Biomedical Engineering Reference
In-Depth Information
(A)
(B)
40
30
20
10
0
CMF (nm)
Figure 5.3
Normal CMF displayed as color code over the shape of the RBC for a representative healthy
(A) and ethanol-fixed cell (B). Inset contains the mean
SD (nm) of the CMF of the
representative cell. Source: Modified from Ref.
[142]
.
6
As the measured CMF amplitude corresponds to fluctuations with an orientation parallel to
the coverslip and not to the RBC membrane, further corrections should be applied to take
into account the membrane slope and extrapolate the real fluctuations amplitude, normal to
the membrane, described in Ref.
[142]
(
Figure 5.3
).
The local phase shift is proportional to the specimen thickness with an accuracy of
5
10 nm. As a noninvasive full-field technique, DHM is particularly well suited to assess
and study membrane fluctuations of a large number of cells simultaneously. CMF have a
mean fluctuation amplitude of 47 nm amplitudes and are heterogeneously distributed on the
cellular surface and seem to correlate with the biconcave equilibrium shape of erythrocytes
[141,153]
.
5.3.5 Neuroscience
Glutamate is the major excitatory neurotransmitter in the central nervous system and
contributes to the synaptic transmission between neurons. One of its main actions is
mediated by the glutamate N-Methyl-D-aspartate (NMDA) receptor which allows the flow
of Na
1
and small amounts of Ca
2
1
ions into the cell and K
1
out of the cell in a voltage-
dependent manner. The NMDA receptor is the predominant molecular device for
controlling synaptic plasticity and memory function.
The passive diffusion or active transport of water through the plasma membrane is
associated with several cellular processes. As far as the nervous system is concerned, the
neuronal activity, i.e., mediated by the release of glutamate, has been shown to result in cell
swelling linked to water diffusion. Consequently, neuronal volume changes could be used
as an indirect marker of neuronal activity with relevance to functional imaging.
At the cellular level, the monitoring of absolute cell volume as well as the associated
transmembrane flow of water can be achieved by DHM with recent studies having shown that
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