Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “HEXOSES”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 523 records · Page 29Linked to original sources
PubMed1986

Uptake of hexoses and lipids into rabbit jejunum and colon following ileal resection: effect of variations in the cholesterol and fat content of the diet.

After 6 weeks feeding on either a high-cholesterol/fat (H) or a low-cholesterol/fat (L) diet, jejunal and colonic uptake was measured using a previously validated in vitro technique in control rabbits with an intact intestinal tract (C) and in animals submitted to the surgical removal of the distal half of the small intestine (R). The uptake of hexoses and fatty acids was influenced by ileal resection and by diet. Dietary manipulation altered the passive and active transport properties of the intestine and had a different effect on intestinal transport in animals with an ileal resection than in animals with an intact small intestine.

Animals↗
PubMed1987

Potentiation of insulin stimulation of hexose transport by kallikrein and bradykinin in isolated rat adipocytes.

Kallikrein and bradykinin additively increased adipocyte hexose transport under conditions of maximal intrinsic insulin stimulation, while no such effect occurred in the absence of insulin. The potentiation of insulin action follows a dose-response relationship with kallikrein and bradykinin concentrations consistent with a physiological role for the latter in the modulation of insulin action. Insulin degradation by isolated adipocytes and insulin binding to its receptors on adipocyte plasma membranes were not affected by either kallikrein or bradykinin. Thus, the kallikrein and bradykinin potentiation of insulin action occur at post-insulin binding sites. In conclusion, the kallikrein-bradykinin system increases the supply of substrates to target tissues through vasodilation and augmented blood perfusion, and it also stimulates glucose uptake and metabolism via its potentiation of insulin action. These actions suggest that the kallikrein-bradykinin system regulate both the availability and utilization of metabolic substrates, in target tissues.

Adipose Tissue↗
PubMed1976

Effect of hexoses and mannoheptulose on cyclic AMP accumulation and insulin secretion in rat pancreatic islets.

The effects of various sugars on the simultaneous release of insulin and accumulation of cyclic AMP were studied in collagenase isolated rat pancreatic islets. D-Glucose stimulated the formation of cyclic AMP at 3 and 60 min of incubation, whether measured by a label incorporation technique, or by the protein kinase binding assay of Gilman. Only D-glucose and D-mannose were able to stimulate insulin release and cyclic [3H]AMP accumulation in the absence of other substrate. D-fructose had a stimulatory effect in the presence of 3.3 mM D-glucose only at a high concentration (33.8 mM), and enhanced the effects of 8.3 mM glucose when added at the concentration of 8.3 mM. D-Galactose was effective only together with 8.3 mM D-glucose. The order of potency of these hexoses, both regarding insulin secretion and cyclic [3H]AMP accumulation, was glucose-mannose-fructose-galactose. L-Glucose and 3-O-methylglucose had no effects at 60 min when incubated together with 8.3 mM D-glucose, whereas at 3 min, 3-O-methylglucose induced a small stimulation of the cyclic [3H]AMP response. D-mannoheptulose and D-glucosamine inhibited the insulin and cyclic [3H]AMP responses to 27.7 mM glucose. Mannoheptulose suppressed completely the glucose effect on cyclic nucleotide accumulation within 90 s. Although under all incubation conditions, the threshold stimulatory or inhibitory concentration of a given agent was identical for insulin release and cyclic [3H]AMP accumulation, these two variables showed quantitative differences in incubations of 60 min, the magnitude of the changes in insulin secretion being larger than that for the cyclic nucleotide. It is suggested that modulation of islet cyclic AMP level is an important step in the transmission of the effect of various sugars on insulin release; however, glucose and possibly other sugars may also enhance insulin release by additional mechanisms not involving the adenylate cyclase-cyclic AMP system of the beta-cell.

Animals↗
PubMed2006

Molecular dynamics simulation of the P2Y14 receptor. Ligand docking and identification of a putative binding site of the distal hexose moiety.

A rhodopsin-based homology model of the P2Y14 receptor was inserted into a phospholipid bilayer and refined by molecular dynamics (MD) simulation. The binding modes of several known agonists, namely UDP-glucose and its analogues, were proposed using automatic molecular docking combined with Monte Carlo Multiple Minimum calculations. Compared to other P2Y receptors, the P2Y14 receptor has an atypical binding mode of the nucleobase, ribose, and phosphate moieties. The diphosphate moiety interacts with only one cationic residue, namely Lys171 of EL2, while in other P2Y receptor subtypes three Arg or Lys residues interact with the phosphate chain. Two other conserved cationic residues, namely Arg253 (6.55) and Lys277 (7.35) of the P2Y14 receptor together with two anionic residues (Glu166 and Glu174, located in EL2), are likely involved in interactions with the distal hexose moiety.

Binding Sites↗
PubMed2006

Hexose uptake in the plant symbiotic ascomycete Tuber borchii Vittadini: biochemical features and expression pattern of the transporter TBHXT1.

Here, we report the first evidence of a hexose transporter gene, Tbhxt1, in the ectomycorrhizal ascomycete Tuber borchii Vittadini. The protein encoded by Tbhxt1 functionally complements the hxt-null mutant Saccharomyces cerevisiae EBYVW.4000. TBHXT1 has a strong preference for d-glucose (K(m)=38+/-10 microM) over d-fructose (K(m)=16+/-5mM) and uncoupling experiments indicate that TBHXT1 catalyzes the transport via a proton-symport mechanism. The investigations on the substrate specificity reveal that TBHXT1 also imports d-mannose, and the use of deoxyglucose analogues shows that the hydroxyl groups at C1, C3 and C4 are important for substrate recognition. Tbhxt1 is not regulated by fructose, but it reaches its highest level of expression at 3mM glucose and is repressed by very high glucose concentration. Prolonged carbon starvation condition upregulates Tbhxt1, while its expression remains at basal level in the ectomycorrhizal tissue. The mode of regulation of Tbhxt1 is consistent with its role as a high-affinity d-glucose transporter.

Amino Acid Sequence↗
PubMed2003

Suppressive effects of Active Hexose Correlated Compound on the increased activity of hepatic and renal ornithine decarboxylase induced by oxidative stress.

Active Hexose Correlated Compound (AHCC), an extract derived from fungi of Basidiomycetes family has been shown to act as a biological response modifier in various disorders. In our present study, ferric nitrilotriacetate (Fe-NTA), which generates hydroxyl radicals in vivo, was given intraperitoneally to rats and AHCC was tested for its ability to suppress oxidative stress and the activity of ornithine decarboxylase (ODC) in the liver and kidney. Substantial increments in glutathione-related enzymes including glutathione reductase, glutathione peroxidase activity as well as oxidized glutathione contents were shown in the liver at 12 h after treatment with Fe-NTA (7.5 mg Fe/kg body weight). Effects of oxidative stress induced by Fe-NTA were also demonstrated by the increase in serum lipid peroxidation, aminotransferases and urinary 8-hydroxy-2'-deoxyguanosine. However, the increases in these parameters were restored to normal in AHCC-pretreated rats. The ODC activity in the liver and kidney was significantly increased by Fe-NTA, while the increased ODC activity induced by Fe-NTA was normalized in AHCC-pretreated rats. These results suggest AHCC acts as a potent antioxidant and protects against disorders induced by oxidative stresses.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed1996

Kinetic analysis of hexose uptake in Saccharomyces cerevisiae cultivated in continuous culture.

As the expression of the hexose transporters in Saccharomyces cerevisiae is regulated by the external fructose concentration, in vivo fructose transport was investigated at a number of different but constant fructose concentrations in a continuous culture. The in vitro uptake rate and kinetic parameters were studied by uptake of 14C-labelled fructose. From Eadie-Hofstee plots, based on the results of the in vitro uptake experiment, K(m) and Vmax for the different steady-state conditions were determined. These results demonstrate that as fructose concentrations increase, fructose consumption rates and K(m) increase and Vmax slightly decreases. However, remarkably a large discrepancy was observed between in vivo determined consumption rates in the continuous culture and the in vitro uptake rates from the 14C-labelled fructose uptake experiment on cells from an identical steady-state condition. In every condition the in vivo consumption rate was approx. 2-3 times higher than the in vitro uptake rate. A comparable discrepancy was observed for glucose uptake rates; however, in vivo and in vitro galactose uptake rates were identical. These observations imply that kinetic analyses of sugar transport mechanisms can only be performed correctly when accompanied by a comparison with in vivo determined consumption rates.

Carbon Radioisotopes↗
PubMed2000

Syntheses of four D- and L-hexoses via diastereoselective and enantioselective dihydroxylation reactions.

An expeditious approach to various protected hexoses has been developed by the use of the Sharpless catalytic asymmetric dihydroxylation reaction. Applying the Sharpless catalytic asymmetric dihydroxylation reaction on vinylfuran, diols with high enantioexcess are produced. The resulting diols can be stereoselectively transformed into either protected D- or L-mannose in five steps and approximately 39% yield from furfural. Similarly, both D- and L-talose and gulose have been synthesized in 19% overall yields, respectively. Using a modified strategy, both protected D- and L-gulo- and allo-sugar-delta-lactones were synthesized in eight steps and approximately 20%, overall yield from furfural.

Furaldehyde↗
PubMed1975

Biosynthesis of D- and L-glycero-L-galacto-octulose from pentoses and hexoses.

D-glycero-L-galacto-Octulose and L-glycero-L-galacto-octulose accumulated when leaves of Kenland red clover (Trifolium pratense) were allowed to imbibe solution of D-gulose or D-xylose and L-mannose or L-arabinose, respectively. The octuloses were isolated and identified by paper chromatography and by oxidative degradations to the corresponding lower sugars. Assignments of the D and L configuration were made on the basis of optical rotation. It is suggested that formation of the octuloses from the hexoses and pentoses is mediated through transketolase and aldolase or transaldolase catalysis, respectively.

Chromatography, Paper↗
PubMed1979

Structural studies on the hexose region of the Enterobacteriaceae type R3 core polysaccharide.

The structure of the hexose region of the Enterobacteriaceae type R3 core polysaccharide, which is the common core in Shigella flexneri and some Escherichia coli lipopolysaccharides (LPS), has been investigated. The principal method used in these studies involved methylation analysis of the original and modified materials. The polysaccharide was modified by N-deacetylation-deamination and by Smith degradation. As a result of these studies, the following structure is proposed: alpha-D-Glcp-(1 leads to 2)-alpha-D-Glcp-(1 leads to 2)-[alpha-D-GlcNAcp-(1 leads to 3)]-alpha-D-Galp-(1 leads to 3)-alpha-D-Glcp-(1 leads to.

Antigens, Bacterial↗
PubMed1986

Synthesis of 3,6-dideoxy-3-(methylamino)hexoses for g.l.c.-m.s. identification of Rhizobium lipopolysaccharide components.

A direct synthetic route from methyl alpha-D-glucopyranoside to 3,6-dideoxy-3-(methylamino)hexoses having the D-gluco, D-galacto, and D-manno configurations has been developed. Methyl alpha-D-glucoside was converted into the 4,6-O-benzylidene-2,3-di-O-tosyl derivative, which was then transformed into the 4-O-benzyl-6-deoxy 2,3-ditosylate (5) by successive reductive cleavage of the acetal ring, iodination, and reduction. The intermediate 5 was readily converted into the allo 2,3-epoxide, which yielded the pivotal intermediate methyl 4-O-benzyl-3,6-dideoxy-3-(methylamino)-alpha-D-glucopyranoside (7) by cleavage of the oxirane ring with methylamine. The amino compound 7 can be directly converted into the derivatized galacto and manno derivatives for mass-spectrometric identification by selective inversion at C-4 and C-2, respectively, followed by hydrolysis, reduction, and acetylation.

Amino Sugars↗
PubMed2001

Synthesis and characterisation of N-glycosyl amines from the reaction between 4,6-O-benzylidene-D-glucopyranose and substituted aromatic amines and also between 2-(o-aminophenyl)benzimidazole and pentoses or hexoses.

Twelve N-glycosyl amines were synthesised using 4,6-O-benzylidene-D-glucopyranose and different substituted aromatic amines, including some diamines that resulted in bis-glycosyl amines. Another set of six N-glycosyl amines was synthesised using different hexoses and pentoses and 2-(o-aminophenyl)benzimidazole. All compounds were isolated as solid products and purified, their elemental compositions were established, and these were characterised by NMR (1H and 13C), UV-Vis, and FTIR spectroscopy, by FAB mass spectrometry (molecular-ion peaks gave molecular weights), and by their optical rotations. While the protected saccharide, 4,6-O-benzylidene-D-glucopyranose, exists as a mixture of beta and alpha anomers in solution, the corresponding N-glycosyl amines were of only the beta anomeric form as determined by NMR and FTIR spectroscopy. On the other hand, N-glycosyl amines synthesised from 2-(o-aminophenyl)benzimidazole prefer the alpha anomeric form, and in two cases a mixture of both the beta and the alpha anomers were observed. The trends observed in the chemical shifts were compared among different products.

Amines↗
PubMed1998

Kinetics and mechanism of oxidation of erythro-series pentoses and hexoses by N-chloro-p-toluenesulfonamide.

The kinetics and mechanism of oxidation of D-glucose, D-mannose, D-fructose, D-arabinose, and D-ribose with chloramine-T in alkaline medium were studied. The rate law, rate = k [Chloramine-T] [Sugar] [HO-]2, was observed. The rate of the reaction was influenced by a change in ionic strength of the medium, and the dielectric effect was found to be negative. The latter enabled the computation of dAB, the size of the activated complex. The reaction rate was almost doubled in deuterium oxide. Activation energies were calculated from the Arrhenius plots. HPLC and GLC-MS analyses of the products indicated that the sugars were oxidized to a mixture of aldonic acids, consisting of arabinonic, ribonic, erythronic, and glyceric acids. Based on these data, a plausible mechanism involving the aldo-enolic anions of pentoses and keto-enolic anions of hexoses is suggested.

Chemical Phenomena↗
PubMed1980

Critical study of the alditol acetate method for quantitating small quantities of hexoses and hexosamines in gangliosides.

An extensive investigation of and improvement in the method for quantitating the carbohydrates of glycolipids by the gas--liquid chromatography of their alditol acetate derivatives is described. The effects of duration and temperature of hydrolysis, neutralization after hydrolysis, and acetylation time and temperature on the relative detector responses of mixtures of free as well as ganglioside hexoses and hexosamines were extensively studied. It is concluded that optimum results are obtained with the following conditions: hydrolysis at 100 degree C for 8 to 12 h, a 40--60 min reduction, acetylation at 100 degree C for 30 min. When quantitating the carbohydrate components of gangliosides, the most reliable results will be obtained using as an external standard a glycolipid whose chemical structure is similar to that of the sample. Using this procedure, reliable results can be obtained with the initial glycolipid sample containing as little as 1 microgram of each sugar.

Chromatography, Gas↗
PubMedDate not supplied

Placental transport of hexoses: a comparative study with antipyrine and amino acids.

A comparative study of the transplacental passage of some labelled hexoses, amino acids and antipyrine leads to the following conclusions: The maternal-fetal transfer of D-glucose, which amounted to 90 per cent of antipyrine, is very efficient. D-glucose, 3-O-methylglucose and 2-deoxyglucose, for which equivalent transfers were obtained, appear to share the same carrier system. L-glucose transport occurs by simple diffusion. 3-O-methylglucose did not accumulate in the placental tissue. Similarly, maternal and fetal concentrations of 2-deoxyglucose were nearly at equilibrium. It is concluded that the transport of D-glucose is not concentrative. These observations provide further evidence of a facilitated diffusion process for the transport of D-glucose across the human placental membrane.

Amino Acids↗
PubMed1996

Hexose keto-C-glycoside conjugates: design, synthesis, cytotoxicity, and evaluation of their affinity for the glucose transporter Glut-1.

The design, synthesis, cytotoxicity, and biological evaluation of carbohydrate/C-glycoside conjugates are described. The design concept is predicted on the idea that physiological barriers like the blood brain barrier could be crossed selectively by using glucose or glucose derivative/drug conjugates. The study demonstrates that, (1) carbohydrates and C-glycosides can be bonded at nonanomeric positions by the reaction of carbohydrate triflates with C-glycoside alkoxydes in the presence of DMPU; (2) there is a structure-activity relationship between the cytotoxicity of the conjugate and the nature of the carbohydrate residue; and (3) peracetylated hexose keto-C-glycoside conjugates are the most cytotoxic keto-C-glycosides.

Erythrocytes↗
PubMed1981

Effect of temperature on kinetics and symmetries of the hexose transporter of Novikoff rat hepatoma cells.

We have used rapid kinetic techniques to measure the accumulation of radioactively labeled 3-O-methyl-D-glucose to transmembrane equilibrium in Novikoff cell suspensions as a function of temperature. Arrhenius plots of the maximum velocities of isotopic exchange and zero-trans entry were continuous between 6 and 39 degrees C (Ea = 15-19 kcal/mol). Equilibrium exchange and zero-trans entry of 3-O-methyl-glucose at six concentrations (1-30 mM) at 16, 27, and 35 degrees C conformed to appropriate integrated rate equations derived for a single transporter. The hexose transporter exhibited directional symmetry, but the loaded carrier moved about 2 times faster than the empty carrier at all three temperatures investigated. Thus, the differential mobilities of loaded and empty carrier are not affected by temperature in this range. The Michaelis--Menten constant for equilibrium exchange increased about 2-fold with increase in temperature between 16 and 35 degrees C.

Animals↗
PubMed2006

Crystal structure of homo-DNA and nature's choice of pentose over hexose in the genetic system.

An experimental rationalization of the structure type encountered in DNA and RNA by systematically investigating the chemical and physical properties of alternative nucleic acids has identified systems with a variety of sugar-phosphate backbones that are capable of Watson-Crick base pairing and in some cases cross-pairing with the natural nucleic acids. The earliest among the model systems tested to date, (4' --> 6')-linked oligo(2',3'-dideoxy-beta-d-glucopyranosyl)nucleotides or homo-DNA, shows stable self-pairing, but the pairing rules for the four natural bases are not the same as those in DNA. However, a complete interpretation and understanding of the properties of the hexapyranosyl (4' --> 6') family of nucleic acids has been impeded until now by the lack of detailed 3D-structural data. We have determined the crystal structure of a homo-DNA octamer. It reveals a weakly twisted right-handed duplex with a strong inclination between the hexose-phosphate backbones and base-pair axes, and highly irregular values for helical rise and twist at individual base steps. The structure allows a rationalization of the inability of allo-, altro-, and glucopyranosyl-based oligonucleotides to form stable pairing systems.

DNA↗