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La luz en la biología como una herramienta de medición y como un estímulo medioambiental
No full text"Tanto en los organismos como en la biología las interacciones de la luz con la
materia tienen varias consecuencias. Para los organismos, una de las
consecuencias ha sido el desarrollo de proteínas fotorreceptoras, con las cuales
los organismos pueden adaptase mejor a las condiciones impuestas por la
radiación solar. Por otro lado, la biología actual se beneficia de las interacciones
luz-materia por medio de técnicas ópticas como la microscopía, la espectroscopia
y los ensayos de fluorescencia entre muchos otros. En este trabajo se presentan
dos técnicas ópticas para el estudio de procesos biológicos y se describe un
nuevo efecto de la luz azul sobre el fotorreceptor VIVID (VVD). Primero, se
presenta un método para potenciar la microscopía de campo claro por medio del
procesamiento digital de imágenes, el cual permite visualizar objetos de fase con
suficiente contraste tal que, por primera vez, fue posible adquirir la función de
dispersión de punto para objetos de fase (FDPf) y se mostró que es posible aplicar
algoritmos de deconvolución estándar para mejorar la calidad de las imágenes de
células no teñidas. En segundo lugar, se construyó un sistema de pinzas ópticas
para el estudio de moléculas individuales. El correcto funcionamiento de nuestro
sistema de pinzas ópticas fue validado por medio de dos ensayos estándar: se
midieron las propiedades elásticas de una cadena de ADN y se midió la fuerza
máxima ejercida y el tamaño de paso del motor molecular cinesina. En tercer
lugar, se trabajó con la flavoproteína fotorreceptora de luz azul VVD, la cual
pertenece al hongo filamentoso Neurospora crassa. Se mostró que en condiciones
in vitro VVD presenta agregación al ser oxidada por especies reactivas de oxígeno
producidas por la misma proteína. Encontramos que la sensibilidad de VVD a la
luz, el oxígeno y la temperatura regulan la cinética de agregación de la proteína.
Con base en nuestras observaciones dilucidamos la ruta de agregación de VVD y
proponemos que su agregación podría tener efectos en el hongo N. crassa.""For organisms as for biology the light-matter interactions have several
consequences. For organisms, one of these consequences has been the
development of proteins specialized in light detection which provide organisms with
a better fit to sunlight cues. On the other hand, current biology exploits the lightmatter
interactions through optical techniques such as microscopy, spectroscopy,
and fluorescence assays among many others. Herein two optical techniques to
study biological processes and a new effect of blue light over the photoreceptor
protein VIVID (VVD) are presented. First, the power of bright field light microscopy
was enhanced by digital image processing, which allows us to visualize subdiffraction
phase objects with enough contrast to acquire, for the first time, the
phase point-spread function (PSFP) of a bright field light microscope. As a proof of
concept, we used the measured PSFP to apply conventional deconvolution to
bright field images, increasing image contrast and the definition of boundaries in
unstained cellular samples. Second, an optical tweezers apparatus for singlemolecule
studies was built and tested by performing two standard single-molecule
assays: stretching single dsDNA molecules, and measuring the step size and
maximum sustainable load for the molecular motor kinesin. Third, the flavin-binding
blue-light (BL) photoreceptor VIVID from the filamentous fungus Neurospora
crassa was shown to present an in vitro aggregation mechanism triggered by a
self-produced reactive oxygen species (ROS). We found that VIVID (VVD) is
sensitive to light, oxygen and temperature and these factors modulate the
aggregation of the protein. Based on our observations we elucidate an aggregation
pathway for VVD and propose aggregation as a possible mechanism to regulate
diverse processes in N. crassa.
Combined effect of water potential and temperature on seed germination and seedling development of cacti from a mesic Argentine ecosystem
Get PDF"Global climatic change will be associated with an increase of droughts and heat waves, which can affect seed germination and plant population dynamics. Cactus species from mesic ecosystems are likely to be more affected by these events than species from arid ecosystems. The aim of the study was to assess the combined effect of water potentials and temperatures on seed germination and seedling traits in six globose cactus species from Córdoba Mountains: Echinopsis candicans, Gymnocalycium bruchii, G. capillense, G. mostii, G. quehlianum and Parodia mammulosa. A factorial experiment was performed in which four water potential levels (0, ?0.2, ?0.4 and ?0.6 MPa) were combined with two temperature levels (25 and 32 °C). Germination (%) and mean germination time (T50) were recorded and seedling shape (width and length) was measured. In general, a decrease in water potential and an increase in temperature resulted in low germination, with different behaviors among species. At 32 °C and low water potentials, germination was low or null for almost all species. There was not a clear trend in the response of T50 to the treatments. Seedling development was highly and negatively affected by the combination of factors, particularly at low water potentials. The responses of the analyzed cactus species to low water potential were similar to those of cactus species from more arid ecosystems. Our results suggest that the studied species would be severely affected by changes in temperature and precipitation as predicted under a climate change scenario.
A pilot study applying the plant Anchored Hybrid Enrichment method to New World sages (Salvia subgenus Calosphace; Lamiaceae)
Get PDF"We conducted a pilot study using Anchored Hybrid Enrichment to resolve relationships among a mostly Neotropical sage lineage that may have undergone a recent evolutionary radiation. Conventional markers (ITS, trnL-trnF and trnH-psbA) have not been able to resolve the relationships among species nor within portions of the backbone of the lineage. We sampled 12 representative species of subgenus Calosphace and included one species of Salvia’s s.l. closest relative, Lepechinia, as outgroup. Hybrid enrichment and sequencing were successful, yielding 448 alignments of individual loci with an average length of 704 bp. The performance of the phylogenomic data in phylogenetic reconstruction was superior to that of conventional markers, increasing both support and resolution. Because the captured loci vary in the amount of net phylogenetic informativeness at different phylogenetic depths, these data are promising in phylogenetic reconstruction of this group and likely other lineages within Lamiales. However, special attention should be placed on the amount of phylogenetic noise that the data could potentially contain. A prior exploration step using phylogenetic informativeness profiles to detect loci with sites with disproportionately high substitution rates (showing “phantom” spikes) and, if required, the ensuing filtering of the problematic data is recommended. In our dataset, filtering resulted in increased support and resolution for the shallow nodes in maximum likelihood phylogenetic trees resulting from concatenated analyses of all the loci. Additionally, it is expected that an increase in sampling (loci and taxa) will aid in resolving weakly supported, short deep internal branches.
Germination characteristics of Gymnocalycium monvillei (Cactaceae) along its entire altitudinal range
Get PDF"Germination characteristics are important for understanding how species cope with environmental variation. The aims of this work were to analyze the effect of different temperatures (25 and 32 °C), water potentials (0, −0.2, −0.4, and −0.6 MPa), and light conditions (light vs. darkness) on the germination of five populations of the cactus Gymnocalycium monvillei (Lem.) Britton & Rose along its entire altitudinal distribution. The experiments to assess the effects of temperature, water potential, and light conditions were performed in germination chambers, and total germination (%) and mean germination time (T50) were recorded. Germination decreased in provenances from higher to lower altitudes, and the effect was very pronounced at temperatures of 32 °C. For all of the altitudinal provenances, germination decreased with lower water potential, with this effect being more pronounced at 32 °C. On the other hand, provenances at lower altitudes were less affected by lower water potentials than higher provenances. Provenances at all altitudes showed very low germination under dark conditions. T50 did not vary among altitudinal provenances at a temperature of 25 °C, but at 32 °C germination was slower at intermediate altitudes. Our results show that germination characteristics differ considerably among altitudinal provenances and seem to be important in determining the capacity of the species to inhabit such a broad gradient.
Las modificaciones de la cromatina y su rol en la percepción de las señales externas en Trichoderma atroviride
Get PDFTesis (Doctorado en Ciencias en Biología Molecular)"Las enzimas que modifican la cromatina modulan las respuestas a las señales ambientales de los organismos a través de la reprogramación de la transcripción génica. Sin embargo, elementos adicionales en el contexto de la cromatina que integren la vía de la regulación a los estímulos de estrés no se han identificado. En el presente trabajo, evaluamos la función de HDA-2 y SET-5 en la respuesta a la luz azul y al estrés oxidante en T. atroviride. Las mutantes Δhda-2 presentaron un crecimiento lento, ausencia de conidiación y bajos niveles de expresión del gen con-1. En cambio, la cepa Δset-5 mostró una mayor conidiación y la rápida expresión de con-1 y hymA en respuesta a la luz azul. La transcripción de hda-2 inducida por la luz fue dependiente de la proteína BLR-1, mientras que HDA-2 es esencial para la transcripción de los genes responsivos a la luz, que incluyen a blr-1 y -2 (Blue Light Regulator-1 y -2). En la presencia de estrés oxidante, las mutantes Δhda-2 mostraron un fenotipo sensible, mientras que las cepas Δset-5 y Δblr exhibieron un fenotipo opuesto. Estos resultados fueron consistentes con la inducción de los genes relacionados a EORs en la cepas wt, Δset-5 y Δblrs, y su baja expresión en Δhda-2. De manera interesante, los niveles de la acetilación en los promotores de los genes cat-3 y gst-1 depende HDA-2 y de las proteinas BLR. Nuestros resultados sugieren la dependencia mutua de HDA-2 y los reguladores BLR para regular la transcripción génica en respuesta a la luz azul y al estrés oxidante. Por otra parte, La maquinaria de la biogénesis de los sRNAs de T. atroviride se han visto implicados en el desarrollo del hongo. Nuestros resultados indican que los genes dcr y ago, son regulados por la luz azul. Sin embargo, la ausencia de la acetiltransferasa de histonas TGF-1 desregula la expresión de estos genes. Estos datos sugieren que TGF-1 regula positivamente la expresión de los genes dcr y ago debido a que esta proteína regularmente actúa como coactivador de la transcripción.""Fungal blue-light photoreceptors have been proposed as integrators of light and oxidative stress. However, additional elements participating in the integrative pathway remain to be identified. In Trichoderma atroviride, the blue-light Regulator (BLR) proteins BLR-1 and -2 are known to regulate gene transcription, mycelial growth and asexual development upon illumination. Here, we evaluate the role of HDA-2 and SET-5 in the regulation of genes responsive to light and oxidative stress by assessing responses to stimuli in wild-type, Δhda-2 and Δset-5 strains. Δhda-2 strains present reduced growth, misregulation of the con-1 gene and absence of conidia in response to light and mechanical injury. Furthermore, Δset-5 showed more conidiation induced by blue light and early induction of con-1 and hymA genes. We found that the expression of hda-2 is BLR-1 dependent and HDA-2 in turn is essential for the transcription of light-responsive genes that include blr-1 and blr-2. When subject to reactive oxygen species (ROS), Δhda-2 mutants displayed high sensitivity whereas Δset-5 and Δblr strains exhibited the opposite phenotype. Consistently, in the presence of ROS, ROS-related genes show high transcription levels in wild-type, Δset-5 and Δblr strains but misregulation in Δhda-2. Finally, chromatin immunoprecipitations of histone H3 acetylated at Lys9/Lys14 on cat-3 and gst-1 promoters display low accumulation of H3K9K14ac in Δblr and Δhda-2 strains. Our results point to a mutual dependence between HDA-2 and BLR and reveal the role of these proteins in an intricate generegulation landscape in response to blue light and ROS. Moreover, the biogenesis machinery components of small RNAs from T. atroviride regulate fungal development. Here we showed that expression of dcr and ago genes increased after a brief pulse of blue light in T. atroviride wild type, whereas it dropped in a Δtgf-1 background, whose product codes for a histone acetyltransferase. These data suggest that TGF-1 acts as positive regulator of dcr and ago transcription, similarly to TGF-1 orthologs have been described as transcription coactivators.
Índices de calidad del agua subterránea para uso agrícola en el Soconusco, Chiapas, México
Get PDF"In Soconusco, Chiapas, in spite of the high availability of surface water, it is resorting to the use of groundwater. Knowledge about the quality of surface or groundwater used to irrigate crops in that region is low. This paper aims to contribute to the knowledge of the quality of groundwater for agricultural use through the characterization of the spatial variability. Assuming a random spatial distribution of 45 samples which were collected in situ were determined: acidity and alkalinity (pH), electrical conductivity (EC), Total Dissolved Solids (TDS), cations and anions and trace elements; in addition to the agricultural index: Sodium Adsorption Ratio (SAR), Residual Sodium Carbonate (RSC), Soluble Sodium Percentage (SSP), Sodium Percentage (% Na), Kelly Ratio (KR), Magnesium Adsorption Ratio (MAR), Permeability Index (PI), Effective Salinity (ES), Salinity Potential (SP) and Osmotic Potential (OP). In general, SSP, % Na, KR, PI are low, there is only one anomalous point (9) with high values at W of the study area. Similarly, PS, ES, Cl, Na and SAR are low except point 16 and conversely, RSC and pH are high, except at this point located in the center of the study area. The results allow us to infer that the water in that aquifer presents no problems or sodicity toxic ions. In 27 sites sampled values above 250 µmhos/cm were found at 25°C, classified as medium to high risk of salinity, unsuitable for agricultural use. Analysis of the combined effect of the presence of sodium (SAR) and salinity (EC or TDS) shows that 27 of analyzing sites have restricted water medium at very high for use in irrigation.""En el Soconusco, Chiapas, a pesar de la alta disponibilidad de agua superficial, se recurre al uso del agua subterránea. El conocimiento de la calidad del agua superficial o subterránea utilizada para el riego de los cultivos en la región es bajo. Este trabajo contribuye al conocimiento de la calidad del agua subterránea para uso agrícola a través de la caracterización de su variabilidad espacial. Asumiendo una distribución espacial aleatoria, se colectaron 45 muestras, a las que se les determinó: acidez y alcalinidad (pH), conductividad eléctrica (CE), Sólidos Totales Disueltos (TDS), cationes y aniones y oligoelementos; además se determinaron índices agrícolas: Índice de adsorción de sodio (SAR), Carbonato de sodio residual (CSR), Porcentaje de sodio soluble (PSS), Porcentaje de sodio (% Na), Relación de Kelly (RK), Relación de Absorción de Magnesio (RAM), Índice de Permeabilidad (IP), Salinidad Efectiva (SE), Salinidad Potencial (SP) y Potencial Osmótico (OP). En general, el PSS, % Na, RK, IP son bajas, sólo hay un punto anómalo (9) con valores altos en la parte oeste del área de estudio. Del mismo modo, SP, SE, Cl, Na y el RAS son bajos, excepto en el punto 16 y en contraste, CSR y pH son altos, excepto en este punto ubicado en el centro del área de estudio. Los resultados nos permiten inferir que el agua en ese acuífero no presenta problemas de sodicidad y de tóxicos. En 27 sitios se encontraron valores superiores a 250 µm/cm a 25 ° C, clasificados como de riesgo medio a alto de salinidad, es decir inadecuados para uso agrícola. El análisis del efecto combinado de la presencia de sodio (RAS) y salinidad (CE o SDT) muestra que 27 de los sitios analizados presentan restricciones de medias a muy altas para su uso en riego.
Síntesis de arseniatos de calcio (Guerinita, haidingerita y farmacolita) morfológicamente similares a los encontrados en suelos contaminados
Get PDF"En el acuífero somero de Matehuala y Cerrito Blanco, en el estado de San Luis Potosí, México, se han reportado concentraciones de hasta 158 mg/L de arsénico cuya movilidad ha podido ser representada por la disolución de Ca5H2(AsO4)4·n H2O, según modelaciones hidrogeoquímicas. Con la finalidad de probar la posible precipitación de este arseniato de calcio, en este estudio se llevaron a cabo experimentos de laboratorio de precipitación de arseniatos de calcio a pH y relación molar Ca/As similares a las encontradas en el acuífero somero de Matehuala y Cerrito Blanco. Los experimentos de precipitación de arseniatos de calcio se llevaron a cabo en dos síntesis. Para la síntesis 1, se mezclaron soluciones 85.9 mM de Na2HAsO4·7H2O con suspensiones 0.93 % (m/v) de Ca(OH)2. Para la síntesis 2 se mezclaron soluciones 114.4 mM de Na2HAsO4·7H2O con suspensiones 0.97 % (m/v) de Ca(OH)2. En total, se prepararon 6 reactores que se almacenaron a temperatura ambiente por 500 h. La temperatura, las concentraciones de arsénico, calcio y pH fueron medidos a lo largo del tiempo, mientras que los precipitados obtenidos fueron identificados por análisis de difracción de rayos X (DRX) y observados por microscopía electrónica de barrido (MEB). Los resultados de DRX muestran la precipitación de un arseniato de calcio [guerinita, Ca5H2(AsO4)4·9H2O] con una estequiometría similar a la obtenida por modelación hidrogeoquímica [Ca5H2(AsO4)4·nH2O]. Adicionalmente, se obtuvieron otros dos arseniatos de calcio llamados haidingerita (CaHAsO4·H2O) y farmacolita (CaHAsO4·2H2O). La observación de los precipitados obtenidos por MEB permitió la identificación de hábitos laminares, laminares aplanados y aciculares que se asociaron a haidingerita, guerinita y farmacolita, respectivamente. La morfología de los arseniatos de calcio precipitados en este estudio coincide con la observada en arseniatos de calcio encontrados en suelos contaminados en Matehuala. Los resultados de este estudio aportan al reconocimiento morfológico de arseniatos de calcio presentes en el ambiente.""Total dissolved arsenic concentrations up to 158 mg/L have been reported in the Matehuala and Cerrito Blanco aquifer in San Luis Potosi, Mexico from the dissolution of Ca5H2(AsO4)4·n H2O, as determined by hydrogeochemical modelling. In order to test the precipitation of this calcium arsenate, in this study, calcium arsenates were synthesized at similar pH and Ca/As aquifer conditions. Precipitation experiments were carried out in two synthesis. For synthesis 1, calcium arsenates were prepared by mixing 85.9 mM Na2HAsO4·7H2O solutions with slurries of 0.93 % (w/v) Ca(OH)2. For synthesis 2, calcium arsenates were prepared by mixing 114.4 mM Na2HAsO4·7H2O solutions with slurries of 0.97 % (w/v) Ca(OH)2. A total of six reactors were prepared, they were stored at room temperature for 500 h. Temperature, arsenic, calcium concentrations and pH were measured over time while the precipitates were identified by X-ray diffraction analyses and observed by scanning electron microscopy. According to X-ray diffraction results and the experimental conditions, a calcium arsenate, namely guerinite [Ca5H2(AsO4)4·9H2O] with the predicted stoichiometry, precipitated. Additionally, other two calcium arsenate mineral phases, namely haidingerite (CaHAsO4·H2O) and pharmacolite (CaHAsO4·2H2O) precipitated. The observation of the calcium arsenates precipitates allowed the identification of laminar, platty, and acicular habits associated to haidingerite, guerinite and pharmacolite, respectively. The morphology of the calcium arsenates precipitates in this study agrees with the morphology observed in calcium arsenates found in contaminated soils in Matehuala. Results from this study contribute to the morphological identification of calcium arsenates in the environment.
Understanding the ion-induced elongation of silver nanoparticles embedded in silica
Get PDF"In this work we have studied the elongation of silver nanoparticles irradiated with 40 MeV Bromine ions by means of in situ optical measurements, transmission electron microscopy and molecular dynamics simulations. The localized surface plasmon resonance of silver nanoparticles has a strong dependence on the particle shape and size, which allowed us to obtain the geometrical parameters with remarkable accuracy by means of a fit of the optical spectra. Optical results have been compared with transmission electron microscopy images and molecular dynamics simulations and the agreement is excellent in both cases. An important advantage of in situ measurements is that they yield an extremely detailed information of the full elongation kinetics. Final nanoparticle elongation depends on a complex competition between single-ion deformation, Ostwald ripening and dissolution. Building and validating theoretical models with the data reported in this work should be easier than with the information previously available, due to the unprecedented level of kinetic details obtained from the in situ measurements.
Generación de polvos de madera en talleres de la escuela de laudería del Instituto Nacional de Bellas Artes y Literatura, México
Get PDF"El objetivo del presente trabajo fue identificar el riesgo por la exposición a polvos de madera en los talleres de construcción de instrumentos musicales de cuerda frotada, de la Escuela de Laudería del Instituto Nacional de Bellas Artes y Literatura, México, pues dicha exposición está asociada con enfermedades alérgicas y no alérgicas como dermatitis, conjuntivitis-rinitis, asma, alveolitis alérgica extrínseca y cáncer, entre otras. Se analizó la cantidad de partículas de madera iguales o menores a 2.5 μm presentes en el aire del interior de tres talleres de construcción de instrumentos. Asimismo, se realizaron dos análisis gravimétricos: uno por cuatro días en ciclos de 24 h en tres talleres y otro durante 10 días en ciclos de 4 h en tres talleres. Los resultados gravimétricos evidencian que la concentración de polvos de madera en el aire del interior de los talleres estudiados supera las normas nacionales, así como algunas internacionales. Lo anterior se manifiesta con malestares y síntomas expresados por los usuarios de los talleres de construcción de instrumentos musicales. Adicionalmente, se realizó una encuesta sobre la percepción pública de la contaminación del aire del interior con énfasis en los efectos de los polvos de madera sobre la salud, que fue aplicada a los alumnos y profesores de la institución.""The aim of this work was to identify the risk of exposure to wood dust in workshops of musical instruments, at Instituto Nacional de Bellas Artes y Literatura's Violin Making School, Mexico, since such exposure is associated to allergic and non-allergic diseases, such as dermatitis, conjunctivitis-rhinitis, asthma, extrinsic allergic alveolitis and cancer, among others. The amount of particles equal to or less than 2.5 μm present in the air of three workshops of musical instruments was analyzed. Two gravimetric analyses were made: one for four days in twenty-four-hour cycles in three workshops, and the other for ten days in four-hour cycles in three workshops. Additionally, a survey on public perception of indoor air pollution with an emphasis on the effects of wood dust on health was performed. This survey was applied to students and professors of the institution. The gravimetric results showed that the concentration of wood dust on indoor air of the studied workshops exceeds national and several international standards, evidenced through malaise and symptoms expressed by users of the workshops of musical instruments.
Modificación del criterio de Mikhailov para sistemas conmensurados de orden fraccionario
Get PDF"En este trabajo se presenta la modificación del criterio de estabilidad de Mikhailov para sistemas lineales fraccionarios de orden conmensurado. Dicha modificación consiste en determinar la medida apropiada del cambio total del argumento misma que depende del máximo orden fraccionario del sistema alpha_n=nalpha y no solo del entero n como se establece en la literatura. Para ilustrar la validez del resultado se presentan algunos ejemplos.