1. Electron Microscopy Unit, Department of Anatomy, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand
2. Department of Anatomy, Faculty of Medicine, Princess of Naradhiwas University, Narathiwat, Thailand
3. Department of Anatomy, Graduate School of Medicine, Hokkaido University, Sapporo, Japan
4. Department of Anatomy, Graduate School of Medicine, Tohoku University, Sendai, Japan