摘要:

A variety of reports indicate that some kind of interaction may exist between the pineal gland and cations. Of particular interest are the reports that indicate comparatively high levels of copper, manganese, and zinc in the pineal gland and that the pineal gland exhibits a circadian rhythm in calcium, magnesium, potassium, and sodium. There are, unfortunately, no reports suggesting a functional role for these findings. This study investigated circadian rhythms in circulating plasma cations in rats under 12/12 h light‐dark cycle and in rats whose pineal function had been suppressed by exposure to constant light for 1 and 7 days. Neither of the treatments affected circulating potassium levels but had some significant effects on sodium concentration at a number of time points without affecting the total amount of sodium circulating in a 24 h period. Calcium, magnesium, and zinc plasma concentrations were little affected by 1 day of constant light, while 7 days of constant light caused a dramatic and highly significant increase in the circulating levels of the three cations. The plasma levels of copper, on the other hand, while also being unaffected by 1 day were significantly depressed by 7 days of constant light. It is apparent, therefore, that the pineal gland may be involved in regulation of circulating levels of the cations measured. The functional significance of these observations is not clear at this stage but warrants further investigatio

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1990.tb00697.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

EGTA, a nonspecific ion chelator, showed very good potential for preventing the loss of serotonin N‐acetyl transferase activity (arylamine: acetyl‐CoA: N‐acetyltransferase, EC 2. 3. 1. 5.) (SNAT) from rat and chicken pineal glands during preincubation at 37°C before substrate addition. SNAT activity was higher than that of the controls when EGTA was present in the homogenization buffer due to the prevention of the loss of activity probably not only during the preincubation period but also during incubation with its substrates. This characteristic of EGTA suggests that its use is suitable in the improved SNAT assay described in this paper since higher SNAT activities were found in both rat and chicken pineal glands than the activities recorded with the usual m

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1990.tb00698.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Six healthy adult male volunteers underwent serial blood drawings at 4‐hour intervals over 24 hours for the definition of melatonin (MT), prolactin (PRL), cortisol, and testosterone circadian patterns. Serum levels of triiodotironine (T3) and thyroxine (T4) were determined at 0800. Systolic and diastolic blood pressure and heart rate were automatically recorded every 30 minutes for 24 hours. The responses of luteinizing hormone (LH), follicle stimulating hormone (FSH), PRL, thyroid stimulating hormone (TSH), cortisol, and aldosterone to a stimulation test with gonadotrophinreleasing hormone (Gn‐RH), thyrotrophin‐releasing hormone (TRH), adrenocorticotrophin (ACTH), and testosterone to human chorionic gonadotrophin (HCG) were also evaluated. The same protocol was repeated after a two‐month course of treatment with MT, 2 mg per os daily at 1800. After treatment, we recorded a marked elevation of mean serum MT levels with a significant phase‐advance of its circadian rhythm. The 24‐hour patterns of cortisol and testosterone displayed an anticipation of the morning acrophase of about 1.5 hour (not significant) for cortisol and three hours (P<0.05) for testosterone. PRL pattern was unchanged as well as serum levels of thyroid hormones. The circadian organization of the cardiovascular variables did not show any changes after MT supplementation; the pituitary, adrenal, and testicular responses to specific stimuli were comparable before and after treatment. These results are compatible with the view that the MT signal may provide temporal cues to the neuroendocrine network for the organization of testicular circadian

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1990.tb00699.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The gonads of male hamsters exposed to short photoperiod (LD, 10: 14) or treated with melatonin in the late afternoon under long photoperiod (LD, 14: 10) had undergone complete regression by the end of the treatments (8 weeks). Animals treated for the same period of time with prazosin (a putative melatonin analogue) under the same conditions failed to show a difference in their gonadal status as compared to the long photoperiod controls. Prazosin was unable to prevent melatonin‐induced gonadal atrophy when injected either in the morning or 30 min before melatonin. Moreover, prazosin was without any effect on (and unable to prevent the melatonin‐stimulated) progesterone production by rat adrenals under in vitro conditions. These data demonstrate that prazosin, which reportedly inhibits 2‐[1251]iodomelatonin binding in the hamster brain in an affinity‐related manner, does not possess properties of a biological melatonin analogue under conditions of two different model systems in two

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1990.tb00700.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Twenty‐four hour patterns of urinary 6‐sulphatoxymelatonin excretion were monitored in eight healthy adult subjects in two bed rest constant routines, one with normal nocturnal sleep and one with continuous wakefulness. The implementation of dim light “constant routines” enabled the effect of the sleep wake/state on melatonin to be tested without the confounding effects of body activity and normal room lighting. In both conditions 6‐sulphatoxymelatonin excretion was significantly higher during the nighttime hours (2200‐1000) than during the daytime hours (1000‐2200) producing averages of 80% and 78.5% of the total 24 hour output in the sleep and wakeful conditions, respectively. The large differences between subjects in nocturnal melatonin excretion (38 to 150 nmol) were highly consistent between the two conditions. There were no differences between the nocturnal wakeful and sleep conditions in total nighttime melatonin excretion nor in the nighttime percentage of the 24 hour total melatonin excretions. Therefore, the sleep/wake state alone had no effect on nocturnal melatonin excretion. On the other hand, a significant correlation between the nighttime melatonin percentage and sleep length suggested the need to investigate further the relation between the amplitude of the melatonin circadian rhythm and sleep lengt

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1990.tb00701.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

In the newborn southern elephant seal the pineal gland is very large, and both pineal and plasma melatonin concentration is elevated. The pineal gland was investigated during the first 24 h, and up to 20 days of age, in elephant seal pups. A primary aim of this investigation was to determine whether there are obvious ultrastructural characteristics of pinealocytes that are exhibiting extraordinarily high levels of activity. Blood and pineal glands were collected from thirty seven pups of known age which were sampled at random from early September to early November (1985) at Macquarie Island. The pineal gland is large (mean weight, 4.71 ± 0.35 gm, range 1–9.3 gm) and actively secreting melatonin at birth. Melatonin concentrations were extremely variable, yet very high in pups during the first 24 h post‐partum. Mean melatonin plasma concentration for pups 0–24 h was 17632.8 ± 5723.8 pmol/l (4090.8 ± 1327.9 pg/ml), ranging from 126 pmol/l (29 pg/ml) to 297000 pmol/l (68904 pg/ml). Electron microscopic examination did not reveal any marked changes in pinealocyte ultrastructure suggestive of increased secretory activity during this period. The large and extremely active pineal gland in newborn southern elephant seal suggests that it is actively involved in thermore

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1990.tb00702.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Circadian patterns of plasma melatonin, FSH, LH, prolactin, and testosterone were studied in 10 healthy men, 20 men with oligozoospermia, and 8 men with azoosper‐mia. Circadian rhythms were found in concentrations of melatonin and prolactin, with higher values at night in comparison with daytime levels. In patients with oligozoospermia and azoospermia an elevation in melatonin levels was observed, and an increase in melatonin concentrations occurred before onset of darkness (i. e., at 2000 h). Levels of FSH, LH, and prolactin were elevated in infertile patients. The possibilities that an increase in melatonin concentrations is either the primary feature that leads to the regression of the seminiferous epithelium or is secondary and depends on elevated gonadotropins and/or prolactin levels are discusse

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1990.tb00703.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The effect of acute cold exposure for 6 hours on nocturnal type II thyroxine 5′‐ deiodinase (5′‐D) activity was studied in brown adipose tissue (BAT), Harderian gland, cerebral cortex, and pineal gland of the rat. Moreover, the effect of iopanoic acid (IOP), a potent inhibitor of 5′‐D activity, on both pineal N‐acetyltransferase (NAT) activity and melatonin content in rats maintained in a cold environment was also examined. Results show that acute cold exposure significantly increases 5′‐D activity in BAT but not in either the pineal gland, Harderian gland, or cerebral cortex. In all tissues, the injection of IOP reduced dramatically 5′‐D activity, while exposure of the animals to light at night reduced 5′‐D activity in pineal gland but not in either the Harderian gland or BAT while light exposure at night increased cerebrocorticol 5′‐D activity. Cold exposure did not change either pineal NAT activity or the melatonin content of the gland. Finally, when pineal 5′‐D activity was inhibited by IOP treatment, neither nocturnal pineal NAT activity n

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1990.tb00704.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY