Analysing the motile behaviour of cells: a general approach with special reference to pairs of cells in collision.

As a measure of the change in motion of locomoting cells, acceleration has several advantages over more conventional measures such as rate of change in speed and rate of change in direction. In particular the instantaneous acceleration vector associated with a specific event, such as the collision of the cell with another, may be correlated with directional information contained in the structure of the cell and in the geometrical configuration of the event. It is hoped that this will prove to be a generally useful method for examining the relation between cell structure and motion during both normal and aberrant behaviour. Preliminary results obtained with this method to examine the changes in motion of a normal cell and a malignant cell on colliding with each other are already of interest for elucidating the mechanism of contact inhibition of locomotion and its failure during malignant invasion.