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L Cabrini

Publications and source records attributed to L Cabrini.

51 records · Page 3Linked to original sources
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↗
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↗
PubMed1979

Lipid protein interactions in mitochondria. VII. A comparison of the effects of lipid removal and lipid perturbation of the kinetic properties of mitochondrial ATPase.

We investigated the kinetics of mitochondrial ATPase in bovine heart mitochondria and submitochondrial particles upon treatment with phospholipase A2, or upon addition of n-butanol to perturb the lipid protein interactions. The changes observed are the following: (1) Lipid removal or perturbation with butanol is accompanied by loss of ATPase activity with decrease of both V and of the KM for ATP. (2) There are changes of activation energy of ATPase activity at temperatures above the discontinuity normally observed for membrane-bound enzymes in mitochondria. In particular, butanol abolishes the discontinuity, and induces a constant activation energy of about 32 kcal/mol in the range 8--37 degrees C. (3) Butanol modifies the pH dependence of ATPase shifting the pH optimum from around 10 to less alkaline values. The optimum for Mg2+ concentrations is increased by the solvent. (4) Treatment with phospholipase A2 results in a removal of oligomycin-sensitive ATPase, whereas butanol addition prevents oligomycin inhibition of ATPase. (5) In beef heart mitochondria, a spin-labelled analog of the inhibitor, dicyclohexyl carbodiimide, did not show any change in environment upon butanol addition, unlike that found in mitochondria from Saccharomyces cerevisiae.

Adenosine Triphosphatases↗
PubMedDate not supplied

Coenzyme Q-3 as an antioxidant. Its effect on the composition and structural properties of phospholipid vesicles.

Coenzyme Q-3 incorporated into the lipid bilayer at physiological concentration provided an 80% inhibition of the lipid peroxidation induced by ferrous ions. In coenzyme Q-containing vesicles, the fluorescence lifetime and the fluorescence anisotropy decay of the probe, 1,6-diphenyl-1,3,5-hexatriene, were measured in order to find out if the presence of the quinone can cause variations in the membrane organization. Our data show that two distinct populations of the probe were present and that both populations were available to quenching by coenzyme Q. The overall effects of coenzyme Q on the static and dynamic properties of the model membranes were: a very small effect in the ordering of the fatty acid chain, and a more noticeable decrease of the probe correlation time and, therefore, an increase in membrane fluidity at increasing quinone concentration. When vesicles were peroxidized in the absence of the coenzyme Q, the fluidity markedly decreased; in its presence, the fluidity was nearly unchanged. The results suggest that the antioxidant properties of coenzyme Q can be ascribed to its ability to react with free radicals. The effect on the fluidity of the lipid bilayer might imply that a requisite for a molecule to act as an efficient antioxidant could be its ability to readily diffuse within the membrane.

Antioxidants↗
PubMedDate not supplied

Effects of short-term dietary administration of marginal levels of vitamin B(6)and fish oil on lipid composition and antioxidant defences in rat tissues.

Previous reports have shown that vitamin B(6)deficiency leads to peroxidative stress in rat organs. In this paper, we evaluated the effects on lipid peroxidation of short-term (six weeks) dietary administration of marginal contents of vitamin B(6). A further risk factor of susceptibility to peroxidation was the presence of fish oil with higher contents of n-3 polyunsaturated fatty acid (LCPUFA). The contemporaneous vitamin B(6)deficiency and presence of fish oil caused a C18:2 increase, a C20:4 decrease, and replacement of some n-6 LCPUFA with n-3 LCPUFA, without changes in the unsaturation index. In liver, TBARS production did not show any differences between dietary conditions, whereas the activities of glutathione-dependent enzymes were stimulated. In heart, fish oil increased lipid peroxidation, especially in the vitamin B(6)-deficient group.

Animals↗
PubMedDate not supplied

Reactions of oxygen radicals with the quinone ring of coenzyme Q.

Coenzyme Q, besides its role in electron transfer reactions, may act as a radical scavenger. The effect of oxygen radicals produced by ultrasonic irradiation on the quinone ring was investigated. Aqueous solutions of a Q homologue, completely lacking the side chain, were irradiated and the modifications were spectrophotometrically followed. The experimental results show that both degradation and reduction of the benzoquinone ring took place when the irradiation was performed in water. Data obtained when ultrasonic irradiation was carried out in the presence of OH. scavengers, as formate, organic and inorganic buffers, suggest: a) the responsible species for most the ubiquinol generated by sonication appeared to be the superoxide radical b) addition reactions of OH. radicals with the aromatic ring led probably to the degradation of Coenzyme Q molecules.

Formates↗
PubMedDate not supplied

Incorporation of ubiquinones into lipid vesicles and inhibition of lipid peroxidation.

Ubiquinone incorporation into vesicles to evaluate its antioxidative effect on lipid peroxidation has been studied. Only sonication and not vortication allows comparable incorporation patterns of the various ubiquinone homologues into lipid vesicles. The measure of malondialdehyde, a convenient index for determining the extent of autoxidation, shows that both the naturally occurring homologues and synthetic shorter-chain ones, also in the oxidized form, possess similar antioxidant efficiency.

Antioxidants↗
PubMedDate not supplied

Effects of extraction of ubiquinone on succinate-ferricyanide reductase activity.

The effects of extraction and reincorporation of ubiquinone on succinate dehydrogenase of mitochondrial membranes have been studied. The succinate dehydrogenase activity, measured with ferricyanide as electron acceptor, was diminished by approximatively 75% upon the extraction of ubiquinone and was restored when ubiquinone was reincorporated into the membranes. A study in a model system represented by ubiquinols incorporated in liposomes shows that the initial rates of ubiquinol oxidation by external ferricyanide are almost two order of magnitude lower than the rates of succinate-ferricyanide reductase in mitochondria. It is therefore concluded that the compound feeding electrons to ferricyanide in damaged mitochondria is either ubiquinone in a bound form or a compound between UQ and the antimycin block.

Animals↗