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P Dubois

Publications and source records attributed to P Dubois.

At least 19 recordsLinked to original sources
PubMed2006

[Tissue resistance: what about tension-free?].

OBJECTIVES: The purpose is to quantify objective tissue resistances before healing of prostheses used in pelvic floor surgery. PATIENTS AND METHODS: We measured tissue resistances offered to five types of meshes by four classical surgical routes. We also tested the incidence of the modification of the width of meshes on tissue resistance. This study was realized on frozen cadavers, by pull on prostheses just after implantation. Tests are realized with a dynamometer and results obtained in Newton. RESULTS: In the Retzius space, TVT offers a better resistance than IVS or LIFT meshes. We did not bring to the fore a significant difference between four routes for 1 cm wide prosthesis. The increase of width of Prolene meshes improves their resistance in tissues and thus quality of their fixation. We underscore a better resistance of the trans sacrospinous route with regard to the trans muscular one. DISCUSSION AND CONCLUSION: The increase of resistance is bound to the increase of the contact area between the prosthesis and the tissues. This increase of resistance should be taken into account in prolapse surgery: constraints are stronger than for stress incontinence. The posterior arms of meshes have to measure more than 1 cm wide and be set up through the sacrospinous ligament rather than through the elevator muscles. The type of knitting of prostheses is important and influences the resistance in tissues in the immediate postoperative time. Manufacturers should be interested in conceiving specific meshes for the tension-free fixation, with special and adapted mechanical properties.

Cadaver↗
PubMed2006

Controlled synthesis and interface properties of new amphiphilic PCL-g-PEO copolymers.

Novel biodegradable and biocompatible poly(epsilon-caprolactone)-graft-poly(ethylene oxide), PCL-g-PEO, copolymers consisting of biocompatible blocks have been synthesized by ring-opening copolymerization of epsilon-caprolactone (epsilon CL) and a poly(ethylene oxide) (PEO) macromonomer, i.e., PEO end-capped by an epsilon-caprolactone unit (gamma PEO.CL). The control is effective on the composition and length of both the hydrophobic polyester backbone and the hydrophilic PEO grafts. The reactivity ratios have been determined by monitoring the copolymer composition in relation to the comonomer conversion. The PCL-g-PEO copolymers have a tapered (gradient) rather than a random structure consistent with r(epsilon)CL = 3.95 and r(gamma)PEO.CL = 0.05. The amphiphilic graft copolymers display surfactant properties similar to those of PEO-b-PCL diblock copolymers of comparable composition and solubility, as supported by CHCl3/water interfacial tension measured by the pendant drop method.

Hydrophobic and Hydrophilic Interactions↗
PubMed2006

Influence of DNA condensation state on transfection efficiency in DNA/polymer complexes: an AFM and DLS comparative study.

Atomic force microscopy (AFM) is used to describe the formation process of polymer/DNA complexes. Two main objectives of this research are presented. The first one is to apply AFM as an effective tool to analyse DNA molecules and different polycation/DNA complexes in order to evaluate their degree of condensation (size and shape). The other one is to search for a relationship between the condensation state of DNA and its transfection efficiency. In this study, linear methacrylate based polymers and globular SuperFect polymers are used in order to induce DNA condensation. Ternary complexes, composed of methacrylate based polymers and polyethylene glycol (PEG)-based copolymers, are also investigated. AFM allows us to confirm good condensation conditions and relate them (or not) to transfection efficiencies. These AFM results (obtained after drying in air) are compared with measurements deduced from Dynamic Light Scattering (DLS) experiments performed in water. This comparison allowed us to identify the structural modifications resulting from deposition on the mica surface.

Animals↗
PubMed2005

Development and characterization of sub-micron poly(D,L-lactide-co-glycolide) particles loaded with magnetite/maghemite nanoparticles.

PURPOSE: The objective of this study is to develop biodegradable sub-micron poly(lactide-co-glycolide) particles loaded with magnetite/maghemite nanoparticles for intravenous drug targeting. METHOD: Sub-micron magnetite/PLGA particles (also called composite nanoparticles) were prepared by a modified double emulsion method (w/o/w) or by an emulsion-evaporation process (o/w). To optimize the composite nanoparticles formulation, the influence of some experimental parameters, such as types of magnetite/maghemite nanoparticles, volume of magnetite suspension and amount of polymer were investigated. The morphology, size and zeta potential of the magnetite/PLGA nanoparticles were determined. The magnetite entrapment efficiency and magnetite content were assessed by dosing iron in the composite nanoparticles. RESULTS: TEM photomicrographs showed that the composite nanoparticles were almost spherical in shape with a rather monomodal distribution in size. All composite nanoparticle formulations were found to have the mean diameter within the range of 268-327 nm with polydispersity index within the range of 0.02-0.15. Magnetite nanoparticles coated with oleic acid showed more efficient entrapment (60%) as compared to uncoated magnetite nanoparticles (48%). In both cases, when the volume of magnetite suspension increased, the magnetite entrapment efficiency decreased but the magnetite content increased. In addition, the two-fold rise in the amount of polymer did not significantly affect the composite nanoparticle characteristics except the magnetite content. Finally, none modification of the mean diameter of the composite nanoparticles was observed after storage for 3 months at 4 degrees C. CONCLUSIONS: Magnetite/PLGA nanoparticles were prepared and the influence of some process parameters have been assessed. Improvement of the magnetite entrapment efficiency are in progress and the magnetization properties of the composite nanoparticles will subsequently be tested.

Adsorption↗
PubMed2005

Echinoderm reactive oxygen species (ROS) production measured by peroxidase, luminol-enhanced chemiluminescence (PLCL) as an immunotoxicological tool.

The importance of reactive oxygen species (ROS) production in invertebrate immunity prompted the use of this response in immunotoxicological studies in several taxa including marine organisms. In this chapter, we review the effects of environmental factors and contaminants such as heavy metals and polychlorinated biphenyls (PCBs) on the production of ROS by the main immune effector cells of echinoderms, the so-called amoebocytes. ROS production was measured by the peroxidase, luminol-enhanced chemiluminescence (PLCL) method. This method was found to predominantly reflect the production of superoxide anions and peroxides, among which hydrogen peroxide and peroxynitrite are the main species detected. Exogenous factors such as water temperature and salinity can influence this immune response in echinoderms. However, gender, handling stress and parasitism by a castrating ciliate apparently did not affect it. The impact of metals on ROS production differed greatly according to the duration and routes of exposure; in vitro and short-term in vivo exposures to metals caused an inhibition of this immune response, while the opposite effect was observed in a long-term in vivo exposure study. On the other hand, PCBs systematically had a stimulatory effect on ROS production independent of the echinoderm species or exposure routes. From the study of complex field contaminations, it appeared that contaminants released in the environment, such as metals, modulate starfish amoebocyte ROS production. This impact potentially represents a threat to the sustainability of natural populations of echinoderms and thereby to the stability of benthic ecosystems.

Allergy and Immunology↗
PubMed2004

What can the operator actually feel when performing a laparoscopy?

The designing of a laparoscopic simulator, particularly the parameterizing of a force feedback system, has drawn attention to the question of characterizing laparoscopic gestures and effecting quantitative measurement of the various interactions between the organs and the instruments used to operate in the case of animals. These measurements use an instrument previously developed by the authors' team. Laparoscopic gestures are characterized by a visual component and a haptic component. The visual component cannot, of course, be disregarded. The amplitude of the forces generated by interaction between organ and instrument in relation to that of the forces linked with other mechanical phenomena interfering with somesthesic information, such as friction of the operative instrument in the trocar or resistance of the abdominal wall to tilting movement, has led to a discussion about the extent of haptic components involved in the performance of laparoscopic gestures. After describing the measurement's device and the different forces applied on the surgical instrument, the authors describe the measurement of the rubbing strengths caused by the slippage of the instrument in the trocar and one of the elastic torques induced by the abdominal wall when the trocar in slanted. Comparison of values with those obtained during interactions with various organs shows that during some delicate surgical gestures, the influence of the instrument can disturb the haptic sensation. Interference of haptic sensation is greatest at maximal tilting angles and at maximal velocity of insertion and removal movement.

Animals↗
PubMed2004

Relationship between computed tomographic image analysis and histomorphometry for microarchitectural characterization of human calcaneus.

The present study aimed to characterize the relationships between several variables reflecting bone microarchitecture assessed by both computed tomographic (CT) image analysis and histomorphometry (conventional CT system) at the calcaneus. A total of 24 cadaveric specimens were studied. The mean age at death was 78 +/- 10 years (range, 53-93 years). A total of 15 sagittal sections (1 mm in width and spaced 2 mm apart) were selected for CT analysis; 6 undecalcified sections (7 microm) were analyzed for histomorphometry. The histomorphometric analysis was performed on a Leica Quantimet Q570 image analyzer. Features measured by both methods were: bone volume/tissue volume (BV/TV), trabecular thickness (Tb.Th), trabecular separation (Tb.Sp), trabecular number (Tb.N), interconnectivity index (ICI), number of nodes (N Nd), number of terminus (N Tm), node-to-node strut count (NNS), node-to-terminus strut count (NTS), terminus-to-terminus strut count (TTS), marrow space star volume (SV), Euler number (EN), and fractal dimension (FD). The coefficient of correlations' values (simple linear regression) between histomorphometry and CT image analysis varied according to the parameters selected. R values were high for BV/TV, Tb.N, and Tb.Sp (range, 0.69-0.90; P < 0.01). R values were less significant for some variables also obtained from the binary image: SV (0.5, P < 0.05) and EN (0.43, P < 0.05). Finally R values were also significant for (two) variables obtained from skeletonized images, i.e., N Nd (0.4, P < 0.05) and N Tm (0.61, P < 0.01). Other correlations were not statistically significant. Moreover, for some variables the relationships between the two methods (CT analysis and histomorphometry) seemed best-described by using nonlinear models. For example, a logarithmic model was more appropriate for SV (r = 0.71, P < 0.01), N Nd (r = 0.52, P < 0.01). Finally the relationship between apparent (App) N Tm and N Tm was most satisfying when using an exponential model (r = 0.64, P < 0.01). In conclusion, trabecular bone structure measures determined on CT images show highly significant correlations with those determined using histomorphometry. The level of correlation varies according to the type of method used for characterizing bone structure, however, and the strongest correlations were found for the most basic features (Parfitt's parameters). Finally, for some variables, nonlinear models seem more appropriate.

Absorptiometry, Photon↗
PubMed2004

[Effect of laparoscopic trocar model on the quality of the movement: experimental study of friction].

OBJECTIVE: To keep the pneumoperitoneum and the tightness of the abdominal and pelvic cavity during a laparoscopy, the sheaths of trocar are provided with a device (valvule, membranes etc.) inducing a friction during the handling of the instrument. The objective of this article is to analyse friction from different types of trocar's port. MATERIALS AND METHODS: We present here the experimental results obtained during a testing bench of three different trocar sheaths. The mechanism of tightness of the first trocar sheath is made of a fine membrane associated to a valve, of a thick membrane for the second trocar sheath, whereas the third trocar sheath is made of two membranes, a fine and a thick, associated to a valve. After reporting the experimental device and the analytic model adopted to describe the relationship between the measured physical parameters, we lay out our results. The identification of parameters of this model makes it possible to objectively compare the three trocars. RESULTS: Our results revealed that, under experimental conditions, the amplitude of friction was significantly lower with trocar's port provided with a valve and a fine membrane than with both other ports (fivefold weaker). DISCUSSION AND CONCLUSION: We evoke the importance of the possible disruption brought by these frictions while referring these values to those of other measurements concerning interactions between instrument and organs. These different behaviours of the material could have some consequences in choosing the tools for the performance of precise gestures.

Laparoscopy↗
PubMed2003

Does quantitative ultrasound of bone reflect more bone mineral density than bone microarchitecture?

Relationships among quantitative ultrasound of bone (QUS), bone mineral density (BMD) and bone microarchitecture have been poorly investigated in human calcaneus.Twenty-four specimens, from 12 men and 12 women (mean age 78 +/- 10 years; range 53-93), removed from cadavers were studied. The feet were axially sectioned above the ankle. Two variables were measured for QUS (Achilles, Lunar): broadband ultrasound attenuation (BUA) and speed of sound (SOS). A third variable, the stiffness index (SI), which is a combination of both BUA and SOS, was also calculated. BMD (a lateral view) was measured on a QDR 2000 densitometer (Hologic). Bone microarchitecture was assessed by computed tomography (CT) using a conventional CT-system. Fifteen sagittal sections (1 mm in width and 2 mm apart) were selected for CT. Methods used for characterizing bone microarchitecture consisted in structural (trabecular network characterization) and a fractal analyses. The relationships between QUS and bone microarchitecture were assessed by simple linear regression analysis with and without adjustment for BMD (partial correlation) and by backward stepwise regression analysis. Strong relationships were found between BMD and QUS. Adjusted r(2) values were 0.545 for SOS and 0.717 for SI. Two microarchitectural variables were also significantly correlated with both SOS and SI: apparent trabecular separation (App Tr Sp) and trabecular bone pattern factor (App TBPF). After adjustment for BMD few correlations between QUS and microarchitectural variables were always significant. Adjusted squared semipartial coefficients of correlation (rsp2) values between SOS and bone microarchitecture were 6%, 6.8%, 13.2% and 4.6% for App BV/TV, App Tr Sp, App TBPF and fractal dimension (FD), respectively. For SI, corresponding figures were 3.7%, 4.1%, 5.2% and 3.2%. Backward stepwise regression analysis using BMD and microarchitecture showed a slight increase of r(2) values that varied from 8.4% for SI to 17.8% for SOS, compared with BMD alone. The current study suggests that although BMD is a major determinant of acoustic properties of human calcaneus, significant density independent relationships with bone microarchitecture should also be taken into account.

Aged↗
PubMed2002

Computed tomography image analysis of the calcaneus in male osteoporosis.

The present study aimed to characterize bone microarchitecture assessed by computed tomography (CT) at the calcaneus in male subjects suffering from osteoporosis. Seventy-nine subjects were assessed (45 with osteoporosis and 34 control subjects matched for age). Osteoporosis was defined according to the World Health Organization classification either at the lumbar spine or at the femoral neck. Thirty-three subjects (73%) had a past history of low-energy fracture mainly represented by vertebral fractures (24/33). Nine axial sections (1 mm in width and 2 mm apart) were selected for each subject. Bone microarchitecture analysis was performed using structural (binary and skeletonized images but also skeletonization from gray levels) and fractal analyses. Bone densitometry by dual-energy X-ray absorptiometry (DXA) at the calcaneus was also performed in 73 cases. Bone mineral density (BMD) was decreased in osteoporotic patients compared with controls both at the lumbar spine and hip and also at the calcaneus (p<0.01). Also 14 microarchitectural features among 25 measured were significantly different between the two groups (p<0.01). The odds ratio for fracture per 1 control group standard deviation decrease were also significant for 13 structural features but also for BMD at the calcaneus. The odds ratios after adjustment for BMD at the calcaneus were significant for the following features (p<0.05): number of valleys, 2.8 (1.2-6.9); trabecular partition, 3.3 (1.3-7.9); apparent trabecular spacing, 1.8 (1.0-3.1); trabecular bone pattern factor, 2.2 (1.1-4.3); Euler number, 3.0 (1.1-8.7); node-to-terminus strut count, 3.3 (1.4-7.8); terminus-to-terminus strut count, 2.9 (1.2-6.9); and fractal dimension, 3.7 (1.5-9.7). Few and weak correlations were found between BMD at the calcaneus measured with DXA and features obtained from CT, suggesting that these two methods give different information about bone status. In conclusion, male osteoporosis is a disease characterized by decreased bone mass but also by microarchitectural deterioration of bone tissue which is partly independent of BMD.

Absorptiometry, Photon↗
PubMed2001

Regeneration of spines and pedicellariae in echinoderms: a review.

Morphogenesis of tissues during regeneration of echinoderm spines and pedicellariae is reviewed. Regeneration of the skeleton is rather well documented while that of associated soft tissues is poorly investigated. In particular, little information is available on the early regeneration stages which follow wound healing. From the available information, it is suggested that regeneration of broken spines proceeds through a morphallactic process of which the organizational information, as well as the involved cells, lies in the stump. In contrast, regeneration of removed spines and pedicellariae may depend on an epimorphic process whose organizational information could be located in the mutable connective tissue that joins the appendage to the main body wall.

Animals↗
PubMed2001

Proteins and saccharides of the sea urchin organic matrix of mineralization: characterization and localization in the spine skeleton.

Properties of the echinoderm skeleton are under biological control, which is exerted in part by the organic matrix embedded in the mineralized part of the skeleton. This organic matrix consists of proteins and glycoproteins whose carbohydrate component is specifically involved in the control mechanisms. The saccharide moiety of the organic matrix of the spines of the echinoid Paracentrotus lividus was characterized using enzyme-linked lectin assays (ELLAs). O-glycoproteins, different types of complex N-glycoproteins, and terminal sialic acids were detected. Sialic acids are known to interact with Ca ions and could play an important role in the mineralization process. Some of the carbohydrate components detected by ELLAs as well as two organic matrix proteins (SM30 and SM50) were localized within different subregions of the spine skeleton using field-emission scanning electron microscopy. The mappings show that some of these components are not homogeneously distributed in the different skeletal subregions. For example, some N-glycoproteins were preferentially located in the putative amorphous subregion of the skeleton, whereas some O-glycoproteins were localized in the subregion where skeletal growth is inhibited. These results suggest that the biological control exerted on the skeletal properties can be partly modulated by local differences in the organic matrix composition.

Animals↗
PubMed2001

Effects of PCBs on reactive oxygen species (ROS) production by the immune cells of Paracentrotus lividus (Echinodermata).

The impact of four PCB congeners: 3,3',4,4'-tetrachlorobiphenyl (IUPAC congener #77), 3,3',4,4',5-pentachlorobiphenyl (IUPAC #126), 2,2',4,4',5,5'-hexachlorobiphenyl (IUPAC #153) and 3,3',4,4',5,5'-hexachlorobiphenyl (IUPAC #169) was investigated on the reactive oxygen species (ROS) production by coelomocytes of the echinoid Paracentrotus lividus, an important species in marine benthic ecosystems. PCBs were found to increase ROS production and to delay the time of peak production. These effects were stronger on bacteria-stimulated cells and were congener-specific: coplanar congeners (#77, 126 and 169) had more effect than the non-coplanar PCB #153. Among coplanar congeners, PCB #169 showed dose-dependent effects whereas PCB #77 and 126 were more toxic at high and low doses, respectively. The relative immunotoxicity of the different PCB congeners is discussed in the light of their structural properties and biological affinities.

Animals↗
PubMed2001

Mechanisms and kinetics of thermal degradation of poly(epsilon-caprolactone).

Thermogravimetric analysis (TGA) simultaneously coupled with mass spectrometry (MS) and Fourier transform infrared spectrometry (FTIR) was developed as an original technique to study the thermal modification/degradation of poly(epsilon-caprolactone) (PCL) through in depth analysis of the evolved gas. Perfectly well-defined PCL samples with controlled end groups, predictable molecular weight, and narrow molecular weight distribution were synthesized by living "coordination-insertion" ring-opening polymerization of epsilon-caprolactone initiated by aluminum triisopropoxide. TGA analyses carried out on purified PCL samples, deprived from any residual catalyst or monomer, highlighted a two-step thermal degradation. Evolved gas analysis by both MS and FTIR showed that the first process implies a statistical rupture of the polyester chains via ester pyrolysis reaction. The produced gases were identified as H(2)O, CO(2), and 5-hexenoic acid. The second step leads to the formation of epsilon-caprolactone (cyclic monomer) as result of an unzipping depolymerization process. The influence of parameters such as polyester molecular weight, nature of the PCL end groups, and presence of catalytic residues as well as the type of purge gas were investigated. The activation energy of the thermal degradation was also studied.

Chromatography, Gel↗
PubMed2001

Cold-adapted beta-galactosidase from the Antarctic psychrophile Pseudoalteromonas haloplanktis.

The beta-galactosidase from the Antarctic gram-negative bacterium Pseudoalteromonas haloplanktis TAE 79 was purified to homogeneity. The nucleotide sequence and the NH(2)-terminal amino acid sequence of the purified enzyme indicate that the beta-galactosidase subunit is composed of 1,038 amino acids with a calculated M(r) of 118,068. This beta-galactosidase shares structural properties with Escherichia coli beta-galactosidase (comparable subunit mass, 51% amino sequence identity, conservation of amino acid residues involved in catalysis, similar optimal pH value, and requirement for divalent metal ions) but is characterized by a higher catalytic efficiency on synthetic and natural substrates and by a shift of apparent optimum activity toward low temperatures and lower thermal stability. The enzyme also differs by a higher pI (7.8) and by specific thermodynamic activation parameters. P. haloplanktis beta-galactosidase was expressed in E. coli, and the recombinant enzyme displays properties identical to those of the wild-type enzyme. Heat-induced unfolding monitored by intrinsic fluorescence spectroscopy showed lower melting point values for both P. haloplanktis wild-type and recombinant beta-galactosidase compared to the mesophilic enzyme. Assays of lactose hydrolysis in milk demonstrate that P. haloplanktis beta-galactosidase can outperform the current commercial beta-galactosidase from Kluyveromyces marxianus var. lactis, suggesting that the cold-adapted beta-galactosidase could be used to hydrolyze lactose in dairy products processed in refrigerated plants.

Adaptation, Physiological↗
PubMed2001

[Right ventricular migration of a stent after endovascular treatment of a superior vena cava syndrome].

The authors report a case of migration of a Palmaz stent used for treatment of a patient with a malignant superior vena caval syndrome. Transoesophageal echocardiography showed the metallic device in the tricuspid subvalvular apparatus. Several attempts to recover the stent percutaneously failed. This case illustrates a rare but serious complication of endovascular stenting: migration of the material. Although it is often possible to reposition the stent by radiological interventional techniques, when the stent is located in the right ventricle, the procedure is more difficult and usually fails. Transoesophageal echocardiography enables accurate localisation of the material with respect to the surrounding cardiac structures, especially the tricuspid valve.

Adult↗
PubMed2000

Ultrastructure of sea urchin calcified tissues after high-pressure freezing and freeze substitution.

The improvements brought by high-pressure freezing/freeze substitution fixation methods to the ultrastructural preservation of echinoderm mineralized tissues are investigated in developing pedicellariae and teeth of the echinoid Paracentrotus lividus. Three freeze substitution (FS) protocols were tested: one in the presence of osmium tetroxide, one in the presence of uranyl acetate, and the last in the presence of gallic acid. FS in the presence of osmium tetroxide significantly improved cell ultrastructure preservation and should especially be used for ultrastructural studies involving vesicles and the Golgi apparatus. With all protocols, multivesicular bodies, suggested to contain Ca(2+), were evident for the first time in skeleton-forming cells. FS in the presence of gallic acid allowed us to confirm the structured and insoluble character of a part of the organic matrix of mineralization in the calcification sites of the tooth, an observation which modifies the current understanding of biomineralization control in echinoderms.

Animals↗