Another difference is that most of the electrically activated pig oocytes did not form a male pronucleus after sperm penetration; our unpublished data), but most of the A23187-treated pig oocytes did (Tables 2-4). In the present study, sperm may have penetrated only the oocytes that had actually not been activated, because A23187 induced nuclear activation in only 19.8-62.3% of the oocytes, and the sperm penetration rates were also very low (341%). It is also possible that sperm penetration occurred before the oocytes were fully activated by A23187. buy ortho tri-cyclen
3.5 h before insemination.
According to studies in bovine oocytes, histone HI kinase activity (which was used as a measure of the activity of maturation-promoting factor) was reduced at 30-60 min after electrical pulse, but not until at least 5 h after A23187 treatment. Calcium transients were also different for the two stimulators; present study) in pig oocytes. Electrical pulse induced very fast and high Ca2+ transients, but A23187 induced a small Ca2+ transient. In addition, we also found that most of electrically pulsed oocytes did not release a second polar body and were penetrable by sperm, whereas A23187-treated oocytes released a second polar body and were not penetrable by sperm. Sperm-penetrated oocytes also released a second polar body and were not penetrable by sperm after reinsemination (unpublished observation). Putting these results together, we suggest that the mechanisms are completely different for electrical activation and A23187 activation, with A23187 more closely mimicking sperm penetration.