摘要:

The various pineal gland tryptophan metabolites were administered to male rats intraperitoneally (100 μg/kg) and rectal temperatures were recorded. Of the compounds tested, hydroxytryptophan, N‐acetylserotonin, hydroxytryptophol, and their corresponding methoxyindoles all caused a marked hypothermia, indicating that several indolic products may be involved in thermoregulation. Although the brain penetration of indoles is poor, a central site of action would be most likely, although peripheral actions cannot be excluded. The mechanism of induction of hypothermia may involve peptides, the pituitary‐thyroid axis, the adrenal gland, or a combination of these. These results may suggest that the pineal gland integrates environmental cues to act in concert with physiological thermostats in the fine tuning of thermoregula

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1987.tb00835.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Pineal glands were incubated in the presence of [3H] methoxytryptophan with and without methoxamine, epinephrine, and norepinephrine. The beta‐adrenoceptor‐stimulated pineal glands were capable of converting methoxytryptophan to methoxytryptamine, melatonin, methoxyindole acetic acid, and methoxytryptophol, albeit in small quantities. Only methoxyindole acetic acid was detectable after incubation of unstimulated and alpha‐adrenergic‐agonist‐treated pineal glands. These results support the proposal that melatonin can be formed from methoxytryptophan although this is a minor synthetic pathway, and the classic pathway from serotonin via N‐acetylserotonin should be considered to be responsible for the majority of pineal melatonin

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1987.tb00836.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The aim of the study was to determine the effect of exogenous melatonin treatment on circulating prolactin levels in red deer. Melatonin was administered from 12 June 1984 (day 1) to lactating and non‐lactating hinds in the feed daily at 1600 h, and to non‐lactating hinds by a subcutaneous implant. Average concentrations (ng/ml) of prolactin in plasma taken serially over 15‐h periods were significantly higher for untreated hinds than for melatonin‐treated animals on day 15 whether lactating (66–133 v. 23–28,P<0.05) or non‐lactating (28–174 v. 8–13,P<0.01), remained higher on day 36 (lactating: 41–152 v. 15–21,P<0.05; non‐lactating: 21–50 v. 1–7,P<0.001) but had decreased to similar levels on day 72 (lactating: 5–24 v. 7–17; non‐lactating: 2–9 v. 0–4).The advanced reduction in plasma prolactin for all melatonin‐treated hinds was associated with an advan

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1987.tb00837.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Plasma concentrations of immunoreactive melatonin, estradiol, progesterone, follicle stimulating hormone (FSH), and β‐human chorionic gonadotropin (βhCG) were studied between 1000 and 1230 h in 105 Chinese females during six periods of normal pregnancy and 1–5 min after normal delivery. We have also examined the midday levels of immunoreactive melatonin in the cord blood of fetuses and plasma collected 1–5 min after and 24 h after delivery from their mothers. Concentrations of hormone immunoreactivities were determined by radioimmunoassay, and distinct fluctuations of all hormones were recorded during pregnancy. In the pregnant females, there were significant negative correlations between 1) melatonin and estradiol, 2) melatonin and progesterone, 3) βhCG and progesterone, and 4) βhCG and estradiol, and positive correlations between 1) melatonin and FSH and 2) progesterone and estradiol. Furthermore, plasma melatonin levels in the cord blood demonstrated no sex difference and were significantly lower than and correlated positively with the levels in their mothers. Our results suggest that 1) sex steroids may inhibit and FSH may potentiate circulating melatonin levels in gravid women; 2) changes in the levels of melatonin during pregnancy may affect the in utero development of the human embryo; and 3) circulating melatonin in the mother may be the major source of blood melatonin in the fetus before pa

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1987.tb00838.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Adult female Long‐Evans rats were maintained on an automatically regulated artificial lighting schedule of light:dark (L:D) 14.5:9.5 for 12 wk. After sacrifice at 0630, 1130, 1600, 1800, 2000, 2200, 0230, or 0400, the pineals were removed, weighed, and assayed forN‐acetyltransferase (NAT), melatonin, Mg++‐paranitrophenylphosphatase (pNPPase), and K‐pNPPase activity. The brains were quickly dissected into the following areas: cerebellum, superior colliculi, inferior colliculi, visual cortex, auditory cortex, sensorimotor cortex, and the hypothalamic area around the suprachiasmatic nucleus. These regions were weighed and 10% sucrose homogenates were prepared for determinations of protein, Mg++‐pNPPase, and K+‐pNPPase activity. Pineal melatonin rose over six‐fold from 144 ± 70 pg/gland at 1130 to 981 ± 173 pg/gland at 0230. Similarly, pineal NAT activity rose over 11‐fold, from 119 ± 12 pmol/gland/h to 1315 ± 232 pmol/gland/h at the same times. K+‐pNPPase activity rose by about two‐thirds, from 133 ± 12.8 nmol/gland/h to 224 ± 22.3 nmol/gland/h from 1600 to 0230. However, when expressed per mg protein, these differences inpNPPase activity were not significant. There were no significant daily rhythms discernible in any of the seven other brain regions across these times. We conclude that cation pump enzyme activity varies only slightly with time in the rat brain and pineal gland, in spite of definite daily rhythms of pineal m

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1987.tb00839.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Dense‐cored vesicles (DCV) and synaptic ribbons (SR) were quantified in the pineal gland of the rat (Sprague‐Dawley) and mouse (Sasco/ ICR strain), and day/ night differences in frequency of these organelles correlated with levels of indoles determined by high performance liquid chromatography (HPLC). There were significant day/night differences in levels of serotonin (5HT), 5‐hydroxyindole acetic acid (5HIAA), N‐acetyl‐5HT, and melatonin in the rat gland. Melatonin and N‐acetyl‐5HT were not detectable in the mouse gland sampled every 4 h over the light:dark cycle. The concentrations of 5HT and 5HIAA (ng/μg protein) were similar in light‐adapted rats and mice, but these indoles did not exhibit a circadian rhythm in the mouse gland. Correlative ultrastructural/biochemical results suggest that DCV do not contain physiologically important stores of 5HT since 1) the mouse gland contains the same number of DCV as the rat during the daytime, but only one‐tenth the levels of 5HT, 2) day/night 5HT levels do not vary in the mouse gland, but there is a significant nocturnal decline in DCV numbers, and 3) 5HT levels in the rat gland decline at night when DCV numbers increase. Numbers of SR were significantly elevated at night in the rat and mouse, and the frequency of this organelle was similar in both species. However, ribbon‐type SR predominated in rat pinealocytes, whereas SR in the mouse were almost exclusively spherical in shape. Day/night diffferences in SR numbers in the mouse gland suggest that cellular mechanisms regulating the frequency of this organelle do not involve factors related to indole metabolism. Because of the lack of photoperiodic effects on indole metabolism in the mouse pineal gland, this species is a potentially important model to study the functional relationship of pinealocyte organelles to cyclical changes in pineal products other than indoles (e.g., pepti

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1987.tb00840.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Granular vesicles are present in pinealocytes and in rudimentary photoreceptor cells of many vertebrates, sometimes in large amounts. Their dense cores have been shown to store proteinaceous compounds, but the way they are released remains speculative. The aim of this study was to demonstrate whether or not exocytosis is the mechanism by which secretory products stored within granular vesicles are released. Therefore, a method has been used allowing a clear ultrastructural study of secretory products by exocytosis, even in tissues in which this process of secretion is quite rare and/or very slow. Exocytotic figures have been clearly demonstrated in the three species studied: golden hamster, snake, and parakeet. Nevertheless, they were never commonly observed as it was the case in neurohypophysis, even in such animals as the parakeet and snake, in which granular vesicles are very numerous. The possible reasons of this observation are discussed.

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1987.tb00841.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

A diurnal rhythm of sensitivity to exogenous melatonin was defined in adult male Turkish hamsters,Mesocricetus brandti.Melatonin was administered daily by subcutaneous injections (15 μg in 0.1 ml 10% ethanolic saline) for 10 weeks in animals exposed to 16 L:8 D. As in golden and Djungarian hamsters, two periods of melatonin sensitivity were identified. The first, in late afternoon, persisted for 6 hr, from 7 hr to 1 hr before lights off. The second period was briefer, of only 2 hr duration in the late night, terminating at the time of lights on. Melatonin injections given during these sensitive periods promoted testicular regression in most animals; melatonin administered at other times of the day was without effect on testicular function in most animals of these groups. Gonadal regression induced by properly timed melatonin injections was rapid, in many groups nearly complete in 6 to 7 weeks. The results are discussed in relation to the function of pineal melatonin in photoperiodic time measurement in hamsters

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1987.tb00842.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The role of the pineal and of photoperiod in the regulation of gonadal activity has been studied in the European hamster, a wild hamster commonly found in the vicinity of Strasbourg, France. Besides the presence of a probable endogenous circannual rhythm in reproductive capacities, it appears that, as in all other hamster species studied to date, the sexual activity of this animal is directly regulated by changes in the photoperiodic environment.Pinealectomy as well as a constant release of melatonin or of 5‐methoxytryptamine has no effect on the gonadal atrophy induced by short photoperiod, but induces testicular regression in animals kept under long photoperiod. The pineal in this species appears thus to be involved in the maintenance of sexual activity in long photoperiod, while it is apparently not required for the gonadal inhibitory effect of short photoperiod. These results are similar to those obtained in the Turkish hamster. 5‐Methoxytryptophol is not implicated in the phenomenon of synchronization of the sexual activity with the photoperiodic chan

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1987.tb00843.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The binding characteristics of the tritiated pineal hormone, [3H] melatonin, were studied in brain tissues using in vitro binding techniques. In synaptosomal membranes prepared from rat hippocampus and subjected to preincubation at 37°C and multiple washings, high‐affinity binding of [3H] melatonin significantly exceeds that previously reported for membrane or cytosol fractions from mammalian brain. Scatchard analysis of saturation binding data indicates that binding affinities are similar in membrane (Kd= 15 nM) and cytosol (Kd=11 nM) preparations. However, binding is about sevenfold greater in membranes than in cytosol prepared by centrifugation of homogenates at 104,000g for 60 min. Specific binding is also present in both particulate and soluble fractions from calf brain.Inhibition experiments, in rat hippocampal membranes, indicate that norepinephrine is the most potent inhibitor of about 55% of total binding. Serotonin also exhibited high affinity for about 25% of total binding, suggesting that [3H] melatonin labels both adrenergic and serotonergic sites in this brain region.Further studies are required to characterize the serotonergic and adrenergic sites labelled by [3H] melatonin and to determine whether these sites are functionally important receptors for melaton

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1987.tb00844.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY