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Heteromeric channels with different phenotypes are generated when coexpressing two P2X2 receptor isoforms
Get PDFTesis (Doctorado en Ciencias en Biología Molecular)"Para determinar si al coexpresar dos isoformas del receptor P2X2 en ovocitos de Xenopus laevis se forman canales heteroméricos con diferente estequiometria. Tomando ventaja de una mutante (P2X2-2bm) debido a que tiene una menor sensibilidad al ATP que el receptor P2X2-2b (wild type), y a su vez incrementa las diferencias entre esta y la variante P2X2-1a. Los canales P2X son triméricos con tres sitios de unión al agonista, dos posibles combinaciones pueden dar lugar a los canales heteroméricos: i) 2(P2X2-1a) +1(P2X2-2bm); o ii) 1(P2X2-1a) +2(P2X2- 2bm). Debido a que la apertura de los canales P2X se da por la unión de dos moléculas del ATP, se esperaría diferente sensibilidad al ATP entre estos heterómeros. En apoyo a esta hipótesis, la coexpresión de las dos isoformas de receptor P2X2 resultó en dos poblaciones de ovocitos con sensibilidad al ATP y coeficientes de Hill diferentes. Una población (P2X2-1a like), fue similar a los ovocitos en que solo se expresaron canales P2X2-1a, mientras la otra (P2X2-2bm like) fue similar a cuando solo se expresaron canales P2X2-2bm. Sin embargo, el análisis de sus cinéticas, descarta la expresión de canales homoméricos. Los datos también indican que, la heteromerización de los canales, provoca cambios en la cinética de desensibilización. En conclusión, cuando las isoformas de P2X2 son coexpresadas, los ovocitos expresan principalmente una de las dos estequiometrias de canales heteroméricos.""To investigate if channels with different stoichiometry are formed from two P2X2 receptor splice variants during their co-expression in Xenopus laevis oocytes. We used a mutant (P2X2-2bm) because it has a lower ATP sensitivity than the wild type receptor. P2X channels are trimeric proteins with three agonist binding sites; therefore, only two homomeric and two heteromeric stoichiometries are possible, the heteromeric channels might be formed by: i) 2(P2X2-1a) +1(P2X2-2bm); or ii) 1(P2X2-1a) +2(P2X2-2bm). Because P2X2 channels open when two binding sites are occupied, these stoichiometries are expected to have different sensitivities to ATP. In agreement with this, coexpressing both P2X2 isoforms, two oocyte populations were distinguished based on their channel sensitivities to ATP and Hill coefficients. For the first population (P2X2-1a like), such parameters were not different than those of homomeric P2X2-1a channels, and for the second population (P2X2-2bm like), these parameters were also not different than for homomeric P2X2- 2bm channels. Kinetics analysis indicates that heteromeric channel expression is occurring, and homomeric channel expression is not responsible for such differences. Our data indicate that oocytes expressed heteromeric channels with mainly one (of the two possible) stoichiometry when P2X2-1a and P2X2-2bm subunits are coexpressed, and the expression of homomeric channels is also not detectable.
Efectividad de la transferencia de suelo para la restauración de bosques de Quercus spp
Get PDFTesis (Maestría en Ciencias Ambientales)"La deforestación y cambio de uso de suelo, provocan el deterioro de la estructura y funcionamiento de los bosques, de manera que la regeneración natural de los ecosistemas degradados, se ve limitada. Los filtros ecológicos son las variables y procesos que determinan la composición actual de especies en un sitio determinado. Si mediante un disturbio, se alteran las propiedades físicas o químicas del suelo, este se puede convertir en un filtro ecológico que limite la regeneración. En este trabajo, se determinó el impacto de condiciones contrastantes de suelo como filtros ecológicos, en la emergencia y supervivencia de tres especies de Quercus (Q. eduardii, Q. viminea y Q. resinosa). Se usó un diseño aleatorio con bloques para monitorear durante 32 semanas, 1500 bellotas sembradas en dos hábitats contrastantes (claro y bosque), tanto en el suelo nativo como en suelo transferido (del bosque al claro y viceversa). Los resultados indican que la transferencia de suelo forestal al claro no influyen significativamente en la germinación de Q. viminea, pero sí para Q. eduardii, en el claro. Para la supervivencia, no existieron diferencias significativas con la transferencia de suelo ni en la supervivencia de Q. eduardii y Q. viminea. Respecto a las bellotas no germinadas, hubo mayor cantidad de bellotas deshidratadas en el claro con suelo del claro.""Deforestation, degradation and land use change in forest ecosystems reduces natural regeneration and simplifies its structure and ecological functioning. Ecological filters are variables and processes that determine the actual species composition in a given site. Disturbances that alters physical or chemical soil properties can become a limiting ecological filter for regeneration. In this dissertation, the impact of contrasting soil conditions in seedling emergence and survival of three species of oaks (Q. eduardii, Q. viminea and Q. resinosa) is evaluated in two contrasting habitats (clearings vs forests). Herefore, circular patches of forest soil were transferred to clearings and vice versa, so each habitat had sites with local and transferred soil. The fate of 1500 acorns were monitored during 32 weeks using a randomized block design. The results indicate that transferred forest soil in clearings does not affect germination of Q. viminea, but it does for Q. eduardii. Furthermore, more ungerminated acorns due to dehydration were found in clearings with native soil. As for seedling survival, no significant differences between transferred and native soil were detected for any of both species.
Study and application of a desingularization algorithm for driftless control systems
Get PDF"En este trabajo se aborda el problema de planeación de movimiento (MPP por sus siglas en inglés) en modelos cinemáticos de robots móviles tipo carro con restricciones no holonómicas, también conocido como state steering. En particular, se toma en consideración la posible existencia de puntos singulares en dichos modelos y se estudia un algoritmo de desingularización propuesto en [Chitour et al., 2013], el cual garantiza que las señales de control que resuelven el MPP en el sistema desingularizado también lo resuelven en el sistema singular y son presumiblemente menos complejas que las que se obtendrán resolviendo el mismo problema para el sistema singular. Además se presentan aplicaciones a sistemas particulares tanto del algoritmo de desingularización como de una metodología de control propuesta en [Chitour et al., 2013] para sistemas sin deriva regulares y nilpotentes.""This work addresses the motion planning problem (MPP) for kinematic models of car-like mobile robots with nonholonomic constraints, also known as the state steering problem. In particular, the possible existence of singular points for these models is considered and a desingularization algorithm, proposed in [Chitour et al., 2013], is studied. This algorithm ensures that the control signals that solve the MPP for the \desingularized" system also solve it for the singular system and are presumably less complex than those that would be obtained by solving the same problem for the singular system. In addition, we present applications of both the desingularization algorithm and a control methodology proposed in [Chitour et al., 2013] for particular examples of regular, nilpotent, driftless systems.
El sistema hidrológico Esperanza-Oriental y su impacto sobre el acuífero de Tecamachalco, Puebla, México
Get PDF"El sistema hidrológico Esperanza-Oriental se alimenta principalmente de los deshielos de los volcanes Pico de Orizaba y La Malinche, que se traducen en la disponibilidad de agua subterránea para el valle de Esperanza, con su consecuente aporte al valle de Tehuacán y la formación de cuerpos de agua superficiales en el valle Del Oriental (lagos de Totolcingo y Tepeyahualco). Estos valles han reducido sus áreas de captación y disponibilidad, así como la presencia de un gran número de lagos-cráter (axalapazcos), don-de se observan los niveles estáticos del agua subterránea en la zona (algunos de ellos presentan descensos importantes); ambos sistemas alimentan al acuífero de Tecamachalco, que ha disminuido su disponibilidad de agua subterránea. Con base en un sistema de información geográfica, levantado por el Instituto Nacional de Estadística y Geografía, se identificaron las cargas hidráulicas que dan origen a los flujos subterráneos que alimentan el acuífero de Tecamachalco, así como la evolución fisicoquímica que presenta el agua subterránea, identificada mediante diagramas de Mifflin (1988), Gibbs (1970), Piper (1953), Durov (1948) y relaciones iónicas, lo que ayudó a delinear los patrones de flujos para conocer la dependencia de este acuífero con el sistema Esperanza-Oriental.""The Esperanza-Oriental hydrological system is fed mainly by the meltings that take place in Orizaba and La Malinche volcanoes, which mean availability of groundwater for Esperanza valley, with its consequent contribution to Tehuacan valley and the formation of surface water-bodies in the Del Oriental valley (Totolcingo and Tepeyahualco lakes), which have reduced their water collecting areas and availability, as well as the presence of a large number of crater-lakes (axalapazcos), since static groundwater levels are observed in the area (some of them have significant decreases). Both systems feed Tecamachalco aquifer, which has reduced its groundwater availability. Based on a Geographic Information System created by the National Institute of Statistics and Geography, the hydraulic loads that give rise to those underground streams that feed the aquifer Tecamachalco were identified as well as the physicochemical evolution present in groundwater. This was identified by Mifflin (1988), Gibbs (1970), Piper (1953), and Durov diagrams (1948), together with ionic relations, which helped to delineate those flow patterns that determine to what extent this aquifer is dependent on Esperanza-Oriental hydrological system.
Estimación de biomasa forestal de la sierra de San Miguelito por medio de imágenes de satélite
Get PDF"La cantidad de biomasa en ecosistemas forestales sin valor comercial ha sido poco estudiada en México, debido a procedimientos costosos y destructivos para obtener las mediciones. La evaluación de biomasa por medio de percepción remota es una alternativa que se ha desarrollado en diferentes países y que en México ha sido relativamente poco aplicada. En este trabajo se aplicó una metodología integrada para la evaluación de biomasa forestal de la Sierra de San Miguelito por medio de imágenes de Satélite Landsat de los años 1987, 1996, 2005 y 2014. Se aplicaron los procedimientos de corrección radiométrica y atmosférica de las imágenes, para después implementar el algoritmo ISO-DATA de clasificación digital para la identificación de cubiertas vegetales. El cálculo de biomasa se realizó por medio de la aplicación de índices de vegetación NDVI, SAVI, y IAF. Estos índices precisaron la información recolectada en campo y la información recogida en otros trabajos de investigación. El índice NDVI es el parámetro adecuado para una mejor identificación del estado de conservación de los bosques y en la discriminación de la densidad de vegetación, con el cual se obtuvieron los valores de distribución de las cubiertas densas de vegetación con respecto de otras. El pino – encino se identificó con valores de 0.4 - 0.1. Los resultados de este trabajo revelan que el uso de imágenes de satélite LANDSAT es una buena alternativa para evaluar biomasa a nivel regional y los datos pueden ser usados para la cuantificación de gases liberados por los incendios forestales producidos en la región. Donde se obtuvieron 3 categorías en el aporte de biomasa por hectárea; aporte bajo < 13 toneladas, 23 toneladas aporte medio y 41 toneladas aporte alto.""The amount of biomass in forest ecosystems without commercial value has been few studied in Mexico, due to costly and destructive procedures to obtain measurements. The evaluation of biomass through remote sensing is an alternative that has been developed in different countries but in Mexico has been poorly applied. In this paper, an integrated methodology was applied for the evaluation of forest biomass in the Sierra de San Miguelito through Landsat satellite images of the 1987, 1996, 2005 and 2014 years. Radiometric and atmospheric correction methods were applied, posteriorly it was implemented a digital classification algorithm ISO-DATA to identify land cover. Biomass calculation was performed by the application of the vegetation indices NDVI, SAVI, and IAF. These indices support the information collected in the field and the information gathered in other research. The NDVI is the appropriate setting for better identification of the condition of forests and the discrimination of vegetation density, in which the values of distribution of dense vegetation cover were obtained in relation to others. The pine - oak vegetation was identified with values between 0.4 and 0.1. The results of this study show that the use of Landsat satellite images is a good alternative to evaluate biomass at regional level and the resulting data can be used for quantification of gas released by forest fires in the region. Three categories were obtained in the contribution of biomass per hectare; low contribution < 13 tons, 23 tons average contribution and 41 tons high contribution.
Adiabatic magnetocaloric effect in Ni50Mn35In15 ribbons
Get PDF"Heusler-type Ni-Mn-based metamagnetic shape memory alloys (MetaMSMAs) are promising candidates for magnetic refrigeration. To increase heat exchange rate and efficiency of cooling, the material should have a high surface/volume ratio. In this work, the typical Ni50Mn35In15 MetaMSMA was selected to fabricate thin ribbons by melt-spinning. The characteristic transformations of the ribbons were determined by calorimetry, X-ray diffraction, scanning electron microscopy and thermomagnetization measurements. The inverse and conventional magnetocaloric effects (MCEs) associated with the martensitic transformation (MT) and the ferromagnetic transition of the austenite (TCA), respectively, were measured directly by the adiabatic method (Delta T-ad) and indirectly by estimating the magnetic entropy change from magnetization measurements. It is found that the ribbons exhibit large values of Delta T-ad = -1.1K at mu(0)Delta H = 1.9 T, in the vicinity of the MT temperature of 300K for inverse MCE, and Delta T-ad = 2.3K for conventional MCE at TCA = 309 K. This result strongly motivates further development of different MetaMSMA refrigerants shaped as ribbons. Published by AIP Publishing.
Structural elucidation and evaluation of multidrug-resistance modulatory capability of amarissinins A–C, diterpenes derived from Salvia amarissima
Get PDF"Three new diterpenes (amarissinins A-C, 1–3) containing several oxygenated functionalities were isolated from the leaves and flowers of Salvia amarissima. The structures of these compounds were established through the analysis of their NMR spectroscopy and mass spectrometry data. The structures of compounds 1 and 2 were confirmed by single crystal X-ray diffraction. Compound 2was identified as a C-10 epimer of dugesin F (5). The cytotoxic activity of these compounds against five human cancer cell lines was determined. Additionally, the capability to modulate the multidrug resistance (MDR) in the MCF-7 cancer cell line resistant to vinblastine was tested.
Modelado de deslizamientos de terreno utilizando GPS y percepción remota: caso Ahualulco, S.L.P.
Get PDF"El fenómeno de deslizamientos de terreno es un evento cuya ocurrencia puede causar severos daños a la población y medio ambiente, ya que al tratarse de fenómenos complejos en el que intervienen múltiples factores, es muy difícil poder predecirlos. La zona de estudio se encuentra dentro del municipio de Ahualulco, S.L.P., la cual se caracteriza por una ladera de montaña con incidencia de deformaciones y escarpes pronunciados, que son fácilmente visibles a distancia. La carretera que atraviesa la zona presenta deformaciones y daños causados por el deslizamiento en el área y es reparada constantemente para su correcto funcionamiento. Con la metodología propuesta en este trabajo de investigación se lograron integrar técnicas basadas en la percepción remota, la geofísica, la observación geológica y las técnicas informáticas para desarrollar un esquema alternativo para la modelación de deslizamientos que integre dentro de una misma metodología evidencias geológicas, monitoreo a base de puntos de medición GPS y la unificación de la información recabada con técnicas basadas en percepción remota de alta y muy alta resolución, apoyados por el uso el uso de vehículos aéreos no tripulados (AUV), también conocidos como drones empleando sensores ópticos-multiespectrales. Se logró obtener información geológica de la zona de estudio en base a muestreos se realizados en las zonas de afloramientos y paredes expuestas, con el análisis de las muestras fue posible identificar los tipos de roca, su disposición en el subsuelo y su densidad aparente. Asimismo, se obtuvieron datos estructurales de las fracturas y cavidades. Mediante la aplicación de métodos eléctricos fue posible determinar la distribución de las rocas en el subsuelo, conocer los espesores y profundidades de las diferentes capas bajo la superficie, con esto se alimentó el modelo numérico, siendo un factor determinante para su implementación.""Landslides is one of the most dangerous natural phenomena to people and infrastructure, causing huge human and economic losses. It is a persistent event that can happen in any environment where gravity directly associated with subsurface instability causes the occurrence of these phenomena, which behavior is complex and difficult to predict. The study area is located within the municipality of Ahualulco, S.L.P. The site consists of a mountain slope with incidence of deformities and pronounced escarpments, easily visible from the distance. The road that crosses through the site shows evidence of deformation and damage caused by landslides in the area, and is constantly repaired for a proper operation. The methodology proposed in this research aims to develop an alternative scheme for landslides modeling. This method can combine geological evidence, geophysics methods, GPS technology and data collected by remote sensing techniques. All within a single methodology, all this possible by the use of using multispectral optical sensors, supported by unmanned aerial vehicles (UAV), also known as drones. Geological information of the study area was obtained from samples of outcrops and exposed walls, with the analysis of the samples was possible to identify rock types, their distribution on the study area, and obtain its bulk density. Structural data of fractures and cavities were found by applying electrical methods, which was possible to determine the distribution of the underground rock layers, knowing the thicknesses and depths of the layers below the surface. At the end, this information was introduced in the numerical model for its implementation. Furthermore, to propose a unique technique for the suitable management of the huge amount of resulting data during processing. With the optimization of computing processes and the proper manipulation of massive data was possible reach the integration of different techniques in a simulation model, with which it was possible to describe the behavior of landslide.
Biohydrogen production by the psychrophilic G088 strain using single carbohydrates as substrate
Get PDF"The production of biohydrogen by psychrophilic G088 strain ([EU636029]), closely related to Polaromonas rhizosphaerae ([EF127651]) was evaluated using xylose, glucose, fructose, galactose, lactose or sucrose as a carbon source. Biohydrogen production was performed in 120 ml serological bottles with a production medium containing 2.75 g/l tryptone, 0.25 g/l yeast extract, and 20 g/l of each carbohydrate. Results showed that the G088 strain produced biohydrogen using all the evaluated substrates, ranging from 91.7 to 439.8 ml for lactose and glucose, respectively. However, glucose was the substrate with the highest consumption rate, accompanied by the maximum values of biohydrogen production rate and a biohydrogen yield of 50.1 ml/l/h and 1.7 mol H2/mol glucose, respectively. Analysis of the secreted metabolites showed that ethanol and organic acids were the main by-products. Our results demonstrate that the G088 strain has potential to be used for developing new biotechnological processes for biohydrogen production.
Antifungal Nanocomposites Inspired by Titanate Nanotubes for Complete Inactivation of Botrytis cinerea Isolated from Tomato Infection
Get PDF"Antifungal silver nanocomposites inspired by titanate nanotubes (AgTNTs) were successfully evaluated for the effective inactivation of the phytopathogenic fungus Botrytis cinerea within 20 min. One-dimensional H2Ti3O7 nanotubes functionalized with silver nanoparticles (AgNPs) exhibit unique surface and antifungal properties for the photoinactivation of B. cinerea. Nanostructured titanates were synthesized by the eco-friendly, practical, microwave-induced, hydrothermal method followed by a highly monodispersive AgNP UV-photodeposition. Protonated nanotubes of ∼11 nm in diameter and four-layers displayed high surface areas, 300 m2/g, with a size functionalization of 5 nm for the AgNPs. UV–vis DRS and XPS allowed the characterization and/or quantification of surface reactive species and cytotoxic silver species such as Ag°, Ag+. The effective biocidal properties of the nanocomposites were confirmed by using the well-known Gram-negative bacteria Escherichia coli, and then proceeding to the effective inactivation of the phytopathogenic fungus under visible light. The photoassisted inactivation mechanism was examined by HAADF-STEM, HRTEM, and FESEM electronic microscopies. A plasmalemma invagination due to oxidative stress caused by reactive oxygen, silver cytotoxicity species, and AgTNT sharp morphology damage expands the conidia to induce the cell death. The impact of the eco-friendly inactivation is significant because of the ease with which it is carried out and the possibility of being performed in situ with plants like tomato and grapes, which are ranked among the most valuable agricultural products worldwide.