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Biomedical subjects

J Clarke

Publications and source records attributed to J Clarke.

At least 217 records · Page 12Linked to original sources
PubMed1991

Candida cell wall mannan in the vagina and its association with the signs and symptoms of vaginal candidosis.

Measurement of Candida cell wall polysaccharide (mannan) with an enzyme-linked immunosorbent assay (ELISA) was evaluated as an alternative to viable counting for the enumeration of yeast cell numbers in the human vagina. A statistically significant association was found between mannan levels and the number of colony forming units in vaginal washings collected from 40 women infected with Candida albicans (r = 0.81), indicating the accuracy of mannan levels in reflecting yeast cell load in vulvo-vaginal candidosis. Subsequent comparisons revealed a significant association between mannan levels and clinical signs in the vagina, so reflecting the importance of vulvitis and vaginitis as clinical markers for determining the severity of infection. No association was found between yeast load and the clinical symptoms, indicating the high degree of patient subjectivity. Estimation of mannan levels could be developed and used for the rapid laboratory investigation of chronic vulvo-vaginal candidosis.

Candida albicans↗
PubMed1991

Interaction of neuropeptide Y and the sympathetic nervous system in vascular control in man.

BACKGROUND: There is increasing evidence that neuropeptide Y (NPY) contributes to the autonomic control of the circulation. NPY coexists with noradrenaline in perivascular nerve terminals, may be released during sympathetic stimulation, and is a potent constrictor of the human coronary circulation and other vascular beds. In vitro studies show that NPY can act either directly on vascular smooth muscle or indirectly by modulation of the presynaptic release or the postsynaptic actions of noradrenaline. It is unclear to what extent these mechanisms operate in vivo. METHODS AND RESULTS: The effect on forearm blood flow of intra-arterial NPY was studied in six volunteers during coinfusion of noradrenaline and during reflex sympathetic stimulation induced by lower-body negative pressure. NPY alone induced a dose-dependent reduction of forearm blood flow in all subjects studied, to a maximum of 49 +/- 6.1%. The reduction of flow during infusion of noradrenaline alone was 42 +/- 8%. The response to noradrenaline was unaffected by coinfusion of a threshold constrictor dose of NPY (50 pmol/min). Furthermore, the reflex sympathetic vasoconstrictor response to 20 cm H2O of lower-body negative pressure was similar in both the infused and control arms during the infusion of 50 pmol/min NPY. The response to noradrenaline was abolished by alpha-blockade with phentolamine, but the flow reduction induced by NPY was unaffected by alpha-blockade. CONCLUSIONS: NPY is a potent constrictor of human forearm resistance vessels and has a direct effect independent of alpha-receptors. NPY has no detectable modulating effect in vivo on the action of endogenous or infused noradrenaline.

Adult↗
PubMed1991

Moral dilemmas in nursing research.

This paper addresses the important issue of moral dilemmas which can arise in nursing research. It argues that with the increase in nursing research, emphasis must be placed upon a greater understanding of ethical principles and codes of research for the protection of human subjects from possible exploitation. Two such dangers are identified as breach of confidentiality and not securing informed consent. These areas are used to illustrate possible dilemmas, together with discussion of relevant measures to avoid such exploitation.

Codes of Ethics↗
PubMed1991

The use of the Roy Adaptation Model in nursing administration.

In recent years, considerable attention has been paid to the use of a nursing conceptual model for nursing practice. Although many of the theorists and early writers on the subject suggested that a nursing conceptual model could be used to guide nursing administration, there has been little attention given to this in the literature. This article describes the process that one hospital engaged in as they implemented the Roy Adaptation Model for nursing administration. The article discusses the use of the Roy Model in creating a nursing philosophy, mission statements, standards of practice, job descriptions, performance planning and appraisal system and a quality monitoring system. The authors conclude that the use of the Roy Model has contributed to the development of a highly integrated system of nursing administration and practice.

Adaptation, Psychological↗
PubMed1990

Interleukin-1 beta inhibits glucokinase activity in clonal HIT-T15 beta-cells.

Interleukin-1 beta (IL-1 beta) has been implicated in the pathogenesis of insulin-dependent diabetes mellitus. In the present study we have investigated the effects of IL-1 beta on glucose metabolism in clonal HIT-T15 beta cells. In the short-term (1 h), 25 U/ml IL-1 beta significantly increased the rates of insulin release and glucose utilisation, but not glucose oxidation. In contrast, after 48 h, IL-1 beta inhibited insulin release and glucose utilisation and oxidation. By assaying enzymes (hexokinase, glucokinase, pyruvate dehydrogenase, glucose 6-phosphatase) and nucleotides (ATP, ADP) associated with the regulation of glycolysis and glucose oxidation, we conclude that the inhibitory effects of IL-1 beta may be due to impaired glucokinase activity.

Adenine Nucleotides↗
PubMed1990

Measuring changes in membrane thickness by scanning tunneling microscopy.

We investigated the feasibility of using the scanning tunneling microscope (STM) as a morphometric tool to measure the thickness of biomembranes. Planar monolayers of oriented purple membrane (PM) were prepared, nitrogen-dried or freeze-etched, and coated with metal. PM thickness was quantified by STM and transmission electron microscopy. STM calibration and the effect of contamination-mediated surface deformation on measurements of PM thickness were evaluated. The thickness of PM attached to mica and glass and the effect of papain on PM thickness were also examined. The apparent thickness of enzymatically modified PM increased after papain treatment. The mean thickness of both nitrogen-dried PM on mica and freeze-etched PM on glass was 4.6 nm. After papain treatment PM thickness on mica increased to 4.8 nm and on glass to 5.4 nm. These results demonstrate that STM analysis of metal-coated planar membrane monolayers can be used to measure changes in average membrane thickness at sub-nanometer resolution.

Amino Acids↗
PubMed1990

Insulin-secreting beta-cells possess specific receptors for interleukin-1 beta.

The effect of the cytokine interleukin-1 beta on the insulin secretory responsiveness of single beta-cells (HIT-T15) was investigated. In the short-term, IL-1 beta induced a dosage-dependent stimulation of insulin release. In contrast, in the long-term, IL-1 beta, inhibited both basal and secretagogue-stimulated insulin secretion. We also demonstrate the simultaneous presence of specific high and low affinity binding sites for IL-1 beta on beta-cells. IL-1 beta, which has been implicated in the pathogenesis of insulin-dependent diabetes, may therefore mediate its opposing effects on beta-cells through a specific plasma membrane receptor.

Calcium↗
PubMed1990

Scanning tunneling microscopy of planar biomembranes.

We combined planar membrane monolayer techniques with scanning tunneling microscopy (STM) to measure the thickness of metal-coated purple membrane (PM) isolated from Halobacterium halobium. Although the metal coating precluded obtaining high-resolution lateral information, it facilitated obtaining high-resolution vertical information. For example, the apparent mean thickness of planar PM and variations in thickness of enzyme-treated PM could be detected and quantified at sub-nanometer resolution.

Cell Membrane↗