| The electromagnetic fields including X-ray, y-ray, high frequency electromagnetic field (HFEMF) , nuclear electromagnetic pulse (NEMP), extremely low frequency electromagnetic fields (ELF-EMF). With the development of electrical technology, the possible health hazard of exposure to electromagnetic fields has become an issue of considerable public concern. However, there are also many inconsistent and contradictory reports. NEMP is provided with the ability of damaging to the electronic equipment and communication facilities severely. It has widely used as methods of electronic interference and electronic counter measure in the war, it has aroused attention to the bio-effects of it. The US and Soviet Union, have performed more investigation on the bio-effects of it. Though some notable changes have been found, the overt data is so little that we can hardly get it.AIM: There needs such an exigent investigation on the bio-effects of electromagnetic fields and NEMP, because it may be applied in military affairs. Besides, Our study also provides valuable information for government to establish safty criterion to electromagnetic fields.METHODS: 1. In this study, Chinese hamster ovary(CHO-Kl) and Ku80-- 4 -deficient(xrsS) cell line were used. The cell survival, cell cycle distribution, apoptosis and the expression of their related gene (p53, caspaseS, bcl-2, p21) were determined by the methods of PI staining, western blotting and apoptosis staining in CHO-K1 and xrs5 cells following exposure to magnetic fields(60Hz,5mT) alone or in combination with X-rays. 2. To find genes differentially expressed in hippocampus induced by NEMP so as to elucidate the molecular mechanism of hippocampus of NEMP. mRNA differential display was used to study the difference of expressed genes.The genes were cloned and dot blot hybridized were wood to confirm its specificity. 3. The human malignant glioma(MO54) cells were exposed to HFEMF at SAR 20, 60 and lOOW/kg, at a temperature of up to 39癈. Cell survival and Western blots (Hsp70 protein) was determined in MO54 cells following exposure sham and 39癈, SAR 5, 20, 60 and lOOW/kg HFEMF.RESULTS: 1. It was found that exposure of xrs5 and CHO-K1 cells to 60 Hz ELF had no effect on cell survival, cell cycle distribution and protein expression. Exposure of xrs5 cells to 60 Hz ELF for 5h after irradiation significantly inhibited GI cell cycle arrest induced by X-rays (IGy) and resulted in elevated bcl-2 expression. A significant decrease in the induction of P53. phospho-P53, Caspase-3 and P21 proteins was observed in xrs5 cells when irradiation by X-rays (8Gy) was followed by exposure to 5mT ELF magnetic fields. Exposure of xrs5 cells to the ELF for lOh following irradiation significantly decreased X-ray-induced apoptosis from about 1.7% to 0.7%. However, this effect was not found in CHO-K1 cells within 24h of irradiation by X-rays alone and by X-rays combined with ELF.2. 29 cDNA fragments differentially expressed in two groups were obtained. One cDNA fragment was hybridized to mRNA in two groups, which confirms that one of fragments was differentially expressed. Results of-5-sequencing and GenBank searching confirming that one sequence were Chk2 gene. lOOkV/m NEMP can produce an increased level of Chk2 expression in mice hippocampus RNA after exposure for 16h.3 Little or no cell death was observed in the sham-exposed cell, nor for incubation at 39癈 for up to 16h .Cell survival decreased to about 30% after exposure to HFEMF for 24h at SAR 1 OOW/kg. With increasing exposure time, Hsp70 expression increased except for SAR 5W/kg. In the raised temperature control at 39 癈, HspVO expression also increased as the incubation time increased. However, the expression level of Hsp70 for the HFEMF exposure was greater than that only raised temperature control.CONCLUSION: 1. Exposure of xrs5 cells to 60 Hz ELF fields following irradiation can affect cell cycle distribution and transiently suppress apoptosis by decreasing the levels of Caspase-3, P21, P53 and phospho-P53 and b...
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