Stability and Determination of Metamizole Sodium by Capillary Electrophoresis Analysis Combined

合集下载

注射液中酚磺乙胺及焦亚硫酸钠含量的同时测定

第28卷第11期2016年11月化学研究与应用^Chemical Research and Application Vol.28,No. 11 Nov. ,2016文章编号：1004-1656(2016) 11-1610-04注射液中酚磺乙胺及焦亚硫酸钠含量的同时测定杨凤珍％袁华，范小振，张文育(沧州师范学院化学与化工学院，河北沧州061001)摘要：©磺乙胺及焦亚硫酸钠均在酸性的吐温80-罗丹明6G体系中产生化学发光，但具体发光条件不同，因此利用化学发光分析法，在同一体系中根据不同条件可对针剂注射液中酚磺乙胺及焦亚硫酸钠的含量进行同时测定。

酚磺乙胺的质量浓度在〇.〇5 ~3.(Vg• m T1范围内与光信号呈现良好的线性关系，检出限为0. 01网• m l/1，相对标准偏差小于3.5% 〇 = 5)。

测定焦亚硫酸钠的工作曲线线性范围为0. 07 ~ 5. 0叫•m l/1,检出限为0.02叫•m l/1,相对标准偏差小于4.2%〇= 5)。

该测定方法可用于针剂药物中酚磺乙胺及焦亚硫酸钠的含量测定，结果令人满意。

关键词:化学发光;酸磺乙胺;焦亚硫酸钠;吐温80;罗丹明6G中图分类号=0657. 3 文献标志码:ASimultaneous determination of etamsylate and sodium pyrosulfite in injectionY A N G Feng-z h e n*，Y U A N H u a，F A N X ia o-z h e n，Z H A N G W e n-yu(College of Chemistry and Chemical engineering,Cangzhou Normal University,Cangzhou 061001,China) Abstract：The chemiluminescence emission was generated by mixing etamsylate or sodium pyrosulfite with acidic tween80-rhoda- mine6G. The specific luminescent conditions were different, so the content of etamsylate and sodium pyrosulfite could be determined in the same chemiluminescence system according to the different conditions. The quantitation range was from 0. 05 to 3. Ojjig • mL 1with a detection limit of 0. 01 jjig • mL 1 ,and a relative standard deviation of less than 3. 5% (n = 5)for etamsylate. The working curve liner range was 0. 07 to 5. Ojjig *mL4with a detection limit of 0. 02 |jig *mL 1 , and arelative standard deviation of less than 4. 2% (n = 5)for the determination of sodium pyrosulfite. The proposed method was applied to the quantitation of etamsylate and sodium pyrosulfite in injection with satisfactory results.Key words ：chemiluminescence ；etamsylate ； sodium pyrosulfite ；tween80；rhodamine 6G酚磺乙胺又名止血敏。

《2024年Meta分析系列之十五_Meta分析的进展与思考》范文

《Meta分析系列之十五_Meta分析的进展与思考》篇一Meta分析系列之十五_Meta分析的进展与思考Meta分析系列之十五：Meta分析的进展与思考一、引言随着科学研究的深入发展，Meta分析作为一种重要的统计方法，被广泛应用于多个学科领域，成为了研究热点之一。

本文旨在探讨Meta分析的进展及其在科学研究中的应用与思考。

二、Meta分析的概述Meta分析是一种利用统计方法对多个独立研究结果进行综合分析的技术，其目的是为了解决单个研究结果可能存在的局限性，提高研究结果的可靠性和稳定性。

Meta分析通过整合多个独立研究的数据，从而揭示出更具有普遍性的结论。

三、Meta分析的进展自Meta分析技术问世以来，其在多个领域的应用已经取得了显著的进展。

以下是近年来Meta分析的主要进展：1. 拓展应用领域：Meta分析不再局限于医学、心理学等传统领域，而是逐渐扩展到生物学、社会科学等多个领域。

这些领域的学者们开始运用Meta分析技术来探讨各种问题，如基因多态性与疾病的关系、社会现象的成因等。

2. 改进方法与技术：随着计算机技术的发展，Meta分析的方法与技术也在不断改进。

例如，利用大数据技术，Meta分析可以更准确地提取和分析大量数据，从而提高了结果的准确性。

此外，随机效应模型、贝叶斯统计等方法的应用，使得Meta分析更加适用于异质性较高的研究数据。

3. 优化检索策略：Meta分析中一个重要的步骤是确定检索策略和选择合适的研究文献。

随着数据库技术的不断发展，研究人员可以更加便捷地检索和筛选相关文献，提高了Meta分析的效率和准确性。

四、Meta分析在科学研究中的应用与思考1. 科学决策的依据：Meta分析可以为政策制定和科学决策提供依据。

通过对大量相关研究的综合分析，可以揭示出某一现象或问题的普遍规律，为政策制定提供科学依据。

例如，在公共卫生领域，通过Meta分析可以评估不同干预措施的效果，为政策制定者提供决策依据。

isotope_labeling_metabolomics

Metabolomics is a rapidly growing field of
postgenomic biology focusing on system-wide studies of metabolite levels and transformations in biological samples. Recent advances in modern high-throughput bioanalytical platforms, in combination with rapidly improving computational capabilities for data analysis and interpretation, and the free availability of numerous organism-specific metabolite databases, make it possible to annotate and quantify hundreds of metabolites in a single experiment. The resulting metabolite profiles provide a highly informative snapshot of an organism’s physiology and are widely used both in fundamental biology and in clinical research. A major benefit of metabolomics is the un biased approach and the resulting ability to generate and test hypotheses based on the behavior of the whole biological system [1]. While it is not possible to detect every metabolite in a system, untargeted studies involve large-scale detection of a wide range of structurally diverse metabolite features and offer semiquantitative information about metabolite abundance. These untargeted studies can generate hypotheses about novel or important metabolites and pathways, but generally require follow-up targeted studies to confirm metabolite identities and accurately measure metabolite concentrations [2]. A major limitation of many metabolomics studies is the lack of dynamic information to allow interpretation of data in the context of metabolic fluxes [3, 4]. While metabolomics may

《2024年Meta分析系列之十五_Meta分析的进展与思考》范文

《Meta分析系列之十五_Meta分析的进展与思考》篇一Meta分析系列之十五_Meta分析的进展与思考Meta分析系列之十五：Meta分析的进展与思考一、引言随着科学研究的深入发展，Meta分析作为一种重要的统计方法，逐渐在各个领域中发挥着越来越重要的作用。

本文旨在探讨Meta分析的进展，以及在当代科学研究中的思考与应用。

二、Meta分析的概述Meta分析，即元分析，是一种利用统计方法对多个独立研究结果进行综合分析的方法。

它通过对不同研究结果进行量化评估和合并，从而得出更可靠、更全面的结论。

Meta分析在许多领域都有广泛的应用，如医学、心理学、社会科学等。

三、Meta分析的进展（一）方法论的完善随着Meta分析的不断发展，其方法论得到了进一步的完善。

在研究设计、数据采集、统计分析等方面，都出现了更多的方法和工具。

例如，通过系统评价和文献计量学的方法，可以更全面地收集和筛选相关研究；通过随机效应模型等统计方法，可以更准确地评估不同研究结果之间的异质性。

（二）应用领域的拓展Meta分析的应用领域不断扩大，不仅在医学、心理学、社会科学等领域得到广泛应用，还在生物学、计算机科学等领域得到尝试。

这表明Meta分析具有广泛的应用前景和潜力。

（三）与其他方法的结合Meta分析可以与其他统计方法相结合，如系统评价、网络元分析等，从而更好地解决实际问题。

此外，随着大数据和人工智能技术的发展，Meta分析与这些技术的结合也将为科学研究带来更多的可能性。

四、对Meta分析的思考（一）研究质量的保证在进行Meta分析时，需要保证所纳入的研究质量可靠。

这需要对研究的设计、数据采集、统计分析等方面进行全面评估。

同时，还需要注意研究间的异质性，避免因异质性过大而影响结果的可靠性。

（二）结果解读的准确性在进行Meta分析时，需要准确解读结果。

这需要对统计方法和结果进行深入理解，避免误解或误用。

同时，还需要注意结果的适用范围和局限性，避免过度解读或滥用结果。

[生物工程]Nature-medicine近期精彩文章摘要

[生物工程]Nature medicine近期精彩文章摘要2004年10月大麻素可能与异位妊娠有关发表在10月号《自然—医学》上的一篇研究报告首次揭示了大麻素与异位妊娠的关系。

这篇研究报告表明，胚胎在输卵管内的运送过程中，大麻素类受体起了重要作用。

异位妊娠是指受精卵在子宫内膜以外的部位植入和发育生长，胚胎持续停留在输卵管就会形成输卵管妊娠。

Sudhansu Dey及合作者通过老鼠实验发现，如果由于遗传或药物作用使得大麻素受体CB1不起作用，则大量胚胎会滞留在输卵管内，最终导致受孕失败。

因为乙型交感神经刺激剂能够部分抵消这种效应，研究人员提出，在胚胎正常进入子宫的“旅途”中，大麻素和肾上腺素受体共同调节着输卵管的运动。

除了揭示出生殖管道中胚胎运送的新的调节机制而外，这一成果对于异位妊娠的临床研究也颇具价值。

2004年10月新生儿肺性高血压新疗法在发生氰化物中毒时，常常采用吸入亚硝酸盐来消除毒性。

10月号《自然—医学》发表的一篇“快报”表明，吸入亚硝酸盐还可用于治疗新生儿肺性高血压。

这是一种具有致命危险的疾病，会引起肺部血管收缩，导致机体血氧水平低下。

Gordon Power等利用患此病的新生羊羔测试吸入亚硝酸盐的疗效，结果发现这种疗法能使血压持续保持较低水平，并且没有明显副作用。

2004年10月精密观察血管10月号《自然—医学》发表了一篇技术报告，介绍了一种能比以往更清晰地观察活体组织及其相连血管的新方法，这一新方法可望为诊断治疗研究“锻造”一柄利器。

Fabian Kiessling及合作者试验了一种新型的“测定体积计算断层摄影扫描仪”，能够实现高分辨率三维成像。

利用此项技术，研究人员对移植到老鼠体内的人类肿瘤结构进行了分析，比现有技术如磁共振和血管造影等更清楚地观察到了肿瘤的状况。

他们甚至成功地观察到了肿瘤中直径50微米的小血管，同时还能清楚地区分活组织与死组织。

2004年9月肿瘤追踪9月号《自然医学》上发表的一篇研究报告介绍了一项在活体内追踪肿瘤细胞的新技术。

基于熵最小化的LFM信号调频率估计算法

收稿日期：2016-03-25修回日期：2016-04-10基金项目：军队预研基金资助项目（51333030103）作者简介：袁园（1990-），女，河南洛阳人，助理工程师。

研究方向：通信对抗。

*摘要：利用LFM 信号频谱的熵随着调频率减小而降低的性质，提出了一种基于频谱熵最小化的LFM 信号调频率的估计SEM 方法。

建立参数待估的相位补偿因子，通过搜索得到使得补偿后信号频谱熵全局最小的调频率估值。

在搜索过程中，采用两级搜索策略，并引入牛顿迭代算法，有效降低了算法复杂度。

理论推导和仿真结果证明，该算法为有偏算法，估计偏差量与初始频率相关，理论估计方差比较CR 下界低12dB 。

对雷达实测回波信号进行验证，与离散多项式变换算法相比发现，提出算法估计的鲁棒性更好，并具有较高的测速精度，具有一定的应用价值。

关键词：LFM 信号，最小熵，有偏估计，Cramer-Rao 下界中图分类号：TN911.7文献标识码：A基于熵最小化的LFM 信号调频率估计算法*袁园，蔡啸，郭蓓蓓（中国洛阳电子装备试验中心，河南洛阳471003）Estimation Method of LFM Signal Chirp RateBased on Entropy MinimizationYUAN Yuan ，CAI Xiao ，GUO Bei-bei（Luoyang Electronic Equipment Testing Center ，Luoyang 471003，China ）Abstract ：Based on the fact that the spectrum entropy decreases with the chirp rate being smaller ，this paper proposes a spectrum entropy minimization （SEM ）based chirp rate estimation method.A phase filter is established and the chirp rate estimation is accomplished via minimization of the spectrum entropy.In this process ，a two-step search strategy is utilized.In step one ，a large searching step is chosen to achieve the coarse estimation of the parameter and then Newton iterative search algorithm is used in step two to estimation the chirp rate accurately.Theoretical derivation shows that the proposed algorithm is biased ，which is related to the fractional part of the initial frequency and the variance is about 12dB lower than Cramer-Rao lower bound.Simulation result proves the correctness of the derivation and the comparison with classic discrete polynomial phase transform is made.Key words ：LFM signal ，minimum entropy ，biased estimation ，cramer-rao lower bound 0引言线性调频（Linear Frequency Modulation ，LFM ）信号以其良好的时域压缩特性和大的发射能量等诸多优点，在雷达、声呐、生物医学及通信工程等领域得到了广泛应用。

Kryazhimskiy_eta...

3 JUNE 2011 VOL 332 SCIENCE 1160PERSPECTIVESPropagating bacteria in a lab f or thousands of genera-tions may seem tedious, oreven irrelevant, to most evolution-ary biologists. Nonetheless, such experiments provide an opportunity to deduce quantitative principles ofevolution and directly test them in controlled environments. Combined with modern sequencing technolo-gies, as well as theory, recent micro-bial experiments have suggested a critical role for genetic interactions among mutations, called epistasis, in determining the pace of evolution. T wo papers in this issue, by Khan et al . on page 1193 ( 1) and Chou et al . ( 2) on page 1190, present precise experimental measurements of these epistatic interactions.Microbial evolution experiments in a simple, constant environmentreveal a characteristic pattern: At ﬁ rst, a population rapidly acquires benef icial mutations, but then adaptation progressively slows sothat thousands of generations pass between subsequent beneﬁ cial substitutions ( 3). Unexpected outcomes, however, can and do occur even in these simple experimental conditions. Populations evolve a dramatically elevated mutation rate ( 4), discover rare phe-notypic innovations ( 5), or diverge into dis-tinct lineages that either coexist ( 6) or com-pete vigorously as each strain races to acquire more adaptive mutations ( 7). Recent theory suggests that a common cause underlies all these phenomena: the structure of epistatic interactions among mutations.Epistasis describes how the ﬁ tness conse-quence of a mutation depends on the status of the rest of the genome. In one extreme exam-ple, called sign epistasis, a mutation may be beneﬁ cial if it arises on one genetic back-ground, but detrimental on another. Although interactions among genes may seem an obvi-ous fact of biology, the myriad possible forms of epistasis have made it difﬁ cult to formu-late predictive evolutionary models or to infer such interactions from empirical data. Nev-ertheless, epistasis is at the heart of classi-cal theories, such as the evolution of sex ( 8), and also of modern concepts such as robust-ness and evolvability (a population’s ability to evolve) ( 9). Moreover, recent theoretical work ( 10) suggests that the overall dynami-cal pattern of adaptation observed in long-term microbial experiments can be explained by a prevalence of what is called antagonistic epistasis, in which beneﬁ cial mutations con-fer less beneﬁ t in combination than they do individually.To quantify epistasis among benef icial mutations and to test these theoretical predic-tions, both Khan et al . and Chou et al . exam-ined the initial substitutions that occurred in populations of bacteria adapting in the labo-ratory. The researchers identiﬁ ed the hand-ful of mutations across the genome that had substituted in an evolved strain, and then con-structed intermediate strains containing com-binations of these mutations. By measuringthe ﬁ tness beneﬁ ts conferred by these muta-tions, individually and in combination, the researchers were able to directly quantify the extent and form of epistasis (see the ﬁ gure).Both studies found a predominance of antagonistic epistasis, which impeded the rate of ongoing adaptation relative to a null model of independent mutational eff ects. Chou et al . further interpreted the prevalence of antagonistic epistasis in terms of meta-bolic costs and beneﬁ ts. The concordance of results from the two studies is noteworthy, especially because Khan et al . analyzed Esch-erichia coli populations [from the long-term experiments of Lenski ( 3)], whereas Chou et al . studied an engineered strain of Methylo-bacterium extorquens . The remarkable preci-sion with which both studies quantiﬁ ed epis-tasis among beneﬁ cial mutations was made possible only by leveraging whole-genome sequencing combined with the ability to reconstruct mutational combinations andassay them in the same environment in whichthe mutations ﬁ rst arose.The view of epistasis across a genome that emerges from this work contrasts sharply In Evolution, the Sum Is Less than Its PartsEVOLUTIONSergey Kryaz himskiy ,1,2 Jeremy A. Draghi ,1 Joshua B. Plotkin 1Laboratory experiments with bacteria shedlight on how epistatic interactions inﬂ uence the pace of evolution.Ancestor strain Adapted strain Reconstruct intermediates Evolves in labDiminishing returns Fitness W abFitness W b Fitness W a 1st mutation 2nd mutation 3rdmutation F i t n e s sAntagonistic epistasis W ab < W a • W b Antagonistic epistasis. Bacteria adapt to a laboratory environment by acquiring beneﬁ cial mutations. Khan et al . and Chou et al . identiﬁ ed the mutations that accrued in an adapted strain, and measured their ﬁ tness beneﬁ ts (growth advantage relative to the ancestor). The mutations conferred smaller marginal beneﬁ ts in combination than they didindividually. This antagonistic epistasis causes progressively slower rates of adaptation over time.C R E D I T : A D A P T E D B Y P . H U E Y /S C I E N C E1Department of Biology, University of Pennsylvania, Phila-delphia, PA 19103, USA. 2Department of Organismic andEvolutionary Biology, Harvard University, Cambridge, MA 02138,USA.E-mail:******************.eduPublished by AAASo n J u n e 2, 2011w w w .s c i e n c e m a g .o r g D o w n l o a d e d f r o mPERSPECTIVESwith the type of epistasis found among adap-tive mutations within a single protein ( 11). Notably, Weinreich et al. studied mutations in an antibiotic resistance gene, β-lactamase, and found a prevalence of sign epistasis, which limits the number of genetic paths that evolution can follow ( 11). In contrast, the epistasis documented by Khan et al. and Chou et al. exerts less constraint on the order of substitutions that increase ﬁ tness, so that the speciﬁ c path that evolution will take is less predictable. At the same time, the pre va-lence of antagonistic epistasis measured by the two groups ensures a predictable tempo of adaptation characterized by diminishing marginal returns ( 10).Although these new experiments suggest a consistent principle of how epistasis shapes the pattern of adaptation, many questions must be answered before their results can be extended to evolution outside the labora-tory. It remains unclear, for instance, whether these results would be altered by changing fundamental evolutionary parameters, such as population size, rate of mutation, and rate of re combination. Likewise, it is uncle ar whether experiments in simple environments,with only one or a few niches for coexistingstrains, will reﬂ ect the pattern of adaptation inmore complex ecologies, such as Pseudomo-nas ﬂ uorescens in structured environments( 6). Nonetheless, the compelling consistencybe twe e n the se two studie s should inspireefforts to test the generality of their ﬁ ndings,by measuring epistasis in a wide range ofexperimental and even natural systems.These studies, and the long-term labora-tory evolution experiments from which theyderive, represent a resounding achievementfor the reductionist approach to studyingbiology. The mechanistic picture they paintof evolution is complex but not incompre-hensible; although epistatic interactions leadto surprising phenomena, the advantagesof a frozen “fossil record” of laboratory-raised isolates, and the ease of manipulat-ing—and, now, fully sequencing—evolvedstrains enables researchers to tease apart andexamine the underlying causes of these phe-nomena. Moreover, the theory and conceptsdeveloped to explain these simple experi-me nts may have broad payoffs. Alre ady,epistasis has been implicated in the evolu-tion of drug resistance in inﬂ uenza viruses( 12) and in bacterial pathogens ( 13). Ulti-mately, populations of bacteria tediouslypropagated in the lab may be key to predict-ing the next moves of the most mutable anddangerous human pathogens.References1. A. I. Khan, D. M. Dinh, D. Schneider, R. E. Lenski, T. F.Cooper, Science332, 1193 (2011).2. H.-H. Chou, H.-C. Chiu, N. F. Delaney, D. Segrè, C. J.Marx, Science332, 1190 (2011).3. S. F. Elena, R. E. Lenski, Nat. Rev. Genet.4, 457 (2003).4. P. D. Sniegowski, P. J. Gerrish, R. E. Lenski, Nature387,703 (1997).5. Z. D. Blount, C. Z. Borland, R. E. Lenski, Proc. Natl. Acad.Sci. U.S.A.105, 7899 (2008).6. P. B. Rainey, M. Travisano, Nature394, 69 (1998).7. R. J. Woods et al., Science331, 1433 (2011).8. A. S. Kondrashov, Nature336, 435 (1988).9. G. P. Wagner, L. Altenberg, Evolution50, 967 (1996).10. S. Kryazhimskiy, G. Tkačik, J. B. Plotkin, Proc. Natl. Acad.Sci. U.S.A.106, 18638 (2009).11. D. M. Weinreich, N. F. Delaney, M. A. Depristo, D. L.Hartl, Science312, 111 (2006).12. J. D. Bloom, L. I. Gong, D. Baltimore, Science328, 1272(2010).13. S. Trindade et al., PLoS Genet.5, e1000578 (2009).10.1126/science.1208072Behavior and the Dynamic Genome GENOMICSAlison M. Bell 1,3 and Gene E. Robinson 2,3Does behavior evolve through gene expression changes in the brain in response to the environment?W he n circumstance s change, an organism’s ﬁ rst response is oftenbehavioral. But how does adap-tive behavior evolve, given that it requires constant and often instantaneous interac-tions between an individual and its environ-ment? The dominant view emphasizes new random DNA mutation as the starting point. This may lead to behavioral variation. If the resulting variants have different ﬁ tness values, then natural selection could result in behavioral evolution through changes in allele frequencies across generations. An alternative theory proposes environmentally induced change in an organism’s behavior as the starting point ( 1), and “phenotypic plas-ticity” that is inherited across generations through an unspeciﬁ ed process of “genetic assimilation” ( 2). Despite numerous exam-ples ( 3), the latter as a driver of behavioralevolution has never been widely accepted,perhaps as a reaction against Lamarckian-ism—the idea that characteristics acquiredby habit, use, or disuse can be passed onacross ge ne rations. Howe ve r, be havioralgenetics and genomics, especially for ani-mals in natural populations, lend some plau-sibility to the phenotypic plasticity view.The ability to analyze genome-wide geneexpression through “transcriptomics” hasshown that the genome responds dynami-cally to stimuli ( 4). One illustrative exam-ple is the honey bee. The African honey bee(Apis mellifera scutellata) responds muchmore ﬁ ercely when its hive is attacked thando other subspecies of honey bee. Evolu-tionary changes in brain gene expressionmay have resulted in an increase in respon-siveness to alarm pheromone (the chemicalbees use to alert each other to danger) forAfrican honey bees ( 5). About 10% of thesame genes regulated in the brain by alarmpheromone are also differentially expressedbe twe e n African and the le ss aggre ssiveEuropean honey bees. These genes, actingover both physiological and evolutionarytime scales, provide a possible mechanismfor how behavioral plasticity might driverapid behavioral evolution through changesin gene regulation. In an environment withmore predators, colonies producing morebees with lower thresholds for respondingto alarm pheromone would have fared bet-ter, which would then result in a popula-tion with patterns of gene expression whoseoutput was an “aroused” behavior, even inthe absence of alarm pheromone. Althoughthis view does not rule out the possibilitythat these differences in aggression arosethrough new mutation, the transcriptomicsagrees with the idea of “genetic accommo-dation” ( 3), the modern, more inclusive ver-sion of genetic assimilation, which couldinvolve e ithe r e volutionary incre ase s ordecreases in plasticity. In certain environ-ments, plastic genotypes might be favored,but in other environments, nonplastic gen-otypes might be preferred instead. Futurestudies will determine whether differencesin honey bee aggression can be explainedby selection on regulatory regions of the1Department of Animal Biology, University of Illinois,Urbana-Champaign, IL 61801, USA. 2Department of Ento-mology, University of Illinois, Urbana-Champaign, IL 61801,USA. 3Neuroscience Program, Program in Ecology, Evolution-ary Biology and Conservation, Institute for Genomic Biology,University of Illinois, Urbana-Champaign, IL 61801, USA.E-mail:******************.eduPublished by AAAS o n J u n e 2 , 2 0 1 1 w w w . s c i e n c e m a g . o r g D o w n l o a d e d f r o m SCIENCE VOL 332 3 JUNE 20111161。

生活史进化

第2章生活史进化张大勇生活史进化对策的研究起始于本世纪40年代末~50年代初，主要是由动物种群统计学（demography）和进化理论相结合而形成的。

在1920~1950年这一时期，生态学家已经开始广泛地运用寿命表方法研究动物种群，因而对于生活史的定量种群统计学后果已经具备了一个有效的分析方法。

这种方法考察的是特定年龄个体的死亡率和生育率。

生态学家已清楚地知道，这些生活史参数无论是在种内还是在种间都有很大的变异。

种群遗传学和数量遗传学的迅猛发展同时也为达尔文关于表型性状适应价值的论述提供了坚实基础。

在第1章内，我们已经提到，早期的种群生态学并不关注种群内部的遗传变异，而种群遗传学也基本上忽略了种群动态过程。

二者之间的有机结合是生态学领域内长期没有得到很好解决的一个难题；而这对于生活史对策研究却是至关重要的。

尽管Fisher（1930）早在30年代就已经提出应把种群统计学性状看作为表型的一部分并探索它们的适应性基础，但人们公认现代生活史进化理论创立于40年代末到50年代初Lack（1947）关于鸟类窝卵数、Medawar（1946，1952）关于衰老、以及Cole（1954）关于单次生殖/多次生殖进化的研究。

其后，生活史进化方面的研究蓬勃兴起，有关文献可说是浩如烟海。

但在本章内我们并不打算对整个领域进行全面地综述，而是选择几个有代表性的核心问题介绍其理论背景和发展趋势。

如果读者想要更全面地了解该领域，可以参阅Roff（1992）以及Stearns （1992）的专著。

侧重于基础理论方面的书籍有Charlesworth（1994）。

在进入本章具体内容之前，我们有必要首先熟悉一下生活史进化研究的基本途径—表型优化理论（参见第3章）。

2.1 进化生物学中的表型优化研究途径近些年，进化生物学家和生态学家已经开始广泛采用工程学和经济学领域内的数学方法来认识生命的多样性问题（Maynard Smith 1978）。

知母活性成份ZMS药理研究中几种动物模型的建立和比较

ｂｅｔａＴｈｅｒｅｓｕｌｔｓｓｈｏｗｓｔｈａｔｔｈｅｍｏｄｅｌｉｓａｖｅｒｙｕｓｅｆｕｌｔｏｏｌｆｏｒｉｎｖｅｓｔｉｇａｔｉｎｇｔｈｅｐａｔｈｏｇｅｎｉｃｍｅｃｈａｎｉｓｍｓｌｅａｄｉｎｇｔｏＡＤａｎｄｄｅｖｅｌｏｐｉｎｇｎｅｗｐｈａｒｍａｃｅｕｔｉｃａｌｔｒｅａｔｍｅｎｔｓｔｏＡＤ．Ａｆｔｅｒｍｏｄｅｌ
ＺＭＳｏｎｔｈｅｔｏｘｉｃｉｔｙｏｆＡＢ．Ｉｎａｄｄｉｔｉｏｎ．ｗｅａｌｓｏｅｓｔａｂｌｉｓｈｅｄＳｃｏｐｏｌａｍｉｎｅｍｏｄｅｌａｎｄＤ— ｇａｌａｃｔｏｓｅｍｅｄｅｌ．１１ｌｅｒｅｓｎｉｔｓｉｎｄｉｃａｔｅｔｈａｔａｌｌｔＩｌｅｓｅａｎｉｍａｌｍｏｄｅｌｓｈａｄｓｉｇｎｉｆｉｃａｎｔｄｅｆｉｔｉｔｓｏｆｌｅａｒｎｉｎｇａｎｄｍｅｍｏｒｙ．ＯｒａｌａｄｍｉｎｉｓｔｒａｔｉｏｎｏｆＺＭＳｃｏｕｌｄｎｏｔａｂｌｙｉｍｐｒｏｖｅｔｈｅｌｅａｒｎｉｎｇａｎｄｍｅｍｏｒｙａｂｉｌｉｔｙ，ｉｍｐｒｏｖｅｔｈｅａｃｔｉｖｉｔｙｏｆＣｈＡＴａｎｄｉｎｃｒｅａｓｅｔｈｅｄｅｎｓｉｔｙｏｆＭｒｅｃｅｐｔｏｒ．
ｂｅｔａａｎｄＩＢＯＣＯｕｌｄｄｅｃｒｅａｓｅｎｕｍｂｅｒｏｆｎｅｕｒｏｎａｒｏｕｎｄｔｈｅｍａｒｋｓａｎｄｌｅａｄｔｏｄｅｇｅｎｅｒａｔｉｏｎ．ＴｈｅｄｅｎｓｉｔｙｏｆＭｒｅｃｅｐｔｏｒｉｎｃｏｒｔｅｘ，ｈｉｐｐｏｃａｍｐｕｓａｎｄｓｍａｔｕｍｄｅｃｒｅａｓｅｄａｆｔｅｒｉｎｊｅｃｔｉｏｎｏｆＡ
ｍｅｃｈａｎｉｓｍｓｏｆＺＭＳｉｎｉｍｐｒｏｖｉｎｇｔｈｅｆｕｎｃｔｉｏｎｏｆｃｈｏｌｉｎｅｒｇｉｃｓｙｓｔｅｍｍａｙｂｅａｃｈｉｅｖｅｄｂｙｅｆｆｅｃｔｉｖｅｌｙｐｒｏｔｅｃｔｉｎｇｎｅｕｒｏｎｓａｇａｉｎｓｔｔｏｘｉｃｉｔｙｏｆＡｂｅｔａ，ｐｒｏｍｏｔｉｎｇｔｈｅｓｙｎｔｈｅｓｉｓｏｆｌｏｗｄｅｎｓｉｔｙｏｆＭｒｅｃｅｐｔｏｒａｎｄｉｎｃｒｅａｓｉｎｇｔｈｅａｃｔｉｖｉｔｙｏｆＣｈＡＴｉｎｂｒａｉｎ

分光光度法测定维生素C的含量外文翻译原文

1 IntroductionVitamin C occurs in different concentrations in a vari-ety of natural samples. It is added to several pharma-ceutical products as an essential ingredient, a stabilizer for vitamin B complex, and as an antioxidant.Consequent upon its desirable effects, it is widely used in the treatment of certain diseases such as scurvy,common cold, anemia, haemorrhagic disorders, wound healing, and even infertility, to mention some stark cases. It is considered essential for the development and regeneration of muscles, bones, teeth and skin.The increasing use of pharmaceuticals and other natural samples containing vitamin C has meant that the practi-cising chemists should develop analytical procedures for its determination which are simple to operate, rapid,accurate, sensitive and selective. The desire to develop methods with ideal characteristics has resulted a large number of procedures with varying applicability. Many instrument-based analyses including fluorometry 1–4,HPLC 5–10, polarography 11–13and enzymatic 14,15methods are reported in the literature. But due to their inherent limitations, these techniques are not commonly used for routine analyses. However, photometric methods are particularly attractive because of their speed and sim-plicity. Consequently, a large number of such proce-dures have been developed for the determination of ascorbic acid (AA). Though some short reviews 16–18have been reported, a critical assessment of these meth-ods is desirable to examine their salient features and utility. This review is an attempt to assess exclusively the existing spectrophotometric methods for the deter-mination of vitamin C as regards their simplicity, rapid-ity, Beer’s law range, sensitivity, selectivity and applic-ability. It is primarily based on the information collect-ed through the Chemical Abstracts for the period 1970to mid-1997.2 Results and DiscussionSeveral dyes such as 2,6-dichlorophenolindophenol (DCIP), dimethoxydiquinone (DMDQ), ninhydrin, fast red AL salt and 2′,7′-dichlorofluorescein etc . have been used for the determination of vitamin C. Among these dyes, DCIP has been most extensively studied. It is included in the official titrimetric methods as reported in different pharmacopoeias 19–21and it also forms the basis of many colorimetric methods. The blue dye DCIP is reduced to the colorless form on addition of ascorbic acid as shown in Fig.1, but it gives a pink color to the acidic solutions. Using the dye, ascorbic acid present in human urine 22and processed potatoes 23has been determined. The excess dye can be extracted with xylene or butanol.24Many substances which are capable of reducing the dye resulting from the prepara-tion and processing of food samples interfere. Flow dialysis proposed by Gary et al .25and continuous flow systems have been used to monitor the decrease in absorbance of DCIP. Such automated systems appear to be justified only when routine analysis of a largeANALYTICAL SCIENCES OCTOBER 1998, VOL. 14Photometric Methods for the Determination of Vitamin CSatya P. A RYA †, Meenakshi M AHAJAN and Preeti J AINDepartment of Chemistry, Kurukshetra University, Kurukshetra –136119, Haryana State, IndiaThe importance of vitamin C to the human body is widely acknowledged throughout the globe. The deficiency of this vitamin leads to various diseases. In view of its importance, numerous methods including spectrophotometric ones have been developed for its determination in pharmaceuticals, foods and biological samples. A comprehensive review of the available spectophotometric methods for the determination of ascorbic acid is presented.Keywords Vitamin C determination, spectrophotometric method†To whom correspondence should be addressed.Fig.1The reduction of DCIP with ascorbic acid.Ascorbic acidDCIP(Oxidized, Blue-Pink)Dehydroascorbic acid DCIP (Reduced, Colorless)number of samples is needed; otherwise it is tedious to use for a single estimation.Dimethoxydiquinone 26gives a violet-colored product with ascorbic acid in a phosphate buffer (pH 6.6). The reduced “indigoid” quinhydrone form is perhaps responsible for the formation of violet-colored product as shown in Fig. 2. After diluting with dioxane,absorbance of the colored solution which is stable over 24 h only under dark conditions is measured at 510 nm.Heating leads to a decrease in color intensity. Beer’s law holds good up to 80 µg ml –1with a detection limit of 10 µg ml –1. Riboflavin and copper interfere. The interference of iron(II) sulfate responsible for precipita-tion can be removed by centrifugation. Though the method is not sufficiently sensitive (ε=1.62×103), it can still be applied to the analysis of citrus fruits 27after extracting the colored product into chloroform (λmax =530 nm). Lin et al .28and Pandey 29reported pro-cedures based on the reaction of ascorbic acid with fast Red AL salt (1)(zinc chloride salt of diazotized 1-aminoanthraquinone) and tetrachlorobenzoquinone (2).The reaction of (1)proceeds in acid medium but the blue color develops only after the addition of alkali,which exhibits three absorption bands between 500–630 nm. If one uses the latter reagent (2), ascorbic acid is determined at 336 nm (ε=535 cm 2mol –1) via a decrease in absorbance of 7×10–4M tetrachlorobenzo-quinone (chloranil) in 80% acetone –water (v/v) medi-um. With these methods, mixtures of ascorbic acid with thiols like o -mercaptobenzoic acid, mercaptosuc-cinic acid, 3-mercaptopropionic acid can not be resolved.Methylene Blue 30, (3)and ninhydrin 31,32(4)find applications with the determination of ascorbic acid in food products. The colorless form of the dye (3)is extracted into chloroform after its reduction with ascor-bic acid; back oxidation of the dihydro derivative to Methylene Blue has been used for the assay of ascorbic acid (λmax =653 nm). The method is reported to be highly sensitive. The reaction of ascorbic acid with ninhydrin carried out on a boiling water bath using 80% aqueous solution as a medium in 0.01 M NH 4OH is used for its determination in pharmaceuticals (λmax =415 nm), but without added advantages.In the sixties, many methods based on the coupling of ascorbic acid with aniline diazonium salts were report-ed. A purplish or blue colored species is produced by these salts with ascorbic acid in alkaline medium.Diazotized-4-methoxy-2-nitroaniline couples withascorbic acid in oxalic acid medium in the presence of ethanol or isopropanol, giving a purplish color in alka-line solutions. Though Fe(II), Sn(II) and dehydroascor-bic acid (DHAA) do not interfere, the presence of reductones and reductic acid requires formaldehyde condensation. Low contents of vitamin C in the pres-ence of flavanoids and pectic substances are also detected. The reaction of ascorbic acid with 4-nitrobenzene diazonium fluoroborate in acetic acid medium was used for its determination at λmax 415 nm.But the mixture has to be kept for 25 min in the dark,followed by the addition of sodium hydroxide. The sensitivity of a large number of stabilized diazonium salts was evaluated; diazotized 4-nitroaniline-2:5-dimethoxy-aniline was found to give the most intense color reaction.Enzymic 33–35colorimetric determinations of ascorbic acid in commercial vitamin C tablets and in fruits and vegetables were made by measuring the absorbance at 358 nm or 320 nm of the resulting products obtained by oxidation of o -phenylenediamine/1,4-diaminobenzene using ascorbate oxidase or peroxidase in presence of H 2O 2at pH 5.3. Ascorbic acid is determined after oxi-dation with mercuric chloride and condensing the DHAA with 4,5-disubstituted phenylenediamine 36,which gives the quinoxaline derivative used for absorbance measurement. The method involving 4-nitro-1,2-phenylenediamine 37(λmax =375 nm) is very complex and laborious, since it involves many time-consuming steps including purification of the sample with anionic Sephadex column.In the recent past, the determination of oxidized and reduced vitamin C in pharmaceuticals, foods and bio-logical samples has gained importance since AA and DHAA redox couple is an important component of many biological systems. Simultaneous measurement of both AA and DHAA using HPLC has been carried out by various workers 38–45in different laboratories.Rose and Nahrwold 38determined AA and DHAA by monitoring UV absorbance at 254 nm and 210 nm respectively for the analysis of foods, biological sam-ples and pharmaceutical preparations. Graham and Donald 39have carried out the analysis at 254 nm after extracting the food samples with 62.5 mM metaphos-phoric acid using an ion exchange column (Aminex-HPX 87H). Both these forms have also been deter-mined in vegetable samples 40using a UV detector (254nm). Yasui and Hayashi 41made such determinations by converting to compounds having λmax at 300 nm under alkaline conditions. Derivatization of DHAA is accel-erated in the presence of sodium borohydride.Validation of the micromethod for the determination of the oxidized and reduced vitamin C in plasma by HPLC fluorescence method has been reported by Tessier et al .45These methods are useful and a single step HPLC assay of such detections has been helpful in overcoming the burden of derivatization.Ascorbic acid gives colored species with substituted benzene such as m -dinitrobenzene 46in formaldehydeFig.2Reduction reaction of dimethoxydiquinone (DMDQ).‘Indigoid’quinhydroneDMDQand trinitrobenzene47in tartrate buffer when studied for its determination over the concentration ranges 2–50 and 0–125 µg ml–1of ascorbic acid respectively. Methanolic solution of resorcinol48gives a pale yellow color (λmax=425 nm) with ascorbic acid in hydrochloric acid medium, obeying Beer’s law for 80–400 µg ml–1. 4-Chloro-7-nitrobenzofurazane49forms a bluish green colored species with ascorbic acid in presence of 0.2 M sodium hydroxide. The absorbance is measured at 582 nm after diluting the reaction contents with 50% (v/v) aqueous acetone solution. Beer’s law is obeyed in the concentration range 5–20 µg ml–1. The colored prod-uct is stable for 30 min only when kept away from direct sunlight or artificial day light. The method is reported free from the interference of all other vitamins and minerals present in multivitamin preparations and can be applied to the analysis of pharmaceuticals, fresh fruit juices and vegetables.Hashmi et al.50proposed a method based on the reac-tion of 2,3,5-triphenyltetrazolium chloride with ascor-bic acid in alkaline medium. The pink solution is allowed to stand in the dark for 30 min at 25˚C; it obeys Beer’s law over the range 5–25 µg ml–1. Sugars (>15 µg ml–1) except sucrose interfere by forming a similar color to that of the reagent. Riboflavin, cyanocobalamin and folic acid interfere due to their own color. Beutler et al.51,52investigated the use of methylthiazolyltetrazolium salt in presence of ascorbate oxidase enzyme and 3-(4,5-dimethylthiazolyl-2-yl)-2,5-diphenyltetrazolium chloride or bromide in the pres-ence of 5-methylphenazinium methyl sulfate (electron carrier) at pH 3.5 for the determination of ascorbic acid in foods, fruit juices and vegetables juices. These reac-tions involve the formation of formazon (λmax=578 nm). The interference of sulfur dioxide requires treat-ment with formaldehyde, and color interference from dark juices is removed by decolorization with 1% polyvinylpolypyrrolidone before filtration. Sorbitol, alcohol and oxalate interfere with the ascorbic acid oxi-dase. However, the effect of oxalate can be checked by adding a slight excess of Ca(II) ions. Other derivatives such as 2,5-diphenyl-3-thiazolyl tetrazolium chloride53 at pH 12.2, 2-(p-iodophenyl)-3-(p-nitrophenyl)-5-phenyltetrazolium chloride at pH 10.5 (λmax=540 nm) and 2,2′,5,5′-tetra-(4-nitrophenyl)-3,3′-(3,3′-dimethoxy-4,4′-biphenyl)ditetrazolium chloride54have also been employed for the assay of ascorbic acid.The coupling of 2,4-dinitrophenylhydrazine (DNPH) with ketonic groups of DHAA and diketogulonic acid (DKGA) has been the basis of many methods for the determination of total vitamin C contents. Proteins present in the samples are precipitated by adding trichloroacetic acid (TCA) and aliquots of filtrate are shaken with acid–washed charcoal (norit) or activated charcoal55to clarify the solutions and to oxidize AA to DHAA. A reducing medium is produced by adding thiourea prior to DNPH addition, otherwise unspecific coloration is given by oxidants. The osazones (λmax=545 nm) thus formed during the 3 h incubation at 37˚C by the reaction of DNPH and DHAA are dis-solved by adding 85% H2SO4. Vitamin C can be extracted with metaphosphoric acid–stannous chloride solution without charcoal treatment for differential determination of DKGA, DHAA and AA in the same tissue extracts. The interference of sugars can be mini-mized by carrying out incubation at 15˚C and measur-ing the absorbance only after adding sulfuric acid for 75 min.56The use of several acid mixtures has been proposed for replacing the tedious dropwise addition of sulfuric acid. Lack of specificity is found with many of these methods; interfering osazones can be separated by chromatographic methods such as TLC57and HPLC58, but at the cost of making these procedures tedious and cumbersome. The nature of DNPH meth-ods for total vitamin C also makes it amenable to auto-matic flow through analyses.59–61 Phenylhydrazinium chloride62produces a yellow color (λmax=395 nm) when treated with ascorbic acid in0.1 M HCl medium. The reaction contents are kept for1 h in an incubator or water bath at 50±2˚C, thus mak-ing the method time-consuming. Beer’s law is obeyed in the range 25–100 µg of ascorbic acid. No interfer-ence is observed from other vitamins, minerals, glucose, sucrose, excipients and reducing agents. However, the presence of excessive amounts of riboflavin requires the addition of 0.5 g talc, which imparts a yellow color to the solution. 3-Methyl-2-benzothiazolone hydrazone63reacts in the presence of sodium metaperiodate to form a blue colored solution (λmax=630 nm) which helps in the determination of ascorbic acid over the range 6–14 meq ml–1.Wang64suggested the use of potassium iodate for the determination of vitamin C in pharmaceuticals. The absorbance is measured either in the UV region (288 nm) or in the visible region (445 nm). Besides aqueous phase measurements, the yellow precipitate can be extracted into chloroform65(λmax=514 nm). The ICl2–generated in the oxidation of AA by iodate66in acid medium in the presence of Cl–ions has been used to iodinate 2′,7′-dichlorofluorescein dye. The iodinated dye (λmax=525 nm) obeys Beer’s law up to 300 µg (ε=8.81×103). Soft drinks67have been analyzed using the reaction of iodine in an acetic acid medium (λmax= 350 nm). Sirividya and Balasubramanian68reported an indirect procedure based on the oxidation of ascorbic acid by a known excess of iodate in the presence of acid for the analysis of pharmaceuticals and fresh fruit juices. The unreacted iodate is used for hydroxylamine oxidation to generate nitrite, which is then diazotized with sulfanilic acid. The resulting diazonium salt is coupled with N-(1-naphthyl)ethylenediamine dihy-drochloride to form an azo dye (λmax=540 nm). The procedure is a complicated one as it involves many steps.The reaction of hexacyanoferrate(III)69(5)was used for the determination of micro quantities of vitamin C by measuring the decrease in color intensity of the reagent (5)(λmax=420 nm) in McIlvaine buffer (pH 5.2)solutions. Beer’s law is restricted within the range 180–270 µg of AA. A 200-fold amount of glucose, urea,citric acid and tartaric acid; 50-fold excess of creatineand 2-fold excess of creatinine do not interfere, but apositive error is observed even with very small quanti-ties of uric acid. In general, all such reagents thatreduce hexacyanoferrate(III) or oxidize hexacyanofer-rate(II) under experimental conditions interfere.Further the utility of the method is limited to colorlesssolutions. Yet another method involving the oxidationof phthalophenone to phenolphthalein by the reagent(5)in alkaline solution was proposed by Al-Tamrah.70This obeys Beer’s law up to 7 µg ml–1(λmax=553 nm). Sugars are tolerated only in microgram amounts. Therelative standard deviation and detection limit are0.65% and 0.1 µg ml–1respectively.Direct UV spectrophotometry71–73with backgroundcorrection methods such as thermal decomposition, UVlight irradiation, catalytic destruction and alkaline treat-ment has been used for the determination of AA in softdrinks, fruit juices and pharmaceuticals. However, therate of thermal decomposition is found to be very low72and fruit juice samples that are unstable to alkalinetreatment, have fine particles, have a deep coloration orcontain high concentrations of caffeine, saccharin,caramel and tannic acid can not be analyzed. Somemethods based on the Cu(II)-catalyzed oxidation arereported for the assay of pharmaceuticals, fruits andbeverages74–77allowing the determination of AA up to120 µg ml–1at λmax=267 nm. Fe(II) interferes seriously. Only minute amounts of folic acid are tolerated. Thepresence of Al(III), Mg(II) or Zn(II) gives a negativeerror due to their catalytic effect.Some methods involving the coinage metal (Cu, Ag,Au) complexes have been worked out. The reductionof Cu(II) in a biphasic system of isopentyl alcohol andan aqueous solution of pH 4.6 to Cu(I), followed by itscomplexation with cuproine to give a colored complex(λmax=454 nm), was reported by Contreras et al.78for the analysis of foods and vegetables. Fresh fruits andvegetables and dehydrated samples were analyzed afterextracting with 5% HPO3and with a 1:1 mixture of0.5% HPO3and 0.05 M H2SO4respectively. Also thecolored complexes of Cu(I) with 2,2-biquinoline79(λmax=540 nm), rhodanine80(λmax=473 nm) and 2,9-dimethyl-1,10-phenanthroline81–83(λmax=450 nm) have been used to determine ascorbic acid in different sam-ples. However, the method using 2,9-dimethyl-1,10-phenanthroline obeys Beer’s law over the range 2–20µg ml–1, though it requires 1 h waiting time for full color intensity. These methods based on the complex-ation of reduced Cu(I) are rather unselective, since sub-stances such as Fe(II), cysteine, or sodium thiosulfatewhich lead to the reduction of Cu(II) to Cu(I) interfereseriously. The gelatin complexes84,85of Ag(I)(λmax=415 nm; ε=2.2×103) and Au(III) (λmax=540 nm;ε=2.3×103) give colored products on adding AA to their alkaline solutions. The procedure as suggested by Pal et al.84is not interfered with by glycine, alanine, fruc-tose, sucrose, citric acid, tartaric acid or other reducingagents.Analytical applications of Molybdenum Blue formedon reduction of phosphomolybdate complex86, ammoni-um molybdate87–89or molybdic acid90have been report-ed by many workers for the determination of ascorbicacid in pharmaceuticals, fruits and vegetables, pastriesand beverages. Ammonium molybdate–sulfuric acidsystem requires 1 h for complete development of colorwith ascorbic acid.87However, such waiting time canbe decreased to 15 min by the addition of metaphos-phoric acid–acetic acid solution.88The colored speciesobeys Beer’s law over the range 2–32 µg ml–1at 760nm (ε=4.3×104). Serious interferences are observed due to phenolic compounds such as catechins, gallicacid, pyrogallol and gallotannins; thiosulfate ions andthiourea. Recently, P-Sb-Mo heteropoly acid91hasbeen used to produce heteropoly blue (λmax=710 nm) for the assay of ascorbic acid over the range 1–50 µgml–1(ε=3.68×103). The use of folin reagent92and folin phenol93(λmax=760 nm) has also been described for the assay of biological samples after deproteinizing withTCA. Beer’s law is obeyed up to 45 µg ml–1. Thecolor development is not obstructed by bovine serumalbumin, adenine, guanine, thymol and oxyhaemoglo-bin. Folin-ciocalteu94reagent reacts with ascorbic acidto give a blue colored complex (λmax=730 nm) as well. However, the method is time-consuming, as the fullcolor intensity requires 40–50 min. Ammonium meta-vanadate95gives a green color (λmax=680 nm) on heat-ing for 10 min in the presence of ascorbic acid.Though the method has been put to use for the analysisof some samples, it is not sufficiently sensitive.Many spectrophotometric methods based on thereduction of Fe(III) to Fe(II) with ascorbic acid, fol-lowed by the complexation of reduced Fe(II) with dif-ferent reagents, have been reported. Amongst them,α,α′-bipyridyl96–101and 1,10-phenanthroline102–109(o-phen) find extensive use in the development of analyti-cal procedures. Most of these methods are time-con-suming, as full color development is achieved onlyafter waiting for 30–60 min. Micromodification97ofthe procedure applicable to human plasma and animaltissue has been reported without the interference of glu-cose, fructose, sucrose, glutathione and cysteine.Recently, the procedure has been simplified by Aryaand Mahajan99so as to require only 5 min waiting time,instead of 30 or 60 min, with Beer’s law range up to 12µg ml–1(λmax=522 nm). Total ascorbic acid has been determined in blood plasma100after reducing DHAA with dithiothreitol at pH 6.5–8.0, removing the excess of dithiothreitol with N-ethylmaleimide and in urine101 by acidifying with TCA and shaking with activated chorcoal. The reduced Fe(II) forms a water-soluble colored complex with o-phenanthroline (λmax=510–515 nm) at pH 1.5–6.5, with obedience of Beer’s law up to 8 µg ml–1(ε=2.2×104). Background correction104 as achieved by Cu(II)-catalyzed oxidation is necessary for most samples, while the addition of NH4F106as theinhibitor of light reduction of Fe(III)-phen complex is needed in some cases. Selectivity for some of these methods is poor. However, an improvement using orange-red ferroin chelate in aqueous micellar medium formed in the presence of the cationic surfactant cetylpyridinium bromide109has been reported (ε=2.6×104at 510 nm). Ascorbic acid in fruits was determined after extracting the ternary complex of Fe(II) with α,α′-bipyridyl/o-phen and sulfophthalein110 dyes into chloroform (λmax=602 nm).Many other compounds including oximes111–113(6), 2-oximinocyclohexanone thiosemicarbazone114(2-OCHT) (7), 2-(5-bromo-2-pyridylazo)-5-dimethyl-aminophenol115(8)and 2-nitroso-5-(N-propyl-N-sulfo-propylamino)phenol116(9)have been investigated for their use in the analysis of pharmaceuticals and biologi-cal samples for ascorbic acid contents. The earlier reported extraction111of Fe(II)-dimethylglyoxime com-plex into chloroform, which allows the determination of 0.04–0.5 mM ascorbic acid, was modified by Arya et al.112They determined its concentration up to 14 µg ml–1at 514 nm. A proportionate decrease in color intensity of Fe(III)-resacetophenone oxime113complex in sodium acetate–acetic acid buffer (pH 5) with the increasing amounts of ascorbic acid was used for its assay in the range 3.5–17.5 µg (ε=4×103). The method using 2-OCHT determines ascorbic acid up to 12 µg ml–1(ε=1.49×104), but is interfered with by metal ions such as Cu(II), Co(II), Ni(II) and Pd(II), in addition to the interference caused by the oxalic acid, riboflavin, oxidants and reductants. Color-forming reactions of Fe(II) with ferrozine117–119(λmax=562 nm) in acidic solu-tions (pH 3–6), TPTZ120–122(λmax=593, 595 nm), quinaldic acid in presence of pyridine123(λmax=380 nm), picolinic acid in presence of pyridine124(λmax=400 nm) and nitroso-R salt125(λmax=705 nm) have been used for the determination of vitamin C in a variety of samples. The reagents picolinic acid and quinaldic acid, when complexed with iron(II) in the presence of pyridine, resulted in methods used successfully in the analysis of pharmaceuticals, food products and biologi-cal samples. The respective colored complexes getting extracted into chloroform obey Beer’s law in the range 0.4–5.6 µg ml–1and 2.5–25 µg ml–1ascorbic acid without the interference of common ingredients of the samples studied. Though the method using ferrozine117 is not interfered with by sucrose, glucose, mannose, fructose and formaldehyde, yet it suffers interferences from tartaric acid, citric acid, Co(II), Ni(II) and Fe(II). However, reactions of citric acid and tartaric acid can be masked by adding Al(III) or La(III) ions and that of iron(II) by passing the solution through a cation exchanger.Most of the reported methods based on the reducing action of ascorbic acid on metal ions invariably make use of an iron(III)–iron(II) redox system. A few use copper(II)–copper(I), vanadium(V)–vanadium(IV) or molybdenum/tungsten blue formation reactions, as mentioned earlier in the text. Arya et al. have reported a new redox system involving Cr(VI)-diphenyl-carbazide complex126(λmax=540 nm), which obeys Beer’s law up to 3.2 µg ml–1. Common additives of pharmaceutical preparations have no adverse effect on the absorbance of the complex. Another fast and facile method based on the proportionate decrease in absorbance of iron(III)-ferronate complex127(λmax=465 nm) by the addition of ascorbic acid was proposed by the same authors after extracting the complex into TBA/CHCl3solution. Beer’s law is valid up to 10 µg ml–1.3 ConclusionEven after the introduction of other instrument-based procedures, photometric methods continue to be of interest because of the ease in accessibility and their quick applicability to the routine analyses. The molar absorptivity for most of the colored species used in col-orimetric analysis of vitamin C lies over the range 103 to 1041 mol–1cm–1at the wavelength of maximum absorbance. This enables the precise determination of vitamin C in a variety of samples. The presence of cer-tain substances, especially the matrix constituents, may cause serious interferences. However, attempts to over-come such interferences either by using masking agents or making preliminary separations are invariably tried, but sometimes without much success, thus resulting in methods of varying selectivity. It has not been possible to categorize the methods based on the selectivity since the relevant data is found to be missing in the summary part of most methods reported in Chemical Abstracts. But none of the methods is found entirely specific for vitamin C. Despite the reporting of several new photo-metric methods, old procedures still continue to be cited in different pharmacopoeias, indicating either the lack of reliability or of general applicability of these methods of vitamin C determination. Research workers try to justify their work in terms of specific applica-tions, but seldom give an comparative account with other methods regarding analysis of particular type of matrix. Therefore, to incorporate the comparative use of such methods under specific analytical environment requires some patience.The authors wish to thank the Chairman, Department of Chemistry, Kurukshetra University, Kurukshetra, for necessary library facilities and Dr. Meenakshi Mahajan is grateful to CSIR for financial assistance.4 References1.H. Nie and S. Peng, Yingyang Xuebao, 6, 293 (1984).2.X. Shao and Y. Zhang, Guangpuxue Yu Guangpu Fenxi,14, 125 (1994).3.K. Vamos, Elmelz Ip., 43, 16 (1989).4.H. P. Huang, R. X. Cai, Y. M. Du and Y. E. Zeng, Chin.Chem.Lett., 6, 235 (1995).5. D. B. Dennison, G. B. Troy and L. D. Hunter, J.Agric.Food Chem., 29, 927 (1981).6.M. Yoshida, T. Nishimune and K. Sureki, Korean J.Pharmacol., 28, 53 (1992).7. E. Racz, K. Parlagh-Huszar and T. Kecskes, Period.Polytech.,Chem.Eng., 35, 23 (1991).8.H. Iwase, J.Chromatogr., 606, 277 (1992).9.R. Leubolt and H. Klein, J.Chromatogr., 640, 271 (1993).10.X. Chen and M. Sato, Anal.Sci., 11, 749 (1995).11. F. Sahbaz and G. Somer, Food Chem., 44, 141 (1992).12.R. Barbera, R. Farre, M. J. Legarda and R. Pintor,Alimentaria, 247, 89 (1993).13.G. Lu, Y. Wang, L. Yao and S. Hu, Food Chem., 51, 237(1994).14. A. Lechien, P. Valenta, H. W. Naurnberg and G. J.Partriarche, Fresenius’Z.Anal.Chem., 311, 105 (1982).15.I. D. H. C. Marques, E. T. A. Jr. Marques, A. C. Silva, W.M. Ledingham, E. H. M. Melo, V. L. da Silva and J. L.Lima Filho, Appl.Biochem.Biotechnol., 44, 81 (1994). 16.W. Zang, J. Wang and L. Jianyan, Huaxue Fence, 32, 239(1996).17.Y. Liu, Huaxue Shiji, 16, 282 (1994).18. F. Kober, Prax.Naturwiss.Chem., 37, 27 (1988).19.Indian Pharmacopoeia, Photolitho Press, Faridabad, p. 49,1985.20.Pharmacopoeia of the United States XVIII, pp. 51, 52,Mack Printing Co., Easton PA, 1970.21.British Pharmacopeia, p. 901, H. M. Stationary Office,London, 1988.22.T. Koba, M. Motomura, A. Tsuboi, T. Abekawa and K.Ito,Eisei Kensa, 35, 1565 (1986).23.M. J. Egoville, J. F. Sullivan, M. F. Kozempel and W. J.Jones, Am.Potato J., 65, 91 (1988).24.R. Hernandez and F. Bosch, Ars.Pharm., 15, 39 (1974).25.P. J. Gary, G. M. Owen and D. W. Lashley and P. C. Ford,Clin.Biochem., 7, 131 (1974).26.M. A. Eldawy, A. S. Tawfik and S. R. Elshabouri, Anal.Chem., 47, 461 (1975).27.T. Kamangar, A. B. Fawzi and R. H. Maghssoudi, J.Assoc.Off.Anal.Chem., 60, 528 (1977).28.S. Y. Lin, K. J. Duan and C. L. Tsung, Pharm.Acta.Helv., 69, 39 (1994).29.N. K. Pandey, Anal.Chem., 54, 793 (1982).30. A. M. Frigola Canovas and F. Bosch Serrat, An.Bromatol,40, 79 (1988).31.I. A. Biryuk, B. P. Zorya, V. V. Petrenko and S. B. But,Izobreteniya, 19, 194 (1993).32.I. A. Biryuk and V. V. Petrenko, Farm.Zh., 6, 52 (1991).33.M. R. Esteban and C. N. Ho, Microchem.J., 56, 122(1997).34.L. Casella, M. Gulloti, A. Marchesini and A. Petrarulo, J.Food Sci., 54, 374 (1989).35.W. Lee, S. M. Roberts and R. F. Labbe, Clin.Chem., 43,154 (1997).36.G. Szepesi, Fresenius’ Z.Anal.Chem., 265, 334 (1973).37. C. F. Bourgeosis and P. R. Mainguy, Intern.J.Vit.Nutr.Res., 45, 70 (1975).38.R. C. Rose and D. L. Nahrwold, Anal.Biochem., 114, 140(1981).39.W. D. Graham and A. Donald, J.Chromatogr., 594, 187(1992).40.T. Tsutui and T. Adachi, Kyoto-fu Eisei Kogai KenkyushoNenpo, 35, 42 (1990).41.Y. Yasui and M. Hayashi, Anal.Sci., 7, 125 (1991).42.M. O. Nisperos-Carriedo, B. S. Busling and P. E. Shaw, J.Agric.Food Chem., 40, 1127 (1992).43.J. Commack, A. Oke and R. N. Adama, J.Chromatogr.,565, 529 (1991).44.M. J. Esteve, R. Fare, A. Frigola and J. M. Garcia-Cantabella, J.Chromatogr.B.Biomed.Appl., 688, 345 (1997).45. F. Tessier, I. Birlouez-Aragon, G. Jani-Chantal and C.Jean, Vitam.Nutr.Res., 66, 166 (1996).46.S. Z. Qureshi, A. Saeed and T. Hasan, Anal.Lett., 22,1927 (1989).47.V. Nirmalchandar and N. Balasubramanian, Z.GesamteHyg.Ihre.Grenzgeb, 33, 497 (1987).48.R. G. Bhatkar and M. H. Saldonha, East Pharm., 25, 117(1982).49.O. H. Abdelmageed, P. Y. Khashaba, H. F. Askal, G. A.Saleh and I. H. Reffat, Talanta, 42, 573 (1995).50.M. H. Hashmi, A. S. Adil, A. Viegas and A. I. Ajmol,Mikrochim.Acta, 3, 457 (1970).51.H. O. Beutler and G. Beinstingl, Dtsch.Lebensm.Rundsch., 76, 69 (1980).52.H. O. Beutler, G. Beinstingl and G. Michal, Ber.—Int.Fruchtsaft Union Wiss—Tech.Komm, 16, 325 (1980). 53.P. W. Alxandrova and A. Nejtscheva, Mikrochim.Acta,1982 I, 387.54.P. V. Aleksandrova and A. Neicheva, Mikrochim.Acta,1979 II, 337.55.G. Xiao and G. Zhao, Shipin Yu Fajiao Gongye, 5, 35(1987).56.O. Pelletier and R. Brassard, J.Food Sci., 42, 1471(1977).57.Z. Zloch, Mikrochim.Acta, 1975, 213.58.S. Garcia-Castineiras, V. D. Bonnet, R. Figueroa and M.Miranda, J.Liq.Chromatogr., 4, 1619 (1981).59.O. Pelletier and R. Brassard, Adv.Automat.Anal.Technicon Int.Congr., 9, 73 (1973).60.O. Pelletier and R. Brassard, J.Assoc.Off.Anal.Chem.,58, 104 (1975).61.W. A. Behrens and R. Madere, Anal.Biochem., 92, 510(1979).62.N. Wahba, D. A. Yassa and R. S. Labib, Analyst[London], 99, 397 (1974).63.M. N. Reddy, G. K. Mohan, N. R. P. Singh and D. G.Sankar, Indian Drugs, 25, 204 (1988).64.Z. Wang, Yingyand Xuebao, 9, 174 (1987).65.W. Zhang, Zhongguo Yiyuan Yaoxue Zazhi, 12, 409(1992).66.N. Balasubramanian, S. Usha and K. Sirividya, IndianDrugs, 32, 73 (1995).67.Y. Yonemura, Y. Miura and T. Koh, Bunseki Kagaku, 39,567 (1990).68.K. Sirividya and N. Balasubramaninan, Analyst[London],121, 1653 (1996).69.N. Burger and V. Karas-Gasparec, Talanta, 20, 782(1973).70.S. A. Al-Tamrah, Anal.Chim.Acta, 209, 309 (1988).71.S. Baczyk and K. Swizinska, Farm.Pol., 31, 399 (1975).72.Y. S. Fung and S. F. Luk, Analyst[London], 110, 201(1985).73.Y. S. Fung and S. F. Luk, Analyst[London], 110, 1439(1985).74.O. W. Lau, S. F. Luk and K. S. Wong, Analyst[London],112, 1023 (1987).75.J. Yan, Zhongguo Yaoxue Zazhi, 25, 478 (1990).。

《2024年Meta分析系列之六_间接比较及网状分析》范文

《Meta分析系列之六_间接比较及网状分析》篇一Meta分析系列之六_间接比较及网状分析Meta分析系列之六：间接比较及网状分析一、引言随着科研领域的快速发展，传统的前瞻性实验已经难以满足越来越多的科研需求。

于是，通过文献检索和汇总信息进行的Meta分析成为重要的辅助手段。

Meta分析中除了直接的同质实验结果对比，还有一种常见的策略，即间接比较和网状分析。

本文旨在介绍如何高质量地进行间接比较及网状分析。

二、方法论1. 间接比较间接比较是通过综合多个独立研究的多个变量来估计研究效应，通过将各个研究的直接效应进行比较和转换，再进一步比较间接效应。

这种方法的优点在于可以扩展到复杂的研究设计，并可以整合那些无法直接比较的异质性研究。

2. 网状分析网状分析是一种综合多种不同类型证据的统计方法，用于评估不同干预措施的相对效果。

它通过构建一个复杂的网络图来展示不同研究之间的相互关系，并使用贝叶斯模型或多元回归模型等统计方法进行综合分析。

三、间接比较与网状分析的应用本文以一个药物研究的Meta分析为例，通过将多篇药物干预的研究成果进行整合和对比，评估其效果。

我们采用间接比较和网状分析的方法，对不同药物干预的疗效进行综合评估。

首先，我们收集了多篇关于该药物研究的文献，并对这些文献进行了筛选和评估。

然后，我们使用间接比较的方法，对不同研究中的药物剂量、药物作用机制、研究人群等因素进行综合比较，得出各研究的直接效应。

接下来，我们利用这些直接效应构建了一个复杂的网络图，进行网状分析。

在网状分析中，我们采用了贝叶斯模型来评估不同药物干预之间的相对效果。

四、结果与讨论通过综合分析和比较各研究的直接效应，我们得出了各种药物干预的相对效果排序。

在网状分析中，我们发现某些药物在特定情况下具有较好的疗效，而其他药物在另一些情况下可能更有效。

此外，我们还发现某些因素（如药物剂量、研究人群等）对药物疗效的影响较大。

这些结果为临床实践提供了重要的参考依据。

Meta分析中效应尺度指标的选择

通常相对效应指标比绝对效应指标的一致性好。因此，可以认为 SMD 的一致性比 WMD 好， OR 和 RR 的一致性比 RD 好。而且，OR 和 RR 在一致性方面差别不大。一般不推荐使用基于特定情况下才最具一致性的效应尺度指标。
例如，某研究试验组和对照组的 A 事件率分别是 20％和 10％，另一相同研究试验组和对照组 A 事件率分别是 10％和 5％。选择相对效应指标 RR，则两个原始研究的 RR 值均为 2；若选择绝对效应指标 RD，则一个研究 RD 为 10％，另一个为 5％。如此，当进行 Meta 分析时，选择合并统计量为 RR 时可能异质性检验提示同质性好，而选择合并统计量为 RD 时则很可能提示原始研究间统计异质性较大。 2.1.3.2 数学特性（mathematical properties）最重要的数学特性就是可靠方差估计值的可得性。研究表明，常用的分类变量效应尺度指标中，OR 的数学特性最好。连续性变量一般都能对方差进行较好的估计，故 WMD 与 SMD 的数学特性相近。
中国循证医学杂志 , 2007, 7(8): 606-613.
Practice and Communication
证据是循证医学的核心，系统评价或 Meta 分析是公认的最高级别证据。来自 Meta 分析的证据总是通过一定的效应尺度（effect size, ES; 或 effect magnitude, EM）指标来表示。但国内外杂志上发表的 Meta 分析在选择效应尺度指标时常存在误用指标或错误解释指标结果的情况。因此，深刻理解 Meta 分析中各种常用效应尺度指标的意义，对正确选择效应指标、理解和应用统计结果至关重要。 Meta 分析中使用的定量合成效应尺度指标，也被称为合并统计量（summary statistic）。

On Maximizing the Second Smallest Eigenvalue of a

On Maximizing the Second Smallest Eigenvalue of aState-Dependent Graph LaplacianYoonsoo Kim and Mehran MesbahiAbstract—We consider theset consisting of graphs of ﬁxed order andweighted edges.The vertex set of graphsinwill correspond to point masses and the weight for an edge between two vertices is a functional of the distance b etween them.We pose the prob lem of ﬁnding the b est vertex po-sitional conﬁguration in the presence of an additional proximity constraint,in the sense that,the second smallest eigenvalue of the corresponding graph Laplacian is maximized.In many recent applications of algeb raic graph theory in systems and control,the second smallest eigenvalue of Laplacian has emerged as a critical parameter that inﬂuences the stability and ro-bustness properties of dynamic systems that operate over an information network.Our motivation in the present work is to “assign”this Laplacian eigenvalue when relative positions of various elements dictate the intercon-nection of the underlying weighted graph.In this venue,one would then b e able to “synthesize”information graphs that have desirable system theo-retic properties.Index Terms—Euclidean distance matrix,graph Laplacian,networked dynamic systems,semideﬁnite programming.I.I NTRODUCTIONConsider the set of n mobile elements as vertices of a graph,with the edge set determined by the relative positions between the respective elements.Speciﬁcally,we let G denote the set of graphs of order n with vertex set V =f 1;2;...;n g and edge set E =f e ij ;i =1;2;...;n 01;j =2;...;n;i <j g with the weight functionw :R 32R 3!R +assigning to eachedge e ij ,a function of the distance between the two nodes i and j .Thus,we havew ij :=w (x i ;x j )=f (k x i 0x j k )(1)for some f :R +!R +,with x i 2R 3denoting the position of ele-ment i .In our setup the function f in (1)will be required to exhibit a distinct behavior as it traverses the positive real line.For example,we will require that this function assume a constant value of one when the distance between i and j is less than some threshold and then rapidly drop to zero (or some small value)as the distance between these el-ements increases.Such a requirement parallels the behavior of an in-formation link in a wireless network where the signal power at the re-ceiver side is inversely proportional to the some power of the distance between transmitting and receiving elements [18].Using this frame-work,we now consider the conﬁguration problem3:maxx2(L G (x ))(2)where x :=[x 1;x 2;...;x n ]T 2R 3n is the vector of positions for the distributed system,the matrix L G (x )is a weighted graph Laplacian deﬁned element-wise as[L G (x )]ij:=0w ij ;if i =js =iw is ;if i =j(3)Manu script received April 29,2004;revised March18,2005and Au gu st 1,2005.Recommended by Associate Editor C.D.Charalambous.This work was supported by the National Science Foundation under Grant NSF/CMS-0301753.Y .Kim is withth e Department of Engineering,University of Leicester,Lei-ceister LE17RH,U.K.(e-mail:yk17@).M.Mesbahi is with the Department of Aeronautics and Astronautics,Univer-sity of Washington,Seattle,W A 98195-2400USA (e-mail:mesbahi@).Digital Object Identiﬁer 10.1109/TAC.2005.861710and 2(L G (x ))denotes the second smallest eigenvalue of the state-dependent Laplacian matrix L G (x )withits spectru m ordered as1(L G ) 2(L G ) 111 n (L G ):Furthermore,we restrict the feasible set of (2)by imposing the prox-imity constraintd ij :=k x i 0x j k 2 1;for all i =j (4)preventing the elements from getting arbitrary close to each other intheir desire to maximize 2(L G )in (2).The second smallest eigenvalue of the graph Laplacian L G ,also known as the algebraic connectivity of G [4],[8],[14],has emerged as an important parameter in many systems problems deﬁned over net-works [7],[12],[15],[17],[20].In fact,in several recent works [7],[17],[19],it has been observed that 2(L G )is a measure of stability and robustness of the networked dynamic system.This observation im-plies,for example,that small perturbations in the conﬁguration of the networked system will be attenuated back to its equilibrium state(s)witha rate th at is proportional to 2(L G ).When this important graph parameter is considered in a state-dependent setting as proposed in [15],the characterization of a distributed system states that maximize 2(L G )emerges as a natural optimization problem.In this venue how-ever,there are only a handful of studies in the literature that are re-lated to su cha grapheigenvalu e assignment problem (2).In particu lar we mention the work of Fallat and Kirkland [6]where a graph-the-oretical approachh as been proposed to extremize 2(L G )over the set of trees of ﬁxed diameter.Also related to the present work are those by Chung and Oden [5]pertaining to bounding the gap between the ﬁrst two eigenvalues of graph Laplacians,and Berman and Zhang [2]and Guattery and Miller [11],where,respectively,isoperimetric numbers of weighted graphs and graph embeddings are employed for lower bounding the second smallest Laplacian eigenvalue.We note that maximizing the second smallest eigenvalue of state dependent graph Laplacians over arbitrary graphconstraints is a difﬁcu lt compu tational problem [16].The contribution of this note is to propose an iterative greedy-type algorithm for problem (2)with a guaranteed local conver-gence behavior.Although the convergence of this algorithm is provably local in nature,extensive simulations suggest that it often converges to the global maximum when the initial graph is taken to be a path.The outline of the note is as follows.In Section II-A we delineate on the various possible choices for the edge weights for our state-depen-dent weighted Laplacians.Sections II-B and C are devoted to the main result of the note where an iterative semideﬁnite programming-based approachis proposed for th e solu tion of problem 3(2).A numerical example is then presented in Section III followed by a few concluding remarks.A few words on the notation.The 2-norm of vector x will be denoted by k x k .The spaces of n 2n real matrices and n 2n real symmetric matrices are designated by R n 2n and S n ,respectively;I n will be the n 2n identity matrix.The inequalities between symmetric matrices are interpreted in the sense of Löwner ordering,i.e.,A >B and A B indicate,respectively,the positive deﬁniteness and positive semideﬁ-niteness of the matrix difference A 0B .II.M ETHODAs we mentioned in Section I,the general formulation of the problem 3(2)does not readily hint at being tractable,in the sense of admit-ting an efﬁcient algorithm for its solution.Generally,maximizing the second smallest eigenvalue of a symmetric matrix subject to matrix inequalities,does not yield to a standard linear matrix inequality ap-proach[3]and,su bsequ ently,a solu tion procedu re th at relies solely0018-9286/$20.00©2006IEEEFig.1.Several candidates for the function f in(1)where =1and =2.on an interior point method[1].The previous complication however is alleviated in case of graph Laplacians,where the smallest eigenvalue 1(L G)is always zero withth e associated eigenvector of1composed of unit entries.This observation follows directly from the deﬁnition(3). Nevertheless,due to the nonlinear dependency of entries of L G on the relative distance d ij and the presence of constraints(4),the problem 3(2)assumes the form of a nonconvex optimization.In light of this fact,we will proceed to propose an iterative SDP-based approachfor this problem.However,before we proceed,we make a few remarks on some judicious choices for the function f in(1).The choice of f in(1)is not only guided by particular applications but also by numerical considerations.A few candidate functions are shown in Fig.1.Although there are a host of choices for f,for our analysis and numerical experimentation we have chosen to work with Type-IV functions(the lower right corner in Fig.1),where f assumes the formf(d ij)= ( 0d)=( 0 ); >0(5) given that d ij 1.1We note that f( 1)=1and f( 2)= .Among the advantages of working with functions(5)are their differentiability properties,as well as their ability to capture a situations that is of prac-tical relevance.In many su chsitu ations,th e strengthof an information link is inversely proportional to the relative distance and decays expo-nentially after a given threshold is passed.Furthermore,and possibly more importantly,functions(5)lead to a stable algorithm for our nu-merical experimentation;a representative set of examples is discussed in Section III.1We have also used functions of the form(1=d),where is a positive number and f( )= .Our simulation results in Section III turned out to be exactly the same for these functions as compared with those obtained using functions of the form(5).A.Maximizing 2(L G)Weﬁrst present a linear algebraic resu lt in conju nction withth e gen-eral problem of maximizing the second smallest eigenvalue of graph Laplacians.Proposition2.1:Consider the m-dimensional subspace P R n spanned by the vectors p i2R n,i=1;...;m.Denote P:=[p1;...;p m]2R n2m.Then,for M2S n one hasx T Mx>0for all nonzero x2Pif and only ifP T MP>0:(6)Proof:An arbitrary nonzero element x2P can be written asx= 1p1+ 2p2+111+ m p mfor some 1;...; m2R,not all zeros and,thus,x=P y,where y:=[ 1; 2;...; m]T.Consequently,theﬁrst inequality in(6)is equivalent to(P y)T M(P y)=y T P T MP y>0for all nonzero y2R m,or in other words,having P T MP>0;we note that P T MP2S m.Corollary2.2:For a graphLaplacian L G the constraint2(L G)>0(7) is equivalent toP T L G P>0(8)where P=[p1;p2;...;p n01],and the unit vectors p i2R n are chosen such thatp T i1=0;(i=1;2;...;n01)andp T i p j=0;(i=j):(9) Proof:It is well-known that for G2GL G 0and L G1=0(10)and,thereby,the smallest eigenvalue of L G is always zero and rank L G n01.This implies that(7)is equivalent to havingx T L G x>0;for all nonzero x21?(11) where1?:=f x2R n j1T x=0g:(12)In view of Proposition2.1,the condition(11)is equivalent to having P T L G P>0,with P denoting the matrix of vectors spanning the subspace1?.Without loss of generality,this subspace can be identiﬁed withth e basis u nit vectors satisfying(9).Corollary2.3:The problem3(2)is equivalent to3:maxx(13)s:t:d ij:=k x i0x j k2 1(14)P T L G(x)P I n01(15)where i=1;2;...;n01,j=2;...;n,i<j,and the pairwise or-thogonal unit vectors p0i s forming the columns of P span the subspace 1?(12).Proof:The proof follows from Corollary2.2.One of the consequences of Corollary2.3pertains to the following graphsynth esis problem2:determine graphs satisfying an upper bound on the number of their edges with maximum smallest second Laplacian eigenvalue.Although this problem will not be further considered in this note,we point out that it can be reformulated asmaxG2Gf j Trace L G ;P T L G P I n01gwhere P is deﬁned as in Corollary2.3and is twice the maximum number of edges allowed in the desired graph.In this venue,a compli-cation that needs to be further addressed pertains to the integrality of the entries of the sought matrix L G.B.Discrete and GreedyWe now proceed to view the problem3(2)in an iterative setting, where the goal is shifted towardﬁnding an algorithm that attempts to maximize the second smallest eigenvalue of the graph Laplacian at each step.Toward this aim,weﬁrst differentiate(14)with respect to time as 2f_x i(t)0_x j(t)g T f x i(t)0x j(t)g=_d ij(t)(16) and then employ Euler’sﬁrst discretization method,with1t as the sampling timex(t)!x(k);_x(t)!x(k+1)0x(k)1t2This connection was pointed to us by one of the referees.to rewrite(14)as2f x i(k+1)0x j(k+1)g T f x i(k)0x j(k)g=d ij(k+1)+d ij(k): Similarly,the state dependent Laplacian L G(x)in(15)is discretized by ﬁrst differentiating the terms w ij with respect to time,and then having w ij(k+1)=w ij(k)0 ( 0d(k))=( 0 )f d ij(k+1)0d ij(k)grecall that we are employing functions of the form(5)in(1).The dis-crete version of the state dependent Laplacian,L G(k),assumes the form[L G(k)]ij=0w ij(k);if i=js=iw is(k);if i=j.Putting it all together,we arrive at the iterative step of solving the op-timization problem3k:maxx(k+1)(17)s:t:2f x i(k+1)0x j(k+1)g T f x i(k)0x j(k)g=d ij(k+1)+d ij(k)(18)d ij(k+1) 1(19)P T L G(k+1)P I n01(20)for i=1;2;...;n01,j=2;...;n,i<j,and x(k):= [x1(k);x2(k);...;x n(k)]T2R3n.Thereby,the algorithm is ini-tiated at time k=0withan initial graph(conﬁgu ration)G0,and then for k=0;1;2;...,we proceed to iterativelyﬁnd a graphth at maximizes 2(L G(k+1)).This greedy procedure is then iterated upon until the value of 2(L G(k))can not be improved further.We note that the proposed greedy algorithm converges,as the sequence generated by it is nondecreasing and bounded from above.3C.Further ConsiderationsIn previous section,we proposed an algorithm that converges to a local optimal vertex positional conﬁguration,in terms of maximizing the quantity 2(L G).However,by replacing the nonconvex constraint (14)withits linear approximation(18)–(19),one introdu ces a poten-tial inconsistency between the position and the distance vectors.In this section,we provide two remedies to avoid such potential com-plications.Let usﬁrst recall the notion of Euclidean distance matrix (EDM).Given the position vectors x1;x2;...;x n2R3,the EDM D=[d ij]2R n2n is deﬁned entry-wise as[D]ij=d ij=k x i0x j k2;for i;j=1;2;...;n:The EDM matrices are nicely characterized in terms of linear matrix inequalities[10].Theorem2.4:A matrix D=[d ij]2R n2n is an EDM if and only ifJDJ 0(21)d ii=0;for i=1;2;...;n(22) where J:=I n011T=n.3The second smallest eigenvalue ofL for a graphof order n is bounded from above by n01[9].Fig.2.Trajectory generated by the proposed algorithm for six nodes in R:the conﬁguration evolves from a path(circles)to a truss(squares).Fig.3.Trajectory generated by the proposed algorithm for six nodes in R:the conﬁguration evolves from a path(circles,1;...;6)to an octahedron(squares, 1;...;6).Theorem2.4allows us to guarantee that by adding the two convexconstraints(21)–(22)to problem3k(17)–(20),we always obtainconsistency among the position and distance variables at each iterationstep.Moreover,by updating the values of d ij(k)’s and[L(k)]ij’s in(18)and(20)after calculating the values of x(k),we can furtherreduce the effect of linearization in the proposed procedure.To furtherexpand on this last point,suppose that x1(k);x2(k);...;x n(k), d ij(k)’s and[L(k)]ij,i=1;2;...;n01,j=2;...;n,i<j,h ave been obtained after solving the problem3k(17)–(20).Our proposed modiﬁcation to the original algorithm thus amounts to updating the values of d ij(k)and[L(k)]ij,based on the computed values of x1(k);x2(k);...;x n(k),before initiating the next iteration.III.S IMULATION R ESULTSFor our simulations we used SeDuMi[1]to solve the required semideﬁnite programs.Fig.2depicts the behavior of six mobile elements under the guidance of the proposed algorithm,leading to a planar conﬁguration that locally maximizes 2(L G).The constants , 1,and 2in(5)are chosen to be0.1,1,and1.5,respectively. The algorithm was initialized with a conﬁguration that corresponds to a path.The sequence of conﬁgurations thereafter converges to the truss-shape graph with the 2(L G)of1.6974.For these set of param-eters,the truss-shape graph as suggested by the algorithm is the global maximum over the set of graphs on six vertices that can be conﬁgured in R2.4Using the same simulation scenario,but this time,in search of an optimal positional conﬁguration in R3,the algorithm leads to the trajectories shown in Fig.3.In this case,the graph sequence converges to an octahedron-shape conﬁguration with 2(L G)=4:02. Increasing the number of nodes to eight,the algorithm was initial-ized as the unit cube;the resulting trajectories are shown in Fig.4.4A global maximum may be found in the following exhaustive manner:First, deﬁne a space large enou ghgu aranteed to contain th e optimal conﬁgu ration. Then grid this region and search over the set of all n grid points for the conﬁg-uration that leads to maximum (L).Fig.4.Evolution of the proposed algorithm for eight nodes in R :the conﬁguration evolves from 3-cube (circles)to octahedron (squares).TABLE IC OMPARING THE V ALUES FOR THE T YPE -IV W EIGHTED G RAPH G AS R EALIZED BY THE A LGORITHM AND T HOSE C ORRESPONDING TO THEA SSOCIATED 0–1W EIGHTED G RAPHGIn this ﬁgure,the edges between vertices i and j indicate that d ij 2=1:5.The solid lines in Fig.4represent the ﬁnal conﬁguration with 2(L G )=2:7658.Once again,an exhaustive search procedure indicates that the proposed algorithm does lead to the global optimal conﬁguration (see Table I).We like to remark however that the choice for the function f in (5)and the initial conﬁguration,are critical to the performance of the proposed algorithm.For example,when this func-tion is chosen to be of Type-I in Fig.1and the initial graph as a dis-connected graph,the algorithm terminates right after initialization,as any small perturbation on the initial graph does not lead to an improve-ment in the value of 2(L G ).Choosing a Type-IV function in Fig.1on the other hand,always lead to a connected conﬁguration with a posi-tive 2(L G ),even when the algorithm is initialized via a disconnected graph.IV .C ONCLUDING R EMARKSWe considered the problem of maximizing the second smallest eigenvalu es of a state-dependent graphLaplacian.Th is problem is of importance,for example,when the positions of a set of dynamic elements-operating over an information network-can be chosen for robust system performance.We proposed an iterative algorithm for this problem that employs a semideﬁnite programming solver at each recursive step.Although the algorithm has a local convergence behavior,extensive simulations suggest that it often leads to a globally optimal state conﬁguration.A CKNOWLEDGMENTThe authors gratefully acknowledge suggestions and comments by the anonymous reviewers.R EFERENCES[1]SeDuMi.McMaster Univ..[Online].Available:http://sedumi.mc-master.ca[2] A.Berman and X.-D.Zhang,“Lower bounds for the eigenvalues of Laplacian matrices,”Linear Alg.Appl.,vol.316,pp.13–20,2000.[3]S.Boyd and L.Vandenberghe,Convex Programming .Cambridge,U.K.:Cambridge Univ.Press,2003.[4] F.R.K.Chung,Spectral Graph Theory .Providence,RI:AMS,1997.[5]F.R.K.Chung and K.Oden,“Weighted graph Laplacians and isoperi-metric inequalities,”Paciﬁc J.Math.,vol.192,no.2,pp.257–273,2000.[6]S.Fallat and S.Kirkland,“Extremizing algebraic connectivity subject to graphth eoretic constraints,”Elect.J.Linear Alg.,vol.1,no.3,pp.48–74,1998.[7]J.A.Fax and R.M.Murray,“Information ﬂow and cooperative control of vehicle formations,”IEEE Trans.Autom.Control ,vol.49,no.9,pp.1465–1476,Sep.2004.[8]M.Fiedler,“A property of eigenvectors of nonnegative symmetric ma-trices and its applications in graphth eory,”Czech.Math.J.,vol.100,no.26,pp.619–633,1975.[9] C.Godsil and G.Royle,Algebraic Graph Theory .New York:Springer-Verlag,2001.[10]J.Gower,“Properties of Euclidean and non-Euclidean distance ma-trices,”Linear Alg.Appl.,vol.1,no.67,pp.81–97,1985.[11]S.Guattery and ler,“On the quality of spectral separators,”SIAM J.Matrix Anal.Appl.,vol.19,no.3,pp.701–719,1998.[12] A.Jadbabaie,J.Lin,and A.S.Morse,“Coordination of groups of mobile autonomous agents using nearest neighbor rules,”IEEE Trans.Autom.Control ,vol.48,no.9,pp.988–1001,Sep.2003.[13]Y .Kim and M.Mesbahi,“Quadratically constrained attitude control via semideﬁnite programming,”IEEE Trans.Autom.Control ,vol.49,no.5,pp.731–735,May 2004.[14]R.Merris,“Laplacian matrices of graphs:A survey,”Linear Alg.Appl.,vol.197,no.1,pp.143–176,1994.[15]M.Mesbahi,“On state-dependent dynamic graphs and their control-lability properties,”IEEE Trans.Autom.Control ,vol.50,no.3,pp.387–392,Mar.2005.[16]H.Q.Ngo and D.-Z Du,“Notes on the complexity of switching net-works,”in Advances in Switching Networks ,H.Q.Ngo and D.-Z.Du,Eds.Norwell,MA:Kluwer,2000,pp.307–357.[17]R.Olfati-Saber and R.M.Murray,“Consensus problems in networks of agents withswitch ing topology and time-delays,”IEEE Trans.Autom.Control ,vol.49,no.9,pp.1520–1533,Sep.2004.[18]K.Pahlavan and A.H.Levesque,Wireless Information Networks .New York:Wiley,1995.[19]H.Tanner, A.Jadbabaie,and G.Pappas,“Flocking in ﬁxed and switching networks,”Automatica,submitted for publication.[20]L.Xiao and S.Boyd,“Fast linear iterations for distributed averaging,”Syst.Control Lett.,vol.53,pp.65–78,2004.。

汉恒生物线粒体自噬的研究方法

第49卷第5期兰州大学学报（自然科学版）Vol.49No.5文章编号:0455-2059(2013)05-0693-07线粒体自噬的研究方法张迎梅,邱倩,漆永梅兰州大学生命科学学院,兰州730000摘要:线粒体自噬是一种选择性清除多余或受损线粒体的自噬过程,在调节细胞内线粒体数量和维持线粒体正常功能等方面发挥重要作用,并涉及诸多生理和病理学过程.有关线粒体自噬的研究报道始于21世纪初,近年来发展十分迅速.目前,研究线粒体自噬的方法众多,各有利弊,但没有一种检测手段可以独立说明线粒体自噬的发生或反映线粒体自噬的活性.本文旨在对目前有关线粒体自噬的研究方法与技术及其优缺点等方面做一总结,供线粒体自噬研究者参考.关键词:线粒体自噬;线粒体自噬体;线粒体自噬溶酶体;检测方法中图分类号:Q5;Q2;Q95文献标识码:AMethods in studying mitophagyZHANG Ying-mei,QIU Qian,QI Yong-meiSchool of Life Sciences,Lanzhou University,Lanzhou730000,ChinaAbstract:Mitophagy,the selective removal of dysfunctional mitochondria by autophagy,is an important mitochondrial quality control and function stabilizing mechanism which has been implicated in many diﬀerent physiological and pathological processes.The research on mitophagy was begun in the beginning of this century with rapid development.However,numerous methods in mitophagy research have some shortcomings and there are still no eﬀective or standard methods for monitoring or assessing mitophagy.This review aims to show those current techniques and methods with their advantages and disadvantages in the study of mitophagy.Key words:mitophagy;mitophagosomes;mitolysosomes;detection method线粒体是真核细胞进行生物氧化和能量转换的重要场所,涉及细胞内稳态、增殖、能动性、衰老和死亡等多种生物学过程[1].线粒体因其DNA 缺乏组蛋白的保护且修复机制不健全而易受外源或自身代谢产生的自由基(Reactive oxygen species, ROS)的攻击或因其他胁迫而发生损伤[2],线粒体受损后发生膜通透性转变(Mitochondrial perme-ability transition,MPT),氧化磷酸化解耦联,ATP 过度消耗引发细胞坏死,或者线粒体肿胀后细胞色素c释放到细胞质触发凋亡[3].适时清除受损线粒体以保持其数量和质量的稳定对于细胞正常生长和代谢具有非常重要的意义[4−5].线粒体自噬是一种选择性清除受损线粒体的特异性自噬现象[6−7],根据线粒体自噬过程的特征,可将其分为4个时期[8]:1)前期线粒体受损后发生通透性转变,导致线粒体去极化,诱导线粒体自噬相关蛋白活化[9];2)早期自噬体包裹受损线粒体,形成线粒体自噬体(Mitophagosomes)[10];3)中期线粒体自噬体与溶酶体融合后形成成熟的线粒体自噬溶酶体(Mitolysosomes)[11];4)末期线粒体被溶酶体降解.以上各期特点如图1所示.线粒体自噬除了介导受损或者多余线粒体的降解,对网织红细胞成熟过程及受精后精子来源的线粒体清除有重要意义[12−13],与局部缺血或药物诱导的组织损伤以及许多神经退行性疾病和癌症的发生发展也密切相关[14],因此有关线粒体自噬的问题越来越受到学者们的关注.目前研究线粒体自噬及其活性的方法主要包括以下3种类型:MP线粒体自噬体(Mitophagosomes);ML线粒体自噬溶酶体(Mitolysosomes);∆Ψm线粒体膜电位(Mitochondrial membrane potential)图1线粒体自噬过程的4个时期Figure1Four stages of mitophagy1)通过电子显微镜或荧光显微镜直接观察线粒体自噬体的结构或线粒体自噬的动态过程;2)通过流式细胞术检测线粒体膜电位、线粒体总量及免疫印迹技术检测线粒体自噬相关蛋白表达量的变化等方法间接反映线粒体自噬活性;3)通过人为对线粒体自噬通路进行实验性调节来全面评价线粒体自噬对细胞或机体形态和功能的影响.本文就目前线粒体自噬不同时期的研究方法和技术及其优缺点等方面综述如下,供线粒体自噬研究者参考.1电子显微镜技术自20世纪50年代比利时科学家Duve[15]在溶酶体的研究中通过电镜第一次观察到自噬现象至今,透射电镜技术(Transmission electron mi-croscopy,TEM)始终被认为是研究自噬发生的最直接、最可靠的手段.线粒体自噬早期形成的线粒体自噬体可以通过线粒体特有的双层膜、嵴等特征辨别,而其与溶酶体融合形成的线粒体自噬溶酶体仅能通过单层膜或消化后的残留物来大体识别[14](表1b).尽管如此,电镜技术也受到诸多因素的影响,获得的结果存在很大的变性,如因切片等人为因素造成的膜结构的改变,其他双层膜细胞器的干扰或者低电子密度空泡的误导等[16].因此,常规的透射电镜观察方法仅能对完整的线粒体自噬体进行观察,由于选取细胞数量有限,无法反映自噬活性,在定量分析中存在很大的不足.近年来,免疫金电镜技术开始用于自噬的定量分析,在线粒体自噬的研究中,利用线粒体蛋白如Tom20, CypD等和自噬体标记蛋白的抗体共定位标记线粒体自噬体,通过测量自噬囊泡面积对其进行定量分析,结合其他检测方法可反映线粒体自噬的活性变化[17−18].2荧光显微镜技术电镜观察线粒体亚结构的变化及线粒体自噬体的形成,仅能初步证明线粒体自噬是否发生,但不充分,还需要进一步结合线粒体与自噬体及溶酶体共定位的方法才能证明线粒体自噬是否发生.通过特异性荧光标记的手段,利用荧光显微镜技术,可进行线粒体溶酶体的荧光共定位观察.目前,用于线粒体自噬荧光标记的方法主要有3种:荧光标记基因转染技术、荧光探针标记技术及自噬相关蛋白免疫荧光技术.2.1荧光标记基因转染技术将自噬体和线粒体特异性蛋白的基因与天然荧光蛋白基因连接起来构成融合基因,导入细胞内表达,借助荧光显微镜对标记蛋白进行细胞内活体跟踪,可对线粒体和自噬体进行共定位分析. Gottlieb等[19]利用发射红色荧光且定位于线粒体的融合蛋白基因pDsRed2-mito与GFP-LC3联合转染细胞,进行线粒体和自噬体的共定位,通过去卷积运算及3维立体重构技术得到自噬体包裹线粒体的3维结构图,可直观反映线粒体自噬体的形成及其结构.但此方法仅适用于线粒体自噬早期的检测,无法反映其末期的降解情况.而另一种融合蛋白基因mKeima稳定表达一种在酸性和中性条件下分别发射红色和绿色荧光的天然蛋白,可用于线粒体自噬体和线粒体自噬溶酶体的定性和定量分析[20].Katayama等[21]通过将COX VⅢ的前导肽序列与mKeima串联起来构成一种融合基因mt-mKeima,使其所表达的Keima蛋白定位于线粒体基质,当线粒体自噬体与酸性溶酶体融合后Keima蛋白的荧光信号由绿色转为红色,荧光信号的转换可定量反映线粒体自噬的活性[8](图2和表1f).但是,长时间激发光照射对转染细胞样品的荧光强度有较大影响,而且溶酶体酶活力和胞浆的酸化程度也会影响到荧光信号的检测.a正常未处理的神经细胞中,只有少数的线粒体呈酸性状态;b诱导线粒体自噬后,大量线粒体酸化图2转染mito-Keima的神经细胞中Keima蛋白的荧光变化[8]Figure2Neurons transfected mito-Keima showing the change of Keima2.2荧光探针标记技术利用线粒体和溶酶体特异性染色技术也可对线粒体和自噬体进行共定位.在培养细胞中可利用线粒体特异性荧光探针TMRM(Tetramethylrho-damine methylester),MitoTracker 和溶酶体特异性荧光探针LysoTracker 染色并结合自噬体的荧光标记技术来追踪线粒体自噬的动态过程.MitoTracker ,LysoTracker 也可用于固定细胞的线粒体和溶酶体染色[22].线粒体去极化(Mitochon-drial depolarization)是线粒体自噬前期的重要事件[9],可利用线粒体膜电位依赖性荧光探针TMRM ,MFFR(Mitoﬂuor far red)、罗丹明123(Rhodamine 123)或JC-1(5,5′,6,6′-Tetrachloro-1,1′,3,3′-tetraethyl-imidacarbocyanine iodide)染色后通过流式细胞术或荧光显微镜技术检测.但这些染料的荧光强度随膜电位降低而减弱,因此无法进行细胞固定后检测.另外,非培养条件下线粒体膜电位也会有所变化,因此染色后必须尽快完成后续表1线粒体自噬各期的检测方法[23−24]Table 1Detection methods on diﬀerent stages of mitophagy时期检测指标原理检测方法分析与评价早期线粒体自噬EM 结果变性较大,不适于做定量体直接观察分析,仅作定性参考线粒体和自噬FM 直接反映自噬体包裹线粒体的体荧光共定位事实,但无法说明线粒体自噬末期的降解情况末期线粒体总量检测−FC 可快速检测线粒体总量的改变,但荧光极易淬灭线粒体蛋白表达量检测−IB定量分析的高效方法,但线粒体自噬特异性蛋白的选择尚有疑问mtDNA 定性和FM 线粒体总量变化受多种因素影响,定量分析FC仅依靠mtDNA 降解程度难以反映线粒体自噬活性情况MP 线粒体自噬体(Mitophagosomes),ML 线粒体自噬溶酶体(Mitolysosomes),Ψm 线粒体膜电位(Mitochondrial membrane potential),EM 电子显微镜技术(Electron microscopy),FM 荧光显微镜技术(Fluorescence microscopy),IF 免疫荧光技术(Immunoﬂuorescence),IB 免疫印迹技术(Immunoblotting),FC 流式细胞技术(Flow cytometry),TMRM 四甲基罗丹明甲酯(Tetramethylrhodamine methylester),MTG 线粒体示踪绿(MitoTracker green),LTR 溶酶体示踪红(LysoTracker red).检测.MitoTracker是一种持久的线粒体特异性荧光探针,可被活细胞摄取和累积,较之传统的线粒体荧光探针TMRM等,其荧光不依赖膜电位而变化,仅需一个温和的共价巯基结合于线粒体蛋白并在线粒体去极化后仍保持不变[25].MitoTracker 具有多个颜色的变体,可结合其他荧光标记手段选择所需荧光色彩进行双染或者三联染色,如LC3-GFP,MTR(MitoTracker red)联合标记(表1c),用于线粒体自噬体的定位[14].LysoTracker是一种偏酸性的胺类荧光探针,可用于对活细胞内的酸性区室(如溶酶体、内吞体、自噬体等)染色示踪,其敏感度极高,并可在乙醛固定后稳定保持[26],也有多个荧光色彩的变体可选.但是这种探针作为溶酶体非特异性的探针不能单独用于线粒体自噬的分析,必须与其他的方法相结合,如LTR(LysoTracker red)与MTG(MitoTracker green)联合染色(表1d),用于线粒体自噬体与溶酶体融合的共定位[27]. TMRM,MTG两种荧光染料均可在极化的线粒体中蓄积,TMRM可以通过荧光共振能量转移使MTG荧光淬灭,单独发红色荧光.但当线粒体去极化后,TMRM被释放,MTG发出绿色荧光,聚集在细胞核周围[28].因此,用TMRM,MTG联合染色可特异性标记新的去极化线粒体(表1a).当对细胞同时进行TMRM,MTG,LTR染色时,可以通过荧光显微镜观察去极化的线粒体是否与溶酶体融合,亦即是否发生了线粒体自噬[25]. Kim等[29]利用发蓝色荧光的MFFR代替TMRM,联合GFP-LC3及LTR在线粒体动态监测中可更方便地观察线粒体自噬的动态变化过程.此外,荧光探针标记技术也可与荧光标记的线粒体自噬标志蛋白基因转染技术结合来示踪线粒体自噬[30]. 2.3免疫荧光技术在固定细胞中,选用线粒体和溶酶体特异性蛋白的抗体对线粒体自噬体和线粒体自噬溶酶体进行免疫荧光标记,如溶酶体膜蛋白LAMP-1或LAMP-2,线粒体基质蛋白Hsp60和CypD(表1e),线粒体膜蛋白VDAC1,Tom20等.然而,线粒体自噬并非受损线粒体蛋白的唯一降解方式,研究者发现许多线粒体外膜及膜间隙蛋白的降解是由Parkin依赖性的泛素蛋白酶系统介导的,还有一部分线粒体外膜蛋白在Parkin的介导下逃逸至内质网以躲避降解[31],而大多数的线粒体内膜蛋白及基质蛋白的降解则是由Parkin依赖性的线粒体自噬介导的,但其具体机制还不清楚[32].因此,同时选用CypD,Hsp60等线粒体基质蛋白或者内膜蛋白的抗体进行免疫荧光标记来检测线粒体自噬可能会更严谨.除了通过线粒体溶酶体的共定位来说明线粒体自噬之外,也可以通过线粒体DNA(mtDNA)的降解来反映线粒体自噬的活性.线粒体中ROS的累积可导致mtDNA的突变,并进一步诱导线粒体自噬.PicoGreen是一种可穿透线粒体膜,对mtDNA进行特异性标记的荧光探针,通过免疫荧光技术检测PicoGreen的荧光信号强度可反映mtDNA的降解程度[33].PicoGreen也可用于活细胞染色,Kim等[10]利用PicoGreen,TM-RM和LTR对来源于野生型小鼠的肝脏细胞线粒体自噬过程中mtDNA的降解进行监测(表1g).3免疫印迹技术免疫印迹技术(Immunoblotting,IB)可用于线粒体自噬的定量分析,通过检测线粒体蛋白的表达量变化可反映末期线粒体总量(Mitochondrial mass)的改变,从而间接反映线粒体自噬的活性.通常选线粒体基质蛋白Hsp60,CypD,线粒体膜蛋白VDAC1,Tom20等,但考虑到不同线粒体蛋白降解过程的线粒体自噬依赖性的不同[32],最好分别选取线粒体内外膜蛋白、基质与膜间隙蛋白,从而全面反映线粒体总量的变化.在酵母线粒体自噬的定量分析中用GFP标记的线粒体外膜蛋白基因GFP-Om45转染细胞,线粒体自噬过程中Om45降解,释放出游离的GFP可稳定存在,通过免疫印迹检测GFP的含量即可定量分析线粒体自噬的活性[34],但由于哺乳动物细胞溶酶体酸性状态可使GFP快速降解,此方法不适用其线粒体自噬的检测.此外,通过标准比色法检测柠檬酸合酶的活力也可以反映线粒体的总量[35].介导线粒体自噬的一些特异性蛋白的稳定性、表达量及活性的变化也可以通过免疫印迹技术来分析,进而定量地反映线粒体自噬的发生及其活性.如在PINK1/Parkin介导的线粒体自噬途径中, PINK1在正常条件下以线粒体膜电位依赖性的方式被蛋白水解酶快速降解,而线粒体去极化能使其稳定,并在线粒体膜上累积聚集[30,36],进而通过磷酸化Parkin使之从细胞质向功能紊乱的线粒体上募集[37],以介导线粒体自噬性的降解.另外,低氧条件下,NIX表达量的显著上升和FUNDC1的去磷酸化[38−39],也可介导线粒体自噬的发生.4流式细胞技术流式细胞技术(Flow cytometry,FC)作为单细胞定量分析和分选的手段,在线粒体自噬的检测中被广泛应用.通过流式细胞技术定量检测TMRM、罗丹明123或JC-1染色后线粒体荧光强度的变化可反映线粒体的损伤程度.线粒体自噬性降解会导致细胞内线粒体总量的减少[8]. Zhang等[40]在网织红细胞成熟过程线粒体自噬清除的研究中,利用线粒体特异荧光探针MTG对线粒体染色后通过流式细胞技术检测荧光总量来反映末期线粒体总量的变化.而Yoshii等[32]通过流式细胞技术检测稳定表达GFP标记的线粒体外膜蛋白GFP-Omp25的Parkin野生型MEFs细胞经CCCP(Carbonyl cyanide3-chlorophenyl hydra-zone)处理诱导线粒体自噬,发现GFP-Omp的含量在线粒体自噬诱导后随时间的延长而降低,也可反映线粒体自噬的活性.但以线粒体的总量变化来反映其自噬活性的方法必须联合其他检测手段才能说明线粒体自噬.5线粒体自噬的诱导与抑制在线粒体自噬对机体或细胞的行为和效应分子影响的研究中,一般通过人为干预的方式来诱导或抑制线粒体自噬,方法主要包括药物处理、物理损伤、饥饿及线粒体自噬基因敲除、沉默或过表达等.有关线粒体自噬的分子途径和功能研究中,常用线粒体的解偶联剂CCCP和FCCP(Carbonyl cyanide4-(triﬂuoromethoxy)phenylhydrazone)作为诱导剂,引发细胞内全部线粒体短时间内剧烈的去极化及线粒体自噬的发生,但这两种诱导剂也可造成细胞骨架的破坏及溶酶体酸化的抑制,因此,实验中也会用到如K+载体缬氨霉素(Valino-mycin)、抗霉素A(Antimycin A)等一些比较温和的诱导药物[41].此外,饥饿和光照辐射也可以诱导部分线粒体发生自噬[10,22,29].在表达KillerRed-d Mito(一种光敏蛋白,定位于线粒体基质)的Parkin 野生型细胞中,通过光照辐射激发KillerRed发射荧光,可导致ROS的急剧增加,诱导线粒体自噬的发生,这是一种可在时间和空间上进行人为控制的线粒体自噬诱导方法[42].线粒体的保护剂,包括影响ATP生成与降解的药物、降低线粒体膜通透性的药物、铁依赖脂质过氧化作用的抑制剂、Ca2+阻滞剂和Ca2+依赖蛋白酶抑制剂等.乙酰左旋肉毒碱(Acetyl-L-carnitine,ALC)作为细胞呼吸的替代底物,可恢复呼吸效率,促进ATP生成,维持线粒体膜电位,抑制脂质过氧化,常用于线粒体紊乱导致的神经退行性疾病及病理性损伤的治疗研究[43].环孢菌素A(CyclosporinA,CsA)是一种线粒体通透性转变的特异性抑制剂,可通过干扰亲环素D(Cyclophilin D)和线粒体通透性转变孔的相互作用抑制线粒体的去极化和线粒体自噬体的形成[44].在Rodriguez等[27]的研究中,作为线粒体自噬诱导后的保护剂,可明显降低线粒体自噬体的总量.此外,非免疫抑制剂NIM811(N-methyl-4-isoleucine cyclosporin)也可发挥同样作用[45].线粒体自噬相关基因的敲除、沉默或过表达,可用于某一特定基因在整个线粒体自噬通路中功能的研究.如在果蝇PINK1/Parkin依赖性线粒体自噬途径的研究中发现,敲除PINK1和Parkin,可造成线粒体自噬的抑制[46],PINK1过表达不能补偿Parkin缺失所造成的线粒体自噬阻滞,而Parkin的过表达却可以部分缓解PINK1缺失造成的线粒体自噬阻滞[47].6小结线粒体自噬的研究方法众多,各有优势,但没有一种手段可以独立说明线粒体自噬的发生并反映其活性.受损的线粒体不仅可通过自噬的方式得到清除,也可能发生线粒体凋亡(Mitoptosis)[48].因此,研究线粒体自噬形态与功能,需针对其各期特点和发生机制,多指标与多技术联合,体内与体外、定性与定量实验相结合,并通过人为干预的实验性调节来研究线粒体自噬对机体或细胞的行为和效应分子的影响.在目前线粒体自噬尚无标准化的检测或监控技术的情况下,建议研究者理性地分析和对待采用不同技术手段所获得的有关线粒体自噬的实验结果,并在现有基础上寻找和创新线粒体自噬研究的新方法和新技术.这不仅是线粒体自稳态调节的深入研究所必需的,更对线粒体自噬的调控在衰老、神经退行性疾病和癌症治疗中的研究有重要意义.参考文献[1]Detmer S A,Chan D C.Functions and dysfunc-tions of mitochondrial dynamics[J].Mol Cell Biol, 2007,8(11):870−879.[2]Yakes F M,Van Houten B.Mitochondrial DNAdamage is more extensive and persists longer than nuclear DNA damage in human cells following oxida-tive stress[J].Proc Natl Acad Sci USA,1997,94(2): 514−519.[3]Lemasters J J,Nieminen A-L,Qian T,et al.The mitochondrial permeability transition in cell death:a common mechanism in necrosis,apopto-sis and autophagy[J].Biochim Biophys Acta,1998, 1366(177/196):177−196.[4]Guarente L.Mitochondria:a nexus for aging,calorie restriction,and sirtuins?[J].Cell,2008, 132(2):171−176.[5]Melser S,Chatelain Etienne H,La vieJ,et al.Rheb regulates mitophagy induced by mitochondrial energetic status[J].Cell,2013,17(5): 719−730.[6]Lemasters J J.Selective mitochondrialautophagy,or mitophagy,as a targeted defense against oxidative stress,mitochondrial dysfunction, and aging[J].Rejuv Res,2005,8(1):3−5.[7]Fimia G M,Kroemer G,Piacentini M.Molecu-lar mechanisms of selective autophagy[J].Cell Death Diﬀer,2013,20(1):1−2.[8]Klionsky D J,Abdalla F C,Abeliovich H,et al.Guidelines for the use and interpretation of as-says for monitoring autophagy[J].Autophagy,2012, 8(4):445−544.[9]Rodriguez E S,He L,Lemasters J J.Role ofmitochondrial permeability transition pores in mito-chondrial autophagy[J].Int J Bilchem Cell B,2004, 36(12):2463−2472.[10]Kim I,Lemasters J J.Mitochondrial degradationby autophagy(mitophagy)in GFP-LC3transgenic hepatocytes during nutrient deprivation[J].Am J Physiol Cell Physiol,2011,300(2):C308−317. [11]Xie R,Nguyen S,McKeehan W,et al.Acety-lated microtubules are required for fusion of au-tophagosomes with lysosomes[J].BMC Cell Biology, 2010,11(1):89.[12]Sandov al H,Thiagarajan P,Dasgupta S K,et al.Essential role for Nix in autophagic matura-tion of erythroid cells[J].Nature,2008,454(7201): 232−235.[13]Sato M,Sato K.Degradation of paternalmitochondria by fertilization-triggered autophagy inC.elegans embryos[J].Science,2011,334(6059):1141−1144.[14]Ding W en-xing,Yin X iao-ming.Mitophagy:mechanisms,pathophysiological roles,and analy-sis[J].Biol Chem,2012,393(7):547−564.[15]Duve C D.The Lysosome[J].Sci Am,1963,208:64−73.[16]Eskelinen E L.To be or not to be?Examples ofincorrect identiﬁcation of autophagic compartmentsin conventional transmission electron microscopy of mammalian cells[J].Autophagy,2008,4(2): 257−260.[17]Swanlund J M,Kregel K C,Oberley TD.Investigating autophagy:quantitative mor-phometric analysis using electron microscopy[J].Autophagy,2010,6(2):270−277.[18]Rizzuto R,Nakase H,Darras B,et al.A genespecifying subunitⅧof human cytochrome c oxidase is localized to chromosome11and is expressed in both muscle and non-muscle tissues[J].J Biol Chem, 1989,264:10595−10600.[19]Gottlieb R A,Carreira R S.Autophagyin health and disease:5.mitophagy as a way of life[J].Am J Physiol Cell Physiol,2010,299(2): C203−C210.[20]Kogure T,Karasa wa S,Araki T,et al.Aﬂuorescent variant of a protein from the stony coral Montipora facilitates dual-color single-laserﬂuores-cence cross-correlation spectroscopy[J].Nat Biotech-nol,2006,24(5):577−581.[21]Katayama H,Kogure T,Mizushima N,et al.A sensitive and quantitative technique for detectingautophagic events based on lysosomal delivery[J].Chem Biol,2011,18(8):1042−1052.[22]Chambers K,Manda villi B,Batchelor R,et al.Tools and techniques to measure mitophagy usingﬂuorescence microscopy[J].Autophagy,2013, 9(9):0−1.[23]Mizushima N,Yoshimori T,Levine B.Methodsin mammalian autophagy research[J].Cell,2010, 140(3):313−326.[24]马泰,孙国平,李家斌.细胞自噬的研究方法[J].生物化学与生物物理进展,2012,39(3):204−209. [25]Elmore S P,Qian T,Grissom S F,et al.The mitochondrial permeability transition initiates autophagy in rat hepatocytes[J].The F ASEB Jour-nal,2001,15(12):2286−2287.[26]Chazotte beling lysosomes in live cells withLysoTracker[J].Cold Spring Harb Protoc,2011, 2011(2):210−212.[27]Rodriguez E S,Kim I,Currin R T,et al.Tracker dyes to probe mitochondrial autophagy(mi-tophagy)in rat hepatocytes[J].Autophagy,2006, 2(1):39−46.[28]Okatsu K,Saisho K,Shimanuki M,et al.p62/SQSTM1cooperates with Parkin for perinucle-ar clustering of depolarized mitochondria[J].Genes Cells,2010,15(8):887−900.[29]Kim I,Lemasters J J.Mitophagy selectivelydegrades individual damaged mitochondria after photoirradiation[J].Antioxid Redox Signal,2011, 14(10):1919−1928.[30]Narendra D P,Jin S M,Tanaka A,et al.PINK1is selectively stabilized on impaired mito-chondria to activate Parkin[J].PLoS Biol,2010, 8(1):e1000298.[31]Saita S,Shirane M,Nakayama K I.Selec-tive escape of proteins from the mitochondria during mitophagy[J].Nat Commun,2013,4:1410. [32]Yoshii S R,Kishi C,Ishihara N,et al.Parkin mediates proteasome-dependent protein degradation and rupture of the outer mitochon-drial membrane[J].J Biol Chem,2011,286(22): 19630−19640.[33]Ashley N,Harris D,Poulton J.Detection ofmitochondrial DNA depletion in living human cells using PicoGreen staining[J].Exp Cell Res,2005, 303(2):432−446.[34]Kanki T,W ang K,Cao Y,et al.Atg32is amitochondrial protein that confers selectivity dur-ing mitophagy[J].Dev Cell,2009,17(1):98−109.[35]W atts J.Metabolic dysfunction and depletion ofmitochondria in hearts of septic rats[J].J Mol Cell Cardiol,2004,36(1):141−150.[36]何云凌,吴丽颖,朱玲玲,等.线粒体自噬在低氧适应中的作用[J].生物化学与生物物理进展,2012, 39(3):217−223.[37]Kim Y,Park J,Kim S,et al.PINK1controlsmitochondrial localization of Parkin through direct phosphorylation[J].Biochem Biophys Res Commun, 2008,377(3):975−980.[38]Guo K,Searfoss G,Krolikowski D,et al.Hy-poxia induces the expression of the pro-apoptotic gene BNIP3[J].Cell Death Diﬀer,2001,8: 367−376.[39]Liu L ei,Du F eng,Guo C hen,et al.Mitochon-drial outer-membrane protein FUNDC1mediates hypoxia-induced mitophagy in mammalian cells[J].Nat Cell Biol,2012,14(2):177−185.[40]Zhang J A,Ney P.Reticulocyte mitophagyMonitoring mitochondrial clearance in a mammalian model[J].Autophagy,2010,6(3):405−408. [41]Ashrafi G,Schwarz T L.The pathways of mi-tophagy for quality control and clearance of mito-chondria[J].Cell Death Diﬀer,2013,20(1):31−42.[42]Yang J Y,Yang W Y.Spatiotemporally con-trolled initiation of Parkin-mediated mitophagy within single cells[J].Autophagy,2011,7(10): 1230−1238.[43]Scafidi S,Fiskum G,Lindauer S L,et al.Metabolism of acetyl-L-carnitine for energy and neu-rotransmitter synthesis in the immature rat brain[J].J Neurochem,2010,114(3):820−831.[44]Halestrap A P,Connern C P,GriffithsE J,et al.Cyclosporin A binding in mitochon-drial cyclophilin inhibits the permeability tran-sition pore and protects hearts from ischaemia/ reperfusion injury[J].Mol Cell Biochem,1997, 174(1/2):167−172.[45]W aldmeier P C,Feldtrauer J J,Qian T,et al.Inhibition of the mitochondrial permeability transition by the nonimmunosuppressive cyclosporin derivative NIM811[J].Mol Pharmacol,2002,62(1): 22−29.[46]Vincow E S,Merrihew G,Thomas R E,et al.The PINK1-Parkin pathway promotes both mi-tophagy and selective respiratory chain turnover in vivo[J].Proc Natl Acad Sci USA,2013,110(16): 6400−6405.[47]Clark I E,Dodson M W,Jiang C,et al.Drosophila PINK1is required for mitochondrial function and interacts genetically with Parkin[J].Nature,2006,441(7097):1162−1166.[48]Lyamzaev K G,Nepryakhina O K,Sapruno-v a V B,et al.Novel mechanism of elimination of malfunctioning mitochondria(mitoptosis):for-mation of mitoptotic bodies and extrusion of mito-chondrial material from the cell[J].Biochim Biophys Acta,2008,1777(7/8):817−825.(责任编辑:王春燕)。

噶米meta分析中固定效应模型、随机效应模型和混合OLS模型的选择

meta分析中固定效应模型、随机效应模型和混合OLS模型的选择在Meta分析中最常用的是固定效应模型、随机效应模型。

怎样理解这两种模型呢？举个简单的例子：让十个学生去测量操场中的同一根旗杆，旗杆长度的测量值可以看作是一个固定效应模型；然而如果让一个学生去测量操场上长度不同的十根旗杆，旗杆长度的测量值则是随机效应模型。

一般来说，随机效应模型得出的结论偏向于保守，置信区间较大，更难以发现差异，带给我们的信息是如果各个试验的结果差异很大的时候，是否需要把各个试验合并需要慎重考虑，作出结论的时候就要更加小心。

从另一个角度来说，Meta分析本来就是用来分析结论不一致甚至是相反的临床试验，通过Meta分析提供一个可靠的综合的答案，如果每个试验的结果都一模一样，根本就没有必要作Meta分析，因此要通过齐性检验来解决这对矛盾。

一般来说判断方法是根据I2来确定。

1.就是根据I2值来决定模型的使用，大部分认为＞50%，存在异质性，使用随机效应模型，≤50%，用固定效应模型，有了异质性，通过敏感性分析，或者亚亚组分析，去探求异质性的来源，但是这两者都是定性的，不一定能找到，即使你做了，研究数目多的话，可以做个meta回归来找异质性的来源2.在任何情况下都使用随机效应模型，因为如果异质性很小，那么随即和固定效应模型最终合并结果不会有很大差别，当异质性很大时，就只能使用随机效应模型，所以可以说，在任何情况下都使用随机效应模型3.还有一种，看P值，一般推荐P的界值是0.1，但现在大部分使用0.05，就是说P ＞0.05，用固定，≤0.05用随机效应模型。

但是这些都没有统一的说法，存在争议，如果你的审稿人是其中一种，你和他相冲突了，你只能按照他说的去修改，因为没有谁对谁错，但是现在你的文章在人家手里，如果模型不影响你的结果，你就遵照他们的建议但是，也不必过度强调哪种方法，更重要的是找到异质性根源。

meta分析中，异质性是天然存在的。

领导者上下关系认定与部属利社会行为：

98 51 1 121-138Chinese Journal of Psychology 2009, V ol. 51, No. 1, 121-138Roethlisberger & Dickson, 1939 2005 Leader-member exchange model, LMX; Graen,1976; Graen, Novak, & Sommerkamp, 1982LMX Graen et al., 1982 ； Meglino, Ravlin, & Adkins, 1989; Weiss, 1978 ；領導者上下關係認定與部屬利社會行為：權力距離之調節效果06032 2006 8 2 2007 6 30 2008 1 25 2008 4 14 2008 11 4 2009 1 4106 E-mail: chengbor@.tw1 2 3 4 51 2 345； 795 ： 1 ； 2 ； 3 ：；： -1221995 1995LMX ； Graen, et al., 1982 ？？？？Brewer Gardner 1996 representation of the self Sluss Ashforth 2007 relational identity Flynn, 2005; Sluss & Ashforth, 2007Hsu, 1985 Ptolemian ； Galilean 2001 Hofstede 1980 Hofstede, 1980; Kim, Triandis, Kagiticibasi, Choi, & Yoon, 1994 ； Hofstede, 1980, 1991；？ relational self, Ho, 1995 1991 relational schema Baldwin, 1992; Baldwin, Carrell, & Lopez, 1990; Planalp, 1987 Fiske & Taylor, 1984 ； Baldwin, 19921991 glue Brewer & Gardner, 1996？Aryee Chen Sun Debrah 2007 trickle-down model123？ prosocial organizational behavior Katz, 1964 Baruch, O’ Creevy, Hind, & Vigoda-Gadot, 2004 organizational citizenship behavior O rg a n, 1988 e m p l o y e e-organization relationship, EOR Shore & Coyle-Shapiro, 2003 EOR 1 2 3 ？social cognitive dimensions 2001 power distance Bochner & Hesketh, 1994 ；？ ——leader-subordinate relational identity 1. 領導者與部屬關係vertical dyad linkage, VDL; Dansereau, Graen, & Haga, 1975 leader-member exchange model, LMX; Graen, 1976; Graen, et al., 1982 VDL Dansereau et al., 1975 V D L L M X compatibility competence loyalty in-group out-group ：；Lincoln & Miller, 1979; Tsui & O’ Reilly, 1989; Zenger & Lawerence, 1989 Meglino, et al., 1989; Weiss, 1978 ；1995 ：；LMX LMX124？ LMXFlynn, 2005Wood, 1982 m i n i-culture Baxter, 1987 ； 2005 ：；；— consequence2. 領導者之上下關係認定：？1988 ： 11 ？； expressive ties ； instrumental ties ； mixed ties2001 Fiske, Haslam, & Susan, 1991Schein, 1991instrumental identity125？prosocial organizational behaviorsprosocial behaviors Brief & Motowidlo, 1986 Katz 1964 ： 1 ； 2 ； 3 prosocial organizational behaviorsBrief Motowidlo 1986 ： 1 ； 2 ； 3 ； Brief & Motowidlo, 1986; Organ, 1988multiple foci ：Brief Motowidlo 1986 LePine, Erez, & Johnson, 2002 ： 1 prosocial organizational behavior toward individual, POB-I ； 2 prosocial organizational behavior toward organization, POB-O Coleman & Borman, 2000; McNeely & Meglino, 1994prosocial organizational behavior toward leader, POB-L 1999 POB-L POB-I POB-O1988 Brewer Gardner 1996 Flynn 2005 11／／／；126Atkinson, 2004 ； 1988 ； 2001；Flynn, 2005 1988 2001 guanxi 2002 2001 2006 Flynn, 2005 1. 情感性關係認定與利社會組織行為— 1988 2005；Cheng, Chou, Huang, Wu, & Farh, 2004; Liden, Wayne, & Stilwell, 1993 Cheng, Huang, & Chou, 2002 2003？ social learning theory vicarious learning Bandura, 1977 Konovsky & Pugh, 1994; Wat & Shaffer, 20051 ：假設1 主管的領導者－部屬關係之情感性關係認定與部屬利社會組織行為具正向關係。

metastasize词根词缀

Metastasize 词根词缀—探究恶性肿瘤转移的复杂过程一、介绍Metastasize这一词根词缀源自希腊语metastasis，元含义为“转移”，在医学上指的是原发肿瘤细胞侵入其他组织或器官，形成新的肿瘤病灶的过程。

恶性肿瘤的转移是癌症严重发展的标志，也是治疗上的难题。

本文将通过对Metastasize这一词根词缀的探讨，深入探究恶性肿瘤转移的复杂过程及其影响。

二、从简到繁：深入理解肿瘤转移的基本概念1. Metastasize的基本概念：Metastasize一词是由meta-和-stasis组成的，其中meta-表示“转移”，stasis表示“状态”。

Metastasize即意味着“状态转移”，在医学上特指肿瘤的转移过程。

肿瘤细胞首先从原发病灶中脱落，进入血管或淋巴管系统，随后通过血液或淋巴液传播到其他部位，最终定居并生长形成新的肿瘤。

2. 肿瘤转移的影响：恶性肿瘤的转移是癌症严重发展的标志，也是治疗上的难题。

一旦肿瘤发生转移，治疗的难度将会大大增加，预后也将变得更加不确定。

深入理解肿瘤转移的原理和影响对于癌症的治疗和预防具有重要意义。

三、由浅入深：探究肿瘤转移的复杂过程及其影响1. 肿瘤细胞的脱落：在原发病灶内，由于肿瘤细胞的快速增殖和扩散，肿瘤组织的内部环境往往非常恶劣，细胞间的黏附力降低，这使得肿瘤细胞较容易脱落。

2. 循环系统的传播：脱落的肿瘤细胞首先进入血管或淋巴管系统，随着血液或淋巴液的流动，它们可以在体内迅速传播到其他部位。

3. 定居和生长：传播到其他部位的肿瘤细胞需在新的部位定居，并开始生长。

这个过程对肿瘤细胞来说是相当复杂的，需要满足许多条件，如细胞自身的特性、新部位的环境等。

四、总结与回顾：深刻理解肿瘤转移的意义与挑战肿瘤的转移是肿瘤学研究的重要课题。

通过对Metastasize这一词根词缀的深度探讨，我们深入了解了肿瘤转移的基本概念和复杂过程。

我们意识到，对肿瘤转移的深入理解将有助于更好地预防和治疗癌症。

Metabolic Stability

Prepare 3× NADPH solution in 0.1 M K-phosphate buffer :
6mM NADPH solution : Dissolve 5 mg of NADPH tetrasodium salt in 1 mL of 0.1 M Buffer C.
Prepare 3× liver microsomes solutions in 0.1 M K-phosphate buffer :
Liver microsomes are stored at -70 ℃. Keep liver microsomes on ice when they are used.
Important Notes Things to do before starting Important point before starting
Hepatic Blood Flow (mL/min/kg) 90 55.2 30.9 44 20.7
Factor = (microsomal protein per gram of liver) × (liver weight per kilogram of body weight)
Important Notes
Microsomal Protein per Gram of Liver 45 44.8 77.9 45 48.8
Liver Weight per Kilogram of Body Weight 87.5 40 32 32.5 25.7
Scaling Factora 3937.5 1792 2492.8 1462.5 1254.2
Metabolic stability
ADME, ChemPartner Feb, 2009

卡西米力及卡西米尔效应(The Casimir Effect)

卡西米尔效应（The Casimir Effect）是量子场论的一个重要结果。

在量子力学创建之后，人们理解了由于海森伯不确定性原理（The Heisenberg Uncertainty Principle），真空不是空的，而是充满了量子涨落（Quantum Fluctuation）。

量子涨落带来非零的真空能量，物理上称之为零点能（Zero Point Energy）。

卡西米尔效应正是零点能存在的一个直接结果。

如果去计算真空的零点能，由于不确定性原理，所有频率的量子场涨落模都需要考虑，零点能形如：E≌(1/2)∫dω hω. 由于没有频率的截断，这个计算显然会带来无穷大的零点能，这正是量子场论紫外发散的体现。

1948年，荷兰物理学家 Hendrik Casimir 有了一个绝妙的想法：如果我们去扰动真空（Disturb the Vacuum）会怎么样？虽然真空能是无穷大，可是会不会在扰动真空之后，扣除掉原先的真空能，会得出一个有限大小的能量呢？这是一个极具物理趣味的想法。

因为，物理体系是需要被测量的。

在一个体系中引入外加可控约束条件，研究体系对该条件的响应，正是物理的研究方法。

并且，我们知道，除了引力之外，所有其他的物理理论中能量只具有相对意义。

Casimir于是在真空中引入了两个平行的中性理想导电金属平板，要求平板是无穷大和无穷薄的。

经过数学计算，Casimir发现扣除掉原先的真空能后，约束的两平板真空能量是一个随着板间距离变化的有限能量，如果计算该变化率，可以得到两板之间的一个吸引力，著名的卡西米尔力（The Casimir Force）公式如下：(1)注意，由于字母录入限制，这里的h=h\bar=h/(2\pi)。

a是板间距离。

这是两平板之间单位面积的力量大小，又称为卡西米尔压（The Casimir Pressure）。

从卡西米尔力的公式可以知道：1. 由于h的存在，这个力在经典电动力学是不存在的（两个中性导体板之间没有经典力），卡西米尔力是一个纯粹的量子效应。

1、下载文档前请自行甄别文档内容的完整性，平台不提供额外的编辑、内容补充、找答案等附加服务。
2、"仅部分预览"的文档,不可在线预览部分如存在完整性等问题,可反馈申请退款(可完整预览的文档不适用该条件!)。
3、如文档侵犯您的权益，请联系客服反馈,我们会尽快为您处理(人工客服工作时间：9:00-18:30)。

Stability and Determination of Metamizole Sodium by Capillary Electrophoresis Analysis Combined

注射液中酚磺乙胺及焦亚硫酸钠含量的同时测定

《2024年Meta分析系列之十五_Meta分析的进展与思考》范文

isotope_labeling_metabolomics

《2024年Meta分析系列之十五_Meta分析的进展与思考》范文

[生物工程]Nature-medicine近期精彩文章摘要

基于熵最小化的LFM信号调频率估计算法

Kryazhimskiy_eta...

生活史进化

知母活性成份ZMS药理研究中几种动物模型的建立和比较

分光光度法测定维生素C的含量 外文翻译原文

《2024年Meta分析系列之六_间接比较及网状分析》范文

Meta分析中效应尺度指标的选择

On Maximizing the Second Smallest Eigenvalue of a

汉恒生物线粒体自噬的研究方法

噶米meta分析中固定效应模型、随机效应模型和混合OLS模型的选择

领导者上下关系认定与部属利社会行为：

metastasize词根词缀

Metabolic Stability

卡西米力及卡西米尔效应(The Casimir Effect)

分光光度法测定维生素C的含量外文翻译原文