辐照诱导的人正常肝细胞系HL-7702细胞远后效应

近年来，放射治疗在肿瘤治疗中的作用受到了越来越多的重视，放疗技术和手段的迅速发展为人们选择放疗创造了更多的机会[1]。放疗是利用电离辐射对细胞，特别是细胞中的遗传物质DNA的损伤作用，诱发病灶部位不正常细胞的凋亡和坏死来治疗肿瘤的。即使制定了周密的放疗方案和计划，放疗过程中难免也会对正常组织和细胞造成一定程度的损伤，而且辐射的远后效应和旁效应的发现，也使得放射治疗肿瘤的安全性受到了很大的关注。要想充分发挥放疗的优势，而又使其对人体正常组织的毒副作用尽可能降低，就必须搞清楚电离辐射对细胞造成的各种损伤的类型及其分子机理。自从电离辐射的远后效应和旁效应被发现以来就一直是辐射生物医学领域的研究热点，国内外的科研人员进行了大量的实验试图解释它们的本质，可是几十年来相关领域的研究一直局限于细胞学的水平，在向分子水平前进的道路上遇到了巨大的困难[2,3]。目前对于电离辐射远后效应和旁效应的研究是相对独立进行的，很少有探讨二者相互关系的论文发表。本文试图在总结前人科研成果并结合对自己所取得的实验数据进行分析的基础上对电离辐射的远后效应、旁效应、基因不稳定性与电离辐射所产生的活性氧自由基的关系进行初步的探讨。实验方法与结果： 1.用X射线辐照人正常肝细胞系HL-7702细胞，运用胞质分离阻滞微核实验检测细胞微核率，AnnexinV-FITC细胞凋亡检测试剂盒检测细胞凋亡率，细胞微核率和凋亡率随着辐照剂量的增加而显著增加。X射线照射后细胞继续传代培养，第七代时不同剂量辐照后子代细胞微核率和凋亡率同未辐照细胞的微核率和凋亡率相比已经没有明显区别。对不同剂量辐照后传代七代的细胞再次照射2.5Gy相同的剂量，发现受初次不同剂量辐照的细胞其微核率和凋亡率再次出现明显差异，初次辐照剂量高的细胞再次相同剂量辐照后的微核率和凋亡率也高。 2.对不同剂量X射线辐照后的细胞继续传代到第十五代时用H2O2浓度为1ul/ml的培养基处理15min，发现受初次不同剂量辐照的细胞其微核率再次出现比较明显差异，初次辐照剂量高的细胞H2O2处理后的微核率也高。 3.对受到不同剂量X射线辐照的人正常肝细胞存活后代进行二次辐照，分两组分别给予1.5GyX射线和1Gy碳离子束辐照，并检测二次辐照后细胞的微核率，发现重离子束二次辐照后并不像X射线一样可以诱发初次X射线辐照造成的损伤信息的表达，而只是表现出二次重离子辐照所造成的损伤。结论： 1.X射线辐照导致了HL-7702细胞基因组不稳定性这一辐射远后效应，X射线二次辐照辐照存活细胞的子代细胞可以诱发辐射的远后效应（如基因组不稳定性）明显的表现； 2.X射线辐照导致的HL-7702细胞后代基因组不稳定性，可以通过H2O2处理而得以诱发，揭示电离辐射过程中产生的氧自由基可能与辐射的远后效应存在密切的联系； 3.电离辐射产生的ROS在诱发细胞产生微核中具有重要的作用，但是并非唯一的影响因素。 4.X射线和12C6+重离子束辐照后存活细胞的后代中的细胞损伤类型可能存在着本质上的区别

Extract of Ginkgo biloba leaves reverses yohimbine-induced spatial working memory deficit in rats

Extract of Ginkgo biloba is used to alleviate age-related decline in cognitive function, which may be associated with the loss of catecholamines in the prefrontal cortex. The purpose of this study was to verify whether alpha-2 adrenergic activity is involved in the facilitative effects of extract of Ginkgo biloba on prefrontal cognitive function. Male Wistar rats were trained to reach criterion in the delayed alternation task (0, 25, and 50-s delay intervals). A pilot study found that 3 or 4 mg/kg of yohimbine (intraperitoneal) reduced the choice accuracy of the delayed alternation task in a dose and delay-dependent manner, without influencing motor ability or perseverative behaviour. Acute oral pre-treatment with doses of 50, 100, or 200 mg/kg (but not 25 mg/kg) of extract of Ginkgo biloba prevented the reduction in choice accuracy induced by 4 mg/kg yohimbine. These data suggest that the prefrontal cognition-enhancing effects of extract of Ginkgo biloba are related to its actions on alpha-2-adrenoceptors.

Enhanced biological effect induced by a radioactive C-9-ion beam at the depths around its Bragg peak

To explore the potential of double irradiation source, radioactive C-9-ion beam, in tumor therapy, a comparative study oil the surviving effect of human salivary gland cells at different penetration depths between C-9 and C-12-ion beams has been carried out. The 9C-ion C beam, especially at the distal side of the beam came out more efficient in cell killing at the depths around its Bragg peak than the 12 Bragg peak. Compared to the C-12 beam, an increase in RBE by a factor of up to 2.13 has been observed at the depths distal to the Bragg peak of the 9C beam. The 9C beam showed an enhanced biological effect at the penetration depths around its Bragg peak, corresponding to the stopping region of the incident C-9-ions and where the delayed low-energy particles were emitted. Further analysis revealed that cell lethality by the emitted particles from the stopping C-9-ions is responsible for the excessive biological effect at the penetration depths around the Bragg peak of the C-9 beam.

Deformation, Phase Transformation and Recrystallization in the Shear Bands Induced by High-Strain Rate Loading in Titanium and its Alloys

alpha-titanium and its alloys with a dual-phase structure (alpha+beta) were deformed dynamically under strain rate of about 10(4) s(-1). The formation and microstructural evolution of the localized shear bands were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results reveal that both the strain and strain rate should be considered simultaneously as the mechanical conditions for shear band formation, and twinning is an important mode of deformation. Both experimental and calculation show that the materials within the bands underwent a superhigh strain rate (9 x 10(5) s(-1)) deformation, which is two magnitudes of that of average strain rate required for shear band formation; the dislocations in the bands can be constricted and developed into cell structures; the phase transformation from alpha to alpha(2) within the bands was observed, and the transformation products (alpha(2)) had a certain crystallographic orientation relationship with their parent; the equiaxed grains with an average size of 10 mu m in diameter observed within the bands are proposed to be the results of recrystallization.

Experimental Study on Vortex-Induced Vibrations of a Pipeline Near a Plane Boundary in Steady Flow

对单向水流作用下近壁管道横向涡激振动进行了实验模拟,重点探讨了管道与壁面间隙比(e/D)对管道涡激振动幅值和涡激振动频率响应特性的影响规律.实验结果表明,管道与壁面间隙宽度对管道涡激振动特性有较明显影响.在较大间隙比(e/D＞0.66)下,管道振幅随着Vr数的增大先快速增长到最大值,然后平缓下降;在振动初期(即Vr数较小时),管道振动频率变化基本符合Strouhal规律;在振动中后期(即Vr数较大时),管道振动频率变化不符合Strouhal规律,而在管道固有频率附近缓慢增长.在较小间隙比(e/D＜0.30)下,管道振幅随Vr数的增大先平缓上升到最大值,随后较快速下降;在振动初期,管道振动频率变化不遵循Strouhal规律;在整个振动范围内,与较大间隙比情况相比,随着Vr数增加,管道振动频率增长幅度明显较大.

Intensity Distribution Design for Laser-Induced Thermal Loading Based on Numerical Simulation

To accomplish laser-induced thermal loading simulation tests for pistons,the Gaussian beam was modulated into multi-circular beam with specific intensity distribution.A reverse method was proposed to design the intensity distribution for the laser-induced thermal loading based on finite element(FE) analysis.Firstly,the FE model is improved by alternating parameters of boundary conditions and thermal-physical properties of piston material in a reasonable range,therefore it can simulate the experimental resul...

Microstructure and Evolution of Mechanically-Induced Ultrafine Grain in Surface Layer of Al-Alloy Subjected to USSP

Experiments were conducted to investigate the ultrafine-grained (UFG) microstructures in the surface layer of an aluminum alloy 7075 heavily worked by ultrasonic shot peening. Conventional and high-resolution electron microscopy was performed at various depths of the deformed layer. Results showed that UFG structures were introdued into the surface layer of 62 μm thick. With increasing strain, the various microstructural features, e.g., the dislocation emission source, elongated microbands, dislocation cells, dislocation cell blocks, equiaxed submicro-, and nano-crystal grains etc., were successively produced. The grain subdivision into the subgrains was found to be the main mechanism responsible for grain refinement. The simultaneous evolution of high boundary misorientations was ascribed to the subgrain boundary rotation for accommodating further strains. Formed microstructures were highly nonequilibratory.  2002 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.