1,721,192 research outputs found
Bryan Steven Morales, violín (Colombia) y Cuerdas al viento, ensamble de música llanera (Colombia)
No full textConcierto en dos partes, interpretado por violinista Bryan Steven Morales López y por la agrupación de música llanera Cuerdas al Viento. En compañía de la pianista Dilva Isabel Sánchez, Morales interpretó obras de Vittorio Monto, Charles de Bériot, Catalicio Rojas, Fritz Kreisler, entre otros. En la segunda parte la agrupación Cuerdas al Viento, interpretó música de Hildo Ariel Aguirre, Jairo Marta, Jorge Guerrero, entre otros
Untersuchung der Oligomerisierungs- und Genregulationsmechanismen des Enzyms Nicotinamid/Nicotinat-Mononukleotid-Adenylyltransferase aus Leishmania braziliensis
No full textilustracionesLa Leishmaniasis es una enfermedad que puede manifestarse en tres formas clínicas: cutánea, mucocutánea y visceral, siendo causada por parásitos protozoarios del género Leishmania, del cual se conocen 22 especies patogénicas para el hombre. Según la Organización Mundial de la Salud, anualmente se registran 1,3 millones de casos, siendo Colombia uno de los países afectados, donde circulan varias especies, incluyendo Leishmania braziliensis.
Actualmente, no se dispone de vacunas aprobadas para la prevención de la Leishmaniasis y el tratamiento de primera línea, como son los antimoniatos pentavalentes, generan diversos y graves efectos adversos destacándose nefrotoxicidad, hepatotoxicidad y mialgias. Adicionalmente, se ha reportado la aparición de cepas farmacorresistentes. Por lo tanto, se requiere la exploración de nuevas dianas terapéuticas, como, por ejemplo, la síntesis del dinucleótido de nicotinamida y adenina (NAD), que se destaca como una ruta metabólica promisoria, dada la importancia de este transportador electrónico.
En los últimos años, nuestro grupo de investigación se ha enfocado en la obtención y caracterización de las proteínas del metabolismo del NAD de protozoarios como Giardia lamblia, Plasmodium falciparum, Trypanosoma cruzi y L. braziliensis. Específicamente en Leishmania, se han realizado trabajos para la caracterización de proteínas como la NAD quinasa y la nicotinamida/nicotinato mononucleótido adenilil transferasa (LbNMNAT); sin embargo, estos estudios se han enfocado principalmente en su actividad enzimática y estructura cuaternaria en ausencia de sustratos.
En este trabajo se analizó el efecto que ejercen los sustratos de la enzima LbNMNAT sobre su oligomerización, encontrándose que sus organizaciones en forma de dímeros, trímeros y tetrámeros, no es modificada por la presencia de los sustratos analizados. Esta evidencia estructural es concordante con la cinética de tipo Michaelis-Menten reportada para la enzima, puesto que los sustratos no ejercen regulación homo-trópica sobre la LbNMNAT.
Por otro lado, considerando que uno de los principales niveles de regulación de expresión génica en los tripanosomátidos es post-transcripcional, entonces se efectuó una aproximación bioinformática basada en la identificación de sitios aceptores de splicing, para delimitar las regiones no codificantes (UTRs) del gen lbnmnat. En este sentido, se encontraron numerosos sitios aceptores que podrían generar UTRs de diferentes longitudes, como se ha reportado para otras especies del parásito.
Adicionalmente, se identificaron 29 proteínas de unión a ARN (RBPs) con probabilidad de reconocer dichas UTRs, las cuales participan en procesos diversos como splicing, poli-adenilación y represión post-transcripcional. De este modo, se indican proteínas que posiblemente explican las diferencias reportadas por otros autores para la abundancia del transcrito del gen lbnmnat a través del ciclo biológico de L. braziliensis.
Con el propósito de comprobar experimentalmente algunos de los hallazgos bioinformáticos de este trabajo, se implementó la técnica de Retro-Transcripción acoplada a PCR (RT-PCR), partiendo del ARN obtenido de promastigotes de L. braziliensis, para identificar los UTRs asociados al gen lbnmnat en este estadio del parásito. Dicha técnica permitió la síntesis de ADN complementario apropiado para el estudio de UTRs y la amplificación de un producto de menor tamaño al esperado para el UTR 5’. Este resultado indica la necesidad de determinar la secuencia exacta del amplicón mediante eventuales técnicas de aislamiento y secuenciamiento de ADN.
En conclusión, el presente trabajo aporta evidencia experimental y bioinformática acerca del efecto estructural que ejercen los sustratos de la enzima LbNMNAT sobre su oligomerización y acerca de sus UTRs y proteínas de unión, que podrían explicar mecanismos de regulación de la expresión del gen lbnmnat en el parásito L. braziliensis. (Texto tomado de la fuente)Leishmaniasis is a disease that can manifest in three clinical forms: cutaneous, mucocutaneous, and visceral. This illness is caused by protozoan parasites of the genus Leishmania. There are 22 human pathogenic species. According to the World Health Organization, 1.3 million cases are recorded annually. Colombia is one of the affected countries, where several species circulate, including Leishmania braziliensis.
Currently, there are no approved vaccines available for the prevention of Leishmaniasis, and first-line treatment, such as pentavalent antimonates, generate various and serious adverse effects, including nephrotoxicity, hepatotoxicity, and myalgia. Additionally, drug-resistant strains have been reported. Therefore, the exploration of new therapeutic targets is required, such as the synthesis of nicotinamide adenine dinucleotide (NAD), which stands out as a promising metabolic pathway, since the importance of this electronic transporter.
In recent years, our research group has focused on obtaining and characterizing NAD metabolism proteins from protozoa such as Giardia lamblia, Plasmodium falciparum, Trypanosoma cruzi and L. braziliensis. Specifically, in Leishmania research has been carried out to characterize these kinds of proteins: NAD kinase and nicotinamide/nicotinate mononucleotide adenylyl transferase (LbNMNAT); however, these studies have mainly focused on their enzymatic activity and quaternary structure in the absence of substrates.
In this Thesis, the effect of the substrates of the LbNMNAT enzyme on its oligomerization was analyzed, finding that its organizations in the form of dimers, trimers, and tetramers, is not modified by the presence of the analyzed substrates. This structural evidence is consistent with the Michaelis-Menten kinetics reported for the enzyme since the substrates do not exert homotropic regulation on LbNMNAT.
On the other hand, considering that one of the main levels of regulation of gene expression in trypanosomatids is post-transcriptional, a bioinformatics approach based on the identification of splicing acceptor sites was carried out to delimit the non-coding regions (UTRs) of the lbnmnat gene. In this sense, numerous acceptor sites were found that could generate UTRs of different lengths, as has been reported for other species of the parasite.
Additionally, 29 RNA-binding proteins (RBPs) were identified with a probability of recognizing these UTRs, which participate in various processes, for instance, splicing, polyadenylation, and post-transcriptional repression. In this way, this study indicates proteins that possibly explain the differences reported by other authors for the abundance of the lbnmnat gene transcript throughout the life cycle of L. braziliensis.
In order to experimentally verify some of the bioinformatic findings of this work, the Retro-Transcription coupled to PCR (RT-PCR) technique was implemented, starting from the RNA obtained from L. braziliensis promastigotes, to identify the UTRs associated with the lbnmnat gene in this stage of the parasite. This technique allowed the synthesis of complementary DNA appropriate for studying UTRs and amplifying a product smaller than expected for the 5' UTR. This result indicates the need to determine the exact sequence of the amplicon by possible DNA isolation and sequencing techniques.
In conclusion, the present work provides experimental and bioinformatic evidence about the structural effect of the LbNMNAT enzyme's substrates on its oligomerization and its UTRs and binding proteins, which could explain mechanisms of regulation of the expression of the lbnmnat gene in the parasite L. braziliensis.MaestríaMagíster en Ciencias - Bioquímicabioquímica básic
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
No full text“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Bryan, Steven
No full textSee entry in Hale County, volume 1, page 113: https://digital.archives.alabama.gov/digital/collection/voter1867/id/389
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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