1. Department of Obstetrics and Gynecology, Center for Reproductive Biology (D.T.B., B.K.C., L.M.H.), University of Edinburgh, Edinburgh, Scotland EH3 9EW, United Kingdom;
2. Roslin Institute (Edinburgh) (R.W.), Roslin, Midlothian, Scotland EH 259PS, United Kingdom
3. Department of Physiology (R.G.G.), University of Edinburgh, Edinburgh, Scotland EH3 9EW, United Kingdom;