摘要:

The present study was undertaken to evaluate carefully the influence of age on physiological levels of arginine vasotocin‐like peptide in rat pineal glands. Glands were collected from male and female rats aged 13, 33, 53, and 73 days on August 4, 12, and 19, 1984. Individual extracts were assayed for arginine vasotocin (AVT) by radioimmunoassay. The results confirm our previous observation that rat pineal AVT immunoactivity (iAVT) increases significantly during August each year; and in this study, each group of rats reached the same peak level of iAVT (700–750 pg/gland) regardless of age or gender. Thus we do not confirm a previously reported decrease in AVT activity with age. In our studies thus far, season of the year is the physiological variable with the most significant influence on pineal AVT activity lev

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1989.tb00397.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Changes in immunoreactivity in rat pineal gland were investigated in S‐antigen (S‐Ag)‐induced pinealitis. Anti‐S antibodies were used to study the accessibility of pathogenic epitopes in the organ, and phosphatidyl inositol 4, 5‐bisphospate (PI[4,5]P2) antibodies were chosen to study changes in functional phospholipid in membranes. Control pineal gland (without inflammation) did not show much reactivity toward these antibodies. Immunoreactivity toward both antibodies was markedly increased throughout the organ at the peak of inflammation and decreased almost to control level in the postinflammatory stage. The rise and fall of immunoreactivity were attributed to changes in the accessibility of antigenic sites rather than changes in the amounts of S‐Ag and P(4, 5)P2The transient enhancement in immunoreactivity, probably consequential to tissue damage, suggests that the pineal gland, unlike the retinal photoreceptors, is capable of quick repai

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1989.tb00398.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

In a previous study, we identified in the bovine pineal gland two [H]spiroperidol‐binding sites with KD values of 0.18 and 2.1 nM and Bmax values of 37 and 630 fmol/mg protein, respectively. In this study, the status of dopamine in the bovine pineal glands was delineated further by measuring the relative concentrations of dopamine and norepinephrine and the relative concentrations of serotonin and melatonin. Furthermore, the presence of 4.0 ± 0.6 μg/dopamine/gm tissue encouraged us to delineate the effects of select dopaminergic receptor agonists and antagonists on the synthesis of melatonin in vivo and on the activity of N‐acetyltransferase in the rat pineal gland in culture. The acute1administration of haloperidol (3 mg/kg intraperitoneally [ip]) or sulpiride (200 mg/kg ip) increased the concentration of melatonin in the pineal gland from 160.6 ± 8.18 to 327.6 ± 45.43 and 306.5 ± 40.53 pg/gland, respectively. Dopamine exhibited dual effects on the activity of N‐acetyltransferase, inhibiting the basal activity at 0.1 μM and stimulating it at 10 μM, and the later effect was blocked by propranolol. D2‐dopaminergic receptor agonists such as bromocriptine (4.0 μM) or LY‐171555 (10.0 μM) partially attenuated the norepinephrine‐induced stimulation of N‐acetyltransferase, and these attenuating effects were reversed by D2‐do‐paminergic antagonists such as haloperidol (10 μM) or domperidone (10 μM). The results of these studies are interpreted to indicate that for the synthesis of melatonin, the pineal D2‐dopaminergic receptors may function independently from those of the betai‐adrenergic receptor sites. Furthermore, the said D2‐dopaminergic receptors are amenable to down regulation since the activity of N‐acetyltransferase remained unaltered (0.0717 vs. 0.0729 nmol/gland/h) following chronic treatment (4 mg/kg ip

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1989.tb00399.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Melatonin influences prolactin (PRL) secretion through unknown mechanisms. This work was undertaken to study the effects of melatonin administration on PRL secretion in pituitary‐grafted male rats. Melatonin administration 5 hours before dark resulted in a marked decrease of previously high basal plasma PRL levels in pituitary‐grafted rats, whereas a marked increase was detected in sham‐operated animals. Vehicle treatment did not modify basal PRL values in grafted or sham‐operated animals. Luteinizing hormone‐releasing hormone (LHRH) administration resulted in a marked decrease of plasma PRL levels in vehicle‐treated, sham‐operated or grafted rats, as well as in melatonin‐treated sham‐operated rats. An increase in PRL levels was shown in grafted rats treated with melatonin. Estradiol benzoate (EB) administration resulted in an increase in plasma PRL levels both in sham‐operated and grafted vehicle‐treated rats. No PRL response could be detected in sham‐operated, melatonin‐treated animals after EB administration. In pituitary‐grafted animals given melatonin, PRL response to EB administration was slight and delayed. From these data, melatonin appears to modify PRL secretion through multiple complex mechanisms that may depend on the physiological status (hormonal and neurotransmitter) of the animals. A direct effect at the pituitary level altering lactotroph sensitivity seems to be one plausible explanation for the current findings, although an hypothalamic site o

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1989.tb00400.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The newly born of many mammalian species are ectothermic, and it is possible that biochemical processes important for the metabolism of endocrine hormones might vary with alterations in the environmental temperature. Temperature‐induced fluctuations in pineal gland N‐acetyltransferase activity were investigated in 4‐, 12‐, and 20‐day‐old rats placed for 4 hr in 23 or 34°C environments. Enzyme activity increased dramatically in ectothermic 4‐ and 12‐day‐old animals exposed to the 23°C environment, but not in endothermic 20‐day‐old rats. The elevations in daytime pineal gland NAT activity seen in cold‐exposed animals were absent in rats previously subjected to chemical sympathectomy induced by 6‐hydroxydopamine, or in animals treated with the beta‐noradrenoceptor antagonist drug propranolol. Catecholaminergic nerves and beta‐noradrenoceptors known to be important for light‐induced changes in mammalian pineal gland biochemistry also appear essential for environmental temperature‐dependent elevations in neonatal

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1989.tb00401.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Ultrastructural observations of the pineal gland ofPhodopus sungorusrevealed different morphological forms of endoplasmic reticulum. These included crystalloids composed of 200Å‐wide tubules with an intervening space of 200Å and connected at right angles to form a rectangular lattice; complexes of undulating 500Å‐wide tubules in an electron‐dense cytoplasmic matrix; and stacks of flattened cisternae covered with granular electron‐dense material. All these structures are continuous with the surrounding endoplasmic reticulum. Frequently one structure is directly connected with another. The exact function of these structures derived from the endoplasmic reticulum is still unclear, but they can be assumed to be morphological features of augmented secretor

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1989.tb00402.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

A daily rhythm in melatonin concentration in Harderian glands (HG) of female golden hamsters is described and is characterized by significant reductions following lights‐on. Concentrations in HG of intact or pinealectomized males are low and consistent over a 24‐hour period. Castration of males is accompanied by increased levels of melatonin in the HG to approach those of females. When castrated males are exposed to short photoperiods, however, melatonin levels are typically low. Levels of serotonin (5‐HT), 5‐hydroxytryptophan (5‐HTP), and 5‐hydroxyindoleacetic acid (5‐HIAA) are extremely variable in HG of both males and females, precluding definitive conclusions. Melatonin concentrations in HG of females do not appear to be affected by light or stress per se, nor are the superior cervical ganglia the pathway by which concentrations

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1989.tb00403.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The mutagenicity of melatonin and its major metabolite 6‐hydroxymelatonin were evaluated using the Ames test and three strainsof Salmonella typhimurium‐TA 97, TA 98, and TA 100. Neither compound exhibited mutagenicity whether in the presence or absence of an activation system derived from rats induced with Aroclor 1254. Positive controls were employed throughout and gave the expected response. We conclude that melatonin, 6‐hydroxymelatonin, and their microsomal metabolites are not mutagenic in the Ames

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1989.tb00404.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The studies described here were undertaken to characterize the hepatic insulin and glucagon receptors of control (C), pinealectomized (Pn), and melatonin‐treated pinealectomized (Pn + Mel) rats. Compared with C rats, an increase in plasma glucose and glucagon levels and a reduction in circulating concentrations of insulin in Pn animals were observed. Melatonin treatment of Pn rats reverses all three parameters toward the normal values. In liver membranes, insulin binding was lower in Pn than in C rats, and glucagon binding was greater in Pn than in C animals; in Pn + Mel rats both insul in and glucagon binding reverse toward the normal values that were observed in C rats. The modifications in hormone binding reflect changes in the number of receptors but not in the affinity constants. The time courses of hormone association and dissociation from liver membranes were similar in all three experimental groups. The degradation of both hormones by liver membranes was similar in all three groups. Insulin receptor degradation also was similar in the three groups, while glucagon receptor degradation was similar in the liver membranes of C and Pn rats but smaller in Pn + Mel animals. These findings suggest that the pineal gland may modulate the circulating levels and liver receptor concentrations of insulin and glucagon. In addition, our results indicate that insulin and glucagon did not induce a down‐regulation of liver receptors in Pn r

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1989.tb00405.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Effects of melatonin and serotonin on ethanol ulceration and mucosal blood flow in the rat stomach were investigated. Melatonin and serotonin (5‐HT) administration did not produce observable gastric injury in the ex vivo stomach, but the 5‐HT dose dependently reduced glandular mucosal blood flow (GMBF) in this organ. Ethanol depressed GMBF and induced visible glandular mucosal injury. The latter effect was prevented by melatonin preincubation. Serotonin pretreatment aggravated the gastric mucosal injury and GMBF changes induced by ethanol; these actions were partially reversed by melatonin. The findings indicate that the GMBF and gastric injury are related; the reduction in GMBF, however, may not be the sole factor responsible for ulceration. The antagonistic effects of melatonin on 5‐HT action on the stomach suggest that melatonin may act as a modulator for 5‐HT action on the gastrointestina

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1989.tb00406.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY