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Biomedical subjects

J Mansfield

Publications and source records attributed to J Mansfield.

At least 19 recordsLinked to original sources
PubMed2000

Isolation of a ribonucleoprotein complex involved in mRNA localization in Drosophila oocytes.

Localization of bicoid (bcd) mRNA to the anterior and oskar (osk) mRNA to the posterior of the Drosophila oocyte is critical for embryonic patterning. Previous genetic studies implicated exuperantia (exu) in bcd mRNA localization, but its role in this process is not understood. We have biochemically isolated Exu and show that it is part of a large RNase-sensitive complex that contains at least seven other proteins. One of these proteins was identified as the cold shock domain RNA-binding protein Ypsilon Schachtel (Yps), which we show binds directly to Exu and colocalizes with Exu in both the oocyte and nurse cells of the Drosophila egg chamber. Surprisingly, the Exu-Yps complex contains osk mRNA. This biochemical result led us to reexamine the role of Exu in the localization of osk mRNA. We discovered that exu-null mutants are defective in osk mRNA localization in both nurse cells and the oocyte. Furthermore, both Exu/Yps particles and osk mRNA follow a similar temporal pattern of localization in which they transiently accumulate at the oocyte anterior and subsequently localize to the posterior pole. We propose that Exu is a core component of a large protein complex involved in localizing mRNAs both within nurse cells and the developing oocyte.

Amino Acid Sequence↗
PubMed2000

The RPM1 plant disease resistance gene facilitates a rapid and sustained increase in cytosolic calcium that is necessary for the oxidative burst and hypersensitive cell death.

Early events occurring during the hypersensitive resistance response (HR) were examined using the avrRpm1/RPM1 gene-for-gene interaction in Arabidopsis challenged by Pseudomonas syringae pv. tomato. Increases in cytosolic Ca2+ were measured in whole leaves using aequorin-mediated bioluminescence. During the HR a sustained increase in Ca2+ was observed which was dependent on the presence of both a functional RPM1 gene product and delivery of the cognate avirulence gene product AvrRpm1. The sequence-unrelated avirulence gene avrB, which also interacts with RPM1, generated a significantly later but similarly prolonged increase in cytosolic Ca2+. Accumulation of H2O2 at reaction sites, as revealed by electron microscopy, occurred within the same time frame as the changes in cytosolic Ca2+. The NADPH oxidase inhibitor diphenylene iodonium chloride did not affect the calcium signature, but did block H2O2 accumulation and the HR. By contrast, the calcium-channel blocker LaCl3 suppressed the increase in cytosolic Ca2+ as well as H2O2 accumulation and the HR, placing calcium elevation upstream of the oxidative burst.

Aequorin↗
PubMed1999

Early events in host-pathogen interactions.

Research focused on early events in host-pathogen interactions has provided new insights into fundamental aspects of microbial pathogenicity and plant responses. Considerable progress has been made in understanding regulation of the delivery of pathogenicity determinants from bacteria into plant cells, signal cascades involved in fungal pathogenicity, the co-ordinating role of the plant cytoskeleton in plant defence and calcium flux as a primary signalling function during the hypersensitive reaction.

Bacteria↗
PubMed1999

Using population-based data to enhance clinical practice guideline development.

OBJECTIVES: Working with the College of Physicians and Surgeons of Manitoba, and using tonsillectomies as a basis of inquiry, MCHPE examined surgical rates and patterns of practice. This project had three major aims: to review whether current patterns of delivery provide optimal care; to enhance the development of clinical guidelines; and to inform and influence physician practice. RESEARCH DESIGN: Both a population-based method of inquiry (which permits comparisons across population groups) and a provider-based approach (which offers insights into differences in the nature of care offered by different types of hospitals and physicians) were used. MEASURES: Synergies between these two approaches offered useful insight into aspects of quality and efficiency of care. RESULTS: Consistent with other jurisdictions, there was a high degree of variability across regions. However, there were also a number of surprising findings, including high rates of surgery in females, in older children, and among residents of rural areas. Data analysis raised a number of quality-of-care issues related to small caseload volumes, performance of procedures in very young children, and patterns of postoperative care in rural hospitals. The analyses provided impetus for addressing these issues in the guideline and suggested that the target audience for intervention should be rural physicians rather than urban specialists. CONCLUSIONS: This project demonstrated that data analysis can provide a powerful adjunct to the development and implementation of clinical practice guidelines.

Adolescent↗
PubMed1997

Expression of avrPphB, an avirulence gene from Pseudomonas syringae pv. phaseolicola, and the delivery of signals causing the hypersensitive reaction in bean.

Protein production encoded by the avirulence gene avrPphB from Pseudomonas syringae pv. phaseolicola was examined. Incorporation of [35S]-labeled methionine into the AvrPphB protein indicated processing of the full-length peptide in Escherichia coli to give a major 28-kDa product. The 28-kDa native peptide was isolated from E. coli following over-expression of avrPphB and found not to elicit the hypersensitive response (HR) after infiltration into bean leaves. Antiserum raised to the 28-kDa peptide allowed expression of avrPphB and processing of AvrPphB protein to be examined in P. syringae pv. phaseolicola; immunoreactive peptides of both 35 and 28-kDa were detected in races 3 and 4 (which contain avrPphB) only after induction in minimal medium + 10 mM sucrose. Antiserum raised to a synthetic peptide, derived from the sequence of the 62 amino acids found to be cleaved from the full-length AvrPphB protein, revealed the accumulation of peptides corresponding to the smaller cleavage products, in both E. coli and P. syringae pv. phaseolicola. Biochemical localization experiments showed that all AvrPphB peptides were cytoplasmic in P. syringae pv. phaseolicola. No AvrPphB peptides were produced in a hrpL mutant unless expression of the gene was directed by a strong vector promoter; induction kinetics similar to wild type were observed in a hrpY- strain, although it also failed to cause a confluent HR. Growth of P. syringae pv. phaseolicola under inducing conditions removed the requirement for rifampicin-sensitive mRNA synthesis by bacteria to allow HR development (the induction time) in bean and lettuce leaves. Constitutive expression of hrpL reduced but did not remove the induction time. Expression of the hrp gene cluster of P. syringae pv. phaseolicola from plasmid pPPY430 in E. coli enabled phenotypic expression of avrPphE (also carried by pPPY430) and avrPphB (if over-expressed from pPPY3031). Despite constitutive expression of the hrp and avr genes in E. coli, a protein synthesis dependent induction time was still required for development of the HR in bean genotypes with matching resistance genes. The significance of processing for the function of AvrPphB peptides and the delivery of elicitors of the HR are discussed.

Amino Acid Sequence↗
PubMed1996

TNF2, a polymorphism of the tumour necrosis-alpha gene promoter, is a component of the celiac disease major histocompatibility complex haplotype.

Celiac disease (CD) is an immune disease triggered by the cereal antigen gliadin, resulting in villous atrophy in the small intestine. Susceptibility to the development of CD is strongly influenced by genes in the major histocompatibility complex, in particular alleles of the DQ genes in the class II region. However recent evidence has suggested that the major histocompatibility complex (MHC) class III region may be linked to celiac disease independently of the class II region. Among the genes located in this area is TNF-alpha, which encodes the cytokine tumor necrosis factor-alpha which has a broad range of pro-inflammatory, immunomodulatory and catabolic activities. Therefore, aberrant expression of TNF-alpha could be important in the pathogenesis of MHC-associated immune disorders. A TNF-alpha variant with a polymorphism in its promoter region has been described and designated TNF2. TNF2 has been associated with a variety of MHC-linked diseases, including systemic lupus erythematosus, dermatitis herpetiformis and insulin-dependent diabetes mellitus (IDDM), as well as parasitic infections. TNF2 has previously been shown to be associated with the MHC haplotype HLA A1-B8-DR3-DQ2, which confers susceptibility to CD. We have analyzed the distribution of TNF2 alleles in a group of celiac patients (n = 52) compared to controls (n = 52) in an effort to evaluate its role, if any, in susceptibility to the condition. TNF2 has a frequency of 0.5000 (SE +/- 0.0490) in CD, compared to 0.1635 (+/- 0.0362) in a control sample (p < 10(-6)). Of 52 patients, 44 carried one or more TNF2 alleles. Analysis indicates that the distribution of TNF2 is best explained by assuming 100% allelic association between it and HLA-DQB1*0201 (frequency = 0.7791 +/- 0.0447). However, the number of TNF2 heterozygotes significantly exceeds expectations and measurements of linkage disequilibrium confirm that allelic associations spanning the DQ and TNF regions are strongly maintained in CD. Taken together, these results indicate that TNF2 may have a role in the pathogenesis of CD; however, since it is not an independent association, the possibility that TNF2 constitutes a passive component of the CD haplotype cannot be excluded.

Alleles↗
PubMed1996

Biochemical and mutational analysis of the histidine residues of staphylococcal enterotoxin A.

The goal of this study was to examine the role of histidine residues in the biological activities of staphylococcal enterotoxin A (SEA). Carboxymethylated SEA was unable to stimulate murine T-cell proliferation but was resistant to monkey stomach lavage fluid degradation, suggesting that native conformation was intact. Site-directed mutagenesis of the histidine residues of SEA was subsequently performed. SEA-H44A (SEA with histidine 44 replaced with alanine), SEA-H44D, SEA-H50A, SEA-H50D, SEA-H114A, SEA-H114D, SEA-H187A, and SEA-H187D retained superantigen and emetic activities, whereas SEA-H225A and SEA-H225D were defective in the ability to stimulate T-cell proliferation. These mutants were unable to compete with SEA for binding to Raji cells, suggesting that the defect in SEA-H225A and SEA-H225D is due to impaired major histocompatibility complex class II binding. SEA-H225D provoked an emetic response in monkeys only if fed at high doses, while SEA-H225A did not provoke an emetic response at low or high doses. In comparison, SEA-H61A and SEA-H61D were defective in emetic activity but not in the ability to stimulate murine T-cell proliferation. Overall, these studies show that the carboxy-terminal histidine at residue position 225 of SEA is important for both the superantigen and emetic activities of this enterotoxin. Histidine 61 appears to be important for emetic activity but not for superantigen activity, consistent with the hypothesis that the two activities are separable in staphylococcal enterotoxins.

Animals↗
PubMed1995

Neural network classification of infrared spectra of control and Alzheimer's diseased tissue.

Artificial neural network classification methods were applied to infrared spectra of histopathologically confirmed Alzheimer's diseased and control brain tissue. Principal component analysis was used as a preprocessing technique for some of these artificial neural networks while others were trained using the original spectra. The leave-one-out method was used for cross-validation and linear discriminant analysis was used as a performance benchmark. In the cases where principal components were used, the artificial neural networks consistently outperformed their linear discriminant counterparts; 100% versus 98% correct classifications, respectively, for the two class problem, and 90% versus 81% for a more complex five class problem. Using the original spectra, only one of the three selected artificial neural network architectures (a variation of the back-propagation algorithm using fuzzy encoding) produced results comparable to the best corresponding principal component cases: 98% and 85% correct classifications for the two and five class problems, respectively.

Alzheimer Disease↗
PubMed1993

Quantitative assessment of four men using above-elbow prosthetic control.

We studied the relationship between kinematically unconstrained activities of daily living (ADL) tasks and a kinematically constrained task in above-elbow (AE) amputee subjects using myoelectrically controlled prostheses. Four men, 24 to 49 years old, with unilateral AE amputation wore a prosthesis interfaced to a programmable controller to emulate two different elbow control schemes, conventional velocity and a new "natural" controller. Subjects were timed during three ADL tasks--cutting meat, donning socks, and rolling dough--with both controllers. The prosthesis emulator was then connected to a crank device with a handle, and the subjects turned the crank from bottom to top positions in a vertical plane using each controller. Synergistic shoulder-elbow joint coordination required for crank turning was quantified as the maximum slope of the change in elbow torque versus the change in crank-angle. Performance between the two controllers differed significantly for the crank test but not for ADL tasks. One subject did not complete all crank turning tests. Positive canonical correlation of 0.77 was found between time and crank domain measures. We conclude that biomechanical assessments should be integrated with time-based clinical tests to comprehensively evaluate performance of AE amputee subjects with a myoelectric device.

Activities of Daily Living↗
PubMed1992

Functional homologs of the Arabidopsis RPM1 disease resistance gene in bean and pea.

We showed that a bacterial avirulence (avr) gene function, avrPpiA1, from the pea pathogen Pseudomonas syringae pv pisi, is recognized by some, but not all, genotypes of Arabidopsis. Thus, an avr gene functionally defined on a crop species is also an avr gene on Arabidopsis. The activity of avrPpiA1 on a series of Arabidopsis genotypes is identical to that of the avrRpm1 gene from P.s. pv maculicola previously defined using Arabidopsis. The two avr genes are homologous and encode nearly identical predicted products. Moreover, this conserved avr function is also recognized by some bean and pea cultivars in what has been shown to be a gene-for-gene manner. We further demonstrated that the Arabidopsis disease resistance locus, RPM1, conditioning resistance to avrRpm1, also conditions resistance to bacterial strains carrying avrPpiA1. Therefore, bean, pea, and conceivably other crop species contain functional and potentially molecular homologs of RPM1.

Amino Acid Sequence↗
PubMed1992

Eat a live toad.

Explore the source record for details and available documents.

Education, Nursing, Continuing↗
PubMed1989

Practical phase identification by convergent beam electron diffraction.

The purpose of this article is to present a practical guide to the identification of phases in the analytical electron microscope with the aid of convergent beam electron diffraction. There is included a step-by-step approach to phase analysis, from the possible choices of the form of the specimen through how to explore reciprocal space in order to perform a full phase identification, either by symmetry analysis or by simple comparison of a pattern observed in the microscope with a previously recorded pattern (fingerprinting). There is a strong emphasis on practical hints and useful shortcuts.

Crystallography↗
PubMed1988

Treatment with dexamethasone of androgen excess in adolescent patients.

Fourteen hirsute girls, ages 12 to 22 years (mean +/- SD: 17.2 +/- 2.6 years), in whom 21-hydroxylase deficiency was excluded by a 1-hour intravenous alpha 1-24 corticotropin test, were evaluated by a 4-day dexamethasone test and then treated with a bedtime dose of dexamethasone (0.5 mg in 10 patients, 0.25 mg in four) for 0.6 to 3.4 years (1.3 +/- 0.8 years). Hirsutism decreased in four patients, did not change in nine, and increased in one. Of the 10 patients with irregular menses, only three developed regular cycles while taking dexamethasone. During long-term dexamethasone therapy, serum levels of testosterone decreased from 102 +/- 22 to 72 +/- 27 ng/dL, free testosterone from 35 +/- 11 to 19 +/- 8 pg/mL, and dehydroepiandrosterone sulfate from 396 +/- 138 to 171 +/- 101 micrograms/dL. Although free testosterone decreased to less than 15 pg/mL in eight of 14 patients with the suppression test, only four patients had free testosterone levels less than 15 pg/mL during therapy. Two of the 14 patients have had no recurrence of hirsutism or increase in serum androgens after 28 and 29 months, respectively, after dexamethasone therapy was discontinued. Oral contraceptives were given to nine patients inadequately responsive to bedtime dexamethasone therapy. The mean percent decrease of testosterone and free testosterone levels during oral contraceptive therapy was significantly greater than during long-term treatment with dexamethasone, and hirsutism lessened in all. We conclude that a single bedtime dose of dexamethasone is satisfactory only in patients who maintain serum free testosterone values less than 15 pg/mL without side effects. For other patients, either another glucocorticoid or, in most cases, ovulation suppression should be prescribed for adolescents with progressive hirsutism and elevated androgen levels.

17-Ketosteroids↗
PubMed1984

The relationships of calculated percent body fat, sports participation, age, and place of residence on menstrual patterns in healthy adolescent girls at an independent New England high school.

A prospective study was undertaken to determine normal menstrual patterns in healthy girls in an independent high school and assess the effects of exercise (type and hours per day), age (chronologic and gynecologic), calculated estimate of body fat, and place of residence (boarding and day students) on menstrual function. Three hundred twenty-seven girls (means age 15.5 +/- 1.1 years) answered a questionnaire on menstrual history; 306 (93.6%) were postmenarchal and 21 (6.4%) premenarchal. Calculated estimate of percent body fat was significantly lower in premenarchal than postmenarchal girls (22.4% versus 27.3% p less than 0.0001). Ninety-three percent of adolescents reported flow lasting 4-7 days; 59.7% dysmenorrhea; and 63% premenstrual symptoms. There was no correlation between estimated body fat or hours per day of exercise and the regularity of menses, duration of flow, or dysmenorrhea. With the exception of gymnastics and dancing, sports participation had little or no impact on menstrual patterns. Follow up questionnaires and menstrual calendars were obtained from 87 girls eight to fifteen months after the initial questionnaires. All girls whose cycles had changed from regular to irregular were boarding students, confirming previous anecdotal reports that separation from home may be a significant stress for adolescents.

Adipose Tissue↗
PubMed1981

Lumbar myelography today. Experience with metrizamide, a water-soluble, non-ionic contrast medium.

A clinical assessment of metrizamide (Amipaque) lumbar myelography in 150 patients is reported, and the adverse reactions encountered are presented and discussed. Minor adverse reactions--headache (48%), nausea (10%) and vomiting (7%)--were common, and the incidence reflected overseas experience. Severe headache occurred in a significant proportion of patients (20%), despite adequate hydration and the use of a small-gauge needle. There were no major adverse reactions such as epilepsy or severe muscle spasm. The study suggests that metrizamide is well tolerated, gives good anatomical demonstration and should replace iophendylate (Myodil) in this region. Recent reports of occasional, but sometimes severe, neurological complications indicate that further cautious assessment is required.

Adolescent↗