1. Institute of Animal Physiology and Genetics AS CR, v.v.i., Libechov, Czech Republic, Institute of Microbiology AS CR, v.v.i., Prague, Czech Republic, Assisted Reproduction Centre, Department of Obstetrics and Gynecology, General Teaching Hospital, Prague, Czech Republic, Sigma-Aldrich spol. s.r.o., Prague, Czech Republic, and Millipore Bioscience, 15 Research Park Drive, St. Charles, Missouri 63304