| The electromagnetic fields including X-ray, γ-ray, and so on.They are associaticd with the use of electric power applied in residential and occupational cnvironmcnts(50-60HZ). Hxtremcly low frequency (ELF) fields (0-300 Hz) arc one kind of electromagnetic fields, which are common used in people's daily life. With the development of electrical technology, the possible health ha/ard of exposure to electromagnetic fields has become an issue of considerable public concern. However, there arc also many inconsistent and contradictory reports. In order to clarify the biological effect of exposure to ELF, a lot of research work had been done, but because of methodological differences, it is far to draw a conclusion. Till now, little study has been done in China. It is of great importance to understand the health hazards of exposure to ELF.AIM: To investigate biological effect of ELF on intracelluar free calcium concentration, cellular viability, cell cycle, ultraslructure change, percentage of apoptotic cells, the expression of their related gene bel-2, changes of eytokeralin and expression of nuclear factor kB in Hep G 2 cells .METHODS:1. In this study. Hep G-2 cell line was used. To investigate the intraccllular free calcium concentration in Hep G-2 cells exposed to 135Hz extremely lowfrequency electromagnetic fields for 1 h, Hep G~2 cells were loaded with Huo-3/AM. The fluorescent intensity (FI) changes of control and exposurecd groups were measured by laser confoeal microscopy. To find out the possible mechanism of free calcium concentration change, nifedipine was used.2. Hep G2 cells were exposurcd to a 135Hz ELF for6, 12, 24h .Cellular viability , cell cycle , percentage of apoptotic cells and ultrastructurc change were measured by methyl thiazolyl tetra/ohum (MIT ) reduction assay. flow cytometry, scanning and transmission electron microscopy.3. Hep G-2 cells were cxposured to 135 Hz ELF for 6, 12,24 h .The laser scanning confoeal microscopy was employed.To find out the effect of exposure to 135ELF on cell pan-cytokcrtain, we observed cell cytokcrtain change of control and exposured groups at same time point.4. NF-kB and its fluorescence intensity were measured for 6, 12, 24 h cxposured and control groups by immunofluorcsccnt immunochemistry and quantitative analysis.5. Fluorescence intensity of Bel-2 were measured after 6, 12, 24 h exposure and control groups. At same time, distribution change of Mitochondria was also observed by immunofiuorescencc method and laser confoeal microscopy.RKSUITS:1. 135Hz ELF induced a rapid increase fluorescent intensity of intracellular free calcium in Hep-G2 cells cxposured for 1h. Fluorescent intensity in nifedipine group was significantly lower than that in exposed group .2. Hxposure of Hep G 2 cells to 135Hz ELF had effect on cellular viability, cell cycle. Exposure of Hep G-2 cells to 135Hz ELF for 6, 12, 24h,significantly G1 cell cycle arrest was induced. Apoptosis induced by 135 Hz ELF was significantly increased, from 6% up to 18.6%. Following is ultrastructure change of Hep G-2celis induced by 135Hz ELF. The early stage appeared as cellular shrinking, rnicrovillus disappearing, the cell edge smoothening and membrane budding. The later stage showed karvolysis and apoptotic body formation.3. Exposure of Hep G 2 cells to 135Hz ELF for 6h, the number of cell cytokeratin filament was decreased, granular (luorcsccncc enhancement around nuclear can be found; Fxposured for 12h, the cell shapes changed from spreading to contracting, granular (luorcsccncc enhancement, clumping chromatin were observed; Fxposurcd for 24h, cell cytokeratin network in some area oi eeiis were obviously shortened, enhanced Fluorescence of cell cytokeratin network was around cell envelope. Some caduceus cell cylokertain were found between cells.4. The NF-kB expression of the exposure groups were higher than the control groups. By immunofluorcsccnt, it could be found that the immune reactive positive substances mainly cxistai in cytoplasm of Hep G-2 cells cxposurcd to 135Hz ELF for 6h and control groups. In Hep G-2 cells cxposurcd to 135Hz ELF for 12h, NF kB were found around cellular nucleus . Exposure of Hep G-2 cells to 135Hz ELF for24h, some NF-kB were found in nuclei.5. Fxposurc of Hep G-2 cells to 135Hz ELF for 6h, Bel-2 expression of the exposure groups were higher than the control groups. F.xposurcd for 12h , Bel-2 expression of the exposure groups were weaker. Disposition of mitochondria was changed, to be missing directionality.Cell outline has turned round partly. Fxposurcd for 24h, weak Bcl-2 flourcsccncc and fuzzy mitochondria were...
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