الفهرس 
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Abstract
In the present study, the influence of selected 1,2,4-triazine compounds on Cx. pipiens immature stages was evaluated under laboratory conditions through the determination of LC50 of the tested compounds against the 3rd larval instar. Also, we studied the effect of the active compounds on mosquito biology such as development, fecundity and hatchability. The Mode of action of the active compounds was studied by the determination of larval weight, activity, and metabolic reserve contents as well as the total antioxidant capacity and Glutathione-s-transferase. Moreover, the persistence of the active compounds in water is also investigated. Finally, the cytotoxicity of the active compounds on the human cells (cell culture) was monitored. 6.1. Effect of the synthesized triazine derivatives on Cx. pipiens larvae The mortality rate of Cx. pipiens 3rd instar larvae treated with 100 mg/L of different 1,2,4-triazine derivatives (MSA 25, 26, 27, 31, 32, 34, 35, and 102) after 24h and 48h was screened. No mortality was recorded in the control group. Mortality of larvae increased significantly by the compounds MSA 25, 26, 27, 34, 35, and 102 at 48h compared to those at 24h. MSA35 and MSA102 had the highest mortality rate. 6.2. LC50 of the tested compounds against Cx. pipiens larvae To evaluate the effect of Triazine derivatives against Cx. pipiens 3rd instar larvae, concentration-mortality curves were created and then the respective LC50 values were calculated. The probit analysis of the mortality data caused by the tested compounds indicated that LC50s were arranged as 0.333, 0.457, and 2.042 mg/L for MSA102, MSA35, and reference insecticide, respectively. - 6.3. Effect of LC50 of the insecticide candidates on larval mortality, one-week post-treatment Effects of LC50 values of MSA35 and MSA102 along with the reference insecticide on the mortality rate and mortality time were studied. The mortality rate was ascendingly arranged as MSA102 > pymetrozine > MSA35. The lethal time of MSA102 was the shortest (1.41±0.15), followed by MSA35 (1.89±0.35), and finally came the reference insecticide with (3.64±0.11) days. 4.4. Effect of LC50 of the insecticide candidates on the development and emergence of Cx. pipiens The developmental time of Cx. pipiens immature stages since the exposure of 3rd instar larvae with LC50 of MSA35 and MSA102, as well as the reference insecticide was determined. MSA102 and the reference insecticide induced a significant increase in developmental time (delay) compared with the controls. The reference insecticide delayed the time required for development two-fold as that in the control. The significant difference in the GENMOD model was attributed to the significant decrease in the emergence rate after the application of MSA102. 6.5. Effect of LC50 of the insecticide candidates on the adult fecundity and egg hatchability of Cx. pipiens The effects of 1,2,4-triazine compounds at LC50 on Cx. pipiens adult fecundity and hatchability of eggs laid were investigated. Cx. pipiens females treated with MSA102 produced no eggs at all, whereas the females treated with MSA35 or the reference insecticide showed a slight non-significant reduction in the egg numbers. The hatch rate of the control eggs was 94.29±3.01. The treatment with the reference insecticide showed a slight non-significant decrease in the hatch rate in comparison with the control group. 6.6. Effect of LC50 of the insecticide candidates on the weight of third-instar larvae of Cx.pipiens The larvae treated with all triazine derivatives exhibited significantly lower weight than those in the control. The strongest effect was observed in larvae treated with MSA102. 6.7. Effect of LC50 of the insecticide candidates on the activity of third instar Cx. pipiens larvae: Only, larvae treated with MSA102 showed a significant reduction in their activity compared to the control of other treatments. Whereas the other treatments did not show significant differences compared with the controls. 6.8. Effect of LC50 of the insecticide candidates on the metabolic reserves (proteins, carbohydrates and lipids) Cx. pipiens third-instar larvae In carbohydrate determination, Multiple comparisons showed that MSA35 induced a higher (P>0.017) carbohydrate, while MSA102 induced lower carbohydrate contents in the larvae compared with the controls. Regarding lipid content, there was only a significant difference (higher) in lipid content of larvae treated with the reference insecticide compared with the control or other treatments. In protein determination, we found that the larvae treated with all triazine compounds showed significantly lower protein contents than that in the control. 6.9. Total antioxidant capacity in Cx. pipiens third-instar larvae All the tested compounds induced a significant reduction in the antioxidant capacity in the treated larvae compared with the control. However, the antioxidant capacity of the reference insecticide was even significantly less than that in larvae treated with MSA35. 6.10. Glutathione s-transferase in Cx. pipiens third-instar larvae The treatment with all compounds induced lower GST activity (P>0.017) in the treated larvae than that in the controls. The reference insecticide induced the GST activity even lower (P>0.017) than that of the tested compounds 6.11. Persistence of the active compound in water (1 week, 1 month, six months) Within one week, MSA35 and MSA102 lost up to 75% and 70% of their initial concentrations, respectively. The half-life time of MSA35 and MSA102 in water was estimated to be 5 and 5.5 days, respectively. This is near the estimated half-life time calculated for Pymetrozine 6 days in water. 6.12. Cytotoxicity of the insecticide candidates on the human cell line (WI) The toxicity of MSA 102 appeared to be lower than those of MSA35 and the reference insecticide. IC50 of MSA102, MSA35 and reference insecticide were 10.38, 3.466 and 3.177 μg/ml, respectively.