remorse is an emotional expression of personal regret - that is, the emotion felt by the injurer after he or she has injured. Remorse is closely allied to guilt and self directed resentment (e.g. - The boy felt much remorse after hitting the old lady. The idea of remorse is used in restorative justice).
One incapable of feeling remorse is often labelled a sociopath (US) or psychopath (UK) - formerly a DSM III condition. Some researchers have lately suggested that this lack is more characteristic of the INTJ personality, a highly rational temperament that relies very little on emotion, but the scientific worth and psychological accuracy of the Myers-Briggs Type Indicator test have been strongly questioned. In general, a person needs to be unable to feel fear, as well as remorse in order to develop psychopathic traits.
"Buyer's remorse" is the concept of regretting a purchase after the fact of buying it.
Regretting one's earlier action or failure to act may be because of remorse or to various other consequences, including being punished for it.
# Expressing remorse
Despite the role apologies play in our lives and the almost daily news reports of the latest celebrity or political apology, there is a surprising dearth of systematic empirical research on the subject of apologies as expressions of remorse.
Two notable exceptions are The Five Languages of Apology by Gary Chapman and Jennifer Thomas, and On Apology by Aaron Lazare. The consensus emerging from these and other studies is quite clear - effective apologies that express remorse typically include the following components: a detailed account of the offense; acknowledgment of the hurt or damage done; acceptance of the responsibility for, and ownership of, the mistake; an explanation that recognizes ones role; a statement or expression of regret, humility or remorse; a request for forgiveness; and an expression of a credible commitment to change or a promise that it won't happen again; and some form of restitution, compensation or token gesture in line with the damage that you caused.
Perhaps the most active research on the relevance of apologies as an expression of remorse appears in the legal and business professions, primarily because of the potential litigation and financial implications.
When an apology is delayed, for instance if a friend has been wronged and the offending party does not apologize, the perception of the offense can compound over time. This is sometimes known as compounding remorse. | https://www.wikidoc.org/index.php/Remorse | |
e60b45a908dbd8100d7dcb235bcb9cdda4eef56d | wikidoc | Repetin | Repetin
Repetin is an extracellular matrix protein expressed in the epidermis. In humans it is encoded by the RPTN gene. Repetin is part of the S100 fused-type protein family and contains a EF hand structural domain.
It functions in the cornified cell envelope formation. It is a multifunctional epidermal matrix protein. RPTN reversibly binds calcium.
RPTN is 5,634 bases long. It starts 152,126,071 base pairs from pter. It ends 152,131,704 base pairs from pter. It has a minus strand orientation.
RPTN is one of the genes that differ between present-day humans and Neanderthals.
RPTN helps protect skin cells, and since the Neanderthals were missing this protein, the Neanderthals were better adapted to the cold, but less so to disease. RPTN is one of 30 specific differences between modern man's DNA and Neanderthal's. | Repetin
Repetin is an extracellular matrix protein expressed in the epidermis. In humans it is encoded by the RPTN gene. Repetin is part of the S100 fused-type protein family and contains a EF hand structural domain.
It functions in the cornified cell envelope formation. It is a multifunctional epidermal matrix protein. RPTN reversibly binds calcium.
RPTN is 5,634 bases long. It starts 152,126,071 base pairs from pter. It ends 152,131,704 base pairs from pter. It has a minus strand orientation.
RPTN is one of the genes that differ between present-day humans and Neanderthals.[1]
RPTN helps protect skin cells, and since the Neanderthals were missing this protein, the Neanderthals were better adapted to the cold, but less so to disease. RPTN is one of 30 specific differences between modern man's DNA and Neanderthal's.[citation needed] | https://www.wikidoc.org/index.php/Repetin | |
a31e6d284247ef3cea4384e781c30bc9aa2bd0fa | wikidoc | Reprimo | Reprimo
Reprimo (RPRM), is a gene located at human chromosome 2q23 whose expression in conjunction with p53, along with other genes which are p53-induced, is associated with the arrest of the cell cycle at the G2 phase.Reprimo's protein product is a highly glycosylated polypeptide which, upon its expression, is localized to the cytoplasm where it is primarily active. As the expression of reprimo is controlled by p53, which is in turn controlled by a wide array of convergent signal pathways pertaining to DNA damage or nutrient depravity, its presence is expected within cells which would cause damage should they be freely allowed to replicate. Pursuant to this, reprimo's expression during the G2 phase of the cell cycle ultimately results in the reduction of Cdc2 expression, and in the inhibition of the nuclear translocation of cyclin B1 which is necessary to its function. Reprimo is known to collaborate with p21 to achieve these specific effects, and in a more general sense collaborates with the other p53-induced proteins and effectors to produce the overall cellular response. These regulatory actions help to render the afflicted cell into an arrested state which is less immediately threatening to the whole organism due to the inability of afflicted cells to replicate with damaged DNA, among other potential circumstances, giving the cell an opportunity to undergo DNA repair or apoptosis as the level of damage will dictate. Indefinite cell cycle arrest is another potential outcome. For this reason, it is considered to be a tumor suppressor gene.
Identification of this gene's repression via methylation to its upstream promoter region within various types of cancerous tissue have been used to suggest a connection to the formation of said cancer. These methylation events commonly cause aberrant DNA splicing which may cause one of many potential errors within the resulting mutant reprimo that ultimately undermine its ability to be expressed, have its intended effects, or to accumulate in sufficient quantities to produce the expected arrest reaction. The variability of these outcomes is owed to the large probability space for these point mutations. There is also research to suggest that this gene's expression status within specific tissues may be useful information for the diagnosis or prognosis of certain types of cancer.
# Utility in cancer detection and prognosis
Given reprimo's inherent role in cancer prevention, investigations have focused on whether it is a point of failure worth monitoring for the purposes of diagnosis. In contrast to non-malignant tissues, in which it has been found in less than eleven percent of samples, methylations to reprimo's promotor region have been detected in a majority of gastric, gallbladder, lymphoma, and colorectal cancers, and in significant proportions of esophageal adinocarcinomas, breast cancers and leukemias. In other types of cancer, the presence of these methylations aren't significantly more common than the baseline non-cancerous tissues.
In those whom have already been diagnosed with primary pancreatic cancer, there is a correlative relationship to suggest there will be a much worse prognosis when said tissues were found to contain these methylations to reprimo's promoter.
In terms of early detection, the methylation status of reprimo in esophageal and gastric tissues have had some success in predicting the development of cancer. In the case of gastric cancer, detection methods include sampling of blood plasma. | Reprimo
Reprimo (RPRM), is a gene located at human chromosome 2q23 whose expression in conjunction with p53, along with other genes which are p53-induced, is associated with the arrest of the cell cycle at the G2 phase.[1][2]Reprimo's protein product is a highly glycosylated polypeptide which, upon its expression, is localized to the cytoplasm where it is primarily active.[2] As the expression of reprimo is controlled by p53, which is in turn controlled by a wide array of convergent signal pathways pertaining to DNA damage or nutrient depravity, its presence is expected within cells which would cause damage should they be freely allowed to replicate.[2] Pursuant to this, reprimo's expression during the G2 phase of the cell cycle ultimately results in the reduction of Cdc2 expression, and in the inhibition of the nuclear translocation of cyclin B1 which is necessary to its function.[1] Reprimo is known to collaborate with p21 to achieve these specific effects,[2] and in a more general sense collaborates with the other p53-induced proteins and effectors to produce the overall cellular response. These regulatory actions help to render the afflicted cell into an arrested state which is less immediately threatening to the whole organism due to the inability of afflicted cells to replicate with damaged DNA, among other potential circumstances, giving the cell an opportunity to undergo DNA repair or apoptosis as the level of damage will dictate. Indefinite cell cycle arrest is another potential outcome. For this reason, it is considered to be a tumor suppressor gene.[3]
Identification of this gene's repression via methylation to its upstream promoter region[2][4] within various types of cancerous tissue have been used to suggest a connection to the formation of said cancer.[5] These methylation events commonly cause aberrant DNA splicing which may cause one of many potential errors within the resulting mutant reprimo that ultimately undermine its ability to be expressed, have its intended effects, or to accumulate in sufficient quantities to produce the expected arrest reaction.[2] The variability of these outcomes is owed to the large probability space for these point mutations. There is also research to suggest that this gene's expression status within specific tissues may be useful information for the diagnosis or prognosis of certain types of cancer.[3]
# Utility in cancer detection and prognosis
Given reprimo's inherent role in cancer prevention, investigations have focused on whether it is a point of failure worth monitoring for the purposes of diagnosis. In contrast to non-malignant tissues, in which it has been found in less than eleven percent of samples, methylations to reprimo's promotor region have been detected in a majority of gastric, gallbladder, lymphoma, and colorectal cancers, and in significant proportions of esophageal adinocarcinomas, breast cancers and leukemias.[5] In other types of cancer, the presence of these methylations aren't significantly more common than the baseline non-cancerous tissues.[5]
In those whom have already been diagnosed with primary pancreatic cancer, there is a correlative relationship to suggest there will be a much worse prognosis when said tissues were found to contain these methylations to reprimo's promoter.[4]
In terms of early detection, the methylation status of reprimo in esophageal and gastric tissues have had some success in predicting the development of cancer.[6][7] In the case of gastric cancer, detection methods include sampling of blood plasma. | https://www.wikidoc.org/index.php/Reprimo | |
1ad2fc8e0e6da3d3fe3381fcea4d5db3ec1f1db5 | wikidoc | Reptile | Reptile
Reptiles are air-breathing, cold-blooded vertebrates that have skin covered in scales as opposed to hair or feathers. They are tetrapods (having or having descended from vertebrates with four limbs) and amniotes, whose embryos are surrounded by an amniotic membrane. Modern reptiles inhabit every continent with the exception of Antarctica, and are represented by four living orders:
- Crocodilia (crocodiles, gharials, caimans and alligators): 23 species
- Sphenodontia (tuatara from New Zealand): 2 species
- Squamata (lizards, snakes and amphisbaenids ("worm-lizards")): approximately 7,900 species
- Testudines (turtles and tortoises): approximately 300 species
The majority of reptile species are oviparous (egg-laying) although certain species of squamates are capable of giving live birth. This is achieved, either through ovoviviparity (egg retention), or viviparity (offspring born without use of calcified eggs). Many of the viviparous species feed their fetuses through various forms of placenta analogous to those of mammals with some providing initial care for their hatchlings. Extant reptiles range in size from the newly-discovered Jaragua Sphaero, at 1.6 cm (0.6 in), to the Saltwater Crocodile, at up to at least 7 m (23 feet).
# Classification
## History of classification
From the classical standpoint, reptiles included all the amniotes except birds and mammals. Thus reptiles were defined as the set of animals that includes crocodiles, alligators, tuatara, lizards, snakes, amphisbaenians and turtles, grouped together as the class Reptilia (Latin repere, "to creep"). This is still the usual definition of the term. However, in recent years, many taxonomists have begun to insist that taxa should be monophyletic, that is, groups should include all descendants of a particular form. The reptiles as defined above would be paraphyletic, since they exclude both birds and mammals, although these also developed from the original reptile. Colin Tudge writes:
The terms "Sauropsida" ("Lizard Faces") and "Theropsida" ("Beast Faces") were coined in 1916 by E.S. Goodrich to distinguish between lizards, birds, and their relatives on one hand (Sauropsida) and mammals and their extinct relatives (Theropsida) on the other. Goodrich supported this division by the nature of the hearts and blood vessels in each group, and other features such as the structure of the forebrain. According to Goodrich, both lineages evolved from an earlier stem group, the Protosauria ("First Lizards") which included some Paleozoic amphibians as well as early reptiles.
In 1956 D.M.S. Watson observed that the first two groups diverged very early in reptilian history, and so he divided Goodrich's Protosauria among them. He also reinterpreted the Sauropsida and Theropsida to exclude birds and mammals respectively. Thus his Sauropsida included Procolophonia, Eosuchia, Millerosauria, Chelonia (turtles), Squamata (lizards and snakes), Rhynchocephalia, Crocodilia, "thecodonts" (paraphyletic basal Archosauria), non-avian dinosaurs, pterosaurs, ichthyosaurs, and sauropyterygians.
This classification supplemented, but was never as popular as, the classification of the reptiles (according to Romer's classic Vertebrate Paleontology) into four subclasses according to the positioning of temporal fenestrae, openings in the sides of the skull behind the eyes. Those divisions were:
- Anapsida - no fenestrae
- Synapsida - one low fenestra (no longer considered true reptiles)
- Euryapsida - one high fenestra (now included within Diapsida)
- Diapsida - two fenestrae
All of the above but Synapsida fall under Sauropsida.
## Taxonomy
Classification to order level, after Benton, 2004.
- Series Amniota
Class Synapsida
Order Pelycosauria*
Order Therapsida
Class Mammalia
Class Sauropsida
Subclass Anapsida
Order Testudines (turtles)
Subclass Diapsida
Order Araeoscelidia
Order Younginiformes
Infraclass Ichthyosauria
Infraclass Lepidosauromorpha
Superorder Sauropterygia
Order Placodontia
Order Nothosauroidea
Order Plesiosauria
Superorder Lepidosauria
Order Sphenodontida (tuatara)
Order Squamata (lizards & snakes)
Infraclass Archosauromorpha
Order Prolacertiformes
Division Archosauria
Subdivision Crurotarsi
Superorder Crocodylomorpha
Order Crocodylia
Subdivision Avemetatarsalia
Infradivision Ornithodira
Order Pterosauria
Superorder Dinosauria
Order Saurischia
Class Aves
Order Ornithischia
- Class Synapsida
Order Pelycosauria*
Order Therapsida
Class Mammalia
- Order Pelycosauria*
- Order Therapsida
Class Mammalia
- Class Mammalia
- Class Sauropsida
Subclass Anapsida
Order Testudines (turtles)
Subclass Diapsida
Order Araeoscelidia
Order Younginiformes
Infraclass Ichthyosauria
Infraclass Lepidosauromorpha
Superorder Sauropterygia
Order Placodontia
Order Nothosauroidea
Order Plesiosauria
Superorder Lepidosauria
Order Sphenodontida (tuatara)
Order Squamata (lizards & snakes)
Infraclass Archosauromorpha
Order Prolacertiformes
Division Archosauria
Subdivision Crurotarsi
Superorder Crocodylomorpha
Order Crocodylia
Subdivision Avemetatarsalia
Infradivision Ornithodira
Order Pterosauria
Superorder Dinosauria
Order Saurischia
Class Aves
Order Ornithischia
- Subclass Anapsida
Order Testudines (turtles)
- Order Testudines (turtles)
- Subclass Diapsida
Order Araeoscelidia
Order Younginiformes
Infraclass Ichthyosauria
Infraclass Lepidosauromorpha
Superorder Sauropterygia
Order Placodontia
Order Nothosauroidea
Order Plesiosauria
Superorder Lepidosauria
Order Sphenodontida (tuatara)
Order Squamata (lizards & snakes)
Infraclass Archosauromorpha
Order Prolacertiformes
Division Archosauria
Subdivision Crurotarsi
Superorder Crocodylomorpha
Order Crocodylia
Subdivision Avemetatarsalia
Infradivision Ornithodira
Order Pterosauria
Superorder Dinosauria
Order Saurischia
Class Aves
Order Ornithischia
- Order Araeoscelidia
- Order Younginiformes
- Infraclass Ichthyosauria
- Infraclass Lepidosauromorpha
Superorder Sauropterygia
Order Placodontia
Order Nothosauroidea
Order Plesiosauria
Superorder Lepidosauria
Order Sphenodontida (tuatara)
Order Squamata (lizards & snakes)
- Superorder Sauropterygia
Order Placodontia
Order Nothosauroidea
Order Plesiosauria
- Order Placodontia
- Order Nothosauroidea
- Order Plesiosauria
- Superorder Lepidosauria
Order Sphenodontida (tuatara)
Order Squamata (lizards & snakes)
- Order Sphenodontida (tuatara)
- Order Squamata (lizards & snakes)
- Infraclass Archosauromorpha
Order Prolacertiformes
Division Archosauria
Subdivision Crurotarsi
Superorder Crocodylomorpha
Order Crocodylia
Subdivision Avemetatarsalia
Infradivision Ornithodira
Order Pterosauria
Superorder Dinosauria
Order Saurischia
Class Aves
Order Ornithischia
- Order Prolacertiformes
- Division Archosauria
Subdivision Crurotarsi
Superorder Crocodylomorpha
Order Crocodylia
Subdivision Avemetatarsalia
Infradivision Ornithodira
Order Pterosauria
Superorder Dinosauria
Order Saurischia
Class Aves
Order Ornithischia
- Subdivision Crurotarsi
Superorder Crocodylomorpha
Order Crocodylia
- Superorder Crocodylomorpha
Order Crocodylia
- Order Crocodylia
- Subdivision Avemetatarsalia
Infradivision Ornithodira
Order Pterosauria
Superorder Dinosauria
Order Saurischia
Class Aves
Order Ornithischia
- Infradivision Ornithodira
Order Pterosauria
Superorder Dinosauria
Order Saurischia
Class Aves
Order Ornithischia
- Order Pterosauria
- Superorder Dinosauria
Order Saurischia
Class Aves
Order Ornithischia
- Order Saurischia
Class Aves
- Class Aves
- Order Ornithischia
## Phylogeny
The cladogram presented here illustrates the "family tree" of reptiles, and follows a simplified version of the relationships found by Laurin and Gauthier (1996), presented as part of the Tree of Life Web Project.
# Evolution
Hylonomus is the oldest-known reptile, and was about 8 to 12 inches (20 to 30 cm) long. Westlothiana has been suggested as the oldest reptile, but is for the moment considered to be more related to amphibians than amniotes. Petrolacosaurus and Mesosaurus are other examples. The earliest reptiles were found in the swamp forests of the Carboniferous, but were largely overshadowed by bigger labyrinthodont amphibians such as Proterogynrius. It was only after the small ice age at the end of the Carboniferous that the reptiles grew to big sizes, producing species such as Edaphosaurus and Dimetrodon.
The first true "reptiles" (Sauropsids) are categorized as Anapsids, having a solid skull with holes only for nose, eyes, spinal cord, etc. Turtles are believed by some to be surviving Anapsids, as they also share this skull structure; but this point has become contentious lately, with some arguing that turtles reverted to this primitive state in order to improve their armor. Both sides have strong evidence, and the conflict has yet to be resolved.
Shortly after the first reptiles, two branches split off, one leading to the Anapsids, which did not develop holes in their skulls. The other group, Diapsida, possessed a pair of holes in their skulls behind the eyes, along with a second pair located higher on the skull. The Diapsida split yet again into two lineages, the lepidosaurs (which contain modern snakes, lizards and tuataras, as well as, debatably, the extinct sea reptiles of the Mesozoic) and the archosaurs (today represented by only crocodilians and birds under dinosaurs, but also containing pterosaurs and non-avian dinosaurs).
The earliest, solid-skulled amniotes also gave rise to a separate line, the Synapsida. Synapsids developed a pair of holes in their skulls behind the eyes (similar to the diapsids), which were used to both lighten the skull and increase the space for jaw muscles. The synapsids eventually evolved into mammals, and are often referred to as mammal-like reptiles, though they are not true members of Sauropsida. (A preferable term is "stem-mammals".)
# Systems
## Circulatory
Most reptiles have closed circulation via a three-chamber heart consisting of two atria and one, variably-partitioned ventricle. There is usually one pair of aortic arches. In spite of this, because of the fluid dynamics of blood flow through the heart, there is little mixing of oxygenated and deoxygenated blood in the three-chamber heart. Furthermore, the blood flow can be altered to shunt either deoxygenated blood to the body or oxygenated blood to the lungs, which gives the animal greater control over its blood flow, allowing more effective thermoregulation and longer diving times for aquatic species. There are some interesting exceptions among reptiles. For instance, crocodilians have an anatomically four-chambered heart that is capable of becoming a functionally three-chamber heart during dives (Mazzotti, 1989 pg 47). Also, it has been discovered that some snake and lizard species (e.g., monitor lizards and pythons) have three-chamber hearts that become functional four-chamber hearts during contraction. This is made possible by a muscular ridge that subdivides the ventricle during ventricular diastole and completely divides it during ventricular systole. Because of this ridge, some of these squamates are capable of producing ventricular pressure differentials that are equivalent to those seen in mammalian and avian hearts (Wang et al, 2003).
## Respiratory
All reptiles breathe using lungs. Aquatic turtles have developed more permeable skin, and some species have modified their cloaca to increase the area for gas exchange (Orenstein, 2001). Even with these adaptations, breathing is never fully accomplished without lungs. Lung ventilation is accomplished differently in each main reptile group. In squamates the lungs are ventilated almost exclusively by the axial musculature. This is also the same musculature that is used during locomotion. Because of this constraint, most squamates are forced to hold their breath during intense runs. Some, however, have found a way around it. Varanids, and a few other lizard species, employ buccal pumping as a complement to their normal "axial breathing." This allows the animals to completely fill their lungs during intense locomotion, and thus remain aerobically active for a long time. Tegu lizards are known to possess a proto-diaphragm, which separates the pulmonary cavity from the visceral cavity. While not actually capable of movement, it does allow for greater lung inflation, by taking the weight of the viscera off the lungs (Klein et al, 2003). Crocodilians actually have a muscular diaphragm that is analogous to the mammalian diaphragm. The difference is that the muscles for the crocodilian diaphragm pull the pubis (part of the pelvis, which is movable in crocodilians) back, which brings the liver down, thus freeing space for the lungs to expand. This type of diaphragmatic setup has been referred to as the "hepatic piston."
How turtles and tortoises breathe has been the subject of much study. To date, only a few species have been studied thoroughly enough to get an idea of how turtles do it. The results indicate that turtles & tortoises have found a variety of solutions to this problem. The problem is that most turtle shells are rigid and do not allow for the type of expansion and contraction that other amniotes use to ventilate their lungs. Some turtles such as the Indian flapshell (Lissemys punctata) have a sheet of muscle that envelopes the lungs. When it contracts, the turtle can exhale. When at rest, the turtle can retract the limbs into the body cavity and force air out of the lungs. When the turtle protracts its limbs, the pressure inside the lungs is reduced, and the turtle can suck air in. Turtle lungs are attached to the inside of the top of the shell (carapace), with the bottom of the lungs attached (via connective tissue) to the rest of the viscera. By using a series of special muscles (roughly equivalent to a diaphragm), turtles are capable of pushing their viscera up and down, resulting in effective respiration, since many of these muscles have attachment points in conjunction with their forelimbs (indeed, many of the muscles expand into the limb pockets during contraction). Breathing during locomotion has been studied in three species, and they show different patterns. Adult female green sea turtles do not breathe as they crutch along their nesting beaches. They hold their breath during terrestrial locomotion and breathe in bouts as they rest. North American box turtles breathe continuously during locomotion, and the ventilation cycle is not coordinated with the limb movements (Landberg et al., 2003). They are probably using their abdominal muscles to breathe during locomotion. The last species to have been studied is red-eared sliders, which also breathe during locomotion, but they had smaller breaths during locomotion than during small pauses between locomotor bouts, indicating that there may be mechanical interference between the limb movements and the breathing apparatus. Box turtles have also been observed to breathe while completely sealed up inside their shells (ibid).
Most reptiles lack a secondary palate, meaning that they must hold their breath while swallowing. Crocodilians have evolved a bony secondary palate that allows them to continue breathing while remaining submerged (and protect their brains from getting kicked in by struggling prey). Skinks (family Scincidae) also have evolved a bony secondary palate, to varying degrees. Snakes took a different approach and extended their trachea instead. Their tracheal extension sticks out like a fleshy straw, and allows these animals to swallow large prey without suffering from asphyxiation.
## Excretory
Excretion is performed mainly by two small kidneys. In diapsids uric acid is the main nitrogenous waste product; turtles, like mammals, mainly excrete urea. Unlike the kidneys of mammals and birds, reptile kidneys are unable to produce liquid urine more concentrated than their body fluid. This is because they lack a specialized structure present in the nephrons of birds and mammals, called a Loop of Henle. Because of this, many reptiles use the colon to aid in the reabsorption of water. Some are also able to take up water stored in the bladder. Excess salts are also excreted by nasal and lingual salt-glands in some reptiles.
## Nervous
The reptilian nervous system contains the same basic part of the amphibian brain, but the reptile cerebrum and cerebellum are slightly larger. Most typical sense organs are well developed with certain exceptions most notably the snakes lack of external ears (middle and inner ears are present). All reptilians have advanced visual depth perception compared to other animals.
There are twelve pairs of cranial nerves.
## Reproductive
Most reptiles reproduce sexually, though some are capable of asexual reproduction. All reproductive activity occurs with the cloaca, the single exit/entrance at the base of the tail where waste is also eliminated. Tuataras lack copulatory organs, so the male and female simply press their cloacas together as the male excretes sperm. Most reptiles, however, have copulatory organs, which are usually retracted or inverted and stored inside the body. In turtles and crocodilians, the male has a single median penis, while squamates including snakes and lizards possess a pair of hemipenes.
Most reptiles lay amniotic eggs covered with leathery or calcareous shells. An amnion, chorion and allantois are present during embryonic life. There are no larval stages of development. Viviparity and ovoviviparity have only evolved in Squamates, and a substantial fraction of the species utilize this mode of reprduction, including all boas and most vipers. The degree of viviparity varies: some species simply retain the eggs until just before hatching, others provide maternal nourishment to supplement the yolk, while still others lack any yolk and provide all nutrients via a placenta.
Asexual reproduction has been identified in squamates in six families of lizards and one snake. In some species of squamates, a population of females are able to produce a unisexual diploid clone of the mother. This asexual reproduction called parthenogenesis occurs in several species of gecko, and is particularly widespread in the teiids (especially Aspidocelis) and lacertids (Lacerta). In captivity Komodo dragons (varanidae) have reproduced by parthenogenesis.
Parthenogenetic species are also suspected to occur among chameleons, agamids, xantusiids, and typhlopids . | Reptile
Template:Sprotect2
Reptiles are air-breathing, cold-blooded vertebrates that have skin covered in scales as opposed to hair or feathers. They are tetrapods (having or having descended from vertebrates with four limbs) and amniotes, whose embryos are surrounded by an amniotic membrane. Modern reptiles inhabit every continent with the exception of Antarctica, and are represented by four living orders:
- Crocodilia (crocodiles, gharials, caimans and alligators): 23 species
- Sphenodontia (tuatara from New Zealand): 2 species
- Squamata (lizards, snakes and amphisbaenids ("worm-lizards")): approximately 7,900 species
- Testudines (turtles and tortoises): approximately 300 species
The majority of reptile species are oviparous (egg-laying) although certain species of squamates are capable of giving live birth. This is achieved, either through ovoviviparity (egg retention), or viviparity (offspring born without use of calcified eggs). Many of the viviparous species feed their fetuses through various forms of placenta analogous to those of mammals with some providing initial care for their hatchlings. Extant reptiles range in size from the newly-discovered Jaragua Sphaero, at 1.6 cm (0.6 in), to the Saltwater Crocodile, at up to at least 7 m (23 feet).
# Classification
## History of classification
From the classical standpoint, reptiles included all the amniotes except birds and mammals. Thus reptiles were defined as the set of animals that includes crocodiles, alligators, tuatara, lizards, snakes, amphisbaenians and turtles, grouped together as the class Reptilia (Latin repere, "to creep"). This is still the usual definition of the term. However, in recent years, many taxonomists have begun to insist that taxa should be monophyletic, that is, groups should include all descendants of a particular form. The reptiles as defined above would be paraphyletic, since they exclude both birds and mammals, although these also developed from the original reptile. Colin Tudge writes:
The terms "Sauropsida" ("Lizard Faces") and "Theropsida" ("Beast Faces") were coined in 1916 by E.S. Goodrich to distinguish between lizards, birds, and their relatives on one hand (Sauropsida) and mammals and their extinct relatives (Theropsida) on the other. Goodrich supported this division by the nature of the hearts and blood vessels in each group, and other features such as the structure of the forebrain. According to Goodrich, both lineages evolved from an earlier stem group, the Protosauria ("First Lizards") which included some Paleozoic amphibians as well as early reptiles.[2]
In 1956 D.M.S. Watson observed that the first two groups diverged very early in reptilian history, and so he divided Goodrich's Protosauria among them. He also reinterpreted the Sauropsida and Theropsida to exclude birds and mammals respectively. Thus his Sauropsida included Procolophonia, Eosuchia, Millerosauria, Chelonia (turtles), Squamata (lizards and snakes), Rhynchocephalia, Crocodilia, "thecodonts" (paraphyletic basal Archosauria), non-avian dinosaurs, pterosaurs, ichthyosaurs, and sauropyterygians.[3]
This classification supplemented, but was never as popular as, the classification of the reptiles (according to Romer's classic Vertebrate Paleontology[4]) into four subclasses according to the positioning of temporal fenestrae, openings in the sides of the skull behind the eyes. Those divisions were:
- Anapsida - no fenestrae
- Synapsida - one low fenestra (no longer considered true reptiles)
- Euryapsida - one high fenestra (now included within Diapsida)
- Diapsida - two fenestrae
All of the above but Synapsida fall under Sauropsida.
## Taxonomy
Classification to order level, after Benton, 2004.[5]
- Series Amniota
Class Synapsida
Order Pelycosauria*
Order Therapsida
Class Mammalia
Class Sauropsida
Subclass Anapsida
Order Testudines (turtles)
Subclass Diapsida
Order Araeoscelidia
Order Younginiformes
Infraclass Ichthyosauria
Infraclass Lepidosauromorpha
Superorder Sauropterygia
Order Placodontia
Order Nothosauroidea
Order Plesiosauria
Superorder Lepidosauria
Order Sphenodontida (tuatara)
Order Squamata (lizards & snakes)
Infraclass Archosauromorpha
Order Prolacertiformes
Division Archosauria
Subdivision Crurotarsi
Superorder Crocodylomorpha
Order Crocodylia
Subdivision Avemetatarsalia
Infradivision Ornithodira
Order Pterosauria
Superorder Dinosauria
Order Saurischia
Class Aves
Order Ornithischia
- Class Synapsida
Order Pelycosauria*
Order Therapsida
Class Mammalia
- Order Pelycosauria*
- Order Therapsida
Class Mammalia
- Class Mammalia
- Class Sauropsida
Subclass Anapsida
Order Testudines (turtles)
Subclass Diapsida
Order Araeoscelidia
Order Younginiformes
Infraclass Ichthyosauria
Infraclass Lepidosauromorpha
Superorder Sauropterygia
Order Placodontia
Order Nothosauroidea
Order Plesiosauria
Superorder Lepidosauria
Order Sphenodontida (tuatara)
Order Squamata (lizards & snakes)
Infraclass Archosauromorpha
Order Prolacertiformes
Division Archosauria
Subdivision Crurotarsi
Superorder Crocodylomorpha
Order Crocodylia
Subdivision Avemetatarsalia
Infradivision Ornithodira
Order Pterosauria
Superorder Dinosauria
Order Saurischia
Class Aves
Order Ornithischia
- Subclass Anapsida
Order Testudines (turtles)
- Order Testudines (turtles)
- Subclass Diapsida
Order Araeoscelidia
Order Younginiformes
Infraclass Ichthyosauria
Infraclass Lepidosauromorpha
Superorder Sauropterygia
Order Placodontia
Order Nothosauroidea
Order Plesiosauria
Superorder Lepidosauria
Order Sphenodontida (tuatara)
Order Squamata (lizards & snakes)
Infraclass Archosauromorpha
Order Prolacertiformes
Division Archosauria
Subdivision Crurotarsi
Superorder Crocodylomorpha
Order Crocodylia
Subdivision Avemetatarsalia
Infradivision Ornithodira
Order Pterosauria
Superorder Dinosauria
Order Saurischia
Class Aves
Order Ornithischia
- Order Araeoscelidia
- Order Younginiformes
- Infraclass Ichthyosauria
- Infraclass Lepidosauromorpha
Superorder Sauropterygia
Order Placodontia
Order Nothosauroidea
Order Plesiosauria
Superorder Lepidosauria
Order Sphenodontida (tuatara)
Order Squamata (lizards & snakes)
- Superorder Sauropterygia
Order Placodontia
Order Nothosauroidea
Order Plesiosauria
- Order Placodontia
- Order Nothosauroidea
- Order Plesiosauria
- Superorder Lepidosauria
Order Sphenodontida (tuatara)
Order Squamata (lizards & snakes)
- Order Sphenodontida (tuatara)
- Order Squamata (lizards & snakes)
- Infraclass Archosauromorpha
Order Prolacertiformes
Division Archosauria
Subdivision Crurotarsi
Superorder Crocodylomorpha
Order Crocodylia
Subdivision Avemetatarsalia
Infradivision Ornithodira
Order Pterosauria
Superorder Dinosauria
Order Saurischia
Class Aves
Order Ornithischia
- Order Prolacertiformes
- Division Archosauria
Subdivision Crurotarsi
Superorder Crocodylomorpha
Order Crocodylia
Subdivision Avemetatarsalia
Infradivision Ornithodira
Order Pterosauria
Superorder Dinosauria
Order Saurischia
Class Aves
Order Ornithischia
- Subdivision Crurotarsi
Superorder Crocodylomorpha
Order Crocodylia
- Superorder Crocodylomorpha
Order Crocodylia
- Order Crocodylia
- Subdivision Avemetatarsalia
Infradivision Ornithodira
Order Pterosauria
Superorder Dinosauria
Order Saurischia
Class Aves
Order Ornithischia
- Infradivision Ornithodira
Order Pterosauria
Superorder Dinosauria
Order Saurischia
Class Aves
Order Ornithischia
- Order Pterosauria
- Superorder Dinosauria
Order Saurischia
Class Aves
Order Ornithischia
- Order Saurischia
Class Aves
- Class Aves
- Order Ornithischia
## Phylogeny
The cladogram presented here illustrates the "family tree" of reptiles, and follows a simplified version of the relationships found by Laurin and Gauthier (1996), presented as part of the Tree of Life Web Project.[6]
Template:Clade
# Evolution
Hylonomus is the oldest-known reptile, and was about 8 to 12 inches (20 to 30 cm) long. Westlothiana has been suggested as the oldest reptile, but is for the moment considered to be more related to amphibians than amniotes. Petrolacosaurus and Mesosaurus are other examples. The earliest reptiles were found in the swamp forests of the Carboniferous, but were largely overshadowed by bigger labyrinthodont amphibians such as Proterogynrius. It was only after the small ice age at the end of the Carboniferous that the reptiles grew to big sizes, producing species such as Edaphosaurus and Dimetrodon.
The first true "reptiles" (Sauropsids) are categorized as Anapsids, having a solid skull with holes only for nose, eyes, spinal cord, etc. Turtles are believed by some to be surviving Anapsids, as they also share this skull structure; but this point has become contentious lately, with some arguing that turtles reverted to this primitive state in order to improve their armor. Both sides have strong evidence, and the conflict has yet to be resolved.
Shortly after the first reptiles, two branches split off, one leading to the Anapsids, which did not develop holes in their skulls. The other group, Diapsida, possessed a pair of holes in their skulls behind the eyes, along with a second pair located higher on the skull. The Diapsida split yet again into two lineages, the lepidosaurs (which contain modern snakes, lizards and tuataras, as well as, debatably, the extinct sea reptiles of the Mesozoic) and the archosaurs (today represented by only crocodilians and birds under dinosaurs, but also containing pterosaurs and non-avian dinosaurs).
The earliest, solid-skulled amniotes also gave rise to a separate line, the Synapsida. Synapsids developed a pair of holes in their skulls behind the eyes (similar to the diapsids), which were used to both lighten the skull and increase the space for jaw muscles. The synapsids eventually evolved into mammals, and are often referred to as mammal-like reptiles, though they are not true members of Sauropsida. (A preferable term is "stem-mammals".)
# Systems
## Circulatory
Most reptiles have closed circulation via a three-chamber heart consisting of two atria and one, variably-partitioned ventricle. There is usually one pair of aortic arches. In spite of this, because of the fluid dynamics of blood flow through the heart, there is little mixing of oxygenated and deoxygenated blood in the three-chamber heart. Furthermore, the blood flow can be altered to shunt either deoxygenated blood to the body or oxygenated blood to the lungs, which gives the animal greater control over its blood flow, allowing more effective thermoregulation and longer diving times for aquatic species. There are some interesting exceptions among reptiles. For instance, crocodilians have an anatomically four-chambered heart that is capable of becoming a functionally three-chamber heart during dives (Mazzotti, 1989 pg 47). Also, it has been discovered that some snake and lizard species (e.g., monitor lizards and pythons) have three-chamber hearts that become functional four-chamber hearts during contraction. This is made possible by a muscular ridge that subdivides the ventricle during ventricular diastole and completely divides it during ventricular systole. Because of this ridge, some of these squamates are capable of producing ventricular pressure differentials that are equivalent to those seen in mammalian and avian hearts (Wang et al, 2003).
## Respiratory
All reptiles breathe using lungs. Aquatic turtles have developed more permeable skin, and some species have modified their cloaca to increase the area for gas exchange (Orenstein, 2001). Even with these adaptations, breathing is never fully accomplished without lungs. Lung ventilation is accomplished differently in each main reptile group. In squamates the lungs are ventilated almost exclusively by the axial musculature. This is also the same musculature that is used during locomotion. Because of this constraint, most squamates are forced to hold their breath during intense runs. Some, however, have found a way around it. Varanids, and a few other lizard species, employ buccal pumping as a complement to their normal "axial breathing." This allows the animals to completely fill their lungs during intense locomotion, and thus remain aerobically active for a long time. Tegu lizards are known to possess a proto-diaphragm, which separates the pulmonary cavity from the visceral cavity. While not actually capable of movement, it does allow for greater lung inflation, by taking the weight of the viscera off the lungs (Klein et al, 2003). Crocodilians actually have a muscular diaphragm that is analogous to the mammalian diaphragm. The difference is that the muscles for the crocodilian diaphragm pull the pubis (part of the pelvis, which is movable in crocodilians) back, which brings the liver down, thus freeing space for the lungs to expand. This type of diaphragmatic setup has been referred to as the "hepatic piston."
How turtles and tortoises breathe has been the subject of much study. To date, only a few species have been studied thoroughly enough to get an idea of how turtles do it. The results indicate that turtles & tortoises have found a variety of solutions to this problem. The problem is that most turtle shells are rigid and do not allow for the type of expansion and contraction that other amniotes use to ventilate their lungs. Some turtles such as the Indian flapshell (Lissemys punctata) have a sheet of muscle that envelopes the lungs. When it contracts, the turtle can exhale. When at rest, the turtle can retract the limbs into the body cavity and force air out of the lungs. When the turtle protracts its limbs, the pressure inside the lungs is reduced, and the turtle can suck air in. Turtle lungs are attached to the inside of the top of the shell (carapace), with the bottom of the lungs attached (via connective tissue) to the rest of the viscera. By using a series of special muscles (roughly equivalent to a diaphragm), turtles are capable of pushing their viscera up and down, resulting in effective respiration, since many of these muscles have attachment points in conjunction with their forelimbs (indeed, many of the muscles expand into the limb pockets during contraction). Breathing during locomotion has been studied in three species, and they show different patterns. Adult female green sea turtles do not breathe as they crutch along their nesting beaches. They hold their breath during terrestrial locomotion and breathe in bouts as they rest. North American box turtles breathe continuously during locomotion, and the ventilation cycle is not coordinated with the limb movements (Landberg et al., 2003). They are probably using their abdominal muscles to breathe during locomotion. The last species to have been studied is red-eared sliders, which also breathe during locomotion, but they had smaller breaths during locomotion than during small pauses between locomotor bouts, indicating that there may be mechanical interference between the limb movements and the breathing apparatus. Box turtles have also been observed to breathe while completely sealed up inside their shells (ibid).
Most reptiles lack a secondary palate, meaning that they must hold their breath while swallowing. Crocodilians have evolved a bony secondary palate that allows them to continue breathing while remaining submerged (and protect their brains from getting kicked in by struggling prey). Skinks (family Scincidae) also have evolved a bony secondary palate, to varying degrees. Snakes took a different approach and extended their trachea instead. Their tracheal extension sticks out like a fleshy straw, and allows these animals to swallow large prey without suffering from asphyxiation.
## Excretory
Excretion is performed mainly by two small kidneys. In diapsids uric acid is the main nitrogenous waste product; turtles, like mammals, mainly excrete urea. Unlike the kidneys of mammals and birds, reptile kidneys are unable to produce liquid urine more concentrated than their body fluid. This is because they lack a specialized structure present in the nephrons of birds and mammals, called a Loop of Henle. Because of this, many reptiles use the colon to aid in the reabsorption of water. Some are also able to take up water stored in the bladder. Excess salts are also excreted by nasal and lingual salt-glands in some reptiles.
## Nervous
The reptilian nervous system contains the same basic part of the amphibian brain, but the reptile cerebrum and cerebellum are slightly larger. Most typical sense organs are well developed with certain exceptions most notably the snakes lack of external ears (middle and inner ears are present). All reptilians have advanced visual depth perception compared to other animals.[citation needed]
There are twelve pairs of cranial nerves.[1]
## Reproductive
Most reptiles reproduce sexually, though some are capable of asexual reproduction. All reproductive activity occurs with the cloaca, the single exit/entrance at the base of the tail where waste is also eliminated. Tuataras lack copulatory organs, so the male and female simply press their cloacas together as the male excretes sperm.[7] Most reptiles, however, have copulatory organs, which are usually retracted or inverted and stored inside the body. In turtles and crocodilians, the male has a single median penis, while squamates including snakes and lizards possess a pair of hemipenes.
Most reptiles lay amniotic eggs covered with leathery or calcareous shells. An amnion, chorion and allantois are present during embryonic life. There are no larval stages of development. Viviparity and ovoviviparity have only evolved in Squamates, and a substantial fraction of the species utilize this mode of reprduction, including all boas and most vipers. The degree of viviparity varies: some species simply retain the eggs until just before hatching, others provide maternal nourishment to supplement the yolk, while still others lack any yolk and provide all nutrients via a placenta.
Asexual reproduction has been identified in squamates in six families of lizards and one snake. In some species of squamates, a population of females are able to produce a unisexual diploid clone of the mother. This asexual reproduction called parthenogenesis occurs in several species of gecko, and is particularly widespread in the teiids (especially Aspidocelis) and lacertids (Lacerta). In captivity Komodo dragons (varanidae) have reproduced by parthenogenesis.
Parthenogenetic species are also suspected to occur among chameleons, agamids, xantusiids, and typhlopids . | https://www.wikidoc.org/index.php/Reptile | |
e3a81185c4dcab67e86349e7b35fe2f6893164ee | wikidoc | Rhombus | Rhombus
In geometry, a rhombus (from Ancient Greek ῥόμβος - rhombos, “rhombus, spinning top”), (plural rhombi or rhombuses) or rhomb (plural rhombs) is an equilateral parallelogram. In other words, it is a four-sided polygon in which every side has the same length.
The rhombus is often casually called a diamond, after the diamonds suit in playing cards, or a lozenge, because those shapes are rhombi, although rhombi are not necessarily diamonds or lozenges.
A rhombus is a variety of quadrilateral. A rectangular rhombus is known as a square.
## Area
The area of any rhombus is the product of the lengths of its diagonals divided by two:
Area=({D_1 \times D_2}) /2
Because the rhombus is a parallelogram, the area also equals the length of a side (B) multiplied by the perpendicular distance between two opposite sides(H)
Area=B \times H
The area also equals the square of the side multiplied by the sine of any of the exterior angles:
Area=a^2 \sin\theta
where a is the length of the side and \theta is the angle between two sides.
## A proof that the diagonals are perpendicular
One of the five 2D lattice types is the rhombic lattice, also called centered rectangular lattice.
If A, B, C and D were the vertices of the rhombus, named in agreement with the figure (higher on this page). Using \overrightarrow{AB} to represent the vector from A to B, one notices that
\overrightarrow{AC} = \overrightarrow{AB} + \overrightarrow{BC}
\overrightarrow{BD} = \overrightarrow{BC}+ \overrightarrow{CD}= \overrightarrow{BC}- \overrightarrow{AB}.
The last equality comes from the parallelism of CD and AB.
Taking the inner product,
since the norms of AB and BC are equal and since the inner product is bilinear and symmetric. The inner product of the diagonals is zero if and only if they are perpendicular.
## Tilings
This is also a called Tessellation.
# Origin
The word rhombus is from the Greek word for something that spins. Euclid used ρόμβος (rhombos), from the verb ρέμβω (rhembo), meaning "to turn round and round". Archimedes used the term "solid rhombus" for two right circular cones sharing a common base. | Rhombus
In geometry, a rhombus (from Ancient Greek ῥόμβος - rhombos, “rhombus, spinning top”), (plural rhombi or rhombuses) or rhomb (plural rhombs) is an equilateral parallelogram. In other words, it is a four-sided polygon in which every side has the same length.
The rhombus is often casually called a diamond, after the diamonds suit in playing cards, or a lozenge, because those shapes are rhombi, although rhombi are not necessarily diamonds or lozenges.
A rhombus is a variety of quadrilateral. A rectangular rhombus is known as a square.
## Area
The area of any rhombus is the product of the lengths of its diagonals divided by two:
<math>Area=({D_1 \times D_2}) /2</math>
Because the rhombus is a parallelogram, the area also equals the length of a side (B) multiplied by the perpendicular distance between two opposite sides(H)
<math>Area=B \times H</math>
The area also equals the square of the side multiplied by the sine of any of the exterior angles:
<math>Area=a^2 \sin\theta</math>
where a is the length of the side and <math>\theta</math> is the angle between two sides.
## A proof that the diagonals are perpendicular
One of the five 2D lattice types is the rhombic lattice, also called centered rectangular lattice.
If A, B, C and D were the vertices of the rhombus, named in agreement with the figure (higher on this page). Using <math>\overrightarrow{AB}</math> to represent the vector from A to B, one notices that
<math>\overrightarrow{AC} = \overrightarrow{AB} + \overrightarrow{BC}</math>
<math>\overrightarrow{BD} = \overrightarrow{BC}+ \overrightarrow{CD}= \overrightarrow{BC}- \overrightarrow{AB}</math>.
The last equality comes from the parallelism of CD and AB.
Taking the inner product,
<\overrightarrow{AC}, \overrightarrow{BD}> = <\overrightarrow{AB} + \overrightarrow{BC}, \overrightarrow{BC} - \overrightarrow{AB}></math>
since the norms of AB and BC are equal and since the inner product is bilinear and symmetric. The inner product of the diagonals is zero if and only if they are perpendicular.
## Tilings
This is also a called Tessellation.
# Origin
The word rhombus is from the Greek word for something that spins. Euclid used ρόμβος (rhombos), from the verb ρέμβω (rhembo), meaning "to turn round and round".[1][2] Archimedes used the term "solid rhombus" for two right circular cones sharing a common base.[3] | https://www.wikidoc.org/index.php/Rhombic | |
f8fa096a147b6336f868773a5938ce9d1b91d31c | wikidoc | Rhonchi | Rhonchi
# Overview
Rhonchi is the "coarse rattling sound somewhat like snoring, usually caused by secretion in bronchial airways". Rhonchi is the plural form of the singular word "rhonchus".
# Description
It is an abnormal or adventitious sound heard when listening to the chest as the person breathes. Wheezing noises are heard during inspiration, expiration or both. They are present when an airway is partially obstructed owing to secretions, mucosal swelling, or tumor tissue pressing on the passage. The sounds are gurgling noises heard on auscultation of the lungs with a stethoscope during inhalation or exhalation. The sounds are caused by the flow of air through thick mucous secretions in the larger air passages such as the bronchioles but can also be associated with smaller structures such as the alveoli.
Rhonchi can be heard in patients with chronic obstructive pulmonary disease (COPD) and acute or severe bronchitis.
COPD is an all inclusive syndrome that stems from the reduction of surface area associated with emphysema and the production of mucous secretions, bronchospasm and inflammation associated with bronchitis. | Rhonchi
# Overview
Rhonchi is the "coarse rattling sound somewhat like snoring, usually caused by secretion in bronchial airways". Rhonchi is the plural form of the singular word "rhonchus".
# Description
It is an abnormal or adventitious sound heard when listening to the chest as the person breathes. Wheezing noises are heard during inspiration, expiration or both. They are present when an airway is partially obstructed owing to secretions, mucosal swelling, or tumor tissue pressing on the passage. The sounds are gurgling noises heard on auscultation of the lungs with a stethoscope during inhalation or exhalation. The sounds are caused by the flow of air through thick mucous secretions in the larger air passages such as the bronchioles but can also be associated with smaller structures such as the alveoli.
Rhonchi can be heard in patients with chronic obstructive pulmonary disease (COPD) and acute or severe bronchitis.
COPD is an all inclusive syndrome that stems from the reduction of surface area associated with emphysema and the production of mucous secretions, bronchospasm and inflammation associated with bronchitis. | https://www.wikidoc.org/index.php/Rhonchi | |
6be09b357a3ad48eeed7c3ba72311e00e36422d9 | wikidoc | Rhubarb | Rhubarb
# Overview
Rhubarb is a perennial plant that grows from thick short rhizomes, comprising the genus Rheum. This genus is in the family Polygonaceae, along with dock, sorrel, knotweeds, knotgrasses and buckwheat. The large, somewhat triangular leaf blades are elevated on long, fleshy petioles. The flowers are small, greenish-white, and borne in large compound leafy inflorescences.
Rhubarb is actually a herb, but is often used in food as a fruit. In the United States until the 1940s it was considered a vegetable. It was reclassified as a fruit when US customs officials, baffled by the foreign food, decided it should be classified according to the way it was eaten.
# Cultivation and use
The plant is indigenous to Asia, and many suggest that it was often used by the Mongolians; particularly, the Tatars tribes of the Gobi. The plant has grown wild along the banks of the Volga for centuries; it may have been brought there by Eurasian tribes, such as the Scythians, Huns, Magyars or Mongols. Varieties of rhubarb have a long history as medicinal plants in traditional Chinese medicine, but the use of rhubarb as food is a relatively recent innovation, first recorded in 17th century England, after affordable sugar became available to common people.
Rhubarb is now grown in many areas, primarily for its fleshy petioles, commonly known as rhubarb sticks or stalks. In temperate climates rhubarb is one of the first food plants to be ready for harvest, usually in mid to late Spring (April/May in the Northern Hemisphere, October/November in the Southern). The petioles can be cooked in a variety of ways. Stewed, they yield a tart sauce that can be eaten with sugar and other stewed fruit or used as filling for pies (see rhubarb pie), tarts, and crumbles. This common use led to the slang term for rhubarb, "pie plant". In Germany, this slang term is also used; the common name being Rhabarber in German. Cooked with strawberries as a sweetener, rhubarb makes excellent jam. It can also be used to make wine. Recently, it has been used in cake.
In former days, a common and affordable sweet for children in parts of the United Kingdom and Sweden was a tender stick of rhubarb, dipped in sugar. In the UK the first rhubarb of the year is grown by candlelight in dark sheds dotted around the noted "Rhubarb Triangle" of Wakefield, Leeds and Morley.
In warm climates, rhubarb will grow all year round, but in colder climates the parts of the plant above the ground disappear completely during winter, and begin to grow again from the root in early spring. It can be forced, that is, encouraged to grow early, by raising the local temperature. This is commonly done by placing an upturned bucket over the shoots as they come up.
Rhubarb is used as a strong laxative and for its astringent effect on the mucous membranes of the mouth and the nasal cavity.
# Species
The plant is represented by about 60 extant species. Among species found in the wild, those most commonly used in cooking are the Garden Rhubarb (R. rhabarbarum) and R. rhaponticum, which, though a true rhubarb, bears the common name False Rhubarb. The many varieties of cultivated rhubarb more usually grown for eating are recognised as Rheum x hybridum in the Royal Horticultural Societies list of recognised plant names. The drug rheum is prepared from the rhizomes and roots of another species, R. officinale or Medicinal Rhubarb. This species is also native to Asia, as is the Turkey Rhubarb (R. palmatum). Another species, the Sikkim Rhubarb (R. nobile), is limited to the Himalayas.
Rheum species have been recorded as larval food plants for some Lepidoptera species including Brown-tail, Buff Ermine, Cabbage Moth, Large Yellow Underwing, The Nutmeg, Setaceous Hebrew Character and Turnip Moth.
# Toxic effects
Rhubarb leaves contain poisonous substances. Rhubarb leaves contain oxalic acid, a corrosive and nephrotoxic acid that is present in many plants. The Template:LD50 (median lethal dose) for pure oxalic acid is predicted to be about 375 mg/kg body weight, or about 25 g for a 65 kg (~140 lb) human. While the oxalic acid content of rhubarb leaves can vary, a typical value is about 0.5%, so a rather unlikely five kilograms of the extremely sour leaves would have to be consumed to reach an Template:LD50 dose of oxalic acid. However, the leaves are believed to also contain an additional, unidentified toxin. In the petioles, the amount of oxalic acid is much lower, especially when harvested before mid-June (in the northern hemisphere), but it is still enough to cause slightly rough teeth.
The roots and stems are rich in anthraquinones, such as emodin and rhein. These substances are cathartic and laxative, which explains the sporadic abuse of Rhubarb as a slimming agent. Anthraquinones are yellow or orange and may colour the urine.
# Other uses of the word
It is or was common for a crowd of extras in acting to shout the word "rhubarb" repeatedly and out of step with each other, to cause the effect of general hubbub. As a result, the word "rhubarb" sometimes is used to mean "length of superfluous text in speaking or writing", or a general term to refer to irrelevant chatter by chorus or extra actors. The American equivalent is walla.
Possibly from this usage, possibly from a variant on "rube", or perhaps some of both, the word also denotes a loud argument. The term has been most commonly used in baseball.
The term "rhubarb" as it relates to baseball is an antiquated reference to a fight amonst many players. The iconic bench-clearing brawl is known as a "rhubarb".
In the 1989 film Batman, The Joker (Jack Nicholson) tells Bruce Wayne (Michael Keaton) to "never rub another man's rhubarb". The term was used as a threat to Bruce Wayne warning him to leave both men's love interest Vicki Vale (Kim Basinger) alone.
The phrase "out in the rhubarb patch" can be used to describe a place being in the far reaches of an area. Rhubarb is usually grown at the outer edges of the garden in the less desirable and unkept area.
"Donkey Rhubarb" refers to Japanese knotweed and is used as a term when referring to the drug-oriented uses of cannabis. For example, the word takes the place of words such as "weed" or "pot" in some places in Canada.
Rhubarb, specifically in the form of the fictitious product "Be-Bop-A-Re-Bop Rhubarb Pie," is frequently mentioned in 'A Prairie Home Companion'. In the 2006 film adaptation of the program, the pies are not mentioned, but rhubarb itself is, including an explanation of the source of the name. | Rhubarb
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
# Overview
Rhubarb is a perennial plant that grows from thick short rhizomes, comprising the genus Rheum. This genus is in the family Polygonaceae, along with dock, sorrel, knotweeds, knotgrasses and buckwheat. The large, somewhat triangular leaf blades are elevated on long, fleshy petioles. The flowers are small, greenish-white, and borne in large compound leafy inflorescences.
Rhubarb is actually a herb, but is often used in food as a fruit. In the United States until the 1940s it was considered a vegetable. It was reclassified as a fruit when US customs officials, baffled by the foreign food, decided it should be classified according to the way it was eaten.[1]
# Cultivation and use
The plant is indigenous to Asia, and many suggest that it was often used by the Mongolians; particularly, the Tatars tribes of the Gobi. The plant has grown wild along the banks of the Volga for centuries; it may have been brought there by Eurasian tribes, such as the Scythians, Huns, Magyars or Mongols. Varieties of rhubarb have a long history as medicinal plants in traditional Chinese medicine, but the use of rhubarb as food is a relatively recent innovation, first recorded in 17th century England, after affordable sugar became available to common people.
Rhubarb is now grown in many areas, primarily for its fleshy petioles, commonly known as rhubarb sticks or stalks. In temperate climates rhubarb is one of the first food plants to be ready for harvest, usually in mid to late Spring (April/May in the Northern Hemisphere, October/November in the Southern). The petioles can be cooked in a variety of ways. Stewed, they yield a tart sauce that can be eaten with sugar and other stewed fruit or used as filling for pies (see rhubarb pie), tarts, and crumbles. This common use led to the slang term for rhubarb, "pie plant". In Germany, this slang term is also used; the common name being Rhabarber in German. Cooked with strawberries as a sweetener, rhubarb makes excellent jam. It can also be used to make wine. Recently, it has been used in cake.
In former days, a common and affordable sweet for children in parts of the United Kingdom and Sweden was a tender stick of rhubarb, dipped in sugar. In the UK the first rhubarb of the year is grown by candlelight in dark sheds dotted around the noted "Rhubarb Triangle" of Wakefield, Leeds and Morley[2].
In warm climates, rhubarb will grow all year round, but in colder climates the parts of the plant above the ground disappear completely during winter, and begin to grow again from the root in early spring. It can be forced, that is, encouraged to grow early, by raising the local temperature. This is commonly done by placing an upturned bucket over the shoots as they come up.
Rhubarb is used as a strong laxative and for its astringent effect on the mucous membranes of the mouth and the nasal cavity.
# Species
The plant is represented by about 60 extant species.[3] Among species found in the wild, those most commonly used in cooking are the Garden Rhubarb (R. rhabarbarum) and R. rhaponticum, which, though a true rhubarb, bears the common name False Rhubarb.[4] The many varieties of cultivated rhubarb more usually grown for eating are recognised as Rheum x hybridum in the Royal Horticultural Societies list of recognised plant names. The drug rheum is prepared from the rhizomes and roots of another species, R. officinale or Medicinal Rhubarb. This species is also native to Asia, as is the Turkey Rhubarb (R. palmatum). Another species, the Sikkim Rhubarb (R. nobile), is limited to the Himalayas.
Rheum species have been recorded as larval food plants for some Lepidoptera species including Brown-tail, Buff Ermine, Cabbage Moth, Large Yellow Underwing, The Nutmeg, Setaceous Hebrew Character and Turnip Moth.
# Toxic effects
Rhubarb leaves contain poisonous substances. Rhubarb leaves contain oxalic acid, a corrosive and nephrotoxic acid that is present in many plants. The Template:LD50 (median lethal dose) for pure oxalic acid is predicted to be about 375 mg/kg body weight,[citation needed] or about 25 g for a 65 kg (~140 lb) human. While the oxalic acid content of rhubarb leaves can vary, a typical value is about 0.5%,[5] so a rather unlikely five kilograms of the extremely sour leaves would have to be consumed to reach an Template:LD50 dose of oxalic acid. However, the leaves are believed to also contain an additional, unidentified toxin.[6] In the petioles, the amount of oxalic acid is much lower, especially when harvested before mid-June (in the northern hemisphere), but it is still enough to cause slightly rough teeth.[citation needed]
The roots and stems are rich in anthraquinones, such as emodin and rhein. These substances are cathartic and laxative, which explains the sporadic abuse of Rhubarb as a slimming agent. Anthraquinones are yellow or orange and may colour the urine.[citation needed]
# Other uses of the word
It is or was common for a crowd of extras in acting to shout the word "rhubarb" repeatedly and out of step with each other, to cause the effect of general hubbub. As a result, the word "rhubarb" sometimes is used to mean "length of superfluous text in speaking or writing", or a general term to refer to irrelevant chatter by chorus or extra actors. The American equivalent is walla.
Possibly from this usage, possibly from a variant on "rube", or perhaps some of both, the word also denotes a loud argument. The term has been most commonly used in baseball.
The term "rhubarb" as it relates to baseball is an antiquated reference to a fight amonst many players. The iconic bench-clearing brawl is known as a "rhubarb".
In the 1989 film Batman, The Joker (Jack Nicholson) tells Bruce Wayne (Michael Keaton) to "never rub another man's rhubarb". The term was used as a threat to Bruce Wayne warning him to leave both men's love interest Vicki Vale (Kim Basinger) alone.
The phrase "out in the rhubarb patch" can be used to describe a place being in the far reaches of an area. Rhubarb is usually grown at the outer edges of the garden in the less desirable and unkept area.[citation needed]
"Donkey Rhubarb" refers to Japanese knotweed[7] and is used as a term when referring to the drug-oriented uses of cannabis.[citation needed] For example, the word takes the place of words such as "weed" or "pot" in some places in Canada.
Rhubarb, specifically in the form of the fictitious product "Be-Bop-A-Re-Bop Rhubarb Pie," is frequently mentioned in 'A Prairie Home Companion'. In the 2006 film adaptation of the program, the pies are not mentioned, but rhubarb itself is, including an explanation of the source of the name. | https://www.wikidoc.org/index.php/Rhubarb | |
ef6b6c9dca11e43dca11b286a3e8117a98aacdd7 | wikidoc | Rifater | Rifater
Rifater® is a fixed dose combination tablet manufactured by Aventis used in the treatment of tuberculosis. Each tablet contains 120 mg rifampicin, 50 mg isoniazid and 300 mg pyrazinamide.
It is used in the first two months of tuberculosis treatment. The dose given depends on the patient's weight:
- up to 40 kg, 3 tablets daily;
- 40 to 49 kg, 4 tablets daily;
- 50 to 64 kg, 5 tablets daily;
- 65 kg or more, 6 tablets daily.
Rifater should not be used in children (the doses are wrong for them).
The purpose of the fixed dose combination is to make it easier for patients to take their medication; but also to ensure that if patients forget to take one or two of their drugs, they do not then develop resistance to the remaining drugs. | Rifater
Rifater® is a fixed dose combination tablet manufactured by Aventis used in the treatment of tuberculosis. Each tablet contains 120 mg rifampicin, 50 mg isoniazid and 300 mg pyrazinamide.
It is used in the first two months of tuberculosis treatment. The dose given depends on the patient's weight:
- up to 40 kg, 3 tablets daily;
- 40 to 49 kg, 4 tablets daily;
- 50 to 64 kg, 5 tablets daily;
- 65 kg or more, 6 tablets daily.
Rifater should not be used in children (the doses are wrong for them).
The purpose of the fixed dose combination is to make it easier for patients to take their medication; but also to ensure that if patients forget to take one or two of their drugs, they do not then develop resistance to the remaining drugs. | https://www.wikidoc.org/index.php/Rifater | |
4c69033f5de1181806f48e2a522ebc21cb3e7db5 | wikidoc | Rolfing | Rolfing
Rolfing is a system of soft tissue manipulation, with the objective of realigning the body structurally and harmonizing its fundamental movement patterns in relation to gravity (see Structural Integration). Though the service mark Rolfing® belongs to The Rolf Institute of Structural Integration, the term Rolfing is generally used to apply to a range of systems based on the teachings of Dr. Ida Pauline Rolf. Practitioners of Rolfing believe it to enhance vitality and well-being, and claim that after sessions, many clients stand up straighter, gain in height, and that soft-tissue bodily asymmetries tend to disappear. Rolfing is in some ways similar to deep tissue massage (see especially Myofascial Release), however, practitioners stress that Rolfing's attention to the balance of the body in gravity sets the practice apart.
# History
Rolf developed a method in the early to mid 1950s with the goal of organizing the human structure in relation to gravity. This method was originally called Postural Release, and later, Structural Integration of the Human Body. Early consumers of Structural Integration coined the term "Rolfing".
In 1971, Rolf founded The Rolf Institute of Structural Integration.
The Rolf Institute and a number of other schools, including the Guild for Structural Integration, the Institute for Psycho-Structural Balancing, and Hellerwork Structural Integration, currently teach the method presented by Rolf. In addition, many modern modalities of "deep tissue bodywork" can trace their lineage back to Rolfing and the legacy of Ida Rolf's theories about the fascia.
# Theory and practice
Rolf theorized that 'bound up' fascia (or connective tissue) often restricts opposing muscles from functioning independently from each other, much in the way water, having crystallized, forms hard, unyielding ice. Her practice aimed to separate bound up fascia by deeply separating the fibers manually so as to loosen them up and allow effective movement patterns. Rolf believed that an adequate knowledge of living human anatomy and hands-on training were required in order to safely negotiate the appropriate manipulations and depths necessary to free the bound-up fascia.
Rolfers often prescribe a sequence of ten sessions to gradually "unlock" the whole body, usually beginning with the muscles that regulate and facilitate breathing. During a Rolfing session, a client generally lies down and is guided through specific movements. During these, the Rolfer manipulates the fascia until they are believed to have returned to their 'original length'. This takes place over the course of ten one-hour sessions, with a specific goal for each session, and an overall goal of cumulative results. Some clients find the experience of Rolfing painful, but Rolfing has continued to evolve over the decades into a practice far more gentle than in its early origins.
In addition to the "Basic Ten" series of sessions created by Rolf, an "Advanced Series" of five sessions, and a "Tune-Up series" consisting of a variable number of sessions, are also available, typically after a period of time to allow the client to settle.
# Criticisms
Rolfing practitioners have suggested its use for a wide variety of medical conditions. Some scientific studies have reported possible improvement from using Rolfing for low back pain, cerebral palsy, and chronic fatigue syndrome, however, there is insufficient data to endorse its effectiveness as a therapy.
Rolfing is generally regarded as safe. Because it involves deep tissue manipulation, pregnant women and people with skeletal, vascular, or clot disorders should consult a health care provider before undertaking Rolfing sessions.
Some within the Rolfing community question the original emphasis placed on fascia by Rolf and now believe that the symptoms they detect and treat may have more to do with abnormally high muscle tonus than actual fascial restrictions. | Rolfing
Template:Tfd
Rolfing is a system of soft tissue manipulation, with the objective of realigning the body structurally and harmonizing its fundamental movement patterns in relation to gravity (see Structural Integration). Though the service mark Rolfing® belongs to The Rolf Institute of Structural Integration, the term Rolfing is generally used to apply to a range of systems based on the teachings of Dr. Ida Pauline Rolf[1]. Practitioners of Rolfing believe it to enhance vitality and well-being, and claim that after sessions, many clients stand up straighter, gain in height, and that soft-tissue bodily asymmetries tend to disappear. Rolfing is in some ways similar to deep tissue massage (see especially Myofascial Release), however, practitioners stress that Rolfing's attention to the balance of the body in gravity sets the practice apart[2].
# History
Rolf developed a method in the early to mid 1950s with the goal of organizing the human structure in relation to gravity. This method was originally called Postural Release, and later, Structural Integration of the Human Body. Early consumers of Structural Integration coined the term "Rolfing".[citation needed]
In 1971, Rolf founded The Rolf Institute of Structural Integration.[3]
The Rolf Institute and a number of other schools, including the Guild for Structural Integration, the Institute for Psycho-Structural Balancing, and Hellerwork Structural Integration, currently teach the method presented by Rolf. In addition, many modern modalities of "deep tissue bodywork" can trace their lineage back to Rolfing and the legacy of Ida Rolf's theories about the fascia[citation needed].
# Theory and practice
Rolf theorized that 'bound up' fascia (or connective tissue) often restricts opposing muscles from functioning independently from each other, much in the way water, having crystallized, forms hard, unyielding ice. Her practice aimed to separate bound up fascia by deeply separating the fibers manually so as to loosen them up and allow effective movement patterns. Rolf believed that an adequate knowledge of living human anatomy and hands-on training were required in order to safely negotiate the appropriate manipulations and depths necessary to free the bound-up fascia[citation needed].
Rolfers often prescribe a sequence of ten sessions to gradually "unlock" the whole body, usually beginning with the muscles that regulate and facilitate breathing[4]. During a Rolfing session, a client generally lies down and is guided through specific movements. During these, the Rolfer manipulates the fascia until they are believed to have returned to their 'original length'. This takes place over the course of ten one-hour sessions, with a specific goal for each session, and an overall goal of cumulative results. Some clients find the experience of Rolfing painful, but Rolfing has continued to evolve over the decades into a practice far more gentle than in its early origins[4].
In addition to the "Basic Ten" series of sessions created by Rolf, an "Advanced Series" of five sessions, and a "Tune-Up series" consisting of a variable number of sessions, are also available, typically after a period of time to allow the client to settle[citation needed].
# Criticisms
Rolfing practitioners have suggested its use for a wide variety of medical conditions. Some scientific studies have reported possible improvement from using Rolfing for low back pain, cerebral palsy, and chronic fatigue syndrome, however, there is insufficient data to endorse its effectiveness as a therapy[5].
Rolfing is generally regarded as safe. Because it involves deep tissue manipulation, pregnant women and people with skeletal, vascular, or clot disorders should consult a health care provider before undertaking Rolfing sessions[5].
Some within the Rolfing community question the original emphasis placed on fascia by Rolf and now believe that the symptoms they detect and treat may have more to do with abnormally high muscle tonus than actual fascial restrictions.[6] | https://www.wikidoc.org/index.php/Rolfing | |
49dda10182bdcee860fe6e7ac7f51541f54a4180 | wikidoc | Rooibos | Rooibos
Rooibos, (Template:PronEng, like "roy-boss"), Afrikaans for "red bush"; scientific name Aspalathus linearis) is a broom-like member of the legume family of plants and is used to make a tisane (herbal tea). Commonly called South African red tea or simply red tea or bush tea, the product has been popular in South Africa for generations and is now consumed in many countries. It is sometimes spelled rooibosch in accordance with the Dutch etymology, but "roy-boss" remains the correct pronunciation.
# Production
Rooibos is grown only in a small area in the Cederberg region of the Western Cape province. Generally, the leaves are oxidized, a process often, and inaccurately, referred to as fermentation by analogy with tea processing terminology. This process produces the distinctive reddish-brown color of rooibos and enhances the flavour. Unoxidized "green" rooibos is also produced, but the more demanding production process for green rooibos (similar to the method by which green tea is produced) makes it more expensive than traditional rooibos.
# Use
In South Africa it is more common to drink rooibos with milk and sugar, but elsewhere it is usually served without. The flavor of rooibos tea is often described as being sweet (without sugar added) and slightly nutty. Preparation of rooibos tea is essentially the same as black tea save that the flavour is improved by longer brewing. The resulting brew is a reddish brown color, explaining why rooibos is sometimes referred to as "red tea".
Several coffee shops in South Africa have recently begun to sell red espresso, which is concentrated rooibos served and presented in the style of ordinary espresso (which is normally coffee-based). This has given rise to rooibos-based variations of coffee drinks such as red lattes and red cappuccinos.
# Nutritional and health benefits
Rooibos is becoming more popular in Western countries particularly among health-conscious consumers, due to its high level of antioxidants such as aspalathin and nothofagin, its lack of caffeine, and its low tannin levels compared to fully oxidized black tea or unoxidized green tea leaves.
"Green" rooibos (see above) has a higher antioxidant capacity than fully oxidised rooibos.
# History
Although rooibos was first reported in 1772 by botanist Carl Thunberg, the Khoisan people of the area had been using it for a long time and were aware of its medicinal valuep. 52. The Dutch settlers to the Cape adopted rooibos as an alternative to black tea, an expensive commodity for the settlers who relied on supply ships from Europe. Until the 19th century, however, Dutch usage of the tea was minimal.
In 1903, Benjamin Ginsberg, a Russian settler to the Cape and descendant of a famous tea family, saw potential in rooibos and began trading with the local Khoisan people who were harvesting it. He sold his "Mountain Tea" to settlers in the Cape and shortly became the first exporter of rooibos using contacts from the family tea business.
In the 1930s, Ginsberg convinced a local doctor and Rhodes scholar, Dr. Peter Nortierp. 52, to experiment with cultivation of the plant.
Dr. Nortier cultivated the first plants at Clanwilliam on the Klein Kliphuis farm, owned by W.T. Riordan, a retired magistrate. The tiny seeds were difficult to obtain, as they dispersed as soon as the pods cracked, and would not germinate without scarifying. Dr. Nortier paid farmers to collect seeds. An aged Khoi woman had found a rather unusual source of supply. She came again and again, receiving a shilling for each matchbox filled with seed. She had chanced upon ants dragging seed one day, followed them back to their nest and, on breaking it open, found a granarypp. 53-4. The attempts by Dr. Nortier were ultimately successful, which led Ginsberg to encourage local farmers to cultivate the plant in the hope that it would become a profitable venture. Klein Kliphuis became a tea farm, and within ten years the price of seeds soared to an astounding £80 a pound, the most expensive vegetable seed in the world. Today the seed is gathered by special sifting processes, and Klein Kliphuis is now a guest farm.
Since then, rooibos has grown in popularity in South Africa, and has gained considerable momentum in the worldwide market too. A growing number of brand-name tea companies sell this tea, either by itself or as a component in an ever-growing variety of blends.
The popularity of rooibos has also gained from its association with Precious Ramotswe, the Tswana detective in Alexander McCall Smith's series of novels about The No. 1 Ladies' Detective Agency. Mma Ramotswe's favourite drink is red bush tea (rooibos), which she often promotes as a therapeutic drink to her friends and clients - and hence the readers of the books.
## Trademark controversy
In 1994, Burke International registered the common name rooibos with the US Patent and Trademark Office, exploiting its status as virtually unknown in the US to establish a monopoly on the name in America. When the plant later entered more widespread use, it attempted to force companies to either pay fees for use of the name, or cease its use. After a decade, the American Herbal Products Association and a number of import companies finally succeeded in defeating this trademark through petitions and lawsuits, causing Burke to "voluntarily surrender" the name to the public domain after losing one of the ongoing cases. | Rooibos
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Rooibos, (Template:PronEng, like "roy-boss"), Afrikaans for "red bush"; scientific name Aspalathus linearis) is a broom-like member of the legume family of plants and is used to make a tisane (herbal tea). Commonly called South African red tea or simply red tea or bush tea, the product has been popular in South Africa for generations and is now consumed in many countries. It is sometimes spelled rooibosch in accordance with the Dutch etymology, but "roy-boss" remains the correct pronunciation.
# Production
Rooibos is grown only in a small area in the Cederberg region of the Western Cape province.[1] Generally, the leaves are oxidized, a process often, and inaccurately, referred to as fermentation by analogy with tea processing terminology. This process produces the distinctive reddish-brown color of rooibos and enhances the flavour. Unoxidized "green" rooibos is also produced, but the more demanding production process for green rooibos (similar to the method by which green tea is produced) makes it more expensive than traditional rooibos.
# Use
In South Africa it is more common to drink rooibos with milk and sugar, but elsewhere it is usually served without. The flavor of rooibos tea is often described as being sweet (without sugar added) and slightly nutty. Preparation of rooibos tea is essentially the same as black tea save that the flavour is improved by longer brewing. The resulting brew is a reddish brown color, explaining why rooibos is sometimes referred to as "red tea".
Several coffee shops in South Africa have recently begun to sell red espresso[1], which is concentrated rooibos served and presented in the style of ordinary espresso (which is normally coffee-based). This has given rise to rooibos-based variations of coffee drinks such as red lattes and red cappuccinos.
# Nutritional and health benefits
Rooibos is becoming more popular in Western countries particularly among health-conscious consumers, due to its high level of antioxidants such as aspalathin and nothofagin, its lack of caffeine, and its low tannin levels compared to fully oxidized black tea or unoxidized green tea leaves.[citation needed]
"Green" rooibos (see above) has a higher antioxidant capacity than fully oxidised rooibos.
# History
Although rooibos was first reported in 1772 by botanist Carl Thunberg, the Khoisan people of the area had been using it for a long time[citation needed] and were aware of its medicinal value[2]p. 52. The Dutch settlers to the Cape adopted rooibos as an alternative to black tea, an expensive commodity for the settlers who relied on supply ships from Europe. Until the 19th century, however, Dutch usage of the tea was minimal.
In 1903, Benjamin Ginsberg, a Russian settler to the Cape and descendant of a famous tea family, saw potential in rooibos and began trading with the local Khoisan people who were harvesting it. He sold his "Mountain Tea" to settlers in the Cape and shortly became the first exporter of rooibos using contacts from the family tea business.
In the 1930s, Ginsberg convinced a local doctor and Rhodes scholar, Dr. Peter Nortier[2]p. 52, to experiment with cultivation of the plant.
Dr. Nortier cultivated the first plants at Clanwilliam on the Klein Kliphuis farm, owned by W.T. Riordan, a retired magistrate. The tiny seeds were difficult to obtain, as they dispersed as soon as the pods cracked, and would not germinate without scarifying. Dr. Nortier paid farmers to collect seeds. An aged Khoi woman had found a rather unusual source of supply. She came again and again, receiving a shilling for each matchbox filled with seed. She had chanced upon ants dragging seed one day, followed them back to their nest and, on breaking it open, found a granary[2]pp. 53-4. The attempts by Dr. Nortier were ultimately successful, which led Ginsberg to encourage local farmers to cultivate the plant in the hope that it would become a profitable venture. Klein Kliphuis became a tea farm, and within ten years the price of seeds soared to an astounding £80 a pound, the most expensive vegetable seed in the world. Today the seed is gathered by special sifting processes, and Klein Kliphuis [2] is now a guest farm.
Since then, rooibos has grown in popularity in South Africa, and has gained considerable momentum in the worldwide market too. A growing number of brand-name tea companies sell this tea, either by itself or as a component in an ever-growing variety of blends.
The popularity of rooibos has also gained from its association with Precious Ramotswe, the Tswana detective in Alexander McCall Smith's series of novels about The No. 1 Ladies' Detective Agency. Mma Ramotswe's favourite drink is red bush tea (rooibos), which she often promotes as a therapeutic drink to her friends and clients - and hence the readers of the books.
## Trademark controversy
In 1994, Burke International registered the common name rooibos with the US Patent and Trademark Office, exploiting its status as virtually unknown in the US to establish a monopoly on the name in America. When the plant later entered more widespread use, it attempted to force companies to either pay fees for use of the name, or cease its use. After a decade, the American Herbal Products Association and a number of import companies finally succeeded in defeating this trademark through petitions and lawsuits, causing Burke to "voluntarily surrender" the name to the public domain after losing one of the ongoing cases.[3] | https://www.wikidoc.org/index.php/Rooibos | |
7eb6cd6c3592f5ea79952fe89b5cfac1840f0cfe | wikidoc | Rotifer | Rotifer
The rotifers make up a phylum of microscopic and near-microscopic pseudocoelomate animals. They were first described by John Harris in 1696 (Hudson and Gosse, 1886). Leeuwenhoek is mistakenly given credit for being the first to describe rotifers but Harris had produced sketches in 1703. Most rotifers are around 0.1-0.5 mm long, and are common in freshwater throughout the world with a few saltwater species. Rotifers may be free swimming and truly planktonic, others move by inchworming along the substrate whilst some are sessile, living inside tubes or gelatinous holdfasts. About 25 species are colonial (e.g. Sinantherina semibullata), either sessile or planktonic.
# Structure and form
Rotifers get their name (derived from Greek and meaning "wheel-bearer"; they have also been called wheel animalcules) from the corona, which is composed of several ciliated tufts around the mouth that in motion resemble a wheel. These create a current that sweeps food into the mouth, where it is chewed up by a characteristic pharynx (called the mastax) containing a tiny, calcified, jaw-like structure called the trophi. The cilia also pull the animal, when unattached, through the water. Most free-living forms have pairs of posterior toes to anchor themselves while feeding. Rotifers have bilateral symmetry and a variety of different shapes. There is a well-developed cuticle which may be thick and rigid, giving the animal a box-like shape, or flexible, giving the animal a worm-like shape; such rotifers are respectively called loricate and illoricate.
Like many other microscopic animals, adult rotifers frequently exhibit eutely - they have a fixed number of cells within a species, usually on the order of one thousand.
Males in the class Monogononta may be either present or absent depending on the species and environmental conditions. In the absence of males, reproduction is by parthenogenesis and results in clonal offspring that are genetically identical to the parent. Individuals of some species form two distinct types of parthenogenetic eggs; one type develops into a normal parthenogenetic female, while the other occurs in response to a changed environment and develops into a degenerate male that lacks a digestive system, but does have a complete male reproductive system that is used to inseminate females thereby producing fertilized 'resting eggs'. Resting eggs develop into zygotes that are able to survive extreme environmental conditions such as may occur during winter or when the pond dries up. These eggs resume development and produce a new female generation when conditions improve again. The life span of monogonont females varies from a couple of days to about three weeks.
Bdelloid rotifers are unable to produce resting eggs, but many can survive prolonged periods of adverse conditions after desiccation. This facility is termed anhydrobiosis, and organisms with these capabilities are termed anhydrobionts. Under drought conditions, bdelloid rotifers contract into an inert form and lose almost all body water; when rehydrated, however, they resume activity within a few hours. Bdelloids can survive the dry state for prolonged periods, with the longest well-documented dormancy being nine years. While in other anhydrobionts, such as the brine shrimp, this desiccation tolerance is thought to be linked to the production of trehalose, a non-reducing disaccharide (sugar), bdelloids apparently lack the ability to synthesise trehalose.
Bdelloid rotifer genomes contain two or more divergent copies of each gene, suggesting a long term asexual evolutionary history. Four copies of hsp82 are, for example, found. Each is different and found on a different chromosome excluding the possibility of homozygous sexual reproduction.
# Taxonomy
There are about 2000 species of rotifers, divided into three classes, Monogononta, Bdelloidea, and Seisonidea. The parasitic Acanthocephala is closely related to these groups as well. Currently these four taxa are within the superphyla Platyzoa. Monogononta is the largest group with around 1500 different species.
Bdelloida is of particular note because of the absence of males and the ability of an individual to survive by drying themselves out (known as cryptobiosis). Bdelloids can then become active again when conditions are right.
# Habitat
Rotifers of all types are relatively easy to find. Many live in ponds, moist soil, or any stagnant water. Rotifers can be free swimming or sessile. Rotifers are mostly omnivorous and some have been observed to be cannibalistic. They normally eat algae or decomposing organic material. | Rotifer
The rotifers make up a phylum of microscopic and near-microscopic pseudocoelomate animals. They were first described by John Harris in 1696 (Hudson and Gosse, 1886).[citation needed] Leeuwenhoek is mistakenly given credit for being the first to describe rotifers but Harris had produced sketches in 1703.[citation needed] Most rotifers are around 0.1-0.5 mm long, and are common in freshwater throughout the world with a few saltwater species. Rotifers may be free swimming and truly planktonic, others move by inchworming along the substrate whilst some are sessile, living inside tubes or gelatinous holdfasts. About 25 species are colonial (e.g. Sinantherina semibullata), either sessile or planktonic.
# Structure and form
Rotifers get their name (derived from Greek and meaning "wheel-bearer";[1] they have also been called wheel animalcules) from the corona, which is composed of several ciliated tufts around the mouth that in motion resemble a wheel. These create a current that sweeps food into the mouth, where it is chewed up by a characteristic pharynx (called the mastax) containing a tiny, calcified, jaw-like structure called the trophi. The cilia also pull the animal, when unattached, through the water. Most free-living forms have pairs of posterior toes to anchor themselves while feeding. Rotifers have bilateral symmetry and a variety of different shapes. There is a well-developed cuticle which may be thick and rigid, giving the animal a box-like shape, or flexible, giving the animal a worm-like shape; such rotifers are respectively called loricate and illoricate.
Like many other microscopic animals, adult rotifers frequently exhibit eutely - they have a fixed number of cells within a species, usually on the order of one thousand.
Males in the class Monogononta may be either present or absent depending on the species and environmental conditions. In the absence of males, reproduction is by parthenogenesis and results in clonal offspring that are genetically identical to the parent. Individuals of some species form two distinct types of parthenogenetic eggs; one type develops into a normal parthenogenetic female, while the other occurs in response to a changed environment and develops into a degenerate male that lacks a digestive system, but does have a complete male reproductive system that is used to inseminate females thereby producing fertilized 'resting eggs'. Resting eggs develop into zygotes that are able to survive extreme environmental conditions such as may occur during winter or when the pond dries up. These eggs resume development and produce a new female generation when conditions improve again. The life span of monogonont females varies from a couple of days to about three weeks.
Bdelloid rotifers are unable to produce resting eggs, but many can survive prolonged periods of adverse conditions after desiccation. This facility is termed anhydrobiosis, and organisms with these capabilities are termed anhydrobionts. Under drought conditions, bdelloid rotifers contract into an inert form and lose almost all body water; when rehydrated, however, they resume activity within a few hours. Bdelloids can survive the dry state for prolonged periods, with the longest well-documented dormancy being nine years. While in other anhydrobionts, such as the brine shrimp, this desiccation tolerance is thought to be linked to the production of trehalose, a non-reducing disaccharide (sugar), bdelloids apparently lack the ability to synthesise trehalose.
Bdelloid rotifer genomes contain two or more divergent copies of each gene, suggesting a long term asexual evolutionary history.[2] Four copies of hsp82 are, for example, found. Each is different and found on a different chromosome excluding the possibility of homozygous sexual reproduction.
# Taxonomy
There are about 2000 species of rotifers, divided into three classes, Monogononta, Bdelloidea, and Seisonidea.[3] The parasitic Acanthocephala is closely related to these groups as well. Currently these four taxa are within the superphyla Platyzoa.[4] Monogononta is the largest group with around 1500 different species.[3]
Bdelloida is of particular note because of the absence of males and the ability of an individual to survive by drying themselves out (known as cryptobiosis). Bdelloids can then become active again when conditions are right.[3]
# Habitat
Rotifers of all types are relatively easy to find. Many live in ponds, moist soil, or any stagnant water. Rotifers can be free swimming or sessile. Rotifers are mostly omnivorous and some have been observed to be cannibalistic. They normally eat algae or decomposing organic material.[3] | https://www.wikidoc.org/index.php/Rotifer | |
0c9150b41b65860effc9e6e9538171b519214652 | wikidoc | Roundup | Roundup
Roundup is the brand name of a systemic, broad-spectrum herbicide produced by the U.S. company Monsanto and contains the active ingredient glyphosate. Glyphosate is the most used herbicide in the USA and is the most-sold agrichemical of all time. In the US 5-8 million pounds are used every year on lawns and yards and 85-90 million pounds are used annually in US agriculture.
Monsanto developed and patented the glyphosate molecule in the 1970s, and marketed Roundup from 1973. It retained exclusive rights in the US until its US patent expired in September, 2000, and maintained a predominant marketshare in countries where the patent expired earlier.
The active ingredient of Roundup is the isopropylamine salt of glyphosate. Glyphosate's mode of action is to inhibit an enzyme involved in the synthesis of the amino acids tyrosine, tryptophan and phenylalanine. It is absorbed through foliage and translocated to growing points. Weeds and grass will generally re-emerge within one to two months after usage. Because of this mode of action, it is only effective on actively growing plants; it is not effective as a pre-emergence herbicide.
Monsanto also produces seeds which grow into plants genetically engineered to be tolerant to glyphosate which are known as Roundup Ready crops. The genes contained in these seeds are patented. Such crops allow farmers to use glyphosate as a post-emergence pesticide against both broadleaf and cereal weeds. Soy was the first Roundup Ready crop and was produced at Monsanto's Agracetus Campus located in Middleton, Wisconsin. Current Roundup Ready crops include maize (corn), sorghum, cotton, soy, canola and alfalfa. In May 2007, a federal court decision barred new plantings of Roundup Ready alfalfa and the resale of seeds, due to the failure of regulators to complete an environmental impact statement examining the potential that genetically-modified alfalfa would contaminate non-GM alfalfa crops, encourage new weeds tolerant to herbicides and limit export markets.
The largest single user of Roundup reportedly is the U.S. Government, which sprays huge quantities of the herbicide over the northern countries of South America in an effort to discourage cultivation of the coca plant. (See article Plan Colombia).
# Chemistry
Glyphosate is an aminophosphonic analogue of the natural amino acid glycine and the name is a contraction of glycine, phospho- and -ate. It was first discovered to have herbicidal activity in 1970 by John Franz, a scientist that worked for the Monsanto company. Franz received the National Medal of Technology in 1987 from Ronald Reagan for his discoveries and in 1990 received the Perkin Medal for Applied Chemistry.
# Biochemistry
Glyphosate kills plants by inhibiting the enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), which catalyzes the reaction of shikimate-3-phosphate (S3P) and phosphoenolpyruvate to form 5-enolpyruvyl-shikimate-3-phosphate (ESP). ESP is subsequently dephosphorylated to chorismate an essential precursor in plants for the aromatic amino acids: phenylalanine, tyrosine and tryptophan. These amino acids are used as building blocks in peptides and to produce secondary metabolites such as folates, ubiquinones and naphthoquinone. X-ray crystallographic studies of Glyphosate and EPSPS shows that glyphosate functions by occupying the binding site of the phosphoenol pyruvate, mimicking an intermediate state of the ternary enzyme substrates complex. The shikimate pathway is not present in animals, which obtain aromatic amino acids from their diet. Glyphosate has also been shown to inhibit other plant enzymes and also has been found to affect animal enzymes.
# Health, ecological concerns and controversy
## Toxicity and ecological impact
Glyphosate is classed as a moderately toxic herbicide and in EPA toxicity class III. A 2000 review of the available literature concluded that "under present and expected conditions of new use, there is no potential for Roundup herbicide to pose a health risk to humans". The Northwest Coalition for Alternatives to Pesticides disputes this classification.
## Scientific fraud and false advertising
On two occasions the American EPA has caught scientists deliberately falsifying test results at research laboratories hired by Monsanto to study glyphosate. In the first incident involving "Industrial Biotest Laboratories", a reviewer stated after finding "routine falsification of data" that it was "hard to believe the scientific integrity of the studies when they said they took specimens of the uterus from male rabbits". In the second incident of falsifying test results in 1991, the owner of the lab (Craven Labs), and three employees were indicted on 20 felony counts, the owner was sentenced to 5 years in prison and fined 50,000 dollars, the lab was fined 15.5 million dollars and ordered to pay 3.7 million in restitution. Craven laboratories performed studies for 262 pesticide companies including Monsanto. Monsanto has been accused of false and misleading advertising of glyphosate products, prompting a law suit by the New York State attorney general. Monsanto has also been accused of the false advertising of roundup in Europe where it is currently appealing a law suit on the issue.
## Human and mammalian toxicity
Outside its intended use, glyphosate can be lethal. For example, with intentional poisonings (e.g. suicide), there is approximately a 10% mortality for those ingesting Roundup, compared to 70% for those ingesting paraquat.
A review of the toxicological data on Roundup shows that there are at least 58 studies of the effects of Roundup itself on a range of organisms. This review concluded that "for terrestrial uses of Roundup minimal acute and chronic risk was predicted for potentially exposed nontarget organisms". It also concluded that there were some risks to aquatic organisms exposed to Roundup in shallow water. More recent research indicates glyphosate induces a variety of functional abnormalities in fetuses and pregnant rats. Also in recent mammalian research, glyphosate has been found to interfere with an enzyme involved testosterone production in mouse cell culture and to interfere with an estrogen biosynthesis enzyme in cultures of Human Placental cells.
In controlled residue studies the WHO found "significant residues" on wheat with residues not lost during baking.
Concerns have been raised abouts Roundup's effect on flora, mammals and birds brought about through habitat destruction.
The United States Environmental Protection Agency, the EC Health and Consumer Protection Directorate, and the UN World Health Organization have all concluded that pure glyphosate is not carcinogenic. Opponents of glyphosate claim that Roundup has been found to cause genetic damage, citing Peluso et al. The authors concluded that the damage was "not related to the active ingredient, but to another component of the herbicide mixture.
## Aquatic effects
Fish and aquatic invertebrates are more sensitive to roundup than terrestrial organisms. Glyphosate is generally less persistent in water than in soil, with 12 to 60 day persistence observed in Canadian pond water, yet persistence of over a year have been observed in the sediments of ponds in Michigan and Oregon.
Roundup is not registered for aquatic uses and studies of its effects on amphibians indicates it is toxic to them. Glyphosate formulations that are registered for aquatic use have been found to have negligible adverse effects on sensitive amphibians.
## Environmental degradation and effects
When glyphosate comes into contact with the soil it can be rapidly bound to soil particles and be inactivated. Unbound glyphosate can be degraded by bacteria. Low activity because of binding to soil particles suggests that glyphosate's effects on soil flora will be limited. Low glyphosate concentrations can be found in many creeks and rivers in U.S. and Europe, and in the US glyphosate has been called "relatively persistent" by its EPA.
In soils, half lives vary from as little as 3 days at a site in Texas, 141 days at a site in Iowa, to between 1 - 3 years in Swedish forest soils. It appears that more northern sites have the longest soil persistences such as in Canada and Scandinavia.
However, the binding of glyphosate to particulates can be an advantage. Treatment of industrial wastewater using immobilized bacteria showed complete conversion of glyphosate to nontoxic aminomethylphosphonic acid.
The US EPA concluded that many endangered species of plants, as well as the Houston toad, may be at risk from glyphosate use. One study has shown an effect on growth and survival of earthworms. The results of this study are in conflict with other data and has been criticized on methodological grounds. In other studies nitrogen fixing bacteria have been impaired, and also crop plant susceptibility to disease has been increased. Monsanto firmly denies any negative impact on anything, including wildlife, and has many studies it has funded to back up its position. They would also be quick to point out that any possible negative impact on earthworms and nitrogen fixing bacteria, etc., would be offset by greater yields as of the elimination of weeds, and also would point to soil benefits from less mechanical cultivation of weeds by using Roundup and similar products.
# Reproductive health concerns and EDC activity
There are concerns about the effects of glyphosate (and Roundup) on possible human reproductive dysfunction.
## Endocrine disruptor debate
In-vitro studies have shown glyphosate to have an effect on progesterone production in mammalian cells and can affect mortality of placental cells in-vitro. Whether these studies classify glyphosate as an endocrine disruptor is a matter of debate.
Some feel that in-vitro studies are insufficient, and are waiting to see if animal studies show a change in endocrine activity, since a change in a single cell line may not occur in an entire organism. Additionally, current in-vitro studies expose cell lines to concentrations orders of magnitude greater than would be found in real conditions, and through pathways that would not be experienced in real organism.
Others feel that in-vitro studies, particularly ones identifying not only an effect, but a chemical pathway, are sufficient evidence to classify glyphosate as an endocrine disruptor, on the basis that even small changes in endocrine activity can have lasting effects on an entire organism that may be difficult to detect through whole organism studies alone. Further research on the topic has been planned.
# Glyphosate resistance in weeds and microorganisms
The first documented cases of weed resistance to glyphosate were found in Australia, involving rigid ryegrass near Orange, New South Wales. Some farmers in the United States have expressed concern that weeds are now developing with glyphosate resistance, with 13 states now reporting resistance, and this poses a problem to many farmers, including cotton farmers, that are now heavily dependent on glyphosate to control weeds. Farmers associations are now reporting 103 biotypes of weeds within 63 weed species with herbicide resistance, and this will continue to grow as a problem.
Some microorganisms have a version of 5-enolpyruvoyl-shikimate-3-phosphate synthetase (EPSPS) that is resistant to glyphosate inhibition. The version used in genetically modified crops was isolated from Agrobacterium strain CP4 (CP4 EPSPS) that was resisitant to glyphosate. The CP4 EPSPS gene was cloned and inserted into soybeans. The CP4 EPSPS gene was engineered for plant expression by fusing the 5' end of the gene to a chloroplast transit peptide derived from the petunia EPSPS. This transit peptide was used because it had shown previously an ability to deliver bacterial EPSPS to the chloroplasts of other plants. The plasmid used to move the gene into soybeans was PV-GMGTO4. It contained three bacterial genes, two PC4 EPSPS genes, and a gene encoding beta-glucuronidase (GUS) from Escherichia coli as a marker. The DNA was injected into the soybeans using the particle acceleration method. Soybean cultivar A54O3 was used for the transformation. The expression of the GUS gene was used as the initial evidence of transformation. GUS expression was detected by a staining method in which the GUS enzyme converts a substrate into a blue precipitate. Those plants that showed GUS expression were then taken and sprayed with glyphosate and their tolerance was tested over many generations.
# Genetically modified crops
In 1996, genetically modified soybeans were available commercially . This greatly improved conventional farmers' ability to control weeds in soybean fields since glyphosate could be sprayed on fields without hurting the crop. As of 2005, 87% of U.S. soybean fields were planted to glyphosate resistant varieties.
# Tradenames
It was first sold by Monsanto under the tradename Roundup, and the Roundup trademark is registered with the US Patent Office and still extant. However, the chemical formulation is not patented, so similar products are available from other maufacturers and marketed under various names (for example TOP UP48 in Thailand).
# Other uses
Glyphosate is one of a number of herbicides used by the United States government to spray Colombian coca fields through Plan Colombia. Its health effects, effects on legal crops, and effectiveness in fighting the war on drugs have been widely disputed. Widespread application of glyphosate in attempts to destroy coca crops in South America have resulted in the development of glyphosate-resistant strains of coca which have been selectively bred to be both "Roundup ready" and also larger and higher yielding than the original strains of the plant. | Roundup
Template:Chembox new
Roundup is the brand name of a systemic, broad-spectrum herbicide produced by the U.S. company Monsanto and contains the active ingredient glyphosate. Glyphosate is the most used herbicide in the USA[1] and is the most-sold agrichemical of all time.[citation needed] In the US 5-8 million pounds are used every year on lawns and yards and 85-90 million pounds are used annually in US agriculture.[1]
Monsanto developed and patented the glyphosate molecule in the 1970s, and marketed Roundup from 1973. It retained exclusive rights in the US until its US patent expired in September, 2000, and maintained a predominant marketshare in countries where the patent expired earlier.
The active ingredient of Roundup is the isopropylamine salt of glyphosate. Glyphosate's mode of action is to inhibit an enzyme involved in the synthesis of the amino acids tyrosine, tryptophan and phenylalanine. It is absorbed through foliage and translocated to growing points. Weeds and grass will generally re-emerge within one to two months after usage. Because of this mode of action, it is only effective on actively growing plants; it is not effective as a pre-emergence herbicide.
Monsanto also produces seeds which grow into plants genetically engineered to be tolerant to glyphosate which are known as Roundup Ready crops. The genes contained in these seeds are patented. Such crops allow farmers to use glyphosate as a post-emergence pesticide against both broadleaf and cereal weeds. Soy was the first Roundup Ready crop and was produced at Monsanto's Agracetus Campus located in Middleton, Wisconsin. Current Roundup Ready crops include maize (corn), sorghum, cotton, soy, canola and alfalfa. In May 2007, a federal court decision barred new plantings of Roundup Ready alfalfa and the resale of seeds, due to the failure of regulators to complete an environmental impact statement examining the potential that genetically-modified alfalfa would contaminate non-GM alfalfa crops, encourage new weeds tolerant to herbicides and limit export markets.
The largest single user of Roundup reportedly is the U.S. Government, which sprays huge quantities of the herbicide over the northern countries of South America in an effort to discourage cultivation of the coca plant. (See article Plan Colombia).
# Chemistry
Glyphosate is an aminophosphonic analogue of the natural amino acid glycine and the name is a contraction of glycine, phospho- and -ate. It was first discovered to have herbicidal activity in 1970 by John Franz, a scientist that worked for the Monsanto company. Franz received the National Medal of Technology in 1987 from Ronald Reagan for his discoveries[2] and in 1990 received the Perkin Medal for Applied Chemistry.[3]
# Biochemistry
Glyphosate kills plants by inhibiting the enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), which catalyzes the reaction of shikimate-3-phosphate (S3P) and phosphoenolpyruvate to form 5-enolpyruvyl-shikimate-3-phosphate (ESP). ESP is subsequently dephosphorylated to chorismate an essential precursor in plants for the aromatic amino acids: phenylalanine, tyrosine and tryptophan.[4][5] These amino acids are used as building blocks in peptides and to produce secondary metabolites such as folates, ubiquinones and naphthoquinone. X-ray crystallographic studies of Glyphosate and EPSPS shows that glyphosate functions by occupying the binding site of the phosphoenol pyruvate, mimicking an intermediate state of the ternary enzyme substrates complex.[6] The shikimate pathway is not present in animals, which obtain aromatic amino acids from their diet. Glyphosate has also been shown to inhibit other plant enzymes[7][8] and also has been found to affect animal enzymes.[9]
# Health, ecological concerns and controversy
## Toxicity and ecological impact
Glyphosate is classed as a moderately toxic herbicide and in EPA toxicity class III. A 2000 review of the available literature concluded that "under present and expected conditions of new use, there is no potential for Roundup herbicide to pose a health risk to humans".[10] The Northwest Coalition for Alternatives to Pesticides disputes this classification.[11]
## Scientific fraud and false advertising
On two occasions the American EPA has caught scientists deliberately falsifying test results at research laboratories hired by Monsanto to study glyphosate.[12][13][14] In the first incident involving "Industrial Biotest Laboratories", a reviewer stated after finding "routine falsification of data" that it was "hard to believe the scientific integrity of the studies when they said they took specimens of the uterus from male rabbits".[15][16][17] In the second incident of falsifying test results in 1991, the owner of the lab (Craven Labs), and three employees were indicted on 20 felony counts, the owner was sentenced to 5 years in prison and fined 50,000 dollars, the lab was fined 15.5 million dollars and ordered to pay 3.7 million in restitution.[18][19][20] Craven laboratories performed studies for 262 pesticide companies including Monsanto. Monsanto has been accused of false and misleading advertising of glyphosate products, prompting a law suit by the New York State attorney general.[21] Monsanto has also been accused of the false advertising of roundup in Europe where it is currently appealing a law suit on the issue.[22]
## Human and mammalian toxicity
Outside its intended use, glyphosate can be lethal. For example, with intentional poisonings (e.g. suicide), there is approximately a 10% mortality for those ingesting Roundup, compared to 70% for those ingesting paraquat.[23]
A review of the toxicological data on Roundup shows that there are at least 58 studies of the effects of Roundup itself on a range of organisms.[24] This review concluded that "for terrestrial uses of Roundup minimal acute and chronic risk was predicted for potentially exposed nontarget organisms". It also concluded that there were some risks to aquatic organisms exposed to Roundup in shallow water. More recent research indicates glyphosate induces a variety of functional abnormalities in fetuses and pregnant rats.[25] Also in recent mammalian research, glyphosate has been found to interfere with an enzyme involved testosterone production in mouse cell culture[26] and to interfere with an estrogen biosynthesis enzyme in cultures of Human Placental cells.[27]
In controlled residue studies the WHO found "significant residues" on wheat with residues not lost during baking.[28]
Concerns have been raised abouts Roundup's effect on flora, mammals and birds brought about through habitat destruction.[29]
The United States Environmental Protection Agency,[30] the EC Health and Consumer Protection Directorate, and the UN World Health Organization have all concluded that pure glyphosate is not carcinogenic. Opponents of glyphosate claim that Roundup has been found to cause genetic damage, citing Peluso et al.[31] The authors concluded that the damage was "not related to the active ingredient, but to another component of the herbicide mixture.
## Aquatic effects
Fish and aquatic invertebrates are more sensitive to roundup than terrestrial organisms.[24] Glyphosate is generally less persistent in water than in soil, with 12 to 60 day persistence observed in Canadian pond water, yet persistence of over a year have been observed in the sediments of ponds in Michigan and Oregon.[32]
Roundup is not registered for aquatic uses[33] and studies of its effects on amphibians indicates it is toxic to them.[34] Glyphosate formulations that are registered for aquatic use have been found to have negligible adverse effects on sensitive amphibians.[35]
## Environmental degradation and effects
When glyphosate comes into contact with the soil it can be rapidly bound to soil particles and be inactivated.[32] Unbound glyphosate can be degraded by bacteria.[36] Low activity because of binding to soil particles suggests that glyphosate's effects on soil flora will be limited.[citation needed] Low glyphosate concentrations can be found in many creeks and rivers in U.S. and Europe,[citation needed] and in the US glyphosate has been called "relatively persistent" by its EPA.[32]
In soils, half lives vary from as little as 3 days at a site in Texas, 141 days at a site in Iowa, to between 1 - 3 years in Swedish forest soils.[37] It appears that more northern sites have the longest soil persistences such as in Canada and Scandinavia.
However, the binding of glyphosate to particulates can be an advantage. Treatment of industrial wastewater using immobilized bacteria showed complete conversion of glyphosate to nontoxic aminomethylphosphonic acid.[38]
The US EPA concluded that many endangered species of plants, as well as the Houston toad, may be at risk from glyphosate use.[citation needed] One study has shown an effect on growth and survival of earthworms.[39] The results of this study are in conflict with other data and has been criticized on methodological grounds.[24] In other studies nitrogen fixing bacteria have been impaired, and also crop plant susceptibility to disease has been increased.[40][41][42][43][44][45] Monsanto firmly denies any negative impact on anything, including wildlife, and has many studies it has funded to back up its position. They would also be quick to point out that any possible negative impact on earthworms and nitrogen fixing bacteria, etc., would be offset by greater yields as of the elimination of weeds, and also would point to soil benefits from less mechanical cultivation of weeds by using Roundup and similar products.
# Reproductive health concerns and EDC activity
There are concerns about the effects of glyphosate (and Roundup) on possible human reproductive dysfunction.
## Endocrine disruptor debate
In-vitro studies[46] have shown glyphosate to have an effect on progesterone production in mammalian cells and can affect mortality of placental cells in-vitro.[27] Whether these studies classify glyphosate as an endocrine disruptor is a matter of debate.
Some feel that in-vitro studies are insufficient, and are waiting to see if animal studies show a change in endocrine activity, since a change in a single cell line may not occur in an entire organism. Additionally, current in-vitro studies expose cell lines to concentrations orders of magnitude greater than would be found in real conditions, and through pathways that would not be experienced in real organism.
Others feel that in-vitro studies, particularly ones identifying not only an effect, but a chemical pathway, are sufficient evidence to classify glyphosate as an endocrine disruptor, on the basis that even small changes in endocrine activity can have lasting effects on an entire organism that may be difficult to detect through whole organism studies alone. Further research on the topic has been planned.
# Glyphosate resistance in weeds and microorganisms
The first documented cases of weed resistance to glyphosate were found in Australia, involving rigid ryegrass near Orange, New South Wales.[47] Some farmers in the United States have expressed concern that weeds are now developing with glyphosate resistance, with 13 states now reporting resistance, and this poses a problem to many farmers, including cotton farmers, that are now heavily dependent on glyphosate to control weeds.[48][49] Farmers associations are now reporting 103 biotypes of weeds within 63 weed species with herbicide resistance, and this will continue to grow as a problem.[50][51]
Some microorganisms have a version of 5-enolpyruvoyl-shikimate-3-phosphate synthetase (EPSPS) that is resistant to glyphosate inhibition. The version used in genetically modified crops was isolated from Agrobacterium strain CP4 (CP4 EPSPS) that was resisitant to glyphosate.[52][53] The CP4 EPSPS gene was cloned and inserted into soybeans. The CP4 EPSPS gene was engineered for plant expression by fusing the 5' end of the gene to a chloroplast transit peptide derived from the petunia EPSPS. This transit peptide was used because it had shown previously an ability to deliver bacterial EPSPS to the chloroplasts of other plants. The plasmid used to move the gene into soybeans was PV-GMGTO4. It contained three bacterial genes, two PC4 EPSPS genes, and a gene encoding beta-glucuronidase (GUS) from Escherichia coli as a marker. The DNA was injected into the soybeans using the particle acceleration method. Soybean cultivar A54O3 was used for the transformation. The expression of the GUS gene was used as the initial evidence of transformation. GUS expression was detected by a staining method in which the GUS enzyme converts a substrate into a blue precipitate. Those plants that showed GUS expression were then taken and sprayed with glyphosate and their tolerance was tested over many generations.
# Genetically modified crops
In 1996, genetically modified soybeans were available commercially [30]. This greatly improved conventional farmers' ability to control weeds in soybean fields since glyphosate could be sprayed on fields without hurting the crop. As of 2005, 87% of U.S. soybean fields were planted to glyphosate resistant varieties.[54][55]
# Tradenames
It was first sold by Monsanto under the tradename Roundup, and the Roundup trademark is registered with the US Patent Office and still extant. However, the chemical formulation is not patented, so similar products are available from other maufacturers and marketed under various names (for example TOP UP48 in Thailand).[citation needed]
# Other uses
Glyphosate is one of a number of herbicides used by the United States government to spray Colombian coca fields through Plan Colombia. Its health effects, effects on legal crops, and effectiveness in fighting the war on drugs have been widely disputed. Widespread application of glyphosate in attempts to destroy coca crops in South America have resulted in the development of glyphosate-resistant strains of coca which have been selectively bred to be both "Roundup ready" and also larger and higher yielding than the original strains of the plant. [31][56]
# External links
- Graphic network of Business and political connections for Monsanto [32]
- Roundup website (Monsanto)
- Roundup website (French Website)
- EPA's Integrated Risk Information System entry for Roundup
- EPA's ground & drinking water consumer factsheet for glyphosate
- Greenpeace: A Critique of Monsanto's Risk Evaluation
- Monsanto and the Roundup Ready Controversy
- Greenpeace: Why Consumers and Farmers Should Avoid Monsanto's GE Soybeans
- Greenpeace: Glyphosate and Your Food
- http://www.gene.ch/genet/1999/Jun/msg00012.html
- University of Pittsburgh professor finds herbicide kills frogs (an article from 2005)
- Fact Sheet on Glyphosate, includes 14 references, by the Sierra Club of Canada
- NPR News 2007/08/20 - Farmers Switch Course in Battle Against Weeds | https://www.wikidoc.org/index.php/Roundup | |
b73b6474235480171fd81052dc322cdfe01dc3d1 | wikidoc | RuBisCO | RuBisCO
Ribulose-1,5-bisphosphate carboxylase/oxygenase, most commonly known by the shorter name RuBisCO
, is an enzyme (EC 4.1.1.39) that is used in the Calvin cycle to catalyze the first major step of carbon fixation, a process by which the atoms of atmospheric carbon dioxide are made available to organisms in the form of energy-rich molecules such as sucrose. RuBisCO catalyzes either the carboxylation or oxygenation of ribulose-1,5-bisphosphate (also known as RuBP) with carbon dioxide or oxygen.
RuBisCO is very important in terms of biological impact because it catalyzes the most commonly used chemical reaction by which inorganic carbon enters the biosphere. RuBisCO is apparently the most abundant protein in leaves, and it may be the most abundant protein on Earth. Given its important role in the biosphere, there are currently efforts to genetically engineer crop plants so as to contain more efficient RuBisCO (see below).
# Structure
In plants, algae, cyanobacteria, and phototropic and chemoautotropic proteobacteria the enzyme usually consists of two types of protein subunit, called the large chain (L, about 55,000 Da) and the small chain (S, about 13,000 Da). The enzymatically active substrate (ribulose 1,5-bisphosphate) binding sites are located in the large chains that form dimers as shown in Figure 1 (above, right) in which amino acids from each large chain contribute to the binding sites. A total of eight large chain dimers and eight small chains assemble into a larger complex of about 540,000 Da. In some proteobacteria and dinoflagellates, enzymes consisting of only large subunits have been found .
Magnesium ions (Mg2+) are needed for enzymatic activity. Correct positioning of Mg2+ in the active site of the enzyme involves addition of an "activating" carbon dioxide molecule (CO2) to a lysine in the active site (forming a carbamate). Formation of the carbamate is favored by an alkaline pH. The pH and the concentration of magnesium ions in the fluid compartment (in plants, the stroma of the chloroplast) increases in the light. The role of changing pH and magnesium ion levels in the regulation of RuBisCO enzyme activity is discussed below.
# Enzymatic activity
As shown in Figure 2 (left), RuBisCO is one of many enzymes in the Calvin cycle.
Substrates. During carbon fixation, the substrate molecules for RuBisCO are ribulose 1,5-bisphosphate, carbon dioxide (distinct from the "activating" carbon dioxide) and water . RuBisCO can also allow a reaction to occur with molecular oxygen (O2) instead of carbon dioxide (CO2).
Products. When carbon dioxide is the substrate, the product of the carboxylase reaction is a highly unstable six-carbon phosphorylated intermediate which virtually instantaneously decays into two molecules of glycerate 3-phosphate . The extremely unstable actual molecule created by the initial carboxylation was unknown until 1988 when it was isolated. The 3-phosphoglycerate can be used to produce larger molecules such as glucose. When molecular oxygen is the substrate, the products of the oxygenase reaction are phosphoglycolate and 3-phosphoglycerate. Phosphoglycolate initiates a sequence of reactions called photorespiration which involves enzymes and cytochromes located in the mitochondria and peroxisomes. In this process, two molecules of phosphoglycolate are converted to one molecule of carbon dioxide and one molecule of 3-phosphoglycerate, which can reenter the Calvin cycle. Some of the phosphoglycolate entering this pathway can be retained by plants to produce other molecules such as glycine. At air levels of carbon dioxide and oxygen, the ratio of the reactions is about 4 to 1, which results in a net carbon dioxide fixation of only 3.5. Thus the inability of the enzyme to prevent the reaction with oxygen greatly reduces the photosynthetic potential of many plants. Some plants, many algae and photosynthetic bacteria have overcome this limitation by devising means to increase the concentration of carbon dioxide around the enzyme, including C4 carbon fixation, crassulacean acid metabolism and using pyrenoid.
Rate of enzymatic activity. Some enzymes typically can carry out thousands of chemical reactions each second. However, RuBisCO is slow, being able to "fix" only 3 carbon dioxide molecules each second. Nevertheless, because of its extremely large concentration, under most conditions, and when light is not otherwise limiting photosynthesis, the reaction of RuBisCO responds positively to increasing carbon dioxide concentration, therefore the concentration of carbon dioxide is limiting. The ultimate rate-limiting factor of the Calvin cycle is RuBisCo that cannot be ameliorated in short time by any other factor .
## Regulation of its enzymatic activity
RuBisCO is usually only active during the day because ribulose 1,5-bisphosphate is not being produced in the dark, due to the regulation of several other enzymes in the Calvin cycle. In addition, the activity of Rubisco is coordinated with that of the other enzymes of the Calvin cycle in several ways:
- Regulation by ions. Upon illumination of the chloroplasts, the pH of the stroma rises from 7.0 to 8.0 because of the proton (hydrogen ion, H+) gradient created across the thylakoid membrane. At the same time, magnesium ions (Mg2+) move out of the thylakoids, increasing the concentration of magnesium in the stroma of the chloroplasts. RuBisCO has a high optimal pH (can be >9.0, depending on the magnesium ion concentration) and thus becomes "activated" by the addition of carbon dioxide and magnesium to the active sites as described above.
- Regulation by activase. In plants and some algae, another enzyme, RuBisCO activase is required to allow the rapid formation of the critical carbamate in the active site of RuBisCO. Activase is required because the ribulose 1,5-bisphosphate (RuBP) substrate binds more strongly to the active sites lacking the carbamate and markedly slows down the "activation" process. In the light, RuBisCO activase promotes the release of the inhibitory, or in some views storage , RuBP from the catalytic sites. Activase is also required in some plants (e.g. tobacco and many beans) because in darkness, RuBisCO is inhibited by a competitive inhibitor synthesized by these plants, a substrate analog 2-Carboxy-D-arabitinol 1-phosphate (CA1P). CA1P binds tightly to the active site of carbamylated RuBisCO and inhibits catalytic activity. In the light, RuBisCO activase also promotes the release of CA1P from the catalytic sites. After the CA1P is released from RuBisCO, it is rapidly converted to a non-inhibitory form by a light-activated CA1P-phosphatase. Finally, once every several hundred reactions, the normal reactions with carbon dioxide or oxygen are not completed and other inhibitory substrate analogs are formed in the active site. Once again, RuBisCO activase can promote the release of these analogs from the catalytic sites and maintain the enzyme in a catalytically active form. In the initial reaction of RuBisCO in the light, the RuBP that was separated from RuBisCO binds with the carbamylated enzyme and after proton abstraction produces Enediol that can react with carbon dioxide. A limitation of either RuBisCO or RuBP at any stage will make the reaction insensitive to any other factor including carbon dioxide. For this reason models that are based on a limitation of RuBisCO at low carbon dioxide levels such as compensation point, cannot support life on the planet.
The properties of activase limit the photosynthetic potential of plants at high temperatures . CA1P has also been shown to keep Rubisco in a conformation that is protected from proteolysis.
- Regulation by ATP/ADP and stromal reduction/oxidation state through the activase. The removal of the inhibitory RuBP, CA1P, and the other inhibitory substrate analogs by activase requires the consumption of ATP. This reaction is inhibited by the presence of ADP and thus activase activity depends on the ratio of these compounds in the chloroplast stroma. Furthermore in most plants, the sensitivity of activase to the ratio of ATP/ADP is modified by the stromal reduction/oxidation (redox) state through another small regulatory protein, thioredoxin. In this manner, the activity of activase and the activation state of Rubisco can be modulated in response to light intensity and thus the rate of formation of the ribulose 1,5-bisphosphate substrate.
- Regulation by phosphate. In cyanobacteria, inorganic phosphate (Pi) participates in the co-ordinated regulation of photosynthesis. Pi binds to the RuBisCO active site and to another site on the large chain where it can influence transitions between activated and less active conformations of the enzyme. Activation of bacterial RuBisCO might be particularly sensitive to Pi levels which can act in the same way as RuBisCO activase in higher plants .
- Regulation by carbon dioxide. Since carbon dioxide and oxygen compete at the active site of RuBisCO, carbon fixation by RuBisCO can be enhanced by increasing the carbon dioxide level in the compartment containing RuBisCO (chloroplast stroma). Several times during the evolution of plants, mechanisms have evolved for increasing the level of carbon dioxide in the stroma (see C4 carbon fixation). The use of oxygen as a substrate is an apparently-puzzling process, since it seems to throw away captured energy. However it may be a mechanism for preventing overload during periods of high light flux. This weakness in the enzyme is the cause of photorespiration such that healthy leaves in bright light may have zero net carbon fixation when the ratio of O2 to CO2 reaches a threshold at which oxygen is fixed instead of carbon. This phenomenon is primarily temperature dependent. High temperature decreases the concentration of CO2 dissolved in the moisture in the leaf tissues. This phenomenon is also related to water stress. Since plant leaves are evaporatively cooled, limited water causes high leaf temperatures. C4 plants use the enzyme PEP carboxylase initially, which has a higher affinity for CO2. The process first makes a 4-carbon intermediate compound which is shuttled into a site of C3 photosynthesis then de-carboxylated releasing CO2 to boost the concentration of CO2, hence the name C4 plants.
Crassulacean acid metabolism (CAM) plants keep their stomata (on the underside of the leaf) closed during the day, which conserves water but prevents photosynthesis, which requires CO2 to pass by gas exchange through these openings. Evaporation through the upper side of a leaf is prevented by a layer of wax.
## Genetic engineering
Since RuBisCO is often rate limiting for photosynthesis in plants, it may be possible to improve photosynthetic efficiency by modifying RuBisCO genes in plants to increase its catalytic activity and/or decrease the rate of the oxygenation activity. Approaches that have begun to be investigated include expressing RuBisCO genes from one organism in another organism, increasing the level of expression of RuBisCO subunits, expressing RuBisCO small chains from the chloroplast DNA, and altering RuBisCO genes so as to try to increase specificity for carbon dioxide or otherwise increase the rate of carbon fixation.
One particularly interesting avenue is to introduce RuBisCO variants with naturally high specificity values such as the ones from the red alga Galdieria partita into plants. This would be expected to improve the photosynthetic efficiency of crop plants . Important advances in this area include the replacement of the tobacco enzyme with that of the purple photosynthetic bacterium Rhodospirillum rubrum .
A recent theory explores the trade off between the relative specificity (i.e. ability to favour CO2 fixation over O2 incorporation, which leads to the energetically wasteful process of photorespiration) and the rate at which product is formed. The authors conclude that RuBisCO may actually have evolved to reach a point of 'near perfection' in many plants (with widely varying substrate availabilities and environmental conditions), reaching a compromise between specificity and rate of reaction.
# RuBisCO and carbon sequestration
In view of greenhouse gas-induced climate change, it is speculated whether forests could be fertilized with nitrogen to increase foliar biomass in forests and thereby raise RuBisCO concentration to increase carbon sequestration and fixation in tree cellulosic structures (e.g., trunks, branches). | RuBisCO
Template:Protbox
Ribulose-1,5-bisphosphate carboxylase/oxygenase, most commonly known by the shorter name RuBisCO
[1]
, is an enzyme (EC 4.1.1.39) that is used in the Calvin cycle to catalyze the first major step of carbon fixation, a process by which the atoms of atmospheric carbon dioxide are made available to organisms in the form of energy-rich molecules such as sucrose. RuBisCO catalyzes either the carboxylation or oxygenation of ribulose-1,5-bisphosphate (also known as RuBP) with carbon dioxide or oxygen.
RuBisCO is very important in terms of biological impact because it catalyzes the most commonly used chemical reaction by which inorganic carbon enters the biosphere. RuBisCO is apparently the most abundant protein in leaves, and it may be the most abundant protein on Earth[2]. Given its important role in the biosphere, there are currently efforts to genetically engineer crop plants so as to contain more efficient RuBisCO (see below).
# Structure
In plants, algae, cyanobacteria, and phototropic and chemoautotropic proteobacteria the enzyme usually consists of two types of protein subunit, called the large chain (L, about 55,000 Da) and the small chain (S, about 13,000 Da)[3]. The enzymatically active substrate (ribulose 1,5-bisphosphate) binding sites are located in the large chains that form dimers as shown in Figure 1 (above, right) in which amino acids from each large chain contribute to the binding sites. A total of eight large chain dimers and eight small chains assemble into a larger complex of about 540,000 Da[4]. In some proteobacteria and dinoflagellates, enzymes consisting of only large subunits have been found [5].
Magnesium ions (Mg2+) are needed for enzymatic activity. Correct positioning of Mg2+ in the active site of the enzyme involves addition of an "activating" carbon dioxide molecule (CO2) to a lysine in the active site (forming a carbamate)[6]. Formation of the carbamate is favored by an alkaline pH. The pH and the concentration of magnesium ions in the fluid compartment (in plants, the stroma of the chloroplast[7]) increases in the light. The role of changing pH and magnesium ion levels in the regulation of RuBisCO enzyme activity is discussed below.
# Enzymatic activity
As shown in Figure 2 (left), RuBisCO is one of many enzymes in the Calvin cycle.
Substrates. During carbon fixation, the substrate molecules for RuBisCO are ribulose 1,5-bisphosphate, carbon dioxide (distinct from the "activating" carbon dioxide) and water [8]. RuBisCO can also allow a reaction to occur with molecular oxygen (O2) instead of carbon dioxide (CO2).
Products. When carbon dioxide is the substrate, the product of the carboxylase reaction is a highly unstable six-carbon phosphorylated intermediate which virtually instantaneously decays into two molecules of glycerate 3-phosphate . The extremely unstable actual molecule created by the initial carboxylation was unknown until 1988 when it was isolated. The 3-phosphoglycerate can be used to produce larger molecules such as glucose. When molecular oxygen is the substrate, the products of the oxygenase reaction are phosphoglycolate and 3-phosphoglycerate. Phosphoglycolate initiates a sequence of reactions called photorespiration which involves enzymes and cytochromes located in the mitochondria and peroxisomes. In this process, two molecules of phosphoglycolate are converted to one molecule of carbon dioxide and one molecule of 3-phosphoglycerate, which can reenter the Calvin cycle. Some of the phosphoglycolate entering this pathway can be retained by plants to produce other molecules such as glycine. At air levels of carbon dioxide and oxygen, the ratio of the reactions is about 4 to 1, which results in a net carbon dioxide fixation of only 3.5. Thus the inability of the enzyme to prevent the reaction with oxygen greatly reduces the photosynthetic potential of many plants. Some plants, many algae and photosynthetic bacteria have overcome this limitation by devising means to increase the concentration of carbon dioxide around the enzyme, including C4 carbon fixation, crassulacean acid metabolism and using pyrenoid.
Rate of enzymatic activity. Some enzymes typically can carry out thousands of chemical reactions each second. However, RuBisCO is slow, being able to "fix" only 3 carbon dioxide molecules each second. Nevertheless, because of its extremely large concentration, under most conditions, and when light is not otherwise limiting photosynthesis, the reaction of RuBisCO responds positively to increasing carbon dioxide concentration, therefore the concentration of carbon dioxide is limiting. The ultimate rate-limiting factor of the Calvin cycle is RuBisCo that cannot be ameliorated in short time by any other factor [1].
## Regulation of its enzymatic activity
RuBisCO is usually only active during the day because ribulose 1,5-bisphosphate is not being produced in the dark, due to the regulation of several other enzymes in the Calvin cycle. In addition, the activity of Rubisco is coordinated with that of the other enzymes of the Calvin cycle in several ways:
- Regulation by ions. Upon illumination of the chloroplasts, the pH of the stroma rises from 7.0 to 8.0 because of the proton (hydrogen ion, H+) gradient created across the thylakoid membrane[9]. At the same time, magnesium ions (Mg2+) move out of the thylakoids, increasing the concentration of magnesium in the stroma of the chloroplasts. RuBisCO has a high optimal pH (can be >9.0, depending on the magnesium ion concentration) and thus becomes "activated" by the addition of carbon dioxide and magnesium to the active sites as described above.
- Regulation by activase. In plants and some algae, another enzyme, RuBisCO activase[10] is required to allow the rapid formation of the critical carbamate in the active site of RuBisCO[11]. Activase is required because the ribulose 1,5-bisphosphate (RuBP) substrate binds more strongly to the active sites lacking the carbamate and markedly slows down the "activation" process. In the light, RuBisCO activase promotes the release of the inhibitory, or in some views storage [2], RuBP from the catalytic sites. Activase is also required in some plants (e.g. tobacco and many beans) because in darkness, RuBisCO [3] is inhibited by a competitive inhibitor synthesized by these plants, a substrate analog 2-Carboxy-D-arabitinol 1-phosphate (CA1P)[12]. CA1P binds tightly to the active site of carbamylated RuBisCO and inhibits catalytic activity. In the light, RuBisCO activase also promotes the release of CA1P from the catalytic sites. After the CA1P is released from RuBisCO, it is rapidly converted to a non-inhibitory form by a light-activated CA1P-phosphatase. Finally, once every several hundred reactions, the normal reactions with carbon dioxide or oxygen are not completed and other inhibitory substrate analogs are formed in the active site. Once again, RuBisCO activase can promote the release of these analogs from the catalytic sites and maintain the enzyme in a catalytically active form. In the initial reaction of RuBisCO in the light, the RuBP that was separated from RuBisCO binds with the carbamylated enzyme and after proton abstraction produces Enediol that can react with carbon dioxide. A limitation of either RuBisCO or RuBP at any stage will make the reaction insensitive to any other factor including carbon dioxide. For this reason models that are based on a limitation of RuBisCO at low carbon dioxide levels such as compensation point, cannot support life on the planet[4].
The properties of activase limit the photosynthetic potential of plants at high temperatures [13]. CA1P has also been shown to keep Rubisco in a conformation that is protected from proteolysis[14].
- Regulation by ATP/ADP and stromal reduction/oxidation state through the activase. The removal of the inhibitory RuBP, CA1P, and the other inhibitory substrate analogs by activase requires the consumption of ATP. This reaction is inhibited by the presence of ADP and thus activase activity depends on the ratio of these compounds in the chloroplast stroma. Furthermore in most plants, the sensitivity of activase to the ratio of ATP/ADP is modified by the stromal reduction/oxidation (redox) state through another small regulatory protein, thioredoxin. In this manner, the activity of activase and the activation state of Rubisco can be modulated in response to light intensity and thus the rate of formation of the ribulose 1,5-bisphosphate substrate[15].
- Regulation by phosphate. In cyanobacteria, inorganic phosphate (Pi) participates in the co-ordinated regulation of photosynthesis. Pi binds to the RuBisCO active site and to another site on the large chain where it can influence transitions between activated and less active conformations of the enzyme. Activation of bacterial RuBisCO might be particularly sensitive to Pi levels which can act in the same way as RuBisCO activase in higher plants [16].
- Regulation by carbon dioxide. Since carbon dioxide and oxygen compete at the active site of RuBisCO, carbon fixation by RuBisCO can be enhanced by increasing the carbon dioxide level in the compartment containing RuBisCO (chloroplast stroma). Several times during the evolution of plants, mechanisms have evolved for increasing the level of carbon dioxide in the stroma (see C4 carbon fixation). The use of oxygen as a substrate is an apparently-puzzling process, since it seems to throw away captured energy. However it may be a mechanism for preventing overload during periods of high light flux. This weakness in the enzyme is the cause of photorespiration such that healthy leaves in bright light may have zero net carbon fixation when the ratio of O2 to CO2 reaches a threshold at which oxygen is fixed instead of carbon. This phenomenon is primarily temperature dependent. High temperature decreases the concentration of CO2 dissolved in the moisture in the leaf tissues. This phenomenon is also related to water stress. Since plant leaves are evaporatively cooled, limited water causes high leaf temperatures. C4 plants use the enzyme PEP carboxylase initially, which has a higher affinity for CO2. The process first makes a 4-carbon intermediate compound which is shuttled into a site of C3 photosynthesis then de-carboxylated releasing CO2 to boost the concentration of CO2, hence the name C4 plants.
Crassulacean acid metabolism (CAM) plants keep their stomata (on the underside of the leaf) closed during the day, which conserves water but prevents photosynthesis, which requires CO2 to pass by gas exchange through these openings. Evaporation through the upper side of a leaf is prevented by a layer of wax.
## Genetic engineering
Since RuBisCO is often rate limiting for photosynthesis in plants, it may be possible to improve photosynthetic efficiency by modifying RuBisCO genes in plants to increase its catalytic activity and/or decrease the rate of the oxygenation activity[17]. Approaches that have begun to be investigated include expressing RuBisCO genes from one organism in another organism, increasing the level of expression of RuBisCO subunits, expressing RuBisCO small chains from the chloroplast DNA, and altering RuBisCO genes so as to try to increase specificity for carbon dioxide or otherwise increase the rate of carbon fixation[18].
One particularly interesting avenue is to introduce RuBisCO variants with naturally high specificity values such as the ones from the red alga Galdieria partita into plants. This would be expected to improve the photosynthetic efficiency of crop plants [19]. Important advances in this area include the replacement of the tobacco enzyme with that of the purple photosynthetic bacterium Rhodospirillum rubrum [20].
A recent theory [21] explores the trade off between the relative specificity (i.e. ability to favour CO2 fixation over O2 incorporation, which leads to the energetically wasteful process of photorespiration) and the rate at which product is formed. The authors conclude that RuBisCO may actually have evolved to reach a point of 'near perfection'[5] in many plants (with widely varying substrate availabilities and environmental conditions), reaching a compromise between specificity and rate of reaction.
# RuBisCO and carbon sequestration
In view of greenhouse gas-induced climate change, it is speculated whether forests could be fertilized with nitrogen to increase foliar biomass in forests and thereby raise RuBisCO concentration to increase carbon sequestration and fixation in tree cellulosic structures (e.g., trunks, branches).[22][23] | https://www.wikidoc.org/index.php/RuBisCO | |
919bd5d3c8e946c91cf15ab815c517b4195a9fe3 | wikidoc | s-block | s-block
The s-block of the periodic table of elements consists of the first two groups: the alkali metals and alkaline earth metals, plus hydrogen and helium.
These elements are distinguished by the property that in the atomic ground state, the highest-energy electron is in an s-orbital. Except in hydrogen and helium, these electrons are very easily lost to form positive ions. The helium configuration is chemically exceedingly stable and thus helium has no known stable compounds; thus it is generally grouped with the noble gases.
The other elements of the s-block are all extremely powerful reducing agents, so much so that they never occur naturally in the free state. The metallic forms of these elements can only be extracted by electrolysis of a molten salt, since water is much more easily reduced to hydrogen than the ions of these metals. Sir Humphry Davy, in 1807 and 1808, was the first to isolate all of these metals except lithium, beryllium, rubidium and caesium. Beryllium was isolated independently by F. Wooler and A.A. Bussy in 1828, whilst lithium was isolated by Robert Bunsen in 1854, who isolated rubidium nine years later after having observed it and caesium spectroscopically. Caesium was not isolated until 1881 when Carl Setterberg electrolysed the molten cyanide.
The s-block metals vary from extremely soft (all the alkali metals) to quite hard (beryllium). With the exception of beryllium and magnesium, the metals are too reactive for any structural use except as very minor components (<2%) of alloys with lead. Beryllium and magnesium, though very expensive, are valuable for uses that require strength and lightness. They are extremely valuable as reducing agents to extract titanium, zirconium, thorium and tantalum from their ores, and have other uses as reducing agents in organic chemistry.
All the s-block metals are dangerous fire hazards which require special extinguishants to extinguish. Except for beryllium and magnesium, storage must be under either argon or an inert liquid hydrocarbon. They react vigorously with water to liberate hydrogen, except for magnesium, which reacts slowly, and beryllium, which reacts only when amalgamated with mercury to destroy the oxide film. Lithium has similar properties to magnesium due to the diagonal relationship with magnesium in the periodic table. | s-block
The s-block of the periodic table of elements consists of the first two groups: the alkali metals and alkaline earth metals, plus hydrogen and helium.
These elements are distinguished by the property that in the atomic ground state, the highest-energy electron is in an s-orbital. Except in hydrogen and helium, these electrons are very easily lost to form positive ions. The helium configuration is chemically exceedingly stable and thus helium has no known stable compounds; thus it is generally grouped with the noble gases.
The other elements of the s-block are all extremely powerful reducing agents, so much so that they never occur naturally in the free state. The metallic forms of these elements can only be extracted by electrolysis of a molten salt, since water is much more easily reduced to hydrogen than the ions of these metals. Sir Humphry Davy, in 1807 and 1808, was the first to isolate all of these metals except lithium, beryllium, rubidium and caesium. Beryllium was isolated independently by F. Wooler and A.A. Bussy in 1828, whilst lithium was isolated by Robert Bunsen in 1854, who isolated rubidium nine years later after having observed it and caesium spectroscopically. Caesium was not isolated until 1881 when Carl Setterberg electrolysed the molten cyanide.
The s-block metals vary from extremely soft (all the alkali metals) to quite hard (beryllium). With the exception of beryllium and magnesium, the metals are too reactive for any structural use except as very minor components (<2%) of alloys with lead. Beryllium and magnesium, though very expensive, are valuable for uses that require strength and lightness. They are extremely valuable as reducing agents to extract titanium, zirconium, thorium and tantalum from their ores, and have other uses as reducing agents in organic chemistry.
All the s-block metals are dangerous fire hazards which require special extinguishants to extinguish. Except for beryllium and magnesium, storage must be under either argon or an inert liquid hydrocarbon. They react vigorously with water to liberate hydrogen, except for magnesium, which reacts slowly, and beryllium, which reacts only when amalgamated with mercury to destroy the oxide film. Lithium has similar properties to magnesium due to the diagonal relationship with magnesium in the periodic table. | https://www.wikidoc.org/index.php/S-block | |
62aba78c9ee195c17e8ebbc9dac126001eee5451 | wikidoc | S-layer | S-layer
An S-layer (surface layer) is a part of the cell envelope commonly found in bacteria, as well as among archaea. It consists of a monomolecular layer composed of identical proteins or glycoproteins. This two dimensional structure is built via self-assembly and encloses the whole cell surface. Thus, the S-layer protein can represent up to 10-15% of the whole protein content of a cell
. S-layer proteins are poorly or not conserved at all and can differ markedly even between related species.
Depending on species the S-layers have a thickness between 5 and 25 nm and possess identical pores with 2-8 nm in diameter . S-layers exhibit either an oblique (p1, p2), square (p4) or hexagonal (p3, p6) lattice symmetry. Depending on the lattice symmetry the S-layer is composed of one (P1), two (P2), three (P3), four (P4) or six (P6) identical protein subunits, respectively. The centre to centre spacings (or unit cell dimensions) between these subunits range between 2.5 and 35 nm.
# Fixation of S-layers in the cell wall
- In Gram-negative bacteria S-layers are associated to the LPS via ionic, carbohydrate-carbohydrate, protein carbohydrate interactions and/or protein-protein interactions.
- In Gram-positive bacteria whose S-layers contain surface layer homology (SLH) domains the binding occurs to the peptidoglycan and to a secondary cell wall polymer (e.g. teichuronic acids). In the absence of SLH domains the binding occurs via electrostatic interactions between the positively charged N-terminus of the S-layer protein and a negatively charged secondary cell wall polymer.
- In Gram-negative archaea S-layer proteins possess a hydrophobic anchor that is associated with the underlying lipid membrane.
- In Gram-positive archaea the S-layer proteins bind pseudomurein or to methanochondritin.
# Biological functions of the S-layer
As for many bacteria the S-layer represents the outermost interaction zone with their respective environment, its functions are very diverse and vary from species to species.
In Gram-negative archaea the S-layer is the only cell wall component and therefore is important for mechanical stabilisation. Additional functions associated with S-layers include:
- protection against bacteriophages and phagocytosis
- resistance against low pH
- barrier against high molecular weight substances (e.g. lytic enzymes)
- adhesion (for glycosylated S-layers)
- stabilisation of the membrane
- provide adhesion sites for exoproteins
- provide a periplasmic compartment in Gram-positive prokaryotes together with the peptidoglycan and the cytoplasmic membrane | S-layer
An S-layer (surface layer) is a part of the cell envelope commonly found in bacteria, as well as among archaea. It consists of a monomolecular layer composed of identical proteins or glycoproteins. This two dimensional structure is built via self-assembly and encloses the whole cell surface. Thus, the S-layer protein can represent up to 10-15% of the whole protein content of a cell
[1]
[2]
[3]. S-layer proteins are poorly or not conserved at all and can differ markedly even between related species.
Depending on species the S-layers have a thickness between 5 and 25 nm and possess identical pores with 2-8 nm in diameter [4]. S-layers exhibit either an oblique (p1, p2), square (p4) or hexagonal (p3, p6) lattice symmetry. Depending on the lattice symmetry the S-layer is composed of one (P1), two (P2), three (P3), four (P4) or six (P6) identical protein subunits, respectively. The centre to centre spacings (or unit cell dimensions) between these subunits range between 2.5 and 35 nm.
# Fixation of S-layers in the cell wall
- In Gram-negative bacteria S-layers are associated to the LPS via ionic, carbohydrate-carbohydrate, protein carbohydrate interactions and/or protein-protein interactions.
- In Gram-positive bacteria whose S-layers contain surface layer homology (SLH) domains the binding occurs to the peptidoglycan and to a secondary cell wall polymer (e.g. teichuronic acids). In the absence of SLH domains the binding occurs via electrostatic interactions between the positively charged N-terminus of the S-layer protein and a negatively charged secondary cell wall polymer.
- In Gram-negative archaea S-layer proteins possess a hydrophobic anchor that is associated with the underlying lipid membrane.
- In Gram-positive archaea the S-layer proteins bind pseudomurein or to methanochondritin.
# Biological functions of the S-layer
As for many bacteria the S-layer represents the outermost interaction zone with their respective environment, its functions are very diverse and vary from species to species.
In Gram-negative archaea the S-layer is the only cell wall component and therefore is important for mechanical stabilisation. Additional functions associated with S-layers include:
- protection against bacteriophages and phagocytosis
- resistance against low pH
- barrier against high molecular weight substances (e.g. lytic enzymes)
- adhesion (for glycosylated S-layers)
- stabilisation of the membrane
- provide adhesion sites for exoproteins
- provide a periplasmic compartment in Gram-positive prokaryotes together with the peptidoglycan and the cytoplasmic membrane | https://www.wikidoc.org/index.php/S-layer | |
79369f7bcd0defc64733b449b5e7160ab9df334b | wikidoc | S100A10 | S100A10
S100 calcium-binding protein A10 (S100A10), also known as p11, is a protein that is encoded by the S100A10 gene in humans and the S100a10 gene in other species. S100A10 is a member of the S100 family of proteins containing two EF-hand calcium-binding motifs. S100 proteins are localized in the cytoplasm and/or nucleus of a wide range of cells. They regulate a number of cellular processes such as cell cycle progression and differentiation. The S100 protein is implicated in exocytosis and endocytosis by reorganization of F-actin.
The p11 protein is linked with the transport of neurotransmitters. Found in the brain of humans and other mammals, it has been implicated in the regulation of mood. In addition, due to its interaction with serotonin-signaling proteins and its correlation with symptoms of mood disorders, p11 is a new potential target for drug therapy.
# Gene
The S100 gene family includes at least 13 members that are located as a cluster on chromosome 1q21. In humans, 19 family members are
currently known, with most S100 genes (S100A1 to S100A16).
# Structure
The p11 protein can be found as a free monomer, a homodimer, or a heterotetramer composed of a p11 dimer complex with two molecules of annexin II. The homodimer or heterotetramer can, in turn, dimerize through formation of two disulfide bonds (see figure to the left). The p11 monomer is an asymmetric protein composed of four alpha helices. The dimerized form of the protein is created by packing between the H1 and H4 helices in an antiparallel arrangement with the hydrophobic regions residing in the core.
The structure of p11 is classified by a pair of the helix-loop-helix motif, also known as the EF-hand-type that recognizes and binds calcium ions. This is common to all known S-100 proteins. The EF-hand types, united by an anti-parallel beta-strand between loops L1 and L3, are located on the same side of the molecule, opposite the N-and C-termini. As a member of the S-100 family, its structure resembles that of the S-100A1 and S-100B proteins. This class of proteins has been implicated in the regulation of cytoskeleton assembly, cytosolic enzymes, and membrane dynamics.
P11's involvement with the cytoskeleton may aid the transport of other proteins throughout the cell and to the cell membrane. Unlike other S-100 proteins, the second EF-hand of protein p11 is incapable of binding calcium due to a series of mutations caused by deletions and substitutions. Annexin II, which is attracted to negatively charged phospholipids, binds to p11 at the Ca2+ binding site. In addition, Annexin II has been implicated in membrane-cytoskeleton interactions and in regulations of ion currents and substances across the membrane. P11 and annexin II form a heterotetrameric protein complex that imitates the structure and function of S-100 proteins activated by the binding of calcium. This tetrameric complex is more stable than the p11 dimer, therefore the overexpression of the annexin II gene results in higher levels of p11 protein.
# Function
P11 is an integral part of cellular structural scaffolding that interacts with plasma membrane proteins through its association with annexin II. Recently, it was discovered to form a complex with annexin I though the mechanism remains unknown. It works together with cytosolic and peripheral membrane-associated proteins such as AHNAK in the development of the intracellular membrane. P11 has been implicated in the transportation of proteins involved in mood regulation, nociception, and cell polarization. It is found in cell types throughout the body though it is located predominantly in the lungs and kidneys. It is involved in the trafficking of proteins to the plasma membrane and can be expressed on the cell surface as a receptor. Many of the transported proteins are cell surface receptors in signal transduction pathways and ion channels. P11 facilitates nociception, Ca2+ uptake, and cell polaraization. Complexed with the annexin II, p11 binds receptor and channel proteins and guides them to the cell surface, resulting in increased membrane localization and consequent magnified functional expression of these proteins.
Ion channels are among the several proteins that are transported through the interaction with p11. Some of these proteins include Nav1.8, TRPV5, TRPV6, TASK-1, and ASIC1a. Nav1.8 is a tetrodotoxin-resistant sodium channel that replaces lost sodium after cell damage. Increased expression of these channels alters the magnitude of the sodium current across the membrane. TRPV5 and TRPV6 are transient receptor potential channels selective for Ca+ and Mg2+ ions. TASK-1 is a two-pore domain K+ channel TWIK-related acid-sensitive K (TASK). P11 can also function as a retention factor, preventing TASK-1 from leaving the endoplasmic reticulum. ASIC1a is an acid-sensing ion channel involved in the pain sensory pathway, which is regulated by p11.
Although the exact mechanism is unclear, p11 protein has shown to be essential in the regulation of serotonin signaling in the brain. Serotonin (5-hydroxytryptamine or 5-HT), is a neurotransmitter found in the central and peripheral nervous systems. It is involved in mechanisms responsible for memory formation and learning, but is most known for its role in the regulation muscle contraction, appetite, sleep, and mood. Varying levels of serotonin found in the brain are associated with the development of mood disorders, such as clinical depression. P11 interacts with the serotonin receptor proteins, 5-HT receptors such as 5-HT1B, modulating the receptor signal transduction pathways activated by the binding of serotonin. P11 also recruits the cell surface expression of the 5-HT4 receptor, increasing its concentration at the synapse. This results in more rapid serotonin-dependent activities. 5-HT4 is involved in the regulation of kinase activity in the central nervous system, phosphorylating target proteins, and facilitating endosomal activities. P11 is coexpressed with 5-HT4 mRNA and its protein in parts of the brain associated with depression, suggesting that their functions are linked and influence mood.
Protein p11 can also be presented on the cell surface as a receptor for tissue-type plasminogen activator (tPA) and plasminogen. Plasmin production by many cells is dependent on p11.
# Interactions
S100A10 has been shown to interact with TRPV5, TRPV6, TASK-1, ASIC1a, CTSB, BAD, KCNK3, UBC and ANXA2.
There is a specificity in the interaction between p11 and 5-HT1B. In a two-hybrid screen using twenty six out of 29 double-positive prey clones containing the gene encoding p11. This study showed that p11 interacted with 5-HT1B receptors but not with 5-HT1A, 5-HT2A, 5-HT5A, 5-HT6, dopamine D1 or D2 receptors, two irrelevant baits (C{Delta}115 and pRP21), or the empty plasmid. The specific interaction has been verified in three other ways: In HeLa cells and brain tissue p11 was found to coimmunoprecipitate with 5-HT1B receptors; Immunofluorescence studies show colocalization between p11 and 5-HT1B receptors at the cell surface; and distribution of p11 mRNA in the brain resembles that of 5-HT1B receptor mRNA.
The table below shows the proteins that interact with p11 and the functional role of p11 in these interactions
## Table 1
# Regulation
## Regulation of protein activity
The p11 and annexin II complex is regulated by the phosphorylation of SerII on the annexin II molecule by protein kinase C (PKC). This phosphorylation hinders the complex's ability to bind to certain target molecules. Protein Kinase A (PKA) reverses the effects of PKC by activating a phosphatase, which reactivates the complex through dephosphorylation.
## Regulation of transcription
Current experiments on animals have shown that various factors and physiological stimuli have been successful in regulating the levels of p11 protein transcription. Some of these factors are shown in the table below.
### Table 2
# Clinical significance
## Depression
Depression is a widespread, debilitating disease affecting persons of all ages and backgrounds. Depression is characterized by a plethora of emotional and physiological symptoms including feelings of sadness, hopelessness, pessimism, guilt, a general loss of interest in life, and a sense of reduced emotional well-being or low energy. Very little is known about the underlying pathophysiology of clinical depression and other related mood-disorders including anxiety, bipolar disorder, ADD, ADHD, and Schizophrenia.
The p11 protein has been intimately linked to mood disorders, to be specific, depression, due to its role in serotonin systems via its interactions with serotonin 5-HT receptors. Serotonin affects diverse systems including the cardiovascular, renal, immune, and gastrointestinal systems. Current research focuses on the neurotransmitter's relationship with mood-regulation.
Under experimentation, mice deficient in the p11 protein display depression-like behaviors. Knockout experiments in which the gene coding for protein p11 was deleted from the mouse genome caused them to show signs of depression. This is also observed in humans. On the other hand, those with sufficient amount of p11 protein behave normally. When mice that showed depressive symptoms were administered anti-depressant drugs, their levels of p11 were found to increase at the same rate, as antidepressants affected their behavioral changes. In addition, post-mortem comparisons of brain tissues showed much lower levels of p11 in depressed compared to control subjects. Levels of p11 have been found to be substantially lower in depressed humans and helpless mice, which suggests that altered p11 levels may be involved in the development of depression-like symptoms.
## Treatment
Most of the current drugs and treatments for depression and anxiety increase levels of serotonin transmission among neurons. Selective Serotonin Reuptake Inhibitors (SSRIs), a very successful class of drugs, are known to increase the amount of serotonin available to brain cells quite rapidly. Despite this, their therapeutic effects take a period of several weeks to months. Recent studies show that protein p11 increases the concentration of the serotonin 5-HT receptors at neuronal synapses, thereby rendering serotonin signaling much more efficient. The interaction with the serotonin 1b receptor (5-HT1B) and p11 can be summarized as follows: When p11 levels increases, the number of 5-HT1B receptors on the cell surface increase proportionately. An increase in the number of 5-HT1B receptors on the surface of the neuron increase the effectiveness of serotonin communication across the synapse. On the other hand, when p11 levels decrease, fewer 5-HT1B receptors migrate from inside the neuron to the cell membrane at the synaptic cleft, thus lowering the efficiency with which serotonin signaling can occur across the synapse. These findings suggest that, although the serotonin levels are immediately introduced via medication, the period of time within which the medicine alleviates the patient's depression most likely relies on other regulatory proteins. Thus, given protein p11's interaction with serotonin 5-HT receptors and the increasing evidence of the protein's correlation to mood disorders, this protein has been identified as a target for research in the development of future antidepressants.
Treatment with antidepressants (a tricyclic and monoamine oxidase inhibitor) and electroconvulsive therapy (ECT) caused an increase in the amount of p11 in the brain of these mice - the same biochemical change. The levels of the p11 protein in humans and mice with symptoms of depression were substantially lower in comparison to the levels of p11 in non-depressed animals. Leading researcher Paul Greengard and his colleagues hypothesized that increasing p11 levels would result in the mice exhibiting antidepressant-like behaviors, and the opposite if p11 protein levels were reduced. They used a test that is used to measure antidepressant-like activity to affirm this hypothesis. In their findings, over-expressed p11 genes, compared to the control mice, had increased mobility and more 5-HT1B receptors at the cell surface, which made possible more serotonin transmission. When researchers "knocked out" the p11 gene in mice, they found that the knockout mice had fewer receptors at the cell surface, reduced serotonin signaling, reduced responsiveness to sweet reward, and decreased mobility, behaviors all characteristic of depression-like behaviors. Also, the 5-HT1B receptors of p11 knockout mice were less responsive to serotonin and antidepressant drugs compared to those of control mice, which further implicates p11 in the main action of antidepressant medications. Antidepressant manipulations increase the p11 levels, whereas depressant manipulations reduce it. Therefore, in order to achieve an anti-depression effect, antidepressant medications should focus on the main action of the p11 proteins and increase levels of the protein.
## Future clinical trials
At the current time, a study by the National Institutes of Health Clinical Center (CC) is recruiting participants for a study that will compare levels of p11 protein in people with and without Major Depressive Disorder (MDD) and determine whether p11 levels in patients are affected by treatment with citalopram (Celexa), a serotonin reuptake inhibitor. If successful, a more personalized treatment of MDD will be available in the future. | S100A10
S100 calcium-binding protein A10 (S100A10), also known as p11, is a protein[1] that is encoded by the S100A10 gene in humans and the S100a10 gene in other species.[2][3] S100A10 is a member of the S100 family of proteins containing two EF-hand calcium-binding motifs. S100 proteins are localized in the cytoplasm and/or nucleus of a wide range of cells. They regulate a number of cellular processes such as cell cycle progression and differentiation. The S100 protein is implicated in exocytosis and endocytosis by reorganization of F-actin.[3]
The p11 protein is linked with the transport of neurotransmitters. Found in the brain of humans and other mammals, it has been implicated in the regulation of mood. In addition, due to its interaction with serotonin-signaling proteins and its correlation with symptoms of mood disorders, p11 is a new potential target for drug therapy.[4]
# Gene
The S100 gene family includes at least 13 members that are located as a cluster on chromosome 1q21.[5] In humans, 19 family members are
currently known, with most S100 genes (S100A1 to S100A16).
# Structure
The p11 protein can be found as a free monomer, a homodimer, or a heterotetramer composed of a p11 dimer complex with two molecules of annexin II. The homodimer or heterotetramer can, in turn, dimerize through formation of two disulfide bonds (see figure to the left). The p11 monomer is an asymmetric protein composed of four alpha helices. The dimerized form of the protein is created by packing between the H1 and H4 helices in an antiparallel arrangement with the hydrophobic regions residing in the core.
The structure of p11 is classified by a pair of the helix-loop-helix motif, also known as the EF-hand-type that recognizes and binds calcium ions. This is common to all known S-100 proteins. The EF-hand types, united by an anti-parallel beta-strand between loops L1 and L3, are located on the same side of the molecule, opposite the N-and C-termini.[6] As a member of the S-100 family, its structure resembles that of the S-100A1 and S-100B proteins. This class of proteins has been implicated in the regulation of cytoskeleton assembly, cytosolic enzymes, and membrane dynamics.
P11's involvement with the cytoskeleton may aid the transport of other proteins throughout the cell and to the cell membrane. Unlike other S-100 proteins, the second EF-hand of protein p11 is incapable of binding calcium due to a series of mutations caused by deletions and substitutions. Annexin II, which is attracted to negatively charged phospholipids, binds to p11 at the Ca2+ binding site. In addition, Annexin II has been implicated in membrane-cytoskeleton interactions and in regulations of ion currents and substances across the membrane.[6] P11 and annexin II form a heterotetrameric protein complex that imitates the structure and function of S-100 proteins activated by the binding of calcium. This tetrameric complex is more stable than the p11 dimer, therefore the overexpression of the annexin II gene results in higher levels of p11 protein.[6][7]
# Function
P11 is an integral part of cellular structural scaffolding that interacts with plasma membrane proteins through its association with annexin II. Recently, it was discovered to form a complex with annexin I though the mechanism remains unknown. It works together with cytosolic and peripheral membrane-associated proteins such as AHNAK in the development of the intracellular membrane. P11 has been implicated in the transportation of proteins involved in mood regulation, nociception, and cell polarization. It is found in cell types throughout the body though it is located predominantly in the lungs and kidneys. It is involved in the trafficking of proteins to the plasma membrane and can be expressed on the cell surface as a receptor. Many of the transported proteins are cell surface receptors in signal transduction pathways and ion channels. P11 facilitates nociception, Ca2+ uptake, and cell polaraization. Complexed with the annexin II, p11 binds receptor and channel proteins and guides them to the cell surface, resulting in increased membrane localization and consequent magnified functional expression of these proteins.[8]
Ion channels are among the several proteins that are transported through the interaction with p11. Some of these proteins include Nav1.8, TRPV5, TRPV6, TASK-1, and ASIC1a. Nav1.8 is a tetrodotoxin-resistant sodium channel that replaces lost sodium after cell damage. Increased expression of these channels alters the magnitude of the sodium current across the membrane. TRPV5 and TRPV6 are transient receptor potential channels selective for Ca+ and Mg2+ ions. TASK-1 is a two-pore domain K+ channel TWIK-related acid-sensitive K (TASK). P11 can also function as a retention factor, preventing TASK-1 from leaving the endoplasmic reticulum. ASIC1a is an acid-sensing ion channel involved in the pain sensory pathway, which is regulated by p11.[8]
Although the exact mechanism is unclear, p11 protein has shown to be essential in the regulation of serotonin signaling in the brain. Serotonin (5-hydroxytryptamine or 5-HT), is a neurotransmitter found in the central and peripheral nervous systems. It is involved in mechanisms responsible for memory formation and learning, but is most known for its role in the regulation muscle contraction, appetite, sleep, and mood. Varying levels of serotonin found in the brain are associated with the development of mood disorders, such as clinical depression. P11 interacts with the serotonin receptor proteins, 5-HT receptors such as 5-HT1B, modulating the receptor signal transduction pathways activated by the binding of serotonin. P11 also recruits the cell surface expression of the 5-HT4 receptor, increasing its concentration at the synapse. This results in more rapid serotonin-dependent activities. 5-HT4 is involved in the regulation of kinase activity in the central nervous system, phosphorylating target proteins, and facilitating endosomal activities. P11 is coexpressed with 5-HT4 mRNA and its protein in parts of the brain associated with depression, suggesting that their functions are linked and influence mood.[9]
Protein p11 can also be presented on the cell surface as a receptor for tissue-type plasminogen activator (tPA) and plasminogen.[10] Plasmin production by many cells is dependent on p11.
# Interactions
S100A10 has been shown to interact with TRPV5,[11] TRPV6, TASK-1, ASIC1a, CTSB,[12] BAD,[13] KCNK3,[14] UBC[15] and ANXA2.[6][15]
There is a specificity in the interaction between p11 and 5-HT1B. In a two-hybrid screen using twenty six out of 29 double-positive prey clones containing the gene encoding p11. This study showed that p11 interacted with 5-HT1B receptors but not with 5-HT1A, 5-HT2A, 5-HT5A, 5-HT6, dopamine D1 or D2 receptors, two irrelevant baits (C{Delta}115 and pRP21), or the empty plasmid.[16] The specific interaction has been verified in three other ways: In HeLa cells and brain tissue p11 was found to coimmunoprecipitate with 5-HT1B receptors; Immunofluorescence studies show colocalization between p11 and 5-HT1B receptors at the cell surface; and distribution of p11 mRNA in the brain resembles that of 5-HT1B receptor mRNA.
The table below shows the proteins that interact with p11 and the functional role of p11 in these interactions[17]
## Table 1
# Regulation
## Regulation of protein activity
The p11 and annexin II complex is regulated by the phosphorylation of SerII on the annexin II molecule by protein kinase C (PKC). This phosphorylation hinders the complex's ability to bind to certain target molecules. Protein Kinase A (PKA) reverses the effects of PKC by activating a phosphatase, which reactivates the complex through dephosphorylation.[8]
## Regulation of transcription
Current experiments on animals have shown that various factors and physiological stimuli have been successful in regulating the levels of p11 protein transcription. Some of these factors are shown in the table below.[17]
### Table 2
# Clinical significance
## Depression
Depression is a widespread, debilitating disease affecting persons of all ages and backgrounds. Depression is characterized by a plethora of emotional and physiological symptoms including feelings of sadness, hopelessness, pessimism, guilt, a general loss of interest in life, and a sense of reduced emotional well-being or low energy. Very little is known about the underlying pathophysiology of clinical depression and other related mood-disorders including anxiety, bipolar disorder, ADD, ADHD, and Schizophrenia.
The p11 protein has been intimately linked to mood disorders, to be specific, depression, due to its role in serotonin systems via its interactions with serotonin 5-HT receptors. Serotonin affects diverse systems including the cardiovascular, renal, immune, and gastrointestinal systems. Current research focuses on the neurotransmitter's relationship with mood-regulation.[9]
Under experimentation, mice deficient in the p11 protein display depression-like behaviors. Knockout experiments in which the gene coding for protein p11 was deleted from the mouse genome caused them to show signs of depression. This is also observed in humans. On the other hand, those with sufficient amount of p11 protein behave normally. When mice that showed depressive symptoms were administered anti-depressant drugs, their levels of p11 were found to increase at the same rate, as antidepressants affected their behavioral changes. In addition, post-mortem comparisons of brain tissues showed much lower levels of p11 in depressed compared to control subjects. Levels of p11 have been found to be substantially lower in depressed humans and helpless mice, which suggests that altered p11 levels may be involved in the development of depression-like symptoms.
## Treatment
Most of the current drugs and treatments for depression and anxiety increase levels of serotonin transmission among neurons. Selective Serotonin Reuptake Inhibitors (SSRIs), a very successful class of drugs, are known to increase the amount of serotonin available to brain cells quite rapidly. Despite this, their therapeutic effects take a period of several weeks to months. Recent studies show that protein p11 increases the concentration of the serotonin 5-HT receptors at neuronal synapses, thereby rendering serotonin signaling much more efficient. The interaction with the serotonin 1b receptor (5-HT1B) and p11 can be summarized as follows: When p11 levels increases, the number of 5-HT1B receptors on the cell surface increase proportionately.[4] An increase in the number of 5-HT1B receptors on the surface of the neuron increase the effectiveness of serotonin communication across the synapse. On the other hand, when p11 levels decrease, fewer 5-HT1B receptors migrate from inside the neuron to the cell membrane at the synaptic cleft, thus lowering the efficiency with which serotonin signaling can occur across the synapse. These findings suggest that, although the serotonin levels are immediately introduced via medication, the period of time within which the medicine alleviates the patient's depression most likely relies on other regulatory proteins. Thus, given protein p11's interaction with serotonin 5-HT receptors and the increasing evidence of the protein's correlation to mood disorders, this protein has been identified as a target for research in the development of future antidepressants.[31]
Treatment with antidepressants (a tricyclic and monoamine oxidase inhibitor) and electroconvulsive therapy (ECT) caused an increase in the amount of p11 in the brain of these mice - the same biochemical change.[4] The levels of the p11 protein in humans and mice with symptoms of depression were substantially lower in comparison to the levels of p11 in non-depressed animals. Leading researcher Paul Greengard and his colleagues hypothesized that increasing p11 levels would result in the mice exhibiting antidepressant-like behaviors, and the opposite if p11 protein levels were reduced. They used a test that is used to measure antidepressant-like activity to affirm this hypothesis. In their findings, over-expressed p11 genes, compared to the control mice, had increased mobility and more 5-HT1B receptors at the cell surface, which made possible more serotonin transmission. When researchers "knocked out" the p11 gene in mice, they found that the knockout mice had fewer receptors at the cell surface, reduced serotonin signaling, reduced responsiveness to sweet reward, and decreased mobility, behaviors all characteristic of depression-like behaviors. Also, the 5-HT1B receptors of p11 knockout mice were less responsive to serotonin and antidepressant drugs compared to those of control mice, which further implicates p11 in the main action of antidepressant medications.[16] Antidepressant manipulations increase the p11 levels, whereas depressant manipulations reduce it. Therefore, in order to achieve an anti-depression effect, antidepressant medications should focus on the main action of the p11 proteins and increase levels of the protein.[16]
## Future clinical trials
At the current time, a study by the National Institutes of Health Clinical Center (CC) is recruiting participants for a study that will compare levels of p11 protein in people with and without Major Depressive Disorder (MDD) and determine whether p11 levels in patients are affected by treatment with citalopram (Celexa), a serotonin reuptake inhibitor. If successful, a more personalized treatment of MDD will be available in the future.[32] | https://www.wikidoc.org/index.php/S100A10 | |
9e4b246909650252e1049965b6826ae2c19a247f | wikidoc | S100A11 | S100A11
S100 calcium-binding protein A11 (S100A11) is a protein that in humans is encoded by the S100A11 gene.
# Function
The protein encoded by this gene is a member of the S100 family of proteins containing 2 EF-hand calcium-binding motifs. S100 proteins are localized in the cytoplasm and/or nucleus of a wide range of cells, and involved in the regulation of a number of cellular processes such as cell cycle progression and differentiation. S100A11 is localized in the cytoplasm of resting human keratinocytes in vitro.
S100A11, along with all 13 members of the S100 family, are located as a cluster on chromosome 1q21. The protein may function in motility, invasion, and tubulin polymerization. Chromosomal rearrangements and altered expression of this gene have been implicated in tumor metastasis.
Suppression of S100A11 by small interfering RNA caused cells to apoptosis, and overexpression of S100A11 has been found to inhibit apoptosis in tumor cells. Furthermore, the knock-down of S100A11 via siRNA reduces the sister-chromatid exchange and the viability of cells.
IL-8 and TNF-alpha induce S100A11 expression and release in chondrocytes in culture and exogenous S100A11 causes chondrocyte hypertrophy.
It has been shown that S100A11 enhances the recombination activity of human RAD51 in vitro. A knock-down leads to diffuse distribution of RAD54B. These finding suggest a potential role of S100A11 in the process of homologous recombination repair of double-strand breaks.
# Interactions
S100A11 has been shown to interact with Nucleolin, S100B and RAD54B. | S100A11
S100 calcium-binding protein A11 (S100A11) is a protein that in humans is encoded by the S100A11 gene.[1][2]
# Function
The protein encoded by this gene is a member of the S100 family of proteins containing 2 EF-hand calcium-binding motifs. S100 proteins are localized in the cytoplasm and/or nucleus of a wide range of cells, and involved in the regulation of a number of cellular processes such as cell cycle progression and differentiation.[3] S100A11 is localized in the cytoplasm of resting human keratinocytes in vitro.[4]
S100A11, along with all 13 members of the S100 family, are located as a cluster on chromosome 1q21. The protein may function in motility, invasion, and tubulin polymerization. Chromosomal rearrangements and altered expression of this gene have been implicated in tumor metastasis.[2]
Suppression of S100A11 by small interfering RNA caused cells to apoptosis, and overexpression of S100A11 has been found to inhibit apoptosis in tumor cells.[5] Furthermore, the knock-down of S100A11 via siRNA reduces the sister-chromatid exchange and the viability of cells.
IL-8 and TNF-alpha induce S100A11 expression and release in chondrocytes in culture and exogenous S100A11 causes chondrocyte hypertrophy.[6]
It has been shown that S100A11 enhances the recombination activity of human RAD51 in vitro. A knock-down leads to diffuse distribution of RAD54B.[7] These finding suggest a potential role of S100A11 in the process of homologous recombination repair of double-strand breaks.[8]
# Interactions
S100A11 has been shown to interact with Nucleolin,[9] S100B[10] and RAD54B.[7] | https://www.wikidoc.org/index.php/S100A11 | |
33089af54e1c201eb6e2c6424c6d9b97179a67c9 | wikidoc | S100A13 | S100A13
S100 calcium-binding protein A13 (S100A13) is a protein that in humans is encoded by the S100A13 gene.
# Function
The protein encoded by this gene is a member of the S100 family of proteins containing 2 EF-hand calcium-binding motifs. S100 proteins are localized in the cytoplasm and/or nucleus of a wide range of cells, and involved in the regulation of a number of cellular processes such as cell cycle progression and differentiation. S100 genes include at least 13 members which are located as a cluster on chromosome 1q21. This protein is widely expressed in various types of tissues with a high expression level in thyroid gland. In smooth muscle cells, this protein co-expresses with other family members in the nucleus and in stress fibers, suggesting diverse functions in signal transduction. Multiple alternatively spliced transcript variants encoding the same protein have been found for this gene.
# Interactions
S100A13 has been shown to interact with SYT1 and FGF1.
# Pathology
Up-regulation of S100A13 was detected in cystic papillary thyroid carcinoma and association of S100A13 expression and chemotherapy resistance was shown in proteomics study of melanoma. | S100A13
S100 calcium-binding protein A13 (S100A13) is a protein that in humans is encoded by the S100A13 gene.[1][2]
# Function
The protein encoded by this gene is a member of the S100 family of proteins containing 2 EF-hand calcium-binding motifs. S100 proteins are localized in the cytoplasm and/or nucleus of a wide range of cells, and involved in the regulation of a number of cellular processes such as cell cycle progression and differentiation. S100 genes include at least 13 members which are located as a cluster on chromosome 1q21. This protein is widely expressed in various types of tissues with a high expression level in thyroid gland. In smooth muscle cells, this protein co-expresses with other family members in the nucleus and in stress fibers, suggesting diverse functions in signal transduction. Multiple alternatively spliced transcript variants encoding the same protein have been found for this gene.[2]
# Interactions
S100A13 has been shown to interact with SYT1[3][4] and FGF1.[3][4]
# Pathology
Up-regulation of S100A13 was detected in cystic papillary thyroid carcinoma[5] and association of S100A13 expression and chemotherapy resistance was shown in proteomics study of melanoma.[6] | https://www.wikidoc.org/index.php/S100A13 | |
75523014b990fb876163dde9603b5e0fe25c0ea4 | wikidoc | S100A15 | S100A15
S100 calcium-binding protein A15 (S100A15), also known as koebnerisin and S100 calcium-binding protein A7A (S100A7A), is a protein that in humans is encoded by the S100A7A (alias:S100A15) gene.
S100 proteins are a diverse calcium-binding family that regulate fundamental cellular and extracellular processes including cell proliferation and differentiation, cell migration, and the antimicrobial host defense as antimicrobial peptides.
Koebnerisin (S100A15) was first identified upregulated in inflammation-prone psoriatic skin, suggesting involvement in the lesional phenotype of the disease, Koebner phenomenon. Today, the protein is of further interest because of its role in antimicrobial defence, innate immunity, epidermal cell maturation and epithelial tumorigenesis.
# Function
## Epithelial homeostasis and antimicrobial host defense
Skin: In normal epidermis, koebnerisin (S100A15) is expressed by epidermal basal and differentiated keratinocytes, melanocytes, and Langerhans cells. Within the pilosebaceous unit, S100A15 is found in the inner and external root sheath and the basal layer of the sebaceous gland. In the dermis, koebnerisin (S100A15) is produced by dendritic cells, smooth muscle cells, endothelial cells, as well as fibroblasts to control tissue regeneration.
Breast: Koebnerisin (S100A15) is expressed by alveolar and small duct luminal cells and by epithelial-derived myoepithelial cells around acini and by surrounding blood vessels.
Koebnerisin (S100A15) functions as an antimicrobial peptide (AMP) reducing survival of E. coli and was strongly regulated by several bacterial components, such as P. aeruginosa and S. aureus. Thus, koebnerisin participates in the antimicrobial host defence of the skin and in the digestive tract of breast-feeding newborns.
## Epithelial carcinogenesis
Breast cancer: Koebnerisin (S100A15) is overexpressed in ER/PR negative tumors suggesting a regulation with tumor progression. The secreted koebnerisin (S100A15) acts as a chemoattractant, enhances inflammation and thus could drive breast carcinogenesis.
## Inflammation
Koebnerisin (S100A15) is overexpressed in inflammatory skin diseases, such as psoriasis and eczema. It is regulated through Th1 and Th17 but not Th2 proinflammatory cytokines. When released into the extracellar space, koebnerisin (S100A15) induces inflammation. It acts as a chemoattractant for myeloid leukocytes through a pertussis toxin sensitive Gi protein coupled receptor. Koebnerisin (S100A15) amplifies inflammation with related psoriasin (S100A7) that is co-regulated and proinflammatory through RAGE.
# Genomic organization and mRNA splice variants
Koebnerisin (S100A15) maps to the S100 gene cluster within the epidermal differentiation complex (EDC, chromosome 1q21) and reveals an unusual genomic organization compared to other S100 members. The two alternative mRNA-isoforms of koebnerisin share the same coding region, but show differences in composition and length of adjacent untranslated regions (S100A15-short (S): 0.5 kb vs. hS100A15-long (L): 4.4 kb). Both splice variants are differently regulated in inflammatory skin diseases suggesting usage of alternate promoters.
# Protein
The amino acid sequence reveals a conserved C-terminal and a variant N-terminal EF-hand typical for S100 proteins (101 amino acids, 11.305 Da, calculated pI of 7.57 kDa). Compared to most S100 proteins, koebnerisin (S100A15) is basic.
# Evolution
## Primate
Koebnerisin (S100A15) has lately evolved by gene duplications within the Epidermal Differentiation Complex (EDC, chromosome 1q21) during primate evolution forming a novel S100 subfamily together with Psoriasin (S100A7). Therefore, koebnerisin is almost identical to psoriasin in sequence (>90%). Despite their high homology, koebnerisin (S100A15) and psoriasin (S100A7) are distinct in tissue distribution, regulation, structure and function and, thus exemplary for the diversity within the S100 family. Their different properties are compelling reasons to discriminate S100A15 (koebnerisin) and S100A7 (psoriasin) in epithelial homeostasis, inflammation and cancer.
## Rodent
Koebnerisin (S100A15) and psoriasin (S100A7) share a common protein in mice encoded by the S100a7a15 (alias: mS100A7, mS100A15, mS100a7a) gene. It can be used to study the significance of the corresponding human proteins for epidermal maturation, inflammation and epithelial carcinogenesis. | S100A15
S100 calcium-binding protein A15 (S100A15), also known as koebnerisin and S100 calcium-binding protein A7A (S100A7A), is a protein that in humans is encoded by the S100A7A (alias:S100A15) gene.[1]
S100 proteins are a diverse calcium-binding family that regulate fundamental cellular and extracellular processes including cell proliferation and differentiation, cell migration, and the antimicrobial host defense as antimicrobial peptides.
Koebnerisin (S100A15) was first identified upregulated in inflammation-prone psoriatic skin, suggesting involvement in the lesional phenotype of the disease,[2] Koebner phenomenon. Today, the protein is of further interest because of its role in antimicrobial defence, innate immunity, epidermal cell maturation and epithelial tumorigenesis.[3][4]
# Function
## Epithelial homeostasis and antimicrobial host defense
Skin: In normal epidermis, koebnerisin (S100A15) is expressed by epidermal basal and differentiated keratinocytes, melanocytes, and Langerhans cells. Within the pilosebaceous unit, S100A15 is found in the inner and external root sheath and the basal layer of the sebaceous gland. In the dermis, koebnerisin (S100A15) is produced by dendritic cells, smooth muscle cells, endothelial cells, as well as fibroblasts to control tissue regeneration.[5][6][7][8]
Breast: Koebnerisin (S100A15) is expressed by alveolar and small duct luminal cells and by epithelial-derived myoepithelial cells around acini and by surrounding blood vessels.[9]
Koebnerisin (S100A15) functions as an antimicrobial peptide (AMP) reducing survival of E. coli and was strongly regulated by several bacterial components, such as P. aeruginosa and S. aureus. Thus, koebnerisin participates in the antimicrobial host defence of the skin and in the digestive tract of breast-feeding newborns.[10]
## Epithelial carcinogenesis
Breast cancer: Koebnerisin (S100A15) is overexpressed in ER/PR negative tumors suggesting a regulation with tumor progression.[9] The secreted koebnerisin (S100A15) acts as a chemoattractant,[6] enhances inflammation and thus could drive breast carcinogenesis.
## Inflammation
Koebnerisin (S100A15) is overexpressed in inflammatory skin diseases, such as psoriasis and eczema.[11] It is regulated through Th1 and Th17 but not Th2 proinflammatory cytokines.[12][13] When released into the extracellar space, koebnerisin (S100A15) induces inflammation. It acts as a chemoattractant for myeloid leukocytes through a pertussis toxin sensitive Gi protein coupled receptor. Koebnerisin (S100A15) amplifies inflammation with related psoriasin (S100A7) that is co-regulated and proinflammatory through RAGE.
# Genomic organization and mRNA splice variants
Koebnerisin (S100A15) maps to the S100 gene cluster within the epidermal differentiation complex (EDC, chromosome 1q21) and reveals an unusual genomic organization compared to other S100 members. The two alternative mRNA-isoforms of koebnerisin share the same coding region, but show differences in composition and length of adjacent untranslated regions (S100A15-short (S): 0.5 kb vs. hS100A15-long (L): 4.4 kb). Both splice variants are differently regulated in inflammatory skin diseases suggesting usage of alternate promoters.[2][12]
# Protein
The amino acid sequence reveals a conserved C-terminal and a variant N-terminal EF-hand typical for S100 proteins (101 amino acids, 11.305 Da, calculated pI of 7.57 kDa). Compared to most S100 proteins, koebnerisin (S100A15) is basic.
# Evolution
## Primate
Koebnerisin (S100A15) has lately evolved by gene duplications within the Epidermal Differentiation Complex (EDC, chromosome 1q21) during primate evolution forming a novel S100 subfamily together with Psoriasin (S100A7).[14][15] Therefore, koebnerisin is almost identical to psoriasin in sequence (>90%). Despite their high homology, koebnerisin (S100A15) and psoriasin (S100A7) are distinct in tissue distribution, regulation, structure[16][17] and function and, thus exemplary for the diversity within the S100 family. Their different properties are compelling reasons to discriminate S100A15 (koebnerisin) and S100A7 (psoriasin) in epithelial homeostasis, inflammation and cancer.
## Rodent
Koebnerisin (S100A15) and psoriasin (S100A7) share a common protein in mice encoded by the S100a7a15 (alias: mS100A7, mS100A15, mS100a7a) gene.[18] It can be used to study the significance of the corresponding human proteins for epidermal maturation, inflammation and epithelial carcinogenesis.[15][19][20][21] | https://www.wikidoc.org/index.php/S100A15 | |
ebcdba54c979af2d80396accb3ac495ecbc87d94 | wikidoc | SAPS II | SAPS II
# Overview
SAPS II is a severity of disease classification system (Le Gall, Lemeshow, Saulnier, 1993). Its name stands for "Simplified Acute Physiology Score", and is one of several ICU scoring systems.
# Application
SAPS II was designed to measure the severity of disease for patients admitted to Intensive care units aged 15 or more.
24 hours after admission to the ICU, the measurement has been completed and resulted in an integer point score between 0 and 163 and a predicted mortality between 0% and 100%. No new score can be calculated during the stay. If a patient is discharged from the ICU and readmitted, a new SAPS II score can be calculated.
This scoring system is mostly used to:
- describe the morbidity of a patient when comparing the outcome with other patients.
- describe the morbidity of a group of patients when comparing the outcome with another group of patients
# Calculation
The point score is calculated from 12 routine physiological measurements during the first 24 hours, information about previous health status and some information obtained at admission. The calculation method is optimized for paper schemas. In contrast to APACHE II, the resulting value is much better at comparing patients with different diseases.
The calculation method results in a predicted mortality, that is pure statistics. It does not tell the individual patient's chance of survival. The main purpose of this calculation is to provide a value that can be averaged for a group of patients, since it gives very unprecise values to calculate an average of the scores of a group of patients. | SAPS II
# Overview
SAPS II is a severity of disease classification system (Le Gall, Lemeshow, Saulnier, 1993). Its name stands for "Simplified Acute Physiology Score", and is one of several ICU scoring systems.
# Application
SAPS II was designed to measure the severity of disease for patients admitted to Intensive care units aged 15 or more.
24 hours after admission to the ICU, the measurement has been completed and resulted in an integer point score between 0 and 163 and a predicted mortality between 0% and 100%. No new score can be calculated during the stay. If a patient is discharged from the ICU and readmitted, a new SAPS II score can be calculated.
This scoring system is mostly used to:
- describe the morbidity of a patient when comparing the outcome with other patients.
- describe the morbidity of a group of patients when comparing the outcome with another group of patients
# Calculation
The point score is calculated from 12 routine physiological measurements during the first 24 hours, information about previous health status and some information obtained at admission. The calculation method is optimized for paper schemas. In contrast to APACHE II, the resulting value is much better at comparing patients with different diseases.
The calculation method results in a predicted mortality, that is pure statistics. It does not tell the individual patient's chance of survival. The main purpose of this calculation is to provide a value that can be averaged for a group of patients, since it gives very unprecise values to calculate an average of the scores of a group of patients. | https://www.wikidoc.org/index.php/SAPS_II | |
48b869c765d60040d3c4182698721534182aa681 | wikidoc | SCGB1D2 | SCGB1D2
Secretoglobin family 1D member 2 is a protein that in humans is encoded by the SCGB1D2 gene.
# Function
The protein encoded by this gene is a member of the lipophilin subfamily, part of the uteroglobin superfamily, and is an ortholog of prostatein, the major secretory glycoprotein of the rat ventral prostate gland. Lipophilin gene products are widely expressed in normal tissues, especially in endocrine-responsive organs. Assuming that human lipophilins are the functional counterparts of prostatein, they may be transcriptionally regulated by steroid hormones, with the ability to bind androgens, other steroids and possibly bind and concentrate estramustine, a chemotherapeutic agent widely used for prostate cancer. Although the gene has been reported to be on chromosome 10, this sequence appears to be from a cluster of genes on chromosome 11 that includes mammaglobin 2.
SCGB1D2 expression is high in mammary tissue, and is sometimes used for identification and detection of disseminated breast cancer cells. | SCGB1D2
Secretoglobin family 1D member 2 is a protein that in humans is encoded by the SCGB1D2 gene.[1][2][3]
# Function
The protein encoded by this gene is a member of the lipophilin subfamily, part of the uteroglobin superfamily, and is an ortholog of prostatein, the major secretory glycoprotein of the rat ventral prostate gland. Lipophilin gene products are widely expressed in normal tissues, especially in endocrine-responsive organs. Assuming that human lipophilins are the functional counterparts of prostatein, they may be transcriptionally regulated by steroid hormones, with the ability to bind androgens, other steroids and possibly bind and concentrate estramustine, a chemotherapeutic agent widely used for prostate cancer. Although the gene has been reported to be on chromosome 10, this sequence appears to be from a cluster of genes on chromosome 11 that includes mammaglobin 2.[3]
SCGB1D2 expression is high in mammary tissue, and is sometimes used for identification and detection of disseminated breast cancer cells.[4] | https://www.wikidoc.org/index.php/SCGB1D2 | |
34d241f21913b0467c116697914b323c5f524a49 | wikidoc | SEQUEST | SEQUEST
SEQUEST is a tandem mass spectrometry data analysis program used for protein identification. Sequest identifies collections of tandem mass spectra to peptide sequences that have been generated from databases of protein sequences.
# Applications
This tool is most useful in the context of proteomics. Starting with a complex mixture of proteins, this strategy typically employs trypsin to digest proteins. These peptides are separated by liquid chromatography en route to a tandem mass spectrometer. The mass spectrometer then isolates ions of a particular peptide, subjects them to collision-induced dissociation, and records the produced fragments in a tandem mass spectrum. This process, repeated for several hours, will produce thousands of tandem mass spectra. Identifying such a data collection requires automation, and Sequest was the first software to fill that need.
Sequest identifies each tandem mass spectrum individually. The software evaluates protein sequences from a database to compute the list of peptides that could result from each. The peptide's intact mass is known from the mass spectrum, and Sequest uses this information to determine the set of candidate peptides sequences that could meaningfully be compared to the spectrum by including only those which are near the mass of the observed peptide ion. For each candidate peptide, Sequest projects a theoretical tandem mass spectrum, and Sequest compares these theoretical spectra to the observed tandem mass spectrum by the use of cross correlation. The candidate sequence with the best matching theoretical tandem mass spectrum is reported as the best identification for this spectrum. | SEQUEST
Template:Infobox Software
SEQUEST is a tandem mass spectrometry data analysis program used for protein identification.[1] Sequest identifies collections of tandem mass spectra to peptide sequences that have been generated from databases of protein sequences.
# Applications
This tool is most useful in the context of proteomics. Starting with a complex mixture of proteins, this strategy typically employs trypsin to digest proteins. These peptides are separated by liquid chromatography en route to a tandem mass spectrometer. The mass spectrometer then isolates ions of a particular peptide, subjects them to collision-induced dissociation, and records the produced fragments in a tandem mass spectrum. This process, repeated for several hours, will produce thousands of tandem mass spectra. Identifying such a data collection requires automation, and Sequest was the first software to fill that need.
Sequest identifies each tandem mass spectrum individually. The software evaluates protein sequences from a database to compute the list of peptides that could result from each. The peptide's intact mass is known from the mass spectrum, and Sequest uses this information to determine the set of candidate peptides sequences that could meaningfully be compared to the spectrum by including only those which are near the mass of the observed peptide ion. For each candidate peptide, Sequest projects a theoretical tandem mass spectrum, and Sequest compares these theoretical spectra to the observed tandem mass spectrum by the use of cross correlation. The candidate sequence with the best matching theoretical tandem mass spectrum is reported as the best identification for this spectrum. | https://www.wikidoc.org/index.php/SEQUEST | |
743e839222f9459fb2f1b5fb42bdc730cb55dcaf | wikidoc | SH-SY5Y | SH-SY5Y
# History
The cell line SH-SY5Y is a third generation neuroblastoma, cloned from SH-SY5, which is from SH-SY, which is from SK-N-SH. The original cell line was isolated from a woman's metastatic bone tumor in 1970. In each successive generation, the nucleus was removed and put into a new cytoplasm in the process known as cloning. The SH-SY5Y cells possess two X chromosomes (making them genetically female), and have blood type A with a positive Rh group (A+).
# Morphology
The cells possess an abnormal chromosone 1, where there is an additional copy of a 1q segment and is referred to trisomy 1q. SH-SY5Y cells are known to be dopamine beta hydroxylase active, acetylcholinergic, glutamatergic and adenosinergic. The cells have very different growth phases, outlined in the surrounding pictures. The cells both propagate via mitosis and differentiate by extending neurites to the surrounding area. While dividing, the aggregated cells can look so different from the differentiated cells, that new scientists often mistake one or the another for contamination. The dividing cells can form clusters of cells which are reminders of their cancerous nature, but certain treatments such as retinoic acid and BDNF can force the cells to dendrify and differentiate.
# Media and Cultivation
The most common growing cocktail used is a 1:1 mixture of DMEM and Ham's F12 medium and 10% supplemental fetal bovine serum. The DMEM usually contains 1.5g/L sodium bicarbonate, 2mM L-Glutamine, 1mM sodium pyruvate and 0.1 mM nonessential amino acids. The cells are always grown at 37 degrees Celsius with 95% air and 5% carbon dioxide. It is advised to cultivate the cells in flasks which are coated for cell culture adhesion, this will aid in differention and dendrification of the hybridoma.
Recommended culture medium: Ham's F12:EMEM (EBSS) (1:1) + 2 mM L-Glutamine + 1% Non-essential amino acids (NEAA) + 15% FBS.
Subculture: Split at 70-80% confluency, approx. 1:10 to 1:100, seed at 1x103 to 1x104 viable cells/cm2. Trypsinize using 0.25% solution, with or without EDTA, 37oC and 5% CO2. Cells may reattach slowly and may remain in suspension for several days
NOTE: Do not continue culture beyond 20 passages.
This cell line is a thrice-cloned sub-line of bone marrow biopsy-derived SK-N-SH. SH-SY5Y has a dopamine-β-hydroxylase activity and can convert glutamate to GABA. Will form tumors in nude mice in approx. 3-4 weeks. The loss of neuronal characteristics has been described with increasing passage numbers. Therefore it is recommended not to be used after passage 20 or verify specific characteristics such as noradrenalin uptake or neuronal tumor markers.
## Splitting
Splitting is the act of taking a cell rich culture and dividing it up into many less dense cultures. This is done either for preventing overcrowding, or for expanding the number of cultivated flasks. Although every lab does this differently, the general procedure is as follows.
- Aspirate off the old cell media
- Rinse twice with sterile PBS
- Add about 2 milliliters of Trypsin with 0.53mM EDTA: a protease and a metal chelator, respectively
This will break apart all of the cellular proteins that adhere the cells to the flask.
If the trypsin is left too long, the cells will fall apart, but not long enough and the cells won't seed very well.
For SH-SY5Y cells, the best time is around two to three minutes.
Tap, and rock by hand such that all of the cells are covered with trypsin
Be sure that the cells begin to flow with the liquid with each rocking.
- This will break apart all of the cellular proteins that adhere the cells to the flask.
If the trypsin is left too long, the cells will fall apart, but not long enough and the cells won't seed very well.
For SH-SY5Y cells, the best time is around two to three minutes.
- If the trypsin is left too long, the cells will fall apart, but not long enough and the cells won't seed very well.
- For SH-SY5Y cells, the best time is around two to three minutes.
- Tap, and rock by hand such that all of the cells are covered with trypsin
- Be sure that the cells begin to flow with the liquid with each rocking.
- Add an approproate amount of fresh, prewarmed feeding media (5mL, 3mL).
Note: It doesn't matter, but just know that it must be a set amount, so that it can be further diluted to the correct ratio. The optimum ratio is around 1:30, but 1:50, 1:200, and 1:1000 have all been used.
Note: The DMEM has protease inhibitors, which neutralize the actions of the Trypsin.
- Note: It doesn't matter, but just know that it must be a set amount, so that it can be further diluted to the correct ratio. The optimum ratio is around 1:30, but 1:50, 1:200, and 1:1000 have all been used.
- Note: The DMEM has protease inhibitors, which neutralize the actions of the Trypsin.
- Take pipette into the cell-rich media and titrate gently.
Do not tritrate too hard, or the cells will not survive, but not enough and the cells growth will be chunky (it is better to err on the chunky side).
When finished, the flakes and clumps of cells should be mostly gone and the media should resemble something like cloudy grapefruit juice.
- Do not tritrate too hard, or the cells will not survive, but not enough and the cells growth will be chunky (it is better to err on the chunky side).
- When finished, the flakes and clumps of cells should be mostly gone and the media should resemble something like cloudy grapefruit juice.
- Take one milliliter and place into a sterile centrifuge tube. Dilute as needed, (29mL works well).
- Seed or take the diluted cell media and place into a fresh, sterile flask, or dish, or plate.
- Redilute the original flask as needed (or not, newer flasks grow better)
- Place on cap and place flask/dish/plate into incubator
# Related Links
- ATCC
- Molecular mechanisms involved in the adenosine A and A receptor-induced neuronal differentiation in neuroblastoma cells and striatal primary cultures.
- Coaggregation, cointernalization, and codesensitization of adenosine A2A receptors and dopamine D2 receptors.
- Parkinsonism-preventing activity of 1-methyl-1,2,3,4-tetrahydroisoquinoline derivatives in C57BL mouse in vivo. | SH-SY5Y
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
# History
The cell line SH-SY5Y is a third generation neuroblastoma, cloned from SH-SY5, which is from SH-SY, which is from SK-N-SH. The original cell line was isolated from a woman's metastatic bone tumor in 1970. In each successive generation, the nucleus was removed and put into a new cytoplasm in the process known as cloning. The SH-SY5Y cells possess two X chromosomes (making them genetically female), and have blood type A with a positive Rh group (A+).
# Morphology
The cells possess an abnormal chromosone 1, where there is an additional copy of a 1q segment and is referred to trisomy 1q. SH-SY5Y cells are known to be dopamine beta hydroxylase active, acetylcholinergic, glutamatergic and adenosinergic. The cells have very different growth phases, outlined in the surrounding pictures. The cells both propagate via mitosis and differentiate by extending neurites to the surrounding area. While dividing, the aggregated cells can look so different from the differentiated cells, that new scientists often mistake one or the another for contamination. The dividing cells can form clusters of cells which are reminders of their cancerous nature, but certain treatments such as retinoic acid and BDNF can force the cells to dendrify and differentiate.
# Media and Cultivation
The most common growing cocktail used is a 1:1 mixture of DMEM and Ham's F12 medium and 10% supplemental fetal bovine serum. The DMEM usually contains 1.5g/L sodium bicarbonate, 2mM L-Glutamine, 1mM sodium pyruvate and 0.1 mM nonessential amino acids. The cells are always grown at 37 degrees Celsius with 95% air and 5% carbon dioxide. It is advised to cultivate the cells in flasks which are coated for cell culture adhesion, this will aid in differention and dendrification of the hybridoma.
Recommended culture medium: Ham's F12:EMEM (EBSS) (1:1) + 2 mM L-Glutamine + 1% Non-essential amino acids (NEAA) + 15% FBS.
Subculture: Split at 70-80% confluency, approx. 1:10 to 1:100, seed at 1x103 to 1x104 viable cells/cm2. Trypsinize using 0.25% solution, with or without EDTA, 37oC and 5% CO2. Cells may reattach slowly and may remain in suspension for several days
NOTE: Do not continue culture beyond 20 passages.
This cell line is a thrice-cloned sub-line of bone marrow biopsy-derived SK-N-SH. SH-SY5Y has a dopamine-β-hydroxylase activity and can convert glutamate to GABA. Will form tumors in nude mice in approx. 3-4 weeks. The loss of neuronal characteristics has been described with increasing passage numbers. Therefore it is recommended not to be used after passage 20 or verify specific characteristics such as noradrenalin uptake or neuronal tumor markers. <http://www.sigmaaldrich.com/catalog/search/ProductDetail/SIGMA/94030304>
## Splitting
Splitting is the act of taking a cell rich culture and dividing it up into many less dense cultures. This is done either for preventing overcrowding, or for expanding the number of cultivated flasks. Although every lab does this differently, the general procedure is as follows.
- Aspirate off the old cell media
- Rinse twice with sterile PBS
- Add about 2 milliliters of Trypsin with 0.53mM EDTA: a protease and a metal chelator, respectively
This will break apart all of the cellular proteins that adhere the cells to the flask.
If the trypsin is left too long, the cells will fall apart, but not long enough and the cells won't seed very well.
For SH-SY5Y cells, the best time is around two to three minutes.
Tap, and rock by hand such that all of the cells are covered with trypsin
Be sure that the cells begin to flow with the liquid with each rocking.
- This will break apart all of the cellular proteins that adhere the cells to the flask.
If the trypsin is left too long, the cells will fall apart, but not long enough and the cells won't seed very well.
For SH-SY5Y cells, the best time is around two to three minutes.
- If the trypsin is left too long, the cells will fall apart, but not long enough and the cells won't seed very well.
- For SH-SY5Y cells, the best time is around two to three minutes.
- Tap, and rock by hand such that all of the cells are covered with trypsin
- Be sure that the cells begin to flow with the liquid with each rocking.
- Add an approproate amount of fresh, prewarmed feeding media (5mL, 3mL).
Note: It doesn't matter, but just know that it must be a set amount, so that it can be further diluted to the correct ratio. The optimum ratio is around 1:30, but 1:50, 1:200, and 1:1000 have all been used.
Note: The DMEM has protease inhibitors, which neutralize the actions of the Trypsin.
- Note: It doesn't matter, but just know that it must be a set amount, so that it can be further diluted to the correct ratio. The optimum ratio is around 1:30, but 1:50, 1:200, and 1:1000 have all been used.
- Note: The DMEM has protease inhibitors, which neutralize the actions of the Trypsin.
- Take pipette into the cell-rich media and titrate gently.
Do not tritrate too hard, or the cells will not survive, but not enough and the cells growth will be chunky (it is better to err on the chunky side).
When finished, the flakes and clumps of cells should be mostly gone and the media should resemble something like cloudy grapefruit juice.
- Do not tritrate too hard, or the cells will not survive, but not enough and the cells growth will be chunky (it is better to err on the chunky side).
- When finished, the flakes and clumps of cells should be mostly gone and the media should resemble something like cloudy grapefruit juice.
- Take one milliliter and place into a sterile centrifuge tube. Dilute as needed, (29mL works well).
- Seed or take the diluted cell media and place into a fresh, sterile flask, or dish, or plate.
- Redilute the original flask as needed (or not, newer flasks grow better)
- Place on cap and place flask/dish/plate into incubator
# Related Links
- ATCC
- Molecular mechanisms involved in the adenosine A and A receptor-induced neuronal differentiation in neuroblastoma cells and striatal primary cultures.
- Coaggregation, cointernalization, and codesensitization of adenosine A2A receptors and dopamine D2 receptors.
- Parkinsonism-preventing activity of 1-methyl-1,2,3,4-tetrahydroisoquinoline derivatives in C57BL mouse in vivo.
Template:WikiDoc Sources | https://www.wikidoc.org/index.php/SH-SY5Y | |
a73e3dddb9e570a2c1def3e4d205e736f9a66bfe | wikidoc | SH3KBP1 | SH3KBP1
SH3 domain-containing kinase-binding protein 1 (synonyms - CIN85, in rodents - Ruk) is an adaptor protein that in humans is encoded by the SH3KBP1 gene.
# Function
CBL (MIM 165360) constitutively interacts with SH3 domain-containing proteins and, upon tyrosine phosphorylation, with SH2 domain-containing proteins. The SH3KBP1 gene encodes an 85-kD CBL-interacting protein that enhances tumor necrosis factor (MIM 191160)-mediated apoptotic cell death (Narita et al., 2001).
# Interactions
SH3KBP1 has been shown to interact with B-cell linker, Grb2, SH3GLB2, SH3GL3, SH3GL2, BCAR1, Epidermal growth factor receptor, CBLB, Cbl gene, SOS1, CRK and PAK2. | SH3KBP1
SH3 domain-containing kinase-binding protein 1 (synonyms - CIN85[1], in rodents - Ruk[2]) is an adaptor protein that in humans is encoded by the SH3KBP1 gene.[3][4]
# Function
CBL (MIM 165360) constitutively interacts with SH3 domain-containing proteins and, upon tyrosine phosphorylation, with SH2 domain-containing proteins. The SH3KBP1 gene encodes an 85-kD CBL-interacting protein that enhances tumor necrosis factor (MIM 191160)-mediated apoptotic cell death (Narita et al., 2001).[supplied by OMIM][5]
# Interactions
SH3KBP1 has been shown to interact with B-cell linker,[6] Grb2,[7][8] SH3GLB2,[9][10] SH3GL3,[9] SH3GL2,[10] BCAR1,[6] Epidermal growth factor receptor,[10][11] CBLB,[11] Cbl gene,[6][8][9][10][11] SOS1,[6] CRK[6] and PAK2.[12] | https://www.wikidoc.org/index.php/SH3KBP1 | |
15c5c52f9fa3251aa9254664ab093af2d46d2be6 | wikidoc | SHROOM3 | SHROOM3
Protein shroom3 also known as shroom-related protein is a protein that in humans is encoded by the SHROOM3 gene.
Protein shroom3 is a PDZ domain-containing protein that belongs to a family of Shroom-related proteins. This protein may be involved in regulating cell shape in certain tissues.
# Clinical relevance
Mutations in this gene have been shown to cause heterotaxy. A similar protein in mice is required for proper neurulation, eye, and gut development. | SHROOM3
Protein shroom3 also known as shroom-related protein is a protein that in humans is encoded by the SHROOM3 gene.[1][2][3]
Protein shroom3 is a PDZ domain-containing protein that belongs to a family of Shroom-related proteins. This protein may be involved in regulating cell shape in certain tissues.
# Clinical relevance
Mutations in this gene have been shown to cause heterotaxy.[4] A similar protein in mice is required for proper neurulation,[1][3] eye,[5] and gut development.[6][7] | https://www.wikidoc.org/index.php/SHROOM3 | |
05c8022a52b3bdabdb52739a2696202b54798ec3 | wikidoc | SIGLEC8 | SIGLEC8
Sialic acid-binding Ig-like lectin 8 is a protein that in humans is encoded by the SIGLEC8 gene. This gene is located on chromosome 19q13.4, about 330 kb downstream of the SIGLEC9 gene. Within the siglec family of transmembrane proteins, Siglec-8 belongs to the CD33-related siglec subfamily, a subfamily that has undergone rapid evolution.
# Initial characterization
Siglec-8 was first identified by CD33 homology screening of ESTs from a cDNA library generated from a patient diagnosed with idiopathic hypereosinophilic syndrome and was originally termed SAF-2 (sialoadhesin family 2).
At the tissue level, Siglec-8 mRNA was found to be most highly expressed in lung, PBMCs, spleen, and kidney.
# Expression
Siglec-8 is expressed by human eosinophils, mast cells, and, to a lesser extent, basophils. It has thus garnered attention as a molecule that is uniquely expressed by immune effector cells involved in asthma and allergy. In both eosinophils and mast cells, Siglec-8 is expressed late in development. Siglec-8 transcript and protein are detectable at day 12 during the in vitro differentiation of eosinophils from cord blood precursors, whereas the transcription factor GATA-1 peaks at day 2 and the secondary granule protein MBP-1 peaks at day 4 in this differentiation system. In mast cells generated from CD34+ precursors, Siglec-8 expression peaks at 4 weeks of differentiation, in parallel with FcεRIα surface expression.
Consistent with the concept that Siglec-8 is a late differentiation marker, Siglec-8 has not been detected on the surface of relatively undifferentiated eosinophilic cell lines, such as EoL-1, AML14, AML14.3D10, or K562, the basophilic leukemia cell line KU812, nor on cells such as HL60 or EoL-3 that have been differentiated towards an eosinophil-like lineage. Only low levels are detected on the human mast cell sub-line HMC-1.1; however, the HMC-1.2 cell line, which bears a second KIT mutation (D816V, in addition to the V560G mutation found in both HMC-1.1 and HMC-1.2 cells) that may induce further differentiation, expresses Siglec-8 at the cell surface. However, based on a small sampling of patients, all eosinophils from patients with chronic eosinophilic leukemia (CEL), hypereosinophilic syndrome, or chronic myeloid leukemia (CML), all basophils from patients with CEL or CML, and all bone marrow mast cells from patients with indolent systemic mastocytosis or aplastic anemia express Siglec-8, providing a potential target for these cells in the context of these hematologic malignancies.
In addition, baboon eosinophils as well as monocytes, a subset of lymphocytes, and neutrophils express on their cell surface a protein or proteins that are recognized by polyclonal human Siglec-8-specific antibody, consistent with genetic analyses indicating the existence of a Siglec-8 ortholog in this species. However, the 2C4, 2E2, and 7C9 monoclonal antibodies against human Siglec-8 were not found to bind to targets on baboon cells, indicating that these particular epitopes are not conserved.
# Structure
Two splice variants of Siglec-8 exist. The initially characterized form contains 431 amino acid residues in total, 47 of which comprise an uncharacteristically short cytoplasmic tail compared to most CD33-associated siglecs. Subsequently, a longer form of Siglec-8, initially termed Siglec-8L, that contains 499 amino acid residues was identified. This longer form of Siglec-8 shares the same extracellular region but includes a longer cytoplasmic tail with two tyrosine-based motifs (an immunoreceptor tyrosine-based inhibitory motif and an immunoreceptor tyrosine-based switch motif ). Both forms of Siglec-8 are found in eosinophils and contain a V-set domain with lectin activity and two C2-type Ig repeat domains in the extracellular region. Given that the longer version is felt to be the normal version, the term Siglec-8 is best used to refer to the 499 amino acid version, while the 431 amino acid version is best referred to as the “short form” of Siglec-8.
# Ligand binding
Potential glycan ligands for Siglec-8 have been screened by glycan array. The glycan NeuAcα2–3(6-O-sulfo)Galβ1–4GlcNAc, also known as 6′-sulfo-sialyl Lewis X, binds with high affinity to both Siglec-8 and to a mouse siglec, Siglec-F, which appears to have acquired a similar but not identical function and pattern of expression to human Siglec-8 through convergent evolution (the two siglecs are not orthologous). Rescreening on a more expanded glycan array reconfirmed this finding, but also identified a second closely related ligand in which the fucose is absent (NeuAcα2–3(6-O-sulfo)Galβ1–4GlcNAc, or 6′-sulfated sialyl N-acetyl-D-lactosamine. These interactions are quite specific; no binding could be detected between these siglecs and unsulfated sialyl Lewis X or sialyl Lewis X sulfated at carbon 6 of GlcNAc (6-sulfo-sialyl Lewis X) rather than carbon 6 of galactose as in 6′-sulfo-sialyl Lewis X. Similarly, no other siglecs bind effectively to these Siglec-8 ligands, as demonstrated by selective binding to eosinophils in human blood of a polymer decorated with 6′-sulfo-sialyl Lewis X. The natural ligand or ligands for Siglec-8 have not yet been positively identified, but ongoing studies have determined that there are sialidase-sensitive glycoprotein ligands for Siglec-F in mouse airways that require the activity of the α2,3 sialyltransferase 3 (ST3Gal-III) enzyme for their generation.
# Signaling and function
## Eosinophils
Consistent with the role of most siglecs and the presence of the intracellular ITIM, Siglec-8 has been found to function as an inhibitory immunoregulatory receptor. Ligation of Siglec-8 induces apoptosis in eosinophils, and, surprisingly, the normally pro-survival cytokines interleukin (IL)-5 and GM-CSF have been found to potentiate this apoptotic effect. IL-33, which activates and maintains eosinophils, also exerts a similar potentiating effect on Siglec-8-induced apoptosis. Inhibitor studies demonstrate that apoptosis induced by crosslinking Siglec-8 through the use of an anti-Siglec-8 mAb and a secondary antibody is mediated sequentially through reactive oxygen species (ROS) production, loss of mitochondrial membrane potential, and caspase activation. In the presence of IL-5, the loss of mitochondrial membrane integrity is accelerated and the secondary crosslinking antibody is no longer necessary to induce apoptosis. IL-5 stimulation also appears to alter the mode of cell death of eosinophils induced by Siglec-8 ligation in that cell death becomes a caspase-independent process. Costimulation of the IL-5 receptor and Siglec-8 leads to a type of cell death resembling regulated necrosis that is promoted by MEK1/ERK signaling. Because inhibition of MEK1 does not alter ROS generation but the ROS inhibitor diphenyleneiodonium inhibits ERK1/2 phosphorylation and cell death, the production of ROS appears to be upstream of MEK1/ERK signaling in this pathway. Cell death induced by Siglec-8 in the presence of IL-33, in contrast, is mediated primarily by a caspase-dependent pathway, and IL-33 is capable of synergizing with IL-5 in potentiating cell death induced by Siglec-8 ligation.
## Mast cells and basophils
While Siglec-8 ligation does not cause mast cell apoptosis, it inhibits FcεRIα-mediated Ca2+ flux and release of prostaglandin D2 and histamine. However, the release of IL-8 is not prevented by Siglec-8 ligation in mast cells. In experiments using the rat basophilic leukemia cell line RBL-2H3 stably transfected with Siglec-8, the inhibitory effect of Siglec-8 ligation on FcεRIα-mediated degranulation and Ca2+ flux was found to be dependent on the intact ITIM. There are no published data regarding the function of Siglec-8 on basophils.
# Relationships with other siglecs
## CD33-related siglec subfamily
Due to its high level of sequence homology with CD33 (Siglec-3), Siglec-8 is grouped within the CD33-related siglec subfamily. This family is composed of a rapidly evolving group of siglecs that share 50–99% sequence identity. Most members of the subfamily also possess conserved cytoplasmic ITIM and ITIM-like sequences.
## Mouse Siglec-F
While SIGLEC8 and mouse Siglecf do not appear to derive from the same ancestral gene (they are paralogous, not orthologous), they share a binding preference for 6′-sulfo-sialyl Lewis X and 6′-sulfated sialyl N-acetyl-D-lactosamine, similar but distinct patterns of cellular expression, and similar inhibitory functions. For example, Siglec-F is expressed by eosinophils, like Siglec-8, but is also expressed by alveolar macrophages and has not been detected on mouse mast cells or basophils. This functional convergence of Siglec-8 and Siglec-F has permitted in vivo studies to be performed in mouse models of eosinophil-mediated disorders that may provide information about the human system. In a chicken ovalbumin (OVA) model of allergic airway inflammation, the Siglec-F knockout mouse exhibits increased lung eosinophilia, enhanced inflammation, delayed resolution, and exacerbated peribronchial fibrosis. Antibody ligation of Siglec-F has also been shown to inhibit eosinophil-mediated intestinal inflammation and airway remodeling in OVA challenge models. The ST3Gal-III enzyme is necessary for the generation of the natural Siglec-F ligand, which remains unknown but is induced by IL-4 and IL-13 in the airway. Loss of this enzyme leads to enhanced allergic eosinophilic airway inflammation. Despite evidence that Siglec-F binds specifically to 6′-sulfo-sialyl Lewis X and 6′-sulfated sialyl N-acetyl-D-lactosamine, in which galactose is sulfated at carbon 6, mice deficient in the two known galactose 6-O-sulfotransferases, keratan sulfate galactose 6-O-sulfotransferase (KSGal6ST) and chondroitin 6-O-sulfotransferase 1 (C6ST-1), express equivalent levels of Siglec-F ligand. These models may shed some light on the regulation of human eosinophil biology by Siglec-8 and the production of natural Siglec-8 ligands in humans. Also like Siglec-8, Siglec-F ligation leads to the apoptosis of eosinophils. However, Siglec-F–induced eosinophil apoptosis is mediated by a mechanism distinct from that employed by Siglec-8, hindering direct comparisons between the mouse and human systems. Siglec-F-induced apoptosis is mediated by caspase activation in mouse eosinophils and does not involve ROS, in contrast to the mechanism reported in Siglec-8–induced apoptosis of human eosinophils. This apoptotic mechanism also does not involve Src family kinases, SHP-1, or NADPH. | SIGLEC8
Sialic acid-binding Ig-like lectin 8 is a protein that in humans is encoded by the SIGLEC8 gene.[1][2] This gene is located on chromosome 19q13.4, about 330 kb downstream of the SIGLEC9 gene.[1][3] Within the siglec family of transmembrane proteins, Siglec-8 belongs to the CD33-related siglec subfamily, a subfamily that has undergone rapid evolution.[4][5][6]
# Initial characterization
Siglec-8 was first identified by CD33 homology screening of ESTs from a cDNA library generated from a patient diagnosed with idiopathic hypereosinophilic syndrome and was originally termed SAF-2 (sialoadhesin family 2).[1][4]
At the tissue level, Siglec-8 mRNA was found to be most highly expressed in lung, PBMCs, spleen, and kidney.[4]
# Expression
Siglec-8 is expressed by human eosinophils, mast cells, and, to a lesser extent, basophils.[4] It has thus garnered attention as a molecule that is uniquely expressed by immune effector cells involved in asthma and allergy. In both eosinophils and mast cells, Siglec-8 is expressed late in development. Siglec-8 transcript and protein are detectable at day 12 during the in vitro differentiation of eosinophils from cord blood precursors, whereas the transcription factor GATA-1 peaks at day 2 and the secondary granule protein MBP-1 peaks at day 4 in this differentiation system.[7][8] In mast cells generated from CD34+ precursors, Siglec-8 expression peaks at 4 weeks of differentiation, in parallel with FcεRIα surface expression.[9]
Consistent with the concept that Siglec-8 is a late differentiation marker, Siglec-8 has not been detected on the surface of relatively undifferentiated eosinophilic cell lines, such as EoL-1, AML14, AML14.3D10, or K562, the basophilic leukemia cell line KU812, nor on cells such as HL60 or EoL-3 that have been differentiated towards an eosinophil-like lineage.[4][7] Only low levels are detected on the human mast cell sub-line HMC-1.1; however, the HMC-1.2 cell line, which bears a second KIT mutation (D816V, in addition to the V560G mutation found in both HMC-1.1 and HMC-1.2 cells) that may induce further differentiation, expresses Siglec-8 at the cell surface.[7] However, based on a small sampling of patients, all eosinophils from patients with chronic eosinophilic leukemia (CEL), hypereosinophilic syndrome, or chronic myeloid leukemia (CML), all basophils from patients with CEL or CML, and all bone marrow mast cells from patients with indolent systemic mastocytosis or aplastic anemia express Siglec-8, providing a potential target for these cells in the context of these hematologic malignancies.[7]
In addition, baboon eosinophils as well as monocytes, a subset of lymphocytes, and neutrophils express on their cell surface a protein or proteins that are recognized by polyclonal human Siglec-8-specific antibody, consistent with genetic analyses indicating the existence of a Siglec-8 ortholog in this species.[5][7] However, the 2C4, 2E2, and 7C9 monoclonal antibodies against human Siglec-8 were not found to bind to targets on baboon cells, indicating that these particular epitopes are not conserved.[7]
# Structure
Two splice variants of Siglec-8 exist.[3] The initially characterized form contains 431 amino acid residues in total, 47 of which comprise an uncharacteristically short cytoplasmic tail compared to most CD33-associated siglecs. Subsequently, a longer form of Siglec-8, initially termed Siglec-8L, that contains 499 amino acid residues was identified. This longer form of Siglec-8 shares the same extracellular region but includes a longer cytoplasmic tail with two tyrosine-based motifs (an immunoreceptor tyrosine-based inhibitory motif [ITIM] and an immunoreceptor tyrosine-based switch motif [ITSM]). Both forms of Siglec-8 are found in eosinophils and contain a V-set domain with lectin activity and two C2-type Ig repeat domains in the extracellular region.[10] Given that the longer version is felt to be the normal version, the term Siglec-8 is best used to refer to the 499 amino acid version, while the 431 amino acid version is best referred to as the “short form” of Siglec-8.
# Ligand binding
Potential glycan ligands for Siglec-8 have been screened by glycan array.[11][12] The glycan NeuAcα2–3(6-O-sulfo)Galβ1–4[Fucα1–3]GlcNAc, also known as 6′-sulfo-sialyl Lewis X, binds with high affinity to both Siglec-8 and to a mouse siglec, Siglec-F, which appears to have acquired a similar but not identical function and pattern of expression to human Siglec-8 through convergent evolution (the two siglecs are not orthologous).[11][12] Rescreening on a more expanded glycan array reconfirmed this finding, but also identified a second closely related ligand in which the fucose is absent (NeuAcα2–3(6-O-sulfo)Galβ1–4GlcNAc, or 6′-sulfated sialyl N-acetyl-D-lactosamine.[13] These interactions are quite specific; no binding could be detected between these siglecs and unsulfated sialyl Lewis X or sialyl Lewis X sulfated at carbon 6 of GlcNAc (6-sulfo-sialyl Lewis X) rather than carbon 6 of galactose as in 6′-sulfo-sialyl Lewis X. Similarly, no other siglecs bind effectively to these Siglec-8 ligands, as demonstrated by selective binding to eosinophils in human blood of a polymer decorated with 6′-sulfo-sialyl Lewis X. The natural ligand or ligands for Siglec-8 have not yet been positively identified, but ongoing studies have determined that there are sialidase-sensitive glycoprotein ligands for Siglec-F in mouse airways that require the activity of the α2,3 sialyltransferase 3 (ST3Gal-III) enzyme for their generation.[13][14][15]
# Signaling and function
## Eosinophils
Consistent with the role of most siglecs and the presence of the intracellular ITIM, Siglec-8 has been found to function as an inhibitory immunoregulatory receptor. Ligation of Siglec-8 induces apoptosis in eosinophils, and, surprisingly, the normally pro-survival cytokines interleukin (IL)-5 and GM-CSF have been found to potentiate this apoptotic effect.[16] IL-33, which activates and maintains eosinophils, also exerts a similar potentiating effect on Siglec-8-induced apoptosis.[17][18][19] Inhibitor studies demonstrate that apoptosis induced by crosslinking Siglec-8 through the use of an anti-Siglec-8 mAb and a secondary antibody is mediated sequentially through reactive oxygen species (ROS) production, loss of mitochondrial membrane potential, and caspase activation.[20] In the presence of IL-5, the loss of mitochondrial membrane integrity is accelerated and the secondary crosslinking antibody is no longer necessary to induce apoptosis.[21] IL-5 stimulation also appears to alter the mode of cell death of eosinophils induced by Siglec-8 ligation in that cell death becomes a caspase-independent process. Costimulation of the IL-5 receptor and Siglec-8 leads to a type of cell death resembling regulated necrosis that is promoted by MEK1/ERK signaling.[22] Because inhibition of MEK1 does not alter ROS generation but the ROS inhibitor diphenyleneiodonium inhibits ERK1/2 phosphorylation and cell death, the production of ROS appears to be upstream of MEK1/ERK signaling in this pathway.[22] Cell death induced by Siglec-8 in the presence of IL-33, in contrast, is mediated primarily by a caspase-dependent pathway, and IL-33 is capable of synergizing with IL-5 in potentiating cell death induced by Siglec-8 ligation.[18]
## Mast cells and basophils
While Siglec-8 ligation does not cause mast cell apoptosis, it inhibits FcεRIα-mediated Ca2+ flux and release of prostaglandin D2 and histamine.[23] However, the release of IL-8 is not prevented by Siglec-8 ligation in mast cells. In experiments using the rat basophilic leukemia cell line RBL-2H3 stably transfected with Siglec-8, the inhibitory effect of Siglec-8 ligation on FcεRIα-mediated degranulation and Ca2+ flux was found to be dependent on the intact ITIM.[23] There are no published data regarding the function of Siglec-8 on basophils.
# Relationships with other siglecs
## CD33-related siglec subfamily
Due to its high level of sequence homology with CD33 (Siglec-3), Siglec-8 is grouped within the CD33-related siglec subfamily. This family is composed of a rapidly evolving group of siglecs that share 50–99% sequence identity.[24] Most members of the subfamily also possess conserved cytoplasmic ITIM and ITIM-like sequences.
## Mouse Siglec-F
While SIGLEC8 and mouse Siglecf do not appear to derive from the same ancestral gene (they are paralogous, not orthologous), they share a binding preference for 6′-sulfo-sialyl Lewis X and 6′-sulfated sialyl N-acetyl-D-lactosamine, similar but distinct patterns of cellular expression, and similar inhibitory functions. For example, Siglec-F is expressed by eosinophils, like Siglec-8, but is also expressed by alveolar macrophages and has not been detected on mouse mast cells or basophils.[25][26][27] This functional convergence of Siglec-8 and Siglec-F has permitted in vivo studies to be performed in mouse models of eosinophil-mediated disorders that may provide information about the human system. In a chicken ovalbumin (OVA) model of allergic airway inflammation, the Siglec-F knockout mouse exhibits increased lung eosinophilia, enhanced inflammation, delayed resolution, and exacerbated peribronchial fibrosis.[26][28] Antibody ligation of Siglec-F has also been shown to inhibit eosinophil-mediated intestinal inflammation and airway remodeling in OVA challenge models.[29][30] The ST3Gal-III enzyme is necessary for the generation of the natural Siglec-F ligand, which remains unknown but is induced by IL-4 and IL-13 in the airway.[13][15][28] Loss of this enzyme leads to enhanced allergic eosinophilic airway inflammation.[13][15] Despite evidence that Siglec-F binds specifically to 6′-sulfo-sialyl Lewis X and 6′-sulfated sialyl N-acetyl-D-lactosamine, in which galactose is sulfated at carbon 6, mice deficient in the two known galactose 6-O-sulfotransferases, keratan sulfate galactose 6-O-sulfotransferase (KSGal6ST) and chondroitin 6-O-sulfotransferase 1 (C6ST-1), express equivalent levels of Siglec-F ligand.[11][12][31] These models may shed some light on the regulation of human eosinophil biology by Siglec-8 and the production of natural Siglec-8 ligands in humans. Also like Siglec-8, Siglec-F ligation leads to the apoptosis of eosinophils.[26][27] However, Siglec-F–induced eosinophil apoptosis is mediated by a mechanism distinct from that employed by Siglec-8, hindering direct comparisons between the mouse and human systems. Siglec-F-induced apoptosis is mediated by caspase activation in mouse eosinophils and does not involve ROS, in contrast to the mechanism reported in Siglec-8–induced apoptosis of human eosinophils.[32] This apoptotic mechanism also does not involve Src family kinases, SHP-1, or NADPH.[32] | https://www.wikidoc.org/index.php/SIGLEC8 | |
a56ebbd1fcb0a29ec634e7aa352cecada0182373 | wikidoc | SLC10A1 | SLC10A1
Sodium/bile acid cotransporter also known as the Na+-taurocholate cotransporting polypeptide (NTCP) or liver bile acid transporter (LBAT) is a protein that in humans is encoded by the SLC10A1 (solute carrier family 10 member 1) gene.
# Structure
Sodium/bile acid cotransporters are integral membrane glycoproteins. Human NTCP contains 349 amino acids and has a mass of 56 kDa.
# Function
Bile acid:sodium symporters participate in the enterohepatic circulation of bile acids. Two homologous transporters are involved in the reabsorption of bile acids. One of these absorbs bile acids from the intestinal lumen, the bile duct, and the kidney with an apical localization (ileal sodium/bile acid cotransporter). The other is this protein and is expressed in the basolateral membranes of hepatocytes (NTCP).
As a cotransporter, NTCP binds two sodium ions and one (conjugated) bile salt molecule, thereby providing an hepatic influx of bile salts. Other transported molecules include steroid hormones, thyroid hormones and various xenobiotics:
## Hepatitis virus entry
NTCP is a cell surface receptor necessary for the entry of hepatitis B and hepatitis D virus. This entry mechanism is inhibited by myrcludex B, cyclosporin A, progesterone, propranolol, bosentan, ezetimibe, as well as NTCP substrates like taurocholate, tauroursodeoxycholate and bromosulfophthalein. | SLC10A1
Sodium/bile acid cotransporter also known as the Na+-taurocholate cotransporting polypeptide (NTCP) or liver bile acid transporter (LBAT) is a protein that in humans is encoded by the SLC10A1 (solute carrier family 10 member 1) gene.[1][2]
# Structure
Sodium/bile acid cotransporters are integral membrane glycoproteins. Human NTCP contains 349 amino acids and has a mass of 56 kDa.[3]
# Function
Bile acid:sodium symporters participate in the enterohepatic circulation of bile acids. Two homologous transporters are involved in the reabsorption of bile acids. One of these absorbs bile acids from the intestinal lumen, the bile duct, and the kidney with an apical localization (ileal sodium/bile acid cotransporter). The other is this protein and is expressed in the basolateral membranes of hepatocytes (NTCP).[3]
As a cotransporter, NTCP binds two sodium ions and one (conjugated) bile salt molecule, thereby providing an hepatic influx of bile salts. Other transported molecules include steroid hormones, thyroid hormones and various xenobiotics:[3]
## Hepatitis virus entry
NTCP is a cell surface receptor necessary for the entry of hepatitis B and hepatitis D virus.[4] This entry mechanism is inhibited by myrcludex B,[5] cyclosporin A, progesterone, propranolol, bosentan, ezetimibe, as well as NTCP substrates like taurocholate, tauroursodeoxycholate and bromosulfophthalein.[3] | https://www.wikidoc.org/index.php/SLC10A1 | |
85acf2e59283310bbf2a653bdc07fed298c9fe4a | wikidoc | SLC10A2 | SLC10A2
The SLC10A2 (solute carrier family 10 member 2) gene in humans encodes the bile acid:sodium symporter known as the apical sodium–bile acid transporter (ASBT) or as the ileal bile acid transporter (IBAT).
ASBT/IBAT is most highly expressed in the ileum, where it is found on the brush border membrane of enterocytes. It is responsible for the initial uptake of bile acids, particularly conjugated bile acids, from the intestine as part of their enterohepatic circulation.
# As a drug target
Several medications to inhibit IBAT are under development. They include elobixibat, under development for the treatment of constipation and irritable bowel syndrome, and volixibat, under development for the treatment of nonalcoholic steatohepatitis. | SLC10A2
The SLC10A2 (solute carrier family 10 member 2) gene in humans encodes the bile acid:sodium symporter known as the apical sodium–bile acid transporter (ASBT) or as the ileal bile acid transporter (IBAT).[1][2]
ASBT/IBAT is most highly expressed in the ileum, where it is found on the brush border membrane of enterocytes. It is responsible for the initial uptake of bile acids, particularly conjugated bile acids, from the intestine as part of their enterohepatic circulation.[3]
# As a drug target
Several medications to inhibit IBAT are under development. They include elobixibat, under development for the treatment of constipation and irritable bowel syndrome,[4] and volixibat, under development for the treatment of nonalcoholic steatohepatitis.[5] | https://www.wikidoc.org/index.php/SLC10A2 | |
979bfdef82d7fe42c7b40de18020e95061da604a | wikidoc | SLC13A5 | SLC13A5
Solute carrier family 13 (sodium-dependent citrate transporter), member 5 also known as the Na+/citrate cotransporter is a protein that in humans is encoded by the SLC13A5 gene.
# Function
SLC13A5 is a tricarboxylate plasma transporter with a preference for citrate.
# Clinical significance
In 2014, by means of exome sequencing it was determined that a genetic mutation of the SLC13A5 gene is the cause of an extremely rare citrate transporter disorder.
Mutations in SLC13A5 cause autosomal recessive epileptic encephalopathy with seizure onset in the first days of life. Those afflicted suffer from seizures, global developmental delay, movement disorder and hypotonia.
The site www.citratetransporterdisorders.org aims to unite families, doctors and researchers in their efforts to find treatment options. | SLC13A5
Solute carrier family 13 (sodium-dependent citrate transporter), member 5 also known as the Na+/citrate cotransporter is a protein that in humans is encoded by the SLC13A5 gene.[1]
# Function
SLC13A5 is a tricarboxylate plasma transporter with a preference for citrate.[1]
# Clinical significance
In 2014, by means of exome sequencing it was determined that a genetic mutation of the SLC13A5 gene is the cause of an extremely rare citrate transporter disorder.[2]
Mutations in SLC13A5 cause autosomal recessive epileptic encephalopathy with seizure onset in the first days of life.[2] Those afflicted suffer from seizures, global developmental delay, movement disorder and hypotonia.
The site www.citratetransporterdisorders.org aims to unite families, doctors and researchers in their efforts to find treatment options. | https://www.wikidoc.org/index.php/SLC13A5 | |
c9410d383eed1012282f7f087a723f961b74ea18 | wikidoc | SLC17A5 | SLC17A5
Solute carrier family 17 (anion/sugar transporter), member 5, also known as SLC17A5 or sialin, is a protein which in humans is encoded by the SLC17A5 gene.
# Clinical significance
A deficiency of this protein causes Salla disease. and Infantile Sialic Acid Storage Disease (ISSD).
The gene for HP59 contains, entirely within its coding region, the Sialin Gene SLC17A5. Member 5, also known as SLC17A5 or sialin is a lysosomal membrane sialic acid transport protein which in humans is encoded by the SLC17A5 gene on Chromosome 6 | SLC17A5
Solute carrier family 17 (anion/sugar transporter), member 5, also known as SLC17A5 or sialin, is a protein which in humans is encoded by the SLC17A5 gene.[1][2][3]
# Clinical significance
A deficiency of this protein causes Salla disease.[3][4] and Infantile Sialic Acid Storage Disease (ISSD).
The gene for HP59 contains, entirely within its coding region, the Sialin Gene SLC17A5. Member 5, also known as SLC17A5 or sialin is a lysosomal membrane sialic acid transport protein which in humans is encoded by the SLC17A5 gene on Chromosome 6[5][6][7] | https://www.wikidoc.org/index.php/SLC17A5 | |
83c7b0e6daaaa462cba9b77e0c15a07db5ffae97 | wikidoc | SLC17A8 | SLC17A8
Solute carrier family 17 member 8 (SLC17A8) also known as the vesicular glutamate transporter 3 (VGluT3) is a protein that in humans is encoded by the SLC17A8 gene.
# Function
This gene encodes a vesicular glutamate transporter. The encoded protein transports the neurotransmitter glutamate into synaptic vesicles before it is released into the synaptic cleft.
# Clinical significance
Mutations in this gene are the cause of autosomal-dominant nonsyndromic deafness type 25 (DFNA25). | SLC17A8
Solute carrier family 17 member 8 (SLC17A8) also known as the vesicular glutamate transporter 3 (VGluT3) is a protein that in humans is encoded by the SLC17A8 gene.[1]
# Function
This gene encodes a vesicular glutamate transporter. The encoded protein transports the neurotransmitter glutamate into synaptic vesicles before it is released into the synaptic cleft.[1]
# Clinical significance
Mutations in this gene are the cause of autosomal-dominant nonsyndromic deafness type 25 (DFNA25).[2][3] | https://www.wikidoc.org/index.php/SLC17A8 | |
07681a449c4d6d0474e8cc9e3024e98569b159cb | wikidoc | SLC19A1 | SLC19A1
Solute carrier family 19 (folate transporter), member 1, also known as SLC19A1 or RFC1, is a protein which in humans is encoded by the SLC19A1 gene.
# Function
Transport of folate compounds into mammalian cells can occur via receptor-mediated (see folate receptor 1) or carrier-mediated mechanisms. A functional coordination between these 2 mechanisms has been proposed to be the method of folate uptake in certain cell types. Methotrexate (MTX) is an antifolate chemotherapeutic agent that is actively transported by the carrier-mediated uptake system. RFC1 plays a role in maintaining intracellular concentrations of folate.
# Clinical significance
Individuals carrying a specific polymorphism of SLC19A1 (c.80GG) have lower levels of folate. Other studies have also shown that individuals carrying the c.80AA polymorphism who are treated with methotrexate have higher levels of this anti-folate chemotherapeutic agent. Personalized dosing of the drug depending on the patient's genotype may therefore be required. | SLC19A1
Solute carrier family 19 (folate transporter), member 1, also known as SLC19A1 or RFC1, is a protein which in humans is encoded by the SLC19A1 gene.[1]
# Function
Transport of folate compounds into mammalian cells can occur via receptor-mediated (see folate receptor 1) or carrier-mediated mechanisms. A functional coordination between these 2 mechanisms has been proposed to be the method of folate uptake in certain cell types. Methotrexate (MTX) is an antifolate chemotherapeutic agent that is actively transported by the carrier-mediated uptake system. RFC1 plays a role in maintaining intracellular concentrations of folate.[2]
# Clinical significance
Individuals carrying a specific polymorphism of SLC19A1 (c.80GG) have lower levels of folate.[3] Other studies have also shown that individuals carrying the c.80AA polymorphism who are treated with methotrexate have higher levels of this anti-folate chemotherapeutic agent. Personalized dosing of the drug depending on the patient's genotype may therefore be required. | https://www.wikidoc.org/index.php/SLC19A1 | |
2d764c648f2236955256a78e3c33fbf35ebbb3cb | wikidoc | SLC19A2 | SLC19A2
Thiamine transporter 1, also known as thiamine carrier 1 (TC1) or solute carrier family 19 member 2 (SLC19A2) is a protein that in humans is encoded by the SLC19A2 gene. SLC19A2 is a thiamine transporter. Mutations in this gene cause thiamine-responsive megaloblastic anemia syndrome (TRMA), which is an autosomal recessive disorder characterized by diabetes mellitus, megaloblastic anemia and sensorineural deafness.
# Structure
The SLC19A2 gene is located on the q arm of chromosome 1 in position 24.2 and spans 22,062 base pairs. The gene produces a 55.4 kDa protein composed of 497 amino acids. In the encoded protein (TC1), a multi-pass membrane protein located in the cell membrane, the N-terminus and C-terminus face the cytosol. This gene has 6 exons while the protein has 12 putative transmembrane domains, with 3 phosphorylation sites in putative intracellular domains, 2 N-glycolysation sites in putative extracellular domains, and a 17-amino acid long G protein-coupled receptor signature sequence. The thiamine transporter protein encoded by SLC19A2 has a 40% shared amino acid identity with the folate transporter SLC19A1. The N-terminal domain and the sequence between the C-terminal domain and sixth transmembrane domain are required for proper localization of this protein to the cell membrane.
# Function
The encoded protein is a high-affinity transporter specific to the intake of thiamine. Thiamine transport is not inhibited by other organic cations nor affected by sodium ion concentration; it is stimulated by a proton gradient directed outward, with an optimal pH between 8.0 and 8.5. TC1 is transported to the cell membrane by intracellular vesicles via microtubules.
# Clinical significance
Mutations in the SLC19A2 gene can cause thiamine-responsive megaloblastic anemia syndrome (TRMA), which is an autosomal recessive disease characterized by megaloblastic anemia, diabetes mellitus, and sensorineural deafness. Onset is typically between infancy and adolescence, but all of the cardinal findings are often not present initially. The anemia, and sometimes the diabetes, improves with high doses of thiamine. Other more variable features include optic atrophy, congenital heart defects, short stature, and stroke.
A 3.8 kb transcript is expressed variably in most tissues, highest in skeletal and cardiac muscle, followed by medium expression placenta, heart, liver, kidney cells and low expression in lung cells. In melanocytic cells SLC19A2 gene expression may be regulated by MITF.
# Interactions
This protein interacts with CERS2. | SLC19A2
Thiamine transporter 1, also known as thiamine carrier 1 (TC1) or solute carrier family 19 member 2 (SLC19A2) is a protein that in humans is encoded by the SLC19A2 gene.[1] SLC19A2 is a thiamine transporter. Mutations in this gene cause thiamine-responsive megaloblastic anemia syndrome (TRMA), which is an autosomal recessive disorder characterized by diabetes mellitus, megaloblastic anemia and sensorineural deafness.[2][3][4]
# Structure
The SLC19A2 gene is located on the q arm of chromosome 1 in position 24.2 and spans 22,062 base pairs.[3] The gene produces a 55.4 kDa protein composed of 497 amino acids.[5][6] In the encoded protein (TC1), a multi-pass membrane protein located in the cell membrane, the N-terminus and C-terminus face the cytosol.[7][8] This gene has 6 exons while the protein has 12 putative transmembrane domains, with 3 phosphorylation sites in putative intracellular domains, 2 N-glycolysation sites in putative extracellular domains, and a 17-amino acid long G protein-coupled receptor signature sequence. The thiamine transporter protein encoded by SLC19A2 has a 40% shared amino acid identity with the folate transporter SLC19A1.[9] The N-terminal domain and the sequence between the C-terminal domain and sixth transmembrane domain are required for proper localization of this protein to the cell membrane.[10][11]
# Function
The encoded protein is a high-affinity transporter specific to the intake of thiamine.[7][8] Thiamine transport is not inhibited by other organic cations nor affected by sodium ion concentration; it is stimulated by a proton gradient directed outward, with an optimal pH between 8.0 and 8.5.[9] TC1 is transported to the cell membrane by intracellular vesicles via microtubules.[10][11]
# Clinical significance
Mutations in the SLC19A2 gene can cause thiamine-responsive megaloblastic anemia syndrome (TRMA), which is an autosomal recessive disease characterized by megaloblastic anemia, diabetes mellitus, and sensorineural deafness. Onset is typically between infancy and adolescence, but all of the cardinal findings are often not present initially. The anemia, and sometimes the diabetes, improves with high doses of thiamine. Other more variable features include optic atrophy, congenital heart defects, short stature, and stroke.[7][8]
A 3.8 kb transcript is expressed variably in most tissues, highest in skeletal and cardiac muscle, followed by medium expression placenta, heart, liver, kidney cells and low expression in lung cells. In melanocytic cells SLC19A2 gene expression may be regulated by MITF.[12]
# Interactions
This protein interacts with CERS2.[13] | https://www.wikidoc.org/index.php/SLC19A2 |
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