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At least 955 records · Page 53Linked to original sources
PubMed1995

Comparison of hexose acetate-specific receptors isolated from human leukocytes showing competitive inhibition of human CD56+NK and LAK cytotoxicity.

Specific cytotoxicity of human CD56+NK and LAK cells was quantitatively inhibited by acetylated mannose, galactose and glucose (Scand. J. Immunol., in press). The respective NK cell receptors were isolated from human leukocyte lysates by affinity chromatography based on 60% deacetylated penta-acetates of mannose, galactose and glucose. All three affinity isolates contained a main component with +/- 87 kDa molecular mass exhibiting about the same patterns of isoforms at pI 4.90, 4.75, 4.60 and 4.50 in isoelectric focusing. Moreover, preincubation of tumor target cells with the three 87-kDa receptors revealed very similar inhibitory potentials for human NK and LAK cytotoxicity showing dose-dependent inhibition between 20 (no inhibition) and 700 pmol/ml (100% inhibition) receptor concentration. The data support the assumption that the three affinity isolates contain the same type of receptor directed against a unique epitope common to acetylated mannose, galactose and glucose.

Binding, Competitive↗
PubMed1991

Hexose metabolism in pancreatic islets: pyruvate carboxylase activity.

The anaplerotic hypothesis for insulin release postulates that an increased generation of malonyl-CoA, acyl residues and diacylglycerol in nutrient-stimulated pancreatic islets may couple the catabolism of nutrient secretagogues to more distal events in the secretory sequence. In the light of this hypothesis, pyruvate carboxylase activity was measured in rat pancreatic islets using two distinct radioisotopic procedures. The first procedure is based on the conversion of oxalacetate generated from pyruvate to 14C-labelled citrate in the presence of [1-14C]acetyl-CoA and citrate synthase. The second technique involves the conversion of 14C-labelled oxalacetate generated from [1-14C]pyruvate to radioactive aspartate in the presence of L-glutamate and glutamate-oxalacetate transaminase. Pyruvate carboxylase activity amounted to 10 pmol/min per islet, was restricted to mitochondria, displayed a Km for pyruvate close to 0.4 mM, and demonstrated dependency towards ATP (apparent Ka close to 0.1 mM), Mg2+ and acetyl-CoA. It is proposed that pyruvate carboxylase activity accounts for the generation of 14C-labelled amino acids other than alanine in islets exposed to D-[3,4-14C]glucose and participates to the pyruvate/citrate shuttle for the transport of acetyl-CoA out of the mitochondria in nutrient-stimulated islets.

Acetyl Coenzyme A↗
PubMed1991

Hexose metabolism in pancreatic islets. Effect of (-)-hydroxycitrate upon fatty acid synthesis and insulin release in glucose-stimulated islets.

Anaplerotic reactions leading to the de novo synthesis of fatty acids, were recently proposed to participate in the coupling of metabolic to secretory events in the process of glucose-stimulated insulin release. In an attempt to validate such a proposal, the effect of (-)-hydroxycitrate upon fatty acid synthesis and insulin release was investigated in glucose-stimulated rat pancreatic islets. The inhibitor of ATP citrate-lyase, when tested in the 1.0-2.0 mM range, failed to affect glucose-stimulated insulin release, but also failed to inhibit the incorporation of 14C-labelled acetyl residues derived from L-[U-14C]leucine into islet lipids. A partial inhibition of fatty acid labelling by 3H2O was only observed in islets incubated for 120 min in the presence of 5.0 mM (-)-hydroxycitrate and absence of CaCl2. These findings suggest that (-)-hydroxycitrate is not, under the present experimental conditions, a useful tool to abolish fatty acid synthesis in intact pancreatic islets.

Animals↗
PubMed1987

Hexose metabolism in pancreatic islets. Absence of glucose-6-phosphatase in rat islet cells.

Homogenates of either rat or mouse pancreatic islets, pure rat B cells or insulin-producing cells of the RINm5F line catalyzed the hydrolysis of D-glucose-6-phosphate. Relative to protein content, the enzymic activity, which was mainly associated with particulate rather than soluble subcellular material, was much lower in endocrine pancreatic cells than in liver. The rat islet enzyme differed from liver glucose-6-phosphate by its lower affinity for D-glucose-6-phosphate, its lower pH optimum, its greater relative efficiency towards L-glycerol-3-phosphate as distinct from D-glucose-6-phosphate, its restricted lability during exposure to pH 5.0, its inability to act as a glucose-6-phosphate:glucose phosphotransferase, and its insensitivity to inhibition by D-glucose. It is concluded that rat islet cells are virtually devoid of true glucose-6-phosphatase activity.

Animals↗
PubMed1976

Polychlorinated biphenyls (phenoclor and pyralene) and intestinal transport of hexoses and amino acids in mice.

1. Using mouse everted whole small intestine 7 days after a single dose of Phenoclor DP6 (hexachlorobiphenyl) at 1.0 g kg-1 body wt, absorption of D-glucose decreased significantly, probably owing to toxic traces of pentodicholobenzofuran in the PCB preparation and not its high chlorine content. D-glucose tissue accumulation decreased. The serosal fluid transfer also fell but not the gut fluid uptake. D-glucose absorption and fluid transfer remained unchanged following doses of other Phenoclor and Pyralene (PCB) compounds. 2. Using DP6, malabsorption of D-glucose and impaired serosal fluid transfer were not evident 7 days after a single dose of 0.1, 0.25 and 0.50 g kg-1 body wt. One to 21 days after a single dose (1.0 g kg-1 body wt) of DP6, D-glucose absorption and serosal fluid transfer decreased from 3 to 14 days but thereafter became normal. 3. Although absorption of D-galactose, D-glucose following membrane hydrolysis of D-maltose, and L-arginine, L-histidine, L-ornithine and L-proline decreased slightly 7 days after a single dose of Phenoclor DP6,the results were not significant, nor were changes in fluid transfer. 4. Following Phenoclor DP6-treatment, D-glucose malabsorption was abolished by an exogenous energy supply (D-mannose). DP6 affected intracellular metabolism and not the glucose carrier at the membrane brush border. 5. The body-weights and fresh small intestinal weights of mice treated with different PCBs remained unchanged after seven days. The histology of the small intestine showed minimal changes.

Amino Acids↗
PubMed1982

Effects of the bipyridilium herbicides, diquat and paraquat, on in vivo hexose absorption and fluid transfer in adult mice.

1. The effects of single LD50 oral or subcutaneous doses of diquat and paraquat at different time-intervals on in vivo intestinal absorption of glucose and galactose and concomitant mucosal fluid transfer were investigated. 2. Generally, both herbicides retarded the absorption of either monosaccharide, although the effects of the treatments at different time-intervals were sometimes inconclusive. 3. The mucosal fluid transfer was unaffected, as was the fresh or dry intestinal weights or the intestinal length.

Administration, Oral↗