The arachidonic acid effect on platelet nitric oxide level

Arachidonic acid can act as a second messenger regulating many cellular processes among which is nitric oxide (NO) formation. The aim of the present study was to investigate the molecular mechanisms involved in the arachidonic acid effect on platelet NO level. Thus NO, cGMP and superoxide anion level, the phosphorylation status of nitric oxide synthase, the protein kinase C (PKC), and NADPH oxidase activation were measured. Arachidonic acid dose-dependently reduced NO and cGMP level. The thromboxane A(2) mimetic U46619 behaved in a similar way. The Arachidonic acid or U46619 effect on NO concentration was abolished by the inhibitor of the thromboxane A(2) receptor SQ29548 and partially reversed by the PKC inhibitor GF109203X or by the phospholipase C pathway inhibitor U73122. Moreover, it was shown that Arachidonic acid activated PKC and decreased nitric oxide synthase (eNOS) activities. The phosphorylation of the inhibiting eNOSthr495 residue mediated by PKC was increased by Arachidonic acid, while no changes at the activating ser1177 residue were shown. Finally, Arachidonic acid induced NADPH oxidase activation and superoxide anion formation. These effects were greatly reduced by GF109203X, U73122, and apocynin. Likely Arachidonic acid reducing NO bioavailability through all these mechanisms could potentiate its platelet aggregating power

Review of nuclear microreactors: Status, potentialities and challenges

Nuclear energy is being reconsidered worldwide as a low-carbon and dispatchable energy source. Following the development of Small Modular Reactors (SMR) to reduce the capital costs and increase the safety of new nuclear power plants, microreactors are being designed by several companies. Microreactors are usually defined as SMR with a power output in the range 1–20 MWe. They can operate as part of the electric grid, independently from the electric grid or as part of a microgrid to produce electricity and process heat. In the present paper, some microreactors at an advanced design stage are presented: eVinci™, Aurora, Holos Generators, Xe-Mobile, NuScale, Sealer, U-Battery and Micro Modular Reactor. The main applications of microreactors and the technology features are then discussed to present the main potentialities and challenges. The main advantages are the small size, the simple plant layout and the fast on-site installation. The main challenges are the limited fuel availability, the security and proliferation risk and the licensing process. Finally, an economic analysis shows that, due to an economy of scale, despite the capital cost reduction, microreactors are not cost competitive with large nuclear plants, but they are competitive with technologies with similar scale and application, such as diesel generators and renewable sources in microgrids

Homocysteine decreases platelet NO level via protein kinase C activation

Hyperhomocysteinaemia has been associated with increased risk of thrombosis and atherosclerosis. Homocysteine produces endothelial injury and stimulates platelet aggregation. Several molecular mechanisms related to these effects have been elucidated. The study aimed to deeply investigate the homocysteine effect on nitric oxide formation in human platelets. The homocysteine-induced changes on nitric oxide, cGMP, superoxide anion levels and nitrotyrosine formation were evaluated. The enzymatic activity and the phosphorylation status of endothelial nitric oxide synthase (eNOS) at thr495 and ser1177 residues were measured. The protein kinase C (PKC), assayed by immunofluorescence confocal microscopy technique and by phosphorylation of p47pleckstrin, and NADPH oxidase activation, tested by the translocation to membrane of the two cytosolic subunits p47phox and p67phox, were assayed. Results show that homocysteine reduces platelet nitric oxide and cGMP levels. The inhibition of eNOS activity and the stimulation of NADPH oxidase primed by PKC appear to be involved. PKC stimulates the eNOS phosphorylation of the negative regulatory residue thr495 and the dephosphorylation of the positive regulatory site ser1177. GF109203X and U73122, PKC and phospholipase C\u3b32 pathway inhibitors, respectively, reverse this effect. Moreover, homocysteine stimulates superoxide anion elevation and NADPH oxidase activation. These effects are significantly decreased by GF109203X and U73122, suggesting the involvement of PKC in NADPH oxidase activation. Homocysteine induces formation of the peroxynitrite biomarker nitrotyrosine. Taken together these results suggest that the homocysteine-mediated responses leading to nitric oxide impairment are mainly coupled to PKC activation. Thus homocysteine stimulates platelet aggregation and decreases nitric oxide bioavailability

Exploration of power conversion thermodynamic cycles for ARC fusion reactor

In the worldwide energy industry, nuclear fusion could be a breakthrough in the medium-long term. One promising fusion machine under design at Massachusetts Institute of Technology is ARC reactor. It is likely that the first nuclear fusion plants will rely on a traditional thermodynamic cycle for the downstream power energy conversion. In this framework, one of the design aspects is to maximize the thermal efficiency. In the present paper the thermodynamic cycles, which could be adopted in ARC rector, are explored. Three cycles have been considered: the Rankine, the Brayton and a combined cycle. For the gas adopted in the Brayton and combined cycles, two options have been investigated: supercritical Helium and supercritical CO2. A comparison among thermal efficiency and preliminary considerations on component integrity's, plant feasibility and economics of each studied configurations has been discussed to identify the possible best option for ARC reactor. The results show that a regenerative CO2 Brayton cycle with intercooler and re-heating systems is the most promising one. Such configurations is able to reach a thermodynamic efficiency of up to 0.6