1996 Fiscal Year Final Research Report Summary
Frog brain can perceive light : Identification of visual pigments and analysis of photoreceptive mechanism
| Project/Area Number |
07839009
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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 | 時限 |
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| Research Field |
光生物学
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| Research Institution | Nara Women's University |
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Principal Investigator |
OISHI Tadashi Faculty of Science, Nara Women's University, Professor, 理学部, 教授 (30112098)
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| Project Period (FY) |
1995 – 1996
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| Keywords | Visual pigment / Brain / Pireal / Hypothalamus / frog / Immunohirtochemistry / Photoreceptor gene |
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| Research Abstract |
Antiserum agaisnt toad rhodopsin (BufoRh-As) was prepared and immunohistochemical studies were performed on the localization of visual pigments in the brain of four species of anuran amphibians (Rana nigromaculata, Rana catesbeiana, Bufo bufo japonicus, Xenopus laevis). In all four species, BufoRh-As recognized the outersegments of rods in the retina. The outersegments of pinealocytes in the pineal of Rana nigromaculata was also recognized by BufoRh-As. The hypothalamus (preoptic nucleus and suprachiasmatic nucleus) was stained in Rana catesbeiana and Bufo bufo japonicus, but not in Xenopus laevis. The results obtained were very similar to those obtained by use of antiserum agaisnt bovine rhodopsin and suggest that rhodopsin-like phto-pigments exist in the pineal and deep brain of frogs. Visual pigment genes were cloned from PCR products of the toad hypothalamus cDNA library. The amino acid sequence of this toad deep brain photoreceptor (toad DBP) indicated 76%, 49% and 46% homology to chick pinopsin, chicken rhodopsin and frog rhodopsin, respectively. It belongs to the pinopsin group which branches from the group L in the phylogenetic tree of visual pigments.
In Xenopus laevis, we studied circadian oscillator system and extra-retinal photoreception for the entrainment of the rhythm. Intact animals exhibited nocturnal activity and freerunning rhythms under constant darkness and constant light. Blinded animals were also entrained to light-dark cycles indicating involvement of extraretinal photoreceptors. The period of freerunning rhythms was significantly shorter in blinded animals than inact animals. The electric lesion of the suprachiasmatic nucleus (SCN) completely abolished the circadian rhythms in animals whose SCN was destroyed more than 70%. The results obtained suggest that the SCN is important for generation of the circadian rhythm and the cyc is also involved in the circadian system by changing freerunning periods.
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