Abstract
A biological assessment of cosmic radiation has been requested as many projects start in the International Space Station (ISS). On our data of biological effects of cosmic rays and microgravity during embryonic development of the silkworm eggs using a Space Shuttle, Atlantis, the authors have the following plan to load diapausing eggs of the silkworm, Bombyx mori. The eggs will be loaded for more than 6 months into the ISS, and we wil examine the relationship between cumulative dose equivalent of cosmic rays and the incidence of somatic mutation, and a specific gene expression. As ground experiments, the exposure of diapause eggs of the black-striped strain (PS) of the silkworm to heavy ion particles resulted in somatic mutation appearing as a white spot on the black integument during larval stage. Neon beam irradiation of diapause eggs displayed dose- and linear energy transfer (LET)-dependent effects. The highest sensitivity to radiation is the eggs 2 days after the resumption of embryogenesis of diapause-terminated eggs, which exhibited a specific gene expression, indicating the possible establishment of the biological assessment of the low-dose radiation in space. We also examine the enhancement of somatic mutation and the gene expression by synergistic effect of microgravity and cosmic radiation. In addition, we have a plan to verify whether blastokinesis will proceed during embryogenesis of B. mori under microgravity, because it proceeded abnormally in the Space Shuttle.
