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Toxoplasma gondii is an opportunistic intracellular parasite that is highly prevalent in human and warm-blooded animals throughout the world, leading to potentially severe congenital infections. Although the abortion caused by T. gondii is believed to be dependent on the timing of maternal infection during pregnancy, the mechanism remains unclear. This study was focused on the effects of T. gondii excreted-secreted antigens on pregnant outcomes and CD4+CD25+ Foxp3+ regulatory T cells at different stages of pregnancy. The results showed that in mice the frequency and suppressive function of CD4+CD25+ regulatory cells were diminished after injection of T. gondii excreted-secreted antigens at early and intermediate stages of pregnancy. The abortion caused by T. gondii excreted-secreted antigens at early pregnancy could be partly prevented by adoptively transferring of CD4+CD25+ cells from the mice injected with T. gondii excreted-secreted antigens at late pregnancy, but not from the mice with the same treatment at early pregnancy. Furthermore, T. gondii excreted-secreted antigens induced apoptosis of CD4+CD25+ regulatory cells of mice in early and intermediate stages of pregnancy by down-regulating their Bcl-2 expressions and Bcl-2/Bax ratio. This study provides new insights into the mechanism that T. gondii infection is the high risk factor for abortion in early pregnancy.

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This study tested the hypothesis that oocyte aging could be prevented for a longer time by reducing the culture temperature while supplementing the culture medium with more pyruvate. Newly ovulated mouse oocytes were cultured at various temperatures for various times in HCZB medium (Kimura and Yanagimachi, Biol Reprod 1995; 52:709-720) containing various concentrations of pyruvate before examining for aging parameters and developmental potential. The increase in susceptibility to activating stimuli was efficiently prevented when oocytes were cultured in HCZB with 10.27 mM pyruvate at 37°C for 6 h, 25°C for 24 h, 15°C for 96 h, and 5°C for 48 h. Satisfactory blastocyst development of both parthenotes and fertilized zygotes was achieved after oocyte culture in HCZB containing 10.27 mM pyruvate at 37°C for 6 h, 25°C for 24 h, 15°C for 36 h, and 5°C for 24 h. Transfer of two-cell embryos or blastocysts showed no difference between newly ovulated control oocytes and oocytes cultured at 15°C for 36 h in either term pregnancy, live young per pregnant recipient, live young/transferred embryos, or birth weight of young. Oocytes with impaired developmental potential after culture at 15°C for 96 h and at 5°C for 48 h showed unrecoverable decreases in the content of glutathione, the glutathione/oxidized glutathione ratio, the BCL2 content, and in the numbers of oocytes with normal spindles and cortical granule distribution, suggesting induction of oxidative stress, which caused oocyte apoptosis and cytoskeleton alterations by downregulating BCL2. Because oocytes cultured at 15°C for 36 h were activated or fertilized after a 6-h recovery culture, aging of ovulated mouse oocytes has been successfully prevented for 42 h without impairing their developmental potential.