Biomedical subjects

B Soussi

Publications and source records attributed to B Soussi.

44 records · Page 3Linked to original sources

PubMed1990

1H-n.m.r. evaluation of the ferricytochrome c-cardiolipin interaction. Effect of superoxide radicals.

The interaction between ferricytochrome c and cardiolipin was investigated by 1H n.m.r. at 270 MHz. From the phospholipid-induced changes of the protein spectral features it is concluded that the first 2 equivalents of cardiolipin cause a conformational change at the lower part of the solvent-exposed haem edge, involving a rearrangement of the hydrogen-bond interactions of propionate 6, thus partly accounting for the lowered redox potential of cytochrome c in the presence of cardiolipin. The increased value for the pK of the alkaline isomerization of ferricytochrome c shows that cardiolipin stabilizes the native structure of the protein, indicating that the oxidized form assumes ferrocytochrome c-like properties. Peroxidation of cardiolipin by superoxide radical ions drastically decreases the protein binding to this phospholipid. The implications of this finding, and the likelihood of the ternary cytochrome c-cardiolipin-cytochrome c oxidase complex, for the binding of cytochrome c to cytochrome c oxidase in vivo, are discussed in relation to peroxidative damage following ischaemia and reperfusion.

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PubMed1990

Dynamics of skeletal muscle energetics during ischemia and reperfusion assessed by in vivo 31P NMR.

The dynamics of rat skeletal muscle energy metabolism in response to ischemia and reperfusion have been investigated by in vivo 31P NMR spectroscopy. The time course of changes in the phosphocreatine, inorganic phosphate, ATP peaks and in intracellular pH during 2 and 4 h of tourniquet ischemia followed by up to 24 h of tissue reperfusion have been determined. Furthermore, the ATP and IMP concentrations in the soleus and tibialis muscles have been determined by high performance liquid chromatography analysis in response to ischemia and subsequent reperfusion. The results demonstrate an initial overshoot in the pH during the first minutes of ischemia. It is also shown that the muscles recover completely after 2 h of ischemia whereas the energy state of the muscle cell is not restored after 4 h of ischemia followed by up to 24 h of reperfusion. However, the soleus muscle recovers better than the tibialis. The results are discussed in terms of oxygen availability, reperfusion injury, IMP accumulation and different response between muscles with different fibre composition.

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PubMed1990

Analysis of purine nucleotides in muscle tissue by HPLC.

Optimal conditions for simultaneous analysis of the purine nucleotides adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP), inosine monophosphate (IMP), inosine, adenosine, hypoxanthine, xanthine and uric acid in muscle samples by high-performance liquid chromatography (HPLC) were evaluated. A neutralized perchloric acid extract of freeze-dried human or rat skeletal muscle tissue was injected on to a reversed-phase silica column and eluted by a gradient composed of ammonium dihydrogen phosphate buffer and methanol. Good resolution for all the nucleotides was achieved within a retention time of about 20 min. Linearity for each of the nucleotides within the concentration intervals obtained in the samples was demonstrated. Purity of each peak was verified by use of the photodiode array technique. Reproducibility for biological samples with variation coefficients below 3.6% for ATP, ADP, AMP, inosine and hypoxanthine and 6.7% for IMP was obtained. The stability of the compounds after extraction was specifically addressed. Storing of frozen extracts at -20 degrees C for 24 h gave acceptable values, while storage for 7 days cannot be recommended. Storage of unfrozen extracts at 4 degrees C was acceptable for (up to) 7 h. This technique provides a sensitive, convenient and reliable method for simultaneous analysis of a large number of purine nucleotides in small skeletal muscle biopsies, provided that certain precautions are taken with respect to the instability of these metabolites.

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PubMed1990

Cytochrome c oxidase and cardiolipin alterations in response to skeletal muscle ischaemia and reperfusion.

The effect of 2 and 4 h of tourniquet ischaemia followed by 1 h of reperfusion on the major mitochondrial phospholipids and on the cytochrome c oxidase kinetic parameters has been investigated in rat skeletal muscle. There was no change either in the mitochondrial phospholipid content or in the Vmax and the Km of the enzyme after 2 h of ischaemia with and without subsequent reperfusion. Four hours of ischaemia had no effect on the lecithin and the cephalin content, while the cardiolipin content decreased as well as the Vmax of the enzyme (P less than 0.05). Tissue reperfusion caused a dramatic decrease in both cardiolipin (55% of the control, P less than 0.001) and Vmax (38% of the control, P less than 0.001). The corresponding reduction in lecithin and cephalin contents was 12% and 14% respectively (P less than 0.05). The Km remained unchanged at all conditions. These findings suggest that mitochondrial dysfunction in response to ischaemia and reperfusion could be a consequence of the reperfusion itself following severe ischaemia. The results are discussed in terms of cardiolipin peroxidation and cytochrome oxidase as a functional parameter.

Animals↗

PubMed1990

Purine metabolism after in vivo ischemia and reperfusion in rat skeletal muscle.

An in vivo rat hindlimb tourniquet ischemia model was used to study the purine nucleotide metabolism in response to 2, 4, and 6 h of ischemia and to the same ischemia periods followed by 1 h of reperfusion. All purine intermediates from ATP to uric acid were determined in skeletal muscle with a high-performance liquid chromatography (HPLC) system. The major metabolic event during ischemia is to temporarily save the nucleotide pool as inosine-5'-monophosphate (IMP. On restitution of the circulation as the energy state recovers, the IMP is converted back to AMP via the purine nucleotide cycle. Six hours of ischemia is associated with irreversible damage and no recovery fo the adenine nucleotides on reperfusion. Fast-twitch muscles appear to be more susceptible than slow-twitch muscles in response to ischemia and reperfusion. A severalfold increase of intracellular hypoxanthine occurred during ischemia, whereas uric acid formation is observed only after reperfusion. These findings are discussed in relation to the proposed role of xanthine oxidase, as an enzyme generating tissue-injurious oxygen free radicals.

Animals↗

PubMed1989

Kinetic parameters of cytochrome c oxidase in rat skeletal muscle: effect of endurance training.

The kinetic properties of cytochrome c oxidase (EC 1.9.3.1) in skeletal muscle tissue of sedentary and endurance-trained rats were studied. The initial velocity of the cytochrome c oxidase reaction was determined polarographically over a large range of cytochrome c concentrations and the maximal velocity (Vmax) and the Michaelis constant (Km) were calculated. The catalytic activity of cytochrome c oxidase in isolated mitochondria was also investigated. The training programme consisted of treadmill running for 2 h a day, 6 days a week, at a speed of 30 m min-1 and 30 degrees elevation, for 4 weeks. Vmax of cytochrome oxidase with respect to cytochrome c increased significantly from 254 to 310 mumol O2 min-1 g-1 protein in response to training (P less than 0.001), whereas Km remained unchanged (18.9 and 18.7 microM). The turnover number (TN) increased from 11.1 S-1 in sedentary rats to 16.6 S-1 in trained rats (P less than 0.001). The results suggest a qualitative change in the enzyme molecule in addition to a true Vmax change of cytochrome c oxidase in response to endurance training.

Animals↗

PubMed1986

Influence of endurance training on glucose transport and uptake in rat skeletal muscle.

The paired tracer-dilution method applied to the rat hindlimb perfusion technique was used to investigate the effect of a 10-wk treadmill training program on glucose transport and net uptake in rat skeletal muscles. Glycolytic and oxidative marker enzyme activities were determined. The rats were allowed to rest for 2 days before the experiments were carried out, since long-term adaptive changes were to be studied. The endurance training program caused a 30% increase in the 3-hydroxyacyl-CoA dehydrogenase and citrate synthase activities, but no changes in glycolytic enzymes, confirming that endurance training provokes an increase in the oxidative capacity of the muscle. No significant differences were found in glucose transport rate or net glucose uptake between trained and sedentary rats, which indicates that no long-term adaptive changes in glucose utilization occur in response to endurance training.

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PubMedDate not supplied

Singlet oxygen energy illumination during moderate cold ischemia prolongs the survival of concordant hamster xeno-heart transplants.

INTRODUCTION: Singlet oxygen energy (SOE) is a potent inhibitor of reactive oxygen species (ROS) in vitro and in vivo in certain dose ranges and can improve the levels of high-energy phosphates (HEP) in concordant hamster xeno-heart transplants. Some data indicate that a certain degree of cold ischemia (CI) might be beneficial to xenotransplants. We investigated if SOE illumination of hamster xeno-hearts during moderate cold ischemia (CI) improved graft survival. MATERIALS AND METHODS: Eighteen hearts from Golden Syrian hamsters (70 to 80 g) were subjected to 8 hours of CI in cold (+4 degrees C) saline solution (NaCL, 0.9%) before heterotopic cervical transplantation to Lewis rats (220 g). Among the treatment group (n = 8), SOE was produced by illuminating the hearts for 10 minutes every 30 minutes with photons at lambda 634 nm with the Oxylight equipment. Graft function was evaluated every 6 hours after transplantation with digital exam until cessation of heart beats. RESULTS: The graft survival of SOE-illuminated ischemic hamster xenografts was 2.34 +/- 0.56 versus 1.15 +/- 0.37 days in the control group (P < .05). All hearts displayed immediate graft function versus 70% in the controls (NS). CONCLUSIONS: SOE illumination at lambda 634 nm during moderate cold ischemia (+4 degrees C) can improve the survival of concordant hamster xeno-heart transplants. The exact mechanism(s) are currently unknown, but the effect might in part be exerted by a combination of reduced production of ROS and increased oxidative phosphorylation.

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