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At least 793 records · Page 44Linked to original sources
PubMed1975

Induction of sugar transport in chick embryo fibroblasts by hexose starvation. Evidence for transcriptional regulation of transport.

Incubation of chick embryo fibroblasts in glucose-free medium resulted in a dramatic increase in the rate of 2-deoxy-D-glucose transport. The greatest increase in rate occurred during the first 20 hours of incubation in glucose-free medium and was blocked by actinomycin D, dordycepin, or cycloheximide. The conditions of 2-deoxy-D-glucose concentration and time of incubation with the sugar were determined where transport rather than phosphorylation was rate-limiting in sugar uptake. These studies demonstrated that the transport of 2-deoxy-D-glucose was rate-limiting for only 1 or 2 min when the concentration of sugar in the medium was near the Km for transport, i.e. 2mM. No difference was found in the level of hexokinase activity in homogenates prepared from cells incubated glucose-free medium or standard medium when either 2-deoxy-D-[14C]glucose or D-glucose was used as substrate. A kinetic analysis of the initial rates of 2-deoxy-D-glucose transport by Lineweaver-Burk plots showed that the Vmax for sugar transport increased from 18 to 95 nmol per mg of protein per min when fibroblasts were incubated in glucose-free medium for 40 hours. The Km remained constant at 2 mM. Analysis of the initial rates of 3-omicron-methyl-D-glucose transport by Lineweaver-Burk plots further substantiated that the increase in sugar transport was due to an increase in the Vmax for transport with the Km remaining constant. The activation energy for the transport reaction calculated from an Arrhenius plot was 17.4 Cal per mol for cells cultured in the standard medium and 17.2 Cal per mol for cells cultured in the glucose-free medium. These results are consistent with the interpretation that the Vmax increase observed in hexose-starved cells is due to an increase in the number of transport sites.

Animals↗
PubMed2000

[Amplification, cloning and expression of a gene encoding hexose transporter of Plasmodium falciparum].

OBJECTIVE: To amplify, clone and express of a gene encoding hexose transporter of Plasmodium falcipuram (PfHT1) from Southern China isolate FCC1/HN for studing the immune of recombinant which protective from malaria parasite infection. METHODS: Cultivation of P. falciparum isolate FCC1/HN in vitro; extraction of genomic DNA from FCC1/HN using the alkali specific cleavage method; PCR amplification of PfHT1 and cloning into eukaryotic expression vector, pEGFPN3. The recombinant as introduced into mammalian cells, HEPG2 by using liposome-mediated transfection. RESULTS: The gene encoding PfHT1 was specifically amplified from the genomic DNA of P. falciparum isolate FCC1/HN. The size of amplified fragment was 1,516 base pair. The eukaryotic expression recombinant, pN3-HT1, was constructed and expressed steadily in the hepatocarcinoma cell lines, HEPG2. CONCLUSION: The gene encoding PfHT1 was successfully amplified and cloned. The pN3-HT1/HEPG2 cell line was built for expressing fusion protein of GFP-HT1.

Animals↗
PubMed2006

Prognostic improvement of patients with advanced liver cancer after active hexose correlated compound (AHCC) treatment.

Most patients with liver cancer are diagnosed when they are not suitable for resection. Although some palliative approaches can be applied to these patients, the overall survival rate remains unsatisfactory. Active hexose correlated compound (AHCC), a newly developed functional food, has been shown to act as a potent biological response modifier in in vitro experiments. Recently, AHCC was found to improve the prognosis of hepatocellular carcinoma patients following surgical treatment. We investigated whether AHCC could prolong survival and improve the prognosis of patients with advanced liver cancer. A prospective cohort study was performed with 44 patients with histologically confirmed liver cancer. All of the patients underwent supportive care. Survival time, quality of life, clinical and immunological parameters related to liver function, cellular immunity, and patient status were determined. Of the 44 patients, 34 and 10 received AHCC and placebo (control) orally, respectively. Patients in the AHCC treated-group had a significantly prolonged survival when compared to the control group by Mann-Whitney test (95% CI, p = 0.000). Quality of life in terms of mental stability, general physical health status, and ability to have normal activities were significantly improved after 3 months of AHCC treatment when tested using the Wilcoxon signed-rank test (on one-sided test, p = 0.028, 0.037, and 0.040, respectively). The apparent different clinical parameters between the two groups were the levels of albumin and percentage of lymphocytes with p-values of 0.000 and 0.026 at 1 and 2 months after treatment, respectively. Unlike the control patients, AHCC treated-patients with longer survival time had the tendency of better outcomes since the levels of AST and ALT had not increased rapidly from their baselines at follow-up. In addition, the levels of total IL-12 and neopterin were slightly increased in AHCC treated-patients. This study suggests that AHCC intake could prolong the survival and improve the prognosis of patients with advanced liver cancer and delay the gradual decline of their physiological status.

Albumins↗
PubMed1991

Dimethyl sulfoxide enhances hexose monophosphate shunt activity in cultured glomerular mesangial cells, leukocytes and erythrocytes.

The effect of dimethyl sulfoxide (DMSO) on the rate of glucose oxidation by cultured rat glomerular mesangial cells, human erythrocytes and peritoneal exudate cells was studied. Mesangial cells, erythrocytes and peritoneal exudate cells incubated with DMSO showed enhancement of 14CO2 production from D-[1-14C] glucose but not from D-[6-14C] glucose. The concentration of DMSO required to stimulate respiratory burst activity was lowest for erythrocytes and highest for peritoneal exudate cells. Studies utilizing tritiated deoxyglucose revealed that the increased glucose oxidation associated with DMSO exposure was not due to increased transmembrane glucose movement at low concentrations of DMSO, and only partially responsible at high concentrations of DMSO. This study documents the ability of DMSO to specifically enhance the activity of the hexose monophosphate shunt pathway in all cells studied. The precise mechanism whereby DMSO stimulates shunt activity remains unknown.

Animals↗
PubMed1976

Amino acid and hexose transport of normal and simian virus 40-transformed human cells.

Studies on amino acid and hexose transport were performed on human WI-38 cells and WI-38 SV40-transformed cells (VA13A and VA13-2RA). Depending upon cell line or conditions, either no difference or a relative decrease in initial uptake by transformed cells was found. Under similar growth conditions, transformed hamster cells (PyBHK-21/C13) had increased uptake, compared with the normal hamster cells (BHK-21/C13). The normal and transformed human cells were also similar in sialic acid content and agglutinated when treated with concanavalin A.

Agglutination Tests↗
PubMed1990

Microsomal hexose-6-phosphate and 6-phosphogluconate dehydrogenases in extrahepatic tissues: human placenta and pig kidney cortex.

An oxidative pathway of glucose-6-phosphate was found in the microsomal fraction of two extra-hepatic tissues: human placenta and pig kidney cortex. Oxidation activity in microsomes, measured by the formation of 14CO2 from [1-14C] glucose-6-phosphate, was observed only after Triton X-100 treatment and in the presence of methylene blue and NADP. Hexose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase were present in a latent form and required treatment with detergent for full activation. Our results suggest that these enzymes are located in the luminal space of placental and kidney microsomes, and that, as in the liver, they generate NADPH on the inner side of the endoplasmic reticulum when G6P and NADP are available.

Animals↗
PubMed1990

Hexose transport stimulation and membrane redistribution of glucose transporter isoforms in response to cholera toxin, dibutyryl cyclic AMP, and insulin in 3T3-L1 adipocytes.

Exposure of 3T3-L1 adipocytes to 100 ng/ml of cholera toxin or 1 mM dibutyryl cyclic AMP caused a marked stimulation of deoxyglucose transport. A maximal increase of 10- to 15-fold was observed after 12-24 h of exposure, while 100 nM insulin elicited an increase of similar magnitude within 30 min. A short term exposure (4 h) of cells to cholera toxin or dibutyryl cyclic AMP resulted in a 3- to 4-fold increase in deoxyglucose transport which was associated with significant redistribution of both the HepG2/erythrocyte (GLUT1) and muscle/adipocyte (GLUT4) glucose transporters from low density microsomes to the plasma membrane fraction. Total cellular amounts of both transporter proteins remained constant. In contrast, cells exposed to cholera toxin or dibutyryl cyclic AMP for 12 h exhibited elevations in total cellular contents of GLUT1 (but not GLUT4) protein to about 1.5- and 2.5-fold above controls, respectively. Although such treatments of cells with cholera toxin (12 h) versus insulin (30 min) caused similar 10-fold enhancements of deoxyglucose transport, a striking discrepancy was observed with respect to the content of glucose transporter proteins in the plasma membrane fraction. While insulin elicited a 2.6-fold increase in the levels of GLUT4 protein in the plasma membrane fraction, cholera toxin increased the amount of this transporter by only 30%. Insulin or cholera toxin increased the levels of GLUT1 protein in the plasma membrane fraction equally (1.6-fold). Thus, a greater number of glucose transporters in the plasma membrane fraction is associated with transport stimulation by insulin compared to cholera toxin. We conclude that: 1) at early times (4 h) after the addition of cholera toxin or dibutyryl cyclic AMP to 3T3-L1 adipocytes, redistribution of glucose transporters to the plasma membrane appears to contribute to elevated deoxyglucose uptake rates, and 2) the stimulation of hexose uptake after prolonged treatment (12-18 h) of cells with cholera toxin may involve an additional increase in the intrinsic activity of one or both glucose transporter isoforms.

Adipose Tissue↗
PubMed1989

The pentose cycle (hexose monophosphate shunt). Rigorous evaluation of limits to the flux from glucose using 14CO2 data, with applications to peripheral ganglia of chicken embryos.

The difference between the 14CO2 outputs from [1-14C]glucose and [6-14C]glucose has frequently been used as a measure of activity in the hexose monophosphate shunt without considering the exact significance of this difference. Assuming only 1) that all C-1 of glucose is released to CO2 on entry to the shunt and 2) that the shunt provides the only mechanism for increasing C-1 of glucose over C-6 of glucose in CO2, it is very simply shown that the flux from glucose to the shunt is not less than the difference between the 14CO2 outputs at any time after adding labeled glucose nor more than the steady-state output of 14CO2 from [1-14C]glucose. Moreover, absence of a 14CO2 difference does not prove that the shunt is absent or inactive. The value for the minimum flux rate can be maximized by following the time course of the C-1 - C-6 difference in 14CO2 during the transient phase before isotopic equilibration is complete, but useful values can be obtained when the time course is not available. The above relationships are applicable to gluconeogenic as well as non-gluconeogenic tissues. Applications of these relationships to peripheral ganglia from chicken embryos, in which the 14CO2 difference passes through a maximum during incubation, show that 27-37% of the glucose taken up enters the pentose cycle in sympathetic ganglia from 10-day-old embryos, while 17-36% enters the cycle in 15-day-old dorsal root ganglia.

Animals↗
PubMed1989

Stimulation of rat-kidney hexose monophosphate shunt dehydrogenase activity by chronic metabolic acidosis.

The effect of chronic metabolic acidosis on the kinetic behaviour of renal glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase have been investigated. Acidosis induced a significant increase in both enzyme activities at all substrate concentrations used. Saturation curves of both dehydrogenases were hyperbolic with no evidence of sigmoidicity. Maximum activities were found after 7 days of acidosis with no significant change in the Km values. The results suggest that stimulated renal hexose monophosphate dehydrogenases activities are probably due to an increased intracellular concentration of these enzymes. The relationship between these changes and those generated in the metabolic acidosis are also discussed.

Acidosis↗
PubMed1989

Evaluation of a modified hexose sugar, amiprilose hydrochloride, in experimental models of synovitis.

Amiprilose HC1 (SM-1213), a nontoxic modified hexose sugar, was evaluated in in vivo and in vitro models of synovitis. In 8 sequential trials, 90 Louvain (LOU) rats and 91 Sprague-Dawley (SD) rats were immunized with chick type II collagen and given amiprilose HC1 in water (1 mg/ml) or water alone. In the LOU rats, the arthritis incidence was 7/46 (15%) in the amiprilose HC1 group vs 16/44 (36%) in the water group (p less than 0.01). In the SD rats, the incidence was 28/46 (60%) in the experimental vs 33/45 (73%) in the control group (p greater than NS), although the prevalence of arthritis on Days 16 and 21 was significantly (p less than 0.03) lower in the experimental group. Amiprilose HC1 did not affect the antibody titers or delayed-type hypersensitivity to collagen, or T cell subset distribution in the LOU experiments. Two analogues, SM-1211 and SM-1212, did not alter this disease. No toxicity was noted. At a nontoxic concentration of 1 mg/ml, amiprilose HC1 suppressed 3H thymidine incorporation in cultured rabbit synovial fibroblasts by 78% and resulted in the appearance of numerous intracytoplasmic granules/vacuoles. These effects were partially antagonized by indomethacin or dexamethasone at 10(-7) M. SM-1211 was inert in this system. Amiprilose HC1 system also reduced rabbit synoviocyte supernatant prostaglandin E2 levels up to 73% in a dose related fashion, but did not affect collagenase activity. These morphologic changes in synoviocytes, combined with anti-inflammatory and antiproliferative effects, provide evidence that amiprilose HC1 possesses modest and nontoxic antirheumatic properties. A search for analogues of this sugar with more substantial clinical activities is warranted.

Adjuvants, Immunologic↗
PubMed1988

Hexose metabolism in pancreatic islets: the Pasteur effect.

In rat pancreatic islets, hypoxia severely decreased both the oxidation of D-[U-14C]glucose and the release of insulin evoked by D-glucose. The production of [14C]lactate was increased in the hypoxic islets, the relative magnitude of such an increment being greater at low (2.8 mM) than high (8.3 and 16.7 mM) D-glucose concentrations. Hypoxia increased the detritiation of D-[5-3H]glucose at low glucose concentration (2.8 mM), failed to affect 3H2O production at an intermediate glucose level (8.3 mM), and inhibited the utilization of D-[5-3H]glucose at a higher hexose concentration (16.7 mM). In tumoral islet cells (RINm5F line) exposed to 16.7 mM D-glucose, hypoxia decreased D-[U-14C]glucose oxidation to the same extent as in normal islet cells, but increased the production of [14C]lactate and 3H2O to a greater extent than in normal islets. These findings indicate that the Pasteur effect is operative in islet cells. The experimental data also suggest that, under normal conditions of oxygenation, high concentrations of D-glucose lead to both activation of phosphofructokinase and stimulation of mitochondrial oxidative events in normal, but not tumoral, islet cells.

Adenoma, Islet Cell↗
PubMed1987

Hexose monophosphate shunt in rat lens: stimulation by vitamin C.

The metabolism of glucose through the hexose monophosphate (HMP) shunt has been studied in rat lens in vitro, in the absence and presence of ascorbic and dehydroascorbic acids. Both forms of the vitamin stimulated the utilization of glucose through the HMP shunt, the stimulatory effect of dehydroascorbate being substantially greater than that of ascorbate. The stimulatory effect of ascorbate, as well as of dehydroascorbate, was antagonized by sodium iodide, and N,N-bis (dichloroethyl)-N-nitrosourea, compounds known to inhibit glutathione reductase. N-ethylmaleimide also antagonized the stimulation. These findings, therefore, suggest that the DHA/AA redox couple acts in concert with the GSSG/GSH couple in stimulating the tissue shunt activity.

Animals↗
PubMed1987

Reassessment of insulin effects on the Vmax and Km values of hexose transport in isolated rat epididymal adipocytes.

Effects of insulin on the kinetic parameters of hexose transport in rat epididymal adipocytes were re-examined. The transport activity was assessed by measuring the rate of uptake of 3-O-[3H]methyl-D-glucose (MeGlc) under equilibrium exchange and zero-trans conditions. The incubation was carried out at 37 degrees C in an infant incubator. During the incubation, the cell suspension (25%, v/v, in a total volume of 48 microliter) was mechanically swirled at a rate of 600 rpm (r = 2 mm). The swirling facilitated the rapid uptake of MeGlc without stimulating the basal transport activity by "mechanical agitation". The basal and insulin-treated cells were incubated under identical conditions, except for the length of the incubation period. The incubation was terminated by the addition of 350 microliters of 1 mM phloretin, which inhibited transport in approximately 0.06 s. The time course of MeGlc uptake was consistent with the view that the process was a multiple-phase reaction. The initial phase of the reaction was completed when the intracellular distribution space of MeGlc was approximately 1% of the total cell volume. Insulin (10 nM) increased the Vmax value of MeGlc uptake 16-fold in equilibrium exchange experiments and 18-fold in zero-trans experiments. At the same time, the hormone decreased the Km value of MeGlc uptake from 11.7 to 5.4 mM in equilibrium exchange experiments and from 9.7 to 4.8 mM in zero-trans experiments. It is concluded that the major effect of insulin on MeGlc uptake is to increase the Vmax value, but the hormone has the additional effect of lowering the apparent Km value.

3-O-Methylglucose↗
PubMed1987

Erythrocyte metabolism in hyperthyroidism: a microcalorimetric study on changes in the Embden-Meyerhof and the hexose monophosphate pathways.

Erythrocyte metabolism was studied in vitro by microcalorimetry in 10 hyperthyroid subjects before and after treatment. By inhibiting the enzyme enolase in the Embden-Meyerhof pathway with sodium fluoride (NaF) we have recorded the anaerobic and aerobic contributions in erythrocyte thermogenesis. The decrease in heat production rate in samples with NaF corresponds to the anaerobic contribution, whereas the values from samples with NaF reflect aerobic processes. Before treatment, total heat production rate was 120 +/- 2 mW/l erythrocytes which was higher than the post-treatment value of 99 +/- 2 (P less than 0.001) as well as the value for 14 euthyroid subjects, 108 +/- 2 mW/l (P less than 0.001). The NaF inhibitable rate was 73 +/- 2 before and 63 +/- 1 mW/l after therapy (P less than 0.01). These values correspond to 61 +/- 1 and 64 +/- 1% (n.s.) of the total heat production rate, and were similar to that of 61 +/- 2% for the controls. Heat production rates in the presence of NaF were 47 +/- 1 before and 36 +/- 1 mW/l after therapy (P less than 0.001), representing 39 +/- 1 and 36 +/- 1% of total values, respectively. The present results show that overall metabolism is increased in erythrocytes from hyperthyroid subjects before treatment and returns to normal after normalization of the thyroid function. Moreover, by using microcalorimetry we found that the metabolic activity along the Embden-Meyerhof anaerobic pathway as well as along the hexose monophosphate aerobic pathway in erythrocytes is stimulated by thyroid hormones.

Adult↗
PubMed1975

Energy coupling in the uptake of hexose phosphates by Escherichia coli.

Several methods were used to study the source of energy in the uptake of hexose phosphates by Escherichia coli K12. The uptake was sensitive to inhibition by agents that affect electron transport, such as lack of oxygen, cyanide, and heptylhydroxyquinoline-N-oxide, and by agents that affect ATP utilization, such as dicyclohexylcarbodiimide and arsenate. It was also sensitive to uncouplers in the presence of absence of oxygen. The strain of E. coli used extruded protons during respiration. Uncer anaerobic conditions, the uptake of approximately 1 eg to H+ per glucose 6-phosphate. These observations are consistent with a chemiosmotic mechanism of genergized glucose 6-phosphate uptake. The rate of glucose 6-phosphate uptake was maximal in KC1, but was also stimulated by MgC12 or CaC12. Inhibition by A217, a nigericin-like antibiotic, was prevented by K+ whereas valinomycin and gramicidin inhibited in the presence or absence of K+.

Anaerobiosis↗
PubMed1984

Effect of Coxiella burnetii on the stimulation of hexose monophosphate shunt and on superoxide anion production in human polymorphonuclear leukocytes.

Killed Coxiella burnetii (C.b.) cells in phase II but not in phase I had a mild stimulatory effect on hexose monophosphate shunt (HMPS) and superoxide anion production by human polymorphonuclear (PMN) leukocytes. Preincubation of C.b. cells of either phase with serum of a leukocyte donor lacking detectable antibodies to C.b. did not affect the studied activities of PMN leukocytes. In contrast, both HMPS stimulation and superoxide production were enhanced by specific opsonization of C.b. cells with rabbit immune sera containing corresponding phase I and/or phase II antibodies. Stimulatory effect was observed also with lipopolysaccharide-protein-phospholipid (LPS-Pr-Pl) complex but not with lipopolysaccharide-protein (LPS-Pr) complex and with purified lipopolysaccharide (LPS) isolated from phase I C.b. cells. Possible consequences of these findings for explanation of C.b. resistance to intracellular killing by professional phagocytes are discussed.

Coxiella↗
PubMed1980

Studies on the hexose monophosphate shunt in the myocardium during development of hypertrophy.

In rat hearts hypertrophying because of aortic constriction and isoproterenol administration, the activity of glucose-6-phosphate dehydrogenase and the available pool of 5-phosphoribosyl-l-pyrophosphate were found to be increased, indicating an enhancement of the flow through the hexose monophosphate shunt. In triiodothyronine-treated animals only the cardiac pool of 5-phosphoribosyl-l-pyrophosphate was elevated. In all three models of experimentally induced cardiac hypertrophy, the enhancement of myocardial adenine nucleotide biosynthesis was potentiated by ribose. Since ribose gives rise to a considerable elevation of the available 5-phosphoribosyl-l-pyrophosphate, it appears that this is the limiting factor for the increase of adenine nucleotide biosynthesis in hypertrophying hearts. Constant intravenous infusion of ribose for 24 hr prevented the decrease of myocardial ATP concentration is isoproterenol-treated rats.

Adenine Nucleotides↗
PubMed1984

A 31P NMR study on uptake and metabolism of hexose monophosphates in rat diaphragm muscle.

Phosphorus nuclear magnetic resonance spectroscopy was used to study uptake and metabolic conversion of glycolytic intermediates in rat diaphragm muscles. The resonances of several phosphorus-containing metabolites were identified in the intact tissues and in their ethanolic extracts. Experiments on muscles preincubated with glucose 6-phosphate or glucose 1-phosphate indicated that: 1) both substrates penetrate into the tissue and actively participate in glycolytic reactions; 2) glucose 1-phosphate is completely converted into other metabolites, including glucose 6-phosphate and its products; 3) preincubation with either hexose monophosphate in the presence or in the absence of insulin produced the same set of phosphorylated metabolites. Addition of insulin to preincubation media induced a conspicuous spread of chemical shifts in the band arising from phosphorylated sugars in tissues incubated with glucose 1-phosphate but not in those treated with glucose 6-phosphate. The different responses to insulin exhibited by the 31P n.m.r. spectral profiles of tissues incubated with the two substrates substantiate the hypothesis that glucose 6-phosphate and its products may undergo their metabolic conversions in the tissue along distinct intracellular enzymatic pathways, on which insulin would exert different regulatory effects. This study indicates that 31P n.m.r. may provide a useful approach to the elucidation of metabolic processes involving sugar phosphates in intact tissues.

Adenosine Diphosphate↗