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Amplitude windows and transiently augmented transcription from exposure to electromagnetic fields (1990)

Litovitz, T. A. ; Montrose, C. J. ; Goodman, Reba ; [et al.]

New York, NY [u.a.] : Wiley-Blackwell

Bioelectromagnetics 11 (1990), S. 297-312

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ISSN: 0197-8462

Keywords: ELF fields ; transient response ; chemical-reaction model ; rate constant ; RNA synthesis ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Physics

Notes: The exposure of cells to relatively low-intensity, pulsed, low-frequency electromagnetic fields can result in a transient augmentation of mRNA synthesis. Under certain conditions of irradiation, the augmentation is a function of the strength of the electromagnetic field. A linear, multi-step, chemical-reaction model accounts for many of the principal features that are observed in both the time- and intensity-dependent variations of transcriptional effects. The crucial assumption in the model is that the direct effect of electromagnetic fields on exposed cells is an increase in the rate constant that characterizes one of the intermediate sequential reactions in the synthesis of mRNA.

Additional Material: 10 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/bem.2250110406

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Effects of continuous and pulsed 2450-MHz radiation on spontaneous lymphoblastoid transformation of human lymphocytes in vitro (1992)

Czerska, Ewa M. ; Elson, Edward C. ; Davis, Christopher C. ; [et al.]

New York, NY [u.a.] : Wiley-Blackwell

Bioelectromagnetics 13 (1992), S. 247-259

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ISSN: 0197-8462

Keywords: 2450-MHz microwaves ; pulsed and continuous waves ; thermal effects ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Physics

Notes: Normal human lymphocytes were isolated from the peripheral blood of healthy donors. One-ml samples containing (106) cells in chromosome medium 1A were exposed for 5 days to conventional heating or to continuous wave (CW) or pulsed wave (PW) 2450-MHz radiation at non-heating (37°C) and various heating levels (temperature increases of 0.5, 1.0, 1.5, and 2 °C). The pulsed exposures involved 1-μs pulses at pulse repetition frequencies from 100 to 1,000 pulses per second at the same average SAR levels as the CW exposures. Actual average SARs ranged to 12.3 W/kg. Following termination of the incubation period, spontaneous lymphoblastoid transformation was determined with an image analysis system. The results were compared among each of the experimental conditions and with sham-exposed cultures. At non-heating levels, CW exposure did not affect transformation. At heating levels both conventional and CW heating enhanced transformation to the same extent and correlate with the increases in incubation temperature. PW exposure enhanced transformation at non-heating levels. This finding is significant (P 〈 .002). At heating levels PW exposure enhanced transformation to a greater extent than did conventionalor CW heating. This finding is significant at the .02 level. We conclude that PW 2450-MHz radiation acts differently on the process of lymphoblastoid transformation in vitro compared with CW 2450-MHz radiation at the same average SARs. © 1992 Wiley-Liss, Inc.

Additional Material: 3 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/bem.2250130402

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The role of coherence time in the effect of microwaves on ornithine decarboxylase activity (1993)

Litovitz, T. A. ; Krause, D. ; Penafiel, Miguel ; [et al.]

New York, NY [u.a.] : Wiley-Blackwell

Bioelectromagnetics 14 (1993), S. 395-403

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ISSN: 0197-8462

Keywords: coherence time ; microwave ; amplitude modulation ; ornithine decarboxylase ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Physics

Notes: Previously, we demonstrated the requirement for a minimum coherence time of an applied, small amplitude (10 μT) ELF magnetic field if the field were to produce an enhancement of ornithine decarboxylase activity in L929 fibroblasts. Further investigation has revealed a remarkably similar coherence time phenomenon for enhancement of ornithine decarboxylase activity by amplitude-modulated 915 MHz microwaves of large amplitude (SAR 2.5 W/kg). Microwave fields modulated at 55, 60, or 65 Hz approximately doubled ornithine decarboxylase activity after 8 h. Switching modulation frequencies from 55 to 65 Hz at coherence times of 1.0 s or less abolished enhancement, while times of 10 s or longer provided full enhancement. Our results show that the microwave coherence effects are remarkably similar to those observed with ELF fields. © 1993 Wiley-Liss. Inc.

Additional Material: 3 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/bem.2250140502

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Characteristics of microwave evoked body movements in mice (1994)

Brown, Dennis O. ; Lu, Shin-Tsu ; Elson, Edward C.

New York, NY [u.a.] : Wiley-Blackwell

Bioelectromagnetics 15 (1994), S. 143-161

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ISSN: 0197-8462

Keywords: high peak power microwaves ; response latency ; subcutaneous temperature ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Physics

Notes: Microwave evoked body movements were studied in mice. A resonant cavity was used to provide head and neck exposure of the mouse to pulsed and gated continuous wave (CW) 1.25 GHz microwaves. No difference in response to pulsed and gated CW stimuli of equal average power was found. The incidence of the microwave evoked body movements increased proportionally with specific absorption (dose) when the whole-body average specific absorption rate was at a constant level (7300 W/kg). Under a constant average specific absorption rate, the response incidence reached a plateau at 0.9 kJ/kg. For doses higher than 0.9 kJ/kg, response incidence was proportional to the specific absorption rate and reached a plateau at 900 W/kg. Body movements could be evoked by a single microwave pulse. The lowest whole-body specific absorption (SA) tested was 0.18 kJ/kg, and the corresponding brain SA was 0.29 kJ/kg. Bulk heating potentials of these SAs were less than 0.1 °C. For doses higher than 0.9 kJ/kg, the response incidence was also proportional to subcutaneous temperature increment and subcutaneous heating rate. The extrapolated absolute thresholds (0% incidence) were 1.21 °C temperature increment and 0.24 °C/s heating rate. Due to high subcutaneous heating rates, these microwaves must be perceived by the mouse as an intense thermal sensation but not a pain sensation because the temperature increment was well below the threshold for thermal pain. Results of the present study should be considered in promulgation of personnel protection guideline against high peak power but low average power microwaves. © 1994 Wiley-Liss, Inc.

Additional Material: 9 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/bem.2250150206

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