Solubilization and chemical and immunochemical characterization of sparingly soluble canine gastric mucin

Analysis of cancer-associated colonic mucin by ion-exchange chromatography: evidence for a mucin species of lower molecular charge and weight in cancer

Cancer-associated mucins in the colon are antigenically distinct and glycosylated differently from their normal counterparts. Mucin-rich glycoconjugate preparations were made from nine non-neoplastic colons, seven colon cancers, and two different xenografts from mucin-producing human colon cancer cell lines, and radiolabeled with 3H. The preparation was applied to a DEAE-cellulose ion-exchange column, and eluted with a discontinuous ascending NaCl gradient resulting in seven discrete fractions or 'species'. Over half of the 3H-labeled glycoconjugates from specimens of non-neoplastic colonic epithelium eluted in fraction V (eluted with 0.25 NaCl). Significantly less of the 3H-labeled glycoconjugates from specimens of colon cancer eluted in fraction V (34%, P less than 0.0005), and there were significant increases in glycoconjugates eluted in fractions IV (P less than 0.008), III (P less than 0.0005), and II (P less than 0.028). Additional samples were prepared without the radiolabeling procedures, chromatographed on a DEAE-cellulose ion-exchange column, and analyzed for monosaccharide content. Each of the fractions contained the monosaccharides expected in mucin-type glycoproteins, but only sialic acid was differentially expressed in the seven fractions or 'species', occurring principally in the more charged species. However, differences in sialic acid content were not sufficient to explain the differences in retention on the ion-exchange column, nor were differences in O-acetylation of the mucins. Mucin-type glycoconjugates from colon cancers are relatively less charged than those from the normal colon, and elute at lower ionic strengths. Of interest, cancer-associated mucins appear to be of lower molecular weight than their normal counterparts. Additional studies of oligosaccharide and apomucin structure will be required to explain the molecular basis of these differences in charge.

Arteriovenous differences for amino acids across control and acid-secreting rat stomach in vivo

1. A method is described for measuring arteriovenous differences across the rat stomach in vivo. 2. Notable results were the uptake of branched-chain amino acids, the uptake of arginine, which was approximately balanced by an output of ornithine, and the output of alanine. 3. The fractional extraction of glutamine from the blood by the stomach wall of pentagastrin-stimulated rats was 4.7%. 4. The arteriovenous differences for ammonia depended upon the blood ammonia concentration. 5. Arteriovenous differences were not affected by the stimulation of acid secretion with pentagastrin. 6. It is concluded that the high activity of branched-chain-amino-acid aminotransferase (EC 2.6.1.42) in the gastric mucosa is associated with metabolism of these amino acids, but that the stomach wall is a less avid user of glutamine than is the small intestine.

Factors influencing the viscous properties of chicken tracheal mucins

1. Reduced viscosities, in water, of different types of mucin, such as fibrillar, gelatinous and soluble phase, separated from chicken tracheal secretions were measured. 2. H-bond breaking agents caused a significant decrease in the reduced viscosity of these mucins, but thiol-reagents alone did not have any effect. 3. Papain and Pronase did not cause any decrease in the reduced viscosity of these mucins. Neuraminidase decreased the reduced viscosity of soluble phase mucin by 50% by removing about 30% of its N-acetylneuraminic acid but had no effect on fibrillar and gelatinous mucins. Sulphatase neither removed any sulphate ester groups nor decreased the reduced viscosity. Due to some nonspecific intermolecular interaction, mixtures of mucins and enzymes or ovalbumin exhibited elevated reduced viscosities. 4. Ionic strength of the solutions appeared to decrease the reduced viscosity of these mucins. Increasing concentrations of Ca2+ in solutions of ionic strength of approx. 0.1 caused significant decrease in the reduced viscosity, but had no such effect in solutions of ionic strength of more than 0.1. 5. N-Acetylneuraminic acid and sulphate ester residues were 46.6 +/- 0.2, 43.4 +/- 0.6, 27.9 +/- 3.3 mg/g and 66.0 +/- 2.0, 34.2 +/- 3.3, 2.5 +/- 0.8 mg/g for fibrillar, gelatinous and soluble phase mucins, respectively. There appeared to be a good correlation between viscosity and N-acetylneuraminic acid contents among mucins of low reduced viscosities and between viscosity and sulphate ester residues among mucins of high reduced viscosities.

Histochemical reactions of gastrointestinal mucosubstances with high iron diamine after prior oxidation and methylation of tissue sections

High iron diamine reactions after the prior methylation and oxidation of tissue sections with performic acid or potassium permanganate (metox-HID or ox-met-HID) in epithelial mucosubstances and in mucosal mast cells were studied in tissue samples from the human gastrointestinal tract and were compared with reactions with high iron diamine without any pretreatment (HID) and high iron diamine with the prior methylation (met-HID). High iron diamine reactions after the prior oxidation (met-ox-HID, ox-met-Hid and ox-Hid) demonstrated mucosubstances in a way which seemed to operate by the staining of acidic groups evoked by the oxidation of the tissue sections. These acidic groups were not blocked by the methylation. It was supposed that they are sulphonic acids resulting from sulphur groups (sulphydryls or disulphides) in some mucus glycoproteins. Met-ox-HID and ox-met-HID reactions seemed to stain mucosubstances and mast cells in a similar way but differed from the ox-HID reactions with the manner which could be interpretated to be due to the blocking of free sulphate ester groups in reactions of the former. Met-ox-HID (and ox-met-HID) positive and in goblet cells of small and large bowel.

The glycoprotein content of meconium

Meconium pooled according to blood group activity has been studied. It was found to consists largely of glycoproteins. Two glycoprotein fractions have been isolated, one of which consisted of mucous-type glycoproteins and the other of "mannose-containing" glycoproteins.

Characterization of gastric mucoproteins isolated by equilibrium density-gradient centrifugation in caesium chloride

1. The mucoprotein from pig gastric mucus has been purified by equilibrium centrifugation in a CsCl gradient. 2. This procedure removes the non-covalently bound protein, which is closely associated with the mucoprotein and not easily removed from it by gel filtration. 3. The purified mucoprotein is separable by gel filtration into a high-molecular-weight mucoprotein A (mol.wt. 2.3x10(6)) and a low-molecular-weight mucoprotein B/C (mol.wt. 1.15x10(6)). 4. These two mucoproteins have the same chemical analysis namely fucose 11.3%, galactose 26%, glucosamine 19.5%, galactosamine 8.3% and protein 13.6%. 5. Mucoprotein A contains 3.1% ester sulphate. 6. These mucoproteins are isolated without enzymic digestion and have a higher protein content than the blood-group-substance mucoproteins from proteolytic digestion of gastric mucus. Detailed amino acid analysis shows that the extra protein in the non-enzymically digested material is composed of amino acids other than serine and threonine. 7. Mucoproteins A and B/C contain respectively 130 and 9 half-cystine residues per molecule of which about 78 and 6 residues are involved in disulphide linkages. 8. Cleavage of these disulphide linkages by mercaptoethanol splits both mucoproteins into four equally sized subunits of mol.wt. 5.2x10(5) for mucoprotein A and 2.8x10(4) for mucoprotein B/C. 9. The sole N-terminal amino acid of mucoprotein A is aspartic acid, whereas mucoprotein B/C has several different N-terminal amino acid residues.

Glycosyltransferases in human blood. II. Study of serum galactosyltransferase and N-acetylgalactosaminyltransferase in patients with liver diseases

Serum galactosyltransferase activity was found to be elevated in patients with alcoholic and other liver disorders but remained at a normal level in patients with a variety of nonhepatic diseases. The properties of the galactosyltransferase in patients with liver disease were compared with those of the enzyme in the serum of normal subjects. The possible presence of inhibitors or activators in the serum was examined. Results indicated that in patients with liver disease, the rise in the serum galactosyltransferase was due to an increase in the level of the enzyme present in normal serum and not due to the appearance of a new enzyme. In the cases examined, the level of the enzyme increased with the deterioration of liver function and declined in a patient recovering from acute alcoholic hepatitis. Another glycosyltransferase, an N-acetylgalactosaminyltransferase, was not elevated in the serum of liver disease patients and, unlike the galactosyltransferase, was not detected in normal liver. The results suggest that the serum galactosyltransferase originates from the liver and that an abnormal rise in the level of this enzyme in serum is due to hepatocellular damage.