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Biomedical subjects

M Vigas

Publications and source records attributed to M Vigas.

At least 91 records · Page 5Linked to original sources
PubMed1985

Endocrine response to acute changes of brain blood flow due to lower body negative pressure in man.

The decrease of brain flow due to lower body negative pressure (LBNP) was used to study the role of cerebral glucopenia in the activation of anterior pituitary function in 10 young healthy men. During LBNP with a maximum negative pressure of--50 mm Hg the changes in heart rate, blood pressure cerebral blood flow (with the aid of rheoencephalography) and electrocardiogram were recorded and the levels of hGH, ACTH, hPRL, insulin and cortisol were measured with the aid of radioimmunoassay. During the first investigation an infusion of 20% glucose (1 g per min for first 30 min and 0.5 g per min for next 30 min) was used, while during the second investigation (one week later) the infusion of saline was applied. It was found that the infusion of glucose prevented the increase of hGH which was observed only during the infusion of saline. No differences in the level of ACTH, cortisol and hPRL were observed between the investigations with glucose and saline infusion. The increased level of insulin was related to the level of glucose during the infusion, while no changes were found during saline infusion. It was suggested that the increase of hGH level during LBNP resulted from glucopenia in cerebral tissue.

Adrenocorticotropic Hormone↗
PubMed1985

Effect of growth hormone on the activity of some lysosomal enzymes in neutrophilic polymorphonuclear leukocytes of hypopituitary dwarfs.

Elevated activities of beta-D-glucuronidase, myeloperoxidase, and lysozyme were found in polymorphonuclear leukocytes (PMNs) of both hypopituitary dwarfs and normal subjects after the administration of growth hormone (GH), as compared to the activities in PMNs from blood drawn immediately before the administration of GH. During in vitro incubation, GH was able to inhibit the release of lysosomal enzymes from resting PMNs. This inhibition may be one of the reasons for the elevated lysosomal enzyme activities observed in PMNs after the administration of GH. GH can also affect hexose monophosphate shunt (HMPS) activity and superoxide production by PMNs. The activity of HMPS is stimulated by GH in resting PMNs, while in PMNs incubated with zymosan the GH inhibits both HMPS and superoxide production.

Adolescent↗
PubMed1985

C-peptide-like material in rat brain: response to fasting and glucose ingestion.

Because of controversial data on the presence of insulin in the central nervous system, the presence of C-peptide immunoreactivity was followed in acid/ethanol extracts of the rat brain. C-peptide-like material was detected in whole brain extracts as well as in several brain fragments. Immunoreactive C-peptide concentrations were significantly higher in hypothalamus and olfactory bulb as compared to those in other brain regions sampled. Fasting for 72 h resulted in a decrease and oral glucose administration (0.75-1.5 g given in form of 25% water solution 30 min before sacrifice) was followed by an increase of C-peptide-like immunoreactivity in both plasma and hypothalamus.

Animals↗
PubMed1985

Impaired glucose utilization in man during acute exposure to environmental heat.

In 6 healthy males the oral glucose tolerance test (OGTT) was performed after the administration of 100 g glucose during the hyperthermic Finnish sauna bath (85 degrees C) of 30 min duration. The lowered insulin response (P less than 0.001) to glucose challenge during heating and the subsequent prolonged hyperglycemia (P less than 0.001) after heating were observed, when compared to OGTT under thermoneutral conditions (23 degrees C). It is suggested that the heat-induced decrease in visceral blood flow and stimulation of sympathoadrenomedullary and pituitary activity may be responsible for this effect.

Baths↗
PubMed1984

The effects of open heart surgery on growth hormone, cortisol and insulin levels in man. Hormone levels during open heart surgery.

Plasma growth hormone, cortisol, insulin and blood glucose concentrations were measured intra- and postoperatively in ten patients who underwent open heart surgery with moderate hypothermia. Diazepam-ketamine anaesthesia for 10-20 min failed to precipitate any significant alterations in the levels of measured hormones and blood glucose. In the pre-bypass period of surgery, an increase in cortisol and a slight elevation in growth hormone levels was observed; insulin level showed no change in spite of marked hyperglycaemia. The bypass period, including hypothermia and haemodilution, was accompanied by unchanged cortisol and elevated growth hormone levels, while insulin demonstrated a slight rise which did not correspond with the degree of hyperglycaemia. The post-bypass period with rewarming the restoring spontaneous circulation was characterized by further marked increase in cortisol and growth hormone levels and, in spite of decreasing levels of blood glucose, by a paradoxical elevation in plasma insulin. It is suggested that hypothermia, haemodilution, reduced tissue perfusion affecting endocrine glands, as well as denaturation of some hormones in the oxygenator, participate in the moderate endocrine response, disproportionate to the stress of cardiopulmonary bypass surgery. The rise in hormone levels on terminating bypass seems to be dependent on the improved blood flow to endocrine glands due to recovered spontaneous circulation, rewarming and, as for insulin, presumably even on the reduced inhibitory effect of catecholamines.

Adolescent↗
PubMed1984

In vitro study of hormone degradation by heart-lung machine with bubble oxygenator.

In the present experiment with heart-lung machine set in a closed system in vitro, the blood containing increased levels of hormones was circulated at 30 degrees C for 90 min and at 37 degrees C for 30 min; a fraction of the priming perfusate was studied in parallel at the same temperatures in an incubator. The level of growth hormone decreased gradually to a mean of 76% at 30 degrees C and no further decrease was found at 37 degrees C. The mean insulin level fell within 30 min to 32% and no substantial further changes were observed during the remaining period of study; re-warming failed to produce significant additional changes. Cortisol did not change appreciably. However, the oxygenator altered the level of catecholamines markedly. At 30 degrees C the initial level of noradrenaline fell precipitously to 9% within 30 min and this excessively low level was sustained throughout the study. Adrenaline showed even more pronounced changes. Denaturation of dopamine was less marked falling to about 70% within 30 min. The present experiment revealed that the levels of hormones respond differently to artificial oxygenation during extracorporeal circulation. Cortisol resisted degradation by the oxygenator, while growth hormone and insulin were denatured significantly. The moderate degradation of growth hormone by the machine may not play an important role during open heart surgery. However, a marked oxidation denaturation of catecholamines by 90% and 70% and denaturation of insulin by 70%, might prove relevant during surgery.

Catecholamines↗
PubMed1984

TSH response to 30 min stay in sauna in the morning and during evening hours.

The response of plasma TSH to 30 min stay in sauna was compared in the morning and in the evening. Both in the morning and in the evening plasma TSH was significantly elevated after sauna, with more prolonged response in the evening. This difference resembles the different reactivity of TSH to exogenous TRH administration in various times of day.

Adult↗
PubMed1984

Role of alpha 1- and alpha 2-adrenergic receptors in the growth hormone and prolactin response to insulin-induced hypoglycemia in man.

The effects of intravenous infusion of the nonselective alpha-adrenergic antagonist phentolamine or of the selective alpha 2-adrenergic antagonist yohimbine on growth hormone (GH), prolactin (PRL) and cortisol secretion during insulin-induced hypoglycemia were studied in 11 healthy young men. The GH response was blunted following each antagonist used, PRL secretion was higher after yohimbine and diminished after phentolamine when compared to controls. The plasma cortisol response was not influenced by either compound. In another series of experiments no effect of an oral administration of prazosin, a selective alpha 1-adrenergic antagonist, on the secretion of GH, PRL and cortisol was found in any of 7 subjects. Prazosin inhibited blood pressure increase during hypoglycemia and induced slight drowsiness and fatigue in the subjects. It is concluded that in man alpha-adrenergic stimulation of GH secretion during hypoglycemia is transmitted via alpha 2-receptors, PRL secretion is mediated via alpha 1-receptors, whereas inhibition of PRL release is mediated via alpha 2-receptors. In this experiment no effect of alpha 1- or alpha 2-blockade on cortisol response to hypoglycemia was seen.

Adult↗
PubMed1984

Response of prolactin, growth hormone and corticosterone secretion to morphine administration or stress exposure in Wistar-AVN and Long Evans rats.

The effect of exposition to novel environment or of morphine administration on the release of prolactin, growth hormone and corticosterone by rats of a strain exhibiting high sensitivity to acoustic epileptogenic stimulus (Wistar-AVN) was compared to that of normally sensitive rats of the Long Evans strain. Novelty stress for 15 min resulted in an enhanced prolactin secretion in Long Evans rats only, whereas morphine administration (6 mg kg-1) increased plasma prolactin levels in both strains, the response of the Long Evans animals being significantly higher. The stress-induced inhibition of growth hormone was observed in Long Evans rats only, whereas the morphine stimulated plasma growth hormone increase was observed in animals of both strains. In stress, the corticosterone release was significantly more pronounced in Long Evans than in Wistar-AVN rats. After morphine administration no significant enhancement of corticosterone release was observed in either strain, but in the Long Evans animals the post-morphine values were significantly higher than in the Wistar-AVN rats. The results show a weaker endocrine activation in Wistar-AVN than in Long Evans rats and suggest different neuroendocrine responsiveness of the animals of these strains to exogenous stimuli.

Animals↗
PubMed1984

Endocrine response to physical efforts with equivalent total work loads but different intensities in man.

The purpose of this study was to determine relationships between some exercise-induced neurohormonal changes and either exercise intensity, or its duration, or the total work output. Plasma catecholamine, cortisol, growth hormone and insulin concentrations were measured in healthy male subjects having performed three bicycle-ergometer exercise tests of the same total work output (2160 J kg-1) but differing in intensity and duration. The results showed that during the relatively short exercise plasma noradrenaline, adrenaline and cortisol responses depend more on work intensity than on the total work output. No relationship was demonstrated between the exercise-induced increases in plasma growth hormone concentration and work intensity or its duration, while the plasma insulin concentration was more decreased during the effort of lower intensity, but longer duration than during a short exercise of high intensity.

Adult↗
PubMed1983

Greater serum GH response to arm than to leg exercise performed at equivalent oxygen uptake.

The aim of this study was to provide information concerning the mechanism of exercise-induced stimulation of growth hormone (GH) release in human subjects. For this reason serum GH as well as some hemodynamic variables and blood concentrations of noradrenaline (NA), insulin (IRI), lactate (LA), glucose (BG), and free fatty acids (FFA) were determined in seven healthy male subjects exercising on a bicycle ergometer with arms or legs and running on a treadmill at equivalent oxygen consumption levels. Significantly greater increases in serum GH concentration accompanied arm exercises than those observed during the leg exercises. This was accompanied by greater increases in heart rate, blood pressure, and plasma NA and blood lactate concentrations. Serum IRI decreased during both leg exercises and did not change during the arm exercise. There were no differences in BG and plasma FFA concentrations between the three types of exercise. The role of humoral and neural signals responsible for the greater GH response to arm exercise is discussed. The findings are consistent with the hypothesis that neural afferent signals sent by muscle "metabolic receptors" participate in the activation of GH release during physical exercise. It seems likely that the stimulation of these chemoreceptors is more pronounced when smaller muscle groups are engaged at a given work load. However, a contribution of efferent impulses derived from the brain motor centres to the control system of GH secretion during exercise is also possible.

Adult↗