352 research outputs found
Adsorptive endocytosis and membrane recycling by cultured primary bovine brain microvessel endothelial cell monolayers
The dynamics of membrane recycling were examined
in primary cultures of brain microvessel endothelial
cells (BMECs). Because the BMEC surface was dominated
by galactosylated glycoconjugates, ricin agglutinin
(RCAI) was used as a tracer to follow the
endocytosis and recycling of RCAI binding sites.
These binding sites accounted for 75 % of the iodinatable
or most externally disposed plasma membrane
proteins. Because greater than 90 % of the RCAI that
had bound to BMECs was removed by a brief, nontoxic
treatment with galactose, the amounts and
kinetics for internalization and efflux of [125I]RCAI
were measured. Both endocytosis and efflux were
energy dependent. By using pseudo-first-order kinetics,
the £j values for RCAI binding, internalization
and efflux were 5, 18 and 13-14 min, respectively. By
comparing efflux with and without galactose present,
we found that 60 % of the RCAI binding sites that had
been internalized were returned to the cell surface
and reinternalized. Quantifying the distribution of
gold-RCAI following internalization showed kinetics
consistent with that obtained using radiolabeled
RCAI. Both horseradish peroxidase (HRP) and
gold-conjugated RCAI that had bound BMEC at 4°C
became localized within more caveolae within
2.5 min of warming to 37 °C to permit endocytosis.
With time, RCAI appeared within endosomes and
tubules and vesicles of which some were located in
the trans-Golgi network (TGN). The distribution of
HRP-RCAI contrasted with that of free HRP, which
was not routed to the TGN. The absence of RCAI
conjugates in association with the basolateral membrane
domain suggested the presence of functional
tight junctions and maintenance of polarity throughout
the duration of these experiments. These results
showed that membrane recycling was more extensive
and much slower than fluid-phase endocytosis in
cultured BMECs. Moreover, we found that endocytosis
of membrane by BMECs in culture was similar
to that reported for brain endothelium in vivo in
that a fraction of the cell surface membrane was
routed to the TGN
Overcoming the blood-brain barrier to taxane delivery for brain tumors and neurodegenerative diseases and brain tumors
The original publication is available at www.springerlink.comThe blood-brain barrier (BBB) effectively prevents microtubule stabilizing drugs from readily entering the central nervous system (CNS). A major limiting factor for microtubule stabilizing drug permeation across the BBB is the active efflux back into the circulation by the over-expression of the multidrug resistant gene product (MDR1) or P-glycoprotein (P-gp). This study has focused on strategies to overcome P-gp-mediated efflux of taxol analogues, microtubule (MT) stabilizing agents that could be used to treat brain tumors and, potentially, neurodegenerative diseases such as Alzheimer’s disease. However, taxol is a strong P-gp substrate which limits its distribution across the BBB and therapeutic potential in the CNS. We have found that addition of a succinate group to the C-10 position of taxol results in an agent, Tx-67, with reduced interactions with P-gp and enhanced permeation across the BBB in both in vitro and in situ models. Our studies demonstrate the feasibility of making small chemical modifications to taxol to generate analogues with reduced affinity for the P-gp but retention of MT-stabilizing properties, i.e., a taxane that may reach and treat therapeutic targets in the CNS
Paclitaxel Succinate Analogs: Anionic Introduction as a Strategy to Impart Blood Brain Barrier Permeability
A focused library of TX-67 (C10 hemi-succinate) analogs have been prepared including regioisomeric, functional group, and
one-carbon homologs. These were prepared to investigate TX-67’s lack of interaction with P-glycoprotein (Pgp). Tubulin stabilization
ability, cytotoxicity, and Pgp interactions were evaluated. All carboxylic acid analogs had no apparent interactions with Pgp whereas the
ester variants of the same compounds displayed characteristics of Pgp substrates. Furthermore, it is demonstrated that hydrogen-bonding
properties were significant with respect to Pgp interactions. This anionic introduction strategy may allow for delivery of paclitaxel into
the CNS as well as establishing a new method for delivery of other, non-CNS permeable drugs
Targeting carrier-mediated transport to improve the blood-brain barrier permeation of paclitaxel
A relevant in vitro rat model for the evaluation of blood-brain barrier translocation of nanoparticles
Poly(MePEG2000cyanoacrylate-co-hexadecylcyanoacrylate) (PEG-PHDCA) nanoparticles have demonstrated their capacity to reach the rat central nervous system after intravenous injection. For insight into the transport of colloidal systems across the blood-brain barrier (BBB), we developed a relevant in vitro rat BBB model consisting of a coculture of rat brain endothelial cells (RBECs) and rat astrocytes. The RBECs used in our model displayed and retained structural characteristics of brain endothelial cells, such as expression of P-glycoprotein, occludin and ZO-1, and immunofluorescence studies showed the specific localization of occludin and ZO1. The high values of transendothelial electrical resistance and low permeability coefficients of marker molecules demonstrated the functionality of this model. The comparative passage of polyhexadecylcyanoacrylate and PEG-PHDCA nanoparticles through this model was investigated, showing a higher passage of PEGylated nanoparticles, presumably by endocytosis. This result was confirmed by confocal microscopy. Thanks to a good in vitro/in vivo correlation, this rat BBB model will help in understanding the mechanisms of nanoparticle translocation and in designing new types of colloidal carriers as brain delivery systems
Action potentials in abscisic acid-deficient tomato mutant generated spontaneously and evoked by electrical stimulation
Action potentials generated spontaneously (SAPs) and evoked by electrical stimulation (APs) in tomato plants (Solanum lycopersicum L.) cv. Micro-Tom ABA-deficient mutants (sitiens—MTsit) and its wild type (MTwt) were characterized by continuous monitoring of electrical activity for 66 h and by application of an electrical stimulation supplied extracellularly. MTsit generated SAPs which spread along the stem, including petioles and roots with an amplitude of 44.6 ± 4.4 mV, half-time (t½) of 33.1 ± 2.9 s and velocity of 5.4 ± 1.0 cm min−1. Amplitude and velocity were 43 and 108 % higher in MTsit than in MTwt, respectively. The largest number of SAPs was registered in the early morning in both genotypes. MTsit was less responsive to electrical stimuli. The excitation threshold and the refractory period were greater in MTsit than in MTwt. After current application, APs were generated in the MTwt with 21.2 ± 2.4 mV amplitude and propagated with 5.6 ± 0.5 cm min−1 velocity. Lower intensity stimuli did not trigger APs in these plants. In MTsit APs were measured with amplitude of 26.8 ± 4.8 mV and propagated with velocity of 8.5 ± 0.1 cm min−1
Estudos anatômicos de folhas de espécies de plantas daninhas de grande ocorrência no Brasil: III - Galinsoga parviflora, Crotalaria incana, Conyza bonariensis e Ipomoea cairica
Efeitos de retardadores de crescimento na frutificação da videira 'Niagara Rosada'
Studies were carried out to establish the effects of exogenous growth regulators on Vitis (labrusca x vinifera) 'Niagara Rosada' fruiting. The investigations were done in the Jundiaà Research Station, Agronomic Institute State of São Paulo, always using disease-free vineyards of good productivity. The morphological transformations of clusters were studied under the following aspects: weight, length and width of cluster; weight, length average and width average of berries: length average/width average ratio of berries; length and diameter of rachis; width of cluster minus berries; length and diameter of secondary rachis. The yield for the first half of the period from flowering to maturation was first determined. The same characteristics were determined at the time of maturity plus the number of berries, number of seeds, total sugars, total acid, Maturity Index and reducing sugars in samples of all treatments. The experiment was conducted in order to determine the doses that resulted in the most beneficial effects, always using applications by immersion of the inflorescence. In the experiment was realized applications of (2-chloroethyl) trimethylammonium chloride (CCC) and succinic aeid-2, 2-dimethylhydrazide (SADH) at concentrations of 50, 100, 250, 500, 1000 and 2000 ppm; CCC 500 ppm plus SADH 500 ppm and nontreated, 5 days before flowering, in 1971. The concentrations of CCC applied before flowering did not affect favorably cluster morphology under the conditions of the experiment. Application of SADH at 250 ppm before flowering increased the cluster weight and length, berries number and weight, and seed number. In the first yield treatment of 1000 ppm of SADH increased the cluster weight and lenght, berry weight and rachis lenght.Estudou-se a influência da aplicação por imersão, de retardadores de crescimento (CCC e SADH), 5 dias antes do florescimento, nas caracterÃsticas morfológicas da panÃcuia da videira Vitis (labrusca x vinifera) 'Niagara Rosada'. Neste ensaio verificou-se que as concentrações de CCC aplicadas em pré-florescimento, não afetaram favoravelmente a morfologia das panÃculas da cultivar estudada, nas condições do ensaio. SADH na dosagem de 1000 ppm provocou, na primeira colheita, aumento no peso e comprimento da panÃcula, no peso das bagas, e no comprimento da ráquis, proporcionando a formação desejada de uma panÃcula mais alongada, nas condições estudadas. Aplicação de SADH na concentração de 250 ppm em pré-florescimento, promoveu aumento no peso e comprimento da panÃcula, número e peso das bagas, além do inconveniente de elevar o número de sementes
Paroxetine and bupropion have no in vitro effects on lynphocyte proliferation and viability
On the Integration of Carbon Capture and Storage into the International Climate Regime
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