11 results on '"Ventura-Clapier R"'
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2. Preface
- Author
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Saks, V. A., Ventura-Clapier, R., Rigoulet, M., Gellerich, F. N., and Leverve, X.
- Published
- 2004
3. On the regulation of cellular energetics in health and disease
- Author
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Saks, V. A., primary, Tiivel, T., additional, Kay, L., additional, Novel-Chat�, V, additional, Daneshrad, Z., additional, Rossi, A., additional, Fontaine, E., additional, Keriel, C., additional, Leverve, X., additional, Ventura-Clapier, R., additional, Anflous, K., additional, Samuel, J. -L., additional, and Rappaport, L., additional
- Published
- 1996
- Full Text
- View/download PDF
4. Functional coupling of creatine kinases in muscles: Species and tissue specificity
- Author
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Ventura-Clapier, R., Kuznetsov, A., Veksler, V., Boehm, E., and Anflous, K
- Abstract
Creatine kinase (CK) isoenzymes are present in all vertebrates. An important property of the creatine kinase system is that its total activity, its isoform distribution, and the concentration of guanidino substrates are highly variable among species and tissues. In the highly organized structure of adult muscles, it has been shown that specific CK isoenzymes are bound to intracellular compartments, and are functionally coupled to enzymes and transport systems involved in energy production and utilization. It is however, not established whether functional coupling and intracellular compartmentation are present in all vertebrates. Furthermore, these characteristics seem to be different among different muscle types within a given species. This study will review some of these aspects. It has been observed that: (1) In heart ventricle, CK compartmentation and coupling characterize adult mammalian cells. It is almost absent in frogs, and is weakly present in birds. (2) Efficient coupling of MM-CK to myosin ATPase is seen in adult mammalian striated muscles but not in frog and bird heart where B-CK is expressed instead of M-CK. Thus, the functional efficacy of bound MM-CK to regulate adenine nucleotide turnover within the myofibrillar compartment seems to be specific for muscles expressing M-CK as an integral part of the sarcomere. (3) Mi-CK expression and/or functional coupling are highly tissue and species specific; moreover, they are subject to short term and long term adaptations, and are present late in development. The mitochondrial form of CK (mi-CK) can function in two modes depending on the tissue: (i) in an ≪ADP regeneration mode≫ and (ii) in an ≪ADP amplification mode≫. The mode of action of mi-CK seems to be related to its precise localization within the mitochondrial intermembrane space, whereas its amount might control the quantitative aspects of the coupling. Mi-CK is highly plastic, making it a strong candidate for fine regulation of excitation-contraction coupling in muscles and for energy transfer in cells with large and fluctuating energy demands in general. (4) Although CK isoforms show a binding specificity, the presence of a given isoform within a tissue or a species only, does not predict its functional role. For example, M-CK is expressed before it is functionally compartmentalized within myofibrils during development. Similarly, the presence of ubiquitous or sarcomeric mi-CK isoforms, is not an index of functional coupling of mi-CK to oxidative phosphorylation. (5) Amongst species or muscles, it appears that a large buffering action of the CK system is associated with rapid contraction and high glycolytic activity. On the other hand, an oxidative metabolism is associated with isoform diversity, increased compartmentation, a subsequent low buffering action and efficient phosphotransfer between mitochondria and energy utilization sites. It can be concluded that, in addition to a high variation of total activity and isoform expression, the role of the CK system also critically depends on its intracellular organization and interaction with energy producing and utilizing pathways. This compartmentation will determine the high cellular efficiency and fine specialization of highly organized and differentiated muscle cells.
- Published
- 1998
- Full Text
- View/download PDF
5. Evaluation of quantitative and qualitative aspects of mitochondrial function in human skeletal and cardiac muscles.
- Author
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N'Guessan B, Zoll J, Ribera F, Ponsot E, Lampert E, Ventura-Clapier R, Veksler V, and Mettauer B
- Subjects
- Humans, Oxidation-Reduction, Mitochondria, Heart physiology, Mitochondria, Muscle physiology
- Abstract
Techniques and protocols of assessment of mitochondrial properties are of physiological and physiopathological important significance. A precise knowledge of the advantages and limitations of the different protocols used to investigate the mitochondrial function, is therefore necessary. This report presents examples of how the skinned (or permeabilized) fibers technique could be applied for the polarographic determination of the actual quantitative and qualitative aspects of mitochondrial function in human muscle samples. We described and compared the main available respiration protocols in order to sort out which protocol seems more appropriate for the characterization of mitochondrial properties according to the questions under consideration: quantitative determination of oxidative capacities of a given muscle, characterization of the pattern of control of mitochondrial respiration, or assessment of a mitochondrial defect at the level of the respiratory chain complexes. We showed that while protocol A, using only two levels of the phosphate acceptor adenosine diphosphate (ADP) concentration and the adjunction of creatine, could be used for the determination of quantitative changes in very small amount of muscle samples, the ADP sensitivity of mitochondrial respiration was underestimated by this protocol in muscles with high oxidative capacities. The actual apparent Km for ADP and the role of functional activation of miCK in ATP production and energy transfer in oxidative muscles, are well-assessed by protocol B (in the absence of creatine) together with protocol C (in the presence of creatine) that use increasing concentrations of ADP ranging from 2.5-2000 microM. Protocol D is well-adapted to investigate the potential changes at different levels of the respiratory chain, by the use of specific substrates and inhibitors. As can be seen from the present data and the current review of previous reports in the literature, a standardization of the respiration protocols is needed for useful comparisons between studies.
- Published
- 2004
- Full Text
- View/download PDF
6. Post-translational modifications of cardiac tubulin during chronic heart failure in the rat.
- Author
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Belmadani S, Poüs C, Ventura-Clapier R, Fischmeister R, and Méry PF
- Subjects
- Animals, Aorta pathology, Blotting, Western, Hypertrophy, Immunoblotting, Male, Microtubules metabolism, Myocardium cytology, Protein Isoforms, Rats, Rats, Wistar, Thorax pathology, Heart Failure metabolism, Myocardium metabolism, Protein Processing, Post-Translational, Tubulin biosynthesis, Tubulin chemistry
- Abstract
Cytoskeletal reorganization has been shown to participate in cellular remodeling and in the alterations of mechanical function of isolated cardiomyocytes during pressure overload hypertrophy. Post-translational modifications of tubulin towards stabilization of microtubules have also been described in animal models of compensatory hypertrophy, but the status of the microtubules network in end stage heart failure is not clearly established. Using a rat model of congestive heart failure (CHF) induced by aortic banding, we studied the expression of alpha- and beta-tubulin, as well as their post-translational modification and distribution in the soluble and polymerized fraction by immunoblotting. We found an accumulation of alpha- and beta-tubulin protein content specifically in the soluble fraction with no change in the polymerized fraction. Amongst the several variants of alpha-tubulin examined, only detyrosinated Glu-tubulin and deglutamylated delta2-tubulin levels were selectively increased during heart failure. Glu-tubulin accumulated in the polymerized fraction while delta2-tubulin levels were increased in the soluble fraction in CHF hearts. These results show that a profound remodeling of the microtubule network occurs in heart failure. This remodeling suggests an increase in the stability of the microtubule network which is discussed in terms of possible functional consequences.
- Published
- 2002
- Full Text
- View/download PDF
7. Developmental changes in regulation of mitochondrial respiration by ADP and creatine in rat heart in vivo.
- Author
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Tiivel T, Kadaya L, Kuznetsov A, Käämbre T, Peet N, Sikk P, Braun U, Ventura-Clapier R, Saks V, and Seppet EK
- Subjects
- Animals, Body Weight, Cell Respiration, Electrophoresis, Polyacrylamide Gel, Fluorescent Dyes, Heart drug effects, Kinetics, Microscopy, Confocal, Mitochondria, Muscle metabolism, Mitochondrial ADP, ATP Translocases metabolism, Muscle, Skeletal metabolism, Myocardium cytology, Organ Size, Rats, Rats, Wistar, Trypsin pharmacology, Adenosine Diphosphate metabolism, Creatine metabolism, Creatine Kinase metabolism, Heart growth & development, Mitochondria, Heart metabolism, Muscle Fibers, Skeletal metabolism, Myocardium metabolism, Oxidative Phosphorylation
- Abstract
In saponin-skinned muscle fibers from adult rat heart and m. soleus the apparent affinity of the mitochondrial oxidative phosphorylation system for ADP (Km = 200-400 microM) is much lower than in isolated mitochondria (Km = 10-20 microM). This suggests a limited permeability of the outer mitochondrial membrane (OMM) to adenine nucleotides in slow-twitch muscle cells. We have studied the postnatal changes in the affinity of mitochondrial respiration for ADP, in relation to morphological alterations and expression of mitochondrial creatine kinase (mi-CK) in rat heart in vivo. Analysis of respiration of skinned fibers revealed a gradual decrease in the apparent affinity of mitochondria to ADP throughout 6 weeks post partum that indicates the development of mechanism which increasingly limits the access of ADP to mitochondria. The expression of mi-CK started between the 1st and 2nd weeks and reached the adult levels after 6 weeks. This process was associated with increases in creatine-activated respiration and affinity of oxidative phosphorylation to ADP thus reflecting the progressive coupling of mi-CK to adenine nucleotide translocase. Laser confocal microscopy revealed significant changes in rearrangement of mitochondria in cardiac cells: while the mitochondria of variable shape and size appeared to be random-clustered in the cardiomyocytes of 1 day old rat, they formed a fine network between the myofibrils by the age of 3 weeks. These results allow to conclude that in early period of development, i.e. within 2-3 weeks, the diffusion of ADP to mitochondria becomes progressively restricted, that appears to be related to significant structural rearrangements such as formation of the mitochondrial network. Later (after 3 weeks) the control shifts to mi-CK, which by coupling to adenine nucleotide translocase, allows to maximally activate the processes of oxidative phosphorylation despite limited access of ADP through the OMM.
- Published
- 2000
- Full Text
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8. What do we not know of cellular bioenergetics?--a general view on the state of the art.
- Author
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Saks VA, Ventura-Clapier R, Leverve X, Rossi A, and Rigoulet M
- Subjects
- Creatine Kinase metabolism, Electron Transport, Mitochondria metabolism, Oxidative Phosphorylation, Proton-Motive Force, Signal Transduction, Energy Metabolism
- Published
- 1998
9. Compartmentation of creatine kinases during perinatal development of mammalian heart.
- Author
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Hoerter JA, Ventura-Clapier R, and Kuznetsov A
- Subjects
- Animals, Animals, Newborn, Embryonic and Fetal Development, Guinea Pigs, Heart growth & development, Isoenzymes, Mitochondria, Heart enzymology, Myocardium cytology, Myofibrils enzymology, Rabbits, Rats, Creatine Kinase metabolism, Fetal Heart enzymology, Myocardium enzymology
- Abstract
Maturation of the cardiac cell is characterized by increasing diversity of isozymic expression of creatine kinases. Expression of the M-CK isozyme always precedes that of mitochondrial isozyme (mi-CK), however the expression of an isoform does not inform about its localization or cellular function. The functional role of isozymes binding to sites of energy utilization and production characteristic of the adult myocardium can be evidenced by the functional coupling of M-CK to myofibrillar ATPase and mito-CK to translocase in Triton X-100 and saponin skinned fibers. Functional activity of M-CK and mito-CK were investigated during perinatal development. Both functional activities appear during late fetal life in species mature at birth like guinea pig, and in the first postnatal weeks in immature species like rat or rabbit. Thus, the functional activity of bound CK isozymes is not associated with birth per se but with the general process of cell maturation. Localization of CK in the cytosol appears optimal for the transfer of glycolytic production of ATP to sites of utilization in an immature heart. During cell maturation, the increasing contribution of oxidative phosphorylation to ATP production, the apparition and binding of mi-CK to mitochondria, the binding of M-CK to myofibrils, turn the cell in a compartmentalized system of energy production. This provides the cellular basis for energy transfer by the PCr-Cr-CK system between sites of ATP production and utilization. Compartmentation of both Ca handling and energy turnover leads to a highly structured cell organization and could be essential for the efficiency of heart function.
- Published
- 1994
- Full Text
- View/download PDF
10. Myofibrillar creatine kinase and cardiac contraction.
- Author
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Ventura-Clapier R, Veksler V, and Hoerter JA
- Subjects
- Actin Cytoskeleton enzymology, Adenosine Triphosphate pharmacology, Animals, Biomechanical Phenomena, Energy Metabolism, Humans, In Vitro Techniques, Myocardial Contraction drug effects, Myocardial Ischemia physiopathology, Myosins metabolism, Sarcomeres physiology, Creatine Kinase metabolism, Myocardial Contraction physiology, Myofibrils enzymology
- Abstract
This article is a review on the organization and function of myofibrillar creatine kinase in striated muscle. The first part describes myofibrillar creatine kinase as an integral structural part of the complex organization of myofibrils in striated muscle. The second part considers the intrinsic biochemical and mechanical properties of myofibrils and the functional coupling between myofibrillar CK and myosin ATPase. Skinned fiber studies have been developed to evidence this functional coupling and the consequences for cardiac contraction. The data show that creatine kinase in myofibrils is effective enough to sustain normal tension and relaxation, normal Ca sensitivity and kinetic characteristics. Moreover, the results suggest that myofibrillar creatine kinase is essential in maintaining adequate ATP/ADP ratio in the vicinity of myosin ATPase active site to prevent dysfunctioning of this enzyme. Implications for the physiology and physiopathology of cardiac muscle are discussed.
- Published
- 1994
- Full Text
- View/download PDF
11. In situ study of myofibrils, mitochondria and bound creatine kinases in experimental cardiomyopathies.
- Author
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Veksler V and Ventura-Clapier R
- Subjects
- Adenosine Diphosphate metabolism, Animals, Cardiomyopathies etiology, Cardiomyopathies physiopathology, Disease Models, Animal, Energy Metabolism, Humans, Isoenzymes, Mitochondria, Heart enzymology, Myocardial Contraction physiology, Myofibrils enzymology, Cardiomyopathies enzymology, Creatine Kinase metabolism
- Abstract
Human cardiomyopathy has been extensively studied in the last decade, and knowledge of the functional and structural alterations of the heart has grown. However, understanding of the pathogenesis has come mostly from experimental studies. A number of work have been designed to elucidate if alterations of the contractile apparatus of cardiac cells contribute to the impairment of heart mechanics in cardiomyopathies. As well, an important question is to be solved: whether energy supply of the contraction-relaxation cycle is sufficient in the myopathic heart. Use of cardiac fibers skinned by different techniques allows to evaluate functional ability of myofibrils, mitochondria and bound creatine kinase which plays an important role in cardiomyocyte energy metabolism. The data presented in this chapter show that experimental cardiomyopathies of various types have some common features. These are an increase in calcium sensitivity of myofibrils and a depression of functional activity of mitochondrial creatine kinase. Possible mechanisms and physiological significance of these changes are discussed.
- Published
- 1994
- Full Text
- View/download PDF
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