Biomedical Engineering Reference
In-Depth Information
a developmental need within a cell cycle. In this second case a
cell nucleus is assumed to have dissolved, releasing its contents,
including the constituent elements of the spindle poles that are
charged and form microtubule attachments to the inside of the
membrane of some central cell. This process within a central cell
forms the biogenic electric field, causing the electrophoresis of
membrane proteins in a population of neighbouring cells. In these
cases very large enhancements can occur, for example, the liver
(
10
7
).
The speed of the overall division process can vary; it is known
fo,r instance, that in general malignant cancer cells proliferate
very rapidly relative to normal healthy cells. This fact can be used
to selectively destroy melanomas in the treatment using surface
dipoles devised by Kirson et al., as discussed inChapter 1.
A related effect to this picture of cell polarisation leading to
large enhancement of the initial signal occurs when a magnetic
effect is also present. The observation of dispersion levels across
the spectrum is thought to be due to various biological interactions,
including magnetorotation of cells. Dispersion levels involve com-
ponents of various sizes increasingly getting smaller as frequency
grows. Smaller and smaller time constants are involved. At the
ELF,
α
-dispersion, it is not only the size and the time constant
that determine the dispersion magnitude but also the enhancement
phenomenonofcell-cellcooperationacrosspopulationsofcellsthat
are undergoing membrane electrophoresis that cause ionic current
flows within the cell. The constrained membrane diffusion theory
discussed above is connected to the well-known voltage-gated
transmembranediffusiontheoryofHodgkinandHuxleywithitson-
gate potentials typically around 65 mV where cells are activated
from a resting state.
In a recent study static H fields of varying size 10, 14, 18 and
22 mT were shown to have an effect upon the dielectric response of
ratliver.Theratswerewhole-body-exposedtotheseintensities,one
hour daily for one week. The results showed noticeable variations
in normal values of,
σ
of liver tissue after exposure to all H field
intensities. This demonstrates the link between static H fields and
electrophoresis, as with other experiments where magnetorotation
of cells has been observed.
ε
liver
r
≈
