1-M1-甲基环丙烯和氯化钙处理对鲜切西瓜果实脂质水解酶的作用(英文)

无籽西瓜(Citrullus　lanatus　Thunb.　Mansfeld,　cv.　Millionaire)果实在10　μL/L　1-甲基环丙烯(1-MCP)或正常空气中预贮18　h后,切取内果皮肉柱　(直径7　mm,长40　mm),再用2%　CaCl2或去离子水冲淋肉柱,然后将肉柱贮藏于10　℃。测定贮藏过程中的果肉硬度、电导率、磷脂酶D　(PLD)、磷脂酶C　(PLC)和脂氧合酶　(LOX)的活性变化。结果显示,2%　CaCl2刺激PLD、PLC和LOX的活性,维持果肉的硬度。单独用CaCl2处理并不足以维持切割西瓜的品质,还可能因刺激脂质水解酶而发生不良的作用。1-MCP能够抵抗CaCl2对PLD、PLC和LOX的刺激作用。与对照相比,1-MCP与CaCl2结合处理能延缓西瓜果肉的衰老过程,表现出较高的果肉硬度和较低的脂质水解酶活性。     

1-甲基环丙烯和氯化钙处理对鲜切西瓜果实脂质水解酶的作用

无籽西瓜(Citrullus lanatus Thunb．Mansfeld,cv．Millionaire)果实在10μL／L 1-甲基环丙烯(1-MCP)或正常空气中预贮18h后,切取内果皮肉柱(直径7mm,长40mm),再用2％CaCl2或去离子水冲淋肉柱,然后将肉柱贮藏于10℃。测定贮藏过程中的果肉硬度、电导率、磷脂酶D(PLD)、磷脂酶C(PLC)和脂氧合酶(LOX)的活性变化。结果显示,2％CaCl2刺激PLD、PLC和LOX的活性,维持果肉的硬度。单独用CaCl2处理并不足以维持切割两瓜的品质,还可能因刺激脂质水解酶而发生不良的作用。1-MCP能够抵抗CaCl2对PLD、PLC和LOX的刺激作用。与对照相比,1-MCP与CaCl2结合处理能延缓两瓜果肉的衰老过程,表现出较高的果肉硬度和较低的脂质水解酶活性。     

纽荷尔脐橙留树和低温贮藏效果比较

以纽荷尔脐橙(citrus sinensis'Newhall')果实为试材,对50%留果量的留树贮藏和果实6℃低温贮藏过程中不同时期的果肉硬度、果皮总色差、O2产生速率、脯氨酸(Pro)含量、相对电导率、丙二醛(MDA)含量及脂氧合酶(LOX)、超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活性进行测定.结果表明:两种贮藏方式下果肉硬度均下降,果皮总色差上升;LOX活性增加,SOD、CAT活性下降;O2、MDA、Pro积累,细胞膜受到伤害,导致胞内物质外流,细胞电导率增加.贮藏47d时,两种贮藏方式各指标基本上没有显著差异;贮藏47d至75d,留树贮藏的果实无论外观(果肉硬度、色泽)还是细胞膜的完整性都显著优于低温贮藏.     

干旱胁迫下磷脂酶Dδ和9-脂氧合酶对拟南芥茉莉酸合成及种子萌发的影响

以拟南芥哥伦比亚野生型(WT)、磷脂酶Dδ(PLDδ)缺失型突变体pldδ和9-脂氧合酶(9-LOX)缺失型突变体lox1、lox5实生苗为材料,以0.3 mol·L-1甘露醇模拟干旱胁迫,分析PLDδ和9-LOX参与干旱胁迫下拟南芥茉莉酸(JA)生物合成和在种子萌发中作用。结果表明:干旱胁迫显著提高PLDδ和LOX1基因表达以及PLD和LOX酶活性;干旱胁迫下,pldδ突变体幼苗的LOX活性和JA含量显著低于WT,外源添加磷脂酸(PA)后LOX活性和JA含量显著上升,并高于WT;干旱胁迫显著抑制pldδ、lox1和lox5突变体的种子萌发,以对lox1的抑制效果最为明显;干旱胁迫下PLD活性上升与PLDδ基因表达上调有关,LOX活性上升与LOX1和LOX5基因表达上调有关,其中LOX1基因起主要作用;PLDδ/PA位于9-LOX上游参与9-LOX诱导的JA合成过程;PLDδ、LOX1和LOX5基因均参与干旱胁迫下拟南芥的种子萌发,LOX1在此过程中作用最为明显;PLDδ和9-LOX均参与PA和JA介导的种子萌发过程。     

CO2和1-MCP组合处理对磨盘柿贮藏效果的影响

以磨盘柿采后果实为材料,研究1-MCP的处理以及CO2脱涩与1-MCP组合处理对磨盘柿室温和0~1℃贮藏过程中果实硬度、可溶性单宁含量、总抗坏血酸(TAA)含量以及抗氧化活性的影响。结果显示:(1)贮藏过程中柿果实硬度随时间延长呈下降趋势,室温贮藏CO2处理5 d、CO2处理后进行1-MCP(CO2//1-MCP)处理10 d、1-MCP处理后进行CO2(1-MCP//CO2)处理15 d、CO2与1-MCP同时(CO2+1-MCP)处理30 d均完全软化,0~1℃贮藏75 d后硬度最高的是CO2+1-MCP处理(12.43 kg.cm-2),最低的是CO2//1-MCP处理(2.80 kg.cm-2),甚至低于CO2处理(5.71 kg.cm-2);(2)柿果实可溶性单宁和总抗坏血酸(TAA)含量与脱涩有关,CO2处理、CO2//1-MCP处理、1-MCP//CO2处理和CO2+1-MCP处理大幅低于CK和1-MCP处理,1-MCP处理抑制了可溶性单宁和TAA含量的下降;(3)室温贮藏中除CO2处理之外的处理柿果实总酚含量呈小幅上升趋势,0~1℃贮藏中CK、1-MCP处理、1-MCP//CO2处理和CO2+1-MCP处理的总酚含量稳定在9.91~12.38 mg.g-1FW之间,CO2处理和CO2//1-MCP处理于30 d之后迅速下降,至75 d时分别只有6.83和6.32 mg.g-1FW;(4)各组处理柿果实ABTS自由基清除能力和氧自由基清除能力值(ORAC)的变化趋势与总酚含量大致相当。研究发现,1-MCP能有效阻止磨盘柿果实贮藏期间的硬度、可溶性单宁含量、TAA含量以及抗氧化活性的下降,CO2脱涩与1-MCP处理的不同顺序对硬度和抗氧化活性影响巨大,但对可溶性单宁和TAA含量影响甚微;先CO2脱涩后1-MCP处理对磨盘柿贮藏效应影响不大,1-MCP处理和高浓度CO2脱涩同时进行是磨盘柿脱涩保鲜的最优方案。     

枇杷幼果PLD和LOX对低温胁迫的响应

以3年生枇杷品种‘早钟6号’(Eriobotrya japonica‘Zaozhong No.6’)容器嫁接苗为试材,于0℃、-1℃、-3℃人工气候室内进行低温胁迫处理,探讨枇杷幼果细胞膜磷脂及相关酶对低温胁迫的响应机制。结果显示,在不同温度胁迫过程中,枇杷幼果磷脂酶D(PLD,EC 3.1.4.4)和脂氧合酶(LOX,EC 1.13.11.12)活性均呈上升趋势;质膜磷脂酰胆碱(PC)和磷脂酰肌醇(PI)含量因逐渐被降解而呈下降趋势,磷脂酸(PA)含量出现积累、增加,而膜结合Ca2+含量有不同程度的降低。随处理时间的延长和处理温度的降低,枇杷幼果细胞PLD和LOX活性增幅加大,从而加速了膜PC和PI的降解和PA的积累。低温胁迫过程中幼果细胞膜PC含量的降幅大于PI,膜结合Ca2+含量的变化与PLD和LOX活性变化呈负相关。低温胁迫下枇杷幼果细胞膜结合Ca2+含量的减少诱导了膜脂降解酶PLD和LOX活性的提高,并导致膜结构稳定性下降,加剧了低温胁迫对膜脂的降解和脂质过氧化伤害,其中尤以-3℃胁迫处理4~6 h对幼果细胞质膜的伤害最严重。表明低温胁迫下Ca2+·Ca M信使系统可能参与枇杷幼果细胞膜PLD和LOX活性的调控。     

乙烯诱导西瓜果实的水渍化败坏

为了研究乙烯在西瓜(Citrullus lanatusThunb.Mansfeld)果实水渍化败坏过程中的作用,先将果实在5μL/L 1-甲基环丙烯(1-MCP)气体中处理18 h,然后在50 μL/L乙烯和20℃温度下贮藏.西瓜果实对乙烯处理的最初反应表现为胎座组织的电导率和游离汁液增加,同时出现组织软化和水渍化.水渍化的症状最初在靠近花萼端的内果皮中发生,在乙烯处理的第2天开始出现,ACC合成酶(ACS)和ACC氧化酶(ACO)的活性明显提高.1-MCP单独处理不产生任何明显的作用,但是会完全抑制外源乙烯诱导的水渍化败坏.没有经过乙烯处理的西瓜果实,贮藏2 d以后出现呼吸强度和乙烯释放量的高峰,10 d以后水渍化现象也零星出现.这些结果和1-MCP的预防效果说明,西瓜果实的水渍化败坏是一种由乙烯诱导的衰老现象.     

甜柿采后生理特性及对1-MCP处理的反应

以甜柿品种‘阳丰’为材料,在20℃和0℃贮藏条件下研究了1-MCP(1-甲基环丙烯)处理对不同成熟度甜柿果实采后乙烯释放速率、呼吸速率和品质特性的影响。结果表明:1-MCP处理可延缓贮藏和货架期间甜柿果实的软化、抑制呼吸速率和可溶性固形物含量(SSC)的变化,但对乙烯释放速率的作用不一致。1-MCP处理对成熟度I果实的效果优于成熟度Ⅱ。低温贮藏虽然能显著延缓果实硬度的下降,但在0℃贮藏30、60和90 d后7 d货架期结束时,对照果完全软化,而经1-MCP处理后果实果肉硬度仍保持“脆”性。因此,贮前0.50μL.L-11-MCP处理结合低温贮藏是延长‘阳丰’甜柿贮藏期的有效途径,具有广泛的应用前景。     

IAA、ABA和乙烯利对梨枣采后某些生理指标的影响

梨枣采后乙烯释放量、丙二醛(MDA)含量和脂氧合酶(LOX)活性呈上升而硬度、维生素C(VC)含量和好果率呈逐渐下降趋势.IAA、ABA、乙烯利促进枣果采后初期的乙烯生成,提高梨枣中MDA含量和LOX活性,加速梨枣软化,降低梨枣的VC含量和好果率;ABA的作用更加明显.LOX活性与果肉硬度及好果率呈显著负相关,暗示LOX与枣果的软化衰老有一定关系.     

1-MCP对‘珍珠’番石榴采后生理和品质的影响

为探讨改善番石榴贮藏性能的方法,番石榴(Psidium guajava L. ‘Pearl’)果实用1-甲基环丙烯(1-MCP)结合冷藏(15℃)处理,研究其贮藏生理和品质的变化。结果表明：1 μL L-1 1-MCP处理能有效抑制番石榴果实软化和果皮退绿;1-MCP处理抑制了可溶性固形物(TSS)含量上升和维生素C含量的下降;同时,超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和过氧化物酶(POD)活性升高,多酚氧化酶(PPO)活性下降,延缓了果实中丙二醛(MDA)的积累。因此,1-MCP处理结合低温可有效改善珍珠番石榴的贮藏性能。 关键词：番石榴;1-MCP;贮藏生理;品质     

NPC1L1:固醇脂质吸收的关键蛋白质

NPC1L1是最近发现的一种与NPC1同源的蛋白质。在体内的分布有物种差异性,其亚细胞定位存在很大争议。近些年发现NPC1L1在固醇类脂质代谢途径中起着重要作用,是肠道吸收固醇类脂质尤其是胆固醇的关键蛋白质,这项新发现使得人们对固醇类脂质的吸收机制有了了解。高胆固醇血症是心血管系统疾病的一个高危因子,因此,对NPC1L1的研究具有重大的实际意义,正逐渐成为研究的热点。     

Stoichiometry studies reveal functional properties of KDC1 in plant shaker potassium channels

Functional heteromeric plant Shaker potassium channels can be formed by the assembly of subunits from different tissues, as well as from diverse plant species. KDC1 (K(+) Daucus carota 1) produces inward-rectifying currents in Xenopus oocytes when coexpressed with KAT1 and other subunits appertaining to different plant Shaker subfamilies. Owing to the presence of KDC1, resulting heteromeric channels display slower activation kinetics, a shift of the activation threshold toward more negative membrane potentials and current potentiation upon the addition of external zinc. Despite available information on heteromerization of plant Shaker channels, very little is known to date on the properties of the various stoichiometric configurations formed by different subunits. To investigate the functional properties of heteromeric nKDC1/mKAT1 configurations, we realized a series of dimeric constructs combining KDC1 and KAT1 alpha-subunits. We found that homomeric channels, formed by monomeric or dimeric alpha-subunit constructs, show identical biophysical characteristics. Coinjections of diverse tandem constructs, instead, displayed significantly different currents proving that KDC1 has high affinity for KAT1 and participates in the formation of functional channels with at most two KDC1 subunits, whereas three KDC1 subunits prevented the formation of functional channels. This article brings a contribution to the understanding of the molecular mechanisms regulating plant Shaker channel functionality by association of modulatory subunits.     

Variation in salinity tolerance and shoot sodium accumulation in Arabidopsis ecotypes linked to differences in the natural expression levels of transporters involved in sodium transport

Salinity tolerance can be attributed to three different mechanisms: Na⁺ exclusion from the shoot, Na⁺ tissue tolerance and osmotic tolerance. Although several key ion channels and transporters involved in these processes are known, the variation in expression profiles and the effects of these proteins on Na⁺ transport in different accessions of the same species are unknown. Here, expression profiles of the genes AtHKT1;1, AtSOS1, AtNHX1 and AtAVP1 are determined in four ecotypes of Arabidopsis thaliana. Not only are these genes differentially regulated between ecotypes, the expression levels of the genes can be linked to the concentration of Na⁺ in the plant. An inverse relationship was found between AtSOS1 expression in the root and total plant Na⁺ accumulation, supporting a role for AtSOS1 in Na⁺ efflux from the plant. Similarly, ecotypes with high expression levels of AtHKT1;1 in the root had lower shoot Na⁺ concentrations, due to the hypothesized role of AtHKT1;1 in retrieval of Na⁺ from the transpiration stream. The inverse relationship between shoot Na⁺ concentration and salinity tolerance typical of most cereal crop plants was not demonstrated, but a positive relationship was found between salt tolerance and levels of AtAVP1 expression, which may be related to tissue tolerance.     

人骨髓间充质干细胞向神经细胞分化过程中Notch通路信号分子表达的变化

本研究探讨Noah信号通路在人骨髓间充质干细胞（human mesenchymal stem cells,hMSCs）体外增殖及向神经细胞分化过程中的作用。采集健康自愿者骨髓,体外培养获得hMSCs,取第3代hMSCs,在诱导剂（β-ME,DMSO,BHA）作用下向神经细胞分化。诱导后用免疫细胞化学鉴定神经元特异性烯醇化酶（neuron-specific enolase,NSE）和尼氏体的表达以确定诱导效果：用流式细胞术检测细胞生长周期时相的变化。在诱导前后,用免疫荧光和RT-PCR方法检测Notch通路中Notch1受体蛋白、配体Jagged1（JAG1）、调节蛋白活化相关物早老素1（presenilin 1,PS1）、靶基因hairy and enhancer of split1（HES1）信号分子表达的变化。结果显示：诱导前,处于G0/G1期的hMSCs占58．5％,S＋G2/M期的细胞占41．5％;诱导后,G0/G1期细胞比例升高,而S＋G2/M期细胞比例下降,NSE阳性细胞率达（77±0．35）％,细胞质中可见深蓝色的块状或颗粒状尼氏体。免疫荧光显示,诱导前后hMSCs内Notch1和JAG1均呈阳性表达,但RT-PCR检测发现诱导后Notch1、JAG1、PSl和HES1 mRNA表达量较诱导前明显降低（均P〈0．05）。结果表明,诱导hMSCs向神经细胞分化能抑制Notch信号分子表达,低水平的Notch信号激活可能有利于神经细胞的分化。     

Carboxamide SIRT1 inhibitors block DBC1 binding via an acetylation-independent mechanism

SIRT1 is an NAD⁺-dependent deacetylase that counteracts multiple disease states associated with aging and may underlie some of the health benefits of calorie restriction. Understanding how SIRT1 is regulated in vivo could therefore lead to new strategies to treat age-related diseases. SIRT1 forms a stable complex with DBC1, an endogenous inhibitor. Little is known regarding the biochemical nature of SIRT1-DBC1 complex formation, how it is regulated and whether or not it is possible to block this interaction pharmacologically. In this study, we show that critical residues within the catalytic core of SIRT1 mediate binding to DBC1 via its N-terminal region, and that several carboxamide SIRT1 inhibitors, including EX-527, can completely block this interaction. We identify two acetylation sites on DBC1 that regulate its ability to bind SIRT1 and suppress its activity. Furthermore, we show that DBC1 itself is a substrate for SIRT1. Surprisingly, the effect of EX-527 on SIRT1-DBC1 binding is independent of DBC1 acetylation. Together, these data show that protein acetylation serves as an endogenous regulatory mechanism for SIRT1-DBC1 binding and illuminate a new path to developing small-molecule modulators of SIRT1.     

Enhancement of hepatic microsomal drug oxidation and glucuronidation in rat by 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT)

A single dose of 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) (160 mg/kg i.p.) enhanced the monooxygenase step of drug biotransformation in rat liver. The O-demethylation of p-nitroanisole was especially increased, a peak in activity approximately 5-fold compared with controls being attained in 7 days. On the other hand, there was only a 2-fold increase in aryl hydrocarbon hydroxylase activity.DDT increased the cytochrome P-450 content of the liver, this increase coincided well with that in p-nitroanisole O-demethylation activity.The UDPglucuronosyltransferase activity of liver microsomes was not enhanced by DDT administration, unless the microsomes were pretreated to reveal latent activity prior to assay. After trypsin digestion of microsomes a maximum increase in activity of approximately 3-fold was observed as a result of DDT dosage. The canonic surfactant cetylpyridinium chloride was less active in revealing the latent UDP-glucuronosyltransferase activity, and two other membrane perturbants, the detergent digitonin and phospholipase A, were unable to show enhancement in UDPglucuronosyltransferase as a result of DDT dosage.     

CYP1A1基因单核苷酸多态性与肺癌的相关性研究

目的:探讨代谢酶CYP1A1基因MspI位点多态性与新疆汉族人群肺癌遗传易感性之间的相关性.方法:应用聚合酶链式反应(PCR)-限制性片段长度多态性(RFLP)技术检测59例新疆汉族肺癌和84例新疆汉族健康人的CYP1A1基因MspI位点多态性分布频率,并分析了CYP1A1基因MspI位点多态性与新疆汉族人群肺癌遗传易感性和患者性别之间的相关性.结果:(1)CYP1A1基因MspI位点3种多态基因型分布频率在两组间比较差异有统计学意义(χ2=6.682,P=0.035),CC基因型在病例组的分布频率显著高于正常对照组.(2)携带突变CC基因型的个体较携带TT基因型的个体患肺癌的危险性增加(OR=3.759.95%CI=1.228-11.494,P=0.035).(3)男女肺癌患者的CYP1A1基因MspI位点基因型及等位基因频率的差异均无显著性(P>0.05).结论:(1)CC突变基因型可能是新疆汉族人群的肺癌易感因素.(2)CYP1A1基因MspI位点多态性可能与新疆汉族肺癌患者的性别无关.     

粘膜系统鳞状细胞癌(SCC)相关蛋白(DCUN1D1)的表达、纯化和晶体生长

目的:SCCRO/RP42/DCUN1D1是粘膜系统鳞片状细胞癌(SCC)发生时人类基因组3q区域扩增的潜在靶标之一,其蛋白作用机制尚不清楚,本文拟通过表达并大量纯化SCC相关蛋白DCUN1D1用于蛋白结晶以求获得其三维结构。方法:使用人肝脑组织RNA反转录产物为模板扩增出DCUN1D1基因cDNA片断并将其克隆至原核表达载体PGEX-6P-1中,通过IPTG诱导获得大量可溶性表达,再经过GST亲和层析和Sephadex G-200层析柱纯化。结果:获得了纯度95%以上的蛋白,采用悬滴气相扩散法筛选蛋白晶体,获得显微镜下可见的微晶。结论:初步得出DCUN1D1晶体生长条件及范围,为解析DCUN1D1的三维结构并进一步认识其生物功能奠定了基础。