létale – -Translation – Keybot Dictionary

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  Arctostaphylos uva-ursi...  
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Contrairement à ce qui se produit avec plusieurs autres plantes médicinales présentées ici, l'écart entre la dose efficace et la dose toxique ou létale de raisin d'ours est si important que les adeptes des plantes médicinales qui décident de se soigner par eux-mêmes risqueront peu de s'intoxiquer et profiteront probablement des bienfaits de cette plante.
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The main active chemical of interest is the phenolic glycoside arbutin, a hydroquinone, usually making up 5-12%, sometimes more than 15%, of the dry weight of the foliage. The leaves also contain the pharmacologically active monotropein (an iridoid), and numerous other constituents, including trace amounts of aspirin. The leaves contain large amounts of tannins, so much so that the plants were once commonly employed to tan leather - a use that persists to this day in Scandinavia.
  Évaluation de l'efficac...  
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Parmi les huiles essentielles susmentionnées, celle de patchouli s'est avérée la plus toxique pour les tordeuses (concentration létale 50 moyenne de 0,227 p. 100), suivie de l'huile de thym commun (CL50 moyenne de 0,524 p. 100).
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Among the essential oils listed above, patchouli oil was determined to be the most toxic to leafrollers with an average LC50 of 0.227%, while white thyme oil was the next most toxic with an average LC50 of 0.524%. In both cases, use of the synergist, piperonyl butoxide (PBO) or the natural PBO analog, camphor wood oil, reduced the LC50 substantially. None of the carrier oils, nor EcoTrol was particularly effective against the leafrollers (LC50 for EcoTrol was over 10%). Prototype Formulation ECX, an essential oil/pyrethrum based formulation, was the most effective, with an LC50 of 0.068% as an aqueous emulsion. Further work is required before any of these active ingredients can be formulated and the presubmission consultation process can begin. The ECX product is being considered for US EPA registration as a biopesticide, which could facilitate regulatory approval in Canada.
  Lethal and sublethal to...  
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Nous avons mis au point un bioessai normalisé utilisant le scatophage du fumier (Scathophaga stercoraria L.) (Diptera: Scathophagidae) pour évaluer la toxicité létale et sublétale des résidus de pesticides dans les déjections du bétail.
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A standardized bioassay using the yellow dung fly, Scathophaga stercoraria L. (Diptera: Scathophagidae), was developed to test the lethal and sublethal toxicity of parasiticide residues in livestock dung. The repeatability of the bioassay was assessed for the parasiticide, ivermectin, in thirteen tests performed in seven laboratories in Germany, the UK, Switzerland and Canada. Test results had an acceptable range of heterogeneity. The calculated concentration at which 50% egg-adult mortality was observed (Effect Concentration (EC50) averaged 20.8 ± 19.1 (Standard Deviation (SD)) microg ivermectin / kg fresh dung (range: 6.33 - 67.5). Mortality was not observed below an average calculated No Observable Effect Concentration (NOEC) of 8.1 ± 7.7 microg / kg. However, prolonged developmental time, and in a subset of tests reduced body size, was observed above an average calculated NOEC of 0.8 ± 0.8 microg / kg. An oviposition choice test revealed further that yellow dung fly females do not discriminate among dung of different ivermectin concentrations. We conclude that the yellow dung fly is suitably sensitive, and the methods sufficiently repeatable, to support use of this standardized bioassay by the international community in the registration of new veterinary pharmaceuticals.
  Threat of Infection and...  
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La consommation d’œufs d’Ephestia kuehniella par les prédateurs survivants a été considérablement réduite durant six jours. Cette tendance semble attester des effets d’une infection sublétale. Les nymphes d’aleurodes infectées par le P. fumosoroseus trois jours avant d’être offertes au prédateur ont été acceptées comme proies, mais pas celles qui avaient été traitées cinq jours avant d’être offertes au prédateur.
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The nature and severity of intraguild interactions between predators and entomopathogens will be determined, in part, by a combination of threat of infection, and avoidance of that threat by the predator. We determined the threat of infection posed by the entomopathogen, Paecilomyces fumosoroseus (as PFR-97™) to the generalist predator, Dicyphus hesperus. We then asked if D. hesperus displays behavioral avoidance of infection while foraging for whitefly nymphs at different stages of infection by the pathogen. When exposed to leaf surfaces treated with the pathogen, 28% of adult female predators died due to infection. Consumption of Ephestia kuehniella eggs by surviving predators over 6 d was significantly reduced, suggesting effects of a sublethal infection. Whitefly nymphs that had been treated with P. fumosoroseus 3 d prior were acceptable as prey to D. hesperus but whitefly nymphs that had been treated with P. fumosoroseus 5 days prior were not. When foraging for whitefly nymphs, adult D. hesperus females rejected infected nymphs 96% of the time, compared to 39% of non-infected nymphs. Paecilomyces fumosoroseus therefore presents a measurable threat to D. hesperus through mortality and reduced prey consumption. Dicyphus hesperus does not avoid initial contact with infected prey but does not feed on such prey. The mechanism underlying these rejections could be due to either avoidance of infection or rejection of prey already consumed by the infectious agent. These results suggest that predation by D. hesperus foraging among infected whitefly nymphs under greenhouse or natural conditions could be reduced through a combination of pathogenicity and reduced efficiency of foraging.
  Cold-induced biochemica...  
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Nous avons d’abord évalué les populations et matériels génétiques initiaux, issus des cultivars Apica et Evolution, quant à leur tolérance au gel et aux changements moléculaires induits par le froid, chez des sujets ayant été acclimatés aux conditions de température extérieures dans une serre non chauffée. La sélection récurrente a fait augmenter de manière significative la tolérance au gel indiquée par la TL50 (température létale pour 50 % des sujets).
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Synthetic populations obtained after successive cycles of recurrent selection for superior tolerance to freezing were used to probe the molecular bases of superior adaptation to cold in alfalfa (Medicago sativa L.). The initial genetic backgrounds and populations derived from the cultivars Apica and Evolution were assessed for their freezing tolerance and cold-induced molecular changes using plants acclimated to natural hardening conditions in an unheated greenhouse. Signifi cant increase in freezing tolerance in response to recurrent selection was confi rmed by the determination of the lethal temperature for 50% of the plants (LT50). Improvement of freezing tolerance was associated with differences in cold-induced molecular changes. Starch reserves in crowns progressively declined during fall hardening with a more extensive mobilization observed in advanced cycles of selection. Concentrations of cryoprotective sugars and of the amino acids proline, asparagine, and arginine increased during fall hardening and were signifi cantly higher in recurrently selected populations than in the initial backgrounds. Transcript levels of two cold-regulated (COR) genes, cas15 and GaS, were strongly up-regulated during fall hardening and signifi cantly increased in response to selection mostly in the Apica background. Our results provide evidence that recurrent selection for superior freezing tolerance in alfalfa induces marked changes in traits associated with the cold acclimation process.
  Variability for Freezin...  
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Nous avons ainsi observé une grande variabilité parmi les écotypes quant à leur tolérance au gel exprimée en termes de température létale pour 50 % des sujets (TL50); cette température allait de moins de -27,0 à -17,0 °C.
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Limited information exists on the extent of genetic variability for freezing tolerance among perennial biotypes of annual bluegrass (Poa annua L.) that evolved under golf greens management. We characterized the freezing tolerance of 42 ecotypes collected across the United States and in Québec using plants hardened to low temperatures during fall and winter. We subsequently analyzed cold-induced biochemical changes in a subset of ecotypes with varied levels of tolerance. There was a large variability among ecotypes for freezing tolerance expressed as the lethal temperature for 50% of the plants (LT50) with values ranging from <-27.0 to -17.0°C. Variation was observed between ecotypes originating from the same region and even the same golf course. Ecotypes from Québec-better insulated from extreme subfreezing temperatures by reliable and abundant snow cover-developed less freezing tolerance than those evolving under milder winter climates. Significant differences in the concentrations of specific amino acids and carbohydrates were observed among ecotypes. Only fructans of high molecular weight, however, were significantly correlated with freezing tolerance and accounted for as much as 50% of the LT50 variance. A 26-kDa polypeptide that markedly accumulated in cold acclimated crowns was more abundant in plants from Québec. Extensive genetic variability for freezing tolerance among perennial biotypes of annual bluegrass can thus be exploited to mitigate winter damage to golf greens.