摘要:

Abstract:In the study rainbow trout, pinealectomized at two different periods of their sexual cycle, i.e., at either 1 or 5 months before spawning, were studied. It was found that the lack of the pineal gland in the period directly preceding the spawning had no statistical effect on either spawning or the number of females that produced eggs.Pinealectomy performed during vitellogenesis delayed spawning by about 2 weeks and resulted in the absence of ovulation in 20% of the females. The results suggest that the pineal gland may influence the hypothalamo‐pituitary‐gonadal axis by altering the maturation period and controlling spawning in the rainbow tr

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1992.tb00061.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract:The molecular mechanism underlying the role of calcium influx in the regulation of retinal serotonin N‐acetyltransferase (NAT) activity was studied in vivo in chickens. Systemic administration of organic antagonists of voltage‐sensitive calcium channels (VSCC), i.e., nimodipine and nifedipine, resulted in a marked suppression of the nocturnal increase of NAT activity in chicken retina. In contrast, NAT activity stimulated by nonhydrolysable analogs of cyclic AMP (dibutyryl‐cyclic AMP and 8‐bromo‐cyclic AMP), forskolin, a direct activator of adenylate cyclase, and by phosphodiesterase inhibitors (aminophylline and 3‐isobutyl‐l‐methylxanthine), was not significantly affected by various tested VSCC antagonists. The inhibitory effect of nimodipine on the dark‐dependent increase in NAT activity of chicken retina was abolished by Bay K 8644, a selective VSCC agonist. The results presented in this paper indicate an important role of calcium influx through L‐type of VSCC in the induction of NAT activity in chicken retina, and suggest that a requirement of calcium ions in the process of NAT induction in the retina may be primarily at the level of cy

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1992.tb00062.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract:A study was carried out to determine the possible influence of melatonin on the proliferation of Kirkman‐Robbins hepatoma cells in Syrian hamsters, both in vivo and in vitro. A highly significant inhibition of the proliferation of transplanted hepatoma cells was observed in vivo following melatonin administration (proliferation index 10.3 ± 1.5; mean ± SD) in comparison with controls (proliferation index 23.3 ± 2.2), whereas in vitro melatonin (at concentrations of 10−5‐10−11M) was ineffective. These results indicate that inhibitory effect of melatonin on transplantable hepatoma cells in vivo may b

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1992.tb00063.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract:The aim of this study was to determine whether pineal indoles affect cyclic nucleotide levels in mammary gland slices of BALB/c adult mice. Melatonin at 0.1 nM ‐ 10 μM concentrations decreased cAMP and augmented cGMP concentration in murine mammary gland slices in the presence of a phosphodiesterase inhibitor (1 mM theophylline), an index of cyclic nucleotide synthesis. Melatonin‐induced changes in cyclic nucleotide levels were significantly larger at the end of the light period (2000) than in the morning (at 1000). Indole‐induced inhibition of cyclic AMP levels by mammary slices exhibited the following order of potency: 5‐methoxytryptamine>melatonin>6‐hydroxymelatonin>serotonin, N‐acetylserotonin>5‐hydroxytryptophol. The order of potency for indole‐induced augmentation of cyclic GMP levels was: 5‐methoxytryptamine>melatonin>6‐hydroxymelatonin>serotonin, N‐acetylserotonin, 5‐hydroxytryptophol. When melatonin or 5‐methoxytryptamine (10 nM) were examined for their effects on cAMP and cGMP levels in mammary glands of mice killed at six different time intervals during the 24‐hr cycle, the activity was maximal during night. The data demonstrate that 5‐methoxytryptamine and melatonin decreased cAMP and increased cGMP levels in mammary gland slices. Methoxyindole‐induced changes in cyclic nucleotide synthesis in murine mammary glands exhibit the time‐dependency known to occur in several ot

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1992.tb00064.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract:The existence of the major urinary metabolite of melatonin, 6‐sulphatoxymelatonin (aMT6s), was validated for mink and the 24 hr urinary excretion pattern was determined in intact and superior cervical ganglionectomized animals under different photoperiodic conditions. Within‐and between‐assay variations, parallelism between serially mid‐night pooled urine dilutions and standard curves in aMT6s free urine of mink at 1:125 dilution and recovery of aMT6s in mid‐day pooled urine at 1:125 dilution provided a good validation for the mink urinary a MT6s assay. In natural photoperiods (January, LD 9:15; April, LD 13:11) the diurnal rhythm was characterized by low aMT6s values during the day and high values at night. There were no differences in the nocturnal values measured under long‐ (April, 4.11 ± 0.40 ng/hr) or short‐day (January, 4.74 ± 0.36 ng/hr) conditions. In an experimental long photoperiod (LD 15:9), the same result was obtained on the 24 hr rhythm in intact animals, but in ganglionectomized mink the nocturnal rise in aMT6s was abolished and the nocturnal values were always low (0.88 ± 0.09 ng/hr). Our results agree with those obtained in other species concerning plasma melatonin rhythm and urinary aMT6s excretion; we thus conclude that this is an effective assay for measuring pineal

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1992.tb00065.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract:The mammalian pineal gland and its main hormone, melatonin, working in conjunction with the hypothalamic suprachiasmatic nuclei, synchronize circadian rhythm and hence refine numerous physiological and biochemical parameters. An interaction among melatonin, opioids, and analgesia has been suspected for many years, since during nighttime, when the level of melatonin is high, the mammals are less sensitive to pain. In studying this phenomenon further, we have identified a single population of opioid receptors in the bovine pineal gland using [3H]‐diprenorphine and other ligands. The receptors have a dissociation equilibrium constant (Kd) of 1.36 ± 0.31 nM and a density (Bmax) of 17.93 ± 5.22 fmol/mg protein. In competitive experiments, the concentration of drugs required to inhibit 50% of the [3H]‐diprenorphine binding (IC50) in descending order of potency was found to be naltrexone>fentanyl>naloxone>nalbuphine>morphine>nalorphine>DAGO>dynorphin>metenkephalin. In order to delineate the function of the opioid system in the pineal gland, the effects of both opioid receptor agonists and antagonists on the basal activity of N‐acetyltransferase were examined in the bovine pineal expiants in culture. Morphine, an opioid receptor agonist, increased significantly the activity of N‐acetyltransferase in a dose‐dependent fashion. In addition, the stimulatory effect of morphine was inhibited by naloxone, an opioid receptor antagonist. The results of these studies indicate the existence of pineal opioid receptors, which play a pivotal role in the synthesis of melatonin and its action in synchronizing pi

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1992.tb00066.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract:Cultured chick pineal glands show a persistent rhythm in the rate of cumulative incorporation of thymidine into DNA. In this study we have examined the effects of pulse‐exposure to aphidicolin in the dark on the first day of culture on thymidine incorporation during the second and third days of culture in the dark with aphidicolin‐free medium. The phase of the rhythm in the rate of thymidine incorporation was delayed in a concentration‐dependent manner by a 4‐hr exposure to aphidicolin, commencing in the final hour of the photoperiod. This effect was phase‐dependent and not seen when exposure to aphidicolin began earlier in the ph

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1992.tb00067.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Abstract:There is evidence to indicate that pinealectomy may enhance wool growth in the sheep. The aim of this study was to determine the effect of pinealectomy on wool growth and wool follicle density in Merino sheep.Castrated Merino rams (4 months old) were either pinealectomized (P), sham‐pinealectomized (S) or not treated (C). Wool growth on mid‐side patches was measured every 4 weeks and follicle density was monitored in skin biopsies collected before treatment and at regular intervals for 60 weeks. Venous blood samples were taken on each of these occasions for prolactin analysis. Melatonin concentrations were determined in venous blood collected pre‐ and posttreatment from samples taken over a 24‐hr period during the winter solstice.Pre‐ and posttreatment plasma melatonin levels (mean ± SEM) 65 ± 17 and<13 pg/ml for P, 86 ± 21 and 69 ± 20 pg/ml for S, and 94 ± 41 and 122 ± 37 pg/ml for C, respectively, indicated that the pineal glands had been successfully removed. Wool growth, total follicle density and liveweight (mean ± SEM) did not differ between treatment groups. Measurements at week 60 were 3.9 ± 0.3, 4.1 ± 0.2, and 3.8 ± 0.3 gm clean wool/100 cm2; 66 ± 6, 69 ± 7, and 64 ± 3 follicles/mm2; and 50.4 ± 1.3, 50.8 ± 1.4, and 52.6 ± 1.1 kg liveweight for groups P, S, and C, respectively. There was no difference in plasma prolactin levels between the groups during the experiment (P:179 ± 37, S:183 ± 37, C.189 ± 37 ng/ml), but the expected seasonal prolactin rhythm was absent in all animals. These results indicate that the removal of endogenous pineal hormones by pinealectomy has no effect on wool growth and wool foll

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1992.tb00068.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY