Somatic mutation in larvae of the silkworm, Bombyx mori, induced by heavy ion irradiation to diapause eggs.

In order to investigate whether eggs of the black-striped strain (P(S)) of the silkworm, Bombyx mori, represent an appropriate model for estimating the biological effect of cosmic radiation, radiosensitivity of the eggs against X-rays and heavy ion particles was examined as ground-based experiments. The exposure of diapause eggs to X-rays or heavy ion particles resulted in somatic mutations appearing as a white spot on the black integument during larval stage. Irradiation of non-diapause eggs with X-rays demonstrated a significant difference in frequency of the mutation between fractionated and single administration doses, but no difference was observed in diapause eggs.

Effect of space flight on the frequency of micronuclei and expression of stress-responsive proteins in cultured mammalian cells.

Results of past space experiments suggest that the biological effect of space radiation could be enhanced under microgravity in some cases, especially in insects. To examine if such a synergistic effect of radiation and microgravity also exists in human cells, frequencies of chromosome instability and cellular levels of several stress-responsive proteins were analyzed in cultured human and rodent cells after space flight. Human (MCF7 and AT2KY), mouse (m5S) and hamster (SHE) cell lines were loaded on the Space Shuttle Discovery (STS-95 mission) and grown during a 9-day mission.