Mammalian oocytes undergo growth and development through prenatal and postnatal periods. This is an investigation of development in vitro of oocytes and ovarian tissues from fetal gonads of the 12.5 days post coitus. Cultured tissues survived and the oocytes entered the growth phase, subsequently achieving long-term (14-30 days) culture. Growing oocytes were observed in their general morphology and were enclosed within 1-2 layers of granulosa cells, which resembled primary or secondary follicles. However, no follicular structures were also found in the cultures despite the existence of growing oocytes. The oocytes enclosed in very flattened cells were detected as in histological structure on day 18 of culture. The oocyte diameter became approximately 50 μm under culture conditions supplemented with 15% fetal bovine serum or Ehrlich ascites tumor fluid. These results indicate that the maximum culture period for oocyte growth in this organ culture is approximately 3 weeks and that the oocytes can grow in vitro to at least a medium size even if normal follicular structure is not formed.

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This study was conducted to induce immunotolerance to human chorionic gonadotropin (hCG) as a heterologous protein in neonatal mice. Ovulatory responses after repeated induction of superovulation were also investigated in the animals. Subcutaneous injection of hCG (100 IU) was performed in female mice within 24 hours after birth. Serum anti-hCG antibody titers were assayed and ovulatory responses were observed after the repeated superovulation with pregnant mare serum gonadotropin (PMSG) and hCG.
As a result, the production of anti-hCG antibody was suppressed. Thus, tolerance induction to hCG was achieved, although it was incomplete. Compared with the control mice, the ovulatory rate was higher after the induction of immunotolerance to hCG. It was suggested that the production of anti-hCG antibody has a close relation with a decrease in the ovulatory response after the repeated induction of superovulation by gonadotropins.

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To investigate the developmental competence in vitro of female germ cells in fetal gonads, gonadal ridges of 12.5 days post coitus (dpc) were organ-cultured for 18 days, and then oocyte-granulosa cell complexes (OGCs) were isolated from the cultures. Collected OGCs were further cultured for 11 days. The oocytes grown in vitro reached 64.1 ± 0.4 μm. Transmission electron microscopy analysis showed that oocytes grown in vitro had maintained connection with surrounding somatic cells. Some oocytes resumed meiosis by 1 μM okadaic acid or 10 ng/ml epidermal growth factor (EGF). The oocytes that underwent germinal vesicle breakdown reached 71.3 ± 0.5 μm. This study showed growth and meiotic resumption in vitro of oocytes through the support of ovarian tissue from fetal gonads.

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Midkine (MK) is a heparin-binding growth factor, the expression of which is strong in the midgestation period, is highly restricted in the adult, and is increased in many human carcinomas. In the present investigation, we determined serum levels of MK by an enzyme immunoassay, and found that in many patients with gynecological tumors, the values increased above the cut off value of 500 pg/ml. All control subjects (n=49) including pregnant women exhibited values not more than 500 pg/ml. The percentage of positive cases was as follows; ovarian carcinoma (n=15), 87%; uterine cervical carcinoma (n=18), 67%; uterine endometrial carcinoma (n=10), 50%; ovarian cyst (n=25), 72%; leiomyoma (n=29), 72%. CA-125 and MK levels were not correlated in ovarian carcinoma and ovarian cyst; a combination of the two assays may be helpful in increasing specificity or sensitivity. Furthermore, increased MK levels were found even in patients with early stages of uterine cervical and endometrial carcinomas. Serum MK levels might become helpful in the initial screening of gynecological tumors.

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