Search PubMed⌕ Search

Biomedical subjects

E Engvall

Publications and source records attributed to E Engvall.

At least 127 records · Page 7Linked to original sources
PubMed1981

Two-site sandwich enzyme immunoassay with monoclonal antibodies to human alpha-fetoprotein.

Monoclonal antibodies reacting with different antigenic determinants on the alpha-fetoprotein (AFP) molecule were used to develop a simplified 'sandwich' ELISA (enzyme-linked immunospecific assay) in which one monoclonal antibody was immobilized and another labeled with an enzyme. Due to their different specificities the antibody attached to the solid phase and the one conjugated to the enzyme did not compete for binding to AFP making it possible to complete the two antigen-antibody reactions required in a single, short incubation. The rapidity, simplicity and excellent sensitivity of this assay combined with the exquisite specificity associated with the use of two monoclonal antibodies make us believe that assays based on this principle will be useful in the quantitation of substances of medical and biological importance.

Animals↗
PubMed1981

Affinity chromatography of collagen on collagen-binding fragments of fibronectin.

The affinity of fibronectin for collagen was exploited in biospecific affinity chromatography of collagen. Matrices with excellent capacity and stability were obtained by coupling collagen-binding fragments of fibronectin to Sepharose. Collagen-binding tryptic (30,000 daltons) and chymotryptic (45,000 daltons) fragments, lacking the binding sites of intact fibronectin for various other substances, were coupled to Sepharose and used to chromatograph gelatin and type I collagen. Gelatin was rapidly and quantitatively bound to these matrices at 4 degrees C and 37 degrees C, while binding of type I collagen took place more slowly and was temperature dependent. The collagen did not bind at 4 degrees C but bound quantitatively at 37 degrees C if preincubated at this temperature. These results suggest that a temperature-dependent perturbation of the triple helical structure of the collagen uncovers the binding site for fibronectin, allowing the collagen to bind to the insolubilized collagen-binding fibronectin fragments. Enzyme affinity assays showed that the conformational change in the fibronectin-binding region of collagen was irreversible. Affinity chromatography on collagen-binding fragments of fibronectin could provide a method for the study of structure and function of collagens and may prove useful for the isolation of minor collagens.

Binding Sites↗
PubMed1981

Laminin and fibronectin in cell adhesion: enhanced adhesion of cells from regenerating liver to laminin.

Laminin, a basement membrane glycoprotein isolated from cultures of mouse endodermal cells and rat yolk sac carcinoma cells, promoted the attachment of liver cells obtained from regenerating mouse liver. Cells from normal mouse liver attached readily to dishes coated with fibronectin but attached poorly to surfaces coated with laminin. Both proteins efficiently promoted the attachment of cells from livers undergoing regeneration. After regeneration, the attachment to laminin returned to the low levels found in animals not subjected to partial hepatectomy but attachment to fibronectin remained high. Immunofluorescent staining of sections of normal liver with antilaminin revealed the presence of laminin in or adjacent to the walls of the bile ducts and blood vessels. After induction of regeneration by partial hepatectomy, increased amounts of laminin appeared in the sinusoidal areas. After carbon tetrachloride poisoning, staining for laminin was especially pronounced in the necrotic and postnecrotic areas around the central veins. This additional expression of laminin was transient. It reached a maximum around 5--6 days after the injury and then gradually disappeared. These findings show that laminin is an adhesive protein. The increase of laminin in regenerating liver and the adhesiveness of cells from such livers to laminin suggest a role for laminin in the maintenance of a proper tissue organization during liver regeneration.

Animals↗
PubMed1981

Differentiation of fetal liver cells in vitro.

Fetal mouse liver hepatocytes proliferate on a substrate of irradiated pigskin epidermis scored with scalpel blade slits to permit cell access to the basement membrane. At the time the cells are explanted, fetal genes, such as those responsible for production of alpha-fetoprotein (AFP) and gamma-glutamyltransferase (GGTase), are strongly expressed. The levels of GGTase decrease rapidly and become undetectable within 2 weeks. The levels of AFP decrease more gradually but become undetectable after 3-5 weeks in culture. As the AFP levels decrease, there is a concomitant increase in albumin production. Hydrocortisone prolongs production of AFP (for up to 8 weeks) but not of GGTase, and it decreases albumin production for up to 8 weeks. Once cells lose AFP expression, addition of hydrocortisone does not restart it. Based on these data, fetal mouse liver hepatocytes, cultured on pigskin, seem to be an excellent in vitro model for liver cell maturation.

Animals↗
PubMed1981

Concomitant loss of cell surface fibronectin and laminin from transformed rat kidney cells.

Both fibronectin and laminin were found by immunofluorescence as a matrix at the surface of normal rat kidney cells. These matrices were absent from the surface of virally transformed rat kidney cells. Soluble fibronectin and laminin were detected in the culture media of the transformed as well as the normal cells. Culture supernates of the transformed cells contained even more fibronectin than the supernates of the transformed cells contained even more fibronectin than the supernates of the normal cells while laminin was present in similar amounts in both culture media. This shows that the loss of fibronectin and laminin from the surface of the transformed cells is caused by failure of the cells to deposit these proteins into an insoluble matrix and not caused by inadequate production. Fibronectins isolated from culture media of the normal and transformed cells were similar in SDS polyacrylamide gel electrophresis. Laminin isolated from culture media by affinity chromatography on heparin-Sepharose followed by immunoprecipitation was composed of three main polypeptides, one with a molecular weight of 400,000 and two with a molecular weight close to 200,000 in both cell types. Fibronectins from both cell types were equally active in promoting cell attachment. Rat fibronectin from transformed cells, like normal cells, when applied to culture dishes coated with fibronectin, readily attached and spread on the substratum, requiring approximately the same amount of fibronectin as the normal cells. On the basis of these results it seem that the failure of the transformed cells to incorporate fibronectin into an insoluble cell surface matix is not a consequence of a demonstrable change in the functional characteristics of the fibronectin molecule or in the ability of the cells to interact with fibronectin. It may depend on as yet unidentified interactions of the cell surface. Similar interactions may be needed for the deposition of laminin into the matrix, because laminin was also absent from the surface of transformed cells, despite its being synthesized by these cells.

Animals↗
PubMed1981

Basement membrane changes in breast cancer detected by immunohistochemical staining for laminin.

The distribution of the basement membrane glycoprotein laminin was studied by the immunoperoxidase technique in benign and malignant human breast tissue and in axillary lymph nodes from patients with breast cancer. An antiserum prepared against rat laminin was used. The specificity of this antiserum against human laminin was studied using the FL cell line of human epithelial-like cells derived from normal amniotic membrane. The antiserum reacted with these cells in immunoperoxidase staining and precipitated metabolically labeled secreted polypeptides which comigrated with polypeptides with molecular weights of 400,000 and 200,000 of rat laminin in sodium dodecyl sulfate:polyacrylamide gel electrophoresis. The neoplastic cells in malignant breast tissues showed strong cytoplasmic staining for laminin, and a positive reaction was aslo found in lymph node metastases. In some cases in which only micrometastases were present, these cells also stained strongly for laminin. In nonmalignant breast tissues, the epithelial cells of the duct were positive for laminin, but the staining was weaker than in the carcinomas. Pretreatment of the fixed tissue sections with trypsin markedly enhanced the staining of basement membranes for laminin. In trypsin-treated sections of normal breast tissue and benign lesions, the laminin staining delineated continuous basement membranes. In carcinomas representing the more differentiated types, basement membranes presumably produced by the tumor cells could be revealed by laminin staining, but they were thinner and discontinuous. The poorly differentiated carcinomas lacked organized basement membranes detectable by laminin staining. Our studies suggest that staining for laminin may be a useful adjunct test for detection of micrometatases in lymph nodes. The correlation of disintegration of the laminin-containing basement membranes of tumors with increasingly anaplastic appearance supports the notion that basement membranes may play a role in tumor invasion.

Basement Membrane↗
PubMed1980

Interrelationships of human chorionic gonadotropin, human placental lactogen, and pregnancy-specific beta 1-glycoprotein throughout normal human gestation.

Human chorionic gonadotropin (hCG), human placental lactogen (hPL), and pregnancy-specific beta 1-glycoprotein (PSBG) were measured by radioimmunoassay in 270 samples of serum from women with uncomplicated pregnancies. All three proteins were significantly correlated with each other in individual samples of serum and with the estimated trophoblastic mass during the first trimester. No significant correlation could be demonstrated between the concentrations of hCG and PSBG in maternal serum during the second or third trimesters or between the concentrations of hCG and hPL during the second trimester. Levels of PSBG and hPL in serum were significantly correlated throughout all three trimesters. These findings suggest that the secretion of hCG, hPL, and PSBG may be regulated by similar control mechanisms during the first trimester of pregnancy. However, after this period, the factors that modulate the production of hCG differ from those that regulate the production of hPL and PSBG.

Chorionic Gonadotropin↗
PubMed1980

Trophoblastic disease monitoring: Evaluation of pregnancy-specific beta 1-glycoprotein.

Pregnancy-specific beta 1-glycoprotein (SP1) was evaluated as a potential marker protein for monitoring trophoblastic disease. Four patients with post-molar pregnancy accompanied by spontaneous titer remission and three patients with nonmetastatic trophoblastic disease were found to have regression curves for both human chorionic gonadotropin (hCG) and SP, which closely followed each other. Of three patients with metastatic choriocarcinoma, two were shown to have discordant hCG and SP1 patterns, SP1 in both cases was plateauing or rising while hCG continued to fall. Two other patients are described, one with a spontaneous remission, and one who previously had had choriocarcinoma and was found to have low levels of hCG with higher levels of SP1.

Adolescent↗
PubMed1980

Complexing of fibronectin glycosaminoglycans and collagen.

Collagen-fibronectin complexes, formed by binding of fibronectin to gelatin or collagen insolubilized on Sepharose, were found to bind 20-40% of radioactivity in [35S]heparin. Fibronectin attached directly to Sepharose also bound [35S]heparin, while gelatin-Sepharose without fibronectin did not. Unlabeled heparin and highly sulfated heparan sulfate efficiently inhibited the binding of [35S]heparin, hyaluronic acid and dermatan sulfate were slightly inhibitory, while chondroitin sulfates and heparan sulfate with a low sulfate content did not inhibit. The interaction of heparin with fibronectin bound to gelatin resulted in complexes which required higher concentrations of urea to dissociate than complexes of fibronectin and gelatin alone. Heparin as well as highly sulfate heparan sulfate and hyaluronic acid brought about agglutination of plastic beads coated with gelatin when fibronectin was present. Neither fibronectin nor glycosaminoglycans alone agglutinated the beads. It is proposed that the multiple interactions of fibronectin, collagen and glycosaminoglycans revealed in these assays could play a role in the deposition of these substances as an insoluble extracellular matrix. Alterations of the quality or quantity of any one of these components could have important effects on cell surface interactions, including the lack of cell surface fibronectin in malignant cells.

Animals↗
PubMed1980

Direct tissue visualization of normal cross-reacting antigen in neoplastic granulocytes.

Normal cross-reacting antigen, a glycoprotein that shares some antigenic determinants with carcinoembryonic antigen, was consistently demonstrated by tissue immunoperoxidase staining in the cytoplasm of both non-neoplastic and neoplastic neutrophilic granulocytes. It was absent in lymphoid cells, but occasional cells of the macrophage/histiocyte series showed variable staining. Malignant cells from patients who had non-Hodgkin or Hodgkin lymphomas were negative for normal cross-reacting antigen. These findings were in contrast to the findings of specific normal cross-reacting antigen positivity in neoplastic granulocytes from three patients who had acute granulocytic leukemia, three who had chronic granulocytic leukemia, and one who had a granulocytic sarcoma. Similar normal cross-reacting antigen positivity was also seen in granulocytes from two patients who had granulocyte dysplasia. It is suggested that direct tissue visualization of normal cross-reacting antigen using immunoperoxidase technics may be of value in the classification and diagnosis of hematologic malignancies, and may provide an additional marker for cells of the granulocytic series.

Antigens, Neoplasm↗
PubMed1980

Ectopic production of pregnancy-specific beta 1-glycoprotein by a nontrophoblastic tumor in vitro.

To demonstrate the ectopic production of pregnancy-specific beta 1-glycoprotein (PSbetaG) by a nontrophoblastic tumor, the in vitro secretion of this glycoprotein was evaluated in an hCG-producing ovarian cystadenocarcinoma cell line maintained in long term cell culture. Parallelism was demonstrated between the immunoreactive material present in the tissue culture media and highly purified PSbetaG measured by a sensitive and specific RIA. The immunoreactive material was shown to cochromatograph with purified PSbetaG present in normal term pregnancy serum on a Sephadex G-150 column. The tumor PSbetaG was adsorbed to concanavalin A-Sepharose and eluted with alpha-D-methyl-glucoside in a manner similar to purified PSbetaG. The indirect immunoperoxidase method with anti-PSbetaG sera localized PSbetaG in secretory vesicles and in the endoplasmic reticulum of the tumor cells by light and electron microscopy. The addition of sodium butyrate to the tissue culture media stimulated PSbetaG production in a fashion quantitatively similar to that seen with hCG. The number of PSbetaG-staining intracellular vesicles also increased after exposure to butyrate. These studies provide direct evidence for the ectopic production of PSbetaG by a nontrophoblastic tumor cell line.

Cell Count↗
PubMed1980

Pregnancy-specific beta 1-glycoprotein (SP1). Purification and partial characterization.

The pregnancy-specific beta 1-glycoprotein, SP1, was purified to homogeneity from placental extract and from serum using immunoadsorbent techniques. The isolated SP1 had a molecular weight of 90,000-110,000 daltons and an amino acid and amino sugar composition typical of an acidic glycoprotein. The availability of purified SP1 will be of value in the further evaluation of the role and importance of SP1 in malignancies as well as in normal development.

Amino Acids↗
PubMed1980

Molecular interactions of fibronectin.

Fibronectin mediates attachment of cells to surfaces in vitro, and its abundance in basement membrane structures suggests that it serves a similar function in vivo. The cell attachment promoting activity of fibronectin depends on its capacity to interact with a number of other macromolecules. These include collagen, fibrin(ogen), glycosaminoglycans, and as yet unidentified receptors on the surfaces of various mammalian and avian cells and on the surfaces of Staphylococci. Denatured collagens bind more avidly to fibronectin than the native forms. Of the latter, type III is the most active one. The collagen-binding is inhibited by fibrinogen and vice versa, indicating that the same (or overlapping) binding site are responsible for the binding of fibronectin to collagen and fibrinogen. The binding site for collagen in fibronectin can be localized in a homogeneous fragment with a molecular weight of 30,000. This binding site is distinct from the one interacting with cell surfaces, since the cell attachment promoting activity is found associated with collagen-nonbinding fragments of fibronectin. These same fragments also bind to Staphylococci, suggesting that the cell surface receptor in these bacteria may be similar to that of eukaryotic cells. Glycosaminoglycans bind to collagen-fibronectin complexes resulting in a complex more stable to disruption with urea than complexes of any two of the components. This phenomenon may be important in the formation of the fibronectin-containing, adhesive, extracellular matrix, and its significance to the apparent disturbances that many malignant cells have in forming such a matrix in particular, warrants further study.

Cell Adhesion↗