早晚季不同耐光氧化特性水稻品种籽粒灌浆关键酶活性变化

选用光氧化敏感和不敏感的两大类型4个水稻品种研究早晚季耐光氧化反应特性与其稻米品质稳定性密切相关的生理生化原因.结果表明,耐光氧化反应特性强的适强光生态型水稻品种的平均灌浆速率(G_mean)、达最大灌浆速率时间(T_max.G)和达最大灌浆速率百粒重(W_max.G)等参数在早晚季灌浆结实期间保持相对稳定;而对光氧化敏感的弱光生态型品种佳禾早占以上参数的早晚季稳定性较差.比较早晚季籽粒灌浆充实过程中关键酶活性的变化结果可见,耐光氧化反应特性强的品种,灌浆速率高峰到灌浆终期ADPG-焦磷酸化酶和淀粉合成酶活性早晚季变异比耐光氧化反应特性弱的品种小,且耐光氧化反应特性强的品种灌浆高峰前后酶活性变异的幅度早晚季也较一致.     

竹红菌甲素敏化质粒pBR 322 DNA光氧化——使封闭环DNA转变为开环DNA

甲素可敏化质粒pBR 322 DNA光氧化断链的使其封闭环DNA转变为开环DNA。甲素敏化pBR 322 DNA光氧化反应可被单线态氧淬灭剂-NaN_3抑制,证明此光敏氧化机制属Ⅱ型过程。     

2型糖尿病发生大血管并发症的危险因素分析

目的:探讨2型糖尿病患者发生大血管并发症的危险因素.方法:选取哈尔滨医科医科大学附属第四医院内分泌科2012年1月至2012年12月住院的2型糖尿病患者共计200例,根据相关辅助检查结果将其分为2型糖尿病无大血管并发症(DMl)组和2型糖尿病合并大血管并发症(DM2)组,比较2组患者血清胆红素水平及相关指标的差异.应用多因素非条件Logistic回归分析法对2型糖尿病大血管并发症危险因素建立方程.结果:2型糖尿病合并大血管并发症组患者血清胆红素水平低于2型糖尿病无大血管并发症组(P＜0.01),以糖尿病合并大血管并发症为因变量,年龄、病程、糖化血红蛋白、低密度脂蛋白胆固醇、甘油三酯、总胆红素、总胆固醇、直接胆红素、间接胆红素水平为自变量,进行Logistic逐步回归分析,结果显示病程、血清低密度脂蛋白胆固醇、年龄和总胆固醇是2型糖尿病合并大血管并发症的独立危险因素,血清胆红素水平是其保护性因素.结论:病程、年龄、血清低密度脂蛋白胆固醇和总胆固醇水平是2型糖尿病合并大血管并发症的独立危险因素,而血清胆红素水平是其保护性因素.     

在光氧化条件下不同类型高产稻的叶绿素荧光特性和膜脂过氧化特点

用不同类型高产稻(Oryza sativa L.)粳稻9516、具有粳型成分的两系法亚种间杂交稻培矮64/E32、两优培九(培矮64/9311)和籼型杂交稻X07S/紫恢100、冈优881、汕优63为材料,研究了孕穗期叶片在光氧化条件下的叶绿素荧光特性和膜脂过氧化表现.光氧化处理后,与籼型杂交稻比较,粳稻和具有粳型组分的亚种间杂交稻的PSⅡ原初光化学效率(Fv/Fm)、PSⅡ的线性电子传递的量子效率(ΦPSⅡ)和光化学猝灭系数(qP)下降的较少;超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、过氧化物酶(POD)诱导的活性较高,活性氧 (O(-)/()2、H2O2)和丙二醛(MDA)的产生积累较少,叶绿素和蛋白质含量下降较少,表现出耐光氧化特性,这与在自然条件下生育后期叶绿素含量变化相一致.相关分析表明它们的耐光氧化特性与结实率密切相关,说明耐光氧化品种抗早衰,有利籽粒充实.这些结果启示我们:从超高产育种出发,兼顾杂种优势利用和抗早衰两方面考虑,在母本不育系中引入粳型成分是一个值得重视的育种策略.     

慢性充血性心力衰竭血清胆红素与心功能参数的相关性研究

目的:探讨慢性充血性心力衰竭患者血清胆红素(TBIL)水平与左心室功能的关系及其,临床意义.方法:采用钒酸氧化法测定128例心力衰竭患者和63例对照组血清胆红素水平;用心脏彩色多普勒超声诊断仪测定并比较各组左室射血分数(LVEF)及左室舒张末期横径(LVEDD);同时进行6分钟步行实验(6MWT).结果:心力衰竭患者血清胆红素显著高于对照组(P＜0.01),而LVEF与6分钟步行距离(6MWD)对照组明显减少(P＜0.01),且心力衰竭患者随着心功能NYHA分级程度的加重血清胆红素水平及LVEDD逐步递增,LVEF与6MWD也相应减少,各亚组问比较仍有统计学差异(P＜0.05).血清胆红素水平与LVEDD呈正相关(r=0.78,P＜0.01),而与LVEF呈负相关(r=-0.42,P＜0.01).结论:血清胆红素水平随着心力衰竭严重程度的增加而升高,并与左心室功能存在相关性,对慢性充血性心衰患者的诊断、病情及预后判断具有一定的临床意义.     

原发性高血压患者α-Adducin基因单核苷酸多态性(Gly460Trp)与血清胆红素含量相关性

探讨了自 2 0 0 0年 9月到 2 0 0 1年 1月来自安徽省霍邱县地区原发性高血压人群中α Adducin基因单核苷酸多态性与血清中总胆红素、直接胆红素和间接胆红素含量的相关性。在原发性高血压女性患者中 ,在校正了许多可能影响胆红素含量的重要因素后 ,与携带有Gly4 6 0Gly基因型的高血压女性患者相比较 ,携带有Trp4 6 0Trp基因型的高血压女性患者血清平均总胆红素 (β =- 1 2 μmol/L ;P =0 0 1)、直接胆红素 (β =- 0 4 μmol/L ;P =0 0 2 )和间接胆红素 (β=- 0 8μmol/L ;P =0 0 3)的含量比较低。在女性中抽取总胆红素、直接胆红素和间接胆红素含量最高和最低的各 2 5 % ,在校正了重要的变量后发现携带Trp/Trp基因型的女性比Gly4 6 0Gly基因型的女性有更大的可能性血清总胆红素含量 (OR值 =4 0 ;95 %可信区间 :1 6～ 10 2 ;P <0 0 1)、直接胆红素含量 (OR值 =4 0 ;95 %可信区间 :1 6～ 9 7;P <0 0 1)和间接胆红素含量 (OR值 =2 7;95 %可信区间 :1 1～ 6 7;P =0 0 3)更低。然而 ,在男性高血压患者中没有发现任何明显的相关性。以上的结果认为在中国原发性高血压女性患者中 ,Trp/Trp基因型与低的血清胆红素含量有直接关系 ,因为Trp/Trp基因型的女性的低血清胆红素 ,进而认为也许增加了患心血     

水稻耐光氧化和耐荫特性的生理基础

用简易、有效的人工光氧化和遮荫技术对30个水稻(Oryza sativa L.)种质进行筛选,鉴定出既耐光氧化又耐荫、耐光氧化不耐荫、耐荫不耐光氧化、既不耐荫又不耐光氧化等4种品种类型,并用既耐光氧化又耐荫的品种"武育粳3号"和对光氧化和遮荫均敏感的品种"香籼"进行光合特性研究.结果表明:在遮荫条件下,与对光氧化和遮荫敏感的品种"香籼"比较,"武育粳3号"的PSⅡ活性差异不大,RuBisCO活性降低较少,光合能力、光合生产力较高.在光抑制条件下,"武育粳3号"的PSⅡ活性,PSⅡ光化学效率(Fv/Fm),PSⅡ-D1蛋白含量降低较少,光合作用光抑制较轻.在光氧化条件下,内源活性氧清除剂SOD诱导活性高,清除O-能力强,因而叶绿素衰减较慢.上述研究为水稻育种提供了配套的优良生理特性的鉴定技术和生理依据.     

竹红菌甲素敏化嘌呤和嘧啶碱的光氧化作用及其影响因素

本工作利用光吸收和高效液相色谱(HPLC)技术研究了甲素对DNA分子中四种碱基A、G、C和T光氧化的敏化作用,发现在反应体系的pH为9.0、甲素浓度为3×10~(-5)mol/L、光照40分钟时,G和T紫外吸收明显降低;HPLC分析发现甲素敏化的G光氧化体系比对照体系多出现一组分峰(滞留时间0.927分钟),该峰用475nm波长检测比260nm波长检测灵敏。根据反应机制推测是G环破裂产物。在反应条件固定时,甲素敏化G的光氧化作用受pH、光照时间及甲素浓度影响极大。单线态氧淬灭剂——叠氮钠浓度在40—110mmol/L可部分抑制甲素敏化G的光氧化作用,>110mmol/L时反应完全被阻断,提示甲素对G光氧化的敏化作用主要通过单线态氧(~1O_2)即Ⅱ型机制起作用。本文还讨论了G光氧化的可能途径。     

兼性CAM植物长叶景天叶片在C3和CAM型时的光氧化作用

通过停止浇水产生水分胁迫使兼性CAM植物长叶景天(Sedum spectabile Boreau)叶片光合途径由C3型转为CAM型.干旱15 d时观察到典型的CAM生理特征,且叶片的δ13C值与含水量成线性相关.水分胁迫改变了叶绿素荧光参数和抗氧化能力,ΦPSⅡ和qP降低50%和34%,NPQ提高约180%,SOD活性和清除DPPH@ 自由基能力也明显下降, 但膜半透性变化不大.当将处于C3(浇水)和诱导为CAM(缺水)型的叶圆片用外源甲基紫精(MV)和强光作光氧化处理后,与C3型叶片相比,诱导CAM型叶片的NPQ不能提高,qP和ΦPSⅡ降至很低水平,光系统处于高还原态,光能供给与消耗失衡(1-qP=0.86和(1-qP)/NPQ>1),膜系统几乎失去完整性.这种严重的光氧化损伤表明,与我们以前报告的专性CAM植物不同,以兼性CAM植物诱导表达的CAM型未能显示比C3型较强的耐光氧化优势.讨论了出现这种光氧化敏感性差别的可能原因.     

血卟啉衍生物光敏引起NAD(P)H氧化作用研究

血卟啉衍生物(HPD)光敏引起NAD(P)H氧化为中介的luminol化学发光(CL)与多种因素有关,如pH、激光功率密度、照光时间以及luminol、HPD以及底物NAD(P)H浓度等的改变都可引起CL的变化.当NAD(P)H浓度远远大于HPD浓度时,CL强度与HPD浓度成正比关系,这表明化学发光测定可以作为检测HPD光敏反应的指标,而且HPD敏化的NAD(P)H光氧化过程中化学发光的产生是与活性氧物质(ROS)有关的.选择性应用O_2、H_2O_2、OH、~1O_2的专一性清除剂研究ROS及~1O_2在HPD敏化的NAD(P)H氧化过程中的作用,其主要结果如下:(1)NAD(P)H光氧化为中介的lumlnol化学发光在水溶液中受到铜锌超氧化物岐化酶(CuZn-SOD)、过氧化氢酶(CAT)和甲酸钠(F)的抑制,在D_2O中受到His和Met的抑制.1μg/ml的CuZn-SOD抑制可达84%,但再增加酶量,抑制程度不再增加;CAT的抑制作用也出现类似情况;F的抑制作用较弱,在14—42mM浓度范围内,抑制程度不超过60%.(2)CuZn-SOD对化学发光的抑制作用随照光时间延长而持续下降,而CAT和F的抑制作用却随照光时间延长而有上升的趋势.His和Met在D_2O中的作用比较复杂.(3)观察伴随NAD(P)H光氧化失活时OD_(340)值的变化,发现ROS清除剂在H_2O中对失活有保护作用,而~1O_2猝灭剂His和Met在D_2O中对失活有保护作用.上述清除剂和猝灭剂     

Cutting edge: HLA-B27 can form a novel beta 2-microglobulin-free heavy chain homodimer structure

HLA-B27 has a striking association with inflammatory arthritis. We show that free HLA-B27 heavy chains can form a disulfide-bonded homodimer, dependent on residue Cys67 in their extracellular alpha 1 domain. Despite the absence of beta 2-microglobulin, HLA-B27 heavy chain homodimers (termed HC-B27) were stabilized by a known peptide epitope. HC-B27 complexes were recognized by the conformation-specific Ab W6/32, but not the ME1 Ab. Surface labeling and immunoprecipitation demonstrated the presence of similar W6/32-reactive free heavy chains at the surface of HLA-B27-transfected T2 cells. HC-B27 homodimer formation might explain the ability of HLA-B27 to induce spondyloarthropathy in beta 2-microglobulin-deficient mice.     

Wavelength dependence of bilirubin photoreactivity

The rates and products of the self-sensitized photoreactions of bilirubin IXα vary with excitation wavelength, solvent and the presence or absence of oxygen. Radical or Type I photooxidation reactions of bilirubin are implicated in degassed chloroform or methanol. Quantum yields for the disappearance of bilirubin vary from 10^?2 to 10^?4 with excitation wavelengths of 440, 340 and 280 nm and with the higher quantum yield generally appearing in chloroform solvent and/or excitation at 280 nm. Bilirubin is stable in degassed chloroform to irradiation at 440 nm.     

Weak chemiluminescence of bilirubin and its stimulation by aldehydes

Bilirubin in an alkaline solution exhibits a weak chemiluminescence (CL) under aerobic conditions. This spontaneous CL was markedly enhanced by the addition of various aldehydes. The fluorescent emission spectrum of bilirubin, excited by weak intensity light at 350 nm, coincided with its CL emission spectrum (peak at 670 nm). CL emission from bilirubin was not quenched by active oxygen scavengers. This suggests that triplet oxygen reacts with bilirubin, and forms an oxygenated intermediate (hydroperoxide) as a primary emitter (oxidative scission of tetrapyrrole bonds in bilirubin is not involved in this CL). The Ehrlich reaction (test for monopyrroles) and hydrolsulphite reaction (test for dipyroles) on the CL reaction mixture and unreacted bilirubin showed no differences. When the CL was initiated by singlet oxygen, rather than superoxide anion, monopyrrole, was detected in the reaction products by gel chromatography. The inhibitory effect of a scavenger of singlet oxygen on CL was eliminated in the presence of formaldehyde. Therefore, triplet carbonyl, formed by singlet oxygen through the dioxetane structure in bilirubin, is not an emitter. The reaction mechanism of bilirubin CL and the formation of a hydroperoxide intermediate is discussed in relation to the chemical structure of luciferin molecules from bioluminescent organisms.     

Bilirubin chemiluminescence induced by the attack of active oxygen species

Ultraweak chemiluminescence (CL) from bilirubin occurs in the presence of triplet oxygen and is stimulated by the addition of aldehydes. Active oxygen species also enhance bilirubin CL, in the absence of aldehydes. An inhibitory effect of active oxygen scavengers on the CL indicated that active oxygens generated from the decomposition of added hydrogen peroxide or from the xanthine-xanthine oxidase reaction contributed to the CL from bilirubin molecules. However, the contribution of singlet oxygen to the CL disappeared in the presence of formaldehyde. This suggested that the scission of tetrapyrrole bonds via a dioxetane intermediate or the production of triplet carbonyls from the oxidation of aldehydes by singlet oxygen was not involved in the CL, at least in the presence of formaldehyde. The spectrum of CL induced by the generation of active oxygen was the same as that from the aldehyde-enhanced CL reaction. We propose that the formation of a hydroperoxide (and/or hydroxide) bilirubin intermediate, but not a dioxetane, may be involved in the excitation of bilirubin molecules for CL.     

Concealed by conspicuousness: distractive prey markings and backgrounds

High-contrast markings, called distractive or dazzle markings, have been suggested to draw and hold the attention of a viewer, thus hindering detection or recognition of revealing prey characteristics, such as the body outline. We tested this hypothesis in a predation experiment with blue tits (Cyanistes caeruleus) and artificial prey. We also tested whether this idea can be extrapolated to the background appearance and whether high-contrast markings in the background would improve prey concealment. We compared search times for a high-contrast range prey (HC-P) and a low-contrast range prey (LC-P) in a high-contrast range background (HC-B) and a low-contrast range background (LC-B). The HC-P was more difficult to detect in both backgrounds, although it did not match the LC-B. Also, both prey types were more difficult to find in the HC-B than in the LC-B, in spite of the mismatch of the LC-P. In addition, the HC-P was more difficult to detect, in both backgrounds, when compared with a generalist prey, not mismatching either background. Thus, we conclude that distractive prey pattern markings and selection of microhabitats with distractive features may provide an effective way to improve camouflage. Importantly, high-contrast markings, both as part of the prey coloration and in the background, can indeed increase prey concealment.     

The mechanism of haem catabolism. Bilirubin formation in living rats by [18O]oxygen labelling.

1. The pathway of haem breakdown in living rats was studied by using 18O in the oxygen that the animals consumed. By cannulation of the common bile duct and collection of bile, labelled bilirubin was isolated and its mass spectrum determined. One set of results was obtained for a rat to which haemoglobin had been intravenously administered and another set obtained for a rat that was not given exogenous haem. Isomerization of bilirubin IXalpha to the XIIIalpha and IIIalpha isomers did not occur to any significant extent. The 18O-labelling pattern obtained in the bilirubin was consistent with a Two-Molecule Mechanism, whereby the terminal lactam oxygen atoms of bilirubin are derived from different oxygen molecules. The consequences of this mechanism are discussed in terms of the possible intermediates of the catabolic pathway. 2. 18O-labelled bilirubin appeared in the bile in less than 10 min after exposure of the animals to labelled oxygen. This result suggests that all of the chemical transformations involving production of biliverdin, reduction to bilirubin and conjugation of the bilirubin are fast processes. 3. The quantitative recovery of label obtained in the experiments suggests that there is little or no exchange of newly synthesized bilirubin with existing bilirubin pools in the animal.     

Porphyrin-induced photooxidation of conjugated bilirubin

Visible light irradiation of 18 microM bilirubin ditaurate (BR-DT) at pH 7.0 for 30 min showed a 10% decrease in absorbance at 445 nm. When the reaction was carried out in the presence of a trace amount of uroporphyrin (UP), the spectrum of BR-DT disappeared without a concomitant formation of biliverdin. Photooxidation products were confirmed to be dipyrrole-containing compounds. Photo-bleaching of BR-DT was accelerated by the increasing concentration of UP and was inhibited, when UP was replaced by Cu2+UP. Formation of 2,2,6,6-tetramethylpiperidine N-oxyl through the irradiation of UP was diminished by sodium azide, a potent scavenger of singlet oxygen. The efficiency of singlet oxygen formation through visible light irradiation was in the order UP, coproporphyrin > Cu2+UP. Both bilirubin and BR-DT bound to human serum albumin (HSA) were photooxidized effectively in the presence of UP. The results indicate that irradiation of UP produces singlet oxygen with high efficiency which then rapidly oxidizes free and conjugated bilirubin.     

An 18O double-labelling study of haemoglobin catabolism in the rat.

The degradation of haemoglobin to bilirubin in the rat was investigated by 18O labelling of the molecular oxygen consumed by the animal. The oxygen atoms incorporated into bilirubin were derived from two different oxygen molecules. Implications of this finding for the mechanism of haem catabolism in vivo are discussed; both verdohaem and a dioxygen-bridged compound appear to be excluded at intermediates.     

Personality and self-motivation during biochemical fatigue

The present study was conducted to determine whether females exhibiting the Type A behavior pattern would exert greater effort and work to higher levels of physiological fatigue in a self-motivated ergometer test. Twenty female subjects, half of them Type A and the other half Type B, were administered an incremental ergometer test to determine their peak oxygen consumption value. On the first experimental session no experimenter encouragement was given to the subjects. Consequently the test measured physical motivation levels. During a second laboratory session, each subject was continuously encouraged by the experimenter to maintain exercising until she was truly incapable of further work. The highest rate of oxygen extraction during this latter session was considered the subject's maximum oxygen consumption (i.e., VO2 max). Type A and B subjects were compared in the nonmotivated testing session (experimental session 1) to their "true" individual capacities (maximum oxygen consumption demonstrated in experimental session 2). ANOVAs indicated no significant differences in self-initiated competitive behavior during a physical stressor.     

Role of heme oxygenase-1 in hypoxia-reoxygenation: requirement of substrate heme to promote cardioprotection

Heme oxygenase-1 (HO-1) catalyzes the enzymatic degradation of heme to carbon monoxide, bilirubin, and iron. All three products possess biological functions; bilirubin, in particular, is a potent free radical scavenger of which its antioxidant property is enhanced at low oxygen tension. Here, we investigated the effect of severe hypoxia and reoxygenation on HO-1 expression in cardiomyocytes and determined whether HO-1 and its product, bilirubin, have a protective role against reoxygenation damage. Hypoxia caused a time-dependent increase in both HO-1 expression and heme oxygenase activity, which gradually declined during reoxygenation. Reoxygenation of hypoxic cardiomyocytes produced marked injury; however, incubation with hemin or bilirubin during hypoxia considerably reduced the damage at reoxygenation. The protective effect of hemin is attributable to increased availability of substrate for heme oxygenase activity, because hypoxic cardiomyocytes generated very little bilirubin when incubated with medium alone but produced substantial bile pigment in the presence of hemin. Interestingly, incubation with hemin also maintained high heme oxygenase activity levels during the reoxygenation period. Reactive oxygen species generation was enhanced after hypoxia, and hemin and bilirubin were capable once again to attenuate this effect. These results indicate that the HO-1-bilirubin pathway can effectively defend hypoxic cardiomyocytes against reoxygenation injury and highlight the issue of heme availability in the cytoprotective action afforded by HO-1.