Alternative magnetic field exposure metrics: relationship to TWA, appliance use, and demographic characteristics of children in a leukemia survival study.

The ongoing Childhood Leukemia Survival Study is examining the possible association between magnetic field exposure and survival of children with newly diagnosed acute lymphocytic leukemia (ALL). We report the results of the first year 24 h personal magnetic field monitoring for 356 US and Canadian children by time weighted average TWA and alternative exposure metrics. The mean TWA of 0.12 microT was similar to earlier personal exposure studies involving children. A high correlation was found between 24 h TWA and alternative metrics: 12 h day TWA, 12 night TWA, geometric mean, 95th percentile value, percentage time over 0.2 and 0.3 microT, and an estimate of field stability (Constant Field Metric). Two measures of field intermittency, rate of change metric (RCM) and standardized rate of change metric (RCMS), were not highly correlated with TWA. The strongest predictor of TWA was location of residence, with highest TWAs associated with urban areas. Residence in an apartment, lower paternal educational level, and residential mobility were also associated with higher TWAs. There were no significant differences in the appliance use patterns of children with higher TWA values. Children with the highest field intermittency (high RCM) were more likely to sit within 3 feet of a video game attached to the TV. Our results suggest that 24 h TWA is a representative metric for certain patterns of exposure, but is not highly correlated with two metrics that estimate field intermittency.     

Occupational magnetic field exposures of garment workers: results of personal and survey measurements

To explore the feasibility of performing an epidemiologic study of female breast cancer and magnetic field (MF) exposures, we chose to study garment workers, who reportedly have some of the highest MF exposures. We collected personal exposure (PE, n = 48) and survey measurements (n = 77) near commercial sewing machines at three garment facilities and conducted a pilot interview among 25 garment workers asking about exposure duration, activities, and machine characteristics. MF levels were higher for older machines with alternating current (AC) than newer machines with direct current (DC) motors. MF levels were comparable for both idling and sewing activities. Most interviewed workers could describe duration of exposure and machine type (automatic/manual), but not other machine characteristics. Measurements were lower than previously reported for garment workers but were higher than exposures to most women. A historical exposure assessment can be conducted by linking duration of exposure with reconstructed exposure measurements but may be limited by the accuracy of work history data.     

Effects of prenatal exposure to 50 Hz magnetic fields on development in mice: I. Implantation rate and fetal development

Pregnant CD1 mice were exposed or sham-exposed from day 0 to day 17 of gestation to a 50 Hz sinusoidal magnetic field at 20 mT (rms). Preimplantation and postimplantation survival were assessed and fetuses examined for the presence of gross external, internal, and skeletal abnormalities. There were no statistically significant field-dependent effects on preimplantation or postimplantation survival, sex ratio, or the incidence of fetuses with internal or skeletal abnormalities. Magnetic field exposure was, however, associated with longer and heavier fetuses at term, with fewer external abnormalities. The results lend no support to suggestions of increased rates of spontaneous abortion or congenital malformation following prenatal exposure to power frequency magnetic fields. © 1994 Wiley-Liss, Inc.     

Absence of genotoxicity in human blood cells exposed to 50 Hz magnetic fields as assessed by comet assay, chromosome aberration, micronucleus, and sister chromatid exchange analyses

In the past, epidemiological studies indicated a possible correlation between the exposure to ELF fields and cancer. Public concern over possible hazards associated with exposure to extremely low frequency magnetic fields (ELFMFs) stimulated an increased scientific research effort. More recent research and laboratory studies, however, have not been able to definitively confirm the correlation suggested by epidemiological studies. The aim of this study was to evaluate the effects of 50 Hz magnetic fields in human blood cells exposed in vitro, using several methodological approaches for the detection of genotoxicity. Whole blood samples obtained from five donors were exposed for 2 h to 50 Hz, 1 mT uniform magnetic field generated by a Helmholtz coil system. Comet assay, sister chromatid exchanges (SCE), chromosome aberrations (CA), and micronucleus (MN) tests were used to assess DNA damage, one hallmark of malignant cell transformation. The effects of a combined exposure with X-rays were also evaluated. Results obtained do not show any significant difference between ELFMFs exposed and unexposed samples. Moreover, no synergistic effect with ionizing radiation has been observed. A slight but significant decrease of cell proliferation was evident in ELFMFs treated samples and samples subjected to the combined exposure.     

Lack of alterations on meiotic chromosomes and morphological characteristics of male germ cells in mice exposed to a 60 Hz and 2.0 mT magnetic field

The effect of in vivo exposure of mice to a 60 Hz sinusoidal magnetic field (MF) at 2.0 mT on male germ cells was studied. The cytological endpoints measured included meiotic chromosome aberrations in spermatocytes and sperm morphology. Three independent experiments were carried out: (a) animals exposed for 72 h, (b) 10 days/8 h daily, and (c) 72 h exposure to MF plus 5 mg/kg of Mitomycin-C. No statistically significant differences indicative of MF effects were observed between MF exposed and control animals. In addition, an opposite effect between MF exposure and Mitomycin-C treatment in terms of chromosomal aberrations and sperm morphology was observed.     

The impact of extremely low frequency electromagnetic fields on stream periphyton: an eleven-year study

Potential effects of extremely low frequency (ELF) electromagnetic fields on periphyton were studied from 1983 to 1993 using a Before, After, Control and Impact design. The study was conducted at two sites on the Ford River, a fourth-order brown water trout stream in Dickinson County, Michigan. The Reference site received 4.9–6.5 times less exposure to ground electric fields and from 300 to 334 times less exposure to magnetic flux from 1989 to 1993 when the antenna was operational at 76 Hz than did the Antenna site. The objective of the study was to determine if ELF electromagnetic fields had caused changes in structure and/or function of algal communities in the Ford River. Significant differences in chlorophyll a standing crop and daily accumulation rate (a surrogate for primary productivity), and organic matter standing crop and daily accumulation rate were observed between the Reference and Antenna site after the antenna became operational. These four related community function variables all increased at the Antenna site with largest and most consistent increases occurring for chlorophyll measures. Compared to pre-operational data, the increase in chlorophyll at the Antenna site also occurred during a period of low amperage testing in 1986–1988, and did not increase further when the antenna became fully operational in 1989, indicating a low threshold for response. There was no significant differences between the Antenna and Reference sites in community structure variables such as diversity, evenness and the relative abundance of dominant diatoms. Thus, 76 Hz ELF electromagnetic radiation apparently did not change the basic makeup of the diatom community but did increase accumulation rates and standing crops of chlorophyll a and organic matter.     

Cytological effects of 60 Hz magnetic fields on human lymphocytes in vitro: sister-chromatid exchanges, cell kinetics and mitotic rate

Incubation for 72 h of human peripheral blood cultures in the presence of 60 Hz sinusoidal magnetic fields (MF) at magnetic flux densities of 1.0, 1.5, and 2.0 mT led to stimulation of lymphocyte proliferation but had no influence on the frequency of sister-chromatid exchanges (SCE). The cytotoxic potential of MF combined with the mutagen Mitomycin-C also was analyzed. An opposite effect between MF exposure and Mitomycin-C treatment in terms of cell kinetics and mitotic rate was found, whereas no variation in SCE frequency was observed for this coexposure condition.     

An in vitro study of the effects of exposure to a GSM signal in two human cell lines: monocytic U937 and neuroblastoma SK-N-SH

The use of mobile phones is increasing, which also increases the population's exposure to global system of mobile communications (GSM) signals. Questions of safety and possible biological effects are of concern and to date, remain largely unanswered. In order to examine possible biological effects of a GSM-like signal at a cellular level, we exposed two human cell lines (one of neuronal (SK-N-SH) and the other of monocytoid (U937) origin) to a 900 MHz RF signal, pulsed at 217 Hz, producing a specific absorption rate (SAR) of 0.2 W/kg. Putative effects were assessed by comparing radiofrequency-exposed cells to sham-exposed cells using a variety of assay techniques. For the cell line SK-N-SH, effects were specifically assessed by gene microarray, followed by real-time PCR of the genes of interest, Western blot analysis was used to measure heat shock protein levels, and flow cytometry to measure cell cycle distributions and apoptosis. Effects of radiofrequency on the cell line U937 were assessed by cell viability and cell cycle analysis. From our study of these two cell lines, we found no significant difference between sham-exposed versus radiofrequency-exposed cells in any of the assays or conditions examined.     

Effect of coexposure to 50 Hz magnetic fields and an aneugen on human lymphocytes,determined by the cytokinesis block micronucleus assay

Interference of 50 Hz extremely low frequency magnetic fields (ELF-MF) with the known aneugen vinblastine (VBL) on micronucleus formation was tested with the in vitro cytokinesis block micronucleus assay in human lymphocyte cultures. Isolated lymphocyte cultures were prepared from 18 individuals. Three groups of quadruplicate cultures from six unrelated individuals were exposed to 50 Hz ELF-MF of background (bkg), 80 and 800 microT, respectively, during the complete incubation period (72 h). Twenty-four hours after culture initiation, one replicate culture from each individual within each ELF-MF group was exposed to 0, 5, 10, or 15 ng/ml VBL. The isolated lymphocyte cultures were scored for the presence of micronuclei, the nuclear division index (NDI), and apoptosis. As expected, increased VBL concentration resulted in an increased micronucleus and apoptosis frequency and in a decreased NDI. In the presence of VBL, there was a systematic tendency for increased micronucleus and apoptosis frequency in the ELF-MF exposed groups compared to the bkg group. In the absence of VBL, we observed no statistically significant effect of ELF-MF on micronucleus induction or apoptosis frequency, but the NDI was significantly higher in the 800 microT group compared to the other groups, suggesting an effect of ELF-MF on cell proliferation. An interaction between ELF-MF and VBL on NDI was observed. This interaction reflected the drastic decrease in NDI due to coexposure to VBL.     

High-voltage overhead power lines in epidemiology: Patterns of time variations in current load and magnetic fields

In epidemiological studies of electromagnetic fields and health effects, exposure classification is crucial. There is no generally accepted biophysical interaction mechanism, but many studies are based on the hypothesis of a causal relationship with the strength of magnetic field. Some definition of the magnitude of exposure must be used, e.g., mean magnetic flux density, the integral of magnetic flux and time, or a peak value. Magnetic fields around a particular power line depend on the current load. The aim of the present study was to follow variations in line current load in the power supply system of the largest Norwegian city on a yearly, monthly, daily, and diurnal basis. Fairly large variations in load were found, but increases in consumption were not necessarily reflected in current load on high voltage lines. The correlation between outdoor temperature and current load varied widely, depending on the type of power station feeding the line in question. The registered time variations are large enough to interfere with epidemiological classification of residences and testing of epidemiological hypotheses. © 1996 Wiley-Liss, Inc.     

Risk of malignant childhood germ cell tumors in relation to demographic,gestational, and perinatal characteristics

BackgroundChildhood germ cell tumors (GCTs) are a rare assortment of neoplasms, with mostly unknown etiology, that are believed to originate very early in life. Few studies have examined risk factors by histologic subtype, despite evidence of different risk profiles.Materials and methodsIn this population-based case-control study, 451 childhood malignant GCT cases ages 0–5 years were identified from the California Cancer Registry. Differentiating between common histologic subtypes, we identified 181 yolk sac tumors, 216 teratomas, and 54 rarer subtypes. Cases were linked to their birth certificates and 271,381 controls, frequency matched by birth year, were randomly selected from California birthrolls to investigate the contributions of demographic, gestational, and pregnancy factors using unconditional logistic regression analysis.ResultsCompared to non-Hispanic whites, Asian/Pacific Islander children were at an increased risk for developing GCTs (odds ratio [OR] = 1.94; 95% confidence interval [CI] = 1.47, 2.56). Among pregnancy complications and procedures, yolk sac tumors were positively associated with the presence of fetopelvic disproportion (OR = 2.97; 95% CI = 1.55, 5.68), while teratomas were strongly associated with polyhydramnios or oligohydramnios (OR = 14.76; 95% CI = 7.21, 30.19) and the presence of an ear, face, or neck anomaly at birth (OR = 93.70; 95% CI = 42.14, 208.82).ConclusionsMalignant yolk sac tumors and malignant teratomas exhibited distinct demographic and gestational characteristics; additionally, complications in pregnancy and labor may be brought on by specific histologic subtypes.     

Effects of 50 Hz magnetic fields on fMLP-induced shape changes in invertebrate immunocytes: The role of calcium ion channels

Plasma membrane Ca(2+) channels in immunocytes from the mussel Mytilus galloprovincialis exposed to 50 Hz sine wave magnetic fields (MFs) of various strengths were studied. At levels of 300 microT and above, MFs reduce shape changes in immunocytes induced by the chemotactic substance N-formyl-Meth-Leu-Phe, and this effect involves L-type Ca(2+) channels. Upon the addition of the Ca(2+) blocker verapamil to molluscan immunocytes exposed to MFs results in a synergistic cytotoxic action, while in the presence of the Ca(2+) opener SDZ-202, 791, a reactivation of the cells is observed. This suggests that, as previously reported for potassium channels, the damage to Ca(2+) channels induced by short exposure to MF at appropriate intensities is not permanent.     

Deprotonation of glutamic acid induced by weak magnetic field: an FTIR-ATR study

It has been claimed that weak extremely low frequency electromagnetic fields (ELF‐EMFs) can affect biochemical reactions and a wide‐ranging body of literature is available on this topic. Nevertheless, the physical nature of these effects remains largely unknown. We investigated the influence of ELF‐EMF on glutamic acid solutions using Fourier transform infrared‐attenuated total reflectance (FTIR‐ATR) spectra. Samples were exposed for 10, 20, or 30 min to a weak EMF generated by Helmoltz coils, and then placed in a spectrometer. After exposure, those solutions that had a pH lower than the isoelectric point tended to show a shift toward the deprotonation of the carboxylic group, while solutions having a pH greater than the isoelectric point showed the deprotonation of the residual amine group. Moreover, at low pH values, we also detected a shift of the δ_antisym band of the amine. The effects lasted a few minutes after exposure before the native configuration was restored. The spectral modifications were observed after each independent exposure to EMFs, and the same effects were seen by varying the frequencies in the range of 0–7 kHz. Therefore, the hypothesis of the existence of a resonant frequency that has been proposed elsewhere cannot be supported by the results of this study. The most surprising characteristic of this effect is the long‐lasting nature of the perturbation, which is hard to be explained in terms of short‐living excitations in biological matter. Bioelectromagnetics 32:218–225, 2011. © 2010 Wiley‐Liss, Inc.     

A Lorentz model for weak magnetic field bioeffects: Part II—Secondary transduction mechanisms and measures of reactivity

In Part I it was shown that the thermal component of the motion of a charged particle in an oscillator potential, that is, within a molecular binding site, rotates at the Larmor frequency in an applied magnetic field. It was also shown that the Larmor angular frequency is independent of the thermal noise strength and thus offers a mechanism for the biological detection of weak (µT‐range) magnetic fields. Part II addresses the question of how the Larmor trajectory could affect biological reactivity. The projection of the motion onto a Cartesian axis measures the nonuniformity of the Larmor trajectory in AC and combined AC/DC magnetic fields, suggesting a means of assessing resonances. A physically meaningful measure of reactivity based upon the classical oscillator trajectory is suggested, and the problem of initial conditions is addressed through averaging over AC phases. AC resonance frequencies occur at the Larmor frequency and at other frequencies, and are dependent upon the ratio of AC/DC amplitudes and target kinetics via binding lifetime. The model is compared with experimental data reported for a test of the ion parametric resonance (IPR) model on data from Ca²⁺ flux in membrane vesicles, neurite outgrowth from PC‐12 cells and a cell‐free calmodulin‐dependent myosin phosphorylation system, and suggests Mg²⁺ is the target for these systems. The results do not require multiple‐ion targets, selection of isotopes, or additional curve fitting. The sole fitting parameter is the binding lifetime of the target system and the results shown are consistent with the literature on binding kinetics. Bioelectromagnetics 30:476–488, 2009. © 2009 Wiley‐Liss, Inc.     

Ovarian and uterine characteristics and onset of puberty in adolescent offspring: Effects of maternal diet and selenium supplementation in sheep

The aim of this study was to determine the effects of maternal diet with adequate (A) or high (H) selenium (Se) supplementation on ovarian and uterine characteristics, and onset of puberty in adolescent offspring. Sheep were fed a maintenance (M) diet with ASe or HSe levels from breeding to parturition. From Day 50 to parturition, a portion of the ewes from ASe and HSe groups was fed restricted (R, 60% of M) or excess (E, 140% of M) diet. Immediately after birth, lambs were separated from their dams and given artificial colostrum for 20 hours, followed by milk replacer. From Day 57.3 ± 0.6, ewe lambs were fed a pelleted grower diet until Day 116.3 ± 0.6 when they were transitioned to a finisher diet. From Day 99 to 180, serum samples were collected weekly from jugular vein for progesterone analysis to determine onset of puberty. Reproductive tissues were collected on Day 180.1 ± 0.4 of age. Maternal diet or Se supplementation did not affect uterine or ovarian weight and onset of puberty. However, area under the curve for progesterone was greater (P = 0.05) in ASe compared with HSe groups, and was greater in ASeM than HSeM group. In CLs, labeling index (LI; a proportion of proliferating cells) was less (P < 0.04) in HSeM than ASeM group, and in stroma was less (P < 0.05) in R and E groups than M group. Maternal diet did not affect the LI of any follicle types. For all groups combined, LI was the greatest (P < 0.001) in antral, less in early antral and secondary, and the least in atretic follicles. Our results demonstrate that maternal diet influenced ovarian but not uterine characteristics or onset of puberty. These results indicate that maternal plane of nutrition and/or Se supplementation may have specific effects on reproductive function in offspring.     

Assessment of the efficacy and safety of low frequency,low intensity magnetic fields in patients after knee endoprosthesis plasty. Part 1: In vitro safety

The purpose of this in vitro study was to assess the potential influence of low frequency, low intensity magnetic fields (rectangular pulse, 5 mT, 30 Hz) applied in therapy on the temperature, contact electric potential, and magnetization in knee endoprosthesis, which might be dangerous for implantation and stability of knee prosthesis, and later slacking it off, causing postoperative complications. The experimental investigation was carried out on a knee endoprosthesis which had been placed in a container with physiological saline. The prosthesis located inside the container was under the exposure of the magnetic field applied by a solenoid. The results indicated that magnetic fields did not influence thermal and electromagnetic properties of knee endoprosthesis in vitro. The magnetic fields of examined parameters should not be dangerous for implantation and stability of knee endoprosthesis. Bioelectromagnetics 30:159–162, 2009. © 2008 Wiley‐Liss, Inc.     

Expression of T-cadherin (CDH13, H-Cadherin) in human brain and its characteristics as a negative growth regulator of epidermal growth factor in neuroblastoma cells

In the present study, we first examined the expression of T-cadherin in human CNS by northern blot analysis, immunohistochemical staining, and in situ hybridization. Northern blot analysis demonstrated expression of T-cadherin in human adult cerebral cortex, medulla, thalamus, and midbrain. Immunohistochemical staining with a newly generated monoclonal antibody, designated MA-511, revealed strong expression of T-cadherin in neural cell surface membrane and neurites in adult cerebral cortex, medulla oblongata, and nucleus olivaris. Little or no expression of T-cadherin was found in spinal cord. We further examined T-cadherin expression in various developing nervous systems, and found that T-cadherin expression was lower in developing brain than in adult brain. In situ hybridization revealed that neural cells in medulla oblongata and nucleus olivaris, but not in spinal cord, possessed T-cadherin molecules. We transfected T-cadherin-negative TGW and NH-12 neuroblastoma cells with a T-cadherin cDNA-containing expression vector. T-cadherin-expressing neuroblastoma cells lost mitogenic proliferative response to epidermal growth factor. Epidermal growth factor is known to be required for proliferation of neural stem cells. This finding, together with those of the present study, suggests that T-cadherin functions as a negative regulator of neural cell growth.     

磁场对环磷酰胺杀伤人白血病细胞K562协同作用的研究初报

目的:研究不同处理时间稳恒磁场协同抗癌药物环磷酰胺对人白血病细胞K5 6 2的杀伤作用。方法:K5 6 2细胞经不同浓度的环磷酰胺和/或磁场处理12h或2 4h后,MTT法检测。数据进行统计学分析处理。结果:单纯磁场处理时,磁场对K5 6 2细胞的杀伤作用表现在2 4h(P <0 .0 1) ;环磷酰胺单纯处理K5 6 2细胞12h ,在0 .4和0 .8mg/mL浓度时对肿瘤细胞的生长没有影响(P >0 .0 5 ) ,在1.6和3.2mg/mL浓度下环磷酰胺对细胞有杀伤作用(P <0 .0 1) ;0 .4mg/mL环磷酰胺联合磁场处理K5 6 2细胞12～2 4h后,细胞活性均极显著的低于单纯环磷酰胺处理组(P <0 .0 1)。结论:9mT稳恒磁场对环磷酰胺杀伤肿瘤细胞具有一定的协同作用,磁场处理可以增加环磷酰胺的抗肿瘤效应。