bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cytochemical demonstration of the effects of the acylureas flufenoxuron and diflubenzuron on the incorporation of chitin into insect cuticle
Authors: Lee Susan A. , Clarke Barry S. , Jenner Donald W. , Williamson Francis A. 
Published: November 2006

AbstractFlufenoxuron (“Cascade”) is a novel acylurea with acaricidal and insecticidal properties. It acts in a similar manner to diflubenzuron (DFB) by impairing chitin incorporation into insect cuticle.Chitin can be localised cytochemically using the lectin, wheat germ agglutinin (WGA), which binds specifically to N‐acetylglucosamine‐containing polymers. WGA adsorbed to monodisperse colloidal gold (WGA‐gold) was used as an electron‐dense marker for localising chitin in the cuticle of sixth‐instar Spodoptera littoralis.In the cuticle of control insects, the deposition zone and endocuticle were heavily labelled. In flufenoxuron‐ and DFB‐treated insects, only the endocuticle (formed before treatment) was labelled, the deposition zone being devoid of label.These results show that flufenoxuron and DFB act in similar manner in reducing chitin incorporation in the cuticle of S. littoralis.
The inhibition of chitin synthesis in spodoptera littoralis larvae by flufenoxuron, teflubenzuron and diflubenzuron
Authors: Clarke Barry S. , Jewess Philip J. 
Published: November 2006

AbstractThe chitin precursor [14C] N‐acetylglucosamine injected into the haemolymph of Spodoptera littoralis (Boisduval) larva was incorporated into the chitin exponentially with time. When caterpillars were injected with precursor at the commencement of feeding on acylurea‐treated leaf discs, flufenoxuron, teflubenzuron and diflubenzuron were found to be equally effective inhibitors of chitin synthesis, measured after 21 h. The dose response curves by feeding are not parallel, indicating that the relative potency of the compounds will vary across the dose range.When chitin precursor was injected simultaneously with topically applied diflubenzuron, flufenoxuron or teflubenzuron, all three acylureas were found to be equally effective as inhibitors of chitin synthesis when measured after five hours. The I50values (50% inhibition of chitin synthesis) were not significantly different; average 600 ng, compared with LD50values (50% lethal dose) of ∼ 13 ng for flufenoxuron and teflubenzuron but 130 ng for diflubenzuron (topical application). Injection of precursor 24 h after topical application of insecticide gave an I50value which had dropped 670‐ and 150‐fold for flufenoxuron and teflubenzuron respectively but only 20‐fold for diflubenzuron. It is postulated that the reason for the low increase in diflubenzuron effectiveness with time was due either to less diflubenzuron than flufenoxuron reaching the site of action, or more probably, a faster rate of metabolism and excretion for diflubenzuron.The lower toxicity of diflubenzuron compared with flufenoxuron and teflubenzuron may not be due to any inherent differences in biochemical effectiveness, but rather to different penetration/metabolism properties.
Activity of abamectin against larval stages of Spodoptera littoralis boisduval and Heliothis armigera hübner (Lepidoptera: Noctuidae) and possible mechanisms determining differential toxicity
Authors: Christie Paul T. , Wright Denis J. 
Published: November 2006

AbstractMarked changes in the relative toxicity of topically‐applied abamectin were found between larval instars of Spodoptera littoralis, toxicity decreasing up to the fifth instar but increasing over 500‐fold (at LD50 level) in the sixth instar. By contrast, the toxicity of abamectin remained constant from fifth to sixth instar Heliothis armigera and there was an increase in the toxicity of two chemically unrelated insecticides, malathion (4‐fold) and lambda‐cyhalothrin (2.5‐fold), from fifth to sixth instar S. littoralis. Prior topical application or injection of the microsomal oxidase inhibitor, piperonyl butoxide (PB) increased the toxicity of abamectin (6–8 and 16‐fold respectively) against fifth instar S. littoralis, while topically‐applied PB increased the proportion of radioactivity present as abamectin in the ventral nerve cord of this instar following topical application with [3H]abamectin. Topically‐applied PB also enhanced the toxicity of abamectin against third (4‐fold) and fourth instar (5‐fold) S. littoralis but had no significant effect on sixth instar S. littoralis, fifth instar H. armigera, or on the toxicity of malathion and lambda‐cyhalothrin against fifth instar S. littoralis. Topical application of the esterase inhibitor, S,S,S‐tributyl phosphorothioate (DEF) significantly increased the toxicity of abamectin at the LD50 level (3‐fold) against fifth instar S. littoralis. The toxicity of injected abamectin against fifth instar S. littoralis was greater (20‐fold) than with topical application but injected abamectin was less toxic (2‐fold) against sixth instar S. littoralis and had no significant effect on fifth instar H. armigera. It is suggested that differential toxicity of abamectin is due in part to greater metabolism and reduced penetration in fifth instar S. littoralis than in sixth instar S. littoralis or fifth instar H. armigera.
Acidic isostere design: Synthetic strategies and recent progress in understanding electronic properties and metabolic stability
Authors: Lipinski Christopher A. , Chenard Bert L. 
Published: November 2006

AbstractThe efficient synthesis of a family of twelve acidic heterocycles of varying acidity from a single common intermediate facilitates the search for new acidic bioisosteres. An extension of this chemical approach led to a new family of phosphonate replacements in prototypes related to the N‐methyl Dasparate (NMDA) antagonist 2‐amino‐7‐phosphonoheptanoic acid (AP7). Acidic isostere design may be facilitated by grouping hydroxylic heterocyclic carboxylic isosteres into one of two electronic classes based on the Gandour hypothesis. The limitations of normal hydroxamic acids as carboxylic acid surrogates suggest that the excellent metabolic stability of reverse hydroxamic acids may be useful in prospective acidic isostere design.
Chemistry of sulfonylurea herbicides
Authors: Hay James V. 
Published: November 2006

AbstractThe discovery of the sulfonylurea class of herbicides is one of the most dramatic breakthroughs in herbicide research in several decades. Sulfonylureas possess unprecedented levels of herbicidal activity–as low as 1 g ha−1–very low mammalian toxicity, and very desirable environmental properties. This review will discuss the structure‐activity relationships of sulfonylureas, their physical and chemical properties, and their methods of synthesis.
Mode of action, crop selectivity, and soil relations of the sulfonylurea herbicides
Authors: Brown Hugh M. 
Published: November 2006

AbstractThe sulfonylurea herbicides are characterized by broad‐spectrum weed control at very low use rates (c. 2–75 g ha−1), good crop selectivity, and very low acute and chronic animal toxicity. This class of herbicides acts through inhibition of acetolactate synthase (EC 4.1.3.18; also known as acetohydroxyacid synthase), thereby blocking the biosynthesis of the branched‐chain amino acids valine, leucine and isoleucine. This inhibition leads to the rapid cessation of plant cell division and growth. Crop‐selective sulfonylurea herbicides have been commercialized for use in wheat, barley, rice, corn, soybeans and oilseed rape, with additional crop‐selective compounds in cotton, potatoes, and sugarbeet having been noted. Crop selectivity results from rapid metabolic inactivation of the herbicide in the tolerant crop. Under growth‐room conditions, metabolic half‐lives in tolerant crop plants range from 1–5 h, while sensitive plant species metabolize these herbicides much more slowly, with half‐lives > 20 h. Pathways by which sulfonylurea herbicides are inactivated among these plants include aryl and aliphatic hydroxylation followed by glucose conjugation, sulfonylurea bridge hydrolysis and sulfonamide bond cleavage, oxidative O‐demethylation and direct conjugation with (homo)glutathione. Sulfonylurea herbicides degrade in soil through a combination of bridge hydrolysis and microbial degradation. Hydrolysis is significantly faster under acidic (pH 5) than alkaline (pH 8) conditions, allowing the use of soil pH as a predictor of soil residual activity. Chemical and microbial processes combine to give typical field dissipation half‐lives of 1–6 weeks, depending on the soil type, location and compound. Very short residual sulfonylurea herbicides with enhanced susceptibility to hydrolysis (DPX‐L5300) and microbial degradation (thifensulfuron‐methyl) have been developed.
Structure‐activity relationships among the imidazolinone herbicides
Authors: Ladner David W. 
Published: November 2006

AbstractThe structure of the imidazolinone herbicides consists of three distinct moieties: the imidazolinone ring, the carboxylic acid and the backbone. The effect of changes in each of these on herbicidal activity, crop selectivity and AHAS enzyme inhibition has been studied. Though both whole‐plant and enzyme activity were drastically affected by changes in the carboxylic acid or imidazolinone ring portions of the molecule, a variety of backbones and of substituents on the backbones afforded good activity. Methyl‐isopropyl was found to be the best combination of substituents on the imidazolinone ring. While pyridine backbones generally gave the most active herbicides, benzene backbones led to the strongest enzyme inhibition. A QSAR study in the pyridine series generated two equations which proved useful for guiding the analog program toward the synthesis of potent heteropyridyl compounds. Selectivity in wheat is dependent upon differences in the rate of metabolism of key groups. Rapid metabolism of either the imidazolinone ring or backbone alkyl groups occurs rapidly in soybeans compared with susceptible weeds.
New herbicidal derivatives of 1,2,4‐triazolo [1,5‐a] pyrimidine
Authors: Kleschick William A. , Costales Mark J. , Dunbar Joseph E. , Meikle Richard W. , Monte William T. , Pearson Norman R. , Snider Sigrid W. , Vinogradoff Anna P. 
Published: November 2006

AbstractTwo new structural classes of herbicide have been discovered which are based on the 1,2,4‐triazolo[1,5‐a]pyrimidine ring system. These compounds are related to the known herbicidal sulfonylureas and imidazolinones and other studies have shown that they have a similar mode of action, involving the inhibition of branched‐chain amino acid biosynthesis, the site of action being the enzyme acetolactate synthase. The design, synthesis and structure‐ activity relationships of these new classes of compounds are described.
Mechanism of action of the 1,2,4‐triazolo[1,5‐a] pyrimidines
Authors: Gerwick B. Clifford , Subramanian Mani V. , Loney‐Gallant Vivian I. , Chandler Darrell P. 
Published: November 2006

AbstractThe substituted 1,2,4‐triazolo[1,5‐a]pyrimidines are a new class of highly active herbicides. Protection of Arabidopsis thaliana seedlings from triazolopyrimidine‐induced injury by the branched‐chain amino acids was observed. Acetolactate synthase (EC 4.1.3.18) was isolated and found to be quite sensitive to inhibition. I50 values for inhibition of the enzyme from a number of plant sources show little variation and no correlation to whole‐plant response, suggesting uptake, translocation and metabolism play key roles in modulating herbicidal activity. Further studies indicate that these chemicals are slow, tight‐binding inhibitors that are readily dissociated by gel filtration. Some correlations between in‐vitro activity and in‐vivo activity were observed for ortho‐substituted analogs on selected broadleaf species.
Leaching potential and decomposition of fluroxypyr in Swedish soils under field conditions
Authors: Bergström Lars F. , McGibbon Alec S. , Day Steve R. , Snel Marten 
Published: November 2006

AbstractThe mobility and decomposition of the herbicide fluroxypyr (4‐amino‐3,5‐dichloro‐6‐fluoro‐2‐pyridyloxyacetic acid) was studied under field conditions in a sandy soil and a clay soil. Leachate was collected in lysimeters with undisturbed soil (sand) and in tile‐drained plots (clay). Soil samples to a depth of one metre were also collected in both soils to characterize the temporal depth distribution of fluroxypyr in the profiles. The herbicide was applied as the I‐methylheptyl ester of fluroxypyr at two rates, 187.5 and 375.0 g a.e. ha−1, representing the normal and double the dose of the compound used for spring cereals. Some lysimeters received supplementary watering. Only two leachate samples (one from each soil) had concentrations of fluroxypyr above the detection limit (1 μg litre−1), i.e. 2 and 5 μg litre−1. Both samples were collected within two months after application, when less than 2 mm of drainage had been collected. The methylheptyl ester of fluroxypyr was not found in any of the samples. Fluroxypyr levels above the detection limit in soil (5 μg kg−1 dry soil), were never found below the topsoil (0.2 m) in the clay profile, while, in the sandy profile, levels just above the detection limit were found occasionally in deeper soil layers. Concentrations were reduced to undetectable or very low levels within three months after spraying.
Degradation of pendimethalin by soil fungi
Authors: Barua Atri S. , Saha Jayanta , Chaudhuri Subhendu , Chowdhury Ashim , Adityachaudhury Narayan 
Published: November 2006

AbstractSeveral soil fungi, Aspergillus flavus, A. terreus, Fusarium solani, F. oxysporum, Penicillium citrinum and P. simplicissimum effectively degrade pendimethalin [N‐(I‐ethylpropyl)‐2,6‐dinitro‐3,4‐xylidine] supplied as sole carbon source in mineral solution. Degradation of pendimethalin by F. solani resulted in the isolation and identification of N‐propyl‐3‐methyl‐4‐hydroxy‐2,6‐dinitroaniline, N‐(I‐ethylpropyl)‐2‐amino‐6‐nitro‐3,4‐xylidine and 2,6‐dinitro‐3,4‐xylidine. The partial pathways involved in the degradation of pendimethalin have also been proposed.
An evaluation of the herbicidal and plant growth regulatory activity of a novel class of carbohydrate‐derived 6,8‐dioxabicyclo[3.2.1]octanes
Authors: Henzell Ronald F. , Furneaux Richard H. , Tyler Peter C. 
Published: November 2006

AbstractThirty‐five carbohydrate‐derived dioxabicyclo[3.2.l]octane derivatives have been tested for herbicidal and plant growth regulatory (PGR) activity in an Arabidopsis thaliana assay. Nine of these were herbicidal at concentrations of ⩽ 16 μg ml−1 in the growth medium. Three compounds, viz, 1,6‐anhydro‐3‐deoxy‐4‐O‐(2,6‐dichlorobenzyl)‐2‐O‐methyl‐β‐D‐ribo‐hexopyranose(I), its 4‐O‐benzyl analogue (II), and l,6‐anhydro‐2‐azido‐4‐O‐benzyl‐2,3‐dideoxy‐β‐D‐ribo‐hexopyranose (III) were very active herbicides, killing plants by the rosette stage at 1 μg ml−1 or less. At lower rates, the herbicides acted as growth regulators, reducing growth rates of shoots and roots as well as flowering and seed‐pod development. A further 14 compounds exerted PGR effects only, while 12 compounds were virtually inactive at 16 μg ml−1, the highest rate tested. The ability of the active compounds to reduce seed viability on mature plants at sublethal concentrations was demonstrated in four cases.
Predicting pesticide percutaneous penetration
Authors: Hadgraft Jonathan , Brain Keith R. 
Published: November 2006

AbstractIt is important to be able to predict the absorption of materials through the skin, particularly if there are toxicological implications. However, for pesticides which are known to be toxic, there are ethical considerations in conducting in‐vivo human evaluations of percutaneous absorption. It would therefore be desirable to obtain an indication of the amount of pesticide that can penetrate the skin from a simple knowledge of its physico‐chemical properties. It has been shown that the rate of penetration of a range of drugs through intact skin can be estimated from parameters such as partition coefficient, molecular size and solubility. These parameters will be equally applicable to pesticides and the relevant mathematical expressions are discussed.
Review—mechanism of action of herbicidal and fungicidal compounds on cell membranes
Authors: Burden Raymond S. , Cooke David T. , Hargreaves John A. 
Published: November 2006

AbstractThe eukaryotic cell membrane is thought to consist of a mobile bilayer of phospholipid, sometimes intercalated with sterols, in which peripheral and transmembrane proteins are embedded. This provides a model whereby the mode of action of many fungicidal and herbicidal compounds can be rationalised and understood. Some compounds, such as the polyene antibiotics, steroidal saponins and certain phytoalexins, induce membrane malfunction by direct insertion, often complexing with vital components. Others, such as paraquat and the nitrodiphenyl ether herbicides, cause membrane damage by inducing lipid peroxidations. Furthermore, there are many compounds, including the sterol‐biosynthesis‐inhibiting fungicides and the aryloxyphenoxypropionate and cyclohexanedione herbicides, which interfere with the biosynthesis of membrane components. Because membrane structure is fundamentally similar in eukaryotes, it is important to discover the reasons for any differential toxicity displayed by these compounds and, if necessary, to find ways of optimising desirable patterns of selectivity.
Chitin biosynthesis inhibition and fungicidal effect of thiosemicarbazones of 2‐formyl‐ and 2‐acetylpyridine, their hydrogenated derivatives and copper complexes thereof
Authors: Wengel Anita , Jacobsen Niels , Kolind‐Andersen Hans , Bjerregaard Poul 
Published: November 2006

AbstractSeveral thiosemicarbazones of 2‐formyl‐ and 2‐acetylpyridine dialkylated on N4 and non‐alkylated on N2 were found to be broad‐spectrum protectant fungicides with activity particularly against oomycetes. The effect of some of the compounds on chitin biosynthesis was studied, but the low inhibitory activity observed combined with the fungicidal activity spectrum—particularly the high activity against oomycetes—excludes this as their main mode of action. Attempts at enhancing the systemic properties of the compounds by chemical modifications failed.
Effect of 4‐amino‐6‐methyl‐3‐phenylamino‐1,2,4‐triazin‐5(4H)‐one on the integrity of chloroplasts from barley leaves
Authors: Muñoz Romualdo , Martínez‐Martínez Antonio , Ros‐Barceló Alfonso , Pedreño M. Angeles 
Published: November 2006

Abstract4‐Amino‐6‐methyl‐3‐phenylamino‐1,2,4‐triazin‐5(4H)‐one alters the integrity of chloroplasts in barley (Hordeum vulgare L. var. Hassan) leaves as judged by their sedimentation profiles in linear gradients of sucrose. This effect may be related to the inhibition caused by 4‐amino‐6‐methyl‐3‐phenylamino‐1,2,4‐triazine‐5(4H)‐one of both ascorbate peroxidase and superoxide dismutase activities, and could thus be explained by an accumulation of toxic reduced‐oxygen species in illuminated chloroplasts.
Synthesis and structure‐activity relationships of 1‐aryl‐4‐substituted‐1,4‐dihydro‐5H‐tetrazol‐5‐ones, a novel class of pre‐ and post‐emergence herbicides
Authors: Theodoridis George , Hotzman Frederick W. , Scherer Lynn W. , Smith Bruce A. , Tymonko John M. , Wyle Michael J. 
Published: November 2006

AbstractL‐Aryl‐4‐substituted‐1,4‐dihydro‐5H‐tetrazol‐5‐ones (I) represent a new class of herbicides, which, when applied pre‐ or post‐emergence in the presence of light, control several agriculturally important weed species. Forty‐eight analogues have been synthesized and their herbicidal activities determined in order to study structure‐activity relationships. In general, these compounds demonstrated: (l) optimum herbicidal activity when the 4‐ substituent on the tetrazole ring was – CH2CH2CH2F, and the aryl group 2‐ fluoro‐4‐chloro‐5‐substituted phenyl; (2) optimum herbicidal activity over a broad spectrum of grass and broad leaf weeds, with marginal crop selectivity when the C5 substituent on the phenyl group was – OCH2CCH; and (3) a high degree of selectivity on several major crops and primarily broadleaf weed control when this substituent was – NHSO2CH2CH3.
The synthesis and fungicidal activity of a series of 1‐aryltetrazole‐5‐sulphones
Authors: Richards Ian C. , Thomas Peter S. 
Published: November 2006

AbstractThe synthesis and fungicidal activity of a series of l‐aryltetrazole‐5‐sulphones are reported. Their activity against Plasmopara viticola is described. It is proposed that the compounds act as general electrophiles. Structure‐activity relationships are discussed in broad terms.
Direct and indirect effects of four herbicides on the activity of carabid beetles (coleoptera: Carabidae)
Authors: Brust Gerald E. 
Published: November 2006

AbstractFour herbicides, atrazine, simazine, paraquat, and glyphosate were tested for their acute and chronic toxicity as well as repellent effects on five common carabid beetles (Amara sp., Agonum sp., Pterostichus sp., Anisodactylus sp., and Harpalus sp.) in laboratory and greenhouse experiments. These carabid species are potential biocontrol agents and interference with their biology through herbicide applications, either directly or indirectly, could lead to soil pest outbreaks. Short‐term field studies also were conducted to verify laboratory and greenhouse results. The four herbicides did not have significant acute or chronic effects on male or female carabid longevity or food consumption during one year after exposure to initial field‐rate applications. Only simazine and atrazine had a repellent effect on carabids, which lasted approximately three days in greenhouse studies. Behavioral studies indicate that once carabids, especially smaller ones (< 10 mm in length), establish burrows and foraging territories, they tend to remain in these areas and migrate out of them only slowly. There was no toxic or repellent effect of any herbicide in the field. Carabids, instead, apparently responded to the destruction of plant material which provided a less favorable habitat for the larger (> 10 mm length) carabids. Glyphosate and paraquat had the greatest effect on carabids by the second week in field studies, with significantly fewer large carabids found in these two treatments than in the control. Large carabids did not return to paraquat‐ and glyphosate‐treated field areas until approximately 28 days after application; consequently, lower rates of predation of early‐season lepidopteran pests by these carabid species may occur in no‐tillage corn fields that utilize herbicides for weed control.
The role of protoporphyrin IX in the mechanism of action of diphenyl ether herbicides
Authors: Duke Stephen O. , Becerril José M. , Sherman T. D. , Lydon John , Matsumoto Hiroshi 
Published: November 2006

AbstractPhotobleaching diphenyl ether, cyclic imide and oxadiazole herbicides inhibit protoporphyrinogen oxidase (Protox), resulting in uncontrolled, non‐enzymic oxidation of accumulated protoporphyrinogen to protoporphyrin IX (Proto). Proto accumulation is stimulated by deregulation of the porphoyrin pathway due to blockage of heme synthesis. Heme is a Proto product and a feedback inhibitor of δ‐aminolevulinic acid synthesis. Strong correlations were found in several species under various conditions (e.g. sprayed on intact plants or taken up by leaf dises) between the accumulation of Proto and the degree of herbicidal damage caused by these herbicides. Levels of protochlorophyllide, Mg‐Proto, or Mg‐Proto monomethyl ester did not correlate significantly with herbicidal damage. Kinetic data indicated that elevated levels of protochlorophyllide in tissues treated with these herbicides only occurred after Proto had accumulated to high levels. Thus, Proto apparently re‐enters the porphyrin pathway to a significant extent after other cellular sites are saturated. Fluorescence microscopy indicated that considerable amounts of Proto accumulated outside the plastid in herbicide‐treated cells. All of the data were consistent with the hypothesis that Proto plays a critical role as a photosensitizing pigment in the mode of action of Protox‐inhibiting herbicides and that chlorophyll precursors that are derivatives of Proto are not significantly involved in the mode of action of these herbicides.