Non-pharmacological Strategies to Suppress Triggers of Cardiac Arrhythmias by Targeting L-Type Ca2+ Channels

Sudden cardiac death is one of the major leading causes of death in the United States, affecting about 300,000 people annually on average. Cardiac arrhythmias and ventricular fibrillation can be triggered, at the cellular level, by the presence of aberrations of the cardiac action potential (AP) known as early afterdepolarizations (EADs). EADs are single or multiple voltage oscillations largely induced by the reactivation of L-type Ca2+ currents (ICa,L) during phase 2 and phase 3 of a cardiac AP. Our recent studies using dynamic clamp techniques have suggested that EADs and their arrhythmogenic consequences can be potently suppressed by subtle reduction the ICa,L current non-inactivating (pedestal) component and/or minimal changes (3-5 mV) in the voltage dependence of activation. Exploiting the modulatory effects of L-type Ca2+ channel (LTCC) auxiliary β2 subunits on the non-inactivating component of ICa,L, we sought to investigate the effects of knocking down Cavβ2 subunit expression levels in rabbit ventricular myocytes in the presence of an oxidative stress known to trigger EADs (H2O2). We hypothesized that reducing the expression level of endogenous Cavβ2 decreases the probability of EAD occurrence in cardiomyocytes exposed to H2O2. Using an adenoviral infection to deliver a short hairpin RNA (shRNA) specific for targeting Cavβ2 that inhibits its gene expression by binding to its mRNA transcripts, our results showed that myocytes expressing less Cavβ2 mRNA exhibited no EADs; whereas, the control myocytes infected with GFP alone as a control group were more susceptible to EAD occurrence in 0.6 mM H2O2. These results suggest that Cavβ2 could be a potential target for gene therapy and could give insights to other therapeutic strategies that could possibly be implemented

Non-pharmacological Strategies to Suppress Triggers of Cardiac Arrhythmias by Targeting L-Type Ca2+ Channels

Sudden cardiac death is one of the major leading causes of death in the United States, affecting about 300,000 people annually on average. Cardiac arrhythmias and ventricular fibrillation can be triggered, at the cellular level, by the presence of aberrations of the cardiac action potential (AP) known as early afterdepolarizations (EADs). EADs are single or multiple voltage oscillations largely induced by the reactivation of L-type Ca2+ currents (ICa,L) during phase 2 and phase 3 of a cardiac AP. Our recent studies using dynamic clamp techniques have suggested that EADs and their arrhythmogenic consequences can be potently suppressed by subtle reduction the ICa,L current non-inactivating (pedestal) component and/or minimal changes (3-5 mV) in the voltage dependence of activation. Exploiting the modulatory effects of L-type Ca2+ channel (LTCC) auxiliary β2 subunits on the non-inactivating component of ICa,L, we sought to investigate the effects of knocking down Cavβ2 subunit expression levels in rabbit ventricular myocytes in the presence of an oxidative stress known to trigger EADs (H2O2). We hypothesized that reducing the expression level of endogenous Cavβ2 decreases the probability of EAD occurrence in cardiomyocytes exposed to H2O2. Using an adenoviral infection to deliver a short hairpin RNA (shRNA) specific for targeting Cavβ2 that inhibits its gene expression by binding to its mRNA transcripts, our results showed that myocytes expressing less Cavβ2 mRNA exhibited no EADs; whereas, the control myocytes infected with GFP alone as a control group were more susceptible to EAD occurrence in 0.6 mM H2O2. These results suggest that Cavβ2 could be a potential target for gene therapy and could give insights to other therapeutic strategies that could possibly be implemented

Erythrocyte and plasma oxidative stress appears to be compensated in patients with sickle cell disease during a period of relative health, despite the presence of known oxidative agents

Sickle cell disease (SCD) is a monogenetic disease that results in the formation of hemoglobin S. Due to more rapid oxidation of hemoglobin S due to intracellular heme and adventitious iron in SCD, it has been thought that an inherent property of SCD red cells would be an imbalance in antioxidant defenses and oxidant production. Less deformable and fragile RBC in SCD results in intravascular hemolysis and release of free hemoglobin (PFHb) in the plasma, which might be expected to produce oxidative stress in the plasma. Thus, we aimed to characterize intracellular and vascular oxidative stress in whole blood and plasma samples from adult SCD patients and controls recruited into a large study of SCD at Children's Hospital of Los Angeles. We evaluated the cellular content of metHb and several components of the antioxidant system in RBC as well as oxidation of GSH and Prx-2 oxidation in RBC after challenge with hydroperoxides. Plasma markers included PFHb, low molecular weight protein bound heme (freed heme), hemopexin, isoprostanes, and protein carbonyls. While GSH was slightly lower in SCD RBC, protein carbonyls, NADH, NAD+ and total NADP+ + NADPH were not different. Furthermore, GSH or Prx-2 oxidation was not different after oxidative challenge in SCD vs. Control. Elevated freed heme and PFHb had a significant negative, non-linear association with hemopexin. There appeared to be a threshold effect for hemopexin (200 μg/ml), under which the freed heme rose acutely. Plasma F2-isoprostanes were not significantly elevated in SCD. Despite significant release of Hb and elevation of freed heme in SCD when hemopexin was apparently saturated, there was no clear indication of uncompensated vascular oxidative stress. This somewhat surprising result, suggests that oxidative stress is well compensated in RBCs and plasma during a period of relative health

Trial design of a dome roof for an church

The paper describes some construction solutions for a metalic dome roof of an orthodox church. The authors describe three alternative variants (with different structural diagrams) of designing its dome framework. The paper introduces ribbed ring-shaped, grid and webbed geodesic dome constructions which are aimed to be used in the same operation conditions. The researchers calculated structural design, strength, proportioning of members and weight index as well as geometrically arranged elements of each dome design structure. Then their general total economic parameters were compared