Histochemistry profile of the biceps brachii muscle fibres of capuchin monkeys (Cebus apella, Linnaeus, 1758) / Perfil histoquímico das fibras do músculo bíceps braquial do macaco-prego (Cebus apella, Linnaeus, 1758)

A general analysis of the behaviour of “Cebus” shows that when this primate moves position to feed or perform another activity, it presents different ways of locomotion. This information shows that the brachial biceps muscle of this animal is frequently used in their locomotion activities, but it should also be remembered that this muscle is also used for other development activities like hiding, searching for objects, searching out in the woods, and digging in the soil. Considering the above, it was decided to research the histoenzimologic characteristics of the brachial biceps muscle to observe whether it is better adpted to postural or phasic function. To that end, samples were taken from the superficial and deep regions, the inserts proximal (medial and lateral) and distal brachial biceps six capuchin monkeys male and adult, which were subjected to the reactions of m-ATPase, NADH-Tr. Based on the results of these reactions fibres were classified as in Fast Twitch Glycolitic (FG), Fast Twitch Oxidative Glycolitic (FOG) and Slow Twitc (SO). In general, the results, considering the muscle as a whole, show a trend of frequency FOG> FG> SO. The data on the frequency were studied on three superficial regions FOG=FG>SO; the deep regions of the inserts proximal FOG=FG=SO and inserting the distal FOG>FG=SO. In conclusion, the biceps brachii of the capuchin monkey is well adapted for both postural and phasic activities.

Uma análise geral do comportamento do “Cebus apella” mostra que este primata quando desloca para se alimentar ou realizar outra atividade apresenta diferentes maneiras de locomoção. Estas informações mostram que o músculo bíceps braquial deste animal é usado freqüentemente nas suas atividades de locomoção, mas deve ser lembrado ainda que este músculo é usado também para desenvolvimento de outras atividades como esconder-se, procurar objetos, vasculhar arboredos, além de cavar o chão. Considerando-se o exposto acima decidiu-se pesquisar as características histoenzimológicas do músculo bíceps braquial do macaco-prego com o objetivo de comparar se este músculo esta melhor adaptado para funções posturais ou fásicas. As amostras foram retiradas das regiões superficiais e profundas; inserções proximais (medial e lateral) e distal de seis macacos-prego machos e adultos, os quais foram submetidos às reações de m-ATPase, NADH-Tr. Baseado nos resultados das reações, as fibras foram classificadas em Fast Twitch Glycolitic (FG), Fast Twitch Oxidative Glycolitic (FOG) e Slow Twitch (SO). Quanto à área dos diferentes tipos de fibras, os resultados encontrados foram semelhantes em todas as amostras estudadas, e as fibras de contração rápida foram sempre maiores do que as de contração lenta (FG=FOG>SO). Os dados obtidos sobre a frequência foram: nas três regiões superficiais estudadas FOG=FG>SO; nas regiões profundas das inserções proximais FOG=FG=SO e na inserção distal FOG>FG=SO. Baseado nestes dados pode-se concluir que o músculo bíceps braquial do macaco-prego está bem adaptado tanto para atividades posturais como fásicas.

Effect of thyroid hormone on contractility and sarco/endoplasmic Reticulum Ca[2+] ATPase -1 [SERCA1] expression in adult rats; role in thermogenesis

Thyroid hormone is one of the main factors that determine skeletal muscle contractile properties and the slow-twitch vs. fast twitch muscle fiber phenotype. Sarcoplasmic reticulum Ca[2+] ATPase is one of the principal regulators of Ca[2+] homeostasis in the skeletal muscle cells. It has been previously shown that modification of thyroid hormone levels has a profound impact on cardiac function, predominantly through a direct regulation of the sarcoplasmic reticulum protein levels. The present study aimed to investigate the effects of thyroid hormone treatment for 4 weeks on slow twitch soleus muscle of rats via recording twitch tension, time to peak tension, and half relaxation time and determination of soleus muscle SERCA1 expression. 24 male rats of local strain were randomly divided into 2 groups [n=12], control euthyroid group and hyperthyroid group in which hyperthyroidism was induced by intra peritoneal [i.p] injection of L-troxin 200microg/kg B.W./day, for 4 weeks. The in-situ isometric measures were done for soleus muscle and twitch tension [TT], [expressed as screen units], time to peak tension [TPT], and half relaxation time, 1/2 Rt [expressed in milliseconds] were recorded. SERCA1 protein expression in rat soleus muscle was measured. Thyroid hormone treatment significantly reduced time to peak tension and half relaxation time and increased twitch tension. These contractile changes were accompanied with significant increase in expression of SERCA1 in soleus muscle of rats. Thyroid hormone stimulates the expression of SERCA1 in slow soleus muscle in rats, thereby speeding-up the contraction-relaxation cycle and this increases energy expenditure and these effects of thyroid hormone participate at least in part to thermogenic action of thyroid hormone

Cyclosporin A preferentially attenuates skeletal slow-twitch muscle regeneration

Calcineurin, a Ca2+/calmodulin-dependent phosphatase, is associated with muscle regeneration via NFATc1/GATA2-dependent pathways. However, it is not clear whether calcineurin preferentially affects the regeneration of slow- or fast-twitch muscles. We investigated the effect of a calcineurin inhibitor, cyclosporin A (CsA), on the morphology and fiber diameter of regenerating slow- and fast-twitch muscles. Adult Wistar rats (259.5 ± 9 g) maintained under standard conditions were treated with CsA (20 mg/kg body weight, ip) for 5 days, submitted to cryolesion of soleus and tibialis anterior (TA) muscles on the 6th day, and then treated with CsA for an additional 21 days. The muscles were removed, weighed, frozen, and stored in liquid nitrogen. Cryolesion did not alter the body weight gain of the animals after 21 days of regeneration (P = 0.001) and CsA significantly reduced the body weight gain (15.5 percent; P = 0.01) during the same period. All treated TA and soleus muscles showed decreased weights (17 and 29 percent, respectively, P < 0.05). CsA treatment decreased the cross-sectional area of both soleus and TA muscles of cryoinjured animals (TA: 2108 ± 930 vs 792 ± 640 µm²; soleus: 2209 ± 322 vs 764 ± 439 m²; P < 0.001). Histological sections of both muscles stained with Toluidine blue revealed similar regenerative responses after cryolesion. In addition, CsA was able to minimize these responses, i.e., centralized nuclei and split fibers, more efficiently so in TA muscle. These results indicate that calcineurin preferentially plays a role in regeneration of slow-twitch muscle.

Estudo das alteraçöes das fibras musculares estriadas esqueléticas desnervadas por longo período / A study of the long-term denervation on the striated muscle

A porcentagem de células satélites rapidamente diminui no músculo sóleo de rato em regeneraçäo desprovido de inervaçäo. Assim também a desnervaçäo de músculos intactos causa a degeneraçäo e a perda de fibras sendo o comportamento das células satélites nestas condiçöes desconhecido. Mionúcleos com características de apoptósis têm sido observados em músculos desnervados, porém sem comprovaçäo deste fenômeno. Os músculos sóleo e extensor longo dos dedos (EDL) foram desnervados experimentalmente em ratos com 5 semanas de idade e investigados em diferentes períodos pós-desnervaçäo. A técnica do Ensaio Cometa foi utilizada em músculos desnervados por mais de 30 semanas para se detectar possíveis quebras de DNA associadas com apoptósis. Miotubos indicando regeneraçäo foram observados no músculo sóleo e parte profunda do músculo EDL após 7 semanas de desnervaçäo e na parte superficial do músculo EDL somente 16 semanas após desnervaçäo. Quase todas as células satélites desapareceram após 30 semanas de cirurgia em ambos os músculos. A desnervaçäo de músculos esqueléticos de ratos causa em adiçäo a atrofia de suas fibras, perda de fibras com subsequente regeneraçäo. A proliferaçäo das células satélites em músculos desnervados leva a exaustäo de "pool" de células satélites. Mionúcleos em músculos desnervados exibem quebras do DNA as quais podem ser demonstradas através da técnica do Ensaio Cometa.