Fig. 3.

The proliferation rate of adult and perinatal OPCs in culture. Purified adult (P60) (A, C) and perinatal (P8) (B, D) OPCs were cultured at clonal density in serum-free medium containing PDGF and insulin. The number of cells per clone was determined after 4 d (A, B) and 8 d (C,D) of culture. Under these culture conditions, which lack T3, most of the clones consisted predominantly of OPCs. Note that the average size of adult OPC clones is significantly smaller than is that of the perinatal clones.