SEARCH · PubMed Health

Results for “GLUCOSE, RADIOACTIVE”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 667 records · Page 37Linked to original sources

PubMed1991

Metabolism of tritiated D-glucose in rat erythrocytes.

The metabolism of D-[U-14C]glucose, D-[1-14C]glucose, D-[6-14C]glucose, D-[1-3H]glucose, D-[2-3H]glucose, D-[3-3H]glucose, D-[3,4-3H]glucose, D-[5-3H]glucose, and D-[6-3H]glucose was examined in rat erythrocytes. There was a fair agreement between the rate of 3HOH production from either D-[3-3H]glucose and D-[5-3H]glucose, the decrease in the 2,3-diphosphoglycerate pool, its fractional turnover rate, the production of 14C-labeled lactate from D-[U-14C]glucose, and the total lactate output. The generation of both 3HOH and tritiated acidic metabolites from D-[3,4-3H]glucose indicated incomplete detritiation of the C4 during interconversion of fructose-1,6-bisphosphate and triose phosphates. Erythrocytes unexpectedly generated 3HOH from D-[6-3H]glucose, a phenomenon possibly attributable to the detritiation of [3-3H]pyruvate in the reaction catalyzed by glutamate pyruvate transaminase. The production of 3HOH from D-[2-3H]glucose was lower than that from D-[5-3H]glucose, suggesting enzyme-to-enzyme tunneling of glycolytic intermediates in the hexokinase/phosphoglucoisomerase/phosphofructokinase sequence. The production of 3HOH from D-[1-3H]glucose largely exceeded that of 14CO2 from D-[1-14C]glucose, a situation tentatively ascribed to the generation of 3HOH in the phosphomannoisomerase reaction. It is further speculated that the adjustment in specific radioactivity of D-[1-3H]glucose-6-phosphate cannot simultaneously match the vastly different degrees of isotopic discrimination in velocity at the levels of the reactions catalyzed by either glucose-6-phosphate dehydrogenase or phosphoglucoisomerase. The interpretation of the present findings thus raises a number of questions, which are proposed as a scope for further investigations.

Acids↗

PubMed1977

[Physiology and biochemistry of streptomycetes. XIII. Biosynthesis of paromomycin by Streptomyces albus var. metamycinus nov. var. supplied with 14C-glucose, 14C-glucosamine, 14C-2-desoxystreptamine and 14C-ribose].

Distribution of radioactivity in paromomycin ascertained after application of 14C-D-glucose, 14C-D-glucosamine, 14C-2-deoxystreptamine, respectively, 14C-D-ribose is taken as basis for a biosynthesis scheme: While ribose bound in the antibiotic originates from glucose by oxidation and following decarboxylation, glucosamine is formed via fructose-6-phosphate. Paromose I arises from glucosamine, but not the cyclohexan derivative 2-deoxystreptamine, whose biosynthesis pathway is directly branching off glucose.

Carbon Radioisotopes↗

PubMed1960

Effects of veratrine and cocaine on cerebral carbohydrate-amino acid interrelations.

The rate of aerobic transformation of glucose-U-C(14) into radioactive amino acids by slices of rat-brain cortex is greatly influenced by the K(+)/Ca(++) ratio in the incubating medium. Protoveratrine has effects on the amino acid pattern resembling that due to an increase in the K(+)/Ca(++) ratio. These effects are antagonized by cocaine and may be correlated with the neurophysiological activities of these drugs.

Amino Acids↗

PubMed1971

Biosynthesis of T1 antigen in Salmonella: biosynthesis in a cell-free system.

A particulate fraction from a T1 form of Salmonella typhimurium incorporated radioactivity from uridine diphosphate (UDP)-(14)C-glucose into products associated with the particulate enzyme. A major fraction of the incorporated radioactivity was found in the cell wall lipopolysaccharide fraction. Acid hydrolysis of incorporation products produced labeled galactose, ribose, and also glucose. The incorporation of glucose could be dissociated from the incorporation of galactose and ribose under certain conditions, and was assumed to represent incorporation into a polymer not related to T1 antigen. The incorporation of galactose and ribose probably represented the synthesis of T1 side chains of lipopolysaccharide, because (i) particulate fractions from non-T1 strains incorporated much less of these sugars and (ii) periodate oxidation and borohydride reduction converted a large portion of incorporated galactose residues into arabinose. The latter finding indicates that the galactose residues are galactofuranosides substituted either at C2 or C3; about 70% of the galactose residues in T1 side chains are known to be galactofuranosides substituted at C3. UDP-(14)C-galactose preparation used was not contaminated by UDP-(14)C-galactofuranose; therefore pyranose-to-furanose conversion must have taken place at some step during the reactions described above. The mechanism of conversion of galactose to ribose is not clear, but it was not found to involve a selective elimination of C1 or C6 of galactose or glucose.

Antigens↗

PubMed1983

Method for the study of metabolite transfer from rat mother to fetus.

Infusion medium containing a tracer was introduced through the left uterine artery to 20.5-day pregnant rats. In this way, the left uterine horn received the tracer directly while it reached the right horn after dilution in the mother's circulation. When U-14C-D-glucose or U-14C-L-alanine was infused, radioactivity in fetal blood from the left uterine horn was 3 or 8 times higher respectively than in the right horn and 2 or 6 times higher than in maternal blood. When the infusion was carried out with 125I-labelled growth hormone, which is known not to cross the placental barrier, very little radioactivity was found in fetuses compared with that in the mother's plasma and no differences were observed in blood radioactivity levels of fetuses from either horn. After infusion of U-14C-D-glucose through the maternal jugular vein instead of left uterine artery, radioactivity was the same in fetuses from the left and right horns, indicating that manipulations of the left uterine side did not greatly affect its circulation. These findings. together with the determination of specific radioactivity of the tracer used in both maternal and fetal plasma, validate the technique as a semiquantitative means to determine the direct transfer of any product through the placental barrier in the rat.

Alanine↗

PubMed1978

Origins of fermentation products formed during growth of Bacteroides ruminicola on glucose.

Bacteriodes ruminicola grown on complex medium with glucose as carbon source gave acetate, CO2, formate and succinate as main fermentation products. No evidence was found for significant glucose catabolism by pathways other than the Embden-Meyerhof sequence. However, [U-14C]glucose fermentation gave products whose specific radioactivities were much lower than expected. There appear to be two main causes. Firstly, a rapid exchange occurred between metabolic intermediates and CO2, probably due to reversibility of the pathway between phosphoenolpyruvate and fumarate. Secondly, non-glucose precursors, mainly peptides and acetate, added to the medium as growth factors, also gave rise to the above end-products. The distortions that such reactions introduce into measurements of ATP molar growth yields based on product analyses and measurements of carbon flux based on radioactivity recovered in products are discussed.

Acetates↗

PubMed1984

Evidence for coupling between transport of UDP-glucose and its synthesis by membrane-bound pyrophosphorylase in Golgi apparatus of cat liver.

Incubation of sealed vesicles of cat-liver Golgi apparatus with UDP[14C]glucose showed that the vesicles accumulated radioactivity. After Triton X-100 treatment or sonication of washed vesicles, soluble radiolabeled species were released and identified by paper chromatography as UDP[14C]glucose, [14C]glucose 1-phosphate and free glucose. In the incubation medium, UDPglucose was effectively protected by addition of dimercaptopropanol and UTP. Presence of glucose 1-phosphate and glucose within the vesicles most probably arose from luminal pyrophosphatase and phosphatase. A portion of the [14C]glucose moiety became covalently linked to endogenous acceptors. Uptake of UDPglucose was saturable and dependent on time and on the concentration of sugar nucleotide. Together, these results were consistent with a transport system for UDPglucose in Golgi vesicles. Furthermore, penetration rate was considerably higher with UDPglucose synthetized in situ from glucose 1-phosphate by membrane-bound pyrophosphorylase than from added UDPglucose: Vmax values were respectively 10 and 2 pmol/15 min per mg protein. This result allows the conclusion that a coupling between translocase and synthetase is involved in UDPglucose transport through Golgi apparatus membranes. The mechanism of this 'kinetic advantage' is discussed.

Animals↗

PubMed2004

Signals in the activation of opioid mu-receptors by loperamide to enhance glucose uptake into cultured C2C12 cells.

In an attempt to understand the signal pathways of opioid mu-receptors for glucose metabolism, we used loperamide to investigate the glucose uptake into the myoblast C2C12 cells. Loperamide enhanced the uptake of radioactive deoxyglucose into C2C12 cells in a concentration-dependent manner that was abolished in cells pre-incubated with naloxone or naloxonazine at concentrations sufficient to block opioid mu-receptors. Pharmacological inhibition of phospholipase C (PLC) by U73122 resulted in a concentration-dependent decrease in loperamide-stimulated uptake of radioactive deoxyglucose into C2C12 cells. This inhibition of glucose uptake by U73122 was specific since the inactive congener, U73343, failed to modify loperamide-stimulated glucose uptake. Moreover, both chelerythrine and GF 109203X diminished the action of loperamide at concentrations sufficient to inhibit protein kinase C (PKC). The obtained data suggest that an activation of opioid mu-receptors in C2C12 cells by loperamide may increase glucose uptake via the PLC-PKC pathway.

Animals↗

PubMed1996

Separate compartments for the production of sterols, carotenoids and gibberellins in Gibberella fujikuroi.

Substrate flows in the sterol, carotenoid and gibberellin pathways of Gibberella fujikuroi were examined by isotope-dilution experiments. The wild type and two carotenoid mutants of this fungus were grown in minimal medium with abundant glucose, limiting ammonium nitrate and a radioactively labelled precursor (either acetate, mevalonate or leucine). The precursors did not affect growth or terpenoid production, with two exceptions; leucine allowed additional growth, as expected from the nitrogen limitation in the medium, and mevalonate inhibited the accumulation of gibberellins, but only if added before the onset of gibberellin production. The relative contributions of glucose, mevalonate, leucine and acetate as terpenoid precursors, calculated from the specific radioactivities of ergosterol, neurosporaxanthin and phytoene, were different for different products and different precursors. We conclude that the biosyntheses of sterols, gibberellins and carotenoids in Gibberella are physically separated in different subcellular compartments with independent substrate pools. The same results were obtained with the three strains, except for carotenoid production, indicating that this pathway is regulated independently from other terpenoid pathways.

Acetates↗

PubMed1993

Effects of arterial-portal glucose difference on gluconeogenesis from lactate in the isolated bivascular-perfused rat liver.

The effects of arterial-portal glucose difference on the gluconeogenesis from lactate were studied using the bivascular perfused liver isolated from the fasted rat. The liver was cyclically perfused at flow rates of 14 ml/min from the portal vein and of 7 ml/min from the hepatic artery with the total volume of 35 ml of perfusion medium containing 2 mM glucose, 3 mM lactate and (U-14C)-lactate for 20 min. Glucose was infused at a rate of 27.75 mumol/min into the arterial cannula (A-experiment) or the portal cannula (P-experiment), making each arterial-portal glucose gradient of +3.96 mM (arterial glucose > portal glucose) and -1.98 mM (arterial glucose < portal glucose) throughout the experiment. Perfusate lactate concentration was lower in A-experiment than in P-experiment (1.40 +/- 0.25 vs 1.93 +/- 0.23 mM at 20 min, mean +/- SD, p < 0.05). Incorporation of radioactivity from (U-14C)-lactate into glucose carbon 1 in perfusate was 5.7 +/- 0.8% of total radioactivity per 20 min in A-experiment vs 2.8 +/- 0.6%/20 min in P-experiment (p < 0.01). These results suggest that the arterial-portal glucose difference is an important factor to regulate the hepatic gluconeogenesis.

Animals↗

PubMed1978

Sodium concentrations affect metabolite uptake and cellular metabolism.

Rates of uptake of glucose (measured with 3H-2-deoxy-d-glucose), galactose, and leucine after exposure of chick embryo cells to increasing concentrations of Na+ over the range 100 to 200 mM. Uptake of nucleosides was unaffected by [Na+] over this range. Prior exposure of cells was required for the [Na+] effect on uptake. Changes were measureable within two hours after changing [Na+], and although the capacity for deoxyglucose uptake remained constant thereafter, the capacity for leucine uptake continued to change during the next few hours. Inhibition of protein synthesis by cycloheximide, or of RNA synthesis by Actinomycin D, failed to prevent these uptake changes. Analysis of the kinetics of uptake showed that only the Km for uptake of deoxyglucose or leucine was affected by [Na+]; the maximum V for each compound remained the same. Effects of [Na+]; could be distinguished from the increased capacity for glucose uptake induced by glucose starvation. Incorporation of both radioactive uridine into RNA, and radioactive thymidine into DNA, were affected by [Na+[, but the differences were not correlated with uptake of other metoblites. No differences in countable mitoses were apparent, although the growth of chick embryo cells in increased slightly with increasing [Na+]. Changes in uptake due to differing [Na+] also were observed in mammalian (rat NRK) cells. However, no effects of [Na+] on rates of cell growth or saturation density were observed with these cells.

Animals↗

PubMed1978

Effect of L-alanine infusion on gluconeogenesis and ketogenesis in the rat in vivo.

1. In 48 h-starved 6-week-old rats the 14C incorporation in vivo into blood glucose from a constant-specific-radioactivity pool of circulating [14c]actateconfirmed that lactate is the preferred gluconeogenic substrate. 2. Increasing the blood [alanine] to that occurrring in the fed state increased 14C incorporation into blood glucose 2.3-fold from [14c]alanine and 1.7-fold from [14c]lactate. 3. When the blood [alanine] was increased to that in the fed state, the 14C incorporation into liver glycogen from circulating [14c]alanine or [14c]lactate increased 13.5- and 1.7-fold respectively. 4. The incorporation of 14C into blood acetoacetate and 3-hydroxybutyrate from a constant-specific-radioactivity pool of circulating [14c]oleate was virtually abolished by increasing the blood [alanine] to that existing in the fed state. However, the [acetoacetate] remained unchanged, whereas [3-hydroxybutyrate] decreased, although less rapidly than did its radiochemical concentration. 5. It is concluded that during starvation in 6-week-old rats, the blood [alanine] appears to influence ketogenesis for circulating unesterfied fatty acids and inversely affects gluconeogenesis from either lactate or alanine. A different pattern of gluconeogenesis may exist for alanine and lactate as evidenced by comparative 14C incorporation into liver glycogen and blood glucose.

Acetoacetates↗

PubMed1980

Glucose and lactate metabolism in vivo in ovine fetus.

The metabolism of glucose and lactate by the ovine fetus (123-128 days of gestation) was studied; a primed, continuous infusion of [2-3H]glucose and [U-14C]lactate into the brachial vein of six fetuses was used. Fetal plasma lactate concentrations averaged 2.12 +/- 0.25 mM and glucose concentrations averaged 9.3 +/- 1.3 mg/100 ml. Total plasma turnover of lactate was 5.22 +/- 0.7 nmol/h and that of glucose was 3.48 +/- 0.63 nmol x h-1 x kg fetal weight-1. Lactate was converted to glucose at a rate of 1.35 +/- 0.64 mmol x h-1 x kg fetal weight-1, which represented 21.6 +/- 6.0% of the lactate turnover. The percentage of glucose coming from lactate was 48.9 +/- 15.2. The specific activity of maternal plasma glucose was less than 4% of the specific activity of glucose observed in fetal plasma. No radioactivity could be detected in maternal plasma lactate. The data show that the ovine fetus or the fetal-placental unit can convert lactate to glucose by days 123-128 of gestation. A general model presented describes carbohydrate metabolism in the ovine placenta and fetus.

Animals↗

PubMed2005

Measurement of exogenous carbohydrate oxidation: a comparison of [U-14C]glucose and [U-13C]glucose tracers.

The purpose of this study was to assess the level of agreement between two techniques commonly used to measure exogenous carbohydrate oxidation (CHO(EXO)). To accomplish this, seven healthy male subjects (24 +/- 3 yr, 74.8 +/- 2.1 kg, V(O2(max)) 62 +/- 4 ml x kg(-1) x min(-1)) exercised at 50% of their peak power for 120 min on two occasions. During these exercise bouts, subjects ingested a solution containing either 144 g glucose (8.7% wt/vol glucose) or water. The glucose solution contained trace amounts of both [U-13C]glucose and [U-14C]glucose to allow CHO(EXO) to be quantified simultaneously. The water trial was used to correct for background 13C enrichment. 13C appearance in the expired air was measured using isotope ratio mass spectrometry, whereas 14C appearance was quantified by trapping expired CO(2) in solution (using hyamine hydroxide) and adding a scintillator before counting radioactivity. CHO(EXO) measured with [13C]glucose ([13C]CHO(EXO)) was significantly greater than CHO(EXO) measured with [14C]glucose ([14C]CHO(EXO)) from 30 to 120 min. There was a 15 +/- 4% difference between [13C]CHO(EXO) and [14C]CHO(EXO) such that the absolute difference increased with the magnitude of CHO(EXO). Further investigations suggest that the difference is not because of losses of CO2 from the trapping solution before counting or an underestimation of the "strength" of the trapping solution. Previous research suggests that the degree of isotopic fractionation is small (S. C. Kalhan, S. M. Savin, and P. A. Adam. J Lab Clin Med89: 285-294, 1977). Therefore, the explanation for the discrepancy in calculated CHO(EXO) remains to be fully understood.

Administration, Oral↗

PubMed1998

Role of microtubules in glucose uptake by C6 glioma cells.

Drugs that influence tubulin function were used to investigate the role of microtubules in hexose uptake by C6 glioma cells. In C6 cells, colchicine and vinblastine (which inhibit tubulin polymerization) inhibited radioactive [3H]2-deoxy-D-glucose uptake by about 30%. Paclitaxel (which promotes tubulin polymerization) stimulated hexose uptake by about 25%. To further demonstrate that microtubules play a role in hexose uptake, C6 cells were transfected with GLUT1 cDNA and then challenged with 100 nM paclitaxel. In GLUT1-transfected cells paclitaxel stimulated 2-deoxy-D-glucose uptake by about 35%. To study the role of tubulin in agonist-stimulated hexose uptake, the effect of colchicine on carbachol-induced uptake was next examined. Hexose uptake was increased with carbachol in concentration-dependent manner which was abolished by pretreatment with colchicine. To examine the specificity of the inhibitory effect of colchicine on G protein-mediated signal transduction pathway, the influence of colchicine on insulin (which acts via tyrosine kinase pathway) stimulation of 2-deoxy-D-glucose uptake was investigated. Hexose uptake was increased by insulin in a concentration-dependent manner which was unaffected by pretreatment with colchicine. These results suggest that microtubules are involved in basal and carbachol-stimulated glucose uptake by C6 cells.

Animals↗

PubMed1972

Extent of propionate metabolism during absorption from the bovine ruminoreticulum.

1. Solutions containing acetate, [2-(14)C]propionate and butyrate were placed into the ruminoreticulum of calves to measure the extent to which propionate is metabolized by ruminoreticulum epithelium. In response to five different combinations of pH and total volatile fatty acid concentrations, propionate absorption rates ranged from 89 to 341mmol/h. 2. The extent of propionate conversion into lactate, calculated from both concentration and specific radioactivity in portal and arterial blood, averaged 4.9 (range 2.5-9.1)%. 3. Circulating glucose synthesized from propionate had a higher specific radioactivity than arterial lactate and was converted into lactate by gastrointestinal tissues. Thus conversion of propionate into lactate was overestimated but was corrected to average 2.3 (1.0-4.6)%. 4. The estimates of propionate conversion into lactate were negatively correlated with its rate of absorption.

Absorption↗

PubMed1993

Equilibration of hexose concentration in erythrocytes from normal and diabetic rats.

The uptake and efflux of radioactivity was monitored in rat erythrocytes exposed to or prelabeled with either 3-O-methyl-D[U-14C]glucose or D-[U-14C]glucose. In the case of 3-O-methyl-D-[U-14C]glucose uptake, the half-life for equilibration of hexose concentration between the extracellular medium and the intracellular 3H2O space increased from 12.5 to 32.5 min as the concentration of the D-glucose analog was raised from 8.3 to 33.3 mM. In erythrocytes preincubated for 60 min with 3-O-methyl-D-[U-14C]glucose at the latter two concentrations, the half-life for the fall in cell radioactive content, after correction for the residual radioactivity recovered in the cells after prolonged incubation, amounted to respectively 6.5 and 9.5 min. Thus, whether in terms of uptake or efflux, the equilibration of hexose concentrations across the plasma membrane represented a delayed phenomenon. In this respect, there was no difference between erythrocytes from control or diabetic rats. Comparable conclusions were reached in the study of influent and effluent radioactivity in rat erythrocytes exposed to or prelabeled with D-[U-14C]glucose. In such a case, the measurement of radioactive acidic metabolites and L-lactic acid indicated that, even after 90 min incubation, the concentration of the hexose in the intracellular 3H2O space remained lower than its extracellular concentration. It is proposed that the delayed equilibration of hexose concentrations accounts, in part at least for an artifact of isotopic dilution in the study of radioactive D-glucose metabolism by erythrocytes from control or diabetic rats.

3-O-Methylglucose↗

PubMed1974

The relationship of root-cap slimes to pectins.

1. The patterns of incorporation of radioactivity from d-[U-(14)C]glucose into the pectic components of sections of sycamore roots changed so that sections nearer the tip incorporated relatively more label into arabinose and galactose compared with uronic acid. 2. Radioactive maize root-cap slime was prepared and found to contain three water-soluble component polymers which were electrophoretically (i) neutral, (ii) weakly acidic and (iii) strongly acidic at pH6.5. The neutral component was a glucan. The other components, which could be degraded by trans-elimination, consisted of an acidic backbone chain composed of galacturonic acid and glucose, attached to which were different proportions of neutral sugars. Arabinose, galactose and fucose, the main neutral sugars of the weakly and strongly acidic materials, were absent from the neutral fraction. 3. Fucose was a major sugar in maize-root slime and in a slime of similar composition synthesized by a maize callus of shoot origin. Only trace amounts were found in sycamore, pea and wheat root tips, and in pectin prepared from maize roots and coleoptiles. A high proportion of fucose is therefore a chemical characteristic of maize slime, and slime synthesis indicated a state of differentiation of the tissue. 4. The similarity between the slime and pectin is discussed; slime is a form of pectin modified in such a way as to provide a hydrated protective coating around the root tip.

Arabinose↗