Repositorio IPICYT
Not a member yet
1534 research outputs found
Sort by
High resistance to oxidative stress in the fungal pathogen Candida glabrata is mediated by a single catalase, Cta1p, and is controlled by the transcription factors Yap1p, Skn7p, Msn2p, and Msn4p
No full text"We characterized the oxidative stress response of Candida glabrata to better understand the virulence of this fungal pathogen. C. glabrata could withstand higher concentrations of H2O2 than Saccharomyces cerevisiae and even Candida albicans. Stationary-phase cells were extremely resistant to oxidative stress, and this resistance was dependent on the concerted roles of stress-related transcription factors Yap1p, Skn7p, and Msn4p. We showed that growing cells of C. glabrata were able to adapt to high levels of H2O2 and that this adaptive response was dependent on Yap1p and Skn7p and partially on the general stress transcription factors Msn2p and Msn4p. C. glabrata has a single catalase gene, CTA1, which was absolutely required for resistance to H2O2 in vitro. However, in a mouse model of systemic infection, a strain lacking CTA1 showed no effect on virulence.
Inclusión de bioseñales como funciones de peso en un sistema de control retroalimentado para manejo de glucemia en Diabetes Mellitus Tipo 1
Get PDF"En esta tesis, se aborda el diseño de controladores de glucosa para su aplicación en la terapia llamada páncreas endocrino artificial en Diabetes Mellitus Tipo 1. La aportación principal es el diseño de controladores que permitan calcular la cantidad y la forma en la que la insulina deba ser suministrada a una persona con Diabetes Mellitus Tipo 1 para que se suministro exógeno sea millar al patrón de secreción de insulina de una persona sana. El principal objetivo de los controladores de glucosa propuestos es evitar tanto escenarios de hipoglucemia como hiperglucemia, así como manejo de la glucemia durante escenarios de ejercicio. Con la finalidad de diseñar esquemas de control que manejaran los escenarios anteriores, se propone la inclusión de información sobre de las relaciones entre glucosa y la insulina, lactato y adrenalina; bioseñales relacionadas con los escenarios de hiperglucemia, ejercicio e hipoglucemia, respectivamente. Dicha información es incluida en forma de funciones de peso en el sistema retroalimentado de control. Los controladores de glucosa fueron diseñados haciendo uso de la teoría de coontrol robusto H∞ y probados mediante simulaciones numéricas sobre un modelo matemático del metabolismo de glucosa en una persona con Diabetes Mellitus Tipo 1. Las simulaciones numéricas que se realizaron permiten sugerir que los controladores de glucosa que se proponen en esta tesis mejorarían el manejo de la glucemia en personas con Diabetes Mellitus Tipo 1 ya que el suministro exógeno sería una mejor aproximación a la liberación pancreática de insulina de una persona sana. Lo anterior con el uso de una bomba de insulina capaz de suministrar la cantidad y la forma que indican los controladores, así como un sistema de medición de glucosa adecuado.""In this thesis, the design of feedback-based glucose controllers for artificial endocrine pancreas therapy in Type 1 Diabetes Mellitus is addressed. The main contribution of the proposed controllers is to compute the amount and pattern of exogenous insulin release to accurately reproduce the pancreatic pattern of a healthy person. The aim of the controllers is to avoid hyper-hypoglycemic and exercise scenarios. In order to achieve this objective, metabolic information was added into the feedback control. Three weighting functions were identified which contain information about the relationship between glucose and insulin, lactate and epinephrine, all of them being biosignals involved in hyperglycemic, exercise and hypoglycemic scenarios, respectively. The glucose controllers were synthetized via robust H∞ control theory and implemented via numerical simulations in a mathematical model describing the glucose metabolism in a Type 1 Diabetes Mellitus patient. The numerical simulations suggest that the controllers enhance the glucose management in Type 1 Diabetes Mellitus, because the exogenous release which they reproduce could be closer to the pancreatic insulin release of a healthy person. Such enhancement can be effective if we have an insulin pump able to release the insulin amount and pattern required and a suitable monitoring glucose system.
Supersymmetric methods in the traveling variable: inside neurons and at the brain scale
Get PDF"We apply the mathematical technique of factorization of differential operators to two different problems. First we review our results related to the supersymmetry of the Montroll kinks moving onto the microtubule walls as well as mentioning the sine-Gordon model for the microtubule nonlinear excitations. Second, we find analytic expressions for a class of one-parameter solutions of a sort of diffusion equation of Bessel type that is obtained by supersymmetry from the homogeneous form of a simple damped wave equation derived in the works of P.A. Robinson and collaborators for the corticothalamic system. We also present a possible interpretation of the diffusion equation in the brain context.
Synthesis, characterization and physical properties of carbon and boron nitride low dimensional systems.
Get PDFTesis (Doctorado en Nanociencias y Materiales)"Carbon nanotubes are versatile materials with promising applications based on their exceptional physical properties. Their applications depend strongly on the interactions that nanotubes have with their environment. In this sense, doping of carbon
nanotubes, understood as the incorporation of foreign species into the nanotube lattice, has proven as a very good method for modifying and tuning their physical and chemical properties, broadening the range of possible applications. In this work, the heteroatomic doping of multiwalled carbon nanotubes with
phosphorus and nitrogen atoms is presented. These nanotubes were successfully synthesized and thoroughly characterized by several electron microscopy and microanalysis techniques, and changes in their chemical properties were surveyed by
thermogravimetric analysis. In addition, first principles calculations were performed to understand the structural and electronic modifications that heteroatomic doping cause on single walled nanotubes. In the other hand, small carbon clusters and one-dimensional nanostructures could occur during doping of carbon nanostructures by heat treatment procedures. In this context, the energetic and electronic properties of small carbon clusters of
10, 12 and 14 atoms were studied by ab initio calculations, with special interest in their spin polarization. In addition, the vibrational properties of monoatomic carbon chains occurring during the boron doping process of double walled nanotubes and their relation with the Coalescence Induce Mode of their Raman spectra was also studied. Finally, the properties of boron nitride nanoribbons synthesized by a substitution reaction in carbon nanostructures that exhibit a surprising metallic behavior are explored by ab initio calculations.
Perfil de expresión a nivel transcripcional en cáncer cervicouterino y su relación con la vía de señalización Notch
Get PDFTesis (Doctorado en Ciencias en Biología Molecular)"El cáncer cervicouterino (CaCU) es la primer causa de mortalidad en mujeres en México, y la segunda a nivel mundial. Entre las causas principales para el desarrollo de cáncer se encuentran la presencia de mutaciones, deleciones, translocaciones e inserciones virales en los genes. El Virus de Papiloma Humano (VPH) está asociado en el 99% de los casos diagnosticados, aunque no es el único factor determinante. El sistema de señalización Notch está implicado en eventos celulares esenciales como el desarrollo, diferenciación, proliferación y apoptosis, esta vía está involucrada en varias de enfermedades humanas principalmente en cáncer, se ha reportado que la desregulación de los genes Notch, sin embargo el mecanismo exacto de participación de esta vía para la generación de neoplasia no es claro, se desconoce aún la existencia de componentes que puedan interactuar con la vía y que además pueden estar involucrados en la diferenciación tumoral. Se ha demostrado que dependiendo del nivel de expresión y del contexto celular, los receptores de membrana Notch contribuyen claramente en la resistencia a apoptosis en células tumorales. En este trabajo, se evaluó el perfil del transcriptoma de CaCU para la identificación de los genes que se inducen y/o reprimen en presencia de fenotipo neoplásico y la posible participación que tiene en la regulación de la vía Notch. El estudio se realizó en biopsias de pacientes con cáncer cervicouterino en los diferentes estadios de la enfermedad (NIC I, NIC II, NIC III y cáncer Invasor).""The cervical cancer (CC) is the first cause of death in women in Mexico and the second worldwide. 99% of the cases diagnosed with CC are affected by the Human Papilloma Virus (HPV), however other factors are involved. In the last years, there are reports about over expression of the Notch signaling pathway elements in a great variety of a human tumors including CC. However, the exact mechanism of the participation of this pathway is not clear. It is unknown yet the existence of elements that could interact with this pathway and that possibly involved in the tumor differentiation. Among the main causes for the development of CC are the presence of mutations, deletions, translocations, and insertions of viral genes. The Notch signaling pathway is involved in essential cellular events such as development, differentiation, proliferation, and apoptosis. In addition, this pathway has been involved in several human diseases, mainly in cancer. It has been demonstrated that depending of the expression level and the cellular context, the Notch receptors contribute clearly in the resistances to apoptosis in tumor cells. In this work, we study the transcriptome profile in CC for identification of genes that are induced and /or repressed in the present of a neoplastic phenotype and the possible participation in the Notch via. In this study we used biopsies from patients with CC in the different stages of the disease (CIN I, CIN II, CIN III, and invasive cancer).
Modelado del flujo de fluidos en una bomba para suministro de medicamento.
Get PDFTesis (Maestría en Control y Sistemas Dinámicos)"Esta tesis trata sobre el modelado de la mecánica de fluidos en un Actuador/Dosificador (AD) que formara parte de una bomba automática para suministró de medicamento. La geometría del AD propuesto se basa en tubos de curvatura variable siguiendo en su linea central una espiral de Arquímedes. Lo novedoso de este diseño radica en la doble funcionalidad del AD, porque permitirá contener y a la vez dosificar el medicamento. Las dimensiones del recipiente (el cual tiene la capacidad de contener 1 mL de medicamento) son de 32.8 cm de longitud con un diámetro de 2 mm. Así, las dimensiones totales del AD incluyendo el recipiente son de 6.89 cm de base x 6.80 cm de altura x 1.5 cm de espesor. Por otro lado, los pasos seguidos para modelar la mecánica de fluidos en este trabajo fueron: 1. Primero, aproximando secciones de la espiral por medio de toros de curvatura constante; se extendió el modelo de Dean [20], el cual aplica para fluidos incompresibles fluyendo a través de tubos con curvatura constante, al caso de fluidos compresibles. 2. Segundo, considerando el radio de la espiral variable se modela la mecánica del fluido en el AD y se extiende el modelo de Dean-Germano [25], el cual aplica para fluidos incompresibles fluyendo en tubos con torsion y curvatura constante, al caso de tubo con curvatura variable. Por ultimo, la importancia de los modelos obtenidos radica no solo porque permitirá simular la mecánica del fluido dentro del AD, sino por sus aplicaciones potenciales en diferentes áreas de la ingeniera. Por ejemplo, el modelo obtenido en el paso 1 permite modelar la mecánica de fluidos tanto de líquidos como de gases fluyendo a través de tubos curvos de curvatura constante.""This thesis deals with the modeling of the fluid mechanics within an Actuator/Dispenser (AD) which will be part of a automatic pump to supply a medicine. The proposed AD geometry, is based in curved pipes of variable curvature that follow up an Archimedes spiral in their center line. The innovation of this design lies in the double functionality of the AD, because it will be both the container and dispenser of the medicine. The container, which has a capacity of one mililiter (mL) of medicine, is 12.9 inches long and has a diameter of 0.78 inches. The total AD dimensions, including the container, are 2.71 inches x 2.67 inches x 0.59 inches. On the other hand, the followed steps for modeling the fluids mechanics in the AD were: 1. First, approximating sections of the spiral by means of the torus with constant curvature. The classical Dean’s model [20], which describes incompressible fluids flowing across pipes with constant curvature, is extended to the compressible fluid case. 2. Second, considering the variable radius of the spiral, we extended the Dean-Germano model [25], which describes incompressible fluids flowing within pipes with constant curvature and torsion to the variable curvature case. To conclude, the obtained models are not only important for modeling the fluid mechanics within the AD, but they have also potential applications in different areas of engineering. For instance, the model obtained in the step one, lets modeling the fluid mechanics either gases or liquids flowing across of curved pipes with constante curvature.
Effect of salt stress, proline, and polyamines on seed germination of Opuntia streptacantha
Get PDF"In this study we conducted experiments in order to determine whether polyamines (putrescine, spermidine, and spermine) and proline treatments help to break seed dormancy of Opuntia streptacantha and also if they facilitate seed germination under salt stress. The results showed that 1mM proline stimulated a better germination percentage as compared to untreated seeds, although the difference was not statistically significant. With respect to polyamines, they did not break seed dormancy. On the other hand, salinity affected seed germination at the higher concentrations (50 and 75 mM NaCl) used, whereas, at 25 mM NaCl, results were similar to the control. The germination percentage in the treatments with proline (1 and 10 mM) and with polyamines (1μM each) diminished significantly when increasing the concentration of NaCl. The exception was spermine treatment, which alleviates seed germination at the higher concentration of NaCl used (75 mM).
Effect of cytokinins on the in vitro propagation of Mexican agaves
Get PDF"La falta de sistemas eficientes de propagación es un factor que limita el aprovechamiento racional de varias especies de Agave, que en muchos casos han tenido una reducción peligrosa de sus poblaciones debido a la sobreexplotación de materiales silvestres. En este estudio se desarrollaron protocolos para la propagación in vitro de Agave cupreata, A. difformis, A. karwinskii, A. obscura y A. potatorum. Como explantes se utilizaron tejidos meristemáticos extraídos de plántulas germinadas in vitro. Se logró la formación de brotes múltiples en explantes basales en medio MS adicionado con 30 g L-1 de sacarosa, 8 g L-1 de agar y varios tratamientos con citocininas [6- bencilaminopurina (BA), 6-γ,γ-dimetilalilaminopurina (2iP), cinetina (Cin), tidiazurón (TDZ) y meta-topolina o N6-(metahidroxibencil) adenina (MT)]. Las eficiencias más altas en producción de brotes en A. cupreata y A. karwinskii se obtuvieron con 1.5 y 1 mg L-1 de BA, donde se generaron 10.5 y 6.1 brotes por explante, respectivamente. En A. difformis y A. obscura las mejores respuestas se obtuvieron con 0.2 mg L-1 TDZ con 8.5 y 11 brotes por explante, respectivamente. En A. potatorum la mejor respuesta ocurrió con 3 mg L-1 Cin, en el que se produjeron 6.9 brotes por explante. El enraizamiento de los brotes generados in vitro se alcanzó en medio MS basal con eficiencias entre 80 y 100 %, y la frecuencia de supervivencia de las plantas una vez transferidas a suelo fue de 72 % en promedio.""The lack of efficient propagation systems is one factor limiting the rational use of several species of Agave, which in many cases have had a dangerous reduction of their populations due to the over-exploitation of wild materials. In this work in vitro propagation protocols were developed for Agave cupreata, A. difformis, A. karivinskii, A. obscura and A. polatorum. Meristematic tissues front in vitro germinated seedlings were used as explants. Multiple shoot formation from basal explants was achieved oil MS medium supplemented with 30 g L(-1) sucrose, 8 g L(-1) agar and various treatments with cytokinins [6-benzylaminopurine (BA) 6-gamma,gamma-dimethylallylaminopurine (2iP), kinetin (Kin), thidiazuron (TDZ) and meta-topolin or N(6)-(meta-hydroxylbenzyl)adenine (M)]. The highest shoot production efficiencies for A. cupreata and A. karivinskii were obtained with 1.5 and 1 mg L(-1) BA, which rendered 10.5 and 6.1 shoots per explant, respectively. In A. difformis and A. obscura the best responses were obtained with 0.2 mg L(-1) TDZ, which yielded 8.5 and 11 shoots per explant, respectively. In A. potatorum the best response occurred with 3 mg L(-1) Kill where 6.9 shoots per explant were produced. Rooting of the in vitro generated shoots was achieved on MS basal media with frequencies ranging from 80 to 100%, and survival of plants transferred to soil was 72%, on the average.
Effect of salt stress on polyamine metabolism in two bean cultivars
Get PDF"In agricultural areas, salinity affects plant growth, development and productivity, causing loss of economically important crops. Nitrogenderived compounds such as polyamines (PAs) are differentially accumulated in diverse plants species in response to salinity. PA and chlorophyll (Chl) contents, as well as water potential (w), were assessed in leaves of two common bean cultivars subjected to salt stress for one and seven days; these bean cultivars, ‘Pinto Villa’ and ‘Canario 60’, differ in their drought tolerance phenotype. Salt stress induced a phenotypic behaviour similar to that of drought in which the sensitive ‘Canario 60’ showed a pronounced decrease in w, in comparison to the tolerant ‘Pinto Villa’. Regarding PAs, after the first day of treatment, the levels of all of them (putrescine (Put), spermidine (Spd) and spermine (Spm)) increased in tolerant cultivar (‘Pinto Villa’) while in the sensitive one (‘Canario 60’) the levels of Spd and Spm only increased at 400 mM NaCl. At the seventh day, the tolerant cultivar showed an accumulation of Spm at the higher concentrations of NaCl used (150 and 400 mM), whereas a decrease in PA content occurred in the sensitive cultivar at all concentrations assayed. Furthermore, the effect of salt stress on the expression of the main genes involved in PA biosynthesis, including a new S-adenosylmethionine decarboxylase (SAMDC) gene identified in this work, was analysed. It is suggested that Spm accumulation in ‘Pinto Villa’ might be part of the mechanism conferring salt tolerance.
Inmovilización de mediadores redox en matrices poliméricas y su aplicación en la biotrasformación reductiva de un colorante azo.
Get PDFTesis (Maestría en Ciencias Ambientales)"En esta investigación se evaluó la capacidad de tres matrices poliméricas para adsorber dos catalizadores con propiedades de óxido reducción (redox), bajo diferentes condiciones experimentales, como temperatura y diferentes concentraciones de PO4 3-, con el fin de optimizar la inmovilización de al menos un catalizador (sin afectar su
reactividad) para su posterior aplicación en el tratamiento de efluentes contaminados con colorantes azo. Se caracterizaron las matrices poliméricas seleccionadas en términos de porosidad, área específica, intercambio iónico y distribución de carga superficial, con el fin de predecir su capacidad de adsorber distintos mediadores redox.
Además, se determinó el grado de desorción de las quinonas inmovilizadas en las matrices, mediante un ciclo de desorción con medio basal, a diferentes temperaturas. También, se cuantificaron las especies presentes en el medio basal, después del ciclo de desorción a diferentes temperaturas, mediante electroforesis capilar, para identificar las
especies causantes de la desorción. Los resultados mostraron que la resina esférica (R) y la resina fibrosa (RF) tienen una mayor capacidad de adsorber antraquinona-2,6-disulfonato (AQDS) (1.72 meq AQDS/g de R y 3.12 meq AQDS/g RF) en comparación con naftoquinona-4-sulfonato (NQS) (1.42 meq NQS/g de R y 2.00 meq NQS/g RF).
Durante el proceso de desorción (con medio basal fresco para cada ciclo) se observó menor cantidad de quinona desorbida en R (0.03 meq NQS/g y 0.01 meq AQDS/g, con un ciclo de desorción). Para ambas resinas evaluadas, se observó cómo la temperatura afecta significativamente la desorción, aumentando ésta conforme aumenta la
temperatura. Se presentó una desorción prácticamente igual con R y RF a las tres temperaturas probadas (0.06 meq/g de R y 0.06 meq/g de RF a 35°C, 0.09 meq/g de R y 0.07 meq/g de RF a 45°C y 0.13 meq/g de R y 0.09 meq/g de RF a 55°C). Los resultados obtenidos de la cuantificación de aniones, presentes en el sobrenadante de los
experimentos de desorción con medio basal, a diferentes temperaturas, indican que para ambas resinas la concentración de SO4- y PO4
3- disminuyó conforme aumentó la temperatura (35, 45, y 55°C). Sin embargo, la disminución de la concentración de PO4 3- fue mucho mayor, lo que sugiere que la concentración de especies aniónicas de PO4 3- no encontrados en solución (<100 mg/L) se adsorbieron en las resinas, y por consiguiente se señala a este anión como el principal causante de la desorción de quinonas. Las cinéticas de decoloración realizadas con lodo anaerobio en presencia de resinas saturadas tanto con NQS como con AQDS mostraron que las quinonas inmovilizadas, conservaron su capacidad catalítica. El mejor tratamiento observado fue
el que contenía lodo, colorante (Rojo reactivo 2) y una concentración de 4.8 mM de NQS inmovilizada, dicho tratamiento redujo proximadamente el 90% del colorante después de 24 horas, que representa un aumento de 6.5 veces en la tasa de decoloración comparado con el control biológico sin quinona. Estos resultados indican que las resinas
de intercambio iónico pueden actuar como excelentes matrices de inmovilización de mediadores redox, como NQS y AQDS. También se comprobó que los mediadores redox mantienen su capacidad catalítica aún después de ser inmovilizados, por lo que, este mecanismo de inmovilización puede ser considerado como propicio para retener
este tipo de catalizadores en sistemas de tratamiento de aguas residuales.""In this research, the adsorption capacity of three polymeric matrices to fix two catalysts with oxidation reduction (redox) properties was evaluated. The studies were carried out under different experimental conditions, such as temperature and concentrations of PO4 3-. The main goal was to immobilize at least one catalyst (without affecting its catalytic capacity), in order to apply it in wastewater treatment systems for azo dyes reduction. The polymeric materials were characterized in order to know their porosity, surface area, ion interchange properties, and surfaces charge distribution. All this information enables us to know the adsorption properties of the redox mediators. Therefore, it was determined the desorption rate of fixed quinone on the surface matrices, using desorption cycles in basal medium at different temperatures. Using capillary electrophoresis, we determined the concentration anionic of species present in the basal medium, after each desorption cycle at different temperatures, in order to know the chemical species that cause desorption of catalysts. The results showed that the spherical resin (R) and fibrous resin (RF) exhibit high adsorption properties using antraquinone-2,6-disulphonate (AQDS) (1.72 meq AQDS/g de R and 3.12 meq AQDS/g RF) compared to naphtoquinone-4-sulphonate (NQS) (1.42 meq NQS/g de R and 2.00 meq NQS/g RF). During desorption cycles with basal medium (fresh basal medium in each cycle), the lower desorption always occurred with R (0.03 meq NQS/g and 0.01 meq AQDS/g), with one desorption cycle. In both resins, we observed that the temperature significantly affects the desorption rate of AQDS. Similar desorption rates in both materials along the temperature range (0.06 meq/g of R and 0.06 meq/g of RF to 35°C, 0.09 meq/g R and 0.07 meq/g of RF to 45°C and 0.13 meq/g of R and 0.09 meq/g of RF to 55°C). The obtained results showed that the SO4 - and PO4 3- concentrations decrease when the temperature was increased (35, 45, and 55°C). PO4 3- was identified as the principal cause of the quinones desorption as its concentration decreased up to <100 mg/L during desorption procedures. Decolourisation assays conducted in the presence of anaerobic sludge and saturated resins (with NQS and AQDS) showed that the immobilized quinones preserved their catalytic capacity. The experimental treatment with sludge, azo dye (Red reactive 2) and immobilized NQS (4.8 mM) onto R showed the best decolourisation performance.