Analyses of the yeast Rad51 recombinase A265V mutant reveal different in vivo roles of Swi2-like factors

The Saccharomyces cerevisiae Swi2-like factors Rad54 and Rdh54 play multifaceted roles in homologous recombination via their DNA translocase activity. Aside from promoting Rad51-mediated DNA strand invasion of a partner chromatid, Rad54 and Rdh54 can remove Rad51 from duplex DNA for intracellular recycling. Although the in vitro properties of the two proteins are similar, differences between the phenotypes of the null allele mutants suggest that they play different roles in vivo. Through the isolation of a novel RAD51 allele encoding a protein with reduced affinity for DNA, we provide evidence that Rad54 and Rdh54 have different in vivo interactions with Rad51. The mutant Rad51 forms a complex on duplex DNA that is more susceptible to dissociation by Rdh54. This Rad51 variant distinguishes the in vivo functions of Rad54 and Rdh54, leading to the conclusion that two translocases remove Rad51 from different substrates in vivo. Additionally, we show that a third Swi2-like factor, Uls1, contributes toward Rad51 clearance from chromatin in the absence of Rad54 and Rdh54, and define a hierarchy of action of the Swi2-like translocases for chromosome damage repair

2018 Research & Innovation Day Program

A one day showcase of applied research, social innovation, scholarship projects and activities.https://first.fanshawec.ca/cri_cripublications/1005/thumbnail.jp

Biopharmaceutical considerations in paediatrics with a view to the evaluation of orally administered drug products – a PEARRL review.

Objectives: In this review, the current biopharmaceutical approaches for evaluation of oral formulation performance in paediatrics are discussed. Key findings: The paediatric gastrointestinal (GI) tract undergoes numerous morphological and physiological changes throughout its development and growth. Some physiological parameters are yet to be investigated, limiting the use of the existing in vitro biopharmaceutical tools to predict the in vivo performance of paediatric formulations. Meals and frequencies of their administration evolve during childhood and affect oral drug absorption. Furthermore, the establishment of a paediatric Biopharmaceutics Classification System (pBCS), based on the adult Biopharmaceutics Classification System (BCS), requires criteria adjustments. The usefulness of computational simulation and modeling for extrapolation of adult data to paediatrics has been confirmed as a tool for predicting drug formulation performance. Despite the great number of successful physiologically based pharmacokinetic models to simulate drug disposition, the simulation of drug absorption from the GI tract is a complicating issue in paediatric populations. Summary: The biopharmaceutics tools for investigation of oral drug absorption in paediatrics need further development, refinement and validation. A combination of in vitro and in silico methods could compensate for the uncertainties accompanying each method on its own

Aspirin and clonidine in non-cardiac surgery: acute kidney injury substudy protocol of the Perioperative Ischaemic Evaluation (POISE) 2 randomised controlled trial

IntroductionPerioperative Ischaemic Evaluation-2 (POISE-2) is an international 2×2 factorial randomised controlled trial of low-dose aspirin versus placebo and low-dose clonidine versus placebo in patients who undergo non-cardiac surgery. Perioperative aspirin (and possibly clonidine) may reduce the risk of postoperative acute kidney injury (AKI).Methods and analysisAfter receipt of grant funding, serial postoperative serum creatinine measurements began to be recorded in consecutive patients enrolled at substudy participating centres. With respect to the study schedule, the last of over 6500 substudy patients from 82 centres in 21 countries were randomised in December 2013. The authors will use logistic regression to estimate the adjusted OR of AKI following surgery (compared with the preoperative serum creatinine value, a postoperative increase ≥26.5 μmol/L in the 2 days following surgery or an increase of ≥50% in the 7 days following surgery) comparing each intervention to placebo, and will report the adjusted relative risk reduction. Alternate definitions of AKI will also be considered, as will the outcome of AKI in subgroups defined by the presence of preoperative chronic kidney disease and preoperative chronic aspirin use. At the time of randomisation, a subpopulation agreed to a single measurement of serum creatinine between 3 and 12 months after surgery, and the authors will examine intervention effects on this outcome.Ethics and disseminationThe authors were competitively awarded a grant from the Canadian Institutes of Health Research for this POISE-2 AKI substudy. Ethics approval was obtained for additional kidney data collection in consecutive patients enrolled at participating centres, which first began for patients enrolled after January 2011. In patients who provided consent, the remaining longer term serum creatinine data will be collected throughout 2014. The results of this study will be reported no later than 2015.Clinical Trial Registration NumberNCT01082874

Simulation of Bacterial Motion in Sterically Complex Environments

Project files are comprised of 1 page pdf and presentation recording in mp4 format.Many species of bacteria navigate complex and heterogeneous environments to search for metabolic resources and avoid toxins. Common among such complexities is steric structure – solid objects whose surface curvature alters bacterial trajectories upon impact. In previous experiments, we characterized scattering of bacteria from vertical pillars of different radii, which provides the basis for understanding how impact with a solid, curved object alters bacterial motion. However, it remains poorly understood how multiple interactions affect bacterial trajectories and whether distinct object curvatures or length-scales of separation between steric objects have qualitatively distinct effects on bacterial motion. We address this question using agent-based computer simulations of cells moving within 2D environments. Each environment presents simulated cells with steric objects (i.e. circular pillars) of radius 8.3µm and a controlled separation between pillars of µm, where is a parameter of the simulation. Cells then diffuse through this environment, scattering with pillars they encounter. By measuring the mean squared displacement (MSD) of the ensemble of trajectories in time for different values of , we are able to quantify precisely how the length-scales of separation between steric structures affect bacterial trajectories. These MSD measurements will also allow us to compare our results with future experimental work. Ultimately, we hope that our results may contribute to a more realistic model of the behavior of motile cells in natural environments such as soils or a mammalian gut.CURE SUR