木本植物木质部空穴和栓塞化研究(综述)

木本植物木质部空穴和栓塞化现象的发现至今已近80年历史,国外学者对此做了较多的研究,国内此方面的研究极少。木质部空穴和栓塞化研究是木本植物体内水分传输研究的前沿所在,不同学者在不同地区对不同材料的研究结果各异,争议颇多。本文对这一研究方向近年来的资料作了概括和总结,包括栓塞化现象的发现、检测方法、诱因及形成机理、木质部栓塞化同输水结构间的关系等方面。     

京津唐城市生态系统能值比较

运用能值(emergy)分析方法,以京津冀地区的北京、天津、唐山为研究对象,建立了复合生态系统与可持续发展的能值指标,对3个城市1991～2005年自然环境与社会经济可持续发展状况进行了比较分析.研究结果表明:1991～2005年期间,由于北京、天津的本地资源能值对经济发展的驱动力不足,城市发展对外部输入能值的依赖程度越来越高;北京、天津、唐山社会子系统的能值指标均呈上升趋势,城市居民生活水平和经济发展水平不断提高;北京经济子系统的各项指标均优于天津和唐山,但环境子系统和能值可持续指标体现出,北京的环境压力最大、可持续发展能力低于天津和唐山.在此分析基础上,对北京、天津、唐山的可持续发展提出了几点建议,为制定城市发展策略和产业调整提供科学依据.     

植物的低温蛋白

综述了与植物耐冻性有关的一些植物内源蛋白质或多肽 ,包括低温防护蛋白、抗冻蛋白、植物脱水素、膜关联耐冻性多肽蛋白质。结果表明 ,植物的耐冻性与其低温蛋白 (cold induced proteins)有着密切的关系 ,并指出了抗冻蛋白行使功能的两种可能的作用方式。同时 ,耐冻性与除低温外的其它环境胁迫因子的植物抗性如抗干旱、抗病虫、高盐耐性、乙烯耐性等密切相关     

Polysaccharide analysis using carbohydrate gel electrophoresis: a method to study plant cell wall polysaccharides and polysaccharide hydrolases.

A method to characterize plant cell wall polysaccharides is presented. The complexity of the polymer structures and the large number of different charged and uncharged monosaccharides that make up plant polysaccharides have previously made analysis technically demanding and laborious. Polysaccharide analysis using carbohydrate gel electrophoresis (PACE) relies on derivatization of reducing ends of sugars and oligosaccharides with a fluorophore, followed by electrophoresis under optimized conditions in polyacrylamide gels. We show that PACE is a sensitive and simple tool for studying the monosaccharide composition of polysaccharides and of cell wall preparations. In combination with specific hydrolases, it can be used to analyze the structure of polysaccharides. Moreover, the specificity and kinetics of the plant polysaccharide hydrolases themselves can be quickly and effectively studied. PACE can detect as little as 500 fmol of monosaccharides and 100 fmol of oligosaccharides, and it is fast and quantitative.     

塔里木河上游土地利用变化中的生态价值损益分析

利用1990和2000年2期TM影像,对塔里木河上游典型绿洲的土地利用面积变化进行了研究,在土地利用变化背景下,通过货币化生态服务功能,揭示塔里木河上游典型绿洲生态价值的变化。研究表明,1990~2000年研究区土地利用变化显著。农田、居民点、盐碱地大面积增加,草地、林地、水域、湿地都有不同程度的减少;10年间研究区生态价值为负增长,减少了1.055×109元,由于土地利用变化而造成的生态价值损失巨大,而国民生产总值增加了3.652×109元。不顾生态环境的损失,盲目追求经济的增长,最终无法实现经济与社会的最大效益。评估区域生态价值,并将其纳入区域环境与经济综合核算体系意义重大。     

EMG power spectra of elbow extensors during ramp and step isometric contractions

The goal of the present study was to compare electromyogram (EMG) power spectra obtained from step (constant force level) and ramp (progressive increase in the force level) isometric contractions. Data windows of different durations were also analysed for the step contractions, in order to evaluate the stability of EMG power spectrum statistics. Fourteen normal subjects performed (1) five ramp elbow extensions ranging from 0 to 100% of the maximum voluntary contraction (MVC) and (2) three stepwise elbow extensions maintained at five different levels of MVC. Spectral analysis of surface EMG signals obtained from triceps brachii and anconeus was performed. The mean power frequency (MPF) and the median frequency (MF) of each power spectrum were obtained from 256-ms windows taken at 10, 20, 40, 60 and 80% MVC for each type of contraction and in addition on 512-, 1024- and 2048-ms windows for the step contractions. No significant differences (P greater than 0.05) were found in the values of both spectral statistics between the different window lengths. Even though no significant differences (P greater than 0.05) were found between the ramp and the step contractions, significant interactions (P less than 0.05) between these two types of contraction and the force level were found for both the MPF and the MF data. These interactions point out the existence of different behaviours for both the MPF and the MF across force levels between the two types of contraction.     

太湖湖滨生态修复区大型底栖动物群落结构及梯度分布

2010—2011年对太湖贡湖湾湖滨带生态修复区滨岸挺水植物带(Ⅰ)、湾相沉水植物带(Ⅱ)和堰外开敞水体(Ⅲ)3个滨岸生境梯度带的水质状况和底栖动物群落特征进行了研究。结果表明:调查共发现底栖动物13科18种,其中仅出现于1个生境梯度带的物种7个;在其余的11个物种中,有5个种群的密度在生境梯度带间存在显著差异;比较发现,按底栖动物摄食功能类群的相对比例,刮食者相对丰度在带Ⅰ最高,收集者在带Ⅱ最高,滤食者在带Ⅲ最高,不同生境梯度带间底栖动物的摄食功能类群构成存在显著差异。对底栖动物相对丰度和水环境参数的冗余分析显示,环节动物和昆虫与DO、NO3--N和PO43--P浓度正相关,软体动物则与NO3--N和PO43--P负相关,一些腹足类对低DO耐受能力较强,与NH4+-N和COD正相关。修复区3个梯度带水动力条件、水质状况和底质类型的差异性对底栖动物的分布有重要影响,形成了生活习性、摄食特征等显著不同的3个底栖动物群落。     

新城疫分离毒HN蛋白的抗原性初步分析及分子特性研究

运用针对NDV囊膜糖蛋白(HN)的单克隆抗体(MAbs),对2005～2006年间自我国江苏和广西部分地区的20株NDV分离株进行排谱试验,初步分析了不同毒株之间HN蛋白的抗原表位差异;并应用RT-PCR技术成功扩增了其HN基因整个编码区,经克隆、测序最终获得13株鸡源NDV与7株鹅源NDV HN基因的编码区序列,分析测定核苷酸序列及推导的氨基酸序列,并将鹅源NDV与鸡源NDV相应序列进行了比较.结果单抗排谱试验表明,20株NDV分离株之间HN蛋白的抗原表位存在差异;测序结果表明,测定的HN基因的编码区长度皆为1716nt编码571个氨基酸;分离株中18株基因Ⅶ型NDV分离株之间HN基因编码区核苷酸序列具有较高的同源性,达94.8%～100%;与近几年国内流行的其它基因Ⅶ型NDV之间的核苷酸序列同源性为92.1%～99.6%.对其推导的HN蛋白一级结构中潜在的糖基化位点及HN蛋白细胞受体结合相关区域的氨基酸序列等进行了比较分析.结果显示,单抗排谱差异显著株在部分氨基酸位点发生了突变;同时揭示我国部分地区同期流行的鹅源NDV与鸡源NDV HN基因之间具有较近的亲缘关系.     

大肠癌发病地理特征的趋势面分析

了解嘉善县大肠癌发病的地理分布特征及地理趋势,为研究大肠癌的病因提供一些线索,嘉善县大肠癌发病率有地域差异,应进一步研究各地区地理环境、生活习惯、经济状况等因素的差异及其与大肠癌的关系,对于存在异常残差值的地区,应作为重点研究对象。探讨这些地区可能存在的某种保护或危险因素。     

Changes in DNA base sequences in the mutant of Arabidopsis thaliana induced by low-energy N+ implantation

To reveal the mutation effect of low-energy ion implantation on Arabidopsis thaliana in vivo, T80II, a stable dwarf mutant, derived from the seeds irradiated by 30 keV N⁺ with the dose of 80×10¹⁵ ions/cm² was used for Random Amplified Polymorphic DNA (RAPD) and base sequence analysis. The results indicated that among total 397 RAPD bands observed, 52 bands in T80II were different from those of wild type showing a variation frequency 13.1%. In comparison with the sequences of A. thalianain GenBank, the RAPD fragments in T80II were changed greatly in base sequences with an average rate of one base change per 16.8 bases. The types of base changes included base transition, transversion, deletion and insertion. Among the 275 base changes detected, single base substitutions (97.09%) occurred more frequently than base deletions and insertions (2.91%). And the frequency of base transitions (66.55%) was higher than that of base transversions (30.55%). Adenine, thymine, guanine or cytosine could be replaced by any of other three bases in cloned DNA fragments in T80II. It seems that thymine was more sensitive to the irradiation than other bases. The flanking sequences of the base changes in RAPD fragments in T80II were analyzed and the mutational “hotspot” induced by low-energy ion implantation was discussed.