Groepering in de eerste fase van het voortgezet onderwijs:Heterogeen gooit hoge ogen

Heterogeen of homogeen groeperen. Wat is dat? Wie doet wat, waarom, en hoe? Vooral nu in het advies van de Wetenschappelijke Raad voor het Regeringsbeleid (WRR) wordt voorgesteld de invulling van de groeperingsstructuur aan de scholen zelf over te laten, is het antwoord op die vraag interessant. Vier onderzoekers van het RION instituut voor onderwijsonderzoek in Groningen, voerden een voorstudie uit, die de basis van een later onderzoek moet vormen. Twee van hen geven hieronder enige van de resultaten weer

Changes in Red Blood Cell Properties and Platelet Function during Extracorporeal Membrane Oxygenation

Extracorporeal membrane oxygenation (ECMO) is associated with frequent hemorrhagic and thromboembolic complications. The multiple effects of ECMO include inflammatory response on contact with the circuit; hemolysis acquired von Willebrand syndrome likely affects the function of red blood cells (RBC) and platelets. The aim of this prospective observational study was to analyze RBC aggregation and elongation (deformability) and platelet aggregation in the first week of ECMO. Sixteen patients were included. Blood samples were taken prior to initiation of ECMO and on days 1, 2, 3, 5, and 7. RBC aggregation and elongation were analyzed using the laser-assisted optical rotational red cell analyzer (Lorrca). Upstroke, top, and amplitude as indices of aggregation showed significant time effects. RBC elongation was not affected at low shear stress. At high shear stress there was an increase in the elongation index at day 2 (p = 0.004), followed by a decrease. Platelet function was analyzed using multiple electrode aggregometry (Multiplate®). In pairwise comparison in the days 1–7 to the value prior to ECMO there was no significant difference in platelet aggregation by any of the three agonists (ADP p = 0.61; TRAP p = 0.77; Ristocetin p = 0.25). This implies that the rheology of RBCs seemed to be more affected by ECMO than platelets. Especially the red blood cell deformability continues to decline at higher shear stress

Tethered imidazole mediated duplex stabilization and its potential for aptamer stabilization

Previous investigations of the impact of an imidazole-tethered thymidine in synthetic DNA duplexes, monitored using UV and NMR spectroscopy, revealed a base context dependent increase in thermal stability of these duplexes and a striking correlation with the imidazolium pK(a). Unrestrained molecular dynamics (MD) simulations demonstrated the existence of a hydrogen bond between the imidazolium and theHoogsteen side of a nearby guanosine which, together with electrostatic interactions, form the basis of the so-called pK(a)-motif responsible for these duplex-stabilizing and pK(a)-modulating properties. Here, the robustness and utility of this pK(a)-motif was explored by introducing multiple imidazoletethered thymidines at different positions on the same dsDNA duplex. For all constructs, sequence based expectations as to pK(a)-motif formation were supported by MD simulations and experimentally validated using NOESY. Based on the analysis of the pK(a) values and melting temperatures, guidelines are formulated to assist in the rational design of oligonucleotides modified with imidazoliumtethered thymidines for increased thermal stability that should be generally applicable, as demonstrated through a triply modified construct. In addition, a proof-of-principle study demonstrating enhanced stability of the L-argininamide binding aptamer modified with an imidazole-tethered thymidine in the presence and absence of ligand, demonstrates its potential for the design of more stable aptamers