B-arrestin-2 Signaling Is Important to Preserve Cardiac Function During Aging

Experiments reported here tested the hypothesis that β-arrestin-2 is an important element in the preservation of cardiac function during aging. We tested this hypothesis by aging β-arrestin-2 knock-out (KO) mice, and wild-type equivalent (WT) to 12–16months. We developed the rationale for these experiments on the basis that angiotensin II (ang II) signaling at ang II receptor type 1 (AT1R), which is a G-protein coupled receptor (GPCR) promotes both G-protein signaling as well as β-arrestin-2 signaling. β-arrestin-2 participates in GPCR desensitization, internalization, but also acts as a scaffold for adaptive signal transduction that may occur independently or in parallel to G-protein signaling. We have previously reported that biased ligands acting at the AT1R promote β-arrestin-2 signaling increasing cardiac contractility and reducing maladaptations in a mouse model of dilated cardiomyopathy. Although there is evidence that ang II induces maladaptive senescence in the cardiovascular system, a role for β-arrestin-2 signaling has not been studied in aging. By echocardiography, we found that compared to controls aged KO mice exhibited enlarged left atria and left ventricular diameters as well as depressed contractility parameters with preserved ejection fraction. Aged KO also exhibited depressed relaxation parameters when compared to WT controls at the same age. Moreover, cardiac dysfunction in aged KO mice was correlated with alterations in the phosphorylation of myofilament proteins, such as cardiac myosin binding protein-C, and myosin regulatory light chain. Our evidence provides novel insights into a role for β-arrestin-2 as an important signaling mechanism that preserves cardiac function during aging.

Estimating Safety Impacts of Adaptive Signal Control Technology Using a Full Bayesian Approach

Adaptive signal control technology (ASCT) is a traffic management strategy that optimizes signal timing based on real-time traffic demand. Although the primary intent of ASCT is to improve the operational performance of signalized intersections, the technology may also have substantial safety benefits. This study explored the potential safety benefits of the ASCT strategy deployed at signalized intersections in Florida, U.S. An observational before-after full Bayes (FB) approach with a comparison group was adopted to develop crash modification factors (CMFs) for total crashes, rear-end crashes, and specific crash severity levels (fatal plus injury [FI], and property damage only [PDO] crashes). The analysis was based on 20 intersections equipped with ASCT and their corresponding 40 comparison intersections without ASCT. The ASCT deployment was found to significantly reduce total crashes by 7.8% (CMF = 0.922), rear-end crashes by 8.7% (CMF = 0.913), and PDO crashes by 8.1% (CMF = 0.919). The 8.6% reduction in FI crashes (CMF = 0.914) was not significant at a 90% Bayesian credible interval. These findings provide researchers and practitioners with an effective means to quantify the safety benefits of the ASCT strategy and conduct economic appraisals of ASCT deployments.

Assessment of Operational Effectiveness of SynchroGreen Adaptive Signal Control System in South Carolina

An adaptive signal control system (ASCS) can adjust signal timings in real time based on traffic demands. The operational benefits of ASCS vary depending on the type of ASCS, corridor characteristics, and geographical area. This paper evaluates the operational performance of 11 ASCS corridors located throughout South Carolina. These corridors are operated using SynchroGreen, one of several types of ASCS, developed by TrafficWare. Based on the operational analysis, it is found that when SynchroGreen is operational, it reduces the travel time on the corridor by an average of 6.4% and improves travel time reliability by an average of 31.4% compared with when the conventional traffic signal control system (e.g., pre-timed and actuated signal control) is operational. SynchroGreen reduces travel time on a corridor on average 61% of the time during a day and on average 77% of the time during peak periods. Additionally, SynchroGreen improves travel time reliability on average 53% of the time during a day and on average 52% of the time during peak periods. The operational effectiveness of SynchroGreen in reducing travel time and improving travel time reliability is consistent in both directions on an hourly basis for eight corridors and five corridors, respectively. Lastly, SynchroGreen is found to produce greater operational benefits by reducing travel time if the average speed of a corridor is lower than or equal to 35 mph and the number of signals on a corridor is more than 10.