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排序方式: 共有114条查询结果,搜索用时 15 毫秒
1.
Troy D Anderson 《Pesticide biochemistry and physiology》2004,80(1):54-64
The acute toxicities of two organophosphorodithioate (dimethoate and disulfoton) and two organophosphorothioate (omethoate and demeton-S-methyl) insecticides were evaluated individually and in binary combination with the herbicide atrazine using fourth-instar larvae of the aquatic midge, Chironomus tentans. Atrazine alone up to 1000 μg/L did not show significant toxicity to the midges in a 48-h bioassay. However, atrazine concentrations as low as 1 μg/L in combination with dimethoate at EC25 (concentration to affect 25% of tested midges), 100 μg/L in combination with disulfoton (EC25), and 10 μg/L in combination with demeton-S-methyl (EC25) significantly enhanced the toxicity of each organophosphate insecticide. In contrast, atrazine concentrations of 10 μg/L and above in combination with omethoate (EC25) significantly decreased the toxicity of the insecticide. Biochemical analysis indicated that increased toxicity of dimethoate, disulfoton, and demeton-S-methyl in binary combination with atrazine correlated to the increased inhibition of acetylcholinesterase. Furthermore, cytochrome P450-dependent O-deethylation activity in the midges exposed to atrazine at 1000 μg/L was 1.5-fold higher than that in the control midges. Thus, atrazine appeared to induce cytochrome P450 monooxygenases in the midges. Elevated cytochrome P450 monooxygenase activity may increase the toxicities of dimethoate, disulfoton, and demeton-S-methyl by enhancing the oxidative activation of dimethoate into omethoate, and disulfoton and demeton-S-methyl into their sulfoxide analogs with increased anticholinesterase activity. In contrast, atrazine reduced the toxicity of omethoate possibly by enhancing the oxidative metabolic detoxification since omethoate does not require oxidative activation. 相似文献
2.
3.
Tomoko Takeda 《Pesticide biochemistry and physiology》2006,86(1):15-22
Insecticidal tests using diazinon showed that the mortality of Plutella xylostella larvae parasitized by Cotesia plutellae was reduced by 4.6-fold compared to that of the nonparasitized hosts. The use of chemicals with synergistic effect to insecticides in toxicity assay helps to elucidate the kind of enzyme involved in lowering insect mortality. Synergism of diethyl maleate and piperonyl butoxide with diazinon resulted to 2.4- and 1.9-fold increase, respectively, in susceptibility of parasitized larvae compared to those of nonparasitized larvae. These results indicated the possibility that the decrease in susceptibility to diazinon was due to the elevated activities of glutathione-S-transferase (GST) and cytochrome P450 monooxygenase (CYP), respectively. The GST activities in parasitized larvae were significantly higher than those of nonparasitized ones starting from three days post-parasitization until emergence of parasitoid larva. High GST activities during late parasitism could be attributed to both enzyme activities toward diazinon of parasitized P. xylostella larva itself and C. plutellae larva inside larval host. High GST activity one day after parasitization, although statistical significance was not detected, was caused by polydnavirus (PDV) and the venom of C. plutellae not by parasitoid larvae. Artificial injection of PDV plus venom demonstrated that the resulting increase in GST activity is similar to the increase brought by parasitization. High CYP activity after 3 days post-parasitization in parasitized larva was attributed mainly to the activity of parasitoid larva. Carboxylesterase activity in the parasitized host remained at a high level, while that in the nonparasitized host decreased slightly as pupation approaches. On the other hand, acetylcholinesterase activity also remained constant after parasitization until larval emergence, while that of the nonparasitized hosts decreased gradually as the host larvae approach pupation. These results were supported by inhibition tests using diazoxon in vitro. 相似文献
4.
L. M. DELSERONE K. McCLUSKEY D. E. MATTHEWS H. D. VANETTEN 《Physiological and Molecular Plant Pathology》1999,55(6):317
Previous studies have indicated that detoxification of their hosts' phytoalexins is a tolerance mechanism for some true fungi, but not the fungus-like Oomycota, and may be involved in determining the virulence of a pathogen. In the present study, the associations between demethylation of the pea phytoalexin pisatin, tolerance to pisatin, and virulence on pea were examined for 50 fungal isolates which represent 17 species of pathogens and nonpathogens of pea. All isolates ofPythium coloratum and P. irregulare failed to metabolize and were sensitive to pisatin, consistent with previous observations that members of the Oomycota generally lack the ability to metabolize and are sensitive to their hosts' phytoalexins. Among true fungi tested, the ability to demethylate pisatin was common, regardless of whether the particular isolate was pathogenic on pea or not. However, when the rate of pisatin demethylation was compared to virulence, all but one of the moderate to highly virulent isolates rapidly demethylated pisatin. In addition, the more rapidly demethylating isolates were generally more tolerant of pisatin. These results suggest that a specialized enzyme system for quickly detoxifying pisatin might be present in most pea pathogens. In previous studies a specific cytochrome P450 enzyme for demethylating pisatin was identified in the pea pathogen Nectria haematococca mating population VI, and genes (PDA genes) encoding that enzyme have been cloned from this fungus. When DNA specific for these genes was used to probe genomic DNA from other fungi that demethylate pisatin, significant hybridization was detected with only one fungus, the pea pathogen Fusarium oxysporum f. sp. pisi. If the other pea pathogens possess a specific cytochrome P450 system for detoxification of pisatin, the genes encoding these enzymes apparently share limited nucleotide similarity with N. haematococca PDA genes. 相似文献
5.
Erich Inselsbacher Nina Hinko-Najera Umana Markus Gorfer Katrin Ripka Rebecca Hood-Novotny Wolfgang Wanek 《Soil biology & biochemistry》2010,42(2):360-372
Agricultural systems that receive high amounts of inorganic nitrogen (N) fertilizer in the form of either ammonium (NH4+), nitrate (NO3−) or a combination thereof are expected to differ in soil N transformation rates and fates of NH4+ and NO3−. Using 15N tracer techniques this study examines how crop plants and soil microbes vary in their ability to take up and compete for fertilizer N on a short time scale (hours to days). Single plants of barley (Hordeum vulgare L. cv. Morex) were grown on two agricultural soils in microcosms which received either NH4+, NO3− or NH4NO3. Within each fertilizer treatment traces of 15NH4+ and 15NO3− were added separately. During 8 days of fertilization the fate of fertilizer 15N into plants, microbial biomass and inorganic soil N pools as well as changes in gross N transformation rates were investigated. One week after fertilization 45-80% of initially applied 15N was recovered in crop plants compared to only 1-10% in soil microbes, proving that plants were the strongest competitors for fertilizer N. In terms of N uptake soil microbes out-competed plants only during the first 4 h of N application independent of soil and fertilizer N form. Within one day microbial N uptake declined substantially, probably due to carbon limitation. In both soils, plants and soil microbes took up more NO3− than NH4+ independent of initially applied N form. Surprisingly, no inhibitory effect of NH4+ on the uptake and assimilation of nitrate in both, plants and microbes, was observed, probably because fast nitrification rates led to a swift depletion of the ammonium pool. Compared to plant and microbial NH4+ uptake rates, gross nitrification rates were 3-75-fold higher, indicating that nitrifiers were the strongest competitors for NH4+ in both soils. The rapid conversion of NH4+ to NO3− and preferential use of NO3− by soil microbes suggest that in agricultural systems with high inorganic N fertilizer inputs the soil microbial community could adapt to high concentrations of NO3− and shift towards enhanced reliance on NO3− for their N supply. 相似文献
6.
Savlík M Polácková L Szotáková B Lamka J Velík J Skálová L 《Research in veterinary science》2007,83(1):20-26
Basal activities of certain pheasant hepatic and intestinal biotransformation enzymes and modulation of their activities by anthelmintics flubendazole (FLBZ) and mebendazole (MBZ) were investigated in subcellular fractions that were prepared from liver and small intestine of control and FLBZ or MBZ treated birds. Several oxidation, reduction and conjugation enzyme activities were assessed. In the liver, treatment of pheasants by FLBZ or MBZ caused very slight or no changes in monooxygenase activities and conjugation enzymes. More significative changes were detected in small intestine. Metyrapone and daunorubicin reductase activities were increased by both substances in the liver. This is the first evidence that certain benzimidazoles modulate reductases of carbonyl group. With respect to the relatively slight extent of the changes caused by FLBZ or MBZ we can assume that repeated administration of therapeutic doses of both FLBZ and MBZ has probably no serious influence on pheasant biotransformation enzyme system. 相似文献
7.
对烟草喷施不同浓度(0,50,200,300,500和1000mg·L-1)的氯化胆碱(CC)后,可提高烟草的株高,尤其对茎粗生长、叶数和叶面积等有明显的促进作用。CC对增强烟草苗期根系活力和提高苗期的抗寒性也有明显作用。其中以喷施200和300mg·L-1的CC者对烟草生长的促进效果最大。 相似文献
8.
We investigated the effect of Z-ligustilide (LIG) on scopolamine-induced memory impairment in ICR mice. LIG (2.5–40 mg/kg) or tacrine (10 mg/kg) was orally administrated for 26 days. Behavior was examined in the Morris water maze and Y-maze after scopolamine administration (2 mg/kg, i.p.). The central acetylcholinesterase (AChE) and choline acetyltransferase (ChAT) activities were assessed spectrophotometrically. LIG significantly improved spatial long-term memory and short-term memory impairment, inhibited AChE activity and increased ChAT activity. Moreover, LIG and tacrine showed the comparable efficacy in both neurobehavioral and cholinergic evaluation. These data suggest that LIG may alleviate memory deficits probably via enhancing cholinergic function. 相似文献
9.
Evaluation of alternative substrates for determining methane-oxidizing activities and methanotrophic populations in soils 总被引:1,自引:0,他引:1
The magnitude of methane emission is a net result of methane production and the oxidation rate. The possibility of measuring oxidized products of alternative substrates of methane monooxygenase was examined to determine methane-oxidizing ability of soils, and to count methanotrophic populations in soils. Wetland rice soils were incubated under methane containing air to enirch the methanotrophs. Methane loss and oxygen uptake were inhibited by acetylene, dimethylether, and nitrapyrin (N-Serve). Acetylene was used routinely, because it inhibited methane oxidation even at a low concentration of 0.03 to 0.06 l ml-1 in the incubation headspace. Propylene at 10 kPa was used as an alternative substrate of methane monooxygenase, and the formation of propylene oxide was measured. When soils were incubated under methane, their methane-oxidizing activity increased. Propylene oxide formation increased simultaneously. Acetylene also blocked propylene oxidation. The results of several experiments and propylene oxide formation (r=0.87 after long-transformation). These results indicate that propylene oxide formation can be used as a semiquantitative measure of the methane-oxidizing activity of soils. The colonies of soluble methane monooxygenase-forming methanotrophs were counted on Cu-deficient methanotroph agar medium by the formation of naphthol from haphthalene. The counts increased from 104 (0 days) to 107 (21 days) g-1 soil during oxic incubation under methane. 相似文献
10.
脱毒和生长调节剂对甘薯内源激素含量及块根产量的影响 总被引:9,自引:1,他引:9
【目的】研究脱毒苗和植物生长调节剂对甘薯内源激素含量及块根产量的影响。【方法】以徐薯18甘薯苗为材料,设置脱毒原种苗(VF)、氯化胆碱(LH)浸根、叶面喷洒壮丰安(ZFA)、未脱毒徐薯18苗(CK)4个处理,测定不同处理对块根产量、块根日增长速率、T/R值、不同时期叶片及块根内源激素的影响。【结果】VF和LH处理使甘薯块根干物质产量两年平均分别增产21.0%和24.2%,达极显著水平;ZFA处理使块根干物质产量两年平均增产5.2%,未达显著水平;与对照比较,各处理均可显著提高膨大高峰期块根的日鲜重增长速率;脱毒和氯化胆碱浸根处理可显著降低生长前、中期的T/R值,不同程度地提高功能叶叶片的IAA含量、CTKs含量和GA4含量,提高膨大高峰期块根的CTKs含量、ABA含量和IAA含量,并使高峰期提早出现3~4周;壮丰安处理显著降低了中后期叶片的GA4含量和ABA含量,提高了叶片CTKs含量、IAA含量及生长后期块根的CTKs、ABA及IAA含量,但均未达显著水平。【结论】VF、LH和ZFA处理全面改变了甘薯源、库器官多种激素的含量水平,有效延缓叶片的衰老,延长叶片功能期,控制甘薯地上部的群体并防止茎叶的徒长,使地上部茎叶的生长与地下部块根的膨大更为协调。有利于块根产量的提高。 相似文献