Laboratory investigation; a journal of technical methods and pathology
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Comparative Study
Expression of WT1 protein in fetal kidneys and Wilms tumors.
Wilms' tumors are embryonic kidney neoplasms believed to result from a perturbation in the development of the metanephric blastema. A candidate gene (WT1) has been cloned that has been found to be mutated in a number of Wilms' tumors, consistent with its suggested role as a tumor suppressor gene. This gene has been shown to be essential to the normal development of the embryonic kidney. ⋯ The results show that in fetal kidney, WT1 transcripts and protein are coordinately expressed, and strongly associated with differentiation of metanephric blastemal cells into epithelial cells. Furthermore, the finding that WT1 transcripts and protein are coordinately expressed, suggests that WT1 gene expression is primarily regulated at the level of transcription.
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Vascular endothelial growth factor (VEGF) is a specific endothelial cell mitogen with potent angiogenic properties. In tumors, VEGF has been localized to the most necrotic and ischemic areas of the tissues, suggesting that local hypoxia is a potent inducer of VEGF production. Initial experiments in vitro confirmed the stimulatory effect of hypoxia on VEGF expression. The extent of this response and the mechanisms involved in oxygen sensing are poorly characterized. ⋯ Hypoxia is a potent inducer of VEGF expression in malignant as well as normal cultured cells. It is also a stimulator of VEGF expression in vivo. The VEGF gene appears to respond to hypoxia like the erythropoietin gene, and the mechanism of oxygen sensing probably is mediated by a heme-containing protein.
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High concentrations of active transforming growth factor-beta (TGF-beta) have been found in synovial fluids from arthritic joints. TGF-beta stimulates articular cartilage proteoglycan synthesis and suppresses proteoglycan degradation in vitro. In an earlier study, we found no effect on cartilage proteoglycan metabolism shortly after a single intra-articular injection of TGF-beta 1. In the present study, we used multiple intra-articular injections and a longer time-scale. ⋯ Our data indicate that TGF-beta 1 injection into a normal joint induces inflammation, synovial hyperplasia, osteophyte formation, and prolonged elevation of proteoglycan synthesis and content in articular cartilage.
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Monocyte adhesion to the vascular endothelium, an important component of an inflammatory response, is one of the earliest detected events in the pathogenesis of atherosclerosis. We have identified a monocyte adhesion molecule, recognized by monoclonal antibody (mAb) IG9, on the cell surface of human umbilical vein endothelial cells (HUVEC) treated with tumor necrosis factor-alpha (TNF-alpha), interleukin-1, or lipopolysaccharide. Endothelial cell expression in vitro and in vivo of the protein recognized by mAb IG9 (IG9 protein) was further characterized. ⋯ The IG9 protein, undetected on untreated HUVEC, was expressed on their cell surface within 3 hours of treatment with TNF-alpha, peaked at 4 to 9 hours, and persisted for up to 48 hours as determined by enzyme-linked immunosorbent assay. A similar kinetic profile was elicited by interleukin-1 and lipopolysaccharide, whereas interferon-gamma (IFN-gamma) had minimal effect on IG9 expression. The IG9 protein has a molecular weight of 105,000 as determined by immunoprecipitation studies with TNF-alpha-treated HUVEC protein lysates. mAb IG9 significantly inhibited the binding of U937 cells and human peripheral blood monocytes to TNF-alpha-treated HUVEC and had no effect on peripheral blood lymphocyte or granulocyte adhesion. Treatment of human aortic endothelial cells or HUVEC with MM-LDL for 24 hours induced IG9 protein expression 3-fold above background with no concomitant increase in binding of antibodies to intercellular adhesion molecule-1 (ICAM-1), E-selectin, or vascular cell adhesion molecule-1 (VCAM-1), endothelial cell adhesion proteins involved in monocyte binding. mAb IG9 F(ab')2 inhibited MM-LDL-induced monocyte adhesion to HAEC by 23%. Immunohistochemical analysis demonstrated that the endothelial cell lining of vessels in human lung and heart with evidence of inflammation characterized by an extensive mononuclear cell infiltration exhibited reactivity with mAb IG9, whereas vessels with no evidence of inflammation in the same sections as well as in sections from normal lung and heart were nonreactive.(ABSTRACT TRUNCATED AT 250 WORDS)
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Comparative Study
Mitochondrial schwannopathy and peripheral myelinopathy in a rabbit model of dideoxycytidine neurotoxicity.
The reverse transcriptase inhibitor, 2',3'-dideoxycytidine (ddC), causes a dose-limiting peripheral neuropathy in humans, the mechanism of which is unknown. Rabbits given ddC develop peripheral myelinopathy and axonopathy, but it has not been determined if either the myelin or axonal changes are primary or if they occur concurrently. ⋯ The peripheral neuropathy caused by ddC in rabbits is characterized as a myelinopathy of the proximal portion of the nerve fibers and as an axonopathy involving both proximal and distal fibers. The myelinopathy was associated with enlarged and abnormally shaped mitochondria in Schwann cells and is consistent with an effect of ddC on structure and function of Schwann cell mitochondria. Altered Schwann cell metabolism was evident by reduced levels of P0 messenger RNA, loss of homophilic myelin adhesion at the intraperiod line, and subsequent intramyelinic edema. Because axonal degeneration occurred concurrently with the myelin changes, it could not be determined if axonal changes were secondary to serve myelinic edema or if they represented a primary effect of ddC on neurons.