mBAND analysis of chromosome aberrations in lymphocytes exposed in vitro to α-particles and γ-rays

Purpose:?To investigate the profiles of chromosome damage induced in vitro by exposure to α-particles and γ-rays.

Materials and methods:?Human peripheral blood lymphocytes were exposed to three dose regimes: α-particle doses of 0.2 and 0.5 Gy and a γ-ray dose of 1.5 Gy. After culturing for 47 hours, chromosome aberrations involving the number 5 chromosomes were identified using a multi-coloured banding (mBAND) technique.

Results:?Analysis of the frequencies of chromosome 5 breaks within aberrant cells and within aberrant number 5 chromosomes demonstrated that α-particle irradiation is more likely to result in multiple breaks in a chromosome than γ-irradiation. Additionally, overdispersion was observed for all doses for the distribution of breaks amongst all cells analysed and breaks amongst total number 5 chromosomes, with this being greatest for the 0.2 Gy α-particle dose. The ratio of interchanges to intrachanges (F ratio) was 1.4 and 2.4 for 0.2 and 0.5 Gy α-particles respectively and 5.5 for 1.5 Gy γ-rays. Evaluation of simple versus complex exchanges indicated ratios of 1.9 and 2.7 for 0.2 and 0.5 Gy α-particles respectively and 10.6 for 1.5 Gy γ-rays. The majority of the intrachanges involving chromosomes 5 induced by α-particle radiation were associated with more complex exchanges.

Conclusions:?This study has confirmed that exchanges induced by exposure to high linear energy transfer (LET) α-particle radiation comprise a greater proportion of intrachanges than those induced by exposure to low LET γ-rays. However, since the majority of these are associated with complex rearrangements and likely to be non-transmissible, this limits their applicability as a marker of past in vivo exposure.     

Absence of A Dose-rate Effect in the Transformation of C3H 10T1/2 Cells by α-particles

Summary

The findings of Hill et al. (1984) on the greatly enhanced transformation frequencies at very low dose rates of fission neutrons induced us to perform an analogous study with α-particles at comparable dose rates. Transformation frequencies were determined with γ-rays at high dose rate (0·5 Gy/min), and with α-particles at high (0·2 Gy/min) and at low dose rates (0·83–2·5 mGy/min) in the C3H 10T1/2 cell system.

α-particles were substantially more effective than γ-rays, both for cell inactivation and for neoplastic transformation at high and low dose rates. The relative biological effectiveness (RBE) for cell inactivation and for neoplastic transformation was of similar magnitude, and ranged from about 3 at an α-particle dose of 2 Gy to values of the order of 10 at 0·25 Gy. In contrast to the experiments of Hill et al. (1984) with fission neutrons, no increased transformation frequencies were observed when the α-particle dose was protracted over several hours.     

2016-2020年山东省部分放射工作人员职业性外照射个人剂量监测结果分析

目的总结山东省部分放射工作人员个人剂量监测情况, 分析其剂量变化趋势, 为放射工作人员健康管理提供科学依据。方法按照《职业性外照射个人监测规范》《外照射个人剂量系统性能检测规范》的相关要求进行实验检测和质量控制, 对山东省所辖16市疾病预防控制中心监测的全部放射工作人员职业性外照射个人剂量监测的结果, 采用SPSS 23. 0软件进行回顾性分析。结果本次共调查25 523人, 人均年有效剂量为0.28 mSv, 不同年份放射工作人员人均年有效剂量之间差异有统计学意义(H =2 815.91,P<0.001), 人均年有效剂量总体呈先升后降趋势。医学应用中核医学放射工作人员人均年有效剂量最高, 为0.55 mSv, 医学应用中不同职业类别放射工作人员人均年有效剂量之间差异有统计学意义(H=310.37,P<0.001);工业应用中测井放射工作人员人均年有效剂量最高, 为0.37 mSv, 工业应用中不同职业类别放射工作人员人均年有效剂量之间差异有统计学意义(H=448.07,P<0.001)。医学应用放射工作人员人均年有效剂量高于工业应用中放射工作人员, 差异有统计学意...     

阳江高本底辐射地区家庭成员外周血淋巴细胞非稳定性染色体畸变的剂量效应关系初探

用改良的技术方法研究高本底辐射诱发染色体畸变剂量效应关系。方法２８名受检者选自高本底和对照地区１０个家庭中的祖、父、子三代。个体累积剂量分别为２５．２～２４４．８和５．４～５１．７ｍＧｙ。分离淋巴细胞培养法制备染色体标本。每例分析２０００～３０００细胞。结果高本底地区家庭成员非稳定性染色体畸变率随年龄增长而增高（Ｙ＝０．６３２３＋０．０４６３Ｘ，ｒ＝０．８７５０）；并且其中年组和老年组平均畸变率显著高于对照组（２．５６ｖｓ．１．２５，Ｐ＜０．０５和３．６０ｖｓ．１．２２，Ｐ＜０．００１）。在对照地区未见到染色体畸变率与年龄增长相关。高本底地区个体畸变率和累积剂量间呈明显的直线相关（Ｙ＝０．７４４１＋０．０１５４Ｄ，ｒ＝０．８６）。结论高本底持续照射诱发的人体内非稳定性染色体畸变可随受照射时间的延长而持续升高，但当累积剂量降至约５０ｍＧｙ时，用目前方法进行定量分析是有困难的。     

Relative biological effectiveness of mammography X-rays at the level of DNA and chromosomes in lymphocytes

Abstract

Purpose: In many countries, breast cancer screening programs based on periodic mammography exist, giving a large group of women regularly a small dose of ionizing radiation. In order to assess the benefit/risk ratio of those programs the relative biological effectiveness (RBE) of mammography X-rays needs to be determined.

Materials and methods: Blood of five healthy donors was irradiated in vitro with 30 kV X-rays and ⁶⁰Co γ-rays with doses between 5 and 2000 mGy. The phosphorylated histone subtype H2A isoform X-foci (γH2AX-foci) technique was used to quantify the number of DNA double-strand breaks (DSB) after irradiation. Chromosomal damage resulting from non- or misrepaired DNA DSB was quantified with the micronucleus (MN)-assay and the sensitivity was improved by counting only centromere negative micronuclei (MNCM?).

Results: The threshold detection dose obtained with the γH2AX-foci test was 10 mGy for mammography X-rays compared to 50 mGy for γ-rays. With the MN-assay respectively MN-centromere-assay threshold detection doses of 100, respectively, 50 mGy were obtained for mammography X-rays compared to 200 respectively 100 mGy for γ-rays. An RBE of 1.4 was obtained with the γH2AX-foci assay. With the MN-assays low-dose RBE values between 3 and 4 were determined.

Conclusion: Our results indicate that exposure to mammography X-rays resulted in a modest increase in the induction of DSB compared to γ-rays. However, due to the higher linear energy transfer (LET) of mammography X-rays more clustered DNA damage is produced that is more difficult to repair and results in a more pronounced increase in micronucleus formation.     

Effects of Low- and High-LET Cyclotron-accelerated Alpha-particles on Longevity of Drosophila Melanogaster

Summary

An investigation of the effects of exposing Drosophila melanogaster to γ-rays and α-particle radiation of low- and high-LET has resulted in dose-mean longevity curves of the exponential type. The effect of low-LET particles was similar to that of ⁶⁰Co, whereas the high-LET α-particles were more effective than the two other types of radiation with an RBE of 1·3. No protective effect of low doses (3 and 5 krads) was observed. No dose-rate effect was observed in the range 4 to 256 krads/min.     

Induction of Cytogenetic Adaptive Response of Somatic and Germ Cells in Vivo and in Vitro by Low-dose X-irradiation

Summary

The cytogenetic adaptive response induced by low-level radiation was studied using human and rabbit lymphocytes in vitro and bone marrow cells and germ cells in vivo. The inductive dose of X-rays was 10 mGy for the in vitro studies at a dose rate of 10 mGy/min, and 2, 10, 50, 75 and 100 mGy for the in vivo studies at a dose rate of 50 mGy/min. The challenging dose was 1·5 Gy X-rays for the in vitro experiments and 0·65 or 0·75 Gy for the in vivo experiments at a dose rate of 0·44 Gy/min. The results reported here, in addition to those that have appeared in the literature, show the following characteristics documented for the first time: (1) 10 mGy could induce the adaptive response in human as well as rabbit lymphocytes irradiated not only in G₁, S and G₂ phases, but also in the G₀ state; (2) although the induced adaptive response could only last three cell cycles, it could be revived when the inductive dose was repeated after the third cell cycle; (3) the adaptive response could be induced by low-dose X-rays in somatic cells, both in vitro (lymphocytes) and in vivo (bone marrow cells), and also in germ cells (spermatocytes); (4) the magnitude of the adaptive response induced by whole-body irradiation was found to be dose-dependent–the lower the inductive dose the more the reduction of the frequency of chromatid aberrations following the challenging dose.     

外照射慢性放射病的胸腺肽治疗及追踪观察

目的本文观察１１例慢性放射病的胸腺肽治疗结果及病程转归。方法以临床症状变化、造血系统造血功能、Ｔ淋巴细胞百分率、染色体畸变率变化作为慢放病恢复的综合判断标准进行分析。结果胸腺肽能促使患者的无力型神经衰弱征候群明显好转；能显著提高Ｔ淋巴细胞百分率，进而增强机体免疫力，治愈口腔粘膜溃疡。追踪观察表明，慢放病恢复时间依次为细胞免疫功能（２年），无力型神经衰弱综合症（３．５年），造血组织造血功能（５～８年），染色体畸变率（１０年）。结论按照我们拟定的慢放病恢复综合判断标准，慢放病是一种可以恢复的职业性疾病。胸腺肽有助于慢放病的治疗，且方法简单，值得临床试用     

湖北省2009-2018年放射工作人员职业性外照射剂量监测结果分析

目的 回顾性分析湖北省2009-2018年间放射工作人员职业性外照射个人剂量水平与分布情况,预防和控制放射性职业照射的风险.方法 以2009-2018年委托湖北省疾病预防控制中心进行个人剂量监测的放射工作人员外照射个人剂量为研究对象,共50 070人.按照相关国家标准的要求,采用热释光方法监测放射工作人员的外照射剂量当...     

Doses and lung cancer risks from exposure to radon and plutonium

Abstract

Purpose: Epidemiological studies of the French uranium miners and the plutonium workers at the Mayak nuclear facility have provided excess relative risk (ERR) estimates per unit absorbed lung dose from alpha radiation. The aim of this paper was to review these two studies and to derive values of the relative biological effectiveness (RBE) of alpha particles for the induction of lung cancer.

Materials and methods: We examined and compared the dosimetry assumptions and methodology used in the epidemiological studies of uranium miners and the plutonium workers. Values of RBE were obtained by comparing risk coefficients including comparison of lifetime risks for a given population. To do this, preliminary calculations of lifetime risks following inhalation of plutonium were carried out.

Results and conclusions: Published values of risk per unit dose following inhalation of radon progeny and plutonium were in agreement despite the very different dose distributions within the lungs and the different ways the doses were calculated. Values of RBE around 10–20 were obtained by comparing ERR values, but with wide uncertainty ranges. Comparing lifetime risks gave similar values (10, 19 and 21). This supports the use of a radiation weighting factor of 20 for alpha particles for radiation protection purposes.     

Chromosome analysis of workers occupationally exposed to radiation at the Sellafield nuclear facility

PURPOSE: To investigate the relationship between stable chromosome aberration frequency in peripheral blood lymphocytes and occupational cumulative radiation exposure. MATERIALS AND METHODS: Cytogenetic analysis using G-banding was performed on peripheral blood lymphocyte cultures from 104 workers from the British Nuclear Fuels PLC facility at Sellafield, UK. The study group comprised 61 men with lifetime cumulative doses > 500 mSv, 39 men with minimal exposure (i.e. < 50 mSv) who formed a control group and 4 men with intermediate doses. RESULTS: The slope of the dose-response, adjusted for smoking status, for translocations and insertions was 0.55+/-0.31 x 10(-2)/cell/Sv. Consideration of chromosome breakpoints for all aberrations combined in the radiation workers revealed an excess in the C group chromosomes and a deficit in the F group chromosomes with breakpoints being concentrated in the terminal regions whereas the distribution in the control group did not deviate from expectation. CONCLUSIONS: The dose-response was not significantly different from the parallel FISH analysis (Tucker et al. 1997) and confirms that chronic radiation exposure appears to be substantially less effective at inducing stable chromosome aberrations in comparison with acute exposure.     

The Effect of 238Pu α-particles on the Mouse Fibroblast Cell Line C3H 10T1/2: Characterization of Source and RBE for Cell Survival

Summary

Considerable interest has been aroused in recent years by reports that the transforming and carcinogenic effectiveness of low doses of high LET radiations can be increased by reducing the dose rate, especially for transformation of 10T1/2 cells in vitro by fission-spectrum neutrons. We report on conditions which have been established for irradiation of 10T1/2 cells with high LET monoenergetic α-particles (energy of 3·2 MeV, LET of 124 keV μm^?1) from ²³⁸Pu. The α-particle irradiator allows convenient irradiation of multiple dishes of cells at selectable high or low dose rates and temperatures. The survival curves of irradiated cells showed that the mean lethal dose of α-particles was 0·6 Gy and corresponded to an RBE, at high dose rates, of 7·9 at 80 per cent survival and 4·6 at 5 per cent survival, relative to ⁶⁰Co γ-rays. The mean areas of the 10T1/2 nuclei, perpendicular to the incident α-particles, was measured as 201 μm², from which it follows that, on average, only one in six of the α-particle traversals through a cell nucleus is lethal. Under the well-characterized conditions of these experiments the event frequency of α-particle traversals through cell nuclei is 9·8 Gy^?1.     

2017年我国放射工作人员职业性外照射个人剂量水平与分析

目的了解并分析2017年我国放射工作人员职业性外照射个人剂量水平与分析,为职业性放射性疾病的预防与控制提供基础数据和科学依据。方法通过国家个人剂量登记系统,采集我国从事医学应用和工业应用放射工作人员职业性外照射个人剂量监测结果等相关数据,运用Kruskal-Wallis H检验、Mann-Whitney U检验和Bonferroni法进行分析。结果收集2017年从事医学应用和工业应用工作人员共361727人,医学应用人数占81.6%,工业应用人数占18.4%。人均年有效剂量分别为0.353和0.270 mSv,从事医学应用的放射工作人员所受到的人均年有效剂量显著高于工业应用(Z=48.547,P<0.05)。医学应用中,不同职业类别间放射工作人员人均年有效剂量差异有统计学意义(H=1136.217,P<0.05),从事核医学和介入放射学的放射工作人员所受到的人均年有效剂量显著高于其他职业类别(Z=2.877~26.967,P<0.05)。三级医院、二级医院和一级及未定级医院放射工作人员人均年有效剂量分别为0.361、0.397和0.308 mSv。工业应用中,从事工业探伤和测井的放射工作人员的人均年有效剂量显著高于其他5类工业应用职业类别(Z=4.172~36.908,P<0.05)。结论我国放射工作人员人均年有效剂量满足国家法规标准要求。从事核医学、介入放射学、工业探伤和测井的工作人员受照剂量相对偏高,应进一步加强相关辐射防护措施、设施等,以减少职业暴露。     

Chromosome analysis of workers occupationally exposed to radiation at the Sellafield nuclear facility

Purpose : To investigate the relationship between stable chromosome aberration frequency in peripheral blood lymphocytes and occupational cumulative radiation exposure. Materials and methods : Cytogenetic analysis using G-banding was performed on peripheral blood lymphocyte cultures from 104 workers from the British Nuclear Fuels PLC facility at Sellafield, UK. The study group comprised 61 men with lifetime cumulative doses > 500mSv, 39 men with minimal exposure (i.e. < 50 mSv) who formed a control group and 4 men with intermediate doses. Results : The slope of the dose-response, adjusted for smoking status, for translocations and insertions was 0.55 +/- 0.31 x 10 -2 /cell/Sv. Consideration of chromosome breakpoints for all aberrations combined in the radiation workers revealed an excess in the C group chromosomes and a deficit in the F group chromosomes with breakpoints being concentrated in the terminal regions whereas the distribution in the control group did not deviate from expectation. Conclusions : The dose-response was not significantly different from the parallel FISH analysis (Tucker et al. 1997) and confirms that chronic radiation exposure appears to be substantially less effective at inducing stable chromosome aberrations in comparison with acute exposure.     

Radiation absorbed dose calculations for samarium-153-EDTMP localized in bone

Calculations have been undertaken to estimate the likely radiation dose received by patients undergoing treatment with samarium-153-EDTMP. Previously known bone structure parameters have been employed to partition correctly the energy absorbed in the bone matrix between red bone marrow, yellow marrow, and various types of mineral bone. Both uniform surface and volume distribution of the radioactivity are considered. The key findings of the calculations can be stated in terms of the MIRD "S-factors" for red bone marrow and the endosteal layer of cells on bone surfaces. In particular, the S-factor for red bone marrow is either 0.0276 mGy/MBq.h or 0.0077 mGy/MBq.h for surface and volume distributed radioactivity, respectively. For the endosteal layer of thickness (10 microns) on bone surfaces, the corresponding values are 0.0723 mGy/MBq.h and 0.0213 mGy/MBq.h, respectively.     

2015-2019年内蒙古地区部分医学应用放射工作人员职业性外照射个人剂量监测结果与分析

目的 了解、分析2015-2019年内蒙古地区医学应用放射工作人员职业外照射个人剂量水平,为放射工作人员健康管理和辐射防护管理提供数据基础和科学依据.方法 通过国家个人剂量登记系统采集内蒙古地区医学应用放射工作人员个人剂量监测数据,并进行统计与分析.结果 2015-2019年各年度医学应用放射工作人员人均年有效剂量依次...     

Measurement of the G-value for 1·5 keV X-rays

Summary

Although there are several theoretical predictions of the dependence of the G-value on X-ray energy, measurements have not been made below ≈ 7 keV. Using a ferrous sulfate solution modified by the addition of benzoic acid, we have measured the relative G-values for Al_k characteristic X-rays (1·5 keV), ²³⁸Pu α-particles (3·7 MeV), ⁶⁰Co (1·17 MeV) and ¹³⁷Cs (0·66 MeV) γ-rays. This modified ferrous sulfate solution gave a 4-fold increase in sensitivity relative to the conventional solution, making measurements with the Al_k X-rays feasible. The relative ferrous-to-ferric conversions as a function of dose were similar for the two γ-ray energies, yielding G-values of 1·62 and 1·59 µmol J^?1 for the ⁶⁰Co and ¹³⁷Cs radiations, respectively. The α-particle G-value was 0·52 µmol J^?1, or 31 per cent of that for the ⁶⁰Co γ-rays, in good agreement with previous measurements. The Al_k X-rays had a G-value of 0·92 µmol J^?1 or 57 per cent of that of the ⁶⁰Co radiation. This G-value for the 1·5 keV X-rays is within 20 per cent of the values predicted by current theories, and theoretical values are within the error range of our measurement. The consistency between the experimental value reported here and theoretical G-values for ultrasoft X-rays should be valuable for models of radiation action on biological systems.     

移动CT头部扫描辐射剂量场的空间分布

目的 初步探究移动CT在进行头部扫描时产生的杂散辐射在空间中的分布,以期为移动CT的辐射防护提供科学依据。方法 选择CareTom移动式多排CT头部序列进行单次扫描,用TLD（LiF：Mg,Cu,P）型热释光探测器测得辐射剂量值,并用Matlab软件绘制出辐射剂量场的空间分布。结果 移动CT前方的辐射剂量稍高于后方,周围空间辐射剂量场则大致呈从前向后的“倒三角”形分布。最大数值出现在中心水平层面,移动CT正前方距离扫描孔中心最近的测量点（距中心0.5 m）,为0.255 mGy。结论 移动CT头部扫描产生的杂散辐射剂量较低,但为了避免长期低剂量辐射的损伤,检查技师和其他医护人员应尽量站在移动CT机的侧面和后方2 m以外的地方,并在扫描时尽可能地配置放射防护装备。     

Modelling hematological parameters after total body irradiation

Abstract

Purpose: The time- and dose-dependent reconstitution of hematopoiesis after radiation exposure is strongly related to the stem cell population and can be used to predict hematological parameters. These parameters allow further insight into the hematopoietic system and might lead to the development of novel stem cell transplantation models.

Materials and methods: CD4-/- C57Bl/6 mice, transgenic for human CD4 and HLA-DR3, were irradiated in a single (3, 6, 8 and 12 Gy) and fractionated (6 × 1 Gy, 6 × 1.5 Gy, 6 × 2 Gy; twice daily) dose regimen. Blood was analyzed weekly for red blood cells (RBC), hemoglobin concentration (Hb), hematocrit (HCT) and white blood cells (WBC). Organ and tissue damage after irradiation were examined by histopathology.

Results: The recovery curves for RBC, Hb, HCT and WBC showed the same velocity (< 1 week) for all radiation doses (3–12 Gy) starting at different, dose-dependent times. The only dose-dependent parameter was defined by the beginning of the recovery process (dose-dependent shift) and higher doses were related to a later recovery of the hematopoietic system. The RBC, Hb and HCT recovery was followed by a saturation curve reaching a final concentration independent of the radiation dose. Histological analysis of the bone marrow in the single dose cohort showed a dose-dependent reduction of the cellularity in the bone marrow cavities. The fractioned radiation dose cohort resulted in a regeneration of all bone marrow cavities.

Conclusion: Specific functions were developed to describe the reconstitution of hematological parameters after total body irradiation.     

The biological hazards of plutonium

The health hazards associated with exposure to low levels of plutonium are reviewed since, though the world may escape a nuclear war, there may be virtually permanent contamination of the biosphere by plutonium from a number of sources. It would seem that it is possible to offer workers in the nuclear industry an acceptable level of protection but that low levels of pollution around such sites may build up until there is a hazard for people in the vicinity. The cases of childhood leukaemia found in the vicinity of the Sellafield facility may or may not be related to contamination in the area; however, plutonium is a potent carcinogen, and the foetus seems to be particularly vulnerable to it. The disposal of nuclear waste must be monitored more closely, and it is suggested that the International Atomic Energy Agency should take on this added responsibility.