摘要:

The studies described in this paper were undertaken to characterize the circulating and hepatic insulin and glucagon receptor concentrations of control (C), diabetic (Db), and pinealectomized‐diabetic (Pn + Db) rats. Compared with C rats, an increase in plasma glucose and glucagon levels and a reduction in circulating insulin concentrations in Db animals was observed; these differences were greater in Pn + Db rats. In liver membranes, insulin binding was lower in Db and in Pn + Db than in C rats, and glucagon binding was greater in Db and in Pn + Db than in C rats. The modifications in hormone binding did not reflect changes in the affinity constants. The time courses of hormone association and dissociation from liver membranes were similar in all three experimental groups. The degradation of both hormones and their receptors was similar in all three groups. These findings indicate that in either pinealectomized‐diabetic or diabetic rats there were significant changes in the circulating and liver insulin and glucagon receptor concentrations and that the changes in the circulating levels of both pancreatic hormones were more pronounced in pinealectomized‐diabetic animals. In addition, the absence in Db and in Pn + Db rats of the insulin and glucagon down‐regulation of their own receptors could further modify metabolic activities in these

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1989.tb00425.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The aim of this study was to investigate the localization in the superior cervical ganglia (SCG) of neuropeptide Y‐containing neurons innervating the pineal gland. Following injection of the fluorescent tracer Fluoro‐Gold (FG) into the superficial part of the pineal gland and retrograde axonal transport, labeled cells were observed predominantly in the rostral third to half of SCG sections (average number 239 per ganglion). Incubation of the sections with neuropeptide Y (NPY) antiserum showed that the vast majority of neurons exhibit NPY‐like immunoreactivity (NPY‐LI). The comparison of cells labeled with FG and those containing NPY revealed that nearly three fourths of retrogradely labeled neurons also exhibit NPY‐LI. Incubation of pineal gland sections with NPY antiserum showed immunoreactive axons, relatively sparse and scattered throughout the superficial part of the organ and the pineal stalk. The present results confirm the assumption that, in rodents, pineal NPY originates from the superior cervica

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1989.tb00426.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The effects of exogenous thyroid hormone administration on melatonin‐induced gonadal atrophy were studied in young adult male hamsters. Animals were given daily afternoon injections of 25 μg melatonin and/or thrice‐weekly injections of 7 μg thyroxine. A control group received injections of saline vehicle only. No significant effect of either treatment was seen on body weight. Melatonin‐treated animals had significantly reduced testicular and seminal vesicle weights, compared with vehicle‐treated control animals: serum T4 levels and the FT4I were reduced by melatonin treatment, but serum T3 and the FT3I were increased. No effect of melatonin was seen on in vitro T3 uptake. Thyroxine treatment alone, while leading to elevated serum T4 levels and FT4I, had no effect on T3, the FT3I, or T3 uptake. Thyroxine treatment normalized circulating T4 levels and the FT4I in melatonin‐treated animals, without preventing the melatonin‐induced testicular regression. The results are taken as evidence that the inhibitory effects of melatonin on gonadal and thyroid function are independe

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1989.tb00427.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

In a double‐blind study, melatonin (50 mg) or placebo was administered daily to 25 subjects at 9 am or 7 pm for 1 week. Self‐rated fatigue as evaluated by the Stanford Sleepiness Scale (SSS) was significantly increased during the 3 hours following melatonin intake in the morning, whereas, after administration in the evening, no difference between melatonin and placebo could be distinguished. Sleep onset latency slightly decreased in both melatonin groups without reaching statistical significance. No cumulative effects on sleep or behavior were observed. Twelve pituitary and peripheral hormones measured under baseline and partly (in the evening groups) under stimulated conditions before and after the trial did not change. The two most important conclusions are that: 1) the sedative potency of exogenous melatonin depends on the daily time of administration; and 2) the high pharmacological doses used for acute sedation do not seem to have cumulative effects after prolonged applicat

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1989.tb00428.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

InHeteropneustes fossilis, the adrenocortical cells were highly active, hypertrophied, and degranulated after 15 and 30 days of pinealectomy in spawning/postspawning phase. Besides, several cells had undergone pycnotic changes in the 30‐day group. The plasma Cortisol level increased significantly (P<0.05) in the pinealectomized fish in comparison to those of the sham pinealectomized and unoperated control fish. The increase was higher in the 15‐day group than in the 30‐day‐pinealectomized group. The results suggest that the pineal organ exerts an inhibitory influence on the activity of the adrenal in the

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1989.tb00429.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The in vitro effects of 13 indole compounds on the synthesis of glucocorticoids and of adrenal androgens in sheep adrenal glands has been studied from 11 ‐deoxycortisol as a precursor. This work demonstrates the activating effect of some indole compounds on 11β‐hydroxylase and 17,20‐desmolase and the inhibitory effect of most of them on 11β‐hydroxysteroid dehydrogenase. Three categories could be distinguished: 1) compounds without any effect (5‐hydroxytryptophan, 5‐hydroxytryptamine); 2) compounds moderately increasing (10—30% as compared with controls) Cortisol yields (tryptamine, melatonin, 6‐hydroxymelatonin, 5‐methoxytryptophol, indomethacin); and 3) compounds markedly increasing (80–100%) Cortisol yields (5‐methoxyindole acetic acid, 5‐hydroxyindole acetic acid, 2‐methylindole, 5‐hydroxytryptophol,N‐acetyl‐5‐hydroxytryptamine). In fact, since most of the studied indoles reduced 11β‐hydroxysteroid dehydrogenase activity, the actual activation of Cortisol synthesis was four to five times less. Lastly, all the studied compounds, but melatonin, increased the activity of 17,20 desmolase as seen from 11β‐hydroxyandrostenedione and 11‐ketoandrostenedione yields. The possible in vivo effects of the indoles

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1989.tb00430.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

When injected into rodents, the bovine pineal tripeptide threonylseryllysine (TSL) elicits diverse antireproductive effects in a number of animal models. Extensive studies of its effects on pubertal development have not been carried out, however. In the present study, 1.0 μg of T‐S‐L was administered daily to female Charles River CD rats throughout the peripubertal period, and effects on vaginal opening time, ovarian histology, and serum luteinizing hormone (LH) levels were observed. Since TSL is known to alter the action of luteinizing hormone releasing hormone (LHRH), it was postulated that this antireproductive tripeptide would delay the time of vaginal opening associated with first ovulation. Two hundred eighty‐seven weanling females were housed at 22°C under a 14L:10D photoperiod. They were divided into three groups for daily intraperitonal injections of either saline (SAL), 1.0 μg TSL, or 5.0 μg melatonin (aMT) beginning on the 23rd day of life. Subgroups of nine to ten rats from each treatment group were sacrificed on days 28, 30, 32, 33, 34, 35, 36, 37, 38, and 40. Although the body weights of all animals increased significantly during the course of the study, no significant differences were observed in this parameter among rats treated with saline, aMT, or TSL. Vaginal opening time was significantly delayed by TSL between days 32 and 40, and uterine weights were significantly lower in this group. Prepubertal increases in serum levels of LH were also significantly reduced. At the dose utilized, aMT was without significant effects on these parameters. Rats sacrificed between 32 and 38 days of age were classified on the basis of uterine weights and ovarian histology as either anestrous or in early proestrus, late proestrus, or estrus. Compared with the SAL‐ or aMT‐treated groups, TSL treatment increased the percentage of animals in both anestrus and early proestrus. At the dose utilized the bovine pineal peptide TSL effectively delayed the onset of puberty, probably through its known inhibitory action on gonadotropin secretion. This observation may reflect the demonstrated ability of TSL to bind to LHRH in a sequence‐ and residue‐specific manner, resulting in modulation of this peptide's gonadotropin r

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1989.tb00431.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The role of pinealectomy and continuous light in the regulation of sexual activity was studied in the male rat. The parameters studied in order to evaluate the sexual behavior were initial latency, ejaculatory latency, refractory period, neuromotor activity, number of ejaculations, intromissions (false, real, and total) and percentage of ejaculating male rats. Pinealectomy as well as continuous light induced a marked facilitation of the animal's sexual behavior as shown by the shorter initial latency and refractory period, as well as by the increase in the number of intromissions (real and total) showed in the tests. However, the ejaculatory latencies did not change. There was also an enhanced neuromotor activity. An increase in the number of ejaculations as well as in the percentage of ejaculating male rats was produced by continuous light. From the results it is concluded that pineal hormones play an important role in male rat sexual behavior.

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1989.tb00432.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Female hamsters were treated each afternoon for 8 weeks with subcutaneous injections of 25 μg of either melatonin or vehicle solution. Animals were sacrificed in either the morning or afternoon of diestrus and proestrus, along with their respective melatonin‐induced acyclic pairs. Melatonin‐treated hamsters had significantly greater mean body weights than did the vehicle‐treated hamsters (P<0.05). Terminal mean serum T4 levels and free thyroxine index (FT41) were significantly reduced (P<0.05) in melatonin‐treated hamsters compared with values obtained from animals subjected to the vehicle alone. In addition, T4 levels, FT41, T3 levels, and FT31 were significantly influenced by day and time of sacrifice independently of the melatonin treatment. T3 uptake was significantly lower on the morning of proestrus in melatonin‐treated animals. These results demonstrate that chronic afternoon melatonin administration in female hamsters results in the loss of estrous cyclicity, a significant gain in body weight, and the reduction of T4 levels and T3 uptake. Changes in serum T3 levels are a function of the time of sample collection and are not influenced by melatonin treatment. In addition, these data indicate that thyroid function in general changes during the estrous cycle in the

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1989.tb00433.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Previous investigations have shown that an inverse correlation exists between serum thyroxine levels (T4) and serum creatine kinase activity (CK) both in hypothyroid and hyperthyroid states. In the present study, serum T4levels and total serum CK activity were analysed after thyroidectomy (TX), ganglionectomy (extirpation of the superior cervical sympathetic ganglion) (GX), or pinealectomy (PX) four times a year (March, June, September, and December). Blood samples were taken four times daily (at midlight, middark, and at 1 hour after the onset of the light and dark periods). Animals were kept under an artificial light schedule that simulated natural light‐dark periods. The annual main values of serum T4levels were significantly decreased after the operations, whereas serum CK activities were increased. Our circannual investigations demonstrated an inverse correlation between serum T4levels and total serum CK activity (under hypothyroid circumstances). In addition, the circannual pattern of the serum CK activity demonstrated maxima under short‐day (winter) conditions and minima under long‐day (summer) conditions. GX and PX provoke an unimportant shift (a little longer than 2 months) in maxima and minima of the annual rhythm. Circannual curves exhibited differences in the degree of the increase of serum CK activity of GX and PX groups. These results indirectly confirm the assumption that experimental sympathetic denervation or removal of the pineal gland will induce a hypothyroid state over the long

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1989.tb00434.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY