1. Department of Pathology, Royal Naval Hospital, Plymouth PL1 3JY, U.K
2. Department of Clinical Biochemistry, Royal Victoria Hospital, Grosvenor Road, Belfast BT12 6BA
3. Department of Neurology, Royal Victoria Hospital, Grosvenor Road, Belfast BT12 6BA
4. Institute of Naval Medicine, Alverstoke, Gosport, Hants. PO12 2DL, U.K