We investigated the extent to which NO participates in the developmental competence (oocyte maturation, fertilization and embryo development to blastocyst) using an in vitro culture system adding sodium nitroprusside (SNP), NO donor, and NOS inhibitor (N‐omega‐nitro‐L‐arginine methyl ester, L‐NAME). We also assessed the effects of NO/NOS system on blastocyst implantation using an in vitro trophoblast outgrowth assay. The treatment of low concentrations of SNP (10−7 M) significantly stimulated meiotic maturation to metaphase II stages in cumulus enclosed oocytes. In contrast, 10−3 and 10−5 M L‐NAME demonstrated a significant suppression in resumption of meiosis. This inhibition was reversed by the addition of SNP. No development beyond the four‐cell stage was observed by the addition of high concentration of SNP (10−3 M). Inhibition of embryo development, especially the conversion of morulae to blastocysts, was also observed in the treatment of lower doses of SNP (10−5 and 10−7 M). Similarly, inhibition of NO by NOS inhibitor resulted in the dose‐dependent inhibition of embryo development and hatching rates, but the concomitant addition of SNP with L‐NAME reversed the inhibitory effect by each SNP or L‐NAME treatment. Furthermore, low concentration of SNP (10−7 M) but not high concentration of SNP (10−3 M) significantly stimulated trophoblast outgrowth, whereas the addition of L‐NAME suppressed the spreading of blastocysts in a dose‐dependent manner. These results suggest that NO may have crucial roles in oocyte maturation and embryogenesis including the process of implantation. The observed differences in required amount of NO and the sensitivity to cytotoxicity of NO in each developmental stage embryos may also suggest that NO/NOS system is tightly regulated in developmental stage specific manner. Mol. Reprod. Dev. 58:262–268, 2001. © 2001 Wiley‐Liss, Inc.

We have identified a region with characteristics of a paternal-specific methylation imprint at the human H19 locus. This region, extending from -2.0 kb upstream to the start of transcription, is heavily methylated in sperm and on the paternal allele in somatic cells. This methylation was preserved during pre-implantation. Structural analysis revealed the presence of CpG islands and a large direct repeat with a 400 bp sequence reiterated several times, but no significant sequence homology to the corresponding region of the mouse H19 gene. These findings could suggest a role for secondary DNA structure in genomic imprinting across the species, and they also present a puzzling aspect of the evolution of the H19 regulatory region in human and mouse.

No abstract

The present study was designed to compare the cycle characteristics of in-vitro fertilization (IVF) and the chromosomal normality of oocytes in patients with polycystic ovarian syndrome (PCOS) with those of patients with tubal factor infertility. In all, 28 cycles of 24 PCOS patients and 55 cycles of 31 patients with tubal factor infertility (control) were investigated. Although a significantly greater number of oocytes were retrieved from PCOS patients (mean +/- SD: 15.6 +/- 6.4 versus 9.0 +/- 4.0, PCOS versus control group, P < 0.05), the percentage of fertilized oocytes was significantly lower in the PCOS group compared with controls (40.1 versus 73.8%, P < 0.01). The pregnancy rate per embryo transfer did not differ between the two groups. Cytogenetic analysis was performed on 74 oocytes from PCOS patients and 73 oocytes from control patients. In the PCOS group, 10 of the 74 oocytes (13.5%) demonstrated aneuploidy, four (5.4%) oocytes were diploid and six (8.1%) oocytes were metaphase II with a prematurely condensed sperm chromosome (PCC). In the tubal infertility group, nine of the 73 (12.3%) oocytes showed aneuploidy, four (5.5%) oocytes were diploid and five (6.8%) oocytes were found to have PCC. There was no significant difference in the aneuploidy, diploidy and PCC rates between the two groups. These results suggest that the reduced fertilization observed in PCOS is not attributable to chromosomal aberrations or immaturity of oocytes recruited from patients with PCOS.

Mn-SOD and Cu, Zn-SOD have different localizations and actions in human ovaries and fallopian tubes. The superoxide radical-SOD system might play an important role in ovulation and in the luteal function of the human ovary.