1. Departments of Pediatrics (V.P.), The University of Michigan, Ann Arbor, Michigan 48109;
2. Biostatistics (M.B.B., D.T.M.), The University of Michigan, Ann Arbor, Michigan 48109;
3. Physiology (F.J.K.), The University of Michigan, Ann Arbor, Michigan 48109;
4. the Reproductive Sciences Program (V.P., G.E.D., N.P.E., F.J.K., J.V.C.), The University of Michigan, Ann Arbor, Michigan 48109;
5. Departments of Physiology and Biophysics (J.D.N.), University of Alabama-Birmingham, Birmingham, Alabama 35294