视力与视觉诱发电位的相关分析

对104例病人的图形翻转VEP的瞬态波形各参数,以及9例正常或近视学生的稳态曲线功率谱与视力之间的关系进行了多元相关统计分析,旨在探讨VEP的哪些参数可客观地评估视力.结果表明,瞬态VEP的波形参数中以13’格诱发的N_1P_1、P_1N_2的峰峰值及P_(100)潜伏期与视力的相关系数最大,故认为,分析视力时以平均P_(100)波的波幅值和P_(100)波潜伏期作指标较为灵敏;而稳态、VEP能谱曲线则显示,视力与平均相叶能谱或刺激频率点的能谱相关性较大,与二次谐波的相关性则小.     

Plant regeneration via somatic embryogenesis of Elymus sibiricus cv. ‘chuancao No. 2’

The mature seeds, mesocotyls, and young leaf tips of Elymus sibiricus L. cv. ‘chuancao No. 2’ were cultured on Murashige and Skoog (MS) medium supplemented with 5.0 mg/L 2,4-dichlorophenoxyacetic acid (2,4-d) and 0.05 mg/L kinetin in the dark at 26°C, the calluses were produced. The rate of callus regeneration depended on the explants source and plant growth regulators. Plants regenerated from whitish-yellow-coloured compact nodular callus formed after subculturing for 8 weeks. Higher frequency (54%) of shoot differentiation was obtained from the embryo tissues of mature seed than from either mesocotyls (24%) or young leaf tip tissues (6%) when these calluses from different types of explants were cultured on plant regeneration medium containing half strength MS salts supplemented with 0.1 mg/L kinetin, 1.5 mg/L 2,4-D and 20 g/L sucrose. The green plants were rooted within 6 weeks in the root regeneration medium, and over 97% of these soil-established plants were obtained in the greenhouse when potted in a sand and peat mixture medium.     

应用基因敲除快速构建大肠杆菌突变体改造脂肪酸代谢途径

【目的】基因敲除技术是研究基因功能的重要手段。我们试图建立一种快速、高效的大肠杆菌基因敲除方法。【方法】利用大肠杆菌(Escherichia coli)BW25113单基因缺失体Keio文库,将经典的Red同源重组技术与P1噬菌体转导技术相结合,对E.coli MG1655脂肪酸代谢基因进行快速敲除。【结果】获得了大肠杆菌β-氧化途径的缺失菌株△fadD、△fadE和△fadD-△fadE;脂肪酸合成途径缺失菌株△fabH、△fabF和△fabH-△fabF。敲除fadD和fadE对生长情况没有影响;敲除fabH后,生长速度明显减慢;敲除fabF对生长几乎没有影响。FadD、FadE及双敲缺失体的脂肪酸含量18.2 mg/L、20.0mg/L和19.2 mg/L,略高于野生型17.5 mg/L;FabH、FabF及双敲缺失体的含量分别为12.6 mg/L、15.2 mg/L和11.2 mg/L,明显低于野生型。【结论】在单基因突变体文库基础上,利用P1噬菌体转导、Red同源重组和抗性基因消除进行基因敲除,简化了构建大肠杆菌单基因和多重突变体的方法。     

竞争性内源RNA的生物学功能及其调控

最新研究表明,RNA之间可以通过竞争结合共同的microRNA反应元件(microRNA response element, MRE)实现相互调节,这种调控模式构成竞争性内源RNA(Competing endogenous RNA, ceRNA)。已发现的ceRNA包括蛋白编码mRNA和非编码RNA,其中后者包括假基因转录物、长链非编码RNA(Long non-coding RNA, lncRNA)、环状RNA(Circular RNA, circRNA)等。文章主要从ceRNA分类的角度,阐述各类ceRNA构成的调控网络发挥的生物学功能在病理和生理相关过程中的作用,以及可能影响ceRNA调控有效性的因素。     

生态系统服务簇空间演变轨迹及其社会-生态驱动的地理探测——以大连市为例

生态系统服务簇是多种生态系统服务的组合,明晰生态系统服务簇及其自然-社会经济驱动因素,对生态系统服务内部相互依赖机制识别、实现多种生态系统服务间良性互动具有重要意义。目前生态系统服务簇的识别已得到广泛应用,但对多种生态系统服务之间交互作用的动态过程与影响机理的认识还不够深刻。针对目前多种生态系统服务间交互作用动态演化分析及其社会-生态驱动机理研究不足的现状,以我国北方沿海重要中心城市——大连市为例,选取食物供给、水源涵养、固碳释氧、土壤保持、生境质量和景观美学6种关键服务。采用Spearman相关性分析方法探究生态系统服务权衡与协同关系,借助自组织网络方法识别生态系统服务簇,进一步分析多种生态系统服务间交互作用的时空分异特征,运用地理探测器探究其空间分异影响因素。结果表明：(1)食物供给与土壤保持存在极显著的权衡关系■,土壤保持与景观美学存在极显著的协同关系■。(2)2005—2015年大连市生态保育簇空间格局较稳定,水源涵养簇、食物供给簇与服务枯竭簇之间轨迹变化明显,城市扩张与服务枯竭簇演变具有一致性。(3)高程、归一化植被指数是影响生态系统服务簇空间分布的关键自然因素,而土地利用强...     

基于能值分析的中国海洋生态经济可持续发展评价

海洋生态经济可持续发展的研究既是生态经济研究的重要领域,也是海洋经济研究的重点领域。运用能值分析构建中国海洋生态经济系统能值分析模型和指标体系,以中国沿海地区及其附近海域为研究区域,利用2013年的数据对中国海洋生态经济系统的可持续发展水平进行能值测度。研究表明:(1)2013年,中国沿海各省的海洋生态经济总能值为1.70×10~(24)sej,可更新资源能值占主体地位。(2)受沿海各省海洋经济发展水平不同和区域海洋资源储量影响,中国沿海地区海洋生态经济能值密度分布差异较大,能值货币比率以上海为界,南高北低,高中低3种能值产出率结构并存且以中能值产出率结构为主。(3)中国海洋生态经济系统的生态承载力以高承载力和较高承载力为主,但局部地区海洋生态承载力偏低影响区域海洋生态系统平衡。中国海洋生态经济系统环境负载率较大,环境负载率高的地区与我国海洋经济发达地区高度耦合。(4)从可持续发展指数来看,中国海洋生态经济发展的整体可持续性较好,局部地区环境负载率过大和生态承载力偏低严重制约着区域海洋生态经济的可持续发展。     

Comparative genomics reveals different population structures associated with host and geographic origin in antimicrobial-resistant Salmonella enterica

Genetic variation in a pathogen, including the causative agent of salmonellosis, Salmonella enterica, can occur as a result of eco-evolutionary forces triggered by dissimilarities of ecological niches. Here, we applied comparative genomics to study 90 antimicrobial resistant (AMR) S. enterica isolates from bovine and human hosts in New York and Washington states to understand host- and geographic-associated population structure. Results revealed distinct presence/absence profiles of functional genes and pseudogenes (e.g., virulence genes) associated with bovine and human isolates. Notably, bovine isolates contained significantly more transposase genes but fewer transposase pseudogenes than human isolates, suggesting the occurrence of large-scale transposition in genomes of bovine and human isolates at different times. The high correlation between transposase genes and AMR genes, as well as plasmid replicons, highlights the potential role of horizontally transferred transposons in promoting adaptation to antibiotics. By contrast, a number of potentially geographic-associated single-nucleotide polymorphisms (SNPs), rather than geographic-associated genes, were identified. Interestingly, 38% of these SNPs were in genes annotated as cell surface protein-encoding genes, including some essential for antibiotic resistance and host colonization. Overall, different evolutionary forces and limited recent inter-population transmission appear to shape AMR S. enterica population structure in different hosts and geographic origins.     

Effects of a Potential Host Gut-Derived Probiotic,Bacillus subtilis 6-3-1, on the Growth,Non-specific Immune Response and Disease Resistance of Hybrid Grouper (Epinephelus fuscoguttatus♀ × Epinephelus lanceolatus♂)

Probiotics and Antimicrobial Proteins - A potential host-derived probiotic, Bacillus subtilis 6-3-1, was successfully screened from 768 isolates from the intestines of healthy hybrid grouper...     

Suppression of defective ribosome assembly in a rbfA deletion mutant by overexpression of Era,an essential GTPase in Escherichia coli

Era is a small GTP-binding protein and essential for cell growth in Escherichia coli. It consists of two domains: N-terminal GTP-binding and C-terminal RNA-binding KH domains. It has been shown to bind to 16S rRNAs and 30S ribosomal subunits in vitro. Here, we report that a precursor of 16S rRNA accumulates in Era-depleted cells. The accumulation of the precursors is also seen in a cold-sensitive mutant, E200K, in which the mutation site is located in the C-terminal domain. The major precursor molecule accumulated seems to be 17S rRNA, containing extra sequences at both 5' and 3' ends of 16S rRNA. Moreover, the amounts of both 30S and 50S ribosomal subunits relative to the amount of 70S monosomes increase in Era-depleted and E200K mutant cells. The C-terminal KH domain has a high structural similarity to the RbfA protein, a cold shock protein that also specifically associates with 30S ribosomal subunits. RbfA is essential for cell growth at low temperature, and a precursor of 16S rRNA accumulates in an rbfA deletion strain. The 16S rRNA precursor seems to be identical in size to that accumulated in Era mutant cells. Surprisingly, the cold-sensitive cell growth of the rbfA deletion cells was partially suppressed by overproduction of the wild-type Era. The C-terminal domain alone was not able to suppress the cold-sensitive phenotype, whereas Era-dE, which has a 10-residue deletion in a putative effector region of the N-terminal domain, functioned as a more efficient suppressor than the wild-type Era. It was found that Era-dE suppressed defective 16S rRNA maturation, resuming a normal polysome profile to reduce highly accumulated free 30S and 50S subunits in the rbfA deletion cells. These results indicate that Era is involved in 16S rRNA maturation and ribosome assembly.     

Mesenchymal stem cells protect islets from hypoxia/reoxygenation-induced injury

Hypoxia/reoxygenation (H/R)‐induced injury is the key factor associated with islet graft dysfunction. This study aims to examine the effect of mesenchymal stem cells (MSCs) on islet survival and insulin secretion under H/R conditions. Islets from rats were isolated, purified, cultured with or without MSCs, and exposed to hypoxia (O₂ ≤ 1%) for 8 h and reoxygenation for 24 and 48 h, respectively. Islet function was evaluated by measuring basal and glucose‐stimulated insulin secretion (GSIS). Apoptotic islet cells were quantified using Annexin V‐FITC. Anti‐apoptotic effects were confirmed by mRNA expression analysis of hypoxia‐resistant molecules, HIF‐1α, HO‐1, and COX‐2, using semi‐quantitative retrieval polymerase chain reaction (RT‐PCR). Insulin expression in the implanted islets was detected by immunohistological analysis. The main results show that the stimulation index (SI) of GSIS was maintained at higher levels in islets co‐cultured with MSCs. The MSCs protected the islets from H/R‐induced injury by decreasing the apoptotic cell ratio and increasing HIF‐1α, HO‐1, and COX‐2 mRNA expression. Seven days after islet transplantation, insulin expression in the MSC‐islets group significantly differed from that of the islets‐alone group. We proposed that MSCs could promote anti‐apoptotic gene expression by enhancing their resistance to H/R‐induced apoptosis and dysfunction. This study provides an experimental basis for therapeutic strategies based on enhancing islet function. Copyright © 2010 John Wiley & Sons, Ltd.