Low temperature exposure increases IL-6 expression in skeletal muscle cells / 生理学报

The shivering and nonshivering thermogenesis in skeletal muscles is important for maintaining body temperature in a cold environment. In addition to nervous-humoral regulation, adipose tissue was demonstrated to directly respond to cold in a cell-autonomous manner to produce heat. However, whether skeletal muscle can directly respond to low temperature in an autoregulatory manner is unknown. Transient receptor potential (TRP) channels TRPM8 and TRPA1 are two important cold sensors. In the current study, we found TRPM8 was expressed in mouse skeletal muscle tissue and C2C12 myotubes by RT-PCR. After exposure to 33 °C for 6 h, the gene expression pattern of C2C12 myotubes was significantly changed which was evidenced by RNA-sequencing. KEGG-Pathway enrichment analysis of these differentially expressed genes showed that low temperature changed several important signaling pathways, such as IL-17, TNFα, MAPK, FoxO, Hedgehog, Hippo, Toll-like receptor, Notch, and Wnt signaling pathways. Protein-protein interaction network analysis revealed that IL-6 gene was a key gene which was directly affected by low temperature in skeletal muscle cells. In addition, both mRNA and protein levels of IL-6 were increased by 33 °C exposure in C2C12 myotubes. In conclusion, our findings demonstrated that skeletal muscle cells could directly respond to low temperature, characterized by upregulated expression of IL-6 in skeletal muscle cells.

Regulation of muscle plasticity and trophism by fatty acids: A short review / Regulação da plasticidade e do trofismo muscular pelos ácidos graxos: uma breve revisão

Summary The skeletal muscle tissue has a remarkable ability to alter its plastic structural and functional properties after a harmful stimulus, regulating the expression of proteins in complex events such as muscle regeneration. In this context, considering that potential therapeutic agents have been widely studied, nutritional strategies have been investigated in order to improve the regenerative capacity of skeletal muscle. There is evidence of the modulatory action of fatty acids, such that oleic and linoleic acids, that are abundant in Western diets, on muscle function and trophism. Thus, fatty acids appear to be potential candidates to promote or impair the recovery of muscle mass and function during regeneration, since they modulate intracellular pathways that regulate myogenesis. This study is the first to describe and discuss the effect of fatty acids on muscle plasticity and trophism, with emphasis on skeletal muscle regeneration and in vitro differentiation of muscle cells.

Resumo O tecido muscular esquelético possui a notável capacidade plástica de alterar suas propriedades estruturais e funcionais após um estímulo lesivo, regulando a expressão de proteínas durante eventos complexos como a regeneração muscular. Nesse contexto, considerando que possíveis agentes terapêuticos vêm sendo amplamente estudados, estratégias nutricionais têm sido investigadas na perspectiva de melhorar a capacidade regenerativa do músculo esquelético. Há evidências da ação modulatória dos ácidos graxos, como os ácidos oleico e linoleico, que são abundantes nas dietas ocidentais, sobre a função muscular e o trofismo. Nesse sentido, os ácidos graxos parecem ser potenciais candidatos para promover ou prejudicar a recuperação da massa e a função muscular durante a regeneração, uma vez que modulam vias intracelulares reguladoras da miogênese. Este trabalho é o primeiro a descrever e discutir o efeito dos ácidos graxos sobre a plasticidade e o trofismo muscular, com ênfase na regeneração do músculo esquelético e na diferenciação de células musculares in vitro.

Myostatin promotes distinct responses on protein metabolism of skeletal and cardiac muscle fibers of rodents

Myostatin is a novel negative regulator of skeletal muscle mass. Myostatin expression is also found in heart in a much less extent, but it can be upregulated in pathological conditions, such as heart failure. Myostatin may be involved in inhibiting protein synthesis and/or increasing protein degradation in skeletal and cardiac muscles. Herein, we used cell cultures and isolated muscles from rats to determine protein degradation and synthesis. Muscles incubated with myostatin exhibited an increase in proteolysis with an increase of Atrogin-1, MuRF1 and LC3 genes. Extensor digitorum longus muscles and C2C12 myotubes exhibited a reduction in protein turnover. Cardiomyocytes showed an increase in proteolysis by activating autophagy and the ubiquitin proteasome system, and a decrease in protein synthesis by decreasing P70S6K. The effect of myostatin on protein metabolism is related to fiber type composition, which may be associated to the extent of atrophy mediated effect of myostatin on muscle.

Three days of intermittent stretching after muscle disuse alters the proteins involved in force transmission in muscle fibers in weanling rats

The aim of this study was to determine the effects of intermittent passive manual stretching on various proteins involved in force transmission in skeletal muscle. Female Wistar weanling rats were randomly assigned to 5 groups: 2 control groups containing 21- and 30-day-old rats that received neither immobilization nor stretching, and 3 test groups that received 1) passive stretching over 3 days, 2) immobilization for 7 days and then passive stretching over 3 days, or 3) immobilization for 7 days. Maximal plantar flexion in the right hind limb was imposed, and the stretching protocol of 10 repetitions of 30 s stretches was applied. The soleus muscles were harvested and processed for HE and picrosirius staining; immunohistochemical analysis of collagen types I, III, IV, desmin, and vimentin; and immunofluorescence labeling of dystrophin and CD68. The numbers of desmin- and vimentin-positive cells were significantly decreased compared with those in the control following immobilization, regardless of whether stretching was applied (P<0.05). In addition, the semi-quantitative analysis showed that collagen type I was increased and type IV was decreased in the immobilized animals, regardless of whether the stretching protocol was applied. In conclusion, the largest changes in response to stretching were observed in muscles that had been previously immobilized, and the stretching protocol applied here did not mitigate the immobilization-induced muscle changes. Muscle disuse adversely affected several proteins involved in the transmission of forces between the intracellular and extracellular compartments. Thus, the 3-day rehabilitation period tested here did not provide sufficient time for the muscles to recover from the disuse maladaptations in animals undergoing postnatal development.

Epidemiology of coronary artery bypass grafting at the Hospital Beneficência Portuguesa, São Paulo / Epidemiologia da cirurgia de revascularização miocárdica do Hospital Beneficência Portuguesa de São Paulo

Introduction: The knowledge of the prevalence of risk factors and comorbidities, as well as the evolution and complications in patients undergoing coronary artery bypass graft allows comparison between institutions and evidence of changes in the profile of patients and postoperative evolution over time. Objective: To profile (risk factors and comorbidities) and clinical outcome (complications) in patients undergoing coronary artery bypass graft in a national institution of great surgical volume. Methods: A retrospective cohort study of patients undergoing coronary artery bypass graft in the hospital Beneficência Portuguesa de São Paulo, from July 2009 to July 2010. Results: We included 3,010 patients, mean age of 62.2 years and 69.9% male. 83.8% of patients were hypertensive, 36.6% diabetic, 44.5% had dyslipidemia, 15.3% were smokers, 65.7% were overweight/obese, 29.3% had a family history of coronary heart disease. The expected mortality calculated by logistic EuroSCORE was 2.7%. The isolated CABG occurred in 89.3% and 11.9% surgery was performed without cardiopulmonary bypass. The most common complication was cardiac arrhythmia (18.7%), especially acute atrial fibrillation (14.3%). Pneumonia occurred in 6.2% of patients, acute renal failure in 4.4%, mediastinites in 2.1%, stroke in 1.8% and AMI in 1.2%. The in-hospital mortality was 5.4% and in isolated coronary artery bypass graft was 3.5%. The average hospital stay was 11 days with a median of eight days (3-244 days). Conclusion: The profile of patients undergoing coronary artery bypass graft surgery in this study is similar to other published studies. .

Introdução: O conhecimento da prevalência dos fatores de risco e comorbidades, bem como a evolução com complicações nos pacientes submetidos à cirurgia de revascularização miocárdica, permite a comparação entre instituições e a comprovação de modificações no perfil de pacientes e na evolução pós-operatória ao longo do tempo. Objetivo: Conhecer o perfil (fatores de risco e comorbidades) e a evolução clínica (complicações) nos pacientes submetidos à cirurgia de revascularização miocárdica em uma instituição nacional de grande volume cirúrgico. Métodos: Estudo de coorte retrospectivo de pacientes submetidos ao procedimento de cirurgia de revascularização miocárdica no Hospital Beneficência Portuguesa de São Paulo, no período de julho de 2009 a julho de 2010. Resultados: Foram incluídos 3010 pacientes, com idade média de 62,2 anos e 69,9% do sexo masculino. 82,8% dos pacientes eram hipertensos, 36,6% diabéticos, 44,5% dislipidêmicos, 15,3% tabagistas, 65,7% com sobrepeso/obesidade e 29,3% tinham antecedentes familiares de doença coronária. A mortalidade média esperada calculada pelo EuroSCORE logístico foi de 2,7%. A cirurgia de revascularização miocárdica isolada ocorreu em 89,3% e em 11,9% foi realizada cirurgia sem circulação extracorpórea. A complicação mais comum foi arritmia cardíaca (18,7%), especialmente a fibrilação atrial aguda (14,3%). Pneumonia ocorreu em 6,2% dos pacientes, lesão renal aguda em 4,4%, mediastinite em 2,1%, acidente vascular encefálico em 1,8% e infarto agudo do miocárdio em 1,2%. A mortalidade intra-hospitalar foi de 5,4% e na cirurgia de revascularização miocárdica isolada foi de 3,5%. O tempo de permanência hospitalar médio foi de 11 dias, com mediana de oito dias (3 - 244 dias). Conclusão: O perfil dos pacientes submetidos à cirurgia de revascularização miocárdica neste estudo assemelha-se ao de outros estudos publicados. .

Envolvimento de mitocôndrias e do retículo endoplasmático da célula muscular esquelética na cistogênese de Toxoplasma gondii / Involvement of mitochondria and endoplasmic reticulum in skeletal muscle cell on Toxoplasma gondii cystogenesis

T. gondii é parasito intracelular obrigatório, agente etiológico datoxoplasmose, doença com ampla distribuição mundial. Os transtornos mais severos(fase aguda) acometem pacientes imunocomprometidos. Hospedeirosimunologicamente sadios, uma vez infectados, apresentam cistos teciduais (fasecrônica) de modo perene. Estudos sugerem que por possuírem um eficientemetabolismo energético, os principais tecidos eleitos para a cistogênese do T.gondii, são o nervoso e o muscular esquelético. O presente trabalho dedicou-se aoestudo das associações de mitocôndrias e do retículo endoplasmßtico (RE) àmembrana do vacúolo parasitóforo (MVP) e à parede cística. Para tanto, foramutilizados bradizoítos e taquizoítos da cepa ME49 (tipo II) e culturas primßrias decélula muscular esquelética (CME) e da linhagem C2C12. Nossas estratégiasmetodológicas contemplaram microscopia de fluorescência, microscopia eletrônicade transmissão, respirometria de alta resolução e ensaios de efeito de um inibidor dafosforilação oxidativa (ISA-34) sobre a cistogênese. Os dados obtidos apontam aocorrência de: (i) associações entre mitocôndrias com a parede cística; (ii) aspectospeculiares ultraestruturais decorrentes de associações entre mitocôndrias e RE(rugoso e liso) da CME com a MVP de vacúolos contendo bradizoítos; (iii)manutenção do metabolismo mitocondrial da CME pelo T. gondii, durante a fasecrônica; (iv) efeito inibitório do composto ISA-34 sobre o desenvolvimento de cistosteciduais. Estes resultados, além de iniciarem uma linha de pesquisa inédita arespeito das respostas do metabolismo energético da CME frente à cistogênese deT. gondii, também abrem novas perspectivas para uma terapia alternativa voltadapara a fase crônica da toxoplasmose...

Toxoplasma gondii is an obligatory intracellular parasite, agent oftoxoplasmosis, disease with a worldwide distribution. The most severe disorders(acute phase) affect immunocompromised patients. Immunologically healthyindividuals, once infected, develop tissue cysts (chronic phase) that can persist forthe host life span. Studies suggest that an efficient energetic metabolism, as innervous and skeletal muscle tissues, leads to the development of T. gondiicystogenesis. The present work aims the study of the association of skeletal musclecell (SkMC) mitochondria and endoplasmic reticulum (ER) to the parasitophorousvacuole membrane (PVM) and to the cyst wall (CW). Bradyzoites and tachyzoitesfrom ME49 strain (type II) of T. gondii and SkMC cultures and C2C12 cell line wereused. The methodological strategies employed were fluorescence microscopy,transmission electron microscopy, high-resolution respirometry and assay using ISA-34, an inhibitor of oxidative phosphorylation. Our data point out: (i) associationsbetween mitochondria and CW; (ii) ultrastructural aspects of the association of SkMCmitochondria and ER (rough and smooth) with PVM of bradyzoite-containingvacuoles; (iii) maintenance of SkMC mitochondrial metabolism by T. gondii and, (iv)inhibitory effect of ISA-34 on the tissue cysts development. These results stimulatefurther investigation concerning the response of SkMC energy metabolism duringcystogenesis of T. gondii and also open novel perspectives for an alternative therapyagainst toxoplasmosis chronic phase...

Analysis of osmotic stress induced Ca2+ spark termination in mammalian skeletal muscle.

Ca2+ sparks represent synchronous opening of the ryanodine receptor (RyR) Ca2+ release channels located at the sarcoplasmic reticulum (SR) membrane. Whereas a quantal nature of Ca2+ sparks has been defined in cardiac muscle, the regulation of Ca2+ sparks in skeletal muscle has not been well-studied. Osmotic-stress applied to an intact skeletal muscle fiber can produce brief Ca2+ sparks and prolonged Ca2+ burst events. Here, we show that termination of Ca2+ bursts occurs in a step wise and quantal manner. Ca2+ burst events display kinetic features that are consistent with the involvement of both stochastic attrition and coordinated closure of RyR channels in the termination of SR Ca2+ release. Elemental unitary transition steps could be defined with a mean DF/F0 of ~0.28, corresponding to the gating of 1-2 RyR channels. Moreover, the amplitude of the elemental transition steps declines at the later stage of the burst event. In tandem Ca2+ burst events where two Ca2+ bursts occur at the same position within a fiber in rapid succession, the trailing event is consistently of lower amplitude than the initial event. These two complementary results suggest that SR Ca2+ release may be associated with local depletion of SR Ca2+ stores in mammalian skeletal muscle.

Effect of Anorexia and Neuropathic Pain Induced by Cisplatin on Hindlimb Muscles of Rat

PURPOSE: The purpose of this study was to examine the effect of anorexia and neuropathic pain induced by cisplatin on hindlimb muscles of rats. METHODS: Adult male Sprague-Dawley rats were divided into two groups, a cisplatin-treated group (n=10) and a control group (n=10). In the cisplatin-treated group, cisplatin at a dose of 2 mg/kg was injected intraperitoneally two times a week up to a cumulative dose of 20 mg/kg over 5 weeks, and in the control group saline (0.9% NaCl) was injected intraperitoneally at the same dose and duration as the cisplatin-treated group. At 34 days all rats were anesthetized, after which the soleus and plantaris muscles were dissected. Withdrawal threshold, body weight, food intake, activity, muscle weight, Type I and II fiber cross-sectional areas and myofibrillar protein content of the dissected muscles were determined. RESULTS: Compared with the control group, the cisplatin-treated group showed significant decreases (p<.05) in withdrawal threshold, activity, food intake, body weight, Type I and II fiber cross-sectional areas, myofibrillar protein content and weight of the soleus and plantaris muscles. CONCLUSION: Muscular atrophy in hindlimb occurs due to anorexia and neuropathic pain induced by the cisplatin treatment.

Immunohistochemical fiber type profile in the human vocal muscle / Perfil inmunohistoquímico de los tipos de fibras en el músculo vocal humano

The vocal muscle is a striated muscle with important functions in the emission of laryngeal sound and physiology of the voice. Therefore the knowledge of its constitution is the basis for the prevention and management of voice disorders. We used 10 samples from the middle third of vocal muscles obtained from autopsies of 6 male and 4 female subjects aged between 36 and 71 years. The samples were analyzed with BA-F8 monoclonal antibody to slow type I fibers, and antimyosin HC monoclonal antibody and antimyosin fast clone MY-32 antibody for types IIA, IIB, IIX, and neonatal fibers. We determined the distribution of the muscle fiber types and morphometric characteristics, evaluating the differences by sex and age group. The human vocal muscle presented a heterogeneous formation with a predominance of type II fibers at 51.99 percent, while type I fibers reached 48.01 percent; this difference was significant (p <0.05). Comparing fiber subtypes IIA and IIX, there is a slight predominance of type IIX fibers, although this is not statistically significant (p>0.05). In conclusion, the human vocal muscle the fibers were predominantly type II fast.

El músculo vocal es un músculo estriado con importantes funciones en la emisión del sonido laringeo y fisiología de la voz. Por ello el conocimiento de su constitución sirve de base para la prevención y manejo de los trastornos vocales. Se realizó un estudio morfométrico e inmunohistoquímico de músculo vocal humano. Se utilizaron 10 muestras del tercio medio del músculo vocal obtenidas de necropsias, 6 de individuos de sexo masculino y 4 femenino, con edades de entre 36 y 71 años. Las muestras fueron analizadas con anticuerpos monoclonales antimyosin skeletal slow BA-F8 para fibras tipo I y antimyosin skeletal fast HC y MY-32 para fibras tipo IIA, IIB, IIX y neonatal. Se determinó la distribución de los distintos tipos de fibras musculares y sus características morfométricas, evaluándose las diferencias por sexo y grupo etáreo. El músculo vocal humano presentó una constitución heterogénea con predominio de fibras tipo II con un 51,99 por ciento, mientras que las tipo I alcanzaron el 48,01 por ciento, estas diferencias resultaron significativas (p<0,05). Al comparar los subtipos de fibras IIA y IIX, se observa un leve predominio de las fibras IIX, aunque no significativo estadísticamente (p>0,05). No se encontraron diferencias en cuanto a los diámetros mayor y menor de las fibras ni en la constitución del músculo por sexo o grupo etáreo. Se concluye que en el músculo vocal humano predominan las fibras musculares rápidas tipo II.

Histochemical and morphological characteristics of the levator ani muscle in rats / Características morfológicas e histoquímicas del músculo elevador del ano en ratas

The current study aimed to analyze the histochemical and morphological characteristics of the levator ani muscle in rats. For this, we used 10 Wistar rats (5 males and 5 females), weighing between 200 and 765g. The animals were dissected fresh and in formalin for the levator ani muscle anatomical observation. Muscle fragments were collected and frozen in n-Hexane previously cooled in liquid nitrogen. Then, the muscles were transferred to a microtome cryostat (HM 505 E Microm), being fixed in metal mounts with the adhesive Tissue Freezing Medium. Histological sections of 6.0um were removed and subjected to HE staining. Other sections were subjected to NADH-TR and SDH reactions. After being dissected and fixed, the architecture of the female pelvic floor revealed the presence of two muscles: iliocaudalis and pubocaudalis. The anatomical inspection in male rats revealed, pronouncedly, the presence of the levator ani muscle: ischiocavernosus and bulbocavernous. We therefore observed a marked anatomical difference between animals of the same species, which does not occur with humans. The HE staining revealed muscular fibers with preserved morphology, contours ranging from polygonal to rounded, acidophilic cytoplasm, one or more peripheral nuclei with rounded shape and dense chromatin aspect. The fibers were organized in fascicles arranged by a dense connective tissue, the perimysium, and each fiber surrounded by the endomysium, composed of loose connective tissue. The sections subjected to NADH-TH and SDH, whose reactions show the activity of oxidative or glycolytic muscle fibers, allowed the identification of the two types of fiber. The fast-twitch fiber shows weaker reactivity, whereas the slow-twitch fiber has small diameter and intense reactivity, especially in the subsarcolemmal, presenting a highly oxidative metabolism. It was found that the pelvic floor muscles in rats are composed primarily by fast-twitch fibers, while in humans they are...

El estudio tuvo como objetivo analizar las características histoquímicas y morfológicas del músculo elevador del ano en ratas. Para esto, se utilizaron 10 ratas Wistar (5 machos y 5 hembras), con un peso entre 200 y 765g. Los animales fueron disecados frescos y en formol para la observación anatómica del músculo elevador del ano. Fragmentos de músculo fueron recogidos y congelados en n-Hexano, previamente enfriado en nitrógeno líquido. Luego, los músculos fueron trasladados a un micrótomo criostato (Microm HM 505 E), fijados en soportes metálicos con adhesivo Tissue Freezing Medium. Cortes histológicos de 6,0 um fueron retirados y sometidos a tinción de H-E. Otras secciones fueron sometidas a las reacciones de NADH-TR y SDH. Después de haber sido disecado y fijado, la arquitectura del suelo de la pelvis de las ratas hembra, reveló la presencia de dos músculos: m. iliocaudalis y m. pubocaudalis. La inspección anatómica de las ratas macho mostró, marcadamente, la presencia del músculo elevador del ano: isquiocavernoso y bulbocavernoso. Por lo tanto, observamos una marcada diferencia anatómica entre los animales de la misma especie, lo que no ocurre con los seres humanos. La tinción HE reveló fibras musculares con morfología conservada, contornos que van desde el esquema poligonal al redondeado, citoplasma acidófilo, uno o más núcleos periféricos con forma redondeada y un aspecto denso de la cromatina. Las fibras se organizaban en fascículos compuestos por un tejido conectivo denso, perimisio, y cada fibra rodeada por el endomisio compuesto por tejido conectivo laxo. En las secciones sometidas a NADH-TH y SDH, cuyas reacciones muestran la actividad oxidativa o glicolítica de las fibras musculares, permitió la identificación de los dos tipos de fibras. Las fibras de contracción rápida muestran más débil reactividad y, las de contracción lenta tienen un diámetro pequeño y reactividad intensa, especialmente en las regiones subsarcolemales, presentando un...

TRPC3 cation channel plays an important role in proliferation and differentiation of skeletal muscle myoblasts

During membrane depolarization associated with skeletal excitation-contraction (EC) coupling, dihydropyridine receptor [DHPR, a L-type Ca2+ channel in the transverse (t)-tubule membrane] undergoes conformational changes that are transmitted to ryanodine receptor 1 [RyR1, an internal Ca2+-release channel in the sarcoplasmic reticulum (SR) membrane] causing Ca2+ release from the SR. Canonical-type transient receptor potential cation channel 3 (TRPC3), an extracellular Ca2+-entry channel in the t-tubule and plasma membrane, is required for full-gain of skeletal EC coupling. To examine additional role(s) for TRPC3 in skeletal muscle other than mediation of EC coupling, in the present study, we created a stable myoblast line with reduced TRPC3 expression and without alpha1SDHPR (MDG/TRPC3 KD myoblast) by knock-down of TRPC3 in alpha1SDHPR-null muscular dysgenic (MDG) myoblasts using retrovirus-delivered small interference RNAs in order to eliminate any DHPR-associated EC coupling-related events. Unlike wild-type or alpha1SDHPR-null MDG myoblasts, MDG/TRPC3 KD myoblasts exhibited dramatic changes in cellular morphology (e.g., unusual expansion of both cell volume and the plasma membrane, and multi-nuclei) and failed to differentiate into myotubes possibly due to increased Ca2+ content in the SR. These results suggest that TRPC3 plays an important role in the maintenance of skeletal muscle myoblasts and myotubes.

Changes in types of muscle fibers induced by transcutaneous electrical stimulation of the diaphragm of rats

The objective of the present study was to assess the effect of transcutaneous electrical diaphragmatic stimulation (TEDS) on different types of diaphragm muscle fibers. Male Wistar rats (8-12 weeks old) were divided into 2 experimental groups (N = 8 in each group): 1) control, 2) animals submitted to TEDS [frequency = 50 Hz; T ON/T OFF (contraction/relaxation time) = 2/2 s; pulse duration = 0.4 ms, intensity = 5 mA with a 1 mA increase every 3 min for 20 min] for 7 days. After completing this treatment period, the I, IIA, IIB, and IID diaphragm muscle fibers were identified using the mATPase technique. Statistical analysis consisted of the normality, homoscedasticity and t-tests (P < 0.05). There was a 19.6 percent (P < 0.05) reduction in the number of type I fibers and a 49.7 percent increase (P < 0.05) in type IID fibers in the TEDS group compared with the control group. An important result of the present study was that electrical stimulation with surface electrodes was efficient in altering the distribution of fibers in diaphragm muscle. This therapeutic resource could be used in the treatment of respiratory muscle alterations.

Efeito da desnutrição protéica pré e pós-natal sobre a morfologia, a diferenciação e o metabolismo do tecido muscular estriado esquelético em ratos / The effects of prenatal and postnatal malnutrition on the morphology, differentiation, and metabolism of skeletal striated muscle tissue in rats

OBJETIVO: Estudar características morfológicas, metabolismo e habilidades contráteis do músculo submetido a desnutrição protéica pré e pós-natal. MÉTODOS: Distribuição dos animais em dois grupos: controle, dieta normoprotéica (GC; n = 15; 5/5/5) e desnutrido, dieta hipoprotéica (GD; n = 15; 5/5/5), observados respectivamente no sétimo, 14º e 28º dia do período experimental. Foram avaliados massa corporal total, peso, habilidades contráteis e a morfologia do músculo tibial anterior. Amostras de tecidos com 8 m de espessura de ratos com idades de 7, 14 e 28 dias, corados por hematoxilina e eosina, e outros submetidos aos métodos histoquímicos nicotinamida adenina tetrazólio redutase (NADH-TR) e miofibrilar (m-ATPase) (pH = 4,4). RESULTADOS: Os pesos corporal e muscular apresentaram-se menores nos grupos desnutridos. Aos 7 dias de desnutrição, o músculo apresentou fibras com menor diâmetro, maior polimorfismo e maior teor de tecido conjuntivo endomisial. Nas histoquímicas, tipos de fibras sem delimitação segura. Aos 14 dias de desnutrição, fibras menores, mais polimórficas, muitas com núcleos centrais e moderado teor de tecido conjuntivo endomisial. Quanto à contração, a reação m-ATPase evidenciou fibras lentas e rápidas. A reação NADH-TR revelou os tipos de fibras slow oxidative, fast oxidative glycolytic e fast glycolytic. Aos 28 dias de desnutrição, fibras menores, agrupadas com contornos variáveis. Quanto ao tipo de contração e metabolismo, os três tipos de fibras apresentaram limites de reconhecimento indistinto. CONCLUSÃO: Os resultados experimentais sugerem que, além da redução no número de fibras, a desnutrição promove um retardamento na diferenciação das características morfológicas, metabólicas e contráteis dos tipos de fibras musculares esqueléticas em ratos na fase de crescimento.

OBJECTIVE: To study the contractile properties, metabolism and morphological characteristics of muscles submitted to prenatal and postnatal protein malnutrition. METHODS: Animals were distributed into two groups: Control, normoprotein diet (CG; n = 15; 5/5/5), and Malnourished, hypoprotein diet (MG; n = 15; 5/5/5), and examined on the 7th, 14th, and 28th days of the experiment. Total body mass, weight, and the contractile properties and morphology of the anterior tibial muscle were assessed. Several 8 µm-thick tissue samples were taken from 7, 14, and 28 day old rats and stained with HE or subjected to NADH-TR or m-ATPase (pH = 4.4) techniques. RESULTS: Body and muscle weight were lower in the malnourished group. On the 7th day of malnutrition, muscle samples exhibited fibers with smaller diameter, higher polymorphism and higher endomysial conjunctive tissue content. Histochemical methods were unable to precisely determine the types of fiber present. On the 14th day, there were smaller muscle fibers, more polymorphism, many of them with central nuclei and moderate endomysial conjunctive tissue content. With reference to contractile properties, the m-ATPase reaction identified both slow and fast fibers. The NADH-TR reaction revealed the following types of fiber: slow oxidative (SO), fast oxidative glycolytic (FOG) and fast glycolytic (FG). On the 28th day smaller, bunched muscle fibers varying shapes. All three types of fiber exhibited unclear recognition limits with respect to contraction and metabolism. CONCLUSION: Our experimental results suggest that, in addition to the reduction in numbers of fibers, malnutrition retards the differentiation of the morphological, metabolic, and contractile characteristics of skeletal muscle fibers in growing rats.

Exercise type and muscle fiber specific induction of caveolin-1 expression for insulin sensitivity of skeletal muscle

It is well known that exercise can have beneficial effects on insulin resistance by activation of glucose transporter. Following up our previous report that caveolin-1 plays an important role in glucose uptake in L6 skeletal muscle cells, we examined whether exercise alters the expression of caveolin-1, and whether exercise-caused changes are muscle fiber and exercise type specific. Fifity week-old Sprague Dawley (SD) rats were trained to climb a ladder and treadmill for 8 weeks and their soleus muscles (SOL) and extensor digitorum longus muscles (EDL) were removed after the last bout of exercise and compared with those from non-exercised animals. We found that the expression of insulin related proteins and caveolins did not change in SOL muscles after exercise. However, in EDL muscles, the expression of insulin receptor beta (IRbeta) and glucose transporter-4 (GLUT-4) as well as phosphorylation of AKT and AMPK increased with resistance exercise but not with aerobic exercise. Also, caveolin-1 and caveolin-3 increased along with insulin related proteins only in EDL muscles by resistance exercise. These results suggest that upregulation of caveolin-1 in the skeletal muscle is fiber specific and exercise type specific, implicating the requirement of the specific mode of exercise to improve insulin sensitivity.

Os radicais livres e o dano muscular produzido pelo exercício: papel dos antioxidantes / Free radicals and exercise-induced muscle: antioxidantes paper

O exercício físico intenso e contínuo é acompanhado pela produçäo de radicais livres, que provocam uma alteraçäo das membranas celulares, o que causa uma lesäo acompanhada por um processo inflamatório ao nível das fibras musculares. Várias causas foram sugeridas para estas alteraçöes, entre as quais o alto grau de estresse provocado pelo exercício, alteraçöes da microcirculaçäo, produçäo de metabólitos, tóxicos e depleçäo intramuscular dos substratos energéticos. O rápido desenvolvimento da lesäo das fibras musculares e do tecido conjuntivo é acompanhado por uma disfunçäo e migraçäo de componentes intracelurares para os espaços intesticial e plasmático. O dano muscular está associado com aumentos dos níveis plamáticos de creatinoquinase (CK) e de lactato desidrogenase (LDH), o que serve como indicador do aumento da permeabilidade celular resultante. A formaçäo de radicais livres e do desencadeamento do processo de peroxidaçäo também contribuem para o dano muscular. Embora o papel do exercício na produçäo de radicais livres näo esteja bem esclarecido, um grande número de autores sugerem que a elevaçäo do consumo de oxigênio durante o exercício induz a produçäo de redicais livres e outras substâncias oxidantes. Recentemente, na literatura foi demonstrado que as vitaminas A (beta-caroteno), E (Tocoferol) e C (ácido ascórbico), junto com minerais como o zinco (Zn), atuam como agentes protetores antioxidantes

Perfil antropométrico y fisiológico de atletas puertorriqueños especialistas en carreras pedestres de media y larga distancia / Anthropometric and physiological profile of Puerto Rican athletes specialists in media and long distance running

Los propósitos de este informe investigativo fueron: 1)revisar la literatura relacionada con los fáctores antropométricos, metabólicos, cardiorespiratórios y neuromusculares asociados con una ejecutoria sobresaliente en carreras pedestres de larga duración (CPLD). 2)como dado ilustrativo describir una serie de características antropométricas, de composición corporal, cardiorespiratorias, metabólicas, y neuromusculares de especialistas puertorriqueños en CPLD de ambos sexos (hombres n+3 y mujeres n+3), y 3) efectuar comparaciones con sus iguales de diferentes países del mundo reportados en la literatura. El grupo de sujetos consistió de ganadores de campeonatos universitarios, nacionales, internacionales, y de eventos locales en las distancias de 1500m hasta 42km. Los datos obtenidos se encontraron dentro de la magnitud demostrada por corredores de classificación élite internacional, excepto en las variables flexibilidad de la parte posterior del muslo/espalda baja y lagartijas efectuadas en un minuto, donde se detectaron notables deficiencias.