References of "Lemaire, Christian"
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See detailBrain energization in response to deep brain stimulation of subthalamic nuclei in Parkinson's disease.
Garraux, Gaëtan ULg; Bahri, Mohamed Ali ULg; Lemaire, Christian ULg et al

in Journal of Cerebral Blood Flow & Metabolism (2011)

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is an effective treatment in a subgroup of medically refractory patients with Parkinson's disease (PD). Here, we compared resting-state (18)F ... [more ▼]

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is an effective treatment in a subgroup of medically refractory patients with Parkinson's disease (PD). Here, we compared resting-state (18)F-fluorodeoxyglucose (FDG) positron emission tomography images in the stimulator off (DBS_OFF) and on (DBS_ON) conditions in eight PD patients in an unmedicated state, on average 2 years after bilateral electrode implantation. Global standardized uptake value (SUV) significantly increased by approximately 11% in response to STN-DBS. To avoid any bias in the voxel-based analysis comparing DBS_ON and DBS_OFF conditions, individual scan intensity was scaled to a region where FDG-SUV did not differ significantly between conditions. The resulting FDG-SUV ratio (FDG-SUVR) was found to increase in many regions in response to STN-DBS including the target area of surgery, caudate nuclei, primary sensorimotor, and associative cortices. Contrary to previous studies, we could not find any regional decrease in FDG-SUVR. These findings were indirectly supported by comparing the extent of areas with depressed FDG-SUVR in DBS_OFF and DBS_ON relatively to 10 normal controls. Altogether, these novel results support the prediction that the effect of STN-DBS on brain activity in PD is unidirectional and consists in an increase in many subcortical and cortical regions.Journal of Cerebral Blood Flow & Metabolism advance online publication, 6 April 2011; doi:10.1038/jcbfm.2011.41. [less ▲]

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See detail[18F]fallypride binding in the mouse brain: test-retest and effects of registration
Bahri, Mohamed Ali ULg; Geuzaine, Annabelle ULg; Warnock, Geoffrey ULg et al

Conference (2011, January 17)

The quantification of in vivo receptor kinetics with PET tracer experiments is an intricate and challenging problem especially for small animals such as rats and mice. A test-retest scan is usually set up ... [more ▼]

The quantification of in vivo receptor kinetics with PET tracer experiments is an intricate and challenging problem especially for small animals such as rats and mice. A test-retest scan is usually set up in order to confirm an observed experimental effect or to examine the reliability of the experiment design. Inadequate processing of the image data may also mask small effects. The purpose of this study was to investigate the effect of image registration on [18F]fallypride binding potentials calculated from PET mouse test-retest data. Sub-optimal registration affected the quantification of in vivo receptor kinetics with [18F]fallypride. The absence of anatomical information in the [18F]fallypride image and the lack of a homogeneous tracer distribution, even during the earlier minutes of the scan, lead to erroneous automatic registration. A FDG scan after each [18F]fallypride test could improve registration as FDG provides a more homogeneous brain image. Variability in the data could also result from stress induced by anaesthesia or the experimental environment. [less ▲]

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See detailThe cerebral metabolic correlates of episodic autobiographical memory in amnestic Mild Cognitive Impairment
Bastin, Christine ULg; Feyers, Dorothée ULg; Jedidi, Haroun ULg et al

in Proceedings of the 5th International Conference on Memory (2011)

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See detailSynthesis and hydrolytic stability of novel 3-[18F]fluoroethoxybis(1-methylethyl)silyl]propanaminebased prosthetic groups
collet, Charlotte; Lamandé-Langle, Sandrine; Balentova, Eva et al

Poster (2011)

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See detailNeural correlates of controlled memory processes in questionable Alzheimer’s disease
Bastin, Christine ULg; Kerrouche, Nacer; LEKEU, Françoise ULg et al

in Ashford, J. Wesson; Rosen, Allyson; Adamson, Maheen (Eds.) et al Advances in Alzheimer's Disease. Volume 2: Handbook of imaging the Alzheimer brain (2011)

Alzheimer’s disease (AD) is characterized by a progressive loss of controlled cognitive processes (processes requiring mental effort and attentional resources), and functional neuroimaging at early stages ... [more ▼]

Alzheimer’s disease (AD) is characterized by a progressive loss of controlled cognitive processes (processes requiring mental effort and attentional resources), and functional neuroimaging at early stages of AD provides an opportunity to tease out the neural correlates of controlled processes. Controlled and automatic memory performance was assessed with the Process Dissociation Procedure in 50 patients diagnosed with questionable Alzheimer’s disease (QAD). The patients’ brain glucose metabolism was measured using FDG-PET. After a follow-up period of 36 months, 27 patients had converted to AD, while 23 remained stable. Both groups showed a similar decrease in controlled memory processes but preserved automatic processes at entry into the study, suggesting that impairment of controlled memory would not be specific for AD. Patients who subsequently converted to Alzheimer type dementia showed significantly decreased brain metabolism at baseline compared to stable QAD in associative cortices known to be involved in AD (the left precuneus, the right inferior parietal lobule and bilateral middle temporal cortex).Voxel-based cognitive and metabolic correlations showed that a decrease in controlled memory processes was preferentially correlated with lower activity in the dorsomedial prefrontal and posterior cingulate cortices in very early AD patients. The dorsomedial prefrontal cortex would play a role in controlled memory processes as they relate to reflective and monitoring processes, while the posterior cingulate cortex is involved in the controlled access to previously encoded episodes. In stable QAD patients, reduced controlled performance in verbal memory correlated with impaired activity in the left anterior hippocampal structure, which would alter the reactivation of associations created at encoding. [less ▲]

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See detailSynthesis and hydrolytic stability of novel 3-[18F]fluoroethoxybis(1-methylethyl)silyl]propanamine-based prosthetic groups
Balentova, Eva; Collet, Charlotte; Lamande-Langle, Sandrine et al

in Journal of Fluorine Chemistry (2011), 132(4), 250-257

Two new silicon-based prosthetic groups, derived from 3-[ethoxybis(1-methylethyl)silyl]propanamine, have been prepd. in good yields. These silicon groups bearing an acid or an azide group were coupled to ... [more ▼]

Two new silicon-based prosthetic groups, derived from 3-[ethoxybis(1-methylethyl)silyl]propanamine, have been prepd. in good yields. These silicon groups bearing an acid or an azide group were coupled to a model tripeptide (Leu-Gly- Gly) either through a classical amide bond formation or through "click chem." via the Huisgen cycloaddn. The radiolabeling with fluorine-18 by substitution of the ethoxy group at silicon has been carried out with success in 51-54% decay cor. radiochem. yields. Radiolabeled peptides were easily prepd. by direct 18F-fluorination of the silicon-bearing tripeptide or by coupling the peptide with a radiolabeled silicon-based prosthetic group. Their stabilities in physiol. medium were studied and proved poor. [less ▲]

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See detailGeneral Method for Labeling siRNA by Click Chemistry with Fluorine-18 for the Purpose of PET Imaging
Mercier, Frédéric; Paris, Jérôme ULg; Kaisin, Geoffroy ULg et al

in Bioconjugate Chemistry (2011), 22(1), 108-114

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See detailIN VIVO PET IMAGING OF THE EFFECT OF THE NMDA ANTAGONIST MEMANTINE ON GLUCOSE METABOLISM IN THE RODENT BRAIN
Warnock, Geoffrey ULg; Dedeurwaerdere, Stefanie; Bahri, Mohamed Ali ULg et al

Poster (2010, September)

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See detailTHE EFFECT OF BETA MICROPROBE IMPLANTATION ON THE BLOOD BRAIN BARRIER
Warnock, Geoffrey ULg; Dedeurwaardere, Stefanie; Bahri, Mohamed Ali ULg et al

Poster (2010, September)

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See detailIs posterior cerebral hypometabolism always predicitve of dementia in Parkinson's disease?
Deville, Benjamin ULg; Lemaire, Christian ULg; Degueldre, Christian ULg et al

Poster (2010, June 08)

In Parkinson's disease, altered activity in posterior associative cortices has often been associated with dementia. It remains to be determined if this pattern is a reliable marker of a progression toward ... [more ▼]

In Parkinson's disease, altered activity in posterior associative cortices has often been associated with dementia. It remains to be determined if this pattern is a reliable marker of a progression toward dementia in patients without demonstratable dementia. In this retrospective analysis, we used positron emission tomography to study resting-state cerebral fluodeoxyglucose uptake in 8 healthy controls and 8 Parkinson's disease patients who did not have evidence of dementia at the time of assessment. For those patients, clinical follow up was available and we know that they did not meet dementia criteria on average 10,37 years after assessment. The results show that patients had reduced fluodeoxyglucose uptake mostly localised in the right hemisphere and including precuneus, superior temporal, middle temporal and inferior parietal cortices. It also includes right insula. These cerebral activity predominating in posterior cortices is present in non-demened patients but is not always predictive of dementia within the 10,34 years. [less ▲]

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See detailControlled Memory Processes in Questionable Alzheimer's Disease: A View from Neuroimaging Research
Bastin, Christine ULg; Kerrouche N; Lekeu, Françoise ULg et al

in Journal of Alzheimer's Disease [=JAD] (2010), 20(2), 547-560

Alzheimer's disease (AD) is characterized by a progressive loss of controlled cognitive processes, and neuroimaging studies at early stages of AD provide an opportunity to tease out the neural correlates ... [more ▼]

Alzheimer's disease (AD) is characterized by a progressive loss of controlled cognitive processes, and neuroimaging studies at early stages of AD provide an opportunity to tease out the neural correlates of controlled processes. Accordingly, controlled and automatic memory performance was assessed with the Process Dissociation Procedure in 50 patients diagnosed with questionable Alzheimer's disease (QAD). The patients' brain glucose metabolism was measured using FDG-PET. After a follow-up period of 36 months, 27 patients had converted to AD, while 23 remained stable. Both groups showed a similar decrease in controlled memory processes but preserved automatic processes at entry into the study. Voxel-based cognitive and metabolic correlations showed that a decrease in controlled memory processes was preferentially correlated with lower activity in the dorsomedial prefrontal and posterior cingulate cortices in very early AD patients. In stable QAD patients, reduced controlled performance in verbal memory correlated with impaired activity in the left anterior hippocampal structure. The results demonstrated the central role of a medial frontal-posterior cingulate network for controlled processing of episodic memory in the early stages of AD. [less ▲]

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See detailClick chemistry : radiolabelling of oligonucleotides with fluorine- 18 for PET
Kaisin, Geoffroy ULg; Flagothier, Jessica ULg; Mercier, Frédéric ULg et al

Poster (2010, June)

Oligonucleotides (ONs), especially small interfering RNA (siRNA), are promising therapeutic agents, but their pharmacokinetics and biodistributions are widely unknown. Positron Emission Tomography (PET ... [more ▼]

Oligonucleotides (ONs), especially small interfering RNA (siRNA), are promising therapeutic agents, but their pharmacokinetics and biodistributions are widely unknown. Positron Emission Tomography (PET) using fluorine-18 is a suitable technique to image and quantify such biological processes. The challenge for the radiochemist is to introduce this short half-life isotope (t1/2(18F)=109.7 min) onto oligonucleotides or, more generally, biomolecules. The most common technique requires the coupling of a prosthetic group bearing the radiotracer with the biomolecule. Current methods for labeling ONs with fluorine-18 have sub-optimal yields and require a long synthesis time.1 Click chemistry, e.g. 1,3-dipolar Huisgen cycloaddition of azides to alkynes, could be an efficient way to increase yields and reduce synthesis time. Conjugations with ONs are usually performed at 3’-ends using a well-chosen linker in order to limit degradation by exonucleases and to avoid alteration of hybridization properties and siRNA gene silencing efficiency. This also allows the development of universal solid supports used for the solidphase synthesis of ONs. Here we report the synthesis of three alkyne-bearing linkers , the synthesis and radiosynthesis of the complementary azido-bearing prosthetic groups (1-(azidomethyl)-4-[18F]- fluorobenzene) and coupling with functionalized ONs. [less ▲]

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See detailAutomated radiosynthesis of [18F]MPPF derivatives for imaging 5-HT1A receptors
Goblet, David ULg; Thonon, David ULg; Plenevaux, Alain ULg et al

Poster (2010, May 30)

TOPIC: Molecular Neuroimaging: from Bench to Bedside Automated radiosynthesis of [18F]MPPF derivatives for imaging 5-HT1A receptors Introduction: Dysfunction of the cerebral serotoninergic system is ... [more ▼]

TOPIC: Molecular Neuroimaging: from Bench to Bedside Automated radiosynthesis of [18F]MPPF derivatives for imaging 5-HT1A receptors Introduction: Dysfunction of the cerebral serotoninergic system is implicated in numerous neurodegenerative disorders such as Alzheimer disease’s, dementia, depression, anxiety, schizophrenia, and Parkinson disease’s. The 5-HT1A serotonin receptors are involved in several physiological functions including sleep, mood, neurogenesis and learning [1]. Consequently, there have been huge efforts in finding ligands for this receptor. [11C]WAY-100635 is a high affinity radioligand used for quantifying serotonin 5-HT1A receptors with positron emission tomography. An 18F-labeled radioligand is advantageous because of higher specific activity and physical/nuclear properties (t1/2= 109 min, 97% of positron decay and positron energy of 635 keV maximum). [18F]MPPF, a selective 5-HT1A antagonist derived from WAY-100635, is currently one of the most successful PET ligand used for 5-HT1A receptor imaging [2]. However the affinity is lower then WAY-100635 and the amount of [18F]MPPF reaching the brain is relatively low since MPPF is a substrate for p-glycoprotein [3]. Methods: In order to improve the brain uptake of the radiotracer, a desmethylated analog has been developed in our lab and preliminary in vitro studies show positive results [4]. Nevertheless, the radiosynthesis take place in two steps as a protecting group removal is needed. A one step procedure with a MPPF derivative could be of very great interest. We have synthesized many MPPF derivatives in our lab (modification on the phenylpiperazine moiety) and developed an automated radiosynthesis procedure for the production of these radiotracers. [18F]MPPF was chosen as the model compound. We used a GE Healthcare FASTlabTM module and made modifications to the [18F]FDG synthesis sequence and cassette. [18F]MPPF was synthesized by coupling of [18F]FBA with the corresponding amine. After coupling, the crude solution was diluted with water and passed through a tC18 cartridge for prepurification. After elution, the [18F]MPPF was purified by semi-preparative HPLC. Results: Total synthesis time, including purification was approximately 100 min. [18F]FBA and [18F]MPPF were obtained at a corrected yield of 55% (n=20) and 25% (n=5) respectively. The radiochemical purity, checked by radio-TLC and UPLC, was >95%. Conclusions: We have developed an automated method for [18F]MPPF and derivatives production using a commercial synthesizer (FASTlabTM from GE Healthcare) and a conventional HPLC system resulting in good yields and high (radio)chemical purity. By simply switching the vial containing the modified amine, an 18F-labeled MPPF derivative could be obtained. Radiosynthesis is still under optimization and the radiotracers synthesized need to be tested as suitable 5-HT1A radioligands. Acknowledgement: This work was supported by the Fondation Rahier. References: [1] Filip M., Bader M. et Al, Pharmacol Rep. 2009 Sep-Oct; 61(5):761-77 [2] Aznavour N, Zimmer L. Et Al, Neuropharmacology. 2007 Mar; 52(3):695-707 [3] Laćan G., Plenevaux A. et Al, Eur J Nucl Med Mol Imaging. 2008 Dec;35(12):2256-66 [4] Defraiteur C., Plenevaux A. et Al., Br J Pharmacol. 2007 Nov; 152(6):952-8 [less ▲]

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See detailFast Production of Highly Reactive No-Carrier-Added [18F]Fluoride for the Labeling of Radiopharmaceuticals
Lemaire, Christian ULg; Aerts, Joël ULg; Voccia, Samuel et al

in Angewandte Chemie (International ed. in English) (2010), 49

The 18F labeling of radiopharmaceuticals requires nearly anhydrous solutions of [18F]fluoride. Aqueous K2CO3 is generally used to elute [18F]fluoride from an anion-exchange resin. Replacing aqueous K2CO3 ... [more ▼]

The 18F labeling of radiopharmaceuticals requires nearly anhydrous solutions of [18F]fluoride. Aqueous K2CO3 is generally used to elute [18F]fluoride from an anion-exchange resin. Replacing aqueous K2CO3 with strong organic bases, such as the phosphazene base P2Et enabled the recovery of highly reactive [18F]fluoride and avoided the azeotropic evaporation of water, which is very difficult on a microchip device. [less ▲]

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See detailFast production of highly concentrated reactive [18F] fluoride for aliphatic and aromatic nucleophilic radiolabelling
Aerts, Joël ULg; Voccia, Samuel; Lemaire, Christian ULg et al

in Tetrahedron Letters (2010), 51

The use of a polymeric solid support loaded with a long alkyl chain quaternary ammonium allows the rapid and efficient recovery of cyclotron produced [18F]F- from [18O]water to a low water content organic ... [more ▼]

The use of a polymeric solid support loaded with a long alkyl chain quaternary ammonium allows the rapid and efficient recovery of cyclotron produced [18F]F- from [18O]water to a low water content organic solution compatible with fast nucleophilic labelling of most precursors for PET radiopharmaceuticals in high yield. [less ▲]

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