DYNAMIC BEHAVIOR ANALYSIS OF THE GLOMERULO-TUBULAR BALANCE MEDIATED BY THE EFFERENT BLOOD VISCOSITY

International audienceA mathematical model of the dynamics of a single nephron function relating glomerulo-tubular balance, tubule-glomerular feedback, and peritubular blood viscosity is developed. Based upon experimental data, the model shows that complex behaviors of the nephron can be modulated by changes in the efferent arteriole blood viscosity. The main hypothesis is that the reabsorbed mass flow is modulated by the hematocrit of the efferent arteriole, in addition to the Starling forces. From a mathematical perspective, these behaviors can be explained by a bifurcation diagram analysis where the efferent blood viscosity is taken as the bifurcation parameter. This analytical description allows to predict changes in proximal convoluted tubule reabsorption, following changes in peritubular capillary viscosity generated by periodic changes in the glomerular filtration rate. Thus, the model links the tubule-glomerular feedback with the glomerular tubular balance

Post-graduate teaching in microsurgery using a combination of alternative non-animal and in vivo methods

Over recent years alternative, non-animal methods have been developed for use in microsurgical training  courses, for the training of suture techniques, dexterity and hand-eye coordination. Nevertheless, it is still  hard to imagine that alternative methods will be able to replace in vivo teaching completely, because  properties of biological tissue are different from those of latex or other artificial materials. Also the  dynamics of biological processes, such as a pulsating bloodstream, are difficult to simulate in alternative  models. However, the number of animals used in microsurgical training courses can be limited by combining  non-animal methods with in vivo training. Moreover, individual techniques can be improved greatly  by using non-animal methods. In a five-day introductory course in microsurgical and experimental  techniques at the Biomedical Laboratory, University of Southern Denmark, we have limited the average  number of animals to one rat per day per participant, by using alternative non-animal methods extensively  on the first course day. Nearly all participants were able to produce a successful end-to-end anastomosis  of the femoral artery during the second or third day of the course. The alternative methods used included  a training device for microsurgical anastomosis and the MD PVC-Rat, an artificial rat with life-size  latex abdominal vessels.