Separation of Monomerizing and Lysozyme Activities of Destabilase from Medicinal Leech Salivary Gland Secretion

Destabilase, endo--(-Glu)-Lys-isopeptidase, was prepared from the salivary gland secretion of the medicinal leech (Hirudo medicinalis). The secretion prepared by the known method of Rigbi et al. (1987) (secretion-K) lacks the destabilase-characteristic highly specific isopeptidase activity (the D-dimer-monomerizing activity) because of its degradation by proteolytic activity (the substrate of Glp-Ala-Ala-Leu-pNA) due to contamination with leech intestinal channel contents. Therefore, we have elaborated a new technique for preparation of a true leech secretion (secretion-I). This secretion is characterized by the complete absence of the leech intestinal channel contents and has no proteolytic activity. For the first time the destabilase-specific D-dimer-monomerizing and lysozyme activities were separated by fractionation of secretion-I by HPLC gel filtration through Superose S-12. For the purified destabilase preparation, these activities were separated by reversed-phase chromatography in an acetonitrile gradient (0-60%) in the presence of 0.1% trifluoroacetic acid. The monomerizing activity of destabilase is responsible for the ability of secretion-I to dissolve stabilized fibrin via isopeptidolysis of - and - fibrin chains bound by -(-Glu)-Lys-isopeptide bonds.     

Dimension reduction strategies for analyzing global gene expression data with a response

The analysis of global gene expression data from microarrays is breaking new ground in genetics research, while confronting modelers and statisticians with many critical issues. In this paper, we consider data sets in which a categorical or continuous response is recorded, along with gene expression, on a given number of experimental samples. Data of this type are usually employed to create a prediction mechanism for the response based on gene expression, and to identify a subset of relevant genes. This defines a regression setting characterized by a dramatic under-resolution with respect to the predictors (genes), whose number exceeds by orders of magnitude the number of available observations (samples). We present a dimension reduction strategy that, under appropriate assumptions, allows us to restrict attention to a few linear combinations of the original expression profiles, and thus to overcome under-resolution. These linear combinations can then be used to build and validate a regression model with standard techniques. Moreover, they can be used to rank original predictors, and ultimately to select a subset of them through comparison with a background 'chance scenario' based on a number of independent randomizations. We apply this strategy to publicly available data on leukemia classification.     

The Relationship Between the Reference Value of Erythrocyte Sedimentation Rate and Geographical Factors

In order to provide a scientific basis for a unified standard of the reference value of erythrocyte sedimentation rate (ESR) in China, the reference value of healthy people's ESR has been collected. The relationship between the reference value of ESR and geographical factors is examined in this paper. Altitude is the most important factor affecting the reference value of ESR, which decreases with increasing altitude; the relationship is quite significant. The method of stepwise regression analysis was used to deduce two regression equations: ₁=12.08-0.00222X₁+0.00114X₅ ± 2.95, ₂=18.81-0.00323X₁+0.239X₄ ± 4.70. If the geographical factor value of a particular area in China is known, the reference value of ESR of Chinese people can be calculated by means of the regression equations. Furthermore, the dependence on geographical factors in China can be classified as six districts: Qingzang, Southwest, Northwest, Southeast, North and Northeast.     

黄土丘陵区沙棘人工林发育过程中物种多样性及种间关联变化

根据野外调查资料,分析了不同发育阶段沙棘人工群落物种多样性及种间关联的变化特征.结果表明,群落各层及总体物种多样性基本呈“S”形波动变化.在不同发育阶段的沙棘群落中,物种丰富度和多样性指数均呈现草本层＞灌木层的趋势.灌木层物种多样性指数在撂荒地中较低,随群落发育逐渐增加,灌木层物种均匀度指数在13年生的沙棘林中较高;草本层多样性指数在3年生的人工林中较高,在8年生的人工林中较低,在25年生的人工林中较高.人工沙棘林中种间关联正负绝对值基本呈抛物线形变化,13年生左右显著程度和联结强度较弱,群落内物种间物种替代速度缓慢,竞争较少,群落组成和结构相对稳定.在沙棘人工林的经营和管理上,应是13年生以前以保护为主,到25年生时进行适度择伐,抚育萌生幼苗,促进种群更新发育.     

西双版纳不同林龄次生植物群落优势树种的热值

该文对西双版纳的4种次生植物群落优势树种的热值进行了研究。4种群落类型分别是山黄麻(Trema orientalis)群落、白背桐(Mallotus paniculatus)群落、中平树(Macaranga denticulata)群落和思茅崖豆(Millettia leptobotrya)群落,群落年龄分别为2、4、6年和大于15年。4种群落各优势树种的平均干重热值分别为19 182.11、19 474.81、19 551.38和19 445.95 J·g^-1。总体来讲,热值随着群落年龄的增加而增加。增长的原因应该是群落光能利用效率的增加。思茅崖豆群落的热值稍有降低,是因为这个群落样地处在阴坡,不能接受到像其它3个群落那样在阳坡的充足光照。先锋树种的热值明显低于顶极树种。可能是因为在群落演替初期,生态系统增加能量耗散的主要方式是通过生物量的增加;而当结构建成,生物量增加到一定程度,已经没有足够增长空间的时候,生态系统将会改变能量储存方式,主要通过单位质量固定能量的增加,也就是热值的增加,来耗散能量。山黄麻群落中叶片的热值非常低,低于根的热值水平,是短命树种将能量更多地投资于繁殖的原因。     

脑磁源的定位研究

在脑电脑磁研究中,常将大脑视为一电磁系统,利用准静态近似下的麦克斯韦方程,可以发现代表脑神经元活动的原在电流密度与脑外磁场之间呈线性关系。在高斯哭喊杨存在的情况下,采用极大似然估计理论,讨论了一种基于脑磁场时域－罕注解磁源定位问题的一般方法。球对称导体模型下的模拟计算表明,这一方法是有效的。对于考虑真实头模型下的磁源定位问题求解磁源定位,提出了一种联合使用脑磁脑电数据的近似方法。     

中国青年人全血比粘度参考值与地理因素的关系

为制定中国青年人全血比粘度参考值的标准提供科学依据,收集了中国各地用毛细管法测定的健康青年人全血比粘度参考值,并对其与地理因素的关系进行了研究,发现海拔高度是影响青年人全血比粘度参考值最主要的因素,随着海拔高度的逐渐增大,青年人全血比粘度参考值也在逐渐的增大,相关性很显著。用逐步回归分析的方法推导出了２个回归方程。如果知道了中国某地的地理因素,就可以用这２回归方程估算这个地区的青年人全血比粘度参考     

海南岛生态系统土壤保持空间分布特征及生态经济价值评估

在地理信息系统的支持下 ,采用通用土壤流失方程 ( USLE)及其修改式估算了海南岛现实土壤侵蚀量和潜在土壤侵蚀量 ,得到了海南岛生态系统土壤保持的空间分布特征 ,研究表明 :中部山区的生态系统的土壤保持能力较其它地区大 ,全岛年土壤保持总量为 1 .58× 1 0 7t,并利用市场价值法 ,机会成本法和影子工程法评价了各类型生态系统的土壤保持价值。海南岛年土壤保持总价值为 74 92 .4 1万元 ,其中减少土地废弃价值为 4 9.37万元 ,保护土壤肥力价值为 72 74 .2 2万元 ,减轻泥沙淤积价值为 1 68.82万元     

发根农杆菌介导的药用植物遗传转化研究进展

发根农杆菌介导的植物遗传转人旨近年来发展起来的一项新的植物遗传转化技术。本文就发根农杆菌Ｒ１闰的结构、发根农杆菌介导的植物遗传转化的方法和步骤,以及运用这一技术获得药用植物次生代谢产物的研究进展作一全面介绍。     

30种植物叶蛋白中氨基酸组成及含量的测定与营养价值评价

评价植物叶蛋白的营养价值,既要考虑“量”,看植物叶蛋白含量的高低,也要考虑“质”,看必需氨基酸的含量及配比[1]。作者取叶蛋白含量50%以上的30种植物进行氨基酸含量测定[2],并进行营养价值评价。1　方　　法应用日立83550型氨基酸自动分析仪进行氨基酸含量的测定,并与?..