The melatonin rhythm: both a clock and a calendar

The paper briefly reviews the data which shows that the circadian production and secretion of melatonin by the pineal gland can impart both daily, i.e., clock, and seasonal, i.e., calendar, information to the organism. The paper summarizes the 3 patterns of nocturnal melatonin production that have been described. Clearly, regardless of the pattern of nocturnal melatonin production a particular species normally displays, the duration of nightime elevated melatonin is proportional to the duration of the night length. Since daylength under natural conditions changes daily the melatonin rhythm, which adjusts to the photoperiod sends time of year information to the organism. The melatonin receptors which subserve the clock message sent by the pineal gland in the form of a melatonin cycle may reside in the biological clock itself, namely, the suprachiasmatic nuclei (SCN). The melatonin receptors that mediate seasonal changes in reproductive physiology are presumably those that are located on the pars tuberalis cells of the anterior pituitary gland. Besides these receptors which likely mediate clock and calendar information, melatonin receptors have been described in other organs. Interestingly, the distribution of melatonin receptors is highly species-specific. Whereas the clock and calendar information that the melatonin cycle imparts to the organism relies on cell membrane receptors, a fact that is of some interest considering the high lipophilicity of melatonin, recent studies indicate that other functions of melatonin may require no receptor whatsoever.     

The pineal and melatonin: Regulators of circadian function in lower vertebrates

Summary The pineal has been identified as a major circadian pacemaker within the circadian system of a number of lower vertebrates although other pacemaking sites have been implicated as well. The rhythmic synthesis and secretion of the pineal hormone, melatonin, is suggested as the mechanism by which the pineal controls circadian oscillators located elsewhere. Both light and temperature cycles can entrain the pineal melatonin rhythm. The pineal, therefore, acts as a photo and thermoendocrine transducer which functions to synchronize internal cycle with cycles in the environment. A model is presented which portrays the pineal as a major component of a multioscillator circadian system and which suggests how these multiple circadian clocks are coupled to each other and to cycles of light and temperature in the external world.     

Pineal ‘synaptic’ ribbon numbers and melatonin synthesis of rat are resistant to guanethidine sympathectomy

Chemical sympathectomy is widely used to study the impact of the noradrenergic system on neuronal and neuroendocrine circuits. We tested the effects of intraperitoneal injections of guanethidine, an adrenergic neuron blocking agent, on selected functional parameters of the rat pineal gland which are known to be under sympathetic influence. The reliability of the method was demonstrated by the clear enophthalmus developed by experimental animals. However, neither the numbers of synaptic ribbons nor melatonin synthesis differed between treated and control rats, both parameters exhibiting the nocturnal increase seen in intact animals. These results are in striking contrast to those obtained upon chemical sympathectomy with 6-hydroxydopamine or surgical superior cervical ganglionectomy. We conclude that guanethidine is not capable of sufficiently removing noradrenergic influence from the rat pineal gland, and that this substance is thus inferior to other experimental methods of sympathectomy.     

褪黑素对持续光照小鼠学习记忆能力的影响

运用Ｙ－迷宫检测小鼠的分辨学习和记忆能力,观察了年龄,每天２４小时连续１个月的持续光照和每日定时注射褪黑素对小鼠分辨学习和记忆能力的影响。结果表明,成年小鼠与青年小鼠相经学习和记忆能力下降;持续光照可引起小鼠学习记忆能力出现不同程度的下降;实验结果提示,褪黑素在维持学习记忆能力中具有重要作用。     

Photoreceptors in the pineal of lower vertebrates: Functional aspects

Summary The pineal of lower vertebrates characteristically contains true and modified photoreceptors with functional und structural homologies to retinal photoreceptors. Afferent nerves convey photic information from the pineal to sensory areas of the brain stem. Light also influences synthetic activity within the organ, controlling the rhythm in melatonin production which is generated endogenously. The molecular mechanisms underlying this rhythmic event are described and the hypothesis advanced that the pineal transduces several forms of environmental stimulus involved in the regulation of rhythmic function.     

信息检索在专利技术开发中的作用

通过对一项公开专利技术CN1440744A(纳米包覆退黑激素复合保健品)的开发提供信息检索跟踪服务的实例，论证了信息检索在专利技术开发中的地位和作用。     

用C18-RPLC柱及UV检测器分离和测定蜥蜴松果体中的褪黑激素

研究了褪黑激素和消炎痛在反相Ｃ１８柱上的色谱行为,流动相为甲醇－磷酸盐缓冲溶液体系,主要考察了ｐＨ值及洗脱液的组成对色谱保留的影响,对蜥蜴松果体中的褪黑色激素进行了完全分离和定量测定。     

3种辐射保护剂对60Co-γ射线辐照小苍兰的保护效应

采用水杨酸（SA）、褪黑素(MT)、赤霉素(GA)3种辐射保护剂对⁶⁰Co-γ射线辐射处理后的小苍兰进行保护处理,以期减轻植物辐照后的损伤,降低辐照后种球的死亡率,增加其存活率和开花率,为花卉品种培育与改良提供行之有效的技术支持和数据参考。     

褪黑素对铝致痴呆模型大鼠空间学习记忆的影响

目的:观察褪黑素对铝致痴呆模型大鼠空间学习记忆的影响,探讨褪黑素改善铝致痴呆模型大鼠学习记忆功能障碍的作用.方法:用腹腔注射三氯化铝的方法建立大鼠学习记忆障碍模型,并用褪黑素进行实验性治疗.采用Morris水迷宫方法测试各组大鼠空间学习记忆能力的改变.结果:大鼠经多次训练后,各组大鼠逃避潜伏期均呈缩短趋势,此现象表明大鼠空间学习记忆能力随训练次数增加而有所增强.但是大鼠在染铝后40、45、50、55、60 d逃避潜伏期明显大于生理盐水对照组,两者比较差异有统计学意义(P<0.01);而用褪黑素治疗组在染铝后40、45、50、55、60d逃避潜伏期明显小于模型组,两者比较差异有统计学意义(P<0.01).在40、50、60 d的时间段中,褪黑素治疗组穿环系数明显大于痴呆模型组(P<0.01).结论:褪黑素对铝致痴呆模型大鼠学习记忆功能障碍有明显的改善作用.     

MT促进毛皮动物毛皮生长的研究

论述了埋植ＭＴ植入物能促使水貂、狐狸、貉等毛皮动物冬皮不同程度的早熟;也能让绒山羊在非和绒期长绒、让安哥拉兔夏毛产量增加;并结结果进行了讨论。