Biomedical subjects

A Slomiany

Publications and source records attributed to A Slomiany.

At least 217 records · Page 12Linked to original sources

PubMed1990

Characterization of gastric mucosal prostaglandin E2 receptor.

1. The binding characteristics of gastric mucosal prostaglandin (PG) E2 (PGE2) receptor were investigated using mucosal cell membranes from rat stomach. The binding was found to be dependent upon PGE2 and membrane protein concentration, the time of incubation and the pH of the mixture, being highest at pH 3.0. 2. Scatchard analysis of the binding data revealed a curvilinear plot with high affinity binding (Kd = 2 nM; Bmax = 0.106 pmol/mg protein) and low affinity binding (Kd = 319 nM; Bmax = 2.262 pmol/mg protein) sites. 3. Competitive displacement study indicated that the receptor was specific for PGs of the E series, as PGF2 alpha and 6-keto-PGF1 alpha failed to displace the PGE2. 4. The study is the first report to provide biochemical parameters of specific PGE receptors in rat gastric mucosa.

Animals↗

PubMed1990

Participation of phosphoinositides in gastric mucosal protection by colloidal bismuth subcitrate against ethanol-induced injury.

The mechanism of gastric mucosal protection by an antiulcer agent, colloidal bismuth subcitrate (CBS), against ethanol-induced injury was investigated using in vivo and in vitro systems. The experiments in vivo were conducted with groups of rats with and without indomethacin pretreatment, and the animals received either a dose of CBS (100 mg/kg) or a vehicle (saline), followed 30 min later by ethanol. In the in vitro studies, gastric mucosa segments were cultured in the presence of CBS, ethanol, or both. The results of in vivo experiments revealed that in the absence of CBS, ethanol caused extensive gastric hemorrhagic lesions which were significantly reduced following CBS pretreatment and this effect of CBS was not prevented by indomethacin. The data obtained with gastric mucosal culture established that in comparison to the controls, ethanol caused a 27% decrease in mucin synthesis, while mucin synthesis in the presence of CBS increased by 48%. The increase in mucin synthesis evoked by CBS was accompanied by the enhanced metabolism of mucosal phosphoinositides, as reflected by a decrease in PI (15%) and PIP2 (30%), and an increase in IP1 (26%) and IP3 (67%). In contrast, ethanol, which exhibited detrimental effect on mucin synthesis, caused a decrease in PIP (35%), IP2 (47%) and IP3 (38%), and an increase in PIP2 (80%), and IP1 (51%). However, when the mucosal culture was carried out in the presence of both CBS and ethanol, the detrimental changes evoked by ethanol on mucin synthesis were prevented, and the phosphoinositide and inositide phosphate distribution patterns were quite similar to those in the mucosa cultured in the presence of CBS only.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1990

Characterization of the epidermal growth factor receptor in the gastric mucosa.

The effects of epidermal growth factor (EGF), a potent mitogen involved in mucosal protection, are mediated by specific cellular receptors. Here, we present the characteristics and binding properties of EGF receptors in the gastric mucosa. The studies were conducted using cell membranes isolated by subcellular fractionation of rat stomach mucosal scrapings. Specific binding of [125I]-EGF to the membrane preparations was assessed at room temperature for various periods of time and at different pHs. The results showed that the binding was proportional to the incubation time up to 1 h and was not affected by a pH change between 4.0 and 7.0. Scatchard analysis of the binding data infer the presence of 2 binding sites, one of high affinity (Kd = 1.34 nM, Bmax = 34 fmol/mg protein) and the other of low affinity (Kd = 484 nM, Bmax = 2.29 pmol/mg protein). Cross-linking experiments using disuccinimidyl suberate to link the [125I]-EGF to gastric membranes followed by polyacrylamide gel electrophoresis and autoradiography revealed that the major receptor for EGF was a protein of 170 kilodaltons. When the solubilized membranes were subjected to wheat germ agglutinin affinity chromatography, the purified material was found to act as substrate for EGF-stimulated phosphorylation. The major component which was labeled by the [gamma-32P]-ATP was also found to be a 170-kilodalton protein. The data are the first to provide evidence that the gastric mucosa possesses a functional EGF receptor and describe its binding characteristics.

Animals↗

PubMed1990

Colloidal bismuth subcitrate inhibits peptic degradation of gastric mucus and epidermal growth factor in vitro.

The effect of an antiulcer drug, colloidal bismuth subcitrate (De-Nol), on the proteolytic activity of pepsin toward gastric mucus and salivary epidermal growth factor was investigated. Samples of pig gastric mucus and mouse epidermal growth factor were incubated with pepsin in the absence and in the presence of De-Nol, and the released alpha-amino acid residues were quantified. Results of analysis revealed that, in the absence of De-Nol, the apparent Km value of pepsin toward gastric mucus was 1.4 g/L and that towards epidermal growth factor 120 microM. Introduction of De-Nol to the incubation mixtures led, in both cases, to reduction of the rates of proteolysis. With gastric mucus, the rate of proteolysis inhibition was proportional to the De-Nol concentration up to 1 x 10(-2) g/L, at which point a 54% reduction in mucus proteolysis occurred, whereas, with epidermal growth factor, this concentration of De-Nol caused nearly 52% inhibition in the rate of proteolysis. The apparent Ki value for peptic degradation of gastric mucus in the presence of De-Nol was 2.1 x 10(-4) g/L and that for peptic degradation of epidermal growth factor 1.8 x 10(-2) g/L. The results suggest that among the beneficial effects of colloidal bismuth subcitrate on ulcer healing is its ability to interfere with peptic digestion of the protective gastric mucus coat and of such important bioactive protein as epidermal growth factor.

Animals↗

PubMed1990

Sucralfate protection of gastric mucosa against alcohol-induced injury: a phosphoinositide mediated process.

The mechanism of protection by sucralfate against gastric mucosal injury induced by ethanol was investigated. The experiments in vivo were conducted with groups of rats with and without indomethacin pretreatment, and the animals received sucralfate followed by ethanol. In the in vitro experiments, gastric mucosa was cultured in the presence of sucralfate, ethanol, or both. The in vivo experiments revealed that ethanol caused extensive gastric hemorrhagic lesions which were significantly reduced following sucralfate pretreatment and that this effect of sucralfate was not prevented by indomethacin. The data with gastric mucosal culture demonstrated that ethanol caused a 24% decrease in mucin synthesis, while mucin synthesis in the presence of sucralfate increased by 32%. This increase was accompanied by the enhanced metabolism of mucosal phosphoinositides, as reflected by a 22% decrease in PI, 1,2-fold increase in IP1 and 3.4-fold increase in IP3. In contrast, ethanol, caused 1.5-fold increase in IP1 and PIP2, and 35% decrease in PIP, 47% decrease in IP2 and 38% decrease in IP3. However, when the mucosal culture was carried out in the presence of both sucralfate and ethanol, the detrimental changes evoked by ethanol in mucin synthesis were prevented. The results suggest that the mucosal protective action of sucralfate involves the metabolism of phosphoinositide-derived messenger molecules.

Animals↗

PubMed1989

Physico-chemical characteristics of mucus glycoproteins and lipids of the human oral mucosal mucus coat in relation to caries susceptibility.

Mucus coat was isolated from oral epithelial surfaces of caries-resistant and caries-susceptible subjects, analysed for content and composition of lipids and mucus glycoproteins, and evaluated for physico-chemical characteristics. The mucus coat from caries-resistant subjects had a protein content similar to that of the caries-susceptible group but a higher content of carbohydrate and a lower content of lipids and covalently bound fatty acid. The carbohydrate component was mainly mucus glycoprotein, which accounted for 28.4% of the dry weight of caries-resistant mucus and 25.3% of caries-susceptible mucus. By chromatographic analysis on Bio-Gel A-50, both types of preparations had high (Mr approximately 2000 kdalton) and low (Mr approximately 300 kdalton) molecular-weight mucus glycoproteins. In the caries-susceptible mucus coat these two glycoproteins were in similar proportions, whereas the low molecular-weight glycoprotein predominated in caries-resistant mucus. In both preparations, the high molecular-weight glycoprotein was characterized by a high content of carbohydrates, associated lipids and covalently bound fatty acids, whereas the low molecular-weight glycoprotein was richer in protein and contained lesser amounts of associated and covalently bound lipids. Although the low molecular-weight glycoprotein showed only minor compositional differences with caries status, the high molecular-weight glycoprotein of the caries-resistant group had a 2.5 times lower content of covalently bound fatty acid, a 1.3 times lower content of associated lipids and contained 1.2 times more sulphate and sialic acid then that of the caries-susceptible group.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1989

Enzymatic sulfation of mucus glycoprotein in rat submandibular salivary gland.

1. The enzymic activity which catalyzes transfer of sulfate ester group from 3'-phosphoadenosine-5'-phosphosulfate to mucus glycoprotein was found associated with Golgi-rich membrane fraction of rat submandibular salivary gland. 2. Optimum enzyme activity was obtained with 0.5% Triton X-100, 4 mM MgCl2 and 25 mM NaF at a pH of 6.8 using desulfated submandibular salivary mucus glycoprotein. The apparent Km of the enzyme for mucus glycoprotein was 11.1 mg/ml. 3. Alkaline borohydride reductive cleavage of the synthesized 35S-labeled glycoprotein led to the liberation of the label into reduced oligosaccharides. A 75.4% of the label was found incorporated in four oligosaccharides. These were identified in order of abundance as sulfated penta-, tri-, hepta- and nonsaccharides. 4. Based on the results of chemical and enzymatic analyses of the intact and desulfated compounds the pentasaccharide was characterized as SO3H----GlcNAc beta----Gal beta----GlcNAc(NeuAc alpha----)GalNAc-ol and the trisaccharide as SO3H----GlcNAc beta----Gal beta----GalNAc-ol.

Animals↗

PubMed1989

Lipolytic activity of Campylobacter pylori: effect of sofalcone.

The lipolytic activity of Campylobacter pylori capable of gastric mucosal lipid degradation was investigated. The colonies of bacteria, cultured from antral mucosal biopsy specimens of patients undergoing endoscopy, were washed with saline and passed through a sterilization filter; the filtrate was examined for lipase and phospholipase A activities, using glycerol trioleate and dipalmitoyl phosphatidylcholine as substrates. The obtained results revealed that both enzymes are present in the C. pylori filtrate. The enzymes exhibited optimal activity at 37 degrees C and the pH range of 7.0-7.4. The major product of the triglyceride degradation was glycerol monoleate, while lysophosphatidylcholine resulted from the degradation of phosphatidylcholine. The lipase activity of the C. pylori filtrate was inhibited by an antiulcer drug, sofalcone, which at a concentration of 200 micrograms/ml caused a 43% reduction in the triglyceride hydrolysis. The sofalcone, however, showed only marginal, if any, inhibitory activity toward C. pylori phospholipase A. The results suggest that C. pylori infection may be detrimental to the integrity of gastric mucosal lipids.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed1989

Nature of the enhancement of the protective qualities of gastric mucus by sucralfate.

The effects of intragastric administration of an antiulcer drug, sucralfate, on the content, composition and physical properties of the mucus component of gastric mucosal barrier were investigated. The experiments were conducted with two groups of rats in which one group received twice daily for five consecutive days a dose of 100 mg sucralfate, while the control group received daily doses of saline. The animals were sacrificed 16 h after the last dose, their stomachs dissected and the mucosa subjected to measurements of the adherent mucus gel dimension and mucin content, evaluation of its viscosity, H+ retardation capacity and hydrophobicity, and analysis of its components and molecular form distribution of elaborated mucin. The results revealed that sucralfate elicited only a minor (8%) increase in mucus gel dimension, while sulfo- and sialomucin contents of the gel increased by 63 and 81%, respectively. The changes in mucus gel mucin content with sucralfate were accompanied by a slight (9.5%) increase in mucus H+ retardation capacity, 1.9-fold increase in viscosity, and a 60% increase in the gel hydrophobicity. Chemical analyses indicated that the mucus elaborated in the presence of sucralfate exhibited 14% lower protein content and 62% higher content of carbohydrate than that of control, displayed similar levels of total lipids and covalently bound fatty acids, but its neutral lipid content was significantly higher. Furthermore, the gastric mucus of the sucralfate group showed a marked increase in the proportion of the high-molecular-weight form of mucin, while the low-molecular-weight form predominated in the control group. The results indicate that the protective qualities of sucralfate lie mainly in its ability to enhance the gastric mucus gel viscosity, hydrophobicity, content of mucin and its proportion in the high-molecular-weight form.

Animals↗

PubMed1989

Colloidal bismuth subcitrate (De-Nol) inhibits degradation of gastric mucus by Campylobacter pylori protease.

There is increased awareness that infection with Campylobacter pylori could be a major factor in the pathogenesis of gastric disease. Here, we present evidence that the extracellular protease elaborated by this bacteria, which causes degradation of gastric mucus, is inhibited by an antiulcer agent, colloidal bismuth subcitrate (CBS; De-Nol). The study was conducted with C. pylori cultured from antral mucosal biopsy specimens of patients undergoing gastroscopy. The grown colonies of bacteria were washed with saline, filtered through sterilization filter, dialyzed, and lyophilized. The powder was used as the enzyme source for proteolytic activity assay employing pig gastric mucus as substrate. Optimum enzymatic activity was obtained at 37 degrees C and at pH 7.0. The apparent Km of C. pylori protease with gastric mucus was 0.71 g/L. Analyses of the degradation products indicated that the protease caused extensive proteolysis of mucus glycoprotein polymer. Introduction of CBS to the incubation mixtures led to a reduction of the rate of mucus degradation. The rate of proteolysis inhibition was proportional to CBS concentration up to 1 X 10(-1) g/L, at which point a 37% reduction in mucus proteolysis was obtained. The Km value for proteolytic degradation of mucus by C. pylori protease in the presence of CBS was 1.25 g/L. The results suggest that CBS is capable of counter-acting the proteolysis of the protective gastric mucus layer by C. pylori.

Animals↗

PubMed1989

Effect of antiulcer agents on the physicochemical properties of gastric mucus.

Although the mechanism of gastric mucosal protection is multicomponential, the initial brunt of luminal insult falls on the layer of mucus weakening its physicochemical characteristics and is intimately associated with gastric disease. Hence, the agents capable of strengthening the qualities of mucus gel, associated with its protective function, are becoming increasingly popular in peptic ulcer therapy. Evaluation of the efficacy of these types of drugs requires delineation of their direct effect on the mucus layer constituents, from those evoked in the chemical composition of mucus as a result of prolonged drug administration. Studies with mucus layer strengthening agents indicate that such drugs as sucralfate and De-Nol interact tenaciously with the mucus gel and in essence seal the underlying mucosal surface from the noxious luminal contents. These drugs and other new antiulcer agents like sofalcone, geranylgeranylacetone and stable prostaglandin analogs are also capable of enhancing mucus gel viscosity and its hydrogen ion impedance ability. Furthermore, the majority of these drugs exert an inhibitory effect on peptic degradation of gastric mucus, and the colloidal bismuth preparation (De-Nol) is also capable of prolongation of the luminal availability of epidermal growth factor. The data on gastric mucus gel, following prolonged administration, show that these drugs enhance the lipid content of the mucus gel, and increase both the mucus coat dimension and the proportion of the high molecular weight form of its mucin component. These changes result in the improvement of viscoelastic, permselective and hydrophobic properties of gastric mucus. Hence, continuity of the function of mucus layer perimeter of mucosal defense is maintained.

Anti-Ulcer Agents↗

PubMed1989

Campylobacter pylori colonization factor shows specificity for lactosylceramide sulfate and GM3 ganglioside.

The specificity of Campylobacter pylori cell surface lectin, a presumptive colonization factor, was investigated using various sulfated and sialic acid containing glycolipids. C. pylori cells, cultured from human antral mucosal biopsies, were incubated with intact and modified glycolipid preparations and examined for agglutination inhibition of human erythrocytes. Titration data revealed that the inhibitory activity was highest with lactosylceramide sulfate and GM3 ganglioside, while galactosylceramide sulfate GM1, GD1a and GD1b gangliosides were less effective. A strong inhibitory activity towards C. pylori hemagglutin was also observed with an antiulcer agent, sucralfate. The inhibitory effect of both types of glycolipids was abolished by the removal of sialic acid and sulfate ester groups, thus indicating that sulfated and sialic acid containing glycolipids with terminal lactosyl moieties serve as mucosal receptors for colonization of gastric epithelium by C. pylori.

Animals↗

PubMed1989

In vitro sulfation of sublingual salivary gland mucin: structures of 35S-labeled oligosaccharides.

The enzyme which catalyzes the transfer of sulfate ester group from 3'-phosphoadenosine-5'-phosphosulfate to salivary mucus glycoprotein was located in the detergent extract of the Golgi-rich membrane fraction of rat sublingual salivary glands. Alkaline borohydride reductive cleavage of the synthesized 35S-labeled glycoprotein led to the liberation of the label into the reduced acidic oligosaccharide fraction. A 90.3% of the total label was found incorporated in two oligosaccharides. These were identified in order of abundance as sulfated penta- and heptasaccharides. The pentasaccharide was characterized as SO3H,6G1cNAc beta 1,3Ga1 beta 1, 4G1cNAc beta 1,3(NeuAc alpha 2,6)Ga1NAc-01, and the heptasaccharide as SO3H,6G1cNAc beta 1,3Ga1 beta 1,4G1cNAc beta 1,3Ga1 beta 1,4 G1cNAc beta 1,3(NeuAc alpha 2,6)Ga1NAc-01.

Animals↗

PubMed1989

Synthesis and initial processing of gastric apomucin.

The initiation of the processing of apomucin was investigated using mucus glycoprotein synthesizing polysomes from rat gastric epithelial cells. The polysomes were isolated from cells labeled with [3H]palmitic acid and [14C]N-acetylgalactosamine, purified on Helix pomatia-Sepharose affinity column, dissociated to release peptidyl-tRNA, and chromatographed on DEAE-HPLC column to separate peptidyl-tRNA complexes from the free and ribosomal RNA and proteins. The analysis of the HPLC purified peptidyl-tRNA revealed that complexes were labeled with [3H]palmitic acid and [14C]N-acetylgalactosamine. Digestion of the peptidyl-tRNA with RNase released 3H and 14C labeled peptides, while alkaline degradation destroyed the complex and rendered the [3H]palmitic acid extractable with hexane. The treatment of the 3H and 14C labeled peptidyl-tRNA complexes with alpha-N-acetylgalactosaminidase led to the release of radiolabeled N-acetylgalactosamine, whereas alkaline borohydride reduction produced N-acetylgalactosaminitol. The fatty acid residues have been detected in peptidyl-tRNA containing 2,000Da peptides, whereas N-acetylgalactosamine was discernible on 5,000Da peptides.

Acetylgalactosamine↗

PubMed1989

Lipolytic activity of Campylobacter pylori: effect of colloidal bismuth subcitrate (De-Nol)

Infection by Campylobacter pylori appears to play a major role in the etiology of gastric disease, but the nature of impairment evoked by this pathogen in gastric mucosal defense is not well understood. We present here evidence that the extracellular material elaborated by this microorganism exhibits lipolytic activity capable of gastric mucosal lipid degradation. The colonies of bacteria, cultured from antral mucosal biopsy specimens of patients undergoing endoscopy, were washed with saline, passed through a sterilization filter, and the filtrate was examined for lipase and phospholipase activities. By following the degradation of glycerol trioleate and dipalmitoyl phosphatidylcholine, we established the presence of lipase and phospholipase A enzymes. The major product of the triglyceride degradation was glycerol monooleate, while lysophosphatidylcholine resulted from the degradation of phosphatidylcholine. The lipolytic activity of C. pylori filtrate was inhibited by an antiulcer drug, De-Nol, which at 150 micrograms/ml caused a 21% reduction in lipase activity and a 60% reduction in the activity of phospholipase A. The results suggest that De-Nol is capable of preventing degradation of mucosal lipids by C. pylori lipases and, hence, helps to preserve the mucosal integrity.

Anti-Ulcer Agents↗

PubMed1988

Enzymatic sulfation of salivary mucins: structural features of 35S-labeled oligosaccharides.

Sulfotransferase activity catalyzing the transfer of sulfate ester group from 3'-phosphoadenosine-5'-phosphosulfate to salivary mucins was found associated with Golgi-rich membrane fraction of rat submandibular salivary glands. Alkaline borohydride reductive cleavage of the synthesized 35S-labeled glycoprotein led to the liberation of the label into reduced acidic oligosaccharides. Most of the label was found incorporated in four oligosaccharides. These were identified as sulfated tri-, penta-, hepta- and nonasaccharides. The trisaccharide was characterized as SO3H,6GlcNAc beta 1,3Gal beta 1,3GalNac-o1, the pentasaccharide as SO3H,6GlcNAc beta 1,3Gal beta 1,4GlcNAc beta 1,3(NeuAc alpha 2,6) GalNAc-o1 and heptasaccharide as SO3H,6Gal beta 1,4GlcNAc beta 1,6(Fuc alpha 1) 2Gal beta 1,4GlcNAc beta 1,3Gal beta 1,3)GalNAc-o1.

Animals↗

PubMed1988

Sulfation in vitro of mucus glycoprotein by submandibular salivary gland: effects of prostaglandin and acetylsalicylic acid.

Enzymatic sulfation of mucus glycoprotein by rat submandibular salivary gland and the effect of prostaglandin and acetylsalicylic acid on this process were investigated in vitro. The sulfotransferase enzyme which catalyzes the transfer of sulfate ester group from 3'-phosphoadenosine-5'-phosphosulfate to submandibular gland mucus glycoprotein has been located in the detergent extracts of Golgi-rich membrane fraction of the gland. Optimum enzyme activity was obtained at pH 6.8 with 0.5% Triton X-100, 25 mM NaF and 4 mM MgCl2, using the desulfated glycoprotein. The enzyme was also capable of sulfation of the intact mucus glycoprotein, but the acceptor capacity of such glycoprotein was 68% lower. The apparent Km of the submandibular gland sulfotransferase for salivary mucus glycoprotein was 11.1 microM. The 35S-labeled glycoprotein product of the enzyme reaction gave in CsCl density gradient a 35S-labeled peak which coincided with that of the glycoprotein. This glycoprotein upon reductive beta-elimination yielded several acidic 35S-labeled oligosaccharide alditols which accounted for 75% of the 35S-labeled glycoprotein label. Based on the analytical data, the two most abundant oligosaccharides were identified as sulfated tri- and pentasaccharides. The submandibular gland sulfotransferase activity was stimulated by 16,16-dimethyl prostaglandin E2 and inhibited by acetylsalicylic acid. The rate of enhancement of the glycoprotein sulfation was proportional to the concentration of prostaglandin up to 2.10(-5) M, at which point a 31% increase in sulfation was attained. The inhibition of the glycoprotein sulfation by acetylsalicylic acid was proportional to the drug concentration up to 2.5.10(-4) M at which concentration a 48% reduction in the sulfotransferase activity occurred. The apparent Ki value for sulfation of salivary mucus glycoprotein in presence of acetylsalicylic acid was 58.9 microM. The results suggest that prostaglandins may play a role in salivary mucin sulfation and that this process is sensitive to such nonsteroidal anti-inflammatory agents as acetylsalicylic acid.

16,16-Dimethylprostaglandin E2↗

PubMed1988

Prostaglandin effect on the enzymatic sulfation of mucus glycoprotein in gastric mucosa.

The effect of 16,16-dimethyl prostaglandin E2 (DMPGE2) on the sulfation of mucus glycoprotein in gastric mucosa was investigated. The enzymatic activity which catalyzes the transfer of the sulfate ester group from 3'-phosphoadenosine-5'-phosphosulfate to gastric mucus glycoprotein was located in the detergent extracts of Golgi-rich membrane fraction of antral and body mucosa of rat stomach. The sulfotransferase activity of this fraction from body mucosa, however, was 35% higher than that from the antrum. The enzyme exhibited optimum activity at pH 6.8 using 0.5% Triton X-100 and 30 mM NaF. The apparent Km of the enzyme for sulfation of mucus glycoprotein was 10.5 microM, and the sulfate ester was found incorporated into the carbohydrate chains of the glycoprotein. Introduction of DMPGE2 to the reaction mixtures led to an enhancement in the rate of mucus glycoprotein sulfation. The rate of enhancement was proportional to the concentration of DMPGE2 up to 1.0 x 10(-4) M and was of the competitive type, with an apparent Km value of 6.7 microM. Since sulfated mucins play an important role in gastric mucosal defense and the increase in their sulfation occurred at levels of prostaglandin present in gastric mucosa, the observed effect may be of significance to gastric mucosal defense in vivo.

16,16-Dimethylprostaglandin E2↗