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B Eymard

Publications and source records attributed to B Eymard.

At least 109 records · Page 6Linked to original sources
PubMed1992

Combined effects of a thymic peptide, thymopoietin and myasthenic patient sera in rat myotube culture.

We investigated in a rat myotube assay the combined effect of 26 myasthenic (MG) patient sera and a thymic peptide, thymopoietin (Tpo) which had previously been shown to bind Torpedo and human AChR and to compete with alpha-bungarotoxin (alpha-Bgt) binding. Cultures were first exposed to Tpo alone for 3 h (0.3, 7.5, 15 nM), then MG sera (5% final dilution) were added for an additional 18 h. Reduction in the amount of 125I-alpha-Bgt binding sites in the presence of various concentrations of Tpo were similar with control sera and in all the patients with low or undetectable anti-AChR Ab (11 cases). In cultures exposed to Tpo and sera with high anti-AChR Ab titre (15 cases), Tpo and anti-AChR Ab have an additive capacity to reduce the number of alpha-Bgt binding sites. The results are compatible with the hypothesis that anti-AChR Ab and Tpo could impair neuromuscular transmission by complementary mechanisms.

Acetylcholinesterase↗
PubMed1992

Decreased cerebral glucose utilization in myotonic dystrophy.

To test the hypothesis that cerebral metabolism is altered in myotonic dystrophy (MyD), we investigated cerebral glucose kinetics and utilization in 11 adult patients with MyD and 14 healthy controls, using 18F-labeled 2-fluoro-2-deoxy-D-glucose (FDG) and dynamic positron emission tomography. Estimation of rate constants in MyD revealed a reduction of FDG delivery to the brain. Cortical glucose utilization rate was reduced by about 20% in MyD. These findings may be related to the presence of neurologic impairment in MyD and prompt further investigations on the metabolic and clinical features of brain dysfunction in this disease.

Adult↗
PubMed1992

Exercise intolerance in patients with McArdle's disease or mitochondrial myopathies.

OBJECTIVES: To assess respiratory and metabolic adaptations in patients with phosphorylase deficiency and mitochondrial myopathies using maximal exercise tests. PATIENTS AND METHODS: Five patients with McArdle's disease and five patients with mitochondrial myopathies performed the same incremental maximal exercise test. Their respiratory gas exchanges and the variation of the venous blood metabolites--lactate (LACT), pyruvate (PYR), alanine (ALA), ammonia (NH3)--were studied in comparison with the results of fourteen control subjects who performed the same test. RESULTS: Compared with controls, the two groups of patients displayed a similar significant decrease of their maximal VO2. In McArdle's patients the limitation of the maximal oxygen consumption was associated with a low respiratory exchange ratio (RER), a high VE/VO2, and characteristic metabolic data: no rise of LACT and PYR, a decrease of ALA and an important rise of NH3. In mitochondrial myopathies low VO2 max were due to a leftwards shift, i.e. towards low powers of exercise, of LACT, PYR, NH3 and ALA values. However the pattern of increase of LACT, PYR and NH3, exponential, and of ALA, linear, as well as respiratory exchange ratios were similar to control values. In this case, the limitation of oxygen consumption was due to a lack of the usual substrate, pyruvate. Low respiratory exchange ratio demonstrated that the muscle metabolism had a tendency to shift to lipid oxidation. CONCLUSION: These results suggest that patients with McArdle's disease may improve their muscle energy production by endurance training which enhances lipid metabolism, whereas in mitochondrial myopathies, the energy production by oxidation of pyruvate or lipids may be improved only by enzymatic substitution.

Adult↗
PubMed1992

Mitochondrial encephalomyopathies.

Molecular genetic studies are now bringing a new classification and new insights into already recognized mitochondrial encephalomyopathies. There are, however, numerous reports on an overlap pattern between mitochondriopathies. In addition, the link between the defect in oxidative phosphorylation (OXPHOS) in the brain and the specific neuropathological pattern is unclear. A better knowledge of nuclear mutations in mitochondriopathies and of the interactions between nuclear and mitochondrial genomes will probably allow new developments.

Biopsy↗
PubMed1991

[Myasthenia].

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Clinical Protocols↗
PubMed1991

Intracranial arachnoid cysts in myotonic dystrophy.

Clinically apparent brain dysfunction is common in myotonic dystrophy. In a sample of fourteen adult patients with the definite form of this disease, brain magnetic resonance imaging detected frequent white matter abnormalities and ventriculomegaly. In addition, two patients exhibited an intracranial arachnoid cyst, a condition of neurosurgical interest that could be related to the generalized dysmaturational process present in this disease. Patients with myotonic dystrophy deserve a careful screening for brain involvement. Further MRI studies should ascertain the actual prevalence of brain anomalies in myotonic dystrophy and define the role of this procedure in the workup of this disease.

Adult↗
PubMed1991

Deletions of mitochondrial DNA in Kearns-Sayre syndrome and ocular myopathies: genetic, biochemical and morphological studies.

Genetic, biochemical and morphological investigations were conducted on skeletal muscle mitochondria from 6 cases of ocular myopathy: 4 cases with Kearns-Sayre syndrome (KSS) and 2 with chronic progressive external ophthalmoplegia. All of these 6 cases showed mitochondrial DNA (mtDNA) deletions in addition to normal sized DNA in the quadriceps muscle. The deletions ranging from 3 to 8 kbp were also mapped between nucleotides 5500 and 16000 by Southern blot. The deleted genes encoded for some subunits of complexes I, IV, V and 5-10 tRNAS. The boundaries of the deletions have been sequenced in three patients. Five patients had mitochondrial respiratory chain deficiency in complex I as shown by the low oxygen consumption in isolated mitochondria using three NAD(+)-linked substrates. Mitochondria with an abnormal ultrastructure were also observed in 2 cases. A good relationship between the cytochrome c oxidase deficiency and the amount of deleted mtDNA was shown in our present investigations.

Adult↗
PubMed1991

Genetic biochemical and pathophysiological characterization of a familial mitochondrial encephalomyopathy (MERRF).

Myoclonic epilepsy with ragged-red fibers (MERRF) syndrome is a neuromuscular disorder characterized by mitochondrial myopathy and progressive myoclonus epilepsy. A heteroplasmic A to G transition mutation in the mitochondrial encoded tRNA(Lys) gene at nucleotide pair 8344 has been suggested to be linked to the MERRF-syndrome. We have investigated biochemically and histochemically muscle biopsies and studied the mitochondrial genomes of hair, blood and muscle tissue of a family including three cases of MERRF-syndrome as well as unaffected relatives within the maternal lineage. Sequence analysis of the mtDNAs, performed after amplification by the polymerase chain reaction (PCR), confirmed the A to G transition mutation in the tRNA(Lys) gene at position 8344. The additional point mutation at nucleotide pair 750 in the 12 S rRNA gene, which was also found by Shoffner et al. (1990), however, was absent in all investigated tissues. Quantitative analysis of the percentage of mutated mtDNA by mispairing PCR (Seibel et al., 1990) revealed variable contents in different tissues and individuals, including unaffected family members. Mitochondrial protein synthesis in cultured fibroblasts from MERRF patients revealed diminished incorporation of 35S-methionine into lysine-containing peptides.

Adolescent↗
PubMed1991

Anti-acetylcholine receptor antibodies in neonatal myasthenia gravis: heterogeneity and pathogenic significance.

Precipitating, blocking and modulating anti-AChR antibodies and their capacity to recognize embryo or adult muscle were investigated in parallel in maternal and neonatal sera of fifty-two newborns and their myasthenic mothers. Twenty-four babies presented neonatal myasthenia gravis (NMG) with a common expression in twenty cases and foetal involvement in four cases. Occurrence of NMG was clearly related to levels of maternal precipitating, decamethonium blocking (DC blocking) and modulating antibodies (respectively P less than 0.001, P less than 0.02, P less than 0.01, Mann-Whitney test), these three parameters being interrelated. The only significant difference between mothers with severely affected babies and others with mild NMG newborns concerned DC blocking antibodies. Transfer fraction of DC blocking antibodies was significantly higher in NMG than in asymptomatic babies. Our data suggest that (1) the amount of anti-AChR antibodies, whatever the tested category, is involved in the pathogeny of NMG in a more direct manner than in adult MG where the correlation with their levels is poor, and (2) among antibodies, those with blocking effects could be preponderant for triggering NMG and be involved in the severity of the disease in the child.

Adult↗
PubMed1991

Exercise-induced muscle modifications: study of healthy subjects and patients with metabolic myopathies with MR imaging and P-31 spectroscopy.

Exercise-induced variations in proton signal intensity at magnetic resonance (MR) imaging and in intracellular pH were studied in the forearm muscles of healthy subjects and patients with muscular glycogenoses. The relative increase in T2 was measured from MR images obtained at 0.5 T, and end-exercise pH was measured with surface coil phosphorus-31 spectroscopy at 2 T. Eight healthy subjects showed a relative increase in T2 ranging from 20% to 44% in the flexor digitorum superficialis muscle and a drop in pH ranging from 0.35 to 1.1. Seven patients with muscular glycogenosis (six with McArdle disease and one with phosphofructokinase deficiency) showed only a slight variation in T2 (0%-17%) and no decrease in pH. Variations in T2 and in end-exercise pH were found to be correlated, perhaps reflecting the stimulation of muscular perfusion caused by acidosis.

Adult↗
PubMed1991

[Clinical and electrophysiologic study of the peripheral nerve in 28 cases of mitochondrial disease].

Twenty-eight patients with mitochondrial disease were systematically investigated on clinical and electrophysiological grounds for peripheral neuropathy (PN): 25 had predominant ophthalmoplegia (including 4 with Kearns-Sayre syndrome) and 3 had predominant central nervous system involvement. There were 11 men and 17 women, mean age 43 years. Nine of the 28 patients had signs of sensory polyneuropathy involving mainly the lower limbs. These 9 patients and another asymptomatic patient had electrophysiological abnormalities: in the lower limbs, sensory potentials were absent or decreased in amplitude in all cases. In peroneal nerves, motor conduction nerve velocities were decreased in 4/10 cases. These data were consistent with an axonopathy. No correlation was found between the presence of PN and the clinical features of the mitochondrial diseases or with the respiratory chain defect (studied in 14 cases).

Action Potentials↗
PubMed1991

[Mitochondrial function and mitochondrial DNA in a series of 64 patients suspected of having mitochondrial myopathy].

Biochemical results concerning 64 patients suspected of mitochondrial myopathies are presented. Four clinical groups were studied including 21 encephalomyopathies, 42 ocular myopathies, 8 isolated myopathies and 3 cardiomyopathies. In 26 cases, the coexistence of a normal mitochondrial DNA and a mutated mitochondrial DNA (heteroplasmy) was found (19 simple deletions, 4 multiple deletions and 3 punctual mutations) and all cases presented with ocular disorders (excepted 2 cases with MERRF). Furthermore, 1 complex I deficiency (1 ocular myopathy), 1 complex IV deficiency (1 adult encephalomyopathy type Leigh), 3 complexes I + IV deficiencies (2 cases with a cardiomyopathy and 1 familial MELAS) and 2 pyruvate (1 adult from of Leigh's encephalomyopathy) dehydrogenase deficiencies (clinically and genetically different) did not show evidence of mitochondrial DNA mutation.

Blotting, Western↗
PubMed1990

Neonatal myasthenia gravis: antigenic specificities of antibodies in sera from mothers and their infants.

Transient neonatal myasthenia gravis (MG) is a human model of passively transferred MG. In an effort to understand the characteristics of the most pathogenic antibodies in MG, we studied the fine antigenic specificities of anti-AChR antibodies in sera from 21 MG mothers (nine of which had transiently transferred the disease) and 17 of their infants. Although in a few cases significant differences in antibody specificities were observed between mothers and infants, whether myasthenic or not, generally the antigenic specificities of the antibodies in sera from infants were very similar to those of their mothers. Furthermore, no characteristic differences were detected between the antibody repertoires of mothers who transferred the disease and those who did not.

Antibodies, Monoclonal↗
PubMed1989

Immunocytological and histochemical correlation in Kearns-Sayre syndrome with mtDNA deletion and partial cytochrome c oxidase deficiency in skeletal muscle.

We report histochemical, immunocytochemical, biochemical and molecular studies of skeletal muscle from a 23-year-old man with Kearns-Sayre syndrome. Southern blot analysis revealed a 4.7 kb heteroplasmic deletion of the mitochondrial DNA mapping within genes coding for subunits of complexes I, IV and V of the respiratory chain and for tRNA. Cytochrome c oxidase activity was decreased by 30% in isolated muscle mitochondria, without alteration of the Km. Histochemical and immunocytochemical correlation studies for cytochrome c oxidase revealed a lack of activity in 34% of individual muscle fibers including all the typical ragged-red fibers and a low percentage of immunodeficient fibers.

Adult↗
PubMed1989

Alpha-bungarotoxin blocking antibodies in neonatal myasthenia gravis: frequency and selectivity.

We have studied antibodies to the acetylcholine receptor (AChR) that inhibit alpha-bungarotoxin binding in 22 mothers with myasthenia gravis (MG) and in their 23 newborns. Of the 13 showing neonatal MG, seven of the mothers had detectable direct blocking antibodies, all 13 had decamethonium-dependent (DC) blocking, and nine had high titres of precipitating antibodies (greater than 40 nM). In those with symptom-free newborns, the corresponding figures were 2/10, 8/10 and 2/10; the mean titres of DC blocking and of precipitating antibodies were 5- and 3-fold lower than in the mothers of affected babies. Thus, blocking antibodies, in addition to high total antibody levels, may help to predict the occurrence of neonatal MG. However, the antibodies appear not to cross the placenta to the same extent in each case. 86, 69 and 84% of the maternal antibodies with precipitating, direct and DC blocking activities, respectively, were found in the myasthenic neonates versus 65, 28 and 44% in the unaffected. These data suggest (1) involvement of blocking antibodies in the pathogenesis of MG, and (2) variable placental transfer of anti-AChR antibodies, which makes neonatal affliction more difficult to predict.

Autoantibodies↗