Search PubMed⌕ Search

Biomedical subjects

C W Todd

Publications and source records attributed to C W Todd.

At least 55 records · Page 3Linked to original sources
PubMed1977

Gas chromatography of methyl glycosides as their tri-methylsilyl ethers. The methanolysis and re-N-acetylation steps.

Gas chromatographic procedures for the analysis of carbohydrates in glyco-proteins frequently include methanolysis and re-N-acetylation steps. The usual methanolysis conditions were found to result in almost complete conversion of the methanolic HCl into methyl chloride. A neutral solution of methyl chloride in methanol was found capable of releasing fucose, sialic acid, and a portion of the galactose from alpha 1-acid glycoprotein. During the re-N-acetylation of the amino sugars O-acetylation of the alditols commonly employed as internal standards occurs. Addition of the standards after the re-N-acetylation step avoided the problem. The complete procedure for the determination of both neutral and amino sugars has been simplified to involve only one transfer step prior to final gas chromatography.

Acylation↗
PubMed1977

Detection of circulating tumor antigens.

A wide variety of malignancies have associated tumor antigens. Two which have proven useful in the clinical detection and management of cancer are alphafetoprotein (AFP) and the carcinoembryonic antigen (CEA). These materials have been determined both by radioimmunoassay and by a newer technique employing enzymes to replace radioisotopea as markers. The interpretation of these immune assay results and the factors governing the shape of the standard curve are discussed. The advantages of 57Co over 22Na as a volume marker in radioimmunoassay are presented.

Animals↗
PubMed1977

Isolation and immunochemical and chemical characterization of carcinoembryonic antigen-like substances in colon lavages of healthy individuals.

Material with carcinoembryonic antigen (CEA)-like activity, isolated from colon lavages of healthy individuals, has been chemically characterized. The CEA-like activity in these lavages was purified by gel filtration on Sepharose 6B and Sephadex G-200 and by affinity chromatography on concanavalin A linked to Sepharose. The purified material migrated in polyacrylamide-sodium dodecyl sulfate electrophoresis as a single diffuse band with mobility identical with that of tumor CEA. The material with CEA activity from tumor tissue and from normal colon lavages gave lines of identity in double diffusion experiments and had similar inhibition curves with esssentially the same specific activities in a radioimmune assay for tumor CEA. The amino acid and carbohydrate compositions were similar to that observed for CEA tumor preparations. Lysine was the single amino terminus. Methylation analysis demonstrated that the monosaccharide linkages were similar to those in CEA isolated from tumor tissue.

Adult↗
PubMed1976

Methylation analysis of the carbohydrate portion of carcinoembryonic antigen.

The carbohydrate structural units of carcinoembryonic antigen samples isolated from four different tumors were quantitated using gas chromatography-mass spectrometery after methylation and subsequent conversion to their alditol acetates. Different carcinoembryonic antigen preparations showed some quantitative but no qualitative differences in the structural units present. The results indicate that a large portion of the fucose residues in the glycoprotein were linked to N-acetylglucosamine and that most of the branching mannose residues were probably linked to three N-acetylglucosamine residues.

Acetylglucosamine↗
PubMed1976

Purification of carcinoembryonic antigen by removal of contaminating mucopolysaccharides.

The fraction of carcinoembryonic antigen preparations not bound by concanavalin A was studied. A significant portion of this nonbound fraction of low antigenic activity was shown to be mucopolysaccharides by gas chromatography-mass spectrometry, cellulose acetate strip electrophoresis, and depolymerization by bovine testicular hyaluronidase.

Carcinoembryonic Antigen↗
PubMed1976

Physical characterization and structural studies of the carcinoembryonic antigen.

Knowledge of the structure of carcinoembryonic antigen (CEA) is essential if we are to understand the relationship of this molecule to similar, possibly cross-reacting, molecules present in nonmalignant states. Electron microscopy shows that at neutral pH, CEA particles consist of homogeneous, morphologically distinctive, twisted rod-shaped particles, about 9 X 40 nm. The carbohydrate structure of CEA has been studied by periodate oxidation. All the N-acetylneuraminic acid and fucose and a portion of the galactose and mannose were destroyed by the first periodate treatment without altering immunological activity. N-Acetylneuraminic acid was shown to be linked to galactose since its prior removal with neuraminidase led to an equivalent increased destruction of galactose by one treatment with periodate. Significantly, even after 100% of the fucose and N-acetylneuraminic acid, 75% of the galactose, and 50% of the N-acetylglucosamine and mannose were destroyed by serial periodate oxidation (Smith degradation), the remaining portion of the CEA molecule lost no more antigenic activity than did control samples where periodate was omitted. No carbohydrate was lost or destroyed in the control reaction.

Carbohydrates↗
PubMed1975

Structural studies on carcinoembryonic antigen. Periodate oxidation.

Periodate oxidation has been applied to examine the carbohydrate structure of carcinoembryonic antigen (CEA) and the possible role of the carbohydrate residues in its antigenic activity. Sialic acid (N-acetylneuraminic acid) and fucose were completely destroyed, and galactose and mannose were partially destroyed by a single periodate treatment. Serial periodate treatment (Smith degradation) destroyed additional amounts of galactose and mannose as well as significant amounts of N-acetylglucosamine. Prior removal of sialic acid by neuraminidase treatment led to increased destruction of galactose by periodate. Antigenic activity persisted indicating that the residues destroyed played little, if any, part in the antigenicity of CEA. These results yield an initial view of the structural arrangement of the carbohydrate residues in the CEA molecule.

Amino Acids↗
PubMed1975

The chemistry of carcinoembryonic antigen.

The structure of carcinoembryonic antigen is being determined as an approach to greater diagnostic specificity in the radioimmune assay. Examination by combined gas chromatography-mass spectrometry of derivatized saccharides from CEA has given a general outline of its carbohydrate structure. Sialic acid and fucose were completely destroyed, and galactose and mannose were partially destroyed by a single periodate treatment. Serial periodate oxidation (Smith degradation) destroyed additional amounts of galactose and mannose, as well as significant amounts of N-acetylglucosamine. Antigenic activity persisted, indicating that the residues destroyed played little, if any, part in the antigenicity of DEA.

Animals↗
PubMed1975

The binding of carcinoembryonic antigen by antibody and its fragments.

In order to assess the potency of antigenic fragments of carcinoembryonic antigen (CEA) in the radioimmune assay; it is necessary to know whether the high affinity of goat anti-CEA antibody (which makes possible the detection of as little as 10--11M CEA) is due to bivalent binding of the CEA molecule. Immunoglobulin G and the F(ab')2 and Fab fragments derived from it were prepared from an anti-CEA serum and tested for their abioity to bind CEA. Equivalent concentrations of binding sites of the bivalent F(ab)2 and univalent Fab fragments of anti-CEA were identical to the immunoglobulin G fraction in the standard inhibition curve. Fragments of CEA obtained by trypsin digestion produced equivalent inhigition curves when tested with either immunoglobulin G, F(ab')2, or Fab". This, increased avidity due to bivalent binding to a single antigen molecule cannot be invoked to explain the sensitivity observed in the CEA assay. This high sensitivity implicates the protein rather than the carbohydrate as an important part of the antigenic determinant(s) of CEA.

Animals↗