scholarly journals Influence of ionic strength on the time course of force development and phosphate release by dogfish muscle fibres

2005 ◽  
Vol 567 (3) ◽  
pp. 989-1000 ◽  
Author(s):  
Timothy G. West ◽  
Michael A. Ferenczi ◽  
Roger C. Woledge ◽  
N. A. Curtin
Keyword(s):  
Ionic Strength ◽  
Time Course ◽  
Muscle Fibres ◽  
Phosphate Release ◽  
Force Development

Cooperative attachment of cross bridges predicts regulation of smooth muscle force by myosin phosphorylation

2004 ◽  
Vol 287 (3) ◽  
pp. C594-C602 ◽  
Author(s):  
Christopher M. Rembold ◽  
Robert L. Wardle ◽  
Christopher J. Wingard ◽  
Timothy W. Batts ◽  
Elaine F. Etter ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Smooth Muscle ◽  
Time Course ◽  
Muscle Force ◽  
Regulatory System ◽  
Force Development ◽  
Cross Bridge ◽  
Cross Bridges ◽  
The Relationship ◽  
Cooperative Activation

Serine 19 phosphorylation of the myosin regulatory light chain (MRLC) appears to be the primary determinant of smooth muscle force development. The relationship between MRLC phosphorylation and force is nonlinear, showing that phosphorylation is not a simple switch regulating the number of cycling cross bridges. We reexamined the MRLC phosphorylation-force relationship in slow, tonic swine carotid media; fast, phasic rabbit urinary bladder detrusor; and very fast, tonic rat anococcygeus. We found a sigmoidal dependence of force on MRLC phosphorylation in all three tissues with a threshold for force development of ∼0.15 mol Pi/mol MRLC. This behavior suggests that force is regulated in a highly cooperative manner. We then determined whether a model that employs both the latch-bridge hypothesis and cooperative activation could reproduce the relationship between Ser19-MRLC phosphorylation and force without the need for a second regulatory system. We based this model on skeletal muscle in which attached cross bridges cooperatively activate thin filaments to facilitate cross-bridge attachment. We found that such a model describes both the steady-state and time-course relationship between Ser19-MRLC phosphorylation and force. The model required both cooperative activation and latch-bridge formation to predict force. The best fit of the model occurred when binding of a cross bridge cooperatively activated seven myosin binding sites on the thin filament. This result suggests cooperative mechanisms analogous to skeletal muscle that will require testing.

Neuromuscular Physiology of the Longitudinal Muscle of the Earthworm, Lumbricus Terrestris

1974 ◽  
Vol 60 (2) ◽  
pp. 453-467
Author(s):  
C. D. DREWES ◽  
R. A. PAX
Keyword(s):  
Time Course ◽  
Longitudinal Muscle ◽  
Lumbricus Terrestris ◽  
Single Pulse ◽  
Repetitive Stimulation ◽  
Muscle Fibres ◽  
Mechanical Responses ◽  
Segmental Nerve ◽  
Earthworm Lumbricus ◽  
Stimulation Of

1. Patterns of innervation of the longitudinal muscle of the earthworm, Lumbricus terrestris, were examined electrophysiologically. 2. The longitudinal musculature of a segment is innervated by relatively few axons, a fast and slow axon being present in segmental nerve I and in the double nerve, segmental nerve II-III. 3. Single-pulse stimulation of the fast axon produces large external muscle potentials and small twitch-like contractions, which with repetitive stimulation are antifacilitating. 4. Repetitive stimulation of the slow axon produces large, slowly developing and sustained mechanical responses, with electrical and mechanical responses showing summation and facilitation. 5. The amplitude and time course of slow mechanical responses are related to the frequency of stimulation. 6. Individual longitudinal muscle fibres are innervated by either the fast or slow axon in a segmental nerve, or by both fast and slow axons. 7. No evidence was found for peripheral inhibitory innervation of the longitudinal muscle.

Potentiation of Neuromuscular Transmission by an Octopaminergic Neurone in the Locust

1979 ◽  
Vol 79 (1) ◽  
pp. 169-190 ◽  
Author(s):  
MICHAEL O'SHEA ◽  
PETER D. EVANS
Keyword(s):  
Indirect Effects ◽  
Neuromuscular Transmission ◽  
Time Course ◽  
Muscle Tone ◽  
Muscle Tension ◽  
Presynaptic Receptors ◽  
Extensor Muscle ◽  
Muscle Membrane ◽  
Muscle Fibres ◽  
Central Synapses

1. Spikes in the octopaminergic dorsal unpaired median (DUM) neurone which innervates the extensor tibiae muscle of the locust metathoracic leg (DUMETi) produce direct and indirect effects on muscle tension. 2. Direct effects include a slowing of an intrinsic rhythm of contraction and relaxation, a relaxation of muscle tone and a small hyperpolarization of the muscle membrane potential. The latter two effects are weak and variable. All three effects are mimicked by superfusion of octopamine and are mediated by octopamine receptors on the muscle fibres. 3. Indirect effects are found when the DUMETi neurone is stimulated at the same time as the motoneurones innervating the extensor muscle. They include (a) potentiation of tension generated in the extensor muscle by spikes in the slow excitatory motoneurone (SETi), (b) reduction in duration of each twitch contraction generated by SETi due to an increase in the rate at which the muscle relaxes, (c) increase in the amplitude of the synaptic potential generated by SETi. These various effects have a time course of several minutes and far outlast the duration of DUMETi stimulation. They can be mimicked by superfusion of octopamine. 4. The effect of DUMETi on neuromuscular transmission is mediated by receptors with a high affinity for octopamine located both on the muscle and on the terminals of the slow motoneurone. The presence of the presynaptic receptors is revealed by the increase in the frequency of spontaneous miniature end plate potentials recorded in the muscle in the presence of octopamine. 5. DUMETi is a member of a group of similar aminergic neurones and it is suggested that they may share a role in modulating transmission at peripheral neuromuscular synapses, and possibly central synapses.

Surface contraction of dividing newt eggs induced by lowering the external ionic strength or pH, or by trypsinization

1986 ◽  
Vol 82 (1) ◽  
pp. 143-154
Author(s):  
T. Kubota
Keyword(s):  
Ionic Strength ◽  
Conformational Changes ◽  
Time Course ◽  
Similar Type ◽  
Vitelline Membrane ◽  
Common Mechanism ◽  
Surface Material ◽  
Sucrose Medium ◽  
Saline Medium ◽  
Partial Reversal

As the first cleavage progresses, newt (Cynopus pyrrhogaster) eggs deprived of their vitelline membrane grow to expose the new, unpigmented surface to a saline medium full-strength Steinberg solution). Further exposure of these eggs to sucrose medium resulted in rapid and extensive contraction of the unpigmented surface. In the sucrose medium the contraction continued until the next cleavage, and eventually the eggs divided into many blastomeres. But partial reversal of the contraction was observed when, after brief treatment with sucrose medium, the eggs were returned to saline medium. This and other experiments indicated that the contraction was due to lowering of the extracellular ionic strength. A similar type of contraction was induced by acidification of the saline medium or by trypsinization. The contractions induced by these treatments did not absolutely require the presence of external Ca2+, had a rapid time course, and were restricted to the unpigmented region, suggesting that they had a common mechanism. Acidification of the egg cytoplasm with CO2 did not result in significant contraction. These findings, together with those of others, suggest that contraction of the unpigmented surface induced by these treatments is due to conformational changes of surface material.

Time-course Of Changes In Maximal Force And Rate Of Force Development After A Plyometric Training Session

2015 ◽  
Vol 47 ◽  
pp. 356
Author(s):  
Gregory C. Bogdanis ◽  
Panagiotis Veligekas ◽  
Panagiotis Roxanas ◽  
Konstantinos Chiotelis ◽  
Stavros Petrou ◽  
...  
Keyword(s):  
Time Course ◽  
Training Session ◽  
Rate Of Force Development ◽  
Plyometric Training ◽  
Force Development ◽  
Maximal Force

scholarly journals Regulation of glucose-6-phosphate dehydrogenase activity in sea urchin eggs by reversible association with cell structural elements.

1986 ◽  
Vol 103 (4) ◽  
pp. 1509-1515 ◽  
Author(s):  
R R Swezey ◽  
D Epel
Keyword(s):  
Ionic Strength ◽  
Sea Urchin ◽  
Time Course ◽  
Calcium Concentration ◽  
Metabolic Activation ◽  
Structural Elements ◽  
Ionic Detergent ◽  
Low Ionic Strength ◽  
Glucose 6 Phosphate Dehydrogenase ◽  
Substrate Concentrations

In unfertilized eggs of the sea urchin, Strongylocentrotus purpuratus, glucose-6-phosphate dehydrogenase (G6PDH) associates with the particulate elements remaining either after homogenization or extraction of eggs with non-ionic detergent in low ionic-strength media. At physiological ionic strength, the extent of G6PDH binding to these particulate elements is proportional to the total protein concentration in the extracts. In fertilized eggs this association is prevented by one or more low molecular weight solutes. The dissociation is reversible, and there are no permanent modifications of either G6PDH or its particulate binding site that affect binding. After fertilization, the time course of dissociation of G6PDH from particulate elements is too fast to be caused by a change in intracellular pH, but it could be triggered, but not maintained, by an increase in the intracellular calcium concentration. Binding of G6PDH to the particulate fraction lowers its catalytic activity at all substrate concentrations. Therefore, release of the enzyme into the cytoplasm may be an important part of the suite of events causing metabolic activation of the egg at fertilization.

Myosin dephosphorylation during rapid relaxation of hog carotid artery smooth muscle

1989 ◽  
Vol 256 (2) ◽  
pp. C315-C321 ◽  
Author(s):  
S. P. Driska ◽  
P. G. Stein ◽  
R. Porter
Keyword(s):  
Smooth Muscle ◽  
Carotid Artery ◽  
Rate Constant ◽  
Light Chain ◽  
Time Course ◽  
Myosin Light Chain ◽  
Force Development ◽  
Relaxation Phase ◽  
Rhythmic Contractions ◽  
Low Levels

Changes in myosin light chain phosphorylation were measured during histamine-induced rhythmic contractions of hog carotid artery smooth muscle strips. Histamine made the muscle strips contract spontaneously every 1-5 min, and this allowed measurement of the time course of phosphorylation in relation to force development under conditions where diffusion of the agonist through tissue would not complicate the interpretation of the data. In the absence of histamine, phosphorylation was low [0.12 +/- 0.04 mol P/mol of the 20,000-Da light chain (LC 20)]. Phosphorylation was slightly (but not significantly) higher in the presence of 10 microM histamine in the relaxed state between contractions (0.20 +/- 0.03 mol P/mol LC 20). In muscle strips frozen during force development, when force had reached half of its peak value, phosphorylation was 0.38 +/- 0.06 mol P/mol LC 20. The highest levels of phosphorylation (0.49 +/- 0.04 mol P/mol LC 20) were found in strips frozen at the peak of the rhythmic contractions. Strips frozen when force had declined to half of the peak force showed low levels of phosphorylation (0.17 +/- 0.07 mol P/mol LC 20), indicating that the myosin light chain phosphatase activity was quite high. Mathematical modeling of the kinase and phosphatase reactions suggested that the apparent first-order phosphatase rate constant was at least 0.08 s-1 under these conditions. To obtain a better estimate of this rate constant, a second series of phosphorylation measurements were made early in the relaxation phase of the rhythmic contractions. The highest phosphatase rate constant obtained from these measurements was 0.23 s-1.(ABSTRACT TRUNCATED AT 250 WORDS)

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