Microdialysis study of ischemia-induced hydroxyl radicals in the canine heart

A new experimental approach for spin-trapping of oxygen radicals in a selected region of the heart in situ is described. This approach is based on microdialysis, and it permits the detection of oxygen radicals in conditions of local ischemia and restoration of normal blood flow. Increased hydroxyl radical generation in an ischemic area of canine myocardium, as a result of 40 min local occlusion, has been studied.     

水溶液中产生(O_2)~·的机理及其自旋捕获研究

研究了氧饱和碱性连二亚硫酸钠（Ｎａ２Ｓ２Ｏ４）水溶液中超氧负离子基（Ｏ２－）产生的机理，ＥＳＲ和ＵＶ光谱结果表明该反应可能经历Ｏ２与ＳＯ２－间单电子转移；体系中Ｏ２－处于产生－消失的动态过程，其稳定性依赖于溶液ｐＨ值；一次充氧饱和条件下，［Ｏ２－］应不超过１０－３ｍｏｌＬ－１；连续充氧条件下Ｏ２－的累积量与ＳＯ２－的累积量有关     

Alzheimer's disease: fundamental and therapeutic aspects

Alzheimer's disease is the most common type of progressive and debilitating dementia affecting aged people. In some early — as well as late-onset familial cases, a genetic linkage with chromosomes 14, 21 (early-onset) or 19 (late-onset) has been indicated. Furthermore, a direct or indirect role has been attributed to normal or structurally altered amyloid -protein (concentrated in senile plaques) and/or excessively phosphorylated tau protein (located in neurofibrillary tangles). Degeneration of cholinergic neurons and concomitant impairment of cortical and hippocampal neurotransmission lead to cognitive and memory deficits. Several compounds are being tested in attempts to prevent and/or cure Alzheimer's disease, including tacrine, which has very modest efficacy in a sub-group of patients, and new acetylcholinesterase inhibitors. Pilot experiments have also been launched using nerve growth factor (NGF) to prevent or stabilize the processes of cholinergic pathway degeneration. Alternatively, antioxidants, free radical scavengers and/or non steroidal anti-inflammatory agents may be screened as potential therapies for neurodegenerative diseases induced by multiple endogenous and/or exogenous factors. The recent use of transgenic mice, in parallel with other genetic, biochemical and neurobiological systems, in vivo and/or in vitro (cell cultures), should accelerate the discovery and development of specific drugs for the treatment of Alzheimer's disease.     

Protein oxidation and 20S proteasome-dependent proteolysis in mammalian cells

The generation of reactive oxygen species is an inevitable aspect of aerobic life. In addition to being exposed to free radicals in the environment, aerobic organisms must also deal with oxygen radicals generated as byproducts of a number of physiological mechanisms - for example, by the mitochondrial and endoplasmic reticulum electron transport chains, and by cells of the immune system. Although most organisms are equipped with several lines of defense against oxidative stress, these defensive mechanisms are not 100% effective, and oxidatively modified forms of proteins accumulate during aging, and in many pathological conditions.?Oxidatively modified proteins can form large aggregates due to covalent cross-linking or increased surface hydrophobicity. Unless repaired or removed from cells, these oxidized proteins are often toxic and can threaten cell viability. Mammalian cells exhibit only limited direct repair mechanisms, and oxidatively damaged proteins appear to undergo selective proteolysis, primarily by the major cytosolic proteinase, the proteasome. Interestingly, it appears that the 20S 'core' proteasome conducts the recognition and elimination of oxidized proteins in an ATP-independent and ubiquitin-independent pathway. Received 31 May 2001; accepted 26 June 2001     

亚甲蓝光敏反应对腹水型肝癌细胞DNA的降解作用

亚甲蓝光敏反应对腹水型肝癌细胞（ＨｅｐＡ）ＤＮＡ合成具有明显的抑制作用，对ＤＮＡ分子具有明显的降解作用，降解作用随照光时间的延长而加剧，避光组织细胞ＤＮＡ分子也有一定的降解，但照光组的降解作用明显高于避光组。     

维生素消除运动性疲劳的研究现状

根据疲劳产生的机制，对维生素消除运动性疲劳的国内外研究现状进行了分析，指出运动员补充维生素所存在的问题。     

一种新的羟自由基生成方法及其在亚甲基蓝降解中的应用

对苯二甲酸是一种羟自由基捕获剂,它与羟自由基作用后生成有荧光的羟基对苯二甲酸,通过测定超声前后对苯二甲酸荧光强度的变化间接测定超声所产生的羟自由基的量.对时间、功率、pH等因素进行初步的研究,考察它们对超声产生羟基自由基的影响,发现超声时间越长、超声功率越大,产生的羟自由基的量越多,在超声时间为10min、超声功率为100W时250mL对苯二甲酸溶液中产生羟自由基浓度31.14μmol/L,且羟自由基产生量与时间呈现出一定的量化关系;此外,pH值对羟自由基的产生量影响不大.本方法可检测到超声产生的羟自由基最短时间为2min,最低检出限达到0.063μmol/L,稳定性好、操作简便,测定快速.采用超声处理亚甲基蓝溶液,亚甲基蓝逐渐被降解,进一步证实羟自由基的产生,为超声降解提供理论依据.     

大鼠肝刺激因子对CCl_4致肝损伤小鼠保护作用的机制研究——Ⅰ.HSS的抗氧化作用

本工作观察了大鼠肝刺激因子(HSS)对CCl_4损伤小鼠后,肝组织和血清脂质过氧化物丙二醛(MDA)及自由基清除剂谷胱甘肽(GSH)含量的影响。结果发现,HSS(0.1mg/g体重,i p)可使CCl_4(10％,5ml/kg)中毒后48h,肝组织MDA值的升高幅度明显降低(6.23±0.98nmol/mg蛋白vs.4.17±1.67nmol/mg蛋白,P<0.005),但血清MDA值的下降幅度不明显。同时肝组织GSH含量明显高于CCl_4损伤组(3236±472μg/g vs.2007±589μg/g,P<0.001)。上述结果提示,HSS具有抗氧化作用,降低CCl_4自由基对肝细胞膜的损伤作用,保护受损肝脏。     

桑叶提取液对体外氧自由基的清除作用以及对果蝇寿命的影响

本文作者应用化学发光法研究了桑叶提取液对体外氧自由基发生系统：黄嘌呤－黄嘌呤氧化酶体系产生的超氧阴离子，Ｆｅｎｔｏｎ体系产生的羟自由基和用过硫酸铵－Ｎ，Ｎ，Ｎ＾′，Ｎ＾′－四甲基乙二胺体系产生的氧自由基的清除作用，同时研究了高浓度桑叶提取对果蝇寿命的影响。结果表明，桑叶提取液对上述系统产生的氧自由基中的羟自由基具有相当强的清除作用，在剂量比中医大辞典规定的大３倍以上时并不降低雌雄果蝇的平均寿命，且     

Density functional theory study of the reaction paths of reactions of CH_3C(O)O_2 radicals with HO_2 in the gas phase

Acetyl peroxyradicals play a major roleinthe at-mospheric degradation of organic compounds .In pol-luted atmospheres ,the reaction between CH3C(O)O2radical and NO2forms the well-known PAN(peroxy-acetyl nitrate , CH3C(O)OONO2) ,an i mportant or-ganic contributor to photochemical smog.Inless pol-luted atmospheres ,the reactions between CH3C(O)O2and HO2radicals become critical as NOxlevels maybe low[1 ,2]. Niki et al . were the first to examine thereactions of CH3C(O)O2with HO2radic…