Reversible changes in protein phosphorylation during germinal vesicle breakdown and pronuclear formation in bovine oocytes in vitro

This study examined the event of protein phosphorylation in bovine oocytes during germinal vesicle breakdown (GVBD) and formation of pronuclei following fertilisation in vitro. Immature oocytes were obtained from abattoir materials and cultured in vitro. The oocytes were labelled with [32P]orthophosphate at 3 h intervals from 0 to 12 h following maturation in culture or from 3 to 18 h following insemination. One-dimensional gel electrophoresis indicated that levels of protein phosphorylation are low prior to GVBD. However, the levels of protein phosphorylation at approximately 40 kDa, 27 kDa, 23 kDa and 18 kDa increased substantially following GVBD and then decreased gradually as maturation in culture progressed. In contrast, the levels of protein phosphorylation increased gradually in the oocytes following pronucleus formation. Further, two-dimensional gel electrophoresis indicated that the protein at approximately 18 kDa reversibly changed in the oocytes during maturation and fertilisation. These results indicate that the reversible changes of this phosphoprotein may be related to either cell cycle transition or pronucleus formation during maturation and fertilisation in bovine oocytes.</p

Effects of duration of cryo-storage of mouse oocytes on cryo-survival, fertilization and embryonic development following vitrification

Purpose To investigate the effects of cryo-storage duration in liquid nitrogen on oocyte cryo-survival, fertilization and embryonic development following vitrification and warming. Methods Mature mouse oocytes were vitrified with McGill Cryoleaf and stored in liquid nitrogen for a period of 8-10 days, 90-92 days and 180-182 days, respectively. After warming, the survived oocytes were inseminated by intracytoplasmic sperm injection (ICSI) and cultured for 120 h. The rates of oocyte cryo-survival, cleavage and embryonic development were compared. Result(s) The oocyte cryo-survival rate declined following cryo-storage duration for 180-182 days (90.4 +/- 7.9%) compared to that of the other two groups (97.4 +/- 3.0% and 98.0 +/- 3.3%). The fertilization rate in the group of 180-182 days (66.6 +/- 22.0%) was also significantly reduced (P &lt; 0.05) compared with the groups of 8-10 days (92.2 +/- 10.8%) and 90-92 days (94.7 +/- 9.1%). In addition, the number of embryos developed to the blastocyst stage declined significantly (P &lt; 0.05) following long cryo-storage duration (72.1 +/- 8.2%, 25.2 +/- 3.8% and 5.5 +/- 13.6%, respectively). Conclusion(s) The cryo-survival, fertilization rate and embryonic development of mouse oocytes are affected significantly, in an adverse manner, by the cryo-storage duration in liquid nitrogen.Genetics &amp; HeredityObstetrics &amp; GynecologyReproductive BiologySCI(E)PubMed8ARTICLE7643-6492