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Dominique Durand

Publications and source records attributed to Dominique Durand.

At least 19 recordsLinked to original sources
PubMed2006

Are liquid crystalline properties of nucleosomes involved in chromosome structure and dynamics?

Nucleosome core particles correspond to the structural units of eukaryotic chromatin. They are charged colloids, 101 Angstrom in diameter and 55 Angstrom in length, formed by the coiling of a 146/147 bp DNA fragment (50 nm) around the histone protein octamer. Solutions of these particles can be concentrated, under osmotic pressure, up to the concentrations found in the nuclei of living cells. In the presence of monovalent cations (Na(+)), nucleosomes self-assemble into crystalline or liquid crystalline phases. A lamello-columnar phase is observed at 'low salt' concentrations, while a two-dimensional hexagonal phase and a three-dimensional quasi-hexagonal phase form at 'high salt' concentrations. We followed the formation of these phases from the dilute isotropic solutions to the ordered phases by combining cryoelectron microscopy and X-ray diffraction analyses. The phase diagram is presented as a function of the monovalent salt concentration and applied osmotic pressure. An alternative method to condense nucleosomes is to induce their aggregation upon addition of divalent or multivalent cations (Mg(2+), spermidine(3+) and spermine(4+)). Ordered phases are also found in the aggregates. We also discuss whether these condensed phases of nucleosomes may be relevant from a biological point of view.

Animals↗
PubMed2006

Coupling between polysaccharide gelation and micro-phase separation of globular protein clusters.

The effect of gelation of the polysaccharide phase on the phase separation was investigated for mixtures of anionic polysaccharide (kappa-carrageenan) and globular protein (beta-lactoglobulin) clusters at pH 7 well above the iso-electric point. Gelation of kappa-carrageenan was induced by cooling in the presence of KCl. In the liquid state the protein clusters phase-separate into relatively dense micro-domains. When the polysaccharide phase gelled during cooling, the turbidity of the systems decreased dramatically. Light scattering experiments showed that the density of the micro-domains decreased, while microscopy showed that the number and size was not strongly modified. It is concluded that smaller protein clusters leave the micro-domains when kappa-carrageenan gels. The effect could be reversed by reheating the samples and thus melting the gel and was observed for repeated heating and cooling cycles. The effect of gelation on phase separation decreases with increasing polysaccharide concentration and with ageing of the liquid mixture. The latter is caused by the formation of bonds between the protein clusters in the micro-domains that slowly reinforce with time.

Carrageenan↗
PubMed2006

Small-angle X-ray scattering reveals an extended organization for the autoinhibitory resting state of the p47(phox) modular protein.

In response to microbial infection, neutrophiles promote the assembly of the NADPH oxidase complex in order to produce superoxide anions. This reaction is activated by the association of cytosolic factors, p47(phox), p67(phox), p40(phox), and a small G protein Rac with the membranous heterodimeric flavocytochrome b(558), composed of gp91(phox) and p22(phox). In the activation process, p47(phox) plays a central role as the target of phosphorylations and as a scaffolding protein conducting the translocation and assembly of cytosolic factors onto the membranous components. The PX and tandem SH3s of p47(phox) have been highlighted as being key determinants for the interaction with membrane lipids and the p22(phox) component, respectively. In the resting state, the two corresponding interfaces are thought to be masked allowing its cytoplasmic localization. However, the resting state modular organization of p47(phox) and its autoinhibition mode are still not fully understood despite available structural information on separate modules. More precisely, it raises the question of the mutual arrangement of the PX domain and the tandem SH3 domains in the resting state. To address this question, we have engaged a study of the entire p47(phox) molecule in solution using small-angle X-ray scattering. Despite internal autoinhibitory interactions, p47(phox) adopts an extended conformation. First insights about the domain arrangement in whole p47(phox) can be derived. Our data allow to discard the usual representation of a globular and compact autoinhibited resting state.

Amino Acid Sequence↗
PubMed2006

Effect of the cluster size on the micro phase separation in mixtures of beta-lactoglobulin clusters and kappa-carrageenan.

The phase separation of globular protein clusters formed by heat-denatured beta-lactoglobulin (beta-lg) in mixtures with the polysaccharide kappa-carrageenan (kappa-car) has been studied at pH 7 and 20 degrees C. The effect of the protein cluster size on the phase separation was investigated by preparing clusters with radii between 20 nm and 1 mum. The formation of protein rich microdomains led to an increase of the turbidity starting at a minimum kappa-car concentration that decreased with increasing cluster size, but was only weakly dependent on the protein concentration. The size and number of microdomains do not depend much on the cluster size, but their density decreases with increasing cluster size leading to a lower turbidity.

Carrageenan↗
PubMed2006

[Laparoscopic live donor nephrectomy: surgical technique and results].

OBJECTIVE: To report the results of laparoscopic live donor nephrectomy (LLDN) and to describe our technique. MATERIAL AND METHODS: We retrospectively reviewed 47 laparoscopic live donor nephrectomies performed between January 1999 and July 2005. Several parameters were studied: donor clinical characteristics, intraoperative and postoperative complications, operating time and warm ischaemia time. This series comprised 26 women (55.31%) and 21 men (44.68%) with a mean age of 48 +/- 20 years. Donor nephrectomy was mainly performed on the left kidney (85.37%). It was performed by lumbar endoscopy in the first 20 cases and by laparoscopy in 27 cases. Kidney extraction was performed via an incision between two trocar orifices for the first cases and via an iliac incision for the last 18 cases. RESULTS: The mean operating time was 189 min with a mean blood loss of 127 ml. Warm ischemia time was 6 minutes. Open conversion was required in two cases: renal vein injury in one case and an obese donor with difficulties of dissection in the other case. Surgical revision was required in only one case (haemoperitoneum secondary to genital vein injury). A trocar orifice abscess was observed in one case and prolonged ileus was reported in 2 cases. In the recipient, a urinary anastomotic fistula was observed secondary to ischaemic necrosis of the distal segment of the ureter. Late complications were essentially vascular (19.14%). A right renal graft was lost due to an error of compatibility. Mean serum creatinine was 132 +/- 6.5 micromol/l at 3 months for the other recipients. CONCLUSION: Our experience confirms the feasibility and efficacy of laparoscopic live donor nephrectomy. Intraoperative and postoperative complications and the conversion rate were low. Renal function was rapidly restored in the recipient. The morbidity of this technique is low, but there is a high risk of vascular complications at the beginning of the operator's experience.

Female↗
PubMed2006

Effects of intraoperative versus postoperative administration of rabbit antithymocyte antibodies on 1-year renal function in renal transplant patients.

OBJECTIVES: The aim of our study was to prospectively assess 1-year allograft outcomes and the evolution of lymphocyte subsets in a group of renal transplant patients who had received intraoperative rabbit antithymocyte antibodies (RATG). MATERIALS AND METHODS: We compared 1-year allograft transplant outcomes in renal transplant recipients who had received intraoperative RATG (group 1, n=53) with the outcomes observed in patients in a historical control group who had received postoperative RATG (group 2, n=49). RATG were given at the same dosage (1 mg/kg) during the first 3 days, and then the dosage was adapted according to CD2 count, until calcineurin inhibitors were started. RESULTS: The overall dosage of RATG administered was significantly lower in group 1. At day 4, CD2, CD3, and CD19 T-cell subset counts were significantly higher in patients in group 1. From 3 months after transplantation, CD4/CD8 ratios were significantly lower in patients in group 1 because of a rapid regeneration of CD8 T cells. One-year total lymphocyte counts were significantly higher in patients in group 1. There were fewer severe infectious complications in patients in group 1. One-year renal function was better in patients in group 2. Donor age was the only independent factor associated with renal function at both 1 month and 1 year after transplantation. CONCLUSIONS: When RATG are infused intraoperatively, a lower total amount of RATG is required to prevent acute rejection as compared with postoperative RATG infusion. Consequently, fewer serious lymphopenia-associated complications are observed during the first year after transplantation.

Adult↗
PubMed2005

Rituximab therapy for de novo mixed cryoglobulinemia in renal transplant patients.

BACKGROUND: Type II or III cryoglobulins are fairly prevalent in renal-transplant (RT) patients, and are often related to chronic hepatitis C virus (HCV) infection. However, they rarely result in graft dysfunction. They are sustained by proliferation of oligoclonal B-cells. Systemic B-cell depletion and clinical remission of the systemic effects of cryoglobulins have been achieved in HCV-positive immunocompetent patients with a human/mouse chimeric monoclonal antibody that specifically reacts with the CD20 antigen (i.e., rituximab). Thus, this provides the rationale to use rituximab for cryoglobulin-related graft dysfunction in RT patients. METHODS: Three RT patients, of whom one was HCV-positive, developed renal-function impairment long after transplantation, as well as de novo nephrotic syndrome (n=2) and severe hypertension (n=2). This latter case was related to type III cryoglobulinemia and was associated with membranoproliferative glomerulonephritis. In addition to their baseline standard immunosuppression, the patients were given weekly rituximab infusions of 375 mg/m (two infusions in patient and four infusions for the other two cases). RESULTS: This treatment resulted in a dramatic improvement in renal parameters, particularly in a sustained remittence of nephrotic syndrome, a sustained clearance of cryoglobulins in two cases, but also in severe infectious complications in two cases. CONCLUSION: We conclude that rituximab therapy is highly effective in cryoglobulin-related renal dysfunction in RT patients; however, due to chronic immunosuppression, this is at the expense of infectious complications.

Antibodies, Monoclonal↗
PubMed2005

Characterization of the initial stages of SBA-15 synthesis by in situ time-resolved small-angle X-ray scattering.

The initial stages of SBA-15 synthesis have been studied by using in situ time-resolved small-angle X-ray scattering with a synchrotron radiation source. The quantitative analysis of X-ray scattering and diffraction intensities allows the structures of intermediates to be identified at the different stages of SBA-15 synthesis. Following tetraethylorthosilicate (TEOS) addition, an intense small-angle scattering and an associated secondary maximum are observed, which are attributed to non-interacting surfactant template micelles encrusted with silicate species. After 25-30 min of the reaction, the broad scattering disappears and narrow Bragg diffraction peaks typical of hexagonally ordered structure are observed. The cylindrical micelles identified from X-ray scattering data appear to be the direct precursors of 2D hexagonal SBA-15 structure. Just after the formation of the SBA-15 hexagonal phase, the cylindrical micelles are only weakly linked in the hexagonal structure. As the synthesis proceeds, the solvent in the void volume between the cylindrical micelles is gradually replaced by more dense silicate species. The unit cell parameter of SBA-15 is progressively decreasing during the SBA-15 synthesis, which can be related to the condensation and densification of silicate fragments in the spaces between the cylinders. The volume fraction of the 2D hexagonally ordered phase is sharply growing during the first 2 h of the reaction. The inner core radius of SBA-15 material remains almost constant during the whole synthesis and is principally affected by the size of the poly(propylene oxide) inner core in the original cylindrical micelles.

Computational Biology↗
PubMed2005

[The evolution of the hypervariable region-1 of hepatitis C virus may predict liver fibrosis outcome after renal transplantation].

The aim of our study was to assess hepatitis C virus (HCV) evolution and long term liver histology outcome in anti-HCV(+)/RNA(+) renal-transplant (RT) patients. Fifty-five anti-HCV(+)/RNA(+) RT patients underwent every 3-4 years after transplantation liver biopsies (LB) (2 LBs, N = 55; 3 LBs, N = 44; 4 LBs, N = 10). The hypervariable region (HVR)-1 of the HCV genome from all patients was characterized over time. Overall, the rate of liver fibrosis progression was 0.07 +/- 0.03 Metavir units/year. We identified three groups of patients: those in whom liver fibrosis remained stable (group I, N = 21), those with progressing liver fibrosis (group II, N = 21), and those with a regression in liver fibrosis (group III, N = 13). Initial fibrosis stage and high diversification of the HVR-1 of HCV genome between the transplantation and the first liver biopsy were independent factors associated with liver fibrosis regression. In conclusion, in this study, after renal transplantation, HCV infection is not harmful upon liver histology in more than fifty percent of the patients. The diversification of the HVR-1 of the HCV genome might be used to predict liver fibrosis outcome.

Adult↗
PubMed2005

Predictive factors of anemia within the first year post renal transplant.

BACKGROUND: The aim of our study was to identify the independent factors that might predict anemia at 6 (M6) and 12 (M12) months posttransplantation. METHODS: Postrenal transplant anemia (PTA) was defined as having a hemoglobin (Hb) level below 13 g/dl for men and below 12 g/dL for women. In this study, we included all the recipients who received a renal transplant in 2001 at our department, and for whom the graft was still functioning 1 year later (n=92). RESULTS: Anemia was observed in 78%, 35.5% and 25% of patients at day (D)0 and at M6 and M12, respectively. Iron deficiency was found in 14% of patients at D0 and in 13% of patients at M12. A total of 59.8% of patients had received at least one blood transfusion in the postoperative period, whereas 41.3% of patients had received recombinant erythropoietin (rEpo) therapy within the first months posttransplantation. In multivariate analysis, the independent predictive factors of anemia at M6 were Epo level at D0, initial nephropathy (polycystic kidney disease vs. others), posttransplantation rEpo therapy, hematocrit at M3, platelets at D7, and sirolimus therapy. The independent predictive factors of anemia at M12 were Epo level at D0, platelets at D7, delayed graft function (DGF), creatinine clearance at M12, serum creatinine at M12, and Hb level at M6. CONCLUSIONS: The prevalence of PTA was 25% at M12. DGF, renal function at M12, and anemia at M6 were independent risk factors for still having anemia at M12.

Anemia↗
PubMed2005

Strain hardening and fracture of heat-set fractal globular protein gels.

Non-linear mechanical behavior at large shear deformation was been investigated for heat-set beta-lactoglobulin gels at pH 7 and 0.1 M NaCl using both oscillatory shear and shear flow. These gels have a self-similar structure at length scales smaller than the correlation length of the gel with fractal dimension d(f)=2. Strain hardening is observed that can be well described using the model proposed by Gisler et al. [T.C. Gisler, R.C. Ball, D.A. Weitz, Phys. Rev. Let. 82 (1999) 1064] for fractal colloidal gels. The increase of the shear modulus normalized by the low strain value (G(0)) is independent of G(0). For weak gels the elasticity increases up to a factor of ten, while for strong gels the increase is very small. At higher deformation irreversible fracture occurs, which leads eventually to macroscopic failure of the gel. For weak gels formed at low concentrations the deformation at failure is about 2, independent of the shear modulus. For strong gels fracture occurs at approximately constant stress (2 x 10(3) Pa).

Fractals↗
PubMed2005

Questionnaire-based evaluation of gastrointestinal disorders in de novo renal-transplant patients receiving either mycophenolate mofetil or enteric-coated mycophenolate sodium.

BACKGROUND: Gastrointestinal (GI) disorders are one of the main adverse events in patients treated by mycophenolic acid (MPA). The aim of our prospective questionnaire-based study was to assess GI side-effects in de novo renal-transplant patients receiving either mycophenolate mofetil (MMF) or enteric-coated mycophenolate sodium (EC-MPS). METHODS: Between January 2002 and April 2003, all patients receiving MPA with a functioning allograft at 1 month post-transplantation were enrolled in this study (n = 130). Ninety-three of them received MMF (group I), and 37 patients received EC-MPS (group II). Each month, every patient completed a questionnaire regarding GI disorders. RESULTS: During the first year post-transplantation, GI disorders occurred in 31 patients from the MMF group (33.3%) and 12 patients from the EC-MPS group (32.4%) (not significant). The incidence of upper GI disorders was also similar in both groups. Diarrhoea was observed in 18 patients (19.3%) from group I, and in five patients from group II (13.5%) (not significant). Its frequency and severity were similar in both groups. Weight loss was observed in three patients receiving MMF. Diarrhoea resolved spontaneously in 10 patients from group I and in all patients from group II. For the other eight patients in group I, the diarrhoea required MMF discontinuation in three patients and dose reduction in five patients. CONCLUSIONS: In conclusion, in this questionnaire-based evaluation, the incidence of GI disorders was similar in patients receiving either MMF or EC-MPS during the first year post-transplantation.

Adult↗
PubMed2005

Dynamic mechanical properties of suspensions of micellar casein particles.

Small micellar casein particles, so-called submicelles, were obtained by removing colloidal calcium phosphate from native casein by adding sodium polyphosphate. Aqueous submicelle suspensions were characterized using light scattering and rheology as a function of concentration and temperature. The casein submicelles behave like soft spheres that jam at a critical concentration (C(c)) of about 100 g L(-1). The viscosity does not diverge at C(c), but increases sharply, similarly to that of multiarm star polymers. C(c) increases weakly with increasing temperature, which leads to a strong decrease of the viscosity close to and above C(c). Concentrated submicelle suspensions show strong shear-thinning above a critical shear rate and the shear stress becomes independent of the shear rate. The critical shear rates at different temperatures and concentrations are inversely proportional to the zero-shear viscosity. At much higher shear rates, the shear stress fluctuates strongly in time indicating inhomogeneous flow. The frequency dependence of casein submicelle suspensions is characterized by elastic behavior at high frequencies (concentrations) and viscous behavior at low frequencies (concentrations).

Calcium Phosphates↗
PubMed2005

Aggregation and gelation of micellar casein particles.

Micellar casein particles (submicelles) are formed by removing calcium phosphate from native casein. The submicelles aggregate and eventually form a gel with a rate that increases strongly with increasing temperature and casein concentration. At low casein concentrations the gel is very weak and collapses under its own weight so that a precipitate is formed. The structure of the aggregates is studied using light scattering and cryo-electron microscopy. It is found that the aggregates have a self-similar structure with fractal dimension 2. The viscoelastic properties of the gel are studied by frequency scans of the loss and storage moduli during the gelation process. The bonds between the submicelles probably involve calcium phosphate complexes.

Calcium Phosphates↗
PubMed2005

Long-term results in renal transplant patients with allograft dysfunction after switching from calcineurin inhibitors to sirolimus.

BACKGROUND: Switching from calcineurin inhibitors (CNIs) to sirolimus might improve renal function in chronic renal transplant patients. METHODS: In a prospective study, we assessed long-term efficacy and safety parameters in 43 renal transplant recipients who were switched from a CNI (cyclosporin A, 65%; and tacrolimus, 35%) to sirolimus for either chronic allograft dysfunction (n = 38) or recurrent cutaneous cancers (n = 5). A kidney biopsy was done in 79% of patients prior to conversion, and showed either chronic allograft nephropathy (n = 26) or CNI nephrotoxicity (n = 7). Conversion was either abrupt or progressive, with CNI withdrawal over 3 weeks. All patients also received steroids with or without mycophenolate mofetil or azathioprin. Patient data were recorded at baseline (D0), at 1 (D30) and 6 months (D180), and at 1, 1.5 and 2 years post-conversion. RESULTS: After a mean post-conversion follow-up of 27+/-1.5 months, 58% of the patients were still on sirolimus. The survival of intent to treat patients and grafts was 95.3 and 93%, respectively. Overall, there was significant improvement in renal function, creatinine clearance increasing from 49.4+/-14.9 to 53+/-16.3 ml/min at D30 (P = 0.01), and to 54.7+/-20 ml/min at D180 (P = 0.01). Thereafter, creatinine clearance was not different from baseline, i.e. 54.7+/-21.7, 52.8+/-20 and 51.7+/-20.3 ml/min at years 1, 1.5 and 2, respectively. We divided the patients into two groups: responders (n = 29), those with an increase in creatinine clearance at 6 months post-conversion compared with D0, and non-responders (n = 14), those with a decrease in creatinine clearance at 6 months post-conversion compared with D0. In univariate analysis, factors predictive of response included proteinuria at D0 and the magnitudes of the differences between D30 and D0 for serum creatinine and lactate dehydrogenase. The conversion was associated with (i) significant decreases in serum calcium, phosphorus and uric acid, and in haemoglobin levels; (ii) significant increases in serum alkaline phosphatase, total cholesterol, parathyroid hormone, and the number of patients on statin and recombinant erythropoietin therapies; and (iii) the appearance of de novo proteinuria of >1 g/day in 28% of patients (P < 0.0009), which was >2 g/day in 12% of the entire cohort. Kidney biopsies in 17 patients 2 years after conversion showed the same Banff scores as observed at baseline. We identified three independent predictive factors for a renal response to the switch: absence of proteinuria, presence of antihypertensive therapy at D0 and serum lactate dehydrogenase level at D30. CONCLUSION: Conversion from CNIs to sirolimus in renal transplant patients with chronic allograft nephropathy was associated with improved renal function; however, 33% of the patients developed overt proteinuria.

Biopsy↗
PubMed2005

Factors accelerating liver fibrosis progression in renal transplant patients receiving ribavirin monotherapy for chronic hepatitis C.

In untreated hepatitis virus (HCV)-positive renal transplant patients, the rate of liver fibrosis progression is low. In contrast, in those treated by ribavirin monotherapy, liver fibrosis score increased significantly after only 1 year of ribavirin monotherapy. The aim of this study was to identify the factors that might contribute to accelerate liver fibrosis progression in this population. Eleven patients were included in the study. Intrahepatic transforming growth factor (TGF)-beta, interferon (IFN)-gamma, and interleukin (IL)-10 mRNA quantification determined by real-time reverse transcription-polymerase chain reaction (RT-PCR) were similar before and after ribavirin therapy. The number of amino acid substitutions observed in the hypervariable region (HVR)-1 of the HCV genome between baseline and 1 year after ribavirin monotherapy was low, i.e., 3 (1-11) amino acid substitutions, suggesting the absence of a high selection pressure induced by ribavirin. In contrast, due to ribavirin-induced hemolysis, there was a significant increase in serum ferritin levels (P = 0.02) and in intrahepatic iron deposition (P = 0.04). Transferrin level and total iron-binding capacity decreased significantly during ribavirin monotherapy (P = 0.004). The increased liver fibrosis observed in renal transplant patients receiving ribavirin monotherapy could be related to ribavirin-induced anemia. Severe chronic hemolysis is responsible for iron overload, liver iron deposition, and an acceleration in the progression of liver fibrosis.

Adult↗
PubMed2005

Intrahepatic cytokine profile in renal-transplant patients infected by hepatitis C virus.

In order to examine the immunopathogenesis of hepatitis C virus (HCV)-related liver injury in renal-transplant patients, intra-hepatic cytokine profiles were examined in 38 liver biopsies from 38 patients by measuring messenger RNA (mRNA) concentrations by a real-time PCR method of a Th1 cytokine (i.e., interferon (IFN)-gamma), a Th2 cytokines (i.e., interleukine (IL)-10), a proinflammatory cytokine (i.e., IL-8), and a potent fibrogenic factor (transforming growth factor [TGF]-beta). There was no significant difference in TGF-beta, IFN-gamma, IL-10, or IL-8 levels of expression according to liver-activity grade, liver-fibrosis stage, the concentration of HCV RNA at liver biopsies, or the HCV genotype. However, IFN-gamma/beta-actin mRNA concentration was higher than the IL-10/beta-actin mRNA concentration in patients with F3 Metavir score. Median IFN-gamma/beta-actin mRNA concentration tended to be higher in patients with A3 and A4 Metavir activity grades compared with those with A0 and A1 activity grades. There was a significant correlation between the duration of HCV infection and both TGF-beta/beta-actin (r(2)=0.19, P=0.04) and IL-8/beta-actin mRNA concentrations (r(2)=0.19, P=0.03). IFN-gamma/beta-actin mRNA concentration also increased according to the duration of HCV (r(2)=0.19, P=0.07). Finally, there was a significant correlation between the duration of HCV infection and liver fibrosis stage (r(2)=0.17, P=0.045). Intrahepatic Th1 cytokine profile seems to be predominant in patients with extensive fibrosis and activity scores, suggesting that it might be responsible for liver injury in renal transplant patients.

Adult↗