1. Labortory of Veterinary Physiology, Cooperative Department of Veterinary Medicine, Faculty of Agriculture, Tokyo University of Agriculture and Technology, Tokyo 183-8509, Japan
2. Department of Physiology, Faculty of Medicine, Srinakharinwirot University, Bangkok 10110, Thailand
3. College of Animal Science and Technology, Nanjing Agricultural University, Nanjing 210095, P. R. China
4. Research Center for Environmental Risk, National Institute for Environmental Studies, Ibaraki 305-8506, Japan
5. Department of Basic Veterinary Science, the United Graduate School of Veterinary Sciences, Gifu University, Gifu 501-1193, Japan