Abstract
Conventional radiation is supposed to cause stochastic effects such as the development of cancer or genetic effects in proportion to the amount of radiation to which the subject is exposed. On the cellular level, it is believed that even small doses can damage DNA and the cell membrane. Olivieri and Wolff et al. discovered in 1984 that lymph cells of humans receiving a weak [3H]thymidine treatment show a radio-adaptive response. The elucidation of this radio-adaptive response drew attention in terms of understanding of radiation hormesis phenomena and evaluation of risk associated with radiation. In the 1990s, phenomenological studies of the cell and on an individual animal level were conducted and the conditions that induce a radio-adaptive response began to be clarified. However, though elucidation of conditions that induce a response indicates the involvement of cell membrane function and signal transduction system, the details were still unknown. In particular, how the radio-adaptive response of cells relates to the radio-adaptive response of individual animals was a mystery. The elucidation of this mystery will be a formidable challenge in future.
