A. E. Bayoumi

Cytotoxic effects of two antimolting insecticides in mammalian CHO-K1 cells

Cytotoxicity of two insect growth regulators, diflubenzuron, a benzoylphenylurea derivative that inhibits the synthesis of new chitin in target organisms, and pyriproxyfen, an insect juvenile hormone analogue, were tested on CHO-K1 cultures, using the neutral red incorporation assay. Both compounds displayed cytotoxic effects that rise with time exposure. The presence of either fetal calf serum or bovine serum albumin diminished significantly the cytotoxicity of both compounds, thus pointing to a strong protein binding. In addition, extensive metabolization with rat liver submitochondrial fraction gave rise to metabolites less toxic than the parent compounds, implying the relative safety of both diflubenzuron and pyriproxyfen in mammals.

Changes in glutathione-redox balance induced by hexachlorocyclohexane and lindane in CHO-K1 cells

1. The basal cytotoxic effect of the organochlorine pesticides hexachlorocyclohexane and lindane on CHO-K1 cultures was assessed at fractions of their lethal doses as determined by the neutral red incorporation (NRI) assay (NRI6.25, NRI12.5 and NRI25). The sulphur-redox cycle enzymes glutathione peroxidase, glutathione reductase and glutathione S-transferase, and total and oxidized glutathione were evaluated at several points during the standard growth curve of the cultures. 2. After incubation with each compound for 24h, both glutathione peroxidase and reductase showed a substantial increase at the lowest exposure doses (NRI6.25) - more significantly for lindane than for 1,2,3,4,5,6-hexachlorocyclohexane (HCH) - and dropped at higher doses of both compounds. The reduced and oxidized glutathione content was greatly diminished at the lower exposures, whereas the total glutathione content was higher at NRI12.5 values. 3. Changes in cell membrane integrity were assessed for a wide range of pesticide concentrations with the lactate dehydrogenase release assay and lipid peroxidation. Membrane leakage and peroxide production were significantly enhanced at concentrations of HCH 50µg ml−1, although this effect was not significant at lindane concentrations <200µg ml−1. 4. Lipid peroxidation increased with exposure to HCH at concentrations as low as NRI6.25, whereas in the case of lindane, this increase was only significant at doses of NRI25 and above.

Alterations on polyamine content and glutathione metabolism induced by different concentrations of paraquat in CHO-K1 cells.

The effect of herbicide paraquat has been assessed on CHO-K1 cultures at different concentrations. Glutathione peroxidase, reductase and S-transferase, as well as total and oxidized glutathione, were evaluated along the standard growth curve of the cultures. Paraquat was then administered during mid-log phase at concentrations that produced a calculated lethality of 6.25%, 12.5% and 25%, using the lysosomal dye assay, neutral red. After 24hr of incubation with paraquat, glutathione peroxidase suffered a large dose-response increase, unlike glutathione reductase and S-transferase, the activities of which were lower than untreated controls. The profile of total glutathione content was similar to that found for glutathione peroxidase, increasing with the administered doses of the herbicide. Polyamine content has been also studied at the same concentrations of paraquat, showing that intracellular spermidine and spermine pools were negatively affected with paraquat in a dose-response manner, unlike putrescine, which maintained elevated pools at the three concentrations assayed.

Monitoring of pesticide residues in some environmental elements at Menofia Governorate, Egypt.

The pesticide residues in drinking water, irrigation water, sediment and soil samples collected from three villages, i.e. Samadon, Ashmon and El-Ramla, located at Menofia Governorate, Egypt were monitored during the period of Septemper 2002 to February 2003. The obtained results showed that the detected pesticide residues were varied in their types and structures in the investigated villages during period of study. It is clear that residues of organochlorine insecticide and the herbicide, atrazine, were the most frequently detected in both of drinking and irrigation water samples. According to the detected amounts and numbers of pesticide residues in all the collected samples, the soil samples contained higher pesticide residues (average of 0.07 ppm)  sediment (average of 0.05 ppm)  irrigation water (average of 0.04 ppm)  drinking water (0.01-0.02 ppm). Comparing between the selected sites, Samadon was the highest site contained pesticide residues more than Ashmon and ElRamla.

The biological activity of some chitin synthesis inhibitors against the cotton leafworm Spodoptera littoralis (Boisd)

The action of three chitin synthesis inhibitors insecticides (chlorfluazuron, teflubenzuron and flufenoxuron) against third and fifth instars of both susceptible and field strains of cotton leafworm Spodoptera littoralis, (Lepidoptera: Noctuidae), were carried out in order to investigate the biological activity of these compounds, in their formulation form, under controlled laboratory conditions. The estimated LC50 values, clearly showed that the third instars were more sensitive to the compounds tested, compared with those of the fifth instars, regardless of strain used. Data from larval dietary bioassay showed an up to 4-fold in LC50 values among the strains tested. Such values, expressed as tolerance level depended largely on the chemical tested and/or the instar used. The tolerance level calculated for the third instars was generally less than that corresponding for the fifth instars, irrespective of compounds tested. The highest tolerance level recorded was observed for chlorfluazuron, whereas the lowest pertained to teflubenzuron. The percentage of accumulative mortality varied according to the compound, concentration, the instar larvae and/or strain studied.