甘蓝多酚氧化酶的生物化学性质及其杀虫剂的诱导作用

采用时间动力学法,在研究了甘蓝多酚氧化酶的最适反应条件的基础上,对有机溶剂和杀虫剂对多酚氧化酶活性的影响进行了研究。结果表明:甘蓝多酚氧化酶反应的最适pH值为6.4,最适反应温度为55℃;丙酮和乙醇对多酚氧化酶活性有明显的激活作用;高效氯氰菊酯、灭多威和辛硫磷以及小菜蛾和桃蚜取食的胁迫会对多酚氧化酶的活性产生影响。     

Comparative bioactivity of selected seed extracts from Brazilian Annona species and an acetogenin-based commercial bioinsecticide against Trichoplusia ni and Myzus persicae

The acute and chronic toxicity of ethanolic seed extracts from selected Brazilian Annona species (Annona montana Macfadyen, Annona mucosa Jacquin, Annona muricata Linnaeus, and Annona sylvatica A. St.-Hil) and an acetogenin-based commercial bioinsecticide (Anosom^®) were investigated against the cabbage looper Trichoplusia ni Hübner (Lepidoptera: Noctuidae) and the green peach aphid Myzus persicae (Sulzer) (Hemiptera: Aphididae). In the laboratory, extracts of A. mucosa and A. sylvatica as well as Anosom^® were especially active through oral and topical administration. A greenhouse trial showed that a formulated A. mucosa extract and Anosom^® were highly effective (>98% mortality) against third instar T. ni larvae, and comparable to a pyrethrin-based commercial insecticide (Insect Spray^®) used as a positive control. Similar to results with T. ni, A. mucosa extract showed the greatest aphicidal activity followed by A. sylvatica extract and Anosom^®. In another greenhouse trial, aphid population reduction from the formulated A. mucosa extract was superior to that provided by other treatments including the positive control. Though inferior to the A. mucosa extract, the acetogenin-based commercial insecticide (Anosom^®) and A. sylvatica extract also reduced aphid populations in a manner comparable to the positive control. Botanical insecticides based on these Annonaceae derivatives could be useful in the framework of Brassica IPM in Brazil and elsewhere, especially for organic production.     

Influence of acute exposure to a low dose of systemic insecticide fipronil on locomotor activity and emotional behavior in adult male mice

Fipronil (FPN) is a systemic insecticide that antagonizes the gamma-aminobutyric acid type A (GABA_A) receptors in insects. Recently, adverse effects of FPN on mammals have been reported, but most of those were caused by high doses of FPN and additives in the products. We investigated the effects of low-dose pure FPN on the emotional behavior of mice. Nine-week-old male mice conducted behavioral tests 24 hr after FPN administration by gavage at doses of 0.05 or 5 mg/kg based on the no-observed-effect level (NOEL), showed a significant increase in locomotor activity and dose-dependent responses on the time they spent in the central zone in the open field test. Pure FPN below the NOEL dose may affect the emotional behavior of mice.     

In-vitro Metabolism of a Novel Monocrotophos Derivative by Rat and Japanese Quail

NADPH-dependent inhibition of hepatic microsomal carboxylesterase by a derivative of monocrotophos (coded as RPR-5) was studied in rat and Japanese quail as a measure of monooxygenase-catalysed activation of RPR-5. There was NADPH-dependent inhibition of hepatic microsomal α-naphthyl acetate esterase (carboxylesterase) both in rat and quail, indicating monooxygenase-catalysed formation of an oxon that subsequently phosphorylated α-NaE. The pattern of in-vitro metabolism of ¹⁴C-labelled RPR-5 by 11000g supernatant (11-S), microsomes and 105000g supernatant (105-S) fractions of rat and quail livers suggested the involvement of microsomal monooxygenases and carboxylesterases. A radiolabelled metabolite (M2) was tentatively identified as an acid produced by carboxyl esterase attack. In rat, metabolism by microsomal and cytosolic (105-S) carboxylesterases appeared to predominate with relatively little oxidative metabolism. In quail, putative microsomal carboxylesterase hydrolysis of RPR-5 was much lower than in the rat with almost neglible hydrolysis by cytosolic fractions. Also, production of M₂ by quail microsomes was substantially reduced after addition of NADPH, suggesting inhibition of a carboxyl esterase by the oxon of RPR-5. Differences in this detoxification of RPR-5 between rat and quail may be an important factor in determining selective toxicity and the results underline the importance of relating metabolism to toxicity when selecting animal models for toxicity testing.