853 resultados para Cationic Liposomes Enhance


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There has been an increased emphasis upon the application of science for humanitarian and development planning, decision-making and practice; particularly in the context of understanding, assessing and anticipating risk (e.g. HERR, 2011). However, there remains very little guidance for practitioners on how to integrate sciences they may have had little contact with in the past (e.g. climate). This has led to confusion as to which ‘science’ might be of use and how it would be best utilised. Furthermore, since this integration has stemmed from a need to be more predictive, agencies are struggling with the problems associated with uncertainty and probability. Whilst a range of expertise is required to build resilience, these guidelines focus solely upon the relevant data, information, knowledge, methods, principles and perspective which scientists can provide, that typically lie outside of current humanitarian and development approaches. Using checklists, real-life case studies and scenarios the full guidelines take practitioners through a five step approach to finding, understanding and applying science. This document provides a short summary of the five steps and some key lessons for integrating science.

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We report on use of iPads (and other IOS devices) for student fieldwork use and as electronic field notebooks and to promote active. We have used questionnaires and interviews of tutors and students to elicit their views and technology and iPad use for fieldwork. There is some reluctance for academic staff to relinquish paper notebooks for iPad use, whether in the classroom or on fieldwork, as well as use them for observational and measurement purposes. Students too are largely unaware of the potential of iPads for enhancing fieldwork. Apps can be configured for a wide variety of specific uses that make iPads useful for educational as well as social uses. Such abilities should be used to enhance existing practice as well as make new functionality. For example, for disabled students who find it difficult to use conventional note taking. iPads can be used to develop student self-directed learning and for group contributions. The technology becomes part of the students’ personal learning environments as well as at the heart of their knowledge spaces – academic and social. This blurring of boundaries is due to iPads’ usability to cultivate field use, instruction, assessment and feedback processes. iPads can become field microscopes and entries to citizen science and we see the iPad as the main ‘computing’ device for students in the near future. As part of the Bring Your Own Technology/Device (BYOD) the iPad has much to offer although, both staff and students need to be guided in the most effective use for self-directed education via development of Personal Learning Environments. A more student-oriented pedagogy is suggested to correspond to the increasing use of tablet technologies by students

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Water soluble anionic and cationic bis-triazine ligands are able to suppress (mask) the extraction of corrosion and fission products such as Ni(II) and Pd(II) that are found in PUREX raffinates. Thus it is possible to separate these elements from the minor actinide Am(III). Although some masking agents have previously been developed that retard the extraction of Pd(II), this is the first time a masking agent has been developed for Ni(II).

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The increasing use of nanoparticles in the pharmaceutical industry is generating concomitant interest in developing nanomaterials that can rapidly penetrate into, and permeate through, biological membranes to facilitate drug delivery and improve the bioavailability of active pharmaceutical ingredients. Here, we demonstrate that the permeation of thiolated silica nanoparticles through porcine gastric mucosa can be significantly enhanced by their functionalization with either 5 kDa poly(2-ethyl-2-oxazoline) or poly(ethylene glycol). Nanoparticle diffusion was assessed using two independent techniques; Nanoparticle Tracking Analysis, and fluorescence microscopy. Our results show that poly(2-ethyl-2-oxazoline) and poly(ethylene glycol) have comparable abilities to enhance diffusion of silica nanoparticles in mucin dispersions and through the gastric mucosa. These findings provide a new strategy in the design of nanomedicines, by surface modification or nanoparticle core construction, for enhanced transmucosal drug delivery.

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Mobile devices can enhance undergraduate research projects and students’ research capabilities. The use of mobile devices such as tablet computers will not automatically make undergraduates better researchers, but their use should make investigations, writing, and publishing more effective and may even save students time. We have explored some of the possibilities of using “tablets” and “smartphones” to aid the research and inquiry process in geography and bioscience fieldwork. We provide two case studies as illustration of how students working in small research groups use mobile devices to gather and analyze primary data in field-based inquiry. Since April 2010, Apple’s iPad has changed the way people behave in the digital world and how they access their music, watch videos, or read their email much as the entrepreneurs Steve Jobs and Jonathan Ive intended. Now with “apps” and “the cloud” and the ubiquitous references to them appearing in the press and on TV, academics’ use of tablets is also having an impact on education and research. In our discussion we will refer to use of smartphones such as the iPhone, iPod, and Android devices under the term “tablet”. Android and Microsoft devices may not offer the same facilities as the iPad/iphone, but many app producers now provide versions for several operating systems. Smartphones are becoming more affordable and ubiquitous (Melhuish and Falloon 2010), but a recent study of undergraduate students (Woodcock et al. 2012, 1) found that many students who own smartphones are “largely unaware of their potential to support learning”. Importantly, however, students were found to be “interested in and open to the potential as they become familiar with the possibilities” (Woodcock et al. 2012). Smartphones and iPads could be better utilized than laptops when conducting research in the field because of their portability (Welsh and France 2012). It is imperative for faculty to provide their students with opportunities to discover and employ the potential uses of mobile devices in their learning. However, it is not only the convenience of the iPad or tablet devices or smartphones we wish to promote, but also a way of thinking and behaving digitally. We essentially suggest that making a tablet the center of research increases the connections between related research activities.

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It is known that roots can respond to patches of fertility; however, root proliferation is often too slow to exploit resources fully, and organic nutrient patches may be broken down and leached, immobilized or chemically fixed before they are invaded by the root system. The ability of fungal hyphae to exploit resource patches is far greater than that of roots due to their innate physiological and morphological plasticity, which allows comprehensive exploration and rapid colonization of resource patches in soils. The fungal symbionts of ectomycorrhizal plants excrete significant quantities of enzymes such as chitinases, phosphatases and proteases. These might allow the organic residue to be tapped directly for nutrients such as N and P. Pot experiments conducted with nutrient-stressed ectomycorrhizal and control willow plants showed that when high quality organic nutrient patches were added, they were colonized rapidly by the ectomycorrhizal mycelium. These established willows (0.5 m tall) were colonized by Hebeloma syrjense P. Karst. for 1 year prior to nutrient patch addition. Within days after patch addition, colour changes in the leaves of the mycorrhizal plants (reflecting improved nutrition) were apparent, and after I month the concentration of N and P in the foliage of mycorrhizal plants was significantly greater than that in non-mycorrhizal plants subject to the same nutrient addition. It seems likely that the mycorrhizal plants were able to compete effectively with the wider soil microbiota and tap directly into the high quality organic resource patch via their extra-radical mycelium. We hypothesize that ectomycorrhizal plants may reclaim some of the N and P invested in seed production by direct recycling from failed seeds in the soil. The rapid exploitation of similar discrete, transient, high-quality nutrient patches may have led to underestimations when determining the nutritional benefits of ectomycorrhizal colonization.

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In ovariectomized rats, administration of estradiol, or selective estrogen receptor agonists that activate either the alpha or beta isoforms, have been shown to enhance spatial cognition on a variety of learning and memory tasks, including those that capitalize on the preference of rats to seek out novelty. Although the effects of the putative estrogen G-protein-coupled receptor 30 (GPR30) on hippocampus-based tasks have been reported using food-motivated tasks, the effects of activation of GPR30 receptors on tasks that depend on the preference of rats to seek out spatial novelty remain to be determined. Therefore, the aim of the current study was to determine if short-term treatment of ovariectomized rats with G-1, an agonist for GPR30, would mimic the effects on spatial recognition memory observed following short-term estradiol treatment. In Experiment 1, ovariectomized rats treated with a low dose (1mug) of estradiol 48h and 24h prior to the information trial of a Y-maze task exhibited a preference for the arm associated with the novel environment on the retention trial conducted 48h later. In Experiment 2, treatment of ovariectomized rats with G-1 (25mug) 48h and 24h prior to the information trial of a Y-maze task resulted in a greater preference for the arm associated with the novel environment on the retention trial. Collectively, the results indicated that short-term treatment of ovariectomized rats with a GPR30 agonist was sufficient to enhance spatial recognition memory, an effect that also occurred following short-term treatment with a low dose of estradiol.

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In southern Bahia, Brazil, large land areas are used for the production of cocoa (Theobroma cacao), which is predominantly grown under the shade of native trees in an agroforestry system locally known as cabruca. As a dominant forest-like landscape element of the cocoa region, the cabrucas play an important role in the conservation of the region`s biodiversity. The purpose of this review is to provide the scientific basis for an action plan to reconcile cocoa production and biodiversity conservation in southern Bahia. The available research collectively highlights the diversity of responses of different species and biological groups to both the habitat quality of the cabrucas themselves and to the general characteristics of the landscape, such as the relative extent and spatial configuration of different vegetation types within the landscape mosaic. We identify factors that influence directly or indirectly the occurrence of native species in the cabrucas and the wider landscape of the cocoa region and develop recommendations for their conservation management. We show that the current scientific knowledge already provides a good basis for a biodiversity friendly management of the cocoa region of southern Bahia, although more work is needed to refine some management recommendations, especially on shade canopy composition and density, and verify their economic viability. The implementation of our recommendations should be accompanied by appropriate biological and socioeconomic monitoring and the findings should inform a broad program of adaptive management of the cabrucas and the wider cocoa landscape.

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Eumenitin, a novel cationic antimicrobial peptide from the venom of solitary wasp Eumenes rubronotatus, was characterized by its effects on black lipid membranes of negatively charged (azolectin) and zwitterionic (1,2-diphytanoyl-sn-glycero-3-phosphocholine (DPhPC) or DPhPC-cholesterol) phospholipids: surface potential changes, single-channel activity, ion selectivity, and pore size were studied. We found that eumenitin binds preferentially to charged lipid membranes as compared with zwitterionic ones. Eumenitin is able to form pores in azolectin (G(1) = 118.00 +/- 3.67 pS or G(2) = 160.00 +/- 7.07 pS) and DPhPC membranes (G = 61.13 +/- 7.57 pS). Moreover, cholesterol addition to zwitterionic DPhPC membranes inhibits pore formation activity but does not interfere with the binding of peptide. Open pores presented higher cation (K (+)) over anion (Cl-) selectivity. The pore diameter was estimated at between 8.5and 9.8 angstrom in azolectin membranes and about 4.3 angstrom in DPhPC membranes. The results are discussed based on the toroidal pore model for membrane pore-forming activity and ion selectivity. (c) 2007 Elsevier Ltd. All rights reserved.

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Candida albicans is the most common opportunistic fungal pathogen and causes local and systemic disease in immunocompromised patients. Alveolar macrophages (AMs) are pivotal for the clearance of C. albicans from the lung. Activated AMs secrete 5-lipoxygenase-derived leukotrienes (LTs), which in turn enhance phagocytosis and microbicidal activity against a diverse array of pathogens. Our aim was to investigate the role of LTB(4) and LTD(4) in AM antimicrobial functions against C. albicans and the signaling pathways involved. Pharmacologic and genetic inhibition of LT biosynthesis as well as receptor antagonism reduced phagocytosis of C. albicans when compared with untreated or WT controls. Conversely, exogenous LTs of both classes augmented base-line C. albicans phagocytosis by AMs. Although LTB(4) enhanced mainly mannose receptor-dependent fungal ingestion, LTD(4) enhanced mainly dectin-1 receptor-mediated phagocytosis. LT enhancement of yeast ingestion was dependent on protein kinase C-delta (PKC delta) and PI3K but not PKC alpha and MAPK activation. Both LTs reduced activation of cofilin-1, whereas they enhanced total cellular F-actin; however, LTB(4) accomplished this through the activation of LIM kinases (LIMKs) 1 and 2, whereas LTD(4) did so exclusively via LIMK-2. Finally, both exogenous LTB(4) and LTD(4) enhanced AM fungicidal activity in an NADPH oxidase-dependent manner. Our data identify LTB(4) and LTD(4) as key mediators of innate immunity against C. albicans, which act by both distinct and conserved signaling mechanisms to enhance multiple antimicrobial functions of AMs.

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The use of liposomes to encapsulate materials has received widespread attention for drug delivery, transfection, diagnostic reagent, and as immunoadjuvants. Phospholipid polymers form a new class of biomaterials with many potential applications in medicine and research. Of interest are polymeric phospholipids containing a diacetylene moiety along their acyl chain since these kinds of lipids can be polymerized by Ultra-Violet (UV) irradiation to form chains of covalently linked lipids in the bilayer. In particular the diacetylenic phosphatidylcholine 1,2-bis(10,12-tricosadiynoyl)- sn-glycero-3-phosphocholine (DC8,9PC) can form intermolecular cross-linking through the diacetylenic group to produce a conjugated polymer within the hydrocarbon region of the bilayer. As knowledge of liposome structures is certainly fundamental for system design improvement for new and better applications, this work focuses on the structural properties of polymerized DC8,9PC:1,2-dimyristoyl-sn-glycero-3-phusphocholine (DMPC) liposomes. Liposomes containing mixtures of DC8,9PC and DMPC, at different molar ratios, and exposed to different polymerization cycles, were studied through the analysis of the electron spin resonance (ESR) spectra of a spin label incorporated into the bilayer, and the calorimetric data obtained from differential scanning calorimetry (DSC) studies. Upon irradiation, if all lipids had been polymerized, no gel-fluid transition would be expected. However, even samples that went through 20 cycles of UV irradiation presented a DSC band, showing that around 80% of the DC8,9PC molecules were not polymerized. Both DSC and ESR indicated that the two different lipids scarcely mix at low temperatures, however few molecules of DMPC are present in DC8,9PC rich domains and vice versa. UV irradiation was found to affect the gel fluid transition of both DMPC and DC8,9PC rich regions, indicating the presence of polymeric units of DC8,9PC in both areas, A model explaining lipids rearrangement is proposed for this partially polymerized system.

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The use of melanin in bioinspired applications is mostly limited by its poor stability in solid films. This problem has been addressed here by incorporating melanin into dipalmitoyl phosphatidyl glycerol (DPPG) liposomes, which were then immobilized onto a solid substrate as an LbL film. Results from steady-state and time-resolved fluorescence indicated an increased stability for melanin incorporated into DPPG liposomes. If not protected by liposomes, melanin looses completely its fluorescence properties in LbL films. The thickness of the liposome-melanin layer obtained from neutron reflectivity data was 4.1 +/- 0.2 nm, consistent with the value estimated for the phospholipid bilayer of the liposomes, an evidence of the collapse of most liposomes. On the other hand, the final roughness indicated that some of the liposomes had their structure preserved. In summary, liposomes were proven excellent for encapsulation, thus providing a suitable environment, closer to the physiological conditions without using organic solvents or high pHs. (C) 2010 Elsevier Inc. All rights reserved.

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Cationic supported bilayers on latex are useful to isolate and immobilize oppositely charged proteins as a monomolecular layer over a range of low protein concentrations and particle number densities. Cholera toxin (CT) from Vibrio cholerae, an 87 kDa AB(5) hexameric protein and bovine serum albumin (BSA) self-assembled on dioctadecyldimethylammonium bromide (DODAB) supported bilayers with high affinity yielding highly organized and monodisperse particulates at 5 x 10(9) particles/mL, over a range of low protein concentrations (0-0.025 mg/mL BSA or CT). Protein association onto the bilayer-covered polystyrene sulfate (PSS) was determined from adsorption isotherms, dynamic light scattering for size distributions and zeta-potential analysis revealing a monomolecular, thin and highly organized protein layer surrounding each particle with potential for biospecific recognition such as antigen-antibody, receptor-ligand, hybridization of oligonucleotide sequences, all of them important in immunodiagnosis, selective biomolecular chromatographic separations, microarrays design and others.

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The interaction between giant bacteriophage DNA and cationic biomimetic particles was characterized from sizing by dynamic light-scattering, zeta-potential analysis, turbidimetry, determination of colloid stability, visualization from atomic force microscopy (AFM), and determination of cytotoxicity against E. coli from colony forming unities counting. First, polystyrene sulfate (PSS) particles with different sizes were covered by a dioctadecyldimethylammonium bromide (DODAB) bilayer yielding the so-called cationic biomimetic particles (PSS/DODAB). These cationic particles are highly organized, present a narrow size distribution and were obtained over a range of particle sizes. Thereafter, upon adding lambda, T5 or T2-DNA to PSS/DODAB particles, supramolecular assemblies PSS/DODAB/DNA were obtained and characterized over a range of DNA concentrations and particle sizes (80-700 nm). Over the low DNA concentration range, PSS/DODAB/DNA assemblies were cationic, colloidally stable with moderate polydispersity and highly cytotoxic against E. coli. From DNA concentration corresponding to charge neutralization, neutral or anionic supramolecular assemblies PSS/DODAB/DNA exhibited low colloid stability, high polydispersity and moderate cytotoxicity. Some nucleosome mimetic assemblies were observed by AFM at charge neutralization (zeta-potential equal to zero).

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Artificial vesicles or liposomes composed of lipid bilayers have been widely exploited as building blocks for artificial membranes, in attempts to mimic membrane interaction with drugs and proteins and to investigate drug delivery processes. In this study we report on the immobilization of liposomes of 1,2-dipalmitoyi-sn-Glycero-3-[Phospho-rac-(1-glycerol)] (Sodium Salt) (DPPG) in layer-by-layer (LbL) films, alternated with poly (amidoamine) G4 (PAMAM) dendrimer layers. The average size of the liposomes in solution was 120 nm as determined by dynamic light scattering, with their spherical shape being inferred from scanning electron microscopy (SEM) in cast films. LbL films containing up to 20 PAMAM/DPPG bilayers were assembled onto glass and/or silicon wafer substrates. The growth of the multilayers was achieved by alternately immersing the substrates into the PAMAM and DPPG solutions for 5 and 10 min, respectively. The formation of PAMAM/DPPG liposome multilayers and its ability to interact with BSA were confirmed by Fourier transform infrared spectroscopy (FTIR). The structural features and film thickness were obtained using X-ray diffraction and surface plasmon resonance (SPR). (c) 2007 Elsevier B.V. All rights reserved.