摘要:

AbstractThe current guideline for exposure to radiofrequency radiation (RFR) was developed through assessment of the biological effects data collected primarily from the rat. The consensus that a lack of hazardous biological effects occurred below a whole‐body‐averaged specific absorption rate (SAR) of 4.0 W/kg led to the proposition of a 0.4 W/kg guideline with a built‐in safety factor of 10. This paper demonstrates that if the RFR absorption rate in the rat had been normalized with respect to total body surface area rather than body mass, the exposure guideline would be 2.3 W/m2, which translates to an SAR of approximately 0.06 W/kg for an adult human. It is further shown that a given RFR absorption rate, normalized as a fraction of a species' heat loss per unit of surface area, is independent of body mass over a range of 0.03‐100 kg; however, a normalization of the RFR absorption rate to heat loss per unit of body mass is highly dependent on the species' mass. Normalizing the rate of RFR absorption to the surface area of the rat indicates that the current RFR exposure guideline of 0.4 W/kg may be t

ISSN:0197-8462    

DOI:10.1002/bem.2250080202

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

年代:1987

数据来源: WILEY

摘要:

AbstractPulsed magnetic fields (PMFs) are widely used to treat difficult fractures of bone and other disorders of connective tissue. It is not clear how they interact with tissue metabolism, although it has been proposed that induced currents or electric fields impinging on cell membranes may modify their ion transport function. This hypothesis was tested by treating in vitro models for ion transport processes with short‐term exposure to PMFs. No change occurred in active transport of potassium or calcium in human red cells or in calcium transport through an epithelial membrane. We considered less direct action on red cell membranes, that their permeability might be modified after PMF treatment, and also that PMFs might alter the extracellular ionic activity within connective tissue by interacting with its Donnan potential. Each of these studies proved negative, and we conclude that the PMF waveforms used here do not exert a general short‐term effect on cellular ion transp

ISSN:0197-8462    

DOI:10.1002/bem.2250080203

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

年代:1987

数据来源: WILEY

摘要:

AbstractFrom a mobile unit, 60‐Hz electric and magnetic fields generated by Hydro‐Québec's distribution network were measured. Nine runs, representative of various human environments, were investigated. Typical values were 32 V/m and 0.16 μT. The electrical distribution networks investigated were major contributors to the electric and magnetic environ

ISSN:0197-8462    

DOI:10.1002/bem.2250080204

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

年代:1987

数据来源: WILEY

摘要:

AbstractAdult male, Long‐Evans rats were exposed 7 h a day for 90 days to continuous wave (CW) 2,450‐MHz microwaves at an average power density of 0.5 mW/cm2. Exposures were in a monopole‐above‐ground radiation chamber with rats in Plexiglas cages. The resulting specific absorption rate (SAR) was 0.14 W/kg (±0.01 SEM). Additional rats served as sham‐exposed and home‐caged controls. All were evaluated daily for body mass and food and water intakes. Once each 30 days, throughout baseline and exposure phases of the experiment, rats in the sham‐ and microwave‐exposed groups were tested for their sensitivity to footshock. After 90‐days of exposure, the rats were evaluated an open field, an active avoidance task and an operant task for food reinforcement. Performance of sham‐and microwave‐irradiated rats was reliably different on only one measure, the lever‐pressing task. The general conclusion reached was that exposure to CW 2,450‐MHz microwave radiation at 0.5 mW/cm2was below the threshold for behavioral effects over a wide range of variables, but did have an effect on a time‐related operant task, although the direction of

ISSN:0197-8462    

DOI:10.1002/bem.2250080205

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe treatment of long‐term, stable para‐ and quadriplegics with pulsed electrical stimulation for pain control resulted in, anecdotally, a significant number of these individuals showing increased motor function as well as sensory awareness. This small pilot study was conducted in order to assess the hypothesis that pulsed electrical fields can effect diseased neurological function. Thirteen para‐ and quadriplegic subjects with 18 months of stable neurological signs and symptoms were exposed daily to pulsed electrical stimulation for a 6‐month period and assessed for any improvement in motor function or sensory perception. The hypothesis is that pulsed electromagnetic fields can normalize viable but dysfunctional neuronal structures. Results were enco

ISSN:0197-8462    

DOI:10.1002/bem.2250080206

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

年代:1987

数据来源: WILEY

摘要:

AbstractA frequent problem in the radiofrequency (RF) irradiation of experimental animals in health effects studies is the temporal variation of the specific absorption rate (SAR) with animal movement. An RF power controller that regulates the energy absorption rate has been designed for use with transmission line exposure systems that utilize the power difference method to monitor the SAR. The controller operates by altering the incident power to the exposure cell in order to compensate for the change in RF energy absorption rate that is due to animal motion. A circuit diagram is presented as well as experimental data under three conditions of exposure. The controller is effective in maintaining the mean value of energy absorption rate at the setpoint value even for the case of a highly active animal.

ISSN:0197-8462    

DOI:10.1002/bem.2250080207

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

年代:1987

数据来源: WILEY

摘要:

AbstractExposure to electrically charged gas molecules (air ions) has been reported to influence physiological and behavioral functions in animals and humans although there is controversy as to whether these findings are valid. A popular hypothesis concerning the reported effects of air ions is that alterations in serotonin (5HT) metabolism, particularly in the brain, are involved. We measured the concentration and turnover of 5HT in rats exposed to 5.0 × 105ions/cm3for up to 66 hours. Contrary to previous reports of other investigators, we were unable to demonstrate any effect of exposure to air ions or associated DC electric fields on the concentration or turnover of 5HT in rats under carefully controlled and characterized exposure conditions

ISSN:0197-8462    

DOI:10.1002/bem.2250080208

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

年代:1987

数据来源: WILEY

摘要:

AbstractTo obtain more detailed information relative to the potential usefulness of using radio frequency (RF) energy in treating hypothermia, anesthetized rhesus monkeys were used in a rewarming study that compared a conventional method (heating pad) with an RF induction coil system. Rectal temperature (Tre) of each subject was monitored, and enzyme and isoenzyme levels were determined from blood samples collected before, during, and up to 48 h after hypothermia in order to assess the effects of each rewarming method. The previously observed postprocedure rise in serum enzymes (most visible at 24 h) was again seen, with no statistically significant difference in the time course of serum enzyme levels between the two treatments for comparable durations of hypothermia. To test the limits of the ability of the RF induction coil system, successively more severe hypothermia was induced in the subjects to the point of cardiovascular collapse (Tre<20°C); RF energy was successful in resuscitating the profoundly hypothermic subjects without discernible harmful effects

ISSN:0197-8462    

DOI:10.1002/bem.2250080209

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

年代:1987

数据来源: WILEY

摘要:

AbstractHyperthermia is attractive as a potential adjunctive modality in the treatment of cancer, especially those cancers that are more resistant to conventional modalities. In the present study, we characterized the response of two pancreatic cancer cell lines to hyperthermia alone. In so doing, we utilized and characterized a novel exposure system that heats by 915‐MHz continuous wave microwave (MW) radiation, with microprocessor control of the power input via temperature monitoring of the sample and simultaneous visualization and recording of temperature parameters. Samples, consisting of cells in 25‐cm2culture flasks with 10 ml of medium, were exposed to MWs in a stripline for 1 h at MW‐induced temperatures of 37, 41.5, 42.5, 43.5, or 44.5 °C. The specific absorption rate was 132 W/kg for all temperatures. In addition, 37 °C waterbath controls were concurrently run. The colony formation assay was used to assess cytotoxicity. No significant difference was found between 37 °C waterbath and 37 °C MW controls. Significant differences in the thermosensitivity of the two cell lines were found, with the most drug‐sensitive cell line showing the greatest thermosensitivity. However, hyperthermia alone was not very effective as a single cytotoxic modality in either cell line. The MW‐hyperthermia‐induction system provided precise, automated temperature control (± 0.2 °C), and ease of utilization an

ISSN:0197-8462    

DOI:10.1002/bem.2250080210

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe ATPase activity in human red blood cell membranes was investigated in vitro as a function of temperature and exposure to 2,450‐MHz continuous wave microwave radiation to confirm and extend a report of Na+transport inhibition under certain conditions of temperature and exposure. Assays were conducted spectrophotometrically during microwave exposure with a custom‐made spectrophotometer‐waveguide apparatus. Temperature profiles of total ATPase and Ca+2ATPase (ouabain‐inhibited) activity between 17 and 31 °C were graphed as an Arrhenius plot. Each data set was fitted to two straight lines which intersect between 23 and 24 °C. The difference between the total and Ca+2ATPase activities, which represented the Na+/K+ATPase activity, was also plotted and treated similarly to yield an intersection near 25 °C. Exposure of membrane suspensions to electromagnetic radiation, at a dose rate of 6 W/kg and at five temperatures between 23 and 27 °C, resulted in an activity change only for the Na+/K+ATPase at 25 °C. The activity decreased by approximately 35% compared to sham‐irradiated samples. A possible explanation for the unusual temperature/microwave interacti

ISSN:0197-8462    

DOI:10.1002/bem.2250080211

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

年代:1987

数据来源: WILEY