Soil aquifer treatment was simulated in 1 m laboratory soil columns containing silica sand under saturated and unsaturated soil conditions to examine the effect of travel length through the unsaturated zone on the removal of wastewater organic matter, the effect of soil type on dissolved organic carbon removal and also the type of microorganisms involved in the removal process. Dissolved organic carbon removal and nitrification did enhance when the wastewater travelled a longer length through the unsaturated zone. A similar consortium of microorganisms was found to exist in both saturated and unsaturated columns. Microbial concentrations however were lowest in the soil column containing silt and clay in addition to silica sand. The presence of silt and clay was detrimental to DOC removal efficiency under saturated soil conditions due to their negative effect on the hydraulic performance of the soil column and microbial growth.

No description available.

Phospholipids are dominant components of bacterial cell membranes, where they create double layers. Bacteria differ in their phospholipid composition determination of which can help in identification of important groups of microorganisms. Phospholipid composition of bacteria is influenced by many environmental factors, therefore its variation can be observed within one bacterial stem also. Because of its simplicity, thin layer chromatography is usually applied to identification and determination of bacterial phospholipids. Disadvantage of this method are the high demands of time, carefulness and skills of the analytical personnel. The increasing interest in the phospholipid double-layer promotes the detailed investigation of their fatty acid composition because the more detailed analyses allows for more information yield about bacteria. Gas chromatography hyphenated with mass spectrometry seems to be the best choice for these purposes. Fatty acid identity and total fatty acid content in phospholipid molecules could be determined by this method. Additionally, number, position and isomerism of double bonds and presence of other functional groups on hydrocarbon chain could be determined. Whereas a suitable and...

INTRODUÇÃO: Os transtornos mentais psicóticos são condições frequentes na população geral e estão associados a grande morbidade e disfuncionalidade. Apesar disso, as bases fisiopatológicas destes transtornos ainda estão em investigação. Estudos neuropatológicos post-mortem e de neuroimagem in vivo sugerem haver comprometimento da microestrutura de substância branca (SB) cerebral nestas condições clínicas, associado a alterações da conectividade cerebral. No entanto, nenhuma investigação prévia de neuroimagem avaliou especificamente se tais anormalidades microestruturais podem ser dependentes do estado clínico do paciente, i.e., se tais alterações podem variar de acordo com a fase da doença. Outra linha de investigação biológica em psicoses aponta para alterações na atividade da fosfolipase A2 (PLA2), uma enzima essencial a diversas funções na homeostase cerebral, incluindo manutenção de membrana celular, mielinização e atividade inflamatória. Estudos prévios sugerem haver relação entre alterações na atividade desta enzima e as fases da esquizofrenia. Entretanto, não há estudos translacionais que tenham avaliado como tais alterações se relacionam com anormalidades microestruturais de SB em pacientes psicóticos. OBJETIVOS: Investigar a hipótese de que alterações de microestrutura de SB presentes em pacientes em fase aguda do primeiro episódio psicótico (PEP) sejam potencialmente reversíveis após estabilização clínica; investigar também possíveis alterações estado-dependentes da atividade de PLA2 no PEP; e examinar interações entre manifestações clínicas, microestrutura de SB cerebral e atividade de PLA2 na fisiopatologia do PEP. METODOLOGIA: Pacientes em PEP não afetivo foram avaliados em dois períodos no tempo: durante a fase aguda da doença (T0); após remissão estável de sintomas (T1). Um grupo controle de voluntários saudáveis (CS) também foi avaliado longitudinalmente. Para investigar alterações de microestrutura de SB estado-dependentes, análises voxel-a-voxel de mapas cerebrais de índices de anisotropia (fractional anisotropy, FA) e difusividade (trace, TR) foram conduzidas, assim como o cálculo de correlações entre tais índices de DTI, variáveis clínicas e atividade de PLA2. A atividade dos três principais subgrupos de PLA2 em plaquetas foi estimada através de um método radioenzimático. RESULTADOS: 25 pacientes PEP e 51 CS foram avaliados em T0, com coleta de dados clínico-demográficos, ressonância magnética (RM) e amostra de sangue. Destes, 21 PEP e 36 CS realizaram a segunda aquisição de RM. No baseline (T0), os pacientes PEP apresentaram redução difusa de FA (p < 0,05, FDR), afetando principalmente SB fronto-límbica e fascículos associativos, projetivos e comissurais. As análises longitudinais demonstraram que a remissão clínica se associou a aumentos de FA em tratos de SB acometidos em T0 (p < 0,001, não corrigido), além de robustas correlações inversas entre aumentos de FA e redução sintomas ao longo do tempo (p < 0,05, FDR). As análises de PLA2 não demostraram efeitos estado-dependentes ou correlações consistentes com os índices de DTI. CONCLUSÃO: Alterações da microestrutura de SB afetando tratos cerebrais essenciais para a integração de informação perceptual, cognição e emoções são detectáveis logo após o início do PEP e podem ser parcialmente revertidas em relação direta com a remissão de sintomas psicóticos agudos. Nossos achados reforçam a visão de que anormalidades de SB de tratos cerebrais são um componente neurobiológico central nos transtornos psicóticos agudos, e que a recuperação de tal patologia de SB pode levar à melhora clínica. Por outro lado, a atividade de PLA2 não parece ter associação direta com o estado de doença ou moderar as alterações microestruturais dinâmicas de SB aqui observadas. Estudos com amostras maiores e com um maior número de avaliações ao longo do tempo são necessários para confirmar e ampliar os resultados aqui apresentados / INTRODUCTION: Psychotic disorders are frequent conditions in the general population and are associated to severe morbidity and functional impairment. Notwithstanding, the pathophysiological basis of such disorders is still under investigation. Post-mortem neuropathologic investigations and in vivo neuroimaging studies have pointed to the occurrence of abnormalities in the microstructure of brain white matter (WM) in such clinical conditions, which are associated to changes in brain connectivity. However, no previous neuroimaging investigation has specifically examined whether such microstructural abnormalities would be state-dependent, i.e., whether such changes could relate to the illness phase. Another field of biological investigation in psychosis points to changes in the activity of phospholipase A2 enzyme (PLA2), which is essential to several functions implicated in brain homeostasis, such as the maintenance of cellular membrane, myelination and inflammatory activity. Previous studies suggest the existence of a relationship between changes on PLA2 activity and schizophrenia phase. Nonetheless, no translational study to date has examined the potential interplay between PLA2 activity and WM microstructural abnormalities in psychotic patients. OBJECTIVES: To investigate the hypothesis that WM microstructural changes observed in patients during the acute first-episode psychosis (FEP) are potentially reversible following clinical remission; to investigate possible state-dependent changes in PLA2 activity in FEP; and to examine interactions between clinical manifestations, brain WM microstructure and PLA2 activity in the pathophysiology of FEP. METODOLOGY: Patients with non-affective FEP were evaluated in two time points: during the acute phase (T0) and following sustained remission (T1). A control group of healthy volunteers (HC) was also longitudinally studied. In order to investigate state-dependent WM microstructure changes, voxelwise analyses of brain maps of anisotropy (fractional anisotropy, FA) and diffusivity (trace, TR) indexes were conducted, as well as correlations between such DTI metrics, clinical variables and PLA2 activity. The activity of the three main PLA2 subgroups was assessed in platelets using a radioenzymatic method. RESULTS: 25 FEP and 51 HC were evaluated at T0 (clinical and demographic data, MRI scanning, and blood collection). Out of these, 21 FEP and 36 HC also underwent a second MRI acquisition. At baseline (T0), FEP patients presented widespread reduction of FA (p < 0.05, FDR), affecting mainly fronto-limbic WM and associative, projective and commissural fasciculi. Longitudinal analyses showed that clinical remission was associated with FA increase in WM tracts that were affected at T0 (p < 0.001, uncorrected), besides robust inverse correlations between FA increase and symptoms reduction over time (p < 0.05, FDR). PLA2 analyses failed to show state-dependent effects or consistent correlations to DTI indexes. CONCLUSION: WM changes affecting brain tracts critical to the integration of perceptual information, cognition and emotions are detectable soon after the onset of FEP and may partially reverse in direct relation to the remission of acute psychotic symptoms. Our findings reinforce the view that WM abnormalities are a key neurobiological feature of acute psychotic disorders, and that recovery from such WM pathology can lead to amelioration of symptoms. In the other hand, it seems that PLA2 activity has no direct relationship to the disease state or modulatory effects on the dynamic WM changes observed herein. Studies with larger samples and with more time points evaluations are necessary to confirm and expand the findings reported herein

INTRODUÇÃO: Os transtornos mentais psicóticos são condições frequentes na população geral e estão associados a grande morbidade e disfuncionalidade. Apesar disso, as bases fisiopatológicas destes transtornos ainda estão em investigação. Estudos neuropatológicos post-mortem e de neuroimagem in vivo sugerem haver comprometimento da microestrutura de substância branca (SB) cerebral nestas condições clínicas, associado a alterações da conectividade cerebral. No entanto, nenhuma investigação prévia de neuroimagem avaliou especificamente se tais anormalidades microestruturais podem ser dependentes do estado clínico do paciente, i.e., se tais alterações podem variar de acordo com a fase da doença. Outra linha de investigação biológica em psicoses aponta para alterações na atividade da fosfolipase A2 (PLA2), uma enzima essencial a diversas funções na homeostase cerebral, incluindo manutenção de membrana celular, mielinização e atividade inflamatória. Estudos prévios sugerem haver relação entre alterações na atividade desta enzima e as fases da esquizofrenia. Entretanto, não há estudos translacionais que tenham avaliado como tais alterações se relacionam com anormalidades microestruturais de SB em pacientes psicóticos. OBJETIVOS: Investigar a hipótese de que alterações de microestrutura de SB presentes em pacientes em fase aguda do primeiro episódio psicótico (PEP) sejam potencialmente reversíveis após estabilização clínica; investigar também possíveis alterações estado-dependentes da atividade de PLA2 no PEP; e examinar interações entre manifestações clínicas, microestrutura de SB cerebral e atividade de PLA2 na fisiopatologia do PEP. METODOLOGIA: Pacientes em PEP não afetivo foram avaliados em dois períodos no tempo: durante a fase aguda da doença (T0); após remissão estável de sintomas (T1). Um grupo controle de voluntários saudáveis (CS) também foi avaliado longitudinalmente. Para investigar alterações de microestrutura de SB estado-dependentes, análises voxel-a-voxel de mapas cerebrais de índices de anisotropia (fractional anisotropy, FA) e difusividade (trace, TR) foram conduzidas, assim como o cálculo de correlações entre tais índices de DTI, variáveis clínicas e atividade de PLA2. A atividade dos três principais subgrupos de PLA2 em plaquetas foi estimada através de um método radioenzimático. RESULTADOS: 25 pacientes PEP e 51 CS foram avaliados em T0, com coleta de dados clínico-demográficos, ressonância magnética (RM) e amostra de sangue. Destes, 21 PEP e 36 CS realizaram a segunda aquisição de RM. No baseline (T0), os pacientes PEP apresentaram redução difusa de FA (p < 0,05, FDR), afetando principalmente SB fronto-límbica e fascículos associativos, projetivos e comissurais. As análises longitudinais demonstraram que a remissão clínica se associou a aumentos de FA em tratos de SB acometidos em T0 (p < 0,001, não corrigido), além de robustas correlações inversas entre aumentos de FA e redução sintomas ao longo do tempo (p < 0,05, FDR). As análises de PLA2 não demostraram efeitos estado-dependentes ou correlações consistentes com os índices de DTI. CONCLUSÃO: Alterações da microestrutura de SB afetando tratos cerebrais essenciais para a integração de informação perceptual, cognição e emoções são detectáveis logo após o início do PEP e podem ser parcialmente revertidas em relação direta com a remissão de sintomas psicóticos agudos. Nossos achados reforçam a visão de que anormalidades de SB de tratos cerebrais são um componente neurobiológico central nos transtornos psicóticos agudos, e que a recuperação de tal patologia de SB pode levar à melhora clínica. Por outro lado, a atividade de PLA2 não parece ter associação direta com o estado de doença ou moderar as alterações microestruturais dinâmicas de SB aqui observadas. Estudos com amostras maiores e com um maior número de avaliações ao longo do tempo são necessários para confirmar e ampliar os resultados aqui apresentados / INTRODUCTION: Psychotic disorders are frequent conditions in the general population and are associated to severe morbidity and functional impairment. Notwithstanding, the pathophysiological basis of such disorders is still under investigation. Post-mortem neuropathologic investigations and in vivo neuroimaging studies have pointed to the occurrence of abnormalities in the microstructure of brain white matter (WM) in such clinical conditions, which are associated to changes in brain connectivity. However, no previous neuroimaging investigation has specifically examined whether such microstructural abnormalities would be state-dependent, i.e., whether such changes could relate to the illness phase. Another field of biological investigation in psychosis points to changes in the activity of phospholipase A2 enzyme (PLA2), which is essential to several functions implicated in brain homeostasis, such as the maintenance of cellular membrane, myelination and inflammatory activity. Previous studies suggest the existence of a relationship between changes on PLA2 activity and schizophrenia phase. Nonetheless, no translational study to date has examined the potential interplay between PLA2 activity and WM microstructural abnormalities in psychotic patients. OBJECTIVES: To investigate the hypothesis that WM microstructural changes observed in patients during the acute first-episode psychosis (FEP) are potentially reversible following clinical remission; to investigate possible state-dependent changes in PLA2 activity in FEP; and to examine interactions between clinical manifestations, brain WM microstructure and PLA2 activity in the pathophysiology of FEP. METODOLOGY: Patients with non-affective FEP were evaluated in two time points: during the acute phase (T0) and following sustained remission (T1). A control group of healthy volunteers (HC) was also longitudinally studied. In order to investigate state-dependent WM microstructure changes, voxelwise analyses of brain maps of anisotropy (fractional anisotropy, FA) and diffusivity (trace, TR) indexes were conducted, as well as correlations between such DTI metrics, clinical variables and PLA2 activity. The activity of the three main PLA2 subgroups was assessed in platelets using a radioenzymatic method. RESULTS: 25 FEP and 51 HC were evaluated at T0 (clinical and demographic data, MRI scanning, and blood collection). Out of these, 21 FEP and 36 HC also underwent a second MRI acquisition. At baseline (T0), FEP patients presented widespread reduction of FA (p < 0.05, FDR), affecting mainly fronto-limbic WM and associative, projective and commissural fasciculi. Longitudinal analyses showed that clinical remission was associated with FA increase in WM tracts that were affected at T0 (p < 0.001, uncorrected), besides robust inverse correlations between FA increase and symptoms reduction over time (p < 0.05, FDR). PLA2 analyses failed to show state-dependent effects or consistent correlations to DTI indexes. CONCLUSION: WM changes affecting brain tracts critical to the integration of perceptual information, cognition and emotions are detectable soon after the onset of FEP and may partially reverse in direct relation to the remission of acute psychotic symptoms. Our findings reinforce the view that WM abnormalities are a key neurobiological feature of acute psychotic disorders, and that recovery from such WM pathology can lead to amelioration of symptoms. In the other hand, it seems that PLA2 activity has no direct relationship to the disease state or modulatory effects on the dynamic WM changes observed herein. Studies with larger samples and with more time points evaluations are necessary to confirm and expand the findings reported herein

The gastrointestinal tract (GIT) regulates nutrient uptake, secretes hormones and has a crucial gut flora and enteric nervous system. Of relevance for these functions are the G protein-coupled receptors (GPCRs) and the solute carriers (SLCs). The Adhesion GPCR subfamily is known to mediate neural development and immune system functioning, whereas SLCs transport e.g. amino acids, fatty acids (FAs) and drugs over membranes. We aimed to comprehensively characterize Adhesion GPCR and SLC gene expression along the rat GIT. Using qPCR we measured expression of 78 SLCs as well as all 30 Adhesion GPCRs in a twelve-segment GIT model. 21 of the Adhesion GPCRs had a widespread (≥5 segments) or ubiquitous (≥11 segments) expression. Restricted expression patterns were characteristic for most group VII members. Of the SLCs, we found the majority (56 %) of these transcripts to be expressed in all GIT segments. SLCs were predominantly found in the absorption-responsible gut regions. Both Adhesion GPCRs and SLCs were widely expressed in the rat GIT, suggesting important roles. The distribution of Adhesion GPCRs defines them as a potential pharmacological target. FAs constitute an important energy source and have been implicated in the worldwide obesity increase. FAs and their ratios – indices for activities of e.g. the desaturase enzymes SCD-1 (SCD-16, 16:1n-7/16:0), D6D (18:3n-6/18:2n-6) and D5D (20:4n-6/20:3n-6) – have been associated with e.g. overall mortality and BMI. We examined whether differences in FAs and their indices in five lipid fractions contributed to obesity susceptibility in rats fed a high fat diet (HFD), and the associations of desaturase indices between lipid fractions in animals on different diets. We found that on a HFD, obesity-prone (OP) rats had a higher SCD-16 index and a lower linoleic acid (LA) proportions in subcutaneous adipose tissue (SAT) than obesity-resistant rats. Desaturase indices were significantly correlated between many of the lipid fractions. The higher SCD-16 may indicate higher SCD-1 activity in SAT in OP rats, and combined with lower LA proportions may provide novel insights into HFD-induced obesity. The associations between desaturase indices show that plasma measurements can serve as proxies for some lipid fractions, but the correlations seem to be affected by diet and weight gain.

Afin d’améliorer l’efficacité des traitements des pathologies articulaires, en tenant compte de leur complexité et de leur ampleur, des études récentes ont mis en évidence le rôle des assemblages lipidiques associés à la structure discontinue du fluide synovial dans le contrôle du fonctionnement tribologique articulaire. Ceci à conduit à la mise au point d’un modèle tribologique ex vivo (thèse AM Sfarghiu, 2006), proposant un « motif élémentaire » de la biolubrification articulaire, constitué de l’empilement d’interfaces phospholipidiques et de couches aqueuses. En utilisant ce modèle, l’objectif de ce travail a été d’étudier l’évolution des interfaces phospholipidiques du fluide synovial en présence de pathologies. Pour ce faire, une méthodologie nano-bio-tribologique alliant des analyses biochimiques, physicochimiques, nano-mécaniques et tribologiques a été utilisée. Les résultats de ces analyses montrent : l’influence de la faible rugosité des surfaces frottantes caractérisant les stades précoces des pathologies et celle des propriétés des interfaces phospholipidiques (liées à la variation de leur composition) sur la résistance mécanique, l’évolution au cours du frottement et la dégradation in situ des assemblages lipidiques des fluides synoviaux pathologiques. Le comportement des assemblages lipidiques est accentué par l’action des enzymes associées aux pathologies. Par conséquent, le fonctionnement articulaire dépend de la résistance mécanique des interfaces phospholipidiques et pour obtenir des coefficients de frottement très bas, l’accommodation de vitesse doit s’effectuer au niveau des couches d’hydratation qui entourent les ions présents dans la couche aqueuse. Ces résultats permettront de comprendre à court terme l’évolution des interfaces phospholipidiques dans les pathologies articulaires et, à plus long terme le bon enchaînement cause/conséquence responsable d’une pathologie articulaire afin de développer des traitements plus efficaces, ciblés et non prothétiques. / In order to improve the effectiveness of joint diseases’ treatments, given their complexity and magnitude, recent studies have highlighted the role of lipid assemblies associated with the discontinuous structure of the synovial fluid (SF) in the tribological performance of joint operation. Thus, an ex vivo tribological model (AM Sfarghiu, PhD thesis, 2006) providing a "basic pattern" for joint biolubrification was developed. It consists of the stack of phospholipidic interfaces and aqueous layers. Using this model, the objective of this work was to study the evolution of phospholipidic interfaces of SF within pathological state. Therefore, a nano-bio-tribological methodology combining biochemical, physicochemical, nano-mechanical and tribological analysis was used. The results of these analyses show: the influence of even small rubbing surfaces’ roughness characteristics of early stage illness and that of phospholipidic interfaces’ properties (related to their composition change) on the mechanical strength, changes in friction and in situ degradation of lipidic assemblies of pathological SF. The tribological operation is highlighted by enzymes’ associated with diseases. Thus, joint operation depends on the mechanical strength of phospholipidic interfaces and to obtain very low friction coefficients, velocity accommodation must be done at the level of hydration layers surrounding ions in the aqueous solution. These results would therefore allow better understanding of the evolution of phospholipidic interfaces in joint diseases and of the proper cause/consequence sequence responsible for a joint disease in order to develop more effective, targeted and non prosthetic treatments.

Des substances toxiques générées par les activités portuaires, urbaines et industrielles sont déversées à certains niveaux du milieu marin côtier marocain. Les mollusques peuvent concentrer les polluants et avoir des effets néfastes sur la santé humaine par l’intermédiaire de la chaîne alimentaire. Malgré le renforcement des mesures de sécurité alimentaire, l’implication de la pollution chimique des aliments dans les troubles métaboliques n’est pas à exclure. Pour prédire l’impact des polluants sur l’écosystème aquatique et sur la santé humaine, le développement d’outils de biosurveillance est nécessaire.Nous avons quantifié les métaux lourds (Cd, Cr et Pb) chez les moules (Mytilus galloprovincialis) issues de la côte atlantique marocaine (site industriel Jorf Lasfar (JL) et site touristique d’Oualidia (OL)) en raison de la proximité d’une plateforme d’extraction de phosphate puis caractérisé leurs profils lipidiques (acides gras, cholestérol, oxystérols, phytostérols et phospholipides). Les extraits lipidiques totaux de moules ont été testés in vivo sur des rats pour déterminer leurs effets sur les paramètres biochimiques plasmatiques et in vitro sur une lignée de cellules β pancréatiques murine (MIN-6) en conditions normo et hyperglycémique. Les effets des extraits de moules JL et OL ont été comparés par rapport à ceux de moules d’origine espagnole (ES) destinées à la consommation en France.Les métaux lourds dans les moules JL dépassent les normes internationales. Les concentrations métalliques dans tous les extraits lipidiques sont à l’état de trace. Les moules JL et OL sont moins riches en acides gras insaturés, plus riches en oxystérols et en phospholipides par rapport aux moules ES, suggérant un stress environnemental. Les extraits lipidiques des moules JL et OL administrés à des rats, ont provoqué une perturbation des paramètres plasmatiques, notamment des taux de glucose, créatinine, triglycérides et transaminases avec une augmentation de cholestérol-HDL. In vitro seuls les extraits lipidiques JL et OL induisent la mort des cellules MIN-6 par un processus non apoptotique. Ce processus est associé à une dépolarisation mitochondriale, une déstabilisation lysosomale et une augmentation de la perméabilité de la membrane cytoplasmique, paramètres mesurés par cytométrie en flux dans une démarche cytomique. Ils provoquent aussi une surproduction de H2O2, une augmentation d’activité catalase, une diminution du glutathion réduit, une peroxydation lipidique et une forte stimulation de la sécrétion d’insuline avec un effet plus marqués en présence des extraits lipidiques JL.Globalement, les lipides de moules JL induisent des effets néfastes in vivo et in vitro par rapport à ceux provenant de OL et ES. Une étude épidémiologique à large échelle dans le contexte des maladies métaboliques pourrait être pertinente chez les populations consommatrices de ces moules. / Toxic substances generated by various human activities are spilled on different area of the Moroccan coast. Shellfishes can concentrate pollutants and have some adverse effects on human health through the food chain. Despite the strengthening of food safety rules, the involvement of chemical pollution of food on metabolic disorders is not known. To predict the impact of pollutants on the aquatic ecosystem and human health, the development of appropriate biomonitoring tools is required.We quantified heavy metals (Cd, Cr and Pb) in mussels (Mytilus galloprovincialis) from two sites of Moroccan Atlantic coast (industrial site Jorf Lasfar (JL) and touristic site Oualidia (OL)) due to the proximity of a phosphate extraction platform, and further characterized their lipid profiles (fatty acids, cholesterol, oxysterols, phospholipids and phytosterols). Total lipid extracts of mussels were tested in vivo in rats to determine their effects on biochemical plasmatic parameters and in vitro on a β pancreatic murine cell line (MIN-6) in normo-and hyperglycemic conditions. The effects of JL and OL mussel extracts were compared to mussels from Spain (ES) used for human consumption in France. Heavy metals in JL mussels exceed international standard level. Metal concentrations in all lipid extracts are present in small quantity. JL and OL mussels are less enriched in unsaturated fatty acids, oxysterols and contain higher levels of phospholipids than ES mussels, suggesting an environmental stress. The lipid extracts of JL and OL mussels administered to rats induce a disruption of plasmatic parameters (glucose, creatinine, transaminases and triglycerides) with an increase of HDL-cholesterol. In vitro, only JL and OL lipid extracts induce MIN-6 cell death by a non-apoptotic process. This process is associated with mitochondrial depolarization, lysosomal destabilization and an increase of the cytoplasmic membrane permeability, parameters measured by flow cytométrie in a cytomic context. They also induce an overproduction of H2O2, an increase of catalase activity, a decrease of reduced glutathion, lipid peroxidation and a strong stimulation of insulin secretion with a more marked effect in presence of JL lipid extracts.Overall, JL mussel lipids induce various side effects in vivo and in vitro, which are more pronounced that those observed with OL and ES. A large-scale epidemiological study could be of interest to confirm the potential side effects of these mussels to favor metabolic disorders.

In the first part of the thesis, the molecular structure and electronic properties of phospholipids at the single molecule level and also for a monolayer structure are investigated via ab initio calculations under different degrees of hydration. The focus of the study is on phosphatidylcholines, in particular dipalmitoylphosphatidylcholine (DPPC), which are the most abundant phospholipids in biological membranes. Upon hydration, the phospholipid shape into a sickle-like structure. The hydration dramatically alters the surface potential, dipole and quadrupole moments of the lipids, and probably guides the interactions of the lipids with other molecules and the communication between cells. The vibrational spectrum of DPPC and DPPC-water complexes are completely assigned and it is shown that water hydrating the lipid head groups enables efficient energy transfer across membrane leaflets on sub-picosecond time scales. Moreover, the vibrational modes and lifetimes of pure and hydrated DPPC lipids, at human body temperature, are estimated by performing ab initio molecular dynamics simulations. The vibrational modes of the water molecules close to the head group of DPPC are active in the frequency range between 0.5 - 55 THz, with a peak at 2.80 THz in the energy spectrum. The computed lifetimes for the high-frequency modes agree well with recent data measured at room temperature, where high-order phonon scattering is not negligible. The structure and auto-ionization of water at the water-phospholipid interface are investigated by ab initio molecular dynamics and ab initio Monte Carlo simulations using local density approximation and generalized gradient approximation for the exchange-correlation energy functional. Depending on the lipid head group, strongly enhanced ionization is observed, leading to dissociation of several water molecules into H+ and OH- per lipid. The results can shed light on the phenomena of the high proton conductivity along membranes that has been reported experimentally. In the second part of the thesis, Monte Carlo simulations of the lipid bilayer, on the basis of a coarse grained model, are performed to gain insight into the mechanical properties of planar lipid bilayers. By using a rescaling method, the Poisson's ratio is calculated for different phases. Additional information on the bending rigidity, determined from height fluctuations on the basis of the Helfrich Hamiltonian, allows for calculation of the Young's modulus for each phase. In addition, the free energy barrier for lipid flip-flop process in the fluid and gel phases are estimated. The main rate-limiting step to complete a flip-flop process is related to a free energy barrier that has to be crossed in order to reach the center of the bilayer. The free energy cost for performing a lipid flip-flop in the gel phase is found to be five times greater than in the fluid phase, demonstrating the rarity of such events in the gel phase. Moreover, an energy barrier is estimated for formation of transient water pores that often precedes lipid translocation events and accounts for the rate-limiting step of these pore-associated lipid translocation processes.

Indiana University-Purdue University Indianapolis (IUPUI) / Autophagy is a conserved cellular process that involves sequestration and degradation of cytosolic contents. The cell can engulf autophagic cargo (lipids, long-lived proteins, protein aggregates, and pathogens) through a double bound membrane called an autophagosome that fuses with a lysosome where hydrolases then degrade these contents. This process is one of the main defenses against starvation and is imperative for newborns at birth. Research on this process has increased exponentially in the last decade since its discovery almost a half a century ago. It has been found that autophagy is an important process in many diseases, continues to be at the forefront of research, and is clearly not fully understood. Our preliminary cell culture data in endothelial and epithelial cells show that a blockade of the de novo ceramide synthesis pathway, during treatment with an autophagy stimulus (cigarette smoke extract exposure), does not result in any reduction in autophagy or autophagic flux. Conversely, when acid sphingomyelinase (ASM) is pharmacologically inhibited, which prevents the generation of ceramide from sphingomyelin in an acidic environment, a profound increase in autophagy is observed. In this work, we hypothesize that (ASM) is an endogenous inhibitor of autophagy. ASM has two forms, a secreted form and a lysosomal form. N-terminal processing in the Golgi determines its cellular fate. In the lysosomal form, the phosphodiesterase is bound in the lysosomal membrane. The pharmacological inhibition mechanism is to release ASM from the membrane and allow other hydrolases to actively degrade the enzyme which, in turn, decreases the activity of ASM. This suggests that either the activity of ASM is a regulator of autophagy or that the presence of ASM, activity aside, is required for the lysosomal nutrient sensing machinery (LYNUS) to function properly. Here, we show that ASM is, in fact, an endogenous inhibitor of autophagy in vitro. The phosphorylation status of P70 S6k, a downstream effector of mammalian target of rapamycin (mTOR), which is part of the LYNUS, shows that dissociation of ASM from the membrane regulates mTOR and disturbs the LYNUS in such a manner as to signal autophagy.