1. Radiation-Applied Biology Division, Japan Atomic Energy Agency, Takasaki 370–1292, Japan (K.K.B., V.V.N., A.R., A.T., I.N., Y.O.); Advanced Science Research Center, Japan Atomic Energy Research Institute, Takasaki 370–1292, Japan (C.O., H.U., Y.O.); Department of Biological Sciences, Graduate School of Science, Tokyo Metropolitan University, Hachioji, Tokyo 192–0397, Japan (K.H., T. Koshiba); Uni