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Biomedical subjects

M Geoffroy

Publications and source records attributed to M Geoffroy.

34 records · Page 2Linked to original sources
PubMed1985

Long-lived radicals in irradiated apatites of biological interest: an e.s.r. study of apatite samples treated with 13CO2.

Hydroxyapatite is used as a model for studying radical formation in the mineral compartment of irradiated calcified tissues. Treating this material with 13C-enriched CO2 confirms that radiogenic long-lived radicals correspond to carbon centred species. It is shown, however, that these radicals are not located on the carbonate ions which substitute either the phosphate or the hydroxyl groups. The conditions which allow the formation and the trapping of these radicals are investigated (role of humidity, CO2 and temperature) and this paramagnetic species is identified as CO-2 adsorbed at the surface of apatite crystallites.

Carbon Dioxide↗
PubMed1984

Spin-labeling study of phosphatidylcholine-cardiolipin binary mixtures.

Electron paramagnetic resonance spectra of the spin-label probe 2,2,6,6-tetramethylpiperidinyl-1-oxy have been used to study the phase behavior of binary mixtures of different phosphatidylcholines (dipalmitoyl, distearoyl, and dioleoyl) with cardiolipin, using either calcium-free or calcium-containing cardiolipin (with a calcium:cardiolipin ratio of 1:2) samples. Results show that the nature of the fatty acid chains of the phosphatidylcholines (chain length and unsaturation) may influence the coexistence of different phases as well as does the nature of the cation linked to the cardiolipin.

Animals↗
PubMed1982

ESR identification of radiation damage in synthetic apatites: a study of the 13C-hyperfine coupling.

Although radiogenic free radicals are widely used as molecular probes in biological calcified tissues, their nature and their location remain controversial. In the present study we have synthesized and irradiated apatites in which 13CO3(2-) ions substitute hydroxyl or phosphate ions in hydroxyapatite. The 13C-couplings show that the carbon-centered radicals are CO2- --rather than CO3(3-)--the locations of which depend on the type of carbonate and the treatment of the sample.

Carbon Isotopes↗
PubMed1978

Mineral substance of bone tissue and of experimental cutaneous calcinosis in rats: chemical analysis and ESR study.

The evolution of the mineral constituents of subcutaneous calcinosis induced in rats by topical calciphylaxis was studied by the method of quantitative chemical analysis, and after treatment with excited gases by electron spin resonance (ESR) analysis. Chemical data show that the genesis of the subcutaneous calcinosis does not significantly alter the concentration of Ca, P, F, CO3, Mg, and Fe in the mineral phase of the femoral bone of calciphylactic rats. In the calcinosis an important increase of the fluoride concentration is noticed in function of the time after challenging. There is also a high concentration of Mg2+ ions in the early stages of the experimental calcification. Iron injected for the challenging is continuously present in the calciphylactic tissue after this treatment. This suggests that subcutaneous calcinosis might be a means of fixing certain heavy metal ions. After treatment with excited gases, the proportions of the trapped CO33- and O3- radicals are of the same order of magnitude in calciphylactic tissue after 12 days and observations in bone mineral. These suggest that after 12 days the mineral of the calciphylactic tissue has a crystalline state close to that of bone.

Animals↗
PubMed1978

Purification and characterization of a long chain, fatty-acid-binding protein supplying the mitochondrial beta-oxidative system in the heart.

A fatty-acid-binding protein with a molecular weight of approximately 12 000 was purified from rat heart and the binding investigated by electron spin resonance. The stearic acid bound to the protein was found to be transferred to the mitochondrial beta-oxidative system, suggesting a role as transcytoplasmic fatty acid carrier for this protein. For the first time a physiological cytoplasmic protein was used as a carrier supplying the mitochondrial beta-oxidative system. A new mechanism of action is proposed to explain the control exerted by this type of protein in some membrane-linked enzymatic processes.

Animals↗
PubMed1978

Paramagnetic and crystallographic effects of low temperature ashing on human bone and tooth enamel.

Low temperature ashing by excited gas (LTA) causes crystallographic and paramagnetic alterations of the human bone and tooth enamel mineral. On the one hand, LTA induces variations of the alpha lattice parameter. These variations depend upon the nature of the gas used, but are little affected by its degree of excitation. Trapping of gas molecules in the crystal structure is demonstrated. On the other hand, LTA produces two preponderant paramagnetic centers in bone and enamel samples at 20 degrees C. Their inorganic origin clearly indicated. One of the two radicals has been identified as O3- (g1 = 2.002, g2 = 2.010, g3 = 2.016) and the other as (CO3-3 (parallel = 1.996, g = perpendicular 2.003). Variations of the alpha lattice parameter and trapping of paramagnetic gas species do not seem to be directly related.

Apatites↗
PubMed1976

Control of long chain fatty acid oxidation in heart mitochondria as studied by spin labeling.

Spin-labeled stearic acid is shown to exhibit the same beta-oxidation kinetics as normal stearic acid. ESR spectra recorded in conditions allowing beta-oxidation indicate that membrane-bound fatty acids can be directly beta-oxidized and that the rate of this reaction depends on the concentration of albumin in the medium. The regulating function of albumin and pool role of the lipidic phase of the mitochondrial membranes are discussed.

Albumins↗
PubMedDate not supplied

Role of autoimmunity in protein S deficiency during HIV-1 infection.

The objective of the study was to evaluate the role of autoimmune mechanisms in the pathophysiology of protein S deficiency during HIV-1 infection. In a prospective study the correlation between protein S activity and the presence of anti-protein S autoantibodies or anti-cardiolipin antibodies in HIV-1-positive patients and in a population of patients without HIV infection was investigated. Fifty-five HIV-1-infected patients and 15 hospitalized patients without HIV infection were analysed for protein S activity (functional assay), complement system activation, presence of autoantibodies against protein S (Dot Immunobinding) and levels of anti-cardiolipin IgG antibodies (ELISA). The presence of anti-protein S antibodies was detected in 31 (56.36%) out of the 55 HIV-1-positive patients and in three (20%) of the 15 control patients (Fisher's exact test, p = 0.012). The average value (+/- standard deviation) of protein S activity was 100.93 (14.73)% in the control group. For the HIV-1-infected patients it was 73.70 (20.67)% in those with anti-protein S antibodies compared to 88.08 (25.48)% in those without (Mann-Whitney U Test, p = 0.01). In the HIV-1-positive group protein S activity was correlated with concentrations of circulating immune complexes (Spearman rank sum test, r = -0.41, p = 0.018) and in the control group with concentrations of anti-cardiolipin antibodies (Spearman rank sum test, r = 0.709, p = 0.032). In conclusion, HIV-1 infection is associated with a high prevalence of antibodies against protein S. These antibodies are associated with a significantly low protein S activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

Bicyclonucleosides and ring-chain interconversion.

Four types of bicyclonucleosides differing in the easiness of their ring-chain interconversion have been prepared, some exhibited anti-HIV activity and the ratio of their cyclic and open-chain forms could have some bearing on their biological activity.

Anti-HIV Agents↗
PubMedDate not supplied

Physical and chemical analyses of the mineral substance during the development of two experimental cutaneous calcifications in rats: topical calciphylaxis and topical calcergy.

In subcutaneous calcinoses induced in rats by topical calciphylaxis and topical calcergy, the ultrastructural aspects related to the evolution of calcified deposits were previously described. In the present study by means of X-ray diffraction, infrared spectrometry and electron spin resonance, different biophysical analyses are performed on the mineral substance deposited during development of calciphylaxis and calcergy. A rapid evolution of the calcium phosphate deposits into hydroxyapatite was noticed along the first 20 days of the calcinoses; from then, there is no important modification even at the later stages, and the characteristics of the mineral substance are mostly similar to that of bone tissue. The concentration of trace elements such as Mg2+ and Fe2+, is found higher in cutaneous calcinoses than in bone tissue.

Animals↗