| 1. |
- Boughan, PK, et al.
(författare)
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Nucleotide-binding oligomerization domain-1 and epidermal growth factor receptor - Critical regulators of beta-defensins during helicobacter pylori infection
- 2006
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Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 281:17, s. 11637-11648
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Tidskriftsartikel (refereegranskat)abstract
- Host-pathogen interactions that allow Helicobacter pylori to survive and persist in the stomach of susceptible individuals remain unclear. Human beta-defensins ( hBDs), epithelial-derived antimicrobial peptides are critical components of host-defense at mucosal surfaces. The role of H. pylori-mediated NF-kappa B and epidermal growth factor receptor ( EGFR) activation on beta-defensin expression was investigated. Transient transfection studies utilizing beta-defensin promoter constructs were conducted in gastric cells with contribution of individual signaling events evaluated by the addition of specific inhibitors, small interference nucleotide-binding oligomerization domain 1( NOD1) RNA or plasmids encoding Vaccinia virus proteins that interrupt interleukin-1 and Toll-like receptor signaling. The role of individual MAPK pathways was further delineated in HEK-293 cells expressing conditional MAPK mutants. We found hBD2 expression exclusively dependent on the presence of the bacterial cag pathogenicity island, with NOD1 a critical host sensor. Impairment of murine beta-defensin 4( an orthologue of hBD2) expression in NOD1-deficient mice 7-days post-infection further confirmed the role of this cytoplasmic pattern-recognition receptor in eliciting host innate immunity. In contrast to hBD2, hBD3 expression was NOD1-independent but EGFR and ERK pathway-dependent. Importantly, Toll-like receptor signaling was not implicated in H. pylori-mediated hBD2 and hBD3 gene expression. The divergent signaling events governing hBD2 and hBD3 expression suggest temporal functional variation, such that hBD2 may contribute to antimicrobial barrier function during the inflammatory phase with hBD3 playing a greater role during the repair, wound healing phase of infection.
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| 2. |
- Cedergren, Joakim, et al.
(författare)
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Three-dimensional analysis of compaction of metal powder
- 2002
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Ingår i: Mechanics of Materials. - 0167-6636. ; 34:1, s. 43-59
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Tidskriftsartikel (refereegranskat)abstract
- Three-dimensional compaction simulations of geometries with circular and quadratic cross-sections are reported using dilatant viscoplastic material models representing a ductile steel powder. The simulations are compared with experiments using in situ measurements of the wall-tractions within the die. Two different porous viscoplastic material models have been used: the combined Fleck-Kuhn-MeMeeking (FKM) and Gurson model and the Shima-Oyane model. The contact between the die and the powder was modelled with Coulomb-type friction. Effects such as the applied traction-density response and average relations for the upper, lower and the normal tractions against the die wall are compared. Comparisons between the numerical results and experimental results show that both material models can well be used to capture the overall density distributions for the geometries studied and that many of the coarse three-dimensional features of the powder-pressing process are well described by the simulations. (C) 2002 Elsevier Science Ltd. All rights reserved.
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