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  • 1
    Keywords: Forschungsbericht ; Ostseeküste ; Mecklenburg-Vorpommern ; Makrophyten
    Type of Medium: Book
    Pages: 84, 198 S , Ill., überw. graph. Darst
    Series Statement: UBA-FB 97-032
    Language: German
    Note: Förderkennzeichen UFOPLAN 102 04 259. - 1. Serie aufgestempelt, Zählung handschriftl
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 30 (1998), S. 0 
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The ability of all 11 variable opacity (Opa) proteins encoded by Neisseria gonorrhoeae MS11 to interact directly with the five CD66 antigens was determined. Transfected HeLa cell lines expressing individual CD66 antigens were infected with recombinant N. gonorrhoeae and Escherichia coli strains expressing defined Opas. Based upon the ability of these bacteria to bind and invade and to isolate specifically CD66 antigens from detergent-soluble extracts of the corresponding cell lines, distinct specificity groups of Opa interaction with CD66 were seen. Defining these specificity groups allowed us to assign a specific function for CD66a in the Opa-mediated interaction of gonococci with two different target cell types, which are both known to co-express multiple CD66 antigens. The competence of individual Opas to interact with CD66a was strictly correlated with their ability to induce an oxidative response by polymorphonuclear neutrophils. The same Opa specificity was observed for the level of gonococcal binding to primary endothelial cells after stimulation with TNFα, which was shown to increase the expression of CD66a rather than CD66e. As CD66e alone is expressed on other target tissues of gonococcal pathogenicity, Opa variation probably contributes to the cell tropism displayed by gonococci.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Type 4 pili produced by the pathogenic Neisseria species constitute primary determinants for the adherence to host tissues. In addition to the major pilin subunit (PilE), neisserial pili contain the variable PilC proteins represented by two variant gene copies in most pathogenic Neisseria isolates. Based upon structural differences in the conserved regions of PilE, two pilus classes can be distinguished in Neisseria meningitidis. For class I pili found in both Neisseria gonorrhoeae and N. meningitidis, PilC proteins have been implicated in pilus assembly, natural transformation competence and adherence to epithelial cells. In this study, we used primers specific for the pilC2 gene of N. gonorrhoeae strain MS11 to amplify, by the polymerase chain reaction, and clone a homologous pilC gene from N. meningitidis strain A1493 which produces class II pili. This gene was sequenced and the deduced amino acid sequence showed 75.4% and 73.8% identity with the gonococcal PilC1 and PilC2, respectively. These values match the identity value of 74.1% calculated for the two N. gonorrhoeae MS11 PilC proteins, indicating a horizontal relationship between the N. gonorrhoeae and N. meningitidispilC genes. We provide evidence that PilC functions in meningococcal class II pilus assembly and adherence. Furthermore, expression of the cloned N. meningitidis pilC gene in a gonococcal pilC1,2 mutant restores pilus assembly, adherence to ME-180 epithelial cells, and transformation competence to the wild-type level. Thus, PilC proteins exhibit indistinguishable functions in the context of class I and class II pili.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: We have analysed the capacity of the 11 phase-variable, opacity-associated (Opa) proteins encoded by Neisseria gonorrhoeae MS11 to mediate traversal across polarized monolayers of the human colonic carcinoma T84 cell line. Gonococci expressing either the heparan sulphate proteoglycan (HSPG) binding Opa protein (Opa50) or no Opa protein (Opa−) did not interact with the apical pole of T84 monolayers, whereas the 10 variant Opa proteins previously shown to bind CD66 receptors were found to mediate efficient gonococcal adherence and transepithelial traversal. Consistent with this, T84 cells were shown by reverse transcriptase–polymerase chain reaction (RT–PCR) and immunoblotting to co-express CD66a (BGP), CD66c (NCA) and CD66e (CEA). The recruitment of CD66 receptors by Opa-expressing gonococci indicates their involvement in mediating adherence to the surface of T84 cells, and these bacterial interactions could be inhibited completely using polyclonal antibodies cross-reacting with all of the CD66 proteins co-expressed on T84 cells. Consistent results were obtained when Opa proteins were expressed in Escherichia coli, suggesting that the Opa–CD66 interaction is sufficient to mediate bacterial traversal. Transcytosis of Opa-expressing N. gonorrhoeae or E. coli did not disrupt the barrier function of infected monolayers, as indicated by a sustained transepithelial electrical resistance (TEER) throughout the course of infection, and confocal laser scanning and electron microscopy both suggest a transcellular rather than a paracellular route of traversal across the monolayers. Parallels between the results seen here and previous work done with organ cultures confirm that T84 monolayers provide a valid model for studying neisserial interactions with the mucosal surface, and suggest that CD66 receptors contribute to this process in vivo.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford BSL : Blackwell Publishing Ltd
    Molecular microbiology 24 (1997), S. 0 
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-0603
    Keywords: Antrum ; Human gastrointestinal epithelium ; Polarized epithelial cells ; Spheroid-like vesicles ; Tissue culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A novel procedure is described for the three-dimensional (3-D) in vitro culture and for maintaining of nontransformed gastric epithelial cells from the human antrum mucosa (HAEC). Biopsies obtained from the antrum were cut into small pieces and the tissue fragments were incubated in culture medium containing the appropriate antibiotics. The suspended mucosal fragments generated small, spheroid-like vesicles consisting of predominantly highly prismatic, mucus-producing cells which mimic the in vivo counterparts structurally and functionally. Electron microscopic investigations revealed a number of ultrastructural and morphological features similar to those of normal gastric cells in vivo such as apical microvilli associated with a glycocalyx, tight junctions, desmosomes, membraneous infoldings, mucous droplets, and an irregular basal lamina. In comparison to the two-dimensional (2-D) gastric cell cultures grown on plane supports, the vesicles maintain an intact epithelial organization of individual cells. The prismatic phenotype, the histophysiology as well as the cytoarchitecture of the non-transformed 3-D cultured gastric epithelial cells are comparable to those of the native tissue and therefore represent a suitable model for defined pathogen-host cell interactions.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of thrombosis and thrombolysis 6 (1998), S. 117-124 
    ISSN: 1573-742X
    Keywords: moesin ; ezrin ; tyrosine phosphorylation ; arachidonic acid ; platelets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Moesin, a member of the ezrin/radixin/moesin (ERM) family of cytoskeletal proteins, has been implicated in dynamic membrane-based processes such as the formation and stabilization of filopodia. Ezrin is known to be a substrate of tyrosine kinases in activated T cells and epithelial growth factor–stimulated A431 cells. For the closely related 77-kD protein moesin, which shares 72% identity with ezrin on the basis of their amino acid sequences, a reversible phosphorylation on tyrosine residues has not yet been described. Because our scanning electron microscopy studies revealed the appearance of multiple, up to 3 μm long filopodia on the surface of activated human platelets, we investigated the participation of moesin in dynamic shape changes on platelet stimulation with arachidonic acid. Antimoesin immunoprecipitates obtained under denaturing conditions from lysates of resting platelets contained only low amounts of tyrosine-phosphorylated moesin. In lysates of arachidonic acid–stimulated platelets, the level of tyrosine phosphorylation was significantly increased. This activation-dependent phosphorylation of moesin was verified by probing antiphosphotyrosine immunoprecipitates from unstimulated and stimulated platelets with antimoesin antibodies. Tyrosine-phosphorylated moesin was detectable only in the presence of the tyrosine phosphatase inhibitor vanadate, suggesting that a coordinated balance between kinase and phosphatase activities controls the steady-state level of moesin phosphorylation.
    Type of Medium: Electronic Resource
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