Abstract
Triploid embryos were produced from degynic ICR eggs fertilized with ICR or C57BL/6J spermatozoa in the presence of 5 μg/ml cytochalasin B in vitro. About 60% of these tripronuclear eggs developed into the blastocyst when cultured in a modified Whitten medium supplemented with 100 μM EDTA. At the eight-cell stage, each of the triploid embryos was aggregated with a normal diploid ICR or F1 (ICR × C57BL) embryo after removing their zona pellucida with pronase. The rate of development to a single blastocyst was 94.0% and 89.5% in the aggregated pairs of 2n (ICR egg × C57BL sperm)↔3n (ICR egg × ICR sperm), and 2n (ICR egg × ICR sperm)↔3n (ICR egg × C57BL sperm), respectively. Karyotyping has revealed that these chimeric blastocysts are composed of both 2n and 3n cells.
