| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1993: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 1992: ¥1,100,000 (Direct Cost: ¥1,100,000)
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| Research Abstract |
1. In cell suspensions of suprachiasmatic nucleus harvested every 3 hr from rats kept under 12 hr : 12hr light-dark cycle and constant darkness, we have detected a Mr 64-kDa protein whose synthesis exhibits two distinct daily peaks in SDS-PAGE.Analysis of densitometer tracings revealed that the synthesis of other proteins was independent of the time of day or not reproducible. Maximum synthesis of the 64-kDa polypeptide occured at around CT6 and CT21, which are almost coincident with the phase advance regions of circadian activity rhythm induced by anisomycin and light pulses [15], respectively. These results suggested that the 64-kDa protein in SDS-PAGE may be a part of the circadian clock mechanism.
2. The avian pineal gland plays an important role in the circadian rhythms of behavior and physiology. However, effects of pinealectomy on circadian rhythms differ widely among species of passerine, gallinaceous or columbine birds. We compared the circadian oscillation of melatonin release
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from cultured pineal cells in japanese quail, pigeon and house sparrow, to determine whether the pineal gland of these species retains the circadian oscillator function in vitro.. After dissociated pineal cells has been cultured for 4 days under 12 h : 12 h light-dark (LD) cycle, they were perfused at a flow rate of 0.25 ml/h for 6-7 days under LD or constant darkness (DD). Melatonin release increased during the dark period and low during the light period in all pineral cell cultures. Under DD conditions, the circadian rhythm of melatonin release persisted for up to 3-4 cycles in pigeon and house sparrow pineal cells. However, the amplitude of the rhythm decreased gradually. However, in Japanese quail pineal cell culture the circadian oscillation of melatonin release was abolished under DD conditions.
These results strengthen the argument that the avian pineal gland's role in circadian organization differs between species. The direct demonstration of species-specific differences in the mechanism of the circadian oscillation of melatonin release from pineal cells should provide a useful model for the analysis of the pineal's circadian system at the cellular level. Less
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