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Biomedical subjects

A G Cooper

Publications and source records attributed to A G Cooper.

At least 37 records · Page 2Linked to original sources
PubMed1976

Demonstration of an idiotypic antigen on a monoclonal cold agglutinin and on its isolated heavy and light chains.

A potent anti-idiotype serum produced in a rabbit immunized with the isolated heavy chains of an IgM cold agglutinin "Col" was rendered specific by solid-state adsorptions. The anit-Col idiotype was shown to bind specifically to both isolated Col heavy (mu) and light (kappa) chains as well as to intact Col IgM by three methods: (i) reversal of anti-idiotype inhibition of Col cold agglutinin in an automated hemagglutination-inhibition assay system; (ii) adsorption of the anti-idiotype by affinity gels consisting of Col IgM, mu, or kappa chains covalently coupled to Sepharose 2B; (iii) binding of Col IgM and its isolated chains by an anti-idiotype affinity gel. Fragments of Col light chain lacking constant region determinants but still capable of inhibiting anti-idiotype were produced by limited pepsin digestion of the light chains. The finding of shared idiotypic determinants on isolated heavy and light chains of a monoclonal antibody suggests that these chains share a common sequence in a hypervariable region. As an extension of the gene insertion theory of Wu and Kabat, we postulate that genes coding for hypervariable regions may be available for insertion into the DNA for both heavy and light chains.

Agglutinins↗
PubMed1975

Anitroxide-sterol derivative potently modifies cholesterol biosynthesis by normal and neoplastic guinea pig lymphocytes.

Leukemic guinea pig lymphocytes (L2C) synthesise cholesterol in vitro at a forty-fold greater rate than normal cells. Equilibration (18 h) with lecithin or lecithin-cholesterol liposomes, respectively, enhances or suppresses sterol manufacture by normal lymphocytes but does not influence sterol production by L2C cells. In contrast, greater than 5-10(9) molecules/cell of a nitroxide-derivative of androstane, (17 beta-hydroxy-4',4'-dimethylspiro [5 alpha-androstan-3,2'-oxazolidin]-3'-yloxyl), commonly used as a membrane spin-probe, drastically inhibit sterol roduction by both normal and leukemic cells (maximum within 2 H). At less than 5-10(9) molecules/cell, this sterol stimulates cholesterol synthesis. 25-Hydroxycholesterol at low concentrations also stimulates sterol manufacture, whereas high concentrations are also inhibitory in both cell types.

Acetates↗
PubMed1975

Evidence that the major cell suface glycoprotein of the TA3-Ha carcinoma contains the Vicia graminea receptor sites.

The Vicia graminea lectin receptor of the nonstrain-specific TA3-Ha mammary carcinoma ascites cell of the strain A mouse was shown to be predominantly or exclusively on a large mucin-type surface glycoprotein. TA3-Ha cells adsorbed the lectin in amounts equivalent to 5-9 mg of this glycoprotein/10-9 cells, which was 100-400 times greater than by the strain-specific TA3-St cell, employed as a control. Release of sialic acid by incubation with neuraminidase increased the adsorptivity of the TA3-Ha cell three to fourfold and of the TA3-St cell six- to ten fold. Proteolysis of TA3-Ha cells released into the supernatant solutions approximately the same amount of inhibitory activity, equivalent to approximately 5 mg of the glycoprotein and only 10 per cent of the original adsorptivity remained on the cells. By contrast, TA3-St cells released no detectable inhibitory activity into the medium when subjected to similar proteolysis, even after neuraminidase treatment. Upon fractionation of released material on gel columns, high-molecular weight material and activity were found in the same fractions, but purified samples differed significantly in specific activity and carbohydrate composition. Heterogeneity in the carbohydrate moieties of the macromolecules was further demonstrated by incubation of these samples with neuraminidase, which enhanced their inhibitory activities from two- to tenfold.

Animals↗
PubMed1975

Reversible loss in suspension culture of a major cell-surface glycoprotein of the TA3-Ha mouse tumor.

A major cell-surface glycoprotein of the TA3-Ha ascites mammary adenocarcinoma diminished during transfer from ascites growth to cell growth in suspension culture. A sensitive, hemagglutination-inhibition assay that used a lectin from Vicia graminea seeds indicated approximately a 50% loss after 7-10 days of culture and a 90% loss after 2 months. These findings were corroborated by carbohydrate and amino acid analysis with gas-liquid chromatography of trypsin glycopeptides released from the cell surface. Repassage of the cultured cells in vivo caused the reappearance of the surface glycoprotein.

Adenocarcinoma↗
PubMed1974

In vivo release of glycoprotein I from the Ha subline of TA3 murine tumor into ascites fluid and serum.

Previous studies have demonstrated that a unique glycoprotein can be cleaved by trypsin from the plasma membrane of the Ha, but not the St, subline of the TA(3) murine mammary adenocarcinoma. Using an automated quantitative method for measurement of trypsincleaved fragments (glycoprotein fraction I) by inhibition of Vicia graminea lectin hemagglutination, we find evidence that glycoprotein fraction I-like molecules appear in the ascites fluid and serum of the Ha-bearing, but not the St-bearing, syngeneic mice. These molecules were shown by gel filtration to be larger than the trypsincleaved glycoprotein fraction I but have a carbohydrate composition very similar to glycoprotein fraction I. It is likely that these ascites and serum glycoproteins have been released in vivo from the membranes of the viable Ha tumor cells. In view of the ability of the Ha, but not the St, cells to grow in allogeneic recipients, it is possible that these circulating membrane-derived molecules may be playing a blocking role in the immune response to the tumor.

Animals↗