1. Department of Biochemistry, University of Otago, PO Box 56, Dunedin 9054, New Zealand and Department of Medicine, University of Otago, PO Box 4345, Christchurch, New Zealand.
2. Department of Medicine, University of Otago, PO Box 4345, Christchurch, New Zealand and Department of Gastroenterology, Christchurch Hospital, Christchurch, New Zealand