WIJESEKARA, GUS2011-02-142011-02-1419971997WIJESEKARA, GUS, A Study of acetylcholinesterase activity in school children, University of Colombo UC(MED), 1997: xi,190p.http://imsear.searo.who.int/handle/123456789/129458Dissertation: M.Sc., University of Colombo: UC(MED), 1997.Acetylcholinesterase activity of one hundred and sixty one school children in the age group 15-16 years, belong to two districts, Kurunegala and Kegalle where Organophosphate and Carbamate pesticides are widely used, were studied. Venous blood samples were collected in the mornings. A rapid, field methods for whole blood cholinesterase assay was developed in the laboratory by modifying the Michel's method. A Lovibond comparator with Bromothymol blue was used instead of a pH meter. The pH of the phosphate buffer was reduced to 7.6 from 8.1. The reaction time was reduced to half an hour. In this method the dercrease of pH was measured and the whole blood cholinesterase activity was reported in ..pH/min. The studies of the stability of the buffer and substrate showed that no statistically significant variation of cholinesterase activity when the buffer and the substrate were stored at room temperature (30 C) for 48 hours. The studies of the effect of temperature on whole blood cholinesterase activity by the Lovibond method showed an increase of 0.0007..pH/m.n/..C from 15 Cto 30C. From 30 C to 35 C no increase in enzyme activity was observed by the Lovibond method and Michel's method, indicating that the enzyme is inactivated at temperatures above 30 C. When the cholinesterase activity was estimated by the Michel's method and Lovibond method, the results obtained were different and the difference was significant to a 0.01 level of the t-test.Acetylcholinesterase activity of one hundred and sixty one school children were determined by the Lovibond method under field conditions in Kurunegala and Kegalle districts. The whole blood cholinesterase activity varied from 0.026..pH/min to 0.04..pH/min. The mean value obtained for enzyme activity was 0.030..pH/min with the standard deviation of +/-0.0043. There was no significant difference between the whole blood cholineaterase activity of childdren exposed to pesticides and children not exposed to pesticides. This indicates very low exposure to pesticides. The studies showed that there was no statistically significant correlation between Erythrocyte cholinesterase activity and Hemoglobin content. Studies of anthropometric measurements showed there was no statistically significant correlation between Erythrocyte cholineaterase activity and Height, and Erythrocyte cholinesterase activity and weight. The results indicate that cholinesterase activity can be measured unde rfield conditions using Lovibond comparator and thus detect Organophosphate poisoning at early stages. In Kurunegala district, the mean plasma cholinesterase activity of males was 3563 U/L with the standard deviation of 807.5 while that of females was 3329U/L with the standard deviation of 791.4. In Kegalle district, the mean plasma cholineasterase activity was 3560U/L with the standard deviation of 512.4. In the study, eighteen (11.2 percent)) subjects had plasma cholinesterase activity higher than the upper limit of the normal range (1700-4100 U/L) of plasma cholinesterase activity. In Kurunegala district, the mean Erythrocyte cholinesterase activity of males was 6300 U/L with the standard deviation of 1020 while that of females was 6335 U/L with the standard deviation of 954. In Kegalle distirct, the mean Erythrocyte cholinesterase avtivity of subjects was 6257 U/L with the standard deviation of 903. In the study, seven (4.3 percent) subjects had Erythrocyte cholinesterase activity higher than the upper limit of the normal range. (4400-8200 U/L). In the present study, none of the subjects had plasma cholineserase activity and Erythrocyte cholinesterase activity lower than the normal range. The studies of the Dibuvcaine inhibition of subjects showed that there were cholinesterase variants in the Kurunegala and Kegalle districts. In the Kurunegala district 30 percent of the females and 16 percent of the males wereheterozygotes (Dibucaine number 40-47 percent) while 70 percent of the females and 84 percent of the males were normal homozygotes (Dibucaine number 70-85 percent). In Kegalle district, only 11 percent heterozygotes were detected. In the study, atypical homozygotes (Dibucaine number 15-30 percent) were not detecte.en-USUniversity of Colombo, UC(MED): Sri Lanka HELLIS NetworkEnzymesAcetylcholinesteraseAcetylcholinesterase-MetabolismAcetylcholinesterase-analysisChildAdolescentThesis