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1.
禽流感病毒与人类禽流感 总被引：15，自引：0，他引：15
禽流感病毒属甲型流感病毒，主要引起禽类流感。1997年首次证明禽
流感病毒(A/Ho
ng Kong/156/97)H5N1亚型可感染人，其后在我国内地、香港及荷兰等地又至少发生了5起禽
流感病毒的人间感染。目前，禽流感病毒正在我国及亚洲部分地区肆虐，已造成很大的经济
损失和社会影响，禽流感已成为严重危害人类健康的新发传染病。本文拟就禽流感病毒的基
因特征、致病性及特异检测等方面的进展做一综述。 相似文献
2.
Avi Arampatzis Konstantinos Zagoris Savvas A. Chatzichristofis 《Information processing & management》2013
Content-based image retrieval (CBIR) with global features is notoriously noisy, especially for image queries with low percentages of relevant images in a collection. Moreover, CBIR typically ranks the whole collection, which is inefficient for large databases. We experiment with a method for image retrieval from multimedia databases, which improves both the effectiveness and efficiency of traditional CBIR by exploring secondary media. We perform retrieval in a two-stage fashion: first rank by a secondary medium, and then perform CBIR only on the top-K items. Thus, effectiveness is improved by performing CBIR on a ‘better’ subset. Using a relatively ‘cheap’ first stage, efficiency is also improved via the fewer CBIR operations performed. Our main novelty is that K is dynamic, i.e. estimated per query to optimize a predefined effectiveness measure. We show that our dynamic two-stage method can be significantly more effective and robust than similar setups with static thresholds previously proposed. In additional experiments using local feature derivatives in the visual stage instead of global, such as the emerging visual codebook approach, we find that two-stage does not work very well. We attribute the weaker performance of the visual codebook to the enhanced visual diversity produced by the textual stage which diminishes codebook’s advantage over global features. Furthermore, we compare dynamic two-stage retrieval to traditional score-based fusion of results retrieved visually and textually. We find that fusion is also significantly more effective than single-medium baselines. Although, there is no clear winner between two-stage and fusion, the methods exhibit different robustness features; nevertheless, two-stage retrieval provides efficiency benefits over fusion. 相似文献
3.
Rupprecht P Golé L Rieu JP Vézy C Ferrigno R Mertani HC Rivière C 《Biomicrofluidics》2012,6(1):14107-1410712
We have developed a method for studying cellular adhesion by using a custom-designed microfluidic device with parallel non-connected tapered channels. The design enables investigation of cellular responses to a large range of shear stress (ratio of 25) with a single input flow-rate. For each shear stress, a large number of cells are analyzed (500–1500 cells), providing statistically relevant data within a single experiment. Besides adhesion strength measurements, the microsystem presented in this paper enables in-depth analysis of cell detachment kinetics by real-time videomicroscopy. It offers the possibility to analyze adhesion-associated processes, such as migration or cell shape change, within the same experiment. To show the versatility of our device, we examined quantitatively cell adhesion by analyzing kinetics, adhesive strength and migration behaviour or cell shape modifications of the unicellular model cell organism Dictyostelium discoideum at 21 °C and of the human breast cancer cell line MDA-MB-231 at 37 °C. For both cell types, we found that the threshold stresses, which are necessary to detach the cells, follow lognormal distributions, and that the detachment process follows first order kinetics. In addition, for particular conditions’ cells are found to exhibit similar adhesion threshold stresses, but very different detachment kinetics, revealing the importance of dynamics analysis to fully describe cell adhesion. With its rapid implementation and potential for parallel sample processing, such microsystem offers a highly controllable platform for exploring cell adhesion characteristics in a large set of environmental conditions and cell types, and could have wide applications across cell biology, tissue engineering, and cell screening. 相似文献
4.
在过去的20年里新的病毒不断产生以前得到控制的病毒死灰复燃新生和再生的病毒病已成为新世纪世界所面临的重要的公共卫生问题。本文简要介绍了国际上相关领域的研究状况和发展趋势,扼要介绍了我国的情况,对如何加强我国新生病毒的研究提出了几点建议。 相似文献
5.
Despite the myriad of soft lithography based micropatterning methods available to researchers, it is still challenging to define small features (10–100 μm) that are spaced far apart (1–10 mm). In this report, we describe a combined microfluidic-microstencil patterning method that can produce multifunctional substrates of small features, O(10 μm), with a large pitch, O(1 mm). In that, we fabricate microstencils using an UV curable polyurethane (Norland Optical Adhesive 81) with dense arrays of 10–100 μm holes. Overlaying arrays of microfluidic channels over these microstencils allow for the control of the spacing between features and the ability to pattern multiple substrates. We show that this method is capable of patterning soluble proteins, fibrillar insoluble collagen, liposomes, cells, and nanoparticles. We demonstrate the utility of the method by measuring platelet adhesion under flow to three adhesive proteins (insoluble fibrillar collagen, laminin, and reconstituted acid solubilized collagen fibers) in a single assay. 相似文献
6.
BackgroundCecropin P1, acting as an antimicrobial, has a broad-spectrum antibacterial activity with some antiviral and antifungal properties. It is a promising natural alternative to antibiotics which is originally isolated from the pig intestinal parasitic nematode Ascaris suum. Many studies have shown that Cecropin P1 is helpful for the prevention or treatment of clinical diseases. Therefore, it is very necessary to establish a safe, nontoxic, and efficient expression method of Cecropin P1.ResultsThe results indicated that the recombinant protein was about 5.5 kDa showed by Tricine–SDS–PAGE and Western blot. And Cecropin P1 was efficiently secreted and expressed after 12 h of induction, with an increasing yield over the course of the induction. Its maximum concentration was 7.83 mg/L after concentration and purification. In addition, in vitro experiments demonstrated that Cecropin P1 not only exerted a strong inhibitory effect on Escherichia coli, Salmonella sp., Shigella sp., and Pasteurella sp., but also displayed an antiviral activity against PRRSV NADC30-Like strain.ConclusionsCollectively, the strategy of expressing Cecropin P1 in Saccharomyces cerevisiae is harmless, efficient, and safe for cells. In addition, the expressed Cecropin P1 has antiviral and antibacterial properties concurrently.How to cite: Jiang R, Zhang P, Wu X, et al., Expression of antimicrobial peptide Cecropin P1 in Saccharomyces cerevisiae and its antibacterial and antiviral activity in vitro. Electron J Biotechnol 2021;50. https://doi.org/10.1016/j.ejbt.2020.12.006 相似文献
7.
Yi-Feng Wang Chunqiu Zhang Keni Yang Yufei Wang Shaobo Shan Yan Yan Kenneth A Dawson Chen Wang Xing-Jie Liang 《国家科学评论(英文版)》2021,8(6)
Liposomes, especially cationic liposomes, are the most common and well-investigated nanocarriers for biomedical applications, such as drug and gene delivery. Like other types of nanomaterials, once liposomes are incubated in a biological milieu, their surface can be immediately cloaked by biological components to form a protein corona, which confers a new ‘biological identity’ and modulates downstream interactions with cells. However, it remains unclear how the protein corona affects the transportation mechanism after liposomes interact with cells. Here, we employed home-made aggregation-induced-emission-visualized nanoliposomes TR4@Lipo as a model to investigate transportation with or without the protein corona by optical imaging techniques. The results show that the protein corona can change the cellular transportation mechanism of TR4@Lipo from energy-independent membrane fusion to energy-dependent endocytosis. The protein corona also modulates the intracellular distribution of loaded cargoes. This knowledge furthers our understanding of bio-nano interactions and is important for the efficient use of cationic liposomes. 相似文献
8.
人类历史上曾暴发过4次流感大流行,即1918年＂西班牙流感＂、1957年＂亚洲流感＂、1968年＂香港流感＂和2009年＂北美流感＂,每一次流感大流行都给全球公共卫生、社会经济等带来极大危害。本文从流感的流行史、流行的特点、死亡率等流行病学特征进行探讨,为全面认识流感,正确面对和科学防控流感大流行提供借鉴。 相似文献
9.
近几十年来,SARS冠状病毒、埃博拉病毒、高致病性禽流感H7N9等新发和烈性传染病接连出现,严重影响人类健康。新发和烈性传染病病原由于没有有效的疫苗和药物,具有传染性强、传播速度快、传播范围广等特点,现代生物学技术的发展使得这些病原有可能作为生物武器,威胁我国生物安全。文章分析国内外新发和烈性传染病流行现状,阐述新发和烈性传染病与生物安全的关系以及可能带来的生物恐怖威胁,探讨新发和烈性传染病防控研究的前沿技术,提出了我国新发和烈性传染病防控中存在的问题,同时针对武汉国家生物安全实验室的落成对新发和烈性传染病的防控和生物安全的防护进行了展望。 相似文献
10.
The way in which bacterial communities colonize flow in porous media is of importance, but basic knowledge on the dynamic of these phenomena is still missing. The aim of this work is to develop microfluidic experiments in order to progress in the understanding of bacteria capture in filters and membranes. PDMS microfluidic devices mimicking filtration processes have been developed to allow a direct dynamic observation of bacteria across 10 or 20 μm width microchannels. When filtered in such devices, bacteria behave surprisingly: Escherichia coli, Pseudomonas aeruginosa or Staphylococcus aureus accumulate in the downstream zone of the filter and form large streamers which oscillate in the flow. In this study, streamer formation is put in evidence for bacteria suspension in non nutritive conditions in less than 1 h. This result is totally different from the one observed in same system with “inert” particles or dead bacteria which are captured in the bottleneck zone and are accumulated in the upstream zone. Observations within different flow geometries (straight channels, connected channels, and staggered row pillars) show that the bacteria streamer development is influenced by the flow configuration and, particularly by the presence of tortuosity within the microchannels zone. These results are discussed at the light of 3D flow simulations. In confined systems and in laminar flow, there is secondary flow (z-velocities) superimposed to the streamwise motion (in xy plane). The presence of the secondary flow in the microsystems has an effect on the bacterial adhesion. A scenario in three steps is established to describe the formation of the streamers and to explain the positive effect of tortuous flow on the development kinetics. 相似文献
11.
目的观察蔷薇科植物果核油性提取物体内外抗呼吸道病毒的效果。方法分别采用红细胞吸附抑制试验和细胞病变作用(CPE)检查,观察不同浓度油性提取物体外抗流感病毒A3株、冠状病毒OC43株和呼吸道合胞病毒E6株的作用。采用小鼠感染模型,观察不同浓度油性提取物滴鼻预防后,抵抗流感病毒A3株和冠状病毒OC43株致死性感染的效果。结果0.5%油性提取物作用1min、0.12%作用5min、0.06%作用10min均可完全抑制流感病毒A3株引起的鸡红细胞吸附现象;0.25%油性提取物作用1min、0.06%作用5min、0.03%作用10min均可完全抑制冠状病毒OC43株引起的小鼠红细胞吸附现象。1.0%油性提取物作用1min、0.25%作用5min、0.12%作用10min均可完全抑制呼吸道合胞病毒E6株引起的CPE。0.12%、0.25%和0.5%油性提取物滴鼻预防后,流感病毒A3株攻击小鼠的存活率分别为30%、90%和100%。0.06%、0.12%和0.25%油性提取物滴鼻预防后,冠状病毒OC43株攻击小鼠的存活率分别为30%、80%和100%。结论较低浓度的蔷薇科植物果核油性提取物即可显示出较强的体内外抗常见呼吸道病毒作用,但体内抗病毒作用有明显的有效剂量阈值。 相似文献
12.
A microfluidic device combined with a light modulation system was developed to assess the inhibitory effect of carrageenan on Dengue virus (DENV) infection via real-time monitoring of cellular oxygen consumption rates (OCRs). Measuring cellular OCRs, which can reflect cellular metabolic activity, enabled us to monitor the process of viral infection in real time and to rapidly determine the antiviral activity of potential drugs/chemical compounds. The time variation of the cellular OCR of single cells that were infected in situ by DENV at different multiplicity of infection (m.o.i.) values was first successfully measured within a microfluidic device. The influence of the timing of carrageenan treatment on DENV infection was then examined by real-time monitoring of cellular OCRs in three groups. Cells that were pre-treated with carrageenan and then infected with DENV served as a pre-treatment group, cells to which carrageenan was added simultaneously with DENV served as a virucide group, and cells that were pre-infected with DENV and then treated with carrageenan served as a post-treatment group. By monitoring cellular OCRs, we could rapidly evaluate the inhibitory effect of carrageenan on DENV infection, obtaining a result within 7 h and showing that carrageenan had strong and effective anti-DENV activity in the three groups. In particular, a strong inhibitory effect was observed in the virucide group. Moreover, once the virus enters host cells in the post-treatment group, the immediate treatment with carrageenan for the infected cells has higher efficiency of antiviral activity. Our proposed platform enables to perform time-course or dose-response measurements of changes in cellular metabolic activity caused by diseases, chemical compounds, and drugs via monitoring of the cellular OCR, with rapid and real-time detection. This approach provides the potential to study a wide range of biological applications in cell-based biosensing, toxicology, and drug discovery. 相似文献
13.
The objective of this work was to investigate the influence of hydrodynamics on the growth kinetics of surface-adhering Pseudomonas putida cells. The results showed in particular that under non substrate-limiting conditions, the early step of bacterial apparent growth rate is lower than those measured with suspended cells. Contrary to previously cited authors which explain this behavior to the different adhesive properties of the “daughter”-cells (which makes more probable the detachment of these daughter-cells), in our experimental conditions, that explanation does not hold and we show a clear dependence of growth kinetics with flow conditions, due to the formation of boundary layer concentration at low Reynolds number. These results revealed that using Monod law in the modeling of biofilm growth in fixed-biomass processes should be performed with care. 相似文献
14.
BackgroundGardnerella vaginalis is a bacterial vaginosis (BV)-associated vaginal bacterium that produces the toxin vaginolysin (VLY). VLY is a pore-forming toxin that is suggested to be the main virulence factor of G. vaginalis. The high recurrence rate of BV and the emergence of antibiotic-resistant bacterial species demonstrate the need for the development of recombinant antibodies as novel therapeutic agents for disease treatment. Single-chain variable fragments (scFvs) generated against VLY exhibited reduced efficacy to neutralize VLY activity compared to the respective full-length antibodies. To improve the properties of scFvs, monospecific dimeric scFvs were generated by the genetic fusion of two anti-VLY scFv molecules connected by an alpha-helix-forming peptide linker.ResultsN-terminal hexahistidine-tagged dimeric scFvs were constructed and produced in Escherichia coli and purified using metal chelate affinity chromatography. Inhibition of VLY-mediated human erythrocyte lysis by dimeric and monomeric scFvs was detected by in vitro hemolytic assay. The circulating half-life of purified scFvs in the blood plasma of mice was determined by ELISA. Dimeric anti-VLY scFvs showed higher neutralizing potency and extended circulating half-life than parental monomeric scFv.ConclusionsThe protein obtained by the genetic fusion of two anti-VLY scFvs into a dimeric molecule exhibited improved properties in comparison with monomeric scFv. This new recombinant antibody might implement new possibilities for the prophylaxis and treatment of the diseases caused by the bacteria G. vaginalis. 相似文献
15.
针对我国禽流感频繁发生和人感染禽流感新发病例不断出现的严峻现状,国家自然科学基金委员会依据国家需求,组织多学科相关领域的专家进行了论证,经过立项、公开申请、项目初评、答辩和自然科学基金委委务会审议,紧急启动了“禽流感关键科学问题的基础研究”这一重大项目,旨在推动禽流感的基础研究,提供人类和动物流感发生与流行的分子生物学和免疫学信息,为禽流感药物和疫苗的研发提供理论依据,并为禽流感科学防控措施的制定提供技术支撑。本文介绍了“禽流感关键科学问题的基础研究”这一问题的提出、立项、科学问题凝练、内容和目标的确立及思考等。 相似文献
16.
Measuring effectiveness of information retrieval (IR) systems is essential for research and development and for monitoring search quality in dynamic environments. In this study, we employ new methods for automatic ranking of retrieval systems. In these methods, we merge the retrieval results of multiple systems using various data fusion algorithms, use the top-ranked documents in the merged result as the “(pseudo) relevant documents,” and employ these documents to evaluate and rank the systems. Experiments using Text REtrieval Conference (TREC) data provide statistically significant strong correlations with human-based assessments of the same systems. We hypothesize that the selection of systems that would return documents different from the majority could eliminate the ordinary systems from data fusion and provide better discrimination among the documents and systems. This could improve the effectiveness of automatic ranking. Based on this intuition, we introduce a new method for the selection of systems to be used for data fusion. For this purpose, we use the bias concept that measures the deviation of a system from the norm or majority and employ the systems with higher bias in the data fusion process. This approach provides even higher correlations with the human-based results. We demonstrate that our approach outperforms the previously proposed automatic ranking methods. 相似文献
17.
Matthew J. Kennedy Harold D. Ladouceur Tiffany Moeller Dickson Kirui Carl A. Batt 《Biomicrofluidics》2012,6(4)
The present work describes the operation and simulation of a microfluidic laminar-flow mixer. Diffusive mixing takes place between a core solution containing lipids in ethanol and a sheath solution containing aqueous buffer, leading to self assembly of liposomes. Present device architecture hydrodynamically focuses the lipid solution into a cylindrical core positioned at the center of a microfluidic channel of 125 × 125-μm2 cross-section. Use of the device produces liposomes in the size range of 100–300 nm, with larger liposomes forming at greater ionic strength in the sheath solution and at lower lipid concentration in the core solution. Finite element simulations compute the concentration distributions of solutes at axial distances of greater than 100 channel widths. These simulations reduce computation time and enable computation at long axial distances by utilizing long hexahedral elements in the axial flow region and fine tetrahedral elements in the hydrodynamic focusing region. Present meshing technique is generally useful for simulation of long microfluidic channels and is fully implementable using comsol Multiphysics. Confocal microscopy provides experimental validation of the simulations using fluorescent solutions containing fluorescein or enhanced green fluorescent protein. 相似文献
18.
Online shared spaces are destinations where people of common interests interact to achieve common goals or borrow each other's expertise for personal pursuits. Due to a multitude of users, such spaces generate large amounts of content, thus creating a potential for information overload. To deal with it, users of online shared spaces develop information management strategies that frequently involve the use of information technology. In this paper we present a case study of the use of widgets as information management tools in uCern, an online shared workspace where healthcare industry stakeholders get involved in various types of interactions. To understand how widgets served the purpose of information management and whether they were considered useful, we administered an online questionnaire (n = 183) followed by qualitative interviews (n = 5). Data analysis revealed that study participants used widgets as tools that promoted their situation and activity awareness of events and activities going on in uCern and helped them with organizing and accessing the content in a quick and efficient manner. We also describe issues associated with the use of widgets and their usefulness as reported by participants and propose implications for design and development of online shared spaces in relation to information management tools. 相似文献
19.
《Information processing & management》2020,57(3):102214
Information systems for un-regimented domains such as museums, art and book collections, face representational and usability challenges that surpass the demands of traditional information systems for regimented domains. While the former require complex conceptual models supporting a set of dynamic and evolving qualitative properties of a small number of objects, the latter focus on the quantitative aspects of a possibly very large number of objects but with a relatively small and stable set of properties. In this paper we study the use of a non-monotonic knowledge-base system for the development of information systems for un-regimented domains. We discuss the ontological assumptions of the formalism, its structure and its inferential mechanisms through a simple example. Then we present an information system for a highly un-regimented domain in the digital humanities with promising results. The present study shows that the so-called extensible, flexible, dynamic or evolving information systems need the expressive power of non-monotonic knowledge-base systems, and that such phenomena should be addressed explicitly. 相似文献
20.
《Journal of The Franklin Institute》2019,356(12):6175-6207
In this paper, we consider leader–follower decentralized optimal control for a hexarotor group with one leader and large population followers. Our hexarotor is modeled based on the quaternion framework to resolve singularity of the rotation matrix represented by Euler angles, and has 6-DoF due to six tilted propellers, which allows to control its translation and attitude simultaneously. In our problem setup, the leader hexarotor is coupled with the follower hexarotors through the followers’ average behavior (mean field), and the followers are coupled with each other through their average behavior and the leader’s arbitrary control. By using the mean field Stackelberg game framework, we obtain a set of decentralized optimal controls for the leader and N follower hexarotors when N is arbitrarily large, where each control is a function of its local information. We show that the corresponding decentralized optimal controls constitute an ϵ-Stackelberg equilibrium for the leader and N followers, where ϵ → 0 as N → ∞. Through simulations with two different operating scenarios, we show that the leader–follower hexarotors follow their desired position and attitude references, and the followers are controlled by the leader while effectively tracking their approximated average behavior. Furthermore, we show the nonsingularity and 6-DoF control performance of the leader–follower hexarotor group due to the novel modeling technique of the hexarotor presented in the paper. 相似文献