Increased susceptibility to maternal aneuploidy demonstrated by comparative genomic hybridization analysis of human MII oocytes and first polar bodies.

Single cell comparative genomic hybridization (CGH) was employed to extensively investigate 24 unfertilized or in vitromatured meiosis II oocytes and their corresponding first polar bodies (PBs), to determine how and whether all 23 chromosomes participate in female meiosis I errors and to accurately estimate the aneuploidy rate in the examined cells. Results were obtained for 15 oocytes and 16 PBs, representing 23 eggs (MII oocyte-PB complexes) donated from 15 patients (average age 32.2 years). Abnormalities were detected in ten eggs, giving an overall aneuploidy rate of 43.5%. In all, fourteen anomalies were scored, with the fertilized oocyte being at risk of monosomy in eight cases and at risk of trisomy in six; chromosomes of various sizes participated. CGH was able to give a comprehensive aneuploidy rate, as both absence of chromosomal material and the presence of extra copies were accurately scored. The aneuploidy mechanisms determined were: classical whole univalent non-disjunction; chromatid predivision prior to anaphase I, leading to metaphase II imbalance. There was also evidence of germinal mosaicism for a trisomic cell line. Three patients appeared to be predisposed to meiosis I errors, based on the presence of either multiple abnormalities in one or more of their examined cells, or of the same type of abnormality in all of their cells. Exclusion of these susceptible patients reduces the aneuploidy rate to 20%. Various hypotheses are put forward to explain these observations in order to stimulate research into the complex nature of female meiotic regulation.

Effects of in-vitro exposure to HCG on subsequent HCG-responsiveness of human granulosa cells obtained following treatment with GnRH analogue and gonadotrophins: an in-vitro model for luteal phase support.

The pregnancy rate in patients undergoing assisted conception treatment following pituitary desensitization with GnRH analogue and ovarian stimulation with gonadotrophins has been reported to be higher when ovarian function is supported in the luteal phase by exogenous human chorionic gonadotrophin (HCG). In the present study, we have examined the effects of culturing monolayers of granulosa cells, collected from such patients at oocyte retrieval, for various time intervals in the presence or absence of HCG on their subsequent ability to secrete progesterone (P4) either spontaneously or in response to further challenge with HCG. When cultured in the absence of HCG, granulosa cells demonstrated a rapid decline in both the spontaneous P4 secretion rate and the ability to secrete P4 in response to HCG. Maintenance in the presence of HCG inhibited the rapid decline in ability to secrete P4 spontaneously and also significantly enhanced the ability to respond to subsequent HCG stimulation. These results suggest that HCG support in the luteal phase in GnRH analogue-treated patients may have a cellular basis for its action both in maintenance of P4 secretion and also in rendering the corpus luteum more sensitive to rescue by conceptus-derived HCG.

Clinical and biochemical pregnancy in two respective recipients without ovarian function following gamete intrafallopian transfers using oocytes from a single donor.

Infertility resulting from premature ovarian failure in two independent patients was treated using a combination of steroid replacement, oocyte donation and gamete intrafallopian transfer (GIFT). Following ovarian stimulation four oocytes were retrieved from a volunteer donor undergoing simultaneous laparoscopic sterilisation. Two oocytes were subsequently replaced into each recipient's fallopian tube together with capacitated sperm from their respective husbands. In one recipient (Turner's syndrome) an intrauterine sac with fetal heart present was observed by ultrasound six weeks post GIFT whereas in the second recipient (premature menopause) plasma beta-hCG reached a peak value of 954mIU/ml eighteen days after GIFT before decreasing rapidly in the absence of ultrasound evidence of pregnancy. Intramuscular administration of progesterone appeared to be necessary during the post-GIFT period for maintenance of pregnancy. The above treatment was carried out on a predominantly out-patient basis in a small assisted conception unit based in a teaching hospital.

Effects of high-dose and multiple-dose gonadotropin stimulation on mouse oocyte quality as assessed by preimplantation development following in vitro fertilization.

The effects of increasing the level of ovarian stimulation on preimplantation embryonic development were assessed using a mouse in vitro fertilization system. When F1 hybrid (C57BL/6 X CBA/Ca) mice received a single injection of 5 IU pregnant mare's serum gonadotropin (PMSG) followed 60 hr later by 5 IU human chorionic gonadotropin (hCG) approximately 50% of the resultant postovulatory oocytes developed to the blastocyst stage following in vitro fertilization. Increasing the single dose of PMSG to 10 or 15 IU resulted in significant reductions in the frequency of development to the blastocyst stage. When one or two additional doses of 5 IU PMSG were administered 24 and 48 hr after an initial injection of 5 IU, lower frequencies of oocytes with the potential for full preimplantation development were again observed. This reduction in gamete quality was significantly greater when the final dose of PMSG was administered only 12 hr prior to hCG. The results suggest that excessive gonadotropin stimulation may compromise the quality of the preimplantation embryos obtained following in vitro fertilization and that the timing of gonadotropin administration may also be critical.

Preimplantation development following in vitro fertilization of mouse oocytes: effects of timing of superovulation and preincubation in vitro.

The early embryonic development of in vitro fertilized oocytes was assessed following superovulation in F1 hybrid (C57BL/6 X CBA/Ca) mice. Decreasing the time interval between the administration of constant doses of pregnant mare's serum gonadotropin (PMSG) and human chorionic gonadotropin (hCG) resulted in decreases in the frequency of development to the blastocyst stage but had no significant effect on development to the two-cell stage. Preincubation of postovulatory oocytes in vitro prior to insemination did not compensate for the reduced preovulatory development in vivo but resulted in decreases in the frequency of development to the blastocyst stage. The results indicate that inadequate preovulatory development of superovulated mouse oocytes can adversely affect the preimplantation development of in vitro fertilized embryos in the absence of a visible inhibitory effect on development to the two-cell stage and also that preincubation of postovulatory oocytes in vitro prior to fertilization reduces subsequent developmental capacity.