FUNCTIONAL ENUCLEATION OF BOVINE OOCYTES - EFFECTS OF CENTRIFUGATION AND ULTRAVIOLET-LIGHT

Functional enucleation is removal or denaturation of an oocytes DNA wi thout piercing the zona pellucida. Two experiments were conducted in t his study to determine the effects of centrifugation, and ultraviolet (UV) light on metaphase II bovine oocytes. Experiment 1 evaluated the effects of centrifugation (12,000 x g for 4 min) on the cleavage rate of in vitro matured oocytes. Centrifugation decreased (P <0.05) the cl eavage rate of oocytes (79.5 vs 70.4%). In addition, it was noted that there were two types of ooplasm after centrifugation, stratified and granular. Developmental potential, as represented by cleavage percent, of the two types of ooplasm was not significantly different. Experime nt 2 was conducted to determine the interactive effects of centrifugat ion (as above) and UV light (254 nm) on cleavage rate of oocytes expos ed as metaphase II oocytes. The UV light decreased (P <0.07) oocyte cl eavage rates (35.4 vs 25.2%). Centrifuging metaphase II oocytes also d ecreased (P <0.07) cleavage rates (34.1 vs 26.5%). In addition, we det ermined the fate of chromosomes of oocytes centrifuged and(or) exposed to UV light. Both centrifugation and UV light alone affected (P <0.05 ) chromosome placement at 42+/-3 h after fertilization. Furthermore, c entrifugation and UV light interactively increased (P <0.05) the perce ntage of non-cleaved oocytes with their DNA located in the perivitelli ne space (17.4, 15.5, 13.1, and 49.2, respectively, for control, UV ex posed, centrifuged, and UVcentrifuged). Collectively. these data indi cate that bovine oocytes at the metaphase II stage can be functionally enucleated with centrifugation and exposure to UV light; however, dev elopmental potential may be diminished by those techniques.