Fig. 7. The behavior of a representative JH10 cell (A), mhcA^- cell (B), 3XALA cell (C) and 3XASP cell (D) in a series of four simulated temporal waves of cAMP. Instantaneous velocity of each cell is plotted as a function of time for each cell. The estimated waves of cAMP are plotted at the top. Difference pictures are presented for each cell in the front, peak and back of the third wave. Velocity above an arbitrary threshold line drawn from 4 to 2 µm per minute over the 28-minute period of analysis was color-coded yellow to accentuate the velocity surges in response to the front of the second, third and fourth wave for JH10 and 3XALA cells, but not for mhcA^- and 3XASP cells. In difference pictures, expansion zones are color-coded green and contraction zones red.