大肠杆菌K99噬菌体的分离鉴定及在小鼠上的防治效果

【背景】产肠毒素大肠杆菌K99是引起仔猪腹泻的主要致病菌之一,目前对该病的治疗主要依赖于抗生素,但大量抗生素的长期使用造成了病原菌耐药性的增强,亟待寻求一种新的产品来解决这一问题。【目的】以一株产肠毒素大肠杆菌K99为宿主菌,从畜禽粪水中分离噬菌体并对其基本生物学特性进行研究,同时在小鼠上检验噬菌体对小鼠大肠杆菌感染的防治效果。【方法】双层平板法分离筛选烈性噬菌体并观察噬菌斑形态;纯化后进行电镜观察、核酸类型鉴定;测定噬菌体热稳定性、p H稳定性、最佳感染复数及一步生长曲线;通过小鼠体内实验检测噬菌体对小鼠大肠杆菌感染的防治效果。【结果】从畜禽粪水中分离出1株产肠毒素大肠杆菌K99强裂解性噬菌体,命名为ФK99-1,经电镜观察及核酸类型鉴定,应属于肌尾噬菌体科(Myoviridae)。噬菌体能耐受50°C左右的高温,在p H 3.0-10.0范围内效价稳定。最佳感染复数为0.000 01,暴发量为108 333 PFU/cell;运用噬菌体ФK99-1预防和治疗小鼠产肠毒素大肠杆菌K99感染,结果显示小鼠发病症状较阳性对照组明显减轻,小鼠血液内大肠杆菌K99含量也显著低于阳性对照组,通过病理切片观察显示脏器发病情况也较阳性对照组减轻。【结论】ФK99-1是一株在不同温度、不同酸碱性环境中有较强适应能力,且在小鼠大肠杆菌感染上表现出良好防治效果的裂解性肌尾科大肠杆菌噬菌体。     

西酞普兰联合利培酮治疗难治性抑郁症的近期临床疗效观察

目的：观察西酞普兰联合利培酮治疗难治性抑郁症的近期临床疗效,探讨提高难治性抑郁症近期临床疗效的药物治疗方案方法：选择难治性抑郁症患者86例,随机均分为对照组与观察组,对照组给予常规西酞普兰治疗,观察组给予西酞普兰联合利培酮治疗,比较两组患者治疗第2周、第4周、第6周汉密尔顿抑郁量表（HAMD）、汉密尔顿焦虑量表（HAMA）和副反应量表（TESS）评分,比较两组患者治疗第6周的临床疗效。结果：观察组近期临床疗效好于对照组,HAMD评分、HAMA评分和临床疗效比较,差异具有统计学意义（P〈0.05）;TESS评分比较,差异无统计学意义（P〉0.05）。结论：药物治疗难治性抑郁症时,应选择西酞普兰联合利培酮治疗,可提高近期临床疗效,且不加重用药不良反应。     

嗜热革节孢多糖单加氧酶氧化方式

多糖单加氧酶(polysaccharidemonooxygenase,PMO)是一种铜离子依赖的氧化酶,属于辅助活性酶类第九家族(auxiliary activity 9,AA9),在存在电子供体维生素C(vitamin C,Vc)的情况下,可以氧化裂解纤维素的多糖链,显著提高纤维素的酶解效率。本文克隆了嗜热革节孢Scytalidium thermophilumAA9家族的一个编码基因pmo7651,并在毕赤酵母GS115进行诱导表达,通过His标签获得了重组蛋白PMO7651-His。以磷酸膨胀纤维素(PASC)为底物进行酶促反应,薄层层析法(TLC)结果显示PMO7651酶解产物主要为纤维二糖至纤维五糖;飞行时间质谱法(MALDI-TOF-MS)和溴氧化法确定PMO7651具有C1、C4、C6位的氧化活性;底物结合平面的3个芳香族氨基酸位点突变对酶的活性具有不同程度的影响;在PMO7651帮助下,纤维素酶的降解效率均具有不同程度的提高。     

土地整理项目区的景观格局及其生态效应

目前项目角度的土地整理生态效应评价较少,受到研究幅度的制约,而且已有研究中对景观格局优化目标和生态效应的系统分析较少.选择典型的土地整理项目作为研究案例,以GIS和景观指数为研究手段,结合景观格局优化目标建立相应的指标体系,对土地整理的生态效应进行评价.研究表明,土地整理项目的生态效应指标体系包括提升生物多样性、维持物质和能量流通、维持景观格局稳定、提升生活环境品质、提高生态服务价值等5个方面.研究区土地整理具有正效应和负效应,最大斑块面积提高、斑块密度减少、聚集度提高、廊道宽度和连通度提高、缓冲区宽度增加、植被覆盖增加、合理功能分区是土地整理的正效应,而景观多样性降低、分维数减少和生态服务价值降低是其负效应.因此,在土地整理规划和设计时应融入景观设计和生态保育思想.     

Synthesis of a dimeric monosaccharide lipid A mimic and its synergistic effect on the immunostimulatory activity of lipopolysaccharide

Bacterial endotoxin lipopolysaccharide (LPS) is a potent immune stimulant, with the recognition of LPS and its active principal lipid A mediated by the Toll-like receptor 4 (TLR4)/MD-2 receptor complex. Due to the broad downstream implications of TLR4-mediated signalling, TLR4 ligands show great potential for immunotherapeutic manipulations. In this paper a dimeric monosaccharide lipid A mimic (3) has been designed as a potential TLR4 ligand. The chemical synthesis and the preliminary biological studies are described. Compound 3 shows a significant synergistic effect on LPS-induced ICAM-1 expression in human monocytic THP-1 cells.     

东莨菪内酯对朱砂叶螨实验种群的亚致死效应

为明确东莨菪内酯对朱砂叶螨Tetranychus cinnabarinus (Boisduval) 实验种群的亚致死效应, 为其作为植物源杀螨剂的进一步开发及应用提供理论依据, 在室内采用叶碟饲养的方法, 并利用生命表技术研究了东莨菪内酯亚致死剂量对朱砂叶螨F₀代和F₁代种群生长发育和繁殖的影响。结果表明： 东莨菪内酯LC₄₀, LC₃₀和LC₂₀剂量处理朱砂叶螨雌成螨后, 可刺激F₀代雌成螨产卵, 使产卵量分别增加了73.82%, 186.97%和70.18%, 而对成螨寿命、 产卵期和雌雄性比没有影响; F₁代的卵期、 幼螨期和若螨期与对照没有显著性差异 (P>0.05), 而成螨期和雌成螨寿命均低于对照; 对F₁代繁殖力的影响主要表现为产卵期缩短、 产卵量减少和雌性比下降; 子代种群的净生殖率(R₀)由50.5976最低降至33.9910, 世代平均历期(T)和种群倍增时间(Dt)均低于对照, 各处理后的朱砂叶螨种群均存在适合度缺陷。这些结果表明, 在亚致死剂量下, 东莨菪内酯能够降低朱砂叶螨种群的发育和繁殖速率, 这对东莨菪内酯在有害生物防治上的应用具有积极意义。     

陕甘宁地区降水稳定同位素特征及水汽来源

依据全球大气降水稳定同位素观测网络(GNIP)和已有研究中陕甘宁地区的大气降水氢氧稳定同位素资料,并结合相关气象数据,分析了陕甘宁地区大气降水氧稳定同位素的时空分布特征及其影响因子,并建立了大气降水线方程.结果表明:3省大气降水线的斜率、截距由小到大依次为:甘肃、陕西、宁夏,且均小于全球大气降水线方程的斜率、截距,表明3省的降水过程受蒸发作用影响程度沿宁夏、陕西、甘肃增强;陕甘宁地区大气降水中δ18O值在时间变化上,表现为夏秋季节富集、冬春季节贫化,从空间分布来看,由西北至东南,加权平均δ18O值呈减小趋势;3省降水中δ18O温度效应显著,但不存在降水量效应,这体现了中高纬度大陆性气候的特征;高程效应的定量关系为-0.12‰·(100 m)^-1,纬度效应更显著(纬度每增加1°,降水中δ18O相应贫化0.27‰);采用HYSPLIT模型对各站点的水汽来源进行追踪,气团聚类轨迹表明,夏半年主要有来自孟加拉湾的水汽、东南季风水汽和西风带水汽,冬半年以西风带水汽为主.     

Magnetic Field–Suppressed Lithium Dendrite Growth for Stable Lithium‐Metal Batteries

Lithium metal is the most attractive anode material due to its extremely high specific capacity, minimum potential, and low density. However, uncontrollable growth of lithium dendrite results in severe safety and cycling stability concerns, which hinders the application in next generation secondary batteries. In this paper, a new and facile method imposing a magnetic field to lithium metal anodes is proposed. That is, the lithium ions suffering Lorentz force due to the electromagnetic fields are put into spiral motion causing magnetohydrodynamics (MHD) effect. This MHD effect can effectively promote mass transfer and uniform distribution of lithium ions to suppress the dendrite growth as well as obtain uniform and compact lithium deposition. The results show that the lithium metal electrodes within the magnetic field exhibit excellent cycling and rate performance in a symmetrical battery. Additionally, full batteries using limited lithium metal as anodes and commercial LiFePO₄ as cathodes show improved performance within the magnetic field. In summary, a new and facile strategy of suppressing lithium dendrites using the MHD effect by imposing a magnetic field is proposed, which may be generalized to other advanced alkali metal batteries.     

Plant regeneration in Stone pine (<Emphasis Type="Italic">Pinus pinea</Emphasis> L.) by somatic embryogenesis

Regeneration of plants by somatic embryogenesis (SE) was achieved in Stone pine (Pinus pinea), one of the most characteristic tree species of the Mediterranean ecosystem. The initial explants were megagametophytes containing zygotic embryos from five selected half-sib families collected at different dates over 2 consecutive years. Rates of extrusion and initiation of SE differed in both years. However, qualitative patterns were very similar: for most families, the responsive developmental window was from late cleavage polyembryony to early cotyledonary stage. The highest overall mean frequencies of extrusion and SE initiation (7 and 0.9%, respectively, for the five families and the eight 2006 collections) were obtained on a modified Litvay’s medium with 9 μM 2,4-D and 4.5 μM BAP, supplemented with L-glutamine and casein hydrolysate. Families showed large differences in frequencies of SE initiation from year to year. Only seven embryogenic lines were induced in 2005, representing three of the five families tested, whereas 34 lines from all the families were obtained in 2006. Proliferation of embryonal masses (EM) was significantly improved when they were subcultured after dispersing in liquid medium and collected on filter paper disks, instead of being subcultured as small clumps. This effect showed a significant interaction with genotype. Several preconditioning treatments and culture media combinations were tested for embryo development and maturation. The high proliferation rate of EM hampered somatic embryo development. However, up to 42 mature embryos from different lines of three of the five families were obtained, 23 of them germinated and seven converted into somatic seedlings.