Biomedical subjects

A Chauvet

Publications and source records attributed to A Chauvet.

17 recordsLinked to original sources

PubMed2005

[Spontaneous intrauterine depression skull: myth or reality?].

In spite of the fact that there are many articles considering that intrauterine depressed skull fractures are caused essentially by instrumental extraction, literature is scarce about spontaneous foetal head injuries. Here, we report the case of two depressed skull fractures and one of linear fracture not associated with any known trauma during the pregnancy or delivery. The etiological process leading to the idiopathic character of such lesions, the aetiology, the treatment and the prognostic will be discussed. The forensic problem raised by such cases is very important.

Forensic Medicine↗

PubMed2002

[Crystalline polymorphism of eflucimibe].

The importance, in therapeutics, of the concept of bioavailability and on-going quality research in the formulation of a drug has prompted us to examine the crystalline polymorphism of eflucimibe as from the research phase. This study has been carried out by re-crystallization of the product in organic solvents having a different polarity in a variety of experimental temperature and pressure conditions, then, subsequently, by re-cooling the previously dissolved substance. The analytical methods applied to identify and then describe the polymorphic forms are thermogravimetry analysis (TGA), differential scanning calorimetry (DSC), X-ray powder diffraction from synchrotron radiation (XRPD), infrared spectrometry (IR), solid-state nuclear magnetic resonance spectrometry (SSNMR) and lastly maximum solubility measurements. By means of XRPD, two polymorphic forms called A and B have been clearly identified at ambient temperature. These two crystalline forms were obtained in a reproducible way, then described by DSC, XRPD, IR and SSNMR. Differential scanning calorimetry analysis has shown for polymorphic form A two endothermic phenomena with low energy at about 35 masculine and 118 degrees C attributed by XRDP to conformational polymorphism. The complex endothermic event that extends between 75 masculine and 105 degrees C appears to correspond to successive alterations of a lamellar structure. The solid-solid transition observed at 110 degrees C is due to a change of crystalline phase, then the melting point occurring at about 130 degrees C. For form B, two changes of crystalline phase are clearly observed at about 80 masculine and 120 degrees C. The reversibility of these changes was observed by thermomicroscopy in polarized light. Form A, which is less soluble in absolute ethanol than form B, is the more stable thermodynamically in the temperature range from 25 masculine to 50 degrees C where the data have been obtained. The Van't Hoff diagram layout for each polymorphic form appears to reveal an A<-->B transition temperature in a temperature range lower than 25 degrees C. This study, undertaken as from the research phase, has enabled us to highlight the polymorphism of this new chemical entity by means of XRDP by explaining the nature of the endothermic phenomena observed by DSC, and lastly identify the thermodynamically more stable polymorphic form, thus contributing to a better knowledge of this future drug.

Anilides↗

PubMed1999

Flurbiprofen-loaded nanospheres: analysis of the matrix structure by thermal methods.

We report the preparation and evaluation of flurbiprofen loaded-poly-epsilon-caprolactone nanospheres obtained by solvent displacement method. Characterization by thermal methods, infrared spectroscopy and X-ray diffraction analysis can reveal the dispersion state of the drug inside the nanospheres. Such information predicts the stability of the particles and the drug release behaviour. The study has indicated the presence of a molecular dispersed system. In addition, construction of a phase diagram has allowed us to determine the drug/polymer ratios at which flurbiprofen has the highest entrapment efficiency.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed1999

Stability and in vitro drug release of flurbiprofen-loaded poly-epsilon-caprolactone nanospheres.

The effects of temperature and two different initial pH (2.67 and 7.00) on poly-epsilon-caprolactone (P epsilon CL) nanospheres loaded with flurbiprofen (FB) (aqueous suspensions) were studied to investigate their influence on the stability and physicochemical characteristics of these drug delivery systems. The drug release behavior was also studied. Release of the associated FB occurred very fast on high dilution in a buffered medium. The stability of the polymeric system depends on the temperature and the initial pH value; it is more degradable with the particles stored at 40 degrees C with an initial pH value of 2.67.

Administration, Topical↗

PubMed1998

An investigation of FB interactions with poly(ethylene glycol) 6000, poly(ethylene glycol) 4000, and poly-epsilon-caprolactone by thermoanalytical and spectroscopic methods and modeling.

The interactions between flurbiprofen (FB) and different polymers are studied in order to improve the bioavailability of FB. FB-polymer phase diagrams [poly(ethylene glycol) (PEG) 4000, PEG 6000, and poly-epsilon-caprolactone] were constructed and compared with the modeling diagrams. Thermoanalytical methods (differential scanning calorimetry, thermomicroscopy) were used to construct the phase diagrams. Thermodynamic data were used to model the FB-polymer systems. The construction of the FB-polymer phase diagrams showed the existence of a stable invariant called "eutectic" characterized by (XE)exp, (TfE)exp, and (DeltaHfE)exp, the experimental eutectic composition, the experimental temperature, and the enthalpy of eutectic melting, respectively. Modeling confirmed the values for these parameters and was used to evaluate the different Flory-Huggins parameters chi for each FB-polymer mixture. chi values and the infrared spectra confirm that the interactions due to hydrogen bonds between FB and PEG 4000 are more numerous than between FB and PEG 6000 and also more numerous than between FB and poly-epsilon-caprolactone.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed1996

PCR methods for identification and specific detection of probiotic lactic acid bacteria.

Probiotics are defined as "microbes improving animal feed." Three lactic acid bacteria, previously selected as probiotic for pig feeding, were identified by sequencing the variable V1 region of the 16S rDNA after PCR amplification primed in the flanking constant region. A VR region showing strong nucleotide differences between the three probiotic and the reference strains was delimited. Oligonucleotides specific for each strain were designed. A specific assay for probiotic detection was developed, based on a PCR reaction with three primers.

Animal Feed↗

PubMed1995

[Characterization of lorazepam and oxazepam by the thermal behavior of their degradation product].

Lorazepam and oxazepam are benzodiazepine which differ by the presence, or not, of chlorine atom on the phenyl ring. These molecules are able of chemical and thermal degradation with water intramolecular elimination between hydroxy and amine functional group and formation of carboxaldehyde quinazoline. These substances characterise lorazepam and oxazepam by their thermal behaviour and melting temperature by heating and cooling cycles.

Anti-Anxiety Agents↗

PubMed1992

Characterization of polymorphs and solvates of 3-amino-1-(m-trifluoromethylphenyl)-6-methyl-1H-pyridazin-4-one.

The characterization of two polymorphs of the title compound (F2692; 1) by differential scanning calorimetry (DSC), microanalysis, proton nuclear magnetic resonance spectroscopy, thermogravimetry, thermomicroscopy, infrared spectroscopy, and X-ray diffractometry is described. Both polymorphs are crystalline, with form II being more stable at temperatures less than 160 degrees C. The thermal behavior was studied at different rates of heating, and the enthalpies of transition were calculated from DSC data. The transformation of aqueous suspensions of form I to the water-stable form II is described, and the heats of solution and intrinsic aqueous dissolution rates of both polymorphs were determined. 1 also formed solvates with dimethyl sulfoxide and 1-methyl-2-pyrrolidinone. The solvates were studied by thermogravimetry, DSC, and infrared spectroscopy.

Anti-Anxiety Agents↗

PubMed1991

Ovine polioencephalomalacia associated with dietary sulphur intake.

Fifty-six female crossbred two-month-old lambs were housed in individual cages, and fed a basic ration of barley (59%), soybean meal (5%), and alfalfa (32%) prepared to meet NRC nutrient requirements. Four percent of the diet contained a standard salt mix to which the factors inorganic sulphur (S) and thiamine (B1) were added. Four treatment groups were used: low sulphur and normal thiamine (0.19% S, 13.7 mg/kg B1) low sulphur and high thiamine (0.19% S, 243 mg/kg B1), high sulphur and normal thiamine (0.63% S, 13.7 mg/kg B1), high sulphur and high thiamine (0.63% S, 243 mg/kg B1). All animals had free access to water and were offered 1 kg/animal/day of diet for 14 weeks, when necropsy was undertaken. Seven lambs fed unsupplemented (normal B1) diets containing added sulphur developed clinical symptoms of polioencephalomalacia (PEM) between the 3rd and 7th week of the trial. Morbidity (P less than 0.013) and mortality (P = 0.08) differences were attributed to S administration. None of the B1 supplemented lambs developed clinical signs of PEM. Body weight and relative organ weights did not differ among treatment groups. Serial sections of all brains were examined grossly and microscopically. Nonparametric statistical analysis revealed sulphur related effects in the cerebrum, midbrain and hindbrain (P less than 0.0001), no thiamine-related effects or interaction between the factors were seen, except in the amygdaloid body. It was concluded that inorganic sulphur was associated with polioencephalomalacia, and that dietary thiamine may decrease the severity of lesions in some affected areas of the central nervous system.

Animal Feed↗

PubMed1990

[Quality control and optimization of therapeutic activity with the use of thermoanalytic methods].

Thermogravimetry, differential scanning calorimetry, thermomicroscopy, transparency measure permit drug quality control: knowledge of solvated or unsolvated mole, thermal stability, identification of crystalline form (polymorphism) quick determination of total impurity with graphs. These methods can be used for therapeutic activity optimization of very weakly soluble drugs: research of the polymorph showing the best kinetic dissolution, establishment of phase diagram drug/inert substance by example for determination invariant composition particularly eutectic for which the drug solubility is increased.

Calorimetry, Differential Scanning↗

PubMed1987