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Biomedical subjects

P Metezeau

Publications and source records attributed to P Metezeau.

26 records · Page 2Linked to original sources
PubMed1982

Botulinum toxin type A: kinetics of calcium dependent paralysis of the neuromuscular junction and antagonism by drugs and animal toxins.

The effect of botulinum Toxin (BoTx), which blocks the mechanism of release of acetylcholine at neuromuscular junctions and induces paralysis of muscles stimulated by nerves, is known to be Ca2+-dependent. Amplitude of muscular contractions evoked by nerve impulse was studied in BoTx poisoned preparations. The present report notes that an increase in Ca2+ concentration in vitro delays paralysis of muscular contractions of the frog evoked by nerve impulse. The restorative effect of different drugs on this paralysis has been tested: 4-aminopyridine, ATXII (toxin isolated and purified from the sea anemone Anemonia sulcata tentacles) and a crude venom isolated from the scorpion Androctonus australis antagonize the BotX induced paralysis at physiological concentrations of Ca2+ (Cao2+ = 2 mM), whereas the restorative effect observed with tetra-ethylammonium or guanidine occurs at higher concentrations of Ca2+ (Cao2+ = 4 mM), as in mammals. ATXII restores in vivo the activity of a BoTx paralysed muscle of guinea pig and this effect is more efficient if the interval between the injection of BoTx and ATXII is shortened. These results on the frog and guinea pig are in agreement with those obtained on other biological preparations by several investigators. Moreover it is suggested that the antagonism of BoTx induced paralysis is a consequence of the increase in Ca2+ at the nerve ending. The efficiency of 4-aminopyridine and animal toxins is explained by an action on the nerve ending, by increasing Ca2+ from an interval compartment of the cell, whereas antagonism produced by guanidine and tetraethylammonium involves uptake of Ca2+ from the external medium. The bathing medium must be at a higher concentration of Ca2+ than usual. This explains the differences in antagonism obtained by these drugs and toxins in vitro and in vivo.

Animals↗
PubMed1982

The kinetics and homogeneity of endocytosis of a receptor-bound ligand in a heterogeneous cell population studied by flow cytofluorometry.

A method is described to study quantitatively and rapidly the kinetics of endocytosis of a receptor-bound ligand by cells of various subclasses within a heterogeneous cell population. The time course of the internalization of the bound ligand is followed by labeling, with a fluorescent antibody, the ligand molecules exposed on the cell surface at various times of the endocytosis process, and by measuring with a flow cytofluorometer the fluorescence of a large number of individual cell within the total cell population. A convenient mathematical treatment of the data is proposed for analyzing the experimental results. This method is applied to the kinetic study of the endocytosis of rabbit antibodies (anti-mouse immunoglobulin) by B-lymphocytes within a mouse spleen cell suspension.

Animals↗
PubMedDate not supplied

Prenatal diagnosis of a (X;X) translocation by fluorescence in situ hybridization and laser scanning image cytometry.

A de novo structural abnormality of one X chromosome was prenatally detected in a female fetus. This chromosomal abnormality has been analyzed by conventional cytogenetic methods, fluorescence in situ hybridization, and laser scanning image cytometry. The association of these techniques has demonstrated that this anomaly corresponds to a (X;X) translocation. Analysis of hybridization signals by laser scanning image cytometry allowed to localize that the breakpoints were at the X-centromeric region and Xp11.3, respectively. These results show the usefulness of image analysis and fluorescence in situ hybridization for a rapid characterization of de novo structural chromosome anomalies in prenatal diagnosis.

Adult↗
PubMedDate not supplied

Isolation of subtelomeric DNA sequences labelling sheep and goat chromosome ends.

Two techniques that make it possible to isolate telomere DNA are presented, using sheep as an example. The first technique is based upon the screening of a sheep BAC library with PCR amplified DNA segments preserved from high-power laser beam irradiation. Twenty-three BACs hybridising to 13 subtelomeric regions in sheep and goats were obtained (out of 27 in the sheep complement), of which 13 recognised more than one region, telomeric or not. Twenty-three microsatellites were isolated from these BACs and 22 were genetically mapped on the sheep international genetic map, always consistently with the cytogenetical localisation in 17 cases out of 22. These results are discussed. The second technique is based upon the selective cloning of subtelomeric enriched DNA. Preliminary results were obtained by this approach.

Journal Article↗
PubMedDate not supplied

Use of a biotinyl-estradiol derivative to demonstrate estradiol-membrane binding sites on adherent human breast cancer MCF-7 cells.

A biotinyl-derivative of 17 beta-estradiol has been used to demonstrate a site of recognition and binding of estradiol located on the plasma membrane of human breast cancer MCF-7 cells by using the biotin/avidin-FITC system. The specificity of this binding has been shown by a displacement of the fluorescent label by 17 beta-estradiol. No displacement was observed when testosterone was added. Quantification of this phenomenon has been shown by laser scanning cytometry while preserving the cells adhesiveness to their growth support as well as their membrane integrity. An analysis by confocal laser scanning microscopy suggested that the fluorescence distribution on MCF-7 cells treated with estradiol-biotin was on the cell periphery. The results obtained are in favour of the recognition and binding site of 17 beta-estradiol located on the plasma membrane of MCF-7 cells and they would indicate that the biological activity of estradiol, among others, could be initiated by an interaction with the membrane.

Binding Sites↗