StateKeyLaboratoryofReproductiveBiofogy;
InstituteofZoofogy;
ChineseAcademyofSciences;
Beijing100080;
P.R.China;
DepartmentofAppliedCellandMolecularBiology;
UmeaUniversity;
S-90187Umea;
Sweden;
DivisionofReproductiveBiology;
DepartmentofObstetricsandGynecology;
StanfordUniversity;
SchoolofMedicine;
300PasteurDrive;
Stanford;
CA94305-5317;
USA;