A physiologically based biokinetic model for cesium in the human body

Associations of Blood and Urinary Heavy Metals with Stress Urinary Incontinence Risk Among Adults in NHANES, 2003-2018

People come into contact with heavy metals in various ways in their daily lives. Accumulating evidence shows that toxic metal exposure is hazardous to human health. However, limited information is available regarding the impact of metal mixtures on stress urinary incontinence (SUI). Therefore, we used data from 10,622 adults from the 2003-2018 National Health and Nutrition Examination Survey (NHANES) to investigate the independent and comprehensive association between heavy metal co-exposure and SUI. Among them, 2455 (23.1%) had been diagnosed with SUI, while the rest had no SUI. We evaluated the independent and combined associations of 3 blood metals and 10 urinary metals with SUI risk, along with subgroup analyses according to age and gender. In the single-exposure model, blood cadmium (Cd), lead (Pb), mercury (Hg), urinary Cd, Pb, and cesium (Cs) were found to be positively connected with SUI risk. Moreover, weighted quantile sum (WQS) regression, quantile-based g-computation (qgcomp), and Bayesian kernel machine regression (BKMR) consistently demonstrated blood and urinary metal-mixed exposure were positively associated with the risk of SUI, and emphasized that blood Pb and Cd and urinary Cd and Cs were the main positive drivers, respectively. This association was more pronounced in the young and middle-aged group (20-59 years old) and the female group. Nevertheless, further research is necessary to validate these significant findings.

Simultaneous removal of caesium and strontium using different removal mechanisms of probiotic bacteria

When radioactive materials are released into the environment due to nuclear power plant accidents, they may enter into the body, and exposing it to internal radiation for long periods of time. Although several agents have been developed that help excrete radioactive elements from the digestive tract, only one type of radioactive element can be removed using a single agent. Therefore, we considered the simultaneous removal of caesium (Cs) and strontium (Sr) by utilising the multiple metal removal mechanisms of probiotic bacteria. In this study, the Cs and Sr removal capacities of lactobacilli and bifidobacteria were investigated. Observation using an electron probe micro analyser suggested that Cs was accumulated within the bacterial cells. Since Sr was removed non metabolically, it is likely that it was removed by a mechanism different from that of Cs. The amount of Cs and Sr that the cells could simultaneously retain decreased when compared to that for each element alone, but some strains showed only a slight reduction in removal. For example, Bifidobacterium adolescentis JCM1275 could simultaneously retain 55.7 mg-Cs/g-dry cell and 8.1 mg-Sr/g-dry cell. These results demonstrated the potentials of utilizing complex biological system in simultaneous removal of multiple metal species.

High-energy SR-XRF Imaging of Cesium and Trace Elements in Mouse Kidneys: Short Communication

For understanding trace element dynamics in tissues, methods for analyzing elemental distribution and localization without destroying tissue structures and cell arrangements are desired. Synchrotron radiation X-ray fluorescence (SR-XRF) analysis is one of the non-destructive and multi-element simultaneous analyses. The kidney is the major excretion pathway of cesium (Cs) taken into the body, and an understanding of cesium distribution in the kidney would be useful for establishing technology to facilitate the excretion of radioactive Cs from the body due to nuclear disasters. In the present study, the distribution of cesium and trace elements, such as iron (Fe) and zinc (Zn), corresponding to the kidney structure was examined in Cs-administered mice by SR-XRF imaging with high-energy excitation X-rays (40 keV). By beam scanning with a 200-µm square beam, clear Cs images corresponding to the renal layer structure were obtained for the renal specimen at the early phase after Cs administration with the mean renal Cs concentration of 24.1 ± 3.2 μg/g. Cs was distributed mainly in the medulla and the outer stripe of the outer medulla located in the center area of the kidney. Unlike the Cs distribution, endogenous Fe and Zn tended to be lower in the medulla than in the outer stripe of the outer medulla and the cortex. This method is effective for analyzing Cs distribution because it can simultaneously analyze the distribution of endogenous trace elements.

Investigating the impact of elevated urinary trace elements on non-alcoholic fatty liver disease using vibration-controlled transient elastography

Introduction

Non-alcoholic fatty liver disease (NAFLD) is a global public health concern. However, limited data are available on urinary trace elements and NAFLD caused by various exposure factors. This study aimed to investigate the relationship between the presence of 16 trace elements in urine and NAFLD using data from the National Health and Nutrition Examination Survey (NHANES).

Methods

By utilizing the NHANES data from 2017 to 2018, 1613 participants who fulfilled the research criteria were identified from the initial pool of 2979 participants with available urine trace element detection data. Among them, 706 individuals had been diagnosed with NAFLD based on a coefficient of attenuation parameter (CAP) value of at least 274 db/m, determined using vibration-controlled transient elastography (VCTE); whereas the remaining 907 participants were classified as non-NAFLD. The data obtained were used to construct univariate and multivariate logistic regression models and restricted cubic spline models (RCS) analyses.

Results

The presence of arsenic, iodine, barium, cesium, molybdenum, lead, tin, and tungsten in the urine of individuals with NAFLD showed a positive correlation with the likelihood of developing NAFLD. The risk of NAFLD had a non-linear dose-dependent relationship with urinary iodine, molybdenum, barium, and cesium. NAFLD was also associated with elevated levels of barium and cesium in urine, which were identified as significant risk factors.

Conclusion

These findings suggest a positive association between exposure to trace elements in the urine and the risk of NAFLD. Specifically, urinary barium and cesium appeared to have the greatest impact on the risk of NAFLD. These results provide novel insights into the diagnosis and treatment of NAFLD.

Phytotoxicity of radionuclides: A review of sources, impacts and remediation strategies

Various anthropogenic activities and natural sources contribute to the presence of radioactive materials in the environment, posing a serious threat to phytotoxicity. Contamination of soil and water by radioactive isotopes degrades the environmental quality and biodiversity. They persist in soils for a considerable amount of time and disturb the fauna and flora of any affected area. Hence, their removal from the contaminated medium is inevitable to prevent their entry into the food chain and the organisms at higher levels of the food chain. Physicochemical methods for radioactive element remediation are effective; however, they are not eco-friendly, can be expensive and impractical for large-scale remediation. Contrastingly, different bioremediation approaches, such as phytoremediation using appropriate plant species for removing the radionuclides from the polluted sites, and microbe-based remediation, represent promising alternatives for cleanup. In this review, sources of radionuclides in soil as well as their hazardous impacts on plants are discussed. Moreover, various conventional physicochemical approaches used for remediation discussed in detail. Similarly, the effectiveness and superiority of various bioremediation approaches, such as phytoremediation and microbe-based remediation, over traditional approaches have been explained in detail. In the end, future perspectives related to enhancing the efficiency of the phytoremediation process have been elaborated.

Cesium activates the neurotransmitter receptor for glycine

The monovalent cations sodium and potassium are crucial for the proper functioning of excitable cells, but, in addition, other monovalent alkali metal ions such as cesium and lithium can also affect neuronal physiology. For instance, there have been recent reports of adverse effects resulting from self-administered high concentrations of cesium in disease conditions, prompting the Food and Drug Administration (FDA) to issue an alert concerning cesium chloride. As we recently found that the monovalent cation NH4+ activates glycine receptors (GlyRs), we investigated the effects of alkali metal ions on the function of the GlyR, which belongs to one of the most widely distributed neurotransmitter receptors in the peripheral and central nervous systems. Whole-cell voltage clamp electrophysiology was performed with HEK293T cells transiently expressing different splice and RNA-edited variants of GlyR α2 and α3 homopentameric channels. By examining the influence of various milli- and sub-millimolar concentrations of lithium, sodium, potassium, and cesium on these GlyRs in comparison to its natural ligand glycine (0.1 mM), we could show that cesium activates GlyRs in a concentration- and post-transcriptional-dependent way. Additionally, we conducted atomistic molecular dynamic simulations on GlyR α3 embedded in a membrane bilayer with potassium and cesium, respectively. The simulations revealed slightly different GlyR-ion binding profiles for potassium and cesium, identifying interactions near the glycine binding pocket (potassium and cesium) and close to the RNA-edited site (cesium) in the extracellular GlyR domain. Together, these findings show that cesium acts as an agonist of GlyRs.

Gamma Radioactivity Detection Limits and Associated Radionuclide Intakes Study in Artificial Human Urine Using Sodium-iodide and High-purity Germanium Detectors

The performance of several gamma detectors was investigated for emergency urine bioassay screening of two radionuclides of concern: 131 I and 137 Cs. Unspiked artificial urine samples were measured for 10 min each on four different gamma detectors: 80% relative efficiency high-purity Ge detector in standard shielding, 102% low-background high-purity Ge detector equipped with top muon shield, 78% high-purity Ge well detector in standard shielding, and 4″ × 4″ NaI well detector in standard shielding. The measured gamma spectra were analyzed in two ways: (1) for the 364-keV peak region of 131 I and 662-keV peak region of 137 Cs and (2) for the total counts in the full energy spectrum (50-2,048 keV). The results were analyzed using the principles of signal detection theory according to the Currie's formalism extended by a complete uncertainty propagation. This enabled calculation of the detection capability in terms of detection limit (Bq L -1 ) of urine, the latter referred to as minimum detectable activity. The NaI well detector had the lowest minimum detectable activities for total spectra, whereas the high-purity Ge well detector had the lowest peak minimum detectable activity values. Minimum detectable inhalation and ingestion intakes from urine bioassay were calculated from the minimum detectable activity values for urine collection 1 d, 1 wk, and 1 mo past the initial intake. The calculated intakes were compared with annual limits on intake. The results are interpreted with respect to a large-scale radiological emergency response.

Methods of improving brain dose estimates for internally deposited radionuclides. JOURNAL OF RADIOLOGICAL PROTECTION : OFFICIAL JOURNAL OF THE SOCIETY FOR RADIOLOGICAL PROTECTION 2022;42:033001. [PMID: 35785774 DOI: 10.1088/1361-6498/ac7e02]

The US National Council on Radiation Protection and Measurements (NCRP) convened Scientific Committee 6-12 (SC 6-12) to examine methods for improving dose estimates for brain tissue for internally deposited radionuclides, with emphasis on alpha emitters. This Memorandum summarises the main findings of SC 6-12 described in the recently published NCRP Commentary No. 31, 'Development of Kinetic and Anatomical Models for Brain Dosimetry for Internally Deposited Radionuclides'. The Commentary examines the extent to which dose estimates for the brain could be improved through increased realism in the biokinetic and dosimetric models currently used in radiation protection and epidemiology. A limitation of most of the current element-specific systemic biokinetic models is the absence of brain as an explicitly identified source region with its unique rate(s) of exchange of the element with blood. The brain is usually included in a large source region calledOtherthat contains all tissues not considered major repositories for the element. In effect, all tissues inOtherare assigned a common set of exchange rates with blood. A limitation of current dosimetric models for internal emitters is that activity in the brain is treated as a well-mixed pool, although more sophisticated models allowing consideration of different activity concentrations in different regions of the brain have been proposed. Case studies for 18 internal emitters indicate that brain dose estimates using current dosimetric models may change substantially (by a factor of 5 or more), or may change only modestly, by addition of a sub-model of the brain in the biokinetic model, with transfer rates based on results of published biokinetic studies and autopsy data for the element of interest. As a starting place for improving brain dose estimates, development of biokinetic models with explicit sub-models of the brain (when sufficient biokinetic data are available) is underway for radionuclides frequently encountered in radiation epidemiology. A longer-term goal is development of coordinated biokinetic and dosimetric models that address the distribution of major radioelements among radiosensitive brain tissues.

Effective and environmental half-lives of radiocesium in game from Poland

For the first time changes in the ¹³⁷Cs activity in game throughout Poland, including its most contaminated part known as the Opole Anomaly, were analyzed. Due to its long physical half-life, ¹³⁷Cs continuously demonstrates high activity both in soil and biota. The species of game mammals, along with forest fruit and mushrooms, tend to accumulate this radionuclide, becoming one of the main sources of secondary contamination in people. In this study the ¹³⁷Cs activity in roe deer, wild boar and red deer muscle tissue samples, within the years of 1986-2019, were studied. The effective and environmental half-lives were determined for each of the mentioned species for four regions including NE Poland and the Opole Anomaly placed in SW Poland. In all examined species at least two different phases of changes in the ¹³⁷Cs activity were distinguished, therefore the values of effective half-lives for the researched period since the Chernobyl accident do not correspond with the values from within last ten years. It was proven for the first time that within the anomalous area, featuring the highest values of gamma surface activity in Poland, the ¹³⁷Cs activity increases with time in the muscle tissues of all three species. No intraspecies, nor interspecies differences of ¹³⁷Cs activity among the studied species were found. In the light of the collected data, monitoring game considering the ¹³⁷Cs activity appears to be valid, as, due to not completely clear trophic dependencies, this radionuclide currently increased its migration to the game species despite passing its physical half-life period.

Absorbed dose rate coefficients for134Cs and137Cs with steady-state distribution in the human body:S-coefficients revisited

In the event of an accidental release of radioactive elements from a nuclear power plant, it has been shown that the radionuclides contributing the most to long-term exposure are¹³⁴Cs and¹³⁷Cs. In the case of nuclear power plant fallout, with subsequent intake of radionuclides through the food chain, the internal absorbed dose to target tissues from protracted intake of radionuclides needs to be estimated. Internal contamination from food consumption is not caused by a single intake event; hence, the committed equivalent dose, calculated by a dose coefficient or dose per content function, cannot be easily used to calculate the cumulative absorbed dose to relevant target tissues in the body. In this study, we calculated updated absorbed dose rate coefficients for¹³⁴Cs and¹³⁷Cs based on data from the International Commission on Radiological Protection (ICRP) on specific absorbed fractions. The absorbed dose rate coefficients are provided for male and female adult reference phantoms, respectively, assuming a steady-state distribution of Cs that we calculated from the ICRP biokinetic model for Cs. With these coefficients, the absorbed dose to the listed target tissues, separately and to the total body, are related to the number of nuclear transitions (time-integrated activity) in each listed source region. Our new absorbed dose rate coefficients are given for the complete set of target tissues and have not been presented before. They are also provided for aggregated categories of organs to facilitate epidemiological studies.

Lowered serum cesium levels in schizophrenia: association with immune-inflammatory biomarkers and cognitive impairments

Objectives:

A previous study has shown that schizophrenia (SCZ) is accompanied by lowered levels of trace/metal elements, including cesium. However, it is not clear whether changes in cesium, rubidium, and rhenium are associated with activated immune-inflammatory pathways, cognitive impairments, and the symptomatology of SCZ.

Methods:

This study measured cesium, rubidium, and rhenium, cognitive impairments (using the Brief Assessment of Cognition in Schizophrenia [BACS]), and the levels of cytokines/chemokines interleukin (IL)-1β, tumor necrosis factor (TNF)-α, and eotaxin (CCL11) in 120 patients with SCZ and 54 healthy controls. Severity of illness was assessed using the Brief Psychiatric Rating Scale (BPRS), the Scale for the Assessment of Negative Symptoms (SANS), the Fibromyalgia and Chronic Fatigue Syndrome Rating (FF) Scale, and the Hamilton Depression Rating Scale (HAM-D).

Results:

Serum cesium was significantly lower in patients with SCZ as compared with controls. Further, serum cesium was significantly and inversely associated with CCL11 and TNF-α, but not IL-1β, in patients with SCZ; significant inverse associations were also noted between serum cesium levels and BPRS, FF, HAM-D, and SANS scores. Finally, cesium was positively correlated with neurocognitive probe results including the Tower of London, Symbol Coding, Controlled Word Association, Category Instances, Digit Sequencing Task, and List Learning tests.

Conclusion:

The results suggest that lowered serum cesium levels may play a role in the pathophysiology of SCZ, contributing to specific symptom domains including negative, depressive and fatigue symptoms, neurocognitive impairments (spatial working, episodic, and semantic memory and executive functions), and neuroimmune pathways.

Phytoremediation of radionuclides in soil, sediments and water

Soil and water contaminated with radionuclides threaten the environment and public health during leaks from nuclear power plants. Remediation of radionuclides at the contaminated sites uses mainly physical and chemical methods such as vitrification, chemical immobilization, electro-kinetic remediation and soil excavation, capping and washing being among the preferred methods. These traditional technologies are however costly and less suitable for dealing with large-area pollution. In contrast to this, cost-effective and environment-friendly alternatives such as phytoremediation using plants to remove radionuclides from polluted sites in situ represent promising alternatives for environmental cleanup. Understanding the physiology and molecular mechanisms of radionuclides accumulation in plants is essential to optimize and improve this new remediation technology. Here, we give an overview of radionuclide contamination in the environment and biochemical characteristics for uptake, transport, and compartmentation of radionuclides in plants that characterize phytoextraction and its efficiency. Phytoextraction is an eco-friendly and efficient method for environmental removal of radionuclides at contaminated sites such as mine tailings. Selecting the most proper plant for the specific purpose, however, is important to obtain the best result together with, for example, applying soil amendments such as citric acid. In addition, using genetic engineering and optimizing agronomic management practices including regulation of atmospheric CO₂ concentration, reasonable measures of fertilization and rational water management are important as well. For future application, the technique needs commercialization in order to fully exploit the technique at mining activities and nuclear industries.

Content of essential and toxic trace elements in organs of obese Wistar and Zucker leprfa rats receiving quercetin

BACKGROUND

The levels of a number of essential and toxic trace elements in organs and tissues are affected by the disruptions in body homeostasis caused by obesity. Some of these elements may also be influenced by the consumption of biologically active substances of polyphenolic origin, which possess potent abilities to complex with transition metal ions.

AIMS

The aim of this study was to determine the content of essential and toxic trace elements in Wistar outbred and hereditary obese Zucker Lepr^fa (Z) rats consuming a standard balanced diet or hypercaloric diet with excess fat and fructose, supplemented with quercetin or not supplemented.

MATERIALS AND METHODS

Male Wistar and Z rats were fed a control AIN-93M-based semi-synthetic diet or a high-fat-high-carbohydrate diet (HFCD, with 30% fat by weight and 20% fructose provided in the drinking water). A portion of the animals in each line and diet group was administered quercetin at 50 mg/kg body weight. Essential trace elements were included in the diets as a high-purity salt mixture. After the termination of feeding on day 63, the livers, kidneys, and brains of the rats were excised and the content of 16 elements (Fe, Mg, Cu, Mn, Co, Se, Zn, Cr, Ni, Al, Cd, As, Pb, V, Cs, and Ag) was measured by inductively coupled plasma mass spectrometry (ICP-MS).

RESULTS

In the livers of the Z rats, the contents of Co, Zn, Mg, Fe, Se, and V were reduced and the content of Cr was increased compared to that of the Wistar rats. Supplementation with quercetin significantly decreased liver Fe, V, and Se content, which was more noticeable in the Wistar rats than in the Z rats. In kidneys of Z rats consuming control diet, the contents of Co, Cu, and Cs were decreased whereas those of Ni, Al, and Se were increased compared with the contents in the Wistar rats. The same trend was observed with HFCD feeding except for Cs content. Quercetin reduced kidney V content in both rat lines fed both diets, whereas it reduced Se and Cs only in the Z rats fed control diet. In the brains of the Z rats, a large increase was observed in some trace elements including Pb, Cd, Al, Cr, Ni, Fe, and V compared with the levels in the Wistar rat brains. Supplementation of the control diet with quercetin decreased Al and Ni in the brains of the Z rats.

CONCLUSION

There were significant differences in the mineral content of organs between the Wistar and Z rats, with different propensities for obesity. Moreover some of these effects had no straightforward association with decreased feed consumption or hepatic fat accumulation. When introduced into the diets, quercetin affected the content of essential and toxic elements, but with ambiguous physiological significance. Thus, indicators of essential and toxic trace elements deserve to be used in the protocols of preclinical as well as clinical trials of biologically active substances and food supplements.

Transition of Radioactive Cesium Deposition in Reproductive Organs of Free-Roaming Cats in Namie Town, Fukushima

We investigated the internal contamination by radioactive cesium associated with the FDNPP accident, in the testes or uterus and ovaries of free-roaming cats (Felis silvestris catus), which were protected by volunteers in the Namie Town, Fukushima. A total of 253 samples (145 testes and 108 uterus and ovaries) obtained from adult cats and 15 fetuses from 3 pregnant female cats were measured. Free-roaming cats in Namie Town had a higher level of radioactive contamination in comparison to the control group in Tokyo, as the ¹³⁴Cs + ¹³⁷Cs activity concentration ranged from not detectable to 37,882 Bq kg^-1 in adult cats. Furthermore, the radioactivity in the fetuses was almost comparable to those in their mother's uterus and ovaries. The radioactivity was also different between several cats protected in the same location, and there was no significant correlation with ambient dose-rates and activity concentrations in soil. Moreover, radioactive cesium levels in cats decreased with each year. Therefore, it is likely that decontamination work in Namie Town and its surroundings could affect radioactive cesium accumulation, and thus possibly reduce the internal radiation exposure of wildlife living in contaminated areas. It is hence necessary to continue radioactivity monitoring efforts for the residents living in Namie Town.

Efficient cesium encapsulation from contaminated water by cellulosic biomass based activated wood charcoal

In this study, cost-effective cellulosic biomass based activated wood charcoal was developed from Japanese Sugi tree (Cryptomeria japonica) by concentrated nitric acid modification for adsorption of Cs from contaminated water. The physicochemical properties of specimens were investigated using N₂ adsorption-desorption isotherms (BET method), FESEM, FTIR, and XPS spectra analysis. The experimental results revealed that the surface area of the raw wood charcoal was significantly decreased after boiling nitric acid modification. However, several oxygen-containing acidic function groups (-COOH, -CO) were introduced on the surface. The adsorption study confirmed that the equilibrium contact time was 1 h, the optimum adsorption pH was neutral to alkaline and the suitable adsorbent dose was 1:100 (solid: liquid). The maximum Cs was removed when the concentration of Na and K were lower (5.0 mM) with Cs in solution. The Cs adsorption processes well approved by the Langmuir isotherm and pseudo-second-order kinetic models and the maximum adsorption capacity was 35.46 mgg^-1. The Cs adsorption mechanism was clearly described and it was assumed that the adsorption was strongly followed by chemisorptions mechanism based on the adsorbent surface properties, kinetic model and Langmuir isotherm model. Most importantly, about 98% of volume reduction was obtained by burning (500 °C) the Cs adsorbed charcoal, which ensured safe storage and disposal of radioactive waste. Therefore, this study can offer a guideline to produce a functional adsorbent for effective Cs removal and safe radioactive waste disposal.

The Effect of the Supplementation of a Diet Low in Calcium and Phosphorus with Either Sheep Milk or Cow Milk on the Physical and Mechanical Characteristics of Bone using A Rat Model

This study assessed the effect of cow milk (CM) and sheep milk (SM) consumption on the micro-structure, mechanical function, and mineral composition of rat femora in a male weanling rat model. Male weanling rats were fed a basal diet with a 50% reduction in calcium and phosphorus content (low Ca/P-diet) supplemented with either SM or CM. Rats were fed for 28 days, after which the femora were harvested and stored. The femora were analyzed by μ-CT, three-point bending, and inductively coupled plasma-mass spectrometry (ICP-MS). The addition of either milk to the low Ca/P-diet significantly increased (p < 0.05) trabecular bone volume, trabecular bone surface density, trabecular number, cortical bone volume, and maximum force, when compared to rats that consumed only the low Ca/P-diet. The consumption of either milk resulted in a significant decrease (p < 0.05) in trabecular pattern factor, and cortical bone surface to volume ratio when compared to rats that consumed only the low Ca/P-diet. The results were achieved with a lower consumption of SM compared to that of CM (p < 0.05). This work indicates that SM and CM can help overcome the effects on bone of a restriction in calcium and phosphorus intake.

Eurados review of retrospective dosimetry techniques for internal exposures to ionising radiation and their applications

This work presents an overview of the applications of retrospective dosimetry techniques in case of incorporation of radionuclides. The fact that internal exposures are characterized by a spatially inhomogeneous irradiation of the body, which is potentially prolonged over large periods and variable over time, is particularly problematic for biological and electron paramagnetic resonance (EPR) dosimetry methods when compared with external exposures. The paper gives initially specific information about internal dosimetry methods, the most common cytogenetic techniques used in biological dosimetry and EPR dosimetry applied to tooth enamel. Based on real-case scenarios, dose estimates obtained from bioassay data as well as with biological and/or EPR dosimetry are compared and critically discussed. In most of the scenarios presented, concomitant external exposures were responsible for the greater portion of the received dose. As no assay is available which can discriminate between radiation of different types and different LETs on the basis of the type of damage induced, it is not possible to infer from these studies specific conclusions valid for incorporated radionuclides alone. The biological dosimetry assays and EPR techniques proved to be most applicable in cases when the radionuclides are almost homogeneously distributed in the body. No compelling evidence was obtained in other cases of extremely inhomogeneous distribution. Retrospective dosimetry needs to be optimized and further developed in order to be able to deal with real exposure cases, where a mixture of both external and internal exposures will be encountered most of the times.

The effect of chronic low-dose environmental radiation on organ mass of bank voles in the Chernobyl exclusion zone

PURPOSE

Animals are exposed to environmental ionizing radiation (IR) externally through proximity to contaminated soil and internally through ingestion and inhalation of radionuclides. Internal organs can respond to radioactive contamination through physiological stress. Chronic stress can compromise the size of physiologically active organs, but studies on wild mammal populations are scarce. The effects of environmental IR contamination on organ masses were studied by using a wild rodent inhabiting the Chernobyl exclusion zone (CEZ).

MATERIAL AND METHODS

The masses of brain, heart, kidney, spleen, liver and lung were assessed from bank voles (Myodes glareolus) captured from areas across radioactive contamination gradient within the CEZ. Relative organ masses were used to correct for the body mass of an individual.

RESULTS

Results showed a significant negative correlation between IR level in the environment and relative brain and kidney mass. A significant positive correlation between IR and relative heart mass was also found. Principal component analysis (PCA) also suggested positive relationship between IR and relative spleen mass; however, this relationship was not significant when spleen was analyzed separately. There was no apparent relationship between IR and relative liver or lung mass.

CONCLUSIONS

Results suggest that in the wild populations even low but chronic doses of IR can lead to changes in relative organ mass. The novelty of these result is showing that exposure to low doses can affect the organ masses in similar fashion as previously shown on high, acute, radiation doses. These data support the hypothesis that wildlife might be more sensitive to IR than animals used in laboratory studies. However, more research is needed to rule out the other indirect effects such as radiosensitivity of the food sources or possible combined stress effects from e.g. infections.

INTERNAL DOSIMETRY TOOL FOR THE IMPLEMENTATION AND USE OF NEW ICRP/OIR MODELS: A CAESIUM STUDY

In case of accidental intake of radioactive material, the dose assessment requires information on the radionuclide distribution in the body. Measurements of retention or excretion are compared with model's predictions to estimate the intake. The reference models for internal dosimetry purposes are those proposed by ICRP and have been recently updated in the 'Occupational Intakes of Radionuclides (OIR)' series. This work focusses on the implementation of the new caesium model in a computer package, ICRP130Models (integrated in the toolbox BIOKMOD), together with new features aimed at estimating the intake and the dose from bioassay measurements. The software gives the best fitted intake and the committed effective dose, as well as the chi-squared test and the p-value as an indication of the goodness of the fit in the assessment process. The possibility to build the model as a function of a parameter allows the user to look for different options when fitting the bioassay measurements.

Co-exposure to internal and external radiation alters cesium biokinetics and retention in mice

Exposures in post-accidental situations are complex and include both external exposure and internal contamination with several radionuclides. However, in vivo and in vitro studies generally use simplified exposures, while a recent study suggested that combined external irradiation and internal contamination may induce more severe biological effects compared to single exposures. In an attempt to test the hypothesis of potential non-additive effects of multiple radiological exposures, we used a mouse model of combined external x-ray irradiation at 1 and 5 Gy and internal contamination with injection of 20 KBq ¹³⁷Cs. The results showed differential kinetics of ¹³⁷Cs elimination in irradiated animals compared to sham-irradiated, ¹³⁷Cs injected animals. Moreover, changes in plasma potassium and in relative testis weight were observed 38 days after irradiation and injection in co-exposed animals compared to ¹³⁷Cs injection alone. These results demonstrate that an external exposure combined with an internal contamination may lead to unexpected changes in biokinetics of radionuclides and biological effects compared to single exposures.

The Effect of Sheep and Cow Milk Supplementation of a Low Calcium Diet on the Distribution of Macro and Trace Minerals in the Organs of Weanling Rats

The aim of this study was to investigate the effect of either sheep or cow milk supplementation to a low calcium and phosphorus diet on growth and organ mineral distribution in weanling rats. Rats were fed diets consisting of either a control chow, a 50% reduced calcium and phosphorous chow (low Ca/P), low Ca/P and sheep milk, or low Ca/P and cow milk diet for 28 days. Food intake of the rats, the growth rate of the rats, and the concentrations of minerals in the soft organs and serum were determined. Rats fed the low Ca/P diet alone had lower weight gain than rats consuming either of the milk-supplemented diets (p < 0.05). Both sheep milk and cow milk supplementation overcame the effects of consuming a diet restricted in calcium and phosphorus but the sheep milk was effective at a significantly lower level of milk intake (p < 0.05). Significant differences (p < 0.05) in essential and trace mineral concentrations due to milk type were observed in the kidney, spleen, and liver. For non-essential minerals, significant differences (p < 0.05), related to diet, were observed in all organs for arsenic, cesium, rubidium, and strontium concentrations.

Comparison of urine and blood as a convenient and practical sample for estimating the contamination level of live cattle with radioactive cesium

Blood and urine were compared to clarify which is a better sample for estimating the concentration of radioactive cesium in muscles of live cattle. The most probable concentration of ¹³⁷ Cs in muscles was 21.0 times that in blood, and the error of this estimation was 28%. The concentration of ¹³⁷ Cs in blood was estimated accurately using urine samples. The estimation error did not increase so much (33%), even when the concentration of ¹³⁷ Cs in muscles was estimated using urine samples. On the other hand, the maximum volume of blood that can be collected with one syringe is 50 ml, whereas it is easy to collect 1,000 ml of urine. It took at least 360 min to confirm that a cow meets the legal standard by inspecting 50 ml of blood. However, with 1,000 ml of urine, a 20 min measurement time was sufficient for this purpose. This difference in the required measurement time is critically important for practical use. In addition, urine can be collected by farmers themselves, whereas the blood collection requires a veterinarian. Therefore, urine is a more convenient and practical sample for estimating the contamination level of live cattle with radioactive cesium.

Effect of dose and dose rate on temporal γ-H2AX kinetics in mouse blood and spleen mononuclear cells in vivo following Cesium-137 administration

Background

Cesium-137 (¹³⁷Cs) is one of the major and most clinically relevant radionuclides of concern in a radiological dispersal device, “dirty bomb” scenario as well as in nuclear accidents and detonations. In this exposure scenario, a significant amount of soluble radionuclide(s) may be dispersed into the atmosphere as a component of fallout. The objectives of the present study were to investigate the effect of protracted ¹³⁷Cs radionuclide exposures on DNA damage in mouse blood and spleen mononuclear cells (MNCs) in vivo using the γ-H2AX biomarker, and to develop a mathematical formalism for these processes.

Results

C57BL/6 mice were injected with a range of ¹³⁷CsCl activities (5.74, 6.66, 7.65 and 9.28 MBq) to achieve total-body committed doses of ~ 4 Gy at Days 3, 5, 7, and 14. Close to 50% of ¹³⁷Cs was excreted by day 5, leading to a slower rate of decay for the remaining time of the study; ¹³⁷Cs excretion kinetics were independent of activity level within the tested range, and the absorbed radiation dose was determined by injected activity and time after injection. Measurements of γ-H2AX fluorescence in blood and spleen MNCs at each time point were used to develop a new biodosimetric mathematical formalism to estimate injected activity based on γ-H2AX fluorescence and time after injection. The formalism performed reasonably well on blood data at 2–5 days after injection: Pearson and Spearman’s correlation coefficients between actual and predicted activity values were 0.857 (p = 0.00659) and 0.929 (p = 0.00223), respectively.

Conclusions

Despite the complicated nature of the studied biological system and the time-dependent changes in radiation dose and dose rate due to radionuclide excretion and other processes, we have used the γ-H2AX repair kinetics to develop a mathematical formalism, which can relatively accurately predict injected ¹³⁷Cs activity 2–5 days after initial exposure. To determine the assay’s usefulness to predict retrospective absorbed dose for medical triage, further studies are required to validate the sensitivity and accuracy of the γ-H2AX response after protracted exposures.

Electronic supplementary material

The online version of this article (10.1186/s12860-019-0195-2) contains supplementary material, which is available to authorized users.

Intestinal Bacteria as Powerful Trapping Lifeforms for the Elimination of Radioactive Cesium

In March 2011, an accident at the Fukushima Daiichi Nuclear Power Plant led to major problems, including the release of radionuclides such as Cesium (Cs)-137 into the environment. Ever since this accident, Cs-137 in foods has become a serious problem. In this study, we determined the concentration of Cs-137 in the feces, urine, and ruminal contents of cattle and demonstrated the possibility of its elimination from the body by intestinal bacteria. The results revealed a high Cs-137 concentration in the feces; in fact, this concentration was higher than that in skeletal muscles and other samples from several animals. Furthermore, intestinal bacteria were able to trap Cs-137, showing an uptake ratio within the range of 38–81% in vitro. This uptake appeared to be mediated through the sodium–potassium (Na⁺-K⁺) ion pump in the bacterial cell membrane. This inference was drawn based on the fact that the uptake ratio of Cs-137 was decreased in media with high potassium concentration. In addition, it was demonstrated that intestinal bacteria hindered the trapping of Cs-137 by the animal. Cattle feces showed high concentration of Cs-137 and intestinal bacteria trapped Cs-137. This study is the first report showing that intestinal bacteria contribute to the elimination of Cs-137 from the body.

Consumption of sheep milk compared to cow milk can affect trabecular bone ultrastructure in a rat model

Cow milk has a positive effect on bone health due to the effects of its protein, fat, lipid, vitamin, and mineral components. Sheep milk contains a unique composition of all of these components. However, to the best of our knowledge the benefits of sheep milk in relation to bone development have not been studied. The aim of the present study was to determine the effects of the consumption of sheep milk in comparison to cow milk on the structural and physical characteristics of growing bone in a rat model. Newly weaned male rats were fed either cow milk, sheep milk or sheep milk diluted to the same total solids content as cow milk for 28 days in addition to a basal chow. At the end of the feeding period animals were euthanized, the femora harvested and stored. The femora were analysed by μ-CT, mechanical bending tests, and ICP-MS. Rats consuming sheep milk in the trial were found to have significantly higher trabecular bone surface density and trabecular bone surface to volume ratio (p < 0.05) when compared to the rats consuming cow milk. No significant differences were observed in the mechanical properties and the mineral composition of the bones (p > 0.05). With the exception of Rb, which was found to be present in higher concentrations in rats consuming sheep milk (p < 0.05). Our results indicate that consumption of sheep milk may positively influence the structural integrity of bone, which may result in an enhancement of bone health.

Modeling the Optimum Prussian Blue Treatment for Acute Radiation Syndrome Following 137Cs Ingestion

Accidents or radiological attacks may lead to ingestion of Cs by large numbers of the public. This work models the efficacy of Prussian blue, the medical countermeasure for internal contamination with Cs, to prevent acute radiation syndrome as a function of the duration of treatment and the time that treatment starts after uptake. Risk of acute radiation syndrome is modeled using the International Commission on Radiological Protection's acute radiation hazard model. Dose rates to target organs from Cs ingestion were based on the data published by the US Environmental Protection Agency and the retention of Cs in the reference man. Modeling found that treatment is most effective if begun within 15 d of ingestion, and the course length should be at least 75 d to mitigate cancer risk and 290 d to mitigate fatalities due to acute radiation syndrome. Both of these course lengths are much longer than the minimum Prussian blue treatment regimen of 30 d. Extending the treatment time for contaminated individuals would increase demand for Prussian blue following an accident or attack and in turn, would require a larger stockpile of Prussian blue to meet demand. Not enough data is available to determine if this longer treatment time would lead to adverse medical outcomes due to the toxicity of the treatment itself.

The Distribution of Essential, Trace, and Nonessential Minerals in Weanling Male Rats Fed Sheep or Cow Milk

SCOPE

The aim of the study is to determine the effects of sheep milk consumption in comparison to cow milk on the mineral distribution in the soft organs and serum in a growing animal model system. As the mineral composition of cow and sheep milk differs, different effects on the bio-accumulations in the body may be observed. Differences in the mineral composition of cow and sheep milk may lead to different bioavailability or accumulation of minerals in the body. Newly weaned rats were fed either cow milk, sheep milk, or sheep milk diluted so that it had the same solid content as cow milk. At the end of the feeding trial, the concentration of minerals in the organs and plasma of the rats was assessed. The results indicate that the consumption of the high level of minerals in sheep milk does not have any negative effects in the rat model.

METHODS AND RESULTS

Newly weaned male rats were fed ad libitum for 28 days on either cow milk, sheep milk, or sheep milk diluted to have the same concentration of milk solids as cow milk. Animals were euthanized and the soft organs and serum were harvested and then analyzed for mineral composition by inductively coupled plasma MS. Rats fed sheep milk had lower iron concentrations in the liver and higher concentrations of rubidium and cesium in all of the soft organs. The growth rate of the rats was not affected by the type of milk consumed.

CONCLUSION

The concentration of essential and trace minerals in the liver is found to be significantly different between rats fed sheep milk compared to those fed cow milk (p < 0.05). The consumption of sheep milk does not affect the growth of animals.

Decorporation potential of lansoprazole against radiothallium (201Tl) in internally contaminated BALB/c mice and New Zealand White rabbits

INTRODUCTION:

This study examined the decorporation potential of lansoprazole (LNP) as radioactivity decorporation agent for radiothallium (²⁰¹Tl) in internally contaminated BALB/c mice and New Zealand White rabbits using radiometry and gamma scintigraphy.

METHODS:

Animals were divided into three groups, that is, control, pretreatment-1 (1X LNP), and pretreatment-2 (2X LNP). Mice received LNP intraperitoneally, while in rabbits LNP was given through oral route 0.5 and 1.5 h before radiothallium administration, respectively. Mice and rabbits used in the experiment were administered 1.48 and 11.1 MBq radiothallium (²⁰¹TlCl) through intravenous and oral route, respectively. Once started as prophylactic, LNP was continued as therapeutic twice a day till the end of study period. Radiometry and gamma scintigraphy were used to monitor radiothallium retention and uptake patterns in animals. Gamma scintigraphic images of rabbits were taken at different time intervals up to 72 h and were analyzed for comparative uptake pattern of ²⁰¹TlCl in all the groups.

RESULTS:

LNP treatment significantly increased the ²⁰¹Tl elimination over untreated control and considerably reduced the retention of ²⁰¹Tl in various tissues and organs. Decrease in radiothallium uptake up to 40% was observed in LNP-treated mice as compared to untreated control. While in rabbits, whole-body radioactivity burden at 72 h was found to be 31.24%, 26%, and 18.54% in untreated control, 9 and 18 mg/kg LNP-treated groups, respectively.

CONCLUSION:

LNP exhibited dose-dependent decorporation potential to effectively enhance the elimination of ²⁰¹Tl in mice and rabbits experimentally contaminated with ²⁰¹TlCl.

Biokinetic models for Group VB elements

This paper reviews biokinetic data for the Group VB elements vanadium, niobium, and tantalum, and presents biokinetic models describing their systemic behaviour. The model for systemic niobium in adults was developed earlier and described in Publication 134 of the International Commission on Radiological Protection. The model for niobium is used as a starting point for the development of models for vanadium and tantalum. Published biokinetic data for vanadium, including comparisons with niobium, indicate that the initial distribution of vanadium is broadly similar to that of niobium but that vanadium is less firmly fixed in most tissues and is excreted more rapidly than niobium. Biokinetic data for tantalum are more limited but suggest that its systemic behaviour closely resembles that of niobium at early times after administration. The model for niobium is proposed for application to tantalum in view of the suggested biological similarities of tantalum and niobium, their generally strong coherence in nature due to similar ionic radii and identical valence states, and the difficulties in developing parameter values directly from available data for tantalum. The proposed model for vanadium relies largely on vanadium-specific information and varies considerably from the model for niobium.

Estimation of radiocesium dietary intake from time series data of radiocesium concentrations in sewer sludge

After the Fukushima accident, it became important to determine the quantity of radionuclide ingested by inhabitants. The most common methods currently used to obtain such data are the "market basket" (MB) and "duplicate" (DP) methods. However, it is difficult to conduct monitorings using these methods with sufficient frequency as they are high cost and time-consuming. The present study proposes a new method to estimate the ingestion of radionuclides, based on the time-dependent concentrations of radiocesium in sewer sludge, which addresses the uncertainties of the two common methods. The newly proposed method, which we designate as SL, consists of three steps: (1) the separation of wet weather and dry weather data, (2) determining the mass balance of the wastewater treatment plant (WWTP), and (3) developing a reverse biokinetic model to relate the amount of radionuclides ingested to the amounts contained in the sewer sludge. We tested the new method using the time-dependent radiocesium concentrations in sewer sludge from the WWTP in Fukushima City. The results from the SL method agreed to those from the MB while overestimated those from DP method. The trend lines for all three methods, however, are in good agreement. Sensitivity analyses of SL method indicate further studies on uncertainties of sensitive parameters are deemed necessary to improve the accuracy of the method.

Cesium Removal from Human Blood by Poly(ethylene glycol)-Decorated Prussian Blue Magnetic Nanoparticles

The current oral administration of drugs for cesium (Cs) decorporation treatment are often subject to side effects and low efficiency. Therefore, it is of great significance, yet challenging, to develop novel materials and techniques for efficient removal of Cs from the human body. We report herein a new method for directly removing cesium from blood by poly(ethylene glycol)-decorated Prussian blue magnetic nanoparticles (PEG-PB MNs). The nanoparticles have been successfully synthesized by one-pot hydrothermal reaction. The adsorption of cesium in aqueous solution is a highly selective process and kinetically follows a pseudo-second-order model, which can reach equilibrium with a large capacity of 274.7 mg Cs g^-1 within one hour at 298.15 K. PEG-PB MNs were also efficiently regenerated and reused with high adsorption efficiency after five cycles. The nanoparticles successfully removed cesium ions from human blood with improved biocompatibility. The removal efficiency achieved 64 % in the blood with an initial Cs concentration of 168.4 ppb. This study provides a new approach to directly remove cesium ions from the human body by utilizing biocompatible Prussian blue magnetic nanoparticles.

Evaluation of Reference Urinary Excretion Concentrations of Selected Radionuclides Corresponding to Clinical Decision Guides for Application in Radiological and in Nuclear Emergencies

Radiological or nuclear emergency situations could lead to incorporation of radionuclides by the population. Intakes of radionuclides can be evaluated through measurements of radionuclides present in organs and tissues, or in urinary and/or fecal excretion. In an emergency situation involving a large number of people, the decision to provide medical treatment to an individual will likely be based on a single measurement. For that purpose, the National Council on Radiation Protection and Measurements (NCRP) has presented the Clinical Decision Guide (CDG) quantity, which corresponds to an intake amount of a radionuclide by an individual for which treatment is recommended. However, the NCRP recommends using one-fifth of the CDG for pregnant women and children which could result in an effective or equivalent dose in excess of the dose constraint. Tables of reference urinary excretion concentrations which are associated with an intake of one CDG for inhalation and ingestion intake scenarios of several forms of 60Co, 90Sr, 137Cs, 192Ir, 238Pu, 239Pu and 241Am have been calculated and are presented for the following categories of members of the public: 3 months old, 1 y, 5 y, 10 y, 15 y, adult and pregnant woman.

The Incorporation of Radionuclides After Wounding by a "Dirty Bomb": The Impact of Time for Decorporation Efficacy and a Model for Cases of Disseminated Fragmentation Wounds

Objective: In the case of a terrorist attack by a "dirty bomb" there is a risk of internal contamination with radionuclides through inhalation and wounds. We studied the efficacy of a decorporation treatment depending on the initiation time and duration. Approach: Based on biokinetic models, we simulated the impact of different diethylenetriaminepentaacetic acid treatments on the committed effective dose after the incorporation of plutonium-239. Results: For the same level of radioactivity, the dose was higher after the fast absorption from the wound than after a slow invasion following inhalation. The impact of the treatment initiation time was particularly important in the case of the internal contamination through the wound. Ending the treatment at an early point in time was followed by an augmentation of radioactivity in the blood compartment, reflecting insufficient treatment duration. Treatment efficacy increased only marginally if extended over 90 days. Innovation and Conclusion: For plutonium-239, the committed effective dose and the impact of the treatment initiation time on therapeutic efficacy predominantly depend on the speed of invasion, i.e., the pathway and the physicochemical properties of the compounds involved. Thus, it is prudent to start decorporation therapy as soon as possible, as a loss of efficacy resulting from a delay in treatment initiation cannot be compensated later on. In the case of plutonium-239 incorporation, the treatment must be continued for several months. Multiple fragmentation wounds might be aggregated to a single wound model suited for internal dosimetry calculations by using the "rule of nine."

In situ synthesis of Prussian blue nanoparticles within a biocompatible reverse micellar system for in vivo Cs+uptake

A Prussian blue reverse micellar system forin vivoCs⁺uptake exhibiting high efficiency and a significant dose effect.

Alkali metals levels in the human brain tissue: Anatomical region differences and age-related changes

The link between trace elements imbalances (both "toxic" and "essential") in the human brain and neurodegenerative disease has been subject of extensive research. More recently, some studies have highlighted the potential role of the homeostasis deregulation of alkali metals in specific brain regions as key factor in the pathogenesis of neurodegenerative diseases such as multiple sclerosis and Alzheimer's disease. Using flame atomic emission spectrometry and inductively coupled plasma-mass spectrometry after microwave-assisted acid digestion of the samples, alkali metals (Na, K, Li, Rb and Cs) were determined in 14 different areas of the human brain (frontal cortex, superior and middle temporal gyri, caudate nucleus, putamen, globus pallidus, cingulated gyrus, hippocampus, inferior parietal lobule, visual cortex of the occipital lobe, midbrain, pons, medulla and cerebellum) of adult individuals (n=42; 71±12, range: 50-101 years old) with no known history and evidence of neurodegenerative, neurological or psychiatric disorder. Potassium was found as the most abundant alkali metal, followed by Na, Rb, Cs and Li. Lithium, K and Cs distribution showed to be quite heterogeneous. On the contrary, Rb and Na appeared quite homogeneously distributed within the human brain tissue. The lowest levels of Na, K, Rb and Li were found in the brainstem (midbrain, medulla and pons) and cerebellum, while the lowest levels of Cs were found in the frontal cortex. The highest levels of K (mean±sd; range 15.5±2.5; 8.9-21.8mg/g) Rb (17.2±6.1; 3.9-32.4μg/g and Cs (83.4±48.6; 17.3-220.5ng/g) were found in putamen. The highest levels of Na and Li were found in the frontal cortex (11.6±2.4; 6.6-17.1mg/g) and caudate nucleus (7.6±4.6 2.2-21.3ng/g), respectively. Although K, Cs and Li levels appear to remain largely unchanged with age, some age-related changes were observed for Na and Rb levels in particular brain regions (namely in the hippocampus).

THREE-YEAR RETENTION OF RADIOACTIVE CAESIUM IN THE BODY OF TEPCO WORKERS INVOLVED IN THE FUKUSHIMA DAIICHI NUCLEAR POWER STATION ACCIDENT

Direct measurements of seven highly exposed workers at the Tokyo Electric Power Company Fukushima Daiichi Nuclear Power Station accident have been performed continuously since June 2011. Caesium clearance in the monitored workers is in agreement with the biokinetic models proposed by the International Commission on Radiological Protection. After 500 d from the initial measurement, however, the caesium clearance slowed. It was thought to be unlikely that additional Cs intake had occurred after the initial intake, as activity in foods was kept low. And, the contribution from the detector over the chest was enhanced with time. This indicates that insoluble Cs particles were inhaled and a long metabolic rate showed.

INITIAL AND PRESENT SITUATION OF FOOD CONTAMINATION IN JAPAN AFTER THE ACCIDENT AT THE FUKUSHIMA DAI-ICHI NUCLEAR POWER PLANT

The accident at the Fukushima Dai-ichi Nuclear Power Plant (NPP) in March 2011 affected not only the terrestrial environment of Fukushima prefecture and the surrounding area, but also the marine area facing the NPP. Our present study is focused on the concentrations of radionuclides in agricultural products of Fukushima and sea-foods collected off Fukushima after the accident. The regulation value for radiocesium in vegetables, meat and fish was revised from 500 Bq/kg-wet to 100 Bq/kg-wet on 1 April 2012. The overall activity of radiocesium in these products was found to be within the limit of tolerance in respect to Japanese and also international regulations, but there is still radiocesium found at activities greater than this level in edible wild plants, wild mushrooms and game such as boar meat. Although the activities of radionuclides exceeding the regulatory limits were not detected in marine products collected off Fukushima after April 2015, the commercial marine fishery has not received approval in the affected areas except for certain species. We learned from the Fukushima accident that long-term kinetic studies of radionuclides in terrestrial and marine environments is extremely important for prevention of internal contamination, since contamination with radionuclides occurs via the food chain in the environment.

Evaluation of Chlorella as a Decorporation Agent to Enhance the Elimination of Radioactive Strontium from Body

Background

Release of radionuclides, such as ¹³⁷Cs and ⁹⁰Sr, into the atmosphere and the ocean presents an important problem because internal exposure to ¹³⁷Cs and ⁹⁰Sr could be very harmful to humans. Chlorella has been reported to be effective in enhancing the excretion of heavy metals; thus, we hypothesized that Chlorella could also enhance the elimination of ¹³⁷Cs or ⁹⁰Sr from the body. We evaluated the potential of Chlorella as a decorporation agent in vitro and in vivo, using ⁸⁵Sr instead of ⁹⁰Sr.

Methods

In vitro experiments of adsorption of ¹³⁷Cs and ⁸⁵Sr to Chlorella were performed under wide pH conditions. The maximum sorption capacity of Chlorella to strontium was estimated using the Langmuir model. A ⁸⁵Sr solution was orally administrated to mice pretreated with Chlorella. At 48 h after ⁸⁵Sr administration, the biodistribution of radioactivity was determined.

Results

In the in vitro experiments, although ⁸⁵Sr barely adsorbed to Chlorella at low pH, the ⁸⁵Sr adsorption ratio to Chlorella increased with increasing pH. The maximum sorption capacity of Chlorella to strontium was 9.06 mg / g. ¹³⁷Cs barely adsorbed to Chlorella under any pH conditions. In the biodistribution experiments, bone accumulation of radioactivity after ⁸⁵Sr administration was significantly decreased in the Chlorella pretreatment group compared with the non-treatment control group.

Conclusions

In conclusion, these results indicated that Chlorella could inhibit the absorption of ⁹⁰Sr into the blood and enhance the elimination of ⁹⁰Sr from the body through adsorption in intestine. Further studies are required to elucidate the mechanism and the components of Chlorella needed for adsorption to strontium and could promote the development of more effective decorporation agents.

γ-H2AX Kinetic Profile in Mouse Lymphocytes Exposed to the Internal Emitters Cesium-137 and Strontium-90

In the event of a dirty bomb scenario or an industrial nuclear accident, a significant dose of volatile radionuclides such as 137Cs and 90Sr may be dispersed into the atmosphere as a component of fallout and inhaled or ingested by hundreds and thousands of people. To study the effects of prolonged exposure to ingested radionuclides, we have performed long-term (30 day) internal-emitter mouse irradiations using soluble-injected 137CsCl and 90SrCl2 radioisotopes. The effect of ionizing radiation on the induction and repair of DNA double strand breaks (DSBs) in peripheral mouse lymphocytes in vivo was determined using the γ-H2AX biodosimetry marker. Using a serial sacrifice experimental design, whole-body radiation absorbed doses for 137Cs (0 to 10 Gy) and 90Sr (0 to 49 Gy) were delivered over 30 days following exposure to each radionuclide. The committed absorbed doses of the two internal emitters as a function of time post exposure were calculated based on their retention parameters and their derived dose coefficients for each specific sacrifice time. In order to measure the kinetic profile for γ-H2AX, peripheral blood samples were drawn at 5 specific timed dose points over the 30-day study period and the total γ-H2AX nuclear fluorescence per lymphocyte was determined using image analysis software. A key finding was that a significant γ-H2AX signal was observed in vivo several weeks after a single radionuclide exposure. A mechanistically-motivated model was used to analyze the temporal kinetics of γ-H2AX fluorescence. Exposure to either radionuclide showed two peaks of γ-H2AX: one within the first week, which may represent the death of mature, differentiated lymphocytes, and the second at approximately three weeks, which may represent the production of new lymphocytes from damaged progenitor cells. The complexity of the observed responses to internal irradiation is likely caused by the interplay between continual production and repair of DNA damage, cell cycle effects and apoptosis.