Global Hopf bifurcation in the ZIP regulatory system

Regulation of zinc uptake in roots of Arabidopsis thaliana has recently been modeled by a system of ordinary differential equations based on the uptake of zinc, expression of a transporter protein and the interaction between an activator and inhibitor. For certain parameter choices the steady state of this model becomes unstable upon variation in the external zinc concentration. Numerical results show periodic orbits emerging between two critical values of the external zinc concentration. Here we show the existence of a global Hopf bifurcation with a continuous family of stable periodic orbits between two Hopf bifurcation points. The stability of the orbits in a neighborhood of the bifurcation points is analyzed by deriving the normal form, while the stability of the orbits in the global continuation is shown by calculation of the Floquet multipliers. From a biological point of view, stable periodic orbits lead to potentially toxic zinc peaks in plant cells. Buffering is believed to be an efficient way to deal with strong transient variations in zinc supply. We extend the model by a buffer reaction and analyze the stability of the steady state in dependence of the properties of this reaction. We find that a large enough equilibrium constant of the buffering reaction stabilizes the steady state and prevents the development of oscillations. Hence, our results suggest that buffering has a key role in the dynamics of zinc homeostasis in plant cells.Comment: 22 pages, 5 figures, uses svjour3.cl

Comparative venomics and preclinical efficacy evaluation of a monospecific Hemachatus antivenom towards sub-Saharan Africa cobra venoms

11 páginas, 3 figuras, 3 tablasCobras are the most medically important elapid snakes in Africa. The African genera Naja and Hemachatus include snakes with neurotoxic and cytotoxic venoms, with shared biochemical, toxinological and antigenic characteristics. We have studied the antigenic cross-reactivity of four sub-Saharan Africa cobra venoms against an experimental monospecific Hemachatus haemachatus antivenom through comparative proteomics, preclinical assessment of neutralization, and third generation antivenomics. The venoms of H. haemachatus, N. annulifera, N. mossambica and N. nigricollis share an overall qualitative family toxin composition but depart in their proportions of three-finger toxin (3FTxs) classes, phospholipases A2 (PLA2s), snake venom metalloproteinases (SVMPs), and cysteine-rich secretory proteins (CRISPs). A monospecific anti-Hemachatus antivenom produced by Costa Rican Instituto Clodomiro Picado neutralized the lethal activity of the homologous and heterologous neuro/cytotoxic (H. haemachatus) and cyto/cardiotoxic (N. mossambica and N. nigricollis) venoms of the three spitting cobras sampled, while it was ineffective against the lethal and toxic activities of the neurotoxic venom of the non-spitting snouted cobra N. annulifera. The ability of the anti-Hemachatus-ICP antivenom to neutralize toxic (dermonecrotic and anticoagulant) and enzymatic (PLA2) activities of spitting cobra venoms suggested a closer kinship of H. haemachatus and Naja subgenus Afrocobra spitting cobras than to Naja subgenus Uraeus neurotoxic taxa. These results were confirmed by third generation antivenomics. BIOLOGICAL SIGNIFICANCE: African Naja species represent the most widespread medically important elapid snakes across Africa. To gain deeper insight into the spectrum of medically relevant toxins, we compared the proteome of three spitting cobras (Hemachatus haemachatus, Naja mossambica and N. nigricollis) and one non-spitting cobra (N. annulifera). Three finger toxins and phospholipases A2 are the two major protein families among the venoms analyzed. The development of antivenoms of broad species coverage is an urgent need in sub-Saharan Africa. An equine antivenom raised against H. haemachatus venom showed cross-reactivity with the venoms of H. haemachatus, N. mossambica and N. nigricollis, while having poor recognition of the venom of N. annulifera. This immunological information provides clues for the design of optimum venom mixtures for the preparation of broad spectrum antivenoms.This study was partly supported by grant BFU2017-89103-P from the Ministerio de Ciencia e Innovaci ́on, Madrid (Spain), Project 741-B7-108 from the Vicerrectoría de Investigaci ́on of Universidad de Costa Rica, and Beca del Mill ́on, SEP-484-2019, from the Sistema de Estudios de Posgrado, Universidad de Costa Rica. The collaboration of our col- leagues at Instituto Clodomiro Picado and Laboratorio de Ven ́omica Evolutiva y Traslacional, Instituto de Biomedicina de Valencia, CSIC, is gratefully acknowledged. This work was carried out in partial fulfill- ment of the requirements for the M.Sc. degree for A. S ́anchez at the University of Costa RicaPeer reviewe

Lo glocal y el turismo. Nuevos paradigmas de interpretación.

El estudio del turismo se realiza desde múltiples escalas y enfoques, este libro aborda muchos temas que es necesario discutir desde diversas perspectivas; es el caso de la reflexión sobre la propia disciplina y sus conceptos, así como los asuntos específicos referidos al impacto territorial, los tipos de turismo, las cuestiones ambientales, el tema de la pobreza, la competitividad, las políticas públicas, el papel de las universidades, las áreas naturales protegidas, la sustentabilidad, la cultura, el desarrollo, la seguridad, todos temas centrales documentados y expuestos con originalidad y dominio del asunto. Lo multiescalar es básico para la comprensión del sistema turístico, sistema formado de procesos globales, regionales y locales. El eje de discusión del libro es lo glocal, esa interacción entre lo nacional y local con lo global

Geophysical investigations of the vadose zone in the Valley of Hermosillo aquifer, Sonora, Mexico

En el Valle de Hermosillo, Sonora, Mexico, siete sondeos tipo Schlumberger y tres sondeos azimutales fueron realizados con el fin de investigar la zona vadosa del acuífero del Valle de Hermosillo. Este acuífero costero consiste de material aluvial y es considerado como libre en su parte superior. El estudio de los sondeos muestra que los cambios laterales de las resistividades pueden ser interpretados relativos a un 'valor de fondo' de 100 Ωm. Los valores de la resistividad menores de 50 Ωm fueron encontrados cerca de la costa y de los centros urbanos e industriales de Hermosillo y Miguel Alemán. Estos valores relativamente bajos pueden estar reflejando la presencia de agua de mala calidad en los poros por la irrigación con aguas subterráneas afectadas por intrusión salina, con aguas negras no tratadas, y/o con aguas subterráneas contaminadas con aguas negras de procedencia industrial y doméstica. Basado en la Ley de Archie, la porosidad se estimó en un valor aproximado de 25%. Los sondeos azimutales muestran que existe anisotropía de la resistividad en la superficie; sin embargo, esta disminuye con la profundidad, por lo que se propone que se debe al arreglo de los granos del suelo relacionado con la infiltración del agua de irrigación

Photosynthesis can be enhanced by lateral CO 2

This study examines the extent to which lateral gas diffusion can influence intercellular CO(2) concentrations (c(i)) and thus photosynthesis in leaf areas with closed stomata. Leaves were partly greased to close stomata artificially, and effects of laterally diffusing CO(2) into the greased areas were studied by gas-exchange measurement and chlorophyll fluorescence imaging. Effective quantum yields (Delta F/F(m)') across the greased areas were analysed with an image-processing tool and transposed into c(i) profiles, and lateral CO(2) diffusion coefficients (D(C'lat)), directly proportional to lateral conductivities (), were estimated using a one-dimensional (1D) diffusion model. Effective CO(2) diffusion distances in Vicia faba (homobaric), Commelina vulgaris (homobaric) and Phaseolus vulgaris (heterobaric) leaves clearly differed, and were dependent on D(C'lat), light intensity, [CO(2)], and [O(2)]: largest distances were approx. 7.0 mm for homobaric leaves (with high D(C'lat)) and approx. 1.9 mm for heterobaric leaves (low D(C'lat)). Modeled lateral CO(2) fluxes indicate large support of photosynthesis over submillimeter distances for leaves with low D(C'lat), whereas in leaves with large D(C'lat), photosynthesis can be stimulated over distances of several millimeters. For the plant species investigated, the surplus CO(2) assimilation rates of the greased leaf areas (A(gr)) differed clearly, depending on lateral conductivities of the respective leaves

Promoción de la Salud en Talamanca

Informe de proyecto de voluntariado -- Universidad de Costa Rica, Programa de Voluntariado. 2006Plan de acción para la promoción de la salud en la región de Talamanca desde la óptica de la persona profesional en farmacia.Universidad de Costa Rica. Vicerrectoría de Vida Estudiantil. Programa de Voluntariado. Facultad de Farmacia.UCR::Vicerrectoría de Docencia::Salud::Facultad de Farmaci