Fig. 2. Ventral explants provide a chemorepulsive cue for intermediate explant derived migratory oligodendrocyte precursors. (A) The migration pattern of O4-positive cells from isolated stage 29 intermediate explants was uniformly radial after 3 days in culture. (B) Co-culture of ventral and intermediate explants resulted in non-radial migration of O4-positive cells. More cells migrated away from than toward to the ventral explant. Asterisk indicates position of the ventral explant. (C,D) The morphology of O4-positive cells proximal and distal from the ventral explant was subtly different. Distally (D), O4-positive cells had longer processes, whereas proximally (C) they had shorter and frequently multiple processes. Asterisks in C,D indicate location of intermediate explants. Scale bars: in A, 100 µm for A,B; in D, 20 µm for C,D.