[1] Juntendo Univ, Sch Med, Dept Gastroenterol, Bunkyo Ku, Tokyo 1138421, Japan
[2] Tokyo Inst Technol, Fac Biosci & Biotechnol, Dept Biomol Engn, Yokohama, Kanagawa 227, Japan
[3] Osaka Univ, Sch Med, Dept Med 1, Osaka 553, Japan
[4] Univ N Carolina, Dept Cell Biol & Anat, Cell Biol Labs, Chapel Hill, NC USA