Lotka-Volterra自治竞争系统的共存与绝灭

研究了一类自治n种群Lotka-Volterra竞争系统．建立了一部分种群绝灭,另一部分种群持续生存新的判别准则,推广了已知相关结果．     

人与野生动物共存研究进展

人类和野生动物生存空间高度重叠,冲突不可避免,如何从冲突走向共存是学术研究的热点和难点。研究评述了人与野生动物共存的概念解析、量化评估、影响因素以及实现机制四方面的进展,发现人与野生动物共存的概念定义和量化评估还存在争议。大多研究认为共存并不意味着没有冲突,而是不可避免的冲突被控制在可容忍范围内。研究多采用容忍度、接受度、保护态度和行为等变量对人与野生动物共存状态进行量化。野生动物相关的成本效益是影响人与野生动物共存的关键因素。经济和教育手段是实现共存的重要路径。经济手段包括补偿、保险、生态旅游、保护投资等措施,通过增加野生动物保护效益、减少保护成本可以实现共存。教育手段通过提升社区保护意识和野生动物保护效益感知、增强冲突应对能力实现人与野生动物共存。未来研究可以从生态和生计视角构建主客观相结合的指标体系对人与野生动物共存进行量化;基于社会生态系统框架识别影响人与野生动物共存的关键因素,总结实现共存的成功经验;采用实验经济学方法探索适用于本土的多样化共存干预措施组合。     

危险的共存

许多慢性病人同时服用多种药物和保健品,由于药物间相互作用和药物副作用所带来的伤害也越来越常见。这对药品上市之前的测试也提出了更高要求。     

羊草与其主要伴生种竞争与共存的格局分析

在羊草种群与其它植物种群的交错区,应用频度、格避形式,格局强度指数对羊草及其主要伴生种之间的共存格局进行了分析。结果表明,羊草及其主要伴生种的格局呈多样化,集聚格局形式是羊草抵御外来物种入侵,或者是自身扩散的一种对策,羊草与其主要伴生种之间存在竞争与共存作用,羊草与芦苇之间通过拮抗作用实现竞争与共存,羊草与鸡儿肠通过竞争而实现共存,光稃茅香,碱茅以营养繁殖策略实现与羊草竞争,指子茅的生长受羊草竞争的抑制。     

在住院处深入开展以人为本与和谐共存服务理念的探讨

目的：为构建和谐的医患关系,为病人提供优质服务,结合住院处的实际情况,探讨在医院住院处深入开展以人为本与和谐共存服务理念的重要性和必要性。方法：详细介绍以人为本与和谐共存服务理念,简要概括医院住院处的工作职责及其在医院系统中的作用和地位,将以人为本与和谐共存服务理念与医院住院处的职责相结合,探讨该理念在提升住院处的工作职能、促进与患者的沟通交流、提升医院信誉、维护医院形象中的作用。结果：以人为本与和谐共存服务理念在指导住院处各项工作中确实有一定的引导作用。结论：将以人为本与和谐共存服务理念在提升住院处的工作职能相结合,可以很好地促进医务人员与患者的沟通交流,提升医院信誉,提高医院竞争力。     

凯里生物群腕足动物与游泳动物共存现象研究

腕足动物是贵州凯里生物群中重要的化石门类,不仅化石数量丰富,分异度高,还具有丰富的生态现象.在寒武系的化石记录上,腕足动物常与海绵、藻类、棘皮动物、水母状生物、软舌螺、威瓦西亚虫、其他腕足动物等保存在一起,凯里生物群中的腕足动物也有类似的共存现象.本文就凯里生物群中腕足动物与游泳动物的共存现象进行了初步研究,认为腕足动...     

两种果蝇成虫与幼虫期的竞争及其对二者共存的影响

昆虫均为完全或不完全变态发育,其幼虫和成虫阶段往往有着不同的资源需求。研究昆虫在幼虫和成虫阶段的生态位和适合度,有助于提升我们对昆虫物种共存和群落构建的认识。黑腹果蝇(Drosophilamelanogaster)和伊米果蝇(D.immigrans)是全球广布的两种果蝇,它们常常发生在相同的季节,且均在腐烂的水果上产卵,幼虫寄生在其中完成生长发育。本研究通过转瓶实验评估了这两种果蝇在连续竞争过程中的内禀增长率和种内与种间竞争系数,并进一步检验了它们的成虫对产卵场所,以及幼虫对食物的竞争强度,据此计算了两个物种在成虫和幼虫阶段的生态位分化与适合度差异,在当代物种共存理论的框架下分析了影响两种果蝇共存的关键因素。结果表明,连续饲养过程中,黑腹果蝇表现出更高的适合度,大概率会竞争排斥掉伊米果蝇。具体而言,两种果蝇在幼虫和成虫期均有极大的生态位重叠,虽然伊米果蝇成虫对产卵场所有着更高的利用率,黑腹果蝇的幼虫在生长发育阶段对饲料有着更高的利用率,但两种果蝇在成虫、幼虫阶段竞争的结果更多地取决于谁先占据资源。本研究表明昆虫在不同发育阶段对资源利用率的变化会在一定程度上影响它们共存的可能性。     

病原菌负反馈作用促进物种共存的研究进展

植物病原菌包括真菌、细菌、病毒等,广泛存在于自然界中,可以引起各种植物病害。病原菌对植物的负反馈作用,即植物个体附近的土壤病原菌,可能反过来侵害其自身或同种个体,致死或影响生长植物的现象。植物病原菌对群落中优势种的更新有强烈的抑制作用,从而促进物种的共存。植物病原菌的负反馈作用在植物种群动态和群落演替中起着重要的调控作用。     

两株黄瓜花叶病毒卫星RNA的竞争与共存研究

通过体外转录方法 ,将大小分别为 36 9nt和 385nt的 2个黄瓜花叶病毒 (Cucumbermosaicvirus,CMV)的卫星RNAYi和Yns共同与不含卫星的辅助病毒株CMV_CNa进行假重组 ,接种CMV系统寄主心叶烟。结果表明 :在接种5d的接种叶上同时检测到卫星RNA_Yi和卫星RNA_Yns;在系统叶上 ,接种 5d和 10d亦可同时检测到 2株卫星 ;但接种 15d ,在系统叶组织中只检测到卫星RNA_Yi。再将接种 5d的接种叶扩大接种到几种不同的指示植物后 ,经dsRNA抽提 ,也只获得 1条与卫星RNA_Yi大小相符的条带。通过假重组病毒株中分别获得卫星RNA并测序 ,确定2个卫星RNA的序列没有变化。卫星RNA_Yns和Yi在辅助病毒CMV_CNa作用下 ,表现出明显的竞争性 ,它们在辅助病毒中不能形成稳定的共存关系。     

带扩散项的周期捕食食饵模型的整体共存态的存在唯一性

本文通过构造迭代列,讨论了周期捕食食饵扩散系统的整体共存态的存在唯一性.     

探讨医院图书馆数字化信息建设与服务

数字化信息时代,信息资源建设是主流的业务。本文通过对医院图书馆数字资源建设与知识服务的内容,提出医院图书馆信息资源数字化建设的基本对策和发展方向。     

探讨医院图书馆数字化信息建设与服务

数字化信息时代,信息资源建设是主流的业务。本文通过对医院图书馆数字资源建设与知识服务的内容,提出医院图书馆信息资源数字化建设的基本对策和发展方向。     

Isolation and characterization of a mutant protoporphyrinogen oxidase gene from Chlamydomonas reinhardtii conferring resistance to porphyric herbicides

In plant and algal cells, inhibition of the enzyme protoporphyrinogen oxidase (Protox) by the N-phenyl heterocyclic herbicide S-23142 causes massive protoporphyrin IX accumulation, resulting in membrane deterioration and cell lethality in the light. We have identified a 40.4 kb genomic fragment encoding S-23142 resistance by using transformation to screen an indexed cosmid library made from nuclear DNA of the dominant rs-3 mutant of Chlamydomonas reinhardtii. A 10.0 kb HindIII subclone (Hind10) of this insert yields a high frequency of herbicide-resistant transformants, consistent with frequent non-homologous integration of the complete RS-3 gene. A 3.4 kb XhoI subfragment (Xho3.4) yields rare herbicide-resistant transformants, suggestive of homologous integration of a portion of the coding sequence containing the mutation. Molecular and genetic analysis of the transformants localized the rs-3 mutation conferring S-23142 resistance to the Xho3.4 fragment, which was found to contain five putative exons encoding a protein with identity to the C-terminus of the Arabidopsis Protox enzyme. A cDNA clone containing a 1698 bp ORF that encodes a 563 amino acid peptide with 51% and 53% identity to Arabidopsis and tobacco Protox I, respectively, was isolated from a wild-type C. reinhardtii library. Comparison of the wild-type cDNA sequence with the putative exon sequences present in the mutant Xho3.4 fragment revealed a GA change at 291 in the first putative exon, resulting in a ValMet substitution at a conserved position equivalent to Val-389 of the wild-type C. reinhardtii cDNA. A sequence comparison of genomic Hind10 fragments from C. reinhardtii rs-3 and its wild-type progenitor CC-407 showed this GA change at the equivalent position (5751) within exon 10.     

Mapping of unit boundaries of a protein: exhaustive search for permissive sites for duplication by complementation analysis of random fragment libraries of tryptophan synthase alpha subunit

To identify peptide units that make up a single-domain protein, we searched for possible combinations of N and C-fragments that exhibit functional complementation, and attempted an exhaustive evaluation of peptide unit boundaries. The tryptophan synthase alpha subunit was used as a model enzyme, which has a single TIM (beta8/alpha8) barrel domain. Libraries comprising randomly digested N and C-fragments were constructed, and clones expressing enzymatic activity were selected by the ability to confer growth of the Escherichia coli trpA mutant on a medium lacking tryptophan. More than 50 clones were obtained, and two cleavable positions were found on the loops after extra-helix 2' and helix 5. Half of the clones harbored N and C-fragments having an overlap between two fragments. The remaining clones harbored one fragment made by the fusion of N and C-fragments with insertional sequence duplication. Mapping the frequency of occurrence of fragment overlap and insertional duplication showed significant peaks at two loops, which coincide with the cleavable sites. These results suggest that the boundaries of unit fragments are located at these positions, and that bisection, fragment overlap and insertion are all possible at the unit boundaries.     

Gene isolation through genomic complementation using an indexed library of Chlamydomonas reinhardtii DNA

Hundreds of mutants with defects in a variety of physiologically important functions, such as photosynthesis, respiration, flagellar motility, phototaxis, circadian rhythms and the cell cycle, have been isolated from cultures of Chlamydomonas reinhardtii. In only a few cases have the genes responsible for these mutations been cloned and sequenced. The development of efficient methods for transformation with nuclear genes [7] has allowed the recent demonstration of gene isolation through genomic complementation with a pooled library of C. reinhardtii DNA [9]. To improve the efficiency with which genes complementing a particular mutation can be isolated, we have established an indexed (ordered) cosmid library of 11,280 individual clones contained in the separate wells of 120 microtiter plates. The average insert size is ca. 38 kb. PCR analysis of five sequenced nuclear genes present in the Chlamydomonas library revealed a range from two copies for the ₂ and ₂ tubulin genes to at least seven copies for the agininosuccinate lyase gene. Overall, these five clones were represented an average of >-3.4 times in the library. Thus, the probability that any one particular nuclear gene of < 1000 bp will be found in the library is >-97%, and the probability that a gene of ca. 10 000 bp will be found in the library is ca. 92%. Rapid screening methods with cosmid DNAs pooled from individual microtiter dishes have been applied successfully. Bacteria containing clones of the argininosuccinate lyase gene have been identified through genomic complementation of a Chlamydomonas mutant bearing an inactive arginnosuccinate lyase gene.We are using the nomenclature of indexed library versus ordered library to avoid confusion of this library with a library of ordered contigs.     

Establishment of a Genetic Transformation System and Its Application in Thermoanaerobacter tengcongensis

The whole-genome sequence of Thermoanaerobacter tengcongensis,an anaerobic thermophilic bacterium isolated from the Tengchong hot spring in China,was completed in 2002.However,in vivo studies on the genes of this strain have been hindered in the absence of genetic manipulation system.In order to establish such a system,the plasmid pBOLOl containing the replication origin of the T.tengcongensis chromosome and a kanamycin resistance cassette,in which kanamycin resistance gene expression was controlled by the ttel482 promoter from T.tengcongensis,was constructed and introduced into T.tengcongensis via electroporation.Subsequently,the high transformation efficiency occurred when using freshly cultured T.tengcongensis cells without electroporation treatment,suggesting that T.tengcongensis is naturally competent under appropriate growth stage.A genetic transformation system for this strain was then established based on these important components,and this system was proved to be available for studying physiological characters of T.tengcongensis in vivo by means of hisG gene disruption and complementation.     

Enhanced catalytic efficiency of aminoglycoside phosphotransferase (3')-IIa achieved through protein fragmentation and reassembly

Many monomeric proteins can be split into two fragments, yet the two fragments can associate to make an active heterodimer. However, for most locations in a protein such a conversion is not feasible, presumably due to inefficient assembly or improper folding of the fragments. For some locations, this can be overcome by fusion of the fragments to dimerization domains that facilitate correct assembly. A variety of heterodimers of aminoglycoside phosphotransferase (3')-IIa (Neo) were created in which the Neo fragments required fusion to a pair of leucine zippers for activity in vivo. However, the ability of these heterodimers to confer kanamycin resistance to Escherichia coli cells was impaired compared to wild-type Neo, primarily due to poor production of soluble protein. The mutations R177S and V198E restored the kanamycin resistance to wild-type levels while maintaining the dependence on leucine zippers for activity. These mutations restored high levels of kanamycin resistance not through an improvement in the production of soluble protein but rather by conferring a large improvement in k(cat)/K(m), surpassing that of Neo. Furthermore, whereas R177S and V198E served to improve k(cat)/K(m) 60-fold in the context of the heterodimer, the same mutations in the context of wild-type Neo had a ninefold negative effect on k(cat)/K(m). This demonstrates the possibility that enzymes with improved catalytic properties can be created through a process involving fragmentation and fusion to domains that facilitate assembly of the fragments.     

酵母DNA修复基因RAD16温度敏感突变株的分离及人类互补基因的鉴定

用PCR介导的基因重组法敲除酵母RAD16基因, 用羟胺处理酵母RAD16基因表达质粒, 获得RAD16基因突变库,并将其转化RAD16基因敲除的酵母细胞. 用平皿复制法获得温度敏感突变株 rad16-ts2,经互补试验证实,该突变表型为RAD16基因突变所致.将人cDNA表达文库转化rad16-ts2后筛选温度敏感拯救(rescue)表型, 回收拯救表型酵母细胞中的质粒. 测序结果表明,所获得的人cDNA克隆为HLTF/Zbu1/SMACA3基因.比较分析显示,人类该基因编码蛋白质氨基酸序列与酵母Rad16的同一性为32%,相似性则达50%.人HLTF/Zbu1/MACA3基因在HeLa细胞中过表达,可显著抑制过氧化氢损伤和UV照射诱导的细胞凋亡.