REGULATION OF HUMAN BIOLOGY BY CHANGES IN DAYLENGTH

在这个过程中，大多数生物都表现出惊人的季节性变化 这一年。在许多情况下，这种变化已知是由季节性因素引起的 日长或光周期的变化。光周期的变化 通常以两种方式影响动物。第一，每天不变的 光周期的扩张或收缩会导致动物每天 要扩展或收缩的活动或休息阶段，以便与 光周期。其次，光周期的具体变化可能会引发新的 行为，如冬眠、迁徙或繁殖 对特定季节盛行的条件的适应。这些 新的行为通常伴随着并依赖于 生物体的生化、生理学和解剖学。 基础研究人员提出，光周期控制着 通过它对生物钟机制的影响而产生的 两个独立的昼夜节律振荡器跟踪不断变化的时间 一年中的黎明和黄昏。这个项目是专门设计的 为了研究人类生物学是否同样受制于 光周期的变化。我们监测睡眠荷尔蒙的日常模式 以及按计划生活一个月的人的体温 模拟自然冬日的光照。他们四处走动 每天在自然光和人造光下自由活动10小时，但 每晚都被关在黑暗的房间里14个小时。为 相比之下，我们在相同的人身上进行类似的测量，而 他们按照传统的作息时间生活一周 每天暴露在环境光下16个小时，睡在黑暗中 每晚有八个小时的房间。 实验结果表明，人类的昼夜节律系统 与其他动物相似--它由两个子系统组成， 其中一个与黎明同步，另一个与黄昏同步。这 结论是基于以下观察：夜幕降临后 人为地延长到14小时，睡眠分成两个小时 逐渐分开的组件。晚间成分(E)是 与每日皮质醇分泌的最低点、褪黑素的发作有关 分泌，催乳素分泌开始，睡眠开始，缓慢的高峰 一波又一波的睡眠和体温的下降，把它带到了黄昏。 晨间成分(M)与皮质醇的日峰值有关 分泌，褪黑素分泌抵消，催乳素分泌抵消， 慢波睡眠高峰期、体温升高和 醒着，天快要亮了。光周期的变化 引起褪黑激素、温度、皮质醇和 促甲状腺激素的昼夜节律相互独立。这 观察表明，这些节律中的每一种都可能受到 独立的从属振荡器对。结果很可能会有 对人类生物学和医学的重要影响。

Most living things exhibit striking seasonal changes during the course of the year. In many cases, the changes are known to be induced by seasonal changes in daylength, or photoperiod. Changes in the photoperiod generally affect animals in two ways. First, the constant daily expansion or contraction of the photoperiod can cause an animal's daily activity or rest phase to expand or contract, so that it matches the photoperiod. Second, specific changes in the photoperiod can trigger new behaviors, such as hibernation, migration, or breeding, that represent adaptations to conditions that prevail during a particular season. These new behaviors are often accompanied by and depend on marked changes in the biochemistry, physiology and anatomy of the organism. Basic researchers have proposed that the photoperiod controls the organism through its effects on a biological clock mechanism that employs two separate circadian oscillators to track the constantly changing times of dawn and dusk through the course of the year. This project is designed to investigate whether human biology is similarly subject to control by changes in the photoperiod. We monitor daily patterns of sleep hormones and body temperature in individuals who live for one month on a schedule of light exposures that simulate a natural winter day. They move about freely in ambient natural and artificial light for ten hours each day but are confined to a dark room for fourteen hours each night. For comparison, we make similar measurements in the same individuals while they live for one week on a conventional schedule in which they are exposed to ambient light for sixteen hours each day and sleep in a dark room for eight hours each night. The results of the experiment suggest that the human circadian system is similar to that of other animals-that it is composed of two subsystems, one of which is synchronized with dawn and the other with dusk. This conclusion is based on the following observations: After night was artificially expanded to fourteen hours, sleep divided into two components that gradually moved apart. The evening component (E) was associated with the daily nadir of cortisol secretion, onset of melatonin secretion, onset of prolactin secretion, onset of sleep, peak of slow wave sleep and decline in body temperature, and it was entrained to dusk. The morning component (M) was associated with the daily peak of cortisol secretion, offset of melatonin secretion, offset of prolactin secretion, peak of slow wave sleep, rise in body temperature and onset of wakefulness, and it was entrained to dawn. Changes in the photoperiod induced changes in the timing of melatonin, temperature, cortisol and thyrotropin circadian rhythms that were independent of one another. This observations suggest that each of these rhythms may be controlled by separate pairs of slave oscillators. The results are likely to have important implications for human biology and medicine.