Effect of muscle length on energy balance in frog skeletal muscle.

Curtin, N. A.; Woledge, Roger C.

doi:10.1113/jphysiol.1981.sp013800

Cited by 37 publications

(19 citation statements)

References 28 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Calculations of sarcomere length from compliance measurements indicate that a value of near 2.25 btm was obtained during tetanic contraction when resting sarcomere length was 2.40 btm. The long sarcomere length was needed to empirically eliminate most force generation in the whole muscles (Homsher et al, 1972;Curtin & Woledge, 1981).…”

Section: Resultsmentioning

confidence: 99%

Temperature dependence of the crossbridge cycle during unloaded shortening and maximum isometric tetanus in frog skeletal muscle

Burchfield

Rall

1986

J Muscle Res Cell Motil

View full text Add to dashboard Cite

The primary objective of this study was to determine if the rate limiting step in the crossbridge cycle was the same during maximum rate of shortening and during maintenance of maximum tension in an isometric contraction. To this end the temperature dependence, Q10, of the crossbridge cycle was estimated during unloaded shortening and maximum isometric tetanus. Isolated semitendinosus muscles from the frog were studied at 0 and 10 degrees C. Crossbridge cycling during unloaded shortening was determined from the velocity of unloaded shortening estimated by the slack step technique. Crossbridge cycling during maintained isometric tetanus was determined from the steady rate of energy liberation during the tetanus after allowance for energy liberation due to Ca2+ cycling. The Q10 of the velocity of unloaded shortening was 2.5 and that of the steady rate of energy liberation was 4.6. After correction for the temperature dependence of energy liberation associated with Ca2+ cycling (5.7), the estimated Q10 of the steady rate of energy liberation became 3.9. These estimates of the Q10 of the crossbridge cycle are significantly different. These results support the conclusion that the rate limiting steps during unloaded shortening and maximum isometric force maintenance occur at different steps in the crossbridge cycle. Further the high Q10 of the energy liberation due to Ca2+ cycling may relate to the high concentration of parvalbumin in frog muscle. A second objective of this study was to document in the same muscle the variation of Q10s of mechanical and energetic properties of contraction. Over this temperature range the Q10s ranged from 1.1 to 5.7.

show abstract

Section: Resultsmentioning

confidence: 99%

Temperature dependence of the crossbridge cycle during unloaded shortening and maximum isometric tetanus in frog skeletal muscle

Burchfield

Rall

1986

J Muscle Res Cell Motil

View full text Add to dashboard Cite

show abstract

“…The amount of PCr splitting is strongly dependent on the degree of filament overlap (Infante et al, 1964a, b;Sandberg & Carlson, 1966;Curtin & Woledge, 1981) being less than half as great as muscle lengths where filament overlap is prevented as it is when filament overlap is optimal. As shown in Fig.…”

Section: Discussionmentioning

confidence: 96%

Effects of carbon dioxide and tetanus duration on relaxation of frog skeletal muscle

Curtin

1986

J Muscle Res Cell Motil

View full text Add to dashboard Cite

Sartorius and semitendinosus muscles of the frog Rana temporaria (0 degrees C) were stimulated under isometric (fixed-end) conditions and force during stimulation and relaxation was recorded. Relaxation time was assessed by measuring the time from the last stimulus until force declined to 90% or 50% of its value at that time. The relaxation time increased linearly with concentration of CO2 in the Ringer's solution (pH 7.2), whereas, at constant CO2, relaxation was hardly affected by changes in extracellular HCO3- and pH. This is consistent with the view that CO2 enters the cells, but H+ and HCO3- do not, and that entry of CO2 causes intracellular acidification and slows relaxation. For tetani lasting between 0.5 and 5s, relaxation is slower the longer the tetanus; further increase in tetanus duration to 10 s has little additional effect. The presence of 3.3 mmol 1(-1) CO2 in the Ringer's solution has a small effect on relaxation after a brief tetanus, but greatly slows relaxation as tetanus duration increases. Experiments with paired tetani (conditioning and test) showed that relaxation from a test tetanus was slower if a conditioning tetanus was given. However, the size of this effect was independent of muscle length during the conditioning tetanus. After a conditioning tetanus, an interval of many minutes is required for the muscle to recover its ability to relax quickly from a test tetanus. The results indicate that changes in metabolite levels caused by contraction itself are not responsible for the slowing of relaxation. Possible mechanisms of the effects of CO2 on relaxation are discussed.

show abstract

“…About a quarter of the total ATP split in muscle contraction is used by the sarcoplasmic reticulum calcium pump (Curtin & Woledge, 1981). This ATPase activity is lowered by increased acidity in vitro (MacLennan, 1970), and in vivo it is probably this effect that causes the obvious slowing of relaxation produced by increasing CO2 concentration (for example Fig.…”

Section: Discussionmentioning

confidence: 99%

Effect of intracellular pH on force and heat production in isometric contraction of frog muscle fibres.

Curtin

Kometani

Woledge

1988

The Journal of Physiology

Self Cite

View full text Add to dashboard Cite

SUMMARY1. The intracellular pH (pHi) of live fibres from the anterior tibialis of the frog Rana temporaria was measured at 10 0C (using pH-sensitive microelectrodes) in Ringer solutions containing a fixed bicarbonate concentration (20 mM) and varying PCO2 concentrations of 0-5-54 %. As extracellular pH was changed from 7-99 to 6-00, mean pHi changed from 7-24 to 5-97. Similar results were obtained at 20 0C.2. In parallel experiments force and rate of heat production in 4 s isometric tetani at 100C were measured, and compared to control observations (5% C02, pH1 6-80).3. As the fibres became more acid (to pHi 5-95), force and heat rate were progressively reduced (to 0-75 and 0-71 of the control values, respectively).4. As the fibres became more alkaline (to pHi 7-26), force increased slightly (by a maximum of 0-03 of the control value) but heat rate did not increase.5. When the dependence on pH of the molar enthalpy change for phosphocreatine splitting is taken into account, these results indicate that the force-time integral per cross-bridge cycle increases with pHi over this range.

show abstract

Effect of muscle length on energy balance in frog skeletal muscle.

Cited by 37 publications

References 28 publications

Temperature dependence of the crossbridge cycle during unloaded shortening and maximum isometric tetanus in frog skeletal muscle

Temperature dependence of the crossbridge cycle during unloaded shortening and maximum isometric tetanus in frog skeletal muscle

Effects of carbon dioxide and tetanus duration on relaxation of frog skeletal muscle

Effect of intracellular pH on force and heat production in isometric contraction of frog muscle fibres.

Contact Info

Product

Resources

About