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At least 847 records · Page 47Linked to original sources
PubMed1976

Influence of calcium concentration on the rate of onset of cardiac glycoside and aglycone inotropism.

Isolated rabbit atria were employed to examine the rate of onset of inotropism of two glycosides (strophanthin and ouabain) and aglycones (acetylstrophanthidin and ouabagenin) in the presence of various concentrations of calcium (0.55, 1.1, 2.2, 4.4 and 8.8 mM). The rate of onset of glycoside-induced inotropism was found to be greatly influenced by the calcium concentration. The rate of onset was increased in both low and high calcium, with the minimum rate of onset at 1.1 or 2.2 mM calcium. In contrast, the rate of onset of aglycone-induced inotropism was not dependent on calcium between 0.55 and 4.4 mM calcium. The rate of onset of aglycone-induced inotropism was increased at 8.8 mM calcium. The results are interpreted by postulating that the digitalis inotropic receptor is located in a membrane-limited compartment to which aglycones may gain access via passive diffusion but to which glycosides gain access mainly via a (calcium-dependent) carrier mechanism.

Animals↗
PubMed2000

Flavonol glycosides from Aristeguietia discolor reduce morphine withdrawal in vitro.

The effects of extracts, partially purified fractions and four flavonol glycosides 1-4 from Aristeguietia discolor were investigated on the naloxone-precipitated withdrawal contraction of the acute morphine dependent guinea-pig ileum in vitro. After a 4 min in vitro exposure to morphine a strong contraction of guinea-pig isolated ileum was observed after the addition of naloxone. Both MeOH extract (50, 100 and 200 mg/mL), the partially purified fractions I, L, M and N (50, 100 and 200 mg/mL) and flavonol glycosides 1-4 (1 x 10(-4) 5 x 10(-5) 1 x 10(-5) M), injected 10 min before morphine, were capable of blocking the naloxone-induced contraction after exposure to morphine in a concentration-dependent fashion. The results of the present paper suggest that flavonol glycosides from Aristeguietia discolor may play an important role in the control of morphine withdrawal.

Animals↗
PubMed2003

Indolocarbazole glycosides in inactive conformations.

Indolocarbazole glycosides related to rebeccamycin represent a promising category of antitumor agents targeting DNA and topoisomerase I. These drugs prefer to adopt a closed conformation with an intramolecular hydrogen bond between the indole NH group and the pyranose oxygen atom. Three pairs of indolocarbazole monoglycosides bearing an NH or an N-methyl indole moiety were synthesized and their biological properties investigated at the molecular and cellular level. Replacing the indole NH proton with a methyl group reduces DNA interaction and abolishes activity against DNA topoisomerase I. Surface plasmon resonance studies performed with a pair of water-soluble indolocarbazole glycosides and two hairpin oligonucleotides containing an [AT]4 or a [CG]4 sequence indicate that both the NH and the N-methyl derivative maintain a relatively high affinity for DNA (Keq = 2 - 6 x 10(5) M(-1)) but the incorporation of the methyl group restricts access to the DNA. The number of ligand binding sites (n) on the oligonucleotides is about twice as high for the NH compound compared to its N-methyl analogue. Modeling and 1H NMR studies demonstrate that addition of the N-methyl group drives a radical change in conformation in which the orientation of the aglycone relative to the beta-glucoside is reversed. The loss of the closed conformation by the N-methyl derivatives perturbs thir ability to access DNA binding sites and prevents the drug from inhibiting topoisomerase I. As a consequence, the NH compounds exhibit potent cytotoxicity against CEM leukemia cells with an IC50 value in the 1 microM range, whereas the N-methyl analogues are 10 to 100 times less cytotoxic. These studies offer circumstantial evidence supporting the importance of the closed conformation in the interaction of indolocarbazole glycosides with their molecular targets, DNA and topoisomerase I.

Anti-Bacterial Agents↗
PubMed2005

Developing promiscuous glycosidases for glycoside synthesis: residues W433 and E432 in Sulfolobus solfataricus beta-glycosidase are important glucoside- and galactoside-specificity determinants.

Two residues that have been implicated in determining the substrate specificity of the thermophilic beta-glycosidase from the archaeon Sulfolobus solfataricus (SsbetaG), a member of the glycosyl hydrolase family 1, have been mutated by site-directed mutagenesis so as to create more versatile catalysts for carbohydrate chemistry. The wild-type and mutated sequences were expressed in E. coli with a His(7)-tag to allow one-step chromatographic purification. The E432C and W433C mutations removed key interactions with the OH-4 and OH-3 of the sugar substrates, thus reducing the discrimination of glucose, galactose and fucose with respect to other glycosides. This resulted in two glycosidases with greatly broadened substrate specificities. Observed changes include a 24-fold increase in Man:Gal activity and an 18-fold increase in GalA:Gal activity. This promiscuous substrate tolerance was further illustrated by the parallel synthesis of a beta-glycoside library of glucose, galactose, xylose and mannose in one pot at 50 degrees C, in organic solvent. The synthetic potential of the catalysts was further evaluated through alkyl glycoside transglycosylation yields, including the first examples of synthesis of beta-mannosides and beta-xylosides with SsbetaG.

Alkylation↗
PubMed1985

Developmental toxicity of the cyanogenic glycoside linamarin in the golden hamster.

Cassava, a staple food in many tropical countries, has been suspected as a cause of human congenital defects. Ingestion of the material during pregnancy has been reported to induce limb defects, microcephaly, open eye, and growth retardation in rats. Linamarin is a natural cyanogenic glycoside that occurs in high concentrations in cassava. In the present study, pregnant hamsters received an oral dose of 70,100, 120 or 140 mg/kg linamarin or an equivalent volume of isotonic saline during the early primitive streak stage of gestation. A dose of 120 or 140 mg/kg of the glycoside was associated with an increased incidence of vertebral and rib anomalies as well as the production of encephaloceles in the offspring. These larger doses of linamarin also resulted in obvious maternal toxicity. Linamarin treatment had no effect on fetal body weight, ossification of fetal skeletons, embryonic mortality, or litter size. Although ingestion of the cyanogenic glycoside was associated with a significant teratogenic response, the effects occurred only at doses that elicited signs of maternal intoxication.

Abnormalities, Drug-Induced↗
PubMed1999

Quantitative cleavage of the N-glycosidic bond under the normal conditions of methanolysis used for the analysis of glycoprotein monosaccharides.

The most common method used for the liberation of monosaccharides from glycoprotein N-glycans involves anhydrous methanolysis because it liberates almost quantitatively monosaccharides as O-methylglycosides, which are resistant to further degradation. However, it is generally assumed that this method does not cleave quantitatively the N-glycosidic bonds. This paper demonstrates that classical methanolysis conditions quantitatively cleave the N-glycosidic bond (96%), liberating glucosamine (and not its O-methylglycosides) and other minor reaction products which were identified. Because other N-acetyl-d-glucosamine (GlcNAc) residues are quantitatively liberated as the O-methylglycosides of glucosamine, the GlcNAc residue involved in the N-glycosidic bond is separated from the others using gas chromatography of heptafluorobutyrate derivatives.

Chromatography, Gas↗
PubMedDate not supplied

Release of adenine nucleotide metabolites by toxic concentrations of cardiac glycosides.

In isolated perfused guinea-pig hearts the effect of toxic concentrations of cardiac glycosides on the release of the adenine nucleotide metabolites adenosine, inosine, hypoxanthine, xanthine, and uric acid was investigated. Digoxin concentrations of 0.03-1 mumol.l-1 produced moderate to severe tachyarrhythmias. Large amounts of metabolites were released by concentrations of 0.1 mumol.l-1, and higher. Occurrence of glycoside-induced ventricular fibrillation was associated with a particularly high release. Metabolite release was also obtained when fibrillation was elicited electrically in normal control hearts, or in hearts receiving simultaneously a marginally toxic digoxin concentration (0.03 mumol.l-1). Digoxin-induced tachyarrhythmias and metabolite release were almost completely prevented by a high potassium concentration in the coronary perfusion fluid (8.1 mmol.l-1). The antiarrhythmic effect was also obtained with lidocaine (60 mumol.l-1), but the release was only partially antagonized. Similar results concerning arrhythmias and metabolite release as with digoxin were obtained with ouabain. The findings suggest that the decrease in myocardial ATP observed in glycoside-intoxicated heart preparations is partly due to the loss of nucleotide precursor substances. Moreover, it appears likely that liberated adenosine in the interstitium of severely intoxicated heart preparations reaches pharmacologically effective concentrations.

Adenine Nucleotides↗
PubMed1975

[Cardiac effects and glycoside concentrations in serum and urine after oral administration of beta-methy-digoxin to healthy individuals (author's transl)].

Six healthy individuals were digitalized orally with beta-methyl-digoxin. The serum glycoside concentration, determined radioimmunologically at the end of the digitalization period was 1.2 +/- 0.22 ng/ml. At this period of time renal excretion attained 55.9% of the daily administered oral dose. The calculated renal clearance of beta-methyl-digoxin was 63 +/- 8.1 ml/min e. g. 57.5 +/- 8.3 ml/min/1.73 m2. After discontinuation of the glycoside the serum half life was 54 h. During the digitalization period the cardiac glycoside effects could be measured by ECG changes, especially a shortening of the QT interval as well as a shortening of the left ventricular ejection time and the pre ejection period, corrected for the heart rate.

Administration, Oral↗
PubMed1988

Subchronic treatment with vanadate does not potentiate the toxicity of cardiac glycosides.

Since it has been claimed that vanadate is an endogenous regulator of Na/K-ATPase activity and that it potentiates the toxicity of cardiac glycosides, we were alarmed to discover that certain Finnish physicians were prescribing vanadate in combination with other trace minerals to elderly patients for many different chronic diseases (e.g., cancer, rheumatism). To study the interaction of vanadate and cardiac glycosides, we fed vanadate in the drinking water (25 micrograms/mL) to guinea pigs for 20 d, and studied either their sensitivity to the acute toxicity of the cardiac glycoside ouabain or whether the vanadate would influence the subacute toxicity of ouabain. Vanadate had no influence on the toxicity of ouabain either acute or subchronically administered, nor was there any sign of inhibition of Na/K-ATPase activity as measured by 86Rb-uptake into intact erythrocytes (RBCs), RBC content of sodium or potassium or Na/K-ATPase activity in RBC membranes prepared from the vanadate-treated guinea pigs. Vanadate had been absorbed in substantial quantities from the gastrointestinal tract, since serum, heart, liver, and especially kidney contained measurable amounts of vanadium in contrast to controls, but it is concluded that this vanadate is not in a biologically active form.

Animals↗
PubMed1999

New flavonol glycosides from leaves of Symplocarpus renifolius.

A study was carried out to evaluate flavonol glycosides in leaves of Symplocarpus renifolius (Araceae). From the water fraction of the MeOH extract, three new flavonol glycosides were isolated along with three known compounds, kaempferol-3-O-beta-D-glucopyranosyl-(1-->2)-beta-D-glucopyranosyl-7-O-b eta-D-glucopyranoside,quercetin-3-O-beta-D-glucopyranosyl-(1-->2)-beta-D -glucopyranoside, and caffeic acid. The structures of the new flavonol glycosides were elucidated by chemical and spectral analyses as quercetin-3-O-beta-D-glucopyranosyl-(1-->2)-beta-D-glucopyranosyl-7-O-be ta-D-glucopyranoside, isorhamnetin-3-O-beta-D-glucopyranosyl-(1-->2)-beta-D-glucopyra nos yl-7-O-beta-D-glucopyranoside, and quercetin-3-O-beta-D-glucopyranosyl-(1-->2)-beta-D-glucopyranosyl-7-O-(6 ''''-trans-caffeoyl)-beta-D-glucopyranoside.

Chromatography, High Pressure Liquid↗
PubMed1984

Cardiac glycoside receptors in cultured heart cells--I. Characterization of one single class of high affinity receptors in heart muscle cells from chick embryos.

Binding of (3H)-ouabain and ouabain-induced inhibition of the sodium pump and of the (Na+ + K+)-ATPase have been characterized in cultured cardiac muscle and non muscle cells, as well as in cardiac cell membranes--all obtained from chick embryos. In both cell types, ouabain binds to a single type of binding sites in a temperature-dependent manner. The association rate but not the dissociation rate, is lowered by K+; specific binding is lost after heat-denaturation of the cells. Binding parameters (association and dissociation rate constants, activation energies for association and dissociation) are similar in muscle and non muscle cells. The dissociation constant of specific ouabain binding is 1.5 X 10(-7)M in cardiac muscle cells, and 1.9 X 10(-7)M in cardiac non muscle cells, the binding capacity being 2.6 and 2.1 pmoles/mg protein respectively. Specific binding of ouabain to the cells is coupled to inhibition of the sodium pump, as can be seen from ouabain-induced inhibition of active (86Rb+ + K+)-uptake, decrease in cellular K+, and increase in cellular Na+ (EC50 = 10(-7)-10(-6)M). The data obtained with cardiac cells are in good agreement with results found for ouabain binding (dissociation constant 4.3 X 10(-7)M) and (Na+ + K+)-ATPase inhibition (EC50 = 1.4 X 10(-6)M) in cardiac cell membranes prepared from the same tissue. Due to the experimental evidence it is concluded that the binding site for ouabain is identical with the cardiac glycoside receptor of these cells. In cardiac non muscle cells, binding of ouabain to its receptor is strictly coupled to inhibition of active K+-transport in a stoichiometric manner. In cardiac muscle cells, however, active K+-transport is inhibited by less than 10% when up to 40% of cardiac glycoside receptors have bound ouabain. It is assumed that this non-stoichiometric coupling of receptor occupancy and sodium pump inhibition in cardiac muscle cells may prevent substantial changes of Na+- and K+-contents in the heart in the presence of therapeutic levels of cardiac glycosides.

Animals↗
PubMed1988

Comparison of [3H]ouabain binding sites in intact cells and cell homogenates: apparent lack of glycoside receptors unrelated to sarcolemmal Na+, K+-ATPase in guinea-pig heart.

In intact heart muscle cells incubated in a physiological solution, i.e. under the condition in which the cardiac glycosides produce pharmacological and toxicological effects, receptors for these actions of the glycosides should be available to ouabain. In cell homogenates, [3H]ouabain binding observed in the presence of Mg2+ and inorganic phosphate represents binding of the glycoside to Na+, K+-ATPase. Therefore, numbers of these two types of [3H]ouabain binding sites were compared using viable myocyte preparations obtained from ventricular muscle of guinea-pig heart. The number of ouabain binding sites observed in viable myocytes in the absence of Ca2+ and K+ was not different from the number of ouabain binding sites on Na+, K+-ATPase observed with sodium dodecylsulfate-treated homogenates prepared from isolated myocytes. These results do not support the hypothesis that there are receptors for the pharmacological or toxic actions of ouabain other than those that are associated with sarcolemmal Na+, K+-ATPase.

Animals↗
PubMed1983

O-glycosidic linkage in glycoprotein isolates from human ocular mucus.

Alkaline beta-elimination and sodium borohydride reduction were used to study the O-glycosidic linkage of N-acetylgalactosamine to seryl and threonyl residues in the high molecular weight crude glycoprotein fractions isolated from human ocular mucus. Pure mucins, BSM and OSM, were used as models. Data are presented for the existence of such O-glycosidic linkages. It was estimated from sodium borohydride reaction that at least 22% of the total peptide bonded hydroxyamino acid residues are linked O-glycosidically. These findings, as a continuation of our previous work on the isolation and chemical characterization of human ocular mucus, provided additional evidence of the mucin nature of the glycoprotein isolates.

Acetylgalactosamine↗
PubMed1993

High-performance liquid chromatographic method for measuring hydroxylysine glycosides and their ratio in urine as a possible marker of human bone collagen breakdown.

Glucosyl-galactosyl-hydroxylysine (GGHYL) and galactosyl-hydroxylysine (GHYL) are constituents of collagen protein. The ratio of the two hydroxylysine glycosides varies with the collagen type and, moreover, for a given collagen type, it also varies according to the connective tissue. For example, in type I collagen (the most abundant in the body), the GGHYL/GHYL ratio tends to be greater in soft connective tissues and lower in bone. The hydroxylysine glycosides are not recycled during collagen turnover and are excreted in the urine. Therefore, the urinary GGHYL/GHYL ratio, which reflects the proportion of the two metabolites in the various collagens, may indicate the type of connective tissue affected by pathological turnover, and may thus be a promising marker of bone metabolism. In this paper a method is described for the measurement of urinary hydroxylysine glycosides by reversed-phase liquid chromatography after purification of the sample by solid-phase extraction. The method presented is analytically reliable and suitable for routine use in a clinical laboratory.

Adult↗
PubMed2005

A colorimetric determination for glycosidic and bile salt-based detergents: applications in membrane protein research.

Detergents are crucial to the isolation of integral membrane proteins. During membrane protein purification, it is useful to accurately quantify detergent, especially if concentration steps have been used. Previously, this has been difficult and time-consuming. We present a simple, rapid, and sensitive procedure for the quantification of glycosidic and bile salt-based detergents such as dodecylmaltoside, octylglucoside, and CHAPS. The method directly quantifies sugar or cholate moieties via colorimetric reactions with phenol and sulfuric acid. A number of detergents have been screened, and the assay has been validated in the presence of commonly used reagents. In addition to determining the overall detergent concentration in solution, the procedure allows accurate quantification of specific binding of glycosidic or bile salt-based detergents to purified membrane proteins. Both the colorimetric method and the radiometric 14C method were used to determine detergent binding to two integral membrane proteins: the cytochrome cbb3 oxidase from Pseudomonas stutzeri and the turkey beta-adrenergic receptor. Both methods gave similar results. After separating monomeric glycosidic detergent from micellar solutions by ultrafiltration, we used the colorimetric method to determine the concentration of monomeric detergent present. We observed that values obtained are in close agreement with previously determined critical micelle concentrations.

Bile Acids and Salts↗
PubMed2006

Recent trends in the synthesis of O-glycosides of 2-amino-2-deoxysugars.

The discovery of new methods for stereoselective glycoside synthesis and convergent oligosaccharide assembly has been critical for the area of glycosciences. At the heart of this account is the discussion of the approaches for stereoselective synthesis of glycosides of 2-amino-2-deoxysugars that have emerged during the past two decades. The introductory part provides general background information and describes the key features and challenges for the synthesis of this class of compounds. Subsequently, major approaches to the synthesis of 2-amino-2-deoxyglycosides are categorized and discussed. Each subsection elaborates on the introduction (or protection) of the amino functionality, synthesis of glycosyl donors by introduction of a suitable leaving group, and glycosidation. Wherever applicable, the deprotection of a temporary amino group substituent and the conversion onto the natural acetamido functionality is described. The conclusions part evaluates the current standing in the field and provides a perspective for future developments.

Amides↗
PubMed2005

In vitro availability of kaempferol glycosides from cream formulations of methanolic extract of the leaves of Melilotus elegans.

In Ethiopian traditional medicine, Melilotus elegans Salzm. ex Ser. (Leguminosae) is used for the treatment of haemorrhoids and lacerated wounds. In view of its wide spread use and proven anti-inflammatory activity, 80% methanolic extract of the leaves was formulated into creams. HPLC/UV and MS studies revealed the presence of flavonoids, of which kaempferol was the major aglycone. Quantitative estimation of kaempferol in the hydrolyzed extract as determined by HPLC/UV was found to be 16.3+/-0.93 microg/mg (n=6, range) of extract. The in vitro release profiles of kaempferol glycosides (quantified as kaempferol equivalent) from the cream formulations in a multilayer membrane system indicated that a lipophilic cream of the extract provides higher release of kaempferol glycosides than hydrophilic and amphiphilic ones. Over a study period of 4h, the lipophilic cream released 66+/-5.70% of kaempferol glycosides, while the hydrophilic and amphiphilic creams resulted in 55+/-2.77 and 38+/-2.30% release, respectively.

Anti-Inflammatory Agents↗