This study aimed to evaluate the impact of adding vitamin C and zinc chloride to vitrification medium on viability in vitro maturation and ultrastructure changes of vitrified immature Baladi cow oocytes. Compact cumulus oocytes (COCs) (n=1370) were obtained from slaughtered bovine ovaries. Then the morphology of oocytes was examined using a stereomicroscope. Staining with trypan, the in vitro maturation and ultrastructural changes were studied. The results revealed significant (P<0.05) increase of total and normal survival rate of bovine oocytes vitrified with zinc chloride (90.28 and 81.11%) than in vitamin C media (82.5 and 65.65%) or control medium (74.44 and 54.72%). Recovery rate of abnormal bovine oocytes showed significantly an opposite trend (9.17 vs. 16.94 and 19.72%). Proportion of oocytes with viable cytoplasm and viable cumulus (VOVC) was increased significantly (93.75%, P<0.05) in fresh (control) than in medium supplemented with vitamin C and untreated medium (74.55 and 68.63%), respectively. There were non-significant differences among zinc chloride, control and vitamin C media in oocytes with vaible cytoplasm and unvaiable cumulus (VOUC). Supplementation of the vitrification medium with zinc chloride and vitamin C significantly (P<0.05) improved maturation rates (MII) of recovered cumulus oocyte complexes (COCs) than medium without supplementation. The percentage of ultrastructural alterations in most organelles bovine oocytes significantly (P<0.05) increased in oocytes vitrified without supplementation followed by vitamin C, then zinc chloride medium. Conclusion, supplementation of vitamin C or zinc chloride to the vitrification medium improved survival rate, morphologically and ultrastructural, as well as maturation rate of bovine oocytes
This study aimed to evaluate the effect of adding insulin hormone at different levels (0, 5, 10 and 15 µg/ml) to maturation medium with or without exogenous hormones (FSH, LH and E17β) on the in vitro maturation (IVM) of rabbit oocytes. Total of 20 New Zealand White (NZW) rabbit does (5.5-6 mo of age and 2.5-3 kg LBW) were used as oocyte donors. Oocytes were recovered from ovaries of slaughtered does using slicing technique. All oocytes with evenly granulated dark ooplasm were matured in TCM-199 supplemented with 6% bovine serum albumin. Eight types of TCM-199, four types without and other four with exogenous hormones supplemented with insulin (0, 5, 10 and 15 µg /ml) were used. Oocytes were fixed and stained for examination after 18 h at 38.5°C, 5% CO2 and high humidity as a maturation period. Results showed significant (P<0.05) effect of insulin supplementation on IVM of rabbit oocyte only in terms of oocytes reaching MI, TI+MII and degenerated ones. Percentage of mature oocytes reaching MII was improved by all insulin levels as compared to un-supplemented media (42.1-44.6 vs. 34.1%), but the differences were not significant. Percentage of oocytes reaching both TI+MII increased (P<0.05) with insulin supplementation at a level of 5 µg/ml showing the best (P<0.05) improvement on oocyte maturation (51.0%) as compared to other insulin levels (45.5-47.6%) or the control medium (39.5%). Nuclear maturation of rabbit oocytes was not affected significantly when FSH, LH and E2 were deleted from the maturation medium, but Percentage of oocytes reaching both T1+MII stages was enhanced in the presence of hormones during the maturation period regardless of whether oocytes were treated with insulin or not. Maturation rate in term of oocytes reaching T1+MII was affected significantly (P<0.05) by the interaction between insulin and hormonal addition, reflecting improved percentage of oocytes reaching both T1+MII stages by addition of all insulin levels to hormone-TCM-199 medium. In this respect, insulin addition at a level of 5µg/ml showed the best result (58.7%). In conclusion, the present study demonstrated that the supplementation of the maturation medium with insulin improves the in vitro maturation rate of rabbit oocytes when oocytes are maturated in a defined maturation medium with or without hormones (FSH, LH and E2).
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