The expression of the collagen a,(I) gene in activated stellate cells plays an important role during liver fibrogenesis.To identify the critical cis-elements of the collagen al (I) gene in stellate cells, we used transgenic animals bearing various collagen al(I) regulatory regions directing the expression of either a human growth hormone minigene or the bacterial 8-galactosidase gene. We found that collagen aC (1)-human growth hormone transgene expression was constitutively high in tendon and skin, provided the transgene contained the -2.3 to -0.44 kb collagen regulatory region. However in the liver, expression was stimulated several-fold, as was the endogeneous gene, by the fibrogenic hepatotoxin carbon tetrachloride. This stimulation occurred whether the collagen 5' regulatory region extended -2.3, -1.6 or -0.44 kb, and in the presence or absence of much of the first intron (+292 to +1607 bp). In addition, the -0.44 kb 5' region was sufficient for high-level transgene expression in stellate cells, following their activation by culture on plastic. In contrast, in skin and tendon, high-level transcription of the collagen al(I) gene required the -2.3 to -0.44 kb 5' flanking region. Thus, two different cis-regulatory regions direct cell-specific transcription of the collagen a1 (I) gene in stellate cells and in skin and tendon. (J. Clin. Invest. 1995. 96:2269-2276
D-Galactosamine is an hepatocyte-specific inhibitor of RNA synthesis. It has been used to sensitize animals both to the lethal effects of bacterial endotoxin (lipopolysaccharide) and to a principal lipopolysaccharide-induced mediator of shock, tumor necrosis factor-alpha. The mechanism by which this sensitization occurs is unknown. Because lipopolysaccharide, acting through a network of cytokines, provokes the transcription of a number of hepatic acute-phase proteins, we postulated that the lipopolysaccharide-sensitizing effect of D-galactosamine could be caused by its inhibition of acute-phase product transcription. We confirmed that the acute-phase response to lipopolysaccharide was attenuated by simultaneous administration of D-galactosamine. However, when the acute-phase response was induced by subcutaneous turpentine 24 hr before D-galactosamine administration, the effect of D-galactosamine on circulating acute-phase reactants was negligible. Furthermore, induction of an a priori acute-phase response protected mice from both D-galactosamine/lipopolysaccharide and D-galactosamine/tumor necrosis factor-alpha-induced death. The turpentine-induced acute-phase response did not decrease endogenous tumor necrosis factor-alpha production after lipopolysaccharide, nor did it affect the clearance of larger doses of injected tumor necrosis factor-alpha. Thus we suggest that the acute-phase response protects against death in D-galactosamine-sensitized mice through an interaction with mediators of shock subsequent to tumor necrosis factor-alpha release.
Cirrhosis is characterized by a marked increase in the deposition of type I collagen and in the expression of the type I collagen genes alpha 1(I) and alpha 2(I). Although alpha 1(I) gene regulation has been extensively studied in cultured cells, these results may not be applicable to hepatic fibrogenesis in vivo. Therefore the regulation of the alpha 1(I) endogenous gene and an alpha 1(I) transgene was studied in a transgenic mouse model that has a single copy of a human alpha 1(I) gene segment containing the structural gene and 1.6 Kb of 5' DNA and 20 Kb of 3' DNA. To initiate hepatic fibrogenesis, we treated mice with the hepatotoxin carbon tetrachloride, either in a single dose or in biweekly doses for a period of 3 to 8 wk. Subsequently, hepatic alpha 1(I) messenger RNA levels were determined by a species-specific RNase protection assay. Carbon tetrachloride injections coordinately increased the messenger RNA levels of the alpha 1(I) endogenous gene and the transgene, both immediately and after 8 wk. These experiments demonstrate that this alpha 1(I) transgene fragment contains information sufficient for appropriate basal and carbon tetrachloride-stimulated hepatic expression. They further demonstrate that sufficient homology exists between the human and mouse regulatory elements for the recognition of human cis-acting elements by mouse trans-acting factors. Thus transgenic mice provide a unique model in which to characterize the collagen alpha 1(I) regulatory elements that are required in vivo for pathophysiological responses.
There is neither consensus on the number nor agreement on the location of the anatomic compartments of the foot. This project utilized high-resolution magnetic resonance imaging (MRI) to identify foot compartments. The purpose of this study was to devise a new system using 3-Tesla (3T) MRI that assessed the number and location of these compartments. Six feet from healthy volunteers were imaged. From these, 10 compartments were described: (1) medial, (2) calcaneal, (3) lateral, (4) central superficial, (5) central deep (adductor), (6-9) interossei, and (10) skin. The 3T MRI and foot/ankle coil allowed us to assess the number and location of foot compartments.
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