Hasegawa K, Tanakadate A
Department of Physiology, School of Medicine, Kitasato University, Japan.
J Biol Rhythms. 1987 Winter;2(4):269-78. doi: 10.1177/074873048700200403.
The population of a ciliate protozoan, Paramecium multimicronucleatum, exhibits a circadian rhythm as measured by the number of the cells traversing an observation point ("traverse frequency," or TF). The present study examined phase shifting of the TF rhythm by administering 2-hr light pulses at different phases of the circadian cycle to cultures free-running in constant darkness (DD). The results were summarized in a phase response curve (PRC), categorized as Type 1. This PRC indicated a relatively narrow phase zone insensitive to the light pulse ("dead zone"). Entrainment of the rhythm to light pulses repeated at 24-hr intervals was also examined, and it was found that the rhythm gradually reached a steady state, following several transient cycles, with the pulses falling at a phase corresponding to the narrow dead zone. Such a steady-state rhythm, with a minimum at approximately 3 hr after the pulse and a maximum at approximately 12 hr after the pulse, was mathematically simulated by superimposing a response function to the pulse on a sinusoidal function representative of the free-running rhythm in DD.
多核草履虫这种纤毛原生动物的种群，以通过观察点的细胞数量（“穿越频率”，即TF）来衡量，呈现出昼夜节律。本研究通过在昼夜周期的不同阶段对在持续黑暗（DD）中自由运行的培养物施加2小时的光脉冲，来检测TF节律的相位转移。结果总结在一条相位响应曲线（PRC）中，该曲线归类为1型。这条PRC表明存在一个对光脉冲相对不敏感的较窄相位区（“死区”）。还研究了以24小时间隔重复的光脉冲对节律的同步化情况，结果发现，经过几个瞬态周期后，节律逐渐达到稳定状态，脉冲落在对应于狭窄死区的相位。通过将对脉冲的响应函数叠加在代表DD中自由运行节律的正弦函数上，对这样一种在脉冲后约3小时出现最小值、在脉冲后约12小时出现最大值的稳态节律进行了数学模拟。
