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  • 11
    Electronic Resource
    Electronic Resource
    Phosphorylation of tyrosine 972 of the Helicobacter pylori CagA protein is essential for induction of a scattering phenotype in gastric epithelial cells (2001)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 42 (2001), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Helicobacter pylori colonizes the human stomach and is the causative agent of a variety of gastric diseases. After bacterial attachment, the H. pylori CagA protein is translocated into gastric epithelial cells and tyrosine phosphorylated. This process is associated with characteristic cytoskeletal rearrangements, resulting in a scatter factor-like (‘hummingbird’) phenotype. In this study, using a cagA mutant complemented with wild-type cagA and transiently expressing CagA in AGS cells, we have demonstrated that translocated CagA is necessary for rearrangements of the actin cytoskeleton to occur. Anti-phosphotyrosine immunoblotting studies and treatment of infected cells with phosphotyrosine kinase inhibitors suggested that not only translocation but also phosphorylation of CagA is important in this process. Transient expression of CagA–green fluorescent protein (GFP) fusion proteins and two-dimensional gel electrophoresis of CagA protein species demonstrated tyrosine phosphorylation in the C-terminus. Site-directed mutagenesis of CagA revealed that tyrosine residue 972 is essential for induction of the cellular phenotype. We have also demonstrated that translocation and phosphorylation of CagA is necessary but not sufficient for induction of the hummingbird phenotype in AGS cells, indicating the involvement of as yet unidentified bacterial factor(s).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2001.02649.x
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  • 12
    Electronic Resource
    Electronic Resource
    Helicobacter pylori inhibits phagocytosis by professional phagocytes involving type IV secretion components (2000)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 37 (2000), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Gastric infections by Helicobacter pylori are characteristically associated with an intense inflammation and infiltration of mainly polymorphonuclear lymphocytes (PMNs) and monocytes. The inflammatory response by infiltrated immune cells appears to be a primary cause of the damage to surface epithelial layers and may eventually result in gastritis, peptic ulcer, gastric cancer and/or MALT-associated gastric lymphoma. Our analysis of the interaction between H. pylori and PMNs and monocytes revealed that H. pylori inhibits its own uptake by these professional phagocytes. To some degree, this effect resembles antiphagocytosis by Yersinia enterocolitica. Increasing numbers of bacteria associated per cell are more efficient at blocking their own engulfment. In H. pylori, bacterial protein synthesis is necessary to block phagocytic uptake, as shown by the time and concentration dependence of the bacteriostatic protein synthesis inhibitor chloramphenicol. Furthermore, H. pylori appears broadly to inhibit the phagocytic function of monocytes and PMNs, as infection with H. pylori abrogates the phagocytes' ability to engulf latex beads or adherent Neisseria gonorrhoeae cells. This antiphagocytic phenotype depends on distinct virulence (vir) genes, such as virB7 and virB11, encoding core components of a putative type IV secretion apparatus. Our data indicate that H. pylori exhibits an antiphagocytic activity that may play an essential role in the immune escape of this persistent pathogen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2000.02089.x
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  • 13
    Electronic Resource
    Electronic Resource
    Potential role of two Helicobacter pylori relaxases in DNA transfer? (1998)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 30 (1998), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1998.01086.x
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  • 14
    Electronic Resource
    Electronic Resource
    Helicobacter pylori induce neutrophil transendothelial migration: Role of the bacterial HP-NAP (2005)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 249 (2005), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Continuous recruitment of neutrophils into the inflamed gastric mucosal tissue is a hallmark of Helicobacter pylori infection in humans. In this study, we examined the ability of H. pylori to induce transendothelial migration of neutrophils using a transwell system consisting of a cultured monolayer of human endothelial cells as barrier between two chambers. We showed for the first time that live H. pylori, but not formalin-killed bacteria, induced a significantly increased transendothelial migration of neutrophils. H. pylori conditioned culture medium also induced significantly increased transendothelial migration, whereas heat-inactivated culture filtrates had no effect, suggesting that the chemotactic factor was proteinaceous. Depletion of H. pylori-neutrophil activating protein (HP-NAP) from the culture filtrates resulted in significant reduction of the transmigration. Culture filtrates from isogenic HP-NAP deficient mutant bacteria also induced significantly less neutrophil migration than culture filtrates obtained from wild-type bacteria. HP-NAP did not induce endothelial cell activation, suggesting that HP-NAP acts directly on the neutrophils. In conclusion, our results demonstrate that secreted HP-NAP is one of the factors resulting in H. pylori induced neutrophil transendothelial migration. We propose that HP-NAP contributes to the continuous recruitment of neutrophils to the gastric mucosa of H. pylori infected individuals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/j.femsle.2005.06.008
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  • 15
    Electronic Resource
    Electronic Resource
    Separation of Different Conformations of Plant Mitochondrial DNA Molecules by Field Inversion Gel Electrophoresis (1998)
    Springer
    Plant molecular biology reporter 16 (1998), S. 219-229 
    Details
    ISSN: 1572-9818
    Keywords: field inversion gel electrophoresis ; genome structure ; plant mitochondrial DNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mitochondrial (mt) DNA structure in higher plants is still unclear as to the circularity or linearity of the genome. We have developed a system to electrophoretically separate distinct populations of mtDNA, with some populations enriched for networked linear and circular DNA molecules. Using field inversion gel electrophoresis (FIGE) and electron microscopy (EM), we have identified four distinct populations of mtDNA from two Brassica species. Using FIGE, two slow migrating mtDNA populations ran faster than a 66 kbp Escherichia coli circular plasmid marker, while these same populations comigrated in the compression zone in contour-clamped homogeneous electrophoretic field (CHEF) gels. A fast-migrating mtDNA population was also resolved by FIGE as a diffuse band between 20 to 70 kbp when compared with linear lambda (λ) markers. FIGE resolved the 66 kbp circular marker into several multimers, while CHEF resolved only open-circular monomers and linears. In agreement with FIGE results, EM analysis indicated the two slow migrating mtDNA populations contained circular (both supercoiled and relaxed circles) and free linear molecules of 10-60 kbp, and networked linear molecules of 45–140 kbp total size that may represent recombination intermediates. The fast migrating population consisted of 10–50 kbp linear molecules. Well-bound mtDNA showed only long linear molecules of 40–150 kbp with no detection of circles or complex/rosette molecules. This report shows that FIGE has clear advantages over CHEF for separating large DNA molecules with different conformations, and may be very useful for studies to characterize genome structure in complex systems such as plant mitochondria.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007512108373
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  • 16
    Electronic Resource
    Electronic Resource
    Helicobacter exploits integrin for type IV secretion and kinase activation (2007)
    [s.l.] : Nature Publishing Group
    Nature 449 (2007), S. 862-866 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Integrins are important mammalian receptors involved in normal cellular functions as well as pathogenesis of chronic inflammation and cancer. We propose that integrins are exploited by the gastric pathogen and type-1 carcinogen Helicobacter pylori for injection of the bacterial oncoprotein ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature06187
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  • 17
    Electronic Resource
    Electronic Resource
    Electron microscopic investigation of mitochondrial DNA from Chenopodium album (L.) (1996)
    Springer
    Current genetics 29 (1996), S. 427-436 
    Details
    ISSN: 1432-0983
    Keywords: Key words Mitochondrial DNA ; Mitochondrial plasmid ; Chenopodium album ; Rolling-circle replication ; Plastid DNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  DNA molecules from mitochondria of whole plants and a suspension culture of Chenopodium album were prepared, by a gentle method, for analysis by electron microscopy. Mitochondrial (mt) DNA preparations from both sources contained mostly linear molecules of variable sizes (with the majority of molecules ranging from 40 to 160 kb). Open circular molecules with contour lengths corresponding to 0.3–183 kb represented 23–26% of all mtDNA molecules in the preparations from the suspension culture and 13–15% in the preparations from whole plants. More than 90% of the circular DNA was smaller than 30 kb. Virtually no size classes of the mtDNA molecules could be identified, and circular or linear molecules of the genome size (about 270 kb) were not observed. In contrast, plastid (pt) DNA preparations from the suspension culture contained linear and circular molecules falling into size classes corresponding to monomers, dimers and trimers of the chromosome. About 23% of the ptDNA molecules were circular. DNA preparations from mitochondria contained a higher percentage of more complex molecules (rosette-like structures, catenate-like molecules) than preparations of ptDNA. Sigma-like molecules (putative intermediates of rolling-circle replication) were observed in mtDNA preparations from the suspension culture (18% of the circles), and in much lower amount (1%) in preparations from whole plants. The results are compared with data obtained previously by pulsed-field gel electrophoresis and discussed in relation to the structural organization and replication of the mt genome of higher plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002940050067
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  • 18
    Electronic Resource
    Electronic Resource
    Electron microscopic investigation of mitochondrial DNA fromChenopodium album (L.) (1996)
    Springer
    Current genetics 29 (1996), S. 427-436 
    Details
    ISSN: 1432-0983
    Keywords: Mitochondrial DNA ; Mitochondrial plasmid ; Chenopodium album ; Rolling-circle replication ; Plastid DNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract DNA molecules from mitochondria of whole plants and a suspension culture ofChenopodium album were prepared, by a gentle method, for analysis by electron microscopy. Mitochondrial (mt) DNA preparations from both sources contained mostly linear molecules of variable sizes (with the majority of molecules ranging from 40 to 160 kb). Open circular molecules with contour lengths corresponding to 0.3–183 kb represented 23–26% of all mtDNA molecules in the preparations from the suspension culture and 13–15% in the preparations from whole plants. More than 90% of the circular DNA was smaller than 30 kb. Virtually no size classes of the mtDNA molecules could be identified, and circular or linear molecules of the genome size (about 270 kb) were not observed. In contrast, plastid (pt) DNA preparations from the suspension culture contained linear and circular molecules falling into size classes corresponding to monomers, dimers and trimers of the chromosome. About 23% of the ptDNA molecules were circular. DNA preparations from mitochondria contained a higher percentage of more complex molecules (rosette-like structures, catenate-like molecules) than preparations of ptDNA. Sigma-like molecules (putative intermediates of rollingcircle replication) were observed in mtDNA preparations from the suspension culture (18% of the circles), and in much lower amount (1%) in preparations from whole plants. The results are compared with data obtained previously by pulsed-field gel electrophoresis and discussed in relation to the structural organization and replication of the mt genome of higher plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02221510
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  • 19
    Electronic Resource
    Electronic Resource
    Investigation of plant organellar DNAs by pulsed-field gel electrophoresis (1995)
    Springer
    Current genetics 28 (1995), S. 390-399 
    Details
    ISSN: 1432-0983
    Keywords: Mitochondrial DNA ; Chloroplast DNA ; Pulsed-field gel electrophoresis ; Chenopodium album
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mitochondrial (mt) DNAs from several higher-plant species (Arabidopsis thaliana, Beta vulgaris, Brassica hirta, Chenopodium album, Oenothera berteriana, Zea mays) were separated by pulsed-field gel electrophoresis (PFGE). Hybridization of the separated DNA with mtDNA-specific probes revealed an identical distribution of mtDNA sequences in all cases: part of the DNA formed a smear of linear molecules migrating into the gel, the rest remained in the well. Hybridization signals in the compression zone of the gels disappeared after RNase or alkaline treatment. It was shown that the linear molecules are not products of unspecific degradation by nucleases. All plastid (pt) DNA from leaves of Nicotiana tabacum remained in the well after PFGE. Separation of linear monomers and oligomers of the chloroplast chromosomes of N. tabacum was achieved by mild DNase treatment of the well-bound DNA. DNase treatment of well-bound mtDNA, however, generated a smear of linear molecules. PtDNA from cultured cells of C. album was found after PFGE to be partly well-bound, and partly separated into linear molecules with sizes of monomeric and oligomeric chromosomes. The ease with which it was possible to detect large linear molecules of plastid DNA indicates that shearing forces alone can not explain the smear of linear molecules obtained after PFGE of mtDNA. The results are discussed in relation to the structural organization of the mt genome of higher plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00326439
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  • 20
    Electronic Resource
    Electronic Resource
    Phage T4-like intermediates of DNA replication and recombination in the mitochondria of the higher plant Chenopodium album (L.) (2000)
    Springer
    Current genetics 37 (2000), S. 304-314 
    Details
    ISSN: 1432-0983
    Keywords: Key words Invasion ; Mitochondrial genome ; Plasmid ; Recombination ; Recombination-dependent replication ; Rolling-circle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have studied intermediates of the recombination and replication of chromosomal mitochondrial (mt) DNA prepared from suspension cultured cells of Chenopodium album (L.) by electron microscopy during the whole growth cycle. We identified several types of potential recombination and replication intermediates including rosette-like structures, as well as other branched and sigma-like molecules. The absolute and relative amounts of these structures changed dramatically during the growth cycle, indicating high dynamics in the structural organization of the mt genome. The rosette-like molecules had sizes of 2–5 genome units and were found to contain putative replication forks and `Holliday'-junctions known from recombination intermediates. The high number of rosettes during the first days of culture, and their drastic reduction in the stationary growth stage, were found to be inversely related to changes in the quantity of linear molecules of 40–200 kb. This observation suggests that linear molecules participate in the formation of giant branched rosette-like structures. Most linear molecules were previously found to have at least one single-stranded end, which may allow recombinative invasion of other double-stranded molecules. Thus, recombination events may lead to the formation of more complex molecules and initiate replication similar to phage T4. We propose the coexistence of a recombination-dependent mode of replication with a presumably recombination-independent rolling-circle mode of replication in the mitochondria of C. album.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002940050532
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