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M Potier

Publications and source records attributed to M Potier.

At least 163 records · Page 9Linked to original sources
PubMed1980

Correlation between serum lipoamide dehydrogenase activity and phosphatidylcholine therapy in Friedreich's ataxia.

Serum lipoamide dehydrogenase activity and kinetics were studied in nine patients with Friedreich's ataxia before and three months after therapy with oral lecithin. Results disclosed a significant reduction in LAD inhibition by NADH in all patients after therapy. Three patients normalized their increased Km for lipoamide and one patient showed the opposite results after therapy. Two patients ceased lecithin after one month. All seven patients who remained in the trial group and one additional patient, showed subjective and objective signs of improvement in physical resistance. This study has offered some biochemical basis for the apparent clinical improvement in patients with Friedreich's ataxia who undergo lecithin therapy.

Adolescent↗
PubMed1980

The beta-amino acid transport system in Friedreich's ataxia.

Taurine and beta-alanine uptake in cultured skin fibroblasts proceeds through at least two distinct amino acid transport systems. The predominant beta amino acid uptake system which we refer to as the "Beta" system, incorporates taurine in a proportion of 95%. Beta-alanine in a proportion of 80% and does not incorporate beta-amino-isobutyric acid. A second transport system for beta-alanine seems to be operative cultured skin fibroblasts and this system shares the characteristics of system "L" for branched-chain and ring-side neutral amino acids. Results of ion depletion experiments, metabolic inhibition by drugs and blocking agents and previous kinetic studies of taurine and beta-alanine uptake in cultured skin fibroblasts failed to disclose any major difference in beta-amino acid transport between control individuals and patients with Friedreich's ataxia.

Alanine↗
PubMed1979

Neuraminidase activity in the mucolipidoses (types I, II and III) and the cherry-red spot myoclonus syndrome.

Two neuraminidase (EC 3.2.1.18) comonents, A and B, were distinguished in cultured skin fibroblasts on the basis of thermolability at 37 degrees C. The more labile component (A) t1/2 = 4.7--5.3 min at 37 degrees C, comprises 66--90% of total neuraminidase activity when determined using sodium (4-methylumbelliferyl-alpha-D-N-acetylneuraminate) (MU-alpha-N) as substrate. Activity was assayed at 0 degrees C for 18 h instead of 37 degrees C to fully determine both thermolabile and thermostable components. Diminished activity was noted in cultured fibroblasts from mucolipidoses I, II and III (MLI, MLII, MLIII) and the cherry-red spot myoclonus syndrome (CRSM) patients when assayed at both 0 and 37 degrees C with either MU-alpha-N or each of a series alpha (2 leads to 3)- and alpha (2 leads to 6)-linked N-acetylneuraminyloligosaccharides. Increased sensitivity and rapidity of analyses were achieved using MJ-alpha-N as substrate in determining neuraminidase activity. Results from two obligate heterozygote MLI cell lines (14.5 and 8.0% of control activity) indicate that the MU-alpha-N substrate could be useful for heterozygote detection.

Cells, Cultured↗
PubMed1979

Purification and some properties of liver and brain beta-N-acetyl-hexosaminidase S.

beta-N-Acetyl-hexosaminidase S (2-acetamido-2-deoxy-beta-hexoside acetamido-deoxyhexohydrolase, EC 3.2.1.52) was purified from liver and brain of a patient deceased of type O GM2 gangliosidosis (Sandhoff's disease). Brain beta-N-acetyl-hexosaminidase S was further purified by preparative polyacrylamide gel electrophoresis. The pH optimum of the purified liver and brain enzyme was 5.0 and Km values were 0.8--0.9 mM and 0.3--0.4 mM with 4-methylumbelliferyl-beta-D-N-acetylglucosamine and beta-D-N-acetylgalactosaminide derivatives, respectively. beta-N-Acetyl-hexosaminidase S was thermolabile losing most of its activity after 50 min at 50 degrees C. The apparent molecular weights of the purified liver and brain enzymes were 154 000 and 152 000, respectively. Hexosamines activated beta-N-acetyl-hexosaminidase S whereas the isoenzyme A and B were inhibited. The glycoprotein nature of beta-N-acetyl-hexosaminidase S was suggested by its affinity towards Concanavalin A-Sepharose.

Binding Sites↗
PubMed1979

Neuraminidase in cultured fibroblasts and leucocytes of homozygotes and heterozygotes for the mucolipidosis II gene (I-cell disease).

The significance of neuraminidase deficiency reported to be the primary defect in mucolipidosis II has been evaluated by determination of this enzyme activity in cultured fibroblasts, culture medium, and leucocytes from homozygote and heterozygous carriers of the disease. A new and sensitive fluorometric assay of neuraminidase was used with sodium (4-methylumbeliferyl-alpha-D-N-acetylneuraminate) as substrate. We report: 1) nearly total deficiency of neuraminidase in mucolipidosis fibroblasts, 2) partial deficiency of this enzyme in leucocytes of one patient, 3) this decreased activity ceases to exist following Triton X-100 treatment, and 4) intermediary mean neuraminidase activity in fibroblasts and leucocytes from obligate heterozygotes. Although these results would be consistent with the suggestion that neuraminidase deficiency is the primary defect in this disease, evidence from the work of other authors suggests that the enzyme deficiency results from a secondary effect of the mucolipidosis II mutation.

Cells, Cultured↗
PubMed1979

Pyruvate dehydrogenase, lipoamide dehydrogenase and citrate synthase activity in fibroblasts from patients with Friedreich's and Charlevoix-Saguenay ataxia.

The activity of lipoamide dehydrogenase and two closely related enzymes was studied simultaneously in early, mild, and late passage fibroblast cultures. Friedreich's ataxia fibroblasts tended to lose pyruvate dehydrogenase and citrate synthase activities, while lipoamide dehydrogenase activity remained constant with aging of the cells. Mean pyruvate dehydrogenase activity was lower over-all in fibroblasts from ataxics. Mean citrate synthase activity was higher in ataxic fibroblasts. Present tissue culture media do not represent the best conditions in which to reproduce cofactor binding defects such as those found in other genetic diseases with structural enzyme mutations.

Ataxia↗
PubMed1979

Dicarboxylic amino acid uptake in normal, Friedreich's ataxia, and dicarboxylic aminoaciduria fibroblasts.

Glutamic and aspartic acid uptake was measured in skin fibroblasts from patients with Friedreich's Ataxia, dicarboxylic aminoaciduria, and normal individuals. The results showed no difference in uptake kinetics of either dicarboxylic amino acids between Friedreich's Ataxia and normal cells, but reduced uptake velocities in dicarboxylic aminoaciduria fibroblasts. Friedreich's Ataxia fibroblasts were, however, less calcium-dependent and more magnesium and phosphate-dependent than controls in glucose-free incubation mixture. This difference might be related to some degree of glucose intolerance by Friedreich's Ataxia fibroblasts in culture.

Amino Acids↗
PubMed1979

Origin and developmental patterns of lactase and other glycosidases in sheep amniotic and allantoic fluid.

Intestinal lactase activity (with its associated cellobiase, 4-methylumbelliferyl-beta-galactosidase and -beta-glucosidase activities) was used as a specific intestinal marker enzyme to study the release of protein and enzymes of intestinal origin in sheep amniotic fluid during gestation. In amniotic fluid, intestinal lactase activity peaked at 66--85 days of gestation and then decreased with gestation. This enzyme activity was very low or absent in allantoic fluid throughout gestation suggesting that there is no important transfer of amniotic fluid lactase towards the allantoic cavity. Maltase and 4-methylumbelliferyl-alpha-glucosidase showed no statistically significant variation with gestation in both amniotic and allantoic fluid whereas alpha-galactosidase and N-acetyl-beta-hexosaminidase which were first higher in allantoic than in amniotic fluid increased in amniotic fluid to reach allantoic fluid levels near term. Such patterns are consistent with the suggestion that the fetal urine is a source of alpha-galactosidase and N-acety-beta-hexosaminidase activities and that sheep urine is first accumulated in the allantoic sac via the urachus up to 86--90 days of gestation and thereafter passes more and more into the amniotic sac.

Allantois↗
PubMed1979

[Vascular complications of needle biopsy of the liver (author's transl)].

11 complications were observed in 2,346 cases of needle biopsy (frequency 0.47%) carried out in 1,529 cases under laparoscopy, 527 cases by the intercostal route, and in 290 cases during operation. The symptoms usually appeared early, indicating bleeding. The lesions, isolated or associated were six hemoperitoneums, and 9 hematomas (including 2 subcapsular), 3 intrahepatic (1 FAV), one of the gall bladder, 3 undetermined; 5 patients out of 11 were operated on, 4 out of 11 died. The place of surgical treatment is discussed: one hemoperitoneum led to early surgical operation. An intrahepatic or subscapular hematoma may regress without sequelae. An arteriography after a liver scan should eliminate a major vascular lesion which may eventually require surgery.

Adult↗
PubMed1978

Lipoamide dehydrogenase in cultured human skin fibroblasts.

Lipoamide dehydrogenase was identified in cultured skin fibroblasts of normal individuals and patients with Friedreich's ataxia. The optimum conditions for its assay were defined. Data disclosed a normal range of 36--122 mumol/min/mg protein in control fibroblasts and 61--112 mumol/min/mg protein in patients fibroblasts. Numerous precautions should be taken in handling fibroblast cultures for lipoamide dehydrogenase determination.

Buffers↗
PubMed1978

Developmental patterns of intestinal disaccharidases in human amniotic fluid.

A close relationship exists between relative disaccharidase activities (maltase, sucrase, trehalase, palatinase, turanase, lactase, and cellobiase) in amniotic fluid and corresponding jejunal mucosa of five human fetuses (16 to 21 weeks of gestation) suggesting that these intestinal enzymes pass into amniotic fluid. Serial determination of disaccharidase activities in amniotic fluid samples collected between 10 and 42 weeks of gestation showed maximum mean activities at 14 to 17 weeks of gestation and a rapid drop to less than 12 per cent maximum values at about 22 weeks. This drop is probably caused by combined effects of decreased extrusion rate of intestinal disaccharidases and increased reabsorption of the enzymes in swallowed amniotic fluid with fetal development.

Amniotic Fluid↗