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  • Occupational Health and Environmental Toxicology  (12)
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  • 1
    Electronic Resource
    Electronic Resource
    Equalizing the electric field intensity within chick brain immersed in buffer solution at different carrier frequencies (1981)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 2 (1981), S. 411-413 
    Details
    ISSN: 0197-8462
    Keywords: calcium efflux ; complex permittivity ; amplitude windows ; concentric spheres ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Presented here are the numerical relationships between incident power densities that produce the same average electric field intensity within a chick brain half immersed in buffered saline solution and exposed to a uniform electromagnetic field at carrier frequencies of 50, 147, and 450 MHz. Calculations are based on modeling the buffer solution as a spherical shell in air with an inner concentric sphere of brain tissue. The results support our earlier conclusion that calcium efflux results obtained at different carrier frequencies are in agreement when related by the electric field within the brain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bem.2250020413
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  • 2
    Electronic Resource
    Electronic Resource
    The effects of hyperthermia and hyperthermia plus microwaves on rat brain energy metabolism (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 5 (1984), S. 63-70 
    Details
    ISSN: 0197-8462
    Keywords: hyperthermia ; microwaves ; brain ; ATP ; CP ; energy metabolism ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: The effects of hyperthermia, alone and in conjunction with microwave exposure, on brain energetics were studied in anesthetized male Sprague-Dawley rats. The effect of temperature on adenosine triphosphate concentration [ATP] and creatine phosphate concentration [CP] was determined in the brains of rats that were maintained at 35.6, 37.0, 39.0, and 41.0°C. At 37, 39, and 41°C brain [ATP] and [CP] were down 6.0, 10.8, and 29.2%, and 19.6, 28.7, and 44%, respectively, from the 35.6°C control concentrations. Exposure of the brain to 591-MHz radiation at 13.8 mW/cm2 for 0.5, 1.0, 3.0, and 5.0 min caused further decreases (below those observed for 30°C hyperthermia only) of 16.0, 29.8, 22.5, and 12.3% in brain [ATP], and of 15.6, 25.1, 21.4, and 25.9% in brain [CP] after 0.5, 1.0, 3.0, and 5.0 min, respectively. Recording of brain reduced nicotinamide adenine dinucleotide (NADH) fluorescence before, during, and after microwave exposure showed an increase in NADH fluorescence during microwave exposure that returned to preexposure levels within 1 min postexposure. Continuous recording of brain temperatures during microwave exposures showed that brain temperature varied between -0.1 and +0.05°C. Since the microwave exposures did not induce tissue hyperthermia, it is concluded that direct microwave interaction at the subcellular level is responsible for the observed decrease in [ATP] and [CP].
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bem.2250050107
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  • 3
    Electronic Resource
    Electronic Resource
    Internal field strength measurements in chick forebrains at 50, 147, and 450 MHz. This paper has been reviewed by the Health Effects Research Laboratory, U.S. Environmental Protection Agency, and approved for publication. Mention of trade names or commercial products does not constitute endorsement or recommendation for use. (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 5 (1984), S. 293-304 
    Details
    ISSN: 0197-8462
    Keywords: brain tissue ; radiofrequency (RF) radiation ; dosmetry ; calcium ions ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: This report describes some experimental measurements of the internal field levels induced within isolated chick-forebrains irradiated at 50, 147, and 450 MHz, under essentially the same conditions as those used in the in vitro calcium-ion efflux experiments. Ratios of incident power at 50/147 MHz and 147/450 MHz that are needed to establish the same probe output are given and comparisons made with values predicted by different spherical models. Data predicted by the layered-sphere model were found to be in close agreement with measured values for the 50/147-MHz ratio. Agreement for the 147/450-MHz ratio was poorer.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bem.2250050302
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of continuous-wave, pulsed, and sinusoidal-amplitude-modulated microwaves on brain energy metabolism (1985)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 6 (1985), S. 89-97 
    Details
    ISSN: 0197-8462
    Keywords: CW ; pulsed ; amplitude modulation ; microwaves ; brain ; metabolism ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: A 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 transport chain function of ATP production.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bem.2250060109
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  • 5
    Electronic Resource
    Electronic Resource
    Specific absorption rate in electrically coupled biological samples between metal plates (1986)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 7 (1986), S. 163-176 
    Details
    ISSN: 0197-8462
    Keywords: dipole coupling ; electrical images ; low frequency ; SAR ; internal field ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: The specific absorption rate (SAR) in a biological sample irradiated by electromagnetic fields between the metal plates of a transmission line can be altered significantly by the spacing of the metal plates and the distance between neighboring samples. The SAR in spherical biological samples is calculated for a number of neighboring sample arrangements and metal-plate spacings by using the method of images and induced dipole coupling. For a decrease in metal-plate spacing, the derived equations predict an increase in SAR within a sample and a decrease in SAR with a decrease in neighboring-sample spacing. The calculations are compared with measurements made with the aid of an array of 1-in radius metal hemispheres on the lower plate of two parallel plates (thus forming an image system). The hemisphere on which measurements are taken is insulated from the metal plate and is connected via a coaxial center conductor to an HP 3582A spectrum analyzer that measures the voltage and hence the electric field intensity at the hemisphere. Measurements made at a frequency where wavelength is large compared with sample size (48 Hz) are in good agreement with calculations.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bem.2250070207
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  • 6
    Electronic Resource
    Electronic Resource
    Experimental method for the hyperthermic treatment of cells in tissue culture: Initial application to pancreatic cancer cells (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 8 (1987), S. 195-202 
    Details
    ISSN: 0197-8462
    Keywords: Microwave irradiation ; hyperthermia ; pancreatic cancer ; experimental models ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Hyperthermia 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-cm2 culture 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 and data management.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bem.2250080210
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  • 7
    Electronic Resource
    Electronic Resource
    Effect of ambient levels of power-line-frequency electric fields on a developing vertebrate (1988)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 9 (1988), S. 129-140 
    Details
    ISSN: 0197-8462
    Keywords: ELF fields ; calcium ions ; electromagnetic fields ; brain tissue ; developing organism ; chicken ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Fertilized eggs of Gallus domesticus were exposed continuously during their 21-day incubation period to either 50- or 60-Hz sinusoidal electric fields at an average intensity of 10 Vrms/m. The exposure apparatus was housed in an environmental room maintained at 37°C and 55-60% relative humidity (RH). Within 1.5 days after hatching, the chickens were removed from the apparatus and tested. The test consisted of examining the effect of 50- or 60-Hz electromagnetic fields at 15.9 Vrms/m and 73 nTrms (in a local geomagnetic field of 38 μT, 85°N) on efflux of calcium ions from the chicken brain. For eggs exposed to 60-Hz electric fields during incubation, the chicken brains demonstrated a significant response to 50-Hz fields but not to 60-Hz fields, in agreement with the results from commercially incubated eggs [Blackman et al., 1985a]. In contrast, the brains from chicks exposed during incubation to 50-Hz fields were not affected by either 50- or 60-Hz fields. These results demonstrate that exposure of a developing organism to ambient power-line-frequency electric fields at levels typically found inside buildings can alter the response of brain tissue to field-induced calcium-ion efflux. The physiological significance of this finding has yet to be established.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bem.2250090204
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  • 8
    Electronic Resource
    Electronic Resource
    Off-center spherical model for dosimetry calculations in chick brain tissue (1986)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 7 (1986), S. 209-221 
    Details
    ISSN: 0197-8462
    Keywords: brain tissue ; radiofrequency ; radiation ; dosimetry ; calcium ions ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: This paper presents calculations for the electric field and absorbed power density distribution in chick brain tissue inside a test tube, using an off-center spherical model. It is shown that the off-center spherical model overcomes many of the limitations of the concentric spherical model, and permits a more realistic modeling of the brain tissue as it sits in the bottom of the test tube surrounded by buffer solution. The effect of the unequal amount of buffer solution above the upper and below the lower surfaces of the brain is analyzed. The field distribution is obtained in terms of a rapidly converging series of zonal harmonics. A method that permits the expansion of spherical harmonics about an off-center origin in terms of spherical harmonics at the origin is developed to calculate in closed form the electric field distribution. Numerical results are presented for the absorbed power density distribution at a carrier frequency of 147 MHz. It is shown that the absorbed power density increases toward the bottom of the brain surface. Scaling relations are developed by keeping the electric field intensity in the brain tissue the same at two different frequencies. Scaling relations inside, as well as outside, the brain surface are given. The scaling relation distribution is calculated as a function of position, and compared to the scaling relations obtained in the concentric spherical model. It is shown that the off-center spherical model yields scaling ratios in the brain tissue that lie between the extreme values predicted by the concentric and isolated spherical models.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bem.2250070210
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  • 9
    Electronic Resource
    Electronic Resource
    The differential effects of 200, 591, and 2,450 MHz radiation on rat brain energy metabolism (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 5 (1984), S. 419-433 
    Details
    ISSN: 0197-8462
    Keywords: radiofrequency ; brain ; metabolism ; stripline ; fluorescence ; mechanism ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Three key compounds in brain energy metabolism have been measured during and after exposure to continuous wave radiofrequency radiation at 200, 591, and 2,450 MHz. Frequency-dependent changes have been found for all three compounds. Changes in NADH fluorescence have been measured on the surface of a surgically uncovered rat brain during exposure. At 200 and 591 MHz, NADH fluorescence increased in a dose-dependent manner between approximately 1 and 10 mW/cm2, then became constant at higher exposures. There was no effect at 2,450 MHz. Levels of ATP and CP were measured in whole brain after exposure. The ATP levels were decreased at 200 and 591 MHz but not at 2,450 MHz. The CP levels decreased only at 591 MHz. The effect of duration of exposure (up to 5 min) was investigated for all compounds at 200 MHz and 2,450 MHz, and exposures to 20 minutes were examined at 591 MHz. Temperature in the rat brain was essentially constant for all exposures. A general mechanism for inhibition of the mitochondrial electron transport chain and the CP-kinase reaction pathway by radiofrequency radiation has been proposed.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bem.2250050407
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  • 10
    Electronic Resource
    Electronic Resource
    Microwave effects on energy metabolism of rat brain (1980)
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 1 (1980), S. 171-181 
    Details
    ISSN: 0197-8462
    Keywords: microwaves ; in vivo ; brain ; adenosine triphosphate (ATP) ; creatine phosphate (CP) ; NADH ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Rat brain was exposed to 591-MHz, continuous-wave (CW) microwaves at 13.8 or 5.0 mW/cm2 to determine the effect on nicotinamide adenine dinucleotide, reduced (NADH), adenosine triphosphate (ATP) and creatine phosphate (CP) levels. On initiation of the in vivo microwave exposures, fluorimetrically determined NADH rapidly increased to a maximum of 4.0%-12.5% above pre-exposure control levels at one-half minute, then decreased slowly to 2% above control at three minutes, finally increasing slowly to 5% above control level at five minutes. ATP and CP assays were performed on sham- and microwave-exposed brain at each exposure time. At 13.8 mW/cm2, brain CP level was decreased an average of 39.4%, 41.1%, 18.2%, 13.1%, and 36.4% of control at exposure points one-half, one, two three, and five minutes, respectively, and brain ATP concentration was decreased an average of 25.2%, 15.2%, 17.8%, 7.4%, and 11.2% of control at the corresponding exposure periods. ATP and CP levels of rat brain exposed to 591-MHz cw microwaves at 5 mW/cm2 for one-half and one minute were decreased significantly below control levels at these exposure times, but were not significantly different from the 13.8 mW/cm2 exposures. For all exposures, rectal temperature remained constant. Heat loss through the skull aperture caused brain temperature to decrease during the five-minute exposures. This decrease was the same in magnitude for experimental and control subjects. Changes in NADH, ATP, and CP levels during microwave exposure cannot be attributed to general tissue hyperthermia. The data support the hypothesis that microwave exposure inhibits mitochondrial electron transport chain function, which results in decreased ATP and CP levels in brain.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bem.2250010207
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