ISSN:0028-3835    

DOI:10.1159/000122838

出版商:S. Karger AG    

年代:1979

数据来源: Karger

摘要:

Serum prolactin (Prl) was measured following decapitation at various stages of the estrous cycle in control animals and following cervicovaginal stimulation with a glass rod. Serum Prl was low at 10.00 h at all stages of the estrous cycle but was elevated on the afternoon of proestrus with peak values at 16.00 h and on the afternoon of estrus with peak values at 13.00 h. Cervicovaginal stimulation resulted in 100% incidence of pseudopregnancy when performed on estrus and diestrus I and in a still high incidence when performed on proestrus. However, on diestrous day II, it caused only delayed pseudopregnancy in less than half the rats. Serum Prl was significantly elevated in the afternoon following stimulation on diestrous day I and on estrus, but the already elevated values on proestrus were not further augmented and there was no significant elevation on diestrous day II. Thus, there was a cyclic variation in the response of Prl to cervicovaginal stimulation which correlated with the incidence of immediate pseudopregnancy. Gonadal steroids at this stage of the cycle probably modulate the reflex release or Prl either by an action at the hypothalamic or pituitary level or at both sites. On the basis of evidence provided by others, the immediate release of Prl does not appear to be required for the induction of pseudopregnancy.

ISSN:0028-3835    

DOI:10.1159/000122839

出版商:S. Karger AG    

年代:1979

数据来源: Karger

摘要:

The role of prostaglandins (PG), their active intermediates or the adenylcyclase-cyclic AMP system for gonadotropin release and/or synthesis was evaluated by administering gonadotropin-releasing hormone (Gn-RH) and its superactive analog to normal and aspirin-treated rats. Serum LH levels, anterior pituitary malondialdehyde (MDA) content and cyclic AMP (cAMP) levels were followed. The pituitaries stimulated with Gn-RH or its superactive analog yielded more MDA and cAMP than the controls. Stimulation of the pituitary with the releasing hormones, after aspirin treatment, yielded 40–70% less MDA and lower LH values than the nontreated animals. The cAMP levels were not significantly lowered by the aspirin treatment. These studies suggest that the activation of the PG biosynthesis and the adenyl-cyclase-cyclic AMP system are not sequential but 2 separate physiological events. The active PG intermediates may only be responsible for the release of LH. It is not clear whether the activation of cAMP initiates also the processes preparatory to the synthesis of LH in the endoplasmic reticulum. in vivo studies in rats showed that the analogs (I and II) were 30 times more potent and had a more prolonged action on the pituitary (3 h) than Gn-RH. Ultrastructural studies on the anterior pituitary after hypophyseal stalk portal vessel infusion of Gn-RH and the analog (I and II) provided ample morphological evidence for both Gn-RH and analog induced gonadotropin-release and synthesis. The prolonged action of the superactive analog (I and II) on the gonadotrophs was also indicated by ultrastructural studie

ISSN:0028-3835    

DOI:10.1159/000122840

出版商:S. Karger AG    

年代:1979

数据来源: Karger

摘要:

The presence of vasopressin (VP) in pars distalis of rats and pigs was investigated. Using radioimmunoassay and bioassay of VP, a substance with immunological and biological properties of this hormone was found. This substance was not detected in the adenohypophysis of rats with diabetes insipidus. A partial purification of the VP-like peptide showed that it had the chromatographic and electrophoretic properties of VP. It could be identified with arginine vasopressin (AVP) in the case of the rat and lysine-vasopressin (LVP) in the case of the pig. In the Wistar strain, adrenalectomy induced progressively increasing concentrations of adenohypophysial VP. This increase was significant 15 days after surgery. It could be prevented by treatment with dexamethasone. These results indicate that the presence of VP in the anterior pituitary is related to the regulation of ACTH secretion.

ISSN:0028-3835    

DOI:10.1159/000122841

出版商:S. Karger AG    

年代:1979

数据来源: Karger

摘要:

Crude neutralized acid extracts were made of medial basal hypothalamic (MBH) tissue obtained from adult male hamsters which had been either blinded, blinded and pinealec-tomized or left intact. After 11 weeks of treatment, the reproductive organs of the blind animals were markedly involuted compared to intact controls, an effect completely reversed by pinealectomy. The luteinizing hormone-releasing hormone (LH-RH) and follicle-stimulating hormone-releasing hormone (FSH-RH) activity of the extracts was assessed using an in vitro system in which LH and FSH release into the medium from hemipituitaries, derived from ovariectomized, estrogen-progesterone-treated female rats, was measured by radioimmuno-assay (RIA). LH and FSH release was responsive to synthetic LH-RH in a dose-related manner; however, in the latter case there were no statistically significant differences between the FSH responses to the various doses of LH-RH. The LH-RH activity of hypothalamic extracts from blind hamsters was depressed as compared with intact controls; however, this effect was not reversed by pinealectomy. The FSH-RH activity of hypothalamic extract from blind hamsters was virtually eliminated compared with that in hypothalami of intact controls. Unlike with LH-RH activity, pinealectomy completely reversed the effects of light deprivation on FSH-RH activity with levels returning to normal. These results indicate that the pineal gland of the male hamster is capable of influencing the hypothalamic levels of FSH-RH activity independent of LH-RH activity.

ISSN:0028-3835    

DOI:10.1159/000122842

出版商:S. Karger AG    

年代:1979

数据来源: Karger

摘要:

Serum LH levels were higher in pinealectomized than in sham-operated control rats during all 4 of the last days of pregnancy studied, although reaching significance only during the final 2 days, 21 and 22. Prolactin (Prl) levels in the serum on the final day of pregnancy, and its contents in the pituitary throughout the entire study period, were significantly lower in pinealectomized rats. Pituitary weights were lower in pinealectomized than in control animals during days 21 and 22 of pregnancy, but no differences were found between the 2 groups in the average number of living foetuses and resorptions. The results presented would seem to indicate that during the last phase of pregnancy the pineal gland plays a role in the modification of gonadotropin synthesis and release. It appears that with LH the release, and with Prl mainly the synthesis, is being affected by the pineal, although the release of Prl may be influenced as well.

ISSN:0028-3835    

DOI:10.1159/000122843

出版商:S. Karger AG    

年代:1979

数据来源: Karger

摘要:

Chicken posterior pituitary tissue was partially fractionated by extraction with 0.1 M HC1 followed by gel exclusion chromatography. Two fractions, B and C, bound oxytocin. Two components of fraction B and at least 1 component of fraction C had properties characteristic of mammalian neurophysins: they appeared to be synthesized in the hypothalamus, were depleted upon osmotic stress, were rich in residues of cysteine and the 2 components of B bound to [8-lysinel]-vasopressin coupled to Sepharose.

ISSN:0028-3835    

DOI:10.1159/000122844

出版商:S. Karger AG    

年代:1979

数据来源: Karger

摘要:

Studies were carried out to investigate the negative feedback effect of progesterone on the secretion of prolactin (Prl). Ovariectomized adult rats were treated with either 50 μg of estradiol, 25 mg of progesterone, a combination of both or the oil diluent. 72 h after treatment, progesterone given alone did not modify pituitary weight, Prl synthesis or the serum levels of this hormone, while estradiol alone increased these parameters. When progesterone was injected simultaneously with estradiol, serum Prl levels were reduced, but the other parameters remained unchanged. In rats with electrolytic lesion of the median eminence (ME), pituitary synthesis and serum levels of Prl were increased, and treatment with estradiol or progesterone singly or in combination was unable to modify them. Furthermore, several doses of progesterone administered at different times before sampling also did not change the high Prl titers found in ME-destroyed rats. Finally, the effect of different concentrations of progesterone on the synthesis of Prl by incubated pituitaries was studied; only the highest and probably non-physiological concentration was able to reduce Prl synthesis. Since progesterone action on Prl levels in serum is observed only in rats with a normal brain-pituitary relationship and when high levels of estrogens are present, it is postulated that the negative feedback effect of progesterone on Prl release by the pituitary is in part at the level of the brain, blocking the stimulatory effect of estrogen on Prl secretion

ISSN:0028-3835    

DOI:10.1159/000122845

出版商:S. Karger AG    

年代:1979

数据来源: Karger

ISSN:0028-3835    

DOI:10.1159/000122846

出版商:S. Karger AG    

年代:1979

数据来源: Karger