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 หัวเรื่อง:ไม่มีชื่อไทย (ชื่ออังกฤษ : Synergistic Effects of Sesame Oil with Cypermethrin on the Survival and Detoxification Enzyme Activity of Plutella xylostella L. Larvae) ผู้เขียน: ดร.สุรพล วิเศษสรรค์, รองศาสตราจารย์ ,  John Milne, มัณฑนา มิลน์, Pintip Kanasutar สื่อสิ่งพิมพ์:pdf AbstractTwo types of insect-toxicity tests, (1) contact and (2) no-choice leaf dipping test, were conducted using the insecticide cypermethrin without piperonyl butoxide (PB), cypermethrin with PB and cypermethrin with sesame oil against the 2nd –3rd instar larvae of Plutella xylostella L. Sesame oil showed good synergism with cypermethrin yielding synergistic ratios (SR) that ranged from 1.54 – 6.33 in the contact method and 2.04-5.88 in the no-choice leaf dipping method and were comparable to using PB, which showed SR’s of 6.33 and 6.71, respectively. Both PB and sesame oil mixed together with cypermethrin inhibited monooxygenase activity by approximately two-third but induced glutathione–S-transferase ca. 2-3 folds in both methods. The synergists had no effect on esterase activity (CF ca. 1.2). Residues of cypermethrin in the larvae increased by 1.29 – 2.57 folds in the treatments with added sesame oil compared to a 2.86 fold increase when PB was added, using the contact method. The no choice leaf dipping method revealed that cypermethrin residue levels increased by 2.82 – 6.91 fold with added sesame oil and 8.27 fold with added PB. This indicated that both PB and sesame oil played the same role in the inhibition of an enzyme, possibly monooxygenase. Field trials with Chinese kale showed the same trends that were evident in the laboratory work. The addition of sesame oil to the insecticide reduced the larval population by 70-80 percent while the addition of PB reduced the larval population by up to 88 percent in the kale crop. Monooxygenase activities of insect larvae collected in the field from kale sprayed with cypermethrin plus synergist (sesame oil or PB) were lower than those from kale treated with insecticide alone. The results in terms of synergism and changes in enzyme metabolism were discussed. |
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หัวเรื่อง:ไม่มีชื่อไทย (ชื่ออังกฤษ : Effects of Root Extract from Derris (Derris elliptica Benth) on Mortality and Detoxification Enzyme Levels in the Diamondback Moth Larvae (Plutella xylostella Linn.)) ผู้เขียน:ดร.สุรพล วิเศษสรรค์, รองศาสตราจารย์, มัณฑนา มิลน์ สื่อสิ่งพิมพ์:pdf AbstractTwo types of ethanol extraction methods, Soxhlet and stirring soaking, were carried out. The rotenone content determined by the HPLC was 8.6 % w/w for the former method compared to 5.2% w/w for the latter one. Third instar larvae of the diamond back moth gave LD50 of 24.25 PPM and 89.07 PPM for the Soxhlet and stirring methods, respectively. Triphenyl phosphate (TPP) and Piperonylebutoxide (PB) reduced the LD50 upto ca. 4 folds and also significantly lowered the number of larvae in the field. The optimal medium for the detoxification enzymes, esterase, GSH-S-transferses and monooxygenases, was found to contain 0.1 M phosphate buffer pH 7.5 with 10 mM glutathione (reduced forms), 1 mM EDTA and 50% w/w PVPP. Protein concentrations (BSA as a standard protein) between 50-100 mg protein/g larvae/ml extracted from 2 – 4 instar larvae were used for all enzyme assays. Derris extracts induced ca. 10-20% of all enzyme activities. By adding TPP to the extracts, esterase activity was reduced by 20%. The coefficient of correlation, r2 (mortality against esterase activity), was ca. 0.9. The addition of DEM showed a lower in r2 value (0.62 – 0.77) (mortality against GSH-S-transferases activity). The highest fluctuation of r2 (0.48 – 0.97) (mortality against monooxygenases activity) was observed by the addition of PB to both extracts. |
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