Analysis of muscle adaptations to terrestrial stepping in the Urodelan amphibian Pleurodeles waltlii

Abstract

The changes of myosin isoform pattern and of its associated light chains in relation to the myosin ATPase profile were analysed in different muscles of the hypothyroidian amphibian Pleurodeles waltlii submitted to terrestrial stepping, using electrophoretic and histochemical techniques. These changes were specific to the muscle type but appeared globally characterized by a type-IIB to type-IIA/I fibre transition associated with a transition from fast to intermediate and/or slow myosin isoforms. These results are similar to the effects of endurance training on locomotor muscles of mammals. The diaphragm of experimental animals was also characterized by a complete disappearance of the larval myosin isoforms which were detected in the diaphragm of control animals. The myosin pattern of ventricular muscle did not change following terrestrial stepping. This work indicates that thyroid hormone does not regulate the muscle adaptations that occur following terrestrial stepping and suggests a more complex mechanism of regulation in which innervation could be implicated.

Skull development in the Iberian newt, Pleurodeles waltl (Salamandridae: Caudata: Amphibia): timing, sequence, variations, and thyroid hormone mediation of bone appearance

“…The maximum responsiveness to and dependence on TH are displayed by the metamorphic coronoid resorption and palate remodelling, which are greatly accelerated in the TH-treated newts and arrested in the TU-treated newts. Such a peak in the degree of responsiveness to TH is consistent with the maximum level of TH activity in metamorphosing P. waltl individuals recorded by Launay et al (1998).…”

“…In this study, we chose to use T 3 rather than the usually used thyroxine (T 4 ), because the latter is currently believed to be a prohormone and a reservoir for the more active T 3 (Galton, 2017). The concentrations of T 3 used in our experiment fall within the range of plasma TH levels found by Launay et al (1998) (Smirnov and Vassilieva, 2003;Smirnov and Vassilieva, 2005;Smirnov et al 2011). Similarly, in our previous work (Smirnov and Vasileva, 2001), a 0.02% TU concentration did not cause teratogenic effects in P. waltl larvae, but it was enough to retard metamorphic remodelling.…”

Chronic electrical stimulation drives mitochondrial biogenesis in skeletal muscle of a lizard,Varanus exanthematicus

“…Endurance exercise training of Amphibolurus nuchalis, an Australian agamid lizard, failed to result in an adaptive response (Garland et al, 1987). Nonetheless, modest fast-to-slow shifts in myosin isoforms and ATPase activity were described following 'forced terrestrial stepping', a moderate exercise stimulus, in an Urodelan amphibian (Launay et al, 1998). Organismal limitations bypassed with short term, direct electrical stimulation of the gastrocnemius muscle in the Indian green frog (Rana hexadactyla) revealed increased mitochondrial protein content and cytochrome c oxidase activity (Moorthy et al, 1981).…”