Telomeres in evolution and evolution of telomeres

This paper examines telomeres from an evolutionary perspective. In the monocot plant order Asparagales two evolutionary switch-points in telomere sequence are known. The first occurred when the Arabidopsis-type telomere was replaced by a telomere based on a repeat motif more typical of vertebrates. The replacement is associated with telomerase activity, but the telomerase has low fidelity and this may have implications for the binding of telomeric proteins. At the second evolutionary switch-point, the telomere and its mode of synthesis are replaced by an unknown mechanism. Elsewhere in plants (Sessia, Vestia, Cestrum) and in arthropods, the telomere “typical” of the group is lost. Probably many other groups with “unusual” telomeres will be found. We question whether telomerase is indeed the original end-maintenance system and point to other candidate processes involving t-loops, t-circles, rolling circle replication and recombination. Possible evolutionary outcomes arising from the loss of telomerase activity in alternative lengthening of telomere (ALT) systems are discussed. We propose that elongation of minisatellite repeats using recombination/replication processes initially substitutes for the loss of telomerase function. Then in more established ALT groups, subtelomeric satellite repeats may replace the telomeric minisatellite repeat whilst maintaining the recombination/replication mechanisms for telomere elongation. Thereafter a retrotransposition-based end-maintenance system may become established. The influence of changing sequence motifs on the properties of the telomere cap is discussed. The DNA and protein components of telomeres should be regarded – as with any other chromosome elements – as evolving and co-evolving over time and responding to changes in the genome and to environmental stresses. We describe how telomere dysfunction, resulting in end-to-end chromosome fusions, can have a profound effect on chromosome evolution and perhaps even speciation.     

Isopycnic centrifugation of plant viruses in Nycodenz density gradients

Isopycnic centrifugation of plant viruses in density gradients prepared from a new non-ionic medium (Nycodenz) was investigated. Particle density of luteo-, tymo-, nepo-, cocksfoot mild mosaic, tobamo-, hordei-like, potex- and potyviruses in buffered solutions of Nycodenz ranged between 1.23 and 1.28 g/ml and did not strictly reflect their nucleic acid and protein composition. Isopycnic centrifugation of several partially purified viruses yielded preparations which were pure by electron microscopy and, when used as immunogens in rabbit or hen, gave antisera with low titers of antibodies against host plant antigens, as required for enzyme immunoassays. A preparation of purified potato leafroll virus contained a single dominant protein corresponding to the viral coat protein. It is concluded that isopycnic centrifugation in Nycodenz density gradients is particularly useful for the purification and analysis of plant viruses which are unstable in cesium chloride solutions, such as the luteoviruses, and preferable to zonal centrifugation in sucrose density gradients for the purification of rod-shaped multipartite viruses or viruses which aggregate.     

应用PCR产前诊断胎儿及孕妇梅毒感染的研究

目的:为了研究羊水聚合酶链反应(PCR)方法产前诊断胎儿先天梅毒以及梅毒对妊娠的影响,妊娠期梅毒的诊断治疗预后等问题。方法:对8例不同孕周患梅毒的孕妇抽取羊水用PCR方法检测梅毒螺旋体DNA;对22例患梅毒的孕妇应用青霉素或红霉素进行治疗并随访至分娩后;对261例因不良孕娩史而就诊妇女进行梅毒血清学检测并以无不良孕娩史普通妇科门诊病人111例作为对照。结果:8例羊水梅毒PCR检测结果6例阳性,2例阴性。其中1例阳性者终止妊娠,胎儿病理解剖证实有梅毒感染。22例梅毒孕妇经治疗3例失访,1例早产,18例足月分娩,新生儿临床及血清学检查均未见异常。因不良孕娩史而就诊妇女梅毒血清学阳性率(14.56%),明显高于无不良孕娩史的普通妇科门诊病人(5.40%)(P<0.01)。结论:羊水PCR梅毒DNA检测是诊断先天梅毒较好的方法,妊20周前胎儿可感染上梅毒。患梅毒的孕妇应早期足量正规治疗以防治胎儿感染。梅毒是导致不良孕娩史的重要原因。     

The nonrandom distribution of long clusters of all possible classes of trinucleotide repeats in barley chromosomes

This paper is the first to report the long-range organization of all possible classes of trinucleotide motifs in a higher plant genome. Fluorescent in situ hybridization (FISH), employing the synthetic oligonucleotides (AAC)5, (AAG)5, (AAT)5, (AGG)5, (CAC)5, (CAT)5, (CAG)5, (ACT)5, (ACG)5 and (GCC)5, was used to characterize the nonrandom and motif-dependent distribution of tandem arrays of trinucleotide repeats in the metaphase chromosomes and interphase nuclei of barley (Hordeum vulgare L.). This provided detailed information on the sequence content of barley chromatin and allowed the saturation of the physical map of all barley chromosomes. The following conclusions were also drawn: (1) Except for (AAT)5 and (GCC)5, the studied repetitive motifs have a characteristic pattern of distribution in terms of their in situ FISH signals. Some permit the accurate identification of individual chromosomes. (2) (CAG)5, (CAT)5 and (ACT)5 are not found in all barley chromosomes. (3) With the exception of (ACT)5, the remaining trinucleotide repeats occur predominantly in the heterochromatin and are largely absent from the euchromatic regions. Moreover, (CAC)5, (ACG)5 and (CAG)5 are exclusively concentrated in the centromeres. The employment of simple synthetic probes for the identification of chromosomes and genomic characterization, and their importance in studies on genome organization, function and evolution, are discussed.     

南宋郑樵的本草学成就

南宋著名史学家郑樵不但精通经史百家之说 ,而且对本草学深有研究。他广撷历代本草名著 ,又注重实地调查 ,辩识药用动植物之名实 ,并在《本草经集注》基础上增加药物品种 ,提出科学的动植物分类法 ,在本草学研究上取得一定成就。     

Are Bacillus thuringiensis strains like any other Bacillus cereus strains? Phenotypic-based tools to locate Bacillus thuringiensis in the diversity of the Bacillus cereus sensu lato group

Some Bacillus thuringiensis (Bt) strains are used as pesticide agent. This species belongs to Bacillus cereus (Bc) group which contains many species with a high phenotypic diversity, and could be pathogenic like B. cereus. The aim of this study was to characterize the phenotype of 90 strains belonging to Bc group, half of which were Bt. Knowing that Bt strains belong to different phylogenetic Bc groups, do Bt strains have the same phenotype than other Bc group strains?Five phenotypic parameters were estimated for 90 strains in the Bc group, of which 43 were Bt strains: minimal, maximal and optimal growth temperature, cytotoxicity on Caco-2 cells, heat resistance of spores. The dataset was processed by principal component analysis, showing that 53% of the variance of the profiles corresponded to factors linked to growth, heat resistance and cytotoxicity. The phenotype followed the phylogenetic groups based on panC. Bt strains showed similar behavior to other strains in the Bc group, in our experimental conditions. Commercial bio-insecticide strains were mesophilic with low heat resistance.     

植物精油及其活性成分防治结直肠癌作用机制的研究进展

尽管过去几十年结直肠癌在治疗上取得了较大进展,但放化疗的不良反应、耐药性和高昂的治疗成本仍然是结直肠癌治疗的主要限制因素。具有抗肿瘤活性的植物精油因其低毒、来源广泛在抗结直肠癌药物开发中受到广泛关注。通过搜集和分析相关文献,发现部分植物精油及其活性成分能够有效预防和治疗结直肠癌,其作用机制涉及抑制慢性炎症、抗氧化应激、抑制细胞增殖、诱导细胞凋亡、阻滞细胞周期、抑制血管新生、改善肠道菌群结构,其干预的信号通路包括核因子-κB（nuclear factor-κB,NF-κB）信号通路、Toll样受体4（Toll-like receptor 4,TLR4）信号通路、Wnt/β-连环蛋白（β-catenin）信号通路、表皮生长因子受体（epidermal growth factor receptor,EGFR）信号通路、磷脂酰肌醇-3-激酶（phosphatidylinositol 3-kinase,PI3K）/蛋白激酶B（protein kinase B,Akt）信号通路、丝裂原活化蛋白激酶（mitogen-activated protein kinase,MAPK）/细胞外调节蛋白激酶（extracellular regulated kinases,ERK）信号通路等。对植物精油及其活性成分防治结直肠癌的作用机制和信号途径进行归纳,并进一步讨论当前研究存在的局限性和可能的解决方法,以期为植物精油在结直肠癌防治中的深入研究以及开发应用提供参考依据。     

横经席药材的生药学研究及有效成分测定

目的 对广西民族药材横经席CalophylliHerba进行基原调查和生药学研究,并对有效成分进行测定。方法通过查阅文献厘清横经席的历史使用沿革及植物分布情况,野外实地调研横经席的植物基原,采集并制作腊叶标本,通过药材性状、显微特征等方法进行生药学研究,采用岛津液相色谱仪Nexera LC-40,岛津Shim-pack GIST C18-AQ HP色谱柱（100 mm×2.1 mm,1.9μm）,乙腈-0.4%甲酸水为流动相,体积流量0.3 mL/min,梯度洗脱,柱温35℃,PDA检测器,检测波长275nm,建立横经席药材中穗花杉双黄酮和异棘苷的含量测定方法。结果 横经席的野外资源日益匮乏,市场上常见东南亚进口的红厚壳属植物与横经席混用,采用建立的方法能够有效地鉴别横经席药材。所建立的含量测定方法稳定性和重复性良好,线性范围宽（5.360～379.800μg/mL）、线性较好（R2>0.999）,平均回收率在98.3%～99.0%。结论为完善横经席药材质量标准和药合理应用提供依据。     

地桃花的本草考证、生药学研究及其有效成分定量测定

目的 对地桃花Urenalobata进行本草考证、生药学分析及有效成分测定。方法 通过查阅文献厘清地桃花的历史使用沿革及植物分布情况,野外实地调研地桃花的植物基原,采集并制作腊叶标本,通过原植物形态、药材性状、显微特征等方法进行生药学研究;采用Waters e2695型液相色谱仪,CAPCELL PAK MGⅡC18色谱柱（250 mm×4.6 mm,5μm）,乙腈-0.1%甲酸溶液为流动相,体积流量1.0 mL/min,梯度洗脱,柱温30℃,PDA检测器,检测波长315 nm,建立地桃花药材中N-反式-阿魏酰酪胺和银锻苷的HPLC测定方法。结果 对地桃花药材的性状及显微特征进行了归纳,建立的测定方法稳定性和重复性良好,N-反式-阿魏酰酪胺和银锻苷线性范围0.999～79.890、1.068～85.420μg/mL,R2>0.999,平均回收率95.3%、97.1%。10批样品N-反式-阿魏酰酪胺、银锻苷质量分数为0.003%～0.045%、0.016%～0.046%。结论 建立的方法能够有效鉴别地桃花药材,为完善地桃花药材质量标准和地桃花药材收购提供依据。