Fig. 7. Electron microscopic analysis of Dlk⁺ cells before and after the culture. Dlk⁺ cells isolated from E14.5 fetal liver and the cells collected from the low density culture were fixed and used for preparing thin sections for transmission-electron microscopy. (A) E14.5 Dlk⁺ cells exhibited a round-shaped nucleus, small nucleolus and elongated mitochondria. (B) Cells cultured at low density showed characteristics distinct from freshly isolated cells. A typical type of cells is shown. There are many microvilli on the surface, a cleaved nucleus, larger nucleolus, and many round-shaped mitochondria in the cytoplasm. Bars, 2 µm.