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See detailSerotonin 5HT2 receptor imaging in the human brain using positron emission tomography and a new radioligand, [18F]altanserin: results in young normal controls.
Sadzot, Bernard ULg; Lemaire, Christian ULg; Maquet, Pierre ULg et al

in Journal of Cerebral Blood Flow & Metabolism (1995), 15(5), 787-97

Changes in serotonin-2 receptors have been demonstrated in brain autopsy material from patients with various neurodegenerative and affective disorders. It would be desirable to locate a ligand for the ... [more ▼]

Changes in serotonin-2 receptors have been demonstrated in brain autopsy material from patients with various neurodegenerative and affective disorders. It would be desirable to locate a ligand for the study of these receptors in vivo with positron emission tomography (PET). Altanserin is a 4-benzoylpiperidine derivative with a high affinity and selectivity for S2 receptors in vitro. Dynamic PET studies were carried out in nine normal volunteers with high-specific activity (376-1,680 mCi/mumol) [18F]altanserin. Arterial blood samples were obtained and the plasma time-activity curves were corrected for the presence of labeled metabolites. Thirty minutes after injection, selective retention of the radioligand was observed in cortical areas, while the cerebellum, caudate, and thalamus had low radioactivity levels. Specific binding reached a plateau between 30 and 65 min postinjection at 1.8% of the injected dose/L of brain and then decreased, indicating the reversibility of the binding. The total/nonspecific binding ratio reached 2.6 for times between 50 and 70 min postinjection. The graphical analysis proposed by Logan et al. allowed us to estimate the binding potential (Bmax/KD). Pretreatment with ketanserin was given to three volunteers and brain activity remained uniformly low. An additional study in one volunteer showed that [18F]altanserin can be displaced from the receptors by large doses of ketanserin. At the end of the study, unchanged altanserin was 57% of the total plasma activity. These results suggest that [18F]altanserin is selective for S2 receptors in vivo as it is in vitro. They indicate that [18F]altanserin is suitable for imaging and quantifying S2 receptors with PET in humans. [less ▲]

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See detailSynthesis and biodistribution of [5-131I]iodotropapride: a potential D2 dopamine receptor imaging agent.
Cantineau, Robert; Guillaume, Marcel; Damhaut, Philippe et al

in Nuclear Medicine & Biology (1994), 21(2), 255-62

[5-131I]Iodotropapride is a benzamidic compound which displays high affinity and selectivity for dopaminergic receptors. It was prepared from the corresponding brominated compound by a nucleophilic ... [more ▼]

[5-131I]Iodotropapride is a benzamidic compound which displays high affinity and selectivity for dopaminergic receptors. It was prepared from the corresponding brominated compound by a nucleophilic substitution with [131I]iodine (t1/2 = 8.02 days, E gamma = 364 keV) based on the use of Cu(I) as catalyst and high specific activity of [131I]NaI. After i.v. injection in rats the tracer crosses the blood-brain barrier (0.42 +/- 0.06% of injected dose in the total brain) and demonstrates a high affinity binding to the striatum. The striatum-to-cerebellum ratio increases with time and reaches values of 9 and 22 at 30 and 120 min after injection, respectively. This specific uptake in the striatum is saturable and can be blocked by pretreatment with different D2 antagonists. When labeled with 123I (t1/2 = 13 h, E1 = 159 keV), the corresponding [123I]iodotropapride may be useful for the investigation of the D2 dopamine receptors in humans with single photon emission computer tomography (SPECT). [less ▲]

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See detailNUCLEOPHILIC ENANTIOSELECTIVE SYNTHESIS OF 6-[F-18]FLUORO-L-DOPA VIA 2 CHIRAL AUXILIARIES
Lemaire, Christian ULg; Plenevaux, Alain ULg; Cantineau, Robert et al

in Applied Radiation & Isotopes (1993), 44(4), 737-744

Asymmetric nucleophilic synthesis of 6-[F-18]fluoro-L-dopa was investigated in order to reach an enantiomeric excess of close to 100% of the L form of this amino acid. The radiochemical synthesis required ... [more ▼]

Asymmetric nucleophilic synthesis of 6-[F-18]fluoro-L-dopa was investigated in order to reach an enantiomeric excess of close to 100% of the L form of this amino acid. The radiochemical synthesis required [F-18]fluoride as fluorinating agent and regioselective nucleophilic substitution of commercially available 6-nitroveratraldehyde. The [F-18]fluorobenzaldehyde thus obtained was easily converted to the corresponding 2-[F-18]fluoro-4,5-dimethoxybenzyl bromide. This alkylating agent was added to the lithium enolates of 1-(S)-(-)camphor imine of t-butyl glycinate (1) and (S)-(-)- 1 -Boc-2-t-butyl-3-methyl-4-imidazolidinone [(S)- Boc-BMI] (2) in order to compare the enantiomeric excess of the L form obtained in each case with these two chiral inductors. The L-isomer of fluorodopa was isolated after H1 hydrolysis and HPLC purification in 5-10% radiochemical yield (decay corrected). The overall synthesis time was of 110 min. Through this synthetic pathway, the L-isomer of fluorodopa was obtained in 83% e.e with 1 and 96% e.e with 2 respectively, as determined by chiral HPLC. A practical three step preparative scale synthesis of 6-[F-19]fluoro-D,L-dopa is also presented. [less ▲]

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See detailSYNTHESIS OF F-18 SUBSTITUTED AROMATIC-ALDEHYDES AND BENZYL BROMIDES, NEW INTERMEDIATES FOR NCA [F-18] FLUORINATION
Lemaire, Christian ULg; Damhaut, Philippe; Plenevaux, Alain ULg et al

in Applied Radiation & Isotopes (1992), 43(4), 485-494

The synthesis of various [F-18]fluoroaromatic aldehydes using activated nitro precursors and aminopolyether supported nucleophilic substitution with F-18(-) is reported. These radiolabelled fluorinated ... [more ▼]

The synthesis of various [F-18]fluoroaromatic aldehydes using activated nitro precursors and aminopolyether supported nucleophilic substitution with F-18(-) is reported. These radiolabelled fluorinated aldehydes (radiochemical yields: 50-75%) are powerful key intermediates leading after treatment with NaBH4 and SOBr2 (SOCl2) to further active intermediates for example substituted [F-18]fluorobenzyl bromides (yields 30-50% EOB). These benzaldehydes and bromides are particularly useful for the preparation of new radiopharmaceuticals (e.g. fluorotroprapride, fluorodexetimide) either by reductive amination or by aromatic N-alkylation. The preparation of various amino acids in D, L (50:50) or enriched L form by asymmetric synthesis is also possible (e.g. L-6-[F-18]fluorodopa, L-4-[F-18]fluoro-m-tyrosine). It can be anticipated that the F-18-labelled fluoroaldehydes will find widespread application in radiopharmaceutical chemistry. [less ▲]

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See detail2- and 4-[18F]fluorotropapride, two specific D2 receptor ligands for positron emission tomography: N.C.A. syntheses and animal studies.
Damhaut, Philippe; Cantineau, Robert; Lemaire, Christian ULg et al

in International Journal of Radiation Applications and Instrumentation. Part A : Applied Radiation and Isotopes (1992), 43(10), 1265-74

Tropapride, (exo)-2,3-dimethoxy-N-[8-(phenylmethyl)-8- azabicyclo[3.2.1]oct-3-yl]benzamide hydrochloride, has been labeled with fluorine-18 at the 2- and 4-positions of its benzylic group. Two synthetic ... [more ▼]

Tropapride, (exo)-2,3-dimethoxy-N-[8-(phenylmethyl)-8- azabicyclo[3.2.1]oct-3-yl]benzamide hydrochloride, has been labeled with fluorine-18 at the 2- and 4-positions of its benzylic group. Two synthetic pathways were investigated: the first one required the alkylation of the norbenzyl precursor with 2- or 4-[18F]fluorobenzyl bromide (radiochemical yield of 5% EOB, 180 min); the second method consisted of a reductive amination of norbenzyl tropapride with 2- or 4-[18F]fluorobenzaldehyde (20% EOB, 110 min). In both cases, the specific activity was found to be greater than 1 Ci/mumol (EOS). Animal studies in rats showed the percentage of the injected dose localizing in the whole brain to be 0.6 +/- 0.09 and 0.2 +/- 0.03 at 2 h post injection for the para- and the ortho-[18F]fluoro analogs of tropapride respectively. Cerebral biodistribution studies showed at 4 h a striatum uptake of 5 +/- 0.7% of the injected dose per gram of striatum for the para derivative with a low fixation into the frontal cortex and the cerebellum (% ID/g FC < 0.4 and % ID/g Cb < 0.3). The selectivity of 4-[18F]fluorotropapride for D2 dopaminergic sites was demonstrated through blocking experiments with ketanserin, spiperone and halopemide. The saturability was confirmed by the use of variable specific activities. These preliminary results showed that 4-[18F]fluorotropapride can be considered as a potent radiopharmaceutical for the study of the dopaminergic system with PET. [less ▲]

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See detailAN APPROACH TO THE ASYMMETRIC-SYNTHESIS OF L-6-[F-18]FLUORODOPA VIA NCA NUCLEOPHILIC FLUORINATION
Lemaire, Christian ULg; Guillaume, Marcel; Cantineau, Robert et al

in Applied Radiation & Isotopes (1991), 42(7), 629-635

The NCA asymmetric synthesis of L-6-[F-18]fluorodopa starting from (1R,2R,5R)-[(+)-2-hydroxypinanyl-3-idene]glycine t-butyl ester as chiral agent has been developed. After F-18-fluorination of the two ... [more ▼]

The NCA asymmetric synthesis of L-6-[F-18]fluorodopa starting from (1R,2R,5R)-[(+)-2-hydroxypinanyl-3-idene]glycine t-butyl ester as chiral agent has been developed. After F-18-fluorination of the two commercially available aldehydes either 6-nitroveratraldehyde or 6-nitropiperonal, the required alkylating [F-18]fluorobenzyl bromide derivative can be easily prepared by treatment with NaBH4 followed by SOBr2. Alkylation of the Schiff base was carried out with the lithium salt of 2,2,6,6-tetramethylpiperidine as base in anhydrous THF at -78-degrees-C. Following hydrolysis of the protecting groups with hydroxylamine and Hl, the L-amino acid was obtained in 75% L form (ee 50%) with a 10% decay corrected (120 min) radiochemical yield. [less ▲]

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See detailFluorine-18-altanserin: a radioligand for the study of serotonin receptors with PET: radiolabeling and in vivo biologic behavior in rats.
Lemaire, Christian ULg; Cantineau, Robert; Guillaume, Marcel et al

in Journal of Nuclear Medicine : Official Publication, Society of Nuclear Medicine (1991), 32(12), 2266-72

No-carrier-added [18F]altanserin was synthesized by nucleophilic substitution of the corresponding nitro compound with [18F]fluoride in the presence of kryptofix 222 and K2CO3. After purification by ... [more ▼]

No-carrier-added [18F]altanserin was synthesized by nucleophilic substitution of the corresponding nitro compound with [18F]fluoride in the presence of kryptofix 222 and K2CO3. After purification by preparative HPLC, [18F]altanserin was produced in less than 2 hr with a radiochemical yield of 10% (EOS) and a specific activity of 0.8-1.3 Ci/mumol. In rats, the tracer localized rapidly in the whole brain (0.5% ID/g organ) with a high binding to the frontal cortex. The frontal cortex/cerebellum ratio increased with time and reached a plateau of 11 at 2 hr postinjection. This uptake in S2 receptor regions was saturable and could be blocked by pretreatment with various S2 antagonists. This radiopharmaceutical appears to be more selective for S2 receptor sites than other ligands available today and allows the study of S2 receptors under in vivo conditions. [less ▲]

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See detailSynthesis and tissue distribution of four Se-labeled tertiary amines, potential brain pH imaging agents.
Plenevaux, Alain ULg; Cantineau, Robert; Brihaye, Claude et al

in International Journal of Radiation Applications and Instrumentation. Part B : Nuclear Medicine and Biology (1990), 17(6), 601-7

Four new tertiary amines: bis(3-N,N-dimethyl aminopropyl)selenide (PROMOSE), bis(3-N-(morpholino)propyl)selenide, N-methyl-selenomorpholine and N-phenyl-selenomorpholine structurally related to MOSE ... [more ▼]

Four new tertiary amines: bis(3-N,N-dimethyl aminopropyl)selenide (PROMOSE), bis(3-N-(morpholino)propyl)selenide, N-methyl-selenomorpholine and N-phenyl-selenomorpholine structurally related to MOSE proposed by Kung and Blau, have been labeled through a radiochemical procedure suitable for both 75Se and 73Se. The radiochemical yields of the carrier added synthesis ranged between 64 and 85% for the four 75Se labelings and was 64% EOB time corrected for [73Se]PROMOSE. The chemical and radiochemical purities were higher than 99% after chromatographic purifications. The n-octanol/phosphate buffer partition coefficients (P) were measured at various pH (6.5-8) for each compound and the tissue distributions of PROMOSE in rats were also carried out. The experimental results showed a good correlation between the P = f(pH) function and the in vivo behaviour of the considered compound. PROMOSE was selected for further investigations as a brain pH indicator. [less ▲]

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See detailNo-carrier-added regioselective preparation of 6-[18F]fluoro-L-dopa
Lemaire, Christian ULg; Guillaume, Marcel ULg; Cantineau, Robert et al

in Journal of Nuclear Medicine : Official Publication, Society of Nuclear Medicine (1990), 31(7), 1247-1251

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See detailChemical processing for production of no-carrier-added selenium-73 from germanium and arsenic targets and synthesis of L-2-amino-4-([73Se]methylseleno) butyric acid (L-[73Se]selenomethionine).
Plenevaux, Alain ULg; Guillaume, Marcel; Brihaye, Claude et al

in International Journal of Radiation Applications and Instrumentation. Part A : Applied Radiation and Isotopes (1990), 41(9), 829-38

The Ge(4He, xn) and 75As(p, 3n) reactions were compared as the best potential routes for routine production of selenium-73 (73Se) for medical applications. With 26 MeV alpha particles, available with ... [more ▼]

The Ge(4He, xn) and 75As(p, 3n) reactions were compared as the best potential routes for routine production of selenium-73 (73Se) for medical applications. With 26 MeV alpha particles, available with compact cyclotrons, the first reaction required an enriched 70Ge target of sodium metagermanate to give a production yield of 1 mCi/microAh (0.037 GBq/microAh) in a 105 mg/cm2 target. With 55 MeV protons the As(p, 3n) reaction on natural arsenic yielded 20 mCi/microAh (0.74 GBq/microAh) in a 685 mg/cm2 target. A simple method was developed and optimized for both targets in order to isolate and purify the no-carrier-added selenium in the elemental form with a radiochemical yield greater than 75% in less than 90 min. An automated radiochemical processing unit has been designed for the routine production of 100-150 mCi (3.7-5.5 GBq) batches of carrier-free 73Se ready for radiopharmaceutical labeling. 30 mCi (1.11 GBq) (EOS) of L-2-amino-4-([73Se]methylseleno) butyric acid (L-[73Se]selenomethionine) ready for injection with a specific activity of 5 Ci/mmol (185 GBq/mmol) (EOS) were obtained through a fast chemical synthesis. Radiation absorbed dose estimates for L-[73Se]selenomethionine have been determined. A value of 0.70 rem/mCi (0.19 mSv/MBq) administered was calculated for the risk from irradiation in man. The first human PET investigation with [73Se]selenomethionine showed a very good delineation between liver and pancreas. [less ▲]

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See detailSelenium-73: Un nouvel avenir clinique pour la L-méthionine
Demonceau, Georges; Plenevaux, Alain ULg; Cantineau, Robert et al

in Journal de Biophysique et de Biomécanique (1987), 11

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See detailFast chemical synthesis of [75Se]L-selenomethionine.
Plenevaux, Alain ULg; Cantineau, Robert; Guillaume, Marcel et al

in International Journal of Radiation Applications and Instrumentation. Part A : Applied Radiation and Isotopes (1987), 38(1), 59-61

A fast chemical synthesis of high specific activity [75Se]L-selenomethionine (10 Ci/mmol--370 GBq/mmol) is described with a view to 73Se labeling and PET studies. The overall radiochemical yield of the ... [more ▼]

A fast chemical synthesis of high specific activity [75Se]L-selenomethionine (10 Ci/mmol--370 GBq/mmol) is described with a view to 73Se labeling and PET studies. The overall radiochemical yield of the preparation is better than 80%. The purification method uses commercially available reverse phase HPLC columns and 9% NaCl as mobile phase. The final labeled compound is obtained in less than 3 h and the chemical, radiochemical and optical purities of the L-isomer are higher than 99.0%. [less ▲]

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See detailSynthesis of 75Se-2-phenyl-1,2-benzisoselenazol-3-(2H)-one (PZ 51; EBSELEN*). A novel biologically active organo-selenium compound
Cantineau, Robert; Tihange, Guy; Plenevaux, Alain ULg et al

in Journal of Labelled Compounds & Radiopharmaceuticals (1986), 23(1), 59-65

The preparation of 75Se-ebselen (75Se-PZ 51) in a high radiochemica] yield (~40 %) and with a specific act'ivity of 240 mCi/mM (8.9 GBq/mM) is described.

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See detailHigh-Yield Synthesis of a (3H)Ethylenediamine Ditetrodotoxin Derivative
Bontemps, José; Cantineau, Robert; Grandfils, Christian ULg et al

in Analytical Biochemistry (1984), 139

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See detailBiochemical and biological properties of steroid 16alpha-hydroxylase.
Gielen, Jacques; Cantineau, Robert; Degraeve, Jacques et al

Conference (1980, March)

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