Biomedical subjects

A Slomiany

Publications and source records attributed to A Slomiany.

At least 289 records · Page 16Linked to original sources

PubMed1984

Lipid composition of the secretion from human bronchial explant culture.

In this study, we identified and quantitated the lipid components in the secretions of human bronchial explants cultured in a serum-free medium over a period of 50 days. Total lipids represented 6% of the dry material. This amount is considerably lower than that reported for 'normal' human sputum and suggests that the latter is contaminated by serum transudates, alveolar secretions, and microorganisms. Such serum-free culture systems are highly suitable to study cell physiology as it relates to human disease.

Bronchi↗

PubMed1984

Characterization of mucus glycoprotein fatty acyltransferase from gastric mucosa.

A fatty acyltransferase activity which catalyzes the transfer of palmitic acid from palmitoyl coenzyme A to gastric mucus glycoprotein has been demonstrated in the rat gastric mucosa. Subcellular fractionation studies revealed that the enzyme activity was present in a Golgi-rich membrane fraction. Optimum enzymatic activity for 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 enzymatic activity increased proportionally, over a given range, with increased concentrations of both substrates and of enzyme. The apparent Km of the enzymes for the undegraded mucus glycoprotein was 4.5 X 10(-7) M and for palmitoyl-CoA, 3.8 X 10(-5) M. The 14C-labeled product of the reaction cochromatographed on Bio-Gel A-50 column and migrated on sodium dodecyl sulfate-polyacrylamide gel electrophoresis with gastric mucus glycoprotein. Treatment of this 14C-labeled glycoprotein with mild alkali released hexane-extractable product which was identified as [14C]palmitate. The enzyme was also capable of fatty acylation of the deglycosylated glycoprotein, but did not catalyze the transfer of palmitic acid to the proteolytically degraded mucus glycoprotein. This indicates that the acceptor site for fatty acyltransferase is situated in the protease-susceptible nonglycosylated region of the mucus glycoprotein polymer.

Acyltransferases↗

PubMed1984

In vitro acylation of rat gastric mucus glycoprotein with [3H]palmitic acid.

The incorporation of fatty acids into gastric mucus glycoproteins was studied by incubating rat gastric mucosal cell suspensions with [9,10-3H]palmitic acid and [3H]proline. The mucus glycoprotein polymer, secreted into the growth medium (extracellular) and that contained within the cells (intracellular), was purified from the other components of the secretion, thoroughly delipidated, and then analyzed for the radiolabeled tracers. Both pools of mucus glycoprotein, incubated in the presence of [3H]palmitic acid, contained radioactive label which could not be removed by gel filtration, CsCl density gradient centrifugation, sodium dodecyl sulfate-gel electrophoresis, or lipid extraction. Treatment of the purified mucus glycoprotein with 1 M hydroxylamine or 0.3 M methanolic KOH released the radioactivity, thus indicating that [3H]palmitic acid was covalently bound by ester linkage to the glycoprotein. The released radioactivity was associated mainly (87%) with palmitic acid. The incorporation ratio of [3H]proline to [3H]palmitic acid was 0.12:1.0 in the extracellular glycoprotein and 1.38:1.0 in the intracellular glycoprotein, which suggested that acylation of mucus glycoprotein occurs in the intracellular compartment after completion of its polypeptide core. The fact that incorporation of [3H]palmitic acid was greater in the glycoprotein subunits than in the glycoprotein polymer indicates that acylation takes place near the end of subunit processing but before their assembly into the high molecular weight mucus glycoprotein polymer.

Acylation↗

PubMed1984

Effect of lipids and proteins on the viscosity of gastric mucus glycoprotein.

The effect of associated lipids and covalently bound fatty acids, and the contribution of serum albumin and secretory IgA to the viscosity of dog gastric mucus glycoprotein was investigated. Using a cone/plate viscometer at shear rates between 1.15 - 230s -1, it was found that extraction of associated lipids from the glycoprotein lead to 80-85% decrease in the viscosity. Further loss (39%) in viscosity of the delipidated glycoprotein occurred following removal of covalently bound fatty acids. Reassociation of the delipidated glycoprotein with its neutral lipids increased the viscosity 3-fold, a 2.5-fold increase was obtained with glycolipids, and 2-fold with phospholipids. Preincubation of purified mucus glycoprotein with albumin or IgA resulted in the increase in viscosity. This increase in viscosity was proportional to albumin concentration up to 10%, and to IgA concentration up to 5%. The results show that interaction of lipids and proteins with mucus glycoprotein contributes significantly to the viscosity of gastric mucus.

Animals↗

PubMed1984

Effect of ethanol on the enzymatic sulfation of glycosphingolipids in gastric mucosa.

The enzyme activity which catalyzes the transfer of sulfate group from 3'-phosphoadenosine 5'-phosphosulfate to C-3 of the galactose residue of galactosylceramide and lactosylceramide has been demonstrated in the Triton X-100 extracts of the microsomal fraction of rat gastric mucosa. The sulfotransferase activity of this fraction in antral mucosa was 1.2-1.3 times greater than that of the body and 19-22 times greater than that of the forestomach. The enzyme did not catalyze the transfer of sulfate to glucosylceramide, trihexosylceramide, and triglucosyl monoalkylmonoacylglycerol. Optimum enzymatic activity was obtained using 0.4% Triton X-100, 33 mM NaF, and 15 mM MgCl2 at a pH of 6.8. The sulfotransferase activity was inhibited by ethanol. With both glycolipid substrates, little inhibition of enzyme activity was obtained up to 0.5 M ethanol. However, higher concentrations of ethanol produced severe inhibitory effect. This inhibition of sulfation of galactosylceramide and lactosylceramide by ethanol was of the competitive type. The apparent KI values were 8.3 X 10(-5) for galactosylceramide and 5.6 X 10(-5) for lactosylceramide.

Animals↗

PubMed1984

Structural characterization of neutral oligosaccharides of human H+Leb+ gastric mucin.

The structure of carbohydrate chains of human gastric mucin was investigated. The mucin, purified from pronase-degraded gastric aspirates of the secretors with blood group H+Leb, was subjected to alkaline borohydride treatment and a heterogeneous population of neutral (72.1%) and acidic (27.9%) oligosaccharide alditols was obtained. Ten oligosaccharides (I-X), representing 80.3% of the neutral oligosaccharide fraction, have been purified to homogeneity and their structures determined. These oligosaccharides ranged in length from 4 to 12 sugar units and contained mono-, bi-, and triantennary structures. Based on hemagglutination inhibition data in H-anti-H, Leb-anti-Leb, and I-anti-I systems, and the results of structural analyses, we proposed the following structures for these oligosaccharides: (formula, see text)

Blood Group Antigens↗

PubMed1984

Hydrogen ion diffusion in dog gastric mucus glycoprotein: effect of associated lipids and covalently bound fatty acids.

The effect of neutral lipids, glycolipids and phospholipids associated with dog gastric mucus glycoprotein, and that of covalently bound fatty acids on the ability of glycoprotein to retard the diffusion of hydrogen ion was investigated. Purified mucus glycoprotein in its native form, placed between equimolar (0.155M) solutions of HCl and NaCl in a specially designed two-compartment chamber, caused a 90% reduction in permeability to hydrogen ion when compared with a layer of NaCl. Extraction of associated lipids lead to a 68% increase in permeability of the glycoprotein to hydrogen ion, while removal of the covalently bound fatty acids increased further the diffusion rate by 6%. Reassociation of the delipidated glycoprotein with its neutral lipids reduced the permeability to hydrogen ion by 34%, an 11% reduction was obtained with glycolipids, and 23% with phospholipids. Since neutral lipids account for 47% of the glycoprotein lipids, glycolipids 41.1% and phospholipids 11.9%, the quantitative decrease in permeability of the delipidated glycoprotein following its reassociation with phospholipids is 2.7 times greater than that of neutral lipids and 7.3 times greater than that of glycolipids.

Animals↗

PubMed1984

The role of covalently bound fatty acids in the degradation of human gastric mucus glycoprotein.

The undegraded high-molecular-weight glycoprotein of human gastric mucus has been isolated free of noncovalently bound proteins and lipids, as judged by gel filtration, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, cesium chloride density gradient centrifugation, and lipid analysis. Mild alkaline methanolysis of the thoroughly delipidated glycoprotein revealed that, on the average, the native undegraded glycoprotein contains 2.9 mol of acyl linked fatty acids/mg glycoprotein. The low-molecular-weight glycoprotein subunits, obtained after pepsin digestion, contain 2 nmol of acyl linked fatty acids/mg glycopeptide. The highest content of covalently bound fatty acids was found in the fraction of glycoprotein which remained undegraded after pepsin digestion. On the average, 10.2 mol of fatty acids/mg was substituted on this pepsin-resistant glycoprotein. After deacylation with hydroxylamine, the undegraded pepsin-resistant glycoprotein became susceptible to proteolytic cleavage. The obtained results suggest that fatty acids covalently bound to gastric mucus glycoprotein are involved in the regulation of proteolytic digestion of mucus glycoprotein in the stomach.

Chemical Phenomena↗

PubMed1984

Effect of ranitidine on the content of glyceroglucolipids in gastric secretion of patients with gastric and duodenal ulcer.

The glyceroglucolipids content of basal and pentagastrin-stimulated gastric secretion was measured in male patients with gastric (12) and duodenal (12) ulcer. Six patients in each group received twice daily for a period of 4 weeks 150 mg of ranitidine, whereas the other patients received placebo. The glyceroglucolipids output in the basal secretion of patients with gastric and duodenal ulcer before treatment was similar and increased 2.7-fold after pentagastrin stimulation. In all patients treated with ranitidine, the mean output of glyceroglucolipids after pentagastrin stimulation increased from 1.38 to 2.05 mumol/h (P less than 0.05). This increase, however, was more pronounced in the duodenal ulcer group than in the gastric ulcer patients. No change in glyceroglucolipids output was noted in the patients treated with placebo. The ratio of glyceroglucolipids to HCl increased significantly (P less than 0.02) only in the ranitidine-treated patients.

Adult↗

PubMed1984

Lipid composition of marmoset saliva.

The lipid content and composition of marmoset saliva was investigated. Extraction of the dialyzed and lyophilized saliva with chloroform/methanol yielded 15.6 +/- 3.1 mg of lipids/100 ml of saliva. Of the total lipids, 41.7% were represented by neutral lipids, 50.7% by glycolipids and 7.6% by phospholipids. Neutral lipids had a high content of free fatty acids (67.0%), cholesterol and its esters (20.0%) and triglycerides (11.8%). The glycolipid fraction was comprised of simple glycosphingolipids (13.2%), and of neutral and sulfated glyceroglucolipids (86.8%), whereas sphingomyelin, phosphatidylcholine and phosphatidylethanolamine accounted for 63.6% of the total phospholipids. The results indicate that marmoset saliva, in comparison to that of human, contains twice as much of total lipids and exhibits an elevated level of phospholipids, and glycolipids.

Animals↗

PubMed1984

Effect of acetylsalicylic acid on the constituents of the gastric mucosal barrier.

The effect of luminal application of acetylsalicylic acid (ASA) on the liberation of gastric mucosal barrier constituents at pH 5.0 and 2.0 was investigated. The Lucite chamber stomach-flap preparation was used in 18 dogs whose basal H+ secretion was inhibited by cimetidine. An ASA dose of 10 mmol at pH 5.0 caused a moderate increase in content of proteins, glycoproteins, and glycolipids in the instillates. This was accompanied by an increase in transmucosal potential difference (PD) without concomitant changes in the appearance of the gastric mucosa. However, the content of mannose used as an indicator of plasma leakage remained unchanged. A 20 mmol ASA dose at pH 5.0 produced further enrichment of the instillates in mucus constituents, and an increase in mannose content was observed, but PD still remained elevated. In contrast, the same dose of ASA at pH 2.0 severely depleted the gastric mucosal barrier of its mucus constituents and caused a marked increase in leakage of plasma elements. These changes were accompanied by a substantial drop of PD and gastric mucosal damage. These data indicate that the topical application of ASA causes the liberation of mucus constituents, which results in weakening of the gastric mucosal barrier and thus facilitates the pepsin and acid penetration of gastric mucosa. The extent of mucosal damage caused by aspirin strongly depends on the pH of luminal exposure.

Animals↗

PubMed1983

Retardation of hydrogen ion diffusion by gastric mucus constituents: effect of proteolysis.

The role of mucus glycoprotein, lipid and protein in the retardation of hydrogen ion diffusion by dog gastric mucus was investigated. The uniform layer of mucus (1.0 +/- 0.2mm thick), formed on the sintered glass support placed between equimolar (0.155M) solutions of HCl and NaCl, caused a 73% reduction in hydrogen ion diffusion when compared with a layer of NaCl. The rate of hydrogen ion diffusion through purified mucus glycoprotein was similar to that of native mucus, whereas a 30% increase in permeability of glycoprotein to hydrogen ion was observed following its delipidation. Preincubation of the purified mucus glycoprotein with serum albumin or IgA led to an increase in the ability of glycoprotein to retard the diffusion of hydrogen ion. This effect of albumin and IgA occurred at a physiological dose. About 70% decrease in hydrogen ion retardation was obtained following digestion of purified mucus glycoprotein with pepsin, and 74% following its digestion with pronase. The results show that the ability of gastric mucus to retard the diffusion of hydrogen ion depends upon the polymeric structure of undegraded mucus glycoprotein and the extent of interaction of this glycoprotein with lipids, serum albumin, and secretory IgA.

Animals↗

PubMed1983

Lipids associated with rat small-intestinal mucus glycoprotein.

The lipid content and composition of rat small-intestinal mucus, and the purified mucus glycoprotein before and after Pronase digestion were investigated. The mucus, obtained by the instillation of intestine with 2M NaCl, was fractionated on Bio-Gel A-50 in the presence of 6M urea and the mucus glycoprotein free of noncovalently bound protein was isolated. A portion of the purified glycoprotein was subjected to Pronase digestion to yield glycopeptides. The native mucus, and the purified glycoprotein and glycopeptides were extracted with chloroform-methanol, and the lipids contained in the extracts were analyzed. The lipids accounted for 17.6 of the dry weight of mucus, 26.4 of the mucus glycoprotein, and 25.3% of the glycopeptides. In comparison to mucus, the lipids associated with mucus glycoprotein contained 1.9 times more phospholipids and 2.1 times more glycolipids, showed a 26% increase in neutral lipids, and were virtually free of glycosphingolipids. Treatment of the purified glycoprotein with Pronase led to a moderate (22.3%) loss in neutral lipids, 4.3-fold decrease in phospholipids, and 52.3% increase in glyceroglucolipids. The results indicate that while the interaction of mucus glycoprotein with phospholipids involves its Pronase-susceptible region, the interaction with glyceroglucolipids occurs in the glycosylated region of the glycoprotein that is resistant to proteolysis.

Animals↗

PubMed1983

Covalently linked fatty acids in gastric mucus glycoprotein of cystic fibrosis patients.

Undegraded mucus glycoprotein has been isolated in highly purified form from gastric secretion of cystic fibrosis patients. The purification procedure involved gel filtrations on Bio-Gel P-100 and Bio-Gel A-50 and lipid extractions with five mixtures of the organic solvents. The final preparation represented pure glycoprotein as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, cesium chloride density gradient centrifugation, and lipid analysis. Treatment of the pure and delipidated glycoprotein with methanolic KOH or hydroxylamine resulted in liberation of ester-bound fatty acids. Of the total released fatty acids, 95% were represented by hexadecanoate (36.5%), octadecanoate (48.7%), and octadecenoate (8.6%). The quantitative analysis established that, on the average, 12.2 nmol of fatty acids/mg of glycoprotein were released. The studies on cystic fibrotic glycoprotein susceptibility to proteolytic digestion indicated that fraction of glycoprotein which was resistant to pronase digestion contained on the average 33.1 nmol of fatty acids/mg of glycoprotein. After removal of the fatty acid residues from pronase-resistant glycoprotein, by treatment with hydroxylamine, the glycoprotein became susceptible to proteolytic digestion. Thus, in cystic fibrosis, the covalently bound fatty acids interfere with proteolytic degradation of mucus glycoprotein. Perhaps this is the major defect of cystic fibrosis glycoproteins and the cause of the obstruction of secretory glands and the accumulation of poorly soluble secretions.

Adolescent↗

PubMed1983

Enzymatic sulfation of triglucosyl monoalkylmonoacylglycerol in rat salivary glands.

A sulfotransferase activity present in the cytosol fraction of rat submandibular and parotid salivary glands catalyzes the transfer of sulfate group from 3'-phosphoadenosine-5'-phosphosulfate to C-6 of the terminal glucose residue of Glc alpha 1 leads to 6Glc alpha 1 leads to 6Glc alpha 1 leads to 3-1, (3)-0-alkyl-2-0-acylglycerol to form sulfated triglucosyl glyceroglucolipid. The reaction proceeds at its optimum at pH 7.8, and requires the detergent Triton X-100, F1- and Mg2+. The enzyme does not catalyze the sulfation of glycosphingolipids. The apparent Km of the submandibular enzyme for triglucosyl glyceroglucolipid is 78.4 microM, and that of parotid, 58.8 microM. Analysis of the permethylated 35S-labeled enzymatic product demonstrated that the sulfate group is located at C-6 of the terminal glucose residue.

Animals↗

PubMed1983

Isolation of fatty acids covalently bound to the gastric mucus glycoprotein of normal and cystic fibrosis patients.

Covalently bound fatty acids were found in strictly purified and delipidated gastric mucus glycoprotein of normal and cystic fibrosis individuals. The susceptibility of this linkage to methanolic KOH and hydroxylamine treatment indicated the ester bond between fatty acids and glycoprotein. On the average, 2.9 nmol fatty acid/mg glycoprotein were found in normal samples, and 12.2 nmol/mg glycoprotein in samples derived from cystic fibrosis. In normal gastric mucus glycoprotein the covalently linked fatty acids consisted of hexadecanoate (47.0%), octadecanoate (22.0%), tetracosanoate (5.9%), octadecenoate (14.5%) and tetracosenoate (6.0%). In cystic fibrosis mucus glycoprotein the covalently bound fatty acids were comprised mainly of hexadecanoate (36.5%), octadecanoate (48.7%) and octadecenoate (8.6%). These data indicate that cystic fibrosis gastric mucus glycoprotein is highly acylated and perhaps this is the major defect of glycoproteins in this disease.

Centrifugation, Density Gradient↗

PubMed1983

Lipids of gastric secretion in patients with cystic fibrosis.

Lipids were investigated in gastric secretions of patients with cystic fibrosis and of normal individuals. Organic extracts from dialyzed and lyophilized samples were fractionated on silicic acid columns into neutral lipids, glycolipids and phospholipids. The lipids contained in each fraction were separated into individual components by thin-layer chromatography and quantitated. The gastric secretions of patients with cystic fibrosis contained 80-140% more lipids than those of normal individuals, exhibited an elevated level of neutral lipids and contained alkylglycerols and alkylacylglycerols. The level of glycolipids was higher in normal gastric secretions. The phospholipids of cystic fibrosis secretions exhibited about 50% lower content of lysophosphatidylcholine, lysophosphatidylethanolamine and lysophosphatidylserine. The glycosphingolipids of both types of samples contained mono-, di- and trihexosylceramides. The major glyceroglucolipid of normal gastric secretions was tetraglucosyl glyceroglucolipid, whereas hexa- and octaglucosyl glyceroglucolipids were predominant in cystic fibrosis samples. The sulfated glyceroglucolipids in cystic fibrosis samples were lower than those of normal secretions and represented only 4-37% of total glyceroglucolipid, whereas in normal secretion sulfated glyceroglucolipids averaged 50-62%.

Cholesterol↗

PubMed1983

In-vitro biosynthesis of sulphatoglycosphingolipids by rat submandibular salivary glands.

A sulphotransferase activity, concentrated mainly in the microsomal fraction, which catalyses the transfer of sulphate group from 3'-phosphoadenosine-5'-phosphosulphate to galactosylceramide and lactosylceramide was demonstrated in rat submandibular and sublingual glands. However, the sulphotransferase activity of this fraction in submandibular glands was about ten times higher than in sublingual glands. Optimum enzyme activity was obtained using the detergent Triton X-100, F-, and Mg2+ at a pH of 6.8. The enzyme did not catalyse the transfer of sulphate to glucosylceramide, trihexosylceramide and triglucosyl glyceroglucolipid. The sulphotransferase exhibited similar affinity for both galactosyl- and lactosylceramide. The apparent Km of the enzyme for galactosylceramide was 3.8 X 10(-5) M, and for lactosylceramide, 4.3 X 10(-5) M. The results of compositional analysis and periodate-oxidation studies of the 35S-labelled products of the enzyme reactions established that in both [35S]-sulphatoglycosphingolipids the sulphate-ester group is located at C-3 of the galactose residue.

Animals↗