6,582 research outputs found
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)
Participação no XI Met-Encontro nacional sobre metodologias de laboratório.
bitstream/CNPA/18316/1/DOC161.pd
Confining potential in a color dielectric medium with parallel domain walls
We study quark confinement in a system of two parallel domain walls
interpolating different color dielectric media. We use the phenomenological
approach in which the confinement of quarks appears considering the QCD vacuum
as a color dielectric medium. We explore this phenomenon in QCD_2, where the
confinement of the color flux between the domain walls manifests, in a scenario
where two 0-branes (representing external quark and antiquark) are connected by
a QCD string. We obtain solutions of the equations of motion via first-order
differential equations. We find a new color confining potential that increases
monotonically with the distance between the domain walls.Comment: RevTex4, 5 pages, 1 figure; version to appear in Int. J. Mod. Phys.
Aproveitamento de cascas de banana para a produção de farinha.
Breve revisão sobre casca de banana. Disponibilidade de casca de banana em algumas indústrias do Estado do Rio de Janeiro. Secagem de cascas de banana.bitstream/item/65473/1/CTAA-DOCUMENTOS-34-APROVEITAMENTO-DE-CASCAS-DE-BANANA-PARA-A-PRODUCAO-DE-FARINHA-FL-08851.pd
Can we see pulsars around Sgr A*? - The latest searches with the Effelsberg telescope
Radio pulsars in relativistic binary systems are unique tools to study the
curved space-time around massive compact objects. The discovery of a pulsar
closely orbiting the super-massive black hole at the centre of our Galaxy, Sgr
A*, would provide a superb test-bed for gravitational physics. To date, the
absence of any radio pulsar discoveries within a few arc minutes of Sgr A* has
been explained by one principal factor: extreme scattering of radio waves
caused by inhomogeneities in the ionized component of the interstellar medium
in the central 100 pc around Sgr A*. Scattering, which causes temporal
broadening of pulses, can only be mitigated by observing at higher frequencies.
Here we describe recent searches of the Galactic centre region performed at a
frequency of 18.95 GHz with the Effelsberg radio telescope.Comment: 3 pages, 2 figures, Proceedings of IAUS 291 "Neutron Stars and
Pulsars: Challenges and Opportunities after 80 years", 201
Características químicas de sementes de melancia (Citrullus vulgaris), produzidas espontaneamente numa área cultivada com Atriplex irrigada com água salobra.
o objetivo de identificar e caracterizar as propriedades químicas de sementes de melancia - Citrullus vulgaris, (registro CPATSA n° 017, ano 1977), foram coletadas sementes ao acaso de um lote de frutos colhidos em 2004
Impactos socioeconômicos de cultivares de feijão caupi na Região Meio-Norte do Brasil.
Caracterizacão das cultivares geradas; BR 17-Gurgueia; BR 14-Mulato; Cultivar Monteiro; Impactos socioeconômicos; Desafios.bitstream/item/36496/1/Doc52.pd
Black Widow Pulsars: the Price of Promiscuity
The incidence of evaporating 'black widow' pulsars (BWPs) among all
millisecond pulsars (MSPs) is far higher in globular clusters than in the
field. This implies a special formation mechanism for them in clusters. Cluster
MSPs in wide binaries with WD companions exchange them for turnoff-mass stars.
These new companions eventually overflow their Roche lobes because of
encounters and tides. The millisecond pulsars eject the overflowing gas from
the binary, giving mass loss on the binary evolution timescale. The systems are
only observable as BWPs at epochs where this evolution is slow, making the mass
loss transparent and the lifetime long. This explains why observed BWPs have
low-mass companions. We suggest that at least some field BWPs were ejected from
globular clusters or entered the field population when the cluster itself was
disrupted.Comment: 6 pages, 2 figures, MNRAS in pres
Discovery of three new millisecond pulsars in Terzan 5
We report on the discovery of three new millisecond pulsars (namely
J1748-2446aj, J1748-2446ak and J1748-2446al) in the inner regions of the dense
stellar system Terzan 5. These pulsars have been discovered thanks to a method,
alternative to the classical search routines, that exploited the large set of
archival observations of Terzan 5 acquired with the Green Bank Telescope over 5
years (from 2010 to 2015). This technique allowed the analysis of stacked power
spectra obtained by combining ~206 hours of observation. J1748-2446aj has a
spin period of ~2.96 ms, J1748-2446ak of ~1.89 ms (thus it is the fourth
fastest pulsar in the cluster) and J1748-2446al of ~5.95 ms. All the three
millisecond pulsars are isolated and currently we have timing solutions only
for J1748-2446aj and J1748-2446ak. For these two systems, we evaluated the
contribution to the measured spin-down rate of the acceleration due to the
cluster potential field, thus estimating the intrinsic spin-down rates, which
are in agreement with those typically measured for millisecond pulsars in
globular clusters. Our results increase to 37 the number of pulsars known in
Terzan 5, which now hosts 25% of the entire pulsar population identified, so
far, in globular clusters.Comment: 10 pages, 6 figures. ApJ (accepted
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