Front microrheology of the non-Newtonian behaviour of blood: scaling theory of erythrocyte aggregation by aging.

We introduce a new framework to study the non-Newtonian behaviour of fluids at the microscale based on the analysis of front advancement. We apply this methodology to study the non-linear rheology of blood in microchannels. We carry out experiments in which the non-linear viscosity of blood samples is quantified at different haematocrits and ages. Under these conditions, blood exhibits a power-law dependence on the shear rate. In order to analyse our experimental data, we put forward a scaling theory which allows us to define an adhesion scaling number. This theory yields a scaling behaviour of the viscosity expressed as a function of the adhesion capillary number. By applying this scaling theory to samples of different ages, we are able to quantify how the characteristic adhesion energy varies as time progresses. This connection between microscopic and mesoscopic properties allows us to estimate quantitatively the change in the cell-cell adhesion energies as the sample ages.

Capillary Filling at the Microscale: Control of Fluid Front Using Geometry.

We propose an experimental and theoretical framework for the study of capillary filling at the micro-scale. Our methodology enables us to control the fluid flow regime so that we can characterise properties of Newtonian fluids such as their viscosity. In particular, we study a viscous, non-inertial, non-Washburn regime in which the position of the fluid front increases linearly with time for the whole duration of the experiment. The operating shear-rate range of our apparatus extends over nearly two orders of magnitude. Further, we analyse the advancement of a fluid front within a microcapillary in a system of two immiscible Newtonian liquids. We observe a non-Washburn regime in which the front can accelerate or decelerate depending on the viscosity contrast between the two liquids. We then propose a theoretical model which enables us to study and explain both non-Washburn regimes. Furthermore, our theoretical model allows us to put forward ways to control the emergence of these regimes by means of geometrical parameters of the experimental set-up. Our methodology allows us to design and calibrate a micro-viscosimetre which works at constant pressure.

[Clinical and biochemical characteristics of predialysis patients in terms of 25 hydroxy vitamin D levels]. / Características clínicas y bioquímicas de pacientes en prediálisis con respecto a los niveles de 25 hidroxivitamina D.

INTRODUCTION: Decreased levels of 25 hydroxyvitamin D (25[OH]D) have been reported in patients with chronic kidney disease (CKD). The pleiotropic effects of vitamin D are known to go beyond mineral metabolism. OBJECTIVES: The aims of this study were to: 1) Determine the 25(OH)D levels in predialysis outpatients. 2) Find out the clinical and biochemical characteristics of patients with 25(OH)D deficiency, and predictive factors for the deficiency. PATIENTS AND METHODS: An observational study in 79 predialysis outpatients was performed. Clinical and biochemical parameters were analysed in terms of nutrition, inflammation and mineral metabolism in relation to serum levels of 25(OH)D. Levels of 25(OH)D lower than 15ng/ml were considered to be deficient. RESULTS: Serum levels of 25(OH)D were deficient in 41 patients (52%). The comparative study regarding levels of vitamin 25(OH)D showed the group of patients with a deficiency, i.e. those with less than 15ng/ml, were older (70 ± 11.97 vs. 61 ± 14.5; p = 0.005), had a greater body mass index, BMI, (30±4.06 vs. 27.1 ± 5.08; p = 0.003) and increased proteinuria (1.42g/24h (0.53-2.96) vs. 0.51 (0.20-1.48), p = 0.009). This group included a greater number of diabetic patients: 20 (76.9%) vs. 6 (23%), p = 0.002. They had a higher level of parathyroid hormone (PTH): 359 (239-658) vs. 233 (129-323), p = 0.000; and more patients were under treatment with Calcitriol: 28 (62.2%) vs. 17 (37.8%), p = 0.024. In the multivariate analysis, high levels of PTH (OR 13.38; CI 95% [2.94-60.89]; p=0.001), increased proteinuria (OR 4.41; CI 95% [1.12-17.25]; p = 0.033); and being diabetic (OR 5.713; CI 95% [1.43-22.77]; p = 0.014) were independent predictor factors for patients with 25(OH)D deficiency. CONCLUSIONS: In our study, we observed a high prevalence of 25(OH)D deficiency among patients with CKD. The increased levels of PTH, the increase of proteinuria and the presence of diabetes were independent predictors for 25(OH)D deficiency.

Características clínicas y bioquímicas de pacientes en prediálisis con respecto a los niveles de 25 hidroxivitamina D / Clinical and biochemical characteristics of predialysis patients in terms of 25 hydroxy vitamin D levels

Introducción: Se ha descrito una disminución de los niveles de 25 hidroxivitamina D (25[OH]D) en los pacientes con enfermedad renal crónica (ERC). Conocemos que el efecto pleiotrópico de la vitamina D va más allá del metabolismo mineral. Objetivos: Los objetivos del estudio fueron: 1) determinar los niveles de 25(OH) D en pacientes con ERC seguidos en consulta de prediálisis, y 2) analizar características clínicas y bioquímicas de los pacientes con respecto a los niveles de 25(OH)D y los posibles factores predictivos de la deficiencia en 25(OH)D. Pacientes y métodos: Realizamos un estudio observacional en 79 pacientes con ERC. Analizamos datos clínicos y parámetros bioquímicos en cuanto a nutrición, inflamación y metabolismo mineral en relación con los niveles de 25(..) (AU)

Introduction: Decreased levels of 25 hydroxyvitamin D (25[OH]D) have been reported in patients with chronic kidney disease (CKD). The pleiotropic effects of vitamin D are known to go beyond mineral metabolism. Objetives: The aims of this study were to: 1) Determine the 25(OH)D levels in predialysis outpatients. 2) Find out the clinical and biochemical characteristics of patients with 25(OH)D deficiency, and predictive factors for the deficiency. Patients and methods: An observational study in 79 predialysis outpatients was performed. Clinical and biochemical parameters were analysed in terms of nutrition, inflammation and mineral metabolism in relation to serum levels of 25(OH)D. Levels of 25(OH)D lower than 15ng/ml were considered to be deficient. Results: Serum levels of 25(OH)D were deficient in 41 patients (52%). The comparative study regarding levels of vitamin 25(OH)D showed the group of patients with a deficiency, i.e. those with less than 15ng/ml, were older (70 ± 11.97 vs. 61 ± 14.5; p = 0.005), had a greater body mass index, BMI, (30±4.06 vs. 27.1 ± 5.08; p = 0.003) and increased proteinuria (1.42g/24h (..) (AU)

La importancia de la comorbilidad en el fracaso renal agudo valorado por los nefrólogos / No disponible

Objetivo: analizar las características del fracaso renal agudo(FRA) en nuestro centro y determinar su influencia en el pronóstico del mismo y en la mortalidad. Material y métodos: estudio retrospectivo de los episodios de FRA valorados por nuestro Servicio durante un período de dos años (2005-2007). Los criterios de inclusión fueron: elevación de la creatinina sérica0,5 mg/dl en pacientes con función renal previa normal y de 1 mg/dl en aquéllos con insuficiencia renal crónica previa. Se registraron factores epidemiológicos, clínicos, analíticos, terapéuticos y pronósticos. Resultados: valoramos 201 episodios de FRA. El 62,7% 16,38 (63,68% ±) eran varones. La edad media fue de 67,35 >65 años). El índice de comorbilidad de Charlson (ICCH) mostraba unos valores de 3,49 ± 2,43. Ciento quince pacientes tenían IRC previa al ingreso. El 52,7% fueron prerrenales, el 34,8% parenquimatosos y el 8,5% obstructivos. El 35,8%cursaron con oligoanuria. El tiempo medio de ingreso fue de22,47 ± 21,3 días. El 70,1% de los pacientes recuperaron función renal al alta. La mortalidad fue del 30,8%. En el estudio univariante se asociaron significativamente con la mortalidad(p <0,05): ICCH, oliguria, hipoalbuminemia, niveles bajos de colesterol y anemia. En el análisis de regresión lineal múltiple, los factores que mejor la explicaban fueron: ICCH, oliguria y niveles bajos de colesterol. Realizamos un modelo predictivo de mortalidad con estos factores. Conclusión: la mayor complejidad clínica basal de los pacientes, el desarrollo de oliguria y la presencia de datos de malnutrición-inflamación aparecen como los principales factores pronósticos y de mortalidad en el FRA que valoramos los nefrólogos en el momento actual (AU)

Aims: To study the features of acute renal failure (ARF) in our hospital and to determine prognosis and mortality associated factors. Methods: This is a retrospective study analyzing the ARF episodes observed in our center during a two years period (2005-2007). ARF was considered when a sudden rise in serum creatinine concentration was more than0, 5 mg/dl in patients with normal renal function and more than 1 mg/dl in patients with previous mild to moderate chronic renal failure. We analyzed epidemiologic, clinical, laboratories results, therapeutics and prognosis factors. Results: Two hundred and one patients were evaluated (62,7% males; Age= 67,35 ± 16,38 years (63,68% >65 años); Comorbility Index of Charlson was 3,49 ± 2,43). 115 ARF episodes occurred in patients with previous renal failure. ARF was pre-renal in 52, 7%, renal in 34,8% and post-renal in8,5%. 35,8% of ARF patients had oliguria or anuria. The mean duration of ARF/hospitalization was 22,47 days (22,47± 21,83). The percentage of resolved ARF was 70, 1%.Mortality was 30, 8%. The univariate analysis showed that comorbility Index of Charlson, oliguria, low serum albumin, low cholesterol and anemia were significantly associated with mortality (p <0,05). However, only Charlson Index,oliguria and low serum cholesterol were independent predictors of mortality in multivariate analysis. Mortality predictive model was carried out. Conclusion: Highest basal comorbility of patients, oliguria and malnutrition inflamation dates are independent predictors of mortality in patients with acute renal failure (AU)

Tratamiento de la glomerulonefritis membranosa idiopática con esteroides e inmunosupresores / Steroid and immunosuppressive treatment in idiopathic membranous glomerulonephritis

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