Lily Soo

Increased levels of hsp70 transcripts induced when cells are exposed to low frequency electromagnetic fields

Abstract Previous experiments have shown that the steady state levels of some RNA transcripts are increased when cells are exposed to extremely low frequency electric or magnetic fields. Experiments have exposed a variety of cell types, including dipteran salivary gland cells, yeast and human HL-60 cells. The range of responsive transcripts includes oncogenes such as c-myc, as well as transcripts associated with growth and development. One hypothesized mechanism of how cells respond to electromagnetic (EM) fields assumes that the response represents or mimics a generalized physiological stress response. RNA from exposed HL-60 cells, previously shown to have increased transcript levels for c-myc, was analyzed for hsp70 transcripts levels. The hsp70 transcripts were found to be elevated in all cases, even though the cells were exposed to various fields at normal growth temperatures. The conditions of maximum induction for hsp70 were coordinate with those of c-myc. In yeast cells, the SSA1 gene (homologous to hsp70) was found to be elevated in cells exposed to EM fields at 0.8−80 μT. In the case of yeast, conditions for maximum induction of SSA1 were coordinate with those for URA3, the gene for uracil metabolism. Thus the model of cell interaction with electric and/or magnetic fields appears to be related to the stress response model for heat shock.

Enhancement of cytochrome oxidase activity in 60 Hz magnetic fields

Abstract 60 Hz magnetic fields accelerate the oxidation of cytochrome C , a reaction catalyzed by cytochrome oxidase, an electron transport enzyme of the mitochondrial redox chain. The effects of magnetic fields on this enzyme reaction are similar to effects on the Na,K-ATPase reaction. The acceleration due to the magnetic field, is inversely related to the basal enzyme rate. The greater the normal enzyme activity, the smaller the effect of an applied magnetic field. The acceleration varies with the magnetic field strength. The increase in the oxidation rate constant is 20–30% at field strengths below 3 μ T, and a factor of about 2 between 6–10 μ T. Data at low field strengths suggest that the threshold is below 0.5 μ T, in the same range as thresholds for Na,K-ATPase function (0.3 μ T) and stimulation of transcription ( μ T). The mobile charge interaction (MCI) model, which proposes that electric and magnetic fields interact with moving charges as they would in any conductor, was based on studies of the Na,K-ATPase enzyme reaction. Similar results with cytochrome oxidase support the MCI model in the interaction of magnetic fields with electron transfer during this oxidation reaction.

Changes in transcription in HL-60 cells following exposure to alternating currents from electric fields

Abstract The effect of varying field strength and exposure time on histone H2B and c- myc transcript levels in HL-60 cells exposed to 60 Hz electric fields (sine waves) is reported here. An increase in the basal levels of these normally expressed transcripts was observed, which was dependent on both field strength and time of exposure. β2-microglobulin, a transcript known to be uninducible, was unaffected by cellular exposure to the field strengths used in these experiments.

Electromagnetic acceleration of electron transfer reactions

The Moving Charge Interaction (MCI) model proposes that low frequency electromagnetic (EM) fields affect biochemical reactions through interaction with moving electrons. Thus, EM field activation of genes, and the synthesis of stress proteins, are initiated through EM field interaction with moving electrons in DNA. This idea is supported by studies showing that EM fields increase electron transfer rates in cytochrome oxidase. Also, in studies of the Na,K‐ATPase reaction, estimates of the speed of the charges accelerated by EM fields suggest that they too are electrons. To demonstrate EM field effects on electron transfer in a simpler system, we have studied the classic oscillating Belousov–Zhabotinski (BZ) reaction. Under conditions where the BZ reaction oscillates at about 0.03 cycles/sec, a 60 Hz, 28 μT (280 mG) field accelerates the overall reaction. As observed in earlier studies, an increase in temperature accelerates the reaction and decreases the effect of EM fields on electron transfer. In all three reactions studied, EM fields accelerate electron transfer, and appear to compete with the intrinsic chemical forces driving the reactions. The MCI model provides a reasonable explanation of these observations. J. Cell. Biochem. 80:278–283, 2001.

Optimal frequencies for magnetic acceleration of cytochrome oxidase and Na,K-ATPase reactions

Low frequency magnetic fields increase the activity of the membrane enzymes, Na,K-ATPase and cytochrome oxidase, and the increased activity varies with frequency. Optimal frequencies for increases in the reaction rate constant of cytochrome oxidase and in the rate of splitting of ATP by Na,K-ATPase differ by an order of magnitude, and are in the ranges of the turnover numbers of the respective enzyme reactions. The two frequency dependence curves are similar in that the slope of the low frequency portion is about 10 times greater than the slope of the high frequency portion. The greater slope indicates greater ability to adjust quickly in the low frequency range, which may be significant for optimal biological control of activity.

The effects of alternating currents on Na,K-ATPase function

Abstract We prepared Na, K-ATPase from rabbit kidney have studied the rate of ATP splitting when ac currents flow through the enzyme suspension via platinum electrodes/salt-impregnated agar gels. The ac signals covered an amplitude range of 1 mV–1 V (across an enzyme suspension resistance of 44 Ω) and a frequency range of 10–100,000 Hz. We found the ac decreased ATP splitting by the normal enzyme, with the maximum decrease in the range of 100–1000 Hz and at an estimated current density of about 0.5 mA/cm 2 . The ac signals could also increase the enzyme activity, but only when the control activity was low. The lowered enzyme activity was achieved by natural decay of the enzyme during storage under refrigeration, by lowering the temperature, and by introducing partially effective concentrations of ouabain. The ouabain experiments showed a different quantitative dependence of the enzyme activity on the electric current, suggesting the ac was antagonizing the inhibitory effect of ouabain, probably by increasing the effective K + ion concentration. Our experiments suggest that ac stimulated ion transport in erythrocytes, may be due to AC induced ion migration in solution that perturbs ion activation of the enzyme. The observed enhancement or inhibition of the Na,K-ATPase activity probably depends upon the effects of the ionic changes relative to the optimal ion ratios for activity.

Adsorption of Albumin on Rabbit Sperm Membranes

SummaryWhen mammalian sperm cells are exposed to solutions of albumin there are changes in the membranes of some species that resemble those that normally occur in the uterus prior to fertilization. We have shown that albumin molecules adsorb on to the membranes of ejaculated rabbit sperm cells, and that the equilibrium binding constant,K, (1) varies inversely with the albumin concentration, (2) is independent of the sperm cell concentration in the range 106–107 per ml, (3) is independent of the time of exposure of the sperm cells to the albumin solution, and (4) decreases in the presence of Ca++ and Mg++ ions. An unusual aspect of the adsorption is that if the albumin concentration is given the symbol [A],K[A] is a constant in our measurements. This means that for virtually the entire range of [A] studied, the sperm cells bind albumin so that half of the available surface is coated and half remains uncoated. This situation is rather remarkable and it suggests a role that adsorption could play in the physical processes preceding fertilization. In purely physical systems, the optimum for the bridging and flocculation of particles that are coated with adsorbed macromolecular films occurs when half of the available surface is covered. The sperm cell appears to provide the optimal situation for interacting with itself or with another surface.

EFFECTS OF LOW FREQUENCY MAGNETIC FIELDS ON NA,K-ATPASE ACTIVITY

Abstract Membrane Na,K-ATPase activity is affected in opposite ways by electric and magnetic fields. Under optimal conditions, enzyme activity is inhibited by electric fields and stimulated by magnetic fields. However, both fields cause large increases in enzyme activity when the initial (basal) activity of the enzyme is reduced greatly by aging, by lowering the temperature, or by inhibitors. With the enzyme under basal conditions, magnetic fields (in the range 0–70 Hz and 0–2 G) increase Na,K-ATPase activity 5–10%, with little dependence on field intensity. The optimal frequency in the range studied, around 60 Hz, is very close to the measured enzyme rate at 37 °C, suggesting that the magnetic field affects the ATPase reaction. The effect of an electric field is similar to an increase in binding of activating ions on the enzyme surface. Ion activation would also account for the observed frequency dependence of the electric field effect, as well as the difference between optimal frequencies for ion pump influx and efflux. Although effects of magnetic fields vary with enzyme activity, they cannot act through increases in ion binding, because the effects are in the opposite direction. Magnetic fields probably influence charge flow within the enzyme during the reaction.

Frequency dependence of cytochrome oxidase activity in magnetic fields

Abstract Magnetic fields increase the activity of cytochrome oxidase, apparently accelerating electron movements during the oxidation of cytochrome C . The increase due to magnetic fields varies inversely with the basal enzyme reaction rate. In this paper, we show that increases in the reaction rate constant in magnetic fields vary with frequency, in the range 10–2500 Hz, with a maximum in the range 500–1000 Hz. The frequency dependence of the cytochrome oxidase is similar to earlier described effects of electric and magnetic fields on the membrane enzymes, Na,K-ATPase and F 0 F 1 -ATPase, where optimal frequencies are in ranges of the turnover numbers of the enzyme reactions.

The Na,K-ATPase as a model for electromagnetic field effects on cells

The ATP-splitting activity of the membrane Na,K-ATPase can increase or decrease in alternating current (ac), depending on the level of enzyme activity in the absence of a field. Under optimal conditions, the ac decreases the activity; when the enzyme activity is lowered by ouabain or temperature, the ac increases the activity. Both effects are frequency dependent over a broad band, with maxima in the ELF range at about 100 Hz. The currents can be imposed with electrodes or induced from an alternating magnetic field. At 60 Hz, the threshold for inhibition by an induced ac electric field has been determined to be about 52 μV cm−1 a somewhat higher value than determined earlier at 100 Hz for currents imposed through electrodes.