Numerical and experimental study of extremely low frequency (ELF) electromagnetic field effects on excitable cells

Interest in the interaction of extremely low frequency (ELF) electromagnetic fields with biological systems has been driven not only by concerns of possible human health hazards, but also by the significant progress in developing beneficial applications in diagnostic procedures and therapeutics. Experimental studies with cells in vitro indicate that the observed interactions depend on the E-fields, either applied or induced by time-varying magnetic fields. Moreover, there has been a consensus that the site of interaction appears to be the cell membrane, since changes in ion transport, antibody binding, and G protein activation have been reported in many studies. However, there has been a paucity of information on the levels and spatial distribution of these fields in the vicinity of cells and cell aggregates as well as a lack of a satisfactory explanation on how these fields couple to cells.;The goal of this thesis was to provide a basic understanding of how E-fields (either applied or induced by time-varying magnetic fields) interact with excitable cells. To address this issue, two basic approaches were used. The first involved numerical modeling employing the finite element method. Perturbations in the magnitude and spatial distribution of the E-fields and currents due to the presence of realistic three-dimensional cell morphologies in cell culture preparations exposed to 60 Hz magnetic fields have been computed. In addition, spatial variations in membrane potential of realistic models of single cells as well as chains/aggregates of cells due to the coupling of the E-fields to these cells have been computed. The magnitude and distribution of the induced current density is observed to be substantially affected by cell shape, proximity of cells to each other, and cell orientation with respect to the induced current.;In the second approach, experimental techniques employing fluorescence imaging and a voltage sensitive dye (di-8-ANEPPS) have been used. Spatial variations in membrane potential of single chromaffin cells as well as more complicated arrangements of cells such as occur in tissues due to the exposure to an applied DC E-field were mapped. The combination of the two approaches identified several parameters that may influence the response of cells to E-fields.