The Secretion Of Interferon-Ï„ In Bovine Blastocysts From Different Methods

Interferon-tau (IFN- Ï„ ) is the earliest pregnant signal from ruminant early embryos to maternal uterus. It can inhibit luteolysis and keep the development of the embryos in the uterus. In this thesis, the secretion of IFN-Ï„ in bovine blastocysts at day 7 to 9 after culture in vitro from parthenogenetic activation, in vitro fertilization(IVF), frozen-thawed IVF and somatic cell nuclear transfer(NT) were compared. The parthenogenesis efficiencies of bovine in vitro maturation (IVM) oocytes were also studied between chemical and electric activation. The effect of different culture method on the development of parthenogenetic embryos from chemical activation was investigated in Synthetic Oviduct Fluid (SOF) culture system.The production of IFN-Ï„ was quantified by means of bioassay based on the inhibition of the cytopathic effect of vesicular stomatitis virus on Madin-Darby bovine kidney (MDBK) cells. The results indicated that the IFN-Ï„ secretion levels didn't differ among the parthenogenetic, IVF and frozen-thawed IVF (p>0.05), but they were significantly higher than that of NT blastocysts (p<0.05). According to our results, the secretion levels of IFN-Ï„ didn't correlate with the diameter and the cell number of the blastocyst in parthenogenetic and IVF embryos. There was no significant deference in the IFN-Ï„ secretion of parthenogenetic blastocysts between CR1aa and SOFaa culture systems (p>0.05).In the chemical activation experiment, bovine IVM oocytes were treated with 5 u mol/L ionomycin for 5 minutes, followed by incubation in 2 mmol/L 6-DMAP for 4 h. In the electric activation experiment, bovine IVM oocytes were treated with the direct current pulse of 1.3 kVcm-1, 80 u s for 1 time. The blastocyst rate in chemical activation group was significantly higher than that of the electric activation (12.30% vs 2.4%)(p<0.01).Two methods were used for chemical activation parthenogenetic embryos culture. One was the activated bovine IVM oocytes cultured in the SOFaa medium for 7 days, which we stated as method A. Another was the activated bovine IVM oocytes cultured in the SOFaa medium for 4 days, then transferred into the SOFaa medium supplemented with 10% FBS for 3 days, which we stated as method B. The result showed that the blastocyst rates were significantly different between method A and method B (11.64% vs 3.49%)(p<0.01).