A conserved family of prolyl-4-hydroxylases that modify HIF

Mammalian cells respond to changes in oxygen availability through a conserved pathway that is regulated by the hypoxia-inducible factor (HIF). The alpha subunit of HIF is targeted for degradation under normoxic conditions by a ubiquitin-ligase complex that recognizes a hydroxylated proline residue in HIF. We identified a conserved family of HIF prolyl hydoxylase (HPH) enzymes that appear to be responsible for this posttranslational modification. In cultured mammalian cells, inappropriate accumulation of HIF caused by forced expression of the HIF-1alpha subunit under normoxic conditions was attenuated by coexpression of HPH. Suppression of HPH in cultured Drosophila melanogaster cells by RNA interference resulted in elevated expression of a hypoxia-inducible gene (LDH, encoding lactate dehydrogenase) under normoxic conditions. These findings indicate that HPH is an essential component of the pathway through which cells sense oxygen.     

Structure of an HIF-1alpha -pVHL complex: hydroxyproline recognition in signaling

The ubiquitination of the hypoxia-inducible factor (HIF) by the von Hippel-Lindau tumor suppressor (pVHL) plays a central role in the cellular response to changes in oxygen availability. pVHL binds to HIF only when a conserved proline in HIF is hydroxylated, a modification that is oxygen-dependent. The 1.85 angstrom structure of a 20-residue HIF-1alpha peptide-pVHL-ElonginB-ElonginC complex shows that HIF-1alpha binds to pVHL in an extended beta strand-like conformation. The hydroxyproline inserts into a gap in the pVHL hydrophobic core, at a site that is a hotspot for tumorigenic mutations, with its 4-hydroxyl group recognized by buried serine and histidine residues. Although the beta sheet-like interactions contribute to the stability of the complex, the hydroxyproline contacts are central to the strict specificity characteristic of signaling.     

Climate-forced variability of ocean hypoxia

Oxygen (O(2)) is a critical constraint on marine ecosystems. As oceanic O(2) falls to hypoxic concentrations, habitability for aerobic organisms decreases rapidly. We show that the spatial extent of hypoxia is highly sensitive to small changes in the ocean's O(2) content, with maximum responses at suboxic concentrations where anaerobic metabolisms predominate. In model-based reconstructions of historical oxygen changes, the world's largest suboxic zone, in the Pacific Ocean, varies in size by a factor of 2. This is attributable to climate-driven changes in the depth of the tropical and subtropical thermocline that have multiplicative effects on respiration rates in low-O(2) water. The same mechanism yields even larger fluctuations in the rate of nitrogen removal by denitrification, creating a link between decadal climate oscillations and the nutrient limitation of marine photosynthesis.     

Mitochondrial biogenesis in mammals: the role of endogenous nitric oxide

Nitric oxide was found to trigger mitochondrial biogenesis in cells as diverse as brown adipocytes and 3T3-L1, U937, and HeLa cells. This effect of nitric oxide was dependent on guanosine 3',5'-monophosphate (cGMP) and was mediated by the induction of peroxisome proliferator-activated receptor gamma coactivator 1alpha, a master regulator of mitochondrial biogenesis. Moreover, the mitochondrial biogenesis induced by exposure to cold was markedly reduced in brown adipose tissue of endothelial nitric oxide synthase null-mutant (eNOS-/-) mice, which had a reduced metabolic rate and accelerated weight gain as compared to wild-type mice. Thus, a nitric oxide-cGMP-dependent pathway controls mitochondrial biogenesis and body energy balance.     

腐胺提高黄瓜根际低氧耐性的生理机理

 【目的】明确腐胺（putrescine,Put）对黄瓜根际低氧耐性的作用及其机制。【方法】以黄瓜为材料,分别在抑制和不抑制酸还原过程的条件下,在水培体系中对植物进行Put和根际低氧胁迫处理。【结果】外源Put显著提高了硝酸还原酶的实际（NRact）和最大（NRmax）活性,且这种作用在低氧胁迫植株中表现尤为明显。Put缓解了低氧胁迫下黄瓜叶片的净光合速率（Pn）、气孔导度（Gs）、胞间CO2浓度（Ci）以及根系线粒体总呼吸（Vt）、细胞色素途径呼吸（Vcyt）和交替途径呼吸（Valt）速率的下调。然而,当硝酸还原过程被钨酸钠抑制后,Put不仅失去了对光合作用及线粒体呼吸的缓解作用,反而进一步加剧了这两个基础代谢过程活性的下降。【结论】Put参与提高黄瓜对低氧胁迫抗性的作用和硝酸还原过程有关。     

淡水养殖条件下急性缺氧对凡纳滨对虾表观特征、相关酶活性与基因表达的影响

【目的】深入挖掘凡纳滨对虾应答缺氧胁迫的生理调控机制,为凡纳滨对虾抗缺氧应激新品种的选育提供理论依据,也为营养素调控缺氧应激提供新的作用靶点。【方法】根据水体溶解氧（DO）含量,分别设对照组（5.00 mg/L DO）、低氧组（2.00 mg/L DO）和缺氧组（0.75 mg/L DO）,观测急性缺氧胁迫下凡纳滨对虾的表观特征,于胁迫0、2、6、10和14 h采集凡纳滨对虾肝胰腺组织样品,通过ELISA试剂盒检测LDH、GCK、PK、Cyt c、SOD和CS活性,利用RT-PCR扩增HIF1-α、GLUT、BNIP3、p53、c-fos、Kv1.2、PTEN和VEGF等8个基因,并采用实时荧光定量PCR检测缺氧胁迫下的基因表达变化。【结果】急性缺氧胁迫下,凡纳滨对虾频繁游动,摄食量慢或不进食、蜕壳不遂,虾壳呈黄色或红色,生长速度缓慢并逐渐出现死亡。凡纳滨对虾肝胰腺中HIF1-α、GLUT、BNIP3和VEGF基因相对表达量随缺氧时间的延长呈显著上升趋势（P<0.05,下同）,Kv1.2和PTEN基因相对表达量呈显著下降趋势,c-fos和p53基因相对表达量则表现为先升高后降低。...     

一氧化氮对采后李果实线粒体膜氧化损伤的影响

【目的】研究一氧化氮(NO)对采后李果实线粒体膜氧化伤害的影响。【方法】分别用0、10、15、30μL.L-1NO处理李果实,测定25℃贮藏13d内果实呼吸速率、活性氧(ROS)含量、超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和过氧化物酶(POD)的活性、线粒体通透性转换孔开放程度、膜电位、膜流动性、细胞色素(Cyt)c/a的变化。【结果】与对照和其它NO处理相比,15μL.L-1NO提高了果实中SOD、CAT和POD活性,有效减少了果实中氢过氧化物和超氧阴离子自由基等ROS的含量,抑制了线粒体通透性转换孔的开放,延缓了线粒体膜通透性的升高和Cytc的释放,维持了较高的膜电位。随着浓度升高,30μL.L-1NO对线粒体膜的保护作用降低。【结论】15μL.L-1NO有效减轻了ROS对李果实线粒体膜的氧化伤害,保护线粒体膜的完整性。     

缺氧诱导因子和促红细胞生成素及其受体基因在绵羊各组织中表达量

【目的】研究缺氧诱导因子(HIF)及其下游靶基因促红细胞生成素(EPO)及其受体(EPOR)在绵羊正常生理状况下各组织的表达,为靶向调控或缓解绵羊缺氧应激的研究提供组织学依据。【方法】采用实时荧光定量PCR方法,检测4只新疆细毛羊14种组织中HIF、EPO和EPOR基因的相对表达量。【结果】HIF-1α和HIF-2α基因均在绵羊肺组织的相对表达量最高,且极显著高于其它组织(P<0.01);在肺脏HIF-2α基因的表达量约为HIF-1α表达量的5.2倍。EPO基因在绵羊肾脏的相对表达量最高且显著高于垂体、结肠、脾脏、盲肠、肝脏、肾上腺、瘤胃、下丘脑以及心脏(P<0.05)。EPOR基因在肺脏的表达量最高,肺脏和睾丸的相对表达量显著高于脾脏、下丘脑、肾脏、心脏等组织(P<0.05)。【结论】HIF-1α、HIF-2α和EPO及其受体基因在绵羊的肺部或肾脏的高表达,可能是绵羊缺氧应激感受及其调控的重要器官。     

Anaerobiosis and a theory of growth line formation

Microstructural growth increments within the shells of numerous Recent and fossil molluscs are interpreted as reflections of alternating periods of shell deposition and dissolution, occurring during aerobic and anaerobic respiration, respectively. The acidic end products of anaerobic metabolism are neutralized by calcium carbonate from the shell, leaving a relatively insoluble organic residue at the mantle-shell interface. With the return of oxygenated conditions and resumption of aerobic respiration, this organic material is reincorporated within the shell. Inasmuch as metabolic changes are often synchronized with lunar or solar cycles (or both), we are led to the nearly paradoxical conclusion that, as a result of shell destructive processes, a relatively complete and detailed record of both short- and long-term growth is often preserved within the molluscan exoskeleton. Analyses of relationships between ambient oxygen concentrations and shell structural types may eventually prove useful, in paleoecological studies, for determination of dissolved oxygen gradients in Phanerozoic marine environments.     

一氧化氮对低温贮藏桃果实线粒体氧化损伤的影响

【目的】分析一氧化氮(NO)对冷藏过程中桃果实线粒体氧化损伤的影响。【方法】分别用15 μmol/L NO、5 μmol/L c-PTIO (NO清除剂)、对照(去离子水)浸泡30 min处理桃果实。测定0℃下桃果实的线粒体完整性、活性氧含量、抗氧化酶的活性及相关品质指标。【结果】在桃果实低温冷藏过程中,NO处理可以维持桃果实硬度、色差L值及可溶性固形物含量,降低线粒体耗氧量和减少活性氧的积累,调节线粒体呼吸控制率(RCR)、线粒体膜电势,线粒体细胞色素C含量以及线粒体抗氧化酶活性。【结论】NO通过减少线粒体氧化损伤,维持线粒体的完整性,延长桃果实的贮藏期。     

Calorie restriction promotes mitochondrial biogenesis by inducing the expression of eNOS

Calorie restriction extends life span in organisms ranging from yeast to mammals. Here, we report that calorie restriction for either 3 or 12 months induced endothelial nitric oxide synthase (eNOS) expression and 3',5'-cyclic guanosine monophosphate formation in various tissues of male mice. This was accompanied by mitochondrial biogenesis, with increased oxygen consumption and adenosine triphosphate production, and an enhanced expression of sirtuin 1. These effects were strongly attenuated in eNOS null-mutant mice. Thus, nitric oxide plays a fundamental role in the processes induced by calorie restriction and may be involved in the extension of life span in mammals.     

种子呼吸检测方法及其应用研究进展

种子呼吸反映了种子的多种内在属性和生理生化特征,种子呼吸检测方法的进展对种子呼吸代谢研究具有重要意义。本文从种子呼吸检测方法及其应用2个方面进行了综述,重点综述了小篮子法、瓦氏微量法、Clark氧电极法、红外线二氧化碳分析仪法、氧传感技术检测法(Q₂技术)和可调谐二极管激光吸收光谱(TDLAS)技术检测法等常用种子呼吸检测方法的工作原理、主要检测对象及操作方法,总结了以上种子呼吸检测方法的优缺点及其适用范围。讨论了种子呼吸检测方法在种子呼吸代谢、种子储藏和种子活力测定等几个方面的研究应用,重点阐述了种子呼吸检测技术与种子活力相关的研究进展。根据研究现状对种子呼吸相关检测方法及其研究和应用方向进行了展望：(1)基于TDLAS技术等光学检测技术有望研制出灵敏度更高、操作更为简单的种子呼吸检测方法及装备;(2)种子呼吸代谢及其影响因素研究有利于丰富和深入揭示种子呼吸代谢过程理论;(3)开展种子呼吸指标和种子活力参数研究,为探寻能够将种子呼吸强度作为有效判定种子活力指标提供重要参数支持。表1参60     

Changes of Reactive Oxygen Species and Related Enzymes in Mitochondria Respiratory Metabolism During the Ripening of Peach Fruit

The fruits of peach cultivar Yuhua 3 were used as materials to investigate the changes of active oxygen and related enzymes in mitochondria respiratory metabolism during ripening of peach fruit, involving their influence on the proceeding of peach fruit senescence. The results showed that the large decrease in firmness occurred between maturity II and IV. The decrease in firmness coincided with an increase in respiratory intensity. Obvious peaks of respiratory intensity lagging to the rapid change of fruit firmness could be shown during peach ripening. Reactive oxygen species （ROS） had a cumulative process and positively correlated with respiratory intensity. During peach ripening, the content of Ca^2＋ increased, the activities of succinic dehydrogenase （SDH）, cytochrome C oxidase （CCO）, H＋-ATPase, and Ca^2＋-ATPase decreased varying in different degree at the later step of ripening. These suggested a close relationship existed between ROS metabolism and mitochondrial respiration, namely, both ROS metabolism and mitochondrial respiration probably played important roles in ripening and senescing of peach fruit.     

p53 regulates mitochondrial respiration

The energy that sustains cancer cells is derived preferentially from glycolysis. This metabolic change, the Warburg effect, was one of the first alterations in cancer cells recognized as conferring a survival advantage. Here, we show that p53, one of the most frequently mutated genes in cancers, modulates the balance between the utilization of respiratory and glycolytic pathways. We identify Synthesis of Cytochrome c Oxidase 2 (SCO2) as the downstream mediator of this effect in mice and human cancer cell lines. SCO2 is critical for regulating the cytochrome c oxidase (COX) complex, the major site of oxygen utilization in the eukaryotic cell. Disruption of the SCO2 gene in human cancer cells with wild-type p53 recapitulated the metabolic switch toward glycolysis that is exhibited by p53-deficient cells. That SCO2 couples p53 to mitochondrial respiration provides a possible explanation for the Warburg effect and offers new clues as to how p53 might affect aging and metabolism.     

福建省水口水库网箱养殖鱼类大面积缺氧死亡原因分析

通过对2011年8-9月福建水口水库养殖鱼类大面积缺氧死亡事件期间不同水层溶解氧和水温变化趋势分析,并结合2004年以来水口水库多次发生的缺氧事件发生前和发生期间库区气象、水文等资料。分析发现:在汛期出现持续晴热、少雨的异常天气条件,水口水库会发生"耗氧"和"复氧"失衡,产生水体氧亏损现象;在随之出现的降水降温天气过程中下层缺氧水团上浮造成上层水体严重缺氧,养殖鱼出现大面积突发性缺氧死亡。     

归芪多糖延缓细胞衰老的分子作用机制

以SIRT1和线粒体为切入点,采用分子生物学技术以及多种线粒体分析技术,深入探讨SIRT1和线粒体在衰老细胞中的作用,揭示归芪多糖延缓细胞衰老的分子作用机制。结果表明,AAP显著降低细胞的衰老程度并提高细胞活力,而Ex527阻断AAP的作用。同时,发现AAP增强细胞内SIRT1和CyclinD1的表达,降低p53的表达水平,在Ex527组中未观察到类似的逆转作用。线粒体分析结果显示,AAP可显著降低细胞内的活性氧水平,降低线粒体膜电位,减轻线粒体肿胀程度和增加线粒体内ATP含量,而Ex527的预处理消除这些作用。基于上述结果,推测AAP可能通过信号通路p53/p16和CyclinD/CDK4来改善线粒体功能,从而达到延缓衰老的作用,且这些作用与SIRT1密切相关。