摘要:

The effect of hypocalcemia following parathyroidectomy (PTX) on growth hormone (GH) secretion was investigated in unrestrained, unanesthetized male rats bearing chronically implanted indwelling cannulae. During a 6-hour period, starting at about 10 a.m., control rats with a serum calcium (Ca) value of 8.11 ± 0.38 mg/dl (mean ± SEM) 2 weeks after sham-operation showed secretory bursts of GH similar to those observed in conscious intact rats. Under hypocalcemia of 4.88 ± 0.32 mg/dl 2 weeks after PTX, GH secretory episodes were completely suppressed throughout the study. Plasma prolactin (PRL) levels were also decreased in PTX rats as compared with those of sham-operated rats. Daily food intake and body weight gain as well as serum T4 levels in PTX rats were not different from those of sham-operated and intact rats. Pituitary GH content of PTX rats was significantly lower than that of sham-operated and control rats. Pulsatile GH secretion was partially restored in PTX rats by raising serum Ca to 8.43 ± 0.27 mg/dl through feeding with high Ca diet containing 7% Ca. Immediately after intravenous injection of antisomatostatin sheep serum, pulsatile GH surges recovered in PTX rats despite hypocalcemia of 4.48 ± 0.74 mg/dl. The mean plasma 6-hour GH levels were significantly higher than those of normal sheep-serum-treated PTX rats (p < 0.001). These findings suggest that the episodic release of GH is suppressed in hypocalcemic rats after PTX, at least partially via circulating endogenous somatost

ISSN:0028-3835    

DOI:10.1159/000123416

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

Binding of (3H)-corticosterone in cytosol of hippocampus and hypothalamus has been measured in adrenalectomized (ADX) rats in the presence or absence of corticosterone replacement therapy (suspended shortly before receptor analysis). Corticosterone pellet implantation into female rats or oral corticosterone administration in salinized drinking water given to males for 3 weeks reduced (3H)-corticosterone binding by half in the hippocampus. This reduction was observed whether corticosterone or dexamethasone was employed as competitor to determine nonspecific binding, thus eliminating transcortin as the cause of the corticosterone effect on binding. Scatchard analysis of binding data revealed that the reduction was mostly due to decreased number of receptors. Animals pretreated with corticosterone had a reduction in thymus weight, indicating further the biological effectiveness of the treatment. Further, serum corticosterone in ADX rats pretreated with corticosterone (but with therapy suspended for 24 h) was very low and similar to that of untreated ADX rats. Uptake studies after injection of (3H)-corticosterone intravenously into ADX rats showed that the injected hormone was absent from blood and brain tissues 1 day later, ruling out (in addition to the measurement of serum corticosterone) that the reduction in binding was due to occupation of receptor sites by exogenous corticosterone remaining after withdrawal from therapy. It is suggested that down-regulation of glucocorticoid receptors in brain follows the chronic corticosterone administration. These data are discussed in relation with evidence for down-regulation of other classes of steroid receptors in several tissues, and the consequence that changes in receptor binding in brain may have on the feedback mechanism of corticoids at the central level.

ISSN:0028-3835    

DOI:10.1159/000123429

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

Histamine administered intraperitoneally increased, in a dose-dependent manner, AVP, OXT and PRL levels in plasma of rats, whereas α-MSH levels were not affected. Levels of AVP in plasma after histamine 20.0 mg/kg treatment were approximately 100-fold higher than those of controls, while OXT and PRL levels were approximately 7-fold higher after this treatment. CSF content of AVP, OXT, PRL and α-MSH was not influenced by histamine, indicating that a stimulated release of hormones from the pituitary into the blood is not accompanied by a concomitant increase of secretion of these hormones into the CSF. Convulsions induced by pentylenetetrazol were accompanied by a temporary increase in AVP levels and by strongly and consistently elevated OXT levels in plasma. PRL and α-MSH plasma levels were affected in a biphasic manner. A convulsion type 1 induced elevated PRL levels and diminished α-MSH levels, while a convulsion type 2 had no effect on plasma PRL concentration, but increased the concentration of α-MSH. Only the level of OXT in CSF was increased after a pentylenetetrazol-induced convulsion type 1. The present data suggest that histamine affects the release of AVP, while pentylenetetrazol might act more specifically on the OXT-releasing system. Furthermore, a possible relationship between the pentylenetetrazol-induced increase of OXT levels in the CSF and amnesia is sugge

ISSN:0028-3835    

DOI:10.1159/000123417

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

The vasopressin released by electrical stimulation of the isolated rat neurohypophysis into continuously perifused medium was measured by specific radioimmunoassay. The data revealed that the peak secretory rates achieved in the first few minutes of a period of 13-Hz stimulation are not maintained, but decline to a ‘plateau’ level, above the level of basal secretion, but markedly below the initial stimulated rate. After mathematical correction of the measured profile of peptide secretion to take account of the delayed appearance in the perifusate of hormone released from the interior of the gland it appears that peak secretory rates are not maintained beyond the first 2 min of stimulation: thereafter, stimulated secretion is stable at about 10% of the peak r

ISSN:0028-3835    

DOI:10.1159/000123418

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

Immunocytochemical procedures on thick, unembedded sections were used to visualize the neurons and their processes that contain LHRH-immunoreactive material in the rat central nervous system (CNS). In animals pretreated with colchicine (75 μg, intraventricularly), cell bodies could be observed as far anterior as the olfactory bulb and posterior to the retrochiasmatic area of the basal hypothalamus. Several new observations for the rat were made in this study, including LHRH neurons in the accessory olfactory bulb and other olfactory-related structures, and in the anterior hippocampus and the induseum griseum. As in studies from other laboratories, we observed many LHRH cells in the periventricular medial preoptic area, diagonal band of Broca and septal nuclei, and fewer positive cells in the anterior hypothalamic area and the region of the supraoptic commissure. The LHRH fibers from all of these cells are widely dispersed in the CNS. In addition to the dense innervation of the median eminence, positive fibers are found innervating other circumventricular organs, coursing close to the ependymal wall of the ventricular system or in close association with cerebral arteries and areas of the pia mater and subarachnoid space. LHRH fibers may also innervate neurons in several regions of the CNS. A novel projection of LHRH fibers for the rat was found originating from supracallosal neurons and coursing through both cingulate and neocortex. The possible distribution of efferents from each LHRH cell group is discussed

ISSN:0028-3835    

DOI:10.1159/000123419

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

The plerocercoid larvae of the tapeworm, Spirometra mansonoides, produce a growth factor, called plerocercoid growth factor (PGF) that suppresses endogenous growth hormone (GH). Treatment (infection) with 10 plerocercoids at weaning age (22 days of age) delayed puberty onset in the female rat. First ovulation was at 34.0 ± 0.6 days in controls and at 38.6 ± 0.9 days in worm-treated rats (p < 0.01). When basal serum hormone levels were measured at 08.00–09.00 h at several times during the prepubertal period, no changes were found in FSH, LH or prolactin. Growth hormone (GH) was below measurable levels in both groups before day 27. GH of infected rats remained significantly suppressed at least until the second metestrus. Thyroxine (T4) was significantly lower in worm-treated animals beginning at 26 days of age and remained depressed until 33 days of age. Gonadotrophin regulation was assessed by measuring the rate of rise of serum FSH and LH during the first 48 h after castration at 25, 28 and 32 days of age and on the day of the second metestrus. The rate of increase in FSH fell with age in both groups but was significantly less at all prepubertal ages in worm-treated rats. The LH response was less in castrated postpubertal controls but there was not a clear-cut progressive fall with age. The LH response was less in worm-treated rats at all the prepubertal ages tested but not at second metestrus. To determine whether the lack of difference between the two metestrus groups was due to a diminution of the worm effect, worms were implanted at 30 days of age and the castration response at second metestrus was compared to that obtained in rats given worms at 22 days of age. The FSH and LH responses in both sets of worm-treated rats were comparable, indicating that the loss of suppression relates to age rather than a decreased secretion of PGF. To determine whether the acute suppression of the castration response would persist, measurements of serum FSH and LH were made 4, 7 and 14 days after castration at 25 days of age. By 4 days after castration, FSH and LH were comparable in the two groups. This occurred despite the continuation of T4 and GH deficiency at that age. When the castration response was suppressed by the daily administration of 0.05 or 0.5 μg estradiol benzoate (EB), worm-treated animals showed a greater sensitivity to both doses of EB. Delay in puberty onset in worm-treated animals is associated with both T4 and GH deficiency but the suppression of the response of FSH and LH to castration and the heightened sensitivity to estrogen are not attributable solely to these defi

ISSN:0028-3835    

DOI:10.1159/000123420

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

The present study examines the interrelationship of the ventral noradrenergic (norepinephrinergic) bundle (VB) with brain and hypophyseal pools of endorphins. As compared to sham-operated rats, selective destruction of the VB depressed hypothalamic levels of norepinephrine and abolished the fall in these levels evoked by acute foot shock stress. Stress elevated plasma levels of β-endorphin immunoreactivity (β-EI) and both basal and poststress circulating levels of β-EI were significantly greater in lesioned as compared to sham animals on days 4 and 10, but not 28, postsurgery. At each time, stress depleted the anterior and neurointermediate lobe content of β-EI in both sham-operated and lesioned rats. These data indicate that stress mobilizes β-EI from the pituitary into plasma and that the VB may inhibit the tonic and stress-elicited secretion of β-EI into the circulation. In lesioned rats, a transient depression in basal levels of β-EI in the septum and in those of met-enkephalin immunoreactivity (M-EI) in periventricular midbrain tissue was seen. Stress selectively depleted the β-EI as compared to the M-EI content of discrete brain regions, including the septum and this periventricular tissue, in sham-operated animals. Lesioned rats also responded to stress with a fall in β-EI levels and, in contrast to sham rats, with a decrease in the M-EI levels of the hypothalamus and periventricular tissue. These data demonstrate that the VB does not mediate the activation of brain β-EI elicited by stress and suggest the existence of an interaction of the VB with certain brain pools of β-EI and M-EI both tonically and un

ISSN:0028-3835    

DOI:10.1159/000123421

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

Pineal extract is shown to contain both renin-like and cathepsin D activities. Evidence of renin-like activity in the bovine pineal gland was brought by incubation with natural and synthetic renin substrates and by inhibition by pepstatin. Cathepsin D activity was demonstrated by incubation with hemoglobin and synthetic ñuorogenic peptide. The separation of both activities was performed by affinity chromatography on a caseinyl-Sepharose gel. The elution of the extract on affinity chromatography allowed to separate the renin-like activity, which is not retained by the gel at acid pH, from cathepsin D activity, which binds to the column at acid pH and is eluted at alkaline pH. The isolated pineal renin-like activity was found higher on tetradecapeptide renin substrate than on angiotensinogen at pH 5.5. The pH dependence of pineal renin-like activity showed two peaks of activity. One broad peak between pH 6 and 8 and one sharp peak at pH 3.5–4. These results demonstrate the existence of renin-like and cathepsin D activities in bovine pineal gland. They suggest moreover that the renin-like activity measured might represent a mixture of at least two different enzymatic activiti

ISSN:0028-3835    

DOI:10.1159/000123422

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

Using a simple high performance liquid chromatographic method, we measured melatonin, N-acetyl-5-hydroxytryptamine (NAc-5HT), 5-hydroxytryptophol (5HTOL), 5-hydroxyindoleacetic acid (5HIAA), 5-hydroxytryptamine (5HT) and tryptophan in single rat pineal glands. 5-Methoxytryptophol and 5-methoxyindoleacetic acid were not detected at levels which have been reported previously. 5HTOL, 5HIAA and 5HT showed the opposite diurnal rhythm to NAc-5HT and melatonin. Light during the dark period lowered melatonin while increasing 5HTOL, 5HIAA and 5HT. As the peak 5HTOL levels were higher than the peak melatonin levels, the functional significance of 5HTOL deserves consideration. Tryptophan administration increased melatonin and 5HTOL as well as the other indoles.

ISSN:0028-3835    

DOI:10.1159/000123423

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

The rate of dopamine (DA) synthesis (DOPA accumulation after the administration of an inhibitor of aromatic L-amino acid decarboxylase) was determined in terminals of tuberohypophyseal DA neurons in the neurointermediate lobe (NIL) of the rat hypophysis at various times after the presentation of osmotic stimuli. DA synthesis in the NIL, but not in median eminence or striatum, was increased 24 h but not 4 h after an injection of hypertonic saline (5 ml 15% NaCl/kg, s.c), provided the animals were not permitted access to water after the injection; 24 h of water deprivation per se was without effect on the rate of DA synthesis. DOPA accumulation in the NIL was also increased after an intravenous infusion of mannitol (25 ml 20% mannitol/kg) plus 24 h of water deprivation. These results suggest that the dehydration-induced activation of tuberohypophyseal DA neurons which is normally seen after 2–3 days of water deprivation can be accelerated if water deprivation is preceeded by injections of hypertonic saline or mannito

ISSN:0028-3835    

DOI:10.1159/000123424

出版商:S. Karger AG    

年代:1982

数据来源: Karger