RESUMO
BACKGROUND/AIMS: Skeletal mass loss is reported in several catabolic conditions and it has been associated with a reduced intracellular L-glutamine content. We investigated the association of intracellular L-glutamine concentration with the protein content in skeletal muscle cells. METHODS: We cultivated C2C12 myotubes in the absence or presence of 2 (reference condition), 8 or 16 mM L-glutamine for 48 hours, and the variations in the contents of amino acids and proteins measured. We used an inhibitor of L-glutamine synthesis (L-methionine sulfoximine - MSO) to promote a further reduction in intracellular L-glutamine levels. Amino acids contents in cells and media were measured using LC-MS/MS. We measured changes in phosphorylated Akt, RP-S6, and 4E-BP1contents in the absence or presence of insulin by western blotting. RESULTS: Reduced intracellular L-glutamine concentration was associated with decreased protein content and increased protein breakdown. Low intracellular glutamine levels were also associated with decreased p-Akt contents in the presence of insulin. A further decrease in intracellular L-glutamine caused by glutamine synthetase inhibitor reduced protein content and levels of amino acids generated from glutamine metabolism and increased bAib still further. Cells exposed to high medium glutamine levels did not have any change in protein content but exhibited increased contents of the amino acids derived from L-glutamine metabolism. CONCLUSION: Intracellular L-glutamine levels per se play a role in the control of protein content in skeletal muscle myotubes.
Assuntos
Proteínas de Transporte/metabolismo , Glutamina/metabolismo , Insulina/metabolismo , Fibras Musculares Esqueléticas/metabolismo , Fosfoproteínas/metabolismo , Proteínas Proto-Oncogênicas c-akt/metabolismo , Proteína S6 Ribossômica/metabolismo , Proteínas Adaptadoras de Transdução de Sinal , Animais , Proteínas de Transporte/análise , Proteínas de Ciclo Celular , Linhagem Celular , Cromatografia Líquida , Fatores de Iniciação em Eucariotos , Glutamina/análise , Insulina/análise , Camundongos , Fibras Musculares Esqueléticas/química , Fosfoproteínas/análise , Fosforilação , Proteínas Proto-Oncogênicas c-akt/análise , Proteína S6 Ribossômica/análise , Espectrometria de Massas em TandemRESUMO
Histochemical and morphometric analyses were performed to characterize the fibre-type composition of two forelimb muscles of the South American subterranean rodent Ctenomys talarum. The studied muscles were the triceps lateralis, an extensor of the elbow, and the teres major, a flexor of the shoulder. It was found that these muscles had an elevated proportion of fast oxidative-glycolytic (FOG) fibres, and lower proportions of slow oxidative (SO) and fast glycolytic (FG) fibres. This composition probably qualifies the teres major and triceps muscles to perform the sustained effort required in tunnelling excavation. The results were discussed considering published data on fibre-type composition of mammals having different modes of life and digging behaviour. We here suggest that C. talarum has the potential of generating forces linked to rapid, powerful movements during sustained periods by means of an elevated proportion of FOG fibres, together with osteological changes that result in a great mechanical advantage of the forelimb muscles.
Assuntos
Membro Anterior/anatomia & histologia , Fibras Musculares Esqueléticas/ultraestrutura , Músculo Esquelético/anatomia & histologia , Roedores/anatomia & histologia , Animais , Metabolismo Energético , Feminino , Membro Anterior/fisiologia , Glicólise , Histocitoquímica , Masculino , Contração Muscular , Fibras Musculares Esqueléticas/química , Fibras Musculares Esqueléticas/classificação , Fibras Musculares Esqueléticas/fisiologia , Músculo Esquelético/química , Roedores/fisiologiaRESUMO
Biceps brachii is stated as one of the muscles that shows most frequent anatomical variations. Its most commonly reported anomaly is the presence of an accessory fascicle arising from the humerus which is termed as the humeral head of biceps brachii. Evidence shows a clear racial trend in the incidence of the humeral head of biceps brachii. Therefore, detailed knowledge of this variation in different populations is important for surgical interventions of the arm, nerve compression syndromes and in unexplained pain syndromes in the arm or shoulder region. The goal of this study was to elucidate the incidence and morphological features of this muscle in an adult Sri Lankan population. Upper extremities of the total of one hundred thirty five cadavers were dissected and studied for the presence of accessory heads of the biceps brachii muscle. The proximal and distal attachments of the humeral heads as well as their cranio-caudal, antero-posterior and medio-lateral dimensions were recorded. The incidence of humeral head of biceps brachii was found to be 3.7 percent. In all cases, it was found unilaterally and only in male subjects. The humeral head originated from the antero-medial aspect of the humeral shaft and descended and merged with the other two heads to form a common tendon. The results of the present study further highlight the racial variations in the incidence of humeral head of biceps brachii among Sri Lankans. Knowledge of the occurrence of humeral head of biceps brachii may facilitate preoperative diagnosis as well as the surgical procedures of the upper limb thus avoiding iatrogenic injuries.
El músculo bíceps braquial se conoce como uno de los músculos que muestra las variaciones anatómicas más frecuentes. Su anomalía más común es la presencia de un fascículo accesorio proveniente del húmero, que se denomina cabeza humeral del músculo bíceps braquial. La evidencia muestra una clara tendencia racial en la incidencia de la cabeza humeral del músculo bíceps braquial. El conocimiento acabado de esta variación, en las diferentes poblaciones, es importante para las intervenciones quirúrgicas del brazo, en los síndromes de compresión nerviosa y en los síndromes de dolor inexplicable en la región del brazo o del hombro. El objetivo de este estudio fue determinar la incidencia y las características morfológicas de este músculo en una población adulta de Sri Lanka. Fueron estudiados los miembros superiores en 135 cadáveres, disecados para evaluar la presencia de las cabezas del músculo bíceps braquial accesorio. Fueron registrados el origen e inserción de la cabeza humeral del músculo bíceps braquial, así como su dimensión cráneo-caudal, anteroposterior y mediolateral. La incidencia de la cabeza humeral del músculo bíceps braquial se encontró en el 3,7 por ciento de los miembros estudiados. En todos los casos, su presencia era unilateral y sólo presente en hombres. La cabeza humeral se originó en la región antero-medial de la diáfisis del húmero, descendió y se fusionó con las otras dos cabezas para formar un tendón común. Los resultados de este estudio resaltan aún más las variaciones raciales en la incidencia de la cabeza humeral del músculo bíceps braquial, entre los habitantes de Sri Lanka. El conocimiento de la presencia de la cabeza humeral del músculo bíceps braquial puede facilitar el diagnóstico preoperatorio, así como los procedimientos quirúrgicos del miembro superior, evitando las lesiones iatrogénicas.
Assuntos
Humanos , Masculino , Feminino , Adulto , Circunferência Braquial , Músculos do Pescoço/anatomia & histologia , Músculos do Pescoço/crescimento & desenvolvimento , Músculos do Pescoço/ultraestrutura , Plexo Braquial/anatomia & histologia , Plexo Braquial/embriologia , Plexo Braquial/ultraestrutura , Cadáver , Fibras Musculares Esqueléticas/fisiologia , Fibras Musculares Esqueléticas/química , Úmero/anatomia & histologia , Úmero/anormalidades , Úmero/inervação , Úmero/ultraestruturaRESUMO
In addition to its role as a strong antioxidant, vitamin C regulates the differentiation of several cell lineages. In vertebrate skeletal muscle, the vitamin C transporter SVCT2 is preferentially expressed in slow muscle fibers. To gain insights into the possible involvement of intracellular vitamin C on early myogenesis, we investigated the regulation of SVCT2 expression in cultures of chick fetal myoblasts. SVCT2 expression increases in cultures of both, slow and fast muscle-derived myoblasts, as they fuse to form mainly fast myotubes. Interestingly, we found that SVCT2 could be positively modulated by potassium-induced depolarization of myotubes. These findings suggest that SVCT2-mediated uptake of vitamin C could play diverse roles on skeletal muscle development and physiology.
Assuntos
Diferenciação Celular , Fibras Musculares Esqueléticas/citologia , Transportadores de Ânions Orgânicos Dependentes de Sódio/biossíntese , Simportadores/biossíntese , Regulação para Cima , Animais , Ácido Ascórbico , Polaridade Celular , Células Cultivadas , Embrião de Galinha , Galinhas , Desenvolvimento Muscular , Fibras Musculares Esqueléticas/química , Mioblastos , Transportadores de Sódio Acoplados à Vitamina CRESUMO
We evaluated the effects of chronic allergic airway inflammation and of treadmill training (12 weeks) of low and moderate intensity on muscle fiber cross-sectional area and mRNA levels of atrogin-1 and MuRF1 in the mouse tibialis anterior muscle. Six 4-month-old male BALB/c mice (28.5 ± 0.8 g) per group were examined: 1) control, non-sensitized and non-trained (C); 2) ovalbumin sensitized (OA, 20 µg per mouse); 3) non-sensitized and trained at 50 percent maximum speed _ low intensity (PT50 percent); 4) non-sensitized and trained at 75 percent maximum speed _ moderate intensity (PT75 percent); 5) OA-sensitized and trained at 50 percent (OA+PT50 percent), 6) OA-sensitized and trained at 75 percent (OA+PT75 percent). There was no difference in muscle fiber cross-sectional area among groups and no difference in atrogin-1 and MuRF1 expression between C and OA groups. All exercised groups showed significantly decreased expression of atrogin-1 compared to C (1.01 ± 0.2-fold): PT50 percent = 0.71 ± 0.12-fold; OA+PT50 percent = 0.74 ± 0.03-fold; PT75 percent = 0.71 ± 0.09-fold; OA+PT75 percent = 0.74 ± 0.09-fold. Similarly significant results were obtained regarding MuRF1 gene expression compared to C (1.01 ± 0.23-fold): PT50 percent = 0.53 ± 0.20-fold; OA+PT50 percent = 0.55 ± 0.11-fold; PT75 percent = 0.35 ± 0.15-fold; OA+PT75 percent = 0.37 ± 0.08-fold. A short period of OA did not induce skeletal muscle atrophy in the mouse tibialis anterior muscle and aerobic training at low and moderate intensity negatively regulates the atrophy pathway in skeletal muscle of healthy mice or mice with allergic lung inflammation.
Assuntos
Animais , Masculino , Camundongos , Asma/patologia , Proteínas Musculares/análise , Músculo Esquelético/química , Atrofia Muscular/patologia , RNA Mensageiro/análise , Proteínas Ligases SKP Culina F-Box/análise , Ubiquitina-Proteína Ligases/análise , Asma/fisiopatologia , Doença Crônica , Modelos Animais de Doenças , Expressão Gênica , Camundongos Endogâmicos BALB C , Fibras Musculares Esqueléticas/química , Fibras Musculares Esqueléticas/patologia , Músculo Esquelético/patologia , Atrofia Muscular/genética , Atrofia Muscular/fisiopatologia , Condicionamento Físico Animal , Pneumonia/metabolismo , Pneumonia/patologia , TíbiaRESUMO
We evaluated the effects of chronic allergic airway inflammation and of treadmill training (12 weeks) of low and moderate intensity on muscle fiber cross-sectional area and mRNA levels of atrogin-1 and MuRF1 in the mouse tibialis anterior muscle. Six 4-month-old male BALB/c mice (28.5 +/- 0.8 g) per group were examined: 1) control, non-sensitized and non-trained (C); 2) ovalbumin sensitized (OA, 20 microg per mouse); 3) non-sensitized and trained at 50% maximum speed _ low intensity (PT50%); 4) non-sensitized and trained at 75% maximum speed _ moderate intensity (PT75%); 5) OA-sensitized and trained at 50% (OA+PT50%), 6) OA-sensitized and trained at 75% (OA+PT75%). There was no difference in muscle fiber cross-sectional area among groups and no difference in atrogin-1 and MuRF1 expression between C and OA groups. All exercised groups showed significantly decreased expression of atrogin-1 compared to C (1.01 +/- 0.2-fold): PT50% = 0.71 +/- 0.12-fold; OA+PT50% = 0.74 +/- 0.03-fold; PT75% = 0.71 +/- 0.09-fold; OA+PT75% = 0.74 +/- 0.09-fold. Similarly significant results were obtained regarding MuRF1 gene expression compared to C (1.01 +/- 0.23-fold): PT50% = 0.53 +/- 0.20-fold; OA+PT50% = 0.55 +/- 0.11-fold; PT75% = 0.35 +/- 0.15-fold; OA+PT75% = 0.37 +/- 0.08-fold. A short period of OA did not induce skeletal muscle atrophy in the mouse tibialis anterior muscle and aerobic training at low and moderate intensity negatively regulates the atrophy pathway in skeletal muscle of healthy mice or mice with allergic lung inflammation.
Assuntos
Asma/patologia , Proteínas Musculares/análise , Músculo Esquelético/química , Atrofia Muscular/patologia , RNA Mensageiro/análise , Proteínas Ligases SKP Culina F-Box/análise , Ubiquitina-Proteína Ligases/análise , Animais , Asma/fisiopatologia , Doença Crônica , Modelos Animais de Doenças , Expressão Gênica , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Fibras Musculares Esqueléticas/química , Fibras Musculares Esqueléticas/patologia , Músculo Esquelético/patologia , Atrofia Muscular/genética , Atrofia Muscular/fisiopatologia , Condicionamento Físico Animal , Pneumonia/metabolismo , Pneumonia/patologia , Tíbia , Proteínas com Motivo TripartidoRESUMO
The frontal muscle is formed by a complex of contractile elements which compose the set of facial muscles responsible for the expression of emotions. In view of its functional characteristics the frontal muscle consists of a mixture of high (type I) and low oxidative (type II) muscle fibres. The objective of the present study was to determine the area, diameter, and relative volume occupied by each fibre type in frontal muscles of Norfolk rabbits using nicotinamide adenine dinucleotide tetrazolium reductase (NADH-TR) histochemistry combined with morphometry. In addition, the connective tissue area (endomysium) and the number of blood vessels per fibre were evaluated. Female rabbits ranging in age from 6 to 8 months and weighing 2.8 to 3.1 kg were used. Four quadrants of samples from 12 animals were analysed. Type IIB fibres occupied the largest area compared to the other fibre types. The fibre diameter and relative volume were similar among the different fibre types identified by NADH-TR staining. No significant difference in the number of vessels per fibre was observed between the different fibre types. The endomysial area occupied the smallest area among the parameters analyzed. These findings demonstrated the intense activity of this muscle in the facial architecture of the animal. However, the low oxidative type II fibres predomination indicates more prone to muscle fatigue. The present findings may contribute to the study of myopathies involving this muscle.
El músculo frontal está formado por un complejo de elementos contráctiles que componen el conjunto de músculos faciales responsables de la expresión de emociones. A la vista de las características funcionales, el músculo frontal está constituido de una mezcla de fibras musculares de alto (tipo I) y bajo nivel de oxidación (tipo II). El objetivo del presente estudio fue determinar área, diámetro y volumen relativo ocupado por cada tipo de fibra en los músculos frontales de conejos Norfolk utilizando histoquímica para nicotinamide adenina dinucleotide tetrazolium reductasa (NADH-TR), combinado con su morfología. Además, fueron evaluados la zona de tejido conectivo (endomisio) y el número de vasos sanguíneos por fibras. Fueron utilizados conejos hembras, de edades comprendidas entre los 6 a 8 meses y con un peso de 2,8 a 3,1 kg. Se analizaron cuatro cuadrantes de las muestras de 12 animales. Las fibras tipo IIB ocuparon la mayor superficie, en comparación con los otros tipos de fibras. Los diámetros y volúmenes relativos de las fibras fueron similares entre los diferentes tipos identificados por NADH-TR. No se observaron diferencias significativas en el número de vasos por fibra, entre los diferentes tipos de fibras. El área ocupada por el endomisio fue la superficie más pequeña entre los parámetros analizados. Estos resultados demostraron la intensa actividad de este músculo en la arquitectura facial del animal. Sin embargo, el predominio de las fibras tipo II, de baja oxidación, indica más propensión a la fatiga muscular. El presente hallazgo pueden contribuir al estudio de las miopatías con la participación de este músculo.
Assuntos
Recém-Nascido , Lactente , Coelhos , Fibras Musculares Esqueléticas/classificação , Fibras Musculares Esqueléticas/fisiologia , Fibras Musculares Esqueléticas/química , Fibras Musculares Esqueléticas/ultraestrutura , Músculos Faciais/anatomia & histologia , Músculos Faciais/inervação , Tecido Conjuntivo/anatomia & histologia , Tecido Conjuntivo/ultraestrutura , Músculos do Pescoço/anatomia & histologia , Músculos do Pescoço/cirurgiaRESUMO
Skeletal muscles respond to several stimuli changing their phenotype. Muscular fibers adaptation capability is related to the presence of several myosin heavy chains (MHC). These express four types of pure fibers: I, IIA, IID and IIB containing MHCI, IIa, IId and IIb, respectively. Among pure fibers, there are hybrid fibers, which can express two or more types of myosins. In this study, types of fibers constituting male Wistar rats semitendinous and their myosin heavy chains, as well as influence of intermittent training on hypertrophy of these fibers have been checked through MATPase histochemical technique and electrophoretic proteins separation. All types of pure and hybrid muscular fiber have been found, however the fibers of the types IIA, IID and IIB were predominant, featuring muscle as a fast-contracting one. Training has promoted muscular fibers transition with a significant increase of fibers of IC, IIAD and IIDB type. A cross-section increase of fibers of IIDB and IIB type has also been noticed. In summary, semitendinous muscle is essentially constituted by fast-contracting fibers and training could promote transition and hypertrophy of these fast fibers.
Los músculos esqueléticos responden a diversos estímulos cambiando su fenotipo. La capacidad de adaptación de las fibras musculares está relacionada con la presencia de diversas miosinas de cadena pesada (MHC). Estas miosinas expresan cuatro tipos de fibras puras: I, IIA, IID, IIB, que contienen MHCI IIa IId IIb, respectivamente. Entre las fibras puras hay fibras híbridas, las cuales pueden expresar dos o más tipos de miosinas. En este trabajo, se observaron los tipos de fibras y las cadenas pesadas de miosinas del músculo semitendinoso en ratas Wistar macho, así como también, la influencia del entrenamiento intermitente en la hipertrofia de aquellas fibras, a través de la técnica histoquímica de mATPasa y separación eletroforética de proteínas. Todos los tipos de fibras musculares puras e híbridas fueron encontradas, siendo las fibras de tipo IIA IID y IIB predominantes, por ser un músculo de contracción rápida. El entrenamiento promovió la transición de las fibras musculares con un aumento significativo de las fibras del tipo IC, IIAD y IIDB. En una sección transversal, un incremento de fibras del tipo IIDB y IIB también fue reportada. En resumen, el músculo semitendinoso está compuesto esencialmente por fibras de contracción rápida y el entrenamiento puede promover la transición e hipertrofia de las fibras musculares rápidas.
Assuntos
Animais , Masculino , Ratos , Cadeias Pesadas de Miosina/análise , Fibras Musculares Esqueléticas/fisiologia , Fibras Musculares Esqueléticas/química , Músculo Esquelético/fisiologia , Músculo Esquelético/química , Adaptação Fisiológica , Exercício Físico , Fibras Musculares Esqueléticas/patologia , Hipertrofia , Músculo Esquelético/patologia , Ratos Wistar , Fatores de TempoRESUMO
The muscle-specific intermediate filament protein desmin is expressed in mononucleated myoblasts and in differentiated myotubes. Desmin has been shown to associate with the sarcolemma in specific structures, such as neuromuscular junctions and the dystrophin-associated protein complex. Since these are specialized membrane regions, the study of a possible association between desmin and liquid-ordered membrane microdomains is of particular interest. We have carried out an analysis of the association between desmin and the muscle-specific protein caveolin-3, a major component of caveolar microdomains. Our results demonstrate that (1) desmin precisely co-localizes with caveolin-3 in myoblasts and multinucleated myotubes, (2) caveolin-3 is up-regulated during in vitro chick muscle development, (3) desmin is detectable in caveolae-enriched membrane fractions prepared from skeletal muscle, and (4) caveolin-3 co-immunoprecipitates with desmin. We have thus shown, for the first time, an association between the intermediate filament protein desmin and caveolin-3 in myogenic cells.
Assuntos
Caveolina 3/metabolismo , Desmina/metabolismo , Células Musculares/metabolismo , Desenvolvimento Muscular/fisiologia , Animais , Cavéolas/química , Cavéolas/metabolismo , Caveolina 3/análise , Diferenciação Celular/fisiologia , Células Cultivadas , Embrião de Galinha , Desmina/análise , Imunoprecipitação , Proteínas de Membrana/análise , Proteínas de Membrana/metabolismo , Microscopia de Fluorescência , Células Musculares/química , Fibras Musculares Esqueléticas/química , Fibras Musculares Esqueléticas/metabolismo , Mioblastos Esqueléticos/química , Mioblastos Esqueléticos/metabolismo , Ligação ProteicaRESUMO
To assess the differential expression of adhesion molecules ICAM-1 and VCAM-1 in vessels and muscle fibers in acquired inflammatory myopathy, a series comprising thirty-seven muscle biopsy specimens from patients with JDM, fifteen with DM, fifteen with PM and seven with IBM was studied. Histochemical and immunohistochemical tests (StreptABCcomplex/HRP) for ICAM-1 and VCAM-1 (Dakopatts) were performed in serial frozen sections. ICAM-1 expression in vessels was significantly (p<0.0001) more present in JDM than PM, DM or IBM. However, in muscle fibers, ICAM-1 expression was absent in both JDM and IBM, but present in 33.4% and 40% in PM and DM respectively (p<0.0001). VCAM-1 expression in vessels was significantly more present in PM and DM than JDM and IBM (p<0.0001) while VCAM-1 expression in muscle fibers was almost absent in the four groups (p=0.2632). These findings emphasize the importance of adhesion molecules in the pathophysiology of the inflammatory myopathies, mainly the marked ICAM-1 expression in vessels in JDM, corroborating the microvascular involvement in this disease. In contrast, VCAM-1 seems not to play a major role in JDM, as previously described in PM, DM and IBM. Adhesion molecule expression in JDM presents a differential characteristic when compared to PM, DM and IBM.