摘要:

To investigate the relative importance of pineal and eyes in ovarian activity, catfish subjected to pinealectomy, blinding, or both were exposed to continuous light (LL) or continuous darkness (DD) during the different phases of the annual reproductive cycle. Pineal or eyes have no influence on ovarian activity during the preparatory, prespawning, and spawning periods of the annual reproductive cycle under these photoregimes. However, the pineal accelerated ovarian activity under LL and DD during the postspawning period. Blinding alone has no effect on ovarian recrudescence under these regimes. However, combined surgery (blinded‐pinealectomy) inhibited ovarian development under both these conditions, indicating that the pineal organ is more important than the eyes. Ovarian recrudescence occurred even in the absence of both pineal and eyes, indicating the involvement of extrapineal and extraocular photoreception in the regulation of reproductive activity in the catfis

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1988.tb00763.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

In mammalian pinealocytes “Synaptic” ribbons (SR) are regularly occurring organelles that are functionally poorly understood. Since in a number of studies on the mouse pineal gland the presence of SR has not been mentioned, it was the aim of this investigation to quantitate SR in mice. BALB/c mice were chosen, which have recently been shown to have a genetic defect for melatonin synthesis. The pineals of 15 mice killed at night, when SR numbers are normally high, were examined electron microscopically, scanning an area of>20,000 μm2per gland. In none of these pineals were SR detected. It is concluded that the lack or extreme rarity of SR in laboratory mice may be related to the inability of the gland to synthesize melatonin, not to the absence of melatonin per se, as melatonin administration in mice does not result in the occurrence o

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1988.tb00764.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The relationship between the concentrations of melatonin and prolactin over the 24‐h cycle has been investigated in a group of young men at three times in the year. Melatonin and prolactin showed a significant positive correlation (P<0.001) for all times during the 24‐h period but with a greater contribution from concentrations during the nocturnal period, when both hormones were elevated. The positive correlation for nocturnal concentrations was evident in February and March (P<0.01) but was of greatest significance in June (P<0.001). In blood samples taken at 15‐min intervals during the morning (0800–1200) and evening (2000–2400), melatonin and prolactin concentrations were not significantly correlated. Melatonin concentrations increased before prolactin during the evening and decreased before prolactin in the morning. Oral administration of 6 mg melatonin significantly stimulated prolactin release above concentrations measured after placebo administration, in both the morning (P<0.05) and evening (P<0.01) time periods; the prolactin response being greater in the evening. These results provide evidence for melatonin controlling the nocturnal increase of prolactin via its ability to stimulate prolacti

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1988.tb00765.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Some data from the literature raised the possibility of an interaction between the opioidergic system and pineal secretion. The present study was undertaken in order to investigate the acute influence exerted by opioids upon plasma melatonin levels in the albino rat. Different doses of morphine hydrocloride were injected (1, 1.5, 2, 3 mg/kg) intraperitoneally into anaesthetized adult male rats bearing a cannula previously inserted into the carotid. Blood samples were collected subsequently at 30‐min intervals, within a period of 90 min following drug administration. Plasma melatonin contents were determined by a radioimmu‐noassay (RIA) method. Acute administration resulted in a dose‐dependent increase in plasma melatonin concentration when compared to the respective controls. This effect is blocked by pretreatment with Naloxone. The present result seem to support the hypothesis that the opioidergic system, in certain circumstances, might contribute to the activation of melatonin secr

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1988.tb00766.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

A study of the effects of melatonin injections given to male Syrian hamsters (Mesocricetus auratus) late in the light phase in a 14L:10D photoperiod included control, oil‐injected hamsters that had been transferred from a 16L:8D photoperiod. Many oil‐injected hamsters underwent gonadal regression under these conditions. A literature review indicated that endocrine effects of‘control’injections are fairly common but that they might depend on previous photoperiodic history. A second study found that hamsters born and raised in 16L:8D had larger testes at 150 days of age than those raised in 14L:10D. Transfer from 16L:8D to 14L: 10D caused some unhandled hamsters to show gonadal regression while transfer to 14L:10D combined with daily oil injections caused most hamsters to undergo gonadal regression. Injections in animals maintained in 14L:10D throughout the study did not cause gonadal regression.These results indicate that stress effects can confound interpretation of drug treatments that require daily injections. They also demonstrate that the endocrine system of male Syrian hamsters distinguishes two photoperiods that are longer than the critical daylength (12.5 h). The effects of shortening daylengths may be potentiated by environmental stressors; together these may trigger gonadal regression at variable annual phases in anticipation of the critical da

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1988.tb00767.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The quantitative autoradiographic 2‐[14C]deoxyglucose method was employed to map the metabolic activity of the superior cervical ganglion and the entire brain during unilateral electrical stimulation of the cervical sympathetic trunk in the urethane‐anesthetized rat. Stimulation of the cervical sympathetic trunk increased glucose utilization in the ipsilateral superior cervical ganglion (+95%) but did not produce side‐to‐side differences in glucose utilization in any of the brain structures examined in this study. Compared to the control nonstimulated animals, the rate of glucose metabolism in the pineal gland was increased 71% following stimulation of the cervical sympathetic trunk. The pineal gland was the only brain region out of 87 structures examined in which glucose utilization was increased by electrical stimulation of its sympathetic inne

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1988.tb00768.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The laboratory rat is thought to be a poor model for study of the photoperiodic control of reproduction; however, this has only been investigated in a few rat strains. The purpose of the present investigation was to determine if the neuroendocrine‐reproductive system of the Fisher 344 (F344) rat, an inbreed strain, is sensitive to light deprivation. All treatments were performed on 28‐day‐old female F344 rats and the animals maintained for 8 weeks in a 14:10 light: dark cycle. Blinding resulted in a 65% (P<0.01) reduction in uterine weight and a 25% (P<0.01) decrease in ovarian weight. Accompanying these reductions in blinded animals were significant inhibitions of anterior pituitary weight, serum prolactin levels, and pituitary prolactin synthesis as measured in vitro. Pinealectomy of the blinded animals prevented all of these effects. Additionally, when olfactory bulbectomy, a procedure known to sensitize rats to the effects of photoperiod, was combined with blinding, the results did not differ significantly from that found with blinding alone. From these data we conclude that 1) the neuroendocrine‐reproductive system of the prepubertal F344 female rat is highly sensitive to light deprivation; 2) light deprivation produces its antigonadotrophic effect through the pineal gland; and 3) olfactory bulbectomy does not potentiate the effects of blinding in the F

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1988.tb00769.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Twenty‐four‐h urine samples, divided into two fractions representing night‐ and daytime melatonin production, were collected from 115 healthy individuals between the ages of 3 and 80, of known height and weight, and assayed for 6‐hydroxy melatonin sulphate (SaMT), a major urinary metabolite of melatonin, by gas chromatography mass spectrometry. The population was divided for analytical purposes into children (boys aged 3–10.99, girls aged 3–9.59), adolescents (males aged 11–17.99, females aged 9.60–17.99), and adults (men and women over 18). The results showed approximately the same excretion over 24 h in all 3 groups but that the night/day ratio was considerably greater in children and adolescents compared to adults (P<0.001). However, when the results were expressed as a function of body weight (BW), body surface area (BSA), or creatinine excretion (CE), nocturnal SaMT was higher in children than in adults (P<0.001 for all 3 parameters) or adolescents (BW,P<0.001; BSA,P<0.002; CE,P<0.001) and was higher in adolescents than in adults (BW and BSA,P<0.001). Children also excreted more during the day than adults (BW,P<0.01; CE,P<0.001) or adolescents (BWαCE,P<0.02). Our results show that pineal output barely changes during childhood and adolescence. However, there is an age related decrease in SaMT excretion/unit body mass which correlates with an age‐related increase in body mass. We therefore conclude that the decrease in circulating levels of melatonin during growth and sexual maturation is brought about by an inc

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1988.tb00770.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Melanophores were studied in tadpoles of the South African clawed toad,Xenopus laevis, during the first week after hatching (stages 46–49) at 25°C. The tadpoles had melanophores with dispersed melanosomes in the light and punctate melanophores in the dark in LD12:12. The melanophores remained punctate in constant dark and the melanosomes remained dispersed in constant light. Lights‐out (in the light‐time of LD12:12) caused the melanophores to become punctate, which occurred more quickly than the dispersion of melanosomes, which commenced when the lights were turned on (in the dark‐time of LD12:12). Melanophores with dispersed melanosomes in tadpoles (in constant light) became punctate in response to a series of melatonin concentrations (0.2–5 ng/ml) in their bathing water irrespective of the time of day melatonin was administered. An image‐analysis technique for assessing melanophore response

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1988.tb00771.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Freshly cultured pineal glands respond to the monoamine oxidase A (MAO A) inhibitor clorgyline and to high concentrations of the MAO B inhibitor, deprenyl, with an increase in serotonin N‐acetyltransferase activity and N‐acetylated indoles and a fall in 5‐hydroxylated serotonin degradation products. Glands cultured for 48 hours before challenge respond less. Response is absent in glands cultured for 72 hours and in glands from ganglionectomized animals cultured for 48 hours before challenge. These data are consistent with the hypothesis that these MAO inhibitors stimulate melatonin synthesis by protecting norepinephrine from degrad

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1988.tb00772.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY