Les environnements profonds marins ou continentaux représentent la majorité des biotopes sur Terre. Ils sont colonisés par des organismes, appelés piézophiles, adaptés aux fortes pressions hydrostatiques du milieu, conditions qui sont inhibitrices pour la croissance des organismes de surface. Dans le cadre de ce travail, j'ai cherché à élucider les spécificités de l’adaptation aux hautes pressions hydrostatiques. Pour cela, j'ai étudié un micro-organisme piézophile issu d'une source hydrothermale profonde, la souche MP de Thermococcus barophilus, dont l'optimum de croissance est de 400 fois la pression atmosphérique. J'ai caractérisé l'adaptation particulière de deux cibles cellulaires parmi les plus sensibles à la pression : les membranes et le protéome.Mes résultats montrent que la souche MP accumule des molécules de stress en condition de faible pression hydrostatique, c'est-à-dire que le protéome de cette souche est adapté aux conditions de hautes pressions. Il s'agit de la première démonstration d'une adaptation structurale chez un piézophile, et la démonstration que cette souche est une piézophile vraie. Par ailleurs, j'ai pu démontrer les mécanismes d'adaptation de la membrane en réponse à la pression et à la température. J'ai montré que cette réponse correspond à une adaptation homéovisqueuse de la composition membranaire, et que celle-ci est unique, car elle met en jeu trois mécanismes différents : une régulation du ratio di-/tetraéthers, une régulation du niveau d'insaturation des lipides, et la présence de lipides neutres dans la structure de la membrane. Ceci m'a amenée à proposer un nouveau modèle de membrane pour la souche modèle piézophile T. barophilus. La généralisation de ces observations et la confirmation de leur lien avec la piézophilie passe par l'étude d'autres organismes piézophiles. / Deep marine and continental environments represent the major ecosystems on Earth. They are colonized by organisms named piezophiles, adapted to high pressures of the deep biosphere, conditions that inhibit the growth of surface organisms. My objectives were to elucidate the special features of adaptation to high hydrostatic pressures. My model of study was a piezophilic microorganism isolated from a deep-sea vent; Thermococcus barophilus strain MP, which grows optimally at a pressure of 400 times the atmospheric pressure. I characterized the specific adaptation of two cellular compartments amongst the most sensitive to pressure: membranes and proteome. My results show that strain MP accumulates stress molecules in conditions of low pressure, which mean T. barophilus proteome is adapted to high pressure conditions. This is the first demonstration of structural adaptation in a piezophile, and also shows that T. barophilus is a true piezophile. Besides, I proved membrane adaptation mechanisms in response to pressure and temperature. These mechanisms are based on homeoviscous adaptation of lipids composition. This adaptation is unique and involves three different mechanisms: the regulation of the di-/tetraether ratio, the modulation of lipid unsaturation, and the insertion of neutral lipids in the membrane structure. These results brought me to propose a new membrane model for the piezophilic strain T. barophilus. Before confirming these observations as a possible piezophilic trait of adaptation, this study needs to be extended to other piezophilic organisms.

Tout d’abord considérés comme simples composants d’une barrière imperméable, il a été démontré que les lipides membranaires auraient en fait un rôle biologique bien plus important, pouvant modifier l’environnement des enzymes membranaires et moduler l’activité de ces dernières. Dans la thèse présentée ici, ces relations ont été étudiées dans les mitochondries de l’huître creuse Crassostrea gigas. Les bivalves subissent d’importants changements environnementaux et l’adaptation à ces changements peut passer par un remodelage des membranes, ce qui fait de ces animaux des modèles intéressants pour les études des relations entre la structure des membranes et les activités d’enzymes associées. Des huîtres ont été nourries en écloserie avec deux régimes d’algues monospécifiques, T-Iso et Chaetoceros gracilis, et un mélange équilibré de ces deux algues. Malgré d’importantes modifications de composition en acides gras induites par les différents régimes alimentaires, une grande stabilité des processus membranaires mitochondriaux a été observée. D’un autre côté, la comparaison entre des huîtres élevées en écloserie et des huîtres élevées dans leur milieu naturel a révélé d’importantes modifications de capacités mitochondriales, qui pourraient être liées à une modulation des classes de phospholipides et de leur insaturation. Ces différences ne peuvent pas s’expliquer par une influence des cycles tidaux dans la mesure où, malgré un changement de production d’ATP, l’activité des mitochondries a été montrée comme étant similaire chez les huîtres collectées en émersion et en immersion. L’homéostasie mitochondriale observée dans cette étude pourrait être un moyen pour les huîtres de faire face aux variations biotiques (disponibilité en nourriture) et abiotiques (disponibilité en oxygène) de l’environnement naturel de C. gigas, et de maintenir leurs fonctions physiologiques malgré ces variations. / First considered as simple components of an impermeable barrier, it has been shown that membrane lipids would have a more important biological role. These lipids could modify the environment of membrane enzymes and modulate their activity. In this thesis, these relationships have been studied in mitochondria of the oyster Crassostrea gigas. Bivalves undergo major environmental changes and adaptation to these changes may require a membrane remodelling, which makes these animals interesting models to study the relationship between membrane structure and membrane processes. In this study oysters were fed in hatchery with two monospecific algal diets, T-Iso and Chaetoceros gracilis, and an equilibrated mix of both algae. Despite significant changes in fatty acid composition induced by these diets, mitochondrial capacities remained stable. On the other hand, the comparison between hatchery-reared oysters and oysters reared in their natural environment revealed significant changes in mitochondrial capacity, which could be related to modulation of phospholipid class composition and unsaturation. These differences can not be explained by the influence of tidal cycles. Indeed, despite a change in ATP production, mitochondrial activity was shown to be similar in oysters collected during emersion and immersion.Mitochondrial homeostasis observed in this study could be a way for oysters to cope with biotic (food availability) and abiotic (oxygen availability) variations in the natural environment of C. gigas, and to maintain their physiological functions despite these variations.

No description available.

Eastern Africa has experienced strong climatic changes since the last deglaciation (15 000 years ago). The driving mechanisms and teleconnections of these spatially complex climate variations are yet not fully understood. Although previous studies on lake systems have enhanced our knowledge of Holocene precipitation variation in eastern Africa, relatively few studies have reconstructed the terrestrial temperature history of eastern Africa from lake archives. Here, we present (i) a new branched glycerol dialkyl glycerol tetraether (brGDGT) temperature calibration that includes Bale Mountains surface sediments and (ii) a quantitative record of mean annual air temperature (MAT) over the past 12 ka cal BP using brGDGTs in a sediment core collected from Garba Guracha (3950ma.s.l.) in the Bale Mountains. After adding Bale Mountains surface sediment (n = 11) data (Baxter et al., 2019) to the existing East African lake dataset, additional variation in 6-methyl brGDGTs was observed, which necessitated modifying the MBT'5ME calibration (MBT denotes methylation of branched tetraethers) by adding 6-methyl brGDGT IIIa0 (resulting in the MBT Bale Mountains index, r² = 0:93, p < 0:05). Comparing the MBT'5ME and the new MBT Bale Mountains index, our high-altitude Garba Guracha temperature record shows that warming occurred shortly after the Holocene onset when the temperature increased by more than 3.0°C in less than 600 years. The highest temperatures prevailed between 9 and 6 ka cal BP, followed by a temperature decrease until 1.4 ka cal BP. The reconstructed temperature history is linked to supraregional climatic changes associated with insolation forcing and the African Humid Period (AHP), as well as with local anomalies associated with catchment deglaciation and hydrology.

Symbiotic nitrogen (N) fixation (SNF) occurs in specialized organs called nodules after successful interactions between legume hosts and rhizobia. Within nodule cells, N-fixing rhizobia are surrounded by plant-derived symbiosome membranes, through which the exchange of nutrients and ammonium occurs between bacteria and the host legume. Phosphorus (P) is an essential macronutrient, and N2-fixing legumes have a higher requirement for P than legumes grown on mineral N. First, I investigated the impact of P deprivation on wild-type Medicago truncatula plants. My observations that plants had impaired SNF activity, reduced growth, and accumulated less phosphate in P-deficient tissues (leaves, roots and nodules) is consistent with those of similar previous studies. Galactolipids decreased with increase in phospholipids in all P-starved organs. Matrix-assisted laser desorption/ionization–mass spectrometry imaging (MALDI-MSI) of phosphatidylcholine (PC) species in nodules showed that under low P environments distributions of some PC species changed, indicating that membrane lipid remodeling during P stress is not uniform across the nodule. Secondly, a metabolomics study was carried out to test the alterations in the metabolic profile of the nodules in P-stress. GC-MS based untargeted metabolomics showed increased levels of amino acids and sugars and decline in amounts of organic acids in P deprived nodules. Subsequently, LC-MS/MS was used to quantify these compounds including phosphorylated metabolites in whole plant. My findings showed strong drop in levels of organic acids and phosphorylated compounds in P deprived leaves with moderate reduction in P deprived roots and nodules. Moreover, sugars and amino acids were elevated in whole plant under P deprivation. Finally, the last project of my thesis involved studying the response of PDIL3 (Phosphate Deficiency-Induced LncRNA-3) a long non-coding RNA (lncRNA) mutant under severe P stress. PDIL3 is known to regulate Pi-deficiency signaling and transport in M. truncatula (Wang et al., 2017). My results confirmed that in P starvation, pdil3 plants showed better shoot growth, accumulated more phosphate in shoots, had impaired SNF and less rhizobial occupancy in nodules than WT. Subsequently, MALDI–MS imaging was used to spatially map and compare the distribution of phosphatidylcholine (PC) species in nodules of pdil3 and WT in P-replete and P-depleted conditions. Several PC species showed changes in distributions in pdil3 nodules compared to WT in both P sufficient and P deprived conditions. These data suggest that PDIL3's role is not just suppression of the Pi transporter, but it may also influence P partitioning between shoots and nodulated roots, meriting further investigation.

Cardiovascular diseases are the leading cause of death in most industrialised countries and in developing countries the trend in cardiovascular-related deaths is increasing. World-wide, type 2 diabetes mellitus (T2DM) is an emerging cause of disability and premature death. Both these conditions are closely associated with the consumption of energy-dense foods and food products that are poor in nutrients, as well as with a sedentary lifestyle. Pharmacological and surgical interventions can improve the outcome and delay the progression of the disease, but in terms of population-level prevention there is no substitute for the adoption of a healthy lifestyle. SETTING The underlying studies were conducted in Västerbotten (the VIP study), and in Norrbotten and Västerbotten combined (the MONICA Project). Norrbotten andVästerbotten are the two northernmost counties in Sweden. Since the mid-1980sthe prevalence of cardiovascular disease has decreased and diabetes rates haveremained stable in this region, despite of an unbroken trend of increasing body weight. OBJECTIVE The aim of this thesis is to describe changes in reported dietary habits, estimatetheir relative importance as risk factors for diabetes and cardiovascular disease, and finally to identify lifestyle components as potential targets for intervention. RESULTS The first paper describes changes in self-reported food consumption between 1986 and 1999. During this period, the population in question switched from products with high saturated fatty acid content (e.g. milk containing 3% fat, butter) to foods containing less saturated fat (e.g. milk containing 1.5% fat, vegetable oil, low-fat margarine); pasta and rice were consumed more often, and potatoes were consumed less. Convenience foods (e.g. hamburgers, snacks, sweets) became more popular, whilst traditional dishes (e.g. potato dumplings, black pudding, blöta) decreased in popularity. Fruit and vegetable intake remained low. In paper two we study the effects of these changes in food intake on the risk of developing T2DM using body fat distribution as an early indicator. Increased consumption of convenience foods was associated with unfavourable changes (smaller hip circumference and larger waist circumference), whereas the increased consumption of vegetable oil and pasta was associated with low-risk fat distribution. In the third paper we report studies on the association between fat consumption and T2DM. We used the pattern of fatty acids in the membranes of red blood cells as a marker of fat intake. In addition to confirming earlier findings (markers of the intake of saturated fat are associated with increased risk of T2DM and markers of unsaturated fat are associated with reduced T2DM risk), we also identified associations between two markers of milk-derived saturated fat intake and enterolactone, a biomarker of dietary fibre intake, and the risk of developing myocardial infarction. Our results indicate that moderately high levels of enterolactone intake in men are associated with lower risk of experiencing myocardial infarction. Manuscript 5 ranks education level, physical activity, smoking status, and self-reported intake of dietary fibre and fatty acids according to their effects on body fat distribution. Increased levels of physical activity, a higher education level and a reduced intake of saturated fat from meat were ranked as the most strongly associated factors in both men and women. Increased intake of dietary fibre from grains in women, and increased intake of dietary fibre from fruits and vegetables in men, was also inversely associated with average waist circumference. CONCLUSION Both questionnaire-based and biological markers of the risk of developing diabetes or cardiovascular disease have been identified. Based on available population level measurements, reduced consumption of convenience foods, increased consumption of whole-grain products, fruits and vegetables, vegetable oil and pasta as well as increased physical activity are potential goals for interventions in northern Sweden.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / O efeito antibacteriano de Ãleos essenciais extraÃdos de folhas das espÃcies de Lippia aff. gracilis e Lippia gracilis frente a cepa de Staphylococcus aureus isolada de Ãlcera de paciente com pà diabÃtico foi avaliado mediante experimentaÃÃo in vitro e in vivo, utilizando-se o modelo experimental de ratos diabÃticos aloxano induzidos. Cento e doze ratos machos Wistar diabÃticos com peso mÃdio de 180g foram distribuÃdos ao acaso em dois experimentos. Cada experimento foi dividido em dois procedimentos que avaliaram a atividade antibacteriana de soluÃÃes dos Ãleos essenciais a 5%, em dois diferentes procedimentos: um no ato da administraÃÃo do inÃculo bacteriano e outro apÃs vinte e quatro horas de administraÃÃo. A administraÃÃo tanto do inÃculo 108ufc/ml quanto da suspensÃo dos Ãleos foi por via subcutÃnea no membro pÃlvico dos ratos diabÃticos. CinqÃenta e seis ratos Wistar foram utilizados para cada experimento, no qual os mesmos foram distribuÃdos ao acaso em 8 (oito) diferentes grupos: 4 grupos por experimento, apresentando 7 ratos por grupo (G1-Branco; G2-Controle negativo; G3-Controle positivo; G4-Teste). Foi verificado que no procedimento 1(S.aureus sem Lippia aff gracilis 108  698 versus S.aureus com Lippia aff gracilis 293,1  79,07; S.aureus sem Lippia gracilis 108  873 versus S.aureus com Lippia gracilis 302  57,2) e no procedimento 2 (S.aureus sem Lippia aff gracilis 108  313 versus S.aureus com Lippia aff gracilis 13,28  4,03; S.aureus sem Lippia gracilis 108  818 versus S.aureus com Lippia gracilis 13,14  4,27); houve reduÃÃo na contagem bacteriana tanto para Lippia aff. gracilis quanto para Lippia gracilis. Quando comparados os grupos G4 com G3, observou-se que esta suspensÃo a 5% nÃo apresentou efeito prÃ-inflamatÃrio. Para a validaÃÃo destes resultados, foram utilizados os testes Mann-Whitney e Bartletts &Newman-Keuls (MÃdia  - E.P.M) com nÃvel de significÃncia de (p<0,05). Ainda neste estudo foi avaliado a aÃÃo antioxidante e imunomoduladora da L-glutamina em modelos de ratos Wistar diabÃticos quando administrada por gavagem a uma concentraÃÃo de 0,7g/kg em um perÃodo de 30 dias. Quarenta ratos Wistar machos foram distribuÃdos ao acaso em 5 grupos (GI-nÃo diabÃtico; GII-diabÃtico; GIII-diabÃtico com salina; GIV-diabÃtico com L-glutamina; GV-diabÃtico com ProteÃna do Soro do Leite). Passado este perÃodo, foram determinadas as concentraÃÃes de substÃncias reativas ao Ãcido tiobarbitÃrico (TBARS) e glutationa reduzida (GSH) no soro e nos tecidos hepÃticos, pancreÃticos, mÃsculo esquelÃtico, rins e tecido adiposo. Para as comparaÃÃes entre o grupo tratado com L-glutamina com os demais, utilizou-se a anÃlise de variÃncia (ANOVA-teste Tukey). As comparaÃÃes entre grupos foram feitas utilizando-se o teste t de Student. Valores de p<0,05 foram considerados significantes. A suplementaÃÃo com L-glutamina induziu ao aumento nas concentraÃÃes de GSH (MÃdia  E.P.M) e reduÃÃo significante nas concentraÃÃes de TBARS (MÃdia  E.P.M), quando comparadas com o grupo controle, nos espÃcimes analisados. A aÃÃo imunomoduladora foi avaliada atravÃs da quantificaÃÃo de linfÃcitos CD4+ e CD8+ em sangue total. Vinte e quatro ratos Wistar machos diabÃticos foram distribuÃdos igualmente em 3 grupos (G1-diabÃtico com salina; G2-diabÃtico com L-glutamina; G3- diabÃtico com ProteÃna do Soro do Leite). Observou-se um aumento significante nas populaÃÃes de linfÃcitos CD4+ (MÃdia  E.P.M) com reduÃÃo nas populaÃÃes de linfÃcitos CD8+ (MÃdia  -E.P.M) do grupo G2 quando comparado com o grupo controle, ressaltando a importÃncia da L-glutamina como imunonutriente / The antibacterial effect of essential oils extracted from leaves of the species of Lippia aff. gracilis and Lippia gracilis against strains of Staphylococcus aureus isolated from patients with diabetic foot ulcers were evaluated in vitro and in vivo experimetation utilizing an experimental model of alloxan-induced diabetic rats. One hundred and twelve male diabetic Wistar rats with mean weight of 180g were distributed by chance into two experiments. Each experiment was divided in two procedures with evaluation of antibacterial activity of essential oils at 5% solutions; one procedure in the act of administration of bacterial inoculums and the other one 24 hours later. 108 CFU (Colony Forming Unit) /mL, as well as oils suspension inoculated in the subcutaneous tissue of the pelvic member of diabetic rats. Lower than 5% concentration of administered solution presented antibacterial effect in the in vitro experiment. Fifty-six Wistar rats were utilized in each experiment, randomly distributed in 08 different groups: 04 groups per experiment, each group with 07 rats (G1-White; G2-Negative Control; G3- Positive control; G4-Test). There was decrease in CFU/mL in procedure 1 (S.aureus without Lippia aff gracilis 108  698 versus S.aureus with Lippia aff gracilis 293,1  9,07; S.aureus without Lippia gracilis 108  873 versus S.aureus with Lippia gracilis 302Â57,2), which evaluated antibacterial effect of oils concomitantly with the administration of inocula as well as in procedure 2 (S.aureus without Lippia aff gracilis 108  313 versus S.aureus with Lippia aff gracilis 13,28  4,03; S.aureus without Lippia gracilis 108  818 versus S.aureus with Lippia gracilis 13,14  4,27) , which evaluated antibacterial effect of oils 24 hours after the administration of the inoculum . When comparing group G4 with G3, it was observed that 5% solution presented no pro-inflammatory effect, for analysis of these results, the tests of Mann-Whitney and Bartletts & Newman-Keuls (X  S.E.M) with level of significance (p<0,05) were used. Part of this study evaluated the antioxidant and immunomodulating effect of L-glutamine in models of Wistar diabetic rats when administered by gavages at a 0,7g/kg during 30 days. Fourty Wistar male rats were randomly distributed in 5 groups (GI- non diabetic; GII-diabetic; GIII-diabetic with saline; GIV- diabetic with L-glutamine; GV- diabetic with Whey Protein). After 30 days concentrations of TBARS and GSH in serum and in hepatic, pancreatic, skeletal muscles, kidneys and fat tissues were determined. For comparisons between the group treated with L-glutamine with the others, the ANOVA â Tukey test was utilized and the comparisons between groups were done using Studentâs t test. Values of p<0.05 were considered significant. The supplementation with L-glutamine induced an increase in the concentrations of GSH (Mean&#61617;S.E.M) and significant reduction in the TBARS (mean  S.E.M) concentrations, when compared to the control group, in the analyzed specimens. The immunomodulating effect was evaluated by quantification of CD4+ and CD8+ lymphocytes in total blood. Twenty-four Wistar male diabetic rats were distributed equally in 3 groups (G1-diabetic with saline; G2-diabetic with L-glutamine; G3- diabetic with Whey Protein). It was seen a significant increase of CD4+ (mean  S.E.M) lymphocytes with reduction of CD8+ (mean  S.E.M) lymphocytes in group G2 when compared to the control group, showing the importance of L-glutamine as an immunonutrient

Indiana University-Purdue University Indianapolis (IUPUI) / Cellular membranes contain a staggering diversity of lipids. The lipids are heterogeneously distr ibuted to create regions, or domains, whose physical properties differ from the bulk membrane and play an essential role in modulating the function of resident proteins. Many basic questions pertaining to the formation of these lateral assemblies remain. T his research employs model membranes of well - defined composition to focus on the potential role of polyunsaturated fatty acids (PUFAs) and their interaction with cholesterol (chol) in restructuring the membrane environment. Omega - 3 (n - 3) PUFAs are the main bioactive components of fish oil, whose consumption alleviates a variety of health problems by a molecular mechanism that is unclear. We hypothesize that the incorporation of PUFAs into membrane lipids and the effect they have on molecular organization may be, in part, responsible. Chol is a major constituent in the plasma membrane of mammals. It determines the arrangement and collective properties of neighboring lipids, driving the formation of domains via differential affinity for different lipids . T he m olecular organization of 1 -[ 2 H 31 ]palmitoyl -2- eicosapentaenoylphosphatidylcholine (PEPC - d 31 ) and 1 -[ 2 H 31 ]palmitoyl -2- docosahexaenoylphosphatidylcholine (PDPC -d 31 ) in membran es with sphingomyelin (SM) and chol (1:1:1 mol) was compared by solid - state 2 H NMR spectroscopy. Eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids are the two major n - 3 PUFAs found in fish oil, while PEPC -d 31 and PDPC -d 31 are phospholipids containing the respective PUFAs at the sn - 2 position and a perdeuterated palmitic acid a t the sn - 1 position . Analysis of s pectra recorded as a function of temperature indicate s that in both cases, formation of PUFA - rich (less ordered) and SM - rich (more ordered) domains occurred. A surprisingly substantial proportion of PUFA was found to infil trate the more ordered domain. There was almost twice as much DHA (65%) as EPA (30%) . The implication is that n - 3 PUFA s can incorporate into lipid rafts, which are domains enriched in SM and chol in the plasma membrane, and potentially disrupt the activity of signaling proteins that reside therein. DHA, furthermore, may be the more potent component of fish oil. PUFA - chol interactions were also examined through affinity measurements. A novel method utilizing electron paramagnetic resonance (EPR) was develope d, to monitor the partitioning of a spin - labeled analog of chol , 3β - doxyl - 5α - cholestane (chlstn), between large unilamellar vesicles (LUVs) and met hyl - β - cyclodextrin (mβCD). The EPR spectra for chlstn in the two environments are distinguishable due to the substantial differences in tumbling rates , allowing the population distribution ratio to be determined by spectral simulation. Advantages of this approach include speed of implementation and a vo idance of potential artifact s associated with physical separation of LUV and mβCD . Additionally, in a check of the method, t he relative partition coefficients between lipids measured for the spin label analog agree with values obtained for chol by isothermal titration calorimetry (ITC). Results from LUV with different composition confirmed a hierarchy of decreased sterol affinity for phospholipids with increasing acyl chain unsaturation , PDPC possessing half the affinity of the corresponding monounsaturated phospholipid. Taken together, the results of these studies on model membranes demonstrate the potential for PUFA - driven alteration of the architecture of biomembranes, a mechanism through which human health may be impacted.