الفهرس 
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Abstract
Trichloroethylene (TCE) is one of the organic solvents which used as an industrial solvent in degreasing metals, production of pesticides, several chemical reactions in many factories and dry cleaning as detergent. Recently, TCE is thought to cause adverse health effects through multiple organ toxicities such as the nervous system, liver, kidney, heart, immune system and reproductive system due to its distribution in the environment. Although TCE is classified as ‘‘reasonably anticipated to be a human carcinogen’’ it has been difficult to achieve consensus on its risks to humans. Neural stem cells (NSCs) are considered as somatic stem cells having the ability to self-renew and can give rise to the entire major neural cell types, i.e. neurons, oligodendrocytes and astrocytes. Nowadays the discovery of neurospheres which are the technique that enables us to study the neural stem cells in vitro due to it is difficult to study it in vivo .This may study the behavior and the mechanism of neural stem cell differentiation. This study evaluates for the first time the toxic effect of small dose of trichloroethylene on the proliferation, differentiation and viability of neural stem cells and the effect of trichloroethylene on oxidative stress of the cells. This study was established on brains of Sprague dawley rats (3-5 days).Collected brains were digested in the presence of collagenase to separate healthy cells. Then harvested cells were cultured in DMEM medium supplemented for neural stem cells growth factor N2 and B27 .After ten days; the neurospheres were formed then divided into two groups (treated and control groups). Formed neurospheres were subjected to low dose of 1µm of TCE. After thirteen days of treatment, the effects of TCE on neurospheres assessed as follows: 1- The measurement of cell proliferation by determination of neurospheres diameter as a criterion for cell proliferation and by using Ki67 as marker. 2- Measurement cell viability by using annexine v as a marker for cell apoptosis. 3- The determination of cells differentiation using GFAP as marker. 4- The determination of oxidative stress by measurement the expression of antioxidant enzymes such as myeloperoxidase (MPO) and superoxide dismutase (SOD). After the treatment for thirteen days, the results showed that TCE has harmful effects on neural stem cells, these effects included: 1-Inhibition of neural stem cell proliferation which was manifested as a significant decrease in the diameter of neurosphere (~71%) and inhibition at the expression of Ki67 (~89%).These data were further confirmed using cell cycle flow-cytometrical analyses which showed TCE dependent cell cycle arrest at G2\M phase. 2-It diminished cell viability by inducing cell death through apoptotic and necrotic cell death signals with percentage of ~60%. 3-It also induced oxidative stress of NSCs by down –regulating expression of SOD with percentage 11% and up-regulating expression of MPO with percentage ~72% which been showed by using PCR technique. 4-It inhibited the ability of NSCs to differentiate which were determined by using GFAP antibodies as a marker for differentiated astrocyte using immunocytochemistry technique.