Biology Reference
In-Depth Information
(a)
(b)
(c)
Figure 18.1.
The cytoskeleton of mouse ibroblasts consists of actin (a), microtubules
(b) and intermediate ilaments (c). Scale bars = 10 μm.
18.2 APPROACHES TO STUDYING FORCE TRANSMISSION IN
CELLS
Historically, interest in the mechanical properties of cells and tissues
stems almost from the moment of their discovery. Using some of the irst
microscopes in the seventeenth century, motion of particles in and around
cells was observed. From these microscopic movements, early scientists
postulated that measurements could be taken that would allow for estimates
of viscosity and other physical properties.
Technology at the time did
not allow for quantitative measurements, and it was not until the early
twentieth century that many physical properties began to be determined.
31
Many research groups around the world are investigating the phenomena
of mechanotransduction and force transmission through cells, using a
variety of techniques, and several different models now exist to explain the
observed effects. Though the exact process of mechanotransduction and
force transmission and their pathways have yet to be elucidated, there is
consensus in which cellular structures appear to play an important part.
Foremost among these are the cytoskeleton and its connections to the
extracellular environment through the ERMs, focal adhesion complexes and
mechanosensitive ion channels.
In the late 1980s, a variety of approaches were being employed to
determine the mechanical properties of living cells and intracellular
structures.
31
The most commonly used techniques at the time were
micropipette aspiration,
34
a rudimentary cell poker
36,37
and application of a
shear, twisting force using magnetic ields and ferromagnetic beads.
32-35
32,33,38,39
Micropipette aspiration involves suction of a portion of the cell into a tube
with a diameter of a few micrometres (usually between 1 and 8 μm), using
a known suction pressure (typically between 0.1 and 105 Pa). The geometry
and known pressure are then used to determine the mechanical properties
of the cell.
40
Early work investigated the viscoelasticity and cortical tension
of red blood cells.
34
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