title: Maturation status, protein synthesis and developmental competence of oocytes derived from lambs and ewes.
abstract: The efficacy of oocyte selection for in vitro embryo production depends on the abundance and diameter of follicles, cumulus layers around the oocytes and subsequent fertilization. Application of 'ovum pick-up' technique allows us to utilize partially matured oocytes for embryo production even from juvenile subjects. To compare their developmental competence, oocytes derived from lambs and ewes and cultured in maturation medium for up to 26 h were assessed at 2 h intervals by confocal microscopy after chromatin and microtubulin-specific fluorochrome labelling. Lamb oocytes reached second meiotic metaphase (MII) at lower numbers at 24 h (60.0%) and 26 h (28.6%) whereas 85.7% of adult-derived oocytes attained MII status by 24 h of maturation. Radiolabelling of oocyte proteins revealed higher incorporation of [(35)S-]-methionine and [(35)S]-cysteine in adult-derived oocytes compared to lamb oocytes. Although the cleavage rate of lamb oocytes was similar to that of ewe oocytes, the proportion reaching blastocyst stage was significantly lower (p < 0.05) in the lamb-derived oocytes. However, blastocysts from both types of oocytes displayed similar cell lineage allocations to inner cell mass and trophectoderm.
authors.affiliation: Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada.
authors.forename: H P S
authors.initials: HP
authors.lastname: Kochhar
authors.forename: B
authors.initials: B
authors.lastname: Wu
authors.forename: L H A
authors.initials: LH
authors.lastname: Morris
authors.forename: B C
authors.initials: BC
authors.lastname: Buckrell
authors.forename: J W
authors.initials: JW
authors.lastname: Pollard
authors.forename: P K
authors.initials: PK
authors.lastname: Basrur
authors.forename: W A
authors.initials: WA
authors.lastname: King
mesh_terms: D000818:Animals; D004624:Embryo Transfer; D005260:Female; D005307:Fertilization in Vitro / Q000662:veterinary; D005328:Fetal Viability; D008540:Meiosis / Q000502:physiology; D018613:Microscopy, Confocal / Q000662:veterinary; D009865:Oocytes / Q000166:cytology / Q000502:physiology*; D009866:Oogenesis / Q000502:physiology; D012741:Sexual Maturation / Q000502:physiology; D012756:Sheep / Q000502:physiology*