scholarly journals Can mitochondria and synaptosomes of guinea-pig brain synthesize phospholipids?

1972 ◽  
Vol 126 (4) ◽  
pp. 805-821 ◽  
Author(s):  
E. K. Miller ◽  
R. M. C. Dawson
Keyword(s):  
Endoplasmic Reticulum ◽  
Cytochrome C ◽  
Guinea Pig ◽  
Phosphatidic Acid ◽  
Smooth Endoplasmic Reticulum ◽  
Cytochrome C Reductase ◽  
Nadph Cytochrome ◽  
Pig Brain ◽  
Guinea Pig Brain ◽  
Nadph Cytochrome C Reductase

1. The use of ‘marker’ enzymes for investigating the contamination by endoplasmic reticulum of mitochondrial and synaptosomal (nerve-ending) fractions isolated from guinea-pig brain was examined. NADPH–cytochrome c reductase appeared to be satisfactory. With the synaptosomal preparation there was a non-occluded enzymic activity believed to arise from contaminating microsomes and an occluded form released by detergent, which probably was derived from some type of intraterminal smooth endoplasmic reticulum. 2. Isolated brain mitochondria, both intact and osmotically shocked, could not synthesize more labelled phosphatidylcholine from CDP-[Me-14C]choline or phosphoryl[Me-14C]choline than could be accounted for by microsomal contamination. They could synthesize only phosphatidic acid and diphosphatidylglycerol from a [32P]Pi precursor and not nitrogen-containing phosphoglycerides or phosphatidylinositol. 3. The synaptosomal outer membrane and the intraterminal mitochondria could not synthesize phosphatidylcholine from CDP-[Me-14C]choline but the synaptic vesicles and probably the intraterminal ‘endoplasmic reticulum’ appeared to be capable of catalysing the incorporation of label from this substrate into their phospholipids. 4. Microsomal fractions and synaptosomes from guinea-pig brain could incorporate [Me-14C]choline into their phospholipids by a non-energy-requiring exchange process, which was catalysed by Ca2+. Fractionation of the synaptosomes after such an exchange had taken place revealed that the label was predominantly in the intraterminal mitochondria and not associated with membranes containing NADPH–cytochrome c reductase. 5. On the intraperitoneal injection of [32P]Pi into guinea pigs, incorporation of radioactivity into phosphatidylinositol and phosphatidic acid was much faster than into the nitrogen-containing phosphoglycerides. Mitochondria and microsomal fractions showed a roughly equivalent incorporation into individual phospholipids, and that into synaptosomes was appreciably less, whereas the phospholipids of myelin showed little 32P incorporation up to 10h.

Subcellular distribution of lysophosphatidylinositol and lysophosphatidylcholine acyltransferases in rat brain

1978 ◽  
Vol 56 (8) ◽  
pp. 765-768 ◽  
Author(s):  
J. R. Pik ◽  
W. Thompson
Keyword(s):  
Endoplasmic Reticulum ◽  
Cytochrome C ◽  
Rat Brain ◽  
Subcellular Distribution ◽  
Subcellular Fractions ◽  
Major Site ◽  
Cytochrome C Reductase ◽  
Nadph Cytochrome ◽  
Nadph Cytochrome C Reductase

Lysophosphatidylinositol acyltransferase utilizing arachidonoyl CoA and lysophosphatidylcholine acyltransferase utilizing linoleoyl CoA were measured in subcellular fractions of rat brain. In general, the distribution of activities paralleled that of NADPH–cytochrome c reductase. It is concluded that the endoplasmic reticulum is the major site of these acyltransferase activities in rat brain.

scholarly journals PRODUCTION OF MEMBRANE WHORLS IN RAT LIVER BY SOME INHIBITORS OF PROTEIN SYNTHESIS

1974 ◽  
Vol 62 (1) ◽  
pp. 20-31 ◽  
Author(s):  
Kou M. Hwang ◽  
Linda C. Yang ◽  
Christine K. Carrico ◽  
Rose A. Schulz ◽  
John B. Schenkman ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Protein Synthesis ◽  
Cytochrome C ◽  
Peptide Synthesis ◽  
Reductase Activity ◽  
Cytochrome C Reductase ◽  
Nadph Cytochrome ◽  
Nascent Peptide ◽  
Membrane Bound ◽  
Nadph Cytochrome C Reductase

Inhibitors of protein synthesis capable of differential effects on nascent peptide synthesis on membrane-bound and free polyribosomes were employed to investigate the structure and function of cellular membranes of liver. The formation of membranous whorls in the cytoplasm and distension of nuclear membranes were induced by inhibitors of protein synthesis (i.e., cycloheximide and emetine) which predominantly interfere with nascent peptide synthesis on membrane-bound polyribosomes in situ. Other inhibitors of protein synthesis such as puromycin and fusidic acid, which inhibit nascent peptide synthesis on both free and membrane-bound polyribosomes, and chloramphenicol, which inhibits mitochondrial protein synthesis, did not induce these alterations. Cycloheximide, puromycin, and chloramphenicol produce some common cellular lesions as reflected by similar alterations in morphology, such as swelling of mitochondria, degranulation of rough endoplasmic reticulum, and aggregation of free ribosomes. The process of whorl formation in the cytoplasm, the incorporation of [3H]leucine and of [3H]choline into endoplasmic reticulum and the total NADPH-cytochrome c reductase activity of the endoplasmic reticulum were determined. During maximum formation of membranous whorls, [3H]leucine incorporation into cytoplasmic membranes was inhibited, while [3H]choline incorporation into these structures was increased; maximum inhibition of protein synthesis and stimulation of choline incorporation into endoplasmic reticulum, however, preceded whorl formation. Cycloheximide decreased the activity of NADPH-cytochrome c reductase of rough endoplasmic reticulum, but increased NADPH-cytochrome c reductase activity of smooth endoplasmic reticulum. In addition, cycloheximide decreased the content of hemoprotein in both the microsomal and mitochondrial fractions of rat liver, and the activities of mixed function oxidase and of oxidative phosphorylation were impaired to different degrees. Succinate-stimulated microsomal oxidation was also inhibited. The possible mechanisms involved in the formation of membranous whorls, as well as their functions, are discussed.

scholarly journals Asymmetric distribution of cytochrome P-450 and NADPH–cytochrome P-450 (cytochrome c) reductase in vesicles from smooth endoplasmic reticulum of rat liver

1980 ◽  
Vol 190 (3) ◽  
pp. 737-746 ◽  
Author(s):  
Michael B. Cooper ◽  
John A. Craft ◽  
Margaret R. Estall ◽  
Brian R. Rabin
Keyword(s):  
Endoplasmic Reticulum ◽  
Cytochrome C ◽  
Rat Liver ◽  
Smooth Endoplasmic Reticulum ◽  
Reductase Activity ◽  
Asymmetric Distribution ◽  
Trypsin Treatment ◽  
Cytochrome C Reductase ◽  
Nadph Cytochrome ◽  
Cytochrome P 450

1. The topography of cytochrome P-450 in vesicles from smooth endoplasmic reticulum of rat liver has been examined. Approx. 50% of the cytochrome is directly accessible to the action of trypsin in intact vesicles whereas the remainder is inaccessible and partitioned between luminal-facing or phospholipid-embedded loci. Analysis by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis reveals three major species of the cytochrome. Of these, the variant with a mol.wt. of 52000 is induced by phenobarbitone and this species is susceptible to trypsin. 2. After trypsin treatment of smooth membrane, some NADPH–cytochrome P-450 (cytochrome c) reductase activity remains and this remaining activity is enhanced by treatment with 0.05% deoxycholate, which renders the membranes permeable to macromolecules. In non-trypsin-treated control membranes the reductase activity is increased to a similar extent. These observations suggest an asymmetric distribution of NADPH–cytochrome P-450 (cytochrome c) reductase in the membrane. 3. As compared with dithionite, NADPH reduces only 44% of the cytochrome P-450 present in intact membranes. After tryptic digestion, none of the remaining cytochrome P-450 is reducible by NADPH. 4. In the presence of both a superoxide-generating system (xanthine plus xanthine oxidase) and NADPH, all the cytochrome P-450 in intact membrane (as judged by dithionite reducibility) is reduced. The cytochrome P-450 remaining after trypsin treatment of smooth vesicles cannot be reduced by this method. 5. The superoxide-dependent reduction of cytochrome P-450 is prevented by treatment of the membranes with mersalyl, which inhibits NADPH–cytochrome P-450 (cytochrome c) reductase. Thus the effect of superoxide may involve NADPH–cytochrome P-450 reductase and cytosolically orientated membrane factor(s).

scholarly journals Étude de l’effet du cadmium et du benzo[a]pyrène sur des enzymes de phase I et phase II de biotransformation chez le polychète Nereisdiversicolor

2009 ◽  
Vol 22 (3) ◽  
pp. 451-459
Author(s):  
Zied Bouraoui ◽  
Jihene Ghedira ◽  
Jamel Jebali ◽  
Mohamed Banni ◽  
Cristelle Clerendeau ◽  
...  
Keyword(s):  
Cytochrome C ◽  
Phase I ◽  
Phase Ii ◽  
Nereis Diversicolor ◽  
Cytochrome C Reductase ◽  
Nadph Cytochrome ◽  
Nadph Cytochrome C Reductase

Résumé Le présent travail reporte l’effet du cadmium (Cd), du benzo[a]pyrène (B[a]P) ainsi que leur mélange (Cd/B[a]P), à 1 µM, sur les activités d’enzymes impliqués dans la phase I et la phase II de biotransformation chez le polychète Nereis diversicolor en fonction du temps (après 12, 24, 36 et 48 h). L’effet d’une contamination aiguë par du cadmium à une dose de 1 µM après 12, 24 et 36 h montre une inhibition de l’activité NADPH cytochrome C réductase chez les individus contaminés comparés à leurs témoins relatifs, alors que le seul effet du cadmium sur l’activité glutathion-S-transférase n’est enregistré qu’après 36 h d’exposition. Quant au benzo[a]pyrène, les résultats montrent une augmentation significative de l’activité NADPH cytochrome C réductase après 12, 24 et 36 h d’exposition, alors que pour l’activité glutathion-S‑transférase, la variation significative entre les animaux témoins et traités n’est enregistrée qu’à 36 h d’exposition. Le mélange (Cd/B[a]P) inhibe l’activité NADPH cytochrome C réductase chez les individus traités par comparaison aux témoins relatifs et montre un effet inducteur sur l’activité GST sauf après 36 h d’exposition. Ces résultats montrent ainsi les interactions entre les polluants ainsi que leurs effets sur les organismes.

Sign in / Sign up

Export Citation Format

Share Document