INVERSELY CORRELATED CYCLES IN SPEED AND TURNING IN AN AMEBA - AN OSCILLATORY MODEL OF CELL LOCOMOTION

Previous biophysical models of ameboid crawling have described cell mo vement in terms of a persistent random walk. Speed and orientation wer e treated in the latter model as independent and temporally homogeneou s stochastic processes. We show here that, at least in the case of Dic tyostelium discoideum, both speed control and reorientation processes involve a deterministic, periodic component. We also show that the pro cesses are synchronized and negatively correlated, as was suggested by earlier findings. That is, increased turning correlates with periods of slow movement. Therefore, previous models are inconsistent with the behaivor of cells. Using a heuristic approach, we have developed a ma thematical model that describes the statistical properties of the cell 's velocity and movement of its centroid. Our observations and the mod el are consistent with the phenomenological description of ameboid mot ility as a cyclic process of pseudopod extension and retraction.