Mitochondrial size and shape in equine skeletal muscle: a three-dimensional reconstruction study.
Abstract: Individual mitochondria were reconstructed from ultrathin serial sections of selected muscle fibers in the M. semitendinosus of a horse, over a length of nearly two sarcomeres. Mitochondria were found to be highly variable, with size and complexity of single mitochondria increasing with the fractional part of a fiber occupied by mitochondria. In fibers with a mitochondrial volume density of less than 4%, corresponding to the mitochondrial content of fast-twitch glycolytic fibers, mitochondria were generally rather simple cylindrical shapes, oriented parallel to the myofibrils. In fibers with a mitochondrial volume density of more than 7%, corresponding to the mitochondrial content of slow-oxidative or fast-oxidative glycolytic fibers, mitochondria were generally cylindrical at the A-band and Z-plate level of the muscle sarcomeres. However, these mitochondria often had transverse extensions or interconnections that occurred at the I-band level. Volumes of individual mitochondria ranged from as small as a few thousandths of a micron3 up to several micron3 for the incompletely reconstructed portions of the largest mitochondria. Mitochondrial profiles that one would classify from single sections as subsarcolemmal were found to interconnect with other profiles deeper within the fiber. This suggests that it is unlikely that subsarcolemmal and interfibrillar mitochondria are two structurally distinct populations. However, we found no evidence of a reticulum completely interlinking all mitochondrial material in a muscle fiber.
Publication Date: 1988-12-01 PubMed ID: 3228204DOI: 10.1002/ar.1092220405Google Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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The research article is about a study examining the size and shape of mitochondria in horse muscles, using three-dimensional reconstruction. It highlights the variability in mitochondrial properties dependent on location in muscle fibers and suggests a potential interconnectedness between different types of mitochondria.
Introduction and Methodology
- The researcher conducted three-dimensional reconstructions of individual mitochondria, which were selected from muscle fibers in the M. semitendinosus (a muscle in the back of the thigh) in a horse. The length of examination covered nearly two sarcomeres – the fundamental units of muscle contraction.
- This reconstruction allowed detailed exploration and understanding of the size and complexity of mitochondrial shapes in various parts of muscle fiber.
Findings
- The paper reports a marked variability in the size and complexity of mitochondria, which increased with the portion of a fiber occupied by mitochondria.
- The researchers found that in muscle fibers with a mitochondrial volume density of less than 4% (which corresponded to the mitochondrial content of fast-twitch glycolytic fibers), the mitochondria had simple cylindrical shapes and were oriented parallel to the myofibrils.
- In fibers with a higher mitochondrial volume density of more than 7% (which corresponded to the mitochondrial content of slow-oxidative or fast-oxidative glycolytic fibers), mitochondria were generally cylindrical at the A-band and Z-plate level of the muscle sarcomeres.
- These mitochondria often exhibited transverse extensions or interconnections occurring at the I-band level; essentially, they were complex in morphology.
- The volumes of individual mitochondria varied widely, ranging from a few thousandths of a micron3 up to several micron3 for larger mitochondria.
Connections Between Different Types of Mitochondria
- The researchers discovered that mitochondrial profiles which were initially categorised from single sections as subsarcolemmal interconnected with other profiles deep within the fiber. This new observation challenges the previous conception that subsarcolemmal and interfibrillar mitochondria are two distinct populations.
- Despite this intricacy, the study found no indication of a complete network or reticulum interlinking all mitochondrial material in a muscle fiber.
Conclusions
- The study fosters a new perspective on the microbody complexity of skeletal muscle fibers and their mitochondrial structures. The variability of sizes and shapes within the same cellular territory suggests a much more integrated physiological and possibly metabolic relationship within the mitochondria population.
Cite This Article
APA
Kayar SR, Hoppeler H, Mermod L, Weibel ER.
(1988).
Mitochondrial size and shape in equine skeletal muscle: a three-dimensional reconstruction study.
Anat Rec, 222(4), 333-339.
https://doi.org/10.1002/ar.1092220405 Publication
Researcher Affiliations
- Institute of Anatomy, University of Bern, Switzerland.
MeSH Terms
- Animals
- Horses / anatomy & histology
- Image Processing, Computer-Assisted
- Leg
- Male
- Microscopy, Electron
- Mitochondria, Muscle / ultrastructure
Citations
This article has been cited 15 times.- Hyatt JK. MOTS-c increases in skeletal muscle following long-term physical activity and improves acute exercise performance after a single dose.. Physiol Rep 2022 Jul;10(13):e15377.
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- Memme JM, Hood DA. Molecular Basis for the Therapeutic Effects of Exercise on Mitochondrial Defects.. Front Physiol 2020;11:615038.
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