Abstract 186: Novel Secondary Multifocal No-Reflow Phenomenon Associated with Activated Leukocyte-induced Microcirculatory Obstruction

Background: No-reflow may occur early after reperfusion of ischemic tissues. In a rat model of hepatic ischemia and reperfusion (IR), delayed multifocal no-reflow was observed hours after initial restoration of circulation. We herein sought to characterize this novel phenomenon and investigate its underlying pathophysiological mechanism.

Methods: Hepatic IR of male wistar rats was induced by clamping hepatic artery and portal vein for 60 min, followed by release of the clamp for reperfusion. Intravital optical microscopy was employed to image microcirculation (FITC-dextran), cellular hypoxia-reoxygenation (autofluorescence of mitochondrial flavoproteins), extracellular DNA (propidium iodide, PI) and the interactions among leukocytes, platelets and endothelium.

Results: Multifocal no-reflow was observed in vivo at the early stage of reperfusion revealed by no recovery of microcirculation and cellular autofluorescence. Interestingly, such no-reflow phenomenon recurred sporadically and remittently about 3 h after initial restoration of circulation. This novel secondary no-reflow was associated with recurrent microcirculatory obstruction caused by stagnation of blood cells. Such obstruction was triggered by activated leukocytes as evidenced by their adhesion with platelets and migration along endothelium. Extracellular DNA near the obstructed sinusoids indicates involvement of neutrophil-extracellular traps (NET).

Conclusions: Secondary multifocal no-reflow may occur hours after initial reperfusion. With activated leukocytes and NET playing key roles, the pathogenic mechanism differs distinctly from that of immediate no-reflow and may implicate alternative targets for therapeutic interventions.

Living Liquid: Design and Evaluation of an Exploratory Visualization Tool for Museum Visitors

Interactive visualizations can allow science museum visitors to explore new worlds by seeing and interacting with scientific data. However, designing interactive visualizations for informal learning environments, such as museums, presents several challenges. First, visualizations must engage visitors on a personal level. Second, visitors often lack the background to interpret visualizations of scientific data. Third, visitors have very limited time at individual exhibits in museums. This paper examines these design considerations through the iterative development and evaluation of an interactive exhibit as a visualization tool that gives museumgoers access to scientific data generated and used by researchers. The exhibit prototype, Living Liquid, encourages visitors to ask and answer their own questions while exploring the time-varying global distribution of simulated marine microbes using a touchscreen interface. Iterative development proceeded through three rounds of formative evaluations using think-aloud protocols and interviews, each round informing a key visualization design decision: (1) what to visualize to initiate inquiry, (2) how to link data at the microscopic scale to global patterns, and (3) how to include additional data that allows visitors to pursue their own questions. Data from visitor evaluations suggests that, when designing visualizations for public audiences, one should (1) avoid distracting visitors from data that they should explore, (2) incorporate background information into the visualization, (3) favor understandability over scientific accuracy, and (4) layer data accessibility to structure inquiry. Lessons learned from this case study add to our growing understanding of how to use visualizations to actively engage learners with scientific data.

Corticosteroid effects on blood gene expression in Duchenne muscular dystrophy

Though Deflazacort and prednisone improve clinical endpoints in Duchenne muscular dystrophy (DMD) patients, Deflazacort produces fewer side effects. As mechanisms of improvement and side effect differences remain unknown, we evaluated effects of corticosteroid administration on gene expression in blood of DMD patients. Whole blood was obtained from 14 children and adolescents with DMD treated with corticosteroids (DMD-STEROID) and 20 DMD children and adolescents naïve to corticosteroids (DMD). The DMD-STEROID group was further subdivided into Deflazacort and prednisone groups. Affymetrix U133 Plus 2.0 expression microarrays were used to evaluate mRNA expression. Expression of 524 probes changed with corticosteroids, including genes in iron trafficking and the chondroitin sulfate biosynthesis pathway. Deflazacort compared with prednisone yielded 508 regulated probes, including many involved in adipose metabolism. These genes and pathways help explain mechanisms of efficacy and side effects of corticosteroids, and could provide new treatment targets for DMD and other neuromuscular disorders.