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Biomedical subjects

A Slomiany

Publications and source records attributed to A Slomiany.

At least 271 records · Page 15Linked to original sources
PubMed1986

Effect of sucralfate on the viscosity of gastric mucus and the permeability to hydrogen ion.

The effect of sucralfate on the viscosity of pig gastric mucus and on its ability to retard the diffusion of hydrogen ion was investigated. Using a cone/plate viscometer at shear rates between 1.15 and 230 s-1, it was found that preincubation of mucus with increasing concentrations of sucralfate led to a gradual enhancement of the mucus viscosity. This enhancement in viscosity was proportional to the sucralfate concentration up to 1.0 X 10(-4) M and increased about 18% for each 10-fold increment in its concentration. The permeability measurements, conducted in a specially designed two compartment chamber, revealed that addition of sucralfate to gastric mucus had a profound beneficiary effect on its ability to retard the diffusion of hydrogen ion. In the presence of 1.0 X 10(-6) M sucralfate the permeability of mucus to hydrogen ion decreased by 35%, while the 1.0 X 10(-3) M sucralfate reduced the mucus permeability by 68%. The results show that sucralfate increases the viscosity of gastric mucus and improves its ability to impede the hydrogen ion penetration.

Aluminum↗
PubMed1986

Effect of covalently bound fatty acids and associated lipids on the viscosity of gastric mucus glycoprotein in cystic fibrosis.

The contribution of associated and covalently bound lipids to the viscosity of gastric mucus glycoprotein in healthy and cystic fibrosis (CF) individuals was investigated. While both preparations exhibited similar contents of protein and carbohydrate, the CF glycoprotein contained 1.3 times more associated lipids and 6 times more covalently bound fatty acids. The viscosity of CF mucus glycoprotein was about 1.8 times higher than that of normal glycoprotein. Extraction of associated lipids lead to 3-fold drop in the viscosity of CF glycoprotein and 5-fold drop in the case of normal glycoprotein. Removal of covalently bound fatty acids caused further 1.6-fold reduction in the viscosity of normal mucus glycoprotein and 6-fold in CF glycoprotein. The viscosity of the delipidated and deacylated CF mucus glycoprotein was only about 10% higher than that of the similarly treated normal glycoprotein. The results suggest that the elevated level of covalently bound and associated lipids is responsible for the increased viscosity of CF mucin.

Adolescent↗
PubMed1986

Lysolecithin affects the viscosity, permeability, and peptic susceptibility of gastric mucin.

The effect of lysolecithin and lecithin on gastric mucin viscosity, permeability to hydrogen ion, and degradation by pepsin was investigated. Preincubation with lysolecithin produced a marked decrease in the glycoprotein viscosity. This decrease was concentration-dependent and at 10 mM lysolecithin reached a value of 74%. A 25% increase in mucin viscosity was obtained with 10 mM lecithin. Permeability measurements showed that 10 mM lecithin increased the retardation ability of the glycoprotein to hydrogen ion by 11%, whereas a 12% decrease in the retardation capacity of the glycoprotein was obtained with 10 mM lysolecithin. The results of peptic activity assay indicated that whereas lecithin had no effect on the rate of mucin proteolysis, the lysolecithin exerted significant (75%) stimulatory effect. The results suggest that lysolecithin in the stomach weakens the integrity of the protective mucus layer by promoting peptic degradation, reducing the ability to resist acid penetration, and decreasing viscosity of its mucin component.

Animals↗
PubMed1985

Fatty acid acylation of salivary mucin in rat submandibular glands.

The acylation of salivary mucin with fatty acids and its biosynthesis was investigated by incubating rat submandibular salivary gland cells with [3H]palmitic acid and [3H]proline. The elaborated extracellular and intracellular mucus glycoproteins following delipidation, Bio-Gel P-100 chromatography, and CsCl equilibrium density gradient centrifugation were analyzed for the distribution of the labeled tracers. Both preparations gave single bands at the CsCl density of 1.48, in which carbohydrate peaks coincided with that of the labels. The [3H]palmitic acid in these glycoproteins was susceptible to cleavage by alkali and hydroxylamine, thus indicating the ester nature of the bond. With both intracellular and extracellular glycoproteins deacylation caused the glycoproteins to band in the CsCl gradient at a density of 1.55. The incorporation of both markers into mucus glycoprotein increased steadily with time up to 4 h, at which time about 65% of [3H]palmitate and [3H]proline were found in the extracellular glycoprotein and 35% in the intracellular glycoprotein. The incorporation ratio of proline/palmitate, while showing an increase with incubation time in the extracellular glycoprotein, remained essentially unchanged with time in the intracellular glycoprotein and at 4 h reached respective values of 0.14 and 1.12. The fact that the proline/palmitate incorporation ratio in the intracellular glycoprotein at 1 h of incubation was 22 times higher than in the extracellular and 8 times higher after 4 h suggests that acylation occurs intracellularly and that fatty acids are added after apomucin polypeptide synthesis. As the incorporation of palmitate within the intracellular mucin was greater in the mucus glycoprotein subunit, it would appear that fatty acid acylation of mucin subunits preceeds their assembly into the mucus glycoprotein polymer.

Acylation↗
PubMed1985

Mucus glycoprotein fatty acyltransferase in patients with cystic fibrosis: effect on the glycoprotein viscosity.

The presence of an acyltransferase activity which catalyzes the transfer of palmitic acid from palmitoyl coenzyme A to mucus glycoprotein has been demonstrated in the microsomal fraction of human rectal mucosa. The activity of this enzyme in the mucosa of patients with cystic fibrosis (CF) was found to be 3.5 times higher than that from normal individuals. The CF mucus glycoprotein in comparison to that of normal contained 1.3 times more associated lipids and 6 times more covalently bound fatty acids. The viscosity of the intact CF glycoprotein was 1.8 times higher than that of normal glycoprotein. Extraction of associated lipids led to 3-fold drop in the viscosity of CF glycoprotein and 5-fold drop in the case of normal glycoprotein. Further loss in the viscosity occurred following removal of the covalently bound fatty acids. The viscosity of such modified CF mucus glycoprotein was only about 10% higher than that of similarly treated normal glycoprotein.

Acetyl-CoA C-Acyltransferase↗
PubMed1985

Effect of ethanol on mucus glycoprotein fatty acyltransferase from gastric mucosa.

The enzyme activity that catalyzes the transfer of palmitic acid from palmitoyl coenzyme A to the deacylated intact or deglycosylated gastric mucus glycoprotein was demonstrated in the detergent extracts of the microsomal fraction of antral and body mucosa of the rat stomach. Both types of mucosa exhibited similar acyltransferase activities and acceptor specificities. A 10-14% decrease in the fatty acyltransferase activity was observed with the reduced and S-carboxymethylated mucus glycoprotein, but the proteolytically degraded glycoprotein showed no acceptor capacity. This indicated that the acylation of mucus glycoprotein with fatty acids occurs at its nonglycosylated polypeptide regions and that some of the fatty acids may be linked via thiol esters. Optimum enzyme activity was obtained at pH 7.4 with the detergent Triton X-100, NaF, and dithiothreitol. The apparent Km values for the intact and deglycosylated mucus glycoproteins were 0.45 and 0.89 microM, respectively. The acyltransferase activity of the microsomal enzyme was inhibited by ethanol. With both intact and deglycosylated glycoprotein substrates, the rate of inhibition was proportional to the ethanol concentration up to 0.4 M and was of the competitive type. The K1 values were 0.80 microM for the intact mucus glycoprotein and 1.82 microM for the deglycosylated glycoprotein. Preincubation of the microsomal enzyme with low concentrations of ethanol (up to 0.5 M) did not seem to exert any additional deterrent effect on acyltransferase activity. Higher concentrations of ethanol (1.0 M and above), however, caused substantial reduction in the transferase activity due to denaturation of the enzyme.

Acyltransferases↗
PubMed1985

The synthesis and secretion of gastric mucus glycoprotein by mucosal cells cultured in the presence of ethanol.

The effect of ethanol on the synthesis and secretion of mucus glycoprotein in gastric mucosal cells was investigated. The mucosal cell suspensions were subjected to a short-term (4 h) culture in the presence of 0-1.5 M ethanol, with [3H]proline and [3H]palmitic acid as markers for glycoprotein synthesis and acylation. The synthesized labeled mucus glycoprotein was isolated from the incubation medium (extracellular glycoprotein) and from the mucosal cells (intracellular glycoprotein), and analyzed. Depending upon the ethanol concentration in the cell culture medium, two distinct effects on the synthesis and secretion of mucus glycoprotein were observed. The cells cultured in the presence of 0.02-0.1 M ethanol showed increased ability for the incorporation of [3H]proline and [3H]palmitic acid, and for the secretion of the newly assembled mucus glycoprotein. The synthesis of the glycoprotein increased 18-fold, acylation 5-fold, and secretion 10-fold. The synthesized glycoprotein, however, contained four to five times less of acyl-bound fatty acids. Ethanol at 0.1-1.5 M caused a marked reduction (62-64%) in the mucus glycoprotein synthesis, but the amount of glycoprotein released to the medium remained constant. This indicated that higher concentrations of ethanol caused the release of the preformed intracellular mucus glycoprotein reserves. The results demonstrate that gastric mucosal cells incubated in the presence of ethanol exhibit impaired synthesis and secretion of mucus glycoprotein, and that the severity of impairment depends upon the ethanol concentration.

Animals↗
PubMed1985

Adsorption of human salivary mucins to hydroxyapatite.

The interactions between low (MG2) and high (MG1) molecular-weight human submandibular-sublingual mucin and hydroxyapatite (OHAp) were compared using a quantitative assay. Data obtained appeared to empirically fit the Langmuir adsorption isotherm. Apparent affinity constants derived from this isotherm indicated that MG1 had a greater affinity for OHAp than did MG2. Inhibition studies revealed that salivary glycolipids inhibited the interaction of MG1 and OHAp without influencing MG2 adsorption. In contrast, MG2 adsorption to OHAp was markedly inhibited by cysteine-containing salivary phosphoprotein fractions. Collectively, the data indicate MG1 and MG2 differ in their interaction with OHAp.

Adsorption↗
PubMed1985

Lipids of developing dental plaque in caries-resistant and caries-susceptible adult people.

Dental plaque maturation in both caries-resistant (CR) and caries-susceptible (CS) subjects was accompanied by a decrease in total lipid content but was more pronounced with CR subjects; their plaque after 72 h contained 44.6 per cent less lipids than that of CS. At each stage of maturation, differences were also found in the proportion of lipid classes. In 24 h-plaque, the lipids of CR-group, although containing amounts of glycolipids and phospholipids similar to those of CS, contained 1.6 times less neutral lipids. The 48 h-plaque of CS subjects showed 2.5 times more neutral lipids, 1.2 times more phospholipids and 1.4 times less glycolipids. The 72 h-CR plaque contained 1.9 times less neutral lipids, 1.6 times more glycolipids and 1.3 times more phospholipids than CS-plaque. Among the neutral lipids in both groups, the changes with maturation were associated with decrease in free fatty acids and increase in triglycerides, cholesterol and cholesteryl esters. Phospholipids of CR-plaque contained less phosphatidylcholine and more phosphatidylethanolamine than CS-plaque. With plaque maturation both groups showed decreases in the glycolipids characteristic of saliva and an increase in the content of bacterial type of glycolipids. Plaque maturation is evidently accompanied by dynamic changes in lipids reflecting a shift from salivary to bacterial contribution.

Adult↗
PubMed1985

Lipid composition of squirrel monkey (Saimiri sciureus) saliva.

The content and composition of lipids in saliva of healthy caries-free squirrel monkeys were investigated. The dialyzed and lyophilized saliva on extraction with chloroform/methanol yielded 8.0 +/- 0.9 mg of lipids/100 ml of saliva. Following fractionation on silicic acid column, 30.9% of lipids were found in the neutral lipid fraction, 58.8% in the glycolipid fraction, and 10.3% in the phospholipid fraction. The neutral lipids exhibited high content of free fatty acids (58.8%) and triglycerides (23.3%), the glycolipids consisted mainly of neutral and sulfated glyceroglucolipids (95%), while the phospholipids were rich in sphingomyelin and phosphatidylcholine. The results show that squirrel monkey saliva, while displaying lipid content similar to that of caries-susceptible humans, contains 50% less lipids than saliva of periodontal disease-prone marmoset.

Animals↗
PubMed1985

Effect of sucralfate on the viscosity and retardation of hydrogen ion diffusion by gastric mucus glycoprotein.

The effect of an antiulcer drug (sucralfate) on the viscosity and the ability of pig gastric mucus glycoprotein to retard the diffusion of hydrogen ions was investigated. Preincubation with sucralfate produced a marked enhancement in the glycoprotein viscosity. This enhancement was concentration-dependent and at 1.0 X 10(-3) M sucralfate a 60% increase in viscosity was attained. Permeability measurements revealed that sucralfate caused a substantial improvement in the ability of the glycoprotein to retard the diffusion of hydrogen ions. At 1.0 X 10(-3) M sucralfate, permeability decreased by 25% and a 43% reduction was obtained with 1.0 X 10(-3) M sucralfate. It is suggested that sucralfate, by increasing the viscosity of the glycoprotein and by improving its ability to retard the diffusion of hydrogen ions, strengthens the integrity of gastric mucus.

Aluminum↗
PubMed1985

Effect of ethanol on the peptic degradation of gastric mucus glycoprotein.

The effect of ethanol on the proteolytic activity of pepsin towards gastric mucus glycoprotein was investigated. Undegraded mucus glycoprotein isolated from pig stomach was incubated with pepsin in the presence and absence of ethanol, and the released alpha-amino residues were quantitated by the trinitrophenylation procedure. In the absence of ethanol the rate of proteolysis was proportional to mucus glycoprotein concentration up to 450 micrograms and remained constant with time of incubation for at least 30 min. The apparent Km value of pepsin for pig gastric mucus glycoprotein was 8.7 X 10(-7)M. The proteolytic activity of pepsin towards mucus glycoprotein was inhibited by ethanol. The rate of inhibition was proportional to the ethanol concentration up to 0.8 M and was of competitive type. The apparent K1 value calculated from the double-reciprocal plots for ethanol was 2.2 X 10(-6)M. The inhibitory effect of ethanol on the proteolysis of gastric mucus glycoprotein may be of physiological significance.

Animals↗
PubMed1985

Identification of mucus glycoprotein fatty acyltransferase activity in human gastric mucosa.

The enzymatic activity which catalyzes the transfer of palmitic acid from palmitoyl coenzyme A to gastric mucus glycoprotein was demonstrated in antral and fundic mucosa of normal human stomach. Subcellular fractionation studies revealed that with both types of mucosa the enzyme activity was present in the microsomal fraction. The antral and fundic mucosa also exhibited similar enzyme activities, showed identical pH optimum, and required detergent, NaF and dithiothreitol. Optimum enzymatic activity for fatty acylation of mucus glycoprotein was obtained with 0.5% Triton X-100, 25 mM NaF, and 2 mM dithiothreitol at a pH of 7.4. The 14C-labeled product of the reaction comigrated on CsCl density gradient centrifugation with gastric mucus glycoprotein and contained the ester-bound palmitic acid.

Acylation↗
PubMed1985

In vitro inhibition of peptic degradation of porcine gastric mucus glycoprotein by sucralfate.

The effect of sucralfate on the proteolytic activity of pepsin towards gastric mucus glycoprotein was investigated. Mucus glycoprotein isolated from pig stomach was incubated with pepsin with and without sucralfate, and the released alpha-amino residues were quantitated. In the absence of sulcralfate the rate of proteolysis was proportional to mucus glycoprotein concentration up to 450 micrograms and remained constant with time of incubation for up to 1 h. The apparent Km value of pepsin towards mucus glycoprotein was 8.7 X 10(-7) M. Introduction of sucralfate to the reaction mixtures resulted in reduction of the rate of glycoprotein proteolysis. The rate of inhibition was proportional to the sucralfate concentration up to 1 microM and was of the competitive type, with an apparent Ki value of 2.0 X 10(-6)M. The results suggest that among the beneficial effects of sucralfate on ulcer healing, one may be attributed to its ability to interfere with peptic digestion of gastric mucus glycoprotein.

Aluminum↗
PubMed1985

The role of surface and intracellular mucus in gastric mucosal protection against hydrogen ion. Compositional differences.

The role of surface and intracellular mucus in gastric mucosal protection against hydrogen ion was investigated. Gastric mucosa, prepared from dog and rat stomachs at various stages of mucus depletion, was mounted in the permeability chamber, and the diffusion of hydrogen ion from the luminal to the serosal side was measured. Removal of the surface mucus caused a 42.9% increase in the permeability of rat gastric mucosa and a 47.4% increase in the permeability of dog gastric mucosa. The permeability to hydrogen ion of gastric mucosa depleted of its surface and intracellular mucus increased 216% in the case of the dog and 280% with the rat. Compositional analysis showed that in both animals the intracellular mucus had a higher content of lipids, covalently bound fatty acids, and carbohydrates, whereas the protein content was higher in the surface mucus. The results suggest that, although both the surface and intracellular mucus participate in the retardation of hydrogen ion diffusion, the contribution of the latter appears to be greater.

Animals↗
PubMed1984

Structures of the neutral oligosaccharides isolated from A-active human gastric mucin.

Alkaline borohydride reductive cleavage of the mucin, purified from gastric aspirates of the secretors with blood group A, resulted in a heterogeneous population of neutral (79.7%) and acidic (20.3%) oligosaccharide alditols. Nine oligosaccharides (I-IX), ranging from 6 to 15 sugar units, have been purified from the neutral oligosaccharide fraction. Based on the results of immunological assays, sugar composition, degradation with specific exoglycosidases, and methylation analyses, we propose the following structures for these oligosaccharides: (sequence in text)

Carbohydrate Conformation↗
PubMed1984

Identification of glycosphingolipid-glycoprotein hybrids in gastric epithelium.

A glycolipid fraction, obtained from dog gastric epithelium by detergent solubilization, was found to contain the glycoconjugates with features common to both glycosphingolipids and glycoproteins. Three such compounds have been purified to homogeneity and their composition and structural characteristics determined. The purified glycosphingolipid-glycoprotein hybrids had a molecular weight in the range of 14,000 and contained 88.2 - 91.1% carbohydrate, 3.1 - 4.5% protein, 2.0 - 2.4% sphingosine, and 1.1 - 1.9% fatty acids. The oxidation of the olefinic bond of sphingosine followed by beta-elimination reaction led to the release from each compound of glucose and mannose containing oligosaccharides. Deglycosylation with trifluoromethanesulfonic acid exposed the core regions of the hybrid molecules which were found to consist of sphingosine, glucose, N-acetylglucosamine and amino acids. The data suggest that glycosphingolipid-glycoprotein hybrid molecules are held together by amide linkages between the sphingosine and aspartic or glutamic acid.

Animals↗