Host: Society for Reproduction and Development
Ultrasound stimulation is a new oocyte activation protocol developed recently in our laboratory and we found that the ICSI and cloned embryos activated by ultrasound have the ability to develop into piglets after transfer to recipient females. However, the exocytosis patterns of cortical granules (CGs) of pig oocytes activated in vitro by ultrasound stimulation remain unknown. The objective of this study was to determine the effects of the artificial activation protocols [ultrasound and electricity with or without 2.2 ug/ml cytochalasin B (CB)] on nuclear activation status, CGs distribution and the fertilizing ability of pig oocytes matured and activated in vitro. The second polar body extrusion was significantly inhibited (P<0.05) and CGs centripetal migration observed when oocytes were treated with CB for 2h after artificial stimulation. However, the time courses of CGs exocytosis in oocytes activated in vitro did not differ between the artificial activation protocols. In oocytes activated by artificial stimulation, fluorescent clumps or spots were seen within the perivitelline space 2h after artificial stimulation. At 6 h following activation most oocytes activated by ultrasound remained CGs fluorescent spots of strong intensities while most of those activated by electricity decreased their intensities. The fertilization rate and the numbers of penetrated spermatozoa per oocyte were significantly decreased when the matured oocytes were inseminated in vitro following artificial stimulation compared with the control (P<0.05).
