摘要:

AbstractA system is described that uses an oscillating magnetic field to produce power‐frequency electric fields with strengths in excess of those produced in an animal or human standing under a high‐voltage electric‐power transmission line. In contrast to other types of exposure systems capable of generating fields of this size, no electrodes are placed in the conducting growth media: the possibility of electrode contamination of the exposed suspension is thereby eliminated. Electric fields in the range 0.02–3.5 V/m can be produced in a cell culture with total harmonic distortions less than 1.5%. The magnetic field used to produce electric fields for exposure is largely confined within a closed ferromagnetic circuit, and experimental and control cells are exposed to leakage magnetic flux densities less than 5 μT. The temperatures of the experimental and control cell suspensions are held fixed within ±0.1°C by a water bath. Special chambers were developed to hold cell cultures during exposure and sham exposure. Chinese hamster ovary (CHO) cells incubated in these chambers grew for at least 48 h and had population doubling times of 16–17 h, approximately the same as for CHO cells grown under standard cell‐cult

ISSN:0197-8462    

DOI:10.1002/bem.2250050202

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

年代:1984

数据来源: WILEY

摘要:

AbstractThe radiofrequency absorption rates of five male human volunteers have been measured from 3 to 41 MHz. The subjects were exposed at about 10 μW/cm2inside a very large transverse electromagnetic (TEM) cell and never absorbed more than 1 W. Both the EKH and EHK orientations were employed under both free‐space and grounded conditions. Absorption rates for the EKH orientation exceed those of the EHK orientation by 40% in free space, but only by 6% when grounded. The absorption rates for the grounded men vary with frequency, f, as f1.9from 3 to 25 MHz and then level off at the peak. The freespace absorption rates vary as f1.7from 3 to 18 MHz and as f2.9from 18 to 41 MHz. The average measured absorption rates at 10 MHz exceed the average of the standard model calculations by a factor of three (for free space) or four (grounded). The average man, when exposed grounded in an EKH orientation to the maximum permitted exposure levels under ANSI standard C95.1‐1982, will absorb 0.58 ± 0.14 W/kg over most of the 3 to 41‐MHz frequency range. This slightly exceeds the whole‐body maximum of 0.40 W/kg underlying the

ISSN:0197-8462    

DOI:10.1002/bem.2250050203

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

年代:1984

数据来源: WILEY

摘要:

AbstractBehavioral measures were evaluated in adult CD‐1 and LAF‐1 mice continuously exposed for 72 h to a 1.5‐Tesla (1 T = 104Gauss) homogeneous DC magnetic field, and in LAF‐1 mice continuously exposed for 72 h to a sinusoidal 60‐Hz, 1.65‐mT (rms) homogeneous AC field. Three types of behavioral tests were employed: (1) Memory of an electroshock‐motivated passive avoidance task was assessed in animals that had been trained immediately prior to the field exposure. The strength of memory was varied either by altering the strength of the electric footshock during training, or by administering a cerebral protein synthesis inhibitor, anisomycin, at the time of training. (2) General locomotor activity was measured using a quadrant‐crossing test immediately after termination of the magnetic field exposure. (3) Sensitivity of the experimental subjects to the seizure‐inducing neuro‐pharmacological agent, pentylenetetrazole, was assessed immediately after the field exposure on the basis of three criteria: (a) the percentage of subjects exhibiting a generalized seizure, (b) the mean time to seizure, and (c) the mean seizure level. The results of these studies revealed no behavioral alterations in exposed mice relative to controls in any of the experimental tests with the 1.5‐T DC field or the 60‐Hz,

ISSN:0197-8462    

DOI:10.1002/bem.2250050204

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

年代:1984

数据来源: WILEY

摘要:

AbstractThe effect of 2,450‐MHz pulsed microwave radiation on the enzyme activity of membranefree acetylcholinesterase was studied while the enzyme was in the microwave field. We found no significant effect of microwave radiation on enzyme activity using a wide variety of power densities, pulse widths, repetition rates, and duty cycles. This suggests that simple, direct modification by microwave energy of acetylcholinesterase structure and enzymic activity is not related to microwave alteration of acetylcholinesterase central nervous system level

ISSN:0197-8462    

DOI:10.1002/bem.2250050205

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

年代:1984

数据来源: WILEY

摘要:

AbstractThe aggregation between lectins and lymphocyte surface receptors can be affected strongly by a low‐level electric field induced in the cell suspension by a time‐varying magnetic field. One of the possible mechanisms is the microelectrophoretic effect due to the electric field, which influences the distance (in the mean square sense) between charged ligands and receptors when they are about to separate. On a purely theoretical basis, it is shown that, at low frequencies, an externally induced periodic electric field always decreases the mean lifetime of ligand‐receptor complexes. As a consequence, the mitogenic gain obtained by lectin addition to cell suspension is decreased. These results suggest that such a mechanism, if effective, reduces the lectin mitogenic capability and offers a way of handling similar phenomena which have been described for other biological sy

ISSN:0197-8462    

DOI:10.1002/bem.2250050206

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

年代:1984

数据来源: WILEY

摘要:

AbstractA high coefficient of variation is characteristic of the bioelectric potentials recorded from living long bones. As a consequence, the data collected from animal and human experiments are difficult to use in practical ways. A distribution curve for bone bioelectric potentials has been calculated using polynomial regression analysis to process the voltage values recorded on the whole length of rabbit tibiae, with reference electrodes positioned in three different points of the bone. The distribution curve so obtained is presented to fulfill the need for a reference curve for the bioelectric potentials recorded from rabbit tibial surfaces.

ISSN:0197-8462    

DOI:10.1002/bem.2250050207

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

年代:1984

数据来源: WILEY

摘要:

AbstractTwo series of experiments were performed to study the effects of acute exposure (45 min) to 2,450‐MHz circularly polarized, pulsed microwaves [1 mW/cm2, 2‐μs pulses, 500 pps, specific absorption rate (SAR) 0.6 W/kg] on the actions of pentobarbital in the rat. In the first experiment, rats were irradiated with microwaves and then immediately injected with pentobarbital. Microwave exposure did not significantly affect the extent of the pentobarbital‐induced fall in colonic temperature. However, the rate of recovery from the hypothermia was significantly slower in the microwave‐irradiated rats and they also took a significantly longer time to regain their righting reflex. In a second experiment, rats were first anesthetized with pentobarbital and then exposed to microwaves with their heads either pointing toward the source of microwaves (anterior exposure) or pointing away (posterior exposure). Microwave radiation significantly retarded the pentobarbital‐induced fall in colonic temperature regardless of the orientation of exposure. However, the recovery from hypothermia was significantly faster in posterior‐exposed animals compared to those of the anterior‐exposed and sham‐irradiated animals. Furthermore, the posterior‐exposed rats took a significantly shorter time to regain their righting reflex than both the anterior‐exposed and sha

ISSN:0197-8462    

DOI:10.1002/bem.2250050208

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

年代:1984

数据来源: WILEY

摘要:

AbstractMicrowave irradiation of rats by circularly polarized, 2,450‐MHz, pulsed waves (2‐μs pulses; 500 pps) was performed in waveguides to determine effects on ethanol‐induced hypothermia and on ethanol consumption. Rats injected intraperitoneally with ethanol (3 g/kg in a 25% v/v water solution) immediately after 45 min of microwave irradiation exhibited attenuation of the initial rate of fall in body temperature, which was elicited by the ethanol, but exhibited no significant difference in maximal hypothermia as compared with that of sham‐irradiated rats. Microwave irradiation did not affect the consumption of a 10% sucrose (w/v) solution by water‐deprived rats. However, it enhanced the consumption of a solution of 10% sucrose (w/v) + 15% ethanol (v/v) by water‐deprived animals. These results were obtained at a specific absorption rate (SAR) of 0.6 W/kg, which rate of energy dosing would require a power density of 3–6 mW/cm2if exposure of the animals had occurred to a 12

ISSN:0197-8462    

DOI:10.1002/bem.2250050209

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

年代:1984

数据来源: WILEY

摘要:

AbstractThe electromagnetic power absorption in tissue‐equivalent phantoms that are used for evaluation of diathermy and hyperthermia applicators is analyzed for the purpose of determining the effect of an insulating partition that is frequently used to facilitate separation of the phantom for thermographic analysis of heating distributions. An analysis that is based on the plane wave spectrum decomposition of the electromagnetic field is applied to a simplified model of the medium. The simplified model is valid whenever the insulating partition does not significantly alter the fields in the medium. The curves that are presented indicate that thin partitions do not significantly alter the power absorption for most situations of therapeutic interest. Data on the effects of partition thickness and electrical parameters are presented for microwave and radiofrequencies of interest for diathermy and hyperthermi

ISSN:0197-8462    

DOI:10.1002/bem.2250050210

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

年代:1984

数据来源: WILEY

摘要:

AbstractFive food‐deprived rhesus monkeys were exposed to 225‐MHz continuous‐wave, and 1.3‐GHz, and 5.8‐GHz pulsed radiation to determine the minimal power densities affecting performance. The monkeys were trained to press a lever (observing‐response) thereby producing signals that indicated availability of food. In the presence of the aperiodically appearing food signals, a detection response on a different lever was reinforced by a food pellet. Continuous, stable responding during 60‐min sessions developed and was followed by repeated exposures to radiofrequency radiation. The subjects, restrained in a Styrofoam chair, were exposed to free‐field radiation while performing the task. Colonic temperature was simultaneously obtained. Observing‐response performance was impaired at increasingly higher power densities as frequency increased from the near‐resonance 225 MHz to the above‐resonance 5.8 GHz. The threshold power density of disrupted response rate at 225 MHz was 8.1 mW/cm2; at 1.3 GHz it was 57 mW/cm2, and at 5.8 GHz it was 140 mW/cm2. These power densities were associated with reliable increases in colonic temperatures above sham‐exposure levels. The mean increase was typically in the range of 1°C, and response‐rate changes were not observed in the absence of concomitant temperature increases. In these experiments increase of colonic temperature was a much better predictor of behavioral disruption than was either the power density of the incident field or estimates of whole‐body‐avera

ISSN:0197-8462    

DOI:10.1002/bem.2250050211

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

年代:1984

数据来源: WILEY