Osmotic responses demonstrating the extracellular character of the sarcoplasmic reticulum

Birks, R. I.; Davey, D. F.

doi:10.1113/jphysiol.1969.sp008802

Cited by 91 publications

(47 citation statements)

References 31 publications

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“…On the basis of the assmnptioii that the rapidly exchanging compartment contained Na"* at extracellular concentrations, Rogus and Zierler (1973) determined its volume to be about 14% of fibre volume, suggesting tliat it was the intra-fibre extracellular compartment proposed by previous workers. The volume behaviour of the rapidly exchanging compartment in muscles exposed to anisotonie solutions was consistent with the predicted o.smotic behaviour of the intra-fibre extracellular compartment and virtually identical with the observed volume of the sarcoplasmie rcticulum in Birks and Davey's (1969) fixed material.…”

Section: Introductionsupporting

confidence: 82%

“…If Birks and Davey's (1969) results are artefactual, then rejection of Biiks' (1965) hypothesis must be seriously cousidered. Such rejection would be in accord with the observation that the sarcoplasniic reticulum of frog muscle, fixed by the freezing technique mentioned above and analyzed using an electron probe, does not appear to contaiu atomic sodium aud chlorine at their extracellular ionic c(jncentrations (Somlyo et al, 1977).…”

Section: Sarroplasmic Reticulummentioning

confidence: 99%

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The Sarcoplasmic Reticulum and T‐system of Rat Extensor Digitorum Longus Muscles Exposed to Hypertonic Solutions

Davey

O’Brien

1978

Aust J Exp Biol Med

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Summary. Excised mt extemar difiitortim km^ns muscles were soaked in a Krcbs solution made hypertouie witb extra NaCI and fi.Ked tisiny a combination of acrolcin tind glutaraldehyde dissolved in the same hypertonic Krcbs. Eleetron microscopie examination showed that the sarcoplasniic reticulum (S.R.) of these muscles occupied the .same fraction of fibre volume as it did in control muscles soaked and fixed in normal Krebs solution, contradicting previoas studies on frog muscle. It appears unlikely that the S.R. is the rapidly exchanging Na+-compartment of rat masclf which enlarges in hypertoiiie solutions, or that it is an cxtracellnlar couipartmc-nt. The T-system of hypertonic mnseles was swollen, but its volume is insnffleient to form the rapidly exchanging Na+-ccjmpartment.

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Section: Introductionsupporting

confidence: 82%

Section: Sarroplasmic Reticulummentioning

confidence: 99%

The Sarcoplasmic Reticulum and T‐system of Rat Extensor Digitorum Longus Muscles Exposed to Hypertonic Solutions

Davey

O’Brien

1978

Aust J Exp Biol Med

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“…There is little direct evidence available which would allow us to identify the slow compartment with the sarcoplasmic reticulum. However system and sarcoplasmic reticulum does not seem improbable, as it would appear that much larger molecules such as sucrose (Birks & Davey, 1969), ruthenium red (Luft, 1971;Dulhunty & Gage, 1973) and silver salts (Baker, 1965) can enter the sarcoplasmic reticulum in this way. In glycerol-loaded fibres transferred to Ringer solution, glycerol would rapidly diffuse out of the transverse tubules.…”

Section: Discussionmentioning

confidence: 99%

Differential effects of glycerol treatment on membrane capacity and excitation—contraction coupling in toad sartorius fibres. With an Appendix

Dulhunty¹,

Gage²,

Barry³

1973

The Journal of Physiology

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SUMMARYChanges in membrane capacity and excitation-contraction coupling caused by glycerol movements have been investigated in toad sartorius fibres using a standard glycerol-Ringer solution containing 400 mM glycerol.1. The rates of glycerol movement, in and out of fibres, were determined by measuring diameter changes in single fibres. Glycerol equilibrated across the surface membrane within 20-25 min after changes in extracellular glycerol concentration.2. The reduction in membrane capacity, which occurs when glycerolloaded fibres are returned to Ringer solution, was slower than, and not dependent on, changes in fibre volume.3. To obtain the maximum reduction in membrane capacity, it was necessary to expose fibres to glycerol-Ringer for 50-60 min and then to return them to Ringer for at least 60 min. If preparations were not kept in Ringer for the full 50-60 min, the reduction in membrane capacity could be partially or completely reversed by returning the fibres to glycerolRinger.4. When fibres were exposed to glycerol-Ringer there was an initial transient contracture: twitches and K contractures were rapidly inhibited, and then slowly recovered over the next 40-50 min. In some preparations, eventual potentiation of twitches was seen.5. When returned to Ringer solution after 60 min in glycerol-Ringer, preparations lost twitches and K contractures within 5-10 min. The time course of this effect was very similar to the time course of the recovery of the normal volume after the initial swelling.6. The briefer the exposure to the glycerol-Ringer, the slower the loss of twitches and K contractures on return to Ringer. In contrast to the loss of ANGELA F. DULHUNTY AND P. W. GAGE membrane capacity, the lesion of excitation-contraction coupling was essentially irreversible. Exposure times as brief as 5 min were eventually effective in producing paralysed fibres which, however, still responded to caffeine.7. The differences in the glycerol load-times required to produce decoupling of excitation and contraction, and disconnexion of the transverse tubules, show that the two effects are separable and that the first does not depend on the second.8. It is proposed that the two lesions obtained in glycerol-treated fibres may be related to distension of the transverse tubular system. It is shown in an Appendix that the outward movement of glycerol from sarcoplasm to transverse tubules would be expected to produce some early swelling of the tubules and this is related to the loss of contraction. Furthermore, much greater swelling would occur if a slow-loading compartment (presumed to be the sarcoplasmic reticulum) dumped glycerol into the transverse tubules: it is thought that this is related to the disconnexion of the transverse tubules.

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“…The excitation process, which begins at the muscle fibre surface, evidently reaches the myofibrils by a route along the transverse tubular system (Huxley & Taylor, 1958). But after the sarcolemma has been removed from a muscle fibre, graded or 'all-or-none' activation can also be produced, apparently by depolarization of some element of the internal membrane system which is electrically continuous longitudinally over many sarcomeres (Costantin & Podolsky, 1967; also see Birks & Davey, 1969). Our experiments have shown that a prolonged stimulus inhibits the spread of activation throughout a muscle fibre (Pls.…”

Section: Discussionmentioning

confidence: 99%

The influence of stimulus parameters on contractions of isolated frog muscle fibres

Rüdel¹,

Taylor²

1969

The Journal of Physiology

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SUMMARY1. Reversible changes in twitch and tetanus contractions of isolated frog muscle fibres were produced by varying the duration and strength of a transversely applied d.c. stimulus.2. When the stimulus strength was at least 1 1 times threshold the peak force of the contraction elicited was reduced by stimulus durations longer than 1 msec at 20 0C, and by durations longer than 3 msec at 2-5 0C.3. As the strength of a prolonged stimulus was progressively increased to 3 times rheobase or more, peak twitch and tetanus force declined to 40-70 % of the amplitude with short (0*2-0-5 msec) stimuli. The time to peak of the twitch was slightly decreased and the first phase of relaxation was accelerated.4. Cine-micrography of fibres which were permitted to shorten under a light load revealed that the side of the fibre adjacent to the anode was unactivated under conditions which also reduced peak force output.5. With stimulus durations longer than 20 msec, peak force, time to peak, and relaxation time increased as the stimulus strength increased from 2-5 to 3 times rheobase. This might have been produced by a cathodal contracture following the action potential.6. The results are discussed in relation to previous studies of activation in striated muscle.

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Osmotic responses demonstrating the extracellular character of the sarcoplasmic reticulum

Cited by 91 publications

References 31 publications

The Sarcoplasmic Reticulum and T‐system of Rat Extensor Digitorum Longus Muscles Exposed to Hypertonic Solutions

The Sarcoplasmic Reticulum and T‐system of Rat Extensor Digitorum Longus Muscles Exposed to Hypertonic Solutions

Differential effects of glycerol treatment on membrane capacity and excitation—contraction coupling in toad sartorius fibres. With an Appendix

The influence of stimulus parameters on contractions of isolated frog muscle fibres

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