摘要:

AbstractThe GABAAreceptor‐chloride channel complex is known to be the target of cyclodiene insecticides and of γ‐hexachlorocyclohexane (γ‐HCH, lindane). Dieldrin first enhances, then suppresses, γ‐aminobutyric acid (GABA)‐induced chloride currents, and the latter action results from the acceleration of desensitization. We now report more detailed analyses of the action of dieldrin and γ‐HCH on the GABAAreceptor‐chloride channel complex of rat dorsal root ganglion, using whole‐cell and single‐channel patch clamp techniques. Pre‐application of dieldrin suppressed GABA‐induced chloride currents in a time‐and dose‐dependent manner. No enhancement of current was observed under these conditions, because the enhancing action of dieldrin, which is transient in nature, had ceased by the time GABA‐induced currents were recorded. Both transient and sustained components of chloride currents were suppressed by dieldrin. The effect was almost irreversible, and the current did not recover after 30 min of washout with dieldrin‐free solution. The currents activated by higher concentrations of GABA were more strongly suppressed by dieldrin. Co‐application of γ‐HCH with GABA caused an enhancement of the GABA‐induced chloride currents, which was followed by suppression. Single‐channel currents induced by 1 μM GABA were completely suppressed by 1 μM γ‐HCH. Hyper‐excitation of the nervous system and whole animal caused by dieldrin and γ‐HCH is the result of suppr

ISSN:0031-613X    

DOI:10.1002/ps.2780440102

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractPhloem mobility is a desirable attribute for pesticides in many applications, and the physicochemical properties necessary for phloem mobility are now well understood. However, attempts to derivatize pesticides to make them phloem mobile are often frustrated by a concomitant loss of activity. This study describes a phloem‐mobile pro‐nematicide, a hydroxymethyloxamyl glucuronide (JR522) coupled with an in‐situ activation mechanism in transgenic tobacco expressingEscherichia coliβ‐glucuronidase in its root tips. When applied foliarly to the transgenic tobacco, JR522 and its methyl ester (JM775) showed greater nematicidal activity than oxamyl against root‐knot nematodes. This example of combining pro‐pesticide chemistry with crop genetic engineering for site‐specific activation provides a model system for demonstrating how to circumvent the often mutual exclusivity of phloem mobility and pesticidal activity. Additional advantages of this scheme include the potential mammalian safety of the propesticide, as exhibited by JR522 in this study, and a high degree of site‐specific release of xenob

ISSN:0031-613X    

DOI:10.1002/ps.2780440103

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractStarting from bulk chemicals, novel isoxazoledicarboxylic acid esters were prepared and converted to the corresponding dicarboxylic acid mono‐amides in a few reaction steps and in high overall yields. Key intermediates for the cycloaddition step were chlorooximinoacetates or amides as nitrile oxide equivalents, prepared in one‐pot reactions from diketene or acetoacetic acid esters. Isoxazoledicarboxylic acid monoamides combined good herbicidal activity with chemical flexibility. They were characterized as inhibitors of photosynthesis. Particularly, they affected the photosynthetic electron transport in photosystem II and the rate of carbon dioxide assimilation. Applied post‐emergence, the new compounds were found to control a broad spectrum of key weeds in corn. Excellent activity was found onAbutilon theophrasti(L.) Medik.,Amaranthus retroflexusL.,Chenopodium albumL.,Ipomoea spp., Polygonum persicariaL.,Solanum nigrumL. andXanthium strumariumL. with rates between 0.2 and 0.5 kg ha−1. As a side‐effect, the compounds also showed activity against grass weeds. The compounds are excellent tank‐mix partners, e.g. for sulfonyl‐ureas, to complete the weed spectrum (Chenopodium album L., Solanum nigrumL.) and/or to reduce the risk of developing herbicide‐

ISSN:0031-613X    

DOI:10.1002/ps.2780440104

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractA computer model was constructed based on the observation that a number of structurally dissimilar compounds gave rise to similar biological activity. Mode of action work confirmed the link. The model was then used to prioritise targets for synthesis and successfully predicted many active series. The major limitation of the model was that it was unable to predict potency or spectrum. It is thought likely that the factors controlling these limitations are linked with LUMO energies, but this hypothesis has not been proven.

ISSN:0031-613X    

DOI:10.1002/ps.2780440105

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractResistance to azole fungicides inUstilago maydis(DC) Corda has been examined using the mutant erg 40, a newly isolated mutant TriR‐1and erg 40 revertants. Azole‐induced growth arrest of the wild type did not support an obvious role for 3,6‐diol in the mode of action has is clear forSaccharomyces cerevisiaeMeyer ex Hansen. The level of microsomal P450 of erg 40 was identical to that of the parent, and reversion analysis showed no evidence of mutation in the sterol Δ5(6)desaturase, as would be expected for aS. cerevisiaemutant accumulating 14α‐methylfecosterol. Resistance appeared to be due to a single mutation in P450 14αdm. It is proposed that the orthologous forms of fungal sterol Δ5(6)desaturases have varied responses when attempting to utilise 14α‐methyla

ISSN:0031-613X    

DOI:10.1002/ps.2780440106

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractA series of pyridylcarbamates showed high potency against cucumber gray mould (Botrytis cinereaPers.). The most potent compound, propargyl‐N‐(6‐ethyl‐5‐iodo‐2‐pyridyl)carbamate was effective against an isolate sensitive to benzimidazole and dicarboximide fungicides as well as against an isolate resistant to both types of compound. QSAR analyses and molecular modelling studies were carried out to investigate the structural requirements for highly active compounds and the structural feature of the binding site of each strain. Significantly different QSAR equations were obtained only for substituents at the 6‐position of the pyridine ring. An ethyl‐sized pocket or an ethyl terminal recognition was suggested in the case of the sensitive or resistant isolate respectively. These results could explain the phenomenon of negatively correlated cross‐resistance between benzimidazoles andN‐phenylcarbamate fungicides. Substituent effects at the 5‐ or 2‐position were governed by steric factors. Substituent effects at the 3‐position were explained by steric hindrance or by conformational effects. The propargyl‐substituted compound above was the most desirable o

ISSN:0031-613X    

DOI:10.1002/ps.2780440107

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractA series of 1,3,4(2H)‐isoquinolinetriones have been found to be fast‐acting post‐emergence herbicides, producing symptoms of desiccation. These redox‐active compounds are very potent stimulators of the light‐dependent consumption of oxygen at photosystem I in isolated chloroplasts. Pulse radiolysis studies on 2‐ethyl‐1,3,4(2H)‐isoquinolinetrione have shown it to have free‐radical properties which could enhance the generation of superoxide radicals in plants. Electrochemical studies further support a redox mediator mode of action for the series. The compounds were found to be unstable towards hydrolysis, and this was considered to be a major factor limiting the overall herbicidal effects. Other parameters, related to uptake and/or translocation, which may limit the full expression of the herbicidal activity of certain compoun

ISSN:0031-613X    

DOI:10.1002/ps.2780440108

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractInsecticide penetration studies are usually done by applying a finite dose of material to a finite area of the integument in a solvent, such as acetone, that evaporates very quickly. The time‐course of penetration is then measured either as the buildup of material inside the insect or as the decline of material recoverable in a surface wash. Pharmacokinetic models are often used to describe such experiments, but identical models can be formulated from diffusion theory. Diffusion theory was applied to obtain equations that describe the steady‐state behavior of a single‐layer integument with partitioning between integument and solutions, and a double‐layer integument with partitioning between layers and between each layer and the adjacent solution. The steady‐state flux equations for both models were first‐order, and it was shown that this would be the case for steady‐state flux through any number of layers.The steady‐state analysis has two limitations. First, the assumption of a steady state implies that the concentration gradient across each layer of the integument is linear, and that this could not occur instantaneously. Second, the analysis assumes that material diffuses from a pool on the surface at some external concentration, whereas, ideally, it is applied as a plane source of infinite concentration. If the steady‐state assumption is rejected, the diffusion equation can be solved exactly, using Green's function, for diffusion of a topically applied dose across the integument modeled as a homogeneous plate, if the concentration at the internal face is assumed to remain zero. An analytical expression is obtained for concentration as a function of time and position in the integument, and from it are calculated flux into the insect and disappearance of material recoverable in a solvent wash, where material is assumed to be recoverable to an arbitrary depth. For small values of recovery depth, recovery falls precipitously following application, then progressively more slowly as the experiment proceeds. This phenomenon has been seen in much published data, and is explained adequately for the first time by the theory presented here. Predicted flux into the insect rises with a delay and then falls, but its fall is not exponential, as is often assumed. Peak flux is predicted to be directly related to the diffusion coeficient. The impact of these results on the design of penetration experim

ISSN:0031-613X    

DOI:10.1002/ps.2780440109

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract4‐tert‐Butyl‐2,6,7‐trioxabicyclo[2.2.2]octanes and 5‐tert‐butyl‐1,3‐dithianes with the 4‐ethynylcyclohexyl substituent in the 1‐ and 2‐positions, respectively, are potent insecticides modeled on their 4‐ethynylphenyl and hex‐5‐ynyl analogs. The compounds were prepared from dimethyl 1,4‐cyclohexanedicarboxylate, 4‐(2,2‐dibromovinyl)cyclohexanecarboxylic acid, methyl 4‐(1‐chlorovinyl)cyclohexanecarboxylate, and 4‐ethynylcyclohexylmethanol by wellestablished chemistry. Thecisandtransisomers of the 1‐cyclohexyl‐trioxabicyclooctane and all four geometric isomers of the 2‐cyclohexyl‐1,3‐dithiane were separated by chromatography of the final products or suitable intermediates. High levels of insecticidal activity were found against houseflies, German cockroaches and aphids for trioxabicyclooctanes and dithi

ISSN:0031-613X    

DOI:10.1002/ps.2780440110

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

ISSN:0031-613X    

DOI:10.1002/ps.2780440111

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY