| Abstract: | Embryoid bodies are produced when a transplantable testicular teratoma from strain 129 mice is serially passaged in the peritoneal cavity of these mice. These bodies are roughly spherical containing two morphologically distinct cell types. Scanning and transmission electron microscopy have been employed to show that the endodermal cells of embryoid bodies, like those of the mouse embryo, are on the outer surface and have highly convoluted surfaces containing numerous microvilli-like projections. The inner, embryonal carcinoma cells, are the pluripotent stem cells of this tumor. Intracisternal A-type particles have been observed in electron micrographs and are almost exclusively located in the endodermal cells of the embryoid bodies. The A-type complement-fixing antigen has been identified in extracts prepared from this tumor. When embryoid bodies are placed in culture and allowed to attach to the surface of a petri dish, a large number of new morphologically distinct cell types appear. Attachment to the petri dish surface is required for the generation of these new cell types. Cells of similar morphology in culture, display a distinctly “clonal” distribution on the petri dish surface. |
