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Biomedical subjects

N Moatti

Publications and source records attributed to N Moatti.

At least 109 records · Page 6Linked to original sources
PubMed1987

L-proline uptake in human fibroblasts: evidence for a high-affinity system in addition to system A.

Proline uptake was studied in human skin fibroblasts by simultaneous running of kinetic and inhibition experiments on the same cell lines. Two systems for proline uptake were shown: a high-affinity system not inhibited by alpha-(methylamino)isobutyric acid and a low affinity system inhibited by this amino acid (i.e. system A). These results appear to be of interest, firstly because up till now, system A was considered preferable for proline uptake in human fibroblasts, and secondly because they illustrate the need for combined inhibition and kinetic studies of amino acid uptake, especially when the substrate concentration range used and the respective Km of the systems do not allow their detection by kinetic analysis alone. Furthermore, this high-affinity system may have major physiological implications.

Aminoisobutyric Acids↗
PubMed1986

Antibiotic activity in space.

Environmental factors in space exert an influence on the behaviour of bacteria, particularly on their sensitivity to antibiotics. Thus, G. Taylor and S. Zaloguev observed that bacterial samples collected on the crew during flight in the Apollo-Soyouz Test Project Mission presented higher antibiotic resistance than controls. This paper presents the results of two experiments performed in 1982 and 1985 (Cytos 2 during the French-Soviet Mission and "Antibio" in the Biorack programme of the European Space Agency). The results show an increase of antibiotic resistance in bacteria growth in flight and a modification in the structure of the cell wall. All these modifications are transitory. Two hypotheses are put forward to explain the phenomenon.

Anti-Bacterial Agents↗
PubMed1985

Septic arthritis of the knee due to Neisseria mucosa.

We report a case of septic arthritis of the knee due to Neisseria mucosa a widespread commensal of the oropharynx following an infiltration of the joint. Evolution was favorable in ten weeks, with antibiotics (amoxicillin then erythromycin), and without surgery.

Aged↗
PubMed1985

Preliminary results of Cytos 2 experiment.

Cytos 2 experiment, carried out during the French-Soviet manned flight (July 1982), has studied the antibiotics sensitivity of bacteria cultivated in vitro during the orbital flight. The results show an increase of the antibiotics resistance and a larger thickness of the cellular envelope for the inflight cells. The increase of antibiotics resistance can be related to a stimulating effect of space on the cell growth rate or to changes of the cellular envelope structure.

Anti-Bacterial Agents↗
PubMed1985

Study of minimal inhibitory concentration of antibiotics on bacteria cultivated in vitro in space (Cytos 2 experiment).

The aim of the Cytos 2 experiment, carried out during the French-Soviet manned flight in July 1982, was to study the bacteria's sensitivity to antibiotics cultivated in vitro during the orbital flight, using the bacterial method of minimal inhibitory concentration (MIC). Two species of bacteria were tested with various antibiotics: Staphylococcus aureus with Oxacillin, Chloramphenicol and Erythromycin; Escherichia coli with Colistin and Kanamycin. The results show an increase in resistance to antibiotics particularly strong in E. coli and weaker in Staphylococcus aureus. Considering these results, we think that there might be a relationship between the increase in resistance to antibiotics and a stimulating effect on growth rate by the factors of environmental space.

Anti-Bacterial Agents↗
PubMed1984

Evidence that cycloleucine affects the high-affinity systems of amino acid uptake in cultured human fibroblasts.

The influence of cycloleucine on kinetic parameters of uptake of L-alanine, L-proline and L-leucine into cultured human fibroblasts was examined under initial-rate conditions with substrate concentrations of 0.05-10 mM and 5 mM-cycloleucine. Kinetic data obtained by computer analysis showed that, in the absence of cycloleucine, cell uptake was heterogeneous for each amino acid. L-Alanine and L-leucine entered by two transport systems with different affinities; L-proline was taken up by one saturable transport system plus a diffusion-like process. This heterogeneity disappeared in the presence of cycloleucine, since the high-affinity systems were no longer detectable. The remaining process had the same kinetic constants as the low-affinity system for alanine and leucine and a KD similar to the diffusion constant for proline. The influence of cycloleucine on the amino acid uptake was not specific either to the amino acid concerned or to a particular transport system, since the three neutral amino acid-transport systems, A, ASC and L, were involved in these experiments. This influence was shown to be unaffected by the absence of Na+ (for leucine uptake). ATP content of the cells was identical in the presence or in the absence of cycloleucine.

Adenosine Triphosphate↗
PubMed1984

[Genetic heterogeneity and the diagnosis of hepatic glycogenoses].

Glycogen storage diseases constitute a highly heterogeneous group of disorders, because of the many complex enzyme systems involved in glycogen metabolism, and also because of the diversity of molecular defects connected with gene mutations. To illustrate these features, the authors studied four types of liver glycogen storage diseases, respectively caused by deficiencies of glucose-6-phosphatase, debranching enzyme, phosphorylase and phosphorylase kinase. In each case, the role and functional characteristics of the enzyme system are described, as well as the bioclinical aspects of the deficiency. The only reliable way of diagnosing glycogen storage disease is by assaying the activity of the enzyme concerned. Assay procedure must take account of various factors, especially the progress made in understanding the nature and mechanism of action of enzyme systems, the possible tissular heterogeneity of the deficiency and the functional characteristics of certain enzymes.

Genetic Variation↗
PubMed1983

Transport of L-histidine by human diploid fibroblasts in culture.

The transport of L-histidine has been characterized in skin derived diploid human fibroblasts, cultured under strictly controlled conditions. The transport measurements were made on cells grown to subconfluency after 60 to 90 min timed preincubation. The data, at substrate concentrations ranging from 0.050 to 10 mmol/l, were analyzed by a computer program. A saturable transport system (Km = 0.25 mmol/l, Vmax = 17 nmol/mg protein per min) and a nonsaturable component of influx (Kd = 1.6 +/- 0.4 nmol/mg protein/min per mmol) were found. L-Histidine displayed no Na+ requirement at either low or high concentrations. Inhibition analysis demonstrated that L-histidine uptake at low concentration was poorly inhibited by amino acids known to be effective inhibitors of system A. The largest fraction of L-histidine uptake was inhibited by 2-amino-bicyclo (2,2,1)-heptane-2-carboxylic acid (BCH), leucine, and tryptophan. These results indicated that L-histidine is transported in human fibroblasts mainly by the Na+ independent system L. The differences between this cell type and others studied previously are discussed.

Amino Acids↗
PubMed1983

Defective galactose oxidation in a patient with glycogen storage disease and Fanconi syndrome.

Carbohydrate metabolism was studied in a child with atypical glycogen storage disease and Fanconi syndrome. Massive glucosuria, partial resistance to glucagon and abnormal responses to carbohydrate loads, mainly in the form of major impairment of galactose utilization were found, as reported in previous cases. Increased blood lactate to pyruvate ratios, observed in a few cases of idiopathic Fanconi syndrome, were not present. [1-14C]Galactose oxidation was normal in erythrocytes, but reduced in fresh minced liver tissue, despite normal activities of hepatic galactokinase, uridyltransferase, and UDP-glucose 4-epimerase in homogenates of frozen liver. These data suggest a defect in hepatic galactose metabolism not so far identified.

Child, Preschool↗
PubMed1981

Transport of L-alanine in cultured human fibroblasts: evidence for two kinetically distinguishable systems.

The transport of L-alanine in human diploid fibroblasts was investigated. Transport measurements were performed on subcultures between the third and eighth passages with subconfluent cells growing on glass coverslips. Kinetic analysis of approximate initial rates of transport at substrate concentrations from 0.05 to 10 mmole/liter indicate the presence of two distinguishable systems. The high affinity system has a Km of 0.24 mmole/liter and a Vmax of 6.4 nmole/100 micrograms protein/2 min. For the low affinity system, the contribution of the high affinity system to the uptake must absolutely be taken into account. The Km and Vmax values, obtained by using a computer program, are a Km of 15.0 mmole/liter and a Vmax of 14.7 nmole/100 micrograms protein/2 min. For alanine concentrations below 1 mmole/liter, the contribution of the Na+-independent uptake is less than 10%, and the kinetic constants of the high affinity system are in the same range if this contribution is taken into account. On the contrary the influence of a diffusion-like process is more significant on the low affinity system whose Km is about 49 mmole/liter after subtraction of the Na+-independent uptake from the experimental velocities. Inhibition studies were performed with NCH3-alanine. They permitted us first to confirm the existence of system A in cultured human fibroblasts in agreement with two recent works and second to show how this system contributes to L-alanine uptake. This contribution seems very small in low concentrations but it rises as the concentrations increase.

Alanine↗
PubMed1981

D-glucose uptake in human liver cell cultures.

The kinetics parameters for D-glucose uptake were studied in human liver cell cultures under strictly defined experimental conditions. Using a wide concentration range (0.005 to 30 mmol/l), the kinetic data obtained suggested strongly that D-glucose in human liver cell cultures can be transported by two separate systems. For the high-affinity system, the apparent Km was 0.645 +/- 0.21 mmol/l and the Vmax, 12.49 +/- 3.74 nmol/mg protein per min. For the low-affinity system, the apparent Km was 6.91 +/- 0.58 mmol/l and the Vmax, 79.90 +/- 5.27 nmol/mg protein per min. At a concentration of 2.1 x 10(-7) mol/l, cytochalasin B preferentially inhibited the high-affinity D-glucose site or transport system. The time course of D-glucose uptake, studied in two cell lines from patients with hereditary fructose intolerance, was significantly higher than for the control lines.

Biological Transport↗
PubMed1981

Liver glycogenosis caused by a defective phosphorylase system: hemolysate analysis.

Investigated were 24 cases of glycogenosis caused by a reduction in liver phosphorylase activity. The intravenous glucagon tolerance test could not discriminate between phosphorylase kinase deficiency [glycogen storage disease (GSD) IX] and phosphorylase deficiency (GSD VI). These two subgroups were distinguished by hemolysate enzyme assays: (1) GSD IX was characterized by a residual phosphorylase kinase activity, a low activation curve for endogenous phosphorylase b and increased amylo-1,6-glucosidase activity. (2) GSD VI was characterized by a normal or increased phosphorylase kinase activity, a slight activation of endogenous phosphorylase b and a normal amylo-1,6-glucosidase activity.

Child↗