Localization of circadian clock and its structure

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Circadian rhythm is an about-24 hr endogenous oscillation underlain by a time measuring mechanism (circadian clock). A strategy for elucidating the mechanism includes three progressive stages: (1) localization of candidate clock tissues, (2) demonstrat-tion of a self-oscillating ability of the tissue, and (3) approaches to deeper mechanisms from aspects of cell or molecular biology. This project team comprised 12 active researchers working along this strategy.Results were obtained as follows.1. Localization of the clock in Metazoa: Self-oscillating ability of the cricket optic lobe were demonstrated alomst conclusively. Interspecies transplantation of the suprachiasmatic nuclei were attempted with rodents. Studies on melatonin production , a key factor for controlling overt rhythms, in the pineal body and the eye of vertebrates were deepened.2. Clocks at cellular level: A molecular-biological study clarified that a clock mutant of a Neurospora rhythm is characterized by an abnormal calcium metabolism. Biophysical mechanisms of Paramecium swimming rhythm were analysed using a computerized system for monitoring cell movements. PTTH cells, which may form an essential part of the insect brain clock, were tried to be located by an immunohistochemical method.3. Photoperiodic clocks: How photoperiodism is related to circadian rhythm was also studied. An interesting result was obtained, in a cricket study,that heavy water lengthened the freerunning period of locomotion but did not affect the critical photoperiod. External coincidence model now widely accepted may not apply to this case.4. Gene cloning techniques: Utility of this newly developed techniques was emphasized in studies on brain and prothoracic clock of insects and bird pineal clock.