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Biomedical subjects

R Bressler

Publications and source records attributed to R Bressler.

At least 109 records · Page 6Linked to original sources
PubMed1971

The insulins.

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Diabetes Mellitus↗
PubMed1970

The in vitro inhibition of insulin secretion by diphenylhydantoin.

Glucose intolerance has been observed following diphenylhydantoin (DPH) intoxication. Because of this association between DPH and hyperglycemia, the effect of DPH on insulin release in vitro using preparations of isolated islets of Langerhans and pancreatic pieces was examined. In concentrations identical with those considered necessary for adequate anticonvulsant therapy in man, DPH markedly decreases the insulin secretory response of pancreatic pieces to methacholine, 1 mug/ml, tolbutamide, 250 mug/ml, and glucose, 200 mg/100 ml, without any demonstrable alteration in the oxidative conversion of glucose-1-(14)C or glucose-6-(14)C to (14)CO(2) by isolated islets. This DPH-induced inhibition of insulin secretion is not reversed by higher concentrations of glucose (600 mg/100 ml) or by increasing concentrations of extracellular calcium ion (4-6 mmoles/liter). 0.1 mM potassium and 10(-4) M ouabain, however, effectively restore the DPH-induced block of insulin secretion in pancreatic pieces. 60 mM potassium ion, on the other hand, not only restores the insulin secretory response to glucose (200 mg/100 ml) but results in an added stimulation of insulin secretion in the presence of DPH. In the presence of DPH, (22)Na accumulation by isolated islets is decreased by 26-40% as compared with controls. Such evidence is considered to indirectly support the postulate that the electrophysiological properties of DPH on the pancreas are due to a stimulation of the membrane sodium-potassium-magnesium ATPase.

Animals↗
PubMed1969

The influence of ouabain and alpha angelica lactone on calcium metabolism of dog cardiac microsomes.

The influence of ouabain and alpha angelica lactone on (45)calcium accumulation in cardiac microsomes was studied. Calcium binding (accumulation in the absence of excess oxalate or phosphate) was augmented by both ouabain and alpha angelica lactone in the presence of adenosine triphosphate (ATP) but unaffected in its absence. Calcium turnover (defined as the change in (45)Ca(++) bound to the microsomes after the specific activity is changed) was studied to determine if the augmented bound pool was freely exchangeable at equilibrium. Ouabain and alpha angelica lactone augmented calcium turnover in both the presence and absence of ATP. Calcium-stimulated ATPase was increased by both agents.It is proposed that these two unsaturated lactones, with known cardiotonic activity, may exert their effects by providing an increased contraction-dependent calcium pool to be released upon systolic depolarization.

Adenosine Triphosphatases↗