1. Nihon University Graduate School of Dentistry at Matsudo, Histology and Embryology, Matsudo, Chiba 271-8587, Japan
2. Department of Histology, Nihon University School of Dentistry at Matsudo, Matsudo, Chiba 271-8587, Japan
3. Laboratory for Electron Beam Research and Application(LEBRA), Institute of Quantum Science, Funabashi Campus of College of Science and Technology, Nihon University, Funabashi, Chiba 274-8501, Japan