35 research outputs found
Ătude in vitro de lâeffet antifalcĂ©miant des globules rouges et de lâactivitĂ© antioxydante dâextraits de la poudre de racines de Maytenus senegalensis Lam (Celestraceae)
La drĂ©panocytose est une hĂ©moglobinopathie largement rĂ©pandue chez les populations africaines noires. Actuellement, trĂšs peu de traitements conventionnels existent sur le marchĂ©, dâoĂč le recours Ă la mĂ©decine traditionnelle. Maytenus senegalensis est une plante prescrite par les tradipraticiens dans la prise en charge de la drĂ©panocytose. LâactivitĂ© antifalcĂ©miante des extraits de la poudre de racines de Maytenus senegalensis a Ă©tĂ© Ă©tudiĂ©e dans ce travail. AprĂšs obtention de lâextrait hexanique par extraction Ă lâaide dâun Soxhlet, le marc est macĂ©rĂ© dans de lâacĂ©tate dâĂ©thyle puis dans du mĂ©thanol pour donner les extraits correspondants. LâactivitĂ© des fractions a Ă©tĂ© Ă©valuĂ©e sur des drĂ©panocytes de type SS. Les activitĂ©s antifalcĂ©miantes les plus importantes ont Ă©tĂ© observĂ©es pour les fractions polaires du mĂ©thanol et de lâacĂ©tate dâĂ©thyle avec des taux dâinversion de la falciformation respectivement de 77% et de 65% Ă 10 mg/mL. Les activitĂ©s antioxydantes de M. senegalensis (CI50 = 0,195 ± 0,004 mg/mL) et de lâacide ascorbique (CI50 = 0,078 ± 0,002 mg/mL) ont Ă©tĂ© dĂ©terminĂ©es. Les pouvoirs antioxydants (PA) montrent que lâactivitĂ© antiradicalaire de lâacide ascorbique (PA = 12,85) est 2,5 fois meilleure que celle de M. senegalensis (PA = 5,14). Les rĂ©sultats de lâĂ©tude justifient lâutilisation traditionnelle des racines de Maytenus senegalensis dans la prise en charge de la drĂ©panocytose.Mots clĂ©s : HĂ©moglobine, drĂ©panocytose, Maytenus senegalensis, activitĂ© antifalcĂ©miante, stress oxydant, radicaux libres, activitĂ© antioxydante
Study by atomic force microscopy and fluorescence microscopy of the interaction of silica nanoparticles with supported lipid films
Cette thĂšse sâinscrit dans le cadre des Ă©tudes portant sur la toxicitĂ© des nanoparticules (NPs). Leurs propriĂ©tĂ©s physico-chimiques confĂšrent aux NPs la capacitĂ© de pĂ©nĂ©trer dans les cellules en traversant la membrane plasmique. La comprĂ©hension de lâinteraction NPs-membrane est donc cruciale. La structure complexe des membranes nous a imposĂ© dâĂ©tudier lâinteraction NPs-membrane Ă lâaide de films lipidiques plans (monocouches et bicouches) utilisĂ©s comme modĂšles membranaires simplifiĂ©s, dĂ©posĂ©s sur des surfaces nanostructurĂ©es par le dĂ©pĂŽt prĂ©alable de NPs de silice (4 Ă 100 nm de diamĂštre) ou transfĂ©rĂ©s Ă partir de monocouches Ă©talĂ©es sur une suspension de NPs. Deux mĂ©thodes complĂ©mentaires ont Ă©tĂ© utilisĂ©es, la microscopie de force atomique (AFM) et la microscopie de fluorescence. AprĂšs une premiĂšre phase dâoptimisation des protocoles expĂ©rimentaux (choix des lipides, conditions de prĂ©paration des surfaces nanostructurĂ©es et des films), lâAFM a dâabord rĂ©vĂ©lĂ© lâoxydation des films monocouches constituĂ©s de lipides insaturĂ©s, se traduisant par la formation de domaines surĂ©levĂ©s par rapport Ă la phase lipidique intacte. Dans le cas des films de lipides prĂ©sentant une transition de phase de type liquide expansĂ©/liquide condensĂ©, la prĂ©sence des NPs (le plus souvent sous forme dâagrĂ©gats) semble favoriser la transition vers la phase condensĂ©e, les NPs Ă©tant situĂ©s soit au coeur soit en lisiĂšre des domaines condensĂ©s.Dans le cas des bicouches, lâĂ©tude par AFM en milieu liquide montre des comportements tribologiques diffĂ©rents des agrĂ©gats de NPs, suggĂ©rant deux organisations possibles de la bicouche lipidique, recouvrant les NPs ou formant des pores autour dâelles.The subject of this thesis fits into the large field of the toxicity of nanoparticles (NPs). Thanks to their physico-chemical properties, NPs are able to enter cells through the plasma membrane. Understanding the NPs-membrane interaction is thus very important. Membranes being complex structures, we chose to study this interaction using planar lipid films (monolayers and bilayers) as simplified membrane models, either deposited on nanostructured surfaces prepared by the prior deposition of silica NPs or transferred from monolayers spread on a subphase containing NPs (4-100 nm in diameter). Two complementary methods were used, atomic force microscopy (AFM) and fluorescence microscopy.After a first part devoted to the optimization of the experimental procedure (choice of lipids, design of nanostructured surfaces and films), AFM first revealed the oxidation of transferred monolayers made of unsaturated lipids, leading to the formation of domains raised above the intact lipid phase. In the case of films made of lipids characterized by a liquid expanded/liquid condensed phase transition, the presence of NPs (usually organized in aggregates) seems to favor the transition to the condensed phase, NPs being either embedded in condensed domains or at their edges.The final phase of this work was devoted to the study of NPs / bilayer interaction by AFM in liquid medium. The study shows different tribological behavior of NPs aggregates, suggesting two possible organizations of the lipid bilayer, covering the NPs or forming holes around them
Etude par microscopie Ă force atomique et par microscopie de fluorescence de lâinteraction de nanoparticules de silice avec des films lipidiques plans
The subject of this thesis fits into the large field of the toxicity of nanoparticles (NPs). Thanks to their physico-chemical properties, NPs are able to enter cells through the plasma membrane. Understanding the NPs-membrane interaction is thus very important. Membranes being complex structures, we chose to study this interaction using planar lipid films (monolayers and bilayers) as simplified membrane models, either deposited on nanostructured surfaces prepared by the prior deposition of silica NPs or transferred from monolayers spread on a subphase containing NPs (4-100 nm in diameter). Two complementary methods were used, atomic force microscopy (AFM) and fluorescence microscopy.After a first part devoted to the optimization of the experimental procedure (choice of lipids, design of nanostructured surfaces and films), AFM first revealed the oxidation of transferred monolayers made of unsaturated lipids, leading to the formation of domains raised above the intact lipid phase. In the case of films made of lipids characterized by a liquid expanded/liquid condensed phase transition, the presence of NPs (usually organized in aggregates) seems to favor the transition to the condensed phase, NPs being either embedded in condensed domains or at their edges.The final phase of this work was devoted to the study of NPs / bilayer interaction by AFM in liquid medium. The study shows different tribological behavior of NPs aggregates, suggesting two possible organizations of the lipid bilayer, covering the NPs or forming holes around them.Cette thĂšse sâinscrit dans le cadre des Ă©tudes portant sur la toxicitĂ© des nanoparticules (NPs). Leurs propriĂ©tĂ©s physico-chimiques confĂšrent aux NPs la capacitĂ© de pĂ©nĂ©trer dans les cellules en traversant la membrane plasmique. La comprĂ©hension de lâinteraction NPs-membrane est donc cruciale. La structure complexe des membranes nous a imposĂ© dâĂ©tudier lâinteraction NPs-membrane Ă lâaide de films lipidiques plans (monocouches et bicouches) utilisĂ©s comme modĂšles membranaires simplifiĂ©s, dĂ©posĂ©s sur des surfaces nanostructurĂ©es par le dĂ©pĂŽt prĂ©alable de NPs de silice (4 Ă 100 nm de diamĂštre) ou transfĂ©rĂ©s Ă partir de monocouches Ă©talĂ©es sur une suspension de NPs. Deux mĂ©thodes complĂ©mentaires ont Ă©tĂ© utilisĂ©es, la microscopie de force atomique (AFM) et la microscopie de fluorescence. AprĂšs une premiĂšre phase dâoptimisation des protocoles expĂ©rimentaux (choix des lipides, conditions de prĂ©paration des surfaces nanostructurĂ©es et des films), lâAFM a dâabord rĂ©vĂ©lĂ© lâoxydation des films monocouches constituĂ©s de lipides insaturĂ©s, se traduisant par la formation de domaines surĂ©levĂ©s par rapport Ă la phase lipidique intacte. Dans le cas des films de lipides prĂ©sentant une transition de phase de type liquide expansĂ©/liquide condensĂ©, la prĂ©sence des NPs (le plus souvent sous forme dâagrĂ©gats) semble favoriser la transition vers la phase condensĂ©e, les NPs Ă©tant situĂ©s soit au coeur soit en lisiĂšre des domaines condensĂ©s.Dans le cas des bicouches, lâĂ©tude par AFM en milieu liquide montre des comportements tribologiques diffĂ©rents des agrĂ©gats de NPs, suggĂ©rant deux organisations possibles de la bicouche lipidique, recouvrant les NPs ou formant des pores autour dâelles
Study by atomic force microscopy and fluorescence microscopy of the interaction of silica nanoparticles with supported lipid films
Cette thĂšse sâinscrit dans le cadre des Ă©tudes portant sur la toxicitĂ© des nanoparticules (NPs). Leurs propriĂ©tĂ©s physico-chimiques confĂšrent aux NPs la capacitĂ© de pĂ©nĂ©trer dans les cellules en traversant la membrane plasmique. La comprĂ©hension de lâinteraction NPs-membrane est donc cruciale. La structure complexe des membranes nous a imposĂ© dâĂ©tudier lâinteraction NPs-membrane Ă lâaide de films lipidiques plans (monocouches et bicouches) utilisĂ©s comme modĂšles membranaires simplifiĂ©s, dĂ©posĂ©s sur des surfaces nanostructurĂ©es par le dĂ©pĂŽt prĂ©alable de NPs de silice (4 Ă 100 nm de diamĂštre) ou transfĂ©rĂ©s Ă partir de monocouches Ă©talĂ©es sur une suspension de NPs. Deux mĂ©thodes complĂ©mentaires ont Ă©tĂ© utilisĂ©es, la microscopie de force atomique (AFM) et la microscopie de fluorescence. AprĂšs une premiĂšre phase dâoptimisation des protocoles expĂ©rimentaux (choix des lipides, conditions de prĂ©paration des surfaces nanostructurĂ©es et des films), lâAFM a dâabord rĂ©vĂ©lĂ© lâoxydation des films monocouches constituĂ©s de lipides insaturĂ©s, se traduisant par la formation de domaines surĂ©levĂ©s par rapport Ă la phase lipidique intacte. Dans le cas des films de lipides prĂ©sentant une transition de phase de type liquide expansĂ©/liquide condensĂ©, la prĂ©sence des NPs (le plus souvent sous forme dâagrĂ©gats) semble favoriser la transition vers la phase condensĂ©e, les NPs Ă©tant situĂ©s soit au coeur soit en lisiĂšre des domaines condensĂ©s.Dans le cas des bicouches, lâĂ©tude par AFM en milieu liquide montre des comportements tribologiques diffĂ©rents des agrĂ©gats de NPs, suggĂ©rant deux organisations possibles de la bicouche lipidique, recouvrant les NPs ou formant des pores autour dâelles.The subject of this thesis fits into the large field of the toxicity of nanoparticles (NPs). Thanks to their physico-chemical properties, NPs are able to enter cells through the plasma membrane. Understanding the NPs-membrane interaction is thus very important. Membranes being complex structures, we chose to study this interaction using planar lipid films (monolayers and bilayers) as simplified membrane models, either deposited on nanostructured surfaces prepared by the prior deposition of silica NPs or transferred from monolayers spread on a subphase containing NPs (4-100 nm in diameter). Two complementary methods were used, atomic force microscopy (AFM) and fluorescence microscopy.After a first part devoted to the optimization of the experimental procedure (choice of lipids, design of nanostructured surfaces and films), AFM first revealed the oxidation of transferred monolayers made of unsaturated lipids, leading to the formation of domains raised above the intact lipid phase. In the case of films made of lipids characterized by a liquid expanded/liquid condensed phase transition, the presence of NPs (usually organized in aggregates) seems to favor the transition to the condensed phase, NPs being either embedded in condensed domains or at their edges.The final phase of this work was devoted to the study of NPs / bilayer interaction by AFM in liquid medium. The study shows different tribological behavior of NPs aggregates, suggesting two possible organizations of the lipid bilayer, covering the NPs or forming holes around them
Study by atomic force microscopy and fluorescence microscopy of the interaction of silica nanoparticles with supported lipid films
Cette thĂšse sâinscrit dans le cadre des Ă©tudes portant sur la toxicitĂ© des nanoparticules (NPs). Leurs propriĂ©tĂ©s physico-chimiques confĂšrent aux NPs la capacitĂ© de pĂ©nĂ©trer dans les cellules en traversant la membrane plasmique. La comprĂ©hension de lâinteraction NPs-membrane est donc cruciale. La structure complexe des membranes nous a imposĂ© dâĂ©tudier lâinteraction NPs-membrane Ă lâaide de films lipidiques plans (monocouches et bicouches) utilisĂ©s comme modĂšles membranaires simplifiĂ©s, dĂ©posĂ©s sur des surfaces nanostructurĂ©es par le dĂ©pĂŽt prĂ©alable de NPs de silice (4 Ă 100 nm de diamĂštre) ou transfĂ©rĂ©s Ă partir de monocouches Ă©talĂ©es sur une suspension de NPs. Deux mĂ©thodes complĂ©mentaires ont Ă©tĂ© utilisĂ©es, la microscopie de force atomique (AFM) et la microscopie de fluorescence. AprĂšs une premiĂšre phase dâoptimisation des protocoles expĂ©rimentaux (choix des lipides, conditions de prĂ©paration des surfaces nanostructurĂ©es et des films), lâAFM a dâabord rĂ©vĂ©lĂ© lâoxydation des films monocouches constituĂ©s de lipides insaturĂ©s, se traduisant par la formation de domaines surĂ©levĂ©s par rapport Ă la phase lipidique intacte. Dans le cas des films de lipides prĂ©sentant une transition de phase de type liquide expansĂ©/liquide condensĂ©, la prĂ©sence des NPs (le plus souvent sous forme dâagrĂ©gats) semble favoriser la transition vers la phase condensĂ©e, les NPs Ă©tant situĂ©s soit au coeur soit en lisiĂšre des domaines condensĂ©s.Dans le cas des bicouches, lâĂ©tude par AFM en milieu liquide montre des comportements tribologiques diffĂ©rents des agrĂ©gats de NPs, suggĂ©rant deux organisations possibles de la bicouche lipidique, recouvrant les NPs ou formant des pores autour dâelles.The subject of this thesis fits into the large field of the toxicity of nanoparticles (NPs). Thanks to their physico-chemical properties, NPs are able to enter cells through the plasma membrane. Understanding the NPs-membrane interaction is thus very important. Membranes being complex structures, we chose to study this interaction using planar lipid films (monolayers and bilayers) as simplified membrane models, either deposited on nanostructured surfaces prepared by the prior deposition of silica NPs or transferred from monolayers spread on a subphase containing NPs (4-100 nm in diameter). Two complementary methods were used, atomic force microscopy (AFM) and fluorescence microscopy.After a first part devoted to the optimization of the experimental procedure (choice of lipids, design of nanostructured surfaces and films), AFM first revealed the oxidation of transferred monolayers made of unsaturated lipids, leading to the formation of domains raised above the intact lipid phase. In the case of films made of lipids characterized by a liquid expanded/liquid condensed phase transition, the presence of NPs (usually organized in aggregates) seems to favor the transition to the condensed phase, NPs being either embedded in condensed domains or at their edges.The final phase of this work was devoted to the study of NPs / bilayer interaction by AFM in liquid medium. The study shows different tribological behavior of NPs aggregates, suggesting two possible organizations of the lipid bilayer, covering the NPs or forming holes around them
Study by atomic force microscopy and fluorescence microscopy of the interaction of silica nanoparticles with supported lipid films
Cette thĂšse sâinscrit dans le cadre des Ă©tudes portant sur la toxicitĂ© des nanoparticules (NPs). Leurs propriĂ©tĂ©s physico-chimiques confĂšrent aux NPs la capacitĂ© de pĂ©nĂ©trer dans les cellules en traversant la membrane plasmique. La comprĂ©hension de lâinteraction NPs-membrane est donc cruciale. La structure complexe des membranes nous a imposĂ© dâĂ©tudier lâinteraction NPs-membrane Ă lâaide de films lipidiques plans (monocouches et bicouches) utilisĂ©s comme modĂšles membranaires simplifiĂ©s, dĂ©posĂ©s sur des surfaces nanostructurĂ©es par le dĂ©pĂŽt prĂ©alable de NPs de silice (4 Ă 100 nm de diamĂštre) ou transfĂ©rĂ©s Ă partir de monocouches Ă©talĂ©es sur une suspension de NPs. Deux mĂ©thodes complĂ©mentaires ont Ă©tĂ© utilisĂ©es, la microscopie de force atomique (AFM) et la microscopie de fluorescence. AprĂšs une premiĂšre phase dâoptimisation des protocoles expĂ©rimentaux (choix des lipides, conditions de prĂ©paration des surfaces nanostructurĂ©es et des films), lâAFM a dâabord rĂ©vĂ©lĂ© lâoxydation des films monocouches constituĂ©s de lipides insaturĂ©s, se traduisant par la formation de domaines surĂ©levĂ©s par rapport Ă la phase lipidique intacte. Dans le cas des films de lipides prĂ©sentant une transition de phase de type liquide expansĂ©/liquide condensĂ©, la prĂ©sence des NPs (le plus souvent sous forme dâagrĂ©gats) semble favoriser la transition vers la phase condensĂ©e, les NPs Ă©tant situĂ©s soit au coeur soit en lisiĂšre des domaines condensĂ©s.Dans le cas des bicouches, lâĂ©tude par AFM en milieu liquide montre des comportements tribologiques diffĂ©rents des agrĂ©gats de NPs, suggĂ©rant deux organisations possibles de la bicouche lipidique, recouvrant les NPs ou formant des pores autour dâelles.The subject of this thesis fits into the large field of the toxicity of nanoparticles (NPs). Thanks to their physico-chemical properties, NPs are able to enter cells through the plasma membrane. Understanding the NPs-membrane interaction is thus very important. Membranes being complex structures, we chose to study this interaction using planar lipid films (monolayers and bilayers) as simplified membrane models, either deposited on nanostructured surfaces prepared by the prior deposition of silica NPs or transferred from monolayers spread on a subphase containing NPs (4-100 nm in diameter). Two complementary methods were used, atomic force microscopy (AFM) and fluorescence microscopy.After a first part devoted to the optimization of the experimental procedure (choice of lipids, design of nanostructured surfaces and films), AFM first revealed the oxidation of transferred monolayers made of unsaturated lipids, leading to the formation of domains raised above the intact lipid phase. In the case of films made of lipids characterized by a liquid expanded/liquid condensed phase transition, the presence of NPs (usually organized in aggregates) seems to favor the transition to the condensed phase, NPs being either embedded in condensed domains or at their edges.The final phase of this work was devoted to the study of NPs / bilayer interaction by AFM in liquid medium. The study shows different tribological behavior of NPs aggregates, suggesting two possible organizations of the lipid bilayer, covering the NPs or forming holes around them
Weber's syndrome revealing a Percheron artery infarction: A case report
Key Clinical Message Weber's syndrome revealing a Percheron artery infarction is a rare clinical occurrence. Its diagnosis requires careful clinical examination and brain MRI, which is the gold standard for diagnosis. If this is not available, combined cerebral CT scan with a CT angiography of supraâaortic arteries may be useful for the diagnosis. Abstract Percheron's artery (PA) occlusion is an uncommon type of stroke involving paramedian thalamus and/or midbrain infarction. It accounts for 4%â18% of all thalamic infarcts and 0.1%â2% of all strokes. Its clinical manifestations are variable and its mode of presentation as Weber's syndrome is exceptional due to the unusual clinical presentation
Oxidation of Langmuir-Blodgett films of monounsaturated lipids studied by atomic force microscopy
In this work, we studied the stability in time of Langmuir-Blodgett films of POPC and OPPC, two unsaturated phospholipids with similar chains, differing by the relative position of these chains on the glycerol backbone. These films, transferred from the air-water interface onto freshly cleaved mica, were characterised by Atomic Force Microscopy (AFM) giving information on their topography at a lateral and perpendicular resolution in the nm range. AFM images (obtained in tapping mode) of freshly transferred films are homogenous, in agreement with the fact that these two lipids are in a liquid-expanded phase under our experimental conditions. After two days, small domains are observed, higher than the surrounding phase of about 0.8 nm in both types of samples. These domains are not observed if the samples are kept under vacuum, or if LB films are made of saturated phospholipids, suggesting that they are due to the local oxidation of POPC or OPPC, the oxidation being slightly more pronounced in the last case. Their dispersion in LB films suggests that oxidation occurs at different points at the same time, likely in areas presenting a loose packing or a defect. The local increase of thickness could be due to the reversal of the oxidised chain, raising the oxidised lipid above the surrounding phase
Légumes-feuilles traditionnels et fruits forestiers sauvages au Sénégal : état des connaissances et perspectives de valorisation
Synthesis, characterization and crystal structure of 1-(2-benzamidophenyl)-3-benzoylthiourea Hemihydrate
The dissymmetric compound C21H17N3O2S.0.5H2O obtained by a reaction of 1,2-diaminobenzene, potassium thiocyanate and benzoyl chloride in 1/1/2 ratio is characterized by elemental analyses, IR, and NMR spectroscopies. The structure is elucidated by X-ray diffraction technic. The compound crystallizes in the monoclinic system with a space group of I2. The asymmetric unit contains one hemihydrate organic molecule. The title thiourea derivative, features an almost planar, C2N2S (S1/N1/N2/C7/C8) moiety, with a maximum deviation from the least-squares plane of 0.0422 (3) Ă
. This moiety is flanked by a disubstituted and a monosubstituted phenyl rings. The dihedral angles between the thiourea and the monosubstituted phenyl ring and the thiourea and the central disubstituted phenyl ring are respectively 10.418 (7)° and 60.292 (2)°, indicating twist in the molecule. On the other arm, a phenyl ring supported by an amide function, which is linked to the central ring through the nitrogen atom, is present. The dihedral angle between this phenyl group and the central disubstituted phenyl is 76.862 (7)° showing that their mean planes are not coplanar. Intramolecular S(thiono)âHâŠO(water) hydrogen bonds which close in S(6) and S(7) rings consolidate the conformation. Intermolecular N(amido)âHâŠO(carbonyl) which form layers parallel to the ac plane stabilized the structure