1. M. de Leon, Y. Wang, L. Jones, D. T. Yue, Program in Molecular and Cellular Systems Physiology, Department of Biomedical Engineering, Johns Hopkins University School of Medicine, 720 Rutland Avenue, Baltimore, MD 21205, USA.
2. E. Perez-Reyes, Department of Physiology, Loyola University Chicago, 2160 South First Avenue, Maywood, IL 60153, USA.
3. X. Wei, Institute for Molecular Medicine and Genetics, Medical College of Georgia, 1120 15th Street, Augusta, GA 30912, USA.
4. T. W. Soong and T. P. Snutch, Biotechnology Laboratory, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada.