Figure 1.

The behavior of a cell in the different portions of a natural cAMP wave propagated in a population of developing Dictyostelium discoideum amoebae (A) and in a temporal wave of cAMP generated in a perfusion chamber in the absence of a spatial gradient of cAMP (B). The cyclic behavior of cells responding to natural waves of cAMP is similar to that of cells responding to the different portions of a simulated wave (a, b, c, and d) in all aspects but one. While cells in the front of a natural wave all move in a persistent manner in the same direction (i.e., toward the aggregation center, the source of the wave), cells in the front of a simulated temporal wave move in a persistent manner in all directions. From the similar cyclic pattern of behaviors, the portions of the natural wave were deduced from the known portions of the in vitro generated temporal wave (Wessels et al., 1992). The heavy arrow in (A) indicates the direction of spreading of the nondissipating, relayed natural wave. The bold print in point b refers to the one difference between the behavior in a natural wave and the behavior in a simulated temporal.