[The presence of glycosyltransferases on chromatin acceptors in monkey liver nuclear membranes (author's transl)]. / Présence de glycosyltransferases à accepteurs chromatiniens dans les membranes nucléaires d'hépatocytes de singe.

Nuclei were prepared from monkey hepatocytes by centrifugation of the homogenate on a cushion of 2.3 M sucrose, during 45 min at 100000 X g. The yield was 2.2 x 10(7) nuclei per g of liver, and 70% of te homogenate DNA was recovered in these nuclei. An electron microscopic study as well as a biochemical analysis of marker enzymes showed that the nuclei are not contaminated by other subcellular fractions, especially endoplasmic reticulum. A mannosyltransferase and an N-acetylglucosaminyltransferase, working on endogenous glycoproteic acceptors, are present in the nuclei for 1.4 and 6.5% of the homogenate activities, respectively. The nuclei are hydrolysed by DNAse I. The suspension, adjusted in 1.9 M sucrose, was centrifuged for 2 h at 100000 X g, under buffer layer. Purified nuclear membranes were collected at the interface. These membranes did not contain any more endoplasmic reticulum enzyme activities, but the mannosyl and N-acetylglucosaminyltransferase activities were still present. They essentially work on an exogenous chromatin acceptor, prepared by lysis of the nuclei. The eventual role of these glycosyltransferases in the glycosylation of non-histone proteins is discussed.

[Molecular weight of a membrane receptor of UDP-glucose]. / Poids moléculaire d'un récepteur membranaire d'udp-glucose

Rat liver microsomal membranes have been shown to contain an UDP-glucose binding protein. Its mol. wt was estimated to be 120 000 by gel filtration and by ultracentrifugation in a sucrose gradient. The receptor activity was purified by gel filtration on Sephadex G200 and analysed by gel-electrofocusing.

[A receptor for UDP-glucose in the microsomal membranes of rat hepatocytes]. / Mise en évidence d'un récepteur d'UDP-glucose dans les membranes microsomiques des hepatocytes de rat

Rat liver microsomal membranes have been shown to contain a biosynthetic pathway of UDP-glucose. In addition, they are able to bind UDP-glucose in a reversible manner, As UDP-glucose is also metabolized in these membranes, the study of the binding has been performed with a microsomal Triton X 100 extract. This reversible binding depends on pH (maximum at pH 8.1) and manganous ions, and disappears at pH 6.5. It exhibits a high affinity (K-diss equals 3 mu M), and a narrow specifity for UDP-glucose. Proteolytic digestion inhibits the binding up to 90%, showing that the UDP-glucose receptor has a proteic nature. These binding characteristics have been also found in the membranes themselves, indicating that the detergent solubilization does not destroy the protein binding capacity.

[Presence of a pathway for biosynthesis of UDP-glucose in the Golgi apparatus of rat hepatocytes]. / Présence d'une voie de biosynthèse de l'UDP-glucose dans l'appareil de Golgi des hépatocytes de rat

Glucokinase, phosphoglucomutase and glucose-1-phosphate uridylyltransferase are the three enzymes involved in a microsomic pathway for the synthesis of UDP glucose. Evidence is given, in this paper, for the localization of these three enzymes in a Golgi-rich fraction of rat liver. This fraction is prepared, from smooth microsomes, by the means of a discontinuous four-step sucrose gradient. Three of the lighter fractions (d = 1.08-1.13) are enriched in the Golgi markers (galactosyltransferase, sialytransferase and thiamin pyrophosphatase), especially the one with density 1.13. The three enzymes we are interested in are enriched in the two upper hands (d 1.08-1.11), which display an activity for the biosynthesis of UDP-glucose from glucose equivalent to the one obtained in a crude microsomic preparation, and which are not contaminated by other subcellular components.

[Presence of enzymes catalyzing UDP-glucose biosynthesis in a low density Golgi fractions of cat hepatocytes]. / Présence des enzymes catalysant la biosynthèse d'UDP glucose dans une fraction légère de l'appareil de Golgi des hépatocytes de chat.

A Golgi-rich fraction is prepared from cat hepatocytes by the means of a four-step sucrose density gradient. The material applied to this gradient is composed either of smooth microsomes prepared from healthy animals, or of total microsomes prepared from cat treated by 50 per cent ethanol (0.6 g/100 g body weight, administered by stomach tube). A light fraction (d : 1.10) is obtained by the two procedures. It does not show any glucose-6-phosphatase activity, but is enriched in sialyltransferase, known as a marker enzyme for Golgi apparatus. It also contains the three enzymes implicated in the biosynthetic pathway for UDP-glucose (glucokinase, phosphoglucomutase and UTP : glucose-1-phosphate uridylyltransferase). UDP-glucose being the ultimate substrate in membranous glucosylation reactions, these results could support the hypothesis that sugar-nucleotides necessary for the glycoprotein biosynthesis are produced in the Golgi vesicles directly.

[Perparation and comparative analytical study of cat liver microsomes]. / Préparation et étude analytique comparée des microsomes de foie de chat

Cat liver homogenates have been fractionated by differential centrifugation. Four particulate fractions (1 000 X g, 10 000 X g, and 145 000 X g) and a supernatant have been obtained. The biochemical composition of these fractions has been established from the assay and distribution pattern of 22 enzymatic and chemical constituents including marker enzymes for mitochondria, lysosomes, peroxisomes, plasma membranes, endoplasmic reticulum, Golgi apparatus and cell sap. The microsomal fraction was characterized by a moderate contamination with large cytoplasmic granules and by a low yield in protein and cholesterol. It contained 50 per cent of Golgi complex and about 40 per cent of plasma membranes. Morphological analysis of subcellular fractions was performed and confirmed biochemical results.

[Glycogen synthase activity in parodontal disease (author's transl)]. / Activite glycogene-synthase dans la maladie paradontale.

A biochemical study of an enzyme participating in the synthesis of glycogen is presented, with particular regard to the fluctuations in the amounts of this polysaccharide in human gingival epithelium, during inflammation. The increase in the activity of UDPglucose : glycogen glucosyltransferase can be related to the accumulation of glycogen. Some kinetic parameters of this enzyme are described.

Carnitine metabolism in early stages of Duchenne muscular dystrophy.

Muscle carnitine deficiency was found in 12 children affected with Duchenne muscular dystrophy (DMD), the diagnosis being made at a preclinical stage or at the beginning of the clinical symptoms. Enzymatic activities related to fatty acid transport and carnitine metabolism were studied in these patients and normal subjects: palmitoyl carnitine transferase was increased, palmitoyl carnitine hydrolase was not found in the muscle, palmitoyl coenzyme A synthetase was normal and palmitoyl coenzyme A hydrolase was increased.

[Primary cardiomyopathy in children with lipid infiltration of the myocardium and skeletal muscles and demonstration of a palmityl-carnitine transferase deficiency. Apropos of 4 cases]. / Myocardiopathie primitive de l'enfant avec surcharge lipidique des fibres myocardiques et musculaires et mise en évidence d'un déficit en enzyme palmityl-carnitine-transférase. A propos de 4 observations.

The authors report four cases of metabolic cardiomyopathy with lipid infiltration diagnosed by skeletal muscle and myocardial biopsy in children with no clinical signs of muscular dystrophy. Normal or increased serum and urinary carnitine levels excluded a primary carnitine deficiency. A deficiency in muscular-palmityl-carnitine-transferase was demonstrated. This pathogenic mechanism may be an indication for treatment with carnitine, but the results are less spectacular than in primary carnitine deficiency states.

[Presence of UTP:D-GLUCOSE-1-phosphate uridylyltransferase in liver microsomes of the eel (Conger vulgaris)]. / Présence d'une UTP:D-glucose-1-phosphate uridylyltransférase dans les microsomes du foie de congre (Conger vulgaris).

An activity UTP : D-glucose-1-phosphate uridylyltransferase is located in the microsomal membranes of conger liver. The properties of this enzyme are studied and compared to the soluble activity. The microsomal activity is partially liberated from the membrane by freezing and thawing and by the means of a neutral detergent, Triton X-100. The enzyme is latent in the membranes and totally inhibited by phospholipase A2. This microsomal enzyme could be the last of a membranous biosynthetic pathway for UDP-glucose, as conger liver microsomes contain also a membranous glucokinase and a membranous phosphoglucomutase.