Biomedical Engineering Reference
In-Depth Information
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Figure 5.13
Series resonant frequency shifts for neurons held at 37 1C with addition
of KCl. Black arrows indicate the addition of 15 mM, 30 mM, 60mM
and repeat sequentially. The gray arrows indicate wash-offs. Controls are
shown to the left, from top to bottom: laminin 2 mgcm
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, bare crystal
and cell attachment matrix 5 mgcm
2
.
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(Reprinted by kind permission of the Royal Society of Chemistry.)
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eux of K
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and depolarization of the membrane. Figure 5.13 shows the
frequency response of the cultured neurons to additions of KCl. There are clear
shifts in both fs and Rm. Typical changes in fs for 15, 30 and 60mM KCl
additions were 54, 80 and 142Hz, respectively.
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Analogous changes in Rm for
these KCl additions were 7, 13 and 23 ohms, respectively.
As for the experiments described above, the precise relationship between the
acoustic physics and the depolarization event begs an explanation. In this
regard it is appropriate to consider the nature of propagation of the acoustic at
the cell-sensor interface. The penetration depth of the acoustic wave (decay
length) is of the order of 500 nm in the presence of cells (for a cytoplasmic
viscosity of 5 cP, five times that of water). Accordingly, the acoustic wave will
probe the extracellular membrane (ECM), the cell membrane (lipid bilayer)
typically 10 nm, and also a part of the cytoplasm of the cells. The results,
therefore, appear to indicate that the sensor is detecting not only changes in
charge characteristics but also cellular structural alterations. Possibilities for
the latter may well result from perturbation of coupling between the ECM and
cell, together with membrane viscoelastic effects.
Research has also been conducted on the synchronization of the circadian
rhythm generator of neurons with reference to the effects of glucagon.
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Under
the influence of glucagon, the neurons (two lines, mHypoE-38s and
mHypoE-46) display both short- and long-term changes The effect of
