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Biomedical subjects

Philippe Dubois

Publications and source records attributed to Philippe Dubois.

At least 19 recordsLinked to original sources
PubMed2006

Ionic liquid droplet as e-microreactor.

A powerful approach combining a droplet-based, open digital microfluidic lab-on-a-chip using task-specific ionic liquids as soluble supports to perform solution-phase synthesis is reported as a new tool for chemical applications. The negligible volatility of ionic liquids enables their use as stable droplet reactors on a chip surface under air. The concept was validated with different ionic liquids and with a multicomponent reaction. Indeed, we showed that different ionic liquids can be moved by electrowetting on dielectric (EWOD), and their displacement was compared with aqueous solutions. Furthermore, we showed that mixing ionic liquids droplets, each containing a different reagent, in "open" systems is an efficient way of carrying supported organic synthesis. This was applied to Grieco's tetrahydroquinolines synthesis with different reagents. Analysis of the final product was performed off-line and on-line, and the results were compared with those obtained in a conventional reaction flask. This technology opens the way to easy synthesis of minute amounts of compounds ad libitum without the use of complex, expensive, and bulky robots and allows complete automation of the process for embedded chemistry in a portable device. It offers several advantages, including simplicity of use, flexibility, and scalability, and appears to be complementary to conventional microfluidic lab-on-a-chip devices usually based on continuous-flow in microchannels.

Ions↗
PubMed2006

Polyethylene organo-clay nanocomposites: the role of the interface chemistry on the extent of clay intercalation/exfoliation.

High density polyethylene (HDPE)/clay nanocomposites have been prepared using three different functionalized polyethylene compatibilizers: an ethylene/vinyl acetate copolymer, a polyethylene grafted with maleic anhydride functions and a (styrene-b-ethylene/butylene-b-styrene) block copolymer. The nanocomposites were prepared via two different routes: (1) the dispersion in HDPE of a masterbatch prepared from the compatibilizer and the clay or (2) the direct melt blending of the three components. For each compatibilizer, essentially intercalated nanocomposites were formed as determined by X-ray diffraction and transmission electron microscopy. With the ethylene/vinyl acetate copolymer, a significant delamination of the intercalated clay in thin stacks was observed. This dispersion of thin intercalated stacks within the polymer matrix allowed increasing significantly the stiffness and the flame resistance of the nanocomposite. A positive effect of shear rate and blending time has also been put into evidence, especially for the process based on the masterbatch preparation, improving both the formation of thin stacks of intercalated clay and the mechanical properties and the flame resistance of the formed nanocomposites.

Aluminum Silicates↗
PubMed2005

Polystyrene-supported organotin dichloride as a recyclable catalyst in lactone ring-opening polymerization: assessment and catalysis monitoring by high-resolution magic-angle-spinning NMR spectroscopy.

Dialkyltin dichloride grafted to a cross-linked polystyrene, with the formula [P-H]((1-t))[P-(CH2)nSnBuCl2]t (P=[CH2CH(pC6H4)], t=the degree of functionalization, and n=6 or 11), is investigated as a recyclable catalyst in the ring-opening polymerization (ROP) of epsilon-caprolactone (CL). It is demonstrated that high-resolution magic-angle-spinning (HR-MAS) NMR spectroscopy is an invaluable tool to characterize completely the supported catalyst. The 2D 1H-13C HSQC HR-MAS spectrum, in particular, allowed extensive assignment of the 1H and 13C resonances, as well as accurate measurement of the (n)J((1)H-(117/119)Sn) and (n)J((13)C-(117/119)Sn) coupling constants. 1H and 119Sn HR-MAS NMR spectroscopy is presented as a monitoring tool for catalytic processes based on organotin compounds, particularly for the investigation of the extent to which polymerization residues are observable in situ in the material pores and for the assessment of the chemical integrity and recycling conditions of the grafted catalyst. From polymerization experiments with CL, initiated by n-propanol and with [P-H]((1-t))[P-(CH2)nSnBuCl2]t of various compositions as the supported catalyst, it appears that a partial 'burst' of the polystyrene support occurs when the length of the alkyl spacer is limited to n=6, as a result of polymer chains growing within the pores of the support. However, extension of the length of the aliphatic polymethylene spacer from 6 to 11 carbon atoms preserves the support integrity and allows the production of catalyst-deprived poly(epsilon-caprolactone) (PCL) oligomers. A preliminary attempt to recycle the heterogeneous catalyst has shown that very good reproducibility can be obtained, in terms of both catalyst activity and molecular-weight parameters of the as-recovered PCL polyester chains.

Journal Article↗
PubMed2005

Self-nucleation and crystallization kinetics of double crystalline poly(p-dioxanone)-b-poly(epsilon-caprolactone) diblock copolymers.

The crystallization kinetics of each constituent of poly(p-dioxanone)-b-poly(epsilon-caprolactone) diblock copolymers (PPDX-b-PCL) has been determined in a wide composition range by differential scanning calorimetry and compared to that of the equivalent homopolymers. Spherulitic growth rates were also measured by polarized optical microscopy while atomic force microscopy was employed to reveal the morphology of one selected diblock copolymer. It was found that crystallization drives structure formation and both components form lamellae within mixed spherulitic superstructures. The overall isothermal crystallization kinetics of the PPDX block at high temperatures, where the PCL is molten, was determined by accelerating the kinetics through a previous self-nucleation procedure. The application of the Lauritzen and Hoffman theory to overall growth rate data yielded successful results for PPDX and the diblock copolymers. The theory was applied to isothermal overall crystallization of previously self-nucleated PPDX (where growth should be the dominant factor if self-nucleation was effective) and the energetic parameters obtained were perfectly matched with those obtained from spherulitic growth rate data of neat PPDX. A quantitative estimate of the increase in the energy barrier for crystallization of the PPDX block, caused by the covalently bonded molten PCL as compared to homo-PPDX, was thus determined. This energy increase can dramatically reduce the crystallization rate of the PPDX block as compared to homo-PPDX. In the case of the PCL block, both the crystallization kinetics and the self-nucleation results indicate that the PPDX is able to nucleate the PCL within the copolymers and heterogeneous nucleation is always present regardless of composition. Finally, preliminary results on hydrolytic degradation showed that the presence of relatively small amounts of PCL within PPDX-b-PCL copolymers substantially retards hydrolytic degradation of the material in comparison to homo-PPDX. This increased resistance to hydrolysis is a complex function of composition and its knowledge may allow future prediction of the lifetime of the material for biomedical applications.

Journal Article↗
PubMed2005

Structure of sediment-associated microbial communities along a heavy-metal contamination gradient in the marine environment.

Microbial community composition and structure were characterized in marine sediments contaminated for >80 years with cadmium, copper, lead, and zinc. Four sampling sites that encompass a wide range of sediment metal loads were compared in a Norwegian fjord (Sorfjord). HCl-extractable metals and organic matter constantly decreased from the most contaminated site (S1) to the control site (S4). All sampling sites presented low polychlorinated biphenyl (PCB) concentrations (Sigma(7)PCB < 7.0 ng g [dry weight](-1)). The biomass ranged from 4.3 x 10(8) to 13.4 x 10(8) cells g (dry weight) of sediments(-1) and was not correlated to metal levels. Denaturing gradient gel electrophoresis indicated that diversity was not affected by the contamination. The majority of the partial 16S rRNA sequences obtained were classified in the gamma- and delta-Proteobacteria and in the Cytophaga-Flexibacter-Bacteroides (CFB) bacteria. Some sequences were closely related to other sequences from polluted marine sediments. The abundances of seven phylogenetic groups were determined by using fluorescent in situ hybridization (FISH). FISH was impaired in S1 by high levels of autofluorescing particles. For S2 to S4, the results indicated that the HCl-extractable Cu, Pb, and Zn were negatively correlated with the abundance of gamma-Proteobacteria and CFB bacteria. delta-Proteobacteria were not correlated with HCl-extractable metals. Bacteria of the Desulfosarcina-Desulfococcus group were detected in every site and represented 6 to 14% of the DAPI (4',6'-diamidino-2-phenylindole) counts. Although factors other than metals may explain the distribution observed, the information presented here may be useful in predicting long-term effects of heavy-metal contamination in the marine environment.

Colony Count, Microbial↗
PubMed2004

Contrasting effects of coplanar versus non-coplanar PCB congeners on immunomodulation and CYP1A levels (determined using an adapted ELISA method) in the common sea star Asterias rubens L.

Biological effects of two structurally contrasting PCB congeners (coplanar 77 and non coplanar 153) were investigated by measuring the induction of CYP1A immunopositive protein (CYP1A IPP) in the pyloric caeca and the production of reactive oxygen species (ROS) by amoebocytes in the common sea star Asterias rubens. CYP1A IPP was quantified using a specially designed ELISA which uses competitive binding between sea stars and trout CYP1A IPPs. Only the coplanar congener had a significant effect on the two considered biological responses. Intensity of the effects was dose-dependent. However, the highest dose of PCB 77 induced a dramatic decrease of ROS production. It is concluded that coplanar PCBs straightforwardly affect key biological processes such as the immune system and mixed-function oxidase (MFO) system.

Animals↗
PubMed2004

Controlled polymer grafting on single clay nanoplatelets.

We report on the controlled chemical grafting of well-defined polymer chains onto individual montmorillonite-type clay nanoplatelets and the direct visualization of the formed hybrid material at the nanoscale level. Our approach is based on the use of a surfactant mixture that contains varying proportions of hydroxyl-substituted alkylammonium and unsubstituted alkylammonium cations to exchange the initial Na(+) counterions of the natural montmorillonite. This allows for the exchange of Na(+) by a tunable amount of hydroxyl functions at the surface of the clays. Those functions are then derivatized into aluminum alkoxides in order to initiate the ring-opening polymerization of epsilon-caprolactone directly from the clay surface that was swollen in an organic solvent. Atomic force microscopy measurements on the resulting polymer-grafted nanoplatelets demonstrate the strong dependence of the coating of the individual clay particles with the composition of the surfactant mixture used for the cationic exchange. This allows for the generation of a range of morphologies varying from polymer islands distributed over the clay surface to homogeneous polymer layers thoroughly coating the platelets. Finally, the control that is achievable over the synthesis of this new family of organic-inorganic nanohybrid materials has been extended to the surface grafting of semicrystalline poly(epsilon-caprolactone)-poly(lactic acid) diblock copolymers with defined compositions.

Journal Article↗
PubMed2004

Enhancement of transfection efficiency through rapid and noncovalent post-PEGylation of poly(dimethylaminoethyl methacrylate)/DNA complexes.

PURPOSE: The aim of this work was to develop a new strategy to introduce poly(ethylene glycol) (PEG) into methacrylate-based polymer/ DNA complexes in order to produce hemocompatible particles able to transfect cells in the presence of serum. METHODS: Atom transfer radical polymerization was used to synthesize a well-defined poly(2-(dimethylamino)ethyl methacrylate) homopolymer (PDMAEMA) and a poly(2-(dimethylamino)ethyl methacrylate-b-poly(ethylene glycol) alpha-methyl ether, omega-methacrylate) palm-tree-like copolymer (P(DMAEMA-b-MAPEG)). The complexes obtained by self assembly of the pCMVbeta plasmid and the polymers were used to transfect Cos-7 cells. Their physical properties--particle size and zeta potential--were characterized respectively by dynamic light scattering and electrophoretic mobility measurements. Ex vivo hemocompatibility was also determined. RESULTS: The PDMAEMA/pCMVbeta complexes transfected Cos-7 cells exclusively in the absence of serum. Although the P(DMAEMA-bMAPEG) copolymer had no transfection activity per se, the addition of the latter to pre-formed PDMAEMA/DNA complexes significantly enhanced the activity and allowed transfection even in the presence of serum. The presence of palm-tree-like copolymers also improved the hemocompatibility properties of the complexes. No effect on platelet counts was observed for P(DMAEMA-b-MAPEG)/pCMVbeta complexes, whereas a decrease of platelets was clearly observed when blood cells were incubated with PDMAEMA/pCMVbeta complexes. CONCLUSIONS: Such a synergistic effect of noncovalent PEGylation of poly(amino methacrylate)/DNA complexes allows a new and versatile approach to tune up transfection efficiency.

Animals↗
PubMed2003

Mechanistic study of Bu2SnCl2-mediated ring-opening polymerization of epsilon-caprolactone by multinuclear NMR spectroscopy.

The ring-opening polymerization (ROP) of epsilon-caprolactone (CL) was carried out in toluene at 100 degrees C with n-propanol (nPrOH) in the presence of Bu(2)SnCl(2). It comes out that the molar mass of the polyester chains can be predicted from the initial monomer-to-alcohol molar ratio in accordance with a controlled ROP mechanism involving an O-acyl cleavage of the monomer to selectively form (alpha-propyloxy)(omega-hydroxy)poly(epsilon-caprolactone) chains. In order to gain fundamental understanding of the mechanistic factors governing the polyester chain growth, advanced (1)H, (13)C, and (119)Sn NMR investigations were performed in situ in [D(8)]toluene, as well as with model solutions that contained Bu(2)SnCl(2) and binary mixtures of the components at various concentrations and temperatures. This has enabled us to propose a mechanism in which Bu(2)SnCl(2) behaves as a catalyst, while nPrOH is the actual initiator. It involves non-aggregated, six-coordinate Bu(2)SnCl(2) complexes in which ligands exchange fast on the (119)Sn NMR observational timescale, and the simultaneous interactions of CL and alcohol function in such a way that it favors insertion/propagation reactions over transesterification ones, up to high monomer conversion.

Journal Article↗
PubMed2003

Correction of uterine prolapse by the vaginal route using the uterosacral ligaments: Shirodkar procedure.

OBJECTIVE: To study long-term results of Shirodkar procedure for treatment of uterine prolapse in women wishing to retain their uterus. STUDY DESIGN: Fifty-one patients with a symptomatic uterine prolapse who desire to preserve their uterus without further childbearing were treated between 1988 and 2000. By the vaginal route, uterosacral ligaments were separated from the uterus, shortened, transposed in front of the uterine isthmus, and fixed bilaterally under the opposite lateral surface of the cervix or of the cervical stump after amputation. RESULTS: Median age of patients was 37 years. Median operating time was 120 min (range 60-190). One patient was re-operated four days after the initial surgery to drain a haematoma. Median follow-up was 81 months (range 11-134). Eight patients were lost of follow-up. Eleven (25.6%) patients underwent iterative surgery. The indication for re-operation was recurrence of prolapse in four patients, introital dyspareunia in three patients, cervix stenosis in two patients, urinary incontinence in one patient and pyosalpinx in one patient. Only one patient (2.3%) experienced a recurrence of the uterine prolapse. CONCLUSION: Shirodkar procedure is safe and effective. Long-term functional results are satisfactory but associated procedures may alter patient satisfaction.

Adult↗
PubMed2003

Solvent-free synthesis and purification of poly[2-(dimethylamino)ethyl methacrylate] by atom transfer radical polymerization.

Solvent-free synthesis of well-defined poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) (co)polymers was performed by atom transfer radical polymerization conducted under very mild conditions (in bulk at 25 degrees C). The pH-dependence and the thermo-responsive behaviour of PDMAEMA in aqueous solution were operated to isolate and purify the (co)polymers without using any organic solvent or further catalyst extraction. The viscosity in aqueous solution of so-purified PDMAEMA homopolymers and their block copolymers with poly(ethylene glycol) (PEG) was studied as a function of molar mass and concentration and a typical polyelectrolyte behaviour was observed, these catalyst-deprived polycations are able to form stable and non toxic complexes with DNA, showing good transfection efficacies in gene therapy.

Journal Article↗
PubMed2003

Frozen section examination of the endocervical margin of cervical conization specimens.

OBJECTIVE: We conducted this retrospective study to determine accuracy of frozen section examination of endocervical margin during cold knife conization. METHODS: Between June 1993 and June 2001, 310 consecutive patients underwent cervical conization for squamous intraepithelial lesion or stage IA1 cervical cancer. Before 1997, the surgical specimens of 149 patients were processed following a standard pathological procedure (historical group). After 1997, a frozen section of the upper endocervical margin was processed during surgery for 161 patients. If the upper endocervical margin was involved with intraepithelial neoplasia, the surgeon performed a second resection if possible. Results of the frozen section examination were compared with the final diagnoses to determine sensitivity, specificity, and positive and negative predictive values. The usefulness of this procedure was evaluated by comparison of positive margin status rate with the one of the historical control group. RESULTS: For the diagnosis of intraepithelial neoplasia involving the endocervical margin, the sensitivity, specificity, and positive and negative predictive values of frozen section were 91%, 100%, 100%, and 98%, respectively. Eleven patients had definitive positive endocervical margin in the frozen section group (three false negatives, six patients without additional resection, and two patients with intraepithelial neoplasia involving the upper margin of the additional resection) and 17 patients in the historical group (P =.16). CONCLUSION: Frozen section examination of the endocervical margin of cervical specimen obtained during cold knife conization is highly accurate. Its clinical relevance has to be demonstrated in a multicenter study.

Adult↗
PubMed2003

Inguinofemoral dissection for carcinoma of the vulva: effect of modifications of extent and technique on morbidity and survival.

BACKGROUND: The aim of this study was to evaluate the impact of modifications of extent (medial inguinal and medial femoral lymphadenectomy, inguinal lymphadenectomy, inguinal and medial femoral lymphadenectomy, and inguinofemoral lymphadenectomy) and surgical technique of lymphadenectomy (including sartorius transposition, preservation of the fascia lata, and preservation of the saphenous vein) on morbidity, groin recurrence, and survival in patients with vulvar carcinoma. STUDY DESIGN: A retrospective review of 194 patients with primary squamous cell cancer of the vulva was conducted. Clinical, surgical, histopathologic, postoperative short- and longterm complications, and followup data were collected from patient records. RESULTS: Inguinal lymphadenectomy and medial inguinal and medial femoral lymphadenectomy produced about half fewer nodes than did other surgical procedures. On the other hand, number of lymph nodes removed did not differ notably between inguinofemoral lymphadenectomy and inguinal and medial femoral lymphadenectomy. Logistic regression showed that obesity was associated with increased risk of cellulitis. Age greater than 70, obesity, and extent of lymphadenectomy increased wound breakdown risk. Factors associated with leg edema persisting for more than 6 months were: extent of lymphadenectomy, sartorius transposition, and adjuvant irradiation of groin area. With a mean followup time of 38 months, neither groin recurrence rate nor disease-specific survival markedly differed according to technique of lymphadenectomy. CONCLUSION: Techniques of lymphadenectomy with preservation of fascia lata and saphenous vein are associated with a decreased risk of postoperative morbidity without jeopardizing outcomes.

Age Factors↗
PubMed2003

Field contamination of the starfish Asterias rubens by metals. Part 1: Short- and long-term accumulation along a pollution gradient.

The accumulation of Cd, Pb, Zn, and Cu in the starfish Asterias rubens was studied in a Norwegian fjord characterized by a gradient of metal pollution in the sediments, ranging from very high metal concentrations at its head to much lower levels at its opening. The concentrations of metals in starfish from natural populations along the gradient (long-term accumulation) and in starfish that were transferred up the gradient (short-term accumulation) were compared. At long-term, Cd and Pb accumulations by starfish living at normal salinity (30/1000) were related to the level of contamination of the environment while Cu and, to a lesser extent, Zn accumulations appeared strictly controlled. At short-term, Pb was accumulated steadily, Cd and Zn were accumulated transiently in the pyloric caeca (fast compartment), and Cu was not accumulated at all. Depuration experiments (transfer down the gradient) showed that Cd and Pb were efficiently eliminated from the pyloric caeca but not from the body wall (slow compartment). It is concluded that Pb is chronically accumulated, without apparent control, Cd is subjected to a regulating mechanism in the pyloric caeca which is overwhelmed over the long-term; Zn is tightly controlled in the pyloric caeca and Cu in both pyloric caeca and body wall. A distinct color variety of starfish is restricted to the low salinity (22-26/1000) superficial water layer. This variety showed a different pattern of metal accumulation over the long-term. This pattern is attributed to the particular hydrological conditions prevailing in this upper layer.

Animals↗
PubMed2003

Field contamination of the starfish Asterias rubens by metals. Part 2: Effects on cellular immunity.

To study the effects of metals on starfish in field conditions, immune responses were measured in starfish from natural populations along a metal pollution gradient (long-term contamination) and in starfish that were transferred up the gradient (short-term contamination). Coelomic amoebocyte concentration (CAC) and production of reactive oxygen species (ROS) by amoebocytes were measured in two varieties of Asterias rubens occurring in the fjord: The black variety which lives only in the low salinity upper waters (22-26/1000) and the red variety which live both in the upper layer and in the deeper layer characterized by a salinity close to that of seawater (30/1000). The studied immune responses were stimulated in starfish living along the metal pollution gradient according to the contamination of these starfish by cadmium. However, the sensitivity of these responses toward metals appeared to be strongly modulated by the salinity stress. In red starfish living at 30/1000 and transferred up the contamination gradient, the immune responses were inhibited and closely followed the short-term accumulation of metals in the animal organs. Starfish transferred down the gradient did not recover normal immune responses in the short-term and appeared highly sensitive to caging stress. It is suggested that the impact of metals on the immune responses of A. rubens in field conditions occurs in three phases. Short-term inhibitory effects are exerted by a direct action of metals on the immune cells and are followed by a recovery due to the induction of protective mechanisms. Eventually, when these mechanisms are overwhelmed by a long-term contamination, indirect and durable stimulatory effects on the immune responses appear due to a global disruption of the animal physiology.

Adaptation, Physiological↗
PubMed2003

[Prognostic value of endorectal ultrasonography in rectal cancer: results of a multifactorial analysis].

INTRODUCTION: No study has evaluated the prognostic value of initial endorectal ultrasonography (ERUS) in rectal cancer (RC). AIM: To assess the prognostic value of initial ERUS in operated patients with RC. MATERIAL AND METHODS: Eighty-four patients with non metastatic RC were examined by ERUS before treatment. Forty-two received preoperative radiation therapy and they were resected 7 weeks later on average. The prognostic value of uTN and pTN classification was analysed by means of a Cox model, taking into account the realization of preoperative radiation therapy. RESULTS: In the univariate analysis, 4 variables were predictive of prognosis: elevation of alkaline phosphatases, the degree of circonference, the extension of the resection margin, and the involvement of perirectal lymph nodes. The multivariate analysis showed that when considering only pTN and uTN classifications, only uT and pN kept a significant prognostic value. The better prognostic role of uT was due to a close relationship with preoperative radiation therapy which was responsible for a significant downstaging. CONCLUSION: Since preoperative radiotherapy has become a standard in France, the prognostic value of ERUS has emerged, better than pTN classification when radiotherapy has been preoperatively applied. Other prognostic factors should be investigated in a more homogeneous population of patients, all presurgically irradiated

Aged↗