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Biomedical subjects

H J Allen

Publications and source records attributed to H J Allen.

51 records · Page 3Linked to original sources
PubMed1978

Incorporation of 6-thioguanosine and 4-thiouridine into RNA. Application to isolation of newly synthesised RNA by affinity chromatography.

Isolation of newly synthesised RNA can be achieved by treatment of cells in culture with 6-thioguanosine or 4-thiouridine followed by separation of thiol-containing RNA by affinity chromatography on mercurated cellulose columns. After short periods of treatment with 6-thioguanosine the proportion of RNA retained on mercurated cellulose is the same for both poly(A)-containing and poly(A)-free RNA, indicating similar incorporation of the drug into mRNA and rRNA. However, after longer periods of exposure, the cytotoxic effect of 6-thioguanosine results in diminished incorporation of radioactive uridine into RNA and of radioactive leucine into protein; this suggests that synthesis of both RNA and protein are impaired. On the other hand, even after long exposure to high concentrations of 4-thiouridine, the syntheses of RNA and protein are not significantly affected. Proteins synthesised after treatment of cells with 6-thioguanosine are less stable than proteins synthesised after treatment of cells with 4-thiouridine.

Animals↗
PubMed1977

A simple procedure for the isolation of L-fucose-binding lectins from Ulex europaeus and Lotus tetragonolobus.

L-Fucose-binding lectins from Ulex europeaus and Lotus tetragonolobus were isolated by affinity chromatography on columns of L-fucose-Sepharose 6B. L-Fucose was coupled to Sepharose 6B after divinyl sulfone-activation of the gel to give an affinity adsorbent capable of binding more than 1.2 mg of Ulex lextin/ml of gel, which could then be eluted with 0.1M or 0.05M L-fucose. Analysis of the isolated lectins by hemagglutination assay, by gel filtration, and polyacrylamide disc-electrophoresis revealed the presence of isolectins, or aggregated species, or both. The apparent mol. wt. of the major lectin fraction from Lotus was 35000 when determined on Sephadex G-200 or Ultrogel AcA 34. In contrast, the apparent mol. wt. of the major lectin fraction from Ulex was 68 000 when chromatographed on Sephadex G-200 and 45 000 when chromatographed on Ultrogel AcA 34. The yields of lectins were 4.5 mg/100 g of Ulex seeds and 394 mg/100 g of Lotus seeds.

ABO Blood-Group System↗
PubMed1977

A comparison of the binding specificities of lectins from Ulex europaeus and Lotus tetragonolobus.

The L-fucose-binding lectins present in the seeds of Ulex europaeus and Lotus tetragonolobus have been isolated by affinity chromatography. The binding specificities of the lectins were compared by hemagglutination inhibition analysis. The lectins behaved similarly with respect to a variety of synthetic saccharides. D-Fucose derivatives were inactive as inhibitors. In general, the alpha -L-fucopyranosyl derivatives were better inhibitors than the beta-L-fucopyranosyl derivatives. Aromatic aglycones increased the inhibitory activity of the saccharides with p-nitrophenyl-alpha-L-fucopyranoside being one of the best inhibitors. The major difference between the two lectins was the observation that the Ulex lectin required higher concentrations of saccharides to bring about complete inhibition of hemagglutination than did the Lotus lectin.

ABO Blood-Group System↗
PubMed1976

Isolation and partial characterization of a lectin from Vicia faba.

A lectin present in the broad bean, Vicia faba, was isolated by affinity chromatography on Sephadex G-150. The active lectin had a molecular weight of 50 000. The lectin contained about 3% neutral sugar and it contained two different subunits. The subunits had molecular weights of 17 300 and 14 300. The lectin was mitogenic to human peripheral lymphocytes with some reduction in activity upon acetylation. The lectin competed with pea lectin for binding to murine tumor cells. Binding to tumor cells was inhibited by methyl-alpha-D-mannoside but not by D-galactose; binding was not influenced by the presence or absence of Ca2+, Mn2+ or ethylenediaminetetraacetate.

Amino Acids↗
PubMed1976

Studies on 6C3HED murine ascites tumor cell receptors for mannosyl-binding lectins.

We have investigated the receptor site activity present on 6C3HED tumor cells for concanavalin A, fava, lentil and pea lectins. The binding of the tritiated lectins to the tumor cells was inhibited by methyl-alpha-D-mannoside but not by D-galactose. The number of binding sites for the lectins was 3.5-10(6)/cell for concanavalin A, 3.3-10(6)/cell for fava, 3.6-10(6)/cell for lentil and 4.8-10(6)/cell for pea. The apparent association constants were 3.6 and 1.3 muM-1 for concanavalin A, 3.9 muM-1 for fava, 4.2 muM-1 for lentil and 4.6 and 0.6 muM-1 for pea. Competitive inhibition studies showed that lentil was a good inhibitor of pea binding; concanavalin A was a poor inhibitor of pea binding; and fava was a better inhibitor than concanavalin A but not as good as lentil. Reciprocal inhibition experiments indicated that concanavalin A and pea may bind to different receptors as well as to common receptors. This was also indicated by the observation that trypsin or protease treatment of the cells decreased the binding of pea lectin by 20-40 percent whereas concanavalin A binding was unaffected.

Animals↗
PubMed1976

The isolation of lectins on acid-treated agarose.

The ability of several D-galactose and N-acetyl-D-galactosamine-binding lectins to bind to Sepharose was investigated. Lectins from soybean, Wistaria floribunda, Bauhinia purpurea alba, and Sophora japonica could be isolated by affinity chromatography on acid-treated Sepharose 6B. These lectins would not bind to untreated Sepharose 2B, 4B, and 6B. The binding of B. purpurea alba and S. japonica was temperature-dependent. The S. japonica lectin would bind only at high pH. Ricinus communis toxin also showed a temperature-dependence of binding; acid-treated Sepharose 6B was a better affinity support for the toxin than was untreated Sepharose 4B Lectins from lima bean, Dolichos biflorus, and kidney-bean phytohemagglutinin did not bind to Sepharose under any of the conditions studied.

Binding Sites↗
PubMed1975

Lymphocyte response to autologous tumor antigen(s) and phytohemagglutinin in ovarian cancer patients.

Peripheral blood lymphocytes from 11 patients with ovarian carcinoma were incubated several times with autologous tumor extract as well as phytohemagglutinin (PHA) at different concentrations. Lymphocytes from 10 normal, healthy, age-matched females were also studied similarly. Tritiated thymidine incorporation into DNA of transformed lymphocytes was measured. No significant response was obtained with lymphocytes from ovarian cancer patients or normal individuals in the presence of tumor extracts. Of 6 tumor extracts tested, 5 did not have any cytotoxic effect on autologous or on homologous normal healthy lymphocytes. Hence, with this test system employed, no evidence for a cell-mediated immunity to autologous tumor in ovarian cancer patients was observed. PHA, on the other hand, induced vigorous blastogenic response in several ovarian cancer patient's lymphocytes, as well as in all normal healthy lymphocytes, indicating no inherent defect in the T-lymphocyte system of ovarian cancer patients. Only 2 of the patients, when tested for delayed hypersensitivity reaction against a battery of recall antigens and keyhole limpet hematocyanin, were completely anergic. None of the patients responded when skin tested with their own tumor extracts.

Antigens, Neoplasm↗
PubMed1974

Chemical characterization of the isolated cell surface of Amoeba.

The cell surface has been isolated from uninucleate, freshwater, phagocytic amoebae by a new procedure. Several criteria were employed to demonstrate purity of the cell surface fraction. All morphological components of the tripartite surface were present in the isolated surface and the weight of the isolated surface was quantitatively accounted for by the components analyzed. Chemical analyses showed the presence of lipid, protein, and carbohydrate. Mannose was the predominant neutral sugar. Analyses for three different strains of Amoeba were similar. Phosphate was found to be the major anionic group in the cell surface material. Sulfate, uronic acid, sialic acid, muramic acid, and nonamidated glutamic acid and aspartic acid were absent. Evidence is presented suggesting that the phosphate is associated with an unidentified nonreducing polyol.

Acid Phosphatase↗