Search

Blood-membrane contact in the extracorporeal circuit affects the activation of many biological systems. Among these, phagocytizing activity has been reported to be influenced by the nature of the hemodialysis membrane used, whether cellulosic or synthetic.This work reports on an ex-vivo, comparative test between cellulosics and synthetics concerning the effects of blood-membrane contact on the polymorphonucleate and monocyte phagocytizing function, both during and after the hemodialysis session.By means of flow cytometry, we evaluated the capacity for phagosoma formation and oxidative burst both in polymorphonucleates and monocytes. Ten hemodialysis patients were included in the study. Six separate dialysis procedures for each patient were considered, one per dialyzer (3 cellulosic and 3 synthetic membranes). Tests were performed at 15', 60', 210’ and 4 hours after the session end. Comparative evaluation was made according to Student's t test.Polymorphonucleate phagocytosis and oxidative burst activation were globally more marked for synthetic than cellulosic membranes, tending to level out in the post-dialysis. This result could be affected by their functional exhaustion following pulmonary sequestration. Monocyte intradialytic phagocytosis and oxidative burst proved more activated by cellulosic membrane. All differences tended to vanish in the post-dialysis.

Aortic transplantation has progressively gained interest over the last few years and it is becoming a first choice indication in the substitution of infected prostheses. The most frequent complication in long-term vascular outcome (wall thickening, aneurysmatic dilation, stenosis), may occur through an immunological mechanism.In this study we investigated nine recipients, aged 48 to 65 years, of aorta segment replacement for anti-HLA antibody production (specificity and Ig class), CD3-CD4-CD8 T cell subpopulation dynamics and aorta wall thickness. Mismatch-specific IgG antibodies to HLA class I and HLA class II antingens were detected 1, 3 and 6 months after transplantation and persisted at a high concentration for at least 1 year. Furthermore, the absolute number of CD3, CD4 and CD8 positive lymphocytes increased progressively after aorta allograft.Tomography scanning showed a progressive thickness of the aorta wall. We can speculate that these anti-HLA antibodies in the recipients have the potential to harm the implant; therefore, aorta allograft should involve the induction of immunological tolerance by appropriate immunosuppressants.

Intradialytic coagulative and platelet activation, one of the main consequences of blood-membrane contact, was studied in a group of 5 RDT patients with a comparative evaluation of 3 different dialytic membranes: Cuprophan (CU), Polysulfone (PS) and Cellulose Triacetate (CT). Each patient underwent 5 consecutive dialysis sessions with the above mentioned membranes. Intradialytic platelet activation was studied through a morpho-functional evaluation between the mean platelet volume (MPV) and Serotonin (S), ß-Thromboglobulin (ß-TG) and Platelet Factor 4 (PF4) serum levels. These determinations were made before HD (time 0) and after 30', 120’ and 240'. We also checked the intradialytic status of thrombogenesis and fibrinolysis determining aPTT, thrombin time, fibrinogen, antithrombin III (AT III), α-2 antiplasmin and plasminogen, at the same time intervals. All membranes tested (CU, PS, CT) caused appreciable intradialytic platelet activation, above all after 15’ and at the end of dialysis sessions, more marked for CU than PS or CT. In particular MPV showed a decrease throughout the session (-5% at 30’ and -9% at 240') while S, ßTG and PF4 peripheral blood levels showed a significant increase at the same intervals with CU membrane. Lastly coagulative and fibrinolytic parameters showed no significant differences among any of the membranes tested.

The effects of vessel joint where the both sides have different wall properties on the heart pulse propagation are investigated. Such a local disturbance can influence post-transplantion pathology and evolution of the organ inconsistence.Using a mathematical model, developed in a previous article, we perform analytical analysis and present some qualitative and quantitative estimations. The effects of jointed vessels with different thicknesses and radii on the local concentration of the pressure, radial wall displacement, bending moment and shear force are analyzed in detail. In particular, it is obtained that the bending and shear stresses at a joint sharply and strongly increase in comparison with the uniform vessel ones. (Int J Artif Organs 1998; 21: 114–8)