The threshold potentials were determined for the excitation energy necessary for low energy electrons to induce chemical reactions of carbon monoxide, and of nitric oxide adsorbed on a gold surface. The reactions were studied as a function of temperature (100 °C to 200 °C) and pressure (1.83 x 10-5 to 6.40 x 10-4 torr). The electron source was a thorium oxide coated iridium filament which was heated by a current between 1A and 3A to keep thermal distribution of the electrons to less than 0.4 ev. The reaction surface was a polycrystalline evaporated film prepared by subliming gold onto a stainless steel mesh support. Mass analysis was done by quadrupole mass spectrometry in a flow system. The general results of the research is that a technique has been developed to study the products of reactions of excited state atoms or molecules on metal surfaces. The electron-impact excitation method is an alternative to photochemical and other methods.

Le monoxyde d’azote (NO) est une molécule gazeuse synthétisée par les NO Synthases à partir de L-arginine. NO est une puissante molécule de signalisation dans de nombreux processus physiologiques comme la vasodilatation et la neurotransmission. Il module l’activité de multiples protéines (ex : guanylate cyclase soluble et ribonucléotide réductase) grâce à la nitrosylation de groupements thiol ou de métaux de transition. En tant que radical libre, NO peut réagir avec de nombreuses espèces comme l’oxygène moléculaire, et ainsi former des dérivés réactifs. Grâce à ces propriétés, NO est un acteur majeur de l’immunité innée et de l’inflammation. Les phagocytes produisent de grandes quantités de NO en réponse à des stimuli proinflammatoires, via l’activité NO Synthase inductible (iNOS). En raison des effets délétères des dérivés de NO, l’activité iNOS doit être finement régulée. Le suppresseur de tumeur p53 est capable de réprimer l’expression du gène Nos2 après avoir été lui-même activé en réponse à une accumulation de NO. La protéine p73 est un homologue de p53 encodé par un gène qui génère à la fois des isoformes actives (TAp73) et des isoformes qui sont dépourvues du domaine de transactivation N-terminal et exercent un effet dominant négatif (ΔNp73). Cette étude se focalise sur le rôle des isoformes TAp73 dans la régulation de l’expression de la iNOS. Nous démontrons que les isoformes TAp73 régulent négativement l’expression de la iNOS aux niveaux transcriptionnel et post-traductionnel en potentialisant l’effet répresseur du TGF-β, ce qui résulte en une forte surexpression de la iNOS dans les cellules TAp73-/-. Ces résultats confortent le rôle de la famille p53 comme un réseau essentiel de protéines régulatrices des fonctions du TGF-β. / Nitric oxide (NO) is a gaseous molecule synthesized from L-arginine by Nitric Oxide Synthases. NO acts as a potent signaling molecule in various physiological processes like vasorelaxation and neurotransmission. It modulates the activity of many proteins (e.g. soluble guanylate cyclase and ribonucleotide reductase) through nitrosylation of thiol moieties or transition metal ions. As a free radical, NO can also react with a number of cellular species, notably molecular oxygen, to form reactive oxygen species and reactive nitrogen species. Thanks to these properties, NO appears as a major component of innate immune response and inflammation. Phagocytes produce large amounts of NO in response to proinflammatory through inducible Nitric Oxide Synthase (iNOS) activity. Because of the harmful effects of NO derivatives on cellular components, iNOS activity needs to be tightly regulated. The p53 tumor suppressor has been shown to repress Nos2 after being activated by NO itself. The p73 protein is an homologous encoded by the TP73 gene that generate transcriptionally active TAp73 isoforms and ΔNp73 isoforms that lack the transactivation domain and exert a dominant negative effect. This study focuses on the role of TAp73 isoforms in regulation of iNOS expression. We demonstrate that TAp73 isoforms potentiate the repressive effect of TGF-β on iNOS expression at transcriptional and post-traductional levels, resulting in a substantial iNOS overexpression in TAp73-/- cells. These results emphasize the emerging role of p53 family as a master regulator of TGF-β functions.

This project is concerned with the preparation of electrospun polystyrene (PS) nanofiber materials with covalently bonded NO-photodonor and electrostatically attached tetracationic porphyrinoid photosensitizers. These photofunctional nanofiber materials exhibit effective simultaneous photogeneration of small antibacterial NO and O2(1 ∆g) species under irradiation with daylight creating an antibacterial surface and near surrounding. NO species can be also generated just by gentle heating. Nanofiber materials were analyzed with SEM, FTIR, emission and UV/vis spectroscopy and time-resolved emission and absorption spetroscopy. The antibacterial effect was tested on Escherichia coli. The dual antibacterial action, in combination with the nanoporous character of the material that detains pathogens like bacteria on its surface, is ideal for any application where a sterile environment is neces- sary. The known bimetallic cluster system [(PMe2Ph)4Pt2B10H10] that possesses the propen- sity to reversibly bind small gaseous molecules (O2, SO2, CO) was synthesized in good yields for NO reversible binding investigation. Seven new monometallic precursors (Pt, Pd and Ni) to new bimetallic species were succesfully synthesized with the aim of future study of NO reversible binding. All new compounds were purified by...

Alzheimer's disease is a neurodegenerative disorder with the highest prevalence in the population and for which we do not have a cure so far. The aim of this thesis was to test the mediator system of the N-methyl-D-aspartate receptor and nitric oxide in an animal model of sporadic form of Alzheimer's disease (Samaritan Alzheimer's Rat Model; Taconic Pharmaceuticals, USA). Then compare these results with changes in hippocampal cholinergic system and cognitive tests. The Samaritan rat model is based on the unilateral in vivo application of β-amyloid42 and the pro-oxidative substances (ferrous sulfate heptahydrate and L-buthionine-(S,R)-sulfoximine). Neurochemical methods included testing of the NR1/NR2A/NR2B subunits of the N-methyl-D-aspartate receptor and activity of nitric oxide synthases (neuronal, endothelial, inducible) in the cortex, in both cases in the right and left hemisphere separately. Our results show that Samaritan rats exhibited significant changes in expression of NR2A/NR2B subunits of the N-methyl-D-aspartate receptor and activity of inducible nitric oxide synthase in cortex compared to control rats. The results of glutamatergic system are consistent with changes in activity of cholinergic transporter and cognitive tests (Morris water maze and active allothetic place avoidance)....

Nowadays, there is an increasing risk of bacterial infections from bacteria strains resistant towards antibiotics. Thus, it is of utmost importance to research novel therapies which can overcome this difficulty. The presented thesis focuses on the preparation, characterization and antibacterial evaluation of polystyrene polymer nanomaterials (nanofiber membranes and nanoparticles) modified with compounds that can efficiently inhibit bacterial growth either by their nature (polyethyleneimine) or by photoactivation upon visible light excitation (NO- photodonors, photosensitizers) and consequent production of highly reactive inorganic bactericidal species, nitric oxide (NO) and singlet oxygen (O2(1 g)). All materials were fully characterized by several independent methods. The concentrations of NO and O2(1 g) were measured by amperometric and time-resolved spectroscopic techniques and by variety of chemical analytic procedures. Due to the presence of bactericidal species and the efficient photogeneration of NO and O2(1 g) at physiological conditions, all materials exhibit strong antibacterial action tested on a Gram-negative bacterial strain Escherichia coli. Hence, these functionalized polymer nanomaterials may be intriguing systems for medical-, biological-, or environmental- application where a...

Nitric oxide (NO) is an important signaling molecule in plants. In the pollen of Arabidopsis thaliana, NO causes re-orientation of the growing tube and this response is mediated by 3′,5′-cyclic guanosine monophosphate (cGMP). However, in plants, NO-sensors have remained somewhat elusive. Here, the findings of an NO-binding candidate, Arabidopsis thaliana DIACYLGLYCEROL KINASE 4 (ATDGK4; AT5G57690) is presented. In addition to the annotated diacylglycerol kinase domain, this molecule also harbors a predicted heme-NO/oxygen (H-NOX) binding site and a guanylyl cyclase (GC) catalytic domain which have been identified based on the alignment of functionally conserved amino acid residues across species. A 3D model of the molecule was constructed, and from which the locations of the kinase catalytic center, the ATP-binding site, the GC and H-NOX domains were estimated. Docking of ATP to the kinase catalytic center was also modeled. The recombinant ATDGK4 demonstrated kinase activity in vitro, catalyzing the ATP-dependent conversion of sn-1,2-diacylglycerol (DAG) to phosphatidic acid (PA). This activity was inhibited by the mammalian DAG kinase inhibitor R59949 and importantly also by the NO donors diethylamine NONOate (DEA NONOate) and sodium nitroprusside (SNP). Recombinant ATDGK4 also has GC activity in vitro, catalyzing the conversion of guanosine-5'-triphosphate (GTP) to cGMP. The catalytic domains of ATDGK4 kinase and GC may be independently regulated since the kinase but not the GC, was inhibited by NO while Ca2+ only stimulates the GC. It is likely that the DAG kinase product, PA, causes the release of Ca2+ from the intracellular stores and Ca2+ in turn activates the GC domain of ATDGK4 through a feedback mechanism. Analysis of publicly available microarray data has revealed that ATDGK4 is highly expressed in the pollen. Here, the pollen tubes of mis-expressing atdgk4 recorded slower growth rates than the wild-type (Col-0) and importantly, they showed altered NO responses. Specifically, the mis-expressing atdgk4 pollen tubes have growth rates that were less affected by NO and showed reduced bending angles when challenged by an NO source. Further works on atdgk4 knockout/knockdown mutants will reveal the biological functions of ATDGK4 in NO and/or cGMP signaling in the pollen, and in the broader fertilization process.

Nitric oxide (NO) has been proved to reduce parasite burden in vertebrates infected with Schistosoma, Fasciola, Brugia or Taenia. NO negatively influences parasite growth and development, which then leads to smaller parasite-caused damage to the liver during schistosomosis and stimulates healing processes in muscles infected with Toxocara canis. Peroxynitrite, formed from NO and superoxide, significantly reduces the viability of F. hepatica adults. In case of T. regenti, the neuropathogenic schistosome, the cells capable of NO production (macrophages, neutrophils, eosinophils, microglia and astrocytes) migrate to the site of the infection suggesting that NO might affect T. regenti infection as well. Therefore, the production of NO and its effect on the course of the infection was examined in vivo and the effect of peroxynitrite on T. regenti schistosomula was examined in vitro to assess the role of reactive nitrogen species during the infection. Our results from in vivo experiments demonstrate that although the infection did not significantly elevate nitrite/nitrate results in the sera, NO is locally produced in the early stages of the infection in both the skin and the spinal cord as shown by immunohistochemical detection of inducible NO synthase. Diminishing NO production by aminoguanidine...

BACKGROUND: Pulmonary Hypertension (PH) is a common form of high blood pressure in the lungs. It affects the pulmonary arteries, which normally allow blood to flow from the right heart to the lungs. Nitric Oxide (NO) is a potential mediator for establishing PH and decreasing its availability is implicated in the pathogenesis of PH. HYPOTHESIS: We tested the hypothesis that Fractional Exhaled Nitric Oxide (FeNO) is a good indicator to assess disease severity that may add to understanding the disease. METHODS: The aim of the study was to measure FeNO levels in consecutive PH patients and seek correlations with the 6 Minute walk distance (6MWD) within different World Health Organization (WHO) groups and New York Health Association Function Class (NYHA FC). Assignment to groups I or IV was done respecting the current guidelines. All values were taken at Tufts Medical Center PAH clinic visits. FeNO levels were measured utilizing the NIOX device. RESULTS: FeNO levels were highest in WHO Group 1 and lowest in WHO Group 5 patients. There was a strong inverse correlation between FeNO and 6MWD for each NYHA FC. (Pearson correlation of -0.986, p = 0.014). Within WHO Groups, we found significantly inverse correlations between FeNO and 6MWD in PH Group 4 (p= 0.012) and PH Group 5 (p=0.001). NYHA FC correlated with 6MWD across all WHO Groups (P=0.001). CONCLUSION: We report for the first time FeNO levels in all WHO Groups of PH. FeNO levels are low in early disease. FeNO levels correlate inversely with the severity of PH in WHO Group 4 and 5 patients. The increase in FeNO in more severe patients may reflect the degree of oxidative stress and inflammation in severe PH. Further studies to determine whether FeNO may be a biomarker in early disease, especially in PH Group 4 and 5 warrants further investigation.

The aim of present project was to uncover the effect of pharmacological increase in acute and chronic nitric oxide (NO) production on cardioprotective effect of chronic hypoxia. We studied the effect of NO donor molsidomine on hemodynamic conditions and ischemia - induced myocardium injury. Male Wistar rats were exposed to continual hypoxia in a normobaric chamber (10 % O2, 4 weeks). Rats received molsidomine either chronically (15 mg/kg/day) in drinking water or acutely (10 mg/kg) in saline infused 30 min before ischemia. Control rats were kept under normoxia and treated in a corresponding manner. Adaptation to chronic hypoxia resulted in development of pulmonary hypertension. Chronic treatment with molsidomine slightly reduced these consequences of chronic hypoxia but it had no effect on increased cardiac ischemic tolerance in chronically hypoxic rats. On the other hand acute treatment with molsidomine significantly reduced infarct size and increased the number of arrhythmias in both normoxic and chronically hypoxic animals. In conclusion, our data suggests that acute increase in availability of NO is cardioprotective in both normoxic and chronically hypoxic rats contrary to its chronic increase which seems to have no protective contribution.

>Magister Scientiae - MSc / Nitric oxide (NO) plays a vital role as a biological messenger in biological systems. However, NO detection and quantification have always posed significant complications. There is, therefore, a need to develop new materials or technologies that can be used for sampling and determination of NO species in aqueous environments. The use of Schiff base complexes incorporated onto electrodes to make an electrochemical sensor has been explored as an effective method for the determination and quantification of NO in aqueous solutions. The motivation is based on the precedent of denatured cytochrome C as a suitable complexing site for electron-rich species. The ligands and metals complexes used in this work aim to mimic the square planar arrangement of Fe in denatured cytochrome. It is believed that the accessibility of the haem Fe in this configuration is at the heart of the analyte interactions leading to favourable signal transduction. In preparing the Schiff base and corresponding metal complexes, a microwave-assisted synthetic method, was employed. / 2025