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Search Results: 1 - 10 of 629571 matches for " M. Humberto Reyes Valdés "
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Principales características de la investigación biomédica actual, en Chile
Valdés S,Gloria; Armas M,Rodolfo; Reyes B,Humberto;
Revista médica de Chile , 2012, DOI: 10.4067/S0034-98872012000400009
Abstract: background: biomedical research is a fundamental tool for the development of a country, requiring human and financial resources. aim: to define some current characteristics of biomedical research, in chile. methods: data on entities funding bio-medical research, participant institutions, and the number of active investigators for the period 2007-2009 were obtained from institutional sources; publications indexed in pubmedfor2008-2009 were analysed. results: mostfinancial resources invested in biomedical research projects (approximately us$ 19 million per year) came from the "comisión nacional de investigación científica y tecnológica" (conicyt), a state institution with 3 independent funds administering competitive grant applications open annually to institutional or independent investigators in chile. other sources and universities raised the total amount to us$ 26 million. since 2007 to 2009, 408 investigators participated in projects funded by conicyt. the main participant institutions were universidad de chile and pontificia universidad católica de chile, both adding up to 84% of all funded projects. independently, in 2009,160 research projects -mainly multi centric clinical trials- received approximately us$ 24 million from foreign pharmaceutical companies. publications listed in pubmed were classified as "clinical research" (n = 879, including public health) or "basic biomedical research" (n = 312). conclusions: biomedical research in chile is mainly supported by state funds and university resources, but clinical trials also obtained an almost equivalent amount from foreign resources. investigators are predominantly located in two universities. a small number of md-phd programs are aimed to train and incorporate new scientists. only a few new medical schools participate in biomedical research. a national registry of biomedical research projects, including the clinical trials, is required among other initiatives to stimulate research in biomedical sciences in c
Principales características de la investigación biomédica actual, en Chile Main characteristics of current biomedical research, in Chile
Gloria Valdés S,Rodolfo Armas M,Humberto Reyes B
Revista médica de Chile , 2012,
Abstract: Background: Biomedical research is a fundamental tool for the development of a country, requiring human and financial resources. Aim: To define some current characteristics of biomedical research, in Chile. Methods: Data on entities funding bio-medical research, participant institutions, and the number of active investigators for the period 2007-2009 were obtained from institutional sources; publications indexed in PubMedfor2008-2009 were analysed. Results: Mostfinancial resources invested in biomedical research projects (approximately US$ 19 million per year) came from the "Comisión Nacional de Investigación Científica y Tecnológica" (CONICYT), a state institution with 3 independent Funds administering competitive grant applications open annually to institutional or independent investigators in Chile. Other sources and universities raised the total amount to US$ 26 million. Since 2007 to 2009, 408 investigators participated in projects funded by CONICYT. The main participant institutions were Universidad de Chile and Pontificia Universidad Católica de Chile, both adding up to 84% of all funded projects. Independently, in 2009,160 research projects -mainly multi centric clinical trials- received approximately US$ 24 million from foreign pharmaceutical companies. Publications listed in PubMed were classified as "clinical research" (n = 879, including public health) or "basic biomedical research" (n = 312). Conclusions: Biomedical research in Chile is mainly supported by state funds and university resources, but clinical trials also obtained an almost equivalent amount from foreign resources. Investigators are predominantly located in two universities. A small number of MD-PhD programs are aimed to train and incorporate new scientists. Only a few new Medical Schools participate in biomedical research. A National Registry of biomedical research projects, including the clinical trials, is required among other initiatives to stimulate research in biomedical sciences in Chile.
Cancer Reduces Transcriptome Specialization
Octavio Martínez,M. Humberto Reyes-Valdés,Luis Herrera-Estrella
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0010398
Abstract: A central goal of cancer biology is to understand how cells from this family of genetic diseases undergo specific morphological and physiological changes and regress to a de-regulated state of the cell cycle. The fact that tumors are unable to perform most of the specific functions of the original tissue led us to hypothesize that the degree of specialization of the transcriptome of cancerous tissues must be less than their normal counterparts. With the aid of information theory tools, we analyzed four datasets derived from transcriptomes of normal and tumor tissues to quantitatively test the hypothesis that cancer reduces transcriptome specialization. Here, we show that the transcriptional specialization of a tumor is significantly less than the corresponding normal tissue and comparable with the specialization of dedifferentiated embryonic stem cells. Furthermore, we demonstrate that the drop in specialization in cancerous tissues is largely due to a decrease in expression of genes that are highly specific to the normal organ. This approach gives us a better understanding of carcinogenesis and offers new tools for the identification of genes that are highly influential in cancer progression.
Viabilidad de polen en una línea de girasol cultivado, en el girasol silvestre (Helianthus annuus L. ssp. texanus Heiser) y en su descendencia híbrida
Rosalinda Mendoza Villarreal,M. Humberto Reyes Valdés,Carlos Espinosa Zapata,José ángel Villarreal Quintanilla
Acta botánica mexicana , 2006,
Abstract: Con el propósito de evaluar la posible alteración en el desarrollo de los gametos masculinos en la progenie de un cruzamiento entre dos subespecies de girasol, se estudió la viabilidad del polen en la línea cultivada AN-3, así como en la subespecie silvestre Helianthus annuus ssp. texanus y en la descendencia híbrida resultante del cruzamiento CMS-AN-3 x H. annuus ssp. texanus. De las plantas híbridas, 95% exhibieron fertilidad masculina, lo cual indica la presencia de alelos restauradores de la fertilidad en las poblaciones silvestres. La viabilidad de polen no mostró diferencias significativas entre el híbrido (91.5%), el progenitor cultivado (94.6%) y el silvestre (95.2%). Los resultados sugieren que la viabilidad de polen es una característica mantenida en niveles altos tanto en las poblaciones silvestres como las cultivadas, y que no hay indicios de que la domesticación del girasol haya influido sobre este carácter. En lo que concierne al uso de material silvestre para el mejoramiento genético del girasol cultivado, la viabilidad de polen en los híbridos no es una barrera para el uso de poblaciones locales (sureste de Coahuila) de H. annuus ssp. texanus en programas de cruzamientos con fines de introducción de caracteres de plantas espontáneas a las variedades élite.
Número cromosómico y apareamiento meiótico en Turbinicarpus valdezianus (M ller) Glass & Foster (Cactaceae)
M. Humberto Reyes Valdés,Martha Gómez Martínez,Hermila Trinidad García Osuna
Acta botánica mexicana , 2000,
Abstract: En este trabajo se estudiaron los cromosomas de Turbinicarpus valdezianus en diacinesis y metafase I, de plantas nativas de la región aleda a a Saltillo, Coahuila (México). Se encontró un número cromosómico 2 n = 2 x = 22, lo cual es consistente con el número básico x = 11 previamente conocido para otros miembros de la familia Cactaceae. El apareamiento normal bivalente observado en todas las células analizadas indica que la especie estudiada es diploide con una segregación cromosómica regular. El análisis de frecuencias de configuraciones meióticas apoya la hipótesis de que uno o más pares de cromosomas podrían ser no metacéntricos.
Análisis meiótico de una cruza entre girasol cultivado (Helianthus annuus L. var . ma crocarpus) y girasol silvestre (Helianthus annuus L. ss p. texanus Heiser )
Jesús Rodríguez de la Paz,Martha Gómez Martínez,M. Humberto Reyes Valdés
Acta botánica mexicana , 2007,
Abstract: En el presente trabajo se compararon los patrones de apareamiento cromosómico meiótico del girasol cultivado (Helianthus annuus L. var. macrocarpus, línea pública HA 89), girasol silvestre (Helianthus annuus L. ssp. texanus Heiser, procedente de Saltillo, Coahuila) y del híbrido F1. Para ello se analizaron meiocitos en diacinesis y metafase I, basándose en la frecuencia de las configuraciones meióticas. Se evaluó la viabilidad de polen por medio de un método de tinción. El apareamiento cromosómico fue normal en los tres genotipos, con ausencia de univalentes y multivalentes, y sólo se observaron bivalentes en cadena y anillo, por lo que se concluye que los genomas parentales son altamente compatibles en la meiosis. El híbrido presentó un índice de apareamiento cromosómico de 0.82, próximo al valor medio parental (0.80) y la diferencia del híbrido con cada uno de los taxa parentales (taxon cultivado 0.87 y taxon silvestre 0.75) fue altamente significativa, además de variar dentro de las poblaciones estudiadas. Esto indica que el carácter número de quiasmas está bajo control multigénico y se ve afectado por el ambiente. Así pues, una población formada con los progenitores podría ser utilizada para analizar los loci de atributos cuantitativos (QTLs) para apareamiento cromosómico meiótico. El híbrido tuvo un porcentaje de viabilidad de polen (92.58) comparable con el de las plantas parentales (la silvestre 95.57 y la cultivada 95.33). La viabilidad de polen en la F1 fue alta, mostró fertilidad, y los genomas de los progenitores fueron altamente compatibles en la meiosis, corroborando que no hay barreras para la reproducción sexual. Esto indica que no hay dificultad en el flujo genético y que se pueden transferir caracteres deseables de H. annuus silvestre al cultivado.
Analysis and Optimization of Bulk DNA Sampling with Binary Scoring for Germplasm Characterization
M. Humberto Reyes-Valdés, Amalio Santacruz-Varela, Octavio Martínez, June Simpson, Corina Hayano-Kanashiro, Celso Cortés-Romero
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0079936
Abstract: The strategy of bulk DNA sampling has been a valuable method for studying large numbers of individuals through genetic markers. The application of this strategy for discrimination among germplasm sources was analyzed through information theory, considering the case of polymorphic alleles scored binarily for their presence or absence in DNA pools. We defined the informativeness of a set of marker loci in bulks as the mutual information between genotype and population identity, composed by two terms: diversity and noise. The first term is the entropy of bulk genotypes, whereas the noise term is measured through the conditional entropy of bulk genotypes given germplasm sources. Thus, optimizing marker information implies increasing diversity and reducing noise. Simple formulas were devised to estimate marker information per allele from a set of estimated allele frequencies across populations. As an example, they allowed optimization of bulk size for SSR genotyping in maize, from allele frequencies estimated in a sample of 56 maize populations. It was found that a sample of 30 plants from a random mating population is adequate for maize germplasm SSR characterization. We analyzed the use of divided bulks to overcome the allele dilution problem in DNA pools, and concluded that samples of 30 plants divided into three bulks of 10 plants are efficient to characterize maize germplasm sources through SSR with a good control of the dilution problem. We estimated the informativeness of 30 SSR loci from the estimated allele frequencies in maize populations, and found a wide variation of marker informativeness, which positively correlated with the number of alleles per locus.
Rescate de embriones en híbridos intergenéricos Helianthus annuus x Tithonia rotundifolia
Gómez-Martínez, Martha;Reyes-Valdés, M. Humberto;Martínez-Reyna, Juan Manuel;Escobedo-Bocardo, Leticia;García-Osuna, Hermila T.;
Acta botánica mexicana , 2010,
Abstract: in this research an in vitro technique was developed for production and propagation of intergeneric hybrids from immature seeds produced by crossing the domestic sunflower helianthus annuus and the wild species tithonia rotundifolia (mill.) s. f. blake. for embryo rescue in tissue culture the greatest success was obtained with the sequential use of three murashige-skoog based media: a) with amino acids and growth regulator bap for germination, b) without amino acids and with bap for micropropagation, and c) without vitamins and growth regulator ana for root development. the amino acids were added as a source of organic nitrogen. from a single seedling a total of 130 healthy plantlets were obtained. twenty of them were taken for acclimatization, and only one reached an incomplete flowering stage. therefore, standardizing acclimatization conditions is still required. in particular, it is necessary to establish treatments that allow a clear definition of the specific conditions for the acclimatization of the hybrid, through the test of different substrate mixtures and nutritive solutions under controlled environmental conditions. it is recommended to try the use of retardants and amino acids, as well as modifications in light intensity.
Obtención de híbridos intergenéricos Helianthus annuus x Tithonia rotundifolia y su análisis morfológico y molecular
Luévanos-Escare?o, Miriam Paulina;Reyes-Valdés, M. Humberto;Villarreal-Quintanilla, José ángel;Rodríguez-Herrera, Raúl;
Acta botánica mexicana , 2010,
Abstract: hybridization between the cultivated sunflower helianthus annuus and the wild species with ornamental potential tithonia rotundifolia was performed. from three cultivated materials: an-3, primavera and ha 89, the only success was obtained with the public cultivated sunflower line ha 89 as female parent. the male parent was a t. rotundifolia population collected in the state of guerrero, mexico. a total of 826 well developed hybrid achenes were produced, with a rate of success of four in 1000 potential achenes. in a sample of 49 plants established in the experimental field, two phenotypic classes were observed: a) plants with many small inflorescenses, and b) plants with a single big head and a few or none axillary inflorescenses. both types were morphologically characterized and showed a clearly hybrid morphology. additionally, the aflp-based dna fingerprints were analyzed in a sample of ten familial trios, with an average of 28 polymorphisms per trio. the dna fingerprinting analysis of the plants complemented the morphological study, allowed confirmation of the hybrid nature of the progenies and ruled out the partial hybridization phenomenon. all the hybrid plants showed sterility. from this work, it becomes clear that chromosomic manipulation or tissue culture techniques are needed to develop fertile hybrids with ornamental potential.
OBTENCIóN DE HíBRIDOS INTERGENéRICOS HELIANTHUS ANNUUS X TITHONIA ROTUNDIFOLIA Y SU ANáLISIS MORFOLóGICO Y MOLECULAR
Miriam Paulina Luévanos-Escare?o,M. Humberto Reyes-Valdés,José ángel Villarreal-Quintanilla,Raúl Rodríguez-Herrera
Acta botánica mexicana , 2010,
Abstract: Se realizó el cruzamiento entre el girasol cultivado Helianthus annuus y la especie silvestre con potencial ornamental Tithonia rotundifolia. De tres materiales cultivados: AN-3, Primavera y HA 89, sólo se tuvo éxito con la línea pública de girasol cultivado HA 89 como progenitor femenino. A su vez el masculino fue una población de T. rotundifolia recolectada en el estado de Guerrero, México. Se produjeron 826 aquenios híbridos bien desarrollados, con una tasa de éxito de cuatro en 1000 aquenios potenciales. Dentro de una muestra de 49 plantas establecidas en el campo experimental, se observaron dos clases fenotípicas: a) individuos con muchas inflorescencias peque as y b) otros con cabezuela solitaria grande y con pocas o ninguna inflorescencia axilar. Ambos tipos fueron caracterizados morfológicamente y presentaron rasgos claramente híbridos. Además, se analizó la huella genética, a través del polimorfismo en la longitud de los fragmentos amplificados (AFLPs), de una muestra de diez tríos familiares de cruzamientos, con un promedio de 28 polimorfismos por trío. El análisis de huella genética de las plantas complementó al estudio morfológico, permitió constatar la naturaleza híbrida de las progenies y descartar el fenómeno del cruzamiento parcial. Todas las plantas experimentales obtenidas resultaron ser estériles. Del presente trabajo se desprende que se requiere de manipulación cromosómica o técnicas de cultivo de tejidos para el desarrollo de híbridos fértiles con potencial ornamental.
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