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At least 1,747 records · Page 97Linked to original sources
PubMed2003

An improved baculovirus insecticide producing occlusion bodies that contain Bacillus thuringiensis insect toxin.

Baculovirus occlusion bodies, large proteinaceous structures which contain virions, have recently been engineered to incorporate foreign proteins. The major constituent protein of occlusion bodies from the baculovirus Autographa californica nucleopolyhedrovirus is polyhedrin, and assembly of recombinant occlusion bodies which incorporate a foreign protein depends on an interaction between native polyhedrin and a polyhedrin-foreign protein fusion. This technology has now been applied to the generation of a recombinant baculovirus (ColorBtrus) that produces occlusion bodies incorporating the Bacillus thuringiensis (Bt) insecticidal Cry1Ac toxin protein. ColorBtrus coexpresses native polyhedrin and a fusion protein in which polyhedrin is fused to the Bt toxin, which is in turn fused to green fluorescent protein (GFP). Analysis of ColorBtrus occlusion bodies confirmed that they include both Bt toxin and GFP, yet still incorporate virions. Bioassay of ColorBtrus demonstrated that its speed of action and pathogenicity are strikingly enhanced compared to wild-type virus. ColorBtrus represents a novel, powerful biological insecticide that combines positive attributes of both Bt toxin and baculovirus based systems.

Animals↗
PubMed2000

Anomalies on capture nets of Hydropsyche slossonae larvae (Trichoptera; Hydropsychidae), a potential indicator of chronic toxicity of malathion (organophosphate insecticide).

A laboratory study on the sublethal effects of malathion on the net-spinning behavior of the caddisfly larvae Hydropsyche slossonae was conducted in order to assess the potential of net anomalies as an indicator of chronic exposure to organophosphorus insecticides. Two anomalies were identified after chronic exposure to 0.01, 0.05, 0.1, 0.5 and 1.0 µg l(-1) malathion. The first was a distortion of the midline meshes where the normal diamond shape structure was disrupted and the meshes were separated by extra strands (called 'midline' anomaly). The second aberration observed was a significant decrease in net symmetry. Both anomalies were highly correlated to the toxic action of malathion, i.e. inhibition of the acetylcholinesterase enzyme (AChE). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analyses of capture nets did not show any modification of silk polypeptides after exposure to malathion, indicating that net distortions were not related to silk composition. Both anomalies seem to represent the symptoms of the specific toxic action of malathion; nevertheless, they can serve as an index of the physiological condition of the larvae, especially the midline anomaly. The symmetry of the nets decreased significantly after exposure to 0.5 and 1.0 µg l(-1). However, the toxicity curves (EC(50)) showed that the sensitivity threshold for the midline anomaly ranged from 0.11 to 0.28 µg l(-1), which reflect more realistic exposure to concentrations expected to occur in the field. Hence, the use of capture net anomalies of hydropsychid larvae could represent a valuable indicator of sublethal toxicity induced by malathion and other organophosphorus insecticides in running waters.

Journal Article↗
PubMed1998

Trypanosomiasis and Tsetse Control with Insecticidal Pour-ons- Fact and Fiction?

Insecticidal pour-ons that are applied directly to cattle have been promoted widely in the last decade as a new means of controlling tsetse flies in Africa. Tsetse attracted to treated cattle get a lethal dose of insecticide and die. Following a large trial in Kenya, Matthew Baylis and Peter Stevenson argue here that the reduction in trypanosomiasis incidence caused by pour-ons exceeds that expected from the impact (if there is any) on the tsetse population and that certain other (as yet unknown) factors must also be involved.

Journal Article↗
PubMed1987

Prolonged succinylcholine-induced paralysis in organophosphate insecticide poisoning.

A case of prolonged succinylcholine-induced paralysis in a child with organophosphate insecticide poisoning is presented. Three hours and 15 minutes of apnea after the administration of succinylcholine was attributed to a decreased rate of succinylcholine metabolism from inhibition of pseudocholinesterase by the insecticide. Only one similar case has been reported previously in the English medical literature. If succinylcholine is to be used in patients with organophosphate poisoning, a prolonged paralysis should be anticipated.

Apnea↗
PubMed1997

Novel Bioactive Cubé Insecticide Constituents: Isolation and Preparation of 13-homo-13-Oxa-6a,12a-dehydrorotenoids.

Two novel rotenoid-like compounds isolated from cubé resin, used as an insecticide and piscicide, have an unprecedented skeleton consisting of a 1,5-benzodioxepin (A and B rings) and a chromone (C and D rings). Their structures are assigned as (-)-13-homo-13-oxa-6a,12a-dehydrorotenone (5) and 13-homo-13-oxa-6a,12a-dehydrodeguelin (6) based on (1)H and (13)C NMR, MS, UV, and optical rotation. X-ray structure determination confirmed the assignment of 5 and revealed that the 1-methylethenyl group is disordered into two sets of atoms. Compound 5 from cubé resin was identical with a product previously reported as being formed by reaction of rotenone (1) with acetyl chloride and DMF and misassigned as "6a,12a-epoxyrotenone" (7). A modified procedure was developed for preparation of the new oxarotenoid component of the commercial insecticide. The cubé resin from which 5 and 6 were isolated in equal amounts contains 1 and deguelin (2) in a >10:1 ratio; this large difference in ratio indicates that 5 and 6 are not artifacts formed from 1and 2, respectively. Rotenoid 5 acts as a respiratory inhibitor with 50% inhibition of NADH:ubiquinone oxidoreductase activity at 0.11 &mgr;M, of goldfish survival at 1 ppm, and of the viability of three cell lines at 4-8 &mgr;M.

Journal Article↗
PubMed1995

Amplification of a chimeric Bacillus gene in chloroplasts leads to an extraordinary level of an insecticidal protein in tobacco.

The Bacillus thuringiensis (Bt) crystal toxins are safe biological insecticides, but have short persistance and are poorly effective against pests that feed inside plant tissues. Production of effective levels of these proteins in plants has required resynthesis of the genes encoding them. We report that amplification of an unmodified crylA(c) coding sequence in chloroplasts up to approximately 10,000 copies per cell resulted in the accumulation of an unprecedented 3-5% of the soluble protein in tobacco leaves as protoxin. The plants were extremely toxic to larvae of Heliothis virescens, Helicoverpa zea, and Spodoptera exigua. Since the plastid transgenes are not transmitted by pollen, this report has implications for containment of Bt genes in crop plants. Furthermore, accumulation of insecticidal protein at a high level will facilitate improvement in the management of Bt resistant insect populations.

Animals↗
PubMed2001

Agrobacterium tumefaciens-mediated transformation of rice with the spider insecticidal gene conferring resistance to leaffolder and striped stem borer.

Immature embryos of rice varieties "Xiushuill" and "Chunjiang 11" precultured for 4d were infected and transformed by Agrobacterium tumefaciens strain EHA101/pExT7 (containing the spider insecticidal gene). The resistant calli were transferred onto the differentiation medium and plants were regenerated. The transformation frequency reached 56% approximately 72% measured as numbers of Geneticin (G418)-resistant calli produced and 36% approximately 60% measured as numbers of transgenic plants regenerated, respectively. PCR and Southern blot analysis of transgenic plants confirmed that the T-DNA had been integrated into the rice genome. Insect bioassays using T1 transgenic plants indicated that the mortality of the leaffolder (Cnaphalocrasis medinalis) after 7d of leaf feeding reached 38% approximately 61% and the corrected mortality of the striped stem borer (Chilo suppressalis) after 7d of leaf feeding reached 16% approximately 75%. The insect bioassay results demonstrated that the transgenic plants expressing the spider insecticidal protein conferred enhanced resistance to these pests.

Agrobacterium tumefaciens↗
PubMed2000

Molecular and insecticidal characterization of a Bacillus thuringiensis strain isolated during a natural epizootic.

A new Bacillus thuringiensis strain belonging to the serovar aizawai was isolated from a dead larva of the lepidopteran Mythimna loreyi collected in a corn crop in Spain during a natural epizootic. This strain, which was named Leapi01, was compared with the kurstaki and aizawai strains isolated from Dipel(R) and Xentari(R), by electron microscopy, SDS-PAGE, plasmid pattern, PCR and insecticidal activity. This strain showed similar morphological and biochemical characteristics to the standard strains. The content in cry genes of Leapi01 was analysed with a set of general and specific primers recognizing most of the cry genes reported to date. DNA amplification was obtained with primers corresponding to six genes and, to clearly determine the identity of the genes, the amplified fragments were sequenced and corresponded to cry1Aa, cry1Ab, cry1Ca, cry1Da, cry2Ab and cry1Ia. However, the proteins encoded by two of these genes, Cry2 and Cry1I, were not detected in the SDS-PAGE of the purified parasporal bodies. The insecticidal activity of Leapi01 was determined by bioassays against two Lepidoptera species, Helicoverpa armigera and Spodoptera littoralis, that were found to be very susceptible to Leapi01 purified crystals. Since two of the cry genes identified in Leapi01 appear to be silent, other factors may be involved in the toxicity of the strain. As a result of this study, the potential of Leapi01 as biological control agent is discussed, with special emphasis on the high toxicity and relatively broad spectrum activity compared with two B. thuringiensis strains that are the active ingredients of commercial preparations commonly used as bioinsecticides.

Animals↗
PubMed2001

Introducing insecticide-treated nets in the Kilombero Valley, Tanzania: the relevance of local knowledge and practice for an information, education and communication (IEC) campaign.

Since 1997 the WHO has been recommending an integrative strategy to combat malaria including new medicines, vaccines, improvements of health care systems and insecticide-treated nets (ITNs). After successful controlled trials with ITNs in the past decade, large-scale interventions and research now focus on operational issues of distribution and financing. In developing a social marketing approach in the Kilombero Valley in south-east Tanzania in 1996, a combination of qualitative and quantitative methods was employed to investigate local knowledge and practice relating to malaria. The findings show that the biomedical concept of malaria overlaps with several local illness concepts, one of which is called malaria and refers to mild malaria. Most respondents linked malaria to mosquitoes (76%) and already used mosquito nets (52%). But local understandings of severe malaria differed from the biomedical concept and were not linked to mosquitoes or malaria. A social marketing strategy to promote ITNs was developed on the basis of these findings, which reinforced public health messages and linked them with nets and insecticide. Although we did not directly evaluate the impact of promotional activities, the sharp rise in ownership and use of ITNs by the population (from 10 to > 50%) suggests that they contributed significantly to the success of the programme. Local knowledge and practice is highly relevant for social marketing strategies of ITNs.

Adolescent↗
PubMed1990

Transfer and expression of an organophosphate insecticide-degrading gene from Pseudomonas in Drosophila melanogaster.

The organophosphorus acid hydrolases represent a distinct class of enzymes that catalyze the hydrolysis of a variety of organophosphate substrates, including many insecticides and their structural analogues. The plasmid-borne opd gene of Pseudomonas diminuta strain MG specifies an organophosphorus acid hydrolase, a phosphotriesterase, that has been well characterized and can hydrolyze a broad spectrum of insect and mammalian neurotoxins. The in situ functioning of this enzyme in the metabolism of organophosphates has been analyzed directly in insects by transferring the opd gene into embryos of Drosophila melanogaster by P element-mediated transformation. The chromosomal locations of this stably inherited transgenic locus differed from strain to strain and demonstrated various expressivity on the whole-insect basis. Transcriptional induction of opd in one of these strains under control of the Drosophila heat shock promoter, hsp70, resulted in the synthesis of stable active enzyme that accumulated to high levels with repeated induction. The heat shock-induced synthesis of organophosphorus acid hydrolases in transgenic flies conferred enhanced resistance to toxic paralysis by the organophosphate insecticide paraoxon.

Animals↗
PubMed1995

Cloning and expression of a receptor for an insecticidal toxin of Bacillus thuringiensis.

Environmentally friendly toxins of Bacillus thuringiensis are effective in controlling agriculturally and biomedically harmful insects. However, little is known about the insect receptor molecules that bind these toxins and the mechanism of insecticidal activity. We report here for the first time the cloning and expression of a cDNA that encodes a receptor (BT-R1) of the tobacco hornworm Manduca sexta for an insecticidal toxin of B. thuringiensis. The receptor is a 210-kDa membrane glycoprotein that specifically binds the cryIA(b) toxin of B. thuringiensis subsp. berliner and leads to death of the hornworm. BT-R1 shares sequence similarity with the cadherin superfamily of proteins.

Amino Acid Sequence↗
PubMed1987

Effects of two organophosphorus insecticides on some biochemical constituents in the nervous system and liver of rabbits.

Male Baladi rabbits were acutely and sub-chronically intoxicated with cyanofenphos and profenophos. The levels of cholesterol, triglycerides, B-lipoproteins and total proteins were determined in the serum, brain, spinal cord and sciatic nerve of rabbits. Moreover, the activities of alkaline phosphatase, acid phosphatase and glutamic-pyruvic transaminase were determined in the liver of the animals. The whole studies revealed that the biochemical constituents were highly affected by the tested insecticides. Also, the liver function suffered from adverse effects of the tested insecticides.

Administration, Oral↗
PubMed1991

Chronic toxicity of Thiodan (endosulfan) insecticide to Louisiana crayfish, Procambarus clarkii.

The major objective of this work was to assess the possible long-term effects of Thiodan insecticide on the growth-rate, fecundity and hatching potential of Louisiana crayfish, Procambarus clarkii. Adult males and females were collected from an Experiment Station, and were exposed to 600 ppb Thiodan. Since the aqueous solubility of endosulfan (active ingredient of Thiodan) is very low, the actual concentration of 2, 10, 15 and 600 ppb Thiodan in tap water was determined by electron-capture gas chromatography. The amount of endosulfan I and II in 2 ppb Thiodan was 0.8 and 0.32 ppb, respectively; 10 ppb = 3.8 and 1.52; 15 ppb = 6.3 and 2.52; and 600 ppb = 284 and 113.6 endosulfan I and II, respectively. Male and female crayfish were exposed to 600 ppb Thiodan for 20 weeks during which mating occurred. The mean number of eggs produced by control crayfish (N = 10) was 288 and by treated crayfish (N = 10) was 225, which did not differ significantly. Hatchlings from unexposed crayfish were used to determine the effects of Thiodan on weight, length and molting frequency. Sixty hatchlings were exposed to 2, 10 and 15 ppb Thiodan for a period of 9, 23 and 27 weeks during which they achieved a mean weight (gain) of 0.64, 0.19 and 0.17 g, respectively. Control hatchling gained 0.82, 0.30 and 0.19 g during the same period. These differences were also insignificant statistically. The length (gain) by these hatchlings (control and treated) over the same time period did not differ significantly. There was a slight increase (insignificant) in the molting frequencies of treated hatchlings. Comparative data on the chronic effects of Thiodan for crayfish are not available. Based on the reported LC50 values for grass shrimp, mysid shrimp and Korean shrimp, we conclude that Louisiana crayfish, P. clarkii is more tolerant to this insecticide than the other decapod crustaceans.

Animals↗
PubMed2005

Effects of herbicide and insecticide interaction on soil entomofauna under maize crop.

The aim of this study was to evaluate the impact of the herbicide mixture nicosulfuron + atrazine, with or without the insecticide chlorpyrifos, onto soil entomofauna under maize crop. The treatments, applied 25 days after maize emergence, were represented by a weeded control without insecticide and herbicide, a weeded control with chlorpyrifos, and mixtures of nicosulfuron + atrazine, with or without chlorpyrifos. Arthropods populations, on the soil surface, as well as inside the soil under maize, were principally represented by mites (Arachnida: Acari), decomposer collembolans (Hexapoda:Parainsecta:Collembola) and predator ants (Hymenoptera:Formicidae). The nicosulfuron + atrazine mixture with chlorpyrifos and the isolated chlorpyrifos reduced the population dynamics of all insect groups on the soil surface compared to the weeded control. In the soil, mite and ant populations were reduced after application of the herbicide mixture with chlorpyrifos and of the isolated chlorpyrifos.

Animals↗
PubMed1990

Nutritional status and insecticide tolerance in German cockroaches (Orthoptera: Blattellidae).

The interrelationship of two extrinsic factors-nutrition and pesticide exposure-was studied in German cockroaches, Blattella germanica (L.). Amount of dietary protein had no effect on susceptibility of male German cockroaches to propoxur and chlorpyrifos; however, the source of protein produced significant changes in insecticide susceptibility. Increased total body lipids, carbohydrates, and uric acid may have resulted in increased tolerance to these insecticides. Three days of food or water deprivation (or both) caused significant differences in susceptibility to chlorpyrifos and propoxur.

Animal Nutritional Physiological Phenomena↗
PubMed1978

Studies on L-ascorbic acid metabolism in rats under chronic toxicity due to organophosphorus insecticides: effects of supplementation of L-ascorbic acid in high doses.

The effects of chronic administration of two organophosphorus insecticides, parathion and malathion on the growth rate, ascorbic acid metabolism and some other nutritional and physiological parameters in rats were studied. Both parathion and malathion toxicity retarded the growth rate of rats. Inhibition of brain acetylcholinesterase was taken as an index of organophosphorus insecticide toxicity. Haemoglobin concentration of blood and organ weights were not affected under the toxic conditions. Parathion and malathion administration stimulated the activity of L-gulonolactone oxidase along with a simultaneous increase in the tissue storage and urinary excretion of vitamin C. The activities of other enzymes of ascorbic acid metabolism, dehydroascorbatase, uronolactonase, and L-gulonate dehydrogenase and decarboxylase were altered under the experimental conditions. Only minor histological changes of the liver and kidney tissues were noted under parathion and malathion toxicities. Excess intake of vitamin C under the toxic conditions was found to be very effective in counteracting the growth retardation and also the alterations produced by parathion and malathion both at the enzymatic and histological levels.

Animals↗
PubMed1989

Block of an insect central nervous system GABA receptor by cyclodiene and cyclohexane insecticides.

The effects of a cyclodiene (endrin) and a cyclohexane (lindane) insecticide have been tested on gamma-aminobutyric acid (GABA) receptors in the central nervous system of the cockroach (Periplaneta americana), by using electrophysiological methods and an in vitro functional receptor assay. In electrophysiological experiments on an identified motor neuron (Df), endrin blocked the GABA response with a 50% inhibition concentration of 5.0 x 10(-7) M in a non-competitive manner. The actions of endrin were irreversible under the experimental conditions adopted. Increasing the intracellular chloride concentration reduced the effectiveness of endrin, whereas a change in the potassium concentration failed to influence the block by endrin of GABA responses. Lindane exhibited similar actions to endrin on insect GABA receptors, but was approximately an order of magnitude less effective. In a microsac preparation from cockroach nerve cords, endrin, at a concentration of 1.0 x 10(-5) M, completely blocked GABA-stimulated 36Cl- uptake, whereas the same concentration of lindane was less potent, only blocking about 40% of uptake under similar conditions. Neither insecticide had any effect on L-glutamate-activated chloride channels. The results demonstrate that endrin and lindane block functional insect neuronal GABA receptors.

Animals↗
PubMed1990

Construction of genetically engineered baculovirus insecticides containing the Bacillus thuringiensis subsp. kurstaki HD-73 delta endotoxin.

The delta-endotoxin gene from Bacillus thuringiensis subsp. kurstaki HD-73 was inserted into Autographa californica nuclear polyhedrosis virus (AcMNPV) using two transfer vector systems. In the first, the delta-endotoxin gene was placed under the control of the polyhedrin gene promoter in lieu of the polyhedrin coding sequences, thus deriving a polyhedrin-negative virus. In the second, it was inserted under the control of a copy of the AcMNPV p10 promoter positioned upstream of the polyhedrin gene to produce a polyhedrin-positive virus. Analysis of infected cell extracts showed that the delta-endotoxin was expressed in insect cells as 130K, 62K and 44K proteins, with peak syntheses at 18 h post-infection. Each of these products reacted with antisera specific for the complete protoxin and the cleaved, active form. When extracts from the cells infected with the polyhedrin-negative virus were fed to Trichoplusia ni larvae, feeding by the insects was inhibited and deaths occurred that were inconsistent with virus infection. This effect was also observed after the inoculum had been treated with detergents to inactivate virus particles prior to feeding to the larvae. These data indicate that the expression of the B. thuringiensis delta-endotoxin gene by a baculovirus in insect cells produces material with insecticidal activity. The biological activities of the two recombinant viruses were assessed in conventional bioassay tests by feeding virus particles or occlusion bodies to the insects. The polyhedrin-negative virus preparation appeared to be contaminated with endotoxin which inhibited feeding of the insects and prevented determination of the LD50 value. The polyhedrin-positive virus had an LD50 value about twofold higher than that of unmodified AcMNPV. The significance of these data for the genetic engineering of virus insecticides is discussed.

Animals↗