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At least 19 recordsLinked to original sources
PubMed1977

[Quantitative relationship between the monosaccharide induced change in ion transport and the monosaccharide accumulation in the rat jejunum].

1. In the rat's jejunum, the changes induced by Na+-dependently transported monosaccharides (10 mM) of the unidirectional Na+- and K+-influx across the microvilli membrane were studied under varying metabolic conditions. 2. The monosaccharide induced change of Na+- and K+-influx is a function of the ion gradients active across the microvilli membrane. 3. In the in vitro preparation during the process of energy-dependent accumulation the monosaccharide induced change of permeability in the microvilli membrane decreases the K+ concentration, while the Na+ concentration increases. 4. The monosaccharide concentration in the tissue reaches a final value which is proportional to the change of Na+- and K+-influx and to the change in ion concentrations, and which is retained even upon compensation of the gradient and at low intracellular K+ concentrations. 5. The correlation between the breakdown of the ion gradient and the rise of monosaccharide accumulation is explained by the monosaccharide induced restriction of the active ion transport and the ensuing change of energy dissipation in favour of the monosaccharide transport. The (Na+ + K+)-ATPase in the microvilli membrane is discussed as being transmitter of the energy from the ion gradients.

Animals↗
PubMed1978

Monosaccharides and monosaccharide derivatives in human seminal plasma.

Gas chromatography--mass spectrometry with an on-line data system was used to identify monosaccharides and monosaccharide derivatives in human seminal plasma. The carbohydrates were converted into the methoxime-trimethylsilyl derivatives before separation in open tubular glass capillary columns coated with SE-30. Twenty-one different compounds were detected in the seminal fluid, of which twelve have not been recognized before. Seventeen of the monosaccharides have previously been identified in urine. Similar patterns of sugars were found both in fertile and infertile individuals, including one with azoospermia. The compounds identified are, with the possible exception of D-ribose, present as free monosaccharides at the time of ejaculation, and they do not seem to be preformed by spermatozoa.

Chromatography, Gas↗
PubMedDate not supplied

Monosaccharide transport across membranes of human spermatozoa. I. Development of a radiochemical method of measuring monosaccharide uptake by spermatozoa.

A method for determination of the monosaccharide uptake into human spermatozoa is described. Intracellular monosaccharide concentrations were calculated on the basis of determination of intracellular radioactivity after incubation of the cells with labelled monosaccharide and using a mathematical procedure to approximate the intracellular space of spermatozoa. The D-fructose uptake depends on the extracellular D-fructose concentration in a hyperbolic manner. Half maximal saturation is present at 4,1 mM. This corresponds closely with the lowest limit of D-fructose concentration in human fertile semen.

Biological Transport↗
PubMed1987

[Intestinal liberation and resorption of monosaccharides from carbohydrates of different degrees of polymerization. I. Relation between intestinal hydrolysis of carbohydrates and resorption of monosaccharides].

The study was designed to compare the intestinal absorption of monosaccharides from carbohydrates of different chain length. Furthermore, a correlation between the efficiency of hydrolysis of the polymers and the efficiency of the intestinal absorption was expected to be established. Glucose, the disaccharides maltose and sucrose and the polysaccharides maltodextrin DE 20 , maltodextrin DE 5 and starch were employed as substrates. The whole small intestines of anaesthetized rats were perfused in situ for 60 min with 0.5% solutions of these substrates in an open perfusion system. Initially 3-minute fractions of the perfusion medium, later 10-minute fractions were collected. The parameters determined were: secretion of pancreatic alpha-amylase activity, substrate hydrolysis (by alpha-amylase and by disaccharidases of the brush border membrane), intestinal absorption of the monosaccharides. alpha-amylase activity was significantly higher when the perfusion was carried out with starch solution. The possibility is discussed that this high-polymer substrate might stimulate the pancreas to an elevated alpha-amylase secretion. The highest rate of hydrolysis (45 mumol glucose/min) was determined from maltose as a substrate. The cleavage of the high-polymer substrates was less intensive. The hydrolysis of starch was limited by the capacity of the alpha-amylase, that of the sucrose by low activity of the saccharose. Absorption of glucose was more effective from the maltose solution than from the glucose solution. To understand this phenomenon, an additional "hydrolases-related transport system" could be taken into consideration. Glucose absorption from maltodextrin DE 20 was less effective than might have been expected from the rate of hydrolysis. This fact might possibly be explained by an inhibitory effect of oligosaccharides of chain length 4-10, contained in relatively high amounts in maltodextrin DE 20.

Animals↗
PubMed1987

Synthesis of modified tuftsins containing monosaccharides or monosaccharide derivatives.

Synthesis of some modified tuftsins is described in which a monosaccharide or a monosaccharide derivative was incorporated in the molecule. Acylation of H-Thr-Lys(Z)-Pro-Arg(NO2)-OBzl with D(+)-gluco-1,5-lactone followed by catalytic hydrogenation gave N alpha-gluconyl-tuftsin. Glycosylation of the carboxyl function of the C-terminal arginine has been achieved by reacting, through the mixed anhydride procedure, Boc-Thr-Lys(Z)-Pro-OH with 2-deoxy-2-(NG-nitroargininamido)-D-glucopyranose followed by catalytic hydrogenation and trifluoroacetic acid treatment. O-Glucosyl-tuftsin has been prepared by reacting o-nitrophenyl N-benzyloxycarbonyl-O-[(alpha + beta) 2,3,4,6-tetra-O-benzyl-D-glucopyranosyl]-threoninate with H-Lys(Z)-Pro-Arg(NO2)-OBzl in the presence of 1-hydroxybenzotriazole. Flash chromatography on silica gel allowed a partial separation of the diastereoisomers, one of which has been isolated in a reasonable yield. The single diastereoisomer and the alpha + beta anomeric mixture were separately deblocked by catalytic hydrogenation and purified by RP-HPLC.

Carbohydrates↗
PubMed1987

[Intestinal liberation and resorption of monosaccharides from carbohydrates of different degrees of polymerization. II. Relations between monosaccharide resorption, blood glucose level and serum insulin concentration].

The small intestines of anaesthetized rats were perfused in situ for 60 min with 0.5% solutions of glucose, maltose, sucrose, maltodextrin DE 20, maltodextrin DE 5 or starch. Blood samples were repeatedly taken from the v. portae and the v. femoralis to estimate blood glucose and serum insulin levels as a function of perfusion time. The experiment was also performed to clarify whether a correlation exists between these parameters and the substrate uptake from the intestinal lumen (determined in the first part of the study). The highest glucose levels in v. portae and the highest portal-peripheral differences were found when glucose and maltose solutions were administered. Glucose levels in v. femoralis were almost independent of the substrate perfused. Perfusion with glucose caused a considerable insulin secretion starting immediately with the onset of perfusion. It was concluded that glucose might also stimulate insulin secretion on the intestinal level. Perfusion with maltose also effected a significant insulin output, the start of which was delayed however, compared with the effect of glucose.

Animals↗
PubMed1987

Synthesis and biological activity of tuftsin and rigin derivatives containing monosaccharides or monosaccharide derivatives.

Synthesis of some modified rigins is described in which either D-gluconic acid or 2-amino-2-deoxy-beta-D-glucopyranose have been linked to the parent molecule through amide bonds involving the alpha-amino function, alpha-carboxyl function or the gamma-amide function of glutamine in position 2. Glu2-rigin and D-gluconyl-Glu2-rigin have also been synthesized. Binding and phagocytosis assays have been carried out on the rigin derivatives and on some glycosylated tuftsin derivatives as well. Of all the tested peptides only rigin enhanced the phagocytic capacity of mouse peritoneal macrophages to the same extent as tuftsin. The peptides H-Thr-Lys-Pro-Arg-NH-Glc and N alpha-gluconyl-Gly-Glu-Pro-Arg-OH slightly enhanced phagocytosis. H-Thr[(alpha + beta)-O-glucosyl]-Lys-Pro-Arg-OH was found to displace 3H-tuftsin even better than tuftsin but lacked the ability to stimulate phagocytosis.

Animals↗
PubMed1985

Monosaccharide autoxidation in health and disease.

The reduction of oxygen by the ene-diol tautomer of simple monosaccharides produces hydrogen peroxide and alpha-oxoaldehydes. This process, termed monosaccharide autoxidation, occurs at physiological pH and temperature and may contribute to the development of several pathological processes. Enolization of the monosaccharide to an ene-diol tautomer is a prerequisite for the reaction of the monosaccharides with oxygen. The reaction kinetics suggest a two step process: the enolization of the monosaccharide to the ene-diol followed by the reaction of the ene-diol with oxygen. Free-radical reactive intermediates are formed by the reaction of the ene-diol with oxygen: superoxide, semidione, and 1-hydroxyalkyl radicals are formed under physiological conditions (hydroxyl radicals are also detected at high pH). The autoxidation of monosaccharides stimulates the oxidation of oxyhemoglobin in erythrocytes, producing methemoglobin and hydrogen peroxide, and the oxidation of reduced pyridine nucleotides NAD(P)H to the oxidized congener NAD(P)+ and enzymatically inactive nucleotide. This stimulates oxidative metabolism (via the hexose monophosphate shunt) and alpha-oxoaldehyde metabolism (via the glyoxalase system) in erythrocytes in vitro. The oxidative challenge is relatively mild even with very high concentrations (50 mM) of monosaccharide. However, crosslinking of membrane proteins by alpha-oxoaldehydes is enhanced; this effect may exacerbate ageing and decrease the lifetime of erythrocytes in circulation. In vivo, the autoxidation of monosaccharides is expected to be a chronic oxidative process occurring in biological tissue which utilises simple monosaccharides, e.g., in glycolysis and gluconeogenesis. Monosaccharide autoxidation is suggested to be a determinant in the control of cellular mitosis and ageing, providing physiological substrates for the glyoxalase system, and may contribute to the chronic disease processes associated with diabetes mellitus and the smoking of tobacco.

Aging↗
PubMed1994

Quantitative determination of monosaccharides in glycoproteins by high-performance liquid chromatography with highly sensitive fluorescence detection.

For specific determination of monosaccharides with high sensitivity, glycoprotein acid hydrolysates were derivatized in a simple step with excess anthranilic acid (2-aminobenzoic acid) in the presence of sodium cyanoborohydride to give highly fluorescent stable derivatives. The monosaccharide derivatives were completely separated from the excess reagent and from each other by HPLC on a C-18 reversed-phase column using a 1-butylamine-phosphoric acid-tetrahydrofuran mobile phase. Reductive amination of the monosaccharides in the methanol-acetate-borate medium was complete within 20 min at 80 degrees C. Derivatization of glucosamine with the anthranilic acid was accompanied by epimerization to mannosamine (> 15%) in methanol-acetic acid reaction medium, but it was reduced to < 3% in methanol-acetate-borate reaction medium. Fluorescence intensity of the hexosamines was greater than twice the intensity of the neutral monosaccharides. The fluorescent derivatives had excitation maxima at 230, 245, and 360 nm and an emission maximum at 425 nm. Fluorescence intensity at 230 nm excitation was about 10 times greater than that obtained with excitation at 360 nm for all the monosaccharides. Release and concomitant destruction of the monosaccharides during hydrolysis in 20% TFA at 100 degrees C for 7-8 h resulted in 83-85% recovery of all the monosaccharides from glycoproteins. The monosaccharide compositions determined by this method were in excellent agreement with the expected values for a recombinant immunoglobulin and fetuin and were highly reproducible. Relative standard deviation for the composition determinations and precision was less than 3%.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1996

Eliminating amino acid and peptide interference in high-performance anion-exchange pulsed amperometric detection glycoprotein monosaccharide analysis.

The monosaccharide content of a glycoprotein is often determined by acid hydrolysis at elevated temperature and subsequent high pH chromatography of the released, underivatized monosaccharides on pellicular anion-exchange resin (HPAE) using pulsed amperometric detection (PAD). We have found that for glycoproteins with low levels of glycosylation, monosaccharide quantitation can be compromised by amino acids fouling the working electrode surface. Specifically, lysine elutes on the CarboPac PA1 column just prior to galactosamine, whereas remaining amino acids and most peptides elute after the monosaccharides and do not interfere with monosaccharide quantification. A direct comparison of PAD vs Abs215 detection of lysine using the CarboPac PA1 column as the separator reveals that lysine does not cleanly come off the working electrode. The monosaccharide response inhibition caused by lysine could be corrected by the posthydrolysis addition of a rhamnose internal standard and the determination of "correction factors." We have developed a guard column with an altered selectivity for amino acids which, when used with a new separator, causes lysine to elute after the monosaccharides and also causes hydrophobic amino acids to elute further after the monosaccharides. Together the new separator and guard columns solve the lysine fouling problem, reduce sample-related baseline noise, and reduce the magnitude of correction factors.

Amino Acids↗
PubMed2000

Monosaccharide transporters in plants: structure, function and physiology.

Monosaccharide transport across the plant plasma membrane plays an important role both in lower and higher plants. Algae can switch between phototrophic and heterotrophic growth and utilize organic compounds, such as monosaccharides as additional or sole carbon sources. Higher plants represent complex mosaics of phototrophic and heterotrophic cells and tissues and depend on the activity of numerous transporters for the correct partitioning of assimilated carbon between their different organs. The cloning of monosaccharide transporter genes and cDNAs identified closely related integral membrane proteins with 12 transmembrane helices exhibiting significant homology to monosaccharide transporters from yeast, bacteria and mammals. Structural analyses performed with several members of this transporter superfamily identified protein domains or even specific amino acid residues putatively involved in substrate binding and specificity. Expression of plant monosaccharide transporter cDNAs in yeast cells and frog oocytes allowed the characterization of substrate specificities and kinetic parameters. Immunohistochemical studies, in situ hybridization analyses and studies performed with transgenic plants expressing reporter genes under the control of promoters from specific monosaccharide transporter genes allowed the localization of the transport proteins or revealed the sites of gene expression. Higher plants possess large families of monosaccharide transporter genes and each of the encoded proteins seems to have a specific function often confined to a limited number of cells and regulated both developmentally and by environmental stimuli.

Animals↗
PubMed1998

Carbon allocation in ectomycorrhizas: identification and expression analysis of an Amanita muscaria monosaccharide transporter.

Ectomycorrhizas are formed between certain soil fungi and fine roots of predominantly woody plants. An important feature of this symbiosis is the supply of plant-derived carbohydrates to the fungus. As a first step toward a better understanding of the molecular basis of this process, we cloned a monosaccharide transporter from the ectomycorrhizal fungus Amanita muscaria. Degenerate oligonucleotide primers were designed to match conserved regions from known fungal sugar transporters. A cDNA fragment of the transporter was obtained from mycorrhizal mRNA by reverse transcription-polymerase chain reaction. This fragment was used to identify a clone (AmMst1) encoding the entire monosaccharide transporter in a Picea abies/A. muscaria mycorrhizal cDNA library. The cDNA codes for an open reading frame of 520 amino acids, showing best homology to a Neurospora crassa monosaccharide transporter. The function of AmMST1 as monosaccharide transporter was confirmed by heterologous expression of the cDNA in a Schizosaccharomyces pombe mutant lacking a monosaccharide uptake system. AmMst1 was constitutively expressed in fungal hyphae under all growth conditions. Nevertheless, in mycorrhizas as well as in hyphae grown at monosaccharide concentrations above 5 mM, the amount of AmMst1 transcript increased fourfold. We therefore suggest that AmMst1 is upregulated in ectomycorrhizas by a monosaccharide-controlled mechanism.

Amanita↗
PubMed1987

Digestibility by sheep of total and cell wall monosaccharides of wheat straw treated chemically or chemically plus enzymatically.

Digestibility of total and cell wall monosaccharides was studied in sheep with ruminal and duodenal cannulae and fed three wheat straw-based diets: untreated, treated with SO2, treated with SO2 plus cellulase and a fourth diet, which was barley-based. In untreated straw, 90% of total monosaccharides are cell wall bound. Sulfur dioxide treatment solubilized mainly the matrix sugars, reducing their content from 22.1 to 9.76 g/100 g DM in straw. The combined treatment (SO2 plus cellulase) solubilized most of the cell wall sugars so that the most of the cell wall sugars so that the residual cell wall contained only 31% of the total sugars originally present. Treatments increased total monosaccharide digestibility from 63 to 90% and of cell wall monosaccharides from 58 to 84 and 88%. The proportion of digestible monosaccharides degraded in the rumen was increased up to 95% by the treatments. Total monosaccharide digestibility was similar in both treated straws, but degradation of the residual cell wall monosaccharides was somewhat lower in the combined treatment compared with the SO2-treated straw.

Animal Feed↗
PubMed1992

Inhibition of specific T-cell activation by monosaccharides is through their reactivity as aldehydes.

The effect of monosaccharides on the inductive interaction between antigen-presenting cells and T cells was investigated in a human system. Some monosaccharides, but not others, were found to inhibit antigen-specific T-cell activation. Responses to mitogen were unaffected. In order for inhibition to occur, a high concentration (approximately 50 mM) of monosaccharide was necessary. The role of monosaccharide aldehyde groups in inhibition was investigated using the alpha-methyl pyranoside and the alditol forms of inhibitory monosaccharides. Unlike the native monosaccharides, these molecular configurations possess the ring structure and the open chain structure respectively but do not contain aldehydes. Together they represent all the molecular characteristics of both forms of the monosaccharide except the possession of aldehyde groups. These two molecular species produced no significant inhibition. Modified forms of the sugar moiety of ribofuranosidoadenine (adenosine) were also tested. The periodate oxidized form of the molecule in which the ribose bears two aldehyde groups, was a potent inhibitor of antigen-induced T-cell activation whereas periodate-oxidized, borohydride-reduced ribofuranosidoadenine, in which the ribose aldehydes are converted to alcohols, produced no inhibition. The former was shown to form Schiff bases with ligands on peripheral blood mononuclear cells (PBMC) as predicted whereas the latter did not. Periodate oxidized dextran, but not native dextran, was also inhibitory. Together these data show that inhibition of T-cell activation by sugars requires reactive aldehydes and this is consistent with the Schiff base model of specific antigen-presenting cell (APC)-T cell inductive interaction in which exogenous aldehydes and other carbonyl donors prevent the necessary formation of Schiff bases between cellular ligands.

Aldehydes↗
PubMed1983

Selective inhibition by monosaccharides of tumor cell cytotoxicity mediated by mouse macrophages, macrophage-like cell lines, and natural killer cells.

A series of monosaccharides were tested for their ability to inhibit the effector phase of macrophage-mediated cytolysis against two susceptible murine tumor target cells, L5178Y and RL male I. Two monosaccharides, D-mannose and N-acetyl-D-galactosamine, were found to decrease cytotoxicity consistently in a dose-dependent manner. However, D-mannose preferentially inhibited lysis of RL male I target cells with little effect on lysis of L5178Y target cells, while the reverse was found with N-acetyl-D-galactosamine. Neither monosaccharide interfered with the activation of macrophages by polyinosinic:polycytidylic acid. Natural killer cell activity was decreased by a 25 mM concentration of D-mannose but not by N-acetyl-D-galactosamine, although increasing concentrations of N-acetyl-D-galactosamine were inhibitory. Neither monosaccharide affected cytotoxicity by alloimmune T cells. Cytotoxicity of macrophage-like cell lines against tumor target cells was also decreased by monosaccharides but the pattern of inhibition was different from that seen with activated macrophage effector cells. Both D-mannose and N-acetyl-D-galactosamine inhibited glucose oxidation by activated macrophages but only D-mannose significantly decreased protein synthesis of activated macrophages. These results indicate that monosaccharides can inhibit macrophage-mediated cytotoxicity in a selective manner with the pattern dependent on the tumor target cell used in the assay.

Animals↗
PubMed1984

The production of free radicals during the autoxidation of monosaccharides by buffer ions.

The production of free radicals during the autoxidation of simple monosaccharides at 37 degrees has been studied by the electron spin resonance (e.s.r.) technique of spin trapping. In the presence of the spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO), monosaccharides undergoing autoxidation produced hydroxyl and 1-hydroxyalkyl radical-derived spin adducts, indicating that hydroxyl and hydroxyalkyl free-radicals are involved in the autoxidation of monosaccharides. The pH profile for the production of free radicals from monosaccharides undergoing autoxidation revealed the formation of both hydroxyl and hydroxyalkyl radicals at relatively high pH, whereas at low pH, only the formation of hydroxyalkyl radicals was observed; the transition between these routes for the production of free radicals occurred at pH 8.0-8.5. Glycolaldehyde, glyceraldehyde, dihydroxyacetone, and erythrose are relatively rapidly enolised (to an ene-diol) and autoxidised with the concomitant production of free radicals. Ribose and glucose enolise and autoxidise very slowly without detectable production of free radicals. A comparison of the pH profiles of the rates of enolisation and the pH dependence of the production of free radicals from glyceraldehyde during autoxidation suggests that a change in reaction mechanism occurs at pH 8.2. Below pH 8.2, the rates of enolisation and autoxidation increase with increasing pH, with a concomitant increase in the formation of hydroxyalkyl spin-adducts. Above pH 8.2, glyceraldehyde undergoing autoxidation shows a much higher rate of enolisation than of autoxidation and, although the formation of hydroxyalkyl radicals is decreased, the production of hydroxyl radicals is also observed. A free-radical mechanism for the autoxidation of monosaccharides is proposed, to account for the pH-dependent characteristics of the production of free radicals and the relationships between the production of free radicals, autoxidation, and enolisation of the monosaccharides.

Buffers↗