الفهرس 
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Abstract
Methyl mercury exists in soil, air, water and fishes especially large fishes like tuna, swordfish, tilefish, marlin, shark, and king mackerel. It has become one of the “most hazardous environmental pollutants; reaching levels of potential toxicity especially in our aquatic ecosystems.
It is very important to decide whether the current occupational exposure to mercury is safe for workers or not. And to decide whether the environmental exposure especially the dietary exposure is hazardous or not. The mechanisms of toxicity of mercury have been investigated but not well characterized yet.
The aim of the present study was to assess the health hazards of exposure to methyl mercury chloride especially its cytotoxicity and genotoxicity.
The subjects of the present study were thirty healthy persons with no history of teratogens or mutagen exposure, coming for premarital counseling, ranging in age between 18-30 years. A written informed consent was obtained from each subject.
The study was made of two parts done in the same time. Blood samples were collected from thirty healthy adult subjects and four lymphocyte cultures were done for each subject. Methyl mercury chloride was added 24 hours later in concentration of 0, 50, 500 and 5000 µg/ L respectively for each case. The metaphase chromosomes were analyzed using two stains; Giemsa and GTG banding. One hundred metaphase were analyzed for each lymphocyte culture. A total of 3.000 metaphase for each concentration.
Blood samples were collected from the same individuals and four lymphocyte cultures were done for each subject methyl mercury chloride was added. Those cultures were subjected to the cytokinesis block micro nucleus test using cytochalasion –B.
The results of the present study revealed that:
Chromosomal breaks and satellite associations occurred in control cases in low incidence 0.26% and 0.2% respectively.
Methyl mercury chloride caused chromosomal breaks that increased in frequency in a concentration related manner; 0.26 %, 1.06%, 3.26% and 6.67% with concentrations O, A, B and C respectively.
Methyl mercury chloride increased the satellite association frequency especially in cells exposed to concentration of 50µg/L (conc. A) where it was 6.2% then the frequency of the satellite associations decreased with increase in the concentration of methyl mercury; 3.73% with conc. B and 2.16% with conc. C.
Methyl mercury chloride induced formation of double minutes chromosomes especially in concentration of 50µg/L (conc. A) 0.76% and the frequency of double minutes showed decrease in cells exposed to higher concentrations of methyl mercury chloride; 0.33% with conc. B and 0.2% with conc. C.
Methyl mercury chloride induced different forms of chromosome re arrangements: dicentric chromosome, chromosome triradius and quadriradial chromosome. It induced dicentric chromosomes formation which was shown as the nucleoplasmic bridges in the micronucleus test. The incidences of the nucleoplasmic bridges were 0.1%, 0.44%, 0.9% and 1.3% which correspond to concentrations O. A, B and C of methyl mercury chloride.