Optimization of triacetate cellulose hollow fiber vitrification (HFV) method for cryopreservation of in vitro matured bovine oocytes.

The aim of the current work was to evaluate applicability of triacetate cellulose hollow fiber vitrification (HFV) method for cryopreservation of groups of in vitro matured bovine oocytes (12-17 oocytes per device). We also attempted to optimize HFV protocol by altering concentration of non-permeating cryoprotectant (sucrose) in vitrification solution and concentration of extracellular Ca by using a calcium-free base medium for preparation of vitrification/rewarming solutions with ethylene glycol (EG) as a single permeating cryoprotectant. Neither of modifications of HFV protocol significantly affected survival or fertilization rates of the vitrified bovine oocytes.

Efficiency of asynchronously in vitro-matured oocytes as recipients for nuclear transfer and of blind enucleation in zona-free bovine cloning.

We studied the dynamics of in vitro maturation of bovine oocytes, the efficiency of asynchronously matured oocytes as recipients for the generation of embryos produced by nuclear transfer, and the potential for using blind enucleation of zona-free bovine oocytes in bovine cloning. At 15 h after the initiation of maturation (hpm), oocytes were freed from both cumulus cells and the zona pellucida, and the dynamics of oocyte maturation were monitored every 30 min through the criterion of extrusion of the first polar body (PB1). More than 41% of bovine oocytes had extruded PB1 by 16.