Vijayalaxmi et al. · 2001
Researchers exposed peripheral blood samples from four healthy nonsmoking volunteers to 847.74 MHz CDMA radiation at SARs of 4.9 or 5.5 W/kg for 24 hours. Sham-exposed and gamma-irradiated (1.5 Gy) samples served as controls. No significant differences were found between RF-exposed and sham-exposed lymphocytes in mitotic indices, frequencies of exchange aberrations, excess fragments, binucleate cells, or micronuclei. Gamma-irradiated lymphocytes showed significantly different responses for all indices compared to both RF-exposed and sham-exposed cells. The authors concluded there was no evidence for induction of chromosome aberrations and micronuclei under these exposure conditions.
Vijayalaxmi et al. · 2001
Researchers exposed diluted peripheral blood from four healthy volunteers to 835.62 MHz RF radiation at SARs of 4.4 or 5.0 W/kg for 24 hours. Sham-exposed and gamma-irradiated (1.50 Gy) samples served as negative and positive controls, and lymphocytes were cultured for 48 or 72 hours to assess chromosomal aberrations, micronuclei, mitotic indices, and binucleate cells. No significant differences were found between RF-exposed and sham-exposed lymphocytes for any of the measured endpoints, while gamma radiation produced significantly different responses. The authors concluded there is no evidence for induction of chromosomal aberrations and micronuclei under these exposure conditions.
Maes A, Collier M, Verschaeve L · 2001
Researchers investigated cytogenetic effects of 900 MHz radiofrequency fields using chromosome aberration and sister chromatid exchange frequency methods. They studied three exposure modes (continuous, pseudo-random, dummy burst) at power outputs from 0 to 50 W. Specific absorption rates ranged from 0 to 10 W/kg. The study examined effects of radiation alone and combined with mitomycin C and X-rays. Overall, no mutagenic or co-mutagenic effect was found.
Higashikubo R et al. · 2001
Researchers exposed mouse C3H 10T(1/2) fibroblasts and human U87MG glioma cells to two types of radiofrequency fields at 0.6 W/kg. Five cell cycle parameters including transit through G1, G2, and S phase and probability of cell division were measured immediately and up to 100 hours. No changes in cell cycle parameters were observed in exposed cells compared to sham-exposed cells in either cell line during the entire experimental period.
Li L et al. · 2001
Researchers exposed murine C3H 10T(1/2) fibroblasts to radiofrequency fields at specific absorption rates of 3.2 to 5.1 W/kg. Cell cultures were exposed to 847.74 MHz CDMA and 835.62 MHz FDMA modulated radiations in radial transmission line irradiators with temperature regulated to 37.0 ± 0.3 °C. Using the alkaline comet assay, they found no statistically significant differences in comet moment or comet length between sham-exposed and exposed cells after 2, 4, or 24 hours of exposure, for both exponentially growing and plateau-phase cells. A 4-hour incubation after a 2-hour exposure also resulted in no significant changes in comet moment or comet length. The authors concluded that exposure at 37°C up to 5.1 W/kg did not induce measurable DNA damage.
Lalic H, Lekic A, Radosevic-Stasic B. · 2001
Researchers investigated genotoxic effects of occupational exposure to ionizing and non-ionizing radiation in 25 hospital workers and 20 radio-relay station workers using chromosome aberration analysis of peripheral blood lymphocytes. Total chromosome aberrations were almost equally higher in both exposed groups compared to unexposed controls. Acentric fragments were the most frequent aberration and were significantly higher in both exposed groups than in controls. Dicentric fragments were also elevated in both exposed groups, while chromatid breaks increased only after ionizing radiation.
Jajte J, Zmyślony M, Palus J, Dziubałtowska E, Rajkowska E. · 2001
Researchers used the alkaline comet assay to assess DNA damage in rat peripheral blood lymphocytes exposed in vitro to iron ions and a 50 Hz magnetic field. Cell samples were incubated for 3 hours in Helmholtz coils at 7 mT 50 Hz, and some were treated with ferrous chloride at 10 μg/ml during that exposure. A significant increase in cells with DNA damage was found only after simultaneous exposure to ferrous chloride and the 7 mT 50 Hz magnetic field, compared to control samples or those incubated with ferrous chloride alone. When cells were treated with melatonin before that combined exposure, the number of damaged cells was significantly reduced, with the reduction reaching about 50% at 0.5 mM and about 100% at 1.0 mM.
Sykes PJ, McCallum BD, Bangay MJ, Hooker AM, Morley AA. · 2001
Researchers studied the effect of pulsed 900 MHz radiofrequency radiation at 4 W/kg on somatic intrachromosomal recombination in the spleen of pKZ1 mice. Mice were exposed daily for 30 minutes to 900 MHz fields for 1, 5, or 25 days, and spleen sections were screened for DNA inversion events three days after the last exposure. There was no significant difference between control and treated groups in the 1- and 5-day exposure groups, but a significant reduction in inversions was found in the 25-day group.
Unknown authors · 2000
Researchers incubated isolated rat lymphocytes for three hours in 7 mT static or 50 Hz magnetic fields, with some samples receiving iron chloride or hydrogen peroxide. Magnetic field exposure alone did not increase DNA damage in the comet assay. Iron chloride alone also did not produce detectable DNA damage. However, combined exposure to iron chloride and magnetic fields significantly increased damaged cells to about 20 percent for static fields and 15 percent for 50 Hz fields. Control samples showed about 97 percent of cells without DNA damage.
Unknown authors · 2000
Researchers exposed mouse m5S cells to power-line frequency magnetic fields at flux densities of 5, 50, and 400 mT for 40 hours. Cells were either untreated or pretreated with mitomycin C or X-rays before exposure. Exposure to 400 mT fields significantly increased chromosomal aberration frequency compared to unexposed controls. The induced aberrations were predominantly chromatid-type, with a three-fold increase at 400 mT. ELFMF exposure also deepened S or G2 arrest after DNA damage.
Unknown authors · 2000
Daudi cells were exposed to 60 Hz magnetic fields for 20, 40 or 60 min at flux densities of 12.5, 50, 100 or 500 microT. Exposures included sham/sham, exposed/sham or sham/exposed conditions with blinding, and 12-O-Tetradecanoylphorbol-13-acetate (TPA) treatment was used as a positive control. Human MYC expression was measured by northern blot hybridization as an indicator of the responsiveness of Daudi cells to experimental conditions, and beta-2-microglobulin (B2M) expression was measured simultaneously as an internal control. Exposure to 60 Hz magnetic fields did not significantly alter MYC expression in Daudi cells under any exposure condition.
Unknown authors · 2000
Researchers used a bacterial conjugation assay with Escherichia coli carrying the transposable element Tn5 as the donor strain. Donor cultures exposed to a 50 Hz, 1.2 mT magnetic field showed stimulated transposition of chromosomal Tn5 to an extrachromosomal episome and subsequent transfer to recipient cells. The transposition increase was mediated by induced synthesis and accumulation of the heat shock proteins DnaK/J. Magnetic field exposure was found to be stimulatory to transposition activity, similar to heat shock and UV irradiation.
Unknown authors · 2000
Researchers used Escherichia coli strain XL-1 Blue as the host and hydroxylamine-mutagenized plasmid pUC8 as the vector for assessment. Bacterial transformants exposed to a 50 Hz magnetic field showed lower percentages of white colonies than unexposed transformants. The lower white colony percentage indicated that DNA repair efficiency had improved. The improvement was mediated by induced overproduction of heat shock proteins DnaK/J (Hsp70/40).
Unknown authors · 2000
Maes A, Collier M, Verschaeve L · 2000
Researchers exposed human lymphocytes to 455.7 MHz microwaves from a car phone at a specific absorption rate of approximately 6.5 W/kg. No statistically significant difference was found between microwave-exposed and unexposed control samples for chromosome aberration or sister chromatid exchange frequency. When microwave exposure was followed by MMC treatment, some differences appeared between combined and MMC-only treatments, but results were inconsistent. Combined exposure with X-rays showed no indication of synergistic action between RF fields and X-rays. The authors concluded that the data do not support the hypothesis that RF fields act synergistically with chemical or physical mutagens.
Vijayalaxmi, Leal BZ, Szilagyi M, Prihoda TJ, Meltz ML · 2000
Human peripheral blood samples from three volunteers were exposed to pulsed-wave 2450 MHz radiofrequency radiation for 2 hours. The exposure used a net forward power of 21 W with an average power density of 5 mW/cm2 and a mean specific absorption rate of 2.135 W/kg. DNA damage was measured using the alkaline comet assay immediately and 4 hours after exposure. No significant differences were found in comet tail length, fluorescence intensity, or tail moment between RF-exposed and sham-exposed lymphocytes at either time point. The response of lymphocytes exposed to ionizing radiation was significantly different from RF-radiation- and sham-exposed cells.
Lourencini da Silva R et al. · 2000
Researchers exposed SnCl2-treated pBR322 plasmids to EMF and analyzed conformational changes using agarose gel electrophoresis. EMF exposure increased DNA scission, seen as relaxed plasmids. Plasmids pre-exposed to EMF were less able to transform E. coli. The authors concluded that EMF in the presence of a transition metal can cause DNA damage.
Brezitskaia HV, Timchenko OI · 2000
The study aimed to observe the mechanism of cytogenetic effect of electromagnetic radiation and the role of oxidation homeostasis. Changes in oxidation homeostasis preceded development of cytogenetic effects and could be their reason.
Romano-Spica V, Mucci N, Ursini CL, Ianni A, Bhat NK · 2000
Researchers analyzed gene expression in hemopoietic and testicular cell types after exposure to 50 MHz radiofrequency radiation modulated at 16 Hz. They observed overexpression of ets1 mRNA in Jurkat T-lymphoblastoid and Leydig TM3 cell lines only when the 16 Hz modulation was present. A putative candidate gene was also repressed after EMF exposure.
Gos P, Eicher B, Kohli J, Heyer WD · 2000
Researchers exposed actively growing and resting yeast cells to 900 MHz fields at specific absorption rates of 0.13 and 1.3 W/kg. Assays measured forward mutation rates at CAN1, petite clone formation, intrachromosomal deletion formation, and intragenic recombination in the ADE2 gene. Fields were also tested in combination with the alkylating agent methyl methansulfonate to assess whether they could enhance genotoxic damage. Fluctuation tests failed to detect any significant effect on any of these measures, in the absence or presence of methyl methansulfonate.
Zotti-Martelli L, Peccatori M, Scarpato R, Migliore L · 2000
Researchers exposed human peripheral blood lymphocytes in vitro to electromagnetic fields at two frequencies, 2.45 and 7.7 GHz, at power densities of 10, 20, and 30 mW/cm2 for 15, 30, and 60 minutes. At a power density of 30 mW/cm2 and after exposures of 30 and 60 minutes, both frequencies led to an induction of micronuclei compared to control cultures. The researchers concluded that microwaves are able to cause cytogenetic damage in human lymphocytes mainly for both high power density and long exposure time.
Unknown authors · 1999
Researchers studied DNA migration using the comet assay in brain cells of CBA mice exposed continuously to 50 Hz, 0.5 mT magnetic fields for 2 hours, 5 days, or 14 days. No differences were observed in mice exposed for 2 hours or 5 days compared with controls. Mice exposed for 14 days showed significantly extended DNA migration (0.02 < p < 0.05).
Miyakoshi J, Koji Y, Wakasa T, Takebe H · 1999
Researchers exposed Chinese hamster ovary K1 cells to 5 mT ELFMF at 60 Hz for up to 6 weeks with or without X-irradiation. Long-term exposure to 5 mT ELFMF alone did not increase mutant frequency of the HPRT gene. However, exposure to 5 mT ELFMF after X-irradiation enhanced the X-ray-induced mutation rate. As little as 1 week of ELFMF exposure after X-irradiation increased the mutation rate.
Unknown authors · 1999
Researchers evaluated the effect of a 60 Hz electromagnetic field on NF-kappaB or AP-1-dependent reporter gene expression in human U937 leukemia cells. Reporter genes were electroporated into the cells and pathway activation was measured by CAT protein using CAT ELISA. Magnetic field intensities of 0.08, 0.1, 1.0, and 1.3 mT had no effect on either signaling pathway.
Unknown authors · 1999
HSP70 gene expression is induced by 60-Hz electromagnetic fields. Earlier work showed magnetic field induction occurs at the transcription level through c-myc binding at two nCTCTn sequences at -230 and -160. This study identified a third c-myc binding site between -158 and -162 that regulates magnetic field-induced HSP70 expression. The heat shock element between -180 and -203 is required for magnetic field induction, while the HSE at -100 alone is insufficient.
