1. Medical Research Council Human Reproductive Sciences Unit (K.D.G.P., A.J.P., R.P.M.), Centre for Reproductive Biology, The Queen’s Medical Research Institute, Edinburgh EH16 4TJ, United Kingdom
2. Western Australian Institute for Medical Research/Centre for Medical Research (K.D.G.P.), University of Western Australia, QEII Medical Centre, Nedlands, Western Australia 6009, Australia