PubMed Health⌕ Search

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 811 records · Page 45Linked to original sources
PubMed2003

Uptake of locally applied deoxyglucose, glucose and lactate by axons and Schwann cells of rat vagus nerve.

We asked whether, in a steady state, neurons and glial cells both take up glucose sufficient for their energy requirements, or whether glial cells take up a disproportionate amount and transfer metabolic substrate to neurons. A desheathed rat vagus nerve was held crossways in a laminar flow perfusion chamber and stimulated at 2 Hz. (14)C-labelled substrate was applied from a micropipette for 5 min over a < 0.6 mm band of the surface of the nerve. After 10-55 min incubation, the nerve was lyophilized and the longitudinal distribution of radioactivity measured. When the weakly metabolizable analogue of glucose, 2-deoxy-[U-(14)C]D-glucose (*DG), was applied, the profiles of the radioactivity broadened with time, reaching distances several times the mean length of the Schwann cells (0.32 mm; most of the Schwann cells are non-myelinating). The profiles were well fitted by curves calculated for diffusion in a single compartment, the mean diffusion coefficient being 463 +/- 34 microm(2) s(-1) (+/- S.E.M., n = 16). Applications of *DG were repeated in the presence of the gap junction blocker, carbenoxolone (100 microM). The profiles were now narrower and better fitted with two compartments. One compartment had a coefficient not significantly different from that in the absence of the gap junction blocker (axons), the other compartment had a coefficient of 204 +/- 24 microm(2) s(-1), n = 4. Addition of the gap junction blocker 18-alpha-glycyrrhetinic acid, or blocking electrical activity with TTX, also reduced longitudinal diffusion. Ascribing the compartment in which diffusion was reduced by these treatments to non-myelinating Schwann cells, we conclude that 78.0 +/- 3.6 % (n = 9) of the uptake of *DG was into Schwann cells. This suggests that there was transfer of metabolic substrate from Schwann cells to axons. Local application of [(14)C]glucose or [(14)C]lactate led to variable labelling along the length of the nerve, but with both substrates narrow peaks were often present at the application site; these were greatly reduced by subsequent treatment with amylase, a glycogen-degrading enzyme.

Animals↗
PubMed1970

Metabolic turnover of the polar lipids of Mycoplasma laidlawii strain B.

The fatty acyl groups of the membrane polar lipids of Mycoplasma laidlawii B were radioactively labeled by growth in the presence of (14)C-palmitic, oleic, or linoleic acids. No loss of radioactivity from any of the polar lipids occurred during incubation of radiolabeled cells in growth medium containing various nonradioactive fatty acids, although growth and lipid biosynthesis continued throughout the incubation period. The metabolism of the glucose and phosphate moieties was also studied in a similar fashion by utilizing growth in (14)C-glucose or (32)P-inorganic phosphate to radioactively label these groups. As before, no loss of radioactivity from any of the polar lipids occurred during subsequent growth in medium containing unlabeled glucose or phosphate. The results establish that the glyco- and phospholipids of M. laidlawii B are metabolically stable in actively growing cells. The absence of metabolic turnover is discussed in terms of proposed relationships between lipid metabolism and function in this organism.

Carbon Isotopes↗
PubMed1998

Evaluation of esophageal cancers using fluorine-18-fluorodeoxyglucose PET.

UNLABELLED: To evaluate glucose metabolism in esophageal cancer, 48 patients were studied using PET with 18F-2-fluoro-2-deoxy-D-glucose (FDG). METHODS: After transmission scans were obtained, 18F-FDG (148 MBq) was administered intravenously. In 11 patients, a dynamic study was performed to evaluate glucose metabolism. Using the changes of radioactivity in both plasma and tumor, rate constants (k1-k4) defined in the metabolic model for 18F-FDG were calculated. In 48 patients, static PET scans of the tumor (5-min scans) were obtained 60 min after administration. Fluorine-18-FDG activity within each tumor was corrected for physical decay and normalized by dose administration and patient weight to produce a standardized uptake value (SUV). RESULTS: Both the k3 value (n = 11) reflecting hexokinase activity and SUV (n = 13) were well correlated with hexokinase activity from the resected specimen (p < 0.05). Forty-seven of 48 patients before treatment revealed SUV greater than 2.0, but 10 normal control subjects and 1 esophageal benign tumor revealed less than 2.0 (accuracy rate 98.3%). Although clinicopathological findings did not correlate with SUV, except for two patients with carcinosarcoma, 23 patients with an SUV greater than 7.0 had a poor prognosis compared with 25 patients with SUVs less than 7.0. CONCLUSION: These findings suggest that 18F-FDG PET may be useful in distinguishing malignant tumors from benign lesions and in the preoperative evaluation of the prognostic factor.

Adult↗
PubMed1978

Glyceroneogenesis in rat and guinea pig adipose tissue during the fed and fasted states.

While both pyruvate and lactate are good substrates for glyceride-glycerol synthesis in isolated adipocytes from fed rats and guinea pigs, neither alanine nor serine appear to support glyceroneogenesis. Fasting increases the proportion of radioactive pyruvate or lactate incorporated into glyceride-glycerol and reciprocally decreases the proportion incorporated into fatty acids. However, the total incorporation of radioactivity into triacylglycerol is considerably lower in isolated adipocytes from fasted than from fed animals. Addition of glucose to the incubation medium promotes the incorporation of radioactive lactate into both fatty acids and glyceride-glycerol by adipocytes from fasted as well as fed animals. The concentration of alpha-glycerolphosphate is considerably higher in adipose tissue of fed than fasted animals. In general, these results support the presence of a glyceroneogenic pathway in rat and guinea pig adipose tissue. However, it would appear that the physiologic significance of this pathway is less important in the fasted than the fed state, where it may play some role in the esterification of intracellular fatty acids.

Adipose Tissue↗
PubMed1995

Mechanism of cellulose synthesis in Agrobacterium tumefaciens.

Extracts of Agrobacterium tumefaciens incorporated UDP-[14C]glucose into cellulose. When the extracts were fractionated into membrane and soluble components, neither fraction was able to synthesize cellulose. A combination of the membrane and soluble fractions restored the activity found in the original extracts. Extracts of cellulose-minus mutants showed no significant incorporation of UDP-glucose into cellulose. When mixtures of the extracts were made, the mutants were found to fall into two groups: extracts of mutants from the first group could be combined with extracts of the second group to obtain cellulose synthesis. No synthesis was observed when extracts of mutants from the same group were mixed. The groups of mutants corresponded to the two operons identified in sequencing the cel genes (A. G. Matthysse, S. White, and R. Lightfoot. J. Bacteriol. 177:1069-1075, 1995). Extracts of mutants were fractionated into membrane and soluble components, and the fractions were mixed and assayed for the ability to synthesize cellulose. When the membrane fraction from mutants in the celDE operon was combined with the soluble fraction from mutants in the celABC operon, incorporation of UDP-glucose into cellulose was observed. In order to determine whether lipid-linked intermediates were involved in cellulose synthesis, permeablized cells were examined for the incorporation of UDP-[14C]glucose into material extractable with organic solvents. No radioactivity was found in the chloroform-methanol extract of mutants in the celDE operon, but radioactive material was recovered in the chloroform-methanol extract of mutants in the celABC operon. The saccharide component of these compounds was released after mild acid hydrolysis and was found to be mainly glucose for the celA insertion mutant and a mixture of cellobiose, cellotriose, and cellotetrose for the celB and celC insertion mutants. The radioactive compound extracted with chloroform-methanol form the celC insertion mutant was incorporated into cellulose by membrane preparations from celE mutants, which suggests that this compound is a lipid-linked intermediate in cellulose synthesis.

Agrobacterium tumefaciens↗
PubMed1979

Effects of fructose concentration on carbohydrate metabolism, heat production and substrate cycling in isolated rat hepatocytes.

1. Hepatocytes from starved rats were incubated with 5mm-glucose, labelled uniformly with (14)C and specifically with (3)H at positions 1, 2, 3 or 6, and with fructose at concentrations of 2.5, 7.5 or 25mm. 2. In the absence of other substrates only 1% of the radioactivity initially present in [U-(14)C]glucose appeared in the metabolic products, CO(2), lactate, pyruvate, amino acids and glycogen. 3. Fructose at 2.5mm caused a 30% increase in the glucose concentration and a 4-fold increase in the apparent oxidation of [U-(14)C]-glucose. 4. The formation of (3)H(2)O from [1-(3)H]-, [2-(3)H]-, [3-(3)H]- or [6-(3)H]-glucose was 2.4, 4.3, 2.15 or 1.6% respectively in the control incubations and 4.1, 10.4, 7.7 or 5.1% with 2.5mm-fructose. 5. Fructose at 7.5 and 25mm decreased the (3)H(2)O yields to less than the control values, but had no apparent effect on the amount of [U-(14)C]glucose metabolized. 6. In the incubations with 5mm-glucose and 25mm-fructose there were significant decreases in heat production, O(2) consumption and in the ratio of O(2) uptake to heat output. 7. Fructose at 2.5mm caused a 64% increase in heat output, but only a 43% increase in O(2) uptake. 8. The radioisotopic and calorimetric data demonstrate that physiological concentrations of fructose greatly increase metabolism in hepatocytes from starved rats. These data also indicate increased cycling at glucose/glucose 6-phosphate and at fructose 6-phosphate/fructose 1,6-bisphosphate in the presence of 2.5mm-fructose, although the rates of cycling were actually decreased relative to the amount of glucose catabolized. 9. At concentrations of 2.5, 7.5 and 25mm, fructose depressed hepatocyte ATP concentrations by 20, 65 and 80% respectively. Although fructose at 7.5 and 25mm increased glucose and lactate release, O(2) consumption, production of heat and formation of(3)H(2)O from [1-(3)H]-, [2-(3)H]-, [3-(3)H]- or [6-(3)H]-glucose were lowered to values equal to, or less than, controls. These effects probably reflect a severe derangement of hepatic metabolism due to excess phosphorylation of fructose when present at high concentrations.

Adenosine Triphosphate↗
PubMed1991

Direct Photolabeling with [P]UDP-Glucose for Identification of a Subunit of Cotton Fiber Callose Synthase.

We have identified a 52 kilodalton polypeptide as being a likely candidate for the catalytic subunit of the UDP-glucose: (1-->3)-beta-glucan (callose) synthase of developing fibers of Gossypium hirsutum (cotton). Such a polypeptide migrates coincident with callose synthase during glycerol gradient centrifugation in the presence of EDTA, and can be directly photolabeled with the radioactive substrate, alpha-[(32)P]UDP-glucose. Interaction with the labeled probe requires Ca(2+), a specific activator of callose synthase which is known to lower the K(m) of higher plant callose synthases for the substrate UDP-glucose. Using this probe and several other related ones, several other proteins which interact with UDP-glucose were also identified, but none satisfied all of the above criteria for being components of the callose synthase.

Journal Article↗
PubMed2000

Impairment by cytochalasin B of the inhibitory action of D-mannoheptulose upon D-glucose metabolism in rat pancreatic islets.

D-mannoheptulose was recently found to inhibit D-glucose metabolism in hepatocytes and pancreatic islets, whilst failing to do so in parotid cells, erythrocytes and the exocrine pancreas. In the latter three systems, however, the hexaacetate ester of D-mannoheptulose efficiently inhibits D-glucose metabolism. It was proposed, therefore, that the transport of unesterified D-mannoheptulose into cells may be mediated by GLUT2. Since cytochalasin B is known to inhibit D-glucose transport into pancreatic islet cells, it was now investigated whether the mould metabolite (0.02 mM) also impairs the inhibitory action of D-mannoheptulose (1.0 mM) upon D-glucose metabolism in rat pancreatic islets. The relative extent of D-mannoheptulose inhibitory action on D-[5-3H]glucose utilization and D-[U-14C]glucose conversion to 14CO2, as well as radioactive amino acids and acidic metabolites, was indeed much less marked in the presence of cytochalasin B (13+/-4% inhibition) than in its absence (40+/-3% inhibition). A comparable situation was not observed, however, in the case of glucose-stimulated insulin secretion, cytochalasin B augmenting insulin output to the same relative extent in the absence or presence of D-mannoheptulose. These findings support the view that the entry of D-mannoheptulose into cells may be mediated by a cytochalasin B-sensitive transport system, such as the GLUT2 carrier.

Animals↗
PubMed1975

beta-1, 3-Glucan Synthase from Lilium longiflorum Pollen.

A particulate fraction from pollen tubes and ungerminated pollen of Lilium longiflorum incorporated (14)C-glucose from UDP-glucose-(14)C into a lipid fraction and into beta-1, 3-glucan. Partial hydrolysis of the glucan yielded laminaribiose as the only radioactive disaccharide. The preferred substrate was UDP-glucose, and enzyme activity was stimulated by glucose and by beta-linked di- and trisaccharides. Enzyme from growing pollen tubes synthesized beta-1, 3-glucan more rapidly and produced a higher proportion of alkali-insoluble glucan than did enzyme from ungerminated pollen. The onset of pollen tube growth may be dependent on altered activity of beta-1, 3-glucan synthase.

Journal Article↗
PubMed1980

Transfer across mucosal epithelium, tissue content and metabolic fate of 125I-(ipodate-sodium) on isolated everted segments of rat small intestine.

1. Transfer and tissue content of 125I-radioactivity was measured after administration of 125I-(ipodate-sodium) to everted rat jejunal segments. 2. After having administered 10(-5) M 125I-(ipodate-sodium) on both sides of the everted sacs the S/M ratio of the concentration of 125I-radioactivity was 1.5 in jejunal segments and 2.3 in ileal segments. The tissue content was nearly equal for both segments. According to the apparent partition coefficient for ipodate-sodium at pH 7, the 125I-radioactivity is accumulated in the tissue about 10-fold. 3. Lowering of the temperature of the incubation medium from 37 degrees C to 15 degrees C prevents the building up of a concentration gradient between the serosal and the mucosal side on either jejunal and ileal segments whereas the tissue content of 125I-radioactivity was nearly unchanged. 4. With increasing concentrations (1.6--10(-6)--9.6-10(-4) M) of 125I-(ipodate-sodium) administered on the mucosal side the transfer and the tissue content of 125I-radioactivity were decreased. This appears to be a toxic effect since in jejunal segments also the S/M ratio for the concentration of glucose decreases. 5. The analysis of the 125I-radioactivity in the serosal fluid of jejunal segments showed that the bulk of the 125I-radioactivity was present in the aqueous phase and only 33% as the unchanged ipodate-sodium in the organic phase. 10% of the 125I-radioactivity must be attributed to inorganic iodine. The concentration of 125I-(ipodate-sodium) administered in the mucosal fluid only was 3.2-10(-6) M. At lower temperature (7 degrees C) the bulk of the 125I-radioactivity in the serosal fluid was found in the organic phase, i.e. as unchanged ipodate-sodium. 6. After the incubation of the aqueous phase with beta-glucuronidase or NaOH about 97% of the 125I-radioactivity could be extracted into the organic phase. This means that the bulk of the 125I-radioactivity in the aqueous phase is present as a conjugate, e.g. ester glucuronide of the unchanged ipodate. 7. Apparently, the process of the conjugation of ipodate-sodium in the mucosal cells is involved in the transfer of the 125I-radioactivity across the mucosal epithelium.

Animals↗
PubMed1975

Effects of d-amphetamine on the incorporation of carbon atoms of D-glucose into the brains of differentially-housed mice.

Mice were housed either individually ("isolated") or in groups of 20-25 ("aggregated") for 5-9 weeks or for 22 weeks. A decreased incorporation of radioactivity into brain from subcutaneously-administered U-14C-D-glucose occurred in "isolated" mice as compared to grouped animals. Amphetamine, administered before labelled glucose, produced a dose-dependent decrease of radioactivity which was selective to the brains of the "isolated" mice. The data support the correlation between isolation-induced changes in behavior and central metabolic pathways and indicate further that these changes may be altered by administration of psycho-active agents.

Animals↗
PubMed1980

The metabolic fate of lactate in renal cortical tubules.

1. Isolated kidney cortex tubules prepared from fed rats and incubated with near-physiological concentrations of [(14)C]lactate decrease the specific radioactivity of the added lactate. This effect may be attributable to at least two mechanisms; formation of lactate from endogenous precursors, or entry of unlabelled carbon into the lactate pool as a result of substrate cycling, via phosphoenolpyruvate, pyruvate and oxaloacetate, together with equilibration of the oxaloacetate pool with malate and fumarate. Such substrate cycling could occur within a single cell, or between two populations of different cells, one glycolytic and the other gluconeogenic. These possibilities have been investigated by using metabolic inhibitors or alternative metabolic substrates. 2. Tubules from fed rats produced a fall in specific radioactivity of 14.4% when incubated for 40min with 2mm-lactate alone. A mathematical treatment of this result is presented, which allows the rate of fall in specific radioactivity to be expressed as the addition of unlabelled lactate to the pool. This corresponds to a rate of formation of unlabelled lactate of 121+/-22mumol/h per g dry wt., a rate close to that of gluconeogenesis. In tubules from fasting rats, there was no reduction of the specific radioactivity of lactate, indicating that fasting for 24h suppresses production of unlabelled-lactate carbon. 3. Addition of 2mm-fumarate resulted in a significantly greater decrease in the specific radioactivity of lactate, but aspartate (2mm), malate (2mm) and glucose (5mm) were without effect. Total inhibition of gluconeogenesis with 3-mercaptopicolinate did not prevent the fall in specific radioactivity of lactate observed in tubules from fed-rat kidney, thereby excluding significant activity of the substrate cycle pyruvate-->oxaloacetate-->phosphoenolpyruvate-->pyruvate. 4. The capacity of pyruvate kinase under the test conditions in tubules prepared from kidneys of fed or starved rats was at least ten times higher than the observed rate of production of lactate, so that failure to observe recycling of lactate in starved-rat tubules indicates suppression of pyruvate kinase activity. 5. The endogenous glycogen and glucose content of isolated renal cortex tubules is too low to account for the dilution of label of lactate. Endogenous concentrations of glycerol and amino acids were also very low. As for glycogen, the possibility that very rapid turnover of these metabolites, in fed rats but not in starved rats, may account for formation of unlabelled lactate cannot be excluded. 6. It is concluded that substrate cycling via phosphoenolpyruvate does not occur to any significant extent in either fed or starved-rat kidney. In fed rats recycling of lactate carbon does occur and the rate of this reaction is similar to the rate of gluconeogenesis at physiological concentrations of lactate. The present results favour participation of oxaloacetate decarboxylase rather than ;malic' enzyme in this cycle.

Animals↗
PubMed1994

Profile of energy metabolism in a murine hybridoma: glucose and glutamine utilization.

The antibody-secreting murine hybridoma, CC9C10, was grown in batch culture in a medium containing 20 mM glucose and 2 mM glutamine. After 2 days of exponential growth, the glutamine content of the medium was completely depleted, whereas the glucose content was reduced to 60% of the original concentration. The glucose and glutamine metabolism was analyzed at midexponential phase by use of radioactively labelled substrates. Glycolysis accounted for the metabolism of most of the glucose utilized (> 96%) with flux through the pentose phosphate pathway (3.6%) and the TCA cycle (0.6%) accounting for the remainder. Glutamine was partially oxidised via glutaminolysis to alanine (55%), aspartate (3%), glutamate (4%), lactate (9%), and CO2 (22%). Calculation of the theoretical ATP production from these pathways indicated that glucose could provide 59% and glutamine 41% of the energy requirement of the cells.

Adenosine Triphosphate↗
PubMed1980

An autoradiographic, biochemical, and morphological study of the harderian gland of the mouse.

Biochemical and morphological properties of the Harderian gland of the mouse were examined by combining autoradiographic, biochemical, and electron microscopic techniques. Autoradiographs show that the radioactive carbon from [U-14C]glucose injected to the abdominal cavity is completely incorporated into the acid-insoluble substances within 30 minutes. The results of chemical analysis show that the main components of this gland are glyceryl ether diesters and phospholipids. Scanning electron microscopy shows numerous lipid droplets in the secretory cells and alveolar lumina. Myoepithelial cells lie between the secretory cell base and the basement membrane and have a basket-like distribution of processes as confirmed by hydrochloric acid and collagenase digestions. Myofilaments are demonstrated in the cytoplasm. Two types of secretory cells (A and B) comprise the alveolar epithelium and can be differentiated under the electron microscope. The cytoplasm of both contains numerous vacuoles. The vacuoles are almost empty in A cells, which are more numerous constituent of the alveolar epithelium than B cells. However, the vacuoles of the B cells contain densely osmiophilic material. In both, cell types show a merocrine mode of secretion. Unmyelinated nerve cell endings occur in the interstices of the connective tissue, and contain clear or cored vesicles.

Animals↗
PubMed1975

In vivo biosynthesis of peptidophosphogalactomannan in Penicillium charlesii.

The major exocellular glycopeptide (peptidophosphogalactomannan) produced by Penicillum charlesii first appears in the culture filtrate when the growth medium is nearly depleted of NH4+. The extent of incorporation of exogenously supplied radioactive precursors (D-[U-14C] GLUCOSE, L-[U-14C]threonine and NaH2(32)PO4) into peptidophosphogalactomannan suggests that approximately 20% of the total quantity of peptidophosphogalactomannan is assembled from constituents taken from the growth medium before NH4+ starvation and that the remainder is assembled from constituents in the medium during NH4" starvation. In the absence of NH4+, an increase in dry weight continues until the medium is depleted of glucose. However, peptidophosphogalactomannan accumulation proceeds until after glucose is depleted and growth is halted. These data suggest that peptidophosphogalactomannan is a product of cellular turnover.

Galactose↗
PubMed1971

La localisation microsomale de la synthese des acides gras dans le foie de la souris vivante.

Mice were given glucose-U-(14)C and the radioactivity of triglyceride and phospholipid glycerol and fatty acids was measured 30 sec, 3 or 30 min after the i.v. administration in liver microsomes and supernatant. After the acetate administration the radioactivity of palmitic and stearic acids and that of their carboxyl carbons was also measured. The repartition of the radioactivity was discussed in relation with the localization of fatty acid synthesis. In agreement with our previous results it was suggested that the endoplasmic reticulum is the main site of this synthesis.

Journal Article↗