Fig. 2. Transfilter chemotaxis (A) and chemokinesis (B) of OPCs in response to PDGF. Purified OPCs were placed in the upper wells of the Boyden chamber, and cells that had migrated to the lower side of the filter were counted. (A) OPCs showed chemotaxis to PDGF placed in the lower well. This chemotaxis was inhibited by Endo N or by anti-PSA Ab. For Endo N-treated groups, cells were treated with Endo N for 6 hours before they were prepared for migration assay. In addition, Endo N was present in both upper and lower wells during the migration assay to prevent the recovery of PSA expression. For inactivation of PSA functions, anti-PSA Ab (2 µg/ml) was also applied to both upper and lower wells of the chemotaxis chamber. Values are expressed as a percentage of control value, i.e. the migration of OPCs without PDGF (100%=400±15 cells per mm²). Data represent the mean ± s.e.m. from at least three independent experiments. *P<0.05 and **P<0.01 by two-tailed unpaired t-test, compared with PDGF alone at the same concentrations. (B) PSA removal from the cell surface has no effect on random motility of OPCs stimulated by PDGF (chemokinesis). The same concentrations of PDGF were applied to both the upper and lower wells of the microchemotaxis chamber, so as to eliminate the gradients of PDGF. Chemokinesis of OPCs increases in the presence of PDGF, but PSA removal from the cell surface does not affect this process. Data represent the mean ± s.e.m. from at least three independent experiments.