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8041693 | Late Precambrian bilaterians: grades and clades. | A broad variety of body plans and subplans appear during a period of perhaps 8 million years (my) within the Early Cambrian, an unequaled explosion of morphological novelty, the ancestral lineages represented chiefly or entirely by trace fossils. Evidence from the fossil record can be combined with that from molecular phylogenetic trees to suggest that the last common ancestor of (i) protostomes and deuterostomes was a roundish worm with a blood vascular system and (ii) of arthropods and annelids was similar, with a hydrostatic hemocoel; these forms are probably among trace makers of the late Precambrian. Cell-phenotype numbers in living phyla, and a model of cell-phenotype number increase, suggest an origin of metazoans near 600 my ago, followed by a passive rise in body-plan complexity. Living phyla appearing during the Cambrian explosion have a Hox/HOM gene cluster, implying its presence in the common ancestral trace makers. The explosion required a repatterning of gene expression that mediated the development of novel body plans but evidently did not require an important, abrupt increase in genomic or morphologic complexity. |
8041692 | Proterozoic and early Cambrian protists: evidence for accelerating evolutionary tempo. | In rocks of late Paleoproterozoic and Mesoproterozoic age (ca. 1700-1000 million years ago), probable eukaryotic microfossils are widespread and well preserved, but assemblage and global diversities are low and turnover is slow. Near the Mesoproterozoic-Neoproterozoic boundary (1000 million years ago), red, green, and chromophytic algae diversified; molecular phylogenies suggest that this was part of a broader radiation of "higher" eukaryotic phyla. Observed diversity levels for protistan microfossils increased significantly at this time, as did turnover rates. Coincident with the Cambrian radiation of marine invertebrates, protistan microfossils again doubled in diversity and rates of turnover increased by an order of magnitude. Evidently, the Cambrian diversification of animals strongly influenced evolutionary rates, within clades already present in marine communities, implying an important role for ecology in fueling a Cambrian explosion that extends across kingdoms. |
8041690 | Phylogeny from function: evidence from the molecular fossil record that tRNA originated in replication, not translation. | We propose a phylogeny for the evolution of tRNA that is based on the ubiquity and conservation of tRNA-like structures in the replication of contemporary genomes. This phylogeny is unique in suggesting that the function of tRNA in replication dates back to the very beginnings of life on earth, before the advent of templated protein synthesis. The origin we propose for tRNA has distinct implications for the order in which other components of the modern translational apparatus evolved. We further suggest that the "top half" of modern tRNA-a coaxial stack of the acceptor stem on the T psi C arm--is the ancient structural and functional domain and that the "bottom half" of tRNA--a coaxial stack of the dihydrouracil arm on the anticodon arm--arose later to provide additional specificity. |
8041691 | Disparate rates, differing fates: tempo and mode of evolution changed from the Precambrian to the Phanerozoic. | Over the past quarter century, detailed genus- and species-level similarities in cellular morphology between described taxa of Precambrian microfossils and extant cyanobacteria have been noted and regarded as biologically and taxonomically significant by numerous workers world-wide. Such similarities are particularly well documented for members of the Oscillatoriaceae and Chroococcaceae, the two most abundant and widespread Precambrian cyanobacterial families. For species of two additional families, the Entophysalidaceae and Pleurocapsaceae, species-level morphologic similarities are supported by in-depth fossil-modern comparisons of environment, taphonomy, development, and behavior. Morphologically and probably physiologically as well, such cyanobacterial "living fossils" have exhibited an extraordinarily slow (hypobradytelic) rate of evolutionary change, evidently a result of the broad ecologic tolerance characteristic of many members of the group and a striking example of G. G. Simpson's [Simpson, G.G. (1944) Tempo and Mode in Evolution (Columbia Univ. Press, New York)] "rule of the survival of the relatively unspecialized." In both tempo and mode of evolution, much of the Precambrian history of life--that dominated by microscopic cyanobacteria and related prokaryotes--appears to have differed markedly from the more recent Phanerozoic evolution megascopic, horotelic, adaptationally specialized eukaryotes. |
8041689 | Tempo, mode, the progenote, and the universal root. | Early cellular evolution differed in both mode and tempo from the contemporary process. If modern lineages first began to diverge when the phenotype-genotype coupling was still poorly articulated, then we might be able to learn something about the evolution of that coupling through comparing the molecular biologies of living organisms. The issue is whether the last common ancestor of all life, the cenancestor, was a primitive entity, a progenote, with a more rudimentary genetic information-transfer system. Thinking on this issue is still unsettled. Much depends on the placement of the root of the universal tree and on whether or not lateral transfer renders such rooting meaningless. |
8041687 | Managing rheumatologic disease in nursing home patients. | Precise diagnosis and treatment are essential when dealing with rheumatologic complaints in elderly nursing home patients. National surveys suggest that for every nursing home resident, there are two equally frail elders living in the community. The same principles of diagnosis and management apply to this latter group of patients, including use of multidisciplinary input from nurses and physical and occupational therapists, who are becoming increasingly available in the rapidly expanding and accessible home healthcare system. However, the therapeutic value of the physician's thoughtful and empathic history taking and careful hands-on examination should not be underestimated. |
8041686 | Juvenile rheumatoid arthritis. Old challenges, new insights. | What are the three main types of disease presentation in juvenile rheumatoid arthritis, and how do they relate to prognosis? Does infection or heredity play a role in causing the illness? Should aggressive therapy with multiple drugs be instituted early? Which therapeutic agents have the best chance of inducing remission? Dr Tibbitts addresses these and other questions in this overview of a disease that is a significant cause of chronic illness and disability in children. |
8041685 | Myofascial pain syndrome. Primary care strategies for early intervention. | Diagnosis of myofascial pain syndrome may become less challenging as clinical criteria become better defined. The mechanisms are not well known, and the syndrome occurs in a wide variety of settings. Trigger points with referred pain are the most common feature. Treatment consists of physical modalities (spray-and-stretch techniques and trigger point block) combined with a program of graded muscle stretching and strengthening. Early, aggressive treatment yields an improved prognosis. |
8041684 | Common infections of the skin. Characteristics, causes, and cures. | If the skin's protective mechanisms are disrupted, cutaneous infection may result. Diagnosis is based on recognition of clinical signs. Accurate assessment of these signs and prompt initiation of appropriate treatment can help patients avoid serious complications, such as glomerulonephritis occurring with impetigo contagiosa or gangrene and sepsis occurring with cellulitis. Recurrence of skin infections is difficult to prevent, but patients should be encouraged to practice good hygiene and to avoid irritants and predisposing factors nonetheless. |
8041680 | Middle ear symptoms while flying. Ways to prevent a severe outcome. | In an era when air travel is commonplace, middle ear block is not unusual. Educating patients about the simple techniques they can perform at the first signs of a problem may save a business trip or vacation from becoming a trip to the emergency department and a train ride home. The most important preventive measure is to avoid flying when symptoms of upper respiratory tract infection are present. When this is not possible, passengers should yawn, swallow, or chew to relieve pressure in the middle ear. Use of the Valsalva maneuver and decongestants or antihistamines may be helpful. Serve or unremitting ear block may require the use of the Politzer bag or a myringotomy. |
8041679 | Exercise training in patients with congestive heart failure. How to achieve benefits safely. | Inactivity adds to the decline of patients with congestive heart failure (CHF). However, in prescribing exercise in these patients, three principles must be understood: ejection fraction does not predict functional capacity, exercise can bring marked peripheral improvement without changing ejection fraction or hemodynamics, and benefits accrue slowly. The authors review the mechanisms of exercise intolerance in CHF and the factors to keep in mind when designing an exercise program. |
8041677 | Urinary incontinence in women. How to help patients regain bladder control. | Urinary incontinence can have devastating effects on a woman's social life and physical activities. Simple diagnostic tools, including the Q-tip test and cystometry, can help identify the cause. Many causes are reversible, and an appropriate treatment regimen can bring improvement in or completely restore bladder control. Management options that may help patients avoid surgical intervention include bladder drills, pelvic floor muscle exercises, and functional electrical stimulation. Additional nonsurgical approaches are currently under investigation and should result in more options for treating urinary incontinence in women. |
8041676 | Migraine headaches in children. | Migraine headaches are common in children and adolescents, and stricter diagnostic criteria have been developed. Children have a variety of migraine syndromes, ranging from frequent, mild, bifrontal headaches to severe debilitating, unilateral pain associated with persistent motor or visual deficits. Neurodiagnostic studies are indicated in those individuals who have accompanying signs or symptoms that raise concern. The treatment of migraine must be individualized and requires more than just the use of pharmacotherapy. Reassurance and the elimination of potential triggering factors are essential components of care. Symptomatic therapy with analgesics and rest often is sufficient. Behavioral therapy, consisting of psychological support, relaxation exercises, and biofeedback training, is effective in reducing the frequency and severity of migraine. Ergotamines are valuable agents for abortive treatment, but should be reserved for use in the older child. Parenteral use of DHE is an effective treatment for the rare child who has an acute severe migraine unresponsive to other therapies. A variety of agents are available for the long-term stabilization of childhood migraine. |
8041670 | Hematuria. | Hematuria occurs in approximately 1.5% of children. It is important in evaluating the patient who has hematuria to make sure that a positive dipstick test is accompanied by RBCs on the microscopic examination. Hematuria is defined by several parameters, the most common of which are 6 cells/cc of urine in a counting chamber or 2 cells per high-power field in a urinary sediment. Although the differential diagnosis for hematuria is extensive, the most important differentiating feature is the presence or absence of proteinuria. Those who have significant proteinuria deserve a rapid evaluation and early referral to a nephrologist. Those who do not have proteinuria should be followed and a step-wise evaluation performed. Finally, most patients who have asymptomatic microscopic hematuria do not have clinically significant glomerular pathology. |
8041669 | Clinical analysis of 40 cases of childhood-onset Behçet's disease. | Behçet's disease is a chronic, relapsing, idiopathic, multi-system condition characterized by mucocutaneous, ocular, gastrointestinal, articular, vascular, urogenital, and neurologic involvement. Usually the onset occurs between 20 and 30 years of age; it is very uncommon in children. We analyzed 40 cases of childhood-onset Behçet's disease. The male:female ratio was 0.67. The most frequent major sign was oral ulceration, appearing in all patients. Other major signs were genital ulcers (33 patients), skin lesions (29), and ocular lesions (11). The average time interval between the initial oral ulceration and the second major manifestation was 8.8 years. After the second major manifestation, the third and fourth features rapidly developed within one to two years. The most frequent minor sign was arthritis, occurring in 11 of 40 patients. Intestinal, neurologic, and renal involvement was also present. From our results, we concluded that oral ulceration, which is the most common initial manifestation, should not be neglected in children, since it may signal Behçet's disease. |
8041662 | Juvenile basal cell carcinoma. | A 17-year-old youth had a solitary basal cell carcinoma of the nose. This malignancy is rare in children and usually occurs with another disease or syndrome. The de novo form in this patient is especially rare. |
8041661 | Ulerythema ophryogenes and keratosis pilaris in a child with monosomy 18p. | We report a 13-year-old boy with deletion of the short arm of chromosome 18 and follicular, partially inflammatory, keratotic papules of the eyebrows, foreskin, and cheeks (ulerythema ophryogenes) as well as the shoulders, upper back, upper arms, and thighs (keratosis pilaris), initially diagnosed as atopic dermatitis. Over 100 patients with this genetic defect have been reported, and the 18p- syndrome is considered one of the most frequently occurring deletion syndromes. However, ulerythema ophryogenes and keratosis pilaris have not been described in any of these patients, although the association of the latter with other genetic abnormalities is well known. Keratosis pilaris is a relatively common genodermatosis of ectodermal origin, frequently occurring with ichthyosis or atopy; concomitance with ulerythema ophryogenes has also been reported. The association of chromosome 18p deletion defect and ulerythema ophryogenes may be helpful in future attempts to localize the gene defect responsible for follicular genokeratoses. |
8041660 | Perianal streptococcal dermatitis associated with guttate psoriasis and/or balanoposthitis: a study of five cases. | Perianal streptococcal dermatitis (PSD) is a recently described cutaneous entity caused by group A beta-hemolytic streptococci. It is characterized by perianal erythema, sometimes associated with functional disturbances. We describe four children (2 boys, 2 girls) who had acute guttate psoriasis and also PSD. One of these patients also had balanoposthitis. A fifth patient experienced an association of PSD and balanoposthitis without psoriasis. To our knowledge, the association between guttate psoriasis and PSD has only been reported in five children, and the one with balanitis has not been previously reported. |
8041659 | Benign cephalic histiocytosis: case report and literature review. | A 3-year-old boy had maculopapules on his face and neck since age 6 months. These were yellow-brown, asymptomatic, and clinically similar to flat warts. Histopathologic study revealed a fibrohistiocytic infiltrate in the superficial dermis. Ultrastructurally, comma-shaped bodies, desmosome-like junctions, and coated vesicles were seen; there were no lipid droplets or Birbeck granules. With these data, a diagnosis of benign cephalic histiocytosis was made. Twenty-five cases are reported in the literature: 17 males and 8 females (male:female ratio 2:1). Sixteen patients had lesions on parts of the body other than the head, neck, and shoulders. |
8041658 | Familial lichen sclerosus et atrophicus in childhood. | Lichen sclerosus et atrophicus (LSA) is uncommonly reported in family members and is seen occasionally in young children. We report genital LSA in two young sisters who were diagnosed a year apart. The English language literature on familial LSA in childhood is reviewed and discussed. |
8041657 | Persistent erythema infectiosum-like rash as a prodrome of acute lymphocytic leukemia. | A 7-year-old boy had erythema infectiosum with typical manifestations. Over more than 40 days, these lesions showed no sign of regression, and chronic anemia became progressively more severe. Electron microscopic examination performed 20 days after onset showed abnormal Sezary-like lymphocytes. Bone marrow biopsy, which was performed to evaluate the anemia, was consistent with acute lymphocytic leukemia. Persistent parvovirus B19 infection may be connected with immunosuppression. Therefore, early electron microscopic study and bone marrow biopsy may be helpful for early diagnosis of hematologic malignancies. |
8041656 | Parapsoriasis in two children: a clinical, immunophenotypic, and immunogenotypic study. | Parapsoriasis has been described rarely in childhood; a few reports mention this condition as preceding early mycosis fungoides. We report a boy age 15 and a girl age 8 years with different clinical features of parapsoriasis who were followed clinically and histologically for about four years. Immunophenotyping of the skin infiltrate and a T cell receptor gene rearrangement analysis were performed on each. The infiltrate was composed mainly of CD4+ and CD45+ lymphocytes in the first patient and of CD8+ and CD45+ in the second. No T cell receptor gene rearrangements were found. The paucity of knowledge about the evolution of this entity in childhood and its relationship to mycosis fungoides makes follow-up critical. The importance of immunophenotyping and immunogenotyping is particularly stressed. |
8041655 | Oral pemphigus vulgaris associated with inflammatory bowel disease and herpetic gingivostomatitis in an 11-year-old girl. | An 11-year-old girl with recently diagnosed oral pemphigus vulgaris developed a severe exacerbation of mouth ulceration due to superinfection with herpes simplex virus type I. A concurrent diagnosis of chronic inflammatory bowel disease was established to explain symptoms of weight loss and intermittent bloody diarrhea that predated the oral ulceration by several years. Herpes simplex infection is a recognized complication of pemphigus vulgaris that may be mistaken for a recrudescence of the disease. The association of pemphigus with chronic inflammatory bowel disease has been documented in a small number of adults. Its relationship to pyostomatitis vegetans, an acknowledged marker for ulcerative colitis and Crohn disease, remains unclear. |
8041654 | Linear IgA bullous dermatosis of childhood with autoantibodies to a 230 kDa epidermal antigen. | Linear IgA bullous dermatosis (LABD) is an autoimmune, subepidermal disease defined on the basis of direct immunofluorescence findings. However, more recent techniques used to study bullous dermatoses suggest that LABD may be heterogeneous. A patient with LABD of childhood (chronic benign disease of childhood, CBDC) was studied by indirect immunofluorescence on salt-split skin and by Western blot in an attempt to characterize the involved autoantigen. This young girl's periorificial (mouth, genitalia), erythematovesicular lesions were diagnosed initially as herpes simplex. Histologic examination revealed eosinophilic spongiosis, suggesting the diagnosis of an autoimmune blistering disease. Direct immunofluorescence showed an exclusive linear IgA deposit at the dermoepidermal junction. Indirect immunofluorescence revealed circulating IgA autoantibodies that reacted with the epidermal side of salt-split skin; these reacted by Western blot with a 230 kDa epidermal antigen, as in bullous pemphigoid. This case, fulfilling the diagnostic clinical and direct immunofluorescence criteria for LABD/CBDC, seems to represent IgA bullous pemphigoid. It further underscores the nosologic heterogeneity of LABD, which probably includes, apart from bullous pemphigoid, epidermolysis bullosa acquisita and cicatricial pemphigoid. |
8041653 | Hereditary mucoepithelial dysplasia. | We report an individual with the rare autosomal recessive condition known as hereditary mucoepithelial dysplasia. The diagnosis was based on clinical features and characteristic ultrastructural changes in oral mucosal biopsy specimens. |
8041652 | Atypical varicella exanthems associated with skin injury. | Varicella is a common childhood disease with a typical exanthem. We present four children with severe, localized disease, all associated with some form of trauma to the skin during the incubation period: a 3 1/2-year-old boy sustained wasp stings on the hand, a 5-year-old boy received extensive sun exposure, a neonate had iatrogenic trauma to her arm, and a 13-year-old boy underwent knee arthroscopy and was wearing a cast. It is postulated that such injuries to the skin either allowed more virus-infected cells to enter the skin at the sites, or that factors such as insect venom and ultraviolet light altered local immunity to varicella zoster virus. |
8041651 | Epidemiology of skin disease among children in a referral skin clinic in Singapore. | This retrospective epidemiologic study compared data of skin disease in children less than 16 years old with those of adults attending the same tertiary referral outpatient clinic. Of the 74,589 patients seen in this clinic, 9273 (12.4%) were children. There were significant differences in the types of skin disease between children and adults. In children, eczema was the most common (50%), followed by viral infection (7%), bacterial infection (5%), and insect bite reaction (5%), significantly higher proportions than in adults. In contrast, acne vulgaris (3%), fungal infection (3%), and psoriasis (1.1%) rates were significantly lower in children than in adults. Atopic eczema (51%), followed by endogenous handfoot eczema (9.6%) was the most common type of eczema in children. The number of children with atopic (including asteatotic eczema) and seborrhoeic eczema decreased with age, suggesting that these conditions tend to clear with age, whereas other endogenous eczemas, including hand-foot eczema, nummular eczema, and lichen simplex chronicus, tend to increase with age. Epidemiologic data are useful in monitoring changes in disease trends in children and planning health care programs for them. |
8041650 | Melanocytic nevi in Turner syndrome. | One morphologic feature of Turner syndrome is increased numbers of melanocytic nevi; however, little attention has been given to their characterization. The development of a melanoma in one of our patients with Turner syndrome prompted this study. We prospectively examined 10 patients with the disease, confirmed by karyotype. All patients underwent full body skin examination noting the number, size, distribution, and degree of clinical atypia of melanocytic nevi. Representative and unusual lesions were photographed. An average of 115 nevi were seen, with the majority measuring 1 to 5 mm. Most were located on the back and extremities. Clinical atypia was uncommon. Our patients had larger numbers of benign-appearing nevi than the general population. Large numbers of melanocytic nevi is a risk factor for melanoma, suggesting that these patients have an increase in one risk factor. Longitudinal studies are indicated to clarify this issue; nevertheless, we recommend periodic skin examinations and the regular use of sunscreens for individuals with Turner syndrome. |
8041649 | A survey of childhood psoriasis in Kuwait. | One hundred ninety cases of childhood (age birth-12 yrs) psoriasis constituted 0.3% of the total of new dermatologic outpatients. Girls outnumbered boys by a ratio of 1.5:1. Plaque psoriasis was the commonest clinical variant (84%), followed by guttate psoriasis. The scalp was the most common site of onset (22%). Sites predominantly affected later were the extensor surfaces of the legs and the scalp (63% and 53%, respectively). A majority of the children had a milder form of disease. Nail involvement was seen in 36%, with pitting the most common feature (87%). Seven percent had mucosal involvement. A positive family history of psoriasis was obtained in 28%. Topical therapy (coal tar, anthralin, steroids) was the main treatment in the majority of patients (92%). Sixteen patients (8%) required more aggressive intervention (ultraviolet B, psoralin-UVA, retinoids). This is the first study of this kind from the Middle East, the findings are compared with those reported from other parts of the world. |
8041648 | Prevalence of nail abnormalities in children with alopecia areata. | We assessed the prevalence of nail abnormalities in 272 children with alopecia areata who were seen in our department during an eight-year period. Of these, 126 (46%; 50 girls, 76 boys) had nail abnormalities that were related to alopecia areata. Nail pitting was detected in 92 patients, including 37 with alopecia totalis or alopecia universalis. Three patients experienced an onychomadesis of all 20 nails during the acute onset of alopecia areata universalis. Thirty-two (11.7%) had nail thinning and severe nail plate surface abnormalities that were consistent with a diagnosis of trachyonychia. |
8041647 | Further experience with pemphigus in children. | Seven children had pemphigus: six had pemphigus vulgaris and one pemphigus foliaceus. Four who had pemphigus vulgaris were administered dexamethasone pulses. Follow-up from six months to one year was uneventful; the disease was under control and there were no complications due to therapy. Our observations suggest that the clinical features, course, and principles of therapy for pemphigus in children are essentially the same as those in adults. |
8041646 | Urticaria pigmentosa: a review of 67 pediatric cases. | Mastocytosis is a disorder of mast cell proliferation that may appear during infancy, childhood, or adulthood. We studied 67 consecutive patients (33 males, 34 females) with urticaria pigmentosa and assessed them fully to determine the presence of systemic involvement. Ages at onset of lesions ranged from birth to 11 years, with most developing in the first year of life. Pruritus was the primary symptom. Hematologic and serum chemistry profile, radiologic skeletal surveys, and bone marrow aspirations were performed. Slight anemia was present in three patients. Radiologic bone lesions were observed in eight. Bone marrow aspirates showed slight changes in six patients, with only an increased number of mast cells in an additional patient. The disease tended to resolve spontaneously. This prospective study emphasizes the benign nature of pediatric urticaria pigmentosa. |
8041639 | Standardizing the language for nursing treatments: an overview of the issues. | The development and use of standardized language in nursing marks the development of a new era of nursing science. It will assist the professional nurse to communicate with colleagues in her or his own facility and across the world. Being able to clearly articulate what it is we do makes visible what previously has been invisible about nursing. When we use standardized language to document the care we give, then we can build large databases, which will articulate with those of other health providers, that can be used to demonstrate the effectiveness of nursing care. As we move into the 21st century, the use of standardized nursing language will become one of the hallmarks of the profession. |
8041634 | Multiple genes encode the translation elongation factor EF-1 gamma in Saccharomyces cerevisiae. | A gene encoding a yeast homologue of translation elongation factor 1 gamma (EF-1 gamma), TEF3, was isolated as a gene dosage extragenic suppressor of the cold-sensitive phenotype of the Saccharomyces cerevisiae drs2 mutant. The drs2 mutant is deficient in the assembly of 40S ribosomal subunits. We have identified a second gene, TEF4, that encodes a protein highly related to both the Tef3p protein (Tef3p), and EF-1 gamma isolated from other organisms. In contrast to TEF3, the TEF4 gene contains an intron. Gene disruptions showed that neither gene is required for mitotic growth. Haploid spores containing disruptions of both genes are viable and have no defects in ribosomal subunit composition or polyribosomes. Unlike TEF3, extra copies of TEF4 do not suppress the cold-sensitive 40S ribosomal subunit deficiency of a drs2 strain. Low-stringency genomic Southern hybridization analysis indicates there may be additional yeast genes related to TEF3 and TEF4. |
8041633 | A genetic polymorphism within the third poly(A) signal of the DHFR gene alters the polyadenylation pattern of DHFR transcripts in CHL cells. | Two polymorphic dihydrofolate reductase (DHFR) alleles, termed 20 K and 21 K, exist in Chinese hamster lung cells. Three major transcripts of different lengths are transcribed from each allele, and the expression of these transcripts differs dramatically between the alleles as a result of differential utilization of three poly(A) sites. Transcripts from the 20 K allele are preferentially polyadenylated at the first poly(A) site, while those from the 21 K allele are preferentially polyadenylated at the third site. In this study, transient expression experiments were used to demonstrate that a 2.1 kb genomic fragment containing the three DHFR poly(A) sites is sufficient to reproduce the allele-specific polyadenylation pattern on transiently expressed CAT-DHFR transcripts in COS cells. Site-directed mutagenesis allowed identification of the sequence elements which are responsible for this allele-specific polyadenylation. These studies indicate that a single-base change in the third poly(A) signal sequence, which alters the consensus AAUAAA signal in the 21 K allele to a weak AAUAAU signal in the 20 K allele, is primarily responsible for the dramatic difference in polyadenylation between the two alleles. Thus, as a result of this single-base change in the third poly(A) signal sequence, utilization of the first poly(A) site, located 1.2 kb upstream, changes dramatically. |
8041632 | SCR: novel human suppressors of cdc2/cdc13 mutants of Schizosaccharomyces pombe harbour motifs for RNA binding proteins. | By phenotypic complementation of the cdc2 and the cdc13 mutants of the fission yeast Schizosaccharomyces pombe, we have cloned two novel multicopy suppressors from a cDNA library of the human fibroblast. They encode homologous proteins containing two regions that are highly conserved among RNA binding proteins. We named them scr2 and scr3, the acronyms of the suppressor of cdc2 (cdc13) with RNA binding motif. They encode proteins of 403 (Scr2) and 407 (Scr3) amino acids. Western blot analysis showed that the amount of Cdc2 increased when either rat kidney fibroblasscr2 or scr3 was introduced into the cdc2-L7 and cdc13-117 mutant cells of S.pombe. No conspicuous alteration in the transcript level was detected as judged by Northern analysis. Considering that the cdc2+ suppresses the cdc13 mutant and vice versa, one of the possible interpretations of these result is that these genes suppress the mutants through the induction of the translation of Cdc2. |
8041631 | Translational enhancement of H-ferritin mRNA by interleukin-1 beta acts through 5' leader sequences distinct from the iron responsive element. | Interleukin-1 beta (Il-1 beta), a key cytokine in the acute phase response, elevates hepatic expression of both the heavy (H) and light (L) ferritin subunits without influencing the steady-state levels of either ferritin transcript. Transfection experiments with human hepatoma cells reveal that sequences within the 5' untranslated region (5'UTR) of H-ferritin mRNA confer translational regulation to chimaeric chloramphenicol acetyl transferase (CAT) mRNAs in response to Il-1 beta in the absence of marked changes in CAT mRNA levels. Il-1 beta dependent translational enhancement is mediated by a distinct G + C rich RNA sequence within 70 nucleotides (nt) of the start codon. The upstream Iron Responsive Element RNA stemloop does not confer increased expression to CAT mRNA in Il-1 beta stimulated hepatoma transfectants. A 38 nucleotide consensus sequence within the 5'UTRs of the mRNAs encoding the hepatic acute phase proteins alpha 1-antitrypsin (alpha 1AT), alpha 1-acid glycoprotein (AGP) and haptoglobin (Dente et al., 1985) is similar to sequences in the G + C rich H-ferritin mRNA translational regulatory element. Deletion of three nucleotides from this region of the 61 nt G + C rich element in the H-ferritin mRNA 5' leader eliminates Il-1 beta translational enhancement of the CAT reporter transcripts. |
8041630 | Multiplex strand displacement amplification (SDA) and detection of DNA sequences from Mycobacterium tuberculosis and other mycobacteria. | Strand Displacement Amplification (SDA) is an isothermal, in vitro method of amplifying a DNA target sequence prior to detection [Walker et al (1992) Nucleic Acids Res., 20, 1691-1693]. Here we describe a multiplex form of SDA that allows two target sequences and an internal amplification control to be co-amplified by a single pair of primers after common priming sequences are spontaneously appended to the ends of target fragments. Multiplex SDA operates at a single temperature, under the same simple protocol previously developed for single-target SDA. We applied multiplex SDA to co-amplification of a target sequence (IS6110) that is specific to members of the Mycobacterium tuberculosis-complex and a target (16S ribosomal gene) that is common to most clinically relevant species of mycobacteria. Both targets are amplified 10(8)-fold during a 2 hour, single temperature incubation. The relative sensitivity of the system was evaluated across a number of clinically relevant mycobacteria and checked for crossreactivity against organisms that are closely related to mycobacteria. |
8041629 | Sequencing of oligonucleotide phosphorothioates based on solid-supported desulfurization. | We described a solid-supported desulfurization procedure allowing easy access to the sequence analysis of oligonucleotide phosphorothioates. The described method is based upon selective removal of the 2-cyanoethyl phosphate protecting groups, followed by iodine-promoted desulfurization of the resulting phosphorothioate diesters. Automatic oxidation of oligonucleotide phosphorothioates, anchored via an ester linkage to a standard solid support (LCAA/CPG), is combined with Maxam-Gilbert solid-support sequencing. The overall procedure allows rapid simultaneous sequence analysis of several oligonucleotide analogs. |
8041627 | The RNA polymerase I transcription factor UBF is a sequence-tolerant HMG-box protein that can recognize structured nucleic acids. | Upstream Binding Factor (UBF) is important for activation of ribosomal RNA transcription and belongs to a family of proteins containing nucleic acid binding domains, termed HMG-boxes, with similarity to High Mobility Group (HMG) chromosomal proteins. Proteins in this family can be sequence-specific or highly sequence-tolerant binding proteins. We show that Xenopus UBF can be classified among the sequence-tolerant class. Methylation interference assays using enhancer DNA probes failed to reveal any critical nucleotides required for UBF binding. Selection by UBF of optimal binding sites among a population of enhancer oligonucleotides with randomized sequences also failed to reveal any consensus sequence. The minor groove specific drugs chromomycin A3, distamycin A and actinomycin D competed against UBF for enhancer binding, suggesting that UBF, like other HMG-box proteins, probably interacts with the minor groove. UBF also shares with other HMG box proteins the ability to bind synthetic cruciform DNA. However, UBF appears different from other HMG-box proteins in that it can bind both RNA (tRNA) and DNA. The sequence-tolerant nature of UBF-nucleic acid interactions may accommodate the rapid evolution of ribosomal RNA gene sequences. |
8041628 | The solution structure of the circular trinucleotide cr(GpGpGp) determined by NMR and molecular mechanics calculation. | The 3'-5' circular trinucleotide cr(GpGpGp) was studied by means of 1D and 2D high resolution NMR techniques and molecular mechanics calculations. Analysis of the J-couplings, obtained from the 1H and 13C-NMR spectra, allowed the determination of the conformation of the sugar rings and of the 'circular' phosphate backbone. In the course of the investigations it was found that the Karplus-equation most recently parametrized for the CCOP J-coupling constants could not account for the measured J(C4'P) of 11.1 Hz and a new parametrization for both HCOP and CCOP coupling constants is therefore presented. Subsequent analysis of the coupling constants yielded 'fixed' values for the torsion angles beta and delta (with beta = 178 degrees and delta = 139 degrees). The value of the latter angle corresponds to an S-type sugar conformation. The torsion angles gamma and epsilon are involved in a rapid equilibrium in which they are converted between the gauche(+) and trans and between the trans and gauche(-) domain respectively. We show that the occurrence of epsilon in the gauche(-) domain necessitates S-type sugar conformations. Given the aforementioned values for beta, gamma, delta and epsilon the ring closure constraints for the ring, formed by the phosphate backbone can only be fulfilled if alpha and zeta adopt some special values. After energy minimization with the CHARMm force field only two combinations of alpha and zeta result in energetically favourable structures, i.e. the combination alpha (t)/zeta(g-) in case gamma is in a gauche(+) and epsilon is in a trans conformation, and the combination alpha (t)/zeta (g+) for the combination gamma (t)/epsilon (g-). The results are discussed in relation to earlier findings obtained for cd(ApAp) and cr(GpGp), the latter molecule being a regulator of the synthesis of cellulose in Acetobacter xylinum. |
8041626 | Sequence specificity of the non-natural pyrido[2,3-d]pyrimidine nucleoside in triple helix formation. | The non-natural pyrido[2,3-d]pyrimidine nucleoside F, which pairs preferentially with guanine (G) and adenine (A) within double-helical DNA, recognizes with high selectivity AT base pairs within triple-helical complexes. These observations suggest that F may exist in different tautomeric forms within double-helical and triple-helical complexes. Analysis of the base stacking properties of this extended ring system using two oligodeoxyribonucleotides containing terminal thymines and/or pyrido[2,3-d]pyrimidines bound to adjacent sites showed a decrease in free energy of binding in a triple-helical complex in the order (5'-3') TT > FT > TF > FF. |
8041625 | Sequence similarity of putative transposases links the maize Mutator autonomous element and a group of bacterial insertion sequences. | The Mutator transposable element system of maize is the most active transposable element system characterized in higher plants. While Mutator has been used to generate and tag thousands of new maize mutants, the mechanism and regulation of its transposition are poorly understood. The Mutator autonomous element, MuDR, encodes two proteins: MURA and MURB. We have detected an amino acid sequence motif shared by MURA and the putative transposases of a group of bacterial insertion sequences. Based on this similarity we believe that MURA is the transposase of the Mutator system. In addition we have detected two rice cDNAs in genbank with extensive similarity to MURA. This sequence similarity suggests that a Mutator-like element is present in rice. We believe that Mutator, a group of bacterial insertion sequences, and an uncharacterized rice transposon represent members of a family of transposable elements. |
8041624 | Solid-phase synthesis of chelate-labelled oligonucleotides: application in triple-color ligase-mediated gene analysis. | Oligonucleotides labelled with detectable groups are essential tools in gene detection. We describe here the synthesis of pyrimidine deoxynucleotide-building blocks, modified at their C-5 position with a protected form of a strongly chelating agent. These reagents can be used to introduce multiple metal ions into oligodeoxynucleotides during standard oligonucleotide synthesis. The chelating functions form strongly fluorescent complexes with europium ions, characterized by a wide separation between the excitation and emission spectra. Moreover, the long decay time of the fluorescence permits sensitive time-resolved fluorescence measurements. The chelates also have the stability required to function in triple-color assays involving europium, samarium, and terbium ions. We demonstrate the application of these reagents for ligase-based gene analysis reactions. |
8041623 | Transcriptional activation of NFI/CTF1 depends on a sequence motif strongly related to the carboxyterminal domain of RNA polymerase II. | Initiation of RNA polymerase II-directed transcription is mediated by DNA sequence specific activator proteins interacting with components of the basal transcription machinery. NFI/CTF is a family of such binding proteins which have been shown to stimulate transcription via proline-rich activation domains. In order to identify residues crucial for its activator function, a pool of CTF1 mutants was cloned and fused to the bacterial repressor LexA. Transcriptional activation of these constructs was monitored in a Saccharomyces cerevisiae reporter assay. Our studies reveal the existence of a core domain in CTF1 between residues 463 and 508 essential for transcriptional activation functions. It contains the sequence motif SPTSPSYSP, which is strongly related to the heptapeptide repeat YSPTSPS present in the carboxyterminal domain (CTD) of RNA polymerase II. Removal of the entire CTD related motif, as well as substitution of key amino acids therein, abolish CTF1 mediated transcriptional activation. |
8041622 | Methylphosphonate mapping of phosphate contacts critical for RNA recognition by the human immunodeficiency virus tat and rev proteins. | The HIV-1 regulatory proteins tat and rev are both RNA binding proteins which recognize sequences in duplex RNA which are close to structural distortions. Here we identify phosphate contacts which are critical for each binding reaction by use of a new method. Model RNA binding sites are constructed carrying substitutions of individual phosphodiesters by uncharged methylphosphonate derivatives isolated separately as Rp and Sp diastereoisomers and tested for protein binding by competition assays. In the binding of tat to the trans-activation response region (TAR), three phosphates, P21 and P22 which are adjacent to the U-rich bulge and P40 on the opposite strand, are essential and in each case both isomers inhibit binding. Similarly, in the interaction between the HIV-1 rev protein and the rev-responsive element (RRE) both methylphosphonate isomers at P103, P104, P124 and P125 interfere with rev binding. At P106, only the Rp methylphosphonate isomer is impaired in rev binding ability and it is proposed that the Rp oxygen is hydrogen-bonded to an uncharged amino acid or to a main chain hydrogen atom. Synthetic chemistry techniques also provide evidence for the conformations of non-Watson-Crick G106:G129 and G105:A131 base-pairs in the RRE 'bubble' structure upon rev binding. Almost all functional groups on the 5 bulged residues in the bubble have been ruled out as sites of contact with rev but, by contrast, the N7-positions of each G residue in the flanking base-pairs are identified as sites of likely hydrogen-bonding to rev. The results show that both tat and rev recognize the major groove of distorted RNA helixes and that both proteins make specific contacts with phosphates which are displaced from the sites of base-pair contact. |
8041620 | Analysis of the Escherichia coli genome. V. DNA sequence of the region from 76.0 to 81.5 minutes. | The DNA sequence of a 225.4 kilobase segment of the Escherichia coli K-12 genome is described here, from 76.0 to 81.5 minutes on the genetic map. This brings the total of contiguous sequence from the E.coli genome project to 725.1 kb (76.0 to 92.8 minutes). We found 191 putative coding genes (ORFs) of which 72 genes were previously known, and 110 of which remain unidentified despite literature and similarity searches. Seven new genes--arsE, arsF, arsG, treF, xylR, xylG, and xylH--were identified as well as the previously mapped pit and dctA genes. The arrangement of proposed genes relative to possible promoters and terminators suggests 90 potential transcription units. Other features include 19 REP elements, 95 computer-predicted bends, 50 Chi sites, and one grey hole. Thirty-one putative signal peptides were found, including those of thirteen known membrane or periplasmic proteins. One tRNA gene (proK) and two insertion sequences (IS5 and IS150) are located in this segment. The genes in this region are organized with equal numbers oriented with or against replication. |
8041621 | A rapid and efficient one-tube PCR-based mutagenesis technique using Pfu DNA polymerase. | A rapid method for efficiently generating site-directed mutations on a clean sequence background is described. This modification of the megaprimer PCR mutagenesis approach can be performed in one tube in less than 4.5 hours, and does not require purification of intermediate products. High fidelity of DNA sequence replication is obtained by employing Pfu DNA polymerase and limiting the total number of amplification cycles to 30. The mutagenesis efficiency of the procedure is high enough to allow rapid, direct identification of mutants by restriction digest or sequencing techniques. |
8041619 | The topology of the promoter of RNA polymerase II- and III-transcribed genes is modified by the methylation of 5'-CG-3' dinucleotides. | In eukaryotic cells, RNA polymerase II- and III-transcribed promoters can be inactivated by sequence-specific methylation. For some promoter motifs, the introduction of 5-methyldeoxycytidine (5-mC) residues has been shown to alter specific promoter motif-protein interactions. To what extent does the presence of 5-mC in promoter or regulatory DNA sequences affect the structure of DNA itself. We have investigated changes in DNA bending in three naturally occurring DNA elements, the late E2A promoter of adenovirus type 2 (Ad2) DNA, one of our main model systems, the VAI (virus-associated) RNA gene of Ad2 DNA, and an Alu element associated with the human angiogenin gene. Alterations in electrophoretic mobility of differently permuted promoter segments in non-denaturing polyacrylamide gels have been used as assay system. In the late E2A promoter of Ad2 DNA, a major and possibly some minor DNA bending motifs exist which cause deviations in electrophoretic mobility in comparison to coelectrophoresed marker DNA fragments devoid of DNA bending motifs. DNA elements have been specifically in vitro methylated by the HpaII (5'-CCGG-3'), the FnuDII (5'-CGCG-3'), or the CpG DNA methyltransferase from Spiroplasma species (M-SssI; 5'-CG-3'). Methylation by one of these DNA methyltransferases influences the electrophoretic mobility of the three tested promoter elements very strikingly, though to different extents. It cannot be predicted whether sequence-specific promoter methylation increases or decreases electrophoretic mobility; these changes have to be experimentally determined. Methylation of the E. coli dcm (5'-CCA/TGG-3') sites in some of the DNA constructs does not make a contribution to mobility changes. It is concluded that sequence-specific methylations in promoter or regulatory DNA elements can alter the bending of DNA very markedly. This parameter may contribute significantly to the silencing of promoters, probably via altering spatial relationships among DNA-bound transcription factors. |
8041618 | Genetic and biochemical analysis of the fission yeast ribonucleoprotein particle containing a homolog of Srp54p. | Mammalian signal recognition particle (SRP), a complex of six polypeptides and one 7SL RNA molecule, is required for targeting nascent presecretory proteins to the endoplasmic reticulum (ER). Earlier work identified a Schizosaccharomyces pombe homolog of human SRP RNA and showed that it is a component of a particle similar in size and biochemical properties to mammalian SRP. The recent cloning of the gene encoding a fission yeast protein homologous to Srp54p has made possible further characterization of the subunit structure, subcellular distribution, and assembly of fission yeast SRP. S. pombe SRP RNA and Srp54p co-sediment on a sucrose velocity gradient and coimmunoprecipitate, indicating that they reside in the same complex. In vitro assays demonstrate that fission yeast Srp54p binds under stringent conditions to E. coli SRP RNA, which consists essentially of domain IV, but not to the full-length cognate RNA nor to an RNA in which domain III has been deleted in an effort to mirror the structure of bacterial homologs. Moreover, the association of S. pombe Srp54p with SRP RNA in vivo is disrupted by conditional mutations not only in domain IV, which contains its binding site, but in domains I and III, suggesting that the particle may assemble cooperatively. The growth defects conferred by mutations throughout SRP RNA can be suppressed by overexpression of Srp54p, and the degree to which growth is restored correlates inversely with the severity of the reduction in protein binding. Conditional mutations in SRP RNA also reduce its sedimentation with the ribosome/membrane pellet during cell fractionation. Finally, immunoprecipitation under native conditions of an SRP-enriched fraction from [35S]-labeled fission yeast cells suggests that five additional polypeptides are complexed with Srp54p; each of these proteins is similar in size to a constituent of mammalian SRP, implying that the subunit structure of this ribonucleoprotein is conserved over vast evolutionary distances. |
8041616 | The gene encoding topoisomerase II from Plasmodium falciparum. | The gene for topoisomerase II has been isolated from genomic libraries of strain K1 of the human malarial parasite, Plasmodium falciparum. The sequence reveals an open reading frame of 4194 nucleotides which predicts a polypeptide of 1398 amino acids. There are apparently no introns. The sequence is present as a single copy which has an identity of 47.4% and a similarity of 65.4% with its human homologue. Sequences conserved in topoisomerase II from other species are present in Pftopoisomerase II but in addition it has two adjacent asparagine-rich insertions which are unique to it. We have also detected asparagine-rich regions in the gene for PfDNA polymerase alpha. The gene for Pftopoisomerase II has been localised to chromosome 14 and northern analysis reveals a transcript of 5.8 kb. Two independent antisera raised in mice against glutathione-S-transferase fusion proteins containing the amino terminal portion of the malarial protein detect a weak band on western blots at about 160kDa, the expected size of the protein. Use of the same antisera for immunofluorescence analysis suggests that the protein is present at all stages of intraerythrocytic growth of the parasite. |
8041617 | Detection of dsRNA-binding domains in RNA helicase A and Drosophila maleless: implications for monomeric RNA helicases. | Searches with dsRNA-binding domain profiles detected two copies of the domain in each of RNA helicase A, Drosophila maleless and C. elegans ORF T20G5-11 (of unknown function). RNA helicase A is unusual in being one of the few characterised DEAD/DExH helicases that are active as monomers. Other monomeric DEAD/DExH RNA helicases (p68, NPH-II) have domains that match another RNA-binding motif, the RGG repeat. The DEAD/DExH domain appears to be insufficient on its own to promote helicase activity and additional RNA-binding capacity must be supplied either as domains adjacent to the DEAD/DExH-box or by bound partners as in the eIF-4AB dimer. The presence or absence of extra RNA-binding domains should allow classification of DEAD/DExH proteins as monomeric or multimeric helicases. |
8041614 | Self-splicing group I introns in eukaryotic viruses. | We report the occurrence of self-splicing group I introns in viruses that infect the eukaryotic green alga Chlorella. The introns contained all the conserved features of primary sequence and secondary structure previously described for the group IB introns. The Chlorella viral introns (approximately 400 nt) self-spliced in vitro, yielding the typical group I intron splicing intermediates and products. Contrasting to eukaryotic nuclear group I introns, all of which are located in the rRNA genes, these introns were inserted in genes encoding proteins. In one case, the exons encoded a protein showing significant homology to the eukaryotic transcription factor SII (TFIIS), which may be important for viral gene expression. In another case, the gene for the open reading frame (ORF) of a 14.2 kDa polypeptide with unknown functions contained the intron. Scattered distribution of these introns among the viral species and their structural similarity to the group I introns of algae and protists indicated horizontal intron transmission. These eukaryotic viral introns offer an opportunity to understand how group I introns reach organisms of different phylogenetic kingdoms. |
8041615 | Structural elements of rps0 mRNA involved in the modulation of translational initiation and regulation of E. coli ribosomal protein S15. | Previous experiments showed that S15 inhibits its own translation by binding to its mRNA in a region overlapping the ribosome loading site. This binding was postulated to stabilize a pseudoknot structure that exists in equilibrium with two stem-loops and to trap the ribosome on its mRNA loading site in a transitory state. In this study, we investigated the effect of mutations in the translational operator on: the binding of protein S15, the formation of the 30S/mRNA/tRNA(fMet) ternary initiation complex, the ability of S15 to inhibit the formation of this ternary complex. The results were compared to in vivo expression and repression rates. The results show that (1) the pseudoknot is required for S15 recognition and translational control; (2) mRNA and 16S rRNA efficiently compete for S15 binding and 16S rRNA suppresses the ability of S15 to inhibit the formation of the active ternary complex; (3) the ribosome binds more efficiently to the pseudoknot than to the stem-loop; (4) sequences located between nucleotides 12 to 47 of the S15 coding phase enhances the efficiency of ribosome binding in vitro; this is correlated with enhanced in vivo expression and regulation rates. |
8041613 | Mutagenesis in monkey cells of a vector containing a single d(GPG) cis-diamminedichloroplatinum(II) adduct placed on codon 13 of the human H-ras proto-oncogene. | Cisplatin (cis-[Pt(NH3)2Cl2]) is a widely used antitumor agent whose mutagenic activity raises the possibility of the induction of secondary cancer as a result of treatment. Mutation of the proto-oncogene H-ras is found in more than 30% of all human tumors, where it has been postulated to contribute to the initiation and progression of human cancers. Activating mutations in the H-ras gene are predominantly single-base substitutions, most frequently at codons 12, 13 and 61. In the present work we have studied the mutational spectra induced by a single cis-[Pt(NH3)2d(GpG)] adduct, the most frequent DNA crosslink formed by cisplatin. We have constructed a 25-mer-Pt oligonucleotide singly modified at codon 13 (GGT) within the human H-ras DNA sequence and we have inserted it into a single-stranded SV40-based shuttle vector able to replicate in simian COS7 cells. After replication in the mammalian host, vectors were extracted, amplified in bacteria and DNA from 124 randomly chosen colonies was sequenced. The observed mutation frequency was 21%. Base substitutions were the most frequent modification. 92% of the mutagenic events occurred at one or both of the platinated guanines of codon 13. The single G-->T transversion accounted for 65% of the total mutations scored. All single base substitutions were located at the G in the 3' position showing, for the first time, that the guanine at the 3' side of a cis-[Pt(NH3)2d(GpG)] adduct may be a preferential site for cisplatin induced mutations. The substitution G-->T at this position of the codon 13 of the H-ras proto-oncogene is known to induce the oncogenic properties of the p21ras protein. |
8041612 | Ligation-mediated amplification of RNA from murine erythroid cells reveals a novel class of beta globin mRNA with an extended 5'-untranslated region. | Ligation-mediated RNA amplification was developed as a tool for analysis and determination of the termini of RNA molecules [Volloch et al. (1991) Proc. Natl. Acad. Sci. USA 88: 10671-10675]. In this approach, T4 RNA ligase is used to join cellular RNA with a defined ribo-oligonucleotide. Although several additional enzymatic steps are involved in this type of analysis, the reliability of the entire procedure is determined by the initial ligation step, which marks and preserves the termini of cellular RNA molecules. We applied this approach to the analysis of the 5' terminus of beta globin mRNA in various murine erythroid cells. As expected, we detected RNA molecules with 5' ends terminating at the regular cap site as well as globin RNA molecules truncated at the 5' end. Unexpectedly, we also detected a class of beta globin mRNA which is identical to regular beta globin mRNA in every respect but contains 17, 29, or 31 additional nucleotides 5' to the regular cap site. These extensions correspond precisely to the genomic segments just upstream of the regular cap site and are probably generated by initiation of transcription of the globin gene upstream from the regular cap site. It is likely that the extended globin RNA is transcribed not from the TATA promoter, which regulates the transcription of regular murine globin mRNA, but from the GATA regulatory element located 30 nucleotides upstream of the 31-nucleotide extension, in a position identical to that of the active GATA promoter of the TATA-less chicken beta globin gene. The evolutionary conservation of this relationship suggests the importance of the GATA promoter element of the mouse beta globin gene and its possible involvement in developmental regulation of expression of this gene. |
8041611 | Common structural features of the Ro RNP associated hY1 and hY5 RNAs. | The secondary structures of human hY1 and hY5 RNAs were determined using both chemical modification techniques and enzymatic structure probing. The results indicate that both for hY1 and for hY5 RNA the secondary structure largely corresponds to the structure predicted by sequence alignment and computerized energy-minimization. However, some important deviations were observed. In the case of hY1 RNA, two regions forming a predicted helix appeared to be single-stranded. Furthermore, the pyrimidine-rich region of hY1 RNA appeared to be very resistant to reagents under native conditions, although it was accessible to chemical reagents under semi-denaturing conditions. This may point to yet unidentified tertiary interactions for this region of hY1 RNA. In the case of hY5 RNA, two neighbouring internal loops in the predicted structure appeared to form one large internal loop. |
8041609 | Modular sequence elements associated with origin regions in eukaryotic chromosomal DNA. | We have postulated that chromosomal replication origin regions in eukaryotes have in common clusters of certain modular sequence elements (Benbow, Zhao, and Larson, BioEssays 14, 661-670, 1992). In this study, computer analyses of DNA sequences from six origin regions showed that each contained one or more potential initiation regions consisting of a putative DUE (DNA unwinding element) aligned with clusters of SAR (scaffold associated region), and ARS (autonomously replicating sequence) consensus sequences, and pyrimidine tracts. The replication origins analyzed were from the following loci: Tetrahymena thermophila macronuclear rDNA gene, Chinese hamster ovary dihydrofolate reductase amplicon, human c-myc proto-oncogene, chicken histone H5 gene, Drosophila melanogaster chorion gene cluster on the third chromosome, and Chinese hamster ovary rhodopsin gene. The locations of putative initiation regions identified by the computer analyses were compared with published data obtained using diverse methods to map initiation sites. For at least four loci, the potential initiation regions identified by sequence analysis aligned with previously mapped initiation events. A consensus DNA sequence, WAWTTDDWWWDHWGWHMAWTT, was found within the potential initiation regions in every case. An additional 35 kb of combined flanking sequences from the six loci were also analyzed, but no additional copies of this consensus sequence were found. |
8041610 | Activation of RuvC Holliday junction resolvase in vitro. | The Escherichia coli RuvC protein is an endonuclease that resolves Holliday junctions. In vitro, the protein shows efficient structure-specific binding of Holliday junctions, yet the rate of junction resolution is remarkably low. We have mapped the sites of cleavage on a synthetic junction through which a crossover can branch migrate through 26 bp and find that > or = 90% of the junctions were cleaved at one site. This observation of sequence-specific cleavage suggests that inefficient resolution may be due to DNA binding events which occur away from the cleavage site and are therefore non-productive. Holliday junction resolution by RuvC protein can be stimulated by a number of factors including: (i) the presence of Mn2+ (rather than Mg2+) as the divalent metal cofactor, (ii) alkaline pH (< or = 10), and (iii) elevated temperature. These observations may indicate that other proteins are required for efficient RuvC-mediated resolution. |
8041607 | The carboxyterminus of human c-myb protein stimulates activated transcription in trans. | The cellular c-myb gene encodes a transcription factor composed of a DNA-binding domain, a transactivating domain and a regulatory domain located at its carboxy (C-) terminus. The latter one is deleted in the transforming viral protein v-Myb. Here we show that deletion of the C-terminus of c-Myb increases the transcriptional transactivation activity of c-Myb defining it as cis-acting negative regulatory domain. Cotransfection of the C-terminus in an in vivo competition assay causes stimulation of the transcriptional activity of various v- and c-Myb expression constructs in trans. The effect is dose-dependent and independent of the kind of DNA-binding domain, since c-Myb as well as GAL4-c-Myb chimaeras can be stimulated in trans. Other transcription factors, such as GAL4-VP16, GAL4, c-Jun or C/EBP beta are also stimulated by the cotransfected C-terminus. In contrast, human B-Myb is not stimulated by the c-Myb C-terminus in trans. The data suggest that the C-terminus of c-Myb may interact with a cellular inhibitor which is part of the protein complex mediating activated transcription and may stimulate in trans by sequestering away such an inhibitor. Binding of c-Myb to a putative inhibitor would explain differences between c-Myb in comparison to B- and v-Myb in transcriptional regulation. |
8041608 | Prediction of an rRNA methyltransferase domain in human tumor-specific nucleolar protein P120. | Using computer methods for identification of amino acid motifs in sequence databases and multiple alignment, it is shown that human proliferation-associated nucleolar protein P120 contains a putative methyltransferase domain that is conserved in a group of bacterial proteins. It is hypothesized that P120 and the related prokaryotic proteins are rRNA methylases required for division of all types of cells. |
8041605 | The transcription factor YY1 binds to negative regulatory elements in the human cytomegalovirus major immediate early enhancer/promoter and mediates repression in non-permissive cells. | We have previously shown that repression of human cytomegalovirus (HCMV) major immediate early (IE) gene expression in non-permissive human teratocarcinoma (T2) cells is associated with a number of nuclear factors which bind to the imperfect dyad symmetry located in the modulator region upstream of the major IE enhancer as well as to the 21 bp repeat elements within the enhancer. Differentiation of T2 cells with retinoic acid (RA) results in a decrease in binding of some of these nuclear factors to these sites and deletion of these specific binding sites from major IE promoter/reporter constructs results in increased IE promoter activity in normally non-permissive cells. In this study, we demonstrate that the transcription factor YY1, which can negatively regulate the adeno-associated virus P5 promoter, directly binds to both the imperfect dyad symmetry and the 21 bp repeat elements in the HCMV major IE promoter/regulatory region and mediates repression of HCMV IE gene expression. This strongly suggests that YY1 plays an important role in regulating HCMV expression in non-permissive cells. |
8041606 | Comparison of IR- and UV-matrix-assisted laser desorption/ionization mass spectrometry of oligodeoxynucleotides. | UV-matrix assisted laser desorption/ionization mass spectrometry (UV-MALDI-MS) with 3-hydroxypicolinic acid as matrix and IR-MALDI-MS with succinic acid as matrix have proved their feasibility for highly accurate and sensitive mass determination of nucleic acids (DNA and RNA). In this work, a detailed comparison of these two MALDI-methods and between positive- and negative ion mass spectra for the analysis of oligodeoxynucleotides is undertaken. Mass spectra of DNA sequences with up to 40 nucleotides are shown. Both linear and reflectron time-of-flight mass analyzers were used within this study and are compared for their potential in the MALDI analysis of oligodeoxynucleotides. The role of molecule-ion fragmentation is also discussed. |
8041604 | Formation of extrachromosomal circular DNA in HeLa cells by nonhomologous recombination. | Extrachromosomal circular DNA (eccDNA) generated from chromosomal DNA is found in all mammalian cells and increases with cell stress or aging. Studies of eccDNA structure and mode of formation provide insight into mechanisms of instability of the mammalian genome. Previous studies have suggested that eccDNA is generated through a process involving recombination between repetitive sequences. However, we observed that approximately one half of the small eccDNA fragments cloned from HeLa S3 cells were composed entirely of nonrepetitive or low-copy DNA sequences. We analyzed four of these fragments by polymerase chain reaction and nucleotide sequencing and found that they were complete eccDNAs. We then screened a human genomic library with the eccDNAs to isolate the complementary chromosomal sequences. Comparing the recombination junctions within the eccDNAs with the chromosomal sequences from which they were derived revealed that nonhomologous recombination was involved in their formation. One of the eccDNAs was composed of two separate sequences from different parts of the genome. These results suggest that rejoining of ends of fragmented DNA is responsible for the generation of a substantial portion of the eccDNAs found in HeLa S3 cells. |
8041603 | Codon usage in Caenorhabditis elegans: delineation of translational selection and mutational biases. | Synonymous codon usage varies considerably among Caenorhabditis elegans genes. Multivariate statistical analyses reveal a single major trend among genes. At one end of the trend lie genes with relatively unbiased codon usage. These genes appear to be lowly expressed, and their patterns of codon usage are consistent with mutational biases influenced by the neighbouring nucleotide. At the other extreme lie genes with extremely biased codon usage. These genes appear to be highly expressed, and their codon usage seems to have been shaped by selection favouring a limited number of translationally optimal codons. Thus, the frequency of these optimal codons in a gene appears to be correlated with the level of gene expression, and may be a useful indicator in the case of genes (or open reading frames) whose expression levels (or even function) are unknown. A second, relatively minor trend among genes is correlated with the frequency of G at synonymously variable sites. It is not yet clear whether this trend reflects variation in base composition (or mutational biases) among regions of the C.elegans genome, or some other factor. Sequence divergence between C.elegans and C.briggsae has also been studied. |
8041595 | Object and head orientation effects on symmetry perception defined by shape from shading. | A grey disc which exhibits a vertical gradient of shading usually appears convex if lighter above and concave if lighter below. This phenomenon was investigated by Howard et al (1990) who varied both the shading axis relative to gravity and the orientation of the head. Their results indicated that head-centric or retinocentric coordinates determined the depth effect rather than gravitational axes. However, several possible problems with their study were noted, not the least of which was the possible intrusion of response rather than perceptual factors in the task they used. Here, we attempted to use an indirect measure of the perception of depth from shading; rather than asking subjects whether discs looked convex or concave, we constructed ensembles of shaded discs which, in terms of depth from shading, were or were not bilaterally symmetrical about an horizontal axis. These stimulus displays were briefly flashed to prohibit the intrusion of conscious assumptions about direction of light sources. Subjects were never asked whether any discs looked concave or convex, merely whether the set of discs was or was not depth symmetrical. Results were generally consistent with those of Howard et al and supported the conclusion that depth from shading is largely a low-level and automatic mechanism. |
8041594 | Monocular and dichoptic interactions between moving and stationary stimuli. | Visual motion of a physically stationary stimulus can be induced by the movement of adjacent stimuli. The frequencies of motion reports and the angular separations required to induce motion were determined for a number of stimulus configurations. A stationary stimulus was fixated in the centre of the display and the point at which induced motion was initially reported was measured. In the first experiment either one or two stationary stimuli were presented in the centre of a display and either one or two similar stimuli moved horizontally towards them. The percentage of trials on which motion was induced varied with the display configuration, being greatest with two moving and one stationary stimuli. The angular separations at which motion was reported were about 2 deg for all conditions. In the second experiment the binocular interaction of such induced motion was examined. A single static fixation stimulus was presented binocularly and a range of monocular or dichoptic conditions was examined: a single moving stimulus to one eye, two moving stimuli to one eye, or two moving stimuli dichoptically. Induced motion was reported on about 90% of the trials for the monocular and dichoptic conditions with two moving stimuli. Motion was first induced at similar angular separations by two moving stimuli, whether presented monocularly or dichoptically. Binocular interaction was further examined with a display that induced motion in the stimulus presented to one eye but not in that presented to the other: this resulted in the apparent motion in depth of the binocularly fixated stimulus. |
8041593 | Tests of the dipole model of perceived movement in apertures. | Power and Moulden (1992) have proposed a dipole model to account for the apparent movement of gratings in apertures. This includes movement orthogonal to the orientation of the grating, and the barber pole illusion: the illusion that a grating drifting diagonally across a narrow aperture appears to be moving along it. The essence of the model is that movement is signalled by a large number of dipoles, of many orientations and lengths. These dipoles respond if, and only if, one end is stimulated, and then the other. Three experiments intended to test predictions from the model are reported here. In each case a horizontal grating drifted across an aperture and subjects fixated outside the aperture. In experiment 1 subjects fixated just above or below the aperture, and reported the motion aftereffect (MAE) shown by a set of test spots. As predicted by the model, the spots further from the fixation point showed a strong MAE. Experiment 2 combined both viewing conditions of experiment 1, so that test spots above and below the fixation point were viewed simultaneously. The predictions were confirmed, since test spots further from the fixation point exhibited a stronger MAE than test spots closer to the fixation point. In experiment 3 the fixation point in all conditions was below the aperture, and, as predicted, the MAE of a spot near the bottom of the aperture was diagonally upward, although stimulation was horizontal. Again, as predicted, the MAE of a spot in the middle of the aperture appeared to move horizontally. Finally, it was predicted that a test spot at the top of the aperture would appear to move diagonally downwards, but subjects were unable to report unequivocally the direction of motion, since the MAE was occurring too far from the fovea for clear vision. Overall, then, the predictions from the model were confirmed, although there are associated phenomena the model cannot as yet account for. |
8041592 | The effect of extraneous elements surrounding a Kanizsa-like illusory-figure pattern. | A display in which a Kanizsa-like illusory-figure pattern of three notched circles was accompanied by several other notched circles was found to be relatively ineffective, thus confirming an important, but previously untested, suggestion. This ineffectiveness may have been due to a strengthened tendency of the visual system perceptually to 'explain' each edge of each of the three critical notches as belonging to one of the partial circles themselves, thus tending to preclude any other (ie illusory) 'explanation' of those edges. |
8041591 | Information processing by tree fellers: signal detection analysis. | Eighteen experienced tree fellers and eighteen forestry students watched video recordings of mature eucalypts being felled by a man using a chain saw, and then rated whether each tree had fallen normally or abnormally. Signal-detection analysis showed that the tree fellers were more accurate than the forestry students in predicting eventual outcome. Further, the tree fellers achieved peak accuracy in discrimination by the time the logger had completed cutting the scarf (typically several minutes before the tree hit the ground), whereas the forestry students predicted outcome most accurately only when a tree was falling (and about 1 s from hitting the ground). Study of the bases for information processing and decision making by tree fellers has implications for personnel selection and training, as well as for formulation of effective work practices. |
8041590 | Apparent minification in an imaging display under reduced viewing conditions. | When extended outdoor scenes are imaged with magnification of 1 in optical, electronic, or computer-generated displays, scene features appear smaller and farther than in direct view. This has been shown to occur in various periscopic and camera-viewfinder displays outdoors in daylight. In four experiments it was found that apparent minification of the size of a planar object at a distance of 3-9 m indoors occurs in the viewfinder display of an SLR camera both in good light and in darkness with only the luminous object visible. The effect is robust and survives changes in the relationship between object luminance in the display and in direct view and occurs in the dark when subjects have no prior knowledge of room dimensions, object size or object distance. The results of a fifth experiment suggest that the effect is an instance of reduced visual size constancy consequent on elimination of cues for size, which include those for distance. |
8041589 | Cross-modal transfer of sequential visual and haptic shape information by clumsy children. | The ability of clumsy children aged 9 to 13 years to transfer sequential shape information between the haptic and visual modalities was examined in a matching-to-sample task. In both modalities, spatiotemporal integration of information relevant for shape was involved and transfer was examined between them by using intramodal transfer scores as covariates. The responses of clumsy children were not different from those of nonclumsy children of similar age, sex, and intelligence in the cross-modal condition involving matching of a haptic standard to a visual shape. However, when matching a visual standard to a haptic shape they were consistently both faster and less accurate. It was concluded that a specific visual-to-haptic translation process possibly involving poor visual memory for shape distinguishes clumsy children from their nonclumsy peers. |
8041588 | Quantitative perceptual estimates: verbal versus nonverbal retrieval techniques. | Examples of the inaccessibility of mental processes by means of verbal recall are described with particular reference to the accuracy of quantitative estimates of size, distance, and duration. Evidence is presented in support of the hypothesis that nonverbal retrieval techniques are more accurate than quantitative verbal estimates. Implications for the judicial process are considered. |
8041587 | How the range effect contaminates control scores in studies of visual illusions. | The relationship between mean control scores and mean experimental scores in 23 experiments on alignment illusions has been examined. Evidence is presented to show that, through the operation of the range effect, control scores are biased to a significant degree in the direction of experimental scores. The implications of this are considered, not only as regards the value of control scores in psychophysical studies, but also as further evidence of the dangers of within-subjects experimental designs when issues depend upon the values of extreme points in a range of values. |
8041586 | Occlusion and the distortion of alignment in three-dimensional space. | When observers are asked to align two rectangular stimuli oriented at 45 degrees to the visual axis there is a slight tendency to set the more distant stimulus closer to the eye than its true coplanar position. However, when a large rectangular surface is interpolated between the two oblique stimuli and the observer, errors of alignment become relatively much larger. The displacement caused by the interpolated stimulus occurs both when the display is viewed monocularly and when it is viewed binocularly. Reducing the obliquity of the rectangles results in smaller judgment errors and increasing obliquity increases errors; this is true with and without occlusion. The addition of texture elements to the surfaces of the rectangles reduces judgment errors significantly, but only under conditions of occlusion. It is possible that misalignments recorded for three-dimensional displays have something in common with the two-dimensional Poggendorff illusion. |
8041585 | Stereoscopic slant reversals: a new kind of 'induced' effect. | Data are presented from three experiments confirming an earlier finding that the stereoscopic slant perceived may be opposite to the geometrically predicted direction of slant (Gillam 1967). The stimulus for stereoscopic slant was created by imposing a disparity gradient on a frontal plane surface. Reversals are shown to occur readily for slants around a vertical axis but rarely for slant around a horizontal axis. Reversal frequency is greater for surfaces which have a regular pattern, providing good perspective information about slant. Cue conflict cannot explain reversals because adherence to perspective information predicts a perception of zero slant rather than reverse slant. A new explanation has been proposed attributing reversals to the ambiguity of horizontal disparity gradients and disambiguation of the disparity gradient by its relationship to the perspective gradient. It is shown that for any given disparity gradient there is a physical surface which would give rise to a slant reversed with respect to that normally predicted. Such a surface is eccentric in the field of view, with eccentricity given by the difference between the slants signalled by the disparity gradient and the perspective gradient. This explains why reversal responses to disparity gradients occur in the presence of perspective. It is proposed, on the basis of this analysis and the fact that reversals occur, that, like convergence and vertical disparity, perspective is a factor contributing to the correct scaling of disparity gradients in the horizontal meridian with respect to surface eccentricity. |
8041584 | Asymmetries in the sensitivity to motion in depth: a centripetal bias. | It is reasonable to ask whether observers are more sensitive to the pattern of image motion caused by forward locomotion through the environment than to the pattern caused by backward locomotion. The distribution of sensitivities of cells in MT does show such a bias, although this bias is minimal at small eccentricities. Additionally, both locomotion-induced stimulation and the sensitivities of MT cells suggest greater sensitivity should be obtained in the lower visual field. Previous research on this issue has usually employed frontoparallel motion in patterns presented to one side of the fixation point. Both centrifugal and centripetal biases have been obtained. In this study the stimuli present motion signals that travel radially from (or towards) the fixation point. These stimuli, which produce a strong percept of motion in depth, are an adaptation of the global-dot-motion stimulus employed by Newsome and Pare. With these stimuli we find that sensitivity to motion in depth is greater in the lower visual field than in the upper visual field, and that sensitivity is greater to centripetal motion than to either centrifugal or frontoparallel motion. This centrifugal bias in sensitivity decreases with eccentricity. The last two findings contradict the notion that the bias is produced by the visual experience induced by normal forward locomotion and also that the detection of motion in depth is subserved by MT. |
8041581 | A 30-year-old man with a mass in the distal left thigh and radiating leg pain. | The following case describes the imaging and clinical findings of a condition of interest to the orthopaedic surgeon. Initial history, physical findings, and imaging examinations are presented here for your consideration. The final clinical diagnosis and relevant discussion can be found on the following pages. |
8041580 | Knee arthroscopy using regional nerve blockade. | Regional nerve block anesthesia has been less commonly used and less successful in surgery on the lower extremity than on the upper extremity because of anatomic difficulties associated with lower-extremity nerve blockade. The authors have developed a technique that combines two peripheral nerve blocks with a nerve stimulator. This has provided sufficient anesthesia for the performance of arthroscopic surgery on the knee. It simplifies earlier techniques by decreasing the discomfort associated with the procedure and increasing its accuracy. The technique has also facilitated rapid patient discharge from the same-day unit. No significant complications have been encountered. |
8041579 | Late reconstruction of sagittal band laceration. | Injuries to the sagittal band with subsequent instability of the extensor digitorum communis tendon are uncommon. In an unusual presentation, a laceration to the radial sagittal band of the little finger was manifest as an abduction deformity of the digit. This injury was treated by repair of the sagittal band and extensor digiti minimi tendon transfer. |
8041578 | Subluxation of the cervical spine caused by 3-point seat belt. | Cervical spine injuries associated with 3-point (lap-sash) seat belt restraint systems are uncommon and usually without serious sequelae. However, the potential for unstable subluxation or dislocation due to severe flexion-extension mechanism is present and may result in severe disability if not promptly recognized and treated. Such an unstable injury is reported here and was treated with internal fixation. Further attention should be given to the ability of headrests, air bags, and other restraints to protect the cervical spine. |
8041577 | Pisotriquetral joint ganglion. | Physical examination of a woman with painful swelling about the ulnar side of her dominant right wrist but no history of trauma revealed a freely mobile soft-tissue mass on the ulnar aspect of the wrist. Radiographs of the wrist were normal. At surgery, a 1 cm x 1 cm ganglion immediately adjacent to the hypothenar muscles was dissected circumferentially and found to have a stalk originating from the ulnar aspect of the pisotriquetral joint. This report suggests that ganglions arising from the medial side of the pisotriquetral joint should be included in the differential diagnosis of ulnar wrist pain. |
8041576 | Malignant fibrous histiocytoma at the site of hip replacement in association with chronic infection. | A case of malignant fibrous histiocytoma that developed at the site of an infected metallic implant is presented. The total hip endoprosthesis was composed of a cobalt-chromium alloy. There was a relatively short latency period (less than 2 years) between the initial surgery and the development of malignancy in this patient. The authors urge development of a tumor registry to discover if the association between hip replacement and malignancy is coincidental. |
8041575 | Two- to five-year follow-up of 100 total hip arthroplasties using DF-80 implants. | In an uncontrolled prospective study, 100 primary total hip arthroplasties (THAs) using the DF-80 implant were followed up for a minimum of 2 years with rigorous clinical and radiographic examinations to define the natural history of this prosthetic system. Three groups were identified: (I) hips requiring revision because of failure (n = 3); (II) "impending" failures with radiographic indices of loosening (n = 8); and (III) clinically and radiographically benign, stable implants (n = 89). The preoperative Harris hip score was similar for all groups. Postoperatively, the failure group demonstrated early progressive clinical and radiographic deterioration with surgical revision at an average of 33 months. Male sex, increased weight, and greater intraoperative hemorrhage correlated positively with failure. The impending-failure group developed limited radiolucencies in the later postoperative period. Calcar resorption was noted in 26% of the total population and heterotopic ossification in 46%. We conclude that this series of THAs using DF-80 implants included a subset of patients demonstrating early clinical failure and widespread aggressive bone-cement radiolucencies that required early surgical revision. |
8041574 | Transient regional osteoporosis of the ankle and foot. A report of four cases and review of the literature. | Transient regional osteoporosis of the ankle and foot is an uncommon clinical entity characterized by local tenderness over the involved area. Plain radiographs demonstrate osteopenia of the involved bone and technetium diphosphonate bone imaging shows increased tracer uptake at the same location. This disorder is benign and self-limiting, and treatment is conservative. |
8041573 | Orthopaedic manifestations of Lyme disease. | Lyme disease is caused by the spirochete Borrelia burgdorferi and is transmitted by the Ixodes tick. Early diagnosis is difficult because the tick bite may go unnoticed and the distinguishing rash, erythema chronicum migrans, often does not occur. Serologic tests are both sensitive and specific in the later stages of the disease but not in stage 1. Thus diagnosis of Lyme disease remains clinical. Knowledge of the orthopaedic manifestations of Lyme disease may aid in early diagnosis and help differentiate from possible cases of juvenile rheumatoid arthritis and septic arthritis. If septic arthritis is suspected, appropriate antibiotic therapy should be initiated while awaiting serology for Lyme disease. Recurrence of Lyme arthritis following antibiotic treatment is rare. Lyme disease should be considered in any patient with arthritis and a history of rash, fever, or neurologic or cardiac abnormality. |
8041572 | Lateral ankle sprains. Part I: Anatomy, biomechanics, diagnosis, and natural history. | An understanding of the anatomy and biomechanics of the lateral ankle ligaments is essential to make a proper diagnosis in patients with ankle sprains. Specific radiographic stress tests can aid in differentiating single-versus double-ligament injuries and in determining their severity. Inadequately treated ankle sprains can result in chronic pain, instability, and early osteoarthritis. Thus, the proper diagnosis and initial treatment are important. This paper reviews the essential features of the anatomy, biomechanics, diagnosis, and natural history of lateral ankle sprains. |
8041568 | Motor unit size of M. stylohyoideus and M. stapedius in the mouse. | To elucidate the relation between the caliber of myelinated nerve fibers (MNFs) and motor unit size (i.e., number of muscle fibers per motor unit), motor unit size was measured for the mouse m. stylohyoideus, innervated predominantly by extra large MNFs, and compared with that of the mouse m. stapedius, innervated predominantly by large MNFs. All muscle fibers and MNFs were counted morphologically, and mean motor unit size was calculated for each muscle. The results showed that the average of 12 mean motor unit sizes for the m. stylohyoideus (35.8 +/- 8.2), innervated predominantly by extra large MNFs, was greater than that for the m. stapedius (6.5 +/- 1.3), innervated predominantly by large MNFs. |
8041567 | The superior alveolar nerves: their topographical relationship and distribution to the maxillary sinus in human adults. | The superior alveolar nerves in human adults were investigated macroscopically using whole-mount silver impregnation, paying special attention to their topographical relationship and distribution to the mucous membrane of the maxillary sinus. In addition, the fiber composition of the alveolar nerves was analysed in order to estimate their contribution to teeth innervation. The posterior superior alveolar nerve (PSAN) ran through canaliculi in the lateral wall of the sinus (23 of 37 cases, 62.2%) or under the mucous membrane of the sinus (14 of 37 cases, 37.8%). Moreover, the PSAN gave off many fine twigs to make complex plexus under the mucous membrane of the sinus before joining the superior dental plexus. The plexus of the maxillary sinus was separated from the superior dental plexus by the bony wall of the sinus. After the above gross observations, the perimeter compositions of myelinated fibers of the plexus, PSAN and the anterior alveolar nerve were analysed in the same specimen. The plexus was composed of myelinated fibers of less than 27 microns in circumference perimeter (mean: 14.3 microns) and numerous unmyelinated fibers. The fiber composition suggested that few fibers in the plexus of the maxillary sinus contribute to the formation of the superior dental plexus. The superior dental plexus, innervating the upper teeth, was located in the thick alveolar process of the maxilla, and not on the maxillary sinus wall. The clinical importance of these results was discussed in relation to nerve injury during antrostomy of the maxillary sinus. |
8041566 | Collateral lymphatic configuration of the internal jugular chain and jugulo-omohyoid nodes. | Minute dissection was performed bilaterally on 178 human adult cadavers (356 sides) in order to investigate the collateral lymphatic configurations of the internal jugular node chain. The superior and inferior collateral pathways identified based on the topographical anatomy of the large collecting vessels in the neck region. The superior collateral pathway (in 99 of 208 sides, 47.6%) consisted of a node chain, lying on the common carotid artery or along the medial edge of the internal jugular vein, connecting the submandibular lymphatics to the jugulo-omohyoid node (JO). In contrast, the inferior collateral pathway (in 63 of 356 sides, 17.7%) consisted of a single large collecting vessel, lying immediately superficial to the inferior deep cervical nodes, and which directly connected the JO to the venous angle region. A short cervical lymphatic trunk arising from the inferior deep cervical nodes, was also observed in the inferior collateral pathway. The JO seemed to be located at a critical position, where it connected the two collateral pathways. These results are discussed in relation to the fascial arrangement and development of the lymphatics in the cervical region. |
8041565 | Distribution of facial nerve in parotid gland: analysis of 50 cases. | The purpose of the present study is to reduce the postoperative morbidity related to facial paralysis during parotid surgery and to layout the different characteristics related to intraparotideal distribution and anastomoses of the facial nerve in our community. We also report new variations in the facial nerve branchings that have not been previously published. In this paper, facial nerves from 48 cadavers and 2 patients of which 45(90%) were males and 5(10%) were females; 26(52%) being right and 24(48%) being left facial nerves were put forward. Their photographs were taken and the diagrams of intraparotideal distributions of each facial nerve were drawn. The intraparotideal configuration of the facial nerve was evaluated in 5 types. Twenty-four% of the facial nerves had no anastomoses (Type I); 12% had a ring-like shape anastomosis between the buccal and the zygomatic branches (Type II); 14% anastomoses were between the buccal and the other branches in a ring-like shape (Type III); 38% of the facial nerves had multiple complex anastomoses and were named as multiple loops (Type IV); 12% had two main trunks (Type V). Of the bilateral cadaver dissections, the facial nerve distribution in 9(47.3%) were bilaterally the same and in 10(52.7%) main trunks were different. A facial nerve trifurcation composed of two main trunks were also established. There were no statistical differences between branching of the facial nerves in the right and left side of the faces.(ABSTRACT TRUNCATED AT 250 WORDS) |
8041564 | Vascularization of the long flexor tendon. | The arterial supply of the long flexor tendon of the index and ring fingers were studied morphologically on 36 cadaver hands. Our studies, showed that the long flexor tendons were supplied by two main sources. Primarily by small arteries which ran in the vinculum longum and vinculum brevis and reached the dorsal surface of the tendon. Also by small intrinsic longitudinal vessels which ran parallel to the collagenous fibers of the tendon and extended from the muscular attachment of the long flexor tendons. No morphological difference on the vascularization of the index and ring fingers were observed. |
8041563 | Differentiation of histochemical properties of masticatory muscles in Bovidae and Cervidae (Artiodactyla). | We analyzed the masticatory muscles (masseter, temporal, medial pterygoid and lateral pterygoid muscles) of Bovidae and Cervidae (Artiodactyla) for the histochemical characteristics of their fiber types. Analysis of muscle fiber types in the present study was based on the staining reaction for SDH, Sudan black B, alpha-GPDH, and myosin-ATPase after alkaline preincubations. Histochemical properties were found to contribute to masticatory function, including a slow-twitch fatigue resistant activity derived from the high percentage of red fibers, in spite of the differences in the distributions of fiber types in three portions (superficial, medial and profound portions) of each masticatory muscle. These results indicate a correlation between the histochemical profiles of individual masticatory muscles in these species and their functions during jaw movements. |
8041562 | A morphological study on the crown dimensions of the mandibular molars in Tupaia glis. | The crown dimensions of the mandibular molars in Tupaia glis were measured. All the mean values of crown diameters and areas were larger for the M1 molar than for the M2 and M3. The last two molars were more reduced in the talonid component than in the trigonid compared to the M1, and were more reduced in the buccolingual than in the mesiodistal direction. The most common molar size sequence (MSS) was M1 > M2 > M3, and this pattern was more frequently observed in the talonid component than in the trigonid. In the canonical discriminant analysis, all the cases of the M3 were discriminated correctly, but some cases of the first two molars were confused with each other. The molars size of the mandible was closely related to that of the maxilla. |
8041561 | Crown dimensions of the maxillary molars in Tupaia glis. | The crown dimensions of the maxillary molars in Tupaia glis were measured, and the most common molar size sequence was M1 > M2 > M3. The M2 and M3 molars were smaller than the M1 in the mesiodistal crown diameters. With regard to the buccolingual diameters, the distal part of M1 and mesial part of M2 were relatively larger and less variable in size. This stable area corresponded to the inflection point of the maxillary arch curve. These results could be explained from a functional morphological standpoint. |
8041560 | Autoradiographic evaluation of the cell cycle parameters of the various cells categories of the parotid, submandibular and sublingual glands of the suckling rat. | The evolution of the percentage of radioactive mitosis after a single thymidine-H3 injection, was determined for the various cell categories of the parotid, submandibular and sublingual glands of rats at 5th and 15th day of postnatal age. Estimates of the lengths of the S and the G2 + M/2 phases of the cell cycle were thus obtained, and averaged 9.8 and 2.7 hours, respectively, with extreme values of 9.3-11.2 and 1.6-3.2 hours. |
8041559 | Internalization of large macromolecules in human Chang liver cells by extracellular ATP. | The home of all intermediary metabolism and the cytoskeleton, viz. the cytosol, appears inaccessible to large macromolecules in the living state without severe perturbations. ATP-induced cytosolic penetration due to poration which allow passage of < 1000 mol. wt. particles have been cited. We report here that at similar milli-molar dosage levels of ATP, internalization of 2,000,000 mol. wt dextran particles as well as 0.92 micron and 2.17 microns latex beads could be demonstrated. At ultrastructural level, the internalized beads were seen distributed in 2 sites on the cytoplasm of the cell, viz. (a) inside vacuoles and (b) outside vacuoles, in the cytosol. The vacuolar distribution suggests endocytic entry, while the cytosolic distribution suggests a cellular sorting process where the boundary of the bead is processed or sorted out of the membrane-recycling pathway. |
8041555 | The value of cystoscopy in major vaginal surgery. | This article reviews the case histories of 236 patients who had cystoscopy as part of their major vaginal operations. Seven had cystoscopically detected potential lower urinary tract injuries. Five of these injuries were ureteral obstructions, one occurring after anterior repair, three associated with a McCall culdoplasty, and one associated with a modified Pereyra bladder neck suspension. Two injuries were subtle cystotomies. These compromises of the lower urinary tract were detected during the main operative procedure and immediately rectified. We propose that routine intraoperative cystoscopy associated with intravenous administration of indigo carmine is an excellent method for detecting actual and potential lower urinary tract surgical injury. Cystoscopy cannot distinguish which surgical distortion or injury will spontaneously resolve. The identification of non-blood-tinged urine from both ureteral orifices and the absence of bladder trauma should eliminate the possibility of lower urinary tract surgical injury, except for ischemic necrosis. Cystoscopy, like laparoscopy, is a procedure that should benefit our patients and should not isolate a specialty. |
8041554 | Particle concentration fluorescence immunoassay chemosensitivity assay for human epithelial ovarian cancer. | We adapted particle concentration fluorescence immunoassay technology to develop a new chemosensitivity assay. Six human epithelial ovarian cancer cell lines were incubated with cisplatin for 24 hours. Cells were then labeled with a fluorophore for 30 minutes. Removal of supernatant, washing of tumor cells, and reading of epifluorescence was performed automatically. Percent cell lysis was calculated simultaneously by chromium release assay. The particle concentration fluorescence chemosensitivity assay detected cell lysis in all six cell lines. The chemosensitivity assay detected a larger percent lysis than the chromium release assay in each of the cell lines. The advantages of our chemosensitivity assay are plating efficacy, speed, efficiency, safety, and accuracy. |
8041553 | Is there a relation between student lecture attendance and clinical science subject examination score? | To determine whether there is a relation between lecture attendance and factual knowledge of obstetrics and gynecology, as measured by the National Board of Medical Examiners (NBME) clinical science subject examination. We analyzed data on 197 students completing 8-week obstetrics and gynecology rotations from July 1, 1991 to June 30, 1992. Each student was expected to attend a weekly lecture series, and each completed the NBME clinical science subject examination at the end of the clerkship. Student attendance and board scores were correlated at the end of the academic year overall and by subgroups. Scores in the top and bottom 15% were defined as good and poor performance, respectively. A negative correlation (r = -0.1738, P = .0146) was found between percent absence and examination score. The odds ratio for poor performance was 5.48 (95% confidence interval 1.3-26.5; P = .015) for the subgroup of students with more than 30% absence compared to those without absences. Odds ratios for scoring in the upper 15th percentile were not significant. The negative correlation and the high odds ratio for poor performance suggest the value of monitoring attendance and identifying students at risk for poor performance (more than 30% absence). Lower absence rates did not predict performance. |
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