Comparison of symmetrical hemodialysis catheters using computational fluid dynamics

Purpose: Symmetric-tip dialysis catheters have become alternative devices because of low access recirculation and ease of tip positioning. Flow characteristics of three symmetric catheters were compared based on computational fluid dynamics (CFD) as they relate to catheter function. Materials And Methods: In Palindrome, GlidePath, and VectorFloW catheters, a computational fluid dynamics based approach was used to assess W regions of flow separation, which are prone to thrombus development; (ii) shear-induced platelet activation potency; (iii) recirculation; and (iv) venous outflow deflection. A steady-state, laminar flow model simulated: catheter tip position within the superior vena cava. Catheter performance was investigated at high hemodialysis flow rate (400 mL/min). Blood was assumed as a Newtonian fluid. Results: Wide regions of flow separation downstream of the Palindrome side slot and close to the distal tip were observed in forward and reversed line configurations. Geometric asymmetry of the distal guide wire aperture of the GlidePath catheter produced the highest levels of inverted velocity flow when run in reversed configuration. The lowest mean shear-induced platelet activation was exhibited by GlidePath and VectorFloW catheters; the Palindrome catheter exhibited 152% higher overall platelet activation potency. All catheters were associated with a recirculation close to zero; the helically contoured lumens of the VectorFlow catheter produced the greatest amount of deflection of venous flow away from the arterial lumen. Conclusions: The VectorFlow catheter produced less shear-induced platelet activation than the Palindrome catheter and less flow separation than the Palindrome and GlidePath catheters irrespective of line configuration These findings have,potential implications for differences in thrombogenic risk during clinical performance of these catheters

Mechanotransmission of haemodynamic forces by the endothelial glycocalyx in a full-scale arterial model

The glycocalyx has been identified as a key mechano-sensor of the shear forces exerted by streaming blood onto the vascular endothelial lining. Although the biochemical reaction to the blood flow has been extensively studied, the mechanism of transmission of the haemodynamic shear forces to the endothelial transmembrane anchoring structures and, consequently, to the subcellular elements in the cytoskeleton, is still not fully understood. Here we apply a multiscale approach to elucidate how haemodynamic shear forces are transmitted to the transmembrane anchors of endothelial cells. Wall shear stress time histories, as obtained from image-based computational haemodynamics models of a carotid bifurcation, are used as a load and a continuum model is applied to obtain the mechanical response of the glycocalyx all along the cardiac cycle. The main findings of this in silico study are that: (1) the forces transmitted to the transmembrane anchors are in the range of 1–10 pN, which is in the order of magnitude reported for the different conformational states of transmembrane mechanotranductors; (2) locally, the forces transmitted to the anchors of the glycocalyx structure can be markedly different from the near-wall haemodynamic shear forces both in amplitude and frequency content. The findings of this in silico approach warrant future studies focusing on the actual forces transmitted to the transmembrane mechanotransductors, which might outperform haemodynamic descriptors of disturbed shear as localizing factors of vascular disease.Peer ReviewedPostprint (author's final draft

Mechanotransmission of haemodynamic forces by the endothelial glycocalyx in a full-scale arterial model

The glycocalyx has been identified as a key mechano-sensor of the shear forces exerted by streaming blood onto the vascular endothelial lining. Although the biochemical reaction to the blood flow has been extensively studied, the mechanism of transmission of the haemodynamic shear forces to the endothelial transmembrane anchoring structures and, consequently, to the subcellular elements in the cytoskeleton, is still not fully understood. Here we apply a multiscale approach to elucidate how haemodynamic shear forces are transmitted to the transmembrane anchors of endothelial cells. Wall shear stress time histories, as obtained from image-based computational haemodynamics models of a carotid bifurcation, are used as a load and a continuum model is applied to obtain the mechanical response of the glycocalyx all along the cardiac cycle. The main findings of this in silico study are that: (1) the forces transmitted to the transmembrane anchors are in the range of 1–10 pN, which is in the order of magnitude reported for the different conformational states of transmembrane mechanotranductors; (2) locally, the forces transmitted to the anchors of the glycocalyx structure can be markedly different from the near-wall haemodynamic shear forces both in amplitude and frequency content. The findings of this in silico approach warrant future studies focusing on the actual forces transmitted to the transmembrane mechanotransductors, which might outperform haemodynamic descriptors of disturbed shear as localizing factors of vascular disease.Peer ReviewedPostprint (author's final draft

Alemtuzumab for multiple sclerosis: the new concept of immunomodulation

Abstract Alemtuzumab (Lemtrada®) is a humanized anti-CD52 IgG1 monoclonal antibody that depletes CD52-expressing cells from the circulation. Robust clinical and radiologic data, derived from clinical trials and long-term observational studies, indicate that alemtuzumab induces a marked immunosuppression related to the depletion of circulating T and B lymphocytes. However, recent advances suggest that the long-term clinical effects of alemtuzumab are probably due to unique qualitative changes in the process of lymphocyte repopulation of the immune system. This leads to a particular rebalancing of the immune system. In this paper we review the immunomodulatory mechanisms underlying the therapeutic effect of alemtuzumab in pre-clinical models and in patients with relapsing remitting multiple sclerosis (RRMS), and stress the importance of a monoclonal antibody-based immunosuppression for treating the severe forms of RRMS. Alemtuzumab has many features of the ideal immunomodulatory drug: rapid biological and clinical actions and and long-lasting benefit. Alemtuzumab can be used as rescue therapy or as first line drug in severe-onset MS. Thus, the availability of alemtuzumab constitutes a significant step forward in the therapy of MS

Contabilidad Gerencial: Implementacion de estrategias y decisiones de inversion de capital en la Empresa Gallito Velez Cia, Lda

El presente seminario de graduación, denominado Implementación de las estrategias y decisiones de inversión de capital en la empresa de transporte ¨GALLITO VELOZ CIA, LTDA¨, para el periodo finalizado 2014, se elaboró con la finalidad de caracterizar el papel que desarrolla la contabilidad gerencial en las estrategias y tomas de decisión de inversión de capital, explicar las herramientas que se utilizan en las estrategias y decisiones de inversión de capital. La contabilidad gerencial es una herramienta importante debido a que proporciona información eficaz y oportuna a la hora de tomar decisiones que permitan lograr los objetivos de la empresa y de los inversionistas de la misma, además de estar enfocada en asegurar los recursos obtenidos por la entidad, y administrarlos de manera correcta. El propósito de las estrategias y las decisiones de inversión es indicar mediante el empleo de un criterio acertado que un problema o situación es valorado y considerado profundamente para elegir el mejor camino a seguir según las diferentes alternativas y operaciones, en la toma de decisiones, considerar un problema y llegar a una conclusión, significa que se han examinado todas las alternativas y que la elección ha sido correcta