摘要:

The postnatal development of the luteinizing hormone-releasing hormone (LHRH) system in male and female rats was investigated using light microscopic immunocytochemistry. An identical number of immunoreactive LHRH cells (about 1,300) was observed for males and females throughout development. Two LHRH cell types, based on morphological appearance, were present in both sexes: smooth LHRH cells and LHRH cells with spine-like processes (irregular LHRH cells). In both sexes, the number of smooth LHRH cells decreases and the number of irregular LHRH cells increases during postnatal life, stabilizing shortly after puberty. We propose that smooth LHRH cells transform into irregular LHRH cells during the development of reproductive maturation.

ISSN:0028-3835    

DOI:10.1159/000124516

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

Previous studies have shown that [3H]estradiol is the major nuclear metabolite of [3H]testosterone in the hypothalamus, preoptic area and amygdala of the male rhesus monkey, and it has been proposed that some of the stimulatory effects of testosterone on male sexual behavior may be mediated by estradiol-concentrating neurons. To map these neurons and identify metabolites, 4 castrated male rhesus monkeys were each injected with 0.47 mCi/kg [3H]estradiol, and the brains were removed 60 min later. Left halves were frozen for thaw-mount autoradiography, and right halves were used to isolate cell nuclei from different brain regions. A fifth animal was used to validate the methodology. Radioactive steroids were identified and measured by high performance liquid chromatography. Brain areas previously shown to contain labeled neurons after [3H]testosterone administration were also labeled after [3H]estradiol, including medial preoptic nucleus (n.), anterior hypothalamic area, bed n. of stria terminalis, ventromedial n., premammillary n., and corticomedial amygdala. Some areas not labeled after [3H]testosterone were labeled after [3H]estradiol, including lateral septal n., arcuate n., paraventricular n., claustrum, entorhinal cortex, and spinal cord. The pars distalis of the pituitary gland was heavily labeled. Most (83%) of the radioactivity in cell nuclei was [3H]estradiol while [3H]estrone was a major metabolite (25%) in supernatants. In the brain, the highest nuclear concentration of [3H]estradiol was in the hypothalamus (249.2 ± 20.0 fmol/mg DNA), although in the previous experiments with [3H]testosterone, the highest nuclear concentrations of [3H]estradiol were found in the amygdala. We interpret these results to indicate that local metabolic differences in the brain may underlie some of the different behavioral effects of gonadal steroids in primates

ISSN:0028-3835    

DOI:10.1159/000124536

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

It has now been established that there is an interaction between the cardiovascular control systems and opiate substances. To assess the role of endogenous opiates in the long-term control of blood pressure, the opiate antagonist naloxone (0.5 mg/kg/24 h) was infused intravenously for 7 days. Chronic blockade of endogenous opiates resulted in an elevation in arterial blood pressure which averaged 11% and was sustained throughout the infusion period. This was accompanied by a significant decrease in plasma renin activity averaging -59%. These data provide support for a tonic role of opioids in the long-term control of the cardiovascular system which may involve baroreceptor function.

ISSN:0028-3835    

DOI:10.1159/000124537

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

Female Sprague-Dawley rats were ovariectomized, given estrogen, and blood samples were obtained via an atrial catheter in the afternoon during the prolactin (PRL) surge. Restraint stress applied at 16.00 h and continued for 3 h resulted in marked decrease in plasma prolactin (PRL) and an increase in plasma corticosterone (B). The neural mechanism(s) involved in the plasma PRL decrease to restraint stress in the afternoon were examined using neural agonists and antagonists. The administration of pimozide, a dopamine antagonist, increased plasma PRL and completely prevented the restraint-induced decrease in PRL. This result suggested that an increase in dopamine secretion mediated the stress-induced decrease of PRL in the afternoon. In unrestrained animals, the intravenous administration of atropine (a muscarinic cholinergic antagonist), arecoline (a muscarinic cholinergic agonist), propranolol (a β-adrenergic antagonist) and morphine (a β-endorphin agonist) at 16.00 h decreased plasma PRL from that of vehicle-injected animals. Bicuculline (a GABAergic antagonist) had no effect while phentolamine (an α-adrenergic antagonist) and phenoxybenzamine (an α-adrenergic antagonist) initially increased and then decreased plasma PRL. Naloxone (a β-endorphin antagonist) initially decreased and then increased plasma PRL in unrestrained animals. In restrained animals, the intravenous administration of atropine and naloxone had no effect on the decrease in plasma PRL. Bicuculline and propranolol decreased plasma PRL below that observed for restrained animals alone, while phentolamine and morphine slightly retarded the course of the decrease. Arecoline did not alter the PRL decrease to restraint in the early sample periods but was followed by a rebound increase at later times. Phenoxybenzamine initially elevated the PRL level above that observed at 16.00 h and then the PRL level gradually decreased. Plasma B was similar to control values in both unrestrained and restrained animals when they were administered atropine, arecoline, bicuculline, propranolol, naloxone and morphine. The administration of phentolamine and phenoxybenzamine significantly elevated plasma B in both unrestrained and restrained animals when compared to control values. The data indicated that neural mechanism(s) involved in the stress-induced decrease of PRL in the afternoon differed from that of the stress-induced increase of PRL observed in the morning of ovariectomized, estrogen-treated

ISSN:0028-3835    

DOI:10.1159/000124517

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

The influence of aging on the molecular forms of endorphins in the hypothalamus of rats was investigated. Extracts of individual hypothalami from 8- and 24-month-old male Fischer 344 rats were subjected to high-performance liquid chromatography. Eluate fractions were assayed for β-endorphin-like immunoreactivity (βE-LI) and γ-endorphin-like immunoreactivity (γE-LI). Hypothalami from adult (8-month-old) rats contained predominantly β-endorphin-1–31 with smaller amounts of β-endorphin-1–27 and 1–26. Only 5% of the βE-LI co-eluted with α-N-acetylated forms of β-en-dorphin. In hypothalamic extracts from old rats more than 30% of the βE-LI co-eluted with acetylated forms of β-endor-phin and over 35% of the βE-LI co-eluted with acetylated or unacetylated β-endorphin-1–26. The individual elution profiles of βE-LI were also much more variable among the old rats than among the adult rats. More than 80% of the γE-LI from adult rat extracts co-eluted with γ-endorphin (β-endorphin-1–17) and less than 3% with α-N-acetyl-γ-endorphin. In contrast, more than 35% of the γE-LI from old rat hypothalami was present in the acetylated form. These results suggest that significant alterations in post-translational processing of peptides may occur in neur

ISSN:0028-3835    

DOI:10.1159/000124518

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

The aim of this study was to explore the occurrence of abnormalities in the circannual thyrotropin (TSH) rhythm in Klinefelter’s syndrome (KS). For 3 years, 69 healthy adult males and 73 patients with KS, usually living in Sardinia, were studied by a cross-sectional design. Plasma samples were taken between 08.00 and 09.00 h and TSH was radioimmunoassayed. First, the mean (± SD) of the data, grouped for each month of the year, was estimated to seek any macroscopic annual variation. Then, a cosine function was fitted to the single serially independent data by the single cosinor method in order to test for any statistically significant rhythm and, if the no-rhythm assumption is rejected, to describe the circannual parameters. Our patients showed circannual mean TSH concentrations lower than controls (p < 0.001) without any statistically significant circannual rhythm, which was instead apparent in normal subjects with the annual crest time in December (95% CL November–February). Our results support the hypothesis that in KS the impaired TSH secretion may be related to abnormalities in the hypothalamic-pituitary coordination of the circannual rhythmicity of this hor

ISSN:0028-3835    

DOI:10.1159/000124519

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

We describe how the increase of anterior pituitary dopamine (DA) during aging in female mice is related to altered secretion of ovarian steroids during reproductive senescence. A number of age-correlated neuroendocrine changes in female rodents result from cumulative exposure to ovarian steroids over a lifetime of estrous cycles, or from the altered pattern of ovarian steroid secretion concomitant with reproductive senescence. Pituitary DA has been shown to increase with age in female rats. To examine how the age-correlated increase of pituitary DA may depend on estradiol (E2), we measured pituitary DA and serum prolactin (PRL) in the following groups of female mice: young (7 months) cycling, middle-aged (14 months) cycling and non-cycling, old (17 months) non-cycling, old (17 months) ovariectomized (OVX) at 4 months, and young mice given 0.2 mg E2 valerate or E2 implants. Mice from some of these groups were OVX 1, 4 or 8 weeks before sacrifice. Compared with young controls, 14-month-old cycling or non-cycling mice had 3-fold higher pituitary DA, and 17-month-old non-cycling mice had 5-fold higher pituitary DA. OVX for 2 or 13 months before sacrifice abolished the effect of age; OVX of young mice had no effect on pituitary DA. Three weeks after implantation of E2 into OVX young mice or 7 weeks after injection of E2 valerate in intact young mice, pituitary DA was elevated. The E2-sensitive fraction of pituitary DA does not appear to decrease PRL secretion. We conclude that the age-correlated increase in pituitary DA is primarily dependent upon the effectively enhanced estrogenic stimulation concomitant with reproductive senescence, rather than upon intrinsic pituitary aging or irreversible effects from exposure to E2 over a lifetime of estrous cycles.

ISSN:0028-3835    

DOI:10.1159/000124520

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

We have recently shown that the dopamine-β-hydroxylase inhibitor, U-14,624, decreases the concentration of cytosol estrogen receptors in the mediobasal hypothalamus (MBH) and anterior pituitary gland (AP) in ovariectomized rats, but that it also causes cell nuclear accumulation of estrogen receptors. We tried to determine if this is the mechanism by which other catecholaminergic inhibitors decrease the concentration of cytosol estrogen receptors in either the MBH or AP. The previously reported decrease in the concentration of cytosol estrogen receptors in AP by the tyrosine hydroxylase inhibitor α-methyl-p-tyrosine was confirmed. Also, the decrease in the concentration of cytosol estrogen receptors in MBH after treatment with the dopamine-β-hydroxylase inhibitors, diethyldithiocarbamate and FLA 63 was demonstrated. In no case was an increase in the concentration of nuclear estrogen receptor accumulation detected after treatment with the drugs. Results of assays of norepinephrine and dopamine levels in MBH after the various treatments suggest that, at the dosage used, U-14,624 has a greater effect on norepinephrine and dopamine levels that the other dopamine-β-hydroxylase inhibitors. The results of these experiments suggest that inhibitors of dopamine-β-hydroxylase and tyrosine hydroxylase cause decreases in the concentration of cytosol estrogen receptors in either the MBH or AP that are not referable to increased cell nuclear accumulation of estrogen recep

ISSN:0028-3835    

DOI:10.1159/000124521

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

In order to study further the regulation of steroid hormone receptors in the brain and anterior pituitary gland of ovariectomized rats by catecholamines, the influence of two dopamine-β-hydroxylase inhibitors on the estrogen receptor system was studied. The two inhibitors, FLA 63 and diethyldithiocarbamate (DDC) both caused a biphasic effect on the concentration of cytosol estrogen receptors in the mediobasal hypothalamus without influencing the concentration of cell nuclear estrogen receptors in the absence of estradiol; the concentration of cytosol estrogen receptors first increased and then decreased after treatment. In a study of the neuroanatomical areas in which inhibition of dopamine-β-hydroxylase decreases the concentration of cytosol estrogen receptors, it was found that the concentration of cytosol estrogen receptors decreased after drug treatment in the mediobasal hypothalamus and preoptic area-septum, but not in the amygdala. This suggests that the decrease in concentration of hypothalamic cytosol estrogen receptors caused by dopamine-β-hydroxylase inhibitors is not a nonspecific effect on all cytosol estrogen receptors. Finally, an injection of estradiol-17β in animals that had been pretreated with either DDC or FLA 63 resulted in less accumulation of cell nuclear estrogen receptors in those tissues in which the drug first caused a decrease in the concentration of cytosol estrogen receptors than in vehicle-injected controls. Therefore, under some conditions, pretreatment with a dopamine-β-hydroxylase inhibitor decreased the concentration of functional cytosol estrogen receptors resulting in decreased nuclear estrogen receptor accumulation in response to an estradiol injection. These results support the hypothesis that the catecholamines have a role in modulating the sensitivity to estradiol in some hypothalamic neurons and, in some circumstances, in the anterior pituitary g

ISSN:0028-3835    

DOI:10.1159/000124522

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

A morphological study has been undertaken on the capillaries of 9 microprolactinomas and 9 macroprolactinomas, surgically removed from untreated patients. The study was carried out utilizing light and electron microscopic techniques and electron microscopic morphometry. The frequency of the capillaries and their structural appearance were taken into account. The frequency of capillaries was found to be very different in micro- and macroadenomas. In microadenomas 51.1 capillaries/0.1 mm2 of tissue section were observed; this value was not significantly different from that found in normal human pituitaries (62.0/0.1 mm2). In contrast, in macroprolactinomas a much lower degree of vascularization was found (9.3 capillaries/0.1 mm2 of tissue section). The capillary abnormalities previously reported for pituitary adenomas (endothelial thickening, swelling and blebbing, loss of fenestration, multilayered basal membrane, etc.) were observed in all prolactinomas studied, but no differences were found between the two types of tumors. In both types of tumors, the capillaries generally looked mature. Very rare sprouting capillaries were observed. Angiogenesis is likely to be slow, in agreement with the low frequency of capillaries in the more rapidly proliferating tumors such as macroprolactinomas. The different frequency of capillaries in micro- and macroprolactinomas could have some important consequences as to the regulation of the hormonal secretion. In fact, the different blood supply to the small and large tumors could result in a different availability of regulatory factors for the two types of tumors.

ISSN:0028-3835    

DOI:10.1159/000124523

出版商:S. Karger AG    

年代:1986

数据来源: Karger