Heme oxygenase-1-derived carbon monoxide contributes to the suppression of acute hypertensive responses in vivo

The enzyme heme oxygenase, which exists in inducible (HO-1) and constitutive (HO-2) isoforms, catalyzes the degradation of heme to biliverdin and CO in mammalian tissues. CO has been implicated in the control of vascular tone in a manner similar to that for NO. In the present study, we investigated the contribution of the heme oxygenase/CO pathway to the modulation of acute hypertensive responses in vivo induced by (1) alphaalphaHb, a chemically modified hemoglobin known to scavenge NO, and (2) NG-nitro-L-arginine methyl ester (L-NAME), a competitive NOS inhibitor. Experiments were carried out in conscious rats in which femoral arteries and veins were surgically catheterized 1 or 5 days before treatment with the vasoconstrictor agents. Intravenous infusion of alphaalphaHb (8% solution) or L-NAME (30 micromol/kg) [corrected] produced an acute and significant increase in mean arterial pressure (P<0.05) in rats at 5 days after catheter implantation. In contrast, no change in blood pressure was observed when alphaalphaHb or L-NAME was infused 1 day after the surgical intervention. The suppression of the hypertensive response observed at 1 day after surgery correlated with a significant (P<0.05) HO-1 expression in aorta, heart, and liver as well as increased aortic CO production and cGMP levels. At 1 day after surgery, pretreatment of animals with the heme oxygenase inhibitor zinc protoporphyrin IX (50 micromol/kg IP) markedly decreased aortic CO and cGMP levels and completely restored the vasoconstrictor effects of both alphaalphaHb and L-NAME. These results provide evidence for a crucial role of the heme oxygenase/CO pathway in the regulation of blood pressure under stress conditions in vivo.     

Thiol compounds interact with nitric oxide in regulating heme oxygenase-1 induction in endothelial cells. Involvement of superoxide and peroxynitrite anions

Thiols are very important antioxidants that protect cells against oxidative insults. Recently, a different and new physiological role has been defined for these compounds because of their involvement in nitric oxide (NO) binding and transport in biological systems. In view of these characteristics, we examined the effect of thiols and NO on the expression of the inducible form of heme oxygenase (HO-1), a stress protein that degrades heme to carbon monoxide and biliverdin. Cultured bovine aortic endothelial cells exposed to the NO donors sodium nitroprusside (SNP) and S-nitroso-N-acetylpenicillamine (SNAP) resulted in increased heme oxygenase activity and HO-1 expression. Co-incubation with N-acetylcysteine, a precursor of glutathione synthesis, significantly attenuated heme oxygenase induction by SNP and SNAP, and a reduction in heme oxygenase activity was also observed when cells were preincubated with N-acetylcysteine for 16 h prior to exposure to NO donors. This effect appears to be associated with NO stabilization by thiols through the formation of S-nitrosothiols. Hydroxocobalamin, a specific NO scavenger, significantly decreased endothelial heme oxygenase activity, indicating a direct involvement of NO released by NO donors to regulate the expression of this stress protein. Moreover, superoxide anion (O-2) and its reaction product with NO, peroxynitrite (ONOO-), were found to partially contribute to the observed NO-mediated activation of endothelial heme oxygenase. Thus, we suggest the existence of a dynamic equilibrium among free NO, O-2, and endogenous glutathione, which might constitute an interactive signaling mechanism modulating stress and adaptive responses in tissues.     

Knowledge representation for ambient security

Abstract: Ambient intelligence envisages an articulated, though transparent, interaction between the user and the environment. According to this grand vision, appliances and systems embedded in the environment have to react to the user's presence and provide services in a customized fashion. Therefore, ambient intelligence systems should be endowed with context awareness capabilities in order to provide the proper responses for each user. This paper specifically shows how the system can be instructed to recognize events occurring in the observed environment for security purposes.     

A distributed approach to 3D road scene recognition

A distributed 3D scene recognition system based on a multilevel representation of object models and signals is described. The solution to a recognition problem is obtained through a set of object-observation couples at the different abstraction levels. The various system modules exchange two kinds of information: (1) top-down messages, which are used to communicate to lower modules the predictions made on the basis of a priori knowledge on the application domain, (2) bottom-up messages, which are used to communicate to higher modules the evidence supporting possible local solutions. A local scheme for the combination of message flows is defined, and messages are interpreted by using a probabilistic network of estimators of random variables. The proposed model is suitable for addressing the problem of distributed geometric reasoning aimed at 3D road scene recognition by an autonomous vehicle. Recognition results include road detection and obstacle localization, together with a study of the relative computational load required by different modules of the system. The proposed approach is currently simulated on a workstation, while an effective implementation on board of an autonomous vehicle is under development in the contest of the CEC-EUREKA Prometheus project     

Advanced m-CHP fuel cell system based on a novel bio-ethanol fluidized bed membrane reformer

Distributed power generation via Micro Combined Heat and Power (m-CHP) systems, has been proven to over-come disadvantages of centralized generation since it can give savings in terms of Primary Energy consumption and energy costs.The FluidCELL FCH JU/FP7 project aims at providing the Proof of Concept of an advanced high performance, cost effective bio-ethanol m-CHP cogeneration Fuel Cell system for decentralized off-grid applications by end of 2017. The main idea of FluidCELL is to develop a new bio-ethanol membrane reformer for pure hydrogen production (3.2 Nm³/h) based on Membrane Reactors in order to intensify the process of hydrogen production through the integration of reforming and purification in one single unit. The novel reactor could be more efficient than the state-of-the-art technology due to an optimal design aimed at circumventing mass and heat transfer resistances. Moreover, the design and optimization of the subcomponents for the BoP could also be improved. Particular attention has to be devoted to the optimized thermal integration that can improve the overall efficiency of the system at >90% and reducing the cost due to low temperature reforming. The main results obtained until now in terms of performance of the catalysts, membranes and the membrane reactors will be presented in this work.     

Experimental investigation of PEM fuel cells for a m-CHP system with membrane reformer

An innovative small-scale cogeneration system based on membrane reformer and PEM fuel cells is under development within the FluidCELL project. An experimental campaign has been carried out to characterize the PEM fuel cell and to define the operative conditions when integrated within the system. The hydrogen feeding the PEM is produced by a membrane reactor which in principle can separate pure hydrogen; however, in general, hydrogen purity is around 99.9%–99.99%. The focus of this work is the assessment of the PEM performance under different hydrogen purities featuring actual membrane selectivity and gases build-up by anode off-gas recirculation. Their effects on the cells voltage and local current distribution are measured at different conditions (pressure, humidity, stoichiometry, with and without air bleeding, in flow-through and dead-end operation). In flow-through mode, the cell voltage is relatively insensitive to the presence of inert gases (e.g. ?20 mV with inerts/H₂ from 0 to 20·10^?2 at 0.3 A/cm²), and resistant also to CO (e.g. ?35 mV with inerts/H₂ = 20·10^?2 and CO/H₂ from 0 to 20·10^?6 at 0.3 A/cm²), thanks to the Ru presence in the anode catalyst. Looking at the current density distribution on the cell surface, the most critical areas are the cathode inlet, likely due to insufficient air humidification, and the anode outlet, because of low hydrogen concentration and CO poisoning of the catalyst. Dead-end operation is also investigated using humid or impure hydrogen. In this case relatively small amount of impurities in the hydrogen feed rapidly reduces the cell voltage, requiring frequent purges (e.g. every 30 s with inerts/H₂ = 0.5·10^?2 at 0.3 A/cm²). These experiments set the basis for the management of the PEMFC stack integrated into the m-CHP system based on the FluidCELL concept.