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1.
PLoS One ; 8(11): e80909, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-24260508

RESUMO

In an attempt to shorten recovery time and improve performance, strength and endurance athletes occasionally turn to the illicit use of anabolic-androgenic steroids (AAS). This study evaluated the effects of AAS treatment on the muscle mass and phenotypic characteristics of transgenic mice subjected to a high-intensity, aerobic training program (5d/wk for 6 weeks). The transgenic mice (CETP(+/-)LDLr(-/+)) were engineered to exhibit a lipid profile closer to humans. Animals were divided into groups of sedentary (Sed) and/or training (Ex) mice (each treated orally with AAS or gum arabic/vehicle: Sed-C, Sed-M, ex-C, ex-M). The effects of AAS (mesterolone: M) on specific phenotypic adaptations (muscle wet weight, cross-sectional area, and fiber type composition) in three hindlimb muscles (soleus:SOL, tibialis anterior:TA and gastrocnemius:GAS) were assessed. In order to detect subtle changes in fiber type profile, the entire range of fiber types (I, IC, IIAC, IIA, IIAD, IID, IIDB, IIB) was delineated using mATPase histochemistry. Body weight gain occurred throughout the study for all groups. However, the body weight gain was significantly minimized with exercise. This effect was blunted with mesterolone treatment. Both AAS treatment (Sed-M) and high-intensity, aerobic training (ex-C) increased the wet weights of all three muscles and induced differential hypertrophy of pure and hybrid fibers. Combination of AAS and training (ex-M) resulted in enhanced hypertrophy. In the SOL, mesterolone treatment (Sed-M and ex-M) caused dramatic increases in the percentages of fiber types IC, IIAC, IIAD, IID, with concomitant decrease in IIA, but had minimal impact on fiber type percentages in the predominantly fast muscles. Overall, the AAS-induced differential adaptive changes amounted to significant fiber type transformations in the fast-to-slow direction in SOL. AAS treatment had a significant effect on muscle weights and fiber type composition in SOL, TA and GAS which was even maximized in animals subjected to metabolically high-intensity aerobic exercise.


Assuntos
Anabolizantes/farmacologia , Membro Posterior/efeitos dos fármacos , Mesterolona/farmacologia , Músculo Esquelético/efeitos dos fármacos , Condicionamento Físico Animal , Adaptação Fisiológica , Animais , Peso Corporal/efeitos dos fármacos , Membro Posterior/fisiologia , Masculino , Camundongos , Camundongos Transgênicos , Músculo Esquelético/fisiologia , Resistência Física , Comportamento Sedentário
2.
J Electron Microsc (Tokyo) ; 59(2): 153-64, 2010.
Artigo em Inglês | MEDLINE | ID: mdl-19854955

RESUMO

Light and electron microscopy and quantitative morphometry were used to determine the effects of exercise and mesterolone on the soleus muscles of mice. Both exercise and mesterolone caused a significant hypertrophy of extrafusal muscle fibres. The hypertrophy of Type I fibres was greater than that of Type II fibres. There was no hyperplasia. Mitochondria were more numerous and larger than in the muscles of sedentary animals. Capillarity increased and small centrally nucleated muscle fibres appeared, usually in small clusters and most often in the muscles of animals exposed to mesterolone. A small proportion of satellite cells exhibited signs of activation but there were more in the muscles of mesterolone-treated animals than after exercise. Muscles from animals that had been both exercised and treated with mesterolone exhibited the largest changes: muscle mass and muscle fibre hypertrophy was greater than in all other groups of animals, capillarity was higher and >30% of all recognized satellite cells exhibited signs of activation. Groups of small centrally nucleated muscle fibres were commonly seen in these muscles. They appeared to be the result of splits in the form of sprouts from existing muscle fibres. With both exercise and mesterolone, alone or in combination, there was an increase in the proportion of Type I muscle fibres and a decrease in the proportion of Type II.


Assuntos
Anabolizantes/farmacologia , Mesterolona/farmacologia , Músculo Esquelético/efeitos dos fármacos , Músculo Esquelético/ultraestrutura , Esforço Físico , Anabolizantes/administração & dosagem , Animais , Humanos , Hipertrofia , Masculino , Mesterolona/administração & dosagem , Camundongos , Microscopia/métodos , Microscopia Eletrônica de Transmissão
3.
Can J Vet Res ; 69(1): 46-52, 2005 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-15745222

RESUMO

Mammalian skeletal muscle expresses splice variants of neuronal nitric oxide synthase (nNOS). Skeletal muscles have a metabolically heterogeneous population of myofibers, and fiber composition in equine skeletal muscle is correlated with athletic ability in endurance events. In this study, we investigated whether nNOS expression in equine skeletal muscle is related to fiber type and endurance training. Biopsy samples obtained from the gluteus medius of sedentary- (SH) and endurance-trained (TH) horses were examined for the electrophoretic mobility of myosin heavy chain (MHC) and NOS activity. Serial tissue cross-sections were stained for myosin ATPase and nicotinamide adenine dinucleotide (NADH) reductase, and also immunostained for nNOS. The gluteus medius of TH had higher levels of nNOS expression and activity when compared to muscle from SH. In SH, nNOS was restricted to the subsarcolemmal area while in TH nNOS was also present at cytoplasmic sites. A splice variant of nNOS was heterogeneously distributed among the different myofibers, its expression being higher in fast-oxidative-glycolytic type IIA fibers than in fast-glycolytic type IIX fibers and absent in slow-twitch type I fibers. Trained horses had a significantly higher relative content of type IIA fibers, a greater oxidative capacity, and a lower percentage of type IIX fibers when compared with SH. The differences in muscle fiber typing between the 2 groups of horses reflected alterations that probably resulted from the endurance-training program. Overall, these results show that nNOS is differentially expressed and localized in the gluteus medius according to the fiber type and the athletic conditioning of the horses.


Assuntos
Cavalos/fisiologia , Fibras Musculares Esqueléticas/enzimologia , Músculo Esquelético/metabolismo , Óxido Nítrico Sintase/metabolismo , Condicionamento Físico Animal/fisiologia , Animais , Nádegas , Estudos de Casos e Controles , Feminino , Cavalos/metabolismo , Imuno-Histoquímica/veterinária , Masculino , Fibras Musculares Esqueléticas/metabolismo , Músculo Esquelético/anatomia & histologia , Cadeias Pesadas de Miosina/análise , Resistência Física/fisiologia
4.
Muscle Nerve ; 30(6): 796-8, 2004 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-15389655

RESUMO

This study was designed to assess the size and distribution of muscle fiber types in patients with severe chronic obstructive pulmonary disease and stable chronic hypoxemia. Brachial biceps biopsies were performed in 8 patients and 12 controls. Histochemistry was used to count and determine the cross-sectional area of the various fiber-types (1, 2a, and 2b). A significant reduction (P < 0.05) in the proportion of type 2a fibers and an increase in the proportion and cross-sectional area of type 2b fibers were seen in hypoxemic patients. These findings suggest an adaptation of the muscle fibers to a low partial pressure of oxygen in arterial blood.


Assuntos
Hipóxia/patologia , Fibras Musculares Esqueléticas/patologia , Músculo Esquelético/patologia , Doença Pulmonar Obstrutiva Crônica/patologia , Adulto , Idoso , Doença Crônica , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Fibras Musculares Esqueléticas/química , Músculo Esquelético/química , Estatísticas não Paramétricas
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