加替沙星和环丙沙星体外抗生素后效应期间大肠埃希菌形态学观察及膜电位和膜通透性变化

目的: 通过对加替沙星和环丙沙星体外抗生素后效应(PAE) 期间E.coliATCC25922 的形态学观察以及膜电位、膜通透性变化的研究, 以期为探讨PAE 形成机制提供实验依据。方法: 在不同时间点吸取加替沙星和环丙沙星抗PAE 期间的大肠埃希菌培养液, 用荧光探针碘化丙啶和DiBAC4(3) 进行染色, 应用荧光显微镜观察E.coliATCC25922 的形态学变化, 并采用流式细胞仪分析其膜电位、膜通透性变化。结果: 荧光显微镜结果表明:菌落计数法所测定的PAE 之后仍有丝状体存在, 但流式细胞仪结果表明加替沙星和环丙沙星PAE 期间E.coliATCC25922 膜电位及膜通透性与空白对照组比较无显著性差异。结论: 加替沙星和环丙沙星PAE 期间E.coli 菌体显著延长, 呈丝状体, 而其膜电位及膜通透性比较则无显著性变化, 提示丝状体形成与细胞膜变化不直接相关。     

青蒿琥酯增加小鼠腹腔巨噬细胞内化内毒素、大肠埃希菌的作用及可能机制

目的: 观察青蒿琥酯(artesunate, AS)对小鼠腹腔巨噬细胞内化清除脂多糖/内毒素(lipopolysaccharide/endotoxin, LPS)和吞噬大肠埃希菌的影响,并初步探讨其可能的作用机制。方法: MTT法检测不同浓度网格蛋白抑制剂(monodansylcadaverine, MDC)、内体酸化抑制剂氯喹(chloroquine, CQ)对小鼠腹腔巨噬细胞活力的影响,以选择恰当的药物工作浓度;激光共聚焦法检测青蒿琥酯及MDC、CQ对小鼠腹腔巨噬细胞内化FITC-LPS的影响;分别采用激光共聚焦和菌落集落形成计数实验观察青蒿琥酯对小鼠腹腔巨噬细胞内化大肠埃希菌的影响;逆转录PCR检测青蒿琥酯对小鼠腹腔巨噬细胞清道夫受体A(class A scavenger receptor,SR-A) mRNA表达的影响。结果: MDC和CQ浓度分别小于 25 μg/mL 和 20 μg/mL 时对小鼠腹腔巨噬细胞活力无影响;MDC、CQ可抑制小鼠腹腔巨噬细胞内化LPS,青蒿琥酯可增加小鼠腹腔巨噬细胞对LPS的内化,而且青蒿琥酯可增加MDC和CQ处理的巨噬细胞内化LPS的功能。激光共聚焦和菌落集落形成计数实验均显示青蒿琥酯可增加小鼠腹腔巨噬细胞对大肠埃希菌的内化能力。逆转录PCR结果显示青蒿琥酯可增强LPS处理或未处理的小鼠腹腔巨噬细胞SR-A mRNA的表达。结论: 青蒿琥酯可增强小鼠腹腔巨噬细胞内化LPS、大肠埃希菌的能力,该作用可能与SR-A mRNA表达升高有关。     

内毒素耐受状态小鼠对大肠埃希菌敏感性及促炎细胞因子水平变化的研究

目的: 研究内毒素耐受状态对大肠埃希菌的敏感性及促炎细胞因子水平的变化。方法: 采用小剂量LPS(1 mg/kg)连续腹腔注射 5 d 并在第6天尾静脉注射大剂量LPS(50 mg/kg)建立小鼠内毒素耐受模型。观察小鼠 7 d 存活率或采用ELISA法检测注射大剂量LPS后6、12 h 血清中TNF-α、IL-6水平。然后,采用不同浓度的大肠埃希菌攻击耐受小鼠,观察小鼠 7 d 存活率;或采用血培养方法检测血液中细菌数量,ELISA法检测血清中TNF-α、IL-6水平。结果: 大剂量LPS攻击组(攻击组)小鼠存活率为0 %,LPS耐受组(耐受组)小鼠存活率为100%;耐受组小鼠血清TNF-α、IL-6水平较攻击组显著降低(P＜0.01)。5.0×10⁸ CFU/kg 大肠埃希菌可导致正常小鼠100%死亡,但是仅 1.0×10⁷ CFU/kg大肠埃希菌就可导致耐受组小鼠100%死亡;耐受组给予大肠埃希菌低、高剂量组小鼠血液中细菌数量远远高于相应的正常小鼠大肠埃希菌低或高剂量组(P＜0.01),而血清中TNF-α、IL-6水平则远远低于相应的大肠埃希菌低或高剂量组(P<0.01)。结论: 连续腹腔注射小剂量LPS 5 d 后并在第6天尾静脉注射大剂量LPS可成功建立LPS耐受模型;与正常对照组小鼠比较,较低数量的大肠埃希菌就可导致耐受组小鼠死亡,说明内毒素耐受小鼠对大肠埃希菌的敏感性较正常小鼠明显增高,其机制可能与内毒素耐受后促炎细胞因子水平降低、机体抵抗力降低有关。     

肠道抗生素行肠道准备后对大肠杆菌耐药的影响

目的: 探讨结直肠肿瘤患者术前口服肠道抗生素行肠道准备对大肠杆菌耐药的影响。方法: 对符合要求的100例结直肠肿瘤患者随机分成两组,观察组采用口服肠道抗生素 1 d,对照组口服肠道抗生素 3 d,于术中采集每例病员结肠黏膜附着物行细菌培养及药敏试验,统计两组大肠杆菌培养阳性率及其耐药情况。结果: 1 d 组和 3 d 组结肠黏膜附着物大肠杆菌培养阳性率分别为46%和40%, 3 d 组大肠杆菌较 1 d 组对丁胺卡那霉素、庆大霉素、环丙沙星及左氧氟沙星耐药增加(P＜0.05);两组均对氨苄西林全部耐药,而对厄他培南、亚胺培南及哌拉西/他唑巴坦全部敏感。结论: 肠道抗生素用于结直肠肿瘤患者术前肠道准备, 3 d 方案致大肠杆菌对部分药物耐药性增加,术前肠道准备宜尽量减少服用抗生素。     

Synergistic effect of additives on electrodeposition of copper from cyanide-free electrolytes and its structural and morphological characteristics

Electrodeposition of acid copper plating on mild steel substrate is tedious due to the galvanic displacement reaction of copper on mild steel. This can be avoided by using a proper complexing agent, because the complexing agent tuned the potential of noble direction to less noble direction by complex formation. In this paper, environment friendly electrodeposition of copper from non-cyanide electrolyte using sodium gluconate as complexing agent was investigated in alkaline medium. The effects of additives such as 1, 2, 3-benzotriazole, sodium lauryl sulphate, PEG 8000 and saccharin were studied. These additives are found to reduce the grain size, grain boundaries and improve surface morphology of the copper deposits. Also they improve the throwing power of the depositing electrolytes and hardness of deposits. The electrodeposited copper coatings were characterized by X-ray diffraction technique. XRD results indicate that the electrodeposited copper shows polycrystalline and face centered cubic structure. The crystal size was calculated by XRD and AFM analysis. Among these additives studied, the mixture of benzotriazole and sodium lauryl sulphate acts as the best additive. A uniform pore-free surface observed under SEM and AFM results reveal the grain refining brought about by the additives.     

Effect of negative substrate bias voltage on the nucleation and growth of Cu films during the initial stage of ion beam deposition

We focused the effect of a negative substrate bias voltage on the nucleation and growth of Cu films during the initial stage of ion beam deposition. The resultant microstructure of Cu films was observed by atomic force microscopy (AFM). It was found that Cu films with or without a negative substrate bias voltage have a different dependence of nucleation and growth. It was established that the mechanism of nucleation and growth of Cu films is changed to a progressive nucleation and lateral growth by a sufficient migration of adatoms accelerated by applying a negative substrate bias voltage.     

A comparison of the corrosion behavior of WC-Co-Cr and WC-Co HVOF thermally sprayed coatings by in situ atomic force microscopy (AFM)

The corrosion behavior of WC-Co-Cr and WC-Co high velocity oxygen fuel (HVOF) sprayed coatings were examined in static saline conditions. Direct current (DC) polarization tests were conducted and the electrochemical corrosion behavior was shown, by in situ atomic force microscopy (AFM) and scanning electron microscopy (SEM), to be complex because of the composite ceramic-metal nature of the coating. The addition of chromium to the matrix greatly enhanced the corrosion resistance of the coating.     

Effect of electrolyte solvent on the morphology of polypyrrole films: Application to the use of polypyrrole in pH sensors

Electrochemical and morphological characteristics of polypyrrole (PPy) films electro-deposited from three different electrolyte solutions (acetonitrile, water and acetonitrile + water) have been investigated using atomic force microscopy and scanning electron microscopy. Experimental parameters including the electrolyte and the deposition time were shown to affect the morphologies of polypyrrole films. After characterization of the polypyrrole film morphologies, these polymer films were successfully tested as sensitive layers in pH sensors since the pH sensor responses were fast, linear and sensitive to pH changes. More, these responses of the pH sensors were dependent on the experimental conditions of the electro-deposition (thickness and solvent).     

Atomic force microscopy study of biaxially oriented polypropylene films

Atomic force microscopy (AFM) uses a very sharp pointed mechanical probe to collect real-space morphological information of solid surfaces. AFM was used in this study to image the surface morphology of a biaxially oriented polypropylene film. The polymer film is characterized by a nanometer-scale, fiberlike network structure, which reflects the drawing process used during the fabrication of the film. AFM was used to study polymer-surface treatment to improve wettability by exposing the polymer to ozone with or without ultraviolet (UV) irradiation. Surface-morphology changes observed by AFM are the result of the surface oxidation induced by the treatment. Due to the topographic features of the polymer film, the fiberlike structure has been used to check the performance of the AFM tip. An AFM image is a mixture of the surface morphology and the shape of the AFM tip. Therefore, it is important to check the performance of a tip to ensure that the AFM image collected reflects the true surface features of the sample, rather than contamination on the AFM tip.     

Effects of applied potential and solution temperature on the pitting corrosion of pure aluminium in sulphate ion-containing chloride solution

Effects of applied potential and solution temperatureT _s on the pitting corrosion of pure aluminium (Al) were investigated in 0.01 M NaCl solutions containing various sulphate (SO₄ ^2-) ion concentrations using a potentiodynamic polarisation experiment, the potentiostatic current transient technique, ac impedance spectroscopy and atomic force microscopy (AFM). The potentiodynamic polarisation curves showed a rise in the pitting potentialE _pir values and a simultaneous increase in anodic current density at potentials much higher than theE _pit value as the SO42~ ion concentration increases. This implies that (SO₄ ^2-) ions impede pit initiation at potentials belowE _pit but enhance pit growth aboveE _pit. This was confirmed from the larger pit growth rate parameterb values of pure Al exposed to (SO₄ ^2-) ion-containing chloride solutions during the abrading action than those exposed to (SO₄ ^2-) ion-free chloride solution. Furthermore, at 7_s=25°C, the charge densityQ values for the Al metal dissolution in the presence of (SO₄ ^2-) ions were smaller than the value in its absence. By contrast, as validated by the capacitance values and the AFM images of the re-anodized specimens, an enhanced metal dissolution was observed in (SO₄ ^2-) ion-containing chloride solutions at 7_s=60° and 80°C. From the experimental findings, it is suggested that (SO₄ ^2-) ions act as inhibitors of pitting corrosion on pure Al belowE _pit and at 7_s=25°C, whereas they act as promoters at 7_s=60 ° and 80°C. This originates from the accelerated dissolution of the bare metal extensively exposed to the temperature-sensitive Cl ion attack, which occurs at potentials aboveE _pit     

Atomic force microscope study of the interface of twinned martensite in copper–aluminium–nickel

Atomic force microscopic observations of interfacial structures of twinned γ₁^′ martensite plates in single crystals of Cu–14wt.%Al–3.4wt.%Ni alloy revealed the presence of either side-plate extensions or well-defined twin facets at the martensite/parent phase interface. These results indicate that there are alternative means of accommodating micro-scale mismatch strains at the interface.