Study On Vitrification Of Bovine Ivm Oocytes

This study was conducted to determine optimal conditions for vitrification of in vitro matured(IVM) bovine oocytes and investigate the effects of vitrification on the ultrastructure by electron microscopy.Part 1: Study on vitrification of bovine IVM oocytesExpt I: The toxic effects of different combinations of cryoprotectant agents were examined.the result indicated that EG and DMSO+ EG had lower toxicity than DMSO.Expt II: Oocytes were vitrification in solution containing DMSO and EG by use open pulled straws . Study on effects of equilibration duration of oocytes in CPA. The highest development rate to blastocysts was observed when oocytes were exposed VS1 for 60 second and VS2 for 50 second.Expt III: Bovine oocyte were partly denuded at the 22 hours after the beginning of maturation and vitrified by ops method. The highest development rate to blastocysts was observed when oocytes were exposed VS1 and VS2 for 30 second respectively.Expt IV: Bovine oocyte were partly denuded at the beginning, six hours, twelve hours, twenty-two hours after the beginning of maturation and vitrified by ops method at the end of the maturation process. The development rates toblastocysts(4.1%, 6.3%, 6.3%, 6.8%)did not differ among the three groups.Expt V: Bovine oocyte were partly denuded at the 22 hours after the beginning of maturation and vitrified by ops method,cryoloop,mini-drop. The development rates to blastocysts(6.7%, 7.5%, 5.9%)did not differ among the three groups. The highest recorved rate was observed when oocytes were vitrified by ops method.Expt VI: The effect of duration of exposure of oocytes to sucrose during the one step, two step, three step dilution. The higher development rate to blastocysts was observed during the two step and three step dilution .Part 2: Ultrastrustural changes in bovine oocytes cryopreserved by vitrificationThe bovine oocytes were vitrified after exposure to vitrification solution(VSl consisting of 10%DMSO+%20EG;VS2consisting of 20%DMSO +%20EG+ 0.25Msuc). The bovine oocytes were exposure to WM with two-step dilution after thawed. We investigate the effects of vitrification on the ultrastructure of oocyte by electron microscopy.Oocyte exhibited significant morphological change in microvili ,perivitelline space and CG after vitrification. But Mitochondria,lipid droplets and vesicle in the were similar to that of control.