抗辐射菌Deinococcus radiodurans一种新的DNA修复 …

抗辐射菌Ｄｅｉｎｏｃｏｃｃｕｓ ｒａｄｉｏｄｕｒａｎｓ具有显著的ＤＮＡ修复能力，包括对丝裂霉素，紫外线及γ射线，通过化学诱导野生型菌株ＫＤ８３０１而得到的突变体ＫＨ３１１１，对ＭＣ，ＵＶ及γ射线敏感，对链霉素具有抗性，ＫＨ３１１１的辐射抗性能通过传染野生型抗辐射菌ＫＤ８３０１基因组中一个已被克隆的ＤＮＡ片断而得到恢复。     

抗辐射菌Deinococcus radiodurans辐射抗性研究

观察了野生型抗辐射菌Ｄｅｉｎｏｃｏｃｃｕｓ ｒａｄｉｏｄｕｒａｎｓ ＫＤ８３０１及其修复缺陷突变体ＫＨ３１１１对γ射线的抗性程度,探讨了影响辐射抗性的有关因素。ＫＤ８０３１和ＫＨ３１１１经大剂量γ射线照射（０．５￣１０ｋＧｙ）,制作剂量、存活曲线;利用荧光分光光度法测定细菌的ＤＮＡ含量。结果表明,野生型的ＫＤ８０３１对射线具有显著抗性,推定的ＬＤ９０为９．５ｋＧｙ,而其突变体ＫＨ３１１１的抗性明显     

二株丝裂霉素敏感的抗辐射菌Deinococcus radioduran …

抗辐射菌Ｄｅｉｎｏｃｏｃｃｕｓ ｒａｄｉｏｄｕｒａｎｓ具有显著的ＤＮＡ损伤修复能力，包括对丝裂霉素（ＭＣ），紫外线（ＵＶ）及电离辐射等所致的损伤。在用对ＤＮＡ损伤因子具有抗性的野生型抗辐射菌ＫＤ８３０１的基因组ＤＮＡ构建的基因文库中，有四个克隆能够通过其ＤＮＡ转化，使二株对ＭＣ敏感的Ｄｅｉｎｏｃｏｃｃｕｓ ｒａｄｉｏｄｕｒａｎｓ的突变体ＫＤ２６２１和３０２１回复对ＭＣ的抗性。克隆了二株突变体中受突     

IDENTIFICATION OF uvrA GENE MUTATION SITES IN TWO MITOMYCIN-SENSITIVE Deinococcus radiodurans STRAINS

抗辐射菌Ｄｅｉｎｏｃｏｃｕｓｒａｄｉｏｄｕｒａｎｓ具有显著的ＤＮＡ损伤修复能力,包括对丝裂霉素（ＭＣ）,紫外线（ＵＶ）及电离辐射等所致的损伤。在用对ＤＮＡ损伤因子具有抗性的野生型抗辐射菌ＫＤ８３０１的基因组ＤＮＡ构建的基因文库中,有四个克隆能够通过其ＤＮＡ转化,使二株对ＭＣ敏感的Ｄｅｉｎｏｃｏｃｃｕｓｒａｄｉｏｄｕｒａｎｓ的突变体－２６２１和３０２１回复对ＭＣ的抗性。克隆了二株突变体中受突变（ｍｔｃＡ或ｍｔｃＢ）影响的基因,并测定了该基因的核苷酸序列。理论上推定抗辐射菌ｕｖｒＡ基因产物的氨基酸序列是由１０３６个氨基酸组成,与许多细菌的ＵｖｒＡ蛋白质具有同源性。用ＰＣＲ技术扩增二株突变体基因组中相应的ＤＮＡ片段,并对其加以测序分析,确定了突变发生的位点。对于突变体３０２１,其ｕｖｒＡ基因中发生了１４４个碱基对（ｂｐ）的缺失突变（缺失部分包括ｕｖｒＡ的起始密码）,造成了３０２１的ｕｖｒＡ基因的失活。对于２６２１突变体,其ｕｖｒＡ基因内却发生了一个插入突变,造成了该基因的插入失活。该插入序列由１３２２ｂｐ组成,侧面与１９ｂｐ组成的末端反转重复（ＩｎｖｅｒｔｅｄＴｅｒｍｉｎａｌＲｅｐｅａｔｓ,ＩＴＲ）相连接,并产生     

抗辐射菌Deinococcus radiodurans DNA修复基因的分子克隆和功能分析(英文)

抗辐射菌(Deinococcus radiodurans)具有显著的DNA修复能力,包括对丝裂霉素(MC),紫外线(UV)及γ射线引起的DNA损伤的修复。通过化学诱导野生型菌株KD8301而得到的突变体KH3111,对MC,UV及γ射线敏感,对链霉素(Sm)具有抗性。本研究确定了KH3111内发生突变的基因及其核苷酸序列,该基因(orf144b)所编码的蛋白质由284个氨基酸组成,与其它已知的蛋白质不具有同源性,即它是一种新的蛋白质。KD8301和KH3111的orf144b序列只是一个碱基的改变,即由G突变为A,所编码的第149位氨基酸由甘氨酸变为谷氨酸。说明甘氨酸是DNA修复基因orf144b所编码的蛋白质中的一个重要残基。用KD8301的orf144b基因转染KH3111,得到转染体KH3112,其对MC,UV及γ射线都具有同母本(KD8301)一样的抗性。在抗辐射菌中,这种对多种DNA损伤剂产生抗性所需要的基因(orf144b),我们命名为pprA(Pleiotropic gene promoting DNA repair)基因。该基因能在大肠杆菌JM109中高水平表达,并使宿主大肠杆菌产生对MC,UV和γ射线的抗性。在野生型的KD8301中,正常情况下该基因不表达,经MC,UV和γ射线处理KD8301后,可诱导该基因表达。研究表明,PprA蛋白质是一种胞浆蛋白。     

微细胞介导染色体转移法提高AT5 BIVA细胞对电离辐射的抗性

ＡＴ５ＢＩＶＡ细胞是一株经ＳＶ４０病毒转化的ＡＴ病人皮肤成纤维细胞，对γ射线高度敏感。实验用ＦＤ３（含人第１１号染色体的人鼠杂种细胞）、ＦＤ８（不含人第１１号染色体的人鼠杂种细胞）、ＬＭ／ＴＫ鼠细胞）为洪体，通过微细胞介导染色体转移（ＭＭＣＴ）向ＨＴ５ＢＩＶＡ细胞导入人或鼠的完整染色体，经两次３Ｇｙγ射线照射筛选后，获得ＡＴ５ＢＩＶＡ与ＦＤ３微细胞融合的杂合细胞ＡＴ／ＦＤ３－１，对γ射线抗性有显著提高。而ＦＤ８或ＬＭ／ＴＫ的微细胞与ＡＴ５ＢＩＶＡ细胞的杂合细胞，对γ射线抗性未增加。枝型分析表明ＡＴ／ＦＤ３—１细胞中包含了来源于ＦＤ３细胞的人第１１，１４号染色体和数条鼠染色体。通过对照实验，排除了人１４号和鼠染色体提高ＡＴ／ＦＤ３－１细胞对γ射线抗性的可能性．确认人第１１号染色体与ＡＴ细胞对电离辐射敏感性相关，提示人第１１号染色体上可能存在决定细胞对γ射线抗性的相关基因。     

RADIONUCLIDES IN RICE IN HONG KONG

ＲＡＤＩＯＮＵＣＬＩＤＥＳ　ＩＮ　ＲＩＣＥ　ＩＮ　ＨＯＮＧ　ＫＯＮＧＫ．Ｎ．ＹｕａｎｄＳ．Ｙ．Ｍａｏ（ＤｅｐａｒｔｍｅｎｔｏｆＰｈｙｓｉｃｓａｎｄＭａｔｅｒｉａｌｓＳｃｉｅｎｃｅ，ＣｉｔｙＰｏｌｙｔｅｃｈｎｉｃｏｆＨｏｎｇＫｏｎｇ）Ａｂｓｔｒａｃｔ：...     

抗辐射菌lexA基因的克隆及在大肠杆菌中表达

研究了旨在克隆抗辐射菌Ｄｅｉｎｏｃｏｃｃｕｓ ｒａｄｉｏｄｕｒａｎｓ的ｌｅｘＡ基因并构建其表达载体,以便于进一步研究ｌｅｘＡ基因的功能及其在辐射抗性中的作用。主要的实验步骤包括分离提取抗辐射菌基因组ＤＮＡ,分离出ｌｅｘＡ基因并测定其序列,克隆于质粒载体ＰＵＣ１９,用电击穿孔法将重组的质粒导入在肠杆菌ＪＭ１０９,ＳＤＳ－ＰＡＧＥ检测基因的表达。用定点突变技术,改变ｌｅｘＡ基因核糖体结合位点（ＲＢＳ）     

聚合酶β在肝癌细胞DNA辐射损伤修复中的作用

利用第二军医大学裸鼠移植性肝癌细胞（ＳＭＭＣ－ＬＴＮＭ）和不同的ＤＮＡ聚合酶选择性抑制剂ＮＥＭ与ｄ２ＴＴＰ，探讨了肿瘤细胞核中ＤＮＡ聚合酶β参与γ射线辐射损伤ＤＮＡ修复的作用特点，结果表明，该酶参与真核细胞γ射线辐照损伤的ＤＮＡ修复合成，是一种重要的ＤＮＡ修复酶，与正常肝细胞相比，ＳＭＭＣ－ＬＴＮＭ肝癌细胞ＤＮＡ聚合酶β的ＤＮＡ修复合成反应速度快，修复能力强，提示某些肿瘤细胞中该酶的ＤＮＡ辐射损伤     

微细胞介导染色体转移法提高AT5BIVA细胞对电离辐…

ＡＴ５ＢＩＶＡ细胞是一株经ＳＶ４０病毒转化的ＡＴ病人皮肤成纤维细胞，对γ射线高度敏感。实验用ＦＤ３，ＦＤ８，ＬＭ／ＴＫ为供体，通过微细胞介导染色体转移向ＡＴ５ＢＩＶＡ细胞导入人或鼠的完整染色体，经两次３Ｇｙγ射线照射筛选后，获得ＡＴ５ＢＩＶＡ与ＦＤ３微细胞融合的杂合细胞ＡＴ／ＦＤ３－１，对－γ射线抗性有显著提高。     

Preparation of Zn/TiO2 powder and its photocatalytic performance for oxidation of P-nitrophenol

Zn-doped TiO2 catalysts were prepared using a sol-gel method and characterized by XPS,UV-Vis, BET, XRD in this study. Under the irradiation of simulant sunlight, the photocatalytic activity for the degradation of p-nitrophenol was studied too. After irradiation for 2.5 h, the degradation percentage of p-nitrophenol could rise to more than 80 %. The results showed that the spectrum absorption band edge of Zn/TiO2 powder does not broaden obviously comparing with pure TiO2 powder. Zinc exists as Zn （11）. When calcined at 973 K, there is a new phase as ZnTiO3 in Zn/TiO2 catalyst. The order of photocatalytic activity of Zn/TiO2 catalysts calcined at different temperatures for p-nitrophenol is 773 K 〉 673 K 〉 873 K 〉 573 K 〉 973 K and the photocatalytic activity of Zn/TiO2 catalyst calcined at 773 K is better than TiO2 catalysts heated at the same temperature, and outclasses that of commercial TiO2 catalyst. It also showed that the photocatalytic degradation of p-nitrophenol follows first-order kinetics under the irradiation of simulant sunlight.     

Current status of radiation therapy for prostate cancer

Radiotherapy for the treatment of prostate cancer has been extensively explored in the past. Along with the comprehensive understanding of the biology of prostate cancer and rapid advances in terms of technology, the out- come of treatment for the patients with prostate cancer has improved. The authors review radiotherapy as the primary treatment for the disease, with particular emphasis on the technological advances from both the radiobiological and radiophysics aspects. Nonconventional fractionated irradiation like hyper- or hypo-fractionation has been imple- mented in the clinic, the final results still need to be confirmed in the future. Technological advances like IMRT, IGRT, in the last two decades have significantly improved the delivery of external radiotherapy to the prostate. This has re- sulted in an overall increase in the total dose that can be safely delivered to the prostate, which has led to modest im- provements in the biochemical outcome. However, establishing the standard therapy for prostate cancer remains con- troversial. It is hoped that the next decades will bring continued advances in the development of biologicals that will further improve current clinical outcomes.     

水平管内含空气蒸汽强制对流冷凝换热模型研究

为研究含空气蒸汽在水平管内强制对流冷凝换热特性,基于对传热传质过程的分析,建立了管内为环状流与波状流条件下的流动冷凝换热模型。从潜热、显热和液膜3个环节对整个换热过程进行建模,最终得到计算局部冷凝换热系数的理论关系式。模型预测结果与实验数据的对比表明,二者相对偏差在±20%以内,验证了该换热模型的准确性与适用性。通过进一步的研究发现：从换热管入口至出口,随着冷凝的进行,管内换热主要热阻由液膜热阻向气液界面的凝结热阻转变;主流气体对流换热过程基本可忽略。     

Investigations on landmine detection by BF3 detector

Experiments were carried out to investigate the possible use of neutron backscattering for the detection of polyethylene (PE) sample buried in the soil. In detection of landmine by neutrons, the neutron detector and its shield play an important role. In this paper, the effects of graphite, heavy water, polyethylene and boric acid moderators on the flux of back scattered neutrons were investigated. We have also experimentally verified the effect of BF3 detector shield and obtained good agreement with theory.     

Web Services interface of SSRF archive data analysis system

Accelerator database stores various static parameters and real-time data of accelerator. SSRF (Shanghai Synchrotron Radiation Facility) adopts relational database to save the data. We developed a data retrieval system based on XML Web Services for accessing the archive data. It includes a bottom layer interface and an interface applicable for accelerator physics. Client samples exemplifying how to consume the interface are given. The users can browse, retrieve and plot data by the client samples. Also, we give a method to test its stability. The test result and performance are described.     

Assessment of radioactivity levels in some oil samples from the western desert, Egypt

Distributions of natural gamma-emitting radionuclides were determined in 93 oil samples collected from some petroleum fields in the western desert of Egypt. The radioisotope activities in the area under investigation lay in the range of (21 ± 4) to (38 ± 13) Bq?L-1 for 226Ra, (9 ± 2) to (15 ± 5) Bq?L-1 for 232Th, and (154 ± 28) to (303 ± 54) Bq?L-1 for 40K. The mean values were 27, 12, and 201 Bq?L-1, respectively. Among oils, variations in radionuclide ac- tivities could be on account of differences in TDS, HCO3, and Ba, with high or low pH. In this environment, oil prop- erties differently affected the mobilization of natural radionuclides. The range of 226Ra variation had been compared with available data from other countries. The calculated absorbed dose rate ranged from 22.33 to 32.66 nGy?h-1 in lo- cation (B) and (E) respectively, which was less than the accepted value.     

Preparation and properties of 117m Sn(IV)-TTHMP in in-vitro and in small animals

In this work,TTHMP was synthesized and labelled with 117m Sn.The preparation conditions,stability and lipophilicity of 117m Sn(IV)-TTHMP were investigated.Biodistribution of the complex in rabbits and mice was studied.It was found that the quantity of TTHMP and pH value of the prepararion solution had vital effects on the labeling yield of 117m Sn(IV)-TTHMP.It was also found that 117m Sn(IV)-TTHMP was hydrophilic and stable at room temperature and 37℃ in open air 117m Sn(IV)-TTHMP showed unexpectedly high bone uptake and bone-to-blood ratio in the animals.This made it potentially useful as an reagent for skeletal scintigraphy and radiotherapy of bone tumors.     

The role of AGFA high-energy CR in the calibration and quality control of multileaf collimators （MLC）

Linear accelerators equipped with multileaf collimators （MLC） are becoming more common and are widely used in the intensity-modulated radiotherapy （IMRT）. There is an imperative need to ensure the commissioning specification of the linear accelerators for the sake of quality assurance （QA） and quality control （QC）. This paper is aimed to investigate the role of AGFA high-energy CR （Computed Radiography） in calibrating dynamic multileaf collimators and evaluating the accuracy of the leaf position. The result shows that AGFA high-energy CR can easily and conveniently be used to calibrate MLC and verify its position. Hence, the application of AGFA high-energy CR is proved to be an accurate and time-saving method for routine MLC QC, especially when MLC calibration adjustments are required.     

微型X射线管空气比释动能和能谱的测量

为研究微型X射线管的特性,通过电离室测量光管出射口30 cm远处的空气比释动能,使用高纯锗探测器分别测量了Ag过滤和Cu过滤下的X射线能谱。结果表明,空气比释动能随电流的增加有线性增加的趋势,能谱图明显的观察到银的两个特征X射线。完成了微型X射线管空气比释动能和能谱的测量方法以及实验测量的工作,为微型x射线管下辐射质的建立提够了条件基础。     

Gamma-ray attenuation technique for measuring void fraction in horizontal gas-liquid two-phase flow

The measurement of void fraction is of importance to the oil industry and chemical industry. In this article, the principle and mathematical method of determining the void fraction of horizontal gas-liquid flow by using a single-energy γ-ray system is described. The γ-ray source is the radioactive isotope of 241Am with γ-ray energy of 59.5 keV. The time-averaged value of the void fraction in a 50.0-mm i.d. transparent horizontal pipeline is measured under various combinations of the liquid flow and gas flow. It is found that increasing the gas flow rate at a fixed liquid flow rate would increase the void fraction. Test data are compared with the predictions of the correlations and a good agreement is found. The result shows that the designed γ-ray system can be used for measuring the void fraction in a horizontal gas-liquid two-phase flow with high accuracy.