1. From the Department of Pediatrics, Faculty of Medicine, University of Tokyo, Bunkyo-ku, Tokyo, Japan; the Radiobiology Division, National Cancer Center Research Institute, Chuo-ku, Tokyo, Japan; the 3rd Department of Internal Medicine, Kyoto Prefectural University of Medicine, Kawaramachi-Hirokoji, Kamigyo-ku, Kyoto, Japan; and the Department of Pediatrics, Nippon Medical School, Bunkyo-ku, Tokyo, Japan.