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Biomedical subjects

Y Chevalier

Publications and source records attributed to Y Chevalier.

9 recordsLinked to original sources
PubMed1996

Nature of the Adsorption of Zwitterionic Surfactants at Hydrophilic Surfaces

This paper describes the adsorption of zwitterionic dodecyl-N,N-dimethylammonio alkanoates with polymethylene intercharge arms of different lengths on silica. The data presented were obtained by in situ ellipsometry, allowing time-resolved studies of the surface excess, the mean thickness, and the refractive index of thin interfacial films. It is shown that the mode of adsorption of zwitterionic surfactants is similar to that observed for ethylene-oxide-based nonionic surfactants. The interaction energy between single zwitterionic surfactants and silica is relatively weak and the adsorption process is best described in terms of surfactant self-assembly, promoted by the presence of the solid surface. The mode of adsorption is only weakly affected by increasing the number of intercharge methylene units. The surface aggregation behavior observed at the silica surface displays many parallels with the corresponding solution phase behavior. Finally, the adsorption of zwitterionic surfactants is relatively independent of the pH. However, as the pH is lowered to the pKa values of the terminal carboxyl group (i.e., as the surfactants become increasingly positively charged) desorption is observed.

Journal Article↗
PubMed1995

Evaluation of the efficacy of zwitterionic dodecyl carboxybetaine surfactants for the extraction and the separation of mycoplasma membrane protein antigens.

The ability to extract mycoplasma membrane protein antigens using the alkyl carboxybetaine surfactants (N-dodecyl-N,N-dimethylammonio)butyrate (DDMAB, CMC = 4.3 mM) and (N-dodecyl-N,N-dimethylammonio)undecanoate (DDMAU, CMC = 0.13 mM) was assessed by protein titration and SDS-PAGE analysis. The maximum yields of membrane protein solubilization ranged from 20 to 90%, depending upon both the mycoplasma membrane investigated and the surfactant used. In five of six cases, the extraction was optimal for surfactant concentrations of ca. 25 mM. DDMAB displayed a higher efficiency in membrane protein extraction. The order of efficiency for both surfactants was Spiroplasma melliferum > Acholaplasma laidlawii > Mycoplasma gallisepticum. In contrast, DDMAU proved much more selective. The order of selectivity was M. gallisepticum > S. melliferum > A. laidlawii. The highest selectivity was recorded for the major proteins p67 and spiralin of M. gallisepticum and S. melliferum, respectively. For p67, notably, DDMAU proved superior to 10 other surfactants. Dot immunobinding and crossed immunoelectrophoresis analyses showed that both dodecyl carboxybetaines were suitable as membrane protein-solubilizing agents in immunological techniques. Furthermore, these surfactants did not exhibit effects adverse to the activity of A. laidlawii membrane NADH oxidase. One promising application of DDMAU is the separation of membrane proteins by ion-exchange HPLC as illustrated by the good resolution of M. gallisepticum membrane proteins and purification of p67 to almost homogeneity. These data show that dodecyl carboxybetaine surfactants are useful for the extraction of mycoplasma membrane antigens under mild conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Antigens, Bacterial↗
PubMed1994

[Encephalopathy and Hashimoto thyroiditis].

A generalized epileptic seizure revealed a subactute encephalopathy which was attributed to Hashimoto's thyroiditis. Primary biliary cirrhosis was also discovered. The encephalopathy rapidly followed a favourable course under corticosteroid therapy, which confirms that it was an immune disease.

Adult↗
PubMed1994

Vertigo.

Vertigo is one of the most frequent reasons for consultation in daily medical practice. Recent studies show that vertigo involves considerable social costs before being managed efficiently, as it is often incorrectly diagnosed. Sometimes a psychiatric symptom, the original causes are vestibular in Ménière's disease, vestibular neuritis, and benign positional vertigo. Ménière's disease to some extent resembles that of progressive autoimmune deafness. Soon, perhaps, the target of the long-suspected immune reactions will be identified and specific treatments will be developed for the rapidly progressing forms. Benign paroxysmal positional vertigo is certainly a favorite of practitioners because the treatment is so simple. Not all vertigos are so easily cured, and surgery must sometimes be performed. In most cases, retrolabyrinthine vestibular neurectomy, with its acceptable risks, is the operation of choice. New diagnostic techniques, such as dynamic posturography, are interesting, but their use is not as yet clear.

Cranial Nerve Diseases↗
PubMed1992

Gerstmann-Sträussler-Scheinker disease in an Alsatian family: clinical and genetic studies.

The clinical progression of Gerstmann-Sträussler-Scheinker disease in a family of Alsatian origin is reported. The age of onset and the duration of evolution were variable. The clinical picture became more complex over the generations: in the first generations, isolated dementia and in later generations a triad of pyramidal, pseudobulbar syndromes and dementia associated with spinal cord and cerebellar features. Prion gene analysis showed that four surviving patients carry double missense changes at codons 117 and 129, identical to those found in one case at necropsy and 10 other healthy members of the family. The missense changes were not found in 100 controls. No member of the family had modification of condons 102, 178, or 200. The lod score suggests linkage between the missense change at codon 117 and Gerstmann-Sträussler-Scheinker disease in this family.

Adult↗
PubMed1991

[Mutation of codon 117 of the prion gene in Gerstmann-Sträussler-Scheinker disease].

We report the clinical progression of the Gerstmann-Sträussler-Scheinker disease (GSS) in a family of Alsatian origin. The age of onset and duration of evolution were variable. The clinical picture became more complex over the generations: isolated dementia in the first generations, then, more recently, a triad of pyramidal, pseudobulbar syndrome and dementia associated with symptoms indicating spread of damage to the spinal cord and cerebellum. Study of the prion gene showed that in all patients analyzed and in 10 healthy family members, there is a double mutation of codon 117 leading to loss of the restriction site PvuII and to the replacement of an alanine by a valine. We did not find the mutation of codon 102 reported in 5 GSS families. The role of these mutations in the pathogenesis of the disease is unclear: marker for a particular susceptibility to the encephalopathies due to the prion, or direct role in the disease? Further study of the family, particularly the healthy carriers, could suggest the answer. GSS seems to be an especially useful model for the study of the role of a foreign abnormal protein in the synthesis and regulation of host proteins.

Chromosome Mapping↗