Strategies for activating nuclear transfer oocytes.

The technique of nuclear transfer can have enormous applications in the fields of agriculture and biomedicine. This is especially true if a cell line that has been transformed can be used as a source of nuclei for the nuclear transfer. One major aspect of the nuclear transfer procedures is that of oocyte activation. Without oocyte activation the transferred nucleus would never progress to the first interphase. It is therefore of utmost importance that the oocyte be activated in a fashion that is as normal as fertilization. The inability to obtain development after artificial activation of pig oocytes has been a limiting factor in the application of the nuclear transfer technology. Recently, a number of techniques have been developed that result in blastocyst stage embryos after oocyte maturation in vitro and artificial activation. The theories behind normal oocyte activation are reviewed as well as a number of methods of artificial oocyte activation. It is anticipated that such a review will provide the basis for the development of additional methods that are as efficient, or more efficient, at activating the unfertilized oocyte.