The blebbing response of 2-4 cell stage mouse embryos to cytochalasin B.

In light and electron microscopic examination of 2–4-cell stage mouse embryos, the embryos showed transitory blebs on the blastomere surface when cytochalasin B (CB) was applied shortly before or after mitosis. A similar effect was obtained in blastomeres removed from the drug at these stages but not in blastomeres maintained in the continued presence of the drug. CB also promoted the precocious deposition of crystalloid bodies and inhibited the formation of intercellular contacts. Microvilli and coated pits were not affected.