Comparative analysis of neonicotinoid binding to insect membranes: I. A structure-activity study of the mode of [3H]imidacloprid displacement in Myzus persicae and Aphis craccivora     

Kayser H  Lee C  Decock A  Baur M  Haettenschwiler J  Maienfisch P 《Pest management science》2004,60(10):945-958

Neonicotinoids bind selectively to insect nicotinic acetylcholine receptors with nanomolar affinity to act as potent insecticides. While the members of the neonicotinoid class have many structural features in common, it is not known whether they also share the same mode of binding to the target receptor. Previous competition studies with [3H]imidacloprid, the first commercialised neonicotinoid, indicated that thiamethoxam, representing a novel structural sub-class, may bind in a different way from that of other neonicotinoids. In the present work we analysed the mode of [3H]imidacloprid displacement by established neonicotinoids and newly synthesized analogues in the aphids Myzus persicae Sulzer and Aphis craccivora Koch. We found two classes of neonicotinoids with distinct modes of interference with [3H]imidacloprid, described as direct competitive inhibition and non-competitive inhibition, respectively. Competitive neonicotinoids were acetamiprid, nitenpyram, thiacloprid, clothianidin and nithiazine, whereas thiamethoxam and the N-methyl analogues of imidacloprid and clothianidin showed non-competitive inhibition. The chloropyridine or chlorothiazole heterocycles, the polar pharmacophore parts, such as nitroimino, cyanoimino and nitromethylene, and the cyclic or acyclic structure of the pharmacophore were not relevant for the mode of inhibition. Consensus structural features of the neonicotinoids were defined for the two mechanisms of interaction with [3H]imidacloprid binding. Furthermore, two sub-classes of non-competitive inhibitors can be discriminated on the basis of their Hill coefficients for imidacloprid displacement. We conclude from the present data that the direct competitors share the binding site with imidacloprid, whereas non-competitive compounds, like thiamethoxam, bind to a different site or in a different mode.  相似文献   

Cytologic diagnosis of diseases of invertebrates.     

Arnaud Van Wettere  Gregory A Lewbart 《Veterinary Clinics of North America: Exotic Animal Practice》2007,10(1):235-54, vii-viii

Invertebrate medicine in the context of an exotic or zoo animal veterinary practice is in its infancy. Establishment of species-specific reference values and evaluation of the effectiveness of cytology for diagnosis of specific diseases are necessary. Despite the lack of normal reference parameters for most species encountered in clinical practice, important information may be obtained from cytologic examination of tissue imprints, aspirates, scrapings, and hemolymph. This information may be essential to establish a specific diagnosis, focus investigations, and influence treatments. It is hoped that this article stimulates veterinarians who work with invertebrates to use diagnostic cytology and disseminate the results of their experience.  相似文献   

Sulcotrione versus atrazine transport and degradation in soil columns     

Cherrier R  Boivin A  Perrin-Ganier C  Schiavon M 《Pest management science》2005,61(9):899-904

A soil column experiment under outdoor conditions was performed to monitor the fate of 14C-ring-labelled sulcotrione, 2-(2-chloro-4-mesylbenzoyl)cyclohexane-1,3-dione and atrazine, 6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine, in water leachates and in the ploughed horizon of a sandy loam soil. Two months after treatment, the cumulative amounts of herbicide residues leached from the soil were 14.5% and 7% of the applied radioactivity for sulcotrione and atrazine, respectively. Maximum leachate concentrations for each herbicide were observed during the first month following application: 120 and 95 microg litre(-1) for sulcotrione and atrazine respectively. After 2 weeks, 78% of the sulcotrione and atrazine was extractable from the soil, whereas after two months only 10 and 4%, respectively, could be extracted. The maximum sulcotrione content in the first 10 cm of soil was identical with that of atrazine. For both molecules, the content of non-extractable residues was low, being around 15%. Sulcotrione seems to be more mobile than atrazine but the consequences for water contamination are similar since lower doses are used.  相似文献   

Prevalence of Trypanosoma evansi infection and associated risk factors in camels in eastern Chad     

Delafosse A  Doutoum AA 《Veterinary parasitology》2004,119(2-3):155-164

A cross-sectional study was conducted to estimate the prevalence of Trypanosoma evansi infection (Surra) in herds of camels from the eastern area of Chad. The risk factors associated with disease were also identified. From August 1997 to April 1998, a random sample of 2831 camels from 136 herds was selected. Blood samples were collected and examined for the presence of T. evansi using an antibody (card agglutination test-CATT/T. evansi) and a parasite detection test (buffy-coat technique-BCT). Standardized questionnaires with information about the host and management practices were collected and evaluated for their association with seroprevalence (model 1) and parasitological prevalence (model 2) as indications of host sensitivity. In both models, risk factors were selected using ordinary logistic regression (OLR) and herd effect was evaluated using a generalized estimating equations (GEE) model. The apparent prevalence was 5.3% using BCT and 30.5% with CATT. Real prevalence was estimated at 16.9% +/- 1.4 (alpha = 5%). Overall, 27.9% (BCT) and 94.9% (CATT) of the herds had a least one-positive animal. Real herd prevalence was estimated at 42.6 +/- 8.3% (alpha = 5%). Camels of the large transhumants had the highest prevalence (estimated to 30.3% +/- 2.5; 62.9 +/- 12.0 in herds). Risk factors associated with seroprevalence were age, ethnic group, length of seasonal migration and longitude of pasture area in the dry season. Risk factors associated with BCT prevalence were age, length of seasonal migration, longitude of pasture area in the dry season, latitude of pasture area in the rainy season and season of sampling.  相似文献   

Processive movement of MreB-associated cell wall biosynthetic complexes in bacteria     

Domínguez-Escobar J  Chastanet A  Crevenna AH  Fromion V  Wedlich-Söldner R  Carballido-López R 《Science (New York, N.Y.)》2011,333(6039):225-228

The peptidoglycan cell wall and the actin-like MreB cytoskeleton are major determinants of cell shape in rod-shaped bacteria. The prevailing model postulates that helical, membrane-associated MreB filaments organize elongation-specific peptidoglycan-synthesizing complexes along sidewalls. We used total internal reflection fluorescence microscopy to visualize the dynamic relation between MreB isoforms and cell wall synthesis in live Bacillus subtilis cells. During exponential growth, MreB proteins did not form helical structures. Instead, together with other morphogenetic factors, they assembled into discrete patches that moved processively along peripheral tracks perpendicular to the cell axis. Patch motility was largely powered by cell wall synthesis, and MreB polymers restricted diffusion of patch components in the membrane and oriented patch motion.  相似文献   

Assortative mating in sympatric host races of the European corn borer     

Malausa T  Bethenod MT  Bontemps A  Bourguet D  Cornuet JM  Ponsard S 《Science (New York, N.Y.)》2005,308(5719):258-260

Although a growing body of work supports the plausibility of sympatric speciation in animals, the practical difficulties of directly quantifying reproductive isolation between diverging taxa remain an obstacle to analyzing this process. We used a combination of genetic and biogeochemical markers to produce a direct field estimate of assortative mating in phytophagous insect populations. We show that individuals of the same insect species, the European corn borer Ostrinia nubilalis, that develop on different host plants can display almost absolute reproductive isolation-the proportion of assortative mating was >95%-even in the absence of temporal or spatial isolation.  相似文献   

Rhizosphere effects of <Emphasis Type="Italic">Populus euramericana</Emphasis> Dorskamp on the mobility of Zn,Pb and Cd in contaminated technosols     

Bashar Qasim  Mikael Motelica-Heino  Sylvain Bourgerie  Arnaud Gauthier  Domenico Morabito 《Journal of Soils and Sediments》2016,16(3):811-820

  相似文献   

Hemocyte characteristics in families of oysters, Crassostrea gigas, selected for differential survival during summer and reared in three sites     

Christophe Lambert  Philippe Soudant  Lionel Dgremont  Maryse Delaporte  Jeanne Moal  Pierre Boudry  Frdric Jean  Arnaud Huvet  Jean-Franois Samain 《Aquaculture (Amsterdam, Netherlands)》2007,270(1-4):276-288

High variability among individuals is often encountered when hemocyte characteristics are measured in bivalves. Such variability is suspected to result partly from genetic factors. In this study, hemocyte characteristics of six families of Crassostrea gigas were compared by flow cytometry at one sampling date in October 2001. These families were obtained from a nested, half-sibling cross design, and reared from July to October 2001 at three sites distributed along the French Atlantic coast from north to south: Baie des Veys (Normandy), Rivière d'Auray (Brittany) and Ronce (Marennes-oléron Basin, Poitou Charentes).

Among the 15 measured hemocyte characteristics, production of reactive oxygen species (ROS) of untreated hemocytes (maintained in filtered sterile seawater) and treated hemocytes (zymosan at 20 particles per hemocyte, and with Vibrio sp. S322 at 50 bacteria per hemocyte) was the most notable differences between families. This supports the existence of a genetic basis, at least partly, for the hemocyte characteristics of oysters, and especially for ROS production.

Among the six families analyzed, three have shown high survival during summer (named as “resistant”, mean mortality 5.2%) and three experienced high mortality during summer (named as “susceptible”, 30.6% mean mortality). Families showing high or low survival to summer mortality had similar hemocyte characteristics, regardless of the environmental conditions or reproductive state. Resistant families were observed to have higher total hemocyte counts and lower production of ROS than susceptible families. Moreover, ROS production of hemocytes from susceptible families was diminished significantly more by pathogenic Vibrio than that of resistant families. However, this study demonstrates also that rearing site strongly affected the hemocyte characteristics of all families of oysters, most notably hemocyte concentration and morphology (size and granularity), production of reactive oxygen species (ROS), and susceptibility to the cytotoxic activity of the pathogenic Vibrio sp. S322 (50 bacteria/hemocyte). Food availability and reproductive state are the most probable explanations for the site differences observed. Finally, it appeared difficult to link oyster survival during summer mortality to hemocyte profiles evaluated at one sampling date; other relevant indicators would probably help explaining oyster survival during summer mortality events.  相似文献   

Opposite effects of different mineral oil treatments on <Emphasis Type="Italic">Macrosiphum euphorbiae</Emphasis> survival and fecundity     

Maria Martoub  Aude Couty  Philippe Giordanengo  Arnaud Ameline 《Journal of pest science》2011,84(2):229-233

Mineral oil has been considered for several decades as an effective mean to control aphids and reduce the spread of non-persistent viruses. Mineral oil seems to reduce virus transmission efficiency interfering with the binding of the virions in the aphid stylets. However, several studies have shown the possible disruption of host selection process by mineral oil and some works have demonstrated a direct effect on the aphid vector. In this study the insecticidal properties of mineral oil (Finavestan EMA) alone against Macrosiphum euphorbiae (Thomas) (Homoptera: Aphididae) were evaluated through the three main routes of exposure (topical contact, inhalation and ingestion). Results showed that no aphid survived after topical contact at oil concentrations ranging from 3 to 100% v/v. However, surprisingly, at a lower concentration (0.3%), survival was not affected but fecundity was enhanced. Moreover, exposure to oil volatiles enhanced aphid survival at the highest concentrations (30 and 100%) and daily fecundity at the lowest ones (0.3 and 3%). Delivered via artificial diet, mineral oil only affected aphid survival at the 0.3% concentration. This study demonstrates that mineral oil alone, regardless of a potential plant effect can induce either probiotic effects or toxic effects, depending on the mode of application and the concentration tested. These results can be of significance for the understanding of mineral oil properties in the fields.  相似文献   

Laparoscopic-assisted colopexy and sterilization in male dogs: short-term results and physiologic consequences     

Mathon DH  Palierne S  Meynaud-Collard P  Layssol-Lamour C  Dulaurent-Ferrieres A  Colson A  Lacroix M  Bousquet-Melou A  Delverdier M  Autefage A 《Veterinary surgery : VS》2011,40(4):500-508

Objective: To describe laparoscopic‐assisted colopexy and sterilization, and evaluate outcome and effects in healthy male dogs. Study Design: Experimental study. Animals: Male Beagle dogs (n=7). Methods: A laparoscopic‐assisted, extracorporeally sutured colopexy, and sterilization by ligation and section of the testicular vessels and ductus deferens were evaluated 11 weeks after surgery. Ex vivo tensile tests were performed on the colopexy sites and loss of testicular function was assessed by monitoring serum testosterone, and by ultrasonographic and histologic examinations of the testes. Systemic inflammation and potential iatrogenic colonic functional disorders were investigated by monitoring serum C‐reactive protein (CRP) in the perioperative period and from a sulfapyridine (SP) kinetic profile obtained before and 10 weeks after surgery. Results: No intraoperative complications were recorded and clinical outcome was considered fair in all dogs. A mean tensile force of 42 N was required to disrupt colopexies. No relevant postoperative increase in CRP concentrations or changes in SP kinetics were observed. Testicular function was lost. Conclusions: Laparoscopic‐assisted colopexy achieved adhesion of the colon to the abdominal wall and testicular endocrine function and spermatogenesis were eliminated by laparoscopic castration.  相似文献