Fig. 4. Effect of Endo N on the directional migration of OPCs in response to PDGF. Top view (A) and cross section (B) of Dunn chamber (drawn after Allen et al., 1998) with the overlying coverslip show the position of the inner well, bridge and outer well. Cells over the annular bridge between the inner and outer well of the chamber can be observed under phase-contrast optics (as shown in C). Cell migration was recorded automatically by time-lapse frame grabbing and the migration tracks were plotted in scatter diagrams (D-I) as described in Materials and Methods. The starting point for each cells is at the intersection between X and Y axes (0, 0), and data points indicate the final positions of individual cells at the end of the 6 hour recording period. Chemotaxis on poly-L-lysine (PL) (D-F,I) or laminin (G,H) was tested by placing PDGF at 100 ng/ml (D-H) or 400 ng/ml (I) in the outer well. The direction of the gradient is vertically upwards. In the presence of PDGF gradient, OPCs migrate toward PDGF and display clear directionality of migration (D,G,I). For chemokinesis (E), equal amounts of PDGF (5 ng/ml) were added in both inner and outer wells of the chamber. After PSA removal by Endo N treatment, these cells lose the chemotactic response to PDGF and migrate randomly (F,H). Arrow in C indicates the direction of the outer well of the Dunn chamber. Bar, 50 µm.