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R Rousson

Publications and source records attributed to R Rousson.

35 records · Page 2Linked to original sources
PubMed1991

Type C Niemann-Pick disease: biochemical aspects and phenotypic heterogeneity.

Within Niemann-Pick diseases, type C has now been demonstrated to be a nosological entity totally distinct from types A and B, and is best characterized at present by unique abnormalities of intracellular translocation of exogenous cholesterol, which are briefly reviewed. Although the primary defect is still unknown in type C Niemann-Pick disease, this discovery has had immediate medical applications, by providing the first strategy for reliable prenatal detection of the disorder and easy diagnosis of patients. From our personal experience of 134 cases, diagnosis is best reached by the combined demonstration of a deficient induction of esterification and of an intravesicular cholesterol storage by cytochemistry after filipin staining. The prevalence of the various clinical forms observed is given, together with a brief report of 6 adult-onset cases. The spectrum of phenotypic heterogeneity in relation to abnormal LDL processing has been defined, resulting in the delineation of three biochemical groups, classical (86%), variant (7%) and intermediate (7%). Correlations between clinical and biochemical phenotypes have been studied. To get further insight into genetic heterogeneity, complementation studies were performed. Preliminary results have yet given no evidence of several complementation groups within type C Niemann-Pick disease. The recognition of the three biochemical phenotypes is however critical for diagnosis and genetic counselling.

Adolescent↗
PubMed1990

Abnormal cholesterol metabolism in imipramine-treated fibroblast cultures. Similarities with Niemann-Pick type C disease.

Addition of low-density lipoprotein (LDL) to cholesterol-deprived human skin fibroblast cultures treated by imipramine at a 20 microM concentration induced a significant intracellular accumulation of unesterified cholesterol. Intracytoplasmic inclusions were already visible by histochemical filipin staining after 2 h of LDL uptake and were progressively mobilized towards the perinuclear region within 24 h. At this concentration of the drug, the rate of proteolytic 125I-LDL hydrolysis was similar in treated and untreated cells. Treated cells maintained in lipoprotein-deficient medium showed no abnormality, indicating the exogenous origin of the accumulated sterol. Further, the drug induced a drastic dose-dependent impairment of LDL-stimulated cholesterol esterification, not related to an inhibition of acyl CoA:cholesterol acyltransferase, and a significant delay in down-regulation of de novo cholesterol synthesis. However, imipramine did not affect 25-hydroxycholesterol-mediated regulation of the two latter processes. These results resemble those observed in Niemann-Pick type C disease and suggest an impaired mobilization of LDL-derived cholesterol in imipramine-treated cells.

Acetates↗
PubMed1988

Niemann-Pick disease group C: clinical variability and diagnosis based on defective cholesterol esterification. A collaborative study on 70 patients.

Seventy patients were selected to cover the range of variability in clinical expression of Niemann-Pick disease group C (NP-C). Their individual main clinical features and course of the disease (age at discovery and type of visceromegaly, age at onset and first neurological manifestation, later neurological symptoms) are schematically described. In cultured skin fibroblasts from these patients, sphingomyelinase activities measured in vitro showed decreased values only in approximately half of the cases, and when the metabolic fate of [14C]-sphingomyelin was studied in living cell cultures, still 20% of the cases had a normal hydrolysis rate. Esterification of exogenous cholesterol was investigated in cell lines from these and 5 additional patients and in 21 of their parents. Using a non-lipoprotein [3H]cholesterol source, very low esterification rates were obtained in more than 90% of the cases. All the numerous other pathological conditions studied, including Niemann-Pick disease types A and B, gave normal results. A more sensitive method was elaborated, in which the cells were challenged with pure human low density lipoproteins (LDL) and the early rate of esterification studied. With the latter procedure, a pronounced deficiency could also be demonstrated in the few cases which had shown a milder impairment using a [3H]cholesterol source, and intermediate rates of esterification were obtained in heterozygotes. Discrimination of these difficult cases and of heterozygotes could also be achieved replacing LDL with total unfrozen human serum. Correlations were established between given clinical phenotypes and the severity of the biochemical lesion. Defective intracellular cholesterol esterification is further established as an intrinsic feature of NP-C, and demonstration of this metabolic alteration appears as a major advance in diagnosing the condition.

Age Factors↗
PubMed1988

[Sphingolipidosis. Recent progress in biochemical diagnosis. New pathogenic approaches].

In an increasing number of biochemical variants of the sphingolipidoses, demonstration of the enzyme defect cannot be achieved by the (briefly summarized) conventional techniques. Alternative methods allowing diagnosis of such patients - in particular metabolic studies in living cell cultures - are discussed. The current knowledge and practical impact of molecular biology in the sphingolipidoses field is shortly reviewed. The authors finally discuss the recent findings highlighting in Niemann-Pick disease type C metabolic abnormalities in the cellular processing of cholesterol and their consequences on diagnosis and pathogenesis of this disorder.

Cells, Cultured↗
PubMed1987

Presence of immunoreactive material in Niemann-Pick type A placenta using anti-sphingomyelinase rabbit gammaglobulins.

Human placental sphingomyelinase was highly purified through an original six-step scheme in order to raise a specific rabbit anti-sphingomyelinase antibody. Pure enzyme preparations showed specific activities ranging between 100 and 150 mumol/h per mg protein and gave two constant silver-stained bands (Mr 70,000 and 57,000) on acrylamide after electrophoresis under denaturing conditions. These two bands were the sole areas detected by the described antibody on Western blots from normal placental preparations at various stages of purification. A similar procedure was applied to the separate study of placental sphingomyelinase from two prenatally diagnosed foetuses with confirmed Niemann-Pick disease type A. During purification, the mutant enzyme could be followed owing to its minute but measurable level of catalytic activity, and behaved normally at the various chromatographic steps. In the purified preparations, specific activities of 0.18 and 0.49 mumol/h per mg protein, respectively, were reached. No alteration of the Km value (19 mumol/l) was observed, while the Vmax was 0.5-1% of normal. With immunostaining of Western blots obtained as above, results similar to those described for normal tissue were found, leading to the conclusion that immunoreactive sphingomyelinase is present in Niemann-Pick disease type A.

Animals↗
PubMed1985

Biochemical studies in Niemann-Pick disease. III. In vitro and in vivo assays of sphingomyelin degradation in cultured skin fibroblasts and amniotic fluid cells for the diagnosis of the various forms of the disease.

Sphingomyelinase activities were assayed in vitro in cultured skin fibroblasts of 61 patients with Niemann-Pick disease (NPD). Residual activities found in type A and B were 1% and 4%, respectively, of the mean control values, i.e. significantly higher in type B. In 27 cases with NPD type C, the mean activity was 42% of that in controls, with residual activities ranging from 15% up to normal. Fifteen pregnancies at risk for NPD type A and B were monitored; 4 affected foetuses were found. The uptake of exogenously added radiolabelled sphingomyelin by cultured cells and metabolism of the choline moiety of this lipid were studied in 35 patients with NPD and 14 controls. No difference of uptake between normal and mutant cells was observed. Normally, 77 +/- 5% of the radioactivity taken up was converted to phosphatidylcholine after 18 h incubation, compared to 5 +/- 2% (n = 7) in NPD type A. A substantially greater hydrolysis (31 +/- 12%; n = 8) occurred in NPD type B, and the test allowed complete discrimination between these two types. In NPD type C, 16 patients showed an abnormally low rate of intracellular sphingomyelin degradation (48 +/- 5%) while 4 others were not distinguishable from controls. There was a correlation (r = 0.76) between the results of the in vitro and in vivo assays, but also between the severity of the clinical symptoms and the impairment in sphingomyelin degradation. For the diagnosis of NPD type C, the in vivo test gave more reproducible and more clearcut results than the in vitro assay.

Amniotic Fluid↗
PubMed1984

Long term outcome of organic acidurias: survey of 105 French cases (1967-1983).

The French experience in the long term follow-up of 105 cases of organic aciduria (45 maple syrup urine disease, 12 isovaleric acidaemia, 19 propionic acidaemia, 24 methylmalonic aciduria and some rare allied disorders) is reported. Main conclusions drawn from this survey are the poor overall prognosis and the slow improvement in the outcome of such disorders over the last 15 years. In MSUD, while early diagnosis and early management remain a basic requirement, intellectual development did not improve as much as expected. In propionic and methylmalonic acidaemia modern treatment does not prevent a fatal outcome in the classical neonatal forms. It should be also emphasized that in the rare cases where a coenzyme deficiency has been demonstrated, vitamin therapy is very often ineffective in vivo.

Acids↗
PubMed1983

Chromatofocusing of skin fibroblast sphingomyelinase: alterations in Niemann-Pick disease type C shared by GM1-gangliosidosis.

Sphingomyelinase activity of cultivated skin fibroblast extracts from normal individuals was resolved by chromatofocusing in the pH range 8-5 into three major components with pI's of 7.3, 6.3 and 5.9, respectively. Chromatofocusing proved a more efficient and reproducible separation technique than preparative flat-bed isoelectric focusing and it gave a constant profile even when detergent concentration varied. In skin fibroblasts from five patients with Niemann-Pick disease type C, a varying degree of reduction in the proportion of the 7.3 peak was observed. In a patient with clinical features of Niemann-Pick disease type C, the finding of such a profile would thus be a good argument for the diagnosis, but it is not pathognomonic as we found similar changes in two cases with GM1-gangliosidosis, while some cases of Niemann-Pick disease type C have borderline normal profiles. These results challenge the concept of a specific sphingomyelinase isoenzyme deficiency as the basic defect in Niemann-Pick disease type C.

Fibroblasts↗
PubMed1983

Chromatofocusing of purified placental sphingomyelinase.

To establish the profile of the multiple forms of placental lysosomal sphingomyelinase, we have developed in a preliminary step, a new sequence of purification. This protocol has a good yield such that the final preparation is representative of the whole enzyme. Using chromatofocusing, purified sphingomyelinase is resolved into 4 major forms whose pI's are 7.2, 6.5, 5.9 and 5.2. Chromatofocusing is preferable to isoelectric focusing because it is more rapid, more reproducible and above all it provides a constant profile of activity which is not influenced by experimental conditions, in particular, detergent concentration.

Chromatography↗
PubMed1979

Demonstration of altered acidic hydrolases in fibroblasts from patients with mucolipidosis II by lectin titration.

Decreased binding by the lectins concanavalin A and wheat-germ agglutinin was found for a number of acidic hydrolases from skin fibroblasts of three unrelated patients with mucolipidosis II. This decreased binding as compared with normal controls was demonstrated by titration of hydrolase activities with increasing amounts of immobilized lectins. Neuraminidase treatment slightly improved the binding of enzymes from mucolipidosis-II patients, in contrast with the diminished binding found or hydrolases from control cell lines. The abnormality in binding by lectins of hydrolases of mucolipidosis-II patients was observed for enzymes with various degrees of intracellular deficiency as well as for enzymes with normal intracellular activities. These findings suggest a generalized alteration of fibroblast acidic hydrolase molecules in mucolipidosis II.

Fibroblasts↗
PubMed1979

Multiple carbohydrate-cleaving specificities in human acidic and neutral glycosidases.

The common identity of human acidic beta-D-glucosidase (beta-D-glucoside glucohydrolase, EC 3.2.1.21) and beta-D-xylosidase (1,4-beta-D-xylan xylohydrolase, EC 3.2.1.37) as one enzyme and that of acidic beta-D-galactosidase (beta-D-galactoside galactohydrolase, EC 3.2.1.23), beta-D-fucosidase (no allotted EC number) and alpha-L-arabinosidase (alpha-L-arabinofuranoside arabinohydrolase, EC 3.2.1.55) as another enzyme is indicated by similar binding patterns of glycosidase activities of each enzyme to various lectins. by similar ratios between their intra- and extracellular levels in normal and I-cell fibroblasts and by their deficiencies in liver tissues from patients with Gaucher disease and GM1 gangliosidosis, respectively. A third enzyme, neutral beta-D-galactosidase, purified to homogeneity from human liver has been shown to possess all these five glycosidase activities at neutral pH. These neutral enzymic activities were not bound by any of the lectins examined and found to be reduced in liver and spleen of a patient with neutral beta-D-galactosidase deficiency. An additional form of beta-D-xylosidase with optimal activity at pH 7.4 was bound by the fucose-binding lectin from Ulex eurpaeus while no binding was observed for the acidic (pH 4.8) and neutral (pH 7.0) beta-D-xylosidase activities of the multiple glycosidase enzymes.

Binding Sites↗
PubMedDate not supplied

[HDL-cholesterol: role of its dosage in the assessment of cardiovascular risk].

The interest of HDL-cholesterol (HDLC) to evaluate a cardiovascular risk has been studied since many years. According to Framingham Heart studies, this factor is inversely correlated to a future ischaemic heart disease. At high level, HDLC is considered as a cardiovascular protecting factor, and is known since few years as "good cholesterol". In the year 2000, the ANAES (Agence nationale de l'accréditation et évaluation en santé) has redefined the role of HDLC in the exploration of dyslipidaemia. In the case of a cardiovascular-risk history, HDLC, with total cholesterol, triglycerides, and LDL-cholesterol (by Friedewald method) will be analyzed. Usually, HDLC is not very accessible to conventional treatments. So, according to ANAES, the treatment of dyslipidaemia will be based on LDL-cholesterol levels only. Nevertheless, HDLC is a major lipid factor to evaluate a cardiovascular risk. The object of this review is, on one hand, to situate HDLC in the evaluation of cardiovascular risk, by showing its key role in lipid metabolism, and, on the other hand, to report the main direct assays of this parameter.

Anticholesteremic Agents↗
PubMedDate not supplied

[Cardiac troponin I and C: analytical comparison and clinical-biological interpretation of three troponins assays].

Many assays 1(st), 2(nd) even 3(rd) generation are at present available to determine the concentration of cardiac troponin I and T. With the redefinition of upper reference value in the acute coronary syndromes, the aim of this study was to evaluate the clinical and analytical performance of 2 troponins assays: Troponin Ic 2(nd) generation (AccuTnI) on Access 2 of Beckman Coulter and Troponin Tc 3(rd)generation (Troponin T STAT) on Elecsys 2010 of Roche Diagnostics. The analytical performance observed with these 2 assays are accurate (analytical and functional sensitivity, repetability and reproductibility). Comparing each method with Dade Behring assay (Flex Troponine-I Cardiaque, TROP) on Dimension RxL, the correlation observed with AccuTnI kit on Access 2 can be put into the equation: AccuTnI = 1.08 (TnIc TROP) - 0.34, r = 0.99. On the contrary, it's more difficult to compare cTnI and cTnT. The study of decisonnal values indicated by Beckman Coulter for cTnI (0.04 microg/L at the 99 degrees percentil, 0.06 microg/L for a CV < or =10%) show a better specificity (76%) and predictive positive value (89%) with a sensitivity at 100% at 0.1 microg/L, fixed and used in the laboratory for its better agreement between sensibility / specificity and its imprecision below 10 %. For the cTnT values published by Roche Diagnostics (0.01 microg/L), at the 99 degrees percentil and 0.03 microg/L for a CV < or = 10%, the specificity is lower, so the decisionnal value 0.1 microg/L seems to be more suitable. During this study, few false positive and negative cTnT values have been observed, in patients with complex pathologies; this eventuality must be taken in consideration if clinical findings are not in good accordance with laboratory results.

Angina, Unstable↗