Biomedical subjects

E Dubois

Publications and source records attributed to E Dubois.

At least 19 recordsLinked to original sources

PubMed2006

Diffusion of water in clays on the microscopic scale: modeling and experiment.

Diffusion of water in montmorillonite clays at low hydration has been studied on the microscopic scale by two quasi-elastic neutron scattering techniques, neutron spin-echo (NSE) and time-of-flight (TOF), and by classical microscopic simulation. Experiment and simulation are compared both directly on the level of intermediate scattering functions, I(Q, t), and indirectly on the level of relaxation times after a model of atomic motion is applied. Regarding the dynamics of water in Na- and Cs-monohydrated montmorillonite samples, the simulation and NSE results show a very good agreement, both indicating diffusion coefficients of the order of (1-3) x 10(-10) m(2) s(-1). The TOF technique significantly underestimates water relaxation times (therefore overestimates water dynamics), by a factor of up to 3 and 7 in the two systems, respectively, primarily due to insufficiently long correlation times being probed. In the case of the Na-bihydrated system, the TOF results are in closer agreement with the other two techniques (the techniques differ by a factor of 2-3 at most), giving diffusion coefficients of (5-10) x 10(-10) m(2) s(-1). Attention has been also paid to the elastic incoherent structure factor, EISF(Q). Simulation has played a key role in understanding the various contributions to EISF(Q) in clay systems and in clearly distinguishing the signatures of "apparent" and true confinement. Indirectly, simulation highlights the difficulty in interpreting the EISF(Q) signal from powder clay samples used in experiments.

Aluminum↗

PubMed2006

Transmission electron microscopy characterization of the erbium silicide formation process using a Pt/Er stack on a silicon-on-insulator substrate.

Very thin erbium silicide layers have been used as source and drain contacts to n-type Si in low Schottky barrier MOSFETs on silicon-on-insulator substrates. Erbium silicide is formed by a solid-state reaction between the metal and silicon during annealing. The influence of annealing temperature (450 degrees C, 525 degrees C and 600 degrees C) on the formation of an erbium silicide layer in the Pt/Er/Si/SiO(2)/Si structure was analysed by means of cross-sectional transmission electron microscopy. The Si grains/interlayer formed at the interface and the presence of Si grains within the Er-related layer constitute proof that Si reacts with Er in the presence of a Pt top layer in the temperature range 450-600 degrees C. The process of silicide formation in the Pt/Er/Si structure differs from that in the Er/Si structure. At 600 degrees C, the Pt top layer vanishes and a (Pt-Er)Si(x) system is formed.

Journal Article↗

PubMed2005

[Low-vision rehabilitation of age-related macular degeneration patients with retrofoveal choroidal new-vessels treated with photodynamic therapy with verteporfin].

PURPOSE: To demonstrate the rehabilitation benefit and immediate optical magnification and electronic equipment advantage in an age-related macular degeneration population with retrofoveal choroidal new-vessels treated by photodynamic therapy using Visudyne. PATIENTS AND METHODS: Sixty seven consecutive patients with retrofoveal choroidal new-vessels treated by Photodynamic Therapy using Visudyne were referred to an orthoptist for low-vision rehabilitation. The criteria investigated for this study were: long distance visual acuity, reading ability, contrast sensitivity, (before treatment and during post-treatment examinations), and fixation localization and optical equipment model. RESULTS: This study showed and studied visual acuity variations, mostly for patients with good visual acuity at inclusion. Contrast sensitivity stayed more or less the same. Retinal fixation was foveolar most of the time (68.7%). Optical or electronic devices for low-vision patients are numerous and video systems were the most currently used among our population. 62.7% des patients had low-vision rehabilitation with optic aids. DISCUSSION AND CONCLUSION: This study threw light on patient optic aids which must be prescribed according to his needs and difficulties, without delay. This equipment will then be readapted at each stage of the patient evolution. PDT treatment gives an important role to low-vision rehabilitation associated with optic magnification aids.

Aged↗

PubMed2004

[Prismatic treatment in low-vision rehabilitation of patients with age-related macular degeneration].

PURPOSE: To evaluate visual improvement in an age-related macular degeneration (ARMD) population with bilateral central scotomas, after a 3- to 6-month prismatic treatment. PATIENTS AND METHODS: Prisms prescribed for both eyes were oriented according to eccentric fixation. Criteria were visual acuity (VA), reading ability, contrast sensitivity subjective visual comfort, prism wearing frequency and autonomy level. RESULTS: Thirty-one patients (23 women, 8 men) 65-95 years old (mean, 78 years) were selected. Mean long distance VA remained stable (0.249 at inclusion and 0.261 after prismatic treatment); long distance VA was unchanged for 51.6% of patients, improved by at least one line for 35.5% and decreased for 12.9%. Reading ability was slightly improved (average of 1 line), as was short distance VA (P14 at inclusion, P12 after prismatic treatment); reading ability was unchanged for 45.2% of patients, improved by at least one line for 38.7%, and decreased for 16.1%. Contrast sensitivity was improved for all levels: to 98% of contrasts (mean at inclusion 0.248 and 0.280 after prismatic treatment), to 50% of contrasts (0.214 at inclusion and 0.238 after prismatic treatment) and to 25% of contrasts (0.157 at inclusion and 0.185 after prismatic treatment). Visual comfort improved immediately after prismatic treatment for 90.3% of patients; 80.6% of patients wore their prismatic correction regularly. DISCUSSION AND CONCLUSION: Prismatic treatment in this population mainly improves contrast sensitivity and visual comfort. It provides patients with better initiation and stabilization of their eccentric viewing. Most of the time, prismatic treatment must be associated with low-vision rehabilitation.

Aged↗

PubMed2003

Tuning the interactions of a magnetic colloidal suspension.

We present a versatile experimental system of magnetic charged nanospheres dispersed in water that belongs to both dipolar and electrostatic systems. In this system, the interactions can be continuously tuned by varying the ionic strength I. At low I, the potential is a strongly repulsive Yukawa potential that leads to a phase diagram similar to the one of repulsive spheres (fluid and solid phases). At high I, the potential is a globally attractive Lennard-Jones potential that leads to a phase diagram similar to the one of atomic systems (gas, liquid, fluid, and solid phases).

Journal Article↗

PubMed2002

Identification of bluetongue virus serotype 2 (Corsican strain) by reverse-transcriptase PCR reaction analysis of segment 2 of the genome.

In October 2000, bluetongue virus was detected on the French island of Corsica. The disease was also reported in Sardinia, Calabria, Sicily and on the Spanish islands of Majorca and Minorca. This paper describes the use of molecular techniques for a rapid identification and serotype determination of serotype 2 of the virus. The nucleotide sequences of segments 2 and 7 of the genome of the Corsican strain were determined and its phylogenetic relationships are described.

Animals↗

PubMed2002

Anisotropy of the structure factor of magnetic fluids under a field probed by small-angle neutron scattering.

Small-angle neutron scattering is used to measure the two-dimensional diffraction pattern of a monophasic magnetic colloid, under an applied magnetic field. This dipolar system presents in zero field a fluidlike structure. It is well characterized by an interaction parameter K(0)(T) proportional to the second virial coefficient, which is here positive, expressing a repulsion of characteristic length kappa-10. Under the field a strong anisotropy is observed at the lowest q vectors. The length kappa-10 remains isotropic, but the interaction parameter K(T) becomes anisotropic due to the long-range dipolar interaction. However, the system remains stable, the interaction being repulsive in all directions. Thus we do not observe any chaining of the nanoparticles under magnetic field. On the contrary, the revealed structure of our anisotropic colloid is a lowering of the concentration fluctuations along the field while the fluidlike structure, observed without field, is roughly preserved perpendicularly to the field. It expresses a strong anisotropy of the Brownian motion of the nanoparticles in the solution under applied field.

Journal Article↗

PubMed2002

[Value and practice of in-home "low-vision" rehabilitation in Rhone-Alp region of France].

INTRODUCTION: To demonstrate the interest of patient's home orthoptist deplacement to realize an in-home low-vision rehabilitation and encourage orthoptists to integrate this task in their usual work methods. PATIENTS AND METHODS: Eighty-five consecutive patients coming from a private ophthalmic rehabilitation Center and needing low-vision rehabilitation, were studied. The exercises used at patient's home were usually the same as those used in the rehabilitation Center. The choice in the organization of rehabilitation was always function of patient general health, people vicinity, and social context. RESULTS: Among the 85 patients, 60 (70.6%) were rehabilitated only in the ophthalmic Center, 11 (12.9%) could have a low-vision rehabilitation only thanks to the organization of the home's patient rehabilitation and 14 (16.5%) were both rehabilitated at the ophthalmic Center and, in the patient's home, some training was necessary too. The reasons for in-home low-vision rehabilitation were mainly represented by isolation problems, mobilisation physical capacities, but also, home installation conditions making difficult to realize the orthoptist recommendations. DISCUSSION: Besides some disadvantages: time-consuming, badly paid, decrease of efficiency in familiar environment, advantages are easily objected: ergonomy, training on optic systems, and psychological comfort. CONCLUSION: In-home low-vision rehabilitation is represented by the necessity of correctly taking care of each patient. It is an answer to a social demand and must be an integral part of low-vision orthoptist work.

Adult↗

PubMed2001

A methodological tool for computer-assisted surgery interface design: its application to computer-assisted pericardial puncture.

Computer Assisted Surgery systems are becoming more and more prevalent. Design processes currently used, pay only a small attention to the surgeon's interaction. To address this lack in design, we propose the OP-a-S notation: OP-a-S modeling of a system adopts an interaction-centered point of view and highlights the links between the real world and the virtual world. Based on an OP-a-S modeling, predictive usability analysis can be performed by considering the ergonomic property. We illustrate our method on the retro-design of a computer assisted surgical application, CASPER.

Computer Simulation↗

PubMed2000

Inositol polyphosphate kinase activity of Arg82/ArgRIII is not required for the regulation of the arginine metabolism in yeast.

Arg82, a nuclear regulator of diverse cellular processes in yeast, is an inositol polyphosphate kinase. Some defects such as the regulation of arginine metabolism observed in an arg82Delta, result from a lack of Mcm1 and Arg80 stability. We show here that neither the kinase activity of Arg82 nor inositol phosphates are required for the control of arginine metabolism. Arg82 mutations keeping kinase active affect the expression of arginine genes, whereas mutations in the kinase domain do not impair this metabolic control.

Arginine↗

PubMed2000

Computer-guided pericardiocentesis: experimental results and clinical perspectives.

Percutaneous pericardial puncture is a relatively safe and effective technique in case of large pericardial effusions when practiced under echographic or radiological control. The goal of our project is to improve the performance of this technique, mainly in case of smaller and loculated effusions using an accurate guidance towards a preplanned target, based on a model of the pericardial effusion. This paper presents preclinical results of this new computer-assisted technique used to reach the pericardial cavity. The procedure is divided into 3 steps: 1. acquisition of ultrasound data, using an echocardiographic device connected to a 3-D localizer and to a computer, 2. modeling procedure to define the optimal strategy taking into account the mobility of organs on a digital model, 3. guided puncture with a localized needle to reach the predefined target using a passive guidance system. After validation on a dynamic phantom and a feasibility study on dogs, an accuracy and reliability analysis protocol was realized on pigs with experimental pericardial effusion. Feasibility of the technique is demonstrated on animal study with an accuracy of at least 2.5 mm. Further clinical investigation is in progress using a more ergonomic and less cumbersome system. This study demonstrates the feasibility of computer-assisted pericardiocentesis. Beyond the simple improvement of the current technique, this could be a new way to reach the heart or a new tool for percutaneous access and image-guided puncture of soft tissues.

Animals↗

PubMed2000

Characterisation of a tripartite nuclear localisation sequence in the regulatory protein Lys14 of Saccharomyces cerevisiae.

The Lys14 regulatory protein of Saccharomyces cerevisiae activates the expression of the LYS genes involved in the lysine biosynthetic pathway. Studies with a fused Lys14-green fluorescent protein reveal that Lys14p is localised to the nucleus, even under growth conditions leading to the absence of LYS gene expression. Lys14p nuclear localisation is mediated by a tripartite sequence made up of three short basic motifs located on the C-terminal side of the Zn cluster domain of Lys14p. Substitution of basic residues by alanines in any of the three motifs partially prevents the nuclear import of the protein. Simultaneous mutations in the three basic domains are required to completely abolish the entry into the nucleus and to impair the Lys14 function.

Active Transport, Cell Nucleus↗

PubMed2000

Recruitment of the yeast MADS-box proteins, ArgRI and Mcm1 by the pleiotropic factor ArgRIII is required for their stability.

Regulation of arginine metabolism requires the integrity of four regulatory proteins, ArgRI, ArgRII, ArgRIII and Mcm1. To characterize further the interactions between the different proteins, we used the two-hybrid system, which showed that ArgRI and Mcm1 interact together, and with ArgRII and ArgRIII, without an arginine requirement. To define the interacting domains of ArgRI and Mcm1 with ArgRIII, we fused portions of ArgRI and Mcm1 to the DNA-binding domain of Gal4 (GBD) and created mutations in GBD-ArgRI and GBD-Mcm1. The putative alpha helix present in the MADS-box domain of ArgRI and Mcm1 is their major region of interaction with ArgRIII. Interactions between the two MADS-box proteins and ArgRIII were confirmed using affinity chromatography. The requirement for ArgRIII in the control of arginine metabolism can be bypassed in vitro as well as in vivo by overproducing ArgRI or Mcm1, which indicates that ArgRIII is not present in the protein complex formed with the 'arginine boxes'. We show that the impairment of arginine regulation in an argRIII deletant strain is a result of a lack of stability of ArgRI and Mcm1. A mutation in ArgRI, impairing its interaction with ArgRIII, leads to an unstable ArgRI protein in a wild-type strain. ArgRIII integrity is crucial for Mcm1 function, as shown by the marked decreased expression of five genes controlled by Mcm1. However, ArgRIII is likely to recruit other proteins in the yeast cell, as overexpression of Mcm1 does not compensate some physiological defects observed in an argRIII deletant strain.

Amino Acid Sequence↗

PubMed2000

Three-year study to assess human enteric viruses in shellfish.

The main pathogenic enteric viruses able to persist in the environment, such as hepatitis A virus (HAV), Norwalk-like virus (NLV), enterovirus (EV), rotavirus (RV), and astrovirus (AV), were detected by reverse transcription-PCR and hybridization in shellfish during a 3-year study. Oyster samples (n = 108), occasionally containing bacteria, were less frequently contaminated, showing positivity for AV (17%), NLV (23%), EV (19%), and RV (27%), whereas mussel samples, collected in areas routinely impacted by human sewage, were more highly contaminated: AV (50%), HAV (13%), NLV (35%), EV (45%), and RV (52%). Sequences obtained from HAV and NLV amplicons showed a great variety of strains, especially for NLV (strains close to Mexico, Snow Mountain Agent, or Norwalk virus). Viral contamination was mainly observed during winter months, although there were some seasonal differences among the viruses. This first study of virus detection over a fairly long period of time suggests that routine analysis of shellfish by a molecular technique is feasible.

Animals↗

PubMed2000

In Saccharomyces cerevisiae, expression of arginine catabolic genes CAR1 and CAR2 in response to exogenous nitrogen availability is mediated by the Ume6 (CargRI)-Sin3 (CargRII)-Rpd3 (CargRIII) complex.

The products of three genes named CARGRI, CARGRII, and CARGRIII were shown to repress the expression of CAR1 and CAR2 genes, involved in arginine catabolism. CARGRI is identical to UME6 and encodes a regulator of early meiotic genes. In this work we identify CARGRII as SIN3 and CARGRIII as RPD3. The associated gene products are components of a high-molecular-weight complex with histone deacetylase activity and are recruited by Ume6 to promoters containing a URS1 sequence. Sap30, another component of this complex, is also required to repress CAR1 expression. This histone deacetylase complex prevents the synthesis of the two arginine catabolic enzymes, arginase (CAR1) and ornithine transaminase (CAR2), as long as exogenous nitrogen is available. Upon nitrogen depletion, repression at URS1 is released and Ume6 interacts with ArgRI and ArgRII, two proteins involved in arginine-dependent activation of CAR1 and CAR2, leading to high levels of the two catabolic enzymes despite a low cytosolic arginine pool. Our data also show that the deletion of the UME6 gene impairs cell growth more strongly than the deletion of the SIN3 or RPD3 gene, especially in the Sigma1278b background.

Arginase↗

PubMed2000

ArgRII, a component of the ArgR-Mcm1 complex involved in the control of arginine metabolism in Saccharomyces cerevisiae, is the sensor of arginine.

Repression of arginine anabolic genes and induction of arginine catabolic genes are mediated by a three-component protein complex, interacting with specific DNA sequences in the presence of arginine. Although ArgRI and Mcm1, two MADS-box proteins, and ArgRII, a zinc cluster protein, contain putative DNA binding domains, alone they are unable to bind the arginine boxes in vitro. Using purified glutathione S-transferase fusion proteins, we demonstrate that ArgRI and ArgRII1-180 or Mcm1 and ArgRII1-180 are able to reconstitute an arginine-dependent binding activity in mobility shift analysis. Binding efficiency is enhanced when the three recombinant proteins are present simultaneously. At physiological concentration, the full-length ArgRII is required to fulfill its functions; however, when ArgRII is overexpressed, the first 180 amino acids are sufficient to interact with ArgRI, Mcm1, and arginine, leading to the formation of an ArgR-Mcm1-DNA complex. Several lines of evidence indicate that ArgRII is the sensor of the effector arginine and that the binding site of arginine would be the region downstream from the zinc cluster, sharing some identity with the arginine binding domain of bacterial arginine repressors.

Amino Acid Sequence↗

PubMed1999

In Saccharomyces cerevisae, feedback inhibition of homocitrate synthase isoenzymes by lysine modulates the activation of LYS gene expression by Lys14p.

Expression of the structural genes for lysine biosynthesis responds to an induction mechanism mediated by the transcriptional activator Lys14p in the presence of alpha-aminoadipate semialdehyde (alphaAASA), an intermediate of the pathway acting as a coinducer. This activation is reduced by the presence of lysine in the growth medium, leading to apparent repression. In this report we demonstrate that Saccharomyces cerevisiae possesses two genes, LYS20 and LYS21, encoding two homocitrate synthase isoenzymes which are located in the nucleus. Each isoform is inhibited by lysine with a different sensitivity. Lysine-overproducing mutants were isolated as resistant to aminoethylcysteine, a toxic lysine analog. Mutations, LYS20fbr and LYS21fbr, are allelic to LYS20 and LYS21, and lead to desensitization of homocitrate synthase activity towards lysine and to a loss of apparent repression by this amino acid. There is a fair correlation between the I0.5 of homocitrate synthase for lysine, the intracellular lysine pool and the levels of Lys enzymes, confirming the importance of the activity control of the first step of the pathway for the expression of LYS genes. The data are consistent with the conclusion that inhibition by lysine of Lys14p activation results from the control of alphaAASA production through the feedback inhibition of homocitrate synthase activity.

2-Aminoadipic Acid↗

PubMed1998

A nonameric core sequence is required upstream of the LYS genes of Saccharomyces cerevisiae for Lys14p-mediated activation and apparent repression by lysine.

The expression of the structural genes for lysine (LYS) biosynthesis is controlled by a pathway-specific regulation mediated by the transcriptional activator Lys14 in the presence of alpha-aminoadipate semialdehyde, an intermediate of the pathway acting as a co-inducer. Owing to end product inhibition of the first step of the pathway, excess lysine reduces the production of the co-inducer and causes apparent repression of the LYS genes. Analysis of LYS promoters and insertions within an heterologous reporter gene have allowed the characterization of an upstream activating element (UASLYS) able to confer Lys14- and alpha-amino-adipate semialdehyde-dependent activation as well as apparent repression by lysine to another yeast gene. This DNA motif is present as one of several copies in the promoters of at least six LYS genes. The consensus sequence derived from the comparison of the UASLYS showing the highest activation capacities comprises the nonameric core sequence TCCRNYGGA. The RNY sequence of the 3 bp spacer as well as the presence of flanking AT-rich regions on both sides of the core sequence appear essential for optimal activation. Further evidence that this element is the target of Lys14p was provided by the demonstration that Lys14p binds to UASLYS in vitro. The binding is independent of the presence of the co-inducer and is not affected by lysine. It depends on the integrity of the putative Zn(II)2Cys6 binuclear cluster contained in the Lys14p.

Artificial Gene Fusion↗