303 research outputs found
Cytoskeleton and Cell Motility
The present article is an invited contribution to the Encyclopedia of
Complexity and System Science, Robert A. Meyers Ed., Springer New York (2009).
It is a review of the biophysical mechanisms that underly cell motility. It
mainly focuses on the eukaryotic cytoskeleton and cell-motility mechanisms.
Bacterial motility as well as the composition of the prokaryotic cytoskeleton
is only briefly mentioned. The article is organized as follows. In Section III,
I first present an overview of the diversity of cellular motility mechanisms,
which might at first glance be categorized into two different types of
behaviors, namely "swimming" and "crawling". Intracellular transport, mitosis -
or cell division - as well as other extensions of cell motility that rely on
the same essential machinery are briefly sketched. In Section IV, I introduce
the molecular machinery that underlies cell motility - the cytoskeleton - as
well as its interactions with the external environment of the cell and its main
regulatory pathways. Sections IV D to IV F are more detailed in their
biochemical presentations; readers primarily interested in the theoretical
modeling of cell motility might want to skip these sections in a first reading.
I then describe the motility mechanisms that rely essentially on
polymerization-depolymerization dynamics of cytoskeleton filaments in Section
V, and the ones that rely essentially on the activity of motor proteins in
Section VI. Finally, Section VII is devoted to the description of the
integrated approaches that have been developed recently to try to understand
the cooperative phenomena that underly self-organization of the cell
cytoskeleton as a whole.Comment: 31 pages, 16 figures, 295 reference
Focus on the Physics of Cancer
Despite the spectacular achievements of molecular biology in the second half
of the twentieth century and the crucial advances it permitted in cancer
research, the fight against cancer has brought some disillusions. It is
nowadays more and more apparent that getting a global picture of the very
diverse and interlinked aspects of cancer development necessitates, in synergy
with these achievements, other perspectives and investigating tools. In this
undertaking, multidisciplinary approaches that include quantitative sciences in
general and physics in particular play a crucial role. This `focus on'
collection contains 19 articles representative of the diversity and
state-of-the-art of the contributions that physics can bring to the field of
cancer research.Comment: Invited editorial review for the `Focus on the Physics of Cancer'
published by the New journal of Physics in 2011--201
Universal Critical Behavior of Noisy Coupled Oscillators
We study the universal thermodynamic properties of systems consisting of many
coupled oscillators operating in the vicinity of a homogeneous oscillating
instability. In the thermodynamic limit, the Hopf bifurcation is a dynamic
critical point far from equilibrium described by a statistical field theory. We
perform a perturbative renormalization group study, and show that at the
critical point a generic relation between correlation and response functions
appears. At the same time the fluctuation-dissipation relation is strongly
violated.Comment: 10 pages, 1 figur
Stress Clamp Experiments on Multicellular Tumor Spheroids
The precise role of the microenvironment on tumor growth is poorly
understood. Whereas the tumor is in constant competition with the surrounding
tissue, little is known about the mechanics of this interaction. Using a novel
experimental procedure, we study quantitatively the effect of an applied
mechanical stress on the long-term growth of a spheroid cell aggregate. We
observe that a stress of 10 kPa is sufficient to drastically reduce growth by
inhibition of cell proliferation mainly in the core of the spheroid. We compare
the results to a simple numerical model developed to describe the role of
mechanics in cancer progression.Comment: 5 pages, 4 figure
Undulation Instability of Epithelial Tissues
Treating the epithelium as an incompressible fluid adjacent to a viscoelastic
stroma, we find a novel hydrodynamic instability that leads to the formation of
protrusions of the epithelium into the stroma. This instability is a candidate
for epithelial fingering observed in vivo. It occurs for sufficiently large
viscosity, cell-division rate and thickness of the dividing region in the
epithelium. Our work provides physical insight into a potential mechanism by
which interfaces between epithelia and stromas undulate, and potentially by
which tissue dysplasia leads to cancerous invasion.Comment: 4 pages, 3 figure
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