Ovulation triggering with GnRH agonist vs. hCG in the same egg donor population undergoing donor oocyte cycles with GnRH antagonist: a prospective randomized cross-over trial.

OBJECTIVE: To compare fertilization, implantation and pregnancy rates in donor oocyte cycles triggered for final oocyte maturation with either human chorionic gonadotropin (hCG) or gonadotropin releasing hormone (GnRH) agonist in the same donor population in two sequential stimulation cycles. DESIGN: Prospective randomized cross-over trial. SETTING: Private infertility clinic. PATIENT(S): Eighty-eight stimulation cycles in 44 egg donors. INTERVENTIONS: Controlled ovarian hyperstimulation (COH) with GnRH antagonist protocol triggered with hCG or GnRH agonist (leuprolide acetate 0.15 mg) in the same egg donors in two consecutive cycles. MAIN OUTCOME MEASURE(S): The primary outcome measure was the proportion of mature and fertilized oocytes per donor cycle. Secondary outcome measures were implantation and pregnancy rates in the recipients and incidence of ovarian hyperstimulation syndrome (OHSS) in oocyte donors. RESULT(S): The proportion of mature oocytes, fertilized oocytes and mean embryo scores were comparable between the two triggering agents. While implantation (36.53% vs, 32.93%), pregnancy (69.08% vs. 68.81%) and clinical pregnancy (41.3% vs. 40.2%) rates were comparable for the groups, the incidence of OHSS was significantly lower in GnRH than in hCG triggered cycles. CONCLUSION(S): Fertilization, implantation and pregnancy rates from donor oocytes stimulated with GnRH antagonist protocol were identical for donor cycles triggered with hCG and GnRH agonist. GnRH antagonist triggering in egg donors was associated with lower rates of OHSS.

Impact of oxygen concentration on embryonic development of mouse zygotes.

The aim of the present study was to examine the effect of culture under 5 and 20% oxygen on the development, differentiation and viability of zygotes and in-vivo-produced embryos at the 2-cell and 8-cell stages of development. First, zygotes collected in a common pool were cultured in 20% O2 for 0, 23, 46 and 95 h. Zygotes and in-vivo-produced embryos at the 2-cell and 8-cell stages of development were then cultured in 5 or 20% O2. The proportion of embryos reaching the compaction and blastocyst stages of development did not differ between groups regardless of the period of time embryos were cultured in 20% O2 or the stage at beginning of culture. Duration of culture under 20% O2 had a significant effect on total number of blastocyst cells. A stage-specific effect was observed on total and trophectoderm cell numbers in blastocysts resulting from the culture of zygotes and in-vivo-produced embryos under 20% O2. ICM and percent ICM development was significantly decreased by culture in 20% O2 at all stages examined. Oxygen concentration had no effect on implantation rate and fetal weights upon embryo transfer. However, transfer of zygotes grown to the blastocyst stage in 20% O2 resulted in a dramatic decrease in fetal development per blastocyst and fetal development per implantation. These results demonstrate that culture of F1 mouse zygotes in 20% O2 compromises the developmental potential of resultant blastocysts, which appear to be normal on morphological assessment.

Oxytocin-induced oscillations of cytoplasmic Ca2+ in human myometrial cells.

BACKGROUND: To investigate the mechanisms of oxytocin (OT) induced oscillations of the cytoplasmic Ca2+ concentration ([Ca2+]i) in cultured human myometrial cells. METHODS: [Ca2+]i was measured in individual myometrial cells by dual wavelength spectrophotofluorometry using the fluorescent indicator fura-2. Myometrium was obtained at abdominal hysterectomy (n=8) and during cesarean section (n=7). RESULTS: OT (10-300 nM) typically induced [Ca2+]i oscillations with frequencies in the 0.6-0.8/min range. There were no obvious differences in the responses of cells taken from non-pregnant and term pregnant women. The frequency and amplitude of the oscillations were not significantly affected by OT concentrations up to 300 nM. The amplitude of the oscillations decreased in the presence of the voltage-dependent Ca2+ channel antagonist verapamil and gradually disappeared in Ca2+-free medium. The oscillations were further blocked by the inorganic Ca2+ antagonist La3+ and by the intracellular Ca2+-ATPase inhibitor 2.5-di-tert-butylhydroquinone (DTBHQ). Caffeine inhibited the OT-induced oscillations in a concentration-dependent manner. DTBHQ and high concentrations of OT made [Ca2+]i remarkably sensitive to changes in the external Ca2+ concentration. CONCLUSIONS: The results indicate that OT-induced [Ca2+]i oscillations in human myometrial cells are due to inositol 1,4,5-trisphosphate-mediated release of intracellular Ca2+ combined with capacitative as well as voltage-dependent influx of the ion.

Structural and functional studies of gap junctions in human myometrium.

Gap junctions are of importance in the coordinated contraction of uterine smooth muscle during labor. There are indications that in the human myometrium, gap junctions are much more numerous in the period immediately surrounding parturition. The presence and the functional state of gap junctions in human myometrium was studied by electron microscopical morphometry and by studying the distribution of an injected fluorescent dye. Electron microscopy showed that the number and size of gap junctions was significantly higher during the active phase of labor than during the pre-labor phase. Pressure injection of Lucifer Yellow into myometrial cells in vitro showed only weak coupling in the pre-labor stage. These data support the notion that coupling between myometrial cells develops in immediate association with parturition.