Frog Sartorius Muscle Fibres Research Articles

Membrane activity of chronically denervated frog sartorius muscle fibers.

Membrane activity of chronically denervated frog sartorius muscle fibers.

Effect of dinitrophenol on phosphorylation and bioelectric phenomena of excitable tissues.

The effect of 2, 4-dinitrophenol (DNP) was investigated on the phosphorylation of frog sartorius muscle and ventral nerve roots, using P32 as a tracer. It was possible almost completely to inhibit phosphorylation without significantly altering excitability, although the resting potential and intracellular potassium decreased over 30%. The addition of 0.01 mm DNP to a sodium-free hydrazinium system completely blocked excitability, despite the fact that this concentration of DNP produced no further inhibition of phosphorylation. It was possible to restore the excitability of frog sartorius muscle fibers by anodal polarization after the fibers were rendered inexcitable by immersion in 1 mm DNP. The results were discussed in terms of the role of energy metabolism in excitability and other bioelectric phenomena of muscle and nerve.

The movement of thallium ions in muscle.

Measurements have been made of the fluxes of thallous ions (Tl(+)) across the membrane of frog sartorius muscle fibers. These show that at an external concentration of 74 microM the influx is about 270 x 10(-15) moles/cm.(2) sec., while the efflux from a muscle with an internal concentration equal to the above is 5 x 10(-15) moles/cm.(2) sec. The efflux is increased of the order of 300-fold during a muscle twitch, and Tl(+) reach a steady-state distribution between fiber water and Ringer solution that is very close to the corresponding ratio for K(+). High concentrations of Tl(+) depolarize the membrane about 58 mv. for a tenfold increase in external concentration. The results obtained are consistent with the view that the muscle fiber membrane cannot distinguish between the toxic heavy metal Tl(+) and K(+), provided that the concentrations of the former ion are kept low. High concentrations of Tl(+), if allowed to act for an appreciable period of time, lead to irreversible damage to muscle.

Action of acetylcholine, choline and D-tubocurarine on the membrane of frog sartorius muscle fibers

Resting potentials of frog sartorius muscle fibers were taken with microelectrodes at different distances along the length of muscles before and after adding acetylcholine or choline. The mean membrane potential drop and scatter of the potentials recorded in the relatively nerve-free, and in the more densely innervated parts of the muscle, were similar. The loss of direct excitability to electrical and mechanical stimulation was correlated with the concentration of choline or acetylcholine presented. d-tubocurarine added beforehand protected against the depolarizing effect of acetylcholine and choline everywhere along the length of the muscle. A generalized action of acetylcholine and choline and also of d-tubocurarine all along the muscle fibers was inferred. This generalized action at higher concentrations of acetylcholine and choline is believed to be additional to a more specific end plate action.

Repetitive stimulation of muscle.

DURING a study of the effects of repetitive stimulation on the intracellular electrical activity of frog sartorius muscle fibres, alterations were noticed in the voltages of the second and subsequent spikes. At the same time, there was a progressive decrease in t 1/2 after-potential following the second and following spikes. All the experiments were performed on the green frog Hyla coerulea at a temperature of 22° C.