金属硫蛋白对缺氧／复氧心肌细胞的保护作用

金属硫蛋白 (ＭＴ)是普遍存在各种生物体内、富含硫基的小分子蛋白 ,在缺血 /再灌注 (Ｉ/Ｒ)损伤中通过清除自由基减轻心肌细胞损伤 ,同时ＭＴ参与预缺血保护 (ＩＰＣ)。目前对ＭＴ在ＩＰＣ中的保护作用机制及功效仍无明确研究 ,本实验以培养的乳鼠心肌细胞缺氧 /复氧模拟缺血 /再灌注损伤 ,检测心肌细胞在ＩＰＣ处理后 2 4ｈＭＴ的含量、脂质过氧化程度及Ｎａ Ｋ ＡＴＰ酶、Ｃａ2 Ｍｇ2 ＡＴＰ酶的活力变化 ,锌诱导产生的ＭＴ作用 ,并比较ＭＴ与抗氧化剂谷胱甘肽 (ＧＳＨ)的保护作用 ,初步探讨ＭＴ的心肌保护作用机制及应用价值。1　…     

降钙素基因相关肽参与缺血预处理减轻肾损伤的迟发保护作用

继１９８６年Ｍｕｒｙ等发现多次短暂的缺血再灌流（Ｉｓｃｈｅｍｉｃｒｅｐｅｒｆｕｓｉｏｎ,ＩＲ）的刺激,可使心肌在即后经历的长时性ＩＲ中得到保护而提出缺血预处理（Ｉｓｃｈｅｍｉｃｐｒｅｃｏｎｄｉｔｉｏｎｉｎｇ,ＩＰＣ）的概念以后,Ｍａｒｂｅｒ等表明ＩＰ...     

蛋白激酶C与缺血预处理心肌保护作用

蛋白激酶Ｃ（ＰＫＣ）是心肌细胞磷脂酰肌醇信号转导系统的重要组成部分,ＰＫＣ在缺血预处理（ＩＰ）过程中的移位和激活在ＩＰ的心肌保护中发挥了关键的作用。ＰＫＣ介导ＩＰ心肌保护作用的机制与其磷酸化底物蛋白有关,包括激活细胞外－５‘－核苷酸酶,激活ＡＴＰ敏感性钾通道以及维持细胞内Ｃａ＾２＋稳态。对ＰＫＣ发挥ＩＰ心肌保护作用机制的探索将为人类心血管疾病的治疗提供新的理论基础和药理手段。     

抗氧化剂和糖皮质激素抑制缺氧／复氧时肾小球血管内皮细胞ICAM—1的表达

细胞间粘附分子 1(Ｉｎｔｅｒｃｅｌｌｕｌａｒａｄｈｅｓｉｏｎｍｏｌｅｃｕｌｅ ｌ,ＩＣＡＭ 1)主要在内皮细胞表达 ,作为白细胞 β2 整合素家族的配体在中性粒细胞与内皮细胞紧密结合和随后进入缺血组织中起重要作用。通过降低ＩＣＡＭ 1的表达会减轻缺血 /再灌注损伤 ,这点已在多个脏器的动物实验中得到证实。已有研究发现糖皮质激素和抗氧化剂 ,能降低细胞因子刺激下升高的ＩＣＡＭ 1,本研究旨在探讨抗氧化剂二硫代氨基甲酸吡咯烷 (ｐｙｒｒｏｌｉｄｉｎｅｄｉｔｈｉｏｃａｒｂａｍａｔｅ ,ＰＤＴＣ)和糖皮质激素中的地塞米松 (Ｄｅｘ…     

ATP敏感性钾通道在预缺血对麻醉家兔缺血心肌保护中的作用

在氨基甲酸乙酯和戊巴比妥钠两种不同麻醉的家兔心肌缺血－再灌注模型,观察了ＡＴＰ敏感性钾通道开发剂ｃｒｏｍａｋｌｉｍ（Ｃｒｏ）和预缺血（ＩＰ）对血流动力学和心肌梗塞范围的影响,旨在阐明ＫＡＴＰ通道是否与ＩＰ对ＩＲ心肌的保护机制。     

远端缺血预处理对心肌的保护作用

实验发现,局部缺血预处理对远端(未预处理)心肌组织具有保护作用,而且其它器官的短暂缺血也可实现心肌保护作用,这一现象不同于经典的缺血预处理,因此被命名为远端缺血预处理。研究其机制表明,神经反射调节是机体实现远端缺血预处理保护作用的重要方式,心肌组织中蛋白激酶C激活介导了这一作用。     

探索CO2失汇之谜

Ｓｃｉｅｎｃｅ杂志一年一度的 10大科技进展 (Ｂｒｅａｋ ｔｈｒｏｕｇｈ)评选揭晓。大气“ＣＯ2 失汇” (Ｍｉｓｓｉｎｇｃａｒｂｏｎｓｉｎｋ)现象的阐明被列为其中之一 (ＴｈｅＮｅｗｓａｎｄＥｄ ｉｔｏｒｉａｌＳｔａｆｆｓｏｆＳｃｉｅｎｃｅ ,2 0 0 1)。这是一件令生态     

抗菌肽CM4组分的K562癌细胞染色质DNA断裂作用的SCGE研究

单细胞凝胶电泳法（ｓｉｎｇｅ ｃｅｌｌ ｇｅｌ ｅｌｅｃｔｒｏｐｈｏｒｅｓｉｓ,ＳＣＧＥ）是一种快速,敏感的检测单个哺乳动物细胞ＤＮＡ断裂的技术,也叫彗星实验（ｃｏｍｅｔ ａｓｓａｙ）。此实验首次通过ＳＣＧＥ法观察抗菌肽Ｍ４组分对人髓样白血病Ｋ５６２细胞和正常人白细胞核染色质ＤＮＡ的影响,从而进一步研究抗菌肽抗癌作用的机制。荧光显微镜观察显示经抗菌肽ＣＭ４组分处理过的Ｋ５６２癌细胞核染色质ＤＮＡ出     

磷脂酶C-γ2与信号转导

细胞间信息传递及细胞外信号对靶细胞的调控,多年来一直是生物学和医学界研究的焦点。随着Ｃａ２＋和二酰基甘油（ｄｉａｃｙｌｇｌｙ－ｃｅｒｏｌ,ＤＡＧ）第二信使地位的确定,对磷脂酶Ｃ（ＰＬＣ）的研究引起了人们的关注。ＰＬＣ可水解磷脂酰肌醇４,５－二磷酸（ｐｈｏｓ－ｐｈａｔｉｄｙｌｉｎｏｓｉｔｏｌ４,５－ｂｉｓｐｈｏｓｐｈａｔｅ,ＰＩＰ２）产生肌醇１,４,５－三磷酸（ｉｎｏｓｉｔｏｌ１,４,５－ｔｒｉｐｈｏｓｐｈａｔｅ,ＩＰ３）和ＤＡＧ。ＩＰ３可导致细胞内储存Ｃａ２＋的释放。因此,ＰＬＣ处于Ｃａ２＋和Ｄ…     

脑缺血再灌流大鼠海马hsp70及bcl—2基因的表达

为进一步了解中枢神经系统中选择性易损伤的分子机制,采用大鼠短暂前脑缺血再灌流损伤动物模型,应用Ｎｏｒｔｈｅｒｎ杂交、原位杂交及免疫组织化学方法,检测了ｈｓｐ７０及ｂｃｌ－２基因的表达及其组织学分布。发现易损伤的海马ＣＡ１区锥体细胞出现ｈｓｐ７０基因的诱导表达,ＢＣＬ－２蛋白合成受抑制;而耐受缺血的海马ＣＡ３区锥体细胞则明显地持续表达ＢＣＬ－２蛋白,却未见明显的ｈｓｐ７０基因表达。因此提示,ｈｓｐ７０基因的表达是神经元缺血的应激指征,也可能对神经元有保护作用;ＢＣＬ－２蛋白对神经元有保护作用     

Stereospecific 2'-amination and 2'-chlorination of adenosine by Actinomadura in the biosynthesis of 2'-amino-2'-deoxyadenosine and 2'-chloro-2'-deoxycoformycin

2'-Amino-2'-deoxyadenosine and 2'-chloro-2'-deoxycoformycin (2'-CldCF) are two nucleoside antibiotics produced by Actinomadura. The biosynthesis of these two nucleoside antibiotics has been studied by the addition of [U-14C]adenosine with or without unlabeled adenine to cultures of Actinomadura. By this experimental approach, it is possible to demonstrate that adenosine is the direct precursor for the biosynthesis of 2'-amino-2'-deoxyadenosine and 2'-CldCF. These conclusions are based on the observation that the percentage distribution of 14C in the aglyconic and pentofuranosyl moieties of 2'-amino-2'-deoxyadenosine and 2'-CldCF were similar to the distribution of 14C in the adenine and ribosyl moieties of the [U-14C]adenosine (i.e., 48:52) added to cultures of Actinomadura. Experimentally, the percentage distribution of 14C in the (i) adenine:2-amino-2-deoxy-beta-D-ribofuranose of 2'-amino-2'-deoxyadenosine is 51:49; (ii) 8-(R)-3,6,7,8-tetrahydroimidazo[4,5-d]-[1,3-diazepin-8-o1]:2 -chloro-2- beta-D-ribofuranose of 2'-CldCF is 45:55; and (iii) adenine:ribose of the adenosine isolated from the RNA of Actinomadura is 42:58. Further proof that adenosine is the direct precursor for the biosynthesis 2'-amino-2'-deoxyadenosine and 2'-CldCF was demonstrated by the addition of 75 mumol of unlabeled adenine together with [U-14C]adenosine to nucleoside-producing cultures of Actinomadura. The percentage distribution of 14C in the aglycon and the sugar moieties of 2'-amino-2'-deoxyadenosine and 2'-CldCF were 46:54 and 47:53, respectively; the percentage distribution of 14C in the adenine and ribose moieties of the adenosine isolated from the RNA of Actinomadura was 51:49. These data show that the hydroxyl on C-2' of the ribosyl moiety of adenosine undergoes a replacement by a 2'-amino or a 2'-chloro group to form 2'-amino-2'-deoxyadenosine or 2'-CldCF with retention of stereconfiguration at C-2'. Finally, Actinomadura can utilize inorganic chloride from the medium as demonstrated by the isolation of [36Cl]2'-CldCF following the addition of [36Cl]chloride to the culture medium. Mechanisms for the regioselective modification of the C-2' hydroxyl group and stereospecific insertion of the amino and chloro groups are discussed.     

Ca2+位于H2O2上游参与H2S诱导的拟南芥气孔关闭过程

以拟南芥为材料,利用药理学实验,结合分光光度法和激光共聚焦显微技术,研究了Ca2+在硫化氢(H2S)诱导拟南芥气孔关闭过程中的作用及其与过氧化氢(H2O2)的关系。结果表明： H2S诱导气孔关闭, Ca2+螯合剂EGTA和质膜Ca2+通道阻断剂硝苯地平(Nif)能不同程度抑制H2S诱导的气孔关闭,而内质网钙泵阻断剂毒胡萝卜素(Thaps)对H2S的作用无显著影响。由此推测, Ca2+参与调节H2S诱导的拟南芥气孔关闭过程,且胞质中Ca2+来源于胞外Ca2+的内流。另外, H2S诱导拟南芥叶片NADPH氧化酶基因AtRBOHD和AtRBOHF以及细胞壁过氧化物酶基因AtPRX34表达增强,促进叶片和保卫细胞中H2O2积累, EGTA对此起抑制作用,而外源CaCl2处理上调AtRBOHD、AtRBOHF和AtPRX34的表达。表明Ca2+可能位于H2O2上游参与H2S诱导的拟南芥气孔关闭过程。     

Conditioning in 2 x 2 tables

Summary .  Two-by-two tables arise in a number of diverse settings in biomedical research, including analysis of data from a clinical trial with a binary outcome and gating methods in flow cytometry to separate antigen-specific immune responses from general immune responses. These applications offer interesting challenges concerning what we should really be conditioning on—the total number of events, the number of events in the control condition, etc. We give several biostatistics examples to illustrate the complexities of analyzing what appear to be simple data.     

Detoxification of SO2 in conifers differing in SO2-tolerance

Contents of organic sulfur, sulfate and the inorganic cations K⁺, Ca²⁺, Mg²⁺, Mn²⁺ and Na⁺ were compared in needles of three conifer species differing in tolerance to chronic SO₂ immissions. Sulfate and organic sulfur compounds were also measured in bark and wood. Field material was collected from Norway Spruce (Picea abies (L.) Karst.), Colorado Spruce (Picea pungens Engelm.) and Scots Pine (Pinus sylvestris L.) at sites where the SO₂ concentration in air was high, and at another site where it was low. In general, sulfate contents were higher but cation contents lower at the sites where SO₂ concentrations were high than where they were low. Up to 114mmol · (kg DW)^–1 sulfate was measured in fouryear-old needles of Norway Spruce from the Erzgebirge (annual mean of SO₂ in air 32 nl · 1^–1). Sulfate accumulation in this SO₂-sensitive conifer increased with SO₂ concentration in ambient air and with needle age, indicating that the main part of the sulfate resulted from the oxidative detoxification of SO₂. Loss of inorganic cations from ageing needles was reduced, or cation levels even increased, with increasing needle age, while sulfate accumulated. Apparently, cations served as counter-ions for sulfate, which is sequestered in the vacuoles. Individual trees differed in regard to the nature of cations which accumulated with sulfate. Calcium, potassium and magnesium were the dominating cations. Sodium levels were very low. Needles of the SO₂-tolerant conifers Colorado Spruce and Scots Pine growing next to Norway Spruce in the Erzgebirge did not accumulate, or accumulated less, sulfate with increasing needle age as compared to needles of Norway Spruce. However, somewhat more sulfate was found in the bark of the SO₂-tolerant species than in the bark of Norway Spruce. Scots Pine contained distinctly more sulfate in the wood than the other conifers. Since accumulation of organic sulfur compounds could not be observed with increasing needle age, or in bark and wood, reduction does not appear to play a major role in the detoxification of SO₂ by the investigated species. Physiological mechanisms permitting Colorado Spruce and Scots Pine to avoid the sulfate accumulation in the needles and the accompanying sequestration of cations that are observed in neighbouring Norway Spruce are discussed on the basis of the obtained data.Abbreviations S_org organic sulfur compounds Died June 10, 1991, aged 29, in a traffic accident. He initiated this work.This work was supported by the Sonderforschungsbereich 251 of the University of Würzburg and by the Projektgruppe Bayern zur Erforschung der Wirkung von Umweltschadstoffen (PBWU). The authors with to thank Prof. Dr. W Kaiser and Prof. Dr. W. Urbach (both Julius-von-Sachs-Institut, University of Würzburg, Germany) for HPLC-analysis and ICP-analysis.     

Casein kinase-2 phosphorylates serine-2 in the beta-subunit of initiation factor-2

We have previously presented evidence which suggests that casein kinase-2 phosphorylates a serine residue near the N-terminus of the beta-subunit of the initiation factor eIF-2 (Clark, S.J. et al. Biochim. Biophys. Acta 968, 211-219). We now report further data which confirm that it is serine-2 which is phosphorylated by casein kinase-2. This data includes (1) the electrophoretic mobilities of the phosphopeptides produced by different cleavage techniques, (2) the amino acid composition of the principal phosphopeptide generated by treatment with cyanogen bromide and (3) the resistance of this phosphopeptide to Edman degradation.     

Sulfenylation of ENOLASE2 facilitates H2O2-conferred freezing tolerance in Arabidopsis

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The essential role of H2O2 in the regulation of intracellular Ca2+ by epidermal growth factor in rat-2 fibroblasts

We have investigated a new mechanism by which epidermal growth factor (EGF) increases intracellular Ca(2+) ([Ca(2+)](i)) in Rat-2 fibroblasts. EGF induced a transient increase of [Ca(2+)](i), and sustained Ca(2+) increase disappeared in the absence of extracellular Ca(2+). However, EGF had no effect on the formation of inositol phosphates. Expression of N17Rac or scrape-loading of C3 transferase blocked the elevation of [Ca(2+)](i) by EGF, but not by lysophosphatidic acid (LPA). EGF increased intracellular H(2)O(2), with a maximal increase at 5 min, which was blocked by catalase, scrape-loading of C3 transferase, or expression of N17Rac. H(2)O(2) scavengers, catalase and N-acetyl-L-cysteine, also blocked the Ca(2+) response to EGF, but not to LPA. In the presence of EGTA, preincubation with EGF completely inhibited subsequent Ca(2+) response to extracellular H(2)O(2) and vice versa. Incubation with EGF or phosphatidic acid abolished subsequent elevation of [Ca(2+)](i) by phosphatidic acid or EGF, respectively. Furthermore, preincubation with LPA inhibited the subsequent Ca(2+) response to EGF, but not vice versa. These results suggested that intracellular H(2)O(2) regulated by Rac and RhoA, but not inositol phosphates, was responsible for the EGF-stimulated elevation of [Ca(2+)](i). It was also suggested that EGF cross talked with LPA in the regulation of [Ca(2+)](i) by producing intracellular H(2)O(2).     

2-amino-2-deoxy-D-erythrose in Agaricus bisporus

2-Amino-2-deoxy-D-erythrose was isolated from the cell wall of the fruit body of Agaricus bisporus. The structure of the amino sugar was determined by mass spectrography and 1H-NMR spectrography of its acetylated derivative and by paper chromatographic comparisons with authentic 2-amino-2-deoxy-D-erythrose. This amino sugar is a component of the glycoprotein fraction from the cell wall. Its content in the glycoprotein increased markedly, especially during the ripening stage of the fruit body.