摘要:

Porcine neurophysin-I iodinated with Na125I was injected intravenously into rats and rabbits, and the rate of disappearance of radioactivity from the peripheral system was measured. Radioactively-labeled neurophysin bound to polymethylmethacrylic particles was similarly injected into the animals. The half-time for the loss of radioactivity from samples of whole blood was 6.1–6.4 min as determined over the first 5 min after administration of the protein. There was no significant difference in the half-time calculated when the radioactivity present in the trichloroacetic acid-insoluble material present in the serum was measured. 15 min after the injection of labeled protein there was a maximum and massive uptake of radioactivity in the kidney consistent with this tissue’s being important in the degradation of neurophysin. Immunoperoxidase histochemical techniques were applied to formalin-fixed kidney slices and demonstrated the presence of neurophysin-like material localized in the cells of proximal tubules of the cortex and medulla. On binding neurophysin to acrylic particles there was approximately a 10-fold increase in the uptake of radioactivity in the lungs and a 33% reduction in activity in the kidneys, as measured at the 15-min time interval. Of the other tissues studied, excluding the thyroid gland and lungs, the uterus demonstrated the greatest uptake of radioactivity and fat tissue had the least accumulation of radioactive la

ISSN:0028-3835    

DOI:10.1159/000122401

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

The objective of this study was to determine the influence of estradiol-17β and/or progesterone on gonadotropin secretion at the level of the pituitary. Female rats in which the hypothalamo-hypophyseal connections had been permanently interrupted after castration served as the experimental model in which the effect of estradiol and/or progesterone on LH-RH-induced gonadotropin release was examined. In our experimental animals, LH secretion was readily activated by LH-RH administration. LH release was greatly augmented by the prior administration of estradiol benzoate (1 µg/kg b.w./day). Progesterone (5 mg/day) in the absence of estradiol did not modify the 10-min response to LH-RH but reduced the enhancement of LH secretion caused by estradiol pretreatment. Our findings suggest that estradiol potentiated the releasing effect of LH-RH at the level of the gonadotroph, whereas progesterone interfered with the potentiation effect. Plasma levels of FSH were not significantly elevated above the basal value by the administration of LH-RH alone, or in combination with estradiol and/or progesteron

ISSN:0028-3835    

DOI:10.1159/000122402

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

To evaluate estrogen negative feedback in infantile female rats, 9-day-old rats were ovariectomized (OVX) and treated with different doses of estradiol benzoate (Eb, s.c. once daily for 2 days); plasma LH, FSH and estradiol (E2) levels were then determined by RIA. The responses of these rats were compared with those of 25-day-old rats subjected to the same experimental procedures. In intact sham-operated controls, plasma FSH was elevated on days 9–13 and low on days 25–29, whereas LH did not change significantly throughout the period studied. OVX at day 9 or 25 increased the levels of both hormones, with the response faster and larger in the older rats. Treatment with Eb was more effective in suppressing the post-castration rise in gonadotropin levels in 27-day-old than in 11-day-old rats. At day 27 plasma E2 was elevated to pre-castration values by as little as 10 ng of Eb, whereas at day 11 this dose produced plasma E2 titers even higher than pre-castration values. Plasma E2 titers were high at 9–13 days of age and low at days 25–29. OVX on day 9 decreased E2 2–4 days later to about ½ the initial concentration, whereas adrenalectomy (ADRX) or ADRX-OVX was followed by an almost complete disappearance of the steroid. When E2 was injected at day 10 in intact rats to elevate plasma E2, E2 remained elevated when measured 3 to 120 min after its injection, but on day 25, 50% of the injected E2 had disappeared from plasma in 90 min. These results provide additional support for the view that estrogen negative feedback, even though present in infantile rats, is less effective than later in life and hence indicate that high gonadotropin titers observed at days 9–13 in the presence of high E2 may be caused by the relative ineffectiveness of the feedback at these early ages. The high E2 titers appear to be caused by an enhanced rate of production of E2 by the adrenals and ovaries and by a reduced metabolic clearance of

ISSN:0028-3835    

DOI:10.1159/000122403

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

Mitochondrial preparations from stalk median eminence of female rats were shown to contain an enzymatic system which yielded MSH-RF upon incubation with oxytocin. These enzymes were found present in the hypothalamus of rats at proestrus and estrus and absent in the other stages of the cycle. The MSH contained in plasma was also determined during the estrous cycle in the rat. Serum MSH was released on the morning of proestrus, reached a maximum value at 10.00 a.m., and remained high until 4.00 p.m. Thereafter serum MSH decreased to undetectable levels in the other stages of the cycle. MSH was released into the serum about 6 h before the proestrous peak of the gonadotrophin. A correlation was demonstrated between the hypothalamic enzymes responsible for the formation of both MSH-R-IF and MSH-RF and the MSH released into the serum.

ISSN:0028-3835    

DOI:10.1159/000122404

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

The effects of prolactin and other hormones applied electrophoretically to 400 neurons in the brain were studied in rats under urethane anesthesia. 51 prolactin-activated neurons were distributed mainly in the nucleus dorsomedialis, the upper part of the nucleus ventromedialis, and the nucleus habenulae. 26 prolactin-inhibited neurons were diffusely distributed from the nucleus arcuatus to the zona incerta. Prolactin failed to affect the neurons of the cerebral cortex. Almost all units recorded in the preoptic and lateral hypothalamic areas were not affected. About half of both prolactin-activated and -inhibited neurons were suppressed by estrogen and betamethasone but were not affected by either oxytocin or thyrotropin releasing hormone. This study affords direct evidence for the presence of prolactin-sensitive neurons in the hypothalamus.

ISSN:0028-3835    

DOI:10.1159/000122405

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

250 mg/kg i.p. of the methyl ester of α-methyl-p-tyrosine (α-MpT) produced a rapid increase (by 1 h) in immunoreactive plasma ACTH, whereas the hypothalamic norepinephrine (NE) concentration and plasma corticosterone (B) changed significantly only 6 h after the administration of the inhibitor. These data suggest that the norepinephrinergic inhibitory tonus of CRF-ACTH secretion depends on the availability of a rapidly utilized pool of transmitter, affected in a very short time by α-M

ISSN:0028-3835    

DOI:10.1159/000122406

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

TRH increased cell proliferation in organ-cultured rat adenohypophysis. Thyroxine by itself had no effect on adenohypophysial cell proliferation in vitro but inhibited the mitogenic effect of TRH.

ISSN:0028-3835    

DOI:10.1159/000122407

出版商:S. Karger AG    

年代:1975

数据来源: Karger