Las baterías eléctricas: un invento de las células

This paper studies the electrical phenomena in biological processes, specially through a laboratory studio that reveals that epithelial cells can employ modifications of the electric field to produce structural and functional changes in various physiological circumstances.La comprensión de los fenómenos eléctricos y el diseño de máquinas generadoras y utilizadoras de electricidad han ocurrido en forma relativamente reciente, y han permitido el gran desarrollo científico y tecnológico de los últimos doscientos años. Sin embargo, los fenómenos eléctricos ocurren naturalmente en los procesos biológicos. Se acepta que ya las células primitivas poseían membranas a través de las cuales se generaron diferencias de potencial eléctrico, que constituyeron baterías eléctricas primitivas que las células emplearon con fines energéticos. El gradual incremento de complejidad de las células y el desarrollo de organismos pluricelulares que ocurrieron en el curso de la evolución implicaron el empleo de los fenómenos eléctricos celulares con fines fisiológicos adicionales. Así, la aparición de las células excitables permitió la propagación de señales eléctricas entre células distantes, lo que constituyó la base para diversos procesos biológicos, tales como la cognición y la interacción entre organismos. Recientemente se ha reconocido que las células no excitables también emplean los fenómenos eléctricos de las membranas plasmáticas con fines de señalización. Aquí mostramos algunos resultados de nuestro laboratorio que revelan que las células epiteliales pueden emplear modificaciones del campo eléctrico de dichas membranas para producir cambios estructurales y funcionales en diferentes circunstancias fisiológicas

Benthic response to ammonium pulses in a tropical lagoon : implications for coastal environmental processes

In New Caledonia, the benthic communities living in the coral reef lagoon around Noumea city are subjected to regular shifts from oligotrophic conditions typical of lagoon waters to nutrient enrichment due to waste water inputs. The influence of ammonium pulses on microphytobenthos production was experimentally tested under varying light intensities in the vicinity of Noumea. Benthic oxygen, ammonium and silicon fluxes at the sediment-water interface were measured in situ using benthic enclosures. Three ammonium concentrations were tested. Gross primary production was doubled with a 13.8 mu mol 1(-1) ammonium concentration increase. Fitted PI curves showed that maximum production (F-max) was linearly related to ammonium concentration, but not the optimal irradiance (I-k). Silicon fluxes were characterized by dissolution in the absence of light, a process that declined with increasing illumination. These results were attributed to microphytobenthos activity, mainly diatoms that are nutrient-limited and strongly reactive to ammonium inputs. Production may result from a multiplication of cells, but migration up to the water sediment interface may also be involved. Oxygen consumption was also significantly influenced by ammonium concentration as a positive linear relationship with added ammonium concentration was established. Even during short-term experiments, ammonium enrichment stimulated photoautotrophic production, increasing the energy available to heterotrophs. Furthermore, microbenthic activities as well as nitrate production were increased by ammoniaoxidizing bacteria able to grow chemolithotrophically at the expense of oxygen. Therefore, in the study area, pulses of urban waste waters resulted in a decrease of plant-related autotrophy in benthic communities. (c) 2004 Elsevier B.V. All rights reserved

Wasmannia Forel (Hymenoptera: Formicidae: Myrmicinae) in Argentina: systematics and distribution

The ant genus Wasmannia is endemic to the Neotropics, with 10 species occurring within the presumptive native range for the genus from Mexico to Argentina. Only the little fire ant, Wasmannia auropunctata is widely distributed being present from central-eastern Argentina to Bermuda, and has become infamous due to its recent worldwide expansion and status as an invasive pest. The objective of this work was to study the systematics and distribution of Wasmannia in its southern limit of distribution in Argentina. Out of the three species reported so far for Argentina, only W. auropunctata was found to be widely distributed, but abundant only in disturbed habitats mostly in the Northeast. Herein, the distribution of Wasmannia auropunctata is extended and its queen and male castes are redescribed, along with descriptions of gynandromorphs (specimens with left side of the head similar to a male and right side similar to a queen). Wasmannia sulcaticeps and W. williamsoni are much less common and widespread. W. sulcaticepsis mostly found in mountain forests in northwestern Argentina, whereas W. williamsoni is only found in shrublands and grasslands in central eastern Argentina, and most frequently in mountain grasslands. Both species overlap with W. auropunctata, which is more common in the lowlands, between approximately 400 and 1000 m elevation. The queen of W. williamsoni is described and queen and male of W. sulcaticeps are redescribed. A new species, Wasmannia longiseta n. sp. Cuezzo and Calcaterra, recently found in northeastern Argentina is described based on worker morphology. Wasmannia rochai is recorded for the first time in Misiones, extending its distribution range from São Paulo (Brazil) to Misiones in northeastern Argentina. A key to the worker caste is provided. A cladistic analysis based on discrete and continuous morphological characters is presented as a first attempt to clarify the phylogenetic relationships between the known species of Wasmannia.Fil: Cuezzo, Fabiana del Carmen. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales E Instituto Miguel Lillo. Instituto Superior de Entomología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Calcaterra, Luis Alberto. Fundación Para El Estudio de Especies Invasivas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Chifflet, Lucila. Universidad de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Follet, P. A.. Pacific Basin Agricultural Research Center; Estados Unido

El destino de huevos y larvas de tres especies pelágicas caballa, (Scomber scombrus), jurel (Trachurus trachurus) y sardina (Sardina pilchardus) en relación a las corrientes prevalentes en el área del Golfo de Vizcaya. ¿Podrían afectar a la supervivencia larvaria?

The spatial distribution of eggs and larvae of three pelagic species, mackerel, horse mackerel and sardine, in the Bay of Biscay was studied in 1998, 2001 and 2004. The spatial distribution was clearly different between the years studied and corresponds quite precisely to different water circulation regimes. Mackerel and horse mackerel larvae are more affected by the prevailing currents than sardine, as their spawning grounds are located offshore, far from the shelf break where the current velocities are higher. Survival rates for mackerel and horse mackerel were higher in 2001, when the offshore larval transport was stronger. However, for sardine, the mortality rate hardly varied between years. The abundance of 25-day-old larvae, considered as an index of the survival rate, appears to be a good recruitment indicator, at least for 1998, 2001 and 2004. Our results did not support the hypothesis of Bakun (1996), which states that dispersion of early life stages towards open ocean waters should cause high larval mortality. At least under the conditions observed for the years studied, the retention of larvae offshore appears to have a positive effect on larval growth and/or survival.La distribución espacial de los huevos y larvas de tres especies pelágicas, caballa, jurel y sardina en el Golfo de Vizcaya fue estudiada en 1998, 2001 y 2004. Esta distribución espacial fue claramente diferente entre los años estudiados y se ajustan, bastante bien a los diferentes regímenes de circulación. Las larvas de caballa y jurel resultaron más directamente afectadas por estas corrientes prevalentes que las larvas de sardina. Esto se explica porque las sardinas desovan en la plataforma, relativamente alejadas del cantil, donde las velocidades de las corrientes son más altas. Las tasas de supervivencia larvaria de caballa y jurel fueron superiores en 2001, cuando el transporte de larvas offshore era más importante. Para las larvas de sardina, sin embargo, la tasa de mortalidad apenas varió entre años. La abundancia de larvas mayores de 25 días, considerada aquí como un índice de la tasa de supervivencia larvaria, resultó ser un buen indicador del reclutamiento por lo menos para los años estudiados. Nuestros resultados contradicen la teoría de Bakun (1996), que afirma que la dispersión de las etapas de vida temprana hacia las aguas del océano abierto causa una alta mortalidad larvaria. Por lo menos bajo la condición que se observó durante estos años (temperatura y abundancia de alimento), la retención de larvas en mar abierto parece tener un efecto positivo en el crecimiento larvario y/o supervivencia

The epithelial sodium channel and the processes of wound healing

The epithelial sodium channel (ENaC) mediates passive sodium transport across the apical membranes of sodium absorbing epithelia, like the distal nephron, the intestine, and the lung airways. Additionally, the channel has been involved in the transduction of mechanical stimuli, such as hydrostatic pressure, membrane stretch, and shear stress from fluid flow. Thus, in vascular endothelium, it participates in the control of the vascular tone via its activity both as a sodium channel and as a shear stress transducer. Rather recently, ENaC has been shown to participate in the processes of wound healing, a role that may also involve its activities as sodium transporter and as mechanotransducer. Its presence as the sole channel mediating sodium transport in many tissues and the diversity of its functions probably underlie the complexity of its regulation. This brief review describes some aspects of ENaC regulation, comments on evidence about ENaC participation in wound healing, and suggests possible regulatory mechanisms involved in this participation

Indicación de toracotomía

In the polytraumatized it is necessary and essentialconduct continuous reevaluations to achievediagnoses of injuries that may occur at the beginningunnoticed and be a reason for surgical solutions(94, 95, 96).En los politraumatizados es necesario e imprescindiblerealizar reevaluaciones contínuas para logrardiagnósticos de lesiones que al inicio pueden pasardesapercibidos y ser motivo de soluciones quirúrgicas(94, 95, 96)

Gastrectomía total y anastomosis en y por neoplasma del cardias

Presented at session 30th September 1953Presentado en sesión de 30 de setiembre de 195