B型烟粉虱与浙江非B型烟粉虱的竞争

为了了解近年来入侵中国的B型烟粉虱(Bemisiatabaci)取代本地非B型烟粉虱的潜能,在室内将一个B型与一个浙江非B型烟粉虱种群混合饲养在不同寄主植物上,跟踪观察混合种群中两个生物型个体数量相对比例的变化。结果表明,当两种生物型在棉花(Gossypiumhirsutum)上以相同初始数量共存竞争时,经过6代,非B型完全被B型替代;而在西葫芦(Cucurbitapepo)上以相同初始数量共存竞争时,只经过2代,非B型即完全被B型替代。在棉花上,即使以非B型占87%、B型占13%开始共存竞争,经过225d后,非B型也完全被B型替代。这说明B型烟粉虱具有在短期内竞争取代浙江非B型烟粉虱的能力。经分析,B型除了寄主范围比非B型的宽这一点对其竞争有利外,较强的内在竞争潜能也是其能成功入侵并替代本地非B型烟粉虱的一个重要原因。     

Identification of a novel strain of influenza A (H9N2) virus in chicken

<正>Dear Editor,Avian Influenza virus(AIV)H9N2 subtype viruses circulate widely in domestic fowl,and usually cause mild clinical signs in poultry(Li et al.,2005).Occasionally,avian H9N2 can infect humans and cause mild clinical symptoms(Peiris et al.,1999;Lin et al.,2000).Genetic analysis indicates that the H9N2 genotype viruses exist in major poultry species(such as duck and chicken)and in minor poultry species(such as quail,partridge,chukar,pheasant,and guinea fowl)(Guan et al.,2000;Li et al.,2005).Meanwhile,frequent reassortment events among     

地衣芽胞杆菌FJAT-4脂肽结构鉴定及其对尖孢镰刀菌的抑制作用

【目的】地衣芽胞杆菌FJAT-4产生的脂肽能够有效抑制尖孢镰刀菌的生长,本研究的目的在于探究地衣芽胞杆菌FJAT-4脂肽结构,分析培养基组分和培养温度对FJAT-4产抑菌脂肽的影响,阐述脂肽对尖孢镰刀菌的抑制作用,为菌株抑菌机理的阐释及其在枯萎病防治中的推广应用奠定基础。【方法】通过酸沉醇提法提取地衣芽胞杆菌FJAT-4产生的脂肽;利用液相色谱串联四极杆飞行时间质谱进行地衣芽胞杆菌FJAT-4脂肽组成分析及结构鉴定;以抑菌圈大小为指标评估地衣芽胞杆菌FJAT-4脂肽对尖孢镰刀菌的抑制效果;通过扫描电镜观察地衣芽胞杆菌FJAT-4粗脂肽对尖孢镰刀菌的抑制作用。【结果】地衣芽胞杆菌FJAT-4产生的抑菌脂肽由C_(17)fengycin A、C_(17)fengycin B、C_(17)fengycin B_2、C_(16)fengycin A衍生物、C_(16)fengycin B衍生物、C_(13)–C_(15)surfactin及C_(13)–C_(15)surfactin衍生物组成,其中C_(13)–C_(15) surfactin衍生物(m/z[M+Na]~+=1048.6/1062.6/1076.6)为新化合物。培养基成分不同对菌株FJAT-4脂肽组成影响较小,但温度对菌株FJAT-4产生抑菌脂肽的影响很大,该菌株在较低温度(20–25°C)下培养不产生脂肽,30–40°C下培养能产生抑菌脂肽,且高温有利于提高脂肽中surfactin的比例。该脂肽类物质对辣椒、番茄、香蕉和甜瓜尖孢镰刀菌等多种植物病原真菌均具有很好的抑制效果,且呈剂量依赖性。扫描电镜结果表明地衣芽胞杆菌FJAT-4所产的脂肽会严重影响辣椒、番茄、香蕉和甜瓜尖孢镰刀菌菌丝的正常生长,导致菌丝断裂变形、孢子变形或显著抑制了孢子的生长。【结论】地衣芽胞杆菌FJAT-4产生的抑菌脂肽为fengycin和surfactin类物质,该抑菌脂肽会致使尖孢镰刀菌菌丝体发育畸形,影响尖孢镰刀菌的正常生长。     

Reduced Snow Cover Increases Wintertime Nitrous Oxide (N<Subscript>2</Subscript>O) Emissions from an Agricultural Soil in the Upper U.S. Midwest

Throughout most of the northern hemisphere, snow cover decreased in almost every winter month from 1967 to 2012. Because snow is an effective insulator, snow cover loss has likely enhanced soil freezing and the frequency of soil freeze–thaw cycles, which can disrupt soil nitrogen dynamics including the production of nitrous oxide (N₂O). We used replicated automated gas flux chambers deployed in an annual cropping system in the upper Midwest US for three winters (December–March, 2011–2013) to examine the effects of snow removal and additions on N₂O fluxes. Diminished snow cover resulted in increased N₂O emissions each year; over the entire experiment, cumulative emissions in plots with snow removed were 69% higher than in ambient snow control plots and 95% higher than in plots that received additional snow (P < 0.001). Higher emissions coincided with a greater number of freeze–thaw cycles that broke up soil macroaggregates (250–8000 µm) and significantly increased soil inorganic nitrogen pools. We conclude that winters with less snow cover can be expected to accelerate N₂O fluxes from agricultural soils subject to wintertime freezing.     

Determination of 4-dimethylaminophenol concentrations in dog blood using LC-ESI/MS/MS combined with precolumn derivatization

A sensitive and reproducible LC-ESI/MS/MS method, which was combined with the precolumn dansyl chloride derivatization to enhance the signal intensity of analytes, was developed to determine blood 4-dimethylaminophenol (DMAP) concentrations. The linearity of the method was observed within the concentration range of 2-2000 ng/mL. The precision, accuracy, stability, recovery and matrix effect of the method were also investigated and found to meet the requirements for pharmacokinetic studies of the drug. By using this method, pharmacokinetic studies were conducted in dogs after i.m. and i.v. administrations. The results showed that DMAP could not only be absorbed into blood quickly after i.m., but also can be eliminated rapidly. Both i.m. and i.v. routes are appropriate for DMAP to be used in field first-aid. It has been proved that this LC-MS/MS combined with precolumn derivatization method can be used as a routine analytical method to provide enhanced measurements for blood DMAP concentrations. It is also useful for DMAP pharmacokinetic evaluation.     

An HPLC-ultraviolet detection method for the determination of Z24 in mouse whole blood and its application to pharmacokinetic studies

A sensitive and reproducible high-performance liquid chromatography (HPLC)-UV method for the determination of Z24, a tumorigenesis and angiogenesis inhibitor, has been developed and validated in mouse whole blood. Blood samples were extracted with ether, evaporated, and the residue was reconstituted in mobile phase. An aliquot was separated by isocratic reversed-phase HPLC on a Hypersil ODS-2 column and quantified using UV detection at 390nm. The mobile phase was 50% (v/v) acetonitrile/water with a flow rate of 0.8ml/min. A linear curve over the concentration range of 0.05-6mug/ml (r(2)=0.9976) was obtained. The coefficient of the variation for the intra- and inter-day precision ranged from 3.0 to 10.9% and 5.7 to 10.3%, respectively. The absolute recovery of Z24 was 89.2-108.5%. The method is simple, economical and sufficient for in vivo pharmacokinetic studies on Z24. Nonlinear pharmacokinetics was found in mice at doses from 20 to 80mg/kg.     

Proteomic methodological recommendations for studies involving human plasma, platelets, and peripheral blood mononuclear cells

This study was designed to develop, optimize and validate protocols for blood processing prior to proteomic analysis of plasma, platelets and peripheral blood mononuclear cells (PBMC) and to determine analytical variation of a single sample of depleted plasma, platelet and PBMC proteins within and between four laboratories each using their own standard operating protocols for 2D gel electrophoresis. Plasma depleted either using the Beckman Coulter IgY-12 proteome partitioning kit or the Amersham albumin and IgG depletion columns gave good quality gels, but reproducibility appeared better with the single-use immuno-affinity column. The use of the Millipore Filter Device for protein concentration gave a 16% ( p < 0.005) higher recovery of protein in flow-through sample compared with acetone precipitation. The use of OptiPrep gave the lowest level of platelet contamination (1:0.8) during the isolation of PBMC from blood. Several proteins (among which are alpha-tropomyosin, fibrinogen and coagulation factor XIII A) were identified that may be used as biomarkers of platelet contamination in future studies. When identifying preselected spots, at least three out of the four centers found similar identities for 10 out of the 10 plasma proteins, 8 out of the 10 platelet proteins and 8 out of the 10 PBMC proteins. The discrepancy in spot identifications has been described before and may be explained by the mis-selection of spots due to laboratory-to-laboratory variation in gel formats, low scores on the peptide analysis leading to no or only tentative identifications, or incomplete resolution of different proteins in what appears as a single abundant spot. The average within-laboratory coefficient of variation (CV) for each of the matched spots after automatic matching using either PDQuest or ProteomWeaver software ranged between 18 and 69% for depleted plasma proteins, between 21 and 55% for platelet proteins, and between 22 and 38% for PBMC proteins. Subsequent manual matching improved the CV with on average between 1 and 16%. The average between laboratory CV for each of the matched spots after automatic matching ranged between 4 and 54% for depleted plasma proteins, between 5 and 60% for platelet proteins, and between 18 and 70% for PBMC proteins. This variation must be considered when designing sufficiently powered studies that use proteomics tools for biomarker discovery. The use of tricine in the running buffer for the second dimension appears to enhance the resolution of proteins especially in the high molecular weight range.     

Rice XB15, a protein phosphatase 2C, negatively regulates cell death and XA21-mediated innate immunity

Perception of extracellular signals by cell surface receptors is of central importance to eukaryotic development and immunity. Kinases that are associated with the receptors or are part of the receptors themselves modulate signaling through phosphorylation events. The rice (Oryza sativa L.) XA21 receptor kinase is a key recognition and signaling determinant in the innate immune response. A yeast two-hybrid screen using the intracellular portion of XA21, including the juxtamembrane (JM) and kinase domain as bait, identified a protein phosphatase 2C (PP2C), called XA21 binding protein 15 (XB15). The interaction of XA21 and XB15 was confirmed in vitro and in vivo by glutathione-S-transferase (GST) pull-down and co-immunoprecipitation assays, respectively. XB15 fusion proteins purified from Escherichia coli and from transgenic rice carry PP2C activity. Autophosphorylated XA21 can be dephosphorylated by XB15 in a temporal- and dosage-dependent manner. A serine residue in the XA21 JM domain is required for XB15 binding. Xb15 mutants display a severe cell death phenotype, induction of pathogenesis-related genes, and enhanced XA21-mediated resistance. Overexpression of Xb15 in an XA21 rice line compromises resistance to the bacterial pathogen Xanthomonas oryzae pv. oryzae. These results demonstrate that Xb15 encodes a PP2C that negatively regulates the XA21-mediated innate immune response.     

Pathway crosstalk between Ras/Raf and PI3K in promotion of M-CSF-induced MEK/ERK-mediated osteoclast survival

While M-CSF-mediated MEK/ERK activation promotes osteoclast survival, the signaling pathway by which M-CSF activates MEK/ERK is unresolved. Functions for PI3K, Ras, and Raf have been implicated in support of osteoclast survival, although interaction between these signaling components has not been examined. Therefore, the interplay between PI3K, Ras and Raf in M-CSF-promoted MEK/ERK activation and osteoclast survival was investigated. M-CSF activates Ras to coordinate activation of PI3K and Raf/MEK/ERK, since Ras inhibition decreased PI3K activation and PI3K inhibition did not block M-CSF-mediated Ras activation. As further support for Ras-mediated signaling, constitutively active (ca) Ras promoted MEK/ERK activation and osteoclast survival, which was blocked by inhibition of PI3K or Raf. Moreover, PI3K-selective or Raf-selective caRas were only partially able to promote osteoclast survival when compared to parental caRas. We then examined whether PI3K and Raf function linearly or in parallel downstream of Ras. Expression of caPI3K increased MEK/ERK activation and promoted osteoclast survival downstream of M-CSF, supporting this hypothesis. Blocking Raf did not decrease osteoclast survival and MEK/ERK activation promoted by caPI3K. In addition, PI3K-selective Ras-mediated survival was not blocked by Raf inhibition. Taken together, our data support that Raf signaling is separate from Ras/PI3K signaling and PI3K signaling is separate from Ras/Raf signaling. These data therefore support a role for Ras in coordinate activation of PI3K and Raf acting in parallel to mediate MEK/ERK-promoted osteoclast survival induced by M-CSF.