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The chromosomal normality of rabbit oocytes fertilized in vitro was examined. Ovum donors were superovulated with pregnant mare’s serum gonadotropin and human chorionic gonadotropin (hCG). Follicular oocytes were collected laparoscopically 9–10 h after hCG treatment and incubated in vitro with spermatozoa capacitated in vivo.Of 267 aspirated oocytes, 191 (71.4%) were fertilized in vitro and developed to the 2- to 8-cell stage 24–48 h after insemination. In the chromosomal studies, 121 (63.4%) were examined. Of these, 94 (77.7%) had a normal diploid complement of chromosomes (2n = 44) and 6 (5%) showed aneuploidy. Of the remaining 21, 20 were triploid and one was tetraploid. The incidence of triploid oocytes after in vitro fertilization was higher than the rate in vivo (16.5% vs. 9.0%, respectively). These triploid oocytes were suspected to be the result of polyspermic fertilization in vitro. In addition, at the Metaphase II stage, 62 (89.9%) of 69 induced, preovulatory oocytes had a normal number of chromosomes.

The in vitro maturation sequence of squirrel monkey oocytes and their chromosomal normality was studied. Follicular growth was induced by a hormonal regimen of follicle-stimulating hormone (FSH) and human chorionic gonadotropin (hCG) and oocytes were collected laparoscopically 15–16 h after hCG administration from 55 squirrel monkeys. A total of 666 oocytes were prepared and analyzed for maturational stage and the presence of chromosomal aberrations.At recovery, 84.7% of the aspirated oocytes were in the genninal vesicle or prophase I stage and the numbers of atretic and mature ova were low (15.3% and 8.3%, respectively). The highest rate of in vitro matured oocytes (75.2%) was found after 31 h of incubation.In the chromosomal analysis studies of 366 oocytes, 31(8.5%) metaphase 1, 14 (3.8%) anaphase I and 181 (49.5%) metaphase II oocytes were examined. Of 28 countable metaphase I plates, 21 (75.0%) consisted of 22 bivalents, however meiotic univalents were also observed in 7 (25.0%) cases. Of these, 2 showed a secondary association.Of 181 oocytes, 145 (80.1%) were analyzable numerically. Of these, 88 (60.7%) had the normal haploid 22 chromosome number, whereas 7 (4.8%) showed aneuploidy (4 hyperploidy and 3 hypoploidy). An additional 50 (34.5%) oocytes were found to be at the metaphase II stage with first polar body chromosomes. Of these, 43 had a normal haploid number of chromosomes (22/22). In 7 (4.8%), aneuploidy was observed (6, 21/23 and 1, 20/24). The unequal chromosome number was assumed to be due to a random segregation of univalents at the anaphase I stage.Additionally there was no significant difference in maturation rate among 3 sizes of follicles (1–2 mm, 2–3 mm, >3 mm). A significant correlation was found for the maturation rate between oocytes with and without cumulus cells after 21 h of culture.

The effect of 1 µM dibutyril cAMP (cAMP media) on the chromosomal normality of in vitro fertilized squirrel monkey oocytes was examined. A total of 877 oocytes were collected laparoscopically 15–16 h after hCG injection from hormonally-induced follicles of 65 squirrel monkeys. Of these, 330 (37.6%) were prepared between 6 and 30 h after insemination and analyzed. Sperm penetration and the presence of a swollen sperm head in the ooplasm were observed by 6 h, and the nucleate stage by 10 h. Addition of 1 µM dbcAMP did not affect the oocyte maturation rate, however the in vitro fertilization rate was increased 26.5% over controls (46.3 vs. 36.6%).The first cleavage metaphase was found at 16 h after insemination. Between 24 and 30 h post-insemination, 76.6% of fertilized oocytes had reached the first cleavage metaphase. An incidence of triploidy (including dispermy) of 11.7% was observed.After chromosomal analysis of metaphase I, univalents were observed in 16.7% of the cases. Aneuploidy (8.9%) was also found in metaphase II. Of the first cleavage metaphases, 88.0% had the diploid number of chromosomes. Aneuploidy occurred 12.0% of the time and 5 cases of triploidies were observed.