Enhanced contractility during relaxation of cat papillary muscle

1975 ◽  
Vol 228 (6) ◽  
pp. 1708-1716 ◽  
Author(s):  
BG Bass
Keyword(s):  
Papillary Muscle ◽  
Time Course ◽  
Isometric Tension ◽  
Contractile Element ◽  
Cat Papillary Muscle ◽  
Postextrasystolic Potentiation ◽  
Peak Tension ◽  
Time To Peak ◽  
In Series ◽  
Antecedent Control

Contractility during relaxation of isometric tension was studied in isolated, electrically driven cat papillary muscle by interpolation of test extrasystoles, all of whichpartially fused with their antecedent (control) contractions, were separated by computer from the fused contractions and then analyzed. The time course of the restitutionof contractility during relaxation was defined by plotting maximal positive dT/dt andtime-to-peak tension of the computer-separated extrasystole versus delay preceding the extrasystole. The dT/dt and time-to-peak tension, which steadily decline with progressive prematurity between contractions, both increase again during late relaxation, become progressively greater still earlier in relaxation, peak shortly after peak isometric tension, and then again decline. This phase of an apparently enhanced contractilityduring relaxation is depressed in low Ca'++ and is transmitted into the postextrasystolic period (in which it is superimposed on the usual postextrasystolic potentiation). The possible contributions of variations in series-elastic component and contractile-element lengths, actionpotential characteristics, and other factors on contractility during relaxation are discussed. It is suggested that enhanced contractility during relaxation may also be related in part to the decay of the intracellular free Ca'++ transient.

Effect of rate changes on strength and time course of contraction of papillary muscle

1963 ◽  
Vol 204 (3) ◽  
pp. 451-457 ◽  
Author(s):  
Jan Koch-Weser
Keyword(s):  
Entire Range ◽  
Maximum Rate ◽  
Time Course ◽  
Normal Development ◽  
Papillary Muscles ◽  
Ventricular Muscle ◽  
High Frequencies ◽  
Peak Tension ◽  
Time To Peak ◽  
Opposing Effect

The influence of 14 frequencies of contraction (between 0.2 and 300 beats/min) on the development of tension and on the time course of contraction was determined in 40 isometrically contracting, isolated cat papillary muscles at 38 C. Only cylindrical muscles with radius <0.43 mm were included, since this was found to be the maximum thickness compatible with normal development of tension at high frequencies. Increases in frequency were associated over the entire range with decreases in the time to peak tension (total 40%) and in the relaxation time (total 49%), and increases in the maximum rate of development of tension (total 560%) and in the peak tension developed (total 340%). These findings indicate that changes in heart rate alter both the degree of activation of the contractile elements and the duration of their active state. It is concluded that the opposing effect of both of these changes must be considered in any analysis of the influence of alterations in rate or rhythm of the heart on the strength of contraction of mammalian ventricular muscle.

scholarly journals The Mechanochemistry of Cardiac Muscle

1967 ◽  
Vol 50 (4) ◽  
pp. 951-965 ◽  
Author(s):  
Peter E. Pool ◽  
Edmund H. Sonnenblick
Keyword(s):  
Cardiac Muscle ◽  
Adenosine Triphosphate ◽  
Papillary Muscle ◽  
Coupling Efficiency ◽  
Creatine Phosphate ◽  
Energy Utilization ◽  
Contractile Element ◽  
Cat Papillary Muscle ◽  
Net Production ◽  
Mechanochemical Coupling

The utilization of creatine phosphate (CP) and adenosine triphosphate (ATP) was studied in the iodoacetate (IAA) and nitrogen (N2)-treated cat papillary muscle. Under these conditions the net production of ATP does not occur, and the net utilization of ATP is reflected in a fall in CP concentration. The rate of energy utilization of the IAA-N2-treated cat papillary muscle resting without tension was 0.68 µmole CP/g/min. This rate was increased to 1.07 µmole/g/min when muscles were passively stretched with 2 g of tension. In a series of isometrically contracting muscles CP utilization was found to be proportional to the number of activations and the summated contractile element work. These rates of CP utilization were 0.083 µmole/g/activation and 0.0059 µmole/g-cm of work. The calculated mechanochemical coupling efficiency was 33%.

Chronic levothyroxine and acute T3 treatments enhance the amplitude and time course of uterine contractions in human

2013 ◽  
Vol 304 (5) ◽  
pp. E478-E485 ◽  
Author(s):  
Stéphanie Corriveau ◽  
Jean-Charles Pasquier ◽  
Simon Blouin ◽  
Diego Bellabarba ◽  
Éric Rousseau
Keyword(s):  
Pregnant Women ◽  
Time Course ◽  
Area Under The Curve ◽  
Isometric Tension ◽  
Control Group ◽  
Clinical Practices ◽  
Time To Peak ◽  
Uterine Contractions ◽  
Reduced Frequency

This study compares the functional consequences of levothyroxine (T4) treatment during pregnancy as well as the acute affects of triiodothyronine (T3) on spontaneous uterine contractile activities observed in vitro. Uterine biopsies were obtained from consenting women undergoing elective caesarean at term ( n = 28). Spontaneous contractile activities from T4-treated pregnant women ( n = 8) were compared with control patients ( n = 20) by isometric tension measurements. Effects of acute T3 and T4 on control tissues were also monitored. Area under the curve, amplitude, time to peak, duration, and frequency were quantified. In uterine strips from women treated for hypothyroidism, phasic uterine contractions of larger amplitude (+77%) were observed, with a prolonged duration at 90% relaxation (+138%) and reduced frequency (−55%) compared with values of the control group. The addition of exogenous T3 in vitro on control strips induced a significant increase in the duration of the contractions and a significant decrease in frequency ( P < 0.05), which partially mimics the results obtained in strips from T4-treated women. Significant modifications of contractile properties were observed in strips from pregnant women treated with levothyroxine, consistent with those observed with the addition of exogenous T3. Clinical practices of modern obstetrics should take into account the effect of thyroid hormones on uterine contractions' time course to ensure a tighter followup at the end of pregnancy to achieve safer delivery.

Substance P contracts bovine tracheal smooth muscle via activation of myosin light chain kinase

1990 ◽  
Vol 259 (2) ◽  
pp. C258-C265 ◽  
Author(s):  
M. A. Corson ◽  
J. R. Sellers ◽  
R. S. Adelstein ◽  
M. Schoenberg
Keyword(s):  
Substance P ◽  
Light Chain ◽  
Myosin Light Chain Kinase ◽  
Time Course ◽  
Myosin Light Chain ◽  
Immunoblot Analysis ◽  
Isometric Tension ◽  
Peak Tension ◽  
Tension Response

At near-threshold substance P concentrations, the isometric tension response of bovine tracheal strips is almost completely abolished by atropine, indicating mediation of contraction via substance P-stimulated release of acetylcholine from prejunctional nerve terminals. At near-maximal concentrations, the atropine-inhibited component of the tension response is less than 25%, indicating mainly direct activation. Under conditions in which activation by substance P is direct, peak tension is reached in approximately 11 min. Immunoblot analysis of the time course of phosphorylation of the 20-kDa myosin light chain (LC20) reveals incorporation of approximately 0.5 mol phosphate/mol light chain at 10 min. Two-dimensional tryptic phosphopeptide analysis of phosphorylated light chain reveals a single major phosphopeptide. The peptide migrates identically with that produced by myosin light chain kinase phosphorylation of purified tracheal myosin in vitro. Contraction stimulated by acetylcholine is more rapid, with attainment of peak tension in 2.5 min and a peak LC20 phosphorylation of 0.65 mol/mol. These results indicate that 1) substance P mediates contraction of bovine trachea both directly and indirectly, and 2) under conditions in which activation is direct, the tension and phosphorylation responses qualitatively resemble those observed with acetylcholine.

Adaptation of the rat myocardium to endurance training

1978 ◽  
Vol 44 (1) ◽  
pp. 85-89 ◽  
Author(s):  
G. Tibbits ◽  
B. J. Koziol ◽  
N. K. Roberts ◽  
K. M. Baldwin ◽  
R. J. Barnard
Keyword(s):  
Atpase Activity ◽  
Endurance Training ◽  
Papillary Muscle ◽  
Time Course ◽  
Left Ventricular ◽  
Endurance Running ◽  
Time To Peak ◽  
Membrane Bound ◽  
Isometric Twitch ◽  
Myofibril Atpase

The purpose of this study was to assess cardiac adaptation to endurance training in rats. After 11 wk of progressive treadmill exercise (1 h/day), gastrocnemius cytochrome c oxidase activity was 38% higher (P less than 0.01) in the trained (n = 20) as compared to control (n = 20) rats. Cardiac Mg2+-stimulated myofibril ATPase activity (0.308 +/- 0.012 vs. 0.324 +/- 0.006 micrometer.mg-1.min-1) did not change nor was there any change in myofibril protein concentration (60.0 +/- 1.12 vs. 59.9 +/- 0.85 mg.g-1). The isolated left ventricular papillary muscle showed no significant change in time-to-peak tension (TPT) or half-relaxation time. Tension output, however, was significantly increased with training, 2.2 +/- 0.3 vs. 1.5 +/- 0.1 g.mm-2 (P less than 0.025). Furthermore, when the papillary preparations were perfused with 0.5 mM lanthanum (La3+) to displace membrane-bound Ca2+, the time course for tension decay was significantly prolonged in the trained muscles (P less than 0.001). We conclude that endurance running of this type does not necessarily increase myofibril ATPase activity or the time course of the isometric twitch of rat papillary muscle. However, tension output per unit area does increase and this appears to be due to a greater amount of Ca2+ being made available to the contractile apparatus.

scholarly journals Active State in Heart Muscle

1967 ◽  
Vol 50 (3) ◽  
pp. 661-676 ◽  
Author(s):  
Edmund H. Sonnenblick
Keyword(s):  
Heart Muscle ◽  
Mechanical Response ◽  
Electrical Stimulus ◽  
Isometric Tension ◽  
Maximum Intensity ◽  
Active State ◽  
Tension Development ◽  
Peak Tension ◽  
Time To Peak ◽  
Time Required

The course of active state in heart muscle has been analyzed using a modified quick release method. The onset of maximum active state was found to be delayed, requiring 110–500 msec from time of stimulation, while the time to peak isometric tension required 250–650 msec. Further, the time from stimulation to peak tension was linearly related to the time required to establish maximum intensity of active state as well as to the duration of maximum active state. The duration of maximum active state was prolonged (90–220 msec), occupying most of the latter half of the rising phase of the isometric contraction. Norepinephrine (10-5 M) shortened the latency from electrical stimulus to mechanical response, accelerated the onset of maximum active state, increased its intensity, decreased its duration, and accelerated its rate of decline. These changes were accompanied by an increase in the rate of tension development and the tension developed while the time from stimulation to peak isometric tension was abbreviated. Similar findings were shown for strophanthidin (1 µg/ml) although lesser decrements in the duration of maximum active state and time to peak tension were found than with norepinephrine for similar increments in the maximum intensity of active state.

The mechanics of active muscle

1953 ◽  
Vol 141 (902) ◽  
pp. 104-117 ◽  
Keyword(s):  
Heat Production ◽  
Isometric Contraction ◽  
Time Course ◽  
Contractile Element ◽  
Outer Side ◽  
Active Muscle ◽  
In Series ◽  
The Difference ◽  
Isometric Twitch ◽  
Work Done

When a frog’s or toad’s sartorius is rapidly released during a maintained isometric contraction its tension drops immediately and is redeveloped later. The extent of release required to reduce the tension to zero is 3 to 4 % of the length of the muscle. This is much less than the 10 to 15 % originally stated by Gasser & Hill: the difference is explained. The amount of work done during release by the passive elastic element in series with the contractile element is affected only very slightly by speed of release: the damping of this element is small. The redevelopment of tension after release has been compared with the original development of tension when the stimulus began. Minor and variable differences only have been observed, and these are probably due to redistribution of length, during isometric contraction, between different regions of the muscle. At greater initial extensions the rise of tension during an isometric tetanus is much slower than at smaller initial extensions. This also is attributed to redistribution of length, within the muscle. At an initial extension not greater than that at which the developed tension is a maximum the system is ‘stable’ and the tension reaches its full value sharply: at extensions on the outer side of the maximum the system is ‘unstable’ and a long slow creep of rising tension occurs. The apparent complexity of the time-course of the heat production in an isometric twitch is discussed.

Contribution of activation-inactivation dynamics to the impairment of relaxation in hypoxic cat papillary muscle

1985 ◽  
Vol 248 (1) ◽  
pp. R54-R62 ◽  
Author(s):  
A. Pasipoularides ◽  
I. Palacios ◽  
W. Frist ◽  
S. Rosenthal ◽  
J. B. Newell ◽  
...  
Keyword(s):  
Papillary Muscle ◽  
Rate Constants ◽  
Previous Investigation ◽  
Time Course ◽  
Coupled Processes ◽  
Inactivation Kinetics ◽  
Activation Kinetics ◽  
Cat Papillary Muscle ◽  
First Order ◽  
Isometric Muscle

Previous investigation of conventional isometric twitches of normothermic cat papillary muscle has shown that hypoxia prolongs relaxation, and this prolongation is actually accentuated during early reoxygenation. Our aim was to identify how hypoxia and reoxygenation affect the coupled processes of activation and inactivation that govern the time course of internally generated contractile tension (Ti). Activation and inactivation are modeled as first-order processes with rate constants ka and ki, respectively, and the overall isometric muscle as an underdamped second-order lag system driven by Ti. The analytical expression (To) for the externally recorded tension is dominated by two exponential terms incorporating ka and ki. Accurate least-squares fits of digitized twitches to To yielded estimates of ka and ki at 1- to 3-min intervals during control oxygenation, hypoxia, and early and late reoxygenation. Results follow. Compared with control, normothermic hypoxia prolonged activation [at 15 min ka decreased 61% from control, 35.5 +/- 6 (SE) s-1, P less than 0.05] and accelerated inactivation (at 15 min, ki increased 69% from control, 6.0 +/- 0.5 s-1, P less than 0.05). In early reoxygenation (1-3 min) activation remained impaired and inactivation returned to control levels (ki decreased 16% from control, NS). In late reoxygenation (15 min) both processes reverted to control. Thus inactivation kinetics can be dissociated from activation kinetics. Impaired relaxation in normothermic hypoxia is due to prolonged activation, whereas inactivation is actually accelerated. The further impairment of relaxation in early reoxygenation is due to rapid return of inactivation to control at a time when activation is still prolonged.

Mechanical activity of mammalian heart muscle: variable onset, species differences, and the effect of caffeine

1975 ◽  
Vol 228 (1) ◽  
pp. 250-261 ◽  
Author(s):  
R Bodem ◽  
EH Sonnenblick
Keyword(s):  
Time Course ◽  
Species Differences ◽  
Mammalian Species ◽  
Mechanical Activity ◽  
Contractile Element ◽  
Time To Peak ◽  
Velocity Of Shortening ◽  
Force Peak ◽  
Mammalian Heart Muscle ◽  
Control State

The time course of the ability to shorten during contraction was measured using velocity of shortening of the contractile element corrected for length after quick releases to constant loads, in isolated papillary muscles of the cat, rabbit, dog, and rat. The ratios of time-to-peak shortening ability at preload (TTPA), to time-to-peak active force (TPF), were 0.30, 0.36, 0.32, and 0.70 in the cat, dog, rat and rabbit, respectively. When the pacing rate was increased from 12 to 60/min, peak force was augmented in the cat (36%) and rabbit (108%), while TPF decreased in the cat (by 30%) but not in the rabbit. Various inotropic interventions did not alter the ratio of TTPA/TPF in any species. However, caffeine (10mM) increased this ratio to that normally found in the rabbit, in which it was not altered. Afterloaded force-peak velocity relations of the cat, dog, and rat were curvilinear, but in the rabbit in the control state, and in the cat and dog in the presence of caffeine, these relationships tended to be linear. The differences in the time course of the ability to shorten among these mammalian species may be related to differences in excitation-contraction coupling.

scholarly journals Sodium and calcium currents in dispersed mammalian septal neurons.

1991 ◽  
Vol 97 (2) ◽  
pp. 303-320 ◽  
Author(s):  
A Castellano ◽  
J López-Barneo
Keyword(s):  
Time Constant ◽  
Time Course ◽  
Calcium Currents ◽  
Closing Time ◽  
Patch Clamp Technique ◽  
Average Value ◽  
Time To Peak ◽  
Time Courses ◽  
Fast Activation ◽  
Septal Neurons

Voltage-gated Na+ and Ca2+ conductances of freshly dissociated septal neurons were studied in the whole-cell configuration of the patch-clamp technique. All cells exhibited a large Na+ current with characteristic fast activation and inactivation time courses. Half-time to peak current at -20 mV was 0.44 +/- 0.18 ms and maximal activation of Na+ conductance occurred at 0 mV or more positive membrane potentials. The average value was 91 +/- 32 nS (approximately 11 mS cm-2). At all membrane voltages inactivation was well fitted by a single exponential that had a time constant of 0.44 +/- 0.09 ms at 0 mV. Recovery from inactivation was complete in approximately 900 ms at -80 mV but in only 50 ms at -120 mV. The decay of Na+ tail currents had a single time constant that at -80 mV was faster than 100 microseconds. Depolarization of septal neurons also elicited a Ca2+ current that peaked in approximately 6-8 ms. Maximal peak Ca2+ current was obtained at 20 mV, and with 10 mM external Ca2+ the amplitude was 0.35 +/- 0.22 nA. During a maintained depolarization this current partially inactivated in the course of 200-300 ms. The Ca2+ current was due to the activity of two types of conductances with different deactivation kinetics. At -80 mV the closing time constants of slow (SD) and fast (FD) deactivating channels were, respectively, 1.99 +/- 0.2 and 0.11 +/- 0.03 ms (25 degrees C). The two kinds of channels also differed in their activation voltage, inactivation time course, slope of the conductance-voltage curve, and resistance to intracellular dialysis. The proportion of SD and FD channels varied from cell to cell, which may explain the differential electrophysiological responses of intracellularly recorded septal neurons.

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