A lesion of the transverse tubules of skeletal muscle

Abstract

SUMMARY1. A method is described by which a selective lesion can be made in vitro in the transverse tubules of frog skeletal muscle.2. The method consists of exposing the muscle for 1 hr or more to a buffered salt solution made hypertonic by the inclusion of 400 mm glycerol and then returning the muscle to an isotonic salt solution. The lesion is induced during the washout of the glycerol.3. Electron micrographs reveal that the lesion consists of a rearrangement of the T-system membranes in such a way that the continuity of the tubules is lost. The membranes appear to coalesce into large vesicles scattered irregularly throughout the sarcoplasm.4. The glycerol treatment results in a depression of the resting potential of up to 30 mV. The treated fibres are depolarized by high concentrations of K as are normal muscle fibres.5. T-tubule lesioned fibres are unable to respond mechanically either to electrical stimulation or to elevated K but they do contract in the presence of caffeine and relax when the caffeine is removed.6. Problems concerning the variability of the procedure are presented and certain considerations concerning the mechanism of the effect are discussed.

Hypertonicity-induced inhibition of excitation-contraction coupling in Xenopus twitch fibers.

“…The diameters of the Xenopus transverse tubules are smaller than the Rana ones (OBA et al, 1983). These findings suggest that the hypertonicity disrupts the Xenopus T system osmotically which brings about the permanent detubulation like the glycerol treatment (HOWELL, 1969). However, the mechanism inducing the detubulation may differ from the glycerol case since the molecules such as NaCI or sucrose, unlike glycerol, may be impermeable to the surface and T system membranes as previously mentioned.…”

“…The mechanism of the hypertonicity-induced reduction in Cm in Xenopus fibers accounts for an electrical discontinuity between the surface and T system membranes like the glycerol effect in Rana (FUJINO et al, 1961;HOWELL, 1969) and Xenopus (NAKAJIMA and BASTIAN, 1974). The glycerol treatment is also accompanied by the reduction in Cm (HODGKIN and NAKAJIMA, 1972;DULHUNTY and GAGE, 1973).…”

The Effects of Glycerol Detubulation, of Manganese Ions, of Dantrolene and of Nitrate Ions on the Responses of Isolated Chronically Denervated Soleus Muscles of the Mouse to Acetylcholine

“…Glycerol-treated muscles were unresponsive to K+, but the sensitivity to caffeine was normal (Figure 1) indicating selective destruction of the T-tubules as first shown by Eisenberg & Eisenberg (1968) and by Howell (1969) in frog sartorius muscles. After detubulation the first phase of acetylcholine contractions was almost abolished, but the second phase was still present.…”

“…The T-Tubules were selectively destroyed according to the method described by Eisenberg & Eisenberg (1968) and by Howell (1969 …”

Modification of the Ca²⁺ Release System of Skeletal Muscle Sarcoplasmic Reticulum Vesicles via Sulfhydryl Oxidation and Tryptic Proteolysis

“…Using isolated muscle fibers as a model system, the investigator is sure that all of the essential molecular machinery is present. Also, the sarcolemma can be stripped away if desired (6), yielding direct access to the SR and contractile machinery, or the T-tubules can be disrupted as described above (34,35,36 Chapter IV), and Ca 2 + channels of the terminal cisternae which have been incorporated into artificial membranes are strongly Ca z + dependent (42,43). The Ca 2 + flux rates through these channels and the density of these channels is sufficiently large that these channels could mediate Ca Z + release from the SR in excitation-contraction coupling (66 - The data presented in Chapters II and III show that the …”