Fig. 7. Quantification of chemotaxis in Dunn chambers: v-Src abolishes this response. (A) Rat-1/tsLA29 fibroblasts; (B) MDCK/tsLA31 cells. Same procedure as for Fig. 2, except that 1.33 nM PDGF-BB or 1.66 nM EGF were introduced into the outer well of Dunn chambers, respectively. Recording of cell migration started after 30 minutes of chambers assembly, when a linear diffusion gradient of growth factors had been established. For quantification of directionality, orientation of each cell trajectory was determined in the three zones of decreasing growth factor concentrations defined at Fig. 5A (ranges are indicated below bar histograms and numbers of cells analysed in each group are specified in italics). The fraction of cells that had migrated towards the outer well (positive chemotactic response), the inner well, parallel to both wells of the chamber, or non-motile cells, was determined. Values are pooled from 4-8 experiments (^***P>0.001, ^**P<0.01, ^*P<0.05 by difference-in-probabilities test for the fraction of cells moving towards the growth factor source, as compared with no gradient; or depending on v-Src activation for a comparable level of growth factor/receptor complexes, as indicated by the horizontal bracket).