1. Department of Anatomy, Division of Basic Medical Science, Tokai University School of Medicine, 143 Shimokasuya, Isehara-si 259-1193, Kanagawa, Japan
2. Department of Anatomy, Tokyo Medical University, 6-1-1 Shinjuku, Shinjuku-ku, Tokyo 160-8402, Japan
3. Department of Environmental Preventive Medicine, Yamada Bee Company, Inc., Center for Preventive Medical Sciences, Chiba University, 1-33 Yayoicho, Inage-ku, Chiba-si 263-8522, Chiba, Japan