| 31. |
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| 32. |
- Kadi, Fawzi, 1970-
(författare)
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In response to Point: Counterpoint : "Satellite cell addition is/is not obligatory for skeletal muscle hypertrophy"
- 2007
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Ingår i: Journal of applied physiology. - : American Physiological Society. - 8750-7587 .- 1522-1601. ; 103:3, s. 1105-1105
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- In this letter, the point: counterpoint issue (1, 5) is addressed solely by referring to studies in humans. The analysis of histological sections from skeletal muscle of power lifters with many years of practice leaves no doubt about the role of satellite cells as myonuclei donors in the hypertrophied muscle fibre. The larger the cross-sectional area of fibres, the higher the number of myonuclei per cross-section (2, 4). Importantly, the strong relationship between the cross-sectional area of fibres and the number of myonuclei (r = 0,86; p < 0.0001) is obtained with a range of areas between 2500 µm2 and 14000 µm2 (4). Existing myonuclei are able to sustain an initial hypertrophy of the muscle fibre as long as the transcriptional activity of existing myonuclei does not reach its maximum (2, 3, 5). Satellite cells become myonuclei donors when fibre size reaches the ceiling size (2, 3, 5). Additionally, we should not forget that satellite cells are also donors of myonuclei to newly generated myotubes (2, 4). The intensity of exercise and the initial fibre area of the subjects included in a training program are important factors governing whether daughter cells generated by satellite cell activation and proliferation provide new myonuclei to existing myofibres or to newly generated myotubes. Finally, in parallel with these events, some of the daughter cells can escape differentiation and facilitate renewal of the satellite cell pool. Efforts should be made to better understand key elements guiding the fate of satellite cells.
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| 33. |
- Kadi, Fawzi, et al.
(författare)
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Satellite cells and myonuclei in young and elderly women and men
- 2004
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Ingår i: Muscle and Nerve. - : Wiley. - 0148-639X .- 1097-4598. ; 29:1, s. 120-127
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Tidskriftsartikel (refereegranskat)abstract
- The overall aim of this study was to assess the effects of aging on the satellite cell population. Muscle biopsies were taken from the tibialis anterior muscle of healthy, moderately active young (age range, 20-32 years; n = 31) and elderly (age range, 70-83 years; n = 27) women and men with comparable physical activity pattern. Satellite cells and myonuclei were visualized using a monoclonal antibody against neural cell adhesion molecule and counterstained with Mayer's hematoxylin. An average of 211 (range, 192-241) muscle fibers were examined for each individual. Compared with the young women and men, the elderly subjects had a significantly lower (P < 0.011) number of satellite cells per muscle fiber but a significantly higher (P < 0.004) number of myonuclei per muscle fiber. The number of satellite cells relative to the total number of nuclei [satellite cells/(myonuclei + satellite cells)] was significantly lower in the elderly than in the young women and men. These results imply that a reduction in the satellite cell population occurs as a result of increasing age in healthy men and women.
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| 34. |
- Kadi, Fawzi, et al.
(författare)
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The behaviour of satellite cells in response to exercise : what have we learned from human studies?
- 2005
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Ingår i: Pflügers Archiv. - : Springer Science and Business Media LLC. - 0031-6768 .- 1432-2013. ; 451:2, s. 319-327
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Understanding the complex role played by satellite cells in the adaptive response to exercise in human skeletal muscle has just begun. The development of reliable markers for the identification of satellite cell status (quiescence/activation/proliferation) is an important step towards the understanding of satellite cell behaviour in exercised human muscles. It is hypothesised currently that exercise in humans can induce (1) the activation of satellite cells without proliferation, (2) proliferation and withdrawal from differentiation, (3) proliferation and differentiation to provide myonuclei and (4) proliferation and differentiation to generate new muscle fibres or to repair segmental fibre injuries. In humans, the satellite cell pool can increase as early as 4 days following a single bout of exercise and is maintained at higher level following several weeks of training. Cessation of training is associated with a gradual reduction of the previously enhanced satellite cell pool. In the elderly, training counteracts the normal decline in satellite cell number seen with ageing. When the transcriptional activity of existing myonuclei reaches its maximum, daughter cells generated by satellite cell proliferation are involved in protein synthesis by enhancing the number of nuclear domains. Clearly, delineating the events and the mechanisms behind the activation of satellite cells both under physiological and pathological conditions in human skeletal muscles remains an important challenge.
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| 35. |
- Kadi, Fawzi, et al.
(författare)
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The effects of heavy resistance training and detraining on satellite cells in human skeletal muscles
- 2004
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Ingår i: Journal of Physiology. - : Wiley. - 0022-3751 .- 1469-7793. ; 558:Pt 3, s. 1005-1012
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to investigate the modulation of satellite cell content and myonuclear number following 30 and 90 days of resistance training and 3, 10, 30, 60 and 90 days of detraining. Muscle biopsies were obtained from the vastus lateralis of 15 young men (mean age: 24 years; range: 20-32 years). Satellite cells and myonuclei were studied on muscle cross-sections stained with a monoclonal antibody against CD56 and counterstained with Mayer's haematoxylin. Cell cycle markers CyclinD1 and p21 mRNA levels were determined by Northern blotting. Satellite cell content increased by 19% (P= 0.02) at 30 days and by 31% (P= 0.0003) at 90 days of training. Compared to pre-training values, the number of satellite cells remained significantly elevated at 3, 10 and 60 days but not at 90 days of detraining. The two cell cycle markers CyclinD1 and p21 mRNA significantly increased at 30 days of training. At 90 days of training, p21 was still elevated whereas CyclinD1 returned to pre-training values. In the detraining period, p21 and CyclinD1 levels were similar to the pre-training values. There were no significant alterations in the number of myonuclei following the training and the detraining periods. The fibre area controlled by each myonucleus gradually increased throughout the training period and returned to pre-training values during detraining. In conclusion, these results demonstrate the high plasticity of satellite cells in response to training and detraining stimuli and clearly show that moderate changes in the size of skeletal muscle fibres can be achieved without the addition of new myonuclei.
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| 36. |
- Kadi, Fawzi, et al.
(författare)
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The effects of regular strength training on telomere length in human skeletal muscle
- 2008
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Ingår i: Medicine & Science in Sports & Exercise. - : Lippincott Williams & Wilkins. - 0195-9131 .- 1530-0315. ; 40:1, s. 82-87
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: The length of DNA telomeres is an important parameter of the proliferative potential of tissues. A recent study has reported abnormally short telomeres in skeletal muscle of athletes with exercise-associated fatigue. This important report raises the question of whether long-term practice of sports might have deleterious effects on muscle telomeres. Therefore, we aimed to compare telomere length of a group of power lifters (PL; N = 7) who trained for 8 +/- 3 yr against that of a group of healthy, active subjects (C; N = 7) with no history of strength training. METHODS: Muscle biopsies were taken from the vastus lateralis, and the mean and minimum telomeric restriction fragments (TRF) (telomere length) were determined, using the Southern blot protocol previously used for the analysis of skeletal muscle. RESULTS: There was no abnormal shortening of telomeres in PL. On the contrary, the mean (P = 0.07) and the minimum (P = 0.09) TRF lengths in PL tended to be higher than in C. In PL, the minimum TRF length was inversely correlated to the individual records in squat (r = -0.86; P = 0.01) and deadlift (r = -0.88; P = 0.01). CONCLUSION: These results show for the first time that long-term training is not associated with an abnormal shortening of skeletal muscle telomere length. Although the minimum telomere length in PL remains within normal physiological ranges, a heavier load put on the muscles means a shorter minimum TRF length in skeletal muscle.
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| 37. |
- Kadi, Fawzi, et al.
(författare)
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The number of satellite cells in slow and fast fibres from human vastus lateralis muscle
- 2006
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Ingår i: Histochemistry and Cell Biology. - : Springer Science and Business Media LLC. - 0948-6143 .- 1432-119X. ; 126:1, s. 83-87
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this investigation was to study the distribution of satellite cells in slow (type I fibres) and fast (type II fibres) fibres from human vastus lateralis muscle. This muscle is characterised by a mixed fibre type composition and is considered as the site of choice for biopsies in research work and for clinical diagnosis. Biopsy samples were obtained from five healthy young volunteers and a total of 1,747 type I fibres and 1,760 type II fibres were assessed. Satellite cells and fibre type composition were studied on serial muscle cross-sections stained with specific monoclonal antibodies. From a total of 218 satellite cells, 116 satellite cells were found in contact with type I fibres (53.6+/-8% of the satellite cells associated to type I fibres) and 102 satellite cells in contact with type II fibres (46.4+/-8% of the satellite cells associated to type II fibres). There was no significant difference (P=0.4) between the percentages of satellite cells in contact with type I and with type II fibres. Additionally, there was no relationship between the mean number of satellite cells per fibre and the mean cross-sectional area of muscle fibres. In conclusion, our results show that there is no fibre type-specific distribution of satellite cells in a human skeletal muscle with mixed fibre type composition.
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| 38. |
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| 39. |
- Klasson-Heggebø, L., et al.
(författare)
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Graded associations between cardiorespiratory fitness, fatness, and blood pressure in children and adolescents
- 2006
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Ingår i: British Journal of Sports Medicine. - : BMJ. - 0306-3674 .- 1473-0480. ; 40:1, s. 25-29; discussion 25
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE:To measure the graded relation between cardiorespiratory fitness and sum of skinfolds, waist circumference, and blood pressure in children and adolescents participating in the European youth heart study.METHODS:The participants were 4072 children and adolescents (aged 9 and 15) from Denmark, Portugal, Estonia, and Norway. Cardiorespiratory fitness was indirectly determined using a maximal ergometer cycle test. The sum of four skinfolds, waist circumference, and blood pressure were assessed with a standardised protocol. Linear regression analysis was used to test the graded relation between cardiorespiratory fitness and the dependent variables adjusted for pubertal stage, sex, and country.RESULTS:A significant curvilinear graded relation was found between cardiorespiratory fitness and waist circumference and sum of skinfolds (partial r2 for cardiorespiratory fitness was 0.09-0.26 for the different sexes and age groups). Systolic and diastolic blood pressure also showed a curvilinear relation with cardiorespiratory fitness, and fitness explained 2% of the variance in systolic blood pressure. The difference in systolic blood pressure between the least and most fit was 6 mm Hg.CONCLUSION:A curvilinear graded relation was found between cardiorespiratory fitness and waist circumference, sum of skinfolds, and systolic blood pressure. The greatest difference in these health variables was observed between low and moderate fitness levels.
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| 40. |
- Larsson, Britt, et al.
(författare)
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Blood supply and oxidative metabolism in muscle biopsies of female cleaners with and without myalgia
- 2004
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Ingår i: The Clinical Journal of Pain. - : Ovid Technologies (Wolters Kluwer Health). - 0749-8047 .- 1536-5409. ; 20:6, s. 440-446
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: Pathomechanisms of work-related myalgia are poorly understood. Myalgia is thought to be caused by excitation of nociceptors present in the muscular tissue but not in the muscle fiber itself. Muscle contraction in combination with hypoxia is known to excite nociceptors. Morphologic analysis can contribute to the knowledge of the excitation of nociceptors. This study thoroughly examines the morphology of the trapezius muscle's capillary supply and signs of disturbed oxidative metabolism to understand their role in work-related myalgia. METHODS: Surgical trapezius muscle biopsies were obtained from 25 female cleaners with long-standing work-related myalgia, 25 female cleaners without trapezius myalgia, and 21 healthy teachers. Enzyme and immunohistochemical stainings were performed to highlight fibers with aberrant intermyofibrillar patterns, indicating a disturbed oxidative metabolism (also known as moth-eaten fibers) and a disturbed capillary supply of different fibers. RESULTS: A significantly lower number of capillaries per fiber area in cleaners suffering from myalgia compared with cleaners without trapezius myalgia was found. Moth-eaten fibers were found in the 3 groups, but these fibers were significantly more prevalent in the groups of cleaners than in the healthy teacher group. CONCLUSION: This work indicates that the capillary supply of trapezius is affected in work-related trapezius myalgia. More studies are needed to understand possible mechanisms that would explain the occurrence of moth-eaten fibers.
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