Biomedical subjects

F Puisieux

Publications and source records attributed to F Puisieux.

At least 19 recordsLinked to original sources

PubMed1992

Determination of phospholipids from pulmonary surfactant using an on-line coupled silica/reversed-phase high-performance liquid chromatography system.

A basic normal-phase HPLC separation of phospholipids can be improved by introducing a limited contribution of solvophobic retention. For this purpose, the effect of an additional alkylsilica (C18) column of variable length coupled in series with a silica column was investigated. With increasing percentage of reversed phase in this system, the retention of phosphatidylglycerol increased. Phosphatidylinositol and phosphatidylserine were separated into molecular species. The "selective retention" defined in this study permits an evaluation of the solvophobic retention of phospholipids in the coupled system. An alternative column switching procedure is used for specific applications of the biphasic separation on chosen phospholipids. With this system, determination of phosphatidylglycerol and six other phospholipids from pulmonary surfactant could be performed.

Animals↗

PubMed1992

Polyalkylcyanoacrylate nanoparticles as polymeric carriers for antisense oligonucleotides.

Adsorption of oligothymidylates on polyisobutyl- or polyisohexylcyanoacrylate nanoparticles was achieved in the presence of hydrophobic cations such as tetraphenylphosphonium chloride or quaternary ammonium salts. Results suggested that oligonucleotide adsorption on the nanoparticles was mediated by the formation of ion pairs between the negatively charged phosphate groups of the nucleic acid chain and the hydrophobic cations. The adsorption efficiency of oligonucleotide-cation complexes on nanoparticles was found to be highly dependent upon several parameters: oligonucleotide chain length, nature of the cyanoacrylic monomer, hydrophobicity of cations used as ion-pairing agents, and ionic concentration of the medium. Carrier capacity of polyisohexylcyanoacrylate nanoparticles for oligothymidylates (16 nucleotides) complexed with cetyltrimetylammonium bromide in the presence of 0.15 M NaCl was determined to be 5 mumol/g polymer. The in vitro protection of oligothymidylates adsorbed to nanoparticles against degradation by a 3'-exonuclease (snake venom phosphodiesterase) was also demonstrated. These results showed that nanoparticles can be considered as convenient carriers for the protection and delivery of oligonucleotides to cells in culture and for future applications in vivo.

Cyanoacrylates↗

PubMed1992

[Stabilization and function of liposomes].

Liposomes stability can be improved by covering them with polysaccharide derivatives. The anchoring mechanism of these derivatives into the lipid membrane has been studied and explained. In order to improve liposome specificity, protein transfer from erythrocytes and platelets into liposome membrane has been carried out. The effect of a newly developed phospholipid, DDPC, on the efficiency and the selectivity of protein transfer is reported.

Blood Platelets↗

PubMed1992

Synthesis of the orally macrofilaricidal and stable glycerolipidic prodrug of melphalan, 1,3-dipalmitoyl-2-(4'(bis(2''-chloroethyl)amino)phenylalaninoyl)gl ycerol.

A new strategy is presented to develop macrofilaricidal compounds orally administered and able to concentrate in the lymphatic system. A diglyceride derivative of melphalan, 1,3-dipalmitoyl-2-(4'(bis(2''-chloroethyl)amino)phenylalaninoyl)gl y cerol, was synthesized. The esterification of melphalan by 1,3-dipalmitin allowed chemical stabilization of the alkylating agent in aqueous dispersion. No degradation of this prodrug was observed after a 3-month storage of an aqueous dispersion at 4 degrees C. The filaricidal activity of the prodrug was compared with those of melphalan in vitro against adults, infective larvae and microfilariae of Molinema dessetae, and evaluated in vivo on Molinema dessetae infected Proechimy oris. In vitro, melphalan and the glycerolipidic prodrug were inactive against microfilariae but active at 1 mmol/l against infective larvae and adults. In vivo studies were performed with rodents subcutaneously inoculated with infective larvae from Aedes aegypti. The number of macrofilariae was significantly reduced following treatment with a single oral dose of the alkylating agent prodrug (0.082 mmol/kg).

Aedes↗

PubMed1992

[Determination of an intrinsic value of diffusion coefficient of active principle in polymeric matrix for the formulation of a controlled release system].

The study of diffusion in a polymeric system often poses difficult experimental problems, notably when the rate of release is determined in a liquid receptor phase which can interact with the system. In this publication, we propose two experimental methods to determine the diffusion coefficient by a gel-gel kinetic release study, in which the receptor is a same gel unloaded initially. The first method is based on the use of radioactive tracers and a multi-channel radioactivity counter to obtain, at different times, the concentration profiles in the diffusion medium. The theoretical model is given for a gel donor with the concentration C0 of diffusing molecules is below or above the solubility Cs. The second method is based on the measurement of the displacement of solubility front during the diffusion within the system in the case C0 > Cs. The theoretical model shows that this displacement is a function of square root of t. For illustration, two experimental determinations of testosterone diffusion coefficient on the one hand in a silisic acid gels and on the other hand in an acrylic acid gels are given.

Immunodiffusion↗

PubMed1991

A structural study of interfacial phospholipid and lung surfactant layers by transmission electron microscopy after Blodgett sampling: influence of surface pressure and temperature.

Monolayer studies of the lung surfactant extract (LSE), dipalmitoyl phosphatidilcholine (DPPC) and dioleyl phosphatidilcholine (DOPC) have been performed in the dynamic condition at various temperatures. These compounds were also studied by differential scanning calorimetry, and the Langmuir Blodgett films were examined by electron microscopy. The combination of these techniques allowed us to describe precisely the collapse process, which was found to be different above and below the transition temperature of the lipids. However, whereas a phase separation for DPPC/DOPC mixtures occurred at all temperatures studied, this separation was observed for LSE only at temperatures lower than that characteristic of the "rigid state" to "liquid-like state" transition temperature. The ability of LSE to rapidly respread upon decompression appears to be due to the formation of piled amorphous aggregates formed during compression of its monolayers.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed1991

Anti-metastatic activity in vivo of MDP-L-alanyl-cholesterol (MTP-Chol) entrapped in nanocapsules.

A lipophilic muramylpeptide (MTP-Chol), capable of rendering macrophages cytostatic towards tumour cells, was encapsulated within polyisobutylcyanoacrylate nanocapsules and administered to mice carrying an experimental model of liver metastasis. Treatment by intravenous injections twice a week beginning before the establishment of metastases significantly reduced the number of liver colonies. Treatment started later was less effective. The dose of MTP-Chol in each injection, and the tumour burden in the mice did not change the percentage inhibition of metastases significantly. Anti-metastatic activity was also observed after administering nanocapsules containing MTP-Chol by the oral route.

Acetylmuramyl-Alanyl-Isoglutamine↗

PubMed1991

Efficiency of liposomal ATP in cerebral ischemia: bioavailability features.

This study was performed to elucidate the mechanism by which adenosine triphosphate (ATP) encapsulated into liposomes was able to protect against experimental brain ischemia in the rat. After intracarotidal administration of liposomally entrapped ATP, the ATP blood level increased dramatically whereas no change was observed after administration of free ATP. This suggested that liposomes may protect ATP from its degradation by endothelial ectonucleotidases. On the other hand, it was observed that after administration of liposomally entrapped carboxyfluorescein (CF) to ischemic rats, the distribution of the brain fluorescence under the form of numerous punctiform structures was completely different from the diffuse fluorescence obtained with free CF injections. These data suggest that under certain hypoxic conditions the blood-brain barrier is open allowing the liposomes to reach the cerebral parenchyma. The mechanism of brain uptake is, however, still unclear: endothelial tight junctions opening or endothelial transcytosis.

Adenosine Triphosphate↗

PubMed1991

[Vectorisation of doxorubicin in nanospheres and reversion of pleiotropic resistance of tumor cells].

A multidrug resistance human cell line (Dox-R-MCF7), originating from mammary adenocarcinoma was compared to the drug sensitive parent line (MCF7) to determine whether or not the use of doxorubicin-loaded biodegradable nanospheres (NS-Dox) could circumvent drug resistance. The Dox-R-MCF7 line was shown to resist free doxorubicin (Dox) as the 50% lethal dose for them was 150 times higher than for the sensitive cell-line. Isohexylcyanoacrylate nanospheres, porous matrices of biodegradable innocuous polymer, diameter 300 nm, were loaded with doxorubicin. Free Dox, NS-Dox and Dox-free polymer (NS) were added to the culture medium for 6 hrs. In terms of 50% lethal dose, NS-Dox were cytotoxic for the resistant cell line to an identical extent as for the sensitive parent line. Dox-free nanospheres alone or mixed with free-Dox were noncytotoxic for the resistant line. Drug targetting could be of main importance to overcome multidrug resistance.

Breast Neoplasms↗

PubMed1991

[Tension activity of pulmonary surfactant: adsorption of liposomes of model phospholipids].

One peculiarity of pulmonary surfactant, which is the tensioactive material physiologically present at the surface of alveoli, lies in its very quick localization at in the air-water interface. This being one of the limiting factors of artificial exogenous surfactants for the treatment of patients suffering of respiratory distress syndromes, we have studied the mechanisms which are intervening in the adsorption kinetics of a pure liquid--phase phospholipid, the dioleylphosphatidylcholine (DOPC), and of mixtures of dipalmitoylphosphatidylcholine (DPPC) and phosphatidic acid (PA) in presence of divalent cations (Ca++ and Mg++). The adsorption kinetics of liposomal suspensions of DOPC, which were studied by the Wilhelmy plate method, are determined by the existence of a barrier potential which height depends on the temperature and medium osmolarity, and on the deformability of vesicules. The study of PA-DPPC liposomes was performed with the help of a pulsating bubble surfactometer, a physicochemical instrumentation which mimics the pulmonary alveoli. To obtain performant responses with this model, high concentrations of PA and of divalent cations Ca++ and Mg++ are needed. These results, which are similar to those observed during the study of liposomal fusion, allow to propose a model, according to which adsorption of liposomes at the air-water interface is comparable to liposomal fusion and may be related to the presence of a thin aqueous film.

Adsorption↗

PubMed1990

[Problems posed by the development of exogenous surfactants for the treatment of hyaline membrane disease].

The hyaline membrane disease (HMD) is a respiratory distress occurring at birth of some premature infants, attributed to an endogenous pulmonary surfactant deficiency. The present treatments are iatrogenic and inefficient for the most diseased infants. The exogenous surfactant supplementation intends to give to the baby formulations playing in vivo the role of the natural surfactant. The research developed for the formulation and the diffusion of these exogenous surfactants have to solve physicochemical problems but also of industrial production and of safety use. In spite of their adequate physicochemical and pharmacological properties, surfactants of natural sources, for industrial grounds, are not still distributed at a large scale. The efficiency of artificial surfactants is variable, and the use of non-biodegradable molecules in several preparations let to safety problems. The development of new types of artificial surfactants, more efficient and safe, implies a better knowledge of the physico-chemical mechanisms intervening in the pulmonary surfactant dynamics.

Chemical Phenomena↗

PubMed1979

Dielectric constants of solid-liquid and liquid-liquid systems as a function of composition.

The dielectric constant of a solid substance in the dissolved state may be found by using a solvent with a dielectric constant that remains invariable when the solid substance is dissolved. The slope values obtained from dielectric constant versus concentration plots of the solid substance in two solvents with different dielectric constants are extrapolated or interpolated. The dielectric constant of a solid substance in the dissolved state also can be found directly from the dielectric constants of solutions of the solid in one solvent at two concentrations. The dielectric constants are converted to polarizations, and the two values allow calculations of the polarizations of the solvent and solute separately. From the polarization of the solute, one can calculate its dielectric constant (in dissolved state). Such a procedure is correct only if the dielectric constant is concentration independent.

Chemistry, Pharmaceutical↗

PubMed1979