1. Baylor College of Medecine, Dept. of Obstetrics and Gynecology, One Baylor Plaza, Houston, TX 77030
2. Department of Orthodontics, Osaka University, Faculty of Dentistry, 1-8 Yamadaoka, Suita, Osaka 565, Japan
3. Department of Basic and Behavioral Sciences, Division of Oral Biology, Northwestern University Dental School, 303 East Chicago Avenue, Chicago, Illinois 60611, USA