1. S. C. Chua Jr., W. K. Chung, X. S. Wu-Peng, Y. Zhang, S.-M. Liu, R. L. Leibel, Laboratory of Human Behavior and Metabolism, Rockefeller University, 1230 York Avenue, Box 181, New York, NY 10021, USA.
2. L. Tartaglia, Millennium Pharmaceuticals, 640 Memorial Drive, Cambridge, MA, 02139, USA.