摘要:

The hypothalamic supraoptic (SON) and paraventricular nuclei (PVN), median eminences (ME) and neural lobes (NL) of normally hydrated control rats (group 1), and of rats drinking 2% NaCl for 7 (group 2), 30 (group 3) or 90 days (group 4) were investigated using immunohistochemistry for neurophysins (NP), arginine vasopressin (AVP) or oxytocin (OXY). Animals from the 3 experimental groups showed equivalent decreased levels of immunoreactive NP in the SON and PVN, but the greatest decrease was in the SON. Dendrites of SON and PVN neurons became loaded progressively with immunoreactive NP, AVP and OXY as salt loading proceeded. In rats of group 2, axons leaving the SON and PVN showed a marked depletion of immunoreactive material. The latter was found mainly at the periphery of widely spaced axonal swellings, clearly contrasting with the small and narrowly spaced beads of the neurosecretory axons of control rats. In rats of groups 3 and 4, axons leaving the SON and PVN resembled those of control rats. In the ME of the animals in all experimental groups, the same degree of decrease of immunoreactive NP was observed. In rats of group 3, bundles of axons containing immunoreactive AVP and OXY frequently projected through the ependymal lining of the ME into the third ventricle. In the NL of all experimental animals, a marked decrease occurred in the amount of immunoreactive NP, AVP and OXY. The decrease of immunoreactive AVP, however, was more pronounced in rats of group 2 than in those of groups 3 and 4. The NL of rats in group 4 were approximately 80% larger than those of control rats. Particularly striking in these hypertrophied NL were networks of expanded perivascular basal lamina and large intra-axonal vacuoles. The survival of rats to the long-term salt loading and the changes observed in the hypothalamo-neurohypophysial system indicate that these animals have developed adaptive mechanisms to the salt load.

ISSN:0028-3835    

DOI:10.1159/000124934

出版商:S. Karger AG    

年代:1988

数据来源: Karger

摘要:

In the golden hamster, prolonged exposure to short days (i.e. less than 12.5 h of light/day) induces testicular regression that has usually, but not always, been reported to be accompanied by a decrease in mean serum luteinizing hormone (LH) levels. As LH appears to be released in a pulsatile pattern in most mammalian species, we hypothesized that individual variations in serum LH levels over time may obscure significant changes in pituitary LH release in hamsters exposed to short photoperiods. Therefore, we examined the effects of short day exposure on pulsatile LH release in castrated and intact golden hamsters. Intact and castrated male golden hamsters were maintained on long days (light :dark 14:10 h) or transferred to short days (light:dark 6:18 h). Nine to eleven weeks after transfer, animals from all four groups were fitted with intra-atrial cannulas and bled at 10-min intervals for 6 h. Exposure to short days inhibited LH release in the intact male hamsters. All 6 of the males maintained on long days had pulsatile LH release while only 1 of the 4 intact males maintained on short days showed a pulse of LH during the 6-hour bleeding session. All of the castrates on short days had pulsatile patterns of LH release that were similar in amplitude and frequency to those of the castrates on long days. Castrates on long days had significantly greater LH pulse frequency and amplitude than intacts on long days. From these data we conclude that the pulsatile nature of pituitary LH release in the golden hamster mandates frequent sampling over several hours for accurate determination of serum LH levels and for determining the effects of photoperiod on pituitary gonadotropin release.

ISSN:0028-3835    

DOI:10.1159/000124935

出版商:S. Karger AG    

年代:1988

数据来源: Karger

摘要:

The effect of frontal deafferentation of the medial basal hypothalamus on pro-opiomelanocortin (POMC) gene expression was studied in the intermediate lobe (IL) and anterior lobe (AL) of the pituitary gland in the absence and presence of corticosterone (CORT). The lesion in the basal hypothalamus removed neural inputs to the IL and induced the glucocorticoid receptor (GR) in this tissue. The GR was visualized in the denervated IL by immunocytochemistry. Induction of the GR had a slow onset and was detectable at 3 weeks after lesion, but not at one week after the lesion. In order to study the effect of IL denervation on pro-opiomelanocortin (POMC) gene expression, the level of messenger RNA specifically encoding POMC was measured 1 and 3 weeks after lesion, in the IL and AL. In adrenalectomized (ADX) animals, the changes in POMC mRNA levels were not significant 1 week after lesion in the IL. Three weeks after denervation there was a 3-fold decrease in POMC mRNA in the IL in ADX rats which was blocked by chronic CORT replacement via subcutaneously implanted pellets. In the AL, CORT reduced the level of POMC gene expression in both the lesioned and control animals. It is concluded that (1) removal of neural input induces GR in the denervated IL cells; (2) with the appearance of the GR, POMC gene expression in the IL becomes sensitive to circulating glucocorticoids; (3) under these conditions, CORT may stimulate POMC gene expression in the IL as opposed to its inhibitory effect in the AL.

ISSN:0028-3835    

DOI:10.1159/000124936

出版商:S. Karger AG    

年代:1988

数据来源: Karger

摘要:

Cysteamine (CySH) inhibits the immunodetectability and bioactivity of prolactin (PRL), and we have proposed that it may act by impeding the conversion from secretory granule hormone storage forms to releasable and assayable hormone. This process appears to be dependent upon thiol:disulfide interchange reactions, which can be inhibited by the aminothiol. The present studies utilized [35S]CySH to determine whether preferential interactions could be demonstrated between CySH and bovine pituitary storage hormone forms as opposed to monomeric PRL. [35S]CySH was incubated with purified intact secretory granules, with granule ‘core’ preparations enriched in oligomeric forms by prior hypotonic exposure, with chromatographically isolated oligomers, and with monomeric PRL. Binding to granules was saturable and pH-dependent with greatest binding observed at pH 7.5–8.0. Binding to monomer was much less than binding to all other fractions, being 20% or less than that to any other form. HPLC studies of granules treated with [35S]CySH indicated that exposure to CySH was associated with a predominance of very high molecular weight oligomers. These forms were entrapped on the gel permeation columns, resulting in decreased protein and PRL recovery; as little as 6.6% of the PRL was eluted after 60 min of CySH exposure. CySH not only bound to storage forms of PRL but also to secretory granule membranes; whether the bioeffect is mediated through membrane modifications is unknown. Despite its relative ineffectiveness at altering growth hormone immunoactivity or secretion, CySH nonetheless also bound to growth hormone. Thus, further studies are required to establish with certainty the site(s) of CySH binding and to establish the molecular mechanism which accounts for inhibitory aminothiol effects on PRL storage forms and PRL secr

ISSN:0028-3835    

DOI:10.1159/000124937

出版商:S. Karger AG    

年代:1988

数据来源: Karger

摘要:

Thymic neuroendocrine cells were identified by immunofluorescence in the murine thymus through the use of monoclonal antibody A2B5, and specific polyclonal antisera against neurophysin (NP), oxytocin (OT) and arginine vasopressin (AVP). Two reactive regions were clearly identified: the subcapsular cortex and the medulla. A close correspondence was observed between A2B5-reactive and NP-immunoreactive cells in the medulla. An important epithelial population of the subcapsular cortex, the thymic nurse cells (TNCs), were found to be A2B5-positive and to contain immunoreactive NP, OT and AVP. The neuroendocrine nature of TNCs was further substantiated by their high reactivity with an antiserum against neuron-specific enolase. These observations demonstrate the presence in the thymus gland of an original neuroendocrine microenvironment which could be of functional importance in the mediation of central influences upon T lymphocyte differentiation.

ISSN:0028-3835    

DOI:10.1159/000124938

出版商:S. Karger AG    

年代:1988

数据来源: Karger

ISSN:0028-3835    

DOI:10.1159/000124939

出版商:S. Karger AG    

年代:1988

数据来源: Karger