Myocardial Contraction: Contractile activity of the MYOCARDIUM.Muscle Contraction: A process leading to shortening and/or development of tension in muscle tissue. Muscle contraction occurs by a sliding filament mechanism whereby actin filaments slide inward among the myosin filaments.Ventricular Function: The hemodynamic and electrophysiological action of the HEART VENTRICLES.Myocardium: The muscle tissue of the HEART. It is composed of striated, involuntary muscle cells (MYOCYTES, CARDIAC) connected to form the contractile pump to generate blood flow.Systole: Period of contraction of the HEART, especially of the HEART VENTRICLES.Heart Ventricles: The lower right and left chambers of the heart. The right ventricle pumps venous BLOOD into the LUNGS and the left ventricle pumps oxygenated blood into the systemic arterial circulation.Heart: The hollow, muscular organ that maintains the circulation of the blood.Ventricular Function, Left: The hemodynamic and electrophysiological action of the left HEART VENTRICLE. Its measurement is an important aspect of the clinical evaluation of patients with heart disease to determine the effects of the disease on cardiac performance.Ventricular Dysfunction, Left: A condition in which the LEFT VENTRICLE of the heart was functionally impaired. This condition usually leads to HEART FAILURE; MYOCARDIAL INFARCTION; and other cardiovascular complications. Diagnosis is made by measuring the diminished ejection fraction and a depressed level of motility of the left ventricular wall.Echocardiography: Ultrasonic recording of the size, motion, and composition of the heart and surrounding tissues. The standard approach is transthoracic.Coronary Circulation: The circulation of blood through the CORONARY VESSELS of the HEART.Calcium: A basic element found in nearly all organized tissues. It is a member of the alkaline earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes.Dogs: The domestic dog, Canis familiaris, comprising about 400 breeds, of the carnivore family CANIDAE. They are worldwide in distribution and live in association with people. (Walker's Mammals of the World, 5th ed, p1065)Myocytes, Cardiac: Striated muscle cells found in the heart. They are derived from cardiac myoblasts (MYOBLASTS, CARDIAC).Isometric Contraction: Muscular contractions characterized by increase in tension without change in length.Uterine Contraction: Contraction of the UTERINE MUSCLE.Muscle, Smooth: Unstriated and unstriped muscle, one of the muscles of the internal organs, blood vessels, hair follicles, etc. Contractile elements are elongated, usually spindle-shaped cells with centrally located nuclei. Smooth muscle fibers are bound together into sheets or bundles by reticular fibers and frequently elastic nets are also abundant. (From Stedman, 25th ed)Electric Stimulation: Use of electric potential or currents to elicit biological responses.Muscle, Skeletal: A subtype of striated muscle, attached by TENDONS to the SKELETON. Skeletal muscles are innervated and their movement can be consciously controlled. They are also called voluntary muscles.Isotonic Contraction: Muscle contraction with negligible change in the force of contraction but shortening of the distance between the origin and insertion.Vasoconstriction: The physiological narrowing of BLOOD VESSELS by contraction of the VASCULAR SMOOTH MUSCLE.Guinea Pigs: A common name used for the genus Cavia. The most common species is Cavia porcellus which is the domesticated guinea pig used for pets and biomedical research.Muscle, Smooth, Vascular: The nonstriated involuntary muscle tissue of blood vessels.Muscle Relaxation: That phase of a muscle twitch during which a muscle returns to a resting position.Muscle Fatigue: A state arrived at through prolonged and strong contraction of a muscle. Studies in athletes during prolonged submaximal exercise have shown that muscle fatigue increases in almost direct proportion to the rate of muscle glycogen depletion. Muscle fatigue in short-term maximal exercise is associated with oxygen lack and an increased level of blood and muscle lactic acid, and an accompanying increase in hydrogen-ion concentration in the exercised muscle.Electromyography: Recording of the changes in electric potential of muscle by means of surface or needle electrodes.Potassium Chloride: A white crystal or crystalline powder used in BUFFERS; FERTILIZERS; and EXPLOSIVES. It can be used to replenish ELECTROLYTES and restore WATER-ELECTROLYTE BALANCE in treating HYPOKALEMIA.Gastrointestinal Motility: The motor activity of the GASTROINTESTINAL TRACT.Trachea: The cartilaginous and membranous tube descending from the larynx and branching into the right and left main bronchi.Vasoconstrictor Agents: Drugs used to cause constriction of the blood vessels.Peristalsis: A movement, caused by sequential muscle contraction, that pushes the contents of the intestines or other tubular organs in one direction.Urinary Bladder: A musculomembranous sac along the URINARY TRACT. URINE flows from the KIDNEYS into the bladder via the ureters (URETER), and is held there until URINATION.Muscles: Contractile tissue that produces movement in animals.Norepinephrine: Precursor of epinephrine that is secreted by the adrenal medulla and is a widespread central and autonomic neurotransmitter. Norepinephrine is the principal transmitter of most postganglionic sympathetic fibers and of the diffuse projection system in the brain arising from the locus ceruleus. It is also found in plants and is used pharmacologically as a sympathomimetic.Dose-Response Relationship, Drug: The relationship between the dose of an administered drug and the response of the organism to the drug.Acetylcholine: A neurotransmitter found at neuromuscular junctions, autonomic ganglia, parasympathetic effector junctions, a subset of sympathetic effector junctions, and at many sites in the central nervous system.Rabbits: The species Oryctolagus cuniculus, in the family Leporidae, order LAGOMORPHA. Rabbits are born in burrows, furless, and with eyes and ears closed. In contrast with HARES, rabbits have 22 chromosome pairs.Atropine: An alkaloid, originally from Atropa belladonna, but found in other plants, mainly SOLANACEAE. Hyoscyamine is the 3(S)-endo isomer of atropine.Phenylephrine: An alpha-1 adrenergic agonist used as a mydriatic, nasal decongestant, and cardiotonic agent.Vas Deferens: The excretory duct of the testes that carries SPERMATOZOA. It rises from the SCROTUM and joins the SEMINAL VESICLES to form the ejaculatory duct.Ileum: The distal and narrowest portion of the SMALL INTESTINE, between the JEJUNUM and the ILEOCECAL VALVE of the LARGE INTESTINE.Nifedipine: A potent vasodilator agent with calcium antagonistic action. It is a useful anti-anginal agent that also lowers blood pressure.Aorta, Thoracic: The portion of the descending aorta proceeding from the arch of the aorta and extending to the DIAPHRAGM, eventually connecting to the ABDOMINAL AORTA.Muscle Tonus: The state of activity or tension of a muscle beyond that related to its physical properties, that is, its active resistance to stretch. In skeletal muscle, tonus is dependent upon efferent innervation. (Stedman, 25th ed)Odontogenic Cysts: Cysts found in the jaws and arising from epithelium involved in tooth formation. They include follicular cysts (e.g., primordial cyst, dentigerous cyst, multilocular cyst), lateral periodontal cysts, and radicular cysts. They may become keratinized (odontogenic keratocysts). Follicular cysts may give rise to ameloblastomas and, in rare cases, undergo malignant transformation.Burimamide: An antagonist of histamine that appears to block both H2 and H3 histamine receptors. It has been used in the treatment of ulcers.Histamine: An amine derived by enzymatic decarboxylation of HISTIDINE. It is a powerful stimulant of gastric secretion, a constrictor of bronchial smooth muscle, a vasodilator, and also a centrally acting neurotransmitter.Histamine Antagonists: Drugs that bind to but do not activate histamine receptors, thereby blocking the actions of histamine or histamine agonists. Classical antihistaminics block the histamine H1 receptors only.Cyclic AMP: An adenine nucleotide containing one phosphate group which is esterified to both the 3'- and 5'-positions of the sugar moiety. It is a second messenger and a key intracellular regulator, functioning as a mediator of activity for a number of hormones, including epinephrine, glucagon, and ACTH.Cineradiography: Motion picture study of successive images appearing on a fluoroscopic screen.Risk Factors: An aspect of personal behavior or lifestyle, environmental exposure, or inborn or inherited characteristic, which, on the basis of epidemiologic evidence, is known to be associated with a health-related condition considered important to prevent.Proportional Hazards Models: Statistical models used in survival analysis that assert that the effect of the study factors on the hazard rate in the study population is multiplicative and does not change over time.Cohort Studies: Studies in which subsets of a defined population are identified. These groups may or may not be exposed to factors hypothesized to influence the probability of the occurrence of a particular disease or other outcome. Cohorts are defined populations which, as a whole, are followed in an attempt to determine distinguishing subgroup characteristics.Cardiovascular Diseases: Pathological conditions involving the CARDIOVASCULAR SYSTEM including the HEART; the BLOOD VESSELS; or the PERICARDIUM.Myocardial Infarction: NECROSIS of the MYOCARDIUM caused by an obstruction of the blood supply to the heart (CORONARY CIRCULATION).

Myocardial uptake of digoxin in chronically digitalized dogs. (1/9164)

1 The time course of myocardial uptake of digoxin, increase in contractility and changes in myocardial potassium concentration was studied for 90 min following an intravenous digoxin dose to long-term digitalized dogs. 2 Nineteen dogs were investigated by the use of a biopsy technique which allowed sampling before and after administration of digoxin. 3 Ten minutes after administration of digoxin the myocardial concentration increased from 60 to 306 nmol/kg tissue, the myocardial concentration of digoxin was significantly lower (250 nmol/kg tissue) after 30 min and then increased again. 4 The transmural myocardial distribution of digoxin was uniform before and 90 min after administration of digoxin in long-term digitalized dogs but at 10 min after administration, both the subepicardial and the subendocardial concentration of digoxin were significantly lower than that of the mesocardial layer. 5 During the first 10 min the dp/dtmax increased to 135% of the control level. The increase remained unchanged during the rest of the study. 6 Myocardial potassium decreased throughout the study. 7 The M-configuration of the myocardial uptake curve and the non-uniformity of myocardial distribution of digoxin observed at 10 min after administrating digoxin to long-term digitalized dogs indicate that the distribution of myocardial blood flow may be changed during chronic digitalization.  (+info)

Ventricular pressure-volume curve indices change with end-diastolic pressure. (2/9164)

Many indices have been proposed to describee the diastolic pressure-volume curve mathematically and permit quantification of the elastic properties of the myocardium itself in hopes that changes in the muscle caused by disease would b.e reflected in the diastolic pressure-volume curve. To date, none of the proposed indices has been shown convincingly to discriminate one group of patients from another. While this situation in part arises from the relatively large amount of noise introduced by the technical difficulties of measuring synchronous pressures and volumes during diastole in man, ther is a more fundamental difficulty. In practice, one can measure only a short segment of the entire pressure-volume curve, and the values of all diastolic pressure-volume curve parameters investigated change significantly when one uses different segments of the same pressure-volume curve to compute them. These results were derived from relatively noise-free pressure-volume curves obtained by filling nine excised dog left ventricles at a known rate and monitoring pressure-volume curve used to compute the parameter. Merely increasing measurement fidelity will not resolve this problem, because none of these parameters accurately characterizes the entire diastolic pressure-volume curbe from a segment like that which one can reasonably expect to obtain from humans.  (+info)

The effect of cardiac contraction on collateral resistance in the canine heart. (3/9164)

We determined whether the coronary collateral vessels develop an increased resistance to blood flow during systole as does the cognate vascular bed. Collateral resistance was estimated by measuring retrograde flow rate from a distal branch of the left anterior descending coronary artery while the main left coronary artery was perfused at a constant pressure. Retrograde flow rate was measured before and during vagal arrest. We found that in 10 dogs the prolonged diastole experienced when the heart was stopped caused no significant change in the retrograde flow rate, which indicated that systole has little effect on the collateral resistance. However, when left ventricular end-diastolic pressure was altered by changing afterload or contractility, a direct relationship between end-diastolic pressure and collateral resistance was noted.  (+info)

Evaluation of the force-frequency relationship as a descriptor of the inotropic state of canine left ventricular myocardium. (4/9164)

The short-term force-frequency characteristics of canine left ventricular myocardium were examined in both isolated and intact preparations by briefly pertubing the frequency of contraction with early extrasystoles. The maximum rate of rise of isometric tension (Fmas) of the isolated trabeculae carneae was potentiated by the introduction of extrasystoles. The ratio of Fmas of potentiated to control beats (force-frequency ratio) was not altered significantly by a change in muscle length. However, exposure of the trabeculae to isoproterenol (10(-7)M) significantly changed the force-frequency ratio obtained in response to a constant frequency perturbation. Similar experiments were performed on chronically instrumented conscious dogs. Left ventricular minor axis diameter was measured with implanted pulse-transit ultrasonic dimension transducers, and intracavitary pressure was measured with a high fidelity micromanometer. Atrial pacing was performed so that the end-diastolic diameters of the beats preceding and following the extrasystole could be made identical. Large increases in the maximum rate of rise of pressure (Pmas) were seen in the contraction after the extrasystole. The ratio of Pmax of the potentiated beat to that of the control beat was not changed by a 9% increase in the end-diastolic diameter, produced by saline infusion. Conversely, isoproterenol significantly altered this relationship in the same manner as in the isolated muscle. Thus, either in vitro or in situ, left ventricular myocardium exhibits large functional changes in response to brief perturbations in rate. The isoproterenol and length data indicate that the force-frequency ratio reflects frequency-dependent changes in the inotropic state, independent of changes in length.  (+info)

Adenoviral gene transfer of the human V2 vasopressin receptor improves contractile force of rat cardiomyocytes. (5/9164)

BACKGROUND: In congestive heart failure, high systemic levels of the hormone arginine vasopressin (AVP) result in vasoconstriction and reduced cardiac contractility. These effects are mediated by the V1 vasopressin receptor (V1R) coupled to phospholipase C beta-isoforms. The V2 vasopressin receptor (V2R), which promotes activation of the Gs/adenylyl cyclase system, is physiologically expressed in the kidney but not in the myocardium. Expression of a recombinant V2R (rV2R) in the myocardium could result in a positive inotropic effect via the endogenous high concentrations of AVP in heart failure. METHODS AND RESULTS: A recombinant adenovirus encoding the human V2R (Ad-V2R) was tested for its ability to modulate the cardiac Gs/adenylyl cyclase system and to potentiate contractile force in rat ventricular cardiomyocytes and in H9c2 cardiomyoblasts. Ad-V2R infection resulted in a virus concentration-dependent expression of the transgene and led to a marked increase in cAMP formation in rV2R-expressing cardiomyocytes after exposure to AVP. Single-cell shortening measurements showed a significant agonist-induced contraction amplitude enhancement, which was blocked by the V2R antagonist, SR 121463A. Pretreatment of Ad-V2R-infected cardiomyocytes with AVP led to desensitization of the rV2R after short-term agonist exposure but did not lead to further loss of receptor function or density after long-term agonist incubation, thus demonstrating resistance of the rV2R to downregulation. CONCLUSIONS: Adenoviral gene transfer of the V2R in cardiomyocytes can modulate the endogenous adenylyl cyclase-signal transduction cascade and can potentiate contraction amplitude in cardiomyocytes. Heterologous expression of cAMP-forming receptors in the myocardium could lead to novel strategies in congestive heart failure by bypassing the desensitized beta-adrenergic receptor signaling.  (+info)

Myocardial oxygenation during high work states in hearts with postinfarction remodeling. (6/9164)

BACKGROUND: Postinfarction left ventricular remodeling (LVR) is associated with reductions in myocardial high-energy phosphate (HEP) levels, which are more severe in animals that develop overt congestive heart failure (CHF). During high work states, further HEP loss occurs, which suggests demand-induced ischemia. This study tested the hypothesis that inadequate myocyte oxygen availability is the basis for these HEP abnormalities. METHODS AND RESULTS: Myocardial infarction was produced by left circumflex coronary artery ligation in swine. Studies were performed in 20 normal animals, 14 animals with compensated LVR, and 9 animals with CHF. Phosphocreatine (PCr)/ATP was determined with 31P NMR and deoxymyoglobin (Mb-delta) with 1H NMR in myocardium remote from the infarct. Basal PCr/ATP tended to be decreased in postinfarct hearts, and this was significant in animals with CHF. Infusion of dobutamine (20 microg x kg-1 x min-1 IV) caused doubling of the rate-pressure product in both normal and LVR hearts and resulted in comparable significant decreases of PCr/ATP in both groups. This decrease in PCr/ATP was not associated with detectable Mb-delta. In CHF hearts, rate-pressure product increased only 40% in response to dobutamine; this attenuated response also was not associated with detectable Mb-delta. CONCLUSIONS: Thus, the decrease of PCr/ATP during dobutamine infusion is not the result of insufficient myocardial oxygen availability. Furthermore, in CHF hearts, the low basal PCr/ATP and the attenuated response to dobutamine occurred in the absence of myocardial hypoxia, indicating that the HEP and contractile abnormalities were not the result of insufficient oxygen availability.  (+info)

Hemodialysis with high-calcium dialysate impairs cardiac relaxation. (7/9164)

BACKGROUND: During hemodialysis (HD), serum ionized calcium is directly related to the dialysate calcium concentration. We have recently shown an acute induction of hypercalcemia to impair left ventricular (LV) relaxation. In the current study we sought to establish whether changes in serum Ca++ also affect LV function during HD. METHODS: We echocardiographically examined the LV relaxation and systolic function of 12 patients with end-stage renal disease before and after three HD treatments with dialysate Ca++ concentrations of 1.25 mmol/liter (dCa++1.25), 1.5 mmol/liter (dCa++1.50), and 1.75 mmol/liter (dCa++1.75), respectively. Age- and sex-matched healthy controls were also examined echocardiographically. RESULTS: The LV posterior wall thickness and the interventricular septum thickness, and the LV end-diastolic dimension and the end-systolic dimensions were significantly greater in the patients when compared with the controls, and the LV fractional shortening, the ratio of peak early to peak late diastolic velocities (E/Amax), and the isovolumic relaxation time (IVRT) showed impairment of LV relaxation and systolic function in the patients. Serum ionized calcium increased significantly during the dCa++1.5 HD (1.24 +/- 0.10 vs. 1.34 +/- 0.06 mmol/liter, P = 0. 004) and dCa++1.75 HD (1.19 +/- 0.10 vs. 1.47 +/- 0.06 mmol/liter, P = 0.002), and plasma intact parathyroid hormone decreased significantly during the dCa++1.75 HD (medians 8.2 vs. 2.7 pmol/liter, P = 0.002). LV systolic function was not altered during any of the treatments. The changes in E/Amax and IVRT suggested impairment of relaxation during all sessions, but only during the dCa++1.75 HD was the impairment statistically significant (E/Amax 1. 153 +/- 0.437 vs. 0.943 +/- 0.352, P < 0.05; IVRT 147 +/- 29 vs. 175 +/- 50 msecond, P < 0.05). CONCLUSION: HD with high-calcium (dCa++1. 75 mmol/liter) dialysate impairs LV relaxation when compared with lower calcium dialysate (dCa++1.25 and dCa++1.5 mmol/liter) treatments.  (+info)

Simultaneous assessment of effects of coronary vasodilators on the coronary blood flow and the myocardial contractility by using the blood-perfused canine papillary muscle. (8/9164)

Effects of 6 coronary vasodilators on the coronary blood flow and the contractile force of the ventricular muscle were examined simultaneously by injecting these drugs to the arterially blood-perfused canine papillary muscle preparation. All compounds produced a dose-dependent increase in blood flow rate, and relative potencies determined on the basis of doses producing a 100% increase in blood flow rate, ED100, were in the descending order : nifedipine greater than verapamil greater than diltiazem greater than dilazep greater than dipyridamole greater than carbochromen, and approximately 1 : 1/12 : 1/26 : 1/100 : 1/300 : 1/500. All drugs except for dipyridamole caused a dose-dependent decrease in the developed tension of the papillary muscle, although nifedipine and diltiazem in low doses produced a slight increase. Relative potencies determined on the basis of doses producing a 50% decrease in developed tension, ID50, were as follows: nifedipine (1), verapamil (1/13), diltiazem (1/40), dilazep (1/100), and carbochromen (1/270). Ratios of the ID50 to ED100 were as follows: diltiazem (5.2), nifedipine (3.5), verapamil (3.5), dilazep (2.5), and carbochromen (1.8). The higher the value the more predominant on the coronary vascular bed or the less depressant on the myocardial contractility were their actions.  (+info)

  • Although regional EF and strain imaging, as compared with wall thickening, enhance detection of improvement in complex measures of regional myocardial function, it remains unclear whether such measures are better able to predict meaningful improvement in clinical outcomes. (
  • Instrumentation techniques for measurements of regional myocardial function in conscious animals. (
  • At the cellular level, altered cardiac excitation-contraction coupling has been identified as a major vehicle of impaired cardiac performance. (
  • However, prominent species-specific differences exist in cardiac excitation-contraction coupling and in the relative roles of extracellular and intracellular Ca(2+) sources among the teleostean fish. (
  • Consequently excitation-contraction coupling of the fish cardiac myocytes is not a fixed entity, but rather a highly variable and malleable process that enables fish to have an appropriate cardiac scope to exploit a diverse range of environments. (
  • In spite of the slight discrepancy between DCM blood concentrations and in vitro concentrations of DCM for [Ca2+](i) transient inhibition, present data are consistent with the view that cardiac effects after DCM exposure are mediated by alterations of Ca2+ dynamics during excitation-contraction coupling. (
  • Journal Article] Atrio-ventricular difference in myocardial excitation-contraction coupling-influence of T-tubules and endocardial endothelium. (
  • Journal Article] Species difference in myocardial excitation-contraction coupling featuring the mouse. (
  • Journal Article] Optical bioimaging : from living tissue to a single molecule : atrio-ventricular difference in myocardial excitation-contraction coupling - sequential versus simultaneous activation of SR Ca2+ release units. (
  • Positron emission tomography (PET) imaging revealed that myocardial 2-Fluorine-18-Fluoro-2-deeoxy-D-glucose ( 18 F-FDG) uptake increased after stem cells transplantation 12 , indicating increased glucose metabolism in cardiomyocytes. (
  • So whereas before you had lots of blood flowing through your coronary artery, and therefore your cardiomyocytes were getting lots of oxygen out of that blood, now, because of that huge clot that's in the way, there's way less blood flow in that coronary artery, right? (
  • When the catheter is placed in a coronary artery obstruction, inflation of the balloon produces transient myocardial ischemia. (
  • Conclusions - Myocardial contraction and relaxation were reduced in the mutant β-myosin heavy chain-glutamic acid 403 transgenic rabbit model of human HCM, irrespective of the presence or absence of LVH. (
  • Conclusions: Device closure of ASD results to an acute transient decrease of regional myocardial velocities in the LV and RV, whereas the load-insensitive marker isovolumic acceleration remained stable. (
  • CONCLUSIONS -Young diabetic patients already have significant changes in left ventricular dimensions and myocardial relaxation, with the girls clearly being more affected. (
  • CONCLUSIONS Myocardial hypertrophy and fibrosis in diabetic mice are attenuated by reduction of calpain function. (
  • 0.05) increased the contractile force and membrane action potential duration at 50% and 90% repolarization levels both in normothermia and in hypothermia, whereas the duration of the contraction was not significantly changed. (
  • CONCLUSION: Cooling to 32 degrees C significantly prolongs the myocardial action potential and the contraction duration. (
  • RESULTS Calpain activity, cardiomyocyte cross-sectional areas, and myocardial collagen deposition were significantly increased in both STZ-induced and OVE26 diabetic hearts, and these were accompanied by elevated expression of hypertrophic and fibrotic collagen genes. (
  • INTRODUCTION: Myocardial contraction fraction (MCF) is the ratio of left ventricular (LV) stroke volume to myocardial volume and may serve as a measure of appropriateness of LV mass. (
  • Withholding angiotensin-converting enzyme inhibitors (ACEIs) or angiotensin II receptor blockers (ARBs) 24 hours before noncardiac surgery has been associated with a 30-day lower risk for all-cause death, stroke, myocardial injury , and intra operative hypotension (18% adjusted relative risk reduction). (
  • 13) Other studies have demonstrated that RIPC using brief ischemia and reperfusion of the upper limb could reduce myocardial injury in adult patients undergoing CABG surgery. (
  • Regional LV assessment is traditionally performed with qualitative or quantitative analysis of wall thickening within 16 myocardial segments, but advances in noninvasive imaging permit an increasingly more detailed and accurate evaluation of LV function. (
  • NO may also mediate the parasympathetic control of myocardial function. (
  • Relationship between reduction in regional blood flow and myocardial function. (
  • 2.Negative staircase phenomenon observed specifically in mouse ventricle can be explained by the augmented Ca extrusion via NCX at high frequency of contraction leading to the diminution of the amount of Ca which can be controlled by SR function. (
  • After 45 min of equilibration at 37 degrees C or 32 degrees C, resting and action potentials, time to peak contraction and contractile force were recorded during pacing with a frequency of 60/min. (
  • Here, isolated embryonic cardiomyocytes cultured on a series of flexible substrates show that matrices that mimic the elasticity of the developing myocardial microenvironment are optimal for transmitting contractile work to the matrix and for promoting actomyosin striation and 1-Hz beating. (
  • Spontaneously occurring small animal models of myocardial disease, closely resembling the human condition, have been reported for hypertrophic cardiomyopathy (in cats) and arrhythmogenic right ventricular cardiomyopathy (in cats and boxer dogs). (
  • A primary myocardial disease occurring spontaneously in domestic cats is remarkably similar to restrictive nondilated and nonhypertrophied cardiomyopathy in man and represents another potential animal model for human disease. (
  • We reviewed the literature using search engines MIDLINE, SCOUPS, and EMBASE from 1988 to February 2012 using key words: myocardial viability, hibernation, and stunning, and ischemic cardiomyopathy. (
  • The effects of inhalational anesthetic agents on myocardial contraction have been the focus of extensive investigations for many years, and the depression of force development by different inhalational agents has been repeatedly shown. (
  • The pattern of left ventricular diastolic filling changed, with a decrease of early peak flow (231 +/- 20 versus 217 +/- 21 mL/s, P = .022), of deceleration time (163 +/- 28 versus 116 +/- 26 seconds, P = .001), and of flow area during rapid filling (105 +/- 15 versus 75 +/- 12 mL, P = .004) and an increase of flow area during atrial contraction (39 +/- 4 versus 88 +/- 9 mL, P = .001). (
  • Stimulating endogenous NO production with 10 μM bradykinin more strongly reduced myocardial O 2 consumption in diabetic TG than diabetic WT hearts perfused in normoxia, whereas there was no difference after ischemia-reperfusion. (
  • Simulations demonstrate that a muscle model based on the winding filament hypothesis can predict residual force enhancement on the descending limb of the length-tension curve in muscles during eccentric contraction. (
  • Eccentric, or lengthening, contractions occur in muscles when the external force acting on them is greater than the force that they produce. (
  • During eccentric contractions, muscles respond instantly to stretch imposed by applied loads, whereas stretch reflexes provide a similar response but with a time delay before onset ( Nichols and Houk, 1976 ). (
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