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At least 811 records · Page 45Linked to original sources
PubMed1980

Chemotactic deactivation of human neutrophils: role of stimulation of hexose monophosphate shunt activity in nonspecific deactivation.

We have investigated the mechanism of the nonspecific component of chemotactic deactivation of human neutrophils. This component of deactivation occurs on exposure of neutrophils to larger doses of cytotaxin and is expressed as depressed subsequent spontaneous migration and chemotaxis toward all cytotaxins tested. We demonstrate a possible mechanistic association between stimulation of hexose-monophosphate shunt activity and the nonspecific component of deactivation. This association is evidenced by failure to effect deactivation of 0 degrees C, by the ability of non-chemotactic stimulatory agents to mimic cytotaxin-induced deactivation, by the ability of agents which block shunt activity to protect against deactivation, and by the ability of methylene blue to deactivate neutrophils from individuals with chronic granulomatous disease. Thus, excessive stimulation of shunt activity, possibly through generation of products of oxygen metabolism, appears to have an inhibitory influence on nonspecific neutrophil migratory functions.

Carbon Dioxide↗
PubMed1981

Effect of arachidonic acid on the hexose monophosphate shunt and related coenzymes in human blood platelets.

The aggregation of human platelets after addition of arachidonic acid (AA) is accompanied by a 30 fold increase in the net flux through the hexose monophosphate shunt (HMPS). The levels of reduced glutathione (GSH) and NADPH as well as the NADPH/NADPH+NADP quotient show a temporary fall which is restricted to the interval between AA addition and beginning of aggregation suggesting a lag phase between the onset of enhanced coenzyme consumption and that of increased coenzyme regeneration. together with literature data the results point to a possible regulatory function of reduced coenzymes and the HMPS in the process of platelet activation.

Arachidonic Acid↗
PubMed1982

Hexose-6-phosphate dehydrogenase of rat liver microsomes. Isolation by affinity chromatography and properties.

Hexose-6-phosphate dehydrogenase was purified from rat liver microsomal fraction more than 500-fold with a 45% recovery using DEAE-cellulose and 2',5'-ADP-Sepharose 4B columns. The purified enzyme appeared to be immunologically and electrophoretically homogeneous and had broad substrate and cofactor specificities. The enzyme activity was not inhibited by p-chloromercuribenzoate. The purified enzyme was a glycoprotein in nature, having a Stokes radius of about 55 A, a sedimentation coefficient of about 8.2 s, and an isoelectric point of about 6.4. Minimum molecular weight of the enzyme was about 108,000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, whereas the product cross-linked with glutaraldehyde or dimethyl suberimidate had Mr approximately equal to 220,000, suggesting that the active enzyme existed as a dimer of identical subunits. Antiserum raised against the purified enzyme inhibited the activity of the solubilized enzyme but did not inhibit the cytosol glucose-6-phosphate dehydrogenase activity. The antigenic sites of the enzyme were latent in intact microsomes. Comparison was also made between the enzymes isolated from untreated and phenobarbital-pretreated animals.

Animals↗
PubMed1978

The effect of chemotactic factors and agents which influence neutrophil movement on anaerobic glycolysis and hexose monophosphate shunt activity.

The effects of two chemotactic factors, endotoxin activated serm (EAS) and casein and a number of drugs known to affect intracellular cyclic nucleotide levels and various froms of neutrophil movement, on neutrophil anaerobic glycolysis and hexose monophosphate shunt (HMPS) activity were assessed. EAS caused stimulation of glycolysis. HMPS activity and NBT reduction, but casein was without effect on glycolysis and NBT reduction and inhibited HMPS activity. Drug known to increase intracellular cAMP levels caused a depression of HMPS activity whereas those reported to elevate cGMP had a variety of effects. Glycolysis was not affected by any of these agents. These results indicate a lack of relationship between cyclic nucleotide effect on cell motility and neutrophil glycolysis and HMPS activity.

Caseins↗
PubMed1982

Effect of endotoxin and glucocorticoid pretreatment on hexose monophosphate shunt activity in rat liver.

The acceleration of glycolysis by the Embden-Meyerhof pathway (EMP) in endotoxic and septic states and its counteraction by glucocorticoids has been demonstrated by past research. Although the glycolytic contribution of the hexose monophosphate (HMP) shunt is minor, its response during endotoxemia, if similar to that of EMP, could be theoretical interest, Fasted male rats (150-260 gm) were sacrificed at 5 hr after IV injection of E coli endotoxin in dosages of 2 or 3 mg/100 gm rat weight: LD50 (Nm= 15). A second group received 1 mg dexamethasone (DMS) IV per 100 gm rat weight simultaneously with endotoxin (N = 15). Livers were homogenized in 0.25 M cold sucrose and centrifuged at 15,000 g for 20 min. Specific activity of glucose-6-phosphate dehydrogenase (G6PDH) in control livers (N = 17) was 7.1 nmoles of substrate consumed per min/mg biuret protein. Endotoxin raised G6PDH activity by 49% to 10.64 units, and the endotoxin-DMS-protected group was 6.0 units. Levels of 6-phosphogluconate (6PG) were also measured in frozen liver biopsies from similar groups of rats. Liver 6PG concentrations of control (N = 15), endotoxic (N = 15), and endotoxified-DMS-treated (N = 9) groups were 22.5, 14.3, and 17.6 nmoles/gm wet tissue, respectively. The data indicate a significant 36% acceleration in 6PG consumption during endotoxemia, which is not blocked by DMS. The cofactor, nicotinamide adenine dinucleotide phosphate (NADP), decreased significantly by 18% from the control level of 152 nmoles/gm liver (N = 9) during endotoxemia, and this fall was not corrected by DMS. In a small group (N = 6), sedoheptulose-7-phosphate declined from the control value of 76 nmoles/gm wet liver by 38% after endotoxification. It is concluded that endotoxin stimulates G6PDH, the initial enzyme of the HMP pathway, and accelerates consumption of several intermediates, Glucocorticoid prevents the enzyme activity increase but does not restore 6PC and NADP concentrations to normal levels, suggesting that different enzyme sites along the HMP shunt may have unequal responses to DMS.

Animals↗
PubMed1981

Hexose monophosphate shunt metabolism in sheep: comparison of fetal, newborn and adult erythrocytes.

Glucose utilization through the hexose monophosphate shunt was measured in erythrocytes from fetal sheep, newborn lambs and adult pregnant sheep. Fetal erythrocytes demonstrate dramatically increased glucose oxidation in the presence of the oxidant new methylene blue. This response declines by birth and thereafter until adult sheep erythrocytes show no response. No stimulation was observed in adult sheep red cells under a number of conditions, although when adult sheep red cells were separated according to cell age, young cells were found to respond greatly to new methylene blue. When the rate of glucose oxidation after new methylene blue stimulation is correlated with in vitro glucose-6-phosphate dehydrogenase activity, a highly significant relationship is seen. This suggests that developmental changes in glucose oxidation by sheep red cells may be due to similar changes in glucose-6-phosphate dehydrogenase activity. The relationship also suggests that mature adult erythrocytes may be unable to respond to oxidants because of their low glucose-6-phosphate dehydrogenase activity.

Animals↗
PubMed1981

Hexose transport and phosphorylation by Novikoff rat hepatoma cells as function of extracellular pH.

The effect of extracellular pH on hexose uptake by cultured Novikoff hepatoma cells has been examined with respect to four distinct parameters: i) the transport of 3-O-methyl-D-glucose, ii) the uptake of 2-deoxy-D-glucose by intact cells, iii) the phosphorylation of 2-deoxy-D-glucose in vitro by cell-free preparations, and iv) the intracellular pH as measured by 5,5'-dimethyl[2-14C]oxazolidine-2,4-dione. Transport per se was not affected by pH in the range of 6 to 8, while uptake of 2-deoxy-D-glucose increased with pH 2- to 3-fold over this range. The pH sensitivity of uptake can be explained on the basis of a change in hexokinase activity effective in situ. The pH dependence of hexokinase observed in vitro, however, was insufficient to account for that apparent in situ.

Animals↗
PubMedDate not supplied

Lysis of a temperature conditional thiamineless mutant of Salmonella typhimurium by glucose and other hexoses.

The SM-3 mutant of Salmonella typhimurium was isolated as streptomycin resistant and temperature conditional thiamine auxotroph. At 37 C it required thiamine, although it behaves as a leaky mutant at this temperature in minimal liquid medium. At 30 degrees C it was able to growth without thiamine. In minimal-glucose-aminoacids at 37 C after an initial growth, cellular lysis occurred. The same happened with other hexoses, but it was not observable when glycerol or lactate were used as carbon source. Microscopic examination showed clumps of cellular debris, empty bagshapes and swelling of microorganisms, suggesting a cell wall defect. Sucrose 0.5 M protected SM-3 cells from osmotic fragility. At 30 C growth was normal and at 37 C in presence of exogenous thiamine full growth without bacteriolysis was obtained. Preliminary experiments of bacterial conjugation allowed the identification of a new locus involved in thiamine biosynthesis which was tentatively mapped in the pur A - pro B region of the chromosomal map of S. typhimurium.

Bacteriolysis↗
PubMed1975

The response of red cell hexose monophosphate shunt after sulfhydryl inhibition.

In this investigation, we studied the importance of cellular glutathione (GSH) in the hexose monophosphate shunt (HMPS) activity of unstimulated human erythrocytes and the mechanism by which pyruvate stimulates the HMPS. The rate of HMPS activity was measured by the production of radioactive CO2 from 14C-1-glucose or 14C-1-ribose using a vibrating reed electrometer and ionization chamber. HMPS activity was not significantly impaired by N-ethylmaleimide (NEM) in concentrations which bound all red cell GSH. Red cells incubated under carbon monoxide (CO), an experimental condition which eliminates peroxide production, still had HMPS activity which was 44% of the value under air. Pyruvate stimulation of the HMPS was unaffected by doses of NEM which bound all cellular GSH or by incubation under CO. These data indicated that pyruvate stimulation of the HMPS occurs by pathways which do not involve peroxide formation, GSH, or oxygen. This study indicates that sulfhydryl blockade of GSH does not necessarily inhibit HMPS activity and that HMPS activity in red cells may respond to reactions not linked directly to glutathione reduction.

Blood Glucose↗
PubMed1993

Transcripts for the high and low affinity hexose transporters in rat myoblasts.

The present investigation examined the glucose transporter (GLUT) transcript levels in glucose-grown rat L6 myoblasts, which possessed a high (HAHT) and a low (LAHT) affinity hexose transport system. The most prominent GLUT transcript detected in these cells was a GLUT 3-recognizable 4.1-kilobase transcript. Mutants defective in HAHT contained only residual levels of the GLUT 3 transcript and transporter. Corresponding changes in GLUT 3 transcript levels and HAHT activity were observed in myotubes, confluent cultures, and myogenesis-impaired cells. The other prominent GLUT transcripts detected were the GLUT 4-recognizable 2.8- and 1.4-kilobase transcripts. The close correlation between the GLUT 4 isoform and LAHT activity was indicated by the absence of this isoform in LAHT- mutants, and their corresponding changes in myoblasts grown under different conditions. These findings suggested the HAHT and LAHT transporters might be coded or regulated by the genes responsible for the GLUT 3 and 4 transcripts, respectively. Although relatively high levels of the GLUT 1 transcript and transporter were detected in glucose-grown HAHT-LAHT- mutants, these cells did not exhibit any GLUT 1 transport activity. Since the GLUT 1 transporter was not functional, it was not likely responsible for the HAHT and LAHT activities observed in glucose-grown L6 myoblasts.

Animals↗
PubMed1976

Impermeant maleimides. Identification of an exofacial component of the human erythrocyte hexose transport mechanism.

The facilitated diffusion of D-glucose across human erythrocyte membranes requires an exofacial (outer surface) sulfhydryl group which can be alkylated by the impermeant reagents glutathione-maleimide and dextran-maleimide. The irreversible inhibition produced by these reagents is asymmetric; inhibition of glucose efflux considerably exceeds that of influx when transport is assayed in the absence of glucose on the opposite side of the membrane. Both D-glucose and cytochalasin B protect the exofacial transport site from alkylation by the impermeant maleimides. This masking effect provides the basis for a two-step procedure for differential labeling of the outer transport site with radioactive glutathione-maleimide. The method labels clearly and consistently a component of the membrane proteins which migrates in sodium dodecyl sulfate-polyacrylamide gels between Coomassie brilliant blue-stained Bands 4.2 and 5, corresponding to an apparent molecular weight of 65,000 to 70,000. Transport studies after inhibition with N-ethylmaleimide suggest that the hexose mechanism also requires a second sulfhydryl group which is not accessible at the cell surface.

Binding Sites↗