34 results on '"Challal S"'
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2. Lipschitz continuity of solutions of a free boundary problem involving the p-Laplacian
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Challal, S. and Lyaghfouri, A.
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- 2009
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3. On the A-obstacle problem and the Hausdorff measure of its free boundary
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Challal, S., Lyaghfouri, A., and Rodrigues, J. F.
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- 2012
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4. Gradient estimates for p(x)-harmonic functions
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Challal, S. and Lyaghfouri, A.
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- 2010
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5. A nonlinear two phase fluid flow through a porous medium in presence of a well
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Challal, S. and Lyaghfouri, A.
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- 2001
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6. On the continuity of the free boundary in problems of type [formula omitted]
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Challal, S. and Lyaghfouri, A.
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- 2005
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7. On the behavior of the interface separating fresh and salt groundwater in a heterogeneous coastal aquifer
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Challal, S. and Abdeslem Lyaghfouri
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Physics::Fluid Dynamics ,nonlinear Darcy's law ,comparison and uniqueness ,lcsh:Mathematics ,heterogeneous aquifer ,monotone solution ,Fresh-salt water ,lcsh:QA1-939 - Abstract
We consider a flow of fresh and salt groundwater in a two-dimensional heterogeneous horizontal aquifer. Assuming the flow governed by a nonlinear Darcy law and the permeability depending only on the vertical coordinate, we show the existence of a unique monotone solution that increases (resp. decreases) with respect to the salt (resp. fresh) water discharge. For this solution we prove that the free boundary is represented by the graph $x=g(z)$ of a continuous function. Finally we prove a limit behavior at the end points of the interval of definition of $g$.
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- 2003
8. Continuity of the free boundary in a non-degenerate p-obstacle problem type with monotone solution.
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Challal, S.
- Subjects
- *
CONTINUITY , *BOUNDARY value problems , *MONOTONE operators , *NONLINEAR analysis , *ELLIPTIC equations , *PROOF theory - Abstract
We prove the continuity of the free boundary for a non-degeneratep-obstacle problem with monotone solution. The proof uses techniques of comparison and the growth of the solution near free boundary points. [ABSTRACT FROM AUTHOR]
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- 2013
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9. Second order regularity for the p( x)-Laplace operator.
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Challal, S. and Lyaghfouri, A.
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- 2011
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10. THE HETEROGENEOUS DAM PROBLEM WITH LEAKY BOUNDARY CONDITION.
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CHALLAL, S. and LYAGHFOURI, A.
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- 2011
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11. A stationary flow of fresh and salt groundwater in a coastal aquifer with nonlinear darcy' law.
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Challal, S. and Lyaghfouri, A.
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- 1997
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12. STUDY OF THE LIMIT BEHAVIOR OF A VISCOELASTIC MEDIUM WITH VERY SMALL OBSTACLES.
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CHALLAL, S. and PAULIN, J. SAINT JEAN
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- 1996
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13. Total synthesis of novel conduritol related compounds capable of modulating insulin release.
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Billington, D.C., Perron-Sierra, F., Picard, I., Beaubras, S., Duhault, J., Espinal, J., and Challal, S.
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- 1994
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14. ChemInform Abstract: Total Synthesis of Novel Conduritol Related Compounds Capable of Modulating Insulin Release.
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BILLINGTON, D. C., PERRON-SIERRA, F., PICARD, I., BEAUBRAS, S., DUHAULT, J., ESPINAL, J., and CHALLAL, S.
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- 1995
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15. Natural product-derived therapies for treating drug-resistant epilepsies: From ethnopharmacology to evidence-based medicine.
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Challal S, Skiba A, Langlois M, Esguerra CV, Wolfender JL, Crawford AD, and Skalicka-Woźniak K
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- Animals, Humans, Ethnopharmacology, Anticonvulsants pharmacology, Plant Extracts pharmacology, Plant Extracts therapeutic use, Evidence-Based Medicine, Biological Products therapeutic use, Epilepsy drug therapy, Epilepsy metabolism, Cannabidiol pharmacology, Cannabidiol therapeutic use, Drug Resistant Epilepsy drug therapy, Plants, Medicinal
- Abstract
Ethnopharmacological Relevance: Epilepsy is one of the most prevalent neurological human diseases, affecting 1% of the population in all age groups. Despite the availability of over 25 anti-seizure medications (ASMs), which are approved in most industrialized countries, approximately 30% of epilepsy patients still experience seizures that are resistant to these drugs. Since ASMs target only limited number of neurochemical mechanisms, drug-resistant epilepsy (DRE) is not only an unmet medical need, but also a formidable challenge in drug discovery., Aim: In this review, we examine recently approved epilepsy drugs based on natural product (NP) such as cannabidiol (CBD) and rapamycin, as well as NP-based epilepsy drug candidates still in clinical development, such as huperzine A. We also critically evaluate the therapeutic potential of botanical drugs as polytherapy or adjunct therapy specifically for DRE., Methods: Articles related to ethnopharmacological anti-epileptic medicines and NPs in treating all forms of epilepsy were collected from PubMed and Scopus using keywords related to epilepsy, DRE, herbal medicines, and NPs. The database clinicaltrials.gov was used to find ongoing, terminated and planned clinical trials using herbal medicines or NPs in epilepsy treatment., Results: A comprehensive review on anti-epileptic herbal drugs and natural products from the ethnomedical literature is provided. We discuss the ethnomedical context of recently approved drugs and drug candidates derived from NPs, including CBD, rapamycin, and huperzine A. Recently published studies on natural products with preclinical efficacy in animal models of DRE are summarized. Moreover, we highlight that natural products capable of pharmacologically activating the vagus nerve (VN), such as CBD, may be therapeutically useful to treat DRE., Conclusions: The review highlights that herbal drugs utilized in traditional medicine offer a valuable source of potential anti-epileptic drug candidates with novel mechanisms of action, and with clinical promise for the treatment of drug-resistant epilepsy (DRE). Moreover, recently developed NP-based anti-seizure medications (ASMs) indicate the translational potential of metabolites of plant, microbial, fungal and animal origin., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)
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- 2023
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16. Impact of different types of exercise programs on ankylosing spondylitis: a systematic review and meta-analysis.
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Boudjani R, Challal S, Semerano L, and Sigaux J
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- Humans, Exercise, Exercise Therapy, Research Design, Severity of Illness Index, Spondylitis, Ankylosing therapy
- Abstract
Purpose: This systematic review and meta-analysis of controlled studies aimed to assess the efficacy of different types of exercise programs (EP) on ankylosing spondylitis (AS) activity, function and mobility., Methods: We searched PubMed/Medline, Cochrane Library and Embase databases for reports of controlled trials of patients with AS published up to May 2022. The studies were classified by intervention into categories defined by the 4 exercise domains established by the American College of Sports Medicine and then adopted by the European League Against Rheumatism: aerobic, muscle strength, flexibility, neuromotor performance., Results: We found a moderate effect of EP as a whole on BASDAI (Bath Ankylosing Spondylitis Disease Activity Index) (-0.60, 95% CI -0.95, -0.25, p < 0.001), BASFI (Functional) (-0.63, 95% CI -0.84, -0.42, p < 0.0001) and BASMI (Metrology) (-0.52, 95% CI -0.88, -0.15, p < 0.01). The effect of "flexibility + muscle strength" EP was large for BASMI, moderate for BASDAI and BASFI. The effect of "flexibility + muscle strength + aerobic" EP was large for BASFI, moderate for BASDAI., Conclusions: EP, regardless of the specific type of exercise, have a moderate effect on AS activity, function and mobility. EP including flexibility and muscle strength exercises may have a large effect, especially for mobility. Programs including aerobic exercise showed significant efficacy for function.IMPLICATIONS FOR REHABILITATIONIn ankylosing spondylitis (AS), any exercise program (EP), regardless of the type of exercises involved, showed a moderate effect on disease activity, function and spinal mobility.In AS, EP combining flexibility and strength exercises showed the largest effect on spinal mobility and should be encouraged.In AS, EP combining flexibility, muscle strength and aerobic exercises may be particularly effective on patient function.
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- 2023
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17. A seeding-based neuronal model of tau aggregation for use in drug discovery.
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Amorim IS, Challal S, Cistarelli L, Dorval T, Abjean L, Touzard M, Arbez N, François A, Panayi F, Jeggo R, Cecon E, Oishi A, Dam J, Jockers R, and Machado P
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- Mice, Animals, Humans, tau Proteins genetics, tau Proteins metabolism, Mice, Transgenic, Brain metabolism, Neurons metabolism, Drug Discovery, Tauopathies metabolism, Alzheimer Disease pathology
- Abstract
Intracellular accumulation of tau protein is a hallmark of Alzheimer's Disease and Progressive Supranuclear Palsy, as well as other neurodegenerative disorders collectively known as tauopathies. Despite our increasing understanding of the mechanisms leading to the initiation and progression of tau pathology, the field still lacks appropriate disease models to facilitate drug discovery. Here, we established a novel and modulatable seeding-based neuronal model of full-length 4R tau accumulation using humanized mouse cortical neurons and seeds from P301S human tau transgenic animals. The model shows specific and consistent formation of intraneuronal insoluble full-length 4R tau inclusions, which are positive for known markers of tau pathology (AT8, PHF-1, MC-1), and creates seeding competent tau. The formation of new inclusions can be prevented by treatment with tau siRNA, providing a robust internal control for use in qualifying the assessment of potential therapeutic candidates aimed at reducing the intracellular pool of tau. In addition, the experimental set up and data analysis techniques used provide consistent results in larger-scale designs that required multiple rounds of independent experiments, making this is a versatile and valuable cellular model for fundamental and early pre-clinical research of tau-targeted therapies., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2023 Amorim et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)
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- 2023
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18. Vaginal microbiota as an unusual cause of spondylodiscitis.
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Kolakowska A, El Alaoui F, Ben Alba H, Challal S, Carbonnelle E, and Jaureguy F
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- Female, Gardnerella vaginalis, Humans, Vagina microbiology, Discitis drug therapy, Discitis etiology, Microbiota, Vaginosis, Bacterial diagnosis, Vaginosis, Bacterial drug therapy, Vaginosis, Bacterial microbiology
- Abstract
The incidence of extra pelvic infections due to vaginal microflora bacteria has increased as growth media and methods of isolation have improved. However, bone infections seem to be still relatively rare, and little is known about their risk factors, clinical presentation, treatment and final outcome. We describe here a spondylodiscitis due to Gardnerella vaginalis, Atopobium vaginae, Peptostreptococcus indolicus and Prevotella amnii, anaerobic bacteria from vaginal microbiota. Our patient had no obvious predisposing factor and recovered after antibiotic treatment. To our knowledge, this case is the first reported spondylodiscitis caused by polymicrobial vaginal flora in a healthy, immunocompetent woman., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)
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- 2022
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19. Synovial fluid erythrophagocytosis: Inflammation or drug-induced change?
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Handra-Luca A and Challal S
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- Humans, Synovial Fluid drug effects, Erythrocytes drug effects, Erythrocytes pathology, Inflammation pathology, Phagocytosis drug effects, Pharmaceutical Preparations administration & dosage, Synovial Fluid physiology
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- 2020
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20. Pharmacological characterisation of S 47445, a novel positive allosteric modulator of AMPA receptors.
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Bretin S, Louis C, Seguin L, Wagner S, Thomas JY, Challal S, Rogez N, Albinet K, Iop F, Villain N, Bertrand S, Krazem A, Bérachochéa D, Billiald S, Tordjman C, Cordi A, Bertrand D, Lestage P, and Danober L
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- Animals, Binding Sites, Cell Line, Cells, Cultured, Glutamic Acid pharmacology, Humans, Locomotion drug effects, Male, Maze Learning drug effects, Mice, Neurons drug effects, Neurons metabolism, Oocytes drug effects, Oocytes metabolism, Patch-Clamp Techniques, Rats, Receptors, AMPA chemistry, Xenopus, Allosteric Regulation drug effects, Receptors, AMPA agonists
- Abstract
S 47445 is a novel positive allosteric modulator of alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptors (AMPA-PAM). S 47445 enhanced glutamate's action at AMPA receptors on human and rat receptors and was inactive at NMDA and kainate receptors. Potentiation did not differ among the different AMPA receptors subtypes (GluA1/2/4 flip and flop variants) (EC50 between 2.5-5.4 μM), except a higher EC50 value for GluA4 flop (0.7 μM) and a greater amount of potentiation on GluA1 flop. A low concentration of S 47445 (0.1 μM) decreased receptor response decay time of GluA1flop/GluA2flip AMPA receptors and increased the sensitivity to glutamate. Furthermore, S 47445 (0.1 and 0.3 μM) in presence of repetitive glutamate pulses induced a progressive potentiation of the glutamate-evoked currents from the second pulse of glutamate confirming a rapid-enhancing effect of S 47445 at low concentrations. The potentiating effect of S 47445 (1 μM) was concentration-dependently reversed by the selective AMPA receptor antagonist GYKI52466 demonstrating the selective modulatory effect of S 47445 on AMPA receptors. Using an AMPA-kainate chimera approach, it was confirmed that S 47445 binds to the common binding pocket of AMPA-PAMs. S 47445 did not demonstrate neurotoxic effect against glutamate-mediated excitotoxicity in vitro, in contrast significantly protected rat cortical neurons at 10 μM. S 47445 was shown to improve both episodic and spatial working memory in adult rodents at 0.3 mg/kg, as measured in the natural forgetting condition of object recognition and T-maze tasks. Finally, no deleterious effect on spontaneous locomotion and general behavior was observed up to 1000 mg/kg of S 47445 given acutely in rodents, neither occurrence of convulsion or tremors. Collectively, these results indicate that S 47445 is a potent and selective AMPA-PAM presenting procognitive and potential neuroprotective properties. This drug is currently evaluated in clinical phase 2 studies in Alzheimer's disease and in Major Depressive Disorder.
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- 2017
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21. Conjugation of N-acylhydrazone and 1,2,4-oxadiazole leads to the identification of active antimalarial agents.
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Dos Santos Filho JM, de Queiroz E Silva DMA, Macedo TS, Teixeira HMP, Moreira DRM, Challal S, Wolfender JL, Queiroz EF, and Soares MBP
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- Animals, Antimalarials chemical synthesis, Antimalarials chemistry, Cell Survival drug effects, Dose-Response Relationship, Drug, Hep G2 Cells, Humans, Hydrazones chemistry, Malaria pathology, Mice, Molecular Structure, Oxadiazoles chemistry, Structure-Activity Relationship, Antimalarials pharmacology, Hydrazones pharmacology, Malaria drug therapy, Oxadiazoles pharmacology, Plasmodium falciparum drug effects
- Abstract
Malaria, caused by several Plasmodium species, is the major life-threatening parasitic infection worldwide. Due to the parasite resistance to quinoline based drugs, the search for antimalarial agents is necessary. Here, we report the structural design, synthesis and antiparasitic evaluation of two novel series of 1,2,4-oxadiazoles in conjugation to N-acylhydrazones, both groups recognized as privileged structures, as well as the studies on the antimalarial activity of 16 previous described analogues. By varying substituents attached to the phenyl ring, it was possible to retain, enhance or increase the antiparasitic activity in comparison to the nonsubstituted derivatives. Replacement of substituted aryl rings by ferrocenyl and cinnamyl moieties attached in the N-acylhydrazone ablated the antiparasitic response, evidencing the structural features associated with the activity. Active compounds exhibited in vitro potency similar to mefloquine, but not all inhibited β-hematin formation. Additionally, the active compounds displayed low cytotoxicity in HepG2 cells and did not cause hemolysis in uninfected erythrocytes. In Plasmodium berghei-infected mice, the compounds reduced parasitemia but exhibited limited efficacy in increasing mice survival when compared to chloroquine, suggesting that pharmacological improvement is still necessary., (Copyright © 2016 Elsevier Ltd. All rights reserved.)
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- 2016
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22. Teriparatide for osteoporosis in patients with sarcoidosis: Report on risk-benefit ratio in four cases.
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Challal S, Semerano L, Nunes H, Valeyre D, Boissier MC, and Saidenberg-Kermanac'h N
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- Aged, Female, Fractures, Spontaneous etiology, Fractures, Spontaneous prevention & control, Humans, Male, Middle Aged, Osteoporosis complications, Osteoporotic Fractures etiology, Risk Assessment, Spinal Fractures etiology, Bone Density Conservation Agents therapeutic use, Osteoporosis drug therapy, Osteoporotic Fractures prevention & control, Sarcoidosis complications, Spinal Fractures prevention & control, Teriparatide therapeutic use
- Abstract
Objectives: For patients with sarcoidosis, no consensus exists about the management of osteoporosis, whether related or unrelated to glucocorticoid therapy., Methods: We report the first series of 4patients with histologically documented sarcoidosis who received teriparatide therapy for severe osteoporosis manifesting as a fracture cascade with multilevel vertebral fractures. When teriparatide was started, 1patient was receiving 10mg of prednisone equivalents per day, 1 was progressively tapering glucocorticoid dose, 2 had never received any glucocorticoid treatment., Results: In all 4patients, teriparatide was effective in halting the fracture cascade, including in the 2patients who remained on long-term glucocorticoid therapy. None of the patients developed hypercalcemia. During teriparatide therapy, 3patients underwent a flare or a complication of sarcoidosis. Only the patient on stable glucocorticoid treatment did not present any adverse event. Before teriparatide initiation, sarcoidosis had been well controlled in all 3patients for several years., Conclusions: Even if the implication of teriparatide is unclear, the appearance of adverse events in 3 out of 4patients in this small series suggest caution in the use of teriparatide in patients with sarcoidosis., (Copyright © 2015 Société française de rhumatologie. Published by Elsevier SAS. All rights reserved.)
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- 2016
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23. Cachexia and adiposity in rheumatoid arthritis. Relevance for disease management and clinical outcomes.
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Challal S, Minichiello E, Boissier MC, and Semerano L
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- Arthritis, Rheumatoid complications, Arthritis, Rheumatoid mortality, Arthritis, Rheumatoid therapy, Cachexia etiology, Cardiovascular Diseases etiology, Cardiovascular Diseases physiopathology, Disabled Persons, Disease Management, Exercise physiology, Humans, Treatment Outcome, Adiposity physiology, Arthritis, Rheumatoid physiopathology, Cachexia physiopathology
- Abstract
Altered body composition is a frequent finding in rheumatoid arthritis and is associated with the two major outcomes of the disease: disability and cardiovascular mortality. It is estimated that up to two thirds of patients may be affected by loss of lean mass, the so-called rheumatoid cachexia. Hence, body weight being equal, the relative amount of lean mass is lower and that of body fat is higher in rheumatoid arthritis patients vs. healthy controls. Both disease-related factors and other factors, like drug treatments, physical activity and nutrition contribute to modify body composition in rheumatoid arthritis. The effect of pharmacological treatments, and notably of anti-TNF drugs, on body composition is controversial. Conversely, training programs to stimulate muscle growth can restore lean mass and reduce adiposity. There is good evidence that amelioration of body composition ameliorates function and reduces disability. Currently, there is no evidence that interventions that modify body composition can reduce cardiovascular morbidity and mortality in rheumatoid arthritis., (Copyright © 2015. Published by Elsevier SAS.)
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- 2016
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24. Rational and Efficient Preparative Isolation of Natural Products by MPLC-UV-ELSD based on HPLC to MPLC Gradient Transfer.
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Challal S, Queiroz EF, Debrus B, Kloeti W, Guillarme D, Gupta MP, and Wolfender JL
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- Anacardium chemistry, Morinda chemistry, Biological Products isolation & purification, Chromatography, High Pressure Liquid methods, Chromatography, Liquid methods, Mass Spectrometry methods
- Abstract
In natural product research, the isolation of biomarkers or bioactive compounds from complex natural extracts represents an essential step for de novo identification and bioactivity assessment. When pure natural products have to be obtained in milligram quantities, the chromatographic steps are generally labourious and time-consuming. In this respect, an efficient method has been developed for the reversed-phase gradient transfer from high-performance liquid chromatography to medium-performance liquid chromatography for the isolation of pure natural products at the level of tens of milligrams from complex crude natural extracts. The proposed method provides a rational way to predict retention behaviour and resolution at the analytical scale prior to medium-performance liquid chromatography, and guarantees similar performances at both analytical and preparative scales. The optimisation of the high-performance liquid chromatography separation and system characterisation allows for the prediction of the gradient at the medium-performance liquid chromatography scale by using identical stationary phase chemistries. The samples were introduced in medium-performance liquid chromatography using a pressure-resistant aluminium dry load cell especially designed for this study to allow high sample loading while maintaining a maximum achievable flow rate for the separation. The method has been validated with a mixture of eight natural product standards. Ultraviolet and evaporative light scattering detections were used in parallel for a comprehensive monitoring. In addition, post-chromatographic mass spectrometry detection was provided by high-throughput ultrahigh-performance liquid chromatography time-of-flight mass spectrometry analyses of all fractions. The processing of all liquid chromatography-mass spectrometry data in the form of an medium-performance liquid chromatography x ultra high-performance liquid chromatography time-of-flight mass spectrometry matrix enabled an efficient localisation of the compounds of interest in the generated fractions. The methodology was successfully applied for the separation of three different plant extracts that contain many diverse secondary metabolites. The advantages and limitations of this approach and the theoretical chromatographic background that rules such as liquid chromatography gradient transfer are presented from a practical viewpoint., (Georg Thieme Verlag KG Stuttgart · New York.)
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- 2015
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25. Biomimetic synthesis of Tramadol.
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Lecerf-Schmidt F, Haudecoeur R, Peres B, Ferreira Queiroz MM, Marcourt L, Challal S, Ferreira Queiroz E, Sotoing Taiwe G, Lomberget T, Le Borgne M, Wolfender JL, De Waard M, Robins RJ, and Boumendjel A
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- Chromatography, High Pressure Liquid, Magnetic Resonance Spectroscopy, Mass Spectrometry, Analgesics, Opioid chemical synthesis, Biomimetics, Tramadol chemical synthesis
- Abstract
Tramadol has recently been isolated from the roots and bark of Nauclea latifolia. A plausible biosynthetic pathway has been proposed and the product-precursor relationship has been probed by (13)C position-specific isotope analysis. By further exploring this pathway, we demonstrate that a key step of the proposed pathway can be achieved using mild conditions that mimic in vivo catalysis.
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- 2015
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26. Ehlers-Danlos syndrome in rheumatology: Diagnostic and therapeutic challenges.
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Challal S, Minichiello E, Funalot B, and Boissier MC
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- Humans, Disease Management, Ehlers-Danlos Syndrome diagnosis, Ehlers-Danlos Syndrome genetics, Ehlers-Danlos Syndrome therapy, Rheumatology methods
- Published
- 2015
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27. Positive allosteric modulators of 2-amino-3-(3-hydroxy-5-methylisoxazol-4-yl)propionic acid receptors belonging to 4-cyclopropyl-3,4-dihydro-2h-1,2,4-pyridothiadiazine dioxides and diversely chloro-substituted 4-cyclopropyl-3,4-dihydro-2H-1,2,4-benzothiadiazine 1,1-dioxides.
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Francotte P, Nørholm AB, Deva T, Olsen L, Frydenvang K, Goffin E, Fraikin P, de Tullio P, Challal S, Thomas JY, Iop F, Louis C, Botez-Pop I, Lestage P, Danober L, Kastrup JS, and Pirotte B
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- Allosteric Site, Animals, Calorimetry, Chemistry, Pharmaceutical methods, Crystallography, X-Ray, Dimerization, Drug Design, Electrophysiology, Hippocampus drug effects, Humans, Hydrogen chemistry, Kinetics, Mice, Protein Binding, Rats, Rats, Wistar, Temperature, Thermodynamics, Benzothiadiazines chemistry, Cyclic S-Oxides chemistry, Oxides chemistry, Propionates chemistry, Receptors, AMPA chemistry, Thiadiazines chemistry
- Abstract
Two 4-ethyl-substituted pyridothiadiazine dioxides belonging to α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor positive allosteric modulators were cocrystallized with the GluA2 ligand binding domain in order to decipher the impact of the position of the nitrogen atom on their binding mode at the AMPA receptors. The latter was found to be very similar to that of previously described benzothiadiazine-type AMPA receptor modulators. The affinity of the two compounds for the receptor was determined by isothermal titration calorimetry. Accordingly, the synthesis and biological evaluation of novel 4-cyclopropyl-substituted pyridothiadiazine dioxides was performed and completed with the synthesis of the corresponding chloro-substituted 4-cyclopropyl-3,4-dihydro-2H-benzothiadiazine 1,1-dioxides. The "8-aza" compound 32 was found to be the most potent pyridothiadiazine-type AMPA receptor potentiator in vitro, whereas the 7-chloro-substituted compound 36c emerged as the most promising benzothiadiazine dioxide. Due to proper drug-likeness and low in vivo acute toxicity in mice, 36c was chosen for a more complete preclinical evaluation. The compound was able to easily cross the blood-brain barrier. In an in vivo object recognition test with CD1 mice, oral administration of 36c was found to significantly improve cognition performance at doses as low as 1 mg/kg.
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- 2014
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28. Zebrafish bioassay-guided microfractionation identifies anticonvulsant steroid glycosides from the Philippine medicinal plant Solanum torvum.
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Challal S, Buenafe OE, Queiroz EF, Maljevic S, Marcourt L, Bock M, Kloeti W, Dayrit FM, Harvey AL, Lerche H, Esguerra CV, de Witte PA, Wolfender JL, and Crawford AD
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- Animals, Anticonvulsants pharmacology, Biological Assay methods, Chemical Fractionation methods, Chromatography, High Pressure Liquid methods, Disease Models, Animal, Glycosides pharmacology, Hydrolysis, Larva, Microtechnology methods, Molecular Structure, Oocytes drug effects, Oocytes metabolism, Patch-Clamp Techniques, Pentylenetetrazole, Plant Extracts pharmacology, Receptors, GABA-A genetics, Receptors, GABA-A metabolism, Seizures drug therapy, Xenopus laevis, Zebrafish, Anticonvulsants chemistry, Drug Discovery methods, Glycosides chemistry, Plant Extracts chemistry, Plants, Medicinal chemistry, Solanum chemistry
- Abstract
Medicinal plants used for the treatment of epilepsy are potentially a valuable source of novel antiepileptic small molecules. To identify anticonvulsant secondary metabolites, we performed an in vivo, zebrafish-based screen of medicinal plants used in Southeast Asia for the treatment of seizures. Solanum torvum Sw. (Solanaceae) was identified as having significant anticonvulsant activity in zebrafish larvae with seizures induced by the GABAA antagonist pentylenetetrazol (PTZ). This finding correlates well with the ethnomedical use of this plant in the Philippines, where a water decoction of S. torvum leaves is used to treat epileptic seizures. HPLC microfractionation of the bioactive crude extract, in combination with the in vivo zebrafish seizure assay, enabled the rapid localization of several bioactive compounds that were partially identified online by UHPLC-TOF-MS as steroid glycosides. Targeted isolation of the active constituents from the methanolic extract enabled the complete de novo structure identification of the six main bioactive compounds that were also present in the traditional preparation. To partially mimic the in vivo metabolism of these triterpene glycosides, their common aglycone was generated by acid hydrolysis. The isolated molecules exhibited significant anticonvulsant activity in zebrafish seizure assays. These results underscore the potential of zebrafish bioassay-guided microfractionation to rapidly identify novel bioactive small molecules of natural origin.
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- 2014
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29. Synthesis, pharmacological and structural characterization, and thermodynamic aspects of GluA2-positive allosteric modulators with a 3,4-dihydro-2H-1,2,4-benzothiadiazine 1,1-dioxide scaffold.
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Nørholm AB, Francotte P, Olsen L, Krintel C, Frydenvang K, Goffin E, Challal S, Danober L, Botez-Pop I, Lestage P, Pirotte B, and Kastrup JS
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- Animals, Benzothiadiazines chemical synthesis, Benzothiadiazines chemistry, Calorimetry, Crystallography, X-Ray, Cyclic S-Oxides chemical synthesis, Cyclic S-Oxides chemistry, Dose-Response Relationship, Drug, Models, Molecular, Molecular Structure, Neurons cytology, Neurons drug effects, Rats, Structure-Activity Relationship, Allosteric Regulation drug effects, Benzothiadiazines pharmacology, Cyclic S-Oxides pharmacology, Receptors, AMPA metabolism, Thermodynamics
- Abstract
Positive allosteric modulators of ionotropic glutamate receptors are potential compounds for treatment of cognitive disorders, e.g., Alzheimer's disease. The modulators bind within the dimer interface of the ligand-binding domain (LBD) and stabilize the agonist-bound conformation, thereby slowing receptor desensitization and/or deactivation. Here we describe the synthesis and pharmacological testing at GluA2 of a new generation of 3,4-dihydro-2H-1,2,4-benzothiadiazine 1,1-dioxides. The most potent modulator 3 in complex with GluA2-LBD-L483Y-N754S was subjected to structural analysis by X-ray crystallography, and the thermodynamics of binding was studied by isothermal titration calorimetry. Compound 3 binds to GluA2-LBD-L483Y-N754S with a Kd of 0.35 μM (ΔH = -7.5 kcal/mol and -TΔS = -1.3 kcal/mol). This is the first time that submicromolar binding affinity has been achieved for this type of positive allosteric modulator. The major structural factor increasing the binding affinity of 3 seems to be interactions between the cyclopropyl group of 3 and the backbone of Phe495 and Met496.
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- 2013
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30. Occurrence of the synthetic analgesic tramadol in an African medicinal plant.
- Author
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Boumendjel A, Sotoing Taïwe G, Ngo Bum E, Chabrol T, Beney C, Sinniger V, Haudecoeur R, Marcourt L, Challal S, Ferreira Queiroz E, Souard F, Le Borgne M, Lomberget T, Depaulis A, Lavaud C, Robins R, Wolfender JL, Bonaz B, and De Waard M
- Subjects
- Analgesics, Opioid isolation & purification, Phytochemicals, Plant Extracts chemistry, Plant Extracts isolation & purification, Plant Extracts pharmacology, Plants, Medicinal chemistry, Tramadol isolation & purification, Analgesics, Opioid chemistry, Pain drug therapy, Tramadol chemistry
- Published
- 2013
- Full Text
- View/download PDF
31. Development of thiophenic analogues of benzothiadiazine dioxides as new powerful potentiators of 2-amino-3-(3-hydroxy-5-methylisoxazol-4-yl)propionic acid (AMPA) receptors.
- Author
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Francotte P, Goffin E, Fraikin P, Graindorge E, Lestage P, Danober L, Challal S, Rogez N, Nosjean O, Caignard DH, Pirotte B, and de Tullio P
- Subjects
- Animals, Benzothiadiazines chemistry, Cells, Cultured, Cognition drug effects, Cyclic S-Oxides chemical synthesis, Cyclic S-Oxides chemistry, Cyclic S-Oxides pharmacology, Diazoxide chemistry, Drug Design, Excitatory Amino Acid Agonists chemical synthesis, Excitatory Amino Acid Agonists chemistry, Excitatory Postsynaptic Potentials drug effects, Female, Hippocampus drug effects, Hippocampus physiology, Long-Term Potentiation drug effects, Membrane Potentials drug effects, Mice, Models, Chemical, Molecular Structure, Norepinephrine metabolism, Oocytes drug effects, Oocytes metabolism, Rats, Receptors, AMPA metabolism, Thiadiazines chemical synthesis, Thiadiazines chemistry, Thiadiazines pharmacology, Thiophenes chemistry, Xenopus laevis, alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid pharmacology, Benzothiadiazines pharmacology, Diazoxide pharmacology, Excitatory Amino Acid Agonists pharmacology, Receptors, AMPA agonists
- Abstract
On the basis of the results obtained in previous series of AMPA potentiators belonging to 3,4-dihydro-2H-benzo- and 3,4-dihydro-2H-pyrido-1,2,4-thiadiazine 1,1-dioxides, the present work focuses on the design of original isosteric 3,4-dihydro-2H-thieno-1,2,4-thiadiazine 1,1-dioxides. Owing to the sulfur position, three series of compounds were developed and their activity as AMPA potentiators was characterized. In each of the developed series, potent compounds were discovered. After screening the selected active compounds on a safety in vivo test, 6-chloro-4-ethyl-3,4-dihydro-2H-thieno[2,3-e]-1,2,4-thiadiazine 1,1-dioxide (24) appeared as the most promising compound and was further evaluated. Its effects on long-term potentiation in vivo and on AMPA-mediated noradrenaline release were measured to predict its potential cognitive enhancing properties. Finally, an object recognition test performed in mice revealed that 24 was able to significantly enhance cognition, after oral administration, at doses as low as 0.3 mg/kg. This study validates the interest of the isosteric replacement of the benzene or pyridine nuclei by the thiophene nucleus in the ring-fused thiadiazine dioxides class of AMPA potentiators.
- Published
- 2013
- Full Text
- View/download PDF
32. Rheumatoid arthritis: from autoimmunity to synovitis and joint destruction.
- Author
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Boissier MC, Semerano L, Challal S, Saidenberg-Kermanac'h N, and Falgarone G
- Subjects
- Antirheumatic Agents pharmacology, Antirheumatic Agents therapeutic use, Arthritis, Rheumatoid complications, Arthritis, Rheumatoid drug therapy, Autoantibodies biosynthesis, Autoantibodies immunology, Autoimmunity drug effects, B-Lymphocytes drug effects, B-Lymphocytes immunology, B-Lymphocytes pathology, Cytokines antagonists & inhibitors, Cytokines immunology, Humans, Joints drug effects, Joints immunology, Lymphocyte Activation drug effects, Osteoclasts drug effects, Osteoclasts immunology, Rheumatoid Factor biosynthesis, Rheumatoid Factor immunology, Synovitis complications, Synovitis drug therapy, Th1 Cells drug effects, Th1 Cells immunology, Th1 Cells pathology, Th17 Cells drug effects, Th17 Cells immunology, Th17 Cells pathology, Arthritis, Rheumatoid immunology, Joints pathology, Synovitis immunology
- Abstract
Rheumatoid arthritis is an autoimmune disease characterized by the production of two known antibodies - rheumatoid factor and anti-citrullinated peptide antibody (ACPA) - against common autoantigens that are widely expressed within and outside the joints. The interactions between genes and environment are crucial in all stages of the disease, involving namely genes from major histocompatibility complex locus, and antigens such as tobacco or microbes (e.g. Porphyromonas gingivalis). T and B cells are activated as soon as the earliest phases of the disease, rheumatoid arthritis appearing as a Th1 and Th17 disease. Inflammatory cytokines have a considerable importance in the hierarchy of the processes involved in RA. The joint destruction seen in RA is caused not only by cytokine imbalances, but also by specific effects of the Wnt system and osteoprotegerin on osteoclasts and by matrix production dysregulation responsible for cartilage damage. Both innate and adaptative immunity demonstrated their respective cornerstone position in rheumatoid arthritis, since targeted treatments has been efficiently developed against TNF-α, IL-6 receptor, IL-1β, CD20 B cells and T-cell/Dendritic cell interactions., (Copyright © 2012 Elsevier Ltd. All rights reserved.)
- Published
- 2012
- Full Text
- View/download PDF
33. Zebrafish bioassay-guided microfractionation for the rapid in vivo identification of pharmacologically active natural products.
- Author
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Challal S, Bohni N, Buenafe OE, Esguerra CV, de Witte PA, Wolfender JL, and Crawford AD
- Subjects
- Animals, Biological Products pharmacology, Chromatography, High Pressure Liquid methods, Mass Spectrometry methods, Zebrafish, Biological Assay methods, Biological Products chemistry
- Abstract
The rapid acquisition of structural and bioactivity information on natural products (NPs) at the sub- milligram scale is key for performing efficient bioactivity-guided isolations. Zebrafish offer the possibility of rapid in vivo bioactivity analysis of small molecules at the microgram scale - an attractive feature when combined with high-resolution fractionation technologies and analytical methods such as UHPLC-TOF-MS and microflow NMR. Numerous biomedically relevant assays are now available in zebrafish, encompassing most indication areas. Zebrafish also provide the possibility to screen bioactive compounds for potential hepato-, cardio-, and neurotoxicities at a very early stage in the drug discovery process. Here we describe two strategies using zebrafish bioassays for the high-resolution in vivo bioactivity profiling of medicinal plants, using either a one-step or a two-step procedure for active compound isolation directly into 96-well plates. The analysis of the microfractions by microflow NMR in combination with UHPLC-TOF-MS of the extract enables the rapid dereplication of compounds and an estimation of their microgram quantities for zebrafish bioassays. Both the one-step and the two-step isolation procedures enable a rapid estimation of the bioactive potential of NPs directly from crude extracts. In summary, we present an in vivo , microgram-scale NP discovery platform combining zebrafish bioassays with microscale analytics to identify, isolate and evaluate pharmacologically active NPs.
- Published
- 2012
- Full Text
- View/download PDF
34. Modulatory effects of S 38232, a non alpha-7 containing nicotine acetylcholine receptor agonist on network activity in the mouse hippocampus.
- Author
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Lagostena L, Danober L, Challal S, Lestage P, Mocaër E, Trocmé-Thibierge C, and Cherubini E
- Subjects
- Animals, Cholinergic Agonists pharmacology, Dose-Response Relationship, Drug, Excitatory Postsynaptic Potentials drug effects, Excitatory Postsynaptic Potentials physiology, Female, Hippocampus physiology, Mice, Mice, Inbred C57BL, Mice, Knockout, Nerve Net physiology, Rats, Torpedo, Xenopus laevis, alpha7 Nicotinic Acetylcholine Receptor, Hippocampus drug effects, Nerve Net drug effects, Nicotinic Agonists pharmacology, Receptors, Nicotinic physiology
- Abstract
Extracellular field potentials (fEPSPs) and whole cell patch-clamp recordings were used to test the effect of S 38232, a newly developed potent non-alpha7 nicotinic acetylcholine receptors (nAChR) agonist, on synaptic transmission in hippocampal slices obtained from adult mice. S 38232 increased the amplitude of fEPSPs, evoked in stratum radiatum by Schaffer collateral stimulation. This effect was potentiated by picrotoxin, suggesting that S 38232 exerts at least in part its effect on GABAergic interneurons. The action of S 38232 was mediated by non-alpha7 containing nAChRs since it was prevented by DHbetaE (1muM) but not by alpha-BTX (100nM). A similar potentiating effect on fEPSPs was observed when nicotine (1muM) was applied to hippocampal slices obtained from alpha7 -/- mice in the presence of picrotoxin. The potentiating effect of S 38232 was probably presynaptic in origin since it was associated with a significant reduction in paired-pulse ratio. In addition, in patch clamp experiments, S 38232 enhanced the frequency (but not the amplitude) of spontaneous excitatory and inhibitory postsynaptic currents (sEPSCs, sIPSCs) recorded from CA1 principal cells. Moreover, it enhanced the frequency of miniature IPSCs but not EPSCs, suggesting that it was acting on nAChRs located on presynaptic/pre-terminal regions of GABAergic interneurons. The effect of S 38232 on GABAergic signaling was concentration-dependent with an EC(50) of 43muM. In conclusions, we present evidence that the new nicotine ligand S 38232, by selectively activating non-alpha7 nAChRs located on principal cells and GABAergic interneurons, influences network activity and information processing in the hippocampus., (Copyright 2009 Elsevier Ltd. All rights reserved.)
- Published
- 2010
- Full Text
- View/download PDF
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