Search PubMed⌕ Search

Biomedical subjects

P Scudder

Publications and source records attributed to P Scudder.

32 records · Page 2Linked to original sources
PubMed1984

Blood group-active carbohydrate chains on the receptor for epidermal growth factor of A431 cells.

The antigens expressed on the carbohydrate chains of the receptor for epidermal growth factor of A431 cells were studied by immunoblotting with monoclonal antibodies. Blood group A and the Type 1 based blood group ALeb and Lea antigens were detected as well as antigens associated with unsubstituted, monofucosylated and difucosylated Type 2 blood group chains. The Lea and the difucosylated Type 2 antigen activities were abolished by treating the blotted receptor with endo-beta-galactosidase, indicating that they are expressed on backbone structures of poly-lacto/neolacto type. (The term 'poly-lacto/neolacto' is used here to describe oligosaccharide backbone structures consisting of repeating Type 1, Gal beta 1-3GlcNAc (lacto) or Type 2, Gal beta 1-4GlcNAc (neolacto) sequences.) The glycosidic linkage of oligosaccharides to protein was investigated using Pronase digests of the receptor biosynthetically labelled with [3H]glucosamine or [3H]fucose. The oligosaccharides were alkali-resistant, consistent with N- rather than O-glycosidically linked chains. A proportion of [3H]fucose-labelled glycopeptides was susceptible to endo-beta-galactosidase, confirming the immunoblotting experiment using antibodies against the Lea and the difucosylated Type 2 antigenic determinants. Oligosaccharides were released from the [3H]fucose- and [3H]-glucosamine-labelled glycopeptides by hydrazinolysis. Chromatography of the oligosaccharides on Bio-Gel P6 and Concanavalin A columns indicated a spectrum of oligosaccharides which include those of high mannose type labelled with [3H]glucosamine, and a mixture of oligosaccharides labelled with [3H]fucose and [3H]glucosamine of bi- and multiantennary complex types of which a subpopulation is susceptible to digestion with endo-beta-galactosidase.

ABO Blood-Group System↗
PubMed1984

Further studies of the specificities of monoclonal anti-i and anti-I antibodies using chemically synthesized, linear oligosaccharides of the poly-N-acetyllactosamine series.

The I- and i-antigen activities of chemically synthesized, linear oligosaccharides of the neolacto series containing one, two or three N-acetyllactosamine (Gal beta 1----4GlcNAc) units have been tested by inhibition of binding of five anti-i and eight anti-I monoclonal antibodies to radioiodinated I- and i-active glycoproteins. The inhibitory activities of the milk oligosaccharides lacto-N-neotetraose (Gal beta 1----4GlcNAc beta 1----3Gal beta 1----4Glc) and lacto-N-tetraose (Gal beta 1----3GlcNAc beta 1----3Gal beta 1----4Glc) have also been determined. The results clearly show that: (a) the determinants that best fit the combining sites of anti-i antibodies are at least hexasaccharides of the neolacto series, (b) linear tetra- and hexasaccharides of the neolacto series can strongly inhibit the binding of anti-I antibodies of group 2 which are known to be primarily directed at the repeating Gal beta 1----4GlcNAc beta 1----3 domains of branched neolacto sequences, (c) the beta- but not the alpha-methyl anomer of the glycoside Gal beta 1----4GlcNAc beta 1-O-Me inhibits the binding of anti-I antibodies of group 1 which recognise the branch point sequence Gal beta 1----4GlcNAc beta 1----6-, (d) the reactivity of the beta-methylglycoside is impaired if the sequence is further elongated as in Gal beta 1----4GlcNAc beta 1----3Gal beta 1----4GlcNAc beta-O-Me, and (e) lacto-N-tetraose has no inhibitory activity with any of the anti-i or anti-I antibodies tested.

Amino Sugars↗
PubMed1983

High-molecular-weight glycoproteins are the major carriers of the carbohydrate differentiation antigens I, i and SSEA-1 of mouse teratocarcinoma cells.

The carriers of the carbohydrate differentiation antigens I, i and SSEA-1 were investigated in embryonal carcinoma cell lines of mouse and differentiated cell lines derived from them. Glycoproteins were studied by immunostaining ('Western blotting') of total cell lysates and immunoprecipitation from lysates of galactose oxidase/NaB3H4-labelled cells; glycolipids were investigated by immunostaining of thin layer chromatograms. The antigenic activities detected by immunofluorescence of cell smears were reflected in the antigenicities of high-molecular-weight glycoproteins. These were polydisperse and markedly susceptible to digestion with endo-beta-galactosidase. Only the I antigen was detected on minor glycolipids. These observations indicate that glycoproteins rather than glycolipids are the major carriers of carbohydrate differentiation antigens I, i and SSEA-1 in the teratocarcinoma cell lines.

Animals↗
PubMed1983

Isolation and characterization of an endo-beta-galactosidase from Bacteroides fragilis.

Six strains of Bacteroides fragilis were examined and all found to produce endo-beta-galactosidase, an enzyme that hydrolyses internal beta-galactosidic linkages of oligosaccharides belonging to the poly-N-acetyl-lactosamine series, with the common structure GlcNAc beta 1 leads to 3Gal beta 1 leads to 4GlcNAc/Glc. The enzyme was produced without the addition of an inducer such as keratan sulphate. It was purified 7000-fold from the culture supernatant and obtained with a yield 4-10-fold greater than from sources described previously. The specificity of the enzyme towards bovine corneal keratan sulphate, milk oligosaccharides and the glycolipids lacto-N-neotetraosylceramide and lacto-N-tetraosylceramide closely resembled that of the endo-beta-galactosidase isolated from Escherichia freundii. A novel observation was that both enzymes hydrolysed the type 2 sequence, Gal beta 1 leads to 4GlcNAc beta 1 leads to 3Gal beta 1 leads to 4Glc, at about twice the rate of the type 1 isomer, Gal beta 1 leads to 3GlcNAc beta 1 leads to 3Gal beta 1 leads to 4Glc. Because of the ease of purification of the enzyme and high yield in the absence of contaminating glycosidases and proteinases, Bacteroides fragilis is a valuable source of endo-beta-galactosidase for the structural analysis of carbohydrate chains.

Bacteroides fragilis↗
PubMed1983

Evidence for the occurrence of O-glycosidically linked oligosaccharides of poly-N-acetyllactosamine type on the human leucocyte common antigen.

High molecular weight glycoproteins of human B and T lymphocytes known as leucocyte common antigen or T200 have been shown to carry O- and N-glycosidically linked, sialylated, carbohydrate chains. The O-linked chains are polydisperse and those of B rather than T cell type are highly susceptible to degradation by endo-beta-galactosidase. These differences among lymphocytes that are functionally distinct raise the possibility that the oligosaccharides may contribute to the functions of these differentiation molecules as well as to their electrophoretic diversity.

Antigens↗
PubMed1978

Copper--an index of erosive activity?

Using atomic absorption spectrophotometry the copper content of synovial fluid has been compared in rheumatoid and osteoarthrotic synovial fluids. Synovial fluid caeruloplasmin has been determined by single radial immunodiffusion. Both are significantly increased in the rheumatoid group. Serum copper, similarly estimated, shows a trend to greater elevation with increasing degree of rheumatoid erosion as assessed radiologically.

Arthritis, Rheumatoid↗
PubMed1976

Large-scale purification and characterization of dihydrofolate reductase from a methotrexate-resistant strain of Lactobacillus casei.

Dihydrofolate reductase has been purified from a methotrexate-resistant strain of Lactobacillus casei NCB 6375. By careful attention to growth conditions, up to 2.5 g of enzyme is obtained from a 400 litre culture. The purification procedure, involving poly-ethyleneimine treatment, DEAE-cellulose chromatography and affinity chromatography on methotrexate-aminohexyl-Sepharose, operates on the gram scale, with overall yields of 50-60%. Elution of the affinity column by reverse (upward) flow was used, as it led to recovery of the enzyme in a much smaller volume. The enzyme obtained appears to be more than 98% pure, as judged by gel electrophoresis, isoelectric focusing, and gel filtration. It has a mol.wt. of approx. 17900 and a turnover number of 4s-1 (50mM-triethanolamine/400mM-KCl, pH 7.2, 25 degrees C) with dihydrofolate and NADPH as substrates. The turnover number for folate is 0.02s-1. Michaelis constants for a variety of substrates have been measured by using a new fluorimetric assay (0.36 muM-dihydrofolate; 0.78 muM-NADPH), and binding constants determined by using the quenching of protein fluorescence (dihydrofolate, 2.25 X 10(6)M-1; NADPH, greater than 10(8)M-1). The pH/activity profile shows a single maximum at pH 7.3; at this pH, marked activation by 0.5M-NaCl is observed.

Amino Acids↗
PubMed1976

The relationship between erythrocyte superoxide dismutase activity and erythrocyte copper levels in normal subjects and in patients with rheumatoid arthritis.

A quantitative assay for erythrocyte superoxide dismutase activity using the xanthine-xanthine oxidase-nitro blue tetrazolium system which is applicable to clinical material is described. The in-batch precision of the method is 3.5% and the between-batch precision is 8.8%. Employing this assay, erthrocyte superoxide dismutase activities were measured in 50 normal subjects and in 50 patients with rheumatoid arthritis. There was no significant correlatiion between superoxide dismutase activity and erthrocyte copper concentration. Erythrocyte copper was lower in female rheumatoid patients than in normals. This difference was not accompanied by a difference in superoxide dismutase activity.

Adult↗
PubMed1975

Urinary copper excretion in rheumatoid arthritis.

The pattern of urinary copper excretion in relation to urine osmolality (as shown by series of aliquots of urine) was studied in rheumatoid patients and in control groups. Rheumatoid patients showed an abnormal copper excretion pattern compared with nonrheumatoid subjects. This was not a direct function of the raised serum copper in rheumatoid disease. Measurements based on 24-hour series of aliquots of urine (as distinct from total pooled 24-hour collections) have been shown to be a useful and sensitive method for studying copper excretion patterns.

Adult↗