1. Department of Bioresource Science, Graduate School of Agricultural Science, Kobe University, 1–1 Rokkodai-cho, Nada-ku, Kobe, Hyogo 657–8501, Japan
2. Department of Basic Veterinary Medicine, College of Veterinary Medicine, Inner Mongolia Agricultural University, 306 Zhaowuda Road, Huhhot, Inner Mongolia 010018, P. R. China
3. Department of Anatomy and Neurobiology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kawaramachi-Hirokoji, Kamigyo-ku, Kyoto 602–8566, Japan
4. Department of Veterinary Laboratory Animal Science, Faculty of Agriculture, Tottori University, 4–101 Koyama-cho Minami, Tottori 680–8553, Japan