Human hepatitis B virus (HBV) and hepatitis C virus (HCV) are two major etiologic agents of chronic hepatitis, which is closely related to the development of hepatocellular carcinoma (HCC). A possible involvement of HBV co-infection was investigated in ongoing HCV-related liver diseases in HCV-infected patients. A prevalence of anti-HBc in anti-HCV-positive/HBsAg-negative chronic hepatitis patients and a low copy number of HBV DNA were found in most of the liver biopsy samples of anti-HCV-positive/HBsAg-negative patients. The present data suggest that HBV co-infects frequently with HCV and may play an important role in the development of HCC in the anti-HCV-positive/HBsAg-negative patients with chronic hepatitis.

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␤1-null GD25 fibroblasts adherent to vitronectin fail to bind the N-terminal 70-kDa matrix assembly domain of fibronectin or to assemble fibronectin (Sakai, T., Zhang, Q., Fä ssler, R., and Mosher, D. F. (1998) J. Cell Biol. 141, 527-538). We have made four observations that extend this finding. First, the presence of vitronectin on a substrate that otherwise can support fibronectin assembly has a dominant-negative effect on assembly. Second, the dominant-negative effect is lost when active ␤1A is expressed. Third, ␤1A containing the extracellular D130A inactivating mutation has a dominant-negative effect on fibronectin assembly. Fourth, ␤1-null cells adherent to vitronectin are flat and lack filopodia, whereas ␤1-null cells adherent to fibronectin or ␤1A-expressing cells adherent to either vitronectin or fibronectin are contracted and exhibit numerous filopodia. These results reveal, therefore, that GD25 cells adherent to vitronectin can only assume a shape suitable for assembly of fibronectin when there is a countervailing signal from functional ␤1-integrins.Fibronectin is an extracellular matrix component that is also present as a soluble protein in plasma and other body fluids. The matrix form of fibronectin is believed to support cell adhesion and migration during embryogenesis, tumor growth, wound healing, angiogenesis, and inflammation (1-3). Assembly of soluble fibronectin into matrix is a multistep process under cellular control (4). Among the membrane components implicated in fibronectin matrix assembly, integrins have been firmly demonstrated to have a central role (5-10).Integrins are a group of cell surface heterdimers of ␣-and ␤-glycoprotein subunits that mediate cell adhesion to extracellular matrix proteins such as fibronectin, laminin, vitronectin, and collagen or to countereceptors on other cells (11,12). The interactions between integrins and their ligands influence a number of cellular processes, including proliferation (13), differentiation (14), survival (15, 16), and migration (17, 18). The extracellular domains of the two subunits are noncovalently associated, forming a ligand-binding pocket, and the cytoplasmic domains interact with cytoskeletal proteins and other cytoplasmic components (12). In addition to mediating adherence, ligation of integrins activates signal transduction pathways (19,20).The mechanisms by which integrins modulate fibronectin assembly are not well understood. Transfection of ␣5-integrin and expression of ␣5␤1-integrin by CHO 1 cells results in a large increase in fibronectin assembly (5, 21). A chimera comprising the interleukin 2 receptor and the cytoplasmic tail of ␤1, working presumably in a dominant-negative manner, inhibits assembly (22). Monoclonal antibodies to ␣5 or ␤1 inhibit binding and assembly of fibronectin by fibroblasts and also binding of the N-terminal fibronectin fragment to cell surfaces (23, 24). The 70-kDa N-terminal fragment of fibronectin that mediates binding to assembly sites colocalizes with ␤1-integrin in focal contacts of cycloheximide-...

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Rat pleurisy induced by carrageenin or phorbol myristate acetate (PMA) was utilized for examination of the plasma exudation process of inflammation. Chemical mediators responsible for induction of vascular permeability increase were examined. In carrageenin-induced pleurisy, kinin and PGI₂ were demonstrated as the main mediators, and in PMA pleurisy histamine, PGI₂ and platelet-activating factor were the main mediators. These results indicate that different stimuli may activate different enzymatic processes to produce different mediators, but they may result in similar inflammatory reactions by action of these multiple mediators simultaneously released.