Ds. Adams, MECHANISMS OF CELL-SHAPE CHANGE - THE CYTOMECHANICS OF CELLULAR-RESPONSE TO CHEMICAL ENVIRONMENT AND MECHANICAL LOADING, The Journal of cell biology, 117(1), 1992, pp. 83-93
Processes such as cell locomotion and morphogenesis depend on both the
generation of force by cytoskeletal elements and the response of the
cell to the resulting mechanical loads. Many widely accepted theoretic
al models of processes involving cell shape change are based on untest
ed hypotheses about the interaction of these two components of cell sh
ape change. I have quantified the mechanical responses of cytoplasm to
various chemical environments and mechanical loading regimes to under
stand better the mechanisms of cell shape change and to address the va
lidity of these models. Measurements of cell mechanical properties wer
e made with strands of cytoplasm submerged in media containing deterge
nt to permeabilize the plasma membrane, thus allowing control over int
racellular milieu. Experiments were performed with equipment that gene
rated sinusoidally varying length changes of isolated strands of cytop
lasm from Physarum polycephalum. Results indicate that stiffness, elas
ticity, and viscosity of cytoplasm all increase with increasing concen
tration of Ca2+, Mg2+, and ATP, and decrease with increasing magnitude
and rate of deformation. These results specifically challenge assumpt
ions underlying mathematical models of morphogenetic events such as ep
ithelial folding and cell division, and further suggest that gelation
may depend on both actin cross-linking and actin polymerization.