Biomedical Engineering Reference
In-Depth Information
Figure 3.6.
The final state of the formation of a single spiral domain from a
counter-rotating spiral pair, due to an infinitesimal initial gradient in
G
(see [13] for
details). Figure is reprinted from [13]. (Copyright (1998), with permission from The
American Physical Society).
Understanding the typical structures seen in a fully developed wavefield
is more straightforward than understanding the dynamical process whereby
the wavefield is formed from an initially quiescent set of cells. Observations
reveal that immediately after starvation sets in, there is no wave activity
among the
Dictyostelium
cells. After a few hours, a few bursts can be detected;
these waves propagate short distances and then die away. Subsequently, this
activity becomes more pronounced and, depending on the cell density, one
of two patterns emerge. At low density, some of the sites responsible for the
initial bursts go into a spontaneously oscillating mode and become periodic
pacemakers, sending out circular waves and leading to target patterns that
govern the eventual chemotactic motion. If the cell density is higher, the
initial bursts lead to rotating spiral waves that entrain the local pacemakers
and thereafter dominate the wavefield. A typical set of wavefield snapshots,
