1. J. L. Clements, S. E. Ross-Barta, S. L. Eliason, Department of Internal Medicine, University of Iowa College of Medicine, Iowa City, IA 52242, USA. B. Yang, R. F. Hrstka, R. A. Williamson, Department of Obstetrics and Gynecology, University of Iowa College of Medicine, Iowa City, IA 52242, USA. G. A. Koretzky, Departments of Internal Medicine and Physiology and Biophysics, University of Iowa College of Medicine, Iowa City, IA 52242, USA.