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At least 217 records · Page 12Linked to original sources
PubMed2000

(-)-N-[(11)C]propyl-norapomorphine: a positron-labeled dopamine agonist for PET imaging of D(2) receptors.

Imaging neuroreceptors with radiolabeled agonists might provide valuable information on the in vivo agonist affinity states of receptors of interest. We report here the radiosynthesis, biodistribution in rodents, and imaging studies in baboons of [(11)C]-labeled (-)-N-propyl-norapomorphine [(-)-NPA]. (-)-[(11)C]NPA was prepared by reacting norapomorphine with [(11)C]propionyl chloride and a lithium aluminum hydride reduction. [(11)C]Propionyl chloride was prepared by reacting [(11)C]CO(2) with ethylmagnesium bromide, followed by reacting with phthaloyl chloride. The radiochemical yield of (-)-[(11)C]NPA was 2.5% at end of synthesis (EOS), and the synthesis time was 60 min. The specific activity was 1700+/-1900 mCi/micromol ( N=7; ranged 110-5200 mCi/micromol at EOS). Rodent biodistribution studies showed high uptake of [(11)C](-)-NPA in D(2) receptor-rich areas, and the striatum/cerebellum ratios were 1.7, 3.4, and 4.4 at 5 min, 30 min, and 60 min postinjection, respectively. Pretreating the animals with haloperidol (1 mg/kg) decreased the striatum/cerebellum ratio at 30 min postinjection to 1.3. (-)-[(11)C]NPA was also evaluated via baboon positron emission tomography (PET) studies. Under control conditions ( N=4), rapid uptake of the tracer was observed and the striatum/cerebellum ratio reached 2.86+/-0.15 at 45 min postinjection. Following haloperidol pretreatment (0.2 mg/kg IV), the striatum/cerebellum ratio was 1.29 at 45 min postinjection. The result demonstrated the existence of specific binding of this new tracer to the D(2) receptor. To our knowledge, the current finding of a striatum/cerebellum ratio of 2.8 in baboon was the highest reported with a radiolabeled D(2) agonist. (-)-[(11)C]NPA is a promising new D(2) agonist PET tracer for probing D(2) receptors in vivo using PET.

Animals↗
PubMed2004

Spectroscopic characterization of the uranium carbonate andersonite Na2Ca[UO2(CO3)3] x 6H2O.

The uranium carbonate andersonite Na2Ca[UO2(CO3)3] x 6H2O was synthesized and identified with classical analytical and spectroscopic methods. The classical methods applied were powder X-ray diffraction (XRD), nitric acid digestion, and scanning electron microcopy combined with energy-dispersive spectroscopy (SEM/EDS). To characterize andersonite spectroscopically, time-resolved laser-induced fluorescence spectroscopy (TRLFS), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FT-IR) were used. Natural and synthetic andersonite samples were characterized with the nondestructive TRLFS by six fluorescence emission bands at 470.6, 486.1, 505.4, 526.7, 549.6, and 573.9 nm. In addition, andersonite was characterized by FT-IR measurements by the appearance of the asymmetric stretching vibration of the uranyl cation [v3(UO2(2+))] at 902 cm(-1) with a shoulder at 913 cm(-1). XPS measurements verified the composition of the synthetic andersonite sample. The measured intensity ratios of the XPS lines agree with the stoichiometry of Na2Ca[UO2(CO3)3] x 6H2O. The XPS features of the inner valence molecular orbitals are characteristic of the [UO2(CO3)3]4- structural moiety. These spectroscopic methods can be used to identify in a fingerprinting procedure secondary U(VI) phases in mixtures with other phases or as thin coatings on mineral and rock surfaces.

Carbonates↗
PubMed1978

One-carbon metabolism in methanogenic bacteria: analysis of short-term fixation products of 14CO2 and 14CH3OH incorporated into whole cells.

Methanobacterium thermoautotrophicum, M. ruminantium, and Methanosarcina barkeri were labeled with 14CO2 (14CO2 + H14CO3- + 14CO32-) for from 2 to 45 s. Radioactivity was recovered in coenzyme M derivatives, alanine, aspartate, glutamate, and several unidentified compounds. The properties of one important structurally unidentified intermediate (yellow fluorescent compound) displayed UV absorbance maxima at pH 1 of 290 and 335 nm, no absorbance in the visible region, and a fluorescence maximum at 460 nm. Label did not appear in organic phosphates until after 1 min. 14CH3OH was converted by M. barkeri primarily into coenzyme M derivatives at 25 s. [2-14C]acetate was assimilated by M. thermoautotrophicum mainly into alanine and succinate during 2 to 240 s, but not into coenzyme M derivatives or yellow fluorescent compound. Cell-free extracts of M. thermoautotrophicum lacked ribulose 1,5-bisphosphate carboxylase activity. The data indicated the absence of the Calvin, serine, and hexulose phosphate paths of C1 assimilation in the methanogens examined and indicated that pyruvate was an early intermediate product of net CO2 fixation. The in vivo importance of coenzyme M derivatives in methanogenesis was demonstrated.

Alanine↗
PubMed1984

A balance study of 14C-labelled 3H-imidazo[4,5-f]quinolin-2-amines (IQ and MeIQ) in rats.

The absorption and excretion of 14C-labelled 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) and 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ) were studied in rats of both sexes. The excretion was rapid and within 24 hr more than 90% of the radioactivity had left the rats. After 72 hr the faecal excretion of both compounds was approximately 45-65% and the corresponding excretion via the urine amounted to 37-49%. Only 1-2% was left in the carcasses and less than 0.2% was found in the expired air. About 70% of the IQ and 80% of the MeIQ was found in the bile fluid in a separate 24-hr study. The two compounds had different biliary excretion patterns and the mutagenicity of the bile correlated closely with the excretion of radioactivity.

Animals↗
PubMed1972

Ribitol and flavinogenesis in Eremothecium ashbyii.

1. Supplementation of cultures of Eremothecium ashbyii with ribitol leads to a twofold increase in riboflavin formation compared with unsupplemented cultures or those supplemented with ribose or ribulose phosphate. Addition of unlabelled ribitol decreases the incorporation of [1-(14)C]ribose into riboflavin, indicating that free ribitol is preferred to ribose for incorporation into riboflavin. 2. The enzymes ribitol kinase, d-ribose reductase, d-ribose 5'-phosphatase and GMP nucleosidase were demonstrated in the cell-free extracts. Ribitol induces the formation of ribitol kinase. The enzyme is activated in vitro by the flavinogenic purines, guanine and xanthine. d-Ribose reductase shows a specific requirement for NADPH and forms free ribitol from ribose. 3. The activities of ribitol kinase, ribose 5'-phosphatase and GMP nucleosidase reach their maximal values before riboflavin formation reaches a maximum. 4. [U-(14)C]GMP is taken up intact by the culture of E. ashbyii and is incorporated into riboflavin as well as into a blue fluorescent compound. The radioactivity from this compound is incorporated into riboflavin by the cell-free extract of E. ashbyii.

Ascomycota↗
PubMedDate not supplied

The tissue distribution, metabolism, and excretion of octachlorostyrene in the rat.

The tissue distribution, metabolism, and elimination of 14C-octachlorostyrene (OCS) were studied in the rat. OCS was absorbed in the gastrointestinal tract after oral administration and distributed in all tissues examined. The highest concentrations were found in fat followed by adrenal glands, skin, and lungs. Decay of radioactivity in the tissues followed first-order kinetics. Approximately 8% of an iv dose was excreted in feces during 7 days after administration, while negligible amounts were found in the urine. More than 90% of the radioactivity in feces was due to the unchanged compound, while pentachlorophenyldichloroacetic acid and heptachlorostyrene in equal proportions accounted for the remaining 10%. A small amount (1%) of the dose was detected in the expired air as carbon dioxide.

Adipose Tissue↗
PubMed1988

Topography of basal glucose utilization in the hippocampus determined with [1-14C]glucose and [6-14C]glucose.

The activity of the pentose phosphate shunt was assessed under basal conditions in subregions of the hippocampus by measuring the uptake and retention of [1-14C]glucose and [6-14C]glucose and their 14C-labelled metabolites. The relative and absolute retention of carbon-14 from each of the two compounds was nearly identical in all regions examined. For each compound, the highest accumulation of 14C occurred in the granule cell layer of the dentate gyrus and in the pyramidal cell layer. Relatively high retention of radioactivity was also found in the molecular layer of dentate gyrus and in the stratum lacunosum-molecular. The stratum radiatum and stratum oriens contained the lowest levels of radioactivity among hippocampal regions. The equal retention of radioactivity from [1-14C]glucose and [6-14C]glucose implies that pentose phosphate shunt activity is very low throughout the hippocampus under the conditions of this study. The uptake and retention of radioactivity was evaluated in different hippocampal regions 10 or 30 min following intravenous injection of [1-14C]glucose. Although there was significantly more radioactivity at 30 min than at 10 min, the same topographic pattern of radioactivity within the hippocampus was observed in rats after both survival periods, indicating that an equal fraction of the [1-14C]glucose utilized in different hippocampal regions is oxidized to 14CO2 under these conditions. Most regions of high glucose utilization in the hippocampus determined with [1-14C]glucose and [6-14C]glucose correspond to regions of intense histochemical staining for cytochrome oxidase reported in the literature.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2000

Changes in photosynthetic carbon flow in transgenic rice plants that express C4-type phosphoenolpyruvate carboxykinase from Urochloa panicoides.

A cDNA encoding phosphoenolpyruvate carboxykinase (PCK) of Urochloa panicoides (a PCK-type C4 plant) was expressed in rice (Oryza sativa cv Tsukinohikari) plants under the control of the promoter of a maize (Zea mays) gene for phosphoenolpyruvate carboxylase or pyruvate, orthophosphate dikinase with the transit peptide of the small subunit of Rubisco. Crude extracts prepared from the green leaves of transgenic plants had high PCK activity and the newly expressed PCK was localized in chloroplasts. In labeling experiments with (14)CO(2) up to 20% of the radioactivity was incorporated into 4C compounds (malate, oxaloacetate, and aspartate) in excised leaves of transgenic plants, as compared with about 1% in excised leaves of control plants. There was a positive correlation between PCK activity and the extent of labeling of 4C compounds. When L-[4-(14)C]malate was fed to excised leaves the extent of incorporation of radioactivity into sucrose was 3-fold greater in transgenic plants than in control plants and the level of radiolabeled aspartate was significantly lower in transgenic plants. These results indicate that the ectopic expression of PCK in rice chloroplasts was able partially to change the carbon flow in mesophyll cells into a C4-like photosynthetic pathway. Such a strategy appears to provide a possible method for enhancing the photosynthetic capacity of C3 plants.

Blotting, Western↗
PubMed1986

Distribution of 14C after oral administration of [U-14C]labeled methyl linoleate hydroperoxides and their secondary oxidation products in rats.

To study the toxicity of low molecular weight (LMW) compounds formed during the autoxidation of oils, 14C-labeled primary monomeric compounds (methyl linoleate hydroperoxides) and secondary oxidation products, i.e., polymer and LMW compounds prepared from autoxidized methyl [U-14C]linoleate hydroperoxides (MLHPO) were orally administered to rats, and their radioactive distributions in tissues and organs were compared. The polymeric fraction consisted mainly of dimers of MLHPO. For the LMW fraction, 4-hydroxy-2-nonenal, 8-hydroxy methyl octanoate and 10-formyl methyl-9-decenoate were identified as major constituents by gas chromatography-mass spectrometry (GC-MS) after chemical reduction and derivatization. When LMW compounds were administered to rats, 14CO2 expiration and the excreted radioactivity in urine in 12 hr were significantly higher than those from polymer or MLHPO administration. Maximum 14CO2 expiration appeared 2-4 hr after the dose of LMW compounds. Radioactivity of the upper part of small intestines six hr after the dose of LMW compounds was higher than the values from administered polymer or MLHPO. The remaining radioactivity in the digestive contents and feces 12 hr after administration of LMW compounds was much lower than the values observed from administered polymer or MLHPO. Among internal organs, the liver contained the highest concentration of radioactivities from polymer, MLHPO and LMW fractions, and an especially higher level of radioactivity was found in liver six hr after the administration of LMW compounds. Six hours after the dose of LMW compounds, a relatively higher level of radioactivity also was detected in kidney, brain, heart and lung.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Determination of gluconeogenesis in vivo with 14C-labeled substrates.

A mitochondrial model of gluconeogenesis and the tricarboxylic acid cycle, where pyruvate is metabolized via pyruvate carboxylase and pyruvate dehydrogenase, and pyruvate kinase is examined. The effect of the rate of tricarboxylic acid flux and the rates of the three reactions of pyruvate metabolism on the labeling patterns from [14C]pyruvate and [24C]acetate are analyzed. Expressions describing the specific radioactivities and 14C distribution in glucose as a function of these rates are derived. Specific radioactivities and isotopic patterns depend markedly on the ratio of the rates of pyruvate carboxylation and decarboxylation to the rate of citrate synthesis, but the effect of phosphoenolpyruvate hydrolysis is minor. The effects of these rates on 1) specific radioactivity of phosphoenolpyruvate, 2) labeling pattern in glucose, and 3) contribution of pyruvate, acetyl-coenzyme A, and CO2 to glucose carbon are illustrated. To determine the contribution of lactate or alanine to gluconeogenesis, experiments with two compounds labeled in different carbons are required. Methods in current use to correct for the dilution of 14C in gluconeogenesis from [14C]pyruvate are shown to be erroneous. The experimental design and techniques to determine gluconeogenesis from 14C-labeled precursors are presented and illustrated with numerical examples.

Alanine↗
PubMed1986

Excretion of radioactivity from rats and rabbits following cutaneous application of two 14C-labeled azo dyes.

A benzidine-derived azo dye, C.I. direct black 38 (DB38), and a p-phenylenediamine-derived dye, C.I. direct black 19 (DB19), labeled with carbon-14 in their aromatic amine moieties, were applied to the shaved dorsal skin of male Fischer-344 rats and New Zealand rabbits. Application sites were protected with nylon gauze and elastic bandage assemblies. Following application of measured amounts of radiolabeled dye in 0.1 M pH 10.2 carbonate buffer, serial urine and fecal samples were obtained from individual animals in metabolism cages at 24, 48, 72, 96, 120, and 144 h. Aliquots of urine and fecal homogenates were assayed for radioactivity by scintillation counting. Cumulative excretion of radioactivity from rats receiving DB38 was 0.05% of total dermal dose at 144 h in urine, and 0.16% of total dermal dose in feces. Cumulative excretion of radioactivity from DB38-treated rabbits at 144 h was 3.12% of total dermal dose in urine, and 5.12% in feces. From rats and rabbits receiving topical DB19, cumulative excretion of radioactivity at 144 h was less than that from DB38-treated animals. In rat urine, 0.04% of total dermal dose appeared; in rat feces, no radioactivity was recovered. In rabbit urine, 0.04% of dermal dose was found; 0.01% appeared in rabbit feces.

Animals↗
PubMed1988

Photosynthetic Carbon Fixation in Guard Cell Protoplasts of Vicia faba L. : Evidence from Radiolabel Experiments.

Photosynthetic carbon fixation in guard cells was reexamined in experiments with highly purified guard cell protoplasts from Vicia faba L. irradiated with red light. The fate of (14)CO(2) (4.8 microcuries of NaHCO(3); final concentration: 100 micromolar) supplied to these preparations was investigated with two-dimensional paper, and thin layer chromatography. Rates of CO(2) fixation were 5- to 8-fold higher in the light than in darkness. Separation of acid-stable products into water-insoluble, neutral, and anionic fractions showed that more radioactivity was incorporated into the neutral fraction in the light than in the dark. In the dark, malate and aspartate comprised 90% of the radiolabel found in the anionic fraction, whereas in the light, radioactivity was also found in 3-phosphoglyceric acid (PGA), sugar monophosphates, sugar diphosphates, and triose phosphates. Phosphorylated compounds contained up to 60% of the label in the light-treated anionic fraction. Phosphatase treatment and rechromatography of labeled sugar diphosphate showed the presence of ribulose, a specific metabolite of the photosynthetic carbon reduction pathway (PCRP). In time-course experiments, labeled PGA was detected within 5 seconds. With time, the percentage of label in PGA decreased and that in sugar monophosphate increased. We conclude that PGA is a primary carboxylation product of the PCRP in guard cells and that the activity of the PCRP, and phosphoenolpyruvate-carboxylase is metabolically regulated.

Journal Article↗
PubMed2003

Aryl triflates and [11C]/(13C)carbon monoxide in the synthesis of 11C-/13C-amides.

Palladium(0)-mediated carbonylation reactions using aryl triflates, amines, and a low concentration of [(11)C]carbon monoxide were used in the syntheses of 13 (11)C-labeled amides. Lithium bromide was used as an additive to facilitate the reaction. The (11)C-labeled products were obtained with decay-corrected radiochemical yields in the range of 2-63%. The radiochemical purity of the final products exceeded 98%. As an example, a reaction starting with 1.79 GBq [(11)C]carbon monoxide gave 0.38 GBq of LC-purified N-isopropyl-4-nitro-[(11)C]benzamide within 27 min from the start of the carbonylation reaction (54% decay-corrected radiochemical yield). The specific radioactivity of this compound was 191 GBq/micromol, 35 min after the end of a 10 microAh bombardment. N-Benzylisoquinoline-1-((13)C)carboxamide was prepared and analyzed by NMR for confirmation of the labeling position. The triflates 16, 20, 21, and 22 were synthesized from the corresponding alcohols and trifluoromethanesulfonic anhydride. The reference compounds 30a and 30b were prepared from the corresponding carboxylic acids and benzylamine. The other nine reference compounds 32a to 32i were synthesized from the respective acid chlorides and amines. The presented report shows that the sometimes more easily obtainable aryl triflates can be a useful alternative to the commonly used aryl halides in palladium(0)-mediated synthesis of (11)C/(13)C-amides.

Journal Article↗
PubMed1985

Fluorescent substances in mouse and human sera as a parameter of in vivo lipid peroxidation.

Water-soluble fluorescent substances like lipofuscin were found in the protein fraction of mouse and human sera and had fluorescence characteristics with excitation and emission maxima at 335-340 and 435-440 nm for mice, and at 355-360 and 430-435 nm for human, respectively. When oxidized [U-14 C]linoleic acid was given intraperitoneally to mice, or added to the serum in vitro, both the fluorescence intensity and radioactivity of serum protein increased dose-dependently in the two tests. Also, the fluorescent substances responded well to acceleration of in vivo lipid peroxidation caused by carbon tetrachloride. These results indicate that the substances were some binding compounds between the degraded lipids and serum proteins, and that they could be taken as a parameter of in vivo lipid peroxidation. The distribution of the pigments in the serum proteins, albumin and globulins, was shown to depend upon the number of free amino groups in each protein which appear to be binding sites of degraded lipids. Spectral characteristics and some chemical properties of the substances suggest that they might not be conjugated Schiff bases formed from protein and malondialdehyde but might be due to some other stable compounds. Significantly high levels of the substances were observed in sera of patients with diabetes and hypertension.

Adult↗
PubMed1965

INCORPORATION OF C14 FROM CARBON DIOXIDE INTO SUGAR PHOSPHATES, CARBOXYLIC ACIDS, AND AMINO ACIDS BY CLOSTRIDIUM THERMOACETICUM.

Ljungdahl, Lars (Western Reserve University, Cleveland, Ohio), and Harland G. Wood. Incorporation of C(14) from carbon dioxide into sugar phosphates, carboxylic acids, and amino acids by Clostridium thermoaceticum. J. Bacteriol. 89:1055-1064. 1965.-The mechanism of synthesis of acetate from carbon dioxide by Clostridium thermoaceticum was investigated by incubating cells with glucose or xylose in the presence of C(14)O(2). Sugar phosphates, amino acids, and carboxylic acids were isolated and the specific radioactivities were determined; the distributions of C(14) were also determined in some of the compounds. Only fructose-1,6-diphosphate, formate, and lactate had higher specific activities than the acetate. The specific activities and distribution of C(14) in the fructose-6-phosphate and ribose-5-phosphate were such that we conclude that the synthesis of acetate does not occur via a pathway involving the sugar phosphates as direct intermediates. Likewise, it is shown that pathways including lactate, aspartate, serine, glycine, malate, and succinate are not of importance in the synthesis of acetate from CO(2). The methyl group of free methionine was unlabeled and is not a precursor of the methyl group of acetate.

Acetates↗
PubMed1992

Body distribution of fully biodegradable [14C]-poly(lactic acid) nanoparticles coated with albumin after parenteral administration to rats.

Fully biodegradable polylactic acid (PLA) nanoparticles (90-250 nm) coated with human serum albumin (HSA) were prepared by high-pressure emulsification and solvent evaporation, using the protein as surfactant. A new analytical tool was developed, based on Mie's law and size exclusion chromatography, to establish that, after evaporation of the solvent, the protein saturates the surface of the nanoparticles, masking the PLA core. According to this technique, no HSA is encapsulated in the polymer matrix. A radiolabelled [14C]-PLA50 was synthesized to follow the fate of this new drug carrier after i.v. administration to rats. The time necessary to clear the albumin-coated nanoparticles from the plasma was significantly longer than for the uncoated ones but not extended enough to target cells other than mononuclear phagocytes. As deduced from whole-body autoradiography and quantitative distribution experiments, the 14C-labelled polymer is rapidly captured by liver, bone marrow, lymph nodes, spleen and peritoneal macrophages. Nanoparticle degradation was addressed following 14C excretion. The elimination of the 14C was quick on the first day (30% of the administered dose) but then slowed down. In fact, if the metabolism of the PLA proceeds to lactic acid which is rapidly converted into CO2 via the Krebs cycle (80% of the total excretion was fulfilled by the lungs), anabolism from the lactic acid may also have taken place leading to long-lasting radioactive remnants, by incorporation of 14C into endogenous compounds.

Animals↗
PubMed2003

Process water treatment at the Ranger uranium mine, Northern Australia.

The conceptual development and piloting of an innovative water treatment system for process water produced by a uranium mine mill is described. The process incorporates lime/CO2 softening (Stage 1), reverse osmosis (Stage 2) and biopolishing (Stage 3) to produce water of quality suitable for release to the receiving environment. Comprehensive performance data are presented for each stage. The unique features of the proposed process are: recycling of the lime/CO2 softening sludge to the uranium mill as a neutralant, the use of power station off-gas for carbonation, the use of residual ammonia as the pH buffer in carbonation; and the recovery and recycling of ammonia from the RO reject stream.

Australia↗