1. Drug Research Department, Tokyo Research Laboratories, TOA EIYO Ltd., 2-293-3 Amanuma, Saitama 330-0834, Japan, Graduate School of Pharmaceutical Sciences, Chiba University, 1-33 Yayoicho, Inage, Chiba 263-8522, Japan, Drug Research Department, Fukushima Research Laboratories, TOA EIYO Ltd., 1 Tanaka, Yuno, Iizaka, Fukushima 960-0280, Japan, and Department of Structural Analysis, National Cardiovascular Center Research Institute, 5-7-1 Fujishirodai, Suita, Osaka 565-8565, Japan