Biomedical Engineering Reference
In-Depth Information
synchronizing the neurons prior to glucagon stimulation did not influence the
cellular changes observed. The process of partial and full synchronization of
the cells resulted in different responses. For full synchronization, the addition
of the serum bolus triggered resonant frequency and motional resistance shifts
of
þ
75Hz and
þ
18.5 ohms, respectively, which decayed back to baseline levels
after 30mins. The duration of this decay closely matched the time required for
full synchronization in a separate study.
24
The changes observed for partial
synchronization were significantly different from full synchronization as the
baseline levels in both resonant frequency and motional resistance were not re-
achieved indicative of the cell-sensor system detecting the difference between
full and partial synchronization. Immunocytochemistry and reverse tran-
scriptase-polymerase chain reaction (RT-PCR) studies on these cells supported
the results obtained with the TSM.
Finally, with respect to the experimental use of acoustic wave physics, the
interfacial behavior of hypothalami has been investigated.
25
The surface
attachment of the two cell lines outlined immediately above were investigated in
terms of solution flow, the absence of serum proteins, the effect of reducing
specific cell-surface interactions and the disruption of the neuronal cyto-
skeleton components. With respect to adhesion and deposition of neurons, f
s
and Rm shifts were clearly correlated to the amount of adhered neurons on the
sensor surface, whereas non-adhered neurons did not produce any significant
change in the monitored parameters. In the absence of serum proteins, initial
cell adhesion was followed by subsequent cell death and removal from the
sensor surface. The presence of the peptide, GRGDS, was observed to
significantly reduce cell-surface specific interactions compared with the control
of SDGRG and this produced fs and Rm responses opposite in direction to
that observable for cell adhesion. Cytoskeletal studies, using the drugs noco-
dazole (10mM), colchicine (1mM), cytochalasin B (10mM) and cytochalasin
D (2mM) all elicit neuronal responses that were by phalloidin actin-filament
staining.
d
n
4
t
3
n
g
|
2
n
3
.
5.2.6 Origin of Oscillations and Neuronal Resonance
We choose here to comment on neural oscillations in the light of those
described above that are detected by acoustic physics. The mechanism of
oscillations and neural resonance is fundamental for the functioning of the
human brain. Berger was the first to record the brain rhythms in 1929.
31
Since
then, electroencephalographic patterns have been studied intensively during
different states of consciousness, such as wake and sleep intervals, hypnosis,
anesthesia or epileptic states, when loss of consciousness is expected. Later, the
interest in associating brain oscillations to complex cognitive operations
diminished significantly. Recent observations on single neurons capable of
oscillating and resonate at specific frequencies within neural networks have
renewed the interest in oscillatory explanations of cognition.
Complex analysis shows that oscillatory patterns during sleep can be related
to those occurring during a previous wake period, although at smaller
