Academic literature on the topic 'Cyclic guanosine 3''

1. Both adenosine 3′:5′-cyclic monophosphate and guanosine 3′:5′-cyclic monophosphate phosphodiesterase activities of peripheral blood mononuclear cells were markedly decreased in elderly women as compared with young control women. 2. In contrast, the ability of these cells to bind guanosine 5′-[β, γ-imido]triphosphate, a non-hydrolysable analogue of guanosine 5′-triphosphate, was the same in both groups. 3. These findings are discussed in the context of the decline in immune function which occurs with increasing age.

Abstract Adenosine 3′,5′-cyclic monophosphate and guanosine 3′,5′-cyclic monophosphate are second messengers that regulate multiple physiological functions. The existence of additional cyclic nucleotides in mammalian cells was postulated many years ago, but technical problems hampered development of the field. Using highly specific and sensitive mass spectrometry methods, soluble guanylyl cyclase has recently been shown to catalyze the formation of several cyclic nucleotides in vitro. This minireview discusses the broad substrate-specificity of soluble guanylyl cyclase and the possible second messenger roles of cyclic nucleotides other than adenosine 3′,5′-cyclic monophosphate and guanosine 3′,5′-cyclic monophosphate. We hope that this article stimulates productive and critical research in an area that has been neglected for many years.

A cyclic nucleotide-gated channel present in skeletal muscle plasma membrane has previously been identified as being responsible for insulin-activated sodium entry into muscle cells (J. E. M. McGeoch and G. Guidotti. J. Biol. Chem. 267:832-841, 1992). We have isolated this channel activity to further study and characterize it. The channel was solubilized from rabbit skeletal muscle sarcolemma and functionally reconstituted into phospholipid vesicles, as assayed by patch-clamp analysis of the reconstituted proteins. Channel activity was isolated by 8-bromo-guanosine 3',5'-cyclic monophosphate affinity chromatography, producing two distinct peaks of cyclic nucleotide-gated channel activity. These two types of channel activity differ in guanosine 3',5'-cyclic monophosphate affinity and in the ability to be opened by adenosine 3',5'-cyclic monophosphate. The cyclic nucleotide-gated channel from rod outer segments also forms two peaks of activity when purified in this manner. The presence of two forms of channel activity could have implications for the mechanism of insulin-activated sodium entry.

The potent neutral endopeptidase inhibitor SQ 28 603 (N-(2-(mercaptomethyl)-1-oxo-3-phenylpropyl)-β-alanine) significantly increased excretion of sodium from 4.9 ± 2.3 to 14.3 ± 2.1 μequiv./min and cyclic 3′,5′-guanosine monophosphate from 118 ± 13 to 179 ± 18 pmol/min after intravenous administration of 300 μmol/kg (~80 mg/kg) in conscious female cynomolgus monkeys. SQ 28 603 did not change blood pressure or plasma atrial natriuretic peptide concentrations in the normal monkeys. In contrast, 1-h infusions of 3, 10, or 30 pmol∙kg−1∙min−1 of human atrial natriuretic peptide lowered blood pressure by −3 ± 4, −9 ± 4, and −27 ± 3 mmHg (1 mmHg = 133.322 Pa), increased cyclic guanosine monophosphate excretion from 78 ± 11 to 90 ± 6, 216 ± 33, and 531 ± 41 pmol/min, and raised plasma atrial natriuretic peptide from 7.2 ± 0.7 to 21 ± 4, 62 ± 12, and 192 ± 35 fmol/mL without affecting sodium excretion. In monkeys receiving 10 pmol∙kg−1∙min−1 of atrial natriuretic peptide, 300 μmol/kg of SQ 28 603 reduced mean arterial pressure by −13 ± 5 mmHg and increased sodium excretion from 6.6 ± 3.2 to 31.3 ± 6.0 μequiv./min, cyclic guanosine monophosphate excretion from 342 ± 68 to 1144 ± 418 pmol/min, and plasma atrial natriuretic peptide from 124 ± 8 to 262 ± 52 fmol/mL. In conclusion, SQ 28 603 stimulated renal excretory function in conscious monkeys, presumably by preventing the degradation of atrial natriuretic peptide by neutral endopeptidase.Key words: atrial natriuretic peptide, neutral endopeptidase, natriuresis, cyclic guanosine monophosphate.

Purine 3′:5′-cyclic nucleotides are very well known for their role as the secondary messengers in hormone action and cellular signal transduction. Nonetheless, their solid-state conformational details still require investigation. Five crystals containing purine 3′:5′-cyclic nucleotides have been obtained and structurally characterized, namely adenosine 3′:5′-cyclic phosphate dihydrate, C10H12N5O6P·2H2O or cAMP·2H2O, (I), adenosine 3′:5′-cyclic phosphate 0.3-hydrate, C10H12N5O6P·0.3H2O or cAMP·0.3H2O, (II), guanosine 3′:5′-cyclic phosphate pentahydrate, C10H12N5O7P·5H2O or cGMP·5H2O, (III), sodium guanosine 3′:5′-cyclic phosphate tetrahydrate, Na+·C10H11N5O7P−·4H2O or Na(cGMP)·4H2O, (IV), and sodium inosine 3′:5′-cyclic phosphate tetrahydrate, Na+·C10H10N4O7P−·4H2O or Na(cIMP)·4H2O, (V). Most of the cyclic nucleotide zwitterions/anions [two from four cAMP present in total in (I) and (II), cGMP in (III), cGMP−in (IV) and cIMP−in (V)] aresynconformers about the N-glycosidic bond, and this nucleobase arrangement is accompanied by Crib—H...Npurhydrogen bonds (rib = ribose and pur = purine). The base orientation is tuned by the ribose pucker. An analysis of data obtained from the Cambridge Structural Database made in the context ofsyn–anticonformational preferences has revealed that among thesynconformers of various purine nucleotides, cyclic nucleotides and dinucleotides predominate significantly. The interactions stabilizing thesynconformation have been indicated. The inter-nucleotide contacts in (I)–(V) have been systematized in terms of the chemical groups involved. All five structures display three-dimensional hydrogen-bonded networks.

The discovery in 2009 that 2′,3′-cAMP exists in biological systems was rapidly followed by identification of 2′,3′-cGMP in cell and tissue extracts. To determine whether 2′,3′-cGMP exists in mammals under physiological conditions, we used ultraperformance LC-MS/MS to measure 2′,3′-cAMP and 2′,3′-cGMP in timed urine collections (via direct bladder cannulation) from 25 anesthetized mice. Urinary excretion rates (means ± SE) of 2′,3′-cAMP (15.5 ± 1.8 ng/30 min) and 2′,3′-cGMP (17.9 ± 1.9 ng/30 min) were similar. Mice also excreted 2′-AMP (3.6 ± 1.1 ng/20 min) and 3′-AMP (9.5 ± 1.2 ng/min), hydrolysis products of 2′,3′-cAMP, and 2′-GMP (4.7 ± 1.7 ng/30 min) and 3′-GMP (12.5 ± 1.8 ng/30 min), hydrolysis products of 2′,3′-cGMP. To validate that the chromatographic signals were from these endogenous noncanonical nucleotides, we repeated these experiments in mice ( n = 18) lacking 2′,3′-cyclic nucleotide 3′-phosphodiesterase (CNPase), an enzyme known to convert 2′,3′-cyclic nucleotides to their corresponding 2′-nucleotides. In CNPase-knockout mice, urinary excretions of 2′,3′-cAMP, 3′-AMP, 2′,3′-cGMP, and 3′-GMP were increased, while urinary excretions of 2′-AMP and 2′-GMP were decreased. Infusions of exogenous 2′,3′-cAMP increased urinary excretion of 2′,3′-cAMP, 2′-AMP, 3′-AMP, and adenosine, whereas infusions of exogenous 2′,3′-cGMP increased excretion of 2′,3′-cGMP, 2′-GMP, 3′-GMP, and guanosine. Together, these data suggest the endogenous existence of not only a 2′,3′-cAMP-adenosine pathway (2′,3′-cAMP → 2′-AMP/3′-AMP → adenosine), which was previously identified, but also a 2′,3′-cGMP-guanosine pathway (2′,3′-cGMP → 2′-GMP/3′-GMP → guanosine), observed here for the first time. Because it is well known that adenosine and guanosine protect tissues from injury, our data support the concept that both pathways may work together to protect tissues from injury.

Cyclic guanosine 3', 5'-monophosphate (cGMP) has recently emerged as an endogenous regulator for controlling or reversing cardiac hypertrophy. Increased protein accumulation is a key feature of cardiac hypertrophy; thus, our study investigates the effects of a cGMP analog on protein accumulation in primary culture of adult rat cardiomyocytes and dissects out the mechanisms involved. We confirmed that a cGMP analog, 8-bromo-cGMP, inhibits phenylephrine (PE)-increased accumulation of newly synthesized proteins in cultured adult rat ventricular cardiomyocytes. Firstly, we have obtained data showing that 8-bromo-cGMP does not inhibit phosphorylation of S6K1 by PE during short time treatment (10 min to 2 h), but blocks phosphorylation of S6K1 by PE at 6 h; moreover this blocking effect is completely abolished by phosphatase inhibitor Tautomycin. Then, we have demonstrated that PE and cGMP induce sustained and transient increased phosphorylation of ERK, respectively. Moreover, cGMP inhibits PE-induced phosphorylation of ERK during long term treatment (3 and 6h). We have also shown that 8-bromo-cGMP inhibits ROS generation induced by PE. Other effects of PE that could be related to hypertrophy (i.e. increased concentration of upstream binding factor mRNA and decreased concentration of the mRNAs of Atrogin and muscle specific RING finger) were not abolished by 8-bromo-cGMP. We conclude that cGMP analog blocks protein accumulation by inhibiting the sustained phosphorylation of S6K1 via the activation of phosphatases.

A persistência bacteriana correlacionada à formação de biofilmes bacterianos é, há algum tempo, fonte de grande preocupação médica em virtude de sua ampla associação com a dificuldade de tratamento de infecções crônicas. Por outro lado, as perspectivas de utilização de biofilmes bacterianos em novas aplicações biotecnológicas e até mesmo para fins terapêuticos são promissoras. Há, portanto, grande interesse em compreender os mecanismos que levam as células bacterianas a deixar o estado planctônico, de vida livre, e associarem-se nesses conglomerados celulares altamente complexos. Ao longo das últimas décadas, o segundo mensageiro c-di-GMP – em conjunto com as moléculas que catalisam sua síntese (diguanilato ciclases) e sua degradação (fosfodiesterases) e seus receptores – estabeleceu-se como um elemento central de regulação de uma série de respostas celulares que determinam a formação ou a dispersão de biofilmes. Curiosamente, as proteínas que participam do metabolismo deste segundo mensageiro estão, frequentemente, codificadas múltiplas vezes em um mesmo genoma bacteriano. Em vista dessa observação, estudos mais recentes apontam que, para reger paralelamente uma variedade tão ampla de fenótipos, este sistema opera em modo de alta especificidade de sinalização e que, portanto, o sinal metabolizado por determinados conjuntos de diguanilato ciclases e fosfodiesterases tem alvos celulares específicos. Evidências robustas, porém isoladas até o momento, apontaram que um dos meios pelo qual ocorre a segregação entre sinal produzido e alvo específico é a interação direta entre as proteínas componentes das vias de sinalização. Mais, demonstrou-se que, em algumas vias, a transmissão de sinal ocorre exclusivamente via interação proteica, dispensando a intermediação do sinalizador em si. Para avaliar a validade e relevância global deste mecanismo, propôs-se, neste estudo, a investigação da rede total de interações entre as proteínas tipicamente associadas às vias de sinalização por c-di-GMP em Pseudomonas aeruginosa, utilizando ensaios de duplo-hibrido bacteriano. Para tanto, foram construídas duas bibliotecas de DNA direcionadas e foram feitos testes de interação de forma estratégica para possibilitar o esgotamento e averiguação de todas as possíveis interações entre as proteínas alvo identificadas. O resultado obtido, um mapa inicial, porém abrangente, da rede de interações proteicas em P. aeruginosa, indica uma grande probabilidade de que os mecanismos previamente descritos sejam realmente recorrentes e relevantes para o intermédio da sinalização nesse organismo. Algumas das interações mais robustas encontradas são bastante interessantes e serão, em estudos futuros, mais extensivamente estudadas.
Persister bacteria are correlated to biofilm formation and have been a source of great medical concern due to its close association with the impairment of traditional treatment in combating chronic infections. On the other hand, using bacterial biofilms to create original biotechnological applications or even as a means of therapeutic treatment in medical settings constitutes a promising prospect. There is, therefore, a great interest in understanding the mechanisms that allow bacteria to leave the free-living planktonic lifestyle and associate in these highly complex cellular aggregates. Over the last decades, the second messenger c-di-GMP – and also the molecules involved in its synthesis (diguanylate ciclases) and degradation (phosphodiesterases) along with its receptors – has been established as a key element implicated in regulation of a series of cellular responses that determine biofilm formation or dispersion. Curiously, the proteins that play a part in the metabolism of this second messenger are frequently coded multiple times in single bacterial genomes. Taking this into account, recent studies indicate that, in order to control such a wide range of phenotypes, this system operates via high specificity of signaling – which means that the signal metabolized by a certain set of diguanylate ciclases and phosphodiesterases has specific cellular targets. Robust but yet isolated evidence indicate that a means by which a signal is segregated with its correlated phenotypic response is through direct protein-protein interaction involving the components of these signaling pathways. Even more, there has been strikingly evidence that, in some of these pathways, signal transduction occurs exclusively through protein-protein interaction, entirely dismissing any mediation by the signal molecule. In order to validate and evaluate the global relevance of this type of mechanism, this study proposed the investigation of the entire network of interactions between proteins typically associated with c-di-GMP signaling pathways of Pseudomonas aeruginosa by employing bacterial two-hybrid system assays. To make that possible, two DNA libraries were constructed and interaction essays were performed in a strategic way so that all possibilities of interaction between target proteins were explored. The results obtained from these experiments allowed the construction of a broad map of interactions that, although still primitive, indicates that, chances are, the mechanisms previously described are both recurrent and relevant to signaling regulation in this organism. Some of the interaction partners found are particularly interesting and will be further investigated in future studies.

Les travaux presentes dans ce memoire concernent l'etude des mecanismes de partition des chromosomes chez la bacterie escherichia coli et la mise en evidence du role primordial de la guanosine 3',5'-tetraphosphate (ppgpp) dans la regulation de son cycle cellulaire. E. Coli doit posseder un mecanisme assurant la partition de ses chromosomes. Nous avons montre que l'interaction entre les enveloppes cellulaires et l'origine de replication des chromosomes, oric, n'est pas requise pour que ce processus s'effectue efficacement. Notre travail suggere qu'il existe plusieurs mecanismes de partition agissant simultanement. Le principal mecanisme requiert la proteine mukb, supposee fournir la force necessaire au mouvement des chromosomes. Les proteines tolc (situee dans la membrane externe des cellules) et hu2 (se liant a l'adn) interviendraient dans un second mecanisme, actif uniquement a basse temperature. Nous avons selectionne des mutants alteres probablement dans des elements en interaction avec la proteine mukb, et des mutants chez lesquels un troisieme mecanisme de partition semble active. E. Coli possede deux modes de croissance: l'elongation et la septation ou division cellulaire. L'inhibition specifique, par le beta-lactame mecillinam, de la peptidoglycane synthetase essentielle a l'elongation, pbp2, tue les cellules. Nous avons montre que l'inactivation de la pbp2 ainsi que le transfert a haute temperature d'un mutant rpob(fts), possedant une arn polymerase alteree, entrainent l'inhibition de la septation, qui peut etre levee par l'augmentation de la concentration en ppgpp, le nucleotide effecteur de la reponse stringente, ainsi que par la surproduction de la proteine de division ftsz. Nos resultats suggerent que cette inhibition de la septation est liee a une synthese insuffisante de la proteine ftsz et que le ppgpp est un activateur de l'expression du gene ftsz. Le nucleotide ppgpp, indicateur de l'activite des ribosomes et activateur de la septation, couplerait ce processus au taux de croissance

Orientador: Marcelo Palma Sircili
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia
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Resumo: Escherichia coli (E.coli) enteropatogênica (EPEC), é um dos agentes causadores de diarreia em crianças, principalmente em países em desenvolvimento. EPEC pode ser dividida em típica (tEPEC) ou atípica (aEPEC) pela presença ou ausência do plasmídeo EAF, respectivamente e, mais precisamente pela expressão da fímbria Bfp. Uma característica de EPEC é a capacidade de causar uma lesão histopatológica denominada "attaching and effacing" (lesão A/E) no epitélio intestinal e os genes responsáveis pela formação da lesão A/E estão localizados na ilha de patogenicidade LEE (locus of enterocyte effacement). Outra característica de EPEC é a formação de microcolônias que possibilitam a formação de biofilme. Um dos mecanismos de regulação da formação de biofilme envolve a molécula sinalizadora Bis-(3'-5')-monofosfato de guanosina cíclico (c-di-GMP), um mensageiro secundário universal em bactérias que está envolvido na regulação de uma grande variedade de processos celulares. Para exercer sua função, c-di-GMP precisa se ligar e alterar alostericamente a estrutura de uma molécula efetora. Um dos receptores conhecidos para c-di-GMP é YcgR, uma proteína de domínio PilZ que possui um sítio de ligação para c-di-GMP e está envolvida diretamente na regulação do movimento flagelar através da ligação do complexo YcgR-c-di-GMP às proteínas da base do motor flagelar. Existem poucos dados na literatura sobre as funções de YcgR, todos focados apenas no seu papel na regulação da motilidade. Assim, o presente trabalho teve como objetivo avaliar a influência de YcgR na motilidade, formação de biofilme, adesão e formação de lesão A/E em um amostra de aEPEC do sorotipo O55:H7. O gene ycgR foi deletado da amostra selvagem através da técnica de recombinação homóloga proposta por Datsenko e Wanner (2000). A complementação da amostra mutante foi realizada através da clonagem do gene ycgR no plasmídeo de expressão pBAD Myc HisA. Os resultados obtidos indicam que a deleção do gene ycgR reduz a motilidade e aumenta a formação do biofilme inicial na amostra O55:H7. Além disso, a adesão em células epiteliais e a formação da lesão A/E também foram reduzidas em comparação à amostra selvagem. Os resultados fenotípicos corroboram os observados na análise transcricional dos genes eae, ler e espA, que participam da formação da lesão A/E, e dos genes bscA, fimA e csgD, envolvidos na formação do biofilme inicial. Com exceção do gene csgD que apresentou um aumento na transcrição na amostra mutante, todos os outros genes avaliados apresentaram uma menor transcrição em relação à amostra selvagem. Poucos trabalhos na literatura demonstram o papel do mensageiro secundário em amostras de E. coli patogênicas, assim, estes resultados são os primeiros descritos para uma amostra de aEPEC e possibilitam que no futuro novos estudos possam analisar com mais detalhes a participação de c-di-GMP na regulação de fatores de virulência não só de aEPEC mas também de outras E.coli patogênicas
Abstract: Enteropathogenic Escherichia coli (EPEC) is a causative agent of diarrhea in children, especially in developing countries. EPEC can be categorized in 2 subgroups termed typical (tEPEC) or atypical (aEPEC) by the presence or absence of the EAF plasmid respectively, and more precisely by the expression of the Bfp fimbriae. One characteristic of EPEC is the ability to cause a histopathological lesion on epithelial cells called "attaching and effacing" (A/E lesion). The genes responsible for the production of the A/E lesion are encoded in a pathogenicity island named "locus of enterocyte effacement" (LEE). Another feature of EPEC is the formation of microcolonies, which allow biofilm formation. One of the regulation mechanisms of biofilm formation involves the signaling molecule bis- (3'-5') cyclic guanosine monophosphate (c-di-GMP), a ubiquitous second messenger in bacteria that participates in the regulation of a wide variety of cellular processes. To perform its function, c-di-GMP needs to bind and alter allosterically the structure of an effector molecule. One of the known (many?) receptors for c-di-GMP is YcgR, a Pilz domain protein that has a c-di-GMP binding site and is involved directly in the regulation of flagellar movement through the binding of the YcgR-c-di-GMP complex to flagellar motor proteins. There are few published data on the YcgR functions and they focus mainly on the role of the YcgR in motility regulation. The aim of this study was to evaluate the influence of YcgR in motility, biofilm formation, adhesion and A/E lesion formation in an aEPEC strain serotype O55:H7. ycgR gene deletion was performed by homologous recombination as proposed by Datsenko and Wanner (2000). Complementation of O55:H7 mutant strain was achieved by cloning ycgR in pBAD/Myc-HisA plasmid. The results indicate that the deletion of ycgR gene decreases the motility and increases the formation of initial biofilm on O55:H7 strain. Moreover, the adhesion on epithelial cells and the A/E lesion formation were also diminished in comparision to the wild type strain. The phenotypic results are consistent with the transcriptional analysis of eae, ler and espA genes involved in A/E lesion formation, and of bcsA, fimA and csgD genes involved in the initial steps of biofilm formation. With the exception of csgD gene that showed an increased transcription level in the mutant strain, all other analysed genes showed a decrease in transcription when compared to the wild type strain. Few studies demonstrate the role of a second messenger molecule in Escherichia coli pathogenic samples, and therefore, these results are the first report in this regard for an aEPEC strain. This work should encourage further studies in order to analyze in more detail the involvement of c-di GMP in the regulation of virulence factors not only in aEPEC, but also in other pathogenic Escherichia coli pathotypes
Mestrado
Microbiologia
Mestra em Genética e Biologia Molecular

Presently, the literature regarding vascular smooth muscle contraction is coloured with many contradictory observations and conclusions. However, like many physiological systems, the biochemical pathways and functional events of vascular smooth muscle contraction vary between individual species and/or tissues. Therefore, determination of a ubiquitous excitation-contraction coupling mechanism is unlikely; variations between receptor classes, receptor density, excitation-contraction coupling pathways and the efficiency of the receptor-pathway interaction contribute to the various observations and conclusions. The inositol 1,4,5-trisphosphate (IP₃) second messenger cascade regulates the mobilization of intracellular Ca²⁺, and subsequently contraction, in vascular smooth muscle. However, phospholipase G-mediated production of IP₃ appears to be controlled by tissue-specific regulatory factors. This study examines the effects of three such factors, the presence of extracellular Ca²⁺, the sensitivity of the associated G-protein and inhibition by 8-bromoguanosine 3':5'-cyclic monophosphate (8-brombcGMP), in isolated rat caudal artery. Concentration-response curves were constructed for phenylephrine and isometric contractions measured in isolated tissues. In addition, phosphatidylinositol turnover was assessed using anion exchange chromatography. The effects of 8-bromo-cGMP on phenylephrine-induced contractions and phosphatidylinositol hydrolysis were compared to those of felodipine, a dihydropyridine Ca²⁺-channel antagonist, and ryanodine, a putative depletor of intracellular Ca2* stores in rat caudal artery. Pertussis toxin was used to determine the identity of the G-protein regulating phenyiephrine-induced contraction. Further, the effects of felodipine and ryanodine on contraction were determined in rat thoracic aorta to compare the contribution of extracellular and intracellular Ca²⁺ to contraction between a large conduit vessel and a small conduit vessel. The results of this investigation suggest that phospholipase C-activated phosphatidylinositol hydrolysis in the rat caudal artery is dependent on extracellular Ca²⁺, mediated, in part, through dihydropyridine sensitive Ca²⁺ channels. Phospholipase C activity is not directly inhibited by 8-bromo-cGMP. However, the nucleotide may regulate vascular smooth muscle contraction by inhibition of Ca²⁺ release from IP₃-mediated intracellular stores, but it is unlikely that 8-bromo-cGMP affects ryanodine-sensitive stores. None of the G-proteins coupled to the ctiadrenoceptor mediated excitation-contraction pathway in rat caudal artery appear to be sensitive to pertussis toxin. Rat aortic tissue does not rely on intracellular Ca²⁺ to the same extent that rat caudal artery does, confirming the tissue specificity of ctiadrenoceptor agonist induced excitation-contraction in vascular smooth muscle.

Evaluating aerodynamic noise from aircraft engines is a design stage process, so that it conform to regulations at airports. Aerodynamic noise is also a principal source of structural vibration and internal noise in short/vertical take off and landing and rocket launches. Acoustic loads may be critical for the proper functioning of electronic and mechanical components. It is imperative to have tools with capability to predict noise generation from turbulent flows. Understanding the mechanism of noise generation is essential in identifying methods for noise reduction. Lighthill (1952) and Lighthill (1954) provided the first explanation for the mechanism of aerodynamic noise generation and a procedure to estimate the radiated sound field. Many such procedures, known as acoustic analogies are used for estimating the radiated sound field in terms of the turbulent fluid flow properties. In these methods, the governing equations of the fluid flow are rearranged into two parts, the acoustic sources and the propagation terms. The noise source terms and propagation terms are different in different approaches. A good description of the turbulent flow field and the noise sources is required to understand the mechanism of noise generation. Computational aeroacoustics (CAA) tools are used to calculate the radiated far field noise. The inputs to the CAA tools are results from CFD simulations which provide details of the turbulent flow field and noise sources. Reynolds-Averaged Navier Stokes (RANS) solutions can be used as inputs to CAA tools which require only time-averaged mean quantities. The output of such tools will also be mean quantities. While complete unsteady turbulent flow details can be obtained from Direct Numerical Simulation (DNS), the computation is limited to low or moderate Reynolds number flows. Large eddy simulations (LES) provide accurate description for the dynamics of a range of large scales. Most of the kinetic energy in a turbulent flow is accounted by the large-scale structures. It is also the large-scale structures which accounts for the maximum contribution towards the radiated sound field. The results from LES can be used as an input to a suitable CAA tool to calculate the sound field. Numerical prediction of turbulent flow field, the acoustic sources and the radiated sound field is at the focus of this study. LES based on explicit filtering method is used for the simulations. The method uses a low-pass compact filter to account for the sub-grid scale effects. A one-parameter fourth-order compact filter scheme from Lele (1992) is used for this purpose. LES has been carried out for four different flow situations: (i) round jet (ii) plane jet (iii) impinging round jet and (iv) impinging plane jet. LES has been used to calculate the unsteady flow evolution of these cases and the Lighthill’s acoustic sources. A compact difference scheme proposed by Hixon & Turkel (1998) which involves only bi-diagonal matrices are used for evaluating spatial derivatives. The scheme provides similar spectral resolution as standard tridiagonal compact schemes for the first spatial derivatives. The scheme is computationally less intensive as it involves only bi-diagonal matrices. Also, the scheme employs only a two-point stencil. To calculate the radiated sound field, the Helmholtz equation is solved using the Green’s function approach, in the form of the Kirchhoff-Helmholtz integral. The integral is performed over a surface which is present entirely in the linear region and covers the volume where acoustic sources are present. The time series data of pressure and the normal component of the pressure gradient on the surface are obtained from the CFD results. The Fourier transforms of the time series of pressure and pressure gradient are then calculated and are used as input for the Kirchhoff-Helmholtz integral. The flow evolution for free jets is characterised by the growth of the instability waves in the shear layer which then rolls up into large vortices. These large vortical structures then break down into smaller ones in a cascade which are convected downstream with the flow. The rms values of the Lighthill’s acoustic sources showed that the sources are located mainly at regions immediately downstream of jet break down. This corresponds to the large scale structures at break down. The radiated sound field from free jets contains two components of noise from the large scales and from the small scales. The large structures are the dominant source for the radiated sound field. The contribution from the large structures is directional, mainly at small angles to the downstream direction. To account for the difference in jet core length, the far field SPL are calculated at points suitably shifted based on the jet core length. The peak value for the radiated sound field occurs between 30°and 35°as reported in literature. Convection of acoustic sources causes the radiated sound field to be altered due to Doppler effect. Lighthills sources along the shear layer were examined in the form of (x, t) plots and phase velocity pattern in (ω, k) plots to analyse for their convective speeds. These revealed that there is no unique convective speeds for the acoustic sources. The median convective velocity Uc of the acoustic sources in the shear layer is proportional to the jet velocity Uj at the center of the nozzle as Uc ≈ 0.6Uj. Simulations of the round jet at Mach number 0.9 were used for validating the LES approach. Five different cases of the round jet were used to understand the effect of Reynolds number and inflow perturbation on the flow, acoustic sources and the radiated sound field. Simulations were carried out for an Euler and LES at Reynolds number 3600 and 88000 at two different inflow perturbations. The LES results for the mean flow field, turbulence profiles and SPL directivity were compared with DNS of Freund (2001) and experimental data available in literature. The LES results showed that an increase in inflow forcing and higher Reynolds number caused the jet core length to reduce. The turbulent energy spectra showed that the energy content in smaller scale is higher for higher Reynolds number. LES of plane jets were carried out for two different cases, one with a co-flow and one without co-flow. LES of plane jets were carried out to understand the effect of co-flow on the sound field. The plane jets were of Mach number 0.5 and Reynolds number of 3000 based on center-line velocity excess at the nozzle. This is similar to the DNS by Stanley et al. (2002). It was identified that the co-flow leads to a reduction in turbulence levels. This was also corroborated by the turbulent energy spectrum plots. The far field radiation for the case without co-flow is higher over all angles. The contribution from the low frequencies is directional, mainly towards the downstream direction. The range of dominant convective velocities of the acoustic sources were different along shear layers and center-line. The plane jet results were also used to bring out a qualitative comparison of flow and the radiation characteristics with round jets. For the round jet, the center-line velocity decays linearly with the stream-wise distance. In the plane jet case, it is the square of the center-line velocity excess which decays linearly with the stream-wise distance. The turbulence levels at any section scales with the center-line stream-wise velocity. The decay of turbulence level is slower for the plane jet and hence the acoustic sources are present for longer distance along the downstream direction. Subsonic impinging jets are composed of four regions, the jet core, the fully developed jet, the impingement zone and the wall jet. The presence of the second region (fully developed free jet) depends on the distance of the wall from the nozzle and the length of the jet core. In impinging jets, reflection from the wall and the wall jet are additional sources of noise compared to the free jets. The results are analysed for the contribution of the different regions of the flow towards the radiated sound field. LES simulations of impinging round jets and impinging plane jet were carried out for this purpose. In addition, the results have been compared with equivalent free jets. The directivity plots showed that the SPL levels are significantly higher for the impinging jets at all angles. For free jets, a typical time scale for the acoustic sources is the ratio of the nozzle size to the jet velocity. This is ro/Uj for round jets and h/Uj for plane jets. For impinging jets, the non-dimensionlised rms of Lighthill’s source indicates that the time scale for acoustic sources is the ratio of the height of the nozzle from the wall to the jet velocity be L/Uj. LES of impinging round jets was carried out for two cases with different inflow perturbations. The jets were at Reynolds number of 88000 and Mach number of 0.9, same as the free jet cases. The impingement wall was at a distance L = 24ro from the nozzle exit. For impinging round jets, the SPL levels are found to be higher than the equivalent free jets. From the SPL levels and radiated noise spectra it was shown that the contribution from the large scale structures and its reflection from the wall is directional and at small angles to the wall normal. The difference in the range of angles where the radiation from the large scale structures were observed shows the significance of refraction of sound waves inside the flow. The rms values of the Lighthill’s sources indicate two dominant regions for the sources, just downstream of jet breakdown and in the impingement zone. The LES of impinging plane jet was done for a jet of Mach number 0.5 and Reynolds number of 6000. The impingement wall was at a distance L = 10h from the nozzle exit. The radiated sound field appears to emanate from this impingement zone. The directivity and the spectrum plots of the far field SPL indicate that there is no preferred direction of radiation from the impingement zone. The Lighthill’s sources are concentrated mainly in the impingement zone. The rms values of the sources indicate that the peak values occur in the impingement zone. The results from the different flow situations demonstrates the capability of LES with explicit filtering method in predicting the turbulent flow and radiated noise field. The method is robust and has been successfully used for moderate Reynolds number and an Euler simulation. An important feature is that LES can be used to identify acoustic sources and its convective speeds. It has been shown that the Lighthill source calculations, the calculated sound field and the observed radiation patterns agree well. An explanation for these based on the different turbulent flow structures has also been provided.

Vitiligo is characterized by a patchy loss of inherited skin color affecting approximately 0.5% of individuals of all races. Despite the absence of the protecting pigment and the overwhelming evidence for hydrogen peroxide (H(2)O(2))-induced oxidative stress in the entire epidermis of these patients, there is neither increased photodamage/skin aging nor a higher incidence for sun-induced nonmelanoma skin cancer. Here we demonstrate for the first time increased DNA damage via 8-oxoguanine in the skin and plasma in association with epidermal up-regulated phosphorylated/acetylated p53 and high levels of the p53 antagonist p76(MDM2). Short-patch base-excision repair via hOgg1, APE1, and polymerasebeta DNA repair is up-regulated. Overexpression of Bcl-2 and low caspase 3 and cytochrome c levels argue against increased apoptosis in this disease. Moreover, we show the presence of high epidermal peroxynitrite (ONOO(-)) levels via nitrotyrosine together with high nitrated p53 levels. We demonstrate by EMSA that nitration of p53 by ONOO(-) (300 x 10(-6) M) abrogates DNA binding, while H(2)O(2)-oxidized p53 (10(-3) M) enhances DNA binding capacity and prevents ONOO(-)-induced abrogation of DNA binding. Taken together, we add a novel reactive oxygen species to the list of oxidative stress inducers in vitiligo. Moreover, we propose up-regulated wild-type p53 together with p76(MDM2) as major players in the control of DNA damage/repair and prevention of photodamage and nonmelanoma skin cancer in vitiligo.