Myosin I is located at the leading edges of locomoting Dictyostelium amoebae

Movement of a eukaryotic cell along a substrate occurs by extension of lamellipodia and pseudopodia at the anterior and retraction at the posterior of the cell. The molecular and structural mechanisms of these movements are uncertain. Dictyostelium discoideum contains two forms of myosin. Here we show by immunofluorescence microscopy that non-filamentous myosin I occurs at the leading edges of the lamellipodial projections of migrating Dictyostelium amoebae, which are devoid of myosin II, whereas filamentous myosin II is concentrated in the posterior of the cells. On the basis of these locations of the two forms of myosin and their known biochemical and biophysical properties, we suggest that actomyosin I may contribute to the forces that cause extension at the leading edge of a motile cell, while the contraction of actomyosin II at the rear squeezes the cell mass forward. Myosin I isozymes might have similar roles in metazoan cells, for example at the leading edges of neuronal growth cones, and in the extension of lamellipodia and pseudopodia of leukocytes, macrophages and fibroblasts.     

Stepwise enzymatic dephosphorylation of inositol 1,4,5-trisphosphate to inositol in liver

Many receptors for hormones, neurotransmitters and other signals cause hydrolysis of phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2) and effect a rise in cytosolic Ca2+ concentration. The inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) liberated during PtdIns(4,5)P2 breakdown seems to serve as a second messenger that activates the release of Ca2+ from a nonmitochondrial intracellular compartment. As expected if it is an important intracellular messenger, Ins(1,4,5)P3 is relatively rapidly degraded, both within stimulated cells and when added to homogenates of blowfly salivary gland or to permeabilized, but not intact, hepatocytes. Here we report that the dephosphorylation reactions responsible for the conversion of Ins(1,4,5)P3 to free inositol in rat liver are catalysed by two or more enzymes, and that these reactions are distributed between the plasma membrane and cytosol. The Ins(1,4,5)P3 5-phosphatase and inositol 1-phosphate (Ins(1)P) phosphatase of liver appear similar to enzymes described previously in erythrocytes and brain.     

Occurrence and extracellular actions of inositol pentakis- and hexakisphosphate in mammalian brain

Although inositol 1,3,4,5,6-pentakisphosphate (InsP5) and hexakisphosphate (InsP6) have been recognized for some time as naturally-occurring metabolites of inositol, their occurrence in mammalian cell types, including one of neural origin, has only recently been documented. This is of interest because of the recognized second messenger role of inositol 1,4,5-trisphosphate (InsP3) in intracellular signalling; coupling surface stimuli to cytoplasmic calcium discharge. The metabolism, existence in normal mature tissues, and possible functional roles of these inositol polyphosphates are unknown. Here we report evidence that InsP5 and InsP6 are synthesized in intact brain after labelling with [3H]inositol in vivo. We also show that local infusion of InsP5 and InsP6 into a discrete brain stem nucleus implicated in cardiovascular regulation, results in dose-dependent changes in heart rate and blood pressure.     

逐步回归分析的拓展

给出一种方法,在逐步回归后,使每一前进（后退）步为一单元步,用Ｆ检验来判别这单元步的去留,使回归式子比逐步回归纳入更多的解析变量,同时能减低向后消元法产生多重共线性的可能性．     

关于逐步回归算法的一个修正

将逐步回归算法用于符号回归任务时,会产生计算溢出现象,其原因是在检验因子的显著性时,由于数据精度很高,可能会发生最大偏回归平方和Ｖｍａｘ与残差平方和ｒｙｙ相等或非常接近的情况,从而造成检验式分母的绝对值过小而溢出,对此,提出了两种修正方法,修正后的算法消除了隐患,可用于符号回归等高精度数据拟合任务。     

城市化带来的环境问题

城市化是反映一个国家、一个地区的文明与发展水平的重要标志，然而城市化在给人们提供现代科技、现代文明、现代生活等种种好处的同时，也对环境形成了强大的污染压力。本文以此为核心具体阐述了城市化过程中和城市化后对温度、大气、水分、光照、生物等环境因子的影响。     

染料废水的综合处理

采用硫酸钡、高岭土等无机物来吸附染料废水中的有机染料，使染料废水的ρ(CODCr)从1万多下降至1400mg／L左右，同时得到副产物纸用颜料，对无机物吸附后的废水，进一步用电化学氧化和活性炭吸附处理，使废水的ρ(CODCr)继续下降至100mg／L以下，而达到国家一级排放标准。     

Stepwise evolution of stable sociality in primates

Although much attention has been focused on explaining and describing the diversity of social grouping patterns among primates, less effort has been devoted to understanding the evolutionary history of social living. This is partly because social behaviours do not fossilize, making it difficult to infer changes over evolutionary time. However, primate social behaviour shows strong evidence for phylogenetic inertia, permitting the use of Bayesian comparative methods to infer changes in social behaviour through time, thereby allowing us to evaluate alternative models of social evolution. Here we present a model of primate social evolution, whereby sociality progresses from solitary foraging individuals directly to large multi-male/multi-female aggregations (approximately 52 million years (Myr) ago), with pair-living (approximately 16?Myr ago) or single-male harem systems (approximately 16?Myr ago) derivative from this second stage. This model fits the data significantly better than the two widely accepted alternatives (an unstructured model implied by the socioecological hypothesis or a model that allows linear stepwise changes in social complexity through time). We also find strong support for the co-evolution of social living with a change from nocturnal to diurnal activity patterns, but not with sex-biased dispersal. This supports suggestions that social living may arise because of increased predation risk associated with diurnal activity. Sociality based on loose aggregation is followed by a second shift to stable or bonded groups. This structuring facilitates the evolution of cooperative behaviours and may provide the scaffold for other distinctive anthropoid traits including coalition formation, cooperative resource defence and large brains.     

Stepwise radial complexation of imine groups in phenylazomethine dendrimers

Dendrimers are highly branched organic macromolecules with successive layers or 'generations' of branch units surrounding a central core. Organic-inorganic hybrid versions have also been produced, by trapping metal ions or metal clusters within the voids of the dendrimers. The unusual, tree-like topology endows these nanometre-sized macromolecules with a gradient in branch density from the interior to the exterior, which can give rise to an energy gradient that directs the transfer of charge and energy from the dendrimer periphery to its core. Here we show that tin ions, Sn(2+), complex to the imine groups of a spherical polyphenylazomethine dendrimer in a stepwise fashion. This behaviour reflects a gradient in the electron density associated with the imine groups, with complexation in a more peripheral generation proceeding only after complexation in generations closer to the core has been completed. By attaching an electron-withdrawing group to the dendrimer core, we are able to change the complexation pattern, so that the core imines are complexed last. By further extending this strategy, it should be possible to control the number and location of metal ions incorporated into dendrimer structures, which might find uses as tailored catalysts or building blocks for advanced materials.     

热带终轧温度计算的逐步回归分析模型

基于大量现场工程记录数据,考虑轧制速度、精轧入出口厚度、机架间水量等影响热带终轧温度的主要因素,采用逐步回归分析法进行热带终轧温度计算模型的多元线性回归建模,在模型系数未进行学习时采用线性模型进行模拟计算,将计算结果与工程记录数据进行比较,模型计算结果与记录数据之差小于15℃范围内的达70.1%,表明该模型计算效果能够满足终轧温度控制精度要求.针对线性回归模型的局限性,对该模型系数自学习方法进行了讨论.     

多重共线性的逐步回归检验分析

通过国家财政逐步回归模型实例,本文分析了自变量选取原则,阐明了变量筛选的依据,并在逐步回归具体步骤中,重点描述了多重共线性的解决过程,最后利用积矩相关系数,对多重共线性问题的解决结果进行分析,并给出了合理的实际意义。     

逐步法制备Mg-Al-LDHs与有机-LDHs的插层组装体

通过控制铝组分在溶液中的形态,采用逐步控制的方法制备了Mg-Al-LDHs,经过离子交换,制备了benzoic-LDHs、o-aminobenzoic-LDHs和o-hydroxybenzoic-LDHs。在控制过程中,铝的羟基配合物在室温下与Mg2 和OH-共沉淀生成LDHs,XRD图谱显示生成的LDHs晶相单一、结晶良好,有机-LDHs保持了层状结构。     

逐步法制备Mg-Al-LDHs与有机-LDHs的插层组装体

通过控制铝组分在溶液中的形态，采用逐步控制的方法制备了Mg-Al-LDHs，经过离子交换，制备了benzoic-LDHs、o-aminobenzoic．LDHs和o-hydroxybenzoic-LDHs。在控制过程中，铝的羟基配合物在室温下与Mg^2＋和OH^-共沉淀生成LDHs，XRD图谱显示生成的LDHs晶相单一、结晶良好，有机-LDHs保持了层状结构。     

昆明地区高血压影响因素的逐步判别分析

分析影响血压的重要因素，为有效地预防高血压病及高血压的临床治疗都有重要意义．文中利用逐步判别分析法，将影响血压的多个因素化简出最优的因子，建立判别函数进行逐步分析，估计出判别系数，对数据进行分析判断，得出各因素对高血压的影响     

考虑剪切变形时阶梯连续梁弯曲变形

本文采用考虑剪切变形时梁理论［１］的基本微分方程组，导出了阶梯连续梁弯曲变形的转角及挠曲线的通解。     

逐步回归与判别分析的应用研究--在乳腺疾病建模中的应用

体内激素紊乱是导致乳腺疾病发生的重要原因,将逐步回归法与Fisher判别法结合应用于乳腺疾病建模中,对乳腺疾病与6种内分泌激素及患者年龄的关系进行了多元线性判定分析,建立了变量与相关疾病的逻辑回归模型与判别模型,该模型通过实际应用,判别效果较好,有助于乳腺疾病的诊断。