Search PubMed⌕ Search

Biomedical subjects

T Vartio

Publications and source records attributed to T Vartio.

At least 37 records · Page 2Linked to original sources
PubMed1988

Differential expression of the extra domain-containing form of cellular fibronectin in human placentas at different stages of maturation.

The distribution of the extra domain-containing form of cellular fibronectin was studied in human placentas at different stages of maturation by using the monoclonal antibody 52DH1 in indirect immunofluorescence. In early chorionic tissue (7 to 10 weeks post menstruationem) cellular fibronectin was codistributed with laminin and type IV collagen in the trophoblastic basement membranes. At weeks 11 to 12 the trophoblastic basement membranes were negative but positivity was typically revealed in distinct aggregates in the stromal tissue. In second-trimester and term placentas the immunoreactivity was confined to the vessel endothelia of villous stroma. Extravillous trophoblast cells seen in placentas at different stages did not show positivity. Double staining with the 52DH1 monoclonal antibody and polyclonal fibronectin antibodies showed that both in the early and term placentas there was much fibrillar positivity only revealed with the polyclonal antibodies. The present results show that cellular fibronectin is a prominent component of early trophoblastic basement membranes and may thus play a special role in the maturation of chorionic villi.

Antibodies, Monoclonal↗
PubMed1988

Platelet glycoprotein IIb/IIIa complex in cultured cells. Localization in focal adhesion sites in spreading HEL cells.

A panel of mouse monoclonal antibodies (MoAbs) was raised that react with platelet glycoproteins (GP) IIb or IIIa. On immunofluorescence, the MoAbs reacted with 30% to 40% of the human erythroleukemia (HEL) cells. When the HEL cells were induced to spread on fibronectin in the presence of 12-O-tetradecanoylphorbol-13-acetate (TPA), the MoAbs reacted with the focal adhesion sites. Only some of the GPIIIa MoAbs reacted with cells other than platelets, megakaryocytes, or HEL cells, and these showed focal adhesion sites in cultured human endothelial cells, fibroblasts, and epithelial cells from normal kidney tubules. They did not react, however, with transformed fibroblasts, fibrosarcoma cells, cultured cells from hypernephromas, or cultured human amnion epithelial cells. The results suggest that the platelet-type GPIIb/IIIa complex is only expressed in cells showing an ability to define megakaryoblastic differentiation. Localization of the GPIIb/IIIa complex at the induced focal adhesion sites in HEL cells and localization of the GPIIIa-like molecules in other cells suggest their direct role in the adhesion process and in the actomyocin organization of adherent cells.

Antibodies, Monoclonal↗
PubMed1987

Lack of fibronectin-binding plasma membrane proteins may explain defective pericellular matrix formation in transformed fibroblasts and fibrosarcoma cells.

Affinity of iodinated fibronectin (Fn) and its defined proteolytic fragments to electrophoretically separated polypeptides of normal and malignant cells was studied in an overlay assay. Cellular 125I-Fn and a major 125I-Fn fragment (Mr 120,000-140,000), containing the cell-binding site, revealed in fibroblasts Mr 170,000, Mr 140,000, and Mr 47,000 Fn-binding polypeptides of which the first two could also be found in the plasma membrane preparations. Binding of 125I-Fns to Mr 170,000 and Mr 140,000 polypeptides was inhibited by the synthetic peptide Arg-Gly-Asp-Ser and to all 3 polypeptides by Fns and Mr 120,000-140,000 fibronectin fragment. Both fibrosarcoma cells and SV40-virus-transformed fibroblasts appeared to lack the Mr 140,000 Fn-binding polypeptide. Binding was similar when Fn from normal fibroblasts or fibrosarcoma cells was used in the assay, while plasma 125I-Fn had weaker affinity towards the Mr 140,000 polypeptide. Instead, proteolytic Fn-fragments, lacking the cell binding site, did not bind to any proteins in the assay. Radioactive cell-surface labelling showed differences in the corresponding surface polypeptide profiles of normal and malignant cells. The results suggest that the failure of pericellular matrix deposition in malignant cells could be due to either defective surface exposition or defective binding property of the Fn-receptor-like polypeptides.

Autoradiography↗
PubMed1987

Mitogen stimulation promotes human T lymphocyte adhesion to fibronectin.

Purified human peripheral blood T lymphocytes were shown to adhere to growth substrata coated with purified human plasma fibronectin (pFn) and its Mr 120,000-140,000 proteolytic fragments containing the cell-binding site. In contrast, significant binding to laminin- or type I collagen-coated surfaces could not be demonstrated. Binding of T cells to pFn could be inhibited by the synthetic peptide Arg-Gly-Asp-Ser. Activation of T lymphocytes with concanavalin A (Con A) and a phorbol ester, 12-O-tetradecanoyl-phorbol-13-acetate (TPA), led to a higher adherence to pFn than in unstimulated, resting T cells. Activation with only Con A in the presence of accessory cells also promoted binding. Increased adherence of T cells to pFn could be demonstrated as early as 2 h after the onset of stimulation and reached its maximum in 2-3 days. Furthermore, activated but not resting T cells actively spread on pFn-coated surfaces and displayed an altered F-actin organization. In an overlay assay of electrophoretically separated polypeptides of activated T lymphocytes, pFn bound to a high molecular weight polypeptide of Mr 190,000, suggesting that the cells bind to pFn via a receptor-like molecule. Thus, adhesion ot pFn may be a two-stage process. At the first stage cells bind to Fn. Activated T cells proceed to the second stage, where cells begin to spread on pFn. This may be due to an altered relationship between Fn receptors and microfilaments.

Antigen-Presenting Cells↗
PubMed1987

Differential expression of the ED sequence-containing form of cellular fibronectin in embryonic and adult human tissues.

Monoclonal mouse hybridoma antibodies were obtained for secreted cellular fibronectin (cFn) from A8387 fibrosarcoma cells. One of them, 52-DH1 (DH), reacted exclusively with cFns but not with plasma Fns (pFns) in immunoblotting and solid-phase EIA. The DH antibody also recognized thermolysin cFn fragments and beta-galactosidase-Fn fusion protein which contained the ED sequence specific to at least some forms of cFns. On the other hand, the DH antibody failed to recognize a fusion protein that was otherwise identical but lacked the ED sequence. Thus, the antigenic determinant for the DH antibody was located to the ED sequence. The DH antibody was then used to study the expression of ED sequence containing cFn (EcFn). For comparisons, another monoclonal antibody, 52BF12 (BF), recognizing equally well both pFns and cFns, was used. Immunoblotting of pFn fragments indicated that this antibody had the antigenic determinant at or close to the cell-binding site of Fn. EcFn was revealed by the DH antibody in embryonic and adult fibroblasts and in a variety of other cultured normal and malignant human cells. In embryonic tissues EcFn was abundant in developing basement membranes, as shown in foetal kidney and muscle, while in adult tissues it was confined only to endothelia of larger blood vessels. Furthermore, in embryonic tissues the capillaries showed bright EcFn-positivity not found any more in adult tissues. Human plasma contained a small quantity of EcFn, which may hence have an endothelial origin. EcFn was also prominent in the stroma of malignant tumours as well as in reactive benign conditions, such as granulation tissue and decidual cells. The results suggest that EcFn is a form of the protein which may have a particular role in developing and reactive tissues in embryos and adults.

Adult↗
PubMed1987

Human erythroleukemia cells adhere to fibronectin: evidence for a Mr 190,000-receptor protein.

Human erythroleukemia cells (K562) adhered rapidly on fibronectin (Fn)-coated growth substratum under serum-free conditions. The adhesion could be quantitatively inhibited by the synthetic peptide Arg-Gly-Asp-Ser (RGDS) and upon hemin-induced differentiation or trypsinization of the cells. Many of the cells also displayed rapid spreading that led to a redistribution of F-actin into spreading edges and in many cells also to a formation of typical actin fibers attaching to the ventral aspect of the cells. The spreading of the cells was inhibited by cytochalasin B but not by microtubule-disrupting drugs, suggesting an active role for the microfilament system in the spreading process. Direct overlay assay of electrophoretically separated polypeptides with 125I-Fn showed that in K562 cells there is a major Mr 190,000 Fn-binding protein that is lost upon differentiation. A similar overlay assay with purified plasma and cellular Fns followed by immunostaining with anti-Fn antibodies revealed a reaction with a similar polypeptide. The binding of Fns on the nitrocellulose sheets could be inhibited and the bound Fn eluted by using the RGDS peptide. From octylglucoside extracts of radioactively surface-labeled cells, distinct Mr 190,000/185,000 membrane glycoproteins bound to Fn-heptapeptide-Sepharose, further suggesting that the Mr 190,000 polypeptide would be the Fn-receptor of the K562 cells.

Cell Line↗
PubMed1987

Tumor promoter and fibronectin induce actin stress fibers and focal adhesion sites in spreading human erythroleukemia (HEL) cells.

The effects of plasma fibronectin (pFn) and the tumor promoter 12-0-tetradecanoyl-phorbol-13-acetate (TPA) on adhesion and cytoskeletal organization of human erythroleukemia (HEL) cells were studied. HEL cells, that normally grow in suspension, attached rapidly on pFn-coated growth substratum and some cells showed spreading. Upon exposure to TPA most of the cells adhered and showed some degree of spreading also when plated on plastic. The spread cells showed mostly peripheral accumulations of F-actin in addition to actin fibers seen in some of the cells. When the cells were plated in the presence of TPA on pFn or on pFn-fragments, containing the cell binding site, all the cells adhered rapidly, spread extensively, organized prominent F-actin stress fibers and typical ventral plaques of vinculin and alpha-actinin. Both proteins were revealed also in the suspended cells by Western blot analysis. When plated on substratum coated with other pFn-fragments or laminin, the HEL cells did not adhere or spread. Both adhesion on pFn as well as formation of stress fibers in the presence of TPA could be prevented by the synthetic peptide Arg-Gly-Asp-Ser (RGDS). HEL cells were also able to organize typical ventral fibrillar arrays of Fn. Immunostaining and metabolic labeling experiments showed that the cells did not contain or synthesize Fn, indicating that the plaques were formed from exogenous pFn by the cells. The results suggest that Fn and TPA synergistically induce the organization of the actomyosin system in HEL cells by promoting the formation of prominent actin stress fibers and focal adhesion sites.

Actins↗
PubMed1986

Characterization of a novel gelatin-binding 21 kDa protein secreted by cultured adherent cells.

A novel gelatin-binding 21 kDa protein was identified in the culture medium of fibroblastic and sarcoma cells by affinity chromatography on gelatin-Sepharose. Its affinity for gelatin was lower than that of the other gelatin-binding proteins, fibronectin and the 70 kDa protein, as judged by stepwise elution by urea and arginine. The protein bound also to spermine and to some extent to heparin but not to staphylococcal protein A, bovine serum albumin, concanavalin A or plain Sepharose 4B. In gel filtration chromatography the protein eluted in fractions differing from those of fibronectin and the Mr 70,000 protein and retained its ability to bind to gelatin-Sepharose, indicating that the binding was not mediated by the two other gelatin-binding proteins. It contains intrachain disulfide bridges, as judged by analysis under nonreducing and reducing conditions. The protein is composed of two major subtypes with pI values of 5.85-6.10 and 6.55-6.75. It was sensitive to trypsin but not to collagenase or thrombin. Antiserum was raised in rabbits against the gelatin-binding proteins isolated from serum-free conditioned fibroblast culture medium. The antiserum reacted with fibronectin, the Mr 70,000 protein and the Mr 21,000 protein in immunoprecipitation experiments. Absorption of the antiserum with human plasma fibronectin did not decrease its reactivity with the Mr 70,000 and 21,000 proteins. However, absorption with the Mr 70,000 protein abolished also the reactivity against the Mr 21,000 protein, suggesting immunological cross-reactivity. The protein was synthesized independently from the Mr 70,000 protein, as shown by pulse-chase labeling experiments of cells. The production of the Mr 21,000 protein in cultured cells was enhanced by transforming growth factor-beta.

Carrier Proteins↗
PubMed1986

Disulfide-bonded polymerization of plasma fibronectin in the presence of metal ions.

Incubation of human plasma fibronectin in the presence of low concentrations of FeCl3 or CuSO4 led to the formation of disulfide-bonded multimers as revealed by analysis in sodium dodecyl sulfate-polyacrylamide gel electrophoresis under nonreducing or reducing conditions. The polymers induced by FeCl3 did not enter the spacer gel, and those induced by CuSO4 migrated to the top of the running gel, indicating that the former polymers were larger than the latter, which in gel filtration experiments appeared to be larger than Mr 670,000. The polymerization occurred between pH 7 and 9 and more rapidly at 22 or 37 degrees C than at 4 degrees C and was inhibited by metal-chelating reagents. NaCl, heparin, spermine, urea, or guanidine hydrochloride did not appreciably affect the reaction, whereas dithioerythritol enhanced the CuSO4-induced polymerization of fibronectin. When incubated in the presence of FeCl3, the Mr 30,000 NH2-terminal, Mr 40,000 gelatin-binding, and the Mr 120,000-140,000 COOH-terminal fragments of fibronectin formed disulfide-bonded polymers, whereas only the Mr 140,000 fragment was polymerized in the presence of CuSO4. Disulfide-bonded polymers were also formed in the presence of FeCl3 but not CuSO4 when the free sulfhydryl groups of fibronectin were blocked by N-ethylmaleimide. The results suggest that in the presence of CuSO4, disulfide-bonded polymerization of fibronectin may involve predominantly the free sulfhydryl groups, whereas in the presence of FeCl3, also the intramolecular disulfides may exchange to form disulfides between separate fibronectin molecules. Thus, under different conditions, different parts of fibronectin may be susceptible to disulfide-bonded polymerization.

Chelating Agents↗
PubMed1986

Basement membrane matrix in vitro: focal binding of exogenous fibronectin to the matrix of teratocarcinoma-derived endodermal cells.

Interaction of exogenous fibronectin with the basement membrane-like PYS-2 cell matrix, lacking fibronectin and hyaluronic acid but containing heparan sulfate proteoglycan, was studied in vitro. Both human plasma fibronectin and fibronectin in fetal calf serum bound to PYS-2 matrix; also, fragments of fibronectin containing heparin-binding domains but lacking the collagen-binding domain bound to the matrix. In immunoelectron microscopy the bound fibronectin was found as 20-40 nm globules or patches. Distribution of fibronectin differed from that of laminin and correlated best with that of heparan sulfate proteoglycan. The results suggest that the binding of fibronectin to basement membrane matrices is not due to random adherence but involves specific interactions with other components.

Animals↗
PubMed1986

Aggregation of fibronectin by asbestos fibers in the pericellular matrix of cultured human fibroblasts.

Asbestos fibers, silica dust and glass fibers induced aggregation of the pericellular matrix fibronectin when added to the growth medium of cultured human fibroblasts as judged by immunofluorescence microscopy. Direct binding experiments and analysis of the bound proteins by (SDS-polyacrylamide gel electrophoresis) revealed an adsorption of purified plasma fibronectin to glass fibers, amosite, crocidolite and silica but not to anthophyllite and chrysotile A and B. The results suggest that aggregation of the pericellular fibronectin by these fibrogenic materials may be involved in the initial stages of the development of fibrosis in vivo.

Asbestos↗
PubMed1986

Microtubule disruption does not prevent intracellular transport and secretory processes of cultured fibroblasts.

The effect of microtubule disruption on intracellular protein translocation and secretion of cultured human fibroblasts was studied. Experiments with fluorochrome-labeled wheat germ agglutinin showed that treatments with demecolcine or vinblastine sulfate rapidly brought about dispersal of Golgi organization. Similarly, monoclonal tubulin antibodies revealed in immunofluorescence a complete disappearance of microtubules under these conditions. Cells exposed to demecolcine or vinblastine sulfate appeared to secrete both fibronectin and other polypeptides similar to the control cells, as judged by electrophoretic analysis of the culture medium. In line with this, immunofluorescence studies of the cells, treated with the antimitotic drugs and then exposed to puromycin, showed a rapid depletion of intracellular fibronectin and collagen type III-specific staining. On the contrary, cells exposed first to monensin and then to demecolcine or vinblastine sulfate and puromycin, showed an accumulation of these proteins in vesicles in the Golgi region. The results suggest that in cultured fibroblasts microtubules do not have a direct permissive role in the intracellular translocation of the secreted proteins although they are involved in the maintenance of the Golgi apparatus. The secretory processes, however, appear to continue also in cells with dispersed Golgi organization and lacking microtubules.

Biological Transport↗
PubMed1985

Gelatin-degrading activity secreted by cultured macrophages from human blood.

Gelatin-binding proteins (fibronectin and the 95 000-Mr protein [T. Vartio, T. Hovi & A. Vaheri (1982) J. Biol. Chem. 257, 8862-8866] were isolated by gelatin-agarose from the growth medium of cultured human monocyte/macrophages and the 95 000-Mr protein was further separated from fibronectin under nondenaturing conditions by preparative polyacrylamide gel electrophoresis. In the latter the proteins were eluted from the bottom of the tube gel into fractions which were then tested for ability to degrade native or heat-denatured type I collagen (gelatin). When solutions from fractions containing the 95 000-Mr protein were incubated with gelatin, degradation was revealed by analysis of the reaction mixtures in the sodium dodecyl sulfate/polyacrylamide gel electrophoresis. Native type I collagen as well as native or heat-denatured fibronectin or other plasma proteins were unaffected when tested similarly. The degradation of gelatin was calcium-dependent and was inhibited by serum, sulfhydryl and metal-chelating reagents, but not with serine proteinase inhibitors. Gelatin was degraded optimally at pH 7-9 and at 41 degrees C and 37 degrees C and less effectively at 22 degrees C. Native type I collagen was degraded at 41 degrees C but not at 37 degrees C or 22 degrees C. The results show that cultured human macrophages secrete highly specific gelatin-degrading metal-proteinase activity which is associated with the 95 000-Mr gelatin-binding protein.

Carrier Proteins↗
PubMed1985

Plasminogen and tissue-type plasminogen activator bind to immobilized fibronectin.

Fibronectin immobilized onto polystyrene surface was found to bind plasminogen and tissue-type plasminogen activator (t-PA) but only slightly the urokinase type as determined using mono- and polyclonal antibodies against the activators. Of the defined fibronectin fragments tested, the Mr 120,000-140,000 fragment was found to bind both plasminogen and t-PA. Proteolytically modified plasminogen (Lys-plasminogen) bound considerably better than the native form (Glu-plasminogen). Experiments with 125I-plasminogen yielded Kd = 9.1 X 10(-8) M for the binding to immobilized fibronectin. The partially or completely inactive single-chain form of t-PA (pro-t-PA) bound considerably better than the activated two-chain form. Lysine at greater than 3 mM inhibited the binding of plasminogen. The interaction was independent of calcium ions. CaCl2 (greater than 0.5 mM) and NaCl (greater than 0.2 M) inhibited the binding of pro-t-PA and of t-PA. Fibronectin-bound t-PA retained its ability to activate plasminogen. The observed interactions may operate in directional proteolysis localizing plasminogen and plasminogen activator to degrade fibronectin-containing extracellular matrix including fibrin clots.

Epitopes↗
PubMed1985

The 95000-Mr gelatin-binding protein in human serum and plasma.

A gelatin-binding 95000-Mr protein was detected in human serum and plasma by immunoblotting using antibodies against the 95000-Mr gelatin-binding protein, a major secretory component of cultured adherent human monocyte/macrophages. Serum and plasma were prepared by incubating blood at 4, 22 or 37 degrees C for different periods of time, and gelatin-binding proteins were isolated from 200 microliter portions by gelatin-Sepharose affinity chromatography. The bound material was analysed by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. In protein-stained gels, fibronectin and some minor polypeptides were seen, but not the 95000-Mr protein. In immunoblotting of identical serum samples the antibodies detected apparently two closely spaced polypeptide bands at Mr95000, and in plasma samples a single band at the position of the faster-migrating one of the two above-mentioned bands. The immunoperoxidase reaction was stronger when serum and plasma were prepared by incubating for longer periods of time (up to 8 h) or at higher temperatures (up to 37 degrees C). In samples made from plasma, the immunoperoxidase reactions were weaker than in those from serum, indicating a lower quantity of the protein. The results suggest that the 95000-Mr protein is released from monocytes and granulocytes during the incubation of blood and, more likely, when they possibly interact with the blood clot and may become adherent.

Carrier Proteins↗
PubMed1985

Fibronectin in formation and degradation of the pericellular matrix.

Fibronectin is a large multifunctional glycoprotein present both in soluble form in plasma and other body fluids and in an insoluble form in interstitial connective tissues and in association with most basement membranes. The protein seems to provide a link between circulating body fluids, cell surfaces and the extracellular matrix. At sites of injury, fibronectin, covalently cross-linked to the fibrin clot, may provide a growth substratum for the invading cells and appears through its multiple interactions with other matrix components and cell surfaces to be involved in the organization of the matrix that will replace the clot. Fibronectin deposition may serve as a useful early marker for connective tissue formation in pathological processes and its fragmentation may serve as an indicator of pathological conditions involving proteolytic events.

Animals↗