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Biomedical subjects

L Sacca

Publications and source records attributed to L Sacca.

26 records · Page 2Linked to original sources
PubMed1978

Hyperglycemia inhibits glucose production in man independent of changes in glucoregulatory hormones.

To evaluate the influence of hyperglycemia on hepatic glucose output in the absence of a rise in insulin, glucose was infused for 2 hours into six juvenile-onset diabetics receiving a constant infusion of insulin at a rate of 0.05-0.15 microM kg-1min-1. Prior to the infusion of glucose, insulin administration resulted in stable levels of plasma glucose (76 +/- 8 mg/dl) and glucose output (1.9 +/- 0.1 mg kg-1min-1). The addition of glucose produced a 2-3 fold rise in plasma glucose and a prompt fall in glucose output to 0.2-0.4 mg kg-1min-1, despite the unchanged rate of insulin infusion and the absence of a reduction in plasma glucagon or catecholamines. A similar decline in glucose output was observed when exogenous glucagon (1 ng kg-1-min-1) was added to the glucose infusion. We conclude that in the presence of basal insulin levels hyperglycemia inhibits glucose output independent of a rise in insulin or a fall in anti-insulin hormones.

Adult↗
PubMed1977

Histamine mediation in muscular vasodilatation induced by beta adrenoceptor stimulation in dogs.

This study was designed to investigate the possibility of a histamine mediation in muscular vasodilation induced by beta adrenoceptor stimulation. Accordingly, in seven dogs the effects of isoproterenol administration on the release of 14C-histamine from the perfused gracilis muscle were studied. Beta adrenoceptors stimulation induced a vasodilatation, as shown by a decrease in perfusion pressure(-43 +/- 12 mm Hg); simultaneously, a significant increase of the radioactivity measured in the venous blood effluent from the gracilis muscle was observed. Both these events were blocked by propranolol. In the other five dogs, chlorpheniramine was able to reduce the vasodilatation induced by the injection in the gracilis muscle of isoproterenol. Under control conditions, isoproterenol induced a fall in perfusion pressure of 44 +/- 5 mm Hg while, after chlorpheniramine, perfusion pressure decreased by only 24 +/- 4 mm Hg. The results of this study seem to confirm the possibility of a histamine mediation in isoproterenol-induced vasodilatation. However, further investigation is needed in order to identify the exact role of histamine in the geneis of this phenomenon.

Animals↗
PubMed1976

Participation of beta receptors in reflex vasodilatation in the dog.

The effects of propranolol, given by direct intraarterial injection, on the reflex vasodilatation induced in the atropinized isolated gracilis muscle by rapid intravenous administration of norepinephrine, were studied in dogs. In these studies, both atropine and atropine plus propranolol did not significantly alter the maximum fall in vascular resistance in the perfused gracilis muscle following intravenous norepinephrine; however, if the reflex responses were evaluated as integrated areas of vasodilatation, atropine attenuated the vasodilatation and the administration of propranolol further attenuated the reflex. In fact, the value of the integrated areas of vasodilatation was 52.8 +/- 9 mmHg/min in the basal state, 39 +/- 6 mmHg/min after administration of atropine, and 24 +/- 7 mmHg/min after propranolol, whereas the integrated areas of the systemic hypertension did not show any modification. These results prompt us to conclude that the adrenergic beta receptors participate in the reflex vasodilatation, although the mechanism of their action needs further elucidation.

Animals↗
PubMed1975

Effects of theophylline on glucose kinetics in normal and sympathectomized rats.

The influence of intraperitoneal administration of aminophylline on the rate of hepatic glucose production and peripheral uptake (Ra and Rd) was studied in normal and in adrenodemedullated and reserpinized rats by using the primed constant infusion of Glucose-2-3H. In normal rats, the dose of 100 mg. per kilogram of aminophylline produced a marked increase of Ra and Rd. Since Ra rose more rapidly than Rd did initially, hyperglycemia developed. Thereafter, glucose production and uptake increased to nearly the same extent, and a new steady state was reached at plasma glucose levels almost twice those of the baseline. Smaller and transient modifications were observed after the administration of 20 mg. per kilogram of aminophylline. With the higher dose, insulin levels markedly rose (reaching a tenfold peak above the basal value) while minor increments were observed with the lower dose. In a group of normal rats which were given glucose (10 mg. per kilogram per minute) in order to achieve a degree of hyperglycemia comparable to that brought about by the higher dose of aminophylline, an almost identical enhancement of glucose uptake was recorded. However, insulin levels were much higher in aminophylline-treated rats as compared to normal rats. From these finding it was concluded that aminophylline induces resistance to insulin effect. When aminophylline was injected into demedullated rats pretreated with reserpine, at the dose of 100 mg. per kilogram, a marked enhancement of Ra, and consequently of glycemia, was recorded initially; later, severe hypoglycemia developed depending on both a progressive exhaustion of hepatic glucose production and a marked increase of glucose utilization. Insulin levels dramatically increased in these experiments. These results suggest that aminophylline directly increases glucose production by the liver and insulin secretion. The simultaneous activation of the sympathetic system blunts the insulin response and counteracts the restraining effect of insulin on the liver and the stimulatory effect of insulin on overall glucose uptake as well.

Adrenal Medulla↗
PubMedDate not supplied

Inverted response of arginine vasopressin to postural change in patients with essential hypertension.

1. This study was designed to compare the response of plasma arginine vasopressin (AVP) to head-up tilt in hypertensive patients and in normals. 2. As expected, plasma AVP showed a consistent increase (P less than 0.005) in normal subjects after tilt while plasma volume decreased significantly (P less than 0.02). On the contrary, in hypertensive patients, after tilt both plasma AVP (P less than 0.025) and plasma volume (P less than 0.05) decreased. 3. These findings, thus, indicate that essential hypertension is characterized by an inverted response of arginine vasopressin to postural change.

Adolescent↗