摘要:

Abstract:In order to determine individual variability in the amplitude and duration of the nycthemeral rhythm of the plasma melatonin concentration, 12 ovariectomized estradiol‐treated Ile‐de‐France ewes were submitted to a sequence of 34 long days (LD1, 16L: 8D), 21 short days (SD, 8L: 16D), and 21 LD (LD2). Intensive blood sampling (hourly from 1 hr before dusk to 1 hr after dawn) was performed for 4 consecutive nights in each of the photoperiodic situations (LD1, SD, LD2), i.e., a total of 12 nights per ewe. Plasma melatonin was assayed by radioimmunoassay. Instantaneous amplitude (difference between each hourly measurement of the plasma melatonin concentration during the nocturnal elevation and the mean diurnal melatonin concentration), mean individual amplitude (same definition but using the mean melatonin concentration during the nocturnal elevation) and duration of elevation of plasma melatonin concentrations were calculated for each ewe and each night and analyzed by variance analysis. Instantaneous amplitude varied significantly with photoperiod, with night intra‐photoperiod, with ewes, and time intra‐night. Mean individual amplitude varied significantly with photoperiod and with ewe but not with night intra‐photoperiod. Dramatic differences between individuals appeared in the amplitude and duration of melatonin rhythms. The lowest mean individual amplitude (all nights of measurement) found was 95 pg/ml and the highest was 544 pg/ml. Overall repeatability coefficient of the mean amplitude of melatonin elevation was 0.71 (P<0.001). Duration of melatonin elevation varied significantly with photoperiod, with nights intra‐photoperiod and with ewes. During LD periods, mean duration of melatonin elevation was equivalent to duration of the night (from 7 to 8 hr), while during SD it varied with ewes from 9 to 16 hr. Repeatability coefficient of the duration of melatonin elevation in SD was 0.57 (P<0.05). It is concluded that amplitude and duration (in SD) of the nycthemeral rhythm of the plasma melatonin concentration are highly repeatable individual characteristi

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1996.tb00264.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract:Previous studies in Syrian hamster have shown that the correlations between the daily fluctuations in the contents of pineal indoleamines and methoxyindoles are influenced by the photoperiod, and that dopamine may play a role in the regulation of pineal function. The present study investigated the 24 hour changes in the content of 5‐hydroxytryptophan (5‐HTP), serotonin (5‐HT), 5‐hydroxyindoleacetic acid (5‐HIAA), N‐acetylserotonin (NAS), melatonin, 5‐methoxytryptophol (5‐MT), noradrenaline (NA), dopamine (DA), and 3,4‐dihydroxyphenylacetic acid (DOPAC) in the pineal gland of female Djungarian hamsters exposed to long (LP; LD 16: 8) or short (SP; LD 10: 14) photoperiods for 10 weeks. Pronounced nocturnal increases of N‐acetylserotonin and melatonin content were observed irrespective of the photoperiod regime. The content of 5‐HT was markedly decreased during the first hour of the night in LP, which contrasted with the lack of changes in NAS and melatonin content at this time. In SP, an increased 5‐HTP content and a less obvious decrease in 5‐HT content was observed during the night, although melatonin and NAS content were even higher than in LP. Similar daily patterns as for 5‐HT were observed in the 5‐HT oxidative metabolites (5‐HIAA and 5‐MT). When considering values throughout the day, a poor correlation for 5‐HT vs. NAS and melatonin content was observed, which was particularly evident during the nighttime. These data indicate that the daily variation of pineal indoles may not only be dependent on changes in the N‐acetyltransferase activity but also in other mechanisms regulating pinealocyte 5‐HT availability. As previously reported in other species of hamster, pineal NA content did not show daily variations in LP conditions, although a nocturnal increase was detected in SP. In contrast, pronounced nocturnal increases were observed in the content of DA and its acid metabolite, DOPAC, irrespective of the photoperiod. These data indicate the existence of an increased dopaminergic turnover during the night and further support a role for DA in the regulation of melatonin synthesis and in the

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1996.tb00265.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract:The effects of noradrenergic and cholinergic receptor agonists on intracellular Ca2+concentration ([Ca2+]i) in single dissociated rat pineal cells were investigated by microfluorimetric measurements in Fura‐2 acetoxymethyl ester (Fura‐2/AM) loaded cells. Noradrenaline (NA) evoked characteristic biphasic increments of intracellular Ca2+consisting of one or more leading spikes followed by a plateau, resulting from the release of Ca2+from intracellular stores and from the influx of Ca2+from the external medium, respectively. This response was reproduced by the α1adrenoceptor agonist, phenylephrine (PE), in the presence of the β‐adrenoceptor antagonist, propranolol, and was abolished when NA or PE was applied in conjunction with the α1‐adrenoceptor antagonist, prazosin. The curve relating the peak amplitude of the Ca2+increments to different PE concentrations (0.5–10 μM) showed a half‐maximum response at 0.6 μM PE, and saturation at concentrations greater than 2 μM. Acetylcholine (ACh) also elicited transient Ca2+increments consisting of an abrupt rise to a maximum value which decayed exponentially to the basal Ca2+level. A half‐maximum response was achieved at 59 μM ACh. The muscarinic cholinergic receptor agonist, carbachol (CCh), similarly activated Ca2+increments while the muscarinic antagonist, atropine, abolished them. In the absence of extracellular Ca2+, repetitive stimuli with either α1‐adrenergic and muscarinic agonists produced a progressive decrement in the amplitude of the Ca2+signals because of the depletion of intracellular stores. However, extinction of the response to muscarinic agonists did not preclude a response to adrenergic agonists, while the contrary was not true. These results suggest that these agonists liberate Ca2+from two functionally distinct, caffeine‐insensitive,

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1996.tb00266.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract:It has recently been established that the neuroendocrine pinealocytes of mammals contain several synaptic membrane proteins that are involved in the regulation of vesicle trafficking in the nerve terminal. In the present study, we have conducted immunoblot and immunocytochemical analyses to demonstrate that another key component of the presynaptic plasmalemma, i.e., protein SNAP‐25 (synaptosomal‐associated protein 25 kDa), can be detected in pinealocytes. Immunostaining of serial semi‐thin sections of plastic‐embedded rat and gerbil pineals with monoclonal SNAP‐25 antibodies showed that SNAP‐25 was present in pinealocytes of both species. We proved its coexpression with other synaptic membrane proteins (synaptophysin, synaptotagmin I, synaptobrevin II, and syntaxin I) at the single cell level. Thus, pinealocytes obviously are endowed with the major proteins that are thought to regulate the targeting and exocytosis of secretory vesicles, in particular of synaptic ‐like

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1996.tb00267.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract:The tripeptide bursin (Lys‐His‐Gly‐NH2) is a B cell differentiation hormone derived from the bursa fabricii. The latter is a cloacal diverticulum and the site of B lymphocyte differentiation and selection in aves; also the bursa fabricii is involved in endocrine functions. Herein we demonstrate that in the chicken, the bursa fabricii and bursin are crucial to the ontogeny of both the pineal response to antigenic challenge and pineal circadian synthetic activity. In early embryonically bursectomized chickens, the plasma melatonin response to immunization by porcine thyroglobulin (Tg) was abolished. Also, the amplitudes of both plasma melatonin and pineal N‐acetyltransferase (NAT) circadian rhythms were reduced by 50%, whereas the activity of hydroxyindole‐O‐methyltransferase (HIOMT) remained unchanged. Conversely, administration of either minute amounts (100 pg, 100 fg) or highly dilute (5 × 10−27g) bursin, with the exception of a highest dose (100 μg), to bursaless embryos induced recovery of normal antigen‐induced melatonin response and normal amplitudes of melatonin and NAT rhythms. These findings establish that early in embryonic life, the bursa fabricii and its derived signal (bursin) are essential for normal development of pineal synthetic activity and underline the efficacy of very dilute bursin as an i

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1996.tb00268.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract:There is growing interest in using melatonin as a therapeutic agent for the treatment of a variety of medical conditions, including cancer, heart disease, glaucoma, stress, jet lag, and sleep disorders. In addition, melatonin is being evaluated in a clinical trial to test its efficacy as an oral contraceptive. In order to test any possible adverse effects of melatonin on preimplantation embryos, we used the mouse as a model system. Two strains of mice, aPed fast, melatonin‐deficient strain, C57BL/6, and aPed slowstrain previously found to have detectable melatonin levels at nighttime, CBA/Ca, were studied. Two cell embryos were incubated with melatonin concentrations from 10−5M to 10−13M for 48 or 72 hours and the number of cells per embryo assessed quantitatively at the end of the incubation period. We used sufficiently high levels of melatonin to mimic the pharmacological concentration used in the oral contraceptive. It was found that there was no effect of melatonin on embryos from either mouse strain at any of the concentrations tested. Our results suggest that if conception occurs while melatonin is being administered to treat a range of conditions, it would not adversely affect the e

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1996.tb00269.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Abstract:To clarify whether disorders of gonadotropin releasing hormone (GnRH) deficiency are associated with altered melatonin and pituitary hormones secretory patterns, we studied male patients with hypogonadotropic hypogonadism (IGD; n = 6), delayed puberty (DP; n = 7) and age‐matched pubertal controls (n = 7). Serum samples for the determination of melatonin, luteinizing hormone (LH), prolactin and Cortisol levels were obtained at 15 min intervals from 1900 to 0700 in a controlled light‐dark environment, complete bed‐rest and fasting with simultaneous sleep recordings. Mean (± SD) dark‐time melatonin levels were significantly higher in IGD (286 ± 26 pmol/L) and DP (205 ± 44 pmol/L) compared with 178 + 64 pmol/L in controls (P<0.003). So were the mean (± SD) peak melatonin levels (453 ± 63, 346 ± 106 and 292 ± 96 pmol/L) in IGD, DP and controls, respectively (P<0.03). Integrated nocturnal melatonin (AUC) values were also higher in IGD and DP (184 ± 15 and 134 ± 28 pmol/min/L × 103) compared with 116 ± 42 pmol/min/L × 103in controls (P<0.003). The time of onset of the nocturnal melatonin rise was observed earlier in IGD and DP patients as compared to controls. No correlations were found between melatonin and LH levels, between melatonin and prolactin levels, or between melatonin and Cortisol levels. These data indicate that melatonin secretion is enhanced in male patients with GnRH deficiency. The lack of correlation between melatonin and LH suggest that circulating gonadal steroids, rather than LH, modulate melatonin secretion i

ISSN:0742-3098    

DOI:10.1111/j.1600-079X.1996.tb00270.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY