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Biomedical subjects

J T Lamont

Publications and source records attributed to J T Lamont.

24 records · Page 2Linked to original sources
PubMed1983

Cysteamine and prostaglandin F2 beta stimulate rat gastric mucin release.

Gastric mucin glycoproteins form an adherent gel over the surface epithelium that is thought to protect the stomach against chemical and physical damage. The purpose of this study was to measure the release of mucin glycoproteins from rat stomach after treatment with cysteamine and prostaglandin F2 beta, two structurally unrelated drugs that have been shown to protect the stomach against the noxious effects of alcohol and other damaging agents. Gastric mucin was separated into soluble (washout) and insoluble (adherent) phases before colorimetric quantitation of total mucin, protein-bound hexose, and sialic acid. Cysteamine produced a dose-dependent increase in release of soluble and gel mucin. Prostaglandin F2 beta caused a dose-dependent release of hexose-containing mucin but had no effect on sialic acid-containing glycoproteins. Sepharose 4B chromatography of both the soluble and adherent mucus revealed that greater than 90% was a high molecular weight glycoprotein fraction. N-Ethylmaleimide, a known inhibitor of cytoprotection by cysteamine, had no effect on mucin secretion. Similarly, indomethacin inhibited mucin secretion by cysteamine but did not significantly influence cytoprotection. Thus the secretion of mucin by cytoprotective agents is unlikely by itself to explain the ability of the stomach to resist chemical or physical damage.

Animals↗
PubMed1982

Diarrhea we can treat: antibiotic-associated colitis.

C. difficile, a gram-positive anaerobic bacillus, has emerged in the past five years as a common cause of hospital-acquired diarrhea. The organism usually gains entry to the host during or after antibiotic treatment, which presumably alters the normal barrier function of the colonic microflora. The organism produces a cytotoxin that can be identified in stool samples by its ability to alter the cellular morphology of tissue culture cells. Infection with C. difficile produces a spectrum of diseases ranging from mild diarrhea to fulminating colitis. An important bedside clue is the presence of pseudomembranes in the rectum or sigmoid at proctosigmoidoscopy. The disease may also occur in patients with chronic inflammatory bowel disease where it may be confused with a relapse of the underlying disease. Treatment with vancomycin is effective, but 10% to 15% of patients may experience relapse. The major mode of transmission appears to be environmental acquisition rather than person-to-person spread.

Anti-Bacterial Agents↗
PubMed1980

Synthesis and secretion of colonic glycoproteins: evidence for shedding in vivo of low molecular weight membrane components.

In vivo glycoprotein synthesis and secretion was studied in rat colonic epithelial cells using precursor labelling with radiolabelled glucosamine. Sepharose 4B gel filtration of radiolabelled glycoproteins obtained from isolated colonic epithelial cells revealed two major fractions: (1) high molecular weight mucus in the excluded fraction and (2) lower molecular weight glycoproteins in the included volume. These glycoproteins were further fractionated by affinity chromatography on concanavalin A-Sepharose. The low molecular weight [3H]glucosamine-labelled glycoproteins contained a major subfraction which specifically adhered to concanavalin A, and could be eluted with 0.2 M alpha-methylmannoside. Fractionation of the concanavalin A-reactive glycoproteins on Sephadex G-100 revealed a major peak with a molecular weight of 15 000. In contrast, high molecular weight mucus glycoprotein did not adhere appreciably to concanavalin A-Sepharose. Perfusion experiments indicated that colonic secretions contained both mucus and concanavalin A-reactive glycoproteins. The major concanavalin A-reactive glycoprotein in the colonic perfusate was not derived from serum, but was released directly from the colonic membrane into the lumen.

Animals↗
PubMed1974

Cell surface galactosyltransferase and lectin agglutination of thymus and spleen lymphocytes.

Lectin agglutination and cell surface galactosyltransferase (EC 2.4.1.67; 1-O-alpha-D-galactosyl-myo-inositol:raffinose galactosyltransferase) enzyme activity have been studied with thymus and spleen lymphocytes of neonatal rats. Thymus lymphocytes were more agglutinable by concanavalin A than by wheat germ agglutinin, whereas spleen lymphocytes were more agglutinable by wheat germ agglutinin than by concanavalin A. Thymus lymphocytes, but not spleen lymphocytes, of neonatal rats could be blast transformed by concanavalin A. Cell surface galactosyltransferase activity was present on both types of lymphocytes, but was greatly increased on thymus cells after blast transformation. The differences in lectin agglutination suggest a difference in the surface membranes of thymus and spleen lymphocytes. The increase in cell surface galactosyltransferase activity with blast transformation of thymus lymphocytes may be related to the exteriorization of the Golgi apparatus into the plasma membrane.

Agglutination↗