  We report the phenomenon of periodic shape oscillations occurring in 3T3
fibroblasts merely as a consequence of a loss of cell-substrate adhesion. The
oscillatory behavior can last many hours at a constant frequency, and can be
switched off and on using chemical agents. This robustness allows for the
extraction of quantitative data using single cells. We demonstrate that the
frequency of oscillations increases with increasing actomyosin contractility.
Both the Myosin Light Chain Kinase as well as the Rho Kinase pathways are shown
to operate during this process. Further, we reveal significant similarities
between the oscillatory dynamics and the commonly observed phenomenon of
blebbing. We show that both these processes ceases when extracellular calcium
is depleted or when stretch activated calcium channels are blocked. This, along
with the fact that these dynamical processes require actomyosin contactility
points towards strong similarities in the respective mechanisms. Finally, we
speculate on a possible mechanism for the observed dynamical phenomena.
