Polar relaxation by dynein-mediated removal of cortical myosin II

Nearly 6 decades ago, Lewis Wolpert proposed the relaxation of the polar cell cortex by the radial arrays of astral microtubules as a mechanism for cleavage furrow induction (White and Borisy, 1983; Wolpert, 1960). While this mechanism has remained controversial (Rappaport, 1996), recent work has provided evidence for polar relaxation by astral microtubules (Chen et al., 2008; Dechant and Glotzer, 2003; Foe and Dassow, 2008; Murthy and Wadsworth, 2008; Werner et al., 2007), although its molecular mechanisms remain elusive. Here, using C. elegans embryos, we show that polar relaxation is achieved through dynein-mediated removal of myosin II from the polar cortexes. Mutants that position centrosomes closer to the polar cortex accelerated furrow induction whereas suppression of dynein activity delayed furrowing. We provide evidence that dynein-mediated removal of myosin II from the polar cortexes triggers cortical flow towards the cell equator, which induces the assembly of the actomyosin contractile ring. These studies for the first time provide a molecular basis for the aster-dependent polar relaxation, which works in parallel with equatorial stimulation to promote robust cytokinesis

An Innovation Platform for Diffusing Public Health Practices across a Global Network

Hospitals and health systems in high-income countries (HIC) develop the capacities of peer healthcare organizations around the world by diffusing clinical, quality, and public health improvement practices in lower and middle-income countries (LMIC). In turn, these HIC healthcare institutions are exposed to innovative approaches developed and used by global communities to advance care despite resource constraints in the LMIC contexts. Attention has been growing in recent years to the potential these innovations can have to improve care delivery, lower costs, and drive quality within resource constrained communities in HIC. Often referred to as ‘reverse innovations,’ the identification, adaptation, and diffusion of these practices face challenges in uptake related to limited evidence, perceptions of poor quality or irrelevance, and a complicated regulatory and policy environment. This paper suggests the development of a knowledge platform to support diffusion of innovative health practices along a global community continuum and illustrates its potential use

AutoRL Hyperparameter Landscapes

Although Reinforcement Learning (RL) has shown to be capable of producing impressive results, its use is limited by the impact of its hyperparameters on performance. This often makes it difficult to achieve good results in practice. Automated RL (AutoRL) addresses this difficulty, yet little is known about the dynamics of the hyperparameter landscapes that hyperparameter optimization (HPO) methods traverse in search of optimal configurations. In view of existing AutoRL approaches dynamically adjusting hyperparameter configurations, we propose an approach to build and analyze these hyperparameter landscapes not just for one point in time but at multiple points in time throughout training. Addressing an important open question on the legitimacy of such dynamic AutoRL approaches, we provide thorough empirical evidence that the hyperparameter landscapes strongly vary over time across representative algorithms from RL literature (DQN and SAC) in different kinds of environments (Cartpole and Hopper). This supports the theory that hyperparameters should be dynamically adjusted during training and shows the potential for more insights on AutoRL problems that can be gained through landscape analyses

Declarative Algorithms in Datalog with Extrema: Their Formal Semantics Simplified

Recent advances are making possible the use of aggregates in recursive queries thus enabling the declarative expression classic algorithms and their efficient and scalable implementation. These advances rely the notion of Pre-Mappability (PreM) of constraints that, along with the seminaive-fixpoint operational semantics, guarantees formal non-monotonic semantics for recursive programs with min and max constraints. In this extended abstract, we introduce basic templates to simplify and automate task of proving PreM

The Language of End-of-Life Decision Making: A Simulation Study

Background: Framing is known to influence decision making. Objective: The study objective was to describe language used by physicians when discussing treatment options with a critically and terminally ill elder. Methods: High-fidelity simulation was used, involving an elder with end-stage cancer and life-threatening hypoxia, followed by a debriefing interview. Subjects were hospitalist, emergency medicine, and critical care physicians from three academic medical centers. Measures were observation of encounters in real time followed by content analysis of simulation and debriefing interview transcripts. During the simulation we identified the first mention (?broaching?) of principal treatment options?intubation and mechanical ventilation (life-sustaining treatment [LST]) and palliation in anticipation of death (palliation)?and used constant comparative methods to identify language used. We identified physician opinions about the use of LST in this clinical context during the debriefing interviews, and compared language used with opinions. Results: Among 114 physician subjects, 106 discussed LST, 86 discussed palliation, and 84 discussed both. We identified five frames: will (decided), must (necessary), should (convention), could (option), and ask (elicitation of preferences). Physicians broached LST differently than palliation (p<0.01), most commonly framing LST as necessary (53%), while framing palliation as optional (49%). Among physicians who framed LST as imperative (will or must), 16 (30%) felt intubation would be inappropriate in this clinical situation. Conclusions: In this high-fidelity simulation experiment involving a critically and terminally ill elder, the majority of physicians framed the available options in ways implying LST was the expected or preferred choice. Framing of treatment options could influence ultimate treatment decisions.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140120/1/jpm.2015.0089.pd

Attenuation of corneal myofibroblast development through nanoparticle-mediated soluble transforming growth factor-β type II receptor (sTGFβRII) gene transfer

Purpose: To explore (i) the potential of polyethylenimine (PEI)-DNA nanoparticles as a vector for delivering genes into human corneal fibroblasts, and (ii) whether the nanoparticle-mediated soluble extracellular domain of the transforming growth factor–β type II receptor (sTGFβRII) gene therapy could be used to reduce myofibroblasts and fibrosis in the cornea using an in vitro model. Methods: PEI-DNA nanoparticles were prepared at a nitrogen-to-phosphate ratio of 30 by mixing linear PEI and a plasmid encoding sTGFβRII conjugated to the fragment crystallizable (Fc) portion of human immunoglobulin. The PEI-DNA polyplex formation was confirmed through gel retardation assay. Human corneal fibroblasts (HCFs) were generated from donor corneas; myofibroblasts and fibrosis were induced with TGFβ1 (1 ng/ml) stimulation employing serum-free conditions. The sTGFβRII conjugated to the Fc portion of human immunoglobulin gene was introduced into HCF using either PEI-DNA nanoparticles or Lipofectamine. Suitable negative and positive controls to compare selected nanoparticle and therapeutic gene efficiency were included. Delivered gene copies and mRNA (mRNA) expression were quantified with real-time quantitative PCR (qPCR) and protein with enzyme-linked immunosorbent assay (ELISA). The changes in fibrosis parameters were quantified by measuring fibrosis marker α-smooth muscle actin (SMA) mRNA and protein levels with qPCR, immunostaining, and immunoblotting. Cytotoxicity was determined using cellular viability, proliferation, and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. Results: PEI readily bound to plasmids to form nanoparticular polyplexes and exhibited much greater transfection efficiency (p<0.01) than the commercial reagent Lipofectamine. The PEI-DNA-treated cultures showed 4.5×10[superscript 4] plasmid copies/µg DNA in real-time qPCR and 7,030±87 pg/ml sTGFβRII protein in ELISA analyses, whereas Lipofectamine-transfected cultures demonstrated 1.9×10[superscript 3] gene copies/µg DNA and 1,640±100 pg/ml sTGFβRII protein during these assays. The PEI-mediated sTGFβRII delivery remarkably attenuated TGFβ1-induced transdifferentiation of corneal fibroblasts to myofibroblasts in cultures, as indicated by threefold lower levels of SMA mRNA (p<0.01) and significant inhibition of SMA protein (up to 96±3%; p<0.001 compared to no-gene-delivered cultures) in immunocytochemical staining and immunoblotting. The nanoparticle-mediated delivery of sTGFβRII showed significantly better antifibrotic effects than the Lipofectamine under similar experimental conditions. However, the inhibition of myofibroblast in HCF cultures by sTGFβRII overexpression by either method was significantly higher than the naked vector transfection. Furthermore, PEI- or Lipofectamine-mediated sTGFβRII delivery into HCF did not alter cellular proliferation or phenotype at 12 and 24 h post-treatment. Nanoparticles treated with HCF showed more than 90% cellular viability and very low cell death (2–6 TUNEL+ cells), suggesting that the tested doses of PEI-nanoparticles do not induce significant cell death. Conclusions: This study demonstrated that PEI-DNA nanoparticles are an attractive vector for the development of nonviral corneal gene therapy approaches and that the sTGFβRII gene delivery into keratocytes could be used to control corneal fibrosis in vivo.National Institutes of Health (U.S.) (RO1EB000244

Prediction Criteria for Successful Weaning from Respiratory Support: Statistical and Connectionist Analyses

Objective: To develop predictive criteria for successful weaning from mechanical assistance to ventilation based upon simple clinical tests using discriminant analyses and neural network systems. Design: Retrospective development of predictive criteria and subsequent prospective testing of the same. Setting: Medical intensive care unit of a 300-bed teaching veterans administration hospital. Patients: Twenty-five ventilator-dependent elderly patients with acute respiratory failure. Interventions: Routine measurements of negative inspiratory force (NIF), tidal values (VT), minute ventilation (VE), respiratory rate (RR), vital capacity (FVC), and maximum voluntary ventilation (MVV), followed by weaning trial. Success or failure in 21 efforts analyzed by linear and quadratic discriminant model and neural network formulas to develop prediction criteria. The criteria so developed were tested for predictive power prospectively in nine trials in six patients. The analyses thus obtained predicted the success or failure of weaning within 9O-lOO% accuracy. Conclusion: Use of quadratic discriminant and neural network analyses could be useful in developing accurate predictive criteria for successful weaning based upon simple bedside measurements