PubMed Health⌕ Search

Biomedical subjects

J Chevalier

Publications and source records attributed to J Chevalier.

At least 127 records · Page 7Linked to original sources
PubMed1978

[Homogeneous suspensions of mycobacteria: application to the evaluation of bactericidal activity (author's transl)].

This work describes a technique of emulsification of mycobacterial cells (including tubercle bacilli) in order to obtain homogeneous suspensions containing up to 10(8) cells/ml. The suspensions are used in a modified AFNOR method for the evaluation of bacterial activity: within five min virulent strains are more resistant than are avirulent ones but, within 30 min and in the presence of proteins, the behaviour of all strains is quite similar.

Culture Media↗
PubMed1976

Alterations in membrane-associated particle distribution during antidiuretic challenge in frog urinary bladder epithelium.

Frog urinary bladder epithelium has been examined by freeze-fracture electron microscopy of preparations previously fixed by glutaraldehyde either at rest or during antidiuretic challenge. All the agonists tested were observed to induce membrane particle clustering in the A face of the apical plasma membrane of granular cells. This was the case for the natural hormone (hypophysical extracts) and its presumed cellular mediator, adenosine 3',5'-monophosphate. Particle clustering was observed both in the presence and in the absence of water net flow and is thus independent of these movements. Clusters were also observed during hydrosmotic challenge by hypertonic serosal media, a condition which depresses transepithelial sodium transport. No complementary patterns of these A face clusters could be found on the B face. The significance of these membrane-associated particle clusters is discussed in terms of membrane structure and function.

Animals↗
PubMed1975

Septate-like junctions in abnormal erythroblasts: cytochemical, ultrastructural and freeze-etch studies.

Ultrastructural studies of the bone marrow of a patient with refractory anemia revealed aberrant erythroblasts with unique cell junctions. Periodic structures linked adjacent processes on the same cell as well as surfaces of neighboring erythroblasts. Inclusions circumscribed by similar complexes were also present in the cytoplasm. The junction appeared in cross sections as two rigidly parallel unit membranes separated by 250-300 A interspace with two regular arrays of facing 70 A particles at intervals of 160-200 A. These intracellular specializations were present between erythroblasts at various stages of maturation and between, mono, bi or multinucleated erythroblasts. Junctions were permeable to lanthanum and many that appeared to be intracellular were demonstrated to be continuous with the extracellular space. The fact that others were not penetrated by lanthanum indicates that detachment of the interdigitating processes from cells of origin could have occurred. In freeze-etched replicas, distribution of membrane particles was random in areas of septate-like junctions, although parallel rows were sometimes observed both on A and B inner hydrophobic faces of the membrane leaflets. Junctional complexes in tissue culture appeared to have been disrupted and were not reestablished; however, inclusions resembling internalized junctions were observed associated with multivesicular bodies. Ineffective erythropoiesis and the resulting refractory anemia appear to be associated with the presence of the described anomalous junctional complexes.

Anemia, Aplastic↗
PubMedDate not supplied

[Role of Tween-80 used in the culture of cutaneous corynebacteria (JK group) on the composition of cellular fatty acids].

This study of 8 strains of cutaneous corynebacteria, including 5 strains of "JK corynebacteria", concerns the fatty acid composition of cells grown in the presence or not of Tween 80, which enhances their growth rate. The fatty acid methyl esters were analysed by gas-liquid chromatography. The fatty acid profile of the 8 strains agreed with the general pattern of the genus Corynebacterium, with major amounts of palmitic acid (C16:0) and oleic acid (C18:1) and with only trace amounts of 10-methyl octodecanoic acid (tuberculostearic acid). Iso and anteiso branched acids were not present. The 5 strains had high levels of stearic acid (C18:0). When cells were grown in the presence of Tween-80, the fatty acid composition was modified for all strains: their profiles showed high levels of oleic acid (C18:1) and smaller quantities of palmitoleic acid (C16:1). These results confirm the advantage of fatty acid composition for identification of Corynebacteria, and particularly for cutaneous strains, and emphasize the influence of the culture medium, especially that of Tween-80.

Chromatography, Gas↗
PubMedDate not supplied

Evaluation of a standard scrubbing method for the recovery of aerobic skin flora.

The most reliable method for sampling skin flora is still a matter of debate, although the subject is of importance in many fields ranging from clinical to basic research. For the evaluation of normal skin flora, Williamson and Kligman's scrub method is the most commonly used. In order to determine the value of this method, standardized for the evaluation of topical antimicrobial agents on aerobic skin flora, we compared its results to those obtained both from bacterial counts and from microscopic studies on biopsies performed at the same site. After different experiments had established the optimal experimental conditions on human and pig skin, a comparative study on six healthy subjects was carried out in the peri-umbilical area. The mean log numbers of aerobic bacteria in the scrub samples and in the biopsies were respectively, 3.1 and 2.9, which were not statistically significant. These numerical results were similar to those obtained by electron microscopy. Hence, the standard scrub method may be considered satisfactory for the recovery of aerobic bacteria from healthy human skin.

Animals↗