汉阳陵文物表面硫酸盐形成原因微生物学证据

用仅含硫源的无机盐培养基对采自汉阳陵13号和15号遗址坑文物表面的土样进行细菌富集筛选实验,并对分离的菌株进行生理生化特性研究、16SrDNA序列分析及硫代谢能力测试。分离得到5株细菌:TD1、TD2、TD3、TD15及PL13。其中TD1属于Alcaligenes,TD3属于Bacillus;硫代谢能力测试结果显示TD2、TD15和PL13代谢产生硫酸盐的速率远远小于TD3和TD1,TD3氧化硫源生成硫酸盐的速率是TD1的1.4倍。实验证实这些菌株均能氧化S、S2O32-和S2-生成硫酸盐从而获得能量,这表明微生物氧化土壤中硫化物是汉阳陵文物表面硫酸盐增加的原因,从而为汉阳陵文物表面硫酸盐的形成原因提供了微生物学依据。     

金葡菌L型感染致小鼠肿瘤中CyclinD1、CDK4和P16的表达及意义

目的探讨金黄色葡萄球菌(金葡菌)L型感染C57小鼠致瘤后,CyclinD1、CDK4和P16在小鼠肿瘤及癌前病变中的表达及相关性研究。方法动物实验观察发现金葡菌L型感染90只C57小鼠后11.1%(10/90)发生肿瘤;14.4%(13/90)引起癌前病变。革兰染色、免疫组化染色,检测小鼠肿瘤和癌前病变中金葡菌L型感染率和CyclinD1、CDK4和P16蛋白的阳性表达。结果 10只小鼠肿瘤及13只小鼠癌前病变中金葡菌L型检出率与正常对照组比较差异有明显统计学意义(P0.01)。CyclinD1、CDK4和P16蛋白的阳性表达与正常对照组比较差异有统计学意义(P0.01～0.05),呈正相关。结论金葡菌L型感染可能与CyclinD1、CDK4和P16蛋白在小鼠肿瘤发生和发展中有协同作用。     

海洋喇叭虫rRNA基因18S-ITS1序列及其系统发育分析

海洋喇叭虫Maristentor dinoferus 1996年在关岛(Guam)的珊瑚暗礁上被发现,至今尚未阐明其确切的系统发育地位.克隆到的海洋喇叭虫的18S-ITS1-5.8S rDNA序列包括222 bp的18S序列,77 bp的ITS1序列和22 bp的5.8S序列.比较分析了纤毛虫主要类群的ITS1序列后得出:短的ITS1序列可能是异毛类纤毛虫的特征.根据18S序列,利用邻接法构建,最大简约法和最大似然法构建系统发育树.其拓扑结构显示海洋喇叭虫属于异毛纲纤毛虫,但并不隶属喇叭虫科,应予以新的分类地位.     

The emerging potential of autophagy-based therapies in the treatment of cystic fibrosis lung infections

Cystic fibrosis (CF) is caused by mutations in the CF transmembrane conductance regulator (CFTR), a channel that normally transports anions across epithelial cell membranes. The most common manifestation of CF is buildup of mucus in the airways and bacterial colonization of the lower respiratory tract, accompanied by chronic inflammation. Antibiotics are used to control CF-associated opportunistic infections, but lengthy antibiotic treatment risks the emergence of multiple-drug resistant (MDR) strains. New antimicrobial strategies are needed to prevent and treat infections in these high-risk individuals. Autophagy contributes to the control of a variety of microbial infections. For this reason, the recent discovery of functional impairment of autophagy in CF provides a new basis for understanding susceptibility to severe infections. Here, we review the role of autophagy in host defense against CF-associated bacterial and fungal pathogens, and survey pharmacologic approaches to restore normal autophagy function in these individuals. Autophagy restoration therapy may improve pathogen clearance and mitigate lung inflammation in CF airways.     

Solution structure of ribosomal protein S28E from Methanobacterium thermoautotrophicum

The ribosomal protein S28E from the archaeon Methanobacterium thermoautotrophicum is a component of the 30S ribosomal subunit. Sequence homologs of S28E are found only in archaea and eukaryotes. Here we report the three-dimensional solution structure of S28E by NMR spectroscopy. S28E contains a globular region and a long C-terminal tail protruding from the core. The globular region consists of four antiparallel beta-strands that are arranged in a Greek-key topology. Unique features of S28E include an extended loop L2-3 that folds back onto the protein and a 12-residue charged C-terminal tail with no regular secondary structure and greater flexibility relative to the rest of the protein. The structural and surface resemblance to OB-fold family of proteins and the presence of highly conserved basic residues suggest that S28E may bind to RNA. A broad positively charged surface extending over one side of the beta-barrel and into the flexible C terminus may present a putative binding site for RNA.     

Role of polyamines in regulating silymarin production in Silybum marianum (L.) Gaertn (Asteraceae) cell cultures under conditions of calcium deficiency

As part of our efforts to identify the possible role of polyamines (PAs) in silymarin (Sm) production, the effects of calcium deprivation on cell growth and on endogenous PAs levels and Sm production by milk thistle (Silybum marianum (L.) Gaertn) grown in cell cultures were examined. Young cultured cells of the H2 line of S. marianum were transferred to a medium without calcium and with ethylene glycol-bis-(β-aminoethyl) ether-N,N,N′,N′-tetraacetic acid present to chelate any free calcium in order to analyze the effects of this medium on the levels of PAs and Sm produced by the cells. During the 17 days of exposure to this calcium-free medium most of the cell populations were in the G0/G1 phase (from day 7 to day 14 of culture) while PA levels underwent a progressive decline up to day 17, after which they were no longer detectable. We observed that putrescine (Put) accumulation was always lower than that observed under normal conditions. The lack of calcium in the MS medium advances the onset of the stationary phase, whose beginning is marked by an increase in the Put/spermidine (Spd) index, raising the production of Sm; the suspensions were productive for a longer time and hence produced more of the substance. Our results indicate that under stress conditions the production of Sm in young-cell suspensions of S. marianum is not associated with high levels of PAs in the medium – contrary to what one would expect – allowing us to conclude that growth inhibition appears to be the factor responsible for the maximum Sm accumulation while PAs are not directly involved in the Sm synthesis pathway by milk thistle grown in culture.     

Recombinase-mediated cassette exchange (RMCE) — A rapidly-expanding toolbox for targeted genomic modifications

Starting in 1991, the advance of Tyr-recombinases Flp and Cre enabled superior strategies for the predictable insertion of transgenes into compatible target sites of mammalian cells. Early approaches suffered from the reversibility of integration routes and the fact that co-introduction of prokaryotic vector parts triggered uncontrolled heterochromatization. Shortcomings of this kind were overcome when Flp-Recombinase Mediated Cassette Exchange entered the field in 1994. RMCE enables enhanced tag-and-exchange strategies by precisely replacing a genomic target cassette by a compatible donor construct. After “gene swapping” the donor cassette is safely locked in, but can nevertheless be re-mobilized in case other compatible donor cassettes are provided (“serial RMCE”). These features considerably expand the options for systematic, stepwise genome modifications. The first decade was dominated by the systematic generation of cell lines for biotechnological purposes. Based on the reproducible expression capacity of the resulting strains, a comprehensive toolbox emerged to serve a multitude of purposes, which constitute the first part of this review. The concept per se did not, however, provide access to high-producer strains able to outcompete industrial multiple-copy cell lines. This fact gave rise to systematic improvements, among these certain accumulative site-specific integration pathways. The exceptional value of RMCE emerged after its entry into the stem cell field, where it started to contribute to the generation of induced pluripotent stem (iPS-) cells and their subsequent differentiation yielding a variety of cell types for diagnostic and therapeutic purposes. This topic firmly relies on the strategies developed in the first decade and can be seen as the major ambition of the present article. In this context an unanticipated, potent property of serial Flp-RMCE setups concerns the potential to re-open loci that have served to establish the iPS status before the site underwent the obligatory silencing process. Other relevant options relate to the introduction of composite Flp-recognition target sites (“heterospecific FRT-doublets”), into the LTRs of lentiviral vectors. These “twin sites” enhance the safety of iPS re-programming and -differentiation as they enable the subsequent quantitative excision of a transgene, leaving behind a single “FRT-twin”. Such a strategy combines the established expression potential of the common retro- and lentiviral systems with options to terminate the process at will. The remaining genomic tag serves to identify and characterize the insertion site with the goal to identify genomic “safe harbors” (GOIs) for re-use. This is enabled by the capacity of “FRT-twins” to accommodate any incoming RMCE-donor cassette with a compatible design.     

血卵涡鞭虫核糖体18SrDNA和ITS1-5.8SrDNA-ITS2序列测定与系统发育分析

{{@ convertAbstractHtml(article.abstractinfoCn, "cn")}}       

A diterpenoid derivate compound targets selenocysteine of thioredoxin reductases and induces Bax/Bak-independent apoptosis

We have previously shown that the natural diterpenoid derivative S3 induced Bim upregulation and apoptosis in a Bax/Bak-independent manner. However, the exact molecular target(s) of S3 and the mechanism controlling Bim upregulation are still not clear. Here, we identify that S3 targets the selenoproteins TrxR1 and TrxR2 at the selenocysteine residue of the reactive center of the enzymes and inhibits their antioxidant activities. Consequently, cellular ROS is elevated, leading to the activation of FOXO3a, which contributes to Bim upregulation in Bax/Bak-deficient cells. Moreover, S3 retards tumor growth in subcutaneous xenograft tumors by inhibiting TrxR activity in vivo. Our studies delineate the signaling pathway controlling Bim upregulation, which results in Bax/Bak-independent apoptosis and provide evidence that the compounds can act as anticancer agents based on mammalian TrxRs inhibition.