Juliana Cristina Polizello

Characterization of Fiber Types in Different Muscles of the Hindlimb in Female Weanling and Adult Wistar Rats

We analyzed lesser diameter and distribution of fiber types in different skeletal muscles from female Wistar rats using a histoenzymology Myofibrillar Adenosine Tri-phosphatase (mATPase) method. Fragments from muscles were frozen and processed by mATPase in different pH. Adult and weanling rat soleus muscles presented a predominance of type I fibers and larger fiber diameters. In the plantar muscle in adult rats, the type IIB fibers demonstrated greater lesser diameter while in the weanling animals, types I and IIB fibers were larger. The plantar muscle of animals of both ages was composed predominantly of the type IID fibers. The type IID fibers were observed in similar amounts in the lateral gastrocnemius and the medial gastrocnemius muscles. Type IIB fibers showed predominance and presented higher size in comparison with other types in the EDL muscle. The present study shows that data on fiber type distribution and fiber lesser diameter obtained in adult animals cannot always be applied to weanling animals of the same species. Using the mATPase, despite the difficult handling, is an important tool to determine the different characteristics of the specific fibers in the skeletal muscle tissue.

Propriedades mecânicas do gastrocnêmio eletroestimulado pós-imobilização

Introduction: Mechanical properties (MP) are clinically applicable tools for healthcare professionals working on the musculoskeletal system. Objectives: The aim of this study was to evaluate two protocols of neuromuscular electric stimulation (NMES) to improve MP regeneration of the myotendinous complex after segment immobilization in female rats. Materials and Methods: Fifty animals were equally distributed into five groups: Control (CG, n=10); Immobilized (IG, n=10); Immobilized and freely remobilized (IFG, n=10); Immobilized and NMES once /day (IEG1, n=10); Immobilized and MNES twice/day (IEG2, n=10). Immobilization was kept for 14 days, and remobilization was subsequently released for 10 days. NMES was applied for 10 days, post-immobilization, every morning for 10 minutes to IEG1 animals and every morning and afternoon (total 20 minutes) to the IEG2 group. After these procedures, the gastrocnemius muscle was submitted to the mechanical traction assay to evaluate stiffness, resilience, load and stretching at maximum limit MPs. Results: Immobilization reduced the MP values concerning load and stiffness (p 0.05). Conclusion: It is concluded that the gastrocnemius muscle became structurally better organized through a single NMES application and by remobilization.

Propriedades mecânicas do músculo gastrocnêmio de ratas, imobilizado e posteriormente submetido a diferentes protocolos de alongamento

Stretching is widely employed in physiotherapeutic clinical practice and in sportive activities; however, the mechanical alterations of the skeletal muscle generated by this technique are poorly scientifically investigated. This study evaluated the mechanical alterations suffered by the gastrocnemius muscle of young adult female Wistar rats, submitted to14 days of immobilization followed by passive manual stretching during 10 consecutive days once or twice a day. Fifty animals were equally distributed in five groups, Control (CG); Immobilized (IG); Immobilized and liberated (ILG); Immobilized and submitted to stretching once a day (IEG1); Immobilized and submitted to stretching twice a day (IEG2). The gastrocnemius muscle was analyzed by mechanical traction assay and the properties related to load and maximal and proportional stretching evaluated in addition to stiffness and resilience. Immobilization decreased load at maximal thresholds (MTL), load at proportional thresholds (LPT), stretch at maximal thresholds (SMT), stiffness and resilience were reduced in 44.4%, 34.4%, 27.6%, 64.4% and 54% respectively, compared to CG values. With subsequent free remobilization and stretching, all parameters were restored except for IEG2 in which SMT remained reduced in 31.3%, when compared to CG. It is concluded that after 14 days of segmental immobilization, individual stretching loads and free movements contribute to regain muscle mechanical properties.

Efeitos morfológicos do retorno da sobrecarga após imobilização em alongamento de músculo esquelético de ratas

CONTEXTUALIZACAO: Na reabilitacao, a imobilizacao em alongamento do musculo esqueletico e realizada como contramedida para reverter efeitos de encurtamento muscular severo e em eventos pos-cirurgicos. Acredita-se que o retorno as atividades funcionais normais estimule mecanotransdutores capazes de reorganizar a citoarquitetura normal muscular, porem a descricao das alteracoes histopatologicas relacionadas a esses procedimentos sao escassas na literatura. OBJETIVOS: Avaliar e quantificar anomalias histologicas induzidas pela imobilizacao em alongamento do musculo EDL (Extensor Digitorum Longus) e confronta-las com a livre movimentacao do animal apos esse procedimento. METODOS: Foram utilizadas 18 ratas Wistar, distribuidas nos grupos: controle (GC); imobilizadas em flexao plantar (EDL em posicao alongada) por 14 dias (GI); imobilizadas por 14 dias e liberadas por dez dias (GIL). Fragmentos do EDL foram congelados, seccionados e processados com reacoes imuno-histoquimica para colagenos I e III e histoquimica para Adenosina Trifosfatase Miofibrilar e Hematoxilina-Eosina. RESULTADOS: Os animais do GI apresentaram discreto aumento da expressao de colageno I e de fibras em processo degenerativo/necrotico, reducao da proporcao de fibras tipo (FT) 2A e do diâmetro menor de todos os tipos de fibras, quando comparados com os animais do GC. Para o GIL, observou-se retorno da quantidade de colageno I as condicoes controle, alem de reducao na proporcao de FT2D, aumento do numero de nucleos centralizados e do diâmetro menor das fibras quando comparadas com o GI, porem a expressao de FT2B e FT2D nao atingiu os valores de referencia. CONCLUSOES: Os dados apresentados mostram que a retomada da funcao durante dez dias foi parcialmente eficiente na recuperacao das caracteristicas do musculo EDL apos o periodo de imobilizacao e que, se extrapolados os dados a clinica fisioterapeutica, a adocao de procedimentos orientados as disfuncoes primarias do musculo pode favorecer a resposta morfofuncional do segmento e o seu integro restabelecimento.

Twice a day neuromuscular electrical stimulation postimmobilization alters the mechanical properties and the histomorphometry of the skeletal muscle

Abstract Background: The responses to the use of neuromuscular electrical stimulation (NMES) technique, once or twice a day, are not well described in literature. In this direction, we measured the biomechanical