1. Department of Biochemistry, Charing Cross Hospital Medical School, Fulham Palace Road, Hammersmith, London W6 8RF, U.K.
2. Department of Pathological Biochemistry, The Royal Infirmary, Glasgow G4 0SF, Scotland, U.K.
3. Department of Medical Unit, The Royal Infirmary, Glasgow G4 0SF, Scotland, U.K.
4. Department of Gastroenterology, The Royal Infirmary, Glasgow G4 0SF, Scotland, U.K.