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D Waldron-Edward

Publications and source records attributed to D Waldron-Edward.

At least 19 recordsLinked to original sources
PubMed1993

Clones of T cells discriminate between native and deglycosylated forms of MHC class II antigen in allostimulation.

The aim of this study was to clarify the role of the oligosaccharide side chains of MHC Class II antigens in allostimulation. The approach was to cleave the oligosaccharides from protein by subjecting plasma membranes (PM) of the Daudi cell line to chemical deglycosylation yielding deglycosylated (dgl) proteins and a supernatant fraction containing plasma membrane oligosaccharides (dgl sup). MHC Class II antigens affinity purified from the native and the dgl PM were inserted into the plasma membrane of peripheral blood leukocytes (PBL) used as stimulators in a mixed leukocyte reaction (MLR). Cells used as stimulators and as responders were from the same donor. Both native and to a lesser extent the dgl antigen could elicit a proliferative as well as a cytolytic (CML) response. A comparable reduction in the CML reaction was also obtained when native antigen was used to elicit effector cells, but the target was stripped of N-linked oligosaccharides by pretreatment with tunicamycin (TM). Five clones of responding cells raised against the native antigen were studied. Two gave proliferative reactions of equal magnitude to native and to dgl antigen alike, while three responded only to the native form. These three clones did not lyse TM-treated target cells. Inhibition experiments of CML were performed with either the dgl sup containing Daudi PM oligosaccharides or with an anti MHC-Class II MoAb. CML reactivity of the three clones which responded to native antigen was blocked by the dgl sup but not by the anti-MHC antibody. Conversely, the reaction of the two clones reactive to both forms of antigen was only inhibited by the anti-MHC antibody using intact or TM-treated targets. Accordingly, in terms of the latter set of clones oligosaccharide side chains of MHC may not be required for allostimulation. Data obtained with the set of three clones suggest that oligosaccharides could act as target of cytotoxic T cells.

Cell Line↗
PubMed1984

Incorporation of radioactive proline and fucose in gastric mucosal biopsies. Correlation with histological findings.

Human gastric mucosal biopsies incorporate in vitro radioactive proline and fucose into macromolecular glycoproteins (mucin). Differences were found between the incorporation pattern of antral and fundic mucosae according to their pathology, confirmed by histology. Antral mucosae with abnormal histology showed a significantly higher incorporation of proline than normal samples. Fucose incorporation was also increased. Similar results were found with fundic biopsies. The ratio of total fucose to total proline incorporated into mucin secreted during incubation also increased significantly in these samples. Biochemical analyses on the other hand showed no significant change. The results suggest a breakdown in the processing, storage and secretory processes of mucin-type glycoproteins in pathological mucosae, but not in their biosynthesis. The mucosal samples could be classified as A or B types according to their proline and fucose incorporation: A mucosae have a lower proline incorporation than B mucosae (greater than 380 cpm/micrograms DNA for the antrum and greater than 200 cpm/micrograms DNA for the fundus). These results confirm the possibility of studying abnormal mucus secretion using gastric biopsy samples.

Adult↗
PubMed1980

Isolation and characterization of human and canine gastric mucosal glycoproteins and their degradation by proteases and acid hydrolases.

High molecular weight glycoproteins were isolated and purified from canine antral and fundic mucosal tissue by means of non-degrading techniques. The results disclosed the advantage of urea extraction technique over the culture method in isolating the native glycoproteins. The glycoproteins were susceptible to degradation by protease, thus yielding low molecular weight glycopeptides. Chemical analysis of these glycopeptides and their parent macromolecules revealed that the oligosaccharide residues are attached to threonine, serine and proline residues of the protein chains. Similarly, high molecular weight glycoproteins isolated from human gastric gel mucin showed the same characteristics of canine gastric glycoproteins. Canine fundic glycoprotein or glycopeptide released their prosthetic carbohydrate groups under the lytic effect of fundic acid hydrolases.

Animals↗
PubMed1979

Quantitative evaluation of the in vitro biosynthesis of gastric mucus glycoproteins. Standardization of the methodology.

For the evaluation of a normal or pathological function of gastric mucosa, a reproducible method for the estimation of the biosynthesis of mucus glycoproteins appears to be necessary. Rat gastric mucosal scrapings incorporate in vitro several labeled compounds such as 14C-U-D-glucose, 35SO4, 14C-I-L-fucose and L-G-3H-proline in glycoproteins similar to those synthetized in vivo by native mucosa. The aim of our present work is to describe in detail the procedure we use and to show its reproducibility in 9 separate experiments. Secreted glycoproteins (fraction II) and intracellular glycoproteins (fraction III) obtained during a 4 hours in vitro incubation of rat gastric mucosal scrapings at 37 degrees C in standardized conditions were separately studied. The protein and hexose contents, total incorporated radioactivity and specific radioactivity (cpm/mg protein) were determined in these two fractions. The protein content of fraction II from 2 rat gastric mucosal scrapings incubated in 5 ml was 2 mg +/- 0.4 SEM and its hexose was 38.7 mg per 100 mg protein +/- 3.9. Fraction III contained 6.3 mg protein +/- 1.3 and 15.7 mg hexose per 100 mg protein +/- 3.5. About 27% of the total radioactivity incorporated (from 14C-glucose) was in fraction II (+/- 2.6 SEM) and 73% (+/- 2.6 SEM) in the cell bound fraction III. The distribution of total radioactivity was quite similar to that of total proteins : about 25% proteins were in fraction II and 75% in fraction III with a SEM of about 5 to 10% of the average value. If the biosynthetic activity is expressed as specific radioactivity, i.e. the ratio of incorporated radioactivity to mg proteins, the average for both fraction II and fraction III was about 10,000 cpm/mg protein and the standard error of the mean values are +/- 5.2% of the mean for in vitro secreted mucus glycoproteins (fraction II) and 9.1% in the case of intracellular glycoproteins (fraction III). These values can be considered as a satisfactory index of reproducibility of the method of mucosal scrapings if performed as described above.

Animals↗
PubMed1977

The turnover of mucin glycoprotein in the stomach.

It is proposed that the gastric mucosa, during early stages of fasting, accumulates secreted mucin on the luminal surface of the tissue. The accumulated mucin is subsequently released from its adherent state, on precipitation by freshly secreted acid from the stimulated parietal cells, or, as an alternate mechanism, simply by the passage of ingested food. The gastric mucosa on stimulation by ulcerogenic aspirin, on the other hand, responds immediately to the insult by rapid shedding of its adherent mucin, then, within 5 minutes by an almost complete shut-down of respiration and biosynthesis, not only of glycoproteins but also of proteins and nucleic acids. However, oxygen consumption and biosynthesis quickly revive, in an endeavour to restore the mucosal tissue which has survived, with the result that the turnover of intracellular contents is augmented very much more than its normal rapid rate, illustrated in the gastric epithelial cell by Bennett in 1971 and in the non-secreting duodenal columnar cell by Bennett and Leblond (1970). 14C-Fucose was found in the Golgi apparatus, 2 minutes after injection into the animal, while within 20 minutes it had reached the surface membranes before extrusion.

Animals↗
PubMed1977

Acid hydrolases. Assay of activity and latency in the varied mixed cell populations of canine gastric mucosa.

The specific enzymic properties, membrane or particle binding capacities, and the total activities of certain acid hydrolases, including cathepsin D, acid phosphatase, arylsulfatase, and five acid glycosidases have been compared in normal canine antral and fundic mucosae and in liver. The two major regions of the gastric mucosa, whose cell populations are comparable in type but have very distinct functions, also differ in many properties of their lysosomal enzymes. These differences necessitate several major modification in their method of assay. Using optimal conditions, the activities of most of these enzymes were found to differ: levels in the antrum, in spite of its high water and mucin-glycoprotein content, were significantly greater, suggesting that the high lysosomal hydrolytic activity may be associated with the rapid autophagic processes of normal turnover of its surface epithelial and mucous neck cells. Lysosomal membrane stability or latency is also greater in the antrum; this may account, in part at least, for antral resistance to erosions brought about by stress.

Animals↗
PubMed1977

Effect of bile on lysosomal stability in the mucosa of the canine gastric antrum.

The bound and free acid hydrolases from bile and bile- then acid-treated canine antral mucosa were compared with control tissue, using explants held in a series of Lucite chambers. Normal levels of activity of bound mucosal enzymes decreased as a result of bile acid insult, but "free" activity in the cytosol increased markedly. Organelle membrane stability was "tested" by submitting isolated particulate matter containing lysosomes, to hypoosmotic shock and to mechanical stress. Release of cathepsin D, only, was observed after bile treatment in vivo. Bile, followed by acid, however, damaged organelle integrity causing release or "leakage" of seven acid hydrolases.

Animals↗
PubMed1976

Establishment of the integrity of lysosomes in a glycoprotein-rich matrix. Distribution pattern of seven lysosomal enzymes in gastric mucosa.

Gel-forming mucosal glycoproteins strongly interfere with standard methods of cell fractionation. Thus, acid hydrolase-bound particles imbedded in the gel, sediment on centrifugation, in the nuclear fraction of homogenates of canine antral mucosa. These particles can be cleared by direct solubilization of the gel; however, the viscosity of the solution obtained prevents sedimentation of some of the latent hydrolases, even at very high speeds. The use of a new step-wise scheme of centrifugation and dilution successfully isolates lysosomal particles containing acid hydrolases from mucin-rich mucosa. All of the enzymes investigated, including acid phosphatase, cathepsin D, alpha- and beta-galactosidase, beta-B-acetylhexosaminidases, but with the exception of alpha-fucosidase, were found to be particle bound, exhibiting high degrees of latency. However, active mucosal particles are polydisperase in size and density, sedimenting under different centrifugal forces.

Acetylglucosaminidase↗
PubMed1975

Biosynthesis of gastric mucins. In vitro incorporation of radioactive glucose.

An in vitro model for the study of the mechanism of gastric-glycoprotein (mucin) biosynthesis is described. Gastric mucosa scrapings were incubated in Eagle's minimum medium with U-14C-glucose. Linear incorporation-kinetics were observed during 4 hours. U-14-C-glucose was incorporated into soluble and cell bound glycoproteins. In the acid hydrolysate of soluble and cell bound fractions all the amino acids separated by high voltage electrophoresis and all the carbohydrates separated by thin layer chromatography contained appreciable radioactivity showing the active conversion of the added radioactive glucose to all the amino acid and carbohydrate precursors used by the gastric cells for the biosynthesis of macromolecular glycoprotens. The carbohydrate/protein ratio of the excreted glycoproteins increases steadily during the 4h incubation period suggesting that the chemical composition of the excreted mucins changes during this period. The cell bound glycoprotein fraction retains a constant composition during the 4th incubation period. The high fucose to hexose ratio of the soluble (excreted) glycoproteins suggests that they are probably identical to the gastric mucins isolated from native gastric preparation. This model is therefore considered a valid one for the study of the regulation of the biosynthesis of gastric mucins as well as for the study of drug action.

Amino Acids↗
PubMed1975

Effect of aspirin on ionic movement and acid hydrolase activity of explants of canine antral and duodenal mucosae.

Lucite chambers, applied to antral and proximal duodenal mucosae with blood supply intact, were used to compare ionic flux and the total, labilized activity of several acid hydrolases including cathepsin D, alpha and beta-galactosidase, beta-N-acetyglucosaminidase, arylsulfatase, and acid phosphatase. Insorption of H+ ion by the antrum is increased by the application of aspirin-acid-salt solution, which also stimulates acid hydrolase activity; acute erosions develop very rapidly. On the other hand, H+ ion is much more rapidly removed from chambers applied to the duodenal mucosa, isolated by the chamber from bile and pancreatic secretions. The same aspirin-acid-salt solution reduces net H+ ion loss from the duodenal chamber, depresses levels of the acid hydrolases, and no ulcers develop.

Acetylglucosaminidase↗
PubMed1972

[Gastric mucin].

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Aspirin↗
PubMed1971

Increased prothrombin time and metabolic changes with high serum aluminum levels following long-term exposure to Bayer-process alumina.

Serum aluminum levels twice to three times those in controls were found in 30 of 36 workers in a factory in an atmosphere of alumina dust. Inorganic phosphate and total alkaline phosphatase levels were within normal range, with no clinical evidence of phosphate depletion syndrome. Serum intestinal alkaline phosphatase, acid phosphatase and adenosine triphosphate levels were significantly reduced in the group with high levels of aluminum. The finding that the mean prothrombin time was significantly prolonged is of particular interest with respect to beneficial antithrombogenic effect.

Adenosine Triphosphate↗