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Biomedical subjects

E A Davidson

Publications and source records attributed to E A Davidson.

At least 73 records · Page 4Linked to original sources
PubMed1986

Isolation and characterization of a wheat germ agglutinin-binding glycoprotein from B16 mouse melanoma cells.

Cells of B16 mouse melanoma grown in serum-free medium in the presence of [3H]glucosamine secreted or shed labeled glycoproteins. A wheat germ agglutinin-binding glycoprotein was isolated that accounted for 37% of the total [3H]glucosamine incorporated; it had a molecular weight of approximately 50,000 and was absent in less-tumorgenic wheat germ agglutinin (isolectin I)-resistant variants of the cells. The glycoprotein contained approximately 25% of serine and threonine plus equimolar amounts of glucosamine and galactosamine, indicating both N- and O-linked oligosaccharide chains. Neuraminidase treatment released approximately 60% of the glycoprotein's 3H radioactivity as N-acetylneuraminic acid. The sialoglycoprotein did not, but the desialylated species did, bind (97%) to ricin-Sepharose, suggesting the presence of terminal sialic acid and penultimate galactose residues in most of the saccharide units. Alkaline borohydride released 61% of the glycoprotein's radioactivity as oligosaccharide alcohols that were mainly tetrasaccharides (75%) with some branched trisaccharides (10%) from the O-linked structures. Hydrazinolysis and analysis of the alkaline borohydride-resistant portion of the glycoprotein indicated the presence of mainly triantennary, complex-type structures (N-linked) containing three sialic acids residues plus L-fucose. Serial lectin-affinity chromatography of the hydrazine-released saccharides with concanavalin A-agarose, pea lectin-agarose, L-PHA-agarose, and E-PHA-agarose, indicated the absence of high-mannose or hybrid-type structures and further confirmed the presence of triantennary, complex-type units.

Animals↗
PubMed1986

Structures of O-linked oligosaccharides present in the proteoglycans secreted by human mammary epithelial cells.

The structures of O-glycosidically linked oligosaccharides present in the heparan sulfate and chondroitin sulfate proteoglycans isolated from the culture medium of a normal (HBL-100) and a malignant (MDA-MB-231) human mammary epithelial cell line have been determined. Both proteoglycan types from the two cell lines contain a series of O-linked oligosaccharides ranging in size from di- to hexasaccharide. Cells were grown in the presence of either [3H]glucosamine or [3H]galactose and Na2 35SO4, and the proteoglycans were isolated as described (Gowda, D. C., Bhavanandan, V. P., and Davidson, E. A. (1986) J. Biol. Chem. 261, 4926-4934). The O-linked oligosaccharides were released from the proteoglycans by alkaline borohydride treatment and purified by a combination of gel filtration and high voltage paper electrophoresis. The structures of two neutral and seven acidic oligosaccharides were established based on sugar composition, the results of periodate oxidation, sequential exoglycosidase treatment, and methylation analysis. Periodate oxidation, taking advantage of tritium label at specific positions of constituent sugars, proved to be a valuable tool in establishing the structure of isomeric components in the mixture. The structures of the oligosaccharides were assigned as follows: (Formula: see text) The oligosaccharide containing both sialic acid and ester sulfate is novel and has not been reported previously.

Adenocarcinoma↗
PubMed1986

Isolation and characterization of proteoglycans secreted by normal and malignant human mammary epithelial cells.

The proteoglycans secreted by a malignant human breast cell line (MDA-MB-231) were compared with the corresponding proteoglycans from a normal human breast cell line (HBL-100). The physicochemical characteristics of these proteoglycans were established by hexosamine analysis, chemical and enzymatic degradations, and dissociative cesium chloride density gradient centrifugation, and by gel filtration before and after alkaline beta-elimination. Both cell lines secreted approximately 70% of the synthesized proteoglycans, which were composed of 20% heparan sulfate and 80% chondroitin sulfate proteoglycans. The MDA cell line secreted large hydrodynamic size (major) and small hydrodynamic size heparan sulfate proteoglycan. In contrast HBL cells secreted only one species having a hydrodynamic size intermediate to the above two. The chondroitin sulfate proteoglycans from MDA medium were slightly larger than the corresponding polymers from HBL medium. All proteoglycans except the small hydrodynamic size heparan sulfate proteoglycan from MDA medium were of high buoyant density. The proteoglycans of both cell lines contained significant proportions of disulfide-linked lower molecular weight components which were more pronounced in the proteoheparan sulfate polymers, particularly those from MDA medium, than in chondroitin sulfate proteoglycans. The glycosaminoglycans of heparan sulfate proteoglycans from MDA medium were more heterogeneous than those from HBL medium. The glycosaminoglycan chains of large hydrodynamic size heparan sulfate proteoglycans from MDA medium were larger in size than those from HBL medium while small hydrodynamic size heparan sulfate proteoglycans contained shorter glycosaminoglycan chains. In contrast to the glycosaminoglycans derived from chondroitin sulfate proteoglycans of both MDA and HBL medium were comparable in size. The heparan sulfate as well as chondroitin sulfate proteoglycans of both cell lines contained both neutral (di- and tetrasaccharides) and sialylated (tri- to hexasaccharides) O-linked oligosaccharides.

Adenocarcinoma↗
PubMed1986

Distinguishing between Nitrification and Denitrification as Sources of Gaseous Nitrogen Production in Soil.

The source of N(2)O produced in soil is often uncertain because denitrification and nitrification can occur simultaneously in the same soil aggregate. A technique which exploits the differential sensitivity of these processes to C(2)H(2) inhibition is proposed for distinguishing among gaseous N losses from soils. Denitrification N(2)O was estimated from 24-h laboratory incubations in which nitrification was inhibited by 10-Pa C(2)H(2). Nitrification N(2)O was estimated from the difference between N(2)O production under no C(2)H(2) and that determined for denitrification. Denitrification N(2) was estimated from the difference between N(2)O production under 10-kPa C(2)H(2) and that under 10 Pa. Laboratory estimates of N(2)O production were significantly correlated with in situ N(2)O diffusion measurements made during a 10-month period in two forested watersheds. Nitrous oxide production from nitrification was most important on well-drained sites of a disturbed watershed where ambient NO(3) was high. In contrast, denitrification N(2)O was most important on poorly drained sites near the stream of the same watershed. Distinction between N(2)O production from nitrification and denitrification was corroborated by correlations between denitrification N(2)O and water-filled pore space and between nitrification N(2)O and ambient NO(3). This technique permits qualitative study of environmental parameters that regulate gaseous N losses via denitrification and nitrification.

Journal Article↗
PubMed1986

Environmental Parameters Regulating Gaseous Nitrogen Losses from Two Forested Ecosystems via Nitrification and Denitrification.

Gaseous N losses from disturbed and reference forested watersheds at the Coweeta Hydrologic Laboratory in western North Carolina were studied by in situ N(2)O diffusion measurements and laboratory incubations throughout a 10-month period. Soil temperature, percent base saturation, and water-filled pore space accounted for 43% of the variation in in situ N(2)O diffusion measurements. Laboratory incubations distinguished the gaseous N products of nitrification and denitrification. Nitrifying activity, ambient NO(3), and nitrification N(2)O were positively correlated with percent base saturation. However, differences between watersheds in soil N substrate caused by presence of leguminous black locust in the disturbed watershed were confounded with differences in soil acidity. Denitrification was most strongly affected by soil moisture, which in turn was determined by precipitation events and slope position. Gaseous N losses from well-drained midslope and toeslope landscape positions appeared to be minor relative to other N transformations. Favorable conditions for denitrification occurred at a poorly drained site near the stream of the disturbed watershed. Laboratory incubations revealed high rates of NO(3) reduction in these soils. We speculate that the riparian zone is a major site of depletion of NO(3) from the soil solution via denitrification.

Journal Article↗
PubMed1985

Monoclonal antibodies to cyanogen bromide fragments of glycophorin A.

Eleven mouse monoclonal antibodies directed against epitopes on CNBr peptides of the major sialoglycoconjugate of the human red blood cell, glycophorin A, have been produced by hybridomas derived from P3-X63-Ag8.653 myeloma cells and spleen cells from BALB/c mice immunized with purified glycophorin. The monoclonal antibodies could be divided into four groups according to their reactivities with CNBr peptides in a direct ELISA assay: one antibody (6B5) that binds solely to the aminoterminal octapeptide (CNBr3); two antibodies (8F10 and 9C3) that bind to CNBrl (residues 9-81); two antibodies (3D2 and 4C6) that are reactive with CNBr2, The C-terminal portion of the molecule (residues 82-131); six antibodies (1B4, 4C3, 4E7, 7B10, 7C11 and 9D6) which are cross-reactive with an epitope on both CNBr1 and CNBR3 glycopeptides. This cross-reactive epitope(s) appears to involve both carbohydrate and protein residues.

Amino Acids↗
PubMed1984

Epitopes immunologically related to glycophorin A on human malignant and non-malignant cells in culture.

Nine monoclonal antibodies specific to different antigenic determinants on the cyanogen bromide fragments CNBr3 (1-8) and CNBr1 (9-81) of glycophorin A, the major sialoglycoprotein of human red blood cells, were used for the detection of similar or cross-reactive epitope(s) on nucleated somatic cells. A panel of human malignant and non-malignant cells consisting of erythroleukemia, melanoma and carcinomas of breast, cervix, larynx, nasopharynx and colon, as well as human fibroblasts and mammary cells, were tested using a sensitive enzyme-linked immunoassay. The presence of glycophorin-like epitopes were demonstrated, in varying concentrations, on all cells tested. These epitropes were found to be localized on the cell membranes by indirect immunofluorescence.

Antibodies, Monoclonal↗
PubMed1983

Radioimmunoassay of a glycoprotein associated with malignancy.

A glycoprotein associated with malignancy was purified from the 0.6M perchloric acid-soluble fraction of serum obtained from cancer patients. The purified glycoprotein contained sialic acid, which was responsible for binding to wheat-germ agglutinin-Sepharose. Gel electrophoresis showed one band with an apparent Mr of 50 000-55 000, and the isoelectric point was 4.4 +/- 0.1. The glycoprotein could be distinguished from carcinoembryonic antigen and alpha-fetoprotein. Iodination of this material with chloramine-T permitted development of a radioimmunoassay.

Glycoproteins↗
PubMed1983

Radioimmunoassay of a cancer-related glycoprotein. Circulating levels.

Circulating levels of (a) tumor-related glycoprotein(s) were determined by radioimmunoassay for a variety of patients and controls, and correlated with sialic acid concentration. Levels were highest in patients with metastatic disease and progressively declined to those with localized disease receiving therapy. Values for normal, adjuvant, and cured patients were significantly lower. Sialic acid concentrations correlated best for the metastatic group but not for the normals.

Female↗
PubMed1983

Clones from cultured, B16 mouse-melanoma cells resistant to wheat-germ agglutinin and with altered production of mucin-type glycoproteins.

Several clones resistant to wheat-germ-agglutinin toxicity were isolated from B16 mouse-melanoma cells. The resistance may be explained in part by fewer binding sites for the agglutinin on the variant lines; the total, cellular sialic acid content appeared somewhat reduced. Analysis of cell glycoproteins indicated a decreased content of sialic acid in one glycoconjugate that binds to wheat-germ agglutinin and has O-linked oligosaccharides.

Animals↗
PubMed1983

Mucin and fat emboli in mucinous carcinomas. Cause of hemorrhagic cerebral infarcts.

A patient with a mucin-producing carcinoma of the breast died after three weeks of progressive neurologic deterioration. At autopsy, numerous small hemorrhagic cerebral infarcts of varying ages were found. The infarcts were primarily located in arterial boundary zones of cerebral and cerebellar hemispheres. They were associated with numerous mucin and fat emboli. In any unexplained cerebral infarct in patients with mucin-producing carcinoma, mucin and fat emboli should be considered and searched for.

Adenocarcinoma, Mucinous↗
PubMed1982

Isolation, purification, and properties of respiratory mucus glycoproteins.

The major glycoprotein from human tracheobronchial secretions and from primary explant cultures of human tracheal epithelium has been purified to apparent homogeneity. Mucin was solubilized in buffer and fractionated on Sepharose CL-4B, followed by CsBr density gradient centrifugation of the void volume fraction. High- and low-density fractions were obtained in ratios ranging from 2:1 to 5:1. The high-density (1.46) fraction appeared homogeneous by exclusion chromatography and recentrifugation in CsBr and had an amino acid composition characteristic of a mucin-type structure (threonine, serine, proline, glycine, and alanine comprise two-thirds of the amino acid residues). The carbohydrate, which is nearly 80% by weight, was O-glycosidically linked via GalNAc, sulfated (5.4% by weight), and contained fucose, galactose, glucosamine, galactosamine, and sialic acid. The low-density fraction had an amino acid composition distinct from that of the high-density fraction (threonine, serine, proline, glycine, and alanine comprise 51% of the amino acid residues) and a lower sulfate content. The size distribution of the saccharides in the low-density fraction was similar to that of the high-density fraction; the same sugars were present although the ratios were different. The low-density fraction contained 3 times more noncovalently associated lipid than did the high-density fraction. Several distinct classes of lipids were identified. Neutral lipids (mono-, di-, and triglycerides, cholesterol, and cholesteryl esters) comprised 56% of weight of the total lipid. Glycolipids and phospholipids were also identified. Palmitate (16:0), stearate (18:0), and oleate (18:1) were the major fatty acids in all classes of lipids.

Bronchi↗
PubMed1981

Partial characterization of sialoglycopeptides produced by cultured human melanoma cells and melanocytes.

The sialoglycopeptides produced by HM7 human melanoma and fetal uveal melanocyte cultures grown in the presence of [3H]glucosamine and [35S]sulfate were isolated from the Pronase digests of cells, spent media, and intracellular material. From the melanoma culture, six sialoglycopeptides, accounting for 43% of the total 3H radioactivity in the nondiffusible cell-associated glycopeptides, were purified. A major glycopeptide (GPIb) having an apparent molecular weight in the range 12 000-15 000 showed specific sialic acid dependent to interaction with wheat germ agglutinin (WGA). It was found to contain mainly O-glycosidically linked oligosaccharides having the structure (AcNeu) leads to 0-2[Gal leads to GalNAc]; some N-glycosidically linked saccharides were also present. A second WGA-binding glycopeptide (GPIa) was smaller and less anionic and had a higher proportion of N-glycosidically linked saccharides than GPIb. The normal fetal cultures yielded either no (iris) or markedly reduced (melanocytes) quantities of the WGA-binding glycopeptides. The four WGA-nonbinding sialoglycopeotides purified from melanoma were shown to have complex (N-acetyllactosaminly type) oligosaccharides linked via N-acetylglucosamine to asparagine with either no or insignificant amounts of O-glycosidically linked saccharides. The corresponding glycopeptides from melanocytes were of smaller molecular size and lower anionic charge, reflecting an overall lower degree of glycosylation.

Cell Line↗
PubMed1981

Isolation and partial characterization of a mucin-type glycoprotein from plasma membranes of human melanoma cells.

Plasma membranes were isolated from HM7 melanoma cells grown in the presence of [3H]glucosamine and Na2(35)SO4 or [3H]mannose and [14C]glucosamine. The labeled glycoconjugates were solubilized with 0.6 M lithium diiodosalicylate/0.5% Triton X-100. Fractionation of glycoconjugates by repeated chromatography on columns of Sepharose CL-6B and DEAE-Sepharose and by affinity chromatography on WGA-Sepharose yielded three radiochemically homogeneous glycoproteins. One of these having an apparent molecular weight of 100,000 was found to contain clusters of (AcNeu)1 or 2 leads to [Gal leads to GalNAc] linked O-glycosidically to the protein. One other glycoprotein contained both O-glycosidically and N-glycosidically-linked oligosaccharides, and the third contained only N-glycosidically-linked carbohydrates. Preliminary results indicate that the 100,000 molecular weight mucin-type glycoprotein is present in significantly reduced quantitites in cultured human fetal uveal melanocytes. Further, the bulk of the glycoproteins from the melanocytes were of lower molecular size compared to those from the melanoma cells.

Cell Line↗