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Hypertrophic muscle fibers with fissures in power-lifters; fiber splitting or defect regeneration?
Umeå University, Faculty of Medicine, Integrative Medical Biology, Anatomy.
Umeå University, Faculty of Medicine, Integrative Medical Biology, Anatomy.
Umeå University, Faculty of Medicine, Integrative Medical Biology, Anatomy.
Umeå University, Faculty of Medicine, Integrative Medical Biology, Anatomy.
2006 (English)In: Histochemistry and Cell Biology, ISSN 0948-6143, E-ISSN 1432-119X, Vol. 126, no 4, 409-417 p.Article in journal (Refereed) Published
Abstract [en]

Power-lifters have hypertrophic muscle fibers with fissures seen in cross-sections, called as fiber splitting.Whether this phenomenon is due to real splitting or defective regeneration has not been settled. To elucidate this matter,we have examined biopsies from the trapezius and vastus lateralis of power lifters (P group) and power lifters self-administrating anabolic steroids (PAS group). For this purpose, immunohistochemical staining of serial cross -sections was used. The PAS group had significantly more fibers with fissures than the P group in the vastus lateralis (1.2%+/-0.95% vs 0.35+/-0.34, P < 0.05) but not in the trapezius muscle (1.7% in both groups). Serial sections revealed that the fibers with fissures changed their profile profoundly over short distances. Some such fibers had a mature staining profile, whereas other fibers indicated recent degeneration and/or regeneration. Activation of satellite cells and formation of aberrant segments were also evident. We conclude that the so-called split fibers are due to defect regeneration. Some fibers with fissures are the results of old events of segmental muscle fiber damage, whereas the others reflect an ongoing process. The normal regenerative process is most likely disturbed in power-lifters by their continuous training with repeated high mechanical stress on the muscles.

Place, publisher, year, edition, pages
2006. Vol. 126, no 4, 409-417 p.
Keyword [en]
Adult, Anabolic Agents/administration & dosage, Humans, Hypertrophy, Immunohistochemistry, Male, Muscle Fibers/*pathology/*physiology, Muscle; Skeletal/drug effects/ultrastructure, Regeneration, Self Administration, Steroids/administration & dosage, Weight Lifting
Identifiers
URN: urn:nbn:se:umu:diva-12683DOI: 10.1007/s00418-006-0176-3PubMedID: 16625366OAI: oai:DiVA.org:umu-12683DiVA: diva2:152354
Available from: 2008-01-11 Created: 2008-01-11 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Strenght training and anabolic steroids: a comparative study of the trapezius, a shoulder muscle and the vastus lateralis, a thigh muscle, of strength trained athletes
Open this publication in new window or tab >>Strenght training and anabolic steroids: a comparative study of the trapezius, a shoulder muscle and the vastus lateralis, a thigh muscle, of strength trained athletes
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Strength training is widely used to increase performance in sports with high physical demands. The use of drugs such as anabolic steroids among athletes is a wellknown phenomenon, and the effects of these drugs on physical performance documented.

The studies presented in this thesis focused on the mechanisms of muscle fiber hypertrophy in the vastus lateralis and the trapezius muscles of strength trained elite athletes. The main hypothesis was that the muscle adaptations to strength training and anabolic steroids are muscle specific.

Biopsies were obtained from the trapezius and the vastus lateralis from three groups of elite power lifters. Nine used drugs, ten did not and seven had previously used drugs. Six sedentary males served as controls. The biopsies were frozen and cut in serial cross sections. Histological and immunohistochemical staining techniques were used to analyze muscle fiber morphology and pathology. Fiber type distribution, fiber area, myonuclei number and distribution, satellite cell number and proportion of split fibers were counted and compared for the two muscles within and between the groups.

The main findings were that: a) Muscle fiber hypertrophy by strength training is further increased by anabolic steroids. b) The number of nuclei per muscle fiber is higher in power lifters using anabolic steroids compared to non-steroids using lifters. c) Among power lifters who have withdrawn from anabolic steroid usage and training for several years, the number of myonuclei, both subsarcolemmal and internal, remains high. d) In active power lifters, anabolic steroids have no further effect on the number of satellite cells per fiber. e) Power lifters have a high proportion of split fibers.

High intensity resistance training increases muscle strength and banned substances such as testosterone and anabolic steroids can enhance the training effects. The studies on muscle cell morphology presented in this thesis reveals that anabolic steroids and testosterone increases muscle fiber size and adds more nuclei to the muscle cell.

Based on the morphological appearance of muscle sections from doped and nondoped power lifters, we conclude that testosterone and anabolic steroids enhances the hypertrophic effects of training without adding new features. The addition of myonuclei by training and doping appears to be longer lasting in some muscles than in others. The high proportion of split fibers in power lifter is probably due to high mechanical stress. The findings and conclusions in this thesis raise questions regarding relevant suspension times for athletes caught with banned substances in the body.

Publisher
51 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1032
Keyword
strength training, anabolic steroids, vastus lateralis, trapezius, enzymehistochemistry, immunohistochemistry, muscle fiber, myonuclei, satellite cell
Research subject
Human Anatomy
Identifiers
urn:nbn:se:umu:diva-869 (URN)91-7264-101-0 (ISBN)
Public defence
2006-10-06, Stora föreläsningssalen, Biologihuset, Umeå, 13:00 (English)
Opponent
Available from: 2006-09-19 Created: 2006-09-19 Last updated: 2009-10-02Bibliographically approved
2. Satellite cells in human skeletal muscle: molecular identification quantification and function
Open this publication in new window or tab >>Satellite cells in human skeletal muscle: molecular identification quantification and function
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Satellitceller i human skelettmuskulatur : molekylär identifiering, kvantifiering och funktion
Abstract [en]

Skeletal muscle satellite cells located between the plasma membrane and the basal lamina of muscle fibres, could for many years, only be studied in situ by electron microscopy. The introduction of immunohistochemistry and the discovery of molecular markers of satellite cells then made them accessible for light microscopic studies and a wealth of information is today available. Satellite cells are myogenic stem cells that can be activated from a quiescent state to proliferate for self-renewal or differentiate into myogenic cells. The satellite cells are involved in muscle growth during fetal and postnatal development and play a key role in repair and regeneration of damaged muscle fibres. The satellite cells are also essential for muscle fibre hypertrophy and maintenance of muscle mass in the adult. When the present thesis was initiated, studies on satellite cells in human skeletal muscle relied on the neuronal cell adhesion molecule (NCAM) as a marker for satellite cell identification. The results from different studies varied markedly. Therefore the aims of the present thesis were i) to develop a highly reliable method using light microscopy for satellite cell identification and quantification in biopsies of human skeletal muscle in normal and pathological conditions. A molecular marker for the myofibre basal lamina or plasma membrane to enhance the reliability of myonuclei and satellite cell identification were to be included. Furthermore unbiased morphometric methods should be used in the quantification process. ii) to evaluate which molecular markers which had been described for satellite cell and stem cell identification in different cell states (quiescence, activated or differentiated) are the most useful for studies on human skeletal muscle. iii) to further explore the function and heterogeneity of satellite cells with respect to different markers in human skeletal muscle by studying the effects of strength-training, intake of anabolic substances and pathological conditions.

A new immunofluorescence method was developed where in the same tissue section, two satellite cell markers, the basal lamina and nuclei were monitored. From the evaluation of different markers it was found that both NCAM and Pax7 identified the majority of satellite cells but that both markers were needed for reliable identification. The members of the myogenic regulatory family were evaluated and by using the new method MyoD and myogenin were found to be useful markers to identify activated and differentiated satellite cells. Upon re-examination of biopsies from power-lifters, power-lifters using anabolic substances and untrained subjects it was observed that the new results on satellite cell frequency were significantly different from those obtained when using staining for NCAM and nuclei alone. In addition three subtypes of satellite cells (94.4% NCAM+/Pax7+, 4.2% NCAM+/Pax7 and 1.4% NCAM/Pax7+) were observed. Thus the multiple marker method gave more information about satellite cells heterogeneity in human muscle and we propose that this is more reliable than previous methods. Low numbers of MyoD or myogenin stained satellite cells were observed in both untrained and strength trained subjects. Other markers such as DLK1/FA1, a member of the EGF-like family and c-Met, the receptor for hepatocyte growth factor showed that satellite cell heterogeneity in human muscle is far greater than previously shown. Furthermore, new evidence is presented for so called fibre splitting observed in hypertrophic muscle fibres to be due to defect regeneration of partially damaged fibres.

Place, publisher, year, edition, pages
Umeå: Umeå University, 2009. 56 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1313
Keyword
satellite cell markers, NCAM, Pax7, MyoD, myogenin, DLK1/FA1, c-Met, human skeletal muscle, immunohistochemistry, muscle growth, muscle hypertrophy
National Category
Cell and Molecular Biology
Research subject
Human Anatomy
Identifiers
urn:nbn:se:umu:diva-29817 (URN)978-91-7264-900-2 (ISBN)
Public defence
2009-12-18, Biologihuset, sal BiA201, Umeå Universitet, Umeå, 09:00 (Swedish)
Opponent
Supervisors
Available from: 2009-12-01 Created: 2009-11-24 Last updated: 2011-04-07Bibliographically approved

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