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Biomedical subjects

M L Clark

Publications and source records attributed to M L Clark.

At least 55 records · Page 3Linked to original sources
PubMed1994

Regulation of fatty acid movement in human adipose tissue in the postabsorptive-to-postprandial transition.

There is net outward flow of fatty acids from adipose tissue in the fasted state but net inward flow and storage in the postprandial state. We investigated how this is regulated. Arteriovenous differences were measured across a subcutaneous adipose depot in six normal subjects before and for 5 h after a meal containing 80 g fat and 80 g carbohydrate. In five further experiments, insulin was infused at 40 mU.m-2.min-1 from 30 min after the meal, clamping the plasma glucose. Net transcapillary fatty acid flow changed from negative (outward flow from tissue to capillaries) in the postabsorptive state to consistently positive (net inward flow, implying fat storage) after the meal despite continued net efflux of fatty acids into venous blood. In the "clamped" experiments (with additional insulin), net fatty acid efflux in the venous blood was suppressed and positive transcapillary flux (storage) was more marked. Regulation of fatty acid flow appeared to depend on coordinated changes in hormone-sensitive lipase (HSL) and lipoprotein lipase (LPL) action and fatty acid esterification. Additional insulin caused no further suppression of HSL or activation of LPL but markedly stimulated fatty acid retention (presumed to represent esterification). In the absence of additional insulin, a high proportion of the fatty acids liberated by LPL are released into the venous plasma in both postabsorptive and postprandial states. We hypothesize that this "loss" of fatty acids is necessary to give precise control to the pathway of fat storage.

Absorption↗
PubMed1994

Research priorities for all phases of postanesthesia nursing: a survey by ASPAN.

This ASPAN survey was conducted by Research Committee members regarding the future of research for postanesthesia nursing and asked this question: What do postanesthesia nurses view as priorities for postanesthesia nursing research in various phases of practice? The design for the study was the Delphi technique, which uses a multiple, sequential survey to reach consensus among a group of experts. Four rounds of questionnaires were used to survey volunteer participants (N = 54). The group of experts remained stable (N = 41) for rounds 2 through 4. Findings from the survey indicated several areas of priorities for postanesthesia nursing. Of the top 10 ranked statements, 4 related to discharge criteria. Another high-priority area identified was pain management, with 5 statements pertaining to this subject being ranked in the top 10. Based on this small sample of postanesthesia nurses, this study provides a beginning step for prioritizing areas of research necessary to expand the body of knowledge for postanesthesia nursing.

Adult↗
PubMed1993

Periprandial regulation of lipid metabolism in insulin-treated diabetes mellitus.

We have examined the regulation of lipid and glucose metabolism in the postabsorptive and postprandial states in six subjects with insulin-treated diabetes mellitus, and compared them with eight nondiabetic subjects. Blood or plasma concentrations of metabolites and fluxes across forearm and subcutaneous adipose tissue were studied after an overnight fast and for 6 hours after a mixed meal (3.1 MJ, 41% from fat). In the postabsorptive state, regulation of lipid metabolism in the two groups appeared basically similar except that a wider spread of plasma (free) insulin concentrations in the diabetic group led to a wider range of values of plasma nonesterified fatty acid (NEFA) release from adipose tissue, plasma NEFA concentrations, and blood ketone body concentrations. Extraction of ketone bodies across adipose tissue was positively correlated with arterial concentration in both groups (as it was in the forearm), confirming the ability of human adipose tissue to utilize ketone bodies. A single subcutaneous injection of insulin before the meal in the diabetic group produced a plasma free-insulin profile that was blunted and prolonged compared with the postprandial response in the control group. Postprandial forearm glucose uptake followed very closely the plasma (free) insulin concentration. Postprandial suppression of NEFA release from adipose tissue was essentially normal in the diabetic group, and the normal postprandial decrease in plasma NEFA concentrations was reproduced extremely closely. Forearm and adipose tissue blood flow did not differ between the groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1993

Evidence of a dominant role for low osmolality in the efficacy of cereal based oral rehydration solutions: studies in a model of secretory diarrhoea.

Clinical trials suggest that including naturally occurring complex carbohydrate in oral rehydration solutions (ORS) in place of glucose increases water absorption and reduces stool volume during acute diarrhoea. The mechanisms for this greater clinical efficacy has not been established. This study examined the ability of two hypotonic rice based ORS, RS-ORS (137 mOsm/kg) and RP-ORS (143 mOsm/kg), and HYPO-ORS (240 mOsm/kg) a glucose equivalent ORS, to effect water absorption by in vivo perfusion of normal and secreting rat small intestine. The results were compared with those for two widely used conventional hypertonic ORS, WHO-ORS (331 mOsm/kg) and UK-ORS (310 mOsm/kg). In the normal intestine, water absorption was similar from WHO-ORS (87.4 (45.1-124.6) microliters/min/g; median and interquartile range) and UK-ORS (57.6 (41.5-87)) but less than from the hypotonic solutions (p < 0.02); water absorption from RS-ORS (181.8 (168.5-193.8)) and RP-ORS (195.7 (179.3-207.9)) was similar but less than from HYPO-ORS (241.3 (230.6-279.7); p < 0.005). In the secreting intestine, all ORS reversed net secretion of fluid to net absorption; the hypotonic solutions, HYPO-ORS (105.2 (95.2-111)), RS-ORS (127.7 (118.3-169.4)) and RP-ORS (133.7 (122.1-174.5)), produced more water absorption (p < 0.005) than the hypertonic solutions WHO-ORS (47.1 (29-75.9)) and UK-ORS (24.9 (18.4-29.4)). The rice based ions promoted most water absorption in secreting intestine (p < 0.007). These data indicate that low osmolality is of primary importance in mediating the increased water absorption from cereal based ORS.

Animals↗
PubMed1993

Initial response and subsequent course of Crohn's disease treated with elemental diet or prednisolone.

Elemental diet is as effective as corticosteroids in the treatment of previously untreated Crohn's disease. It is unclear whether a poor nutritional state is a prerequisite for efficacy of elemental diet, whether previously treated patients respond as well, or how duration of remission using elemental diet compares with corticosteroid induced remission. Forty two patients with active Crohn's disease were stratified for nutritional state and randomised to receive Vivonex TEN 2.1 l/day for four weeks, or 0.75 mg prednisolone/kg/day for two weeks and subsequent reducing doses. Nine of 22 (41%) patients assigned to nutritional treatment were intolerant of the diet. Thirty patients completed four weeks treatment. Disease activity decreased on elemental diet from mean (SEM) 4.8 (0.9) to 1.7 (0.6), p < 0.05, and on prednisolone from 5.3 (0.5) to 1.9 (0.6), p < 0.05. For each treatment, nourished and malnourished patients responded similarly. Patients with longstanding disease responded as well as newly diagnosed patients. The probability of maintaining remission at six months was 0.67 after prednisolone, 0.28 after elemental diet, and at one year was 0.35 after prednisolone and 0.09 after elemental diet, p < 0.05. When tolerated, elemental diet is as effective in the short term as prednisolone in newly and previously diagnosed Crohn's disease, and its benefit is independent of nutritional state. The subsequent relapse rate after elemental diet induced remission, however, is greater than after treatment with prednisolone.

Adolescent↗
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↗