The Universidad Nacional de Colombia , also called UNAL or just UN, is a public, national, coeducational, research university, located primarily in Bogotá, Medellín, Manizales and Palmira, Colombia. Established in 1867 by an act of the Congress of Colombia, the university is the largest higher education institution of the country with more than 44,000 students, the largest number of graduated professionals per year, and number of academic programmes at undergraduate and postgraduate levels, with 423 academic programmes, which includes 94 graduate diplomas, 61 Academic specializations, 38 medical specialties, 131 Master's degrees, and 46 doctorates. It is also one of the few universities that employs post-doctorate fellows in the country. Approximately 40,000 students are studying for an undergraduate degree and 4,000 for a graduate degree.The university is a member of the Association of Colombian Universities , the Iberoamerican Association of Postgraduate Universities , and the Iberoamerican University Network Universia. Along with Antioquia and Valle universities, it conforms what is known as the Golden Triangle of higher education in Colombia, being among the most selective and competitive universities in the country. A study by Universia found it to be the Colombian university producing the largest number of scientific papers published in peer-refereed publications in 2005, and the 45th most prolific in Latin America. Furthermore, according to the Latinamerican Web Ranking of Universities, the National University of Colombia ranked in the first place of the country in internet presence, and among the first universities in the region. Regarding the CIVETS universities, the National University occupied the fifth place.The institution offers a wide selection of programmes in both undergraduate and graduate levels, such as medicine, nursing, dentistry, engineering, chemistry, pharmacy, mathematics, physics, geology, biology, psychology, social science, arts , philosophy, and law. Wikipedia.
Lemeshko V.V.,National University of Colombia
Biochimica et Biophysica Acta - Biomembranes
The simplest mechanism of the generation of the mitochondrial outer membrane potential (OMP) by the VDAC (voltage-dependent anion channel)-hexokinase complex (VHC), suggested earlier, and by the VDAC-glucokinase complex (VGC), was computationally analyzed. Even at less than 4% of VDACs bound to hexokinase, the calculated OMP is high enough to trigger the electrical closure of VDACs beyond the complexes at threshold concentrations of glucose. These results confirmed our previous hypothesis that the Warburg effect is caused by the electrical closure of VDACs, leading to global restriction of the outer membrane permeability coupled to aerobic glycolysis. The model showed that the inhibition of the conductance and/or an increase in the voltage sensitivity of a relatively small fraction of VDACs by factors like tubulin potentiate the electrical closure of the remaining free VDACs. The extrusion of calcium ions from the mitochondrial intermembrane space by the generated OMP, positive inside, might increase cancer cell resistance to death. Within the VGC model, the known effect of induction of ATP release from mitochondria by accumulated glucose-6-phosphate in pancreatic beta cells might result not only of the known effect of GK dissociation from the VDAC-GK complex, but also of a decrease in the free energy of glucokinase reaction, leading to the OMP decrease and VDAC opening. We suggest that the VDAC-mediated electrical control of the mitochondrial outer membrane permeability, dependent on metabolic conditions, is a fundamental physiological mechanism of global regulation of mitochondrial functions and of cell death. © 2014 Elsevier B.V. Source
Lemeshko V.V.,National University of Colombia
Archives of Biochemistry and Biophysics
The electrostatic interaction of polycationic peptides with negatively charged biomembranes has been recognized as the first and very important step of their selective binding to many bacteria and transformed cells. In this work we demonstrated the phenomenon of competition of some earlier designed polycationic peptides and fluorescent probes for their binding to the negatively charged inner membrane of mitochondria and to the PC/PG (9:1) liposomes. Rat liver mitochondria swelling induced by the antimicrobial polycationic peptide BTM-P1 (VAPIAKYLATALAKWALKQGFAKLKS) and by the retro-BTM-P1 was significantly diminished in the presence of 10 μM fluorescent probe safranin O. In experiments with liposomes, the polycationic peptides BTM-P1 and P7-5 (IYLATALAKWALKQGF-GG-RRRRRRR) at the concentrations of 2-3 μM completely displaced the membrane-bound fluorescent probe DiSC3(5) in a low ionic strength medium. The developed computational model allowed a mathematical description of such interactions, predicting membrane surface concentrations of bound peptides as the function of the membrane surface charge and lipid quantity in the sample, the peptide charge, hydrophobicity and concentration, the ionic strength of incubation medium and of the presence of a charged fluorescent probe used for monitoring the membrane surface potential under real-time peptide-membrane interactions. © 2014 Elsevier Inc. All rights reserved. Source
De La Hoz F.,National University of Colombia
Background: In Bogotá, the Heptavalent Conjugate Vaccine (PCV7) was introduced into childhood immunization schedule since 2009. The aim of this study was to assess the changes in serotype distribution and penicillin susceptibility of Streptococcus pneumoniae isolates recovered from nasopharyngeal samples and invasive disease among children living in Bogotá, before and after PCV7 introduction. Methods: Nasopharyngeal swabs were collected from healthy children aged between 12 and 18 months of age before (years 2005-2006) and after (2011) PCV7 introduction. Identification of S. pneumoniae was performed by multiplex PCR. Serotype was determined by PCR and Quellung reaction. Susceptibility to penicillin, ceftriaxone, trimethoprim-sulfamethoxazole, chloramphenicol, tetracycline and erythromycin was evaluated. In addition, distribution of serotypes and antimicrobial susceptibility before and after vaccine introduction among invasive isolates recovered from children ≤2 years old living in Bogotá was analyzed. Results: Prevalence of pneumococcal nasopharyngeal carriage declined from 55.7% (137/246) in unvaccinated to 44.2% (87/197) (p = 0.01) in vaccinated children. The proportion of children carrying PCV7 serotypes decreased from 23.6% (58/246) to 7.6% (15/197) (p < 0.001). The decrease was counterbalanced by an increase in the proportion of non-PCV7 serotypes. The most prevalent among emerging serotypes were 15A, 15B, 15. C, 11A and 35B. Among IPD isolates, PCV7 serotypes decreased from 69.1% (235/340) in 2005/2009 to 38.0% (32/84) in 2010/2011 (p < 0.001). The increase of non-PCV7 serotypes was significant. Resistance to penicillin among invasive isolates recovered from meningitis decreased from 41.1% (30/73) in the pre-vaccine period to 14.2% (2/14) in post-vaccine period (p = 0.02). Conclusions: A decrease in the prevalence of pneumococcal nasopharyngeal carriage following the introduction of PCV7 vaccine, have been overshadowed by an important surge in the prevalence of non-PCV7 serotypes. Systematic surveillance combining nasopharyngeal carriage surveys and IPD detection could help in evaluating the impact of conjugate vaccines. © 2013 The Authors. Source
Perez-Quintero A.L.,National University of Colombia
BMC plant biology
BACKGROUND: microRNAs (miRNAs) are non-coding short RNAs that regulate gene expression in eukaryotes by translational inhibition or cleavage of complementary mRNAs. In plants, miRNAs are known to target mostly transcription factors and are implicated in diverse aspects of plant growth and development. A role has been suggested for the miRNA pathway in antiviral defense in plants. In this work, a bioinformatics approach was taken to test whether plant miRNAs from six species could have antiviral activity by targeting the genomes of plant infecting viruses. RESULTS: All plants showed a repertoire of miRNAs with potential for targeting viral genomes. The viruses were targeted by abundant and conserved miRNA families in regions coding for cylindrical inclusion proteins, capsid proteins, and nuclear inclusion body proteins. The parameters for our predicted miRNA:target pairings in the viral genomes were similar to those for validated targets in the plant genomes, indicating that our predicted pairings might behave in-vivo as natural miRNa-target pairings. Our screening was compared with negative controls comprising randomly generated miRNAs, animal miRNAs, and genomes of animal-infecting viruses. We found that plant miRNAs target plant viruses more efficiently than any other sequences, but also, miRNAs can either preferentially target plant-infecting viruses or target any virus without preference. CONCLUSIONS: Our results show a strong potential for antiviral activity of plant miRNAs and suggest that the miRNA pathway may be a support mechanism to the siRNA pathway in antiviral defense. Source
National University of Colombia and Empresas Publicas De Medellin E.S.P. | Date: 2014-03-04
The present invention discloses a method for the detection and diagnosis of faults in running electric machines. The method consists of: i) simultaneously obtaining a current signal and a voltage signal associated with the rotor winding of the electric machine; ii) defining a group of vectors whose components are DC and/or AC values at different separation and amplification levels of the current and voltage signals; iii) simultaneously obtaining a current signal and a voltage signal associated with an emulated fault; iv) defining a group of vectors whose components are DC and/or AC values at different separation and amplification levels of the current and voltage signals associated with an emulated fault; v) determining the variations in the components of the vectors; vi) comparing the vectors that show component variations with the emulated fault vectors; vii) analyzing the variations and comparisons in order to detect whether or not there is at least one type of fault; and viii) reporting the presence or absence of at least one type of fault in the electric machine. The present invention also discloses a system to carry out this method, consisting of: i) a unit that obtains the current and voltage signals associated with the winding of the electric machine; ii) a unit that emulates faults; iii) a unit that sensitizes the signals by separating the DC and/or AC levels and amplifies the resulting signal; iv) a memory unit that stores the DC and/or AC values; and v) a unit that processes, analyzes and reports on the status of the machine.