1. Department of Cell Biology and Histology, Faculty of Medicine, University of Murcia, IMIB-Arrixaca, Murcia, Murcia, Spain
2. Department of Physiology, Faculty of Veterinary, University of Murcia, IMIB-Arrixaca, Murcia, Murcia, Spain
3. Departamento de Reproducción Animal, INIA, Ctra. de la Coruña Km. 5,9 - 28040 Madrid, Spain