| 1. |
- Kadi, Fawzi, et al.
(författare)
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Cellular adaptation of the trapezius muscle in strength-trained athletes
- 1999
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Ingår i: Histochemistry and Cell Biology. - : Springer Science and Business Media LLC. - 0948-6143 .- 1432-119X. ; 111:3, s. 189-195
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to elucidate the cellular events that occur in the trapezius muscle following several years of strength training. In muscle biopsies from ten elite power lifters (PL) and six control subjects (C), several parameters were studied: cross-sectional area of muscle fibres, myosin heavy chain composition (MHC) and capillary supply [capillaries around fibres (CAF) and CAF/fibre area]. A method was also developed for counting the number of myonuclei and satellite cell nuclei. The proportion of fibres expressing MHC IIA, the cross-sectional area of each fibre type and the number of myonuclei, satellite cells and fibres expressing markers for early myogenesis were significantly higher in PL than in C (P<0.05). A significant correlation between the myonuclear number and the cross-sectional area was observed. Since myonuclei in mature muscle fibres are not able to divide, we suggest that the incorporation of satellite cell nuclei into muscle fibres resulted in the maintenance of a constant nuclear to cytoplasmic ratio. The presence of small diameter fibres expressing markers for early myogenesis indicates the formation of new muscle fibres.
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| 2. |
- Kadi, Fawzi, et al.
(författare)
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Effects of anabolic steroids on the muscle cells of strength-trained athletes
- 1999
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Ingår i: Medicine & Science in Sports & Exercise. - : Ovid Technologies (Wolters Kluwer Health). - 0195-9131 .- 1530-0315. ; 31:11, s. 1528-1534
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: Athletes who use anabolic steroids get larger and stronger muscles. How this is reflected at the level of the muscle fibers has not yet been established and was the topic of this investigation. METHODS: Muscle biopsies were obtained from the trapezius muscles of high-level power lifters who have reported the use of anabolic steroids in high doses for several years and from high-level power lifters who have never used these drugs. Enzyme-immunohistochemical investigation was performed to assess muscle fiber types, fiber area, myonuclear number, frequency of satellite cells, and fibers expressing developmental protein isoforms. RESULTS: The overall muscle fiber composition was the same in both groups. The mean area for each fiber type in the reported steroid users was larger than that in the nonsteroid users (P < 0.05). The number of myonuclei and the proportion of central nuclei were also significantly higher in the reported steroid users (P < 0.05). Likewise, the frequency of fibers expressing developmental protein isoforms was significantly higher in the reported steroid users group (P < 0.05). CONCLUSION: Intake of anabolic steroids and strength-training induce an increase in muscle size by both hypertrophy and the formation of new muscle fibers. We propose that activation of satellite cells is a key process and is enhanced by the steroid use. The incorporation of the satellite cells into preexisting fibers to maintain a constant nuclear to cytoplasmic ratio seems to be a fundamental mechanism for muscle fiber growth. Although all the subjects in this study have the same level of performance, the possibility of genetic differences between the two groups cannot be completely excluded.
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| 3. |
- Koutsis, G, et al.
(författare)
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Effects of an endurance training programme on the passive and noradrenaline-activated compliances of rat aorta
- 1995
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Ingår i: European Journal of Applied Physiology and Occupational Physiology. - New York, USA : Springer-Verlag New York. - 0301-5548 .- 1432-1025. ; 71:2-3, s. 173-9
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Tidskriftsartikel (refereegranskat)abstract
- The effects of a 12-week endurance training programme (treadmill) upon the passive and the noradrenaline-activated properties of the aorta were studied in 15 trained and 24 sedentary rats. Aortic compliance was studied by measuring the length-tension curves of rings of the descending aorta without (passive properties) and with noradrenaline (noradrenaline activated) in a bubbling Krebs bath kept at a temperature of 37 degrees. The training effect on aortic volume compliance was studied by transforming the tension-length curves into a cross-sectional area-pressure curve according to Laplace's law. The noradrenaline responsiveness was studied by the dose-effect curve. The mechanical data were correlated with the results of a histomorphometric study which measured the aortic wall thickness and the percentages and amounts of elastic, connective and muscle components. Passive aortic compliance and volume compliance were higher in endurance-trained rats whose tunica media presented a lower percentage of collagen and a larger amount of elastic tissue. The dose-effect curve showed that the maximal aortic response to noradrenaline was stronger in trained rats but that the half maximal effective dose was not different. As a consequence, the length-tension curves of the noradrenaline fully activated aorta were similar in trained and sedentary rats except at the highest tensions where collagen is the main factor determining aortic stiffness. The increased noradrenaline response in trained rats was probably the result of the hypertrophy of the smooth muscle cells as maximal active strain (Newtons per square metre) was similar in trained and sedentary rats.
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