Isolated myofibers from rat skeletal muscle in suspension: Cellular morphology and calcium homeostasis

Abstract

Myofiber suspensions with 80% viability (morphological intactness) were prepared from rat m. flexor digitorum brevis by a 6-hour collagenase treatment. The viable fibers had intact sarcolemmas and generally showed continuous basal laminae. The intracellular compartments exhibited normal muscular morphology. The suspended myofibers showed good tolerance against extracellular calcium (up to 30 mM), but were susceptible to 15 mM EGTA. Calcium ionophore A23187 induced contraction, with loss of viability in both calcium-containing and nominally calcium-free Krebs-Ringer medium. EGTA prevented the ionophore effect, but the muscle cells collapsed as soon as calcium was replenished. A calcium paradox, as observed with perfused heart, could not be induced in isolated skeletal myocytes. This suspended cell system should provide a useful tool for investigating relationships between metabolic parameters and muscle physiology. The extracellular environment can be manipulated easily, and cellular responses of individual skeletal muscle fibers can be measured and visualized.

The influence of temperature on mechanics of red muscle in carp.

“…As an assay of cell viability (some fibres could be killed during dissection or experiments), the bundles were immersed in Trypan Blue solution (1 % in normal Ringer solution) for 1 h (Zuurveld, Veerkamp & Wirtz, 1985) while attached to the servomotor and force transducer. The bundles were then gently blotted with soft filter paper, immersed in a gelatin supportive medium (as in Sosnicki, Lutz, Rome & Goble, 1989) and then rapidly frozen in isopentane cooled with liquid nitrogen while still connected to the servomotor.…”

Plastid genes and parasitic plants

“…Interestingly, the progression of the damage to the isolated fibres described by Menke and Jockusch is not unique to hypo-osmotic shock, but is qualitatively similar to that which occurs in isolated fibres under various forms of stress, including trauma and deliberate elevation of intracellular calcium with the calcium ionophore 4 • It therefore seems necessary to determine whether the decreased stability of mdx muscle found by Menke and Jockusch is a consequence of the hypo-osmotic shock or of the nature of the model system used. Although the results of Menke and Jockusch's report are interesting and potentially important, the 'fragile membrane' theory is by no means proven; for an abnormality such as increased fragility to be important in the pathogenesis of Duchenne and Becker muscular dystrophy, it must be apparent under physiological conditions.…”

“…For the c60 ball, RAe = 3.52 A (this is the distance from the centre of the ball to the centre of the atoms on the ball's surface (T. Siegrist, personal communication)). This yields 8 0 = 843 GPa, which is larger than the modulus of 441 GPa found experimentally for diamond 4 • The molecular radius obtained from the lattice parameter of the closest-packed f. c. c. crystal is Rer = 5.02 A (ref. 1).…”