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Mannheimia haemolytica is an important etiological agent of pneumonia in domestic sheep (DS, Ovis aries). Leukotoxin (Lkt) produced by this organism is the principal virulence factor responsible for the acute inflammation and lung injury characteristic of M. haemolytica caused disease. Previously, we have shown that the leukocyte-specific integrins, beta(2) integrins, serve as the receptor for Lkt. Although it is certain that CD18, the beta subunit of beta(2) integrins, mediates Lkt-induced cytolysis of leukocytes, it is not clear whether CD18 of all three beta(2) integrins, LFA-1, Mac-1 and CR4, mediates Lkt-induced cytolysis of DS leukocytes. Since polymorphonuclear leukocytes, which express all three beta(2) integrins, are the leukocyte subset that is most susceptible to Lkt, we hypothesized that all three beta(2) integrins serve as the receptor for Lkt. The objective of this study was to determine whether DS LFA-1 serves as a receptor for M. haemolytica Lkt. We cloned the cDNA for DS CD11a, the alpha subunit of LFA-1, and co-transfected it along with the previously cloned cDNA for DS CD18, into a Lkt-non-suceptible cell line. Transfectants stably expressing DS LFA-1 were bound by Lkt. More importantly, Lkt lysed the DS LFA-1 transfectants in a concentration-dependent manner. Pre-incubation of Lkt with a Lkt-neutralizing monoclonal antibody (MAb), or pre-incubation of transfectants with MAbs specific for DS CD11a or CD18, inhibited Lkt-induced cytolysis of the transfectants. Exposure of LFA-1 transfectants to low concentrations of Lkt resulted in elevation of intracellular [Ca(2+)](i). Taken together, these results indicate that DS LFA-1 serves as a receptor for M. haemolytica Lkt. 相似文献
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Genetic variation in foot-and-mouth disease virus (FMDV) is of interest for at least two reasons. First, changes to the genes encoding capsid proteins results in antigenic variation, and affects vaccine efficiency and effectiveness of vaccination programs; second, genetic changes can lead to important insights into the transport of virus between countries, regions, herds, and even possibly individuals. Current estimates of RNA virus mutation rates suggest that an average of about one base mis-incorporation is likely to occur each time a single FMDV genome replicates. This should result in the introduction of every possible 1-step mutation from the progenitor genotype into the viraemia of a single infected animal many times a day. In the absence of purifying selection, a single infected animal should therefore generate a genetically very diverse population of virus.Viral-capsid sequences obtained from infected animals sampled over long-term FMDV epidemics suggest that these genetic changes accrue in a remarkably linear 'clock-like' fashion and at rates of around 1% change per year. While such a rate is generally regarded as quite high, it is actually somewhat lower than one might expect based on the rate at which viral diversity could be generated within a single animal. The difference might be explained in a variety of possible ways: (1) the mutation rate has been overestimated; (2) purifying selection is stronger than predicted; (3) only a restricted subset of excreted virus is actually infectious; (4) infected animals only excrete virus from a small partitioned subset of amplified virus, and that most of the generated viral diversity is unable to exit the animal; or (5) only a small fraction of all infected animals participate in the actual disease-transmission process. 相似文献
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Mechanisms associated with bendiocarb resistance were examined in two strains of western flower thrips, Frankliniella occidentalis (Pergande), that differed in their susceptibility to this carbamate by 13.6-fold. No appreciable differences between the two strains in [14C] bendiocarb penetration and excretion were detected; however, bendiocarb was metabolised substantially faster by the resistant KCM thrips than by the more susceptible UMC thrips. No appreciable difference between the two strains was found in the sensitivity of acetylcholinesterase activity to inhibition by bendiocarb. It was concluded that bendiocarb resistance in KCM western flower thrips was due to enhanced metabolism that probably was mainly oxidative in nature. 相似文献
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An investigation of 52 egg production units showed that in battery units, but not under other systems of husbandry, the proportion of defective eggs produced by birds in their second year was more than twice that of the first year. The proportion of defective eggs was unrelated to the shell thickness (measured by the deformation test on random samples of sound eggs from the same flocks). Damage to eggs during collection and packing was trivial, relative to the proportions of defective eggs found in the nests or cages. 相似文献
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R. G. Novy J. L. Whitworth J. C. Stark B. A. Charlton S. Yilma N. R. Knowles M. J. Pavek R. R. Spear T. L. Brandt N. Olsen M. Thornton C. R. Brown 《American Journal of Potato Research》2014,91(4):380-393
Teton Russet is an early-maturing, medium-russeted, potato cultivar with high merit for both fresh-pack and processing. In early harvest trials in the Pacific Northwest, Teton Russet had total yields similar to Russet Norkotah, and higher than Ranger Russet and Russet Burbank. Marketable yield of Teton Russet in the early harvest trials was also comparable to or higher than Russet Norkotah in Washington and Oregon, and higher than Ranger Russet and Russet Burbank at these sites, as well as in Idaho. In full-season trials, while total yield of the earlier-maturing Teton Russet tended to be lower than Ranger Russet and Russet Burbank, marketable yield was generally higher than Russet Burbank across the majority of sites due to its higher percentage of U.S. No. 1 tubers. Teton Russet is suitable for processing, with acceptable fry color following up to 8 months of storage at 8.9 °C. Uniformity of fry color was also very consistent. Teton Russet has shown lower levels of the amino acid asparagine relative to Ranger Russet and Russet Burbank which may contribute to lower acrylamide levels in French fries and other processed potato products. Teton Russet is notable for having resistance to common scab (Streptomyces spp.) and Fusarium dry rot, and is moderately resistant to tuber net necrosis. Analyses have also shown Teton Russet to have significantly higher protein levels than Russet Norkotah, Ranger Russet, and Russet Burbank, as well as higher vitamin C content than Russet Norkotah and Russet Burbank. Teton Russet was released in 2011 by the USDA-ARS and the Agricultural Experiment Stations of Idaho, Oregon, and Washington, and is a product of the Pacific Northwest Potato Variety (Tri-State) Development Program. 相似文献