电磁场曝露对生物组织电磁特性的影响

电磁辐射严重影响着人体的健康.电磁场生物效应的发生机制与电磁场本身的特性相关,同时也与生物组织在电磁场作用下电磁特性的改变密切相关.生物体内的信号分子、自由基以及磁颗粒等处于外加电磁场中时其电磁特性会发生变化,尤其是不同频率电磁场曝露作用下生物组织的导电、介电以及磁学等特性会有非常显著的区别.明确不同频率电磁场作用下生物组织电磁特性的变化规律是研究电磁场生物效应发生机制以及预防问题的关键.综述了近年来电磁场对于生物组织电磁特性影响的研究成果,并对未来的研究方向做了展望.     

Effects of electromagnetic fields on biological systems

The effect of power-frequency electric fields on invertebrate movement and behavior was studied. Data was obtained in the vicinity of an operating 500-kV powerline, and from underneath a simulated powerline (where the electric field could be controlled). Electric fields greater than 8-10 kV/m affected the behavior of flying insects; small insects could not fly, and large insects avoided the high-field region. Electric fields lowered both the activity of mosquitoes (to attack the host) and insect flower attendance. The prevalence of most non-flying insect species was not altered by the electric field, probably because of screening of the electric fields by vegetation and the ability of the insects to migrate. The existing Soviet safety standards for high-voltage powerlines seem sufficient to protect invertebrates.     

Effects of unsignaled delays of reinforcement on fixed-interval schedule performance

Key pecking of pigeons was maintained by a fixed-interval (FI) 61-s schedule. The effects of resetting and nonresetting unsignaled delays of reinforcement then were examined. The resetting delay was programmed as a differential-reinforcement-of-other-behavior schedule, and the nonresetting delay as a fixed-time schedule. Three delay durations (0.5, 1 and 10 s) were examined. Overall response rates were decreased by one and 10-s delays and increased by 0.5-s delays. Response patterns changed from positively accelerated to more linear when resetting or nonresetting 10-s delays were imposed, but remained predominantly positively accelerated when resetting and nonresetting 0.5- and 1-s delays were in effect. In general, temporal control, as measured by quarter-life values, changed less than overall response rates when delays of reinforcement were in effect. The response patterns controlled by FI schedules are more resilient to the nominally disruptive effects of delays of reinforcement than are corresponding overall response rates.     

Effect of short duration electromagnetic field exposures on rat mass.

Daily preexposure and postexposure mass measurements of 65 rats (young males and females, old males) a proprietary pulsed wound healing field, pulsed electromagnetic field, (PEMF), or their control fields for 4 h/day for 21 days. Statistical analysis of mass changes over time showed that young rats exposed to PEMF lost more mass and recovered it more slowly compared to controls (2-4% more loss) than did older PEMF exposed rats or any 60 Hz exposed rats. We conclude that daily preexposure and postexposure mass measurements are needed to adequately assess the effects of electromagnetic fields on body mass.     

低频电磁场对酿酒酵母蛋白质表达及酶活性的影响

【背景】低频电磁场(Lowfrequencyelectromagneticfield,LF-EMF)可导致一系列健康效应的事实已被普遍接受。【目的】进一步探究LF-EMF辐射对细胞蛋白质表达及相关酶活性的影响。【方法】以酿酒酵母为研究对象,采用50HzLF-EMF对其进行持续暴露辐射,随后对其胞内蛋白质表达、相关酶活性进行分析。【结果】LF-EMF辐射对酿酒酵母超氧化物歧化酶(Superoxide dismutase,SOD)、过氧化氢酶(Catalase,CAT)和苹果酸脱氢酶(Malate dehydrogenase,MDH)活性的影响存在先促进后抑制的趋势。辐射处理使SOD活性在72 h提高了43.18%,CAT活性在16 h提高了12.22%,MDH活性在20h提高了12.90%(P0.05);而LF-EMF辐射作用对乙醇脱氢酶(Alcohol dehydrogenase,ADH)和乳酸脱氢酶(Lactatedehydrogenase,LDH)的活性并未观察到显著的影响(P0.05)。此外,蛋白质电泳和蛋白质组学分析的结果表明,LF-EMF可改变酿酒酵母部分胞内蛋白质的表达水平,其中3种蛋白质的表达发生显著上调,9种蛋白质的表达发生显著下调(P0.05)。【结论】LF-EMF辐射可影响酿酒酵母的部分酶活性,改变其胞内部分蛋白质的表达水平。     

No effect of an UMTS mobile phone-like electromagnetic field of 1.97 GHz on human attention and reaction time

Several studies in the past reported influences of electromagnetic emissions of GSM phones on reaction time in humans. However, there are currently only a few studies available dealing with possible effects of the electromagnetic fields emitted by UMTS mobile phones. In our study, 40 healthy volunteers (20 female, 20 male), aged 26.0 years (range 21-30 years) underwent four different computer tests measuring reaction time and attention under three different UMTS mobile phone-like exposure conditions (two exposure levels plus sham exposure). Exposure of the subjects was accomplished by small helical antennas operated close to the head and fed by a generic signal representing the emissions of a UMTS mobile phone under constant receiving conditions as well as under a condition of strongly varying transmit power. In the high exposure condition the resulting peak spatial average exposure of the test subjects in the cortex of the left temporal lobe of the brain was 0.63 W/kg (min. 0.25 W/kg, max. 1.49 W/kg) in terms of 1 g averaged SAR and 0.37 W/kg (min. 0.16 W/kg, max. 0.84 W/kg) in terms of 10 g averaged SAR, respectively. Low exposure condition was one-tenth of high exposure and sham was at least 50 dB below low exposure. Statistical analysis of the obtained test parameters showed that exposure to the generic UMTS signal had no statistically significant immediate effect on attention or reaction. Therefore, this study does not provide any evidence that exposure of UMTS mobiles interferes with attention under short-term exposure conditions.     

Effects of microscope objectives on magnetic field exposures.

Distortions in magnetic field intensity generated by commonly used microscope objectives (1x to 100x) were characterized within a Helmholtz coil-based exposure system. Objectives from a variety of manufacturers distorted applied field intensities by up to 23% in the image plane. Components that contribute to distortions include (1) nickel-chrome plating of objective housings, (2) the presence of steel springs in objectives with compression collars, and (3) steel screws or studs used to hold together separately manufactured parts. Steel springs and screws produce radially asymmetric profiles, whereas distortions generated by nickel-chrome plating are typically radially symmetric. All components can produce spatial gradients in field intensity if objectives are not perfectly aligned with exposure systems or if placed in the earth's magnetic field. Alterations in the magnitude of magnetic field intensities as well as the production of spatial gradients might have an effect on biological responses. By maintaining optical glass components and replacing metallic components, functional objectives can be reconstructed that produce no measurable effects on magnetic flux densities.     

Raman spectroscopy and order in biological systems

The Raman spectra in the low 5–200 cm⁻¹ frequency region of metabolically activeE. coli cells have been analyzed to determine whether they are indicators of a possible in vivo underlying order by applying standard concepts derived from the Raman spectroscopy of crystalline systems with varying degrees of order. The analysis suggests that in-vivo space-time ordered structures involving amino acids associated with DNA exist since the low frequency lines of metabolically active cells can be assigned to lines seen in the spectra of crystals of given amino acids known to associated with DNA early in the lifetime of a cell.     

Effect of a low frequency electromagnetic field on biological cells

Possibility of energy of low frequency electromagnetic waves transformation into the energy of multimodules mechanical vibrations of the biological membrane is proved for spherical and cylindrical models of the cell. Formula for calculating the membrane displacement from equilibrium position is derived.     

Roles of positive and negative feedback in biological systems

We discuss the influence of positive and negative feedback on the stability of a system, which is not clear-cut, and involves complex, mathematical problems. We show in particular that positive feedback can have a stabilising effect on some systems. We also point out the role that positive feedback plays in the digital treatment of signals required by cellular signalling, drawing on analogies from electronics, and the role that negative feedback plays in making a system robust against alteration of its parameters. Both positive and negative feedback can be seen as important enhancers of the properties of biological systems.     

Impacts of statistical feedback on the flexibility-accuracy trade-offin biological systems

Biological systems possess the ability to adapt quickly andadequately to both environmental and internal changes. This vital ability cannot be explained in terms ofconventional stochastic processes because such processes arecharacterized by atrade-off between flexibility and accuracy, that is, they either show shorttransition times (large Kramers escape rates) to broad steady-statedistributions or long transition times to sharply peaked distributions. To develop a stochastic theory for systemsexhibiting both flexibility and accuracy, we study systems under the impact of white noise multiplied with anaccordant statistical measure, here the probability density. Thisresults in negative feedback and circular causality: the more probable a stable state the lessit will be affected by noise and, conversely, the less a stable state is affected by noisethe more probable it is. Using nonlinear Fokker-Planckequations, steady states are computed via transformations ofsolutions of the corresponding linear Fokker-Planck equations. Transients reveal rapidly evolving and sharply peaked probability densities and thus mimic systems characterized by both flexibility and accuracy.     

Recording of elapsed time and temporal information about biological events using Cas9

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Effects of extremely low frequency electromagnetic field on the health of workers in automotive industry

Objective. To observe the effects of extremely low frequency electromagnetic fields (ELF-EMFs) in automotive industry on occupational workers. Methods. A total of 704 workers were investigated, and 374 workers were chosen and divided into two groups (control group and exposure group) according to the inclusive criteria, namely male with age 20–40 years old and ≥ 2 years of exposure. The intensities of ELF-EMFs and noise were detected with EFA-300 Field Analyzer (Narda company, Pfullingen, Germany) and AWA5610D integrating sound level meter (Hangzhou Aihua Instruments Co., Ltd, Hangzhou, China), respectively. Survey data were collected by questionnaire, and the physical check-up was done in hospital. All the data were input into SPSS17.0 software (SPSS Inc, Chicago, USA), and the appropriate statistic analyses were carried out. Results. The intensity of EMFs in exposure group was significantly higher than that in control group (p < 0.05), while the noise in two workplaces showed no difference (p>0.05). The survey data collected by questionnaires showed that the symptoms of loss of hair in exposure group were significantly different as compared with that in control group (p < 0.05). The check-up parameters of cardiovascular, liver and hematology system showed significant differences between the two groups (p < 0.05). Conclusions. Survey and check-up data suggest that exposure to ELF-EMFs might have effects on the nervous, cardiovascular, liver, and hematology system of workers.     

Effects of 5 s exposures to a 50 microT, 20 Hz magnetic field on skin conductance and ratings of affect and arousal

This study investigated the effect of a weak magnetic field (50 microT, 20 Hz sinusoidal, 5 s duration) on concurrent perceptions of visual stimuli. Subjects were seated between Helmholtz coils and gave post-exposure ratings for the affective content and arousing nature of presented images. They were blind as to the presence or absence of a simultaneously presented field. Skin conductance and arousal ratings did not show significant differences between experimental and control conditions, but the affective content rating did (P = 0.041), with the images viewed under field exposure being rated as having a more positive affect. Such measures might thus be useful as additional indicators of magnetic field detection. A post-hoc analysis of skin conductance profiles showed that 48% of subjects exhibited a lowering of skin conductance during field exposure, 34% exhibited no apparent reaction, and 17% exhibited an increase. Overall ratings given by each of the groups appeared to relate to these physiological profiles.     

Effects function simulation of residential appliance field exposures

This paper demonstrates the application of effects function analysis to residential magnetic field exposure, focusing on appliance sources and mitigation choices. Residential field exposure time series were synthesized by using a sample of background household field measurements, a model of average daily appliance use, and a small sample of EMDEX data of field exposure from 12 household appliances. Four alternative effects functions (average field strength with or without a threshold, field strength window, sudden field changes) were simulated by using the synthesized time series data for different exposure situations, such as high and low levels of appliance use, simple avoidance, and use of a set of hypothetical “low field” appliances (50% lower fields). In particular, field exposure from the use of bedside clocks and electric blankets was examined. Results demonstrate that the choice of effects function is critical for the ranks of field sources and exposure reduction choices. For the effects function of average field strength with or without a threshold, exposure from background fields dominated exposure from all appliances except for bedside clocks and electric blankets. In the case of the field strength window effects function, the dominant field sources changed with the width of the window. For the effects function based on rapid field changes, appliance use was the major source of exposure. Because of the small sample size of our data set and other simplifications, specific results should be viewed as illustrative. Bioelectromagnetics 18:116–124, 1997. © 1997 Wiley-Liss, Inc.