黏附分子在肿瘤发生及发展中的作用

细胞黏附分子是以配体和受体相结合的形式,介导细胞与细胞间或细胞与基质间相互作用的一类分子,参与机体的多种重要生理和病理过程.近年来,在对肿瘤发生和发展的研究中发现,黏附分子可通过多种途径影响肿瘤的生长、浸润及转移过程.因此.对黏附分子在肿瘤发生和发展中作用及机制的深入研究,可为肿瘤早期诊断提供重要的分子指标和发现新的治疗靶标.并为进而形成临床诊疗新策略提供重要理论支持.现就几种重要黏附分子在肿瘤生长与转移中的作用进行综述.     

NMDAR/PKC通路介导基底外侧杏仁核的长时程增强

本文在大鼠杏仁核脑片上刺激外囊（external capsule,EC）,在基底外侧杏仁核（basolateral amygdala,BLA）记录场电位,观察能否在杏仁核诱导长时程增强（long—term potentiation,LTP）,并探讨杏仁核LTP形成的可能机制。应用两串间隔10min的0频率波刺激EC,可见BLA的场电位明显增强,持续时间在30min以上。EC—BLA的LTP表现为通路特异性,可被N-甲基-D-天冬氨酸受体（N-methyl—D—aspartate receptor,NMDAR）阻断剂D,L-2-氨基-5磷酸基戊酸（APV）阻断。在灌流液中加入蛋白激酶C（protein kinaseC,PKC）抑制剂chelerythrine chloride,对BLA的基础场电位和配对脉冲比率（pairedpulse ratio,PPR）没有影响;但在chelerythrine chloride存在的情况下,两串θ频率波刺激不能诱导出LTP;若于两串高频刺激10min后,在灌流液中加入chelerythrine chloride不能阻断BLA的LTP。上述结果表明,EC—BLA的LTP为NMDAR依赖性,PKC参与BLA的LTP诱导和早期维持。     

The importance of predation,substrate and spatial refugia in determining lotic insect distributions

An experiment was conducted to evaluate the interaction between predation, substrate, and spatial refugia in the organization of a stream insect community (Reeds Creek, Pendleton Co., West Virginia). Patterns of insect colonization were compared between fish exclusion cages and open controls that allowed access to vertebrate predators. Each cage contained 4 different substrates that varied in the relative amount of spatial refugia. Fish had little influence on the diversity or abundance of any insect taxa, even when spatial refugia were limited. The only significant effect due to predation, was an increased diversity of large (>8 mm) invertebrates in the absence of predators. However, because these taxa were relatively rare, the overall role of fish predation on insect community structure was minimal.In contrast, substrate had a marked effect on insect colonization. Insects were always more abundant (number/basket) on loose substrates containing large numbers of interstitial spaces, compared to cement-embedded substrates with few refuges available. In addition, invertebrates were more abundant on loose gravel compared to loose cobbles. Howver, when substrate preferencesrd were examined according to insect density (number/m²), loose cobbles were generally the preferred substrate. The present experiment rejects the hypothesis that patterns of substrate colonization can be explained as differential insect mortality by predators, due to varying amounts of refugia. Alternative mechanisms such as differing amounts of trapped detritus and substrate surface area may account for substrate preference.     

Enhanced performance in prediction of protein active sites with THEMATICS and support vector machines

Theoretical microscopic titration curves (THEMATICS) is a computational method for the identification of active sites in proteins through deviations in computed titration behavior of ionizable residues. While the sensitivity to catalytic sites is high, the previously reported sensitivity to catalytic residues was not as high, about 50%. Here THEMATICS is combined with support vector machines (SVM) to improve sensitivity for catalytic residue prediction from protein 3D structure alone. For a test set of 64 proteins taken from the Catalytic Site Atlas (CSA), the average recall rate for annotated catalytic residues is 61%; good precision is maintained selecting only 4% of all residues. The average false positive rate, using the CSA annotations is only 3.2%, far lower than other 3D-structure-based methods. THEMATICS-SVM returns higher precision, lower false positive rate, and better overall performance, compared with other 3D-structure-based methods. Comparison is also made with the latest machine learning methods that are based on both sequence alignments and 3D structures. For annotated sets of well-characterized enzymes, THEMATICS-SVM performance compares very favorably with methods that utilize sequence homology. However, since THEMATICS depends only on the 3D structure of the query protein, no decline in performance is expected when applied to novel folds, proteins with few sequence homologues, or even orphan sequences. An extension of the method to predict non-ionizable catalytic residues is also presented. THEMATICS-SVM predicts a local network of ionizable residues with strong interactions between protonation events; this appears to be a special feature of enzyme active sites.     

Phylogenetic analysis of epiphytic marine bacteria on Hole-Rotten diseased sporophytes of <Emphasis Type="Italic">Laminaria japonica</Emphasis>

During an occurrence of Hole-Rotten Disease of Laminaria japonica in a cultivating farm in Ma Shan Shandong province, China, 42 Gram-negative epiphytic marine bacteria were isolated and purified on Zobell 2216E marine agar medium. Morphological and biochemical characteristics of each isolated bacterium were studied, and molecular identification of bacterial strains was conducted with polymerase chain reaction amplification to 16S rRNA gene sequence analysis. Based on nearly full length of 16S rRNA gene sequence analysis, the isolated strains were bacteria that belong to genus Pseudoalteromonas, Vibrio, Halomonas and Bacillus. The percentage of each group was 61.9%, 28.6%, 7.1% and 2.4% respectively. The results of pathogenicity assay showed that 12 strains could cause the disease symptoms in sporophytes of L. japonica. They belonged to the genera Pseudoalteromonas, Vibrio and Halomonas with 58.3%, 33.3%, 8.3% respectively. The results suggest that these bacteria are the dominant marine bacteria on diseased sporophytes of L. japonica and may be the potential pathogenic bacteria associated with Hole-Rotten Disease of L. japonica.     

Comparative evaluation of different cell disruption methods for the release of recombinant hepatitis B core antigen from <Emphasis Type="Italic">Escherichia coli</Emphasis>

A comparative evaluation of five different cell-disruption methods for the release of recombinant hepatitis B core antigen (HBcAg) from Escherichia coli was investigated. The cell disruption techniques evaluated in this study were high-pressure homogenization, batch-mode bead milling, continuous-recycling bead milling, ultrasonication, and enzymatic lysis. Continuous-recycling bead milling was found to be the most effective method in terms of operating cost and time. However, the highest degree of cell disruption and amounts of HBcAg were obtained from the high-pressure homogenization process. The direct purification of HBcAg from the unclarified cell disruptate derived from high-pressure homogenization and bead milling techniques, using batch anion-exchange adsorption methods, showed that the conditions of cell disruption have a substantial effect on subsequent protein recovery steps.     

利用定点突变分析白念珠菌依赖铁基因FRP1启动子元件

通过对白念珠菌高铁还原酶基因FRP1启动子进行突变分析, 确认启动子中特殊调控元件。我们通过分析FRP1起始密码子上游1000 bp序列发现在-160 和-650处有2个推测的Rim101p结合位点, 对其分别进行定点突变, 然后构建启动子与报告基因LacZ融合质粒, 转化整合到白念珠菌rim101-/-株和野生株中, 检测不同缺铁条件下b-半乳糖苷酶活性。结果发现碱性条件, Rim101p能够正向调控FRP1的表达; 启动子-160处突变对启动子功能影响较弱, 而-650突变使启动子活性大大降低, 此结果和双突变的结果相同, 表明Rim101p主要通过与启动子-650处结合位点相互作用来调控FRP1的表达。     

光周期对光敏核不育水稻光敏色素A含量及其mRNA丰度的影响

光敏核不育水稻(农垦58S)是我国特有的水稻(Oryza sativa L.)种质材料,光敏色素是光周期诱导其育性转变的受体。报道了育性转换敏感期间的光周期处理对农垦58S及对照“农垦58”叶片中光敏色素A(Phy A)含量及其mRNA丰度的影响。在10个光周期处理的最后一个暗期结束前,收获每株水稻的上部两片叶,用酶联免疫吸附测定法测定Phy A。和长日照(LD)相比,短日照(SD)处理导致农垦58SPhy A相对含量增加38.5％;而“农垦58”只增加18.5％。显然,在较长的暗期中,农垦58S中Phy A的积累比对照快。在水稻幼苗中也得出相似的结果。以光敏色素A基因(phy A)的特异性片段RPA3作探针,用RNA斑点杂交的方法对叶片中Phy A mRNA丰度进行分析的结果表明,光周期处理5d和10d时,两品种水稻的Phy A mRNA丰度都是SD处理的比LD的高,而且SD下农垦58S Phy A mRNA的丰度均比“农垦58”的高。这些结果表明,甲基化水平较低的农垦58S phy A可能比“农垦58”的phy A更活跃地表达。另外,在育性转换敏感期每日主光期结束时(EOD)进行10次短暂的远红光(FR)照射。结果表明,农垦58S植株抽穗和开花期比SD处理推迟2d,而花粉败育率、种子结实率却无变化。暗示农垦58S开花和育性转变过程的光周期反应可能不同。     

自然保护地生物多样性保护研究进展

建立自然保护地是保护生物多样性最为重要的措施之一。总体来看, 自然保护地生物多样性保护研究主要围绕关键生态系统以及珍稀濒危物种等保护对象的状态以及变化两个层面进行, 并重点关注自然保护地数量与面积、保护了多少重要生态系统和物种、能否有效保护生物多样性等一系列科学问题。然而, 在自然保护地生物多样性保护研究方面, 还缺少针对上述研究领域的系统性综述。为此, 本文系统梳理了自然保护地空间布局及其与生物多样性分布的关系、自然保护地生物多样性变化及其保护成效等近20年来相关领域的研究进展。自然保护地的空间布局以及与生物多样性分布的关系主要围绕自然保护地与生物多样性在某一阶段的状态开展研究, 致力于探究自然保护地“保护多少” “代表性如何” “在哪儿保护”等一系列关键科学问题。同时, 自然保护地内的生物多样性会随着气候变化、人类活动以及自身演替等发生时空动态变化, 基于自然保护地生物多样性变化分析, 各国学者在全球尺度、国家尺度和单个自然保护地进行了大量的保护成效评估研究, 并逐渐发展出了自然保护地内外配对分析方法以提升保护成效评估的精度, 进而识别出不同自然保护地的主要影响因素。在此基础上, 本文进一步对自然保护地生物多样性保护研究提出了展望, 主要包括: (1)综合考虑自然保护地生物多样性状态和变化; (2)开展多目标协同的自然保护地空间优化布局; (3)强化自然保护地主要保护对象的识别、调查与监测; (4)提升自然保护地的质量和连通性; (5)探究自然保护地管理措施与保护成效的关联机制。本文可为“2020年后全球生物多样性框架”的制定与实施特别是在自然保护地体系建设与优化方面提供参考与借鉴。