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71.
Pierrick Fevrier Philippe Gugan Florent Yvergnaux Jean Pierre Callegari Laurent Dufoss Adrien Binet 《Journal of Molecular Catalysis .B, Enzymatic》2001,11(4-6):445-453
Preliminary investigations on the regioselectiviy of various lipases were performed. Ten commercial lipases from different origins, including three immobilized lipases, were tested by esterification reaction between caprylic acid and propyl or isopropyl alcohol in n-hexane. Reaction products were analyzed with a gas chromatograph. Best yields were obtained with immobilized lipase IM60 from Rhizomucor miehei. Therefore, this enzyme was chosen as biocatalyst for a second step of regioselectiviy study with propylene glycol which bears primary and secondary alcohol groups. It was shown, by using several solvents, that polarity could influence the product profile in situations in which multiple products of various polarities can be formed. Furthermore, the major role of silica gel in reaction mixture was established. 相似文献
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Cancer cell dissemination away from the primary tumor and their ability to form metastases remain the major causes of death from cancer. Understanding the molecular mechanisms triggering this event could lead to the design of new cancer treatments. The establishment and the maintenance of tissue architecture depend on the coordination of cell behavior within this tissue. Cell-cell interactions must form adhesive structures between neighboring cells while remaining highly dynamic to allow and control tissue renewal or remodeling. Among intercellular junctions, cadherin-based adherens junctions mediate strong physical interactions and transmit information from the cell microenvironment to the cytoplasm. Disruption of these cell-cell contacts perturbs the polarity of epithelial tissues leading to their disorganization and ultimately to aggressive carcinomas. In non-epithelial tissues, the role of cadherins in the development of cancer is still debated. We recently found that downregulation of N-cadherin in malignant glioma—the most frequent primary brain tumor—results in cell polarization defects leading to abnormal motile behavior with increased cell speed and decreased persistence in directionality. Re-expression of N-cadherin in glioma cells restores cell polarity and limits glioma cell migration, providing a potential therapeutic tool for diffuse glioma. 相似文献
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76.
Nickel binding and immunological properties of the C-terminal domain of the Helicobacter pylori GroES homologue (HspA) 总被引:10,自引:1,他引:9
Imad Kansau Florent Guillain Jean-Michel Thiberge & Agnès Labigne 《Molecular microbiology》1996,22(5):1013-1023
Helicobacter pylori synthesizes a heat-shock protein of the GroES class. The gene encoding this protein (heat-shock protein A, HspA) was recently cloned and it was shown to be unique in structure. H. pylori HspA consists of two domains: the N-terminal domain (domain A) homologous with other GroES proteins, and a C-terminal domain (domain B) corresponding to 27 additional residues resembling a metal-binding domain. Various recombinant proteins consisting of the entire HspA polypeptide, the A domain, or the B domain were produced independently as proteins fused to maltose-binding protein (MBP). Comparison of the divalent cation binding properties of the various MBP and MBP-fused proteins allowed us to conclude that HspA binds nickel ions by means of its C-terminal domain. HspA exhibited a high and specific affinity for nickel ions in comparison with its affinity for other divalent cations (copper, zinc, cobalt). Equilibrium dialysis experiments revealed that MBP–HspA binds nickel ions with an apparent dissociation constant (Kd) of 1.8 μM and a stoichiometry of 1.9 ions per molecule. The analysis of the deduced HspA amino acid sequences encoded by 35 independent clinical isolates demonstrated the existence of two molecular variants of HspA, i.e. a major and a minor variant present in 89% and 11% of strains, respectively. The two variants differed from each other by the simultaneous substitution of seven amino acids within the B domain, whilst the A domain was highly conserved amongst all the HspA proteins (99–100% identity). On the basis of serological studies, the highly conserved A domain of HspA was found to be the immunodominant domain. Functional complementation experiments were performed to test the properties of the two HspA variants. When co-expressed together with the H. pylori urease gene cluster in Escherichia coli cells, the two HspA variant-encoding genes led to a fourfold increase in urease activity, demonstrating that HspA in H. pylori has a specialized function with regard to the nickel metalloenzyme urease. 相似文献
77.
Zahra Keshavarz-Motamed Julio Garcia Emmanuel Gaillard Romain Capoulade Florent Le Ven Guy Cloutier Lyes Kadem Philippe Pibarot 《PloS one》2014,9(1)
Early detection and accurate estimation of aortic stenosis (AS) severity are the most important predictors of successful long-term outcomes in patients. Current clinical parameters used for evaluation of the AS severity have several limitations including flow dependency. Estimation of AS severity is specifically challenging in patients with low-flow and low transvalvular pressure gradient conditions. A proper diagnosis in these patients needs a comprehensive evaluation of the left ventricle (LV) hemodynamic loads. This study has two objectives: (1) developing a lumped-parameter model to describe the ventricular-valvular-arterial interaction and to estimate the LV stroke work (SW); (2) introducing and validating a new index, the normalized stroke work (N-SW), to assess the global hemodynamic load imposed on the LV. N-SW represents the global hemodynamic load that the LV faces for each unit volume of blood ejected. The model uses a limited number of parameters which all can be measured non-invasively using current clinical imaging modalities. The model was first validated by comparing its calculated flow waveforms with the ones measured using Cardiovascular Magnetic Resonance (CMR) in 49 patients and 8 controls. A very good correlation and concordance were found throughout the cycle (median root mean square: 12.21 mL/s) and between the peak values (r = 0.98; SEE = 0.001, p<0.001). The model was then used to determine SW using the parameters measured with transthoracic Doppler-echocardiography (TTE) and CMR. N-SW showed very good correlations with a previously-validated index of global hemodynamic load, the valvular arterial impedance (), using data from both imaging modalities (TTE: r = 0.82, SEE = 0.01, p<0.001; CMR: r = 0.74, SEE = 0.01, p<0.001). Furthermore, unlike , N-SW was almost independent from variations in the flow rate. This study suggests that considering N-SW may provide incremental diagnostic and prognostic information, beyond what standard indices of stenosis severity and provide, particularly in patients with low LV outflow. 相似文献
78.
Muriel Dietrich Florent Kempf Elena Gómez‐Díaz Alexander S. Kitaysky J. Mark Hipfner Thierry Boulinier Karen D. McCoy 《Journal of Biogeography》2012,39(3):545-555
Aim Parasites with global distributions and wide host spectra provide excellent models for exploring the factors that drive parasite diversification. Here, we tested the relative force of host and geography in shaping population structure of a widely distributed and common ectoparasite of colonial seabirds, the tick Ixodes uriae. Location Two natural geographic replicates of the system: numerous seabird colonies of the North Pacific and North Atlantic Ocean basins. Methods Using eight microsatellite markers and tick samples from a suite of multi‐specific seabird colonies, we examined tick population structure in the North Pacific and compare patterns of diversity and structure to those in the Atlantic basin. Analyses included population genetic estimations of diversity and population differentiation, exploratory multivariate analyses, and Bayesian clustering approaches. These different analyses explicitly took into account both the geographic distance among colonies and host use by the tick. Results Overall, little geographic structure was observed among Pacific tick populations. However, host‐related genetic differentiation was evident, but was variable among host types and lower than in the North Atlantic. Main conclusions Tick population structure is concordant with the genetic structure observed in seabird host species within each ocean basin, where seabird populations tend to be less structured in the North Pacific than in the North Atlantic. Reduced tick genetic structure in the North Pacific suggests that host movement among colonies, and thus tick dispersal, is higher in this region. In addition to information on parasite diversity and gene flow, our findings raise interesting questions about the subtle ways that host behaviour, distribution and phylogeographic history shape the genetics of associated parasites across geographic landscapes. 相似文献
79.
Fabien Pille Sébastien Caron Xavier Bonnet Simon Deleuze Delphine Busson Thomas Etien Florent Girard Jean-Marie Ballouard 《Biodiversity and Conservation》2018,27(2):437-457
A lack of long-term monitoring often impedes the evaluation of translocation used to reinforce populations. Crucial questions regarding the exact timing and place of possible settlement remain unanswered. To examine these issues we radio-tracked during three years 24 tortoises (Testudo hermanni hermanni) released to reinforce a resident population impacted by fire. Individuals from the resident population (N = 20) and from a distant control population (N = 11) were also radio-tracked. More than 11,000 fixes were collected, enabling us to precisely describe movement patterns. Most translocated tortoises first dispersed (> 500 m to > 3000 m away) in a random direction and sometimes crossed unfavorable areas. Later, a marked shift in movement pattern, from a relatively unidirectional course to multidirectional displacements indicated settlement. Movement patterns of translocated and resident individuals became undistinguishable after settlement. Most individuals settled during the first year after release but several settled in the second year. Mean annual survival rate (> 85%) remained within the range of the species but was lower compared to the resident (93%) and control tortoises (100%). Overall, most translocated individuals (~ 63%) settled and adapted well to their novel environment. This result is essential regarding current controversies that are unfounded and that limit conservation translocations. Yet, translocation sites should be large enough and/or surrounded by secondary favorable areas to limit the mortality associated with dispersal in hazardous environments. Large numbers of individuals rescued during urbanization works may easily supply conservation translocations to reinforce fragile populations. 相似文献
80.
Oral microbiomes from hunter‐gatherers and traditional farmers reveal shifts in commensal balance and pathogen load linked to diet
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Florent Lassalle Matteo Spagnoletti Matteo Fumagalli Liam Shaw Mark Dyble Catherine Walker Mark G. Thomas Andrea Bamberg Migliano Francois Balloux 《Molecular ecology》2018,27(1):182-195
Maladaptation to modern diets has been implicated in several chronic disorders. Given the higher prevalence of disease such as dental caries and chronic gum diseases in industrialized societies, we sought to investigate the impact of different subsistence strategies on oral health and physiology, as documented by the oral microbiome. To control for confounding variables such as environment and host genetics, we sampled saliva from three pairs of populations of hunter‐gatherers and traditional farmers living in close proximity in the Philippines. Deep shotgun sequencing of salivary DNA generated high‐coverage microbiomes along with human genomes. Comparing these microbiomes with publicly available data from individuals living on a Western diet revealed that abundance ratios of core species were significantly correlated with subsistence strategy, with hunter‐gatherers and Westerners occupying either end of a gradient of Neisseria against Haemophilus, and traditional farmers falling in between. Species found preferentially in hunter‐gatherers included microbes often considered as oral pathogens, despite their hosts' apparent good oral health. Discriminant analysis of gene functions revealed vitamin B5 autotrophy and urease‐mediated pH regulation as candidate adaptations of the microbiome to the hunter‐gatherer and Western diets, respectively. These results suggest that major transitions in diet selected for different communities of commensals and likely played a role in the emergence of modern oral pathogens. 相似文献