1. Department of Cell Biology and Physiology, University of Pittsburgh, Pittsburgh, PA 15261
2. Department of Physiology and Biophysics, Rosalind Franklin University of Medicine and Science, North Chicago, IL 60064
3. School of Pharmacy, Texas Tech. University Health Sciences Center, Amarillo, TX 79106
4. Novartis Horsham Research Centre, Horsham, West Sussex RH12 5AB, UK