| Bioelectric phenomena in cell membranes govern numerous vital functions in living organisms. Many biological effects of externally applied oscillatory electric fields are caused by field-induced changes of transmembrane potential. This produces a variety of biochemical and physiological responses in cells, tissues, and whole body, including nonlinear dielectric effects.;As part of this research program, the author contributed to the development of a new cardiovascular diagnostic technique, called impedance magnetocardiography (IMCG). We recorded impedance magnetocardiograms in a partially shielded environment using high temperature superconducting quantum interference devices (SQUIDs). IMCG measures changes in cardiac blood volume and thus holds potential for clinical diagnostics.;More recently, we measured the 2nd and 3rd harmonics generated by budding yeast (S. cerevisiae) and fission yeast (S. pombe ) cells as functions of applied frequency. The harmonic generation spectra exhibit peaks that correlate with activity of metabolic enzyme complexes. In particular, respiratory inhibitors, which shut down ATP production by suppressing mitochondrial electron transport chain (ETC) complexes, such as ATP-synthase, also suppress the observed peaks in harmonic response. This suggests that the observed nonlinear phenomena are due to modulation of the field across the mitochondrial inner membrane and its effect on the ETC complexes. We also measured the harmonics generated by vascular smooth muscle cells, which are closely related to cardiomyocytes. The observed 2nd and 3rd harmonics are strongly affected by butyrate, an inhibitor of histone deacetylase. In another effort, designed to explore new methods of measuring metabolic activity, we measured the frequency-dependent harmonics generated by a live earthworm ( Lumbricus terrestris) in response to sinusoidal fields.;Numerical simulations and analytical models provide powerful tools for understanding the behavior of biological systems. Thus, we performed simulations using a finite element method (FEM) model to interpret the experimental IMCG results. Finally, analytical models were developed to study the field-induced oscillatory contributions induced across outer plasma membranes and inner organelle membranes, in order to better understand the electromagnetic responses of live cells. |
