Skeletal muscle mitochondria from AZT-treated rats have a diminished response to chronic electrical stimulation

1996 ◽  
Vol 81 (1) ◽  
pp. 326-334 ◽  
Author(s):  
D. T. McCurdy ◽  
J. M. Kennedy
Keyword(s):  
Skeletal Muscle ◽  
Electrical Stimulation ◽  
Volume Fraction ◽  
Mrna Levels ◽  
Chronic Stimulation ◽  
Polymerase Gamma ◽  
Dna Polymerase Gamma ◽  
Skeletal Muscle Mitochondria ◽  
Mtdna Replication ◽  
Mitochondrial Volume

Inhibition of DNA polymerase gamma-function mediated by 3'-azido-3'-deoxythymidine (AZT) has been proposed to cause a myopathy by reducing mitochondrial DNA (mtDNA) replication. Repeated bouts of exercise stimulate an increase in mtDNA replication, mitochondrial content, and mitochondrial volume fraction. Therefore, adaptation of rat skeletal muscle [tibialis anterior (TA)] mitochondria exposed to AZT (1 mg/ml for 35 days) and then to electrical stimulation for 8 h/day (7, 14, 21 days) with continued AZT treatment was examined. Fourteen and 21 days of stimulation increased TA cytochrome oxidase (CO) activity, mtDNA, and CO subunit III and VIc mRNA levels in both groups. The TA CO activity and CO III mRNA increases after 14 and 21 days of stimulation were diminished in AZT-treated rats. TA glyceraldehyde-3-phosphate dehydrogenase was reduced in normal rats after chronic stimulation but was unchanged in AZT-treated rats. Chronic stimulation increased the mitochondrial volume fraction by 80 and 40% in normal and AZT-treated rats, respectively. These results indicate diminution, but not complete inhibition, of mitochondrial adaptation by AZT-treated skeletal muscle in response to stimulation.

241 Skeletal Muscle Mitochondrial Capacities Are Impacted by Breed and Temperament in Young Angus and Brahman Steers

2021 ◽  
Vol 99 (Supplement_3) ◽  
pp. 127-127
Author(s):  
Chloey P Guy ◽  
Lauren T Wesolowski ◽  
Audrey L Earnhardt ◽  
Dustin Law ◽  
Don A Neuendorff ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Fixed Effects ◽  
Linear Models ◽  
Citrate Synthase ◽  
Volume Density ◽  
Skeletal Muscle Mitochondria ◽  
Mitochondrial Volume ◽  
Mitochondrial Volume Density ◽  
Brahman Steers ◽  
The Impact

Abstract Temperament impacts skeletal muscle mitochondria in Brahman heifers, but this has not been investigated in steers or between cattle breeds. We hypothesized mitochondrial measures would be greater in Angus than Brahman, temperamental than calm steers, and the trapezius (TRAP) than the longissimus thoracis (LT) muscle. Samples from calm (n = 13 per breed), intermediate (n = 12 per breed), and temperamental (n=13 per breed) Angus and Brahman steers (mean±SD 10.0±0.8 mo) were evaluated for mitochondrial enzyme activities via colorimetry. Calm and temperamental LT samples were evaluated for oxidative phosphorylation (P) and electron transfer (E) capacities by high-resolution respirometry. Data were analyzed using linear models with fixed effects of breed, muscle, temperament, and all interactions. Brahman tended to have greater mitochondrial volume density (citrate synthase activity; CS) than Angus (P = 0.08), while intrinsic (relative to CS) mitochondrial function (cytochrome c oxidase activity) was greater in Angus than Brahman (P = 0.001) and greater in TRAP than LT (P = 0.008). Angus exhibited greater integrative (per mg tissue) and intrinsic P with complex I (PCI), P with complexes I+II (PCI+II), maximum noncoupled E, and E with complex II (ECII; P ≤ 0.04) and tended to have greater intrinsic leak (P = 0.1) than Brahman. Contribution of PCI to total E was greater in Angus than Brahman (P = 0.01), while contribution of ECII to total E was greater in Brahman than Angus (P = 0.05). A trend for the interaction of breed and temperament (P = 0.07) indicated calm Angus had the greatest intrinsic ECII (P ≤ 0.03) while intrinsic ECII was similar between temperamental Angus and calm and temperamental Brahman. Integrative PCI+II and ECII, and the contribution of PCI and PCI+II to overall E tended to be greater in temperamental than calm steers (P ≤ 0.09), while intrinsic ECII tended to be greater in calm than temperamental steers (P = 0.07). The impact of these mitochondrial differences on meat quality measures remains to be determined.

scholarly journals Changes in Gene Expression of the MCU Complex Are Induced by Electrical Stimulation in Adult Skeletal Muscle

2021 ◽  
Vol 11 ◽  
Author(s):  
Esteban R. Quezada ◽  
Alexis Díaz-Vegas ◽  
Enrique Jaimovich ◽  
Mariana Casas
Keyword(s):  
Gene Expression ◽  
Skeletal Muscle ◽  
Electrical Stimulation ◽  
Muscle Fibers ◽  
Low Frequency ◽  
Extracellular Atp ◽  
Mrna Levels ◽  
Dependent Manner ◽  
Adult Skeletal Muscle ◽  
Muscle Plasticity

The slow calcium transient triggered by low-frequency electrical stimulation (ES) in adult muscle fibers and regulated by the extracellular ATP/IP3/IP3R pathway has been related to muscle plasticity. A regulation of muscular tropism associated with the MCU has also been described. However, the role of transient cytosolic calcium signals and signaling pathways related to muscle plasticity over the regulation of gene expression of the MCU complex (MCU, MICU1, MICU2, and EMRE) in adult skeletal muscle is completely unknown. In the present work, we show that 270 0.3-ms-long pulses at 20-Hz ES (and not at 90 Hz) transiently decreased the mRNA levels of the MCU complex in mice flexor digitorum brevis isolated muscle fibers. Importantly, when ATP released after 20-Hz ES is hydrolyzed by the enzyme apyrase, the repressor effect of 20 Hz on mRNA levels of the MCU complex is lost. Accordingly, the exposure of muscle fibers to 30 μM exogenous ATP produces the same effect as 20-Hz ES. Moreover, the use of apyrase in resting conditions (without ES) increased mRNA levels of MCU, pointing out the importance of extracellular ATP concentration over MCU mRNA levels. The use of xestospongin B (inhibitor of IP3 receptors) also prevented the decrease of mRNA levels of MCU, MICU1, MICU2, and EMRE mediated by a low-frequency ES. Our results show that the MCU complex can be regulated by electrical stimuli in a frequency-dependent manner. The changes observed in mRNA levels may be related to changes in the mitochondria, associated with the phenotypic transition from a fast- to a slow-type muscle, according to the described effect of this stimulation frequency on muscle phenotype. The decrease in mRNA levels of the MCU complex by exogenous ATP and the increase in MCU levels when basal ATP is reduced with the enzyme apyrase indicate that extracellular ATP may be a regulator of the MCU complex. Moreover, our results suggest that this regulation is part of the axes linking low-frequency stimulation with ATP/IP3/IP3R.

NFAT activation by membrane potential follows a calcium pathway distinct from other activity-related transcription factors in skeletal muscle cells

2008 ◽  
Vol 294 (3) ◽  
pp. C715-C725 ◽  
Author(s):  
Juan Antonio Valdés ◽  
Eduardo Gaggero ◽  
Jorge Hidalgo ◽  
Nancy Leal ◽  
Enrique Jaimovich ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Transcription Factors ◽  
Electrical Stimulation ◽  
Stimulus Frequency ◽  
Muscle Cells ◽  
C2c12 Cells ◽  
Skeletal Muscle Cells ◽  
Mrna Levels ◽  
Activated T Cells ◽  
Nfat Activation

Depolarization of skeletal muscle cells triggers intracellular Ca2+ signals mediated by ryanodine and inositol 1,4,5-trisphosphate (IP3) receptors. Previously, we have reported that K+-induced depolarization activates transcriptional regulators ERK, cAMP response element-binding protein, c- fos, c- jun, and egr-1 through IP3-dependent Ca2+ release, whereas NF-κB activation is elicited by both ryanodine and IP3 receptor-mediated Ca2+ signals. We have further shown that field stimulation with electrical pulses results in an NF-κB activation increase dependent of the amount of pulses and independent of their frequency. In this work, we report the results obtained for nuclear factor of activated T cells (NFAT)-mediated transcription and translocation generated by both K+ and electrical stimulation protocols in primary skeletal muscle cells and C2C12 cells. The Ca2+ source for NFAT activation is through release by ryanodine receptors and extracellular Ca2+ entry. We found this activation to be independent of the number of pulses within a physiological range of stimulus frequency and enhanced by long-lasting low-frequency stimulation. Therefore, activation of the NFAT signaling pathway differs from that of NF-κB and other transcription factors. Calcineurin enzyme activity correlated well with the relative activation of NFAT translocation and transcription using different stimulation protocols. Furthermore, both K+-induced depolarization and electrical stimulation increased mRNA levels of the type 1 IP3 receptor mediated by calcineurin activity, which suggests that depolarization may regulate IP3 receptor transcription. These results confirm the presence of at least two independent pathways for excitation-transcription coupling in skeletal muscle cells, both dependent on Ca2+ release and triggered by the same voltage sensor but activating different intracellular release channels.

Angiogenic growth factor mRNA responses to passive and contraction-induced hyperperfusion in skeletal muscle

1998 ◽  
Vol 85 (3) ◽  
pp. 1142-1149 ◽  
Author(s):  
Josep Roca ◽  
Timothy P. Gavin ◽  
Maria Jordan ◽  
Nikos Siafakas ◽  
Harrieth Wagner ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Blood Flow ◽  
Electrical Stimulation ◽  
Growth Factor ◽  
Acute Exercise ◽  
Transforming Growth Factor ◽  
Muscle Blood Flow ◽  
Mrna Levels ◽  
Angiogenic Growth Factor ◽  
Concentration Changes

It has been proposed that, in skeletal muscle, the angiogenic response to exercise may be signaled by the increase in muscle blood flow, via biomechanical changes in the microcirculation (increased shear stress and/or wall tension). To examine this hypothesis, we compared the change in abundance of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), and transforming growth factor-β1(TGF-β1) mRNA in skeletal muscles of the canine leg after 1 h of pump-controlled high blood flow alone (passive hyperperfusion; protocol A) and electrical stimulation of the femoral and sciatic nerves producing muscle contraction ( protocol B). The increase in leg blood flow (5.4- and 5.9-fold change from resting values, respectively) was similar in both groups. Passive hyperperfusion alone did not increase message abundance for VEGF (ratio of mRNA to 18S signals after vs. before hyperperfusion, 0.94 ± 0.08) or bFGF (1.08 ± 0.05) but slightly increased that of TGF-β1 (1.14 ± 0.07; P < 0.03). In contrast, as previously found in the rat, electrical stimulation provoked more than a threefold increase in VEGF mRNA abundance (3.40 ± 1.45; P < 0.02). However, electrical stimulation produced no significant changes in either bFGF (1.16 ± 0.13) or TGF-β1 (1.31 ± 0.27). These results suggest that the increased muscle blood flow of exercise does not account for the increased abundance of these angiogenic growth factor mRNA levels in response to acute exercise. We speculate that other factors, such as local hypoxia, metabolite concentration changes, or mechanical effects of contraction per se, may be responsible for the effects of exercise.

Effect of skeletal muscle fiber type on the pressor response evoked by static contraction in rabbits

1995 ◽  
Vol 79 (5) ◽  
pp. 1744-1752 ◽  
Author(s):  
L. B. Wilson ◽  
C. K. Dyke ◽  
D. Parsons ◽  
P. T. Wall ◽  
J. A. Pawelczyk ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Electrical Stimulation ◽  
Fiber Type ◽  
Pressor Response ◽  
Low Frequency ◽  
Subsequent Increase ◽  
Chronic Stimulation ◽  
Metabolic Characteristics ◽  
Static Contraction ◽  
Stimulation Technique

The purpose of this study was to determine whether the reflex hemodynamic responses to static contraction of predominately glycolytic muscle are greater than the changes elicited by primarily oxidative muscle. Low-frequency electrical stimulation (continuous 21 days) of the tibial nerve of one hindlimb of adult rabbits converted the metabolic characteristics of the predominately glycolytic gastrocnemius to a muscle that was primarily oxidative. After 21 days of stimulation, the rabbits were decerebrated, and static contraction of the glycolytic muscle (unstimulated gastrocnemius) initially decreased heart rate (HR; -16 +/- 3 beats/min) and mean arterial pressure (MAP; -17 +/- 3 mmHg). Thereafter, MAP increased 13 +/- 3 mmHg above baseline. Static contraction of the oxidative muscle (stimulated gastrocnemius) produced similar decreases in HR and MAP (-12 +/- 4 beats/min and -12 +/- 3 mmHg, respectively). However, the subsequent increase in MAP (8 +/- 3 mmHg; above baseline) was less than that evoked by contraction of the glycolytic muscle. The responses evoked by stretch of each muscle and high-intensity electrical stimulation were the same, indicating that the afferents from the muscle were not destroyed by the chronic-stimulation technique. These results support the hypothesis that metabolic by-products play a role in the pressor response to static contraction of skeletal muscle. In addition, these data confirm that contraction of predominately oxidative muscle can evoke a reflex pressor response, albeit smaller than the change elicited from primarily glycolytic muscle.

scholarly journals Camptocormia as a Novel Phenotype in a Heterozygous POLG2 Mutation

Diagnostics ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 68 ◽  
Author(s):  
Diana Lehmann Urban ◽  
Leila Motlagh Scholle ◽  
Kerstin Alt ◽  
Albert C. Ludolph ◽  
Angela Rosenbohm
Keyword(s):  
Clinical Phenotype ◽  
Mitochondrial Diseases ◽  
Mitochondrial Myopathies ◽  
Polymerase Gamma ◽  
Dna Polymerase Gamma ◽  
Phenotypic Spectrum ◽  
Muscle Histology ◽  
History Of ◽  
Mtdna Replication ◽  
Generation Sequencing

Mitochondrial dysfunction is known to play a key role in the pathophysiological pathway of neurodegenerative disorders. Nuclear-encoded proteins are involved in mtDNA replication, including DNA polymerase gamma, which is the only known replicative mtDNA polymerase, encoded by nuclear genes Polymerase gamma 1 (POLG) and Polymerase gamma 2 (POLG2). POLG mutations are well-known as a frequent cause of mitochondrial myopathies of nuclear origin. However, only rare descriptions of POLG2 mutations leading to mitochondriopathies exist. Here we describe a 68-year-old woman presenting with a 20-year history of camptocormia, mild proximal weakness, and moderate CK increase. Muscle histology showed COX-negative fibres. Genetic analysis by next generation sequencing revealed an already reported heterozygous c.1192-8_1207dup24 mutation in the POLG2 gene. This is the first report on a POLG2 mutation leading to camptocormia as the main clinical phenotype, extending the phenotypic spectrum of POLG2 associated diseases. This underlines the broad phenotypic spectrum found in mitochondrial diseases, especially in mitochondrial disorders of nuclear origin.

Activation of a novel metabolic gene regulatory pathway by chronic stimulation of skeletal muscle

1996 ◽  
Vol 270 (5) ◽  
pp. C1413-C1420 ◽  
Author(s):  
S. Cresci ◽  
L. D. Wright ◽  
J. A. Spratt ◽  
F. N. Briggs ◽  
D. P. Kelly
Keyword(s):  
Skeletal Muscle ◽  
Fiber Type ◽  
Nuclear Gene ◽  
Latissimus Dorsi Muscle ◽  
Acid Oxidation ◽  
Mrna Levels ◽  
Gene Encoding ◽  
Chronic Stimulation ◽  
Dorsi Muscle ◽  
Oxidation Enzyme

To determine whether expression of a nuclear gene encoding a mitochondrial fatty acid oxidation enzyme is regulated in parallel with skeletal muscle fibre-type-specific energy substrate preference, expression of the gene encoding medium-chain acyl-CoA dehydrogenase (MCAD) was delineated in canine latissimus dorsi muscle subjected to chronic motor nerve stimulation. In predominantly fast-twitch canine latissimus dorsi muscle, MCAD mRNA levels were regulated by chronic stimulation in a biphasic pattern. During the 1st wk of stimulation, steady-state MCAD mRNA levels decreased to 50% of unstimulated levels. MCAD mRNA levels began to increase during the 3rd wk of stimulation to reach a level 3.0-fold higher than levels in unstimulated contralateral control muscle by day 70. Immunodetectable MCAD mRNA levels throughout the stimulation period. The temporal pattern and magnitude of MCAD mRNA accumulation in response to muscle stimulation was distinct from that of mRNAs encoding other enzymes known to be regulated by this stimulus, including glyceraldehyde phosphate dehydrogenase, citrate synthase, and sarcoplasmic reticulum Ca-ATPase, but paralleled the protein levels of the peroxisome proliferator-activated receptor (PPAR), an orphan member of the nuclear hormone receptor superfamily known to regulate genes encoding fatty acid oxidation enzymes in liver. The skeletal muscle expression pattern of PPAR was also similar to that of MCAD in unstimulated rat skeletal muscles with distinct fiber-type compositions. These results demonstrate that a nuclear gene encoding a mitochondrial beta-oxidation enzyme is dynamically regulated in a pattern that parallels skeletal muscle fiber-type-specific energy substrate utilization and implicate an orphan nuclear receptor transcription factor as a candidate transducer of this response.

Mitochondrial Volume in Skeletal Muscle from Young and Old Physically Untrained and Trained Healthy Men and from Alcoholics

1973 ◽  
Vol 44 (6) ◽  
pp. 547-554 ◽  
Author(s):  
K.-H. Kiessling ◽  
L. Pilström ◽  
J. Karlsson ◽  
Karin Piehl
Keyword(s):  
Skeletal Muscle ◽  
Muscle Weakness ◽  
Considerable Increase ◽  
Volume Fraction ◽  
Young Men ◽  
Young Group ◽  
Quantitative Electron Microscopy ◽  
Healthy Men ◽  
Mitochondrial Volume ◽  
Old Men

1. Using quantitative electron microscopy, the volume fraction of mitochondria has been studied in the fibrillar and the perinuclear zones in leg muscle from young and old healthy men, physically trained and untrained, and from alcoholics with serious muscle weakness. 2. There is a correlation between the volume fractions of mitochondria in the fibrillar and perinuclear zones. 3. In young untrained men, the volume fraction of mitochondria in skeletal muscle is three-quarters of that in old untrained men in both the fibrillar and the perinuclear zone. In the young men, there are few but comparatively large mitochondria, while in old men the mitochondria are small but numerous. 4. Training causes a considerable increase in the volume fraction of mitochondria in young men (approx. 100%) but only a slight increase in old men (approx. 20%). The increase in the young group is caused by an increase in the number of mitochondria without any change of their volume, but in old men it is due to an increase in size. 5. Alcoholics with serious muscle weakness in their legs have a volume fraction of mitochondria which is below that of the healthy untrained controls. The decrease is of the same order as the increase induced by training in the old healthy men.

The “KIMWIPE” Effect in Ultra-Thin Cryosections

1985 ◽  
Vol 43 ◽  
pp. 458-459
Author(s):  
I. Taylor ◽  
P. Ingram ◽  
J.R. Sommer
Keyword(s):  
Skeletal Muscle ◽  
Electrical Stimulation ◽  
Muscle Fibers ◽  
Ice Crystals ◽  
Crystal Formation ◽  
Ice Crystal ◽  
Thin Sections ◽  
Skeletal Muscle Fibers ◽  
Freeze Dried ◽  
Ice Crystal Formation

In studying quick-frozen single intact skeletal muscle fibers for structural and microchemical alterations that occur milliseconds, and fractions thereof, after electrical stimulation, we have developed a method to compare, directly, ice crystal formation in freeze-substituted thin sections adjacent to all, and beneath the last, freeze-dried cryosections. We have observed images in the cryosections that to our knowledge have not been published heretofore (Figs.1-4). The main features are that isolated, sometimes large regions of the sections appear hazy and have much less contrast than adjacent regions. Sometimes within the hazy regions there are smaller areas that appear crinkled and have much more contrast. We have also observed that while the hazy areas remain still, the regions of higher contrast visibly contract in the beam, often causing tears in the sections that are clearly not caused by ice crystals (Fig.3, arrows).

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