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Biomedical subjects

D F Mosher

Publications and source records attributed to D F Mosher.

At least 199 records · Page 11Linked to original sources
PubMed1979

Calcium binding by a myeloma protein.

We describe a patient with immunoglobulin G (IgG)-kappa myeloma and severe, long-standing, asymptomatic hypercalcemia. Serum nonprotein-bound calcium concentration was 5.2 mg/dl (normal 4.2 to 5.0 mg/dl) at a time when total serum calcium concentration was 17.8 mg/dl. The patient's myeloma protein, IgGCAB, and Fab fragments of IgGCAB migrated more anodally when agarose gel electrophoresis was performed in the absence of calcium ion than when electrophoresis was performed in the presence of calcium ion; 60 other myeloma proteins did not demonstrate such behavior. Purified IgGCAB bound 1.5 calcium ions with a single dissociation constant of 1.2 X 10(-4) M. We speculate that the rare syndrome of myeloma and high protein-bound calcium is due to binding of calcium to variable regions of the myeloma antibody molecules.

Calcium↗
PubMed1979

Cross-linking of fibronectin to collagen by blood coagulation Factor XIIIa.

Soluble fibronectin is found in body fluids and media of adherent cultured cells and binds to fibrin and collagen. Insoluble fibronectin is found in tissue stroma and in extracellular matrices of cultured cells. Fibronectin is a substrate for Factor XIIIa (plasma transglutaminase) and can be cross-linked by Factor XIIIa to itself and the the alpha-chain of fibrin. We used sodium dodecyl sulfate-polyacrylamide gel electrophoresis to investigate Factor XIIIa-mediated crosslinking of fibronectin to collagen. At O degrees or 37 degrees C, fibronectin could be cross-linked to iodinated cyanogen bromide fragment 7 of the alpha 1(I) chain. At 22 degrees or 37 degrees C, fibronectin could be cross-linked to isolated alpha 1(I) chains of type I collagen. Fibronectin could also be crosslinked to types I and III collagen, but only at 37 degrees C. alpha 1(I)-CB7, alpha 1(I) collagen chains, type I collagen, type III collagen, and fibrin all blocked cross-linking between 125I-alpha 1 (I)-CB7 and fibronectin. alpha 1(I)-CB7 blocked cross-linking between fibronectin and fibrin. These results indicate that the determinants of fibronectin-fibrin and fibronectin-collagen binding and cross-linking are similar. Cross-linking of fibronectin to collagen likely occurs in vivo and may be important for normal wound healing, collagen fibrillogenesis, and embryogenesis.

Binding Sites↗
PubMed1979

Action of thrombin on surface glycoproteins of human platelets.

We labeled surface glycoproteins of human platelets by the neuraminidase-galactose oxidase/borotritiide and the periodate/borotritiide methods. When labeled platelets were treated with 1-nM thrombin, a minor glycoprotein weighing 68,000-85,000-d was lost from the surface, and a soluble glycoprotein weighing 57,000-68,000-d was found in the supernatant. Treatment of platelets with ADP, collagen, or the calcium ionophore A23187 did not cause loss of the 68,000-85,000-d glycoprotein from platelet surfaces or appearance of the 57,000-68,000-d glycoprotein in the supernatant. However, trace amounts of the intact 68,000-85,000-d glycoprotein were found in the supernatants of platelets that were not treated with thrombin. The numerous effects of thrombin on platelets could be initiated by cleavage and release the thrombin-sensitive glycoprotein.

Blood Platelets↗
PubMed1979

Reversal by glucocorticoid hormones of the loss of a fibronectin and probollagen matrix around transformed human cells.

Confluent cultured human skin fibroblasts had an extracellular fibrillar matrix of fibronectin and procollagen. Human skin fibroblasts transformed by SV40 did not have such a matrix. Treatment of transformed fibroblasts with 10(-5) to 10(-8) M dexamethasone and 10(-5) to 10(-7) M cortisol, but not testosterone or progesterone, caused partial restoration of the matrix. Glucocorticoid-treated transformed human fibroblasts can serve as a model for partial reversion toward normal or differentiation of transformed human fibroblasts.

Cell Membrane↗
PubMed1979

Localization of fibronectin within the renal glomerulus and its production by cultured glomerular cells.

Fibronectin was shown in the kidney glomerulus by the use of the peroxidase-labeled antibody technique. At the ultrastructural level, fibronectin was present in greatest quantities along those cell surfaces that abut the capillary basement membrane, especially along the capillary epithelial cell foot process. Intracellular staining was also seen in the glomerulus, most notably in the mesangial cell. Fibronectin was present extracellularly in large amounts in glomerular cell culture and was also demonstrated on the cell membrane and intracellularly.

Animals↗
PubMed1978

High molecular weight, cell surface-associated glycoprotein (fibronectin) lost in malignant transformation.

Fibronectin is a polymorphic glycoprotein found in blood and tissues of vertebrates and in cultures of adherent vertebrate cells. There are several forms of fibronectin is composed of two high molecular weight subunits held together by forms found in tissues and on and around the surfaces of cultured cells. Soluble fibronectin is composed of two high molecular weight subunits held together by disulfide bonds. Insoluble fibronectin may be covalently cross-linked in larger complexes. Fibronectin has affinities for collagen, fibrin, heparin, and cell surfaces. In culture, fibronectin in growth medium may mediate attachment of cells to substratum, and fibronectin synthesized by cells may mediate adhesion to substratum. The widespread occurrence of fibronectin in basal lamina indicates that may different cell types in vivo abut against a fibronectin-containing matrix. Cultured transformed cells usually lack cell-surface fibronectin, also called large, external transformation-sensitive (LETS) protein. The failure of transformed cells to synthesize or bind fibronectin is paralleled (at least in some systems) by failures to synthesize or bind collagen and proteoglycans. Abnormal synthesis of fibronectin and other matrix components and abnormal interactions with the tissue matrix may account for several phenotypic characteristics of transformed cultured cells and for some of the malignant behavior of neoplastic cells in vivo.

Amino Acids↗
PubMed1978

Synthesis of fibronectin by cultured human endothelial cells.

Plasma fibronectin is probably the major nonimmune particulate opsonin in blood and is cross-linked to fibrin during the final stage of blood coagulation. Fibronectin also occurs in an insoluble form in basement membranes especially those underlying endothelial cells and in loose connective tissue. Fibronectin was demonstrated in cultured human endothelial cells and in the surrounding extracellular matrix by immunofluorescence microscopy by using antibody to human plasma fibronectin. Cultured human endothelial cells released fibronectin into the culture medium which was immunologically identical to the fibronectin in human plasma. Cultured human endothelial cells were labeled with [3H] leucine. The radioactive fibronectin present in the endothelial postculture medium and in urea extracts of cellular monolayers was isolated with either anti-fibronectin coupled to Protein A-Sepharose or double antibody immunoprecipitation and characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. When reduced, the [3H] fibronectin synthesized by cultured endothelial cells had the same mol wt (approximately 200,000) as plasma fibronectin. Unreduced, the [3H] fibronectin synthesized by endothelial cells migrated as a dimer, as did plasma fibronectin. Fibronectin accounted for approximately 15% of the protein synthesized and released by endothelial cells into the culture medium. Thus, cultured endothelial cells synthesize fibronectin, secrete it into the culture medium, and incorporate it into extracellular matrix. The results suggest that the endothelial cell is potentially a major site of synthesis of circulating plasma fibronectin. In addition, fibronectin derived from endothelial cells may be an important structural component of the subendothelium.

Cells, Cultured↗
PubMed1978

Fibronectin concentration is decreased in plasma of severely ill patients with disseminated intravascular coagulation.

Plasma fibronectin (cold-insoluble globulin) is known to be cross-linked to fibrin during the final stage of blood coagulation and is probably the major nonspecific opsonin of blood. We measured the concentration of plasma fibronectin in 36 hospitalized patients (11 with malignancy, 12 with infection, 13 with other underlying diseases) with evidence of fibrin depostion and lysis. Plasma fibronectin concentration was greater than 2 S.D. below the mean of normals in 17 of the patients (p less than 0.001). Depression of fibronectin was not related to severity of disseminated intravascular coagulation, as assessed by fibrinogen concentration and the quantity of FDP in serum. Depressed plasma fibronectin concentration and the quantity of FDP in serum. Depressed plasma fibronectin concentration was an unfavorable prognostic finding, inasmuch as 12 of the 17 patients with depressed fibronectin concentrations died during hospitalization as compared to five of the 19 patients with normal fibronectin concentrations (p less than 0.02). We speculate that specific depletion of plasma fibronectin, because of codeposition with fibrin or due to increased utilization as a nonspecific opsonin, may contribute to the organ failure seen in severely ill patients.

Adult↗
PubMed1978

Effects of cell density and transformation on the formation of a fibronectin extracellular filamentous matrix on human fibroblasts.

We have studied normal and transformed cultured human fibroblasts by ultrastructural immunocytochemistry with antibodies to fibronectin (the large external transformation-sensitive glycoprotein). Human fibroblasts at low density have very little extracellular material organized into a filamentous form. A diffuse membrane component of low-density fibroblasts reacts with fibronectin antibodies. As normal fibroblasts grow to confluence, an extensive extracellular filamentous matrix forms. The filaments are 15 to 20 nm in diameter, lack periodicity, and frequently occur in a meshwork. Antibody to fibronectin reacts with these filaments as well as with a diffusely distributed membrane component. Cultures of SV40-transformed human fibroblasts lack the extracellular filamentous matrix reacting with fibronectin antibodies; however, fibronectin is detected on plasma membranes. These studies indicate that a major difference between normal and transformed human fibroblasts is the failure of transformed fibroblasts to form a fibronectin-containing extracellular filamentous matrix.

Cell Adhesion↗
PubMed1977

Labeling of a major fibroblast surface protein (fibronectin) catalyzed by blood coagulation factor XIIa.

Incubation of cultured human fibroblasts with blood coagulation factor XIIIa (plasma transglutaminase, fibrinoligase) and the fluorescent primary amine, N-(5-aminopentyl)-5-dimethylaminonaphthalene-1-sulfonamide, resulted in fluorescent labeling of three cellular polypeptides. The molecular weights of the labeled polypeptides, estimated by polyacrylamide gel electrophoresis in sodium dodecyl sulfate after reduction, were: greater than 1.2-10(6), 2.2-10(5), and 1.3-10(5). The labeled 2.2-10(5) dalton polypeptide was susceptible to mild trypsinization and not present in cultures of SV-40 transformed fibroblasts, indicating that it is the subunit of cell-surface fibronectin and identical with the external transformation-sensitive polypeptide of similar molecular weight described by others. Upon coelectrophoresis, the labeled 2.2-10(5) dalton polypeptide migrated slightly behind the subunit of plasma fibronectin (cold-insoluble globulin), indicating that the immunologically cross-reactive forms of fibronectin in human plasma and cultured human fibroblasts differ slightly in molecular weight. The identities of the labeled greater than 1.2-10(6) and 1.3-10(5) dalton polypeptides are not known. The XIIa-reactive glutamine residues of fibroblast cell-surface proteins are potential sites for intermolecular cross-linking (by xi-(gamma-glutamyl)lysyl linkages) to other proteins of connective tissue.

Binding Sites↗
PubMed1977

Distribution of a major surface-associated glycoprotein, fibronectin, in cultures of adherent cells.

Fibronectin was present in media and cell layers of cultures of adherent cells from human skin, kidney, lung, chest wall, liver, and heart. Cell-surface fibronectin, visualized by immunofluorescence, was in dense fibrillar (cultures from lung), discrete fibrillar (e.g., cultures from skin), or punctate (some cultures from kidney) structures. The subunit sizes of cell-surface fibronectin and fibronectin soluble in medium appeared identical in sodium dodecyl sulfate-polyacrylamide gels. To explain the polymorphism of cell-surface fibronectin, there must be chemical differences among the fibronectins synthesized by different cell strains or factors in the cell layer which influence fibronectin binding and aggregation.

Animals↗