低剂量辐射效应--辐射防护的基础

低剂量辐射对生物体效应展现出多样性，而且不同LET辐射源的效应差异明显，很难通过大剂量效应中推导。低剂量辐射的健康危害主要是远期致癌风险性，而早期效应随辐射品质、剂量、剂量率以及受照个体的不同会有不同的表现形式，突出的有三个方面：1）细胞在接受一次几个eGy低剂量预照射后，能够对随后大剂量辐照损伤产生一定的防护作用，这种作用被称为适应性反应，或单次低剂量整体照射产生的免疫刺激效应；2）单次低剂量辐照所产生的单位剂量的急性损伤效应比大剂量的更大，这被称为低剂量辐射超敏感性，其剂量大小通常在0．2～0．5Gy的范围内；3）旁效应，是指发生在照射细胞周围的未受照细胞中的生物效应，该效应会导致高于预测值的辐射损伤效应。低剂量辐射的这些多样性效应给辐射防护实践带来了新的思考。     

剂量率对~(60)Co-γ 线诱发双着丝点产额的影响

以不同剂量率照射离体人血样品,发现照射剂量在某一范围内时,剂量率与染色体畸变产额有着明显的相关关系,并证明用各实验室已有的双着丝点与受照剂量关系的回归方程进行不同剂量率效应的推导是可行的。     

低剂量辐射的生物效应：概述与展望

引言尽管对辐射效应的研究已进行了很大的努力,但仍然存在一些重要的未知领域。以往绝大多数研究是直接弄清大剂量的辐射效应,这些研究几乎全部是基于对受大剂量照射的人群或动物的观察。有关低剂量的健康效应,也就是那些受典型职业照射(低于容许     

加速器治疗乳腺癌时靶外组织剂量及防护措施的研究

研究医用电子直线加速器产生的9MeV电子束和6MV-X射线对乳腺癌放射治疗时靶外组织的受照剂量,探讨减少靶外组织受照剂量的方法,为临床优化治疗计划提供剂量学依据。借助非均匀组织等效拟人体模型,模拟乳腺癌放射治疗,处方剂量是胸壁照射总剂量50 Gy、淋巴引流区域照射总剂量60 Gy,每次照射2.0 Gy;采用GR-200A LiF(Mg,Cu,P)TLD,将TLD预置于照射野外所关心的组织或器官中作间接剂量测量。在胸壁照射区域,以9 MeV电子束单独照射时,靶外组织剂量从29.0cGy到295.5cGy;以6MV—X射线单独照射时,靶外组织剂量从32.0 cGy到206.7 cGy;在淋巴引流区域,6MV-X射线照射时靶外组织剂量从22.5 cGy到1650.9 cGy。阴影屏蔽可使电子束造成的靶外组织剂量下降9.4％～53.6％,使X射线造成的靶外组织剂量下降19.7％～56.6％;接触屏蔽可使X射线对靶外组织的剂量贡献下降44.2％～65.6％。胸壁照射采用电子束与X射线的混合比为2:3的照射比单纯用电子束或X射线照射可使靶外高剂量组的组织或器官的受照剂量明显下降。     

国产 TL-101BeO(Na)热释光剂量元件对软 X 线的响应

在研究棉籽、小麦、小鼠及离体人血等受软x线照射后的生物效应时,首先必须确定照射量。由于软x线的有效能量低,国内外曾报道~([1-3])用薄壁电离室及热释光剂量(TLD)元件测定照射量。本文研究用国产TL-101 BeO(Na)TLD元件~([4])测定不同曝光条件下钼靶X线的照射量。     

低剂量照射及其微观剂量分布

辐射防护关心低剂量照射的生物效应,特别是辐射致癌效应。多大水平的照射为低剂量照射并无明确规定。UNSCEAR[1986B-24段,1988F-7段]提出对低LET辐射可以把0-0.2,0.2-2.0,2-10和>1cGy分别称为低、中、高和极高剂量;对高LET辐射(如快中子)把<0.05Gy和>0.05Gy分别称为低和高剂量。对所有辐射,低剂量率指<0.05mGy/min,高剂量率指>0.05Gy/min,介于其问者为中等剂量率。通常的     

25MeVX射线束照射的离体人血中淋巴细胞微核率的剂量-效应关系

本文报告了用 Shimedzu BTR-25型医用感应电子加速器的25MeVX 线照射离体人血,诱发淋巴细胞微核率的剂量-效应关系。结果表明,微核细胞率和微核率与照射剂最可拟配合呈直线方程 Y=a+bD。     

碱性单细胞凝胶电泳技术用于辐射损伤快速剂量估算的时效和量效关系研究

应用碱性单细胞凝胶电泳技术（SCGE）,采用小鼠整体照射和人外周血离体照射方式,检测受^60Co-γ射线照射的外周血细胞DNA损伤修复的时间效应和剂量效应关系,探讨SCGE用于辐射损伤快速剂量估算的可行性。整体实验结果表明,小鼠外周血细胞DNA损伤程度在照射后即刻最明显,照射后2hDNA损伤已基本修复,照射后24h与照射前相比已无显著性差异（P〉0．05）。离体实验结果发现,照射后即刻人外周血细胞尾矩TM值随剂量增加而增加,照射组与未照射组之间有非常显著性差异（P〈0．01）,剂量效应呈现良好的线性关系Y=0．3619＋2．1834D（r=0．9946）;人外周血细胞尾矩TM照射后6h与未照射组相比已无显著性差异（P〉0．05）。以上结果表明,碱性单细胞凝胶电泳是一种快速、灵敏检测DNA损伤的有效方法,具有良好的剂量效应关系;但修复较快,可测时间范围有限。     

低剂量γ辐射对青海弧菌Q67的毒性研究

分别采用生物辐照仪和模拟铀矿室作为γ辐照源,研究了低剂量和超低剂量γ照射对青海弧菌Q67发光强度和光密度(OD₆₀₀)的影响。实验结果表明,青海弧菌Q67在5.5 cGy/min照射剂量率、不同累积照射剂量γ射线照射下,在一定累积照射剂量范围内,发光强度的抑制率无显著差异,当累积照射剂量超过该范围的累积照射剂量的阈值后,发光强度抑制率与累积照射剂量呈正相关。青海弧菌Q67在320 mGy累积照射剂量,5.5、14和51 cGy/min 3个不同照射剂量率γ射线照射下,发光强度在低照射剂量率、长时间的γ射线照射条件下抑制率更大。青海弧菌Q67在长时间超低γ射线照射剂量率的条件下,菌液的OD₆₀₀值的抑制率在24 h达到最大值,此后逐渐降低,其中30和120 μGy/h两组剂量率照射下,青海弧菌Q67菌体数呈现低剂量兴奋效应。通过测定低剂量和超低剂量γ射线照射对青海弧菌Q67的发光强度和菌液OD₆₀₀值的抑制率,可反映一定剂量范围内的γ射线照射对青海孤菌Q67的综合毒性作用。青海孤菌Q67对γ射线具有较好的敏感性,可用作低剂量γ射线毒性评价的生物材料。     

染色体畸变分析作为生物剂量测定方法的研究概况

本文叙述了染色体畸变分析作为生物剂量计的国内外研究概况。文中较详细地介绍了离体照射诱发染色体畸变的剂量-效应关系及其在事故受照人员剂量估算中的应用状况,对局部照射和分次照射条件下确定剂量-效应关系的有关问题进行了分析,对今后研究动向作了简要讨论。     

小剂量辐射影响B16黑色素瘤血道肺转移作用机制研究

Ｃ５７ＢＬ／６小鼠经７．５ｃＧｙＸ线全身照射后２４ｈ静脉注射＾１２５ＩＵｄＲ标记的Ｂ１６黑色素瘤细胞，２４ｈ后测定肺活瘤细胞存留率时发现，照射组小鼠的肺活瘤细胞存瘤率明显降低。与此同时，于照射后２４ｈ检测小鼠的免疫功能发现，照射组小鼠脾脏有核细胞数明显增多，脾细胞ＮＫ细胞毒活性及体内巨噬细胞功能均显著增强，结果提示，小剂量辐射可能通过提高ＮＫ细胞，巨噬细胞功能而加速肺内瘤细胞的清除速率。     

人离体血与整体照射诱发淋巴细胞微核率的研究

报道１例淋巴瘤病人进行全身分次Ｘ射一照射后，发现离全与整体照射诱发的微核率无显著性差异（Ｐ＞０．０５）。经回归分析表明，不仅配合的模式相同，而且同一指标的回归系为九也相当接近。结果表明，在一定的剂量范围内，离体与整体照射的微核剂量效应相同，这使人外周血淋细胞微核率有可能作为估算事故受照人员辐生物剂量的指标。     

Microstructural evolutions of three-dimensional carbon–carbon composite materials irradiated by carbon ions at elevated temperatures

Carbon–carbon composites are deemed as candidate materials for applications in very high temperature reactors (VHTRs). In a VHTR, carbon–carbon composite materials would experience severe environmental impacts of both a high radiation fluence (about 3 × 10¹⁶/cm² per year) and high temperatures (∼1200 °C), and radiation damage is accordingly expected. In this study, samples prepared from a three-dimensional pitch-based carbon–carbon composite material were irradiated with a 4 MeV C²⁺ ion beam emitted by an accelerator to deliberately induce various levels of radiation damage on the samples at 1000 °C. Transmission electron microscopy analyses were then conducted to examine the evolution of microstructures in the samples, and a scanning electron microscope was used to examine the changes in surface morphology. It was found that an accumulated fluence of 7.0 × 10²¹/m² at 1000 °C resulted in cracks between the matrix and the fiber in the sample. These interfacial cracks were all parallel to the fiber orientation. The fiber/matrix bonding strength might play an important role in the mechanical property of the carbon–carbon composite material. In the meantime, cracks were also found at the fiber side of the sample irradiated under the same condition.     

The influence of silicon and helium on the microstructural stability of ion-irradiated incoloy DS alloys

In order to test their void swelling behaviour under irradiation, several alloys based on the solid-solution nickel alloy Incoloy DS (18Cr-38Ni-Fe) with additions of 0.05, 0.43, 0.92 and 2.24 wt% Si have been studied using 4 MeV helium and 46 MeV nickel ion irradiation in the Harwell VEC. For irradiations of 60 dpa with 10 appm He the void swelling decreased from ˜ 0.9% to negligible levels with increasing silicon content. After irradiation to 90 dpa following injection with 10 appm He the 2.24% Si alloy showed <1.0% swelling at an apparent peak swelling temperature of 625° C. This alloy was subsequently irradiated to check the swelling response with concentrations of helium and hydrogen appropriate to fusion-reactor conditions. Following irradiation to 60 dpa after 1000 appm He injection the swelling peak was shifted to 575° C where a swelling maximum of 4% was observed. At 625° C with 1000 appm He alone, swelling was 2.0% compared with 1.2% in samples injected with 1000 appm He +1000 appm H. This small reduction in swelling was associated with a higher cavity (bubble) concentration in the hydrogen implanted sample. Fine-scale precipitation of Ni₃Si(γ'), η-carbide and G-phase was observed after irradiation together with helium bubbles attached to the η- and G-phase precipitates. The precipitation and void swelling was significantly greater in irradiated samples containing 1000 appm He than in those with 10 appm and irradiated to 90 dpa. It is concluded that although the Incoloy DS alloy possibly has a potential for fission-reactor core applications it has little to commend it for fusion-reactor use where the high swelling response, microstructural instability and likely long-term induced activation arising from the higher nickel content are clearly undesirable factors.     

X射线照射对人树突状细胞免疫功能的影响

采用免疫荧光标记、流式细胞仪、3^H-TdR掺入和MTT技术,研究χ射线照射对人外周血来源的树突状细胞（DCs）和T细胞免疫功能的影响。结果显示,不同剂量（0．1～0．5Gy）χ射线照射后使DCs的HLA-DR、CD86和CD40分子表达上调,CD80分子表达下调;与其他剂量组相比,O．2Gy照射DCs可调节T细胞CD4／CD8比值,增强T细胞的增殖能力,同时还可提高特异性CTL细胞的杀伤能力。说明0．2Gyχ射线体外照射可一定程度提高受辐射损伤机体的免疫功能,是体外处理治疗性DCs较为合理的剂量。     

用ICP-AES法分析喂饲辐照食品的大白鼠血清中的微量元素

辐照保鲜是当前发展的一项新的食品保藏技术,其安全性为人们所关注。为此,近卅年来各国对辐照食品进行了大量的研究。结果证明经适当剂量辐照的食品是安全的。但随着生命科学的深入研究,揭示了某些微量元素对健康的密切关系,为此,测定辐照食品喂饲的大白鼠血清中微量元素的变化,以验证辐照食品的安全性。     

Calyculin A诱导早熟染色体凝聚的电离辐射剂量效应曲线

以Calyculin A诱导早熟染色体凝聚(PCC)方法,探索G2/M-PCC细胞中PCC环用于分析电离辐射损伤程度的可行性,用0—20 Gy(剂量率为1 Gy/min)的60Coγ射线照射外周血,培养48 h并用Calyculin A诱导PCC。分析各剂量点G2/M-PCC指数、判断观察到的PCC环是否符合泊松分布,建立PCC环率与剂量之间的剂量效应曲线。结果发现,用Calyculin A可成功诱导人外周血淋巴细胞产生PCC,且G2/M-PCC指数随着剂量水平的增高而降低。除20 Gy剂量外,0—16 Gy各剂量点样品中PCC环的分布符合泊松分布。PCC环率随着剂量增加而增加,剂量-效应曲线可以拟合成y=0.0128x+0.0104直线方程,测得R2=0.9898(y为PCC-R率,x为剂量);二次多项式方程为y=0.00002x2+0.0085x+0.0011 R2=0.9996。由此可见,Calyculin A诱导淋巴细胞G2/M-PCC中的PCC环率可用于生物体电离辐射损伤程度测定。     

电离辐射联合顺铂对人肺癌细胞中BTG3基因表达的影响

加速器产生的6-MV X-射线一次性照射体外培养的人肺腺癌细胞株A549和SPCA-1,细胞的吸收剂量分别设置为0、1、3、5和8 Gy,细胞照射后24 h及单次接受5 Gy照射后6、12和24 h后取样;X-射线联合顺铂对BTG3表达的影响研究设立单纯照射组(5 Gy)、顺铂处理组(20μmol·L-1顺铂)和联合处理组(5 Gy+20μmol·L-1顺铂),上述实验均以未给予任何处理的细胞为对照组;采用Western blot及RT-PCR法检测受到不同剂量电离辐射及照射后不同时间肿瘤细胞中BTG3表达水平。Western blot与PCR检测结果均显示,A549和SPCA-1细胞在受到不同剂量的X-射线照射后24 h,其BTG3蛋白及mRNA表达量均明显增加,并随电离辐射剂量的增加而增加,与对照组比较有统计学差异(t=5.25-15.75,p0.05);照射后不同时间检测结果显示,细胞在X-射线照射4 h后BTG3蛋白及mRNA的表达量即开始上升,并持续到照射后24 h,与照射前相比有统计学差异(t=7.52-11.18,p0.05);联合处理组BTG3的表达量均明显高于单纯照射组、顺铂处理组和对照组(t=7.02-15.86,p0.05)。电离辐射联合顺铂可以上调肺癌细胞株中BTG3的表达,BTG3基因有可能作为肺癌放化疗的靶基因。     

Magnetic behaviour of nanosized zinc ferrite under heavy ion irradiation

Present investigation reports the effect of 100 MeV oxygen beam on the magnetic properties of zinc ferrite nanoparticles. The nanoparticles for this study were synthesized by using the nitrates of zinc and iron in the matrix of citric acid and by sintering the precursor at 500 and 1000 °C. Both these samples were irradiated by 100 MeV oxygen beam with two different fluence 1 × 10¹³ and 5 × 10¹³ ions/cm². Besides the presence of cubic spinel phase, ZnO phase appears after the irradiation in both the samples. A decrease in average particle size was observed in the irradiated samples as estimated by X-ray diffraction pattern. The magnetization versus applied field curves show the decrease in magnetization with the fluence of the beam, which is attributed to the ZnO phase. The thermal magnetization curve for the sample ZF500 shows almost constant value of blocking temperature after irradiation whereas for ZF1000 it increases from 18 K to 32 K at a fluence of 5 × 10¹³ ions/cm².     

Analyses of organics in irradiated aqueous N,N-diethylhydroxylamine solution

The organics in γ-ray irradiated aqueous N, N-diethylhydroxylamine (DEHA) solution, which is used as a reducing agent in reprocessing spent nuclear fuel, were analyzed with gas chromatography equipped with FFAP capil-lary column and flame-ionization detector. It was found that irradiated DEHA solutions contained acetaldehyde, ethanol, and acetic acid. For DEHA of 0.2 mol/L irradiated to 10～1000 kGy, the concents of acetaldehyde, ethanol and acetic acid are (9.7～18.7)×10-3, (0.4～23.4)×10-3 and (6.5～11.7)×10-3 mol/L, respectively. The concentration of DEHA decreases obviously with the dose.