摘要:

AbstractRecent developments in our understanding of the molecular basis of circadian rhythms look set to provide one of the most elegant demonstrations of the relationship between the activity of individual genes and the execution of biologically relevant and complex patterns of behaviour. At the same time the lid is being opened on one of the classic ‘black boxes’ of biology, the circadian cl

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1995.tb00766.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractEnkephalin appears to modulate several aspects of reproductive function in female rats. The purpose of this study was to determine if lactation influences preproenkephalin gene expression in one or more hypothalamic nuclei known to be involved in maternal or reproductive behavior and prolactin secretion. Lactating rats were killed on day 3 (LAC 3) or day 10 (LAC 10) of lactation. Controls consisted of regular 4‐day cycling rats that were killed on diestrous day 1, with 9 to 12 females per group. We usedin situhybridization histochemistry to assess preproenkephalin gene expression in individual cells in the medial preoptic nucleus, anterior, medial and posterior arcuate nucleus, magnocellular and parvocellular aspects of paraventricular nucleus, and ventromedial nucleus. Preproenkephalin mRNA in the anterior arcuate nucleus increased to reach significance (P<0.05) at day 10 of lactation. Levels in the medial arcuate nucleus increased significantly (P<0.001) by day 3 of lactation (LAC 3) and remained elevated on day 10 (LAC 10). No significant differences between lactating and control rats were detected in preproenkephalin mRNA levels in the posterior arcuate nucleus, medial preoptic nucleus or in the ventromedial nucleus. Substantial levels of preproenkephalin mRNA were found in the paraventricular nucleus, particularly in a limited region of the magnocellular portion. However, these levels did not change with lactation. These data provide evidence for differential regulation of the preproenkephalin gene during lactation. This change may contribute to. lactational hyperprolactinemia and suppressed GnRH secretion, leading to reproductive acyclicit

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1995.tb00767.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractLocalization in the nervous system ofDrosophila melanogasterof a clonedDrosophilamuscarinic acetylcholine receptor (mAChR) was investigated using a polyclonal antiserum raised against a peptide corresponding to the predicted receptor carboxyl terminal domain. Immunocytochemical studies on fly sections indicated that the product of the Dm1 mAChR gene was localized in the antennal lobes and in other regions of the brain and thoracic nervous system. Intense staining in the glomeruli of the antennal lobes, the region of the nervous system containing terminals of antennal olfactory sensory neurones and mechanosensory neurones, indicates possible roles for this mAChR gene product in the processing of olfactory and mechanosensory signals in the fly. The staining of a discrete group of neurosecretory cells in the pars intercerebralis of the brain indicates a possible new role for this mAChR in the regulation of neurosecretion. Very little staining is detected in the thoracic nervous system.

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1995.tb00768.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThree dimensional (3‐D) cultures of pineal cell aggregates were obtained by constant gyratory shaking the heterogenous cell populations, obtained from the rat pineals, in the DMEM (Dulbecco's modified Eagle's medium). Within 4 days, the pineal cells became organized into a tissue like configuration appearing as a compact ball, evidenced by the scanning electron microscopy. The 3‐D aggregates seemed to be mainly composed of pinealocytes (round‐oval cells), glial (elongated cells) and other unknown cells. The heterogenous cells were separated by intercellular spaces. The ultrastructural characteristics revealed by transmission electron microscopy exhibited the presence of granular lysosomes, typical of pinealocytes actively involved in the secretion. These pineal cell aggregates secreted melatonin and other indole amines i.e. 5‐methoxytryptamine (5‐MT), indole acetic acid (IAA), 5‐methoxy‐3‐indole acetic acid (5‐MIAA), tryptophol (TOL) and 5‐methoxytryptophol (5‐MTL) in the culture medium, indicating the functional aspect of pinealocytes. The 3‐D aggregates cultures had advantages over the pineal monolayer cultures as, after 4 days of culture, the amounts of indole amines secreted by 3‐D aggregates were higher than those secreted by monolayer cultures. Besides, the 3‐D aggregates remained functional till 24 days in the gyratory culture conditions. In the continuous perifusion system, the 3‐D aggregates secreted melatonin while challanged with isoproterenol. This 3‐D model of pineal cell aggregates might be useful, in future, to perform other kinetic studies of the release of indole amines in perifusion experiments as this system allows the maintenance of pineal

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1995.tb00769.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe nature of melatonin receptor‐G‐protein coupling in ovine pars tuberalis (PT) cells of the pituitary was addressed using cholera (CTX) and pertussis (PTX) toxins. ADP‐ribosylation of ovine PT membrane proteins using32P‐NAD in the presence of CTX radiolabelled several substrates including 44, 51, and 60 kD proteins. Each were clearly distinct from the 40 kD substrate radiolabelled in the presence of PTX. Acute incubation of PT membranes with either toxin reduced the number of high affinity binding sites for125I‐MEL, although the magnitude of the inhibition was much greater for CTX (56%) than for PTX (20%). A CTX‐sensitive component also mediates the inhibition of forskolin‐stimulated cyclic AMP accumulation as pre‐treatment of PT cells with CTX (5μg/ml) for 16 h blocked this response.Gsα is a major substrate for ADP‐ribosylation by CTX, and 16 h pre‐treatment of PT cells with CTX (5μg/ml) caused a down‐regulation of Gsα. Northern analysis showed only one major transcript of Gsα of about 2 kb, which would encompass all of the known splice variants of the Gsgene. Screening of a cDNA library from ovine PT for Gs‐related genes and sequencing of clones, combined with RT‐PCR of PT mRNA, revealed no novel products. On this basis it is concluded that the CTX substrate is unlikely to be a novel splice variant or related gene product of the Gsclass of G‐protein. These results indicate that a distinct CTX‐sensitive mechanism mediates the inhibition of cyclic AMP by the melatonin receptor, which involves either a novel a‐sub‐unit of a heterotrimeric G‐protein or a protein which associates and functionally modulates the activity of

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1995.tb00770.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractAlthough previous studies have demonstrated that acute hypoglycemia inhibits growth hormone (GH) secretion due to stimulation (hypothalamic somatostatin (SS) neurones in the rat, the effect of hypoglycemia on GH secretion has not yet been elucidated in the mouse In this study, the effects of insulin‐induced hypoglycemia on mouse GH secretion, hypothalamicc‐fosexpression, GH‐releasing hormon (GRH) and SS mRNA levels were investigated in conscious male mice. Seven days after implantation of chronic atrial catheters, bloo samples were taken every 20 min from 1200–1600 h under unrestrained conditions. Insulin was administered iv every 20 min fro1 1200‐1240 h to induce moderate hypoglycemia (MH) and severe hypoglycemia (SH), respectively. Expression of hypothalamicc‐fosprotei was examined 30 min and 60 min after induction of hypoglycemia by immunohistochemistry. Hypothalamic GRH and SS mRNA level were examined 1 h and 3 h after induction of hypoglycemia by Northern blot analysis. The lowest mean plasma glucose levels after insuli injections were 49.1 ± 4.1 mg/dl and 34.2 ± 5.6 mg/dl in conscious mice, respectively. However, pulsatile GH secretion was no significantly altered in either group. Although both MH and SH markedly stimulatedc‐fosexpression in specific hypothalamic nuclc including the paraventricular nucleus, they did not inducec‐fosprotein in the periventricular nucleus. Neither MH nor SH altere hypothalamic GRH or SS mRNA levels. These results suggest that hypoglycemia does not activate SS neurons which inhibit GH secr

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1995.tb00771.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe functional relationship between sexually dimorphic neural populations and sex differences in reproductive functioning is unclear. The present study has investigated the function of the sexually dimorphic, estrogen‐receptive, calcitonin gene‐related peptide (CGRP) neurones in the female preoptic area by examining patterns of Fos immunoreactivity within these cells in relation to the luteinizing hormone surge and lordosis behaviour. In the first experiment, ovariectomized rats were treated with estradiol alone or estradiol plus progesterone to induce the luteinizing hormone surge. The percentage of CGRP neurones with Fos‐positive nuclei was not different in estradiol alone (18 ± 4%) and estradiol/progesterone‐treated (24 ± 3%) rats although the number of Fos‐immunoreactive cells in the medial preoptic nucleus was increased 2‐fold (P<0.01) in estrogen/progesterone‐treated rats and 40 ± 5% of luteinizing hormone‐releasing hormone neurones were found to express Fos in this group. In the second experiment, ovariectomized rats were treated with estradiol and progesterone and either, mated with a single male or placed in an empty cage, for 30 min. The number of Fos‐immunoreactive cells in the medial preoptic nucleus was increased 4‐fold in mated rats (P<0.01) and the percentage of CGRP neurones with Fos‐positive nuclei increased from 24 ± 3% to 38 ± 2% (P<0.01) in mated animals. No differences were detected in the number of luteinizing hormone‐releasing hormone neurones with Fos‐positive nuclei in mated and non‐mated animals.These results suggest that a sub‐population of CGRP neurones in the medial preoptic nucleus may express Fos on a constitutive basis in steroid‐treated animals and that, while not altered in relation to the luteinizing hormone surge, Fos expression by these cells is increased following mating. Although the precise role of these CGRP neurones has yet to be ascertained, the present experiments provide direct evidence of a functional relationship between a specific sexually dimorphic neural population and a component of sexually dif

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1995.tb00772.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractIn a previous report, we have shown that intracerebroventricular (icv) administration of the cytokine interleukin‐1a (IL‐1α) in the ovariectomized (OVX) rhesus monkey results in the acute activation of the hypothalamo‐pituitary‐adrenal (HPA) axis and the inhibition of LH and FSH secretion. Here, we compare the cortisol response to IL‐1α administration in OVX monkeys and in OVX animals replaced with estradiol (E) to reproduce E concentrations typical of the early‐mid follicular phase. Cortisol, LH and FSH were measured after an icv infusion of physiological saline or IL‐1α (2.1 or 4.2 μg/30 min) in both groups. E‐containing capsules were implanted sc 5 days prior to the experiment. In OVX, E concentrations were100 pg/ml, confirming our previous observations. While saline infusion did not affect LH (102.3 ± 10.2% of baseline at 5 h) or FSH (102.5 ± 4.4%) secretion in OVX monkeys, there was a significant decrease in both hormones after IL‐1α (LH: 33.3±3.7%, FSH: 66.2 ± 6.5%; P<0.05vssaline). This effect was lessened in OVXE animals: By 5 h, areas under the LH curve were 62.8 ± 10.9% of baseline in grp 1 and 85.3 ± 7.9% in grp 2 (NSvssaline), while those under the FSH curve were 84.0 ± 6.5% in grp 1 and 77.7 ± 4.3% in grp 2 (NSvssaline).The data demonstrate a striking effect of a 5‐day estradiol treatment in preventing the HPA axis response to the cytokine IL‐1α in the OVX monkey. This action, however, occurs only within restricted estradiol concentrations that reproduce E levels typical of the early‐mid follicular phase of the menstrual cycle. While the precise mechanism through which estradiol exerts this action remains to be investigated, the results may have clinical relevance to the issue of est

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1995.tb00773.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractWe investigated the effectiveness of continuousvsintermittent LHRH stimulation of the neonatal female anterior pituitary gland on inducing cellular FSH immunoreactivity in the Golden Syrian hamster. Neonatal female pituitary glands were grafted beneath the right renal capsules of hypophysectomized‐ovariectomized adult hosts with a catheter implanted in the external jugular vein. In experiment 1, vehicle or LHRH (6 ng/h) was infused continuously or LHRH was pulsed at 1 h (6 ng) or 12 h (72 ng) intervals through the catheters for 8 days. Hamsters were decapitated for collection of trunk blood shortly after the end of treatment, and grafts were prepared for immunocytochemical staining for LH and FSH. Anterior pituitary glands removed from neonatal (day 1) and day 9 female pups also were stained for LH and FSH. The mean percentage of adenohypophysial cells staining for LH increased from 11% in neonatal pups to mean percentages (24‐28%) that were similar in day 9 pups and in all groups with grafts. The mean percentage of adenohypophysial cells staining for FSH increased from 1% in neonatal pups to percentages (16–21%) that were similar in day 9 pups and in grafts in hosts administered 6 or 72 ng LHRH pulses. By contrast, the mean percentage of FSH cells did not increase in grafts in hosts administered vehicle or LHRH by continuous infusion. Serum LH concentration was low in hosts given vehicle or LHRH by continuous infusion but elevated in hosts given 72 ng LHRH pulses and in all but one host given 6 ng LHRH pulses. Serum FSH concentration was detectable in some of the hosts given 6 or 72 ng LHRH pulses and non‐detectable in the rest of the hosts. In experiment 2, the mean percentage of adenohypophysial cells staining for FSH did not increase in grafts in hosts infused with LHRH continuously at 72 ng/h compared to that observed in hosts pulsed with vehicle every h for 8 days (1.4vs2.0%). The data demonstrate that intermittent but not continuous stimulation of neonatal female adenohypophysial cells by LHRH is effective in inducing cellular FSH immunoreactivity. The data also strongly suggest that LHRH release is episodic during the first week after birth in the female hamster. To our knowledge, these results are the first to provide evidence suggesting that the episodic LHRH release system is functioning to exert an important biological effect in a neonatal mammal and that the mechanism for down‐regulation of LHRH receptors in gonadotrophs can be activated this earl

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1995.tb00774.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractTo further investigate how sex steroids regulate galanin (GAL) in the rat pituitary and hypothalamus, we examined the effects of prepubertal gonadectomy (Gx) and long‐term (9 weeks) replacement with estradiol (E2) or testosterone (T) on pituitary and hypothalamic GAL concentrations in Wistar rats (5–6/group). Sham‐operated animals served as controls (CTR). Pituitary GAL concentration was markedly higher in random‐cycling CTR‐females than in CTR‐males (1391 ± 247vs39 ± 5 pg/mg protein, P<0.01) and decreased after Gx only in females (20 ± 3 pg/mg protein, P<0.01). E2strongly increased pituitary GAL in Gx‐females and Gx‐males (4470 ± 365 and 3853 ± 347 pg/mg protein, P<0.01), whereas T had no effect. Inversely, hypothalamic GAL was higher in CTR males than in CTR females (5.4 ± 0.3vs4.0 ± 0.5 ng/mg protein, P<0.05), and decreased significantly after gonadectomy in males (3.7 ± 0.2 ng/mg protein, P<0.01). The only steroid treatment that significantly modified hypothalamic GAL in Gx animals was administration of E2to females (5.7 ± 0.4 ng/mg protein, P<0.01vsnon‐treated Gx). We also studied in hypophysectomized (Hx) rats (8/group) the effects of sex steroids on hypothalamic GAL concentration and distribution. The low hypothalamic GAL concentration observed in male and female Hx rats (1.0 ± 0.1 ng/mg protein) was significantly increased by T in males and in females (respectively, by 40% and by 50%, P<0.02) and by E2in males (by 60%, P<0.02). Immunohistochemistry showed that both E2and T increased GAL labeling in fibers restricted to the lateral regions of the median eminence of male and female Hx rats, a distribution corresponding to that of GnRH‐immunoreactive fibers. In conclusion, in addition to the marked stimulatory effect of estradiol on pituitary GAL, endogenous and exogenous sex steroids also modulate hypothalamic GAL in male and female rats. Both E2and T may exert a stimulatory influence on hypothalamic GAL concentration and histochemical analysis shows that sex steroids enhance GAL immunoreactivity in a subset of neurons that closely overlaps the

ISSN:0953-8194    

DOI:10.1111/j.1365-2826.1995.tb00775.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY