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Kinetic and molecular identification of sodium-dependent glucose transporter in normal rat cholangiocytes.

While previous work has demonstrated that monosaccharides can be absorbed from bile, studies of sugar transport by the biliary, epithelia (i.e., cholangiocytes) are lacking. Using a novel model of polarized rat cholangiocytes in primary culture, designated normal rat cholangiocytes (NRC), we examined directly the uptake and transcellular transport of a nonmetabolizable monosaccharide, methyl alpha-D-glucopyranoside (AMG). When the apical or basolateral domain of cholangiocytes was exposed to radiolabeled AMG or sucrose (control), only apical absorption of AMG was evident. This apical uptake was time dependent, saturable, and significantly inhibited (> or = 90%) by removal of Na+ or in the presence of phlorizin (0.1 mM), a competitive inhibitor of the Na(+)-glucose cotransporter. The transcellular flux of AMG was also polar (i.e., apical to basolateral). Reverse transcriptase-polymerase chain reaction (RT-PCR) revealed the presence of the transcript for the specific Na(+)-glucose cotransporter SGLT1 in NRC and in freshly isolated cholangiocytes but not in purified hepatocytes; in contrast, the transcript for SGLT2 was absent in all liver samples. In situ RT-PCR on frozen sections of normal rat liver showed that SGLT1 was expressed exclusively in cholangiocytes. Immunoblot analysis using a specific polyclonal antibody for the facilitative glucose transporter GLUT1 demonstrated it to be present in vesicles derived from NRC enriched in basolateral plasma membrane domains. Our data are consistent with the concept that SGLT1 is present on the apical domain of biliary epithelia and, in conjunction with GLUT1 on the basolateral domain, accounts for glucose absorption from bile.

Animals↗

Osmoltye and tryptophan receptors controlling gastric emptying in the dog.

The effect of three monosaccharides, three disaccharides, two dipeptides, combinations of tryptophan with two hexoses, one hexitol, and two amino acids ongastric emptying was studied in dogs to further define the samll intestinal receptors responsive to osmolytes and tryptophan. On a molar basis the disacchardies and dipeptides were almost twice as potent as their respective constituent monosaccharides or amino acids implying that the osmoreceptor is deep to the brush border disaccharidases and cytosol dipeptidases. Tryptophan probably acts by a mechanism different from the osmoreceptor since slowing of gastric emptying by tryptophan was inhibited by methionine which has no effect on a stimulant of the osmoreceptor mechanism. Lysine unlike methionine does not share the neutral amino acid transport pathway with tryptophan. Lysine did not change the inhibitory effect of tryptophan on gastric emptying. This imples that transport of tryptophan into the intestinal cell is necessary for its slowing effect. Glucose and galactose also inhibited the tryptophan effect whereas a nonabsorbed hexitor, mannitol, was without effect. Interference by the hexoses was also probably by competition with tryptophan for transport into the cell. These studies further indicate that the tryptophan receptor is different from the osmoreceptor.

Alanine↗

Differences in dietary-induced thermogenesis following the ingestion of various carbohydrates.

When the metabolic rate and respiratory quotient are measured up to 180 min after ingesting various monosaccharides, disaccharides and mixtures of monosaccharides no difference between men and women was found. The increase in metabolic rate was greatest when fructose was ingested. The respiratory quotient was greater after fructose ingestion compared with the other carbohydrates. Galactose, when ingested alone, had a significantly higher respiratory quotient than when accompanied by glucose.

Body Temperature Regulation↗

The number of oligosaccharides borne by porcine thyroglobulin is variable.

Purified porcine thyroglobulin (Tg) was fractionated on a concanavalin A-Sepharose 4B column by a step-wise elution with increasing concentrations of methyl alpha-mannoside (fraction A, 50 mM; B, 100 mM; C, 200 mM; D, 500 mM, and E, 1 M), and its fractional ratio was 12.8:28.6:26.4:19.7:12.4. These five fractions showed the same profile in polyacrylamide gel electrophoresis. The subfractions were analyzed for their relative contents in oligosaccharides of each structure type and for their monosaccharide contents. In fractions B, C, D, and E the former varied between 15-22% for triantennary complex-type, 47-60% for biantennary complex-type, and 22-30% for high mannose-type oligosaccharide. Fraction A showed a higher percentage of triantennary complex-type structures (36%) and a lower percentage of biantennary complex-type structures (17%). The monosaccharide numbers increased from fraction A to E: 85 to 135 mannose residues, 60 to 82 galactose residues, 84 to 115 N-acetyl glucosamine residues, and 22 to 28 sialic acid residues. After analysis of the number of mannose residues contained in the high mannose-type structures, it was possible to calculate the number of oligosaccharides borne by each Tg subfraction. This number was approximately the same for fractions A and B (22.4 and 21.7), then it increased from B to E (21.8 to 32.9). These results account for the separation obtained on the concanavalin A-Sepharose 4B column. Separation of the two first subfractions bearing the same number of oligosaccharides is certainly due to the higher number of high mannose-type structures in B. In conclusion, the studies reported here show that porcine Tg is heterogeneous, and mainly so in terms of total number of N-glycan structures.

Animals↗

Binding of lectins to novel migration promoters on cardiac mesenchymal cells in the chick.

Chicken serum promotes migration of cardiac mesenchymal cells of chick embryos in vitro. In the present study, migration promotion of unknown migration promoters in chicken serum was examined by using lectins. Cardiac mesenchymal cells of the conotruncal and atrioventricular cushions were cultured on collagen type-I gel with medium including chicken serum. A concentration (100 micrograms/ml) of Concanavalin A (Con A), peanut agglutinin (PNA), pisum sativum agglutinin (PSA), soybean agglutinin (SBA) or wheat germ agglutinin (WGA) was added to the medium. Con A, PSA, and WGA inhibited migration, while PNA and SBA did not affect migration of cardiac mesenchymal cells. WGA inhibited migration in a concentration dependent manner. Preincubation of WGA with specific binding monosaccharides (alpha-D-N-acetylglucosamine and alpha-D-N-acetylneuraminic acid) clearly reduced the inhibition ability of WGA, while preincubation of Con A and PSA with alpha-D-mannose and alpha-D-glucose did not. On the other hand, Con A-binding proteins, eluted from a Con A affinity column with the buffer including alpha-D-mannose and alpha-D-glucose, promoted migration of cardiac mesenchymal cells, as did WGA-binding proteins. These proteins promoted migration in a concentration dependent manner. Western blotting showed that PSA bound the subunits of collagen type-I, but ConA and WGA did not. In migration inhibition assays by monosaccharides, only N-acetylneuraminic acid inhibited migration of cardiac mesenchymal cells. These results suggested that chicken serum contains novel migration promoters for chick cardiac mesenchymal cells. The promoters are proposed to have the terminal N-acetylglucosamine, N-acetylneuraminic acid, and glucose and/or mannose residues.

Animals↗

Possible role of IgE-constituent carbohydrate in the mediation of histamine release.

A possible role of IgE-constituent carbohydrate in the mediation of histamine release was pharmacologically studied in isolated peritoneal rat mast cells. Among polysaccharides obtained commercially, mannan and dextran induced histamine release, and the ED50 was 4 microgram/ml and 52 microgram/ml, respectively. At doses higher than 1 mg/ml, Ficoll, hyaluronic acid and heparin induced the release, while agarose did not. The weak histamine releasing polysaccharides did not induce inhibition of the dextraninduced histamine release. Monosaccharides such as N-acetylglucosamine, mannose and N-acetylneuraminic acid induced marked inhibition of the mannan-induced histamine release, although other carbohydrate constituents of IgE fucose and galactose were weak inhibitors. The antagonism of the monosaccharides against polysaccharide-induced histamine release was found to be a competitive type. Also, antigen-induced histamine release from peritoneal mast cells actively immunized with egg albumin glucosamine. Hence it appears that IgE-constituent carbohydrate may play an important role in IgE-mediated histamine release.

Acetylglucosamine↗

Enzymatic hydrolysis of ammonia-treated rice straw.

Rice straw pretreated with liquid anhydrous ammonia was hydrolyzed with cellulase, cellobiase, and hemicellulase. Ammonia-processing conditions were 1.5 g of NH3/g of dry matter, 85 degrees C, and several sample moisture contents. There were four ammonia addition time (min)-processing time (min) combinations. Sugars produced were analyzed as reducing sugars (dinitrosalicylic acid method) and by high-performance liquid chromatography. Monomeric sugars increased from 11% in the nontreated rice straw to 61% of theoretical in treated rice straw (79.2% conversion as reducing sugars). Production of monosaccharides was greater at higher moisture content and was processing time dependent. Glucose was the monosaccharide produced in greater amounts, 56.0%, followed by xylose, arabinose, and fructose, with 35.8, 6.6, and 1.4%, respectively.

Agriculture↗

Simultaneous assay of neutral sugars and amino sugars by an automatic sugar analyzer: applications to glycoproteins.

The simultaneous assay of neutral sugars and amino sugars commonly found in glycoproteins is described. The automatic sugar analyzer used for the determination is based on the ion-exchange chromatography of sugar-borate complexes on a strong anion-exchange resin. The sugars are identified with the orcinol/sulfuric acid reagent. While less than 40 nmol of mannose, fucose, galactose, glucose, xylose, or arabinose is sufficient for analysis at least 200 nmol mannosamine, glucosamine, or galactosamine is required; acidic monosaccharides cannot be determined. The technique of sugar analysis is applied to structural studies on natural compounds, e.g. the monosaccharide composition of lichenan and the carbohydrate moiety of the glycoproteins ovomucoid and Collocalia mucoid.

Amino Sugars↗

Effects of carbohydrates on insulin release from the isolated islets.

Effects of monosaccharides and disaccharides on insulin release from the isolated islets were studied. Insulin release from the isolated islets was 26.2 microU/5 islets/hr in carbohydrate-free medium and increased by the addition of D-glucose or D-mannose. L-Glucose was ineffective by itself but potentiated the insulin release stimulated by D-glucose. Effects of glucuronic acid and N-acetyl-D-glucosamine on insulin release were similar to those of L-glucose. Among monosaccharides, 2-deoxy-D-ribose, D-galactosamine, L-fucose, N-acetylneuraminic acid and D-ribose decreased insulin release and had no effect on insulin release by D-glucose. D-Galactose and D-fructose also decreased insulin release. However, they potentiated the insulin release when D-glucose was also present. Cellobiose and lactose, which have a beta(1-4) linkage to glucose molecule at the reducing end, inhibited insulin release stimulated by D-glucose. On the other hand, sucrose and maltose lacking the beta(1-4) linkage, did not inhibit the insulin release stimulated by D-glucose. These results suggest that insulin release from the isolated islets is stimulated by carbohydrates which can be metabolized in B-cells. Non-metabolizable analogues of D-glucose or disaccharides show different effects on glucose transport or glucose metabolism in the B-cells according to their chemical structures.

Animals↗

Immunological and biochemical analysis of glycosylated surface antigens and lipophosphoglycan of Tritrichomonas foetus.

Immunoaffinity-purified TF1.17 adhesin antigen was compared biochemically and antigenically to Tritrichomonas foetus (TF) lipophosphoglycan (LPG) and a soluble glycosylated antigen (SGA) released from T. foetus and implicated in pathogenesis and immunity. The monoclonal antibodies (Mabs TF1.15 and TF1.17) specific for a glycosylated TF1.17 antigen were previously shown to prevent adhesion of the T. foetus parasites to bovine vaginal epithelial cells and to mediate killing by bovine complement. SGA was isolated from T. foetus-conditioned buffer and purified by octyl-Sepharose hydrophobic column chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of SGA showed a major SGA1 component (approximately 190 kDa) and a minor SGA2 component (50-70 kDa), which migrated close to TF-LPG and TF1.17. The carbohydrate and lipid compositional analyses of affinity-purified TF1.17 and SGA2 by high-performance liquid chromatography (HPLC) and gas-liquid chromatography revealed the presence of monosaccharides and fatty acids as found in TF-LPG. All antigens contained terminal fucose as determined by alpha-fucosidase digestion followed by HPLC. ELISA and western blots were used to further characterize these glycosylated antigens and to analyze their relationships. The Mabs TF1.15 and TF1.17 reacted very strongly to TF-LPG and SGA2. as well as TF1.17 antigen, indicating that these molecules share common epitopes. These Mabs did not react with the SGA1 component either in ELISA and western blot analyses. Also, the monosaccharide composition of SGA1 was very different from the other three antigen, suggesting SGA1 was different from LPG, SGA2 and TF1.17. Although LPG reacted with Mabs to native TF1.17 antigen, LPG did not induce an immune response in cattle with the same route and adjuvant used to produce strong antibody responses to the native antigen. The latter response suggests that the tightly bound peptide present in the immunoaffinity-purified antigen is necessary for induction of a response to (an) epitope(s) in TF-LPG and TF1.17. Furthermore, vaginal fluid from T. foetus-infected heifers and serum from a cow with a T. foetus-associated pyometra recognized both TF1.17 and TF-LPG in western blots. These results suggest that T. foetus LPG and SGA2 are related to TF1.17 antigen, which was previously shown to play an important role in the pathogenesis and host response in bovine trichomoniasis.

Animals↗

In vitro nutritional requirements and metabolic products of pathogenic and nonpathogenic strains of Cryptobia salmositica: essential carbohydrates and amino acids.

Pathogenic and nonpathogenic strains of Cryptobia salmositica cultured in minimum essential medium (MEM) with several monosaccharides, disaccharides and amino acids were observed for differences in multiplication and motility. Metabolic end products (i.e. alanine, aspartate, carbon dioxide, lactate and pyruvate) were measured for logarithmically growing cells under aerobic conditions. The pathogenic strain of C. salmositica multiplied more readily in MEM supplemented with D(-)ribose, D(+)xylose, D(+)galactose, D(+)glucose, D(+)mannose and D(-)fructose. However, there were no significant differences in multiplication when the strains were cultured with the monosaccharide D(-)arabinose. The nonpathogenic strain multiplied significantly better than the pathogenic strain in the presence of the disaccharides alpha-lactose, maltose and sucrose. It also multiplied more readily when the amino acids L-glutamine and D(-)proline were added to MEM. The end products of carbohydrate catabolism under aerobic conditions were alanine, aspartate, carbon dioxide, lactate and pyruvate.

Alanine Transaminase↗

[Dosimetric application of lyoluminescence using some saccharides].

A measurement system for lyoluminescence has been constructed using a photon-counting apparatus equipped with a highly sensitive photomultiplier and a microcomputer for a data acquisition and processing. For the lyoluminescent dosimetry, seven saccharide samples, including five monosaccharides (glucose, mannose, galactose, levulose and ribose) and two disaccharides (sucrose and trehalose), were irradiated with 60Co gamma rays. Effects on lyoluminescence were examined of the amounts of the sample, concentration of luminol phosphor in an aqueous solution, elapsed time after mixing the samples in the solution, variations of absorbed doses, annealing treatments and different radiation fields. The results revealed that relatively small amounts of sample, say 3 mg, is sufficient for reproducible routine analyses by using 125 mg luminol/l for 10 s data accumulation, and that the lyoluminescent dosimetry is useful for the significantly high dose regions of 1Gy-10kGy (the use of galactose and trehalose can extend the dose-region to higher levels). The comparison of sensitivity for samples with the same dose (215 Gy) showed the great luminescent changes over one order of magnitude between the highest value for galactose and lowest one for ribose, although there is no substantial difference in the structure. No meaningful radiation-quality effect was observed for monosaccharides irradiated with gamma-rays, X-rays, and neutrons.

Carbohydrates↗

Enhanced antiviral and opsonic activity of a human mannose-binding lectin and surfactant protein D chimera.

The carbohydrate recognition domains (CRDs) of human serum mannose-binding lectin (MBL) and pulmonary surfactant protein D (SP-D) have distinctive monosaccharide-binding properties, and their N-terminal and collagen domains have very different quaternary structures. We produced a chimeric protein containing the N terminus and collagen domain of human SP-D and the neck region and CRD of human MBL (SP-D/MBLneck+CRD) to create a novel human collectin. The chimera bound to influenza A virus (IAV), inhibited IAV hemagglutination activity and infectivity, and induced aggregation of viral particles to a much greater extent than MBL. Furthermore, SP-D/MBLneck+CRD caused much greater increases in neutrophil uptake of, and respiratory burst responses to, IAV than MBL. These results indicate that pathogen interactions mediated by the MBL CRD are strongly influenced by the N-terminal and collagen-domain backbone to which it is attached. The presence of the CRD of MBL in the chimera resulted in altered monosaccharide binding properties compared with SP-D. As a result, the chimera caused greater aggregation and neutralization of IAV than SP-D. Distinctive functional properties of collectin collagenous domains and CRDs can be exploited to generate novel human collectins with potential for therapy of influenza.

Animals↗

Carbohydrates from hydrocarbons. II. Free and bound sugars from yeast cells grown on n-hexadecane.

Candida lipolytica (strain 10) was grown on an n-hexadecane medium with and without yeast extract. The harvested dry cells were weighed at various stages of growth. The free sugars from the cultures were obtained by Soxhlet extraction with 85% ethyl alcohol. Further qualitative and quantitative analyses of free monosaccharides in the concentrated alcoholic extracts were made by paper chromatography. Glucose was the only free monosaccharide that could be identified at various stages of growth. The chromatographic analysis of the acid-hydrolyzed yeast cells indicated the presence of glucose and mannose as dominant bound sugars; galactose and xylose were present in minor quantities. In the harvested dry cells from the yeast extract-containing medium, in general, greater amounts of bound sugars were present.

Alkanes↗

Human urinary bladder carcinoma glycoconjugates expressing T-(Gal beta(1-3)GalNAc alpha 1-O-R) and T-like antigens: a comparative study using peanut agglutinin and poly- and monoclonal antibodies.

T- and T-like antigens on glycoproteins and glycolipids were examined in extracts of human urinary bladder tumors and normal tissue by Western blot analysis and reagent binding to thin layer chromatograms. Three different anti-T-reagents were used: peanut (Arachis hypogaea) lectin (PNA) and mono- and polyclonal antibodies specific for T-antigen (Gal beta(1-3)GalNAc alpha 1-O-R). Immunodetection with the T-specific reagents in nitrocellulose replicas of bladder tumor glycoproteins, separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, demonstrated tumor-specific T-antigen-bearing glycoproteins compared to normal urothelial glycoproteins. In addition, a remarkable difference in binding was found between the immunological reagents and PNA lectin. PNA showed major reactivity to a 28-kD glycoprotein extracted from tumors. Monoclonal anti-T-antibody (clone HH8) showed major reactivity with an M(r) 34,000 glycoprotein, and polyclonal anti-T-antibody showed major reactivity with an M(r) 36,000 glycoprotein. PNA agarose column affinity-purified tumor glycoproteins did not bind the antibodies. Glycoproteins, M(r) 28,000 and 34,000, were shown to be O-linked by stepwise deglycosylation. In solid phase monosaccharide inhibition tests, galactose followed by N-acetyl-galactosamine were the most potent monosaccharides inhibiting binding to immobilized bladder tumor glycoproteins. None of the anti-T-reagents reacted with glycolipids extracted from tumor tissue. It is concluded that PNA lectin, in addition to the T-disaccharide, reacts with other protein-anchored carbohydrate structures in carcinomas.

Antibodies, Monoclonal↗

[Adhesion of lactic acid bacteria to epithelium of different cavities of the human organism].

During investigation of adhesive properties of lactic acid bacteria it was found out that 11 strains adhered to buccal intestinal and vaginal epithelium of human. The highest adhesive activity was detected in enterococci (adhesive index 7.75-14.26), lower one--in streptococci (6.40-9.16). In lactobacilli adhesive properties manifested in different ways: Lactobacillus acidophilus strains adhered more often to buccal epithelium (2.58-4.60) and rarely--to intestinal and vaginal. L. plantarum manifested high adhesive activity (8.03 -9.69) to buccal epithelium and lower one--to the rest of epithelium types. Monosaccharide composition of glycocalix of 6 strains of lactic acid bacteria was studied to understand the adhesion mechanism. It was shown that surface structures of this microorganism interact with plant lectins, specific to certain monosaccharides.

Bacterial Adhesion↗

Changes in saccharide and phospholipid content associated with drug storage in cultured rabbit aorta muscle cells.

In the investigation of cellular changes associated with intracellular drug storage, we incubated cultured rabbit aorta muscle cells with various amphiphilic agents. Disobutamide, chloroquine, and desipramine each increased cellular content of rhamnose, arabinose, mannose, glucose, and total saccharides; these agents also elevated total and individual phospholipid of all classes. Amiodarone did not alter total saccharide content, but increased total phospholipid. Tilorone, in contrast, decreased total saccharides, but phospholipid content was unchanged. All test agents decreased xylose content. By light microscopy, disobutamide, chloroquine, and tilorone induced clear cytoplasmic vacuoles; desipramine induced dense cytoplasmic granules; and amiodarone induced both cytoplasmic changes. By electron microscopy, the content of the cellular alterations induced by disobutamide was primarily electron lucent; that of the alterations induced by desipramine was primarily concentric lamellar bodies/flocculent electron-dense structures; and that of the alterations induced by amiodarone was a mixture of both. There was no correlation, therefore, between the induced cellular chemical contents and morphologic changes. Despite the physicochemical similarity of the amphiphilic drugs (all have cationic and lipophilic moieties), the chemical responses they induced were different. The results suggest that amphiphilic drugs alter processes involving saccharides as well as those of phospholipid metabolism. The origin of the saccharide moieties associated with the induced changes in monosaccharide contents is not known. Increased content of phosphatidylinositol, mannose, and glycosyl residues is consistent with the suggestion that amphiphilic drugs may cause an increase in membrane anchor synthesis. The inhibition of lysosomal enzyme activities responsible for the degradation of phospholipid and other anchors may also account for the observed increase in monosaccharides and phosphatidylinositol content.

Amines↗

Phagocytosis of concanavalin A-treated erythrocytes is mediated by the Fc gamma receptor.

Impaired Fc gamma receptor-mediated phagocytosis has been reported in monocytes from HLA-DR2- and -DR3-positive disease-free individuals compared to normals without these B cell alloantigens. We have noted, however, a decrease in the ingestion of concanavalin A (Con A)-treated rabbit erythrocytes (E-Con A) in the same immunogenetically defined groups (DR2 vs Other: 2.94 +/- 0.84 erythrocytes/monocyte vs 4.16 +/- 1.37, p less than 0.003; DR3 vs Other: 3.35 +/- 1.51 vs 4.16 +/- 1.37, p less than 0.04). These data raised the possibility that carbohydrate-lectin interactions might trigger ingestion mediated by the Fc gamma receptor. To test this hypothesis, we performed receptor modulation and monosaccharide blocking experiments. Modulation of the Fc gamma receptor off the apical cell surface of monocytes by adherence to solid-phase IgG aggregates specifically reduced internalization of E-Con A and IgG-sensitized erythrocytes (EA) to 9.1% and 10.6% of control, respectively (p less than 0.001). Internalization of wheat germ agglutinin-treated erythrocytes, tannic acid-treated erythrocytes, and zymosan was not inhibited. In reciprocal modulation experiments using solid-phase Con A, no effects on phagocytosis of any particle was observed. alpha-Methyl mannoside, 0.1 M in PBS, did not inhibit the internalization of EA but blocked ingestion of E-Con A by 97% (p less than 0.001). Other monosaccharides had little or no effect on the ingestion of any of the phagocytic probes. These data demonstrate that a mechanism integrally involving the Fc gamma receptor mediates the ingestion of E-Con A by human monocytes. This Fc receptor has an oligosaccharide(s) with an exposed mannose which may be functionally significant. Whereas the mannose moiety does not play a crucial role in the interaction of the Fc gamma receptor with the Fc portion of IgG, engagement of the receptor via mannose can initiate internalization. Our findings raise the possibility that nonimmune functions may utilize classical immune system receptors through carbohydrate interactions. Furthermore, the ability of the Fc gamma receptor to trigger internalization is defective in HLA-DR2 and -DR3 normals, whether the receptor is ligated at its classical ligand-binding site or by way of its carbohydrate moieties.

Adult↗