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Search Results: 1 - 10 of 229537 matches for " Alejandra R. Alvarez "
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Herpetofauna de Santiago Jalahui,Oaxaca,Mexico
Alejandra Rendón R.,Ticul Alvarez,Oscar Flores Villela
Acta zoológica mexicana , 1998,
Abstract:
Oxidative Stress: A Pathogenic Mechanism for Niemann-Pick Type C Disease
Mary Carmen Vázquez,Elisa Balboa,Alejandra R. Alvarez,Silvana Zanlungo
Oxidative Medicine and Cellular Longevity , 2012, DOI: 10.1155/2012/205713
Abstract: Niemann-Pick type C (NPC) disease is a neurovisceral atypical lipid storage disorder involving the accumulation of cholesterol and other lipids in the late endocytic pathway. The pathogenic mechanism that links the accumulation of intracellular cholesterol with cell death in NPC disease in both the CNS and the liver is currently unknown. Oxidative stress has been observed in the livers and brains of NPC mice and in different NPC cellular models. Moreover, there is evidence of an elevation of oxidative stress markers in the serumof NPC patients. Recent evidence strongly suggests that mitochondrial dysfunction plays an important role in NPC pathogenesis and that mitochondria could be a significant source of oxidative stress in this disease. In this context, the accumulation of vitamin E in the late endosomal/lysosomal compartments in NPC could lead to a potential decrease of its bioavailability and could be another possible cause of oxidative damage. Another possible source of reactive species in NPC is the diminished activity of different antioxidant enzymes. Moreover, because NPC is mainly caused by the accumulation of free cholesterol, oxidized cholesterol derivatives produced by oxidative stress may contribute to the pathogenesis of the disease.
Comparison of Dennis's technology with the hepatic findings post - mortem for the diagnosis of the bovine fasciolosis Comparación de la técnica de Dennis con los hallazgos hepáticos post - mortem para el diagnóstico de la fasciolosis bovina
Alejandra Alvarez,Mauricio Boyacá
Cultura Científica , 2009,
Abstract: Fasciolosis is a type of parasitism, caused by the trematodes Fasciola hepaticathat uses mollusks lymneids as intermediate hosts. This parasite is widely distributed in the region and the country; its diagnosis is routinely performed through coprologic techniques applied to parasited vertebrates, consisting of egg detection in feces. The most commonly used, due to its brevity and low cost is the Dennis technique. This coprologic technique is based on the principle of eggs sedimentation. There fore, it depends on their outflow in the faecal matter, which makes itlittle sensitive for the parasite detection. Consequently, this study makes acomparison between the finds in the liver of slaughtered cattle of the plant Matadero in Tunja and the results of the Dennis technique, practiced in faecal samples of the same animals. The procedure was developed in a laboratory, getting data that indicates that the Dennis technique is not sensitive enoughto the Fasciola hepatica diagnosis and its continuous use must be evaluated. El presente estudio hace una comparación entre los resultados de la técnica de Dennis para diagnóstico de Fasciolosis bovina, frente a hallazgos post mortem, en hígados de bovinos faenados en la empresa Matadero de Tunja. Es un estudio experimental descriptivo, por cuanto expone los hallazgos en matadero frente a los arrojados por el método de Dennis. La población total de bovinos adultos fue de 2800, de los cuales se tomó una muestra de 139 animales. El muestreo se llevó a cabo durante el mes de febrero del a o 2009. Los resultados indican que la técnica de Dennis no es lo suficientemente sensible para el diagnóstico de Fasciola hepática, por lo que se debe evaluar su uso rutinario.La técnica coprológica se fundamenta en el principio de sedimentación delos huevos, por lo tanto depende la salida de éstos en la materia fecal, lo que la hace poco efectiva para la detección del parásito. La razón de este estudiose sustenta en que la enfermedad se encuentra ampliamente distribuida en la región y en el país. Su diagnóstico se realiza rutinariamente mediante técnicas coprológicas aplicadas a los animales en los que se sospecha la enfermedad.
Role of the Wnt receptor Frizzled-1 in presynaptic differentiation and function
Lorena Varela-Nallar, Catalina P Grabowski, Iván E Alfaro, Alejandra R Alvarez, Nibaldo C Inestrosa
Neural Development , 2009, DOI: 10.1186/1749-8104-4-41
Abstract: We examined the distribution of the Wnt receptor Frizzled-1 in cultured hippocampal neurons and determined that this receptor is located at synaptic contacts co-localizing with presynaptic proteins. Frizzled-1 was found in functional synapses detected with FM1-43 staining and in synaptic terminals from adult rat brain. Interestingly, overexpression of Frizzled-1 increased the number of clusters of Bassoon, a component of the active zone, while treatment with the extracellular cysteine-rich domain (CRD) of Frizzled-1 decreased Bassoon clustering, suggesting a role for this receptor in presynaptic differentiation. Consistent with this, treatment with the Frizzled-1 ligand Wnt-3a induced presynaptic protein clustering and increased functional presynaptic recycling sites, and these effects were prevented by co-treatment with the CRD of Frizzled-1. Moreover, in synaptically mature neurons Wnt-3a was able to modulate the kinetics of neurotransmitter release.Our results indicate that the activation of the Wnt pathway through Frizzled-1 occurs at the presynaptic level, and suggest that the synaptic effects of the Wnt signaling pathway could be modulated by local activation through synaptic Frizzled receptors.The Wnt signaling pathway plays a crucial role during development, regulating specification of cell fate, cell proliferation, migration and morphogenesis [1]. Wnt signaling is activated by the interaction of Wnt ligands with members of the Frizzled (Fz) family of seven-transmembrane cell surface receptors. Three different Wnt pathways have been described downstream of Fz receptors: the canonical Wnt/β-catenin pathway; and the non-canonical pathways involving intracellular signaling by Ca2+ or the c-Jun-N-terminal kinase (JNK) cascade [1,2]. In the canonical Wnt/β-catenin signaling pathway, Wnt ligands interact with Fz receptors and their co-receptor LRP5/6 and signal through Dishevelled to inhibit the kinase activity of glycogen synthase kinase-3β in a protein degradati
EphA4 Activation of c-Abl Mediates Synaptic Loss and LTP Blockade Caused by Amyloid-β Oligomers
Lina M. Vargas, Nancy Leal, Lisbell D. Estrada, Adrian González, Felipe Serrano, Katherine Araya, Katia Gysling, Nibaldo C. Inestrosa, Elena B. Pasquale, Alejandra R. Alvarez
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0092309
Abstract: The early stages of Alzheimer's disease are characterised by impaired synaptic plasticity and synapse loss. Here, we show that amyloid-β oligomers (AβOs) activate the c-Abl kinase in dendritic spines of cultured hippocampal neurons and that c-Abl kinase activity is required for AβOs-induced synaptic loss. We also show that the EphA4 receptor tyrosine kinase is upstream of c-Abl activation by AβOs. EphA4 tyrosine phosphorylation (activation) is increased in cultured neurons and synaptoneurosomes exposed to AβOs, and in Alzheimer-transgenic mice brain. We do not detect c-Abl activation in EphA4-knockout neurons exposed to AβOs. More interestingly, we demonstrate EphA4/c-Abl activation is a key-signalling event that mediates the synaptic damage induced by AβOs. According to this results, the EphA4 antagonistic peptide KYL and c-Abl inhibitor STI prevented i) dendritic spine reduction, ii) the blocking of LTP induction and iii) neuronal apoptosis caused by AβOs. Moreover, EphA4-/- neurons or sh-EphA4-transfected neurons showed reduced synaptotoxicity by AβOs. Our results are consistent with EphA4 being a novel receptor that mediates synaptic damage induced by AβOs. EphA4/c-Abl signalling could be a relevant pathway involved in the early cognitive decline observed in Alzheimer's disease patients.
Free surface instability in a confined suspension jet
Alejandra Alvarez,Eric Clement,Rodrigo Soto
Physics , 2005, DOI: 10.1016/j.physa.2005.05.036
Abstract: A jet of non-Brownian particles confined in a thin cell and driven by gravitational force is studied both numerically and theoretically. We present a theoretical scheme aimed to describe such a system in the Stokes regime. We focus on the dynamics of the interface between the suspension and the pure fluid. Numerical simulations solving Newton's equations for all particles show that the jet free surface becomes unstable: the fastest growing modes at small sizes coarsen up to the largest structures reaching the jet lateral scale. In the bulk, structural waves develop and travel at slightly slower speed than the jet average fall. An analytical model, based on hydrodynamic-like equations for the suspension, is derived and predicts the development of the interfacial instability. It captures in essence, the collective effects driving the interface destabilization i.e. the long range hydrodynamic interactions coupled with the abrupt interface, and no analogous to a surface tension is found.
Submarine topography and faulting in Bahía de Banderas, Mexico
R. Alvarez
Geofísica internacional , 2007,
Abstract: A digital elevation model of Bahía de Banderas and its offshore continuation to the Middle America Trench (MAT) is built from a data set of 6872 bathymetric soundings. Two new, offshore basins and several, previously unknown faults within the bay are also identified. The south flank of Banderas canyon is considerably steeper than the north one. This asymmetry and the seismic activity present lead to propose that Banderas Canyon has a half-graben structure of the fault growth type, and reverse drag geometry, which originates in an extensional basin oriented N-S. The canyon is divided in two sections that trend in different directions. The older section of the canyon, trending E-W, is probably Late Miocene; the associated Banderas Fault is suggested to extend westward, down to the MAT along a section that complements that of the half-graben. The section of Banderas Canyon trending NE and continuing into Banderas Valley is identified as a younger portion of the structure. The older and the younger portions of the canyon appear to be active presently. A group of faults also trending NE seem to be associated with the change in direction of the canyon. These results support the hypothesis that the structure of Banderas Canyon is a half-graben, and strengthen the idea that it is the limit between the region to the north that underwent extension in the Miocene, and the region to the south that did not experienced it.
Caracas: una ciudad de múltiples indefiniciones
Alvarez, R.
CONHISREMI , 2009,
Abstract: The city of Caracas is defined as a unit in space with a complex administrative organization, where a wide diversity of executive authorities coexists (governors, mayors, etc) at different levels and from different entities (Federal District and Miranda State) mixed in an undefined political and administrative space. The main argument for the creation of the Chief Town District was to warrant the city governability and give a chance to enhance decentralization. The final form of this idea, included in the Republic Constitution in 1999, did not solve any of these problems but make them deeper. It is necessary to pose this discussion again recalling the original arguments of the proposers aimed to create a two level govern and then consider a new inclusion in the Constitution to support new changes in the territorial and political division of the country.
Cholinergic Abnormalities, Endosomal Alterations and Up-Regulation of Nerve Growth Factor Signaling in Niemann-Pick Type C Disease
Carolina Cabeza, Alicia Figueroa, Oscar M Lazo, Carolina Galleguillos, Claudia Pissani, Andrés Klein, Christian Gonzalez-Billault, Nibaldo C Inestrosa, Alejandra R Alvarez, Silvana Zanlungo, Francisca C Bronfman
Molecular Neurodegeneration , 2012, DOI: 10.1186/1750-1326-7-11
Abstract: NPC1-deficient cholinergic cells respond to NGF after axotomy and exhibit increased levels of choline acetyl transferase (ChAT), whose gene is under the control of NGF signaling, compared to wild type cholinergic neurons. This finding was correlated with increased ChAT and phosphorylated Akt in basal forebrain homogenates. In addition, we found that cholinergic neurons from NPC1-deficient mice had disrupted neuronal morphology, suggesting early signs of neurodegeneration. Consistently, PC12 cells treated with U18666A presented a clear NPC cellular phenotype with a prominent endocytic dysfunction that includes an increased size of TrkA-containing endosomes and reduced recycling of the receptor. This result correlates with increased sensitivity to NGF, and, in particular, with up-regulation of the Akt and PLC-γ signaling pathways, increased neurite extension, increased phosphorylation of tau protein and cell death when PC12 cells are differentiated and treated with U18666A.Our results suggest that the NPC cellular phenotype causes neuronal dysfunction through the abnormal up-regulation of survival pathways, which causes the perturbation of signaling cascades and anomalous phosphorylation of the cytoskeleton.Neurotrophins (NGF, BDNF, NT3 and NT4) regulate different aspects of the developing and mature nervous system, including neuronal survival and neuronal morphology. These small proteins exert these effects by binding to members of the Trk family of receptor tyrosine kinases (TrkA, TrkB and TrkC) or to the p75 neurotrophin receptor (p75). Whereas p75 binds all neurotrophins, in addition to other ligands (e.g., proneurotrophins and amyloid peptides), each Trk binds preferentially to its cognate neurotrophin. For example, TrkA, TrkB and TrkC bind NGF, BDNF and NT3, respectively [1-3].Several neurodegenerative diseases are produced by alterations in molecules related to endocytosis and vesicular trafficking, which are cellular processes that regulate neurotrophin signal
Cuerpo y medios de comunicación: Viejas obsesiones y nuevas tecnologías: el cuerpo en revistas femeninas argentinas
Roca,Alejandra R.;
Cuadernos de antropolog?-a social , 2003,
Abstract: this paper presents some aspects about the different meanings that refer to the human body in women magazines in buenos aires city. coming from a particular vision of the world, the notion of body and person, providing the model of 'possession' of the body. socioeconomic transformations, their consequences in the personal and domestic relationships and the advances in medical technology have derived in focalizing in corporal beauty and rejection of aging (body project) as moral values. the essentialism/biologicism that is suggested and exposed, contributes to reassert a gender differentiation based on traditional stereotypes.
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