References of "Lemaire, Christian"
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See detailLes corrélats métaboliques des processus contrôlés en mémoire dans la maladie d'Alzheimer très débutante
Bastin, Christine ULg; Kerrouche, Nacer; Lekeu, Françoise ULg et al

in Ergis, Anne-Marie; Fiori, N.; Chaby, L. (Eds.) et al Xème colloque international sur le vieillissement cognitif (2008)

Les processus contrôlés et automatiques de récupération mnésique ont été évalués au moyen de la Procédure de Dissociation des Processus appliquée à une tâche de complètement de trigrammes chez 59 patients ... [more ▼]

Les processus contrôlés et automatiques de récupération mnésique ont été évalués au moyen de la Procédure de Dissociation des Processus appliquée à une tâche de complètement de trigrammes chez 59 patients diagnostiqués comme « questionable Alzheimer’s disease » (QAD ou Mild Cognitive Impairment). Par ailleurs, le métabolisme cérébral du glucose des patients a été mesuré par FDG-PET. Comparativement à des volontaires âgés sains appariés, le profil mnésique des patients QAD était caractérisé par un déficit des processus contrôlés, mais une préservation des processus automatiques. Après un suivi de 30 mois, 27 des patients ont développé une maladie d’Alzheimer, tandis que 23 patients restèrent des QAD stables (9 sujets n’ont pas complété le suivi ou ont reçu un autre diagnostic au terme de celui-ci). Les deux sous-groupes présentaient le même degré de déclin des processus de mémoire contrôlés. Des corrélations cognitivo-métaboliques, ainsi qu’une analyse en composantes principales, ont permis de montrer que les corrélats métaboliques des processus contrôlés (à l’entrée dans l’étude) n’étaient les mêmes chez les patients qui allaient développer la maladie d’Alzheimer et chez les patients qui allaient rester stables. Chez les patients qui développaient ultérieurement une maladie d’Alzheimer, l’utilisation correcte des processus contrôlés était positivement corrélée à l’activité du cortex préfrontal dorsomédian, qui pourrait jouer un rôle dans les processus réflexifs de monitoring agissant sur les produits de la récupération. L’activité du cortex préfrontal dorsomédian était corrélée à l’activité métabolique des régions frontales bilatérales et du cortex cingulaire postérieur. Par contraste, chez les patients QAD stables, nous avons trouvé une corrélation avec la formation hippocampique antérieure, une région qui intervient dans la réactivation de l’épisode d’encodage des événements. [less ▲]

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See detailPET/CT of skull base meningiomas using 2-F-18-fluoro-L-tyrosine: Initial report
Rutten, Isabelle; Cabay, Jean-Evrard ULg; Withofs, Nadia ULg et al

in Journal of Nuclear Medicine (2007), 48(5), 720-725

Precise delineation of the shape of skull base meningiomas is critical for their treatment and follow-up but is often difficult using conventional imaging such as CT and MRI. We report our results with ... [more ▼]

Precise delineation of the shape of skull base meningiomas is critical for their treatment and follow-up but is often difficult using conventional imaging such as CT and MRI. We report our results with PET/CT and 2-(18)F-fluoro-L-tyrosine ((18)F-TYR), a marker of amino acid transport, as part of the yearly follow-up of irradiated patients. METHODS: Eleven patients (mean age, 56.5 y) with skull base meningiomas (n=13 lesions) previously irradiated were included. All patients received 300 MBq of (18)F-TYR and were imaged after 30 min of uptake, using a dedicated PET/CT system. The images were first visually examined, and regions of interest (ROI) were then placed over the transaxial PET slice showing the highest uptake. Another ROI was placed over the normal parietal cortex. Tumor-to-cortex activity ratios were obtained by dividing the maximum pixel value in the tumor ROI by the maximum pixel value in the cortex ROI. The PET/CT images were compared with the MR images obtained as part of routine follow-up. RESULTS: Accumulation of the tracer was higher in all meningiomas than in the surrounding tissue. The tumor-to-cortex activity ratio was 2.53 +/- 0.35 (range, 1.3-6). Nonneoplastic tissue such as hyperemic cavernous sinus did not take up the radionuclide and was therefore easily distinguished from the meningioma. The (18)F-TYR anomalies completely overlapped with the MR image in 54% of the tumors, extended beyond the MRI lesion in 38% of the tumors, and were smaller in 8% of the tumors. CONCLUSION: Meningiomas of the skull base are clearly visualized using (18)F-TYR PET/CT, even after irradiation. In addition to MRI, (18)F-TYR PET/CT images may contribute to the evaluation, delineation, and follow-up of these tumors. [less ▲]

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See detailSynthesis of anhydro-muramic acid derivatives as substrates for MurNAc amidase
Mercier, Frédéric; Zervosen, Astrid ULg; Lemaire, Christian ULg et al

Poster (2007, March 22)

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See detailRadiochemical synthesis and tissue distribution of p-[F-18]DMPPF, a new 5-HT1A ligand for PET, in rats
Defraiteur, Caroline; Lemaire, Christian ULg; Luxen, André ULg et al

in Nuclear Medicine & Biology (2006), 33(5), 667-675

Several studies have demonstrated the potential of p-[F-18]MPPF as a radiophanilaceutical to study the 5-HT1A receptor family in animals and humans. A structural modification leading to a higher ... [more ▼]

Several studies have demonstrated the potential of p-[F-18]MPPF as a radiophanilaceutical to study the 5-HT1A receptor family in animals and humans. A structural modification leading to a higher radioactive signal at an equipotent dose would greatly enhance this potential. With this goal, the desmethylated 4-(2'-methoxyphenyl)-1-[2'-[N-(2"-pyridinyl)-p-fluorobenzamidolethyl]-piperazine (p-MPPF), identified as p-DMPPF, was synthesized, labeled with fluorine-18 and evaluated through ex vivo tissue distribution in rats. The new compounds p-DMPPF, p-DMPPNO2, MEM-p-MPPF and MEM-p-MPPNO2 were isolated and fully identified (H-1 and C-13 NMR, LC-MS). The final compound, p-[F-18]DMPPF, was obtained ready for injection, with an overall radiochemical yield of 10% (EOB corrected) within 90 min and a specific activity of 62 GBq/mu mol. Tissue distributions showed that the carbon-fluorine bond was stable in vivo and that this compound could cross the blood-brain barrier. For kidney, lung, heart, spleen, bone, testicle, liver and muscle, the percentage of injected dose per gram of tissue obtained with p-[F-18]DMPPF was of the same order of magnitude as that of p-[F-18]MPPF. The amount of radioactivity reaching the brain was much higher (approximately fivefold at 60 min) for p-[F-18]DMPPF compared with p-[F-18]MPPF, which was taken as reference. The distribution and specificity were in total agreement with the known localization of 5-HT1A receptors in rats. The radioactivity increase was more important for specific tissues (hippocampus and frontal cortex) than for cerebellum or striatum, leading to better contrast (hippocampus/cerebellum=5.8 at 60 min). The levels of metabolites found in plasma showed that p-[F-18]DMPPF appears to be less metabolized than p-[F-18]MPPF. p-[F-18]DMPPF deserves further evaluation as a radiopharmaceutical candidate. (c) 2006 Elsevier Inc. All rights reserved. [less ▲]

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See detailSynthesis of anhydro-muramic acid derivatives as substrates for MurNAc amidase
Mercier, Frédéric; Lemaire, Christian ULg; Plenevaux, Alain ULg et al

Poster (2006, May 17)

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See detailDecomposition of metabolic brain clusters in the frontal variant of frontotemporal dementia
Salmon, Eric ULg; Kerrouche, Nacer; Herholz, Karl et al

in NeuroImage (2006), 30(3), 871-878

Previous studies that measured brain activity in frontotemporal dementia (FTD) used univariate analyses, examining each region of interest separately. We explored in a multicenter European research ... [more ▼]

Previous studies that measured brain activity in frontotemporal dementia (FTD) used univariate analyses, examining each region of interest separately. We explored in a multicenter European research program the principal brain clusters characterized by a common variability in cerebral metabolism in FTD. Seventy patients with frontal variant (fv) FTD were selected according to international clinical recommendations; principal component analysis (PCA) was performed on FDG-PET metabolic images, looking for covariance clusters in this large population. A first metabolic cluster included most of the lateral and medial prefrontal cortex, bilaterally; PC1 scores correlated with performances on memory and executive neuropsychological tasks. Moreover, FDG-PET images in fv-FTD were further characterized by a metabolic covariance in two clusters comprising the subcallosal medial frontal region, the temporal pole, medial temporal structures and the striatum, separately in the left and in the right hemisphere. The study provides original data-driven arguments for metabolic involvement of separate brain clusters in the rostral limbic system, corresponding to pathological poles differentially affected in each FTD patient. [less ▲]

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See detailDEVELOPPEMENT D'INHIBITEURS SELECTIFS DE LA TRYPTOPHANE HYDROXYLASE
Giacomelli, Fabrice ULg; Luxen, André ULg; Lemaire, Christian ULg et al

Conference (2006, February 03)

Comprendre la façon dont le cerveau travaille et en particulier le mode de communication de ses cellules est un rêve que beaucoup de chercheurs caressent. A l’heure actuelle, une des rares certitudes à ... [more ▼]

Comprendre la façon dont le cerveau travaille et en particulier le mode de communication de ses cellules est un rêve que beaucoup de chercheurs caressent. A l’heure actuelle, une des rares certitudes à son sujet est qu’un de ses modes de transmission d’informations utilise des « messagers » chimiques appelés neurotransmetteurs. Parmi ceux-ci, la sérotonine (5-HT) revêt une importance particulière. En effet, la 5-HT est impliquée dans de nombreuses fonctions (apprentissage, locomotion, sommeil,…) et pathologies (dépressions, démences, schizophrénies,…). Dès lors, l'étude in vivo chez l'homme des neurones sérotoninergiques ainsi que la quantification de la vitesse de biosynthèse de la 5-HT sont des domaines d'études fondamentaux pour lesquels la tomographie à émission de positons (TEP) constitue un outil de choix. Pour mener à bien ces différentes expérimentations, deux stratégies sont envisageables : - L’emploi d'un traceur capable de suivre la chaîne métabolique du tryptophane conduisant à la 5-HT tout en évitant les autres voies métaboliques. - L’utilisation d'un inhibiteur de la TrpOH (enzyme limitant du processus). Dans le cadre de cette présentation, nous nous intéresserons plus particulièrement à la deuxième stratégie. [less ▲]

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See detailOrbitofrontal dysfunction related to both apathy and disinhibition in frontotemporal dementia
Peters, Frederic; Perani, Daniela; Herholz, Karl et al

in Dementia & Geriatric Cognitive Disorders (2006), 21(5-6), 373-379

Orbitofrontal metabolic impairment is characteristic of the frontal variant of frontotemporal dementia (fv-FTD), as are early changes in emotional and social conduct. Two main types of behavioral ... [more ▼]

Orbitofrontal metabolic impairment is characteristic of the frontal variant of frontotemporal dementia (fv-FTD), as are early changes in emotional and social conduct. Two main types of behavioral disturbances have been distinguished in fv-FTD patients: apathetic and disinhibited manifestations. In this study, we searched for relationships between brain metabolism and presence of apathetic or disinhibited behavior. Metabolic activity and behavioral data were collected in 41 fv-FTD patients from European PET centers. A conjunction analysis of the PET data showed an expected impairment of metabolic activity in the anterior cingulate, ventromedial and orbital prefrontal cortex, the dorsolateral prefrontal cortex and the left anterior insula in fv-FTD subjects compared to matched controls. A correlation was observed between disinhibition scores on the Neuropsychiatric Inventory scale and a cluster of voxels located in the posterior orbitofrontal cortex ( 6, 28, - 24). Comparison of brain activity between apathetic and nonapathetic fv-FTD patients from two centers also revealed a specific involvement of the posterior orbitofrontal cortex in apathetic subjects ( 4, 22, - 22). The results confirm that the main cerebral metabolic impairment in fv-FTD patients affects areas specializing in emotional evaluation and demonstrate that decreased orbitofrontal activity is related to both disinhibited and apathetic syndromes in fv-FTD. Copyright (C) 2006 S. Karger AG, Basel. [less ▲]

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See detailSynthesis of protected meso-diaminopimelic acid.
Teller, N.; Lemaire, Christian ULg; Plenevaux, Alain ULg et al

Poster (2005, October 10)

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See detailSynthesis of anhydro-muranic acid derivatives as substrates for MurNAc amidase.
Mercier, F.; Lemaire, Christian ULg; Plenevaux, Alain ULg et al

Poster (2005, October 10)

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See detailRadiochemical Synthesis of OCH2F-[18F]MPPF a New Analogue of p-[18F]MPPF for the Study of 5-HT1A Receptors.
Defraiteur, C.; Lemaire, Christian ULg; Luxen, André ULg et al

in Journal of Labelled Compounds & Radiopharmaceuticals (2005), 48

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See detailEx Vivo Evaluation of p-[18F]D-MPPF for the Study of 5-HT1A Receptors.
Defraiteur, C.; Lemaire, Christian ULg; Luxen, André ULg et al

in Journal of Labelled Compounds & Radiopharmaceuticals (2005), 48

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See detailNew Methods For Halogenation of [18F]Fluorinated Benzyl Derivatives.
Kech, C.; Lemaire, Christian ULg; Brichard, L. et al

in Journal of Labelled Compounds & Radiopharmaceuticals (2005), 48

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See detailHighly enantioselective synthesis of no-carrier-added 6-[18F]Fluoro-L-dopa by chiral phase-transfer alkylation
Lemaire, Christian ULg; Gillet, Steve; Guillouet, Stéphane et al

in European Journal of Organic Chemistry (2004), (13), 2899-2904

[F-18]Fluoro-L-dopa, an important radiopharmaceutical for positron emission tomography (PET), has been synthesized using a phase-transfer alkylation reaction. A chiral quaternary ammonium salt derived ... [more ▼]

[F-18]Fluoro-L-dopa, an important radiopharmaceutical for positron emission tomography (PET), has been synthesized using a phase-transfer alkylation reaction. A chiral quaternary ammonium salt derived from a Cinchona alkaloid served as phase-transfer catalyst for the enantioselective alkylation of a glycine derivative. The active methylene group of this Schiff-base substrate was deprotonated with cesium hydroxide and rapidly alkylated by the 2-[F-18]fluoro-4,5-dimethoxybenzyl halide (X = Br, I). The reaction proceeded with high yield (> 90%) at 0 degreesC or room temperature in various solvents such as toluene or dichloromethane. Preparation of the [F-18]alkylating agent on a solid support was developed. After labelling, the labeled [F-18]fluoroveratraldehyde was trapped on a (t)C18 cartridge and then converted on the cartridge into the corresponding benzyl halide derivatives by addition of aqueous sodium borohydride and gaseous hydrobromic or -iodic acid. Hydrolysis and purification by preparative HPLC made 6-[F-18]fluoro-L-dopa ready for human injection in a 25-30% decay-corrected radiochemical yield in a synthesis time of 100 min. The product was found to be chemically, radiochemically and enantiomerically pure (ee > 95%). (C) Wiley-VCH Verlag GmbH [less ▲]

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See detailTissue distribution and metabolism of D-p-[18F]MPPF in rats.
Defraiteur, C.; Muroni, S.; Lemaire, Christian ULg et al

in Journal of Nuclear Medicine : Official Publication, Society of Nuclear Medicine (2004), 45(S2), 444

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See detailRadiochemical Synthesis of p-[18F]Desmethyl-MPPF (p-[18F]D-MPPF) for the Study of 5-HT1A Receptors
Defraiteur, Caroline; Plenevaux, Alain ULg; Lemaire, Christian ULg et al

in Journal of Labelled Compounds & Radiopharmaceuticals (2003, August), 46(S1), 157

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See detailRadiosynthèses d'antagonistes des récepteurs 5-HT1A.
Defraiteur, C.; Plenevaux, Alain ULg; Lemaire, Christian ULg et al

Poster (2003, June 13)

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