EGb 761 protects liver mitochondria against injury induced by in vitro anoxia/reoxygenation.
; ; Mouithys-Mickalad, Ange et al
in Free Radical Biology & Medicine (1999), 27
The present study investigated the protective effects of Ginkgo biloba extract (EGb 761) on rat liver mitochondrial damage induced by in vitro anoxia/reoxygenation. Anoxia/reoxygenation was known to ... [more ▼]
The present study investigated the protective effects of Ginkgo biloba extract (EGb 761) on rat liver mitochondrial damage induced by in vitro anoxia/reoxygenation. Anoxia/reoxygenation was known to impair respiratory activities and mitochondrial oxidative phosphorylation efficiency. ADP/O (2.57 +/- 0.11) decreased after anoxia/reoxygenation (1.75 +/- 0.09, p < .01), as well as state 3 and uncoupled respiration (-20%, p < .01), but state 4 respiration increased (p < .01). EGb 761 (50-200 microg/ml) had no effect on mitochondrial functions before anoxia, but had a specific dose-dependent protective effect after anoxia/reoxygenation. When mitochondria were incubated with 200 microg/ml EGb 761, they showed an increase in ADP/O (2.09 +/- 0.14, p < .05) and a decrease in state 4 respiration (-22%) after anoxia/reoxygenation. In EPR spin-trapping measurement, EGb 761 decreased the EPR signal of superoxide anion produced during reoxygenation. In conclusion, EGb 761 specially protects mitochondrial ATP synthesis against anoxia/reoxygenation injury by scavenging the superoxide anion generated by mitochondria [less ▲]Detailed reference viewed: 5 (1 ULg)
Identification and characterization of a protozoan uncoupling protein in Acanthamoeba castellanii.
; ; et al
in Journal of Biological Chemistry (1999), 274(33), 23198-23202
An uncoupling protein (UCP) has been identified in mitochondria from Acanthamoeba castellanii, a nonphotosynthetic soil amoeboid protozoon that, in molecular phylogenesis, appears on a branch basal to the ... [more ▼]
An uncoupling protein (UCP) has been identified in mitochondria from Acanthamoeba castellanii, a nonphotosynthetic soil amoeboid protozoon that, in molecular phylogenesis, appears on a branch basal to the divergence points of plants, animals, and fungi. The existence of UCP in A. castellanii (AcUCP) has been revealed using antibodies raised against plant UCP. Its molecular mass (32,000 Da) was similar to those of plant and mammalian UCPs. The activity of AcUCP has been investigated in mitochondria depleted of free fatty acids. Additions of linoleic acid stimulated state 4 respiration and decreased transmembrane electrical potential (DeltaPsi) in a manner expected from fatty acid cycling-linked H(+) reuptake. The half-maximal stimulation by linoleic acid was reached at 8.1 +/- 0.4 microM. Bovine serum albumin (fatty acid-free), which adsorbs linoleic acid, reversed the respiratory stimulation and correspondingly restored DeltaPsi. AcUCP was only weakly inhibited by purine nucleotides like UCP in plants. A single force-flow relationship has been observed for state 4 respiration with increasing concentration of linoleic acid or of an uncoupler and for state 3 respiration with increasing concentration of oligomycin, indicating that linoleic acid has a pure protonophoric effect. The activity of AcUCP in state 3 has been evidenced by ADP/oxygen atom determination. The discovery of AcUCP indicates that UCPs emerged, as specialized proteins for H(+) cycling, early during phylogenesis before the major radiation of phenotypic diversity in eukaryotes and could occur in the whole eukaryotic world. [less ▲]Detailed reference viewed: 8 (1 ULg)
Cyanide-resistant, ATP-synthesis-sustained, and uncoupling-protein-sustained respiration during postharvest ripening of tomato fruit
; ; et al
in Plant Physiology (1999), 119
Tomato (Lycopersicon esculentum) mitochondria contain both alternative oxidase (AOX) and uncoupling protein as energy-dissipating systems that can decrease the efficiency of oxidative phosphorylation. We ... [more ▼]
Tomato (Lycopersicon esculentum) mitochondria contain both alternative oxidase (AOX) and uncoupling protein as energy-dissipating systems that can decrease the efficiency of oxidative phosphorylation. We followed the cyanide (CN)-resistant, ATP-synthesis-sustained, and uncoupling-protein-sustained respiration of isolated mitochondria, as well as the immunologically detectable levels of uncoupling protein and AOX, during tomato fruit ripening from the mature green stage to the red stage. The AOX protein level and CN-resistant respiration of isolated mitochondria decreased with ripening from the green to the red stage. The ATP-synthesis-sustained respiration followed the same behavior. In contrast, the level of uncoupling protein and the total uncoupling-protein-sustained respiration of isolated mitochondria decreased from only the yellow stage on. We observed an acute inhibition of the CN-resistant respiration by linoleic acid in the micromolar range. These results suggest that the two energy-dissipating systems could have different roles during the ripening process. [less ▲]Detailed reference viewed: 11 (2 ULg)
Transport of arginine and ornithine into isolated mitochondria of Saccharomyces cerevisiae.
; ; Elmoualij, Benaïssa et al
in European Journal of Biochemistry (1998), 258(2), 702-9
In this work we have characterised the transport of L-arginine and L-ornithine into mitochondria isolated from a wild-type Saccharomyces cerevisiae strain and an isogenic arg11 knock-out mutant. The Arg11 ... [more ▼]
In this work we have characterised the transport of L-arginine and L-ornithine into mitochondria isolated from a wild-type Saccharomyces cerevisiae strain and an isogenic arg11 knock-out mutant. The Arg11 protein (Arg11p) is a mitochondrial carrier required for arginine biosynthesis [Crabeel, M., Soetens, O., De Rijcke, M., Pratiwi, R. & Pankiewicz, R. (1996) J. Biol. Chem. 271, 25011-25019]. Reconstitution experiments have confirmed that it is an L-ornithine carrier also transporting L-arginine and L-lysine by order of decreasing affinity, but not L-histidine [Palmieri, L., De Marco, V., Iacobazzi, V., Palmieri, F., Runswick, M. & Walker, J. (1997) FEBS Lett. 410, 447-451]. Evidence is presented here that the mitochondrial inner membrane contains an L-arginine and L-ornithine transporting system distinct from Arg11p, in keeping with the arginine leaky phenotype of arg11 knock-out mutants. The newly characterised carrier, which we propose to name Bac1p (basic amino acid carrier), behaves as an antiporter catalysing the electroneutral exchange of the basic amino acids L-arginine, L-lysine, L-ornithine and L-histidine and displays the highest affinity for L-arginine (Km of 30 microM). L-Arginine uptake has a pH optimum in the range of 7.5-9 and is inhibited by several sulphydryl reagents, by pyridoxal 5'-phosphate and by cations [less ▲]Detailed reference viewed: 23 (0 ULg)
Comparative Effects of University of Wisconsin and Euro-Collins Solutions on Pulmonary Mitochondrial Function after Ischemia and Reperfusion
Detry, Olivier ; ; Lambermont, Bernard et al
in Transplantation (1998), 65(2), 161-6
BACKGROUND: The aim of this study was to compare the effects of Euro-Collins and University of Wisconsin solutions on pulmonary mitochondrial function after cold ischemia and subsequent warm reperfusion ... [more ▼]
BACKGROUND: The aim of this study was to compare the effects of Euro-Collins and University of Wisconsin solutions on pulmonary mitochondrial function after cold ischemia and subsequent warm reperfusion. METHODS: Seventeen pigs underwent lung harvesting after classical lung flush with either University of Wisconsin or Euro-Collins solutions. The mitochondria were isolated from fresh swine lungs, from swine lungs subjected to 24 hr of cold ischemia, and from swine lungs subjected to 24 hr of ischemia followed by 30 min of subsequent ex vivo reperfusion at 37 degrees C with Krebs-Henseleit buffer solution and air ventilation. Mitochondrial oxidative phosphorylation parameters were determined in isolated mitochondria by in vitro measurement of oxygen consumption rates. During reperfusion, the lung function was assessed by the pulmonary aerodynamic parameters and the pulmonary vascular resistance. RESULTS: Relative to controls, mitochondria submitted to cold ischemia showed an alteration in the oxidoreductase activities of the respiratory chain. However, the yield of oxidative phosphorylation was conserved. After reperfusion, pulmonary mitochondria underwent a significant worsening in the oxidoreductase activities of the respiratory chain, and a decrease in the respiratory control and the efficiency of oxidative phosphorylation. Meanwhile, the reperfused lungs showed evidence of early dysfunction, assessed by the aerodynamic parameters and pulmonary vascular resistance. In this model, there was no advantage of University of Wisconsin solution over Euro-Collins solution. CONCLUSIONS: The mild mitochondrial alterations after cold ischemia were not sufficient to explain the limited tolerance of lung to ischemia. After reperfusion, the mitochondrial damage was more severe and could be involved in the posttransplant lung dysfunction. [less ▲]Detailed reference viewed: 42 (5 ULg)
Protective effect of Ginkgo biloba extract (Egb 761) on functional impairments of mitochondria induced by anoxia-reoxygenation in situ and in vitro
Sluse, Francis ; ; et al
in Packer, L.; Christen, Y. (Eds.) Gingko biloba extract (EGb 761) : lessons from cell biology (1998)Detailed reference viewed: 18 (6 ULg)
Impairment of mitochondrial functions abolishes NF-kappaB activation by an oxidative stress
Josse, Claire ; Legrand-Poels, Sylvie ; et al
in Free Radical Biology & Medicine (1998)Detailed reference viewed: 5 (0 ULg)
Determination of the respective contributions of energy-dissipating athways to mitochondrial respiration : The ADP/O method
Sluse, Francis ; ; et al
in Moller, I. M.; Gardestrom, P.; Glimelius, K. (Eds.) et al Plant mitochondria : from gene to function (1998)Detailed reference viewed: 8 (1 ULg)
Linoleic acid-induced activity of plant uncoupling mitochondrial protein in purified tomato fruit mitochondria during resting, phosphorylating, and progressively uncoupled respiration.
; ; et al
in Journal of Biological Chemistry (1998), 273(52), 34882-34886
An uncoupling protein was recently discovered in plant mitochondria and demonstrated to function similarly to the uncoupling protein of brown adipose tissue. In this work, green tomato fruit mitochondria ... [more ▼]
An uncoupling protein was recently discovered in plant mitochondria and demonstrated to function similarly to the uncoupling protein of brown adipose tissue. In this work, green tomato fruit mitochondria were purified on a self-generating Percoll gradient in the presence of 0.5% bovine serum albumin to deplete mitochondria of endogenous free fatty acids. The uncoupling protein activity was induced by the addition of linoleic acid during the resting state, and in the progressively uncoupled state, as well as during phosphorylating respiration in the presence of benzohydroxamic acid, an inhibitor of the alternative oxidase and with succinate (+ rotenone) as oxidizable substrate. Linoleic acid strongly stimulated the resting respiration in fatty acid-depleted mitochondria but had no effect on phosphorylating respiration, suggesting no activity of the uncoupling protein in this respiratory state. Progressive uncoupling of state 4 respiration decreased the stimulation by linoleic acid. The similar respiratory rates in phosphorylating and fully uncoupled respiration in the presence and absence of linoleic acid suggested that a rate-limiting step on the dehydrogenase side of the respiratory chain was responsible for the insensitivity of phosphorylating respiration to linoleic acid. Indeed, the ADP/O ratio determined by ADP/O pulse method was decreased by linoleic acid, indicating that uncoupling protein was active during phosphorylating respiration and was able to divert energy from oxidative phosphorylation. Moreover, the respiration rates appeared to be determined by membrane potential independently of the presence of linoleic acid, indicating that linoleic acid-induced stimulation of respiration is due to a pure protonophoric activity without any direct effect on the electron transport chain. [less ▲]Detailed reference viewed: 4 (0 ULg)
Generation of superoxide anion by mitochondria and impairment of their functions during anoxia and reoxygenation in vitro.
; ; Sluse, Francis
in Free Radical Biology & Medicine (1998), 25
A small portion of the oxygen consumed by aerobic cells is converted to superoxide anion at the level of the mitochondrial respiratory chain. If produced in excess, this harmful radical is considered to ... [more ▼]
A small portion of the oxygen consumed by aerobic cells is converted to superoxide anion at the level of the mitochondrial respiratory chain. If produced in excess, this harmful radical is considered to impair cellular structures and functions. Damage at the level of mitochondria have been reported after ischemia and reperfusion of organs. However, the complexity of the in vivo system prevents from understanding and describing precise mechanisms and locations of mitochondrial impairment. An in vitro model of isolated-mitochondria anoxia-reoxygenation is used to investigate superoxide anion generation together with specific damage at the level of mitochondrial oxidative phosphorylation. Superoxide anion is detected by electron paramagnetic resonance spin trapping with POBN-ethanol. Mitochondrial respiratory parameters are calculated from oxygen consumption traces recorded with a Clark electrode. Respiring mitochondria produce superoxide anion in unstressed conditions, however, the production is raised during postanoxic reoxygenation. Several respiratory parameters are impaired after reoxygenation, as shown by decreases of phosphorylating and uncoupled respiration rates and of ADP/O ratio and by increase of resting respiration. Partial protection of mitochondrial function by POBN suggests that functional damage is related and secondary to superoxide anion production by the mitochondria in vitro. [less ▲]Detailed reference viewed: 22 (3 ULg)
Free fatty acids regulate the uncoupling protein and alternative oxidase activities in plant mitochondria.
Sluse, Francis ; ; et al
in FEBS Letters (1998), 433
Two energy-dissipating systems, an alternative oxidase and an uncoupling protein, are known to exist in plant mitochondria. In tomato fruit mitochondria linoleic acid, a substrate for the uncoupling ... [more ▼]
Two energy-dissipating systems, an alternative oxidase and an uncoupling protein, are known to exist in plant mitochondria. In tomato fruit mitochondria linoleic acid, a substrate for the uncoupling protein, inhibited the alternative oxidase-sustained respiration and decreased the ADP/O ratio to the same value regardless of the level of alternative oxidase activity. Experiments with varying concentrations of linoleic acid have shown that inhibition of the alternative oxidase is more sensitive to the linoleic acid concentration than the uncoupling protein activation. It can be proposed that these dissipating systems work sequentially during the life of the plant cell, since a high level of free fatty acid-induced uncoupling protein activity excludes alternative oxidase activity. [less ▲]Detailed reference viewed: 6 (1 ULg)
Impairment of the mitochondrial electron chain transport prevents NF-kappa B activation by hydrogen peroxide.
; ; et al
in Free Radical Biology & Medicine (1998), 25(1), 104-112
A large body of work has been devoted to mechanisms leading to the activation of the transcription factor NF-kappa B in various cell types. Several studies have indicated that NF-kappa B activation by ... [more ▼]
A large body of work has been devoted to mechanisms leading to the activation of the transcription factor NF-kappa B in various cell types. Several studies have indicated that NF-kappa B activation by numerous stimuli depends on the intracellular generation of reactive oxygen species (ROS). In this report, we first demonstrated that inhibition of the electron transport chain by either rotenone or antimycine A gave rise to dose-dependent inhibition of NF-kappa B translocation induced by 150 microM of hydrogen peroxide (H2O2). Conversely, the impairment of the mitochondrial respiratory chain did not affect T lymphocyte treatment by TNF-alpha (tumor necrosis factor alpha) or pre-B lymphocyte treatment with LPS (lipopolysaccharide). We also showed that oligomycine which inhibits ATP synthase and FCCP, which uncouples respiration also led to dose-dependent inhibition of NF-kappa B activation by H2O2. All these inhibitors were also shown to inhibit mitochondrial respiration in lymphocytes assessed by oxygen consumption. Although only a transient drop in ATP concentration was observed when lymphocytes were treated by H2O2, this effect was remarkably reinforced in the presence of oligomycine demonstrating the crucial role of ATP in the signal transduction pathway induced by H2O2. [less ▲]Detailed reference viewed: 9 (1 ULg)
Alternative oxidase in the branched mitochondrial respiratory network: an overview on structure, function, regulation, and role.
Sluse, Francis ;
in Brazilian Journal of Medical and Biological Research = Revista Brasileira de Pesquisas Medicas e Biologicas (1998), 31
Plants and some other organisms including protists possess a complex branched respiratory network in their mitochondria. Some pathways of this network are not energy-conserving and allow sites of energy ... [more ▼]
Plants and some other organisms including protists possess a complex branched respiratory network in their mitochondria. Some pathways of this network are not energy-conserving and allow sites of energy conservation to be bypassed, leading to a decrease of the energy yield in the cells. It is a challenge to understand the regulation of the partitioning of electrons between the various energy-dissipating and -conserving pathways. This review is focused on the oxidase side of the respiratory chain that presents a cyanide-resistant energy-dissipating alternative oxidase (AOX) besides the cytochrome pathway. The known structural properties of AOX are described including transmembrane topology, dimerization, and active sites. Regulation of the alternative oxidase activity is presented in detail because of its complexity. The alternative oxidase activity is dependent on substrate availability: total ubiquinone concentration and its redox state in the membrane and O2 concentration in the cell. The alternative oxidase activity can be long-term regulated (gene expression) or short-term (post-translational modification, allosteric activation) regulated. Electron distribution (partitioning) between the alternative and cytochrome pathways during steady-state respiration is a crucial measurement to quantitatively analyze the effects of the various levels of regulation of the alternative oxidase. Three approaches are described with their specific domain of application and limitations: kinetic approach, oxygen isotope differential discrimination, and ADP/O method (thermokinetic approach). Lastly, the role of the alternative oxidase in non-thermogenic tissues is discussed in relation to the energy metabolism balance of the cell (supply in reducing equivalents/demand in energy and carbon) and with harmful reactive oxygen species formation. [less ▲]Detailed reference viewed: 6 (1 ULg)
Consequences of Cold and Warm Ischemia on Pulmonary Mitochondrial Respiratory Function
Detry, Olivier ; ; Lambermont, Bernard et al
in Transplantation Proceedings (1997), 29(5), 2338-9
IN RECENT years, pulmonary transplantation has become the treatment of choice for several end-stage lung diseases, but remains limited by the scarcity of suitable donors and the lack of reliable prolonged ... [more ▼]
IN RECENT years, pulmonary transplantation has become the treatment of choice for several end-stage lung diseases, but remains limited by the scarcity of suitable donors and the lack of reliable prolonged method of lung preservation.1 Transplantation of lung 6 hours postharvest leads to an increased incidence of primary graft dysfunction, due in part to ischemic damage of pulmonary cell structure and metabolism, and to acute reperfusion injury. However, very little is known about the real mechanisms of pulmonary cell injuries before, during, and after lung transplantation. <br /> <br />During ischemia, the cytosolic and mitochondrial adenine nucleotide content falls,2,3 phospholipids are degraded, membrane permeabilities are increased, and the cytosolic levels of Na+, Ca2+ and phosphate are raised.4 Thus, cold and warm ischemia may induce cell dysfunctions and irreversible injuries responsible for necrosis. As mitochondia are believed to be the site of the determinants of irreversibility,5 the study of permanent oxidative phosphorylation damage after ischemia should be of great interest. <br /> <br />The aim of this present study was to investigate the consequences of warm and cold ischemia on the oxidative phosphorylation of isolated lung mitochondria [less ▲]Detailed reference viewed: 28 (9 ULg)
A Positron Emission Tomography Study of Voluntarily and Electrically Contracted Human Quadriceps
Vanderthommen, Marc ; ; Bauvir, Philippe et al
in Muscle & Nerve (1997), 20(4), 505-7Detailed reference viewed: 26 (4 ULg)
Epitope tagging to study Rirn2p of saccharomyces cerevisiae, a member of the mitochondrial carrier family
Duyckaerts, Claire ; Elmoualij, Benaïssa ; et al
Poster (1997)Detailed reference viewed: 5 (1 ULg)
Phylogenetic classification of the mitochondrial carrier family of Saccharomyces cerevisiae.
Elmoualij, Benaïssa ; Duyckaerts, Claire ; Brasseur, Josette et al
in Yeast (Chichester, England) (1997), 13(6), 573-581
The screening of the open reading frames identified in the whole yeast genome has allowed us to discover 34 proteins belonging to the mitochondrial carrier family. By phylogenetic study, they can be ... [more ▼]
The screening of the open reading frames identified in the whole yeast genome has allowed us to discover 34 proteins belonging to the mitochondrial carrier family. By phylogenetic study, they can be divided into 27 subfamilies including ADP/ATP, phosphate and citrate carriers, putative oxoglutarate and GDC carriers and 22 new subfamilies. Topology predictions using the 'positive inside rule' approach have shown that the yeast carriers are similarly oriented with both extremities exposed to the cytosol. In each subfamily, a strict conservation of the charged residues in the six transmembrane alpha-helices is observed, suggesting a functional role for these residues and the existence of 27 functionally distinct carriers. [less ▲]Detailed reference viewed: 102 (11 ULg)
Reversibility of thiamine deficiency-induced partial necrosis and mitochondrial uncoupling by addition of thiamine to neuroblastoma cell suspensions.
Bettendorff, Lucien ; Goessens, Guy ; Sluse, Francis
in Molecular and Cellular Biochemistry (1997), 174(1-2), 121-4
Culture of neuroblastoma cells in the presence of low thiamine concentration (16 nM) and of the transport inhibitor amprolium leads to the appearance of signs of necrosis: the chromatin condenses, the ... [more ▼]
Culture of neuroblastoma cells in the presence of low thiamine concentration (16 nM) and of the transport inhibitor amprolium leads to the appearance of signs of necrosis: the chromatin condenses, the oxygen consumption decreases and is uncoupled, the mitochondrial cristae are disorganized, the thiamine diphosphate-dependent dehydrogenase activities are impaired. When 10 microM thiamine are added to these cells, the basal respiration increases, the coupled respiration is restored and mitochondrial morphology is recovered within 1 h. Addition of succinate, which is oxidized via a thiamine diphosphate-independent dehydrogenase, to digitonin-permeabilized cells immediately restores a coupled respiration. Our results suggest that the slowing of the citric acid cycle is the cause of the biochemical lesion induced by severe thiamine deficiency and that part of the mitochondria remain functional. [less ▲]Detailed reference viewed: 28 (17 ULg)
Electron partitioning between the two branching quinol-oxidizing pathways in Acanthamoeba castellanii mitochondria during steady-state state 3 respiration.
; ; et al
in Journal of Biological Chemistry (1997), 273(17), 10174-10180
Amoeba mitochondria possess a respiratory chain with two quinol-oxidizing pathways: the cytochrome pathway and the cyanide-resistant alternative oxidase pathway. The ADP/O method, based on the non ... [more ▼]
Amoeba mitochondria possess a respiratory chain with two quinol-oxidizing pathways: the cytochrome pathway and the cyanide-resistant alternative oxidase pathway. The ADP/O method, based on the non-phosphorylating property of alternative oxidase, was used to determine contributions of both pathways in overall state 3 respiration in the presence of GMP (an activator of the alternative oxidase in amoeba) and succinate as oxidizable substrate. This method involves pair measurements of ADP/O ratios plus and minus benzohydroxamate (an inhibitor of the alternative oxidase). The requirements of the method are listed and verified. When overall state 3 respiration was decreased by increasing concentrations of n-butyl malonate (a non-penetrating inhibitor of succinate uptake), the quinone reduction level declined. At the same time, the alternative pathway contribution decreased sharply and became negligible when quinone redox state was lower than 50%, whereas the cytochrome pathway contribution first increased and then passed through a maximum at a quinone redox state of 58% and sharply decreased at a lower level of quinone reduction. This study is the first attempt to examine the steady-state kinetics of the two quinol-oxidizing pathways when both are active and to describe electron partitioning between them when the steady-state rate of the quinone-reducing pathway is varied. [less ▲]Detailed reference viewed: 11 (4 ULg)
Type II to type I transformation of chronically stimulated goat latissimus dorsi muscle: a histoenzymological, biochemical, bioenergetic, and functional study.
; ; et al
in European Surgical Research = Europäische Chirurgische Forschung = Recherches Chirurgicales Européennes (1996), 28
Five goat latissimus dorsi muscles (LDM) were submitted to a progressive chronic electrostimulation program to reach an integrated understanding of the fast-to-slow transformation process in large mammals ... [more ▼]
Five goat latissimus dorsi muscles (LDM) were submitted to a progressive chronic electrostimulation program to reach an integrated understanding of the fast-to-slow transformation process in large mammals. LDM were regularly sampled and followed during a period of 8 months. Each sample was simultaneously assessed for histoenzymological study, myosin and LDH isoforms and bioenergetic capacities [NADH dehydrogenase cytochrome c oxidoreductase (NADH Cyt c OR), succinate dehydrogenase cytochrome c oxidoreductase (Succ Cyt c OR), cytochrome c oxidase (Cyt c Ox) and LDH]. Such muscles were also tested with and without completion of II to I transformation for their mechanical properties in isometric and isotonic strain gauge testing. The conversion of fast-to-slow myosin monitored by heavy chain (HC I) and light chain slow component (LC2s) began a few days after stimulation and was almost 100% after 100 days. The H-LDH isoforms evolved similarly but did not reach 100% conversion after 200 days. The activity of respiratory chain oxidases increased within 36 h but to a variable extent and peaked after 32 days, corresponding to a 75% transformation of myosin compared to initial levels. NADH Cyt c OR, Succ Cyt c OR, and Cyt c Ox, respectively increased 10-, 5- and 5-fold. These activities then significantly decreased before the completion of the myofibrillar transformation and reached a plateau with stable activities that remained 2- to 3-fold higher than the unstimulated LDM. LDH activity sharply decreased until day 62 (5-fold) and then plateaued. Functionally, muscle showed a reduced speed of contraction and moderate reduction in power output but had become fatigue-resistant. This study documents the transformation process in large mammals and suggests the dynamic relation between workload, aerobic-anaerobic metabolism and the contractile myofibrillar system. [less ▲]Detailed reference viewed: 17 (7 ULg)