Crecimiento de plantas jóvenes de Cordia dodecandra (Boraginaceae) en tres etapas sucesionales de vegetación en Calotmul, Yucatán

ResumenLas poblaciones naturales de Cordia dodencandra, siricote, en Yucatán se encuentran amenazadas por la sobreexplotación de su madera, apreciada por su dureza y veteado. Se requiere diseñar programas de reforestación y enriquecimiento de la vegetación en áreas perturbadas que consideren el crecimiento de esta especie en respuesta a los factores ambientales de selvas en diferentes grados de recuperación. El objetivo de este trabajo fue caracterizar las condiciones ambientales de temperatura, humedad y radiación fotosintéticamente activa en diferentes etapas sucesionales de vegetación: avanzada, media, temprana y sin vegetación, para determinar su influencia sobre el área foliar específica y el crecimiento de plantas jóvenes de siricote. En cada etapa sucesional se estableció una parcela con 60 plántulas de siricote, a distancias de 4m entre línea de siembra y 2.7m entre plantas. Después de 19 meses, los sitios en sucesión temprana son los más adecuados para el crecimiento de siricote. Existe una relación inversamente proporcional entre la incidencia de luz y el área foliar específica y una relación directamente proporcional entre humedad relativa y el área foliar específica. Se concluye que el siricote puede utilizarse en programas de enriquecimiento de la vegetación avanzada y para reforestar áreas en sucesión temprana.AbstractNatural populations of Cordia dodencandra (siricote) in Yucatán are threatened due to the overexploitation of their wood, valued by its hardness and grain. Reforestation, enrichment of vegetation in disturbed areas and commercial plantation programs of this species are needed. These programs must take into account the relation between plant growth and its response to the environmental factors occurring in forests in different stages of recovery. The aim of this study was to characterize the environmental conditions; temperature, humidity and photosynthetically active radiation; under different successional stages; advanced, intermediate, early and without vegetation; in order to determine the influence of specific leaf area and growth of siricote seedlings. On a patch of each successional stage, sixty seedlings of siricote were established in a plot. Distribution of seedlings was 4m between rows and 2.7 between plants. After 19 months, the early successional plot was the better site for siricote growth. We observed an inverse relationship between photosynthetically active radiation and specific leaf area and, a direct relationship between relative humidity and specific leaf area. According to our results siricote could be used in programs of enrichment of vegetation in advanced successional stages as well as for reforesting early successional areas

Distinctive PSA-NCAM and NCAM hallmarks in glutamate-induced dendritic atrophy and synaptic disassembly

Dendritic and synapse remodeling are forms of structural plasticity that play a critical role in normal hippocampal function. Neural cell adhesion molecule (NCAM) and its polysialylated form (PSA-NCAM) participate in neurite outgrowth and synapse formation and plasticity. However, it remains unclear whether they contribute to dendritic retraction and synaptic disassembly. Cultured hippocampal neurons exposed to glutamate (5 µM) showed a reduced MAP-2 (+) area in the absence of neuronal death 24 h after the insult. Concomitantly, synapse loss, revealed by decreased synaptophysin and post-synaptic density-95 cluster number and area, together with changes in NCAM and PSA-NCAM levels were found. Dendritic atrophy and PSA-NCAM reduction proved NMDA-receptor dependent. Live-imaging experiments evidenced dendritic atrophy 4 h after the insult; this effect was preceded by smaller NCAM clusters (1 h) and decreased surface and total PSA-NCAM levels (3 h). Simultaneously, total NCAM cluster number and area remained unchanged. The subsequent synapse disassembly (6 h) was accompanied by reductions in total NCAM cluster number and area. A PSA mimetic peptide prevented both the dendritic atrophy and the subsequent synaptic changes (6 h) but had no effect on the earliest synaptic remodeling (3 h). Thus, NCAM-synaptic reorganization and PSA-NCAM level decrease precede glutamate-induced dendritic atrophy, whereas the NCAM level reduction is a delayed event related to synapse loss. Consequently, distinctive stages in PSA-NCAM/NCAM balance seem to accompany glutamate-induced dendritic atrophy and synapse loss.Fil: Podestá, María Fernabda. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Farmacológicas. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Investigaciones Farmacológicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Biología Celular y Neurociencia "Prof. Eduardo de Robertis". Universidad de Buenos Aires. Facultad de Medicina. Instituto de Biología Celular y Neurociencia ; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Farmacología. Cátedra de Farmacología; ArgentinaFil: Yam, Patricia. McGill University. Montreal Neurological Institute and Hospital; CanadáFil: Codagnone, Martín Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Farmacológicas. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Investigaciones Farmacológicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Biología Celular y Neurociencia "Prof. Eduardo de Robertis". Universidad de Buenos Aires. Facultad de Medicina. Instituto de Biología Celular y Neurociencia ; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Farmacología. Cátedra de Farmacología; ArgentinaFil: Uccelli, Nonthué Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Farmacológicas. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Investigaciones Farmacológicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Biología Celular y Neurociencia "Prof. Eduardo de Robertis". Universidad de Buenos Aires. Facultad de Medicina. Instituto de Biología Celular y Neurociencia ; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Farmacología. Cátedra de Farmacología; ArgentinaFil: Colman, David. McGill University. Montreal Neurological Institute and Hospital; CanadáFil: Reines, Analia Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Farmacológicas. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Investigaciones Farmacológicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Biología Celular y Neurociencia "Prof. Eduardo de Robertis". Universidad de Buenos Aires. Facultad de Medicina. Instituto de Biología Celular y Neurociencia ; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Farmacología. Cátedra de Farmacología; Argentin

Cellular response to micropatterned growth promoting and inhibitory substrates

BACKGROUND: Normal development and the response to injury both require cell growth, migration and morphological remodeling, guided by a complex local landscape of permissive and inhibitory cues. A standard approach for studying by such cues is to culture cells on uniform substrates containing known concentrations of these molecules, however this method fails to represent the molecular complexity of the natural growth environment. RESULTS: To mimic the local complexity of environmental conditions in vitro, we used a contact micropatterning technique to examine cell growth and differentiation on patterned substrates printed with the commonly studied growth permissive and inhibitory substrates, poly-L-lysine (PLL) and myelin, respectively. We show that micropatterning of PLL can be used to direct adherence and axonal outgrowth of hippocampal and cortical neurons as well as other cells with diverse morphologies like Oli-neu oligodendrocyte progenitor cell lines and fibroblast-like COS7 cells in culture. Surprisingly, COS7 cells exhibited a preference for low concentration (1 pg/mL) PLL zones over adjacent zones printed with high concentrations (1 mg/mL). We demonstrate that micropatterning is also useful for studying factors that inhibit growth as it can direct cells to grow along straight lines that are easy to quantify. Furthermore, we provide the first demonstration of microcontact printing of myelin-associated proteins and show that they impair process outgrowth from Oli-neu oligodendrocyte precursor cells. CONCLUSION: We conclude that microcontact printing is an efficient and reproducible method for patterning proteins and brain-derived myelin on glass surfaces in order to study the effects of the microenvironment on cell growth and morphogenesis

Swift J2058.4+0516: Discovery of a Possible Second Relativistic Tidal Disruption Flare?

We report the discovery by the Swift hard X-ray monitor of the transient source Swift J2058.4+0516 (Sw J2058+05). Our multi-wavelength follow-up campaign uncovered a long-lived (duration >~ months), luminous X-ray (L_X,iso ~ 3 x 10^47 erg s^-1) and radio (nu L_nu,iso ~ 10^42 erg s^-1) counterpart. The associated optical emission, however, from which we measure a redshift of 1.1853, is relatively faint, and this is not due to a large amount of dust extinction in the host galaxy. Based on numerous similarities with the recently discovered GRB 110328A / Swift J164449.3+573451 (Sw J1644+57), we suggest that Sw J2058+05 may be the second member of a new class of relativistic outbursts resulting from the tidal disruption of a star by a supermassive black hole. If so, the relative rarity of these sources (compared with the expected rate of tidal disruptions) implies that either these outflows are extremely narrowly collimated (theta < 1 degree), or only a small fraction of tidal disruptions generate relativistic ejecta. Analogous to the case of long-duration gamma-ray bursts and core-collapse supernovae, we speculate that rapid spin of the black hole may be a necessary condition to generate the relativistic component. Alternatively, if powered by gas accretion (i.e., an active galactic nucleus [AGN]), Sw J2058+05 would seem to represent a new mode of variability in these sources, as the observed properties appear largely inconsistent with known classes of AGNs capable of generating relativistic jets (blazars, narrow-line Seyfert 1 galaxies).Comment: Minor typos correcte

14-3-3 Proteins Regulate a Cell-Intrinsic Switch from Sonic Hedgehog-Mediated Commissural Axon Attraction to Repulsion after Midline Crossing

SummaryAxons must switch responsiveness to guidance cues during development for correct pathfinding. Sonic Hedgehog (Shh) attracts spinal cord commissural axons ventrally toward the floorplate. We show that after crossing the floorplate, commissural axons switch their response to Shh from attraction to repulsion, so that they are repelled anteriorly by a posterior-high/anterior-low Shh gradient along the longitudinal axis. This switch is recapitulated in vitro with dissociated commissural neurons as they age, indicating that the switch is intrinsic and time dependent. 14-3-3 protein inhibition converted Shh-mediated repulsion of aged dissociated neurons to attraction and prevented the correct anterior turn of postcrossing commissural axons in vivo, an effect mediated through PKA. Conversely, overexpression of 14-3-3 proteins was sufficient to drive the switch from Shh-mediated attraction to repulsion both in vitro and in vivo. Therefore, we identify a 14-3-3 protein-dependent mechanism for a cell-intrinsic temporal switch in the polarity of axon turning responses

Actin–myosin network reorganization breaks symmetry at the cell rear to spontaneously initiate polarized cell motility

We have analyzed the spontaneous symmetry breaking and initiation of actin-based motility in keratocytes (fish epithelial cells). In stationary keratocytes, the actin network flow was inwards and radially symmetric. Immediately before motility initiation, the actin network flow increased at the prospective cell rear and reoriented in the perinuclear region, aligning with the prospective axis of movement. Changes in actin network flow at the cell front were detectable only after cell polarization. Inhibition of myosin II or Rho kinase disrupted actin network organization and flow in the perinuclear region and decreased the motility initiation frequency, whereas increasing myosin II activity with calyculin A increased the motility initiation frequency. Local stimulation of myosin activity in stationary cells by the local application of calyculin A induced directed motility initiation away from the site of stimulation. Together, these results indicate that large-scale actin–myosin network reorganization and contractility at the cell rear initiate spontaneous symmetry breaking and polarized motility of keratocytes

Actitudes y experiencias en el consumo de alimentación saludable en universitarios con antecedentes familiares de diabetes

Introducción. La alimentación de los universitarios se caracteriza por un alto consumo de alimentos ricos en energía, grasas y azúcares. El objetivo del estudio fue describir las actitudes y experiencias de un grupo de universitarios con antecedentes familiares de diabetes tipo 2 (DT2) en el consumo de una alimentación saludable de Tizimín México. Método. Estudio cualitativo, el fenómeno se debeló a partir de dos grupos focales en línea, muestreo por criterio/opinático. Participaron 16 estudiantes entre 18-21 años, siete mujeres y nueve hombres, con antecedentes fami-liares de DT2, análisis con base a la propuesta de Taylor-Bogden inscrito en la teoría fundamental. Estudio apegado a las normas éticas en investigación sin riesgo. Resultados. Se identificaron: a) actitudes: expectativas, principios e influencias sobre una alimentación saludable y b) experiencias: obstáculos y reacción emocional hacia la alimenta-ción. Conclusiones. Las actitudes sobre la alimentación saludable en la población estudiada son a) expectativas en el trabajo, actividades sociales, obligaciones familiares, b) principios de responsabilidad, flexibilidad y plantearse objetivos., y c) influencias personales y creencias; y experiencias a) obstáculos en alimentación, ejercicio y econó-micas, b) emociones sobre pensamientos pasados y presentes, y estrés, c) cambios agradables y desagradables en el cuidado de la saludIntroduction. The diet of university students is characterized by a high consumption of foods rich in energy, fats and sugars. The purpose of the study was to describe the attitudes and experiences of a group of university students in the consumption of a healthy diet. Method. Qualitative study, the phenomenon was discussed from two online focus groups, analysis based on the Taylor-Bogden proposal inscribed in the fundamental theory. Study adhering to ethical standards in risk-free research. Results. Sixteen students aged 18-21, female (7) and male (9) participated, all with a family history of type 2 diabetes. The following were identified: a) attitudes: expectations, principles and influences on healthy eating and b) experiences: obstacles and emotional reaction to food. Conclusions. Attitudes about healthy eating are a) expectations at work, social activities, family obligations, b) principles of responsibility, flexibility and goal setting, and c) personal influences and beliefs; and experiences a) obstacles in diet, exercise and finances, b) emotions about past and present thoughts, and stress, c) pleasant and unpleasant changes in health car