1. Department of Pharmacology, College of Medicine, Chungbuk National University, Cheongju 361-763, Korea.
2. Department of Public Health, Chengdu Medical College, Chengdu, Sichuan 610083, China.
3. Department of Thoracic and Cardiovascular Surgery, College of Medicine, Chungbuk National University, Cheongju 361-763, Korea.