Exosomes: mediators of communication in eukaryotes

In addition to the established mechanisms of intercellular signaling, a new way of communication has gained much attention in the last decade: communication mediated by exosomes. Exosomes are nanovesicles (with a diameter of 40-120 nm) secreted into the extracellular space by the multivesicular endosome after its outer membrane fuses with the plasma membrane. Once released, exosomes modulate the response of the recipient cells that recognize them. This indicates that exosomes operate in a specific manner and participate in the regulation of the target cell. Remarkably, exosomes occur from unicellular organisms to mammals, suggesting an evolutionarily conserved mechanism of communication. In this review we describe the cascade of exosome formation, intracellular traffic, secretion, and internalization by recipient cells, and review their most relevant effects. We also highlight important steps that are still poorly understood.

Influence of Diadema antillarum populations (Echinodermata: Diadematidae) on algal community structure in Jardines de la Reina, Cuba

The 1983-1984 mass mortality of Diadema antillarum produced severe damages on Caribbean reefs contributing to substantial changes in community structure that still persist. Despite the importance of Diadema grazing in structuring coral reefs, available information on current abundances and algal-urchin interactions in Cuba is scarce. We analyzed spatial variations in Diadema abundance and its influence on algal community structure in 22 reef sites in Jardines de la Reina, in June/2004 and April/2005. Urchins were counted in five 30x2m transects per site, and algal coverage was estimated in randomly located 0.25m side quadrats (15 per site). Abundances of Diadema were higher at reef crests (0.013-1.553 ind/m²), while reef slope populations showed values up to three orders of magnitude lower and were overgrown by macroalgae (up to 87%, local values). Algal community structure at reef slopes were dominated by macroalgae, especially Dictyota, Lobophora and Halimeda while the most abundant macroalgae at reef crests were Halimeda and Amphiroa. Urchin densities were negatively and positively correlated with mean coverage of macroalgae and crustose coralline algae, respectively, when analyzing data pooled across all sites, but not with data from separate habitats (specially reef crest), suggesting, along with historical fish biomass, that shallow reef community structure is being shaped by the synergistic action of other factors (e.g. fish grazing) rather than the influence of Diadema alone. However, we observed clear signs of Diadema grazing at reef crests and decreased macroalgal cover according to 2001 data, what suggest that grazing intensity at this habitat increased at the same time that Diadema recruitment began to be noticeable. Furthermore, the excessive abundance of macroalgae at reef slopes and the scarcity of crustose coralline algae seems to be due by the almost complete absence of D. antillarum at mid depth reefs, where local densities of this urchin were predominantly low. Rev. Biol. Trop. 59 (3): 1149-1163. Epub 2011 September 01.

A pesar de la importancia del forrageo de Diadema en la estructuración de los arrecifes de coral, la información disponible sobre la actual abundancia de algas y de las interacciones de erizos en Cuba es escasa. Por lo tanto, se analizan las variaciones espaciales en la abundancia de Diadema antillarum y su influencia sobre las algas en 22 arrecifes en Jardines de la Reina, en junio/2004 y abril/2005. Los erizos se muestrearon en recorridos de 30x2m (5/sitio) y las algas en cuadrículas de 0.25m de lado (15/sitio). Las densidades de Diadema fueron mayores en las crestas arrecifales (0.013-1.553ind/m²) mientras que las pendientes mostraron valores hasta tres ordenes de magnitud menor y presentaron un cubrimiento excesivo de macroalgas (hasta 87%), siendo las más abundantes Dictyota, Lobophora y Halimeda. Las densidades de erizos estuvieron correlacionadas negativa y positivamente con el cubrimiento de macroalgas y algas costrosas, respectivamente, en el análisis global, pero no en hábitats separados (especialmente en crestas), sugiriendo, conjuntamente con la biomasa histórica de peces, que la estructura de las comunidades en las crestas está determinada por la acción sinérgica de otros factores (herbivoría de peces) más que por la influencia de Diadema solo. No obstante, se observaron indicios del forrajeo de Diadema, y el cubrimiento de macroalgas disminuyó desde 2001, lo cual sugiere que la intensidad de la herbivoría aumentó al mismo tiempo que el reclutamiento de Diadema.

Proyectos Fisioma / Physione projects

Los proyectos fisioma están siendo desarrollados por diversa organizaciones y comunidades internacionales. Proponen innovadores enfoques investigativos, formas de organización y utilización de recursos para comprender integralmente, como sistemas, al ser humano y otros eucariotas, desde la concepción hasta la muerte, desde los genes hasta los organismos, a través de multiples escalas de espacio (rango: 10 elevado a 9 en la escala métrica), tiempo (rango: 3 x 10 elevado a 15 en segundos) y organización (moléculas, células, tejidos, organos, organismos). Se pone gran énfasis en el uso de modelos matemáticos/computacionales como herramientas para la integración del conocimiento, la experimentación virtual in sílico, el trabajo colaborativo de numerosos grupos multidisciplinarios internacionales, la creación de grandes bases de datos, ontologías, lenguajes estandarizados, metodologías, infraestructura, repositorios de instrumentos de trabajo; el entrenamiento de nuevos investigadores interdisciplinarios, el desarrollo de organizaciones y comunidades para obtener apoyo financiero, considerar aspectos éticos y legales, validar los modelos, facilitar la aplicación de resultados en la clínica, en la industria, en la enseñanza de los profesionales y en la educación del público, con el fin de maximizar los beneficios sociales. Presentamos el proyecto Fisioma de la Union Internacional de Ciencias Fisiológicas (UICF), y el "Humano Fisiológico Virtual", Eurofisioma, apoyado por la Union Europea. Mencionamos otros proyectos relacionados.

Physiome projects are being developed by several international organizations and communities. They propose innovative approaches to research, organization and resourse allocation aiming to fully understand, as systems, the human being and other eukaryotes, from conception to death, from genes to organisms, through multiple scales of space, time and organization (molecules, cells, tissues, organs, organisms). Great emphasis is placed in the of mathematical/computational modeling, in silico experimentation, international collaborative multidisciplinary work; the creation and share of large data bases, antologies standard languages, methodologies. infrastructures, tools; the training of new interdisciplinary investigators. New organizations are being developed to get funding, to consider ethical and legal aspects, to validate models, to facilitate the application of results from basic research to clinical practice, industry and education of professionals and the general public, in order to maximize social benefits. We will consider the Physiome Projects of the International Union Physiological Sciences (IUPS) and the Virtual Physiological Human (VPH), Europhysiome, supported by the European Union. Other related projects are mentioned.

Sociobiology of biodegradation and the role of predatory protozoa in biodegrading communities.

Predatory protozoa are known to enhance biodegradation by bacteria in a variety of systems including rumen. This is apparently counterintuitive since many protozoa do not themselves produce extracellular degradative enzymes and prey upon bacterial degraders. We propose a mechanism of protozoal enhancement of bacterial biodegradation based on the sociobiology of biodegradation. Since extracellular enzyme production by degraders involves a cost to the bacterial cell, cheaters that do not make the enzyme will have a selective advantage. In the presence of cheaters, degraders that physically attach to water-insoluble substrate will have a selective advantage over free-floating degraders. On the other hand, cheaters will benefit by being free floaters since they consume the solubilized products of extracellular enzymes. Predatory ciliated protozoa are more likely to consume free-floating cheaters. Thus, due to protozoan predation a control is exerted on the cheater population. We illustrate the dynamics of such a system with the help of a computer simulation model. Available data on rumen and other biodegradation systems involving protozoa are compatible with the assumptions and predictions of the model.

Foraminifera of Arasalar estuary, Karaikkal, south east coast of India.

A total of fifty-two foraminiferal species belonging to 23 genera and 16 families were recorded from Arasalar estuary for a period of one year (July 2000 to June 2001). Miliammina fusca, Quinqueloculina agglutinans, Q. seminula, Cibicides refulgens, Ammonia beccarii, Elphidium clavatum, E. incertum are the abundant species. Due to marine water influence the number and populations of foraminifera was high during summer and premonsoon seasons. The various ecological parameters such as temperature, salinity, pH, dissolved oxygen of bottom water and sediment organic matter were studied. Salinity is the key factor for governing distribution and abundance of foraminifera of this estuary.

Effects of Polysispyrenia simulii (Microspora; Duboscqiidae) on development of the gonads of Simulium pertinax (Diptera; Simuliidae)

The effects of the infection caused by the microsporidium Polydispyrenia simulii in gonads of the simuliid Simulium pertinax were evaluated. This blackfly species is the main target of control programmes in southeastern Brazil. Infected and noninfected blackflies were reared from larval stage to adults using a laboratory rearing system. There was no significant difference between the oogenic development and dimensions of ovarian follicles of healthy females compared to those reared from infected larvae. Otherwise, there was a significant difference between the fecundity of healthy females and those reared from infected larvae. In males, there was an evident recuction of motility of spermatozoids of males reared from infected larvae. The results obtained suggest that the microsporidium P. simulii have an important effect on the natural population dynamics of S. pertinax.

Impacto de nuevas metodologías en el estudio de parásitos: V. Dinámica del disparo del filamento polar en el microsporidio Nosema algerae, analizado por videomicroscopía de contraste acentuado electrónicamente / Impact of new methodologies in the study of parasites: V. Dynamics of the polar filament shot in the microsporidium Nosema algerea, analyzed by electronically enhanced contrast videomicroscopy

Por medio de video-microscopía de contraste acentuado electrónicamente, se consiguió el primer análisis cinemático de la descarga del filamento polar y el esporoplasma por esporas de un microsporidio. La estimulación in vitro de esporas de Nosema algerea, un parásito de los mosquitos, provoca la salida explosiva del filamento polar con una velocidad instantánea máxima de 105 µm/s en promedio, seguida por la expulsión del esporoplasma en el extremo del filamento luego de un lapso variable con un máximo de 500 ms. La descarga total se completa en menores de 2 s. La morfología de la parte del filamento ya descargada en cada instante no cambia durante la salida, lo que sugiere que el alargamiento ocurre tan solo en el extremo distal, conforma a la opinión de que el filamento es extruido por eversión. Por lo común, la longitud del filamento disminuye entre 5 y un 10 por ciento después de la expulsión del esporoplasma, lo que indica elasticidad del material constitutivo y presurización interna durante el proceso. Una vez liberado el esporoplasma aumenta de volumen, como es de esperar de una alta presión osmótica residual que, de acuerdo con la hipótesis prevaleciente, es ocasionada por la estimulación. Los resultados apoyan el modelo de que las esporas de los microsporidios germinan cuando el estímulo causa un aumento de presión osmótica interna, que a su vez determina un influjo de agua de manera que la presión hidrostática se eleva y finalmente rompe la tapa polar de la espora, por donde son entonces expulsados el filamento y enseguida el esporoplasma.

Phytoplankton role in waste water treatment by stabilization ponds system

In developing countries, oxidation pond system is considered now as a valid means of wastewater treatment, and the effluent can be reused for fish aquaculture or on agricultural land for crop irrigation. Since oxidation ponds require large areas, land should be available at low cost. This could be applied successfully in aired areas affected by water shortage and protein deficiencies. Maturation pond showed their best performance during spring season and at lower detention times in summer and autumn. It was noticed that high temperature, high intensity of light and longer detention times decreased the efficiency of the pond instead of increasing it as a result of the formation of algal mats on the surface. Although algae produce an additional organic load during hot seasons, yet their merits are as follows: [1] They constitute valuable source of oxygen in facultative and maturation ponds, leading to an acceleration in the aerobic degradation of organic compounds. [2] They remove appreciable amounts of nitrogen and phosphorus from the final effluent. [3] They play an important role in raising the pH which acts as a bactericidal factor. [4] Finally, algae serve as food source for the fish Tilapia nilotica in the aquacultural pond. Phytoplankton diversity was found to maintain high values in the maturation ponds confirming successful performance of the system in wastewater treatment

Análisis cuantitativo y estructura de la comunidad parasitaria de paralonchurus peruanus (pisces: sciaenidae) en la costa peruana / Quantitative analysis and parasitic community structure of paralonchurus peruanus (pisces: sciaenidae) from the peruvian coast

Fueron examinados 124 especímenes de paralonchurus peruanus (sciaenidae) procedentes de la costa central peruana con el objetivo de desarrollar un análisis cuantitativo y de algunos padrones de la estructura de su comunidad parasitaria. Los siguientes parásitos fueron colectados e identificados: henneguya sp.(protozoa), pseudohaliotrema paralonchuri, diplectanum sp., cynoscionicola americana y hargicotyle paralonchuri (monogenea); helicometra fasciata (digenea); corynosoma sp.(acanthocephala); cucullanellus amaruincai (nematoda); piscicólido no identificado (hirudinea); bomolochus peruensis, caligus callaoensis, lernanthropus paralonchuri, neobrachiella chevreuxii y clavellopsis sp.(copepoda); y un cymothoido no identificado (isopoda). Todos los parásitos presentaron el típico padrón de distribución sobredispersa. La intensidad todas las especies de parásitos encontrados no presentó correlación con la longitud total del hospedador. La intensidad y prevalencia parasitarias no fueron influenciadas por el sexo de los hospedadores, con excepción de h. fasciata, que presentó mayor intensidad en los hospedadores hembras. La principal característica de la comunidad parasitaria de p. peruanus es la escasez de endoparásitos y de estados larvales de parásitos tróficamente transmitidos. Adicionalmente, el número de especies satélitales fue predominante en la composición de la comunidad parasitaria

Kudoa sciaenae (Myxozoa: Multivalvulidae) cysts distribution in the somatic muscles of Stellifer minor (Tschudi, 1844) (Pisces: Sciaenidae)

The distribution of Kudoa sciaenae cysts (Myxozoa), in terms of intensity and prevalence, in the somatic muscles of the sciaenid Stellifer minor, shows an apparent preference for the anterior body region, including the head. The observed preference seems to be a consequence of the differential distribution of muscle mass, in the defined area, because when density (cyst/g dry muscle), is considered, all the somatic areas, but not cephalic area, do no show significant differences in terms of mean intensity and prevalence

Estimation of the average swimming speeds of microorganisms by using a simple technique

A method for estimating average speeds of swimming cells has been described. The statistical counting technique based on treating the swimming cells as a dilute gas, and its accuracy has been confirmed by direct measurements. In principle this technique can be applied to any suspension of cells satisfying certain statistical criteria [theory] enough to exert no force on each other except contact forces at the instant of collision. The mean free path is inversely proportional to the concentration of the cells in culture. This definition is readily seen to satisfy the statistical assumptions