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Biomedical subjects

M Duc

Publications and source records attributed to M Duc.

At least 37 records · Page 2Linked to original sources
PubMed1993

[Physiopathology of inorganic lead poisoning].

This paper gives an overview of the hypotheses concerning the mechanisms of inorganic lead toxicity on cells and tissues, with emphasis on the effect of low-concentration lead. Inhibition of heme synthesis is responsible not only for lead-induced anaemia, but also for accumulation of delta-aminolaevulinic acid (ALA) and for lowering the concentration of cytochromes contained in the mitochondrial respiratory chain. Auto-oxidation of ALA is thought to result in the formation of free radicals. On the other hand, lead replaces ionic calcium in its role as second cell messenger. This mechanism would explain the abnormalities observed in synaptic transmission, arteriolar vasoreactivity and functioning of such cells as osteoclasts and osteoblasts. Nuclear toxicity, with abnormal expression of DNA genes and inhibition of certain enzymes such as membrane Na+/K+ ATPase, are also considered. The mechanisms of tissue toxicity are discussed.

Humans↗
PubMed1993

[Abnormalities of the muscular bioenergetics in Steinert's disease].

The thenar muscles and gastrocnemius of a patient with myotonic dystrophy were investigated, at rest, by phosphorus nuclear magnetic resonance spectroscopy. A decrease in phosphocreatine level and an increase in inorganic phosphate and phosphodiester levels were found in the gastrocnemius, which was clinically spared, whilst the thenar muscles, which were wasted and affected by myotonia, exhibited only an increased inorganic phosphate level and an elevated pH. These findings were comparable with those found in other muscular disorders, such as Duchenne's and Becker's dystrophies, as well as in limb girdle dystrophy. They suggested that the abnormalities observed were unrelated to myotonia or wasting, and the possibility of a secondary mitochondrial disorder in myotonic dystrophy, is to be considered.

Adult↗
PubMed1993

[Disorders of hemostasis in dysthyroidism].

Many potentially severe hemostatic disorders have been reported in thyroid diseases. Hyperthyroidism has been associated with thrombocytopenia, coagulation factor abnormalities, and decreased fibrinolytic and plasminogen activities. In hypothyroidism, potentially severe hemorrhagic disorders have been reported, including platelet function abnormalities and coagulation factor alterations such as acquired von Willebrand disease.

Blood Coagulation Disorders↗
PubMed1992

Energetic metabolism in hypothyroid skeletal muscle, as studied by phosphorus magnetic resonance spectroscopy.

Phosphorus nuclear magnetic resonance spectroscopy was used to investigate the muscle bioenergetics in different hypothyroid states. Using the thenar muscle group as reference, 2 patients with chronic and severe hormonal deficiency, 3 patients with subacute hypothyroidism, and 8 patients with moderate thyroid insufficiency with isolated high blood TSH levels were studied at rest, during exercise, and during subsequent recovery. The patients were compared with 15 control subjects. Only 1 patient presented a clinical myopathy. The intracellular pH and the relative measurements of inorganic phosphate, phosphocreatine, phosphodiesters, and ATP were directly calculated from phosphorus spectra. Resting muscle showed a significant rise in the inorganic phosphate to ATP ratio. In working hypothyroid muscle, a more important decrease in phosphocreatine levels was noted in patients with chronic and subacute thyroid deficiency, while the intracellular pH fall was greater in all hypothyroid patients than in control subjects. The phosphocreatine recovery rate was lower in all deficient patients, reflecting a probable mitochondrial metabolism impairment. These results are consistent with a defect of the high energy phosphate metabolism in hypothyroidism, even in moderate or recent hormonal deficiency.

Adenosine Triphosphate↗
PubMed1992

[Hypothyroid myopathy. Physiopathological approach].

Patients with thyroid deficiency often complain of muscular weakness, exercise intolerance, cramps and excessive fatiguability. Hypothyroidism induces a metabolic myopathy, with a fall of the energetic production, and especially of the mitochondrial metabolism. This is due to a global inhibition of the main oxidative pathways (substrate incorporation, substrate oxidation) and of the respiratory chain. A diminished energetic consumption is partially related to a transition in the myosin isoforms, which express a slower ATPase, and to an impairment of the trans-sarcolemic transports. Exercise intolerance could be due to an abnormal recruitment of several metabolic pathways, such as glycolysis, related to the mitochondrial metabolism impairment, and including an abnormal accumulation of protons and monovalent phosphate ions, which are involved in the alteration of the actin-myosin interaction, and also by an abnormal Ca++ metabolism. The decreased number of NA+/K+ ATPase dependent pumps could imply an abnormal intracellular Na+ level and explain the frequent disorders of the membrane excitability.

Energy Metabolism↗
PubMed1992

[Magnetic resonance imaging in lupic chorea].

A case of disseminated lupus erythematosus with chorea is reported. CT was normal. Magnetic resonance imaging showed multiple focal lesions on T2-weighted sequences, predominating in the periventricular white matter. This MRI pattern did not change in a second MRI investigation, 7 months later. The contribution of MRI to our understanding of the neurolupus pathophysiology is discussed.

Adolescent↗
PubMed1991

31P-NMR study of different hypothyroid states in rat leg muscle.

Using phosphorus nuclear magnetic resonance spectroscopy, this study was undertaken to determine the effects of experimental hypothyroidism on muscle bioenergetics. The peaks of phosphocreatine (PCr), Pi, phosphodiesters (PDE), sugar phosphomonoesters, and ATP were obtained at rest, during a 2-Hz hindleg muscle stimulation, and during a subsequent recovery period from four groups of anesthetized rats as follows: one control and three hypothyroid (HT) groups treated by propylthyouracil during 2, 4, and 6 wk, respectively. Resting spectra showed a significant rise in Pi by 30% and decreased intracellular pH and PCr/Pi in all three HT groups. PDE progressively increased to 200% of its initial value with hypothyroidism duration. Muscle stimulation did not lead to significant differences in PCr depletion. The percentage of PCr recovery is less in HT muscle than in control muscle. An abnormal H+ metabolism is obvious in all three HT groups. These results indicate abnormal bioenergetics in HT muscle and suggest an impairment of mitochondrial metabolism and of the H+ efflux. They also evoke a high sensitivity of cellular energetics to thyroid deficiency.

Animals↗
PubMed1991

Muscle bioenergetic impairment in hyperthyroid man: a study by 31P NMR spectroscopy.

Phosphorus nuclear magnetic resonance spectroscopy was used to investigate muscle bioenergetics in 9 hyperthyroid patients who were compared with 9 normal subjects. Using the thenar muscle group as reference, the inorganic phosphate, phosphocreatine and intracellular pH were calculated at rest, during aerobic exercise (0.13 w) and post-exercise recovery. No difference was found at rest. After 5 min of exercise, the hyperthyroid patients exhibited a more important phosphocreatine depletion (41.2 +/- 8.2 vs 31.1% +/- 6.5, p less than 0.02) and a larger pH fall (6.65 +/- 0.04 vs 7.01 +/- 0.10, p less than 0.001) than the control subjects. The phosphocreatine recovery rate was not significantly different in hyperthyroid patients and control subjects. These results suggest that exercise requires more ATP in hyperthyroid patients than in normal subjects and that there is excessive dependence on glycolytic metabolism for ATP synthesis in hyperthyroidism. Phosphocreatine resynthesis, reflecting the oxidative metabolism, is not increased. These metabolic disturbances could also supply a partial explanation to the frequent exercise intolerance in hyperthyroid patients.

Adenosine Triphosphate↗
PubMed1990

[Phosphorus NMR spectroscopy. Its value in the diagnosis of metabolic myopathies. A case of Mac Ardle's disease].

Phosphorus nuclear magnetic resonance spectroscopy is a non-invasive method used to study muscle bioenergetics in vivo. A new case of Mc Ardle's disease (myophosphorylase deficiency) is reported here. In a context of metabolic myopathy this method can provide a diagnosis of glycogenosis. The spectra obtained at exercise and during recovery determine the degree of enzyme deficiency with satisfactory precision.

Adult↗
PubMed1988

[Incidence of waterborne lead poisoning in an internal medicine department in a region with acid soil].

Between 1980 and 1985 patients living in the Vosges mountains and admitted to the internal medicine department of a university hospital were systematically investigated for chronic lead poisoning. The delta-aminolevulinic acid dehydrase assay was used for screening, and when necessary confirmation was obtained with calcium EDTA-induced plumburia test and lead assays in domestic water. Among 366 patients with no suspicion of lead poisoning, the condition was proven in 52 cases and found probable in 15 cases, i.e. in 18 p. 100 of these patients. Obviously, figures cannot be extrapolated to the entire population of the Vosges, but they indicate that lead-induced morbidity is widespread and that saturnism constitutes a major health problem. In one-half of the cases, chronic lead poisoning affected people over 65 while patients of that age group accounted for only 14 p. 100 of non lead-poisoned patients. Prolonged tolerance to the intoxication explains why saturnism has for so long passed unnoticed in the Vosges region, and it may be feared that the same applies to other regions with the same geological features as the Vosges.

Adult↗
PubMed1985

[Treatment of lead poisoning by drinking water using hemofiltration and chelationin a hemodialysed anuric patient].

Lead intoxication was diagnosed in April 1984 in an anuric woman of 65 years of age, whose hemodialysis had begun 9 years previously. Lead poisoning was completely cured by repeated hemofiltration with calcium EDTA. 28.2 mg of lead were extracted during 26 hemofiltration sessions. After the twentieth session, the rate of extracted lead was 500 micrograms per session and the rate of delta-aminolevulinic acid dehydrase was normalized. This exceptional observation allowed a nearly experimental study of the kinetics and metabolism of Ca EDTA chelated lead.

Aged↗