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Effect of nutrients, hormones and serum on survival of rat islet beta cells in culture.

This study quantifies the survival of purified single rat beta cells under different culture conditions. Less than 10% of the cells survive 9 days of culture in Ham's F10 medium without supplements. Addition of fetal calf serum (5%) increases cell survival to 54% in the absence and to 78% in the presence of isobutylmethylxanthine (50 mumol/I). The effect of serum is explained, at least partly, by the presence of albumin and of low molecular weight constituents. In serum-free Ham's F10 with 50 mumol/l isobutylmethylxanthine, 75% of cells survive after the addition of bovine serum albumin (1%) and of ultroser (0.2%), a commercial serum substitute. Survival of at least 75% of cells is also maintained in Ham's F10 with isobutylmethylxanthine plus albumin, and supplemented by metabolizable nutrients or by the peptides glucagon (10(-8) mol/l) or growth hormone (1 micrograms/ml) plus insulin like growth factor-I (50 ng/ml). D-Glucose increases beta-cell survival in a dose-dependent manner up to 10 mmol/l; a beneficial effect is also observed with other metabolizable compounds (leucine and glutamine) but not with non-metabolizable monosaccharides. Glucose-induced survival of islet beta cells can be attributed to its dose-dependent recruitment of cells into metabolic activities; however, a 9-day exposure to excessively high nutrient concentrations (> 20 mmol/l glucose) is deleterious to the cells. These results define culture media, with or without serum, wherein at least 75% of single rat islet beta cells can survive for a minimum of 9 days. This will allow for studies on beta-cell toxic conditions and potentially protective agents.(ABSTRACT TRUNCATED AT 250 WORDS)

1-Methyl-3-isobutylxanthine↗

Lectin histochemistry of scrapie amyloid plaques.

Peroxidase-labeled lectins were used for detection of specific monosaccharide residues in amyloid plaques in brains of scrapie-infected mice. The lectins tested recognize the following residues: beta-D-galactosyl (Ricinus communis agglutinin 120, RCA-1), alpha-D-galactosyl and alpha-D-galactopyranoside (Bandeirea simplicifolia aggl., BSA), alpha-D-mannosyl and alpha-D-glucosyl (Concanavalin A, Con A), N-acetylglucosaminyl and sialyl (Wheat germ aggl., WGA), sialoglycoconjugates (Limulus polyphemus aggl., LPA), alpha-L-fucosyl (Ulex europeus aggl., UEA-1 and Tetragonolobus aggl., TPA), N-acetyl-D-galactosaminyl (Helix pomatia aggl., HPA). The most intense staining reaction in amyloid plaques was observed with BSA and WGA; it was less intense with RCA-1, Con A, and HPA. This indicates that the plaque material contains glycoproteins with abundance of accessible residues of alpha- and beta-galactose, N-acetyl-D-glucosamine and N-acetyl-D-galactosamine, and some types of sialo-glycoconjugates recognized by WGA. Such residues, like alpha-L-flucosyl recognized by UEA-1 and TPA, were almost undetectable in the examined plaques. There were also some differences in the staining intensity between small and large plaques (WGA and HPA) and between central and peripheral areas of the plaques. In the wall of micro-blood vessels relatively strong staining reaction was observed with RCA and BSA and less intense with WGA and Con A.

Amyloid↗

Lectin histochemistry of plaques and tangles in Alzheimer's disease.

Biotinyl derivatives of several lectins and avidin-horseradish peroxidase were used to study the localization of glycoconjugates in amyloid plaques and in neuritic tangles in brains of patients with Alzheimer's disease (AD), Downs syndrome (DS) and Gerstmann-Sträussler syndrome (GSS). The lectins tested recognize the following residues: beta-D-galactosyl [Ricinus communis agglutinin 120, (RCA-1) and peanut agglutinin, (PNA)]; alpha-D-galactosyl [Griffonia simplicifolia agglutinin (GSA)]; alpha-D-mannosyl greater than alpha-D-glucosyl [concanavalin A (Con A) and Lens culinaris agglutinin (LcH)]; N-acetyl- and N-glycolyl-neuraminic acid [Limax flavus agglutinin (LFA) and Limulus polyphemus agglutinin (LPA)]; N-acetyl-glucosaminyl and sialyl [wheat germ agglutinin (WGA)]; N-acetyl-D-galactosaminyl [Helix pomatia agglutinin (HPA) and Dolichos biflorus agglutinin (DBA)] and alpha-L-fucosyl [Ulex europeus agglutinin (UEA-1)]. The majority of lectins listed above bind preferentially to the peripheral area of AD plaques, whereas in plaques of DS they are mainly bound to central amyloid core. In neurofibrillary tangles of AD brains only residues recognized by WGA and HPA or DBA were found, whereas in DS brains, in addition to above mentioned, beta-D-galactose (RCA-1) and sialic acid (LFA) were also present. In brain microblood vessels the strongest reaction in endothelia appeared with UEA-1 and RCA-1, indicating the abundance of alpha-L-fucosyl and beta-D-galactosyl residues. In AD brains deposits of amyloid were noted in the wall of some blood vessels, where monosaccharide residues recognized by RCA-1, GSA, UEA and WGA but not by Con A and LFA were present. However, our studies of some organs (liver, kidney, heart and testes) of patients with generalized amyloidosis revealed a lack of these sugar residues. It indicates, that the composition of amyloid present in brains of AD is different to that in other organs in generalized amyloidosis.

Alzheimer Disease↗

Fine sugar specificity of the Butea frondosa seed lectin.

Various monosaccharides and oligosaccharides were used to define the specificity of the Butea frondosa lectin using the hapten inhibition technique of human erythrocyte agglutination. Although B. frondosa lectin exhibited higher affinity for N-acetylgalactosamine, lactose and N-acetyllactosamine appeared to be relatively good inhibitors of haemagglutination. The behaviour of N-acetyllactosamine-type oligosaccharides and glycopeptides on a column of B. frondosa lectin immobilized on Sepharose 4B showed that the sugar-binding specificity of the lectin is directed towards unmasked N-acetyllactosamine sequences. Substitution of these N-acetyllactosamine sequences by sialic acid residues completely abolished the affinity of the lectin for the saccharides. The presence of one or several alpha Fuc(1-3)GlcNAc groups completely inhibited the interaction between the glycopeptides and the lectin. Substitution of the core beta-mannose residue by an additional bisecting beta(1-4)GlcNAc residue decreases the affinity of the lectin for these structures as compared with the unsubstituted ones.

Carbohydrate Sequence↗

Characterization and distribution of soluble and insoluble carbohydrates in lupin seeds.

White, blue and yellow lupin seeds were analyzed for their soluble and insoluble carbohydrate contents. The seeds contained only traces of starch. Their furfural generator contents were fairly constant (9.3--10.5%) and their soluble sugar contents were in the range of 11.8 to 14.1%. Thin-layer and column chromatography of the ethanol-soluble sugars showed the presence of varying amounts of ajugose, verbascose, stachyose, raffinose and sucrose. Quantitative analysis revealed an average of 25% sucrose in the total sugars, the major part of which is composed of alpha-galactosides. Separate analysis of the cotyledons (including the germ) showed that the latter contain 80% total carbohydrates, most of which were structural polysaccharides. The composition of the cell-wall constituents was examined after acid hydrolysis. Monosaccharides resulting after acid hydrolysis of the hemicelluloses were predominantly xylose and arabinose. Smaller quantities of galactose and glucose, and traces of rhamnose were also present. The cotyledons contain a considerable amount of soluble sugars (19.0%). Small amounts of glucose-containing polymers, soluble in water and dilute acid, were present in the cotyledons (1.0%); they increased to 2.4% in the hulls.

Carbohydrates↗

Duodenal microflora: a prospective study in pediatric gastrointestinal disorders.

Culture of the duodenal microflora was performed on 96 infants and children with a variety of gastrointestinal disorders. The resident microflora consists predominantly of oral-type microorganisms such as alpha-Streptococci and Neisseria. A fecal-type microflora was found in all 6 infants with post-surgical diarrhea and temporary monosachcaride intolerance; 4 of 22 patients with protracted diarrhea of infancy, 3 of 22 patients with celiac disease, and none of 32 patients with nonspecific diarrhea or 14 others with miscellaneous disorders. Anaerobic microorganisms were seldom isolated. Only 9% of the duodenal cultures were completely sterile, although a further 17 had a quantitative culture less than 5 times 10(4) microorganisms/ml. Small-bowel contamination with fecal-type microorganisms is associated with stasis and disturbance of the normal peristaltic-clearing mechanism. Duodenal culture is essential in any infant with temporary monosaccharide intolerance. It is occasionally useful in other situations where motility may be disturbed.

Adolescent↗

[Dietary fiber and pectin fractions of Beta vulgaris var. conditiva].

The alcohol-insoluble substance (AIS) from red beet (Beta vulgaris var. conditiva Alef.) (3.31% of the edible substance) was extracted sequentially with water, ammonium oxalate, 0.05 N HCl and 0.05 N NaOH. Accordingly 3.93 g, about 0.8 g, 2.96 g resp. 3.80 g galacturonan/100 g AIS were extracted with this procedure. These pectin extracts were purified as Cu2 +-salts and fractionated into a water-soluble and a water-insoluble part. The composition of neutral monosaccharide units was estimated in the fractions. Gal, Ara and Glc dominated; Xyl, Rha and Man were also present but in smaller amounts. A higher GalA content was found in the soluble fractions (with the exception of the alkali extract). Pectins from red beet are middle- or low-esterified and partially acetylated. The composition of the AIS and of the residue after pectin extraction (RE) was determined (14.6 resp. 9.5% pectin; 10,6 resp. 17.6% protein; 58.7 resp. 64.9% total polysaccharides). In the AIS 23.3% soluble and 54.7% insoluble dietary fiber were estimated, whereas in RE 15.3 resp. 54.7% were found (enzymatic method). Following dietary fiber fractions were determined by the detergent method for both preparations: 39.0 resp. 52.7% NDF; 6.3 resp. 4.5% NDF filtrate; 23.6 resp. 41.8% ADF; 1.2 resp. 1.8% lignin. The water binding capacity decreased from 19.85 g water (AIS) to 11. 53 g water (RE) related to 1 g AUS. From these just 50% were found in the NDF fractions and about 13% in the ADF fractions. Alterations of the grown biological structures during pectin extraction and dietary fiber analysis (detergent method) were investigated by scanning electron microscopy.

Chromatography, Gas↗

Effects of carbohydrate type on postprandial blood pressure, neuroendocrine and gastrointestinal hormone changes in the elderly.

Previous studies have demonstrated that blood pressure falls postprandially in fit elderly subjects, the greatest changes occurring after meals with a high carbohydrate content. To evaluate the influence of the type of carbohydrate on postprandial blood pressure, the effects of equivalent energy content (2.4 MJ) high complex (starch) and high simple (monosaccharide) carbohydrate meals were studied in seven healthy elderly subjects. Blood pressure, heart rate, autonomic function, plasma catecholamines, insulin and neurotensin levels were measured pre- and postprandially. Greater falls in supine and erect systolic blood pressure occurred after the high simple than the high complex carbohydrate meal (p less than 0.05). No differences were found in supine or erect diastolic blood pressure, heart rate or in any of the biochemical parameters measured between the meal types. It is concluded that a simple carbohydrate meal results in a greater postprandial fall in blood pressure than an equivalent energy complex carbohydrate meal in the elderly, although the mechanisms for these changes are unknown.

Aged↗

Automatic column chromatographic analysis of saccharides and uronic acids.

Using n-proponal/water as the eluting solvent, a flow rate of 50 ml/h and a 90 degrees C column temperature, the separation of a complex mixture of 11 monosaccharides could be much improved over the procedure described by v. Wilm and Sordé using isopropanol/water, 70--100 ml/h flow rate and temperatures of 83--90 degrees C. With a small total error of 3%, the saccharide analysis lies in the region of reproducibility that has also been reached in amino acid analysis. The limit of detection for saccharides lies at 1 x 10(-9) mole/ml.

Autoanalysis↗

Isolation and partial characterization of basic proteinases from stem bromelain.

Crude bromelain extracts from pineapple stems (Ananas comosus) were fractionated by two-step FPLC-cation-exchange chromatography. At least eight basic proteolytically active components were detected. The two main components F4 and F5 together with the most active proteinase fraction F9 were characterized by SDS-PAGE, mass spectroscopy, multizonal cathodal electrophoresis, partial amino acid sequence, and monosaccharide composition analysis. F9 amounts to about 2% of the total protein and has a 15 times higher specific activity against the substrate L-pyroglutamyl-l-phenylanalyl-l-leucine-p-nitroanilide (PFLNA) than the main component F4. The molecular masses of F4, F5, and F9 were determined to 24,397, 24,472, and 23,427, respectively, by mass spectroscopy. Partial N-terminal amino acid sequence analysis (20 amino acids) revealed that F9 differs from the determined sequence of F4 and F5 by an exchange at position 10 (tyrosine-->serine) and position 20 (asparagine-->glycine). F4 and F5 contained fucose, N-acetylglucosamine, xylose, and mannose in ratio of 1.0:2.0:1.0:2.0, but only 50% of the proteins seem to be glycosylated, whereas F9 was found to be unglycosylated. Polyclonal antibodies (IgG) against F9 detected F4 and F5 with tenfold reduced reactivity. The pH optimum of F4 and F5 was between pH 4.0 and 4.5 and for F9 close to neutral pH. The kinetic parameters for PFLNA hydrolysis were similar for F4 (Km 2.30 mM, kcat 0.87 sec-1 and F5 (Km 2.42 mM, kcat 0.68 sec-1), and differed greatly from F9 (Km 0.40 mM, kcat 3.94 sec-1).

Amino Acid Sequence↗

Analysis of carbohydrates in glycoproteins by high-performance liquid chromatography and high-performance capillary electrophoresis.

We describe two methods for the analysis of oligosaccharide chains in glycoproteins by high-performance liquid chromatography (HPLC) and high-performance capillary electrophoresis (HPCE). O- and N-glycosidically linked oligosaccharides released from glycoproteins can be identified as their borohydride-reduced forms by anion-exchange HPLC with pulsed amperometric detection. N-Glycosidically linked oligosaccharides can also be analyzed as 2-aminopyridine derivatives by HPCE in direct zone electrophoresis mode in an acidic phosphate buffer and zone electrophoresis mode as borate complexes in an alkaline buffer. We also present a convenient procedure for the analysis of the constituent monosaccharides of these oligosaccharides chains by HPLC based on reversed-phase partition mode as 1-phenyl-3-methyl-5-pyrazolone derivatives.

Aminopyridines↗

Growth of Candida tropicalis 2838 cells on straw hydrolyzates.

Improved strain of Candida tropicalis 2838 grows on nonseparated straw hydrolyzates with no addition of vitamins and trace elements at a specific growth rate mu = 0.34 and 44% yield coefficient (referred to reducing substances). The reducing substances in hydrolyzates contain predominantly monosaccharides (xylose, glucose, arabinose, mannose). Cells grown in this way are rich in proteins (62%) and essential amino acids (lysine, phenylalanine, leucine, threonine and valine). The product obtained under industrial conditions by fermentation of the nonseparated hydrolyzates contains 8--9% of proteins and it is a suitable supplement of fodder mixtures for monogastric domestic animals. Nutrition tests on rats and pigs indicated that this product can substitute the hay-flour, and, partially, blood-flour barley, and that the strain used is nonpathogenic.

Animal Feed↗

Transport properties of two extremely thermophilic species of Thermus.

Thermus flavus and T. ruber grew optimally at 75 and 60 degrees C, respectively, but transport of monosaccharides (D-quinovose) and amino acids (2-aminoisobutyric acid) had optima about 20 degree C lower. Both transports were active, inhibited by 2,4-dinitrophenol but hardly at all by uranyl(2+) ions. Several transport systems are apparently involved with each class of compounds. Preincubation with glucose curtailed subsequent transport severely. Practical cessation of transport below 35 degrees C may be associated with the rather uniform composition of membrane lipids where iso- and anteiso-C15 and C17 acids are practically the only components.

Amino Acids↗

A lipopolysaccharide from Aspergillus flavus conidia.

A lipopolysaccharide was isolated by extraction of Aspergillus flavus conidia with 45% phenol at 68-70 degrees C. Quantitative analysis revealed 7% nucleic acids, 5.5% proteins, 46% polysaccharides and 49% liquids, of which 12% were covalently bound. Glucose, mannose, galactose and fucose were detected as monosaccharide components of the polysaccharide moiety by gas chromatography; palmitic acid, stearic acid, oleic acid, linoleic acid and myristic acid were mainly present in the lipidic fraction. This material differs from the bacterial lipopolysaccharides, both in composition of the polysaccharide moiety and representation of fatty acids in the lipidic fraction.

Aspergillus flavus↗

On the track to the beta-cell.

The imaging and quantification of the endocrine pancreas by a non-invasive procedure remains a challenge. In the prolongation of prior work on selected succinic acid esters and monosaccharide esters, it is proposed that D-mannoheptulose, which might be transported across the plasma membrane at the intervention of GLUT-2, could be used to label preferentially the endocrine moiety of the pancreatic gland. This heptose is taken up more efficiently by hepatocytes and islet cells, than by erythrocytes, parotid cells, acinar pancreatic cells or tumoural islet cells of either the RINm5F or INS-1 line. Likewise, D-mannoheptulose only inhibits D-glucose metabolism in hepatocytes and isolated islets. Its hexaacetate ester, however, inhibits the catabolism of the hexose in all cell types. The uptake of D-mannoheptulose represents a carrier-mediated process. Human islets behave like rat islets in terms of D-mannoheptulose uptake and inhibition by the heptose of both D-glucose metabolism and insulinotropic action. The use of radiolabelled analogs of D-mannoheptulose suitable for imaging of the endocrine pancreas is discussed. In the same perspective, it is proposed that advantage could be taken of the much greater accumulation of glycogen in insulin-producing cells, as compared to other pancreatic cell types, in situations of sustained hyperglycaemia.

Animals↗

Cell wall of Thermoanaerobacterium thermosulfurigenes EM1: isolation of its components and attachment of the xylanase XynA.

Thermoanaerobacterium thermosulfurigenes EM1 has a gram-positive type cell wall completely covered by a surface layer (S-layer) with hexagonal lattice symmetry. The components of the cell envelope were isolated, and the S-layer protein was purified and characterized. S-layer monomers assembled in vitro into sheets with the same hexagonal symmetry as in vivo. Monosaccharide analysis revealed that the S-layer is associated with fucose, rhamnose, mannosamine, glucosamine, galactose, and glucose. The N-terminal 31 amino acid residues of the S-layer protein showed significant similarity to SLH (S-layer homology) domains found in S-layer proteins of different bacteria and in the exocellular enzymes pullulanase, polygalacturonate hydrolase, and xylanase of T. thermosulfurigenes EM1. The xylanase from T. thermosulfurigenes EM1 was copurified with the S-layer protein during isolation of cell wall components. Since SLH domains of some structural proteins have been shown to anchor these proteins noncovalently to the cell envelope, we propose a common anchoring mechanism for the S-layer protein and exocellular enzymes via their SLH domains in the peptidoglycan-containing layer of T. thermosulfurigenes EM1.

Amino Acid Sequence↗

Capillary electrophoresis: a superior miniaturized tool for analysis of the mono-, di-, and oligosaccharide constituents of glycan moieties in proteoglycans.

Proteoglycans are a major family of glycoconjugates which participate in and regulate several cellular events and biological functions. Their glycan chains determine their physicochemical and biological properties. Capillary electrophoresis, because of its high resolving power and sensitivity, has been successfully used for the analysis of carbohydrates. The monosaccharide constituents, the disaccharide sulfation pattern, and the uronic acid distribution within glycan chains of proteoglycans determine their interactions with matrix effectors and are responsible for numerous effects. Determination of the chemical composition and identification of key structural components and domains of glycans are, therefore, essential in understanding the biological functions of proteoglycans. In this report an overview of the capillary electrophoresis methods used to analyze and characterize the structure of the glycan chains of proteoglycans is presented.

Carbohydrate Sequence↗

Thiosugars: new perspectives regarding availability and potential biochemical and medicinal applications.

Thiosugars, containing a sulfur atom as heteroatom or a disaccharide linked via a sulfur bridge, possess unique physicochemical properties such as water solubility, which differs from conventional functionalized monosaccharides. The differences in biological activities between thiosugars and their oxygen analogs depend on geometric, conformational, and flexibility differences. They depend also on their electronic differences, the sulfide function being less electronegative and more polarizable than the ethereal moiety. Many functionalized thiosugars occur naturally and are potential targets for the development of carbohydrate-based therapeutics. Among the few new examples of the potential new targets are salacinol and kotalanol, tagetitoxin, thiolactomycin and analogues, mycothiol and analogues, and S-nitrosothiols. These new developments and representative examples of functionalized thiosugar prototypes as potential new targets are presented in this mini review.

Carbohydrate Conformation↗