Search PubMed⌕ Search

Biomedical subjects

P Diamond

Publications and source records attributed to P Diamond.

At least 55 records · Page 3Linked to original sources
PubMed1988

Interaction between exercise training and cold acclimation in rats.

Five groups of 10 rats were used. Group A included sedentary rats kept at 24 degrees C, group B exercised-trained rats and group C rats exposed at -15 degrees C for 2 h every day and kept at 24 degrees C for the remaining time. These 3 groups were kept on this regimen for 10 weeks. In addition group D was acclimated to cold (2 h.d-1 at -15 degrees C) for 6 weeks and subsequently deacclimated at 24 degrees C for 4 weeks. Group E was also acclimated to cold for 6 weeks and during the deacclimation, at 24 degrees C period which lasted 4 weeks, the animals were exercised 2 h per day. Following the 10 week experimental period all animals were sacrificed and DNA and protein content of the IBAT as well as its total mass were measured. The results show significant increases in the cold adapted group. Exercise training which had no effect on brown adipose tissue IBAT at room temperature, caused an accelerated reduction in weight, DNA and protein content of the BAT in rats previously acclimated to cold. In spite of this, the thermogenic response to noradrenaline was significantly enhanced in the group which exercised during the deacclimation period. It is suggested that tissues other than IBAT may explain this enhanced heat production capacity.

Acclimatization↗
PubMed1988

A role for insulin in cephalic phase of postprandial thermogenesis in dogs.

The influence of insulin in the cephalic phase of postprandial thermogenesis was investigated in dogs. O2 consumption (VO2) and respiratory quotient (RQ) were continuously monitored 1 h before and 2 h after a 1,015-kcal meal during a control, an atropine, or a pancreatic-denervation experiment. A first phase (cephalic phase) in VO2 increase, lasting at least 50 min, followed by a second phase (digestive phase) were found in the control experiment. During both the atropine and pancreatic-denervation experiment, the first phase of VO2 was inhibited by 52%. The second phase was completely abolished with atropine, whereas it remained comparable to the control in the case of pancreatic denervation. A peak increase for insulin (70 microU/ml over 0 time) was observed 2 min after the onset of feeding in control. It was followed after 25 min by a second increase related to changes in glycemia. Maximal rises of norepinephrine (NE) and epinephrine corresponded to 215 and 120 pg/ml above basal values at 2 min in control experiment. During both atropine and pancreatic denervation the cephalic phase of insulin release was suppressed and the NE increase was inhibited by congruent to 65%. During the digestive phase pancreatic denervation caused an increase in plasma insulin comparable to that of the control, whereas atropine produced no such effect. It is suggested that the cephalic phase of postprandial thermogenesis is mediated through a causal relationship between insulin and NE release.

Animals↗
PubMed1987

Metabolic and hormonal responses to long-distance swimming in cold water.

The acute effects of long-distance swimming in cold water on selected hormonal and metabolic variables were evaluated on 22 long-distance swimmers (16 males and 6 females) during a 32-km swimming competition (La Traversée Internationale du Lac St-Jean). The water temperature was 18.5 degrees C and the mean performance times were 8 h and 32 min for men (M) and 9 h and 1 min for women (F). The blood samples were withdrawn in the fasting state during the week preceding the event and within 30 min after completion of the race. A positive correlation was obtained, for both groups, between percent body fat and rectal temperature measured at the end of the competition. After the competition, an increase in plasma epinephrine, norepinephrine, cortisol, thyroxine, free fatty acids, lactate, a decrease in glucose and insulin and no change in growth hormone, triiodothyronine, triglycerides, and cholesterol concentrations were observed in both groups. The increase in plasma thyroxine was more pronounced in the slower swimmers while the change in blood cortisol concentrations was higher in the subjects having the most acute decrease in body temperature. Male and female swimmers have a similar metabolic and hormonal response to a long-distance swimming competition in cold water.

Adolescent↗
PubMed1987

Role of autonomic nervous system in postprandial thermogenesis in dogs.

Two phases in postprandial thermogenesis have been recently identified in dogs; an initial cephalic phase lasting 45 min and a subsequent digestive phase occurring after 45 min. The objective of this study was to determine the role of the autonomic nervous system during these two phases in dogs. O2 uptake (VO2) as well as respiratory quotient (RQ) were monitored at least 1 h before and 2 h after a meal of 1,034 kcal under the following infusion conditions: saline, propranolol, atropine, propranolol plus atropine, phenoxybenzamine, and propranolol plus phenoxybenzamine. The initial peak value for VO2 increase was 100% in the cephalic phase and 40% in the digestive phase during the saline infusion. The VO2 response during the initial phase was 58 and 56% less with propranolol and atropine, respectively, compared with the control experiment. A 36% decrease in the VO2 response was found during the digestive phase with propranolol, whereas it was abolished by atropine. Propranolol and atropine given together decreased the VO2 response during the cephalic phase by 27% and abolished it completely in the digestive phase. Phenoxybenzamine did not affect the VO2 or RQ responses during the whole period and when given in combination with propranolol the same result as propranolol alone was found. These findings indicate that both the parasympathetic and sympathetic nervous system participate in the control of postprandial thermogenesis during both the cephalic and digestive phases.

Animals↗
PubMed1987

Hormonal control of postprandial thermogenesis in dogs.

The role of catecholamines, insulin, and thyroid hormones on postprandial thermogenesis was determined in dogs. O2 consumption (VO2) and respiratory quotient (RQ) were continuously monitored 1 h before and 2 h after a 1,016-kcal meal under the three following experimental conditions corresponding to 1) normal feeding, 2) sham feeding (with food deflected into an esophageal pouch), and 3) tube feeding intragastrically. A first phase (cephalic phase), lasting at least 45 min, was observed during both normal and sham feeding, whereas a second phase (digestive phase), occurred in both normal and tube feeding. Increases of 260% for norepinephrine (NE) were found during the cephalic phase in both normal and sham feeding. Epinephrine (E) increased by 425 and 600% during this early phase in normal and sham feeding, respectively. No change in plasma catecholamines was found in the tube-feeding experiment. Large increases of 75 and 39 microU/ml of insulin occurred early after the meal in both normal and sham feeding, whereas insulin increased only after 30 min in tube feeding. Thyroxine and triiodothyronine were not changed with any feeding experiment. Insulin change was positively correlated with NE and E changes rather than with glucose change during the cephalic phase after feeding. The results suggest an important role of catecholamines in the increased postprandial thermogenesis during the cephalic phase with a possible modulating effect of insulin.

Animals↗
PubMed1986

Effects of indomethacin on coronary hemodynamics, myocardial metabolism and anginal threshold in coronary artery disease.

The effects of orally administered indomethacin or placebo on coronary hemodynamics were studied in 23 patients with coronary artery disease. After indomethacin administration the systemic arterial pressure increased by 12 +/- 4% and the myocardial oxygen consumption by 24 +/- 11%. Coronary sinus flow did not change and coronary vascular resistance increased slightly. Oxygen saturation of the arterial blood did not change, but coronary sinus saturation decreased substantially. Hemodynamic values returned to normal 150 minutes after administration of indomethacin. During rapid atrial pacing, coronary sinus flow increased 79 +/- 14% above the rest value when pacing was done before indomethacin administration; only a 56 +/- 12% increase was seen when pacing was repeated after indomethacin. Peak heart rate achieved during atrial pacing, severity of angina and the degree of ST-segment depression were not altered by indomethacin treatment. Orally administered indomethacin has a mild coronary vasoconstrictive effect that does not interfere substantially with the expected increase in myocardial blood flow during rapid atrial pacing. Anginal threshold is not altered by orally administered indomethacin.

Administration, Oral↗
PubMed1986

Reproducibility of plasma catecholamine concentrations at rest and during exercise in man.

The purpose of this study was to test the reproducibility of plasma norepinephrine (NE) and epinephrine (E) concentrations, at rest and during exercise, in man. Twelve young men were evaluated on two occasions (one week apart) at rest in supine and sitting positions and during dynamic exercise on bicycle ergometer: 5 min at a low intensity workload (heart rate = 131-133 bt min-1) and 5 and 20 min at a higher intensity (174-175 bt min-1). Mean plasma NE and E concentrations were not significantly different (p less than 0.05) on the two occasions in any of the experimental situations. However large within-subject variations were present, and the "standard errors of a single measurement" corrected for the variability of the catecholamine assay, ranged from 14 to 50% for NE and 14 to 37% for E. These results indicate that the mean plasma NE and E concentrations observed in a group of subjects are reproducible from one week to the other, but that individual plasma NE and E concentrations are not. This lack of reliability of a single determination of plasma catecholamine concentrations might be due to cyclic variations of plasma NE and E concentrations over time.

Adult↗
PubMed1986

Thermogenesis in response to various intakes of palatable food.

Complete energy balance studies were made on groups of overfed (A) and underfed (B) Wistar rats. In experiment A one group was fed cafeteria diet ad libitum (the intake was 29% larger than the control), two other groups were fed the same diet but in restricted quantities (18 and 9% above control), and a fourth group, fed a stock diet, served as control. In experiment B, caloric intake was restricted by 12 and 31% in two groups fed cafeteria diet, and by 21 and 34% in two other groups fed stock diet. The experiments lasted 41 days and during that period the protein gain was comparable between the control and the cafeteria-29% group (643.4 +/- 33.3 vs. 578.1 +/- 25.0) but the fat gain was significantly different between the two groups (863.2 +/- 81.6 vs. 1663.2 +/- 99.8 kJ). When energy expenditure (EE) (metabolizable energy less storage added to the cost of storage) is expressed as a percentage of metabolizable energy (ME) intake no significant difference was found among the groups. The average value was congruent to 75%. This finding would not support the presence of dietary-induced thermogenesis in animals overfed on the cafeteria diet. However, since the obligatory cost associated with storing energy would not explain the higher EE of the overfed groups, it is suggested that the level of ME intake exerts continuous proportional regulatory action on EE and, as a result, energy is spared by underfeeding and it is wasted by overfeeding.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue, Brown↗
PubMed1986

Effect of meal size and frequency on postprandial thermogenesis in dogs.

The influence of meal size and frequency on postprandial thermogenesis was studied in nine mongrel dogs (congruent to 18 kg). Oxygen uptake (VO2) and respiratory quotient (R) were continuously monitored by indirect calorimetry during the following experiments. In expt 1, four dogs were fed on alternated days either a large (3.1 MJ) or small meal (0.77 MJ). In expt 2, five different dogs were fed on alternated days either one large meal (3.1 MJ) or four consecutive small meals (0.77 MJ) spaced at 1.5-h intervals. In expt 3, the four dogs of expt 1 after being sham fed 3 times at 1.5-h intervals were given one large meal (3.1 MJ). The VO2 increase during the initial or cephalic phase (congruent to 50 min) was independent of the meal size but it was directly proportional to the amount of food ingested during the digestive phase. The total thermogenic response to four small meals (125 g) fed at 1.5-h intervals was twice as large as that of one large meal (500 g). One large meal (500 g) preceded by three periods of sham feeding was also found to be more thermogenic than a large meal only. For all experiments the changes in R were seen to parallel the postprandial fluctuations in VO2. These findings indicate that the enhanced heat production obtained when meal frequency is increased is caused by the repeated sensory stimulation produced by palatable food.

Absorption↗
PubMed1986

Million Behavioral Health Inventory: its utility in predicting physical function in patients with low back pain.

The present study evaluated the use of psychologic measures, in particular, the relatively new Million Behavioral Health Inventory (MBHI), in predicting change in physical function of chronic low back pain patients undergoing a functional restoration program. The first 134 consecutive patients completing this program were assessed. Results demonstrated that various clinical scales of the MBHI were predictive of improvement in physical function. In addition, various scales enabled discrimination between patients who completed the program and those who prematurely dropped out. Although this inventory shows promise in helping to predict response to treatment, no single psychologic test can reliably be used as the sole predictor in clinical cases.

Adult↗
PubMed1985

Inhibition of mating by naloxone or morphine in recently castrated, but not intact male rats.

Administration of naloxone (SC 5 mg/kg) significantly reduced ejaculation and mounting in male rats in the weeks following castration. A similar effect was obtained by injecting morphine (SC 1 or 5 mg/kg). In contrast, the same dosages of naloxone or morphine did not affect the sexual performance of gonadally intact males. Opioid peptides may contribute to the temporary persistence of sexual behavior in testosterone-deficient male mammals, in which incentive qualities of the female partner are an important determinant of sexual arousal.

Animals↗
PubMed1985

Palatability and postprandial thermogenesis in dogs.

The role of palatability on postprandial thermogenesis was determined in six mongrel dogs of approximately 16 kg. Oxygen uptake (VO2) was continuously monitored by indirect calorimetry for 1 h before and 2 h after a standard meal of 1,390 kcal. In the first experiment each dog was given access to the meal, which was ingested within 5 min. In a second experiment the same meal was sham fed and collected into an esophageal pouch. In a third experiment the dogs were tube fed. In the first experiment a biphasic response was found in the postprandial increase in metabolic rate; a first phase lasting approximately 40 min and the other from 40 to 125 min. In the second experiment the increase in VO2 was comparable with that of the first experiment for the first 40 min but almost abolished for the remaining period; the sight and smell of food alone produced a similar effect. In the third experiment tube feeding caused a small increase in VO2, which was four times smaller than that found in both the first and the second experiment during the initial phase. However, during the second phase the increase in VO2 was comparable with that of experiment 1. An initial phase of feeding lasting approximately 40 min is identified with food palatability, whereas the second phase would correspond to a large extent to specific dynamic action of food.

Animals↗
PubMed1984

Hormonal factors in reduced postprandial heat production of exercise-trained subjects.

The influence of exercise training on postprandial heat production was investigated in human subjects. Whereas resting metabolic rate was comparable for trained and nontrained subjects, the heat increment of feeding (HIF) after subjects consumed a meal containing 755 kcal was approximately 50% smaller in the trained subjects. Measurements of respiratory quotient also indicated a reduction of about 50% in glucose oxidation associated with exercise training. The levels of plasma norepinephrine increased significantly (P less than 0.01) from 200 to 300 pg/ml in the sedentary subjects, but the changes observed in trained subjects were not significant. During the early phase of the meal, plasma levels of insulin were increased, even before nutrients appeared in the blood. Throughout the study the enhanced sensitivity to insulin of the trained subjects was confirmed. the postprandial heat production was diminished in exercise-trained subjects, and it is suggested that this could be related to a reduced activity of the sympathetic nervous system. Another possibility is that this reduction in HIF is related to a facilitation of glucose disposal in the form of glycogen rather than in the form of lipids.

Adult↗