Study purpose: The mechanism of radiation effects of A-bomb on human body has not been completely explained. It is important now to clarified the effects of radiation, because radiation is used in many fields including medical treatment. The responses of organisms to irradiation are investigated in our department. We study the signal transduction in animals by low dose irradiation at cellular level. We also study radiation sensitivity and repair pathway of radiation-induced DNA damage in cells at molecule level.

Study themes: (1) Signal transduction in organisms by low dose irradiation. (2) Change of radiation-induced cellular signal transduction by mutation of p53. (3) Repair pathway of radiation-induced DNA damage. (4) Cause and mechanism of death of A-bomb survivors irradiated with low doses.

Present and future study: (1) The rate of DNA synthesis in organs of mouse was increased by low dose irradiation. It means that organisms were stimulated by the irradiation. High dose irradiation harms to organisms, but low dose irradiation may stimulate organisms. (2) We got some mutant p53 DNAs and transfected them to Saos-2 cells. We studied the radiation sensitivity of the cells transfected with mutant p53. The cells of hot spot mutations were resistant to irradiation, but the cells of wild type p53 and a mutation of Waf-1 induction were sensitive to irradiation. We are now searching the signal transduction of down stream of p53 and radiation-induced apoptosis in the cells. (3) DNA-PK (DNA-dependent protein kinase) is stimulated by DNA double strand breaks occurred by irradiation and causes repair mechanism to work. The enzyme activity of DNA-PK was sensitive to heat. The cells of scid mouse which is deficient in DNA-PK were sensitive not only to irradiation but also to heat. The participation of DNA-PK to repair mechanism is investigating now. (4) A-bomb radiation induces cancer and increases death rate in survivors. But the death rate of A-bomb survivors irradiated with low doses was lower than that of unirradiated control. The lower death rate was due to low incident of non-cancer death. The cause and mechanism of death of A-bomb survivors irradiated with low doses are analyzing.

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Professor	:	Takashi Kudo
		E-mail : tkudo123@nagasaki-u.ac.jp
Associate professor	:	Kumio OKAICHI
		E-mail : okaichi@nagasaki-u.ac.jp
Instructor	:	Makoto IHARA
		E-mail : m-ihara@nagasaki-u.ac.jp
Research Assistant	:	Naoko MORITA
		E-mail : luna@nagasaki-u.ac.jp
COE Technician	:	Ayumi Sato
		E-mail : ayumi@nagasaki-u.ac.jp