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At least 217 records · Page 12Linked to original sources
PubMed2002

Mobility of ions, sugar, and water in the cytoplasm of Xenopus oocytes expressing Na(+)-coupled sugar transporters (SGLT1).

A model was set up to study water transport in membrane proteins expressed in Xenopus oocytes. The model was tested experimentally using human and rabbit Na+-glucose cotransporters (SGLT1), and was used to explain controversies regarding unstirred layer effects. Cotransport of Na+, sugar and water was monitored by two-electrode voltage clamp and online measurements of oocyte volume. The specific resistance of the oocyte cytoplasm was found by means of microelectrodes to be 263 +/- 91 Omega cm (S.D., n = 52), or 2.5 times that of Kulori medium, in agreement with reported values of intracellular ion concentrations and diffusion constants. Osmotically induced volume and resistance changes were compatible with a model of the oocyte in which 37 +/- 17 % (S.D., n = 66) of the intracellular volume acts as a free solution while the remainder is inert, being occupied by organelles, etc. The model explains the results of several types of experiments: rapid changes in rates of water cotransport induced by changes in clamp voltage followed by osmotic equilibration in sugar-free conditions; volume changes induced by Na+ transport via the ionophore gramicidin; and uphill water transport. Ethanol (0.5 %) induced a marked swelling of the oocytes of about 16 pl x s(-1). If the specific inhibitor of SGLT1 phlorizin is added from stock solutions in ethanol, the effect of ethanol obfuscates the effects of the inhibitor. We conclude that the transport parameters derived for water cotransport by the SGLT1 can be attributed to the protein residing in the plasma membrane with no significant influences from unstirred layer effects.

Animals↗
PubMed1978

Further studies on the structural requirements of sugars as antagonists of the changes in vascular permeability produced by sugar polymers in rat skin.

Hexoses and pentoses, but not tetroses or trioses, are potent inhibitors of the increase in vascular permeability in rat skin produced by the polysaccharides--dextran, mannan and glucan. The most active sugars are those with a D-threo type of structure in their cyclic form. The alcohols corresponding to the active sugars are much less inhibitory in this test. The results provide further information on the possible role of carbohydrate structures in antibody binding.

Animals↗
PubMed2001

D-galactose-specific sea urchin lectin sugar-specifically inhibited histamine release induced by datura stramonium agglutinin: differences between sugar-specific effects of sea urchin lectin and those of D-galactose- or L-fucose-specific plant lectins.

A new sea urchin lectin from Toxopneustes pileolus, is D(+)galactose (Gal)-, D(+)fucose (Fuc)-specific. Incubation of rat peritoneal mast cells with the lectin in the presence of 0.3 mM CaCl2 for 10 min significantly and dose-dependently inhibited the histamine release induced by N-acetyl glucosamine (GlcNAc)-specific Datura stramonium agglutinin (DSA), an activator of the Gi-protein-dependent pathway in mast cells. This inhibition by the sea urchin lectin was sugar-specifically reversed in the presence of D(+)Gal or D(+)Fuc but not L(-)Fuc. The sea urchin lectin had no effect on the histamine release induced by compound 48/80, slightly inhibited the histamine release induced by substance P and mastoparan, and slightly enhanced the histamine release induced by melittin, but these effects were not dose-dependent. Compound 48/80, substance P, mastoparan and melittin are mast cell activators without sugar residues. It is suggested that the lectin binds to D(+)Gal residues of DSA to interfere with mast cell activation induced by DSA, a glycoprotein with arabinose and Gal residues. The effects of plant lectins with affinity to D(+)Gal, N-acetyl galactosamine and/or sialic acid and L(-)Fuc on the histamine release induced by DSA, compound 48/80 and substance P were also examined.

Agglutinins↗
PubMed1994

Sugar-containing or sugar-free paediatric medicines: does it really matter?

The long-term use of sugar-containing medicines has long been considered a cause of dental caries in children. Several studies have examined the role of prescription medicines in dental decay, but what about those that can be bought over the counter and that are used infrequently? In this paper practitioners are advised on how to encourage parents to use sugar-free medicines for the sake of their children's teeth.

Cariogenic Agents↗
PubMed1975

Active antitumor components in a decomposed amino sugar I: Effect of sugar structure on activity.

While pure methyl 5-(2-chloroethylamino)-5-deoxy-2,3-O-isopropylidene-beta-D-ribofuranoside hydrochloride has no L-1210 leukemia activity, a decomposed sample was found to be very active. One of several approaches taken to determine the nature of the active component involved a study of how sugar structure affects antitumor activity. A number of aminoribose derivatives were prepared and tested against the murine L-1210 and P-388 leukemia and the B-16 melanoma tumor systems. Compounds were tested as pure materials and as synthetically degraded mixtures. Both the beta-haloethyl group and a secondary amine were required for highest activity.

Amino Sugars↗
PubMed1983

A microapparatus for liquid hydrogen fluoride solvolysis: sugar and amino sugar composition of Erysiphe graminis and Triticum aestivum cell walls.

The assembly and use of a simple and safe apparatus for HF solvolysis of microgram amounts of cell walls, polysaccharides, or glycoproteins are described. Using this apparatus the cell wall composition of Erysiphe graminis was compared with that of its wheat host. The HF solvolysis combined with TFA posthydrolysis considerably increased sugar yields compared with TFA hydrolysis alone, due mainly to increased yields of glucose from wheat, and glucosamine from Erysiphe, corresponding to cellulose and chitin, respectively. A potentially useful method for determining amounts of fungal hyphae in plant tissue is also provided.

Amino Sugars↗
PubMed1984

Regulation of insulin binding and stimulation of sugar transport in cultured human fibroblasts by sugar levels in the culture medium.

Studies were carried out on cultures of human skin fibroblasts to explore the effects of culture medium glucose levels on insulin binding and action. Cell cultures in 5.55 mM glucose-containing medium depleted their medium glucose within 3 days, and at that time exhibited elevated deoxy-D-glucose (2-DG) transport (84% greater than control cultures fed 22.2 mM glucose) and failure of insulin to stimulate 2-DG transport (an insulin:control transport ratio of 1.02). There was also a significant negative correlation between basal 2-DG transport and insulin binding (r = -0.621; n = 29; P less than 0.01), while insulin binding exhibited a significant positive correlation with insulin action (r = 0.816; n = 12; P less than 0.01). Glucose starvation of cultures for 18 h resulted in several changes: a 49% decrease in specific 125I-insulin binding due to a reduction in binding capacity; elevated basal 2-DG transport; and an absence of insulin stimulation of 2-DG transport. Exposure to increasing concentrations of glucose for 18 h led to a glucose concentration-dependent increase in specific insulin binding. Additionally, the various changes in the glucose-starved group were reversed after as little as 6 h of glucose refeeding. The results indicate that basal sugar transport, and insulin binding and action can be regulated by the amount of glucose in the medium.

Biological Transport↗
PubMed2004

Simultaneous identification and quantification of the sugar, sugar alcohol, and carboxylic acid contents of sour cherry, apple, and ber fruits, as their trimethylsilyl derivatives, by gas chromatography-mass spectrometry.

Our gas chromatography-mass spectrometry method--developed for the simultaneous quantitation of mono-, di-, and trisaccharides, sugar alcohols, caboxylic and amino acids, measured as their trimethylsilyl-(oxime) ether/ester derivatives, from one solution by a single injection, prepared in the presence of the fruit matrix--has been extended/utilized for special purposes. The compositions of (i) freshly harvested and stored sour cherries (Prunus cerasus), (ii) apples obtained from organic and integrated productions (Malus domestica), and (iii) green and ripe bers (Zizyphus mauritiana L.) were compared. On the basis of earlier, basic researches (derivatization, quantitation, and fragmentation studies of authentic compounds), we demonstrate the reproducible quantitation of the main and minor constituents in a wide concentration range (approximately 1 x 10(-)(3) to >/=40%, in total up to < or =98%, calculated on dry matter basis of the fruit matrices). Reproducibility of quantitations, calculated on the basis of their total ion current values, provided an average reproducibility of 3.3 (sour cherries), 6.2 (apple), and 4.3 (ber) RSD %, respectively.

Carbohydrates↗
PubMed2005

De novo enantioselective syntheses of galacto-sugars and deoxy sugars via the iterative dihydroxylation of dienoate.

An efficient route to various sugar lactones has been developed. Key to the overall transformation is the sequential osmium-catalyzed dihydroxylation of 2,4-dienoates. The simplest (one-step/racemic) example of this reaction occurs when the dihydroxylation is performed with aqueous NMO in MeOH. When the first dihydroxylation is performed using the AD-mix procedure, an enantioselective variant results. When a matched AD-mix procedure is used for the second dihydroxylation, an exceedingly diastereo- and enantioselective synthesis of galacto-1,4-lactone results. [Reaction: see text]

Deoxy Sugars↗
PubMed2000

Solute stresses affect growth patterns, endogenous water potentials and accumulation of sugars and sugar alcohols in cells of the biocontrol yeast Candida sake.

AIM: To evaluate the effect of modifications of water activity (aw 0. 996-0.92) of a molasses medium with different solutes (glycerol, glucose, NaCl, proline or sorbitol) on growth, intracellular water potentials (psi(c)) and endogenous accumulation of polyols/sugars in the biocontrol yeast Candida sake. METHODS AND RESULTS: Modification of solute stress significantly influenced growth, psi(c) and accumulation of sugars (glucose/trehalose) and polyols (glycerol, erythritol, arabitol and mannitol) in the yeast cells. Regardless of the solute used to modify aw, growth was always decreased as water stress increased. Candida sake cells grew better in glycerol- and proline-amended media, but were sensitive to NaCl. The psi(c) measured using psychrometry showed a significant effect of solutes, aw and time. Cells from the 0.96 aw NaCl treatment presented the lowest psic value (- 5.20 MPa) while cells from unmodified media (aw = 0. 996) had the highest value (- 0.30 MPa). In unmodified medium, glycerol was the predominant reserve accumulated. Glycerol and arabitol were the major compounds accumulated in media modified with glucose or NaCl. In proline media, the concentration of arabitol increased. In glycerol- and sorbitol-amended media, the concentration of glycerol rose. Some correlations were obtained between compatible solutes and psi(c). CONCLUSIONS AND SIGNIFICANCE: This study demonstrates that subtle changes in physiological parameters significantly affect the endogenous contents of C. sake cells. It may be possible to utilize such physiological information to develop biocontrol inocula with improved quality.

Candida↗
PubMed2006

Molecular analysis of the glucose-specific phosphoenolpyruvate : sugar phosphotransferase system from Lactobacillus casei and its links with the control of sugar metabolism.

Lactobacillus casei transports glucose preferentially by a mannose-class phosphoenolpyruvate : sugar phosphotransferase system (PTS). The genomic analysis of L. casei allowed the authors to find a gene cluster (manLMNO) encoding the IIAB (manL), IIC (manM) and IID (manN) proteins of a mannose-class PTS, and a putative 121 aa protein of unknown function (encoded by manO), homologues of which are also present in man clusters that encode glucose/mannose transporters in other Gram-positive bacteria. The L. casei man operon is constitutively expressed into a manLMNO messenger, but an additional manO transcript was also detected. Upstream of the man operon, two genes (upsR and upsA) were found which encode proteins resembling a transcriptional regulator and a membrane protein, respectively. Disruption of either upsR or upsA did not affect manLMNO transcription, and had no effect on glucose uptake. Cells carrying a manO deletion transported glucose at a rate similar to that of the wild-type strain. By contrast, a manM disruption resulted in cells unable to transport glucose by the PTS, thus confirming the functional role of the man genes. In addition, the manM mutant exhibited neither inducer exclusion of maltose nor glucose repression. This result confirms the need for glucose transport through the PTS to trigger these regulatory processes in L. casei.

Amino Acid Sequence↗
PubMed2006

Catabolism of 1,5-anhydro-D-fructose in Sinorhizobium morelense S-30.7.5: discovery, characterization, and overexpression of a new 1,5-anhydro-D-fructose reductase and its application in sugar analysis and rare sugar synthesis.

The bacterium Sinorhizobium morelense S-30.7.5 was isolated by a microbial screening using the sugar 1,5-anhydro-D-fructose (AF) as the sole carbon source. This strain metabolized AF by a novel pathway involving its reduction to 1,5-anhydro-D-mannitol (AM) and the further conversion of AM to D-mannose by C-1 oxygenation. Growth studies showed that the AF metabolizing capability is not confined to S. morelense S-30.7.5 but is a more common feature among the Rhizobiaceae. The AF reducing enzyme was purified and characterized as a new NADPH-dependent monomeric reductase (AFR, EC 1.1.1.-) of 35.1 kDa. It catalyzed the stereoselective reduction of AF to AM and also the conversion of a number of 2-keto aldoses (osones) to the corresponding manno-configurated aldoses. In contrast, common aldoses and ketoses, as well as nonsugar aldehydes and ketones, were not reduced. A database search using the N-terminal AFR sequence retrieved a putative 35-kDa oxidoreductase encoded by the open reading frame Smc04400 localized on the chromosome of Sinorhizobium meliloti 1021. Based on sequence information for this locus, the afr gene was cloned from S. morelense S-30.7.5 and overexpressed in Escherichia coli. In addition to the oxidoreductase of S. meliloti 1021, AFR showed high sequence similarities to putative oxidoreductases of Mesorhizobium loti, Brucella suis, and B. melitensis but not to any oxidoreductase with known functions. AFR could be assigned to the GFO/IDH/MocA family on the basis of highly conserved common structural features. His6-tagged AFR was used to demonstrate the utility of this enzyme for AF analysis and synthesis of AM, as well as related derivatives.

Amino Acid Sequence↗
PubMed1987

Studies on the physical state of water in living cells and model systems. VI. Concentration-dependent sustained volume changes of dialysis sacs containing aqueous solution of native and denatured protein, gelatin, and oxygen-containing polymers immersed in solutions of Na salt and of sugar and sugar alcohol.

In this paper we studied the volume changes of dialysis sacs containing concentrated solutions of native and denatured proteins and of oxygen-containing polymers after immersion in aqueous solution of Na-citrate, D-glucose, and sorbitol of varying concentration. The results confirm the theory of cell volume regulation: volume changes of living cells in different solutions represent a balance between the tendency of intracellular proteins -- which exist in the fully extended conformation -- to polarize, sorb, and draw into the sac or cell more water and the opposite tendency to lose water from the sac or cell created by the lower level of the solutes in the cell or sac water than in the external medium. The lower level of the solutes is the consequence of the reduced solvency of the polarized water in the sac or cell water for large and complex solutes like sugar and free amino acids. This study adds another important physico-chemical attribute of the living cell that can be duplicated by aqueous solutions of gelatin, oxygen-containing polymers like PEO and PEG as well as urea-denatured proteins but not, or only weakly so, by aqueous solutions of native proteins or SDS-denatured proteins.

Animals↗
PubMed2005

An improvement in the bending ability of a hinged trisaccharide with the assistance of a sugar-sugar interaction.

Hinged di- and trisaccharides incorporating 2,4-diamino-beta-D-xylopyranoside as a hinge unit (Hin) were synthesized. Bridging of the diamino group of Hin by carbonylation or chelation to a metal ion results in a conformational change from (4)C1 to (1)C4, which in turn causes a bending of the oligosaccharides. In this study, the bending abilities of the hinged oligosaccharides were compared, in terms of the reactivities toward carbonylation and chelation. Di- or trisaccharides containing a 6-O-glycosylated mannopyranoside or galactopyranoside at their reducing ends had bending abilities similar to that of the Hin monosaccharide, probably because there were neither attractive nor repulsive interactions between the reducing and nonreducing ends. However, when Hin was attached at O2 of methyl mannopyranoside (Man alphaMe), the bending ability was dependent on the nonreducing sugar and the reaction conditions. Typically, a disaccharide--Hin beta(1,2)Man alphaMe--was difficult to bend under all the tested reaction conditions, and the bent population in the presence of Zn(II) was only 4%. On the other hand, a trisaccharide--Man alpha(1,3)Hin beta(1,2)Man alphaMe--was bent immediately after the addition of Zn(II) or Hg(II), and the bent population reached 75%, much larger than those of all the other hinged trisaccharides ever tested (<40%). This excellent bending ability suggests an attractive interaction between the reducing and nonreducing ends. The extended conformation was recovered by the addition of triethylenetetramine, a metal ion chelator. Reversible, quick, and efficient bending of the hinged trisaccharide was thus achieved.

Carbohydrate Conformation↗
PubMed1977

Induction of an intestinal epithelial sugar transport system by high blood sugar.

Intravenous infusion of glucose produces a marked increase of the mucosal-to-serosal sugar flux in the isolated everted small intestine of rats. The phenomenon is partially substrate specific, is inhibited by phloretin but not by phlorizin and is completely abolished by cycloheximide. The results suggest that sustained hyperglycemia may stimulate the synthesis of new transport receptors (carriers).

Animals↗
PubMed1986

Sugar adducts with alkaline earth metal ions. Interaction of L-arabinose with Sr(II) and Ba(II) ions and the effects of metal ion binding on the sugar anomeric configurations.

The reaction between L-arabinose and hydrated Sr(II) or Ba(II) halide salts has been studied in H2O solution and adducts of the type M(L-arabinose)X(2).4H(2)O, where M = Sr(II) or Ba(II) and X = Cl- or Br- have been isolated and characterized by means of Fourier transform infrared spectroscopy, 1H-NMR spectroscopy, molar conductivity and X-ray powder diffraction measurements. Due to the marked spectral similarities with those of the structurally known Ca(L-arabinose)X2 . 4H2O (X= Cl- or Br-) compounds, the Sr(II) and the BA(II) ions are eight-coordinated, binding to two l-arabinose molecules via O1, O5 of the first and O3, O4 of the second sugar moiety and to four H2O molecules. 1H-NMR spectroscopy indicated that the free L-arabinose has the beta-anomer configuration in aqueous solution, whereas the alpha-anomer isomer is preferred by Mg(II), Ca(II), Sr(II) and Ba(II) ions, on complexation.

Journal Article↗