1. From the MRC Clinical Sciences Centre (C.A., J.S.A., A.S., C.F.H.), Faculty of Medicine, Imperial College, Hammersmith Hospital, Du Cane Road, London, UK; the Department of Vascular Surgery (S.S., A.H.D., R.G.J.G.), Faculty of Medicine, Imperial College, Charing Cross Hospital, Fulham Palace Road, London, UK. Current affiliation for C.A. is Physiology Weihenstephan, Technical University Munich, Weihenstephaner Berg 3, Freising, Germany.