共查询到20条相似文献,搜索用时 31 毫秒
1.
The activity of N-acetyltransferase in the rat pineal gland is more than 15 times higher at night than during the day. This circadian rhythm persists in complete darkness, or in blinded animals, and is suppressed in constant lighting. The N-acetyltransferase rhythm is 180 degrees out of phase with the serotonin rhythm and is similar to the norepinephrine and melatonin rhythms. Experiments in vitro indicate that norepinephrine, not serotonin, regulates the activity of N-acetyl-transferase through a highly specific receptor. 相似文献
2.
Pinealectomized Syrian hamsters were injected thrice daily with 25 micrograms of melatonin per injection. The injections were administered at 3-hour intervals either during the day or during the night of a photoperiodic cycle of 14 hours of light and 10 hours of darkness. After 6 weeks of treatment with melatonin during the night, both pinealectomized and intact hamsters had reduced testis weight, and pinealectomized hamsters showed decreased levels of serum gonadotropins. Injection of melatonin during the day for 7 weeks either once (75 micrograms) a day or thrice (25 micrograms per injection) daily caused a reduction in testis weight in pinealectomized hamsters. Both pinealectomized and intact females injected with melatonin thrice daily during the day became anovulatory by week 7 of treatment. These results are similar to those observed when hamsters are exposed to a short photoperiod, suggesting that melatonin may be acting as a hormone in mediating the effects of photoperiod on the reproductive system of the Syrian hamster. 相似文献
3.
Pineal melatonin may play an important role in regulation of vertebrate circadian rhythms and in human affective disorders. In some mammals, such as hamsters and sheep, melatonin is involved in photoperiodic time measurement and in control of reproduction. Although wild mice (Mus domesticus) and some wild-derived inbred strains of mice have melatonin in their pineal glands, several inbred strains of laboratory mice (for example, C57BL/6J) were found not to have detectable melatonin in their pineal glands. Genetic analysis suggests that melatonin deficiency in C57BL/6J mice results from mutations in two independently segregating, autosomal recessive genes. Synthesis of melatonin from serotonin in the pineal gland requires the enzymes N-acetyltransferase (NAT) and hydroxyindole-O-methyltransferase (HIOMT). Pineal glands from C57BL/6J mice have neither NAT nor HIOMT activity. These results suggest that the two genes involved in melatonin deficiency are responsible for the absence of normal NAT and HIOMT enzyme activity. 相似文献
4.
Circadian rhythm in pineal tyrosine hydroxylase 总被引:4,自引:0,他引:4
Tyrosine hydroxylase is the rate-limiting enzyme in catecholamine synthesis. The rat pineal gland is richly innervated by sympathetic nerves from the superior cervical ganglia. The activity of tyrosine hydroxylase was measured in rat pineal gland at 4-hour intervals over a daily cycle of 12 hours of light (7 a.m. to 7 p.m.) and 12 hours of darkness. The results indicate a circadian rhythm with the maximum activity, at 11 p.m. to 3 a.m., about triple the low values observed at 3 p.m. The pattern is similar in phase to that previously reported for melatonin and hydroxyindole-O-methyl transferase activity. 相似文献
5.
Gonadal growth was controlled in two avian species by corticosterone and prolactin injected daily at various times. Testicular growth was induced in photorefractory house sparrows (Passer domesticus) kept in continuous light by prolactin injected 4 or 8 hours after administration of corticosterone. Other temporal patterns were ineffective. Gonadal growth was also stimulated in photosensitive white-throated sparrows (Zonotrichia albicollis) kept in continuous light by prolactin injected 12 hours after administration of corticosterone. Daily injections of prolactin 8 hours after injection of corticosterone inhibited gonadal growth. The seasonal cycle of reproductive photorefractoriness and photosensitivity is controlled by a changing relation between the daily rhythms of plasma concentrations of corticosterone and prolactin. 相似文献
6.
Melatonin: a coordinating signal for mammalian reproduction? 总被引:14,自引:0,他引:14
There is a daily rhythm in the production of the pineal hormone melatonin in all mammalian species. Production is stimulated by darkness and inhibited by light. This provides a signal reflecting the changing environmental lighting cycle. In seasonally breeding mammals that use changes in the photoperiod to time their reproductive cycles, temporal signals to the reproductive system are controlled by the daily rhythm in melatonin production. 相似文献
7.
黄鳝血清褪黑激素水平日周期性与季节性变化的节律 总被引:8,自引:0,他引:8
通过放射免疫测定方法,本文初步研究了黄鳝血清褪黑激素的分泌特性,实验结果表明,黄鳝血清褪黑激素水平具有明显的日周期性与季节性变化节律。白天血清中褪黑激素水平较低,夜间浓度显著升高,比白天值高1-2倍。随着性腺的发育,从卵巢Ⅱ至Ⅳ期,血清中黑激素含量逐渐升高,到排卵前期则急剧下降。排卵期达到雌性阶段的最优值;排卵后期,血清褪黑激素水平又逐渐加回升:间性期则有下降的趋势;雄鱼血清中褪黑激素水平极低。 相似文献
8.
通过放射免疫测定方法,本文初步研究了黄鳝血清褪黑激素的分泌特性,实验结果表明,黄鳝血清褪黑激素水平具有明显的日周期性与季节性变化节律。白天血清中褪黑激素水平较低,夜间浓度显著升高,比白天值高1-2倍。随着性腺的发育,从卵巢Ⅱ至Ⅳ期,血清中黑激素含量逐渐升高,到排卵前期则急剧下降。排卵期达到雌性阶段的最优值;排卵后期,血清褪黑激素水平又逐渐加回升:间性期则有下降的趋势;雄鱼血清中褪黑激素水平极低。 相似文献
9.
Sleep deprivation in the rat 总被引:1,自引:0,他引:1
R A Levitt 《Science (New York, N.Y.)》1966,153(731):85-87
Sleep deprivation, induced by injections of dextroamphetamine or by forced treadmill activity, resulted in a temporary increase in daily sleep time. However, increasing the period of sleep deprivation above 24 hours to 72 or 120 hours did not result in increased recovery sleep above that present in the 24-hour group. 相似文献
10.
外源褪黑素对氯化钠胁迫下美味猕猴桃实生苗抗氧化物酶和渗透调节物质的影响 总被引:2,自引:0,他引:2
盐胁迫是果树生长发育所面临的主要危机之一。为探讨外源褪黑素对缓解美味猕猴桃Actinidia deliciosa盐胁迫的生理机制,对根灌褪黑素后的美味猕猴桃实生苗进行盐胁迫处理。通过测定对照(ck),氯化钠胁迫(S1),褪黑素预处理和氯化钠胁迫(S2)下的美味猕猴桃实生苗叶片保护酶(超氧化物歧化酶、过氧化物酶、过氧化氢酶)活性、抗坏血酸及渗透调节物质的变化,分析外源褪黑素提高植物耐盐性的生理机理。结果表明:与对照(ck)相比,氯化钠胁迫处理后,美味猕猴桃实生苗叶片中丙二醛、脯氨酸、保护酶活性先升高再下降,抗坏血酸和可溶性蛋白质先下降再升高,过氧化氢和可溶性糖显著上升;而根灌褪黑素可有效缓解美味猕猴桃实生苗膜脂过氧化程度,降低丙二醛和过氧化氢,最多时分别降低102.45%和44.35%。同时,可显著增加脯氨酸、可溶性糖、可溶性蛋白质和抗坏血酸,并提高保护酶活性。外源褪黑素可以通过提高抗氧化物酶活性和渗透调节物质含量有效减缓氯化钠盐胁迫的危害,提高美味猕猴桃的耐盐性。 相似文献
11.
A single daily "surge" in pituitary luteinizing hormone release was observed in ovariectomized-estrogen-treated hamsters expressing an intact circadian rhythm of locomotor activity. In contrast, two luteinizing hormone surges occurred within a single 24-hour period in hamsters whose activity rhythm had dissociated or "split" into two distinct components. These observations indicate that both behavioral and endocrine circadian rhythms are regulated by the same multioscillator system, which seems to be composed of at least two distinct circadian oscillators. 相似文献
12.
Benzodiazepines: anxiety-reducing activity by reduction of serotonin turnover in the brain 总被引:5,自引:0,他引:5
The anxiety-reducing effects of minor tranquilizers in the rat conflict test were mimicked by serotonin antagonists and by p-chlorophenylalanine, an inhibitor of serotonin synthesis; the depressant effects of the minor tranquilizers were mimicked by norepinephrine antagonists. Intraventricular injections of serotonin led to a suppression of behavior, and also antagonized the anxiety-reducing action of benzodiazeprines. Intraventricular injections of norepinephrine led to a release of punished behavior from suppression, and also antagonized the depressant action of benzodiazepines. The anxiety-reducing activity, and the decrease in serotonin turnover induced by benzodiazepines, were maintained over repeated doses, whereas depressant activity, and the decrease induced in norepinephrine turnover, both rapidly underwent tolerance. Tranquilizers may exert their anxiety-reducing effects by a reduction of serotonin activity in a behaviorally suppressive punishment system, and they may exert their depressant effects by a reduction of norepinephrine activity in a behaviorally facilitatory reward system. 相似文献
13.
14.
Exposure of male hamsters to short daily photoperiods (1 hour of light and 23 hours of darkness daily for 9 weeks led to total involution of the testes and accessory sex organs (seminal vesicles and coagulating glands). Pituitary levels of immunoreactive prolaction also decreased by about 60 percent after dark exposure. The inhibitory effects of darkness on the reproductive organs were prevented either by pinealectomy or by the subcutaneous implantation of a melatonin-beeswax pellet into the animals each week. Both pinealectomy and melatonin treatment also returned pituitary levels of prolactin toward normal. The results suggest that melatonin is not the pineal antigonadotrophic factor in the male golden hamster. 相似文献
15.
16.
In rats, multiple daily amphetamine injections (2.5 milligrams per kilogram of body weight, injected subcutaneously every 4 hours for 5 days) resulted in a progressive augmentation in response, characterized by a more rapid onset and an increased magnitude of stereotypy. By contrast, offset times of both the stereotypy and the poststereotypy hyperactivity periods were markedly shortened. When the animals were retested with the same dose of amphetamine 8 days after the long-term treatment was discontinued, the time of offset of the stereotypy and hyperactivity phases had recovered to values found with short-term amphetamine treatment, whereas the more rapid onset of stereotypy persisted. Brain monoamine and amphetamine concentrations and tyrosine hydroxylase activity were determined in comparably treated rats at times corresponding to the behavioral observations. The behavioral data indicate that enhanced responsiveness to amphetamine following its repeated administration may contribute to the development of amphetamine psychosis. 相似文献
17.
Melatonin synthesis: adenosine 3',5'-monophosphate and norepinephrine stimulate N-acetyltransferase 总被引:20,自引:0,他引:20
Treatment of cultured rat pineal glands with norepinephrine or dibutyryl adenosine 3',5'-monophosphate causes a six- to tenfold stimulation of N-acetyltransferase. This enzyme converts serotonin to N-acetylserotonin, the immediate precursor of melatonin. The increased synthesis of melatonin caused by norepinephrine treatment appears to be the result of stimulation of N-acetyltransferase by an adenosine 3',5'-monophosphate mechanism. 相似文献
18.
In organ cultures of intact rat pineal glands, N(6)O(2')-dibutyryl adenosine 3', 5'-monophosphate stimulates the conversion of tritiated trytophan to tritiated melatonin, as does L-norepinephrine. Potential sites of stimulation of melatonin production by dibutyryl cyclic adenosine monophosphate are discussed, based on observations that the dibutyryl analog also stimulates the conversion of serotonin labeled with carbon-14 to carbon-14-labeled melatonin without altering hydroxyin-dole-O-methyl transferase activity or intracellular accumulation of serotonin labeled with carbon-14. 相似文献
19.
为探究褪黑素对桃耐涝性的调控效应,用200 μmol·L-1褪黑素对桃苗进行预处理,再经涝害处理,通过生理指标与转录组分析褪黑素和涝害对桃的影响。结果表明,涝害胁迫下外源褪黑素能保护细胞膜和根系。褪黑素能激活微管形态建成、氧化还原酶活性和蛋白结合相关的基因,巩固根系骨架,激活抗氧化酶活性,提高抗逆性。涝害诱导ERF转录因子家族成员大量表达,通过HRPE和GCC-box顺式作用元件激活下游ADH、ALD、GAPD等糖酵解途径关键酶基因的表达,为低氧胁迫下的植株供能。ERF Ⅶ成员Prupe.8G264900可能是桃响应涝害的关键基因。 相似文献