可控多孔生物陶瓷制备技术中保温时间的影响研究

保温时间是可控多孔生物陶瓷制备技术的重要影响因之一。为了得到这具体影响,特对其进行了研究和探讨。研究结果表明,保温时间对孔结构、气孔率与容重、水渗透率、收缩率以及强度有着重要的影响。     

Extended periods of neural induction and propagation of embryonic stem cell-derived neural progenitors with EGF and FGF2 enhances Lmx1a expression and neurogenic potential

Neural stem (NS) cells are multipotent cells defined by their capacity to proliferate and differentiate into all neuronal and glial phenotypes. NS cells can be obtained from specific regions of the adult brain, or generated from embryonic stem cells (ESCs). NS cells differentiate into neural progenitor (NP) cells and subsequently neural precursors, as transient steps towards terminal differentiation into specific mature neuronal or glial phenotypes. When cultured in EGF and FGF2, ESC-derived NS cells have been reported to be stable and multipotent. Conditions that enable differentiation of NS cells through the committed progenitor and precursor stages to specific neuronal subtypes have not been fully established. In this study we investigated, using Lmx1a reporter ESCs, whether the length of neural induction (NI) dictated the phenotypic potential of cultures of ESC-derived NS cells or NP cells. Following 4, 7 or 10 day periods of NI, ESCs in monolayer culture were harvested and cultured as neurospheres, prior to replating as monolayer cultures for several passages in EGF and FGF2. The NS/NP cultures were then directed towards mature neuronal fates over 16-17 days. 4 and 7-day NS cell cultures could not be differentiated towards dopaminergic, serotonergic or cholinergic fates as determined by the absence of tyrosine hydroxylase, 5-HT or choline acetyltransferase (ChAT) immunolabelling. In contrast NS/NP cultures derived after 10 days of NI were able to generate tyrosine hydroxylase and 5-HT positive neurons (24 ± 6 and 13 ± 1% of the βIII-tubulin positive population, respectively, n = 3). Our data suggest that extended periods of neural induction enhanced the potential of mouse ESC-derived NS/NP cells to generate specific subtypes of neurons. NS/NP cells derived after shorter periods of NI appeared to be lineage-restricted in relation to the neuronal subtypes observed after removal of EGF.     

三门湾大型底栖动物时空分布及其与环境因子的关系

2006年11月、2007年1月、4月和8月在三门湾18个采样点对大型底栖动物进行调查,分析了其时空分布及其与环境因子的关系.结果表明:调查共采集到大型底栖动物124种,其中多毛类44种、软体动物34种、甲壳动物22种、棘皮动物11种、其他类动物13种;多毛类和软体动物种数占总种数的62.9％,二者构成了三门湾大型底栖动物的主要类群.双鳃内卷齿蚕、小头虫和不倒翁虫是春季三门湾大型底栖动物的优势种;不倒翁虫、双鳃内卷齿蚕和海稚虫为夏季的优势种;不倒翁虫、小头虫、双鳃内卷齿蚕和白沙箸为秋季的优势种;双鳃内卷齿蚕、不倒翁虫、小头虫和海稚虫为冬季的优势种.三门湾大型底栖动物年均生物量为17.36 g·m-2,年均栖息密度为72 ind·m-2.不同季节大型底栖动物的平均生物量和平均栖息密度存在显著性差异.大型底栖动物群落平均Shannon多样性指数在1.53 ～ 1.89,平均Margalef物种丰富度指数在2.25 ～2.96,平均均匀度指数在0.83 ～0.94,3个指数在不同季节间均存在显著性差异.经典范对应分析,影响三门湾大型底栖动物群落的主要环境因子包括海水的温度、盐度、溶解性无机氮以及表层沉积物中的有机质、总氮和总磷等,环境变量可以较好地解释主要类群的变化.     

Following cell-fate in E. coli after infection by phage lambda

The system comprising bacteriophage (phage) lambda and the bacterium E. coli has long served as a paradigm for cell-fate determination. Following the simultaneous infection of the cell by a number of phages, one of two pathways is chosen: lytic (virulent) or lysogenic (dormant). We recently developed a method for fluorescently labeling individual phages, and were able to examine the post-infection decision in real-time under the microscope, at the level of individual phages and cells. Here, we describe the full procedure for performing the infection experiments described in our earlier work. This includes the creation of fluorescent phages, infection of the cells, imaging under the microscope and data analysis. The fluorescent phage is a "hybrid", co-expressing wild- type and YFP-fusion versions of the capsid gpD protein. A crude phage lysate is first obtained by inducing a lysogen of the gpD-EYFP (Enhanced Yellow Fluorescent Protein) phage, harboring a plasmid expressing wild type gpD. A series of purification steps are then performed, followed by DAPI-labeling and imaging under the microscope. This is done in order to verify the uniformity, DNA packaging efficiency, fluorescence signal and structural stability of the phage stock. The initial adsorption of phages to bacteria is performed on ice, then followed by a short incubation at 35°C to trigger viral DNA injection. The phage/bacteria mixture is then moved to the surface of a thin nutrient agar slab, covered with a coverslip and imaged under an epifluorescence microscope. The post-infection process is followed for 4 hr, at 10 min interval. Multiple stage positions are tracked such that ~100 cell infections can be traced in a single experiment. At each position and time point, images are acquired in the phase-contrast and red and green fluorescent channels. The phase-contrast image is used later for automated cell recognition while the fluorescent channels are used to characterize the infection outcome: production of new fluorescent phages (green) followed by cell lysis, or expression of lysogeny factors (red) followed by resumed cell growth and division. The acquired time-lapse movies are processed using a combination of manual and automated methods. Data analysis results in the identification of infection parameters for each infection event (e.g. number and positions of infecting phages) as well as infection outcome (lysis/lysogeny). Additional parameters can be extracted if desired.     

间充质干细胞向成骨细胞分化的信号通路

间充质干细胞具有向成骨细胞分化的潜能,可体外分离、培养和扩增,是骨组织工程中理想的种子细胞。近年的研究表明间充质干细胞的成骨分化受到多种信号通路的调控,现就其中研究较为深入的MAPK和Notch通路的情况作一简要综述。     

Low molecular weight polyethylenimines linked by beta-cyclodextrin for gene transfer into the nervous system

BACKGROUND: Polyethylenimines (PEIs) with high molecular weights are effective nonviral gene delivery vectors. However, the in vivo use of these PEIs can be hampered by their cellular toxicity. In the present study we developed and tested a new PEI polymer synthesized by linking less toxic, low molecular weight (MW) PEIs with a commonly used, biocompatible drug carrier, beta-cyclodextrin (CyD). METHODS AND RESULTS: The terminal CyD hydroxyl groups were activated by 1,1'-carbonyldiimidazole. Each activated CyD then linked two branched PEI molecules with MW of 600 Da to form a CyD-containing polymer with MW of 61 kDa, in which CyD served as a part of the backbone. The PEI-CyD polymer developed was soluble in water and biodegradable. In cell viability assays with sensitive neurons, the polymer performed similarly to low-MW PEIs and displayed much lower cellular cytotoxicity compared to PEI 25 kDa. The gene delivery efficiency of the polymer was comparable to, and at higher polymer/DNA ratios even higher than, that offered by PEI 25 kDa in neural cells. Attractively, intrathecal injection of plasmid DNA complexed by the polymer into the rat spinal cord provided levels of gene expression close to that offered by PEI 25 kDa. CONCLUSIONS: The polymer reported in the current study displayed improved biocompatibility over non-degradable PEI 25 kDa and mediated gene transfection in cultured neurons and in the central nervous system effectively. The new polymer would be worth exploring further as an in vivo delivery system of therapeutic genetic materials for gene therapy of neurological disorders.     

彩色豆马勃子实体的化感作用及其化感物质的分离鉴定

彩色豆马勃能与松树、桉树形成外生菌根,研究其次生代谢产物对植物的影响具有重要意义。用水、乙醇和丙酮抽提彩色豆马勃的子实体,发现这些抽提物对稗草和水稻幼苗生长有极显着的抑制作用。丙酮抽提物对狼尾草和油菜幼苗生长有抑制作用。子实体的丙酮抽提物用硅胶柱色谱分离得到2个纯化合物,可鉴定为豆马勃内酯(Pisolactone)和麦角甾醇。该2个化合物在400μg·ml^-1浓度下均显着抑制稗草幼苗根生长。豆马勃内酯在100μg·ml^-1浓度下仍然极显着抑制稗草幼苗根生长.     

副溶血性弧菌全基因组DNA芯片的研制和芯片质量的评价

摘要 目的 研制副溶血性弧菌全基因组芯片,建立芯片杂交方法,并对芯片质量进行评价。方法 利用副溶血性弧菌全基因组序列,挑选出4770条基因,PCR扩增各基因并将PCR产物纯化,点样制备芯片;设计了两个质控杂交组合,采用双色荧光杂交策略,对芯片质量进行评价;PCR方法验证部分芯片结果。结果 芯片杂交与理论预期结果以及PCR验证结果完全一致。结论 成功的研制了一批质量良好的副溶血性弧菌全基因组DNA芯片,并建立了基于DNA芯片的副溶血性弧菌比较基因组学技术平台,建立了一套系统的芯片数据分析的标准方法。     

Aldose reductase is a potent regulator of TGF-β1 induced expression of fibronectin in human mesangial cells

Glomerulosclerosis is considered to be the final pathway leading to the progressive loss of renal function in several kidney diseases, transforming growth factor β1 (TGF-β1) plays a critical role in glomerulosclerosis. However, the mechanisms of TGF-β1 stimulating glomerulosclerosis remain poorly understood. Here we report that TGF-β1-induced expression of fibronectin (FN) depends on the activity of aldose reductase (AR) in human mesangial cells (HMCs).The results show that TGF-β1 increased the expression of FN, which attenuated by pharmacological inhibition of AR or knockdown of the enzyme by small interfering RNA (siRNA). MAPKs (ERK, JNK and p38) signalling pathways were activated in HMCs after stimulated by TGF-β1, inhibition of AR blunted the activation ERK, p38 and JNK signalling pathways. These changes were associated with decreased TGF-β1-induced expression of FN. These results indicate that AR is a potent regulator of TGF-β1 induced expression of FN in human mesangial cells: it suggests that inhibition of this enzyme may be useful to prevented extracellular matrix (ECM) deposition in glomerulosclerosis.