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Biomedical subjects

G Lenaz

Publications and source records attributed to G Lenaz.

At least 145 records · Page 8Linked to original sources
PubMed1981

Interaction between ubiquinone and ATPase in mitochondrial membranes.

The extraction of ubiquinone from mitochondrial membranes produces alterations of ATPase activity including a reversible loss of oligomycin sensitivity which is restored by long-chain Q-homologs, Short-chain ubiquinones like Q3 produce a loss of oligomycin and dicyclohexyl carbodiimide (DCCD) sensitivity in submitochondrial particles. The effect shows uncompetitive or noncompetitive Kinetics with respect to oligomycin or DCCD respectively. Long-chain ubiquinones have a competitive effect with Q3, thus restoring oligomycin sensitivity; they behave, however, in about the same way as Q3 in lowering the DCCD sensitivity in submitochondrial particles. On the basis of these observations we suggest that ubiquinone may be a physiological modulator of ATPase activity in the mitochondrial membrane.

Adenosine Triphosphatases↗
PubMed1981

Effect of ubiquinone extraction on ubiquinol-1 oxidase activity in beef heart mitochondria.

Extraction of endogenous ubiquinone with different methods does not influence ubiquinol oxidase activity in lyophilized mitochondria in terms of KM, although a decrease of Vmax is sometimes observed. Experiments with submitochondrial particles from a UQ-deficient mutant of S. cerevisiae confirm the results with UQ-depleted mitochondria and support the idea that endogenous ubiquinone is not required for the oxidation of exogenous ubiquinols by complex III.

Animals↗
PubMed1981

Effect of CoQ homologues on the fluidity of phospholipid bilayers a studied by fluorescence polarization of perylene.

The effect of Coenzyme Q analogues on the fluidity of egg lecithin bilayers was studied by fluorescence polarization of perylene. The parameter was clearly affected by the side-chain length of the quinones, by their concentration, and by their redox state. With increasing concentration, short-chain quinones decreased the bilayer fluidity, and did so to an even greater extent in their reduced state. On the contrary, long-chain analogues fluidized the bilayer, the effect being independent of their redox state. Such observations might explain the lower efficiency of short-chain quinones, as compared to the long-chain analogues, in restoring, in vitro, the respiratory activity of CoQ2-depleted mitochondria.

Benz(a)Anthracenes↗
PubMed1980

Fluidity of erythrocyte membranes from patients with Duchenne muscular dystrophy: studies in intact erythrocytes and in ghosts.

We have studied the alterations of fluidity in intact erythrocytes and in erythrocyte membranes from patients with Duchenne muscular dystrophy. The interest of this study was to comparison directly two types of results; these demonstrate an increase of fluidity in the erythrocytic membranes, no changes are present when the label is incorporated in intact erythrocytes. It might be inferred that hypotonic haemolysis removes components that are more weakly bound in Duchenne membranes, and that exert an immobilizing effect on the membrane lipids.

Adolescent↗
PubMed1980

Fluidity changes in rat liver plasma membranes during regeneration.

The fluidity of the liver plasma membrane during the first cell cycle of hepatectomized rats has been investigated by means of stearic acid spin labels and of the fluorescence polarization of perylene. The order parameters of 5-doxylstearate, that probes the membrane surface, have been found lowered in the hepatectomized rats after 15 hours from operation, in comparison with anesthetised and sham-operated controls at the same time; on the contrary, the fluidity in the membrane core, as probed by 16-doxylstearate, is increased in all groups. The fluorescence polarization of perylene is also lower in the hepatectomized rats. The results suggest that liver regeneration is accompanied by a fluidity increase of the plasma membrane.

Animals↗
PubMed1980

Effect of anesthesia on membrane fluidity and acetylcholinesterase activity in rat brain synaptosomes.

Anesthesia by means of ketamine induces an increase of fluidity in the hydrophobic area of rat brain synaptic membranes, as proved by the spin label 16-doxyl stearate, in contrast with no change induced in the order parameter of 5-doxylstearate that probes the membrane surface. These effects are qualitatively similar to those observed by ketamine addition in vitro. On the contrary, acetylcholinesterase from synaptic membranes, although inhibited in vitro by ketamine, is activated in ketamine-anesthetised rats suggested that metabolic changes are at the basis of the effects observed in vivo.

Acetylcholinesterase↗
PubMed1980

Effect of some lipophilic substances on mitochondrial ATPase.

This work reports a study about the influence of some lipophilic substances like cholesterol, calciferol and tocopherol on the ATP-hydrolase activity in mitochondria. It is found that the steroids cholesterol and calciferol inhibit ATPase activity and behave like uncompetitive factors towards the enzymatic kinetics. Tocopherol, instead, affects significantly only the DCCD sensitivity of ATPase. Such effects are very probably due to the action of the physico-chemical state of th mitochondrial membrane produced by these lipophilic compounds.

Adenosine Triphosphatases↗
PubMed1980

Effect of some lipophilic substances on fluorescence polarization of perylene in lipid vesicles and mitochondrial membranes.

Short-chain ubiquinones were observed to increase the fluorescence polarization associated with perylene, indicating a decrease in the fluidity of the mitochondrial membrane. The results indicated that the perturbation induced by low homologs results indicated that the perturbation induced by low homologs of ubiquinone on the physical state of membrane lipids is quite different from that of other lipophilic substances which have been considered.

Animals↗
PubMed1980

Plasma membrane changes associated with rat liver regeneration.

The lipid composition and fluidity of plasma membranes have been studied at different stages of liver regeneration (4, 15 and 24 h after surgery). The phospholipid and fatty acid composition is not modified, whereas the cholesterol/phospholipid ratio is lower with respect to control membranes. The modification of the physical properties of the membranes has been studied directly by EPR analysis and indirectly by temperature dependence and cooperativity of some membrane-bound enzymes (Mg2+-ATPase, (Na+ + K+)-ATPase and 5'nucleotidase). Surgical operation or anaesthesia alone causes an early increase in fluidity; such an effect appears to be markedly reduced at a later stage. There seems to be a marked effect of regeneration on plasma membrane fluidity 15 h after partial hepatectomy when several parameters--surface fluidity, cholesterol/phospholipid ratio, and 5'-nucleotidase activity in the presence of concanavalin A -- are modified and indicate an increase in membrane fluidity. It is suggested that this modification of membrane properties could be related to the proliferative process.

Adenosine Triphosphatases↗
PubMed1980

Effect of anesthetics on membrane fluidity tested by two different techniques: EPR spin labels and polarization of perylene fluorescence.

We have investigated the effect of n-butanol on the spectroscopic properties of two types of probes, that are usually employed to detect membrane fluidity, in mitochondrial phospholipid vesicles and mitochondrial membranes. Although both a spin label (16-doxylstearate) and the fluorescent probe perylene detect a higher immobilization of the membrane in comparison with phospholipid vesicles, the effect of butanol in the case of the membrane is strikingly different with the two techniques employed, showing increased fluidity in the case of the spin label and decreased fluidity with the fluorescent probe.

Anesthetics↗
PubMed1979

Uncoupling effect of a low homolog of unbiquinone (UQ-3) in rabbit heart mitochondria.

Short-chain ubiquinone (UQ-3) inhibits ADP-stimulated respiration (state 3) in intact rabbit heart mitochondria. This effect appears to be similar in all the three sites of oxidative phosphorylation by using different respiratory substrates. Ubiquinone-3 also immobilizes lipids into mitochondrial membranes indicating that the uncoupling effect might be a consequence of an altered physical state of membrane lipids.

Animals↗
PubMed1979

Effect of endogenous ubiquinone on the reduction and oxidation of short exogenous ubiquinone homologs in beef heart mitochondria.

The enzymic activities NADH-ubiquinone reductase, succinate-ubiquinone reductase and ubiquinol oxidase were evaluated in beef heart mitochondria in presence of short ubiquinone homologs. Preliminar data obtained indicate that short chain homologs, less lipophilic than natural ubiquinone do not reach the reoxidation site in absence of endogenous ubiquinone.

Animals↗