Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0847097 (acidity)
 15,165 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Amantadine treatment of cells infected with H7 strains of influenza A viruses causes an M2 protein-mediated conversion of hemagglutinin (HA) from its native to its low pH conformation. Immunofluorescence and electron microscopic observations showed that the structural alteration and hence drug action occur shortly after HA exits from the Golgi complex during its passage through the strans Golgi region. Using the DAMP/anti-DNP pH probe it is evident that virus infection causes increased acidity of the trans Golgi region and that vesicles containing low pH HA in amantadine-treated virus-infected cells are particularly acidic. These results indicate therefore that the alteration in HA is the direct consequence of exposure to an adverse low pH and provide further support for the conclusion that the M2 protein, the target of amantadine action, is involved in regulating vesicular pH, a function important for the correct maturation of the HA glycoprotein.
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PMID:Evidence that the amantadine-induced, M2-mediated conversion of influenza A virus hemagglutinin to the low pH conformation occurs in an acidic trans Golgi compartment. 156 69

Basal and pentagastrin- or insulin- stimulated secretion was studied in 72 non ulcer dyspectic patients (NUD), in 289 non operated duodenal ulcer patients (DU), and in 30 DU, before and after highly selective vagotomy (HSV). Acidity, proteolytic activity, choline indicating the presence of duodenogastric refluxed material and sialic acid bound to mucus glycoprotein, marker of mucus erosion, were measured. Basal and pentagastrin-stimulated acid and pepsin secretions in NUD were significantly reduced with regard to those in DU. Sialic acid content was weak in basal secretion and markedly increased in response to pentagastrin reaching the values observed in DU. DU basal secretions of acid and of pepsin were modulated according to the stimulating secretory mechanism. Mucus glycoprotein erosion was related to pepsin mucolytic activity and/or to the presence in gastric juice of refluxed material. In DU the increase of peptic mucolysis corresponded to a biological signal of the ulcer attack when no duodenogastric reflux was identified. High values pepsin output in basal secretion and in response to insulin and of basal sialic acid content combined with a pepsin/acid basal output ratio higher than 80 were biological arguments anticipating the efficacy of HSV in DU. Multiparametric analysis of gastric secretion allows to evaluate the ratio between aggressive factors and mucosal defense corresponding to an equilibrium in NUD and to greater aggressivity in DU whose intensity is related to the course of disease.
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PMID:[Gastric functional exploration. Comparison between secretory results in 72 non-ulcer dyspeptic patients and 289 non-operated duodenal ulcer patients. Predictive criteria for the efficacy of fundus vagotomy in duodenal ulcer]. 181 13

Zinc sulfadiazine (ZnSD) 50, 100, 200 mg/kg ig inhibited the formation of gastric ulcer induced by indomethacin, stress and pyloric ligation in rats respectively and showed dose-dependently. ZnSD 200 mg/kg ig accelerated the healing of gastric ulcer induced by acetic acid. ZnSD 25 mg/kg ig was effective in preventing ethanol-induced damage of rat gastric mucosa. The amount of gastric mucus glycoprotein in gastric tissues was increased by ZnSD. In general, ZnSD did not influence the volume of gastric juice and pepsin output, but ZnSD 200 mg/kg ig decreased gastric acidity. In vitro, ZnSD also influenced the neutralization of acid. It is suggested that antiulcer action of ZnSD may be related to its preservation of the gastric mucosal barrier and neutralization of acid.
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PMID:[Anti-gastric ulcer activity of zinc sulfadiazine in rats]. 213 Jun 5

Amantadine hydrochloride specifically blocks the release of virus particles from H7 influenza virus infected cells. This appears to be the direct consequence of an amantadine induced change in the haemagglutinin (HA) to its low pH conformation. The effect is indirect and mediated via interaction of the drug with the M2 protein since mutants altered in this component alone are insensitive to amantadine. The timing of drug action, some 15-20 min after synthesis, and its coincidence with proteolytic cleavage indicates that the modifications to HA occur late during transport but prior to insertion into the plasma membrane. Reversal by mM concentrations of amines and 0.1 microM monensin indicates that amantadine action causes a reduction in intravesicular pH which triggers the conformational change in HA. We conclude, therefore, that the function of M2 inhibited by amantadine is involved in counteracting the acidity of vesicular compartments of the exocytic pathway in infected cells and is important in protecting the structural integrity of the acid-sensitive glycoprotein.
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PMID:Specific structural alteration of the influenza haemagglutinin by amantadine. 220 54

Structures of the N-linked oligosaccharides of a recombinant soluble form of human CD4 glycoprotein (sCD4) have been investigated by enzymic microsequencing. The glycoprotein has two N-glycosylation sites, Asn271 and Asn300, at both of which evidence for the presence of complex type biantennary sialo-oligosaccharides has been obtained previously by mass spectrometric analyses [Carr, S.A., Hemling, M.E., Folena-Wasserman, G., Sweet, R.W., Anumula, K., Barr, J.R., Huddleston, M.J. & Taylor, P. (1989) J. Biol. Chem. 264, 21,286-21,295]. Among oligosaccharides released from sCD4 by hydrazinolysis and labelled with NaB3H4, neutral (12.8%) and acidic (87.2%) oligosaccharides were detected by paper electrophoresis. The latter were rendered neutral following sialidase treatment indicating that acidity was due exclusively to the presence of sialic acid residues. By enzymic microsequencing of the sialidase-treated oligosaccharides (fractionated on affinity columns of Ricinis communis agglutinin 120 and concanavalin A) in conjunction with methylation data from the earlier study, 14 sequences were identified. These accounted for over 80% of the sialidase-treated oligosaccharides of sCD4 as follows: [formula: see text] where +/- indicates residues present on only a proportion of chains. The spectrum of oligosaccharide structures released from each glycosylation site was assessed as being similar to that of total oligosaccharides on the basis of their chromatographic profiles on the lectin columns and on Bio-Gel P-4.
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PMID:The spectrum of N-linked oligosaccharide structures detected by enzymic microsequencing on a recombinant soluble CD4 glycoprotein from Chinese hamster ovary cells. 220 9

The combined determination in human gastric juice of sialic acid content, a marker of solubilized glycoproteins, and of acidity and proteolytic activity has been performed in 217 gastric secretory studies. Taking 1000 micrograms/h of basal sialic acid output as approximating the upper limit of normal, 33 of 34 normal subjects and 12 of 12 patients without recurrent ulcer after highly selective vagotomy had basal sialic acid output below this value while 139 of 156 duodenal ulcer patients and 15 of 15 patients with Zollinger Ellison syndrome had basal sialic acid output above it. No clear relationship between sialic acid and hydrochloric acid outputs was observed; in contrast, close positive significant correlations were noted between sialic acid and pepsin outputs: r and P values ranging, respectively, from 0.82 to 0.63 and from less than 0.001 to less than 0.02. Measurement of sialic acid output content in basal secretion could thus serve to assess mucus glycoprotein output which appears, in large part, related to gastric juice proteolytic activity.
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PMID:Sialic acid content and proteolytic activity in gastric juice in humans. An approach for appreciating mucus glycoprotein erosion. 259 59

Rats were administered [3H]fucose by intracranial injection and synaptic membranes (SMs) isolated 18 h later. Oligosaccharides associated with SM glycoproteins were prepared by hydrazinolysis and analyzed by a combination of affinity chromatography on concanavalin A (Con A)-agarose, ion-exchange chromatography on DEAE-cellulose, and gel permeation chromatography. Most (94%) of the [3H]fucose-labelled oligosaccharides were present in the fraction that did not bind to Con A. Of these 41% did not bind to DEAE-cellulose, indicating the absence of negatively charged groups and the remainder were resolved into four fractions of increasing acidity. Gel permeation chromatography of the fractions from the DEAE-cellulose column suggested that the major oligosaccharides corresponded to fucosylated triantennary structures containing varying amounts of sialic acid although more highly branched structures containing peripheral branches lacking one or more sugars may also have been present. Comparison of fucosyl oligosaccharides associated with SMs prepared from 10- and 28-day-old animals indicated that although the general oligosaccharide content was similar at both ages, membranes from younger animals were characterized by an increase in the proportion of highly acidic structures. Fucosylated glycans derived from synaptic junctional (SJ) glycoproteins were also characterized by a greater percentage of highly acidic structures than SMs. The results indicate that SMs and SJs are characterized by specific complements of fucosylated glycoprotein oligosaccharides.
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PMID:Characterization of fucosyl oligosaccharides associated with synaptic membrane and synaptic junctional glycoproteins. 355 70

The interaction of ricin with ganglioside GM1 or glycoprotein containing liposomes was investigated. At neutral pH, ricin bound to galactose moieties on the surface of the liposomes to form ricin-liposomes complexes, but did not associate with their lipid bilayers. When these ricin-liposomes complexes were exposed to a pH below 5, ricin bound to GM1-liposomes became associated with the lipid bilayer, whereas ricin bound to glycoprotein-liposomes (containing human erythrocyte Band 3) was only rarely associated. Association of ricin with the lipid bilayer of GM1-liposomes did not occur in the presence of lactose, which inhibits the binding of ricin to ganglioside GM1. Using a hydrophobic probe, 8-amino-1-naphthalene sulfonic acid (ANS), it was revealed that an acidity below pH 5 resulted in exposure of hydrophobic regions on the ricin molecule. These results strongly suggest that association of ricin with the lipid bilayer of GM1-liposomes at acidic pH is mediated by the binding of ricin to ganglioside GM1 at neutral pH and occurs through interaction between the exposed hydrophobic region on the ricin molecule and the lipid bilayer of GM1-liposomes at low pH.
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PMID:Receptor-mediated interaction of ricin with the lipid bilayer of ganglioside GM1-liposomes. 358 69

The fusogenic properties of Semliki Forest virus (SFV) and its mutants were used to follow the kinetics of acidification during the endocytic uptake of virus by BHK-21 cells. It has previously been shown that the low pH of endocytic vacuoles triggers a conformational change in the SFV spike glycoprotein, activating membrane fusion and initiating virus infection. This conformational alteration was here shown to occur in endosomes and to follow the same time course as the intracellular fusion reaction, demonstrating that fusion occurs rapidly after virus exposure to endosome acidity. The kinetics of endosome acidification were monitored using wild type (wt) SFV and fus-1, an SFV mutant with a lower fusion pH threshold. The results presented here demonstrated that wt and mutant virus were internalized with a t1/2 of 10 min, and that endosomes were acidified to the wt threshold of pH 6.2 with a t1/2 of 15 min. In contrast, endosome pH reached the fus-1 threshold of 5.3 with a much longer t1/2 of 45 min. The subsequent degradation of SFV in lysosomes had a t1/2 of 90 min. It was found that after the initial uptake of virus from the plasma membrane, its transit through the endocytic pathway, exposure to endosome acidity and eventual delivery to lysosomes were markedly asynchronous.
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PMID:Kinetics of endosome acidification detected by mutant and wild-type Semliki Forest virus. 381 55

Tracheae, bronchi, nasal epithelial, and nasal polyp tissue slices were incubated in tissue culture with [3H]-glucosamine, and the rate of secretion of labeled mucus glycoproteins was measured. Secretion rates were at least 3- to 6-fold higher for all of the samples from nine patients with cystic fibrosis (CF) who were studied, as compared with values for tissue slices from eight young subjects not affected with this disease. The secreted glycoproteins were further purified into one neutral and three acidic fractions by ion-exchange chromatography on DEAE-cellulose. The glycoproteins secreted by respiratory epithelial tissue from cystic fibrosis subjects contained relatively more of two acidic glycoprotein fractions. Double-label experiments with both [3H]-glucosamine and [35S]-sulfate as mucus glycoprotein precursors further substantiated the shift to more acidic components in the purified mucus glycoproteins and, in addition, suggested a higher level of sulfation of these same two acidic glycoprotein fractions. All four of the labeled glycoprotein fractions secreted by cultured human bronchi cochromatographed with authentic mucus glycoproteins purified from sputum of cystic fibrosis subjects by the same techniques. The differences between mucus glycoproteins from cultured CF airway tissue and mucus glycoproteins from other patients' tissue included relatively increased rates of production, level of sulfation, and greater acidity. Further applications of these in vitro techniques should allow the determination of the enzymatic and biochemical causes of these observed differences in the absence of such potentially confounding variables as concurrent airway infection or of oropharyngeal secretions.
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PMID:Mucus glycoproteins secreted by respiratory epithelial tissue from cystic fibrosis patients. 683 12


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