利用拉曼光谱技术研究低剂量X射线辐射对人神经母细胞瘤细胞的影响

低剂量电离辐射引发的生物效应复杂而多样,其研究往往又受到辐射标志物和检测技术手段的限制。将拉曼光谱技术应用于低剂量辐射生物效应研究,利用10 mW,532 nm共聚焦拉曼光谱对经过100,200和500 mGy三种辐射剂量的X射线辐照之后的人神经母细胞瘤细胞进行检测,发现细胞嘌呤核苷酸（722～728和1 572～1 581 cm-1等等）、嘧啶核苷酸（770～785 cm-1等等）等DNA相关的拉曼特征峰受到电离辐射影响而发生变化,说明低剂量X射线辐照造成细胞DNA水平改变。采用流式细胞术对同样条件辐照后培养6 h的人神经母细胞瘤细胞进行细胞周期分析发现,三种剂量的X射线电离辐射均造成细胞在G2期阻滞,同样提示电离辐射引起DNA水平升高。通过划痕实验分析辐照后20 h的细胞迁移能力,结果显示,相较于未接受X射线照射的对照细胞,受到三种剂量电离辐射的人神经母细胞瘤细胞均出现迁移水平下降。研究结果表明,通过拉曼光谱分析发现低剂量X射线电离辐射引起人神经母细胞瘤细胞DNA水平变化,其结果与细胞周期分析和迁移分析的结果相一致,但检测时间大大提前,利用拉曼光谱技术可以实现低剂量辐射损伤等细胞生物学效应的早期发现与监测。     

BTG1蛋白及其上下游信号通路对X射线和碳离子辐射的应激响应

BTG1是重要的抗细胞增殖蛋白,在细胞对外界胁迫如电离辐射等的应激响应过程中发挥重要功能。到目前为止,电离辐射诱导BTG1蛋白表达水平的长期变化情况、其对细胞基因组稳定性的影响及上下游相关的信号通路仍未完全阐明。通过荧光定量PCR技术发现BTG1对X射线和碳离子的应激呈现出先迅速升高再缓慢下降的过程。此外,微核实验表明,通过转染基因的质粒过表达载体或siRNA的方法外源性增加或抑制786-O细胞内BTG1的表达水平均能够显著影响碳离子辐照诱导的基因组不稳定性。深入研究发现电离辐射诱导的NF-кB的表达和活化可能通过引起SKA2基因的表达而间接地调控BTG1的表达,而BTG1则可能激活PRMT1的活性而引起基因组表观遗传学的改变,进而影响细胞的基因组稳定性、细胞周期调控以及凋亡等进程。BTG1, an important anti-proliferative gene, plays critical roles in cellular response to stresses, including ionizing radiation (IR). However, the long term expression of BTG1 induced by IR and its upstream/downstream signal pathways have not been elucidated clearly until now. The qRT-PCR results showed that the expression level of BTG1 in 786-O cells was rapidly elevated by IR in a short time, and then decreased slowly. In addition, upregulation or downregulation by transfection of BTG1 overexpression vector or siRNA could significantly affect the carbon ion radiation-induced genomic instability. Further study indicated that IRinduced BTG1 expression may be regulated by NF-B-mediated activation of SKA2 indirectly; On the other hand, expression of BTG1 may cause epigenetic changes by activating PRMT1, and subsequently influence the genomic stability, cell cycle regulation and apoptosis.     

MicroRNA-19b通过下调BTG1增加重离子辐射诱导的基因组不稳定性

重离子束放疗可有效杀死肿瘤细胞。研究表明:重离子束能引起癌细胞的基因异常,引发基因组不稳定性。BTG1作为一个重要的G0/G1期相关蛋白,具有强烈的抗细胞增殖能力。以碳离子辐射为手段,通过蛋白质印迹杂交技术发现:人肾癌786-O细胞中BTG1能够对重离子辐射应激产生应答。同时,荧光定量PCR结果显示碳离子辐照后,BTG1转录本与micro RNA-19b的表达水平呈负相关变化。瞬时转染micro RNA-19b类似物于人肾癌786-O细胞中,能够抑制由碳离子辐射引起的BTG1蛋白上调,并增加细胞的微核发生率。因此micro RNA-19b能够通过抑制BTG1的表达,增加重离子辐射诱导的细胞基因组不稳定性。     

表面绝缘对平面钨丝阵Z箍缩早期过程的影响

在"强光一号"装置上研究了表面绝缘对平面钨丝阵早期过程的影响。通过对实验结果的唯象分析,发现相对于标准丝阵,表面绝缘丝阵X射线辐射被强烈延迟,并与丝阵宽度有较强的依赖关系,在X射线辐射之前存在较强的阴极发射;表面绝缘丝阵X射线辐射副脉冲幅值是标准丝阵两倍,且存在较长的平台期,其单丝等离子体膨胀导致的温度降低效应比标准丝阵强;在快速内爆开始之前,两者形成了类似的宏观磁流体不稳定性结构。     

基因芯片技术及其在放射治疗中的应用

基因芯片技术是建立在杂交序列基本理论上的分子生物学技术, 它以一种全面、 综合和系统的思维方式研究生命现象。 基因芯片技术可以完整地研究整个细胞或器官全部基因变化, 可以通过基因分析发现对电离辐射的基因反应差异, 从而建立一种新的分子放射生物学方法。 综述了基因芯片技术及应用领域, 重点介绍了基因芯片技术在辐射治疗癌症中的应用。 概述了重离子治疗肿瘤优于其它射线的原因。 展望了利用基因芯片技术的优势探索肿瘤经重离子辐照前、 中、 后期的生物学效应。     

辐射的生物学效应及应用

广义上讲,辐射是一种由辐射源发出,以电磁波或粒子的形式向外传送能量的方式。按生物学效应的不同,可将辐射分为电离辐射和非电离辐射两大类：量子能量达到12eV以上时,辐射会导致生物组织电离,从而使生物体受到较为严重的损伤,这类辐射叫做电离辐射：量子能量不足12eV,不能使生物组织发生电离的辐射则叫做非电离辐射。     

UV-B诱导的大豆愈伤组织超弱光子辐射的动力学分析

为了研究细胞超弱光子辐射的动力学特征及其所揭示的生物学意义,用20 μW/cm2UV-B辐射大豆愈伤组织2 h,测定停止辐射后4 d内大豆愈伤组织在LED光诱导下的延迟发光.通过建立延迟发光动力学方程和数学拟合得到了大豆愈伤组织超弱光子辐射中的延迟发光积分强度、初始光子数、衰减参数和自发发光,讨论了这些发光动力学参数的生物学意义.研究结果表明,在停止UV-B辐射后的4 d内,大豆愈伤组织的光诱导延迟发光服从双曲线弛豫.动力学分析发现,延迟发光积分强度和初始光子数随处理后时间的进行呈现波动变化,停止UV-B辐射后,自发发光和丙二醛（MDA）含量均呈现升高的趋势,在辐射后2 d附近达到峰值,此后同步下降.用延迟发光积分强度和自发发光的比值定义细胞的状态参量Q和序参量R,发现UV-B辐射后大豆愈伤组织细胞Q值或R值的变化反映了UV-B辐射对大豆愈伤组织细胞的损伤以及细胞的恢复过程.     

基于单边傅里叶变换的非马尔科夫自发辐射研究

基于单边傅里叶变换,本文提出一种研究辐射子的自发衰减动力学演化的普适方法.利用该方法研究了辐射子处于均匀介质、理想微腔和泄露微腔中的自发辐射动力学演化问题,最后并把这种方法用于处理光子带隙材料中的辐射动力学演化问题.结果表明:辐射子的自发辐射动力学特性由局域态密度决定,可以通过调控辐射子周围的局域态密度来调控辐射子的自发辐射特性,为实现新型的光电子器件提供了理论基础.该方法不仅适用于马尔科夫热库的情况也适用于非马尔科夫热库的情况.     

基因芯片技术及其在放射治疗中的应用

基因芯片技术是建立在杂交序列基本理论上的分子生物学技术,它以一种全面、综合和系统的思维方式研究生命现象。基因芯片技术可以完整地研究整个细胞或器官全部基因变化,可以通过基因分析发现对电离辐射的基因反应差异,从而建立一种新的分子放射生物学方法。综述了基因芯片技术及应用领域,重点介绍了基因芯片技术在辐射治疗癌症中的应用。概述了重离子治疗肿瘤优于其它射线的原因。展望了利用基因芯片技术的优势探索肿瘤经重离子辐照前、中、后期的生物学效应。     

电离辐射致植物诱变效应的损伤-修复模型

在电离辐射速率理论的基础上, 结合电离辐射诱导植物的微观与宏观生物效应, 建立了电离辐射致植物诱变效应的损伤-修复模型. 通过对理论模型平衡态的数值求解, 研究了辐照植物各状态相对浓度随电离辐射剂量的变化. 研究表明当考虑植物的修复作用时, 理论模型能够给出“马鞍型”的植物存活率-剂量关系. 为进一步验证模型, 对重离子⁷Li辐射玉米自交系的实验数据进行理论模型拟合, 确定重离子辐射玉米的诱变效应参数, 理论计算的结果与实验数据符合较好. 电离辐射诱导植物的损伤-修复模型的建立为电离辐射诱导植物生物效应的机理研究和辐射诱变植物育种提供了理论依据和参考.     

Beam dynamics simulations of the injector for a compact THz source

Terahertz radiation has broad application prospects due to its ability to penetrate deep into many organic materials without the damage caused by ionizing radiations. A free electron laser (FEL)-based THz source is the best choice to produce high-power radiation. In this paper, a 14 MeV injector is introduced for generating high-quality beam for FEL, is composed of an EC-ITC RF gun, compensating coils and a travelling-wave structure. Beam dynamics simulations have been done with ASTRA code to verify the design and to optimize parameters. Simulations of the operating mode at 6 MeV have also been executed.     

Radiation safety of luggage inspected for explosive materials by photonuclear detectors in airports

Doses of ionizing radiation generated by a luggage simulator are measured. The luggage simulator is irradiated under conditions that occur when luggage is inspected by photonuclear detectors for explosive materials. It is shown that the ionizing radiation caused by induced radiation is not dangerous either to passengers or to airport stuff.     

Nonlinear Dynamics of Wave Beams and Packets in an Ionizable Medium

We present a review of the studies on nonlinear dynamics of the plasma–field system formed in the processes of breakdown of a gas by high-intensity laser or microwave radiation. The ionization instability dominating these processes significantly modifies the known effects of self-action of waves in a medium and gives rise to a number of new effects which are absent for other nonlinearity mechanisms. We describe the most important among these effects, such as the ionization–field instability of a plane wave, the self-channeling of radiation in the form of surface or leaky waves, and the self-conversion of the spectrum of the ionizing radiation. The results of numerical simulations of the dynamics of nonequilibrium freely-localized discharges created by focused microwave and laser pulses are presented.     

Nanostructures in a nematic liquid crystal

The effect of nanoobjects, molecular objects, and α particles introduced into a liquid-crystal matrix that is placed in a dc electric field is studied theoretically and experimentally. The introduced particles form a charged defect, the radius of which is much larger than the particle sizes, in the orientational structure of the liquid crystal. This defect is easily observed under an optical microscope, and its image agrees with calculated data. It is suggested that this effect be used for detection and diagnostics of small objects and for design of ionizing radiation detectors. The phenomena revealed in this work can help in producing new charged-defect-saturated liquid-crystal structures formed by introducing nanoparticles in a medium or by irradiating a medium by ionizing radiation. A nonmechanical principle of transport of nanoparticles and their regular incorporation into the lattice is implemented. The essence of this principle is control of molecular orientations in a liquid crystal by quasi-stationary electric fields.     

New track-structure Monte Carlo code for 4D ionizing photon transport

Radiodiagnosis and radiation treatment, in each of their areas such as imaging, radiotherapy and nuclear medicine, require precise calculations about the energy deposited and scattering of the ionizing radiation used. In healthcare applications, it is required to know the penetration and amount of energy deposited in the biological tissue irradiated by ionizing photons; these parameters are function of the photon interaction processes with matter, which can be analyzed experimentally or by Monte Carlo simulation. Purpose: The aim of this work was to develop a new Monte Carlo code for ionizing photon transport in water with the track structure technique, that allows to discriminate primary and secondary photons, and to determine the energy deposited, interaction coordinates, path length and time of flight (TOF) inside of scatter volume. Methods: C++ programming language was used. In the Compton scattering, the polar angle was sampled by methods: Kahn and EGS. Water spheres centered at the origin with different radius were used, where the isotropic point source was placed at (0, 0, 0) for different energies to compute the energy lost by photons and TOF inside spherical volume. Results: It was determined that the best sampling method for the polar angle generation in each Compton interaction was the EGS method. Energy deposited in target region filled with water was compared with MCNPX 2.6 and others’ results from literature. Mean TOF and pathlength inside region of interest was obtained for 4 radii and 5 energies. Conclusions: Quantities computed with the new code are, according to reported data, and so, the new code is reliable for photon transport in water using the track structure method; this will allow the new code to become a useful tool in the areas of radiology and radiation dosimetry. Also, TOF inside scatter volume was reported.     

An alternative method for using bipolar junction transistors as a radiation dosimetry detector in breast cancer treatment

Silicon photodetectors and MOSFETs (Metal-Oxide-Semiconductor Field Effect Transistors) are frequently used devices for measuring ionizing radiation in health physics instrumentation. The Bipolar Junction Transistor (BJT) is not a typical device used as a detector for measuring some physical quantities in radiotherapy beams due to its loss of sensitivity to ionizing radiation, as a consequence of radiation damage in the silicon semiconductor substrate. Actually, the know-how of the BJT characteristic curves and its response to ionizing radiation leads us to suggest an alternative method to estimate the radiation dose value in breast cancer treatments. The BJT parameter to be evaluated before and after the irradiation procedure is the BJT amplification factor, also called DC gain β. In this work, the study was done using a BJT known as Darlington type, within an Alderson Rando anthropomorphic phantom. Darlington transistors have very high gain and this feature allowed that the BJT gain changes to be correlated with the dose of the radiation beam. The results indicate that this new method could be an alternative option to estimate the dose value in the phantom for measurements in breast cancer radiotherapy.     

Effect of beta-particles on the retinal chromophore in bacteriorhodopsin of Halobacterium salinarium

Bacteriorhodopsin (bR) is an attractive intelligent material. Understanding the mechanism of its light-driven proton pumping outward the cell implicates it in many technical applications, particularly, in what is called optical computers, and the biotechnology is waiting for this promised biological molecule. An ionizing radiation source handling could be computerized in radiation fields. The computer containing such biological material will not be out of reach of the fields of ionizing radiation. So it is interesting to report on the working of such biological computer if it is subjected to ionizing radiation. The functional unit in this molecule is retinal chromophore. In the present work, it is interested to assess the functionality of bR through determining the electronic transition dipole moment of its chromophore. Significant changes in the values of the absorption transition dipole moment were noticed at different doses of beta-particles in the range of 0.1-0.3 kGy. Ionizing radiation-induced changes in bR were followed by intrinsic fluorescence spectroscopy. An analysis of the fluorescence data bears on the tertiary structure of bR. The emission spectrum is, however, red shifted with an increase in intensity with the different doses; in the meanwhile, gradual decrease in the visible absorbance has occurred till almost complete loss is attained. This bleaching due to ionizing radiation may offer an alternative way of data processing in such optical devices based on bR. Nevertheless, bR has proofed to be used as a biological indicator of ionizing radiation. However, the potential of bR for use as a biosensor to detect ionizing radiation should be considered.     

Advances in radiation biology: Radiosensitization in DNA and living cells

One fundamental goal of radiation biology is the evolution of concepts and methods for the elaboration of new approaches and protocols for the treatment of cancers. In this context, the use of fast ions as ionizing particles offers the advantage of optimizing cell killing inside the tumor whilst preserving the surrounding healthy tissues. One extremely promising strategy investigated recently is the addition of radiosensitizers in the targeted tissue. The optimization of radiotherapy with fast ions implies a multidisciplinary approach to ionizing radiation effects on complex living systems, ranging from studies on single molecules to investigations of entire organisms.In this article we review recent studies on ion induced damages in simple and complex biological systems, from DNA to living cells. The specific aspect of radiosensitization induced by metallic atoms is described. As a fundamental result, the addition of sensitizing compounds with ion irradiation may improve therapeutic index in cancer therapy. In conclusion, new perspectives are proposed based on the experience and contribution of different communities including Surface Sciences, to improve the development of radiation biology.