Resumo A seca é um dos estresses abióticos mais prejudiciais que dificultam o crescimento e o desenvolvimento das plantas. O presente estudo teve como objetivo determinar os efeitos de vários quocientes de Ca/Mg sob estresse osmótico induzido por polietilenoglicol (PEG) no crescimento, absorção e translocação de Ca e Mg em Avena sativa L. As plantas foram cultivadas em solução nutritiva suplementada com três diferentes quocientes molares de Ca/Mg (0,18, 2 e 4). Após 30 dias, as plantas foram expostas a duas concentrações diferentes de PEG (0,6 MPa e 0,2 MPa) por 8 dias, e as soluções foram renovadas após 4 dias. Uma solução contendo os nutrientes Ca e Mg mitigou o impacto negativo causado por estresse osmótico na taxa de crescimento relativo (RGR), taxa de crescimento absoluto (AGR), taxa de crescimento da cultura (CGR), razão de área foliar (LAR), razão de índice foliar (LAI), razão raiz-parte aérea (RSR), eficiência do uso da água (WUE) e taxa de assimilação líquida (NAR). Além disso, afetou negativamente os parâmetros de germinação, incluindo porcentagem final de emergência (FEP), tempo médio de germinação (MGT), índice de germinação de Timson (TGI), índice de taxa de germinação (GRI) e capacidade de campo percentual (%FC) de aveia (Avena sativa L.). O Mg e o Ca na parte aérea e raiz e o fator de translocação de Ca diminuíram com o aumento de Ca em solução, enquanto o fator de translocação de Mg aumentou com o aumento de Ca em solução nutritiva. Neste trabalho, são examinados os efeitos combinados de vários quocientes de Ca/Mg e estresse osmótico produzido por PEG em diferentes concentrações (0,6 MPa e 0,2 MPa) no crescimento e na absorção de elementos de Avena sativa L. Como resultado, o quociente de Ca/Mg pode combater naturalmente o estresse hídrico moderado experimentado pelas lavouras.

Abstract Drought is one of the most damaging abiotic stress that hinder plant growth and development. The present study aimed to determine the effects of various Ca/Mg quotients under polyethylene glycol (PEG)–induced osmotic stress on growth, uptake and translocation of Ca and Mg in Avena sativa (L). Plants were grown in nutrient solution supplemented with three different Ca/Mg molar quotients (0.18, 2, and 4). After 30 days plants were exposed to two different PEG (Polyethylene glycol) concentrations (0.6 MPa & 0.2 MPa) for 8 days, and solutions were renewed after 4 days. A solution containing Ca and Mg nutrients has mitigated the negative impact caused via osmotic stress on relative growth rate (RGR), absolute growth rate (AGR), crop growth rate (CGR), leaf area ratio (LAR), Leaf index ratio (LAI), root-shoot ratio (RSR), water use efficiency (WUE) and net assimilation rate (NAR). In addition, it adversely affected germination parameters, including final emergence percentage (FEP), mean germination time (MGT), Timson germination Index (TGI), germination rate index (GRI) and percent field capacity (%FC), of oat (Avena sativa L.). Mg and Ca in shoot and root and Ca translocation factor decreased with increasing Ca in solution, while Mg translocation factor increased with increasing Ca in nutrient solution. In this work, the combined effects of various Ca/Mg quotients and osmotic stress produced by polyethylene glycol (PEG) in different concentrations (0.6 MPa, 0.2 MPa) on the growth and element uptake of Avena sativa L. are examined. As a result, the Ca/Mg Quotient may naturally combat the moderate drought stress experienced by field crops.

We used amplicon sequencing of the 16S rRNA gene to characterize the diversity and assess temporal and spatial patterns of Actinobacteria operational taxonomic units (OTUs) extracted from sediments of the Humboldt Sulfuretum located off the coast of central Chile. The sediment of this zone is rich in sulfur compounds and organic material and supports a vast microbial community that experiences seasonal changes in response to contrasting oceanographic regimes. We distinguished 498 OTUs distributed among 7 orders, 47 families, and 122 genera (5 of these have been widely recognized for their biotechnological applications), and 56 species. The temporal analyses indicated that some OTUs underwent significant temporal changes in abundance, richness, and diversity that allowed samples to be grouped by sampling dates (seasons) but not by sampling depth or location. Since Actinobacteria are mostly aerobic, higher concentrations of dissolved oxygen near the bottom during the austral autumn-winter seasons result in a more benign environment for this phylum than the upwelling-favorable spring-summer seasons when waters over the shelf are oxygen-deficient. To evaluate the taxonomic diversity and inquire into the community dynamic of Actinobacteria present in the Humboldt Sulfuretum and reported as a potentially untapped source for secondary metabolites this work benefited from culture-independent (molecular) techniques.

Se usó pirosecuenciación de la región V6 del gen 16S del ARNr para caracterizar la diversidad y la dinámica espacio-temporal de unidades taxonómicas operacionales (OTUs) del filo Actinobacteria, los que fueron aislados desde sedimentos provenientes del Sulfureto de Humboldt frente a Chile central. Este substrato es rico en compuestos azufrados y material orgánico lo que mantiene una vasta comunidad microbiana que experimenta cambios estacionales en respuesta a regímenes oceanográficos contrastantes. Se identificaron 498 OTUs distribuidas en 7 órdenes, 47 familias, 122 géneros, (5 de los cuales son ampliamente reconocidos por sus aplicaciones biotecnológicas), y 56 especies. El análisis temporal reveló que algunos OTUs presentan diferencias significativas en abundancia, índices de diversidad y riqueza, las que generaron una agrupación de las muestras asociada a la fecha de muestreo (estación del año) y no a la profundidad del sitio de muestreo. Debido a que las Actinobacteria son mayormente aeróbicas, las altas concentraciones de oxígeno disuelto que ocurren en la zona en el otoño-invierno austral, representan condiciones ambientales beneficiosas para este filo, no así las de primavera-verano austral cuando prevalece la hipoxia. El presente trabajo se benefició de la aplicación de métodos cultivo-independientes (métodos moleculares) para evaluar la diversidad taxonómica y examinar la dinámica de uno de los grupos de bacterias presentes en el Sulfureto de Humboldt reportado como una fuente potencial e inexplorada de metabolitos secundarios.

OBJECTIVES: Acute ST-elevation myocardial infarction is associated with ventricular dysfunction due to ischemia-induced progressive myocardial damage. The decrease in ventricular compliance causes left atrial dilatation and stretching of the atrial myocardium, which are the main stimuli for the secretion of atrial natriuretic peptide. The aim of this study was to evaluate left atrial dimensions and atrial natriuretic peptide levels in patients early after their first acute ST-elevation myocardial infarction and assess the probable interaction between coronary lesions and these measurements. METHODS: A total of 110 patients with acute myocardial infarction and 50 controls were studied. Plasma atrial natriuretic peptide was measured at admission. Left ventricular function, diameter, and volume index were evaluated using transthoracic echocardiography. Gensini and vessel scores of the patients who underwent coronary angiography were calculated. RESULTS: Plasma atrial natriuretic peptide in the patients with myocardial infarction was increased compared with that in controls (3.90±3.75 vs. 1.35±0.72 nmol/L, p<0.001). Although the left atrial diameter was comparable in patients and controls, the left atrial volume index was increased in patients with acute myocardial infarction (26.5±7.1 vs. 21.3±4.9 mL/m2, p<0.01). Multivariate regression analysis showed a strong independent correlation between the left atrial volume index and the plasma atrial natriuretic peptide level (β = 0.23, p = 0.03). CONCLUSIONS: The left atrial volume index and plasma atrial natriuretic peptide level were correlated in patients with acute myocardial infarction.