BACKGROUND: Anopheles stephensi is an important urban malaria vector in the Indian subcontinent. Extensive application of insecticides evokes microevolution, which results in resistance that can be traced back to their genotypes. In this study, resistant and susceptible strains of An. stephensi for alphamethrin were selected by selective inbreeding for 27 and ten generations respectively. The biochemical basis of resistance in all the life stages was investigated. Quantitative assays were performed for proteins (total and soluble), esterases ( , and acetylcholine) and phosphatases (acid and alkaline) by spectrophotometry, and qualitative assays for the enzymes by native polyacrylamide gel electrophoresis.
RESULTS:The enzyme quantities significantly varied in all life stages of the resistant strain as compared with the susceptible ones. Qualitative studies showed seven isoforms for -and -esterases, three each for acetylcholinesterase and alkaline phosphatase and two for acid phosphatase. Exclusive bands were found in the resistant strain, such as -Est 1 and -Est 1 in eggs and larvae, -Est 3 in adult males, -Est 2 in adult females and AlkP 1, AlkP 2 and AlkP 3 in adult females, larvae and adult males respectively. CONCLUSION: Variations in the quantity and specific enzyme isoforms play a key role in the development of alphamethrin resistance in An. stephensi.
Polytene chromosomes were prepared from the ovarian nurse cells of semi-gravid females of ten insecticide-resistant strains of Anopheles stephensi. Altogether, 16 heterozygous paracentric inversions, namely b/+ (11D-16C) in alphamethrin; i/+ (14B-18A) and h/+ (27B-28A) in DDT; j/+ (14A-16B) in chlorpyrifos; k/+ (11D-16B) in cyfluthrin; l/+ (11A-16C) in deltamethrin; m/+ (14B-15C) and e/+ (32A-33B) in bifenthrin; n/+ (12D-14B), f/+ (33A-36A) and g/+ (33C-34A) in propoxur; o/+ (11A-12D), h/+ (37A-37C) and i/+ (31C-32C) in temephos; d/+ (33D-35C) in carbofuran and a/+ (41C-43B) in neem strains, were reported. No inversions were observed in X chromosome so far. The frequency of inversions in different insecticides was found to be highest in the 2R arm, followed by the 3R arm. Such inversions were not reported in the corresponding susceptible strains or in the parental stocks.
In the present study we investigated antimicrobial activity of diethyl ether and methanol extractions of bark and leaves of Ficus religiosa plant against three bacteria (E.coli, Staphylococcus aureus and Pseudomonas aurignosa) and one fungi (Aspergillus niger). The results showed that the methanol extracts of both leaves and bark showed antimicrobial activity on three tested bacteria and no effect on A.niger. In methanol extracts S.aureus showed maximum sensitivity (inhibition zone 28mm) followed by E.coli (inhibition zone 16mm) and Pseudomonas aeruginosa (inhibition zone 12mm). Diethyl ether extracts of leaves were also showed maximum inhibition on S.aureus followed by E.coli and P.aeruginosa. Both methanol and diethyl ether extracts of bark showed antimicrobial activity on three types of tested bacteria and very less inhibition activity on A.niger. But comparatively bark extracts of both the solvents were showed less antimicrobial activity than leaves extracts on the tested microbes.
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