基因沉默及其克服策略

基因沉默现象是导致转基因不能正常表达的主要原因,基因沉默发生在两种水平上,一种是由于DNA甲基化、异染色质化以及位置效应等引起的转录水平上的基因沉默,另一种是转录后基因沉默,有活跃的启动子,能转录外源基因,核内有正常水平的mRNA,细胞质不积累mRNA。消除甲基化的影响﹑避免使用同源和重复序列和使用核基质结合序列可有效克服基因沉默。     

食线虫真菌蠕虫埃斯特菌对植物寄生线虫的侵染特性

为评价食线虫真菌蠕虫埃斯特菌Esteya vermicola菌株NKF 13222的生防应用价值,采用2%水琼脂培养基平板接种法测定了该菌株对7种植物寄生线虫的诱引、黏附和侵染能力,并比较了其对不同线虫的侵染特性.结果显示,该菌株的菌丝对松材线虫、拟松材线虫、腐烂茎线虫和水稻干尖线虫均有诱引作用,而对南方根结线虫、禾谷孢囊线虫和穿刺短体线虫无诱引作用;菌株的粘性分生孢子对有诱引现象的4种线虫都能黏附,接种24 h后的黏附率达到82%～99%,对无诱引现象的3种线虫不能黏附;粘性分生孢子黏附虫体后对不同线虫的侵染力存在差异,接种7 d后的松材线虫死亡率可达98%,而拟松材线虫、腐烂茎线虫和水稻干尖线虫死亡率分别为43%、35%和9%.表明蠕虫埃斯特菌不仅是松材线虫的强内寄生真菌,而且对其它重要植物寄生线虫也具有一定的应用潜力.     

Expression of an Episomal Vector in Developing Chicken Embryo and Chicks

The domesticated chicken has important roles in basic and applied research. The vector based on scaffold matrix attachment region （S/MAR） appears to be sufficient to maintain long-term expression in an episomal state in various mammalian cells. To explore the practical use of episomal vector in transgene technology of agricultural chickens, we fused the S/MAR of the human r-interferon gene into the pEGFP vector and transduced it into chickens by sperm-mediated gene transfer （SMGT）. PCR detection indicated the positive rate of transgene chickens was 60%. The RT-PCR detection and fluorescence observation confirmed the expression of the GFP and indicated the existence of the GFP during the chicken embryogenesis and fetal development. The PCR detection and rescue experiments confirmed the episomal state of the pEPI-EGFP in chick embryos and chicks. These results showed that the S/MAR-based vector could function properly in chicken embryos and was a practicable tool combined with the SMGT to study the development of chickens.     

Perceptions of cultural ecosystem services of tree-based green infrastructure: A focus group participatory mapping in Zagreb,Croatia

Urban green infrastructure provides city dwellers numerous benefits. Among them, cultural ecosystem services (CES) are distinguished by being easily perceived and essential for people and their well-being. However, not all CES are equally easy to perceive, resulting with some of the CES categories being weakly explored. Research on CES also rarely considers elements of urban green infrastructure other than parks and forests. Therefore, there is a lack of research on different components of urban green infrastructure, especially tree-based, perceived in relation to CES. This paper presents the results of focus group participatory mapping implemented with citizens in the city districts of Zagreb on the perception of five selected CES categories in various types of urban green infrastructure. Our results show that participants perceived 13 different types of tree-based urban green infrastructure as providers of CES. We also distinguish patterns in the perception of CES categories and their connection with types of tree-based urban green infrastructure. Tree lines are perceived as providers of aesthetical experiences. Furthermore, forests and park forests are perceived in relation to place attachment and recreational activities, while parks are versatile and provide all explored CES. Other types that emerged as important were greenways, greenery around residential buildings and educational institutions, which provokes rethinking of a careful planning of the entire repertoire of urban green infrastructure.     

A method for the attachment of miniature radio tags to small fish

Abstract An attachment technique which gives good tag retention, minimal damage to fish and prevents entanglement with weed is described. Fish carrying transmitters were monitored in semi-natural conditions and appeared to exhibit the same behaviour as untagged fish. Median condition factors of dummy-tagged fish did not differ from those of untagged fish over a 10-week period. Examples of movement patterns obtained using radio tags attached to dace, Leuciscus leuciscus (L.) are given.     

地方依恋中植物景观因素对人类情感的作用

指出了地方依恋是描述人与地方之间的积极情感,它包括地方依赖和地方认同.回顾国内外的地方依恋的研究,人们在与某个地方的长期互动过程中,发展出对该地的依恋.由于目前地方依恋影响因素中的植物景观因素研究较少,因而提出了可通过对植物景观色彩、气味、植物形态、季相变化以及植物不同的观赏部位等的讨论来阐述植物景观与地方依恋关系;在...     

罗氏沼虾胚胎附着机制的初步研究

甲壳动物十足目的大多数种类,其受精卵自产出后就附着于亲体腹部,并完成胚胎发育过程直至孵化,这对于胚胎的发育、保护和幼体散布有重要的生物学意义。胚胎的附着机制较为复杂,与刚毛、卵柄、卵索、卵膜和黏液腺有关:卵柄和卵索的形成决定了胚胎发育的顺利进行;卵膜的变化影响着胚胎的附着;黏液腺在胚胎附着过程中形成卵柄和外层卵膜,胚胎是依靠卵柄或卵索附着于腹肢的刚毛上,进而完成胚胎发育过程。本研究采用常规组织学和扫描电镜的方法研究了罗氏沼虾(Macrobrachium rosenbergii)胚胎及其附着结构。结果表明,胚胎附着与母体腹肢的结构、黏液腺分泌的黏液相关,也与胚胎表面结构、次级卵膜的形态和结构密切相关。原肢底节和内肢刚毛密而长,基部有细小的分支,有利于胚胎的附着,外肢刚毛羽状则有利于胚胎的托附和保护。抱卵雌虾腹肢的原肢和内肢上布满腹肢黏液腺分泌的黏液;携卵刚毛中空、壁厚,刚毛外壁由微绒毛状结构组成,扩大了携卵刚毛的表面积,以利胚胎附着。胚胎外表面由初级卵膜和次级卵膜组成,次级卵膜主要由卵巢黏液腺分泌的黏液参与形成。排卵时,受精卵依靠坚韧的次级卵膜相互粘连,同时,部分受精卵在刚毛上滑动、旋转,并借助次级卵膜逐渐形成了卵柄或卵索固着在腹肢刚毛上。从受精卵到胚胎孵化,胚胎之间最主要的连接方式是依靠次级卵膜的连接。胚胎的表面有许多褶皱和黏液,利于胚胎的附着以及胚胎对溶氧和小分子物质等的通透。以上结构与附着相适应,保证了胚胎发育的顺利进行和幼体的正常孵化。本研究旨为进一步认识甲壳动物胚胎附着机制、胚胎发育和人工育苗的研究提供参考。[中国水产科学,2007,14(1):67-73]     

全射流喷头内部附壁点距离的计算

阐述了全射流喷头中水射流附壁点的距离是喷头射流元件设计的关键尺寸．基于Bourque理论,采用控制面模型,计算了全射流喷头内射流附壁点的距离,并与试验结果和相关文献进行对比,发现在射流扩散系数取9时,计算值与试验值接近．讨论了影响附壁点距离的各种因素,包括位差、壁面倾角、射流流量、射流扩散系数等．研究发现,可通过增大偏移率,增大壁面倾角来增大射流元件中附壁点距离,其中以改变壁面倾角最为显著,流量的改变几乎不影响附壁距离．研究结果对于改进全射流喷头射流元件的设计具有指导意义．     

日本沼虾体表寄生物对胚胎附着的影响

用扫描电镜技术研究了体表寄生物对日本沼虾（Macrobrachium nipponense)受精卵（胚胎）附着的影响，发现在流产个体1－4对腹肢原肢与内肢的表面密布钟虫类原生动物，这些寄生原生动物影响粘液腺的分泌活动，使其不能正常分泌粘液，受精卵的被膜、卵柄及卵索均不能正常形成，卵与卵之间的摩擦力加大，胚胎供氧困难，最终导致死胎和流产，体表寄生物是造成养殖日本沼虾胚胎提早脱落的重要原因之一。     

农业科研单位干部挂职模式探讨

干部挂职是锻炼培养干部、加强信息交流、强化服务意识的一种有效途径,农业科研单位开展干部挂职工作,有助于优化科技人才队伍结构、更新管理理念和创新管理体制。文章通过总结目前干部挂职工作模式中存在的问题,结合农业科研单位的特点,提出了适合农业科研单位干部挂职的模式,并对农业科研单位干部挂职工作提出了建议,如加强思想教育工作、合理编制干部挂职工作规则、拓宽干部挂职培养途径等。