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Biomedical subjects

C Clark

Publications and source records attributed to C Clark.

At least 73 records · Page 4Linked to original sources
PubMed2000

Epidemiologic typing of Salmonella enterica serotype enteritidis in a Canada-wide outbreak of gastroenteritis due to contaminated cheese.

A major Canada-wide outbreak of gastroenteritis due to Salmonella enterica serotype Enteritidis phage type (PT) 8 occurred in 1998, and this was traced to contaminated cheese in a commercial lunch pack product. Phage typing and pulsed-field gel electrophoresis linked the clinical and cheese isolates of serotype Enteritidis but failed to differentiate outbreak from nonoutbreak PT 8 strains. Further differentiation was made by biotyping based on melibiose fermentation.

Bacterial Typing Techniques↗
PubMed2000

Multiculturalism as a concept in nursing.

This article focuses on the theoretical processes of identifying and evaluating concepts in the public domain and the subsequent practical application of such concepts to the provision of nursing care. More specifically, this article identifies the concept of "multiculturalism" as a valuable one for nursing, and then evaluates it via the methodology developed by nursing theorists Wilson (1969) and Meleis (1997).

Attitude of Health Personnel↗
PubMed1999

Investigation of unsteady flow in a model of a ventricular assist device by numerical modelling and comparison with experiment.

Prior to this study, a clinical prototype of a sac-type ventricular assist device (VAD) was investigated experimentally, using both flow visualisation and Laser Doppler anemometry (LDA), in order to optimise its geometry. As poor optical access precluded the experimental investigation of the flow in some areas of the prototype VAD, computational fluid dynamics (CFD) was used in the present work. Flow patterns during one full pumping cycle were investigated in a simplified model of the VAD. The numerical solutions were compared with experimental results from an identical physical model. The model consists of the hemispherical cylinder and two attached tubes for the inflow and outflow. Instead of a diaphragm in the clinical device, which deforms non-uniformly during pumping, a piston with a matching hemispherical crown was used. A finite volume method was employed to solve the governing equations for the three-dimensional, unsteady, laminar flow of an incompressible, Newtonian fluid. The general flow features were predicted very well by the simulation, with some differences in the details of the flow structures. This allows the conclusion that CFD can be used to facilitate improvement of the design of the clinical device. The comparison of one-component velocity time histories at selected points showed that the predicted velocities were approximately 20-50% lower than those measured by LDA. Such underprediction would lead to erroneous results for particle residence times and may result in an underestimation of wall shear stresses.

Algorithms↗
PubMed1999

The pre-operative ECG in day surgery: a habit?

As the population presenting for day-case surgery and anaesthesia increases, so does the challenge of adequate pre-operative assessment. Although an electrocardiogram is frequently performed, its value in day-case surgery remains unproven. One thousand, one hundred and eighty-five patients presenting for day-case surgery were assessed. One hundred and fifty-four (13%) were referred for electrocardiogram according to well-recognised criteria for the prediction of coronary artery disease. They were read independently by the anaesthetist responsible for the case and by an experienced cardiologist. A significant abnormality was noted in 26% of electrocardiograms, most frequently in patients referred with hypertension. There was a good correlation between the reports of the anaesthetist and cardiologist. Only 20% of those patients with an abnormal electrocardiogram had their surgery postponed. No adverse events occurred in patients proceeding to surgery despite the abnormalities. We conclude that a resting electrocardiogram is of limited value in risk stratification of patients undergoing day-case surgery.

Adult↗
PubMed1999

The identification of three biologically relevant globotriaosyl ceramide receptor binding sites on the Verotoxin 1 B subunit.

The Verotoxin 1 (VT1) B subunit binds to the glycosphingolipid receptor globotriaosylceramide (Gb3). Receptor-binding specificity is associated with the terminally linked Galalpha(1-4) Galbeta disaccharide sequence of the receptor. Recently, three globotriose (Galalpha[1-4] Galbeta [1-4] Glcbeta) binding sites per B-subunit monomer were identified by crystallography. Two of these sites (sites I and II) are located adjacent to phenylalanine-30. Site I was originally predicted as a potential Gb3 binding site on the basis of sequence conservation, and site II was additionally predicted based on computer modelling and receptor docking. The third (site III) was also identified by crystallography and is located at the N-terminal end of the alpha-helix. To determine the biological significance of sites II and III, and to support our previous findings of the significance of site I, we examined the binding properties and cytotoxicity of VT1 mutants designed to block Gb3 binding at each site selectively. The Scatchard analysis of saturation-binding data for each mutant revealed that only the amino acid substitutions predicted to affect site I (D-17E) or site II (G-62T) caused reductions in the binding affinity and capacity of VT1 for Gb3. Similarly, those mutations at sites I and II also caused significant reductions in both Vero and MRC-5 cell cytotoxicity (by seven and five logs, respectively, for G-62T and by four and two logs, respectively, for D-17E). In contrast, the substitution of alanine for W-34 at site III did not reduce the high-affinity binding of the B subunit, despite causing a fourfold reduction in the receptor-binding capacity. The corresponding mutant W-34A holotoxin had a two-log reduction in cytotoxicity on Vero cells and no statistically significant reduction on MRC-5 cells. We conclude that the high-affinity receptor binding most relevant for cell cytotoxicity occurs at sites I and II. In contrast, site III appears to mediate the recognition of additional Gb3 receptor epitopes but with lower affinity. Our results support the significance of the indole ring of W-34 for binding at this site.

Animals↗
PubMed1999

Methodological issues in performance improvement in integrated systems.

This article presents an overview of processes necessary for effective performance improvement (PI) projects and includes a discussion of methodological issues that affect the quality of PI projects. Issues related to project design, project purpose, selection of a representative population for the project, and issues of sampling are presented. Data collection methods and instruments are analyzed and issues related to connecting the problem, the intervention, and the outcome are described. The final sections address strategies related to data analysis procedures and interpretation.

Data Collection↗
PubMed1999

Baylor profound mental status examination: a brief staging measure for profoundly demented Alzheimer disease patients.

There is no brief patient-derived rating scale for staging and following profoundly demented Alzheimer disease (AD) patients. We developed the Baylor Profound Mental Status Examination (BPMSE) modeled after the Mini-Mental State Examination (MMSE) to meet this need. The BPMSE consists of 25 cognitive questions that assess orientation, language, attention, and motor functioning; 10 examiner ratings of presence or absence of problem behaviors; and 2 qualitative observations of language and social interaction. Two hundred eight probable or possible AD patients (MMSE scores of 20 or less) received the BPMSE. Some were also rated on the clinical dementia rating (CDR) and Lawton activities of daily living (ADL). A ceiling effect occurred at MMSE scores above 11. BPMSE cognitive scores and MMSE scores correlated significantly (r = 0.76, p < 0.0001). Subareas of the BPMSE also intercorrelated significantly. The BPMSE correlated with both CDR and ADL scores (p < 0.001). Internal consistency, interrater reliability, and test-retest stability were excellent. There was no floor effect, and BPMSE scores continued to decline after the MMSE reached 0. The BPMSE is a quick and easy staging tool with excellent validity and test-retest stability that measures cognitive function successfully in patients with MMSE scores below 12. The scale is sensitive to longitudinal change and continues to assess decline when performance has reached the lowest levels on conventional measures.

Aged↗
PubMed1999

Artifactual elevation of measured plasma L-lactate concentration in the presence of glycolate.

OBJECTIVES: To determine whether glycolate, a toxic metabolite of ethylene glycol that is chemically similar to lactate, can cause artifactual elevation of measured L-lactate concentrations. DESIGN: Prospective in vitro study. SETTING: Intensive care unit and chemical pathology laboratory in a university-affiliated hospital. SUBJECTS: Heparinized normal human blood and four commercially available L-lactate analyzers. INTERVENTIONS: Four analyzers were tested, three of which used L-lactate oxidase and one of which used L-lactate dehydrogenase. Glycolic acid (10 g/L) in saline was added to blood in a series of aliquots. Corresponding plasma L-lactate concentrations and blood pH, PCO2, and hemoglobin concentrations were measured and base excess was calculated initially and after the addition of each aliquot. One of the two L-lactate oxidase-type analyzers, which was found to show interference, was then used to measure plasma L-lactate and glucose concentrations in blood with glycolic, oxalic, or formic acid added until the base excess was reduced by >15 mmol/L. MEASUREMENTS AND MAIN RESULTS: Artifactual plasma L-lactate elevations were observed in two analyzers, both of the L-lactate oxidase type. Small concentrations of glycolic acid (causing reductions of base excess of 2-5 mmol/L) were accompanied by artifactual plasma L-lactate elevations of 4-8 mmol/L. Artifactual plasma L-lactate elevations increased with further glycolic acid-induced reductions in base excess. Oxalate and formate did not interfere with plasma L-lactate measurements, and measured plasma glucose concentrations were unaffected by all three acids. CONCLUSIONS: Glycolate causes large artifactual elevations in plasma L-lactate measurements by two analyzers in common use, with potential for misdiagnosis of lactic acidosis in ethylene glycol poisoning. A possible cause of the interference is incomplete specificity of the analytical reagent L-lactate oxidase, allowing cross-reaction with glycolate.

Acidosis, Lactic↗
PubMed1999

Comparison of flow in numerical and physical models of a ventricular assist device using low- and high-viscosity fluids.

The flows in a model of a ventricular assist device (VAD) were investigated numerically and experimentally for two different Newtonian test fluids. These were a blood analogue fluid and a much higher viscosity fluid. A finite volume method was employed to solve the governing equations for a three-dimensional unsteady laminar flow on a transient grid. The numerical solutions were compared with experimental results from an identical physical model. The experimental flows were investigated by flow visualization and by laser Doppler velocity measurements at selected points in the flow field. The validation was based on comparisons of flow patterns and of non-component velocity-time histories. The maximum Reynolds numbers in the inflow tube of the model VAD were approximately 460 and 3300 using the high- and low-viscosity fluids respectively. The investigation showed that the flow patterns were better predicted for the high-viscosity fluid. However, the agreement between the velocity-time histories was found to be slightly better for the low-viscosity fluid. The discrepancies in the flow patterns may be due to intermittent turbulence with a further contribution from numerical diffusion.

Blood Flow Velocity↗
PubMed1999

Novel PCR-based diagnostic tools for Charcot-Marie-Tooth type 1A and hereditary neuropathy with liability to pressure palsies.

The majority of cases of Charcot-Marie-Tooth type 1A (CMT1A) and hereditary neuropathy with liability to pressure palsies (HNPP) are the result of DNA duplications and deletions respectively of a 1.5 Mb region on 17p11.2. The region contains the peripheral myelin protein 22 gene (PMP-22) and is flanked by homologous proximal and distal CMT1A-REP elements. The majority of duplications and deletions arise during meiotic recombination following misalignment and unequal crossing-over between the proximal and distal CMT1A-REP elements. The cross-over breakpoints are most frequently located within a 1.7 Kb hotspot of recombination and produce novel duplication or deletion junctional CMT1A-REPs with unique restriction patterns. Here we describe the use of PCR based tests, which amplify a 3.6 Kb region including the 1.7 Kb hotspot from specific CMT1A-REPs, for the rapid diagnosis of CMT1A and HNPP patients. In an analysis of 96 CMT1A and 30 HNPP patients, duplication and deletion events were detected in all samples with cross-over breakpoints known to be within the region amplified by PCR.

Charcot-Marie-Tooth Disease↗
PubMed1999

Effect of timing and route of administration of furosemide on pulmonary hemorrhage and pulmonary arterial pressure in exercising thoroughbred racehorses.

OBJECTIVES: To examine effect of pre-exercise administration of furosemide (FUR) on mean pulmonary arterial pressure (PAP) during work and RBC concentration in bronchoalveolar lavage fluid (BALF) collected 40 minutes after exercise. ANIMALS: 10 adult Thoroughbreds. PROCEDURE: A modified 10 X 10 crossover design comprising 10 horses during 10 weeks was used. Each horse received each of 5 treatments twice. Treatment structure included a control plus a 2 X 2 factorial and consisted of the following: A, control; B, FUR, 250 mg, IV, 30 minutes before exercise; C, FUR, 250 mg, IV, 240 minutes before exercise; D, FUR, 250 mg, nebulized, 30 minutes before exercise; and E, FUR, 250 mg, nebulized, 240 minutes before exercise. Mean PAP data were collected, and each horse, after a 500-m warm-up, was galloped at maximal speed for 1,600 m. BALF RBC concentration was determined by hemocytometer. RESULTS: Interaction between treatment method and time of administration was significant (P = 0.04). Treatment B resulted in significantly (P = 0.01) lower BALF RBC concentration than did treatment C. Only BALF RBC count after treatment B was significantly lower than the control value. Horses that received FUR IV had significantly lower peak mean PAP than did those that received the drug by nebulization, regardless of administration time. Only treatment B resulted in peak mean PAP that was significantly lower than that of control. Exercise time was not influenced by treatment. CONCLUSIONS: FUR, administered IV 30 minutes before exercise, significantly reduced peak mean PAP and BALF RBC concentration.

Animals↗
PubMed1998

Is there a relationship between delta sleep at night and afternoon cerebral blood flow, assessed by HMPAO-SPECT in depressed patients and normal control subjects? Preliminary data.

We wished to explore the relationships between waking HMPAO uptake and visually scored polysomnography. We hypothesized that HMPAO activity would correlate positively with slow wave sleep measures the same night. Eight unmedicated unipolar patients with current DSM-IV major depression (17-item Hamilton Depression Rating Scale score 21.5+/-2.9) and seven control subjects received polysomnography on 2 consecutive nights. On the afternoon following the adaptation night, subjects received cerebral SPECT, with 15 mCi Tc-99m-HMPAO injected while subjects performed the Continuous Performance Task. Patients and control subjects did not significantly differ on demographic, polysomnographic, and SPECT variables. Slow wave sleep measures correlated positively (Spearman's) with global and regional tracer activity for depressed (n = 8), control (n = 7) and combined groups (n = 15); in other words, the greater the global or regional afternoon HMPAO uptake, the greater the slow wave sleep measures were the same night. In addition, the greater the waking afternoon global or regional HMPAO activity, the faster subjects fell asleep and the less Stage 2% they had. In patients, global and regional HMPAO activity correlated positively with REM density. Positive correlations between waking tracer activity and subsequent slow wave measures are consistent with previous hypotheses linking slow wave sleep with brain energy conservation and restoration. Further study is needed to determine whether these functional relationships differ in depression.

Adult↗
PubMed1998

Effects of a tryptophan-free amino acid drink challenge on normal human sleep electroencephalogram and mood.

BACKGROUND: Serotonin has been implicated in the regulation of sleep and mood. In animals a tryptophan-free amino acid drink (TFD) challenge has been found to reduce brain serotonin. We hypothesized this TFD would produce alterations in electroencephalographic (EEG) sleep commonly associated with depression, i.e. an enhancement of rapid eye movement (REM) sleep, and adversely affect mood ratings in humans. METHODS: We investigated the effects of a TFD challenge in 11 healthy male subjects on EEG sleep and mood (assessed by Profile of Mood States). All subjects received on separate occasions an experimental drink containing approximately 100 g of an amino acid mixture (100% TFD) and a control drink containing one fourth strength (25% TFD) of the experimental drink 5 hours prior to sleep (6:00 PM). RESULTS: Both drinks significantly decreased plasma tryptophan levels 5 hours postchallenge (11:00 PM). Both drinks significantly decreased REM latency, and the 25% TFD also increased REM time and REM% compared to baseline. No significant changes were found in subjective ratings of depression; however, subjects reported confusion and tension and a decrease in elation, vigor, and friendliness compared with baseline. CONCLUSIONS: These TFD findings further support the involvement of serotonin deficiency in EEG sleep findings commonly seen in depression.

Adult↗