Biological effects induced by low-density heavy ions of space radiation in medaka

Starting Japanese astronauts staying in the International Space Station (ISS), influences of the radiation on human is becoming one of the important risks during space flight. Although the biological effect with high-dose acute irradiation has been examined by epidemiological studies for many years, the risks either acute or chronic with low-dose or low-fluence irradiation equivalent of space environment can only be estimated based on the data with high-dose or high-fluence at present. Our aim is to understand biological influences on living organisms induced by low-dose and low-fluence chronic irradiation (1 mGy/7-8 h) that assumes the space radiation in ISS. So that we focused on the gene and protein expression, and the possibility on carcinogenesis induced by low-dose and -fluence radiation, and planed the experiments to irradiate medaka carbon ions using Heavy Ion Medical Accelerator in Chiba (HIMAC) in National Institute of Radiological Sciences (NIRS). This year, we established the irradiation method to treat medaka with low-dose and -fluence (1 mGy/7-8 h) carbon ions. Also we extracted total RNA from medaka scales and skins to evaluate the effect of irradiation. (author)