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Biomedical subjects

A Vinik

Publications and source records attributed to A Vinik.

32 records · Page 2Linked to original sources
PubMed1982

Fluctuations in basal levels and effects of altered nutrition on plasma somatostatin.

Rapid oscillations in basal plasma levels of insulin, C-peptide, glucagon, and glucose in rhesus monkeys have been reported previously. We now report large minute-to-minute fluctuations in plasma somatostatinlike immunoreactivity (SLI) in undisturbed, chair-adapted, and chronically cannulated male rhesus monkeys. Plasma samples were drawn from eight monkeys at 1- to 2-min intervals for 30-40 min following an overnight fast. Large fluctuations in SLI levels with periods of 4.4-9.4 min/cycle and possibly secondary periods of 14-18 min/cycle with average amplitudes of +/- 23% relative to the respective mean SLI levels were observed both within a single experiment and across monkeys under basal conditions. No consistent relationship was found between SLI fluctuations and that of insulin or glucagon. When portal and central blood samples were drawn precisely simultaneously no consistent portal-central gradient was found. Patterns of fluctuations in central and portal SLI levels were not correlated. Overfeeding significantly increased insulin levels but did not alter SLI levels. After 5 days of food deprivation basal SLI levels were unchanged. These data indicate the need to exercise care in the interpretation of single samples in the measurement of plasma SLI levels. Somatostatin secreted into the blood under basal, unstimulated conditions appears to be unrelated to nutritional balance.

Animals↗
PubMed1981

Plasma pancreatic polypeptide and gastrin in the assessment of autonomic activity in acute myocardial infarction.

Measurements of plasma pancreatic polypeptide and gastrin are reported for the first time in patients with acute myocardial infarction and compared with clinical signs of vagal or sympathetic overactivity. Pancreatic polypeptide concentrations were assessed as an index of vagal activity, but elevated values of pancreatic polypeptide found in 7 of the 13 patients on admission did not correlate with clinical evidence of vagal overactivity. The mean pancreatic polypeptide concentrations were not higher in patients with clinical vagal overactivity than in patients with clinical sympathetic overactivity during the 12 h after the onset of symptoms of acute myocardial infarction. Mean gastrin levels were significantly higher on admission and at 4, 5, 6 and 8 h after the onset of infarction in the patients with clinical features of sympathetic overactivity than in the patients with clinical vagal overactivity. Thus plasma gastrin warrants further assessment as an index of sympathetic overactivity in acute myocardial infarction.

Adrenergic beta-Antagonists↗
PubMed1980

Insulin, glucagon and liver regeneration.

Partially hepatectomized rats receiving intragastric amino acids synthesize less DNA than similar rats receiving intragastric water alone. In the present study insulin and glucagon levels were measured in rats receiving amino acids or water alone. In both groups of rats insulin levels were depressed and glucagon levels elevated. These findings suggest that insulin and glucagon do not play a major role in the regulation of liver regeneration after partial hepatectomy in the rat.

Amino Acids↗
PubMed1977

The effects of TRH on prolactin, plasma renin activity, water and electrolyte excretion in normal males.

The effect of TRH induced secretion of TSH and prolactin (hPrl) on plasma renin activity (PRA), water and electrolyte excretion, was studied in 7 normal males before and after an intravenous injection of 2 ml normal saline or 200 microgram TRH. Plasma hPrl and TSH rose significantly (p less than 0.01) in all 7 subjects after TRH but not after saline injection. No significant differences in the hourly excretion of sodium, potassium and free water clearance were noted before and after either saline or TRH injection. Mean PRA values of the 7 subjects were similar after either the 2 ml saline of TRH injection. Our results indicate that despite a correlation between basal hPrl and sodium excretion as well as free water clearance, acute TRH induced elevation of hPrl is not associated with changes of urinary sodium and potassium excretion, free water clearance and PRA in normal males. These findings provide some evidence against a direct osmoregulatory role of hPrl in man.

Adult↗
PubMed1975

The effect of prolonged lithium carbonate administration on the thyrotrophin and prolactin response to thyrotrophin-releasing hormone.

Thyrotrophin (TSH) and prolactin (PRL) responses to intravenous thyrotrophin-releasing hormone (TRH) were measured in euthyroid patients suffering from psychiatric disease on long-term lithium carbonate (LC) and phenothiazine therapy. These responses were retested after oral tri-iodothyronine (T3) 120 mug/day had been given for a week. The raised basal TSH and the suppression of the exaggerated responses to TRH by T3 found in some of the patients suggest a mild disturbance of thyroid function in patients on long-term LC therapy, even in the face of clinical euthyroidism and otherwise normal thyroid function. Basal serum PRL levels and the responses to TRH were elevated in 2 of 5 patients, probably associated with phenothiazine administration. In all 5, a moderate blunting of the PRL responses after TRH was produced by T3. The suppressive effect of T3 on TRH-induced PRL responses was unexpected and suggests a modifying role of thyroid hormones on PRL secretion, although further studies are needed to confirm this possibility.

Female↗
PubMedDate not supplied

Factors controlling pancreatic islet neogenesis.

We have established a model in which cellophane wrapping induces reiteration of the normal ontogeny of beta-cell differentiation from ductal tissue. The secretion of insulin is physiologic and coordinated to the needs of the animal. Streptozotocin-induced diabetes in hamsters can be "cured" at least half the time. There appears to be activation of growth factor(s) within the pancreas, acting in an autocrine, paracrine, or juxtacrine manner to induce ductal cell proliferation and differentiation into functioning beta cells. Given the results of our studies to date, it does not seem premature to envisage new approaches to the treatment of diabetes mellitus. Identification of the factor(s) regulating islet-cell proliferation and differentiation in our model may permit islets to be grown in culture. This concept could be extended to induce endocrine cell differentiation in vitro as well. Furthermore, islet-cell growth factors could be used to provide "trophic support" to islet transplants as a means of maintaining graft viability. There may also be greater scope for gene therapy when the growth factor(s) have been isolated, purified, sequenced, and cloned.

Animals↗