A new cytotoxic lanostane-type triterpene glycoside from the sea cucumber Holothuria impatiens

A new lanostane-type triterpene glycoside, impatienside A (1), was isolated from the sea cucumber Holothuria impatiens, together with a structurally related, known compound, bivittoside D (2). Their structures were elucidated by in-depth spectroscopic and mass-spectrometric methods, including (1)H-, (13)C-, and 2D-NMR, ESI-MS, and HR-ESI-MS experiments, as well as by chemical evidence. Compounds 1 and 2 possess the same hexasaccharide moieties, but differ slightly in their holostane-type triterpene aglycone. The two glycosides were found to exhibit in vitro cytotoxicities similar to or better than those of the potent anticancer drug etoposide (V-16) against seven different human tumor cells, with IC50 values of 0.37-2.75 microg/ml.     

Neural precursors derived from human embryonic stem cells

Human embryonic stem (hES) cells provide a promising supply of specific cell types for transplantation therapy. We presented here the method to induce differentiation of purified neural precursors from hES cells. hES cells (Line PKU-1 and Line PKU-2) were cultured in suspension in bacteriological Petri dishes, which differentiated into cystic embryoid bodies (EBs). The EBs were then cultured in N₂ medium containing bFGF in poly-L-lysine-coated tissue culture dishes for two weeks. The central, small cells with 2–3 short processes of the spreading outgrowth were isolated mechanically and replated. The resulting neurospheres were cultured in suspension for 10 days, then dissociated into single cell suspension with a Pasteur pipette and plated. Cells grew vigorously in an attached way and were passed every 4–5 days. Almost all the cells were proved nestin positive by immunostaining. Following withdrawal of bFGF, they differentiated into neurons expressing β-tubulin isotype_III, GABA, serotonin and synaptophysin. Through induction of PDGF-AA, they differentiated into astrocytes expressing GFAP and oligodendrocytes expressing O₄. The results showed that hES cells can differentiate into typical neural precursors expressing the specific marker nestin and capable of generating all three cell types of the central nervous system (CNS)in vitro.     

A simple and computationally efficient sampling approach to covariate adjustment for multifactor dimensionality reduction analysis of epistasis

Epistasis or gene-gene interaction is a fundamental component of the genetic architecture of complex traits such as disease susceptibility. Multifactor dimensionality reduction (MDR) was developed as a nonparametric and model-free method to detect epistasis when there are no significant marginal genetic effects. However, in many studies of complex disease, other covariates like age of onset and smoking status could have a strong main effect and may potentially interfere with MDR's ability to achieve its goal. In this paper, we present a simple and computationally efficient sampling method to adjust for covariate effects in MDR. We use simulation to show that after adjustment, MDR has sufficient power to detect true gene-gene interactions. We also compare our method with the state-of-art technique in covariate adjustment. The results suggest that our proposed method performs similarly, but is more computationally efficient. We then apply this new method to an analysis of a population-based bladder cancer study in New Hampshire.     

国产野生薄荷挥发油化学组分变异及其化学型

采用气－质联用的方法,对国产野生薄荷（ＭｅｎｔｈａｈａｐｌｏｃａｌｙｘＢｒｉｑ．）居群的挥发油成分进行了分析,２２个样品可归纳为６个化学型：（１）薄荷酮－胡薄荷酮型（ｍｅｎｔｈｏｎｅ－ｐｕｌｅｇｏｎｅｔｙｐｅ）;（２）胡椒酮型（ｐｉｐｅｒｉｔｏｎｅｔｙｐｅ）;（３）氧化胡椒酮－氧化胡椒烯酮型（ｐｉｐｅｒｉｔｏｎｅｏｘｉｄｅ－ｐｉｐｅｒｉｔｅｎｏｎｅｏｘｉｄｅｔｙｐｅ）;（４）芳樟醇－氧化胡椒酮型（ｌｉｎａｌｏｏｌ－ｐｉｐｅｒｉｔｏｎｅｏｘｉｄｅｔｙｐｅ）;（５）香芹酮型（ｃａｒｖｏｎｅｔｙｐｅ）;（６）薄荷醇－乙酸薄荷酯型（ｍｅｎｔｈｏｌ－ｍｅｎｔｈｙｌａｃｅｔａｔｅｔｙｐｅ）。结合地理分布和薄荷属单萜类成分生物合成途径,对上述主要类型进行了讨论。     

十字花科四属植物叶片的表皮特征

对十字花科岩荠属、阴山荠属、泡果荠属、棒毛荠 属植物的叶表皮特征进行了扫描电镜观察,结果表明：表皮细胞多为不规则形,气孔主要分布于表皮,垂周壁上有明显的波状嵴或沟槽状下陷,平周壁上有各咱条纹状角质层纹饰。这些微形态特征在属间有明显的类群特异性,又有一定的过渡类型,为岩荠属及近缘属的合理划分提供一定的证据。     

Gradient directed regularization for sparse Gaussian concentration graphs, with applications to inference of genetic networks

Large-scale microarray gene expression data provide the possibility of constructing genetic networks or biological pathways. Gaussian graphical models have been suggested to provide an effective method for constructing such genetic networks. However, most of the available methods for constructing Gaussian graphs do not account for the sparsity of the networks and are computationally more demanding or infeasible, especially in the settings of high dimension and low sample size. We introduce a threshold gradient descent (TGD) regularization procedure for estimating the sparse precision matrix in the setting of Gaussian graphical models and demonstrate its application to identifying genetic networks. Such a procedure is computationally feasible and can easily incorporate prior biological knowledge about the network structure. Simulation results indicate that the proposed method yields a better estimate of the precision matrix than the procedures that fail to account for the sparsity of the graphs. We also present the results on inference of a gene network for isoprenoid biosynthesis in Arabidopsis thaliana. These results demonstrate that the proposed procedure can indeed identify biologically meaningful genetic networks based on microarray gene expression data.     

极端嗜热菌海栖热袍菌α-葡萄糖醛酸酶的高效表达和重组酶的纯化

α-葡萄糖醛酸酶作为木聚糖降解的限速酶之一,在木聚糖类半纤维素的生物转化中起着重要的作用。海栖热袍菌Thermotoga maritima是一个嗜极端高温的厌氧细菌,其产生的极耐热性酶类具有非常可观的工业应用前景。但热袍菌属Thermotoga的基因在大肠杆菌中的表达一般较困难。研究了T. maritima中的极耐热性α葡萄糖醛酸酶基因在大肠杆菌不同菌株中的表达水平及纯化技术。结果表明,稀有密码子AGA、AGG和AUA限制了该基因在大肠杆菌中的表达,在大肠杆菌BL21-CodonPlus(DE3)RIL可得到高效表达,重组蛋白表达量达20%,比酶活比野生菌株提高5倍;重组蛋白经热处理和金属Ni²⁺的亲和层析提纯后,达到了电泳纯,提纯倍数为5.1倍,收率为55.1%。对重组菌诱导表达条件的研究表明,营养丰富的TB培养基有助于重组菌的生长, 重组菌生长至OD₆₀₀为0.7～0.8时添加IPTG诱导5h后重组蛋白的表达量最高。     

生长激素促分泌素受体(GHS-R)的发现及影响

生长激素的分泌不仅受到GHRH、SRIF的调节 ,还受到GHS R及其配体GHS的作用。本文综述了GHS R的发现背景、结构特点以及生理功能 ,讨论了GHS R促GH分泌的分子机制及其对多种组织器官可能影响 ,同时还探讨了除Ia和Ib亚型外还存在其它GHS R亚型的可能性。     

人胚不同脑区神经前体细胞的分离培养及分化特性的比较

目的研究人胚不同脑区神经前体细胞(neural progenitor cells,NPCs)培养及增殖分化特性。方法取14-17周人胚脑区组织,分为新皮质、纹状体、间脑、中脑、后脑和延髓组,悬浮培养。鉴定细胞球巢蛋白抗原的表达,分化及自我更新能力。观察各脑区培养细胞的生长、增殖状况。新皮质、纹状体及间脑来源的神经球分化后,运用免疫荧光细胞化学法比较神经元及星形胶质细胞的比例。结果各脑区培养出的悬浮细胞球巢蛋白抗原阳性,可分化为MAP2或GFAP阳性细胞,且BrdU掺入实验阳性。体外培养第3d,纹状体及间脑组均可见大量神经球,且纹状体组明显多于间脑组;新皮质组传代后可见较多神经球;其它组仅见个别神经球。新皮质、纹状体、间脑来源的NPCs诱导分化后,MAP2或GFAP阳性细胞率各组间比较差异无显著性。结论人胚不同脑区均可培养出NPCs,从易到难依次为纹状体、间脑、新皮质及其它脑区。新皮质、纹状体、间脑来源的NPCs体外分化比例一致。     

基于投入产出分析的中国生态足迹模型

基于投入产出分析技术的生态足迹（EF）核算模型是目前国际生态承载力研究的热点模型之一。在已有研究的基础上,引入土地利用差异转化系数（某类土地利用的产量因子与其均衡因子的乘积）改进模型,以保证投入产出表的行、列组分加和操作的有效性。研究以货币型投入产出表为基础核算中国1997年的EF,分析表明：（1）1997年中国为EF净出口国,人均EF贸易逆差0．050hm^2,占生产包含足迹的3．4％;（2）最终使用的人均EF为1．435hm^2（能源足迹占45．1％）,其中,2／3缘于居民消费,另1／3缘于资本形成;（3）第一、二、三产业包含的人均EF依次为0．499、0．721hm^2和0．183hm^2。其中,第一产业以直接占用生态空间为主,而第二、三产业以间接占用为主,如第二产业的隐藏性非能源足迹是其直接值的140余倍;（4）三大产业部门中,第三产业最终产品消费的EF最小,人均0．183hm^2,而其土地利用的经济效率最高,为0．898万元hm^-2。实践表明基于投入产出分析的EF模型不仅承袭了EF基本模型的优点,而且结构性能好,能同时识别社会各生产和消费部门的生态压力及其在不同部门之间的流转情况,并可有效避免足迹组分的重复计算。