Search results for " Barrier"
showing 10 items of 540 documents
Interpretación social y accesibilidad. Una propuesta de conexión disciplinar
2020
El objetivo de este estudio es ofrecer argumentos para entender la actividad propia de la interpretación social como parte del dominio genérico de la accesibilidad. Al hacerlo no ampliamos en realidad el concepto de accesibilidad, sino que reforzamos aquello que justifica el uso de este término, para diferenciar una parcela de actividad dentro de la práctica general de la traducción y la interpretación. Con el tema de la accesibilidad sucede que se ha manejado una etiqueta sin una delimitación conceptual previa de lo que se pretende designar por medio de ella. En este estudio nos ocupamos brevemente de esta tarea de aproximación conceptual, con el objetivo de incluir bajo el abanico de las …
A Polyphenylene Dendrimer Drug Transporter with Precisely Positioned Amphiphilic Surface Patches
2014
The design and synthesis of a polyphenylene dendrimer (PPD 3) with discrete binding sites for lipophilic guest molecules and characteristic surface patterns is presented. Its semi-rigidity in combination with a precise positioning of hydrophilic and hydrophobic groups at the periphery yields a refined architecture with lipophilic binding pockets that accommodate defined numbers of biologically relevant guest molecules such as fatty acids or the drug doxorubicin. The size, architecture, and surface textures allow to even penetrate brain endothelial cells that are a major component of the extremely tight blood-brain barrier. In addition, low to no toxicity is observed in in vivo studies using…
Functional feature of a novel model of blood brain barrier: Studies on permeation of test compounds
2001
Drug delivery to the central nervous system (CNS) is subject to the permeability limitations imposed by the blood-brain barrier (BBB). Several systems in vitro have been described to reproduce the physical and biochemical behavior of intact BBB, most of which lack the feature of the in vivo barrier. We developed a fully formed monolayer of RBE4.B immortalized rat brain microvessel endothelial cells (ECs), grown on top of polycarbonate filter inserts with cortical neuronal cells grown on the outside. Neurons induce ECs to synthesize and sort occludin to the cell periphery. Occludin localization is regulated by both compositions of the substratum and soluble signals released by cortical co-cu…
Studies on a new potential dopaminergic agent: in vitro BBB permeability, in vivo behavioural effects and molecular docking evaluation.
2015
2-Amino-N-[2-(3,4-dihydroxy-phenyl)-ethyl]-3-phenyl-propionamide (DA-PHEN) has been previously synthesized to obtain a potential prodrug capable of release dopamine (DA) into CNS. However, DA-PHEN could act per se as a dopaminergic drug. In this study, the permeability transport (Pe), obtained by parallel artificial permeability assay (PAMPA), indicated a low passive transcellular transport (Pe = 0.32 ± 0.01 × 10(-6 )cm/s). Using the Caco-2 cell system, the Papp AP-BL in absorptive direction (3.36 ± 0.02 × 10(-5 )cm/s) was significantly higher than the Papp BL-AP in secretive direction (1.75 ± 0.07 × 10(-5 )cm/s), suggesting a polarized transport. The efflux ratio (Papp AP-BL/Papp BL-AP = 0…
Adaptation and ecological speciation in seasonally varying environments at high latitudes: Drosophila virilis group
2022
Living in high latitudes and altitudes sets specific requirements on species’ ability to forecast seasonal changes and to respond to them in an appropriate way. Adaptation into diverse environmental conditions can also lead to ecological speciation through habitat isolation or by inducing changes in traits that influence assortative mating. In this review, we explain how the unique time-measuring systems of Drosophila virilis group species have enabled the species to occupy high latitudes and how the traits involved in species reproduction and survival exhibit strong linkage with latitudinally varying photoperiodic and climatic conditions. We also describe variation in reproductive barriers…
Amphiphilic HPMA-LMA copolymers increase the transport of Rhodamine 123 across a BBB model without harming its barrier integrity.
2012
Abstract The successful non-invasive treatment of diseases associated with the central nervous system (CNS) is generally limited by poor brain permeability of various developed drugs. The blood–brain barrier (BBB) prevents the passage of therapeutics to their site of action. Polymeric drug delivery systems are promising solutions to effectively transport drugs into the brain. We recently showed that amphiphilic random copolymers based on the hydrophilic p(N-(2-hydroxypropyl)-methacrylamide), pHPMA, possessing randomly distributed hydrophobic p(laurylmethacrylate), pLMA, are able to mediate delivery of domperidone into the brain of mice in vivo. To gain further insight into structure–propert…
Lipid Nanoparticles for Drug Targeting to the Brain
2012
In this chapter, the main production methods of lipid nanostructures such as solid lipid nanoparticles and nanostructured lipid carriers, and their application are described. In particular, we describe the strategies commonly used to obtain lipid nanoparticles to overcome the blood-brain barrier (BBB) for the treatment of several brain diseases. The use of these carriers as targeted drug delivery systems is associated with many advantages that include excellent storage stability, easy production without the use of any organic solvent, the possibility of steam sterilization and lyophilization, and large scale production. They exhibit good stability during long-term storage, consist of physio…
Potential of biopartitioning micellar chromatography as an in vitro technique for predicting drug penetration across the blood–brain barrier
2004
The blood-brain barrier (BBB) is considered to be the main barrier to drug transport into the central nervous system (CNS). The BBB restricts the passive diffusion of many drugs from blood to brain. The ease with which any particular drug diffuses across the BBB is determined largely by the molecular features of drugs, and it is therefore possible to predict the BBB permeability of a drug from its molecular structure. Biopartitioning micellar chromatography (BMC), a mode of micellar liquid chromatography that uses micellar mobile phases of Brij35 in adequate experimental conditions, can be useful in mimicking the drug partitioning process into biological systems. Retention in BMC depends on…
Amphiphilic Copolymers Shuttle Drugs Across the Blood-Brain Barrier.
2015
Medical treatment of diseases of the central nervous system requires transport of drugs across the blood-brain barrier (BBB). Here, it is extended previously in vitro experiments with a model compound to show that the non-water-soluble and brain-impermeable drug domperidone (DOM) itself can be enriched in the brain by use of an amphiphilic copolymer as a carrier. This carrier consists of poly(N-(2-hydroxypropyl)-methacrylamide), statistically copolymerized with 10 mol% hydrophobic lauryl methacrylate, into whose micellar aggregates DOM is noncovalently absorbed. As tested in a BBB model efficient transport of DOM across, the BBB is achievable over a wide range of formulations, containing 0.…
Electrical and photoelectrical measurements on ZnO-Nanowires coated with PEDOT:PSS for Dye-Sensitized Solar Cells
2011
ABSTRACTDye-sensitized solar cells composed of an n-doped ZnO nanowire array and a p-doped polymer layer appears to be a promising candidate for low-cost production of environment-friendly solar cells. In this work, we investigate hybrid devices consisting of a transparent conducting oxide (TCO) substrate, ZnO-nanowires (ZnO-NW) or a sol-gel prepared ZnO layer, a ruthenium dye (N719) and a PEDOT:PSS or P3HT layer. The dense polycrystalline ZnO layer is able to prevent short circuits, which have a strong effect on the performance of the solar cells. This is demonstrated by the use of only the ZnO layer which improves the open circuit voltage by a factor of 2 and the efficiency by a factor of…