1. Department of Animal Science and Technology, National Taiwan University, Taipei 106, Taiwan; Department of Molecular Biotechnology, Da-Yeh University, Changhwa 515, Taiwan; Department of Life Sciences, National Chung-Hsing University, Taichung 402, Taiwan; China Medical University Hospital, Taichung 404, Taiwan; and Animal Technology, Institute Taiwan, Miaoli, P.O. Box 23, Taiwan