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T Knittel

Publications and source records attributed to T Knittel.

47 records · Page 3Linked to original sources
PubMed1992

Distribution and cellular origin of undulin in rat liver.

BACKGROUND: Undulin is a novel large glycoprotein of the interstitial extracellular matrix belonging to the fibronectin-tenascin glycoprotein gene family. The distribution in diseased liver and the cellular origin of this protein are unknown. EXPERIMENTAL DESIGN: Immunohistochemistry studies were performed on cryostat sections of normal and damaged rat livers (CCl4 model). Hepatocytes, Kupffer cells, fat-storing cells (FSC), and sinusoidal endothelial cells (EC) were isolated by standard methods and kept in culture. Undulin biosynthesis in vitro was studied by indirect immunofluorescence and by immunoprecipitation of endogenously labeled protein followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography. RESULTS: Undulin was demonstrated in portal stroma, in vascular adventitia, and inside the space of Disse of normal liver. Acutely and chronically damaged livers revealed strong staining reactions in damaged areas, scars, and sinusoids. The overall distribution of undulin resembled the pattern noted for fibronectin. In contrast to undulin, tenascin was not detectable within the adventitia of vascular and ductular structures of normal and damaged livers, and tenascin accumulated preferentially at scar-parenchyma interfaces in fibrotic livers. In vivo, desmin and smooth muscle alpha-actin positive cells were in part codistributed with undulin fibers as shown by double staining techniques. In vitro, undulin was detected in granules of freshly isolated FSCs and ECs and was localized as fibers in the extracellular matrix of cultivated FSCs and ECs. Synthesis of undulin was demonstrated by immunoprecipitation of the protein from cultured FSCs and ECs. No experimental evidence was found for undulin synthesis in vitro by hepatocytes and Kupffer cells. CONCLUSIONS: The novel glycoprotein undulin is present in the normal rat liver and accumulates during acute and chronic liver injury. Our results suggest that among the resident cells of the liver, FSCs and ECs are the major sources of undulin.

Actins↗
PubMed1991

Dexamethasone modulates alpha 2-macroglobulin and apolipoprotein E gene expression in cultured rat liver fat-storing (Ito) cells.

Fat-storing (Ito) cells are perisinusoidal liver cells thought to play a central role in vitamin A metabolism and fibrongenesis. Glucocorticoids have been shown to be beneficial in the treatment of certain types of liver diseases by delaying the development of cirrhosis. To study the regulatory effects of dexamethasone on Ito cell gene expression, Ito cells were isolated from normal rat liver and primary cultures were established. The effect of dexamethasone on the synthesis of alpha 2-macroglobulin, apolipoprotein E, fibronectin and actin was examined. Protein synthesis was studied both at the protein level and at the RNA level by means of biosynthetic labeling, immunoprecipitation followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and by Northern blot analysis of total RNA. After exposure to dexamethasone for 20 hr, alpha 2-macroglobulin protein synthesis was increased threefold, whereas apolipoprotein E expression was decreased 80%. Biosynthesis of fibronectin remained unaffected by hormone treatment. The dexamethasone effect became detectable 5 hr after beginning the exposure. Deinduction kinetic experiments showed that the glucocorticoid effect was detectable more than 12 hr after the replacement of the dexamethasone-containing culture medium by medium without the hormone. Corresponding to the data obtained at the protein level, dexamethasone increased the steady-state levels of alpha 2-macroglobulin-specific messenger RNA and reduced apolipoprotein E-specific transcripts, whereas fibronectin and actin messenger mRNA remained unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

Actins↗
PubMed1990

Expression of the gene of the alpha-smooth muscle-actin isoform in rat liver and in rat fat-storing (ITO) cells.

Fat storing cells (FSCs) in the liver represent the main site of vitamin A deposition in the body. These cells are considered to play an important role during scar formation and fibrogenesis in the liver. The putative descent of FSCs from the fibroblastic or from the myofibroblastic system have not been determined yet by morphological or immunohistochemical studies. To further define the origin of these liver cells, we analysed the pattern of expression of three structural proteins: vimentin, desmin and the alpha-smooth muscle (SM)-actin isoform in FSCs of the rat liver, in smooth muscle cells (SMCs) from the aorta and in rat skin fibroblasts. FSCs were studied by immunohistochemical methods immediately after isolation, at days 3 and 7 after plating. FSC-gene-expression was also analysed by Northern blot analysis of total RNA extracted from cells in culture at days 3 and 7 after isolation. Arterial SMCs and skin fibroblasts were studied in a similar way. For comparison, isolated rat hepatocytes and Küpffer cells (Kc) were studied. Of freshly isolated FSCs, 100% were vimentin-positive, 50% were desmin-positive, but all were alpha-SM-actin negative. Three days after isolation, FSCs were clearly positive for vimentin and desmin and weakly alpha-SM-actin-positive, as demonstrated by indirect immunofluorescence as well as by the immunoperoxidase technique. Desmin, alpha-SM-actin and vimentin staining was further increased at day 7 after isolation, and alpha-actin specific transcripts in FSC-RNA were clearly detectable at day 7 after isolation. Passaged arterial SMCs were vimentin- and alpha-SM-actin-positive, but desmin-negative and fibroblasts were only vimentin-positive.(ABSTRACT TRUNCATED AT 250 WORDS)

Actins↗
PubMed1988

Response of melanoma to heat and radiation therapy--a review of the literature and experience from The Prince of Wales Hospital, Sydney.

Our review of the literature indicates that radiotherapy and/or heat therapy can provide local control of recurrent or metastatic melanoma in a large proportion of patients. This has undoubted value in the local palliation of symptoms and, in the absence of disseminated disease, can be curative. At The Prince of Wales Hospital, Sydney, we have studied the response of melanoma lesions to heat and radiation therapy and have assessed the reaction in the adjacent normal skin. Thirty-two melanoma lesions that were measurable in 12 patients received radiotherapy and heat therapy in different combinations and dose schedules (15 lesions received radiotherapy alone, six lesions received heat therapy alone, and 11 lesions received combined radiation and heat therapy). The acute normal skin reaction was compared between lesions that received single modality radiation or heat therapy and those that received the combination of heat and radiation therapy. A moderate or severe reaction developed at six of the 21 sites that were treated by a single modality, and at four of the 11 sites that received combined heat and radiation therapy (P = 0.7), and all healed within a few days. Evaluation of the melanoma response to therapy was possible only in 26 of the 32 lesions that were treated because two patients died soon after therapy and the response of their six lesions was not evaluable. A complete response occurred in 14 (54%) of 26 lesions and a partial response occurred in 10 (38%) of 26 lesions. The objective response by treatment modality was 10 of 15 lesions for radiotherapy, six of six lesions for heat therapy and eight of 11 lesions for both therapies combined. We conclude that radiotherapy and heat therapy, separately or combined, produce acceptably-low damage to normal tissue and highly-satisfactory local control of melanoma.

Dose-Response Relationship, Radiation↗
PubMed1987

Cultured Ito cells of rat liver express the alpha 2-macroglobulin gene.

Ito cells were isolated from rat liver and kept in culture for up to 13 days. The capability of the Ito cells to synthesize alpha 2-macroglobulin was analyzed at different times after isolation and by pulse-chase experiments. Newly synthesized alpha 2-macroglobulin was determined by immunoprecipitation followed by sodium dodecyl sulfate/polyacrylamide gel electrophoresis and fluorography. alpha 2-Macroglobulin synthesis was hardly detectable in Ito cells and their media 3 days after plating. However, 5-11 days after the isolation of the cells, increasing amounts of alpha 2-macroglobulin were synthesized. The results of pulse-chase experiments performed on day 7 showed that radioactively labeled alpha 2-macroglobulin decreased in the intracellular compartment and increased in the culture medium. alpha 2-Macroglobulin was identified by immunoprecipitation and sodium dodecyl sulfate/polyacrylamide gel electrophoresis under reducing and non-reducing conditions. Furthermore, when unlabeled alpha 2-macroglobulin was added during the immunoprecipitation, a competition was observed. Incubation of pancreatic elastase with culture medium of rat Ito cells or rat hepatocytes led to the same cleavage products as found with alpha 2-macroglobulin. alpha 2-Macroglobulin-specific mRNA could be demonstrated by Northern blot analysis of total RNA extracted from rat Ito cells. Under the conditions where alpha 2-macroglobulin was synthesized in Ito cells, no synthesis of alpha 1-macroglobulin, alpha 1-inhibitor 3, alpha 1-proteinase inhibitor, alpha 1-acid glycoprotein, alpha 1-acute-phase globulin (T-kininogen) and albumin could be demonstrated. It is concluded that alpha 2-macroglobulin is a true secretory protein of rat Ito cells in culture. This could be of importance for collagen metabolism in liver diseases.

Animals↗
PubMed1987

Fat storing cells (FSC) of rat liver synthesize and secrete fibronectin. Comparison with hepatocytes.

Fat storing cells (FSC) of rat liver were isolated and kept in culture for up to 2 weeks. Freshly isolated cells and cells in culture were characterized functionally (vitamin A content) and morphologically. Their synthetic capacity for fibronectin was studied quantitatively by ELISA-measurement and qualitatively by biosynthetic labeling, immunoprecipitation and SDS-PAGE analysis. The synthesis product and the kinetics of the synthesis and secretion were compared with those obtained from culture of hepatocytes. FSC were shown to synthesize and secrete fibronectin under the culture conditions used. No fibronectin synthesis was detected during the first 3 days of culture. Thereafter the synthesis increased continuously up to 2600 ng/24 h/100 micrograms cell protein. The molecular weight of fibronectin synthesized by fat storing cells seems to be the same as the one synthesized by hepatocytes, but the secretion proceeds faster in hepatocytes than in FSC. No differences between the two molecules were observed when both cell populations were treated with tunicamycin (TM), an antibiotic which inhibits the N-glycosylation of the primary translation product.

Animals↗