Myocardial energetics during isometric twitch contractions of cat papillary muscle

1979 ◽  
Vol 236 (2) ◽  
pp. H244-H253 ◽  
Author(s):  
G. Cooper
Keyword(s):  
Linear Relationship ◽  
Isometric Tension ◽  
Active Tension ◽  
Continuous Increase ◽  
Time Integral ◽  
Myocardial Energetics ◽  
Isometric Twitch ◽  
Slack Length ◽  
Energy Dependent ◽  
Complete Contraction

During myocardial tetanus, when activation is maximum and constant, there is a linear relationship throughout contraction between oxygen consumption (MVo2) and the cumulative product of active tension and time (integral of AT). The goal of this study was to determine the relation of MVo2 to integral of AT during isometric myocardial twitch contractions. Ten right ventricular cat papillary muscles were studied in a flow respirometer. MVo2 was determined during contractions unloaded from Lmax to a slack length at successive 100-ms intervals after stimulation. In contrast to the linear relationship observed during tetanus, MVo2/integral of AT varied during twitch contractions: when the muscles were made slack 100 ms after stimulation MVo2/integral of AT was 389 +/- 51 (SE) (nl of O2/mg of dry muscle)/(N of active tension/mm2.s of active tension). This value was 94 +/- 7 at peak active tension and was constant thereafter. There was a continuous increase in cumulative MVo2 as integral of AT increased; before integral of AT began, MVo2 was 0.41 +/- 0.04 (nl of O2/mg)/contraction at Lmax and 0.22 +/- 0.04 at a slack length; at peak isometric tension MVo2 was 1.84 +/- 0.19; for a complete contraction MVo2 was 2.89 +/- 0.25. These data support two concepts 1) activation energy is small and dependent on initial length and tension; and 2) integral of AT is variably energy dependent throughout the entire isometric twitch contraction.

Novel method to alter length and load in isolated mammalian cardiac myocytes

1994 ◽  
Vol 267 (4) ◽  
pp. H1619-H1629 ◽  
Author(s):  
S. J. Sollott ◽  
E. G. Lakatta
Keyword(s):  
Ventricular Myocytes ◽  
Contractile Function ◽  
Single Cells ◽  
Elastic Tube ◽  
Cell Length ◽  
Fibrin Matrix ◽  
Time Integral ◽  
Myofilament Activation ◽  
Novel Method ◽  
Slack Length

We have devised a novel technique enabling reversible gradations in the resting and contraction length of intact mammalian ventricular myocytes of up to 15-18% over slack length. Enzymatically isolated single cells are embedded in a transparent, elastic, cross-linked fibrin matrix, contained within a narrow elastic tube. Reversible gradations in cell length are produced via fibrin matrix stretch, produced by stretching the tube. Simultaneous measurement of cell length, edge motion, and indo 1 fluorescence during auxotonic contractions permits characterization of cell contractile function. Although force cannot be directly measured, the time integral of contractile force (i.e., relative contractile impulse, a contractile index that is independent of shortening constraints) is derived combining myocyte shortening and matrix loading. Relatively small degrees of myocyte stretch produce a lightly afterloaded model dominated by variations in preload in which there is parallel augmentation of shortening and contractile impulse (force) development. At higher degrees of stretch, significant afterloading is introduced, resulting in the development of an inverse relationship between shortening and impulse (approaching isometric conditions). Length-dependent Ca2+ myofilament activation and load-dependent relaxation are readily demonstrated in intact isolated mammalian ventricular myocytes.

Effect of low extracellular calcium and ryanodine on muscle contraction of the mouse during postnatal development

1991 ◽  
Vol 69 (9) ◽  
pp. 1294-1300 ◽  
Author(s):  
Josette Dangain ◽  
Ian R. Neering
Keyword(s):  
Time Course ◽  
Age Groups ◽  
Isometric Tension ◽  
Muscle Fibres ◽  
Gradual Change ◽  
Free Solution ◽  
Cobalt Ions ◽  
Contraction Speed ◽  
Single Twitch ◽  
Isometric Twitch

We have examined the effects of low Ca2+ solutions, Co2+, and ryanodine on the isometric tension and contraction speed of isolated, developing mouse EDL muscles. Twitch responses of young muscles (7–14 days postnatal) were more sensitive to lowered [Ca2+]0 than those of more fully developed muscles (22–35 days postnatal). Responses of EDL muscles from a middle-aged group (15–21 days postnatal) were intermediate between the two other groups. Overall, the time course of contraction in a single twitch was accelerated by low [Ca2+]o. Ca2+-free solution induced a 7.95 and 9.25 mV depolarization in young and "old" muscle fibres, respectively. The presence of cobalt ions (5 mM) in the Krebs solution had a similar effect as Ca2+-free Krebs in terms of reduction of the isometric twitch and tetanic tensions of EDL muscles from the various age groups. In contrast, the shortening of the contraction time seen with Ca2+-free solution did not take place following exposure to Co2+-containing solutions. Finally, young (7–14 days postnatal) muscles were less sensitive to the inhibitory action of ryanodine on the twitch compared with more fully developed muscles (22–35 days postnatal). Taken together, our results indicate that from birth to maturity, there is a gradual change in the spectrum of calcium utilization for the contractile process.Key words: mammalian muscle, calcium, development, ryanodine, contraction, sarcoplasmic reticulum.

Comparative contractile dynamics of calling and locomotor muscles in three hylid frogs.

1995 ◽  
Vol 198 (7) ◽  
pp. 1527-1538 ◽  
Author(s):  
D McLister ◽  
E D Stevens ◽  
J P Bogart
Keyword(s):  
Relaxation Time ◽  
Isometric Tension ◽  
Hyla Versicolor ◽  
Hyla Chrysoscelis ◽  
Shortening Velocity ◽  
Call Production ◽  
Mating Call ◽  
Locomotor Muscles ◽  
Force Velocity ◽  
Isometric Twitch

Isometric twitch and tetanus parameters, force-velocity curves, maximum shortening velocity (Vmax) and percentage relaxation between stimuli (%R) across a range of stimulus frequencies were determined for a muscle used during call production (the tensor chordarum) and a locomotor muscle (the sartorius) for three species of hylid frogs, Hyla chrysoscelis, H. versicolor and H. cinerea. The call of H. chrysoscelis has a note repetition rate (NRR) approximately twice as fast as the call of H. versicolor (28.3, 42.5 and 56.8 notes s-1 for H. chrysoscelis and 14.8, 21.1 and 27.4 notes s-1 for H. versicolor at 15, 20 and 25 degrees C, respectively). Hyla cinerea calls at a very slow NRR (Approximately 3 notes s-1 at 25 degrees C). Hyla versicolor evolved from H. chrysoscelis via autopolyploidy, so the mating call of H. chrysoscelis is presumably the ancestral mating call of H. versicolor. For the tensor chordarum of H. chrysoscelis, H. versicolor and H. cinerea at 25 degrees C, mean twitch duration (19.2, 30.0 and 52.9 ms, respectively), maximum isometric tension (P0; 55.0, 94.4 and 180.5 kN m-2, respectively), tetanic half-relaxation time (17.2, 28.7 and 60.6 ms, respectively) and Vmax (4.7, 5.2 and 2.1 lengths s-1, respectively) differed significantly (P < 0.05) among all three species. The average time of tetanic contraction to half-P0 did not differ significantly between H. chrysoscelis (14.5 ms) and H. versicolor (15.8 ms) but was significantly longer for H. cinerea (52.6 ms). At 25 degrees C, Vmax differed significantly among the sartorius muscles of H. chrysoscelis, H. versicolor and H. cinerea (5.2, 7.0 and 9.8 lengths s-1, respectively) but mean twitch duration (29.5, 32.2 and 38.7 ms, respectively), P0 (252.2, 240.7 and 285.1 kN m-2, respectively) and tetanic half-relaxation time (56.3, 59.5 and 60.7 ms, respectively) did not differ significantly. The average time of contraction to half-P0 did not differ significantly between H. chrysoscelis (23.7 ms) and H. versicolor (22.9 ms) but was significantly shorter for H. cinerea (15.6 ms). The only consistent contractile differences found in this study between the calling muscle and locomotor muscle of H. chrysoscelis, H. versicolor and H. cinerea were that the calling muscles generated less tension and their force-velocity relationship was much more linear. These differences may be attributable to ultrastructural differences between calling and locomotor muscles.(ABSTRACT TRUNCATED AT 400 WORDS)

Myosin light chain phosphorylation and tension potentiation in mouse skeletal muscle

1989 ◽  
Vol 257 (5) ◽  
pp. C1012-C1019 ◽  
Author(s):  
B. M. Palmer ◽  
R. L. Moore
Keyword(s):  
Skeletal Muscle ◽  
Light Chain ◽  
Force Production ◽  
Quantitative Relationship ◽  
Isometric Tension ◽  
Contractile Element ◽  
Phosphate Content ◽  
Experimental Conditions ◽  
Intact Mouse ◽  
Isometric Twitch

In intact mammalian fast-twitch skeletal muscle, a quantitative relationship exists between the phosphate content of myosin P-light chain (PLC) and the extent of isometric twitch tension potentiation. It has been proposed that PLC phosphorylation causes twitch potentiation in intact muscle by rendering the contractile element more sensitive to activation by Ca2+. If this hypothesis is correct, then an obligatory experimental outcome is that the slope of the "PLC phosphate vs. isometric tension potentiation (ITP)" relationship should increase when the amount of Ca2+ available to activate the contractile element is decreased. Intact mouse extensor digitorum longus muscles were studied in the absence and presence of sodium dantrolene, an agent that partially inhibits Ca2+ release from the sarcoplasmic reticulum (SR). Treatment of muscles with dantrolene produced a 73% reduction in isometric twitch tension and an approximately threefold increase in the slope of the PLC phosphate vs. ITP relationship. Under experimental conditions that produced fused, tetanic contractions equal to 0.52, 0.72, 0.94, and 1.0 force production, contraction-induced changes in PLC phosphate content were directly proportional to the extent of contractile element activation, whereas the extent of ITP was inversely proportional to the extent of contractile element activation. These data indicate that the slope of the PLC phosphate vs. ITP relationship varies inversely as a function of the amount of Ca2+ that is released from the SR to activate the contractile element during both twitch and fused, submaximal tetanic contractions. Furthermore, these findings support the hypothesis that ITP in intact skeletal muscle is due to a PLC phosphorylation-induced sensitization of the contractile element to activation by Ca2+.

scholarly journals The Effects of Temperature upon Contraction and Ionic Exchange in Rabbit Ventricular Myocardium

1968 ◽  
Vol 52 (4) ◽  
pp. 682-713 ◽  
Author(s):  
G. A. Langer ◽  
A. J. Brady
Keyword(s):  
Ventricular Myocardium ◽  
Isometric Tension ◽  
Active State ◽  
Ionic Exchange ◽  
Active Tension ◽  
Tension Development ◽  
Mechanical Responses ◽  
Abrupt Changes ◽  
Rabbit Ventricular Myocardium ◽  
Temperature Rate

The mechanical responses (active and resting tension, dP/dt, TPT) and ionic exchange characteristics (Ca++, K+, Na+) which follow upon a variation in temperature, rate, and [K+]0 were studied in the rabbit papillary muscle and arterially perfused rabbit interventricular setpum. Abrupt changes in temperature provided a means of separating the contributions of rate of development (intensity) of active state and duration of active state to total active tension development (approximated by isometric tension). Threefold changes in duration of active state with proportional changes in active tension can be induced without evidence for alteration of Ca++, K+, or Na+ exchange. Abrupt cooling produced a moderate (∼15%) increase of dP/dt which suggests an augmentation of active state intensity. Evidence is presented to suggest that this increase of dP/dt is based upon an increase in membrane Ca++ concentration which occurs secondary to inhibition of active Na+ transport. The alterations in ionic exchange and active state produced by variation of temperature are discussed in terms of a five-component control system.

scholarly journals Reciprocal actions of constrictor prostanoids and superoxide in chronic hypoxia-induced pulmonary hypertension: roles of EETs

2019 ◽  
Vol 9 (4) ◽  
pp. 204589401989594
Author(s):  
Sharath Kandhi ◽  
Norah Alruwaili ◽  
Michael S Wolin ◽  
Dong Sun ◽  
An Huang
Keyword(s):  
Pulmonary Hypertension ◽  
Chronic Hypoxia ◽  
Pulmonary Arteries ◽  
Systolic Pressure ◽  
Isometric Tension ◽  
Ejection Time ◽  
Velocity Time Integral ◽  
Ventricular Systolic Pressure ◽  
Time Integral ◽  
Underlying Mechanisms

Epoxyeicosatrienoic acids (EETs) are synthesized from arachidonic acid by CYP/epoxygenase and metabolized by soluble epoxide hydrolase (sEH). Roles of EETs in hypoxia-induced pulmonary hypertension (HPH) remain elusive. The present study aimed to investigate the underlying mechanisms, by which EETs potentiate HPH. Experiments were conducted on sEH knockout (sEH-KO) and wild type (WT) mice after exposure to hypoxia (10% oxygen) for three weeks. In normal/normoxic conditions, WT and sEH-KO mice exhibited comparable pulmonary artery acceleration time (PAAT), ejection time (ET), PAAT/ET ratio, and velocity time integral (VTI), along with similar right ventricular systolic pressure (RVSP). Chronic hypoxia significantly reduced PAAT, ET, and VTI, coincided with an increase in RVSP; these impairments were more severe in sEH-KO than WT mice. Hypoxia elicited downregulation of sEH and upregulation of CYP2C9 accompanied with elevation of CYP-sourced superoxide, leading to enhanced pulmonary EETs in hypoxic mice with significantly higher levels in sEH-KO mice. Isometric tension of isolated pulmonary arteries was recorded. In addition to downregulation of eNOS-induced impairment of vasorelaxation to ACh, HPH mice displayed upregulation of thromboxane A2 (TXA2) receptor, paralleled with enhanced pulmonary vasocontraction to a TXA2 analog (U46619) in an sEH-KO predominant manner. Inhibition of COX-1 or COX-2 significantly prevented the enhancement by ∼50% in both groups of vessels, and the remaining incremental components were eliminated by scavenging of superoxide with Tiron. In conclusion, hypoxia-driven increases in EETs, intensified COXs/TXA2 signaling, great superoxide sourced from activated CYP2C9, and impaired NO bioavailability work in concert, to potentiate HPH development.

Active state of normal and dystrophic mouse muscle

1976 ◽  
Vol 230 (4) ◽  
pp. 1138-1147 ◽  
Author(s):  
RA Sabbadini ◽  
RJ Baskin
Keyword(s):  
Total Duration ◽  
Order Rate Constant ◽  
Isometric Tension ◽  
Active State ◽  
Dystrophic Muscle ◽  
Mouse Muscle ◽  
Rate Of Decay ◽  
Isometric Twitch ◽  
Kinetics Of ◽  
Elastic Elements

Computer-controlled quick releases were used to determine the kinetics of active state tension decay in normal and dystrophic EDL muscles of the mouse (129/Re-J). Also included are measurements of the duration of the active state plateau, isometric twitch and tetanus parameters, and the stress-strain properties of the elastic elements. Alterations in the isometric tension characteristics of dystrophic muscles confirm previous investigations and indicate that dystrophic sarcomeres have a diminished ability to shorten and produce tension. The compliance of the series-elastic elements is not changed, whereas a 50% reduction in the interanl extension of the series elements is noted for dystrophic muscle. The rate of decay and maximum intensity (Po) of active state decay is reduced 60-70% in dystrophic muscles. The first-order rate constant and the total duration of the active state are not altered. These results are discussed in terms of the possible involvement of the contractile proteins and the sarcoplasmic reticulum in determining active state deficits.

Measurement of calcium influx in tethered rings of rabbit aorta under tension

1985 ◽  
Vol 249 (3) ◽  
pp. H470-H476
Author(s):  
M. M. Gleason ◽  
P. H. Ratz ◽  
S. F. Flaim
Keyword(s):  
Steady State ◽  
Contractile Response ◽  
Calcium Influx ◽  
Rabbit Aorta ◽  
Isometric Tension ◽  
Passive Tension ◽  
Active Tension ◽  
Experimental Conditions ◽  
Response Data ◽  
Passive Stretch

Calcium (Ca) influx in vascular smooth muscle is routinely measured in untethered preparations not under passive stretch, and Ca influx data are correlated with data for steady-state isometric tension obtained under parallel conditions from tethered preparations under passive stretch. The validity of this method was tested by simultaneous measurement of Ca influx and tension in tethered rings of rabbit thoracic aorta. Ca influx (45Ca 3-min pulse) and tension were measured at 3 and 30 min after norepinephrine (NE) or KCl and under control (no agonist) conditions. Active tension was significantly altered by variations in passive tension. Ca influx was unaffected by passive tension under control, NE, or KCl conditions, and results were similar at 3 and 30 min. The results confirm the validity of correlating Ca influx data from untethered rings with steady-state contractile response data obtained from tethered rings under similar experimental conditions.

scholarly journals Effects of partial extraction of troponin complex upon the tension-pCa relation in rabbit skeletal muscle. Further evidence that tension development involves cooperative effects within the thin filament.

1986 ◽  
Vol 87 (5) ◽  
pp. 761-774 ◽  
Author(s):  
R L Moss ◽  
J D Allen ◽  
M L Greaser
Keyword(s):  
Functional Groups ◽  
Thin Filament ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Isometric Tension ◽  
Original Position ◽  
Active Tension ◽  
Tension Development ◽  
Psoas Muscles ◽  
Partial Extraction

Partial extraction of troponin C (TnC) decreases the Ca2+ sensitivity of tension development in mammalian skinned muscle fibers (Moss, R. L., G. G. Giulian, and M. L. Greaser. 1985. Journal of General Physiology. 86:585), which suggests that Ca2+-activated tension development involves molecular cooperativity within the thin filament. This idea has been investigated further in the present study, in which Ca2+-insensitive activation of skinned fibers from rabbit psoas muscles was achieved by removing a small proportion of total troponin (Tn) complexes. Ca2+-activated isometric tension was measured at pCa values (i.e., -log[Ca2+]) between 6.7 and 4.5: (a) in control fiber segments, (b) in the same fibers after partial removal of Tn, and (c) after recombination of Tn. Tn removal was accomplished using contaminant protease activity found in preparations of LC2 from rabbit soleus muscle, and was quantitated using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and scanning densitometry. Partial Tn removal resulted in the development of a Ca2+-insensitive active tension, which varied in amount depending on the duration of the extraction, and concomitant decreases in maximal Ca2+-activated tensions. In addition, the tension-pCa relation was shifted to higher pCa values by as much as 0.3 pCa unit after Tn extraction. Readdition of Tn to the fiber segments resulted in the reduction of tension in the relaxing solution to control values and in the return of the tension-pCa relation to its original position. Thus, continuous Ca2+-insensitive activation of randomly spaced functional groups increased the Ca2+ sensitivity of tension development in the remaining functional groups along the thin filament. In addition, the variation in Ca2+-insensitive active tension as a function of Tn content after extraction suggests that only one-third to one-half of the functional groups within a thin filament need to be activated for complete disinhibition of that filament to be achieved.

scholarly journals The active tension-length curve of vascular smooth muscle related to its cellular components.

1979 ◽  
Vol 74 (1) ◽  
pp. 85-104 ◽  
Author(s):  
M J Mulvany ◽  
D M Warshaw
Keyword(s):  
Smooth Muscle ◽  
Vascular Smooth Muscle ◽  
Length Change ◽  
Isometric Tension ◽  
Cellular Damage ◽  
Active Tension ◽  
Contractile Apparatus ◽  
Light Microscopic Observation ◽  
Direct Light ◽  
Cellular Components

The active and passive isometric tension-length (internal circumference) relation of vascular smooth muscle has been investigated using a 100-200-micron lumen diameter artery from the rat mesenteric bed. Conditions were established under which maximal activation was obtained at all lengths. Below L0 (the length at which maximum tension, delta T0, was developed) the active tension fell with decreasing length along a line which extrapolated to 0.38 L0; below 1.1 L0 the relation was reversible regardless of the protocol used. Above L0 the active tension fell linearly with increasing length along a line which extrapolated to zero tension at 1.82 L0. At the longer lengths investigated (up to 1.6 L0) the passive tension upon which the active responses were superimposed was as high as 4.4 delta T0. However, measurements of the dynamic characteristics of the preparation (with a time resolution of 2 ms) suggest that the active tension measured is nevertheless a measure of the active properties of the contractile apparatus. Direct light microscopic observation of the effect of length change on the cells within the walls of the preparation showed that changes in vessel length produced, on average, the same percentage change in cell length. Histological examination showed no signs of cell destruction following large extensions. The results suggest that the decrease in tension with extension above L0 is due to changes in the properties of the contractile apparatus, rather than to cellular damage.

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