摘要:

AbstractFemale CD 1 mice were exposed from the thirty‐fifth day of age for the remainder of their lives to 2.45 GHz, CW‐microwave radiation at a power density of 3 or 10 m W/cm2(SAR = 2.0 or 6.8 W/kg). Exposures took place 1 h/day, 5 day/week in an anechoic chamber at an ambient temperature of 22 °C and a relative humidity of 50%. There were 25 animals in each exposure group, and an equal number of controls were concurrently sham exposed. The average life span of animals exposed at 10 mW/cm2was significantly shorter than that of sham‐exposed controls (572 days vs. 706 days;P= .049; truncation>20%). In contrast, the average lifespan of the animals exposed at 3 mW/cm2was slightly, but not significantly, longer (738 days) than that of controls (706 days). © 1994 Wiley‐Liss, Inc.This article is a US Government work and, as such, is in the public domain in the United States o

ISSN:0197-8462    

DOI:10.1002/bem.2250150302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe effects of a continuous wave or pulse‐modulated, 900 MHz microwave field were studied by in vitro assays of rat chemoreceptors. The pulsed field was modulated as rectangular waves at rates of 1, 6, 16, 32, 75, or 100 pps. The pulse‐period to pulse‐duration ratio was 5 in all cases, and specific absorption rates (SARs) ranged from 0.5 to 18 W/kg. Binding of ligands to cell membranes was differentially affected by exposure to microwaves. For example, binding of H3‐glutamic acid to hippocampal cells was not altered by a 15 min exposure to a continuous wave field at 1 W/kg, but binding of H3‐dihydroalprenolol to liver‐cell membranes of neonates underwent a fivefold decrease under the same field conditions. This effect was not dependent on modulation or on a change in the constant of stimulus‐receptor binding but depended on a shedding of the membrane's receptor elements into solution. The magnitude of inhibition correlated with the oxygen concentration in the exposed suspension. Antioxidants (dithiothreitol and ionol) inhibited the shedding of receptor elements. The microwave exposure did not cause an accumulation of products from the peroxidation of lipids (POL). Ascorbate‐dependent or non‐enzymatic POL was not responsible for the inhibition, and POL was not found in other model systems. However, enzymatic POL mechanisms in localized areas of receptor binding remain a possibility. © 19

ISSN:0197-8462    

DOI:10.1002/bem.2250150303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractPower‐frequency electric and magnetic fields are known to exhibit marked temporal variation, yet in the absence of clear biological indications, the most appropriate summary indices for use in epidemiologic studies are unknown. In order to assess the statistical patterns among candidate indices, data on 4383 worker‐days for magnetic fields and 2082 worker‐days for electric fields collected for the Electric and Magnetic Field Project for Electric Utilities using the EMDEX meter [Bracken (1990): Palo Alto, CA: Electric Power Research Institute] were analyzed. We examined correlations at the individual and job title group levels among indices of exposure to both electric and magnetic fields, including the arithmetic mean, geometric mean, median, 20th and 90th percentiles, time above lower cutoffs of 20 V/m and 0.2 μT, and time above higher cutoffs of 100 V/m and 2.0 μT. For both electric and magnetic fields, the arithmetic mean was highly correlated with the 90th percentile; moderately correlated with the geometric mean, median, and lower and higher cutoff scores; and weakly correlated with the 20th percentile. Electric and magnetic field indices were generally weakly correlated with one another. Rank‐order correlation coefficients were consistently greater than product‐moment correlation coefficients. Job title group summary scores showed higher correlations among electric field indices and magnetic field indices and between electric and magnetic field indices than was found for individual worker‐days, with only the 20th percentile clearly independent of the others. These results suggest that individuals' exposures are adequately characterized by a measure of central tendency for electric and magnetic fields, such as the arithmetic or geometric mean, and an indicator of a lower threshold or cutoff for each field type, such as the 20th percentile or proportion of time above 20 V/m or 0.2 μT. A single measure of central tendency for each type of field appears to be adequate when exposures are assessed at the job title level. © 1994

ISSN:0197-8462    

DOI:10.1002/bem.2250150304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThere is evidence that electromagnetic stimulation may accelerate the healing of tissue damage following ischemia. We undertook this study to investigate the effects of low frequency pulsed electromagnetic field (PEMF) exposure on cerebral injury in a rabbit model of transient focal ischemia (2 h occlusion followed by 4 h of reperfusion). PEMF exposure (280 V, 75 Hz, IGEA Stimulator) was initiated 10 min after the onset of ischemia and continued throughout reperfusion (six exposed, six controls). Magnetic resonance imaging (MRI) and histology were used to measure the degree of ischemic injury. Exposure to pulsed electromagnetic field attenuated cortical ischemic edema on MRI at the most anterior coronal level by 65% (P<0.001). On histologic examination, PEMF exposure reduced ischemic neuronal damage in this same cortical area by 69% (P<0.01) and by 43% (P<0.05) in the striatum. Preliminary data suggest that exposure to a PEMF of short duration may have implications for the treatment of acute stroke. © 1994 Wiley‐Liss, I

ISSN:0197-8462    

DOI:10.1002/bem.2250150305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractTheoretical models proposed to date have been unable to clearly predict biological results from exposure to low‐intensity electric and magnetic fields (EMF). Recently a predictive ionic resonance model was proposed by Lednev, based on an earlier atomic spectroscopy theory described by Podgoretskii and Podgoretskii and Khrustalev. The ion parametric resonance (IPR) model developed in this paper corrects mathematical errors in the earlier Lednev model and extends that model to give explicit predictions of biological responses to parallel AC and DC magnetic fields caused by field‐induced changes in combinations of ions within the biological system. Distinct response forms predicted by the IPR model depend explicitly on the experimentally controlled variables: magnetic flux densities of the AC and DC magnetic fields (Bacand Bdc, respectively); AC frequency (fac); and, implicitly, charge to mass ratio of target ions. After clarifying the IPR model and extending it to combinations of different resonant ions, this paper proposes a basic set of experiments to test the IPR model directly which do not rely on the choice of a particular specimen or endpoint. While the fundamental bases of the model are supported by a variety of other studies, the IPR model is necessarily heuristic when applied to biological systems, because it is based on the premise that the magnitude and form of magnetic field interactions with unhydrated resonant ions in critical biological structures alter ion‐associated biological activities that may in turn be correlated with observable effects in living systems. © 1994 Wiley‐L

ISSN:0197-8462    

DOI:10.1002/bem.2250150306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractA companion paper describes a predictive ion parametric resonance (IPR) model of magnetic field interactions with biological systems based on a selective relation between the ratio of the flux density of the static magnetic field to the AC magnetic field and the charge‐to‐mass ratio of ions of biological relevance. Previous studies demonstrated that nerve growth factor (NGF)‐stimulated neurite outgrowth (NO) in PC‐12 cells can be inhibited by exposure to magnetic fields as a function of either magnetic field flux density or AC magnetic field frequency. The present work examines whether the PC‐12 cell response to magnetic fields is consistent with the quasiperiodic, resonance‐based predictions of the IPR model. We tested changes in each of the experimentally controllable variables [flux densities of the parallel components of the AC magnetic field (Bac) and the static magnetic field (Bdc) and the frequency of the AC magnetic field] over a range of exposure conditions sufficient to determine whether the IPR model is applicable. A multiple‐coil exposure system independently controlled each of these critical quantities. The perpendicular static magnetic field was controlled to less than 2 mG for all tests. The first set of tests examined the NO response in cells exposed to 45 Hz Bacfrom 77 to 468 mG(rms) at a Bdcof 366 mG. Next, we examined an off‐resonance condition using 20 mG Bdcwith a 45 Hz AC field across a range of Bacbetween 7.9 and 21 mG(rms). Finally, we changed the AC frequency to 25 Hz, with a corresponding change in Bdcto 203 mG (to tune for the same set of ions as in the first test) and a Bacrange from 78 to 181 mG(rms). In all cases the observed responses were consistent with predictions of the IPR model. These experimental results are the first to support in detail the validity of the fundamental relationships embodied in the IPR model. © 1994

ISSN:0197-8462    

DOI:10.1002/bem.2250150307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractAdair [Bioelectromagnetics 14:1–4, 1993] writes that “the effects of 60 Hz magnetic fields of 5 μT (50 mG) or less on biological structures holding magnetite (Fe3O4) are shown to be much smaller than those from thermal agitation; hence such interactions cannot be expected to be biologically significant.” This conclusion is questioned, because it appears to be based on a model that probably has very limited validity for pertinent biological systems. Furthermore, biologically plausible parameters can be selected to show that even this particular model does not exclude biologically significant effects of 60 Hz magnetic fields below 5 μT. Reported experimental results indicate effects in mammals of 50 Hz fields at the 1 μT level. © 1994 Wiley

ISSN:0197-8462    

DOI:10.1002/bem.2250150308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe relationship of measured residential magnetic fields and wire codes to pregnancy outcome was examined in data collected for a study of childhood cancer in Denver. Pregnancies in homes with measured fields above 0.2 μT or high wire codes were not more likely to end in miscarriage, low birth weight, or preterm delivery. Lack of data on potential confounders and small numbers of cases limit the study's conclusions. © 1994 Wiley‐Liss,

ISSN:0197-8462    

DOI:10.1002/bem.2250150309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

ISSN:0197-8462    

DOI:10.1002/bem.2250150301

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY