1. Medical Research Council Human Reproductive Sciences Unit (K.E.R., H.M.F., R.S., R.P.M.), The Queen’s Medical Research Institute, Edinburgh EH16 4TJ, Scotland, United Kingdom
2. Peptide Biology Laboratory (J.R.), Salk Institute, La Jolla, California 92037
3. Department of Medical Biochemistry (R.P.M.), University of Cape Town, Observatory 7925, South Africa