scholarly journals MEMBRANE JUNCTIONS IN THE INTERMEMBRANE SPACE OF MITOCHONDRIA FROM MAMMALIAN TISSUES

1974 ◽  
Vol 60 (3) ◽  
pp. 653-663 ◽  
Author(s):  
Akitsugu Saito ◽  
Murray Smigel ◽  
Sidney Fleischer
Keyword(s):  
Skeletal Muscle ◽  
Cross Sections ◽  
Rat Kidney ◽  
Respiratory Control ◽  
Heart Tissue ◽  
Intermembrane Space ◽  
Mitochondrial Membranes ◽  
Fresh Tissue ◽  
Isolated Mitochondria ◽  
Mammalian Tissues

There have been several reports describing paracrystalline arrays in the intermembrane space of mitochondria. On closer inspection these structures appear to be junctions of two adjoining membranes. There are two types. They can be formed between the outer and inner mitochondrial membranes (designated outer-inner membrane junctions) or between two cristal membranes (intercristal membrane junctions). In rat heart, adjoining membranes appeared associated via a central dense midline approximately 30 Å wide. In rat kidney, the junction had a ladder-like appearance with electron-dense "bridges" approximately 80 Å wide, spaced 130 Å apart, connecting the adjoining membranes. We have investigated the conditions which favor the visualization of such structures in mitochondria. Heart mitochondria isolated rapidly from fresh tissue (within 30 min of death) contain membrane junctions in approximately 10–15% of the cross sections. This would indicate that the percentage of membrane junctions in the entire mitochondrion is far greater. Mitochondria isolated from heart tissue which was stored for 1 h at 0°–4°C showed an increased number of membrane junctions, so that 80% of the mitochondrial cross sections show membrane junctions. No membrane junctions are observed in mitochondria in rapidly fixed fresh tissue or in mitochondria isolated from tissue disrupted in fixative. Thus, the visualization of junctions in the intermembrane space of mitochondria appears to be dependent upon the storage of tissue after death. Membrane junctions can also be observed in mitochondria from other stored tissues such as skeletal muscle, kidney, and interstitial cells from large and small intestine. In each case, no such junctions are observed in these tissues when they are fixed immediately after removal from the animal. It would appear that most studies in the literature in which isolated mitochondria from tissues such as heart or kidney were used were carried out on mitochondria which contained membrane junctions. The presence of such structures does not significantly affect normal mitochondrial function in terms of respiratory control and oxidative phosphorylation.

scholarly journals ULTRASTRUCTURE OF ISOLATED KIDNEY MITOCHONDRIA TREATED WITH PHLORIZIN AND ATP

1964 ◽  
Vol 23 (2) ◽  
pp. 207-215 ◽  
Author(s):  
Mario H. Burgos ◽  
Agustin Aoki ◽  
Fabio L. Sacerdote
Keyword(s):  
Rat Kidney ◽  
Heterogeneous Population ◽  
Kidney Cortex ◽  
Mitochondrial Membranes ◽  
Electron Microscopic ◽  
Isolated Kidney ◽  
Rat Kidney Cortex ◽  
Kidney Mitochondria ◽  
Isolated Mitochondria ◽  
The Matrix

Direct electron microscopic evidence is reported of the ultrastructure of mitochondrial membranes and compartments in mitochondria isolated in 0.5 M sucrose from the rat kidney cortex and the experimental changes they undergo with phlorizin and ATP treatment. A heterogeneous population of mitochondria is recognized under control conditions. The mitochondria appear to be of 3 main types, normal, swollen, and contracted. Under phlorizin treatment, most of the mitochondria swell in less than 15 minutes, apparently at the expense of the matrix. Treatment with ATP, on the other hand, produces, during the same time, a marked contraction of the isolated mitochondria, with many refoldings of the inner membrane and marked increase in the electron opacity of the matrix. It is concluded from these observations that mitochondrial swelling and contraction should be related mainly to the matrix content.

Calcium content and respiratory control index of skeletal muscle mitochondria during exercise and recovery

1996 ◽  
Vol 271 (6) ◽  
pp. E1044-E1050 ◽  
Author(s):  
K. Madsen ◽  
P. Ertbjerg ◽  
M. S. Djurhuus ◽  
P. K. Pedersen
Keyword(s):  
Skeletal Muscle ◽  
Human Skeletal Muscle ◽  
Respiratory Control ◽  
Calcium Content ◽  
Exhaustive Exercise ◽  
Isolated Mitochondria ◽  
Skeletal Muscle Mitochondria ◽  
Before And After ◽  
The Relationship ◽  
Muscle Biopsies

The purpose of this study was to evaluate the relationship between mitochondrial Ca2+ concentration and the respiratory control index (RCI; state III/state IV) in isolated mitochondria before and after exhaustive exercise at 75% of maximal O2 consumption. Muscle biopsies of 100-150 mg from 12 moderately trained men were sampled at rest, immediately after exercise, and 30 or 60 min after exercise. The mitochondrial Ca2+ content after exhaustive exercise was significantly higher than the preexercise level [15.1 (range 39.4) vs. 11.6 (range 6.5) nmol/mg protein, respectively; P < 0.05], and RCI increased from 11.6 (range 14.4) at rest to 13.7 (range 15.0) at exhaustion (P < 0.05). After 60 min of recovery, the mitochondrial Ca2+ content was still high [18.8 (range 29.9) nmol/mg protein], but the RCI value was significantly depressed because of the increased state IV value and, in fact, was lower than the preexercise value [8.6 (range 5.1); P < 0.05]. Our results show that the mitochondrial Ca2+ content is increased in human skeletal muscle after prolonged exhaustive exercise and that this is followed by an elevated RCI value, with slightly increased state III and decreased state IV respiration. The restoration of the elevated mitochondrial Ca2+ level is slow and could be related to an increased state IV respiration, which together indicate uncoupled Ca2+ respiration during recovery.

The KATP channel Kir6.2 subunit content is higher in glycolytic than oxidative skeletal muscle fibers

2011 ◽  
Vol 301 (4) ◽  
pp. R916-R925 ◽  
Author(s):  
Krystyna Banas ◽  
Charlene Clow ◽  
Bernard J. Jasmin ◽  
Jean-Marc Renaud
Keyword(s):  
Skeletal Muscle ◽  
Cross Sections ◽  
Fiber Type ◽  
Energy Levels ◽  
Muscle Fibers ◽  
Metabolic Stress ◽  
Oxidative Capacity ◽  
Fiber Types ◽  
Fiber Damage ◽  
The Individual

It has long been suggested that in skeletal muscle, the ATP-sensitive K+ channel (KATP) channel is important in protecting energy levels and that abolishing its activity causes fiber damage and severely impairs function. The responses to a lack of KATP channel activity vary between muscles and fibers, with the severity of the impairment being the highest in the most glycolytic muscle fibers. Furthermore, glycolytic muscle fibers are also expected to face metabolic stress more often than oxidative ones. The objective of this study was to determine whether the t-tubular KATP channel content differs between muscles and fiber types. KATP channel content was estimated using a semiquantitative immunofluorescence approach by staining cross sections from soleus, extensor digitorum longus (EDL), and flexor digitorum brevis (FDB) muscles with anti-Kir6.2 antibody. Fiber types were determined using serial cross sections stained with specific antimyosin I, IIA, IIB, and IIX antibodies. Changes in Kir6.2 content were compared with changes in CaV1.1 content, as this Ca2+ channel is responsible for triggering Ca2+ release from sarcoplasmic reticulum. The Kir6.2 content was the lowest in the oxidative soleus and the highest in the glycolytic EDL and FDB. At the individual fiber level, the Kir6.2 content within a muscle was in the order of type IIB > IIX > IIA ≥ I. Interestingly, the Kir6.2 content for a given fiber type was significantly different between soleus, EDL, and FDB, and highest in FDB. Correlations of relative fluorescence intensities from the Kir6.2 and CaV1.1 antibodies were significant for all three muscles. However, the variability in content between the three muscles or individual fibers was much greater for Kir6.2 than for CaV1.1. It is suggested that the t-tubular KATP channel content increases as the glycolytic capacity increases and as the oxidative capacity decreases and that the expression of KATP channels may be linked to how often muscles/fibers face metabolic stress.

scholarly journals Sorting of a nonmuscle tropomyosin to a novel cytoskeletal compartment in skeletal muscle results in muscular dystrophy

2004 ◽  
Vol 166 (5) ◽  
pp. 685-696 ◽  
Author(s):  
Anthony J. Kee ◽  
Galina Schevzov ◽  
Visalini Nair-Shalliker ◽  
C. Stephen Robinson ◽  
Bernadette Vrhovski ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Muscular Dystrophy ◽  
Actin Cytoskeleton ◽  
Cross Sections ◽  
Thin Filament ◽  
Distinct Structure ◽  
Adjacent Structure ◽  
Cytoskeletal Network ◽  
Ragged Red Fiber

Tropomyosin (Tm) is a key component of the actin cytoskeleton and &gt;40 isoforms have been described in mammals. In addition to the isoforms in the sarcomere, we now report the existence of two nonsarcomeric (NS) isoforms in skeletal muscle. These isoforms are excluded from the thin filament of the sarcomere and are localized to a novel Z-line adjacent structure. Immunostained cross sections indicate that one Tm defines a Z-line adjacent structure common to all myofibers, whereas the second Tm defines a spatially distinct structure unique to muscles that undergo chronic or repetitive contractions. When a Tm (Tm3) that is normally absent from muscle was expressed in mice it became associated with the Z-line adjacent structure. These mice display a muscular dystrophy and ragged-red fiber phenotype, suggestive of disruption of the membrane-associated cytoskeletal network. Our findings raise the possibility that mutations in these tropomyosin and these structures may underpin these types of myopathies.

scholarly journals Mitochondrial mislocalization and altered assembly of a cluster of Barth syndrome mutant tafazzins

2006 ◽  
Vol 174 (3) ◽  
pp. 379-390 ◽  
Author(s):  
Steven M. Claypool ◽  
J. Michael McCaffery ◽  
Carla M. Koehler
Keyword(s):  
Point Mutations ◽  
Mutant Gene ◽  
Barth Syndrome ◽  
Membrane Association ◽  
Intermembrane Space ◽  
Mitochondrial Matrix ◽  
Mitochondrial Membranes ◽  
Membrane Bilayer ◽  
Conserved Residues ◽  
Tm Domain

None of the 28 identified point mutations in tafazzin (Taz1p), which is the mutant gene product associated with Barth syndrome (BTHS), has a biochemical explanation. In this study, endogenous Taz1p was localized to mitochondria in association with both the inner and outer mitochondrial membranes facing the intermembrane space (IMS). Unexpectedly, Taz1p does not contain transmembrane (TM) segments. Instead, Taz1p membrane association involves a segment that integrates into, but not through, the membrane bilayer. Residues 215–232, which were predicted to be a TM domain, were identified as the interfacial membrane anchor by modeling four distinct BTHS mutations that occur at conserved residues within this segment. Each Taz1p mutant exhibits altered membrane association and is nonfunctional. However, the basis for Taz1p dysfunction falls into the following two categories: (1) mistargeting to the mitochondrial matrix or (2) correct localization associated with aberrant complex assembly. Thus, BTHS can be caused by mutations that alter Taz1p sorting and assembly within the mitochondrion, indicating that the lipid target of Taz1p is resident to IMS-facing leaflets.

Functions of selected biochemical systems from the exercised-trained dog heart

1977 ◽  
Vol 42 (3) ◽  
pp. 426-431 ◽  
Author(s):  
L. A. Sordahl ◽  
G. K. Asimakis ◽  
R. T. Dowell ◽  
H. L. Stone
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Calcium Transport ◽  
Calcium Uptake ◽  
Atp Synthesis ◽  
Myocardial Cell ◽  
Ruthenium Red ◽  
Mitochondrial Membranes ◽  
Sedentary Control ◽  
Isolated Mitochondria ◽  
Biochemical Systems

Mitochondria and sarcoplasmic reticulum (SR) fractions were isolated from exercised-trained (E-T) and sedentary control dog hearts. Measurements of mitochondrial respiratory functions indicated no changes in energy-producing (ATP synthesis) capacity in mitochondria from E-T compared to control dog hearts. However, the ability of isolated mitochondria from E-T hearts to retain accumulated calcium was markedly decreased compared to controls. Inhibition of mitochondrial rates of calcium uptake with the inhibitor, ruthenium red, revealed fewer binding and/or transport sites in mitochondrial membranes from exercised-trained heart preparations. ATP-dependent binding (- oxalate) and uptake (+ oxalate) of calcium by SR preparations from E-T hearts were unchanged compared to controls. In contrast, significant differences in the rates of release of bound calcium were found in SR isolated from E-T hearts. Total myocardial protein, nucleic acids, and connective tissue levels were unchanged in E-T hearts compared to controls. The results suggest subtle changes are occurring in the energy-utilizing mechanism(s) involving calcium transport of the myocardial cell during exercise training. These changes may be related to alterations in the performance of the exercised-trained heart.

scholarly journals Inhibiting myosin-ATPase reveals a dynamic range of mitochondrial respiratory control in skeletal muscle

2011 ◽  
Vol 437 (2) ◽  
pp. 215-222 ◽  
Author(s):  
Christopher G. R. Perry ◽  
Daniel A. Kane ◽  
Chien-Te Lin ◽  
Rachel Kozy ◽  
Brook L. Cathey ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Dynamic Range ◽  
Energy Charge ◽  
Respiratory Control ◽  
Basic Research ◽  
Dependent Manner ◽  
Atpase Inhibitor ◽  
Wide Range ◽  
The Impact

Assessment of mitochondrial ADP-stimulated respiratory kinetics in PmFBs (permeabilized fibre bundles) is increasingly used in clinical diagnostic and basic research settings. However, estimates of the Km for ADP vary considerably (~20–300 μM) and tend to overestimate respiration at rest. Noting that PmFBs spontaneously contract during respiration experiments, we systematically determined the impact of contraction, temperature and oxygenation on ADP-stimulated respiratory kinetics. BLEB (blebbistatin), a myosin II ATPase inhibitor, blocked contraction under all conditions and yielded high Km values for ADP of >~250 and ~80 μM in red and white rat PmFBs respectively. In the absence of BLEB, PmFBs contracted and the Km for ADP decreased ~2–10-fold in a temperature-dependent manner. PmFBs were sensitive to hyperoxia (increased Km) in the absence of BLEB (contracted) at 30 °C but not 37 °C. In PmFBs from humans, contraction elicited high sensitivity to ADP (Km<100 μM), whereas blocking contraction (+BLEB) and including a phosphocreatine/creatine ratio of 2:1 to mimic the resting energetic state yielded a Km for ADP of ~1560 μM, consistent with estimates of in vivo resting respiratory rates of <1% maximum. These results demonstrate that the sensitivity of muscle to ADP varies over a wide range in relation to contractile state and cellular energy charge, providing evidence that enzymatic coupling of energy transfer within skeletal muscle becomes more efficient in the working state.

Total Capillary Bed in Striated Muscle of Guinea Pigs Native to the Peruvian Mountains

1958 ◽  
Vol 194 (3) ◽  
pp. 585-589 ◽  
Author(s):  
Enrique Valdivia
Keyword(s):  
Skeletal Muscle ◽  
Cross Sections ◽  
Guinea Pigs ◽  
Striated Muscle ◽  
Exercise Group ◽  
Adaptive Significance ◽  
Free Exercise ◽  
India Ink ◽  
Group A ◽  
Capillary Bed

The total capillary bed in skeletal muscle of guinea pigs has been determined by perfusion with India ink and counting capillaries in cross sections of gelatin embedded muscle. Comparative studies have indicated the importance of age, the muscle studied and the site where counts were performed. Capillaries were more evently distributed in the red than the white areas of the muscle. Free exercise or restriction in cages during the life span did not materially effect the results, although in cross sections some gross enlargement of the red areas was observed in the free exercise group. A significantly greater number of capillaries per square millimeter of muscle tissue were observed in the red area of muscles from animals native to the Peruvian mountains. The red area of these muscles was also more extensive than in the sea level born controls. The possible adaptive significance of these characteristics has been indicated.

Mithcondrial glutamine permeability and renal ammonia production in metabolic acidosis

1980 ◽  
Vol 239 (1) ◽  
pp. E51-E56
Author(s):  
T. C. Welbourne ◽  
G. T. Bazer
Keyword(s):  
Mitochondrial Membrane ◽  
Rat Kidney ◽  
Water Volume ◽  
Reflection Coefficients ◽  
Basal Region ◽  
Ammonia Production ◽  
Isolated Mitochondria ◽  
Membrane Feeding ◽  
Glutamine Uptake

These experiments were undertaken to determine the correspondence between acidosis-induced in situ motochondrial glutamine uptake and the process by which glutamine moves across the mitochondrial membrane. Feeding rats 1.5% NH4Cl for 2 wk accelerated the in situ uptake rate from 0.12 +/- 0.08 to 1.89 +/- 0.28 mu mol/min or some 16-fold. To determine glutamine uptake independent of its metabolic conversion, D-glutamine was employed. In isolated mitochondria from non-acidotic rat kidneys, D-glutamine diffused into 71 +/- 10% of the mitochondria water volume; in acidotic mitochondria the diffusion volume increased to 127 +/- 16%. The reflection coefficients (sigma) for a series of amides, including glutamine, were determined by gravimetrically following volume decrements in increasing concentrations of solute; D-glutamine's sigma fell from 1.05 +/- 0.08 to 0.50 +/- 0.06 in acidotic rat kidney mitchondria, The permeability coefficients corresponding to the measured sigma were 10(-7) cm/s and 10(-5) cm/s in nonacidosis and acidosis, respectively. When viewed in situ proximal tubule mitochondria undergo dramatic alterations during chronic acidosis. These involved an enlargement in the mitochondria particularly in the basal region of the cell and a reduction in number. Furthermore, numerous autophagic vacuoles, containing mitochondria, appear in the basal region. The findings are consistent availability that becomes activated during acidosis as a consequence of mitochondrial glutamine permeability resulting in increased ammoniagenesis and accelerated organelle turnover.

scholarly journals Dynamic Support Culture of Murine Skeletal Muscle-Derived Stem Cells Improves Their Cardiogenic PotentialIn Vitro

2015 ◽  
Vol 2015 ◽  
pp. 1-12 ◽  
Author(s):  
Klaus Neef ◽  
Philipp Treskes ◽  
Guoxing Xu ◽  
Florian Drey ◽  
Sureshkumar Perumal Srinivasan ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Stem Cells ◽  
Cluster Formation ◽  
Mrna Level ◽  
Fatal Outcome ◽  
Heart Tissue ◽  
Culture Conditions ◽  
Whole Cell Patch Clamp ◽  
Specific Culture ◽  
Murine Skeletal Muscle

Ischemic heart disease is the main cause of death in western countries and its burden is increasing worldwide. It typically involves irreversible degeneration and loss of myocardial tissue leading to poor prognosis and fatal outcome. Autologous cells with the potential to regenerate damaged heart tissue would be an ideal source for cell therapeutic approaches. Here, we compared different methods of conditional culture for increasing the yield and cardiogenic potential of murine skeletal muscle-derived stem cells. A subpopulation of nonadherent cells was isolated from skeletal muscle by preplating and applying cell culture conditions differing in support of cluster formation. In contrast to static culture conditions, dynamic culture with or without previous hanging drop preculture led to significantly increased cluster diameters and the expression of cardiac specific markers on the protein and mRNA level. Whole-cell patch-clamp studies revealed similarities to pacemaker action potentials and responsiveness to cardiac specific pharmacological stimuli. This data indicates that skeletal muscle-derived stem cells are capable of adopting enhanced cardiac muscle cell-like properties by applying specific culture conditions. Choosing this route for the establishment of a sustainable, autologous source of cells for cardiac therapies holds the potential of being clinically more acceptable than transgenic manipulation of cells.

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