1. Clinical Research Centre, Harrow, Middlesex, United Kingdom.
2. Gladstone Foundation Laboratories, Cardiovascular Research Institute, Departments of Medicine and Pathology, University of California, San Francisco 94140.
3. Chiron Corporation, Emeryville, California 94608.
4. Roswell Park Memorial Institute, Department of Human Genetics, Buffalo, New York 14263.
5. Department of Pathology, University Hospital, Uppsala, Sweden.