Analisi costi benefici di un'infrastruttura stradale con approccio probabilistico all'analisi di sensitività e di rischio.

L'obiettivo dell'elaborato è definire gli importi delle voci fondamentali in ingresso al metodo di calcolo tramite un'intensa ricerca bibliografica in materia e realizzare un procedimento pratico di riferimento applicato al campo delle infrastrutture stradali. I risultati ottenuti dal calcolo sono stati verificati e confrontati con test di sensitività sulle variabili critiche (Analisi di Sensitività, Analisi di Switch e Analisi di Rischio).

CRRT nel paziente ad alto rischio emorragico: ottimizzazione di un protocollo di anticoagulazione regionale con citrato

L’anticoagulazione regionale con citrato (RCA) è una valida opzione in pazienti ad alto rischio emorragico. Lo scopo del nostro studio è stato di valutare, in pazienti critici sottoposti a CRRT per insufficienza renale acuta post-cardiochirurgica, efficacia e sicurezza di un protocollo di RCA in CVVH con l’impiego di una soluzione di citrato a bassa concentrazione (12mmol/L). Metodi: L’RCA-CVVH è stata adottata come alternativa all’eparina o alla CRRT senza anticoagulante (no-AC). Criteri per lo switch verso l’RCA: coagulazione dei circuiti entro 24h o complicanze legate all’eparina. Per facilitare l’impostazione dei parametri CVVH, abbiamo sviluppato un modello matematico per stimare il carico metabolico di citrato e la perdita di calcio. Risultati: In 36 mesi, sono stati sottoposti a RCA-CVVH 30 pazienti. La durata dei circuiti con RCA (50.5 ± 35.8 h, mediana 41, 146 circuiti) è risultata significativamente maggiore (p<0.0001) rispetto all’eparina (29.2±22.7 h, mediana 22, 69 circuiti) o alla no-AC CRRT (24.7±20.6 h, mediana 20, 74 circuiti). Il numero di circuiti funzionanti a 24, 48, 72 h è risultato maggiore durante RCA (p<0.0001). I target di Ca++ sistemico e del circuito sono stati facilmente mantenuti (1.18±0.13 e 0.37±0.09 mmol/L). Durante l’RCA-CVVH nessun paziente ha avuto complicanze emorragiche e il fabbisogno trasfusionale si è ridotto rispetto alle altre modalità (0.29 vs 0.69 unità/die, p<0.05). Le piastrine (p=0.012) e l’AT-III (p=0.004) sono aumentate durante RCA riducendo la necessità di supplementazione. L’RCA è stata interrotta per accumulo di citrato in un solo paziente (calcemia totale/s-Ca++ >2.5). Conclusioni: L’RCA ha consentito di prolungare la durata dei circuiti riducendo il fabbisogno trasfusionale e la necessità di supplementazione di AT-III e piastrine. L’utilizzo di un modello matematico ha facilitato l’impostazione dei parametri CVVH. L’RCA appare meritevole di maggiore considerazione come metodica di anticoagulazione di prima scelta in pazienti ad alto rischio emorragico sottoposti a CRRT.

A chemical loop approach for methanol reforming

Over the past few years, the switch towards renewable sources for energy production is considered as necessary for the future sustainability of the world environment. Hydrogen is one of the most promising energy vectors for the stocking of low density renewable sources such as wind, biomasses and sun. The production of hydrogen by the steam-iron process could be one of the most versatile approaches useful for the employment of different reducing bio-based fuels. The steam iron process is a two-step chemical looping reaction based (i) on the reduction of an iron-based oxide with an organic compound followed by (ii) a reoxidation of the reduced solid material by water, which lead to the production of hydrogen. The overall reaction is the water oxidation of the organic fuel (gasification or reforming processes) but the inherent separation of the two semireactions allows the production of carbon-free hydrogen. In this thesis, steam-iron cycle with methanol is proposed and three different oxides with the generic formula AFe2O4 (A=Co,Ni,Fe) are compared in order to understand how the chemical properties and the structural differences can affect the productivity of the overall process. The modifications occurred in used samples are deeply investigated by the analysis of used materials. A specific study on CoFe2O4-based process using both classical and in-situ/ex-situ analysis is reported employing many characterization techniques such as FTIR spectroscopy, TEM, XRD, XPS, BET, TPR and Mössbauer spectroscopy.

«L’Eroica» e la xilografia italiana dal tardo simbolismo all’espressionismo (1911-1917)

Il lavoro di ricerca vuole analizzare, attraverso lo studio specifico della rivista artistico letteraria «L’Eroica» fondata a La Spezia nel 1911 da Ettore Cozzani e Franco Oliva, gli artisti e le situazioni in cui si sviluppa e si diffonde in Italia un linguaggio grafico di tipo fauve-espressionista, in perfetta sintonia con le coeve esperienze straniere. Nello specifico, si è focalizzata l’attenzione sui così detti ‘anni eroici de L’Eroica’ (1911-1917), periodo in cui risulta più evidente il passaggio che si ebbe nel panorama dell’illustrazione italiana da uno stile ancora riconducibile a un linguaggio simbolista a uno, per l’appunto espressionista. Questa rivista, infatti, nella fase conosciuta come “gli anni eroici dell’Eroica” (1911-17), s’interessa in modo quasi esclusivo alla xilografia contemporanea avvalendosi in un primo momento della collaborazione di artisti noti nell’ambito del gusto liberty come, ad esempio, Adolfo De Carolis e dei suoi allievi (Gino Barbieri, Ettore di Giorgio, Antonio Moroni). Tale collaborazione però termina con la cosiddetta “Secessione degli Xilografi”, ossia l’abbandono nel 1914 da parte di De Carolis e dei suoi della testata spezzina, circostanza questa che determinerà un nuovo indirizzo stilistico per la rivista in cui prenderanno sempre più spazio artisti di una generazione più giovane, peraltro già attivi su «L’Eroica» stessa, quali ad esempio Lorenzo Viani, Arturo Martini, Emilio Mantelli, Felice Casorati, Giuseppe Biasi, Roberto Melli e Gino Carlo Sensani, questi ultimi tutti rappresentanti di un espressionismo italiano di primo ordine

Dynamics, rheology and critical properties of colloidal fluid mixtures

Liquids under the influence of external fields exhibit a wide range of intriguing phenomena that can be markedly different from the behaviour of a quiescent system. This work considers two different systems — a glassforming Yukawa system and a colloid-polymer mixture — by Molecular Dynamics (MD) computer simulations coupled to dissipative particle dynamics. The former consists of a 50-50 binary mixture of differently-sized, like-charged colloids interacting via a screened Coulomb (Yukawa) potential. Near the glass transition the influence of an external shear field is studied. In particular, the transition from elastic response to plastic flow is of interest. At first, this model is characterised in equilibrium. Upon decreasing temperature it exhibits the typical dynamics of glassforming liquids, i.e. the structural relaxation time τα grows strongly in a rather small temperature range. This is discussed with respect to the mode-coupling theory of the glass transition (MCT). For the simulation of bulk systems under shear, Lees-Edwards boundary conditions are applied. At constant shear rates γ˙ ≫ 1/τα the relevant time scale is given by 1/γ˙ and the system shows shear thinning behaviour. In order to understand the pronounced differences between a quiescent system and a system under shear, the response to a suddenly commencing or terminating shear flow is studied. After the switch-on of the shear field the shear stress shows an overshoot, marking the transition from elastic to plastic deformation, which is connected to a super-diffusive increase of the mean squared displacement. Since the average static structure only depends on the value of the shear stress, it does not discriminate between those two regimes. The distribution of local stresses, in contrast, becomes broader as soon as the system starts flowing. After a switch-off of the shear field, these additional fluctuations are responsible for the fast decay of stresses, which occurs on a time scale 1/γ˙ . The stress decay after a switch-off in the elastic regime, on the other hand, happens on the much larger time scale of structural relaxation τα. While stresses decrease to zero after a switch-off for temperatures above the glass transition, they decay to a finite value for lower temperatures. The obtained results are important for advancing new theoretical approaches in the framework of mode-coupling theory. Furthermore, they suggest new experimental investigations on colloidal systems. The colloid-polymer mixture is studied in the context of the behaviour near the critical point of phase separation. For the MD simulations a new effective model with soft interaction potentials is introduced and its phase diagram is presented. Here, mainly the equilibrium properties of this model are characterised. While the self-diffusion constants of colloids and polymers do not change strongly when the critical point is approached, critical slowing down of interdiffusion is observed. The order parameter fluctuations can be determined through the long-wavelength limit of static structure factors. For this strongly asymmetric mixture it is shown how the relevant structure factor can be extracted by a diagonalisation of a matrix that contains the partial static structure factors. By presenting first results of this model under shear it is demonstrated that it is suitable for non-equilibrium simulations as well.

Control of protein degradation pathways by BAG proteins and changes during aging

Many age-related neurodegenerative disorders such as Alzheimer’s disease, Parkinson’s disease, amyotrophic lateral sclerosis and polyglutamine disorders, including Huntington’s disease, are associated with the aberrant formation of protein aggregates. These protein aggregates and/or their precursors are believed to be causally linked to the pathogenesis of such protein conformation disorders, also referred to as proteinopathies. The accumulation of protein aggregates, frequently under conditions of an age-related increase in oxidative stress, implies the failure of protein quality control and the resulting proteome instability as an upstream event of proteinopathies. As aging is a main risk factor of many proteinopathies, potential alterations of protein quality control pathways that accompany the biological aging process could be a crucial factor for the onset of these disorders.rnrnThe focus of this dissertation lies on age-related alterations of protein quality control mechanisms that are regulated by the co-chaperones of the BAG (Bcl-2-associated athanogene) family. BAG proteins are thought to promote nucleotide exchange on Hsc/Hsp70 and to couple the release of chaperone-bound substrates to distinct down-stream cellular processes. The present study demonstrates that BAG1 and BAG3 are reciprocally regulated during aging leading to an increased BAG3 to BAG1 ratio in cellular models of replicative senescence as well as in neurons of the aging rodent brain. Furthermore, BAG1 and BAG3 were identified as key regulators of protein degradation pathways. BAG1 was found to be essential for effective degradation of polyubiquitinated proteins by the ubiquitin/proteasome system, possibly by promoting Hsc/Hsp70 substrate transfer to the 26S proteasome. In contrast, BAG3 was identified to stimulate the turnover of polyubiquitinated proteins by macroautophagy, a catabolic process mediated by lysosomal hydrolases. BAG3-regulated protein degradation was found to depend on the function of the ubiquitin-receptor protein SQSTM1 which is known to sequester polyubiquitinated proteins for macroautophagic degradation. It could be further demonstrated that SQSTM1 expression is tightly coupled to BAG3 expression and that BAG3 can physically interact with SQSTM1. Moreover, immunofluorescence-based microscopic analyses revealed that BAG3 co-localizes with SQSTM1 in protein sequestration structures suggesting a direct role of BAG3 in substrate delivery to SQSTM1 for macroautophagic degradation. Consistent with these findings, the age-related switch from BAG1 to BAG3 was found to determine that aged cells use the macroautophagic system more intensely for the turnover of polyubiquitinated proteins, in particular of insoluble, aggregated quality control substrates. Finally, in vivo expression analysis of macroautophagy markers in young and old mice as well as analysis of the lysosomal enzymatic activity strongly indicated that the macroautophagy pathway is also recruited in the nervous system during the organismal aging process.rnrnTogether these findings suggest that protein turnover by macroautophagy is gaining importance during the aging process as insoluble quality control substrates are increasingly produced that cannot be degraded by the proteasomal system. For this reason, a switch from the proteasome regulator BAG1 to the macroautophagy stimulator BAG3 occurs during cell aging. Hence, it can be concluded that the BAG3-mediated recruitment of the macroauto-phagy pathway is an important adaptation of the protein quality control system to maintain protein homeostasis in the presence of an enhanced pro-oxidant and aggregation-prone milieu characteristic of aging. Future studies will explore whether an impairment of this adaptation process may contribute to age-related proteinopathies.

Leopoli-Cencelle beyond virtual reality Documentazione, interpretazione e comprensione di una città medievale

La città medievale di Leopoli-Cencelle (fondata da Papa Leone IV nell‘854 d.C. non lontano da Civitavecchia) è stata oggetto di studio e di periodiche campagne di scavo a partire dal 1994. Le stratigrafie investigate con metodi tradizionali, hanno portato alla luce le numerose trasformazioni che la città ha subìto nel corso della sua esistenza in vita. Case, torri, botteghe e strati di vissuto, sono stati interpretati sin dall’inizio dello scavo basandosi sulla documentazione tradizionale e bi-dimensionale, legata al dato cartaceo e al disegno. Il presente lavoro intende re-interpretare i dati di scavo con l’ausilio delle tecnologie digitali. Per il progetto sono stati utilizzati un laser scanner, tecniche di Computer Vision e modellazione 3D. I tre metodi sono stati combinati in modo da poter visualizzare tridimensionalmente gli edifici abitativi scavati, con la possibilità di sovrapporre semplici modelli 3D che permettano di formulare ipotesi differenti sulla forma e sull’uso degli spazi. Modellare spazio e tempo offrendo varie possibilità di scelta, permette di combinare i dati reali tridimensionali, acquisiti con un laser scanner, con semplici modelli filologici in 3D e offre l’opportunità di valutare diverse possibili interpretazioni delle caratteristiche dell’edificio in base agli spazi, ai materiali, alle tecniche costruttive. Lo scopo del progetto è andare oltre la Realtà Virtuale, con la possibilità di analizzare i resti e di re-interpretare la funzione di un edificio, sia in fase di scavo che a scavo concluso. Dal punto di vista della ricerca, la possibilità di visualizzare le ipotesi sul campo favorisce una comprensione più profonda del contesto archeologico. Un secondo obiettivo è la comunicazione a un pubblico di “non-archeologi”. Si vuole offrire a normali visitatori la possibilità di comprendere e sperimentare il processo interpretativo, fornendo loro qualcosa in più rispetto a una sola ipotesi definitiva.

Master Equation: Biological Applications and Thermodynamic Description

It is well known that many realistic mathematical models of biological systems, such as cell growth, cellular development and differentiation, gene expression, gene regulatory networks, enzyme cascades, synaptic plasticity, aging and population growth need to include stochasticity. These systems are not isolated, but rather subject to intrinsic and extrinsic fluctuations, which leads to a quasi equilibrium state (homeostasis). The natural framework is provided by Markov processes and the Master equation (ME) describes the temporal evolution of the probability of each state, specified by the number of units of each species. The ME is a relevant tool for modeling realistic biological systems and allow also to explore the behavior of open systems. These systems may exhibit not only the classical thermodynamic equilibrium states but also the nonequilibrium steady states (NESS). This thesis deals with biological problems that can be treat with the Master equation and also with its thermodynamic consequences. It is organized into six chapters with four new scientific works, which are grouped in two parts: (1) Biological applications of the Master equation: deals with the stochastic properties of a toggle switch, involving a protein compound and a miRNA cluster, known to control the eukaryotic cell cycle and possibly involved in oncogenesis and with the propose of a one parameter family of master equations for the evolution of a population having the logistic equation as mean field limit. (2) Nonequilibrium thermodynamics in terms of the Master equation: where we study the dynamical role of chemical fluxes that characterize the NESS of a chemical network and we propose a one parameter parametrization of BCM learning, that was originally proposed to describe plasticity processes, to study the differences between systems in DB and NESS.

Nano-fabrication of complex functional structures using non- conventional lithography

In Chapter 1 I will present a brief introduction on the state of art of nanotechnologies, nanofabrication techniques and unconventional lithography as a technique to fabricate the novel electronic device as resistive switch so-called memristor is shown. In Chapter 2 a detailed description of the main fabrication and characterization techniques employed in this work is reported. Chapter 3 parallel local oxidation lithography (pLOx) describes as a main technique to obtain accurate patterning process. All the effective parameters has been studied and the optimized condition observed to highly reproducible with excellent patterned nanostructures. The effect of negative bias, calls local reduction (LR) studied. Moreover, the use of AC bias shows faster patterning process respect to DC bias. In Chapter 4 (metal/ e-SiO2/ Si nanojunction) it is shown how the electrochemical oxide nanostructures by using pLOx can be used in the fabrication of novel devices call memristor. We demonstrate a new concept, based on conventional materials, where the lifetime problem is resolved by introducing a “regeneration” step, which restores the nano-memristor to its pristine condition by applying an appropriate voltage cycle. In Chapter 5 (Graphene/ e-SiO2/ Si), Graphene as a building block material is used as an electrode to selectively oxidize the silicon substrate by pLOx set up for the fabrication of novel resistive switch device. In Chapter 6 (surface architecture) I will show another application of pLOx in biotechnology is shown. So the surface functionalization combine with nano-patterning by pLOx used to design a new surface to accurately bind biomolecules with the possibility of studying those properties and more application in nano-bio device fabrication. So, in order to obtain biochips, electronic and optical/photonics devices Nano patterning of DNA used as scaffolds to fabricate small functional nano-components.

Esperimenti di integrazione ViewOS-Rump: lo stack di rete NetBSD

In questo lavoro si indaga la possibilita' di includere lo stack TCP-IP NetBSD, estratto come libreria dinamica ed eseguito all'interno di un kernel rump, come sottomodulo di rete della System Call Virtual Machine UMView di Virtual Square. Il risultato ottenuto consiste in umnetbsd, il modulo che ne dimostra la fattibilita', e libvdeif, una libreria per connettere kernel rump a switch VDE.

Effects of 2013 Cap reform on land market: regionalized farm payments and changes in farmers’ intended behaviour

The CAP reform process has been a central issue for agricultural economics research in recent years, and is gaining further attention in view of the post-2013 perspectives (Viaggi et al., 2010; Bartolini et al., 2011). Today the CAP is in the middle of a new reform process. Through the debate generated by the official proposals, published in October 2011 (COM(2011)625/3), the European Union (EU) engaged in a revision of the CAP ended on 26 June 2013 when a political agreement has been reached (IP/13/613, MEMO-13-621 and IP/13/864). In particular, in Italy the switch of the payment regime from historical to regional bases will take place. The underlying assumption is that the shift to regionalized payments changes the remuneration of inputs and has an impact on farmers’ allocation of fixed resources. In this context, farmers are expected to adjust their plans to the new policy environment as the regionalization of support is meant to create a change in incentives faced by farmers. The objective of this thesis is to provide an ex-ante analysis of the potential impact of the introduction of regionalized payments, within the post-2013 CAP reform, on the land market. Regionalized payments seem to produce differentiated effects and contribute to a general (slight) increase of land exchanges. The individual reaction to the new payments introduction would be different depending on location and specialization. These effects seem to be also strongly influenced by the difference in historical payments endowment and value, i.e. by the previous historical system of distribution of payments.

Progetto di un sistema a microcontrollore per modulazione back-scattering uwb

La tesi tratta il progetto di una piattaforma di simulazione per modulazioni back-scatter UWB su un sistema a microcontrollore PIC. Il sistema utilizza uno switch a UWB per eseguire la modulazione, modificando le condizioni di carico d'antenna; il software implementa la modulazione attraverso la variazione del segnale di controllo dello switch e si interfaccia con l'utente attraverso l'uso di una periferica USB, permettendo la modifica runtime della configurazione. Si interfaccia inoltre con strumenti esterni attraverso segnali di sincronizzazione.

Studio dei circuiti di clamper negli amplificatori operanti in classe e

Questa tesi tratta dell’amplificatore di potenza (PA–Power Amplifier) operante in classe E. Si tratta di un convertitore DC/AC ad elevato rendimento che può trovare impiego in numerose applicazioni in cui il problema della generazione di calore o la necessità di non sprecare energia sono particolarmente stringenti (ad esempio apparati per cui non è previsto un impianto di raffreddamento e/o apparati alimentati a batteria). L’elevato rendimento di un amplificatore operante in classe E deriva dalle specifiche forme d’onda ai capi del dispositivo attivo impiegato, tali per cui la perdita di commutazione durante la fase di accensione dello switch diviene pressoché trascurabile (Zero-Voltage-Switching e Zero-Derivative-Voltage Turn-ON). Il prezzo da pagare per ottenere queste benefiche forme d’onda è quello di avere un valore di cresta della tensione sul dispositivo che commuta assai più elevato del valore medio, coincidente con la tensione di alimentazione DC. In generale si stima una tensione di picco fra le 3 e le 5 volte più elevata della tensione DC, in funzione del Duty-Cycle e dell’assorbimento di corrente sul carico. Occorre poi tenere presente che in condizioni dinamiche (ad esempio qualora si collegasse direttamente l’amplificatore all’alimentazione) potrebbero innescarsi dei transitori tali per cui la tensione di picco ecceda anche il range suddetto. Per questo motivo è bene porre un limite alla massima tensione di picco adottando dei circuiti di protezione del transistore al fine di evitare la sua distruzione per limiti legati alla tensione di breakdown. Questi circuiti sono denominati clamper: in questa tesi valuteremo le modalità con cui si può implementare tale protezione; valuteremo, inoltre, i vantaggi e gli svantaggi derivanti dall’impiego di tali circuiti. Questi clamper sono prevalentemente di tipo dissipativo (Zener); nel corso della tesi si è studiato la realizzazione di un clamper rigenerativo che utilizza un trasformatore, ma si è constatata la irrealizzabilità fisica a causa della inevitabile presenza della induttanza dispersa.

Synthetic strategies of new spin-labelled supramolecular systems

Molecular recognition and self-assembly represent fundamental issues for the construction of supramolecular systems, structures in which the components are held together through non-covalent interactions. The study of host-guest complexes and mechanical interlocked molecules, important examples in this field, is necessary in order to characterize self-assembly processes, achieve more control over the molecular organization and develop sophisticated structures by using properly designed building blocks. The introduction of paramagnetic species, or spin labelling, represents an attractive opportunity that allows their detection and characterization by the Electron Spin Resonance spectroscopy, a valuable technique that provides additional information to those obtained by traditional methods. In this Thesis, recent progresses in the design and the synthesis of new paramagnetic host-guest complexes and rotaxanes characterized by the presence of nitroxide radicals and their investigation by ESR spectroscopy are reported. In Chapter 1 a brief overview of the principal concepts of supramolecular chemistry, the spin labelling approach and the development of ESR methods applied to paramagnetic systems are described. Chapter 2 and 3 are focused on the introduction of radicals in macrocycles as Cucurbiturils and Pillar[n]arenes, due to the interesting binding properties and the potential employment in rotaxanes, in order to investigate their structures and recognition properties. Chapter 4 deals with one of the most studied mechanical interlocked molecules, the bistable [2]rotaxane reported by Stoddart and Heath based on the ciclobis (paraquat-p-phenylene) CBPQT4+, that represents a well known example of molecular switch driven by external stimuli. The spin labelling of analogous architectures allows the monitoring by ESR spectroscopy of the switch mechanism involving the ring compound by tuning the spin exchange interaction. Finally, Chapter 5 contains the experimental procedures used for the synthesis of some of the compounds described in Chapter 2-4.

Effects of glucocorticoids on vascular NADPH oxidases and endothelial NO synthase

Glukokortikoide (GCs) stellen wichtige Hormone in der Regulation der metabolischen Homöostase dar. Synthetische GCs, wie Dexamethasone (DEX), spielen eine essentielle Rolle in der Behandlung inflammatorischer Krankheiten. Jedoch sind unter einer Dexamethason-Therapie zahlreiche Nebenwirkungen bekannt, so z.B. auch die Entwicklung einer Hypertonie, in deren Pathogenese oxidativer Stress eine entscheidende Rolle spielt. Obwohl sich in den vergangenen Jahren zahlreiche Studien zum Ziel setzten die GC-induzierte Hypertonie (GC-HT) aufzuklären, sind die genauen Mechanismen bis heute unklar. Eine erhöhte Expression von NADPH Oxidasen (Nox) und eine Entkopplung der endothelialen NO Synthase (eNOS), die Hauptquellen reaktiver Sauerstoffspezies (ROS) im vaskulären System, tragen maßgeblich zur Pathogenese kardiovaskulärer Erkrankungen bei. Daher ist eine Beteiligung dieser Enzyme in GC-induziertem oxidativen Stress sehr wahrscheinlich. Folglich wurde die Hypothese aufgestellt, dass NADPH Oxidasen und eine entkoppelte eNOS die vielversprechendsten unter den zahlreichen involvierten pro- und anti-oxidativen Enzymen sind. Mit Fokus auf die oben genannten Systeme wurde in der vorliegenden Studie der Effekt von DEX mit Hilfe von in vivo (WKY Ratten) ebenso wie in vitro Experimenten (A7r5 und EA.hy 926 Zellen) untersucht. Dabei zeigte sich, dass Nox1, Nox4 und p22phox durch DEX unterschiedlich reguliert wurden. Nox1 wurde hoch-, Nox4 hingegen herunterreguliert, während p22phox unverändert blieb. Die Modufikation schien hierbei auf transkriptioneller und post-transkriptioneller Ebene stattzufinden. Durch die gegensätzliche Regulation von Nox1 und Nox4 bleibt die Nettowirkung der verschiedenen Nox Isoformen unklar. Immer mehr Studien bringen vaskulären oxidativen Stress mit der Pathogenese einer GC-HT in Zusammenhang, welche letztendlich zu einer verminderten Bioverfügbarkeit von Stickstoffmonoxid (NO) führt. Durch die eNOS produziertes NO stellt einen essentiellen Schutzfaktor der Blutgefäße dar. Eine verminderte NO-Bioverfügbarkeit könnte die Folge einer eNOS-Entkopplung darstellen, ausgelöst durch oxidativen Stress. Da die Verfügbarkeit von Tetrahydrobiopterin (BH4) entscheident ist für die Aktivität und enzymatische Kopplung der eNOS, beschäftigt sich die vorliegende Arbeit mit GC-induzierten Veränderungen in der BH4-Versorgung. Die Behandlung von EA.hy 926 Zellen mit DEX führte zu einer zeit- und konzentrationsabhängigen Herunterregulation von eNOS auf mRNA- und Proteinebene. Gleichzeitig wurde die Phosphorylierung an Serine1177 vermindert. Als maßgeblicher “Kopplungs-Schalter” kann BH4 endogen über zwei verschiedene Signalwege synthetisiert werden, welche durch die Enzyme GCH1 und DHFR reguliert werden. DEX führte zu einer zeit- und konzentrationsabhängigen Herunterregulation von BH4, BH2 und Biopterin, wobei ebenso das BH4 / BH2 -Verhältnis vermindert wurde. Beide Enzyme, GCH1 genauso wie DHFR, wurden auf mRNA- und Proteinebene herunterreguliert, was auf einen Effekt von GCs auf beide rnBH4-produzierenden Signalwege schließen lässt. Nach Behandlung mit DEX wurde die Produktion von NO in Endothelzellen maßgeblich vermindert. In ROS-Messungen zeigte sich eine Tendenz hin zu einer eNOS-Entkopplung, jedoch war es mit unserem experimentellen Aufbau nicht möglich, diese endgültig zu beweisen.rnZusammenfassend lässt sich sagen, dass die Behandlung mit GCs zu Veränderungen in beiden untersuchten Systemen, den NADPH Oxidasen ebenso wie dem eNOS-NO System, führte. DEX erhöhte die Expression von Nox1 in glatten Muskelzellen und reduzierte die Nox4-Expression in Endothelzellen. Gleichzeitig verminderte DEX die Verfügbarkeit von BH4 und inhibierte die Phosphorylierung / Aktivität von eNOS. Mithilfe weiterer Studien muss die endgültige Beteiligung von NADPH Oxidasen und einer eNOS-Entkopplung an oxidativem Stress in GC-HT abschließend aufgeklärt werden.rn