摘要:

AbstractA laboratory facility specifically designed for controlled human exposure to 60‐Hz electric (0 to 16 kV/m) and magnetic (0 to 32 A/m, B = 0 to 40 μT) fields has been constructed. The facility presents uniform fields under controlled temperature and humidity. Special control systems allow collection of physiological data during, as well as before and after, exposure to electric fields at strengths to 16 kV/m under verified double‐blind control. Exposure to continuous or intermittent fields is possible in the facility. The capability of obtaining physiological data during actual exposure to constant or intermittent, 60‐Hz fields, and of doing so without either the subject or the experimenter being aware of actual field conditions, is a critical factor in valid experimentation. © 1992 Wiley‐

ISSN:0197-8462    

DOI:10.1002/bem.2250130302

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

年代:1992

数据来源: WILEY

摘要:

AbstractMany in vitro experiments on the biological effects of extremely low frequency (ELF) electromagnetic fields utilize a uniform external magnetic flux density (B) to expose biological materials. A significant number of researchers do not measure or estimate the resulting electric field strength (E) or current density (J) in the sample medium. The magnitude and spatial distribution of the induced E field are highly dependent on the sample geometry and its relative orientation with respect to the magnetic field. We have studied the E fields induced in several of the most frequently used laboratory culture dishes and flasks under various exposure conditions. Measurements and calculations of the E field distributions in the aqueous sample volume in the containers were performed, and a set of simple, quantitative tables was developed. These tables allow a biological researcher to determine, in a straightforward fashion, the magnitudes and distributions of the electric fields that are induced in the aqueous sample when it is subjected to a uniform, sinusoidal magnetic field of known strength and frequency. In addition, we present a novel exposure technique based on a standard organ culture dish containing two circular, concentric annular rings. Exposure of the organ culture dish to a uniform magnetic field induces different average electric fields in the liquid medium in the inner and outer rings. Results of experiments with this system, which were reported in a separate paper, have shown the dominant role of the magnetically induced E field in producing specific biological effects on cells, in vitro. These results emphasize the need to report data about the induced E field in ELF in‐vitro studies, involving magnetic field exposures. Our data tables on E and J in standard containers provide simple means to enable determination of these parameters. © 1992 Wiley‐Liss,

ISSN:0197-8462    

DOI:10.1002/bem.2250130303

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

年代:1992

数据来源: WILEY

摘要:

AbstractLong‐term studies of the effects of low‐frequency magnetic fields on cells in culture require an incubator that is free of contaminating magnetic fields and that provides automatic control of exposure duration, uniform applied fields, a uniform and well‐controlled environmental temperature, and high reliability of the total system. We describe a dual‐incubator system in which the enclosed solenoid of either unit can provide a sham exposure while the other generates a magnetic induction of up to 500 μT. Each solenoid‐incubator unit contains an enclosed rack that can hold as many as 140 petri dishes for culturing cells; each unit is heated radiantly by circulating warm water. Field‐exposure conditions and temperatures are continuously monitored and controlled by a microcomputer. © 1992 Wi

ISSN:0197-8462    

DOI:10.1002/bem.2250130304

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

年代:1992

数据来源: WILEY

摘要:

AbstractElectric fields induced in a conductive body by the magnetic field of a current‐carrying wire were analyzed theoretically and experimentally to assess the dosimetric importance of highly nonuniform, field‐exposure conditions. Experimentation revealed that a 60‐Hz magnetic field was inversely proportional to the radius of a wire bundle carrying 100 A within a 0.5‐m2test area. A miniaturized electric field probe was used to measure the electric fields induced in 5‐cm‐deep, saline‐filled models. In the theoretical analysis, numerical estimates of induced fields were made by a spreadsheet method. The theoretical calculations and the measured values of induced electric fields were generally in good agreement. The induced fields were in a plane perpendicular to a vertically incident magnetic field; the maximally induced fields were in areas nearest the wire bundle. The strength of the induced field increased with model size: from 96 μV/cm in a 10 × 10 cm model to 176 μV/cm in a 40 × 40 cm model. The strength of the field induced in a 20 × 20 cm model decreased with increasing model‐to‐wire spacing: from 132 μV/cm for a 1‐cm spacing (2‐mT maximum, incident field) to 50 μV/cm for a 6‐cm spacing (0.33‐mT maximum). The results indicate that increases in local values of nonuniformly incident fields produce relatively small increases in induced electric fields. This finding may be important in dosimetric consideration of circumstances, such as use of electric blankets, in which fields of low average strength are accompanied by intense loca

ISSN:0197-8462    

DOI:10.1002/bem.2250130305

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

年代:1992

数据来源: WILEY

摘要:

AbstractPrevious studies in my laboratory have revealed a reproducible and statistically significant increase in the number of malformations in live chicken embryos that had been exposed during the first 48 h of incubation to a pulsed magnetic field (unipolar pulses, 100‐pps, 1‐μT peak density). In marked contrast, no adverse effect was seen following similar exposure to 60‐Hz, bipolar, unipolar, or split‐sine waves at 3‐μT peak‐to‐peak. In the four experiments comprising the present study, differences in the numbers of malformations between control and experimental groups were not statistically significant. Field‐free incubation for an additional 72 h after exposure to a bipolar sine wave for 48 h resulted in anincreasein normal live embryos in both control and treated groups. © 19

ISSN:0197-8462    

DOI:10.1002/bem.2250130306

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

年代:1992

数据来源: WILEY

摘要:

AbstractV. V. Lednev has proposed a mechanism that he suggests would allow very weak magnetic fields, at the cyclotron resonance frequency for Ca2+ions in the earth's field, to induce biological effects. I show that for four independent reasons no such mechanism can operate. © 1992 Wiley‐Liss, I

ISSN:0197-8462    

DOI:10.1002/bem.2250130307

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

年代:1992

数据来源: WILEY

摘要:

AbstractWe performed experiments to investigate subtypes of opioid receptors in the brain involved in the effect of acute (45 min) pulsed microwave exposure (2,450‐MHz, 2‐μs pulses, 500 pps, average power density 1 mW/cm2, peak‐power density, 1 W/cm2, average whole body SAR 0.6 W/kg) on cholinergic activity in the rat brain. Rats were pretreated by microinjection of specific antagonists of μ, δ, and κ opioid‐receptors into the lateral cerebroventricle before exposure to microwaves. The data showed that all three subtypes of opioid receptors are involved in the microwave‐induced decrease in cholinergic activity in the hippocampus. However, the microwave‐induced decrease in cholinergic activity in the frontal cortex was not significantly affected by any of the drug treatments, confirming our previous conclusion that the effect of microwaves on the frontal cortex is not mediated by endogenous opioids. © 1992

ISSN:0197-8462    

DOI:10.1002/bem.2250130308

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

年代:1992

数据来源: WILEY

ISSN:0197-8462    

DOI:10.1002/bem.2250130301

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

年代:1992

数据来源: WILEY