Development of mouse embryos following the destruction of blastomeres

Preimplantation mouse embryos in different stages of development were cultured in vitro following the puncture of one or more blastomeres through the zona pellucida. The percentage of embryos that developed to the blastocyst stage was lower when puncturing was done in later stages than in earlier stages, thus showing that regulation capability diminishes as development proceeds. Cell debris of punctured blastomeres were always found under the zona pellucida, in any sector of the blastocyst, and did not prevent the sealing between the underlying cells. The plasma membrane of the punctured blastomeres vacuolized and disappeared within minutes of the operation. The space left by punctured external blastomeres of 16-cell morulae was filled by neighbour peripheral cells and not by inner cells, suggesting cell differentiation prior to blastocoel formation.