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PubMed1999

Impaired adaptive cytoprotection to ethanol-induced damage in gastric mucosa of portal hypertensive rats.

Portal hypertension predisposes gastric mucosa to increased damage by noxious agents. Adaptive cytoprotection has not been studied in portal hypertensive gastric mucosa. We evaluated adaptive cytoprotection in the gastric mucosa of portal hypertensive rats by exposure to ethanol. The injury index (percent gross lesions) was significantly higher in portal hypertensive rats than in sham-operated rats. The ratio of adaptive cytoprotection, calculated as the degree of decrease in the injury index caused by pre-absolute-ethanol administration of 20% ethanol, was significantly impaired in portal hypertensive rats. Basal levels of gastric mucosal hexosamine were lower in portal hypertensive rats than in controls, and a blunted response to 20% ethanol was associated with portal hypertension. Nitric oxide inhibition (L-NAME, 5 mg/kg) reduced the ratio of adaptive cytoprotection in sham-operated but not in portal hypertensive rats. These results suggest that impaired adaptive cytoprotection in portal hypertensive gastric mucosa may be caused by blunted mucus production.

Adaptation, Physiological↗
PubMed1968

Studies on the enzymic N-acylation of amino sugars in the sheep colonic mucosa.

1. d-[2-(14)C]Glucose, [2-(14)C]acetate, hydroxy[3-(14)C]pyruvate, [3-(14)C]pyruvate and [U-(14)C]glycine were incorporated by surviving scrapings of sheep colonic mucosal tissue into glycoprotein. 2. d-[2-(14)C]Glucose, [2-(14)C]acetate, incorporated hydroxy-[3-(14)C]pyruvate and [3-(14)C]pyruvate resulted in labelling of each of the monosaccharide residues of the glycoprotein, namely N-glycollylneuraminic acid, N-acetylneuraminic acid, galactose, fucose, glucosamine and galactosamine. [U-(14)C]Glycine was incorporated as glycyl and seryl residues of the glycoprotein. 3. Despite N-glycollylneuraminic acid being quantitatively the predominant sialic acid (N-glycollylneuraminic acid and N-acetylneuraminic acid were 8.5 and 5.2% by weight of the glycoprotein respectively) the corresponding ratio of the radio-active labelling from d-[2-(14)C]glucose in N-glycollylneuraminic acid to that in N-acetylneuraminic acid was 1.00:7.27 (expressed as percentages of the total radioactivity in the glycoprotein). Neutral sugar, hexosamine and N-acetylneuraminic acid residues of the mucoprotein were each labelled to a similar extent. 4. Similarly, the ratio of the radioactivity in N-glycollylneuraminic acid to that in N-acetylneuraminic acid in the mucoprotein from tissue incubations with [2-(14)C]-acetate was 1.0:4.0. 5. Both [2-(14)C]acetate and [2-(14)C]glucose with whole tissue led to labelling of the N-glycollyl substituent and of the main nonose skeleton of the N-glycollylneuraminic acid. In whole-tissue incubations, [3-(14)C]pyruvate was also a precursor of radioactive N-glycollylneuraminic acid. 6. Hydroxy[3-(14)C]-pyruvate and [U-(14)C]glycine caused labelling of the carbohydrate and peptide residues of the glycoprotein, but did not give rise to labelling in the N-glycollylneuraminic acid residues. 7. With a wide variety of possible N-glycollyl precursors (fructose 6-phosphate, hydroxypyruvate, glycollate and chemically synthesized glycollyl-CoA) biosynthesis of N-glycollylglucosamine was not observed in cell-free preparations.

Acetates↗
PubMed1968

Carbohydrate content of bovine collagen preparations.

Collagen preparations from bovine tissues were analysed for their carbohydrate content. Crude preparations of tropocollagen and polymeric collagen were found to be contaminated with considerable amounts of mannose, fucose and hexosamine, sugars known to be present in the mucoprotein of the interfibrillar material with which collagen is associated in vivo. A pure preparation of tropocollagen obtained by ethanol precipitation procedures contained only galactose and glucose in the approximate ratio of 7:3 residues/3000 amino acid residues. Purification of crude polymeric collagen by EDTA extraction or by crude bacterial amylase extraction considerably decreased the mucoprotein contamination, particularly in the enzymic treatment, which yielded a preparation containing predominantly galactose and glucose in the ratio of 4:2 residues/3000 amino acid residues. The results confirm previous work that demonstrated the purity of these collagen preparations as inferred by amino acid analysis. The results also indicate the suitability of the pure tropocollagen and the amylase-extracted polymeric collagen for studies on the role of the carbohydrate residues in intramolecular and intermolecular cross-linking in collagen.

Amylases↗
PubMed1968

Determination of amino sugars in mixtures containing glucosamine, galactosamine and muramic acid.

A colorimetric method is described whereby the direct quantitative determination of glucosamine, galactosamine and muramic acid can be achieved without previous treatment of the cell-wall hydrolysate, for example by column chromatography. Molar ratios of hexosamines in cell-wall preparations, from a number of bacterial species, determined by this method were found to be in general agreement with previously published results.

Amino Sugars↗
PubMed1968

The isolation and characterization of a glycoprotein from human thoracic aorta.

1. A glycoprotein extracted by cold alkali from the walls of human aorta was purified by chromatography on DEAE-cellulose. 2. The compound was electrophoretically homogeneous and essentially so by chromatography on DEAE-cellulose. Ultracentrifugal examination revealed two components, and it is suggested that the faster-sedimenting component represents an aggregated form of the glycoprotein. 3. Glycoprotein preparations contained approx. 8% of carbohydrate. Digestion with Pronase yielded a glycopeptide fraction containing all the carbohydrate of the glycoprotein. The glycopeptide, of molecular weight about 7800, contained sialic acid, galactose, mannose, fucose and hexosamine in the approximate molar proportions 5:10:5:2:11. Sialic acid was terminal with respect to the polysaccharide chains. 4. Both elastase and elastomucoproteinases exhibited proteolytic activity towards the glycoprotein. Studies by other investigators have led to the conclusion that elastomucoproteinases attack protein-carbohydrate complexes occurring in intimate association with elastin in aorta and other tissues, and it is suggested that the glycoprotein may be identified with one of these compounds.

Adolescent↗
PubMed1969

The isolation of a component of the venom of Trimeresurus okinavensis that causes the aggregation of blood platelets.

1. A substance has been isolated from the venom of the Okinawan pit viper (Trimeresurus okinavensis) that causes the aggregation of human blood platelets. The reaction resembles that between platelets and thrombin or connective tissue, in that the platelets release ADP. 2. The purified venom fraction is a protein-polysaccharide, and after Pronase digestion had mol.wt. 4x10(6), containing 10% peptide, 85% neutral sugars and 5% hexosamines. It is distinct from the proteolytic, esterolytic and coagulant materials also present in the venom, and has not been shown to possess any enzymic activity. How it reacts with platelets is not yet known.

Adenine Nucleotides↗
PubMed1970

The release of radioactive nucleic acids and mucoproteins by trypsin and ethylenediaminetetra-acetate treatment of baby-hamster cells in tissue culture.

Monolayers of baby-hamster kidney cells were grown on glass in tissue culture and harvested with trypsin or EDTA in order to investigate the cell surface macromolecules removed by these cell-disaggregating agents. The release of nucleic acids from the cells during the harvesting procedure was monitored by labelling the cellular RNA with [5-(3)H]uridine and the cellular DNA with [2-(14)C]thymidine. Treatment of the cells with EDTA was found to cause an increase in the permeability of the plasma membrane with 7.6% of the cellular RNA, but less than 1% of the cellular DNA, being released. Moreover, 61% of the cells harvested with EDTA were permeable to Trypan Blue. With crude trypsin, lysis of the cell occurred with the release of similar amounts of RNA and DNA amounting to about 11% of the total cellular nucleic acid. In contrast, crystalline trypsin released only 1% of the cellular nucleic acids. Since virtually all the cells (99%) after harvesting in crystalline trypsin were impermeable to Trypan Blue, this method was suitable for obtaining cell surface macromolecules without contamination by intracellular damage. [1-(14)C]Glucosamine was incorporated by the cells only into bound hexosamines and sialic acids. [By monitoring the release of radioactivity in high-molecular-weight material in such experiments a measure of the release of macromolecules containing amino sugars was obtained.] Of the total macromolecules containing amino sugars in the cells 33%, 24% and 13% were released when the cells were harvested with crude trypsin, crystalline trypsin or EDTA respectively. Crystalline trypsin also released 39% of the total sialic acid of the cell, whereas less than 1% of the cellular sialic acid was present in the EDTA-treated fraction. It is concluded that the macromolecules containing amino sugars released with crude trypsin and EDTA are likely to be heavily contaminated with intracellular material. However, the macromolecules released by crystalline trypsin appear to come from the cell surface.

Animals↗
PubMed1970

Autolysis of isolated cell walls of Bacillus licheniformis N.C.T.C. 6346 and Bacillus subtilis Marburg Strain 168. Separation of the products and characterization of the mucopeptide fragments.

1. Cell walls were isolated from Bacillus licheniformis N.C.T.C. 6346 and Bacillus subtilis Marburg strain 168 trp grown on casein hydrolysate into exponential phase. Autolysis was carried out and the soluble products, separated by chromatography on DEAE-cellulose, from the two wall preparations are broadly similar in composition and are in agreement with autolysis proceeding with hydrolysis of amide bonds between l-alanine and N-acetylmuramic acid residues in the mucopeptide components. 2. Peptides originating from the mucopeptide components were isolated and shown to be a monomer peptide, l-alanyl-d-glutamyl-meso-diaminopimelic acid and a dimer peptide containing two monomer peptides linked through a residue of d-alanine. Approximately one amide group is present for each equivalent tripeptide unit and is probably substituted on diaminopimelic acid residues. 3. Oligosaccharides originating from the mucopeptide components were isolated and after hydrolysis contained almost equimolar amounts of glucosamine and muramic acid and only very small amounts of amino acids. The number-average chain length, estimated by the release of non-reducing end groups of N-acetylglucosamine with exo-beta-N-acetylglucosaminidase, is approximately ten hexosamine residues for oligosaccharides isolated from either organism. The oligosaccharides are polydisperse. 4. N-Acetylglucosamine residues are the only reducing terminals detectable in the oligosaccharides isolated from B. subtilis or B. licheniformis cell-wall autolysates. The number-average chain lengths of the oligosaccharides were determined by estimation of the content of these residues and are higher than those found by enzymic assay. Possible reasons for the discrepancy are discussed.

Autolysis↗
PubMed1971

Chemical composition of an oestrogen-induced calcium-binding glycolipophosphoprotein in Xenopus laevis.

1. Oestrogen treatment has previously been shown to induce the formation of large amounts of a serum protein, vitellogenin (xenoprotein), in Xenopus laevis. Vitellogenin was purified from serum by dimethylformamide precipitation and was shown to be homogeneous by a variety of electrophoretic techniques. 2. The molecular weight of vitellogenin was estimated by gel filtration to be about 6x10(5). The chemical constituents of vitellogenin were determined and lead to the characterization of this protein as a serum calcium-binding glycolipophosphoprotein. 3. The extractable lipid accounted for 12% of vitellogenin. Gas-liquid-chromatographic analysis of the saponified lipid moiety showed the presence of palmitic acid, palmitoleic acid, stearic acid, oleic acid and linoleic acid in the molecular proportions 6.8: 1.5: 1.0: 3.6: 1.4. 4. The carbohydrate moiety consisted of 0.4g of hexose, 0.77g of hexosamine and 0.18g of sialic acid/100g of vitellogenin. 5. The calcium and phosphorus contents were 0.85 and 1.65g/100g of vitellogenin respectively. 6. Serum from oestrogen-treated animals injected with (45)CaCl(2) contained 9.7 times the radioactivity present in serum from untreated (45)CaCl(2)-injected animals. Of the radioactivity due to (45)CaCl(2) in the serum of oestrogen-treated animals 72% was non-diffusible on dialysis. Of this activity 65.4% was associated with the vitellogenin band on cellulose acetate electrophoresis.

Animals↗
PubMed1971

Studies on gastric mucoproteins. The isolation and characterization of the mucoprotein of the water-soluble mucus from pig cardiac gastric mucosa.

1. Gel filtration of the water-soluble radioactive mucus produced three radioactive fractions, fraction A excluded on Sepharose 4B, fraction B included on Sepharose 4B but excluded on Sephadex G-200, and fraction C included on Sephadex G-200. 2. The specific radioactivities of fractions A and B were the same, with fraction C a little lower, whether the material was labelled with (14)C-labelled carbohydrate or with (3)H-labelled protein prepared by incubation of mucosal scrapings in vitro with [U-(14)C]glucose or [G-(3)H]threonine respectively. 3. Fractions A and B had an analysis of protein 22%, hexose 28%, hexosamine 28%, fucose 10% and sialic acid 1%; fraction C had an analysis closely similar to this, except that it contained about 10% of a protein contaminant. 4. All three fractions had closely similar A and H blood-group activities. 5. Ultracentrifuge studies showed fractions A, B and C were polydisperse with s(0) (25,w) values of 18.7S, 4.9S and 3.9S respectively. 6. The unfractionated water-soluble mucus contained only two peaks, fraction A 18.7S and a peak of 4.4S, which was a combination of fractions B and C. 7. The radioactive mucoprotein accounted for 85% by weight of the soluble mucus and the results show that it consisted of two distinct fractions A and B-C, which were chemically, biosynthetically and immunologically very similar.

ABO Blood-Group System↗
PubMed1971

The isolation, and amino acid and carbohydrate composition, of polymeric collagens prepared from various human tissues.

1. Insoluble polymeric collagens from various human tissues were prepared by the EDTA method. Almost all of the collagen from simple soft tissues such as dermis, tendon, submucosa, sclera and cornea could be extracted, whereas the more complex tissues such as intercostal cartilage and intervertebral disc yielded only small amounts of collagen. Amino acid and carbohydrate analysis indicated that most of the preparations were highly purified on the basis of their tyrosine, hexosamine, mannose, xylose and fucose contents. 2. Wide variation in the total hexose content was observed, the lowest being 8.5 residues/3000 amino acid residues for collagen from dermis and the highest being 42.1 residues/3000 in corneal collagen. The molar ratios of sugars also varied, submucosal collagen having a galactose/glucose ratio of 1.0 and corneal collagen having a ratio of 2.3. 3. The presence of glucosylgalactosylhydroxylysine was confirmed in submucosal collagen by compositional and chromatographic analysis of this component after its isolation from alkaline hydrolysates of the collagen. Evidence was also obtained for the presence of galactosylhydroxylysine. 4. Determination of the hydroxylysyl glycosides was carried out and it was observed that the amounts of these components varied widely from tissue to tissue. Corneal collagen contained 19.1 hydroxylysine-linked carbohydrate units/3000 amino acid residues, whereas tendon collagen contained only 4.1 units/3000. Variation in the ratio disaccharide unit/monosaccharide unit was also observed, the ratio being 1.2 in intercostal cartilage collagen and 4.1 in submucosal collagen. The proportion of the total hydroxylysine that was substituted by carbohydrate also varied from tissue to tissue.

Amino Acids↗
PubMed1971

Biosynthesis of liver membranes. Incorporation of ( 3 H)leucine into proteins and of ( 14 C)glucosamine into proteins and lipids of liver microsomal and plasma-membrane fractions.

1. The smooth-and rough-microsomal and the light and heavy plasma-membrane fractions of mouse liver homogenates were prepared and characterized by using biochemical markers. 2. The hexosamine/protein ratio was threefold higher in the plasma membranes than in the smooth-microsomal fraction. Glucosamine was bound only to protein, and galactosamine was attached mainly to lipids. 3. [(3)H]-Leucine and [(14)C]glucosamine were injected into animals and the rates of incorporation of radioactivity into the fractions were determined. Both precursors were rapidly incorporated into the microsomal fractions, but plasma membranes showed a slower rate of synthesis which reached a maximum at 2-4h after intravenous administration. 4. The light- and heavy-plasma-membrane fractions showed similar patterns of incorporation, and therefore a precursor-product relationship appears unlikely. 5. Plasma membranes, especially the light subfraction, showed appreciable incorporation of hexosamine into chloroform-methanol-soluble components which were shown to be mainly glycolipids. 6. The results indicate that liver plasma-membrane proteins and glycoproteins are synthesized at similar rates. However, glycolipid synthesis in plasma membranes occurred more rapidly.

Animals↗
PubMed1972

The biosynthesis in vitro of keratan sulphate in bovine cornea.

1. Bovine corneas were incubated in vitro with [U-(14)C]glucose. 2. The glycosaminoglycans of corneal stroma were isolated and fractionated on cetylpyridinium chloride-cellulose columns. The major components were keratan sulphate (71%), chondroitin 4-sulphate (17%) and chondroitin 6-sulphate (4%). 3. The acid-soluble nucleotides and intermediates of glycosaminoglycan biosynthesis of corneal stroma were separated on Dowex 1 (formate form) and the tissue content and cellular concentrations were determined. 4. The rates of synthesis of the intermediates of glycosaminoglycan biosynthesis in corneal stroma were determined. 5. The incorporation of radioactivity from [U-(14)C]glucose into the uronic acid and hexosamine components of the glycosaminoglycans present in corneal stroma were measured and the turnover rates of these polymers were calculated. It was found that keratan sulphate was turning over in about 723h and chondroitin 6-sulphate in 251h.

Animals↗
PubMed1972

Pepsin treatment of avian skin collagen. Effects on solubility, subunit composition and aggregation properties.

1. Collagen was extracted from chick skin with dilute acetic acid followed by dilute acetic acid containing pepsin. 2. The solubilized collagens were purified and portions subjected to further digestion by pepsin. 3. This treatment decreased the aldehyde content but contamination by hexosamine was not diminished. 4. Pepsin treatment converted practically all the acid-soluble collagen into monomeric subunits (alpha-chains), but the pepsinsolubilized material retained a significant amount of higher subunits (beta- and gamma-chains). 5. Treatment lowered the rate of fibrillogenesis by acid-soluble collagen, but was without effect on pepsin-solubilized collagen.

Acetates↗
PubMed1973

Isolation and characterization of a glycoprotein from human colostrum.

A glycoprotein was isolated from the M-1 acid glycoprotein fraction of human colostrum. It had a molecular weight of 31200 and contained 27% galactose, 21.7% hexosamine, 8.0% fucose and 10.8% sialic acid by weight. The glycoprotein had no absorption maxima in the 240-300nm region, and was virtually free of ABH(O) and M and N blood-group activity. Alkaline borohydride cleavage of the glycoprotein resulted predominantly in the destruction of threonine and galactosamine.

Borohydrides↗
PubMed1973

Alterations in glycosaminoglycan metabolism in beta-aminopropionitrile-treated chick embryos.

1. Na(2) (35)SO(4), [1-(14)C]glucosamine and [1-(14)C]acetate were used as precursors of the sulphated glycosaminoglycans to study the biochemical effect of beta-aminopropionitrile in chick embryos. The incorporation of all three precursors was decreased in the treated embryos between days 7 and 10 of embryonic development. No inhibition of incorporation of these precursors occurred between days 16 and 20 of embryonic development at the dosages of beta-aminopropionitrile used. 2. beta-Aminopropionitrile treatment also decreased the amount of N-acetylhexosamines in the chick embryo and decreased the percentage of the hexosamine esterified by nucleotides. Respiration was decreased by homogenates prepared from treated embryos. Likewise, UDP-xylosyl- and UDP-galactosyl-transferase activities were decreased in treated embryos and cartilage from embryos and growing chicks. 3. The data suggest that beta-aminopropionitrile, in addition to the known lathyrogenic activity, either is or gives rise to a potent metabolic poison that interferes with basic cellular metabolism. The results are consistent with a decreased rate of ATP generation as an explanation for the decrease in glycosaminoglycan synthesis.

Acetates↗
PubMed1974

The copolymeric structure of pig skin dermatan suplhate. Characterization of D-glucuronic acid-containing oligosaccharides isolated after controlled degradation of oxydermatan sulphate.

Selective periodate oxidation of unsubstituted l-iduronic acid residues in copolymeric dermatan sulphate chains was followed by reduction-hydrolysis or alkaline elimination. By this procedure the glucuronic acid-containing periods were isolated in oligosaccharide form; general formula: [Formula: see text] Further degradation of these oligosaccharides with chondroitinase-AC yielded three types of products: (a) sulphated trisaccharide containing an unsaturated uronosyl moiety in the non-reducing terminal and a C(4) fragment in the reducing terminal, DeltaUA-GalNAc-(-SO(4))-R; (b) monosulphated, unsaturated disaccharide, DeltaUA-GalNAc-SO(4) when n is greater than or equal to 2; and (c) N-acetylgalactosamine with or without sulphate. Oligosaccharides containing a single glucuronic acid residue (n=1) comprised more than half of the glucuronic acid-containing oligosaccharides. The terminal N-acetylgalactosamine moiety of the shortest oligosaccharide was largely 4-sulphated, whereas higher oligosaccharides primarily contained 6-sulphated or unsulphated hexosamine moieties in the same position. Moreover, IdUA-SO(4)-containing oligosaccharides were encountered. These oligosaccharides were resistant to the action of chondroitinase-ABC.

Animals↗
PubMed1975

Chemical and physical characteristics of a phosphoprotein from human parotid saliva.

The isolation of a highly purified phosphoprotein, previously named protein A, from human parotid saliva is described. This protein has an unusually high amount of glycine, proline and dicarboxylic amino acids. Together these amino acids account for 80% of all residues. The protein contains 1.9mol of P/mol of protein, probably as phosphate in an ester linkage to serine, and about 0.5% carbohydrate, but no hexosamine. The N-terminal is blocked and the following C-terminal sequence is proposed: -Aal-Asp-Ser-Gln-Gly-Arg-Arg. The sioelectric point is 4.43. The molecular weight of the protein determined by ultracentrifugation is 9900 and from chemical analyses 11000. Circular-dichrosim and nuclea-magnetic-resonance spectra indicate the absence of polyproline and triple-helical-collagen-like structure for the protein. There is little restriction on the orientation of the single phenylalanine residue in the protein., but there is also an indication of conformational restraint in the protein.

Amino Acids, Dicarboxylic↗