Isomerization of (Z)-asarone to (E)-asarone from Piper marginatum leaves by the Quadrus u-lucida larvae

Despite being rich in phenylpropanoids with insecticidal activity, Piper marginatum leaves are frequently attacked by the larvae of the Quadrus u-lucida moth. GC/MS analysis indicated isomerization of phenylpropanoid (Z)-asarone to (E)-asarone from the leaves by larvae. The phenylpropanoids (Z)-asarone, dillapiole and (E)-asarone were identified in concentrations of 48.01, 24.02 and 36.07 μg/mg, respectively. Only the phenylpropanoid (E)-asarone was found in the larval tissues and regurgitant material in a concentration of 15.52 and 2.53 μg/mg, respectively. Since (Z)-asarone has been reported to be more toxic than (E)-asarone, the isomerization of (Z)-asarone may be associated with the detoxification mechanism of larvae.     

Dynamic state-dependent modelling predicts optimal usage patterns of responsive defences

Chemical defences against predation often involve responses to specific predation events where the prey expels fluids, such as haemolymph or gut contents, which are aversive to the predator. The common link is that each predation attempt that is averted results in an energetic cost and a reduction in the chemical defences of the prey, which might leave the prey vulnerable if the next predation attempt occurs soon afterwards. Since prey appear to be able to control the magnitude of their responses, we should expect them to trade-off the need to repel the current threat against the need to preserve defences against future threats and conserve energy for other essential activities. Here we use dynamic state-dependent models to predict optimal strategies of defence deployment in the juvenile stage of an animal that has to survive to maturation. We explore the importance of resource level, predator density, and the costs of making defences on the magnitude of the responses and optimal age and size at maturation. We predict the patterns of investment and the magnitude of the deployment of defences to potentially multiple attacks over the juvenile period, and show that responses should be smaller when the costs of defences and/or predation risk are higher. The model enables us to predict that animals in which defences benefit the adult stage will employ different strategies than those that do not use the same defences as adults, and thereby experience a smaller reduction in body size as a result of repeated attacks. We also explore the effect of the importance of adult size, and find that the sex and mating system of the prey should also affect defensive strategies. Our work provides the first predictive theory of the adaptive use of responsive defences across taxa.     

Utility and feasibility of the CartoUnivu™ system for atrial flutter ablation in patients with mechanical prosthetic valves

Ablation of macroreentrant atrial tachycardia in patients with mechanical prosthetic valves represents a challenge for electrophysiologists, because of the complexity of the procedure and the potential complications. Moreover, the need for fluoroscopy in this type of procedure is greater, due to the risk of interference between the prosthetic valve and the ablation or mapping catheter. We present two cases of patients with mechanical prosthetic valves and atrial flutter who underwent successful ablation with no complications using the CartoUnivu? tool, which integrates the electroanatomical map and the fluoroscopy image.     

Modeling mitral valve stenosis: A parametric study on the stenosis severity level

New computational techniques providing more accurate representation of human heart pathologies could help uncovering relevant physical phenomena and improve the outcome of medical therapies. In this framework, the present work describes an efficient computational model for the evaluation of the ventricular flow alteration in presence of mitral valve stenosis. The model is based on the direct numerical simulation of the Navier–Stokes equations two-way coupled with a structural solver for the left ventricle and mitral valve dynamics. The presence of mitral valve stenosis is mimicked by a single-parameter constraint acting on the kinematics of the mitral leaflets.Four different degrees of mitral valve stenosis are considered focusing on the hemodynamic alterations occurring in pathologic conditions. The mitral jet, generated during diastole, is seen to shrink and strengthen when the stenosis gets more severe. As a consequence, the kinetic energy of the flow, the tissues shear stresses, the transvalvular pressure drop and mitral regurgitation increase. It results that, as the stenosis severity level increases, the geometric and effective orifice areas decrease up to 50% with respect the normal case due to the reduced leaflets mobility and stronger blood acceleration during the diastolic phase. The modified intraventricular hemodynamics is also related to a stronger pressure gradient that, for severe stenosis, can be more than ten times larger than the healthy valve case. These computational results are fully consistent with the available clinical literature and open the way to the virtual assessment of surgical procedures and to the evaluation of prosthetic devices.