A synthetic peptide that prevents cAMP regulation in mammalian hyperpolarization-activated cyclic nucleotide-gated (HCN) channels

Binding of TRIP8b to the cyclic nucleotide binding domain (CNBD) of mammalian hyperpolarization-activated cyclic nucleotide-gated (HCN) channels prevents their regulation by cAMP. Since TRIP8b is expressed exclusively in the brain, we envisage that it can be used for orthogonal control of HCN channels beyond the central nervous system. To this end, we have identified by rational design a 40-aa long peptide (TRIP8bnano) that recapitulates affinity and gating effects of TRIP8b in HCN isoforms (hHCN1, mHCN2, rbHCN4) and in the cardiac current If in rabbit and mouse sinoatrial node cardiomyocytes. Guided by an NMR-derived structural model that identifies the key molecular interactions between TRIP8bnano and the HCN CNBD, we further designed a cell-penetrating peptide (TAT-TRIP8bnano) which successfully prevented β-adrenergic activation of mouse If leaving the stimulation of the L-type calcium current (ICaL) unaffected. TRIP8bnano represents a novel approach to selectively control HCN activation, which yields the promise of a more targeted pharmacology compared to pore blockers

Serum Albumin Is Inversely Associated With Portal Vein Thrombosis in Cirrhosis

We analyzed whether serum albumin is independently associated with portal vein thrombosis (PVT) in liver cirrhosis (LC) and if a biologic plausibility exists. This study was divided into three parts. In part 1 (retrospective analysis), 753 consecutive patients with LC with ultrasound-detected PVT were retrospectively analyzed. In part 2, 112 patients with LC and 56 matched controls were entered in the cross-sectional study. In part 3, 5 patients with cirrhosis were entered in the in vivo study and 4 healthy subjects (HSs) were entered in the in vitro study to explore if albumin may affect platelet activation by modulating oxidative stress. In the 753 patients with LC, the prevalence of PVT was 16.7%; logistic analysis showed that only age (odds ratio [OR], 1.024; P = 0.012) and serum albumin (OR, -0.422; P = 0.0001) significantly predicted patients with PVT. Analyzing the 112 patients with LC and controls, soluble clusters of differentiation (CD)40-ligand (P = 0.0238), soluble Nox2-derived peptide (sNox2-dp; P < 0.0001), and urinary excretion of isoprostanes (P = 0.0078) were higher in patients with LC. In LC, albumin was correlated with sCD4OL (Spearman's rank correlation coefficient [r(s)], -0.33; P < 0.001), sNox2-dp (r(s), -0.57; P < 0.0001), and urinary excretion of isoprostanes (r(s), -0.48; P < 0.0001) levels. The in vivo study showed a progressive decrease in platelet aggregation, sNox2-dp, and urinary 8-iso prostaglandin F2 alpha-III formation 2 hours and 3 days after albumin infusion. Finally, platelet aggregation, sNox2-dp, and isoprostane formation significantly decreased in platelets from HSs incubated with scalar concentrations of albumin. Conclusion: Low serum albumin in LC is associated with PVT, suggesting that albumin could be a modulator of the hemostatic system through interference with mechanisms regulating platelet activation

An Interior-Point Method for Non-Smooth Multibody System Dynamics

La simulazione dinamica di fenomeni non-smooth in sistemi con corpi sia rigidi che flessibili, richiede la soluzione di problemi di complementarietà affrontabili efficacemente mediante tecniche ad-hoc, sviluppatesi nel campo dell'ottimizzazione convessa. In questa classe di problemi si identificano diverse criticità, quali la possibile presenza di vincoli ridondanti, matrici quasi-singolari, simulazione concorrente di corpi rigidi, flessibili e di oggetti aventi anche differenze significative in termini di massa, rigidezza ed inerzia. È quindi d'obbligo che un eventuale strumento dedicato a questa classe di problemi debba essere in grado, non solo di saperne gestire la tipologia, ma anche di far fronte alle eventuali problematiche che da esso potessero scaturire. La seguente tesi si pone quindi come obbiettivo di dare risposta a questa delicata esigenza, prendendo come punto di riferimento la classe di algoritmi Interior-Point, primo fra tutti la variante Predittore-Correttore proposta da Mehrothra, sviluppandone l'aspetto non solo teorico, ma anche seguendone l'implementazione e la traduzione in codice. Avendo come obbiettivo il raggiungimento delle massime prestazioni, si è indagata la possibilità di sfruttare la naturale sparsità delle matrici descrittive del problema fornendo, laddove necessario, gli strumenti e le interfacce per l'uso e la gestione di software esterni, primo fra tutti Chrono::Engine, libreria dedicata alla simulazione dinamica multibody che ha motivato la realizzazione di questo lavoro. Grazie all'algoritmo sviluppato è ora possibile gestire problemi con contatti rigidi in simulazioni dinamiche che vedono la contemporanea presenza di corpi rigidi e flessibili.----------------------------------------------------------------Simulations of non-smooth dynamic of rigid and flexible body systems, such those involving contacts, require the solution of complementarity problems that can be effectively addressed only with specific solving techniques. A wide variety of issues can arise from this kind of problems, such as ill-posed/redundant matrices, odd mass ratios of bodies in contact, and the concurrent presence of flexible and rigid bodies. The development of this thesis is motivated by the need of an improved scheme that is able to deal with all the aforementioned issues at once. One of the most promising solution strategies for large scale complementarity problems, namely the Interior-Point method, is proposed and implemented in its most performing variant, the primal-dual path-following scheme, according to a custom Mehrotra predictor-corrector scheme. The sparsity of the system is leveraged in order to improve performance, and a whole set of tools, from matrix classes to linear solver interfaces, has been developed in C++ language. The algorithm has been implemented into an open-source dynamic simulation library. Thanks to the novel solver, both unilateral and bilateral constraints, involving flexible and rigid bodies can be fit into the same time-stepping scheme

Complex Eigenvalue Analysis of Multibody Problems via Sparsity-Preserving Krylov–Schur Iterations

In this work, we discuss the numerical challenges involved in the computation of the complex eigenvalues of damped multi-flexible-body problems. Aiming at the highest generality, the candidate method must be able to deal with arbitrary rigid body modes (free–free mechanisms), arbitrary algebraic constraints, and must be able to exploit the sparsity pattern of Jacobians of large systems. We propose a custom implementation of the Krylov–Schur method, proving its robustness and its accuracy in a variety of different complex test cases