NLT-modules volgen in een academische omgeving

Het onderwijzen van een NLT-module vereist gespecialiseerde achtergrondkennis. Menig VO-docent moet er eerst goed voor gaan zitten om een nieuwe module op school te geven. Het BètaPlus programma aan de JCU biedt een extra voorbereidingsmogelijkheid. VO-docenten worden betrokken in NLT-onderwijs dat door een vakspecialist in een academische omgeving wordt gegeven. De leerlingen kunnen zich oriënteren op vervolgstudies: ze maken kennis met universitaire werkwijzen en voorzieningen

Coronary structure and perfusion in health and disease

Blood flow is distributed through the heart muscle via a system of vessels forming the coronary circulation. The perfusion of the myocardium can be hampered by atherosclerosis creating localized obstructions in the epicardial vessels or by microvascular disease. In early stages of the disease, these impediments to blood flow are offset by dilation of the resistance vessels, which normally compensates for a decrease in perfusion pressure or increased metabolism. However, this dilatory reserve can become exhausted, which in general occurs first at the deeper layers of the heart wall where intramural vessels are subjected to compressive forces related to heart contraction. In the catheterization laboratory, guide wires of 0.33 mm diameter are available that are equipped with a pressure and flow velocity sensor at the tip, which can be positioned distal to the stenosis. These signals provide information about the impediment of the stenosis on coronary flow and allow for the evaluation of the status of the microcirculation. However, the interpretation of these signals is strongly model-dependent and therefore it is of paramount importance to develop realistic models reflecting the anatomy and unique physiology of the coronary circulatio

Vascular fluorescence casting and imaging cryomicrotomy for computerized three-dimensional renal arterial reconstruction

OBJECTIVES To assess the combined use of a casting technique, cryomicrotomy imaging, and three-dimensional (3D) computer analysis as a method for visualizing and reconstructing the arterial vascular tree in a porcine renal model. MATERIAL AND METHODS The arterial branches of two porcine kidneys were filled with a fluorescent cast, after which they were cut into slices of 50 mu m in an imaging cryomicrotome. From each section, digital images of the cutting plane of the sample were taken and stored in the computer, after which stacks of images were rendered in 3D. RESULTS A 3D computerized reconstruction of the arterial vascular tree was constructed and showed the complete arterial anatomy up to arterioles of 50 mu m. CONCLUSION With visualization by fluorescence imaging cryomicrotomy, the anatomical and 3D reconstruction of the renal arterial blood supply in a pig kidney is possible up to a resolution of 50 mu

Porcine coronary collateral formation in the absence of a pressure gradient remote of the ischemic border zone

In the current paradigm on coronary collateral development, it is assumed that these vessels develop consequentially from increased fluid shear stress (FSS) through preexisting collateral arteries. The increased FSS follows from an increase in pressure gradient between the region at risk and well-perfused surroundings. The objective of this study was to test the hypothesis that, in the heart, collateral connections can form in the absence of an increased FFS and consequentially at any depth and region within the ventricular wall. In Yorkshire pigs, gradual left circumflex coronary artery occlusion was obtained over 6 wk by an ameroid constrictor, whereas the control group underwent a sham operation. Hearts were harvested and subsequently processed in an imaging cryomicrotome, resulting in 40-μm voxel resolution three-dimensional reconstructions of the intramural vascular vessels. Dedicated software segmented the intramural vessels and all continuous vascular pathways containing a collateral connection. In the ameroid group, 192 collaterals, 22-1,049 μm in diameter, were detected with 62% within the subendocardium. Sixty percent of collaterals bridged from the left anterior descending artery to left circumflex coronary artery. A novel result is that 25% (n = 48) of smaller-radius collaterals (P = 0.047) connected with both origin and terminus in the nontarget area where perfusion was assumed uncompromised. In the porcine heart, collateral vessels develop not only in ischemic border zones with increased FSS but also away from such border zones where increased FSS is unlikely. The majority of collaterals were located at the subendocardium, corresponding to the region with highest prevalence for ischemi

Organization and collateralization of a subendocardial plexus in end-stage human heart failure

van den Wijngaard JP, van Horssen P, ter Wee R, Coronel R, de Bakker JM, de Jonge N, Siebes M, Spaan JA. Organization and collateralization of a subendocardial plexus in end-stage human heart failure. Am J Physiol Heart Circ Physiol 298: H158-H162, 2010. First published October 23, 2009; doi:10.1152/ajpheart.00654.2009.-In the failing myocardium a subendocardial plexus can develop. Detection of the presence or function, however, of such a plexus does not form part of the present diagnostic spectrum for heart failure. This may now change as new methods for high-resolution imaging of myocardial perfusion distribution are being developed. A severely hypertrophic heart was harvested during transplantation and analyzed for morphology of the intramural coronary arterial vasculature. The heart only had one coronary ostium, and the main branches of the coronary artery were cannulated. A fluorescent casting material was infused that was allowed to harden under physiological pressure. The entire heart was frozen and placed in a novel imaging cryomicrotome and sequentially cut in 25-mu m slices. High-resolution images of each cutting plane were acquired, allowing a detailed three-dimensional reconstruction of the arterial vasculature. The epicardial layer of the free wall demonstrated a normal vasculature with penetrating branching arteries. The endocardial layer and the septum revealed a highly interconnected vascular plexus with large vessels oriented parallel to the apicobasal axis. An extensive endocardial network with collaterals was detected, forming connections between the main epicardial branches. We conclude that an outward remodeling of transmural vessels did not prevent the generation and growth of subendocardial conduit arteries. The orientation and vascular volume in the plexus provides an opportunity for detection by novel techniques of MRI contrast imaging currently developed. Knowledge of the effect on perfusion studies is required to prevent a misinterpretation of subendocardial perfusion images in heart failure

A closer look at the trajectory of physical functioning in chronic hemodialysis

Background: in chronic hemodialysis, physical functioning (PF) is known to be poor. We set out to assess to what extent chronic dialysis patients are able to maintain a good physical condition over time and what the influence of age is on the trajectory of PF.Methods: we used data form 714 prevalent hemodialysis patients, enrolled in the CONvective TRAnsport STudy (CONTRAST). The PF subscale of the KDQOL SF-36 was assessed at baseline (n = 679) and during 2 years of follow-up (n = 298). Baseline PF score (0-100) was categorized into tertiles (good, intermediate and low). Change of PF of ≥ 5 points was considered clinically relevant. A regression model was applied to assess factors related to 'decline of PF (≥5 points)/low PF (0-33) at follow-up'.Results: during follow-up, only 15.3 % (1 out of 6) of patients succeeded in maintaining a good physical condition, the remainder deteriorated or died. Of the older patients (≥75) only 3.6% remained in a good physical condition. Factors related to decline/low PF were increasing age (odds ratio [OR] = 1.96 [95% CI: 1.03-3.72] for 65-74 years and OR = 2.38 [95%CI: 1.17-4.84] for ≥75 years compared to <65 years) and albumin (OR = 1.10 [95%CI: 1.01-1.18] per g/L decrease).Conclusion: very few hemodialysis patients maintain a good physical condition over a 2-year time span. Especially in older patients, physical performance is poor and decline is faster than in the healthy population.These findings should be taken into account when considering dialysis in older patients and more emphasis should be placed to attempts for improving physical condition