Synaptic vesicle glycoprotein 2A modulates vesicular release and calcium channel function at peripheral sympathetic synapses

Synaptic vesicle glycoprotein (SV)2A is a transmembrane protein found in secretory vesicles and is critical for Ca2+-dependent exocytosis in central neurons, although its mechanism of action remains uncertain. Previous studies have proposed, variously, a role of SV2 in the maintenance and formation of the readily releasable pool (RRP) or in the regulation of Ca2+ responsiveness of primed vesicles. Such previous studies have typically used genetic approaches to ablate SV2 levels; here, we used a strategy involving small interference RNA (siRNA) injection to knockdown solely presynaptic SV2A levels in rat superior cervical ganglion (SCG) neuron synapses. Moreover, we investigated the effects of SV2A knockdown on voltage-dependent Ca2+ channel (VDCC) function in SCG neurons. Thus, we extended the studies of SV2A mechanisms by investigating the effects on vesicular transmitter release and VDCC function in peripheral sympathetic neurons. We first demonstrated an siRNA-mediated SV2A knockdown. We showed that this SV2A knockdown markedly affected presynaptic function, causing an attenuated RRP size, increased paired-pulse depression and delayed RRP recovery after stimulus-dependent depletion. We further demonstrated that the SV2A–siRNA-mediated effects on vesicular release were accompanied by a reduction in VDCC current density in isolated SCG neurons. Together, our data showed that SV2A is required for correct transmitter release at sympathetic neurons. Mechanistically, we demonstrated that presynaptic SV2A: (i) acted to direct normal synaptic transmission by maintaining RRP size, (ii) had a facilitatory role in recovery from synaptic depression, and that (iii) SV2A deficits were associated with aberrant Ca2+ current density, which may contribute to the secretory phenotype in sympathetic peripheral neurons.

Multiple vesicular morphologies in AB/AC diblock copolymer complexes through hydrogen bonding interactions

We report for the first time multiple vesicular morphologies in block copolymer complexes formed in aqueous media via hydrogen bonding interactions. A model AB/AC diblock copolymer system consisting of polystyrene-block- poly(acrylic acid) (PS-b-PAA) and polystyrene-block-poly(ethylene oxide) (PS-b-PEO) was examined using transmission electron microscopy, small-angle X-ray scattering, and dynamic light scattering. The complexation and morphological transitions were driven by the hydrogen bonding between the complementary binding sites on PAA and PEO blocks of the two diblock copolymers. Upon the addition of PS-b-PEO, a variety of bilayer aggregates were formed in PS-b-PAA/PS-b-PEO complexes including vesicles, multilamellar vesicles (MLVs), thick-walled vesicles (TWVs), interconnected compound vesicles (ICCVs), and irregular aggregates. Among these aggregates, ICCVs were observed as a new morphology. The morphology of aggregates was correlated with respect to the molar ratio of PEO to PAA. At [EO]/[AA] = 0.5, vesicles were observed, while MLVs were obtained at [EO]/[AA] = 1. TWVs and ICCVs were formed at [EO]/[AA] = 2 and 6, respectively. When [EO]/[AA] reached 8 and above, only irregular aggregates appeared. These findings suggest that complexation between two amphiphilic diblock copolymers is a viable approach to prepare polymer vesicles in aqueous media.

Hydrogen bonding induced vesicular morphologies in diblock copolymer complexes

It is well-known that the self-assembly of block copolymers either in water or in organic solvents can form a wide range of morphologies in nanometer dimensions depending on its chemical nature. In the present study, the complexation and aggregate morphologies in a model AB/AC diblock copolymer system consisting of polystyrene-block-poly(acrylic acid) (PS-b-PAA) and polystyrene-block-poly(ethylene oxide) (PS-b-PEO) in water were studied using transmission electron microscopy (TEM), small angle X-ray scattering (SAXS), and dynamic light scattering (DLS). By varying the relative amounts of the two block copolymers, a variety of bilayer aggregates were formed, including vesicles, multilamellar vesicles (MLVs), thick-walled vesicles (TWVs), interconnected compound vesicles (ICCVs), and irregular aggregates. The hydrophobic PS blocks were segregated as the cores while the hydrogen bonded PEO and PAA blocks formed the coronae of bilayer aggregates. We also investigate how the addition of PS-b-PEO into PS-b-PAA solutions influences the aggregate morphology of the resulting complexes. This work introduces a viable route to multicompartment vesicles in aqueous solutions. The formation of block copolymer vesicles in water is of particular interest because of their potential in various applications.

Basalto Vesicular em Arrecife de Lanzarotte - Espanha

Videoaula sobre basalto amigdaloidal em Arrecife de Lanzarotte, Espanha.

Basalto Vesicular em Arrecife de Lanzarotte - Espanha

Apresentação de slides sobre Basalto Amigdaloidal

Erythrocyte ghost cell-alkaline phosphatase: construction and characterization of a vesicular system for use in biomineralization studies

Alkaline phosphatase is required for the mineralization of bone and cartilage. This enzyme is localized in the matrix vesicle, which plays a role key in calcifying cartilage. In this paper we standardize a method to construction a resealed ghost cell-alkaline phosphatase system to mimic matrix vesicles and examine the kinetic behavior of the incorporated enzyme. Polidocanol-solubilized alkaline phosphatase, free of detergent, was incorporated into resealed ghost cells. This process was time-dependent and practically 50% of the enzyme was incorporated into the vesicles in 40 h of incubation, at 25 degreesC. Alkaline phosphatase-ghost cell systems were relatively homogeneous with diameters of about 300 nm and were more stable when stored at -20 degreesC.Alkaline phosphatase was completely released from the resealed ghost cell-system using only phospholipase C. These experiments confirm that the interaction between alkaline phosphatase and the lipid bilayer of resealed ghost cell is exclusively via glycosylphosphatidylinositol (GPI) anchor of the enzyme.An important point shown is that an enzyme bound to resealed ghost cell does not lose the ability to hydrolyze ATP, pyrophosphate and p-nitrophenyl phosphate (PNPP), but the presence of a ghost membrane, as a support of the enzyme, affects its kinetic properties. Moreover, calcium ions stimulate and phosphate ions inhibit the PNPPase activity of alkaline phosphatase present in resealed ghost cells. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Nitrogen-tixing and vesicular-arbuscular mycorrhizal symbioses in some tropical legume trees of tribe Mimoseae

Response to mineral fertilization and inoculation with rhizobia and/or arbuscular mycorrhiza fungi (AMF) of the Anadenanthera colubrina, Mimosa bimucronata and Parapiptadenia rigida (Leguminosae-Mimosoideae) native trees from Brazilian riparian forests, were studied in nursery conditions. Each species was submitted to seven treatments, varying nitrogen and phosphorous fertilization and inoculation with rhizobia (r), mycorrhiza (m) or both (rm): NP, P, P + r, P + rm, N, N + m and N + rm. Results showed that AMF inoculations did not enhance the mycorrhizal colonization, and P uptake was not sufficient to sustain good growth of plants. The level of P mineral added affected negatively the AMF colonization in A. colubrina and M. bimucronata, but not in P. rigida. Native fungi infected the three legume hosts. The absence of mineral N limited growth of A. colubrina and P. rigida, but in M. bimucronata the lack of N was corrected by biological nitrogen fixation. N mineral added inhibited the nodulation, although spontaneous nodulation had occurred in A. colubrina and M. bimucronata. Rhizobia inoculation enhanced the number of nodules, nitrogenase activity and leghemoglobin content of these two species. Thus, the extent of rhizobial and mycorrhizal symbiosis in these species under nursery conditions can affect growth and consequently the post-planting success. (C) 2004 Elsevier B.V. All rights reserved.

Inactivation of vesicular stomatitis virus through inhibition of membrane fusion by chemical modification of the viral glycoprotein

Membrane fusion is an essential step in the entry of enveloped viruses into their host cells triggered by conformational changes in viral glycoproteins. We have demonstrated previously that modification of vesicular stomatitis virus (VSV) with diethylpyrocarbonate (DEPC) abolished conformational changes on VSV glycoprotein and the fusion reaction catalyzed by the virus. In the present study, we evaluated whether treatment with DEPC was able to inactivate the virus. Infectivity and viral replication were abolished by viral treatment with 0.5 mM DEPC. Mortality profile and inflammatory response in the central nervous system indicated that G protein modification with DEPC eliminates the ability of the virus to cause disease. In addition, DEPC treatment did not alter the conformational integrity of surface proteins of inactivated VSV as demonstrated by transmission electron microscopy and competitive ELISA. Taken together, our results suggest a potential use of histidine (His) modification to the development of a new process of viral inactivation based on fusion inhibition. © 2006 Elsevier B.V. All rights reserved.

Morphology and biometric of the vesicular and bulbourethral glands in castrated and non-castrated Santa Ines breed sheep

Introduction: The purpose of this paper is to determine the topography, biometry and light microscopy image of the vesicular and bulbourethral glands in order to analyze morphologic features of the accessory sexual glands in castrated and non-castrated animals. Materials and Methods: The morphology of the accessory sexual glands was investigated in 14 adult Santa Ines breed sheep, weighing 32 kg, on average. Six of them were castrated, and eight, non-castrated. For macroscopic study, the description of these two glands was carried out, as well as dissection and biometry study. Moreover, weight, length, height and width measurements were evaluated. For histological analysis, the vesicular and bulbourethral glands were sampled. Results: The topography of the reproductive glands was similar to bovine species. However, lower macroscopic measurements (p < 0,05) in the glands of the castrated sheep were evidenced when compared with the non-castrated ones. Characteristics such as shape of the glands, composition of the layer mucosa, the lamina propria, muscular, the excretory ducts and the adventitia were determined. Conclusion: Sheep castration promoted changes in the biometric measures of the glands, which were lower in castrated animals. The morphological and biometric characteristics of the vesicular and bulbourethral glands in sheep were determined.

Participação da glia nas alterações morfológicas do cérebro e na produção de beta-quimiocinas na encefalite experimental pelo vírus da estomatite vesicular em camundongos

Pós-graduação em Medicina Veterinária - FCAV

Age-dependent changes in rat lacrimal gland anti-oxidant and vesicular related protein expression profiles

Purpose: Anti-oxidation and exocytosis are important for maintaining exocrine tissue homeostasis. During aging, functional and structural alterations occur in the lacrimal gland (LG), including oxidative damage to proteins, lipids, and DNA. The aims of the present study were to determine in the aging LG: a) the effects of aging on LG structure and secretory activity and b) changes in the expression of oxidative stress markers. Methods: To address these goals, tear secretion composition and corneal impression cytology were compared between male Wistar rats of 2 (control) and 24 (aged) months. LG morphology and the expression levels of vitamin E and malonaldehyde (MDA) were evaluated to determine the anti-oxidant activity and lipid peroxidation, respectively. RT-PCR and western blot analysis were used for the analysis of Ras related in brain GTPase protein (Rab) and soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins of the secretory machinery (i.e.; Rab 3d, Rab 27, vesicle-associated membrane protein-2 (Vamp-2), and syntaxin). Results: Histological analysis of aged rats revealed a higher frequency of corneal epithelia metaplasia. In the acinar cells, organelles underwent degeneration, and lipofucsin-like material accumulated in the cytoplasm along with declines in the anti-oxidant marker vitamin E. Rab3d and Rab27b mRNA levels fell along with Rab3d protein expression, whereas syntaxin levels increased. Conclusions: These findings indicate that exocytotic and anti-oxidant mechanisms become impaired with age in the rat LG. In parallel with these structural alterations, functional declines may contribute to the pathophysiology caused by tear film modification in dry eye disease.

Agregación plaquetaria en perros con cáncer

[ES] Los trastornos psicopatológicos tienen una alta prevalencia (15-25%) y se asocian a numerosas variables. Por otro lado, el envejecimiento poblacional cada vez es mayor y los ancianos constituyen una población de riesgo donde a los factores que afectan a la población adulta se les asocian otros específicos. En este trabajo se evalúa la prevalencia de ansiedad y depresión en la población mayor de 65 años de Las Palmas de Gran Canaria y su relación con variables sociodemográficas y psicosociales. Para ello hemos estudiado en una muestra representativa de esta población: variables sociodemográficas, salud general percibida, hábitos de vida, nivel funcional, rasgos de ansiedad y depresión, acontecimientos vitales estresantes y apoyo social percibido.