Dose estimates to the public from 210Po ingestion via dietary sources at Kalpakkam (India).

Distribution of one of the natural radionuclides 210Po activity in food of plant origin such as cereals, pulses, vegetables and food of animal origin such fish, crab, prawn, chicken, egg etc. were determined in and around Kalpakkam upto a distance of 32 km radius. The general range of 210Po activity levels in all the dietary components (excluding milk and drinking water which are reported in mBq l(-1)) ranged widely from < or = 10 to 122,641 mBq kg(-1) fresh, the minimum being in vegetables and maximum being in the edible portions (muscle) of crab samples. 210Po levels in drinking water and milk samples ranged between 0.6-2.6 and 8-12 mBq l(-1) respectively. 210Po content in cereals ranged from < or = 32 to 745 mBq kg(-1) and in pulses it was found to vary between < or =32 and 294 mBq kg(-1). The range of 210Po activity in different types of vegetables was found to be < or = 10-653 mBq kg(-1). Among the different varieties of vegetables, 210Po was significantly higher in leafy vegetables (28-653 mBq kg(-1)) as compared to rooty and other types of vegetables which ranged from < or = 10-180 mBq kg(-1). In food of animal origin, the observed minimum activity of 210Po was 8 mBq l(-1) in milk and the maximum observed was 122,641 mBq kg(-1) in the muscles of crab. It was also observed that 210Po activity was found to be in higher levels in the food of aquatic animal origin (1414-122,641 mBq kg(-1)) than in the food of terrestrial animal origin (other than milk) which varied from 41 to 963 mBq kg(-1). It is evident from the present study that the foods of animal origin especially crab, fish and prawn deliver significantly greater dose (93-3364 microSv yr(-1)) to the public compared to foods of plant origin whose mean dose ranged 0.08-128 microSv yr(-1). The study showed evidence to suggest that the total ingestion dose due to 210Po received by the Kalpakkam public through dietary sources is significantly higher than the ingestion dose received due to fallout sources such as 137Cs and 90Sr.     

Estimation of annual effective dose due to ingestion of natural radionuclides in foodstuffs and water at a proposed uranium mining site in India

Abstract

Purpose: To study the distribution of ²¹⁰Po, ²²⁶Ra, ²³⁰Th and U(nat) (naturally occurring radioisotopes of uranium [²³⁴U, ²³⁵U and ²³⁸U]) in food and water around the Bagjata uranium mining area in India.

Materials and methods: Radionuclides were analyzed in food samples of plant and animal origin after acid digestion. Intake and ingestion dose of the radionuclides were estimated.

Results: ²¹⁰Po, ²²⁶Ra, ²³⁰Th and U(nat) in all the dietary components ranged widely from < 0.2–36, < 0.02–1.58, < 0.01–2.8 and < 0.017–0.39 Bqkg^-1, respectively. The range of ²²⁶Ra and U(nat) in water was < 3.5–206 and < 12.6–693 mBql^?1, respectively. The intake of radionuclides considering food and water was calculated to be 760 BqY^?1 while the ingestion dose was 601 μSvY^?1. The estimated doses reflect the natural background dose via route of ingestion, which is below the 1 mSvY^?1 limit set by the International Commission on Radiological Protection (ICRP). However, the doses are more than the dose constraint of 300 μSvY^?1 as suggested by the ICRP for members of the public for planned disposal of long-lived radioactive waste.

Conclusion: The study confirms that current levels of radionuclides do not pose significant radiological risk to the local inhabitants, but they need close investigation in the near future.     

Natural radionuclides in fish species from surface water of Bagjata and Banduhurang uranium mining areas,East Singhbhum,Jharkhand, India

Purpose:?To study the natural radionuclides in the freshwater fish samples around the uranium mining areas of Bagjata and Banduhurang, East Singhbhum, Jharkhand, India

Materials and methods:?The naturally occurring radioisotopes of uranium, U(nat), consisting of ²³⁴U, ²³⁵U and ²³⁸U; ²²⁶Ra, ²³⁰Th and ²¹⁰Po were analysed in the fish samples from the surface water of Bagjata and Banduhurang mining areas after acid digestion. The ingestion dose, concentration factor and excess lifetime cancer risk of the radionuclides were estimated.

Results:?The geometric mean activity of U(nat), ²²⁶Ra, ²³⁰Th and ²¹⁰Po in the fish samples was found to be 0.05, 0.19, 0.29 and 0.95 Bq kg^?1_fresh (Becquerel per kilogram fresh fish), respectively, in the Bagjata mining area, while for Banduhurang mining area it was estimated to be 0.08, 0.41, 0.22 and 2.48 Bq kg^?1_fresh, respectively. The ingestion dose was computed to be 1.88 and 4.16?μSvY^?1, respectively, for both the areas which is much below the 1 mSv limit set in the new International Commission on Radiological Protection (ICRP) recommendations. The estimation of the Concentration Factors (CF) reveal that the CF from water is greater than 1 l/kg^?1in most of the cases while from sediment CF is less than 1. The excess individual lifetime cancer risk due to the consumption of fish was calculated to be 2.53?×?10^?5 and 6.48?×?10^?5, respectively, for Bagjata and Banduhurang areas, which is within the acceptable excess individual lifetime cancer risk value of 1?×?10^?4.

Conclusion:?The study confirms that current levels of radioactivity do not pose a significant radiological risk to freshwater fish consumers.     

226Ra 228Ra 210Pb和210Po在水生生物及食物链中转移规律的探讨

目的 为了解天然放射性核素²²⁶Ra、²²⁸Ra、²¹⁰Pb与²¹⁰Po在水生物及食物链中转移和蓄积情况。方法 定点采集养殖水产品及栖息环境中水与底质沉积物, 按不同的实验需要, 每个鲜样分别剥取肉, 骨(壳),鳞片和胃肠。烹饪样品, 洗净、称重、清炖, 熟后分离出骨(壳),余为食物。样品分别测定²²⁶Ra、²²⁸Ra、²¹⁰Pb和²¹⁰Po含量。数据按统计学要求处理, 配对数据, 作了配对显着性检验。结果 ²²⁶Ra、²²⁸Ra和²¹⁰Pb主要沉积于骨(壳)中, 浓集系数为10²～10³,肉中为10⁰～10².²¹⁰Po主要蓄积在水生物胃肠中, 浓集系数在10²～10⁴,鱼类胃肠与贝类肉中可达10⁴.水产食品烹饪加工过程²²⁶Ra、²²⁸Ra和²¹⁰Pb在食物链中转移不明显, 经配对显着性检验, 差异无显着性(P0.05);然而210Po在淡水鱼类和虾类中转移是明显的, 肉配对检验有非常显着性差别(P<0.01).结论水生物对²²⁶Ra、²²⁸Ra、²¹⁰Pb和²¹⁰Po有很强浓集能力。     

Aspects of the geographical variations of naturally occurring 210Pb/210Po in permanent teeth of juveniles in the UK

Purpose: To study geographical variations in the level of naturally occurring ²¹⁰Pb‐supported ²¹⁰Po in permanent teeth of juveniles in the UK.

Materials and methods: Permanent teeth extracted from 278 juveniles for orthodontic purposes were obtained from 48 counties in the UK. ²¹⁰Po activity concentration was measured on the outer enamel surface using TASTRAK α‐particle‐sensitive plastic track detectors.

Results: Geometric mean±SE activity concentrations in teeth from urban, suburban and rural areas, excluding the high radon area of Devon, were 8.41 +0.25/?0.24, 7.76 +0.37/?0.35 and 7.20 +0.49/?0.46?Bq?kg^?1, respectively. Overall, there was no significant association between α‐activity on the outer enamel surface of permanent teeth and proximity to the major UK motorways. However, when the data were considered with respect to the prevailing south‐westerly wind on the western side of the UK, a statistically significant association with respect to donors living downwind (on the easterly side) of the motorways was found. This effect was greater for sections of the M5 and M6 motorways that traverse urban areas. ²¹⁰Po levels in teeth were also associated with domestic radon concentration. This effect was comparable with that from traffic and urban pollution.

Conclusions: Higher levels of ²¹⁰Pb‐supported ²¹⁰Po are seen in permanent teeth of juveniles near sources of increased exposure in the UK. Inhalation uptake is an important pathway of exposure, especially with respect to domestic radon exposure. The results might be important in assessing integrated exposure to ²¹⁰Po in the skeleton and consequent high linear energy transfer dose to bone marrow.     

Evaluation of uncertainty and detection limits in Pb and Po measurement in water by alpha spectrometry using Po spontaneous deposition onto a silver disk

An easy and accurate method for the determination of ²¹⁰Pb and ²¹⁰Po in water using ²¹⁰Po spontaneous deposition onto a silver disk is proposed and assessed for its detection capabilities according to the ISO Guide for the expression of uncertainty in measurement (GUM) and ISO Standard 11929-7 concerning the evaluation of the characteristic limits for ionizing radiation measurements. The method makes no assumption on the initial values of the activity concentrations of ²¹⁰Pb, ²¹⁰Bi and ²¹⁰Po in the sample to be analyzed, and is based on the alpha spectrometric measurement of ²¹⁰Po in two different aliquots: the first one measured five weeks after the sampling date to ensure radioactive equilibrium between ²¹⁰Pb and ²¹⁰Bi and the second after a sufficient time for the ingrowth of ²¹⁰Po from ²¹⁰Pb to be significant. As shown, for a recommended time interval of seven months between ²¹⁰Po measurements, the applicability of the proposed method is limited to water samples with a ²²⁶Ra to ²¹⁰Pb activity ratio C_Ra/C_Pb≤4, as usual in natural waters. Using sample and background counting times of 24 h and 240 h, respectively, the detection limit of the activity concentration of each radionuclide at the sampling time for a 1 L sample typically varies between 0.7 and 16 mBq L⁻¹ for ²¹⁰Pb in water samples with an initial activity of ²¹⁰Po in the range 0-200 mBq L⁻¹, and between 0.6 and 8.5 mBq L⁻¹ for ²¹⁰Po in water samples with an initial activity of ²¹⁰Pb in the same range.     

Optimisation study of α-cyclotron production of At-211/Po-211g for high-LET metabolic radiotherapy purposes

The production of no-carrier-added (NCA) α-emitter ²¹¹At/^211gPo radionuclides for high-LET targeted radiotherapy and immunoradiotherapy, through the ²⁰⁹Bi(α,2n) reaction, together with the required wet radiochemistry and radioanalytical quality controls carried out at LASA is described, through dedicated irradiation experiments at the MC-40 cyclotron of JRC-Ispra. The amount of both the γ-emitter ²¹⁰At and its long half-lived α-emitting daughter ²¹⁰Po is optimised and minimised by appropriate choice of energy and energy loss of α particle beam. The measured excitation functions for production of the main radioisotopic impurity ²¹⁰At→²¹⁰Po are compared with theoretical predictions from model calculations performed at ENEA.     

Morphological features of the microdistribution of naturally occurring 210Pb/210Po and 226Ra in the teeth of children and juveniles

Purpose: To examine the microdistribution of natural α‐radioactivity in deciduous teeth of children and the permanent teeth of juveniles extracted for orthodontic purpose from across the UK.

Materials and methods: The microdistribution of ²¹⁰Pb‐supported ²¹⁰Po and ²²⁶Ra in 708 deciduous and permanent teeth and 32 foetal teeth was measured on 1442 TASTRAK α‐particle track detectors.

Results: Of the various findings, a number are of special interest. Around half of the ²¹⁰Pb activity in the outer enamel of deciduous teeth appears to have been acquired in utero as a result of transplacental transfer. In deciduous and permanent teeth, ²²⁶Ra is concentrated mainly in the circumpulpal region, while the highest levels of ²¹⁰Po are on the highly calcified outer enamel surface. Furthermore, activity concentrations recorded on this surface were ln‐normally distributed.

Conclusions: ²¹⁰Pb‐supported ²¹⁰Po activity on the outer enamel surface of permanent teeth constitutes an assay of cumulative environmental exposure with which to assess exposure in bone, both in utero and in childhood. Such assessment can be used to study geographical variations in the α‐activity in teeth. More work is also required to determine the concentrations of both ²¹⁰Po and ²¹⁰Pb in the foetal skeleton.     

Influence of heavy metals upon the retention and mobilization of polonium‐210 in rats

Purpose: To provide information about the tissue retention and mobilization of the alpha‐emitting radionuclide, polonium‐210 (²¹⁰Po), in rats under combined exposure to heavy metal ions and the chelating agent, 2, 3‐dimercaptopropane‐1‐sulfonate (DMPS).

Materials and methods: Rats were pre‐exposed intraperitoneally to either CdCl₂ or Pb(CH₃COO)₂. 9 or 15?h later they received ²¹⁰Po nitrate intravenously. The retention and excretion of ²¹⁰Po via the urine and faeces of pre‐exposed rats, as well as in pre‐exposed rats treated with DMPS, were followed. The radioactivity due to ²¹⁰Po in a broad spectrum of body tissues and excreta was measured by the liquid scintillation counting after sample digestion in a mixture of perchloric acid and hydrogen peroxide. The immunohistochemical localization of metallothioneins (MT) was studied using a mixture of murine monoclonal antibodies directed against MT I+II.

Results: The present study revealed different tissue distributions of polonium‐210 in the rats pre‐exposed to lead or cadmium ions when compared with that in ²¹⁰Po only controls. Under combined exposure to Pb or Cd, the spontaneous excretion of ²¹⁰Po was enhanced and could be further enhanced by treatment with DMPS. Treatment with this chelator was efficient even when its start was postponed until 24h after internal contamination of the body with ²¹⁰Po.

Conclusions: Polonium‐210 is bound in vivo to binding sites on various biomolecules, among them erythrocytic enzymes and MT. This phenomenon explains the different affinity and overall distribution of ²¹⁰Po in control body tissues. When the appropriate binding sites are occupied by lead or cadmium, enhanced natural excretion of polonium‐210 occurs.     

Low dose radiation induced immunomodulation: Effect on macrophages and CD8+ T cells

Purpose: The aim of the present investigation was to study the effect of fractionated whole body low dose ionizing radiation (LDR) on the functional responses of T lymphocytes, their subpopulations and macrophages.

Materials and methods: C57BL/6 mice were exposed to 4 cGy from a ⁶⁰Co source, at 0.31 cGy/min, at 24 h intervals for 5 days (total dose 20 cGy). Phagocytic activity was measured by flow cytometry using Bioparticles® and nitric oxide generation was estimated by spectrophotometry. Proliferation of lymphocytes in response to concanavalin A (con A) and alloantigens was measured by ³H thymidine incorporation. Expression of cell surface markers was assessed by flow cytometric analysis of antibody labeled cells. Target cell killing by cytotoxic T cells (CTL) generated against allogenic cells was assessed by flow cytometry using PKH26 labeled target cells. Cytokines were estimated by enzyme linked immunosorbent assay.

Results: Exposure to LDR enhanced nitric oxide secretion and phagocytosis. The expression of early activation antigen, CD69, was enhanced in CD8⁺ T lymphocytes concomitant with enhanced proliferation in response to con A. In addition, mixed lymphocyte reaction (MLR) and CTL response were augmented and secretion of interferon gamma (IFN-γ) was suppressed following LDR exposure.

Conclusions: LDR exposure enhanced the function of macrophages and responses of CD8⁺ T cells in C57BL/6 mice.     

应对福岛核事故我国食品和饮用水的放射性监测

目的 汇总分析日本福岛核电站事故发生后我国沿海城市和主要内陆城市食品和饮用水放射性的抽样监测结果,评价是否对我国居民的健康造成影响.方法 根据国家标准方法,制定应对日本福岛核事故对我国食品和饮用水的监测方案,统一数据报送格式,对数据进行对比分析.结果 4月2日北京露天生长菠菜样品中,监测到极微量的人工放射性核素131I,此后在全国范围内10种露天生长的蔬菜中也检测出131I,最高值为菠菜样品3.1 Bq/kg,到5月初未再检测出.牛奶、海产品和饮用水样品中未检测到人工放射性核素.结论 监测到的蔬菜中131I来自日本福岛核电站事故释放,与此次事故期间欧洲一些国家食品中的的131I水平相一致,远低于1986年切尔诺贝利核电站事故时我国蔬菜中131I活度,其对公众所致吸收剂量极其微小,不会对我国境内公众造成影响.     

2017—2020年北京地区大气气溶胶中7 Be和210 Pb放射性活度浓度监测与分析

目的 监测与分析2017—2020年北京地区大气气溶胶中⁷Be和²¹⁰Pb放射性活度浓度变化情况,为有效防治空气污染提供科学依据。方法 利用大流量空气气溶胶采样器（SnowWhite）采集气溶胶样品1 074份,其中春季、夏季、秋季和冬季分别采集275、266、262和271份。使用低本底高纯锗伽马谱仪（ORTEC）分析气溶胶样品中⁷Be和²¹⁰Pb放射性活度浓度。结果 2017—2020年北京地区大气气溶胶中⁷Be放射性活度浓度的变化范围为0.56~14.84 mBq/m³,平均值为6.84 mBq/m³。²¹⁰Pb放射性活度浓度的变化范围为0.01~9.37 mBq/m³,平均值为3.19 mBq/m³。2017—2020年北京大气气溶胶⁷Be和²¹⁰Pb放射性活度浓度在春、夏、秋、冬四季中差异均有统计学意义（F=32.66、93.93,P<0.05）,其中⁷Be放射性活度浓度春季最高,秋季次之,夏季和冬季最低,²¹⁰Pb放射性活度浓度由高到低分别为冬季、秋季、春季、夏季。结论 2017—2020年北京地区大气气溶胶中⁷Be和²¹⁰Pb放射性活度浓度处于正常涨落水平范围内。     

On the variation of the 210Po half-life at low temperature

Experiments were performed to verify the possible influence of the temperature and source matrix on the half-life of ²¹⁰Po. Since the precise measurement of the activity of an α-emitting source at cryogenic temperature is far from trivial, a simpler approach was used: the activity of a ²¹⁰Po source was measured at ambient temperature, but in between the measurements, the source was cooled down during a few weeks in a liquid helium Dewar. A ²¹⁰Po solid source was prepared by electro-deposition on a silver plate. The activity of this source was first measured at room temperature, using the defined solid angle α measurement method. The source was then placed in a specific gastight container inside a liquid helium bath at 4 K during 28 days. Then the source was heated up and measured again using the same instrument in the same geometric conditions. The same experiment was repeated with the source coated with a thin layer of silver, in order to be sure that the radioactive material was fully embedded inside the metallic matrix. Our experiments showed no evidence of ²¹⁰Po half-life change at low temperature. A reduction of the half-life of ²¹⁰Po by 6.3% at low temperature, as claimed by Raiola et al. (2007), would have lead to a decay-corrected activity reduction of about 1% after 29 days, which would have been easily detectable.The paper describes the steps of this experiment and gives a detailed uncertainty budget for the measurements. The half-life of ²¹⁰Po obtained in each measurement is compared with the evaluated value of (138.3763±0.0017) d.     

云南芒市地区野生食用蘑菇中137Cs、40K含量及所致居民剂量估算

目的 检测可食用野生蘑菇中人工放射性核素¹³⁷Cs和天然放射性核素⁴⁰K的含量及分布特点,计算野生蘑菇中放射性核素水平及其所致剂量。方法 采集了产自云南省芒市的18类33份可食用野生蘑菇样品,用实验室低本底高纯锗（HPGe）γ谱仪分析了其中放射性核素¹³⁷Cs、⁴⁰K的含量。结果 33份样品中,仅1份样品¹³⁷Cs的含量在探测限之下,其余32份样品中均可检测出¹³⁷Cs,比活度范围值为0.45~339.58 Bq/kg（干重）,平均值25.47 Bq/kg（干重）。所有样品均检测出天然放射性核素⁴⁰K,核素比活度最小值和最大值分别为453.4、1 882.6 Bq/kg（干重）,平均值为815.1 Bq/kg（干重）。当去除只有1个样品数的蘑菇种类后,毛钉菇、美味牛肝菌、白牛肝菌、锈盖粉孢牛肝菌、香菇、茶褐牛肝菌6个种类蘑菇间¹³⁷Cs含量差异有统计学意义（F=21.13,P<0.05）,而⁴⁰K含量差异无统计学意义。结论 6类不同蘑菇中¹³⁷Cs含量不同,其中毛钉菇、香菇中人工放射性核素¹³⁷Cs含量相对较高。但食入此类蘑菇对成人所致待积有效剂量极其微小,不会影响健康。     

核医学场所空气中131I浓度监测及工作人员内照射剂量评价探讨

目的 了解医疗机构¹³¹I治疗工作场所空气中¹³¹I核素的活度浓度水平，探讨通过空气采样方法估算工作人员内照射剂量的方法并分析其影响因素。方法 选取郑州市10家开展¹³¹I核素治疗的工作场所，采用空气采样方法采集¹³¹I治疗工作场所中放射性气溶胶，用高纯锗γ能谱仪进行γ放射性核素测定并推算工作场所空气中¹³¹I核素的活度浓度水平，根据测量结果和现场调查结果估算放射工作人员因¹³¹I核素吸入导致的内照射剂量。结果 19个分装间空气样品的¹³¹I活度浓度为0.087~570 Bq/m³，平均为（51.04±128.58）Bq/m³；11个病房空气样品的¹³¹I活度浓度为0.162~54.6 Bq/m³，平均为（7.97±15.89）Bq/m³。根据GBZ 129-2016《职业性内照射个人监测规范》推荐的典型工作时间估算，放射工作人员由于吸入¹³¹I核素导致的年待积有效剂量范围为2 μSv~10 mSv，平均为（0.61±1.80）mSv，年有效剂量均未超过国家标准所规定的剂量限值。结论 郑州市10家医疗机构核医学工作场所中¹³¹I核素活度浓度较高的样品多分布在甲状腺癌住院患者较多、核素操作量较大的三甲医院，由此导致的工作人员内照射剂量不容忽视。根据空气样品的测量结果估算内照射剂量带有很大不确定度，但空气采样方法可及时发现异常或事故情况下的放射性污染，为工作人员开展体外直接测量和内照射评价提供预警。     

Chronic exposure by ingestion of environmentally relevant doses of 226Ra leads to transient growth perturbations in fathead minnow (Pimephales promelas,Rafinesque, 1820)

Abstract

Purpose: To assess the impact of environmentally relevant levels of ingested ²²⁶Ra on a common freshwater fish species.

Methods: Fathead minnow (Pimephales promelas, Rafinesque) were obtained at the first feeding stage and established on a commercial fish food diet containing ²²⁶Ra in the activity range 10 mBq/g^?1, –10,000 mBq/g^?1. They remained on this diet for 24 months and were sampled invasively at 1,6,18 and 24 months to assess growth, biochemical indices and accumulated dose and non-invasively also at 12 and 15 months to assess growth.

Results: Fish fed 10 and 100 mBq/g^?1 diet showed a small transitory deregulation of growth at 6 and 12 months. Fish fed higher activities showed less significant or insignificant effects. There was a trend at 18 months which was stronger at 24 months for the population distribution to change in all of the ²²⁶Ra fed groups so that smaller fish were smaller and bigger fish were bigger than the controls. There were also significant differences in the ratios of protein:DNA at 24 months which were seen as a trend but were not significant at earlier time points.

Conclusions: Fish fed a radium diet for 2 years show a small and transitory growth dysregulation at 6 and 12 months. The effects predominate at the lower activities suggesting hormetic or homeostatic adjustments. There was no effect on growth of exposure to the high activities ²²⁶Ra. This suggests that radium does not have a serious impact on the ecology of the system and the level of radium that would be transferred to humans is very low. The results may be important in the assessment of long-term environmental impacts of ²²⁶Ra exposure.     

Activity size distributions for long-lived radon decay products in aerosols collected in Barcelona (Spain)

The activity median aerodynamic diameters (AMADs) of long-lived radon decay product (²¹⁰Pb, ²¹⁰Po) in aerosols collected in the Barcelona area (Northeast Spain) during the period from April 2006 to February 2008 are presented. The ²¹⁰Po mean AMAD was 420 nm, while the ²¹⁰Pb mean AMAD was 500 nm. The temporal evolution of ²¹⁰Pb and ²¹⁰Po AMADs shows maxima in autumn and winter and minima in spring and summer. ²¹⁰Pb AMAD are being used to estimate the mean-residence time of atmospheric aerosols.     

Repeated 0.5-Gy γ-ray irradiation attenuates autoimmune manifestations in MRL-lpr/lpr mice

Purpose: MRL-lpr/lpr mice, a model for various autoimmune diseases, were repeatedly irradiated with 0.5 Gy of γ-rays, and changes in their autoimmune manifestations were investigated.

Materials and methods: MRL-lpr/lpr mice at 13 weeks of age were maintained in plastic cages and exposed whole-body to 0.5 Gy γ-ray irradiation from a ¹³⁷Cs source 5 times per week for 4 weeks, from the time they were 13 weeks old until they reached 17 weeks old. Changes of autoimmune manifestations were examined 3 weeks later at the 20th week.

Results: Splenomegaly, lymphadenopathy, and proteinuria in MRL-lpr/lpr mice were clearly ameliorated by a total dose of 10 Gy (0.5 Gy/day×5 days/week for 4 weeks). Histologically severe disease-specific damage to the kidney and the salivary gland, i.e., glomerulonephritis and sialoadenitis, was also improved after irradiation. CD3⁺ CD4^? CD8^? CD45R/B220⁺ T cell numbers, which proliferate abnormally in MRL-lpr/lpr mice, were significantly decreased by the irradiation, possibly through induction of apoptosis. The elevated NO₂^? and NO₃^? (NO_x^?) production by macrophages of MRL-lpr/lpr mice was lowered by the irradiation. The irradiation also prolonged the life span of MRL-lpr/lpr mice. These phenomena may contribute to the amelioration of autoimmune manifestations in MRL-lpr/lpr mice exposed to repeated small-doses of γ-rays.

Conclusions: Repeated small-dose γ-ray exposure ameliorates the autoimmune manifestations in MRL-lpr/lpr model mice.     

Monte Carlo-simulated Auger electron spectra for nuclides of radiobiological and medical interest – a validation with noble gas ionization data

Abstract

Purpose: To further validate Monte Carlo calculation codes simulating cascades of Auger electron transitions in radionuclides that decay by electron capture or internal conversion. In particular, the need for an appropriate kinetic energy determination of the Auger electrons emitted from multiple-ionized atoms as well as the consideration of shake-off electrons would be investigated implicitly.

Methods: Charge distributions of noble gases after photoionization for different photon energies were calculated and compared with experimental data from the literature. In addition, new electron emission spectra were generated for ^99mTc and ¹²³I.

Results: By including strict energy book-keeping and allowing shake-off electrons, the agreement between experimentally detected charge distributions and Monte Carlo simulations was very good. On this basis, the number of emitted electrons per decay was found to be between 1 and 17 with a mean of 4.0 for ^99mTc and between 1 and 26 with a mean of 7.4 for ¹²³I.

Conclusions: Because of the good agreement with the experimental findings, the validation can be considered to be successful.     

Effect of 211At α-particle irradiation on expression of selected radiation responsive genes in human lymphocytes

Purpose: Analysis of the relative expression of radiation responsive genes (previously shown to respond to γ-radiations) after exposure of human lymphocytes to ²¹¹At α-particles and the suitability of these genes as potential markers for α-biodosimetry.

Materials and methods: Lymphocytes isolated from the peripheral blood of two healthy human donors were exposed in triplicate for 30 min to different concentrations of Na²¹¹At at 37°C (absorbed doses: 0.05–1.6 Gy). Following an incubation period (2 h), the total RNA was isolated from the irradiated lymphocytes and the relative expression of the following 18 genes was tested for change using TaqMan? probes based upon the real-time quantitative polymerase chain reaction.

Method: BBC3 (B-cell lymphoma 2 binding component 3), CD69 (cluster of differentiation 69), CDKN1A (cyclin-dependent kinase inhibitor 1A), DUSP8 (dual specificity phosphatase 8) EGR1 (early growth response 1), EGR4 (early growth response 4), GADD45A (growth arrest and DNA-damage-inducible, alpha), GRAP (growth factor receptor-bound protein 2-related adaptor protein), LAP1B (TOR1AIP1; torsin A interacting protein 1), IFNG (interferon gamma), ISG20L1 (interferon-stimulated exonuclease gene 20kDa – like 1), c-JUN (jun oncogene), MDM2 (mouse double minute 2), PCNA (proliferating cell nuclear antigen), PLK2 (polo-like kinase 2), RND1 (rho family GTPase 1), TNFSF9 (tumour necrosis factor superfamily member 9) and TRAF4 (tumour necrosis factor receptor-associated factor 4).

Results: The expressions of the 18 genes, except GRAP, were up-regulated following exposure to α-radiation. A comparison of the results of two individuals tested here showed great variability. Dependence of gene expression upon α-dose was observed in certain dose intervals for BBC3 (R² = 0.61 [individual 1] / 0.81 [individual 2], significance 0.2–1.6 Gy [1] / 0.05–0.1 Gy [2]) and MDM2 (R² = 0.78/0.54; 0.8–1.6 Gy [1], 0.05–0.1 Gy [2]) genes in both individuals. Additionally, for individual 1 the dose dependence was found for the following genes: ISG20L1 (R² = 0.69, 0.05–0.1 Gy), PCNA (R² = 0.59, 0.8–1.6 Gy) and IFNG (R² = 0.74 up to 0.4 Gy, 0.05–0.1 Gy).

Conclusion: Candidate genes for a possible role in future early-phase (2 h) α-biodosimetry are BBC3, ISG20L1, MDM2, PCNA and IFNG.