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Title: OOCYTE NUCLEAR MATURATION AT THE TIME OF OOCYTE ASPIRATION IS INDEPENDENT OF IN VITRO FERTILIZATION POTENTIAL IN THE DOMESTIC CAT

Author
item BYERS A P - NATIONAL ZOO
item Donoghue, Ann - Annie
item ROTH T V - NATIONAL ZOO
item WILDT D E - NATIONAL ZOO

Submitted to: Journal of Experimental Zoology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/28/1995
Publication Date: N/A
Citation: N/A

Interpretive Summary: This study determined the timing of nuclear maturation at and after follicular egg aspiration and the significance of variations in nuclear maturation and sperm-egg co-incubation interval on in vitro fertilization (IVF) in the cat. Cats were treated with exogenous hormones and eggs were aspirated laparoscopically and classified according to morphological criteria. Eggs classified as mature were cultured for 0, 2, 4, 6 or 8 h and then stained for nuclear maturation. Despite differences in nuclear maturation at the time of oocyte recovery, IVF success was unaffected by pre-insemination culture interval. The majority of oocytes recovered from cats treated with this gonadotropin regimen have not achieved metaphase II by follicular aspiration. These oocytes appear grossly mature, but nuclear maturation is incomplete until 4-8 h in culture. Ability of these oocytes to fertilize in vitro is independent of stage of nuclear maturation at recovery.

Technical Abstract: This study determined (1) the temporal kinetics of nuclear maturation at and after follicular oocyte aspiration and (2) the significance of variations in nuclear maturation and sperm-oocyte co-incubation interval on in vitro fertilization (IVF) in the domestic cat. Female cats were treated with pregnant mares' serum gonadotropin followed 84 h later with human chorionic gonadotropin (hCG). Twenty-five h after hCG, ovarian follicular oocytes were aspirated laparoscopically and classified according to morphological criteria. Oocytes classified as mature were cultured for 0, 2, 4, 6 or 8 h in Ham's F10 medium and then stained for nuclear maturation. The proportion of oocytes at metaphase II was similar at 0 (38.2%) and 2 (48.5%) h of culture, but was higher (P<0.05) at 4 (76.5%), 6 (82.8%) and 8 (92.3%) h. Oocytes also were collected and cultured as described above and then co-incubated for 2 to 18 h with 5x105 motile sperm/ml. Despite differences in nuclear maturation at the time of oocyte recovery, IVF success was unaffected by pre-insemination culture interval. The majority of oocytes recovered from cats treated with this gonadotropin regimen have not achieved metaphase II by follicular aspiration. These oocytes appear grossly mature, but nuclear maturation is incomplete until 4-8 h in culture. Ability of these oocytes to fertilize in vitro is independent of stage of nuclear maturation at recovery.