1. Department of Developmental Biotechnology, Azabu University School of Veterinary Medicine, Sagamihara, Kanagawa 229-8501, Japan
2. Department of Comparative Toxicology, Azabu University School of Veterinary Medicine, Sagamihara, Kanagawa 229-8501, Japan
3. Department of Anatomy II, Azabu University School of Veterinary Medicine, Sagamihara, Kanagawa 229-8501, Japan
4. Department of Neurosurgery, Toho University, Meguro, Tokyo 153-8515, Japan