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Search Results: 1 - 10 of 152954 matches for " ARTURO H; SANHUEZA "
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Caracterización trófica del placóforo intermareal Enoplochiton niger en el norte de Chile: variación ambiental y patrones dietarios a nivel local y region
SANHUEZA,ALVARO G; NAVARRETE,ARTURO H; OPAZO,L. FELIPE; CAMUS,PATRICIO A;
Revista chilena de historia natural , 2008, DOI: 10.4067/S0716-078X2008000400007
Abstract: the role and impact of herbivores on rocky intertidal food webs could be more complex and diverse than previously considered, particularly in the case of larger and more abundant consumers such as the placophoran mollusc enoplochiton niger. this species is one of the largest (up to 20 cm) and ecologically most important grazers on rocky shores of northern chile, but also one of the lesser known species in trophic terms. this work presents an assessment of the dietary patterns of e. niger in four communities of northern chile, distributed along 1,000 km of coastline and sampled seasonally from winter 2004 to autumn 2006. the analysis included the relationship of its diet with physical and biological factors, and particularly the potential effect of the 2004-2005 el ni?o event that occurred during the study period. at a regional level, the dietary spectrum of e. niger comprised a total of 98 food resources (60 algal ítems and 38 invertebrate ítems), and the most important ítems were sessile organisms of encrusting and layer-forming growth habits. e. niger exhibited a very high niche breadth at both local and regional levels (ranging from 20.7 to 28.0; levins' index), and its dietary richness at the individual level was independent from its body size. both the number of dietary ítems consumed per individual and the taxonomic composition of the diet did not show statistical differences among communities, but they were significantly different between the el ni?o and non-el ni?o periods. there was no clear relationship between the dietary patterns of e. niger and the contrasting levels of upwelling intensity among the communities studied. the results show that e. niger is a generalist polyphagous consumer, and a potential omnivore, which could have a high level of impact on space occupancy patterns in the intertidal community.
Trophic ecology of the chiton Acanthopleura echinata on Chilean rocky shores
CAMUS,PATRICIO A; NAVARRETE,ARTURO H; SANHUEZA,áLVARO G; OPAZO,L. FELIPE;
Revista chilena de historia natural , 2012, DOI: 10.4067/S0716-078X2012000100010
Abstract: polyplacophorans are common herbivores on rocky shores, but basic aspects of their ecology remain scarcely studied and their role within communities could be more complex than previously considered. such is the case of acanthopleura echinata (barnes), one of the largest and most conspicuous chitons in the world, and at the same time, one of the least known intertidal species in the southeastern pacific. to improve the basic ecological knowledge of this potentially important intertidal consumer, we studied the diet of a. echinata and its variation among sites of varying levels of coastal upwelling spread over 1000 km along the coast of northern chile. a seasonal evaluation of diet, body size distribution and density at sites expected to vary in overall nutrient loadings, benthic algal productivity and sea surface temperature, allowed us to examine plasticity in acantholeura diet and body size. overall, a. echinata consumed 85 items of algae (64.7 %, mainly fleshy and calcified encrusting thalli) and invertebrates (35.3 %, mainly barnacles). diet was always dominated by encrusting corallines, although the proportion of algae increased with body size suggesting an ontogenetic variation in feeding habits. although the number and occurrence frequency of dietary items varied significantly in time and space, there were no consistent seasonal patterns and the dominant items in the diet remained the same at all places. the density of a. echinata showed no significant spatial variation, but its body size and diet breadth correlated positively among sites and both tended to increase with latitude. our results show that a. echinata is a generalist, polyphagous consumer with a high potential for affecting the space-occupancy dynamics in the intertidal system, and also that among site variation in diet bears no simple relationship with variation in sea surface temperature and upwelling intensity.
Caracterización trófica del placóforo intermareal Enoplochiton niger en el norte de Chile: variación ambiental y patrones dietarios a nivel local y region Trophic characterization of the intertidal placophoran Enoplochiton niger in northern Chile: environmental variation and dietary patterns at local and regional levels
ALVARO G SANHUEZA,ARTURO H NAVARRETE,L. FELIPE OPAZO,PATRICIO A CAMUS
Revista chilena de historia natural , 2008,
Abstract: El rol e impacto de los herbívoros en la trama trófica de comunidades intermareales rocosas podría ser más diverso y complejo de lo considerado hasta ahora, particularmente en el caso de consumidores de mayor tama o y abundancia como el molusco placóforo Enoplochiton niger. Esta especie es uno de los pastoreadores de mayor tama o (hasta 20 cm) e importancia ecológica en las costas rocosas del norte de Chile, pero también una de las especies menos conocidas en términos tróficos. Este trabajo presenta una evaluación de los patrones dietarios de E. niger en cuatro comunidades del norte de Chile, distribuidas en 1.000 km de costa y muestreadas estacionalmente entre invierno 2004 y oto o 2006. Además se analizó la relación de su dieta con factores biológicos y físicos, incluyendo el efecto potencial del evento El Ni o 2004-2005 ocurrido durante el período de estudio. A nivel regional, el espectro dietario de E. niger abarcó un total de 98 recursos (60 ítemes algales y 38 ítemes invertebrados), y los ítemes más importantes fueron organismos sésiles con formas de crecimiento incrustante o en capa. E. niger mostró una gran amplitud de nicho tanto a nivel regional como local (rango: 20,7-28,0; índice de Levins), con una riqueza dietaria a nivel individual independiente del tama o corporal. Tanto el número de ítemes dietarios consumidos por individuo como la composición taxonómica de la dieta no mostraron diferencias significativas entre comunidades, pero variaron significativamente entre el período asociado al evento El Ni o y el período posterior. No hubo ninguna relación clara entre los patrones dietarios de E. niger y los niveles contrastantes de intensidad de surgencia entre las comunidades estudiadas. Los resultados muestran que E. niger es un consumidor generalista y polífago, y un potencial omnívoro, el cual podría tener un alto impacto sobre los patrones de ocupación de espacio en la comunidad intermareal. The role and impact of herbivores on rocky intertidal food webs could be more complex and diverse than previously considered, particularly in the case of larger and more abundant consumers such as the placophoran mollusc Enoplochiton niger. This species is one of the largest (up to 20 cm) and ecologically most important grazers on rocky shores of northern Chile, but also one of the lesser known species in trophic terms. This work presents an assessment of the dietary patterns of E. niger in four communities of northern Chile, distributed along 1,000 km of coastline and sampled seasonally from winter 2004 to autumn 2006. The analysis included the relatio
Trophic ecology of the chiton Acanthopleura echinata on Chilean rocky shores Ecología trófica del chitón Acanthopleura echinata en costas rocosas de Chile
PATRICIO A CAMUS,ARTURO H NAVARRETE,áLVARO G SANHUEZA,L. FELIPE OPAZO
Revista chilena de historia natural , 2012,
Abstract: Polyplacophorans are common herbivores on rocky shores, but basic aspects of their ecology remain scarcely studied and their role within communities could be more complex than previously considered. Such is the case of Acanthopleura echinata (Barnes), one of the largest and most conspicuous chitons in the world, and at the same time, one of the least known intertidal species in the southeastern Pacific. To improve the basic ecological knowledge of this potentially important intertidal consumer, we studied the diet of A. echinata and its variation among sites of varying levels of coastal upwelling spread over 1000 km along the coast of northern Chile. A seasonal evaluation of diet, body size distribution and density at sites expected to vary in overall nutrient loadings, benthic algal productivity and sea surface temperature, allowed us to examine plasticity in Acantholeura diet and body size. Overall, A. echinata consumed 85 items of algae (64.7 %, mainly fleshy and calcified encrusting thalli) and invertebrates (35.3 %, mainly barnacles). Diet was always dominated by encrusting corallines, although the proportion of algae increased with body size suggesting an ontogenetic variation in feeding habits. Although the number and occurrence frequency of dietary items varied significantly in time and space, there were no consistent seasonal patterns and the dominant items in the diet remained the same at all places. The density of A. echinata showed no significant spatial variation, but its body size and diet breadth correlated positively among sites and both tended to increase with latitude. Our results show that A. echinata is a generalist, polyphagous consumer with a high potential for affecting the space-occupancy dynamics in the intertidal system, and also that among site variation in diet bears no simple relationship with variation in sea surface temperature and upwelling intensity. Los poliplacóforos son herbívoros comunes en costas rocosas, pero los aspectos básicos de su ecología han sido escasamente estudiados y su rol trófico dentro de las comunidades podría ser más complejo de lo considerado hasta ahora. Tal es el caso de Acanthopleura echinata (Barnes), uno de los chitones más grandes y conspicuos en el mundo, pero a la vez una de las especies intermareales menos conocidas del Pacífico sudeste. A fin de mejorar el conocimiento ecológico básico de este consumidor intermareal potencialmente importante, estudiamos la dieta de A. echinata y su variación entre sitios con distintos niveles de surgencia costera distribuidos a través de 1000 km en la cost
TRP, TRPL and Cacophony Channels Mediate Ca2+ Influx and Exocytosis in Photoreceptors Axons in Drosophila
Guadalupe Astorga, Steffen H?rtel, Magdalena Sanhueza, Juan Bacigalupo
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0044182
Abstract: In Drosophila photoreceptors Ca2+-permeable channels TRP and TRPL are the targets of phototransduction, occurring in photosensitive microvilli and mediated by a phospholipase C (PLC) pathway. Using a novel Drosophila brain slice preparation, we studied the distribution and physiological properties of TRP and TRPL in the lamina of the visual system. Immunohistochemical images revealed considerable expression in photoreceptors axons at the lamina. Other phototransduction proteins are also present, mainly PLC and protein kinase C, while rhodopsin is absent. The voltage-dependent Ca2+ channel cacophony is also present there. Measurements in the lamina with the Ca2+ fluorescent protein G-CaMP ectopically expressed in photoreceptors, revealed depolarization-induced Ca2+ increments mediated by cacophony. Additional Ca2+ influx depends on TRP and TRPL, apparently functioning as store-operated channels. Single synaptic boutons resolved in the lamina by FM4-64 fluorescence revealed that vesicle exocytosis depends on cacophony, TRP and TRPL. In the PLC mutant norpA bouton labeling was also impaired, implicating an additional modulation by this enzyme. Internal Ca2+ also contributes to exocytosis, since this process was reduced after Ca2+-store depletion. Therefore, several Ca2+ pathways participate in photoreceptor neurotransmitter release: one is activated by depolarization and involves cacophony; this is complemented by internal Ca2+ release and the activation of TRP and TRPL coupled to Ca2+ depletion of internal reservoirs. PLC may regulate the last two processes. TRP and TRPL would participate in two different functions in distant cellular regions, where they are opened by different mechanisms. This work sheds new light on the mechanism of neurotransmitter release in tonic synapses of non-spiking neurons.
Occurrence of killer yeast strains in industrial and clinical yeast isolates
BAEZA,MARCELO E; SANHUEZA,MARIO A; CIFUENTES,VíCTOR H;
Biological Research , 2008, DOI: 10.4067/S0716-97602008000200007
Abstract: the secretion of proteinaceous toxins is a widespread characteristic in environmental and laboratory yeast isolates, a phenomenon called "killer system". the killer phenotype (k+) can be encoded by extrachromosomal genetic elements (eges) as double stranded dna or rna molecules (dsdna, dsrna) or in nuclear genes. the spectrum of action and the activity of killer toxins are influenced by temperature, salinity and ph of media. in the present work we determined the existence of k+ in a collection of s. cerevisiae and p. anómala yeasts isolated from environmental, industrial and clinical sources. the assays were performed in strains belonging to three yeast genera used as sensitive cells and under a wide range of ph and temperatures. approximately 51 % of isolates tested showed toxicity against at least one sensitive yeast strain under the conditions tested. the k+ p. anómala isolates showed a wide spectrum of action and two of them had toxic activity against strains of the three yeast genera assayed, including c. albicans strains. in all s. cerevisiae k+ isolates an extrachromosomal dsrna molecule (4.2 kb) was observed, contrary to p. anómala k+ isolates, which do not possess any eges. the k+ phenotype is produced by an exported protein factor and the kinetics of killer activity production was similar in all isolates with high activity in the log phase of growth, decaying in the stationary phase.
Effects of sulfur fertilization on wheat production and industrial quality (Triticum aestivum)
Herrera,Luis E; Pinilla,Hernán; Sanhueza,Héctor;
Ciencia e investigación agraria , 2012, DOI: 10.4067/S0718-16202012000100016
Abstract: two wheat fertilization experiments were conducted during the 2005-2006 and 2007-2008 seasons using a medial, mesic, seric, typic placandept soil to determine the effect of sulfur on the yield, percentage of protein, gluten content, and sedimentation volume of the grain and the nutrient availability in the soil. during the 2005-06 season, the fertilization treatments consisted of a base fertilization plus various sulfur treatments: 0 kg s ha-1 (t1); 27 kg s ha-1 (t2); 54 kg s ha-1 (t3) or 108 kg s ha-1 (t4). during the 2007-08 season, the fertilization treatments were 0 kg s ha-1 (t1), 9 kg s ha-1 (t2), 18 kg s ha-1 and 36 kg s ha-1 (t4). the results showed no differences (p<0.05) in the grain yield for any of the treatments evaluated. furthermore, no increases were found for any of the industrial quality variables analyzed. in contrast, increases in the availability of sulfur in the soil were observed. sulfur application in soils having contents of 12 and 13 mg kg-1 s did not increase the grain yield, protein content, gluten, or sedimentation volume.
An extension of the skew-generalized normal distribution and its derivation
Venegas,Osvaldo; Sanhueza,Antonio I; Gómez,Héctor W;
Proyecciones (Antofagasta) , 2011, DOI: 10.4067/S0716-09172011000300008
Abstract: in this paper, we introduce a new class of skew-symmetric distributions which are formulated based on cumulative distributions of skew-symmetric densities. this new class is an extension of other skew-symmetric distributions that have already been studied. we give special attention to a family from this class that could be seen as an extension ofthe skew-generalized-normal model introduced by arellano-valle et al.(2004). we study the main properties, stochastic representation, moments and an extension of this new model.
Impacto de la contaminación del aire por PM10 sobre la mortalidad diaria en Temuco
Sanhueza H,Pedro; Vargas R,Claudio; Mellado G,Paula;
Revista médica de Chile , 2006, DOI: 10.4067/S0034-98872006000600012
Abstract: background: temuco (304,000 inhabitants) has high levels of air pollution, mainly due to fine particulate matter of less than 10 μm (pm10). the effects of this pollution on population health have not been studied. aim: to study the short-term effects of pm10 on daily mortality in temuco, in southern chile, due to respiratory and cardiovascular causes. material and methods: we followed the aphea methodology (air pollution and health european approach) by estimating poisson multivariate regression models and controlling by trends, seasonality and meteorology. the pm10 variable was introduced after controlling by the confounders and checking by statistical adjustment and autocorrelation of errors. mortality data was obtained from the ministry of health, registering age, gender, place of residence and cause of death. cancer, respiratory and cardiovascular deaths, occurring between 1997 and 2002, were recorded for this study. results: there was a significant and positive association between pm10 concentration and daily mortality caused by respiratory disease (p-value=0.046, relative risk (rr) 1.236, 95% confidence interval (ci) 1.004-1.522) and cardiovascular diseases in people aged 65 years and more (p-value=0.042; rr 1.176 95% ci 1.006-1.374). conclusions: there is a significant association between daily air pollution by pm10 particulate matter and mortality in temuco, chile
Occurrence of killer yeast strains in industrial and clinical yeast isolates
MARCELO E BAEZA,MARIO A SANHUEZA,VíCTOR H CIFUENTES
Biological Research , 2008,
Abstract: The secretion of proteinaceous toxins is a widespread characteristic in environmental and laboratory yeast isolates, a phenomenon called "killer system". The killer phenotype (K+) can be encoded by extrachromosomal genetic elements (EGEs) as double stranded DNA or RNA molecules (dsDNA, dsRNA) or in nuclear genes. The spectrum of action and the activity of killer toxins are influenced by temperature, salinity and pH of media. In the present work we determined the existence of K+ in a collection of S. cerevisiae and P. anómala yeasts isolated from environmental, industrial and clinical sources. The assays were performed in strains belonging to three yeast genera used as sensitive cells and under a wide range of pH and temperatures. Approximately 51 % of isolates tested showed toxicity against at least one sensitive yeast strain under the conditions tested. The K+ P. anómala isolates showed a wide spectrum of action and two of them had toxic activity against strains of the three yeast genera assayed, including C. albicans strains. In all S. cerevisiae K+ isolates an extrachromosomal dsRNA molecule (4.2 Kb) was observed, contrary to P. anómala K+ isolates, which do not possess any EGEs. The K+ phenotype is produced by an exported protein factor and the kinetics of killer activity production was similar in all isolates with high activity in the log phase of growth, decaying in the stationary phase.
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