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排序方式: 共有814条查询结果,搜索用时 15 毫秒
41.
Stéphanie Suarez Agnès Ferroni Aurélie Lotz Keith A. Jolley Philippe Guérin Julie Leto Brunhilde Dauphin Anne Jamet Martin C.J. Maiden Xavier Nassif Jean Armengaud 《Journal of microbiological methods》2013
Whole-cell matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS) is a rapid method for identification of microorganisms that is increasingly used in microbiology laboratories. This identification is based on the comparison of the tested isolate mass spectrum with reference databases. Using Neisseria meningitidis as a model organism, we showed that in one of the available databases, the Andromas database, 10 of the 13 species-specific biomarkers correspond to ribosomal proteins. Remarkably, one biomarker, ribosomal protein L32, was subject to inter-strain variability. The analysis of the ribosomal protein patterns of 100 isolates for which whole genome sequences were available, confirmed the presence of inter-strain variability in the molecular weight of 29 ribosomal proteins, thus establishing a correlation between the sequence type (ST) and/or clonal complex (CC) of each strain and its ribosomal protein pattern. Since the molecular weight of three of the variable ribosomal proteins (L30, L31 and L32) was included in the spectral window observed by MALDI-TOF MS in clinical microbiology, i.e., 3640–12000 m/z, we were able by analyzing the molecular weight of these three ribosomal proteins to classify each strain in one of six subgroups, each of these subgroups corresponding to specific STs and/or CCs. Their detection by MALDI-TOF allows therefore a quick typing of N. meningitidis isolates. 相似文献
42.
目的建立长爪沙鼠原代肝细胞分离培养体系。方法以雄性长爪沙鼠为供体,采用组织消化法和Seglen两步灌流法分离肝细胞,以台盼蓝染色检测细胞得率和活率,过碘酸-希夫氏反应(PAS)鉴定肝细胞,倒置显微镜观察肝细胞形态变化,并使用含有多种细胞因子的培养基维持培养。结果组织消化法和Seglen两步灌流法平均每只长爪沙鼠可分别获得肝细胞(1.33±0.34)×107个、(3.97±1.15)×107个,细胞活率分别为(29.4±6.05)%、(80.3±4.56)%,这两种方法在细胞得率及活率方面存在显著差异。肝细胞内因有大量的糖原颗粒,经PAS染色后被染成红色。结果表明肝细胞在贴壁后72 h内,肝细胞形态发生显著变化。结论采用胶原酶经肝门静脉灌流分离肝细胞是一种高效获得肝细胞的方法。各种细胞因子有利于维持肝细胞在体外的生长分化,长爪沙鼠原代肝细胞分离培养体系的建立将为肝脏相关疾病研究和防治药物的开发提供技术支持。 相似文献
43.
Polyketides induce prestalk cell differentiation in Dictyostelium. In the double-knockout mutant of the SteelyA and B polyketide synthases, most of the pstA cells—the major part of the prestalk cells—are lost, and we show by whole mount in situ hybridization that expression of prestalk genes is also reduced. Treatment of the double-knockout mutant with the PKS inhibitor cerulenin gave a further reduction, but some pstA cells still remained in the tip region, suggesting the existence of a polyketide-independent subtype of pstA cells. The double-knockout mutant and cerulenin-treated parental Ax2 cells form fruiting bodies with fragile, single-cell layered stalks after cerulenin treatment. Our results indicate that most pstA cells are induced by polyketides, but the pstA cells at the very tip of the slug are induced in some other way. In addition, a fruiting body with a single-cell layered, vacuolated stalk can form without polyketides. 相似文献
44.
Endothelial progenitor cells (EPC) participate in revascularization and angiogenesis. EPC can be cultured in vitro from mononuclear cells of peripheral blood, umbilical cord blood or bone marrow; they also can be transdifferentiated from mesenchymal stem cells (MSC). We isolated EPCs from Wharton's jelly (WJ) using two methods. The first method was by obtaining MSC from WJ and characterizing them by flow cytometry and their adipogenic and osteogenic differentiation, then applying endothelial growth differentiating media. The second method was by direct culture of cells derived from WJ into endothelial differentiating media. EPCs were characterized by morphology, Dil-LDL uptake/UEA-1 immunostaining and testing the expression of endothelial markers by flow cytometry and RT-PCR. We found that MSC derived from WJ differentiated into endothelial-like cells using simple culture conditions with endothelium induction agents in the medium. 相似文献
45.
Ranguelova K Girotto S Gerfen GJ Yu S Suarez J Metlitsky L Magliozzo RS 《The Journal of biological chemistry》2007,282(9):6255-6264
Catalase-peroxidase (KatG) from Mycobacterium tuberculosis, a Class I peroxidase, exhibits high catalase activity and peroxidase activity with various substrates and is responsible for activation of the commonly used antitubercular drug, isoniazid (INH). KatG readily forms amino acid-based radicals during turnover with alkyl peroxides, and this work focuses on extending the identification and characterization of radicals forming on the millisecond to second time scale. Rapid freeze-quench electron paramagnetic resonance spectroscopy (RFQ-EPR) reveals a change in the structure of the initially formed radical in the presence of INH. Heme pocket binding of the drug and knowledge that KatG[Y229F] lacks this signal provides evidence for radical formation on residue Tyr(229). High field RFQ-EPR spectroscopy confirmed a tryptophanyl radical signal, and new analyses of X-band RFQ-EPR spectra also established its presence. High field EPR spectroscopy also confirmed that the majority radical species is a tyrosyl radical. Site-directed mutagenesis, along with simulations of EPR spectra based on x-ray structural data for particular tyrosine and tryptophan residues, enabled assignments based on predicted hyperfine coupling parameters. KatG mutants W107F, Y229F, and the double mutant W107F/Y229F showed alteration in type and yield of radical species. Results are consistent with formation of a tyrosyl radical reasonably assigned to residue Tyr(229) within the first few milliseconds of turnover. This is followed by a mixture of tyrosyl and tryptophanyl radical species and finally to only a tyrosyl radical on residue Tyr(353), which lies more distant from the heme. The radical processing of enzyme lacking the Trp(107)-Tyr(229)-Met(255) adduct (found as a unique structural feature of catalase-peroxidases) is suggested to be a reasonable assignment of the phenomena. 相似文献
46.
Genome sequence of Babesia bovis and comparative analysis of apicomplexan hemoprotozoa 总被引:1,自引:0,他引:1
Brayton KA Lau AO Herndon DR Hannick L Kappmeyer LS Berens SJ Bidwell SL Brown WC Crabtree J Fadrosh D Feldblum T Forberger HA Haas BJ Howell JM Khouri H Koo H Mann DJ Norimine J Paulsen IT Radune D Ren Q Smith RK Suarez CE White O Wortman JR Knowles DP McElwain TF Nene VM 《PLoS pathogens》2007,3(10):1401-1413
47.
Felkner M Suarez L Liszka B Brender JD Canfield M 《Birth defects research. Part A, Clinical and molecular teratology》2007,79(8):617-621
BACKGROUND: Previous findings for the Texas Neural Tube Defects Project suggested that while maternal access to nutrients is adequate, bioavailability of nutrients to the fetus is compromised in NTD-affected pregnancies. Helicobacter pylori could cause nutrient loss to the fetus. Folate, B12, and ferritin are depleted in H. pylori infection; these same deficiencies are related to NTD risk. METHODS: Using H. pylori IgG ELISA Test System, we tested for H. pylori serum antibodies in participants in the population-based case-control study component of the Texas Neural Tube Defect Project conducted along the Texas-Mexico border. Case-women had pregnancies affected by NTD (anencephalus, spina bifida, encephalocele) and resided and delivered in one of the 14 Texas-Mexico border counties from 1995 through 2000. Control-women were study area residents delivering normal live births during the same period. RESULTS: Of 225 case- and 378 control-women, 103 cases and 156 controls provided questionnaire and H. pylori antibody data. H. pylori seropositivity was modestly associated with NTD-affected pregnancies (OR 1.4; 95% CI: 0.8-2.4). ORs of 2.0 or greater were seen in women younger than age 25 and with less than 7 years education. CONCLUSIONS: Our findings intimate that H. pylori could play a role in NTD causation in certain populations. While results did not provide compelling support for this proposal, subgroup findings prompt us to advocate an evaluation of this hypothesis in developing nations among populations with higher prevalence of H. pylori, marginal nutrient intake, and young childbearing age. 相似文献
48.
【背景】杨树溃疡病是一种主要由葡萄座腔菌引起的杨树枝干病害,危害严重。前期从杨树中分离到一株内生拮抗细菌N6-34,研究表明该菌株拮抗效果好,对多种植物病原菌均有较强的拮抗作用。【目的】对拮抗细菌N6-34产生的抗菌活性物质进行分离纯化,并鉴定了活性物质组分的结构。【方法】通过硫酸铵盐析、甲醇抽提、分子筛、高效液相色谱等方法分离纯化N6-34菌株的抗菌活性物质,并对其进行结构鉴定。【结果】N6-34菌株发酵液经多步分离纯化,共获得14个组分,其中有13个组分具有抗菌活性,经一级质谱分析,获得了13种抗菌活性组分的分子量;经二级质谱分析,将13种抗菌活性物质鉴定为Fengycin A或Fengycin B的同系物或同分异构体。【结论】从N6-34菌株发酵液中分离获得了13种抗菌成分,为杨树溃疡病的生物防治提供了理论依据。 相似文献
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