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PubMedDate not supplied

Extracellular matrix arrangement in the papillary muscles of the adult rat heart. Alterations after doxorubicin administration and experimental hypertension.

In the present study, we analyzed the components of the extracellular matrix (ECM) and its arrangement at the level of the papillary muscles in the adult rat heart using light and transmission and scanning electron microscopy techniques. Our results reveal that after a single dose (6 mg/kg) of dexorubicin to cause a significant decrease and disorganization of the endomysium and perimysium in the first week after injection, affecting the endomysial struts and perimysial strands. Degenerating myocytes and alterations of the coiled perimysial fibers were characteristic 4 weeks after treatment. After 8 weeks, ultrastructural alterations at the level of the plasma membrane of the myocytes and adjacent collagen network were present in the tip of the papillary muscles. These alterations may be responsible for the inefficiency of the valvular apparatus as an initial factor implicated in doxorubicin-induced congestive heart failure. Experimental hypertension, produced by constriction of the abdominal aorta, induced hypertrophy of the left ventricle, with increased perimysium and endomysium of the ECM at the level of the papillary muscles 4 weeks after aortic banding. Interstitial and perivascular fibrosis were observed 8 weeks after surgical treatment, and macrophages around the degenerating myocytes were characteristic 16 weeks after treatment. These alterations of the ECM network have been correlated with their possible implication in ventricular biomechanical properties.

Animals↗
PubMed2003

The negative inotropic effect of sevoflurane is not mediated through nitric oxide synthase in rat papillary muscle.

Sevoflurane has dose-dependent negative inotropic effects on myocardial contractility. The current study investigated whether the nitric oxide pathway is involved in these effects. A laboratory, ex-vivo experiment was performed on 66 isolated papillary muscles. Effects of increasing concentrations of sevoflurane (1, 2 and 3 MAC) were assessed in control conditions, in the presence of Nw-nitro-L-arginine (L-NOARG) and in beta-adrenergic stimulated rat papillary muscles. Contractility was assessed by total developed tension. In baseline conditions, the administration of increasing concentrations of sevoflurane caused a dose-dependent reduction in contractility of respectively 8.6 +/- 1.7%, 14.4 +/- 4.8% and 23.6 +/- 3.9%. This negative inotropic effect was not significantly altered by the administration of the NO-synthase inhibitor L-NOARG (p = 0.09). Under continuous administration of 3 MAC sevoflurane, 4 consecutive concentrations of isoproterenol induced a mean increase of contractility of respectively 43.0 +/- 13.7%, 65.9 +/- 22.6%, 131.2 +/- 25.6% and 122.3 +/- 31.2%. After administration of L-NOARG, the 4 consecutive concentrations of isoproterenol induced a mean increase in contractility of respectively 36.0 +/- 8.5%, 75.0 +/- 17.8%, 143.0 +/- 42.8% and 120.0 +/- 51.4% (p = 0.85). These data indicated that the negative inotropic effects of sevoflurane in rat papillary muscles, both in basic as in beta-adrenergic stimulated conditions, were not altered by blocking the NO-cGMP-system.

Adrenergic beta-Agonists↗
PubMedDate not supplied

Relationship between the in-situ activity of ornithine decarboxylase and contractile function of the rabbit papillary muscle.

The relationship between isometric contraction and myocardial ornithine decarboxylase (ODC; EC.4.1.1.17) activity was studied in right ventricular papillary muscles isolated from rabbits. ODC specific activity and polyamine content were significantly increased in papillary muscles contracting isometrically 90 times per minute at the apex of the length-tension relationship for 4 to 5 hours when compared with paired non-contracting muscles or isometrically contracting muscles stimulated at 30 times per min. The increase in ODC activity appeared to be due to new protein synthesis since cycloheximide blocked the increase in ODC activity without affecting isometric function. Thus, the present results suggest that increased contractile demands of the heart may stimulate the synthesis of myocardial ODC, increase ODC activity and polyamine content.

Animals↗
PubMed1999

Cold acclimation of guinea pig depressed contraction of cardiac papillary muscle.

Guinea pigs were exposed to 5 degrees C for 3 wk, and the contractions of myocardial papillary muscle were compared with preparations dissected from control animals kept at approximately 25 degrees C. Developed tension of the papillary muscle per cross-sectional area was significantly (t-test, P < 0.05) decreased after cold exposure (19,200 +/- 8,160 vs. 3,020 +/- 2,890 dyne/cm2; 1 Hz). Time to peak tension was significantly faster in cold-exposed guinea pigs (126.4 +/- 11.1 ms; 1 Hz) than in controls (162.7 +/- 8. 7 ms). The magnitude of the developed tension after application of ryanodine (2 mM) to muscles from cold-exposed animals was decreased to 37.5 +/- 8.3% of control at 1 Hz, whereas in muscles from control animals, tension was decreased to 82.4 +/- 7.7%. The ryanodine-sensitive component of contraction was not significantly changed in control guinea pigs at frequencies >0.5 Hz, whereas in muscles from cold-acclimated guinea pigs, there was a "positive staircase." These results suggested that reversal of the Na+/Ca2+ exchanger is predominantly involved in the positive staircase in control guinea pigs, whereas rate-dependent increases in the Ca2+ store in the sarcoplasmic reticulum may be involved in the staircase after cold acclimation.

Acclimatization↗
PubMed1992

Differential sensitivity of diabetic rat papillary muscles to negative inotropic effects of oxybarbiturates versus thiobarbiturates.

The negative inotropic effects of oxybarbiturates and thiobarbiturates were examined in papillary muscles isolated from streptozotocin-induced diabetic rats and in papillary muscles from age-matched control rats. The muscles from diabetic rats exhibited less negative inotropic responses to pentobarbital and secobarbital than the muscles from control rats. Conversely, the negative inotropic responses to thiopental and thiamylal were significantly enhanced in diabetic muscles. Differences in sensitivity to pentobarbital between control and diabetic muscles became less marked by treatment with ouabain or by lowering [Na+]o. Enhancement of the negative inotropic effect of thiamylal observed in diabetic muscles remained unchanged with these treatments. In both control and diabetic muscles, the negative inotropic effect of pentobarbital was completely reversed by increasing [Ca2+]o, but the effect of thiamylal was only partially reversed. These results suggest a difference in mechanism of action involved in establishment of the negative inotropic effects of oxybarbiturates vs thiobarbiturates. Oxybarbiturates appear to exclusively reduce the influx of extracellular Ca2+, whereas thiobarbiturates appear to affect Ca2+ movements at the Ca2+ storage sites in addition to the Ca2+ influx inhibition.

Animals↗
PubMed2002

Rupture of the anterolateral papillary muscle caused by a single diagonal branch obstruction.

This report presents the first case of anterolateral papillary muscle rupture caused by a diagonal branch occlusion only. Although the patient was in shock on admission, he was successfully treated by emergency surgery after hemodynamic stabilization by a percutaneous cardiopulmonary support system. This case implies that the anterolateral papillary muscle has a single blood supply and that it can rupture by an occlusion of only one diagonal branch even after balloon angioplasty.

Aged↗
PubMed1980

[Changes in cell membrane excitability during guinea pig papillary muscle after-contractions].

In isolated guinea-pig papillary muscles, the excitability of cellular membrane was investigated during the after contractions induced by cooling of the perfusate to 13--15 degrees C, addition of noradrenaline (2 mg/l), and calcium to 16 MM. At stimulation rate 0.2 Hz the oscillation amplitude was 19 +/- 2% of the initial contraction. The activity of the fast sodium channels was estimated by the threshold for AP initiation and appeared to increase gradually after the end of AP. Slow channel response measured in the high potassium solution (29 MM), significantly decreased during the after contraction. Even at supramaximal amplitude of stimulation the slow responses were about 10--20 mV smaller than those after or before oscillation. Slow channel activity seems to depend on intracellular calcium concentration. Oscillations after contractions were abolished by addition of caffeine (2 mM). The oscillations seem to result from recirculation of calcium between myoplasma and sarcoplasmatic reticulum.

Action Potentials↗
PubMed1985

[Paroxysmal mitral insufficiency caused by ischemic dysfunction of the papillary muscles. Apropos of 39 cases].

Episodic mitral regurgitation due to ischaemia of one or both papillary muscles was studied in a review of 39 cases with complementary investigations and compared with previously reported data. The condition occurred after myocardial infarction in 69 p. 100 of cases (usually after inferior infarction: 54 p. 100) associated with ischaemia of the controlateral territory; there was no history of myocardial infarction in 31 p. 100 of cases. The patients were usually elderly (73 years), often hypertensive (77 p. 100) and diabetic (62 p. 100). The clinical syndrome was that of severe anginal pain, mitral regurgitation and left ventricular failure which was critical in some cases. The ECG showed typical ST depression (4.1 +/- 1.6 mm) especially in the antero-lateral leads; left bundle branch block (28 p. 100) with left axis deviation (18 p. 100), sometimes associated with changes of chronic infarction (64 p. 100) was also recorded. Mitral regurgitation and left ventricular failure regressed almost completely in typical cases between attacks, whilst the ECG showed slight residual sub-endocardial ischaemia (ST depression of 1.5 +/- 0.4 mm) in 30 cases and/or subepicardial ischaemia observed in the anterolateral leads in 13 cases. Phonomechanographic recordings (n = 32) showed moderate mitral regurgitation (1-2/6), usually parasystolic (47 p. 100) or early and mid systolic (36 p. 100) in 87.5 p. 100 of cases between attacks, aggravated by handgrip exercise and improved by trinitrin administration. Echocardiography (n = 27) only showed mitral valve changes in 2 patients (increased density of the papillary muscle in 1 case and prolapse of the anterior leaflet in 1 case); however, segmental wall hypokinetic (51 p. 100) or dyskinetic (15 p. 100) motion, was common with increased left ventricular end diastolic dimensions (mean 56.3 +/- 8.0 mm) and decreased fractional shortening (mean 0.30 +/- 0.07) (67 p. 100). Left atrial dimensions were increased (mean 39.7 +/- 6.4 mm) in 52 p. 100 of patients. Thallium 201 myocardial scintigraphy (n = 32) showed hypofixation in 57 (36 p. 100) and a lacuna in 23 (14 p. 100) of the 160 segments analysed. Left ventricular angioscintigraphy (n = 27; 135 segments) showed hypokinesia in 72 segments (53 p. 100); 2.7 segments per patient), akinesia in 19 segments (15 p. 100; 0.7 segment per patient) and dyskinesia in 2 segments (1.5 p. 100); 0.1 segment per patient). The global ejection fraction was 46 +/- 13 p. 100. Coronary angiography (n = 8) showed significant diffuse atherosclerosis.(ABSTRACT TRUNCATED AT 400 WORDS)

Aged↗
PubMed1979

Influence of stimulation of myocardial alpha- as well as beta-adrenoceptors on the effect of digoxin in isolated electrically driven rabbit papillary muscles.

On isolated electrically driven rabbit papillary muscle the cardiac glycoside digoxin was infused at driving rates of 0.5, 1.0 and 2.0 Hz. Two effective concentrations of digoxin were determined: 1. that inducing the maximal inotropic effect (maximal inotropic concentration) and 2, that causing cardiac arrest (toxic concentration). The influence of the alpha-sympathomimetic drug phenylephrine and for comparison that of the beta-sympathomimetic drug isoprenaline on either concentration of digoxin was investigated. 1. Stimulation of alpha-adrenoceptors by phenylephrine at a rate of 0.5 Hz significantly decreased the maximal inotropic as well as the toxic concentration of digoxin by about 36%; this decrease was maximal under the influence of the EC25 of phenylephrine and could be blocked by phentolamine. Phenylephrine did not alter the maximal inotropic effect of digoxin. At a stimulus rate of 1.0 Hz the EC75 of phenylephrine still diminished significantly the effective concentrations of digoxin whereas under these conditions the EC25 was ineffective. At 2.0 Hz stimulation of myocardial alpha-adrenoceptors had no effect anymore on either the maximal inotropic or the toxic concentration of digoxin. 2. In contrast, stimulation of beta-adrenoceptors by isoprenaline at a driving rate of 2.0 Hz resulted in a pronounced decrease of maximal inotropic and toxic concentration of digoxin while the maximal positive inotropic effect exerted by digoxin was found to be not altered by isoprenaline. The decrease of the effective concentration of digoxin caused by isoprenaline was abolished by pindolol. At a driving rate of 1.0 Hz this effect was slightly attenuated but was completely absent at 0.5 Hz. 3. From these results it can be concluded that stimulation of either adrenoceptor, alpha- and beta-, increases the effectiveness of the cardiac glycoside digoxin, i.e. diminishes the maximal inotropic as well as its toxic concentration. While stimulation of alpha-adrenoceptors is effective only at low rates of stimulation that of beta-adrenoceptors is vice versa at higher ones, thus supporting the view of different mechanisms underlying stimulation of alpha- or beta-adrenoceptors.

Animals↗
PubMed1989

[Rupture of the mitral posteromedial papillary muscle associated with myxomatous mitral valve].

We report a 52 year old man, who without previous thoracic trauma, cardiac diseases or cardiovascular risk factors presented after mild epigastric discomfort acute pulmonary oedema. He did not present clinical, electrocardiographic and biochemical manifestation of acute myocardial infarction. He was hospitalized and 15 days later he was sent to our hospital intubated and with assisted respiration. Haemodynamic studies showed severe acute mitral regurgitation and absence of significant obstructing lesions in the coronaries arteries. He was operated few hours after admission. The surgeon found a dysplasic mitral valve and rupture of a head of the posteromedial papillary muscle. The anatomopathological studies discovered mitral myxoid degeneration and ischemic lesion of the papillary muscle. We review the literature of the exclusive infarction of the papillary muscles and their possible relationships with the mitral prolapse syndrome.

Electrocardiography↗
PubMed1986

Characterization of the mechanical behavior of isolated papillary muscle preparations of the ferret.

The characteristics of isometric and isotonic contraction were studied in isolated papillary muscle preparations from the right ventricle of the ferret and compared with those previously reported for comparable preparations from cat and rat. The effects of stimulation rate, temperature, extracellular calcium concentration, caffeine, verapamil, and ouabain were measured. Afterloaded contractions and load clamps were used to study the mechanics of relaxation. The contractile characteristics of ferret papillary muscle preparation appear to be intermediate in many respects between those reported for cat and rat preparations.

Animals↗
PubMed1996

Acute and chronic effects of ethanol on papillary muscles from spontaneously hypertensive rats.

The effects of chronic ethanol ingestion (12 weeks) on the mechanical properties of hypertrophied papillary muscle and the in vitro effects of ethanol (80-640 mg/dl) was studied. Papillary muscles from spontaneously hypertensive rats (SHRs) and their normotensive controls, the Wistar-Kyoto rat (WKY), were used in this study. Peak-developed tension was significantly less in muscles obtained from SHR compared with WKY even when normalized for muscle cross-sectional area. Chronic ethanol ingestion resulted in a significant shortening of both contraction and relaxation duration in muscles from SHR and WKY. In muscles from SHR and WKY, acute in vitro ethanol exposure produced concentration-dependent negative inotropic effects that were associated with a reduction in the duration of contraction and relaxation and marked slowing in the maximum velocities of tension development and decay. These findings suggest that the contractile response to ethanol exposure, in vitro, is not modified by either chronic ethanol ingestion or hypertension.

Animals↗
PubMed2003

Negative inotropic response to cerium in ventricular papillary muscle is mediated by reactive oxygen species.

This study was performed with the objective of assessing the mechanical response of the myocardium to different levels of cerium and delineation of the mechanism underlying the mediation of the functional changes. Rat ventricular papillary muscle was used as the experimental model. Isolated papillary muscles were exposed to different concentrations of CeCl3 and the force of contraction was measured using a force transducer. Experiments have revealed that the negative inotropic response to CeCl3 was proportional to its concentration. The inotropic changes were found to be completely reversible at concentrations < or =5 microM, and partially reversible at higher concentrations. Neutralization of cerium-induced inotropic changes by the superoxide anion scavenger superoxide dismutase (SOD) at concentrations < or =5 microM indicates that the mechanical changes are mediated by reactive oxygen species. At higher concentrations of Ce3+, SOD partially reversed the contractile changes. The beneficial effect of SOD was seen only if the muscles were pretreated with the scavenger prior to the addition of cerium chloride.

Animals↗
PubMed2002

Papillary muscle rupture after acute myocardial infarction--the importance of transgastric view of TEE.

Transesophageal echocardiography was performed to evaluate the exact cause of severe mitral regurgitation in a 64-year-old man presented with hypotension and dyspnea after acute inferior wall myocardial infarction. In mid-esophageal two- and four-chamber view, the ruptured stump of papillary muscle could not be visualized. However, in transgastric two-chamber view, we could clearly visualize the ruptured head of the posteromedial papillary muscle as a separated mass attached by chorda tendinae, as well as the freely mobile stump of the ruptured papillary muscle within the left ventricle. So, the comprehensive transesophageal echocardiography, including transgastric imaging, is always indicated in patients with severe mitral regurgitation after acute myocardial infarction.

Echocardiography, Transesophageal↗
PubMed1989

[Successful surgical management of rupture of the papillary muscle diagnosed by ultrasound].

The rupture of the papillary muscle is an infrequent complication of myocardial infarction. Survival of the acute phase depends on the severity of the rupture and the remaining function of the left ventricle. Permanent survival may be ensured however only by surgical intervention. The authors present the case record of a patients whose disease in connection with a myocardial infarction was revealed by echocardiography and was operated on successfully. No such data were found in the Hungarian literature.

Humans↗