The cleavage rate of digynic triploid mouse embryos during the preimplantation period.

Triploidy is a lethal condition in mammals, with most dying at some stage between implantation and term. In humans, however, a very small proportion of triploids are liveborn but display a wide range of congenital abnormalities. In particular, the placentas of human diandric triploid embryos consistently display "partial" hydatidiform molar degeneration, while those of digynic triploids generally do not show these histopathological features. In mice, the postimplantation development of diandric and digynic triploid embryos also differs. While both classes are capable of developing to the forelimb bud stage, no specific degenerative features of their placentas have been reported. Diandric triploid mouse embryos are morphologically normal while digynic triploid mouse embryos consistently display neural tube and occasionally cardiac abnormalities. Previously it was shown that the preimplantation development of micromanipulated diandric triploid mouse embryos was similar to developmentally matched diploid control embryos. In this study, the preimplantation development of micromanipulated digynic triploid mouse embryos is analysed and compared with that of diandric triploid mouse embryos in order to determine whether there is any difference in cleavage rate between these two classes of triploids. Standard micromanipulatory procedures were used to insert a female or a male pronucleus into a recipient diploid 1-cell stage embryo. The karyoplast was fused to the cytoplasm of the embryo by electrofusion. These tripronucleate 1-cell stage embryos were then transferred to pseudopregnant recipients and, at specific times after the HCG injection to induce ovulation, the embryos were recovered and total cell counts made. These results were plotted and regression lines drawn.(ABSTRACT TRUNCATED AT 250 WORDS)