الفهرس 
REVIEW OF LITERATUREOnly 14 pages are availabe for public view
 |  | from | 102 |  |  |
| | | from | 102 | | |
Abstract
In the past years and yet, several studies confirmed how dangerous ethidium bromide is, and the problems which are caused to an organism upon exposure. This chemical strongly affects the genetic material as it can intercalate between the bases of nucleic acids even with the nucleus. Frameshift and base-substitution mutations can be induced by EtBr in addition to its proven carcinogenicity and embryotoxicity. Some manifestations of genotoxicity caused by EtBr are chromosomal aberrations, so that EtBr was classified as: carcinogenic, mutagenic, teratogenic, and genotoxic agent. Knowing that all those effects were dependent on used dose, the duration of exposure, and object response. It is interesting that some of the effects resulting from the treatment by EtBr are reversible.
Although spread knowledge about adverse effects of EtBr, it is still used in molecular genetics labs as nucleic acid stain. This is due to the limited information about its harmful effect. On the other hand EtBr has many applications, from which study of chromosomes, microorganisms, and synapses.
The experiment designed to test the EtBr cytotoxicity and genotoxicity while using Lactic Acid Bacteria (LAB) as a protective agent. Seven groups of mice are obtained; each group contains seven male mice with an average weight of 20-30 g. The first group is the control group. The consecutive three groups treated with EtBr added to the drinking water with separate three doses (40 mg∕kg body weight, 50 mg∕kg body weight, and 60 mg∕kg body weight). In the three following groups the same doses of EtBr were used) in addition to a single dose (24 x 107 CFU/g) of probiotic bacteria carried on a commercial powder milk mixed with ordinary food. The used doses of ethidium bromide have been chosen according to previous studies. The experiment is done by adding tested material to the mice daily for a month, and then mice were killed and autopsied. Liver of each mouse are preserved in 10% formalin, and the rest of the liver was reserved in aluminum paper at - 80°C until the performance of scheduled techniques.
The microscopic examination of stained liver sections showing the extent of the harmful impact of EtBr on the liver. The control group showed normal histological feature, while the consecutive three groups where mice treated with EtBr only, many problems have emerged, such as fatty liver, hemorrhage, inflammation, which appeared in varying degrees between doses. High-dose of ethidium is the most seriousness treatment. In the second three groups, in which mice treated with probiotic and EtBr, the results were in favor of probiotics that have proven their relative ability to boost the immune system of the mice in the face of the seriousness of EtBr. In the presence of probiotic, some of cytotoxicity signs were disappeared.
DNA fragmentation analysis, in which DNA is extracted using hypotonic solution, showed no DNA fragmentation occurs in all existing treatments, which impose the hypothesis that EtBr provoke the apoptosis in hepatic cells. In complementary form, the relative expression of the tumor suppressor gene p53 was quantified using quantitative PCR (Real-time qPCR). RNA was extraction from frozen liver and converted into a complementary DNA (cDNA), the qPCR using specific synthesized primers showed full induction of p53 by ethidium bromide in all cases. Expected role of probiotics appeared as anti-tumorigenesis, challenged by the lack of production of the p53 gene, compared with control.
The present study has proved that EtBr is a carcinogenic and genotoxic that depend on the exposed dose. Probiotics didn’t prove its ability to prevent severe damages and in combination with EtBr it stimulates hepato-carcinoma by lowering the p53 expression.
The current study suggests that ethidium bromide possesses a potential threat to the health of who work in biological laboratories. So it recommends the use safe alternatives dyes even if they are more expensive, also confirmatory studies on both EtBr and probiotics are needed.