摘要:

The effects of exogenous melatonin (subcutaneous implants containing 0.031 ± 0.006 mg/gm body mass melatonin) or long photoperiod (18L: 6D) on wild‐caught adult male hedgehogs were studied. Hedgehogs were implanted with melatonin‐filled or empty capsules in May, August, or September, or maintained under long photoperiod from August. Blood samples collected at monthly intervals were assayed for testosterone, melatonin, and thyroxin. Melatonin‐filled capsules elevated plasma melatonin concentrations for 4‐6 months. Although melatonin administration in May depressed plasma testosterone levels, testicular reactivation was advanced by 1 month the following year, and the characteristic prehibernal gain in body mass was abolished. Melatonin administration in August had no effect on plasma testosterone concentrations but reduced body mass fluctuations before and during hibernation. Hedgehogs receiving melatonin in September recovered early from hibernal body mass loss and showed a 2 month advance in testicular reactivation the following year. Maintaining hedgehogs at 18L: 6D photoperiod, however, elevated plasma melatonin concentrations. Testicular reactivation the following spring was delayed by 1 month, ended 3 months early, and testosterone concentrations were depressed. All treatments depressed plasma thyroxin levels. These results suggest that elevated melatonin levels during winter are important in the regulation of endogenous endocrine cycles in the hedgehog. Hedgehogs do not respond positively to melatonin at the end of the breeding season, but are again responsive to melatonin as early as S

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1990.tb00679.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Pineal synaptic ribbon (SR) populations of the early posthatch white leghorn chick were counted to determine if they demonstrate a rhythm that is in accordance with the light/dark cycle. SRs were counted between day 7 and day 10 and on day 14 of posthatch development, with samples at midlight, middark (14L:10D), and constant darkness. SR populations did not exhibit significant changes on days 7 and 8 under cycled lighting conditions nor on days 9 and 10 under constant darkness. A second experiment demonstrated that the dark:light ratio of SR populations of day 14 chicks, under cycled lighting, was 3.4:1.0, indicating SR rhythmicity by that stage of development. In that a preliminary experiment had demonstrated a 4.2:1.0 darklight ratio in SR populations in a predominantly day‐10 population of chicks, we believe that SR rhythmicity begins on, or near, day 10 of posthatch development. To determine if the invasion of sympathetic fibers from the superior cervical ganglion (SCG) correlates with the initiation of SR light/dark population differences, we employed tyrosine hydroxylase immunofluorescence to reveal the distribution of catecholaminergic fibers in chick pineal follicles Follicular innervation doubled over the day 7 to day 14 period, during which time light/dark differences in SR populations were established. There is a correlation, in time, between the invasion of the pineal by the sympathetic fibers and the initiation of SR light/dark differences. The circadian rhythm of pineal N‐acetyltransferase (NAT) activity, the rate‐limiting enzyme in the melatonin pathway, is established earlier (day 2) than the light/dark differences in SR populations (day 10). It is possible that SR rhythmicity is influenced by the ingrowth of the pineal sympathetic innervation, and that SRs respond to an extrapineal oscillator rather than the independent oscillators of the chick pineal responsible for the rhythm of NAT activity and melatonin synt

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1990.tb00680.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Daily Melatonin Injections Have Only Minor Effects on Gonadotropins of Intact or Castrated Male Rats Kept Under Constant or Periodic LightIntact and castrated adult male Wistar rats were kept under constant or periodic (lights on 0600 and off 1800 h) light for 1 wk. During the study they received melatonin or saline injections daily either at 0900 or 1600 h. After each experiment, serum samples and the adenohypophyses were collected between 1000 and 1100 h and the gonadotropin concentrations were measured radioimmunologically. We had previously found changes in light sensitivity of the hypothalamo‐pituitary axis of castrated rats and hypothesized that this axis could also involve changes in sensitivity to exogenous melatonin. However, the results of the present study do not support the hypothesi

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1990.tb00681.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The Harderian glands of Syrian hamsters contain melatonin and the enzymes N‐acetyltransferase (NAT) and hydroxyindole‐O‐methyltransferase (HIOMT) which synthesize melatonin from serotonin. Because the Harderian glands share this metabolic pathway with the pineal gland, we examined the effects of short‐day photoperiods, which stimulate pineal‐mediated gonadal regression, and N‐(2,4‐dinitrophenyl)‐5‐methoxytryptamine (ML‐23), which has been described as a melatonin antagonist, on melatonin synthesis in the Harderian glands of the hamster.Harderian glands of male hamsters kept in short days had reduced NAT activity and melatonin concentration, but HIOMT activity was unchanged from that of longday controls. In males kept in short days, ML‐23 restored melatonin concentrations to levels seen in long days but did not affect the short‐day induced reduction in NAT activity. ML‐23 had no effect upon NAT or HIOMT activity or melatonin concentration in male hamsters kept on long days.Harderian glands of female hamsters kept on short days had reduced melatonin concentrations, but NAT and HIOMT activities similar to those of long‐day controls. ML‐23 had no effect on Harderian NAT or HIOMT activities or melatonin concentration in females kept in short days. However, in females kept in long days, ML‐23 treatment led to increased NAT activity and decreased melatonin concentrations.We conclude from these results that short‐day photoperiods alter some aspects of melatonin synthesis in hamster Harderian glands and that these effects differ in males and females. ML‐23 does not usually prevent the effects of short days on Harderian melatonin synthesis, suggesting that it is not a melaton

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1990.tb00682.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The secretion of plasma melatonin exhibits a diurnal variation in the common marmoset (Callithrix jacchus jacchus) (n = 12) with mean values of 125.8 fmol/ml during darkness and below assay sensitivity (mean 70.5 fmol/ml) during the light period. Both melatonin secretion and the rest activity cycle appeared to be phase advanced with relation to the light dark cycle which is consistent with an endogenous circadian period (tau) of<24 h in this species.

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1990.tb00683.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The ultrastructure of the dog pineal gland from the first postnatal day to the seventh month is described. In the first postnatal stages, pineal parenchyma only shows immature proliferative cells with abundant cytoplasmic glycogen. Nerve fibers are seen in the pineal connective tissue spaces. The differentiation of the dog pineal cell types begins in the first postnatal week. Both pinealocytes and pigmented cells are first seen on the fourth postnatal day. The pineal astrocytes are observed on the tenth day. Immature cells are still found in the pineal gland of 1 mo‐old dogs. The differentiation of the dog pineal cell types is completed by the second postnatal mont

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1990.tb00684.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

In order to analyze whether the bovine pineal gland is a homogeneous or a heterogeneous structure as far as monoamine content, the regional differences in norepinephrine (NE), dopamine (DA), serotonin (5HT), and 5‐hydroxyindoleacetic acid (5HIAA) contents were assessed by high‐pressure liquid chromatography. NE content was maximal in the proximal (close to the recessus pinealis) region and decreased in a rostral‐caudal direction to achieve minimal values at the distal region. DA exhibited an opposite trend to NE, NE/DA ratios varying from 3.2 (proximal region) to 1.4 (distal region). Significantly lower NE content was found at the inferior as compared to the superior pineal region, and at the cortex as compared to the medulla. No significant differences were detected in DA concentration of these latter pineal regions, or in 5HT or 5HIAA concentration as a function of the region examined.3H‐5HT and3H‐NE uptake were maximal at the proximal zone in a rostral‐caudal direction, at the superior as compared to the inferior region, and at the medulla as compared to the cortex. Unlabeled NE was equally effective to compete with3H‐5HT uptake in the several pineal regions studied. While NE increased maximally3H‐5HT release in a rostral‐caudal direction, DA exhibited an opposite trend, displaying maximal 5HT release activity at the distal pineal region. DA and NE 5HT‐releasing activity were greater in the pineal medulla than in the cortex, and did not exhibit differences in the superior as compared to the inferior pineal aspects. Excess (55 mM) K+released3H‐5HT to a similar extent regardless of the p

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1990.tb00685.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

The daily pattern of the major urinary metabolite of melatonin, 6‐sulphatoxymelatonin (aMT6s), was determined in women prior to having a breast biopsy. Women with malignant tumors appeared to have significantly lower 24 h concentrations of aMT6s with a decrease in the amplitude of the rhythm compared to women with benign tumors. The amount of urinary aMT6s was dependent upon the age of the subject but was not affected by either menopausal status or body mass index. However, when the women with malignant tumors were compared with a large group of normal women of the same age their aMT6s levels were not outside the normal range. The results show that a large control group and very accurate age matching are essential when investigating melatonin production in different groups of subject

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1990.tb00686.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

InChanna punctatus, day‐night variations in hypothalamic 5‐HT (serotonin) and monoamine oxidase (MAO) activity were noticed in preparatory but not other phases (prespawning and postspawning) of the annual reproductive cycle. Hypothalamic MAO, 5‐HT, and norepinephrine (NE) activity was found to be high in the prespawning phase and low in the postspawning phase. Dopamine (DA) activity, on the other hand, was high in the postspawning season and low in the prespawning phase. Pinealectomy caused season‐dependent effects on hypothalamic monoaminergic activity, with a significant increase in serotonergic activity and a significant reduction in MAO activity at midscotophase during the preparatory phase (March) but not in the prespawning (May‐June) or postspawning (September) phases. Hypothalamic catecholaminergic (CA) activity was not influenced by pinealectomy during any of the seasons. To determine whether or not the photoperiodic influences on daily variations of 5‐HT and MAO in the preparatory phase are mediated via pineal and/or lateral eyes, fish were pinealectomized and/or blinded in January, when there is no rhythm, and sacrificed in February, when a day‐night variation normally sets in. The day‐night difference in 5‐HT content and activity and MAO activity was not abolished by pinealectomy or blinding alone; but the combination (pinealectomy + blinding) obliterated the daily variation only in 5‐HT content and in MAO activity. However, pinealectomy and blinding, alone or in combination, caused a significant elevation of 5‐HT activity (not its level) and a significant decrease in MAO activity at midscotophase, with the combination having an additive effect. Hypothalamic CA content or activity was not affected by these regimes. The results show that photoperiodic influence on the daily pattern of 5‐HT and MAO activity is mediated through and by the interaction of the

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1990.tb00687.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY