1. Laboratory of Membrane Transport and Pulmonary Division, Department of Internal Medicine, University of Iowa College of Medicine, Iowa City, IA 52242.
2. Cystic Fibrosis Center, Departments of Pediatrics and Physiology and Biophysics, School of Medicine, Case Western Reserve, Cleveland, OH 44106.
3. Laboratory of Molecular and Cellular Neuroscience, Rockefeller University, New York, NY 10021.