title: Influence of stage of maturation of bovine oocytes at time of vitrification on the incidence of diploid metaphase II at completion of maturation.
abstract: The present study was to verify the incidence of bovine diploid oocytes when vitrified at various maturation stages. Bovine cumulus-oocyte complexes were recovered from ovaries at a slaughterhouse and then divided into five groups: control group (unvitrified oocytes), 0 h group (composed of oocytes vitrified before the onset of maturation) and 8, 12, and 22 h groups (vitrified respectively at 8, 12 and 22 h after the onset of maturation). The oocytes remained vitrified for 24 h, and then were thawed. In all groups, the oocytes completed 24 h of maturation. Subsequently, the cumulus cells were removed, and the denuded oocytes fixed on slides and stained with aceto-orcein. No differences (P>0.05) in the incidence of diploid metaphase II oocytes were observed between the control, non-vitrified group (2.4%, 1/41) and oocytes vitrified at 12 h (6.9%, 3/43) or 22 h (2%, 1/50). However, significantly (P<0.05) more diploid oocytes were detected after vitrification at 0 h (28.5%, 10/35) or 8 h (35.4%, 11/31) of maturation. These results suggest that the nuclear stage at which bovine oocytes are vitrified may affect the incidence of diploid oocytes, especially in oocytes vitrified before maturation or 8 h after the onset of maturation.
authors.affiliation: Laboratory of Genetics, Faculty of Medicine, University of Brasília, Brasília, Brazil. hsluna@ig.com.br
authors.forename: H S
authors.initials: HS
authors.lastname: Luna
authors.forename: I
authors.initials: I
authors.lastname: Ferrari
authors.forename: R
authors.initials: R
authors.lastname: Rumpf
mesh_terms: D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D002875:Chromosomes / Q000502:physiology*; D015925:Cryopreservation / Q000379:methods / Q000662:veterinary*; D004171:Diploidy; D005260:Female; D015994:Incidence; D008677:Metaphase; D009865:Oocytes / Q000166:cytology / Q000502:physiology*; D010053:Ovary; D011897:Random Allocation; D012741:Sexual Maturation; D013997:Time Factors