Articles de revues : « Metabolismo, Flusso »

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Hammers, A. « Diagnostica per immagini cerebrale tramite tomografia a emissione di positroni in neurologia : dalla misurazione del flusso sanguigno e del metabolismo all’esplorazione della neurotrasmissione ». EMC - Neurologia 15, n^o 2 (avril 2015) : 1–9. http://dx.doi.org/10.1016/s1634-7072(15)70502-7.

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Medina-Galván, Julio, Juan Manuel Audelo-Naranjo et José Alfredo Arreola-Lizárraga. « Importancia del monitoreo de procesos biogeoquímicos en lagunas costeras : Área Natural Protegida estero El Soldado como estudio de caso ». Investigación y Ciencia de la Universidad Autónoma de Aguascalientes, n^o 77 (31 mai 2019) : 12–18. http://dx.doi.org/10.33064/iycuaa2019772087.

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Esta contribución presenta estimaciones de los flujos de nutrientes y el metabolismo neto en una laguna costera prístina del Golfo de California. Durante primavera se realizaron muestreos de variables del agua en la laguna y el mar adyacente. Los flujos de nutrientes y el metabolismo neto del ecosistema fueron estimados con el modelo biogeoquímico propuesto por el programa LOICZ (Interacciones Tierra Océano en la Zona Costera). La tasa de renovación del agua fue de 3 días. La laguna El Soldado funcionó como fuente de nitrógeno (+61mol día–1) y como sumidero de fósforo (-42 mol día–1). El metabolismo neto fue autótrofo (73 mmol C m2 mes-1) y dominó la fijación de nitrógeno. Estas observaciones en la laguna El Soldado ayudan al entendimiento de los procesos biogeoquímicos y exhibe la importancia de su monitoreo a través del ciclo anual, así como en periodos de largo plazo.

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Martin, W. R. Wayne, et Michael R. Hayden. « Cerebral Glucose and Dopa Metabolism in Movement Disorders ». Canadian Journal of Neurological Sciences / Journal Canadien des Sciences Neurologiques 14, S3 (août 1987) : 448–51. http://dx.doi.org/10.1017/s0317167100037896.

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ABSTRACT:The development of positron emission tomography (PET) has enabled us to perform in vivo measurements of certain aspects of regional cerebral function. Regional cerebral glucose metabolism may be readily quantified with [18F] fluoro-2-deoxyglucose (FDG) and presynaptic dopaminergic function may be studied with the labelled dopa analog 6-[18F] fluoro-L-dopa. We have applied a model to the analysis of 6-FD/PET data with which in vivo age-related changes in dopaminergic function may be demonstrated in normal subjects. With this technique, we have studied a series of asymptomatic MPTP-exposed subjects and have shown evidence of subclinical nigrostriatal pathway damage. Studies of regional cerebral glucose metabolism with FDG in early Huntington's disease have shown a characteristic impairment in caudate function which precedes the development of caudate atrophy. In addition, some asymptomatic individuals who are at risk for HD have caudate hypometabolism. We feel that, at the present time, PET provides information which is complementary to the clinical examination in establishing a diagnosis of HD. In the future these studies may also help in the investigation of at risk individuals

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Sylvia, A. L., et C. A. Piantadosi. « Brain Oxygen Metabolism in Fluosol-43 Circulated Rats ». Biomaterials, Artificial Cells and Artificial Organs 16, n^o 1-3 (janvier 1988) : 679–80. http://dx.doi.org/10.3109/10731198809132637.

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Hasselbalch, Steen G., Peter L. Madsen, Gitte M. Knudsen, Søren Holm et Olaf B. Paulson. « Calculation of the FDG Lumped Constant by Simultaneous Measurements of Global Glucose and FDG Metabolism in Humans ». Journal of Cerebral Blood Flow & ; Metabolism 18, n^o 2 (février 1998) : 154–60. http://dx.doi.org/10.1097/00004647-199802000-00005.

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The lumped constant defined as the conversion factor between the net uptake of fluoro-2-deoxy-D-glucose (FDG) and glucose was calculated from global CMRglc and from positron emission tomography (PET) using FDG as tracer (CMRFDG). Fifteen healthy, normal volunteers (mean age 24 ± 4 years) were studied. Global CBF and CMRglc were measured with the Kety-Schmidt technique using 133Xe as tracer, and values were corrected for errors from incomplete diffusion equilibrium for inert gas tracer between brain tissue and cerebral venous blood. Measurements of CMRFDG were obtained with PET using the dynamic and single-scan methods and the K1–k3 model. Measurements with the Kety-Schmidt technique and PET-FDG were performed simultaneously. Global CBF was 47.1 ± 8.0 mL · 100 g−1 · min−1, and CMRglc was 22.8 ± 4.1 μmol · 100 g−1 · min−1. No difference in CMRFDG was found with the two methods (17.8 ± 1.6 and 18.2 ± 1.3 μmol · 100 g−1 · min−1, dynamic and single scan methods, respectively). Accordingly, the lumped constant ranged from 0.80 ± 0.16 to 0.82 ± 0.15, with a mean value of 0.81 ± 0.15. The mean ratio between phosphorylation of FDG and glucose (k3*/k3) was 0.39 ± 0.25. The discrepancy between the lumped constant determined in this study and previously obtained values can be explained partly by methodologic problems, and we conclude that most of the discrepancy results from previous overestimation of global CBF. Key Words: Positron emission tomography—18F-Fluro-deoxy-D-glucose—Lumped constant—Brain glucose metabolism.

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Medina-Galván, Julio, Carmen Cristina Osuna-Martínez, Gustavo Padilla-Arredondo, Martín Gabriel Frías-Espericueta, Ramón Héctor Barraza-Guardado, Jesús Armando León-Cañedo et José Alfredo Arreola-Lizárraga. « Estado trófico, dinámica de nutrientes y metabolismo neto de una laguna costera subtropical (Golfo de California) receptora de aguas residuales ». Revista Internacional de Contaminación Ambiental 38 (31 octobre 2022) : 449–63. http://dx.doi.org/10.20937/rica.54396.

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Se evaluaron el estado trófico, la dinámica de nutrientes y el metabolismo neto de una laguna costera subtropical ubicada en la costa este del Golfo de California. La laguna Santa María es un sistema receptor de aguas residuales urbanas, camaronícolas y agrícolas. En la laguna y el mar adyacente se realizaron muestreos de agua en verano e invierno para obtener información de temperatura, salinidad, oxígeno disuelto, nutrientes inorgánicos disueltos y clorofila a. El estado trófico se estimó con el índice TRIX, mientras que los flujos de nutrientes y el metabolismo neto se estimaron con el modelo biogeoquímico LOICZ. La laguna exhibió un estado mesotrófico en verano e invierno. Las tasas de renovación del agua estimadas fueron de 22 días en verano y 10 días en invierno. Los flujos de nutrientes mostraron que la laguna fue sumidero en verano (ΔNID = –0.84 mmol/m2/día y ΔFID = –0.12 mmol/m2/día) y fuente en invierno (ΔNID = 0.04 mmol/m2/día y ΔFID = 0.15 mmol/m2/día). En verano, el metabolismo neto del ecosistema (MNE) fue autótrofo (13 mmol C/m2/día) y predominó el proceso de fijación de nitrógeno (+ 1.2 mmol/m2/día). En invierno, el MNE fue heterótrofo (–16.36 mmol/m2/día) y predominó la desnitrificación (–2.3 mmol/m2/día). Se concluye que la laguna Santa María funciona asimilando nutrientes con predominancia de metabolismo autótrofo y fijación de nitrógeno en verano, así como exportando nutrientes con predominancia de metabolismo heterótrofo y desnitrificación en invierno. La laguna mantiene un estado mesotrófico en ambas estaciones del año mostrando capacidad de asimilar, transformar y exportar las cargas de nutrientes sin manifestar procesos adversos de eutrofización.

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Osorio O., José Henry. « Metabolismo de los lípidos durante el embarazo ». Revista Colombiana de Obstetricia y Ginecología 51, n^o 2 (30 juin 2000) : 113–17. http://dx.doi.org/10.18597/rcog.692.

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El flujo neto de nutrientes, electrolitos, vitaminas, y otros compuestos de la madre a el feto es necesario para asegurar un suministro constante para el metabolismo energético fetal así como para el crecimiento y diferenciación de tejidos. En la formación de sistemas fetales como el nervioso y en el balance de requerimientos extra de energía en el embarazo avanzado es indispensable la utilización de los lípidos. En la presente revisión podemos recordar los mecanismos básicos y la secuencia de eventos metabólicos relacionados con estos durante la gestación.

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Haggstrom, Lucy R., Julia A. Nelson, Eva A. Wegner et Gideon A. Caplan. « 2-18F-fluoro-2-deoxyglucose positron emission tomography in delirium ». Journal of Cerebral Blood Flow & ; Metabolism 37, n^o 11 (28 mars 2017) : 3556–67. http://dx.doi.org/10.1177/0271678x17701764.

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Delirium is a common, serious, yet poorly understood syndrome. Growing evidence suggests cerebral metabolism is fundamentally disturbed; however, it has not been investigated using 2-18F-fluoro-2-deoxyglucose (FDG) positron emission tomography (PET) in delirium. This prospective study thus explored FDG PET patterns of cerebral glucose metabolism in older inpatients with delirium. A particular emphasis was on the posterior cingulate cortex (PCC), a key region for attention, which is a central feature of delirium. Delirium scans were compared with post-delirium scans using visual analysis and semi-quantitative analysis with NeuroQ; 13 participants (8 female, median 84 y) were scanned during delirium, and 6 scanned again after resolution. On visual analysis, cortical hypometabolism was evident in all participants during delirium (13/13), and improved with delirium resolution (6/6). Using NeuroQ, glucose metabolism was higher post-delirium in the whole brain and bilateral PCC compared to during delirium ( p < 0.05). Greater metabolism in both PCCs correlated with better performance on a neuropsychological test of attention, the WAIS-IV Digit Span Test forwards, and with shorter delirium duration. This research found widespread, reversible cortical hypometabolism during delirium and PCC hypometabolism was associated with inattention during delirium.

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Dutta, Prasanta, Travis C. Salzillo, Shivanand Pudakalakatti, Seth T. Gammon, Benny A. Kaipparettu, Florencia McAllister, Shawn Wagner et al. « Assessing Therapeutic Efficacy in Real-time by Hyperpolarized Magnetic Resonance Metabolic Imaging ». Cells 8, n^o 4 (11 avril 2019) : 340. http://dx.doi.org/10.3390/cells8040340.

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Precisely measuring tumor-associated alterations in metabolism clinically will enable the efficient assessment of therapeutic responses. Advances in imaging technologies can exploit the differences in cancer-associated cell metabolism as compared to normal tissue metabolism, linking changes in target metabolism to therapeutic efficacy. Metabolic imaging by Positron Emission Tomography (PET) employing 2-fluoro-deoxy-glucose ([18F]FDG) has been used as a routine diagnostic tool in the clinic. Recently developed hyperpolarized Magnetic Resonance (HP-MR), which radically increases the sensitivity of conventional MRI, has created a renewed interest in functional and metabolic imaging. The successful translation of this technique to the clinic was achieved recently with measurements of 13C-pyruvate metabolism. Here, we review the potential clinical roles for metabolic imaging with hyperpolarized MRI as applied in assessing therapeutic intervention in different cancer systems.

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Rodríguez Jàcome, Gabriela, et Asunción Blanco-Romero. « Metabolismo insular : flujos y retos del desarrollo territorial en las Islas Galápagos (Ecuador) ». Anales de Geografía de la Universidad Complutense 38, n^o 1 (28 mai 2018) : 113–35. http://dx.doi.org/10.5209/aguc.60471.

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Los espacios insulares son territorios cuyo tamaño, disponibilidad de recursos y accesibilidad son limitados. La insularidad marca unas dinámicas territoriales singulares en estos espacios, que a pesar de su gran valor estratégico los hacen dependientes de las relaciones con el exterior. Las islas Galápagos, pertenecientes a la República del Ecuador, constituyen un caso muy particular de estudio. Si bien las categorías de Patrimonio Natural Mundial y Parque Nacional le dan condiciones de protección de la naturaleza, únicas en el mundo, sus habitantes soportan la misma, o incluso mayor, problemática asociada a la insularidad e isleidad que afrontan otras islas. El presente estudio analiza las relaciones de dependencia de los flujos de turismo, abastos y combustibles entre las islas Galápagos con el Ecuador continental desde la perspectiva del metabolismo insular y la necesidad de adaptación de las políticas y planificación territorial a este contexto. Con este marco este estudio plantea: a) Entender cuáles son los retos del desarrollo territorial considerando el metabolismo insular, b) Considerar la planificación territorial como un aliado de la conservación ambiental, y c) Entender los flujos estratégicos como un factor para reducir la vulnerabilidad y promover la viabilidad insular.

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Gierlinger, Sylvia, Friedrich Hauer, Gudrun Pollack et Fridolin Krausmann. « Metabolismo y paisaje acuático en una ciudad en la industrialización : una evaluación cuantitativa del uso de los recursos y su relación con la transformación del paisaje acuático urbano en Viena del siglo XIX ». Agua y Territorio, n^o 7 (30 juin 2016) : 109–24. http://dx.doi.org/10.17561/at.v0i7.2966.

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En este trabajo tomamos la perspectiva del metabolismo urbano para investigar la transformación del paisaje acuático de Viena. Mostramos cómo el metabolismo de la ciudad se entrelaza profundamente con el paisaje acuático y cómo esta relación cambió durante la industrialización. El eje metodológico de esta investigación parte de una evaluación cuantitativa del uso de los recursos urbanos utilizando métodos de contabilidad de flujos metabólicos. Se presentan los datos sobre la entrada de energía (1800 a 1914), materiales (1830-1874) y agua (1860 a 1910), así como los flujos de las aguas residuales de los hogares (1800 y 1910). Se añade además una discusión crítica sobre las fuentes más importantes de esta investigación. Nuestros hallazgos sugieren que en la transformación de una economía agraria a una sociedad industrial se afectó profundamente el paisaje acuático dentro de la ciudad y en sus alrededores. Funciones tradicionalmente desempeñadas por los ríos y arroyos, que van desde el transporte, el suministro de energía, el suministro de agua dulce o la descarga y limpieza de las aguas residuales fueron sustituidas por la oferta de nuevas tecnologías basadas en combustibles fósiles y en la separación de los materiales de los cuerpos de agua. Se detectaron cambios y presiones ecológicas en la calidad del agua, originando complejas intervenciones hidrológicas que alteraron profundamente el paisaje acuático y su papel en el funcionamiento urbano. Algunos legados de estas transformaciones todavía influyen hoy en día en el metabolismo de la ciudad.

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Kawagoe, Fumihiro, Sayuri Mototani, Kaori Yasuda, Hiroki Mano, Toshiyuki Sakaki et Atsushi Kittaka. « Stereoselective Synthesis of 24-Fluoro-25-Hydroxyvitamin D3 Analogues and Their Stability to hCYP24A1-Dependent Catabolism ». International Journal of Molecular Sciences 22, n^o 21 (1 novembre 2021) : 11863. http://dx.doi.org/10.3390/ijms222111863.

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Two 24-fluoro-25-hydroxyvitamin D3 analogues (3,4) were synthesized in a convergent manner. The introduction of a stereocenter to the vitamin D3 side-chain C24 position was achieved via Sharpless dihydroxylation, and a deoxyfluorination reaction was utilized for the fluorination step. Comparison between (24R)- and (24S)-24-fluoro-25-hydroxyvitamin D3 revealed that the C24-R-configuration isomer 4 was more resistant to CYP24A1-dependent metabolism than its 24S-isomer 3. The new synthetic route of the CYP24A1 main metabolite (24R)-24,25-dihydroxyvitamin D3 (6) and its 24S-isomer (5) was also studied using synthetic intermediates (30,31) in parallel.

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Honka, Miikka-Juhani, Eleni Rebelos, Simona Malaspina et Pirjo Nuutila. « Hepatic Positron Emission Tomography : Applications in Metabolism, Haemodynamics and Cancer ». Metabolites 12, n^o 4 (2 avril 2022) : 321. http://dx.doi.org/10.3390/metabo12040321.

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Evaluating in vivo the metabolic rates of the human liver has been a challenge due to its unique perfusion system. Positron emission tomography (PET) represents the current gold standard for assessing non-invasively tissue metabolic rates in vivo. Here, we review the existing literature on the assessment of hepatic metabolism, haemodynamics and cancer with PET. The tracer mainly used in metabolic studies has been [18F]2-fluoro-2-deoxy-D-glucose (18F-FDG). Its application not only enables the evaluation of hepatic glucose uptake in a variety of metabolic conditions and interventions, but based on the kinetics of 18F-FDG, endogenous glucose production can also be assessed. 14(R,S)-[18F]fluoro-6-thia-Heptadecanoic acid (18F-FTHA), 11C-Palmitate and 11C-Acetate have also been applied for the assessment of hepatic fatty acid uptake rates (18F-FTHA and 11C-Palmitate) and blood flow and oxidation (11C-Acetate). Oxygen-15 labelled water (15O-H2O) has been used for the quantification of hepatic perfusion. 18F-FDG is also the most common tracer used for hepatic cancer diagnostics, whereas 11C-Acetate has also shown some promising applications in imaging liver malignancies. The modelling approaches used to analyse PET data and also the challenges in utilizing PET in the assessment of hepatic metabolism are presented.

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Soares, Pierre Castro, Celso Akio Maruta, Maria Claudia Araripe Sucupira, Clara Satsuki Mori, Sandra Satiko Kitamura, Alexandre Coutinho Antonelli et Enrico Lippi Ortolani. « Diagnóstico de carência energética em bovinos por testes de metabolismo ruminal ». Brazilian Journal of Veterinary Research and Animal Science 43, n^o 1 (1 février 2006) : 33. http://dx.doi.org/10.11606/issn.1678-4456.bjvras.2006.26515.

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Avaliou-se o metabolismo ruminal de bovinos submetidos ou não a dietas carentes em energia, por meio de provas bioquímicas e funcionais no fluido ruminal e urinário com finalidade diagnóstica. Para tal, foram utilizados 10 garrotes mestiços providos de cânula ruminal que foram divididos em dois grupos, ou seja: controle (C; n=4) dieta balanceada para ganho diário de 900 g e carência pronunciada de energia (CP; n=6) recebendo 30% a menos do nível de mantença em energia. Após os bovinos serem alimentados por 140 d foram coletadas amostras de fluido ruminal e urina antes da alimentação e nas 1ª, 3ª, 6ª e 9ª h seguintes. A carência energética provocou diminuição significativa nos teores ruminais de AGVs totais, ácidos propiônico e butírico, amônio, elevando-se o tempo da prova de redução do azul de metileno (RAM) e menor produção de gases no teste de fermentação de glicose (FG); o índice de excreção urinária de alantoína (IEUA) também foi menor. A carência provocou aumento na porcentagem molar de ácido acético. Não se verificou efeito dos tratamentos sobre o pH ruminal. Existiram correlações positivas de grande intensidade entre FG e AGVs e amônia, e de média intensidade entre FG e amônia e IEUA, assim como de correlação negativa, de média intensidade, entre RAM e AGVs, amônia, FG e IEUA. Com exceção do pH todas as análises estudadas detectaram alterações no metabolismo ruminal provocada pela carência energética. Porém, considerando-se a praticidade dos testes, recomenda-se a prova do RAM, seguida pela FG para um diagnóstico rápido e sensível deste quadro carencial.

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Offer, J., J. C. Metcalfe et G. A. Smith. « The uptake of 3H-labelled monodeoxyfluoro-myo-inositols into thymocytes and their incorporation into phospholipid in permeabilized cells ». Biochemical Journal 291, n^o 2 (15 avril 1993) : 553–60. http://dx.doi.org/10.1042/bj2910553.

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Monodeoxyfluoro-myo-inositols were applied to electropermeabilized and intact thymocyte preparations to study their metabolism and uptake in order to investigate their suitability as potential inhibitors of phosphoinositide-mediated cellular responses. Only three of the monodeoxyfluoro-myo-inositols were incorporated into the phospholipids of thymocytes: 1D-3-deoxy-3-fluoro-myo-inositol, 5-deoxy-5-fluoro-myo-inositol and 1D-6-deoxy-6-fluoro-myo-inositol, all of which were weaker substrates for phosphatidylinositol synthase than was myo-inositol. The 3-, 5- and 6-fluoro analogues also behaved as competitive inhibitors, with K1 values of 350 +/- 5 microM, 350 +/- 5 microM and 2.9 +/- 2 mM respectively, compared with a Km for myo-inositol of 31 +/- 4 microM. When incubated with electropermeabilized thymocyte preparations, these three analogues of myo-inositol all formed phospholipids with chromatographic properties which corresponded to those of substituted phosphatidylinositol and phosphatidylinositol monophosphate. The uptake of myo-inositol and of the monodeoxyfluoro-myo-inositols into intact thymocytes was studied by a dual-label technique. All the monodeoxyfluoro-myo-inositols were taken up to some extent, but only 2-deoxy-2-fluoro-myo-inositol and 1D-3-deoxy-3-fluoro-myo-inositol were actively concentrated. The monodeoxyfluoro-myo-inositols were also assayed for their ability to inhibit the uptake of myo-inositol into cells. Both 2-deoxy-2-fluoro-myo-inositol and 1D-3-deoxy-3-fluoro-myo-inositol were effective inhibitors of myo-inositol uptake. Furthermore, 1D-1-deoxy-1-fluoro-myo-inositol, which was not taken up actively, was an effective inhibitor of myo-inositol uptake. The three effective inhibitors all showed Ki values of approximately 150 microM, close to the apparent Km for inositol uptake of 180 microM, and the 4-, 5- and 6-fluoro analogues had Ki values in excess of 10 mM.

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Novak, Marie M. A., Katherine Shimizu et Barry J. Blackburn. « A fluorine-19 nuclear magnetic resonance study of 5-fluorouracil metabolism in Mesocestoides corti tetrathyridia ». Canadian Journal of Zoology 70, n^o 2 (1 février 1992) : 406–10. http://dx.doi.org/10.1139/z92-061.

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Fluorine-19 nuclear magnetic resonance spectra of live tetrathyridia of Mesocestoides corti incubated in 10 mM 5-fluorouracil (5-FU) showed that these larvae metabolize 5-FU to α-fluoro-β-ureidopropionic acid (FUPA), α-fluoro-β-alanine (FBA1) and fluoronucleotides (FNuct). This metabolism is predominantly catabolic, since as time progressed (up to 7 h) the 5-FU signal continuously decreased while the FBA1 signal correspondingly increased and the composite FNuct peak remained small. Similar spectra were obtained from acid extracts of tetrathyridia, except that an additional, very small fluoronucleoside (FNuc) composite peak could be detected. We found 5-FU to be unsuccessful in inhibiting the growth of M. corti tetrathyridia in mice; it is postulated that this was due to the failure of the larvae to effectively anabolize 5-FU.

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Barrio, Jorge R., Sung-Cheng Huang, Dan-Chu Yu, William P. Melega, Javier Quintana, Simon R. Cherry, Andrew Jacobson, Mohammad Namavari, Nagichettiar Satyamurthy et Michael E. Phelps. « Radiofluorinated L-m-Tyrosines : New In-Vivo Probes for Central Dopamine Biochemistry ». Journal of Cerebral Blood Flow & ; Metabolism 16, n^o 4 (juillet 1996) : 667–78. http://dx.doi.org/10.1097/00004647-199607000-00018.

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In this work, we introduce 6-[18F]fluoro-L- m-tyrosine (6-FMT) and compare its in-vivo kinetic and biochemical behaviors in monkeys and rodents with those of 4-FMT and 6-[18F]fluoro-L-3,4-dihydroxyphenylalanine (DOPA) (FDOPA). These radiofluorinated m-tyrosine presynaptic dopaminergic probes, resistant to peripheral 3- O-methylation, offer a nonpharmacological alternative to the use of catechol- O-methyltransferase inhibitors. Like FDOPA, 4-FMT and 6-FMT are analogs that essentially follow the L-DOPA pathway of central metabolism. After i.v. administration in nonhuman primates and rodents, these new radiofluorinated m-tyrosine analogs accumulate selectively in striatal structures and allow for the detection of additional innervation sites (e.g., brain stem) rich in aromatic amino acid decarboxylase. Biochemical analyses in rodents and monkeys revealed the specificity of their central and peripheral metabolism. Molecular and enzymatic mechanisms involved in their retention in central brain structures are consistent with involvement of dopaminergic neurons. The high signal-to-noise ratios observed make these radiofluorinated m-tyrosine analogs outstanding candidates for probing the integrity of central dopaminergic mechanisms in humans.

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Berkowitz, B. A., T. Moriyama, H. M. Fales, R. A. Byrd et R. S. Balaban. « In vivo metabolism of 3-deoxy-3-fluoro-D-glucose. » Journal of Biological Chemistry 265, n^o 21 (juillet 1990) : 12417–23. http://dx.doi.org/10.1016/s0021-9258(19)38363-2.

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Junck, Larry, Sid Gilman, Jill R. Rothley, Annette T. Betley, Robert A. Koeppe et Richard D. Hichwa. « A Relationship between Metabolism in Frontal Lobes and Cerebellum in Normal Subjects Studied with PET ». Journal of Cerebral Blood Flow & ; Metabolism 8, n^o 6 (décembre 1988) : 774–82. http://dx.doi.org/10.1038/jcbfm.1988.132.

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Lesions of one cerebral hemisphere are associated with decreased glucose metabolism, oxygen metabolism, and blood flow in the contralateral cerebellar hemisphere. We used positron emission tomography to look for a functional relationship in cerebral metabolism between the cerebral cortex and the contralateral cerebellum in normal human subjects. Twenty-four normal subjects were scanned with [18F]fluoro-2-deoxy-D-glucose while in a resting state. Asymmetry in local CMRglu (LCMRglu) in the frontal cortex was strongly correlated with asymmetry in LCMRglu in the opposite direction in the cerebellar hemispheres ( r = −0.60, p < 0.001). Widespread subregions of the frontal cortex were found to contribute to this relationship. Considering these results together with previous studies demonstrating that frontal lesions are associated with decreased metabolism in the contralateral cerebellum, we conclude that the frontal cortex exerts a strong modulating influence on metabolism in the contralateral cerebellum in normal subjects, and that this influence may be asymmetrical.

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Hunt, Aoife, Uwe Haberkorn, Johannes Schröder et Peter Schönknecht. « Neural Correlates of Executive Dysfunction in Prodromal and Manifest Alzheimer’s Disease ». GeroPsych 24, n^o 2 (juin 2011) : 77–81. http://dx.doi.org/10.1024/1662-9647/a000038.

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Executive function is frequently impaired in patients with Alzheimer’s disease (AD) and its prodromal stage, and can be assessed using the Trail-Making Test (TMT). We aimed to elicit the neural and cognitive correlates of TMT subtests using positron emission tomography with 18-fluoro-D-deoxy-glucose, and neuropsychological testing in 20 patients with prodromal or manifest AD as well as 14 controls. TMT-A correlated with glucose metabolism in the left middle frontal cortex, TMT-B performance correlated with the metabolism in the right middle frontal cortex and the right precentral gyrus, and TMT-Q performance correlated with metabolism in the right middle frontal cortex. The present findings reveal functional imaging evidence that executive dysfunction in AD as measured by TMT is frontal lobe mediated.

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MacLusky, N. J., L. C. Krey, B. Parsons, G. R. Merriam, D. L. Loriaux, D. G. Pfeiffer et F. Naftolin. « Are catechol oestrogens obligatory mediators of oestrogen action in the central nervous system ? II. Potencies of natural and synthetic oestrogens for induction of gonadotrophin release and female sexual behaviour in the rat ». Journal of Endocrinology 110, n^o 3 (septembre 1986) : 499–505. http://dx.doi.org/10.1677/joe.0.1100499.

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ABSTRACT The role of catechol oestrogen formation in the mechanism by which circulating oestrogens facilitate gonadotrophin release and female sexual behaviour was explored in adult female rats. The effects of oestradiol-17β were compared with those of a group of oestrogens with either a reduced affinity for oestrogen receptors (oestradiol-17α) or a reduced ability to act as substrates for catechol oestrogen formation (2-fluoro-oestradiol, 4-fluoro-oestradiol and moxestrol (11β-methoxy-17α-ethynyloestradiol)). Rats were ovariectomized on the evening of dioestrus day 1 of the 4-day oestrous cycle and implanted s.c. 12 h later with infusion pumps containing either one of the test oestrogens or vehicle alone. Infusion rates for oestradiol-17β, moxestrol, 2-fluoro-oestradiol and 4-fluoro-oestradiol were adjusted to give concentrations of nuclear oestrogen receptors in the brain and pituitary gland within the range of those found in intact female rats during pro-oestrus. Oestradiol-17α was infused at the same and at a tenfold higher rate than that of oestradiol-17β; neither of these treatments with oestradiol-17α significantly increased brain or pituitary gland nuclear oestrogen receptor levels. On the day after the pump was implanted, samples of tail vein blood were withdrawn at 12.00, 14.00, 16.00 and 18.00 h for LH assay. All animals were then injected s.c. with 1 mg progesterone in propylene glycol, and tested for feminine sexual behaviour 5 h later. Oestradiol-17β, moxestrol, 2-fluoro-oestradiol and 4-fluoro-oestradiol all elicited pronounced LH surges and facilitated progesterone-triggered proceptive and lordosis behaviours. In contrast, oestradiol-17α was without effect on LH secretion and sexual behaviours. These results are consistent with the hypothesis that catechol oestrogen biosynthesis is not an obligatory step in the mechanism by which circulating oestrogens induce LH release and feminine sexual behaviour in the rat. J. Endocr. (1986) 110, 499–505

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Pfeiffer, D. G., N. J. MacLusky, E. Barnea, F. Naftolin, L. C. Krey, D. L. Loriaux et G. R. Merriam. « Are catechol oestrogens obligatory mediators of oestrogen action in the central nervous system ? I. Characterization of pharmacological probes with different receptor binding affinities and catechol oestrogen formation rates ». Journal of Endocrinology 110, n^o 3 (septembre 1986) : 489–97. http://dx.doi.org/10.1677/joe.0.1100489.

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ABSTRACT In an attempt to define pharmacological probes with which to test the role of catechol oestrogen formation in the central nervous system, five oestrogens (oestradiol-17β, oestradiol-17α, 4-fluoro-oestradiol, 2-fluoro-oestradiol and moxestrol (11β-methoxy-17α-ethynyloestradiol) were studied for binding to oestrogen receptors and conversion to catechol metabolites. Binding to cytosol oestrogen receptors was measured in the hypothalamus–preoptic area–amygdala (HPA), pituitary gland and uterus of ovariectomized rats. Conversion to catechol oestrogens was tested in microsomes from the HPA, pituitary gland and liver, using a catechol-O-methyltransferase-coupled radioenzymatic assay. Oestradiol-17α was the only weak oestrogen receptor ligand. Binding affinities of the other compounds tested were much higher and comparable to those of oestradiol-17β. In contrast, oestradiol-17α was rapidly converted to catechol metabolites, while moxestrol was a relatively poor substrate for catechol oestrogen formation. 4-Fluoro-oestradiol could be 2-hydroxylated but not 4-hydroxylated. 2-Fluoro-oestradiol exhibited impaired 2-hydroxylation but normal 4-hydroxylation. J. Endocr. (1986) 110, 489–497

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Gallego Sánchez-Torij, J., E. Larrumbide Gómez-Rubiera et C. Bedoya Frutos. « Metabolismo en los edificios. Estudio de medidas para el ahorro del consumo de agua en tres centros docentes en Madrid ». Informes de la Construcción 72, n^o 557 (21 février 2020) : 325. http://dx.doi.org/10.3989/ic.67829.

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Estudios previos han investigado sobre el desempeño energético de centros docentes. Sin embargo, no parece haberse explorado suficientemente la relación entre consumo de energía y consumo de agua en este tipo de edificios. Este artículo presenta los resultados de un estudio empírico, basado en la metodología de la auditoría energética operativa, realizado en tres centros docentes ubicados en la Comunidad de Madrid. Los resultados sugieren que las medidas de ahorro en el consumo de agua, como implantar perlizadores, temporizadores o doble pulsadores, son relevantes en cuanto a la mejora de la eficiencia energética, suponen inversiones moderadas y obtienen unos periodos de retorno simple de la inversión atractivos para los gestores de los edificios. Se abren nuevas vías de investigación que apuntan a realizar el análisis de otros flujos de materia e información, de manera que se establezca la relación entre dichos flujos y el consumo de energía que llevan aparejados.

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Kim, Shin, Hyon-Ah Yi, Kyoung Sook Won, Ji Soo Lee et Hae Won Kim. « Association between Visceral Adipose Tissue Metabolism and Alzheimer’s Disease Pathology ». Metabolites 12, n^o 3 (17 mars 2022) : 258. http://dx.doi.org/10.3390/metabo12030258.

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The visceral adipose tissue (VAT) has been recognized as an endocrine organ, and VAT dysfunction could be a risk factor for Alzheimer’s disease (AD). We aimed to evaluate the association of VAT metabolism with AD pathology. This cross-sectional study included 54 older subjects with cognitive impairment who underwent 2-deoxy-2-[fluorine-18]-fluoro-D-glucose (18F-FDG) torso positron emission tomography (PET) and 18F-florbetaben brain PET. 18F-FDG uptake in VAT on 18F-FDG PET images was used as a marker of VAT metabolism, and subjects were classified into high and low VAT metabolism groups. A voxel-based analysis revealed that the high VAT metabolism group exhibited a significantly higher cerebral amyloid-β (Aβ) burden than the low VAT metabolism group. In the volume-of-interest analysis, multiple linear regression analyses with adjustment for age, sex, and white matter hyperintensity volume revealed that 18F-FDG uptake in VAT was significantly associated with the cerebral Aβ burden (β = 0.359, p = 0.007). In conclusion, VAT metabolism was associated with AD pathology in older subjects. Our findings suggest that VAT dysfunction could contribute to AD development.

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March Corbella, Hug, et David Saurí Pujol. « Flujos de agua, flujos de capital : sistemas de abastecimiento y gobernanza del agua en Madrid y Barcelona ». Investigaciones Geográficas, n^o 51 (15 avril 2010) : 7. http://dx.doi.org/10.14198/ingeo2010.51.01.

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El agua es un elemento clave para el sustento del metabolismo de las ciudades. Sin embargo, los orígenes, métodos de «producción», y modelos de gestión del flujo de urbano de agua pueden variar geográficamente. En este artículo se comparan los sistemas de abastecimiento y gestión de agua potable en las dos principales regiones metropolitanas del Estado: Barcelona y Madrid. En Barcelona, el agua procede de distintas fuentes entre las cuales destaca la desalación, vigente desde el verano de 2009. En Madrid, el sistema de abastecimiento depende fuertemente de las aguas superficiales procedentes de diversos ríos que atraviesan la Comunidad. Por lo que respeta a la gestión de estos sistemas el presente trabajo hace hincapié sobre las importantes diferencias que giran entorno al distinto balance entre participación pública y privada en el ciclo del agua en ambas áreas. Finalmente el artículo reflexiona sobre los puntos de convergencia y divergencia entre ambos modelos de abastecimiento así como sus perspectivas de futuro.

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Parrado Rodríguez, Cristhian, Andrea Cevallos Aráuz et Leonardo Arias Álvarez. « Metabolismo urbano en la ciudad de Baeza, Ecuador. Análisis de sus flujos del agua ». Bitácora Urbano Territorial 28, n^o 3 (1 septembre 2018) : 131–41. http://dx.doi.org/10.15446/bitacora.v28n3.72183.

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A partir del concepto de metabolismo urbano el artículo analiza el estado de los flujos de entrada y salida del agua de la zona antigua de la ciudad de Baeza, la cabecera cantonal de Quijos (Ecuador). Detalla la existencia de procesos metabólicos entrópicos donde no hay una reintegración efectiva del recurso hídrico al ecosistema urbano. Igualmente, desde la visión de ecobarrio presenta una propuesta de intervención que establece lineamientos para generar una mejor recirculación del agua en el territorio. En esa medida, el artículo procura incentivar la discusión sobre cómo lograr un equilibrio urbano ambiental en torno al agua.

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Wiese, Claudia, Marianne Cogoli-Greuter, Mario Argentini, Thomas Mäder, Regin Weinreich et Kaspar H. Winterhalter. « Metabolism of 5-fluoro-DOPA and 6-fluoro-DOPA enantiomers in aggregating cell cultures of fetal rat brain ». Biochemical Pharmacology 44, n^o 1 (juillet 1992) : 99–105. http://dx.doi.org/10.1016/0006-2952(92)90043-i.

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Feng, Han, Xiaobo Wang, Jian Chen, Jing Cui, Tang Gao, Yongju Gao et Wenbin Zeng. « Nuclear Imaging of Glucose Metabolism : Beyond 18F-FDG ». Contrast Media & ; Molecular Imaging 2019 (26 mars 2019) : 1–12. http://dx.doi.org/10.1155/2019/7954854.

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Glucose homeostasis plays a key role in numerous fundamental aspects of life, and its dysregulation is associated with many important diseases such as cancer. The atypical glucose metabolic phenomenon, known as the Warburg effect, has been recognized as a hallmark of cancer and serves as a promising target for tumor specific imaging. At present, 2-deoxy-2-[18F]fluoro-glucose (18F-FDG)-based positron emission tomography/computed tomography (PET/CT) represented the state-of-the-art radionuclide imaging technique for this purpose. The powerful impact of 18F-FDG has prompted intensive research efforts into other glucose-based radiopharmaceuticals for positron emission tomography (PET) and single-photon emission computed tomography (SPECT) imaging. Currently, glucose and its analogues have been labeled with various radionuclides such as 99mTc, 111In, 18F, 68Ga, and 64Cu and have been successfully investigated for tumor metabolic imaging in many preclinical studies. Moreover, 99mTc-ECDG has advanced into its early clinical trials and brings a new era of tumor imaging beyond 18F-FDG. In this review, preclinical and early clinical development of glucose-based radiopharmaceuticals for tumor metabolic imaging will be summarized.

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Reith, Jakob, Suzan Dyve, Hiroto Kuwabara, Mark Guttman, Mirko Diksic et Albert Gjedde. « Blood—Brain Transfer and Metabolism of 6-[18F]Fluoro-L-DOPA in Rat ». Journal of Cerebral Blood Flow & ; Metabolism 10, n^o 5 (septembre 1990) : 707–19. http://dx.doi.org/10.1038/jcbfm.1990.124.

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In a study designed to reveal the rates of blood–brain transfer and decarboxylation of fluoro-L-3,4-dihydroxyphenylalanine (FDOPA), we discovered a major discrepancy between the DOPA decarboxylase activity reported in the literature and the rate of FDOPA decarboxylation measured in the study. “Donor” rats received intravenous injections of 6 mCi fluorine-18-labeled FDOPA. The donor rats synthesized methyl-FDOPA. Arterial plasma, containing both FDOPA and methyl-FDOPA, was sampled from the donor rats at different times and reinjected into “recipient” rats in which it circulated for 20 s. The blood–brain clearance of the mixture of labeled tracers in the plasma was determined by an integral method. The individual permeabilities were determined by linear regression analysis, according to which the average methyl-FDOPA permeability in the blood–brain barrier was twice that of FDOPA, which averaged 0.037 ml g−1 min−1. The permeability ratio was used to determine the fractional clearance from the brain of FDOPA (and hence of methyl-FDOPA), which averaged 0.081 min−1. In the striatum, the measured average FDOPA decarboxylation rate constant ( kD3) was 0.010 min−1, or no more than 1% of the rate of striatal decarboxylation of DOPA measured in vitro and in vivo. We interpreted this finding as further evidence in favor of the hypothesis that striatum has two dopamine (DA) pools, of which only DA in the large pool is protected from metabolism. Hence, no more than 1% of the quantity of fluoro-DA theoretically synthesized was actually retained in striatum.

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Li, Jing, Yumei Wang, Kejie He, Chong Peng, Peilong Wu, Chenyun Li et Xinsheng Lai. « Effect of Acupuncture at LR3 on Cerebral Glucose Metabolism in a Rat Model of Hypertension : A 18F-FDG-PET Study ». Evidence-Based Complementary and Alternative Medicine 2018 (2018) : 1–8. http://dx.doi.org/10.1155/2018/5712857.

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Our objective was to investigate the effect of acupuncture at LR3 on cerebral glucose metabolism in spontaneously hypertensive rats (SHRs). We used 18F-2-fluoro-deoxy-D-glucose positron emission tomography (18F-FDG-PET) to examine the effects of acupuncture at LR3 on cerebral glucose metabolism in SHRs. SHRs were randomly allocated to receive no treatment (SHR group), needling at LR3 (SHR + LR3 group), or sham needling (SHR + sham group). Rats received 10 min acupuncture once per day for 7 days and were compared to normotensive Wistar Kyoto (WKY) rats. Blood pressure (BP) measurement and PET were performed after the first needling and the 7-day treatment period. BP was lower in the SHR + LR3 group compared to the other SHR groups between 30 and 60 min after the first needling and at 24 and 48 h after the 7-day treatment period. Glucose metabolism in the motor, sensory, and visual cortices was decreased in SHR group compared to WKY group. Needling at LR3 was associated with decreased glucose metabolism in the dorsal thalamus, thalamus, and hypothalamus and with increased metabolism in the cerebellar anterior and posterior lobes, medulla oblongata, and sensory cortex compared to the SHR group. These findings suggest that LR3 acupuncture improves hypertension through a mechanism involving altered brain activation in SHRs.

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Huang, Yung-Cheng, Chien-Chin Hsu, Wei-Che Lin, Tang-Kai Yin, Chi-Wei Huang, Pei-Wen Wang, Han-Hsuan Chang et Nan-Tsing Chiu. « Effects of Metformin on the Cerebral Metabolic Changes in Type 2 Diabetic Patients ». Scientific World Journal 2014 (2014) : 1–8. http://dx.doi.org/10.1155/2014/694326.

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Metformin, a widely used antidiabetic drug, has numerous effects on human metabolism. Based on emerging cellular, animal, and epidemiological studies, we hypothesized that metformin leads to cerebral metabolic changes in diabetic patients. To explore metabolism-influenced foci of brain, we used 2-deoxy-2-[18F]fluoro-D-glucose (FDG) positron emission tomography for type 2 diabetic patients taking metformin (MET,n=18), withdrawing from metformin (wdMET,n=13), and not taking metformin (noMET,n=9). Compared with the noMET group, statistical parametric mapping showed that the MET group had clusters with significantly higher metabolism in right temporal, right frontal, and left occipital lobe white matter and lower metabolism in the left parahippocampal gyrus, left fusiform gyrus, and ventromedial prefrontal cortex. In volume of interest (VOI-) based group comparisons, the normalized FDG uptake values of both hypermetabolic and hypometabolic clusters were significantly different between groups. The VOI-based correlation analysis across the MET and wdMET groups showed a significant negative correlation between normalized FDG uptake values of hypermetabolic clusters and metformin withdrawal durations and a positive but nonsignificant correlation in the turn of hypometabolic clusters. Conclusively, metformin affects cerebral metabolism in some white matter and semantic memory related sites in patients with type 2 diabetes.

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Firnau, G., S. Sood, R. Chirakal, C. Nahmias et E. S. Garnett. « Cerebral Metabolism of 6?[18F]Fluoro-l-3,4-Dihydroxyphenylalanine in the Primate ». Journal of Neurochemistry 48, n^o 4 (avril 1987) : 1077–82. http://dx.doi.org/10.1111/j.1471-4159.1987.tb05629.x.

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GRUN, Bernhard R., Ulrike BERGER, Franz OBERDORFER, William E. HULL, Hermann OSTERTAG, Eckhard FRIEDRICH, Jochen LEHMANN et Dietrich KEPPLER. « Metabolism and actions of 2-deoxy-2-fluoro-d-galactose in vivo ». European Journal of Biochemistry 190, n^o 1 (mai 1990) : 11–19. http://dx.doi.org/10.1111/j.1432-1033.1990.tb15539.x.

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Sbrissa, Diego, J. M. McIntosh et Norman F. Taylor. « The metabolism of 4-deoxy-4-fluoro-d-glucose in Pseudomonas putida ». Carbohydrate Research 203, n^o 2 (août 1990) : 271–80. http://dx.doi.org/10.1016/0008-6215(90)80024-w.

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Fraternale, Alessandra, Luigia Rossi et Mauro Magnani. « Encapsulation, metabolism and release of 2-fluoro-ara-AMP from human erythrocytes ». Biochimica et Biophysica Acta (BBA) - General Subjects 1291, n^o 2 (octobre 1996) : 149–54. http://dx.doi.org/10.1016/0304-4165(96)00059-1.

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Baek, Suji, Jisu Kim, Byung Seok Moon, Sun Mi Park, Da Eun Jung, Seo Young Kang, Sang Ju Lee et al. « Camphene Attenuates Skeletal Muscle Atrophy by Regulating Oxidative Stress and Lipid Metabolism in Rats ». Nutrients 12, n^o 12 (3 décembre 2020) : 3731. http://dx.doi.org/10.3390/nu12123731.

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Sarcopenia- or cachexia-related muscle atrophy is due to imbalanced energy metabolism and oxidative stress-induced muscle dysfunction. Monoterpenes play biological and pharmacological reactive oxygen species (ROS) scavenging roles. Hence, we explored the effects of camphene, a bicyclic monoterpene, on skeletal muscle atrophy in vitro and in vivo. We treated L6 myoblast cells with camphene and then examined the ROS-related oxidative stress using Mito TrackerTM Red FM and anti-8-oxoguanine antibody staining. To investigate lipid metabolism, we performed real-time polymerase chain reactions, holotomographic microscopy, and respiratory gas analysis. Rat muscle atrophy in in vivo models was observed using 18F-fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography and immunocytochemistry. Camphene reversed the aberrant cell size and muscle morphology of L6 myoblasts under starvation and in in vivo models. Camphene also attenuated E3 ubiquitin ligase muscle RING-finger protein-1, mitochondrial fission, and 8-oxoguanine nuclear expression in starved myotubes and hydrogen peroxide (H2O2)-treated cells. Moreover, camphene significantly regulated lipid metabolism in H2O2-treated cells and in vivo models. These findings suggest that camphene may potentially affect skeletal muscle atrophy by regulating oxidative stress and lipid metabolism.

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Vitti, Dorinha Miriam Silber Schmidt, Carlos Eduardo Furtado, João Batista da Silva Quadros, João Batista Lopes, Ives Cláudio da Silva Bueno, Eduardo Fernando Nozella et Patrícia Barboza de Godoy. « Efeitos de diferentes níveis de cálcio dietético na cinética de cálcio e fósforo em eqüinos ». Revista Brasileira de Zootecnia 37, n^o 3 (mars 2008) : 478–86. http://dx.doi.org/10.1590/s1516-35982008000300013.

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Objetivou-se estudar o metabolismo de cálcio (Ca) e fósforo (P) nos eqüinos em crescimento que receberam diferentes níveis de suplementação de Ca: 0,15; 0,45 e 0,75% na dieta, utilizando-se o modelo determinístico e compartimental. Foram utilizadas informações sobre o estudo de metabolismo e cinética de Ca e P em tecidos, obtidas pela técnica da diluição isotópica. Constatou-se que os níveis dietéticos de Ca tiveram influência na absorção real do Ca, sendo menor para o nível 0,15% (4,97 g Ca/dia). As trocas de Ca entre o sangue e o trato digestivo foram menores para o nível 0,15%. A mobilização entre o sangue e os ossos e sangue e tecidos moles não foi influenciada pelos tratamentos, mas o balanço nos ossos e tecidos foi menor para o nível 0,15%. Os níveis de Ca dietéticos tiveram influência no P eliminado através da urina, sendo este valor maior para o tratamento 0,15% (2,49 g/animal/dia). A absorção real média do P foi de 83%, não havendo diferenças para os tratamentos. Verificou-se deposição óssea média de 9,69 g P/animal/dia, indicando que a quantidade de P fornecida foi adequada em relação à tolerância permissível à amplitude na relação Ca:P para a espécie na categoria animal estudada. Não houve diferenças significativas entre os fluxos de P nos diversos compartimentos, por intermédio do modelo de metabolismo. A ingestão de níveis crescentes de Ca afetou o metabolismo e a cinética deste elemento, entretanto, a proporção Ca:P é o fator predominante para determinar a excreção, retenção e absorção de Ca. A deposição de Ca no osso foi influenciada pela quantidade ingerida deste mineral. O metabolismo de P em eqüinos em crescimento não foi afetado pelos teores de Ca. O fornecimento de 13,4 g P/animal/dia foi suficiente para manter o metabolismo de P nos padrões considerados normais.

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Daniellou, Richard, Hongyan Zheng et David RJ Palmer. « Kinetics of the reaction catalyzed by inositol dehydrogenase from Bacillus subtilis and inhibition by fluorinated substrate analogs ». Canadian Journal of Chemistry 84, n^o 4 (1 avril 2006) : 522–27. http://dx.doi.org/10.1139/v06-033.

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Inositol dehydrogenase (EC 1.1.1.18) from Bacillus subtilis catalyzes the oxidation of myo-inositol to scyllo-inosose by transfer of the equatorial hydride of the substrate to NAD+. This is a key enzyme in the metabolism of myo-inositol, a primary carbon source for soil bacteria. In light of our recent discovery that the enzyme has a broad substrate spectrum while maintaining high stereoselectivity, we seek a more thorough understanding of the enzyme and its active site. We have examined the kinetics of the recombinant enzyme, and synthesized fluorinated substrate analogues as competitive inhibitors. We have evaluated all rate constants in the ordered, sequential Bi Bi mechanism. No steady-state kinetic isotope effect is observed using myo-[2-2H]-inositol, indicating that the chemical step of the reaction is not rate-limiting. We have synthesized the substrate analogs 2-deoxy-2-fluoro-myo-inositol, its equatorial analog 1-deoxy-1-fluoro-scyllo-inositol, the gem-difluorinated analog 1-deoxy-1,1-difluoro-scyllo-inositol, and the sugar analog α-D-glucosyl fluoride. Of these, 1-deoxy-1-fluoro-scyllo-inositol showed no inhibition, while all others tested had Ki values comparable to the Km values of the analogous substrates myo-inositol and α-D-glucose.Key words: inositol dehydrogenase, enzyme mechanism, kinetics, competitive inhibitor, substrate analogue.

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Mouttaki, Housna, Mark A. Nanny et Michael J. McInerney. « Metabolism of Hydroxylated and Fluorinated Benzoates by Syntrophus aciditrophicus and Detection of a Fluorodiene Metabolite ». Applied and Environmental Microbiology 75, n^o 4 (29 décembre 2008) : 998–1004. http://dx.doi.org/10.1128/aem.01870-08.

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ABSTRACT Transformations of 2-hydroxybenzoate and fluorobenzoate isomers were investigated in the strictly anaerobic Syntrophus aciditrophicus to gain insight into the initial steps of the metabolism of aromatic acids. 2-Hydroxybenzoate was metabolized to methane and acetate by S. aciditrophicus and Methanospirillum hungatei cocultures and reduced to cyclohexane carboxylate by pure cultures of S. aciditrophicus when grown in the presence of crotonate. Under both conditions, transient accumulation of benzoate but not phenol was observed, indicating that dehydroxylation occurred prior to ring reduction. Pure cultures of S. aciditrophicus reductively dehalogenated 3-fluorobenzoate with the stoichiometric accumulation of benzoate and fluorine. 3-Fluorobenzoate-degrading cultures produced a metabolite that had a fragmentation pattern almost identical to that of the trimethylsilyl (TMS) derivative of 3-fluorobenzoate but with a mass increase of 2 units. When cells were incubated with deuterated water, this metabolite had a mass increase of 3 or 4 units relative to the TMS derivative of 3-fluorobenzoate. 19F nuclear magnetic resonance spectroscopy (19F NMR) detected a metabolite in fluorobenzoate-degrading cultures with two double bonds, either 1-carboxyl-3-fluoro-2,6-cyclohexadiene or 1-carboxyl-3-fluoro-3,6-cyclohexadiene. The mass spectral and NMR data are consistent with the addition of two hydrogen or deuterium atoms to 3-fluorobenzoate, forming a 3-fluorocyclohexadiene metabolite. The production of a diene metabolite provides evidence that S. aciditrophicus contains dearomatizing reductase that uses two electrons to dearomatize the aromatic ring.

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García Serna, María Isabel, Tito Morales-Pinzón et Jhoniers Guerrero Erazo. « Análisis de flujos de agua en áreas metropolitanas desde la perspectiva del metabolismo urbano ». Luna Azul, n^o 39 (6 juin 2014) : 234–49. http://dx.doi.org/10.17151/luaz.2014.39.14.

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Hasselbalch, S. G., P. L. Madsen, L. P. Hageman, K. S. Olsen, N. Justesen, S. Holm et O. B. Paulson. « Changes in cerebral blood flow and carbohydrate metabolism during acute hyperketonemia ». American Journal of Physiology-Endocrinology and Metabolism 270, n^o 5 (1 mai 1996) : E746—E751. http://dx.doi.org/10.1152/ajpendo.1996.270.5.e746.

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During starvation, brain energy metabolism in humans changes toward oxidation of ketone bodies. To investigate if this shift is directly coupled to circulating blood concentrations of ketone bodies, we measured global cerebral blood flow (CBF) and global cerebral carbohydrate metabolism with the Kety-Schmidt technique before and during intravenous infusion with ketone bodies. During acute hyperketonemia (mean beta-hydroxybutyrate blood concentration 2.16 mM), cerebral uptake of ketones increased from 1.11 to 5.60 mumol.100 g-1.min-1, counterbalanced by an equivalent reduction of the cerebral glucose metabolism from 25.8 to 17.2 mumol.100 g-1.min-1, with the net result being an unchanged cerebral uptake of carbohydrates. In accordance with this, global cerebral oxygen metabolism was not significantly altered (144 vs. 135 mumol.100 g-1.min-1). The unchanged global cerebral metabolic activity was accompanied by a 39% increase in CBF from 51.0 to 70.9 ml.100 g-1.min-1. Regional analysis of the glucose metabolism by positron emission tomography-[18F]fluoro-2-deoxy-D-glucose indicated that mesencephalon does not oxidize ketone bodies to the same extent as the rest of the brain. It was concluded that the immediate oxidation of ketone bodies induced a decrease in cerebral glucose uptake in spite of an adequate glucose supply to the brain. Furthermore, acute hyperketonemia caused a resetting of the coupling between CBF and metabolism that could not be explained by alterations in arterial CO2 tension or pH.

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Murakami, Eisuke, Congrong Niu, Haiying Bao, Holly M. Micolochick Steuer, Tony Whitaker, Tammy Nachman, Michael A. Sofia, Peiyuan Wang, Michael J. Otto et Phillip A. Furman. « The Mechanism of Action of β-d-2′-Deoxy-2′-Fluoro-2′-C-Methylcytidine Involves a Second Metabolic Pathway Leading to β-d-2′-Deoxy-2′-Fluoro-2′-C-Methyluridine 5′-Triphosphate, a Potent Inhibitor of the Hepatitis C Virus RNA-Dependent RNA Polymerase ». Antimicrobial Agents and Chemotherapy 52, n^o 2 (12 novembre 2007) : 458–64. http://dx.doi.org/10.1128/aac.01184-07.

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ABSTRACT β-d-2′-Deoxy-2′-fluoro-2′-C-methylcytidine (PSI-6130) is a potent inhibitor of hepatitis C virus (HCV) RNA replication in an HCV replicon assay. The 5′-triphosphate of PSI-6130 is a competitive inhibitor of the HCV RNA-dependent RNA polymerase (RdRp) and acts as a nonobligate chain terminator. Recently, it has been shown that the metabolism of PSI-6130 also results in the formation of the 5′-triphosphate of the uridine congener, β-d-2′-deoxy-2′-fluoro-2′-C-methyluridine (PSI-6206; RO2433). Here we show that the formation of the 5′-triphosphate of RO2433 (RO2433-TP) requires the deamination of PSI-6130 monophosphate and that RO2433 monophosphate is subsequently phosphorylated to the corresponding di- and triphosphates by cellular UMP-CMP kinase and nucleoside diphosphate kinase, respectively. RO2433-TP is a potent inhibitor of the HCV RdRp; however, both enzymatic and cell-based assays show that PSI-6130 triphosphate is a more potent inhibitor of the HCV RdRp than RO2433-TP.

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Bøgesø, Klaus P., et Michael Bech Sommer. « The effect of aromatic substitution on neuroleptic activity in 1-piperazino-3-phenylindans. A comparison based on a new D-2 receptor model with corresponding 10-piperazino-10,11-dihydrodibenzo[b,f]thiepins ». Collection of Czechoslovak Chemical Communications 56, n^o 11 (1991) : 2456–67. http://dx.doi.org/10.1135/cccc19912456.

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The validity of a new dopamine D-2 receptor interaction model based on conformational analysis and least-squares superimposition studies of the indan derivative tefludazine and the thiepin derivative octoclothepin was further tested by comparison of the effect of aromatic substitution on D-2 antagonistic activity in two series of indan and thiepin derivatives. The indan series include new derivatives substituted in the 4-, 7-, 2’- and 3’-position. The substitution effects were largely parallel with one important exception: Only 6-substituted indans have significant neuroleptic activity while both 8- and 7-substituted thiepin derivatives have neuroleptic activity. In indans additional fluorination in the 2’- or 4’-position is demanded to give potent neuroleptic activity, while a 3’-fluoro-substituted derivative was inactive. Fluorination is not necessary in thiepins although 3-fluoro derivatives have a significant prolonged duration of action. Considering the differences in physico-chemical properties, metabolism and pharmacokinetics between the two series, the largely parallel substitution effects support the new D-2 receptor model.

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Conceição, Luís, Sofia Morais et Cláudia Aragão. « Fluxos de nutrientes em larvas de peixes : aplicação de técnicas com marcadores isotópicos e de modelação ». Revista Brasileira de Zootecnia 36, suppl (juillet 2007) : 11–20. http://dx.doi.org/10.1590/s1516-35982007001000002.

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Um modelo mecanístico que simule o crescimento durante a fase larvar de peixes deverá contribuir para um melhor conhecimento do processo de crescimento e respectivo metabolismo, com a intenção de elucidar as suas necessidades alimentares e desenvolver estratégias de alimentação adequadas. O modelo desenvolvido simula o crescimento e a evolução da composição bioquímica das larvas ao longo do tempo. O modelo depende essencialmente do consumo de alimento, sendo os nutrientes absorvidos usados para a produção de energia ou em processos de biossíntese e é baseado na estequiometria do metabolismo intermediário. Simulações utilizando este modelo sugerem que se deve prestar mais atenção a possíveis desequilíbrios no perfil de aminoácidos (AA) e a eventuais excessos de lípidos no alimento usado em cultivo larvares, de forma a optimizar o crescimento. Estudos usando marcadores isotópicos têm sido utilizados para estudar o metabolismo de AA e de lípidos em larvas de peixes e técnicas de modelação foram aplicadas de forma a permitir uma melhor compreensão dos resultados obtidos nestes estudos. A capacidade digestiva, bem como a utilização energética de diferentes AA, ácidos gordos e classes de lípidos, tem sido estudada utilizando a administração de nutrientes marcados (normalmente com 14C) directamente no tubo digestivo, através de um microcapilar. Este método permite a quantificação do nutriente marcado presente nas fezes, retido nos tecidos da larva e catabolizado. Um outro método, combinando a utilização de alimento vivo cujas proteínas estão marcadas com um isótopo estável com uma técnica espectroscópica/espectrométrica, permite a determinação do enriquecimento isotópico de AA individuais e pode ser usado para estimar o perfil ideal de AA indispensáveis na dieta. Em conjunto, estes dois tipos de técnicas de análise de fluxos de nutrientes têm permitido avanços importantes na compreensão da fisiologia da nutrição e crescimento de larvas de peixes.

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Huber, M., B. Kittner, C. Hojer, G. R. Fink, M. Neveling et W. D. Heiss. « Effect of Propentofylline on Regional Cerebral Glucose Metabolism in Acute Ischemic Stroke ». Journal of Cerebral Blood Flow & ; Metabolism 13, n^o 3 (mai 1993) : 526–30. http://dx.doi.org/10.1038/jcbfm.1993.68.

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In a randomized double-blind placebo-controlled study in 30 patients with acute ischemic stroke, the effect of the adenosine uptake blocker propentofylline on regional brain glucose metabolism (rCMRglu) was investigated using repeated positron emission tomography (PET) with 2-[18F]fluoro-2-deoxy-d-glucose (FDG). Treatment was initiated within 48 h after onset of symptoms. The clinical course was followed for 3 months. In the propentofylline group, after 14 days rCMRglu was increased in the infarct by 37.3% and was practically unchanged in other brain regions, whereas in the control group glucose metabolism had decreased in all regions (1.4–13.4%). These differences were significant between the two groups [Analysis of variance (ANOVA) p = 0.005]. Although there was a trend toward greater clinical improvement in the propentofylline-treated patients, this did not reach statistical significance. The results correspond to experimental data showing that propentofylline improves energy metabolism in cerebral ischemia. A clinical trial is needed to determine whether this new therapeutic principle can be successfully used in acute human stroke.

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Melega, William P., Scott T. Grafton, Sung-Cheng Huang, Nagichettiar Satyamurthy, Michael E. Phelps et Jorge R. Barrio. « L-6-[18F]Fluoro-DOPA Metabolism in Monkeys and Humans : Biochemical Parameters for the Formulation of Tracer Kinetic Models with Positron Emission Tomography ». Journal of Cerebral Blood Flow & ; Metabolism 11, n^o 6 (novembre 1991) : 890–97. http://dx.doi.org/10.1038/jcbfm.1991.154.

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Characterization of peripheral and cerebral l-3,4-dihydroxy-6-[18F]fluorophenylalanine (FDOPA) metabolism in humans and monkeys has shown FDOPA to be an analogue of l-DOPA for the study of the dopaminergic system with positron emission tomography (PET). In human studies with carbidopa pretreatment, l-3,4-dihydroxy-6-[18F]fluoro-3- O-methylphenylalanine (3-OMFD) was the only FDOPA metabolite detected in plasma. FDOPA administration in monkeys resulted in selective accumulation of FDOPA metabolites in central dopaminergic regions, whereas 3-OMFD of peripheral origin was uniformly distributed among putamen, caudate, frontal cortex, and cerebellum. At 60 min, 3-OMFD and 6-[18F]fluorodopamine (FDA) each represented ∼35% of the total activity, the remainder being FDOPA and FDA metabolites. These data on monkey and human FDOPA metabolism provide the basis for the configuration of an FDOPA tracer kinetic model with PET.

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CUI, YUNFENG, JING BAI, YINGMAO CHEN et JIAHE TIAN. « A DIGITAL MODEL FRAMEWORK OF METABOLIC SYSTEM BASED ON VISIBLE HUMAN DATA SET ». International Journal of Image and Graphics 07, n^o 01 (janvier 2007) : 143–57. http://dx.doi.org/10.1142/s0219467807002593.

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Digital model of human metabolic system incorporated with real anatomical structure can be seen as an important tool in order to understand and study the processes of metabolism. This paper presented a whole body digital model framework of [18F]2-fluoro-2-deoxy-D-glucose (FDG) metabolism based on the segmented Visible Human Project (VHP) data set as the anatomical structure framework. First, the blood time-activity curve (BTAC) and the tissues time-activity curves (TTAC) were obtained from kinetic analysis. According to the obtained BTAC and TTACs, a set of corresponding values were assigned to the segmented VHP image frames. Thus a set of dynamic volume data were derived to show the 18F distribution in human body for the predetermined sampling schedule. Finally, the simulated FDG distribution was visualized by coronal, axial, and sagittal slices and volume rendering method. The model established here was especially for the metabolism of FDG; however, the modeling method is general for all tracers. The proposed model represented functional information of dynamical process of human metabolism with high visualization resolution. The results of modeling and visualization provide a useful tool for education and research on nuclear imaging, and may provide a novel technical platform for the study of pharmacokinetics.

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Tsurumi, Yuji, Motonobu Kameyama, Kiichi Ishiwata, Ryuichi Katakura, Minoru Monma, Tatsuo Ido et Jiro Suzuki. « 18F-fluoro-2′-deoxyuridine as a tracer of nucleic acid metabolism in brain tumors ». Journal of Neurosurgery 72, n^o 1 (janvier 1990) : 110–13. http://dx.doi.org/10.3171/jns.1990.72.1.0110.

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✓ The value of 18F-fluoro-2′-deoxyuridine (18F-FUdR) as a tracer for nucleic acid metabolism was studied using an experimental rat brain-tumor model. The 18F activity in the tumor tissue 45 minutes after intravenous injection of 18F-FUdR was about 12 times higher than that in the contralateral cortex. Double-labeled autoradiography with 18F-FUdR and 14C-thymidine revealed similar brain-tumor images. In contrast, an autoradiographic comparison of 18F-FUdR with 14C-aminoisobutyric acid, which reveals the impairment of the blood-brain barrier, showed very different images. Also, the 18F radioactivity in the tumor tissue was at a constant level for 30 to 120 minutes, whereas a notable increase in 18F activity with time was observed in nucleotides and acid-insoluble fractions. These results suggest that the distribution pattern of 18F-FUdR closely correlates with the metabolism of nucleic acid and that this drug could be a useful tracer for positron emission tomography.

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Dimming, P., B. E. Boyes, W. R. W. Martin, M. Adam, J. Grierson, T. Ruth et E. G. McGeer. « The Metabolism of [18F]6-Fluoro-l-3,4-Dihydroxyphenylalanine in the Hooded Rat ». Journal of Neurochemistry 48, n^o 2 (février 1987) : 601–8. http://dx.doi.org/10.1111/j.1471-4159.1987.tb04135.x.

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Fedders, Gönna, Rüdiger Kock, Eddy Van de Leur et Helmut Greiling. « 015 The metabolism of 2-fluoro-2-deoxy-D-glucose in human chondrocytes ». Fresenius' Journal of Analytical Chemistry 343, n^o 1 (janvier 1992) : 66–67. http://dx.doi.org/10.1007/bf00332009.

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