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Biomedical subjects

P W Kent

Publications and source records attributed to P W Kent.

At least 37 records · Page 2Linked to original sources

Glucosamine synthetase activity of the colonic mucosa in ulcerative colitis and Crohn's disease.

Glucosamine synthetase is the first enzyme in glycoprotein biosynthesis, catalysing the formation of glucosamine-6-phosphate, from which N-acetylglucosamine is formed. The levels of this enzyme in normal human colonic mucosa (in colectomy specimens and rectal biopsies) were found to be 13-8 +/- 4-0 micron mol glucosamine synthesised/h/g wet wt. In the colonic mucosa in ulcerative colitis and Crohn's colitis the enzyme level was diminished when there was loss of epithelial cells in the mucosa, although not when there was just loss of goblet cells. In patients recovering from an acute attack of ulcerative colitis, the enzyme levels rose to a peak above the normal range, an effect which did not occur in patients who did not recover promptly. This recovery peak may be related to the synthesis of gastrointestinal mucus, or immunoglobulin, or the secretory component of IgA, all of which contain large amounts of N-acetylglucosamine.

Carbohydrate Epimerases↗

Glucosamine synthetase activity of the colonic mucosa in membranous colitis.

Glucosamine synthetase, the first enzyme in glycoprotein synthesis, has been measured in serial rectal biopsies in four patients with membranous colitis. In two of the patients the levels of the enzyme were very high initially and in the other two patients the enzyme levels rose to a peak above the normal range after a delay of up to 10 days. These high levels may be related to the mucus hypersecretion which is a feature of membranous colitis but it seems more likely that they represent the healing of the mucosa.

Aged↗

Inhibition of glucosamine synthesis by salicylates, hydrocortisone and two non-ulcerogenic drugs.

The in vitro inhibition of the glucosamine synthetase activity of rat gastric mucosal homogenates by sodium salicylate and phenylbutazone has been previously reported and has been adduced as a possible mechanism for the ulcerogenic effect of these drugs. This inhibition has been confirmed in human gastric and colonic mucosal homogenates and it is also shown by acetylsalicylic acid and by hydrocortisone hemisuccinate. However, paracetamol and gentamicin, neither of which is known to be ulcerogenic, also inhibited the enzyme to a similar degree to the ulcergenic drugs. This refutes glucosamine synthetase inhibition as the mechanism of the ulcerogenic action of anti-inflammatory drugs.

Acetaminophen↗

Structure and metabolism of glycoproteins and glycosaminoglycans secreted by organ cultures of rabbit trachea.

1. When cultured in medium 199 in an atmosphere of O2+CO2 (95:5) rabbit tracheal explants retained their viability for up to 21 days. 2. The explants secreted into the culture medium three electrophoretically separable components which were eluted in the non-retarded fraction from Sephadex G-200. 3. Digestion with papain and fractionation with a LiCl gradient on DEAE-cellulose resulted in the separation of these components, which were identified as a sialic acid-rich glycoprotein of epithelial origin, and chondroitin sulphate and hyaluronic acid from sub-epithelial cartilage and connective tissue. 4. Incorporation of radioactive precursors ( D-[U-14-C]glucose, D-[1-14-C]glucosamine, D-[1-14-C]galactose and Na2-35SO4) into these secreted macromolecules was indicative of their active biosynthesis by the tracheal tissue.

Animals↗