Biomedical subjects

A Slomiany

Publications and source records attributed to A Slomiany.

At least 163 records · Page 9Linked to original sources

PubMed1992

Cigarette smoking reduces human salivary eicosanoids.

The effect of cigarette smoking on salivary eicosanoid levels was investigated in 10 smoker and 10 non-smoker volunteers. The smokers consumed an average of 20 cigarettes/day for the past 5 years or longer. The smoking status was validated by salivary cotinine level. Eicosanoids were extracted from saliva with ethanol, and the radioimmunoassay was performed to determine the concentrations of four major eicosanoids, i.e. prostaglandin E2 (PGE2), PGF2 alpha, 6-sulphidopeptide-containing leukotrienes (LTs) and 12-hydroxyeicosatetraenoic acid (12-HETE). The levels of PGE2, PGF2 alpha, and LTs were significantly lower in the saliva of smokers as compared to that of the non-smokers (1.74 +/- 0.32 vs 2.41 +/- 0.64, p = 0.006; 0.36 +/- 0.12 vs 0.54 +/- 0.18, p = 0.04; 2.24 +/- 0.96 vs 4.92 +/- 1.29, p = 0.006; mean +/- SD, ng/ml saliva). No significant differences were found in the levels of 12-HETE between the two groups. The results suggest that cigarette smoking reduces the concentrations of both the cyclooxygenase and 5-lipoxygenase products in saliva.

Cotinine↗

PubMed1992

Synthesis and macromolecular organization of gastrointestinal mucin: evidence for the origin of mucin "link protein".

Mucus glycoproteins (mucins), the principal determinants of mucus protective qualities and mucosal defense, have been studied extensively to define pathological aberrations in relation to gastrointestinal disease. Recent work from our laboratory provided evidence as to the initial stages of gastrointestinal mucin synthesis, the molecular size of the apomucin, and its macromolecular organization. Using monoclonal antibodies (MAbs) against apomucin (clone 1H7), O-glycosylated with N-acetylgalactosamine apomucin (clone 2B4), and that against carboxyl terminal of the apomucin (clone 3G12), the mucin synthesizing polysomes were isolated and glycosylated peptides ranging in size from 6 to 60 kDa identified. In vitro synthesis in a cell-free system also afforded 60- to 64-kDa products recognized by 1H7 and 3G12 antimucin MAbs. The results obtained provided evidence that the mucin core consists of 60-kDa peptide that at the cotranslational stage is O-glycosylated with N-acetylgalactosamine. Studies on mucin polymer assembly revealed that mucin preparations prepared by equilibrium density gradient centrifugation and Sepharose 2B chromatography are not completely purified and contain DNA and extraneous proteins. The evidence was obtained that so-called mucin "link protein", a 118-kDa glycopeptide, is a N-glycosylated fragment of fibronectin, whereas the supposedly native undergraded mucin isolated by Carlstedt et al. was found to contain mucin-fibronectin-DNA complexes. The general picture that emerged from the studies is that the pure mucin consists of 60 kDa glycosylated peptides only. The carboxyl terminal (8- to 12-kDa fragment) of these peptides is not glycosylated (naked) and is responsible for mucin interaction with fibronectin and other fibronectin-like extracellular matrix proteins. Although the formation of the mucosal coat depends on many other factors and extracellular components, our findings on mucin structure and interaction with the extracellular matrix proteins provide an explanation as to the possible mechanism of mucin adherence to the epithelial surfaces.

Antibodies, Monoclonal↗

PubMed1992

Effects of sofalcone administration on the physicochemical properties of gastric mucus.

The effect of prolonged administration of an antiulcer drug, sofalcone, on the physicochemical properties of gastric mucus was investigated. The experiments were conducted with two groups of rats in which one group received a dose of 100 mg/kg of sofalcone twice daily for three consecutive days, and the control group received daily doses of vehicle. The rats were killed 16 h after the last dose, their stomachs dissected, and the mucosa subjected to physicochemical measurements. The results revealed that sofalcone evoked a 23% increase in mucus gel thickness, and its content of sulfo- and sialomucins increased by 54 and 25%, respectively. These changes in mucus with sofalcone were accompanied by a 16% increase in H+ retardation capacity, twofold increase in viscosity, and a 39% increase in the gel hydrophobicity. The mucus elaborated in the presence of sofalcone exhibited a 10% lower content of protein, 30% higher content of carbohydrate, and 18% higher content of total lipids, which were particularly enriched (20%) in phospholipids and contained 67% more covalently bound fatty acids. Furthermore, the high molecular weight mucus glycoprotein form accounted for about 30% of gel mucin in the control group, whereas its content in mucus gel of animals receiving sofalcone reached 50%. The results indicate that sofalcone enhances the protective qualities of the mucus component of the gastric mucosal barrier and hence strengthens the gastric mucosal integrity.

Animals↗

PubMed1992

Membrane biogenesis in the presence of ethanol.

To investigate the effect of ethanol on the intracellular transport in gastric epithelial cells, the in vitro system, generating transport vesicles which transfer mucus glycoprotein apopeptide (apomucin) from rough endoplasmic reticulum (RER) to Golgi, was assembled. The vesicles, generated from gastric mucous cell RER microsomes and labeled with [3H]palmitic acid, were isolated from the maternal RER and characterized. The electron microscopy revealed that these RER products consisted of 80 to 100 nm smooth membrane vesicles, while the immunochemical analyses showed that they contain apomucin but were devoid of the characteristic integral proteins of the RER membrane. Incubation of apomucin transporting vesicles with Golgi in the presence of UDP-[3H]galactose resulted in the formation of glycosylated mucin and fusion of the vesicles with Golgi. Formation of ER transport vesicles was dependent on the supply of lipid precursors, and the activity of phosphoglyceride and sphingolipid synthesizing enzymes. In the presence of 60 and 120 mM ethanol, the vesicles were formed, but their lipid composition was modified. The results suggest that ethanol-induced membrane alterations are initiated at the early stages of the membrane biogenesis and are first reflected in the lipid composition of the intracellular transport vesicles.

Animals↗

PubMed1992

Identification of tyrosylprotein sulfotransferase in rat gastric mucosa.

An enzyme activity which catalyzes the transfer of the sulfate group from 3'-phosphoadenosine 5'-phosphosulfate (PAPS) to poly-Glu6,Ala3,Tyr1 (EAY; M(r) 47,000) has been demonstrated in the antral and body mucosa of the rat stomach. The distribution of this tyrosylprotein sulfotransferase was similar to that of the Golgi marker enzyme, glycoprotein sulfotransferase, and its activity from body mucosa was 23% higher than that from the antrum. The optimum for tyrosylprotein sulfotransferase activity was obtained at pH 6.8, in the presence of 0.5% Triton X-100, 20 mmol/l MnCl2, 50 mmol/l NaF, 2 mmol/l 5'-AMP, and 1 mmol/l DTT, whereas Ca2+, Mg2+, Cu2+, Zn2+, EDTA, NEM, NaCl and Na2SO4 were inhibitory. The apparent Km of the sulfotransferase for EAY was 1.5 x 10(-6) mol/l and for PAPS 0.75 x 10(-6) mol/l. The enzyme was 28 times less susceptible to 2,6-dichloro-4-nitrophenol inhibition as compared to that required for phenol sulfotransferase inhibition. The tyrosine sulfation by the tyrosylprotein sulfotransferase was independent of the sulfation of carbohydrate residues in mucous glycoproteins and glycolipids, thus indicating that the identified sulfotransferase is specific for sulfation of the tyrosyl residues in the peptide core.

Animals↗

PubMed1992

Transforming growth factor alpha and epidermal growth factor in protection and healing of gastric mucosal injury.

Transforming growth factor alpha (TGF) and epidermal growth factor (EGF) present in the gastric mucosa are polypeptides with similar biologic activity. This study compares the activity of TGF and EGF in the protection against injury by 100% ethanol and stress and in healing of acute gastric ulcerations. TGF and EGF (12.5-100 micrograms/kg-h) infused subcutaneously 30 min before and during ethanol or stress decreased mucosal lesions dose-dependently. The ID50 for ethanol- and stress-induced lesions after TGF were 40 and 70 micrograms/kg-h and after EGF 60 and 100 micrograms/kg-h. TGF and EGF infused subcutaneously into intact rats inhibited gastric acid secretion but did not affect the gastric blood flow or mucosal generation of prostaglandin E2 (PGE2). Both TGF and EGF also significantly enhanced the healing of stress-induced lesions and the restoration of DNA synthesis. Ethanol and stress reduced blood flow in the oxyntic mucosa by 68% and 51%, respectively, and this effect was partially reversed by EGF and TGF. Pretreatment with indomethacin (5 mg/kg intraperitoneally), which reduced mucosal generation of PGE2 by 85%, decreased in part the protection by TGF and EGF against ethanol-induced damage and virtually abolished the protective action of these peptides against stress-induced injury.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗

PubMed1992

Adrenergic and cholinergic regulation of gastric mucus phospholipid secretion.

The influence of adrenergic and cholinergic agonists on phospholipid secretion in gastric mucosal cells maintained in the presence of [3H]choline was investigated. The secretion of [3H]choline phospholipids over a 30-min period averaged 1.98% of the total cellular labeled phospholipids in the absence of any mediator and was enhanced by the beta-adrenergic agonist isoproterenol to a greater extent than by the cholinergic agonist pilocarpine. A 2-fold increase in phospholipid secretion was achieved with isoproterenol, whereas pilocarpine produced a 1.3-fold increase. The stimulatory effect of isoproterenol was inhibited by alprenolol, and that of pilocarpine by atropine. The phospholipids secreted in response to isoproterenol showed a 30% decrease in lysophosphatidylcholine, whereas a 2.1-fold enrichment in this phospholipid occurred with pilocarpine. The results demonstrate the involvement of neural mediators in the regulation of phospholipid secretion in gastric mucus.

Alprenolol↗

PubMed1992

Inhibition of EGF-induced gastric mucosal calcium channel phosphorylation by ebrotidine.

A gastric mucosal calcium channel-epidermal growth factor (EGF) receptor complex was isolated from solubilized epithelial cell membranes by means of a wheat germ agglutinin affinity. The complex, following reconstitution into phosphatidylcholine vesicles, exhibited active 45Ca2+ uptake as evidence by concentration-dependent response to the calcium channel activator BAY K8644, and the calcium channel antagonist PN200-110. The complex on the addition of EGF and ATP showed an increase in tyrosine phosphorylation of both a 55 and a 170kDa protein, while the vesicles containing the phosphorylated complex displayed a 48% greater 45Ca2+ uptake. The phosphorylation process was inhibited by an anti-ulcer agent, ebrotidine, which also interfered with the binding of EGF to calcium channel protein. The results suggest that ebrotidine protects the cellular integrity from calcium imbalance by modulating the EGF-stimulated gastric mucosal calcium channel activation.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗

PubMed1992

Modulation of gastric mucosal calcium channel activity by sucralfate.

A gastric mucosal calcium channel complex was isolated from solubilized epithelial cell membranes by affinity chromatography on wheat germ agglutinin. The complex following reconstitution into phosphatidylcholine vesicles exhibited an active 45Ca2+ uptake and responded to calcium channel activator, BAY K8644, and the antagonist, PN200-110. The uptake of 45Ca2+ was inhibited by an antiulcer agent, sucralfate, which at 100 micrograms/ml evoked maximal inhibitory effect of 52%. The channel complex on epidermal growth factor (EGF) binding in the presence of ATP showed an increase in tyrosine phosphorylation of 55 and 170kDa proteins, and the vesicles containing the phosphorylated channels displayed a 48% greater 45Ca2+ uptake. The phosphorylation process was inhibited by sucralfate, which also interfered with the binding of EGF to calcium channel protein. The results indicate that sucralfate has the ability to protect the cellular integrity from calcium imbalance.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗

PubMed1992

Modulation of gastric mucosal calcium channels activity by platelet-derived growth factor.

A dihydropyridine-sensitive gastric mucosal calcium channels were isolated from the solubilized epithelial cell membranes by affinity chromatography on wheat germ agglutinin. The channels following labeling the calcium antagonist receptor site with [3H]PN200-100 were reconstituted into phospholipid vesicles which exhibited active 45Ca2+ uptake as evidenced by La3+ displacement assays. The uptake of calcium was independent of sodium and potassium gradients indicating the electroneutral nature of the process. The channels responded in a dose dependent manner to dihydropyridine calcium antagonist, PN200-110, which at 0.5 microns exerted maximal inhibitory affect of 66% on 45Ca2+ uptake, while a 52% enhacement in 45Ca2+ uptake occurred with a specific calcium channel activator, BAY K8644. On platelet-derived growth factor (PDGF) binding in the presence of ATP, channel protein showed an increase in tyrosine phosphorylation of 55 and 170 kDa calcium channel proteins. Such phosphorylated channels following reconstitution into vesicles displayed a 78% greater 45Ca2+ uptake. The results demonstrate the importance of PDGF in the regulation of gastric mucosal calcium uptake.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗

PubMed1992

Identification of human salivary protease activity toward mucin: differences with caries.

A protease activity directed toward high molecular weight salivary mucus glycoprotein was identified in the secretion of human submandibular salivary gland. The protease exhibited maximum activity at pH 7.0-7.4, and following ammonium sulfate fractionation yielded an active enzyme at 60% saturation which on SDS-PAGE gave 48 and 53kDa protein bands. The enzyme exhibited serine-protease properties by showing susceptibility to phenyl methyl sulfonyl fluoride, alpha 1-antitrypsin, and egg white and soybean inhibitors. The protease activity in submandibular saliva of caries-resistant subjects was found to be 3.8-fold greater than that in saliva of caries-susceptible individuals, thus suggesting that the enzyme expression may be linked to the resistance to caries.

Adult↗

PubMed1992

Expression of salivary mucin bacterial aggregating activity: difference with caries.

The low and high molecular weight mucin forms were isolated from saliva of individuals with different caries status and assessed for their bacterial aggregating potential towards S. mutans and S. sanguis. The high molecular weight mucin from both groups exhibited similar protein and carbohydrate content, but the level of covalently bound fatty acids was lower in the caries-resistant group. The mucin from caries-resistant group showed only a weak inhibitory potential, while no inhibitory activity was observed with the mucin of caries-susceptible group. The low molecular weight mucins from both groups, while displaying compositional similarities, showed a marked variation in the bacterial aggregating activity, and the titer of the mucin from caries-resistant group was at least 128-fold greater than that of caries-susceptible group. The results demonstrate that the bacterial aggregating epitope of salivary mucins is expressed to a greater extent in caries-resistant individuals, and that this epitope is apparently more accessible to bacteria in the low molecular weight mucin form.

Dental Caries↗

PubMed1992

Effect of GM1-ganglioside on gastric mucosal epidermal growth factor and platelet-derived growth factor receptor expression.

The effect of intragastric administration of GM1-ganglioside on the expression of gastric mucosal epidermal growth factor (EGF) and platelet derived growth factor (PDGF) receptors was investigated. Gastric mucosal cell membranes were isolated from the stomach of groups of rats, one receiving twice daily for 3 consecutive days a dose of 0.25 mg/100g GM1-ganglioside, and the other only vehicle. Binding assays revealed the presence of both types of receptors, activation of which led to the elevation of tyrosine kinase activity as evidenced by a marked increase in membrane protein tyrosine phosphorylation patterns. The specific receptor binding in the control group was 2.47 fmol/mg protein for EGF and 1.46 fmol/mg protein for PDGF, whereas the respective binding values in the GM1-ganglioside treated group increased by 45% and 38%. The results suggest that GM1-ganglioside is capable of enhancement of gastric mucosal EGF and PDGF receptor activities.

Animals↗

PubMed1992

Control of salivary phospholipid content and composition.

The mediation of phospholipid secretion in rat sublingual salivary gland cells maintained in the presence of [3H]choline was investigated. The secretion of [3H]choline-containing phospholipids was enhanced by beta-adrenergic agonist, isoproterenol, to a greater extent than the cholinergic agonist carbachol. A 2.9-fold increase in phospholipid secretion occurred with isoproterenol, while carbachol evoked only about 1.3-fold increase. In contrast to carbachol, the enhanced phospholipid secretion due to isoproterenol was accompanied by an increase in cAMP concentration. The secretion of phospholipids was also stimulated by dibutyryl-cAMP and the protein kinase C activator, phorbol myristate acetate, but not by 4 alpha-phorbol 12, 13-didecanoate which does not activate protein kinase C. Furthermore, the effects of dibutyryl-cAMP and phorbol myristate acetate were additive. The phospholipids secreted in response to isoproterenol exhibited a 52% decrease in lysophosphatidylcholine, while those secreted in response to carbachol showed a 23% lower content of phosphatidylcholine, and were enriched in lysophosphatidylcholine (2.8-fold) and sphingomyelin (1.4-fold). The results suggest that salivary phospholipid secretion remains mainly under beta-adrenergic control, while the phospholipid makeup is under cholinergic regulation.

Animals↗

PubMed1992

Ebrotidine--a new H2-receptor antagonist with mucosal strengthening activity.

The mechanism of gastric mucosal protection by ebrotidine against ethanol-induced mucosal injury was investigated in rats treated intragastrically either with the drug or vehicle. Results of macroscopic assessment revealed that ebrotidine at doses of 50mg and higher/kg body weight effectively prevented mucosal injury, and that the maximal protective effect was achieved by 1h. Physicochemical analysis established that ebrotidine evoked 30% increase in mucus gel dimension, and showed 20% increase in phospholipids, and the content of sulfo- (18%) and sialomucins (21%). This was accompanied by 1.4-fold increase in mucus gel viscosity, 16% increase in H+ retardation capacity, and 65% increase in hydrophobicity. Our data show that ebrotidine is a unique H2-antagonist capable of enhancement of the physicochemical characteristics of gastric mucus.

Animals↗

PubMed1992

Mechanism of Helicobacter pylori pathogenesis: focus on mucus.

Although the clinical data provide increasingly convincing indications that Helicobacter pylori (H. pylori) is a causative factor in gastritis and peptic ulcer, the advances toward the clear understanding of this bacterium's pathogenic action are slow in coming. Having a niche bordering two major perimeters of gastric mucosal defense, H. pylori is capable of exerting detrimental effects on the mucus layer, as well as surface cells of the gastric epithelium. To cause such an effect, the bacteria must first, however, attach to the mucosa. Our findings indicate that this attachment involves specific structures on the epithelial cell surfaces, namely lactosylceramide sulfate and GM3 ganglioside. The analysis of the glycolipid distribution pattern in different regions of human stomach revealed that the antral mucosal content of GM3 and lactosylceramide sulfate are considerably higher than that of the fundus, which may account for the prevalence of H. pylori colonization of the antrum. We have also established that H. pylori causes considerable untoward changes in gastric mucus coat integrity. These changes are reflected in the loss of protective qualities of mucus due to the action of H. pylori-elaborated proteases and lipases. The result of H. pylori protease action is disintegration of the polymeric structure of mucin, whereas the elaborated lipases and phospholipase A2 in particular result in mucus lipid degradation, loss of mucosal surface, hydrophobicity, and lysophospholipid generation. The lytic activity of the resulting lysophospholipids is detrimental not only to mucus gel integrity, but even more so to the cell membrane of gastric epithelium.(ABSTRACT TRUNCATED AT 250 WORDS)

Anti-Ulcer Agents↗

PubMed1992

Glycosulfatase activity of H. pylori toward human gastric mucin: effect of sucralfate.

Colonization of gastric mucosa by Helicobacter pylori, a bacterium implicated in the etiology of gastric disease, involves the cell surface sulfated glycosphingolipid receptors for the attachment. Evidence has also been obtained recently that sulfated mucus glycoproteins have the ability to interfere with this process. Here, we show that H. pylori displays glycosulfatase activity, and report the specificity of this enzyme toward gastric mucosal sulfated glycoproteins and glycolipids. With 35S-labeled human gastric sulfated mucin as substrate, the enzyme activity was identified in the extracellular material elaborated by the bacterium. The glycosulfatase exhibited maximum activity at pH 5.7 in the presence of Triton X-100 and CaCl2, and gave on SDS-PAGE a protein band of 30 kDa. Specificity studies revealed that the enzyme effectively caused desulfation of N-acetylglucosamine-6-sulfate and galactose-6-sulfate present in carbohydrate chains of gastric mucins, as well as that of glucose-6-sulfate, a constituent of mucus glyceroglucolipids. However, the H. pylori glycosulfatase was ineffective toward galactosyl- and lactosylceramide sulfates which serve as receptors for this bacterium attachment and contain the sulfate ester group at C-3 of galactose. The glycosulfatase activity toward human sulfated gastric mucin was inhibited by sucralfate. The inhibitory effect was proportional to the concentration of sucralfate up to 120 micrograms/ml, at which a 78% decrease in mucin desulfation occurred. The results demonstrate that H. pylori, through its glycosulfatase activity, affects the sulfated mucin and glyceroglucolipid content of the protective mucus layer, and that antiucler drug sucralfate is able to counteract the detrimental action of this enzyme.

Gastric Mucins↗

PubMed1992

Synthesis and macromolecular organization of gastrointestinal mucin.

Mucus glycoproteins (mucins), the principal determinants of mucus protective qualities and mucosal defense, are studied extensively to define pathological aberrations in the relation to gastrointestinal disease and to develop the mucous barrier strengthening agents. Recent work from our laboratory provided evidence as to the initial stages of the gastrointestinal mucin synthesis, molecular size of the apomucin, its macromolecular organization and interaction with other elements of gastrointestinal mucus. Using monoclonal antibodies against apomucin (clone 1H7), O-glycosylated with N-acetylgalactosamine apomucin (clone 2B4), and that against carboxyl terminal of the apomucin (clone 3G12), the mucin synthesizing polysomes were isolated and glycosylated peptides ranging in size from 6-60 kDa identified. The in vitro synthesis in the cell-free system also afforded 60-64 kDa products recognized by 1H7 and 3G12 antimucin MAbs. The obtained results provided evidence that the mucin core consists of 60 kDa peptide which at cotranslational stage is O-glycosylated with N-acetylgalactosamine. Studies on mucin polymer assembly revealed that mucin preparations prepared by equilibrium density gradient centrifugation and Sepharose 2B chromatography (Mantle, M., Mantle, D., and Allen, A. (1981) Biochem. J. 195, 277-285) are not completely purified and contain DNA and extraneous proteins. The evidence was obtained that so called mucin "link protein", 118 kDa glycopeptide, is a N-glycosylated fragment of fibronectin, whereas the supposedly native undegraded mucin isolated by Carlstedt et al. (Biochem. J. (1983) 211, 13-22) was found to contain mucin-fibronectin-DNA complexes. The general picture that emerged from the studies is that the pure mucin consists of 60 kDa glycosylated peptides only. The carboxyl terminal (8-12 kDa fragment) of these peptides is not glycosylated (naked) and is responsible for mucin interaction with fibronectin and other fibronectin-like extracellular matrix proteins. While the formation of the mucosal coat depends on many other factors and extracellular components, our findings on mucin structure and interaction with the extracellular matrix proteins provide explanation as to the possible mechanism of mucin adherence to the epithelial surfaces.

Amino Acids↗