1. BioAnalytical Science, Metabonomics & Biomarkers, Nestlé Research Center, P.O. Box 44, CH-1000 Lausanne 26, Switzerland, and Department of Biomolecular Medicine, Division of Surgery, Oncology, Reproductive Biology and Anaesthetics, Faculty of Medicine, Sir Alexander Fleming Building, Imperial College London, London SW7 2AZ, U.K.