1. From the Department of Population Dynamics, Johns Hopkins University School of Hygiene and Public Health, the James Buchanan Brady Urological Institute, Johns Hopkins Hospital, and the Department of Urology, Johns Hopkins University School of Medicine, Baltimore, Maryland;
2. The Research Department, Pharmaceuticals Division, CIBA-GEIGY Corporation, Summit, New Jersey
3. The Department of Physiology and Biophysics, Colorado State University, Fort Collins, Colorado