696 research outputs found

    Risk factors for fatality in HIV-infected patients with dideoxynucleoside-induced severe hyperlactataemia or lactic acidosis.

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    BACKGROUND: Lactic acidosis (LA) and severe hyperlactataemia (HL) are infrequent but serious complications of antiretroviral therapy that have been associated with a high fatality rate. METHODS: In a multinational retrospective cohort study, LA was defined as arterial blood pH5 mmol/l. Logistic regression was used to identify factors associated with fatality. Sensitivity and specificity of different case definitions as predictors of death were compared. RESULTS: The overall case-fatality rate was 19/110 (17.3%), but among acidotic patients it was 33% (16/49 cases). There were 10 asymptomatic patients and none of them died as a consequence of the event. The median lactate for fatal, non-fatal and all patients was 8.3 mmol/l (IQR 7.2-13.1), 6.4 mmol/l (IQR 5.4-7.8) and 6.7 mmol/l (IQR 5.5-8.1), respectively. After adjusting for age and current CD4(+) T-cell count, lactate >7 mmol/l (OR 6.27, 95% CI 1.13-34.93), blood bicarbonate 18 mmol/l, 95% CI 1.33-75.65) and concurrent opportunistic infections (OR 8.69, 95% CI 1.45-52.22) were independently associated with case fatality. Blood lactate >7 mmol/l showed a sensitivity of 84% for fatality with a specificity of 60%, whereas bicarbonate 7 mmol/l and blood bicarbonate <18 mmol/l appear to predict death and might help clinicians in selecting patients who may benefit from more intense monitoring

    Assessment of liver fibrosis and associated risk factors in HIV-infected individuals using transient elastography and serum biomarkers

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    Background: Liver fibrosis in human immunodeficiency virus (HIV)-infected individuals is mostly attributable to co-infection with hepatitis B or C. The impact of other risk factors, including prolonged exposure to combined antiretroviral therapy (cART) is poorly understood. Our aim was to determine the prevalence of liver fibrosis and associated risk factors in HIV-infected individuals based on non-invasive fibrosis assessment using transient elastography (TE) and serum biomarkers (Fibrotest [FT]). Methods: In 202 consecutive HIV-infected individuals (159 men; mean age 47 ± 9 years; 35 with hepatitis-C-virus [HCV] co-infection), TE and FT were performed. Repeat TE examinations were conducted 1 and 2 years after study inclusion. Results: Significant liver fibrosis was present in 16% and 29% of patients, respectively, when assessed by TE (≥ 7.1 kPa) and FT (> 0.48). A combination of TE and FT predicted significant fibrosis in 8% of all patients (31% in HIV/HCV co-infected and 3% in HIV mono-infected individuals). Chronic ALT, AST and γ-GT elevation was present in 29%, 20% and 51% of all cART-exposed patients and in 19%, 8% and 45.5% of HIV mono-infected individuals. Overall, factors independently associated with significant fibrosis as assessed by TE (OR, 95% CI) were co-infection with HCV (7.29, 1.95-27.34), chronic AST (6.58, 1.30-33.25) and γ-GT (5.17, 1.56-17.08) elevation and time on dideoxynucleoside therapy (1.01, 1.00-1.02). In 68 HIV mono-infected individuals who had repeat TE examinations, TE values did not differ significantly during a median follow-up time of 24 months (median intra-patient changes at last TE examination relative to baseline: -0.2 kPa, p = 0.20). Conclusions: Chronic elevation of liver enzymes was observed in up to 45.5% of HIV mono-infected patients on cART. However, only a small subset had significant fibrosis as predicted by TE and FT. There was no evidence for fibrosis progression during follow-up TE examinations

    Metabolic and functional consequences of cytosolic 5′-nucleotidase-IA overexpression in neonatal rat cardiomyocytes

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    Adenosine exerts a spectrum of energy-preserving actions on the heart negative chronotropic effects. The pathways leading to adenosine formation have remained controversial. In particular, although cytosolic 5′-nucleotidases can catalyze adenosine formation in cardiomyocytes, their contribution to the actions of adenosine has not been documented previously. We recently cloned two closely related AMP-preferring cytosolic 5′-nucleotidases (cN-IA and -IB); the A form predominates in the heart. In this study, we overexpressed pigeon cN-IA in neonatal rat cardiomyocytes using an adenovirus. cN-IA overexpression increased adenosine formation and release into the medium caused by simulated hypoxia and by isoproterenol in the absence and presence of inhibitors of adenosine metabolism. Adenosine release was not affected by an ecto-5′-nucleotidase inhibitor, α,β-methylene-ADP, but was affected by a nucleoside transporter, dipyridamole. The positive chronotropic effect of isoproterenol (130 ±3 vs. 100 ±4 beats/min) was inhibited (107 ±3 vs. 94 ±3 beats/min) in cells overexpressing cN-IA, and this was reversed by the addition of the adenosine receptor antagonist 8-(p-sulfophenyl)theophilline (120 ± 3 vs. 90 ± 4 beats/min). Our results demonstrate that overexpressed cN-IA can be sufficiently active in cardiomyocytes to generate physiologically effective concentrations of adenosine at its receptors.Fil: Sala-Newby, Graciela B.. University of Bristol; Reino UnidoFil: Freeman, Nicola V. E.. University of Bristol; Reino UnidoFil: Curto, Maria de Los Angeles. University of Bristol; Reino Unido. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres"; ArgentinaFil: Newby, Andrew C.. University of Bristol; Reino Unid

    Hydroacylation and C-N Coupling Reactions. Mechanistic Studies and Application in the Nucleoside Synthesis

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    The PhD work "Hydroacylation and C-N coupling Reactions. Mechanistic Studies and Application in the Nucleoside Synthesis" tackle two different objectives, a) developing new methods of synthesis of nucleosides (introduction, and chapters 1 and 2) and b) to carry out a mechanistic study of the intermolecular hydroacylation and hydroiminoacylation reaction with and cationic rhodium complexes (chapter 3). Concerning the synthesis nucleosides, in chapter 1 we have explored new methods of synthesis of 2',3'-dideoxynucleosides and isonucleosides using a palladium or copper catalyzed C-N coupling reaction, aiming to overcome the stereoselectivity problems of the glycosylation reaction. The synthesis of the iodo-vinyl derivatives required as starting materials has been tried by different procedures, all of them unsuccessful. Finally, the coupling reaction has been explored in 1-iodo-glucal derivatives. Palladium catalysts were unsuccessful in coupling with benzimidazol used as model of purinic bases. Copper catalysts provided very low conversions. However, the oxidative addition of 1-iodo-glucal to palladium was proved and it was also observed that the reaction with aniline proceeds. That, suggest that the problem is in the steps involving the benzimidazol.In chapter 2, it has been developed a new method of synthesis of carbocyclic nucleosides using and enantioselective intramolecular hydroacylation reaction as a key step. This reaction leaded to the 3-hydroxymethyl-cyclopentanones in good yields and excellent enantioselectivities. When (S,S)-Me-Duphos was used the 3S-cyclopentanone was obtained, in contrast whether the (R,R)-Me-Duphos was employed the reaction proceed giving the opposite enantiomer. In both cases. The reduction of the ketone can be carried out in a stereoselective way using a hydroxyl-assited reduction with NaBH(OAc)3. Alternatively, the diastereomeric mixture obtained by a direct reduction can be resolved by using a DKR process using a combined enzyme/Ru complex catalytic system. A Mitsunobu reaction has allowed finally to link adenine to the cyclopentane moiety. In the third chapter, the mechanism of both cationic and neutral rhodium catalyst precursors in the hydroiminoacylation of alkenes was studied. The oxidative addition step was studied using both NMR and DFT techniques. Using the neutral complex, this step is a thermodynamically favoured process, as demonstrated by the isolation of the stable complex. Furthermore, DFT calculations showed the existence of an agostic intermediate on the route to the C-H activation product. In the cationic system, the oxidative addition reaction was shown by DFT calculations to be an endothermic process, hence un-favoured. This was in agreement with the NMR experiments, in which an oxidative addition product was only detected in the presence of a chloride source. Furthermore, the transition states involved in both systems were identified using DFT calculations, which proved that the presence of chloride not only stabilize the oxidative addition product but also lower the energy barrier of the overall process.Using the neutral system, it was identified the coupling product still coordinated to rhodium, which is in an enamine tautomeric form. After removal of the coupling product the stable complex [Rh(&#956;-Cl)(PPh3)2]2 was formed. This species was reported as a precursor for the oxidative addition step, from which the catalytic cycle can start again. However in the cationic system, the system did not yield any stable rhodium species and quickly evolved towards decomposition.Durante la última década la terapia del SIDA ha experimentado una evolución notable. El conocimiento del modo de actuación y proliferación del virus ha permitido incrementar el número de dianas biológicas para su neutralización. Así, hoy en día se conocen compuestos que inhiben la entrada del virus en la célula, la transcripción del RNA en DNA, la integración del DNA vírico en DNA celular, la producción del envolvente proteico del virus, entre otros. Todo ello, ha permitido la realización de tratamientos dirigidos a diferentes dianas, que han neutralizado la evolución del virus mejorando la calidad de vida de los pacientes.Existen numerosas metodologías diseñadas para obtener los retrovirales mencionados anteriormente, pero en la mayoría de ellas se requieren numerosos pasos de síntesis y además en muchas de ellas se obtienen mezclas de los isómeros &#945;/&#946;. De este modo se pretende diseñar una alternativa sintética general para la preparación de la familia de nucleósidos arriba indicadas y al mismo tiempo que sea una alternativa práctica y eficaz a los métodos descritos hasta el momento.En el capítulo uno la obtención de isonucleosidos y 2',3'-dideoxinucleosidos se abordó utilizando como etapa clave de reacción el acoplamiento C-N entre los derivados de 4-halo-2,3-dihidrofurano y 5-halo-2,3-dihidrofurano con bases púricas y pirimidínicas, la posterior hidrogenación enantioselectiva del doble enlace nos permitiría obtener los mencionados compuestos de una forma sencilla. En el estudio realizado bajas conversiones de los productos de acoplamiento cruzado fueron detectados aunque actualmente se están intentado mejorar los resultados.Referente a la obtención de carbociclonucleosidos abordada en el capítulo 2, se ha llevado cabo una nueva metodología sintética en la que se ha aplicado la reacción de hidroacilación intramolecular enantioselectiva catalizada por rodio. Así pentenales substituidos en posición cuatro han sido convertidos en las ciclopentanonas correspondientes. En función de la quiralidad de la fosfina empleada se han obtenido tanto los enantiomeros R como S con excelentes conversiones y enantioselectividades.Con el fin de incorporar la base nitrogenada en la ciclopentanona la reducción diastereoselectiva se ha llevado a cabo dos procedimientos: a) reducción racémica de la ciclopentanona y posterior resolución cinética dinámica, b) reducción diastereoselectiva utilizando como agente reductor el triacetoxiborohidruro de sodio. En ambos casos se obtuvieron diastereoselectividades excelentes pudiendo así obtener un distereoisomero u otro en función del procedimiento y el enantiomero utilizado como material de partida. La posterior reacción de Mitsunobu sobre el alcohol y la desprotección del grupo protector nos ha permitido obtener el carbociclonucleosido con buenos rendimientos y excelentes esteroselectividades.En el capitulo tres se ha realizado un estudio sobre la reacción de hidroacilación intramolecular de alquenos cataliza por rodio, donde se ha estudiado la diferencia de comportamiento de los sistemas catiónicos y neutros de rodio en la etapa de adición oxidante. Estos estudios se han realizado utilizando técnicas espectroscópicas de resonancia magnética nuclear y cálculos teóricos mediante técnicas DFT. El estudio computacional ha mostrado que en el caso de los sistemas neutros la etapa de adición oxidante es una etapa termodinámicamente favorable hecho que se gratifica con el hecho de que el producto de adición oxidante es estable y aislable. Además se ha encontrado la existencia de un intermedio agóstico en el proceso de activación del enlace C-H. Sin embargo, en los sistemas catiónicos la etapa de adición oxidante resultó ser un proceso endotérmico. Los estados de transición encontrados no solo han demostrado que la presencia de cloruro estabiliza el producto de adición oxidante sino que también disminuye la barrera energética del proceso global. La etapa de inserción del alqueno también fue estudiada para ambos sistemas utilizando estireno como sustrato. En el sistema neutro se detectó una nueva especie de rodio la cual no había sido descrita anteriormente y fue completamente caracterizada mediante RMN multinuclear.En el sistema catiónico se consiguió detectar el hidruro correspondiente al producto de adición oxidante el cual también fue completamente caracterizado por técnicas de RMN. Sin embargo, en el estudio de la inserción del alqueno no se observó la ningún producto que indicase que el mencionado proceso se llevará acabo indicado que la inserción de alqueno es además la etapa lenta del proceso

    Aeromonas hydrophila strains as biocatalysts for transglycosylation

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    Microbial transglycosylation is useful as a green alternative in the preparation of purine nucleosides and analogues, especially for those that display pharmacological activities. In a search for new transglycosylation biocatalysts, two Aeromonas hydrophila strains were selected. The substrate specificity of both micro-organisms was studied and, as a result, several nucleoside analogues have been prepared. Among them, ribavirin, a broad spectrum antiviral, and the well-known anti HIV didanosine, were prepared, in 77 and 62% yield using A. hydrophila CECT 4226 and A. hydrophila CECT 4221, respectively. In order to scale-up the processes, the reaction conditions, product purification and biocatalyst preparation were analyzed and optimized.Fil: Nóbile, Matías Leonardo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes; ArgentinaFil: Terreni, Marco. Universita degli Studi di Pavia; ItaliaFil: Lewkowicz, Elizabeth Sandra. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes; ArgentinaFil: Iribarren, Adolfo Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres"; Argentina. Universidad Nacional de Quilmes; Argentin

    Synthesis and evaluation of some novel nucleotide derivatives as potential anti-AIDS drugs.

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    Many nucleoside analogues are known to inhibit human immunodeficiency virus (HIV), the causative agent of the disease acquired immunodeficiency syndrome (AIDS). In order to act these nucleosides must be phosphorylated to their corresponding 5'-triphosphates, which can then inhibit reverse-transcriptase (RT), a key viral enzyme. These phosphorylations are catalysed by cellular kinases. The synthesis of a number of nucleoside 5'-dialkyl phosphates is described in this thesis, along with the results of the biological evaluation of some of these derivatives against HIV. It was thought that the 5'-dialkyl phosphates might have been able to act as prodrugs for the corresponding 5'-monophosphates. Firstly the synthesis of 5'-dialkyl phosphates of 3'-0-mesylthymidine, 3'-0-acetylthymidine and 3'-0-ethylthymidine is described, along with the synthesis of some 5'-dialkyl phosphates of 3'-azido-3'-deoxythymidine, 2',3'-dideoxycytidine and 2',3'-dideoxyadenosine. However, when tested, all of the above 5'-dialkyl phosphates were found to be inactive against HIV in vitro. It was thought that this inactivity arose from the metabolic stability of the simple dialkyl esterifying groups present in these compounds. With this in mind some nucleoside 5'-bis(2,2,2-trihaloethyl) phosphate derivatives were synthesised as it was hoped that 2,2,2- trihaloethyl groups would be more labile than simple alkyl ones. Both 3'-azido-3'-deoxythymidine 5'-bis(2,2,2-trifluoroethyl) phosphate and 3'-azido-3'-deoxythymidine 5'-bis(2,2,2-trichloroethyl) phosphate were found to be inhibitors of HIV in vitro. In view of these results, the synthesis of some 5'-bis(2,2,2-trihaloethyl) phosphate derivatives of 2',3'-dideoxycytidine and 3'-fluoro-3'-deoxythymidine was undertaken. The synthesis of some mixed 5'-(alkyl 2,2,2-trihaloethyl) phosphate derivatives of 3'-azido-3'-deoxythymidine was also carried out. The 5'-bis(2,2,2-trichloroethyl) phosphates of 3'-0-mesylthymidine, 3'-0-acetylthymidine, 3'-0-ethylthymidine and 3'-amino-3'-deoxythymidine were also synthesised. As 3'-azido-3'-deoxythymidine 5'-bis(2,2,2-trichloroethyl) phosphate was able to inhibit HIV in vitro, the 5'-bis(2-chloroethyl) phosphate and the 5'-bis(2,2-dichloroethyl) phosphate of 3'-azido-3'-deoxythymidine were prepared, in order to ascertain if these compounds were able to inhibit HIV also. The 5'-bis(2-chloroethyl) phosphate of 3'-azido- 3'-deoxythymidine does indeed display activity against HIV in vitro. An attempt was made to synthesise a thymidine 5'-dialkyl phosphonate species, by a Michaelis-Arbuzov type reaction between 5'-bromo-5'-deoxythymidine and diethyl phosphite. However, it was only possible to isolate a 3'-hydrogenphosphate species from this reaction. As the method by which 3'-azido-3'-deoxythymidine 5'-bis(2,2,2-trichloroethyl) phosphate acts as an inhibitor of HIV probably involves the hydrolysis of the phosphate moiety to either the 5'-monophosphate or the parent nucleoside, some studies on the hydrolysis of 3'-azido-3'-deoxythymidine 5'-bis(2,2,2-trichloroethyl) phosphate at a variety of pH were carried out
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