1. Center for Pregnancy and Newborn Research; Department of Obstetrics; University of Texas Health Sciences Center San Antonio; San Antonio; Texas; USA
2. Department of Animal Science; University of Wyoming Laramie; Laramie; Wyoming; USA
3. Department of Animal and Veterinary Sciences; Clemson University; Clemson; South Carolina; USA
4. Departamento de Biología de la Reproducción; Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán; México City; D.F.; México