University of the Republic of Chile

Santiago, Chile

University of the Republic of Chile

Santiago, Chile
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Santibanez J.F.,University of the Republic of Chile | Obradovic H.,Laboratory for Experimental Hematology and Stem Cells | Kukolj T.,Laboratory for Experimental Hematology and Stem Cells | Krstic J.,Institute for Medical ResearchUniversity of BelgradeBelgrade Republic of Serbia
Developmental Dynamics | Year: 2017

Transforming growth factor-β (TGF-β) is a pleiotropic factor that acts as a tumor suppressor in the early stages, while it exerts tumor promoting activities in advanced stages of cancer development. One of the hallmarks of cancer progression is the capacity of cancer cells to migrate and invade surrounding tissues with subsequent metastasis to different organs. Matrix metalloproteinases (MMPs) together with urokinase-type plasminogen activator (uPA) and its receptor (uPAR), whose main original function described is the proteolytic degradation of the extracellular matrix, play key cellular roles in the enhancement of cell malignancy during cancer progression. TGF-β tightly regulates the expression of several MMPs and uPA/uPAR in cancer cells, which in return can participate in TGF-β activation, thus contributing to tumor malignancy. TGF-β is one of the master factors in the induction of cancer-associated epithelial to mesenchymal transition (EMT), and recently both MMPs and uPA/uPAR have also been shown to be implicated in the cancer-associated EMT process. In this review, we analyze the main molecular mechanisms underlying MMPs and uPA/uPAR regulation by TGF-β, as well as their mutual implication in the development of EMT in cancer cells. © 2017 Wiley Periodicals, Inc.

Orellana J.A.,University of Santiago de Chile | Shoji K.F.,University of Santiago de Chile | Abudara V.,Collège de France | Ezan P.,University of the Republic of Chile | And 7 more authors.
Journal of Neuroscience | Year: 2011

The mechanisms involved in Alzheimer's disease are not completely understood and how glial cells contribute to this neurodegenerative disease remains to be elucidated. Because inflammatory treatments and products released from activated microglia increase glial hemichannel activity, we investigated whether amyloid-β peptide (Aβ) could regulate these channels in glial cells and affect neuronal viability. Microglia, astrocytes, or neuronal cultures as well as acute hippocampal slices made from GFAP-eGFP transgenic mice were treated with the active fragment of Aβ. Hemichannel activity was monitored by single-channel recordings and by time-lapse ethidium uptake, whereas neuronal death was assessed by Fluoro-Jade C staining. We report that low concentrations of Aβ25-35 increased hemichannel activity in all three cell types and microglia initiate these effects triggered by Aβ. Finally, neuronal damage occurs by activation of neuronal hemichannels induced by ATP and glutamate released from Aβ25-35-activated glia. These responses were observed in the presence of external calcium and were differently inhibited by hemichannel blockers, whereas theAβ25-35-induced neuronal damage was importantly reduced in acute slices made from Cx43 knock-out mice. Thus, Aβ leads to a cascade of hemichannel activation in which microglia promote the release of glutamate and ATP through glial (microglia and astrocytes) hemichannels that induces neuronal death by triggering hemichannels in neurons. Consequently, this work opens novel avenues for alternative treatments that target glial cells and neurons to maintain neuronal survival in the presence of Aβ. © 2011 the authors.

Pan Y.-C.,University of Illinois at Urbana - Champaign | Foley R.J.,University of Illinois at Urbana - Champaign | Kromer M.,StockholmUniversity | Fox O.D.,University of California | And 25 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2015

SN 2013dy is a Type Ia supernova (SN Ia) for which we have compiled an extraordinary data set spanning from 0.1 to ~ 500 d after explosion. We present 10 epochs of ultraviolet (UV) through near-infrared (NIR) spectra with Hubble Space Telescope/Space Telescope Imaging Spectrograph, 47 epochs of optical spectra (15 of them having high resolution), and more than 500 photometric observations in the BVrRiIZYJH bands. SN 2013dy has a broad and slowly declining light curve (Δm15(B)=0.92 mag), shallow Si II λ6355 absorption, and a low velocity gradient. We detect strong C II in our earliest spectra, probing unburned progenitor material in the outermost layers of the SN ejecta, but this feature fades within a few days. The UV continuum of SN 2013dy, which is strongly affected by the metal abundance of the progenitor star, suggests that SN 2013dy had a relatively high-metallicity progenitor. Examining one of the largest single set of high-resolution spectra for an SN Ia, we find no evidence of variable absorption from circumstellar material. Combining our UV spectra, NIR photometry, and high-cadence optical photometry, we construct a bolometric light curve, showing that SN 2013dy had a maximum luminosity of 10.0+4.8 -3.8 × 1042 erg s-1. We compare the synthetic light curves and spectra of several models to SN 2013dy, finding that SN 2013dy is in good agreement with a solar-metallicity W7 model. © 2015 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

Valladares Faundez P.,University of Tarapacá | Alvarez Henriquez N.,University of the Republic of Chile | Urrutia Osorio N.,University of the Republic of Chile | Olivares Zuleta F.,Tierra del Sol Investigacion y Desarrollo Consultores | Alvarado Orellana S.,University of Chile
Gayana | Year: 2015

The Variable Hawk (Geranoaetus polyosoma) is a raptor species distributed from Arica to Tierra del Fuego in Chile. It consumes small vertebrates and invertebrates, particularly insects and arachnids. The biological information of this species is scarce for northern Chile, particularly about their reproduction, diet, etc. We evaluated the diet of the Variable Hawk, by means of pellets collected between Vallenar to Copiapó, in Atacama region, a hyper-arid area. This information was compared with the available scientific literature in Chile and neighboring countries. Because of the environmental conditions of extreme aridity, we expect to find a low diversity of prey, characteristic of the raptors of arid ecosystems. In the case of the Variable Hawk populations from Atacama region, the most consumed species were reptilians (57,1%) corresponding to small lizards of the Liolaemus spp (30,4%), L. bisignatus (17%) and Callopiste maculatus (5,3%). Other prey corresponded to rodents (19.8%) and coleopterans of the genus Gyriosomus (18.9%). There was no positive correlation between frequency of prey and their body mass (r2= -0.267, p> 0.05) indicating that this raptor does not select their prey by body size. The biomass of reptiles in the diet (55.3%) was slightly higher than mammals (42.7%), but the largest individual contribution was given by Phyllotis darwini with 27.6%. Both the Simpson (SI = 0.1833) and the Shannon index (H ‘= 0.8463) indicate that this species consume a low diversity of prey, which is consistent with the others raptors that inhabit arid environments. © 2015, Universidad de Concepcion. All rights reserved.

Tasca F.,University of Santiago de Chile | Recio F.J.,University of Santiago de Chile | Recio F.J.,University of the Republic of Chile | Venegas R.,University of Santiago de Chile | And 3 more authors.
Electrochimica Acta | Year: 2014

For electrochemical reactions catalyzed by electrodes modified with MN4 macrocyclic transition metal complexes, it is commonly accepted that d-band vacancy, surface lattice strain, and eg-orbital filling the transition metals are essential parameters to take in account for an optimum catalysis. These parameters affect the formal potential of the catalyst which is related to the free energy of the adsorption of the reacting molecule to a point that volcano correlations have been reported when plotting the activity of the catalyst versus the Mz+/M(z-1)+ formal potential of the catalyst (M (II) = Fe, Co). The highest catalytic activity is achieved when the formal potential of the catalyst is close to -0.5 V vs SCE regardless of whether the central metal is Fe or Co. In this work, we review the work done until now on the oxidation of hydrazine in alkaline medium at metallophthalocyanines modified graphite electrodes and we show that for some complexes the redox potential of the MN4 macrocyclic transition metal complex can be varied changing the concentration of the catalyst at the electrode surface. Therefore we show that if log i (normalized for the actual surface concentrations of M(II) active sites (M = Fe, Co) at constant potential is plotted versus the M(II)/(I), the correlations is linear with a slope close to 2RT/F. © 2014 Elsevier Ltd.

Moreno A.A.,University of the Republic of Chile | Orellana A.,University of the Republic of Chile
Biological Research | Year: 2011

Unfolded protein response (UPR) is a signaling mechanism activated by misfolded protein accumulation in the endoplasmic reticulum. It is a widespread process that has been described in organisms ranging from yeasts to mammals. In recent years, our understand ing of UPR signaling pathway in plants has advanced. Two transcription factors from Arabidopsis thaliana have been reported to function as the sensor/ transducer of this response (AtbZIP60 and AtbZIP28). They seem to be involved in both heat and biotic stress. Furthermore, overexpression of one of them (AtbZIP60) produces plants with a higher tolerance for salt stress, suggesting that this transcription factor may play a role in abiotic stress. Furthermore, some data suggest that crosstalk between genes involved in abiotic stress and UPR may also exist in plants. On the other hand, UPR is related to programmed cell death (PCD) in plants given that that triggering UPR results in induction of PCD-related genes. This article reviews the latest progress in understand ing UPR signaling in plants and analyzes its relationship to key processes in plant physiology.

By means of the conceptual density functional theory, the so-called dual descriptor (DD) has been adapted to be used in any closed-shell molecule that presents degeneracy in its frontier molecular orbitals. The latter is of paramount importance because a correct description of local reactivity will allow to predict the most favorable sites on a molecule to undergo nucleophilic or electrophilic attacks; on the contrary, an incomplete description of local reactivity might have serio us consequences, particularly for those experimental chemists that have the need of getting an insight about reactivity of chemical reagents before using them in synthesis to obtain a new compound. In the present work, the old approach based only on electronic densities of frontier molecular orbitals is replaced by the most accurate procedure that implies the use of total electronic densities thus keeping consistency with the essential principle of the DFT in which the electronic density is the fundamental variable and not the molecular orbitals. As a result of the present work, the DD will be able to properly describe local reactivities only in terms of total electronic densities. To test the proposed operational formula, 12 very common molecules were selected as the original definition of the DD was not able to describe their local reactivities properly. The ethylene molecule was additionally used to test the capability of the proposed operational formula to reveal a correct local reactivity even in absence of degeneracy in frontier molecular orbitals. © 2016 Wiley Periodicals, Inc.

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