Biomedical subjects

A Slomiany

Publications and source records attributed to A Slomiany.

At least 181 records · Page 10Linked to original sources

PubMed1992

Inhibition of gastric mucosal laminin receptor by Helicobacter pylori lipopolysaccharide: effect of ebrotidine.

The effect of lipopolysaccharide from H. pylori, a bacteria implicated in the etiology of gastric disease, on the gastric mucosal laminin-receptor interaction was investigated. The receptor protein, prepared from rat gastric epithelial cell membrane by affinity chromatography on laminin-coupled Sepharose, was radioiodinated, and incorporated into liposomes which exhibited specific affinity towards laminin-coated surface. The binding was inhibited by H. pylori lipopolysaccharide, which caused a maximum inhibition of 96% at 50 micrograms/ml. The inhibitory effect of the lipopolysaccharide was prevented by an antiulcer agent, ebrotidine that evoked essentially complete restoration in binding at 6-8 micrograms/ml. The results demonstrate that H. pylori through its lipopolysaccharide interferes with gastric epithelial cell-laminin binding, and that this disruptive effect could be successfully countered by ebrotidine.

Animals↗

PubMed1992

Tyrosylprotein sulfotransferase activity is increased in human gastric mucosa of alcoholics.

Sulfation plays a major role in the processing of secretory proteins. We report here on tyrosylprotein sulfotransferase activity in human gastric mucosa of normal and alcoholics. The tyrosylprotein sulfotransferase was identified in the Golgi-enriched fraction. In alcoholics, the activity of sulfotransferase was 2- to 3-fold higher than in normals. However, no change in the activity of UDP-glucose-ceramide glucosyltransferase, a marker for Golgi, between alcoholics and normals was observed. The tyrosylprotein sulfotransferase enzyme required Triton X-100, MnCl2 and 5'-AMP, and obtained optimum activity at pH 6.8 in the presence of 0.5% Triton X-100, 20 mM MnCl2, 50 mM NaF, and 2 mM 5'-AMP. The apparent Km for poly-Glu6, Ala3, Tyr1 (EAY; 47,000) was 1.9 x 10(-6) M and for 3'-phosphoadenosine 5'-phosphosulfate (PAPS), 1.4 x 10(-6) M. The results suggest that alcohol abuse causes enhancement in the expression of gastric mucosal tyrosylprotein sulfotransferase activity.

Adult↗

PubMed1992

Effect of Helicobacter pylori lipopolysaccharide on the synthesis of sulfated gastric mucin.

The effect of H. pylori lipopolysaccharide on the synthesis and secretion of sulfated mucus glycoprotein in gastric mucosa was investigated. The lipopolysaccharide, while showing no discernible effect on the apomucin synthesis, exerted a profound inhibitory effect on the process of mucus glycoprotein glycosylation and sulfation, and evoked a rapid (within 15 min) inhibition (65%) in both mucin glycosylation and sulfation at its optimal concentration of 100 micrograms/ml. The data on mucin secretory responses indicated that the added lipopolysaccharide caused a 57% stimulation in sulfated mucin secretion within 15 min followed thereafter by inhibition, which reached a maximum of 32% by 45 min. The high molecular weight mucin form predominated in the initial secretion, while prolonged exposure to the lipopolysaccharide caused a significant increase in the low molecular weight mucin form. The results suggest that H. pylori lipopolysaccharide exerts detrimental effect on mucus glycoprotein sulfation and assembly.

Animals↗

PubMed1992

Synthesis and secretion of gastric sulfomucin in the presence of ebrotidine, a new antiulcer agent.

The effect of a new antiulcer agent, ebrotidine, on the synthesis and secretion of gastric sulfomucin was investigated using mucosal segments incubated in the presence of [3H]proline, [3H]glucosamine and [35S]Na2SO4. The drug, while showing no discernible effect on the apomucin synthesis, evoked a dose-dependent increase in mucin glycosylation and sulfation, which at 100 microM ebrotidine, attained its maximum of 2.4 and 2.7-fold stimulation, respectively. The analysis of mucin secretory responses revealed that ebrotidine caused a concentration-dependent enhancement in sulfomucin secretion which attained its maximum increase of 3.3-fold at 100-120 microM ebrotidine. The sulfomucin elaborated in the presence of ebrotidine exhibited a higher content of a large molecular-weight mucus glycoprotein form, the assembly of which is intimately associated with the sulfation event. The results suggest that the ability of ebrotidine to enhance gastric sulfomucin synthesis and secretion may play an important role in the gastroprotective mechanism of action of this agent.

Animals↗

PubMed1992

Effect of sucralfate on the degradation of human gastric mucus by Helicobacter pylori protease and lipases.

Among the factors implicated in the weakening of mucus perimeter of gastric mucosal defense is Helicobacter pylori, the pathogenic action of which appears to be exerted through the elaborated protease and lipase enzymes. We present evidence that the activities of these enzymes are inhibited by an antiulcer agent, sucralfate. The grown colonies of bacteria were washed with saline, filtered through sterilization filter, and the filtrate used as the enzyme source. In the absence of sucralfate, the H. pylori protease caused extensive degradation of human gastric mucus protein, whereas free fatty acids, glycerol monooleate and lysophatidylcholine, were produced by the action of H. pylori lipase and phospholipase A enzymes. Introduction of sucralfate to the incubation systems led to the reduction in the rate of mucus protein and lipid degradation. The rate of proteolysis inhibition was proportional to sucralfate concentration up to 90 micrograms/ml, at which point a 32.5% reduction in mucus degradation was obtained, whereas the maximum inhibition of lipase (35.5%) and phospholipase A (48%) activities occurred at sucralfate concentration of 200 micrograms/ml. The results demonstrate that sucralfate is capable of counteracting in vitro the mucolytic activity of H. pylori toward human gastric mucus proteins and lipids.

Gastric Mucosa↗

PubMed1992

Inhibition of Helicobacter pylori glycosulfatase activity toward gastric sulfomucin by nitecapone.

A glycosulfatase activity toward gastric sulfomucin was identified in the extracellular material elaborated by H. pylori. The enzyme exhibited maximum activity at pH 5.7 in the presence of Triton X-100 and CaCl2, and displayed on SDS-PAGE an apparent molecular weight of 30kDa. The H. pylori glycosulfatase effectively caused desulfation of N-acetylglucosamine-6-sulfate and galactose-6-sulfate of the carbohydrate chains of mucins, as well as that of glucose-6-sulfate of glyceroglucolipids, but was ineffective towards galactosyl- and lactosylceramide sulfates which contain galactose-3-sulfate. The glycosulfatase activity towards human gastric sulfomucin was affected by an antiulcer agent, nitecapone, which at its optimal concentration (100 micrograms/ml) caused a 61% inhibition. The results show that H. pylori through its glycosulfatase activity causes desulfation of sulfated mucins and glyceroglucolipids of the protective mucus layer, and that nitecapone is able to interfere with this detrimental action.

Anti-Ulcer Agents↗

PubMed1991

Enhancement of the protective qualities of gastric mucus by sucralfate: role of phosphoinositides.

The effects of intragastric administration of sucralfate on the physicochemical properties of gastric mucus, and the mechanism of its protective action against alcohol-induced mucosal injury were investigated using in vivo and in vitro models. The experiments in vivo were conducted with groups of rats receiving a dose of 100 mg sucralfate twice daily for 5 consecutive days. The animals were sacrificed 16 hours after the last dose, their stomachs dissected, and the mucosa subjected to physicochemical measurements. In the in vitro studies, gastric mucosa was cultured in the presence of sucralfate, ethanol, or both. The in vivo results revealed that sucralfate elicited an 8% increase in mucus gel dimension, while its sulfo- and sialomucin content increased by 63% and 81%, respectively. The changes in mucus gel mucin content with sucralfate were accompanied by a 9.5% increase in mucus hydrogen ion (H+) retardation capacity, 1.9-fold increase in viscosity, and a 60% increase in the gel hydrophobicity. The mucus elaborated in the presence of sucralfate exhibited 14% lower protein content and 62% higher content of carbohydrate than that of control, and contained more neutral lipids. Furthermore, the gastric mucus of the sucralfate group showed a marked increase in mucus glycoprotein polymeric form. The data obtained with gastric mucosal culture demonstrated that sucralfate elicited a significant increase in mucin synthesis, which was reflected in the enhanced metabolism of mucosal phosphoinositides. In contrast, ethanol, which exhibited detrimental effects on mucin synthesis, also caused alterations in the phosphoinositide signal pathway. The changes in mucin and phosphoinositide distribution patterns evoked by ethanol were prevented by sucralfate. Our results suggest that the mucosal strengthening action of sucralfate occurs through the stimulation of the metabolism of phosphoinositide-derived messenger molecules.

Animals↗

PubMed1991

Identity of mucin's "118-kDa link protein" with fibronectin fragment.

Human and rat intestinal mucin was purified by equilibrium density gradient centrifugation and Sepharose 2B chromatography according to M. Mantle, D. Mantle, and A. Allen (1981, Biochem. J. 195, 277-285) and analyzed using mucin, DNA, and fibronectin-specific antibodies in dot-blot, ELISA, and Western blotting. The 118-kDa component of the mucins and the 118-kDa fragment of fibronectin from the same source displayed affinity for concanavalin A and immunoreacted with fibronectin antibodies. The amino acid and carbohydrate compositions of the 118-kDa peptide electroeluted by gel electrophoresis of mucin and fibronectin preparations were identical within each pair of glycopeptides and closely resembled the "link protein component" of human and rat intestinal mucin preparations of R. E. F. Fahim, R. D. Specian, G. G. Forstner, and J. F. Forstner (1987, Biochem. J. 243, 631-640) and M. Mantle and G. Stewart (1989, Biochem. J. 259, 631-640). We therefore conclude that the "link protein" claimed to be an integral part of mucus glycoproteins in actuality is the 118-kDa fragment of fibronectin.

Amino Acids↗

PubMed1991

Inhibition of gastric mucosal laminin receptor by Helicobacter pylori lipopolysaccharide.

Laminin receptor was isolated from gastric epithelial cell membrane by the procedure involving membrane solubilization with octylglucoside followed by affinity chromatography on laminin-coupled Sepharose. The receptor protein, eluted from the matrix with cation-free EDTA buffer, yielded on SDS-PAGE a single 67kDa band. After radioiodination, the protein was incorporated into liposomes which displayed specific affinity toward the laminin-coated surface. The binding of liposomal receptor to the laminin-coated surface was inhibited by lipopolysaccharide from H.pylori. The inhibitory effect was proportional to the concentration of lipopolysaccharide up to 50 micrograms/ml at which point a 96% decrease in the receptor binding occurred. It is suggested that a similar process may account for the loss of mucosal integrity in the pathogenesis of H. pylori associated gastric disease.

Animals↗

PubMed1991

Inhibition of bovine gingival laminin receptor by bacterial lipopolysaccharide.

A laminin receptor was isolated from bovine gingival epithelial-cell membrane. After solubilization with octylglucoside, the receptor was subjected to affinity chromatography on laminin-coupled Sepharose and eluted with cation-free EDTA buffer yielding on SDS-PAGE a 67 kDa protein band. After radioiodination, the protein was incorporated into liposomes which displayed specific affinity towards laminin-coated surfaces, as well as to tooth cementum. The binding of receptor protein to cementum was inhibited by lipopolysaccharide from Bacteroides gingivalis. Preincubation of cementum with the lipopolysaccharide decreased the binding of the liposomal laminin-receptor preparation by 35.8%, while a 59.2% decrease in binding occurred when the lipopolysaccharide was preincubated with the receptor, suggesting that the lipopolysaccharide interfered with the laminin binding site on the receptor. The results demonstrate the existence of a specific gingival cell-surface laminin receptor, show that it is capable of binding to cementum, and provide evidence for the disruption of this process by bacterial lipopolysaccharide. This mechanism may account for the loss of gingival attachment in the pathogenesis of periodontal disease.

Affinity Labels↗

PubMed1991

Prostaglandin E2 receptor of rat submandibular salivary glands.

The binding characteristics of the PGE2 receptor were investigated in membrane preparations from these glands. Specific [3H]PGE2 binding was linear as a function of the membrane protein concentration and reached steady state by 40 min of incubation at 37 degrees C under neutral pH. Scatchard analysis of the binding data produced a curvilinear plot with a Kd of 0.18 nM and Bmax of 1.02 fmol/mg protein for the high-affinity binding sites, and a Kd of 181 nM and Bmax of 5.72 pmol/mg protein for the low-affinity binding sites. A competitive displacement study indicated that the receptor was specific for prostaglandins of the E series. The study is the first to demonstrate the presence of the PGE2 receptor in rat submandibular gland and to provide its biochemical features.

Animals↗

PubMed1991

Role of sulphation in post-translational processing of rat salivary mucins.

Segments of rat submandibular salivary gland were incubated in MEM supplemented with 10-800 microM sulphate in the presence of [3H]-glucosamine, [3H]-proline and [35S]-Na2SO4, with 0-8 mM chlorate, an inhibitor of 3'-phosphoadenosine-5'-phosphosulphate formation. Incorporation of glucosamine and sulphate depended upon the sulphate content of the medium and reached a maximum at 400 microM sulphate. The introduction of chlorate into the medium, while having no effect on the protein synthesis as shown by [3H]-proline incorporation, caused, at its optimal concentration of 4 mM, a 90% decrease in mucin sulphation and a 29% drop in mucin glycosylation. At low sulphate content in the medium and in the presence of chlorate the incorporation of sulphate and glucosamine was mainly into the low molecular-weight form of mucin. An increase in sulphate in the medium caused an increase in the high molecular-weight form of mucin and in the extent of sulphation in its carbohydrate chain. This effect of sulphate was, however, inhibited by chlorate. The results suggest that sulphation takes place at an early stage of mucin assembly and that sulphate availability is essential for the formation of the high molecular-weight mucin.

Animals↗

PubMed1991

Impairment by ethanol of prostaglandin production in rat salivary glands.

Sublingual salivary acini and submandibular tissue were incubated in DMEM medium in the presence of various concentrations (0-5%) of ethanol and the content of the three major prostaglandins, PGE2, PGF2 alpha and 6-keto-PGF1 alpha, were determined by radioimmunoassay. In In the sublingual gland, ethanol caused a decrease in PGE2 and PGF2 alpha levels, but had no effect on 6-keto-PGF1 alpha, while all three prostaglandins were affected in the submandibular gland. At 2.5% ethanol, the production of PGF2 alpha and PGE2 in sublingual gland decreased by 10% and reached maximum inhibition at 5% ethanol, at which concentration there was a 20 and 30% decrease in their levels. In submandibular gland, 2.5% ethanol caused a 20% decrease in PGE2, 30% in PGF2 alpha and 50% in 6-keto-PGF1 alpha; 40% inhibition in PGE2, 57% in 6-keto-PGF1 alpha and 65% in PGF2 alpha occurred in the presence of 5% ethanol. These findings suggest that alcohol impairs the function of salivary glands by inhibiting prostaglandin production.

6-Ketoprostaglandin F1 alpha↗

PubMed1991

Identification of laminin receptor in gingival tissue and its interaction with tooth cementum laminin.

1. A gingival epithelial cell surface receptor for laminin was isolated from bovine gingival tissue by affinity chromatography on laminin. 2. The protein bound by the affinity matrix from octylglucoside extracts of gingival membrane preparation eluted from the column with the cation-free buffer containing EDTA, and exhibited a mol. wt of 67 kDa. 3. The 67 kDa protein following radioiodination was incorporated into liposomes, which showed a specific affinity towards laminin-coated surfaces, as well as to the tooth cementum. 4. The results provide for the first time evidence for the existence of a gingival cell surface laminin receptor, and indicate that the maintenance of the cemento-epithelial junction involves the interaction between the cementum laminin and its receptor on gingival epithelium.

Animals↗

PubMed1991

Transglutaminase activity in human colorectal carcinomas of differing metastatic potential.

Transglutaminase (TGA) activity in four human colorectal carcinoma cell lines of differing metastatic potential, and the effects of mild proteolysis on this activity, was investigated. Rank order of metastatic activity measured in nude mice (intrasplenic injection) was found to be LS174T greater than SW620 greater than WiDr greater than SW480. Rank orders of TGA activity were SW480 greater than WiDr greater than SW620 greater than LS174T. Proteolysis of cell lysates increased LS174T TGA activity 42-fold, SW620 2-fold without affecting WiDr or SW480 activity. Hence a negative association exists between metastatic potential and TGA activity in human colorectal carcinoma cells. Furthermore, a positive association exists between proteolytic activation of TGA and metastatic potential.

Animals↗

PubMed1991

Adrenergic and cholinergic regulation of phospholipid release in sublingual salivary gland in vitro.

1. The role of adrenergic and cholinergic mediators in the regulation of salivary phospholipid secretion was investigated using rat sublingual acinar cells maintained in the presence of [3H]choline. 2. The release of [3H]choline containing phospholipids was enhanced by beta-adrenergic agonist, isoproterenol to a greater extent than the cholinergic agonist, pilocarpine. 3. The effect of isoproterenol on phospholipid release was observed even after 5 min and by 30 min a 1.7-fold increase in secretion occurred, whereas pilocarpine evoked 1.2-fold increase by 30 min with no discernible effect in 5 min. The isoproterenol effect was blocked by alprenolol, and an inhibition of pilocarpine effect was observed with atropine. 4. In the absence of mediators, 82% of secreted labeled phospholipids were represented by phosphatidylcholine (PC), 4.3% by lysophosphatidylcholine (LPC) and 12.1% by sphingomyeline (Sph), those secreted in the presence of isoproterenol showed significantly lower (37%) content of LPC, while those secreted in response to pilocarpine were substantially richer in LPC (2.5 times) and Sph (27%), and contained less (17%) PC. 5. The results provide first evidence for the involvement of adrenergic and cholinergic mediators in the regulation of salivary phospholipid secretion.

Alprenolol↗

PubMed1991

Protection against alcohol-induced gastric mucosal injury by nitecapone.

1. The mechanism of gastric mucosal protection by an anticular agent, nitecapone, against injury was investigated in rats with and without indomethacin pretreatment. 2. Animals received intragastrically either a dose of nitecapone or vehicle alone, followed by ethanol given at various intervals up to 5 hr, and their gastric mucosa subjected to histologic and physicochemical assessment. 3. Ethanol caused extensive gastric hemorrhagic lesions which were essentially prevented by nitecapone at doses of 30 mg and higher per kg body weight. The maximal protection was achieved by 1.5 hr which persisted up to 4 hr and was not thwarted by indomethacin. 4. Physicochemical measurements revealed that nitecapone evoked 78% increase in mucus gel dimension, and showed 21% increase in phospholipids, and the content of sulfo-(22%) and sialomucins (72%). This was accompanied by 1.6-fold increase in mucus viscosity, 31% increase in H+ retardation capacity and 2.2-fold increase in hydrophobicity. 5. The results suggest that the gastroprotective action of nitecapone occurs through the enhancement of the physicochemical characteristics of mucus layer.

Animals↗

PubMed1991

Inhibition of gastric mucosal laminin receptor by Helicobacter pylori lipopolysaccharide: effect of nitecapone.

1. A gastric mucosal laminin receptor has been isolated from the epithelial cell membrane by affinity chromatography on Sepharose-bound laminin, and following radioiodination was incorporated into liposomes which displayed specific affinity towards the laminin-coated surface. 2. The binding of liposomal receptor to the laminin-coated surface was inhibited by Helicobacter pylori lipopolysaccharide and reached a maximum value of 96% at 50 micrograms/ml. 3. The inhibitory effect of H. pylori lipopolysaccharide on the receptor-laminin binding was prevented by an antiulcer agent, nitecapone. The effect was concentration dependent and produced a maximum response of 83% at 30 micrograms/ml of drug concentration. 4. The results demonstrate that H. pylori is capable of disrupting gastric mucosal integrity by interfering with epithelial cell-laminin binding, and that an antiucler agent, nitecapone, counteracts this effect.

Animals↗