一类抽象方程的解集的稳定性与本质连通区

用集值分析的方法,讨论了抽象方程解集的稳定性,得到了通有稳定的结果,并给出了本质连通区存在的充分条件.讨论了抽象方程近似解集的稳定性,得到了通有稳定的结果,同时指出包含精确解的连通分支都是本质的,并且这样的连通分支只有有限个.最后作为应用,对非线性方程组的解集进行了讨论.     

Stage-specific control of neuronal migration by somatostatin.

Developing neurons transiently express somatostatin and its receptors, but little is known about their function at these early stages. As we thought that endogenous somatostatin might control the migratory behaviour of immature neurons, we have examined the effects of somatostatin in cerebellar granule cells of early postnatal mice, because these cells express all five types of somatostatin receptors before the initiation of their migration. Here we show that somatostatin has opposite and stage-specific effects on the migration of cerebellar granule cells. Activation of somatostatin receptors increases the rate of granule cell migration near their birthplace, but decreases the rate near their final destination. Furthermore, somatostatin enhances the size and frequency of spontaneous Ca2+ fluctuations in the early phase of migration, whereas it eliminates spike-like Ca2+ transients in the late phase. Somatostatin-induced changes at both early and late phases are reversed by a blockade of K+ channel activity. These results indicate that somatostatin may provide an essential cue for accelerating the movement of granule cells in the early phase and for terminating the movement in the late phase through altering intracellular Ca2+ concentrations and K+ channel activity.     

蛇床子挥发油化学成分的分析

蛇床子经水蒸气蒸馏,挥发油得率为1．07％,GC—MS联用对其化学成分进行了分析和鉴定．经DB-1柱分离出79个峰,鉴定了其中的70种化合物,占挥发油总含量的95．17％．其主要成分为乙酸龙脑酯、D-芋烯、丙酸香芹酯、蛇床子素、β-雪松烯、α-金合欢烯、α-蒎烯等．     

Directional guidance of neuronal migration in the olfactory system by the protein Slit.

Although cell migration is crucial for neural development, molecular mechanisms guiding neuronal migration have remained unclear. Here we report that the secreted protein Slit repels neuronal precursors migrating from the anterior subventricular zone in the telencephalon to the olfactory bulb. Our results provide a direct demonstration of a molecular cue whose concentration gradient guides the direction of migrating neurons. They also support a common guidance mechanism for axon projection and neuronal migration and suggest that Slit may provide a molecular tool with potential therapeutic applications in controlling and directing cell migration.     

Tyrosine phosphatase CD45 is essential for coupling T-cell antigen receptor to the phosphatidyl inositol pathway

Stimulation of T lymphocytes through their antigen receptor (T-cell receptor; TCR) results in the activation of a tyrosine kinase and the generation of phosphatidyl inositol (PtdIns)-derived second messengers. Several reports have indicated that CD45, a haematopoietic cell-specific surface glycoprotein with tyrosine phosphatase activity in its cytoplasmic domain, is important in lymphocyte activation. To examine the possibility that CD45 might influence proximal signal transduction events through the TCR, we have isolated a variant of the human T-cell leukaemic line, HPB-ALL, which fails to express this phosphatase. Unlike cells expressing CD45, stimulation of the TCR in the CD45-negative cell does not result in PtdIns-derived second messengers. Reconstitution of CD45 expression restored early signalling events through the TCR. To localize the site of CD45 action, the human muscarinic type 1 receptor, which also activates the PtdIns second messenger pathway, was transfected into the CD45-negative cell. Although stimulation of the TCR failed to generate PtdIns-derived second messengers, there was normal activity of the PtdIns pathway when human muscarinic receptor type 1 was stimulated, despite the absence of CD45. These data indicate that CD45 influences a cellular component that is essential for effective coupling of the TCR to the PtdIns second messenger pathway.     

四川杜鹃花中挥发性成分的研究

水蒸气蒸馏法从四川杜鹃的花中提取挥发油,用气相色谱-质谱联用技术对其挥发油化学成分进行分离和结构鉴定,从四川杜鹃的花挥发油中总共分离出53个组分,鉴定出51个组分。用气相色谱面积归一化法确定了各个组分的相对百分含量,其挥发油主要组分是石竹烯(12.48%)、愈创醇(8.83%)、α-蒎烯(8.32%)、β-蒎烯(7.78%)、β-紫罗兰酮(6.83%)等。     

草果香气成分研究

采用固相微萃取法萃取粉碎草果香气成分,然后用GC-MS进行成分分析,并与水蒸气蒸馏萃取法获得的精油成分进行比较.萃取柱为CAR/PDMS时共检测出30个成分,解析鉴定出占总挥发性成分的97.635%的27种物质.水蒸气蒸馏萃取法以1.87%(w/w)的产率获得精油,共检测出38个成分,解析出的成分占精油质量的98.393%的32种成分,主要成分是1,8-桉树脑(40.891%)(质量分数,以下同),α-水芹烯(9.769%),2-异丙基苯甲醛(6.988%),(E)-柠檬醛(4.949%),α-蒎烯(4.36%).     

塔里木盆地塔中地区油气运移输导体系研究

构成塔中地区输导网络格架的输导体包括断裂、不整合面、裂缝和孔隙等。利用分形方法,对塔中地区4个重要构造面的断裂体系进行了分形研究。结果表明,塔中地区下奥陶统顶（Tg5′）的分形维数最高,为1.39;其次是寒武系膏盐岩层顶（Tg7）,为1.24;最小的是石炭系生屑灰岩顶（Tg2″）,为1.05。按其流体运动特点,塔中地区不整合面上、下输导体分属于两个不同的流体流动场,不整合面以下输导体主要由孔-洞-缝体系构成;不整合面以上输导体为层状渗透体,在大多数情况下属于孔隙型介质。根据塔中地区输导网络的特征,提出了以限制性横向输导为主的输导网络和以非限制性纵向输导为主的输导网络的分类方案。     

塔里木盆地塔中地区油气运移输导体系研究

构成塔中地区输导网络格架的输导体包括断裂、不整合面、裂缝和孔隙等.利用分形方法,对塔中地区4个重要构造面的断裂体系进行了分形研究.结果表明,塔中地区下奥陶统顶(Tg5′)的分形维数最高,为1.39;其次是寒武系膏盐岩层顶(Tg7),为1.24;最小的是石炭系生屑灰岩顶(Tg2"),为1.05.按其流体运动特点,塔中地区不整合面上、下输导体分属于两个不同的流体流动场,不整合面以下输导体主要由孔-洞-缝体系构成;不整合面以上输导体为层状渗透体,在大多数情况下属于孔隙型介质.根据塔中地区输导网络的特征,提出了以限制性横向输导为主的输导网络和以非限制性纵向输导为主的输导网络的分类方案.     

保存方法对桂花精油提取及香气成分的影响

通过水蒸气蒸馏法分别对冷冻、氯化钠、柠檬酸及自然干燥保存的桂花进行精油提取,并采用GC-MS对所得精油的有效成分进行分析,比较不同保存方法处理及保存30、60和90 d后桂花的精油得率及香气成分的差别。结果表明:冷冻保存、氯化钠保存及柠檬酸保存是较好桂花的保存方法,自然干燥保存法不可取;氯化钠、柠檬酸保存桂花较合适的保存时间为60 d。     

ClpS is an essential component of the N-end rule pathway in Escherichia coli

The N-end rule states that the half-life of a protein is determined by the nature of its amino-terminal residue. Eukaryotes and prokaryotes use N-terminal destabilizing residues as a signal to target proteins for degradation by the N-end rule pathway. In eukaryotes an E3 ligase, N-recognin, recognizes N-end rule substrates and mediates their ubiquitination and degradation by the proteasome. In Escherichia coli, N-end rule substrates are degraded by the AAA + chaperone ClpA in complex with the ClpP peptidase (ClpAP). Little is known of the molecular mechanism by which N-end rule substrates are initially selected for proteolysis. Here we report that the ClpAP-specific adaptor, ClpS, is essential for degradation of N-end rule substrates by ClpAP in bacteria. ClpS binds directly to N-terminal destabilizing residues through its substrate-binding site distal to the ClpS-ClpA interface, and targets these substrates to ClpAP for degradation. Degradation by the N-end rule pathway is more complex than anticipated and several other features are involved, including a net positive charge near the N terminus and an unstructured region between the N-terminal signal and the folded protein substrate. Through interaction with this signal, ClpS converts the ClpAP machine into a protease with exquisitely defined specificity, ideally suited to regulatory proteolysis.     

四方蒿挥发油化学成分及应用研究

采用G-MS-DC联用方法，测定和鉴定了四方蒿精油的化学成分，其主要成分为蛇麻烯（12.02%)。β-蒎烯（11.98%)，异蒎莰酮（10.03%)，石竹烯氧化物（6.27%)，檀萜烯（4.28%),叶绿醇（8.12%)等45个化合物，其中有31个成分为首次从四方蒿中检出。     

超临界流体萃取佛手挥发油的气相色谱/质谱分析

采用超临界流体CO2萃取法提取新鲜佛手和干佛手的挥发油,经气相色谱-质谱联机分析,新鲜佛手挥发油的得率为16.2 mL/kg,鉴定出34个组分,主成分为丁二醇,占16.28%;干佛手挥发油的得率为9.6 mL/kg,分2个不同时段用不同的条件萃取,第1个时段鉴定出51个组分,第2个时段鉴定出40个组分,干佛手挥发油的主成分为5,7-二甲氧基香豆素,占19.49%.而且,干佛手第2个时段的挥发油中含有较多的中长链脂肪酸,总量达26.47%.     

云南一种羽苔科植物精油脂肪成分分析研究

通过GC/M S对云南玉龙雪山一种羽苔科植物精油脂肪成分进行了分析,共鉴定脂肪成分35种,其中脂肪烃9种、脂肪醇和脂肪酮各1种、脂肪酸3种、脂肪酸甲酯21种。     

Tyro-3 family receptors are essential regulators of mammalian spermatogenesis

We have generated and analysed null mutations in the mouse genes encoding three structurally related receptors with tyrosine kinase activity: Tyro 3, Axl, and Mer. Mice lacking any single receptor, or any combination of two receptors, are viable and fertile, but male animals that lack all three receptors produce no mature sperm, owing to the progressive death of differentiating germ cells. This degenerative phenotype appears to result from a failure of the tropic support that is normally provided by Sertoli cells of the seminiferous tubules, whose function depends on testosterone and additional factors produced by Leydig cells. Tyro 3, Axl and Mer are all normally expressed by Sertoli cells during postnatal development, whereas their ligands, Gas6 and protein S, are produced by Leydig cells before sexual maturity, and by both Leydig and Sertoli cells thereafter. Here we show that the concerted activation of Tyro 3, Axl and Mer in Sertoli cells is critical to the role that these cells play as nurturers of developing germ cells. Additional observations indicate that these receptors may also be essential for the tropic maintenance of diverse cell types in the mature nervous, immune and reproductive systems.     

Functional genomics reveal that the serine synthesis pathway is essential in breast cancer

Cancer cells adapt their metabolic processes to drive macromolecular biosynthesis for rapid cell growth and proliferation. RNA interference (RNAi)-based loss-of-function screening has proven powerful for the identification of new and interesting cancer targets, and recent studies have used this technology in vivo to identify novel tumour suppressor genes. Here we developed a method for identifying novel cancer targets via negative-selection RNAi screening using a human breast cancer xenograft model at an orthotopic site in the mouse. Using this method, we screened a set of metabolic genes associated with aggressive breast cancer and stemness to identify those required for in vivo tumorigenesis. Among the genes identified, phosphoglycerate dehydrogenase (PHGDH) is in a genomic region of recurrent copy number gain in breast cancer and PHGDH protein levels are elevated in 70% of oestrogen receptor (ER)-negative breast cancers. PHGDH catalyses the first step in the serine biosynthesis pathway, and breast cancer cells with high PHGDH expression have increased serine synthesis flux. Suppression of PHGDH in cell lines with elevated PHGDH expression, but not in those without, causes a strong decrease in cell proliferation and a reduction in serine synthesis. We find that PHGDH suppression does not affect intracellular serine levels, but causes a drop in the levels of α-ketoglutarate, another output of the pathway and a tricarboxylic acid (TCA) cycle intermediate. In cells with high PHGDH expression, the serine synthesis pathway contributes approximately 50% of the total anaplerotic flux of glutamine into the TCA cycle. These results reveal that certain breast cancers are dependent upon increased serine pathway flux caused by PHGDH overexpression and demonstrate the utility of in vivo negative-selection RNAi screens for finding potential anticancer targets.     

集值映射平衡点集的本质连通区及其应用

用统一的本质连通区的存在性定理重新推导出了集值映射平衡点集的本质连通区的存在性,并给出一个在不动点集中的应用。