56 research outputs found
Recommended from our members
MSH Activity in Plasma and Pituitaries of Rats with Large Hypothalamic Lesions
The effect of medial basal hypothalamic lesions on plasma and pituitary melanocyte-stimulating hormone (MSH) was determined in albino rats. 32 days postoperatively, plasma levels of MSH were elevated (p < 0.05) in female rats, whereas pituitary MSH activity was the same as in controls. Male rats also demonstrated elevated plasma MSH levels (p < 0.05) when measured 23 days postoperatively. Histological evaluation of pituitaries from these animals revealed no changes in the intermediate lobe. These data suggest that MSH release from the pituitary of the albino rat is inhibited by central neural factors
Recommended from our members
Use of the Mouse Vas deferens Assay to Evaluate the Action of Somatostatin Peptides on Gastric Acid Secretion
Six closely related analogues of somatostatin were tested for their ability to inhibit electrically induced contractions of the mouse vas deferens. Their inhibiting activities tended to parallel their reported effects on gastric acid secretion in vivo, while no correlation to their in vitro growth hormone release-inhibiting activities was observed. It is suggested that information derived from the vas deferens assay may provide a relatively rapid and inexpensive assessment of the effects of somatostatin analogues on gastric acid secretion. The vas deferens assay was also used to test several somatostatin analogues for antagonistic activity, which was not found
Recommended from our members
Distribution, Half-Life, and Excretion of 14C- and 3H-Labeled L-Prolyl-L-Leucyl-GIycinamide in the Rat
H-Pro-Leu-Gly-NH2, a potentinhibitor of melanocyte stimulating hormone (MSH) release [MSH-release inhibiting factor (MIF)], was labeled with 14C-leucine or 3H-proline and injected i.v. into rats. H-Pro-14C-Leu-Gly-NH2 was found to have a half-life of approximately 9 min and to be distributed in a space greater than that of the plasma volume. Relatively little radioactivity and no intact H-Pro-Leu-Gly-NH2 could be found in the urine 1 h after administration. 3H- and 14C-labeled-H-Pro-Leu-Gly-NH2 accumulated in the pineal, pituitary, kidney, liver, and adrenals; the elevated tissue to plasma ratio in the pineal, along with the identification of unchanged H-Pro-Leu-Gly-NH2 there, suggests the possibility of a direct influence of the hypothalamus upon the pineal gland
Recommended from our members
Effect of Septal Lesions on Plasma Levels of MSH, Corticosterone, GH and Prolactin Before and After Exposure to Novel Environment: Role of MSH in the Septal Syndrome
Recommended from our members
Delayed Disappearance of 14C-Labeled-Pro-Leu-Gly-NH2 from the Blood of Hypophysectomized Rats
The disappearance of radioactivity after the injection of 14C-labeled-Pro-Leu-Gly-NH2, an MSH release-inhibiting factor (MIF-I), was measured in rats which had been subjected to various procedures. Delayed disappearance of the radioactivity to a small but statistically highly significant extent was found in hypophysectomized rats compared to rats with an intact pituitary. Pinealectomy and adrenalectomy did not change the half-time disappearance. Dehydration, hypothalamic destruction, or administration of excess saline, MSH, and large amounts of unlabeled MIF-I were all used as control procedures. These failed to demonstrate the mechanism by which the prolonged disappearance occurred, but did raise other questions. The half-time disappearance of tritiated inulin was not significantly different in hypophysectomized or intact rats. The results indicate that the absence of the pituitary gland prolongs the half-time disappearance of radioactivity from the blood of rats injected with labeled MIF-I
Recommended from our members
Activity and specificity of synthetic thyrotropin-releasing hormone in man
The serum levels of thyrotropin (TSH) increased two minutes after a quick single iv. injection of 800 μg of synthetic thyrotropin releasing hormone (TRH) into a normal male subject. The peak elevation of TSH occurred after 30 minutes, and was 370% higher than the level at 0 time; after 3 hours, the level decreased to normal. The levels of GH, LH, and FSH did not significantly change, but the plasma level of cortisol rose slightly. These studies show the hormonal activity and specificity of synthetic TRH to release TSH in man and indicate its future use for studying the pituitary-thyroid system of man in health and disease
Recommended from our members
Thyroid stimulating and pigmentary effects of synthetic peptides related to α-MSH and ACTH
Seven synthetic peptides related to α-MSH and ACTH and eleven stereoisomeric fragments of α-MSH (sequence 6–10) were tested for their thyroid stimulating effects. This TSH-like activity was determined by following
131I release in mice injected with
131I and treated with thyroxine. N-α-acetyl-β-corticotropin-(1–24)-tetracosapeptide and β-corticotropin-(1–24)-tetracosapeptide hydrazide had the highest MSH activity and elicited the greatest effects on the blood levels of
131I. The α-MSH-(7–13)-heptapeptide which had a moderate MSH activity, also caused a significant stimulation of
131I release in mice. On the other hand, β-corticotropin-(11–24)-tetradecapeptide, which had virtually no MSH activity, possessed some TSH-like activity. D-His-D-Phe-D-Arg-D-Trp-Gly and the analogous L-pentapeptide, which were essentially free of MSH activity, had no effect on the thyroid at doses up to 100 μg. per mouse. Seven MSH-ACTH stereoisomers, which individually assayed up to 1,200 MSH U/mg., similarly had no effect on the thyroid, but L-His-D-Phe-L-Arg-L-Trp-Gly and three stereoisomers which had a low but definite MSH activity, did exert some TSH-like effects. These studies reveal that, although some relationship between MSH and TSH-like activity can be observed among peptides of the MSH-ACTH group, there is no definite correlation between these activities
- …