FOLLICLE-OOCYTE-SPERM INTERACTIONS IN-VIVO AND IN-VITRO IN PIGS

In vitro culture has provided new information on the mechanisms involv ed in fertilization where two completely different cells fuse together . At the same time, results obtained in vitro have led to new question s. Does the follicle influence the final maturation process of the ooc yte and does the oviduct regulate the normal behaviour of spermatozoa? Recent studies indicate a critical influence of both the follicular c ompartment and the oviduct on the normal fertilization process. Oocyte s matured in vivo are more competent to induce pronuclear formation, b ut are still susceptible to polyspermy. Oocytes matured in vitro can d evelop fully after fertilization, but require the presence of follicul ar factors during culture td enhance their developmental competence. F resh or frozen spermatozoa can penetrate oocytes in vitro, but their c onditioning by differential centrifugation or oviductal cells influenc es the rate of polyspermy. The understanding of these influences is a prerequisite to enhancing in vitro production of pig embryos.