Division of Genetic Resources, National Institute of Health Japan, Toyama, Shinjukuku, Tokyo 162, Japan
Department of Radiology, The Jikei University School of Medicine, Nishishinbashi, Minatoku, Tokyo 105, Japan

Division of Genetic Resources, National Institute of Health Japan, Toyama, Shinjukuku, Tokyo 162, Japan

Laboratory of Cell Growth and Differentiation, Tsukuba Life Science Centre, The Institute of Physical and Chemical Research (RIKEN), Koyadai, Tsukuba, Ibaraki 305, Japan