Study of the characteristics of the inotropic effect of insulin in rabbit papillary muscle.

The effect of insulin was examined with emphasis on the alteration in the force-frequency relation. The results show that insulin does not change the time to peak tension nor the time of contraction. The inotropic effect was significant and did not depend upon the frequency of stimulation. However, there was a definite dependence of the magnitude of the inotropic effect on temperature. Previous studies have indicated that the inotropic effect is not a result of increased substrate availability or changes in cAMP phosphodiesterase activity. These results and those reported here are consistant with the hypothesis that insulin's inotropic effect is due to increases in intracellular Ca++.     

Influence of alpha-MSH and ACTH on cortical bone remodelling in hypophysectomized rats.

Hypophysectomy increases both periosteal resorption and endosteal apposition along the femur diaphysis in rat. Administration of alpha-MSH decreased the periosteal resorption but had no effect on the endosteal apposition. ACTH had only minor effects on the endosteum. Thus, alpha-MSH and ACTH, in the doses used, have different effects on cortical bone in rat. The effect of alpha-MSH on cortical bone could be an effect of the hormone alone or by its stimulation of other factors.     

Adenyl cyclase activity at different environmental temperatures in the isolated rat anterior pituitary membranes.

The effect of different environmental temperatures on adenyl cyclase was studied. An increase in temperature appears to increase TRH-induced activity of adenyl cyclase, and possible causes an increases sensitivity to the hormone. Cyclic AMP levels of the pituitaries showed change at different environmental temperatures.     

Effect of clofibrate on the phospholipid biosynthesis in rat liver.

The effect of clofibrate on rat liver phospholipid biosynthesis was studied using 32P as a precursor. Phospholipid classes, levels and specific radioactivity were evaluated. Significant increases in levels of phosphatidylethanolamine and phosphatidylcholine were found and could account for the observed increase in total phospholipids. Specific activity of phosphatidylserine increased and that of phosphatidylethanolamine decreased. This fact suggests that clofibrate seems to alter the systems engaged in the transformation occurring within the different classes of phospholipids but not the de novo biosynthesis.     

Effect of orotic acid on liver glycogen of different animal species.

The effect of orotic acid on the liver glycogen content in the mice, frogs and catfish was studied. It was observed that the orotic acid significantly increases the glycogen content in the liver of mice and catfish as it does in rats. On the other hand it causes a fall of the glycogen level in frogs in experiments made both in autumn and spring. This effect was modified by amino acids administered together with orotic acid.     

Corticosteroidogenesis by isolated human adrenal cells: effect of serotonin and serotonin antagonists.

The direct effect of serotonin and antiserotonin agents on adrenal steroid biosynthesis was studied in isolated adrenal cells derived from patients with Cushing's syndrome. The results indicate that serotonin increases corticosterone production, while the serotonin antagonists cyproheptadine and methysergide depress adrenal steroid - particularly cortisol and aldosterone - biosynthesis.     

Study of the characteristics of the inotropic effect of insulin in rabbit papillary muscle

Summary The effect of insulin was examined with emphasis on the alteration in the force-frequency relation. The results show that insulin does not change the time to peak tension nor the time of contraction. The inotropic effect was significant and did not depend upon the frequency of stimulation. However, there was a definite dependence of the magnitude of the inotropic effect on temperature. Previous studies have indicated that the inotropic effect is not a result of increased substrate availability or changes in cAMP phosphodiesterase activity. These results and those reported here are consistant with the hypothesis that insulin's inotropic effect is due to increases in intracellular Ca⁺⁺.This work was supported by a grant from the U. S. Public Health Service HL-02285.     

Serum and bile modifications in the guinea-pig following chronic treatment with PGE1 and PGE2.

PGE1 increases cholesterolemia without lipemia modifications. In bile there are not modifications in cholesterol levels and total lipids appear diminished. PGE2 raise the lipemia and have no effect in cholesterolemia, moreover bile cholesterol and total lipids exhibit no changes. Both PGE1 and PGE2 decreased the bile volume.     

Role of acoustic stress on the development of polyoma tumors in immunized golden hamsters]

An acoustic stress increases the metastatic spread of polyoma virus-induced tumors in syrian Hamsters. To try to elucidate the mechanism of this action, we studied the effect of stress on the protection afforded by the virus against tumour challenge. Exposure to ultrasonics during the immunization period markedly decreased the protective effect of the virus.     

Potentiation of ethanol narcosis by dopamine- and l-DOPA-based isoquinolines.

The isoquinolines, salsolinol and 3-carboxysalsolinol, prolong ethanol-induced narcosis in mice. Pretreatment with carbidopa increases the effect of 3-carboxysalsolinol but not of salsolinol. These results suggest that ethanol sleeping-time potentiation by l-LOPA may involve a partial conversion to the isoquinoline in vivo. A central depressant action of salsolinol or the 3-carboxy analogue is suggested.     

Evidence against the involvement of cyclic GMP in the insulin-stimulation of lipoprotein lipase activity in fat cells

Under in vitro experimental conditions in which insulin increases adipose tissue lipoprotein lipase, cyclic GMP or dibutyryl cyclic GMP has no effect on this enzyme in rat adipose tissue fragments, or on either the intra- or extracellular forms of this enzyme in isolated fat cells. These results do not support the involvement of cyclic GMP in the insulin-stimulation of lipoprotein lipase in adipose tissue.     

Effect of diet on the mitotic activity and rate of cytolysis of intestinal epithelial cells in tadpoles of the common toad, Bufo bufo (Amphibia, Anura)]

Effects of diet on the mitotic activity and cellular mortality rate of the intestinal epithelium cells have been examined in Toad tadpoles. As yolk is utilized, the composition of diet has little effect on these 2 parameters. As development goes on, the cellular mortality rate increases with dietary carbohydrate, fat or protein supplementation. But only the fats affect the mitotic activity.     

Pancreastatin (33–49) enhances the priming effect of glucose in the rat pancreas

Short-term exposure to glusoe increases insulin secretion during subsequent stimulation. We investigated the effect of the new regulatory peptide pancreastatin on this priming effect of glucose in the perfused rat pancreas. Pancreastatin (33–49) at a concentration of 10^–8 M inhibited insulin release when stimulated by glucose at a concentration of 16.7 mM. However, after a second pulse of 16.7 mM glucose, pancreastatin potentiated the priming effect of glucose on insulin secretion. The modulation of insulin secretion by pancreastatin results in a potentiation of the priming effect of glucose in the rat pancreas, suggesting a role for pancreastatin in the adaptation of the B cell to glucose-stimulated insulin secretion.     

The influence of ingested fluoride on the ascorbic acid concentration in guinea-pig tissues

Summary Fluoride added to drinking water at concentrations of 50 and 70 ppm provided highly significant increases in the ascorbic acid concentration in tissues but was without effect on the serum alkaline phosphatase and cholesterol.JEWD was supported by a Beecham Products grant.     

Phosphoramidon enhances allatostatin-mediated inhibition of juvenile hormone biosynthesis in the corpora allata of the cockroach, Diploptera punctata.

Use of enkephalinase inhibitor phosphoramidon in the in vitro radiochemical assay for juvenile hormone biosynthesis enhanced allatostatin-mediated inhibition of hormone production by corpora allata of the cockroach, Diploptera punctata. Significant increases in inhibition in day 2 virgin female CA by AST 1 (at 10(-7) M) and AST 4 (10(-8)-10(-7) M) were observed in the presence of phosphoramidon (10(-5) M or greater). No significant increase in inhibition were seen in CA from day 6 mated females with AST 4 (10(-9)-10(-7) M) and phosphoramidon combined. Phosphoramidon alone had no effect on JH biosynthesis. Analysis of allatostatin content of the CA, as determined by ELISA, revealed that addition of phosphoramidon to the medium increased the endogenous allatostatin content in CA of virgin and mated females. The similarity in primary structure between allatostatins and enkephalin-like peptides and their similar distribution makes it probable that phosphoramidon acts by preventing breakdown of allatostatins within the CA.     

High potassium intake increases the plasma concentration and urinary excretion of vasopressin in the rat

Summary The effect of alterations of dietary potassium intake on the plasma concentration and the urinary excretion of vasopressin was studied in male rats. Ingestion of a high potassium diet resulted in increases in the plasma concentrations of potassium and vasopressin, systolic blood pressure, urine flow, and urinary vasopressin excretion. Ingestion of a low potassium diet had little effect on the plasma vasopressin concentration and systolic blood pressure but caused decreases in the plasma potassium concentration and urinary vasopressin excretion. The results indicate that physiological changes in the plasma potassium concentration or some other consequence of altered dietary potassium intake can affect vasopressin release and excretion.     

High potassium intake increases the plasma concentration and urinary excretion of vasopressin in the rat

The effect of alterations of dietary potassium intake on the plasma concentration and the urinary excretion of vasopressin was studied in male rats. Ingestion of a high potassium diet resulted in increases in the plasma concentrations of potassium and vasopressin, systolic blood pressure, urine flow, and urinary vasopressin excretion. Ingestion of a low potassium diet had little effect on the plasma vasopressin concentration and systolic blood pressure but caused decreases in the plasma potassium concentration and urinary vasopressin excretion. The results indicate that physiological changes in the plasma potassium concentration or some other consequence of altered dietary potassium intake can affect vasopressin release and excretion.     

Single injections of triazolam, a short-acting benzodiazepine, lengthen the period of the circadian activity rhythm in golden hamsters

Single injections of the benzodiazepine, triazolam, induce phase shifts and cause a lengthening of the circadian activity rhythm in the golden hamster. The effect of triazolam on period depends on the phase of injection, but is not dependent on the direction of the phase shifts. Triazolam injections caused increases in period that were associated with phase advances as well as phase delays in the activity rhythm. This relationship between triazolam-induced phase shifts and changes in period is different from the relationship between light-induced phase shifts and period changes.     

Single injections of triazolam,a short-acting benzodiazepine,lengthen the period of the circadian activity rhythm in golden hamsters

Single injections of the benzodiazepine, triazolam, induce phase shifts and cause a lengthening of the circadian activity rhythm in the golden hamster. The effect of triazolam on period depends on the phase of injection, but is not dependent on the direction of the phase shifts. Triazolam injections caused increases in period that were associated with phase advances as well as phase delays in the activity rhythm. This relationship between triazolam-induced phase shifts and changes in period is different from the relationship between light-induced phase shifts and period changes.     

The adenohypophysial hormone content of the rat pars tuberalis.

The pars tuberalis of the hypophysis was shown to contain LH, which increases after castration, TSH and a very low amount of PRL. FSH was found after castration.