FOLLICLE-OOCYTE ATRESIA AND TEMPORAL TAPHONOMY IN COLD-STORED DOMESTIC CAT OVARIES

In vitro oocyte maturation followed by in vitro fertilization (IVM/IVF ) success in the domestic cat remains inferior to commonly studied liv estock or laboratory species. The objectives here were [1) to histolog ically assess atresia status of freshly excised follicle/oocyte comple xes, and (2) to evaluate taphonomic change (deterioration after excisi on) of these complexes after ovarian cold storage for up to 48 h. Afte r excision of 50 ovarian pairs, one ovary was preserved immediately an d the other stored in phosphate buffered saline (4 degrees C for 4, 8, 12, 24, or 48 h before fixation and examination. Ovals were classifie d as luteal if prominent corpora lutea (CL) were present or as follicu lar if antral follicles and no CL were present. Two classes of follicl e-oocyte complexes (preantral and antral) were microscopically evaluat ed. Of the 2,280 complexes examined, 64.3% demonstrated clear evidence of slight to severe degeneration, with various stages being described and photographed for the first lime. There was no histological eviden ce indicating distinctive morphological[ differences between oocytes r ecovered from follicular Versus luteal donors. Storage of whole ovarie s in cold saline inhibited taphonomic changes for 48 h after excision, in summary,there is marked variability in the number and quality of f ollicle populations in cat ovaries. A high percentage of full-sized fo llicular oocytes are under going atresia at any given time. However ad ditional gross degeneration as a result of cold-storage appears modest for up to 48 h. Nonetheless, this high level of natural atresia in th e cat likely contributes to comparatively lower IVM/IVF success than i n other species. (C) 1997 Wiley-Liss, inc.