40 research outputs found

    Shoot tip necrosis of in vitro plant cultures: a reappraisal of possible causes and solutions

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    Shoot tip necrosis is a physiological condition and disorder that can arise in plantlets or shoots in vitro that results in death of the shoot tip. This condition, which can spread basipetally and affect the emergence of axillary shoots from buds lower down the stem, is due to the cessation of apical dominance. STN can occur at both shoot multiplication and rooting stages. One of the most common factors that cause STN is nutrient deficiency or imbalance. Moreover, the presence or absence of plant growth regulators (auxins or cytokinins) at specific developmental stages may impact STN. The cytokinin to auxin ratio within an in vitro plant can be modified by varying the concentration of cytokinins used in the culture medium. The supply of nutrients to in vitro shoots or plantlets might also affect their hormonal balance, thus modifying the occurrence of STN. High relative humidity within culture vessels and hyperhydricity are associated with STN. An adequate supply of calcium as the divalent cation (Ca2+) can hinder STN by inhibiting the accumulation of phenolic compounds and thus programmed cell death. Moreover, the level of Ca2+ affects auxin transport and ethylene production, and higher ethylene production, which can occur as a result of high relative humidity in or poor ventilation of the in vitro culture vessel, induces STN. High relative humidity can decrease the mobility of Ca2+ within a plant, resulting in Ca2+ deficiency and STN. STN of in vitro shoots or plantlets can be halted or reversed by altering the basal medium, mainly the concentration of Ca2+, adjusting the levels of auxins or cytokinins, or modifying culture conditions. This review examines the literature related to STN, seeks to discover the associated factors and relations between them, proposes practical solutions, and attempts to better understand the mechanism(s) underlying this condition in vitroThis research was financed by the Higher Education Institutional Excellence Programme (NKFIH-1150-6/2019) of the Ministry of Innovation and Technology in Hungary, within the framework of the Biotechnology thematic programme of the University of Debrecen. The study and submission for publication were approved by the University of Debrecen (BPTR/DEENK/0008/2019). Esmaeil Nezami-Alanagh thanks the Biotechnology Department at Imam Khomeini International University (IKIU) for their assistance in carrying out a part of the experiment work and also to Science and Technology Park of East-Azarbaijan, Islamic Republic of Iran, for financial support. The Spanish work on STN modeling was funded by Xunta de Galicia, Spain (CITACA Strategic Partnership, Reference: ED431E 2018/07 and REDES, Reference: ED431D-2017/19)S

    26 Oraal vast

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    Análisis de las oportunidades políticas en el Ecuador, desde el año 1997 hasta el 2007

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    Este trabajo tiene como objeto aportar con una interpretación de los sucesos políticos ocurridos en los derrocamientos de los presidentes Abdalá Bucaram, Jamil Mahuad y Lucio Gutiérrez, en tanto tiene que ver solamente con las oportunidades políticas, generadas dentro de esos escenarios, para los movimientos sociales en el Ecuador.En los tres casos se observa con claridad la caracterización de lo que es y como surgen las oportunidades, cuyo concepto: Lo define Tarrow como el grado de probabilidad que los grupos tienen de acceder al poder e influir sobre el sistema político. En donde encontramos cuatro características, una de las cuales es la contradicción existente entre el discurso político y la realidad de la gestión de los grupos que tienen el poder, como decíamos en los tres casos se han referido a combatir la pobreza, luchar contra la corrupción, dar solución a los problemas de vivienda, mayor atención a la educación; pero en la práctica casi nada de estas ofertas se han concretado. La segunda característica, penurias súbitas. La tercera característica, es la ilegitimidad del régimen, en los tres casos perdieron el respaldo popular por haber demostrado un compromiso con las clases dominantes y con los organismos de crédito internacionales. La cuarta característica, la presencia de un marco innovador, hemos analizado como los grupos sociales organizados y la población en general han sido capaces de diseñar estrategias distintas, bastante creativas para expresar su descontento y presionar a los gobernantes para que presenten su renuncia y lo lograron en los tres casosLicenciado en Desarrollo SocialCuenc

    Controlled release of rAAV-2 viral vectors from alginate-poloxamer complex systems

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    Antibiotic-free diet supplemented with live yeasts decreases inflammatory markers in the ileum of weaned piglets

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    Emerging bacterial resistance to antibiotics increases the need for effective alternatives to control intestinal inflammation and thus gut disorders in piglets. This study evaluated the effects of including Saccharomyces cerevisiae (strain 1026) and Saccharomyces boulardii (CNCM I-1079) as antibiotic alternatives in the starter diets of pigs on the concentrations of ileal inflammatory markers (nuclear factor-κB (NF-κB)), interleukin-6 (IL-6), tumour necrosis factor alpha (TNF-α), and interleukin-12 subunit p40 (IL-12p40), and villus height. Forty piglets were assigned to four experimental diets, namely basal diet (C−), basal diet with antibiotics (C+), basal diet with S. cerevisiae (Sc), and basal diet with S. boulardii (Sb). At 7 and 14 days post weaning, five piglets per diet group were euthanized to quantify the inflammatory markers and to measure villus height. The C− group exhibited the highest concentration of inflammatory markers and the most atrophied villi. The Sc group had intermediate values for both variables. The C+ group had the lowest values for inflammatory markers and the highest villus height was similar to that of the Sb group, which showed low concentrations of inflammatory markers, although not so low as those of the C+ group. Both yeasts could be used as antibiotic alternatives to reduce the use of antibiotics in pig starter diets. However, S. boulardii CNCM I-1079 supplementation controls inflammation and preserves intestinal mucosa more effectively than S. cerevisiae strain 1026.Keywords: cytokines, pigs, probiotic, Saccharomyces, weanin
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