Effects of 50 Hz magnetic fields exposure on secretion of primary human villous trophoblasts / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To explore the possible effects of 50 Hz magnetic fields (MF) exposure on HCG and progesterone secretion of human villous trophoblasts in vitro.</p><p><b>METHODS</b>The trophoblasts were isolated from human villus by trypsin digestion and incubated in DMEM medium. Then the trophoblasts were exposed to 0.2 mT, 0.4 mT 50 Hz MF for 6 h, 12 h, 24 h, 48 h and 72 h, respectively. Each exposure group was matched to one control group which was from the same villus and cultured with the same condition except the 50 Hz MF exposure. The concentration of human chorionic gonadotropin (HCG) and progesterone in the culture medium was detected by electrochemiluminescence immunoassay. Statistical significance of differences between means was determined by one way-ANOVA with P < 0.05 considered significant.</p><p><b>RESULTS</b>Exposure of trophoblasts to 50 Hz MF at 0.2 mT intensity within 72 h did not affect the secretion level of HCG and progesterone (compared with blank control, P > 0.05). There was also no significant change of the secretion level of HCG and progesterone when trophoblasts were exposed to 0.4 mT 50 Hz MF within 48 h (compared with blank control, P > 0.05). However, 50 Hz MF inhibited the HCG and progesterone secretion significantly with exposure for 72 h (compared with blank control, P < 0.05).</p><p><b>CONCLUSION</b>The exposure to 50 Hz MF for long period could inhibit trophoblasts excreting the HCG and progesterone, and the threshold intensity may be between 0.2 mT and 0.4 mT.</p>

GSM 1,800 MHz radiofrequency electromagnetic fields induced clustering of membrane surface receptors and interference by noise magnetic fields / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To investigate the possible effect of exposure to GSM 1,800 MHz radiofrequency electromagnetic fields (RF EMF) on epidermal growth factor (EGF) receptor and its possible interference by noise magnetic fields (MF).</p><p><b>METHODS</b>Chinese hamster lung fibroblasts (CHL) were exposed to 1,800 MHz RF EMF (modulated by 217 Hz or 50 Hz, or unmodulated), 2 microT noise MF, and RF EMF combined with 2 microT noise MF for 15 min, respectively. The specific absorption rates (SARs) of RF EMF were 0.1, 0.5, 1.0, 2.0 and 4.0 W/kg. Commercial EGF (1 ng/ml) treatment was used as positive control. EGF receptors on the cell membrane were observed under a laser scanning confocal microscope after indirect immunofluorescence staining.</p><p><b>RESULTS</b>EGF receptor clustering was induced after exposure to GSM 1,800 MHz RF EMF modulated by 217 Hz or 50 Hz MF at SARs of 0.5, 1.0, 2.0, 4.0 W/kg for 15 min as induced by 1 ng/ml EGF, but not at SAR of 0.1 W/kg. And no EGF receptor clustering was found in cells after exposure to unmodulated RF EMF or 2 microT noise MF. In addition, superposition of 2 microT noise MF could inhibit the EGF receptor clustering induced by GSM 1,800 MHz RF EMF.</p><p><b>CONCLUSION</b>EGF receptor clustering in CHL cells can be induced by GSM 1,800 MHz RF EMF at the lowest SAR of 0.5 W/kg and inhibited by noise MF. The modulation of wave may play an important role in the inducement of receptor clustering after RF exposure.</p>

Effects of mobile-phone microwave on dimethylbenz (a) anthracene induced mammary carcinoma development in rats / 中华预防医学杂志

<p><b>OBJECTIVE</b>To investigate whether exposure to 900 MHz GSM wireless communication signals enhances mammary tumor development and growth induced by low dose dimethylbenz (a) anthracene (DMBA).</p><p><b>METHODS</b>Five hundred female Sprague Dawley (SD) rats were treated with a single dose of 35 mg/kg. DMBA and then divided into 5 groups: one control group without exposure, and 4 groups with exposure in blinded fashion. The specific absorption rates (SAR) were 0, 0.44, 1.33 and 4.00 W/kg for the 4 exposure groups, respectively. Exposure started on the next day after DMBA administration and lasted 4 hours/day, 5 days/week for 26 weeks. Rats were weighted and palpated weekly for the presence of tumors, and killed at the end of 26-week exposure period. All mammary glands were examined histopathologically.</p><p><b>RESULTS</b>The incidence of mammary carcinoma in sham-exposure group was 37% (37/100). And mammary carcinoma incidences in the other groups of the exposure dose (0.44, 1.33 and 4.00 W/kg) were 25% (25/100), 34% (34/99) and 38% (38/100) respectively. There were no statistically significant differences between sham- and mobile phone microwave-exposed groups. In addition, the histopathological morphology of mammary tumor model in SD rats was observed. By microscopical examination two types of mammary tumor in this model were found, that was malignant or benign one. The former included adenocarcinoma and squamous cell carcinoma, and the latter included adenoma, fibroadenoma and cyst. Sometimes the histopathological morphology of mammary tumor appeared various since several kinds of histopathological features existed in the same individual.</p><p><b>CONCLUSION</b>This study does not provide the evidence that 900 MHz GSM microwave exposure might promote DMBA-induced mammary tumor development in rats.</p>

Superposition of noise magnetic fields inhibits clustering of fibroblast membrane surface receptors induced by 50 Hz magnetic fields in Chinese hamster lungs / 中华预防医学杂志

<p><b>OBJECTIVE</b>To study the possible induction effect of exposure to 50 Hz magnetic field (MF) on clustering of cell membrane surface receptors for epidermal growth factor (EGF) and tumor necrosis factor (TNF), the starting site of signals of biological effects, and its possible intervention effect.</p><p><b>METHODS</b>Lung fibroblasts of Chinese hamster (CHL) were exposed to EGF, TNF, 0.4 mT 50 Hz MF, 0.4 mT noise MF, and 0.4 mT 50 Hz MF combined with 0.4 mT noise MF. Respectively, for different durations, following the treatment, EGF and TNF receptors on the cell membrane were marked by corresponding antibodies with immunohistochemical method, then observed under a confocal microscope.</p><p><b>RESULTS</b>Clustering of cell membrane receptors could be induced 5 min after treatment with EGF and TNF, as well as with 50 Hz MF at 0.4 mT, which reached the peak in 15 min. While noise MF with the same intensity did not induce clustering of cell membrane receptors. Superposition of noise MF with the same intensity could inhibit clustering of cell membrane receptors induced by 50 Hz MF.</p><p><b>CONCLUSION</b>Clustering of EGF and TNF receptors on the cell membrane could be induced by 50 Hz MF, suggesting that membrane receptors would be one of the sites where MF signals coupled, and noise MF with the same intensity could inhibit these effects.</p>

Noise magnetic fields block co-suppression effect induced by power frequency magnetic field and phorbol ester / 中华预防医学杂志

<p><b>OBJECTIVES</b>To explore intervention with electromagnetic noise for co-suppression effect on gap-junctional intercellular communication (GJIC) induced or strengthened by low intensity magnetic field with carcinogen 12-O-tetradecanoylphorbol-13-acetate (TPA).</p><p><b>METHODS</b>Fibroblast cells from NIH 3T3 mice were exposed to extremely low intensity magnetic field (MF) 0.2 mT, 0.2 mT + TPA or/and electromagnetic noise with the same intensity of MF for 24 h, and GJIC was determined using fluorescence recovery analysis after photobleaching (FRAP) with a laser-scanning confocal microscope (Leica, Germany).</p><p><b>RESULTS</b>GJIC function could be co-suppressed by MF of 0.2 mT with TPA, with fluorescence recovery of (23 +/- 11)%, lower than that in the control group [(46 +/- 19)%] and in the group with TPA only [(34 +/- 17) %] (P < 0.01), indicating 0.2 mT MF plus TPA could co-inhibit GJIC (P < 0.01). Superposition of 0.2 mT noise MF could get a fluorescence recovery of (35 +/- 19)% and significantly antagonize its co-suppression by TPA.</p><p><b>CONCLUSION</b>Electromagnetic noise of 0.2 mT could block the intensifying effect of power frequency magnetic field on TPA-induced GJIC inhibition.</p>