Fig. 1. PLP mRNA in situ hybridization in primary rat oligodendrocyte cultures. Phase contrast image analysis shows bipolar processes that are characteristic of progenitors (A), multiple branched processes characteristic of oligodendrocytes (C), and flat fibroblastic morphology of astrocytes (E). Brightfield images show that PLP mRNA was not detectable in cultured progenitors (B, same field as A) or astrocytes (F, same field as E). High levels of PLP mRNA (blue/black signal) accumulated in differentiated oligodendrocytes (D, same field as C). Bar, 50 µm.