|Budget Amount *help
¥1,800,000 (Direct Cost : ¥1,800,000)
Fiscal Year 1992 : ¥300,000 (Direct Cost : ¥300,000)
Fiscal Year 1991 : ¥1,500,000 (Direct Cost : ¥1,500,000)
It has been recently suggested that low doses of ionizing radiation have a stimulating or activating effects on living organisms. Also, some evidence has been obtained for the induction, by low doses, of an"adaptive response" that reduces the yield of chromosomal damage in cultured mammalian cells. Our early investigations suggest the involvement of an unknown inducible repair machanism in the novel chromosomal response to low doses of ionizing radiation. The mechanism underlying adaptive response remains, however,very uncertain. In this project, in order to understand its molecular basis of such an inducible defense functions of mammalian cells, we decided to study in more detail the process of the expression of adaptive response after low dose irradiation, and finally to obtain the evidence for the presence for genes responsible to adaptive repair of radiation damage in Chinese hamster V79 cells in vitro. The results of experiments done in this project are as follows. 1. The expression of adaptive repair by very low doses of gamma rays was repressed by either metabolic inhibitors of RNA synthesis (actinomycin D, a-amanitine), protein synthesis (cycloheximide) or protein kinase (H-7). These results indicate that the expression of adaptive repair might be brought about through an active intracellular process: signal transduction pathway mediated by protein kinase C, gene activation and protein synthesis. 2. An analysis of newly synthesized proteins after low dose irradiation by two-dimensional acrylamide gel electrophoresis has indicated that these proteins are rather different from metal-induced proteins. 3. Enhanced repair of gamma-ray induced DNA damage in pre-irradiated cells was observed using micro-gel electrophoresis of single-cell DNA. 4. Isolation of poly(A) ^+ RNA was done from irradiated cells and the activity was tested by in vitro translation system.