Effects of ELF electric fields on the isolated frog heart.
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A number of physical and chemical agents in the environment have been studied for their ability to induce or alter DNA repair mechanisms in human cells. We have investigated the effects of 60 Hz, 1000 V/cm electric fields on DNA repair in normal human fibroblasts in vitro. An examination was done on the ability of electric fields suspected to cause damage which could be repaired by thymine dimer excision and measurable by the bromodeoxyuridine photolysis assay. The thymine dimer assay with enzyme-sensitive site analysis was used to measure the cells' capacity for removing ultraviolet light (u.v.)-induced pyrimidine dimers; during exposure to electric field 24 hr before u.v. irradiation; 24 hr after u.v. irradiation; and up to 48 hr continuously after u.v. irradiation. Cell growth and cell survival following electric field exposure were also studied. Within the limits of these experiments, it was found that exposure to such electric fields did not alter cell growth or survival, and no DNA repair or alteration in DNA excision repair capacity was observed as compared with unexposed control cultures.
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A study was carried out to determine possible effects of 60-Hz electromagnetic-field exposure on pineal gland function in humans. Overnight excretion of urinary 6-hydroxymelatonin sulfate (6-OHMS), a stable urinary metabolite of the pineal hormone melatonin, was used to assess pineal gland function in 42 volunteers who used standard (conventional) or modified continuous polymer wire (CPW) electric blankets for approximately 8 weeks. Volunteers using conventional electric blankets showed no variations in 6-OHMS excretion as either a group or individuals during the study period. Serving as their own controls, 7 of 28 volunteers using the CPW blankets showed statistically significant changes in their mean nighttime 6-OHMS excretion. The CPW blankets switched on and off approximately twice as often when in service and produced magnetic fields that were 50% stronger than those from the conventional electric blankets. On the basis of these findings, we hypothesize that periodic exposure to pulsed DC or extremely low frequency electric or magnetic fields of sufficient intensity and duration can affect pineal gland function in certain individuals.
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The aim of the study was to investigate the possible acute effects of exposure to electric and magnetic fields. Twenty six experienced linesmen, aged 25 to 52, were studied during two working days while performing a simulated routine inspection of insulators on steel poles of a 400 kV power line. During one of the working days the inspection was performed on a power line in operation and on the other day the same procedure was performed on an identical power line, which was not in operation. The two days were found to be comparable with regard to the physical workload which, on the basis of heart rate measurements, was estimated to be high. Exposure to the electric and magnetic fields was measured using a device designed for on-worker sampling on each linesman. The mean exposure for the working day was estimated to be 2.8 kV/m (SD = 0.35) and 23.3 microT (SD = 4.2). The possible effects of exposure were studied using a battery of four automated performance tests, EEG, a mood scale, and a questionnaire to assess subjective symptoms. All workers were examined immediately before and after each workday. Furthermore, blood samples were collected for each subject on three different occasions during each workday. The battery of behavioural tests comprised a test of simple reaction time, a vigilance test, a test of short term memory (digit span), and a perceptual test (symbol digit). The four EEG recordings for each worker were judged blindly and sorted with regard to amount and stability of alpha activity. The blood samples were used for an analysis of possible changes during the workday with regard to the following hormones: thyroid stimulated hormone, luteinising hormone, follicle stimulating hormone, prolactin, cortisol, testosterone, and neopterin. Detailed analyses of the results using both parametric and nonparametric tests showed no statistically significant difference between the two conditions which could be attributed to exposure to electric and magnetic fields.
OBJECTIVE: The purpose of this study was to evaluate the role of the Ets factor NERF in the regulation of the Tie1 and Tie2 genes during chicken blood vessel development. METHODS AND RESULTS: We have isolated the full-length cDNA for the chicken homologue of the human Ets factor NERF2 (cNERF2). Northern blot analysis and in situ hybridization demonstrate that cNERF2 is enriched in the developing blood vessels of the chicken chorioallantoic membrane. Interestingly, cNERF2 functions as a competitive inhibitor of a highly related Ets factor cELF-1, which we have previously shown to be enriched in chicken blood vessel development. Although in vitro-translated cELF-1 and cNERF2 can bind equally well to conserved Ets binding sites in the promoters of the Tie1 and Tie2 genes, cELF-1 preferentially binds to the Ets sites in these promoters during early stages of chicken blood vessel development, suggesting that cNERF may bind during later stages of blood vessel development and vascular remodeling. CONCLUSIONS: cNERF2 is enriched during embryonic and extraembryonic blood vessel development in the chicken and facilitates tight control of Tie1 and Tie2 gene regulation.
We have examined mutations in the supF gene carried by pTN89 plasmids in Escherichia coli (E. coli) to examine the effects of extremely low frequency magnetic fields (ELFMFs) and/or X-rays to the plasmids. The plasmids were subjected to sham exposure or exposed to an ELFMF (5 mT), with or without X-ray irradiation (10 Gy). For the combined treatments, exposure to the ELFMF was immediately before or after X-ray irradiation. The mutant fractions were 0.94x10(-5 )for X-rays alone, 1.58x10(-5) for an ELFMF followed by X-rays, and 3.64x10(-5) for X-rays followed by an ELFMF. Increased mutant fraction was not detected following exposure to a magnetic field alone, or after sham exposure. The mutant fraction for X-rays followed by an ELFMF was significantly higher than those of other treatments. Sequence analysis of the supF mutant plasmids revealed that base substitutions were dominant on exposure to X-rays alone and X-rays plus an ELFMF. Several types of deletions were detected in only the combined treatments, but not with X-rays alone. We could not find any mutant colonies in sham irradiated and an ELFMF alone treatment, but exposure to ELFMFs immediately before or after X-ray irradiation may enhance the mutations. Our results indicate that an ELFMF increases mutation and alters the spectrum of mutations.
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