In vitro degradation of biodegradable polylactic acid/magnesium composites: Relevance of Mg particle shape.

Absorbable medical devices must be developed in order to have an appropriate degradation rate in agreement with the healing rate of bone in the implantation site. In this work, biodegradable composites formed by a polylactic acid matrix reinforced with 10%wt. magnesium microparticles were processed and their in vitro degradation investigated during 28 days. A joint analysis of the amount of H2 released, the changes in pH in buffered (PBS) and non-buffered media (distilled water), the variations in mass, microstructure and the mechanical performance of the specimens was developed. The main aim was to elucidate the relevance of Mg particles shape on tailoring the degradation kinetics of these novel composites. The results show that the shape of the Mg reinforcing particles plays a crucial role in the degradation rate of PLA/Mg composites, with spherical particles promoting a lower degradation rate than irregular particles. This fact is only partially due to the smaller surface area to volume ratio of the spherical particles. Irregular particles promote a faster formation of cracks and, therefore, an increasingly faster degradation of the polymeric matrix. In every case, the amount of H2 released by the composites was well below that released by monolithic Mg. The pH of PBS during degradation remained always within 7.2 and 7.4. PLA/Mg reinforced with spherical particles retains more than 90% of its mechanical properties after 7 days of immersion and more than 60% after 28 days. STATEMENT OF SIGNIFICANCE: The increasing demand for temporary orthopaedic implants is the driving force to seek new strategies to decrease costs and simultaneously improve patients comfort as well as simplify surgical procedures. Resorbable medical devices must be developed in order to have an appropriate degradation rate in agreement with the healing rate of bone. We are presenting for the first time results of the degradation kinetics of a new material based on polylactic acid reinforced with 10%wt. Mg microparticles. This work analyzes the relevance of Mg particle shape (irregular and spherical) on tailoring the degradation behaviour of these composites. Conclusions withdrawn from this study help to customize bioabsorbable materials in order to meet the requirements for a specific application and patient.

Factores predictores de mortalidad en la sepsis urinaria con obstrucción ureteral / Mortality predictive factors in patients with urinary sepsis associated to upper urinary tract calculi

OBJETIVO: El objetivo de este estudio fue conocer las características clínicas de los pacientes con sepsis urológica obstructiva por litiasis ureteral que ingresaron en la Unidad de Cuidados Intensivos e identificar los factores predictores de mortalidad en las primeras 24 horas del ingreso. DISEÑO: Estudio observacional retrospectivo durante un periodo de 16 años (1996-2011). ÁMBITO: Unidad de Cuidados Intensivos polivalente de 20 camas de un hospital universitario de 2.° nivel. PACIENTES: Todos los pacientes que ingresaron en Unidad de Cuidados Intensivos por sepsis urológica obstructiva. INTERVENCIONES: Ninguna. VARIABLES DE INTERÉS PRINCIPALES: Variables clínicas y analíticas generales y relacionadas con el proceso urológico. Método diagnóstico, técnica desobstructiva, germen aislado y tratamiento. Análisis de factores de riesgo mediante regresión logística múltiple. RESULTADOS: Ciento siete pacientes ingresados con una mortalidad del 19,6%. El diagnóstico fue mayoritariamente por ecografía y la técnica descompresiva más utilizada fue la colocación de catéter ureteral doble J. Se aisló germen en el 48,6% de los pacientes. El 20,6% presentaron bacteriemia. En el análisis multivariante, la edad, el fallo renal agudo y el uso de drogas vasoactivas en las primeras 24 horas del ingreso se relacionaron de forma independiente con la mortalidad. CONCLUSIONES: La edad avanzada, el fallo renal agudo y la necesidad de fármacos vasoactivos se relacionaron con un aumento de riesgo de mortalidad en los pacientes con urosepsis secundaria a litiasis ureteral

PURPOSE: The aims of this study were to determine the clinical characteristics of patients with urinary sepsis associated to ureteral calculi admitted to the Intensive Care Unit (ICU), and to identify predictors of mortality in the first 24 hours of admission. DESIGN: A retrospective observational study covering a 16-year period (2006-2011) was carried out. SETTING: The combined clinical/surgical ICU of a secondary-level University hospital. PATIENTS: All patients admitted to the ICU due to obstructive urinary sepsis. INTERVENTIONS: None. MAIN VARIABLES: We analyzed general clinical and laboratory test and urological data. The diagnostic technique, affected side, decompression technique, isolated microorganism and antibiotic therapy used were also considered. The assessment of risk factors was performed by multiple logistic regression analysis. RESULTS: A total of 107 patients admitted to the ICU were included in the study, with a mortality rate of 19.6%. The diagnosis was mainly established by ultrasound, and the most commonly used decompression technique was retrograde JJ stenting. Microorganisms were isolated in 48.6% of the patients. In total, 20.6% of the patients had bacteremia. Multivariate analysis found age, acute renal failure and the use of vasoactive drugs administered continuously for the first 24hours of admission to be independently associated to mortality. CONCLUSIONS: Advanced age, acute renal failure and the need for vasoactive drugs were associated to an increased risk of mortality in patients with urinary sepsis associated to upper urinary tract calculi

[Mortality predictive factors in patients with urinary sepsis associated to upper urinary tract calculi]. / Factores predictores de mortalidad en la sepsis urinaria con obstrucción ureteral.

PURPOSE: The aims of this study were to determine the clinical characteristics of patients with urinary sepsis associated to ureteral calculi admitted to the Intensive Care Unit (ICU), and to identify predictors of mortality in the first 24 hours of admission. DESIGN: A retrospective observational study covering a 16-year period (2006-2011) was carried out. SETTING: The combined clinical/surgical ICU of a secondary-level University hospital. PATIENTS: All patients admitted to the ICU due to obstructive urinary sepsis. INTERVENTIONS: None. MAIN VARIABLES: We analyzed general clinical and laboratory test and urological data. The diagnostic technique, affected side, decompression technique, isolated microorganism and antibiotic therapy used were also considered. The assessment of risk factors was performed by multiple logistic regression analysis. RESULTS: A total of 107 patients admitted to the ICU were included in the study, with a mortality rate of 19.6%. The diagnosis was mainly established by ultrasound, and the most commonly used decompression technique was retrograde JJ stenting. Microorganisms were isolated in 48.6% of the patients. In total, 20.6% of the patients had bacteremia. Multivariate analysis found age, acute renal failure and the use of vasoactive drugs administered continuously for the first 24 hours of admission to be independently associated to mortality. CONCLUSIONS: Advanced age, acute renal failure and the need for vasoactive drugs were associated to an increased risk of mortality in patients with urinary sepsis associated to upper urinary tract calculi.

Alpine cushion plants inhibit the loss of phylogenetic diversity in severe environments.

Biotic interactions can shape phylogenetic community structure (PCS). However, we do not know how the asymmetric effects of foundation species on communities extend to effects on PCS. We assessed PCS of alpine plant communities around the world, both within cushion plant foundation species and adjacent open ground, and compared the effects of foundation species and climate on alpha (within-microsite), beta (between open and cushion) and gamma (open and cushion combined) PCS. In the open, alpha PCS shifted from highly related to distantly related with increasing potential productivity. However, we found no relationship between gamma PCS and climate, due to divergence in phylogenetic composition between cushion and open sub-communities in severe environments, as demonstrated by increasing phylo-beta diversity. Thus, foundation species functioned as micro-refugia by facilitating less stress-tolerant lineages in severe environments, erasing a global productivity - phylogenetic diversity relationship that would go undetected without accounting for this important biotic interaction.

Some aspects about the climate/vegetation relationships in the Iberian Central System

Iberian Central System (Spain-Portugal) has the suitable conditions to make a phytoclimatic study. We have realized as example of these bioclimatic procedures, a study about linear regression of it (thermicity index of Rivas-Martinez) on altitude. The results are given in the present paper (AU)