To improve survival rates of vitrified pig oocytes, the treatment of cytoskeletal stabilizer on an appropriate time is one of the possible approaches. However, the exact treatment timing and effect of cytoskeletal stabilizer such as cytochalasin B (CB) is not well known during oocyte vitrification procedures. Thus, the present study was conducted to determine optimal treatment timing of CB during vitrification and warming procedures. In experiment 1, the survival rates of the post-warming pig oocytes were analyzed by fluorescein diacetate (FDA) assays with 4 classifications. In results, post-warming oocytes showed significantly (p<0.05) decreased number of alive oocytes (31.8% vs. 86.4%) compared to fresh control. In detail, the significant difference (p<0.05) was found only in strong fluorescence (18.2% vs. 70.5%) not in intermediate fluorescence groups (13.6% vs. 15.9%). In experiment 2, CB was treated before (CB-Vitri) and after (Vitri-CB) vitrification. In results, group of Vitri-CB showed significantly (p<0.05) higher (91.6%) survival rates compared to group of CB-Vitri (83.7%), significantly (p<0.05) and comparable with group of Vitri Control (88.7%) by morphological inspection. In FDA assay results, group of Vitri-CB showed significantly (p<0.05) higher (44.2%) survival rates compared to groups of CB-Vitri (36.7%) and Vitri Control (35.1%). In conclusion, the increased survival rates of post-warming pig oocyte treated with Vitri-CB method are firstly described here. The main finding of present study is that the CB treatment during recovery could be helpful to refresh the post-warming pig oocyte resulting its improved survival rates.

ABSTRACT
 INTRODUCTION
 MATERIALS & METHODS
  1. Experimental design
  2. In vitro maturation oocytes
  3. Vitrification and warming of oocytes
  4. Recovery culture and treatment of cytochalasin B
  5. Analysis of post-warming survival rates
  6. Statistical analysis
 RESULTS
  1. Survival rates of post-warming pig oocytes
  2. Effect of CB treatment timing on vitrified-warmed pig oocytes
 DISCUSSION
 REFERENCES

• In-Sul Hwang(Animal Biotechnology Division, National Institute of Animal Science)
• Mi-Ryung Park(Animal Biotechnology Division, National Institute of Animal Science)
• Tae-Uk Kwak(Animal Biotechnology Division, National Institute of Animal Science)
• Sang-Hyun Park(Animal Biotechnology Division, National Institute of Animal Science)
• Ji-Hyun Lim(Animal Biotechnology Division, National Institute of Animal Science)
• Sung Woo Kim(Animal Genetics Resources Research Center, National Institute of Animal Science)
• Seongsoo Hwang(Animal Biotechnology Division, National Institute of Animal Science) Corresponding Author