1. Departament de Fisiologia (M.D., J.V.P.), Facultat de Biologia, Universitat de Barcelona, 08028 Barcelona, Spain
2. Programme in Cell Biology (C.N.A., A.K.), The Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8
3. Department of Pharmacological Sciences (E.C.), Stony Brook University, Stony Brook, New York 11794-8651