ELF in vitro exposure systems for inducing uniform electric and magnetic fields in cell culture media

Abstract

Many in vitro experiments on the biological effects of extremely low frequency (ELF) electromagnetic fields utilize a uniform external magnetic flux density (B) to expose biological materials. A significant number of researchers do not measure or estimate the resulting electric field strength (E) or current density (J) in the sample medium. The magnitude and spatial distribution of the induced E field are highly dependent on the sample geometry and its relative orientation with respect to the magnetic field. We have studied the E fields induced in several of the most frequently used laboratory culture dishes and flasks under various exposure conditions. Measurements and calculations of the E field distributions in the aqueous sample volume in the containers were performed, and a set of simple, quantitative tables was developed. These tables allow a biological researcher to determine, in a straightforward fashion, the magnitudes and distributions of the electric fields that are induced in the aqueous sample when it is subjected to a uniform, sinusoidal magnetic field of known strength and frequency. In addition, we present a novel exposure technique based on a standard organ culture dish containing two circular, concentric annular rings. Exposure of the organ culture dish to a uniform magnetic field induces different average electric fields in the liquid medium in the inner and outer rings. Results of experiments with this system, which were reported in a separate paper, have shown the dominant role of the magnetically induced E field in producing specific biological effects on cells, in vitro. These results emphasize the need to report data about the induced E field in ELF in-vitro studies, involving magnetic field exposures. Our data tables on E and J in standard containers provide simple means to enable determination of these parameters.

Numerical computation of distortions in magnetic fields and induced currents in physiological solutions produced by microscope objectives

“…Figure 8 shows the induced current density along a radial line (y-axis) from the center to the edge of the Petri dish. Also shown in Figure 8 is the theoretically calculated induced current in the Petri dish obtained from the equation [Bassen et al, 1992]:…”

“…The dish contained a 4 mm height of a physiological buffer whose electrical conductivity was assumed to be 1.5 S/m [Bassen et al, 1992]. The objective was placed 2 mm below the Petri dish in the``inverted microscope'' position.…”

Measurement support for the U. S. electric-power industry in the era of deregulation, with focus on electrical measurements for transmission and distribution

“…The fields are also readily verified experimentally [145,148,149] An electrical model of a biological cell used by researchers includes the assumption that the cell membrane and ion conducting channels that penetrate the membrane can be represented as a capacitor (the membrane) and resistors (the ion channels) in parallel [151]. One method for verifying aspects of this model is by applying alternating extremely-low-frequency electric fields across a planar membrane and examining the real and imaginary components of the current through the membrane for one or more ion channels, that is, as the frequency of the electric field is varied, the rms value of the current through the resistors should remain unchanged.…”

“…Induced electric fields in cell culture media for widely dispersed cells in suspension are readily modeled, as illustrated in a number of publications [145,146,147,148,149]. The fields are also readily verified experimentally [145,148,149] An electrical model of a biological cell used by researchers includes the assumption that the cell membrane and ion conducting channels that penetrate the membrane can be represented as a capacitor (the membrane) and resistors (the ion channels) in parallel [151].…”

Neuronal differentiation of chromaffin cells in vitro, induced by extremely low frequency magnetic fields or nerve growth factor: A histological and ultrastructural comparative study

“…Primary chromaffin cell cultures were exposed to extremely low frequency magnetic fields as described by Bassen et al (1992) following the results derived by Drucker-Colín et al (1994). Cultures were placed between two coils, which were separated from each other at a distance of 21 cm.…”