Afterload-induced homeometric autoregulation in isolated cardiac muscle

1976 ◽  
Vol 231 (2) ◽  
pp. 545-550 ◽  
Author(s):  
TC Donald ◽  
DM Peterson ◽  
AA Walker ◽  
LL Hefner
Keyword(s):  
Steady State ◽  
Right Ventricle ◽  
Cardiac Muscle ◽  
Isometric Contraction ◽  
Calcium Level ◽  
Opposite Effect ◽  
Higher Temperature ◽  
Homeometric Autoregulation ◽  
Mammalian Ventricle

Pressure-induced homeometric autoregulation (HAR) has been demonstrated by many investigators in the mammalian ventricle; In isolated cardiac muscle, however, several investigators have reported the opposite effect (anti-HAR); namely, that the first beat after a transition from isotonic to isometric contraction is the most forceful, with a decline over several beats to a steady state. In the present study we find that trabeculae from the canine right ventricle demonstrate either HAR or anti-HAR, depending on the rate of stimulation, the calcium level, and the temperature. Higher calcium, higher temperature, and lower rate of stimulation produce either less HAR or more anti-HAR. When only temperature and rate of stimulation are varied, in each muscle there is a unique rate for each temperature above which HAR occurs and below which anti-HAR occurs.

Preload-adjusted maximal power of right ventricle: contribution of end-systolic P-V relation intercept

2002 ◽  
Vol 283 (4) ◽  
pp. H1681-H1687 ◽  
Author(s):  
Patrick Segers ◽  
H. Alex Leather ◽  
Pascal Verdonck ◽  
Yuan-Yuan Sun ◽  
Patrick F. Wouters
Keyword(s):  
Steady State ◽  
Pulmonary Artery ◽  
Right Ventricle ◽  
Right Ventricular ◽  
Pulmonary Artery Pressure ◽  
Strong Relationship ◽  
Maximal Power ◽  
State Data ◽  
End Diastolic Volume ◽  
Inotropic Stimulation

To assess whether preload-adjusted maximal power (PAMP), which is calculated asW˙max/V[Formula: see text] (whereW˙max is maximal power and Ved is end-diastolic volume with β = 2) is an index of right ventricular (RV) contractility, we measured RV pressure (P) and volume (V) and pulmonary artery pressure and flow in 10 dogs at baseline and after inotropic stimulation. PAMP was derived from steady-state data, whereas the slope ( E es) and intercept (Vd) of the end-systolic P-V relationship were derived from data obtained during vena caval occlusion. Inotropic stimulation increased E es (from 0.96 ± 0.25 to 1.62 ± 0.28 mmHg/ml; P < 0.001) and Vd (from −3.0 ± 17.2 to 12.4 ± 10.8 ml; P < 0.05) but not PAMP (from 0.24 ± 0.10 to 0.36 ± 0.22 mW/ml2; P = 0.09). We found a strong relationship between the optimal β-factor for preload adjustment and Vd. A corrected PAMP, PAMPc= W˙max/(Ved − Vd)2, which incorporated the Vddependency, was sensitive to the inotropic changes (from 0.23 ± 0.12 to 0.54 ± 0.17 mW/ml2; P < 0.001) with a good correlation with E es( r = 0.88; P < 0.001).

scholarly journals Sarcoplasmic reticulum and endothelium independently regulate venous smooth muscle [Ca2+]iand contraction

1999 ◽  
Vol 277 (2) ◽  
pp. H749-H755
Author(s):  
Régent Laporte ◽  
Ismail Laher
Keyword(s):  
Smooth Muscle ◽  
Steady State ◽  
Sarcoplasmic Reticulum ◽  
Salt Solution ◽  
Isometric Contraction ◽  
Cyclopiazonic Acid ◽  
Physiological Salt Solution ◽  
Sustained Contraction ◽  
Facial Vein ◽  
State Increase

In rings of rabbit facial vein (RFV), depletion of sarcoplasmic reticulum (SR) Ca2+ by caffeine abolished the subsequent isometric contraction to 25 mM K+ physiological salt solution (25K-PSS). However, the associated steady-state increase of smooth muscle intracellular free Ca2+concentration ([Ca2+]i), measured using fura PE3 and cuvette photometry, was not altered. Treatment with the specific SR Ca2+ pump inhibitor cyclopiazonic acid (30 μM) after caffeine-induced SR Ca2+ depletion restored and greatly augmented the 25K-PSS-induced contraction. This suggests that SR Ca2+ depletion leads to a dissociation of K+-induced [Ca2+]iincrease from contraction that was dependent on Ca2+ pump-mediated SR Ca2+ uptake. Endothelium removal augmented the 25K-PSS-induced [Ca2+]iincrease after caffeine-induced SR Ca2+ depletion. However, this was associated with only a small and transient contraction. Exposure of endothelium-denuded RFV to cyclopiazonic acid after caffeine-induced SR Ca2+ depletion further amplified the 25K-PSS-induced [Ca2+]iincrease, which was associated with a large and sustained contraction. However, the latter [Ca2+]iincrease was still higher than in endothelium-intact RFV. This suggests that the endothelium dampens the [Ca2+]irise associated with K+-induced Ca2+ influx, but independently of Ca2+ pump-mediated SR Ca2+ uptake.

scholarly journals Myosin types and fiber types in cardiac muscle. I. Ventricular myocardium.

1981 ◽  
Vol 88 (1) ◽  
pp. 226-233 ◽  
Author(s):  
S Sartore ◽  
L Gorza ◽  
S Pierobon Bormioli ◽  
L Dalla Libera ◽  
S Schiaffino
Keyword(s):  
Left Ventricle ◽  
Right Ventricle ◽  
Cardiac Muscle ◽  
Muscle Fibers ◽  
Ventricular Myocardium ◽  
Rabbit Heart ◽  
Fiber Types ◽  
Ventricular Muscle ◽  
The Right ◽  
Atrial Myosin

Antisera against bovine atrial myosin were raised in rabbits, purified by affinity chromatography, and absorbed with insolubilized ventricular myosin. Specific anti-bovine atrial myosin (anti-bAm) antibodies reacted selectively with atrial myosin heavy chains, as determined by enzyme immunoassay combined with SDS-gel electrophoresis. In direct and indirect immunofluorescence assay, anti-bAm was found to stain all atrial muscle fibers and a minor proportion of ventricular muscle fibers in the right ventricle of the bovine heart. In contrast, almost all muscle fibers in the left ventricle were unreactive. Purkinje fibers showed variable reactivity. In the rabbit heart, all atrial muscle fibers were stained by anti-bAm, whereas ventricular fibers showed a variable response in both the right and left ventricle, with a tendency for reactive fibers to be more numerous in the right ventricle and in subepicardial regions. Diversification of fiber types with respect to anti-bAm reactivity was found to occur during late stages of postnatal development in the rabbit heart and to be influenced by thyroid hormone. All ventricular muscle fibers became strongly reactive after thyroxine treatment, whereas they became unreactive or poorly reactive after propylthiouracil treatment. These findings are consistent with the existence of different ventricular isomyosins whose relative proportions can vary according to the thyroid state. Variations in ventricular isomyosin composition can account for the changes in myosin Ca2+-activated ATPase activity previously observed in cardiac muscle from hyper- and hypothyroid animals and may be responsible for the changes in the velocity of contraction of ventricular myocardium that occur under these conditions. The differential distribution of ventricular isomyosins in the normal heart suggests that fiber types with different contractile properties may coexist in the ventricular myocardium.

The Investigation of Creep Behavior for NiAl-28Cr-5.5Mo-0.5Hf-0.02wt.%P Alloy at High Temperature

2011 ◽  
Vol 279 ◽  
pp. 28-32
Author(s):  
Guang Ye Zhang ◽  
Dong Wen Ye ◽  
Jin Lin Wang ◽  
You Ming Chen ◽  
Long Fei Liu ◽  
...  
Keyword(s):  
Steady State ◽  
High Temperature ◽  
Creep Behavior ◽  
Fracture Behavior ◽  
Primary Creep ◽  
Dislocation Climb ◽  
Steady State Creep ◽  
Creep Fracture ◽  
Creep Mechanisms ◽  
Higher Temperature

The Microstructure and creep behavior for NiAl-28Cr-5.5Mo-0.5Hf-0.02wt.%P alloy at high temperature have been investigated in this paper. The results reveal that the high temperature creep behavior of the NiAl-28Cr-5.5Mo-0.5Hf-0.02wt.%P alloy is characterized by transient primary creep and dominant steady-state creep as well as ternary creep behavior. The primary creep can be described by Garofalo equation and the steady-state creep can be depicted by Dorn equation. The creep mechanisms are viscous glide of dislocations at lower and middle testing temperatures and dislocation climb at higher temperature. No change of the microstructure for the testing alloy indicates that the creep fracture is controlled by the formation and propagation of cavities and cracks, and the creep fracture behavior obeys Monk man-Grant relationship.

scholarly journals Effect of Active Lengthening and Shortening on Small-Angle X-ray Reflections in Skinned Skeletal Muscle Fibres

2021 ◽  
Vol 22 (16) ◽  
pp. 8526
Author(s):  
Venus Joumaa ◽  
Ian C. Smith ◽  
Atsuki Fukutani ◽  
Timothy R. Leonard ◽  
Weikang Ma ◽  
...  
Keyword(s):  
Steady State ◽  
Small Angle ◽  
Isometric Contraction ◽  
Sarcomere Length ◽  
Force Enhancement ◽  
X Ray ◽  
Cross Bridge ◽  
Residual Force ◽  
Residual Force Enhancement ◽  
Cross Bridges

Our purpose was to use small-angle X-ray diffraction to investigate the structural changes within sarcomeres at steady-state isometric contraction following active lengthening and shortening, compared to purely isometric contractions performed at the same final lengths. We examined force, stiffness, and the 1,0 and 1,1 equatorial and M3 and M6 meridional reflections in skinned rabbit psoas bundles, at steady-state isometric contraction following active lengthening to a sarcomere length of 3.0 µm (15.4% initial bundle length at 7.7% bundle length/s), and active shortening to a sarcomere length of 2.6 µm (15.4% bundle length at 7.7% bundle length/s), and during purely isometric reference contractions at the corresponding sarcomere lengths. Compared to the reference contraction, the isometric contraction after active lengthening was associated with an increase in force (i.e., residual force enhancement) and M3 spacing, no change in stiffness and the intensity ratio I1,1/I1,0, and decreased lattice spacing and M3 intensity. Compared to the reference contraction, the isometric contraction after active shortening resulted in decreased force, stiffness, I1,1/I1,0, M3 and M6 spacings, and M3 intensity. This suggests that residual force enhancement is achieved without an increase in the proportion of attached cross-bridges, and that force depression is accompanied by a decrease in the proportion of attached cross-bridges. Furthermore, the steady-state isometric contraction following active lengthening and shortening is accompanied by an increase in cross-bridge dispersion and/or a change in the cross-bridge conformation compared to the reference contractions.

Dissolution of carbon from coke and char in liquid Fe-C alloys

2018 ◽  
Vol 1 (92) ◽  
pp. 22-27
Author(s):  
X. Xing ◽  
S. Jahanshahi ◽  
J. Yang ◽  
O. Ostrovski
Keyword(s):  
Steady State ◽  
Design Methodology ◽  
Mineral Matter ◽  
Carbonaceous Materials ◽  
Carbon Dissolution ◽  
Initial Carbon ◽  
Higher Temperature ◽  
Far From Equilibrium ◽  
Metallurgical Processes ◽  
Different Origin

Purpose: The aim of this paper was to study dissolution of carbon from carbonaceous materials of different origin with different morphology, microtexture and microstructure in the liquid Fe-C alloys. Design/methodology/approach: The dissolution of carbon from coke, char and glassy carbon in the molten Fe-C alloy (initial carbon concentration 2.46 wt.%) at 1350°C was measured and compared with that from graphite. The dissolution of carbon from demineralised coke and char in the Fe-C solution was also examined to study the effect of mineral matter on the carbon dissolution. Findings: The concentration of carbon in the Fe-C solution dissolved from graphite was higher than that from coke and char. Demineralisation of coke and char had a significant effect on the carbon dissolution. The concentration of carbon dissolved from demineralised coke and char in the Fe-C alloy approached the solubility of graphite in this alloy under the same conditions. Results obtained in this work confirmed that ash has a strong effect on the carbon dissolution. Research limitations/implications: Investigations in this paper were conducted at 1350°C. At higher temperatures; (1) the degree of coke and char graphitisation increases changing the microstructure of carbonaceous materials; (2) the ash can melt, and (3) some of the metal oxides in the ash can be reduced by carbon to the metal phase, thereby weakening the effect of ash on the carbon dissolution. Demineralisation of coke was incomplete; it reached 70-80% with some effect on the carbon dissolution. The effect of ash composition and further coke demineralisation on the carbon dissolution at higher temperature will be investigated in the future study. Originality/value: This study demonstrated that dissolution of carbon from coke and char was strongly affected by ash. Reactions of dissolution of carbon from coke and char in liquid Fe-C alloy reached a steady state within 1-2 hours. In this state, the coke/char – metal system was far from equilibrium. The “apparent” activity which can be assigned to carbon in the steady state is below one for graphite with significant implications for metallurgical processes.

scholarly journals Contractile Strength during Variable Heart Duration Is Species and Preload Dependent

2011 ◽  
Vol 2011 ◽  
pp. 1-6 ◽  
Author(s):  
Carlos A. A. Torres ◽  
Paul M. L. Janssen
Keyword(s):  
Steady State ◽  
Right Ventricle ◽  
Cardiac Contractility ◽  
Beagle Dogs ◽  
Fixed Rate ◽  
Optimal Length ◽  
Average Force ◽  
Before And After ◽  
The Right ◽  
Nonsignificant Decrease

We investigate the effect of beat-to-beat variability on cardiac contractility. Cardiac trabeculae were isolated from the right ventricle of rabbits and beagle dogs and stimulated to isometrically contract, alternating between fixed steady state versus variable interbeat intervals. Trabeculae were stimulated at physiologically relevant frequencies for each species (dog 1 and 4 Hz; rabbit 2 and 4 Hz) intercalating fixed periods with 40% variability. A subset of the trabeculae (at 90% of optimal length) was stretched prior to stimulation between 5 and 13% and stimulated at the same frequencies with a fixed versus 40% variation. Fixed rate response at the same base frequency was measured before and after each variable period and the average force reported. In canine preparations no change in force was observed as a result of the imposed variability in beat-to-beat duration. In the rabbit, we observed a nonsignificant decrease in force between fixed and variable pacing at both 2 and 4 Hz (n= 8) when 40% variability was introduced. When a 5% and 13% stretch was applied, the correlation coefficient sharply increased, indicating a more prominent impact of the prebeat duration on the following cycle with higher preload.

Regional myoglobin concentration in the myocardium of the dog

1968 ◽  
Vol 46 (6) ◽  
pp. 908-910 ◽  
Author(s):  
Naomi M. Anderson ◽  
Giorgio Brandi
Keyword(s):  
Blood Flow ◽  
Right Ventricle ◽  
Cardiac Muscle ◽  
Chronic Hypoxia ◽  
Left Ventricular ◽  
Left Ventricular Wall ◽  
Ventricular Wall

It has been demonstrated previously that chronic hypoxia leads to an increase in myoglobin concentration. Evidence of differences in [Formula: see text] and blood flow in deep and superficial layers of cardiac muscle suggest that there might be a corresponding difference in myoglobin concentration in the myocardium. Results showed an even distribution of myoglobin concentration in inner and outer layers of the left ventricular wall, right ventricle, and septum, suggesting that [Formula: see text] in inner layers of the left ventricular wall is not sufficiently diminished to stimulate an increase in myoglobin concentration.

Steady State Conduction Behaviour of Liquid Crystalline Polyurethane

2013 ◽  
Vol 856 ◽  
pp. 210-214
Author(s):  
Jitender Kumar Quamara ◽  
Satish Kumar Mahna ◽  
Sohan Lal ◽  
Pushkar Raj
Keyword(s):  
Activation Energy ◽  
Steady State ◽  
Temperature Region ◽  
Liquid Crystalline ◽  
Ionic Conduction ◽  
Schottky Type ◽  
Order Of Magnitude ◽  
Higher Temperature ◽  
Lower Temperature ◽  
Type Conduction

The steady state measurements in Liquid crystalline polyurethane (LCPU) have been investigated for different fields (4 - 45 kV/cm) and temperatures (50°-220°C). The nature of conduction processes has been determined by estimating ion jump distances (a) and Schottky coefficients. The order of magnitude of a in the temperature region 150°C and below does not seem to support an ionic conduction. However the magnitude of a at higher temperatures (180°C and above) indicates the possibility of ionic conduction. There is a definite possibility of a Schottky type conduction at lower temperature and a Poole Frankel type conduction at higher temperature (100°C). The activation energy associated with the high temperature region lies between 0.26 eV and 0.65 eV depending on the field whereas in the low temperature region the activation energy lies between 0.82 eV and 0.95 eV depending on the applied electric field. The dual slopes in the log I versus 1/T curves indicate the presence of more than one type of trapping levels.

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