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PubMed1991

The male antifertility activity of 6-chloro-6-deoxyglucose.

6-Chloro-6-deoxy[U-14C]glucose is not metabolised by mature boar spermatozoa nor has it any specific inhibitory action on their metabolic activity in vitro. The compound is metabolised by the male rat and the identification of two urinary metabolites as alpha-chlorohydrin and 3-chlorolactate confirmed that (S)-3-chlorolactaldehyde is produced by this species in vivo. A tissue distribution study revealed that radioactivity from 6-chloro-6-deoxy[U-14C]glucose was more concentrated in rat caudal spermatozoa than in any other of the major tissues.

Animals↗
PubMed1995

Architecture of the yeast cell wall. The linkage between chitin and beta(1-->3)-glucan.

To isolate the putative linkage region between chitin and beta(1-->3)-glucan, Saccharomyces cerevisiae cell walls were digested with beta(1-->3)-endoglucanase and the reducing ends of the enzyme-resistant glucose chain stubs were labeled by reduction with borotritide. The radioactive material was further digested with exochitinase to remove the bulk of the chitin, and the liberated oligosaccharides were fractionated on a sizing column. A single peak (compound I) was found to consist of N-acetylglucosamine, glucose, and glucitol residues in the ratio 1:2:1. By digestion with beta-N-acetylglucosaminidase and by NMR spectroscopy, N-acetylglucosamine was identified as the nonreducing terminus, linked to laminaritriitol by a beta(1-->4) bond. Five additional oligosaccharides were recovered, two being analogs of compound I, with 1 or 3 glucose units, respectively; the remaining three were shown to be the reduced analogs of laminaribiose, laminaritriose, and laminaritetraose. The presence of N-acetylglucosamine-containing oligosaccharides arises from the activity of chitinase in cleaving 2 sugar units sequentially in those chains containing an odd number of N-acetylglucosamine residues; correspondingly, oligosaccharides containing only glucose and sorbitol derived from even-numbered chitin chains, a result implying that chitinase can hydrolyze the linkage between N-acetylglucosamine and glucose. It is concluded that the terminal reducing residue of a chitin chain is attached to the nonreducing end of a beta(1-->3)-glucan chain by a beta(1-->4) linkage. Experiments with appropriate mutants showed that synthesis of the chitin combined with glucan is catalyzed by chitin synthetase 3. The timing and possible mechanism of formation of the chitin-glucan linkage is discussed.

Acetylglucosaminidase↗
PubMed2002

Contrasting effects of exercise and NOS inhibition on tissue-specific fatty acid and glucose uptake in mice.

Isotopic techniques were used to test the hypothesis that exercise and nitric oxide synthase (NOS) inhibition have distinct effects on tissue-specific fatty acid and glucose uptakes in a conscious, chronically catheterized mouse model. Uptakes were measured using the radioactive tracers (125)I-labeled beta-methyl-p-iodophenylpentadecanoic acid (BMIPP) and deoxy-[2-(3)H]glucose (DG) during treadmill exercise with and without inhibition of NOS. [(125)I]BMIPP uptake at rest differed substantially among tissues with the highest levels in heart. With exercise, [(125)I]BMIPP uptake increased in both heart and skeletal muscles. In sedentary mice, NOS inhibition induced by nitro-L-arginine methyl ester (L-NAME) feeding increased heart and soleus [(125)I]BMIPP uptake. In contrast, exercise, but not L-NAME feeding, resulted in increased heart and skeletal muscle [2-(3)H]DG uptake. Significant interactions were not observed in the effects of combined exercise and L-NAME feeding on [(125)I]BMIPP and [2-(3)H]DG uptakes. In the conscious mouse, exercise and NOS inhibition produce distinct patterns of tissue-specific fatty acid and glucose uptake; NOS is not required for important components of exercise-associated metabolic signaling, or other mechanisms compensate for the absence of this regulatory mechanism.

Administration, Oral↗
PubMed1990

Change in hexose distribution volume and fractional utilization of [18F]-2-deoxy-2-fluoro-D-glucose in brain during acute hypoglycemia in humans.

We used positron emission tomography (PET) to study the effects of mild hypoglycemia on cerebral glucose uptake and metabolism. Nine healthy men were studied under basal saline-infusion conditions, and during euglycemic and hypoglycemic clamp studies. Insulin was infused at the same rate (1 mU.kg-1.min-1) in both clamp studies. In euglycemic clamp studies, glucose was infused at a rate sufficient to maintain the basal plasma glucose concentration, whereas in hypoglycemic clamp studies, the glucose infusion rate was reduced to maintain the plasma glucose at 3.1 mM. Each study lasted 3 h and included a 30-min baseline period and a subsequent 150-min period in which insulin or glucose was administered. Blood samples for measurement of insulin, glucose, cortisol, growth hormone, and glucagon were obtained at 20- to 30-min intervals. A bolus injection of 5-10 mCi [18F]-2-deoxy-2-fluoro-D-glucose (2-DFG) was administered 120 min after initiation of the study, and plasma radioactivity and dynamic PET scans were obtained at frequent intervals for the remaining 40-60 min of the study. Cerebral regions of interest were defined, and concentrations of radioactivity were calculated and used in the three-compartment model of 2-DFG distribution described by Sokoloff. Glucose levels were similar during saline-infusion (4.9 +/- 0.1 mM) and euglycemic clamp (4.8 +/- 0.1 mM) studies, whereas the desired degree of mild hypoglycemia was achieved during the hypoglycemic clamp study (3.1 +/- 0.1 mM, P less than 0.05). The insulin level during saline infusion was 41 +/- 7 pM.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1999

Two new functions of inositol in the eye lens: antioxidation and antiglycation and possible mechanisms.

The extent of glycation of human eye lens proteins with glucose in presence of added inositol was examined in vitro using [U14C] glucose. Lens homogenate was reacted with varying concentrations of glucose and glucose + inositol. At the end of the reaction, the proteins were precipitated with TCA, centrifuged, dissolved in NaOH and the radioactivity was measured. Inositol decreased the glycation by 57-67%. Pure inositol and glucose suitably labelled with 3H or 14C when reacted and followed by paper chromatography and HPLC showed that glucosyl inositol was present along with unreacted free glucose. Preliminary studies made of the UV spectra of pure inositol (i) when reacted with H2O2 showed that inositol removed H2O2 from the reaction mixture (ii) when reacted with arachidonic acid showed that they formed a conjugate. The observations indicate that the antioxidant property of inositol could be the result of its' quenching action on reactive oxygen, intermediates and conjugate-formation with compounds like arachidonic acid and the antiglycating property due to scavenging of glucose. The antioxidant and the antiglycating properties of inositol may be beneficial in delaying or averting cataract.

Antioxidants↗
PubMed1980

Regulation of ethanolamine and choline phosphatide biosynthesis in isolated rat intestinal villus cells.

The effects of ethanolamine, choline, and different fatty acids on phospholipid synthesis via the CDP-ester pathways were studied in isolated rat intestinal villus cells. The incorporation of [14C]glucose into phosphatidylethanolamine was stimulated severalfold by the addition of ethanolamine and long-chained unsaturated fatty acids, while the addition of lauric acid inhibited the incorporation of radioactivity into phosphatidylethanolamine. At concentrations of ethanolamine higher than 0.2 mM, phosphoethanolamine accumulated, but the concentrations of CDP-ethanolamine and the incorporation of radioactivity into phospatidylethanolamine did not increase further. The incorporation of [14C]glucose into phosphatidylcholine responded in a way similar to that of phosphatidylethanolamine, except that a 10-fold higher concentration of choline was required for maximal stimulation. CCC inhibited the incorporation of choline into phosphatidylcholine. In contrast with hepatocytes, villus cells did not form phosphatidylcholine via phospholipid N-methylation. The data indicate that, in intestinal villus cells, the cytidylyltransferase reactions are rate limiting in the synthesis of phosphatidylethanolamine and probably also of phosphatidylcholine. The availability of diacylglycerol and its fatty acid composition may also significantly affect the rate of phospholipid synthesis.

Animals↗
PubMed1979

Treponema succinifaciens sp. nov., an anaerobic spirochete from the swine intestine.

The morphology, the general physiological characteristics, and the energy-yielding metabolism of an obligately anaerobic spirochete isolated from the colon of a swine were studied. Electron microscopy showed that the helical spirochetal cells possessed an outer sheath, a protoplasmic cylinder, and 4 periplasmic fibrils in a 2-4-2 arrangement. The spirochete grew in an atmosphere of N2 in prereduced media containing a carbohydrate, NaHCO3, rumen fluid, yeast extract, peptone, L-cysteine, and inorganic salts. The spirochete fermented carbohydrates and required substrate amounts of CO2 (HCO3-) for growth. Amino acids were not fermented. Major fermentation products of cells growing with glucose as the substrate and in the presence of CO2 were acetate, formate, succinate, and lactate. Small amounts of 2,3-butanediol, pyruvate, and acetoin were also formed. Determinations of enzymatic activities in cell extracts, and of radioactivity in products formed by growing cells from [1-14C]glucose, indicated that this sugar was dissimilated to pyruvate via the Embden-Meyerhof pathway. The spirochetes used a coliform-type clastic reaction to metabolize pyruvate. Determinations of radioactivity in products formed from [14C]NaHCO3 indicated that CO2 was assimilated and used in succinate production. The guainine + cytosine content of the DNA was 36 mol %. This study indicates that this intestinal spirochete represents a new species of Treponema. It is proposed that the new species be named Treponema succinifaciens.

Anaerobiosis↗
PubMed2006

Low-intensity tensile loading increases intratendinous glucose uptake in the Achilles tendon.

The metabolic activity of tendinous tissues has traditionally been considered to be of limited magnitude. However, recent studies have suggested that glucose uptake increases in the force-transmitting tissues as a response to contractile loading, which in turn indicates an elevated tissue metabolism. The purpose of the present study was to investigate whether such a mechanism could be observed for the human Achilles tendon following tensile loading. Six subjects participated in the study. Unilateral Achilles tendon loading was applied by 25-min intermittent voluntary plantar flexor contractions. A radioactive tracer ([18F]-2-fluoro-2-deoxy-D-glucose) was administered during muscle action, and glucose uptake was measured by use of PET. Regions of interest were defined on the PET images corresponding to the cross section of Achilles tendon at two longitudinally separated sites (insertion and free tendon). Glucose uptake index was determined within respective regions of interest for the active and resting leg. Tendon force during voluntary contractions was approximately 13% of maximal voluntary contraction force. Tendon loading induced an elevated glucose uptake index compared with that of the contralateral resting tendon in the region of tendon insertion (0.13 +/- 0.05 vs. 0.09 +/- 0.02; P < 0.05) and at the free tendon (0.12 +/- 0.01 vs. 0.08 +/- 0.02; P < 0.05). The present data suggest that tissue metabolism is elevated in the human Achilles tendon in response to low-intensity loading.

Achilles Tendon↗
PubMed1989

[Double tracer whole body autoradiography using a short-lived positron emitter and a long-lived beta emitter].

We investigated glucose and amino acid metabolism in tumors and other organs using whole body autoradiography with a short-lived positron emitter and a long-lived beta emitter. The radioactive compounds used were 2-deoxy-2-[18F]-fluoro-D-glucose (18F-FDG) with a half life of 109.8 min and L-[methyl-14C]-methionine (14C-MET) with a half life of 5,730 years. A Donryu rat weighing about 150 g was subcutaneously inoculated at the back with experimental tumors of AH109A and AH272. 74 MBq (2 mCi) of 18F-FDG and 740 kBq (20 microCi) of 14C-MET was administered and after 30 min, the rat was sacrificed. Whole body frozen sections were obtained using autocryotome. For the 18F-FDG autoradiogram, the frozen sections were exposed to an X-ray film for 6 h. After seven days, these frozen sections were again exposed to 14C-MET for a week. Cross-contamination was minimized by adjusting the exposure time, the interval of exposures and the administered dose. The accumulation of the tracers was represented as the optical density ratio of the tissue of interest to the muscle. The tumor ratios were 12.5 for 18F-FDG and 8.6 for 14C-MET showing the highest accumulation in the whole body autoradiogram. In contrast the inflammatory tissue ratios were 1.27 for 18F-FDG and 0.77 for 14C-MET showing very low amino acid metabolism. With the present double tracer whole body autoradiogram, 18F-FDG accumulation was seen in the brain and the heart but not to the liver as against 14C-MET accumulation which was seen to the liver but not to the brain and the heart.

Animals↗
PubMed1987

Glucose and amino acid metabolism in chick telencephalon slices: changes with incubation conditions and animals' development.

Glucose and amino acid metabolism in 1- and 30-day-old chick telencephalon slices was studied in two incubation media in the presence or in the absence of a continuous oxygenation. Medium 1 has a composition and a tonicity similar to cerebrospinal fluid, medium 2 is hypertonic and does not contain any K+ ions. The incorporation of glucose carbon into amino acids and the distribution of radioactivity between the different amino acids are close to the ones observed in the chick brain in vivo only when the slices are incubated in medium 1, with oxygen at 30 days and without oxygen for the 1-day-old chick. It also appears that if oxygenation is necessary for incubation of mature brain tissue in vitro, the absence of the medium oxygenation is more suitable for the study of glucose metabolism in 1-day-old chick brain slices.

Aging↗
PubMedDate not supplied

Metabolism of thymoxamine. III. Structure elucidation of the metabolites and interspecies comparison.

The structures of six metabolites were elucidated using rat urine after intragastric administration of 14C-thymoxamine by means of enzyme incubations, mass spectrometry and synthesis of metabolites: desacetylthymoxamine, N-demethyl-desacetylthymoxamine, the corresponding sulfates and glucuronides. The nature of the conjugates was confirmed by biosynthesis, i.e., co-administration of unlabelled thymoxamine and 35S-sulfate or 14C-glucose. The system high performance liquid chromatography-radioactivity detection was used for interspecies comparison. All biotransformation pathways are seen in rat and man. In dog and cat demethylation is a very minor reaction. Glucuronidation is not observed in the cat.

Animals↗
PubMed1979

Regulation of insulin biosynthesis in vivo by glucose in the newborn rat.

The effects of glucose on insulin biosynthesis in vivo were investigated in the 3-day-old rat. The extent of insulin synthesized was determined by following the incorporation of 3H-leucine into immunoreactive insulin (3H-IRI) and pancreatic proteins (3H-PROT). Blood glucose levels increased 2.3 +/- 0.2 g/liter and plasma insulin increased 208 +/- 10 muU/ml after an intraperitoneal injection of 3H-leucine plus glucose (2 g/kg, body wt) in neonates. Hyperglycemia resulted in a decrease of basal plasma specific radioactivity of leucine and 3H-PROT radioactivity by about 40%. Determination of the 3H-IRI/3H-PROT incorporation ratio shows that the glucose load induced a significant stimulation of insulin biosynthesis 120 min after the injections. The present data indicate that (1) short-term variations of blood glucose are efficient in the regulation of insulin biosynthesis, and (2) insulin biosynthesis in vivo is likely to operate at a basal level of blood glucose in the 3-day-old rat. The results suggested that the variations of blood glucose in a concentration range found under physiologic conditions may play a role in the regulation of insulin biosynthesis in vivo.

Animals↗
PubMed1982

Protein turnover in brain during the development of alcohol dependence.

The chronic effect of ethanol on central nervous system protein turnover was investigated in selected regions of brain following intoxication and withdrawal in a strain of ethanol preferring mice. Mice were serially injected with [14C]glucose in order to achieve a constant specific radioactivity of brain glutamate. Protein turnover was calculated from the specific activities of extracted protein and free glutamate. Results from these studies show that ethanol causes a significant increase in protein turnover in all sections of brain. The brain protein turnover in animals following alcohol withdrawal also shows an increase which deviates significantly from controls in 2 of the 3 regions examined.

Alcohol Drinking↗
PubMed1994

Effects of MK-801 and NBQX on acute recovery of piglet cerebral metabolism after hypothermic circulatory arrest.

Brain protection during open heart surgery in the neonate and infant remains inadequate. Effects of the excitatory neurotransmitter antagonists MK-801 and NBQX on recovery of brain cellular energy state and metabolic rates were evaluated in 34 4-week-old piglets (10 MK-801, 10 NBQX, 14 controls) undergoing cardiopulmonary bypass and hypothermic circulatory arrest at 15 degrees C nasopharyngeal temperature for 1 h, as is used clinically for repair of congenital heart defects. MK-801 (dizocilpine) (0.75 mg/kg) or NBQX [2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(F)quinoxaline] (25 mg/kg) was given intravenously before cardiopulmonary bypass. Equivalent doses were placed in the cardiopulmonary bypass prime plus continuous infusions after reperfusion (0.15 mg kg-1h-1 and 5 mg kg-1h-1). Changes in high-energy phosphate concentrations and pH were analyzed by magnetic resonance spectroscopy in 17 animals until 225 min after reperfusion. Cerebral blood flow determined by radioactive microspheres as well as cerebral oxygen and glucose consumption were studied in 17 other animals. Cerebral blood flow and oxygen consumption were depressed relative to control by both MK-801 and NBQX at baseline. Recovery of phosphocreatine (p = 0.010), ATP (p = 0.030), and intracellular pH (p = 0.004) was accelerated by MK-801 and retarded by NBQX over the 45 min of rewarming reperfusion and the first hour of normothermic reperfusion. The final recovery of ATP at 3 h and 45 min reperfusion was significantly reduced by NBQX (46 +/- 26% baseline, mean +/- SD) versus control (81 +/- 19%) and MK-801 (75 +/- 8%) (p = 0.030). Cerebral oxygen consumption recovered to 105 +/- 30% baseline in group MK-801 and 94 +/- 31% in control but only to 61 +/- 22% in group NBQX (p = 0.070). Cerebral blood flow stayed significantly lower in group NBQX relative to control. Thus, MK-801 accelerates recovery of cerebral high-energy phosphates and metabolic rate after cardiopulmonary bypass and hypothermic circulatory arrest in the immature animal. At the dosage used NBQX exerts an adverse effect.

Animals↗
PubMed1993

Identification of the putative hexose-phosphate translocator of amyloplasts from cauliflower buds.

Starch synthesis in amyloplasts isolated from cauliflower buds is strongly inhibited by the addition of micromolar concentrations of 4,4'-di-isothiocyano-2,2'-stilbenedisulphonic acid (DIDS). Using [3H]DIDS it was possible to label specifically a 31.6 kDa membrane protein of the envelope fraction of isolated amyloplasts. The intensity of the radioactive label was decreased in the presence of glucose 6-phosphate or dihydroxyacetone phosphate, indicating that this protein might be the amyloplastic hexosephosphate translocator.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed2003

Procyclic Trypanosoma brucei do not use Krebs cycle activity for energy generation.

The importance of a functional Krebs cycle for energy generation in the procyclic stage of Trypanosoma brucei was investigated under physiological conditions during logarithmic phase growth of a pleomorphic parasite strain. Wild type procyclic cells and mutants with targeted deletion of the gene coding for aconitase were derived by synchronous in vitro differentiation from wild type and mutant (Delta aco::NEO/Delta aco::HYG) bloodstream stage parasites, respectively, where aconitase is not expressed and is dispensable. No differences in intracellular levels of glycolytic and Krebs cycle intermediates were found in procyclic wild type and mutant cells, except for citrate that accumulated up to 90-fold in the mutants, confirming the absence of aconitase activity. Surprisingly, deletion of aconitase did not change differentiation nor the growth rate or the intracellular ATP/ADP ratio in those cells. Metabolic studies using radioactively labeled substrates and NMR analysis demonstrated that glucose and proline were not degraded via the Krebs cycle to CO(2). Instead, glucose was degraded to acetate, succinate, and alanine, whereas proline was degraded to succinate. Importantly, there was absolutely no difference in the metabolic products released by wild type and aconitase knockout parasites, and both were for survival strictly dependent on respiration via the mitochondrial electron transport chain. Hence, although the Krebs cycle enzymes are present, procyclic T. brucei do not use Krebs cycle activity for energy generation, but the mitochondrial respiratory chain is essential for survival and growth. We therefore propose a revised model of the energy metabolism of procyclic T. brucei.

Aconitate Hydratase↗
PubMed1977

Effect of 2-deoxy-D-glucose on the cell-surface glycoproteins of hamster fibroblasts,.

1. Growth of baby hamster kidney (BHK) cells in medium containing 2-deoxy-D-glucose is retarded in direct proportion of the 2-deoxyglucose concentration. The severity of the effect is reduced in medium containing high relative concentrations of glucose. 2. 2-Deoxyglucose inhibits the incorporation of radioactivity from mannose, galactose, glucosamine, fucose and N-acetylmannosamine precursors into acid-insoluble cellular material. Incorporation of radioactively labelled leucine into protein is not affected by 2-deoxyglucose. 3. BHK cells grown in the presence of 2-deoxyglucose become less sensitive to the toxic action of certain plant lectins, ricin of Ricinus communis and Phaseolus vulgaris phytohaemagglutinin, which bind specifically to cell surface galactose and N-acetyl-galactosamine residues. By contrast, 2-deoxyglucose increased the sensitivity of BHK cells to the weak toxicity of concanavalin A, which binds to surface mannosides. Treated cells also become more agglutinable with concanavalin A. 4. Cell surface glycoprotein labelled by lactoperoxidase-catalysed iodination have been examined by dodecylsulphate-polyacrylamide gel electrophoresis. The radio-iodinated glycoprotein prepared from cells grown in medium containing 2-deoxyglucose migrate more rapidly than glycoproteins from cells grown in the absence of inhibitor.

Cell Division↗