Alkaline Step Elution Analysis of Gamma-ray Induced DNA Strand Breaks and Repair in Diploid Yeast

Summary

Gamma-ray induction of DNA strand breaks and their repair was analysed in the diploid yeast strain D7 (Saccharomyces cerevisiae) by means of the alkaline step elution technique. A dose-dependent increase of DNA strand breakage was observed in the dose range 25–2000 Gy corresponding to 100 and 0·01 per cent survival. When, after exposure to γ-irradiation, the cells were incubated for 2 h in liquid growth medium, the elution profiles reached the pattern of unirradiated controls, thus indicating the restoration of cellular DNA due to repair. The alkaline step elution analysis is found to be a useful and reproducible technique for studying the induction of DNA strand breaks and repair in yeast. In comparison with other current methods, such as alkaline sucrose gradients and DNA unwinding, this method appears to be more rapid, versatile and easier to handle.     

X-ray Induced Free Radicals in Single Crystals of N-acetyl-L-leucine

Summary

Double-stranded DNA from calf thymus was irradiated in the presence of bovine serum albumin (BSA) at a ratio of 1:10 by mass under air, N₂ or N₂O, with and without ethanol, tert-butanol or isopropanol in 10^?2 mol dm^?3 sodium phosphate buffer, pH 7·0. The irradiated solutions were analysed by a nitrocellulose filter assay and by high-performance liquid gel chromatography. The results show that OH^· radicals as well as hydrated electrons induce protein—DNA crosslinks. Further, alcohol radicals react with BSA producing protein radicals which become crosslinked to DNA. If OH radicals are scavenged by alcohol, strand breakage of DNA does not occur.     

茶多酚对轻度低压缺氧引起的小鼠肺自由基代谢异常的保护作用.

目的观察天然抗氧化剂茶多酚(Teapolyphenols,TP)对重复轻度低压缺氧引起的小鼠肺自由基代谢异常的保护作用.方法42只雄性昆明种小鼠随机分为3组对照组(A);1500m低压缺氧组(B)和TP保护组(C).低压舱暴露时间为2h/d,3d/wk,共8wk.上舱暴露前,C组灌胃给予TP100mg/kg,另2组给予蒸馏水.末次实验后次日将小鼠断头处死,迅速取出肺组织.测定肺超氧化物歧化酶(SOD)活性和丙二醛(MDA)、一氧化氮(NO)含量.另外,用免疫组化法对肺组织CuZn-SOD和诱生型NO合酶(iNOS)的含量进行定性观察.结果与对照组比较,重复轻度低压缺氧暴露使肺MDA水平和NO含量明显升高(P<0.01),但TP防护组肺MDA生成和NO含量恢复正常.B组肺SOD活性有升高趋势,该组细支气管上皮细胞CuZn-SOD酶含量和支气管上皮细胞及肺间质血管内皮细胞和平滑肌细胞的iNOS酶含量明显增加.重复给予TP使这些酶的异常表达恢复正常.结论天然抗氧化剂茶多酚对重复轻度低压缺氧引起的肺自由基代谢异常具有保护作用.     

He-Ne激光照射对老龄小鼠机体内氧自由基的影响

目的 探讨He-Ne激光照射对老龄小鼠机体内氧自由基的影响，为临床应用提供依据。方法 实验采用波长为632．8nm的He-Ne激光。30只14月龄的昆明种老龄小鼠随机分为A组、B组、C组和D组4个组；A、D组各8只鼠，B、C组各7只鼠；A、B、C组为实验组，D组为老龄对照组。另8只6～7周龄相同昆明种小鼠作为青龄对照(E)组。以能量密度为4．68、12．48和18．72J／cm^2的He-Ne激光分别照射A、B、C3组小鼠的肝区，D、E组鼠不照射激光。照射后观察超氧化物歧化酶(T-SOD)、Cu，Zn-SOD、Mn-SOD、谷胱苷肽(GSH)、丙二醛(MDA)等指标的变化。结果 能量密度为4．68、12．48和18．72J／cm^2的低强度He-Ne激光可提高Cu，Zn-SOD、Mn-SOD及总SOD活性，提高GSH含量，降低MDA含量。其中尤以能量密度为18．72J／cm^2的激光照射的效果最为显著，使老龄小鼠以上各项指标恢复接近正常青龄组水平。结论 He-Ne激光照射可以提高机体抗氧化酶的活性和抗氧化剂的含量，增强机体抗氧化能力。     

针刺足三里穴对运动小鼠体内自由基代谢的影响

为探讨针刺足三里穴对小鼠运动能力和自由基代谢的影响,采用小鼠游泳训练模型,观察体重等一般状况,游泳耐力,血浆、肝脏及肌肉组织中SOD、GSH-Pxx活力和MDA含量.结果表明,针刺足三里穴能改善训练小鼠整体健康状况,提高小鼠游泳耐力和血浆、肝脏、肌肉中SOD、GsH-Px活力,降低MDA含量.提示针刺足三里穴能提高小鼠运动能力,其机理与纠正运动小鼠自由基代谢失衡有关,为运动性疲劳的防治提供了有效的方法.     

The Influence of Oxygen and Temperature on the Radiosensitivity of Soaked Barley Seeds

Summary

(1) The radiosensitivity of soaked barley seeds was directly dependent on their stage of development in relation to the cell cycle.

(2) At any given stage of development there was a pronounced oxygen effect, but no effect of irradiation temperature in the range 2° to 20°c. There was no evidence of any temperature-dependent recovery process.

(3) Similar responses were obtained when radiobiological damage was measured in terms of induced mutation, sterility, or growth inhibition.     

葛根制剂对小鼠乙醇性肝损伤的保护作用研究

目的研究葛根制剂对小鼠乙醇性肝损伤的保护作用.方法采用乙醇肝损伤模型小鼠,以海王牌金樽片为阳性对照,观察葛根制剂低、中、高剂量组对模型小鼠MDA、GSH、AST、ALT及病理损伤的保护作用.结果葛根制剂中、高剂量组均可降低乙醇诱发肝损伤小鼠MDA含量,升高GSH水平,低、中剂量组对小鼠的肝脏病理损害有一定的改善作用.结论葛根制剂对小鼠乙醇性肝损伤有保护作用.     

葛根素对氧自由基的清除和抗氧化性损伤作用

目的　研究葛根素 (Puerarin ,Pue)对氧自由基的清除以及抗氧化性损伤作用。方法　以核黄素 -光系统产生超氧阴离子 ,Fenton反应产生羟自由基 (·OH) ,研究Pue对氧自由基的清除作用 ;以过氧化氢 (H2 O2 )引起红细胞溶血 ,黄嘌呤 -黄嘌呤氧化酶 (X -XOD)致豚鼠心室乳头肌损伤 ,研究Pue的抗氧化性损伤作用。结果　Pue能清除超氧阴离子和·OH ;抑制H2 O2 引起红细胞溶血和脂质过氧化物生成 ;增强心室乳头肌超氧化物歧化酶 (SOD)活性 ,降低丙二醛 (MDA)含量 ,保护乳头肌免受超氧阴离子的损伤。结论　Pue对氧自由基有清除作用 ,并能预防性对抗H2 O2 和超氧阴离子引起的氧化性损伤     

牛磺酸对长期大强度运动训练后大鼠自由基代谢、膜流动性及钙转运的影响

70只雄性Wistar大鼠（80-100g）,随机分为3组：对照组（G1）、游泳训练组（G2）和游泳训练＋牛磺酸组（G3）。牛磺酸补充方式为每日灌服1次（500mg／Kg）。递增负荷训练6周,观察牛磺酸对长期大强度运动训练后大鼠自由基代谢、膜流动性及钙转运的影响。结果显示：运动后即刻,G3组血NH3、BLA、BUN明显低于G2组（P＜0．05）;运动后24小时,G3组血NH3、BLA与对照组比较已无显著性差异（P＞0．05）,而G3组BUN明显低于G2组（P＜0．05）。运动后即刻及24小时,G3组RBC、血浆及心肌线粒体MDA含量明显低于G2组（P＜0．05）;G3组RBC及心肌线粒体GPX活力明显高于G1和G2组（P＜0．05）;G3组心肌线粒体膜荧光偏振度P明显低于G2组（P＜0．05）;G3组心肌线粒体Ca2+浓度明显低于G2组（P＜0．05）;G3组SRCa2+－Atpase活性和摄钙率明显高于G2组（P＜0．05）。以上结果表明,牛磺酸的抗自由基损伤,稳定生物膜和调节钙转运作用可能是其对抗运动性疲劳的重要机制。     

Reactions of OH Radicals with Poly(U) in Deoxygenated Solutions: Sites of OH Radical Attack and the Kinetics of Base Release

Summary

Pulse radiolysis of N₂O-saturated solutions of poly(U) in the presence of tetranitromethane showed that 81 per cent of the radicals formed are reducing in nature. Using data from other sources it has been estimated that 70 per cent of the OH radicals add to the base at C(5) and 23 per cent at C(6) while only 7 per cent abstract an H-atom from the sugar moiety. To a large extent the C(5) OH adduct radicals attack the sugar moiety of poly(U) thereby inducing strand breakage and base release. G (base release) = 2·9 can be subdivided into three components: (a) immediate (20 per cent), (b) fast (50 per cent) and (c) slow (30 per cent). The immediate base release must occur either during the free-radical stage or as a result of the rapid (t_½ < 4 min at 0°C) decomposition of a diamagnetic product. The fast and the slow processes are only readily observable at elevated temperatures, e.g. at 50°C the half lives are 83 min and 26 h, respectively (E_a (fast) = 68 kJ mol^?1, E_a (slow) = 89 kJ mol^?1, A (fast) = 1·5 × 10⁷ s^?1, A (slow) = 1·9 × 10⁹ s^?1. It is concluded that there are three different types of sugar lesions giving rise to base release, structures for which are tentatively proposed.     

Free Radical Formation in Crystals of Guanine Hydrochloride Dihydrate: An ESR and ENDOR Study

Summary

Radiation-induced free radical formation in single crystals of guanine hydrochloride dihydrate has been studied at temperatures between 20 and 300 K using ESR and ENDOR spectroscopy. At low temperatures three radical species are trapped. Two of these are the C8 H-addition radical R1 previously analysed by Alexander and Gordy (1967) and the O6-protonated anion radical R2. The third species (R4) remains unidentified. Upon annealing at 280 K for an extended period the protonated anion R2 transforms into a new radical R3 which exhibit a well-defined hyperfine pattern but still could not be identified unambiguously. Also radical R4 probably transforms into a new radical (R5) upon such treatment. One proton coupling due to R5 was detected. A scheme of radical reactions incorporating these five radicals is proposed. This scheme also suggests that differences in radical formation between the monohydrate and dihydrate crystals of guanine hydrochloride depends upon differences in the hydrogen bonding network.     

褪黑素对重离子辐射损伤小鼠肺的防护作用研究

目的探讨褪黑素(melatonin,MLT)对重离子辐射损伤小鼠肺的防护作用。方法预先给小鼠腹腔注射10mg/kg的MLT,1h后给予0、0.5、1.0、2.0及4.0Gy的全身12C6+束均匀照射,剂量率约1.4Gy/min,辐射后8h,检测辐射损伤小鼠肺组织的SOD活性和MDA、GSH含量,并通过单细胞凝胶电泳技术检测辐射损伤小鼠肺细胞的拖尾长度和尾距。结果和单纯辐射组相比,10mg/kg的MLT腹腔注射能有效抑制重离子辐射引起的小鼠肺组织SOD活性降低、GSH含量下降和MDA含量提高;同时,MLT还能使受损小鼠肺细胞的拖尾长度和尾距显著降低,且都存在剂量效应关系。结论MIT对重离子全身辐射所致小鼠的抗氧化系统有一定的激活效应,对辐射损伤有一定的防护作用,这可能与对抗膜脂质过氧化、清除自由基及其减轻DNA损伤有一定的关系。     

茶多酚对5500m低压条件下吸纯氧引起的小鼠心肌自由基代谢异常的保护作用

目的 观察天然抗氧化剂茶多酚（Tea Polyphenols,TP)对模拟飞行低压吸纯氧引起的小鼠心肌自由基代谢异常的保护作用。方法 42只雄性昆明种小鼠随机分为3组（n=14):对照组（A）、5500m低压吸氧组（B）和TP保护组（C）。B、C两组置于动物低压舱在5500m低压下吸氧（＞96％）,2h/d,3d/wk,共8wk。上舱暴露前,C组灌胃给予TP100mg/kg,另2组给予蒸馏水。末次实验后次日将小鼠断头处死,迅速取出心肌组织。测定心肌超氧化物歧化酶（SOD）活性和丙二醛（MDA）、一氧化氮（NO）含量。另外,用免疫组化法对心肌组织Cu,Zn-SOD和诱生型NO合酶（iNOS)的含量进行定性观察。结果 与对照比较,B组MDA水平、SOD添性和Cu,Zn-SOD酶含量明显升高（P＜0．05）;TP有明显保护作用：降低MDA生成（P＜0．01）,SOD活性和含量恢复正常。与之相反,重复5500m低压吸氧暴露后,心肌NO含量和iNOS表达明显降低。重复给予TP使NO代谢恢复正常。结论 天然抗氧化剂茶多酚对模拟飞行低压吸纯氧引起的心肌自由基代谢异常具有保护作用。     

氧自由基及脂质过氧化在烧伤后免疫功能改变中的作用

研究了氧自由基和脂质过氧化在烧伤后免疫功能异常中的作用。结果显示，小鼠１１％－１２％总体表面积全层皮肤烧伤后第６天所测定的淋巴细胞增殖反应、白细胞介素－２生成、空斑形成细胞形成和迟发性超敏反应均处于抑制状态，血、肝、脾中过氧化脂质水平明显升高，谷胱甘肽含量减少；经过维生素Ｅ和ＳＯＤ处理的烧伤动物在致伤后第６天的上述免疫功能受抑制的程度明显减轻，血、肝、脾中过氧化脂质水平升高不明显，ＧＳＨ含量无明显     

运动性内源自由基对大鼠心肌线粒体功能的影响

为探讨长时间有氧运动至力竭时引起的自由基积累对线粒体正常生理功能的影响，本实验让大白鼠进行游泳运动至力竭，取心肌作为实验材料，研究力竭运动对自由基生成、线粒体膜通透性、线粒体内游离Ｃａ２＋浓度等一系列因素的影响。结果显示，大白鼠游泳至力竭时，心肌线粒体丙二醛（ＭＤＡ）含量显著升高（Ｐ＜０．０１），还原型谷胱甘肽（ＧＳＨ）含量下降（Ｐ＜０．０５内自由基生成和清除失衡，自由基在体内积累，即运动性内源自由基增生。同时观察到琉基含量下降（Ｐ＜０．０１），ＮＡＤＨ荧光值降低（Ｐ＜０．０５）利用Ｆｕｒａ－２ＡＭ做为荧光探针还测到游离Ｃａ２＋浓度下降（Ｐ＜０．０５），提示自由基攻击膜上巯基，膜的完整性受到一定程度损伤，导致Ｃａ２＋外流。Ｃａ２＋浓度下降，削弱了Ｃａ２＋对线粒体内Ｃａ２＋──敏感脱氢酶的激活作用，抑制了线粒体氧化代谢，使还原当量（ＮＡＤＨ）水平降低。而还原当量减少使膜上巯基更易受到自由基攻击，导致Ｃａ２＋进一步外流，形成恶性循环，结果是导致线粒体功能下降，机体产生疲劳。     

杏丁注射液对原发性高血压患者氧自由基和血液流变学的影响

目的 观察杏丁注射液（银杏达莫注射液）对原发性高血压患者氧自由基和血液流变学的影响，探讨杏丁注射液防治高血压病的药理基础。方法 选择血压控制正常高血压患者62例，随机分为杏丁治疗组30例和时照组32例，对照组服用肠溶阿司匹林片，每次75mg，每日1次，作对照，杏丁治疗组用杏丁注射液20ml＋5％葡萄糖注射液250ml静脉滴注，每日1次。分别于治疗前、治疗后14天检测血清超氧化物歧化酶（SOD）活性、丙二醛（MDA）含量。结果 杏丁注射液能明显提高血清超氧化物歧化酶（SOD）活性，降低血清丙二醛（MDA）含量，降低全血粘度（高切、低切）、血浆粘度，其药理效应优于肠溶阿司匹林片。结论 杏丁注射液有明确的抗氧化、消除氧自由基、改善血液流变性的作用。     

Sites of Termination of in Vitro DNA Synthesis on Psoralen Phototreated Single-stranded Templates

Summary

Single-stranded DNA has been photochemically induced to react with 4′-hydroxymethyl-4,5′,8-trimethylpsoralen (HMT) and used as substrate for DNA replication with E. coli DNA polymerase I large fragment. By using the dideoxy sequencing procedure, it is possible to map the termination sites on the template photoreacted with HMT. These sites occur at the nucleotides preceding each thymine residue (and a few cytosine residues), emphasizing the fact that in a single-stranded stretch of DNA, HMT reacts with each thymine residue without any specificity regarding the flanking base sequence of the thymine residues. In addition, termination of DNA synthesis due to psoralen-adducted thymine is not influenced by the efficiency of the 3′-5′exonuclease proof-reading activity of the DNA polymerase.     

吸氧对大强度运动后自由基代谢、红细胞抗氧化系统的影响

目的：观察吸氧对大强度运动后自由基代谢、红细胞抗氧化系统的影响。２０名男子受试者参加本实验。结果：（１）运动后即刻，７０％Ｏ２吸氧组与不吸氧组的血清、红细胞中的ＭＤＡ、血清中的ＳＯＤ和ＧＳＨ显著高于安静水平。（２）运动结束后３０分钟，７０％Ｏ２吸氧组的红细胞中的ＭＤＡ显著低于不吸氧组。（３）运动结束后３０分钟，７０％Ｏ２吸氧组的血清ＳＯＤ和血液、血清中的ＧＳＨ显著高于不吸氧组。结果表明，运动后恢复期吸７０％Ｏ２对运动造成的自由基损伤有明显的抑制作用，可加速运动后体内代谢产物自由基的清除及加快疲劳的消除。     

Heavy Ion Effects on Cellular DNA: Strand Break Induction and Repair in Cultured Diploid Lens Epithelial Cells

Summary

The relative biological effectiveness (RBE) for the induction of DNA strand breaks and the efficiency of repair of these breaks in cultured diploid bovine lens epithelial cells was measured, using accelerated heavy ions in the linear energy transfer (LET)-range up to 16 200 keV/µm. At LET values above 800 keV/µm, the number of DNA strand breaks induced per particle increases both with the atomic number of the projectile and with its kinetic energy. About 90 per cent or more of the strand breaks induced by ions with an LET of less than 10 000 keV/µm are repaired within 24 h. Repair kinetics show a dependence on the particle fluence (irradiation dose). At higher particle fluences a higher proportion of non-rejoined breaks is found, even after prolonged periods of incubation. At any LET value, repair is much slower after heavy-ion exposure than after X-irradiation. This is especially true for low energetic particles with a very high local density of energy deposition within the particle track. At the highest LET value (16 200 keV/µm), no significant repair is observed.