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.     

Evidence for a slow time-scale of interaction for magnetic fields inhibiting tamoxifen’s antiproliferative action in human breast cancer cells

One critical biophysical feature of environmental-level magnetic field (MF) interactions with biological systems is the time-scale of interaction. A recently proposed fast/slow hypothesis states that a fast mechanism can only sense the instantaneous absolute value of the MF, and that a slow mechanism is potentially capable of sensing features such as frequency and relative orientation and magnitude of the field components. Here we applied the fast/slow hypothesis to a breast cancer model system: A 1.2 μT(rms), 60-Hz field inhibits tamoxifen’s (TAM’s) cytostatic action in MCF-7 cells via a MF interaction. We measured the growth of MCF-7 cells treated with TAM over 7 d, within different MFs: a sinusoidal, 60-Hz, 0.2-μT(rms) field; a sinusoidal, 60-Hz, 1.2-μT(rms) field; and a full-wave rectified version of the 1.2-μT(rms) sinusoidal field. A fast mechanism should not be able to distinguish between the latter two exposures. We observe that the rectified 1.2-μT field does not inhibit TAM’s action, but that the 1.2-μT sinusoidal field does. Therefore, the 1.2-μT MF inhibition of TAM’s cytostatic action operates via a relatively slow mechanism, and we predict that there exists a biologically dynamic complex capable of sensing a 1.2-μT, 60-Hz sinusoidal MF with an intrinsic time-scale of 17 ms or longer, the period of the 60-Hz applied field.     

Pulsed electromagnetic fields regulate osteocyte apoptosis,RANKL/OPG expression,and its control of osteoclastogenesis depending on the presence of primary cilia

Growing evidence has shown that pulsed electromagnetic fields (PEMF) can modulate bone metabolism in vivo and regulate the activities of osteoblasts and osteoclasts in vitro. Osteocytes, accounting for 95% of bone cells, act as the major mechanosensors in bone for transducing external mechanical signals and producing cytokines to regulate osteoblastic and osteoclastic activities. Targeting osteocytic signaling pathways is becoming an emerging therapeutic strategy for bone diseases. We herein systematically investigated the changes of osteocyte behaviors, functions, and its regulation on osteoclastogenesis in response to PEMF. The osteocyte-like MLO-Y4 cells were exposed to 15 Hz PEMF stimulation with different intensities (0, 5, and 30 Gauss [G]) for 2 hr. We found that the cell apoptosis and cytoskeleton organization of osteocytes were regulated by PEMF with an intensity-dependent manner. Moreover, PEMF exposure with 5 G significantly inhibited apoptosis-related gene expression and also suppressed the gene and protein expression of the receptor activator of nuclear factor κB ligand/osteoprotegerin (RANKL/OPG) ratio in MLO-Y4 cells. The formation, maturation, and osteoclastic bone-resorption capability of in vitro osteoclasts were significantly suppressed after treated with the conditioned medium from PEMF-exposed (5 G) osteocytes. Our results also revealed that the inhibition of osteoclastic formation, maturation, and bone-resorption capability induced by the conditioned medium from 5 G PEMF-exposed osteocytes was significantly attenuated after abrogating primary cilia in osteocytes using the polaris siRNA transfection. Together, our findings highlight that PEMF with 5 G can inhibit cellular apoptosis, modulate cytoskeletal distribution, and decrease RANKL/OPG expression in osteocytes, and also inhibit osteocyte-mediated osteoclastogenesis, which requires the existence of primary cilia in osteocytes. This study enriches our basic knowledge for further understanding the biological behaviors of osteocytes and is also helpful for providing a more comprehensive mechanistic understanding of the effect of electromagnetic stimulation on bone and relevant skeletal diseases (e.g., bone fracture and osteoporosis).     

Effects of low-level combined static and weak low-frequency alternating magnetic fields on cytokine production and tumor development in mice

We investigated the effects of weak combined magnetic fields (MFs) produced by superimposing a constant MF (in the range 30 - 150 µT) and an alternating MF (100 or 200 nT) on cytokine production in healthy Balb/C male mice exposed 2 h daily for 14 days. The alternating magnetic field was a sum of several frequencies (ranging from 2.5 - 17.5 Hz). The frequencies of the alternating magnetic field were calculated formally based on the cyclotron resonance of ions of free amino acids (glutamic and aspartic acids, arginine, lysine, histidine, and tyrosine). The selection of different intensity and frequency combinations of constant and alternating magnetic fields was performed to find the optimal characteristics for cytokine production stimulation in immune cells. MF with a constant component of 60 μT and an alternating component of 100 nT, which was a sum of six frequencies (from 5 to 7 Hz), was found to stimulate the production of tumor necrosis factor-α, interferon-gamma, interleukin-2, and interleukin-3 in healthy mouse cells and induce cytokine accumulation in blood plasma. Then, we studied the effect of this MF on tumor-bearing mice with solid tumors induced by Ehrlich ascite carcinoma cells by observing tumor development processes, including tumor size, mouse survival rate, and average lifespan. Tumor-bearing mice exposed to a combined constant magnetic field of 60 μT and an alternating magnetic field of 100 nT containing six frequencies showed a strong suppression of tumor growth with an increase in survival rate and enhancement of average lifespan.     

还田秸秆分解与氮素释放的动态模拟

还田秸秆的分解与氮素释放动态是作物养分管理的重要依据。建立了秸秆分解氮素释放动态的“整吞”式动态模拟模型。模型由秸秆有机质分解和残余有机质含氮率动态模拟两部分组成,有机质分解的温度效应用指数函数描述,水分效应用分段线性函数描述,用“标准天”反映温度与水分的综合影响,残余有机质含氮率动态变化用“标准天”为变量的函数模拟,初始秸秆含氮量与残余秸秆含氮量之差即为秸秆分解的氮素净释放。“整吞”式较之“吃馅饼”式建模构思,所需参数少且易通过实验获得,增加了模型的可用性,利用在淮北滨海地区小麦的试验资料对模型的有效性进行了验证。     

Effect of aliphatic alcohols on the conformation of poly (l-ornithine hydrobromide) as studied by square-pulse and reversing-pulse electric birefringence

The electric birefringence and circular dichroism spectra of poly(l-ornithine hydrobromide) have been measured in ethanol/water, 2-propanol/water and tertiary butyl alcohol/water mixtures of various compositions. This charged polypeptide underwent a transition from the coil conformation to the helical conformation at high alcohol content in every case tested. Anomalous birefringence signals, indicative of a field-induced helix-to-coil transition. were observed at high electric fields only in the case of ethanol/water mixtures. The reversing-pulse electric birefringence of this polypeptide has been studied in ethanol/water mixtures and in neutral aqueous solution. Upon rapid reversal of the pulse field, no transient could be observed. This confirms that the electric-field orientation of poly(l-ornithine hydrobromide) results predominantly from the contribution of the counterion-induced dipole moment, regardless of its molecular conformations. It is very probable that the backbone permanent dipole moment of the helical conformation is largely suppressed by the counterion-induced dipole moment in the ionized form.     

Determination of electric current distributions in animals and humans exposed to a uniform 60-Hz high-intensity electric field

The thermographic method for determining specific absorption rate (SAR) in animals and models of tissues or bodies exposed to electromagnetic fields was applied to the problem of quantifying the current distribution in homogeneous bodies of arbitrary shape exposed to 60-Hz electric fields. The 60-Hz field exposures were simulated by exposing scale models of high electrical conductivity to 57.3-MHz VHF fields of high strength in a large 3.66 × 3.66 × 2.44-m TE₁₀₁ mode resonant cavity. After exposure periods of 2–30 s, the models were quickly disassembled so that the temperature distribution (maximum value up to 7 °C) along internal cross-sectional planes of the model could be recorded thermographically. The SAR, W′, calculated from the temperature changes at any point in the scale model was used to determine the SAR, W, for a full-scale model exposed to a 60-Hz electric field of the same strength by the relation W = (60/ f² · (σ′/σ) · W′ where f′ is the model exposure frequency, σ′ is the conductivity of the scale model at the VHF exposure frequency, and σ is the conductivity of the full-scale subject at 60 Hz. The SAR was used to calculate either the electric field strength or the current density for the full-scale subject. The models were used to simulate the exposure of the full-scale subject located either in free space or in contact with a conducting ground plane. Measurements made on a number of spheroidal models with axial ratios from 1 to 10 and conductivity from 1 to 10 s/m agreed well with theoretical predictions. Maximum current densities of 200 nA/cm² predicted in the ankles of man models and 50 nA/cm² predicted in the legs of pig models exposed to 60-Hz fields at 1kV/m agreed well with independent measurements on full-scale models.     

内植静磁柱联合脉冲电磁场对骨组织修复作用的Micro-CT研究

目的:以永磁体构建静磁柱体内植入物,应用Micro-CT技术,探索研究内植静磁柱联合脉冲电磁场对骨组织的修复作用。方法:选取新西兰兔24只建立右侧股骨髁骨缺损模型,并随机分为联合磁场组,脉冲电磁场组和对照组。联合磁场组自兔右侧股骨干远端向髓内植入静磁柱,并联合施加体外脉冲电磁场(1 h/d);脉冲电磁场组及对照组均将无磁性钛合金棒植入右侧股骨干髓腔,同时,脉冲电磁场组于体外加载脉冲电磁场(1 h/d)。术后5周处死取材,应用Micro-CT对股骨远端样本进行扫描检测,并对骨缺损区域显微结构进行三维重建分析。结果:与非磁场组相比,联合磁场组骨缺损区域骨小梁相对体积及数目明显增加(P均0.05),骨小梁分离度下降(P0.01)。与传统脉冲电磁场组相比,联合磁场组骨小梁数目增加(P0.05),骨小梁分离度下降(P0.01)。扫描及重建图像可见,联合磁场组骨缺损区域骨量增多,外侧皮质区愈合完整,骨小梁结构连续致密,具有更好的骨显微结构。结论:内植静磁柱与脉冲电磁场的联合磁场干预方式能够在早期获得更好的成骨修复能力,为磁场治疗相关骨病的临床及基础研究提供了新的方向。     

Analysis of three-dimensional SAR distributions emitted by mobile phones in an epidemiological perspective

The three‐dimensional distribution of the specific absorption rate of energy (SAR) in phantom models was analysed to detect clusters of mobile phones producing similar spatial deposition of energy in the head. The clusters' characteristics were described from the phones external features, frequency band and communication protocol. Compliance measurements with phones in cheek and tilt positions, and on the left and right side of a physical phantom were used. Phones used the Personal Digital Cellular (PDC), Code division multiple access One (CdmaOne), Global System for Mobile Communications (GSM) and Nordic Mobile Telephony (NMT) communication systems, in the 800, 900, 1500 and 1800 MHz bands. Each phone's measurements were summarised by the half‐ellipsoid in which the SAR values were above half the maximum value. Cluster analysis used the Partitioning Around Medoids algorithm. The dissimilarity measure was based on the overlap of the ellipsoids, and the Manhattan distance was used for robustness analysis. Within the 800 MHz frequency band, and in part within the 900 MHz and the 1800 MHz frequency bands, weak clustering was obtained for the handset shape (bar phone, flip with top and flip with central antennas), but only in specific positions (tilt or cheek). On measurements of 120 phones, the three‐dimensional distribution of SAR in phantom models did not appear to be related to particular external phone characteristics or measurement characteristics, which could be used for refining the assessment of exposure to radiofrequency energy within the brain in epidemiological studies such as the Interphone. Bioelectromagnetics. Bioelectromagnetics 32:634–643, 2011. © 2011 Wiley Periodicals, Inc.