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S Galland

Publications and source records attributed to S Galland.

13 recordsLinked to original sources
PubMed2002

Thyroid hormone controls carnitine status through modifications of gamma-butyrobetaine hydroxylase activity and gene expression.

The carnitine system plays a key role in beta-oxidation of long-chain fatty acids by permitting their transport into the mitochondrial matrix. The effects of hypothyroidism and hyperthyroidism were studied on gamma-butyrobetaine hydroxylase (BBH), the enzyme responsible for carnitine biosynthesis in the rat. In rat liver, BBH activity was decreased in the hypothyroid state and increased in hyperthyroid animals. The modifications in BBH activity correlated with changes in the enzyme Vmax values. These changes were shown to be related to hepatic BBH mRNA abundance. Thyroid hormones are known to interact with lipid metabolism, in particular by increasing long-chain fatty acid oxidation through activation of carnitine-dependent fatty acid import into mitochondria. Our study showed that thyroid hormones also increased carnitine bioavailability.

Animals↗
PubMed2000

Carnitine transport into muscular cells. Inhibition of transport and cell growth by mildronate.

Carnitine is involved in the transfer of fatty acids across mitochondrial membranes. Carnitine is found in dairy and meat products, but is also biosynthesized from lysine and methionine via a process that, in rat, takes place essentially in the liver. After intestinal absorption or hepatic biosynthesis, carnitine is transferred to organs whose metabolism is dependent on fatty acid oxidation, such as heart and skeletal muscle. In skeletal muscle, carnitine concentration was found to be 50 times higher than in the plasma, implicating an active transport system for carnitine. In this study, we characterized this transport in isolated rat myotubes, established mouse C2C12 myoblastic cells, and rat myotube plasma membranes and found that it was Na(+)-dependent and partly inhibited by a Na(+)/K(+) ATPase inhibitor. L-carnitine analogues such as D-carnitine and gamma-butyrobetaine interfere with this system as does acyl carnitine. Among these inhibitors, the most potent was mildronate (3-(2,2,2-trimethylhydrazinium)propionate), known as a gamma-butyrobetaine hydroxylase inhibitor. It also induced a marked decrease in carnitine transport into muscle cells. Removal of carnitine or treatment with mildronate induced growth inhibition of cultured C2C12 myoblastic cells. These data suggest that myoblast growth and/or differentiation is dependent upon the presence of carnitine.

Animals↗
PubMed1999

Molecular cloning and characterization of the cDNA encoding the rat liver gamma-butyrobetaine hydroxylase.

Carnitine biosynthesis from lysine and methionine involves five enzymatic reactions. gamma-butyrobetaine hydroxylase (BBH; EC 1.14. 11.1) is the last enzyme of this pathway. It catalyzes the reaction of hydroxylation of gamma-butyrobetaine to carnitine. The cDNA encoding this enzyme has been isolated and characterized. The cDNA contained an open reading frame of 1161 bp encoding a protein of 387 amino acids with a deduced molecular weight of 44.5 kDa. The sequence of the cDNA showed an important homology with the human cDNA recently isolated. Northern analysis showed gamma-butyrobetaine hydroxylase expression in the liver and in some extend in the testis and the epididymis. During this study, it also appeared that BBH mRNA expression was undetectable by Northern analysis during the perinatal period. During the development of the rat, the amount of BBH mRNA appeared after the weaning of the young rat and reached a maximal expression at the adult stage.

Amino Acid Sequence↗
PubMed1998

Purification and characterization of the rat liver gamma-butyrobetaine hydroxylase.

The biosynthesis of carnitine from lysine and methionine involves five enzymatic reactions. Gamma-butyrobetaine hydroxylase (BBH; EC 1.14.11.1) is the last enzyme of this pathway. It catalyzes the reaction of hydroxylation of gamma-butyrobetaine to carnitine. This enzyme had never been purified to homogeneity from rat tissue. This paper describes the purification and characterization of the rat liver BBH. This protein has been purified some 413 fold by ion exchange, affinity and gel-filtration chromatographies and appears as a dimere of 43,000 Daltons subunits by PAGE. The affinity chromatography column used in the purification process utilizes 3-(2,2,2-trimethylhydrazinium)propionate (THP), a BBH inhibitor, as the ligand. Polyclonal antibodies were raised against the liver enzyme. They were able to precipitate BBH activity in either a crude liver extract or a purified fraction of the enzyme. Furthermore, it crossreacts with a 43 kDa protein in the liver. No evidence for extra hepatic enzyme was found.

Animals↗
PubMed1990

Kidney cell lysates contain an activity that stimulates mature erythroid burst-forming-unit (mBFU-E) proliferation.

This study reports the detection of an activity that stimulates the development of a subclass of burst-forming unit-erythroid (BFU-E) progenitors giving rise to small bursts in semi-solid cultures established in the presence of saturating concentrations of erythropoietin. These progenitors are considered to be mature BFU-E. The activity is found in extracts from kidney cells and appears to be physiologically regulated as it was respectively enhanced and decreased in kidneys from anemic and polycythemic mice. The disappearance of activity in kidney-cell extracts during long-term polycythemia correlated with an accumulation of mature BFU-E in the spleen and bone marrow of polycythemic mice. Using specific neutralizing antibodies and in vitro tests, we also show that this activity is different from hemopoietins known to share burst promoting activity (Interleukin-3 [IL-3], granulocyte-macrophage colony-stimulating factor [GM-CSF], Interleukin-4 [IL-4], erythropoietin [EPO], human interleukin for DA cells [HILDA]) and that it can stimulate erythroid differentiation in long term bone marrow cell cultures.

Animals↗
PubMed1990

Effect of vitamin A deficiency on the in vitro transfer of mannose and N-acetylglucosamine in rat liver nuclei.

Liver nuclei, prepared from normal and vitamin A-deficient rats, were incubated in the presence of GDP-(14C)mannose or UDP-N-acetyl(14C)glucosamine and the labelled glycoproteins analysed by SDS PAGE. Fluorographic analysis has shown that (14C) mannose labelling is enhanced by vitamin A deficiency whereas N-acetyl(14C)glucosamine transfer remains approximately at the same level regardless of the vitamin A status; we did not notice any modification when the proteins were monitored by Coomassie blue or by silver nitrate.

Acetylglucosamine↗
PubMed1988

Glycoprotein mannosylation in rat liver nuclei.

Nuclei and non-nuclear membranes were tested for their ability to transfer in vitro (14C)mannose from GDP-(14C)mannose to endogenous glycoprotein acceptors in the presence and in the absence of exogenous retinyl-phosphate. Electrophoretic analysis shows that retinylphosphate is responsible for the labeling of a few endogenous acceptors only in the non-nuclear membranes; in the nuclei the mannosylation reaction is not retinylphosphate dependent and the electrophoretic profile of the labeled protein acceptors is different from that of the non-nuclear membranes.

Animals↗
PubMed1988

Transfer of N-acetylglucosamine to endogenous glycoproteins in the nucleus and in non-nuclear membranes of rat hepatocytes: electrophoretic analysis of the endogenous acceptors.

The transfer of N-acetyl(14C)glucosamine from UDP-N-acetyl(14C)glucosamine to endogenous glycoproteins acceptors were studied comparatively in the nuclei and in the non-nuclear membranes of rat hepatocytes. Electrophoretic and autoradiographic analysis show that most of the glycoprotein acceptors of the nuclei differ from those of the non-nuclear membranes in terms of molecular weight. In addition, it may interesting to mention that in the nuclear fraction a 30% inhibition by tunicamycin is obtained for concentrations as low as 0.03 microM, whereas at this concentration no effect is detected in the non-nuclear membranes. In the presence of 0.2 microM tunicamycin, the inhibition does not go beyond 25% in the latter fraction but goes up to 80% in the former. The previous results demonstrate clearly that a particular glycosylation reaction occurs in the nucleus.

Acetylglucosamine↗