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  • 1
    ISSN: 0197-8462
    Keywords: skin ; mouse ; tumor promotion ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: This paper describes preliminary findings on the influence of 60-Hz (2-mT) magnetic fields on tumor promotion and co-promotion in the skins of mice. The effect of magnetic fields on natural killer (NK) cell activity in spleen and blood was also examined. Groups of 32 juvenile female mice were exposed to the magnetic field as described in part I. The dorsal skin of all animals was treated with a subthreshold dose of the carcinogen 7, 12-dimethylbenz(a)anthracene (DMBA). One week after the treatment, two groups were sham exposed (group A) or field exposed at 2 mT (group B) 6 h/day for 21 weeks, to test whether the field would act as a tumor promoter. No tumors developed in these two groups of mice. To test whether the magnetic field would modify tumor development by directly affecting tumor growth or by suppressing immune surveillance, two additional groups of mice were treated weekly with the tumor promoter 12-0-tetradecanoylphorbol-13-acetate (TPA) and then either sham exposed (group C) or field exposed (group D). The time to appearance of tumors was shorter (but not statistically so) in the group exposed to magnetic fields and TPA. Some differences in NK cell activity and spleen size were observed between the sham- and field-exposed groups.
    Additional Material: 3 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Bioelectromagnetics 4 (1983), S. 123-139 
    ISSN: 0197-8462
    Keywords: microwave immunosuppression ; natural killer cells ; hamster immune system ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Hamsters were exposed to repeated or single doses of microwave energy and monitored for changes in core body temperature. circulating leukocyte profiles, serum corticosteroid levels, and natural killer (NK) cell activity in various tissues. NK cytotoxicity was measured in a 15Crrelease assay employing baby hamster kidney (BHK) targets or BHK infected with herpes simplex virus. Repeated exposure of hamsters at 15 mW/cm2 for 60 min/day had no significant effect on natural levels of spleen-cell NK activity against BHK targets. Similarly, repeated exposure at 15 mW/cm2 over a 5-day period had no demonstrable effect on the induction of spleen NK activity by vaccinia virus immunization, that is. comparable levels of NK were induced in untreated and microwave-treated animals. In contrast, treatment of hamsters with a single 60-min microwave exposure at 25 mW/cm2 caused a significant suppression in induced spleen NK activity. A similar but less marked decrease in spleen NK activity was observed in sham-exposed animals. Moreover, the sham effects on NK activity were not predictable and appeared to represent large individual animal variations in the response to stress factors. Depressed spleen NK activity was evident as early as 4 h postmicrowave treatment and returned to normal levels by 8 h. Hamsters exposed at 25 mW/cm2 showed an elevated temperature of 3.0-3.5 °C that returned to normal within 60 min after termination of microwave exposure. These animals also showed a marked lymphopenia and neutrophilia by 1 h posttreatment that returned to normal by 8-10 h. Serum glucocorticosteroids were elevated between 1 and 8 h after microwave treatment. Sham-exposed animals did not demonstrate significant changes in core body temperature. peripheral blood leukocyte (PBL) profile, or glucocorticosteroid levels as compared to minimum-handling controls.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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