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Interaction of Extremely Low–Frequency Electromagnetic Fields
4.5.2.3 Coupling with Other Models
Tenforde (1992) mentioned that an important aspect of understanding the possible effects
of ELF EMF on living systems is the analysis of ionic and molecular pathways involved
in the interaction of these fields at the cellular and subcellular levels, called microscopic
dosimetry. The interactions between the applied magnetic fields and living systems
depend on the induced electric fields and currents. So, microdosimetry is used to characterize the induced electric fields and currents at a cellular level when cells are exposed to
magnetic fields. There have been several studies on the calculation of the induced electric
fields and currents in biological cells exposed to ELF EMF. Hart (1996) showed the current densities and electric field distributions induced in the simplified two-dimensional
cell cultures in a petri dish exposed to ELF magnetic fields. In this case, the cells were
regarded as conducting squares surrounded by insulating membranes. The gap junctions
were considered to connect the interiors of adjacent cells. For vertically applied magnetic
fields only, the induced currents and the electric field distributions may deviate from the
homogeneous medium model when the cells bind tightly with each other. The presence
of a gap junction can produce large transmembrane electric fields or intracellular current densities. Using three-dimensional IM, Stuchly and Xi (1994) computed the average
magnetic field induced electric fields and currents of two simplified, more realistically
modeled cells placed in a petri dish containing culture medium. They considered a cell
monolayer with a random distribution of different cell densities and a cell monolayer with
gap junctions. In this study, biological cells were represented by cubes due to the limitations of the computational method. The cell monolayer with random distributions showed
that the pattern of the induced current flow for higher cell densities had a limited dependence on the size and shape of the cell container. Perturbations in the spatial distribution
of the induced currents were observed when the cells bound with each other in a monolayer. The authors pointed out that the cell densities and cell positions in the culture dish
were important factors in determining the induced current distribution. Gap junctions
increased the current densities only when their resistance was sufficiently low. The authors
emphasized that these results highlighted the complexities involved the determination of
the induced current patterns and magnitudes even in a simple preparation of biological
cells. This was nearly similar to the results obtained by Hart (1996). These results give
insights into macroscopic dosimetry.
Hassan et al. (2003) calculated the induced current perturbations in the vicinity
of excitable cells exposed to ELF magnetic fields. In order to calculate the current
densities, realistic three-dimensional cell models were used. Three cell morphologies,
single spherical adrenal chromaffin cells, single elongated smooth muscle cells, and
chromaffin cells, were modeled and calculated using FEM. For a spherical cell, the
alterations of the magnitude and spatial distribution of the induced current densities
in the immediate vicinity of the cells were obtained. For an elongated cell, cell orientation with respect to the direction of the induced currents highly influenced the induced
current densities. These results gave insights into how magnetic field induced electric
fields can be applied to target specific cellular processes at the whole tissue level. A simpler model developed by Tarao, Hayashi, and Isaka (2000, 2001) was used to calculate
the distributions and characteristics of the induced currents in the modeled structure