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PubMed2005

Mechanism of uranium removal from the aqueous solution by elemental iron.

The effectiveness of elemental iron (Fe(0)) to remove uranium (U) from the aqueous phase has been demonstrated. While the mitigation effect is sure, discrepancies in the removal mechanism have been reported. The objective of this study was to investigate the mechanism of U(VI) removal from aqueous phases by Fe(0). For this purpose, a systematic sequence of bulk experiments was conducted to characterize the effects of the availability and the abundance of corrosion products on U(VI) removal. Results indicated that U(VI) removal reactions did not primary occur at the surface of the metallic iron. It is determined that U(VI) co-precipitation with aging corrosion products is a plausible explanation for the irreversible fixation under experimental conditions. Results of XRD analyses did no show any U phases, whereas SEM-EDX analyses showed that U tended to associate with rusted areas on the surface of Fe(0). Recovering U with different leaching solutions varied upon the dissolution capacity of the individual solutions for corrosion products, showing that the irreversibility of the removal depends on the stability of the corrosion products. U(VI) co-precipitation as removal mechanism enables a better discussion of reported discrepancies.

Adsorption↗
PubMed1979

Studies on the mechanism of lanosterol 14 alpha-demethylation. A requirement for two distinct types of mixed-function-oxidase systems.

Carbon monoxide inhibited the removal of C-32 of dihydrolanosterol (I), but not of its metabolites 5 alpha-lanost-8-ene-3 beta,32-diol (II) and 3 beta-hydroxy-5 alpha-lanost-8-en-32-al (III). It appears therefore that cytochrome P-450 is a component of the enzyme system required to initiate oxidation of the 14 alpha-methyl group, but not of that responsible for the subsequent oxidation steps required for elimination of C-32 as formic acid. Non-radioactive compounds (II) and (III), when added to cell-free systems actively converting dihydrolanosterol into cholesterol, inhibited 14 alpha-demethylation measured by the rate of formation of labelled cholesterol from dihydro[1,7,15,22,26,30-14C]lanosterol or of labelled formic acid from dihydro[32-14C]lanosterol. However, neither compound (II) nor compound (III) accumulated radioactive label under these conditions. These observations could be attributed partly to inhibition of the initial oxidation of the 14 alpha-methyl group by compounds (II) and (III).

Animals↗
PubMedDate not supplied

[Study of volatile substances produced during the melanoidin synthesis in the model system: glyceraldehyde + glycine].

Volatile compounds produced during the synthesis of melanoidins in the model system: glyceraldehyde + glycine were studied. The reactions that resulted in the formation of melanoidins yielded carbon dioxide and trace amounts of ammonia and carbonyl compounds. With a rise in the incubation temperature the browning rate and quantities of gaseous substances increased, although there was no correlation between the two latter parameters. The experiments with 1-14C- and 2-14C-glycine showed that at 80 degrees about 6% and at 37 degrees less than 1% of the amino acid degraded to form CO2. The only source of CO2 was the carboxyl group. No radioactivity occurred in volatile carbonyl compounds. It is suggested that decarboxylation and deamination of the amino acid during its interaction with glyceraldehyde do not play an important part in the mechanism of melanoidin synthesis.

Amino Sugars↗
PubMed1979

Metabolism of tritium- and carbon-14-labeled tiamulin in dogs, rats, and pigs.

The metabolism of tiamulin hydrogen fumarate, labeled with 3H, 14C, or both, was studied in dogs, rats, and weanling pigs. After a dose of radiolabeled tiamulin, all three species excreted more radioactivity in feces (via bile) than in urine. Dogs absorbed 86% of a single oral dose of tiamulin-3H, and the disposition of the compound was similar after a single or multiple dosage regimen. The ratio of antimicrobial activity to total radioactivity in dog plasma was only about 0.25, and was still less in dog urine. After dosing with tiamulin-14C, rats and pigs excreted at least 1% of the dose as 14CO2 in expired air. In dual-labeled studies, pigs excreted less total 14C than 3H and had greater residues of 14C than 3H in edible tissues, blood, and plasma. After the administration of tiamulin-14C to pigs, radioactivity was incorporated into liver glycogen, indicating metabolic cleavage of the side chain of tiamulin. Tiamulin-3H is the isotopically-labeled compound of choice for studying metabolism and tissue residues in animals.

Administration, Oral↗
PubMedDate not supplied

Use of urease-bromothymol blue-agar method for large-scale testing of urine on grain and seeds.

The current AOAC method (963.28) for large-scale (50 g) testing of urine on grain is based on the reaction of sodium in urine with magnesium uranyl acetate. Detection of sodium suggests that urine is present and that a test for urea is appropriate. Urea is detected with urease-bromothymol blue-paper and is confirmed through its reaction with xanthydrol to form dixanthylurea crystals, which are detected microscopically. The initial nonspecific test for sodium can be influenced by the presence of salt or other sodium compounds. Furthermore, the magnesium uranyl acetate spray used in Method 963.28 potentially exposes the analyst to the aerosol of a volatile, toxic uranium compound. Excess reagents and analyzed test portions must be disposed of as radioactive waste. In addition, Method 963.28 requires several steps to determine the presence of urea. The alternative AOAC method (972.41) tests for the presence of urea from urine on individual seeds. Urea is enzymatically decomposed to ammonia and carbon dioxide by urease. Liberated ammonia shifts the pH, changing the color of the indicator in the agar from yellow to blue. This study adapts Method 972.41 to larger test samples. Up to 25 g grains and seeds are sprayed with urease test agar instead of being individually immersed in the urease test agar. The modified method was used to analyze urea on seeds and grains of 24 plants from 4 families. The method has a limit of detection of one seed contaminated with 1 microgram urea.

Aerosols↗
PubMedDate not supplied

[Carbon assimilation pathways in the methylotrophy of Pseudomonas gazotropha].

The dynamics of label distribution was studied in the products of 14CH3OH assimilation by the cells of Pseudomonas gazotropha Z-1156. Substances to be first detected were glycolate, glycine and those of the chromatogram "start" spot. Later, the radioactivity was detected in phosphorylated compounds and glycerate. Cell extracts of Ps. gazotropha Z-1156 contained ribosephosphate isomerase, phosphoribulokinase and glyceraldehyde dehydrogenase but not ribulosediphosphate carboxylase. Distribution of the label in the products of 14CH3OH assimilation and the presence of active hydroxypyruvate reductase in the extract suggest that the serine cycle is involved in methylotrophy of Ps. gazotropha Z-1156. This suggestion is confirmed by the presence of active formate dehydrogenase, phosphoenolpyruvate carboxylase, (NADP+, Mn2+)-specific isocitrate dehydrogenase, (NAD, Mg2+)-specific malate dehydrogenase, malate lyase, and isocitrate lyase. The citric acid cycle is open at the alpha-ketoglutarate dehydrogenase system. The dry biomass of Ps. gazotropha Z-1156 contains over 70% of protein.

Carbon↗
PubMed1977

Bunolol metabolism by dogs: identification of basic metabolites and their conjugates.

Female beagles dosed once with encapsulated 14C-bunolol (10 mg/kg) excreted 61% of the isotope in urine in 24 hr. The pooled urine contained a minimum of 18 labeled compounds. Two previously unknown metabolites were purified and were identified by UV and mass spectral data; they were hydroxybunolol (10.1% of urinary radioactivity) and hydroxydihydrobunolol (9.8%). The urine also contained bunolol (0.7% of urinary carbon-14), dihydrobunolol (0.5%), conjugated dihydrobunolol (2.8%), beta-(5-oxytetralonyl)lactic acid (16.3%), and (5-oxytetralonyl) acetic acid (7.1%).

Animals↗
PubMed1989

Uptake and metabolism of iproplatin in murine L1210 cells.

Iproplatin is structurally unique among the platinum (Pt) agents in the clinic because it is a quadrivalent complex. On the basis of the redox parameters for the Pt(IV) and Pt(II) oxidation states in a chloride system, it has been suggested that Pt(IV) complexes will be reduced to Pt(II) complexes in a biological environment. To test this hypothesis, uptake and metabolism studies of [14C]-iproplatin were carried out in L1210 cells. The L1210 cells raised in DBA2/J mice were incubated in vitro with 50 and 100 microM [14C]-iproplatin at 37 degrees C in Hanks' balanced salt solution, and total uptake and radioactivity associated with acid-insoluble fractions were measured for up to 3 h. Under these conditions, the uptake of iproplatin was linear with time and increased with increasing concentrations of iproplatin in the medium. At all times measured, greater than 35% of radioactivity was associated with the acid-insoluble fraction, suggesting binding to macromolecules. The [14C]-labelled compounds in neutralized acid extracts of cells were separated by reverse-phase high-performance liquid chromatography (HPLC). Three labelled compounds were detected; based on chromatographic elution times, they appeared to be iproplatin, cis-dichloro-bis-isopropylamine platinum(II) (CIP), the reduction product of iproplatin, and a third compound more polar than iproplatin and CIP. The finding of free CIP and the macromolecular binding of radioactivity in the cells suggests that iproplatin is reduced intracellularly.

Animals↗
PubMed1982

Pyruvate carboxylation as an anaplerotic mechanism in the isolated perfused rat heart.

1. The role of pyruvate carboxylation in the net synthesis of tricarboxylic acid-cycle intermediates during acetate metabolism was studied in isolated rat hearts perfused with [1-14C]pyruvate. 2. The incorporation of the 14C label from [1-14C]pyruvate into the tricarboxylic acid-cycle intermediates points to a carbon input from pyruvate via enzymes in addition to pyruvate dehydrogenase and citrate synthase. 3. On addition of acetate, the specific radioactivity of citrate showed an initial maximum at 2 min, with a subsequent decline in labelling. The C-6 of citrate (which is removed in the isocitrate dehydrogenase reaction) and the remainder of the molecule showed differential labelling kinetics, the specific radioactivity of C-6 declining more rapidly. Since this carbon is lost in the isocitrate dehydrogenase reaction, the results are consistent with a rapid inactivation of pyruvate dehydrogenase after the addition of acetate, which was confirmed by measuring the 14CO2 production from [1-14C]pyruvate. 4. The results can be interpreted to show that carboxylation of pyruvate to the C4 compounds of the tricarboxylic acid cycle occurs under conditions necessitating anaplerosis in rat myocardium, although the results do not identify the enzyme involved. 5. The specific radioactivity of tissue lactate was too low to allow it to be used as an indicator of the specific radioactivity of the intracellular pyruvate pool. The specific radioactivity of alanine was three times that of lactate. When the hearts were perfused with [1-14C]lactate, the specific radioactivity of alanine was 70% of that of pyruvate. The results suggest that a subcompartmentation of lactate and pyruvate occurs in the cytosol.

Acetates↗
PubMed1971

Sterol and triterpene synthesis in the developing and germinating pea seed.

Developing and germinating pea seeds were compared with respect to their capacity to incorporate mevalonate into sterols and triterpenes. The capacity for sterol synthesis is greatest in the least mature fruits and decreases during their development. Label is shown, by gas-liquid chromatography and counting the radioactivity of trapped fractions, to be associated with campesterol, beta-sitosterol and isofucosterol. During early stages of germination sterol synthesis is insignificant. The triterpene fraction becomes heavily labelled during both development and germination. The label is associated almost exclusively with beta-amyrin during germination but with cycloartenol and 24-methylenecycloartanol during development. It is only in the terminal stages of maturation that beta-amyrin becomes significantly labelled. At the same time an unidentified radioactive polar compound appears. The possible significance of the appearance of this polar compound and the regulation of the synthesis of these higher terpenoids is discussed.

Carbon Isotopes↗
PubMed1985

Preparation of CH3 203HgCl of high specific activity.

In order to have a methylmercury compound of much higher specific activity than was obtainable from commercial suppliers of the compound, a procedure for the methylation of radioactive mercuric chloride with no addition of non-radioactive mercury has been developed. Methylation is accomplished by reacting the mercuric chloride with tetramethyl tin. Extractions into and out of benzene twice produces a methylmercury compound which is finally dissolved in a dilute sodium carbonate solution suitable for biological experiments. The entire procedure to produce a batch of the compound may be accomplished within a single day.

Indicators and Reagents↗
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↗