摘要:

AbstractWe have previously shown that 16‐Hz, sinusoidal electromagnetic fields can cause enhanced efflux of calcium ions from chick brain tissue, in vitro, in two intensity regions centered on 6 and 40 Vp‐p/m. Alternatively, 1‐Hz and 30‐Hz fields at 40 Vp‐p/m did not cause enhanced efflux. We now demonstrate that although there is no enhanced efflux associated with a 42‐Hz field at 30, 40, 50, or 60 Vp‐p/m, a 45‐Hz field causes enhanced efflux in an intensity range around 40 Vp‐p/m that is essentially identical to the response observed for 16‐Hz fields. Fields at 50 Hz induce enhanced efflux in a narrower intensity region between 45 and 50 Vp‐p/m, while radiofrequency carrier waves, amplitude modulated at 50 Hz, also display enhanced efflux over a narrow power density range. Electromagnetic fields at 60 Hz cause enhanced efflux only at 35 and 40 Vp‐p/m, intensities slightly lower than those that are effective at 50 Hz. Finally, exposures over a series of frequencies at 42.5 Vp‐p/m reveal two frequency regions that elicit enhanced efflux—one centered on 15 Hz, the other

ISSN:0197-8462    

DOI:10.1002/bem.2250060102

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

年代:1985

数据来源: WILEY

摘要:

AbstractThis paper gives current densities measured in homogeneous grounded human models exposed to vertical, 60‐Hz electric fields. The methods used for these measurements were validated by measuring the current densities induced in a grounded hemisphere and in a grounded prolate hemispheroid; agreement between measurement and theory was good. For an unperturbed field strength of 10 kV/m, current densities measured in the human chest were in the range 125–300 nA/cm2. A strong horizontal current‐density enhancement was observed in the axillae, with peak values of about 400 nA/cm2. The vertical current density in the arms, when held downward, was in the opposite direction to that in the chest. Current densities in the abdomen, pelvis, and legs were a strong function of whether the body was grounded through one or both feet. With one foot grounded, the horizontal current density in the lower pelvic region, just above the crotch, was 770 nA/cm2. This value was the largest of those measured in the head, arms, or torso of the human model. Scaling factors derived from these data and similar data for animals will provide a quantitative basis for comparing animal and human exposure to 60‐Hz electric fields. In addition, current‐density data given in this paper can be directly extrapolated to higher frequencies, at least to 1 MHz. These extrapolated data may be useful to individuals and groups involved in the determination of safety standards for the lower radiofrequen

ISSN:0197-8462    

DOI:10.1002/bem.2250060103

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

年代:1985

数据来源: WILEY

摘要:

AbstractFurther studies of human whole‐body radiofrequency (RF) absorption rates were carried out using a TEM‐cell exposure system. Experiments were done at one frequency near the grounded resonance frequency ( ∼ 40 MHz), and at several below‐resonance frequencies. Absorption rates are small for the K and H orientations of the body, even when grounded. For the body trunk in an E orientation, the absorption rate of a sitting person is about half of the rate for the same person standing with arms at the sides; the latter in turn is about half the rate for the same subject standing with arms over the head. Two‐body interactions cause no increase in absorption rates for grounded people. They do, however, increase the absorption rates for subjects in an E orientation in free space; the largest interaction occurs when one subject is λ/2 behind the other (as seen by the incident wave). When these results are applied to practical occupational exposure situations, the whole‐body specific absorption rate does not exceed the ANSI limit of 0.4 W/kg for exposures permitted by the ANSI standard (C95.1‐1982) at frequencies fr

ISSN:0197-8462    

DOI:10.1002/bem.2250060104

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

年代:1985

数据来源: WILEY

摘要:

AbstractMicrowave exposure has been reported to affect various components of the immune system. In this study, we examined the effect of a single whole‐body exposure of hamsters to microwave (mw) energy (2.45 GHz; 5–25 mW/cm2; 1 h) on the IgM antibody (Ab) response of spleen cells to sheep red blood cells (SRBC). MW‐exposed, sham‐exposed, and cage‐control hamsters were immunized with SRBC and plaque‐forming cells (PFC) in spleens assayed using the direct hemolytic plaque assay. In cage‐control hamsters the Ab response was highest between days 4 and 5, returning to baseline by day 9. MW exposure (25 mW/cm2for 1 h) significantly augmented PFC response only on days 4 and 5 postimmunization, causing approximately a 4.3‐ and 3.5‐fold increase over controls, respectively. Exposure to 15 mW/cm2 caused a lesser, but significant increase in PFC. Exposure to intensities below 15 mW/cm2for 1 h did not produce any increase in Ab response. Immunization with different concentrations of SRBC following 1 h of 25 mW/cm2MW exposure revealed a stimulation in PFC at all concentrations ranging from 5 × 107to 5 × 108SRBC. Pretreatment of hamsters with MW radiation prior to immunization showed that the animals retained an increased sensitivity to SRBC for as long as 4 days after MW exposure. In contrast, exposure of hamsters to MW energy on different days after immunization showed an effect of the PFC response only if given between 0 and 1 day after immunization. These results suggest that MW exposure augments the primary IgM response to SRBC by affecting some early event in the immune response process. The various possible explanations for this pheno

ISSN:0197-8462    

DOI:10.1002/bem.2250060105

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

年代:1985

数据来源: WILEY

摘要:

AbstractRabbit polymorphonuclear leucocytes (PMN, neutrophils) obtained from peritoneal exudate were exposed in vitro for one‐half or one hour to continuous wave or amplitudemodulated (20‐Hz) 100‐MHz RF radiation in a temperature‐controlled coaxial exposure chamber at field strengths from 2.5 to 4.1 V/cm (SARs of 120 to 341 W/kg). RF exposure at 37° 0.2°C had no detectable effect on PMN viability or phagocytosis compared to sham‐exposed cells simultaneously subjected to the same time‐temperature regime. Temperature control studies indicated that at 37°C no effect on PMN viability would be expected but phagocytosis would be reduced by approximately 6%/°C temperature increase. The absence of an effect of RF exposure suggests that there was minimal undetected intrasample heating and that phagocytosis was not affected by 100‐MHz RF radiation under the conditi

ISSN:0197-8462    

DOI:10.1002/bem.2250060106

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe eukaryotic protozoan,Paramecium, was examined as a model for effects of pulsated electromagnetic fields (PEMF) on cells. A 72‐Hz PEMF similar to fields employed clinically increased cell division rates inParameciumby 8.5%. Two calcium transport mutants of these organisms showed differential responses to the same field. Verapamil, a calcium channel blocker, abolished any effect of PEMFs on cell division rates. A fluorescent probe that is thought to sense changes in membrane potential also manifested an altered response in the PEMF‐exposed cells whereas a fluorescent lipid bilayer fluidity probe produced evidence of decreased membrane fluidity in the exposed cells. An effect of PEMFs on ion transport mediated by either a direct or indirect effect on the cell membrane is suggestd by these stud

ISSN:0197-8462    

DOI:10.1002/bem.2250060107

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

年代:1985

数据来源: WILEY

摘要:

AbstractBoth positive and negative biological effects of microwaves on drug actions in rats exposed to 1‐mW/cm2, 2,450‐MHz microwaves have been reported by several investigators. We conducted dosimetry studies for seven different exposure conditions to determine whether these different results could be due to the rats having been exposed differently. They included anterior and posterior exposures in a circular waveguide, near field, far field with E‐or H‐field parallel to the long axis of the body and dorsal exposure in a miniature anechoic chamber with E‐ or H‐field parallel to the long axis of the body. The average specific absorption rates (SARs) in the head, tail, and body of the exposed rats were measured by means of a calorimetry system. The local SARs at eight locations in the brain were determined by temperature measurement with Vitek probes. Intensive coupling of energy to the tail when it was exposed parallel to the E‐field was shown by thermography. For the same average incident power density, the average SARs in the heads of rats were about two times higher in the circular waveguide than for other exposures. The local SARs in the brain varied for different exposure conditions. Statistical comparisons of SARs under the different exposure conditions

ISSN:0197-8462    

DOI:10.1002/bem.2250060108

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

年代:1985

数据来源: WILEY

摘要:

AbstractA comparison of the effects of continuous‐wave, sinusoidal‐amplitude‐modulated, and pulsed square‐wave‐modulated 591‐MHz microwave exposures on brain energy metabolism was made in male Sprague‐Dawley rats (175–225 g). Brain NADH fluorescence, adenosine triphosphate (ATP) concentration, and creatine phosphate (CP) concentration were determined as a function of modulation frequency. Brain temperatures of animals were maintained between −0.1 and −0.4°C from the preexposure temperature when subjected to as much as 20 mW/cm2(average power) CW, pulsed, or sinusoidal‐amplitude modulated 591‐MHz radiation for 5 min. Sinusoidal‐amplitude‐modulated exposures at 16–24 Hz showed a trend toward preferential modulation frequency response in inducing an increase in brain NADH fluorescence. The pulse‐modulated and sinusoidal‐amplitudemodulated (16 Hz) microwaves were not significantly different from CW exposures in inducing increased brain NADH fluorescence and decreased ATP and CP concentrations. When the pulse‐modulation frequency was decreased from 500 to 250 pulses per second the average incident power density threshold for inducing an increase in brain NADH fluorescence increased by a factor of 4—ie, from about 0.45 to about 1.85 mW/cm2. Since brain temperature did not increase, the microwave‐induced increase in brain NADH and decrease in ATP and CP concentrations was not due to hyperthermia. This suggests a direct interaction mechanism and is consistent with the hypothesis of microwave inhibition of mitochondrial electron tr

ISSN:0197-8462    

DOI:10.1002/bem.2250060109

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

年代:1985

数据来源: WILEY

摘要:

AbstractFemale rats were trained to detect a vertical, 60‐Hz electric field using the same apparatus and procedure we used previously to study behavioral detection of the field by male rats. Each rat was trained individually to press a lever in the presence of the field and not to press in its absence. Correct detections occasionally produced a food pellet. The probability of detecting the field increased as field strength increased. The threshold of detection —ie, the field strength required for detections at a probability of 0.5 after correction for errors—varied among rats between 3 and 10 kV/m. Behavioral detection by female rats was indistinguishable from that by male

ISSN:0197-8462    

DOI:10.1002/bem.2250060110

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

年代:1985

数据来源: WILEY

摘要:

AbstractMice given ELF electric field exposures of 50‐400 Vm−10at frequencies of 15, 30, and 50 Hz failed to display any significant changes in barbiturate sleeping time or exploratory activ

ISSN:0197-8462    

DOI:10.1002/bem.2250060111

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

年代:1985

数据来源: WILEY