Nitric oxide (NO) plays an important role in intracellular signaling, but its role during the activation of mammalian oocytes is little understood. In our study, in vitro matured pig oocytes were cultured with NO-donors-S-nitroso-N-acetylpenicillamine (SNAP) or sodium nitropruside (SNP). These treatments were able to induce parthenogenetic activation of pig oocytes matured in vitro. The specificity of this effect was confirmed by the activation of oocytes by exogenous endothelial nitric oxide synthase (eNOS) microinjected in the oocyte with its activator calmodulin. Relatively long exposure (10 hr) is needed for activation of pig oocytes with 2.0 mM SNAP. An active NOS is necessary for the NO-dependent activation of pig oocytes because NOS inhibitors L-NMMA or L-NAME are able to inhibit activation of oocytes with NO-donor SNAP. On the basis of our data, we conclude that the NO-dependent activating stimulus seems inadequate because it did not induce the exocytosis of cortical granules. Also, the cleavage of parthenogenetic embryos was very low, and embryos did not develop beyond the stage of eight blastomeres.

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Contents of aflatoxin B 1 (AFB 1 ) and ochratoxin A (OA) in the samples of wheat and barley were detected by RIA method. Average contents of AFB 1 in the samples of wheat and barley were 2.4 µg/kg and 2.2 µg/kg, respectively. Average contents of OA in the samples of wheat and barley were 3.1 µg/kg and 2.4 µg/kg, respectively. The contents of mycotoxins corresponded to the allowed limits in food. During the studies of mutagenic activity of mycotoxins and their combinations by means of Ames test it was found that OA could increase the mutagenicity of AFB 1 in the case of their simultaneous occurrence in the same substrate. For free full paper in pdf format see

In this paper we assessed: (i) the change in nitric oxide synthase (NOS) isoforms' expression and intracellular localization and in NOS mRNA in porcine oocytes during meiotic maturation; (ii) the effect of NOS inhibition by N(omega)-nitro-l-arginine methyl ester (l-NAME) and aminoguanidine (AG) on meiotic maturation of cumulus-oocyte complexes (COC) as well as denuded oocytes (DO); and (iii) nitric oxide (NO) formation in COC. All three NOS isoforms (eNOS, iNOS and nNOS) and NOS mRNA (eNOS mRNA, iNOS mRNA and nNOS mRNA) were found in both porcine oocytes and their cumulus cells except for nNOS mRNA, which was not detected in the cumulus cells. NOS isoforms differed in their intracellular localization in the oocyte: while iNOS protein was dispersed in the oocyte cytoplasm, nNOS was localized in the oocyte cytoplasm and in germinal vesicles (GV) and eNOS was present in dots in the cytoplasm, GV and was associated with meiotic spindles. l-NAME inhibitor significantly suppressed metaphase (M)I to MII transition (5.0 mM experimental group: 34.9% MI, control group: 9.5% MI) and at the highest concentration (10.0 mM) also affected GV breakdown (GVBD); in contrast also AG inhibited primarily GVBD. The majority of the oocytes (10.0 mM experimental group: 60.8%, control group: 1.2%) was not able to resume meiosis. AG significantly inhibited GVBD in DO, but l-NAME had no significant effect on the GVBD of these cells. During meiotic maturation, NO is formed in COC and the NO formed by cumulus cells is necessary for the process of GVBD.

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