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At least 145 records · Page 8Linked to original sources
PubMed2000

The effects of sugar-free vs sugar-rich beverages on feelings of fullness and subsequent food intake.

This study compared the effects of equal volumes of sugar-rich and sugar-free beverages on feelings of hunger and fullness and the ad libitum consumption of a palatable, fat-rich snack. Eleven healthy males consumed equal volumes (375 mL) of three drinks (sugar-rich cola, sugar-free cola, mineral water) in random order on separate mornings. After 20 min, the subjects were able to snack freely on potato crisps during the next 90 min. Each subject's individual bowl of potato crisps was covertly replenished at 15 min intervals while the subjects were completing appetite and mood ratings. After the 110 min experimental period, the subjects' ad libitum food intake from a buffet-style lunch was covertly recorded. On leaving the laboratory, the subjects filled in a weighed food dairy for the rest of the day. The equal-volume preloads initially decreased hunger to a similar degree and potato crisp intake during the first 15 min interval was not significantly different among the three preloads. On average, total energy intakes from the crisps and lunch were not significantly different among the preloads, and by the end of the day, total energy intakes were similar for the three test conditions. Therefore, the low-calorie/low-sugar drinks did not facilitate a reduced energy intake by the lean, non-dieting male subjects.

Adult↗
PubMed1993

Effects of preblood-meal sugar on sugar seeking and upwind flight by gravid and parous Aedes aegypti (Diptera: Culicidae).

Sugar seeking and upwind flight of gravid and parous female Aedes aegypti (L.) was measured by their attraction to honey in a dual-port airflow olfactometer at selected time intervals after a blood meal. Comparisons were made between pre-blood-meal sugar-fed and unfed females. Sugar-fed females had greater total energy reserves, mostly because of elevated lipid levels. Gravid mosquitoes in both groups showed a strong tendency to fly upwind. This appears to be a pre-ovipositional response. Gravid female orientation to honey was greater in unfed females than in sugar-fed females. After oviposition, parous females became more strongly attracted to honey, if their honey response was not already high.

Aedes↗
PubMed1995

Whole body metabolism is not restricted to D-sugars because energy metabolism of L-sugars fits a computational model in rats.

Can L-sugars contribute to whole body energy metabolism? Energy balance studies were undertaken in rats fed L-sugars at a rate of 10 g/100 g basal diet. Partial metabolizable energy values (MEVp) during the last 28 of 56 d while consuming the L-sugar diets showed that L-glucose contributed no energy (0.3 +/- 0.9 kJ/g, P > 0.5, mean +/- SEM), whereas L-fructose and L-glucose contributed 6.9 +/- 0.9 (P < 0.001) and 8.8 +/- 1.8 (P < 0.001) kJ/g, respectively. Over periods from 0 to 28 and 0 to 56 d of L-sugar treatment, measurements were made of energy intake, the average lean mass of animals, fat and lean mass deposition. Using these measurements and a computational model, estimates were made of each supplement's net metabolizable energy value for maintenance (NEVs). These estimates confirmed the supply of energy from L-fructose, with NEVs of 5.6 +/- 3.2 (P < 0.32) and 6.1 +/- 1.7 (P < 0.01) kJ/g over 28 and 56 d, respectively, and L-gulose with NEVs of 10.2 +/- 3.4 (P < 0.01) and 11.4 +/- 1.8 (P < 0.001) kJ/g over 28 and 56 d, respectively. A lack of energy supply from L-glucose was confirmed with NEVs of -2.6 +/- 3.2 (P > 0.5) and 0.0 +/- 1.6 (P > 0.5) kJ/g over 28 and 56 d, respectively. As reference substrates, sucrose and cellulose gave expected energy values in all determinations. Methods comparison analysis showed no differences between MEVp and NEVS. The assimilation of energy from L-fructose and L-gulose is probably via large bowl microorganisms. These observations show that L-gulose and L-fructose contribute to whole body energy metabolism while L-glucose does not.

Animals↗
PubMed2006

The PNA-DNA hybrid I-motif: implications for sugar-sugar contacts in i-motif tetramerization.

We have created a hybrid i-motif composed of two DNA and two peptide nucleic acid (PNA) strands from an equimolar mixture of a C-rich DNA and analogous PNA sequence. Nano-electrospray ionization mass spectrometry confirmed the formation of a tetrameric species, composed of PNA-DNA heteroduplexes. Thermal denaturation and CD experiments revealed that the structure was held together by C-H+-C base pairs. High resolution NMR spectroscopy confirmed that PNA and DNA form a unique complex comprising five C-H+-C base pairs per heteroduplex. The imino protons are protected from D2O exchange suggesting intercalation of the heteroduplexes as seen in DNA4 i-motifs. FRET established the relative DNA and PNA strand polarities in the hybrid. The DNA strands were arranged antiparallel with respect to one another. The same topology was observed for PNA strands. Fluorescence quenching revealed that both PNA-DNA parallel heteroduplexes are intercalated, such that both DNA strands occupy one of the narrow grooves. H1'-H1' NOEs show that both heteroduplexes are fully intercalated and that both DNA strands are disposed towards a narrow groove, invoking sugar-sugar interactions as seen in DNA4 i-motifs. The hybrid i-motif shows enhanced thermal stability, intermediate pH dependence and forms at relatively low concentrations making it an ideal nanoscale structural element for pH-based molecular switches. It also serves as a good model system to assess the contribution of sugar-sugar contacts in i-motif tetramerization.

Base Pairing↗
PubMed1996

Binding of anti-band 3 autoantibody to sialylated poly-N-acetyllactosaminyl sugar chains of band 3 glycoprotein on polyvinylidene difluoride membrane and sepharose gel: further evidence for anti-band 3 autoantibody binding to the sugar chains of oxidized and senescent erythrocytes.

Binding specifically of naturally occurring anti-band 3 IgG antibody isolated from human plasma was investigated in a cell-free binding system. 125I-labeled human anti-band 3 IgG specifically bound to band 3 glycoprotein and lactoferrin, a glycoprotein that has poly-N-acetyllactosamine-type sugar chains like band 3, on the polyvinylidene difluoride blotting membrane. Binding was decreased by 50-70% when band 3 and lactoferrin were pretreated with N-glycosidase F, endo-beta-galactosidase, or neuraminidase. Binding of 125I-anti-band 3 IgG to band 3-Sepharose gel was partially inhibited by band 3 oligosaccharides or lactoferrin, but was less inhibited by them after they had been treated with N-glycosidase F or endo-beta-galactosidase. A significant part of 125I-anti-band 3 IgG that bound to the band 3-Sepharose gel was released upon treatment of the gel with N-glycosidase F or endo-beta-galactosidase. IgG that binds to lactoferrin (anti-lactoferrin IgG) was isolated from normal human plasma. 125I-Anti-lactoferrin IgG bound to the band 3-Sepharose gel as effectively as to the lactoferrin-Sepharose. The antibody specifically bound to the band 3- and lactoferrin-blotted membrane depending on the poly-N-acetyllactosaminyl sugar chains of the blotted glycoproteins. The results indicate that a major part (about 70%) of anti-band 3 IgG recognizes the sialylated poly-N-acetyllactosaminyl sugar chains of band 3 and lactoferrin, and the remaining part (about 30%) of the antibody may recognize the polypeptide portion of band 3. This was supported by the observation that anti-band 3 IgG effectively bound to lactoferrin-Sepharose but 33% of the antibody did not. Anti-band 3 IgG with the carbohydrate-binding property was equally obtained whether fully denatured or barely denatured band 3 was used for isolation of anti-band 3 IgG by affinity chromatography. These results provide further evidence for our proposal that the binding sites of anti-band 3 IgG to oxidized and senescent erythrocytes reside on the locally condensed sialylated poly-N-acetyllactosaminyl sugar chains of band 3 on the cell surface.

Anion Exchange Protein 1, Erythrocyte↗
PubMed1969

Sugar transport in conducting elements of sugar beet leaves.

Autoradiography was used to determine the distribution of labeled sugar in conducting elements of the blade and petiole of sugar beet leaves at intervals ranging from 5 sec to 24 hr. The processes of assimilation by the green cells, collection of sugar in the minor veins and export in phloem elements were demonstrated visually. It appears that in minor veins sugar is translocated in companion cells rather than sieve tubes. In major veins translocation occurs in sieve tubes.

Journal Article↗
PubMed1996

Differential requirement of the yeast sugar kinases for sugar sensing in establishing the catabolite-repressed state.

Addition of rapidly fermentable sugars to cells of the yeast Saccharomyces cerevisiae grown on nonfermentable carbon sources causes a variety of short-term and long-term regulatory effects, leading to an adaptation to fermentative metabolism. One important feature of this metabolic switch is the occurrence of extensive transcriptional repression of a large group of genes. We have investigated transcriptional regulation of the SUC2 gene encoding repressible invertase, and of HXK1, HXK2 and GLK1 encoding the three known yeast hexose kinases during transition from derepressed to repressed growth conditions. Comparing yeast strains that express various combinations of the hexose kinase genes, we have determined the importance of each of these kinases for establishing the catabolite-repressed state. We show that catabolite repression involves two distinct mechanisms. An initial rapid response is mediated through any kinase, including Glk1, which is able to phosphorylate the available sugar. In contrast, long-term repression specifically requires Hxk2 on glucose and either Hxk1 or Hxk2 on fructose. Both HXK1 and GLK1 are repressed upon addition of glucose or fructose. However, fructose repression of Hxk1 is only transient, which is in line with its preference for fructose as substrate and its requirement for long-term fructose repression. In addition, expression of HXK1 and GLK1 is regulated through cAMP-dependent protein kinase. These results indicate that sugar sensing and establishment of catabolite repression are controlled by an interregulatory network, involving all three yeast sugar kinases and the Ras-cAMP pathway.

Base Sequence↗
PubMed1982

Effects of sugared and sugar-free chewing gum on the accumulation of plaque and debris on the teeth.

The aim of this study was to determine the effects of sugar-free and sugar-containing gums on plaque formation, established plaque and salivary debris. Plaque accumulating during three 5-day periods was recorded in a group of 10 students who, in the absence of normal oral hygiene methods, chewed sugar-free or sugar-containing chewing gum or did not chew gum. In a second group of 10 students the effect of chewing the two types of gum on 3-day accumulations of plaque was recorded. Finally, the wet weight of liquorice debris present in saliva with and without gum chewing, was recorded. During the no chewing periods distinct and significant differences in the amounts of plaque accumulating at different sites were apparent. Both types of chewing gum significantly and comparably reduced plaque accumulation during the 5-day period. The chewing gums also significantly reduced established plaque on many tooth surfaces. Salivary debris was significantly reduced by 50% after chewing gum. It was noted that plaque removal occurred primarily from sites remote from the gingival margin and interdental areas and therefore it was concluded that the observed effects of chewing gum on plaque would not be reflected in a reduction in gingival inflammation.

Adult↗
PubMed1968

Relationship between sugar structure and competition for the sugar transport system in Bakers' yeast.

Twenty-five sugars have been compared as inhibitors of l-sorbose or d-xylose transport by the constitutive, monosaccharide transport system in bakers' yeast. d-Glucose showed the highest activity (i.e., apparent K(i) = 5 mm). Since all sugars except 2-deoxyglucose showed a decrease in activity relative to glucose (i.e., apparent K(i) = 25 - >2,000 mm), an attempt was made to relate the activity of each sugar with the way its structure differs from that of d-glucose. Assuming that the inhibition was the result of sugar-carrier complex formation, the analysis showed that the transport system has a rather broad specificity for pyranoses. Single changes at each of the five carbons of d-glucose (except for the 2-deoxy derivative) result in variable decreases in activity depending upon the carbon number and the alteration. The largest decrease in activity effected by a single change is the methylation or glucosylation of the anomeric hydroxyl. The combination of two or more changes leads to a decrease which is greater than the decrease in activity resulting from the individual changes occurring alone.

Arabinose↗
PubMed1987

Comparison of different dietary sugars as inducers of intestinal sugar transporters.

Intestinal sugar transport increases with dietary carbohydrate levels, but the specific regulatory signals involved have been little studied. Hence we compared rations containing one of five sugars [D-glucose, D-galactose, 3-O-methyl-D-glucose (3-O-MG), D-fructose, and maltose] in their effects on brush-border uptake of five transported solutes (D-glucose, D-galactose, 3-O-MG, D-fructose, and L-proline) by everted sleeves of mouse small intestine. As confirmed by transepithelial potential difference (PD) measurements, there is a distinct fructose transporter that does not evoke a PD, along with one or more aldohexose transporters that do evoke a PD. Galactose and 3-O-MG rations cause a twofold increase in feeding rates, mucosal hyperplasia, and hence nonspecific increases in uptake per unit length of intestine for all transported solutes. Dietary fructose is by far the best specific inducer of the fructose transporter. The five dietary sugars are of fairly similar potency as specific inducers of aldohexose transport, but dietary galactose and fructose may be slightly more potent than glucose. Regulatory signals need not be transported substrates, or vice versa, and need not be metabolizable. Variation in uptake ratios of pairs of aldohexoses with ration and intestinal position suggest multiple aldohexose transporters of overlapping specificity, with different relative activities at different positions and with different susceptibilities to induction by different dietary sugars.

3-O-Methylglucose↗
PubMed1991

An analysis of lactose permease "sugar specificity" mutations which also affect the coupling between proton and lactose transport. I. Val177 and Val177/Asn319 permeases facilitate proton uniport and sugar uniport.

The sugar specificity mutants of the lactose permease containing Val177 or Val177/Asn319 were analyzed with regard to their ability to couple H+ and sugar co-transport. Both mutants were able to transport lactose downhill to a significant degree. The Val177 mutant was partially defective in the active accumulation of galactosides, whereas the Val177/Asn319 mutant was completely defective in the uphill accumulation of sugars. With regard to coupling, the Val177 mutant was shown to catalyze the uncoupled transport of H+ to a substantial degree. This led to a decrease in the H+ electrochemical gradient under aerobic conditions and also resulted in faster H+ uptake when a transient H+ electrochemical gradient was generated under anaerobic conditions. Interestingly, galactosides were shown to diminish the rate of uncoupled H+ transport in the Val177 strain. The Val177/Asn319 strain also catalyzed uncoupled H+ transport, but to a lesser degree than the single Val177 mutant. In addition, the Val177/Asn319 mutant was shown to transport galactosides with or without H+. The observed H+/lactose stoichiometry was 0.30 in the double mutant compared to 0.98 in the wild-type strain. When an H+ electrochemical gradient was generated across the membrane, the Val177/Asn319 mutant permease was shown to facilitate an extremely rapid net H+ leak if nonmetabolizable galactosides had been equilibrated across the membrane. The mechanism of this leak is consistent with a circular pathway involving H+/galactoside influx and uncoupled galactoside efflux. The magnitude of the H+ leak in the presence of nonmetabolizable galactosides was so great in the double mutant that low concentrations of certain galactosides (i.e. 0.5 mM thiodigalactoside) resulted in a complete inhibition of growth. These results are discussed with regard to the possibility that cation and sugar binding to the lactose permease may involve a direct physical coupling at a common recognition site.

Biological Transport↗
PubMed1993

Sugar chains of human cord serum alpha-fetoprotein: characteristics of N-linked sugar chains of glycoproteins produced in human liver and hepatocellular carcinomas.

Human serum alpha-fetoprotein (AFP) is elevated in not only hepatocellular carcinoma (HCC) but also benign liver diseases. AFP produced in HCC and benign liver diseases was separated into several isoforms corresponding to different sugar chain structures by several types of lectin affinity electrophoresis, and the HCC-specific AFP isoform was discriminated from those of benign liver diseases. Because a small amount of HCC-specific AFP isoform was detected in cord serum AFP, the whole sugar chain structures of human cord serum AFP were determined, as follows: Neu5Ac alpha 2-->Gal beta 1-->4GlcNAc beta 1-->2Man alpha 1-->6(Neu5Ac alpha 2 -->6Gal beta 1-->4GlcNAc beta 1-->2Man alpha 1-->3)Man beta 1-->4R1 and R2, Gal beta 1-->4GlcNAc beta 1-->2Man alpha 1-->6(Neu5Ac alpha 2-->6Gal beta 1 -->4GlcNAc beta 1-->2Man alpha 1-->3)Man beta 1-->4R1 and R2, and Neu5Ac alpha 2-->3Gal beta 1-->4GlcNAc beta 1-->2Man alpha 1-->6(Neu5Ac alpha 2 -->6Gal beta 1-->4GlcNAc beta 1-->2Man alpha 1-->3)Man beta 1-->4R1 and R2 in the ratio of 81.6:8.9:9.5. R1 and R2 denote GlcNAc beta 1-->4GlcNAcOT (subscript OT represents an NaB3H4-reduced oligosaccharide) and GlcNAc beta 1-->4(Fuc alpha 1-->6)GlcNAcOT, respectively, and the ratio between R1 and R2 in the respective fractions was approximately 19:1. In contrast, the sugar chain structure of HCC highly specific AFP isoform was found to comprise a monosialyl-biantennary sugar chain with additional fucosylation of the proximal N-acetylglucosamine. Fucosylation of AFP produced in fetal liver increased in inverse proportion to the gestation period, in weeks, indicating that fucosylation of AFP in HCC may be related to the dedifferentiation of human hepatocytes through malignant transformation.

Biomarkers, Tumor↗
PubMed1994

Separation and analysis of 4'-epimeric UDP-sugars, nucleotides, and sugar phosphates by anion-exchange high-performance liquid chromatography with conductimetric detection.

An anion-exchange HPLC method coupled with conductimetric detection was developed for the analysis of UDP-sugars, nucleotides, and sugar phosphates, each in a single chromatographic run. The analysis was applicable to concentrations over 50 pmol. The utility of this technique was demonstrated by the measurement of UDP-sugar 4'-epimerase activity of cell-free extracts from wild-type and mutant Neisseria meningitidis serogroup B strains. Additionally, the method has been applied to the analysis of the intermediates of glycolysis in human erythrocytes.

Chromatography, High Pressure Liquid↗
PubMed1984

Thermal stabilization of antithrombin III by sugars and sugar derivatives and the effects of nonenzymatic glycosylation.

A variety of neutral and acidic sugars and related compounds were evaluated in terms of their effect on the midpoint, Td, of the thermal denaturation curve of antithrombin III. The objectives were to determine which structural features of these molecules are responsible for their stabilizing properties and to identify more efficient stabilizers which combine the effects of lyotropic anions such as citrate with those of the polyols in a single molecule. The presence of one or more carboxylate groups in a sugar molecule invariably increased its stabilizing potency, whereas the number and position of hydroxyl groups appeared to have no influence on the molecules' stabilizing ability. Several compounds were shown to be effective in preserving antithrombin III activity during pasteurization for 10 h at 60 degrees C. However, the presence of reducing sugars invariably resulted in a decrease in activity following pasteurization, in spite of their ability to increase Td. In fact, when antithrombin III was pasteurized in the presence of 2 M glucose and 0.5 M citrate, it steadily lost its ability to inhibit thrombin even though Td under these conditions was 10 degrees C higher than in citrate alone where activity was preserved. This effect was shown to be coincident with the covalent incorporation of glucose into the protein molecule.

Anilino Naphthalenesulfonates↗
PubMed1978

High-performance liquid chromatographic investigation of the amino acid, amino sugar and neutral sugar content in glycoproteins.

A methods for the simultaneous separation and determination of amino acids, amino sugars and neutral carbohydrates is described. Stepwise elution systems with sodium citrate and borate buffers have developed for the ion-exchange liquid chromatographic separation of amino acids and sugars, using 8-micrometer particle size resins and the Stein and Moore and orcinol colorimetric method for detection. With the aid of this system, the direct quantitative comparison of sugars and amino acids by liquid chromatography becomes possible for the first time.

Amino Acids↗
PubMed1980

Estimation of neutral sugars and sugar alcohols in biological fluids by gas-liquid chromatography.

Gas-liquid chromatographic procedures for measuring sugar and polyol concentrations in biological fluids are reviewed. Such methods require the preparations of derivatives such as methyl ethers, trimethylsilyl ethers or acetyl esters. Prior to derivatisation samples must be deproteinised and dried. Complex mixtures of sugars and sugar alcohols may be resolved. Quantitative analyses are precise, sensitive and linear. If internal standardisation is used recoveries approaching 100% are obtained.

Carbohydrates↗
PubMed2004

Unusually broad substrate tolerance of a heat-stable archaeal sugar nucleotidyltransferase for the synthesis of sugar nucleotides.

Herein, we report the first cloning, recombinant expression, and synthetic utility of a sugar nucleotidyltransferase from any archaeal source and demonstrate by an electrospray ionization mass spectrometry (ESI-MS)-based assay its unusual tolerance of heat, pH, and sugar substrates. The metal-ion-dependent enzyme from Pyrococcus furiosus DSM 3638 showed a relatively high degree of acceptance of glucose-1-phosphate (Glc1P), mannose-1-phosphate (Man1P), galactose-1-phosphate (Gal1P), fucose-1-phosphate, glucosamine-1-phosphate, galactosamine-1-phosphate, and N-acetylglucosamine-1-phosphate with uridine and deoxythymidine triphosphate (UTP and dTTP, respectively). The apparent Michaelis constants for Glc1P, Man1P, and Gal1P are 13.0 +/- 0.7, 15 +/- 1, and 22 +/- 2 microM, respectively, with corresponding turnover numbers of 2.08, 1.65, and 1.32 s(-1), respectively. An initial velocity study indicated an ordered bi-bi catalytic mechanism for this enzyme. The temperature stability and inherently broad substrate tolerance of this archaeal enzyme promise an effective reagent for the rapid chemoenzymatic synthesis of a range of natural and unnatural sugar nucleotides for in vitro glycosylation studies and highlight the potential of archaea as a source of new enzymes for synthesis.

Amino Acid Sequence↗
PubMed1995

Regulation of sugar transport via the multiple sugar metabolism operon of Streptococcus mutans by the phosphoenolpyruvate phosphotransferase system.

In this report, we provide evidence that the transport of sugars in Streptococcus mutans via the multiple sugar metabolism system is regulated by the phosphoenolpyruvate phosphotransferase system. A ptsI-defective mutant (DC10), when grown on the multiple sugar metabolism system substrate raffinose, exhibited reduced growth, transport, and glycolytic activity with raffinose relative to the parent strain BM71. Inhibition of [3H]raffinose uptake was also observed in both BM71 and DC10 with increasing concentrations of glucose and the glucose analogs alpha-methyl glucoside and 2-deoxyglucose.

Biological Transport, Active↗