title: Effects of activation timing on the fertilization rate and early embryo development in porcine ROSI procedure.
abstract: OBJECTIVE
  This study was undertaken to evaluate the optimal exposure time for nuclear envelope breakdown (NEBD) after injection of a round spermatid and to investigate the effect of oocyte activation timing on the fertilization rate and early embryo development in porcine round spermatid injection procedure.
  
  
  METHODS
  Injected oocytes were fixed at 0.5, 1, 2, 3, and 4 h before activation, and NEBD state was examined. The three groups of oocytes were activated before and after the injection of spermatid using a single direct current pulse (100 V/mm, 50 micros): group 1) at 2 h before the injection (pre), group 2) within 0.5 h after the injection (immediate), and group 3) at 2 h after the injection (post). Activated oocytes were cultured and pronucleus formation and blastocyst development was evaluated at 15-18 h and 7-8 days after the injection, respectively.
  
  
  RESULTS
  The proportion of oocytes with NEBD significantly increased in the groups with over 2 h of exposure time (p < 0.05) and oocyte with premature chromosome condensation began to appear 3 h after the injection. Normal fertilization and development rate to the blastocyst stage were significantly higher in the post group than in those of the pre or immediate group (p < 0.05).
  
  
  CONCLUSIONS
  The optimal exposure time for NEBD is 2 h after the injection, and activation in 2 h after round spermatid injection improved the normal fertilization and early embryo development rate.
authors.affiliation: Infertility Clinic, Samsung Medical Center, School of Medicine, Sungkyunkwan University Kangnam-Ku, Seoul, Korea.
authors.forename: Jong Yeob
authors.initials: JY
authors.lastname: Choi
authors.forename: Eun Young
authors.initials: EY
authors.lastname: Lee
authors.forename: Hee Tae
authors.initials: HT
authors.lastname: Cheong
authors.forename: Byung Koo
authors.initials: BK
authors.lastname: Yoon
authors.forename: Duk Soo
authors.initials: DS
authors.lastname: Bae
authors.forename: Doo Seok
authors.initials: DS
authors.lastname: Choi
mesh_terms: D000818:Animals; D047108:Embryonic Development; D005260:Female; D005306:Fertilization; D008297:Male; D009685:Nuclear Envelope / Q000378:metabolism*; D009865:Oocytes / Q000502:physiology*; D020554:Sperm Injections, Intracytoplasmic / Q000662:veterinary*; D013087:Spermatids; D013552:Swine; D013997:Time Factors