In Vitro and In Vivo Evaluation of DTPA-HPMA Copolymers as Potential Decorporating Agents for Prophylactic Therapy of Actinide Contamination.

The release of actinides into the environment represents a significant potential public health concern. Chelation therapy utilizing diethylenetriamine pentaacetate (DTPA) is a U.S. Food and Drug Administration (FDA)-approved therapy capable of mitigating the deposition of some absorbed actinides in the body. However, the pharmacokinetic profile of DTPA is not ideal for prophylactic applications. In this study, we examine the incorporation of DTPA into a HPMA copolymer (P-DTPA) to investigate if the enhanced blood circulation time can offer superior prophylactic protection and of improving in vivo radiometal decorporation. Utilizing lutetium-177 (177Lu) as an actinide model, the performance of P-DTPA and DTPA (control) were evaluated using selectivity studies in the presence of competing biological metals, chelation and stability assays in human serum and cytotoxicity studies using human umbilical vein endothelial cells (HUVEC). The in vivo decorporation efficiency of P-DTPA relative to DTPA and untreated controls was also evaluated over two weeks in CF-1 mice. In the experimental groups, the mice were prophylactically treated with P-DTPA or DTPA (30 µmol/kg) 6 or 24 h prior to 177LuCl3 administration. The in vitro results reveal that P-DTPA gives efficient complexation yields relative to DTPA with a tolerable cytotoxicity profile and good serum stability. The in vivo decorporation studies demonstrated enhanced total excretion of the 177Lu using P-DTPA compared to DTPA in both the 6 and 24 h prophylactic treatment study arms. This enhanced decorporation effect is certainly attributable to the expected prolonged biological half-life of DTPA when grafted to the HPMA polymer.

Ischemic Heart Disease Mortality and Occupational Radiation Exposure in a Nested Matched Case-Control Study of British Nuclear Fuel Cycle Workers: Investigation of Confounding by Lifestyle, Physiological Traits and Occupational Exposures.

Epidemiological studies have suggested a link between low-level radiation exposure and an increased risk of cardiovascular disease, but the possibility of bias or confounding must be considered. We analyzed data from a matched case-control study nested in a cohort of British male industrial (i.e., blue-collar) nuclear fuel cycle workers using paired conditional logistic regression. The cases were comprised of workers from two nuclear sites who had died from ischemic heart disease (IHD) and were matched to controls on nuclear site, date of birth and first year of employment (1,220 pairs). Radiation doses from external sources and to the liver from internally deposited plutonium and uranium were obtained. Models were adjusted for age at start of employment at either site, decade of start, age at exit from study (death or censoring), process/other worker and socio-economic status. Included potential confounding factors of interest were occupational noise, shift work, pre-employment blood pressure, body mass index and tobacco smoking. Cumulative external doses ranged from 0-1,656 mSv and cumulative internal doses for those monitored for radioactive intakes ranged from 0.004-5,732 mSv. In a categorical analysis, additionally adjusted for whether or not a worker was monitored for internal exposure, IHD mortality risk was associated with cumulative external unlagged dose with a 42% excess risk (95% CI: 4%, 95%) at >103 mSv (highest quartile relative to lowest quartile), and 35% (95% CI: -1%, 84%) at >109 mSv 15-year lagged dose. The log-linear increase in risk per 100 mSv was 2% (95% CI: -4%, 8%) for unlagged external dose and 5% (95% CI: -2%, 11%) for 15-year lagged dose. Associations with external dose for workers monitored only for exposure to external radiation reflected those previously reported for the cohort from which the cases and controls were drawn. There was little evidence of excess risk associated with cumulative doses from internal sources, which had not been assessed in the cohort study. The impact of the included potential confounding variables was minimal, with the possible exception of occupational noise exposure. Subgroup analyses indicated evidence of heterogeneity between sites, occupational groups and employment duration, and an important factor was whether workers were monitored for the potential presence of internal emitters, which was not explained by other factors included in the study. In summary, we found evidence for an increased IHD mortality risk associated with external radiation dose, but little evidence of an association with internal dose. External dose associations were minimally affected by important confounders. However, the considerable heterogeneity in the associations with external doses observed between subgroups of workers is difficult to explain and requires further work.

Investigation of low-level 242Pu contamination on nutrition disturbance and oxidative stress in Solanum tuberosum L.

Plutonium associated with higher molecular weight molecules is presumed to be poorly mobile and hardly plant available. In our present study, we investigate the uptake and effects of Pu treatments on Solanum tuberosum plants in amended Hoagland medium at concentrations of [242Pu] = 100 and 500 nm, respectively. We found a direct proof of oxidative stress in the plants caused by these rather low concentrations. For the confirmation of oxidative stress, we explored the production of nitric oxide (NO) and hydrogen peroxide (H2O2) by epifluorescence microscopy. Oxidative stress markers like lipid peroxidation and superoxide radicals (O2•-) are monitored through histochemical analysis. The biochemical parameters i.e. chlorophyll and carotenoids are measured as an indicator of cellular damage in the tested plants including the enzymatic parameters such as catalase and glutathione reductase. From our work, we conclude that Pu in low concentration has no significant effects on the uptake of many trace and macroelements. In contrast, the content of O2•- , malondialdehyde (MDA), and H2O2 increases with increasing Pu concentration in the solution, while the opposite effects was found for NO, catalase, and glutathione reductase. These findings prove that even low concentration of Pu regulates ROS production and generate oxidative stress in S. tuberosum L.

Decorporation of Pu/Am Actinides by Chelation Therapy: New Arguments in Favor of an Intracellular Component of DTPA Action.

Diethylenetriaminepentaacetic acid (DTPA) is currently still the only known chelating drug that can be used for decorporation of internalized plutonium (Pu) and americium (Am). It is generally assumed that chelation occurs only in biological fluids, thus preventing Pu/Am deposition in target tissues. We postulate that actinide chelation may also occur inside cells by a mechanism called "intracellular chelation". To test this hypothesis, rats were given DTPA either prior to (termed "prophylactic" treatment) or belatedly after (termed "delayed" treatment) Pu/Am injection. DTPA decorporation efficacy was systematically tested for both plutonium and americium. Both prophylactic and delayed DTPA elicited marked decreases in liver Pu/Am. These results can be explained by chelation within subcellular compartments where DTPA efficacy increased as a function of a favorable intracellular DTPA-to-actinide molar ratio. The efficacy of intracellular chelation of liver actinides decreased with the delay of treatment. This is probably explained by progressive actinide binding to the high-affinity ligand ferritin followed by migration to lysosomes. Intracellular chelation was reduced as the gap between prophylactic treatment and contamination increased. This may be explained by the reduction of the intracellular DTPA pool, which declined exponentially with time. Skeletal Pu/Am was also reduced by prophylactic and delayed DTPA treatments. This decorporation of bone actinides may mainly result from extracellular chelation on bone surfaces. This work provides converging evidence for the involvement of an intracellular component of DTPA action in the decorporation process. These results may help to improve the interpretation of biological data from DTPA-treated contamination cases and could be useful to model DTPA therapy regimens.

Combined drug and surgery treatment of plutonium-contaminated wounds: indications obtained using a rodent model.

There is an important requirement following accidental actinide contamination of wounds to limit the dissemination and retention of such alpha-emitting radionuclides. To reduce wound and systemic contamination, treatment approaches include chelation therapy with or without wound excision. However, it has been hypothesized that wound excision could lead to increased contaminant release and systemic organ retention. This study in the rat addresses this question. Anesthetized rats were contaminated with plutonium nitrate following wounding by deep incision of hind leg muscle. Excision of tissue at the contaminated site was performed 7 d later with or without Diethylene Triamine Pentaacetic Acid (DTPA) treatment (30 µmol kg⁻¹ i.v.). Pu urinary excretion was then measured for a further 3 d, and animals were euthanized at 14 d after contamination. Tissue samples were evaluated for Pu activity and histology. At 7 d after contamination, around 50% of the initial activity remained at the wound site. An average of 16% of this activity was then removed by surgery. Surgery alone resulted in increased urinary excretion, suggesting release from the wound site, but no subsequent increases in organ retention (bone, liver) were observed at 14 d. Indeed, organ Pu activity was slightly reduced. The combination of surgery and DTPA or DTPA treatment alone was much more effective than excision alone as shown by the markedly increased urinary Pu excretion and decreased tissue levels. This is the first report in an experimental rodent model of resection of Pu-contaminated wound. Urinary excretion data provide evidence for the release of activity as a result of surgery, but this does not appear to lead to further Pu organ retention. However, a combination of prior DTPA treatment with wound excision is particularly effective.

Comparison of cytotoxic and genotoxic effects of plutonium-239 alpha particles and mobile phone GSM 900 radiation in the Allium cepa test.

The goal of this study was to compare the cytotoxic and genotoxic effects of plutonium-239 alpha particles and GSM 900 modulated mobile phone (model Sony Ericsson K550i) radiation in the Allium cepa test. Three groups of bulbs were exposed to mobile phone radiation during 0 (sham), 3 and 9h. A positive control group was treated during 20min with plutonium-239 alpha-radiation. Mitotic abnormalities, chromosome aberrations, micronuclei and mitotic index were analyzed. Exposure to alpha-radiation from plutonium-239 and exposure to modulated radiation from mobile phone during 3 and 9h significantly increased the mitotic index. GSM 900 mobile phone radiation as well as alpha-radiation from plutonium-239 induced both clastogenic and aneugenic effects. However, the aneugenic activity of mobile phone radiation was more pronounced. After 9h of exposure to mobile phone radiation, polyploid cells, three-groups metaphases, amitoses and some unspecified abnormalities were detected, which were not registered in the other experimental groups. Importantly, GSM 900 mobile phone radiation increased the mitotic index, the frequency of mitotic and chromosome abnormalities, and the micronucleus frequency in a time-dependent manner. Due to its sensitivity, the A. cepa test can be recommended as a useful cytogenetic assay to assess cytotoxic and genotoxic effects of radiofrequency electromagnetic fields.

One perspective on stakeholder involvement at Hanford.

The Hanford nuclear site in Washington State had a major role in the production of nuclear weapons materials during the Manhattan Project in World War II and during the Cold War that followed. The production of weapons-grade radionuclides produced a large amount of radioactive byproducts that have been stored since the mid-1900s at the Hanford Site. These by-product radionuclides have leaked from containment facilities into the groundwater, contaminated buildings used for radionuclide processing, and also contaminated the nuclear reactors used to produce weapons-grade uranium and plutonium. This issue has been a major concern to Hanford stakeholders for several decades, and the U.S. Department of Energy, the U.S. Environmental Protection Agency, and the Washington State Department of Ecology established a Tri-Party Agreement in 1989, at which time Hanford ceased production of nuclear weapons materials and began a major effort to clean up and remediate the Hanford Site's contaminated groundwater, soil, and facilities. This paper describes the concerns of stakeholders in the production of nuclear weapons, the secrecy of Hanford operations, and the potential impacts to public health and the environment from the unintended releases of weapons-grade materials and by-products associated with their production at the Hanford Site. It also describes the involvement of public stakeholders in the development and oversight by the Hanford Advisory Board of the steps that have been taken in cleanup activities at the Hanford Site that began as a major effort about two decades ago. The importance of involvement of the general public and public interest organizations in developing and implementing the Hanford cleanup strategy are described in detail.

Practical action levels for chelation therapy in plutonium inhalation using nose swab.

The aim of this study is to propose action levels for chelation therapy in the case of inhalation of plutonium compounds using nose swabs. The relationship between the activity found in the nose swabs and early faecal excretion was investigated using actual cases at JAEA-NFCEL. The ratio was found to be in log-normal distribution. The action levels based on the activity of nose swab corresponding to 10 ALI (=200 mSv) are determined for the facilities at JAEA-NFCEL by using the relationship and specific information such as isotopic ratio and physicochemical characteristics of plutonium compounds.

Chelating agents used for plutonium and uranium removal in radiation emergency medicine.

The prospects of using chelating agents for increasing the excretion of actinides are reviewed. The removal of plutonium by chelating agents is of great importance because plutonium is extremely dangerous and induces cancer due to radiation toxicity. Similarly, uranium is a radionuclide, which causes severe renal dysfunction within a short time period due to chemical toxicity. It may also induce cancers such as leukemia and osteosarcoma in cases of long-term internal radiation exposure. Investigations on chelating agents for the removal of plutonium were initiated in the 1960's and 1970's. Diethylenetriaminepentaacetic acid (DTPA) is recognized as a chelating agent that accelerates the excretion of plutonium in early treatment after an accident. Thereafter, there has long been an interest in finding new chelating agents with radionuclide removal properties for use in therapy, and many chelating agents such as 3,4,3-LIHOPO and CBMIDA have been studied for their ability to remove plutonium and uranium. Recently, the focus has turned to drugs that have been used successfully in the treatment of a variety of other diseases, for example the iron chelating drug deferiprone or 1,2-dimethyl-3-hydroxypyrid-4-one (L1), which is used in thalassaemia and ethane-1-hydroxy-1,1-bisphosphonate (EHBP), which is used in osteoporosis. Within this context, it is important to examine the clinical use of these two drugs as well as the properties of the experimental chelators 3,4,3-LIHOPO and CBMIDA in order to identify possible uses in the treatment of radiation workers contaminated with plutonium and uranium.

Efficacy of 3,4,3-LI(1,2-HOPO) for decorporation of Pu, Am and U from rats injected intramuscularly with high-fired particles of MOX.

This study aimed to assess the efficacy of 3,4,3-LI(1,2-HOPO) for reducing uranium, plutonium and americium in rats after intramuscular injection of (U-Pu)O2 particles (MOX). Sixteen rats were contaminated by intramuscular injection of a 1 mg MOX suspension and then treated daily for 7 d with LIHOPO (30 or 200 micromol kg(-1)) or DTPA (30 micromol kg(-1)). LIHOPO was inefficient for removing Pu, Am and U from the wound site. However, it reduced Pu retention in carcass and liver by factors of 2 and 6 respectively, and Am retention in carcass and liver by factors of 10 and 30. In contrast, the effect of LIHOPO on U was to decrease the retention in kidneys by a factor of 75. These results confirm that LIHOPO is a good candidate for use after contamination with MOX, in combination with localised wound lavage or surgical treatment aimed at removing most of the contaminant at the wound site.

Successful DTPA therapy in the case of 239Pu penetration via injured skin exposed to nitric acid.

This paper presents results of the radiological study and DTPA therapy for a worker exposed to a plutonium nitrate solution. Plutonium levels were measured in excreta, blood, plasma and wound for several weeks. Plutonium renal clearance ranged from 110-190 ml min(-1) to 3-4 ml min(-1) at different stages of chelation therapy. Plutonium absorption into blood from the injured skin amounted to 4.3%. As a result of intensive therapy, 96% of absorbed plutonium was successfully excreted.

Comparative decorporation efficacy of 3,4,3-LIHOPO, 4,4,4-LIHOPO and DTPA after contamination of rats with soluble forms of 238Pu and 233U.

The aim of this study was to compare the efficacies of DTPA, 3,4,3-LIHOPO and a newly synthesised molecule, 4,4,4-LIHOPO, in removing 233U and 238Pu after internal contamination by soluble forms of those nuclides. For this purpose, intravenous injections of DTPA (30 micromol kg(-1)) or 3,4,3-LIHOPO or 4,4,4-LIHOPO at dosages of 0.3 or 30 micromol kg(-1) were performed 1, 6 and 24 h after contamination of rats by intravenously injected 238Pu citrate and 1 h after intravenous injection of 233U nitrate. Actinide content in the main retention organs and cumulated excretion were measured 48 h after contamination. These experiments show similar decorporation efficacies of 4,4,4-LIHOPO and 3,4,3-LIHOPO for Pu, which are much higher than that of DTPA. At a dosage of 0.3 micromol kg(-1), the two LIHOPO analogues were as efficient as DTPA at a dosage of 30 micromol kg(-1). After U contamination, a 20% decorporation efficacy was obtained for either 3,4,3-LIHOPO or 4,4,4-LIHOPO at a dosage of 30 micromol kg(-1).

Tumorigenic target cell regions in bone marrow studied by localized dosimetry of 239Pu, 241Am and 233U in the mouse femur.

PURPOSE: To study the temporal change in microdistribution of plutonium-239, americium-241 and uranium-233 in the mouse distal femur and to compare and combine calculated radiation doses with those obtained previously for the femoral shaft. Also, to relate doses to relative risks of osteosarcoma and acute myeloid leukaemia. MATERIALS AND METHODS: Computer-based image analysis of neutron-induced and alpha-track autoradiographs of sections of mouse femora was used to quantify the microdistribution of (239)Pu, (241)Am and (233)U from 1 to 448 days after intraperitoneal injection. Localized dose-rates and cumulative doses over this period were calculated for different regions of the marrow spaces in trabecular bone. The results were then combined with previous data for doses to the cortical marrow of the femoral shaft. A morphometric analysis of the distal femur was carried out. RESULTS: Initial deposition on endosteal surfaces and dose-rates near to the trabecular surfaces at 1 day were two to four times greater than corresponding results for cortical bone. Burial was most rapid for (233)U, about twice the rate in cortical bone. As in cortical bone, subsequent uptake into the marrow was seen for (239)Pu and (241)Am but not (233)U. Cumulative doses to 448 days for different regions of trabecular marrow were greater than corresponding values for cortical marrow for each radionuclide. Combined doses reflected the greater overall volume of cortical marrow. CONCLUSIONS: Cumulative radiation doses to the 10 microm thick band of marrow adjacent to all endosteal surfaces were in the ratio of approximately 7:3:1 for (239)Pu:(241)Am:(233)U. This ratio is not inconsistent with observed incidences of osteosarcoma induction by the three nuclides. Analysis of doses to different depths of marrow, however, showed that although ratios were probably not significantly different to that for a 10 microm depth, better correlations with osteosarcomagenic risk were obtained with 20-40 microm depths. For acute myeloid leukaemia, the closest relationship between relative risk and doses was obtained by considering only the central 5-10% of marrow, which gave a dose ratio of approximately 12:11:1 for (239)Pu:(241)Am:(233)U respectively.

[A comparative evaluation of the efficacy of different methods for the decorporation of plutonium from the respiratory organs]. / Sravnitel'naia otsenka éffektivnosti razlichnykh metodov dekorporatsii organov dykhaniia ot plutoniia.

The behavior of plutonium in the organism and the mechanism of formation of absorbed doses in rats of different age were studied in a comparative aspect. The efficiency of CaDTPA depending on the animal's age and the usage was estimated. Under similar conditions, the efficiency of early single injections of CaDTPA to rat cubs was 2.3 (skeleton) or 3.3 (liver) times lower than that for mature rats. Attempts of modifying the kinetics of low-transportable plutonium-239 by stimulation of pulmonary alveolar macrophages failed.

The distribution and retention of plutonium, americium and uranium in CBA/H mice.

Groups of male and female CBA/H mice were given intraperitoneal injections of 40 kBq kg-1 of 239Pu, 241Am and 233U citrate solutions and the retention and distribution of the three radionuclides compared at times up to 448 days. Similar results were obtained for males and females and showed that: 1. Whole body retention at 448 days was very similar for 239Pu and 241Am, accounting for about 20% of injected activity for each nuclide; retention of 233U was much lower at about 3%. 2. The skeleton accounted for 85% or more of retained 239Pu, 241Am and 233U activity from 6 weeks after injection. 3. The greatest concentrations of each radionuclide were measured in the main body of the spine, limb girdles and ribs, with lowest concentrations in the paw bones, head bones and caudal vertebrae. The inhomogeneity of distribution was in the order Pu > U > Am; with a trend to more uniform activity with time. 4. Average bone doses to 448 days were calculated as about 1.6 and 1.7 Gy for 239Pu and 241Am, respectively, and 0.3 Gy for 233U, with ranges for individual bones of 0.7-3.0 Gy, 1.1-2.5 Gy and 0.1-0.6 Gy, respectively. Average liver doses to 448 days were calculated as about 0.9 Gy, 0.6 Gy and 0.007 Gy for 239Pu, 241Am and 233U respectively, whilst the dose to the kidney for 233U was about 0.1 Gy. 5. Autoradiographic studies of the distribution of the nuclides in the femur showed differences in their initial distribution and subsequent movement. Initially, concentrations of 239Pu were greater on endosteal than periosteal surfaces while 241Am distributed more evenly on bone surfaces. The initial deposition of 233U on all surfaces was uneven with concentrations probably on active surfaces. Burial of all three nuclides in areas of bone growth was observed. Transfer of activity to the marrow was greatest for 239Pu and least for 233U.

[Quantitative assessment of inhalation exposure to various transuranium radionuclide compounds by integral nonstochastic criteria]. / Kolichestvennaia otsenka ingaliatsionnogo vozdeistviia raznymi soedineniiami transuranovykh radionuklidov po integral'nym nestokhasticheskim kriteriiam.

The comparison of the danger from inhalation of radionuclide transuranium compounds differently transferred within the body was made by the results of an examination of 169 mongrel dogs and 2000 Wistar rats. Effective and ineffective levels of the radionuclide inhaled were determined by integral nonstochastic criteria, that is, 50 per cent death rate, shortening and increase of the average life and reduction of body mass.

The biodistribution and toxicity of plutonium, americium and neptunium.

In the nuclear fuel cycle the transuranic radionuclides plutonium-239, americium-241 and neptunium-237 would probably present the most serious hazard to human health if released into the environment. Despite differences in their solution chemistry the three elements exhibit remarkable similarity in their biochemical behaviour, apparently sharing similar transport pathways in blood and cells. After entering the blood the elements deposit predominantly in liver and skeleton, where retention appears to be prolonged, with half-times of the order of years. The principal late effects of all three radionuclides are the induction of cancers of bone, lung or liver. For the latter tumours the induction risk per unit radiation dose appears similar for the three radionuclides. But in bone there are indications that, due to microscopic differences in the distribution of the alpha-particle radiation dose, the efficiency of bone cancer induction may increase in the order americium-241 less than plutonium-239 less than neptunium-237. No case of human cancer induced by these radionuclides is known.

Tumour development following internal exposures to radionuclides during the perinatal period.

Exposure to radiation from internally deposited radionuclides during the prenatal and/or neonatal periods bears a distinct oncogenic potential. The fundamental mechanisms of perinatal radionuclide carcinogenesis seem to be generally similar to those that pertain to external radiation exposures and other carcinogenic agents, but unique interactions may be superimposed. Specific dose-effect relationships differ among radionuclides; in many studies, there have been dose-related increases in the incidence of tumours or decreases in age at tumour appearance following prenatal or neonatal radiation exposure. Tumour incidences may be decreased, especially at high dose levels; these are usually attributable to cell death, inhibited development of target tissues or to endocrine malfunction. Age-related differences in predominant tumour types and/or sites of tumour development are often detected, and are explainable by the existence of nuclide-specific target organs or tissues, dosimetric factors and developmental considerations.

Computer simulation of metal ion equilibria in biofluids. IV. Plutonium speciation in human blood plasma and chelation therapy using polyaminopolycarboxylic acids.

An investigation by computer simulation into the nature of Pu(IV) binding to low-molecular ligands in human blood plasma is described. Particular consideration is given to the interactions of various chelating agents which have been or might be used for treating plutonium intoxication. Formation constants of EDTA and DTPA with Cu(II), Mg(II), Mn(II), Zn(II), and Cd(II) have been measured under biologic conditions of temperature and background electrolyte. The relative ability of these and other chelating agents to cause excretion of plutonium and the concomitant loss of certain essential trace metals has thus been assessed.