1. Department of Anatomy, Ewha Womans University School of Medicine, Seoul 03760, Korea.
2. Division of Nephrology, College of Medicine, University of Florida, Gainesville, FL 32608, USA.
3. Nephrology Section, North Florida/South Georgia Veterans Health System (NF/SGVHS), Gainesville, FL 32608, USA.
4. Department of Anatomy, College of Medicine, The Catholic University of Korea, Seoul 06591, Korea.