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See detailChlamydomonas can play a role in the study of a heteroplasmic human mitochondrial mutation
Larosa, Véronique ULg; Coosemans, Nadine ULg; Bonnefoy, Nathalie et al

Scientific conference (2011)

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See detailThe Chlamydomonas genome reveals the evolution of key animal and plant functions.
Merchant, Sabeeha S.; Prochnik, Simon E.; Vallon, Olivier et al

in Science (2007), 318(5848), 245-50

Chlamydomonas reinhardtii is a unicellular green alga whose lineage diverged from land plants over 1 billion years ago. It is a model system for studying chloroplast-based photosynthesis, as well as the ... [more ▼]

Chlamydomonas reinhardtii is a unicellular green alga whose lineage diverged from land plants over 1 billion years ago. It is a model system for studying chloroplast-based photosynthesis, as well as the structure, assembly, and function of eukaryotic flagella (cilia), which were inherited from the common ancestor of plants and animals, but lost in land plants. We sequenced the approximately 120-megabase nuclear genome of Chlamydomonas and performed comparative phylogenomic analyses, identifying genes encoding uncharacterized proteins that are likely associated with the function and biogenesis of chloroplasts or eukaryotic flagella. Analyses of the Chlamydomonas genome advance our understanding of the ancestral eukaryotic cell, reveal previously unknown genes associated with photosynthetic and flagellar functions, and establish links between ciliopathy and the composition and function of flagella. [less ▲]

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See detailA Chlamydomonas mutant locked in anaerobiosis
Ghysels, Bart ULg; Matagne, René-Fernand ULg; Franck, Fabrice ULg

Conference (2011, May)

The soil dwelling microalga Chlamydomonas reinhardtii most likely encounters transient periods of anaerobiosis in its natural environment, for instance at night time or when photosynthesis is turned down ... [more ▼]

The soil dwelling microalga Chlamydomonas reinhardtii most likely encounters transient periods of anaerobiosis in its natural environment, for instance at night time or when photosynthesis is turned down in response to macronutrient limitation. Anoxic conditions trigger state I to state II transition in C.r. and the induction of a chloroplast hydrogenase., which ability to accept electrons from reduced Fd results in a transient light driven H2 evolution. We present evidence that hydrogenase induction and state transitions are required for the induction of photosynthesis in anaerobiosis and therefore critical for this alga in order to survive transient anaerobic periods in the dark. In an anaerobic metabolic context the induction of photosynthesis is severely slowed down. The highly reduced state of the NAD(P) pools and the absence of O2 as electron sink hamper light driven reoxydation of the intersystem electron carriers while CO2 assimilation by the Calvin cycle is inhibited by ATP deficiency. We have seen that gradual increase of hydrogenase activity during anaerobiosis restores a PSI acceptor pool and leads to a reduction of the induction lag of oxygenic photosynthesis. A mutant HydEF devoid of hydrogenase maturation genes typically shows 3 to 4 times longer lag phases that the WT. State transitions provide another mechanism by which photosynthetic electron transport can be unlocked in anaerobic conditions. A state II conformation is known to stimulate photo-phosphorylation, and may therefore restore Calvin cycle activity in an ATP depleted metabolic context. We observed that an anaerobically adapted stt7 mutant locked in state I is only able to induce oxygenic photosynthesis upon hydrogenase expression. We therefore constructed a double mutant Stt7HydEF impaired of state transition ability and hydrogenase activity and found it to have lost the capacity of inducing photosynthesis in anaerobic conditions. [less ▲]

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See detailChlamydomonas reinhardtii as a eukaryotic photosynthetic model for studies of heavy metal homeostasis and tolerance
Hanikenne, Marc ULg

in New Phytologist (2003), 159(2), 331-340

The green alga Chlamydomonas reinhardtii is a useful model of a photosynthetic cell. This unicellular eukaryote has been intensively used for studies of a number of physiological processes such as ... [more ▼]

The green alga Chlamydomonas reinhardtii is a useful model of a photosynthetic cell. This unicellular eukaryote has been intensively used for studies of a number of physiological processes such as photosynthesis, respiration, nitrogen assimilation, flagella motility and basal body function. Its easy-to-manipulate and short life cycle make this organism a powerful tool for genetic analysis. Over the past 15 yr, a dramatically increased number of molecular technologies (including nuclear and organellar transformation systems, cosmid, yeast artificial chromosome (YAC) and bacterial artificial chromosome (BAC) libraries, reporter genes, RNA interference, DNA microarrays, etc.) have been applied to Chlamydomonas . Moreover, as parts of the Chlamydomonas genome project, molecular mapping, as well as whole genome and extended expressed sequence tag (EST) sequencing programs, are currently underway. These developments have allowed Chlamydomonas to become an extremely valuable model for molecular approaches to heavy metal homeostasis and tolerance in photosynthetic organisms. [less ▲]

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See detailChlamydomonas reinhardtii proteomics adaptations in response to the absence of the energy-dissipating alternative oxidase
Mathy, Grégory ULg

Poster (2008, May 28)

The Alternative oxidase (AOX) is an ubiquinol-oxygen oxidoreductase found in the mitochondrial inner membrane of plants, fungi and protists. In mitochondria, AOX activation creates an electron ... [more ▼]

The Alternative oxidase (AOX) is an ubiquinol-oxygen oxidoreductase found in the mitochondrial inner membrane of plants, fungi and protists. In mitochondria, AOX activation creates an electron partitioning between the cytochrome pathway (CIII + CIV) and AOX. This partitioning leads to a decrease of proton pumping efficiency by the respiratory chain complexes per O2 consumed. Two closely related physiological roles are attributed to AOX: First, AOX in conjunction with rotenone insensitive NADH dehydrogenases, generates a fully non-coupled (energy dissipative) electron transport chain in the mitochondria, which is believed to play an important role in regenerating oxidized cofactors required for others metabolic demands. The second proposed role of AOX is to prevent an important increase the QR/Qt ratio and consequently, to prevent reactive oxygen species (ROS) production. In Chlamydomonas reinhartii AOX is encoded by two different genes, the AOX1 gene being much more transcribed than AOX2. In addition, the expression of the AOX1 gene is generally unresponsive to a number of known AOX allosteric effectors, but is down-regulated by ammonium and up-regulated by nitrate. In the present work, we performed a comparative proteomic study of isolated mitochondria by using the 2D-DIGE methodology to evidence the effects of AOX1 silencing on Chlamydomonas mitochondrial soluble proteome cultivated on nitrate in myxotrophic conditions [less ▲]

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See detailChlamydophila felis infection. ABCD guidelines on prevention and management
Gruffydd-Jones, T.; Addie, D.; Belak, B. et al

in Journal of Feline Medicine and Surgery (2009), 11

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See detailChlamydophila psittaci chez les canards d’élevages et d’ornement en Région Wallonne
Delleur, Valery ULg; Marlier, Didier ULg

in Proceedings du 3ème colloque international de bactériologie francophone (2006, July)

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See detailChlordecone Exposure and Risk of Prostate Cancer
Multigner, Luc; NDong, Jean-Rodrigue; Giusti, Arnaud ULg et al

in Journal of Clinical Oncology (2010)

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See detailChlordecone exposure, length of gestation, and risk of preterm birth
Kadhel, P; Monfort, C; Costet, N et al

in American Journal of Epidemiology (2014), 179(5), 536-544

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See detailChloride and Inorganic Phosphate Modulate Binding of Oxygen to Bovine Red Blood Cells
Gustin, Pascal ULg; Detry, Benoît; Cao, M. L. et al

in Journal of Applied Physiology (Bethesda, Md. : 1985) (1994), 77(1), 202-208

The influence of Pi and Cl on the equilibrium of oxygen binding to bovine red blood cells was assessed by plotting the whole blood oxygen dissociation curve measured under standard conditions with and ... [more ▼]

The influence of Pi and Cl on the equilibrium of oxygen binding to bovine red blood cells was assessed by plotting the whole blood oxygen dissociation curve measured under standard conditions with and without added KCl and K2HPO4. Both salts shifted the oxygen dissociation curve to the right. This effect was more marked at the highest saturation levels. At a given saturation level, the anion-induced shift was linearly related to the concentration of salt added to the blood. Cl had a greater effect than Pi. The relationship between changes in Po2 at 50% hemoglobin saturation (in Torr) and concentrations of ions added (in mmol/l) was equal to 0.0515[Cl] + 0.0302[Pi] (r2 = 0.94; P < 0.001). These changes were not due to the hyperosmolality induced by salt addition, since sucrose added in place of salts was without effect on the measured parameters. The oxygen exchange fraction expressed as percentage of saturation, i.e., the difference in hemoglobin saturation when Po2 decreases from 130 to 40 Torr, was linearly correlated to added anion concentration (in mmol/l) (= 0.102[Cl] + 0.059[Pi] (r2 = 0.95; P < 0.001)). No significant interaction between the anions was observed; their effects were purely additive. This original mechanism of controlling the oxygen affinity of bovine blood may have clinical relevance: Cl and Pi could be used to increase oxygen transport efficiency in hypoxic animals [less ▲]

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See detailChloride channels and endocytosis: new insights from Dent's disease and ClC-5 knockout mice.
Devuyst, Olivier; JOURET, François ULg; Auzanneau, Celine et al

in Nephron. Clinical Practice (2005), 99(3), 69-73

Dent's disease is a hereditary renal tubular disorder characterized by low-molecular weight (LMW) proteinuria, hypercalciuria and nephrolithiasis. The disease is due to mutations of ClC-5, a member of the ... [more ▼]

Dent's disease is a hereditary renal tubular disorder characterized by low-molecular weight (LMW) proteinuria, hypercalciuria and nephrolithiasis. The disease is due to mutations of ClC-5, a member of the family of voltage-gated CLC chloride channels. ClC-5 is expressed in part in cells lining the proximal tubule (PT) of the kidney, where it colocalizes with albumin-containing endocytic vesicles belonging to the receptor-mediated endocytic pathway that ensures efficient reabsorption of ultrafiltrated LMW proteins. Since progression along the endocytic apparatus requires endosomal acidification, it has been suggested that dysfunction of ClC-5 in endosomes may lead to inefficient reabsorption of LMW proteins and dysfunction of PT cells. Analysis of a ClC-5 knockout (KO) mouse model, displaying all the characteristic renal tubular defects of Dent's disease, showed evidence of a severe LMW proteinuria. Cytochemical studies with the endocytic tracer, peroxidase, showed poor transfer into early endocytic vesicles, suggesting that impairment of receptor-mediated endocytosis in PT cells is the basis for the defective uptake of LMW proteins in patients with Dent's disease. Endocytosis and processing of LMW proteins involve the multiligand tandem receptors, megalin and cubilin, that are abundantly expressed at the brush border of PT cells. Characterization of the endocytic defect in ClC-5 KO mice revealed that ligands of both megalin and cubilin were affected. The total kidney content of megalin and especially cubilin at the protein level was decreased but, more importantly, using analytical subcellular fractionation and quantitative immunogold labelling we demonstrated a selective disappearance of megalin and cubilin at the brush border of PT cells. These observations allowed us to conclude that defective protein endocytosis linked to ClC-5 inactivation is due at least in part to a major and selective loss of megalin and cubilin at the brush border, reflecting a trafficking defect in renal PT cells. These results improve our understanding of Dent's disease, taken as a paradigm for renal Fanconi syndrome and nephrolithiasis, and demonstrate multiple roles for ClC-5 in the kidney. These studies also provided insights into important functions such as apical endocytosis, handling of proteins by renal tubular cells, calcium metabolism, and urinary acidification. [less ▲]

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See detailChloride Permeability of Rat Brain Membrane Vesicles Correlates with Thiamine Triphosphate Content
Bettendorff, Lucien ULg; Hennuy, Benoît ULg; De Clerck, Anne et al

in Brain Research (1994), 652(1), 157-160

Incubation of rat brain homogenates with thiamine or thiamine diphosphate (TDP) leads to a synthesis of thiamine triphosphate (TTP). In membrane vesicles subsequently prepared from the homogenates ... [more ▼]

Incubation of rat brain homogenates with thiamine or thiamine diphosphate (TDP) leads to a synthesis of thiamine triphosphate (TTP). In membrane vesicles subsequently prepared from the homogenates, increased TTP content correlates with increased 36Cl- uptake. A hyperbolic relationship was obtained with a K0.5 of 0.27 nmol TTP/mg protein. In crude mitochondrial fractions from the brains of animals previously treated with thiamine or sulbutiamine, a positive correlation between 36Cl- uptake and TTP content was found. These results, together with other results previously obtained with the patch-clamp technique, suggest that TTP is an activator of chloride channels having a large unit conductance. [less ▲]

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See detail(Chloro-4 phenyl) thiomethylene bisphosphonate in Paget’s bone disease
Reginster, Jean-Yves ULg; DEROISY, Rita ULg; Lecart, MP et al

in Acta Belgica. Medica Physica (1989), 12

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See detail(Chloro-4-phenyl) thiomethylene bisphosphonate in Paget's bone disease
Reginster, Jean-Yves ULg; DEROISY, Rita ULg; Lecart, MP et al

in Journal Belge de Médecine Physique et de Réhabilitation = Belgisch Tijdschrift voor Fysische Geneeskunde en Rehabilitatie (1989), 12

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See detailThe chlorophyll a fluorescence induction curve in the green microalga Haematococcus pluvialis: Further insight into the nature of the P-S-M fluctuation and its relationship with the "low-wave" phenomenon at steady-state
Fratamico, Anthony ULg; Tocquin, Pierre ULg; Franck, Fabrice ULg

in Photosynthesis Research (2016), 128(3), 271-285

Chlorophyll fluorescence is an information-rich signal which provides an access to the management of light absorbed by PSII. A good example of this is the succession of fast fluorescence fluctuations ... [more ▼]

Chlorophyll fluorescence is an information-rich signal which provides an access to the management of light absorbed by PSII. A good example of this is the succession of fast fluorescence fluctuations during light-induced photosynthetic induction after dark-adaptation. During this period, the fluorescence trace exhibits several inflexion points: O-J-I-P-S-M-T. Thereas the OJIP part of this kinetics has been the subject of many studies, the processes that underly the PSMT transient are less understood. Here, we report an analysis of the PSMT phase in the green microalga Haematococcus pluvialis in terms of electron acceptors and light use by photochemistry, fluorescence and non-photochemical quenching (NPQ). We identify additional sub-phases between P and S delimited by an inflexion point, that we name Q, found in the second time-scale. The P-Q phase expresses a transient photochemical quenching specifically due to alternative electron transport to oxygen. During the transition from Q to S, the NPQ increases and then relaxes during the S-M phase in about 1 min. It is suggested that this transient NPQ observed during induction is a high energy state quenching (qE) dependent the alternative electron transport to molecular oxygen. We further show that this NPQ is of the same nature than the NPQ, known as the low-wave phenomenon, which is transiently observed after a saturating light pulse given at steady-state. In both cases, the NPQ is oxygen-dependent. This NPQ is observed at external pH 6.0, but not at pH 7.5, which seems correlated with faster saturation of the PQ pool at pH 6.0. [less ▲]

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