| Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1993: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1992: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1991: ¥700,000 (Direct Cost: ¥700,000)
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| Research Abstract |
1. Effects of methylmercury(MeHg) in vivo on the protein phosphorylation in vitro of the brain cytosol fraction in acutely poisoned rats.
(1) The total protein phosphorylation activity, determined in the presence or absence of protein kinase effectors(Ca and cAMP) and specific substrates(casein, histone and PKC substrate) did not significantly change during the period of intoxication in the animals. (2) Two-dimensional electrophoresis of the phosphorylated proteins detected the 70 proteins as autoradiographic spots. Among these proteins, 24 major protein species were analyzed and it was revealed that the effect of MeHg on the phosphorylation was not uniform regarding the individual proteins. It was also demonstrated that in the symptomatic period, many protein species showed elevated phosphorylation, while a few proteins showed decreaed phosphorylation activity. (3) Phosphorylation of alpha-tubulin was low for the period examined when assayd in the presence of Ca, while that of beta-tubulin was elevated at the symptomatic period.
2. Effects of MeHg in vivo on the protein phosphorylation in vitro of the purfied brain nuclear fractions.
(1) The total protein phosphorylation activity of the whole nuclei was deacreased at the early and latent period, but it was recovred at the symptomatic period. (2) Phosphorylating activities of the nuclear extracts and the membrane fractions showed the differnt properties as regards the dependency on effectors and substrates. (3) SDS/PAGE electrophoresis of the phosphorylatd proteins revealed that the changes of phosphorylation patterns (extent, decrease/increase) during the intoxication period differed greatly from each other.
3. These results suggest that MeHg acts differntially on the phosphorylation of cytoplasmic and nuclear proteins, and that the neurotoxic action of MeHg could be mediated through the modification of functional protein species due to excess phosphorylation that leads to impairment of the normal celular processes.
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