Influence of mixed-ligand complexes on retention and distribution of radioniobium in mice

The individual effects of desferrioxamine B (DFOA), Na3Ca diethylenetriaminepentaacetic acid (DTPA), Na-salicylate, DL-penicillamine, and 2-aminoethylisothiouronium bromide hydrobromide, as well as the effect of mixed-ligand treatment on the retention and elimination of 95Nb in mice have been examined. It was found that 95Nb could easily be mobilized by a single dose of DFOA, but the best result was obtained with the DFOA and DTPA combination. Mixed-ligand treatment did not change the deposition characteristics and translocation kinetics of 95Nb.     

Modification of 144Ce tissue deposition by mixed ligand complex treatment in mice

The individual effect of desferrioxamine-B (DFOA), Na3Ca-diethylene-triaminepentaacetic acid (DTPA), DL-penicillamine (PA) and Na-salicylate (SA) has been examined as well as the effect of mixed-ligand treatment on the retention and elimination of 144Ce in mice. It was found that 144Ce could easily be mobilized by a single dose of DTPA. Mixed-ligand (MLCs) treatment did not change the deposition characteristics and translocation kinetics of 144Ce.     

Natural and man–made radionuclide concentrations in lichens at several locations in Austria

Regions of elevated natural radioactivity (Gastein–valley, Waldviertel) were compared to regions of low natural radioactivity (surroundings of Salzburg City). The natural radionuclides 238U, 40K and 7Be and the man–made nuclides 137Cs, 144Ce, 95Ze95Nb were measured by gamma ray spectrometry. No statistically significant difference was found between samples of the Gastein–valley, Waldviertel, Salzburg, Grossarl and Dachstein concerning the content of natural radionuclides. The amount of the short–lived fission products 144Ce, 95Zr–95Nb as well as of the natural 7Be increased with altitude. The specific nuclide concentration varies with species but was almost independent of growth form and substrate.     

Behavior of neutron-activated uranium dioxide dust particles in the gastrointestinal tract of the rat

The behavior of neutron-irradiated, simulated Chernobyl UO2 particles containing 141Ce, 144Ce, 95Zr, 95Nb, and 103Ru in the gastrointestinal tract was investigated to obtain basic information for dosimetric and risk analyses of nuclear accidents. After the UO2 particles were administered to rats intragastrically, the distribution and retention of specific radionuclides were studied by using whole-body autoradiography and gamma-spectrometric analysis of tissues. None of the radionuclides were detected in liver, kidney, muscle, bone, brain, blood, and urine. Approximately 98% of the total administered radioactivity was excreted in feces within 3 days. A two times greater intestinal retention (about 6%) of 95Nb than for the other radionuclides was observed 1 day after administration. The results indicate that this kind of relatively insoluble particulate material is not absorbed or retained significantly in the epithelial cells of the intestinal wall. Fallout particles containing high-energy beta sources, 106Ru and 144Ce, result in a very high radiation dose (up to several Gy/day) in the vicinity of a hot particle. Niobium-95 with low average beta energy (0.043 MeV (100%)) does not increase the total dose to the GI tract significantly despite its longer retention in the intestine. Evaluation of the biological effects of these particles in the GI tract by using a dosimetric model based on uniform distribution of activity may be misleading.     

Chelation therapy of incorporated plutonium-238 and americium-241: comparison of LICAM(C), DTPA and DFOA in rats, hamsters and mice

The carboxylated catechoylamide 3,4,3-LICAM(C) was tested for removal of 238Pu and 241Am from small laboratory rodents. The effectiveness of treatment was compared with that of two ligand preparations approved for clinical use: calcium-trisodium diethylenetriaminepentaacetate (DTPA) and desferrioxamine (DFOA). With early treatment and at the dosage used clinically for the decorporation of actinides with DTPA (30 mumol/kg body weight) LICAM(C) was superior to DFOA but when compared with DTPA, the effect of LICAM(C) on 238Pu was greater only in bone; as little as 1 mumol LICAM(C)/kg was as effective as 30 mumol DTPA/kg. However, in all animals treated with LICAM(C) there was a large increase in the 238Pu content of the kidney. With 241Am the effect of DTPA was always superior to that of LICAM(C). The best overall results early (1 day) after injection of 238Pu and 241Am were achieved by a combination of a single injection of LICAM(C) and DTPA with subsequent continuous administration of DTPA in drinking water. LICAM(C) affected the retention of 238Pu even if given orally; the data suggested that about 3 per cent of ingested LICAM(C) was absorbed. When the beginning of treatment was delayed, LICAM(C) became equally effective or less effective than DTPA even as far as 238Pu retention in bone was concerned, but it still increased the accumulation of 238Pu in the kidneys.     

Effective chelation therapy after incorporation of neptunium-239 in rats

It was demonstrated in rats that it is possible to reduce the retention of 239Np in all body tissues by an early combined treatment with small doses of DTPA and DFOA. The content of 239Np can be decreased in soft tissues even if treatment is delayed. Promptly administered LICAM(C) proved more effective than the above chelate combination in reducing 239Np retention in the bones but increased that in the muscles and especially in the kidneys. This side effect of LICAM(C) could be partly prevented by simultaneous treatment with DTPA.     

Fission-product radionuclides in sediments from the north-east irish sea

Summary 1. Gamma radiation dose-rates over mud-flat areas are shown to be at least ten times those measured over sandy beaches.2. Analysis of the surface sediment layer in an estuarine area 6 miles from the Windscale effluent pipeline shows the major gamma-emitting radionuclides to be⁹⁵Zr,⁹⁵Nb and¹⁰⁶Rh.3. Core sampling has indicated that the radioactivity concentration in silt decreases exponentially with depth from the surface layer.4. It is shown that the gamma dose-rate above silt banks is largely accounted for by the concentration of⁹⁵Zr/⁹⁵Nb in the surface silt layer. The residual gamma dose is probably accounted for by¹⁰⁶Ru/¹⁰⁶Rh distributed beneath the surface layer.5. The accumulation factors of⁹⁵Zr +⁹⁵Nb and¹⁰⁶Ru in the surface silt layer are approximately 1.5×10⁴.6. The relationship of radioactivity concentration in surface silt to distance from the effluent pipeline can be described by a simple power function of distance.

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Spaltprodukt-Radionuklide in Sedimenten der nordöstlichen Irischen See

Kurzfassung Als Teil einer Untersuchung über die Verbreitung von radioaktivem Abwasser, das von der radiochemischen Aufarbeitungsanlage in Windscale stammt, wurden Messungen der Gamma-Dosisleistung auf Schlickböden in Ästuaren vorgenommen. Es zeigte sich, daß die Dosisleistungen hier mindestens um eine Größenordnung höher sind als die, welche auf reinem Sandboden gemessen wurden. Oberflächensedimente, die hinsichtlich ihrer Radioaktivität untersucht wurden, enthalten als wichtigste Radionuklide die Spaltprodukte⁹⁵Zr +⁹⁵Nb,¹⁰⁶Ru,¹⁴⁴Ce und¹³⁷Cs. Die Konzentrationen der einzelnen Radionuklide stehen in Beziehung zur Abwassermenge. Probebohrungen in Sedimenten zeigten, daß sich die Konzentration der Radioaktivität exponentiell mit der Tiefe ändert. Der Anreicherungsfaktor von⁹⁵Zr +⁹⁵Nb,¹⁰⁶Ru in Oberflächensedimenten von Ästuaren beträgt ungefähr 1,5 × 10⁴, für¹³⁷Cs dagegen 1,0 × 10³. Die Konzentrationen von⁹⁵Zr +⁹⁵Nb,¹⁰⁶Ru und¹⁴⁴Ce in Oberflächensedimenten sind abhängig vom Abstand der Abwassereinleitung bei Windscale.

     

The distribution in mice of intravenously administered labelled Candida albicans.

The time dependence of the distribution of intravenously injected radiolabelled Candida albicans in the body of mice was studied. The Candida cells were labelled by cultivating them 7 days at 28 degrees C in a medium containing one of the following radionuclides: 46Sc, 95Nb, 59Fe, 144ce, 89Sr, 60Co, 65Zn, 54Mn, 45Ca, 51Cr and 91Y, which are listed in decreasing order in respect to amount bound. The labelled cells were killed by heating them 120 min at 60 degrees C, without loss of immunologic properties. Owing to the amount and strength of binding, 144Ce labelled Candida, together with 14C labelled cells was used in animal kinetic study. A rapid disappearance of the labelled cells from blood, interrupted by a small peak, was paralleled by a transient uptake in lungs and followed by a long lasting accumulation in the liver. The kidneys and spleen revealed only small uptakes of the labelled material.     

A Discrete Fruit Fly Optimization Algorithm for the Traveling Salesman Problem

The fruit fly optimization algorithm (FOA) is a newly developed bio-inspired algorithm. The continuous variant version of FOA has been proven to be a powerful evolutionary approach to determining the optima of a numerical function on a continuous definition domain. In this study, a discrete FOA (DFOA) is developed and applied to the traveling salesman problem (TSP), a common combinatorial problem. In the DFOA, the TSP tour is represented by an ordering of city indices, and the bio-inspired meta-heuristic search processes are executed with two elaborately designed main procedures: the smelling and tasting processes. In the smelling process, an effective crossover operator is used by the fruit fly group to search for the neighbors of the best-known swarm location. During the tasting process, an edge intersection elimination (EXE) operator is designed to improve the neighbors of the non-optimum food location in order to enhance the exploration performance of the DFOA. In addition, benchmark instances from the TSPLIB are classified in order to test the searching ability of the proposed algorithm. Furthermore, the effectiveness of the proposed DFOA is compared to that of other meta-heuristic algorithms. The results indicate that the proposed DFOA can be effectively used to solve TSPs, especially large-scale problems.     

Biosorption of radionuclides by Rhizopus arrhizus

The sorption of various radionuclides viz. 233U, 239Pu, 241Am, 144Ce, 147Pm, 152+154Eu and 95Zr from aqueous nitrate medium has been studied using biomass Rhizopus arrhizus. The biosorption of 233U and 239Pu was found to be maximum at pH 6-7 whereas for other trivalent actinides and fission products viz. 241Am, 144Ce, 147Pm, 152+154Eu and tetravalent 95Zr, it was more effective at pH 2. This biomass is a promising sorbant for the treatment of radioactive effluents from nuclear industry. © Rapid Science Ltd. 1998     

Radionuclide transfer to marine biota species: review of Russian language studies

An extensive programme of experiments on transfer of radionuclides to aquatic species was conducted in the former USSR starting from the early 1950s. Only a few of these studies were made available in the English language literature or taken into account in international reviews of radionuclide behaviour in marine ecosystems. Therefore, an overview of original information on radionuclide transfer to marine biota species available from Russian language literature sources is presented here. The concentration ratio (CR) values for many radionuclides and for marine species such as: ²³⁹Pu, ¹⁰⁶Ru and ⁹⁵Zr (crustacean), ⁵⁴Mn, ⁹⁰Sr, ⁹⁵Nb, ¹⁰⁶Ru, ¹³⁷Cs ²³⁹Pu, ²⁴¹Am and natural U (molluscs), and ⁵⁴Mn, ⁹⁰Sr, ¹³⁷Cs and ¹⁴⁴Ce (fish) are in good agreement with those previously published, whilst for some of them, in particular, for ³²P and ¹¹⁰Ag (crustaceans), ³⁵S (molluscs), ³²P, ³⁵S, ⁹⁵Nb, and ¹⁰⁶Ru (macroalgae) and ⁶⁰Co and ^239,240Pu (fish) the data presented here suggest that changes in the default CR reference values presented in recent marine reviews may be required. The data presented here are intended to supplement substantially the CR values being collated within the handbook on Wildlife Transfer Coefficients, coordinated under the IAEA EMRAS II programme.     

Sorption of plutonium, americium and fission products from reprocessing effluents using Rhizopus arrhizus

Rhizopus arrhizus biomass removed more than 95% of 239Pu, 241Am, 95Zr, 144Ce and 152+154Eu from different waste streams generated in Purex as well as Truex processes after suitable adjustment of pH. © Rapid Science Ltd. 1998     

Effect of 60Co-Gamma whole body irradiation and treatment with radioprotector on the retention of 144Ce, in mice

In animal experiments the effects of 7.5 Gy whole-body irradiation (LD50/30) and/or of radioprotecting compound (WR-2721) on the retention and elimination of 144Ce were investigated. It was stated that in the first three days there was an increase in the deposition of 144Ce after whole-body irradiation and upon treatment with radioprotective compound WR-2721.     

Repeated inhalation exposure of rats to aerosols of 144CeO2. II. Effects on survival and lung, liver, and skeletal neoplasms.

Groups of 94-day-old F344/Crl rats were exposed repeatedly to aerosols of 144CeO2 to reestablish desired lung burdens of 1.9, 9.2, 46, or 230 kBq of 144Ce every 60 days for 1 year (seven exposures). Other 94-day-old rats were exposed once to achieve similar desired initial lung burdens of 144Ce. Older rats were exposed once to achieve desired initial lung burdens of 46 or 230 kBq when 500 days of age, the same age at which rats had the last of the repeated exposures. Control rats were either unexposed, sham-exposed once or repeatedly, or exposed once or repeatedly to stable CeO2. Approximately equal numbers of male and female rats were used. The median survival time and cumulative percentage survival curves were significantly decreased only in male and female rats exposed repeatedly to reestablish a 230-kBq lung burden and among the 94-day-old male rats exposed once to achieve a 230-kBq lung burden of 144Ce. The crude incidences of primary lung cancers (well described by a single Weibull distribution function), time to death with lung tumors, and risk of lung cancer per unit of beta-radiation dose to the lungs were correlated with the cumulative beta-radiation dose rather than the rate at which the dose was accumulated. A linear function, 70 (+/- 7.3) + -0.15 (+/- 0.056) x dose (+/- SD), adequately described the excess numbers of rats with lung cancers over a beta-radiation dose range to the lungs of 6.8 to 250 Gy for two groups of rats with the highest doses to the lungs after a single exposure and for two groups with the highest doses after repeated exposure.     

Uptake of natural and man-made radionuclides by lichens and mushrooms

Summary Due to the large absorbing surface of the mycelium that grows in the upper parts of the soil mushrooms take up higher amounts of¹³⁷Cs and⁴⁰K than lichens. Besides these nuclides only the long-lived radionuclides¹²⁵Sb and⁶⁰Co could be measured; but not the short-lived fission-products¹⁴⁴Ce,⁹⁵Zr and⁹⁵Nb which probably decayed before absorption into the mycelium. These nuclides, however, are present in lichens because of their surface structures which enable high foliar deposition.The¹³⁷Cs-content of lichens is probably due to absorption by the mycobiont and seems to be used to satisfy their potassium-requirements. Mushrooms on the other hand are characterized by a relatively stable potassium-content and a wide ranging¹³⁷Cs-content which depends on the availability in different substrates. Occasionally the natural radionuclides²³⁸U and²²⁶Ra could be detected in mushroom and lichen samples, showing no correlation with the natural radionuclide content of the soil.     

Lung lavage therapy to lessen the biological effects of inhaled 144Ce in dogs

To evaluate the therapeutic effects of removal of an internally deposited radionuclide on long-term biological effects, lung lavage was used to treat dogs that had inhaled 144Ce in a relatively insoluble form, in fused aluminosilicate particles. Either 10 lung lavages were performed between Days 2 and 56 after exposure or 20 lung lavages were performed between Days 2 and 84 after exposure. Approximately one-half of the 144Ce was removed by the lavages, resulting in a corresponding reduction in the total absorbed beta dose to lung. The mean survival time of the treated dogs was 1270 days compared to 370 days for untreated dogs whose initial pulmonary burdens of 144Ce were similar. Treated dogs died late from cancers of the lung or liver, whereas the untreated dogs died at much earlier times from radiation pneumonitis. Dogs treated with lung lavage but not exposed to 144Ce had a mean survival of 4770 days. We concluded that removal of 144Ce from the lung by lavage resulted in increased survival time and in a change in the biological effects from inhaled 144Ce from early-occurring inflammatory disease to late-occurring effects, principally cancer. In addition, the biological effects occurring in the treated dogs could be better predicted from the total absorbed beta dose in the lung and the dose rate after treatment rather than from the original dose rate to the lung. Therefore, we concluded that prompt treatment to remove radioactive materials could be of significant benefit to persons accidentally exposed to high levels of airborne, relatively insoluble, radioactive particles.     

Repeated inhalation exposure of rats to aerosols of 144CeO2. I. Lung, liver, and skeletal dosimetry.

To develop a better understanding of the influence of cumulative radiation dose and dose rate to the lungs on the biological responses to inhaled radionuclides, several studies are in progress at this institute in which laboratory animals have been exposed once or repeatedly to aerosols of insoluble particles containing 144Ce or 239Pu. In the study reported here, F344 rats were exposed repeatedly to aerosols of 144CeO2 beginning at 94 days of age to reestablish desired lung burdens of 1.9, 9.2, 46, or 230 kBq of 144Ce every 60 days for 1 year (seven exposures). Other 94-day-old rats were exposed once to achieve similar desired initial lung burdens of 144Ce. Older rats were exposed once to achieve desired initial lung burdens of 46 or 230 kBq when 500 days of age, the age of the repeatedly exposed rats when exposed for the last time. Control rats were either unexposed, sham-exposed once or repeatedly, or exposed once or repeatedly to stable CeO2. Approximately equal numbers of male and female rats were used. The cumulative beta-radiation doses to the lungs, liver, and skeleton of rats exposed repeatedly were similar to those of rats with similar total lung burdens of 144Ce from a single inhalation exposure. The average beta-radiation dose rate to the lungs of the rats exposed repeatedly was about one-fifth of that in rats with similar total lung burdens after a single exposure.     

Radioactive contamination of bottom sediments in the upper reaches of the Techa river: analysis of the data obtained in 1950 and 1951

A stationary sorption model has been developed for re-evaluating and analysing archive data from 1950-1951 on the radioactive contamination of Techa river bottom sediments close to the site of liquid radioactive waste discharge. In general, good agreement was obtained between calculations and measurements, which substantiates further the assumptions and conclusions in two preceding articles, on the radionuclide composition of discharged liquid radioactive waste. Estimates on the effective liquid radioactive waste discharges given here are significantly different from those deduced in the 1950s, i.e. in summer 1950 and October 1951. The results are discussed in relation to the Techa River Dosimetry System 2000 (TRDS-2000) that has recently been presented to serve as a means for estimating doses to the Techa river residents. Parameter values describing the exponential decrease of bottom sediment contamination along the river due to short-lived radionuclides, such as (106)Ru, and (144)Ce, agree reasonably with those used in TRDS-2000. However, for other radionuclides, such as (95)Zr, (95)Nb, (91)Y, (90)Sr and (137)Cs, substantial differences are found. It is demonstrated that water flow rate, width of the river, and surface area of bottom sediments are important parameters which were not adequately taken into account in TRDS-2000. Also, the stirring-up of contaminated bottom sediments and their subsequent transport by the water flow are seen to be an important mechanism that governs the radionuclide transport downstream. This mechanism was not included in the TRDS-2000 model. It is concluded that the sorption model used in TRDS-2000 for the reconstruction of radioactive contamination of water and bottom sediments of the Techa river in 1949-1951, is subject to considerable errors. While the present paper is focussed on details of the dosimetric modelling, the implications for the Techa river dosimetry are major. They will be further elucidated in a forthcoming paper.     

Modulation of transferrin receptor expression by inhibitors of nucleic acid synthesis

We investigated the effects of the iron chelator desferrioxamine on the expression of transferrin receptors (TfR) by CCRF-CEM human T-cell leukaemia and B16 mouse melanoma cells growing in tissue culture. Desferrioxamine (DFOA) enhanced TfR expression when added in the dose range of 10(-5)-10(-4) to CCRF-CEM cells, but was toxic to these cells, the lower concentrations producing a slowing of cell growth with a build up in S-phase, while higher concentrations caused cell death with a block at the G1/S-phase interface. These toxic effects are compatible with its previously reported inhibition of the non-haem iron containing (M2) subunit of ribonucleotide reductase. In marked contrast, DFOA caused the growth of B16 melanoma cells to arrest in G1, without loss of cloning efficiency, and resulted in a fall in TfR expression to approximately 50% of control values. These results suggested that the effects of DFOA on TfR expression were linked to DNA synthesis rather than to a more generalised inhibition of iron-dependent cellular processes. It was subsequently found that inhibition of the M2 subunit of ribonucleotide reductase in CCRF-CEM cells with 5 X 10(-5) M hydroxyurea, which is not an iron chelator, also enhanced TfR expression, as did thymidine and cytosine arabinoside, which have different enzyme targets. By measuring cellular DNA and RNA content simultaneously it was shown that all of these agents caused unbalanced growth, i.e., inhibited DNA synthesis more than RNA synthesis. In contrast, 6-thioguanine was more inhibitory to RNA synthesis, and treatment with this drug caused a fall in TfR expression. Thus, although CCRF-CEM cells treated with DFOA show enhanced TfR expression, similar effects are also seen with other inhibitors of DNA synthesis, provided that RNA synthesis is allowed to continue. These results provide further evidence that the regulation of TfR expression by proliferating cells is specifically linked to DNA synthesis rather than to the iron requirements of other cellular processes.     

Structure of Oxalacetate Acetylhydrolase,a Virulence Factor of the Chestnut Blight Fungus

Oxalacetate acetylhydrolase (OAH), a member of the phosphoenolpyruvate mutase/isocitrate lyase superfamily, catalyzes the hydrolysis of oxalacetate to oxalic acid and acetate. This study shows that knock-out of the oah gene in Cryphonectria parasitica, the chestnut blight fungus, reduces the ability of the fungus to form cankers on chestnut trees, suggesting that OAH plays a key role in virulence. OAH was produced in Escherichia coli and purified, and its catalytic rates were determined. Oxalacetate is the main OAH substrate, but the enzyme also acts as a lyase of (2R,3S)-dimethyl malate with ∼1000-fold lower efficacy. The crystal structure of OAH was determined alone, in complex with a mechanism-based inhibitor, 3,3-difluorooxalacetate (DFOA), and in complex with the reaction product, oxalate, to a resolution limit of 1.30, 1.55, and 1.65 Å, respectively. OAH assembles into a dimer of dimers with each subunit exhibiting an (α/β)₈ barrel fold and each pair swapping the 8th α-helix. An active site “gating loop” exhibits conformational disorder in the ligand-free structure. To obtain the structures of the OAH·ligand complexes, the ligand-free OAH crystals were soaked briefly with DFOA or oxalacetate. DFOA binding leads to ordering of the gating loop in a conformation that sequesters the ligand from the solvent. DFOA binds in a gem-diol form analogous to the oxalacetate intermediate/transition state. Oxalate binds in a planar conformation, but the gating loop is largely disordered. Comparison between the OAH structure and that of the closely related enzyme, 2,3-dimethylmalate lyase, suggests potential determinants of substrate preference.