Browsing by Author "Ayala, M."

Now showing 1 - 4 of 4
  • No Thumbnail Available
    Item
    Calcium absorption by fruit and leaves of sweet cherry trees (Prunus avium L.) by isotope labeling
    (2024) Matteo, M.; Zoffoli, J. P.; van der Heijden, G.; Ayala, M.
    In sweet cherry, foliar Calcium-based products are used to mitigate rain-cracking in fruit and to improve its firmness during storage. Information on foliar Calcium (Ca) absorption efficiency by fruit and leaves in the field is scarce. In part, this is due to the limitations of the traditional analytical techniques for assessing Ca levels in these organs. Here, we hypothesize that leaves and fruit differ in their abilities to uptake surface applications of Ca and, moreover, that their abilities are influenced by phenology. To test this hypothesis, foliar Ca-44 (0.05% (CaCl2)-Ca-44) was used to enrich sweet cherry fruit and leaves of the combination 'Lapins'/'Colt' during the 2019-2020 growing season in the Central Valley of Chile (34 degrees 0' S, 71 degrees 41' W). Six treatments were applied, represented by different timings (days after full bloom, DAFB) of isotopic labeling of either fruit or leaves. Labeling was applied at Stage I, SII and SIII of fruit development. Fruit or leaves were 'painted' with (CaCl2)-Ca-44 (0.05%, 97 atom%) using a brush. Each labeling date considered a different group of similar fruiting spurs on the two-year-old wood of individual vertical branches. Additional samples were collected to measure natural abundance of Ca-44. Labeled fruit were removed 48 h after aerial Ca-44 enrichment and at harvest (87 DAFB). Uptake of Ca-44 by fruit and leaves was observed throughout the period of fruit development. Fruiting spur leaves (FSL) and fruit absorbed (CaCl2)-Ca-44 and were highly enriched 48 h after labeling. The earlier the labeling date, the higher the Ca-44 tracer recovery detected in both organs. However, FSL showed higher delta Ca-44 parts per thousand, Ca-44 concentrations and Ca-44 contents than fruit during the whole period of fruit development. After 48 h, the aerial uptake at SI (expressed as delta Ca-44 parts per thousand) was 3.4 times higher in immature FSL and 5.7 times higher in immature fruit than SIII of fruit development, which indicates that Ca sprays should start soon after fruit set. We conclude that in sweet cherry, foliar Ca is absorbed by fruit and spur leaves, but the absorption is more efficient in the early stages of fruit development and for young leaves.
  • Thumbnail Image
    Item
    Enhancement of Peroxidase Stability Against Oxidative Self-Inactivation by Co-immobilization with a Redox-Active Protein in Mesoporous Silicon and Silica Microparticles
    (2016) Sahare, P.; Osorio Román, Igor; Ayala, M.; Vazquez-Duhalt, R.; Pal, U.; Loni, A.; Canham, L. T.; Agarwal, V.
    Abstract The study of the stability enhancement of a peroxidase immobilized onto mesoporous silicon/silica microparticles is presented. Peroxidases tend to get inactivated in the presence of hydrogen peroxide, their essential co-substrate, following an auto-inactivation mechanism. In order to minimize this inactivation, a second protein was co-immobilized to act as an electron acceptor and thus increase the stability against self-oxidation of peroxidase. Two heme proteins were immobilized into the microparticles: a fungal commercial peroxidase and cytochrome c from equine heart. Two types of biocatalysts were prepared: one with only covalently immobilized peroxidase (one-protein system) and another based on covalent co-immobilization of peroxidase and cytochrome c (two-protein system), both immobilized by using carbodiimide chemistry. The amount of immobilized protein was estimated spectrophotometrically, and the characterization of the biocatalyst support matrix was performed using Brunauer–Emmett–Teller (BET), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX), and Fourier transform infrared (FTIR) analyses. Stability studies show that co-immobilization with the two-protein system enhances the oxidative stability of peroxidase almost four times with respect to the one-protein system. Thermal stability analysis shows that the immobilization of peroxidase in derivatized porous silicon microparticles does not protect the protein from thermal denaturation, whereas biogenic silica microparticles confer significant thermal stabilization.Abstract The study of the stability enhancement of a peroxidase immobilized onto mesoporous silicon/silica microparticles is presented. Peroxidases tend to get inactivated in the presence of hydrogen peroxide, their essential co-substrate, following an auto-inactivation mechanism. In order to minimize this inactivation, a second protein was co-immobilized to act as an electron acceptor and thus increase the stability against self-oxidation of peroxidase. Two heme proteins were immobilized into the microparticles: a fungal commercial peroxidase and cytochrome c from equine heart. Two types of biocatalysts were prepared: one with only covalently immobilized peroxidase (one-protein system) and another based on covalent co-immobilization of peroxidase and cytochrome c (two-protein system), both immobilized by using carbodiimide chemistry. The amount of immobilized protein was estimated spectrophotometrically, and the characterization of the biocatalyst support matrix was performed using Brunauer–Emmett–Teller (BET), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX), and Fourier transform infrared (FTIR) analyses. Stability studies show that co-immobilization with the two-protein system enhances the oxidative stability of peroxidase almost four times with respect to the one-protein system. Thermal stability analysis shows that the immobilization of peroxidase in derivatized porous silicon microparticles does not protect the protein from thermal denaturation, whereas biogenic silica microparticles confer significant thermal stabilization.
  • Thumbnail Image
    Item
  • Thumbnail Image
    Item
    Guías Latinoamericanas de Hipertensión Arterial
    (2010) Sánchez, R. A.; Ayala, M.; Baglivo, H.; Velázquez, C.; Burlando, G.; Kohlmann, O.; Jiménez, J.; López J, P.; Brandao, A.; Valdés Stromilli, Gloria; Alcocer, L.; Bendersky, M.; Ramírez, A. J.; Zanchetti, A.
    La hipertensión es un factor de riesgo cardiovascular muy prevalente en el mundo, y especialmente abrumador en los países de bajos y medianos ingresos. Informes recientes de la OMS y del Banco Mundial destacan la importancia de las enfermedades crónicas tales como la hipertensión, como obstáculo al logro de un buen estado de salud. Se debe agregar que, para la mayoría de los países de bajos y medianos ingresos, estrategias deficientes de la atención primaria de la salud son obstáculos mayores par el logro del control de la presión arterial. Es más, la epidemiología de la hipertensión y enfermedades relacionadas, los recursos y las prioridades de salud, el estado socioeconómico de la población, varían considerablemente en diferentes países y en diferentes regiones de países individuales. Teniendo en cuenta las bajas tasas de control de la presión arterial logrados en Latinoamérica y los beneficios que se puede esperar de un mejor control, se decidió invitar a especialistas de diferentes países latinoamericanos a analizar la situación de la región y redactar un documento de consenso sobre la detección, evaluación y tratamiento de la hipertensión que podría ser adecuado del punto de vista costo-utilidad. Las recomendaciones incluidas aquí son el resultado de documentos preparatorios escritos por expertos invitados y el muy activo debate posterior en diferentes paneles de discusión, realizados durante dos días en Asunción, Paraguay en Mayo del año 2008. Por último, para mejorar la práctica clínica, la publicación de estas pautas debe ser seguida por la implementación de intervenciones efectivas capaces de vencer las barreras (cognitivas, de comportamiento y afectivas) que previenen los cambios de actitud tanto en médicos como en pacientes.