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Late Effects of Radiation on Skeletal Muscle: An Open Field of Research  [PDF]
Wilson Viana, Daniel Lambertz, Edvane Borges, Jonathan Melo, Karla Lambertz, Ademir Amaral
Journal of Biomedical Science and Engineering (JBiSE) , 2015, DOI: 10.4236/jbise.2015.88052
Abstract: This paper presents an overview of the state of the art about the late effects of ionizing radiation on skeletal muscle, helping new research and showing unexplored areas. For this, it was evaluated the interest reported by the scientific literature regarding the late effects in skeletal muscle resulting from exposure to ionizing radiation. Original and experimental papers mainly containing the key expressions “ionizing radiation” and “effects on skeletal muscle” were searched in computerized databases, and published in any language. Only 33 papers matched the search criteria. Analyzing the investigated radioinduced biological effects in those contributions, four topics were identified as being of major interest: 1) alterations in cellular metabolism and protein degradation; 2) repercussions on satellite cells; 3) formation of fibrosis and muscle atrophy; 4) tissue regeneration. It was verified that no study evaluated possible late effects related to either morphology or properties of skeletal muscles after an exposure to ionizing radiation. Several aspects do not make possible a successful replication; all experiments of eligible group of articles are discussed, such as, lack of raw data, use of no sound methodology and inappropriate statistical technique. Briefly, the subject of this review is an open field of research.
Effects of anabolic hormones on structural, metabolic and functional aspects of skeletal muscle
Flávio de Oliveira Pires,Adriano Eduardo Lima Silva,Valmor Tricoli
Revista Brasileira de Cineantropometria e Desempenho Humano , 2009,
Abstract: This study reviewed information regarding the effects of anabolic hormones on strength gain and muscle hypertrophy, emphasizing the physiological mechanisms that may increase muscle strength. Structural, metabolic and functional aspects were analyzed and special attention was paid to the dose-response relationship. The Pubmed database was searched and studies were selected according to relevance and date of publication (last 15 years). The administration of high testosterone doses (~600 mg/week) potentiates the effects of strength training, increasing lean body mass, muscle fiber type IIA and IIB cross-sectional area, and the number of myonuclei. There is no evidence of conversion between MHC isoforms. The interaction between testosterone administration and strength training seems to modify some metabolic pathways, increasing protein synthesis, glycogen and ATP-CP muscle stores and improving fat mobilization. Changes in 17 -estradiol concentration or in the ACTH-cortisol and insulin-glucagon ratios seem to be associated with these metabolic alterations. Regarding performance, testosterone administration may improve muscle strength by 5-20% depending on the dose used. On the other hand, the effects of growth hormone on the structural and functional aspects of skeletal muscle are not evident, with this hormone more affecting metabolic aspects. However, strictly controlled human studies are necessary to establish the extent of the effects of anabolic hormones on structural, metabolic and functional aspects.
Apoptosis and physical exercise: effects on skeletal muscle
Fabrício Azevedo Voltarelli,Maria Alice Rostom de Mello,José Alberto Ramos Duarte
Revista Brasileira de Cineantropometria e Desempenho Humano , 2008,
Abstract: This brief review will discuss an exciting new area in exercise science, namely the role of apoptosis programmed cell death in exercise. Apoptotic cell death differs morphologically and biochemically from necrotic cell death, although both appear to occur after exercise. Accelerated apoptosis has been documented to occur in a variety of disease states, such as AIDS and Alzheimer’s disease, as well as in the aging heart. In striking contrast, failure to activate this genetically regulated cell death may result in cancer and certain viral infections. Here, the apoptosis phenomenon will be discussed, as it occurs in skeletal muscle, and its relation to physical exercise, as well as the interaction with the HSP70 protein. We speculate that exercise-induced apoptosis is a normal regulatory process that serves to remove certain damaged cells without a pronounced inflammatory response, thus ensuring optimal organism function. Resumo Esta breve revis o irá discutir uma nova e excitante área em ciências do exercício, conhecida como o papel da apoptose ou morte celular programada no exercício. A morte celular por apoptose difere morfológica e bioquimicamente da morte celular por necrose, embora ambas parecem ocorrer após o exercício. A ocorrência de apoptose acelerada tem sido relatada em uma grande variedade de doen as, tais como a AIDS e o mal de Alzheimer, bem como em problemas cardíacos relacionados com o envelhecimento. Por outro lado, falhas ao ativar essa regula o genética de morte celular pode resultar em cancer e em certas infec es virais. Aqui será discutido o fen meno da apoptose, na musculatura esquelética, relacionado com o exercício físico, assim como a intera o com a proteína HSP70. Nós especulamos que a apoptose induzida pelo exercício é um processo regulatório normal, que se torna útil no sentido de remover certas células lesadas com ausência de resposta inflamatória pronunciada, otimizando, assim, as fun es do organismo.
Effects of Fiber Type and Size on the Heterogeneity of Oxygen Distribution in Exercising Skeletal Muscle  [PDF]
Gang Liu, Feilim Mac Gabhann, Aleksander S. Popel
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0044375
Abstract: The process of oxygen delivery from capillary to muscle fiber is essential for a tissue with variable oxygen demand, such as skeletal muscle. Oxygen distribution in exercising skeletal muscle is regulated by convective oxygen transport in the blood vessels, oxygen diffusion and consumption in the tissue. Spatial heterogeneities in oxygen supply, such as microvascular architecture and hemodynamic variables, had been observed experimentally and their marked effects on oxygen exchange had been confirmed using mathematical models. In this study, we investigate the effects of heterogeneities in oxygen demand on tissue oxygenation distribution using a multiscale oxygen transport model. Muscles are composed of different ratios of the various fiber types. Each fiber type has characteristic values of several parameters, including fiber size, oxygen consumption, myoglobin concentration, and oxygen diffusivity. Using experimentally measured parameters for different fiber types and applying them to the rat extensor digitorum longus muscle, we evaluated the effects of heterogeneous fiber size and fiber type properties on the oxygen distribution profile. Our simulation results suggest a marked increase in spatial heterogeneity of oxygen due to fiber size distribution in a mixed muscle. Our simulations also suggest that the combined effects of fiber type properties, except size, do not contribute significantly to the tissue oxygen spatial heterogeneity. However, the incorporation of the difference in oxygen consumption rates of different fiber types alone causes higher oxygen heterogeneity compared to control cases with uniform fiber properties. In contrast, incorporating variation in other fiber type-specific properties, such as myoglobin concentration, causes little change in spatial tissue oxygenation profiles.
The effects of pentoxifylline on skeletal muscle contractility and neuromuscular transmission during hypoxia  [cached]
Simsek-Duran Fatma,Ertunc Mert,Onur Rustu
Indian Journal of Pharmacology , 2009,
Abstract: Objectives : The objective of this study was to investigate the effects of pentoxifylline (PTX), a drug that is mainly used for indications related to tissue hypoxia, on hypoxia-induced inhibition of skeletal muscle contractility and neuromuscular transmission in mice. We hypothesized that chronic PTX treatment alters skeletal muscle contractility and hypoxia-induced dysfunction. Materials and Methods : Mice were treated with 50 mg/kg PTX or saline intraperitoneally for a week. Following ether anesthesia, diaphragm muscles were removed; isometric muscle contractions and action potentials were recorded. Time to reach neuromuscular blockade and the rate of recovery of muscle contractility were assessed during hypoxia and re-oxygenation. Results : The PTX group displayed 90% greater twitch amplitudes (P < 0.01). Hypoxia depressed twitch contractions and caused neuromuscular blockade in both groups. However, neuromuscular blockade occurred earlier in PTX-treated animals (P < 0.05). Muscle contractures developed during hypoxia were more pronounced in the PTX group (P < 0.05). Re-oxygenation reduced contracture and indirect muscle contractions resumed. The rate of recovery of contractions was faster (P < 0.05) and the amplitude of contractions was greater (P < 0.01) in the PTX group. PTX treatment increased amplitude (P < 0.05) and shortened action potential (P < 0.05) without altering resting membrane potential, excitation threshold, and neurotransmitter release. Conclusion : Chronic PTX treatment increases diaphragm contractility, but amplifies hypoxia-induced contractile dysfunction in mice. These results may implicate important clinical consequences for clinical usage of PTX in hypoxia-related conditions.
Effects of ractopamine and gender on protein turnover in skeletal muscle of implanted steers and heifers
DK Walker, EC Titgemeyer, DE Johnson, SB Laudert, BJ Johnson
South African Journal of Animal Science , 2011,
Abstract: Effects of the β-agonist, ractopamine-HCl (ractopamine), on skeletal muscle protein turnover were evaluated in 16 steers (512 kg) and 16 heifers (473 kg). Treatments were arranged in a 2 × 2 factorial design and included gender (steer vs. heifer) and ractopamine (0 or 200 mg/d). Steers were implanted with 120 mg trenbolone acetate and 24 mg estradiol-17β, heifers with 140 mg trenbolone acetate and 14 mg estradiol-17β. Cattle were fed a diet based on steam-flaked maize. Muscle biopsy samples were collected from m. longissimus and m. biceps femoris on day 0 (prior to ractopamine feeding) and after 14 and 28 d of ractopamine feeding. In vitro protein synthesis rates in m. longissimus tended to be greater for steers than for heifers, but no effect of gender was observed in m. biceps femoris. Gender did not affect in vitro protein degradation rates for either muscle. Ractopamine significantly decreased rates of in vitro protein degradation in m. longissimus, but rates in m. biceps femoris were not affected by ractopamine. Ractopamine did not affect in vitro protein synthesis rates. In general, there were no striking differences between steers and heifers in response to ractopamine, indicating that its effectiveness should be similar between genders.
Functional and morphological effects of resistance exercise on disuse-induced skeletal muscle atrophy
Nicastro, H.;Zanchi, N.E.;da Luz, C.R.;Lancha Jr., A.H.;
Brazilian Journal of Medical and Biological Research , 2011, DOI: 10.1590/S0100-879X2011007500125
Abstract: abstract the reduction of skeletal muscle loss in pathological states, such as muscle disuse, has considerable effects in terms of rehabilitation and quality of life. since there is no currently effective and safe treatment available for skeletal muscle atrophy, the search for new alternatives is necessary. resistance exercise (re) seems to be an important tool in the treatment of disuse-induced skeletal muscle atrophy by promoting positive functional (strength and power) and structural (hypertrophy and phenotypic changes) adaptive responses. human and animal studies using different types of resistance exercise (flywheel, vascular occlusion, dynamic, isometric, and eccentric) have obtained results of great importance. however, since re is a complex phenomenon, lack of strict control of its variables (volume, frequency, intensity, muscle action, rest intervals) limits the interpretation of the impact of the manipulation on skeletal muscle remodeling and function under disuse. the aim of this review is to critically describe the functional and morphological role of resistance exercise in disuse-induced skeletal muscle atrophy with emphasis on the principles of training.
Effects of Sustanon on the Distribution of Satellite Cells and The Morphology of Skeletal Muscle Fibers During Maturation  [PDF]
Mohammed Z. Allouh,Mohammed H. Aldirawi
Pakistan Journal of Biological Sciences , 2012,
Abstract: Sustanon is one of the most commonly used anabolic androgenic drugs to increase skeletal muscle mass and strength. This drug is a blend of four esterized testosterone derivatives: Testosterone propionate, testosterone phenylpropionate, testosterone isocaproate and testosterone decanoate. Little is known about the effects of this drug on skeletal muscle at the cellular level. This study aimed to investigate the influence of Sustanon on the morphology of skeletal muscle fibers and the distribution of myogenic stem cells known as Satellite Cells (SCs) during postnatal growth. We hypothesized that Sustanon-induced skeletal muscle hypertrophy is associated with an increase in the number of SCs. Robust immunocytochemical techniques and morphometric analyses were used to calculate the numbers of SCs and myonuclei within the pectoralis muscle of chickens. Also, DNA concentration and Pax7 protein levels were measured to confirm immunocytochemical findings. Sustanon significantly increased pectoralis mass and fiber size. All SC indices and the number of myonuclei increased significantly by Sustanon administration. In addition, greater DNA concentration and Pax7 protein expression were found in Sustanon-treated birds. This study indicates that Sustanon can induce avian skeletal muscle hypertrophy and that this is correlated with increased numbers of SCs and myonuclei.
Performances in extreme environments: effects of hyper/hypobarism and hypogravity on skeletal muscle  [cached]
Gerardo Bosco,Vittore Verratti,Giorgio Fanò
European Journal of Translational Myology , 2010, DOI: 10.4081/bam.2010.3.83
Abstract: Many environmental factors may affect muscle plasticity but some have exclusive characteristics that allow them to play a key role to maintain the muscle capacity to generate force; these factors are: i) the oxygen availability and ii) the load applied to muscle fibres. Hyperbarism is a condition that occurs when a man is subjected to pressure increases. To keep the lungs from collapsing, the air is supplied to him under high pressure which exposes the blood in the lungs to high alveolar gas pressures. Under this condition, the PO2 become sufficiently increased, serious disorders may occur, such as modification of oxygen delivery and/or oxygen availability to permit regular muscle contraction. Also altitude hypobaric hypoxia induces modification of muscle capacity to generate work. Prolonged exposure to high altitude leads significant loss in body mass, thigh muscle mass, muscle fiber area and volume density of muscle mitochondria. Spaceflight results in a number of adaptations to skeletal muscle, including atrophy and early muscle fatigue. Muscle atrophy is observed in a wide range of muscles, with the most extensive loss occurring in the legs, because astronauts are no longer needed to support the body's weight. This review will describe the background on these topics suggesting the strategies to correct the specific muscle changes in presence of environmental stresses, such as the alteration in oxygen-derived signaling pathways or the metabolic consequence of microgravity that may indicate rational interventions to maintain muscle mass and function.
Effects of electrical stimulation and stretching on the adaptation of denervated skeletal muscle: implications for physical therapy
Salvini, Tania F.;Durigan, Jo?o L. Q.;Peviani, Sabrina M.;Russo, Thiago L.;
Brazilian Journal of Physical Therapy , 2012, DOI: 10.1590/S1413-35552012005000027
Abstract: background: this review will describe the main cellular mechanisms involved in the reduction and increase of myoproteins synthesis commonly associated with muscle atrophy and hypertrophy, respectively. objective: we analyzed the effects of electrical stimulation (es) and stretching exercise on the molecular pathways involved in muscle atrophy and hypertrophy. we also described the main effects and limits of these resources in the skeletal muscle, particularly on the denervated muscle. discussion: recently, our studies showed that the es applied in a similar manner as performed in clinical practice is able to attenuate the increase of genes expression involved in muscle atrophy. however, es was not effective to prevent the loss of muscle mass caused by denervation. regarding to stretching exercises, their mechanisms of action on the denervated muscle are not fully understood and studies on this area are scarce. studies from our laboratory have found that stretching exercise increased the extracellular matrix remodeling and decreased genes expression related to atrophy in denervated muscle. nevertheless, it was not enough to prevent muscle atrophy after denervation. conclusions: in spite of the use of stretching exercise and es in clinical practice in order to minimize the atrophy of denervated muscle, there is still lack of scientific evidence to justify the effectiveness of these resources to prevent muscle atrophy in denervated muscle.

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