摘要:

In this study we examined the cerebrospinal fluid (CSF) for regional differences in the concentration of melatonin. Cerebrospinal fluid samples were collected at hourly intervals from either the lateral ventricle or the cisterna magna of nine Merino ewes and were compared against jugular plasma. The study revealed that the CSF of the cisterna magna and the lateral ventricle had temporal patterns of melatonin that were similar to those found in jugular plasma. However, the concentrations of melatonin within the CSF obtained from the lateral ventricle were one order of magnitude higher than those of the jugular plasma, as verified by gas chromatography and mass spectrometery, while the melatonin concentrations within the CSF obtained from the cisterna magna were comparable to those of the jugular plasma. The data from this study suggest that there may be regional differences in the concentration of melatonin within the CSF and indicate that this medium is an important route of transport for melatonin from the pineal gland to putative target tissues.

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1989.tb00416.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The effects of a glucose tolerance test (GTT) and an insulin response test (IRT) on blood glucose levels were evaluated in pinealectomized and nonpinealectomized pigeons during the breeding and nonbreeding months. The tests revealed increased glucose tolerance and insulin sensitivity in pinealectomized birds during the breeding season. In the nonbreeding season, both the pinealectomized and the control birds tended to show more or less similar responses for both GTT and IRT. These changes confirm the anti‐insulin role of the pineal in wild pigeons during the breeding season and the possible significance of the pineal gland in modulating seasonal changes in carbohydrate metabolis

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1989.tb00417.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The influence of the pineal gland on the histopathologic changes induced in mammary glands by 7, 12‐dimethylbenz(a)‐anthracene (DMBA) has been studied. To achieve the maximum expression of pineal action in animals, 28‐day‐old female Sprague‐Dawley rats were subjected to one of the following treatments: blindness + olfactory bul‐bectomy (BA), blindness + underfeeding (BU), or blindness + cold exposure (BC). Half of the rats in each group were also pinealectomized. Animals that were intact or only pinealectomized served as controls. Each animal received a single intragastrical dose of DMBA (20 mg) 4 weeks after performing the treatments mentioned above. At 28 weeks of age animals were sacrificed, and mammary tumors as well as mammary glands without macroscopic lesions were collected. Animals of the BU group failed to develop any tumors throughout the 20‐week control period. In the remaining groups, tumors were found; the relation between number of adenocarcinomas (AC) and fibroadenomas was similar, always with a greater incidence of ACs. Some ACs showed areas with changes in the ductal epithelium that are considered signs of tumoral regression; pinealectomized animals had the lowest incidence of ACs with signs of regression. Ductule hyperplasia, considered as a premalignant lesion, was more frequent in pinealectomized rats than in controls and in animals with enhanced pineal function (BA, BU, and BC). Some nontumoral mammary glands showed dysplastic lesions; these lesions were less frequent in BU rats than in controls. We conclude that suppression of pineal function sensitizes the ductule cells to the initiation of neoplastic processes and hinders the development of regre

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1989.tb00418.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

In female European hamsters killed in spring and early summer, pineal melatonin content exhibited no day/night rhythm. Absolute levels measured were relatively low, being on the order of daytime levels detected in other hamster species. An absence of day/night changes in the activity of N‐acetyltransferase was also observed. However, a marked rhythm in pineal serotonin (5‐HT) was found, an abrupt large increase being observed at the beginning of the light period. The day /night rhythm of pineal 5‐HIAA content is similar to that of 5‐HT. This absence of rhythm in pineal melatonin formation might mean that in the European hamster it is not melatonin but another substance that is of importance in photoperiodism. An absence of melatonin rhythm, however, could also be simply a peculiar pattern of melatonin production observed at a given period of the year. In this case, melatonin would be able to transduce photoperiodic information in the European hamster, as in other photope riodic

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1989.tb00419.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

We have investigated the profiles of prolactin secretion in relation to onset of breeding activity in Suffolk‐Cross ewes with artificially modified melatonin rhythms. With treatments commencing in midsummer, groups of ewes were 1) subjected to a 8L:16D photoperiod, 2) maintained under a “short” (6L:16D) photoperiod repeated over a 22‐h cycle that induces an elevation in plasma melatonin that does not endure for the entire dark phase, 3) pinealectomized (pnx) to abolish plasma melatonin levels, and 4) pinealectomized and treated with a melatonin implant (subcutaneous) to provide a constant (no 24‐h rhythm) elevation in plasma melatonin. The onset of breeding activity was significantly advanced in both the 8L:16D and pnx/implant groups compared to the 6L:16D and untreated pnx ewes. The two latter groups displayed a normal timing in seasonal breeding activity. Low and high plasma prolactin levels corresponded with short and long photoperiods during both the 24 and 22‐h cycles. There was no clearcut “seasonal” rhythm in plasma prolactin in either of the pnx groups. A clear differentiation was seen between reproductive response and prolactin response, particularly in the case of ewes monitored on 22‐h cycles of

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1989.tb00420.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Several studies suggest that GABAergic mechanisms may be involved in the modulation of melatonin secretion. However, conflicting results have been reported in animal studies; in humans the issue has not been widely investigated. In the present study, using a double‐blind design, six healthy men received orally, at midnight, 10 mg of diazepam, a GABAergic agent, or placebo, on two different occasions 1 week apart. Blood samples were collected, in the dark, immediately before the drug administration, and at 12:30, 1, 2, 3, and 4 AM. Serum melatonin was measured by a radioimmunological method with [125I]melatonin as a tracer. Two‐way ANOVA with repeated measurements disclosed a significant effect for treatment (P<0.01), for time (P<0.0004), and for treatment X time interaction (P<0.05). Following diazepam administration, serum melatonin levels observed at 2, 3, and 4 AM were significantly lower than the corresponding values following placebo (P<0.02 at 2 and 4 AM;P<0.03 at 3 AM [Students' paired t test]). These results show that nocturnal blood melatonin levels may be suppressed by the acute administration of a GABAergic agent, suggesting that GABA may be involved in the modulation of pineal activity in

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1989.tb00421.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The effect of pteridines and sex hormones on hydroxyindole‐O‐methyltransferase (HIOMT) catalysis was examined. Equivalent quantities of partially purified bovine HIOMT was incubated in the presence and absence of the various test substances and the results fitted to the Michaelis‐Menten equation. The pteridines (triampterene and xanthopterin) had no noticeable effect on HIOMT catalysis, while all the sex hormones examined were found to be competitive inhibitors of the enzyme with respect to the hydroxy‐substrate. Testosterone concentrations causing noticeable inhibition were above physiological while estrone, estradiol, and progesterone all caused inhibition within the physiological range; estrone was the most potent and progesterone the least potent inhibitor. The possible significance of these findings are di

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1989.tb00422.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The common procedures used for preparing some organs and tissues for electron microscopy, in which a fixative with the buffer portion adjusted to near‐isotonicity to plasma is perfused in vivo, causes intolerable shrinkage of rat pineal cells. The present study was undertaken to optimize the parameters involved in the fixation of the pineal gland. The buffer and its concentration and the aldehyde or aldehydes used were among the variables investigated. The buffers tried were phosphate, cacodylate, PIPES, and HEPES. Decreasing the buffer concentration prevented shrinkage with all four buffers. The optimum concentrations were 0.05 M phosphate, 0.07 M cacodylate, 0.05 M or 0.057 M PIPES, and 0.1 M HEPES. PIPES and HEPES were clearly superior in retaining cytoplasmic density when compared with phosphate or cacodylate. The use of lithium PIPES and HEPES instead of the sodium equivalents enhanced membrane detail. A small volume of more concentrated aldehyde fixative perfused ahead of the main perfusate (a strong prewash) definitely helped prevent shrinkage. Using a mixture of aldehydes consisting of glutaraldehyde, formaldehyde, and acrolein reduced the tendency for shrinkage when compared with glutaraldehyde only. Some of the shrinkage space artefacts could be easily misinterpreted as normal features. Since the pineal gland commonly contains degenerating structures, a dependable fixation procedure is particularly needed. Also, accurate preservation is essential in the evaluation of physiological change

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1989.tb00423.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

A method for measuring tryptophan hydroxylase activity by assaying the product 5‐HTP using high‐performance liquid chromatography (HPLC) with electrochemical detection is described. A nocturnal elevation (80%) in rat pineal gland tryptophan hydroxylase activity was detected. Experiments on isolated rat pinealocytes with the protein synthesis inhibitor cycloheximide indicate that tryptophan hydroxylase turns over rapidly in these cells. This method will be valuable in studies of the adrenergic mechanisms regulating pineal tryptophan hydroxylase activ

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1989.tb00424.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY