Unknown authors · 2000
Researchers investigated whether exposure to 60-Hz sinusoidal magnetic fields (0.3-1.2 G for 3-72 h) would cause proliferation of human astrocytoma cells. Sixty-Hertz magnetic fields caused a time- and dose-dependent increase in proliferation of astrocytoma cells, measured by (3)H-thymidine incorporation and by flow cytometry, and strongly potentiated the effect of two agonists. However, magnetic fields had no effect on DNA synthesis of rat cortical astrocytes, which are similar nontransformed cells. A protein kinase C inhibitor and down-regulation of protein kinase C inhibited the effect of magnetic fields on basal and agonist-stimulated thymidine incorporation.
Unknown authors · 2000
University of Washington researchers exposed human brain tumor cells (astrocytomas) to 60-Hz magnetic fields at household appliance levels (0.3-1.2 gauss) for up to 72 hours. The magnetic fields caused these cancer cells to multiply faster in a dose-dependent manner, while having no effect on normal brain cells. This provides a potential biological mechanism for epidemiological studies linking magnetic field exposure to increased brain tumor risk.
Unknown authors · 2000
Unknown authors · 2000
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 examined the effect of 50 mT, 60 Hz ELFMF on heat-induced HSP-70 expression in HL60RG cells. Exposure to 50 mT ELFMF alone did not increase HSP-70 production. Combined exposure to 50 mT ELFMF and mild heat at 40°C and 42°C suppressed heat-induced HSP-70 expression. This suppression required simultaneous exposure for more than 5 hours. Lower magnetic densities of 5 mT and 0.5 mT did not suppress HSP-70.
Unknown authors · 2000
Researchers from Löscher's group in Germany exposed Sprague-Dawley rats to 50-Hz magnetic fields at microtesla flux densities for 13 or 27 weeks using a DMBA breast cancer model. The exposure significantly increased mammary tumor development and growth in those experiments. A similar study by Battelle in the United States did not replicate the effect.
Unknown authors · 2000
German researchers found that 50 Hz magnetic fields at 100 microtesla significantly increased mammary tumor development in rats treated with a cancer-causing chemical. However, when U.S. researchers tried to replicate the study using similar methods, they could not reproduce these findings, highlighting challenges in EMF research reproducibility.
Unknown authors · 2000
Unknown authors · 2000
Scientists exposed human mammary and leukemia cells to 60 Hz magnetic fields (the frequency from power lines) for 24 hours to see if this would change cancer-related gene activity. While some genes showed temporary changes, no consistent pattern emerged across repeated experiments, and the researchers found no reliable evidence that power line frequency magnetic fields alter cancer gene expression.
Unknown authors · 2000
Researchers exposed human breast and leukemia cells to 60 Hz magnetic fields (the same frequency as power lines) for 24 hours to see if it changed cancer-related gene activity. While some genes showed temporary changes, no consistent pattern emerged across repeated experiments, suggesting 60 Hz fields don't systematically alter cancer gene expression in these cell types.
Unknown authors · 2000
Researchers attempted to replicate earlier findings by testing whether a 1.5-G 50-Hz magnetic field alters intracellular free calcium in Jurkat lymphocyte T-cells. Cells were randomly assigned to magnetic field, sham field, or no-field exposures for 8 minutes each in a blinded design. The percentage of cells showing calcium transients was 16.5% for magnetic field, 14.6% for sham, and 14.2% for no field, with no statistically significant differences among them. The authors concluded that their methods did not identify responsive cells, if such cells exist, and that the results do not rule out a magnetic field effect on calcium.
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.
Grant FH, Schlegel RE, · 2000
Researchers evaluated 20 pacemaker-phone combinations involving 6 pacemakers and 9 phones in vitro under worst-case conditions. The phones represented CDMA, TDMA-11 Hz, TDMA-22 Hz, TDMA-50 Hz, and TDMA-217 Hz digital wireless technologies. Small increases in the perpendicular air gap between the phone and the saline surface resulted in a dramatic reduction in interaction, with approximately half of the 208 test runs showing interaction at 1 cm no longer interacting at 2 cm. At a gap of 7.4 cm the percentage of runs with interaction decreased to 1.4%, and the overall interaction rate was less than 0.07% at a perpendicular distance of 8.6 cm.
Jauchem JR, Ryan KL, Freidagger MR · 2000
Ketamine-anesthetized male Sprague-Dawley rats were exposed to 1 GHz, 10 GHz, or combined 1 and 10 GHz microwaves at a whole-body specific absorption rate of 12 W/kg. Exposures were conducted in E and H orientations under far-field conditions until lethal temperatures were reached. Survival time was shortest at 1 GHz, intermediate for combined frequencies, and longest at 10 GHz, with most differences statistically significant. Temperature values at most sites for combined exposure fell between those of the single-frequency groups. Arterial blood pressure initially increased then decreased until death, heart rate increased throughout, and patterns were similar across all groups.
Unknown authors · 2000
Pashovkina MS, Akoev IG · 2000
Researchers studied the activity of alkaline phosphatase during exposure to pulse-modulated microwave radiation. The carrier frequency was 2375 MHz with modulation pulse rates of 10-390 Hz, on-off time ratio 2, and specific absorption rates of 8 and 0.8 microW/cm2. At a modulation frequency of 70 Hz, alkaline phosphatase activity increased 1.8-2.0 times. Exposure times were 1 and 3 minutes under continuous temperature control.
Gapeev AB, Chemeris NK · 2000
Researchers used a mathematical model to analyze how modulated extremely high frequency electromagnetic radiation affects intracellular calcium concentration in neutrophils. The model showed that the calcium rise depends on both the frequency and phase of the modulating signal relative to chemical stimulation. A rise above 50% of the initial calcium level occurred at about 1 Hz and phase range 0.3-2.5 radians, but only when modulating signal intensity exceeded a threshold and chemical stimulus intensity was high. Added noise changed the phase-frequency characteristics and created multiple response bands with higher Q-factors. The model results matched earlier experimental data showing effects only with extracellular calcium and high calcium ionophore A23187 concentrations.
Nakamura H, Nagase H, Ogino K, Hatta K, Matsuzaki I · 2000
Researchers exposed rats to continuous-wave microwaves at 2 mW/cm² and 2450 MHz for 90 minutes and measured uteroplacental blood flow and hormone levels. Colonic temperature did not change significantly in either virgin or pregnant rats. Microwave exposure decreased uteroplacental blood flow and increased progesterone and PGF2α in pregnant rats but not in virgin rats. Pretreatment with angiotensin II prevented these changes in pregnant rats. Corticosterone increased and estradiol decreased during exposure regardless of pregnancy status or angiotensin II pretreatment.
Yoshikawa T et al. · 2000
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.
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 · 1999
Researchers conducted a case-control study of 399 children with leukemia and 399 controls across five Canadian provinces from 1990 to 1994. Exposure assessment included 48-hour personal EMF measurement, wire coding, residential magnetic field measurements from conception to diagnosis, and 24-hour bedroom magnetic field measurement. Personal magnetic fields were not related to risk of leukemia (adjusted OR = 0.95, p for trend = 0.73) or acute lymphatic leukemia (OR = 0.93, p for trend = 0.64). No clear associations were found with predicted magnetic field exposure two years before diagnosis, over the lifetime, or with personal electric field exposure.
Unknown authors · 1999
Unknown authors · 1999
Researchers studied 142 male electric utility workers in Colorado to see how 60 Hz magnetic fields affect melatonin, a hormone that regulates sleep. Workers exposed to temporally stable magnetic fields had reduced levels of melatonin metabolites in their urine, but only when they also had low light exposure at work. This suggests that power line frequency magnetic fields can disrupt the body's natural hormone production.
