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C Garnier

Publications and source records attributed to C Garnier.

At least 19 recordsLinked to original sources
PubMed2006

Voltammetric procedure for trace metal analysis in polluted natural waters using homemade bare gold-disk microelectrodes.

Voltammetric procedures for trace metals analysis in polluted natural waters using homemade bare gold-disk microelectrodes of 25- and 125-microm diameters have been determined. In filtered seawater samples, square wave anodic stripping voltammetry (SWASV) with a frequency of 25 Hz is applied for analysis, whereas in unfiltered contaminated river samples, differential pulse anodic stripping voltammetry (DPASV) gave more reliable results. The peak potentials of the determined trace metals are shifted to more positive values compared to mercury drop or mercury-coated electrodes, with Zn always displaying 2 peaks, and Pb and Cd inversing their positions. For a deposition step of 120 s at -1.1 V, without stirring, the 25-microm gold-disk microelectrode has a linear response for Cd, Cu, Mn, Pb and Zn from 0.2 microg L(-1) (1 microg L(-1) for Mn) to 20 microg L(-1) (30 microg L(-1) for Zn, Pb and 80 microg L(-1) for Mn). Under the same analytical conditions, the 125-microm gold-disk microelectrode shows linear behaviour for Cd, Cu, Pb and Zn from 1 microg L(-1) (5 microg L(-1) for Cd) to 100 microg L(-1) (200 microg L(-1) for Pb). The sensitivity of the 25-microm electrode varied for different analytes from 0.23 (+/-0.5%, Mn) to 4.83 (+/-0.9%, Pb) nA L micromol(-1), and sensitivity of the 125-microm electrode varied from 1.48 (+/-0.7%, Zn) to 58.53 (+/-1.1%, Pb nA L micromol(-1). These microelectrodes have been validated for natural sample analysis by use in an on-site system to monitor Cu, Pb and Zn labile concentrations in the Deûle River (France), polluted by industrial activities. First results obtained on sediment core issued from the same location have shown the ability of this type of microelectrode for in situ measurements of Pb and Mn concentrations in anoxic sediments.

Journal Article↗
PubMed2004

[Metal logarithmic scale titration as a tool for complexing ligand distribution determination: an application by DPASV].

A new logarithmic scale titration is proposed for the characterisation of natural organic matter-trace metals interactions in natural systems. The Suwannee River Fulvic Acid complexation with Cd and Pb ions has been analysed by this technique, using Differential Pulse Anodic Stripping Voltammetry (DPASV) for labile metal concentrations measurement. Results of titrations have been modelled by four ligands. Their complexing properties (CLi, Ki(Cd), Ki(Pb)) have been determined by a non-linear optimisation based on the speciation program MINEQL, coupled with a simplex. These ligands were called "very weak, weak, strong and very strong" with respect to their complexing constants (Ki(Cd), Ki(Pb)) ranging from 10(4) to 10(11). The obtained ligands concentrations (CLi) are respectively 1.9 microM, 150 nM, 25.1 nM and 21.1 nM for a 7.9 ppm carbon content. Moreover, this model takes account of the pH dependency and metals competition respectively by experiments at pH 7.8 and 4.6, and by definition of stability constants for each ligand toward each analysed metal. As a conclusion, the authors suggest a systematic use of the logarithmic scale titrations when full characterisation of the metal-organic matter interactions is necessary.

Cadmium↗
PubMed2002

Native vs. damaged milk fat globules: membrane properties affect the viscoelasticity of milk gels.

The storage modulus G' of rennet and acid milk gels filled with milk fat globules was measured as a function of the fat globule surface composition (native milk fat globule membrane, caseins and whey proteins, or a mixture of the three due to mechanical treatments) and surface area (i.e., the fat globule size). By different technological procedures, it was possible to obtain fat globules of constant surface composition but various sizes, and vice-versa, which had never been done. For both rennet and acid gels, a critical fraction of the fat globule surface covered by caseins and whey proteins was identified (approximately 40%), beyond which G' increased. Below this threshold, the gel viscoelasticity was unaffected by mechanical treatments. When the diameter of native milk fat globules decreased, the G' of rennet gels increased slightly, whereas that of acid gels decreased sharply. For both types of gels, G' increased when the diameter of partially disrupted fat globules decreased. For recombined globules completely covered with caseins and few whey proteins, G' increased with fat globule surface area for rennet gels whereas it decreased for acid gels. With the help of confocal microscopy and in the light of general structural differences between rennet and acid gels, a mechanism is proposed for the effect of fat globule damage and diameter on G', depending on the interactions the globules can undergo with the casein network.

Animals↗
PubMed2002

[Symetric lipomatosis of the hands].

INTRODUCTION: We report a case of symmetric lipomatosis in an unusual palmary topography. CASE REPORT: A 56 year-old woman was referred for evaluation of scleroderma. The diagnosis was made 10 years earlier because of acrosclerosis of the distal phalanges of both hands. The disease began 2 months after administration of systemic steroids for severe asthma. Since then, she was followed up for her scleroderma every 2 years without any evidence of systematization of the disease. On examination, the first phalanges appeared protruding and podgy on the palms of both hands. On palpation, the consistence was suggestive of lipomas. Similar nodules were present on the back of both hands at the proximal part of the interdigital spaces. Tomodensitometry confirmed the lipomatous nature of nodules. DISCUSSION: This patient presented with a symmetric lipomatosis of a very unusual distal localization on both hands. This unusual aspect mimicked acrosclerosis. In this case report, chronology suggests that systemic steroids might have induced this lipohypertrophy.

Adrenal Cortex Hormones↗
PubMed2001

Phosphorylation and oligomerization states of native pig brain HSP90 studied by mass spectrometry.

HSP90 is one of the most abundant proteins in the cytosol of eukaryotic cells. HSP90 forms transient or stable complexes with several key proteins involved in signal transduction including protooncogenic protein kinases and nuclear receptors, it interacts with cellular structural elements such as actin-microfilament, tubulin-microtubule and intermediate filaments, and also exhibits conventional chaperone functions. This protein exists in two isoforms alpha-HSP90 and beta-HSP90, and it forms dimers which are crucial species for its biological activity. PAGE, ESI-MS and MALDI-MS were used to study HSP90 purified from pig brain. The two protein isoforms were clearly distinguished by ESI-MS, the alpha isoform being approximately six times more abundant than the beta isoform. ESI-MS in combination with lambda phosphatase treatment provided direct evidence of the existence of four phosphorylated forms of native pig brain alpha-HSP90, with the diphosphorylated form being the most abundant. For the beta isoform, the di-phosphorylated was also the most abundant. MALDI mass spectra of HSP90 samples after chemical cross-linking showed a high percentage of alpha-alpha homodimers. In addition, evidence for the existence of higher HSP90 oligomers was obtained.

Animals↗
PubMed2000

Gelation by phase separation in a whey protein system: in-situ kinetics of aggregation.

The aggregation and gelation properties of beta-lactoglobulin (BLG), a globular protein from milk, was studied in aqueous ethanol solutions at room temperature. The phase state diagrams as a function of pH and ethanol concentration showed that a gel structure appeared after a period ranging from 1 min to 1 week, depending on the physico-chemical conditions. The in-situ kinetics of aggregation were followed by several methods in order to obtain a better understanding of the building of aggregates by the addition of ethanol. It was shown that the aggregation kinetics highly depended upon the pH, the process being fastest at pH 7. Viscoelasticity and infrared measurements indicated that alcohol-induced gelation would proceed via a two-step mechanism: small aggregates loosely connected between them were first built up; a real network took place in a second step. The coarse and irregular structures formed in aqueous ethanol gels revealed by confocal laser scanning microscopy could be analysed in terms of a phase separation. This observation was supported by a syneresis phenomenon visible in the final gel state. BLG in water-ethanol solution would undergo either an inhibition of the demixing by gelation or a binary phase separation accompanied by an irreversible gelation transition.

Ethanol↗
PubMed1999

Biophysical characterization of lithostathine. Evidences for a polymeric structure at physiological pH and a proteolysis mechanism leading to the formation of fibrils.

Lithostathine is a calcium carbonate crystal habit modifier. It is found precipitated under the form of fibrils in chronic calcifying pancreatitis or Alzheimer's disease. In order to gain better insight into the nature and the formation of fibrils, we have expressed and purified recombinant lithostathine. Analytical ultracentrifugation and quasi-elastic light scattering techniques were used to demonstrate that lithostathine remains essentially monomeric at acidic pH while it aggregates at physiological pH. Analysis of these aggregates by electron microscopy showed an apparently unorganized structure of numerous monomers which tend to precipitate forming regular unbranched fibrils. Aggregated forms seem to occur prior to the apparition of fibrils. In addition, we have demonstrated that these fibrils resulted from a proteolysis mechanism due to a specific cleavage of the Arg(11)-Ile(12) peptide bond. It is deduced that the NH(2)-terminal undecapeptide of lithostathine normally impedes fiber formation but not aggregation. A theoretical model explaining the formation of amyloid plaques in neurodegenerative diseases or stones in lithiasis starting from lithostathine is described. Therefore we propose that lithostathine, whose major function is unknown, defines a new class of molecules which is activated by proteolysis and is not involved in cytoskeleton nor intermediate filament functions.

Alzheimer Disease↗
PubMed1999

Pathological prognostic factors in a series of 137 stage I TNM/UICC endometrial carcinomas.

PURPOSE: We report on the long-term results of combination surgery-radiotherapy in cT1 carcinoma of the endometrium according to prognostic factors. PATIENTS AND METHODS: From 1974 to 1993, 130 women suffering from cT1Nx-O Mo endometrial carcinoma, underwent surgical resection. The median age was 62 years. Thirteen received pre-operative irradiation, two pre-operative brachytherapy followed by post-operative external irradiation and 115 patients (88.35%) underwent post-operative irradiation therapy by brachytherapy or external beam irradiation. RESULTS: The median follow-up is 67 months. Overall and specific survival rates for patients with cT1pT1 tumours were 71.1 and 85% at 10 years. For overall survival, lymph node invasion was the most powerful prognostic factor in the multivariate analysis (P = 0.02). If lymph node invasion is not taken into account, the WHO histological grade exerts a significant prognostic impact (P = 0.001). CONCLUSION: For stage cT1 endometrial carcinoma, primary surgery allows radiotherapy to be adjusted according to the WHO histological grade, myometrial invasion and the pelvic lymph node status.

Adult↗
PubMed1998

Heat-shock protein 90 (hsp90) binds in vitro to tubulin dimer and inhibits microtubule formation.

Hsp90 interacts with steroid hormone receptors, protein kinases, and cytoskeletal proteins. The mode of action of hsp90 on microtubules and tubulin has not been investigated. Using isolated purified hsp90 and isolated tubulin, we demonstrated in vitro by difference absorption and fluorescence spectroscopy that hsp90 bound to tubulin with an apparent affinity constant of 5 x 10(5) M-1, assuming an apparent stoichiometry of 1 at 25 degrees C. Using microcalorimetry, we found a delta H of -9.8 +/- 0.8 kJ.mol-1. The binding of hsp90 to tubulin was confirmed by a sedimentation assay. Moreover, we showed that hsp90 inhibited tubulin polymerisation.

Animals↗
PubMed1998

The two-state process of the heat shock protein 90 thermal denaturation: effect of calcium and magnesium.

Scanning microcalorimetry, native PAG electrophoresis, and circular dichroism were used to characterize thermal denaturation and oligomerization of heat shock protein 90 (hsp90) and the calcium and magnesium effect on these processes. The calorimetric curve of the hsp90 dimer consists of two transitions centered at 53.8 and 63.1 degrees C. Using specific ligand geldanamycin, we have found that N-terminal domains in the hsp90 dimer are melted independently in the lower-temperature peak, while the higher-temperature one comprises unfolding of two non-interacting parts of the middle domains and dimerization region. Unfolding of the N-terminal domain gives start to oligomerization of dimers; oligomers consist of dimers not dissociating upon denaturation. Calcium and magnesium strongly decrease the hsp90 thermostability and thereby cause oligomerization at lower temperature. We suggest that calcium affects the hsp90 oligomerization, known to be important for its chaperone activity, by shifting the unfolding temperature of the hsp90 N-terminal domain close to the heat shock temperature range.

Animals↗
PubMed1998

'ER degradation' of a mutant yeast plasma membrane protein by the ubiquitin-proteasome pathway.

The yeast plasma membrane, uracil permease, undergoes ubiquitin-dependent endocytosis and subsequent degradation in the vacuole via a process that does not involve the proteasome. Cell-surface ubiquitination of this protein is mediated by the ubiquitin-protein ligase Npi1p/Rsp5p and involves Lys63-linked ubiquitin chains. This report describes the intracellular fate of a mutant form of uracil permease carrying a three amino acid insertion in a cytoplasmic loop. Most of this protein is not deployed beyond the ER, and is degraded by the 26S proteasome. Mutant permease degradation is almost unaffected in cells with impaired Npi1p/Rsp5p, but is dependent on the Ubc6p and Ubc7p ubiquitin-conjugating enzymes, suggesting that proteolysis of the protein requires its prior ubiquitination. Overproduction of a derivative of ubiquitin with a modified Lys48 strongly impairs mutant permease degradation. This suggests that, like other proteasome substrates, mutant permease might be polyubiquitinated with Lys48-linked ubiquitin chains. These findings provide an example of a yeast plasma membrane protein that is routed to the 'ER degradation' pathway, and highlight the versatility of the ubiquitin system.

Cell Membrane↗
PubMed1997

Development of the striatal projection from embryonic neurons from the lateral or medial frontal cortex grafted homo- or heterotopically into the medial frontal cortex of newborn rats.

The present study was designed to further investigate the effects of intrinsic or extrinsic influences on the development of the efferent connectivity of frontal neocortical neurons. The lateral or medial parts of the frontal neocortex of embryonic (E) day 16 fetuses were grafted into homo- (medial-to-medial) or heterotopic (lateral-to-medial) position in the medial part of the left frontal cortex of newborn hosts. Three to four months after grafting, a retrograde neurotracer was injected into the dorsomedial or ventrolateral quadrant of the left caudate-putamen (CPU). The ensuing retrograde labeling in the transplants was then compared to that found in an equivalent cortical area in control animals. Medial-to-medial transplants developed a striatal projection whose mediolateral organization conforms to that of the projection arising from the medial part of the intact frontal cortex. The mediolateral distribution of the projection arising from lateral-to-medial transplants was not fundamentally different from that originating from medial-to-medial transplants, a finding which stands in marked contrast with what was found recently [7] with medial-to-lateral transplants. These results indicate that inside the frontal cortex, different subregions are not totally interchangeable, at least in terms of development of efferent connectivity.

Animals↗
PubMed1997

A technique based on the use of activated charcoal for easier subsequent retrieval of neocortical grafts placed in the neocortex of newborn rats.

The mechanisms underlying the differentiation of neocortical areas are still largely unknown. The development of neural connectivity constitutes one important step in neocortical differentiation. One way to study the mechanisms guiding this developmental stage is to examine the connections established by transplants of neocortical tissue of varying embryonic age placed in varying areas of the neocortex of newborn hosts. Neurotracer injection into the transplant at different intervals following transplantation is then used to identify the development of host-transplant connectivity. In most cases, however, it is rather difficult to retrieve the transplant within the host cortex even shortly after grafting. Hence, it is very difficult to perform tracer injections limited to the transplant without any involvement of the host cortex. In some instances, the transplant position can be predicted by some weaker vascularization within or at the surface of the graft. This is not, however, a reliable criterion to establish the rostrocaudal and mediolateral coordinates of the tracer injection. In this report, we describe the use of activated charcoal to mark the transplant at the time of transplantation. The transplant containing black dots can subsequently be easily distinguished from the host pale pink cortex.

Animals↗
PubMed1996

Development of projections from transplants of embryonic medial or lateral frontal cortex placed in the lateral frontal cortex of newborn hosts.

Several recent experiments using neocortical transplantation paradigms indicated that embryonic neurons grafted in a heterotopic locus retain development characteristics corresponding to their site of origin. In the present study, limited portions of lateral (lateral-to-lateral) or medial (medial-to-lateral) sectors of embryonic (E16) frontal cortex were grafted into the lateral frontal cortex of newborn rats. A retrograde tracer was injected 3-4 months later into the dorsomedial or ventrolateral sectors of the host caudate-putamen (CPU). The results indicate that the mediolateral arrangement of striatal projection developed by lateral-to-lateral transplants is virtually identical to that found in intact rats. A very weak proportion of the transplanted cells distribute fibers to the dorsomedial sector of the CPU. In marked contrast, the proportion of efferents from medial-to-lateral transplants projecting to the dorsomedial CPU is by far larger than the one directed to the ventrolateral CPU. Our findings provide evidence that even within one single neocortical area (the frontal neocortex) some degree of prespecification (medial versus lateral patterns of efferent projections) is already present at E16.

Age Factors↗
PubMed1996

Solution conformations of pectin polysaccharides: determination of chain characteristics by small angle neutron scattering, viscometry, and molecular modeling.

The solution behavior of pectin polysaccharides has been investigated by small angle neutron scattering (SANS), viscosimetric, and molecular modeling studies. The samples used in the experimental study were obtained from apple and citrus and had degrees of methylation ranging from 28 to 73%, with a rhamnose content lying between 0.6 and 2.2%. Persistence lengths, derived from intrinsic viscosity measurements, ranged from 59 to 126 A, whereas those derived by SANS were between 45 and 75 A. These values correspond to 10-17 monomer units. The modeling simulations were performed for both homogalacturonan itself and homogalacturonan carrying various degrees of rhamnose inserts (rhamnogalacturonan). This required the evaluation of the accessible conformational space for the eight disaccharides that represent the constituent repeating segments of the homogalacturonan and rhamnogalacturonan polysaccharides. For each dimer, complete conformational analysis was accomplished using the flexible residue method of the MM3 molecular mechanics procedure and the results used to access the configurational statistics of representative pectic polysaccharide chains. For homogalacturonan, an extended chain conformation having a persistence length of 135 A (corresponding to 30 monomers) was predicted. The inclusion of varying amounts of rhamnose units (5-25%) in the model in strict alternating sequence with galacturonate residues (equivalent to the rhamnogalacturonan "hairy region" chains) only slightly reduced the calculated persistence length. The extended overall chain conformation remained relatively unchanged as a consequence of the self-cancellation of the kinking effects of successive paired rhamnose units.

Carbohydrate Conformation↗
PubMed1996

Membrane topology of the yeast uracil permease.

The uracil permease of Saccharomyces cerevisiae is a 633 residue polytopic plasma membrane protein. Hydropathy profile analysis indicates that this protein has long hydrophilic N- and C-termini and 10-12 potential transmembrane segments. Previous results based on analysis of hybrid proteins allowed identification of the first transmembrane segment of uracil permease, and provided a preliminary indication of the cytoplasmic orientation of its N-terminus. In this work, other experimental approaches were used to confirm this orientation, and to determine that of the C-terminus. Epitopes in the N- and the C-termini of the protein were protected against trypsin degradation on intact protoplasts, but readily digested on permeabilized protoplasts. Immunofluorescent analysis showed that antibodies to the last 10 amino acids of uracil permease bind to detergent-treated protoplasts, but not to intact ones. Carboxypeptidase digested the C-terminus of uracil permease inserted into the sealed dog-pancreas microsomes. These results establish that both N- and C-termini are cytoplasmic, the permease polypeptide spanning the membrane an even number of times. The orientation of several hydrophilic loops with respect to the membrane was investigated by introducing potential glycosylation sites into these regions. We checked whether the resulting mutant proteins were glycosylated when expressed in the presence of dog-pancreas microsomes. Our data show that two loops of the protein are lumenal. Together with previous results, this work indicates that uracil permease is a 10 membrane-spanning protein, with rather small external loops and three main cytoplasmic regions (the N- and C-termini and a central 60-residue loop).

Amino Acid Sequence↗
PubMed1995

The topographic distribution of the efferents from neocortical neurons is not only dependent upon where in the neocortex the cells develop. A transplantation study within one single neocortical region.

It has been proposed that the distribution of efferents developed by neocortical neurons depends upon where in the neocortex the cells develop, not where they were generated. However, the capacity of diverse isocortical areas to differentiate connectional characteristics belonging to other isocortical areas has recently been questioned in several experiments using heterotopic transplantation paradigms. The present study was designed to determine whether the principle of multipotentiality is still valid within one single isocortical region. Mediolateral bands of embryonic (E16) frontal neocortex were dissected out and grafted into the left frontal cortex of neonate hosts according to either correct or inverted mediolateral orientation. Five to six months after grafting, a retrograde tracer was injected into the dorsomedial or ventrolateral left neostriatum of the host. The mediolateral distribution of the cell labeling within the transplant was then compared to that of an equivalent frontal cortical area (ECA) in control cases. The results indicate that strips of embryonic frontal neocortex transplanted according to a correct mediolateral orientation are able to develop a projection towards the host striatum whose mediolateral topographical distribution is not significantly different from that arising from the frontal neocortex of control animals. The percentages of transplant cells labeled in the medial or lateral division of the grafts were not significantly different from those found medially or laterally in the ECA in control cases. Following inversion of the mediolateral orientation of the grafts at the time of transplantation, the percentages of cells labeled in the medial or lateral division of the grafts were nearly equal whatever the site of tracer deposit within the host neostriatum. These results indicate that even within one single neocortical region the principle of areal interchangeability is not entirely validated and that the development of neocortical efferents is not only guided by extrinsic factors.

Animals↗