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

1968 ◽  
Vol 52 (3) ◽  
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+]o 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 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.

Calcium-dependent resistance to stretch and stress relaxation in resting smooth muscles

1976 ◽  
Vol 231 (5) ◽  
pp. 1501-1508 ◽  
Author(s):  
MJ Siegman ◽  
TM Butler ◽  
SU Mooers ◽  
RE Davies
Keyword(s):  
Stress Relaxation ◽  
Smooth Muscles ◽  
Muscle Length ◽  
Taenia Coli ◽  
Tetraacetic Acid ◽  
Active Tension ◽  
Tension Development ◽  
Calcium Dependent ◽  
Mechanical Responses ◽  
State Force

Mechanical responses to stretch and length-tension relations were examined in rabbit taenia coli, mesenteric vein, aorta, and myometrium and in guinea pig taenia coli made atonic by incubation in Krebs-bicarbonate solution at 20-22 degrees C. When stretched 10% of the length at which maximum active tension is observed (Lo) in 0.5 s, the muscles showed a transient large force (resistance to stretch) that decayed to a new constant level within minutes (stress relaxation). The resistance to stretch decreased markedly in Ca2+-free [disodium ethylene glycolbis-(beta-aminoethylether)-N,N-tetraacetic acid (EGTA)] Krebs but was restored in normal Krebs solution. Calcium removal did not affect the passive length-tension curve. The absence of Ca2+ did not change the steady-state force maintained by the muscle; thus stretch resistance was not due to tone. Blockade of Ca2+ influx associated with electrical activity with 5-[3,4-dimethoxyphenethyl)methylamino]-2-(3,4,5-trimethoxyphenyl-2-isoprop ylvaleronitrile (D-600) and of Ca2+ release from intracellular sites with thymol (1 mM) completely blocked contraction but did not alter the responses to stretch, thus dissociating the responses to stretch from these processes and tension development. The Ca2+-dependent stress relaxation showed a dependence on muscle length similar to that for active tension development. Except at long muscle lengths, where connective tissue markedly affects length-tension relations, most of the "viscoelasticity" of these smooth muscles is dependent on calcium and may be largely due to the straining of crossbridges that are attached, but not generating a net force, in the resting state.

Influence of poststimulation potentiation and heart rate on the fetal lamb heart

1975 ◽  
Vol 229 (2) ◽  
pp. 318-323 ◽  
Author(s):  
SE Kirkpatrick ◽  
J Naliboff ◽  
PT Pitlick ◽  
WF Friedman
Keyword(s):  
Heart Rate ◽  
Recovery Period ◽  
Control Level ◽  
Ventricular Myocardium ◽  
Left Ventricular ◽  
Isometric Tension ◽  
Atrial Pacing ◽  
Tension Development ◽  
Time To Peak ◽  
Fetal Lamb

Isolated cardiac muscle techniques and studies of the chronically instrumented fetal lamb heart were employed to evaluate the ability of fetal myocardium to exhibit poststimulation potentiation. Isometric tension development and the response to paired electrical stimulation were significantly reduced in isolated fetal ventricular myocardium when compared to the adult (P less than 0.001). As in the adult, increasing stimulation frequency raised fetal isometric tension via an increase in the rate of rise of tension development in the presence of reduction in time-to-peak tension. In seven fetal lambs the left ventricle was chronically instrumented with endocardial ultrasonic crystals and a high-fidelity micromanometer. After a 2-wk recovery period, heart rate was increased by atrial pacing from an average control level of 150 to 300 beats/min. Left ventricular dP/dt increased progressively and then fell beyond a heart rate of 270/min. When comparable pre- and immediate postpacing beats were analyzed, a step-wise increase in the velocity of left ventricular shortening and the mean rate of circumferential fiber shortening was observed in association with an increase in the extent of shortening. Thus, increases in the frequency of contraction exert a significant positive inotropic effect on the fetal heart.

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 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.

scholarly journals Studies on conformation of F-actin in muscle fibers in the relaxed state, rigor, and during contraction using fluorescent phalloidin.

1983 ◽  
Vol 97 (6) ◽  
pp. 1663-1667 ◽  
Author(s):  
E Prochniewicz-Nakayama ◽  
T Yanagida ◽  
F Oosawa
Keyword(s):  
Conformational Changes ◽  
Isometric Contraction ◽  
Fluorescein Isothiocyanate ◽  
Isometric Tension ◽  
Molar Ratio ◽  
Active Tension ◽  
Polarized Fluorescence ◽  
Tension Development ◽  
Rigor Solution ◽  
Glycerinated Muscle

F-actin in a glycerinated muscle fiber was specifically labeled with fluorescent phalloidin-(fluorescein isothiocyanate) FITC complex at 1:1 molar ratio. Binding of phalloidin-FITC to F-actin affected neither contraction of the fiber nor its regulation by Ca2+. Comparison of polarized fluorescence from phalloidin-FITC bound to F-actin in the relaxed state, rigor, and during isometric contraction of the fiber revealed that the changes in polarization accompanying activation are quantitatively as well as qualitatively different from those accompanying transition of the fiber from the relaxed state to rigor. The extent of the changes of polarized fluorescence during isometric contraction increased with decreasing ionic strength, in parallel with increase in isometric tension. On the other hand, polarized fluorescence was not affected by addition of ADP or by stretching of the fiber in rigor solution. It is concluded from these observations that conformational changes in F-actin are involved in the process of active tension development.

scholarly journals Cellular Uncoupling During Ischemia in Hypertrophied and Failing Rabbit Ventricular Myocardium

Circulation ◽  
1998 ◽  
Vol 97 (17) ◽  
pp. 1724-1730 ◽  
Author(s):  
Lukas R. C. Dekker ◽  
Han Rademaker ◽  
Jessica T. Vermeulen ◽  
Tobias Opthof ◽  
Ruben Coronel ◽  
...  
Keyword(s):  
Ventricular Myocardium ◽  
Rabbit Ventricular Myocardium
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