The relationship of esterases to organophosphorus insecticide tolerance in mosquitofish

The levels of peripheral acetylcholinesterase and carboxylesterases and their organophosphate sensitivities were studied in two populations of mosquitofish (Gambusia affinis). One population, highly resistant to organochlorine insecticides, demonstrated a low tolerance to parathion and methyl parathion. The organochlorine resistant fish possessed higher levels of both peripheral acetylcholinesterase and carboxylesterases. The sensitivities of these esterases to organophosphate inhibition were the same in both populations. The esterases were more sensitive to paraoxon than to methyl paraoxon. Carboxylesterases were far more sensitive to organophosphate inhibition than was acetylcholinesterase. Carboxylesterases, by their higher affinity for the organophosphates, may serve to protect acetylcholinesterase from inhibition.     

The mobility of some organophosphorus sheep dip insecticides in soil

The technique of soil thin-layer chromatography has been adapted to permit the use of repeated or prolonged irrigation procedures so that the mobility characteristics of relatively non-mobile insecticides may be studied. The procedure has been used to study the relative movement of organophosphorus insecticides such as chlorfenvinphos, trithion, delnav and dichlofenthion which are widely used as sheep dips.     

Interactions of carotenoids with some organophosphorus insecticides

The interactions of some organophosphorus insecticides (OPI) with carotenoids from oranges were studied in vitro. In the initial step, 5,6-epoxy (di-epoxy) xanthophylls are isomerised to 5,8-furano (di-furano) xanthophylls. This reaction can also be brought about by hydrogen ions. Degradation products of OPI or impurities present in commercial samples may be acidic. Subsequent reactions lead to complete loss of the long wavelength chromophore.     

Photolysis of organophosphorus insecticides on soil surfaces

Photolysis on soil surfaces of the organophosphorus insecticides diazinon, methidathion and profenofos was studied under artificial sunlight conditions. All three compounds were readily degraded under the conditions used. The rate of degradation decreased in the order diazinon, profenofos, methidathion and was always greater in moist than in dry soil. The same order of stability was also observed from photolysis studies in aqueous solution. The major photolysis products identified were 2-isopropyl-6-methylpyrimidin-4-ol from diazinon, 5-methoxy-3H-1,3,4-thiadiazol-2-one from methidathion and 4-bromo-2-chlorophenol and 4-bromo-2-chlorophenyl ethyl hydrogen phosphate from profenofos. The same compounds were formed in hydrolysis studies and also upon photodecomposition in aqueous solutions of diazinon and methidathion. Profenofos, however, showed a different photolytic reaction in aqueous systems, forming O-(2-chlorophenyl) O-ethyl S-propyl phosphorothioate. Soil photolysis studies together with hydrolysis experiments could be a useful quick method for obtaining early information on the chemical breakdown products which are to be expected in the soil environment.     

The toxicity of mixtures of a pyrethroid with organophosphorus insecticides to Tetranychus urticae Koch

Laboratory studies of the cotoxicity of a pyrethroid insecticide, fenvalerate, and several organophosphorus insecticides against the two-spotted spider mite, Tetranychus urticae Koch, showed that a useful degree of potientation of toxicity occurred. The most effective combination of fenvalerate and azinphos-methyl was found to be a 1:1 ratio. Phosphates and phosphorodithioates in combination with fenvalerate were more toxic than phosphoromonothioates. The results suggest a practical method of improving the acaricidal activity of pyrethroid insecticides.     

城市公共服务设施与居住小区空间匹配性研究——以兰州市为例

借助网络爬虫软件收集到兰州市4593个公共服务设施网点和1291个居住小区的POI数据,运用核密度估计、最近邻指数、协同区位商以及耦合度模型等方法,定量分析公共服务设施与居住小区的空间关联性、与居住小区人口的空间耦合性,测度公共服务设施与居住小区空间匹配性。结果表明:①公共服务设施与居住小区的空间形态和集聚强度均存在显著差异,但二者的KDE栅格值相关系数表明二者具有一定的相关性;②居住小区具有临近公共服务设施布局的倾向,反之则不明显,空间匹配呈单向非对称性;③公共服务设施与人口耦合度在街道尺度上差异性显著,城市核心区域耦合度普遍较高,不过部分街道仍存在盲区,而城市边缘区域耦合度普遍偏低,表明二者的耦合性存在诸多不匹配现象。     

Fibre-reactive insect-resist agents for wool: The synthesis and effectiveness of some organophosphorus compounds

Fibre-reactive derivatives of 10 organophosphorus compounds were synthesised and evaluated as insect-resist agents for wool. Some were very effective against wool pests and, when the fibre-reactive group was a 2-bromoacrylic ester group. these compounds also exhibited good fastness to washing and dry-cleaning.     

Control of wireworms with organophosphorus and carbamate insecticides

Carbaryl, chlorfenvinphos, diazinon, disulfoton, parathion, phorate, fenitrothion, thionazin and trichlorphon were tested for their effectiveness in killing wireworms by broadcast treatments. Each insecticide was tested once or more in two field trials cropped with wheat and two cropped with potatoes. Phorate and parathion were very lethal to wireworms at 4 Ib active ingredient per acre (4–48 kg/ha). Thionazin and diazinon were intermediate in effectiveness and the other insecticides ineffective.     

Persistence of some organophosphorus insecticides in hen-house litter

Thin-layer chromatography was used to assess semi-quantitively the persistence of six organophosphorus insecticides in hen-house litter. Malathion disappeared within 4 h of application. Carbofenthion was the most persistent. Four weeks after treatment the proportions of the applied doses extracted from the litter were: carbofenthion 46%, phorate 21%, diazinon 13%, coumaphos 7% and fenitrothion 3%.     

The effects of small applications of an organophosphorus poison,fenthion on the weaver-bird Quelea quelea

Experiments were carried out in East Africa to determine the effects of single-drop applications of the avicide Queletox (active ingredient fenthion) on the Red-billed Quelea Q. quelea, an important agricultural pest. Birds treated with relatively large amounts of Queletox died within a few hours, as expected. Most of those receiving the smallest lethal doses died 12 to 48 h after treatment. From their terminal fat and muscle condition it was concluded that they died of starvation, despite their apparently healthy appearance following treatment and the easy availability of suitable food. LD₅₀'s of 80 and 220 mg/kg were obtained for Queletox applied to the feathers of the back in drops of varying sizes or concentrations, the amount of solvent having an important effect on the toxicity. The possibility is raised of reducing the amounts of Queletox used in control operations against the birds, making them safer and cheaper.     

The effect of organophosphorus compounds and oxime carbamates on the potato cyst nematode Heterodera rostochiensis woll

The effect of organophosphate and oxime carbamates on the potato cyst nematode, Heterodera rostochiensis was investigated. Although aldicarb slightly delayed emergence of second stage larvae, none of the chemicals decreased total hatch. Aldicarb had a marked effect on second stage larvae in soil which was subsequently reflected in root invasion counts. Comparisons between the initial and final populations (multiplication rate) of the potato cyst nematode are very useful for determining the efficacy of treatment. The evidence from these experiments suggests that organophosphoros compounds and oxime carbamates, although “systemic”, act against plant parasitic nematodes in the soil phase of the life cycle and not in the plant.     

Determination of the products of surface-induced hydrolysis of organophosphorus pesticides

A procedure which enables the identification of the hydrolysis products of a number of phosphoric and phosphorothioic esters was developed. This procedure, which includes thin-layer chromatography (t.l.c.), gas chromatography and u.v. spectroscopy, has been used to demonstrate that surface hydrolysis on kaolinite is a general property of bioactive phosphoric and phosphorothioic esters. The path of hydrolysis was shown to be the breakage of the P? O A or P? SA bond, where A is the electron attracting moiety of the organic molecule.     

Iodometric calibration of organophosphorus insecticides and measurement of hydrolysis products

Dialkylphosphoro-thioic and -dithioic acids, hydrolysis products of most organophosphorus insecticides, react stoichiometrically with iodoacetic acid, under controlled conditions, to release iodide. At room temperature, dialkylphosphorodithioic acids react with iodoacetic acid at pH 7–9, and dialkylphosphoro-thioic and -dithioic acids react with iodoacetic acid at pH 2 and below. This last reaction may be used for the determination of breakdown products in the presence of insecticides, such as fenitrothion, that are sufficiently stable to acid hydrolysis. The methods are suitable for measuring both active ingredients and hydrolysis products in formulations and in waterdiluted sprays.     

On the mode of action of the organophosphorus fungicide Hinosan

Samenvatting In onderzoek naar werkingsmechanismen van fungicide organische fosforverbindingen werd aangetoond dat Hinosan bijPiricularia oryzae tussenprodukten van de chitinesynthese kan doen ophopen. Dit duidt op een beïnvloeding van de chitinesynthese. De verbinding heeft ook een effect op de permeabiliteit van de celwandmembraan. Waarschijnlijk is dit effect primair verantwoordelijk voor de fungitoxiciteit van Hinosan en moet de remming van de chitinesynthese als een indirect effect worden beschouwd.     

Gel filtration clean-up for multi-residues of organophosphorus pesticides in rice

Gel filtration on Bio-Beads S-X8 and Sephadex LH-20 columns has been successfully applied to the clean-up of multiple residues of malathion, fenitrothion and dichlorvos in rice. Recoveries were checked by gas-liquid chromatography using CsBr-thermionic detector and ranged from 77 to 104% at 5 mg/kg level. The clean-up was found to be highly effective. No interference was observed in the gas chromatograms.     

Mercury(II) ion-promoted hydrolysis of some organophosphorus pesticides

The promotion of hydrolysis of some organophosphorus pesticides by mercury(II) ion was studied. The presence of mercuric chloride at 20 mg litre^?1 increased the initial hydrolysis rates of malathion, fenitrothion, fenthion and parathion-methyl in pH 5.5 buffer by two to three orders of magnitude. The hydrolysis was found to be first order with respect to both mercury(II) ion and the pesticide. The main hydrolysis product was 3-methyl-4-nitrophenol for fenitrothion, and 4-nitrophenol for parathion-methyl. It is postulated that the reaction involves the formation of a 1:1 complex and a very slow regeneration of the mercury(II) ion from the reacted complex. Mercury(II) ion had little effect on the organophosphorus pesticide dichlorvos.     

有机磷悬浮种衣剂稳定性研究

本文通过对悬浮种衣剂中有机磷成分的稳定性进行稳定，证明：某些有机磷较为稳定，适合作为悬浮种衣剂的有效城分；而某些则不然。     

The biochemical basis of resistance to organophosphorus insecticides in the sheep blowfly, Lucilia cuprina

The metabolism in vivo and in vitro of [¹⁴C]parathion and [¹⁴C]paraoxon was studied in a susceptible (LS) and an organophosphorus-resistant (Q) strain of the sheep blowfly, Lucilia cuprina. Both strains detoxified the insecticides in vivo via a number of pathways, but the resistant strain produced more of the metabolites diethyl phosphate and diethyl phosphorothionate. No difference was found between strains in the rate of penetration of the compounds used. Also, in vitro studies showed no difference between strains in the sensitivity of head acetylcholinesterase to inhibition by paraoxon. Both the microsomal and the 100,000g supernatant fractions degraded paraoxon, but resistance in Q could be explained by the eightfold greater rate of diethyl phosphate production with or without added NADPH. Parathion was also degraded to diethyl phosphorothionate by an NADPH-requiring enzyme in microsomal preparations from both strains. However, Q produced significantly more diethyl phosphorothionate in vivo than LS. It was concluded that organophosphorus resistance in Q was due mainly to a microsomal phosphatase hydrolyzing phosphate but not phosphorothionate esters, probably enhanced by a microsomal oxidase detoxifying the latter.     

手性除草剂研究进展

以几大类已经商品化或具有较好市场前景的手性除草剂为对象,综述了各除草剂的除草活性、对非靶标生物的毒性及其在环境迁移中的对映异构体选择性现象及机理的研究成果。由于对映异构体间的生物学性质迥异,因此,手性除草剂对映异构体的活性、作用机理、代谢转化及其在生物体内的转移等都具有手性选择性差异。同时,手性除草剂对植物的选择性作用还会因作用对象及环境因素的改变而改变,其在环境中的选择性降解情况也十分复杂,不仅与该除草剂自身的理化性质有关,还与其所处的环境因素有关,诸如土壤类型、植物种类、微生物群落结构、温度、pH值等均会改变手性除草剂对映异构体的环境归趋。