1. Laboratory of Theriogenology, College of Bioresource Sciences, Nihon University, 1866 Kameino, Fujisawa, Kanagawa 252-0880, Japan
2. Laboratory of Veterinary Physiology, Cooperative Department of Veterinary Medicine, Faculty of Agriculture, Tokyo University of Agriculture and Technology, Fuchu, Tokyo 183-8509, Japan
3. Department of Basic Veterinary Science, the Graduate School of Veterinary Sciences, Gifu University, Gifu 501-1193, Japan
4. Cooperative Division of Veterinary Science, Graduate School of Agriculture, Tokyo University of Agriculture and Technology, Tokyo 183-8509, Japan