1. The Wolfson Institute for Biomedical Research, University College London, The Cruciform Building, Gower Street, London, WC1E 6BT, United Kingdom, BHF Laboratories, Department of Medicine, University College London, 5 University Street, London, WC1E 6JJ, United Kingdom, and University of Kuopio, A.I. Virtanen-Institute, P.O. Box 1627, FIN-70211 Kuopio, Finland