1. M. M. Reddy and P. M. Quinton, Division of Biomedical Sciences, University of California, Riverside, CA 92521, USA.
2. C. Haws and J. J. Wine, Cystic Fibrosis Research Laboratory, Department of Psychology, Stanford University, Stanford, CA 94305, USA.
3. R. Grygorczyk, J. A. Tabcharani, J. W. Hanrahan, Department of Physiology, McGill University, Montreal, Quebec, H3G 1Y6, Canada.
4. K. L. Gunderson and R. R. Kopito, Department of Biological Sciences, Stanford University, Stanford, CA 94305-5020, USA.