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Tulua, Colombia

Ortega-Rojas J.,Antonio Narino University
Alzheimer Disease and Associated Disorders | Year: 2016

OBJECTIVE:: We evaluated the association of several single-nucleotide polymorphisms in different genes including APOE, TOMM40, CR1, PVRL2, SORL1, PICALM, and GWA_14q32.13 in a Colombian sample of Late-Onset Alzheimer disease (LOAD) patients. METHODS:: A case-control study was conducted in 362 individuals (181 LOADs and 181 controls) to determine the association of single-nucleotide polymorphisms in APOE (e2, e3, and e4), TOMM40 (rs2075650), CR1 (rs665640), PVRL2 (rs6859), SORL1 (rs11218304), PICALM (rs3851179), and GWA_14q32.13 (rs11622883) with LOAD in a sample from Colombia. RESULTS:: We were able to confirm the previously reported association of the APOE4 allele with AD. In addition, we report a new significant association with rs2075650 of TOMM40 for LOAD in our sample. We did not detect any significant interaction between TOMM40 and APOE4 carriers (heterozygous or homozygous) for disease risk development. However, Kaplan-Meier survival analyses suggest that AD patients with TOMM40 allele rs2075650-G have an average age of disease onset of 6 years earlier compared with carriers of the A allele. In addition, the age of disease onset is earlier if APOE4/4 is present. CONCLUSION:: Our findings suggest that rs2075650 of TOMM40 could be involved in earlier presentation of LOAD in the Colombian population. Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved Source

ReyesHerrera P.H.,Antonio Narino University | Ficarra E.,Polytechnic University of Turin
Genomics, Proteomics and Bioinformatics | Year: 2012

Nearly two decades have passed since the publication of the first study reporting the discovery of microRNAs (miRNAs). The key role of miRNAs in post-transcriptional gene regulation led to the performance of an increasing number of studies focusing on origins, mechanisms of action and functionality of miRNAs. In order to associate each miRNA to a specific functionality it is essential to unveil the rules that govern miRNA action. Despite the fact that there has been significant improvement exposing structural characteristics of the miRNA-mRNA interaction, the entire physical mechanism is not yet fully understood. In this respect, the development of computational algorithms for miRNA target prediction becomes increasingly important. This manuscript summarizes the research done on miRNA target prediction. It describes the experimental data currently available and used in the field and presents three lines of computational approaches for target prediction. Finally, the authors put forward a number of considerations regarding current challenges and future directions. © 2012. Source

Bueno Sanchez J.C.,University of Santiago de Cali | Bueno Sanchez J.C.,Antonio Narino University | Bueno Sanchez J.C.,Industrial University of Santander | Bueno Sanchez J.C.,Complutense University of Madrid
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2014

Single-field inflation, arguably the simplest and most compelling paradigm for the origin of our Universe, is strongly supported by the recent results of the Planck satellite and the BICEP2 experiment. The results from Planck, however, also confirm the presence of a number of anomalies in the Cosmic Microwave Background (CMB), whose origin becomes problematic in single-field inflation. Among the most prominent and well-tested of these anomalies is the Cold Spot, which constitutes the only significant deviation from Gaussianity in the CMB. Planck's non-detection of primordial non-Gaussianity on smaller scales thus suggests the existence of a physical mechanism whereby significant non-Gaussianity is generated on large angular scales only. In this Letter, we address this question by developing a localized version of the inhomogeneous reheating scenario, which postulates the existence of a scalar field able to modify the decay of the inflaton on localized spatial regions only. We demonstrate that if the Cold Spot is due to an overdensity in the last scattering surface, the localization mechanism offers a feasible explanation for it, thus providing a physical mechanism for the generation of localized non-Gaussianity in the CMB. If, on the contrary, the Cold Spot is caused by a newly discovered supervoid (as recently claimed), we argue that the localization mechanism, while managing to enhance underdensities, may well shed light on the rarity of the discovered supervoid. © 2014 The Author. Source

Camargo M.,Heinrich Heine University Dusseldorf | Camargo M.,Antonio Narino University | Likos C.N.,Heinrich Heine University Dusseldorf | Likos C.N.,University of Vienna
Physical Review Letters | Year: 2010

We investigate the influence of the addition of polymer chains on the effective interaction between star polymers, as a model for the depletion potential in ultrasoft mixtures. The effects of size ratio and chain polymer concentration on the chain-modified star-star interactions at good (athermal) solvent conditions are investigated. For both hard sphere mixtures and colloid-nonadsorbing polymer mixtures the range of the depletion interaction increases with the size ratio. For the systems at hand, the range of the depletion potential is insensitive to the size of the depletant polymer. The physical origin of this and the associated effects, as well as a mapping of the mixtures onto a one-component system, are discusssed. © 2010 The American Physical Society. Source

Rodriguez Y.,Antonio Narino University | Rodriguez Y.,Industrial University of Santander | Valenzuela-Toledo C.A.,Industrial University of Santander
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2010

We calculate the trispectrum Tζ of the primordial curvature perturbation ζ, generated during a slow-roll inflationary epoch by considering a two-field quadratic model of inflation with canonical kinetic terms. We consider loop contributions as well as tree-level terms, and show that it is possible to attain very high, including observable, values for the level of non-Gaussianity τNL if Tζ is dominated by the one-loop contribution. Special attention is paid to the claim in J. Cosmol. Astropart. Phys.1475-7516 02 (2009) 01710.1088/1475-7516/2009/02/017 that, in the model studied in this paper and for the specific inflationary trajectory we choose, the quantum fluctuations of the fields overwhelm the classical evolution. We argue that such a claim actually does not apply to our model, although more research is needed in order to understand the role of quantum diffusion. We also consider the probability that an observer in an ensemble of realizations of the density field sees a non-Gaussian distribution. In that respect, we show that the probability associated to the chosen inflationary trajectory is non-negligible. Finally, the levels of non-Gaussianity fNL and τNL in the bispectrum Bζ and trispectrum Tζ of ζ, respectively, are also studied for the case in which ζ is not generated during inflation. © 2010 The American Physical Society. Source

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