Theoretic considerations regarding slow cooling and vitrification during cryopreservation.

This review presents the methodology of using theoretic models for development of cryopreservation protocols by designing specific cooling profiles and selecting appropriate external conditions to optimize cryopreservation survival. Biophysical events during the processes of cryopreservation were examined and corresponding theoretic equations were used to simulate cryopreservation procedures under various slow cooling conditions for rat zygotes in the presence of DMSO, using a 0.25-mL plastic straw as the container. Simulation revealed three regions with their own characteristics and cryopreservation relevance. In addition, this review discusses vitrification cryopreservation using two-step additions. The effects of exposure durations and exposure temperatures on cell survival and subsequent development rates were examined in a series of cryopreservation experiments. Values of accumulative osmotic damage were used to quantitatively examine the magnitude of the associated osmotic damage during cryoprotective agent (CPA) additions and dilutions. In these investigations, oocyte blastocyst rates were highly correlated with the values of accumulative osmotic damage in the processes of CPA additions/dilutions. This review emphasizes the most essential step of the selection of the cell container in the process of cryopreservation, and provides practical suggestions and guidelines for optimizing slow cooling protocols. The review stresses that conducting CPA addition steps at 25 °C would be preferable for vitrification. It also suggests that the final dilution process needs more systematic research to optimize vitrification procedures.

Transvaginal ultrasound detection of multifollicular ovaries in non-hirsute ovulatory women.

OBJECTIVES: To characterize ovarian morphology in a group of ovulatory, non-hirsute women with infertility and normal circulating levels of gonadotropins and sex steroids. METHODS: Thirty-three women with normal physical examinations, regular ovulatory menses, and absence of hirsutism (Ferriman-Gallwey score < or = 7) were studied. No woman had thyroid disease, galactorrhea, polycystic ovary syndrome, 21-hydroxylase deficiency or diabetes. Two-dimensional (2D) transvaginal sonography (TVS) was used to measure follicle size and ovarian volume on menstrual cycle day 5. Three-dimensional (3D) TVS images were stored to determine the number of follicles (measuring 2-10 mm in diameter) in the largest sonographic plane. Fasting blood sampling and oral glucose tolerance testing were performed to assess serum gonadotropin and sex steroid levels as well as glucose tolerance. RESULTS: The median ovarian volume by 2D-TVS imaging was 7.2 (range, 2.3-15.8) cm(3) (n = 64 ovaries). No follicles were > 10 mm in diameter. The median number of follicles by 3D-TVS was 4 (range, 2-8) (n = 63 ovaries) in the largest sonographic plane. Fourteen of 63 ovaries (22%) had six or more small follicles in one plane distributed within normal stroma (multifollicular ovary, MFO). No ovary had 10 or more follicles in one plane located within abundant stroma (polycystic ovary). Of 33 women examined, 20 women (61%) had apparently normal ovaries bilaterally, while 13 (39%) had at least one MFO. There were no significant differences between women with and those without MFO in serum gonadotropin and steroid levels or glucose tolerance. CONCLUSIONS: MFO is a common morphological variant in non-hirsute ovulatory women with normal gonadotropin secretion and ovarian steroidogenesis.