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  • 1995-1999  (3)
  • 1
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Aspergillus fumigatus is an important pathogen causing invasive pulmonary aspergillosis in immunocompromised patients. The fungus propagates by conidia, which are the infectious structures inhaled by the human host. Opsonophagocytosis is thought to contribute to clearance of the inhaled conidia, a process that is facilitated by complement deposition on conidial surfaces. We now show that conidial colour mutants exhibit significant increases in C3 binding capacity compared with wild type. A reddish-pink mutation that led to enhanced C3 binding was complemented by a cosmid clone. A 3.3 kb DNA fragment from the subsequently rescued cosmid was sufficient to restore the bluish-green conidial pigment. The bluish-green transformant exhibited a level of C3 binding similar to that of the parental strain. A gene, designated arp1, was responsible for the complementation. Comparison of the genomic and cDNA sequences of arp1 revealed that it has two introns and encodes a putative protein of 168 amino acids. Arp1 is very similar to scytalone dehydratase, an enzyme involved in 1,8-dihydroxynaphthalene-melanin synthesis in Colletotrichum lagenarium and Magnaporthe grisea. Northern hybridization analysis revealed that arp1 is developmentally regulated, being expressed during conidiation. Disruption of arp1 resulted in reddish-pink conidia and increased C3 binding. Our studies suggest that arp1 modulates the bluish-green pigmentation of conidia as well as complement deposition.
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  • 2
    ISSN: 1523-5378
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background.Human serum represents an important barrier to the entry of most mucosal organisms into tissues and to the systemic circulation. If at all present, Helicobacter pylori within gastric tissue is rare, and bacteremia for this organism has been described only once. Methods. To assess the susceptibility of H. pylori to the bactericidal activity present in normal human serum (NHS), we examined 13 H. pylori isolates. To assess the contributions of the classical and alternative complement pathways to killing, we added either C2-deficient or factor B-deficient serum, respectively, to heat-inactivated NHS. Also we assessed the ability of the strains to bind 125I-C3. Results.After incubation for 60 minutes at 37°C, all 13 H. pylori strains were killed by NHS; heating to 56°C for 30 minutes ablated killing, indicating complement dependence for this phenomenon. In the absence of an antibody source, there was no killing when either an alternative or classical complement pathway source was used. Adding B-deficient serum to heat-inactivated normal human serum did not restore killing, but adding C2-deficient serum permitted partial killing. All of the 13 strains bound 125I-C3. Although the kinetics varied from strain to strain, C3 bound was significantly correlated (r= 0.61, p= 0.03) with serum susceptibility. Conclusions. H. pylori are susceptible to complement, alternative pathway activation appears critical, and C3 binding is a major locus of variability.
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  • 3
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: We previously have shown that vascular catheters made of silicone elastomer carry a greater risk of subcutaneous infection with Staphylococcus aureus than do polyurethane (PU), polyvinylchloride (PVC), or Teflon® catheters. We further have shown that there is greater inflammation surrounding silicone catheters than there is surrounding catheters made of the other materials, suggesting that silicone produces a greater chemotactic gradient than do the other materials. This study used a functional complement opsonization assay and radioimmunoassays to compare the relative abilities of silicone, polyurethane, and polyvinylchloride to activate complement. Serum incubated in silicone catheters for 24 h had less than 30% of the opsonizing ability of fresh serum while ≥78% of the opsonizing ability remained with serum incubated in PU or PVC catheters. Measurement of C3a des Arg, C4a des Arg, C5a des Arg, and SC5b-9 demonstrated that the loss of opsonizing ability was due to 10-fold greater alternate pathway complement activation by silicone than by PU or PVC. This finding suggests that excessive complement activation by silicone may explain the greater inflammation seen around silicone catheters in vivo and also might play a role in silicone's creating a greater risk of infection. © 1996 John Wiley & Sons, Inc.
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