摘要:

Growth hormone releasing factor (GRF) was purified from ovine hypothalami on a Sephadex G-25 column. Three fractions from one of the major protein peaks induced the release of radioimmunoassayable growth hormone (GH) from rat pituitaries incubated in vitro, but did not induce any appreciable release of other anterior pituitary hormones. The kinetics of GH release from rat pituitaries included an initial phase with an exponential release of hormones, a subsequent phase with a constant rate of release, and a terminal declining rate of release seen with high GRF doses. The minimally effective dose of this GRF preparation which stimulated GH secretion in vitro contained 1.5 µg of protein. No change in pituitary cyclic AMP was observed following the exposure of the explants to 3 or 6 µg of GRF for 10 min, but proportional increases in pituitary cyclic GMP were observed at this time period. Although the synthetic decapeptide, Val-His-Leu-Ser-Ala-Glu-Glu-Lys-Glu-Ala, has been shown to deplete bioassayable pituitary GH, it did not stimulate the release of radioimmunoassayable GH nor did it substantially elevate the pituitary cyclic AMP content at the dose levels and time intervals tested. The synthetic decapeptide did not alter pituitary cyclic GMP content after 10 or 60 min of incubation. These observations further substantiate that GRF capable of releasing radioimmunoassayable GH can be isolated from hypothalamic tissue. Preliminary studies of the mechanism of action of GRF indicate that cyclic GMP rather than cyclic AMP plays a central role in mediating the neurohormonal control of GH releas

ISSN:0028-3835    

DOI:10.1159/000122322

出版商:S. Karger AG    

年代:1974

数据来源: Karger

摘要:

The infusion of 50 µg norepinephrine (NE) into the third ventricle of the brain was found to be highly effective in stimulating the release of an ovulatory surge of LH from the pituitary gland in estrogen-primed rabbits. Intraventricular dopamine (D), in dosages of 5 and 50 µg, was not only completely ineffective in inducing ovulation, but the higher dosage actually blocked the ovulatory effect of NE, often for a month or more after infusion. In experimentts in which LH was measured by radioimmunoassay, intraventricular NE stimulated a marked rise in LH starting within minutes, peaking at 2 h and returning to pre-infusion levels by 6 h. No rise in serum LH was observed following the intraventricular infusion of D. Both dosages of D were quite effective in blocking LH output in response to NE infused 2 h later, and the 50-µg dosage of D generally prevented any rise in serum LH concentration for some weeks after the infusion of intraventricular NE. The results are consistent with the hypothesis that a noradrenergic synapse is functional in hypothalamic mechanisms activating the release of pituitary

ISSN:0028-3835    

DOI:10.1159/000122323

出版商:S. Karger AG    

年代:1974

数据来源: Karger

摘要:

The effects of renal denervation on the catecholamine concentrations in different areas of the central nervous system of the male Wistar rat were studied. Catecholamines were extracted following von Euler and Lishajko’s [1959] and Cohen and Goldenberg’s [1957] methods. Norepinephrine increased in the hypo thalami of denervated animals, 3, 7, and 30 days after the operation, compared to sham-operated animals. There were no modifications in the norepinephrine or epinephrine content in cerebral hemispheres, cerebellum, peduncles, pons and medulla oblongata, or in hypothalamic epinephrine after the same periods of time. Coincidentally, plasma renin activity decreased in denervated animals 7 days after the operation. The increase of endogenous norepinephrine found in hypothalamus might be attributed to the drop in plasma renin caused by renal denervation and a subsequent decrease in circulating angiotensin. This would be translated into a lower inhibition of neuronal re-uptake and a decrease in the neurotransmitter rele

ISSN:0028-3835    

DOI:10.1159/000122324

出版商:S. Karger AG    

年代:1974

数据来源: Karger

摘要:

An intraventricular injection of 100 µg of norepinephrine (NE), but not of dopamine, induced ovulation in more than 50 % of rats made anovulatory by electrolytic lesions in the anterior hypothalamus. Ovulation also occurred 2 days after an intraventricular injection of 50 µg of NE in more than 50 % of rats made anovulatory by exposure to continuous illumination. The percentage of rats which ovulated after the intraventricular injection of 100 µg of NE was much lower in rats made anovulatory by a frontal cut in the anterior hypothalamus or by the neonatal administration of testosterone than in rats made anovulatory from either anterior hypothalamic lesions or continuous illumination. The results of this experiment suggest that when they are stimulated by NE the LRF-producing neurons in rats made anovulatory by various experimental procedures do synthesize and release LRF in an amount sufficient to induce ovulati

ISSN:0028-3835    

DOI:10.1159/000122325

出版商:S. Karger AG    

年代:1974

数据来源: Karger

摘要:

Changes in plasma testosterone (T) levels following the placement of a receptive female into a male’s cage and after exposure to the odor of vaginal discharge in the absence of a female were studied in the male hamster. Plasma T was determined by radioimmunoassay. Both treatments produced significant increases in T levels. The degree of interest in the odor was positively related to the males’ baseline T levels. The results demonstrate a direct effect of a sex-related odor on neuroendocrine activity in a male mam

ISSN:0028-3835    

DOI:10.1159/000122326

出版商:S. Karger AG    

年代:1974

数据来源: Karger

摘要:

The possible binding of 3H-dexamethasone (Dx)to the anterior pituitary and the effect of the steroid on neo-synthesis and release of ACTH of glands incubated with crude CRF extracts were examined. Neosynthesis of ACTH was determined by immunoprecipitation after incorporation of 14C-phenylalanine into the peptide. Using a cell-free system, 3H-Dx was shown to combine with the nuclear fraction of the pituitary. Short-term in vitro pre-treatment with Dx suppressed the CRF-induced hormonal release, but did not alter ACTH biosynthesis. The releasing mechanism, on the other hand, did not appear to be related to de novo synthesis. Prolonged in vivo administration of high concentrations of Dx initially caused a decrease of ACTH synthesis and, later, also impaired the synthesis of total proteins. Synthesis and release of ACTH may be dissociated, but there is a possibility that a correlation exists between these two processes. On the other hand and as far as the direct effect of Dx on the pituitary is concerned, the nuclear uptake of the steroid probably reflects an early step in the modulation of corticotropic activity.

ISSN:0028-3835    

DOI:10.1159/000122327

出版商:S. Karger AG    

年代:1974

数据来源: Karger

ISSN:0028-3835    

DOI:10.1159/000122328

出版商:S. Karger AG    

年代:1974

数据来源: Karger

ISSN:0028-3835    

DOI:10.1159/000122329

出版商:S. Karger AG    

年代:1974

数据来源: Karger

ISSN:0028-3835    

DOI:10.1159/000122321

出版商:S. Karger AG    

年代:1974

数据来源: Karger