2001 Fiscal Year Final Research Report Summary
A study of putative brain circadiom oscillators in amphibians and fish
| Project/Area Number |
11640686
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
動物生理・代謝
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| Research Institution | Sophia University |
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Principal Investigator |
CHIBA Atsuhiko Sophia University, Faculty of Science & Technology, Associate Professor, 理工学部, 助教授 (40207288)
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| Co-Investigator(Kenkyū-buntansha) |
IIGO Masayuki St.Marianna University, School of Medicine, Lecturer, 医学部, 講師 (10232109)
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| Project Period (FY) |
1999 – 2000
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| Keywords | pineal organ / melatonin / circadian oscillator / circadian rhythm / clock gene / suprachiasmatic nucleus / amphibian / fish |
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| Research Abstract |
1. To obtain the insight on the molecular mechanisms of the circadian clock in amphibians and fish, we isolated partial cDNAs encoding Per2 from the Japanese newt (Cynops pyrrhogaster) and Per2, Per3, Clock and Bmall from the ayu (Plecoglossus altivels).
2. Plasma melatonin levels in the newt, ayu and rainbow trout (Oncorhynchus mykiss) determined by radioimmuno-assay exhibited significant daily variation under light-dark cycles. In the newt, the day-night change in plasma melatonin level was abolished by either pinealectomy or bilateral ocular enucleation. Plasma melatonin levels exhibit circadian variation under constant darkness in the ayu but not in the rainbow trout.
3. We characterized and localized melatonin receptors in the newt brain. The melatonin receptors are highly specific for melatonin with picomolar affinity. Autoradiographic studies revealed uneven distribution in the brain with the highest density observed in the optic tectum.
4. By using the number of synaptic ribbon in
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the pineal photoreceptor as a phase marker of the pineal circadian clock, we showed that daily melatonin injections entrained the pineal circadian clock as well as circadian locomotor activity rhythm in the newt.
5. We covered the newt's skull with aluminum foil and simultaneously reversed the light-dark cycle. Locomotor activity rhythm of the head-covered animals was entrained to the reversed light-dark cycle while the rhythm of pineal synaptic ribbon number remained almost the same phase as the original one. These data suggest that under light-dark cycle retinally perceived light can entrain the circadian clock in the brain without help from the pineal circadian clock.
6. The effects of pinealectomy on circadian rhythms in the demand-feeding activity of the rainbow trout were examined. Pinealectomy affected the demand-feeding activity under neither light-dark nor constant light conditions, indicating that the pineal organ is not essential to maintain the function of the circadian clock in the brain. Less
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[Publications] Amano, M, Iigo, M, Ikuta, K, Kitamura, S, Yamada, H, Yamamori, K: "Roles of melatonin in gonadal maturation of underyearling precocious male masu salmon"General and Comparative Endocrinology. 120. 190-197 (2000)
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[Publications] Hara, M, Yoshida, M, Nisijima, H, Yokosuka, M, Iigo, M., Ohtani-Kaneko, R., Shimada, A., Hasegawa, T., Akama, Y., Hirata, K: "Melatonin, s pirenl secretory product with antioxidant properties protects against Cisplatin-induced nephrotoxicity in rats"Journal of apineal Research. 30. 129-138 (2000)
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「研究成果報告書概要(欧文)」より
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