Getting the jump on skeletal muscle disuse atrophy: preservation of contractile performance in aestivatingCyclorana alboguttata(Günther 1867)

Abstract

SUMMARY Prolonged immobilisation or unloading of skeletal muscle causes muscle disuse atrophy, which is characterised by a reduction in muscle cross-sectional area and compromised locomotory function. Animals that enter seasonal dormancy, such as hibernators and aestivators, provide an interesting model for investigating atrophy associated with disuse. Previous research on the amphibian aestivator Cyclorana alboguttata (Günther 1867)demonstrated an absence of muscle disuse atrophy after 3 months of aestivation, as measured by gastrocnemius muscle contractile properties and locomotor performance. In this study, we aimed to investigate the effect of aestivation on iliofibularis and sartorius muscle morphology and contractile function of C. alboguttata over a longer, more ecologically relevant time-frame of 9 months. We found that whole muscle mass, muscle cross-sectional area, fibre number and proportions of fibre types remained unchanged after prolonged disuse. There was a significant reduction in iliofibularis fibre cross-sectional area (declined by 36% for oxidative fibre area and 39% for glycolytic fibre area) and sartorius fibre density (declined by 44%). Prolonged aestivation had little effect on the isometric properties of the skeletal muscle of C. alboguttata. There was a significant reduction in the isometric contraction times of the relatively slow-twitch iliofibularis muscle, suggesting that the muscle was becoming slower after 9 months of aestivation (time to peak twitch increased by 25%, time from peak twitch to half relaxation increased by 34% and time from last stimulus to half tetanus relation increased by 20%). However, the results of the work-loop analysis clearly demonstrate that, despite changes to muscle morphology and isometric kinetics, the overall contractile performance and power output levels of muscles from 9-month aestivating C. alboguttata are maintained at control levels.

Explosive Jumping: Extreme Morphological and Physiological Specializations of Australian Rocket Frogs (Litoria nasuta)

“…In each case, data represent means for all muscles tested (with SD bars added for data point 1 from this study). Data were taken from the following studies: 1, plantaris longus muscle from Litoria nasuta (this study); 2, sartorius muscle from Cyclorana alboguttata (Symonds et al 2007; the same species as Litoria alboguttata in Fig. 3); 3, ileofibularis muscle from C. alboguttata (Symonds et al 2007; the same species as L. alboguttata in Fig.…”

“…Data were taken from the following studies: 1, plantaris longus muscle from Litoria nasuta (this study); 2, sartorius muscle from Cyclorana alboguttata (Symonds et al 2007; the same species as Litoria alboguttata in Fig. 3); 3, ileofibularis muscle from C. alboguttata (Symonds et al 2007; the same species as L. alboguttata in Fig. 3); 4, peroneus muscle from Xenopus laevis (Wilson et al 2002); 5, sartorius muscle from X. laevis ; 6, plantaris longus muscle from Bufo viridis (Wilson et al 2004); 7, sartorius muscle from Bufo americanus (Stevens 1993); 8, adductor magnus muscle from X. laevis appears to be insufficient to power jumping in these frogs, never mind the much higher instantaneous power output value required at takeoff.…”

Aspectos fisiológicos e ecológicos da estivação em Pleurodema diplolistris (Leiuperidae/Anura)

“…Cabe ainda salientar que a inatividade durante a fase de estivação em anuros poderia levar a alterações na composição estrutural dos tecidos, como a atrofia muscular, caracterizada pela redução da área transversal do músculo e comprometimento da função locomotora (SYMONDS et al, 2007b). Assim, a ausência de atividade per se constitui um desafio fisiológico para anuros estivadores.…”

Mechanisms underlying inhibition of muscle disuse atrophy during aestivation in the green-striped burrowing frog, Cyclorana alboguttata

“…Similarly, six months of aestivation had no effect on the total cross-sectional area of cruralis muscle (Hudson et al, 2006;Mantle et al, 2009). However, aestivation had different effects on muscle fibre cross-sectional area in distinct muscles, with 6-9 months of aestivation leading to significant reductions in cross-sectional area of both oxidative and glycolytic fibres in cruralis and iliofibularis muscles (Hudson et al, 2006;Mantle et al, 2009;Symonds et al, 2007).…”

“…Prolonged aestivation has been shown to cause minimal changes to the in vitro skeletal muscle mechanics of burrowing frogs (Hudson and Franklin, 2002a;Hudson et al, 2006;Symonds et al, 2007). The isometric twitch (e.g.…”