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Biomedical subjects

M L Clark

Publications and source records attributed to M L Clark.

At least 19 recordsLinked to original sources
PubMed1995

Modification and validation of a commercially available portable detector for measurement of adipose tissue blood flow.

Adipose tissue blood flow is measured from the clearance of radioactive xenon from a depot. Traditionally, a NaI detector has been used to measure the residual depot of xenon. However, this is sensitive to movement artefacts. We tested a commercially available lightweight CsI detector which can be strapped to the anterior abdominal wall. In pilot studies the CsI detector produced higher values for adipose tissue blood flow than did a conventional NaI detector. It was modified by inclusion of spacers to distance it from the skin. Flow results generated by the modified detector were similar to those generated by the NaI detector, both after an overnight fast and during the increased blood flow after a meal. Individual decay patterns generated by the CsI detector were, however, significantly smoother than those from the NaI detector.

Abdominal Muscles↗
PubMed1994

Symptom relief and quality of life after stenting for malignant bile duct obstruction.

Palliative treatment is appropriate for most patients with cancer of the head of pancreas. Insertion of a biliary stent relieves jaundice and pruritus but it is not known if stenting affects other symptoms or changes the quality of life. Nineteen patients have completed a standard questionnaire to assess symptom relief and quality of life after stent insertion. After stenting there was complete relief of jaundice and pruritus. Furthermore, there was also considerable improvement in anorexia and indigestion. All patients had anorexia before stent insertion, this was moderate/severe in 13 (68.4%). Anorexia was significantly better (p < 0.01) a week after stenting and this benefit was maintained at 12 weeks (p < 0.01). Sixteen (84.2%) patients complained of indigestion before stenting, moderate/severe in 11 (57.9%). This was significantly better (p < 0.01) a week after stenting with complete relief in six at eight weeks (p < 0.01). Fifteen (78.9%) felt that their mood was good/very good before stent insertion and this was unchanged even at the 12 week assessment. A similar result was obtained for physical health and level of activity. In conclusion stent insertion not only relieves jaundice and pruritus in these patients but also improves other symptoms and quality of life. The considerable improvement in appetite after stenting was of particular benefit.

Affect↗
PubMed1992

Misuse of ecstasy.

Explore the source record for details and available documents.

3,4-Methylenedioxyamphetamine↗
PubMed1992

Friendship similarity during early adolescence: gender and racial patterns.

We studied the relationship of reciprocity, gender, and racial composition (Caucasian, African American, cross-race) of adolescent friendship dyads to similarity and proximity in 136 young adolescents. We found that adolescents selected friends who were of the same gender and race and that female dyads were more similar than male dyads on verbal achievement and several personality dimensions. Caucasian dyads were more similar than African American dyads on verbal achievement, mental alertness, and dominance. African American adolescents had more contact with their best friends outside school, whereas Caucasian adolescent friends had more in-school contact. African American students had fewer reciprocal relationships than the Caucasian students. Cross-race friendships were less reciprocal than same-race friendships. Race and gender were important in determining friendship patterns. Similarity and proximity were more important than reciprocity in understanding early adolescent friendships.

Achievement↗
PubMed1992

A new model of human secretory diarrhoea using cholera toxin.

Secretory diarrhoea is a major cause of morbidity and mortality worldwide. However, there is no biologically relevant test system in man for assessing new anti-diarrhoeal therapies prior to clinical trial. We have used highly purified cholera toxin in combination with the triple lumen jejunal perfusion technique to establish a subclinical model of cholera in man. Cholera toxin was administered either by mouth with sodium bicarbonate or directly into a 30 cm 'open' or 'closed' (isolated between two inflated balloons) jejunal segment in healthy adult volunteers. Both oral dosing and direct delivery into an 'open' jejunal segment failed to produce consistent secretion of water and electrolytes. In contrast 15 micrograms or 25 micrograms of cholera toxin elicited secretion of water and sodium 3 h after instillation into the balloon occluded 'closed' jejunal segment (P less than 0.05 vs. controls). The rate of secretion was constant over the maximal period studied (4.5 h) and was similar to that reported in human cholera. None of the subjects experienced troublesome diarrhoea. We believe this model offers a relevant test system for assessing anti-diarrhoeal therapy in man.

Administration, Oral↗
PubMed1992

Water and solute absorption from hypotonic glucose-electrolyte solutions in human jejunum.

While oral rehydration therapy with glucose-electrolyte solutions is highly effective, the optimal formulation has not yet been defined. Recent clinical studies suggest that stool volume, and thus water losses, may be reduced if glucose is replaced by a polymeric substrate which reduces osmolality. It is possible that the efficacy of glucose monomer based oral rehydration solutions (ORS) will also improve if osmolality is decreased. Using jejunal triple lumen perfusion in healthy adult volunteers net water and solute absorption were studied from three hypotonic solutions with different sodium concentrations (46, 60, 75 mmol/l) but identical glucose concentrations (90 mmol/l), thus allowing osmolality to rise (210, 240, and 270 mOsm/kg, respectively). Results from these solutions (ORS 45:210, ORS 60:240, and ORS 75:270) were compared with the World Health Organisation oral rehydration solution (WHO-ORS). Greatest water absorption was seen with ORS 60:240 (p less than 0.01). Sodium absorption from ORS 60:240 and WHO-ORS was similar and greater than sodium absorption from ORS 45:210 (p less than 0.05). Potassium and glucose absorption were greater from ORS 60:240 than from any of the other hypotonic solutions (p less than 0.05) and were equal to absorption from WHO-ORS). These results in a short segment of healthy human jejunum suggest that hypotonic ORS containing monomeric glucose may increase water absorption.

Adolescent↗
PubMed1990

Safety of azathioprine in pregnancy in inflammatory bowel disease.

Although azathioprine has been reported to be safe during pregnancy in renal transplant recipients and patients with systemic lupus erythematosus, opinions vary whether it should be continued in pregnancy in inflammatory bowel disease. A retrospective analysis of the outcome of 16 pregnancies in 14 women receiving azathioprine for inflammatory bowel disease was performed. There was one infective complication of pregnancy (hepatitis B virus infection), but there were no congenital abnormalities or subsequent health problems in the children. This preliminary study suggests that azathioprine is safe in pregnancy in inflammatory bowel disease patients and that termination of pregnancy is not mandatory for those who conceive while taking the drug.

Adult↗
PubMed1990

Role of cigarette use in hyponatremia in schizophrenic patients.

Urine volume and osmolality were studied in two schizophrenic patients with hyponatremia and six normal subjects after they smoked or ingested cigarettes. The results suggest that cigarette use may contribute to the development of hyponatremia by impairing water excretion.

Adult↗
PubMed1990

Stability of plasma glucose during storage.

Plasma glucose concentrations were found to decrease during storage. This phenomenon was not method-dependent; it was demonstrated using both a Beckman Glucose Analyser 2 (based on glucose oxidase) and a hexokinase-based technique on a centrifugal analyser. The loss of glucose was typically of the order of 10% in plasma frozen for periods from 24 h to 14 months. Repeated freezing and thawing (weekly for 1 month) did not produce additional loss of glucose compared with aliquots thawed for the first time at 1 month. Fluoride did not reduce the loss of glucose. Glucose was also lost from frozen neutralized perchloric acid extracts of blood (mean +/- SD: 7 +/- 2 per cent over 1 year). We conclude that this variable loss of glucose on storage may complicate the interpretation of metabolic research procedures.

Blood Glucose↗
PubMed1989

Evidence that blockade of post-synaptic 5-HT1 receptors elicits feeding in satiated rats.

The effects of nine central 5-HT antagonists on food intake in free feeding male rats were examined. The 5-HT2 antagonists ritanserin and ketanserin and the selective 5-HT3 antagonists ICS 205-930 and MDL 72222 had no effect on food intake. In contrast, the non-selective 5-HT antagonists metergoline, methiothepin, mesulergine, mianserin and methysergide (all of which have high affinity for various 5-HT1 receptor subtypes), dose-dependently increased food intake during a 4-h daytime test. Furthermore, metergoline dose dependently increased food intake over a 24-h period. Surprisingly, mesulergine decreased food intake over a 24-h period at the same doses that increased daytime food intake. This may indicate that the increase in daytime feeding produced by mesulergine is a non-specific response. Although the antagonists used have varying degrees of selectivity for 5-HT receptor subtypes, the pattern of results suggests that postsynaptic 5-HT1 receptors (possibly of the 5-HT1C type) play an important role in the control of feeding in rats.

Animals↗
PubMed1988

Relative contribution of ribcage and abdomen during augmented breaths in infants.

Changes in the relative contribution of ribcage and abdomen during augmented breaths were assessed in two groups of infants (less than 2 weeks and 4-12 weeks old). In both groups ribcage and abdominal movements increased during augmented breaths in quiet sleep. In the older infants the relative increase was greater for the ribcage (P less than 0.05) when expressed either as a ribcage to abdominal movement ratio or as a percent of the respective movements during control breaths. In contrast, no significant change of the relative contribution was observed in the younger age group. During active sleep paradoxical movement of the ribcage, observed during tidal breaths, continued during the first phase of the augmented breath; however, during the second phase of inspiration, the ribcage moved outward in all but one infant. Our results show that marked increases in tidal volume are associated with greater increases in ribcage contribution in infants beyond the neonatal period. This may reflect differences in recruitment patterns of intercostal muscles during development.

Abdominal Muscles↗
PubMed1988

8-OH-DPAT elicits feeding and not chewing: evidence from liquid diet studies and a diet choice test.

There have been recent claims that the 5-HT1A agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) elicits chewing and eating of solid but not liquid foods. Therefore, the effects of 8-OH-DPAT and another 5-HT1A agonist gepirone on the consumption of a liquid chow diet, by free feeding male rats, were examined. Both drugs produced a dose-dependent increase in the consumption of liquid diet during a 2 h test. The doses of 8-OH-DPAT and gepirone which increased liquid diet intake in this study were in the same range as those which were found previously to increase food pellet consumption by free feeding rats. The effects of 8-OH-DPAT were also examined in a feeding choice test in which free feeding animals were allowed to choose between food pellets and a liquid chow diet. In this test, 8-OH-DPAT significantly increased total food intake (liquid plus pellet) but had no significant effect on the consumption of either liquid or pellet diets when analysed separately. Thus, there were large individual differences in diet choice after 8-OH-DPAT injection. However, rats did not consistently choose to eat food pellets rather than the liquid diet, as would be predicted if the drug elicited chewing rather than eating. These results provide strong evidence that 8-OH-DPAT elicits a behaviourally specific hyperphagia and not chewing or gnawing.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1988

Dyadic peer interaction and task orientation in attention-deficit-disordered children.

A sequential observational approach was used to compare peer interactions in 10 mixed dyads of ADD-H and non-Add-H boys and 10 dyads of non-ADD-H boys in laboratory cooperative and school classroom task analogue activities. Mixed dyads were found to have a greater frequency of aggression and less joint activity than control dyads in specific situations. No differences were found for measures of functional attention as measured by frequency, duration, and mean duration of task-oriented behavior. Lag sequential analyses revealed two major sequences that differentiated mixed from normal dyads. These were Verbal Reciprocity (a measure of reciprocal verbal interaction) and Retreat (a measure of social withdrawal following aggression).

Aggression↗