RESUMO
This study aimed to evaluate myosin heavy chain (MyHC) isoform expression and muscle fiber types of Longissimus dorsi (LD) and Semitendinosus (ST) in Mediterranean buffaloes and possible fibers muscles modulation according to different slaughter weights. The presence of MyHC IIb isoforms was not found. Only three isoforms of MyHC (IIa, IIx/d and I) were observed and their percentages did not vary significantly among slaughter weights. The confirmation of the presence of hybrid muscles fibers (IIA/X) in LD and ST muscles necessitated classifying the fiber types into fast and slow according to their contractile activity, by m-ATPase assay. For both muscles, the muscle fiber frequency was higher for fast than for slow fibers in all weight groups. There was a difference (P<0.05) in the frequency of LD and ST muscle fiber types according to slaughter weights, which demonstrate that the slaughter weight influences the profile of muscle fibers from buffaloes.
Assuntos
Búfalos , Carne/análise , Fibras Musculares Esqueléticas/classificação , Fibras Musculares Esqueléticas/metabolismo , Cadeias Pesadas de Miosina/metabolismo , Criação de Animais Domésticos , Animais , Peso Corporal , Búfalos/crescimento & desenvolvimento , Búfalos/metabolismo , Dieta/veterinária , Masculino , Fibras Musculares de Contração Rápida/metabolismo , Fibras Musculares de Contração Lenta/metabolismo , Músculo Esquelético/metabolismo , Músculo Esquelético/ultraestrutura , Miosinas/metabolismo , NADH Tetrazólio Redutase/metabolismo , Especificidade de Órgãos , Isoformas de Proteínas/metabolismo , Distribuição Aleatória , Miosinas de Músculo Esquelético/metabolismoRESUMO
O grande interesse atual em tirar proveito das variações na performance humana, nos levam a busca do entendimento as adaptações fisiológicas, bioquímicas e morfológicas nos tecidos envolvidos. Os resultados obtidos através de modelos experimentais fornecem informações para melhor entender a função muscular, e com isso permitir planejar um treinamento adequado ao objetivo pretendido, tendo como base adaptações fisiológicas. A performance esportiva depende de um grande número de fatores, o tipo do músculo e os estímulos a que ele é submetido e são sem dúvida parâmetros importantes para o desempenho atlético. Para cada modalidade é ideal ter um grupo de fibras predominante adequado às características específicas da atividade. Dependendo do tipo de estímulo podemos obter um aumento de força, sendo esta adaptação uma das mais importantes para a manutenção da saúde ou a melhora do desempenho atlético.
Assuntos
Humanos , Fibras Musculares Esqueléticas/citologia , Fibras Musculares Esqueléticas/fisiologia , Fibras Musculares Esqueléticas , Fenômenos Fisiológicos Musculoesqueléticos , Fenótipo , Miosinas de Músculo Esquelético , Sistema Musculoesquelético/anatomia & histologia , Exercício Físico , MiosinasRESUMO
It is now generally accepted that hybrid skeletal muscle fibres are not experimental artefacts, but complex molecular systems that expand the functional repertoire of the muscle to which they belong. The purpose of this review is to highlight the cognitive value of hybrid fibres by discussing several insights into skeletal muscle biology produced by studies using hybrid fibres and/or muscles containing hybrid fibres. There is strong evidence that hybrid fibres can be used as indicators of muscle remodeling and specialization. Also, there is increasing evidence that hybrid fibres are suitable for investigating issues related to (i) the coexpression of different myosin heavy chain (MHC) isoforms and their assembly in the sarcomeric structure, (ii) the operation of the muscle cell as a multinuclear system, (iii) the tightness of the relationship between MHC isoform expression and expression of other polymorphic muscle proteins, (iv) the tightness of the relationship between MHC isoform expression and various contractile parameters, and (v) the extent of the neural input into defining the molecular and functional phenotype of skeletal muscle cells. It is predicted that, when used together with imaginatively designed methods, the hybrid fibres will further our (still limited) understanding of the regulation of muscle gene expression in multinuclear cells and of the interactions of gene products within and across different intracellular signalling pathways.
Assuntos
Denervação , Isoformas de Proteínas/fisiologia , Cadeias Pesadas de Miosina , Miosinas , Músculo Esquelético/fisiologia , Polimorfismo Genético , Proteínas Musculares/metabolismo , Troponina C , Cadeias Pesadas de Miosina/biossíntese , Isoformas de Proteínas/química , Músculo Esquelético/irrigação sanguínea , Miosinas de Músculo EsqueléticoRESUMO
Eucalyptol is an essential oil that relaxes bronchial and vascular smooth muscle although its direct actions on isolated myocardium have not been reported. We investigated a putative negative inotropic effect of the oil on left ventricular papillary muscles from male Wistar rats weighing 250 to 300 g, as well as its effects on isometric force, rate of force development, time parameters, post-rest potentiation, positive inotropic interventions produced by Ca2+ and isoproterenol, and on tetanic tension. The effects of 0.3 mM eucalyptol on myosin ATPase activity were also investigated. Eucalyptol (0.003 to 0.3 mM) reduced isometric tension, the rate of force development and time parameters. The oil reduced the force developed by steady-state contractions (50% at 0.3 mM) but did not alter sarcoplasmic reticulum function or post-rest contractions and produced a progressive increase in relative potentiation. Increased extracellular Ca2+ concentration (0.62 to 5 mM) and isoproterenol (20 nM) administration counteracted the negative inotropic effects of the oil. The activity of the contractile machinery evaluated by tetanic force development was reduced by 30 to 50% but myosin ATPase activity was not affected by eucalyptol (0.3 mM), supporting the idea of a reduction of sarcolemmal Ca2+ influx. The present results suggest that eucalyptol depresses force development, probably acting as a calcium channel blocker.
Assuntos
Cicloexanóis/farmacologia , Monoterpenos/farmacologia , Contração Miocárdica/efeitos dos fármacos , Óleos Voláteis/farmacologia , Músculos Papilares/efeitos dos fármacos , Retículo Sarcoplasmático/efeitos dos fármacos , Animais , Relação Dose-Resposta a Droga , Avaliação Pré-Clínica de Medicamentos , Eucaliptol , Contração Isométrica/efeitos dos fármacos , Masculino , Ratos , Ratos Wistar , Miosinas de Músculo Esquelético/efeitos dos fármacosRESUMO
Eucalyptol is an essential oil that relaxes bronchial and vascular smooth muscle although its direct actions on isolated myocardium have not been reported. We investigated a putative negative inotropic effect of the oil on left ventricular papillary muscles from male Wistar rats weighing 250 to 300 g, as well as its effects on isometric force, rate of force development, time parameters, post-rest potentiation, positive inotropic interventions produced by Ca2+ and isoproterenol, and on tetanic tension. The effects of 0.3 mM eucalyptol on myosin ATPase activity were also investigated. Eucalyptol (0.003 to 0.3 mM) reduced isometric tension, the rate of force development and time parameters. The oil reduced the force developed by steady-state contractions (50 percent at 0.3 mM) but did not alter sarcoplasmic reticulum function or post-rest contractions and produced a progressive increase in relative potentiation. Increased extracellular Ca2+ concentration (0.62 to 5 mM) and isoproterenol (20 nM) administration counteracted the negative inotropic effects of the oil. The activity of the contractile machinery evaluated by tetanic force development was reduced by 30 to 50 percent but myosin ATPase activity was not affected by eucalyptol (0.3 mM), supporting the idea of a reduction of sarcolemmal Ca2+ influx. The present results suggest that eucalyptol depresses force development, probably acting as a calcium channel blocker.
Assuntos
Animais , Masculino , Ratos , Cicloexanóis/farmacologia , Monoterpenos/farmacologia , Contração Miocárdica/efeitos dos fármacos , Óleos Voláteis/farmacologia , Músculos Papilares/efeitos dos fármacos , Retículo Sarcoplasmático/efeitos dos fármacos , Relação Dose-Resposta a Droga , Avaliação Pré-Clínica de Medicamentos , Contração Isométrica/efeitos dos fármacos , Ratos Wistar , Miosinas de Músculo Esquelético/efeitos dos fármacosRESUMO
Myosin is an asymmetric protein that comprises two globular heads (S1) and a double-stranded alpha-helical rod. We have investigated the effects of urea and the methylamines trimethylamine oxide (TMA-O) and glycine betaine (betaine) on activity and structure of skeletal muscle myosin. K(+) EDTA ATPase activity of myosin was almost completely inhibited by urea (2M); TMA-O stimulated myosin activity, whereas betaine had no effect. When combined with urea (0-2M), TMA-O or betaine (1 M) effectively protected the ATPase activity of myosin against inhibition. Intrinsic fluorescence measurements showed that in urea or TMA-O (0-2M), there were no shifts in the center of mass of the fluorescence spectrum of myosin, despite a decrease in fluorescence intensity. However, these osmolytes at concentrations above 2M produced a red shift in the emission spectrum. Betaine alone did not alter the center of mass at any concentration tested up to 5.2M. Thus, modifications in ATPase activity induced by low concentrations of solutes (<2M) are not directly correlated with the modifications in myosin structure detected by fluorescence. Both methylamines (>or=1M) were also able to protect myosin structure against urea-induced effects (2-8M). Protection was not observed for S1, supporting the hypothesis that these osmolytes have a biphasic effect on myosin: at lower concentrations there is an effect on the globular portion (S1), and at higher concentrations there is an effect on the coiled-coil (rod) portion of myosin.