1. Institute of Membrane and Systems Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, U.K.
2. MRC Human Reproductive Sciences Unit, Centre for Reproductive Biology, Queen's Medical Research Institute, University of Edinburgh, 47 Little France Crescent, Edinburgh EH16 4TJ, U.K.
3. Department of Psychological Medicine, Cardiff University, Cardiff CF14 4XN, U.K.