Cumulus cell, ooplasmic, and nuclear morphology of periovulatory equine oocytes and ova by confocal laser scanning microscopy

The objectives of this study were to determine if horse ova are surrounded by cumulus cells at the time of fertilization, to test if fertilization stage ova from normal mares have an equal distribution of even or uneven ooplasm morphology, to define nuclear morphology of in vivo peri-ovulatory oocytes and ova, and to define the nuclear morphology of recently fertilized equine ova using laser confocal microscopy.;When ovarian follicles developed to 30 mm in diameter, mares were scheduled for oocyte or ova recovery in 64 hours and injected with hCG at either 48, 44, 40, 36, 32, 28, or 24 h preceding the recovery of oocytes or ova. Half of these mares were inseminated 36 h prior to oocyte or ovum recovery. Non-ovulated oocytes were dissected from 59/74 (79.7%) pre-ovulatory follicles and ovulated ova were flushed from 124/147 (84.4%) post-ovulatory oviducts. Most recently ovulated ova were not denuded of cumulus cells as 90/124 (72.6%) post-ovulatory ova were surrounded with cumulus cells and each of five post-ovulatory cleaved ova were surrounded with fully expanded cumulus cells.;Oocytes and ova were stained with propidium, iodide fluorochrome and scanned with confocal laser microscopy. Fifty-nine oocytes were dissected from 74 pre-ovulatory follicles and 36 of the 59 oocytes were suitable for evaluation. Sixty-three ova were flushed from 75 post-ovulatory oviducts and 48 of the 63 ova were suitable for evaluation. In conclusion, hCG-treated mares ovulated both Metaphase I and Metaphase II ova, some of the pre-ovulatory oocytes and post-ovulatory ova were negative for chromatin, the Anaphase stage was long in duration, and some ova were fragmented and degenerated in appearance.;Ova from inseminated mares were stained with propidium iodide fluorochrome and studied by confocal laser scanning microscopy. Sixty-one ova were recovered from 74 oviductal flushes, of which 40 were subsequently evaluated. In 6 of 9 two polar body-stage ova one polar body was adjacent to the maternal chromatin and the other polar body was in the opposite pole of the ova. One of 19 fertilized ova had more than one sperm in the periviteline space. Two pronuclear-stage ova were recovered, one presented the pronuclei in the cortical ooplasm, and the other had the pronuclei near its center. One ovum had male and female chromatin (syngamy) intermixed near its center. (Abstract shortened by UMI.).