Biomedical Engineering Reference
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Fig. 9 Left panels : AFM image of live myocytes ( a , inset shows myofi bril structure), defl ection
image of fi xed cell ( b ), and fl uorescence image after staining for F actin. Center panels ( vertical )
show local contractile activity of beating atrial cell recorded with AFM tip, under 1.8 mM ( a ) and
5 mM ( b ) extracellular calcium ions, and 4 mM butanedione monoxime with 5 mM calcium con-
centration ( c ). Right panels ( vertical ): Micromechanical properties of quiescent atrial cells. Model
( a ) and indentation data ( b ). Response of a cell ( solid line ) to sinusoidal Z perturbation ( dashed
line ) ( c , four experimental conditions). Frequency spectra of magnitude and phase of transfer func-
tion ( d ) on cells, and ( e ) using mechanical analogue. Bottom right : Changes in cell stiffness during
single contraction. For details, see text and Shroff et al. ( 1995 )
4.2
Cell Mechanics
Proper cellular function is dependent on biochemical processes as well as cytoskel-
etal structure. Reorganization of cytoskeleton and changes in its mechanical proper-
ties play key roles in cell development and growth (Lal et al. 1995 ) . The local
mechanical properties of a cell are closely associated with biochemical gradients
across the membrane, but most techniques to study single cells average over the
entire cell (Brady 1991 ). AFM gives the opportunity to measure the mechanical
properties of cells with high spatial resolution. For instance, rat atrial myocytes
were imaged showing clearly the cytoskeletal network beneath the cell membrane
and myofi brillar structure [ Fig. 9 , left panel (Shroff et al. 1995 ) ].
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