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We have previously reported that in vitro HCV infection of cells of hepatocyte origin attenuates complement system at multiple steps, and attenuation also occurs in chronically HCV infected liver, irrespective of the disease stage. However, none of these regulations alone completely impaired complement pathways. Modulation of the upstream proteins involved in proteolytic processing of the complement cascade prior to convertase formation is critical in promoting the function of the complement system in response to infection. Here, we examined the regulation of C2 complement expression in hepatoma cells infected in vitro with cell culture grown virus, and validated our observations using randomly selected chronically HCV infected patient liver biopsy specimens. C2 mRNA expression was significantly inhibited, and classical C3 convertase (C4b2a) decreased. In separate experiments for C3 convertase function, C3b deposition onto bacterial membrane was reduced using HCV infected patient sera as compared to uninfected control, suggesting impaired C3 convertase. Further, iC3b level, a proteolytically inactive form of C3b, was lower in HCV infected patient sera, reflecting impairment of both C3 convertase and Factor I activity. The expression level of Factor I was significantly reduced in HCV infected liver biopsy specimens, while Factor H level remained unchanged or enhanced. Together, these results suggested that inhibition of C3 convertase activity is an additional cumulative effect for attenuation of complement system adopted by HCV for weakening innate immune response. 相似文献
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Zabardast T. Buriev Sukumar Saha Ibrokhim Y. Abdurakhmonov Johnie N. Jenkins Abdusattor Abdukarimov Brian E. Scheffler David M. Stelly 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2010,120(3):587-606
MIC-3 is a recently identified gene family shown to exhibit increased root-specific expression following nematode infection of
cotton plants that are resistant to root-knot nematode. Here, we cloned and sequenced MIC-3 genes from selected diploid and tetraploid cotton species to reveal sequence differences at the molecular level and identify
chromosomal locations of MIC-3 genes in Gossypium species. Detailed sequence analysis and phylogenetic clustering of MIC-3 genes indicated the presence of multiple MIC-3 gene members in Gossypium species. Haplotypes of a MIC-3 gene family member were discovered by comparative analysis among consensus sequences across genotypes within an individual
clade in the phylogram to overcome the problem of duplicated loci in the tetraploid cotton. Deficiency tests of the SNPs delimited
six At-genome members of the MIC-3 family clustered to chromosome arm 4sh, and one Dt-genome member to chromosome 19. Clustering was confirmed by long-PCR amplification of the intergenic regions using At-genome-specific MIC-3 primer pairs. The clustered distribution may have been favored by selection for responsiveness to evolving disease and/or
pest pressures, because large variants of the MIC-3 gene family may have been recovered from small physical areas by recombination. This could give a buffer against selection
pressure from a broad range of pest and pathogens in the future. To our knowledge, these are the first results on the evolution
of clustering and genome-specific haplotype members of a unique cotton gene family associated with resistant response against
a major pathogen. 相似文献
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Stephen H. Jenkins 《Oecologia》1975,21(2):157-173
Summary Multidimensional contingency tables provide a powerful new statistical tool for analyzing interactions among several variables in an ecological study. This technique is applied to a study of selectivity in tree-cutting by two colonies of beavers in central Massachusetts.At the Blue Heron Cove colony, selection depends jointly on genus and diamter. Beavers cut birch of all diameters available but avoid large diameter maples, pines, and oaks. These beavers are choosy generalists: they show clear preferences in cutting various genera of trees for food yet they cut substantial numbers of trees of non-preferred genera. At the Tamplin Road Pond colony, discrete sites of concentrated cutting activity differ in genera and diameters of trees selected. Trees of all diameters are cut at one site close to water, small diameter trees are selected at two other sites farther from water. Ironwood is preferred at one site but selected against at two other sites. This difference between sites in generic selectivity has two plausible explanations: (1) tree species differ in nutritional and other chemical value between sites, (2) beavers sample trees of the various species present at some sites in order to assess the value of such sites as foraging areas. 相似文献
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M D Keppler M A Read P J Perry J O Trent T C Jenkins A P Reszka S Neidle K R Fox 《European journal of biochemistry》1999,263(3):817-825
We have used quantitative DNase I footprinting to measure the relative affinities of four disubstituted and two monosubstituted amidoanthraquinone compounds for intermolecular DNA triplexes, and have examined how the position of the attached base-functionalized substituents affects their ability to stabilize DNA triplexes. All four isomeric disubstituted derivatives examined stabilize DNA triplexes at micromolar or lower concentrations. Of the compounds studied the 2,7-disubstituted amidoanthraquinone displayed the greatest triplex affinity. The order of triplex affinity for the other disubstituted ligands decreases in the order 2,7 > 1,8 = 1,5 > 2,6, with the equivalent monosubstituted compounds being at least an order of magnitude less efficient. The 1,5-disubstituted derivative also shows some interaction with duplex DNA. These results have been confirmed by molecular modelling studies, which provide a rational basis for the structure-activity relationships. These suggest that, although all of the compounds bind through an intercalative mode, the 2,6, 2,7 and 1,5 disubstituted isomers bind with their two side groups occupying adjacent triplex grooves, in contrast with the 1,8 isomer which is positioned with both side groups in the same triplex groove. 相似文献
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The segmentum accelerans in geese is a constriction in the caudal end of the primary bronchus. Experimental evidence suggests that this part of the airway functions as an inspiratory aerodynamic valve, accelerating the incoming airstream past the ventrobronchial openings. The luminal diameter of the segmentum accelerans dilates in the presence of elevated CO2 levels, probably through relaxation of smooth muscle. Physiological control of the segmentum accelerans may permit inspiratory aerodynamic valving to be maintained throughout a wide range of ventilatory flows. 相似文献
20.
Form of inorganic carbon involved as a product and as an inhibitor of c(4) Acid decarboxylases operating in c(4) photosynthesis 总被引:1,自引:1,他引:0
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These studies demonstrated that CO2 rather than HCO3− is the inorganic carbon metabolite produced by the C4 acid decarboxylases involved in C4 photosynthesis (chloroplast located NADP malic enzyme, mitochondrial NAD malic enzyme, and cytosolic phosphoenolpyruvate [PEP] carboxykinase). The effect of varying CO2 or HCO3− as a substrate for the carboxylation reaction catalyzed by these enzymes or as inhibitors of the decarboxylation reaction was also determined. The KmCO2 was 1.1 millimolar for NADP malic enzyme and 2.5 millimolar for PEP carboxykinase. For these two enzymes the velocity in the carboxylating direction was substantially less than for the decarboxylating direction even with CO2 concentrations at the upper end of the range of expected cellular levels. Activity of NAD malic enzyme in the carboxylating direction was undetectable. The decarboxylation reaction of all three enzymes was inhibited by added HCO3−. For NADP malic enzyme CO2 was shown to be the inhibitory species but PEP carboxykinase and NAD malic enzyme were apparently inhibited about equally by CO2 and HCO3−. 相似文献