Translocating the blood-brain barrier using electrostatics

Copyright © 2012 Ribeiro,Domingues, Freire,Santos and Castanho. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in other forums, provided the original authors and source are credited and subject to any copyright notices concerning any third-party graphics etc.Mammalian cell membranes regulate homeostasis, protein activity, and cell signaling. The charge at the membrane surface has been correlated with these key events. Although mammalian cells are known to be slightly anionic, quantitative information on the membrane charge and the importance of electrostatic interactions in pharmacokinetics and pharmacodynamics remain elusive. Recently, we reported for the first time that brain endothelial cells (EC) are more negatively charged than human umbilical cord cells, using zeta-potential measurements by dynamic light scattering. Here, we hypothesize that anionicity is a key feature of the blood-brain barrier (BBB) and contributes to select which compounds cross into the brain. For the sake of comparison, we also studied the membrane surface charge of blood components—red blood cells (RBC), platelets, and peripheral blood mononuclear cells (PBMC).To further quantitatively correlate the negative zeta-potential values with membrane charge density, model membranes with different percentages of anionic lipids were also evaluated. From all the cells tested, brain cell membranes are the most anionic and those having their lipids mostly exposed, which explains why lipophilic cationic compounds are more prone to cross the blood-brain barrier.Fundação para a Ciência e Tecnologia — Ministério da Educação e Ciência (FCT-MEC, Portugal) is acknowledged for funding (including fellowships SFRH/BD/42158/2007 to Marta M.B. Ribeiro, SFRH/BD/41750/2007 to Marco M. Domingues and SFRH/BD/70423/2010 to João M. Freire) and project PTDC/QUI-BIQ/119509/2010. Marie Curie Industry-Academia Partnerships and Pathways (European Commission) is also acknowledged for funding (FP7-PEOPLE-2007-3-1-IAPP, Project 230654)

Cleavages of photochromic compounds derived from heterocycles under electrospray tandem mass spectrometry : study of the influence of the heteroatom in fragmentation mechanisms

In this paper we report the fragmentation pathways of chromenes derived from carbazole, dibenzofuran and dibenzothiophene, under ESI-MS/MS experimental conditions, and their relationship with structural features, specially focused on the heteroatom’s effect on the fragmentation mechanisms.Fundação para a Ciência e Tecnologia (FCT

Thymus citriodorus: phenolic characterization and antioxidant activity

The present work aims to determine the phenolic composition of Thymus citriodorus and to estimate its antioxidant capacity. An ethanolic extract was prepared from the plant and its total phenolic and flavone contents were determined. The phenolic extract was fractionated by reversed-phase HPLC and the major phenolic compounds of each fraction were identified by ESI-MS and MSn analysis, in order to establish the specific phenolic profile of the plant. The total phenolic compounds in the ethanolic extract of Thymus citriodorus accounted for 138,75±13,56 mg/g, and its content of flavones was estimated as 27,30±2,15 mg/g. Moreover, the interpretation of the fragmentation pathways under ESI-MS/MS of the collected HPLC fractions allowed concluding that the major phenolic compounds in the plant included some glycoside derivatives of luteonin, naringenin and eriodictyol. Also, the phenolic extract showed a considerable antioxidant activity, as evaluated by the 2,2-diphenyl-1-picrylhydrazyl radical scavenging potential and the reducing potential, suggesting that Thymus citriodorus can be an important source of natural antioxidants

Mentha aquatica: source of flavanone glycosides

Mentha aquatica L., commonly known as water mint, is a perennial herb that grows in Europe temperate regions. This plant is used in traditional medicine for the treatment of external inflammation, rheumatism, colds, respiratory problems and difficult menstruation [1]. It has been described as a good source of phenolic compounds with high scavenger activity [2]. In this study, a purified ethanolic extract of M. aquatica was prepared and its specific phenolic composition was determined. The extract of the aerial parts of M. aquatica was prepared according the procedure described by Pereira et al [3] and analyzed by high performance liquid chromatography with diode array detection with quantification of main phenolic compounds, using the external standard method. In order to determine the exact structure of phenolic compounds, the HPLC eluted fractions were manually collected and further analyzed by tandem electrospray mass spectrometry. The purified ethanolic extract of M. aquatica was mainly rich in flavanones comprises eriodictyol, hesperitin and naringenin glycosides. Moreover, the purified ethanolic extract of M. aquatica contained moderate amounts of rosmarinic acid, a phenolic acid very common in Mentha species and in Lamiaceae family

Ethanol production from high-glucose industrial substrates using ethanol-tolerant Saccharomyces cerevisiae strains

Ethanol is well known as a toxic metabolite for yeast cells. Thus, strains that can grow well under high ethanol stress condition are highly desirable. This work aims to select and characterize Saccharomyces cerevisiae strains with improved ethanol tolerance. Moreover, it aims to evaluate the feasibility of industrial residues as fermentation media and to optimize the composition of such media. The ethanol production and tolerance of the yeast strains have been evaluated, carrying out batch alcoholic fermentations with high-glucose YP medium. The most ethanol-tolerant strain was able to ferment 300 g/L glucose producing up to 17.4 % (v/v) of ethanol in trials carried out in anaerobic shake-flasks. Aiming to develop a fermentation medium based in industrial substrates, corn steep liquor (CSL) has been tested as medium supplement, in order to replace nutrients that are needed to allow both cellular growth and fermentation. Supplementation of 300 g/L glucose medium with CSL concentrations around 90 - 110 g/L has resulted in fermentation performance similar to that observed in YP medium with the same glucose concentration, thus confirming the feasibility of CSL as peptone and yeast extract substitute

An open and parallel multiresolution framework using block-based adaptive grids

A numerical approach for solving evolutionary partial differential equations in two and three space dimensions on block-based adaptive grids is presented. The numerical discretization is based on high-order, central finite-differences and explicit time integration. Grid refinement and coarsening are triggered by multiresolution analysis, i.e. thresholding of wavelet coefficients, which allow controlling the precision of the adaptive approximation of the solution with respect to uniform grid computations. The implementation of the scheme is fully parallel using MPI with a hybrid data structure. Load balancing relies on space filling curves techniques. Validation tests for 2D advection equations allow to assess the precision and performance of the developed code. Computations of the compressible Navier-Stokes equations for a temporally developing 2D mixing layer illustrate the properties of the code for nonlinear multi-scale problems. The code is open source

Congenital syphilis: a sentinel event in antenatal care quality.

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Fermentation of high concentrations of lactose to ethanol by engineered flocculent saccharomyces cerevisiae

The development of microorganims that efficiently ferment lactose has a high biotechnological interest, particularly for cheese whey bioremediation processes with simultaneous bio-ethanol production. The lactose fermentation performance of a recombinant Saccharomyces cerevisiae flocculent strain was evaluated. The yeast consumed rapidly and completely lactose concentrations up to 150 g l-1 in either well- or micro-aerated batch fermentations. The maximum ethanol titre was 8% (v/v) and the highest ethanol productivity was 1.5–2 g l-1 h-1, in micro-aerated fermentations. The results presented here emphasise that this strain is an interesting alternative for the production of ethanol from lactose-based feedstocks.Fundação para a Ciência e a Tecnologia (FCT

Alcoholic fermentation of lactose by engineered flocculent Saccharomyces cerevisiae

The construction of Saccharomyces cerevisiae strains with the ability to ferment lactose has biotechnological interest, particularly for cheese whey fermentation to ethanol. Direct fermentation of whey to ethanol is generally not economically feasible because the low lactose content (ca. 5% w/v) results in low ethanol titre (2 – 3% v/v), making the distillation process too expensive. Concentration of whey lactose (e.g. by ultrafiltration) prior to fermentation is an option to obtain higher ethanol titres. Microbial strains are therefore needed that can efficiently convert high concentrations of lactose into ethanol. We describe here the engineering of a S. cerevisiae strain for efficient lactose fermentation, involving genetic and evolutionary engineering strategies. The evolved strain obtained fermented efficiently lactose concentrations up to 150 g L-1, including 3-fold concentrated cheese whey, producing ethanol titres up to 8% v/v. The strain is highly flocculent, a property that makes it particularly suitable for the development of high cell density fermentation processes