Biomedical subjects

M Fauré

Publications and source records attributed to M Fauré.

4 recordsLinked to original sources

PubMed2005

Domain structure in a superconducting ferromagnet.

The domain structure is inherent to all ferromagnets and the recent discovery of the superconducting ferromagnets raises the question of the modification of this domain structure by superconductivity. In the framework of the general London theory, applicable to both singlet and triplet superconductors, we demonstrate that superconductivity leads to a dramatic shrinkage of the domain width. The presence of this dense domain structure has to be taken into account for all magnetic measurements on superconducting ferromagnets, and the study of the domain structure evolution could provide important information on the mechanisms of superconductivity and magnetism interplay.

Journal Article↗

PubMed1991

Evaluation of the antioxidant properties of thyroid hormones and propylthiouracil in the brain-homogenate autoxidation system and in the free radical-mediated oxidation of erythrocyte membranes.

The antioxidant capacity of thyroid hormones and the antithyroid drug propylthiouracil was studied in three model systems, namely, autoxidation of rat brain homogenates and oxidation of rat erythrocyte plasma membranes (EPM) induced by either 2,2'-azobis-(2-amidinopropane) (AAP) thermolysis or by gamma irradiation. Thyroid hormones significantly inhibited the development of lipid peroxidation in these systems at micromolar concentrations, as assessed either by visible light emission, thiobarbituric acid reactive substances accumulation or oxygen uptake. This behaviour was not observed when L-3,3',5-triiodothyronine (T3) and L-thyroxine (T4) were assayed at nanomolar concentrations. In EPM exposed to AAP or gamma irradiation, propylthiouracil inhibited the induced lipid peroxidation, with Q1/2 values of 112-150 microM. It is concluded that the antioxidant capacity of thyroid hormones found in vitro may not be of relevance in physiological conditions, which exhibit variations of T3 and T4 levels in the nanomolar range. On the other hand, the behaviour of propylthiouracil as an inhibitor of EPM lipid peroxidation is observed at concentrations close to the therapeutic levels, thus representing a possible complementary action to its antithyroid activity.

Animals↗

PubMed1991

2,2'-Azo-bis-amidinopropane as a radical source for lipid peroxidation and enzyme inactivation studies.

1. 2,2'-Azo-bis-amidinopropane (ABAP) thermal decomposition produces free radicals that initiate the lipid peroxidation of erythrocyte ghost membranes. 2. Addition of 6-n-propyl-2-thiouracil decreases the rate of the process, both by decreasing consumption of the natural antioxidants of the membranes and by direct interaction with the free radicals involved in the lipid peroxidation. 3. Peroxyl radicals produced in ABAP thermal decomposition inactivate lysozyme, horseradish peroxidase (HRP) and glucose oxidase, in that order. The number of enzyme molecules inactivated per radical introduced into the system increases with enzyme concentration. 4. Competitive studies employing mixtures of enzymes show that the order of reactivity of these enzymes towards the peroxyl radicals is the opposite to that obtained for the rate of enzyme inactivation. It is concluded that inactivation efficiency is determined mainly by the average number of free radicals that must react with an enzyme molecule to produce its inactivation, and that this number is directly related to the molecular weight of the enzyme.

Amidines↗

PubMed1990

Antioxidant capacity of allopurinol in biological systems.

The antioxidant capacity of allopurinol was investigated in three biological systems by measurements of visible chemiluminescence, oxygen uptake and production of thiobarbituric acid reactive substances (TBARS). The addition of allopurinol to rat brain homogenates undergoing autoxidation and erythrocyte ghost membranes supplemented with 2,2'-azo-bis-(2-amidinopropane), in concentrations up to 2 mM, has a negligible effect on lipid peroxidation development. In erythrocyte ghost membranes exposed to gamma irradiation (9.5 Gy/min), allopurinol inhibits the radiation-induced lipid peroxidation with a Q(1/2) of 2.0 mM. It is suggested that allopurinol may have an alternative antioxidant pathway of action in biological systems, probably through a scavenging action upon hydroxyl radicals.

Allopurinol↗