1. Department of Anatomy, University of California, San Francisco, California 94143-0452
2. G.W. Hooper Foundation, Department of Microbiology and Immunology, Department of Biopharmaceutical Sciences, and Department of Pharmaceutical Chemistry, University of California, San Francisco, California 94143-0552
3. Cell Genesis, Foster City, California 94404
4. Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15261