Use of arginine-glycine-aspartic acid adhesion peptides coupled with a new collagen scaffold to engineer a myocardium-like tissue graft.

PubMed

Schussler, O; Coirault, C; Louis-Tisserand, M; Al-Chare, W; Oliviero, P; Menard, C; Michelot, R; Bochet, P; Salomon, D R; Chachques, J C; Carpentier, A; Lecarpentier, Y

2009-03-01

Cardiac tissue engineering might be useful in treatment of diseased myocardium or cardiac malformations. The creation of functional, biocompatible contractile tissues, however, remains challenging. We hypothesized that coupling of arginine-glycine-aspartic acid-serine (RGD+) adhesion peptides would improve cardiomyocyte viability and differentiation and contractile performance of collagen-cell scaffolds. Clinically approved collagen scaffolds were functionalized with RGD+ cells and seeded with cardiomyocytes. Contractile performance, cardiomyocyte viability and differentiation were analyzed at days 1 and 8 and/or after culture for 1 month. The method used for the RGD+ cell-collagen scaffold coupling enabled the following features: high coupling yields and complete washout of excess reagent and by-products with no need for chromatography; spectroscopic quantification of RGD+ coupling; a spacer arm of 36 A, a length reported as optimal for RGD+-peptide presentation and favorable for integrin-receptor clustering and subsequent activation. Isotonic and isometric mechanical parameters, either spontaneous or electrostimulated, exhibited good performance in RGD+ constructs. Cell number and viability was increased in RGD+ scaffolds, and we saw good organization of cell contractile apparatus with occurrence of cross-striation. We report a novel method of engineering a highly effective collagen-cell scaffold based on RGD+ peptides cross-linked to a clinically approved collagen matrix. The main advantages were cell contractile performance, cardiomyocyte viability and differentiation.

Catecholamines and myocardial contractile function during hypodynamia and with an altered thyroid hormone balance

NASA Technical Reports Server (NTRS)

Pruss, G. M.; Kuznetsov, V. I.; Zhilinskaya, A. A.

1980-01-01

The dynamics of catecholamine content and myocardial contractile function during hypodynamia were studied in 109 white rats whose motor activity was severely restricted for up to 30 days. During the first five days myocardial catecholamine content, contractile function, and physical load tolerance decreased. Small doses of thyroidin counteracted this tendency. After 15 days, noradrenalin content and other indices approached normal levels and, after 30 days, were the same as control levels, although cardiac functional reserve was decreased. Thyroidin administration after 15 days had no noticeable effect. A detailed table shows changes in 17 indices of myocardial contractile function during hypodynamia.

Passive heat acclimation improves skeletal muscle contractility in humans.

PubMed

Racinais, S; Wilson, M G; Périard, J D

2017-01-01

The aim of this study was to investigate the effect of repeated passive heat exposure (i.e., acclimation) on muscle contractility in humans. Fourteen nonheat-acclimated males completed two trials including electrically evoked twitches and voluntary contractions in thermoneutral conditions [Cool: 24°C, 40% relative humidity (RH)] and hot ambient conditions in the hyperthermic state (Hot: 44-50°C, 50% RH) on consecutive days in a counterbalanced order. Rectal temperature was ~36.5°C in Cool and was maintained at ~39°C throughout Hot. Both trials were repeated after 11 days of passive heat acclimation (1 h per day, 48-50°C, 50% RH). Heat acclimation decreased core temperature in Cool (-0.2°C, P < 0.05), increased the time required to reach 39°C in Hot (+9 min, P < 0.05) and increased sweat rate in Hot (+0.7 liter/h, P < 0.05). Moreover, passive heat acclimation improved skeletal muscle contractility as evidenced by an increase in evoked peak twitch amplitude both in Cool (20.5 ± 3.6 vs. 22.0 ± 4.0 N·m) and Hot (20.5 ± 4.7 vs. 22.0 ± 4.0 N·m) (+9%, P < 0.05). Maximal voluntary torque production was also increased both in Cool (145 ± 42 vs. 161 ± 36 N·m) and Hot (125 ± 36 vs. 145 ± 30 N·m) (+17%, P < 0.05), despite voluntary activation remaining unchanged. Furthermore, the slope of the relative torque/electromyographic linear relationship was improved postacclimation (P < 0.05). These adjustments demonstrate that passive heat acclimation improves skeletal muscle contractile function during electrically evoked and voluntary muscle contractions of different intensities both in Cool and Hot. These results suggest that repeated heat exposure may have important implications to passively maintain or even improve muscle function in a variety of performance and clinical settings. Copyright © 2017 the American Physiological Society.

Store-Operated Ca2+ Entry (SOCE) Contributes to Normal Skeletal Muscle Contractility in young but not in aged skeletal muscle

PubMed Central

Brotto, Leticia S.; Bougoin, Sylvain; Nosek, Thomas M.; Reid, Michael; Hardin, Brian; Pan, Zui; Ma, Jianjie; Parness, Jerome

2011-01-01

Muscle atrophy alone is insufficient to explain the significant decline in contractile force of skeletal muscle during normal aging. One contributing factor to decreased contractile force in aging skeletal muscle could be compromised excitation-contraction (E-C) coupling, without sufficient available Ca2+ to allow for repetitive muscle contractility, skeletal muscles naturally become weaker. Using biophysical approaches, we previously showed that store-operated Ca2+ entry (SOCE) is compromised in aged skeletal muscle but not in young ones. While important, a missing component from previous studies is whether or not SOCE function correlates with contractile function during aging. Here we test the contribution of extracellular Ca2+ to contractile function of skeletal muscle during aging. First, we demonstrate graded coupling between SR Ca2+ release channel-mediated Ca2+ release and activation of SOCE. Inhibition of SOCE produced significant reduction of contractile force in young skeletal muscle, particularly at high frequency stimulation, and such effects were completely absent in aged skeletal muscle. Our data indicate that SOCE contributes to the normal physiological contractile response of young healthy skeletal muscle and that defective extracellular Ca2+ entry through SOCE contributes to the reduced contractile force characteristic of aged skeletal muscle. PMID:21666285

Store-operated Ca(2+) entry (SOCE) contributes to normal skeletal muscle contractility in young but not in aged skeletal muscle.

PubMed

Thornton, Angela M; Zhao, Xiaoli; Weisleder, Noah; Brotto, Leticia S; Bougoin, Sylvain; Nosek, Thomas M; Reid, Michael; Hardin, Brian; Pan, Zui; Ma, Jianjie; Parness, Jerome; Brotto, Marco

2011-06-01

Muscle atrophy alone is insufficient to explain the significant decline in contractile force of skeletal muscle during normal aging. One contributing factor to decreased contractile force in aging skeletal muscle could be compromised excitation-contraction (E-C) coupling, without sufficient available Ca(2+) to allow for repetitive muscle contractility, skeletal muscles naturally become weaker. Using biophysical approaches, we previously showed that store-operated Ca(2+) entry (SOCE) is compromised in aged skeletal muscle but not in young ones. While important, a missing component from previous studies is whether or not SOCE function correlates with contractile function during aging. Here we test the contribution of extracellular Ca(2+) to contractile function of skeletal muscle during aging. First, we demonstrate graded coupling between SR Ca(2+) release channel-mediated Ca(2+) release and activation of SOCE. Inhibition of SOCE produced significant reduction of contractile force in young skeletal muscle, particularly at high frequency stimulation, and such effects were completely absent in aged skeletal muscle. Our data indicate that SOCE contributes to the normal physiological contractile response of young healthy skeletal muscle and that defective extracellular Ca(2+) entry through SOCE contributes to the reduced contractile force characteristic of aged skeletal muscle.

Protective effects of anisodamine on cigarette smoke extract-induced airway smooth muscle cell proliferation and tracheal contractility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Guang-Ni; Yang, Kai; Xu, Zu-Peng

2012-07-01

Anisodamine, an antagonist of muscarinic acetylcholine receptors (mAChRs), has been used therapeutically to improve smooth muscle function, including microvascular, intestinal and airway spasms. Our previous studies have revealed that airway hyper-reactivity could be prevented by anisodamine. However, whether anisodamine prevents smoking-induced airway smooth muscle (ASM) cell proliferation remained unclear. In this study, a primary culture of rat ASM cells was used to evaluate an ASM phenotype through the ability of the cells to proliferate and express contractile proteins in response to cigarette smoke extract (CSE) and intervention of anisodamine. Our results showed that CSE resulted in an increase in cyclinmore » D1 expression concomitant with the G0/G1-to-S phase transition, and high expression of M2 and M3. Functional studies showed that tracheal hyper-contractility accompanied contractile marker α-SMA high-expression. These changes, which occur only after CSE stimulation, were prevented and reversed by anisodamine, and CSE-induced cyclin D1 expression was significantly inhibited by anisodamine and the specific inhibitor U0126, BAY11-7082 and LY294002. Thus, we concluded that the protective and reversal effects and mechanism of anisodamine on CSE-induced events might involve, at least partially, the ERK, Akt and NF-κB signaling pathways associated with cyclin D1 via mAChRs. Our study validated that anisodamine intervention on ASM cells may contribute to anti-remodeling properties other than bronchodilation. -- Highlights: ► CSE induces tracheal cell proliferation, hyper-contractility and α-SMA expression. ► Anisodamine reverses CSE-induced tracheal hyper-contractility and cell proliferation. ► ERK, PI3K, and NF-κB pathways and cyclin D1 contribute to the reversal effect.« less

Effects of milrinone and epinephrine or dopamine on biventricular function and hemodynamics in an animal model with right ventricular failure after pulmonary artery banding.

PubMed

Hyldebrandt, Janus Adler; Sivén, Eleonora; Agger, Peter; Frederiksen, Christian Alcaraz; Heiberg, Johan; Wemmelund, Kristian Borup; Ravn, Hanne Berg

2015-07-01

Right ventricular (RV) failure due to chronic pressure overload is a main determinant of outcome in congenital heart disease. Medical management is challenging because not only contractility but also the interventricular relationship is important for increasing cardiac output. This study evaluated the effect of milrinone alone and in combination with epinephrine or dopamine on hemodynamics, ventricular performance, and the interventricular relationship. RV failure was induced in 21 Danish landrace pigs by pulmonary artery banding. After 10 wk, animals were reexamined using biventricular pressure-volume conductance catheters. The maximum pressure in the RV increased by 113% (P < 0.0001) and end-diastolic volume by 43% (P < 0.002), while left ventricular (LV) pressure simultaneously decreased (P = 0.006). Concomitantly, mean arterial pressure (MAP; -16%, P = 0.01), cardiac index (CI; -23%, P < 0.0001), and mixed venous oxygen saturation (SvO2 ; -40%, P < 0.0001) decreased. Milrinone increased CI (11%, P = 0.008) and heart rate (HR; 21%, P < 0.0001). Stroke volume index (SVI) decreased (7%, P = 0.03), although RV contractility was improved. The addition of either epinephrine or dopamine further increased CI and HR in a dose-dependent manner but without any significant differences between the two interventions. A more pronounced increase in biventricular contractility was observed in the dopamine-treated animals. LV volume was reduced in both the dopamine and epinephrine groups with increasing doses In the failing pressure overloaded RV, milrinone improved CI and increased contractility. Albeit additional dose-dependent effects of both epinephrine and dopamine on CI and contractility, neither of the interventions improved SVI due to reduced filling of the LV. Copyright © 2015 the American Physiological Society.

Acute decrease of left ventricular mechanical dyssynchrony and improvement of contractile state and energy efficiency after left ventricular restoration.

PubMed

Schreuder, Jan J; Castiglioni, Alessandro; Maisano, Francesco; Steendijk, Paul; Donelli, Andrea; Baan, Jan; Alfieri, Ottavio

2005-01-01

Surgical left ventricular restoration by means of endoventricular patch aneurysmectomy in patients with postinfarction aneurysm should result in acute improved left ventricular performance by decreasing mechanical dyssynchrony and increasing energy efficiency. Nine patients with left ventricular postinfarction aneurysm were studied intraoperatively before and after ventricular restoration with a conductance volume catheter to analyze pressure-volume relationships, energy efficiency, and mechanical dyssynchrony. The end-systolic elastance was used as a load-independent index of contractile state. Left ventricular energy efficiency was calculated from stroke work and total pressure-volume area. Segmental volume changes perpendicular to the long axis were used to calculate mechanical dyssynchrony. Statistical analysis was performed with the paired t test and least-squares linear regression. Endoventricular patch aneurysmectomy reduced end-diastolic volume by 37% (P < .001), with unchanged stroke volume. Systolic function improved, as derived from increased +dP/dt(max), by 42% (P < .03), peak ejection rate by 28% (P < .02), and ejection fraction by 16% (P < .0002). Early diastolic function improved, as shown by reduction of -dP/dt(max) by 34% (P < .006) and shortened tau by 30% (P < .001). Left ventricular end-systolic elastance increased from 1.2 +/- 0.6 to 2.2 +/- 1 mm Hg/mL (P < .001). Left ventricular energy efficiency increased by 36% (P < .002). Left ventricular mechanical dyssynchrony decreased during systole by 33% (P < .001) and during diastole by 20% (P < .005). Left ventricular restoration induced acute improvements in contractile state, energy efficiency, and relaxation, together with a decrease in left ventricular mechanical dyssynchrony.

First report on an inotropic peptide activating tetrodotoxin-sensitive, "neuronal" sodium currents in the heart.

PubMed

Kirchhof, Paulus; Tal, Tzachy; Fabritz, Larissa; Klimas, Jan; Nesher, Nir; Schulte, Jan S; Ehling, Petra; Kanyshkova, Tatayana; Budde, Thomas; Nikol, Sigrid; Fortmueller, Lisa; Stallmeyer, Birgit; Müller, Frank U; Schulze-Bahr, Eric; Schmitz, Wilhelm; Zlotkin, Eliahu; Kirchhefer, Uwe

2015-01-01

New therapeutic approaches to improve cardiac contractility without severe risk would improve the management of acute heart failure. Increasing systolic sodium influx can increase cardiac contractility, but most sodium channel activators have proarrhythmic effects that limit their clinical use. Here, we report the cardiac effects of a novel positive inotropic peptide isolated from the toxin of the Black Judean scorpion that activates neuronal tetrodotoxin-sensitive sodium channels. All venoms and peptides were isolated from Black Judean Scorpions (Buthotus Hottentotta) caught in the Judean Desert. The full scorpion venom increased left ventricular function in sedated mice in vivo, prolonged ventricular repolarization, and provoked ventricular arrhythmias. An inotropic peptide (BjIP) isolated from the full venom by chromatography increased cardiac contractility but did neither provoke ventricular arrhythmias nor prolong cardiac repolarization. BjIP increased intracellular calcium in ventricular cardiomyocytes and prolonged inactivation of the cardiac sodium current. Low concentrations of tetrodotoxin (200 nmol/L) abolished the effect of BjIP on calcium transients and sodium current. BjIP did not alter the function of Nav1.5, but selectively activated the brain-type sodium channels Nav1.6 or Nav1.3 in cellular electrophysiological recordings obtained from rodent thalamic slices. Nav1.3 (SCN3A) mRNA was detected in human and mouse heart tissue. Our pilot experiments suggest that selective activation of tetrodotoxin-sensitive neuronal sodium channels can safely increase cardiac contractility. As such, the peptide described here may become a lead compound for a new class of positive inotropic agents. © 2014 American Heart Association, Inc.

Impact of exercise programs among helicopter pilots with transient LBP.

PubMed

Andersen, Knut; Baardsen, Roald; Dalen, Ingvild; Larsen, Jan Petter

2017-06-20

Flight related low back pain (LBP) among helicopter pilots is frequent and may influence flight performance. Prolonged confined sitting during flights seems to weaken lumbar trunk (LT) muscles with associated secondary transient pain. Aim of the study was to investigate if structured training could improve muscular function and thus improve LBP related to flying. 39 helicopter pilots (35 men and 4 women), who reported flying related LBP on at least 1 of 3 missions last month, were allocated to two training programs over a 3-month period. Program A consisted of 10 exercises recommended for general LBP. Program B consisted of 4 exercises designed specifically to improve LT muscular endurance. The pilots were examined before and after the training using questionnaires for pain, function, quality of health and tests of LT muscular endurance as well as ultrasound measurements of the contractility of the lumbar multifidus muscle (LMM). Approximately half of the participants performed the training per-protocol. Participants in this subset group had comparable baseline characteristics as the total study sample. Pre and post analysis of all pilots included, showed participants had marked improvement in endurance and contractility of the LMM following training. Similarly, participants had improvement in function and quality of health. Participants in program B had significant improvement in pain, function and quality of health. This study indicates that participants who performed a three months exercise program had improved muscle endurance at the end of the program. The helicopter pilots also experienced improved function and quality of health. Identifier: NCT01788111 Registration date; February 5th, 2013, verified April 2016.

Short term doxycycline treatment induces sustained improvement in myocardial infarction border zone contractility

PubMed Central

Collins, Alexander; Faraji, Farshid; Wang, Guanying; Aguayo, Esteban; Ge, Liang; Saloner, David; Wallace, Arthur W.; Baker, Anthony J.; Lovett, David H.

2018-01-01

Decreased contractility in the non-ischemic border zone surrounding a MI is in part due to degradation of cardiomyocyte sarcomeric components by intracellular matrix metalloproteinase-2 (MMP-2). We recently reported that MMP-2 levels were increased in the border zone after a MI and that treatment with doxycycline for two weeks after MI was associated with normalization of MMP-2 levels and improvement in ex-vivo contractile protein developed force in the myocardial border zone. The purpose of the current study was to determine if there is a sustained effect of short term treatment with doxycycline (Dox) on border zone function in a large animal model of antero-apical myocardial infarction (MI). Antero-apical MI was created in 14 sheep. Seven sheep received doxycycline 0.8 mg/kg/hr IV for two weeks. Cardiac MRI was performed two weeks before, and then two and six weeks after MI. Two sheep died prior to MRI at six weeks from surgical/anesthesia-related causes. The remaining 12 sheep completed the protocol. Doxycycline induced a sustained reduction in intracellular MMP-2 by Western blot (3649±643 MI+Dox vs 9236±114 MI relative intensity; p = 0.0009), an improvement in ex-vivo contractility (65.3±2.0 MI+Dox vs 39.7±0.8 MI mN/mm2; p<0.0001) and an increase in ventricular wall thickness at end-systole 1.0 cm from the infarct edge (12.4±0.6 MI+Dox vs 10.0±0.5 MI mm; p = 0.0095). Administration of doxycycline for a limited two week period is associated with a sustained improvement in ex-vivo contractility and an increase in wall thickness at end-systole in the border zone six weeks after MI. These findings were associated with a reduction in intracellular MMP-2 activity. PMID:29432443

Short term doxycycline treatment induces sustained improvement in myocardial infarction border zone contractility.

PubMed

Spaulding, Kimberly; Takaba, Kiyoaki; Collins, Alexander; Faraji, Farshid; Wang, Guanying; Aguayo, Esteban; Ge, Liang; Saloner, David; Wallace, Arthur W; Baker, Anthony J; Lovett, David H; Ratcliffe, Mark B

2018-01-01

Decreased contractility in the non-ischemic border zone surrounding a MI is in part due to degradation of cardiomyocyte sarcomeric components by intracellular matrix metalloproteinase-2 (MMP-2). We recently reported that MMP-2 levels were increased in the border zone after a MI and that treatment with doxycycline for two weeks after MI was associated with normalization of MMP-2 levels and improvement in ex-vivo contractile protein developed force in the myocardial border zone. The purpose of the current study was to determine if there is a sustained effect of short term treatment with doxycycline (Dox) on border zone function in a large animal model of antero-apical myocardial infarction (MI). Antero-apical MI was created in 14 sheep. Seven sheep received doxycycline 0.8 mg/kg/hr IV for two weeks. Cardiac MRI was performed two weeks before, and then two and six weeks after MI. Two sheep died prior to MRI at six weeks from surgical/anesthesia-related causes. The remaining 12 sheep completed the protocol. Doxycycline induced a sustained reduction in intracellular MMP-2 by Western blot (3649±643 MI+Dox vs 9236±114 MI relative intensity; p = 0.0009), an improvement in ex-vivo contractility (65.3±2.0 MI+Dox vs 39.7±0.8 MI mN/mm2; p<0.0001) and an increase in ventricular wall thickness at end-systole 1.0 cm from the infarct edge (12.4±0.6 MI+Dox vs 10.0±0.5 MI mm; p = 0.0095). Administration of doxycycline for a limited two week period is associated with a sustained improvement in ex-vivo contractility and an increase in wall thickness at end-systole in the border zone six weeks after MI. These findings were associated with a reduction in intracellular MMP-2 activity.

Triiodothyronine Facilitates Weaning From Extracorporeal Membrane Oxygenation by Improved Mitochondrial Substrate Utilization

PubMed Central

Files, Matthew D.; Kajimoto, Masaki; O'Kelly Priddy, Colleen M.; Ledee, Dolena R.; Xu, Chun; Des Rosiers, Christine; Isern, Nancy; Portman, Michael A.

2014-01-01

Background Extracorporeal membrane oxygenation (ECMO) provides a bridge to recovery after myocardial injury in infants and children, yet morbidity and mortality remain high. Weaning from the circuit requires adequate cardiac contractile function, which can be impaired by metabolic disturbances induced either by ischemia‐reperfusion and/or by ECMO. We tested the hypothesis that although ECMO partially ameliorates metabolic abnormalities induced by ischemia‐reperfusion, these abnormalities persist or recur with weaning. We also determined if thyroid hormone supplementation (triiodothyronine) during ECMO improves oxidative metabolism and cardiac function. Methods and Results Neonatal piglets underwent transient coronary ischemia to induce cardiac injury then were separated into 4 groups based on loading status. Piglets without coronary ischemia served as controls. We infused into the left coronary artery [2‐13C]pyruvate and [13C6, 15N]l‐leucine to evaluate oxidative metabolism by gas chromatography‐mass spectroscopy and nuclear magnetic resonance methods. ECMO improved survival, increased oxidative substrate contribution through pyruvate dehydrogenase, reduced succinate and fumarate accumulation, and ameliorated ATP depletion induced by ischemia. The functional and metabolic benefit of ECMO was lost with weaning, yet triiodothyronine supplementation during ECMO restored function, increased relative pyruvate dehydrogenase flux, reduced succinate and fumarate, and preserved ATP stores. Conclusions Although ECMO provides metabolic rest by decreasing energy demand, metabolic impairments persist, and are exacerbated with weaning. Treating ECMO‐induced thyroid depression with triiodothyronine improves substrate flux, myocardial oxidative capacity and cardiac contractile function. This translational model suggests that metabolic targeting can improve weaning. PMID:24650924

Triiodothyronine facilitates weaning from extracorporeal membrane oxygenation by improved mitochondrial substrate utilization.

PubMed

Files, Matthew D; Kajimoto, Masaki; O'Kelly Priddy, Colleen M; Ledee, Dolena R; Xu, Chun; Des Rosiers, Christine; Isern, Nancy; Portman, Michael A

2014-03-20

Extracorporeal membrane oxygenation (ECMO) provides a bridge to recovery after myocardial injury in infants and children, yet morbidity and mortality remain high. Weaning from the circuit requires adequate cardiac contractile function, which can be impaired by metabolic disturbances induced either by ischemia-reperfusion and/or by ECMO. We tested the hypothesis that although ECMO partially ameliorates metabolic abnormalities induced by ischemia-reperfusion, these abnormalities persist or recur with weaning. We also determined if thyroid hormone supplementation (triiodothyronine) during ECMO improves oxidative metabolism and cardiac function. Neonatal piglets underwent transient coronary ischemia to induce cardiac injury then were separated into 4 groups based on loading status. Piglets without coronary ischemia served as controls. We infused into the left coronary artery [2-(13)C]pyruvate and [(13)C6, (15)N]l-leucine to evaluate oxidative metabolism by gas chromatography-mass spectroscopy and nuclear magnetic resonance methods. ECMO improved survival, increased oxidative substrate contribution through pyruvate dehydrogenase, reduced succinate and fumarate accumulation, and ameliorated ATP depletion induced by ischemia. The functional and metabolic benefit of ECMO was lost with weaning, yet triiodothyronine supplementation during ECMO restored function, increased relative pyruvate dehydrogenase flux, reduced succinate and fumarate, and preserved ATP stores. Although ECMO provides metabolic rest by decreasing energy demand, metabolic impairments persist, and are exacerbated with weaning. Treating ECMO-induced thyroid depression with triiodothyronine improves substrate flux, myocardial oxidative capacity and cardiac contractile function. This translational model suggests that metabolic targeting can improve weaning.

Fat Graft, Laser CO₂ and Platelet-Rich-Plasma Synergy in Scars Treatment

PubMed Central

Nita, AC; Orzan, OA; Filipescu, M; Jianu, D

2013-01-01

Abstract Rationale: Many treatments have been proposed for cosmetic or functional improvement of scars. It is known that fat grafts and laser treatment can have beneficial effects on the remodeling of scar tissue, and platelet-rich plasma (PRP) can be effective during the wound-healing process. We hypothesized that laser and PRP can enhance fat graft survival and the combination would be effective in improving scars appearance. Objective: The purpose of this study was to evaluate the efficacy of these combinations in the treatment of atrophic and contractile scars. Methods and Results: From 2008-2013, we treated with this combination 64 patients affected by atrophic and contractile scars involving different body parts. At 6 months the patients’ overall satisfaction rate was excellent for over 50% of the patients. Discussion: The association of an ablative laser CO2 with PRP and autologous fat graft seems to be a promising and effective therapeutic approach for atrophic and contractile scars. Abbreviations: PRP platelet-rich plasma, OTI orotracheal intubation, HLLT high level laser therapy, LLLT low level laser therapy PMID:24868255

Ca2+ sensitizers: An emerging class of agents for counterbalancing weakness in skeletal muscle diseases?

PubMed

Ochala, Julien

2010-02-01

Ca(2+) ions are key regulators of skeletal muscle contraction. By binding to contractile proteins, they initiate a cascade of molecular events leading to cross-bridge formation and ultimately, muscle shortening and force production. The ability of contractile proteins to respond to Ca(2+) attachment, also known as Ca(2+) sensitivity, is often compromised in acquired and congenital skeletal muscle disorders. It constitutes, undoubtedly, a major physiological cause of weakness for patients. In this review, we discuss recent studies giving strong molecular and cellular evidence that pharmacological modulators of some of the contractile proteins, also termed Ca(2+) sensitizers, are efficient agents to improve Ca(2+) sensitivity and function in diseased skeletal muscle cells. In fact, they compensate for the impaired contractile proteins response to Ca(2+) binding. Currently, such Ca(2+) sensitizing compounds are successfully used for reducing problems in cardiac disorders. Therefore, in the future, under certain conditions, these agents may represent an emerging class of agents to enhance the quality of life of patients suffering from skeletal muscle weakness. Copyright 2009 Elsevier B.V. All rights reserved.

Optimization of Electrical Stimulation Parameters for Cardiac Tissue Engineering

PubMed Central

Tandon, Nina; Marsano, Anna; Maidhof, Robert; Wan, Leo; Park, Hyoungshin; Vunjak-Novakovic, Gordana

2010-01-01

In vitro application of pulsatile electrical stimulation to neonatal rat cardiomyocytes cultured on polymer scaffolds has been shown to improve the functional assembly of cells into contractile cardiac tissue constrcuts. However, to date, the conditions of electrical stimulation have not been optimized. We have systematically varied the electrode material, amplitude and frequency of stimulation, to determine the conditions that are optimal for cardiac tissue engineering. Carbon electrodes, exhibiting the highest charge-injection capacity and producing cardiac tissues with the best structural and contractile properties, and were thus used in tissue engineering studies. Cardiac tissues stimulated at 3V/cm amplitude and 3Hz frequency had the highest tissue density, the highest concentrations of cardiac troponin-I and connexin-43, and the best developed contractile behavior. These findings contribute to defining bioreactor design specifications and electrical stimulation regime for cardiac tissue engineering. PMID:21604379

[Gallbladder contractility in children with functional abdominal pain or irritable bowel syndrome].

PubMed

Iwańczak, Franciszek; Siedlecka-Dawidko, Jolanta; Iwanczak, Barbara

2013-07-01

III Rome Criteria of functional gastrointestinal disorders in children, distinguished the disturbances with abdominal pain, to which irritable bowel syndrome, functional abdominal pains, functional dyspepsia and abdominal migraine were included. THE AIM OF THE STUDY was sonographic assessment of the gallbladder and its contractility in functional abdominal pain and irritable bowel syndrome in children. The study comprised 96 children aged 6 to 18 years, 59 girls and 37 boys. Depending on diagnosis, the children were divided into three groups. 38 children with functional abdominal pain constituted the first group, 26 children with irritable bowel syndrome were included to the second group, the third group consisted of 32 healthy children (control group). Diagnosis of functional abdominal pain and irritable bowel syndrome was made based on the III Rome Criteria. In irritable bowel syndrome both forms with diarrhea (13) and with constipation (13) were observed. Anatomy and contractility of the gallbladder were assessed by ultrasound examination. The presence of septum, wall thickness, thick bile, vesicle volume in fasting state and 30th and 60th minute after test meal were taken into consideration. Test meal comprised about 15% of caloric requirement of moderate metabolism. Children with bile stones and organic diseases were excluded from the study. Thickened vesicle wall and thick bile were present more frequently in children with irritable bowel syndrome and functional abdominal pain than in control group (p < 0.02). Fasting vesicle volume was significantly greater in children with functional abdominal pain than in irritable bowel syndrome and control group (p = 0.003, p = 0.05). Vesicle contractility after test meal was greatest in children with functional abdominal pain. Evaluation of diminished (smaller than 30%) and enlarged (greater then 80%) gallbladder contractility at 30th and 60th minute after test meal demonstrated disturbances of contractility in children with irritable bowel syndrome and functional abdominal pain. In children with functional abdominal pain and irritable bowel syndrome disturbances of gallbladder anatomy, fasting volume and contractility after test meal were demonstrated. The observed disturbances require further studies for explanation of their role in functional gastrointestinal disturbances with abdominal pain in children.

Cardiac Dysfunction in HIV-1 Transgenic Mouse: Role of Stress and BAG3.

PubMed

Cheung, Joseph Y; Gordon, Jennifer; Wang, JuFang; Song, Jianliang; Zhang, Xue-Qian; Tilley, Douglas G; Gao, Erhe; Koch, Walter J; Rabinowitz, Joseph; Klotman, Paul E; Khalili, Kamel; Feldman, Arthur M

2015-08-01

Since highly active antiretroviral therapy improved long-term survival of acquired immunodeficiency syndrome (AIDS) patients, AIDS cardiomyopathy has become an increasingly relevant clinical problem. We used human immunodeficiency virus (HIV)-1 transgenic (Tg26) mouse to explore molecular mechanisms of AIDS cardiomyopathy. Tg26 mice had significantly lower left ventricular (LV) mass and smaller end-diastolic and end-systolic LV volumes. Under basal conditions, cardiac contractility and relaxation and single myocyte contraction dynamics were not different between wild-type (WT) and Tg26 mice. Ten days after open heart surgery, contractility and relaxation remained significantly depressed in Tg26 hearts, suggesting that Tg26 mice did not tolerate surgical stress well. To simulate heart failure in which expression of Bcl2-associated athanogene 3 (BAG3) is reduced, we down-regulated BAG3 by small hairpin ribonucleic acid in WT and Tg26 hearts. BAG3 down-regulation significantly reduced contractility in Tg26 hearts. BAG3 overexpression rescued contractile abnormalities in myocytes expressing the HIV-1 protein Tat. We conclude: (i) Tg26 mice exhibit normal contractile function at baseline; (ii) Tg26 mice do not tolerate surgical stress well; (iii) BAG3 down-regulation exacerbated cardiac dysfunction in Tg26 mice; (iv) BAG3 overexpression rescued contractile abnormalities in myocytes expressing HIV-1 protein Tat; and (v) BAG3 may occupy a role in pathogenesis of AIDS cardiomyopathy. © 2015 Wiley Periodicals, Inc.

Repeated high-intensity exercise modulates Ca(2+) sensitivity of human skeletal muscle fibers.

PubMed

Gejl, K D; Hvid, L G; Willis, S J; Andersson, E; Holmberg, H-C; Jensen, R; Frandsen, U; Hansen, J; Plomgaard, P; Ørtenblad, N

2016-05-01

The effects of short-term high-intensity exercise on single fiber contractile function in humans are unknown. Therefore, the purposes of this study were: (a) to access the acute effects of repeated high-intensity exercise on human single muscle fiber contractile function; and (b) to examine whether contractile function was affected by alterations in the redox balance. Eleven elite cross-country skiers performed four maximal bouts of 1300 m treadmill skiing with 45 min recovery. Contractile function of chemically skinned single fibers from triceps brachii was examined before the first and following the fourth sprint with respect to Ca(2+) sensitivity and maximal Ca(2+) -activated force. To investigate the oxidative effects of exercise on single fiber contractile function, a subset of fibers was incubated with dithiothreitol (DTT) before analysis. Ca(2+) sensitivity was enhanced by exercise in both MHC I (17%, P < 0.05) and MHC II (15%, P < 0.05) fibers. This potentiation was not present after incubation of fibers with DTT. Specific force of both MHC I and MHC II fibers was unaffected by exercise. In conclusion, repeated high-intensity exercise increased Ca(2+) sensitivity in both MHC I and MHC II fibers. This effect was not observed in a reducing environment indicative of an exercise-induced oxidation of the human contractile apparatus. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

The Pivotal Role of Airway Smooth Muscle in Asthma Pathophysiology

PubMed Central

Ozier, Annaïg; Allard, Benoit; Bara, Imane; Girodet, Pierre-Olivier; Trian, Thomas; Marthan, Roger; Berger, Patrick

2011-01-01

Asthma is characterized by the association of airway hyperresponsiveness (AHR), inflammation, and remodelling. The aim of the present article is to review the pivotal role of airway smooth muscle (ASM) in the pathophysiology of asthma. ASM is the main effector of AHR. The mechanisms of AHR in asthma may involve a larger release of contractile mediators and/or a lower release of relaxant mediators, an improved ASM cell excitation/contraction coupling, and/or an alteration in the contraction/load coupling. Beyond its contractile function, ASM is also involved in bronchial inflammation and remodelling. Whereas ASM is a target of the inflammatory process, it can also display proinflammatory and immunomodulatory functions, through its synthetic properties and the expression of a wide range of cell surface molecules. ASM remodelling represents a key feature of asthmatic bronchial remodelling. ASM also plays a role in promoting complementary airway structural alterations, in particular by its synthetic function. PMID:22220184

The contractile ring coordinates curvature-dependent septum assembly during fission yeast cytokinesis.

PubMed

Zhou, Zhou; Munteanu, Emilia Laura; He, Jun; Ursell, Tristan; Bathe, Mark; Huang, Kerwyn Casey; Chang, Fred

2015-01-01

The functions of the actin-myosin-based contractile ring in cytokinesis remain to be elucidated. Recent findings show that in the fission yeast Schizosaccharomyces pombe, cleavage furrow ingression is driven by polymerization of cell wall fibers outside the plasma membrane, not by the contractile ring. Here we show that one function of the ring is to spatially coordinate septum cell wall assembly. We develop an improved method for live-cell imaging of the division apparatus by orienting the rod-shaped cells vertically using microfabricated wells. We observe that the septum hole and ring are circular and centered in wild-type cells and that in the absence of a functional ring, the septum continues to ingress but in a disorganized and asymmetric manner. By manipulating the cleavage furrow into different shapes, we show that the ring promotes local septum growth in a curvature-dependent manner, allowing even a misshapen septum to grow into a more regular shape. This curvature-dependent growth suggests a model in which contractile forces of the ring shape the septum cell wall by stimulating the cell wall machinery in a mechanosensitive manner. Mechanical regulation of the cell wall assembly may have general relevance to the morphogenesis of walled cells. © 2015 Zhou et al. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).

Is depressed myocyte contractility centrally involved in heart failure?

PubMed

Houser, Steven R; Margulies, Kenneth B

2003-03-07

This review examines the evidence for and against the hypothesis that abnormalities in cardiac contractility initiate the heart failure syndrome and drive its progression. There is substantial evidence that the contractility of failing human hearts is depressed and that abnormalities of basal Ca2+ regulation and adrenergic regulation of Ca2+ signaling are responsible. The cellular and molecular defects that cause depressed myocyte contractility are not well established but seem to culminate in abnormal sarcoplasmic reticulum uptake, storage, and release. There are also strong links between Ca2+ regulation, Ca2+ signaling pathways, hypertrophy, and heart failure that need to be more clearly delineated. There is not substantial direct evidence for a causative role for depressed contractility in the initiation and progression of human heart failure, and some studies show that heart failure can occur without depressed myocyte contractility. Stronger support for a causal role for depressed contractility in the initiation of heart failure comes from animal studies where maintaining or improving contractility can prevent heart failure. Recent clinical studies in humans also support the idea that beneficial heart failure treatments, such as beta-adrenergic antagonists, involve improved contractility. Current or previously used heart failure treatments that increase contractility, primarily by increasing cAMP, have generally increased mortality. Novel heart failure therapies that increase or maintain contractility or adrenergic signaling by selectively modulating specific molecules have produced promising results in animal experiments. How to reliably implement these potentially beneficial inotropic therapies in humans without introducing negative side effects is the major unanswered question in this field.

TGF-β improves myocardial function and prevents apoptosis induced by anoxia-reoxygenation, through the reduction of endoplasmic reticulum stress.

PubMed

Wang, Yufeng; Zong, Ligeng; Wang, Xiaolei

2016-01-01

Transforming growth factor-β (TGF-β) is known for its role in ventricular remodeling, inflammatory response, cell survival, and apoptosis. However, its role in improving myocardial function in rat hearts subjected to ischemia-reperfusion (I/R) and protecting against apoptosis induced in cardiomyocytes by anoxia-reoxygenation (A/R) has not been elucidated. This study investigated the protective effects and molecular mechanisms of TGF-β on myocardial function and cardiomyocyte apoptosis. We used TUNEL staining, we tested cell viability, and we measured mitochondrial membrane potential and levels of mitochondrial ROS after 6 h of simulated anoxia together with various durations of simulated reoxygenation in H9c2 cells. We further observed the contractile function in rat hearts after they were subjected to 30 min global ischemia and 180 min reperfusion. Pretreatment with TGF-β markedly inhibited apoptosis in H9c2 cells, as evidenced by increased cell viability and decreased numbers of TUNEL-positive cells, maintained mitochondrial membrane potential, and diminished mitochondrial production of reactive oxygen species (ROS). These changes were associated with the inhibition of endoplasmic reticulum (ER) stress-dependent markers of apoptosis (GRP78, CHOP, caspase-12, and JNK), and the modulation of the expression of Bcl2/Bax. Furthermore, TGF-β improved I/R-induced myocardial contractile dysfunction. All of these protective effects were concentration-dependent. Our results show that TGF-β prevents A/R-induced apoptosis of cardiomyocytes and improves myocardial function in rat hearts injured by I/R.

Cardiac myofibrillar contractile properties during the progression from hypertension to decompensated heart failure.

PubMed

Hanft, Laurin M; Emter, Craig A; McDonald, Kerry S

2017-07-01

Heart failure arises, in part, from a constellation of changes in cardiac myocytes including remodeling, energetics, Ca 2+ handling, and myofibrillar function. However, little is known about the changes in myofibrillar contractile properties during the progression from hypertension to decompensated heart failure. The aim of the present study was to provide a comprehensive assessment of myofibrillar functional properties from health to heart disease. A rodent model of uncontrolled hypertension was used to test the hypothesis that myocytes in compensated hearts exhibit increased force, higher rates of force development, faster loaded shortening, and greater power output; however, with progression to overt heart failure, we predicted marked depression in these contractile properties. We assessed contractile properties in skinned cardiac myocyte preparations from left ventricles of Wistar-Kyoto control rats and spontaneous hypertensive heart failure (SHHF) rats at ~3, ~12, and >20 mo of age to evaluate the time course of myofilament properties associated with normal aging processes compared with myofilaments from rats with a predisposition to heart failure. In control rats, the myofilament contractile properties were virtually unchanged throughout the aging process. Conversely, in SHHF rats, the rate of force development, loaded shortening velocity, and power all increased at ~12 mo and then significantly fell at the >20-mo time point, which coincided with a decrease in left ventricular fractional shortening. Furthermore, these changes occurred independent of changes in β-myosin heavy chain but were associated with depressed phosphorylation of myofibrillar proteins, and the fall in loaded shortening and peak power output corresponded with the onset of clinical signs of heart failure. NEW & NOTEWORTHY This novel study systematically examined the power-generating capacity of cardiac myofilaments during the progression from hypertension to heart disease. Previously undiscovered changes in myofibrillar power output were found and were associated with alterations in myofilament proteins, providing potential new targets to exploit for improved ventricular pump function in heart failure. Copyright © 2017 the American Physiological Society.

In vitro Differentiation of Functional Human Skeletal Myotubes in a Defined System

PubMed Central

Guo, Xiufang; Greene, Keshel; Akanda, Nesar; Smith, Alec; Stancescu, Maria; Lambert, Stephen; Vandenburgh, Herman; Hickman, James

2013-01-01

In vitro human skeletal muscle systems are valuable tools for the study of human muscular development, disease and treatment. However, published in vitro human muscle systems have so far only demonstrated limited differentiation capacities. Advanced differentiation features such as cross-striations and contractility have only been observed in co-cultures with motoneurons. Furthermore, it is commonly regarded that cultured human myotubes do not spontaneously contract, and any contraction has been considered to originate from innervation. This study developed a serum-free culture system in which human skeletal myotubes demonstrated advanced differentiation. Characterization by immunocytochemistry, electrophysiology and analysis of contractile function revealed these major features: A) well defined sarcomeric development, as demonstrated by the presence of cross-striations. B) finely developed excitation-contraction coupling apparatus characterized by the close apposition of dihydropyridine receptors on T-tubules and Ryanodine receptors on sarcoplasmic reticulum membranes. C) spontaneous and electrically controlled contractility. This report not only demonstrates an improved level of differentiation of cultured human skeletal myotubes, but also provides the first published evidence that such myotubes are capable of spontaneous contraction. Use of this functional in vitro human skeletal muscle system would advance studies concerning human skeletal muscle development and physiology, as well as muscle-related disease and therapy. PMID:24516722

In vitro Differentiation of Functional Human Skeletal Myotubes in a Defined System.

PubMed

Guo, Xiufang; Greene, Keshel; Akanda, Nesar; Smith, Alec; Stancescu, Maria; Lambert, Stephen; Vandenburgh, Herman; Hickman, James

2014-01-01

In vitro human skeletal muscle systems are valuable tools for the study of human muscular development, disease and treatment. However, published in vitro human muscle systems have so far only demonstrated limited differentiation capacities. Advanced differentiation features such as cross-striations and contractility have only been observed in co-cultures with motoneurons. Furthermore, it is commonly regarded that cultured human myotubes do not spontaneously contract, and any contraction has been considered to originate from innervation. This study developed a serum-free culture system in which human skeletal myotubes demonstrated advanced differentiation. Characterization by immunocytochemistry, electrophysiology and analysis of contractile function revealed these major features: A) well defined sarcomeric development, as demonstrated by the presence of cross-striations. B) finely developed excitation-contraction coupling apparatus characterized by the close apposition of dihydropyridine receptors on T-tubules and Ryanodine receptors on sarcoplasmic reticulum membranes. C) spontaneous and electrically controlled contractility. This report not only demonstrates an improved level of differentiation of cultured human skeletal myotubes, but also provides the first published evidence that such myotubes are capable of spontaneous contraction. Use of this functional in vitro human skeletal muscle system would advance studies concerning human skeletal muscle development and physiology, as well as muscle-related disease and therapy.

Effects of beta-hydroxy-beta-methylbutyrate (HMB) on the expression of ubiquitin ligases, protein synthesis pathways and contractile function in extensor digitorum longus (EDL) of fed and fasting rats.

PubMed

Gerlinger-Romero, Frederico; Guimarães-Ferreira, Lucas; Yonamine, Caio Yogi; Salgueiro, Rafael Barrera; Nunes, Maria Tereza

2018-03-01

Beta-hydroxy-beta-methylbutyrate (HMB), a leucine metabolite, enhances the gain of skeletal muscle mass by increasing protein synthesis or attenuating protein degradation or both. The aims of this study were to investigate the effect of HMB on molecular factors controlling skeletal muscle protein synthesis and degradation, as well as muscle contractile function, in fed and fasted conditions. Wistar rats were supplied daily with HMB (320 mg/kg body weight diluted in NaCl-0.9%) or vehicle only (control) by gavage for 28 days. After this period, some of the animals were subjected to a 24-h fasting, while others remained in the fed condition. The EDL muscle was then removed, weighed and used to evaluate the genes and proteins involved in protein synthesis (AKT/4E-BP1/S6) and degradation (Fbxo32 and Trim63). A sub-set of rats were used to measure in vivo muscle contractile function. HMB supplementation increased AKT phosphorylation during fasting (three-fold). In the fed condition, no differences were detected in atrogenes expression between control and HMB supplemented group; however, HMB supplementation did attenuate the fasting-induced increase in their expression levels. Fasting animals receiving HMB showed improved sustained tetanic contraction times (one-fold) and an increased muscle to tibia length ratio (1.3-fold), without any cross-sectional area changes. These results suggest that HMB supplementation under fasting conditions increases AKT phosphorylation and attenuates the increased of atrogenes expression, followed by a functional improvement and gain of skeletal muscle weight, suggesting that HMB protects skeletal muscle against the deleterious effects of fasting.

IMPACT OF CALCIUM-CHANNEL BLOCKERS ON RIGHT HEART FUNCTION IN A CONTROLLED MODEL OF CHRONIC PULMONARY HYPERTENSION

PubMed Central

Zierer, Andreas; Voeller, Rochus K.; Melby, Spencer J.; Steendijk, Paul; Moon, Marc R.

2009-01-01

Purpose Patients with chronic pulmonary hypertension (CPH) who demonstrate a pulmonary vasodilation following calcium channel blocker (CCB) administration are defined as “responders”. In contrast, “non-responders” are patients who do not show such a pulmonary vasodilation with CCB therapy. The purpose of this investigation was to study the effects of CCB therapy on right heart mechanics in experimental CCB responders versus CCB non-responders. Methods In 12 dogs, right atrial (RA) and ventricular (RV) pressure and volume (conductance catheters) were simultaneously recorded after 3 months of progressive pulmonary artery (PA) banding. Diltiazem was given at 10 mg/hr with the PA constricted (simulated CCB non-responder). Responders were then created by releasing the PA band to unload the ventricle. RA and RV contractility and diastolic stiffness (slope of end-systolic and end-diastolic pressure-volume relations) were calculated and RA reservoir and conduit function were quantified as RA inflow with the tricuspid valve closed versus open, respectively. Results With CCB, RA contractility (p<0.03) and cardiac output (p<0.004) were compromised in simulated non-responders while RA stroke work was pharmacologically depressed in the setting of an unchanged afterload. After simulating a responder by controlled PA band release, the RA became less distensible, causing a shift from reservoir to conduit function (p<0.001) towards physiologic baseline conditions and a recovery in the hyperdynamic compensatory response in both chambers (p<0.007) as evidenced in a declined RA and RV contractility with an improved cardiac output as compared to CPH and simulated non-responders. RA and RV diastolic function in both groups was not affected by CCB. Conclusions CCB did not impact RV function in simulated non-responders, but significantly impaired RA contractility and cardiac output. In simulated responders, afterload fell substantially, thereby allowing the RA and RV to recover from their pathological hyperdynamic contractile response to CPH. This affect was able to outweigh the intrinsic negative effects of CCB therapy on systolic RA function. Current data suggest that the RA in CPH is much more sensitive to CCB therapy than the RV and delineate for the first time why CCB therapy in CPH has been empirically restricted to documented responders. PMID:19237986

The effect of obesity on the contractile performance of isolated mouse soleus, EDL, and diaphragm muscles.

PubMed

Tallis, Jason; Hill, Cameron; James, Rob S; Cox, Val M; Seebacher, Frank

2017-01-01

Obesity affects the major metabolic and cellular processes involved in skeletal muscle contractility. Surprisingly, the effect of obesity on isolated skeletal muscle performance remains unresolved. The present study is the first to examine the muscle-specific changes in contractility following dietary-induced obesity using an isolated muscle work-loop (WL) model that more closely represents in vivo muscle performance. Following 16-wk high-calorific feeding, soleus (SOL), extensor digitorum longus (EDL), and diaphragm (DIA) were isolated from female (CD-1) mice, and contractile performance was compared against a lean control group. Obese SOL produced greater isometric force; however, isometric stress (force per unit muscle area), absolute WL power, and normalized WL power (watts per kilogram muscle mass) were unaffected. Maximal isometric force and absolute WL power of the EDL were similar between groups. For both EDL and DIA, isometric stress and normalized WL power were reduced in the obese groups. Obesity caused a significant reduction in fatigue resistance in all cases. Our findings demonstrate a muscle-specific reduction in contractile performance and muscle quality that is likely related to in vivo mechanical role, fiber type, and metabolic profile, which may in part be related to changes in myosin heavy chain expression and AMP-activated protein kinase activity. These results infer that, beyond the additional requirement of moving a larger body mass, functional performance and quality of life may be further limited by poor muscle function in obese individuals. As such, a reduction in muscle performance may be a substantial contributor to the negative cycle of obesity. The effect of obesity on isolated muscle function is surprisingly underresearched. The present study is the first to examine the effects of obesity on isolated muscle performance using a method that more closely represents real-world muscle function. This work uniquely establishes a muscle-specific profile of mechanical changes in relation to underpinning mechanisms. These findings may be important to understanding the negative cycle of obesity and in designing interventions for improving weight status. Copyright © 2017 the American Physiological Society.

Triiodothyronine facilitates weaning from extracorporeal membrane oxygenation by improved mitochondrial substrate utilization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Files, Matthew D.; Kajimoto, Masaki; Priddy, Colleen M.

2014-03-20

Extracorporeal membrane oxygenation (ECMO) provides a bridge to recovery after myocardial injury in infants and children, yet morbidity and mortality remain high. Weaning from the circuit requires adequate cardiac contractile function, which can be impaired by metabolic disturbances induced either by ischemia-reperfusion and / or by ECMO.

Apelin Increases Cardiac Contractility via Protein Kinase Cε- and Extracellular Signal-Regulated Kinase-Dependent Mechanisms

PubMed Central

Perjés, Ábel; Skoumal, Réka; Tenhunen, Olli; Kónyi, Attila; Simon, Mihály; Horváth, Iván G.; Kerkelä, Risto; Ruskoaho, Heikki; Szokodi, István

2014-01-01

Background Apelin, the endogenous ligand for the G protein-coupled apelin receptor, is an important regulator of the cardiovascular homoeostasis. We previously demonstrated that apelin is one of the most potent endogenous stimulators of cardiac contractility; however, its underlying signaling mechanisms remain largely elusive. In this study we characterized the contribution of protein kinase C (PKC), extracellular signal-regulated kinase 1/2 (ERK1/2) and myosin light chain kinase (MLCK) to the positive inotropic effect of apelin. Methods and Results In isolated perfused rat hearts, apelin increased contractility in association with activation of prosurvival kinases PKC and ERK1/2. Apelin induced a transient increase in the translocation of PKCε, but not PKCα, from the cytosol to the particulate fraction, and a sustained increase in the phosphorylation of ERK1/2 in the left ventricle. Suppression of ERK1/2 activation diminished the apelin-induced increase in contractility. Although pharmacological inhibition of PKC attenuated the inotropic response to apelin, it had no effect on ERK1/2 phosphorylation. Moreover, the apelin-induced positive inotropic effect was significantly decreased by inhibition of MLCK, a kinase that increases myofilament Ca2+ sensitivity. Conclusions Apelin increases cardiac contractility through parallel and independent activation of PKCε and ERK1/2 signaling in the adult rat heart. Additionally MLCK activation represents a downstream mechanism in apelin signaling. Our data suggest that, in addition to their role in cytoprotection, modest activation of PKCε and ERK1/2 signaling improve contractile function, therefore these pathways represent attractive possible targets in the treatment of heart failure. PMID:24695532

Smooth muscle architecture within cell-dense vascular tissues influences functional contractility.

PubMed

Win, Zaw; Vrla, Geoffrey D; Steucke, Kerianne E; Sevcik, Emily N; Hald, Eric S; Alford, Patrick W

2014-12-01

The role of vascular smooth muscle architecture in the function of healthy and dysfunctional vessels is poorly understood. We aimed at determining the relationship between vascular smooth muscle architecture and contractile output using engineered vascular tissues. We utilized microcontact printing and a microfluidic cell seeding technique to provide three different initial seeding conditions, with the aim of influencing the cellular architecture within the tissue. Cells seeded in each condition formed confluent and aligned tissues but within the tissues, the cellular architecture varied. Tissues with a more elongated cellular architecture had significantly elevated basal stress and produced more contractile stress in response to endothelin-1 stimulation. We also found a correlation between the contractile phenotype marker expression and the cellular architecture, contrary to our previous findings in non-confluent tissues. Taken with previous results, these data suggest that within cell-dense vascular tissues, smooth muscle contractility is strongly influenced by cell and tissue architectures.

Optimum periodicity of repeated contractile actions applied in mass transport

NASA Astrophysics Data System (ADS)

Ahn, Sungsook; Lee, Sang Joon

2015-01-01

Dynamically repeated periodic patterns are abundant in natural and artificial systems, such as tides, heart beats, stock prices, and the like. The characteristic repeatability and periodicity are expected to be optimized in effective system-specific functions. In this study, such optimum periodicity is experimentally evaluated in terms of effective mass transport using one-valve and multi-valve systems working in contractile fluid flows. A set of nanoscale gating functions is utilized, operating in nanocomposite networks through which permeates selectively pass under characteristic contractile actions. Optimized contractile periodicity exists for effective energy impartment to flow in a one-valve system. In the sequential contractile actions for a multi-valve system, synchronization with the fluid flow is critical for effective mass transport. This study provides fundamental understanding on the various repeated periodic patterns and dynamic repeatability occurring in nature and mechanical systems, which are useful for broad applications.

Effects of regular exercise training on skeletal muscle contractile function

NASA Technical Reports Server (NTRS)

Fitts, Robert H.

2003-01-01

Skeletal muscle function is critical to movement and one's ability to perform daily tasks, such as eating and walking. One objective of this article is to review the contractile properties of fast and slow skeletal muscle and single fibers, with particular emphasis on the cellular events that control or rate limit the important mechanical properties. Another important goal of this article is to present the current understanding of how the contractile properties of limb skeletal muscle adapt to programs of regular exercise.

Role of microtubules in the contractile dysfunction of hypertrophied myocardium

NASA Technical Reports Server (NTRS)

Zile, M. R.; Koide, M.; Sato, H.; Ishiguro, Y.; Conrad, C. H.; Buckley, J. M.; Morgan, J. P.; Cooper, G. 4th

1999-01-01

OBJECTIVES: We sought to determine whether the ameliorative effects of microtubule depolymerization on cellular contractile dysfunction in pressure overload cardiac hypertrophy apply at the tissue level. BACKGROUND: A selective and persistent increase in microtubule density causes decreased contractile function of cardiocytes from cats with hypertrophy produced by chronic right ventricular (RV) pressure overloading. Microtubule depolymerization by colchicine normalizes contractility in these isolated cardiocytes. However, whether these changes in cellular function might contribute to changes in function at the more highly integrated and complex cardiac tissue level was unknown. METHODS: Accordingly, RV papillary muscles were isolated from 25 cats with RV pressure overload hypertrophy induced by pulmonary artery banding (PAB) for 4 weeks and 25 control cats. Contractile state was measured using physiologically sequenced contractions before and 90 min after treatment with 10(-5) mol/liter colchicine. RESULTS: The PAB significantly increased RV systolic pressure and the RV weight/body weight ratio in PAB; it significantly decreased developed tension from 59+/-3 mN/mm2 in control to 25+/-4 mN/mm2 in PAB, shortening extent from 0.21+/-0.01 muscle lengths (ML) in control to 0.12+/-0.01 ML in PAB, and shortening rate from 1.12+/-0.07 ML/s in control to 0.55+/-0.03 ML/s in PAB. Indirect immunofluorescence confocal microscopy showed that PAB muscles had a selective increase in microtubule density and that colchicine caused complete microtubule depolymerization in both control and PAB papillary muscles. Microtubule depolymerization normalized myocardial contractility in papillary muscles of PAB cats but did not alter contractility in control muscles. CONCLUSIONS: Excess microtubule density, therefore, is equally important to both cellular and to myocardial contractile dysfunction caused by chronic, severe pressure-overload cardiac hypertrophy.

Relationship between systolic and diastolic function with improvements in forward stroke volume following reduction in mitral regurgitation

NASA Technical Reports Server (NTRS)

Firstenberg, M. S.; Greenberg, N. L.; Smedira, N. G.; McCarthy, P. M.; Garcia, M. J.; Thomas, J. D.

2001-01-01

Efforts to improve mitral regurgitation (MR) are often performed in conjunction with coronary revascularization. However, the independent effects of a reduced MR area (MRa) are difficult to quantify. Using a previously developed cardiovascular model, ventricular contractility (elastance 1-8 mmHg/ml) and relaxation (tau: 40-150 msec) were independently adjusted for four grades of MR orifice areas (0.0 to 0.8 cm2). Improvements in forward stroke volume (fSV) were determined for the permutations of reduced MRa. For all conditions, LV end-diastolic pressure and volumes ranged from 7.3-24.2 mmHg and 64.8-174.3 ml, respectively. Overall, fSV ranged from 36.0-89.4 (mean: 64.2 +/- 12.8) ml, improved between 6.4 and 35.3% (mean: 15.6 +/- 8.1%), and was best predicted by (r=0.97, p<0.01) %delta(fSV)[correction of fVS]=34[MRa initial] - 46[MRa final] -0.5[elastance]. Reduced MRa, independent of relaxation and minimally influence by contractility, yield improved fSVs.

Estrogen and testosterone in concert with EFNB3 regulate vascular smooth muscle cell contractility and blood pressure.

PubMed

Wang, Yujia; Wu, Zenghui; Thorin, Eric; Tremblay, Johanne; Lavoie, Julie L; Luo, Hongyu; Peng, Junzheng; Qi, Shijie; Wu, Tao; Chen, Fei; Shen, Jianzhong; Hu, Shenjiang; Wu, Jiangping

2016-04-01

EPH kinases and their ligands, ephrins (EFNs), have vital and diverse biological functions, although their function in blood pressure (BP) control has not been studied in detail. In the present study, we report that Efnb3 gene knockout (KO) led to increased BP in female but not male mice. Vascular smooth muscle cells (VSMCs) were target cells for EFNB3 function in BP regulation. The deletion of EFNB3 augmented contractility of VSMCs from female but not male KO mice, compared with their wild-type (WT) counterparts. Estrogen augmented VSMC contractility while testosterone reduced it in the absence of EFNB3, although these sex hormones had no effect on the contractility of VSMCs from WT mice. The effect of estrogen on KO VSMC contractility was via a nongenomic pathway involving GPER, while that of testosterone was likely via a genomic pathway, according to VSMC contractility assays and GPER knockdown assays. The sex hormone-dependent contraction phenotypes in KO VSMCs were reflected in BP in vivo. Ovariectomy rendered female KO mice normotensive. At the molecular level, EFNB3 KO in VSMCs resulted in reduced myosin light chain kinase phosphorylation, an event enhancing sensitivity to Ca(2+)flux in VSMCs. Our investigation has revealed previously unknown EFNB3 functions in BP regulation and show that EFNB3 might be a hypertension risk gene in certain individuals. Copyright © 2016 the American Physiological Society.

Contractile function recovery in severely injured gastrocnemius muscle of rats treated with either oleic or linoleic acid.

PubMed

Abreu, Phablo; Pinheiro, Carlos H J; Vitzel, Kaio F; Vasconcelos, Diogo A A; Torres, Rosângela P; Fortes, Marco S; Marzuca-Nassr, Gabriel N; Mancini-Filho, Jorge; Hirabara, Sandro M; Curi, Rui

2016-11-01

What is the central question of this study? Oleic and linoleic acids modulate fibroblast proliferation and myogenic differentiation in vitro. However, their in vivo effects on muscle regeneration have not yet been examined. We investigated the effects of either oleic or linoleic acid on a well-established model of muscle regeneration after severe laceration. What is the main finding and its importance? We found that linoleic acid increases fibrous tissue deposition and impairs muscle regeneration and recovery of contractile function, whereas oleic acid has the opposite effects in severely injured gastrocnemius muscle, suggesting that linoleic acid has a harmful effect and oleic acid a potential therapeutic effect on muscle regeneration. Oleic and linoleic acids control fibroblast proliferation and myogenic differentiation in vitro; however, there was no study in skeletal muscle in vivo. The aim of this study was to evaluate the effects of either oleic or linoleic acid on the fibrous tissue content (collagen deposition) of muscle and recovery of contractile function in rat gastrocnemius muscle after being severely injured by laceration. Rats were supplemented with either oleic or linoleic acid for 4 weeks after laceration [0.44 g (kg body weight) -1 day -1 ]. Muscle injury led to an increase in oleic-to-stearic acid and palmitoleic-to-palmitic acid ratios, suggesting an increase in Δ 9 desaturase activity. Increased fibrous tissue deposition and reduced isotonic and tetanic specific forces and resistance to fatigue were observed in the injured muscle. Supplementation with linoleic acid increased the content of eicosadienoic (20:2, n-6) and arachidonic (20:4, n-6) acids, reduced muscle mass and fibre cross-sectional areas, increased fibrous tissue deposition and further reduced the isotonic and tetanic specific forces and resistance to fatigue induced by laceration. Supplementation with oleic acid increased the content of docosahexaenoic acid (22:6, n-3) and abolished the increase in fibrous tissue area and the decrease in isotonic and tetanic specific forces and resistance to fatigue induced by muscle injury. We concluded that supplementation with linoleic acid impairs muscle regeneration and increases fibrous tissue deposition, resulting in impaired recovery of contractile function. Oleic acid supplementation reduced fibrous tissue deposition and improved recovery of contractile function, attenuating the tissue damage caused by muscle injury. © 2016 The Authors. Experimental Physiology © 2016 The Physiological Society.

Losartan increases NO release in afferent arterioles during regression of L-NAME-induced renal damage.

PubMed

Helle, Frank; Iversen, Bjarne M; Chatziantoniou, Christos

2010-05-01

Inhibition of nitric oxide synthesis (NOS) induces hypertension and heavy proteinuria. Renal structure and function have shown striking improvement after interventions targeting ANG II or endothelin (ET) receptors in rats recovering after long-term NOS inhibition. To search for mechanisms underlying losartan-assisted regression of renal disease in rodents, we measured NO release and contractility to ET in afferent arterioles (AAs) from Sprague-Dawley rats recovering for 2 wk after 4 wk of N(G)-nitro-L-arginine methyl ester treatment. Losartan administration during the recovery period decreased blood pressure (113 ± 4 vs. 146 ± 5 mmHg, P < 0.01), reduced protein/creatinine ratio more (proteinuria decrease: Δ1,836 ± 214 vs. Δ1,024 ± 180 mg/mmol, P < 0.01), and normalized microvascular hypertrophy (AA media/lumen ratio: 1.74 ± 0.05 vs. 2.09 ± 0.08, P < 0.05) compared with no treatment. In diaminofluorescein-FM-loaded AAs from losartan-treated animals, NO release (% of baseline) was increased compared with untreated animals after stimulation with 10(-7) M ACh (118 ± 4 vs. 90 ± 7%, t = 560 s, P < 0.001) and 10(-9) M ET (123 ± 4 vs. 101 ± 5%, t = 560 s, P < 0.001). There was also a blunted contractile response to 10(-7) M ET in AAs from losartan-treated animals compared with untreated animals (Δ4.01 ± 2.9 vs. Δ14.6 ± 1.7 μm, P < 0.01), which disappeared after acute NOS inhibition (Δ10.7 ± 3.7 vs. Δ12.5 ± 2.9 μm, not significant). Contractile dose responses to ET (10(-9), 10(-8), 10(-7) M) were enhanced by NOS inhibition and blunted by exogenous NO (10(-2) mM S-nitroso-N-acetyl-penicillamine) in losartan-treated but not in untreated vessels. Reducing blood pressure similar to losartan with hydralazine did not improve AA hypertrophy, ET-induced contractility, ET-induced NO release, and NO sensitivity. In conclusion, blockade of the local action of ANG II improved endothelial function in AAs, a mechanism that is likely to contribute to the beneficial effects of AT(1a)R antagonism during the recovery of renal function after long-term NOS inhibition in rats.

Effects of intra-aortic balloon pump counterpulsation on left ventricular mechanoenergetics in a porcine model of acute ischemic heart failure.

PubMed

Malliaras, Konstantinos; Charitos, Efstratios; Diakos, Nikolaos; Pozios, Iraklis; Papalois, Apostolos; Terrovitis, John; Nanas, John

2014-12-01

We investigated the effects of intra-aortic balloon pump (IABP) counterpulsation on left ventricular (LV) contractility, relaxation, and energy consumption and probed the underlying physiologic mechanisms in 12 farm pigs, using an ischemia-reperfusion model of acute heart failure. During both ischemia and reperfusion, IABP support unloaded the LV, decreased LV energy consumption (pressure-volume area, stroke work), and concurrently improved LV mechanical performance (ejection fraction, stroke volume, cardiac output). During reperfusion exclusively, IABP also improved LV relaxation (tau) and contractility (Emax, PRSW). The beneficial effects of IABP support on LV relaxation and contractility correlated with IABP-induced augmentation of coronary blood flow. In conclusion, we find that during both ischemia and reperfusion, IABP support optimizes LV energetic performance (decreases energy consumption and concurrently improves mechanical performance) by LV unloading. During reperfusion exclusively, IABP support also improves LV contractility and active relaxation, possibly due to a synergistic effect of unloading and augmentation of coronary blood flow.

A novel cardiac extracorporeal shock wave for enhancing the efficacy of cell therapy

NASA Astrophysics Data System (ADS)

Khaled, Walaa; Assmus, Birgit; Lutz, Andreas; Walter, Dirk; Leistner, David; Dimmeler, Stefanie; Zeiher, Andreas

2012-11-01

Targeted therapy can maximize therapeutic efficiency and minimize the side effects of drug treatments, especially for cancer and cardiovascular disease. In previous in-vitro experiments, it was shown that shock wave (SW) application can change the permeability of cell membranes for tumor therapy. Similarly, in animal studies, extracorporeal SWs were proven to increase expression of growth and homing factors like SDF-1 and vascular endothelial growth factor (VEGF) within a targeted ischemic tissue. This pretreatment increased the homing and neovascularization following application of bone marrow-derived mononuclear cells (BMC). In a randomized, double blinded, placebo-controlled clinical trial, 103 patients were recruited with stable chronic post-infarction heart failure (CHF). The goal of this work was to demonstrate improved recovery of left ventricular contractile function (LVEF) by combining targeted SW application with subsequent BMC administration. Results showed that the shock wavefacilitated intracoronary BMC administration in patients with chronic post-infarction heart failure is associated with significant persistent improvements in LVEF contractile function, NYHA class, and reduction of major adverse clinical events during extended clinical follow-up. (clinicaltrials.gov: NCT00326989).

Early treatment with losartan effectively ameliorates hypertension and improves vascular remodeling and function in a prehypertensive rat model.

PubMed

He, De-Hua; Lin, Jin-Xiu; Zhang, Liang-Min; Xu, Chang-Sheng; Xie, Qiang

2017-03-15

Pharmacological treatment of prehypertension may ameliorate hypertension and improve vascular structure and function. This study investigated 1) whether early treatment with either losartan or amlodipine at the onset of prehypertension can prevent hypertension and 2) whether losartan and amlodipine equally improve vascular remodeling and function in a rat model of hypertension. Stroke-prone spontaneously hypertensive (SHRSP) rats were administered losartan, amlodipine or saline for 6 or 16weeks at the onset of prehypertension. Wistar-Kyoto rats were used as a control. All groups were observed for 40weeks. Systolic blood pressure was measured using the tail-cuff method. Vascular structure and function were determined by microscopy and vascular ring contractility assays, respectively. Angiotensin II (Ang II) and aldosterone (Aldo) were measured by radioimmunoassays. Angiotensin II type 1 receptor (AT1R) and angiotensin II type 2 receptor (AT2R) expression was measured by western blot. Losartan effectively reduced progression from prehypertension to hypertension as well as vascular remodeling and improved vascular contractility in SHRSP rats. Long-term losartan (16weeks) had greater benefits than short-term (6weeks) treatment. Losartan increased Ang II and decreased Aldo levels in the serum and vessel walls of resistance vessels in a time-dependent manner. Losartan significantly decreased AT1R and increased AT2R vascular expression. Amlodipine had no effect on vascular AT1R and AT2R expression. Losartan administered at the onset of prehypertension is more effective than amlodipine in ameliorating hypertension and improving vascular remodeling and function, which is likely mediated by the renin-angiotensin-aldosterone system. Copyright © 2017 Elsevier Inc. All rights reserved.

β-Arrestin2 Improves Post-Myocardial Infarction Heart Failure via Sarco(endo)plasmic Reticulum Ca2+-ATPase-Dependent Positive Inotropy in Cardiomyocytes.

PubMed

McCrink, Katie A; Maning, Jennifer; Vu, Angela; Jafferjee, Malika; Marrero, Christine; Brill, Ava; Bathgate-Siryk, Ashley; Dabul, Samalia; Koch, Walter J; Lymperopoulos, Anastasios

2017-11-01

Heart failure is the leading cause of death in the Western world, and new and innovative treatments are needed. The GPCR (G protein-coupled receptor) adapter proteins βarr (β-arrestin)-1 and βarr-2 are functionally distinct in the heart. βarr1 is cardiotoxic, decreasing contractility by opposing β 1 AR (adrenergic receptor) signaling and promoting apoptosis/inflammation post-myocardial infarction (MI). Conversely, βarr2 inhibits apoptosis/inflammation post-MI but its effects on cardiac function are not well understood. Herein, we sought to investigate whether βarr2 actually increases cardiac contractility. Via proteomic investigations in transgenic mouse hearts and in H9c2 rat cardiomyocytes, we have uncovered that βarr2 directly interacts with SERCA2a (sarco[endo]plasmic reticulum Ca 2+ -ATPase) in vivo and in vitro in a β 1 AR-dependent manner. This interaction causes acute SERCA2a SUMO (small ubiquitin-like modifier)-ylation, increasing SERCA2a activity and thus, cardiac contractility. βarr1 lacks this effect. Moreover, βarr2 does not desensitize β 1 AR cAMP-dependent procontractile signaling in cardiomyocytes, again contrary to βarr1. In vivo, post-MI heart failure mice overexpressing cardiac βarr2 have markedly improved cardiac function, apoptosis, inflammation, and adverse remodeling markers, as well as increased SERCA2a SUMOylation, levels, and activity, compared with control animals. Notably, βarr2 is capable of ameliorating cardiac function and remodeling post-MI despite not increasing cardiac βAR number or cAMP levels in vivo. In conclusion, enhancement of cardiac βarr2 levels/signaling via cardiac-specific gene transfer augments cardiac function safely, that is, while attenuating post-MI remodeling. Thus, cardiac βarr2 gene transfer might be a novel, safe positive inotropic therapy for both acute and chronic post-MI heart failure. © 2017 American Heart Association, Inc.

Operative contractility: a functional concept of the inotropic state.

PubMed

Curiel, Roberto; Perez-Gonzalez, Juan; Torres, Edwar; Landaeta, Ruben; Cerrolaza, Miguel

2005-10-01

1. Initial unsuccessful attempts to evaluate ventricular function in terms of the 'heart as a pump' led to focusing on the 'heart as a muscle' and to the concept of myocardial contractility. However, no clinically ideal index exists to assess the contractile state. The aim of the present study was to develop a mathematical model to assess cardiac contractility. 2. A tri-axial system was conceived for preload (PL), afterload (AL) and contractility, where stroke volume (SV) was represented as the volume of the tetrahedron. Based on this model, 'operative' contractility ('OperCon') was calculated from the readily measured values of PL, AL and SV. The model was tested retrospectively under a variety of different experimental and clinical conditions, in 71 studies in humans and 29 studies in dogs. A prospective echocardiographic study was performed in 143 consecutive subjects to evaluate the ability of the model to assess contractility when SV and PL were measured volumetrically (mL) or dimensionally (cm). 3. With inotropic interventions, OperCon changes were comparable to those of ejection fraction (EF), velocity of shortening (Vcf) and dP/dt-max. Only with positive inotropic interventions did elastance (Ees) show significantly larger changes. With load manipulations, OperCon showed significantly smaller changes than EF and Ees and comparable changes to Vcf and dP/dt-max. Values of OperCon were similar when AL was represented by systolic blood pressure or wall stress and when volumetric or dimensional values were used. 4. Operative contractility is a reliable, simple and versatile method to assess cardiac contractility.

Different Roles for Contracture and Calpain in Calcium Paradox-Induced Heart Injury

PubMed Central

Zhang, Jian-Ying; Bi, Sheng-Hui; Xu, Ming; Jin, Zhen-Xiao; Yang, Yang; Jiang, Xiao-Fan; Zhou, Jing-Jun

2012-01-01

The Ca2+ paradox represents a good model to study Ca2+ overload injury in ischemic heart diseases. We and others have demonstrated that contracture and calpain are involved in the Ca2+ paradox-induced injury. This study aimed to elucidate their roles in this model. The Ca2+ paradox was elicited by perfusing isolated rat hearts with Ca2+-free KH media for 3 min or 5 min followed by 30 min of Ca2+ repletion. The LVDP was measured to reflect contractile function, and the LVEDP was measured to indicate contracture. TTC staining and the quantification of LDH release were used to define cell death. Calpain activity and troponin I release were measured after Ca2+ repletion. Ca2+ repletion of the once 3-min Ca2+ depleted hearts resulted in almost no viable tissues and the disappearance of contractile function. Compared to the effects of the calpain inhibitor MDL28170, KB-R7943, an inhibitor of the Na+/Ca2+ exchanger, reduced the LVEDP level to a greater extent, which was well correlated with improved contractile function recovery and tissue survival. The depletion of Ca2+ for 5 min had the same effects on injury as the 3-min Ca2+ depletion, except that the LVEDP in the 5-min Ca2+ depletion group was lower than the level in the 3-min Ca2+ depletion group. KB-R7943 failed to reduce the level of LVEDP, with no improvement in the LVDP recovery in the hearts subjected to the 5-min Ca2+ depletion treatment; however, KB-R7943 preserved its protective effects in surviving tissue. Both KB-R7943 and MDL28170 attenuated the Ca2+ repletion-induced increase in calpain activity in 3 min or 5 min Ca2+ depleted hearts. However, only KB-R7943 reduced the release of troponin I from the Ca2+ paradoxic heart. These results provide evidence suggesting that contracture is the main cause for contractile dysfunction, while activation of calpain mediates cell death in the Ca2+ paradox. PMID:23284963

Prevalence of scarred and dysfunctional myocardium in patients with heart failure of ischaemic origin: A cardiovascular magnetic resonance study

PubMed Central

2011-01-01

Background Cardiovascular magnetic resonance (CMR) with late gadolinium enhancement (LGE) can provide unique data on the transmural extent of scar/viability. We assessed the prevalence of dysfunctional myocardium, including partial thickness scar, which could contribute to left ventricular contractile dysfunction in patients with heart failure and ischaemic heart disease who denied angina symptoms. Methods We invited patients with ischaemic heart disease and a left ventricular ejection fraction < 50% by echocardiography to have LGE CMR. Myocardial contractility and transmural extent of scar were assessed using a 17-segment model. Results The median age of the 193 patients enrolled was 70 (interquartile range: 63-76) years and 167 (87%) were men. Of 3281 myocardial segments assessed, 1759 (54%) were dysfunctional, of which 581 (33%) showed no scar, 623 (35%) had scar affecting ≤50% of wall thickness and 555 (32%) had scar affecting > 50% of wall thickness. Of 1522 segments with normal contractile function, only 98 (6%) had evidence of scar on CMR. Overall, 182 (94%) patients had ≥1 and 107 (55%) patients had ≥5 segments with contractile dysfunction that had no scar or ≤50% transmural scar suggesting viability. Conclusions In this cohort of patients with left ventricular systolic dysfunction and ischaemic heart disease, about half of all segments had contractile dysfunction but only one third of these had > 50% of the wall thickness affected by scar, suggesting that most dysfunctional segments could improve in response to an appropriate intervention. PMID:21936915

Lack of miR-133a Decreases Contractility of Diabetic Hearts: A Role for Novel Cross Talk Between Tyrosine Aminotransferase and Tyrosine Hydroxylase

PubMed Central

Nandi, Shyam Sundar; Zheng, Hong; Sharma, Neeru M.; Shahshahan, Hamid R.; Patel, Kaushik P.

2016-01-01

MicroRNAs (miRNAs) have a fundamental role in diabetic heart failure. The cardioprotective miRNA-133a (miR-133a) is downregulated, and contractility is decreased in diabetic hearts. Norepinephrine (NE) is a key catecholamine that stimulates contractility by activating β-adrenergic receptors (β-AR). NE is synthesized from tyrosine by the rate-limiting enzyme, tyrosine hydroxylase (TH), and tyrosine is catabolized by tyrosine aminotransferase (TAT). However, the cross talk/link between TAT and TH in the heart is unclear. To determine whether miR-133a plays a role in the cross talk between TH and TAT and regulates contractility by influencing NE biosynthesis and/or β-AR levels in diabetic hearts, Sprague-Dawley rats and miR-133a transgenic (miR-133aTg) mice were injected with streptozotocin to induce diabetes. The diabetic rats were then treated with miR-133a mimic or scrambled miRNA. Our results revealed that miR-133a mimic treatment improved the contractility of the diabetic rat’s heart concomitant with upregulation of TH, cardiac NE, β-AR, and downregulation of TAT and plasma levels of NE. In miR-133aTg mice, cardiac-specific miR-133a overexpression prevented upregulation of TAT and suppression of TH in the heart after streptozotocin was administered. Moreover, miR-133a overexpression in CATH.a neuronal cells suppressed TAT with concomitant upregulation of TH, whereas knockdown and overexpression of TAT demonstrated that TAT inhibited TH. Luciferase reporter assay confirmed that miR-133a targets TAT. In conclusion, miR-133a controls the contractility of diabetic hearts by targeting TAT, regulating NE biosynthesis, and consequently, β-AR and cardiac function. PMID:27411382

Adaptations of mouse skeletal muscle to low intensity vibration training

PubMed Central

McKeehen, James N.; Novotny, Susan A.; Baltgalvis, Kristen A.; Call, Jarrod A.; Nuckley, David J.; Lowe, Dawn A.

2013-01-01

Purpose We tested the hypothesis that low intensity vibration training in mice improves contractile function of hindlimb skeletal muscles and promotes exercise-related cellular adaptations. Methods We subjected C57BL/6J mice to 6 wk, 5 d·wk−1, 15 min·d−1 of sham or low intensity vibration (45 Hz, 1.0 g) while housed in traditional cages (Sham-Active, n=8; Vibrated-Active, n=10) or in small cages to restrict physical activity (Sham-Restricted, n=8; Vibrated-Restricted, n=8). Contractile function and resistance to fatigue were tested in vivo (anterior and posterior crural muscles) and ex vivo on the soleus muscle. Tibialis anterior and soleus muscles were evaluated histologically for alterations in oxidative metabolism, capillarity, and fiber types. Epididymal fat pad and hindlimb muscle masses were measured. Two-way ANOVAs were used to determine effects of vibration and physical inactivity. Results Vibration training resulted in a 10% increase in maximal isometric torque (P=0.038) and 16% faster maximal rate of relaxation (P=0.030) of the anterior crural muscles. Posterior crural muscles were unaffected by vibration, with the exception of greater rates of contraction in Vibrated-Restricted mice compared to Vibrated-Active and Sham-Restricted mice (P=0.022). Soleus muscle maximal isometric tetanic force tended to be greater (P=0.057) and maximal relaxation was 20% faster (P=0.005) in Vibrated compared to Sham mice. Restriction of physical activity induced muscle weakness but was not required for vibration to be effective in improving strength or relaxation. Vibration training did not impact muscle fatigability or any indicator of cellular adaptation investigated (P≥0.431). Fat pad but not hindlimb muscle masses were affected by vibration training. Conclusion Vibration training in mice improved muscle contractility, specifically strength and relaxation rates, with no indication of adverse effects to muscle function or cellular adaptations. PMID:23274599

Changes in contractile activation characteristics of rat fast and slow skeletal muscle fibres during regeneration.

PubMed

Gregorevic, Paul; Plant, David R; Stupka, Nicole; Lynch, Gordon S

2004-07-15

Damaged skeletal muscle fibres are replaced with new contractile units via muscle regeneration. Regenerating muscle fibres synthesize functionally distinct isoforms of contractile and regulatory proteins but little is known of their functional properties during the regeneration process. An advantage of utilizing single muscle fibre preparations is that assessment of their function is based on the overall characteristics of the contractile apparatus and regulatory system and as such, these preparations are sensitive in revealing not only coarse, but also subtle functional differences between muscle fibres. We examined the Ca(2+)- and Sr(2+)-activated contractile characteristics of permeabilized fibres from rat fast-twitch (extensor digitorum longus) and slow-twitch (soleus) muscles at 7, 14 and 21 days following myotoxic injury, to test the hypothesis that fibres from regenerating fast and slow muscles have different functional characteristics to fibres from uninjured muscles. Regenerating muscle fibres had approximately 10% of the maximal force producing capacity (P(o)) of control (uninjured) fibres, and an altered sensitivity to Ca(2+) and Sr(2+) at 7 days post-injury. Increased force production and a shift in Ca(2+) sensitivity consistent with fibre maturation were observed during regeneration such that P(o) was restored to 36-45% of that in control fibres by 21 days, and sensitivity to Ca(2+) and Sr(2+) was similar to that of control (uninjured) fibres. The findings support the hypothesis that regenerating muscle fibres have different contractile activation characteristics compared with mature fibres, and that they adopt properties of mature fast- or slow-twitch muscle fibres in a progressive manner as the regeneration process is completed.

Rhythmic contractility in the hepatic portal "corkscrew" vein of the rat snake.

PubMed

Conklin, Daniel J; Lillywhite, Harvey B; Bishop, Barbara; Hargens, Alan R; Olson, Kenneth R

2009-03-01

Terrestrial, but not aquatic, species of snakes have hepatic portal veins with a corkscrew morphology immediately posterior of the liver. Relatively large volumes of venous blood are associated with this region, and the corkscrew vein has been proposed to function as a bidirectional valve that impedes gravitational shifts of intravascular volume. To better understand the functional significance of the corkscrew anatomy, we investigated the histology and contractile mechanisms in isolated corkscrew segments of the hepatic portal vein of a yellow rat snake (Pantherophis obsoletus). Morphologically, the corkscrew portal vein is here shown to have two distinct layers of smooth muscle--an inner circular layer, and an outer longitudinal layer, separated by a layer of collagen--whereas only a single circular layer of smooth muscle is present in the adjacent posterior caval vein. Low frequency (approximately 0.3 cycles*min(-1)) spontaneous and catecholamine-induced rhythms were observed in 11% and 89% of portal vein segments, respectively, but neither spontaneous nor agonist-induced cycling was observed in adjacent posterior (non-corkscrew) caval veins. Catecholamines, angiotensin II, or stretch increased the amplitude and/or frequency of contractile cycles. Ouabain, verapamil or indomethacin, but not tetrodotoxin, alpha-, or ss-adrenergic receptor antagonists, inhibited cyclical contractions indicating a dependence of these cycles on Na+/K+ ATPase, extracellular Ca2+ and prostanoid(s). These data suggest that the rhythmic contractility of the corkscrew segment of the ophidian portal vein may act in conjunction with its morphological features to improve venous return and to prevent retrograde shifts of blood that might otherwise pool in posterior veins.

Microtubule depolymerization normalizes in vivo myocardial contractile function in dogs with pressure-overload left ventricular hypertrophy

NASA Technical Reports Server (NTRS)

Koide, M.; Hamawaki, M.; Narishige, T.; Sato, H.; Nemoto, S.; DeFreyte, G.; Zile, M. R.; Cooper G, I. V.; Carabello, B. A.

2000-01-01

BACKGROUND: Because initially compensatory myocardial hypertrophy in response to pressure overloading may eventually decompensate to myocardial failure, mechanisms responsible for this transition have long been sought. One such mechanism established in vitro is densification of the cellular microtubule network, which imposes a viscous load that inhibits cardiocyte contraction. METHODS AND RESULTS: In the present study, we extended this in vitro finding to the in vivo level and tested the hypothesis that this cytoskeletal abnormality is important in the in vivo contractile dysfunction that occurs in experimental aortic stenosis in the adult dog. In 8 dogs in which gradual stenosis of the ascending aorta had caused severe left ventricular (LV) pressure overloading (gradient, 152+/-16 mm Hg) with contractile dysfunction, LV function was measured at baseline and 1 hour after the intravenous administration of colchicine. Cardiocytes obtained by biopsy before and after in vivo colchicine administration were examined in tandem. Microtubule depolymerization restored LV contractile function both in vivo and in vitro. CONCLUSIONS: These and additional corroborative data show that increased cardiocyte microtubule network density is an important mechanism for the ventricular contractile dysfunction that develops in large mammals with adult-onset pressure-overload-induced cardiac hypertrophy.

Left atrial strain predicts hemodynamic parameters in cardiovascular patients.

PubMed

Hewing, Bernd; Theres, Lena; Spethmann, Sebastian; Stangl, Karl; Dreger, Henryk; Knebel, Fabian

2017-08-01

We aimed to evaluate the predictive value of left atrial (LA) reservoir, conduit, and contractile function parameters as assessed by speckle tracking echocardiography (STE) for invasively measured hemodynamic parameters in a patient cohort with myocardial and valvular diseases. Sixty-nine patients undergoing invasive hemodynamic assessment were enrolled into the study. Invasive hemodynamic parameters were obtained by left and right heart catheterization. Transthoracic echocardiography assessment of LA reservoir, conduit, and contractile function was performed by STE. Forty-nine patients had sinus rhythm (SR) and 20 patients had permanent atrial fibrillation (AF). AF patients had significantly reduced LA reservoir function compared to SR patients. In patients with SR, LA reservoir, conduit, and contractile function inversely correlated with pulmonary capillary wedge pressure (PCWP), left ventricular end-diastolic pressure, and mean pulmonary artery pressure (PAP), and showed a moderate association with cardiac index. In AF patients, there were no significant correlations between LA reservoir function and invasively obtained hemodynamic parameters. In SR patients, LA contractile function with a cutoff value of 16.0% had the highest diagnostic accuracy (area under the curve, AUC: 0.895) to predict PCWP ≥18 mm Hg compared to the weaker diagnostic accuracy of average E/E' ratio with an AUC of 0.786 at a cutoff value of 14.3. In multivariate analysis, LA contractile function remained significantly associated with PCWP ≥18 mm Hg. In a cohort of patients with a broad spectrum of cardiovascular diseases LA strain shows a valuable prediction of hemodynamic parameters, specifically LV filling pressures, in the presence of SR. © 2017, Wiley Periodicals, Inc.

Expression of mitochondrial regulatory genes parallels respiratory capacity and contractile function in a rat model of hypoxia-induced right ventricular hypertrophy

USDA-ARS?s Scientific Manuscript database

Chronic hypobaric hypoxia (CHH) increases load on the right ventricle (RV) resulting in RV hypertrophy. We hypothesized that CHH elicits distinct responses, i.e., the hypertrophied RV, unlike the left ventricle (LV), displaying enhanced mitochondrial respiratory and contractile function. Wistar rats...

Global Intracoronary Infusion of Allogeneic Cardiosphere-Derived Cells Improves Ventricular Function and Stimulates Endogenous Myocyte Regeneration throughout the Heart in Swine with Hibernating Myocardium

PubMed Central

Suzuki, Gen; Weil, Brian R.; Leiker, Merced M.; Ribbeck, Amanda E.; Young, Rebeccah F.; Cimato, Thomas R.; Canty, John M.

2014-01-01

Background Cardiosphere-derived cells (CDCs) improve ventricular function and reduce fibrotic volume when administered via an infarct-related artery using the “stop-flow” technique. Unfortunately, myocyte loss and dysfunction occur globally in many patients with ischemic and non-ischemic cardiomyopathy, necessitating an approach to distribute CDCs throughout the entire heart. We therefore determined whether global intracoronary infusion of CDCs under continuous flow improves contractile function and stimulates new myocyte formation. Methods and Results Swine with hibernating myocardium from a chronic LAD occlusion were studied 3-months after instrumentation (n = 25). CDCs isolated from myocardial biopsies were infused into each major coronary artery (∼33×106 icCDCs). Global icCDC infusion was safe and while ∼3% of injected CDCs were retained, they did not affect ventricular function or myocyte proliferation in normal animals. In contrast, four-weeks after icCDCs were administered to animals with hibernating myocardium, %LADWT increased from 23±6 to 51±5% (p<0.01). In diseased hearts, myocyte proliferation (phospho-histone-H3) increased in hibernating and remote regions with a concomitant increase in myocyte nuclear density. These effects were accompanied by reductions in myocyte diameter consistent with new myocyte formation. Only rare myocytes arose from sex-mismatched donor CDCs. Conclusions Global icCDC infusion under continuous flow is feasible and improves contractile function, regresses myocyte cellular hypertrophy and increases myocyte proliferation in diseased but not normal hearts. New myocytes arising via differentiation of injected cells are rare, implicating stimulation of endogenous myocyte regeneration as the primary mechanism of repair. PMID:25402428

Recovery time course in contractile function of fast and slow skeletal muscle after hindlimb immobilization

NASA Technical Reports Server (NTRS)

Witzmann, F. A.; Kim, D. H.; Fitts, R. H.

1982-01-01

The present study was undertaken to characterize the time course and extent of recovery in the isometric and isotonic contractile properties of fast and slow skeletal muscle following 6 wk of hindlimb immobilization. Female Sprague-Dawley rats were randomly assigned to an immobilized group or a control group. The results of the study show that fast and slow skeletal muscles possess the ability to completely recover normal contractile function following 6 wk of hindlimb immobilization. The rate of recovery is dependent on the fiber type composition of the affected muscle.

Novel approaches to determine contractile function of the isolated adult zebrafish ventricular cardiac myocyte.

PubMed

Dvornikov, Alexey V; Dewan, Sukriti; Alekhina, Olga V; Pickett, F Bryan; de Tombe, Pieter P

2014-05-01

The zebrafish (Danio rerio) has been used extensively in cardiovascular biology, but mainly in the study of heart development. The relative ease of its genetic manipulation may indicate the suitability of this species as a cost-effective model system for the study of cardiac contractile biology. However, whether the zebrafish heart is an appropriate model system for investigations pertaining to mammalian cardiac contractile structure-function relationships remains to be resolved. Myocytes were isolated from adult zebrafish hearts by enzymatic digestion, attached to carbon rods, and twitch force and intracellular Ca(2+) were measured. We observed the modulation of twitch force, but not of intracellular Ca(2+), by both extracellular [Ca(2+)] and sarcomere length. In permeabilized cells/myofibrils, we found robust myofilament length-dependent activation. Moreover, modulation of myofilament activation-relaxation and force redevelopment kinetics by varied Ca(2+) activation levels resembled that found previously in mammalian myofilaments. We conclude that the zebrafish is a valid model system for the study of cardiac contractile structure-function relationships.

Porcine uterus cryopreservation: an analysis of contractile function using different uterotonics.

PubMed

Schölch, Daniel; Schölch, Sebastian; Strahl, Olga; Hoffmann, Inge; Beckmann, Matthias W; Dittrich, Ralf

2012-10-01

Cryopreservation of whole organs has become increasingly successful in recent years, and establishing reliable methods for confirming the success of specific cryopreservation procedures has therefore become extremely important. On the assumption that methods such as histological evaluation do not provide definitive evidence of long-term cryopreservation and that clear signs of conserved function in an organ are good evidence of its viability, contractile function was analysed in porcine uteri (n=60), either after long-term (group A) or short-term (group B) cryopreservation and post-thaw treatment with three different uterotonics. A slow freezing protocol was used to preserve the organs. Fifteen fresh uteri were analysed similarly for contractile function, which was evaluated by measuring intrauterine pressure after administration of oxytocin, prostaglandin E(1) (PGE(1)), and carbachol. After cryopreservation, all but three uteri (95%) showed rhythmic contractions similar to those in fresh uteri except for differences in the heights of contraction peaks, with lower contractions in PGE(1) subgroup B (P<0.05). With the exception of three nonresponsive uteri in group A, there were no differences in contractility between uteri after long-term cryopreservation and fresh uteri. The results of this study thus contribute to the debate on whether slow freezing or vitrification techniques are best for whole-organ cryopreservation. In summary, (1) preservation of muscular function in porcine uteri is feasible with a slow freezing protocol; (2) measurement of contractile function following administration of uterotonics is a useful method of confirming functionality; and (3) long-term cryopreservation does not significantly impair post-thaw contractibility in comparison with fresh uteri. Copyright © 2012 Elsevier Inc. All rights reserved.

Muscle-derived Decellularised Extracellular Matrix Improves Functional Recovery in a Rat Latissimus Dorsi Muscle Defect Model

DTIC Science & Technology

2013-12-01

battlefield wounds, often involving volumetric muscle loss (VML). The physical loss of muscle results in functional deficits and cosmetic ...repair with M-ECM and 3) sham (all procedures except muscle excision). Four and 8 weeks post- surgery , the isometric contractile properties of the LD... Surgery (2013) 66, 1750e1758 Report Documentation Page Form ApprovedOMB No. 0704-0188 Public reporting burden for the collection of information is

Amalaki rasayana, a traditional Indian drug enhances cardiac mitochondrial and contractile functions and improves cardiac function in rats with hypertrophy.

PubMed

Kumar, Vikas; Aneesh, Kumar A; Kshemada, K; Ajith, Kumar G S; Binil, Raj S S; Deora, Neha; Sanjay, G; Jaleel, A; Muraleedharan, T S; Anandan, E M; Mony, R S; Valiathan, M S; Santhosh, Kumar T R; Kartha, C C

2017-08-17

We evaluated the cardioprotective effect of Amalaki Rasayana (AR), a rejuvenating Ayurvedic drug prepared from Phyllanthus emblica fruits in the reversal of remodeling changes in pressure overload left ventricular cardiac hypertrophy (LVH) and age-associated cardiac dysfunction in male Wistar rats. Six groups (aging groups) of 3 months old animals were given either AR or ghee and honey (GH) orally; seventh group was untreated. Ascending aorta was constricted using titanium clips in 3 months old rats (N = 24; AC groups) and after 6 months, AR or GH was given for further 12 months to two groups; one group was untreated. Histology, gene and protein expression analysis were done in heart tissues. Chemical composition of AR was analyzed by HPLC, HPTLC and LC-MS. AR intake improved (P < 0.05) cardiac function in aging rats and decreased LVH (P < 0.05) in AC rats as well as increased (P < 0.05) fatigue time in treadmill exercise in both groups. In heart tissues of AR administered rats of both the groups, SERCA2, CaM, Myh11, antioxidant, autophagy, oxidative phosphorylation and TCA cycle proteins were up regulated. ADRB1/2 and pCREB expression were increased; pAMPK, NF-kB were decreased. AR has thus a beneficial effect on myocardial energetics, muscle contractile function and exercise tolerance capacity.

Overexpression of Hsp20 Prevents Endotoxin-Induced Myocardial Dysfunction and Apoptosis via Inhibition of NF-κB Activation

PubMed Central

Wang, Xiaohong; Zingarelli, Basilia; Connor, Michael O’; Zhang, Pengyuan; Adeyemo, Adeola; Kranias, Evangelia G.; Wang, Yigang; Fan, Guo-Chang

2009-01-01

The occurrence of cardiovascular dysfunction in sepsis is associated with a significantly increased mortality rate of 70% to 90% compared with 20% in septic patients without cardiovascular impairment. Thus, rectification or blockade of myocardial depressant factors should partly ameliorate sepsis progression. Heat shock protein 20 (Hsp20) has been shown to enhance myocardial contractile function and protect against doxorubicin-induced cardiotoxicity. To investigate the possible role of Hsp20 in sepsis-mediated cardiac injury, we first examined the expression profiles of five major Hsps in response to lipopolysaccharide (LPS) challenge, and observed that only the expression of Hsp20 was downregulated in LPS-treated myocardium, suggesting that this decrease might be one of mechanisms contributing to LPS-induced cardiovascular defects. Further studies using loss-of-function and gain-of function approaches in adult rat cardiomyocytes verified that reduced Hsp20 levels were indeed correlated with the impaired contractile function. In fact, overexpression of Hsp20 significantly enhanced cardiomyocyte contractility upon LPS treatment. Moreover, after administration of LPS (25μg/g) in vivo, Hsp20 transgenic mice (10-fold overexpression) displayed: 1) an improvement in myocardial function; 2) reduced the degree of cardiac apoptosis; and 3) decreased NF-κB activity, accompanied with reduced myocardial cytokines IL-1β and TNF-α production, compared to the LPS-treated non-transgenic littermate controls. Thus, the increases in Hsp20 levels can protect against LPS-induced cardiac apoptosis and dysfunction, associated with inhibition of NF-κB activity, suggesting that Hsp20 may be a new therapeutic agent for the treatment of sepsis. PMID:19501592

Myocardial Adeno-Associated Virus Serotype 6–βARKct Gene Therapy Improves Cardiac Function and Normalizes the Neurohormonal Axis in Chronic Heart Failure

PubMed Central

Rengo, Giuseppe; Lymperopoulos, Anastasios; Zincarelli, Carmela; Donniacuo, Maria; Soltys, Stephen; Rabinowitz, Joseph E.; Koch, Walter J.

2009-01-01

Background The upregulation of G protein–coupled receptor kinase 2 in failing myocardium appears to contribute to dysfunctional β-adrenergic receptor (βAR) signaling and cardiac function. The peptide βARKct, which can inhibit the activation of G protein–coupled receptor kinase 2 and improve βAR signaling, has been shown in transgenic models and short-term gene transfer experiments to rescue heart failure (HF). This study was designed to evaluate long-term βARKct expression in HF with the use of stable myocardial gene delivery with adeno-associated virus serotype 6 (AAV6). Methods and Results In HF rats, we delivered βARKct or green fluorescent protein as a control via AAV6-mediated direct intramyocardial injection. We also treated groups with concurrent administration of the β-blocker metoprolol. We found robust and long-term transgene expression in the left ventricle at least 12 weeks after delivery. βARKct significantly improved cardiac contractility and reversed left ventricular remodeling, which was accompanied by a normalization of the neurohormonal (catecholamines and aldosterone) status of the chronic HF animals, including normalization of cardiac βAR signaling. Addition of metoprolol neither enhanced nor decreased βARKct-mediated beneficial effects, although metoprolol alone, despite not improving contractility, prevented further deterioration of the left ventricle. Conclusions Long-term cardiac AAV6-βARKct gene therapy in HF results in sustained improvement of global cardiac function and reversal of remodeling at least in part as a result of a normalization of the neurohormonal signaling axis. In addition, βARKct alone improves outcomes more than a β-blocker alone, whereas both treatments are compatible. These findings show that βARKct gene therapy can be of long-term therapeutic value in HF. PMID:19103992

Cell biology, MRI and geometry: insight into a microscopic/macroscopic marriage.

PubMed

de Oliveira, Sérgio Almeida; Gowdak, Luís Henrique W; Buckberg, Gerald; Krieger, José Eduardo

2006-04-01

The concept of cell therapy as an adjunctive therapy to myocardial surgical revascularization for patients with severe coronary artery disease is illustrated by two case reports of ischemic cardiac disease that were unsuitable for revascularization by coronary grafting. The potential interaction of cell therapy, magnetic resonance imaging (MRI) of viability, and left ventricle (LV) restoration is described. Each patient had an ejection fraction below 30%, a relatively conical heart, and MRI gadolinium scan showing predominantly viable muscle. Intramyocardial injections of autologous bone marrow-derived cells (BMC) were performed along with either incomplete coronary artery bypass grafting (CABG) (to mother regions) or with transmyocardial laser revascularization (TMLR). An improvement in contractile function was seen at 6-12-month intervals after the procedure. The implications of possible underlying mechanisms of improvement in both myocardial perfusion and contractility suggest the striking importance of both micro- and macroenvironment for any cell-based therapeutic strategy. These observations imply that the interaction of cell biology, viability by MRI and geometry may be important in the future, as geometry can be restored surgically, and the new architectural form may develop enhanced function if it contains viable tissue and cell-based treatment can be delivered.

Nanotechnology Enhanced Functional Assays of Actomyosin Motility - Potentials and Challenges

NASA Astrophysics Data System (ADS)

Månsson, A.; Nicholls, I. A.; Omling, P.; Tågerud, S.; Montelius, L.

Muscle contraction occurs as a result of force-producing interactions between the contractile proteins myosin II and actin with the two proteins highly ordered in the filament lattice of the muscle sarcomere. In contrast to this wellordered structure, most in vitro studies are performed with the contractile proteins in a disordered arrangement. Here we first review the existing in vitro motility assays and then consider how they can be improved by the use of nanotechnology. As a basis for such improvement we describe our recent work where we used chemically and topographically patterned surfaces to achieve selective localization of actomyosin motor function to predetermined areas of sub-micrometer dimensions. We also describe guidance and unidirectional actin filament sliding on nanosized tracks and suggest how such tracks can be combined with 1. microfluidics-based rapid solution exchange and 2. application of electromagnetic forces of well-defined orientation, thus simulating the lifting of a weight by actomyosin. As a related issue we discuss the usefulness of nanotechnology based assay systems for miniaturized highthroughput drug screening systems with molecular motors as drug targets. Finally, we consider the potentials and challenges in using nanotechnology to reconstruct the most essential aspects of cellular order within the muscle sarcomere.

Loss of β-adrenergic-stimulated phosphorylation of CaV1.2 channels on Ser1700 leads to heart failure.

PubMed

Yang, Linghai; Dai, Dao-Fu; Yuan, Can; Westenbroek, Ruth E; Yu, Haijie; West, Nastassya; de la Iglesia, Horacio O; Catterall, William A

2016-12-06

L-type Ca 2+ currents conducted by voltage-gated calcium channel 1.2 (Ca V 1.2) initiate excitation-contraction coupling in the heart, and altered expression of Ca V 1.2 causes heart failure in mice. Here we show unexpectedly that reducing β-adrenergic regulation of Ca V 1.2 channels by mutation of a single PKA site, Ser1700, in the proximal C-terminal domain causes reduced contractile function, cardiac hypertrophy, and heart failure without changes in expression, localization, or function of the Ca V 1.2 protein in the mutant mice (SA mice). These deficits were aggravated with aging. Dual mutation of Ser1700 and a nearby casein-kinase II site (Thr1704) caused accelerated hypertrophy, heart failure, and death in mice with these mutations (STAA mice). Cardiac hypertrophy was increased by voluntary exercise and by persistent β-adrenergic stimulation. PKA expression was increased, and PKA sites Ser2808 in ryanodine receptor type-2, Ser16 in phospholamban, and Ser23/24 in troponin-I were hyperphosphorylated in SA mice, whereas phosphorylation of substrates for calcium/calmodulin-dependent protein kinase II was unchanged. The Ca 2+ pool in the sarcoplasmic reticulum was increased, the activity of calcineurin was elevated, and calcineurin inhibitors improved contractility and ameliorated cardiac hypertrophy. Cardio-specific expression of the SA mutation also caused reduced contractility and hypertrophy. These results suggest engagement of compensatory mechanisms, which initially may enhance the contractility of individual myocytes but eventually contribute to an increased sensitivity to cardiovascular stress and to heart failure in vivo. Our results demonstrate that normal regulation of Ca V 1.2 channels by phosphorylation of Ser1700 in cardiomyocytes is required for cardiovascular homeostasis and normal physiological regulation in vivo.

Development and characterization of a 3D multicell microtissue culture model of airway smooth muscle.

PubMed

West, Adrian R; Zaman, Nishat; Cole, Darren J; Walker, Matthew J; Legant, Wesley R; Boudou, Thomas; Chen, Christopher S; Favreau, John T; Gaudette, Glenn R; Cowley, Elizabeth A; Maksym, Geoffrey N

2013-01-01

Airway smooth muscle (ASM) cellular and molecular biology is typically studied with single-cell cultures grown on flat 2D substrates. However, cells in vivo exist as part of complex 3D structures, and it is well established in other cell types that altering substrate geometry exerts potent effects on phenotype and function. These factors may be especially relevant to asthma, a disease characterized by structural remodeling of the airway wall, and highlights a need for more physiologically relevant models of ASM function. We utilized a tissue engineering platform known as microfabricated tissue gauges to develop a 3D culture model of ASM featuring arrays of ∼0.4 mm long, ∼350 cell "microtissues" capable of simultaneous contractile force measurement and cell-level microscopy. ASM-only microtissues generated baseline tension, exhibited strong cellular organization, and developed actin stress fibers, but lost structural integrity and dissociated from the cantilevers within 3 days. Addition of 3T3-fibroblasts dramatically improved survival times without affecting tension development or morphology. ASM-3T3 microtissues contracted similarly to ex vivo ASM, exhibiting reproducible responses to a range of contractile and relaxant agents. Compared with 2D cultures, microtissues demonstrated identical responses to acetylcholine and KCl, but not histamine, forskolin, or cytochalasin D, suggesting that contractility is regulated by substrate geometry. Microtissues represent a novel model for studying ASM, incorporating a physiological 3D structure, realistic mechanical environment, coculture of multiple cells types, and comparable contractile properties to existing models. This new model allows for rapid screening of biochemical and mechanical factors to provide insight into ASM dysfunction in asthma.

Contractile function is unaltered in diaphragm from mice lacking calcium release channel isoform 3

NASA Technical Reports Server (NTRS)

Clancy, J. S.; Takeshima, H.; Hamilton, S. L.; Reid, M. B.

1999-01-01

Skeletal muscle expresses at least two isoforms of the calcium release channel in the sarcoplasmic reticulum (RyR1 and RyR3). Whereas the function of RyR1 is well defined, the physiological significance of RyR3 is unclear. Some authors have suggested that RyR3 participates in excitation-contraction coupling and that RyR3 may specifically confer resistance to fatigue. To test this hypothesis, we measured contractile function of diaphragm strips from adult RyR3-deficient mice (exon 2-targeted mutation) and their heterozygous and wild-type littermates. In unfatigued diaphragm, there were no differences in isometric contractile properties (twitch characteristics, force-frequency relationships, maximal force) among the three groups. Our fatigue protocol (30 Hz, 0.25 duty cycle, 37 degrees C) depressed force to 25% of the initial force; however, lack of RyR3 did not accelerate the decline in force production. The force-frequency relationship was shifted to higher frequencies and was depressed in fatigued diaphragm; lack of RyR3 did not exaggerate these changes. We therefore provide evidence that RyR3 deficiency does not alter contractile function of adult muscle before, during, or after fatigue.

Injectable Microsphere Gel Progressively Improves Global Ventricular Function, Regional Contractile Strain, and Mitral Regurgitation after Myocardial Infarction

PubMed Central

McGarvey, Jeremy R; Kondo, Norihiro; Witschey, Walter RT; Takebe, Manabu; Aoki, Chikashi; Burdick, Jason A.; Spinale, Francis G; Gorman, Joseph H; Pilla, James J; Gorman, Robert C

2014-01-01

Background There is continued need for therapies which reverse or abate the remodeling process following myocardial infarction (MI). In this study, we evaluate the longitudinal effects of calcium hydroxyapatite microsphere gel on regional strain, global ventricular function, and mitral regurgitation (MR) in a porcine MI model. Methods Twenty five Yorkshire swine were enrolled. Five were dedicated weight-matched controls. Twenty underwent posterolateral infarction by direct ligation of the circumflex artery and its branches. Infarcted animals were randomly divided into four groups: one week treatment, one week control, four week treatment, and four week control. Following infarction, animals received either twenty 150μl calcium hydroxyapatite gel or saline injections within the infarct. At their respective timepoints, echocardiograms, cardiac MRI, and tissue were collected for evaluation of MR, regional and global left ventricular function, wall thickness, and collagen content. Results Global and regional LV function were depressed in all infarcted subjects at one week compared to healthy controls. By four weeks post-infarction, global function had significantly improved in the calcium hydroxyapatite group compared to infarcted controls (EF 48.5±1.9% vs. 38.0±1.7%, p<0.01). Similarly, regional borderzone radial contractile strain (16.3±1.5% vs. 11.2±1.5%, p=0.04), MR grade (0.4±0.2 vs. 1.2±0.2, p=0.04), and infarct thickness (7.8±0.5mm vs. 4.5±0.2mm, p<0.01) were improved at this timepoint in the treatment group compared to infarct controls. Conclusions Calcium hydroxyapatite injection following MI progressively improves global LV function, borderzone function, and mitral regurgitation. Using novel biomaterials to augment infarct material properties is viable alternative in the current management of heart failure. PMID:25524397

Functional, structural, and chemical changes in myosin associated with hydrogen peroxide treatment of skeletal muscle fibers.

PubMed

Prochniewicz, Ewa; Lowe, Dawn A; Spakowicz, Daniel J; Higgins, LeeAnn; O'Conor, Kate; Thompson, LaDora V; Ferrington, Deborah A; Thomas, David D

2008-02-01

To understand the molecular mechanism of oxidation-induced inhibition of muscle contractility, we have studied the effects of hydrogen peroxide on permeabilized rabbit psoas muscle fibers, focusing on changes in myosin purified from these fibers. Oxidation by 5 mM peroxide decreased fiber contractility (isometric force and shortening velocity) without significant changes in the enzymatic activity of myofibrils and isolated myosin. The inhibitory effects were reversed by treating fibers with dithiothreitol. Oxidation by 50 mM peroxide had a more pronounced and irreversible inhibitory effect on fiber contractility and also affected enzymatic activity of myofibrils, myosin, and actomyosin. Peroxide treatment also affected regulation of contractility, resulting in fiber activation in the absence of calcium. Electron paramagnetic resonance of spin-labeled myosin in muscle fibers showed that oxidation increased the fraction of myosin heads in the strong-binding structural state under relaxing conditions (low calcium) but had no effect under activating conditions (high calcium). This change in the distribution of structural states of myosin provides a plausible explanation for the observed changes in both contractile and regulatory functions. Mass spectroscopy analysis showed that 50 mM but not 5 mM peroxide induced oxidative modifications in both isoforms of the essential light chains and in the heavy chain of myosin subfragment 1 by targeting multiple methionine residues. We conclude that 1) inhibition of muscle fiber contractility via oxidation of myosin occurs at high but not low concentrations of peroxide and 2) the inhibitory effects of oxidation suggest a critical and previously unknown role of methionines in myosin function.

Dietary nitrate increases tetanic [Ca2+]i and contractile force in mouse fast-twitch muscle

PubMed Central

Hernández, Andrés; Schiffer, Tomas A; Ivarsson, Niklas; Cheng, Arthur J; Bruton, Joseph D; Lundberg, Jon O; Weitzberg, Eddie; Westerblad, Håkan

2012-01-01

Dietary inorganic nitrate has profound effects on health and physiological responses to exercise. Here, we examined if nitrate, in doses readily achievable via a normal diet, could improve Ca2+ handling and contractile function using fast- and slow-twitch skeletal muscles from C57bl/6 male mice given 1 mm sodium nitrate in water for 7 days. Age matched controls were provided water without added nitrate. In fast-twitch muscle fibres dissected from nitrate treated mice, myoplasmic free [Ca2+] was significantly greater than in Control fibres at stimulation frequencies from 20 to 150 Hz, which resulted in a major increase in contractile force at ≤50 Hz. At 100 Hz stimulation, the rate of force development was ∼35% faster in the nitrate group. These changes in nitrate treated mice were accompanied by increased expression of the Ca2+ handling proteins calsequestrin 1 and the dihydropyridine receptor. No changes in force or calsequestrin 1 and dihydropyridine receptor expression were measured in slow-twitch muscles. In conclusion, these results show a striking effect of nitrate supplementation on intracellular Ca2+ handling in fast-twitch muscle resulting in increased force production. A new mechanism is revealed by which nitrate can exert effects on muscle function with applications to performance and a potential therapeutic role in conditions with muscle weakness. PMID:22687611

Dietary nitrate increases tetanic [Ca2+]i and contractile force in mouse fast-twitch muscle.

PubMed

Hernández, Andrés; Schiffer, Tomas A; Ivarsson, Niklas; Cheng, Arthur J; Bruton, Joseph D; Lundberg, Jon O; Weitzberg, Eddie; Westerblad, Håkan

2012-08-01

Dietary inorganic nitrate has profound effects on health and physiological responses to exercise. Here, we examined if nitrate, in doses readily achievable via a normal diet, could improve Ca(2+) handling and contractile function using fast- and slow-twitch skeletal muscles from C57bl/6 male mice given 1 mm sodium nitrate in water for 7 days. Age matched controls were provided water without added nitrate. In fast-twitch muscle fibres dissected from nitrate treated mice, myoplasmic free [Ca(2+)] was significantly greater than in Control fibres at stimulation frequencies from 20 to 150 Hz, which resulted in a major increase in contractile force at ≤ 50 Hz. At 100 Hz stimulation, the rate of force development was ∼35% faster in the nitrate group. These changes in nitrate treated mice were accompanied by increased expression of the Ca(2+) handling proteins calsequestrin 1 and the dihydropyridine receptor. No changes in force or calsequestrin 1 and dihydropyridine receptor expression were measured in slow-twitch muscles. In conclusion, these results show a striking effect of nitrate supplementation on intracellular Ca(2+) handling in fast-twitch muscle resulting in increased force production. A new mechanism is revealed by which nitrate can exert effects on muscle function with applications to performance and a potential therapeutic role in conditions with muscle weakness.

Remodeling the zonula adherens in response to tension and the role of afadin in this response

PubMed Central

Acharya, Bipul R.; Peyret, Grégoire; Fardin, Marc-Antoine; Mège, René-Marc; Ladoux, Benoit; Yap, Alpha S.; Fanning, Alan S.

2016-01-01

Morphogenesis requires dynamic coordination between cell–cell adhesion and the cytoskeleton to allow cells to change shape and move without losing tissue integrity. We used genetic tools and superresolution microscopy in a simple model epithelial cell line to define how the molecular architecture of cell–cell zonula adherens (ZA) is modified in response to elevated contractility, and how these cells maintain tissue integrity. We previously found that depleting zonula occludens 1 (ZO-1) family proteins in MDCK cells induces a highly organized contractile actomyosin array at the ZA. We find that ZO knockdown elevates contractility via a Shroom3/Rho-associated, coiled-coil containing protein kinase (ROCK) pathway. Our data suggest that each bicellular border is an independent contractile unit, with actin cables anchored end-on to cadherin complexes at tricellular junctions. Cells respond to elevated contractility by increasing junctional afadin. Although ZO/afadin knockdown did not prevent contractile array assembly, it dramatically altered cell shape and barrier function in response to elevated contractility. We propose that afadin acts as a robust protein scaffold that maintains ZA architecture at tricellular junctions. PMID:27114502

Effect of hypokinesia on contractile function of cardiac muscle

NASA Technical Reports Server (NTRS)

Meyerson, F. Z.; Kapelko, V. I.; Trikhpoyeva, A. M.; Gorina, M. S.

1980-01-01

Rats were subjected to hypokinesia for two months and the contractile function of isolated papillary muscle was studied. Hypokinesia reduced significantly the isotonic contraction rate which depended on the ATPase activity of the myofibrils; it also reduced the rate and index of relaxation which depended on the functional capacity of the Ca(++) pump of the sarcoplasmic reticulum. The maximum force of isometric contraction determined by the quantity of actomyosin bridges in the myofibrils did not change after hypokinesia. This complex of changes is contrary to that observed in adaptation to exercise when the rate of isotonic contraction and relaxation increases while the force of isometric contraction does not change. The possible mechanism of this stability of the contractile force during adaptation and readaptation of the heart is discussed.

Muscle, functional and cognitive adaptations after flywheel resistance training in stroke patients: a pilot randomized controlled trial.

PubMed

Fernandez-Gonzalo, Rodrigo; Fernandez-Gonzalo, Sol; Turon, Marc; Prieto, Cristina; Tesch, Per A; García-Carreira, Maria del Carmen

2016-04-06

Resistance exercise (RE) improves neuromuscular function and physical performance after stroke. Yet, the effects of RE emphasizing eccentric (ECC; lengthening) actions on muscle hypertrophy and cognitive function in stroke patients are currently unknown. Thus, this study explored the effects of ECC-overload RE training on skeletal muscle size and function, and cognitive performance in individuals with stroke. Thirty-two individuals with chronic stroke (≥6 months post-stroke) were randomly assigned into a training group (TG; n = 16) performing ECC-overload flywheel RE of the more-affected lower limb (12 weeks, 2 times/week; 4 sets of 7 maximal closed-chain knee extensions; <2 min of contractile activity per session) or a control group (CG; n = 16), maintaining daily routines. Before and after the intervention, quadriceps femoris volume, maximal force and power for each leg were assessed, and functional and dual task performance, and cognitive functions were measured. Quadriceps femoris volume of the more-affected leg increased by 9.4 % in TG. Muscle power of the more-affected, trained (48.2 %), and the less-affected, untrained limb (28.1 %) increased after training. TG showed enhanced balance (8.9 %), gait performance (10.6 %), dual-task performance, executive functions (working memory, verbal fluency tasks), attention, and speed of information processing. CG showed no changes. ECC-overload flywheel resistance exercise comprising 4 min of contractile activity per week offers a powerful aid to regain muscle mass and function, and functional performance in individuals with stroke. While the current intervention improved cognitive functions, the cause-effect relationship, if any, with the concomitant neuromuscular adaptations remains to be explored. Clinical Trials NCT02120846.

Milrinone and levosimendan administered after reperfusion improve myocardial stunning in swine.

PubMed

Shibata, Itsuko; Cho, Sungsam; Yoshitomi, Osamu; Ureshino, Hiroyuki; Maekawa, Takuji; Hara, Tetsuya; Sumikawa, Koji

2013-02-01

We assessed the effect of milrinone application timing after reperfusion against myocardial stunning as compared with levosimendan in swine. Furthermore, we examined the role of p38 mitogen-activated protein kinase (p38 MAPK) in the milrinone-induced cardioprotection. All swine were subjected to 12-minutes ischemia followed by 90-minutes reperfusion to generate stunned myocardium. Milrinone or levosimendan was administered intravenously either for 20 minutes starting just after reperfusion or for 70 minutes starting 20 minutes after reperfusion. In another group, SB203580, a selective p38 MAPK inhibitor, was administered with and without milrinone. Regional myocardial contractility was assessed by percent segment shortening (%SS). Milrinone starting just after reperfusion, but not starting 20 minutes after reperfusion, improved %SS at 30, 60, and 90 minutes after reperfusion compared with that in the control group. SB203580 abolished the beneficial effect of milrinone. On the other hand, levosimendan starting 20 minutes after reperfusion, but not for 20 minutes starting just after reperfusion, improved %SS at 60 and 90 minutes after reperfusion. Milrinone should be administered just after reperfusion to protect myocardial stunning through p38 MAPK, whereas levosimendan improvement of contractile function could be mainly dependent on its positive inotropic effect.

Curcumin Alleviates the Functional Gastrointestinal Disorders of Mice In Vivo.

PubMed

Yu, Jing; Xu, Wen-Hua; Sun, Wei; Sun, Yi; Guo, Zhi-Li; Yu, Xiao-Ling

2017-12-01

Curcumin is a natural polyphenol extracted from the turmeric rhizome, which has a wide range of biological activities, but until now the effects of curcumin on the gastrointestinal peristalsis have not been fully understood. In vivo study, we observed the effects of curcumin on gastric emptying and intestinal propulsion rates of mice in normal state and in delayed state by atropine (ATR) or nitric oxide precursor L-arginine (L-Arg). An in vitro study explored the direct effects of curcumin on the intestinal contractility, but were studied through measuring spontaneous contraction of isolated jejunum of mice. Our results showed that intragastric administration of curcumin (200 mg/kg/day) for 10-20 days significantly improved gastric emptying and intestinal propulsion rates of mice delayed by ATR. Moreover, intragastric administration of curcumin (200 mg/kg/day) for 15 days also significantly improved mice gastric emptying and intestinal propulsion rates delayed by L-Arg. There was no significant effect on normal gastrointestinal propulsion of mice after intragastric administration of curcumin (200 mg/kg/day) for 1-20 days. When normal isolated jejunum of mice were incubated with curcumin in vitro, the amplitude of the spontaneous contractile waves of jejunum was reduced in a concentration-dependent manner. Moreover, curcumin reduced the amplitude of the contractile waves of jejunum in both contracted and relaxed state induced by acetylcholine or ATR individually. Taken together, our results suggest that curcumin has quite different effects on gastrointestinal peristalsis in vivo and in vitro. Moderate dose of curcumin by intragastric administration for more than 10 days can alleviate the functional gastrointestinal disorders of mice, but cannot affect normal gastrointestinal propulsion.

Cardiomyocytes from late embryos and neonates do optimal work and striate best on substrates with tissue-level elasticity: metrics and mathematics.

PubMed

Majkut, Stephanie F; Discher, Dennis E

2012-11-01

In this review, we discuss recent studies on the mechanosensitive morphology and function of cardiomyocytes derived from embryos and neonates. For early cardiomyocytes cultured on substrates of various stiffnesses, contractile function as measured by force production, work output and calcium handling is optimized when the culture substrate stiffness mimics that of the tissue from which the cells were obtained. This optimal contractile function corresponds to changes in sarcomeric protein conformation and organization that promote contractile ability. In light of current models for myofibillogenesis, a recent mathematical model of striation and alignment on elastic substrates helps to illuminate how substrate stiffness modulates early myofibril formation and organization. During embryonic heart formation and maturation, cardiac tissue mechanics change dynamically. Experiments and models highlighted here have important implications for understanding cardiomyocyte differentiation and function in development and perhaps in regeneration processes.

Extracellular signal-regulated kinase (ERK) activation preserves cardiac function in pressure overload induced hypertrophy.

PubMed

Mutlak, Michael; Schlesinger-Laufer, Michal; Haas, Tali; Shofti, Rona; Ballan, Nimer; Lewis, Yair E; Zuler, Mor; Zohar, Yaniv; Caspi, Lilac H; Kehat, Izhak

2018-05-24

Chronic pressure overload and a variety of mediators induce concentric cardiac hypertrophy. When prolonged, cardiac hypertrophy culminates in decreased myocardial function and heart failure. Activation of the extracellular signal-regulated kinase (ERK) is consistently observed in animal models of hypertrophy and in human patients, but its role in the process is controversial. We generated transgenic mouse lines with cardiomyocyte restricted overexpression of intrinsically active ERK1, which similar to the observations in hypertrophy is phosphorylated on both the TEY and the Thr207 motifs and is overexpressed at pathophysiological levels. The activated ERK1 transgenic mice developed a modest adaptive hypertrophy with increased contractile function and without fibrosis. Following induction of pressure-overload, where multiple pathways are stimulated, this activation did not further increase the degree of hypertrophy but protected the heart through a decrease in the degree of fibrosis and maintenance of ventricular contractile function. The ERK pathway acts to promote a compensated hypertrophic response, with enhanced contractile function and reduced fibrosis. The activation of this pathway may be a therapeutic strategy to preserve contractile function when the pressure overload cannot be easily alleviated. The inhibition of this pathway, which is increasingly being used for cancer therapy on the other hand, should be used with caution in the presence of pressure-overload. Copyright © 2017. Published by Elsevier B.V.

Skeletal muscle contractile properties in a novel murine model for limb girdle muscular dystrophy 2i.

PubMed

Rehwaldt, Jordan D; Rodgers, Buel D; Lin, David C

2017-12-01

Limb-girdle muscular dystrophy (LGMD) 2i results from mutations in fukutin-related protein and aberrant α-dystroglycan glycosylation. Although this significantly compromises muscle function and ambulation, the comprehensive characteristics of contractile dysfunction are unknown. Therefore, we quantified the in situ contractile properties of the medial gastrocnemius in young adult P448L mice, an affected muscle of a novel model of LGMD2i. Normalized maximal twitch force, tetanic force, and power were significantly smaller in P448L mice, compared with sex-matched, wild-type mice. These differences were consistent with the replacement of contractile fibers by passive tissue. The shape of the active force-length relationships were similar in both groups, regardless of sex, consistent with an intact sarcomeric structure in P448L mice. Passive force-length curves normalized to maximal isometric force were steeper in P448L mice, and passive elements contribute disproportionately more to total contractile force in P448L mice. Sex differences were mostly noted in the force-velocity curves, as normalized values for maximal and optimal velocities were significantly slower in P448L males, compared with wild-type, but not in P448L females. This suggests that the dystrophic phenotype, which may include possible changes in cross-bridge kinetics and fiber-type proportions, progresses more quickly in P448L males. These results together indicate that active force and power generation are compromised in both sexes of P448L mice, while passive forces increase. More importantly, the results identified several functional markers of disease pathophysiology that could aid in developing and assessment of novel therapeutics for LGMD2i and possibly other dystroglycanopathies as well. NEW & NOTEWORTHY Comprehensive assessments of muscle contractile function have, until now, never been performed in an animal model for any dystroglycanopathy. This study suggests that skeletal muscle contractile properties are significantly compromised in a recently developed model for limb-girdle muscular dystrophy 2i, the P448L mouse. It further identifies novel pathological markers of muscle function that are suitable for developing therapeutics and for better understanding of disease pathogenesis.

Structure of the Elastin-Contractile Units in the Thoracic Aorta and How Genes That Cause Thoracic Aortic Aneurysms and Dissections Disrupt This Structure.

PubMed

Karimi, Ashkan; Milewicz, Dianna M

2016-01-01

The medial layer of the aorta confers elasticity and strength to the aortic wall and is composed of alternating layers of smooth muscle cells (SMCs) and elastic fibres. The SMC elastin-contractile unit is a structural unit that links the elastin fibres to the SMCs and is characterized by the following: (1) layers of elastin fibres that are surrounded by microfibrils; (2) microfibrils that bind to the integrin receptors in focal adhesions on the cell surface of the SMCs; and (3) SMC contractile filaments that are linked to the focal adhesions on the inner side of the membrane. The genes that are altered to cause thoracic aortic aneurysms and aortic dissections encode proteins involved in the structure or function of the SMC elastin-contractile unit. Included in this gene list are the genes encoding protein that are structural components of elastin fibres and microfibrils, FBN1, MFAP5, ELN, and FBLN4. Also included are genes that encode structural proteins in the SMC contractile unit, including ACTA2, which encodes SMC-specific α-actin and MYH11, which encodes SMC-specific myosin heavy chain, along with MYLK and PRKG1, which encode kinases that control SMC contraction. Finally, mutations in the gene encoding the protein linking integrin receptors to the contractile filaments, FLNA, also predispose to thoracic aortic disease. Thus, these data suggest that functional SMC elastin-contractile units are important for maintaining the structural integrity of the aorta. Copyright © 2016 Canadian Cardiovascular Society. Published by Elsevier Inc. All rights reserved.

Prevalence of Regional Myocardial Thinning and Relationship With Myocardial Scarring in Patients With Coronary Artery Disease

PubMed Central

Shah, Dipan J.; Kim, Han W.; James, Olga; Parker, Michele; Wu, Edwin; Bonow, Robert O.; Judd, Robert M.; Kim, Raymond J.

2014-01-01

Importance Regional left ventricular (LV) wall thinning is believed to represent chronic transmural myocardial infarction and scar tissue. However, recent case reports using delayed-enhancement cardiovascular magnetic resonance (CMR) imaging raise the possibility that thinning may occur with little or no scarring. Objective To evaluate patients with regional myocardial wall thinning and to determine scar burden and potential for functional improvement. Design, Setting, and Patients Investigator-initiated, prospective, 3-center study conducted from August 2000 through January 2008 in 3 parts to determine (1) in patients with known coronary artery disease (CAD) undergoing CMR viability assessment, the prevalence of regional wall thinning (end-diastolic wall thickness ≤5.5 mm), (2) in patients with thinning, the presence and extent of scar burden, and (3) in patients with thinning undergoing coronary revascularization, any changes in myocardial morphology and contractility. Main Outcomes and Measures Scar burden in thinned regions assessed using delayed-enhancement CMR and changes in myocardial morphology and function assessed using cine-CMR after revascularization. Results Of 1055 consecutive patients with CAD screened, 201 (19% [95% CI, 17% to 21%]) had regional wall thinning. Wall thinning spanned a mean of 34% (95% CI, 32% to 37% [SD, 15%]) of LV surface area. Within these regions, the extent of scarring was 72% (95% CI, 69% to 76% [SD, 25%]); however, 18% (95% CI, 13% to 24%) of thinned regions had limited scar burden (≤50% of total extent). Among patients with thinning undergoing revascularization and follow-up cine-CMR (n=42), scar extent within the thinned region was inversely related to regional (r=−0.72, P<.001) and global (r=−0.53, P<.001) contractile improvement. End-diastolic wall thickness in thinned regions with limited scar burden increased from 4.4 mm (95% CI, 4.1 to 4.7) to 7.5 mm (95% CI, 6.9 to 8.1) after revascularization (P<.001), resulting in resolution of wall thinning. On multivariable analysis, scar extent had the strongest association with contractile improvement (slope coefficient, −0.03 [95% CI, −0.04 to −0.02]; P<.001) and reversal of thinning (slope coefficient, −0.05 [95% CI, −0.06 to −0.04]; P<.001). Conclusions and Relevance Among patients with CAD referred for CMR and found to have regional wall thinning, limited scar burden was present in 18% and was associated with improved contractility and resolution of wall thinning after revascularization. These findings, which are not consistent with common assumptions, warrant further investigation. PMID:23462787

Levothyroxine treatment generates an abnormal uterine contractility patterns in an in vitro animal model.

PubMed

Corriveau, Stéphanie; Blouin, Simon; Raiche, Évelyne; Nolin, Marc-Antoine; Rousseau, Éric; Pasquier, Jean-Charles

2015-12-01

Abnormal uterine contraction patterns were recently demonstrated in uterine strips from pregnant women treated with Levothyroxine (T4). These abnormalities were correlated with an increased risk of C-section delivery and associated surgical complications. To date, no study has investigated whether uterine contractility is modified by hypothyroidism or T4 treatment. Herein, we analyze the physiological role of T4 on uterine contractions. Female non-pregnant Sprague-Dawley rats ( N  = 22) were used and divided into four groups: 1) control, 2) hypothyroidism, 3) hypothyroidism treated with low T4 doses (20 μg/kg/day) and 4) with high T4 doses (100 μg/kg/day). Hypothyroidism was induced by an iodine-deficient diet. Isometric tension measurements were performed in vitro on myometrium tissues in isolated organ baths. Contractile activity parameters were quantified (amplitude, duration, frequency and area under the curve) using pharmacological tools to assess their effect. Screening of thyroid function confirmed a hypothyroid state for all rats under iodine-free diet to which T4 was subsequently administered to counterbalance hypothyroidism. Results demonstrate that hypothyroidism significantly decreased contractile duration (-17%) and increased contractile frequency (+26%), while high doses of T4 increased duration (+200%) and decreased frequency (-51%). These results thus mimic the pattern of abnormal contractions previously observed in uterine tissue from T4-treated hypothyroid pregnant women. Our data suggest that changes in myometrial reactivity are induced by T4 treatment. Thus, in conjunction with our previous observations on human myometrial strips, management of hypothyroidism should be improved to reduce the rate of C-sections in this group of patients.

Akt2 ablation prolongs life span and improves myocardial contractile function with adaptive cardiac remodeling: role of Sirt1-mediated autophagy regulation.

PubMed

Ren, Jun; Yang, Lifang; Zhu, Li; Xu, Xihui; Ceylan, Asli F; Guo, Wei; Yang, Jian; Zhang, Yingmei

2017-10-01

Aging is accompanied with unfavorable geometric and functional changes in the heart involving dysregulation of Akt and autophagy. This study examined the impact of Akt2 ablation on life span and cardiac aging as well as the mechanisms involved with a focus on autophagy and mitochondrial integrity. Cardiac geometry, contractile, and intracellular Ca 2+ properties were evaluated using echocardiography, IonOptix ® edge-detection and fura-2 techniques. Levels of Sirt1, mitochondrial integrity, autophagy, and mitophagy markers were evaluated using Western blot. Our results revealed that Akt2 ablation prolonged life span (by 9.1%) and alleviated aging (24 months)-induced unfavorable changes in myocardial function and intracellular Ca 2+ handling (SERCA2a oxidation) albeit with more pronounced cardiac hypertrophy (58.1%, 47.8%, and 14.5% rises in heart weight, wall thickness, and cardiomyocyte cross-sectional area). Aging downregulated levels of Sirt1, increased phosphorylation of Akt, and the nuclear transcriptional factor Foxo1, as well as facilitated acetylation of Foxo1, the effects of which (except Sirt1 and Foxo1 acetylation) were significantly attenuated or negated by Akt2 ablation. Advanced aging disturbed autophagy, mitophagy, and mitochondrial integrity as evidenced by increased p62, decreased levels of beclin-1, Atg7, LC3B, BNIP3, PTEN-induced putative kinase 1 (PINK1), Parkin, UCP-2, PGC-1α, and aconitase activity, the effects of which were reversed by Akt2 ablation. Aging-induced cardiomyocyte contractile dysfunction and loss of mitophagy were improved by rapamycin and the Sirt1 activator SRT1720. Activation of Akt using insulin or Parkin deficiency prevented SRT1720-induced beneficial effects against aging. In conclusion, our data indicate that Akt2 ablation protects against cardiac aging through restored Foxo1-related autophagy and mitochondrial integrity. © 2017 The Authors. Aging Cell published by the Anatomical Society and John Wiley & Sons Ltd.

Afterload mismatch in aortic and mitral valve disease: implications for surgical therapy.

PubMed

Ross, J

1985-04-01

In the management of patients with valvular heart disease, an understanding of the effects of altered loading conditions on the left ventricle is important in reaching a proper decision concerning the timing of corrective operation. In acquired valvular aortic stenosis, concentric hypertrophy generally maintains left ventricular chamber size and ejection fraction within normal limits, but in late stage disease function can deteriorate as preload reserve is lost and aortic stenosis progresses. In this setting, even when the ejection fraction is markedly reduced (less than 25%), it can improve to normal after aortic valve replacement, suggesting that afterload mismatch rather than irreversibly depressed myocardial contractility was responsible for left ventricular failure. Therefore, patients with severe aortic stenosis and symptoms should not be denied operation because of impaired cardiac function. In chronic severe aortic and mitral regurgitation, operation is generally recommended when symptoms are present, but whether to recommend operation to prevent irreversible myocardial damage in patients with few or no symptoms has remained controversial. In aortic regurgitation, left ventricular function generally improves postoperatively, even if it is moderately impaired preoperatively, indicating correction of afterload mismatch. Most such patients can be carefully followed by echocardiography. However, in some patients, severe left ventricular dysfunction fails to improve postoperatively. Therefore, when echocardiographic studies in the patient with severe aortic regurgitation show an ejection fraction of less than 40% (fractional shortening less than 25%) plus enlarging left ventricular end-diastolic diameter (approaching 38 mm/m2 body surface area) and end-systolic diameter (approaching 50 mm or 26 mm/m2), confirmation of these findings by cardiac catheterization and consideration of operation are advisable even in patients with minimal symptoms. In chronic mitral regurgitation, maintenance of a normal ejection fraction can mask depressed myocardial contractility. Pre- and postoperative studies in such patients have shown a poor clinical result after mitral valve replacement, associated with a sharp decrease in the ejection fraction after operation. This response appears to reflect unmasking of decreased myocardial contractility by mitral valve replacement, with ejection of the total stroke volume into the high impedance of the aorta (afterload mismatch produced by operation).(ABSTRACT TRUNCATED AT 400 WORDS)

Aerobic exercise training induces skeletal muscle hypertrophy and age-dependent adaptations in myofiber function in young and older men

PubMed Central

Konopka, Adam R.; Undem, Miranda K.; Hinkley, James M.; Minchev, Kiril; Kaminsky, Leonard A.; Trappe, Todd A.; Trappe, Scott

2012-01-01

To examine potential age-specific adaptations in skeletal muscle size and myofiber contractile physiology in response to aerobic exercise, seven young (YM; 20 ± 1 yr) and six older men (OM; 74 ± 3 yr) performed 12 wk of cycle ergometer training. Muscle biopsies were obtained from the vastus lateralis to determine size and contractile properties of isolated slow [myosin heavy chain (MHC) I] and fast (MHC IIa) myofibers, MHC composition, and muscle protein concentration. Aerobic capacity was higher (P < 0.05) after training in both YM (16 ± 2%) and OM (13 ± 3%). Quadriceps muscle volume, determined via MRI, was 5 ± 1 and 6 ± 1% greater (P < 0.05) after training for YM and OM, respectively, which was associated with an increase in MHC I myofiber cross-sectional area (CSA), independent of age. MHC I peak power was higher (P < 0.05) after training for both YM and OM, while MHC IIa peak power was increased (P < 0.05) with training in OM only. MHC I and MHC IIa myofiber peak and normalized (peak force/CSA) force were preserved with training in OM, while MHC I peak force/CSA and MHC IIa peak force were lower (P < 0.05) after training in YM. The age-dependent adaptations in myofiber function were not due to changes in protein content, as total muscle protein and myofibrillar protein concentration were unchanged (P > 0.05) with training. Training reduced (P < 0.05) the proportion of MHC IIx isoform, independent of age, whereas no other changes in MHC composition were observed. These data suggest relative improvements in muscle size and aerobic capacity are similar between YM and OM, while adaptations in myofiber contractile function showed a general improvement in OM. Training-related increases in MHC I and MHC IIa peak power reveal that skeletal muscle of OM is responsive to aerobic exercise training and further support the use of aerobic exercise for improving cardiovascular and skeletal muscle health in older individuals. PMID:22984247

Investigating Cardiac MRI Based Right Ventricular Contractility As A Novel Non-Invasive Metric of Pulmonary Arterial Pressure

PubMed Central

Menon, Prahlad G; Adhypak, Srilakshmi M; Williams, Ronald B; Doyle, Mark; Biederman, Robert WW

2014-01-01

BACKGROUND We test the hypothesis that cardiac magnetic resonance (CMR) imaging-based indices of four-dimensional (4D) (three dimensions (3D) + time) right ventricle (RV) function have predictive values in ascertaining invasive pulmonary arterial systolic pressure (PASP) measurements from right heart catheterization (RHC) in patients with pulmonary arterial hypertension (PAH). METHODS We studied five patients with idiopathic PAH and two age and sex-matched controls for RV function using a novel contractility index (CI) for amplitude and phase to peak contraction established from analysis of regional shape variation in the RV endocardium over 20 cardiac phases, segmented from CMR images in multiple orientations. RESULTS The amplitude of RV contractility correlated inversely with RV ejection fraction (RVEF; R2 = 0.64, P = 0.03) and PASP (R2 = 0.71, P = 0.02). Phase of peak RV contractility also correlated inversely to RVEF (R2 = 0.499, P = 0.12) and PASP (R2 = 0.66, P = 0.04). CONCLUSIONS RV contractility analyzed from CMR offers promising non-invasive metrics for classification of PAH, which are congruent with invasive pressure measurements. PMID:25624777

Left atrial volume and function in dogs with naturally occurring myxomatous mitral valve disease.

PubMed

Höllmer, M; Willesen, J L; Tolver, A; Koch, J

2017-02-01

Myxomatous mitral valve disease (MMVD) induces progressive left atrial (LA) enlargement. The LA modulates left ventricular filling and performance through its reservoir, conduit, and contractile function. Assessment of LA size and function may provide valuable information on the level of cardiac compensation. Left atrial function in dogs with naturally occurring MMVD remains largely unexplored. The objective of this study was to evaluate LA volume and function in dogs with naturally occurring MMVD. This prospective study included 205 client-owned dogs of different breeds, 114 healthy dogs, and 91 dogs with MMVD of different disease severities. Using two-dimensional echocardiography, the biplane area-length method was applied to assess LA volume and calculate volumetric indices of LA reservoir, conduit, and contractile function. Left atrial volume and LA stroke volume increased, whereas LA reservoir and contractile function decreased with increasing disease severity. A maximal LA volume <2.25mL/kg was the optimal cut off identified for excluding congestive heart failure in dogs with chronic MMVD with a sensitivity of 96% and a specificity of 100%. An active LA emptying fraction <24% and/or a LA expansion index <126% were suggestive of congestive heart failure in dogs with chronic MMVD with a sensitivity of 77% and a specificity of 89% and a sensitivity of 82% and a specificity of 82%, respectively. Dogs with MMVD appear to have larger LA volumes with poorer LA function. Deteriorating LA function, characterized by a decreasing reservoir and active contractile function, was evident in dogs with MMVD with increasing disease severity. Copyright © 2016 Elsevier B.V. All rights reserved.

Correlation between cardiac remodelling, function, and myocardial contractility in rat hearts 5 weeks after myocardial infarction.

PubMed

Gosselin, H; Qi, X; Rouleau, J L

1998-01-01

Early after infarction, ventricular dysfunction occurs as a result of loss of myocardial tissue. Although papillary muscle studies suggest that reduced myocardial contractility contributes to this ventricular dysfunction, in vivo studies indicate that at rest, cardiac output is normal or near normal, suggesting that contractility of the remaining viable myocardium of the ventricular wall is preserved. However, this has never been verified. To explore this further, 100 rats with various-sized myocardial infarctions had ventricular function assessed by Langendorff preparation or by isolated papillary muscle studies 5 weeks after infarction. Morphologic studies were also done. Rats with large infarctions (54%) had marked ventricular dilatation (dilatation index from 0.23 to 0.75, p < 0.01) and papillary muscle dysfunction (total tension from 6.7 to 3.2 g/mm2, p < 0.01) but only moderate left ventricular dysfunction (maximum developed tension from 206 to 151 mmHg (1 mmHg = 133.3 Pa), p < 0.01), a decrease less than one would expect with an infarct size of 54%. The contractility of the remaining viable myocardium of the ventricle was also moderately depressed (peak systolic midwall stress 91 to 60 mmHg, p < 0.01). Rats with moderate infarctions (32%) had less marked but still moderate ventricular dilatation (dilatation index 0.37, p < 0.001) and moderate papillary muscle dysfunction (total tension 4.2 g/mm2, p < 0.01). However, their decrease in ventricular function was only mild (maximum developed pressure 178 mmHg, p < 0.01) and less than one would expect with an infarct size of 32%. The remaining viable myocardium of the ventricular wall appeared to have normal contractility (peak systolic midwall stress = 86 mmHg, ns). We conclude that in this postinfarction model, in large myocardial infarctions, a loss of contractility of the remaining viable myocardium of the ventricular wall occurs as early as 5 weeks after infarction and that papillary muscle studies slightly overestimate the degree of ventricular dysfunction. In moderate infarctions, the remaining viable myocardium of the ventricular wall has preserved contractility while papillary muscle function is depressed. In this relatively early postinfarction phase, ventricular remodelling appears to help maintain left ventricular function in both moderate and large infarctions.

Pressure overload differentially affects respiratory capacity in interfibrillar and subsarcolemmal mitochondria.

PubMed

Schwarzer, Michael; Schrepper, Andrea; Amorim, Paulo A; Osterholt, Moritz; Doenst, Torsten

2013-02-15

Years ago a debate arose as to whether two functionally different mitochondrial subpopulations, subsarcolemmal mitochondria (SSM) and interfibrillar mitochondria (IFM), exist in heart muscle. Nowadays potential differences are often ignored. Presumably, SSM are providing ATP for basic cell function, whereas IFM provide energy for the contractile apparatus. We speculated that two distinguishable subpopulations exist that are differentially affected by pressure overload. Male Sprague-Dawley rats were subjected to transverse aortic constriction for 20 wk or sham operation. Contractile function was assessed by echocardiography. Heart tissue was analyzed by electron microscopy. Mitochondria were isolated by differential centrifugation, and respiratory capacity was analyzed using a Clark electrode. Pressure overload induced left ventricular hypertrophy with increased posterior wall diameter and impaired contractile function. Mitochondrial state 3 respiration in control was 50% higher in IFM than in SSM. Pressure overload significantly impaired respiratory rates in both IFM and SSM, but in SSM to a lower extent. As a result, there were no differences between SSM and IFM after 20 wk of pressure overload. Pressure overload reduced total citrate synthase activity, suggesting reduced total mitochondrial content. Electron microscopy revealed normal morphology of mitochondria but reduced total mitochondrial volume density. In conclusion, IFM show greater respiratory capacity in the healthy rat heart and a greater depression of respiratory capacity by pressure overload than SSM. The differences in respiratory capacity of cardiac IFM and SSM in healthy hearts are eliminated with pressure overload-induced heart failure. The strong effect of pressure overload on IFM together with the simultaneous appearance of mitochondrial and contractile dysfunction may support the notion of IFM primarily producing ATP for contractile function.

Cytoskeletal role in the transition from compensated to decompensated hypertrophy during adult canine left ventricular pressure overloading

NASA Technical Reports Server (NTRS)

Tagawa, H.; Koide, M.; Sato, H.; Zile, M. R.; Carabello, B. A.; Cooper, G. 4th

1998-01-01

Increased microtubule density causes cardiocyte contractile dysfunction in right ventricular (RV) pressure-overload hypertrophy, and these linked phenotypic and contractile abnormalities persist and progress during the transition to failure. Although more severe in cells from failing than hypertrophied RVs, the mechanical defects are normalized in each case by microtubule depolymerization. To define the role of increased microtubule density in left ventricular (LV) pressure-overload hypertrophy and failure, in a given LV we examined ventricular mechanics, sarcomere mechanics, and free tubulin and microtubule levels in control dogs and in dogs with aortic stenosis both with LV hypertrophy alone and with initially compensated hypertrophy that had progressed to LV muscle failure. In comparing initial values with those at study 8 weeks later, dogs with hypertrophy alone had a very substantial increase in LV mass but preservation of a normal ejection fraction and mean systolic wall stress. Dogs with hypertrophy and associated failure had a substantial but lesser increase in LV mass and a reduction in ejection fraction, as well as a marked increase in mean systolic wall stress. Cardiocyte contractile function was equivalent, and unaffected by microtubule depolymerization, in cells from control LVs and those with compensated hypertrophy. In contrast, cardiocyte contractile function in cells from failing LVs was quite depressed but was normalized by microtubule depolymerization. Microtubules were increased only in failing LVs. These contractile and cytoskeletal changes, when assayed longitudinally in a given dog by biopsy, appeared in failing ventricles only when wall stress began to increase and function began to decrease. Thus, the microtubule-based cardiocyte contractile dysfunction characteristic of pressure-hypertrophied myocardium, originally described in the RV, obtains equally in the LV but is shown here to have a specific association with increased wall stress.

Contractile reserve and calcium regulation are depressed in myocytes from chronically unloaded hearts

NASA Technical Reports Server (NTRS)

Ito, Kenta; Nakayama, Masaharu; Hasan, Faisal; Yan, Xinhua; Schneider, Michael D.; Lorell, Beverly H.

2003-01-01

BACKGROUND: Chronic cardiac unloading of the normal heart results in the reduction of left ventricular (LV) mass, but effects on myocyte contractile function are not known. METHODS AND RESULTS: Cardiac unloading and reduction in LV mass were induced by heterotopic heart transplantation to the abdominal aorta in isogenic rats. Contractility and [Ca(2+)](i) regulation in LV myocytes were studied at both 2 and 5 weeks after transplantation. Native in situ hearts from recipient animals were used as the controls for all experiments. Contractile function indices in myocytes from 2-week unloaded and native (control) hearts were similar under baseline conditions (0.5 Hz, 1.2 mmol/L [Ca(2+)](o), and 36 degrees C) and in response to stimulation with high [Ca(2+)](o) (range 2.5 to 4.0 mmol/L). In myocytes from 5-week unloaded hearts, there were no differences in fractional cell shortening and peak-systolic [Ca(2+)](i) at baseline; however, time to 50% relengthening and time to 50% decline in [Ca(2+)](i) were prolonged compared with controls. Severe defects in fractional cell shortening and peak-systolic [Ca(2+)](i) were elicited in myocytes from 5-week unloaded hearts in response to high [Ca(2+)](o). However, there were no differences in the contractile response to isoproterenol between myocytes from unloaded and native hearts. In 5-week unloaded hearts, but not in 2-week unloaded hearts, LV protein levels of phospholamban were increased (345% of native heart values). Protein levels of sarcoplasmic reticulum Ca(2+) ATPase and the Na(+)/Ca(2+) exchanger were not changed. CONCLUSIONS: Chronic unloading of the normal heart caused a time-dependent depression of myocyte contractile function, suggesting the potential for impaired performance in states associated with prolonged cardiac atrophy.

Protective effects of hydroalcoholic extract from rhizomes of Cynodon dactylon (L.) Pers. on compensated right heart failure in rats.

PubMed

Garjani, Alireza; Afrooziyan, Arash; Nazemiyeh, Hossein; Najafi, Moslem; Kharazmkia, Ali; Maleki-Dizaji, Nasrin

2009-08-05

The rhizomes of Cynodon dactylon are used for the treatment of heart failure in folk medicine. In the present study, we investigated the effects of hydroalcoholic extract of C. dactylon rhizomes on cardiac contractility in normal hearts and on cardiac functions in right-heart failure in rats. Right-heart failure was induced by intraperitoneal injection of monocrotaline (50 mg/kg). Two weeks later, the animals were treated orally with different doses of the extract for fifteen days. At the end of the experiments cardiac functions and markers of myocardial hypertrophy were measured. The treated rats showed very less signs of fatigue, peripheral cyanosis and dyspnea. The survival rate was high in the extract treated groups (90%). Administration of C. dactylon in monocrotaline-injected rats led to profound improvement in cardiac functions as demonstrated by decreased right ventricular end diastolic pressure (RVEDP) and elevated mean arterial pressure. RVdP/dtmax, and RVdP/dt/P as indices of myocardial contractility were also markedly (p < 0.001; using one way ANOVA) increased by the extract. The extract reduced heart and lung congestion by decreasing tissue wet/dry and wet/body weight ratios (p < 0.01). In the isolated rat hearts, the extract produced a remarkable (P < 0.001) positive inotropic effect concomitant with a parallel decrease in LVEDP. The results of this study indicated that C. dactylon exerted a strong protective effect on right heart failure, in part by positive inotropic action and improving cardiac functions.

[Subcellular basis of disorders of the contractile capacity of the heart in L-thyroxine-induced thyrotoxicosis].

PubMed

Karsanov, N V; Melashvili, N O; Khugashvili, Z G; Mamulashvili, L D; Azrumelashvili, M I; Khaindrava, G K; Kapanadze, R V

1990-02-01

In experiments on dogs, the authors examined the functional activity of three cardiomyocyte systems responsible for contraction-relaxation (the systems of contractile proteins, calcium transport and energy supply) in the dynamics of L-thyroxine-induced toxicosis. A fall in the capacity of the contractile protein system to generate energy and to perform was shown to play the leading role in decrease of myocardial reserve forces and reduction in cardiac contractility. There was a drop in the intensity of calcium transport through the membranes of the sarcoplasmic reticulum and mitochondria and a deficiency of the direct energy source for contraction only in the late period of the disease.

Contractile function of the myocardium with prolonged hypokinesia in patients with surgical tuberculosis

NASA Technical Reports Server (NTRS)

Zakutayeva, V. P.; Matiks, N. I.

1978-01-01

The changes in the myocardial contractile function with hypokinesia in surgical tuberculosis patients are discussed. The phase nature of the changes is noted, specifically the changes in the various systoles, diastole, and other parts of the cardiac cycle. The data compare these changes during confinement in bed with no motor activity to and with a return to motor activity after leaving the in-bed regimen.

A human in vitro model of Duchenne muscular dystrophy muscle formation and contractility.

PubMed

Nesmith, Alexander P; Wagner, Matthew A; Pasqualini, Francesco S; O'Connor, Blakely B; Pincus, Mark J; August, Paul R; Parker, Kevin Kit

2016-10-10

Tongue weakness, like all weakness in Duchenne muscular dystrophy (DMD), occurs as a result of contraction-induced muscle damage and deficient muscular repair. Although membrane fragility is known to potentiate injury in DMD, whether muscle stem cells are implicated in deficient muscular repair remains unclear. We hypothesized that DMD myoblasts are less sensitive to cues in the extracellular matrix designed to potentiate structure-function relationships of healthy muscle. To test this hypothesis, we drew inspiration from the tongue and engineered contractile human muscle tissues on thin films. On this platform, DMD myoblasts formed fewer and smaller myotubes and exhibited impaired polarization of the cell nucleus and contractile cytoskeleton when compared with healthy cells. These structural aberrations were reflected in their functional behavior, as engineered tongues from DMD myoblasts failed to achieve the same contractile strength as healthy tongue structures. These data suggest that dystrophic muscle may fail to organize with respect to extracellular cues necessary to potentiate adaptive growth and remodeling. © 2016 Nesmith et al.

Recovery in skeletal muscle contractile function after prolonged hindlimb immobilization

NASA Technical Reports Server (NTRS)

Fitts, R. H.; Brimmer, C. J.

1985-01-01

The effect of three-month hindlimb immobilization (IM) in rats on contractile properties of slow-twitch soleus (SOL), fast-twitch extensor digitorum longus, and fast-twitch superficial region of the vastus lateralis were measured after 0, 14, 28, 60, and 90 days of recovery on excized, horizontally suspended muscles stimulated electrically to maximal twitch tension. IM caused decreases in muscle-to-body weight ratios for all muscles, with no complete recovery even after 90 days. The contractile properties of the fast-twitch muscles were less affected by IM than those of the slow-twitch SOL. The SOL isometric twitch duration was shortened, due to reduced contraction and half-relaxation time, both of which returned to control levels after 14 days of recovery. The peak tetanic tension, P(O), g/sq cm,, decreased with IM by 46 percent in the SOL, but recovered by the 28th day. The maximum shortening velocity was not altered by IM in any of the muscles. Thus, normal contractile function could recover after prolonged limb IM.

High-fat diet induces protein kinase A and G-protein receptor kinase phosphorylation of β2 -adrenergic receptor and impairs cardiac adrenergic reserve in animal hearts.

PubMed

Fu, Qin; Hu, Yuting; Wang, Qingtong; Liu, Yongming; Li, Ning; Xu, Bing; Kim, Sungjin; Chiamvimonvat, Nipavan; Xiang, Yang K

2017-03-15

Patients with diabetes show a blunted cardiac inotropic response to β-adrenergic stimulation despite normal cardiac contractile reserve. Acute insulin stimulation impairs β-adrenergically induced contractile function in isolated cardiomyocytes and Langendorff-perfused hearts. In this study, we aimed to examine the potential effects of hyperinsulinaemia associated with high-fat diet (HFD) feeding on the cardiac β 2 -adrenergic receptor signalling and the impacts on cardiac contractile function. We showed that 8 weeks of HFD feeding leads to reductions in cardiac functional reserve in response to β-adrenergic stimulation without significant alteration of cardiac structure and function, which is associated with significant changes in β 2 -adrenergic receptor phosphorylation at protein kinase A and G-protein receptor kinase sites in the myocardium. The results suggest that clinical intervention might be applied to subjects in early diabetes without cardiac symptoms to prevent further cardiac complications. Patients with diabetes display reduced exercise capability and impaired cardiac contractile reserve in response to adrenergic stimulation. We have recently uncovered an insulin receptor and adrenergic receptor signal network in the heart. The aim of this study was to understand the impacts of high-fat diet (HFD) on the insulin-adrenergic receptor signal network in hearts. After 8 weeks of HFD feeding, mice exhibited diabetes, with elevated insulin and glucose concentrations associated with body weight gain. Mice fed an HFD had normal cardiac structure and function. However, the HFD-fed mice displayed a significant elevation of phosphorylation of the β 2 -adrenergic receptor (β 2 AR) at both the protein kinase A site serine 261/262 and the G-protein-coupled receptor kinase site serine 355/356 and impaired adrenergic reserve when compared with mice fed on normal chow. Isolated myocytes from HFD-fed mice also displayed a reduced contractile response to adrenergic stimulation when compared with those of control mice fed normal chow. Genetic deletion of the β 2 AR led to a normalized adrenergic response and preserved cardiac contractile reserve in HFD-fed mice. Together, these data indicate that HFD promotes phosphorylation of the β 2 AR, contributing to impairment of cardiac contractile reserve before cardiac structural and functional remodelling, suggesting that early intervention in the insulin-adrenergic signalling network might be effective in prevention of cardiac complications in diabetes. © 2016 The Authors. The Journal of Physiology published by John Wiley & Sons Ltd on behalf of The Physiological Society.

High‐fat diet induces protein kinase A and G‐protein receptor kinase phosphorylation of β2‐adrenergic receptor and impairs cardiac adrenergic reserve in animal hearts

PubMed Central

Hu, Yuting; Wang, Qingtong; Liu, Yongming; Li, Ning; Xu, Bing; Kim, Sungjin; Chiamvimonvat, Nipavan

2017-01-01

Key points Patients with diabetes show a blunted cardiac inotropic response to β‐adrenergic stimulation despite normal cardiac contractile reserve.Acute insulin stimulation impairs β‐adrenergically induced contractile function in isolated cardiomyocytes and Langendorff‐perfused hearts.In this study, we aimed to examine the potential effects of hyperinsulinaemia associated with high‐fat diet (HFD) feeding on the cardiac β2‐adrenergic receptor signalling and the impacts on cardiac contractile function.We showed that 8 weeks of HFD feeding leads to reductions in cardiac functional reserve in response to β‐adrenergic stimulation without significant alteration of cardiac structure and function, which is associated with significant changes in β2‐adrenergic receptor phosphorylation at protein kinase A and G‐protein receptor kinase sites in the myocardium.The results suggest that clinical intervention might be applied to subjects in early diabetes without cardiac symptoms to prevent further cardiac complications. Abstract Patients with diabetes display reduced exercise capability and impaired cardiac contractile reserve in response to adrenergic stimulation. We have recently uncovered an insulin receptor and adrenergic receptor signal network in the heart. The aim of this study was to understand the impacts of high‐fat diet (HFD) on the insulin–adrenergic receptor signal network in hearts. After 8 weeks of HFD feeding, mice exhibited diabetes, with elevated insulin and glucose concentrations associated with body weight gain. Mice fed an HFD had normal cardiac structure and function. However, the HFD‐fed mice displayed a significant elevation of phosphorylation of the β2‐adrenergic receptor (β2AR) at both the protein kinase A site serine 261/262 and the G‐protein‐coupled receptor kinase site serine 355/356 and impaired adrenergic reserve when compared with mice fed on normal chow. Isolated myocytes from HFD‐fed mice also displayed a reduced contractile response to adrenergic stimulation when compared with those of control mice fed normal chow. Genetic deletion of the β2AR led to a normalized adrenergic response and preserved cardiac contractile reserve in HFD‐fed mice. Together, these data indicate that HFD promotes phosphorylation of the β2AR, contributing to impairment of cardiac contractile reserve before cardiac structural and functional remodelling, suggesting that early intervention in the insulin–adrenergic signalling network might be effective in prevention of cardiac complications in diabetes. PMID:27983752

Calcineurin Regulates Myocardial Function during Acute Endotoxemia

PubMed Central

Joshi, Mandar S.; Julian, Mark W.; Huff, Jennifer E.; Bauer, John A.; Xia, Yong; Crouser, Elliott D.

2006-01-01

Rationale: Cyclosporin A (CsA) is known to preserve cardiac contractile function during endotoxemia, but the mechanism is unclear. Increased nitric oxide (NO) production and altered mitochondrial function are implicated as mechanisms contributing to sepsis-induced cardiac dysfunction, and CsA has the capacity to reduce NO production and inhibit mitochondrial dysfunction relating to the mitochondrial permeability transition (MPT). Objectives: We hypothesized that CsA would protect against endotoxin-mediated cardiac contractile dysfunction by attenuating NO production and preserving mitochondrial function. Methods: Left ventricular function was measured continuously over 4 h in cats assigned as follows: control animals (n = 7); LPS alone (3 mg/kg, n = 8); and CsA (6 mg/kg, n = 7), a calcineurin inhibitor that blocks the MPT, or tacrolimus (FK506, 0.1 mg/kg, n = 7), a calcineurin inhibitor lacking MPT activity, followed in 30 min by LPS. Myocardial tissue was then analyzed for NO synthase-2 expression, tissue nitration, protein carbonylation, and mitochondrial morphology and function. Measurements and Main Results: LPS treatment resulted in impaired left ventricular contractility, altered mitochondrial morphology and function, and increased protein nitration. As hypothesized, CsA pretreatment normalized cardiac performance and mitochondrial respiration and reduced myocardial protein nitration. Unexpectedly, FK506 pretreatment had similar effects, normalizing both cardiac and mitochondrial parameters. However, CsA and FK506 pretreatments markedly increased protein carbonylation in the myocardium despite elevated manganese superoxide dismutase activity during endotoxemia. Conclusions: Our data indicate that calcineurin is a critical regulator of mitochondrial respiration, tissue nitration, protein carbonylation, and contractile function in the heart during acute endotoxemia. PMID:16424445

Store-operated Ca2+ entry supports contractile function in hearts of hibernators

PubMed Central

Nakipova, Olga V.; Averin, Alexey S.; Evdokimovskii, Edward V.; Pimenov, Oleg Yu.; Kosarski, Leonid; Ignat’ev, Dmitriy; Anufriev, Andrey; Kokoz, Yuri M.; Reyes, Santiago; Terzic, Andre; Alekseev, Alexey E.

2017-01-01

Hibernators have a distinctive ability to adapt to seasonal changes of body temperature in a range between 37°C and near freezing, exhibiting, among other features, a unique reversibility of cardiac contractility. The adaptation of myocardial contractility in hibernation state relies on alterations of excitation contraction coupling, which becomes less-dependent from extracellular Ca2+ entry and is predominantly controlled by Ca2+ release from sarcoplasmic reticulum, replenished by the Ca2+-ATPase (SERCA). We found that the specific SERCA inhibitor cyclopiazonic acid (CPA), in contrast to its effect in papillary muscles (PM) from rat hearts, did not reduce but rather potentiated contractility of PM from hibernating ground squirrels (GS). In GS ventricles we identified drastically elevated, compared to rats, expression of Orai1, Stim1 and Trpc1/3/4/5/6/7 mRNAs, putative components of store operated Ca2+ channels (SOC). Trpc3 protein levels were found increased in winter compared to summer GS, yet levels of Trpc5, Trpc6 or Trpc7 remained unchanged. Under suppressed voltage-dependent K+, Na+ and Ca2+ currents, the SOC inhibitor 2-aminoethyl diphenylborinate (2-APB) diminished whole-cell membrane currents in isolated cardiomyocytes from hibernating GS, but not from rats. During cooling-reheating cycles (30°C–7°C–30°C) of ground squirrel PM, 2-APB did not affect typical CPA-sensitive elevation of contractile force at low temperatures, but precluded the contractility at 30°C before and after the cooling. Wash-out of 2-APB reversed PM contractility to control values. Thus, we suggest that SOC play a pivotal role in governing the ability of hibernator hearts to maintain their function during the transition in and out of hibernating states. PMID:28531217

Skeletal muscle morphology and contractile function in relation to muscle denervation in diabetic neuropathy

PubMed Central

Major, Brendan; Kimpinski, Kurt; Doherty, Timothy J.; Rice, Charles L.

2013-01-01

The objective of the study was to assess the effects of diabetic polyneuropathy (DPN) on muscle contractile properties in humans, and how these changes are related to alterations in muscle morphology and denervation. Patients with DPN (n = 12) were compared with age- and sex-matched controls (n = 12). Evoked and voluntary contractile properties, including stimulated twitch responses and maximal voluntary contractions, of the dorsiflexor muscles were assessed using an isometric ankle dynamometer. Motor unit number estimates (MUNE) of the tibialis anterior (TA) were performed via quantitative electromyography and decomposition-enhanced spike-triggered averaging. Peak tibialis anterior (TA) cross-sectional area (CSA; cm2), and relative proportion of contractile to noncontractile tissue (%) was determined from magnetic resonance images. Patients with DPN demonstrated decreased strength (−35%) and slower (−45%) dorsiflexion contractile properties for both evoked and voluntary contractions (P < 0.05). These findings were not accounted for by differences in voluntary activation (P > 0.05) or antagonist coactivation (P > 0.05). Additionally, patients with DPN were weaker when strength was normalized to TA total CSA (−30%; P < 0.05) or contractile tissue CSA (−26%; P < 0.05). In the DPN patient group, TA MUNEs were negatively related to both % noncontractile tissue (P < 0.05; r = 0.72) and twitch half-relaxation time (P < 0.05; r = 0.60), whereas no relationships were found between these variables in controls (P > 0.05). We conclude that patients with DPN demonstrated reduced strength and muscle quality as well as contractile slowing. This process may contribute to muscle power loss and functional impairments reported in patients with DPN, beyond the loss of strength commonly observed. PMID:24356519

LncRNA ZFAS1 as a SERCA2a Inhibitor to Cause Intracellular Ca2+ Overload and Contractile Dysfunction in a Mouse Model of Myocardial Infarction.

PubMed

Zhang, Ying; Jiao, Lei; Sun, Lihua; Li, Yanru; Gao, Yuqiu; Xu, Chaoqian; Shao, Yingchun; Li, Mengmeng; Li, Chunyan; Lu, Yanjie; Pan, Zhenwei; Xuan, Lina; Zhang, Yiyuan; Li, Qingqi; Yang, Rui; Zhuang, Yuting; Zhang, Yong; Yang, Baofeng

2018-05-11

Ca 2+ homeostasis-a critical determinant of cardiac contractile function-is critically regulated by SERCA2a (sarcoplasmic reticulum Ca 2+ -ATPase 2a). Our previous study has identified ZFAS1 as a new lncRNA biomarker of acute myocardial infarction (MI). To evaluate the effects of ZFAS1 on SERCA2a and the associated Ca 2+ homeostasis and cardiac contractile function in the setting of MI. ZFAS1 expression was robustly increased in cytoplasm and sarcoplasmic reticulum in a mouse model of MI and a cellular model of hypoxia. Knockdown of endogenous ZFAS1 by virus-mediated silencing shRNA partially abrogated the ischemia-induced contractile dysfunction. Overexpression of ZFAS1 in otherwise normal mice created similar impairment of cardiac function as that observed in MI mice. Moreover, at the cellular level, ZFAS1 overexpression weakened the contractility of cardiac muscles. At the subcellular level, ZFAS1 deleteriously altered the Ca 2+ transient leading to intracellular Ca 2+ overload in cardiomyocytes. At the molecular level, ZFAS1 was found to directly bind SERCA2a protein and to limit its activity, as well as to repress its expression. The effects of ZFAS1 were readily reversible on knockdown of this lncRNA. Notably, a sequence domain of ZFAS1 gene that is conserved across species mimicked the effects of the full-length ZFAS1 . Mutation of this domain or application of an antisense fragment to this conserved region efficiently canceled out the deleterious actions of ZFAS1 . ZFAS1 had no significant effects on other Ca 2+ -handling regulatory proteins. ZFAS1 is an endogenous SERCA2a inhibitor, acting by binding to SERCA2a protein to limit its intracellular level and inhibit its activity, and a contributor to the impairment of cardiac contractile function in MI. Therefore, anti- ZFAS1 might be considered as a new therapeutic strategy for preserving SERCA2a activity and cardiac function under pathological conditions of the heart. © 2018 The Authors.

Cardiac-Specific Knockout of ETA Receptor Mitigates Paraquat-Induced Cardiac Contractile Dysfunction.

PubMed

Wang, Jiaxing; Lu, Songhe; Zheng, Qijun; Hu, Nan; Yu, Wenjun; Li, Na; Liu, Min; Gao, Beilei; Zhang, Guoyong; Zhang, Yingmei; Wang, Haichang

2016-07-01

Paraquat (1,1'-dim ethyl-4-4'-bipyridinium dichloride), a highly toxic quaternary ammonium herbicide widely used in agriculture, exerts potent toxic prooxidant effects resulting in multi-organ failure including the lung and heart although the underlying mechanism remains elusive. Recent evidence suggests possible involvement of endothelin system in paraquat-induced acute lung injury. This study was designed to examine the role of endothelin receptor A (ETA) in paraquat-induced cardiac contractile and mitochondrial injury. Wild-type (WT) and cardiac-specific ETA receptor knockout mice were challenged to paraquat (45 mg/kg, i.p.) for 48 h prior to the assessment of echocardiographic, cardiomyocyte contractile and intracellular Ca(2+) properties, as well as apoptosis and mitochondrial damage. Levels of the mitochondrial proteins for biogenesis and oxidative phosphorylation including UCP2, HSP90 and PGC1α were evaluated. Our results revealed that paraquat elicited cardiac enlargement, mechanical anomalies including compromised echocardiographic parameters (elevated left ventricular end-systolic and end-diastolic diameters as well as reduced factional shortening), suppressed cardiomyocyte contractile function, intracellular Ca(2+) handling, overt apoptosis and mitochondrial damage. ETA receptor knockout itself failed to affect myocardial function, apoptosis, mitochondrial integrity and mitochondrial protein expression. However, ETA receptor knockout ablated or significantly attenuated paraquat-induced cardiac contractile and intracellular Ca(2+) defect, apoptosis and mitochondrial damage. Taken together, these findings revealed that endothelin system in particular the ETA receptor may be involved in paraquat-induced toxic myocardial contractile anomalies possibly related to apoptosis and mitochondrial damage.

The Reliability of Pharyngeal High Resolution Manometry with Impedance for Derivation of Measures of Swallowing Function in Healthy Volunteers

PubMed Central

Omari, Taher I.; Savilampi, Johanna; Kokkinn, Karmen; Schar, Mistyka; Lamvik, Kristin; Doeltgen, Sebastian; Cock, Charles

2016-01-01

Purpose. We evaluated the intra- and interrater agreement and test-retest reliability of analyst derivation of swallow function variables based on repeated high resolution manometry with impedance measurements. Methods. Five subjects swallowed 10 × 10 mL saline on two occasions one week apart producing a database of 100 swallows. Swallows were repeat-analysed by six observers using software. Swallow variables were indicative of contractility, intrabolus pressure, and flow timing. Results. The average intraclass correlation coefficients (ICC) for intra- and interrater comparisons of all variable means showed substantial to excellent agreement (intrarater ICC 0.85–1.00; mean interrater ICC 0.77–1.00). Test-retest results were less reliable. ICC for test-retest comparisons ranged from slight to excellent depending on the class of variable. Contractility variables differed most in terms of test-retest reliability. Amongst contractility variables, UES basal pressure showed excellent test-retest agreement (mean ICC 0.94), measures of UES postrelaxation contractile pressure showed moderate to substantial test-retest agreement (mean Interrater ICC 0.47–0.67), and test-retest agreement of pharyngeal contractile pressure ranged from slight to substantial (mean Interrater ICC 0.15–0.61). Conclusions. Test-retest reliability of HRIM measures depends on the class of variable. Measures of bolus distension pressure and flow timing appear to be more test-retest reliable than measures of contractility. PMID:27190520

Beta1-adrenoceptor antagonist, metoprolol attenuates cardiac myocyte Ca2+ handling dysfunction in rats with pulmonary artery hypertension.

PubMed

Fowler, Ewan D; Drinkhill, Mark J; Norman, Ruth; Pervolaraki, Eleftheria; Stones, Rachel; Steer, Emma; Benoist, David; Steele, Derek S; Calaghan, Sarah C; White, Ed

2018-07-01

Right heart failure is the major cause of death in Pulmonary Artery Hypertension (PAH) patients but is not a current, specific therapeutic target. Pre-clinical studies have shown that adrenoceptor blockade can improve cardiac function but the mechanisms of action within right ventricular (RV) myocytes are unknown. We tested whether the β 1 -adrenoceptor blocker metoprolol could improve RV myocyte function in an animal model of PAH, by attenuating adverse excitation-contraction coupling remodeling. PAH with RV failure was induced in rats by monocrotaline injection. When PAH was established, animals were given 10 mg/kg/day metoprolol (MCT + BB) or vehicle (MCT). The median time to the onset of heart failure signs was delayed from 23 days (MCT), to 31 days (MCT + BB). At 23 ± 1 days post-injection, MCT + BB showed improved in vivo cardiac function, measured by echocardiography. RV hypertrophy was reduced despite persistent elevated afterload. RV myocyte contractility during field stimulation was improved at higher pacing frequencies in MCT + BB. Preserved t-tubule structure, more uniform evoked Ca 2+ release, increased SERCA2a expression and faster ventricular repolarization (measured in vivo by telemetry) may account for the improved contractile function. Sarcoplasmic reticulum Ca 2+ overload was prevented in MCT + BB myocytes resulting in fewer spontaneous Ca 2+ waves, with a lower pro-arrhythmic potential. Our novel finding of attenuation of defects in excitation contraction coupling by β 1 -adrenoceptor blockade with delays in the onset of HF, identifies the RV as a promising therapeutic target in PAH. Moreover, our data suggest existing therapies for left ventricular failure may also be beneficial in PAH induced RV failure. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

Frequent premature atrial contractions impair left atrial contractile function and promote adverse left atrial remodeling.

PubMed

John, Anub G; Hirsch, Glenn A; Stoddard, Marcus F

2018-06-10

This study assessed if frequent premature atrial contractions (PACs) were associated with decreased left atrial (LA) strain and adverse remodeling. Left atrial dysfunction and enlargement increases risk of stroke. If frequent PACs cause LA dysfunction and remodeling, PAC suppressive therapy may be beneficial. Inclusion criteria were age ≥18 years and sinus rhythm. Exclusion criteria were atrial fibrillation or any etiology for LA enlargement. Hundred and thirty-two patients with frequent PACs (≥100/24 hours) by Holter were matched to controls. Speckle tracking strain of the left atrium was performed from the 4-chamber view. Strain measurements were LA peak contractile, reservoir and conduit strain and strain rates. In the frequent PAC vs control group, PACs were more frequent (1959 ± 3796 vs 28 ± 25/24 hours, P < .0001). LA peak contractile strain was reduced in the group with frequent PACs vs controls (-7.85 ± 4.12% vs -9.33 ± 4.45%, P = .006). LA peak late negative contractile strain rate was less negative in the frequent PAC vs control group (-0.63 ± 0.27 s -1 vs -0.69 ± 0.32 s -1 , P = .051). LA reservoir and conduit strain and strain rates did not differ. LA volume index (LAVI) was larger in the frequent PAC vs control group (26.6 ± 7.8 vs 24.6 ± 8.8 mL/m 2 , P < .05). Frequent PACs were an independent predictor of reduced LA peak contractile strain and reduced LA peak late negative contractile strain rate. Patients with frequent PACs have reduced LA peak contractile strain and strain rates and larger LAVI compared to controls. Frequent PACs are an independent predictor of reduced LA peak contractile strain and strain rate. These findings support the hypothesis that frequent PACs impair LA contractile function and promote adverse LA remodeling. © 2018 Wiley Periodicals, Inc.

Triiodothyronine activates lactate oxidation without impairing fatty acid oxidation and improves weaning from extracorporeal membrane oxygenation.

PubMed

Kajimoto, Masaki; Ledee, Dolena R; Xu, Chun; Kajimoto, Hidemi; Isern, Nancy G; Portman, Michael A

2014-01-01

Extracorporeal membrane oxygenation (ECMO) provides a rescue for children with severe cardiac failure. It has previously been shown that triiodothyronine (T3) improves cardiac function by modulating pyruvate oxidation during weaning. This study focused on fatty acid (FA) metabolism modulated by T3 for weaning from ECMO after cardiac injury. METHODS AND RESULTS: Nineteen immature piglets (9.1-15.3 kg) were separated into 3 groups with ECMO (6.5 h) and wean: normal circulation (Group-C); transient coronary occlusion (10 min) for ischemia-reperfusion (IR) followed by ECMO (Group-IR); and IR with T3 supplementation (Group-IR-T3). 13-Carbon ((13)C)-labeled lactate, medium-chain and long-chain FAs, was infused as oxidative substrates. Substrate fractional contribution (FC) to the citric acid cycle was analyzed by(13)C-nuclear magnetic resonance. ECMO depressed circulating T3 levels to 40% of the baseline at 4 h and were restored in Group-IR-T3. Group-IR decreased cardiac power, which was not fully restorable and 2 pigs were lost because of weaning failure. Group-IR also depressed FC-lactate, while the excellent contractile function and energy efficiency in Group-IR-T3 occurred along with a marked FC-lactate increase and [adenosine triphosphate]/[adenosine diphosphate] without either decreasing FC-FAs or elevating myocardial oxygen consumption over Group-C or -IR. T3 releases inhibition of lactate oxidation following IR injury without impairing FA oxidation. These findings indicate that T3 depression during ECMO is maladaptive, and that restoring levels improves metabolic flux and enhances contractile function during weaning.

Aerobic exercise reduces oxidative stress and improves vascular changes of small mesenteric and coronary arteries in hypertension

PubMed Central

Roque, Fernanda R; Briones, Ana M; García-Redondo, Ana B; Galán, María; Martínez-Revelles, Sonia; Avendaño, Maria S; Cachofeiro, Victoria; Fernandes, Tiago; Vassallo, Dalton V; Oliveira, Edilamar M; Salaices, Mercedes

2013-01-01

Background and Purpose Regular physical activity is an effective non-pharmacological therapy for prevention and control of hypertension. We investigated the effects of aerobic exercise training in vascular remodelling and in the mechanical and functional alterations of coronary and small mesenteric arteries from spontaneously hypertensive rats (SHR). Experimental Approach Normotensive Wistar Kyoto (WKY), SHR and SHR trained on a treadmill for 12 weeks were used to evaluate vascular structural, mechanical and functional properties. Key Results Exercise did not affect lumen diameter, wall thickness and wall/lumen ratio but reduced vascular stiffness of coronary and mesenteric arteries from SHR. Exercise also reduced collagen deposition and normalized altered internal elastic lamina organization and expression of MMP-9 in mesenteric arteries from SHR. Exercise did not affect contractile responses of coronary arteries but improved the endothelium-dependent relaxation in SHR. In mesenteric arteries, training normalized the increased contractile responses induced by U46619 and by high concentrations of acetylcholine. In vessels from SHR, exercise normalized the effects of the NADPH oxidase inhibitor apocynin and the NOS inhibitor l-NAME in vasodilator or vasoconstrictor responses, normalized the increased O2− production and the reduced Cu/Zn superoxide dismutase expression and increased NO production. Conclusions and Implications Exercise training of SHR improves endothelial function and vascular stiffness in coronary and small mesenteric arteries. This might be related to the concomitant decrease of oxidative stress and increase of NO bioavailability. Such effects demonstrate the beneficial effects of exercise on the vascular system and could contribute to a reduction in blood pressure. PMID:22994554

Aerobic exercise reduces oxidative stress and improves vascular changes of small mesenteric and coronary arteries in hypertension.

PubMed

Roque, Fernanda R; Briones, Ana M; García-Redondo, Ana B; Galán, María; Martínez-Revelles, Sonia; Avendaño, Maria S; Cachofeiro, Victoria; Fernandes, Tiago; Vassallo, Dalton V; Oliveira, Edilamar M; Salaices, Mercedes

2013-02-01

Regular physical activity is an effective non-pharmacological therapy for prevention and control of hypertension. We investigated the effects of aerobic exercise training in vascular remodelling and in the mechanical and functional alterations of coronary and small mesenteric arteries from spontaneously hypertensive rats (SHR). Normotensive Wistar Kyoto (WKY), SHR and SHR trained on a treadmill for 12 weeks were used to evaluate vascular structural, mechanical and functional properties. Exercise did not affect lumen diameter, wall thickness and wall/lumen ratio but reduced vascular stiffness of coronary and mesenteric arteries from SHR. Exercise also reduced collagen deposition and normalized altered internal elastic lamina organization and expression of MMP-9 in mesenteric arteries from SHR. Exercise did not affect contractile responses of coronary arteries but improved the endothelium-dependent relaxation in SHR. In mesenteric arteries, training normalized the increased contractile responses induced by U46619 and by high concentrations of acetylcholine. In vessels from SHR, exercise normalized the effects of the NADPH oxidase inhibitor apocynin and the NOS inhibitor l-NAME in vasodilator or vasoconstrictor responses, normalized the increased O(2) (-) production and the reduced Cu/Zn superoxide dismutase expression and increased NO production. Exercise training of SHR improves endothelial function and vascular stiffness in coronary and small mesenteric arteries. This might be related to the concomitant decrease of oxidative stress and increase of NO bioavailability. Such effects demonstrate the beneficial effects of exercise on the vascular system and could contribute to a reduction in blood pressure. © 2012 The Authors. British Journal of Pharmacology © 2012 The British Pharmacological Society.

Effects of long-term treatment with eicosapentaenoic acid on the heart subjected to ischemia/reperfusion and hypoxia/reoxygenation in rats.

PubMed

Takeo, S; Nasa, Y; Tanonaka, K; Yabe, K; Nojiri, M; Hayashi, M; Sasaki, H; Ida, K; Yanai, K

1998-11-01

The effects of eicosapentaenoic acid (EPA) and long-term treatment with EPA-ethylester (EPA-E) were examined in perfused rat hearts subjected to ischemia/reperfusion and adult rat cardiomyocytes subjected to hypoxia/reoxygenation. EPA (0.1 microM) improved postischemic contractile dysfunction of the ischemic/reperfused heart. EPA (10 microM) attenuated hypoxia/reoxygenation-induced morphological deterioration of cardiomyocytes. The results suggest the presence of direct cardioprotective effects of EPA. Rats were orally treated for 4 weeks with 1 g/kg/day of EPA-E to elucidate ex vivo effects of EPA, and the fatty acid composition of cardiac phospholipids was determined. The percent ratio of EPA in total fatty acids of cardiac phospholipids increased whereas that of arachidonic acid decreased. The percent ratio of n-3/n-6 fatty acid did not increase. Treatment with EPA-E did not improve the post-ischemic contractile function, but attenuated the ischemia/reperfusion-induced release of prostaglandins during reperfusion. Treatment with EPA-E preserved a better morphological appearance of the cardiomyocytes subjected to hypoxia/reoxygenation. The results suggest that the mechanisms responsible for cytoprotective effects of hypoxic/reoxygenated cardiomyocytes or inhibition of metabolic alterations of the ischemic/reperfused heart by long-term EPA-E treatment did not contribute substantially to recovery of post-ischemic contractile dysfunction. The direct in vitro effects of EPA may play a role in the protection of the heart from ischemia/reperfusion or hypoxia/reoxygenation injury.

Identification of biochemical adaptations in hyper- or hypocontractile hearts from phospholamban mutant mice by expression proteomics.

PubMed

Pan, Yan; Kislinger, Thomas; Gramolini, Anthony O; Zvaritch, Elena; Kranias, Evangelia G; MacLennan, David H; Emili, Andrew

2004-02-24

Phospholamban (PLN) is a critical regulator of cardiac contractility through its binding to and regulation of the activity of the sarco(endo)plasmic reticulum Ca2+ ATPase. To uncover biochemical adaptations associated with extremes of cardiac muscle contractility, we used high-throughput gel-free tandem MS to monitor differences in the relative abundance of membrane proteins in standard microsomal fractions isolated from the hearts of PLN-null mice (PLN-KO) with high contractility and from transgenic mice overexpressing a superinhibitory PLN mutant in a PLN-null background (I40A-KO) with diminished contractility. Significant differential expression was detected for a subset of the 782 proteins identified, including known membrane-associated biomarkers, components of signaling pathways, and previously uninvestigated proteins. Proteins involved in fat and carbohydrate metabolism and proteins linked to G protein-signaling pathways activating protein kinase C were enriched in I40A-KO cardiac muscle, whereas proteins linked to enhanced contractile function were enriched in PLN-KO mutant hearts. These data demonstrate that Ca2+ dysregulation, leading to elevated or depressed cardiac contractility, induces compensatory biochemical responses.

Functional vascular smooth muscle cells derived from human induced pluripotent stem cells via mesenchymal stem cell intermediates

PubMed Central

Bajpai, Vivek K.; Mistriotis, Panagiotis; Loh, Yuin-Han; Daley, George Q.; Andreadis, Stelios T.

2012-01-01

Aims Smooth muscle cells (SMC) play an important role in vascular homeostasis and disease. Although adult mesenchymal stem cells (MSC) have been used as a source of contractile SMC, they suffer from limited proliferation potential and culture senescence, particularly when originating from older donors. By comparison, human induced pluripotent stem cells (hiPSC) can provide an unlimited source of functional SMC for autologous cell-based therapies and for creating models of vascular disease. Our goal was to develop an efficient strategy to derive functional, contractile SMC from hiPSC. Methods and results We developed a robust, stage-wise, feeder-free strategy for hiPSC differentiation into functional SMC through an intermediate stage of multipotent MSC, which could be coaxed to differentiate into fat, bone, cartilage, and muscle. At this stage, the cells were highly proliferative and displayed higher clonogenic potential and reduced senescence when compared with parental hair follicle mesenchymal stem cells. In addition, when exposed to differentiation medium, the myogenic proteins such as α-smooth muscle actin, calponin, and myosin heavy chain were significantly upregulated and displayed robust fibrillar organization, suggesting the development of a contractile phenotype. Indeed, tissue constructs prepared from these cells exhibited high levels of contractility in response to receptor- and non-receptor-mediated agonists. Conclusion We developed an efficient stage-wise strategy that enabled hiPSC differentiation into contractile SMC through an intermediate population of clonogenic and multipotent MSC. The high yield of MSC and SMC derivation suggests that our strategy may facilitate an acquisition of the large numbers of cells required for regenerative medicine or for studying vascular disease pathophysiology. PMID:22941255

Impaired M3 and enhanced M2 muscarinic receptor contractile function in a streptozotocin model of mouse diabetic urinary bladder

PubMed Central

Pak, K. J.; Ostrom, R. S.; Matsui, M.

2010-01-01

We investigated the contractile roles of M2 and M3 muscarinic receptors in urinary bladder from streptozotocin-treated mice. Wild-type and M2 muscarinic receptor knockout (M2 KO) mice were given a single injection of vehicle or streptozotocin (125 mg kg−1) 2–24 weeks prior to bladder assays. The effect of forskolin on contractions elicited to the muscarinic agonist, oxotremorine-M, was measured in isolated urinary bladder (intact or denuded of urothelium). Denuded urinary bladder from vehicle-treated wild-type and M2 KO mice exhibited similar contractile responses to oxotremorine-M, when contraction was normalized relative to that elicited by KCl (50 mM). Eight to 9 weeks after streptozotocin treatment, the EC50 value of oxotremorine-M increased 3.1-fold in urinary bladder from the M2 KO mouse (N = 5) compared to wild type (N = 6; P < 0.001). Analogous changes were observed in intact bladder. In denuded urinary bladder from vehicle-treated mice, forskolin (5 µM) caused a much greater inhibition of contraction in M2 KO bladder compared to wild type. Following streptozotocin treatment, this forskolin effect increased 1.6-fold (P = 0.032). At the 20- to 24-week time point, the forskolin effect increased 1.7-fold for denuded as well as intact bladders (P = 0.036, 0.01, respectively). Although streptozotocin treatment inhibits M3 receptor-mediated contraction in denuded urinary bladder, muscarinic contractile function is maintained in wild-type bladder by enhanced M2 contractile function. M2 receptor activation opposes forskolin-induced relaxation of the urinary bladder, and this M2 function is enhanced following streptozotocin treatment. PMID:20349044

Impaired M3 and enhanced M2 muscarinic receptor contractile function in a streptozotocin model of mouse diabetic urinary bladder.

PubMed

Pak, K J; Ostrom, R S; Matsui, M; Ehlert, F J

2010-05-01

We investigated the contractile roles of M2 and M3 muscarinic receptors in urinary bladder from streptozotocin-treated mice. Wild-type and M2 muscarinic receptor knockout (M2 KO) mice were given a single injection of vehicle or streptozotocin (125 mg kg(-1)) 2-24 weeks prior to bladder assays. The effect of forskolin on contractions elicited to the muscarinic agonist, oxotremorine-M, was measured in isolated urinary bladder (intact or denuded of urothelium). Denuded urinary bladder from vehicle-treated wild-type and M2 KO mice exhibited similar contractile responses to oxotremorine-M, when contraction was normalized relative to that elicited by KCl (50 mM). Eight to 9 weeks after streptozotocin treatment, the EC(50) value of oxotremorine-M increased 3.1-fold in urinary bladder from the M2 KO mouse (N = 5) compared to wild type (N = 6; P < 0.001). Analogous changes were observed in intact bladder. In denuded urinary bladder from vehicle-treated mice, forskolin (5 microM) caused a much greater inhibition of contraction in M2 KO bladder compared to wild type. Following streptozotocin treatment, this forskolin effect increased 1.6-fold (P = 0.032). At the 20- to 24-week time point, the forskolin effect increased 1.7-fold for denuded as well as intact bladders (P = 0.036, 0.01, respectively). Although streptozotocin treatment inhibits M3 receptor-mediated contraction in denuded urinary bladder, muscarinic contractile function is maintained in wild-type bladder by enhanced M2 contractile function. M2 receptor activation opposes forskolin-induced relaxation of the urinary bladder, and this M(2) function is enhanced following streptozotocin treatment.

Effect of estrogen on molecular and functional characteristics of the rodent vaginal muscularis

PubMed Central

Basha, Maureen E.; Chang, Shaohua; Burrows, Lara J.; Lassmann, Jenny; Wein, Alan J.; Moreland, Robert S.; Chacko, Samuel K.

2013-01-01

Introduction Vaginal atrophy is a consequence of menopause however little is known concerning the effect of a decrease in systemic estrogen on vaginal smooth muscle structure and function. As the incidence of pelvic floor disorders increases with age, it is important to determine if estrogen regulates the molecular composition and contractility of the vaginal muscularis. Aim The goal of this study was to determine the effect of estrogen on molecular and functional characteristics of the vaginal muscularis utilizing a rodent model of surgical menopause. Methods 3–4 month old Sprague Dawley rats underwent sham laparotomy (Sham, n=18) or ovariectomy (Ovx, n=39). Two weeks following surgery, animals received a subcutaneous osmotic pump containing vehicle (Sham, Ovx) or 17- β estradiol (Ovx). Animals were euthanized one week later and the proximal vagina was collected for analysis of contractile protein expression and in vitro studies of contractility. Measurements were analyzed using a one-way ANOVA followed by Tukey's post hoc analysis (α= 0.05). Main Outcome Measures Protein and mRNA transcript expression levels of contractile proteins, in vitro measurements of vaginal contractility Results Ovariectomy decreased the expression of carboxyl-terminal myosin heavy chain isoform SM1 and h-caldesmon and reduced the amplitude of contraction of the vaginal muscularis in response to KCl. Estradiol replacement reversed these changes. No differences were detected in the % vaginal muscularis, mRNA transcript expression of amino terminal MHC isoforms, l-caldesmon expression and maximal velocity of shortening. Conclusion Systemic estrogen replacement restores functional and molecular characteristics of the vaginal muscularis of ovariectomized rats. Our results indicate that menopause is associated with changes in the vaginal muscularis, which may contribute to the increased incidence of pelvic floor disorders with age. PMID:23438289

Glucagon-like peptide-1 reduces contractile function and fails to boost glucose utilization in normal hearts in the presence of fatty acids.

PubMed

Nguyen, T Dung; Shingu, Yasushige; Amorim, Paulo A; Schwarzer, Michael; Doenst, Torsten

2013-10-09

GLP-1 and exendin-4, which are used as insulin sensitizers or weight reducing drugs, were shown to improve glucose uptake in the heart. However, the direct effects of GLP-1 or exendin-4 on normal hearts in the presence of fatty acids, the main cardiac substrates, have never been investigated. We therefore assessed the effects of GLP-1 or exendin-4 on myocardial glucose uptake (GU), glucose oxidation (GO) and cardiac performance (CP) under conditions of fatty acid utilization. Rat hearts were perfused with only glucose (5 mM) or glucose (5 mM) plus oleate (0.4 mM) as substrates for 60 min. After 30 min, GLP-1 or exendin-4 (0.5 nM or 5 nM) was added. In the absence of oleate, GLP-1 increased both GU and GO. Exendin-4 increased GO but showed no effect on GU. Neither GLP-1 nor exendin-4 affected CP. However, when oleate was present, GLP-1 failed to stimulate glucose utilization and exendin-4 even decreased GU. Furthermore, now GLP-1 reduced CP. In contrast to prior reports, this negative inotropic effect could not be blocked by the protein kinase A inhibitor H-89. We then measured myocardial GO and CP in rats receiving a 4-week GLP-1 infusion. Interestingly, this chronic treatment resulted in a significant reduction in both GO and CP. Under the influence of oleate, GLP-1 reduces contractile function and fails to stimulate glucose utilization in normal hearts. Exendin-4 may acutely reduce cardiac glucose uptake but not contractility. We suggest advanced investigation of heart function and metabolism in patients treating with these peptides. © 2013.

Thrombopoietin modulates cardiac contractility in vitro and contributes to myocardial depressing activity of septic shock serum.

PubMed

Lupia, Enrico; Spatola, Tiziana; Cuccurullo, Alessandra; Bosco, Ornella; Mariano, Filippo; Pucci, Angela; Ramella, Roberta; Alloatti, Giuseppe; Montrucchio, Giuseppe

2010-09-01

Thrombopoietin (TPO) is a humoral growth factor that has been shown to increase platelet activation in response to several agonists. Patients with sepsis have increased circulating TPO levels, which may enhance platelet activation, potentially participating to the pathogenesis of multi-organ failure. Aim of this study was to investigate whether TPO affects myocardial contractility and participates to depress cardiac function during sepsis. We showed the expression of the TPO receptor c-Mpl on myocardial cells and tissue by RT-PCR, immunofluorescence and western blotting. We then evaluated the effect of TPO on the contractile function of rat papillary muscle and isolated heart. TPO did not change myocardial contractility in basal conditions, but, when followed by epinephrine (EPI) stimulation, it blunted the enhancement of contractile force induced by EPI both in papillary muscle and isolated heart. An inhibitor of TPO prevented TPO effect on cardiac inotropy. Treatment of papillary muscle with pharmacological inhibitors of phosphatidylinositol 3-kinase, NO synthase, and guanilyl cyclase abolished TPO effect, indicating NO as the final mediator. We finally studied the role of TPO in the negative inotropic effect exerted by human septic shock (HSS) serum and TPO cooperation with TNF-alpha and IL-1beta. Pre-treatment with the TPO inhibitor prevented the decrease in contractile force induced by HSS serum. Moreover, TPO significantly amplified the negative inotropic effect induced by TNF-alpha and IL-1beta in papillary muscle. In conclusion, TPO negatively modulates cardiac inotropy in vitro and contributes to the myocardial depressing activity of septic shock serum.

Post-exercise contractility, diastolic function, and pressure: Operator-independent sensor-based intelligent monitoring for heart failure telemedicine

PubMed Central

Bombardini, Tonino; Gemignani, Vincenzo; Bianchini, Elisabetta; Pasanisi, Emilio; Pratali, Lorenza; Pianelli, Mascia; Faita, Francesco; Giannoni, Massimo; Arpesella, Giorgio; Sicari, Rosa; Picano, Eugenio

2009-01-01

Background New sensors for intelligent remote monitoring of the heart should be developed. Recently, a cutaneous force-frequency relation recording system has been validated based on heart sound amplitude and timing variations at increasing heart rates. Aim To assess sensor-based post-exercise contractility, diastolic function and pressure in normal and diseased hearts as a model of a wireless telemedicine system. Methods We enrolled 150 patients and 22 controls referred for exercise-stress echocardiography, age 55 ± 18 years. The sensor was attached in the precordial region by an ECG electrode. Stress and recovery contractility were derived by first heart sound amplitude vibration changes; diastolic times were acquired continuously. Systemic pressure changes were quantitatively documented by second heart sound recording. Results Interpretable sensor recordings were obtained in all patients (feasibility = 100%). Post-exercise contractility overshoot (defined as increase > 10% of recovery contractility vs exercise value) was more frequent in patients than controls (27% vs 8%, p < 0.05). At 100 bpm stress heart rate, systolic/diastolic time ratio (normal, < 1) was > 1 in 20 patients and in none of the controls (p < 0.01); at recovery systolic/diastolic ratio was > 1 in only 3 patients (p < 0.01 vs stress). Post-exercise reduced arterial pressure was sensed. Conclusion Post-exercise contractility, diastolic time and pressure changes can be continuously measured by a cutaneous sensor. Heart disease affects not only exercise systolic performance, but also post-exercise recovery, diastolic time intervals and blood pressure changes – in our study, all of these were monitored by a non-invasive wearable sensor. PMID:19442285

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kajimoto, Masaki; Ledee, Dolena R.; Xu, Chun

Background: Extracorporeal membrane oxygenation (ECMO) provides a rescue for children with severe cardiac failure. We previously showed that triiodothyronine (T3) improves cardiac function by modulating pyruvate oxidation during weaning. This study was focused on fatty acid (FA) metabolism modulated by T3 for weaning from ECMO after cardiac injury. Methods: Nineteen immature piglets (9.1-15.3 kg) were separated into 3 groups with ECMO (6.5 hours) and wean: normal circulation (Group-C);transient coronary occlusion (10 minutes) followed by ECMO (Group-IR); and IR with T3 supplementation (Group-IR-T3). 13-Carbon labeled lactate, medium-chain and long-chain FAs were infused as oxidative substrates. Substrate fractional contribution to the citricmore » acid cycle (FC) was analyzed by 13-Carbon nuclear magnetic resonance. Results: ECMO depressed circulating T3 levels to 40% baseline at 4 hours and were restored in Group-IR-T3. Group-IR decreased cardiac power, which was not fully restorable and 2 pigs were lost because of weaning failure. Group-IR also depressed FC-lactate, while the excellent contractile function and energy efficiency in Group-IR-T3 occurred along with a marked FC-lactate increase and [ATP]/[ADP] without either decreasing FC-FAs or elevating myocardial oxygen consumption over Group-C or -IR. Conclusions: T3 releases inhibition of lactate oxidation following ischemia-reperfusion injury without impairing FA oxidation. These findings indicate that T3 depression during ECMO is maladaptive, and that restoring levels improves metabolic flux and enhances contractile function during weaning.« less

Protective effects of hydroalcoholic extract from rhizomes of Cynodon dactylon (L.) Pers. on compensated right heart failure in rats

PubMed Central

Garjani, Alireza; Afrooziyan, Arash; Nazemiyeh, Hossein; Najafi, Moslem; Kharazmkia, Ali; Maleki-Dizaji, Nasrin

2009-01-01

Background The rhizomes of Cynodon dactylon are used for the treatment of heart failure in folk medicine. In the present study, we investigated the effects of hydroalcoholic extract of C. dactylon rhizomes on cardiac contractility in normal hearts and on cardiac functions in right-heart failure in rats. Methods Right-heart failure was induced by intraperitoneal injection of monocrotaline (50 mg/kg). Two weeks later, the animals were treated orally with different doses of the extract for fifteen days. At the end of the experiments cardiac functions and markers of myocardial hypertrophy were measured. Results The treated rats showed very less signs of fatigue, peripheral cyanosis and dyspnea. The survival rate was high in the extract treated groups (90%). Administration of C. dactylon in monocrotaline-injected rats led to profound improvement in cardiac functions as demonstrated by decreased right ventricular end diastolic pressure (RVEDP) and elevated mean arterial pressure. RVdP/dtmax, and RVdP/dt/P as indices of myocardial contractility were also markedly (p < 0.001; using one way ANOVA) increased by the extract. The extract reduced heart and lung congestion by decreasing tissue wet/dry and wet/body weight ratios (p < 0.01). In the isolated rat hearts, the extract produced a remarkable (P < 0.001) positive inotropic effect concomitant with a parallel decrease in LVEDP. Conclusion The results of this study indicated that C. dactylon exerted a strong protective effect on right heart failure, in part by positive inotropic action and improving cardiac functions. PMID:19653918

Development of a pump flow estimator for rotary blood pumps to enhance monitoring of ventricular function.

PubMed

Granegger, Marcus; Moscato, Francesco; Casas, Fernando; Wieselthaler, Georg; Schima, Heinrich

2012-08-01

Estimation of instantaneous flow in rotary blood pumps (RBPs) is important for monitoring the interaction between heart and pump and eventually the ventricular function. Our group has reported an algorithm to derive ventricular contractility based on the maximum time derivative (dQ/dt(max) as a substitute for ventricular dP/dt(max) ) and pulsatility of measured flow signals. However, in RBPs used clinically, flow is estimated with a bandwidth too low to determine dQ/dt(max) in the case of improving heart function. The aim of this study was to develop a flow estimator for a centrifugal pump with bandwidth sufficient to provide noninvasive cardiac diagnostics. The new estimator is based on both static and dynamic properties of the brushless DC motor. An in vitro setup was employed to identify the performance of pump and motor up to 20 Hz. The algorithm was validated using physiological ventricular and arterial pressure waveforms in a mock loop which simulated different contractilities (dP/dt(max) 600 to 2300 mm Hg/s), pump speeds (2 to 4 krpm), and fluid viscosities (2 to 4 mPa·s). The mathematically estimated pump flow data were then compared to the datasets measured in the mock loop for different variable combinations (flow ranging from 2.5 to 7 L/min, pulsatility from 3.5 to 6 L/min, dQ/dt(max) from 15 to 60 L/min/s). Transfer function analysis showed that the developed algorithm could estimate the flow waveform with a bandwidth up to 15 Hz (±2 dB). The mean difference between the estimated and measured average flows was +0.06 ± 0.31 L/min and for the flow pulsatilities -0.27 ± 0.2 L/min. Detection of dQ/dt(max) was possible up to a dP/dt(max) level of 2300 mm Hg/s. In conclusion, a flow estimator with sufficient frequency bandwidth and accuracy to allow determination of changes in ventricular contractility even in the case of improving heart function was developed. © 2012, Copyright the Authors. Artificial Organs © 2012, International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

Automated Video-Based Analysis of Contractility and Calcium Flux in Human-Induced Pluripotent Stem Cell-Derived Cardiomyocytes Cultured over Different Spatial Scales.

PubMed

Huebsch, Nathaniel; Loskill, Peter; Mandegar, Mohammad A; Marks, Natalie C; Sheehan, Alice S; Ma, Zhen; Mathur, Anurag; Nguyen, Trieu N; Yoo, Jennie C; Judge, Luke M; Spencer, C Ian; Chukka, Anand C; Russell, Caitlin R; So, Po-Lin; Conklin, Bruce R; Healy, Kevin E

2015-05-01

Contractile motion is the simplest metric of cardiomyocyte health in vitro, but unbiased quantification is challenging. We describe a rapid automated method, requiring only standard video microscopy, to analyze the contractility of human-induced pluripotent stem cell-derived cardiomyocytes (iPS-CM). New algorithms for generating and filtering motion vectors combined with a newly developed isogenic iPSC line harboring genetically encoded calcium indicator, GCaMP6f, allow simultaneous user-independent measurement and analysis of the coupling between calcium flux and contractility. The relative performance of these algorithms, in terms of improving signal to noise, was tested. Applying these algorithms allowed analysis of contractility in iPS-CM cultured over multiple spatial scales from single cells to three-dimensional constructs. This open source software was validated with analysis of isoproterenol response in these cells, and can be applied in future studies comparing the drug responsiveness of iPS-CM cultured in different microenvironments in the context of tissue engineering.

Analysis of Tyrosine Kinase Inhibitor-Mediated Decline in Contractile Force in Rat Engineered Heart Tissue.

PubMed

Jacob, Fabian; Yonis, Amina Y; Cuello, Friederike; Luther, Pradeep; Schulze, Thomas; Eder, Alexandra; Streichert, Thomas; Mannhardt, Ingra; Hirt, Marc N; Schaaf, Sebastian; Stenzig, Justus; Force, Thomas; Eschenhagen, Thomas; Hansen, Arne

2016-01-01

Left ventricular dysfunction is a frequent and potentially severe side effect of many tyrosine kinase inhibitors (TKI). The mode of toxicity is not identified, but may include impairment of mitochondrial or sarcomeric function, autophagy or angiogenesis, either as an on-target or off-target mechanism. We studied concentration-response curves and time courses for nine TKIs in three-dimensional, force generating engineered heart tissue (EHT) from neonatal rat heart cells. We detected a concentration- and time-dependent decline in contractile force for gefitinib, lapatinib, sunitinib, imatinib, sorafenib, vandetanib and lestaurtinib and no decline in contractile force for erlotinib and dasatinib after 96 hours of incubation. The decline in contractile force was associated with an impairment of autophagy (LC3 Western blot) and appearance of autophagolysosomes (transmission electron microscopy). This study demonstrates the feasibility to study TKI-mediated force effects in EHTs and identifies an association between a decline in contractility and inhibition of autophagic flux.

Analysis of Tyrosine Kinase Inhibitor-Mediated Decline in Contractile Force in Rat Engineered Heart Tissue

PubMed Central

Cuello, Friederike; Luther, Pradeep; Schulze, Thomas; Eder, Alexandra; Streichert, Thomas; Mannhardt, Ingra; Hirt, Marc N.; Schaaf, Sebastian; Stenzig, Justus; Force, Thomas

2016-01-01

Introduction Left ventricular dysfunction is a frequent and potentially severe side effect of many tyrosine kinase inhibitors (TKI). The mode of toxicity is not identified, but may include impairment of mitochondrial or sarcomeric function, autophagy or angiogenesis, either as an on-target or off-target mechanism. Methods and Results We studied concentration-response curves and time courses for nine TKIs in three-dimensional, force generating engineered heart tissue (EHT) from neonatal rat heart cells. We detected a concentration- and time-dependent decline in contractile force for gefitinib, lapatinib, sunitinib, imatinib, sorafenib, vandetanib and lestaurtinib and no decline in contractile force for erlotinib and dasatinib after 96 hours of incubation. The decline in contractile force was associated with an impairment of autophagy (LC3 Western blot) and appearance of autophagolysosomes (transmission electron microscopy). Conclusion This study demonstrates the feasibility to study TKI-mediated force effects in EHTs and identifies an association between a decline in contractility and inhibition of autophagic flux. PMID:26840448

NADPH Oxidase 5 Is a Pro-Contractile Nox Isoform and a Point of Cross-Talk for Calcium and Redox Signaling-Implications in Vascular Function.

PubMed

Montezano, Augusto C; De Lucca Camargo, Livia; Persson, Patrik; Rios, Francisco J; Harvey, Adam P; Anagnostopoulou, Aikaterini; Palacios, Roberto; Gandara, Ana Caroline P; Alves-Lopes, Rheure; Neves, Karla B; Dulak-Lis, Maria; Holterman, Chet E; de Oliveira, Pedro Lagerblad; Graham, Delyth; Kennedy, Christopher; Touyz, Rhian M

2018-06-15

NADPH Oxidase 5 (Nox5) is a calcium-sensitive superoxide-generating Nox. It is present in lower forms and higher mammals, but not in rodents. Nox5 is expressed in vascular cells, but the functional significance remains elusive. Given that contraction is controlled by calcium and reactive oxygen species, both associated with Nox5, we questioned the role of Nox5 in pro-contractile signaling and vascular function. Transgenic mice expressing human Nox5 in a vascular smooth muscle cell-specific manner (Nox5 mice) and Rhodnius prolixus , an arthropod model that expresses Nox5 endogenoulsy, were studied. Reactive oxygen species generation was increased systemically and in the vasculature and heart in Nox5 mice. In Nox5-expressing mice, agonist-induced vasoconstriction was exaggerated and endothelium-dependent vasorelaxation was impaired. Vascular structural and mechanical properties were not influenced by Nox5. Vascular contractile responses in Nox5 mice were normalized by N -acetylcysteine and inhibitors of calcium channels, calmodulin, and endoplasmic reticulum ryanodine receptors, but not by GKT137831 (Nox1/4 inhibitor). At the cellular level, vascular changes in Nox5 mice were associated with increased vascular smooth muscle cell [Ca 2+ ] i , increased reactive oxygen species and nitrotyrosine levels, and hyperphosphorylation of pro-contractile signaling molecules MLC20 (myosin light chain 20) and MYPT1 (myosin phosphatase target subunit 1). Blood pressure was similar in wild-type and Nox5 mice. Nox5 did not amplify angiotensin II effects. In R. prolixus , gastrointestinal smooth muscle contraction was blunted by Nox5 silencing, but not by VAS2870 (Nox1/2/4 inhibitor). Nox5 is a pro-contractile Nox isoform important in redox-sensitive contraction. This involves calcium-calmodulin and endoplasmic reticulum-regulated mechanisms. Our findings define a novel function for vascular Nox5, linking calcium and reactive oxygen species to the pro-contractile molecular machinery in vascular smooth muscle cells. © 2018 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley.

Nitric oxide and CaMKII: Critical steps in the cardiac contractile response To IGF-1 and swim training.

PubMed

Burgos, Juan I; Yeves, Alejandra M; Barrena, Jorge P; Portiansky, Enrique L; Vila-Petroff, Martín G; Ennis, Irene L

2017-11-01

Cardiac adaptation to endurance training includes improved contractility by a non-yet clarified mechanism. Since IGF-1 is the main mediator of the physiological response to exercise, we explored its effect on cardiac contractility and the putative involvement of nitric oxide (NO) and CaMKII in control and swim-trained mice. IGF-1 increased cardiomyocyte shortening (128.1±4.6% vs. basal; p˂0.05) and accelerated relaxation (time to 50% relengthening: 49.2±2.0% vs. basal; p˂0.05), effects abrogated by inhibition of: AKT with MK-2206, NO production with the NO synthase (NOS) inhibitor L-NAME and the specific NOS1 inhibitor nitroguanidine (NG), and CaMKII with KN-93. In agreement, an increase in NO in response to IGF-1 (133.8±2.2%) was detected and prevented by both L-NAME and NG but not KN-93, suggesting that CaMKII activation was downstream NO. In addition, we determined CaMKII activity (P-CaMKII) and phosphorylation of its target, Thr17-PLN. IGF-1, by a NO-dependent mechanism, significantly increased both (227.2±29.4% and 145.3±5.4%, respectively) while no changes in the CaMKII phosphorylation site of ryanodine receptor were evident. The improvement in contractility induced by IGF-1 was associated with increased Ca 2+ transient amplitude, rate of decay and SR content. Interestingly, this response was absent in cardiomyocytes from transgenic mice that express a CaMKII inhibitory peptide (AC3-I strain). Moreover, AC3-I mice subjected to swim training did develop physiological cardiac hypertrophy but not the contractile adaptation. Therefore, we conclude that NO-dependent CaMKII activation plays a critical role in the improvement in contractility induced by IGF-1 and exercise training. Interestingly, this pathway would not contribute to the adaptive hypertrophy. Copyright © 2017 Elsevier Ltd. All rights reserved.

Specific inhibition of mitochondrial oxidative stress suppresses inflammation and improves cardiac function in a rat pneumonia-related sepsis model.

PubMed

Zang, Qun S; Sadek, Hesham; Maass, David L; Martinez, Bobbie; Ma, Lisha; Kilgore, Jessica A; Williams, Noelle S; Frantz, Doug E; Wigginton, Jane G; Nwariaku, Fiemu E; Wolf, Steven E; Minei, Joseph P

2012-05-01

Using a mitochondria-targeted vitamin E (Mito-Vit-E) in a rat pneumonia-related sepsis model, we examined the role of mitochondrial reactive oxygen species in sepsis-mediated myocardial inflammation and subsequent cardiac contractile dysfunction. Sepsis was produced in adult male Sprague-Dawley rats via intratracheal injection of S. pneumonia (4 × 10(6) colony formation units per rat). A single dose of Mito-Vit-E, vitamin E, or control vehicle, at 21.5 μmol/kg, was administered 30 min postinoculation. Blood was collected, and heart tissue was harvested at various time points. Mito-Vit-E in vivo distribution was confirmed by mass spectrometry. In cardiac mitochondria, Mito-Vit-E improved total antioxidant capacity and suppressed H(2)O(2) generation, whereas vitamin E offered little effect. In cytosol, both antioxidants decreased H(2)O(2) levels, but only vitamin E strengthened antioxidant capacity. Mito-Vit-E protected mitochondrial structure and function in the heart during sepsis, demonstrated by reduction in lipid and protein oxidation, preservation of mitochondrial membrane integrity, and recovery of respiratory function. While both Mito-Vit-E and vitamin E suppressed sepsis-induced peripheral and myocardial production of proinflammatory cytokines (tumor necrosis factor-α, interleukin-1β, and interleukin-6), Mito-Vit-E exhibited significantly higher efficacy (P < 0.05). Stronger anti-inflammatory action of Mito-Vit-E was further shown by its near-complete inhibition of sepsis-induced myeloperoxidase accumulation in myocardium, suggesting its effect on neutrophil infiltration. Echocardiography analysis indicated that Mito-Vit-E ameliorated cardiac contractility of sepsis animals, shown by improved fractional shortening and ejection fraction. Together, our data suggest that targeted scavenging of mitochondrial reactive oxygen species protects mitochondrial function, attenuates tissue-level inflammation, and improves whole organ activities in the heart during sepsis.

Effects of propranolol treatment on left ventricular function and intracellular calcium regulation in rats with postinfarction heart failure

PubMed Central

Litwin, Sheldon E; Katz, Sarah E; Morgan, James P; Douglas, Pamela S

1999-01-01

Chronic treatment with beta-adrenergic blocking agents can improve survival in patients with heart failure. The mechanisms underlying the beneficial effects and whether these effects are generalizable to ischaemic heart failure are unresolved.We performed echocardiographic-Doppler examinations in rats (n=28) 1 and 6 weeks after myocardial infarction (MI) or sham surgery. Rats were randomized to no treatment or propranolol (500 mg/l in drinking water) after the first echocardiogram. Isometric contractions and intracellular Ca transients were recorded simultaneously in noninfarcted left ventricular (LV) papillary muscles.Untreated MI rats had significant LV dilatation (10.6±0.4* vs 8.9±0.3 mm, MI vs control), impaired systolic function (fractional shortening=11±2* vs 38±2%), and a restrictive LV diastolic filling pattern. MI rats receiving propranolol had similar LV chamber sizes (10.6±0.5 mm) and systolic function (13±2%). The propranolol treated animals had higher LV end-diastolic pressures (27±2* vs 20±3 mmHg) and a more restricted LV diastolic filling pattern (increased ratio of early to late filling velocities and more rapid E wave deceleration rate). Contractility of papillary muscles from untreated MI rats was depressed (1.6±0.3 vs 2.4±0.5 g mm−2). In addition, Ca transients were prolonged and the inotropic response to isoproterenol was blunted. Propranolol treatment did not improve force development (1.6±0.3 g mm−2) or the duration of Ca transients during isoproterenol stimulation.Chronic propranolol treatment in rats with postinfarction heart failure did not improve LV remodeling or systolic function. LV diastolic pressures and filling patterns were worsened by propranolol. Treatment also did not produce appreciable improvement in contractility, intracellular Ca regulation or beta-adrenergic responsiveness in the noninfarcted myocardium. PMID:10455325

Soluble activin receptor type IIB decoy receptor differentially impacts murine osteogenesis imperfecta muscle function.

PubMed

Jeong, Youngjae; Daghlas, Salah A; Kahveci, Alp S; Salamango, Daniel; Gentry, Bettina A; Brown, Marybeth; Rector, R Scott; Pearsall, R Scott; Phillips, Charlotte L

2018-02-01

Osteogenesis imperfecta (OI) is characterized by skeletal fragility and muscle weakness. In this study we investigated the effects of soluble activin type IIB receptor (sActRIIB-mFc) on muscle mass and function in 2 distinct mouse models of OI: osteogenesis imperfecta murine (oim) and +/G610C. Wild-type (WT), +/G610C, and oim/oim mice were treated from 2 to 4 months of age with Tris-buffered saline (vehicle) or sActRIIB-mFc and their hindlimb muscles evaluated for mass, morphology, and contractile function. sActRIIB-mFc-treated WT, +/G610C, and oim/oim mice had increased hindlimb muscle weights and myofiber cross-sectional area compared with vehicle-treated counterparts. sActRIIB-mFc-treated oim/oim mice also exhibited increased contractile function relative to vehicle-treated counterparts. Blocking endogenous ActRIIB was effective at increasing muscle size in mouse models of OI, and increasing contractile function in oim/oim mice. ActRIIB inhibitors may provide a potential mutation-specific therapeutic option for compromised muscle function in OI. Muscle Nerve 57: 294-304, 2018. © 2017 Wiley Periodicals, Inc.

Contractile ring stability in S. pombe depends on F-BAR protein Cdc15p and Bgs1p transport from the Golgi complex.

PubMed

Arasada, Rajesh; Pollard, Thomas D

2014-09-11

Cdc15p is known to contribute to cytokinesis in fission yeast; however, the protein is not required to assemble the contractile ring of actin and myosin, but it helps to anchor the ring to the plasma membrane. Cdc15p has a lipid-binding F-BAR domain, suggesting that it provides a physical link between the plasma membrane and contractile ring proteins. However, we find that a more important function of Cdc15p during cytokinesis is to help deliver a transmembrane enzyme, Bgs1p (also called Cps1p), from the Golgi apparatus to the plasma membrane, where it appears to anchor the contractile ring. Bgs1p synthesizes the cell wall in the cleavage furrow, but its enzyme activity is not required to anchor the contractile ring. We estimate that ∼ 2,000 Bgs1p molecules are required to anchor the ring. Without Bgs1p anchors, contractile rings slide along the plasma membrane, a phenomenon that depends on an unconventional type II myosin called Myp2p. Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.

Active inhibitor-1 maintains protein hyper-phosphorylation in aging hearts and halts remodeling in failing hearts.

PubMed

Pritchard, Tracy J; Kawase, Yoshiaki; Haghighi, Kobra; Anjak, Ahmad; Cai, Wenfeng; Jiang, Min; Nicolaou, Persoulla; Pylar, George; Karakikes, Ioannis; Rapti, Kleopatra; Rubinstein, Jack; Hajjar, Roger J; Kranias, Evangelia G

2013-01-01

Impaired sarcoplasmic reticulum calcium cycling and depressed contractility are key characteristics in heart failure. Defects in sarcoplasmic reticulum function are characterized by decreased SERCA2a Ca-transport that is partially attributable to dephosphorylation of its regulator phospholamban by increased protein phosphatase 1 activity. Inhibition of protein phosphatase 1 through activation of its endogenous inhibitor-1 has been shown to enhance cardiac Ca-handling and contractility as well as protect from pathological stress remodeling in young mice. In this study, we assessed the long-term effects of inducible expression of constitutively active inhibitor-1 in the adult heart and followed function and remodeling through the aging process, up to 20 months. Mice with inhibitor-1 had normal survival and similar function to WTs. There was no overt remodeling as evidenced by measures of left ventricular end-systolic and diastolic diameters and posterior wall dimensions, heart weight to tibia length ratio, and histology. Higher phosphorylation of phospholamban at both Ser16 and Thr17 was maintained in aged hearts with active inhibitor-1, potentially offsetting the effects of elevated Ser2815-phosphorylation in ryanodine receptor, as there were no increases in arrhythmias under stress conditions in 20-month old mice. Furthermore, long-term expression of active inhibitor-1 via recombinant adeno-associated virus type 9 gene transfer in rats with pressure-overload induced heart failure improved function and prevented remodeling, associated with increased phosphorylation of phospholamban at Ser16 and Thr17. Thus, chronic inhibition of protein phosphatase 1, through increases in active inhibitor-1, does not accelerate age-related cardiomyopathy and gene transfer of this molecule in vivo improves function and halts remodeling in the long term.

Impaired Vascular Contractility and Aortic Wall Degeneration in Fibulin-4 Deficient Mice: Effect of Angiotensin II Type 1 (AT1) Receptor Blockade

PubMed Central

Moltzer, Els; te Riet, Luuk; Swagemakers, Sigrid M. A.; van Heijningen, Paula M.; Vermeij, Marcel; van Veghel, Richard; Bouhuizen, Angelique M.; van Esch, Joep H. M.; Lankhorst, Stephanie; Ramnath, Natasja W. M.; de Waard, Monique C.; Duncker, Dirk J.; van der Spek, Peter J.; Rouwet, Ellen V.; Danser, A. H. Jan; Essers, Jeroen

2011-01-01

Medial degeneration is a key feature of aneurysm disease and aortic dissection. In a murine aneurysm model we investigated the structural and functional characteristics of aortic wall degeneration in adult fibulin-4 deficient mice and the potential therapeutic role of the angiotensin (Ang) II type 1 (AT1) receptor antagonist losartan in preventing aortic media degeneration. Adult mice with 2-fold (heterozygous Fibulin-4+/R) and 4-fold (homozygous Fibulin-4R/R) reduced expression of fibulin-4 displayed the histological features of cystic media degeneration as found in patients with aneurysm or dissection, including elastin fiber fragmentation, loss of smooth muscle cells, and deposition of ground substance in the extracellular matrix of the aortic media. The aortic contractile capacity, determined by isometric force measurements, was diminished, and was associated with dysregulation of contractile genes as shown by aortic transcriptome analysis. These structural and functional alterations were accompanied by upregulation of TGF-β signaling in aortas from fibulin-4 deficient mice, as identified by genome-scaled network analysis as well as by immunohistochemical staining for phosphorylated Smad2, an intracellular mediator of TGF-β. Tissue levels of Ang II, a regulator of TGF-β signaling, were increased. Prenatal treatment with the AT1 receptor antagonist losartan, which blunts TGF-β signaling, prevented elastic fiber fragmentation in the aortic media of newborn Fibulin-4R/R mice. Postnatal losartan treatment reduced haemodynamic stress and improved lifespan of homozygous knockdown fibulin-4 animals, but did not affect aortic vessel wall structure. In conclusion, the AT1 receptor blocker losartan can prevent aortic media degeneration in a non-Marfan syndrome aneurysm mouse model. In established aortic aneurysms, losartan does not affect aortic architecture, but does improve survival. These findings may extend the potential therapeutic application of inhibitors of the renin-angiotensin system to the preventive treatment of aneurysm disease. PMID:21858106

Triiodothyronine Activates Lactate Oxidation Without Impairing Fatty Acid Oxidation and Improves Weaning From Extracorporeal Membrane Oxygenation

PubMed Central

Kajimoto, Masaki; Ledee, Dolena R.; Xu, Chun; Kajimoto, Hidemi; Isern, Nancy G.; Portman, Michael A.

2017-01-01

Background Extracorporeal membrane oxygenation (ECMO) provides a rescue for children with severe cardiac failure. It has previously been shown that triiodothyronine (T3) improves cardiac function by modulating pyruvate oxidation during weaning. This study focused on fatty acid (FA) metabolism modulated by T3 for weaning from ECMO after cardiac injury. Methods and Results Nineteen immature piglets (9.1–15.3 kg) were separated into 3 groups with ECMO (6.5 h) and wean: normal circulation (Group-C); transient coronary occlusion (10 min) for ischemia-reperfusion (IR) followed by ECMO (Group-IR); and IR with T3 supplementation (Group-IR-T3). 13-Carbon (13C)-labeled lactate, medium-chain and long-chain FAs, was infused as oxidative substrates. Substrate fractional contribution (FC) to the citric acid cycle was analyzed by 13C-nuclear magnetic resonance. ECMO depressed circulating T3 levels to 40% of the baseline at 4 h and were restored in Group-IR-T3. Group-IR decreased cardiac power, which was not fully restorable and 2 pigs were lost because of weaning failure. Group-IR also depressed FC-lactate, while the excellent contractile function and energy efficiency in Group-IR-T3 occurred along with a marked FC-lactate increase and [adenosine triphosphate]/[adenosine diphosphate] without either decreasing FC-FAs or elevating myocardial oxygen consumption over Group-C or -IR. Conclusions T3 releases inhibition of lactate oxidation following IR injury without impairing FA oxidation. These findings indicate that T3 depression during ECMO is maladaptive, and that restoring levels improves metabolic flux and enhances contractile function during weaning. PMID:25421230

Single-Cell Functional Analysis of Stem-Cell Derived Cardiomyocytes on Micropatterned Flexible Substrates.

PubMed

Kijlstra, Jan David; Hu, Dongjian; van der Meer, Peter; Domian, Ibrahim J

2017-11-15

Human pluripotent stem-cell derived cardiomyocytes (hPSC-CMs) hold great promise for applications in human disease modeling, drug discovery, cardiotoxicity screening, and, ultimately, regenerative medicine. The ability to study multiple parameters of hPSC-CM function, such as contractile and electrical activity, calcium cycling, and force generation, is therefore of paramount importance. hPSC-CMs cultured on stiff substrates like glass or polystyrene do not have the ability to shorten during contraction, making them less suitable for the study of hPSC-CM contractile function. Other approaches require highly specialized hardware and are difficult to reproduce. Here we describe a protocol for the preparation of hPSC-CMs on soft substrates that enable shortening, and subsequently the simultaneous quantitative analysis of their contractile and electrical activity, calcium cycling, and force generation at single-cell resolution. This protocol requires only affordable and readily available materials and works with standard imaging hardware. © 2017 by John Wiley & Sons, Inc. Copyright © 2017 John Wiley & Sons, Inc.

VITRECTOMY FOR INTERMEDIATE AGE-RELATED MACULAR DEGENERATION ASSOCIATED WITH TANGENTIAL VITREOMACULAR TRACTION: A CLINICOPATHOLOGIC CORRELATION.

PubMed

Ziada, Jean; Hagenau, Felix; Compera, Denise; Wolf, Armin; Scheler, Renate; Schaumberger, Markus M; Priglinger, Siegfried G; Schumann, Ricarda G

2018-03-01

To describe the morphologic characteristics of the vitreomacular interface in intermediate age-related macular degeneration associated with tangential traction due to premacular membrane formation and to correlate with optical coherence tomography (OCT) findings and clinical data. Premacular membrane specimens were removed sequentially with the internal limiting membrane from 27 eyes of 26 patients with intermediate age-related macular degeneration during standard vitrectomy. Specimens were processed for immunocytochemical staining of epiretinal cells and extracellular matrix components. Ultrastructural analysis was performed using transmission electron microscopy. Spectral domain optical coherence tomography images and patient charts were evaluated in retrospect. Immunocytochemistry revealed hyalocytes and myofibroblasts as predominant cell types. Ultrastructural analysis demonstrated evidence of vitreoschisis in all eyes. Myofibroblasts with contractile properties were observed to span between folds of the internal limiting membrane and vitreous cortex collagen. Retinal pigment epithelial cells or inflammatory cells were not detected. Mean visual acuity (Snellen) showed significant improvement from 20/72 ± 20/36 to 20/41 ± 20/32 (P < 0.001) after a mean follow-up period of 19 months (median, 17 months). During this period, none of the eyes required anti-vascular endothelial growth factor therapy. Fibrocellular premacular proliferation in intermediate age-related macular degeneration predominantly consists of vitreous collagen, hyalocytes, and myofibroblasts with contractile properties. Vitreoschisis and vitreous-derived cells appear to play an important role in traction formation of this subgroup of eyes. In patients with intermediate age-related macular degeneration and contractile premacular membrane, release of traction by vitrectomy with internal limiting membrane peeling results in significantly functional and anatomical improvement.

Activation of Akt rescues endoplasmic reticulum stress-impaired murine cardiac contractile function via glycogen synthase kinase-3β-mediated suppression of mitochondrial permeation pore opening.

PubMed

Zhang, Yingmei; Xia, Zhi; La Cour, Karissa H; Ren, Jun

2011-11-01

The present study was designed to examine the impact of chronic Akt activation on endoplasmic reticulum (ER) stress-induced cardiac mechanical anomalies, if any, and the underlying mechanism involved. Wild-type and transgenic mice with cardiac-specific overexpression of the active mutant of Akt (Myr-Akt) were subjected to the ER stress inducer tunicamycin (1 or 3 mg/kg). ER stress led to compromised echocardiographic (elevated left ventricular end-systolic diameter and reduced fractional shortening) and cardiomyocyte contractile function, intracellular Ca(2+) mishandling, and cell survival in wild-type mice associated with mitochondrial damage. In vitro ER stress induction in murine cardiomyocytes upregulated the ER stress proteins Gadd153, GRP78, and phospho-eIF2α, and promoted reactive oxygen species production, carbonyl formation, apoptosis, mitochondrial membrane potential loss, and mitochondrial permeation pore (mPTP) opening associated with overtly impaired cardiomyocyte contractile and intracellular Ca(2+) properties. Interestingly, these anomalies were mitigated by chronic Akt activation or the ER chaperon tauroursodeoxycholic acid (TUDCA). Treatment with tunicamycin also dephosphorylated Akt and its downstream signal glycogen synthase kinase 3β (GSK3β) (leading to activation of GSK3β), the effect of which was abrogated by Akt activation and TUDCA. The ER stress-induced cardiomyocyte contractile and mitochondrial anomalies were obliterated by the mPTP inhibitor cyclosporin A, GSK3β inhibitor SB216763, and ER stress inhibitor TUDCA. This research reported the direct relationship between ER stress and cardiomyocyte contractile and mitochondrial anomalies for the first time. Taken together, these data suggest that ER stress may compromise cardiac contractile and intracellular Ca(2+) properties, possibly through the Akt/GSK3β-dependent impairment of mitochondrial integrity.

T-tubule disease: Relationship between t-tubule organization and regional contractile performance in human dilated cardiomyopathy.

PubMed

Crossman, David J; Young, Alistair A; Ruygrok, Peter N; Nason, Guy P; Baddelely, David; Soeller, Christian; Cannell, Mark B

2015-07-01

Evidence from animal models suggest that t-tubule changes may play an important role in the contractile deficit associated with heart failure. However samples are usually taken at random with no regard as to regional variability present in failing hearts which leads to uncertainty in the relationship between contractile performance and possible t-tubule derangement. Regional contraction in human hearts was measured by tagged cine MRI and model fitting. At transplant, failing hearts were biopsy sampled in identified regions and immunocytochemistry was used to label t-tubules and sarcomeric z-lines. Computer image analysis was used to assess 5 different unbiased measures of t-tubule structure/organization. In regions of failing hearts that showed good contractile performance, t-tubule organization was similar to that seen in normal hearts, with worsening structure correlating with the loss of regional contractile performance. Statistical analysis showed that t-tubule direction was most highly correlated with local contractile performance, followed by the amplitude of the sarcomeric peak in the Fourier transform of the t-tubule image. Other area based measures were less well correlated. We conclude that regional contractile performance in failing human hearts is strongly correlated with the local t-tubule organization. Cluster tree analysis with a functional definition of failing contraction strength allowed a pathological definition of 't-tubule disease'. The regional variability in contractile performance and cellular structure is a confounding issue for analysis of samples taken from failing human hearts, although this may be overcome with regional analysis by using tagged cMRI and biopsy mapping. Copyright © 2015 Elsevier Ltd. All rights reserved.

Pressure-volume analysis reveals characteristic sex-related differences in cardiac function in a rat model of aortic banding-induced myocardial hypertrophy.

PubMed

Ruppert, Mihály; Korkmaz-Icöz, Sevil; Loganathan, Sivakkanan; Jiang, Weipeng; Lehmann, Lorenz H; Oláh, Attila; Sayour, Alex Ali; Barta, Bálint András; Merkely, Béla; Karck, Matthias; Radovits, Tamás; Szabó, Gábor

2018-05-25

Sex differences in pressure overload (PO)-induced left ventricular (LV) myocardial hypertrophy (LVH) have been intensely investigated. Nevertheless, sex-related disparities of LV hemodynamics in LVH were not examined in detail. Therefore, we aimed to provide a detailed characterization of distinct aspects of LV function in male and female rats during different stages of LVH. Banding of the abdominal aorta (AB) was performed to induce PO for 6 or 12 weeks in male and female rats. Control animals underwent sham operation. The development of LVH was followed by serial echocardiography. Cardiac function was assessed by pressure-volume analysis. Cardiomyocyte hypertrophy and fibrosis were evaluated by histology. At week 6, increased LV mass index, heart weight-to-tibial length, cardiomyocyte diameter, concentric LV geometry and moderate interstitial fibrosis were detected in both male and female AB rats, indicating the development of an early stage of LVH. Functionally, at this time point, impaired active relaxation, increased contractility and preserved ventricular-arterial coupling were observed in the AB groups in both genders. In contrast, at week 12, progressive deterioration of LVH-associated structural and functional alterations occurred in male but not in female animals with sustained PO. Accordingly, at this later stage, LVH was associated with eccentric remodeling, exacerbated fibrosis and increased chamber stiffness in male AB rats. Furthermore, augmented contractility declined in male and not in female AB animals, resulting in contractility-afterload mismatch. Maintained contractility augmentation, preserved ventricular-arterial coupling and better myocardial compliance in female rats contribute to sex differences in LV function during the progression of PO-induced LVH.

Molecular Regulation of Parturition: A Myometrial Perspective

PubMed Central

Renthal, Nora E.; Williams, Koriand’r C.; Montalbano, Alina P.; Chen, Chien-Cheng; Gao, Lu; Mendelson, Carole R.

2015-01-01

The molecular mechanisms that maintain quiescence of the myometrium throughout most of pregnancy and promote its transformation to a highly coordinated contractile unit culminating in labor are complex and intertwined. During pregnancy, progesterone (P4) produced by the placenta and/or ovary serves a dominant role in maintaining myometrial quiescence by blocking proinflammatory response pathways and expression of so-called “contractile” genes. In the majority of placental mammals, increased uterine contractility near term is heralded by an increase in circulating estradiol-17β (E2) and/or increased estrogen receptor α (ERα) activity and a sharp decline in circulating P4 levels. However, in women, circulating levels of P4 and progesterone receptors (PR) in myometrium remain elevated throughout pregnancy and into labor. This has led to the concept that increased uterine contractility leading to term and preterm labor is mediated, in part, by a decline in PR function. The biochemical mechanisms for this decrease in PR function are also multifaceted and interwoven. In this paper, we focus on the molecular mechanisms that mediate myometrial quiescence and contractility and their regulation by the two central hormones of pregnancy, P4 and estradiol-17β. The integrative roles of microRNAs also are considered. PMID:26337112

Probing the contractile vacuole as Achilles' heel of the biotrophic grapevine pathogen Plasmopara viticola.

PubMed

Tröster, Viktoria; Setzer, Tabea; Hirth, Thomas; Pecina, Anna; Kortekamp, Andreas; Nick, Peter

2017-09-01

The causative agent of Grapevine Downy Mildew, the oomycete Plasmopara viticola, poses a serious threat to viticulture. In the current work, the contractile vacuole of the zoospore is analysed as potential target for novel plant protection strategies. Using a combination of electron microscopy, spinning disc confocal microscopy, and video differential interference contrast microscopy, we have followed the genesis and dynamics of this vacuole required during the search for the stomata, when the non-walled zoospore is exposed to hypotonic conditions. This subcellular description was combined with a pharmacological study, where the functionality of the contractile vacuole was blocked by manipulation of actin, by Na, Cu, and Al ions or by inhibition of the NADPH oxidase. We further observe that RGD peptides (mimicking binding sites for integrins at the extracellular matrix) can inhibit the function of the contractile vacuole as well. Finally, we show that an extract from Chinese liquorice (Glycyrrhiza uralensis) proposed as biocontrol for Downy Mildews can efficiently induce zoospore burst and that this activity depends on the activity of NADPH oxidase. The effect of the extract can be phenocopied by its major compound, glycyrrhizin, suggesting a mode of action for this biologically safe alternative to copper products.

Moderate ethanol administration accentuates cardiomyocyte contractile dysfunction and mitochondrial injury in high fat diet-induced obesity.

PubMed

Yuan, Fang; Lei, Yonghong; Wang, Qiurong; Esberg, Lucy B; Huang, Zaixing; Scott, Glenda I; Li, Xue; Ren, Jun

2015-03-18

Light to moderate drinking confers cardioprotection although it remains unclear with regards to the role of moderate drinking on cardiac function in obesity. This study was designed to examine the impact of moderate ethanol intake on myocardial function in high fat diet intake-induced obesity and the mechanism(s) involved with a focus on mitochondrial integrity. C57BL/6 mice were fed low or high fat diet for 16 weeks prior to ethanol challenge (1g/kg/d for 3 days). Cardiac contractile function, intracellular Ca(2+) homeostasis, myocardial histology, and mitochondrial integrity [aconitase activity and the mitochondrial proteins SOD1, UCP-2 and PPARγ coactivator 1α (PGC-1α)] were assessed 24h after the final ethanol challenge. Fat diet intake compromised cardiomyocyte contractile and intracellular Ca(2+) properties (depressed peak shortening and maximal velocities of shortening/relengthening, prolonged duration of relengthening, dampened intracellular Ca(2+) rise and clearance without affecting duration of shortening). Although moderate ethanol challenge failed to alter cardiomyocyte mechanical property under low fat diet intake, it accentuated high fat diet intake-induced changes in cardiomyocyte contractile function and intracellular Ca(2+) handling. Moderate ethanol challenge failed to affect fat diet intake-induced cardiac hypertrophy as evidenced by H&E staining. High fat diet intake reduced myocardial aconitase activity, downregulated levels of mitochondrial protein UCP-2, PGC-1α, SOD1 and interrupted intracellular Ca(2+) regulatory proteins, the effect of which was augmented by moderate ethanol challenge. Neither high fat diet intake nor moderate ethanol challenge affected protein or mRNA levels as well as phosphorylation of Akt and GSK3β in mouse hearts. Taken together, our data revealed that moderate ethanol challenge accentuated high fat diet-induced cardiac contractile and intracellular Ca(2+) anomalies as well as mitochondrial injury. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

[Heart functions in monkeys during a 2-week antiorthostatic hypokinesia

NASA Technical Reports Server (NTRS)

Krotov, V. P.; Convertino, V.; Korol'kov, V. I.; Latham, R.; Trambovetskii, E. V.; Fanton, J.; Crisman, R.; Truzhennikov, A. N.; Evert, D.; Nosovskii, A. M.;

Automated Video-Based Analysis of Contractility and Calcium Flux in Human-Induced Pluripotent Stem Cell-Derived Cardiomyocytes Cultured over Different Spatial Scales

PubMed Central

Huebsch, Nathaniel; Loskill, Peter; Mandegar, Mohammad A.; Marks, Natalie C.; Sheehan, Alice S.; Ma, Zhen; Mathur, Anurag; Nguyen, Trieu N.; Yoo, Jennie C.; Judge, Luke M.; Spencer, C. Ian; Chukka, Anand C.; Russell, Caitlin R.; So, Po-Lin

2015-01-01

Contractile motion is the simplest metric of cardiomyocyte health in vitro, but unbiased quantification is challenging. We describe a rapid automated method, requiring only standard video microscopy, to analyze the contractility of human-induced pluripotent stem cell-derived cardiomyocytes (iPS-CM). New algorithms for generating and filtering motion vectors combined with a newly developed isogenic iPSC line harboring genetically encoded calcium indicator, GCaMP6f, allow simultaneous user-independent measurement and analysis of the coupling between calcium flux and contractility. The relative performance of these algorithms, in terms of improving signal to noise, was tested. Applying these algorithms allowed analysis of contractility in iPS-CM cultured over multiple spatial scales from single cells to three-dimensional constructs. This open source software was validated with analysis of isoproterenol response in these cells, and can be applied in future studies comparing the drug responsiveness of iPS-CM cultured in different microenvironments in the context of tissue engineering. PMID:25333967

Multiparity modifies contractile properties of pelvic muscles affecting the genesis of vaginal pressure in rabbits.

PubMed

López-Juárez, Rhode; Zempoalteca, René; Corona-Quintanilla, Dora Luz; Jiménez-Estrada, Ismael; Castelán, Francisco; Martínez-Gómez, Margarita

2018-01-01

To characterize the contractile properties of the bulbospongiosus (Bsm), isquiocavernosus (Ism), and pubococcygeus muscles (Pcm), and their involvement in the genesis of vaginal pressure in nulliparous and multiparous rabbits. Age-matched nulliparous and multiparous rabbits were used to record the isometric contractile responses of each muscle as well as the intravaginal pressure evoked by single square electrical pulses and stimulation trains of ascending frequency. To establish significant differences between groups, two-tail unpaired Student t tests were carried out. The linear correlation between intravaginal pressure and muscle contractile force was analyzed with Pearson correlation tests. For all cases, a P ≤ 0.05 was set as statistically significant. Multiparity decreased the contractile force of Bsm and Ism generated by high-frequency stimulation trains. The normalized force of the Pcm increased when evoked at 1, 4, and 10 Hz while this decreased at higher frequencies (20, 50, and 100 Hz). The contraction of both Bsm and Ism raised particularly the pressure on the perineal vagina while that of the Pcm increased the pressure in the pelvic vagina. Such a functional segregation is still present in multiparous rabbits albeit it was modified. Multiparity induces changes in the contractile responses of Bsm, Ism, and Pcm, which alterates the vaginal pressure. © 2017 Wiley Periodicals, Inc.

Slack length reduces the contractile phenotype of the Swine carotid artery.

PubMed

Rembold, Christopher M; Garvey, Sean M; Tejani, Ankit D

2013-01-01

Contraction is the primary function of adult arterial smooth muscle. However, in response to vessel injury or inflammation, arterial smooth muscle is able to phenotypically modulate from the contractile state to several 'synthetic' states characterized by proliferation, migration and/or increased cytokine secretion. We examined the effect of tissue length (L) on the phenotype of intact, isometrically held, initially contractile swine carotid artery tissues. Tissues were studied (1) without prolonged incubation at the optimal length for force generation (1.0 Lo, control), (2) with prolonged incubation for 17 h at 1.0 Lo, or (3) with prolonged incubation at slack length (0.6 Lo) for 16 h and then restoration to 1.0 Lo for 1 h. Prolonged incubation at 1.0 Lo minimally reduced the contractile force without substantially altering the mediators of contraction (crossbridge phosphorylation, shortening velocity or stimulated actin polymerization). Prolonged incubation of tissues at slack length (0.6 Lo), despite return of length to 1.0 Lo, substantially reduced contractile force, reduced crossbridge phosphorylation, nearly abolished crossbridge cycling (shortening velocity) and abolished stimulated actin polymerization. These data suggest that (1) slack length treatment significantly alters the contractile phenotype of arterial tissue, and (2) slack length treatment is a model to study acute phenotypic modulation of intact arterial smooth muscle. Copyright © 2013 S. Karger AG, Basel.

Macrophage migration inhibitory factor plays a permissive role in the maintenance of cardiac contractile function under starvation through regulation of autophagy.

PubMed

Xu, Xihui; Pacheco, Benjamin D; Leng, Lin; Bucala, Richard; Ren, Jun

2013-08-01

The cytokine macrophage migration inhibitory factor (MIF) protects the heart through AMPK activation. Autophagy, a conserved pathway for bulk degradation of intracellular proteins and organelles, helps preserve and recycle energy and nutrients for cells to survive under starvation. This study was designed to examine the role of MIF in cardiac homeostasis and autophagy regulation following an acute starvation challenge. Wild-type (WT) and MIF knockout mice were starved for 48 h. Echocardiographic data revealed little effect of starvation on cardiac geometry, contractile and intracellular Ca²⁺ properties. MIF deficiency unmasked an increase in left ventricular end-systolic diameter, a drop in fractional shortening associated with cardiomyocyte contractile and intracellular Ca²⁺ anomalies following starvation. Interestingly, the unfavourable effect of MIF deficiency was associated with interruption of starvation-induced autophagy. Furthermore, restoration of autophagy using rapamycin partially protected against starvation-induced cardiomyocyte contractile defects. In our in vitro model of starvation, neonatal mouse cardiomyocytes from WT and MIF-/- mice and H9C2 cells were treated with serum free-glucose free DMEM for 2 h. MIF depletion dramatically attenuated starvation-induced autophagic vacuole formation in neonatal mouse cardiomyocytes and exacerbated starvation-induced cell death in H9C2 cells. In summary, these results indicate that MIF plays a permissive role in the maintenance of cardiac contractile function under starvation by regulation of autophagy.

Smooth muscle-protein translocation and tissue function.

PubMed

Eddinger, Thomas J

2014-09-01

Smooth muscle (SM) tissue is a complex organization of multiple cell types and is regulated by numerous signaling molecules (neurotransmitters, hormones, cytokines, etc.). SM contractile function can be regulated via expression and distribution of the contractile and cytoskeletal proteins, and activation of any of the second messenger pathways that regulate them. Spatial-temporal changes in the contractile, cytoskeletal or regulatory components of SM cells (SMCs) have been proposed to alter SM contractile activity. Ca(2+) sensitization/desensitization can occur as a result of changes at any of these levels, and specific pathways have been identified at all of these levels. Understanding when and how proteins can translocate within the cytoplasm, or to-and-from the plasmalemma and the cytoplasm to alter contractile activity is critical. Numerous studies have reported translocation of proteins associated with the adherens junction and G protein-coupled receptor activation pathways in isolated SMC systems. Specific examples of translocation of vinculin to and from the adherens junction and protein kinase C (PKC) and 17 kDa PKC-potentiated inhibitor of myosin light chain phosphatase (CPI-17) to and from the plasmalemma in isolated SMC systems but not in intact SM tissues are discussed. Using both isolated SMC systems and SM tissues in parallel to pursue these studies will advance our understanding of both the role and mechanism of these pathways as well as their possible significance for Ca(2+) sensitization in intact SM tissues and organ systems. © 2014 Wiley Periodicals, Inc.

Effects of Hypertension and Exercise on Cardiac Proteome Remodelling

PubMed Central

Petriz, Bernardo A.; Franco, Octavio L.

2014-01-01

Left ventricle hypertrophy is a common outcome of pressure overload stimulus closely associated with hypertension. This process is triggered by adverse molecular signalling, gene expression, and proteome alteration. Proteomic research has revealed that several molecular targets are associated with pathologic cardiac hypertrophy, including angiotensin II, endothelin-1 and isoproterenol. Several metabolic, contractile, and stress-related proteins are shown to be altered in cardiac hypertrophy derived by hypertension. On the other hand, exercise is a nonpharmacologic agent used for hypertension treatment, where cardiac hypertrophy induced by exercise training is characterized by improvement in cardiac function and resistance against ischemic insult. Despite the scarcity of proteomic research performed with exercise, healthy and pathologic heart proteomes are shown to be modulated in a completely different way. Hence, the altered proteome induced by exercise is mostly associated with cardioprotective aspects such as contractile and metabolic improvement and physiologic cardiac hypertrophy. The present review, therefore, describes relevant studies involving the molecular characteristics and alterations from hypertensive-induced and exercise-induced hypertrophy, as well as the main proteomic research performed in this field. Furthermore, proteomic research into the effect of hypertension on other target-demerged organs is examined. PMID:24877123

Passive hind-limb cycling improves cardiac function and reduces cardiovascular disease risk in experimental spinal cord injury.

PubMed

West, Christopher R; Crawford, Mark A; Poormasjedi-Meibod, Malihe-Sadat; Currie, Katharine D; Fallavollita, Andre; Yuen, Violet; McNeill, John H; Krassioukov, Andrei V

2014-04-15

Spinal cord injury (SCI) causes altered autonomic control and severe physical deconditioning that converge to drive maladaptive cardiac remodelling. We used a clinically relevant experimental model to investigate the cardio-metabolic responses to SCI and to establish whether passive hind-limb cycling elicits a cardio-protective effect. Initially, 21 male Wistar rats were evenly assigned to three groups: uninjured control (CON), T3 complete SCI (SCI) or T3 complete SCI plus passive hind-limb cycling (SCI-EX; 2 × 30 min day(-1), 5 days week(-1) for 4 weeks beginning 6 days post-SCI). On day 32, cardio-metabolic function was assessed using in vivo echocardiography, ex vivo working heart assessments, cardiac histology/molecular biology and blood lipid profiles. Twelve additional rats (n = 6 SCI and n = 6 SCI-EX) underwent in vivo echocardiography and basal haemodynamic assessments pre-SCI and at days 7, 14 and 32 post-SCI to track temporal cardiovascular changes. Compared with CON, SCI exhibited a rapid and sustained reduction in left ventricular dimensions and function that ultimately manifested as reduced contractility, increased myocardial collagen deposition and an up-regulation of transforming growth factor beta-1 (TGFβ1) and mothers against decapentaplegic homolog 3 (Smad3) mRNA. For SCI-EX, the initial reduction in left ventricular dimensions and function at day 7 post-SCI was completely reversed by day 32 post-SCI, and there were no differences in myocardial contractility between SCI-EX and CON. Collagen deposition was similar between SCI-EX and CON. TGFβ1 and Smad3 were down-regulated in SCI-EX. Blood lipid profiles were improved in SCI-EX versus SCI. We provide compelling novel evidence that passive hind-limb cycling prevents cardiac dysfunction and reduces cardiovascular disease risk in experimental SCI.

Aging and CaMKII alter intracellular Ca2+ transients and heart rhythm in Drosophila melanogaster.

PubMed

Santalla, Manuela; Valverde, Carlos A; Harnichar, Ezequiel; Lacunza, Ezequiel; Aguilar-Fuentes, Javier; Mattiazzi, Alicia; Ferrero, Paola

2014-01-01

Aging is associated to disrupted contractility and rhythmicity, among other cardiovascular alterations. Drosophila melanogaster shows a pattern of aging similar to human beings and recapitulates the arrhythmogenic conditions found in the human heart. Moreover, the kinase CaMKII has been characterized as an important regulator of heart function and an arrhythmogenic molecule that participate in Ca2+ handling. Using a genetically engineered expressed Ca2+ indicator, we report changes in cardiac Ca2+ handling at two different ages. Aging prolonged relaxation, reduced spontaneous heart rate (HR) and increased the occurrence of arrhythmias, ectopic beats and asystoles. Alignment between Drosophila melanogaster and human CaMKII showed a high degree of conservation and indicates that relevant phosphorylation sites in humans are also present in the fruit fly. Inhibition of CaMKII by KN-93 (CaMKII-specific inhibitor), reduced HR without significant changes in other parameters. By contrast, overexpression of CaMKII increased HR and reduced arrhythmias. Moreover, it increased fluorescence amplitude, maximal rate of rise of fluorescence and reduced time to peak fluorescence. These results suggest that CaMKII in Drosophila melanogaster acts directly on heart function and that increasing CaMKII expression levels could be beneficial to improve contractility.

Aim44p regulates phosphorylation of Hof1p to promote contractile ring closure during cytokinesis in budding yeast

PubMed Central

Wolken, Dana M. Alessi; McInnes, Joseph; Pon, Liza A.

2014-01-01

Whereas actomyosin and septin ring organization and function in cytokinesis are thoroughly described, little is known regarding the mechanisms by which the actomyosin ring interacts with septins and associated proteins to coordinate cell division. Here we show that the protein product of YPL158C, Aim44p, undergoes septin-dependent recruitment to the site of cell division. Aim44p colocalizes with Myo1p, the type II myosin of the contractile ring, throughout most of the cell cycle. The Aim44p ring does not contract when the actomyosin ring closes. Instead, it forms a double ring that associates with septin rings on mother and daughter cells after cell separation. Deletion of AIM44 results in defects in contractile ring closure. Aim44p coimmunoprecipitates with Hof1p, a conserved F-BAR protein that binds both septins and type II myosins and promotes contractile ring closure. Deletion of AIM44 results in a delay in Hof1p phosphorylation and altered Hof1p localization. Finally, overexpression of Dbf2p, a kinase that phosphorylates Hof1p and is required for relocalization of Hof1p from septin rings to the contractile ring and for Hof1p-triggered contractile ring closure, rescues the cytokinesis defect observed in aim44∆ cells. Our studies reveal a novel role for Aim44p in regulating contractile ring closure through effects on Hof1p. PMID:24451263

Quantifying esophagogastric junction contractility with a novel HRM topographic metric, the EGJ-Contractile Integral: normative values and preliminary evaluation in PPI non-responders.

PubMed

Nicodème, F; Pipa-Muniz, M; Khanna, K; Kahrilas, P J; Pandolfino, J E

2014-03-01

Despite its obvious pathophysiological relevance, the clinical utility of measures of esophagogastric junction (EGJ) contractility is unsubstantiated. High-resolution manometry (HRM) may improve upon this with its inherent ability to integrate the magnitude of contractility over time and length of the EGJ. This study aimed to develop a novel HRM metric summarizing EGJ contractility and test its ability distinguish among subgroups of proton pump inhibitor non-responders (PPI-NRs). 75 normal controls and 88 PPI-NRs were studied. All underwent HRM. PPI-NRs underwent pH-impedance monitoring on PPI therapy scored in terms of acid exposure, number of reflux events, and reflux-symptom correlation and grouped as meeting all criteria, some criteria, or no criteria of abnormality. Control HRM studies were used to establish normal values for candidate EGJ contractility metrics, which were then compared in their ability to differentiate among PPI-NR subgroups. The EGJ contractile integral (EGJ-CI), a metric integrating contractility across the EGJ for three respiratory cycles, best distinguished the All Criteria PPI-NR subgroup from controls and other PPI-NR subgroups. Normal values (median, [IQR]) for this measure were 39 mmHg-cm [25-55 mmHg-cm]. The correlation between the EGJ-CI and a previously proposed metric, the lower esophageal sphincter-pressure integral, that used a fixed 10 s time frame and an atmospheric as opposed to gastric pressure reference was weak. Among HRM metrics tested, the EGJ-CI was best in distinguishing PPI-NRs meeting all criteria of abnormality on pH-impedance testing. Future prospective studies are required to explore its utility in management of broader groups of gastroesophageal reflux disease patients. © 2013 John Wiley & Sons Ltd.

In a non-human primate model, aging disrupts the neural control of intestinal smooth muscle contractility in a region-specific manner.

PubMed

Tran, L; Greenwood-Van Meerveld, B

2014-03-01

Incidences of gastrointestinal (GI) motility disorders increase with age. However, there is a paucity of knowledge about the aging mechanisms leading to GI dysmotility. Motility in the GI tract is a function of smooth muscle contractility, which is modulated in part by the enteric nervous system (ENS). Evidence suggests that aging impairs the ENS, thus we tested the hypothesis that senescence in the GI tract precipitates abnormalities in smooth muscle and neurally mediated contractility in a region-specific manner. Jejunal and colonic circular muscle strips were isolated from young (4-10 years) and old (18+ years) baboons. Myogenic responses were investigated using potassium chloride (KCl) and carbachol (CCh). Neurally mediated contractile responses were evoked by electrical field stimulation (EFS) and were recorded in the absence and presence of atropine (1 μM) or NG-Nitro-l-arginine methyl ester (l-NAME; 100 μM). The myogenic responses to KCl in the jejunum and colon were unaffected by age. In the colon, but not the jejunum, CCh-induced contractile responses were reduced in aged animals. Compared to young baboons, there was enhanced EFS-induced contractility of old baboon jejunal smooth muscle in contrast to the reduced contractility in the colon. The effect of atropine on the EFS response was lower in aged colonic tissue, suggesting reduced participation of acetylcholine. In aged jejunal tissue, higher contractile responses to EFS were found to be due to reduced nitregic inhibition. These findings provide key evidence for the importance of intestinal smooth muscle and ENS senescence in age-associated GI motility disorders. © 2014 The Authors. Neurogastroenterology & Motility published by John Wiley & Sons Ltd.

Contractile properties of rat skeletal muscles following storage at 4 degrees C.

PubMed

van der Heijden, E P; Kroese, A B; Stremel, R W; Bär, P R; Kon, M; Werker, P M

1999-07-01

The purpose of this study was to assess the potential of preservation solutions for protecting skeletal muscle function during storage at 4 degrees C. The soleus and the cutaneus trunci (CT) from the rat were stored for 2, 8 or 16 h at 4 degrees C in University of Wisconsin solution (UW), HTK-Bretschneider solution (HTK) or Krebs-Henseleit solution (KH). After storage, muscles were stimulated electrically to analyse the isometric contractile properties, such as the maximum tetanic tension (P(0)). Histological analysis was also performed. In separate experiments, the effect of the diffusion distance on muscle preservation was studied by bisecting the soleus. After 8 h of storage in UW or HTK, the contractile properties of the CT were similar to those of the control, whereas those of the soleus were reduced (P(0) values of 16% and 69% of control in UW and HTK respectively). At 16 h, the contractile properties of the CT (P(O) 28%) were again better preserved than those of the soleus (P(0) 9%). Muscle function deteriorated most after storage in KH (P(0) at 16 h: soleus, 3%; CT, 17%). The bisected soleus was equally well preserved as the CT (P(O) of bisected soleus at 8 h in UW and HTK: 86%). The functional data corresponded well with the histological data, which showed increasing muscle fibre derangement with increasing storage time. For both muscles and all solutions, the threshold stimulus current increased with increasing storage time (control, 0.1 mA; 16 h, 1.2 mA) and was strongly correlated with the deterioration in contractile properties. It is concluded that, at 4 degrees C, muscle is preserved better in UW and HTK (intracellular-like solutions) than in KH (extracellular-like solution). The soleus and CT were best protected in HTK. The diffusion distance is a critical factor for successful preservation of muscle function at 4 degrees C. The reduced function after 16 h of storage at 4 degrees C was caused by hypercontraction and necrosis of about 25% of the muscle fibres, and by deterioration of the electrical component of excitation-contraction coupling of the remaining fibres.

Improved Arterial–Ventricular Coupling in Metabolic Syndrome after Exercise Training

PubMed Central

Fournier, Sara B.; Donley, David A.; Bonner, Daniel E.; DeVallance, Evan; Olfert, I. Mark; Chantler, Paul D.

2014-01-01

Purpose The metabolic syndrome (MetS) is associated with a three-fold increase risk of cardiovascular (CV) morbidity and mortality, which is in part, due to a blunted CV reserve capacity, reflected by a reduced peak exercise left ventricular contractility and aerobic capacity, and a blunted peak arterial-ventricular coupling. To date, no study has examined whether aerobic exercise training in MetS can reverse the peak exercise CV dysfunction. Further, examining how exercise training alters CV function in a group of individuals with MetS prior to the development of diabetes and/or overt CVD, can provide insights into whether some of the pathophysiological changes to the CV can be delayed/reversed, lowering their CV risk. The objective of this study was to examine the effects of 8 weeks of aerobic exercise training in individuals with MetS on resting and peak exercise CV function. Methods Twenty MetS underwent either 8 weeks of aerobic exercise training (MetS-ExT; n=10) or remained sedentary (MetS-NonT; n=10) during this time period. Resting and peak exercise CV function was characterized using Doppler echocardiography and gas exchange. Results Exercise training did not alter resting left ventricular diastolic or systolic function and arterial-ventricular coupling in MetS. In contrast, at peak exercise an increase in LV contractility (40%, p<0.01), cardiac output (28%, p<0.05) and aerobic capacity (20%, p<0.01), while a reduction in vascular resistance (30%, p<0.05) and arterial-ventricular coupling (27%, p<0.01), were noted in the MetS-ExT but not the MetS-NonT group. Further, an improvement in Lifetime Risk Score was also noted in the MetS-ExT group. Conclusions These findings have clinical importance as they provide insight that some of the pathophysiological changes associated with MetS can be improved and lower the risk of CVD. PMID:24870568

Improved arterial-ventricular coupling in metabolic syndrome after exercise training: a pilot study.

PubMed

Fournier, Sara B; Donley, David A; Bonner, Daniel E; Devallance, Evan; Olfert, I Mark; Chantler, Paul D

2015-01-01

The metabolic syndrome (MetS) is associated with threefold increased risk of cardiovascular (CV) morbidity and mortality, which is partly due to a blunted CV reserve capacity, reflected by a reduced peak exercise left ventricular (LV) contractility and aerobic capacity and a blunted peak arterial-ventricular coupling. To date, no study has examined whether aerobic exercise training in MetS can reverse peak exercise CV dysfunction. Furthermore, examining how exercise training alters CV function in a group of individuals with MetS before the development of diabetes and/or overt CV disease can provide insights into whether some of the pathophysiological CV changes can be delayed/reversed, lowering their CV risk. The objective of this study was to examine the effects of 8 wk of aerobic exercise training in individuals with MetS on resting and peak exercise CV function. Twenty participants with MetS underwent either 8 wk of aerobic exercise training (MetS-ExT, n = 10) or remained sedentary (MetS-NonT, n = 10) during this period. Resting and peak exercise CV function was characterized using Doppler echocardiography and gas exchange. Exercise training did not alter resting LV diastolic or systolic function and arterial-ventricular coupling in MetS. In contrast, at peak exercise, an increase in LV contractility (40%, P < 0.01), cardiac output (28%, P < 0.05), and aerobic capacity (20%, P < 0.01), but a reduction in vascular resistance (30%, P < 0.05) and arterial-ventricular coupling (27%, P < 0.01), were noted in the MetS-ExT but not in the MetS-NonT group. Furthermore, an improvement in lifetime risk score was also noted in the MetS-ExT group. These findings have clinical importance because they provide insight that some of the pathophysiological changes associated with MetS can be improved and can lower the risk of CV disease.

Protective effect of vitamin B5 (dexpanthenol) on cardiovascular damage induced by streptozocin in rats.

PubMed

Demirci, B; Demir, O; Dost, T; Birincioglu, M

2014-01-01

This study investigated whether Dexpanthenol (DEX) improves diabetic cardiovascular function and cardiac performance by regulating total oxidant and antioxidant status. Diabetes was induced by a single intraperitoneal injection of Streptozocin (50 mg/kg in 1 ml of saline) and treatment groups received DEX (300 mg/kg/day) for 6 weeks. Endothelium (in)dependent relaxation responses were assessed in thoracic aortic rings and coronary vasculature together with alpha receptor and voltage dependant contractile responses of aorta. Myocardial contractility has been recorded by an intra ventricular latex balloon. Total oxidant and antioxidant status were measured from the serum samples. Induction of diabetes resulted in an apparent body weight loss, high blood glucose, endothelial dysfunction and increased serum oxidant status. DEX supplementation restored the endothelial dysfunction, antioxidant status and body weight whereas decreasing blood glucose level. Along with the standard therapy of diabetes, DEX can be used as a safe and economical way of adjuvant therapy to diminish the burden of the disease (Tab. 3, Fig. 3, Ref. 30).

Validation of an in vitro contractility assay using canine ventricular myocytes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harmer, A.R., E-mail: alex.harmer@astrazeneca.com; Abi-Gerges, N.; Morton, M.J.

Measurement of cardiac contractility is a logical part of pre-clinical safety assessment in a drug discovery project, particularly if a risk has been identified or is suspected based on the primary- or non-target pharmacology. However, there are limited validated assays available that can be used to screen several compounds in order to identify and eliminate inotropic liability from a chemical series. We have therefore sought to develop an in vitro model with sufficient throughput for this purpose. Dog ventricular myocytes were isolated using a collagenase perfusion technique and placed in a perfused recording chamber on the stage of a microscopemore » at ∼ 36 °C. Myocytes were stimulated to contract at a pacing frequency of 1 Hz and a digital, cell geometry measurement system (IonOptix™) was used to measure sarcomere shortening in single myocytes. After perfusion with vehicle (0.1% DMSO), concentration–effect curves were constructed for each compound in 4–30 myocytes taken from 1 or 2 dog hearts. The validation test-set was 22 negative and 8 positive inotropes, and 21 inactive compounds, as defined by their effect in dog, cynolomolgous monkey or humans. By comparing the outcome of the assay to the known in vivo contractility effects, the assay sensitivity was 81%, specificity was 75%, and accuracy was 78%. With a throughput of 6–8 compounds/week from 1 cell isolation, this assay may be of value to drug discovery projects to screen for direct contractility effects and, if a hazard is identified, help identify inactive compounds. -- Highlights: ► Cardiac contractility is an important physiological function of the heart. ► Assessment of contractility is a logical part of pre-clinical drug safety testing. ► There are limited validated assays that predict effects of compounds on contractility. ► Using dog myocytes, we have developed an in vitro cardiac contractility assay. ► The assay predicted the in vivo contractility with a good level of accuracy.« less

Use of a Doppler pulmonary artery catheter for continuous measurement of right ventricular pump function and contractility during single lung transplantation.

PubMed

Heerdt, P M; Pond, C G; Kussman, M K; Triantafillou, A N

1993-01-01

Despite numerous technologic advances in intraoperative monitoring, the only methods routinely available for assessment of right ventricular function in lung transplant recipients are continuous measurement of right heart pressures and intermittent thermodilution determination of cardiac output and ejection fraction. Additional data may now be obtained with transesophageal echocardiography, although this technology is expensive and not widely available and requires diverting attention from a potentially unstable patient for data acquisition and analysis. Recently, a Doppler pulmonary artery catheter was introduced that measures beat-to-beat pulmonary artery blood flow-velocity, cross sectional area, and volume flow. Because of data indicating that acceleration of blood in the pulmonary artery (measured as the first derivative of either the velocity or flow waveform) is a sensitive indicator of right ventricular contractility, we have used waveforms obtained with the catheter for assessment of right ventricular pump function (stroke volume and peak pulmonary artery flow rate) and contractility in heart surgery patients. We report here our experience with this method in two patients undergoing left single lung transplantation.

Effect of Substrate Mechanics on Cardiomyocyte Maturation and Growth

PubMed Central

Tallawi, Marwa; Rai, Ranjana; Boccaccini, Aldo. R.

2015-01-01

Cardiac tissue engineering constructs are a promising therapeutic treatment for myocardial infarction, which is one of the leading causes of death. In order to further advance the development and regeneration of engineered cardiac tissues using biomaterial platforms, it is important to have a complete overview of the effects that substrates have on cardiomyocyte (CM) morphology and function. This article summarizes recent studies that investigate the effect of mechanical cues on the CM differentiation, maturation, and growth. In these studies, CMs derived from embryos, neonates, and mesenchymal stem cells were seeded on different substrates of various elastic modulus. Measuring the contractile function by force production, work output, and calcium handling, it was seen that cell behavior on substrates was optimized when the substrate stiffness mimicked that of the native tissue. The contractile function reflected changes in the sarcomeric protein confirmation and organization that promoted the contractile ability. The analysis of the literature also revealed that, in addition to matrix stiffness, mechanical stimulation, such as stretching the substrate during cell seeding, also played an important role during cell maturation and tissue development. PMID:25148904

Pentamidine rescues contractility and rhythmicity in a Drosophila model of myotonic dystrophy heart dysfunction

PubMed Central

Chakraborty, Mouli; Selma-Soriano, Estela; Magny, Emile; Couso, Juan Pablo; Pérez-Alonso, Manuel; Charlet-Berguerand, Nicolas; Artero, Ruben; Llamusi, Beatriz

2015-01-01

ABSTRACT Up to 80% of individuals with myotonic dystrophy type 1 (DM1) will develop cardiac abnormalities at some point during the progression of their disease, the most common of which is heart blockage of varying degrees. Such blockage is characterized by conduction defects and supraventricular and ventricular tachycardia, and carries a high risk of sudden cardiac death. Despite its importance, very few animal model studies have focused on the heart dysfunction in DM1. Here, we describe the characterization of the heart phenotype in a Drosophila model expressing pure expanded CUG repeats under the control of the cardiomyocyte-specific driver GMH5-Gal4. Morphologically, expression of 250 CUG repeats caused abnormalities in the parallel alignment of the spiral myofibrils in dissected fly hearts, as revealed by phalloidin staining. Moreover, combined immunofluorescence and in situ hybridization of Muscleblind and CUG repeats, respectively, confirmed detectable ribonuclear foci and Muscleblind sequestration, characteristic features of DM1, exclusively in flies expressing the expanded CTG repeats. Similarly to what has been reported in humans with DM1, heart-specific expression of toxic RNA resulted in reduced survival, increased arrhythmia, altered diastolic and systolic function, reduced heart tube diameters and reduced contractility in the model flies. As a proof of concept that the fly heart model can be used for in vivo testing of promising therapeutic compounds, we fed flies with pentamidine, a compound previously described to improve DM1 phenotypes. Pentamidine not only released Muscleblind from the CUG RNA repeats and reduced ribonuclear formation in the Drosophila heart, but also rescued heart arrhythmicity and contractility, and improved fly survival in animals expressing 250 CUG repeats. PMID:26515653

Improved sphincter contractility after allogenic muscle-derived progenitor cell injection into the denervated rat urethra.

PubMed

Cannon, Tracy W; Lee, Ji Youl; Somogyi, George; Pruchnic, Ryan; Smith, Christopher P; Huard, Johnny; Chancellor, Michael B

2003-11-01

To study the physiologic outcome of allogenic transplant of muscle-derived progenitor cells (MDPCs) in the denervated female rat urethra. MDPCs were isolated from muscle biopsies of normal 6-week-old Sprague-Dawley rats and purified using the preplate technique. Sciatic nerve-transected rats were used as a model of stress urinary incontinence. The experimental group was divided into three subgroups: control, denervated plus 20 microL saline injection, and denervated plus allogenic MDPCs (1 to 1.5 x 10(6) cells) injection. Two weeks after injection, urethral muscle strips were prepared and underwent electrical field stimulation. The pharmacologic effects of d-tubocurare, phentolamine, and tetrodotoxin on the urethral strips were assessed by contractions induced by electrical field stimulation. The urethral tissues also underwent immunohistochemical staining for fast myosin heavy chain and CD4-activated lymphocytes. Urethral denervation resulted in a significant decrease of the maximal fast-twitch muscle contraction amplitude to only 8.77% of the normal urethra and partial impairment of smooth muscle contractility. Injection of MDPCs into the denervated sphincter significantly improved the fast-twitch muscle contraction amplitude to 87.02% of normal animals. Immunohistochemistry revealed a large amount of new skeletal muscle fiber formation at the injection site of the urethra with minimal inflammation. CD4 staining showed minimal lymphocyte infiltration around the MDPC injection sites. Urethral denervation resulted in near-total abolishment of the skeletal muscle and partial impairment of smooth muscle contractility. Allogenic MDPCs survived 2 weeks in sciatic nerve-transected urethra with minimal inflammation. This is the first report of the restoration of deficient urethral sphincter function through muscle-derived progenitor cell tissue engineering. MDPC-mediated cellular urethral myoplasty warrants additional investigation as a new method to treat stress urinary incontinence.

Sirtuin 1 protects the aging heart from contractile dysfunction mediated through the inhibition of endoplasmic reticulum stress-mediated apoptosis in cardiac-specific Sirtuin 1 knockout mouse model.

PubMed

Hsu, Yu-Juei; Hsu, Shih-Che; Hsu, Chiao-Po; Chen, Yen-Hui; Chang, Yung-Lung; Sadoshima, Junichi; Huang, Shih-Ming; Tsai, Chien-Sung; Lin, Chih-Yuan

2017-02-01

The longevity regulator Sirtuin 1 is an NAD + -dependent histone deacetylase that regulates endoplasmic reticulum stress and influences cardiomyocyte apoptosis during cardiac contractile dysfunction induced by aging. The mechanism underlying Sirtuin 1 function in cardiac contractile dysfunction related to aging has not been completely elucidated. We evaluated cardiac contractile function, endoplasmic reticulum stress, apoptosis, and oxidative stress in 6- and 12month-old cardiac-specific Sirtuin 1 knockout (Sirt1 -/- ) and control (Sirt1 f/f ) mice using western blotting and immunohistochemistry. Mice were injected with a protein disulphide isomerase inhibitor. For in vitro analysis, cultured H9c2 cardiomyocytes were exposed to either a Sirtuin 1 inhibitor or activator, with or without a mitochondrial inhibitor, to evaluate the effects of Sirtuin 1 on endoplasmic reticulum stress, nitric oxide synthase expression, and apoptosis. The effects of protein disulphide isomerase inhibition on oxidative stress and ER stress-related apoptosis were also investigated. Compared with 6-month-old Sirt1 f/f mice, marked impaired contractility was observed in 12-month-old Sirt1 -/- mice. These findings were consistent with increased endoplasmic reticulum stress and apoptosis in the myocardium. Measures of oxidative stress and nitric oxide synthase expression were significantly higher in Sirt1 -/- mice compared with those in Sirt1 f/f mice at 6months. In vitro experiments revealed increased endoplasmic reticulum stress-mediated apoptosis in H9c2 cardiomyocytes treated with a Sirtuin 1 inhibitor; the effects were ameliorated by a Sirtuin 1 activator. Moreover, consistent with the in vitro findings, impaired cardiac contractility was demonstrated in Sirt1 -/- mice injected with a protein disulphide isomerase inhibitor. The present study demonstrates that the aging heart is characterized by contractile dysfunction associated with increased oxidative stress and endoplasmic reticulum stress and Sirtuin 1 might have the ability to protect the aging hearts from the inhibition of endoplasmic reticulum-mediated apoptosis. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Postprandial lymphatic pump function after a high-fat meal: a characterization of contractility, flow, and viscosity

PubMed Central

Kassis, Timothy; Yarlagadda, Sri Charan; Kohan, Alison B.; Tso, Patrick; Breedveld, Victor

2016-01-01

Dietary lipids are transported from the intestine through contractile lymphatics. Chronic lipid loads can adversely affect lymphatic function. However, the acute lymphatic pump response in the mesentery to a postprandial lipid meal has gone unexplored. In this study, we used the rat mesenteric collecting vessel as an in vivo model to quantify the effect of lipoproteins on vessel function. Lipid load was continuously monitored by using the intensity of a fluorescent fatty-acid analog, which we infused along with a fat emulsion through a duodenal cannula. The vessel contractility was simultaneously quantified. We demonstrated for the first time that collecting lymphatic vessels respond to an acute lipid load by reducing pump function. High lipid levels decreased contraction frequency and amplitude. We also showed a strong tonic response through a reduction in the end-diastolic and systolic diameters. We further characterized the changes in flow rate and viscosity and showed that both increase postprandially. In addition, shear-mediated Ca2+ signaling in lymphatic endothelial cells differed when cultured with lipoproteins. Together these results show that the in vivo response could be both shear and lipid mediated and provide the first evidence that high postprandial lipid has an immediate negative effect on lymphatic function even in the acute setting. PMID:26968208

Overcoming the Roadblocks to Cardiac Cell Therapy Using Tissue Engineering.

PubMed

Yanamandala, Mounica; Zhu, Wuqiang; Garry, Daniel J; Kamp, Timothy J; Hare, Joshua M; Jun, Ho-Wook; Yoon, Young-Sup; Bursac, Nenad; Prabhu, Sumanth D; Dorn, Gerald W; Bolli, Roberto; Kitsis, Richard N; Zhang, Jianyi

2017-08-08

Transplantations of various stem cells or their progeny have repeatedly improved cardiac performance in animal models of myocardial injury; however, the benefits observed in clinical trials have been generally less consistent. Some of the recognized challenges are poor engraftment of implanted cells and, in the case of human cardiomyocytes, functional immaturity and lack of electrical integration, leading to limited contribution to the heart's contractile activity and increased arrhythmogenic risks. Advances in tissue and genetic engineering techniques are expected to improve the survival and integration of transplanted cells, and to support structural, functional, and bioenergetic recovery of the recipient hearts. Specifically, application of a prefabricated cardiac tissue patch to prevent dilation and to improve pumping efficiency of the infarcted heart offers a promising strategy for making stem cell therapy a clinical reality. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

Functional Esophageal Disorders.

PubMed

Aziz, Qasim; Fass, Ronnie; Gyawali, C Prakash; Miwa, Hiroto; Pandolfino, John E; Zerbib, Frank

2016-02-15

Functional esophageal disorders consist of a disease category that present with esophageal symptoms (heartburn, chest pain, dysphagia, globus) not explained by mechanical obstruction (stricture, tumor, eosinophilic esophagitis), major motor disorders (achalasia, EGJ outflow obstruction, absent contractility, distal esophageal spasm, jackhammer esophagus), or gastroesophageal reflux disease (GERD). While mechanisms responsible are unclear, it is theorized that visceral hypersensitivity and hypervigilance play an important role in symptom generation, in the context of normal or borderline function. Treatments directed at improving borderline motor dysfunction or reducing reflux burden to sub-normal levels have limited success in symptom improvement. In contrast, strategies focused on modulating peripheral triggering and central perception are mechanistically viable and clinically meaningful. However, outcome data from these treatment options are limited. Future research needs to focus on understanding mechanisms underlying visceral hypersensitivity and hypervigilance so that appropriate targets and therapies can be developed. Copyright © 2016 AGA Institute. Published by Elsevier Inc. All rights reserved.

Maladaptive hypertrophy after acute myocardial infarction positive effect of bone marrow-derived stem cell therapy on regional remodeling measured by cardiac MRI.

PubMed

Rolf, Andreas; Assmus, Birgit; Schächinger, Volker; Rixe, Johannes; Möllmann, Susanne; Möllmann, Helge; Dimmeler, Stefanie; Zeiher, Andreas M; Hamm, Christian W; Dill, Thorsten

2011-11-01

In the aftermath of myocardial infarction, increased loading conditions will trigger hypertrophy of viable myocardium. This in turn causes deterioration of regional contractility. Cardiac magnetic resonance imaging (cMRI) allows the exact differentiation of viable and infarcted myocardium and therefore the measurement of regional wall thickness and function. Bone marrow-derived stem cell (BMC) transfer has been shown to improve global function and remodeling. The present study examines the effect of BMC transfer on regional remodeling and function after myocardial infarction by cMRI. Fifty-four patients of the MR substudy of the REPAIR-AMI trial have been studied at baseline and 12-month follow-up. Enddiastolic wall thickness (EDWT) and wall thickening (WT%) have been measured on SSFP cine sequences. Enddiastolic wall thickness decreased in both placebo and BMC groups in viable as well as infarcted segments. The effect was largest in the pre-specified subgroup of patients below the median EF of 48.9% (infarcted segments -1.14 mm Placebo vs. -1.91 mm BMC, p for interaction 0.01, remote segments -0.19 mm Placebo vs. -0.94 mm BMC, p for interaction 0.00001). Corrected for baseline values BMC therapy yielded smaller EDWT at 12 months in infarcted and remote segments (infarcted 7.58 mm Placebo vs. 6.13 mm BMC p = 0.0001, remote 8.76 mm Placebo vs. 7.32 mm BMC, p = 0.0001). This was associated with better contractility within the infarcted segments among BMC patients (WT% 24.17% Placebo vs. 49.31% BMC, p = 0.0001). The WT% was inversely correlated with EDWT (r = -0.37, p = 0.0001). Bone marrow-derived stem cell therapy yields smaller EDWT when compared with placebo patients suggesting a positive effect on maladaptive hypertrophy of viable myocardium. This notion is supported by the enhanced regional contractility within the BMC group which is inversely correlated with EDWT.

Swim-exercised mice show a decreased level of protein O-GlcNAcylation and expression of O-GlcNAc transferase in heart.

PubMed

Belke, Darrell D

2011-07-01

Swim-training exercise in mice leads to cardiac remodeling associated with an improvement in contractile function. Protein O-linked N-acetylglucosamine (O-GlcNAcylation) is a posttranslational modification of serine and threonine residues capable of altering protein-protein interactions affecting gene transcription, cell signaling pathways, and general cell physiology. Increased levels of protein O-GlcNAcylation in the heart have been associated with pathological conditions such as diabetes, ischemia, and hypertrophic heart failure. In contrast, the impact of physiological exercise on protein O-GlcNAcylation in the heart is currently unknown. Swim-training exercise in mice was associated with the development of a physiological hypertrophy characterized by an improvement in contractile function relative to sedentary mice. General protein O-GlcNAcylation was significantly decreased in swim-exercised mice. This effect was mirrored in the level of O-GlcNAcylation of individual proteins such as SP1. The decrease in protein O-GlcNAcylation was associated with a decrease in the expression of O-GlcNAc transferase (OGT) and glutamine-fructose amidotransferase (GFAT) 2 mRNA. O-GlcNAcase (OGA) activity was actually lower in swim-trained than sedentary hearts, suggesting that it did not contribute to the decreased protein O-GlcNAcylation. Thus it appears that exercise-induced physiological hypertrophy is associated with a decrease in protein O-GlcNAcylation, which could potentially contribute to changes in gene expression and other physiological changes associated with exercise.

Levosimendan Prevents Pressure-Overload-induced Right Ventricular Failure.

PubMed

Hillgaard, Thomas Krarup; Andersen, Asger; Andersen, Stine; Vildbrad, Mads D; Ringgaard, Steffen; Nielsen, Jan M; Nielsen-Kudsk, Jens E

2016-04-01

We investigated if chronic levosimendan treatment can prevent and revert pressure-overload-induced right ventricular hypertrophy and failure in rats. Right ventricular hypertrophy and failure was induced in Wistar rats by pulmonary trunk banding (PTB). The PTB rats were treated with levosimendan (3 mg·kg·d) 3 days before surgery [n = 10, prevention (PREV)], 3 weeks after surgery [n = 10, reversal (REV)] or vehicle (n = 10, VEH). Sham-operated rats received vehicle (n = 16, SHAM). Right ventricular function was evaluated 7 weeks after surgery by echocardiography, magnetic resonance imaging, pressure-volume relations, gross anatomy, and histology. PTB induced right ventricular hypertrophy and compensated heart failure evident by reduced cardiac index (CI) without extra cardiac signs of heart failure. Levosimendan treatment prevented deterioration of right ventricular function measured by CI and right ventricular ejection fraction (RVEF) (CI: VEH vs. PREV 281 ± 17 vs. 362 ± 34 mL·min·kg, P ≤ 0.05, RVEF: VEH vs. PREV 57 ± 2% vs. 68 ± 3%, P ≤ 0.01) to values similar to SHAM (CI: 345 ± 21 mL·min·kg, RVEF: 71 ± 2%). RV contractility was improved in the REV group measured by preload recruitable stroke work (VEH vs. REV 39 ± 3 vs. 66 ± 10 mmHg P ≤ 0.05). Chronic treatment with levosimendan prevents the development of right ventricular failure and improves contractility in established pressure-overload-induced right ventricular failure.

Postactivation Potentiation of the Plantar Flexors Does Not Directly Translate to Jump Performance in Female Elite Young Soccer Players.

PubMed

Prieske, Olaf; Maffiuletti, Nicola A; Granacher, Urs

2018-01-01

High-intensity muscle actions have the potential to temporarily improve muscle contractile properties (i.e., postactivation potentiation, PAP) thereby inducing acute performance enhancements. There is evidence that balance training can improve performance during strength exercises. Taking these findings together, the purpose of this study was to examine the acute effects of a combined balance and strength (B+S) exercise vs. a strength only (S) exercise on twitch contractile properties, maximum voluntary strength, and jump performance in young athletes. Female elite young soccer players ( N = 12) aged 14-15 years conducted three experimental conditions in randomized order: S included 3 sets of 8-10 dynamic leg extensions at 80% of the 1-repetition maximum, B+S consisted of 3 sets of 40 s double-leg stances on a balance board prior to leg extensions (same as S), and a resting control period. Before and 7 min after exercise, participants were tested for their electrically-evoked isometric twitches (i.e., twitch peak torque, twitch rate of torque development) and maximal voluntary contraction (MVC) torque of the plantar flexor muscles. Additionally, countermovement (CMJ) and drop jump (DJ) performances (i.e., CMJ/DJ height, DJ ground contact time) were assessed. Significant effects of condition on twitch contractile properties ( p < 0.05, d = 1.1) and jump performance outputs ( p < 0.05, 1.1 ≤ d ≤ 1.2) were found. Post-hoc tests revealed that S compared to control produced larger PAP for twitch peak torques by trend ( p = 0.07, d = 1.8, 33 vs. 21%) and significantly larger PAP for twitch rate of torque development ( p < 0.05, d = 2.4, 55 vs. 43%). Following B+S compared to control, significant improvements in CMJ height ( p < 0.01, d = 1.9, 3%) and DJ contact time were found ( p < 0.01, d = 2.0, 10%). This study revealed protocol-specific acute performance improvements. While S resulted in significant increases in twitch contractile properties, B+S produced significant enhancements in jump performance. It is concluded that PAP effects in the plantar flexors may not directly translate to improved jump performance in female elite young soccer players. Therefore, the observed gains in jump performance following B+S are most likely related to neuromuscular changes (e.g., intramuscular coordination) rather than improved contractile properties.

Postactivation Potentiation of the Plantar Flexors Does Not Directly Translate to Jump Performance in Female Elite Young Soccer Players

PubMed Central

Prieske, Olaf; Maffiuletti, Nicola A.; Granacher, Urs

2018-01-01

High-intensity muscle actions have the potential to temporarily improve muscle contractile properties (i.e., postactivation potentiation, PAP) thereby inducing acute performance enhancements. There is evidence that balance training can improve performance during strength exercises. Taking these findings together, the purpose of this study was to examine the acute effects of a combined balance and strength (B+S) exercise vs. a strength only (S) exercise on twitch contractile properties, maximum voluntary strength, and jump performance in young athletes. Female elite young soccer players (N = 12) aged 14–15 years conducted three experimental conditions in randomized order: S included 3 sets of 8–10 dynamic leg extensions at 80% of the 1-repetition maximum, B+S consisted of 3 sets of 40 s double-leg stances on a balance board prior to leg extensions (same as S), and a resting control period. Before and 7 min after exercise, participants were tested for their electrically-evoked isometric twitches (i.e., twitch peak torque, twitch rate of torque development) and maximal voluntary contraction (MVC) torque of the plantar flexor muscles. Additionally, countermovement (CMJ) and drop jump (DJ) performances (i.e., CMJ/DJ height, DJ ground contact time) were assessed. Significant effects of condition on twitch contractile properties (p < 0.05, d = 1.1) and jump performance outputs (p < 0.05, 1.1 ≤ d ≤ 1.2) were found. Post-hoc tests revealed that S compared to control produced larger PAP for twitch peak torques by trend (p = 0.07, d = 1.8, 33 vs. 21%) and significantly larger PAP for twitch rate of torque development (p < 0.05, d = 2.4, 55 vs. 43%). Following B+S compared to control, significant improvements in CMJ height (p < 0.01, d = 1.9, 3%) and DJ contact time were found (p < 0.01, d = 2.0, 10%). This study revealed protocol-specific acute performance improvements. While S resulted in significant increases in twitch contractile properties, B+S produced significant enhancements in jump performance. It is concluded that PAP effects in the plantar flexors may not directly translate to improved jump performance in female elite young soccer players. Therefore, the observed gains in jump performance following B+S are most likely related to neuromuscular changes (e.g., intramuscular coordination) rather than improved contractile properties. PMID:29628898

Role of endothelin-1 and big endothelin-1 in modulating coronary vascular tone, contractile function and severity of ischemia in rat hearts.

PubMed

Grover, G J; Sleph, P G; Fox, M; Trippodo, N C

1992-12-01

The effect of endothelin-1 (ET-1) and big ET-1 on coronary flow and contractile function was determined in isolated nonischemic and ischemic rat hearts. Both ET-1 (IC50 = 12 pMol) and big ET-1 (IC50 = 2 nMol) reduced coronary flow in a concentration-dependent manner, although ET-1 was > 100-fold more potent. Both compounds decreased contractility, an effect which was lost when coronary flow was held constant, indicating that ET-1 and big ET-1 decrease contractility secondary to reducing coronary flow. Mechanical reduction in coronary flow to levels equivalent to those seen for ET-1 or big ET-1 caused similar reductions in contractility. Both 30 pMol ET-1 and 10 nMol big ET-1 pretreatment significantly reduced the time to contracture in globally ischemic rat hearts, suggesting a proischemic effect. Phosphoramidon (100 microM, endothelin-converting enzyme inhibitor) and BQ-123 (0.3 microM, ETA receptor antagonist) abolished the preischemic increase in coronary perfusion pressure induced by big ET-1 as well as its proischemic effect, whereas only BQ-123 abolished the cardiac effect of ET-1. Neither phosphoramidon nor BQ-123 had an effect on severity of ischemia when given alone. Phosphoramidon was also given i.v. to rats subjected to coronary occlusion and reperfusion and was found to significantly reduce infarct size 24 hr postischemia. Thus, in isolated rat hearts, big ET-1 appears to be converted to ET-1 and is a potent coronary constrictor.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac-Specific Overexpression of Catalase Attenuates Lipopolysaccharide-Induced Myocardial Contractile Dysfunction: Role of Autophagy

PubMed Central

Turdi, Subat; Han, Xuefeng; Huff, Anna F.; Roe, Nathan D.; Hu, Nan; Gao, Feng; Ren, Jun

2012-01-01

Lipopolysaccharide (LPS) from Gram-negative bacteria is a major initiator of sepsis, leading to cardiovascular collapse. Accumulating evidence has indicated a role of reactive oxygen species (ROS) in cardiovascular complication in sepsis. This study was designed to examine the effect of cardiac-specific overexpression of catalase in LPS-induced cardiac contractile dysfunction and the underlying mechanism(s) with a focus on autophagy. Catalase transgenic and wild-type FVB mice were challenged with LPS (6 mg/kg) and cardiac function was evaluated. Levels of oxidative stress, autophagy, apoptosis and protein damage were examined using fluorescence microscopy, Western blot, TUNEL assay, caspase-3 activity and carbonyl formation. Kaplan-Meier curve was constructed for survival following LPS treatment. Our results revealed a lower mortality in catalase mice compared with FVB mice following LPS challenge. LPS injection led to depressed cardiac contractile capacity as evidenced by echocardiography and cardiomyocyte contractile function, the effect of which was ablated by catalase overexpression. LPS treatment induced elevated TNF-α level, autophagy, apoptosis (TUNEL, caspase-3 activation, cleaved caspase-3), production of ROS and O2−, and protein carbonyl formation, the effects of which were significantly attenuated by catalase overexpression. Electron microscopy revealed focal myocardial damage characterized by mitochondrial injury following LPS treatment, which was less severe in catalase mice. Interestingly, LPS-induced cardiomyocyte contractile dysfunction was prevented by antioxidant NAC and the autophagy inhibitor 3-methyladenine. Taken together, our data revealed that catalase protects against LPS-induced cardiac dysfunction and mortality, which may be associated with inhibition of oxidative stress and autophagy. PMID:22902401

Effects of the Tibetan herbal formula Padma Lax on visceral nociception and contractility of longitudinal smooth muscle in a rat model.

PubMed

Gschossmann, J M; Krayer, M; Flogerzi, B; Balsiger, B M

2010-09-01

The high prevalence of functional bowel disorders among the general population contrasts with the limited number of pharmacological treatment options for this condition. This has led to an interest for alternative therapeutic approaches. Padma Lax is an herbal laxative on the basis of Tibetan formulas. Our aim is to examine the effect of Padma Lax on visceral nociception in vivo and (B) on contractile activity of longitudinal smooth muscle of the lower gut in vitro and ex vivo. (A) Visceral sensory function in response to colorectal distension was assessed by abdominal wall electromyography in male Wistar rats pretreated with Padma Lax. (B) Effects of Padma Lax on contractility of gut smooth muscles were studied both in vitro with superfusion of the agent and ex vivo following oral administration of the preparation. Activities were measured as area under the curve. (A) For visceral sensitivity, no differences were observed between the Padma Lax and the control group. (B) Proximal colon muscle strips of the Padma Lax pretreated group showed significantly lower spontaneous contractility ex vivo than controls. Cholinergic procontractile stimulation was reduced in Padma Lax pretreated group and in colon strips of naive rats when Padma Lax was superfused in vitro (all P < 0.05). Cholinergic mechanisms appear to be important in the modulation of rat proximal colon contractility of orally and directly applied Padma Lax. These findings help elucidate a potential mechanism of action of this herbal remedy which has undergone clinical testing in patients with constipation predominant irritable bowel syndrome.

Inhibitory effects of botulinum toxin on pyloric and antral smooth muscle.

PubMed

James, Arlene N; Ryan, James P; Parkman, Henry P

2003-08-01

Botulinum toxin injection into the pylorus is reported to improve gastric emptying in gastroparesis. Classically, botulinum toxin inhibits ACh release from cholinergic nerves in skeletal muscle. The aim of this study was to determine the effects of botulinum toxin on pyloric smooth muscle. Guinea pig pyloric muscle strips were studied in vitro. Botulinum toxin type A was added; electric field stimulation (EFS) was performed every 30 min for 6 h. ACh (100 microM)-induced contractile responses were determined before and after 6 h. Botulinum toxin caused a concentration-dependent decrease of pyloric contractions to EFS. At a low concentration (2 U/ml), botulinum toxin decreased pyloric contractions to EFS by 43 +/- 9% without affecting ACh-induced contractions. At higher concentrations (10 U/ml), botulinum toxin decreased pyloric contraction to EFS by 75 +/- 7% and decreased ACh-induced contraction by 79 +/- 9%. In conclusion, botulinum toxin inhibits pyloric smooth muscle contractility. At a low concentration, botulinum toxin decreases EFS-induced contractile responses without affecting ACh-induced contractions suggesting inhibition of ACh release from cholinergic nerves. At higher concentrations, botulinum toxin directly inhibits smooth muscle contractility as evidenced by the decreased contractile response to ACh.

Decreased intracellular [Ca2+ ] coincides with reduced expression of Dhprα1s, RyR1, and diaphragmatic dysfunction in a rat model of sepsis.

PubMed

Wang, Meng-Meng; Hao, Li-Ying; Guo, Feng; Zhong, Bin; Zhong, Xiao-Mei; Yuan, Jing; Hao, Yi-Fei; Zhao, Shuang; Sun, Xue-Fei; Lei, Ming; Jiao, Guang-Yu

2017-12-01

Sepsis can cause decreased diaphragmatic contractility. Intracellular calcium as a second messenger is central to diaphragmatic contractility. However, changes in intracellular calcium concentration ([Ca 2+ ]) and the distribution and co-localization of relevant calcium channels [dihydropyridine receptors, (DHPRα1s) and ryanodine receptors (RyR1)] remain unclear during sepsis. In this study we investigated the effect of changed intracellular [Ca 2+ ] and expression and distribution of DHPRα1s and RyR1 on diaphragm function during sepsis. We measured diaphragm contractility and isolated diaphragm muscle cells in a rat model of sepsis. The distribution and co-localization of DHPRα1s and RyR1 were determined using immunohistochemistry and immunofluorescence, whereas intracellular [Ca 2+ ] was measured by confocal microscopy and fluorescence spectrophotometry. Septic rat diaphragm contractility, expression of DHPRα1s and RyR1, and intracellular [Ca 2+ ] were significantly decreased in the rat sepsis model compared with controls. Decreased intracellular [Ca 2+ ] coincides with diaphragmatic contractility and decreased expression of DHPRα1s and RyR1 in sepsis. Muscle Nerve 56: 1128-1136, 2017. © 2017 Wiley Periodicals, Inc.

TRPM4 Is a Novel Component of the Adhesome Required for Focal Adhesion Disassembly, Migration and Contractility

PubMed Central

Cáceres, Mónica; Ortiz, Liliana; Recabarren, Tatiana; Romero, Anibal; Colombo, Alicia; Leiva-Salcedo, Elías; Varela, Diego; Rivas, José; Silva, Ian; Morales, Diego; Campusano, Camilo; Almarza, Oscar; Simon, Felipe; Toledo, Hector; Park, Kang-Sik; Trimmer, James S.; Cerda, Oscar

2015-01-01

Cellular migration and contractility are fundamental processes that are regulated by a variety of concerted mechanisms such as cytoskeleton rearrangements, focal adhesion turnover, and Ca2+ oscillations. TRPM4 is a Ca2+-activated non-selective cationic channel (Ca2+-NSCC) that conducts monovalent but not divalent cations. Here, we used a mass spectrometry-based proteomics approach to identify putative TRPM4-associated proteins. Interestingly, the largest group of these proteins has actin cytoskeleton-related functions, and among these nine are specifically annotated as focal adhesion-related proteins. Consistent with these results, we found that TRPM4 localizes to focal adhesions in cells from different cellular lineages. We show that suppression of TRPM4 in MEFs impacts turnover of focal adhesions, serum-induced Ca2+ influx, focal adhesion kinase (FAK) and Rac activities, and results in reduced cellular spreading, migration and contractile behavior. Finally, we demonstrate that the inhibition of TRPM4 activity alters cellular contractility in vivo, affecting cutaneous wound healing. Together, these findings provide the first evidence, to our knowledge, for a TRP channel specifically localized to focal adhesions, where it performs a central role in modulating cellular migration and contractility. PMID:26110647

Simultaneous determination of dynamic cardiac metabolism and function using PET/MRI.

PubMed

Barton, Gregory P; Vildberg, Lauren; Goss, Kara; Aggarwal, Niti; Eldridge, Marlowe; McMillan, Alan B

2018-05-01

Cardiac metabolic changes in heart disease precede overt contractile dysfunction. However, metabolism and function are not typically assessed together in clinical practice. The purpose of this study was to develop a cardiac positron emission tomography/magnetic resonance (PET/MR) stress test to assess the dynamic relationship between contractile function and metabolism in a preclinical model. Following an overnight fast, healthy pigs (45-50 kg) were anesthetized and mechanically ventilated. 18 F-fluorodeoxyglucose ( 18 F-FDG) solution was administered intravenously at a constant rate of 0.01 mL/s for 60 minutes. A cardiac PET/MR stress test was performed using normoxic gas (F I O 2  = .209) and hypoxic gas (F I O 2  = .12). Simultaneous cardiac imaging was performed on an integrated 3T PET/MR scanner. Hypoxic stress induced a significant increase in heart rate, cardiac output, left ventricular (LV) ejection fraction (EF), and peak torsion. There was a significant decline in arterial SpO 2 , LV end-diastolic and end-systolic volumes in hypoxia. Increased LV systolic function was coupled with an increase in myocardial FDG uptake (Ki) during hypoxic stress. PET/MR with continuous FDG infusion captures dynamic changes in both cardiac metabolism and contractile function. This technique warrants evaluation in human cardiac disease for assessment of subtle functional and metabolic abnormalities.

BK Channel-Mediated Relaxation of Urinary Bladder Smooth Muscle: A Novel Paradigm for Phosphodiesterase Type 4 Regulation of Bladder Function

PubMed Central

Xin, Wenkuan; Li, Ning; Cheng, Qiuping

2014-01-01

Elevation of intracellular cAMP and activation of protein kinase A (PKA) lead to activation of large conductance voltage- and Ca2+-activated K+ (BK) channels, thus attenuation of detrusor smooth muscle (DSM) contractility. In this study, we investigated the mechanism by which pharmacological inhibition of cAMP-specific phosphodiesterase 4 (PDE4) with rolipram or Ro-20-1724 (C15H22N2O3) suppresses guinea pig DSM excitability and contractility. We used high-speed line-scanning confocal microscopy, ratiometric fluorescence Ca2+ imaging, and perforated whole-cell patch-clamp techniques on freshly isolated DSM cells, along with isometric tension recordings of DSM isolated strips. Rolipram caused an increase in the frequency of Ca2+ sparks and the spontaneous transient BK currents (TBKCs), hyperpolarized the cell membrane potential (MP), and decreased the intracellular Ca2+ levels. Blocking BK channels with paxilline reversed the hyperpolarizing effect of rolipram and depolarized the MP back to the control levels. In the presence of H-89 [N-[2-[[3-(4-bromophenyl)-2-propenyl]amino]ethyl]-5-isoquinolinesulfonamide dihydrochloride], a PKA inhibitor, rolipram did not cause MP hyperpolarization. Rolipram or Ro-20-1724 reduced DSM spontaneous and carbachol-induced phasic contraction amplitude, muscle force, duration, and frequency, and electrical field stimulation-induced contraction amplitude, muscle force, and tone. Paxilline recovered DSM contractility, which was suppressed by pretreatment with PDE4 inhibitors. Rolipram had reduced inhibitory effects on DSM contractility in DSM strips pretreated with paxilline. This study revealed a novel cellular mechanism whereby pharmacological inhibition of PDE4 leads to suppression of guinea pig DSM contractility by increasing the frequency of Ca2+ sparks and the functionally coupled TBKCs, consequently hyperpolarizing DSM cell MP. Collectively, this decreases the global intracellular Ca2+ levels and DSM contractility in a BK channel-dependent manner. PMID:24459245

Identification of Contractile Vacuole Proteins in Trypanosoma cruzi

PubMed Central

Park, Miyoung; Martins, Vicente P.; Atwood, James; Moles, Kristen; Collins, Dalis; Rohloff, Peter; Tarleton, Rick; Moreno, Silvia N. J.; Orlando, Ron; Docampo, Roberto

2011-01-01

Contractile vacuole complexes are critical components of cell volume regulation and have been shown to have other functional roles in several free-living protists. However, very little is known about the functions of the contractile vacuole complex of the parasite Trypanosoma cruzi, the etiologic agent of Chagas disease, other than a role in osmoregulation. Identification of the protein composition of these organelles is important for understanding their physiological roles. We applied a combined proteomic and bioinfomatic approach to identify proteins localized to the contractile vacuole. Proteomic analysis of a T. cruzi fraction enriched for contractile vacuoles and analyzed by one-dimensional gel electrophoresis and LC-MS/MS resulted in the addition of 109 newly detected proteins to the group of expressed proteins of epimastigotes. We also identified different peptides that map to at least 39 members of the dispersed gene family 1 (DGF-1) providing evidence that many members of this family are simultaneously expressed in epimastigotes. Of the proteins present in the fraction we selected several homologues with known localizations in contractile vacuoles of other organisms and others that we expected to be present in these vacuoles on the basis of their potential roles. We determined the localization of each by expression as GFP-fusion proteins or with specific antibodies. Six of these putative proteins (Rab11, Rab32, AP180, ATPase subunit B, VAMP1, and phosphate transporter) predominantly localized to the vacuole bladder. TcSNARE2.1, TcSNARE2.2, and calmodulin localized to the spongiome. Calmodulin was also cytosolic. Our results demonstrate the utility of combining subcellular fractionation, proteomic analysis, and bioinformatic approaches for localization of organellar proteins that are difficult to detect with whole cell methodologies. The CV localization of the proteins investigated revealed potential novel roles of these organelles in phosphate metabolism and provided information on the potential participation of adaptor protein complexes in their biogenesis. PMID:21437209

A new twist on an old idea part 2: cyclosporine preserves normal mitochondrial but not cardiomyocyte function in mini‐swine with compensated heart failure

PubMed Central

Hiemstra, Jessica A.; Gutiérrez‐Aguilar, Manuel; Marshall, Kurt D.; McCommis, Kyle S.; Zgoda, Pamela J.; Cruz‐Rivera, Noelany; Jenkins, Nathan T.; Krenz, Maike; Domeier, Timothy L.; Baines, Christopher P.; Emter, Craig A.

2014-01-01

Abstract We recently developed a clinically relevant mini‐swine model of heart failure with preserved ejection fraction (HFpEF), in which diastolic dysfunction was associated with increased mitochondrial permeability transition (MPT). Early diastolic function is ATP and Ca2+‐dependent, thus, we hypothesized chronic low doses of cyclosporine (CsA) would preserve mitochondrial function via inhibition of MPT and subsequently maintain normal cardiomyocyte Ca2+ handling and contractile characteristics. Left ventricular cardiomyocytes were isolated from aortic‐banded Yucatan mini‐swine divided into three groups; control nonbanded (CON), HFpEF nontreated (HF), and HFpEF treated with CsA (HF‐CsA). CsA mitigated the deterioration of mitochondrial function observed in HF animals, including functional uncoupling of Complex I‐dependent mitochondrial respiration and increased susceptibility to MPT. Attenuation of mitochondrial dysfunction in the HF‐CsA group was not associated with commensurate improvement in cardiomyocyte Ca2+ handling or contractility. Ca2+ transient amplitude was reduced and transient time to peak and recovery (tau) prolonged in HF and HF‐CsA groups compared to CON. Alterations in Ca2+ transient parameters observed in the HF and HF‐CsA groups were associated with decreased cardiomyocyte shortening and shortening rate. Cellular function was consistent with impaired in vivo systolic and diastolic whole heart function. A significant systemic hypertensive response to CsA was observed in HF‐CsA animals, and may have played a role in the accelerated the development of heart failure at both the whole heart and cellular levels. Given the significant detriment to cardiac function observed in response to CsA, our findings suggest chronic CsA treatment is not a viable therapeutic option for HFpEF. PMID:24963034

Soluble CD14 inhibits contractile function and insulin action in primary adult rat cardiomyocytes.

PubMed

Overhagen, Sabrina; Blumensatt, Marcel; Fahlbusch, Pia; Herzfeld de Wiza, Daniella; Müller, Heidi; Maxhera, Bujar; Akhyari, Payam; Ouwens, D Margriet

2017-02-01

Epicardial adipose tissue (EAT) from patients with type 2 diabetes (T2D) is characterized by monocyte infiltrations and displays an elevated release of the monocyte marker soluble cluster of differentiation 14 (sCD14) versus EAT from patients without T2D. We propose that an increased abundance of sCD14 in EAT from patients with T2D may impair the function and insulin sensitivity of the adjacent cardiomyocytes. To examine this, primary adult rat cardiomyocytes were incubated with increasing concentrations of sCD14 in the presence and absence of the co-receptor lipopolysaccharide (LPS), and analyzed for effects on determinants of contractile function, activation of inflammation signalling and insulin action. Exposing cardiomyocytes to sCD14 increased the phosphorylation of the stress kinases p38 and extracellular-signal regulated kinase (ERK). In contrast, insulin-mediated phosphorylation of Akt on Thr308 and Ser473 was inhibited. Furthermore, sCD14 impaired sarcomere shortening and cytosolic Ca 2+ -fluxes. All responses were concentration-dependent and became significant at 1ng/ml sCD14. LPS, either alone or in complex with sCD14, did not affect contractile function or the activation of stress kinases and insulin signalling pathways. Similar data on protein phosphorylation were obtained when exposing human umbilical vein endothelial cells to sCD14. Finally, pharmacological inhibition of p38 reversed the detrimental effects of sCD14 on contractile function, but not on sCD14-induced insulin resistance. Collectively, these data show that sCD14 impairs the function and insulin sensitivity of cardiomyocytes, suggesting that an enhanced sCD14 release from EAT in patients with T2D may contribute to the pathogenesis of diabetes-related cardiometabolic complications. Copyright © 2016 Elsevier B.V. All rights reserved.

Adenosine triphosphate as a molecular mediator of the vascular response to injury.

PubMed

Guth, Christy M; Luo, Weifung; Jolayemi, Olukemi; Chadalavada, Kalyan S; Komalavilas, Padmini; Cheung-Flynn, Joyce; Brophy, Colleen M

2017-08-01

Human saphenous veins used for arterial bypass undergo stretch injury at the time of harvest and preimplant preparation. Vascular injury promotes intimal hyperplasia, the leading cause of graft failure, but the molecular events leading to this response are largely unknown. This study investigated adenosine triphosphate (ATP) as a potential molecular mediator in the vascular response to stretch injury, and the downstream effects of the purinergic receptor, P2X7R, and p38 MAPK activation. A subfailure stretch rat aorta model was used to determine the effect of stretch injury on release of ATP and vasomotor responses. Stretch-injured tissues were treated with apyrase, the P2X7R antagonist, A438079, or the p38 MAPK inhibitor, SB203580, and subsequent contractile forces were measured using a muscle bath. An exogenous ATP (eATP) injury model was developed and the experiment repeated. Change in p38 MAPK phosphorylation after stretch and eATP tissue injury was determined using Western blotting. Noninjured tissue was incubated in the p38 MAPK activator, anisomycin, and subsequent contractile function and p38 MAPK phosphorylation were analyzed. Stretch injury was associated with release of ATP. Contractile function was decreased in tissue subjected to subfailure stretch, eATP, and anisomycin. Contractile function was restored by apyrase, P2X7R antagonism, and p38-MAPK inhibition. Stretch, eATP, and anisomycin-injured tissue demonstrated increased phosphorylation of p38 MAPK. Taken together, these data suggest that the vascular response to stretch injury is associated with release of ATP and activation of the P2X7R/P38 MAPK pathway, resulting in contractile dysfunction. Modulation of this pathway in vein grafts after harvest and before implantation may reduce the vascular response to injury. Copyright © 2017 Elsevier Inc. All rights reserved.

Effects of temperature on power output and contraction kinetics in the locomotor muscle of the regionally endothermic common thresher shark (Alopias vulpinus).

PubMed

Donley, Jeanine M; Sepulveda, Chugey A; Aalbers, Scott A; McGillivray, David G; Syme, Douglas A; Bernal, Diego

2012-10-01

The common thresher shark (Alopias vulpinus) is a pelagic species with medially positioned red aerobic swimming musculature (RM) and regional RM endothermy. This study tested whether the contractile characteristics of the RM are functionally similar along the length of the body and assessed how the contractile properties of the common thresher shark compare with those of other sharks. Contractile properties of the RM were examined at 8, 16 and 24 °C from anterior and posterior axial positions (0.4 and 0.6 fork length, respectively) using the work loop technique. Experiments were performed to determine whether the contractile properties of the RM are similar along the body of the common thresher shark and to document the effects of temperature on muscle power. Axial differences in contractile properties of RM were found to be small or absent. Isometric twitch kinetics of RM were ~fivefold slower than those of white muscle, with RM twitch durations of about 1 s at 24 °C and exceeding 5 s at 8 °C, a Q(10) of nearly 2.5. Power increased approximately tenfold with the 16 °C increase in temperature, while the cycle frequency for maximal power only increased from about 0.5-1.0 Hz over this temperature range. These data support the hypothesis that the RM is functionally similar along the body of the common thresher shark and corroborate previous findings from shark species both with and without medial RM. While twitch kinetics suggest the endothermic RM is not unusually temperature sensitive, measures of power suggest that the RM is not well suited to function at cool temperatures. The cycle frequency at which power is maximized appeared relatively insensitive to temperature in RM, which may reflect the relatively cooler temperature of the thresher RM compared to that observed in lamnid sharks as well as the relatively slow RM phenotype in these large fish.

Fiber-type-specific sensitivities and phenotypic adaptations to dietary fat overload differentially impact fast- versus slow-twitch muscle contractile function in C57BL/6J mice.

PubMed

Ciapaite, Jolita; van den Berg, Sjoerd A; Houten, Sander M; Nicolay, Klaas; van Dijk, Ko Willems; Jeneson, Jeroen A

2015-02-01

High-fat diets (HFDs) have been shown to interfere with skeletal muscle energy metabolism and cause peripheral insulin resistance. However, understanding of HFD impact on skeletal muscle primary function, i.e., contractile performance, is limited. Male C57BL/6J mice were fed HFD containing lard (HFL) or palm oil (HFP), or low-fat diet (LFD) for 5weeks. Fast-twitch (FT) extensor digitorum longus (EDL) and slow-twitch (ST) soleus muscles were characterized with respect to contractile function and selected biochemical features. In FT EDL muscle, a 30%-50% increase in fatty acid (FA) content and doubling of long-chain acylcarnitine (C14-C18) content in response to HFL and HFP feeding were accompanied by increase in protein levels of peroxisome proliferator-activated receptor-γ coactivator-1α, mitochondrial oxidative phosphorylation complexes and acyl-CoA dehydrogenases involved in mitochondrial FA β-oxidation. Peak force of FT EDL twitch and tetanic contractions was unaltered, but the relaxation time (RT) of twitch contractions was 30% slower compared to LFD controls. The latter was caused by accumulation of lipid intermediates rather than changes in the expression levels of proteins involved in calcium handling. In ST soleus muscle, no evidence for lipid overload was found in any HFD group. However, particularly in HFP group, the peak force of twitch and tetanic contractions was reduced, but RT was faster than LFD controls. The latter was associated with a fast-to-slow shift in troponin T isoform expression. Taken together, these data highlight fiber-type-specific sensitivities and phenotypic adaptations to dietary lipid overload that differentially impact fast- versus slow-twitch skeletal muscle contractile function. Copyright © 2015 Elsevier Inc. All rights reserved.

Combining cell sheet technology and electrospun scaffolding for engineered tubular, aligned, and contractile blood vessels.

PubMed

Rayatpisheh, Shahrzad; Heath, Daniel E; Shakouri, Amir; Rujitanaroj, Pim-On; Chew, Sing Yian; Chan-Park, Mary B

2014-03-01

Herein we combine cell sheet technology and electrospun scaffolding to rapidly generate circumferentially aligned tubular constructs of human aortic smooth muscles cells with contractile gene expression for use as tissue engineered blood vessel media. Smooth muscle cells cultured on micropatterned and N-isopropylacrylamide-grafted (pNIPAm) polydimethylsiloxane (PDMS), a small portion of which was covered by aligned electrospun scaffolding, resulted in a single sheet of unidirectionally aligned cells. Upon cooling to room temperature, the scaffold, its adherent cells, and the remaining cell sheet detached and were collected on a mandrel to generating tubular constructs with circumferentially aligned smooth muscle cells which possess contractile gene expression and a single layer of electrospun scaffold as an analogue to a small diameter blood vessel's internal elastic lamina (IEL). This method improves cell sheet handling, results in rapid circumferential alignment of smooth muscle cells which immediately express contractile genes, and introduction of an analogue to small diameter blood vessel IEL. Copyright © 2013 Elsevier Ltd. All rights reserved.

Ginseng Is Useful to Enhance Cardiac Contractility in Animals

PubMed Central

Cherng, Yih-Giun; Chen, Li-Jen; Niu, Ho-Shan; Chang, Chen Kuei; Niu, Chiang-Shan

2014-01-01

Ginseng has been shown to be effective on cardiac dysfunction. Recent evidence has highlighted the mediation of peroxisome proliferator-activated receptors (PPARs) in cardiac function. Thus, we are interested to investigate the role of PPARδ in ginseng-induced modification of cardiac contractility. The isolated hearts in Langendorff apparatus and hemodynamic analysis in catheterized rats were applied to measure the actions of ginseng ex vivo and in vivo. In normal rats, ginseng enhanced cardiac contractility and hemodynamic dP/dt max significantly. Both actions were diminished by GSK0660 at a dose enough to block PPARδ. However, ginseng failed to modify heart rate at the same dose, although it did produce a mild increase in blood pressure. Data of intracellular calcium level and Western blotting analysis showed that both the PPARδ expression and troponin I phosphorylation were raised by ginseng in neonatal rat cardiomyocyte. Thus, we suggest that ginseng could enhance cardiac contractility through increased PPARδ expression in cardiac cells. PMID:24689053

Regional Differences in Rat Vaginal Smooth Muscle Contractility and Morphology

PubMed Central

Skoczylas, Laura C.; Jallah, Zegbeh; Sugino, Yoshio; Stein, Suzan E.; Feola, Andrew; Yoshimura, Naoki

2013-01-01

The objective of this study was to define the regional differences in rat vaginal smooth muscle contractility and morphology. We evaluated circumferential segments from the proximal, middle, and distal rat vagina (n = 21) in vitro. Contractile responses to carbachol, phenylephrine, potassium chloride, and electrical field stimulation (EFS) were measured. Immunohistochemical analyses were also performed. The dose–response curves for carbachol- and phenylephrine-dependent contractions were different in the distal (P = .05, P = .04) compared to the proximal/middle regions. Adjusted for region-dependent changes in contractility, the distal vagina generated lower force in response to carbachol and higher force in response to phenylephrine. There was less force with increasing EFS frequency in the distal (P = .03), compared to the proximal/middle regions. Cholinergic versus adrenergic nerves were more frequent in the proximal region (P = .03). In summary, the results indicate that functional and morphological differences in smooth muscle and nerve fibers of the distal versus proximal/middle regions of the vagina exist. PMID:23298869

Multi-Physics MRI-Based Two-Layer Fluid-Structure Interaction Anisotropic Models of Human Right and Left Ventricles with Different Patch Materials: Cardiac Function Assessment and Mechanical Stress Analysis

PubMed Central

Tang, Dalin; Yang, Chun; Geva, Tal; Gaudette, Glenn; del Nido, Pedro J.

2011-01-01

Multi-physics right and left ventricle (RV/LV) fluid-structure interaction (FSI) models were introduced to perform mechanical stress analysis and evaluate the effect of patch materials on RV function. The FSI models included three different patch materials (Dacron scaffold, treated pericardium, and contracting myocardium), two-layer construction, fiber orientation, and active anisotropic material properties. The models were constructed based on cardiac magnetic resonance (CMR) images acquired from a patient with severe RV dilatation and solved by ADINA. Our results indicate that the patch model with contracting myocardium leads to decreased stress level in the patch area, improved RV function and patch area contractility. PMID:21765559

[Resistance of the functional systems of the smooth muscle cells of isolated myometrium to long-term incubation in Ringer-Locke solution at 4 degrees C].

PubMed

Peshikov, V L; Tsirkin, V I; Burmistrova, T D; Bordunovskaia, V P

1977-09-01

Contractile effects of adrenaline, acethylcholine and hyperpotassium solution on the isolated myometrium strips (non-pregnent rats, and women; pregnant rabbits, cats, and women) are studied. The amplitudes of these contractile effects were seen decreasing if the strips were previously immersed in the Ringer-Lokk solution at 4 degrees C 5--9 days prior to observation.

Some Fundamental Molecular Mechanisms of Contractility in Fibrous Macromolecules

PubMed Central

Mandelkern, L.

1967-01-01

The fundamental molecular mechanisms of contractility and tension development in fibrous macromolecules are developed from the point of view of the principles of polymer physical chemistry. The problem is treated in a general manner to encompass the behavior of all macromolecular systems irrespective of their detailed chemical structure and particular function, if any. Primary attention is given to the contractile process which accompanies the crystal-liquid transition in axially oriented macromolecular systems. The theoretical nature of the process is discussed, and many experimental examples are given from the literature which demonstrate the expected behavior. Experimental attention is focused on the contraction of fibrous proteins, and the same underlying molecular mechanism is shown to be operative for a variety of different systems. PMID:6050598

Body weight-supported training in Becker and limb girdle 2I muscular dystrophy.

PubMed

Jensen, Bente R; Berthelsen, Martin P; Husu, Edith; Christensen, Sofie B; Prahm, Kira P; Vissing, John

2016-08-01

We studied the functional effects of combined strength and aerobic anti-gravity training in severely affected patients with Becker and Limb-Girdle muscular dystrophies. Eight patients performed 10-week progressive combined strength (squats, calf raises, lunges) and aerobic (walk/run, jogging in place or high knee-lift) training 3 times/week in a lower-body positive pressure environment. Closed-kinetic-chain leg muscle strength, isometric knee strength, rate of force development (RFD), and reaction time were evaluated. Baseline data indicated an intact neural activation pattern but showed compromised muscle contractile properties. Training (compliance 91%) improved functional leg muscle strength. Squat series performance increased 30%, calf raises 45%, and lunges 23%. Anti-gravity training improved closed-kinetic-chain leg muscle strength despite no changes in isometric knee extension strength and absolute RFD. The improved closed-kinetic-chain performance may relate to neural adaptation involving motor learning and/or improved muscle strength of other muscles than the weak knee extensors. Muscle Nerve 54: 239-243, 2016. © 2016 Wiley Periodicals, Inc.

Differences in Contractile Function of Myofibrils within Human Embryonic Stem Cell-Derived Cardiomyocytes vs. Adult Ventricular Myofibrils Are Related to Distinct Sarcomeric Protein Isoforms

PubMed Central

Iorga, Bogdan; Schwanke, Kristin; Weber, Natalie; Wendland, Meike; Greten, Stephan; Piep, Birgit; dos Remedios, Cristobal G.; Martin, Ulrich; Zweigerdt, Robert; Kraft, Theresia; Brenner, Bernhard

2018-01-01

Characterizing the contractile function of human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) is key for advancing their utility for cellular disease models, promoting cell based heart repair, or developing novel pharmacological interventions targeting cardiac diseases. The aim of the present study was to understand whether steady-state and kinetic force parameters of β-myosin heavy chain (βMyHC) isoform-expressing myofibrils within human embryonic stem cell-derived cardiomyocytes (hESC-CMs) differentiated in vitro resemble those of human ventricular myofibrils (hvMFs) isolated from adult donor hearts. Contractile parameters were determined using the same micromechanical method and experimental conditions for both types of myofibrils. We identified isoforms and phosphorylation of main sarcomeric proteins involved in the modulation of force generation of both, chemically demembranated hESC-CMs (d-hESC-CMs) and hvMFs. Our results indicate that at saturating Ca2+ concentration, both human-derived contractile systems developed forces with similar rate constants (0.66 and 0.68 s−1), reaching maximum isometric force that was significantly smaller for d-hESC-CMs (42 kPa) than for hvMFs (94 kPa). At submaximal Ca2+-activation, where intact cardiomyocytes normally operate, contractile parameters of d-hESC-CMs and hvMFs exhibited differences. Ca2+ sensitivity of force was higher for d-hESC-CMs (pCa50 = 6.04) than for hvMFs (pCa50 = 5.80). At half-maximum activation, the rate constant for force redevelopment was significantly faster for d-hESC-CMs (0.51 s−1) than for hvMFs (0.28 s−1). During myofibril relaxation, kinetics of the slow force decay phase were significantly faster for d-hESC-CMs (0.26 s−1) than for hvMFs (0.21 s−1), while kinetics of the fast force decay were similar and ~20x faster. Protein analysis revealed that hESC-CMs had essentially no cardiac troponin-I, and partially non-ventricular isoforms of some other sarcomeric proteins, explaining the functional discrepancies. The sarcomeric protein isoform pattern of hESC-CMs had features of human cardiomyocytes at an early developmental stage. The study indicates that morphological and ultrastructural maturation of βMyHC isoform-expressing hESC-CMs is not necessarily accompanied by ventricular-like expression of all sarcomeric proteins. Our data suggest that hPSC-CMs could provide useful tools for investigating inherited cardiac diseases affecting contractile function during early developmental stages. PMID:29403388

Mast cells regulate myofilament calcium sensitization and heart function after myocardial infarction

PubMed Central

Richart, Adèle; Vilar, Jose; Lemitre, Mathilde; Marck, Pauline; Branchereau, Maxime; Guerin, Coralie; Gautier, Gregory; Blank, Ulrich; Heymes, Christophe; Luche, Elodie; Cousin, Béatrice; Rodewald, Hans-Reimer

2016-01-01

Acute myocardial infarction (MI) is a severe ischemic disease responsible for heart failure and sudden death. Inflammatory cells orchestrate postischemic cardiac remodeling after MI. Studies using mice with defective mast/stem cell growth factor receptor c-Kit have suggested key roles for mast cells (MCs) in postischemic cardiac remodeling. Because c-Kit mutations affect multiple cell types of both immune and nonimmune origin, we addressed the impact of MCs on cardiac function after MI, using the c-Kit–independent MC-deficient (Cpa3Cre/+) mice. In response to MI, MC progenitors originated primarily from white adipose tissue, infiltrated the heart, and differentiated into mature MCs. MC deficiency led to reduced postischemic cardiac function and depressed cardiomyocyte contractility caused by myofilament Ca2+ desensitization. This effect correlated with increased protein kinase A (PKA) activity and hyperphosphorylation of its targets, troponin I and myosin-binding protein C. MC-specific tryptase was identified to regulate PKA activity in cardiomyocytes via protease-activated receptor 2 proteolysis. This work reveals a novel function for cardiac MCs modulating cardiomyocyte contractility via alteration of PKA-regulated force–Ca2+ interactions in response to MI. Identification of this MC-cardiomyocyte cross-talk provides new insights on the cellular and molecular mechanisms regulating the cardiac contractile machinery and a novel platform for therapeutically addressable regulators. PMID:27353089

Sex differences and the effects of ovariectomy on the β-adrenergic contractile response

PubMed Central

McIntosh, Victoria J.; Chandrasekera, P. Charukeshi

2011-01-01

The presence of sex differences in myocardial β-adrenergic responsiveness is controversial, and limited studies have addressed the mechanism underlying these differences. Studies were performed using isolated perfused hearts from male, intact female and ovariectomized female mice to investigate sex differences and the effects of ovarian hormone withdrawal on β-adrenergic receptor function. Female hearts exhibited blunted contractile responses to the β-adrenergic receptor agonist isoproterenol (ISO) compared with males but not ovariectomized females. There were no sex differences in β1-adrenergic receptor gene or protein expression. To investigate the role of adenylyl cyclase, phosphodiesterase, and the cAMP-signaling cascade in generating sex differences in the β-adrenergic contractile response, dose-response studies were performed in isolated perfused male and female hearts using forskolin, 3-isobutyl-1-methylxanthine (IBMX), and 8-(4-chlorophenylthio)adenosine 3′,5′-cyclic monophosphate (CPT-cAMP). Males showed a modestly enhanced contractile response to forskolin at 300 nM and 5 μM compared with females, but there were no sex differences in the response to IBMX or CPT-cAMP. The role of the A1 adenosine receptor (A1AR) in antagonizing the β-adrenergic contractile response was investigated using both the A1AR agonist 2-chloro-N6-cyclopentyl-adenosine and A1AR knockout (KO) mice. Intact females showed an enhanced A1AR anti-adrenergic effect compared with males and ovariectomized females. The β-adrenergic contractile response was potentiated in both male and female A1ARKO hearts, with sex differences no longer present above 1 nM ISO. The β-adrenergic contractile response is greater in male hearts than females, and minor differences in the action of adenylyl cyclase or the A1AR may contribute to these sex differences. PMID:21685268

Physiological response of cardiac tissue to bisphenol a: alterations in ventricular pressure and contractility

PubMed Central

Brooks, Daina; Chandra, Akhil; Jaimes, Rafael; Sarvazyan, Narine; Kay, Matthew

2015-01-01

Biomonitoring studies have indicated that humans are routinely exposed to bisphenol A (BPA), a chemical that is commonly used in the production of polycarbonate plastics and epoxy resins. Epidemiological studies have shown that BPA exposure in humans is associated with cardiovascular disease; however, the direct effects of BPA on cardiac physiology are largely unknown. Previously, we have shown that BPA exposure slows atrioventricular electrical conduction, decreases epicardial conduction velocity, and prolongs action potential duration in excised rat hearts. In the present study, we tested if BPA exposure also adversely affects cardiac contractile performance. We examined the impact of BPA exposure level, sex, and pacing rate on cardiac contractile function in excised rat hearts. Hearts were retrogradely perfused at constant pressure and exposed to 10−9-10−4 M BPA. Left ventricular developed pressure and contractility were measured during sinus rhythm and during pacing (5, 6.5, and 9 Hz). Ca2+ transients were imaged from whole hearts and from neonatal rat cardiomyocyte layers. During sinus rhythm in female hearts, BPA exposure decreased left ventricular developed pressure and inotropy in a dose-dependent manner. The reduced contractile performance was exacerbated at higher pacing rates. BPA-induced effects on contractile performance were also observed in male hearts, albeit to a lesser extent. Exposure to BPA altered Ca2+ handling within whole hearts (reduced diastolic and systolic Ca2+ transient potentiation) and neonatal cardiomyocytes (reduced Ca2+ transient amplitude and prolonged Ca2+ transient release time). In conclusion, BPA exposure significantly impaired cardiac performance in a dose-dependent manner, having a major negative impact upon electrical conduction, intracellular Ca2+ handing, and ventricular contractility. PMID:25980024

Activation of Toll-like receptor 3 increases mouse aortic vascular smooth muscle cell contractility through ERK1/2 pathway.

PubMed

Hardigan, Trevor; Spitler, Kathryn; Matsumoto, Takayuki; Carrillo-Sepulveda, Maria Alicia

2015-11-01

Activation of Toll-like receptor 3 (TLR3), a pattern recognition receptor of the innate immune system, is associated with vascular complications. However, whether activation of TLR3 alters vascular contractility is unknown. We, therefore, hypothesized that TLR3 activation augments vascular contractility and activates vascular smooth muscle cell (VSMC) contractile apparatus proteins. Male mice were treated with polyinosinic-polycytidylic acid (Poly I:C group, 14 days), a TLR3 agonist; control mice received saline (vehicle, 14 days). At the end of protocol, blood pressure was measured by tail cuff method. Aortas were isolated and assessed for contractility experiments using a wire myograph. Aortic protein content was used to determine phosphorylated/total interferon regulatory factor 3 (IRF3), a downstream target of TLR3 signaling, and ERK1/2 using Western blot. We investigated the TLR3/IRF3/ERK1/2 signaling pathway and contractile-related proteins such as phosphorylated/total myosin light chain (MLC) and caldesmon (CaD) in aortic VSMC primary cultures. Poly I:C-treated mice exhibited (vs. vehicle-treated mice) (1) elevated systolic blood pressure. Moreover, Poly I:C treatment (2) enhanced aortic phenylephrine-induced maximum contraction, which was suppressed by PD98059 (ERK1/2 inhibitor), and (3) increased aortic levels of phosphorylated IRF3 and ERK1/2. Stimulation of mouse aortic VSMCs with Poly I:C resulted in increased phosphorylation of IRF3, ERK1/2, MLC, and CaD. Inhibition of ERK1/2 abolished Poly I:C-mediated phosphorylation of MLC and CaD. Our data provide functional evidence for the role of TLR3 in vascular contractile events, suggesting TLR3 as a potential new therapeutic target in vascular dysfunction and regulation of blood pressure.

Aging and CaMKII Alter Intracellular Ca2+ Transients and Heart Rhythm in Drosophila melanogaster

PubMed Central

Santalla, Manuela; Valverde, Carlos A.; Harnichar, Ezequiel; Lacunza, Ezequiel; Aguilar-Fuentes, Javier; Mattiazzi, Alicia; Ferrero, Paola

2014-01-01

Aging is associated to disrupted contractility and rhythmicity, among other cardiovascular alterations. Drosophila melanogaster shows a pattern of aging similar to human beings and recapitulates the arrhythmogenic conditions found in the human heart. Moreover, the kinase CaMKII has been characterized as an important regulator of heart function and an arrhythmogenic molecule that participate in Ca2+ handling. Using a genetically engineered expressed Ca2+ indicator, we report changes in cardiac Ca2+ handling at two different ages. Aging prolonged relaxation, reduced spontaneous heart rate (HR) and increased the occurrence of arrhythmias, ectopic beats and asystoles. Alignment between Drosophila melanogaster and human CaMKII showed a high degree of conservation and indicates that relevant phosphorylation sites in humans are also present in the fruit fly. Inhibition of CaMKII by KN-93 (CaMKII-specific inhibitor), reduced HR without significant changes in other parameters. By contrast, overexpression of CaMKII increased HR and reduced arrhythmias. Moreover, it increased fluorescence amplitude, maximal rate of rise of fluorescence and reduced time to peak fluorescence. These results suggest that CaMKII in Drosophila melanogaster acts directly on heart function and that increasing CaMKII expression levels could be beneficial to improve contractility. PMID:25003749

Neuromotor control in chronic obstructive pulmonary disease.

PubMed

Mantilla, Carlos B; Sieck, Gary C

2013-05-01

Neuromotor control of skeletal muscles, including respiratory muscles, is ultimately dependent on the structure and function of the motor units (motoneurons and the muscle fibers they innervate) comprising the muscle. In most muscles, considerable diversity of contractile and fatigue properties exists across motor units, allowing a range of motor behaviors. In diseases such as chronic obstructive pulmonary disease (COPD), there may be disproportional primary (disease related) or secondary effects (related to treatment or other concomitant factors) on the size and contractility of specific muscle fiber types that would influence the relative contribution of different motor units. For example, with COPD there is a disproportionate atrophy of type IIx and/or IIb fibers that comprise more fatigable motor units. Thus fatigue resistance may appear to improve, while overall motor performance (e.g., 6-min walk test) and endurance (e.g., reduced aerobic exercise capacity) are diminished. There are many coexisting factors that might also influence motor performance. For example, in COPD patients, there may be concomitant hypoxia and/or hypercapnia, physical inactivity and unloading of muscles, and corticosteroid treatment, all of which may disproportionately affect specific muscle fiber types, thereby influencing neuromotor control. Future studies should address how plasticity in motor units can be harnessed to mitigate the functional impact of COPD-induced changes.

Ineffective and prolonged apical contraction is associated with chest pain and ischaemia in apical hypertrophic cardiomyopathy.

PubMed

Stephenson, Edward; Monney, Pierre; Pugliese, Francesca; Malcolmson, James; Petersen, Steffen E; Knight, Charles; Mills, Peter; Wragg, Andrew; O'Mahony, Constantinos; Sekhri, Neha; Mohiddin, Saidi A

2018-01-15

To investigate the hypothesis that persistence of apical contraction into diastole is linked to reduced myocardial perfusion and chest pain. Apical hypertrophic cardiomyopathy (HCM) is defined by left ventricular (LV) hypertrophy predominantly of the apex. Hyperdynamic contractility resulting in obliteration of the apical cavity is often present. Apical HCM can lead to drug-refractory chest pain. We retrospectively studied 126 subjects; 76 with apical HCM and 50 controls (31 with asymmetrical septal hypertrophy (ASH) and 19 with non-cardiac chest pain and culprit free angiograms and structurally normal hearts). Perfusion cardiac magnetic resonance imaging (CMR) scans were assessed for myocardial perfusion reserve index (MPRi), late gadolinium enhancement (LGE), LV volumes (muscle and cavity) and regional contractile persistence (apex, mid and basal LV). In apical HCM, apical MPRi was lower than in normal and ASH controls (p<0.05). In apical HCM, duration of contractile persistence was associated with lower MPRi (p<0.01) and chest pain (p<0.05). In multivariate regression, contractile persistence was independently associated with chest pain (p<0.01) and reduced MPRi (p<0.001). In apical HCM, regional contractile persistence is associated with impaired myocardial perfusion and chest pain. As apical myocardium makes limited contributions to stroke volume, apical contractility is also largely ineffective. Interventions to reduce apical contraction and/or muscle mass are potential therapies for improving symptoms without reducing cardiac output. Copyright © 2017 Elsevier B.V. All rights reserved.

[Role of sialic acid loss in the myocardium in depressing the contractile function of the heart muscle during stress].

PubMed

Meerson, F Z; Saulia, A I; Gudumak, V S

1985-01-01

Under conditions of stress a time-dependent decrease in content of sialic acids was found in adult rats; within 9 hrs of the animal immobilization the sialic acid content was decreased by 40% as compared with controls. At the same time, activities of trypsin and LDHI were increased in blood serum. The data obtained suggest that activation of proteases occurring during the stress led to increased hydrolysis of base components of glycocalyx and to impairment of the cardiomyocyte sarcolemma. These phenomena appear to be responsible for the post-stress deterioration of heart muscle contractile functions.

TRPA1-dependent regulation of bladder detrusor smooth muscle contractility in normal and type I diabetic rats

PubMed Central

Philyppov, Igor B.; Paduraru, Oksana N.; Gulak, Kseniya L.; Skryma, Roman; Prevarskaya, Natalia; Shuba, Yaroslav M.

2016-01-01

TRPA1 is a Ca2+-permeable cation channel that is activated by painful low temperatures (˂17 °C), irritating chemicals, reactive metabolites and mediators of inflammation. In the bladder TRPA1 is predominantly expressed in sensory afferent nerve endings, where it mediates sensory transduction. The contractile effect of its activation on detrusor smooth muscle (DSM) is explained by the release from sensory afferents of inflammatory factors – tachykinins and prostaglandins, which cause smooth muscle cell contraction. Diabetes is a systemic disease, with common complications being diabetic cystopathies and urinary incontinence. However, data on how diabetes affects bladder contractility associated with TRPA1 activation are not available. In this study, by using a rat model with streptozotocin-induced type I diabetes, contractility measurements of DSM strips in response to TRPA1-activating and modulating pharmacological agents and assessment of TRPA1 mRNA expression in bladder-innervating dorsal root ganglia, we have shown that diabetes enhances the TRPA1-dependent mechanism involved in bladder DSM contractility. This is not due to changes in TRPA1 expression, but mainly due to the general inflammatory reaction caused by diabetes. The latter leads to an increase in cyclooxygenase-2-dependent prostaglandin synthesis through the mechanisms associated with substance P activity. This results in the enhanced functional coupling between the tachykinin and prostanoid systems, and the concomitant increase of their impact on DSM contractility in response to TRPA1 activation. PMID:26935999

TRPA1-dependent regulation of bladder detrusor smooth muscle contractility in normal and type I diabetic rats.

PubMed

Philyppov, Igor B; Paduraru, Oksana N; Gulak, Kseniya L; Skryma, Roman; Prevarskaya, Natalia; Shuba, Yaroslav M

2016-01-01

TRPA1 is a Ca(2+)-permeable cation channel that is activated by painful low temperatures (<17°C), irritating chemicals, reactive metabolites and mediators of inflammation. In the bladder TRPA1 is predominantly expressed in sensory afferent nerve endings, where it mediates sensory transduction. The contractile effect of its activation on detrusor smooth muscle (DSM) is explained by the release from sensory afferents of inflammatory factors - tachykinins and prostaglandins, which cause smooth muscle cell contraction. Diabetes is a systemic disease, with common complications being diabetic cystopathies and urinary incontinence. However, data on how diabetes affects bladder contractility associated with TRPA1 activation are not available. In this study, by using a rat model with streptozotocin-induced type I diabetes, contractility measurements of DSM strips in response to TRPA1-activating and modulating pharmacological agents and assessment of TRPA1 mRNA expression in bladder-innervating dorsal root ganglia, we have shown that diabetes enhances the TRPA1-dependent mechanism involved in bladder DSM contractility. This is not due to changes in TRPA1 expression, but mainly due to the general inflammatory reaction caused by diabetes. The latter leads to an increase in cyclooxygenase-2-dependent prostaglandin synthesis through the mechanisms associated with substance P activity. This results in the enhanced functional coupling between the tachykinin and prostanoid systems, and the concomitant increase of their impact on DSM contractility in response to TRPA1 activation.

Reduced force of diaphragm muscle fibers in patients with chronic thromboembolic pulmonary hypertension

PubMed Central

Manders, Emmy; Bonta, Peter I.; Kloek, Jaap J.; Symersky, Petr; Bogaard, Harm-Jan; Hooijman, Pleuni E.; Jasper, Jeff R.; Malik, Fady I.; Stienen, Ger J. M.; Vonk-Noordegraaf, Anton; de Man, Frances S.

2016-01-01

Patients with pulmonary hypertension (PH) suffer from inspiratory muscle weakness. However, the pathophysiology of inspiratory muscle dysfunction in PH is unknown. We hypothesized that weakness of the diaphragm, the main inspiratory muscle, is an important contributor to inspiratory muscle dysfunction in PH patients. Our objective was to combine ex vivo diaphragm muscle fiber contractility measurements with measures of in vivo inspiratory muscle function in chronic thromboembolic pulmonary hypertension (CTEPH) patients. To assess diaphragm muscle contractility, function was studied in vivo by maximum inspiratory pressure (MIP) and ex vivo in diaphragm biopsies of the same CTEPH patients (N = 13) obtained during pulmonary endarterectomy. Patients undergoing elective lung surgery served as controls (N = 15). Muscle fiber cross-sectional area (CSA) was determined in cryosections and contractility in permeabilized muscle fibers. Diaphragm muscle fiber CSA was not significantly different between control and CTEPH patients in both slow-twitch and fast-twitch fibers. Maximal force-generating capacity was significantly lower in slow-twitch muscle fibers of CTEPH patients, whereas no difference was observed in fast-twitch muscle fibers. The maximal force of diaphragm muscle fibers correlated significantly with MIP. The calcium sensitivity of force generation was significantly reduced in fast-twitch muscle fibers of CTEPH patients, resulting in a ∼40% reduction of submaximal force generation. The fast skeletal troponin activator CK-2066260 (5 μM) restored submaximal force generation to levels exceeding those observed in control subjects. In conclusion, diaphragm muscle fiber contractility is hampered in CTEPH patients and contributes to the reduced function of the inspiratory muscles in CTEPH patients. PMID:27190061

Administration of imatinib mesylate in rats impairs the neonatal development of intramuscular interstitial cells in bladder and results in altered contractile properties.

PubMed

Gevaert, Thomas; Hutchings, Graham; Everaerts, Wouter; Prenen, Hans; Roskams, Tania; Nilius, Bernd; De Ridder, Dirk

2014-04-01

The KIT receptor is considered as a reliable marker for a subpopulation of interstitial cells (IC), and by persistent neonatal inhibition of KIT we have investigated the role of this receptor in the development of IC-networks in bladder and we have observed the functional consequences of this inhibition. Newborn rat pups were treated daily with the KIT inhibitor imatinib mesylate (IM). After 7 days animals were sacrificed and bladder samples were dissected for morphological and functional studies. Morphological research consisted of immunohistochemistry with IC specific antigens (KIT and vimentin) and electron microscopy. The functional studies were based on isolated bladder strips in organ baths, in which spontaneous bladder contractility and the response to a non-subtype selective muscarinic agonist was evaluated. Suburothelial and intramuscular IC were found and characterized in neonatal rat bladder. IM-treatment induced a significant decrease in numbers of IC based on specific immunohistochemical markers, and electron microscopy revealed evidence of IC cell injury. These morphological alterations were observed on intramuscular IC only and not on IC in the suburothelium. Isolated muscle strips from IM-treated animals had a lower contractile frequency and an altered response to muscarinic agonists. The present study shows the presence of regional subpopulations of IC in neonatal rat bladder, provides evidence for a dependence on KIT of the development of intramuscular IC and supports the hypothesis that a poor development of networks of intramuscular IC might have repercussions on spontaneous and muscarinic-induced bladder contractility. © 2013 Wiley Periodicals, Inc.

Reduced Radial Displacement of the Gastrocnemius Medialis Muscle After Electrically Elicited Fatigue.

PubMed

Macgregor, Lewis J; Ditroilo, Massimiliano; Smith, Iain J; Fairweather, Malcolm M; Hunter, Angus M

2016-08-01

Assessments of skeletal-muscle functional capacity often necessitate maximal contractile effort, which exacerbates muscle fatigue or injury. Tensiomyography (TMG) has been investigated as a means to assess muscle contractile function after fatigue; however, observations have not been contextualized by concurrent physiological measures. To measure peripheral-fatigue-induced alterations in mechanical and contractile properties of the plantar-flexor muscles through noninvasive TMG concurrently with maximal voluntary contraction (MVC) and passive muscle tension (PMT) to validate TMG as a gauge of peripheral fatigue. Pre- and posttest intervention with control. University laboratory. 21 healthy male volunteers. Subjects' plantar flexors were tested for TMG parameters, along with MVC and PMT, before and after either a 5-min rest period (control) or a 5-min electrical-stimulation intervention (fatigue). Temporal (contraction velocity) and spatial (radial displacement) contractile parameters of the gastrocnemius medialis were recorded through TMG. MVC was measured as an indicator of muscle fatigue, and PMT was measured to assess muscle stiffness. Radial displacement demonstrated a fatigue-associated reduction (3.3 ± 1.2 vs 4.0 ± 1.4 mm, P = .031), while contraction velocity remained unaltered. In addition, MVC significantly declined by 122.6 ± 104 N (P < .001) after stimulation (fatigue). PMT was significantly increased after fatigue (139.8 ± 54.3 vs 111.3 ± 44.6 N, P = .007). TMG successfully detected fatigue, evident from reduced MVC, by displaying impaired muscle displacement accompanied by elevated PMT. TMG could be useful in establishing skeletal-muscle fatigue status without exacerbating the functional decrement of the muscle.

The retardation of myometrial infiltration, reduction of uterine contractility, and alleviation of generalized hyperalgesia in mice with induced adenomyosis by levo-tetrahydropalmatine (l-THP) and andrographolide.

PubMed

Mao, Xiaoyan; Wang, Yuedong; Carter, Andrew V; Zhen, Xuechu; Guo, Sun-Wei

2011-10-01

Adenomyosis is a tough disease to manage nonsurgically. Levo-tetrahydropalmatine (l-THP), a known analgesic, and andrographolide, a nuclear factor kappa B (NF-κB) inhibitor, are both active ingredients extracted from Chinese medicinal herbs. We sought to determine whether treatment of l-THP, andrographolide, and valproic acid (VPA) would suppress the myometrial infiltration, improve pain behavior, and reduce uterine contractility in a mice model of adenomyosis. Adenomyosis was induced in 55 female ICR mice neonatally dosed with tamoxifen, while another 8 (group C) were dosed with solvent only. Starting from 4 weeks after birth, hotplate test was administrated to all mice every 4 weeks. At the 16th week, all mice with induced adenomyosis were randomly divided into 6 groups, each receiving different treatment for 3 weeks: low- or high-dose l-THP, andrographolide, low-dose l-THP and andrographolide jointly, VPA, and untreated. Group C received no treatment. After treatment, the hotplate test was administered and all mice were killed. The depth of myometrial infiltration of ectopic endometrium and uterine contractility were measured and compared across groups. We found that induction of adenomyosis resulted in progressive generalized hyperalgesia, along with elevated amplitude and irregularity of uterine contractions. Treatment with either l-THP, andrographolide, VPA, or l-THP and andrographolide jointly suppressed myometrial infiltration, improved generalized hyperalgesia, and reduced the amplitude and irregularity of uterine contractions. These results suggest that increased uterine contractility, in the form of increased contractile amplitude and irregularity, may contribute to dysmenorrhea in women with adenomyosis. More importantly, l-THP, andrographolide, and VPA all seem to be promising compounds for treating adenomyosis.

Coupled expression of troponin T and troponin I isoforms in single skeletal muscle fibers correlates with contractility.

PubMed

Brotto, Marco A; Biesiadecki, Brandon J; Brotto, Leticia S; Nosek, Thomas M; Jin, Jian-Ping

2006-02-01

Striated muscle contraction is powered by actin-activated myosin ATPase. This process is regulated by Ca(2+) via the troponin complex. Slow- and fast-twitch fibers of vertebrate skeletal muscle express type I and type II myosin, respectively, and these myosin isoenzymes confer different ATPase activities, contractile velocities, and force. Skeletal muscle troponin has also diverged into fast and slow isoforms, but their functional significance is not fully understood. To investigate the expression of troponin isoforms in mammalian skeletal muscle and their functional relationship to that of the myosin isoforms, we concomitantly studied myosin, troponin T (TnT), and troponin I (TnI) isoform contents and isometric contractile properties in single fibers of rat skeletal muscle. We characterized a large number of Triton X-100-skinned single fibers from soleus, diaphragm, gastrocnemius, and extensor digitorum longus muscles and selected fibers with combinations of a single myosin isoform and a single class (slow or fast) of the TnT and TnI isoforms to investigate their role in determining contractility. Types IIa, IIx, and IIb myosin fibers produced higher isometric force than that of type I fibers. Despite the polyploidy of adult skeletal muscle fibers, the expression of fast or slow isoforms of TnT and TnI is tightly coupled. Fibers containing slow troponin had higher Ca(2+) sensitivity than that of the fast troponin fibers, whereas fibers containing fast troponin showed a higher cooperativity of Ca(2+) activation than that of the slow troponin fibers. These results demonstrate distinct but coordinated regulation of troponin and myosin isoform expression in skeletal muscle and their contribution to the contractile properties of muscle.

Coupled expression of troponin T and troponin I isoforms in single skeletal muscle fibers correlates with contractility

PubMed Central

BROTTO, MARCO A.; BIESIADECKI, BRANDON J.; BROTTO, LETICIA S.; NOSEK, THOMAS M; JIN, J.-P.

2005-01-01

(Summary) Brotto, Marco A., Brandon J. Biesiadecki, Leticia S. Brotto, Thomas M. Nosek, and J.-P. Jin. Striated muscle contraction is powered by actin-activated myosin ATPase. This process is regulated by Ca2+ via the troponin complex. Slow and fast twitch fibers of vertebrate skeletal muscle express type I and type II myosin, respectively, and these myosin isoenzymes confer different ATPase activities, contractile velocities and force. Skeletal muscle troponin has also diverged into fast and slow isoforms, but their functional significance is not fully understood. To investigate the expression of troponin isoforms in mammalian skeletal muscle and their functional relationship to that of the myosin isoforms, we concomitantly studied myosin and troponin T (TnT) and troponin I (TnI) isoform contents and isometric contractile properties in single fibers of rat skeletal muscle. We characterized a large number of Triton skinned single fibers from soleus, diaphragm, gastrocnemius and extensor digitorum longus muscles and selected fibers with combinations of a single myosin isoform and a single class (slow or fast) of TnT and TnI isoform to investigate their role in determining contractility. Type IIa, IIx and IIb myosin fibers produced higher isometric force than that of type I fibers. Despite the polyploidy of adult skeletal muscle fibers, the expression of fast or slow isoforms of TnT and TnI is tightly coupled. Fibers containing slow troponin had higher Ca2+ sensitivity than that of the fast troponin fibers, while fibers containing fast troponin showed a higher cooperativity of Ca2+ activation than that of the slow troponin fibers. The results demonstrate distinctive, but coordinated, regulation of troponin and myosin isoform expression in skeletal muscle and their contribution to the contractile properties. PMID:16192301

Effects of commonly used inotropes on myocardial function and oxygen consumption under constant ventricular loading conditions

PubMed Central

DeWitt, Elizabeth S.; Black, Katherine J.; Thiagarajan, Ravi R.; DiNardo, James A.; Colan, Steven D.; McGowan, Francis X.

2016-01-01

Inotropic medications are routinely used to increase cardiac output and arterial blood pressure during critical illness. However, few comparative data exist between these medications, particularly independent of their effects on venous capacitance and systemic vascular resistance. We hypothesized that an isolated working heart model that maintained constant left atrial pressure and aortic blood pressure could identify load-independent differences between inotropic medications. In an isolated heart preparation, the aorta and left atrium of Sprague Dawley rats were cannulated and placed in working mode with fixed left atrial and aortic pressure. Hearts were then exposed to common doses of a catecholamine (dopamine, epinephrine, norepinephrine, or dobutamine), milrinone, or triiodothyronine (n = 10 per dose per combination). Cardiac output, contractility (dP/dtmax), diastolic performance (dP/dtmin and tau), stroke work, heart rate, and myocardial oxygen consumption were compared during each 10-min infusion to an immediately preceding baseline. Of the catecholamines, dobutamine increased cardiac output, contractility, and diastolic performance more than clinically equivalent doses of norepinephrine (second most potent), dopamine, or epinephrine (P < 0.001). The use of triiodothyronine and milrinone was not associated with significant changes in cardiac output, contractility or diastolic function, either alone or added to a baseline catecholamine infusion. Myocardial oxygen consumption was closely related to dP/dtmax (r2 = 0.72), dP/dtmin (r2 = 0.70), and stroke work (r2 = 0.53). In uninjured, isolated working rodent hearts under constant ventricular loading conditions, dobutamine increased contractility and cardiac output more than clinically equivalent doses of norepinephrine, dopamine, and epinephrine; milrinone and triiodothyronine did not have significant effects on contractility. PMID:27150829

LET-99 functions in the astral furrowing pathway, where it is required for myosin enrichment in the contractile ring

PubMed Central

Price, Kari L.; Rose, Lesilee S.

2017-01-01

The anaphase spindle determines the position of the cytokinesis furrow, such that the contractile ring assembles in an equatorial zone between the two spindle poles. Contractile ring formation is mediated by RhoA activation at the equator by the centralspindlin complex and midzone microtubules. Astral microtubules also inhibit RhoA accumulation at the poles. In the Caenorhabditis elegans one-cell embryo, the astral microtubule–dependent pathway requires anillin, NOP-1, and LET-99. LET-99 is well characterized for generating the asymmetric cortical localization of the Gα-dependent force-generating complex that positions the spindle during asymmetric division. However, whether the role of LET-99 in cytokinesis is specific to asymmetric division and whether it acts through Gα to promote furrowing are unclear. Here we show that LET-99 contributes to furrowing in both asymmetrically and symmetrically dividing cells, independent of its function in spindle positioning and Gα regulation. LET-99 acts in a pathway parallel to anillin and is required for myosin enrichment into the contractile ring. These and other results suggest a positive feedback model in which LET-99 localizes to the presumptive cleavage furrow in response to the spindle and myosin. Once positioned there, LET-99 enhances myosin accumulation to promote furrowing in both symmetrically and asymmetrically dividing cells. PMID:28701343

Muscle Contractile Properties in Severely Burned Rats

PubMed Central

Wu, Xiaowu; Wolf, Steven E.; Walters, Thomas J.

2010-01-01

Burn induces a sustained catabolic response which causes massive loss of muscle mass after injury. A better understanding of the dynamics of muscle wasting and its impact on muscle function is necessary for the development of effective treatments. Male Sprague-Dawley rats underwent either a 40% total body surface area (TBSA) scald burn or sham burn, and were further assigned to subgroups at four time points after injury (days 3, 7, 14 and 21). In situ isometric contractile properties were measured including twitch tension (Pt), tetanic tension (Po) and fatigue properties. Body weight decreased in burn and sham groups through day 3, however, body weight in the sham groups recovered and increased over time compared to burned groups, which progressively decreased until day 21 after injury. Significant differences in muscle wet weight and protein weight were found between sham and burn. Significant differences in muscle contractile properties were found at day 14 with lower absolute Po as well as specific Po in burned rats compared to sham. After burn, the muscle twitch tension was significantly higher than the sham at day 21. No significant difference in fatigue properties was found between the groups. This study demonstrates dynamics of muscle atrophy and muscle contractile properties after severe burn; this understanding will aid in the development of approaches designed to reduce the rate and extent of burn induced muscle loss and function. PMID:20381255

Contractility in type III cochlear fibrocytes is dependent on non-muscle myosin II and intercellular gap junctional coupling.

PubMed

Kelly, John J; Forge, Andrew; Jagger, Daniel J

2012-08-01

The cochlear spiral ligament is a connective tissue that plays diverse roles in normal hearing. Spiral ligament fibrocytes are classified into functional sub-types that are proposed to carry out specialized roles in fluid homeostasis, the mediation of inflammatory responses to trauma, and the fine tuning of cochlear mechanics. We derived a secondary sub-culture from guinea pig spiral ligament, in which the cells expressed protein markers of type III or "tension" fibrocytes, including non-muscle myosin II (nmII), α-smooth muscle actin (αsma), vimentin, connexin43 (cx43), and aquaporin-1. The cells formed extensive stress fibers containing αsma, which were also associated intimately with nmII expression, and the cells displayed the mechanically contractile phenotype predicted by earlier modeling studies. cx43 immunofluorescence was evident within intercellular plaques, and the cells were coupled via dye-permeable gap junctions. Coupling was blocked by meclofenamic acid (MFA), an inhibitor of cx43-containing channels. The contraction of collagen lattice gels mediated by the cells could be prevented reversibly by blebbistatin, an inhibitor of nmII function. MFA also reduced the gel contraction, suggesting that intercellular coupling modulates contractility. The results demonstrate that these cells can impart nmII-dependent contractile force on a collagenous substrate, and support the hypothesis that type III fibrocytes regulate tension in the spiral ligament-basilar membrane complex, thereby determining auditory sensitivity.

AMP-Activated Protein Kinase Deficiency Rescues Paraquat-Induced Cardiac Contractile Dysfunction Through an Autophagy-Dependent Mechanism

PubMed Central

Wang, Qiurong; Yang, Lifang; Hua, Yinan; Nair, Sreejayan; Xu, Xihui; Ren, Jun

2014-01-01

Aim: Paraquat, a quaternary nitrogen herbicide, is a highly toxic prooxidant resulting in multi-organ failure including the heart although the underlying mechanism still remains elusive. This study was designed to examine the role of the cellular fuel sensor AMP-activated protein kinase (AMPK) in paraquat-induced cardiac contractile and mitochondrial injury. Results: Wild-type and transgenic mice with overexpression of a mutant AMPK α2 subunit (kinase dead, KD), with reduced activity in both α1 and α2 subunits, were administered with paraquat (45 mg/kg) for 48 h. Paraquat elicited cardiac mechanical anomalies including compromised echocardiographic parameters (elevated left ventricular end-systolic diameter and reduced factional shortening), suppressed cardiomyocyte contractile function, intracellular Ca2+ handling, reduced cell survival, and overt mitochondrial damage (loss in mitochondrial membrane potential). In addition, paraquat treatment promoted phosphorylation of AMPK and autophagy. Interestingly, deficiency in AMPK attenuated paraquat-induced cardiac contractile and intracellular Ca2+ derangement. The beneficial effect of AMPK inhibition was associated with inhibition of the AMPK-TSC-mTOR-ULK1 signaling cascade. In vitro study revealed that inhibitors for AMPK and autophagy attenuated paraquat-induced cardiomyocyte contractile dysfunction. Conclusion: Taken together, our findings revealed that AMPK may mediate paraquat-induced myocardial anomalies possibly by regulating the AMPK/mTOR-dependent autophagy. PMID:25092649

Drosophila F-BAR protein Syndapin contributes to coupling the plasma membrane and contractile ring in cytokinesis.

PubMed

Takeda, Tetsuya; Robinson, Iain M; Savoian, Matthew M; Griffiths, John R; Whetton, Anthony D; McMahon, Harvey T; Glover, David M

2013-08-07

Cytokinesis is a highly ordered cellular process driven by interactions between central spindle microtubules and the actomyosin contractile ring linked to the dynamic remodelling of the plasma membrane. The mechanisms responsible for reorganizing the plasma membrane at the cell equator and its coupling to the contractile ring in cytokinesis are poorly understood. We report here that Syndapin, a protein containing an F-BAR domain required for membrane curvature, contributes to the remodelling of the plasma membrane around the contractile ring for cytokinesis. Syndapin colocalizes with phosphatidylinositol 4,5-bisphosphate (PI(4,5)P₂) at the cleavage furrow, where it directly interacts with a contractile ring component, Anillin. Accordingly, Anillin is mislocalized during cytokinesis in Syndapin mutants. Elevated or diminished expression of Syndapin leads to cytokinesis defects with abnormal cortical dynamics. The minimal segment of Syndapin, which is able to localize to the cleavage furrow and induce cytokinesis defects, is the F-BAR domain and its immediate C-terminal sequences. Phosphorylation of this region prevents this functional interaction, resulting in reduced ability of Syndapin to bind to and deform membranes. Thus, the dephosphorylated form of Syndapin mediates both remodelling of the plasma membrane and its proper coupling to the cytokinetic machinery.

Dietary phytoestrogens maintain contractile responses to carbachol with age in the female rat isolated bladder.

PubMed

Owen, Suzzanne J; Rose'Meyer, Roselyn B; Massa, Helen M

2011-08-15

Development of urinary incontinence, for many women, occurs following menopause. Dietary phytoestrogens consumed over the long term may affect the contractile function and maintenance of the urinary bladder in post menopausal women. This study examined the muscarinic receptor mediated contractile responses in the rat isolated bladder in response to ovariectomy and long term dietary phytoestrogen consumption. Ovariectomised or sham-operated female Wistar rats (8 weeks) were fed either normal rat chow (soy, phytoestrogens) or a non-soy (phytoestrogen free) diet. Bladders were dissected from rats at 12, 24 and 52 weeks of age and placed in 25 ml organ baths filled with McEwans solution. The contractile response to carbachol, in 12 week old female rats did not change as a result of dietary phytoestrogens or ovariectomy (P>0.05). At 24 weeks of age, detrusor muscle strip responses to carbachol from non-soy fed ovariectomised rats were attenuated (P<0.05). At 52 weeks, bladder detrusor strip responses to carbachol were reduced in all treatment groups with the exception of the soy-fed sham operated rats. These results suggest an age-related reduction in the contractile response of the detrusor to the muscarinic receptor agonist carbachol, which may be prevented by long term dietary phytoestrogen intake. Copyright © 2011 Elsevier Inc. All rights reserved.

[A basis for application of cardiac contractility variability in the Evaluation and assessment of exercise and fitness].

PubMed

Bu, Bin; Wang, Aihua; Han, Haijun; Xiao, Shouzhong

2010-06-01

Cardiac contractility variability (CCV) is a new concept which is introduced in the research field of cardiac contractility in recent years, that is to say, there are some disparities between cardiac contractilities when heart contracts. The changing signals of cardiac contractility contain a plenty of information on the cardiovascular function and disorder. In order to collect and analyze the message, we could quantitatively evaluate the tonicity and equilibrium of cardiac sympathetic nerve and parasympathetic nerve, and the effects of bio-molecular mechanism on the cardiovascular activities. By analyzing CCV, we could further understand the background of human being's heritage characteristics, nerve types, the adjusting mechanism, the molecular biology, and the adjustment of cardiac automatic nerve. With the development of the computing techniques, the digital signal processing method and its application in medical field, this analysis has been progressing greatly. By now, the assessment of CCV, just like the analysis of heart rate variability, is mainly via time domain and frequency domain analysis. CCV is one of the latest research fields in human cardiac signals being scarcely reported in the field of sports medicine; however, its research progresses are of important value for cardiac physiology and pathology in sports medicine and rehabilitation medicine.

Insulin-Like Growth Factor I (IGF-1) Deficiency Ameliorates Sex Difference in Cardiac Contractile Function and Intracellular Ca2+ Homeostasis

PubMed Central

Ceylan-Isik, Asli F.; Li, Qun; Ren, Jun

2011-01-01

Sex difference in cardiac contractile function exists which may contribute to the different prevalence in cardiovascular diseases between genders. However, the precise mechanisms of action behind sex difference in cardiac function are still elusive. Given that sex difference exists in insulin-like growth factor I (IGF-1) cascade, this study is designed to evaluate the impact of severe liver IGF-1 deficiency (LID) on sex difference in cardiac function. Echocardiographic, cardiomyocyte contractile and intracellular Ca2+ properties were evaluated including ventricular geometry, fractional shortening, peak shortening, maximal velocity of shortening/relengthening (± dL/dt), time-to-peak shortening (TPS), time-to-90% relengthening (TR90), fura-fluorescence intensity (FFI) and intracellular Ca2+ clearance. Female C57 mice exhibited significantly higher plasma IGF-1 levels than their male counterpart. LID mice possessed comparably low IGF-1 levels in both sexes. Female C57 and LID mice displayed lower body, heart and liver weights compared to male counterparts. Echocardiographic analysis revealed larger LV mass in female C57 but not LID mice without sex difference in other cardiac geometric indices. Myocytes from female C57 mice exhibited reduced peak shortening, ± dL/dt, longer TPS, TR90 and intracellular Ca2+ clearance compared with males. Interestingly, this sex difference was greatly attenuated or abolished by IGF-1 deficiency. Female C57 mice displayed significantly decreased mRNA and protein levels of Na+-Ca2+ exchanger, SERCA2a and phosphorylated phospholamban as well as SERCA activity compared with male C57 mice. These sex differences in Ca2+ regulatory proteins were abolished or overtly attenuated by IGF-1 deficiency. In summary, our data suggested that IGF-1 deficiency may significantly attenuated or mitigate the sex difference in cardiomyocyte contractile function associated with intracellular Ca2+ regulation. PMID:21763763

Insulin-like growth factor I (IGF-1) deficiency ameliorates sex difference in cardiac contractile function and intracellular Ca(2+) homeostasis.

PubMed

Ceylan-Isik, Asli F; Li, Qun; Ren, Jun

2011-10-10

Sex difference in cardiac contractile function exists which may contribute to the different prevalence in cardiovascular diseases between genders. However, the precise mechanisms of action behind sex difference in cardiac function are still elusive. Given that sex difference exists in insulin-like growth factor I (IGF-1) cascade, this study is designed to evaluate the impact of severe liver IGF-1 deficiency (LID) on sex difference in cardiac function. Echocardiographic, cardiomyocyte contractile and intracellular Ca(2+) properties were evaluated including ventricular geometry, fractional shortening, peak shortening, maximal velocity of shortening/relengthening (±dL/dt), time-to-peak shortening (TPS), time-to-90% relengthening (TR(90)), fura-fluorescence intensity (FFI) and intracellular Ca(2+) clearance. Female C57 mice exhibited significantly higher plasma IGF-1 levels than their male counterpart. LID mice possessed comparably low IGF-1 levels in both sexes. Female C57 and LID mice displayed lower body, heart and liver weights compared to male counterparts. Echocardiographic analysis revealed larger LV mass in female C57 but not LID mice without sex difference in other cardiac geometric indices. Myocytes from female C57 mice exhibited reduced peak shortening, ±dL/dt, longer TPS, TR(90) and intracellular Ca(2+) clearance compared with males. Interestingly, this sex difference was greatly attenuated or abolished by IGF-1 deficiency. Female C57 mice displayed significantly decreased mRNA and protein levels of Na(+)-Ca(2+) exchanger, SERCA2a and phosphorylated phospholamban as well as SERCA activity compared with male C57 mice. These sex differences in Ca(2+) regulatory proteins were abolished or overtly attenuated by IGF-1 deficiency. In summary, our data suggested that IGF-1 deficiency may significantly attenuated or mitigate the sex difference in cardiomyocyte contractile function associated with intracellular Ca(2+) regulation. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

Device therapy in heart failure with reduced ejection fraction-cardiac resynchronization therapy and more.

PubMed

Duncker, D; Veltmann, C

2018-05-09

In patients with heart failure with reduced ejection fraction (HFrEF), optimal medical treatment includes beta-blockers, ACE inhibitors/angiotensinreceptor-neprilysin inhibitors (ARNI), mineralocorticoid receptor antagonists, and ivabradine when indicated. In device therapy of HFrEF, implantable cardioverter-defibrillators and cardiac resynchronization therapy (CRT) have been established for many years. CRT is the therapy of choice (class I indication) in symptomatic patients with HFrEF and a broad QRS complex with a left bundle branch block (LBBB) morphology. However, the vast majority of heart failure patients show a narrow QRS complex or a non-LBBB morphology. These patients are not candidates for CRT and alternative electrical therapies such as baroreflex activation therapy (BAT) and cardiac contractility modulation (CCM) may be considered. BAT modulates vegetative dysregulation in heart failure. CCM improves contractility, functional capacity, and symptoms. Although a broad data set is available for BAT and CCM, mortality data are still lacking for both methods. This article provides an overview of the device-based therapeutic options for patients with HFrEF.

Training-specific functional, neural, and hypertrophic adaptations to explosive- vs. sustained-contraction strength training.

PubMed

Balshaw, Thomas G; Massey, Garry J; Maden-Wilkinson, Thomas M; Tillin, Neale A; Folland, Jonathan P

2016-06-01

Training specificity is considered important for strength training, although the functional and underpinning physiological adaptations to different types of training, including brief explosive contractions, are poorly understood. This study compared the effects of 12 wk of explosive-contraction (ECT, n = 13) vs. sustained-contraction (SCT, n = 16) strength training vs. control (n = 14) on the functional, neural, hypertrophic, and intrinsic contractile characteristics of healthy young men. Training involved 40 isometric knee extension repetitions (3 times/wk): contracting as fast and hard as possible for ∼1 s (ECT) or gradually increasing to 75% of maximum voluntary torque (MVT) before holding for 3 s (SCT). Torque and electromyography during maximum and explosive contractions, torque during evoked octet contractions, and total quadriceps muscle volume (QUADSVOL) were quantified pre and post training. MVT increased more after SCT than ECT [23 vs. 17%; effect size (ES) = 0.69], with similar increases in neural drive, but greater QUADSVOL changes after SCT (8.1 vs. 2.6%; ES = 0.74). ECT improved explosive torque at all time points (17-34%; 0.54 ≤ ES ≤ 0.76) because of increased neural drive (17-28%), whereas only late-phase explosive torque (150 ms, 12%; ES = 1.48) and corresponding neural drive (18%) increased after SCT. Changes in evoked torque indicated slowing of the contractile properties of the muscle-tendon unit after both training interventions. These results showed training-specific functional changes that appeared to be due to distinct neural and hypertrophic adaptations. ECT produced a wider range of functional adaptations than SCT, and given the lesser demands of ECT, this type of training provides a highly efficient means of increasing function. Copyright © 2016 the American Physiological Society.

Broken heart as work-related accident: Occupational stress as a cause of takotsubo cardiomyopathy in 55-year-old female teacher - Role of automated function imaging in diagnostic workflow.

PubMed

Mielczarek, Agnieszka; Kasprzak, Jarosław Damian; Marcinkiewicz, Andrzej; Kurpesa, Małgorzata; Uznańska-Loch, Barbara; Wierzbowska-Drabik, Karina

2015-01-01

Takotsubo cardiomiopathy (TTC) (known also as "ampulla cardiomyopathy," "apical ballooning" or "broken heart syndrome") is connected with a temporary systolic left ventricular dysfunction without the culprit coronary lesion. Takotsubo cardiomyopathy was first described in 1990 in Japan after octopus trapping pot with a round bottom and narrow neck similar in shape to left ventriculogram in TTC patients. The occurrence of TTC is usually precipitated by a stressful event with a clinical presentation mimicking myocardial infarction: chest pain, ST-T segment elevation or T-wave inversion, a rise in cardiac troponin, and contractility abnormalities in echocardiography. A left ventricular dysfunction is transient and improves within a few weeks. Takotsubo cardiomyopathy typically occurs in postmenopausal women and the postulated mechanism is catecholamine overstimulation. Moreover, the distribution of contractility impairments usually does not correspond with typical region supplied by a single coronary artery. Therefore, the assessment of regional pattern of systolic dysfunction with speckle-tracking echocardiography and automated function imaging (AFI) technique may be important in diagnosis of TTC and may improve our insight into its patophysiology. We described a 55-year-old female teacher with TTC diagnosed after acute psychological stress in workplace. The provoking factor related with occupational stress and pattern of contraction abnormalities documented with AFI technique including basal segments of left ventricle make this case atypical. This work is available in Open Access model and licensed under a CC BY-NC 3.0 PL license.

AMP-Activated Protein Kinase – A Ubiquitous Signalling Pathway with Key Roles in the Cardiovascular System

PubMed Central

Salt, Ian P.; Hardie, D. Grahame

2017-01-01

The AMP-activated protein kinase (AMPK) is a key regulator of cellular and whole body energy homeostasis, which acts to restore energy homoeostasis whenever cellular energy charge is depleted. Over the last two decades, it has become apparent that AMPK regulates a number of other cellular functions and has specific roles in cardiovascular tissues, acting to regulate cardiac metabolism and contractile function as well as promoting anti-contractile, anti-inflammatory and anti-atherogenic actions in blood vessels. In this review, we will discuss the role of AMPK in the cardiovascular system, including the molecular basis of mutations in AMPK that alter cardiac physiology and the proposed mechanisms by which AMPK regulates vascular function under physiological and pathophysiological conditions. PMID:28546359

Nanoscale architecture of the Schizosaccharomyces pombe contractile ring.

PubMed

McDonald, Nathan A; Lind, Abigail L; Smith, Sarah E; Li, Rong; Gould, Kathleen L

2017-09-15

The contractile ring is a complex molecular apparatus which physically divides many eukaryotic cells. Despite knowledge of its protein composition, the molecular architecture of the ring is not known. Here we have applied super-resolution microscopy and FRET to determine the nanoscale spatial organization of Schizosaccharomyces pombe contractile ring components relative to the plasma membrane. Similar to other membrane-tethered actin structures, we find proteins localize in specific layers relative to the membrane. The most membrane-proximal layer (0-80 nm) is composed of membrane-binding scaffolds, formin, and the tail of the essential myosin-II. An intermediate layer (80-160 nm) consists of a network of cytokinesis accessory proteins as well as multiple signaling components which influence cell division. Farthest from the membrane (160-350 nm) we find F-actin, the motor domains of myosins, and a major F-actin crosslinker. Circumferentially within the ring, multiple proteins proximal to the membrane form clusters of different sizes, while components farther from the membrane are uniformly distributed. This comprehensive organizational map provides a framework for understanding contractile ring function.

Nanoscale architecture of the Schizosaccharomyces pombe contractile ring

PubMed Central

McDonald, Nathan A; Lind, Abigail L; Smith, Sarah E; Li, Rong

2017-01-01

The contractile ring is a complex molecular apparatus which physically divides many eukaryotic cells. Despite knowledge of its protein composition, the molecular architecture of the ring is not known. Here we have applied super-resolution microscopy and FRET to determine the nanoscale spatial organization of Schizosaccharomyces pombe contractile ring components relative to the plasma membrane. Similar to other membrane-tethered actin structures, we find proteins localize in specific layers relative to the membrane. The most membrane-proximal layer (0–80 nm) is composed of membrane-binding scaffolds, formin, and the tail of the essential myosin-II. An intermediate layer (80–160 nm) consists of a network of cytokinesis accessory proteins as well as multiple signaling components which influence cell division. Farthest from the membrane (160–350 nm) we find F-actin, the motor domains of myosins, and a major F-actin crosslinker. Circumferentially within the ring, multiple proteins proximal to the membrane form clusters of different sizes, while components farther from the membrane are uniformly distributed. This comprehensive organizational map provides a framework for understanding contractile ring function. PMID:28914606

A WAVE2–Arp2/3 actin nucleator apparatus supports junctional tension at the epithelial zonula adherens

PubMed Central

Verma, Suzie; Han, Siew Ping; Michael, Magdalene; Gomez, Guillermo A.; Yang, Zhe; Teasdale, Rohan D.; Ratheesh, Aparna; Kovacs, Eva M.; Ali, Radiya G.; Yap, Alpha S.

2012-01-01

The epithelial zonula adherens (ZA) is a specialized adhesive junction where actin dynamics and myosin-driven contractility coincide. The junctional cytoskeleton is enriched in myosin II, which generates contractile force to support junctional tension. It is also enriched in dynamic actin filaments, which are replenished by ongoing actin assembly. In this study we sought to pursue the relationship between actin assembly and junctional contractility. We demonstrate that WAVE2–Arp2/3 is a major nucleator of actin assembly at the ZA and likely acts in response to junctional Rac signaling. Furthermore, WAVE2–Arp2/3 is necessary for junctional integrity and contractile tension at the ZA. Maneuvers that disrupt the function of either WAVE2 or Arp2/3 reduced junctional tension and compromised the ability of cells to buffer side-to-side forces acting on the ZA. WAVE2–Arp2/3 disruption depleted junctions of both myosin IIA and IIB, suggesting that dynamic actin assembly may support junctional tension by facilitating the local recruitment of myosin. PMID:23051739

A WAVE2-Arp2/3 actin nucleator apparatus supports junctional tension at the epithelial zonula adherens.

PubMed

Verma, Suzie; Han, Siew Ping; Michael, Magdalene; Gomez, Guillermo A; Yang, Zhe; Teasdale, Rohan D; Ratheesh, Aparna; Kovacs, Eva M; Ali, Radiya G; Yap, Alpha S

2012-12-01

The epithelial zonula adherens (ZA) is a specialized adhesive junction where actin dynamics and myosin-driven contractility coincide. The junctional cytoskeleton is enriched in myosin II, which generates contractile force to support junctional tension. It is also enriched in dynamic actin filaments, which are replenished by ongoing actin assembly. In this study we sought to pursue the relationship between actin assembly and junctional contractility. We demonstrate that WAVE2-Arp2/3 is a major nucleator of actin assembly at the ZA and likely acts in response to junctional Rac signaling. Furthermore, WAVE2-Arp2/3 is necessary for junctional integrity and contractile tension at the ZA. Maneuvers that disrupt the function of either WAVE2 or Arp2/3 reduced junctional tension and compromised the ability of cells to buffer side-to-side forces acting on the ZA. WAVE2-Arp2/3 disruption depleted junctions of both myosin IIA and IIB, suggesting that dynamic actin assembly may support junctional tension by facilitating the local recruitment of myosin.

Role of the Z band in the mechanical properties of the heart.

PubMed

Goldstein, M A; Schroeter, J P; Michael, L H

1991-05-01

In striated muscle the mechanism of contraction involves the cooperative movement of contractile and elastic components. This review emphasizes a structural approach that describes the cellular and extracellular components with known anatomical, biochemical, and physical properties that make them candidates for these contractile and elastic components. Classical models of contractile and elastic elements and their underlying assumptions are presented. Mechanical properties of cardiac and skeletal muscle are compared and contrasted and then related to ultrastructure. Information from these approaches leads to the conclusion that the Z band is essential for muscle contraction. Our review of Z band structure shows the Z band at the interface where extracellular components meet the cell surface. The Z band is also the interface from cell surface to myofibril, from extra-myofibrillar to myofibril, and finally from sarcomere to sarcomere. Our studies of Z band in defined physiologic states show that this lattice is an integral part of the contractile elements and can function as an elastic component. The Z band is a complex dynamic lattice uniquely suited to play several roles in muscle contraction.

Delayed recovery of left ventricular function after antithyroid treatment. Further evidence for reversible abnormalities of contractility in hyperthyroidism.

PubMed Central

Forfar, J C; Matthews, D M; Toft, A D

1984-01-01

Sequential measurements of systolic time intervals, left ventricular dimensions, and the derived indices of contractility were undertaken at rest and during isometric exercise in 15 hyperthyroid patients before, during, and after antithyroid treatment. At rest hyperthyroidism was characterised by a shortened pre-ejection period and increased velocity of circumferential shortening of the left ventricle. During isometric exercise, however, the pre-ejection period increased significantly beyond that predicted for normal subjects, and the velocity of circumferential fibre shortening fell by 30%. In contrast, both the pre-ejection period and the velocity of circumferential fibre shortening were unchanged during exercise after a stable euthyroid state had been achieved for at least three months. Comparison between exercise responses and thyroid status during antithyroid treatment showed that a biochemical euthyroid state may be achieved many weeks before normalisation of contractile response to exercise. These findings support the hypothesis of reversible depression of left ventricular function in hyperthyroidism. Responses at rest principally reflect the peripheral actions of thyroid hormone excess. PMID:6743439

Stimulatory action of itopride hydrochloride on colonic motor activity in vitro and in vivo.

PubMed

Tsubouchi, Tadashi; Saito, Takaharu; Mizutani, Fujie; Yamauchi, Toshie; Iwanaga, Yuji

2003-08-01

We investigated the effects of itopride hydrochloride (itopride, N-[4-[2-(dimethylamino)ethoxy]benzyl]-3,4-dimethoxybenzamide hydrochloride), a gastroprokinetic agent, on the colonic motor activity in vitro and in vivo, in comparison with benzamides, cisapride hydrate (cisapride), and mosapride citrate (mosapride). Itopride stimulated both peristaltic and segmental motility induced by applying intraluminal pressure to the isolated guinea pig colon. Although cisapride and mosapride enhanced the segmental motility, they markedly reduced the peristaltic motility. In conscious dogs with implanted strain gauge force transducers, itopride stimulated contractile activity in the gastrointestinal tract from the stomach to the colon. Cisapride stimulated contractile activity in the gastric antrum, ileum, and ascending colon. Mosapride stimulated contractile activity only in the gastric antrum and ileum. In guinea pigs and rats, itopride accelerated colonic luminal transit. On the other hand, cisapride and mosapride failed to enhance colonic transit. These results demonstrate that itopride has a stimulatory action on colonic peristalsis, propelling colonic luminal contents, different from that of cisapride and mosapride. Therefore, itopride may be a useful drug for the treatment of functional bowel disorders such as functional constipation.

Passive hind-limb cycling improves cardiac function and reduces cardiovascular disease risk in experimental spinal cord injury

PubMed Central

West, Christopher R; Crawford, Mark A; Poormasjedi-Meibod, Malihe-Sadat; Currie, Katharine D; Fallavollita, Andre; Yuen, Violet; McNeill, John H; Krassioukov, Andrei V

2014-01-01

Spinal cord injury (SCI) causes altered autonomic control and severe physical deconditioning that converge to drive maladaptive cardiac remodelling. We used a clinically relevant experimental model to investigate the cardio-metabolic responses to SCI and to establish whether passive hind-limb cycling elicits a cardio-protective effect. Initially, 21 male Wistar rats were evenly assigned to three groups: uninjured control (CON), T3 complete SCI (SCI) or T3 complete SCI plus passive hind-limb cycling (SCI-EX; 2 × 30 min day−1, 5 days week−1 for 4 weeks beginning 6 days post-SCI). On day 32, cardio-metabolic function was assessed using in vivo echocardiography, ex vivo working heart assessments, cardiac histology/molecular biology and blood lipid profiles. Twelve additional rats (n = 6 SCI and n = 6 SCI-EX) underwent in vivo echocardiography and basal haemodynamic assessments pre-SCI and at days 7, 14 and 32 post-SCI to track temporal cardiovascular changes. Compared with CON, SCI exhibited a rapid and sustained reduction in left ventricular dimensions and function that ultimately manifested as reduced contractility, increased myocardial collagen deposition and an up-regulation of transforming growth factor beta-1 (TGFβ1) and mothers against decapentaplegic homolog 3 (Smad3) mRNA. For SCI-EX, the initial reduction in left ventricular dimensions and function at day 7 post-SCI was completely reversed by day 32 post-SCI, and there were no differences in myocardial contractility between SCI-EX and CON. Collagen deposition was similar between SCI-EX and CON. TGFβ1 and Smad3 were down-regulated in SCI-EX. Blood lipid profiles were improved in SCI-EX versus SCI. We provide compelling novel evidence that passive hind-limb cycling prevents cardiac dysfunction and reduces cardiovascular disease risk in experimental SCI. PMID:24535438

Effects of Age on Esophageal Motility: Use of High-resolution Esophageal Impedance Manometry

PubMed Central

Shim, Young Kwang; Kim, Nayoung; Park, Yo Han; Lee, Jong-Chan; Sung, Jihee; Choi, Yoon Jin; Yoon, Hyuk; Shin, Cheol Min; Park, Young Soo; Lee, Dong Ho

2017-01-01

Background/Aims Disturbances of esophageal motility have been reported to be more frequent the aged population. However, the physiology of disturbances in esophageal motility during aging is unclear. The aim of this study was to evaluate the effects of age on esophageal motility using high-resolution esophageal impedance manometry (HRIM). Methods Esophageal motor function of 268 subjects were measured using HRIM in 3 age groups, < 40 years (Group A, n = 32), 40–65 years (Group B, n = 185), and > 65 years (Group C, n = 62). Lower esophageal sphincter (LES) and upper esophageal sphincter (UES) pressures, integrated relaxation pressure, distal contractile integral, contractile front velocity, distal latency, and pressures and duration of contraction on 4 positions along the esophagus, and complete bolus transit were measured. Results Basal UES pressure was lower in Group C (P < 0.001) but there was no significant difference in the LES pressure among groups. Contractile duration on position 3 (10 cm from proximal LES high pressure zone) was longer in Group C (P = 0.001), and the contractile amplitude on position 4 (5 cm from proximal LES high pressure zone) was lower in Group C (P = 0.005). Distal contractile integral was lower in Group C (P = 0.037). Contractile front velocity (P = 0.015) and the onset velocity (P = 0.040) was lower in Group C. There was no significant difference in impedance values. Conclusions The decrease of UES pressure, distal esophageal motility, and peristaltic velocity might be related with esophageal symptoms in the aged population. PMID:28163259

Bladder smooth muscle organ culture preparation maintains the contractile phenotype

PubMed Central

Wang, Tanchun; Kendig, Derek M.; Chang, Shaohua; Trappanese, Danielle M.; Chacko, Samuel

2012-01-01

Smooth muscle cells, when subjected to culture, modulate from a contractile to a secretory phenotype. This has hampered the use of cell culture for molecular techniques to study the regulation of smooth muscle biology. The goal of this study was to develop a new organ culture model of bladder smooth muscle (BSM) that would maintain the contractile phenotype and aid in the study of BSM biology. Our results showed that strips of BSM subjected to up to 9 days of organ culture maintained their contractile phenotype, including the ability to achieve near-control levels of force with a temporal profile similar to that of noncultured tissues. The technical aspects of our organ culture preparation that were responsible, in part, for the maintenance of the contractile phenotype were a slight longitudinal stretch during culture and subjection of the strips to daily contraction-relaxation. The tissues contained viable cells throughout the cross section of the strips. There was an increase in extracellular collagenous matrix, resulting in a leftward shift in the passive length-tension relationship. There were no significant changes in the content of smooth muscle-specific α-actin, calponin, h-caldesmon, total myosin heavy chain, protein kinase G, Rho kinase-I, or the ratio of SM1 to SM2 myosin isoforms. Moreover the organ cultured tissues maintained functional voltage-gated calcium channels and large-conductance calcium-activated potassium channels. Therefore, we propose that this novel BSM organ culture model maintains the contractile phenotype and will be a valuable tool for the use in cellular/molecular biology studies of bladder myocytes. PMID:22896042

Pharmacological action of DA-9701 on the motility of feline stomach circular smooth muscle.

PubMed

Nguyen, Thanh Thao; Song, Hyun Ju; Ko, Sung Kwon; Sohn, Uy Dong

2015-03-01

DA-9701, a new prokinetic agent for the treatment of functional dyspepsia, is formulated with Pharbitis semen and Corydalis tuber. This study wasconducted to determine the pharmacological action of DA-9701 and to identify the receptors involved in DA-9701 -induced contractile responsesin the feline gastric corporal, fundic and antral circular smooth muscle. Concentration-response curve to DA-9701 was established. The tissue trips were exposed to methylsergide, ketanserin, ondansetron, GR 113808, atropine and dopamine before administration of DA-9701. The contractile force was determined before and after administration of drugs by a polygraph.DA-9701 enhanced the spontaneous contractile amplitude of antrum, corpus and fundus. However, it did not change the spontaneous contractile frequency of antrum and corpus, but concentration-dependently reduced that of fundus. In the fundus, DA-9701 -induced tonic contractions were inhibited by dopamine, methylsergide, ketanserine, ondansetron or GR 113808 respectively, but not by atropine, indicating that the contractile responses are mediated by multiple receptors: 5-HT2, 5-HT3, 5-HT4, and dopamine receptors. In the corpus, DA-9701-induced contractions were blocked by atropine, dopamine or GR 113808, but not by methysergide, ketanserin or ondansetron, indicating that they are involved in receptors on both, smooth muscles and neurons: 5-HT4 and dopamine receptors. However, contractile responses to DA-9701 are mainly mediated by dopamine receptors in the antrum. These results suggest that DA-9701 has important roles in gastric accommodation by enhancing tonic activity of fundus, and in gastric emptying and gastrointestinal transit by phasic contractions of corpus and antrum mediated by multiple receptors.

An Approach for Improvement of Carbon Fiber Technique to Study Cardiac Cell Contractility

NASA Astrophysics Data System (ADS)

Myachina, T.; Khokhlova, A.; Antsygin, I.; Lookin, O.

2018-05-01

The technologies to study cardiac cell mechanics in near-physiological conditions are limited. Carbon fiber (CF) technique is a unique tool to study single cardiomyocyte contractility. However, the CF adhesion to a cell is limited and it is difficult to control CF sliding occurred due to inappropriate adhesion. In this study, we present a CF adhesion quality index – a linear coefficient (slope) derived from “end-diastolic cell length - end-diastolic sarcomere length” relationship. Potential applicability of this index is demonstrated on isolated rat and guinea pig ventricular cardiomyocytes. Further improvement of the approach may help to increase the quality of the experimental data obtained by CF technique.

Micropatterned nanostructures: a bioengineered approach to mass-produce functional myocardial grafts.

PubMed

Serpooshan, Vahid; Mahmoudi, Morteza

2015-02-13

Cell-based therapies are a recently established path for treating a wide range of human disease. Tissue engineering of contractile heart muscle for replacement therapy is among the most exciting and important of these efforts. However, current in vitro techniques of cultivating functional mature cardiac grafts have only been moderately successful due to the poor capability of traditional two-dimensional cell culture systems to recapitulate necessary in vivo conditions. In this issue, Kiefer et al introduce a laser-patterned nanostructured substrate (Al/Al2O3 nanowires) for efficient maintenance of oriented human cardiomyocytes, with great potential to open new roads to mass-production of contractile myocardial grafts for cardiovascular tissue engineering.

[The effect of hypothyroidism on cardiac function in dogs].

PubMed

Stephan, I; Nolte, I; Hoppen, H O

2003-06-01

The thyroid hormones have direct and indirect effects on the heart. So it is possible that depression of left ventricular function is associated with hypothyroidism. This publication describes cardiac findings (auscultation, electrocardiography, echocardiography) in ten hypothyroid dogs. Low heart rates, reduced R-amplitudes and bradycardic arrhythmias (first and second-degree AV block) were found on the electrocardiogram before treatment. On the echocardiograms most of the dogs showed reduced contractillity and reduced left ventricular wall thickness. Seven dogs were reexamined after levothyroxine supplementation. Effects of treatment were increased heart rates and R-amplitudes as well as disappearance of the bradycardic arrhythmias in electrocardiographic examination. The echocardiographic examination showed increased contractility and increased left ventricular wall thickness.

Intravital imaging of cardiac function at the single-cell level.

PubMed

Aguirre, Aaron D; Vinegoni, Claudio; Sebas, Matt; Weissleder, Ralph

2014-08-05

Knowledge of cardiomyocyte biology is limited by the lack of methods to interrogate single-cell physiology in vivo. Here we show that contracting myocytes can indeed be imaged with optical microscopy at high temporal and spatial resolution in the beating murine heart, allowing visualization of individual sarcomeres and measurement of the single cardiomyocyte contractile cycle. Collectively, this has been enabled by efficient tissue stabilization, a prospective real-time cardiac gating approach, an image processing algorithm for motion-artifact-free imaging throughout the cardiac cycle, and a fluorescent membrane staining protocol. Quantification of cardiomyocyte contractile function in vivo opens many possibilities for investigating myocardial disease and therapeutic intervention at the cellular level.

Micropatterned nanostructures: a bioengineered approach to mass-produce functional myocardial grafts

NASA Astrophysics Data System (ADS)

Serpooshan, Vahid; Mahmoudi, Morteza

2015-02-01

Cell-based therapies are a recently established path for treating a wide range of human disease. Tissue engineering of contractile heart muscle for replacement therapy is among the most exciting and important of these efforts. However, current in vitro techniques of cultivating functional mature cardiac grafts have only been moderately successful due to the poor capability of traditional two-dimensional cell culture systems to recapitulate necessary in vivo conditions. In this issue, Kiefer et al [1] introduce a laser-patterned nanostructured substrate (Al/Al2O3 nanowires) for efficient maintenance of oriented human cardiomyocytes, with great potential to open new roads to mass-production of contractile myocardial grafts for cardiovascular tissue engineering.

Skeletal myoblasts for heart regeneration and repair: state of the art and perspectives on the mechanisms for functional cardiac benefits.

PubMed

Formigli, L; Zecchi-Orlandini, S; Meacci, E; Bani, D

2010-01-01

Until recently, skeletal myoblasts (SkMBs) have been the most widely used cells in basic research and clinical trials of cell based therapy for cardiac repair and regeneration. Although SkMB engraftment into the post-infarcted heart has been consistently found to improve cardiac contractile function, the underlying therapeutic mechanisms remain still a matter of controversy and debate. This is basically because SkMBs do not attain a cardiac-like phenotype once homed into the diseased heart nor they form a contractile tissue functionally coupled with the surrounding viable myocardium. This issue of concern has generated the idea that the cardiotropic action of SkMBs may depend on the release of paracrine factors. However, the paracrine hypothesis still remains ill-defined, particularly concerning the identification of the whole spectrum of cell-derived soluble factors and details on their cardiac effects. In this context, the possibility to genetically engineering SkMBs to potentate their paracrine attitudes appears particularly attractive and is actually raising great expectation. Aim of the present review is not to cover all the aspects of cell-based therapy with SkMBs, as this has been the object of previous exhaustive reviews in this field. Rather, we focused on novel aspects underlying the interactions between SkMBs and the host cardiac tissues which may be relevant for directing the future basic and applied research on SkMB transplantation for post ischemic cardiac dysfunction.

Swimming exercise reverses aging-related contractile abnormalities of female heart by improving structural alterations.

PubMed

Ozturk, Nihal; Olgar, Yusuf; Er, Hakan; Kucuk, Murathan; Ozdemir, Semir

2017-01-01

The objective of this study was to examine the effect of swimming exercise on aging-related Ca2+ handling alterations and structural abnormalities of female rat heart. For this purpose, 4-month and 24-month old female rats were used and divided into three following groups: sedentary young (SY), sedentary old (SO), and exercised old (Ex-O). Swimming exercise was performed for 8 weeks (60 min/day, 5 days/week). Myocyte shortening, L-type Ca2+ currents and associated Ca2+ transients were measured from ventricular myocytes at 36 ± 1°C. NOX-4 levels, aconitase activity, glutathione measurements and ultrastructural examination by electron microscopy were conducted in heart tissue. Swimming exercise reversed the reduced shortening and slowed kinetics of aged cardiomyocytes. Although the current density was similar for all groups, Ca2+ transients were higher in SO and Ex-O myocytes with respect to the SY group. Caffeine-induced Ca2+ transients and the integrated NCX current were lower in cardiomyocytes of SY rats compared with other groups, suggesting an increased sarcoplasmic reticulum Ca2+ content in an aged heart. Aging led to upregulated cardiac NOX-4 along with declined aconitase activity. Although it did not reverse these oxidative parameters, swimming exercise achieved a significant increase in glutathione levels and improved structural alterations of old rats' hearts. We conclude that swimming exercise upregulates antioxidant defense capacity and improves structural abnormalities of senescent female rat heart, although it does not change Ca2+ handling alterations further. Thereby, it improves contractile function of aged myocardium by mitigating detrimental effects of oxidative stress.

Effects of glycyl-glutamine dipeptide supplementation on myocardial damage and cardiac function in rats after severe burn injury

PubMed Central

Zhang, Yong; Yan, Hong; Lv, Shang-Gun; Wang, Lin; Liang, Guang-Ping; Wan, Qian-Xue; Peng, Xi

2013-01-01

Glutamine decreases myocardial damage in ischemia/reperfusion injury. However, the cardioprotective effect of glutamine after burn injury remains unclear. Present study was to explore the protective effect of glycyl-glutamine dipeptide on myocardial damage in severe burn rats. Seventy-two Wistar rats were randomly divided into three groups: normal control (C), burned control (B) and glycyl-glutamine dipeptide-treated (GG) groups. B and GG groups were inflicted with 30% total body surface area of full thickness burn. The GG group was given 1.5 g/kg glycyl-glutamine dipeptide per day and the B group was given the same dose of alanine via intraperitoneal injection for 3 days. The serum CK, LDH, AST, and, blood lactic acid levels, as well as the myocardium ATP and GSH contents, were measured. The indices of cardiac contractile function and histopathological change were analyzed at 12, 24, 48, and 72 post-burn hours (PBH). The serum CK, LDH, AST and blood lactic acid levels increased, and the myocardium ATP and GSH content decreased in both burned groups. Compared with B group, the CK, LDH, AST and blood lactic acid levels reduced, myocardium ATP and GSH content increased in GG group. Moreover, the inhibition of cardiac contractile function and myocardial histopathological damage were reduced significantly in GG group. We conclude that myocardial histological structure and function were damaged significantly after burn injury, glycyl-glutamine dipeptide supplementation is beneficial to myocardial preservation by improving cardiocyte energy metabolism, increasing ATP and glutathione synthesis. PMID:23638213

Effects of 4 classes of cardiovascular drugs on ventricular function in dogs with mitral regurgitation.

PubMed

Nakayama, Tomohiro; Nishijima, Yoshinori; Miyamoto, Mutsumi; Hamlin, Robert L

2007-01-01

There have been few trials in which dogs with mitral regurgitation (MR) have been treated with various cardioactive drugs to determine effects on left ventricular (LV) function. Four classes of cardiovascular drugs may improve LV function in dogs with MR without increasing MR. Nine mature dogs were included in the study. MR was produced in 9 dogs. Five months later under butorphanol narcosis, parameters of LV function and left atrial dimension (LAD) were monitored by LV micromanometry and echocardiography/Doppler. Dogs were given (in random order) enalaprilat, nitroglycerine, ouabain, milrinone, and placebo. Nitroglycerin produced no significant change; milrinone and ouabain increased contractility; ouabain decreased heart rate; and there was evidence that enalaprilat and milrinone decreased LAD. Milrinone and ouabain decreased isovolumetric contraction time and therefore the time available for MR. There was no evidence that a positive inotrope increased MR despite increasing LV contractility and stroke volume. This study contradicts the hypotheses that (1) strengthening the left ventricle may increase MR and (2) treatment of MR (even before symptoms of heart failure develop) may decrease LAD. It is reasonable that strengthening the force of LV contraction should increase the driving pressure for MR; however, this effect did not appear to increase MR. Although some investigators believe that treating dogs with MR with afterload reducers and decreasing hindrance to ejection of blood from the LV to aorta may lengthen life by decreasing MR, there did not appear to be a reduction in MR, at least in response to the angiotensin-converting enzyme (ACE) inhibitor.

Mast cells regulate myofilament calcium sensitization and heart function after myocardial infarction.

PubMed

Ngkelo, Anta; Richart, Adèle; Kirk, Jonathan A; Bonnin, Philippe; Vilar, Jose; Lemitre, Mathilde; Marck, Pauline; Branchereau, Maxime; Le Gall, Sylvain; Renault, Nisa; Guerin, Coralie; Ranek, Mark J; Kervadec, Anaïs; Danelli, Luca; Gautier, Gregory; Blank, Ulrich; Launay, Pierre; Camerer, Eric; Bruneval, Patrick; Menasche, Philippe; Heymes, Christophe; Luche, Elodie; Casteilla, Louis; Cousin, Béatrice; Rodewald, Hans-Reimer; Kass, David A; Silvestre, Jean-Sébastien

2016-06-27

Acute myocardial infarction (MI) is a severe ischemic disease responsible for heart failure and sudden death. Inflammatory cells orchestrate postischemic cardiac remodeling after MI. Studies using mice with defective mast/stem cell growth factor receptor c-Kit have suggested key roles for mast cells (MCs) in postischemic cardiac remodeling. Because c-Kit mutations affect multiple cell types of both immune and nonimmune origin, we addressed the impact of MCs on cardiac function after MI, using the c-Kit-independent MC-deficient (Cpa3(Cre/+)) mice. In response to MI, MC progenitors originated primarily from white adipose tissue, infiltrated the heart, and differentiated into mature MCs. MC deficiency led to reduced postischemic cardiac function and depressed cardiomyocyte contractility caused by myofilament Ca(2+) desensitization. This effect correlated with increased protein kinase A (PKA) activity and hyperphosphorylation of its targets, troponin I and myosin-binding protein C. MC-specific tryptase was identified to regulate PKA activity in cardiomyocytes via protease-activated receptor 2 proteolysis. This work reveals a novel function for cardiac MCs modulating cardiomyocyte contractility via alteration of PKA-regulated force-Ca(2+) interactions in response to MI. Identification of this MC-cardiomyocyte cross-talk provides new insights on the cellular and molecular mechanisms regulating the cardiac contractile machinery and a novel platform for therapeutically addressable regulators. ©2016 Ngkelo et al.

Contractile properties of muscle fibers from the deep and superficial digital flexors of horses.

PubMed

Butcher, M T; Chase, P B; Hermanson, J W; Clark, A N; Brunet, N M; Bertram, J E A

2010-10-01

Equine digital flexor muscles have independent tendons but a nearly identical mechanical relationship to the main joint they act upon. Yet these muscles have remarkable diversity in architecture, ranging from long, unipennate fibers ("short" compartment of DDF) to very short, multipennate fibers (SDF). To investigate the functional relevance of the form of the digital flexor muscles, fiber contractile properties were analyzed in the context of architecture differences and in vivo function during locomotion. Myosin heavy chain (MHC) isoform fiber type was studied, and in vitro motility assays were used to measure actin filament sliding velocity (V(f)). Skinned fiber contractile properties [isometric tension (P(0)/CSA), velocity of unloaded shortening (V(US)), and force-Ca(2+) relationships] at both 10 and 30°C were characterized. Contractile properties were correlated with MHC isoform and their respective V(f). The DDF contained a higher percentage of MHC-2A fibers with myosin (heavy meromyosin) and V(f) that was twofold faster than SDF. At 30°C, P(0)/CSA was higher for DDF (103.5 ± 8.75 mN/mm(2)) than SDF fibers (81.8 ± 7.71 mN/mm(2)). Similarly, V(US) (pCa 5, 30°C) was faster for DDF (2.43 ± 0.53 FL/s) than SDF fibers (1.20 ± 0.22 FL/s). Active isometric tension increased with increasing Ca(2+) concentration, with maximal Ca(2+) activation at pCa 5 at each temperature in fibers from each muscle. In general, the collective properties of DDF and SDF were consistent with fiber MHC isoform composition, muscle architecture, and the respective functional roles of the two muscles in locomotion.

Parvalbumin Gene Transfer Impairs Skeletal Muscle Contractility in Old Mice

PubMed Central

Murphy, Kate T.; Ham, Daniel J.; Church, Jarrod E.; Naim, Timur; Trieu, Jennifer; Williams, David A.

2012-01-01

Abstract Sarcopenia is the progressive age-related loss of skeletal muscle mass associated with functional impairments that reduce mobility and quality of life. Overt muscle wasting with sarcopenia is usually preceded by a slowing of the rate of relaxation and a reduction in maximum force production. Parvalbumin (PV) is a cytosolic Ca2+ buffer thought to facilitate relaxation in muscle. We tested the hypothesis that restoration of PV levels in muscles of old mice would increase the magnitude and hasten relaxation of submaximal and maximal force responses. The tibialis anterior (TA) muscles of young (6 month), adult (13 month), and old (26 month) C57BL/6 mice received electroporation-assisted gene transfer of plasmid encoding PV or empty plasmid (pcDNA3.1). Contractile properties of TA muscles were assessed in situ 14 days after transfer. In old mice, muscles with increased PV expression had a 40% slower rate of tetanic force development (p<0.01), and maximum twitch and tetanic force were 22% and 16% lower than control values, respectively (p<0.05). Muscles with increased PV expression from old mice had an 18% lower maximum specific (normalized) force than controls, and absolute force was ∼26% lower at higher stimulation frequencies (150–300 Hz, p<0.05). In contrast, there was no effect of increased PV expression on TA muscle contractile properties in young and adult mice. The impairments in skeletal muscle function in old mice argue against PV overexpression as a therapeutic strategy for ameliorating aspects of contractile dysfunction with sarcopenia and help clarify directions for therapeutic interventions for age-related changes in skeletal muscle structure and function. PMID:22455364

Mesenchymal stem cell mechanobiology and emerging experimental platforms

PubMed Central

MacQueen, Luke; Sun, Yu; Simmons, Craig A.

2013-01-01

Experimental control over progenitor cell lineage specification can be achieved by modulating properties of the cell's microenvironment. These include physical properties of the cell adhesion substrate, such as rigidity, topography and deformation owing to dynamic mechanical forces. Multipotent mesenchymal stem cells (MSCs) generate contractile forces to sense and remodel their extracellular microenvironments and thereby obtain information that directs broad aspects of MSC function, including lineage specification. Various physical factors are important regulators of MSC function, but improved understanding of MSC mechanobiology requires novel experimental platforms. Engineers are bridging this gap by developing tools to control mechanical factors with improved precision and throughput, thereby enabling biological investigation of mechanics-driven MSC function. In this review, we introduce MSC mechanobiology and review emerging cell culture platforms that enable new insights into mechanobiological control of MSCs. Our main goals are to provide engineers and microtechnology developers with an up-to-date description of MSC mechanobiology that is relevant to the design of experimental platforms and to introduce biologists to these emerging platforms. PMID:23635493

Distinct contractile and molecular differences between two goat models of atrial dysfunction: AV block-induced atrial dilatation and atrial fibrillation.

PubMed

Greiser, Maura; Neuberger, Hans-Ruprecht; Harks, Erik; El-Armouche, Ali; Boknik, Peter; de Haan, Sunniva; Verheyen, Fons; Verheule, Sander; Schmitz, Wilhelm; Ravens, Ursula; Nattel, Stanley; Allessie, Maurits A; Dobrev, Dobromir; Schotten, Ulrich

2009-03-01

Atrial dilatation is an independent risk factor for thromboembolism in patients with and without atrial fibrillation (AF). In many patients, atrial dilatation goes along with depressed contractile function of the dilated atria. While some mechanisms causing atrial contractile dysfunction in fibrillating atria have been addressed previously, the cellular and molecular mechanisms of atrial contractile remodeling in dilated atria are unknown. This study characterized in vivo atrial contractile function in a goat model of atrial dilatation and compared it to a goat model of AF. Differences in the underlying mechanisms were elucidated by studying contractile function, electrophysiology and sarcoplasmic reticulum (SR) Ca2+ load in atrial muscle bundles and by analyzing expression and phosphorylation levels of key Ca2+-handling proteins, myofilaments and the expression and activity of their upstream regulators. In 7 chronically instrumented, awake goats atrial contractile dysfunction was monitored during 3 weeks of progressive atrial dilatation after AV-node ablation (AV block goats (AVB)). In open chest experiments atrial work index (AWI) and refractoriness were measured (10 goats with AVB, 5 goats with ten days of AF induced by repetitive atrial burst pacing (AF), 10 controls). Isometric force of contraction (FC), transmembrane action potentials (APs) and rapid cooling contractures (RCC, a measure of SR Ca2+ load) were studied in right atrial muscle bundles. Total and phosphorylated Ca2+-handling and myofilament protein levels were quantified by Western blot. In AVB goats, atrial size increased by 18% (from 26.6+/-4.4 to 31.6+/-5.5 mm, n=7 p<0.01) while atrial fractional shortening (AFS) decreased (from 18.4+/-1.7 to 12.8+/-4.0% at 400 ms, n=7, p<0.01). In open chest experiments, AWI was reduced in AVB and in AF goats compared to controls (at 400 ms: 8.4+/-0.9, n=7, and 3.2+/-1.8, n=5, vs 18.9+/-5.3 mmxmmHg, n=7, respectively, p<0.05 vs control). FC of isolated right atrial muscle bundles was reduced in AVB (n=8) and in AF (n=5) goats compared to controls (n=9) (at 2 Hz: 2.3+/-0.5 and 0.7+/-0.2 vs 5.5+/-1.0 mN/mm2, respectively, p<0.05). APs were shorter in AF, but unchanged in AVB goats. RCCs were reduced in AVB and AF versus control (AVB, 3.4+/-0.5 and AF, 4.1+/-1.4 vs 12.2+/-3.2 mN/mm2, p<0.05). Protein levels of protein kinase A (PKA) phosphorylated phospholamban (PLB) were reduced in AVB (n=8) and AF (n=8) vs control (n=7) by 37.9+/-12.4% and 29.7+/-10.1%, respectively (p<0.01), whereas calmodulin-dependent protein kinase II (CaMKII) phosphorylated ryanodine channels (RyR2) were increased by 166+/-55% in AVB (n=8) and by 146+/-56% in AF (n=8) goats (p<0.01). PKA-phosphorylated myosin-binding protein-C and troponin-I were reduced exclusively in AVB goat atria (by 75+/-10% and 55+/-15%, respectively, n=8, p<0.05). Atrial dilatation developing during slow ventricular rhythm after complete AV block as well as AF-induced remodeling are associated with atrial contractile dysfunction. Both AVB and AF goat atria show decreased SR Ca2+ load, likely caused by PLB dephosphorylation and RYR2 hyperphosphorylation. While shorter APs further compromise contractility in AF goat atria, reduced myofilament phosphorylation may impair contractility in AVB goat atria. Thus, atrial hypocontractility appears to have distinct molecular contributors in different types of atrial remodeling.

Rationally engineered Troponin C modulates in vivo cardiac function and performance in health and disease.

PubMed

Shettigar, Vikram; Zhang, Bo; Little, Sean C; Salhi, Hussam E; Hansen, Brian J; Li, Ning; Zhang, Jianchao; Roof, Steve R; Ho, Hsiang-Ting; Brunello, Lucia; Lerch, Jessica K; Weisleder, Noah; Fedorov, Vadim V; Accornero, Federica; Rafael-Fortney, Jill A; Gyorke, Sandor; Janssen, Paul M L; Biesiadecki, Brandon J; Ziolo, Mark T; Davis, Jonathan P

2016-02-24

Treatment for heart disease, the leading cause of death in the world, has progressed little for several decades. Here we develop a protein engineering approach to directly tune in vivo cardiac contractility by tailoring the ability of the heart to respond to the Ca(2+) signal. Promisingly, our smartly formulated Ca(2+)-sensitizing TnC (L48Q) enhances heart function without any adverse effects that are commonly observed with positive inotropes. In a myocardial infarction (MI) model of heart failure, expression of TnC L48Q before the MI preserves cardiac function and performance. Moreover, expression of TnC L48Q after the MI therapeutically enhances cardiac function and performance, without compromising survival. We demonstrate engineering TnC can specifically and precisely modulate cardiac contractility that when combined with gene therapy can be employed as a therapeutic strategy for heart disease.

Rationally engineered Troponin C modulates in vivo cardiac function and performance in health and disease

PubMed Central

Shettigar, Vikram; Zhang, Bo; Little, Sean C.; Salhi, Hussam E.; Hansen, Brian J.; Li, Ning; Zhang, Jianchao; Roof, Steve R.; Ho, Hsiang-Ting; Brunello, Lucia; Lerch, Jessica K.; Weisleder, Noah; Fedorov, Vadim V.; Accornero, Federica; Rafael-Fortney, Jill A.; Gyorke, Sandor; Janssen, Paul M. L.; Biesiadecki, Brandon J.; Ziolo, Mark T.; Davis, Jonathan P.

2016-01-01

Treatment for heart disease, the leading cause of death in the world, has progressed little for several decades. Here we develop a protein engineering approach to directly tune in vivo cardiac contractility by tailoring the ability of the heart to respond to the Ca2+ signal. Promisingly, our smartly formulated Ca2+-sensitizing TnC (L48Q) enhances heart function without any adverse effects that are commonly observed with positive inotropes. In a myocardial infarction (MI) model of heart failure, expression of TnC L48Q before the MI preserves cardiac function and performance. Moreover, expression of TnC L48Q after the MI therapeutically enhances cardiac function and performance, without compromising survival. We demonstrate engineering TnC can specifically and precisely modulate cardiac contractility that when combined with gene therapy can be employed as a therapeutic strategy for heart disease. PMID:26908229

[Effect of different therapy options on bronchial contraction in rats with modeled obstructive pulmonary disease].

PubMed

Kuzubova, N A; Fedin, A N; Lebedeva, E S; Platonova, I S

2014-09-01

In the model of chronic obstructive pulmonary disease, produced in rats by 60-day exposure to nitrogen dioxide, the effect of different options of combination therapy (corticosteroids, anticholinergics, adrenergic agonists) on the functional state of the bronchi was studied. The contractile activity of strips of the bronchi caused by nerve or smooth muscle stimulation was evaluated. Corticosteroid monotherapy resulted in deterioration of the functional state of the bronchial wall neuromuscular apparatus due to corticosteroid resistance, evolving under the influence of long-term exposure to nitrogen dioxide. Application of M-anticholinergic tiotropium had a beneficial effect on the functional state of the bronchi smooth muscles, leading to the full restoration of the bronchial wall contractile activity and removal the morphological manifestations of inflammatory lung tissue remodeling. Most effective in terms of impact on the functional state of the bronchial wall neuromuscular apparatus was corticosteroid therapy combined with M-cholinolytik or beta2-adrenoagonist.

[Effect of dopamine and its antagonists on contractile activity of the lower esophageal sphincter and the stomach (author's transl)].

PubMed

Itoh, Z; Aizawa, I; Nakamura, T

1980-06-01

Effect of dopamine and its antagonists, domperidone and metoclopramide (MCP), on contractile activity of the lower esophageal sphincter (LES) and the stomach was studied in 5 healthy conscious dogs. Contractile activity was measured by means of chronically implanted force transducers. Contractile activity of the LES and the stomach was completely inhibited by an intravenous infusion of dopamine (10, 20 and 40 micrograms/kg-min) during the digestive and interdigestive state. Domperidone, when administered alone (0.5, 1.0 and 2.0 mg/kg), had no effect on contractile activity of the LES and the stomach during the both periods. Though deprived of any noticeable effect on the digestive contractions, MCP (0.25, 0.5 and 1.0 mg/kg) abolished the interdigestive contractions and produced characteristic contractions. Domperidone restored postprandial and interdigestive contractions to their initial stage before dopamine administration in a dose-related fashion. Dopamine-induced inhibition was antagonized by MCP during the digestive state, however, MCP had no effect on the interdigestive contractions that had been inhibited by dopamine. Since domperidone has no activity upon normal contractions of the gastrointestinal tract, it may be assumed that if domperidone alone has some influence upon gut motor activity or any improvement in clinical symptoms is seen after domperidone, a disorder of the dopaminergic system could be strongly suggested.

Long-term effects of extrinsic denervation on VIP and substance P innervation in circular muscle of rat jejunum.

PubMed

Kasparek, Michael S; Fatima, Javairiah; Iqbal, Corey W; Duenes, Judith A; Sarr, Michael G

2007-10-01

Intestinal denervation contributes to enteric motor dysfunction after small bowel transplantation (SBT). Our aim was to determine long-term effects of extrinsic denervation on function of nonadrenergic, noncholinergic innervation with substance P and vasoactive intestinal polypeptide (VIP). Contractile activity of jejunal circular muscle strips from six age-matched, naive control rats (NC) and eight rats 1 year after syngeneic SBT was studied in tissue chambers. Spontaneous contractile activity did not differ between groups. Exogenous VIP inhibited contractile activity dose-dependently to a comparable degree in both groups. The VIP antagonist ([D-p-Cl-Phe(6),Leu(17)]-VIP) and the nitric oxide synthase inhibitor L-NG-nitro-arginine did not affect VIP-induced inhibition but increased contractile activity during electrical field stimulation (EFS) in both groups. Exogenous substance P increased contractile activity dose-dependently, greater in NC than SBT. The substance P antagonist ([D-Pro(2),D-Trp(7,9)]-substance P) inhibited effects of exogenous substance P and decreased the excitatory EFS response. Immunohistofluorescence showed tyrosine hydroxylase staining after SBT indicating sympathetic reinnervation. In jejunal circular muscle after chronic denervation, response to exogenous substance P, but not VIP, is decreased, whereas endogenous release of both neurotransmitters is preserved. Alterations in balance of excitatory and inhibitory pathways occur despite extrinsic reinnervation and might contribute to enteric motor dysfunction after SBT.

Impaired pulmonary artery contractile responses in a rat model of microgravity: role of nitric oxide

NASA Technical Reports Server (NTRS)

Nyhan, Daniel; Kim, Soonyul; Dunbar, Stacey; Li, Dechun; Shoukas, Artin; Berkowitz, Dan E.

2002-01-01

Vascular contractile hyporesponsiveness is an important mechanism underlying orthostatic intolerance after microgravity. Baroreceptor reflexes can modulate both pulmonary resistance and capacitance function and thus cardiac output. We hypothesized, therefore, that pulmonary vasoreactivity is impaired in the hindlimb-unweighted (HLU) rat model of microgravity. Pulmonary artery (PA) contractile responses to phenylephrine (PE) and U-46619 (U4) were significantly decreased in the PAs from HLU vs. control (C) animals. N(G)-nitro-L-arginine methyl ester (10(-5) M) enhanced the contractile responses in the PA rings from both C and HLU animals and completely abolished the differential responses to PE and U4 in HLU vs. C animals. Vasorelaxant responses to ACh were significantly enhanced in PA rings from HLU rats compared with C. Moreover, vasorelaxant responses to sodium nitroprusside were also significantly enhanced. Endothelial nitric oxide synthase (eNOS) and soluble guanlyl cyclase expression were significantly enhanced in PA and lung tissue from HLU rats. In marked contrast, the expression of inducible nitric oxide synthase was unchanged in lung tissue. These data support the hypothesis that vascular contractile responsiveness is attenuated in PAs from HLU rats and that this hyporesponsiveness is due at least in part to increased nitric oxide synthase activity resulting from enhanced eNOS expression. These findings may have important implications for blood volume distribution and attenuated stroke volume responses to orthostatic stress after microgravity exposure.

Adenoviral beta-adrenergic receptor kinase inhibitor gene transfer improves exercise capacity, cardiac contractility, and systemic inflammation in a model of pressure overload hypertrophy.

PubMed

Gupta, Dipin; Molina, Ezequiel J; Palma, Jon; Gaughan, John P; Long, Walter; Macha, Mahender

2008-10-01

We hypothesized that intracoronary adenoviral-mediated delivery of betaARKct would improve heart failure associated pathophysiologic abnormalities related to exercise capacity, cardiac contractility, systemic inflammation and volume overload. After aortic banding, a cohort of Sprague-Dawley rats was followed by echocardiography. When an absolute decline of 25% in fractional shortening was detected, animals were randomized to intracoronary delivery of Ad.ssARKct (n=14), Ad.beta-Gal (n=13), or followed without any other further intervention (n=18). Assessment of exercise tolerance and hemodynamic profile and measurement of markers of systemic inflammation and volume overload was performed at 7, 14, and 21 days after gene delivery. Data were analyzed using ANOVA. Animals receiving Ad.ssARKct showed improved exercise tolerance compared to Ad.Gal-treated animals at 14 days (507+/-26 s vs. 408+/-19 s, P=0.01) and 21 days (526+/-55 s vs. 323+/-19 s, P<0.001) following injection. Animals receiving Ad.ssARKct demonstrated improved +dP/dtmax (mean+/-SD, 5,581+/-960 mmHg/s vs. 3,134+/-438 mmHg/s, P<0.01) and -dP/dtmax (mean+/-SD, -3,494+/-1,269 mmHg/s vs. -1,925+/-638 mmHg/s, P<0.01) compared to Ad.Gal-treated animals at 7 days. These differences were observed up to 21 days following injection. Serum levels of IL-1, IL-6, and TNF-alpha, as well as ANP were also decreased in animals receiving Ad.betaARKct. Genetic modulation of heart failure using the betaARKct gene was associated with improved exercise capacity and cardiac function as well as amelioration in heart failure-associated profiles of systemic inflammation and volume overload.

Formation of contractile networks and fibers in the medial cell cortex through myosin-II turnover, contraction, and stress-stabilization

PubMed Central

Nie, Wei; Wei, Ming-Tzo; Ou-Yang, Daniel H.; Jedlicka, Sabrina S.; Vavylonis, Dimitrios

2015-01-01

The morphology of adhered cells depends crucially on the formation of a contractile meshwork of parallel and cross-linked fibers along the contacting surface. The motor activity and minifilament assembly of non-muscle myosin-II is an important component of cortical cytoskeletal remodeling during mechanosensing. We used experiments and computational modeling to study cortical myosin-II dynamics in adhered cells. Confocal microscopy was used to image the medial cell cortex of HeLa cells stably expressing myosin regulatory light chain tagged with GFP (MRLC-GFP). The distribution of MRLC-GFP fibers and focal adhesions was classified into three types of network morphologies. Time-lapse movies show: myosin foci appearance and disappearance; aligning and contraction; stabilization upon alignment. Addition of blebbistatin, which perturbs myosin motor activity, leads to a reorganization of the cortical networks and to a reduction of contractile motions. We quantified the kinetics of contraction, disassembly and reassembly of myosin networks using spatio-temporal image correlation spectroscopy (STICS). Coarse-grained numerical simulations include bipolar minifilaments that contract and align through specified interactions as basic elements. After assuming that minifilament turnover decreases with increasing contractile stress, the simulations reproduce stress-dependent fiber formation in between focal adhesions above a threshold myosin concentration. The STICS correlation function in simulations matches the function measured in experiments. This study provides a framework to help interpret how different cortical myosin remodeling kinetics may contribute to different cell shape and rigidity depending on substrate stiffness. PMID:25641802

Effect of chronic, extrinsic denervation on functional NANC innervation with vasoactive intestinal polypeptide and substance P in longitudinal muscle of rat jejunum.

PubMed

Kasparek, M S; Fatima, J; Iqbal, C W; Duenes, J A; Sarr, M G

2008-03-01

Intestinal denervation contributes to enteric motor dysfunction after intestinal transplantation [small bowel transplantation (SBT)]. Our aim was to determine long-term effects of extrinsic denervation on functional non-adrenergic, non-cholinergic innervation with vasoactive intestinal polypeptide (VIP) and substance P. Contractile activity of jejunal longitudinal muscle from six age-matched, naïve control rats (NC) and eight rats 1 year after syngeneic SBT were studied in tissue chambers. Spontaneous contractile activity did not differ between groups. Exogenous VIP inhibited contractile activity dose-dependently in both groups, greater in NC than in SBT. The VIP antagonist ([D-p-Cl-Phe(6),Leu(17)]-VIP) and the nitric oxide synthase inhibitor l-N(G)-nitro arginine prevented inhibition by exogenous VIP and electrical field stimulation (EFS) in both groups. Exogenous substance P increased contractile activity dose-dependently, greater in NC than in SBT. The substance P antagonist ([D-Pro(2),D-Trp(7,9)]-substance P) inhibited effects of exogenous substance P and increased the EFS-induced inhibitory response. Immunohistofluorescence showed staining for tyrosine hydroxylase in the jejunoileum 1 year after SBT suggesting sympathetic reinnervation. In rat jejunal longitudinal muscle after chronic denervation, response to exogenous VIP and substance P is decreased, while endogenous release of both neurotransmitters is preserved. These alterations in excitatory and inhibitory pathways occur despite extrinsic reinnervation and might contribute to enteric motor dysfunction after SBT.

Effect of chronic, extrinsic denervation on functional NANC innervation with vasoactive intestinal polypeptide and substance P in longitudinal muscle of rat jejunum1

PubMed Central

KASPAREK, M. S.; FATIMA, J.; IQBAL, C. W.; DUENES, J. A.; SARR, M. G.

2008-01-01

Intestinal denervation contributes to enteric motor dysfunction after intestinal transplantation [small bowel transplantation (SBT)]. Our aim was to determine long-term effects of extrinsic denervation on functional non-adrenergic, non-cholinergic innervation with vasoactive intestinal polypeptide (VIP) and substance P. Contractile activity of jejunal longitudinal muscle from six age-matched, naïve control rats (NC) and eight rats 1 year after syngeneic SBT were studied in tissue chambers. Spontaneous contractile activity did not differ between groups. Exogenous VIP inhibited contractile activity dose-dependently in both groups, greater in NC than in SBT. The VIP antagonist ([D-p-Cl-Phe6,Leu17]-VIP) and the nitric oxide synthase inhibitor L-NG-nitro arginine prevented inhibition by exogenous VIP and electrical field stimulation (EFS) in both groups. Exogenous substance P increased contractile activity dose-dependently, greater in NC than in SBT. The substance P antagonist ([D-Pro2,D-Trp7,9]-substance P) inhibited effects of exogenous substance P and increased the EFS-induced inhibitory response. Immunohistofluorescence showed staining for tyrosine hydroxylase in the jejunoileum 1 year after SBT suggesting sympathetic reinnervation. In rat jejunal longitudinal muscle after chronic denervation, response to exogenous VIP and substance P is decreased, while endogenous release of both neurotransmitters is preserved. These alterations in excitatory and inhibitory pathways occur despite extrinsic reinnervation and might contribute to enteric motor dysfunction after SBT. PMID:17971029

Assessment of human long saphenous vein function with minimally invasive harvesting with the Mayo stripper.

PubMed

O'Regan, D J; Borland, J A; Chester, A H; Pennell, D J; Yacoub, M; Pepper, J R

1997-09-01

The use of the Mayo Stripper to harvest the long saphenous vein has been shown to improve morbidity from leg wound incisions. It has not been universally accepted because of a perceived increase in injury to the venous conduit. To compare the function of undistended autologous long saphenous vein harvested by a Mayo stripper with the traditional 'open' technique in the same patient (n = 12) appearance. Vascular reactivity was assessed in isolated organ baths. Contractile function was measured in response to increasing concentrations (10(-9)-10(-5) mol) of 5-hydroxytryptamine and noradrenaline. This was calculated as a percentage of the maximum contractile response to 90 mM KCl measured in millinewtons (mN) (control 41.4 +/- 12.1, (n = 11), open technique 35.8 +/- 11.1, (n = 11), Mayo stripper 33.7 +/- 15.9, (n = 11)). The endothelial dependent and independent function was assessed with acetylcholine and sodium nitroprusside, respectively. There was no significant difference in response to both constrictors and dilators between vein taken with the Mayo stripper compared with the traditional open technique (n = 6 for each observation; P > 0.05 by ANOVA). Histological examination by light microscopy of the vessel segments removed with the Mayo stripper was unable to show any significant damage to the vessel wall. Both functional and morphological studies were conducted by 'blinded' observers. One-year follow-up with magnetic resonance angiography (MRA) and stress thallium tomography demonstrated a patency rate with lower and upper estimates of 80 and 94%. We have shown that harvesting the long saphenous vein with a Mayo stripper does not compromise vascular reactivity of the long saphenous vein or long-term patency.

Actomyosin contractility rotates the cell nucleus

PubMed Central

Kumar, Abhishek; Maitra, Ananyo; Sumit, Madhuresh; Ramaswamy, Sriram; Shivashankar, G. V.

2014-01-01

The cell nucleus functions amidst active cytoskeletal filaments, but its response to their contractile stresses is largely unexplored. We study the dynamics of the nuclei of single fibroblasts, with cell migration suppressed by plating onto micro-fabricated patterns. We find the nucleus undergoes noisy but coherent rotational motion. We account for this observation through a hydrodynamic approach, treating the nucleus as a highly viscous inclusion residing in a less viscous fluid of orientable filaments endowed with active stresses. Lowering actin contractility selectively by introducing blebbistatin at low concentrations drastically reduced the speed and coherence of the angular motion of the nucleus. Time-lapse imaging of actin revealed a correlated hydrodynamic flow around the nucleus, with profile and magnitude consistent with the results of our theoretical approach. Coherent intracellular flows and consequent nuclear rotation thus appear to be an intrinsic property of cells. PMID:24445418

Actomyosin contractility rotates the cell nucleus.

PubMed

Kumar, Abhishek; Maitra, Ananyo; Sumit, Madhuresh; Ramaswamy, Sriram; Shivashankar, G V

2014-01-21

The cell nucleus functions amidst active cytoskeletal filaments, but its response to their contractile stresses is largely unexplored. We study the dynamics of the nuclei of single fibroblasts, with cell migration suppressed by plating onto micro-fabricated patterns. We find the nucleus undergoes noisy but coherent rotational motion. We account for this observation through a hydrodynamic approach, treating the nucleus as a highly viscous inclusion residing in a less viscous fluid of orientable filaments endowed with active stresses. Lowering actin contractility selectively by introducing blebbistatin at low concentrations drastically reduced the speed and coherence of the angular motion of the nucleus. Time-lapse imaging of actin revealed a correlated hydrodynamic flow around the nucleus, with profile and magnitude consistent with the results of our theoretical approach. Coherent intracellular flows and consequent nuclear rotation thus appear to be an intrinsic property of cells.

[Improvement and the mechanism of cardiac function by knockdown of ADAM10 in adriamycin-induced cardiomyopathy rats].

PubMed

Li, Xiaoou; Xie, Lili; He, Bing; Huang, Wei

2018-01-01

Objective To study the role of a disintegrin and metalloproteinase10 (ADAM10) in shedding neural cadherin (N-cadherin) and develop an approach to interfere the process of ventricular remodeling in adriamycin-induced cardiomyopathy (ACM) rats. Methods In a rat model of ACM, the effects of intraperitoneal injection of the lentiviral RNAi vector of ADAM10 on the morphology of cardiomyocytes and contractile function were observed by HE staining and color Doppler echocardiography. The expressions of N-cadherin and C-terminal fragment 1 (CTF1) were detected by Western blotting and immunohistochemistry. Results In the in vivo experiment, a large amount of fluorescence was seen in the isolated primary cardiomyocytes, which indicated that the transfection in the rat model was successful. In the treatment group, the morphology of cardiomyocytes and function of the heart were evidently improved, N-cadherin protein expression was remarkably up-regulated and CTF1 protein was obviously down-regulated compared with the model group. Conclusion Knock-down of ADAM10 increases N-cadherin expression and decreases CTF1 expression, thus improves cardiac function in the rat model of ACM.

Glucose-6-phosphate dehydrogenase and NADPH redox regulates cardiac myocyte L-type calcium channel activity and myocardial contractile function.

PubMed

Rawat, Dhwajbahadur K; Hecker, Peter; Watanabe, Makino; Chettimada, Sukrutha; Levy, Richard J; Okada, Takao; Edwards, John G; Gupte, Sachin A

2012-01-01

We recently demonstrated that a 17-ketosteroid, epiandrosterone, attenuates L-type Ca(2+) currents (I(Ca-L)) in cardiac myocytes and inhibits myocardial contractility. Because 17-ketosteroids are known to inhibit glucose-6-phosphate dehydrogenase (G6PD), the rate-limiting enzyme in the pentose phosphate pathway, and to reduce intracellular NADPH levels, we hypothesized that inhibition of G6PD could be a novel signaling mechanism which inhibit I(Ca-L) and, therefore, cardiac contractile function. We tested this idea by examining myocardial function in isolated hearts and Ca(2+) channel activity in isolated cardiac myocytes. Myocardial function was tested in Langendorff perfused hearts and I(Ca-L) were recorded in the whole-cell patch configuration by applying double pulses from a holding potential of -80 mV and then normalized to the peak amplitudes of control currents. 6-Aminonicotinamide, a competitive inhibitor of G6PD, increased pCO(2) and decreased pH. Additionally, 6-aminonicotinamide inhibited G6PD activity, reduced NADPH levels, attenuated peak I(Ca-L) amplitudes, and decreased left ventricular developed pressure and ±dp/dt. Finally, dialyzing NADPH into cells from the patch pipette solution attenuated the suppression of I(Ca-L) by 6-aminonicotinamide. Likewise, in G6PD-deficient mice, G6PD insufficiency in the heart decreased GSH-to-GSSG ratio, superoxide, cholesterol and acetyl CoA. In these mice, M-mode echocardiographic findings showed increased diastolic volume and end-diastolic diameter without changes in the fraction shortening. Taken together, these findings suggest that inhibiting G6PD activity and reducing NADPH levels alters metabolism and leads to inhibition of L-type Ca(2+) channel activity. Notably, this pathway may be involved in modulating myocardial contractility under physiological and pathophysiological conditions during which the pentose phosphate pathway-derived NADPH redox is modulated (e.g., ischemia-reperfusion and heart failure).

Paracrine Effects of IGF-1 Overexpression on the Functional Decline Due to Skeletal Muscle Disuse: Molecular and Functional Evaluation in Hindlimb Unloaded MLC/mIgf-1 Transgenic Mice

PubMed Central

Cannone, Maria; Liantonio, Antonella; De Bellis, Michela; Digennaro, Claudio; Gramegna, Gianluca; De Luca, Annamaria; Germinario, Elena; Danieli-Betto, Daniela; Betto, Romeo; Dobrowolny, Gabriella; Rizzuto, Emanuele; Musarò, Antonio; Desaphy, Jean-François; Camerino, Diana Conte

2013-01-01

Slow-twitch muscles, devoted to postural maintenance, experience atrophy and weakness during muscle disuse due to bed-rest, aging or spaceflight. These conditions impair motion activities and can have survival implications. Human and animal studies demonstrate the anabolic role of IGF-1 on skeletal muscle suggesting its interest as a muscle disuse countermeasure. Thus, we tested the role of IGF-1 overexpression on skeletal muscle alteration due to hindlimb unloading (HU) by using MLC/mIgf-1 transgenic mice expressing IGF-1 under the transcriptional control of MLC promoter, selectively activated in skeletal muscle. HU produced atrophy in soleus muscle, in terms of muscle weight and fiber cross-sectional area (CSA) reduction, and up-regulation of atrophy gene MuRF1. In parallel, the disuse-induced slow-to-fast fiber transition was confirmed by an increase of the fast-type of the Myosin Heavy Chain (MHC), a decrease of PGC-1α expression and an increase of histone deacetylase-5 (HDAC5). Consistently, functional parameters such as the resting chloride conductance (gCl) together with ClC-1 chloride channel expression were increased and the contractile parameters were modified in soleus muscle of HU mice. Surprisingly, IGF-1 overexpression in HU mice was unable to counteract the loss of muscle weight and the decrease of fiber CSA. However, the expression of MuRF1 was recovered, suggesting early effects on muscle atrophy. Although the expression of PGC-1α and MHC were not improved in IGF-1-HU mice, the expression of HDAC5 was recovered. Importantly, the HU-induced increase of gCl was fully contrasted in IGF-1 transgenic mice, as well as the changes in contractile parameters. These results indicate that, even if local expression does not seem to attenuate HU-induced atrophy and slow-to-fast phenotype transition, it exerts early molecular effects on gene expression which can counteract the HU-induced modification of electrical and contractile properties. MuRF1 and HDAC5 can be attractive therapeutic targets for pharmacological countermeasures and then deserve further investigations. PMID:23755187

Overexpression Myocardial Inducible Nitric Oxide Synthase Exacerbates Cardiac Dysfunction and Beta-Adrenergic Desensitization in Experimental Hypothyroidism☆,☆☆

PubMed Central

Shao, Qun; Cheng, Heng-Jie; Callahan, Michael F.; Kitzman, Dalane W; Li, Wei-Min; Cheng, Che Ping

2015-01-01

Background Altered nitric oxide synthase (NOS) has been implicated in the pathophysiology of heart failure (HF). Recent evidence links hypothyroidism to the pathology of HF. However, the precise mechanisms are incompletely understood. The alterations and functional effects of cardiac NOS in hypothyroidism are unknown. We tested the hypothesis that hypothyroidism increases cadiomyocyte inducible NOS (iNOS) expression, which plays an important role in hypothyroidism-induced depression of cardiomyocyte contractile properties, [Ca2+]i transient ([Ca2+]iT), and β-adrenergic hyporesponsiveness. Methods and Results We simultaneously evaluated LV functional performance and compared myocyte three NOS, β-adrenergic receptors (AR) and SERCA2a expressions and assessed cardiomyocyte contractile and [Ca2+]iT responses to β-AR stimulation with and without pretreatment of iNOS inhibitor (1400W, 10−5 mol/L) in 26 controls and 26 rats with hypothyroidism induced by methimazole (~30 mg/kg/day for 8 weeks in the drinking water). Compared with controls, in hypothyroidism, total serum T3 and T4 were significantly reduced followed by significantly decreased LV contractility (EES) with increased LV time constant of relaxation. These LV abnormalities were accompanied by concomitant significant decreases in myocyte contraction (dL/dtmax), relaxation (dR/dtmax), and [Ca2+]iT. In hypothyroidism, isoproterenol (10−8 M) produced significantly smaller increases in dL/dtmax, dR/dtmax and [Ca2+]iT. These changes were associated with decreased β1-AR and SERCA2a, but significantly increased iNOS. Moreover, only in hypothyroidism, pretreatment with iNOS inhibitor significantly improved basal and isoproterenol-stimulated myocyte contraction, relaxation and [Ca2+]iT. Conclusions Hypothyroidism produces intrinsic defects of LV myocyte force-generating capacity and relaxation with β-AR desensitization. Up-regulation of cadiomyocyte iNOS may promote progressive cardiac dysfunction in hypothyroidism. PMID:26681542

Overexpression myocardial inducible nitric oxide synthase exacerbates cardiac dysfunction and beta-adrenergic desensitization in experimental hypothyroidism.

PubMed

Shao, Qun; Cheng, Heng-Jie; Callahan, Michael F; Kitzman, Dalane W; Li, Wei-Min; Cheng, Che Ping

2016-02-01

Altered nitric oxide synthase (NOS) has been implicated in the pathophysiology of heart failure (HF). Recent evidence links hypothyroidism to the pathology of HF. However, the precise mechanisms are incompletely understood. The alterations and functional effects of cardiac NOS in hypothyroidism are unknown. We tested the hypothesis that hypothyroidism increases cardiomyocyte inducible NOS (iNOS) expression, which plays an important role in hypothyroidism-induced depression of cardiomyocyte contractile properties, [Ca(2+)]i transient ([Ca(2+)]iT), and β-adrenergic hyporesponsiveness. We simultaneously evaluated LV functional performance and compared myocyte three NOS, β-adrenergic receptors (AR) and SERCA2a expressions and assessed cardiomyocyte contractile and [Ca(2+)]iT responses to β-AR stimulation with and without pretreatment of iNOS inhibitor (1400 W, 10(-5)mol/L) in 26 controls and 26 rats with hypothyroidism induced by methimazole (~30 mg/kg/day for 8 weeks in the drinking water). Compared with controls, in hypothyroidism, total serum T3 and T4 were significantly reduced followed by significantly decreased LV contractility (EES) with increased LV time constant of relaxation. These LV abnormalities were accompanied by concomitant significant decreases in myocyte contraction (dL/dtmax), relaxation (dR/dtmax), and [Ca(2+)]iT. In hypothyroidism, isoproterenol (10(-8)M) produced significantly smaller increases in dL/dtmax, dR/dtmax and [Ca(2+)]iT. These changes were associated with decreased β1-AR and SERCA2a, but significantly increased iNOS. Moreover, only in hypothyroidism, pretreatment with iNOS inhibitor significantly improved basal and isoproterenol-stimulated myocyte contraction, relaxation and [Ca(2+)]iT. Hypothyroidism produces intrinsic defects of LV myocyte force-generating capacity and relaxation with β-AR desensitization. Up-regulation of cardiomyocyte iNOS may promote progressive cardiac dysfunction in hypothyroidism. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Standard and Strain Measurements by Echocardiography Detect Early Overloaded Right Ventricular Dysfunction: Validation against Hemodynamic and Myocyte Contractility Changes in a Large Animal Model.

PubMed

Hodzic, Amir; Bobin, Pierre; Mika, Delphine; Ly, Mohamed; Lefebvre, Florence; Lechêne, Patrick; Le Bret, Emmanuel; Gouadon, Elodie; Coblence, Mathieu; Vandecasteele, Grégoire; Capderou, André; Leroy, Jérôme; Rucker-Martin, Catherine; Lambert, Virginie

2017-11-01

Early detection of right ventricular (RV) failure is required to improve the management of patients with congenital heart diseases. The aim of this study was to validate echocardiography for the early detection of overloaded RV dysfunction, compared with hemodynamic and myocyte contractility assessment. Using a porcine model reproducing repaired tetralogy of Fallot, RV function was evaluated over 4 months using standard echocardiography and speckle-tracking compared with hemodynamic parameters (conductance catheter). Sarcomere shortening and calcium transients were recorded in RV isolated myocytes. Contractile reserve (ΔE max ) was assessed by β-adrenergic stimulation in vivo (dobutamine 5 μg/kg) and ex vivo (isoproterenol 100 nM). Six operated animals were compared with four age- and sex-matched controls. In the operated group, hemodynamic RV efficient ejection fraction was significantly decreased (29.7% [26.2%-34%] vs 42.9% [40.7%-48.6%], P < .01), and inotropic responses to dobutamine were attenuated (ΔE max was 51% vs 193%, P < .05). Echocardiographic measurements of fraction of area change, tricuspid annular plane systolic excursion, tricuspid annular peak systolic velocity (S') and RV free wall longitudinal systolic strain and strain rate were significantly decreased. Strain rate, S', and tricuspid annular plane systolic excursion were correlated with ΔE max (r = 0.75, r = 0.78, and r = 0.65, respectively, P < .05). These alterations were associated in RV isolated myocytes with the decrease of sarcomere shortening in response to isoproterenol and perturbations of calcium homeostasis assessed by the increase of spontaneous calcium waves. In this porcine model, both standard and strain echocardiographic parameters detected early impairments of RV function and cardiac reserve, which were associated with cardiomyocyte excitation-contraction coupling alterations. Copyright © 2017 American Society of Echocardiography. Published by Elsevier Inc. All rights reserved.

Myosin phosphorylation potentiates steady-state work output without altering contractile economy of mouse fast skeletal muscles.

PubMed

Gittings, William; Bunda, Jordan; Vandenboom, Rene

2018-01-30

Skeletal myosin light chain kinase (skMLCK)-catalyzed phosphorylation of the myosin regulatory light chain (RLC) increases (i.e. potentiates) mechanical work output of fast skeletal muscle. The influence of this event on contractile economy (i.e. energy cost/work performed) remains controversial, however. Our purpose was to quantify contractile economy of potentiated extensor digitorum longus (EDL) muscles from mouse skeletal muscles with (wild-type, WT) and without (skMLCK ablated, skMLCK -/- ) the ability to phosphorylate the RLC. Contractile economy was calculated as the ratio of total work performed to high-energy phosphate consumption (HEPC) during a period of repeated isovelocity contractions that followed a potentiating stimulus (PS). Consistent with genotype, the PS increased RLC phosphorylation measured during, before and after isovelocity contractions in WT but not in skMLCK -/- muscles (i.e. 0.65 and 0.05 mol phosphate mol -1 RLC, respectively). In addition, although the PS enhanced work during repeated isovelocity contractions in both genotypes, the increase was significantly greater in WT than in skMLCK -/- muscles (1.51±0.03 versus 1.10±0.05, respectively; all data P <0.05, n =8). Interestingly, the HEPC determined during repeated isovelocity contractions was statistically similar between genotypes at 19.03±3.37 and 16.02±3.41 μmol P; respectively ( P <0.27). As a result, despite performing significantly more work, the contractile economy calculated for WT muscles was similar to that calculated for skMLCK -/- muscles (i.e. 5.74±0.67 and 4.61±0.71 J kg -1  μmol -1 P, respectively ( P <0.27). In conclusion, our results support the notion that myosin RLC phosphorylation enhances dynamic contractile function of mouse fast skeletal muscle but does so without decreasing contractile economy. © 2018. Published by The Company of Biologists Ltd.

Age-dependent effects of milrinone and levosimendan on ventricular function and haemodynamics in newborn and mature pigs.

PubMed

Hyldebrandt, Janus A; Larsen, Signe H; Schmidt, Michael R; Hjortdal, Vibeke E; Ravn, Hanne B

2011-10-01

Inodilators are used in the treatment of low cardiac output, mainly after cardiac surgery. At present, there is little knowledge of the effect of inodilators in the newborn heart. Immediately after birth and in the neonatal period, the metabolism and physiology of the heart undergo major changes. We hypothesised that effects of the inodilators milrinone and levosimendan on myocardial contractility and haemodynamics under normal physiological conditions were age dependent. Animal studies were conducted on 48 pigs using a closed-chest biventricular conductance catheter method. Pigs in two age groups, that is, 5-6 days and 5-6 weeks, were assigned to milrinone, levosimendan, or a control group. We observed that both milrinone - 19.2% with a p value of 0.05 - and levosimendan - 25.7% with a p value of 0.03 compared with the control group increased cardiac output, as well as myocardial contractility with a maximum pressure development over time: milrinone 28.2%, p = 0.01 and levosimendan 19.4%, p = 0.05. Milrinone improved diastolic performance (p < 0.05) in the left ventricle in the 5-6-week-old animals. In the newborn animals, neither of the inodilators increased ventricular contractility or cardiac output; however, we observed a significant decrease in the mean arterial pressure: milrinone 34.6%, p < 0.01 and levosimendan 30.1%, p = 0.02. Both inodilators demonstrated age-dependent haemodynamic effects, and it is noteworthy that neither milrinone nor levosimendan was able to increase cardiac output in the newborn heart.

Predicting changes in cardiac myocyte contractility during early drug discovery with in vitro assays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morton, M.J., E-mail: michael.morton@astrazeneca.com; Armstrong, D.; Abi Gerges, N.

2014-09-01

Cardiovascular-related adverse drug effects are a major concern for the pharmaceutical industry. Activity of an investigational drug at the L-type calcium channel could manifest in a number of ways, including changes in cardiac contractility. The aim of this study was to define which of the two assay technologies – radioligand-binding or automated electrophysiology – was most predictive of contractility effects in an in vitro myocyte contractility assay. The activity of reference and proprietary compounds at the L-type calcium channel was measured by radioligand-binding assays, conventional patch-clamp, automated electrophysiology, and by measurement of contractility in canine isolated cardiac myocytes. Activity inmore » the radioligand-binding assay at the L-type Ca channel phenylalkylamine binding site was most predictive of an inotropic effect in the canine cardiac myocyte assay. The sensitivity was 73%, specificity 83% and predictivity 78%. The radioligand-binding assay may be run at a single test concentration and potency estimated. The least predictive assay was automated electrophysiology which showed a significant bias when compared with other assay formats. Given the importance of the L-type calcium channel, not just in cardiac function, but also in other organ systems, a screening strategy emerges whereby single concentration ligand-binding can be performed early in the discovery process with sufficient predictivity, throughput and turnaround time to influence chemical design and address a significant safety-related liability, at relatively low cost. - Highlights: • The L-type calcium channel is a significant safety liability during drug discovery. • Radioligand-binding to the L-type calcium channel can be measured in vitro. • The assay can be run at a single test concentration as part of a screening cascade. • This measurement is highly predictive of changes in cardiac myocyte contractility.« less

The contractile adaption to preload depends on the amount of afterload

PubMed Central

Schotola, Hanna; Sossalla, Samuel T.; Renner, André; Gummert, Jan; Danner, Bernhard C.; Schott, Peter

2017-01-01

Abstract Aims The Frank–Starling mechanism (rapid response (RR)) and the secondary slow response (SR) are known to contribute to increases contractile performance. The contractility of the heart muscle is influenced by pre‐load and after‐load. Because of the effect of pre‐load vs. after‐load on these mechanisms in not completely understood, we studied the effect in isolated muscle strips. Methods and results Progressive stretch lead to an increase in shortening/force development under isotonic (only pre‐load) and isometric conditions (pre‐ and after‐load). Muscle length with maximal function was reached earlier under isotonic (L max‐isotonic) compared with isometric conditions (L max‐isometric) in nonfailing rabbit, in human atrial and in failing ventricular muscles. Also, SR after stretch from slack to L max‐isotonic was comparable under isotonic and isometric conditions (human: isotonic 10 ± 4%, isometric 10 ± 4%). Moreover, a switch from isotonic to isometric conditions at L max‐isometric showed no SR proving independence of after‐load. To further analyse the degree of SR on the total contractile performance at higher pre‐load muscles were stretched from slack to 98% L max‐isometric under isotonic conditions. Thereby, the SR was 60 ± 9% in rabbit and 51 ± 14% in human muscle strips. Conclusions This work shows that the acute contractile response largely depends on the degree and type of mechanical load. Increased filling of the heart elevates pre‐load and prolongs the isotonic part of contraction. The reduction in shortening at higher levels of pre‐load is thereby partially compensated by the pre‐load‐induced SR. After‐load shifts the contractile curve to a better ‘myofilament function’ by probably influencing thin fibers and calcium sensitivity, but has no effect on the SR. PMID:29154423

Loss of atrial contractility is primary cause of atrial dilatation during first days of atrial fibrillation.

PubMed

Schotten, Ulrich; de Haan, Sunniva; Neuberger, Hans-Ruprecht; Eijsbouts, Sabine; Blaauw, Yuri; Tieleman, Robert; Allessie, Maurits

2004-11-01

Atrial fibrillation (AF) induces a progressive dilatation of the atria which in turn might promote the arrhythmia. The mechanism of atrial dilatation during AF is not known. To test the hypothesis that loss of atrial contractile function is a primary cause of atrial dilatation during the first days of AF, eight goats were chronically instrumented with epicardial electrodes, a pressure transducer in the right atrium, and piezoelectric crystals to measure right atrial diameter. AF was induced with the use of repetitive burst pacing. Atrial contractility was assessed during sinus rhythm, atrial pacing (160-, 300-, and 400-ms cycle length), and electrically induced AF. The compliance of the fibrillating right atrium was measured during unloading the atria with diuretics and loading with 1 liter of saline. All measurements were repeated after 6, 12, and 24 h of AF and then once a day during the first 5 days of AF. Recovery of the observed changes after spontaneous cardioversion was also studied. After 5 days of AF, atrial contractility during sinus rhythm or slow atrial pacing was greatly reduced. During rapid pacing (160 ms) or AF, the amplitude of the atrial pressure waves had declined to 20% of control. The compliance of the fibrillating atria increased twofold, whereas the right atrial pressure was unchanged. As a result, the mean right atrial diameter increased by approximately 12%. All changes were reversible within 3 days of sinus rhythm. We conclude that atrial dilatation during the first days of AF is due to an increase in atrial compliance caused by loss of atrial contractility during AF. Atrial compliance and size are restored when atrial contractility recovers after cardioversion of AF.

Determination of right ventricular ejection fraction in children with cystic fibrosis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Piepsz, A.; Ham, H.R.; Millet, E.

1987-01-01

The radionuclide right ventricular ejection fraction (RVEF) determined by means of Krypton-81m represents a simple, noninvasive, and accurate procedure to quantify the right ventricular contractility. This procedure was applied to 25 young patients with cystic fibrosis. The RVEF tended to decrease with the progression of the lung disease, as assessed by the clinical S-K score, the degree of the defects on lung scintigraphy, the PaO/sub 2/, and the lung function tests. However, the decrease of RVEF in patients with marked lung function tests. However, the decrease of RVEF in patients with marked lung involvement was moderate, and terminal lung diseasemore » was sometimes associated with normal right heart contractility.« less

Diabetic cardiomyopathy: Where are we 40 years later?

PubMed Central

Sharma, Vijay; McNeill, John H

2006-01-01

Diabetic cardiomyopathy is a cardiac disease that arises as a result of the diabetic state, independent of vascular or valvular pathology. It manifests initially as asymptomatic diastolic dysfunction, which progresses to symptomatic heart failure. The compliance of the heart wall is decreased and contractile function is impaired. The pathophysiology is incompletely understood, but appears to be initiated both by hyperglycemia and changes in cardiac metabolism. These changes induce oxidative stress and activate a number of secondary messenger pathways, leading to cardiac hypertrophy, fibrosis and cell death. Alterations in contractile proteins and intracellular ions impair excitation-contraction coupling, while decreased autonomic responsiveness and autonomic neuropathy impair its regulation. Extensive structural abnormalities also occur, which have deleterious mechanical and functional consequences. PMID:16568154

Evaluation of cardiovascular risks of spaceflight does not support the NASA bioastronautics critical path roadmap.

PubMed

Convertino, Victor A; Cooke, William H

2005-09-01

Occurrence of serious cardiac dysrhythmias and diminished cardiac and vascular function are the primary cardiovascular risks of spaceflight identified in the 2005 NASA Bioastronautics Critical Path Roadmap. A review of the literature was conducted on experimental results and observational data obtained from spaceflight and relevant ground simulation studies that addressed occurrence of cardiac dysrhythmias, cardiac contractile and vascular function, manifestation of asymptomatic cardiovascular disease, orthostatic intolerance, and response to exercise stress. Based on data from astronauts who have flown in space, there is no compelling experimental evidence to support significant occurrence of cardiac dysrhythmias, manifestation of asymptomatic cardiovascular disease, or reduction in myocardial contractile function. Although there are post-spaceflight data that demonstrate lower peripheral resistance in astronauts who become presyncopal compared with non-presyncopal astronauts, it is not clear that these differences are the result of decreased vascular function. However, the evidence of postflight orthostatic intolerance and reduced exercise capacity is well substantiated by both spaceflight and ground experiments. Although attenuation of baroreflex function(s) may contribute to postflight orthostatic instability, a primary mechanism of orthostatic intolerance and reduced exercise capacity is reduced end-diastolic and stroke volume associated with lower blood volumes and consequent cardiac remodeling. Data from the literature on the current population of astronauts support the notion that the primary cardiovascular risks of spaceflight are compromised hemodynamic responses to central hypovolemia resulting in reduced orthostatic tolerance and exercise capacity rather than occurrence of cardiac dysrhythmias, reduced cardiac contractile and vascular function, or manifestation of asymptomatic cardiovascular disease. These observations warrant a critical review and revision of the 2005 Bioastronautics Critical Path Roadmap.

Heart repair by reprogramming non-myocytes with cardiac transcription factors

PubMed Central

Song, Kunhua; Nam, Young-Jae; Luo, Xiang; Qi, Xiaoxia; Tan, Wei; Huang, Guo N.; Acharya, Asha; Smith, Christopher L.; Tallquist, Michelle D.; Neilson, Eric G.; Hill, Joseph A.; Bassel-Duby, Rhonda; Olson, Eric N.

2012-01-01

The adult mammalian heart possesses little regenerative potential following injury. Fibrosis due to activation of cardiac fibroblasts impedes cardiac regeneration and contributes to loss of contractile function, pathological remodeling and susceptibility to arrhythmias. Cardiac fibroblasts account for a majority of cells in the heart and represent a potential cellular source for restoration of cardiac function following injury through phenotypic reprogramming to a myocardial cell fate. Here we show that four transcription factors, GATA4, Hand2, MEF2C and Tbx5 can cooperatively reprogram adult mouse tail-tip and cardiac fibroblasts into beating cardiac-like myocytes in vitro. Forced expression of these factors in dividing non-cardiomyocytes in mice reprograms these cells into functional cardiac-like myocytes, improves cardiac function and reduces adverse ventricular remodeling following myocardial infarction. Our results suggest a strategy for cardiac repair through reprogramming fibroblasts resident in the heart with cardiogenic transcription factors or other molecules. PMID:22660318

The effects of space flight on the contractile apparatus of antigravity muscles: implications for aging and deconditioning.

PubMed

Baldwin, K M; Caiozzo, V J; Haddad, F; Baker, M J; Herrick, R E

1994-05-01

Previous studies have shown that the unloading of skeletal muscle, as occurring during exposure to space flight, exerts a profound effect on both the mass (cross sectional area) of skeletal muscle fibers and the relative expression of protein isoforms comprising the contractile system. Available information suggests that slow (type I) fibers, comprising chiefly the antigravity muscles of experimental animals, in addition to atrophying, undergo alterations in the type of myosin heavy chain (MHC) expressed such that faster isoforms become concomitantly expressed in a sub-population of slow fibers when insufficient force-bearing activity is maintained on the muscle. Consequently, these transformations in both mass and myosin heavy chain phenotype could exert a significant impact on the functional properties of skeletal muscle as manifest in the strength, contractile speed, and endurance scope of the muscle. To further explore these issues, a study was performed in which young adult male rats were exposed to zero gravity for six days, following which, the antigravity soleus muscle was examined for a) contractile properties, determined in situ and b) isomyosin expression, as studied using biochemical, molecular biology, and histochemical/immunohistochemical techniques.

The effects of space flight on the contractile apparatus of antigravity muscles: implications for aging and deconditioning

NASA Technical Reports Server (NTRS)

Baldwin, K. M.; Caiozzo, V. J.; Haddad, F.; Baker, M. J.; Herrick, R. E.

1994-01-01

Previous studies have shown that the unloading of skeletal muscle, as occurring during exposure to space flight, exerts a profound effect on both the mass (cross sectional area) of skeletal muscle fibers and the relative expression of protein isoforms comprising the contractile system. Available information suggests that slow (type I) fibers, comprising chiefly the antigravity muscles of experimental animals, in addition to atrophying, undergo alterations in the type of myosin heavy chain (MHC) expressed such that faster isoforms become concomitantly expressed in a sub-population of slow fibers when insufficient force-bearing activity is maintained on the muscle. Consequently, these transformations in both mass and myosin heavy chain phenotype could exert a significant impact on the functional properties of skeletal muscle as manifest in the strength, contractile speed, and endurance scope of the muscle. To further explore these issues, a study was performed in which young adult male rats were exposed to zero gravity for six days, following which, the antigravity soleus muscle was examined for a) contractile properties, determined in situ and b) isomyosin expression, as studied using biochemical, molecular biology, and histochemical/immunohistochemical techniques.

Development and maintenance of force and stiffness in airway smooth muscle.

PubMed

Lan, Bo; Norris, Brandon A; Liu, Jeffrey C-Y; Paré, Peter D; Seow, Chun Y; Deng, Linhong

2015-03-01

Airway smooth muscle (ASM) plays a central role in the excessive narrowing of the airway that characterizes the primary functional impairment in asthma. This phenomenon is known as airway hyper-responsiveness (AHR). Emerging evidence suggests that the development and maintenance of ASM force involves dynamic reorganization of the subcellular filament network in both the cytoskeleton and the contractile apparatus. In this review, evidence is presented to support the view that regulation of ASM contraction extends beyond the classical actomyosin interaction and involves processes within the cytoskeleton and at the interfaces between the cytoskeleton, the contractile apparatus, and the extracellular matrix. These processes are initiated when the muscle is activated, and collectively they cause the cytoskeleton and the contractile apparatus to undergo structural transformation, resulting in a more connected and solid state that allows force generated by the contractile apparatus to be transmitted to the extracellular domain. Solidification of the cytoskeleton also serves to stiffen the muscle and hence the airway. Oscillatory strain from tidal breathing and deep inspiration is believed to be the counter balance that prevents hypercontraction and stiffening of ASM in vivo. Dysregulation of this balance could lead to AHR seen in asthma.

Effects of Chromium Picolinate on Vascular Reactivity and Cardiac Ischemia Reperfusion Injury in Spontaneously Hypertensive Rats

PubMed Central

Abebe, Worku; Liu, Jun Yao; Wimborne, Hereward; Mozaffari, Mahmood S.

2013-01-01

Chromium picolinate [Cr(pic)3] is a nutritional supplement widely promoted to exert beneficial metabolic effects in patients with type 2 diabetes/impaired glucose tolerance. Frequent comorbidities in these individuals include systemic hypertension, abnormal vascular function and ischemic heart disease but information on effects of the supplement on these aspects is sparse. Utilizing male spontaneously hypertensive rats (SHR), we examined potential impact of Cr(pic)3 on blood pressure, vascular reactivity and myocardial ischemia reperfusion injury (IRI). Dietary Cr(pic)3 supplementation (as 10 mg chromium/kg diet for 6 weeks) did not affect blood pressure of the SHR. Also, neither norepinephrine (NE) and potassium chloride (KCl)-induced contractility nor sodium nitroprusside (SNP)-induced relaxation of aortic smooth muscle from the SHR was altered by Cr(pic)3 treatment. However, Cr(pic)3 augmented endothelium-dependent relaxation of aortas, produced by acetylcholine (ACh), and this effect was abolished by N-nitro-L-arginine methyl ester (L-NAME) suggesting induction of nitric oxide (NO) production/release. Treatment with Cr(pic)3 did not affect baseline coronary flow rate and rate-pressure-product (RPP) or infarct size following regional IRI. Nonetheless, Cr(pic)3 treatment was associated with improved coronary flow and recovery of myocardial contractility and relaxation following ischemia reperfusion insult. In conclusion, dietary Cr(pic)3 treatment of SHR neither alters blood pressure nor vascular smooth muscle reactivity, but causes enhancement of endothelium-dependent vasorelaxation associated with NO production/release. Additionally, while the treatment does not affect infarct size, it improves functional recovery of the viable portion of the myocardium following IRI. PMID:20885007

Effects of chromium picolinate on vascular reactivity and cardiac ischemia-reperfusion injury in spontaneously hypertensive rats.

PubMed

Abebe, Worku; Liu, Jun Yao; Wimborne, Hereward; Mozaffari, Mahmood S

2010-01-01

Chromium picolinate [Cr(pic)(3)] is a nutritional supplement widely promoted to exert beneficial metabolic effects in patients with type 2 diabetes/impaired glucose tolerance. Frequent comorbidities in these individuals include systemic hypertension, abnormal vascular function and ischemic heart disease, but information on the effects of the supplement on these aspects is sparse. Utilizing male spontaneously hypertensive rats (SHR), we examined the potential impact of Cr(pic)(3) on blood pressure, vascular reactivity and myocardial ischemia-reperfusion injury (IRI). Dietary Cr(pic)(3) supplementation (as 10 mg chromium/kg diet for six weeks) did not affect blood pressure of the SHR. Also, neither norepinephrine (NE) and potassium chloride (KCl)-induced contractility nor sodium nitroprusside (SNP)-induced relaxation of aortic smooth muscle from the SHR was altered by Cr(pic)(3) treatment. However, Cr(pic)(3) augmented endothelium-dependent relaxation of aortas, produced by acetylcholine (ACh), and this effect was abolished by N-nitro-L-arginine methyl ester (L-NAME), suggesting induction of nitric oxide (NO) production/release. Treatment with Cr(pic)(3) did not affect baseline coronary flow rate and rate-pressure-product (RPP) or infarct size following regional IRI. Nonetheless, Cr(pic)(3) treatment was associated with improved coronary flow and recovery of myocardial contractility and relaxation following ischemia-reperfusion insult. In conclusion, dietary Cr(pic)(3) treatment of SHR alters neither blood pressure nor vascular smooth muscle reactivity but causes enhancement of endothelium-dependent vasorelaxation associated with NO production/release. Additionally, while the treatment does not affect infarct size, it improves functional recovery of the viable portion of the myocardium following IRI.

Spontaneous actin dynamics in contractile rings

NASA Astrophysics Data System (ADS)

Kruse, Karsten; Wollrab, Viktoria; Thiagarajan, Raghavan; Wald, Anne; Riveline, Daniel

Networks of polymerizing actin filaments are known to be capable to self-organize into a variety of structures. For example, spontaneous actin polymerization waves have been observed in living cells in a number of circumstances, notably, in crawling neutrophils and slime molds. During later stages of cell division, they can also spontaneously form a contractile ring that will eventually cleave the cell into two daughter cells. We present a framework for describing networks of polymerizing actin filaments, where assembly is regulated by various proteins. It can also include the effects of molecular motors. We show that the molecular processes driven by these proteins can generate various structures that have been observed in contractile rings of fission yeast and mammalian cells. We discuss a possible functional role of each of these patterns. The work was supported by Agence Nationale de la Recherche, France, (ANR-10-LABX-0030-INRT) and by Deutsche Forschungsgemeinschaft through SFB1027.

Hysteresis in the Cell Response to Time-Dependent Substrate Stiffness

PubMed Central

Besser, Achim; Schwarz, Ulrich S.

2010-01-01

Abstract Mechanical cues like the rigidity of the substrate are main determinants for the decision-making of adherent cells. Here we use a mechano-chemical model to predict the cellular response to varying substrate stiffnesses. The model equations combine the mechanics of contractile actin filament bundles with a model for the Rho-signaling pathway triggered by forces at cell-matrix contacts. A bifurcation analysis of cellular contractility as a function of substrate stiffness reveals a bistable response, thus defining a lower threshold of stiffness, below which cells are not able to build up contractile forces, and an upper threshold of stiffness, above which cells are always in a strongly contracted state. Using the full dynamical model, we predict that rate-dependent hysteresis will occur in the cellular traction forces when cells are exposed to substrates of time-dependent stiffness. PMID:20655823

Cystic Fibrosis Transmembrane Conductance Regulator in Sarcoplasmic Reticulum of Airway Smooth Muscle. Implications for Airway Contractility

PubMed Central

Cook, Daniel P.; Rector, Michael V.; Bouzek, Drake C.; Michalski, Andrew S.; Gansemer, Nicholas D.; Reznikov, Leah R.; Li, Xiaopeng; Stroik, Mallory R.; Ostedgaard, Lynda S.; Abou Alaiwa, Mahmoud H.; Thompson, Michael A.; Prakash, Y. S.; Krishnan, Ramaswamy; Meyerholz, David K.; Seow, Chun Y.

2016-01-01

Rationale: An asthma-like airway phenotype has been described in people with cystic fibrosis (CF). Whether these findings are directly caused by loss of CF transmembrane conductance regulator (CFTR) function or secondary to chronic airway infection and/or inflammation has been difficult to determine. Objectives: Airway contractility is primarily determined by airway smooth muscle. We tested the hypothesis that CFTR is expressed in airway smooth muscle and directly affects airway smooth muscle contractility. Methods: Newborn pigs, both wild type and with CF (before the onset of airway infection and inflammation), were used in this study. High-resolution immunofluorescence was used to identify the subcellular localization of CFTR in airway smooth muscle. Airway smooth muscle function was determined with tissue myography, intracellular calcium measurements, and regulatory myosin light chain phosphorylation status. Precision-cut lung slices were used to investigate the therapeutic potential of CFTR modulation on airway reactivity. Measurements and Main Results: We found that CFTR localizes to the sarcoplasmic reticulum compartment of airway smooth muscle and regulates airway smooth muscle tone. Loss of CFTR function led to delayed calcium reuptake following cholinergic stimulation and increased myosin light chain phosphorylation. CFTR potentiation with ivacaftor decreased airway reactivity in precision-cut lung slices following cholinergic stimulation. Conclusions: Loss of CFTR alters porcine airway smooth muscle function and may contribute to the airflow obstruction phenotype observed in human CF. Airway smooth muscle CFTR may represent a therapeutic target in CF and other diseases of airway narrowing. PMID:26488271

Contractile-Ring Assembly in Fission Yeast Cytokinesis: Recent Advances and New Perspectives

PubMed Central

Lee, I-Ju; Coffman, Valerie C.; Wu, Jian-Qiu

2017-01-01

The fission yeast Schizosaccharomyces pombe is an excellent model organism to study cytokinesis. Here, we review recent advances on contractile-ring assembly in fission yeast. First, we summarize the assembly of cytokinesis nodes, the precursors of a normal contractile ring. IQGAP Rng2 and myosin essential light chain Cdc4 are recruited by the anillin-like protein Mid1, followed by the addition of other cytokinesis node proteins. Mid1 localization on the plasma membrane is stabilized by interphase node proteins. Second, we discuss proteins and processes that contribute to the search, capture, pull, and release mechanism of contractile-ring assembly. Actin filaments nucleated by formin Cdc12, the motor activity of myosin-II, the stiffness of the actin network, and severing of actin filaments by cofilin all play essential roles in contractile-ring assembly. Finally, we discuss the Mid1-independent pathway for ring assembly, and the possible mechanisms underlying the ring maturation and constriction. Collectively, we provide an overview of the current understanding of contractile-ring assembly and uncover future directions in studying cytokinesis in fission yeast. PMID:22887981

Contractile-ring assembly in fission yeast cytokinesis: Recent advances and new perspectives.

PubMed

Lee, I-Ju; Coffman, Valerie C; Wu, Jian-Qiu

2012-10-01

The fission yeast Schizosaccharomyces pombe is an excellent model organism to study cytokinesis. Here, we review recent advances on contractile-ring assembly in fission yeast. First, we summarize the assembly of cytokinesis nodes, the precursors of a normal contractile ring. IQGAP Rng2 and myosin essential light chain Cdc4 are recruited by the anillin-like protein Mid1, followed by the addition of other cytokinesis node proteins. Mid1 localization on the plasma membrane is stabilized by interphase node proteins. Second, we discuss proteins and processes that contribute to the search, capture, pull, and release mechanism of contractile-ring assembly. Actin filaments nucleated by formin Cdc12, the motor activity of myosin-II, the stiffness of the actin network, and severing of actin filaments by cofilin all play essential roles in contractile-ring assembly. Finally, we discuss the Mid1-independent pathway for ring assembly, and the possible mechanisms underlying the ring maturation and constriction. Collectively, we provide an overview of the current understanding of contractile-ring assembly and uncover future directions in studying cytokinesis in fission yeast. Copyright © 2012 Wiley Periodicals, Inc.

Traction force microscopy of engineered cardiac tissues.

PubMed

Pasqualini, Francesco Silvio; Agarwal, Ashutosh; O'Connor, Blakely Bussie; Liu, Qihan; Sheehy, Sean P; Parker, Kevin Kit

2018-01-01

Cardiac tissue development and pathology have been shown to depend sensitively on microenvironmental mechanical factors, such as extracellular matrix stiffness, in both in vivo and in vitro systems. We present a novel quantitative approach to assess cardiac structure and function by extending the classical traction force microscopy technique to tissue-level preparations. Using this system, we investigated the relationship between contractile proficiency and metabolism in neonate rat ventricular myocytes (NRVM) cultured on gels with stiffness mimicking soft immature (1 kPa), normal healthy (13 kPa), and stiff diseased (90 kPa) cardiac microenvironments. We found that tissues engineered on the softest gels generated the least amount of stress and had the smallest work output. Conversely, cardiomyocytes in tissues engineered on healthy- and disease-mimicking gels generated significantly higher stresses, with the maximal contractile work measured in NRVM engineered on gels of normal stiffness. Interestingly, although tissues on soft gels exhibited poor stress generation and work production, their basal metabolic respiration rate was significantly more elevated than in other groups, suggesting a highly ineffective coupling between energy production and contractile work output. Our novel platform can thus be utilized to quantitatively assess the mechanotransduction pathways that initiate tissue-level structural and functional remodeling in response to substrate stiffness.

Vascular delay improves latissimus dorsi muscle perfusion and muscle function for use in cardiomyoplasty.

PubMed

Carroll, S M; Heilman, S J; Stremel, R W; Tobin, G R; Barker, J H

1997-04-01

Ischemia of the distal portion of the latissimus dorsi muscle occurs in muscle transfer for cardiomyoplasty and reduces distal muscle contractility and thus the mechanical effectiveness of cardiomyoplasty. We hypothesized that muscle function would be improved by a vascular delay procedure that increases distal muscle perfusion of the latissimus dorsi muscle. The latissimus dorsi muscles of 10 adult mongrel dogs were subjected to a vascular delay procedure on one side and a sham procedure on the other. Following 10 days of vascular delay, muscle perfusion was measured with a laser-Doppler perfusion imager before and after elevation of the muscles as flaps based only on their thoracodorsal neurovascular pedicles. The muscles were wrapped and sutured around silicone chambers (simulating cardiomyoplasty), a stimulating electrode was placed around each thoracodorsal nerve, and the muscles were stimulated to contract in both rhythmic and tetanic fashion. Circumferential (distal and middle latissimus dorsi muscle function) force generation and fatigue rates were measured independently. Circumferential muscle force, circumferential and longitudinal fatigue rate, and distal, middle, and overall perfusion were significantly (p < 0.05) improved in delayed muscle compared with nondelayed muscle. We found that a vascular delay procedure and a 10-day delay adaptation period significantly improve latissimus dorsi muscle flap perfusion and function, particularly in the distal and middle portions of the muscle. Delay should be considered as a means of improving the clinical outcome in cardiomyoplasty.

Molecular organization of cytokinesis nodes and contractile rings by super-resolution fluorescence microscopy of live fission yeast

PubMed Central

Laplante, Caroline; Huang, Fang; Tebbs, Irene R.; Bewersdorf, Joerg; Pollard, Thomas D.

2016-01-01

Cytokinesis in animals, fungi, and amoebas depends on the constriction of a contractile ring built from a common set of conserved proteins. Many fundamental questions remain about how these proteins organize to generate the necessary tension for cytokinesis. Using quantitative high-speed fluorescence photoactivation localization microscopy (FPALM), we probed this question in live fission yeast cells at unprecedented resolution. We show that nodes, protein assembly precursors to the contractile ring, are discrete structural units with stoichiometric ratios and distinct distributions of constituent proteins. Anillin Mid1p, Fes/CIP4 homology-Bin/amphiphysin/Rvs (F-BAR) Cdc15p, IQ motif containing GTPase-activating protein (IQGAP) Rng2p, and formin Cdc12p form the base of the node that anchors the ends of myosin II tails to the plasma membrane, with myosin II heads extending into the cytoplasm. This general node organization persists in the contractile ring where nodes move bidirectionally during constriction. We observed the dynamics of the actin network during cytokinesis, starting with the extension of short actin strands from nodes, which sometimes connected neighboring nodes. Later in cytokinesis, a broad network of thick bundles coalesced into a tight ring around the equator of the cell. The actin ring was ∼125 nm wide and ∼125 nm thick. These observations establish the organization of the proteins in the functional units of a cytokinetic contractile ring. PMID:27647921

A device for rapid and quantitative measurement of cardiac myocyte contractility

NASA Astrophysics Data System (ADS)

Gaitas, Angelo; Malhotra, Ricky; Li, Tao; Herron, Todd; Jalife, José

2015-03-01

Cardiac contractility is the hallmark of cardiac function and is a predictor of healthy or diseased cardiac muscle. Despite advancements over the last two decades, the techniques and tools available to cardiovascular scientists are limited in their utility to accurately and reliably measure the amplitude and frequency of cardiomyocyte contractions. Isometric force measurements in the past have entailed cumbersome attachment of isolated and permeabilized cardiomyocytes to a force transducer followed by measurements of sarcomere lengths under conditions of submaximal and maximal Ca2+ activation. These techniques have the inherent disadvantages of being labor intensive and costly. We have engineered a micro-machined cantilever sensor with an embedded deflection-sensing element that, in preliminary experiments, has demonstrated to reliably measure cardiac cell contractions in real-time. Here, we describe this new bioengineering tool with applicability in the cardiovascular research field to effectively and reliably measure cardiac cell contractility in a quantitative manner. We measured contractility in both primary neonatal rat heart cardiomyocyte monolayers that demonstrated a beat frequency of 3 Hz as well as human embryonic stem cell-derived cardiomyocytes with a contractile frequency of about 1 Hz. We also employed the β-adrenergic agonist isoproterenol (100 nmol l-1) and observed that our cantilever demonstrated high sensitivity in detecting subtle changes in both chronotropic and inotropic responses of monolayers. This report describes the utility of our micro-device in both basic cardiovascular research as well as in small molecule drug discovery to monitor cardiac cell contractions.

Hydralazine and Organic Nitrates Restore Impaired Excitation-Contraction Coupling by Reducing Calcium Leak Associated with Nitroso-Redox Imbalance*

PubMed Central

Dulce, Raul A.; Yiginer, Omer; Gonzalez, Daniel R.; Goss, Garrett; Feng, Ning; Zheng, Meizi; Hare, Joshua M.

2013-01-01

Although the combined use of hydralazine and isosorbide dinitrate confers important clinical benefits in patients with heart failure, the underlying mechanism of action is still controversial. We used two models of nitroso-redox imbalance, neuronal NO synthase-deficient (NOS1−/−) mice and spontaneously hypertensive heart failure rats, to test the hypothesis that hydralazine (HYD) alone or in combination with nitroglycerin (NTG) or isosorbide dinitrate restores Ca2+ cycling and contractile performance and controls superoxide production in isolated cardiomyocytes. The response to increased pacing frequency was depressed in NOS1−/− compared with wild type myocytes. Both sarcomere length shortening and intracellular Ca2+ transient (Δ[Ca2+]i) responses in NOS1−/− cardiomyocytes were augmented by HYD in a dose-dependent manner. NTG alone did not affect myocyte shortening but reduced Δ[Ca2+]i across the range of pacing frequencies and increased myofilament Ca2+ sensitivity thereby enhancing contractile efficiency. Similar results were seen in failing myocytes from the heart failure rat model. HYD alone or in combination with NTG reduced sarcoplasmic reticulum (SR) leak, improved SR Ca2+ reuptake, and restored SR Ca2+ content. HYD and NTG at low concentrations (1 μm), scavenged superoxide in isolated cardiomyocytes, whereas in cardiac homogenates, NTG inhibited xanthine oxidoreductase activity and scavenged NADPH oxidase-dependent superoxide more efficiently than HYD. Together, these results revealed that by reducing SR Ca2+ leak, HYD improves Ca2+ cycling and contractility impaired by nitroso-redox imbalance, and NTG enhanced contractile efficiency, restoring cardiac excitation-contraction coupling. PMID:23319593

The role of apical contractility in determining cell morphology in multilayered epithelial sheets and tubes

NASA Astrophysics Data System (ADS)

Zhen Tan, Rui; Lai, Tanny; Chiam, K.-H.

2017-08-01

A multilayered epithelium is made up of individual cells that are stratified in an orderly fashion, layer by layer. In such tissues, individual cells can adopt a wide range of shapes ranging from columnar to squamous. From histological images, we observe that, in flat epithelia such as the skin, the cells in the top layer are squamous while those in the middle and bottom layers are columnar, whereas in tubular epithelia, the cells in all layers are columnar. We develop a computational model to understand how individual cell shape is governed by the mechanical forces within multilayered flat and curved epithelia. We derive the energy function for an epithelial sheet of cells considering intercellular adhesive and intracellular contractile forces. We determine computationally the cell morphologies that minimize the energy function for a wide range of cellular parameters. Depending on the dominant adhesive and contractile forces, we find four dominant cell morphologies for the multilayered-layered flat sheet and three dominant cell morphologies for the two-layered curved sheet. We study the transitions between the dominant cell morphologies for the two-layered flat sheet and find both continuous and discontinuous transitions and also the presence of multistable states. Matching our computational results with histological images, we conclude that apical contractile forces from the actomyosin belt in the epithelial cells is the dominant force determining cell shape in multilayered epithelia. Our computational model can guide tissue engineers in designing artificial multilayered epithelia, in terms of figuring out the cellular parameters needed to achieve realistic epithelial morphologies.

Apelin and APJ orchestrate complex tissue-specific control of cardiomyocyte hypertrophy and contractility in the hypertrophy-heart failure transition.

PubMed

Parikh, Victoria Nicole; Liu, Jing; Shang, Ching; Woods, Christopher; Chang, Alex Chia Yu; Zhao, Mingming; Charo, David N; Grunwald, Zachary; Huang, Yong; Seo, Kinya; Tsao, Philip S; Bernstein, Daniel; Ruiz-Lozano, Pilar; Quertermous, Thomas; Ashley, Euan A

2018-05-18

The G protein coupled receptor APJ is a promising therapeutic target for heart failure. Constitutive deletion of APJ in the mouse is protective against the hypertrophy-heart failure transition via elimination of ligand-independent, β-arrestin dependent stretch transduction. However, the cellular origin of this stretch transduction and the details of its interaction with apelin signaling remain unknown. We generated mice with conditional elimination of APJ in the endothelium (APJ endo-/- ) and myocardium (APJ myo-/- ). No baseline difference was observed in LV function in APJ endo-/- , APJ myo-/- or controls (APJ endo+/+ , APJ myo+/+ ). After exposure to transaortic constriction (TAC), APJ endo-/- animals developed left ventricular failure while APJ myo-/- were protected. At the cellular level, carbon fiber stretch of freshly isolated single cardiomyocytes demonstrated decreased contractile response to stretch in APJ -/- cardiomyocytes compared to APJ +/+ cardiomyocytes. Calcium transient did not change with stretch in either APJ -/- or APJ +/+ cardiomyocytes. Application of apelin to APJ +/+ cardiomyocytes resulted in decreased calcium transient. Further, hearts of mice treated with apelin exhibited decreased phosphorylation at Troponin I (cTnI) N-terminal residues (Ser 22,23), consistent with increased calcium sensitivity. These data establish that APJ stretch transduction is mediated specifically by myocardial APJ, that APJ is necessary for stretch-induced increases in contractility, and that apelin opposes APJ's stretch-mediated hypertrophy signaling by lowering calcium transient while maintaining contractility through myofilament calcium sensitization. These findings underscore apelin's unique potential as a therapeutic agent that can simultaneously support cardiac function and protect against the hypertrophy-heart failure transition.

Use of progesterone and progestin analogs for inhibition of preterm birth and other uterine contractility disorders

PubMed Central

Garfield, R.E.; Shi, L.; Shi, S-Q.

2012-01-01

In this paper we focus on preterm birth as a uterine contractility disorder caused by hypercontractility of the myometrium. We describe changes in uterine function during term and preterm labor and delivery. We also examine the usefulness of measurement of uterine electromyographic (EMG) activity, noninvasively monitored from the abdominal surface of pregnant patients. The use of progesterone treatment for preterm birth is discussed and we conclude that present therapies with progesterone could be improved by changing the route of administration. Finally we show the results of recent studies that show that progesterone injections completely inhibit uterine EMG activity when given several days to hours before normal delivery. These studies illustrate how progesterone suppresses labor at term or preterm, probably through repression of genes which control excitability and conduction of electrical activity. However, direct profusion of soluble progesterone into the uterine cavity has little immediate inhibitory action and this may demonstrate that progesterone has no direct, nongenomic effects, at least in the rat model used. Further studies are required to determine the effects of progesterone on human uterine EMG activity and whether progesterone treatments will prevent preterm birth. PMID:24753915

Low Intensity, High Frequency Vibration Training to Improve Musculoskeletal Function in a Mouse Model of Duchenne Muscular Dystrophy

PubMed Central

Novotny, Susan A.; Mader, Tara L.; Greising, Angela G.; Lin, Angela S.; Guldberg, Robert E.; Warren, Gordon L.; Lowe, Dawn A.

2014-01-01

The objective of the study was to determine if low intensity, high frequency vibration training impacted the musculoskeletal system in a mouse model of Duchenne muscular dystrophy, relative to healthy mice. Three-week old wildtype (n = 26) and mdx mice (n = 22) were randomized to non-vibrated or vibrated (45 Hz and 0.6 g, 15 min/d, 5 d/wk) groups. In vivo and ex vivo contractile function of the anterior crural and extensor digitorum longus muscles, respectively, were assessed following 8 wks of vibration. Mdx mice were injected 5 and 1 days prior to sacrifice with Calcein and Xylenol, respectively. Muscles were prepared for histological and triglyceride analyses and subcutaneous and visceral fat pads were excised and weighed. Tibial bones were dissected and analyzed by micro-computed tomography for trabecular morphometry at the metaphysis, and cortical geometry and density at the mid-diaphysis. Three-point bending tests were used to assess cortical bone mechanical properties and a subset of tibiae was processed for dynamic histomorphometry. Vibration training for 8 wks did not alter trabecular morphometry, dynamic histomorphometry, cortical geometry, or mechanical properties (P≥0.34). Vibration did not alter any measure of muscle contractile function (P≥0.12); however the preservation of muscle function and morphology in mdx mice indicates vibration is not deleterious to muscle lacking dystrophin. Vibrated mice had smaller subcutaneous fat pads (P = 0.03) and higher intramuscular triglyceride concentrations (P = 0.03). These data suggest that vibration training at 45 Hz and 0.6 g did not significantly impact the tibial bone and the surrounding musculature, but may influence fat distribution in mice. PMID:25121503

Measurement of Maximum Isometric Force Generated by Permeabilized Skeletal Muscle Fibers.

PubMed

Roche, Stuart M; Gumucio, Jonathan P; Brooks, Susan V; Mendias, Christopher L; Claflin, Dennis R

2015-06-16

Analysis of the contractile properties of chemically skinned, or permeabilized, skeletal muscle fibers offers a powerful means by which to assess muscle function at the level of the single muscle cell. Single muscle fiber studies are useful in both basic science and clinical studies. For basic studies, single muscle fiber contractility measurements allow investigation of fundamental mechanisms of force production, and analysis of muscle function in the context of genetic manipulations. Clinically, single muscle fiber studies provide useful insight into the impact of injury and disease on muscle function, and may be used to guide the understanding of muscular pathologies. In this video article we outline the steps required to prepare and isolate an individual skeletal muscle fiber segment, attach it to force-measuring apparatus, activate it to produce maximum isometric force, and estimate its cross-sectional area for the purpose of normalizing the force produced.

Multichannel impedance monitoring for evaluation of alpha-adrenoblocker effect on the ureteral function in patients with stone disease

NASA Astrophysics Data System (ADS)

Apolikhin, O. I.; Khodyreva, L. A.; Mudraya, I. S.; Kirpatovsky, V. I.; Serdyuk, A. A.

2010-04-01

The study of distal ureter function was carried out on patients with stones in the upper urinary tract, who underwent ureteroscopy and lithotripsy procedures. The parameters of ureteral peristalsis such as peristalsis amplitude, peristalsis rate, ureteral wall tone, contractile wave duration, and its direction obtained by multichannel impedance ureterography were assessed and compared from two groups of patients. The group I patients received tamsulosin in addition to standard regimen, while the group II patients matched according to the stone size and location were managed without tamsulosin medical therapy. In comparison with group II, the group I patients demonstrated smaller average peristalsis amplitude (0.60±0.08 vs 0.81±0.06 Ohm), shorter contractions (7.1±0.3 vs 7.7±0.3 s), greater peristalsis rate (3.3±0.3 vs 2.8±0.2 per minute), and diminished ureteral tone (4.0±0.5 vs 4.7±0.2 Ohm-1). Incidence of the retrograde contractile waves was two-fold greater in the group II, while normal antegrade regular contractions were 30% more frequent in the group I. In addition, our results showed that the effect of tamsulosin on ureteral function was manifested in the patients with different stone size and location in the upper urinary tract, and it depended pronouncedly on individual ureteral tone and contractility parameters.

Interleukin 1 and Tumor Necrosis Factor Inhibit Cardiac Myocyte β -adrenergic Responsiveness

NASA Astrophysics Data System (ADS)

Gulick, Tod; Chung, Mina K.; Pieper, Stephen J.; Lange, Louis G.; Schreiner, George F.

1989-09-01

Reversible congestive heart failure can accompany cardiac allograft rejection and inflammatory myocarditis, conditions associated with an immune cell infiltrate of the myocardium. To determine whether immune cell secretory products alter cardiac muscle metabolism without cytotoxicity, we cultured cardiac myocytes in the presence of culture supernatants from activated immune cells. We observed that these culture supernatants inhibit β -adrenergic agonist-mediated increases in cultured cardiac myocyte contractility and intracellular cAMP accumulation. The myocyte contractile response to increased extracellular Ca2+ concentration is unaltered by prior exposure to these culture supernatants, as is the increase in myocyte intracellular cAMP concentration in response to stimulation with forskolin, a direct adenyl cyclase activator. Inhibition occurs in the absence of alteration in β -adrenergic receptor density or ligand binding affinity. Suppressive activity is attributable to the macrophage-derived cytokines interleukin 1 and tumor necrosis factor. Thus, these observations describe a role for defined cytokines in regulating the hormonal responsiveness and function of contractile cells. The effects of interleukin 1 and tumor necrosis factor on intracellular cAMP accumulation may be a model for immune modulation of other cellular functions dependent upon cyclic nucleotide metabolism. The uncoupling of agonist-occupied receptors from adenyl cyclase suggests that β -receptor or guanine nucleotide binding protein function is altered by the direct or indirect action of cytokines on cardiac muscle cells.

Severe myopathy in mice lacking the MEF2/SRF-dependent gene leiomodin-3

PubMed Central

Cenik, Bercin K.; Garg, Ankit; McAnally, John R.; Shelton, John M.; Richardson, James A.; Bassel-Duby, Rhonda; Olson, Eric N.; Liu, Ning

2015-01-01

Maintenance of skeletal muscle structure and function requires a precise stoichiometry of sarcomeric proteins for proper assembly of the contractile apparatus. Absence of components of the sarcomeric thin filaments causes nemaline myopathy, a lethal congenital muscle disorder associated with aberrant myofiber structure and contractility. Previously, we reported that deficiency of the kelch-like family member 40 (KLHL40) in mice results in nemaline myopathy and destabilization of leiomodin-3 (LMOD3). LMOD3 belongs to a family of tropomodulin-related proteins that promote actin nucleation. Here, we show that deficiency of LMOD3 in mice causes nemaline myopathy. In skeletal muscle, transcription of Lmod3 was controlled by the transcription factors SRF and MEF2. Myocardin-related transcription factors (MRTFs), which function as SRF coactivators, serve as sensors of actin polymerization and are sequestered in the cytoplasm by actin monomers. Conversely, conditions that favor actin polymerization de-repress MRTFs and activate SRF-dependent genes. We demonstrated that the actin nucleator LMOD3, together with its stabilizing partner KLHL40, enhances MRTF-SRF activity. In turn, SRF cooperated with MEF2 to sustain the expression of LMOD3 and other components of the contractile apparatus, thereby establishing a regulatory circuit to maintain skeletal muscle function. These findings provide insight into the molecular basis of the sarcomere assembly and muscle dysfunction associated with nemaline myopathy. PMID:25774500

Myosin-driven rescue of contractile reserve and energetics in mouse hearts bearing familial hypertrophic cardiomyopathy-associated mutant troponin T is mutation-specific.

PubMed

He, Huamei; Hoyer, Kirsten; Tao, Hai; Rice, Ronald; Jimenez, Jesus; Tardiff, Jil C; Ingwall, Joanne S

2012-11-01

The thin filament protein troponin T (TnT) is a regulator of sarcomere function. Whole heart energetics and contractile reserve are compromised in transgenic mice bearing missense mutations at R92 within the tropomyosin-binding domain of cTnT, despite being distal to the ATP hydrolysis domain of myosin. These mutations are associated with familial hypertrophic cardiomyopathy (FHC). Here we test the hypothesis that genetically replacing murine αα-MyHC with murine ββ-MyHC in hearts bearing the R92Q cTnT mutation, a particularly lethal FHC-associated mutation, leads to sufficiently large perturbations in sarcomere function to rescue whole heart energetics and decrease the cost of contraction. By comparing R92Q cTnT and R92L cTnT mutant hearts, we also test whether any rescue is mutation-specific. We defined the energetic state of the isolated perfused heart using (31)P-NMR spectroscopy while simultaneously measuring contractile performance at four work states. We found that the cost of increasing contraction in intact mouse hearts with R92Q cTnT depends on the type of myosin present in the thick filament. We also found that the salutary effect of this manoeuvre is mutation-specific, demonstrating the major regulatory role of cTnT on sarcomere function at the whole heart level.

Improved throughput traction microscopy reveals pivotal role for matrix stiffness in fibroblast contractility and TGF-β responsiveness

PubMed Central

Marinković, Aleksandar; Mih, Justin D.; Park, Jin-Ah; Liu, Fei

2012-01-01

Lung fibroblast functions such as matrix remodeling and activation of latent transforming growth factor-β1 (TGF-β1) are associated with expression of the myofibroblast phenotype and are directly linked to fibroblast capacity to generate force and deform the extracellular matrix. However, the study of fibroblast force-generating capacities through methods such as traction force microscopy is hindered by low throughput and time-consuming procedures. In this study, we improved at the detail level methods for higher-throughput traction measurements on polyacrylamide hydrogels using gel-surface-bound fluorescent beads to permit autofocusing and automated displacement mapping, and transduction of fibroblasts with a fluorescent label to streamline cell boundary identification. Together these advances substantially improve the throughput of traction microscopy and allow us to efficiently compute the forces exerted by lung fibroblasts on substrates spanning the stiffness range present in normal and fibrotic lung tissue. Our results reveal that lung fibroblasts dramatically alter the forces they transmit to the extracellular matrix as its stiffness changes, with very low forces generated on matrices as compliant as normal lung tissue. Moreover, exogenous TGF-β1 selectively accentuates tractions on stiff matrices, mimicking fibrotic lung, but not on physiological stiffness matrices, despite equivalent changes in Smad2/3 activation. Taken together, these results demonstrate a pivotal role for matrix mechanical properties in regulating baseline and TGF-β1-stimulated contraction of lung fibroblasts and suggest that stiff fibrotic lung tissue may promote myofibroblast activation through contractility-driven events, whereas normal lung tissue compliance may protect against such feedback amplification of fibroblast activation. PMID:22659883

SKELETAL MUSCLE ULTRASTRUCTURE AND FUNCTION IN STATIN-TOLERANT INDIVIDUALS

PubMed Central

Rengo, Jason L.; Callahan, Damien M.; Savage, Patrick D.; Ades, Philip A.; Toth, Michael J.

2015-01-01

Skeletal Muscle Ultrastructure and Function in Statin-Tolerant Individuals: Introduction Statins have well-known benefits on cardiovascular mortality, though up to 15% of patients experience side effects. With guidelines from the American Heart Association, American College of Cardiology, and American Diabetics Association expected to double the number of statin users, the overall incidence of myalgia and myopathy will increase. Methods We evaluated skeletal muscle structure and contractile function at the molecular, cellular, and whole tissue levels in 12 statin tolerant and 12 control subjects. Results Myosin isoform expression, fiber type distributions, single fiber maximal Ca2+-activated tension, and whole muscle contractile force were similar between groups. No differences were observed in myosin-actin cross-bridge kinetics in myosin heavy chain (MHC) I or IIA fibers. Discussion We found no evidence for statin-induced changes in muscle morphology at the molecular, cellular, or whole tissue levels. Collectively, our data show that chronic statin therapy in healthy asymptomatic individuals does not promote deleterious myofilament structural or functional adaptations. PMID:26059690

Human engineered heart tissue as a model system for drug testing.

PubMed

Eder, Alexandra; Vollert, Ingra; Hansen, Arne; Eschenhagen, Thomas

2016-01-15

Drug development is time- and cost-intensive and, despite extensive efforts, still hampered by the limited value of current preclinical test systems to predict side effects, including proarrhythmic and cardiotoxic effects in clinical practice. Part of the problem may be related to species-dependent differences in cardiomyocyte biology. Therefore, the event of readily available human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes (CM) has raised hopes that this human test bed could improve preclinical safety pharmacology as well as drug discovery approaches. However, hiPSC-CM are immature and exhibit peculiarities in terms of ion channel function, gene expression, structural organization and functional responses to drugs that limit their present usefulness. Current efforts are thus directed towards improving hiPSC-CM maturity and high-content readouts. Culturing hiPSC-CM as 3-dimensional engineered heart tissue (EHT) improves CM maturity and anisotropy and, in a 24-well format using silicone racks, enables automated, multiplexed high content readout of contractile function. This review summarizes the principal technology and focuses on advantages and disadvantages of this technology and its potential for preclinical drug screening. Copyright © 2015 Elsevier B.V. All rights reserved.

Neurohormonal axis in patients with pulmonary arterial hypertension: friend or foe?

PubMed

de Man, Frances S; Handoko, M Louis; Guignabert, Christophe; Bogaard, Harm J; Vonk-Noordegraaf, Anton

2013-01-01

Despite its description some 25 years ago, neurohormonal activation has long been neglected as an important factor in the pathophysiology of pulmonary arterial hypertension (PAH). Neurohormonal activation was interpreted as a necessary compensatory response to maintain cardiac contractility and systemic blood pressure. Therefore, inhibitors of neurohormonal activity (like β-blockers or angiotensin-converting enzyme inhibitors) are considered contraindicated in current PAH management guidelines. However, recent data revealed that sympathetic overstimulation is strongly related to mortality, and blockade of neurohormonal activity in experimental PAH improved survival and cardiac function. These novel insights shed new light on the role of neurohormonal activity in PAH.

Protective role of Parkin in skeletal muscle contractile and mitochondrial function.

PubMed

Gouspillou, Gilles; Godin, Richard; Piquereau, Jérome; Picard, Martin; Mofarrahi, Mahroo; Mathew, Jasmin; Purves-Smith, Fennigje M; Sgarioto, Nicolas; Hepple, Russell T; Burelle, Yan; Hussain, Sabah N A

2018-04-22

Parkin, an E3 ubiquitin ligase encoded by the Park2 gene, has been implicated in the regulation of mitophagy, a quality control process in which defective mitochondria are degraded. The exact physiological significance of Parkin in regulating mitochondrial function and contractility in skeletal muscle remains largely unexplored. Using Park2 -/- mice, we show that Parkin ablation causes a decrease in muscle specific force, a severe decrease in mitochondrial respiration, mitochondrial uncoupling and an increased susceptibility to opening of the permeability transition pore. These results demonstrate that Parkin plays a protective role in the maintenance of normal mitochondrial and contractile functions in skeletal muscles. Parkin is an E3 ubiquitin ligase encoded by the Park2 gene. Parkin has been implicated in the regulation of mitophagy, a quality control process in which defective mitochondria are sequestered in autophagosomes and delivered to lysosomes for degradation. Although Parkin has been mainly studied for its implication in neuronal degeneration in Parkinson disease, its role in other tissues remains largely unknown. In the present study, we investigated the skeletal muscles of Park2 knockout (Park2 -/- ) mice to test the hypothesis that Parkin plays a physiological role in mitochondrial quality control in normal skeletal muscle, a tissue highly reliant on mitochondrial content and function. We first show that the tibialis anterior (TA) of Park2 -/- mice display a slight but significant decrease in its specific force. Park2 -/ - muscles also show a trend for type IIB fibre hypertrophy without alteration in muscle fibre type proportion. Compared to Park2 +/+ muscles, the mitochondrial function of Park2 -/- skeletal muscles was significantly impaired, as indicated by the significant decrease in ADP-stimulated mitochondrial respiratory rates, uncoupling, reduced activities of respiratory chain complexes containing mitochondrial DNA (mtDNA)-encoded subunits and increased susceptibility to opening of the permeability transition pore. Muscles of Park2 -/- mice also displayed a decrease in the content of the mitochondrial pro-fusion protein Mfn2 and an increase in the pro-fission protein Drp1 suggesting an increase in mitochondrial fragmentation. Finally, Park2 ablation resulted in an increase in basal autophagic flux in skeletal muscles. Overall, the results of the present study demonstrate that Parkin plays a protective role in the maintenance of normal mitochondrial and contractile functions in normal skeletal muscles. © 2018 The Authors. The Journal of Physiology © 2018 The Physiological Society.

Na+,K+-pump stimulation improves contractility in isolated muscles of mice with hyperkalemic periodic paralysis

PubMed Central

Nielsen, Ole Bækgaard; Clausen, Johannes D.; Pedersen, Thomas Holm; Hayward, Lawrence J.

2011-01-01

In patients with hyperkalemic periodic paralysis (HyperKPP), attacks of muscle weakness or paralysis are triggered by K+ ingestion or rest after exercise. Force can be restored by muscle work or treatment with β2-adrenoceptor agonists. A missense substitution corresponding to a mutation in the skeletal muscle voltage-gated Na+ channel (Nav1.4, Met1592Val) causing human HyperKPP was targeted into the mouse SCN4A gene (mutants). In soleus muscles prepared from these mutant mice, twitch, tetanic force, and endurance were markedly reduced compared with soleus from wild type (WT), reflecting impaired excitability. In mutant soleus, contractility was considerably more sensitive than WT soleus to inhibition by elevated [K+]o. In resting mutant soleus, tetrodotoxin (TTX)-suppressible 22Na uptake and [Na+]i were increased by 470 and 58%, respectively, and membrane potential was depolarized (by 16 mV, P < 0.0001) and repolarized by TTX. Na+,K+ pump–mediated 86Rb uptake was 83% larger than in WT. Salbutamol stimulated 86Rb uptake and reduced [Na+]i both in mutant and WT soleus. Stimulating Na+,K+ pumps with salbutamol restored force in mutant soleus and extensor digitorum longus (EDL). Increasing [Na+]i with monensin also restored force in soleus. In soleus, EDL, and tibialis anterior muscles of mutant mice, the content of Na+,K+ pumps was 28, 62, and 33% higher than in WT, respectively, possibly reflecting the stimulating effect of elevated [Na+]i on the synthesis of Na+,K+ pumps. The results confirm that the functional disorders of skeletal muscles in HyperKPP are secondary to increased Na+ influx and show that contractility can be restored by acute stimulation of the Na+,K+ pumps. Calcitonin gene-related peptide (CGRP) restored force in mutant soleus but caused no detectable increase in 86Rb uptake. Repeated excitation and capsaicin also restored contractility, possibly because of the release of endogenous CGRP from nerve endings in the isolated muscles. These observations may explain how mild exercise helps locally to prevent severe weakness during an attack of HyperKPP. PMID:21708955

Oxygen Generating Biomaterials Preserve Skeletal Muscle Homeostasis under Hypoxic and Ischemic Conditions

PubMed Central

Ward, Catherine L.; Corona, Benjamin T.; Yoo, James J.; Harrison, Benjamin S.; Christ, George J.

2013-01-01

Provision of supplemental oxygen to maintain soft tissue viability acutely following trauma in which vascularization has been compromised would be beneficial for limb and tissue salvage. For this application, an oxygen generating biomaterial that may be injected directly into the soft tissue could provide an unprecedented treatment in the acute trauma setting. The purpose of the current investigation was to determine if sodium percarbonate (SPO), an oxygen generating biomaterial, is capable of maintaining resting skeletal muscle homeostasis under otherwise hypoxic conditions. In the current studies, a biologically and physiologically compatible range of SPO (1–2 mg/mL) was shown to: 1) improve the maintenance of contractility and attenuate the accumulation of HIF1α, depletion of intramuscular glycogen, and oxidative stress (lipid peroxidation) that occurred following ∼30 minutes of hypoxia in primarily resting (duty cycle = 0.2 s train/120 s contraction interval <0.002) rat extensor digitorum longus (EDL) muscles in vitro (95% N2–5% CO2, 37°C); 2) attenuate elevations of rat EDL muscle resting tension that occurred during contractile fatigue testing (3 bouts of 25 100 Hz tetanic contractions; duty cycle = 0.2 s/2 s = 0.1) under oxygenated conditions in vitro (95% O2–5% CO2, 37°C); and 3) improve the maintenance of contractility (in vivo) and prevent glycogen depletion in rat tibialis anterior (TA) muscle in a hindlimb ischemia model (i.e., ligation of the iliac artery). Additionally, injection of a commercially available lipid oxygen-carrying compound or the components (sodium bicarbonate and hydrogen peroxide) of 1 mg/mL SPO did not improve EDL muscle contractility under hypoxic conditions in vitro. Collectively, these findings demonstrate that a biological and physiological concentration of SPO (1–2 mg/mL) injected directly into rat skeletal muscle (EDL or TA muscles) can partially preserve resting skeletal muscle homeostasis under hypoxic conditions. PMID:23991116

Contractile markers distinguish structures of the mouse aqueous drainage tract

PubMed Central

Ko, MinHee K.

2013-01-01

Purpose Structures of the aqueous humor drainage tract are contractile, although the tract is not entirely composed of muscle. We characterized the mouse aqueous drainage tract by immunolabeling contractile markers and determined whether profiling these markers within the tract distinguished its key structures of the trabecular meshwork (TM) and ciliary muscle (CM). Methods Enucleated eyes from pigmented C57BL/6 (n=8 mice) and albino BALB/c (n=6 mice) mice were processed for cryo- and formalin-fixed paraffin-embedded sectioning. Immunofluorescence labeling was performed for the following: (a) filamentous actin (using fluorescence-conjugated phalloidin), representing a global contractile marker; (b) α-smooth muscle actin (α-SMA), caldesmon, and calponin, representing classic smooth muscle epitopes; and (c) nonmuscle myosin heavy chain, representing a nonmuscle contractile protein. Tissue labeling was identified by confocal microscopy and analyzed quantitatively. Hematoxylin and eosin staining provided structural orientation. Results A small portion of the TM faced the anterior chamber; the rest extended posteriorly alongside Schlemm’s canal (SC) within the inner sclera. Within the drainage tract, filamentous actin labeling was positive in TM and CM. α-SMA and caldesmon labeling was seen primarily along the CM, which extended from the anterior chamber angle to its posterior termination beyond the SC near the retina. Low intensity, patchy α-SMA and caldesmon labeling was seen in the TM. Myosin heavy chain immunoreactivity was primarily found in the TM and calponin was primarily observed in the CM. C57BL/6 and BALB/c comparison showed that pigment obscured fluorescence in the ciliary body. Conclusions Our strategy of profiling contractile markers distinguished mouse aqueous drainage tract structures that were otherwise indistinguishable by hematoxylin and eosin staining. The mouse TM was seen as an intervening structure between SC, a part of the conventional drainage tract, and CM, a part of the unconventional drainage tract. Our findings provide important insights into the structural and functional organization of the mouse aqueous drainage tract and a basis for exploring the role of contractility in modulating aqueous outflow. PMID:24357924

Cardiac-specific deletion of protein phosphatase 1β promotes increased myofilament protein phosphorylation and contractile alterations

PubMed Central

Liu, Ruijie; Correll, Robert N.; Davis, Jennifer; Vagnozzi, Ronald J.; York, Allen J.; Sargent, Michelle A.; Nairn, Angus C.; Molkentin, Jeffery D.

2015-01-01

There are 3 protein phosphatase 1 (PP1) catalytic isoforms (α, β and γ) encoded within the mammalian genome. These 3 gene products share ~90% amino acid homology within their catalytic domains but each has unique N- and C-termini that likely underlie distinctive subcellular localization or functionality. In this study, we assessed the effect associated with loss of each PP1 isoform in the heart using a conditional Cre-loxP targeting approach in mice. Ppp1ca-loxP, Ppp1cb-loxP and Ppp1cc-oxP alleles were crossed with either an Nkx2.5-Cre knock-in containing allele for early embryonic deletion or a tamoxifen inducible α-myosin heavy chain (αMHC)-MerCreMer transgene for adult and cardiac-specific deletion. We determined that while deletion of Ppp1ca (PP1α) or Ppp1cc (PP1γ) had little effect on the whole heart, deletion of Ppp1cb (PP1β) resulted in concentric remodeling of the heart, interstitial fibrosis and contractile dysregulation, using either the embryonic or adult-specific Cre-expressing alleles. However, myocytes isolated from Ppp1cb deleted hearts surprisingly showed enhanced contractility. Mechanistically we found that deletion of any of the 3 PP1 gene-encoding isoforms had no effect on phosphorylation of phospholamban, nor were Ca2+ handling dynamics altered in adult myocytes from Ppp1cb deleted hearts. However, loss of Ppp1cb from the heart, but not Ppp1ca or Ppp1cc, resulted in elevated phosphorylation of myofilament proteins such as myosin light chain 2 and cardiac myosin binding protein C, consistent with an enriched localization profile of this isoform to the sarcomeres. These results suggest a unique functional role for the PP1β isoform in affecting cardiac contractile function. PMID:26334248

Deficiency in AMPK attenuates ethanol-induced cardiac contractile dysfunction through inhibition of autophagosome formation

PubMed Central

Guo, Rui; Ren, Jun

2012-01-01

Aims Binge drinking often triggers compromised myocardial contractile function while activating AMP-activated protein kinase (AMPK). Given the role of AMPK in the initiation of autophagy through the mammalian target of rapamycin complex 1 (mTORC1) and Unc51-like kinase (ULK1), this study was designed to examine the impact of AMPK deficiency on cardiac function and the mechanism involved with a focus on autophagy following an acute ethanol challenge. Methods and results Wild-type (WT) and transgenic mice overexpressing a kinase-dead (KD) α2 isoform (K45R mutation) of AMPK were challenged with ethanol. Glucose tolerance, echocardiography, Langendorff heart and cardiomyocyte contractile function, autophagy, and autophagic signalling including AMPK, acetyl-CoA carboxylase (ACC), mTOR, the mTORC1-associated protein Raptor, and ULK1 were examined. Ethanol exposure triggered glucose intolerance and compromised cardiac contraction accompanied by increased phosphorylation of AMPK and ACC as well as autophagosome accumulation (increased LC3II and p62), the effects of which were attenuated or mitigated by AMPK deficiency or inhibition. Ethanol dampened and stimulated, respectively, the phosphorylation of mTOR and Raptor, the effects of which were abolished by AMPK deficiency. ULK1 phosphorylation at Ser757 and Ser777 was down-regulated and up-regulated, respectively, by ethanol, the effect of which was nullified by AMPK deficiency or inhibition. Moreover, the ethanol challenge enhanced LC3 puncta in H9c2 cells and promoted cardiac contractile dysfunction, and these effects were ablated by the inhibition of autophagy or AMPK. Lysosomal inhibition failed to accentuate ethanol-induced increases in LC3II and p62. Conclusion In summary, these data suggest that ethanol exposure may trigger myocardial dysfunction through a mechanism associated with AMPK-mTORC1-ULK1-mediated autophagy. PMID:22451512

Hypertrophic Stimulation Increases β-actin Dynamics in Adult Feline Cardiomyocytes

PubMed Central

Balasubramanian, Sundaravadivel; Mani, Santhosh K.; Kasiganesan, Harinath; Baicu, Catalin C.; Kuppuswamy, Dhandapani

2010-01-01

The myocardium responds to hemodynamic stress through cellular growth and organ hypertrophy. The impact of cytoskeletal elements on this process, however, is not fully understood. While α-actin in cardiomyocytes governs muscle contraction in combination with the myosin motor, the exact role of β-actin has not been established. We hypothesized that in adult cardiomyocytes, as in non-myocytes, β-actin can facilitate cytoskeletal rearrangement within cytoskeletal structures such as Z-discs. Using a feline right ventricular pressure overload (RVPO) model, we measured the level and distribution of β-actin in normal and pressure overloaded myocardium. Resulting data demonstrated enriched levels of β-actin and enhanced translocation to the Triton-insoluble cytoskeletal and membrane skeletal complexes. In addition, RVPO in vivo and in vitro hypertrophic stimulation with endothelin (ET) or insulin in isolated adult cardiomyocytes enhanced the content of polymerized fraction (F-actin) of β-actin. To determine the localization and dynamics of β-actin, we adenovirally expressed GFP-tagged β-actin in isolated adult cardiomyocytes. The ectopically expressed β-actin-GFP localized to the Z-discs, costameres, and cell termini. Fluorescence recovery after photobleaching (FRAP) measurements of β-actin dynamics revealed that β-actin at the Z-discs is constantly being exchanged with β-actin from cytoplasmic pools and that this exchange is faster upon hypertrophic stimulation with ET or insulin. In addition, in electrically stimulated isolated adult cardiomyocytes, while β-actin overexpression improved cardiomyocyte contractility, immunoneutralization of β-actin resulted in a reduced contractility suggesting that β-actin could be important for the contractile function of adult cardiomyocytes. These studies demonstrate the presence and dynamics of β-actin in the adult cardiomyocyte and reinforce its usefulness in measuring cardiac cytoskeletal rearrangement during hypertrophic stimulation. PMID:20635003

Hypertrophic stimulation increases beta-actin dynamics in adult feline cardiomyocytes.

PubMed

Balasubramanian, Sundaravadivel; Mani, Santhosh K; Kasiganesan, Harinath; Baicu, Catalin C; Kuppuswamy, Dhandapani

2010-07-12

The myocardium responds to hemodynamic stress through cellular growth and organ hypertrophy. The impact of cytoskeletal elements on this process, however, is not fully understood. While alpha-actin in cardiomyocytes governs muscle contraction in combination with the myosin motor, the exact role of beta-actin has not been established. We hypothesized that in adult cardiomyocytes, as in non-myocytes, beta-actin can facilitate cytoskeletal rearrangement within cytoskeletal structures such as Z-discs. Using a feline right ventricular pressure overload (RVPO) model, we measured the level and distribution of beta-actin in normal and pressure overloaded myocardium. Resulting data demonstrated enriched levels of beta-actin and enhanced translocation to the Triton-insoluble cytoskeletal and membrane skeletal complexes. In addition, RVPO in vivo and in vitro hypertrophic stimulation with endothelin (ET) or insulin in isolated adult cardiomyocytes enhanced the content of polymerized fraction (F-actin) of beta-actin. To determine the localization and dynamics of beta-actin, we adenovirally expressed GFP-tagged beta-actin in isolated adult cardiomyocytes. The ectopically expressed beta-actin-GFP localized to the Z-discs, costameres, and cell termini. Fluorescence recovery after photobleaching (FRAP) measurements of beta-actin dynamics revealed that beta-actin at the Z-discs is constantly being exchanged with beta-actin from cytoplasmic pools and that this exchange is faster upon hypertrophic stimulation with ET or insulin. In addition, in electrically stimulated isolated adult cardiomyocytes, while beta-actin overexpression improved cardiomyocyte contractility, immunoneutralization of beta-actin resulted in a reduced contractility suggesting that beta-actin could be important for the contractile function of adult cardiomyocytes. These studies demonstrate the presence and dynamics of beta-actin in the adult cardiomyocyte and reinforce its usefulness in measuring cardiac cytoskeletal rearrangement during hypertrophic stimulation.

Cardiac Overexpression of Antioxidant Catalase Attenuates Aging-Induced Cardiomyocyte Relaxation Dysfunction

PubMed Central

Ren, Jun; Li, Qun; Wu, Shan; Li, Shi-Yan; Babcock, Sara A.

2007-01-01

Catalase, an enzyme which detoxifies H2O2, may interfere with cardiac aging. To test this hypothesis, contractile and intracellular Ca2+ properties were evaluated in cardiomyocytes from young (3–4 mo) and old (26–28 mo) FVB and transgenic mice with cardiac overexpression of catalase. Contractile indices analyzed included peak shortening (PS), time-to-90% PS (TPS90), time-to-90% relengthening (TR90), half-width duration (HWD), maximal velocity of shortening/relengthening (± dL/dt) and intracellular Ca2+ levels or decay rate. Levels of advanced glycation endproduct (AGE), Na+/Ca2+ exchanger (NCX), sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA2a), phospholamban (PLB), myosin heavy chain (MHC), membrane Ca2+ and K+ channels were measured by western blot. Catalase transgene prolonged survival while did not alter myocyte function by itself. Aging depressed ± dL/dt, prolonged HWD, TR90 and intracellular Ca2+ decay without affecting other indices in FVB myocytes. Aged FVB myocytes exhibited a stepper decline in PS in response to elevated stimulus or a dampened rise in PS in response to elevated extracellular Ca2+ levels. Interestingly, aging-induced defects were nullified or significantly attenuated by catalase. AGE level was elevated by 5-fold in aged FVB compared with young FVB mice, which was reduced by catalase. Expression of SERCA2a, NCX and Kv1.2 K+ channel was significantly reduced although levels of PLB, L-type Ca2+ channel dihydropyridine receptor and β-MHC isozyme remained unchanged in aged FVB hearts. Catalase restored NCX and Kv1.2 K+ channel but not SERCA2a level in aged mice. In summary, our data suggested that catalase protects cardiomyocytes from aging-induced contractile defect possibly via improved intracellular Ca2+ handling. PMID:17250874

Abnormalities in intracellular calcium regulation and contractile function in myocardium from dogs with pacing-induced heart failure

NASA Technical Reports Server (NTRS)

Perreault, C. L.; Shannon, R. P.; Komamura, K.; Vatner, S. F.; Morgan, J. P.

1992-01-01

24 d of rapid ventricular pacing induced dilated cardiomyopathy with both systolic and diastolic dysfunction in conscious, chronically instrumented dogs. We studied mechanical properties and intracellular calcium (Ca2+i) transients of trabeculae carneae isolated from 15 control dogs (n = 32) and 11 dogs with pacing-induced cardiac failure (n = 26). Muscles were stretched to maximum length at 30 degrees C and stimulated at 0.33 Hz; a subset (n = 17 control, n = 17 myopathic) was loaded with the [Ca2+]i indicator aequorin. Peak tension was depressed in the myopathic muscles, even in the presence of maximally effective (i.e., 16 mM) [Ca2+] in the perfusate. However, peak [Ca2+]i was similar (0.80 +/- 0.13 vs. 0.71 +/- 0.05 microM; [Ca2+]o = 2.5 mM), suggesting that a decrease in Cai2+ availability was not responsible for the decreased contractility. The time for decline from the peak of the Cai2+ transient was prolonged in the myopathic group, which correlated with prolongation of isometric contraction and relaxation. However, similar end-diastolic [Ca2+]i was achieved in both groups (0.29 +/- 0.05 vs. 0.31 +/- 0.02 microM), indicating that Cai2+ homeostasis can be maintained in myopathic hearts. The inotropic response of the myopathic muscles to milrinone was depressed compared with the controls. However, when cAMP production was stimulated by pretreatment with forskolin, the response of the myopathic muscles to milrinone was improved. Our findings provide direct evidence that abnormal [Ca2+]i handling is an important cause of contractile dysfunction in dogs with pacing-induced heart failure and suggest that deficient production of cAMP may be an important cause of these changes in excitation-contraction coupling.

Saxagliptin and Tadalafil Differentially Alter Cyclic Guanosine Monophosphate (cGMP) Signaling and Left Ventricular Function in Aortic-Banded Mini-Swine.

PubMed

Hiemstra, Jessica A; Lee, Dong I; Chakir, Khalid; Gutiérrez-Aguilar, Manuel; Marshall, Kurt D; Zgoda, Pamela J; Cruz Rivera, Noelany; Dozier, Daniel G; Ferguson, Brian S; Heublein, Denise M; Burnett, John C; Scherf, Carolin; Ivey, Jan R; Minervini, Gianmaria; McDonald, Kerry S; Baines, Christopher P; Krenz, Maike; Domeier, Timothy L; Emter, Craig A

2016-04-20

Cyclic guanosine monophosphate-protein kinase G-phosphodiesterase 5 signaling may be disturbed in heart failure (HF) with preserved ejection fraction, contributing to cardiac remodeling and dysfunction. The purpose of this study was to manipulate cyclic guanosine monophosphate signaling using the dipeptidyl-peptidase 4 inhibitor saxagliptin and phosphodiesterase 5 inhibitor tadalafil. We hypothesized that preservation of cyclic guanosine monophosphate cGMP signaling would attenuate pathological cardiac remodeling and improve left ventricular (LV) function. We assessed LV hypertrophy and function at the organ and cellular level in aortic-banded pigs. Concentric hypertrophy was equal in all groups, but LV collagen deposition was increased in only HF animals. Prevention of fibrotic remodeling by saxagliptin and tadalafil was correlated with neuropeptide Y plasma levels. Saxagliptin better preserved integrated LV systolic and diastolic function by maintaining normal LV chamber volumes and contractility (end-systolic pressure-volume relationship, preload recruitable SW) while preventing changes to early/late diastolic longitudinal strain rate. Function was similar to the HF group in tadalafil-treated animals including increased LV contractility, reduced chamber volume, and decreased longitudinal, circumferential, and radial mechanics. Saxagliptin and tadalafil prevented a negative cardiomyocyte shortening-frequency relationship observed in HF animals. Saxagliptin increased phosphodiesterase 5 activity while tadalafil increased cyclic guanosine monophosphate levels; however, neither drug increased downstream PKG activity. Early mitochondrial dysfunction, evident as decreased calcium-retention capacity and Complex II-dependent respiratory control, was present in both HF and tadalafil-treated animals. Both saxagliptin and tadalafil prevented increased LV collagen deposition in a manner related to the attenuation of increased plasma neuropeptide Y levels. Saxagliptin appears superior for treating heart failure with preserved ejection fraction, considering its comprehensive effects on integrated LV systolic and diastolic function. © 2016 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley Blackwell.

Selective inhibition of class I but not class IIb histone deacetylases exerts cardiac protection from ischemia reperfusion

PubMed Central

Aune, Sverre E.; Herr, Daniel J.; Mani, Santhosh K.; Menick, Donald R.

2014-01-01

While inhibition of class I/IIb histone deacetylases (HDACs) protects the mammalian heart from ischemia reperfusion (IR) injury, class selective effects remain unexamined. We hypothesized that selective inhibition of class I HDACs would preserve left ventricular contractile function following IR in isolated hearts. Male Sprague Dawley rats (n=6 per group) were injected with vehicle (dimethylsulfoxide, 0.63 mg/kg), the class I/IIb HDAC inhibitor trichostatin A (1 mg/kg), the class I HDAC inhibitor entinostat (MS-275, 10 mg/kg), or the HDAC6 (class IIb) inhibitor tubastatin A (10 mg/kg). After 24 h, hearts were isolated and perfused in Langendorff mode for 30 min (Sham) or subjected to 30 min global ischemia and 120 min global reperfusion (IR). A saline filled balloon attached to a pressure transducer was placed in the LV to monitor contractile function. After perfusion, LV tissue was collected for measurements of antioxidant protein levels and infarct area. At the conclusion of IR, MS-275 pretreatment was associated with significant preservation of developed pressure, rate of pressure generation, rate of pressure relaxation and rate pressure product, as compared to vehicle treated hearts. There was significant reduction of infarct area with MS-275 pretreatment. Contractile function was not significantly restored in hearts treated with trichostatin A or tubastatin A. Mitochondrial superoxide dismutase (SOD2) and catalase protein and mRNA in hearts from animals pretreated with MS-275 were increased following IR, as compared to Sham. This was associated with a dramatic enrichment of nuclear FOXO3a transcription factor, which mediates the expression of SOD2 and catalase. Tubastatin A treatment was associated with significantly decreased catalase levels after IR. Class I HDAC inhibition elicits protection of contractile function following IR, which is associated with increased expression of endogenous antioxidant enzymes. Class I/IIb HDAC inhibition with trichostatin A or selective inhibition of HDAC6 with tubastatin A was not protective. This study highlights the need for the development of new strategies that target specific HDAC isoforms in cardiac ischemia reperfusion. PMID:24632412

Spatio-Temporal Changes of Lymphatic Contractility and Drainage Patterns following Lymphadenectomy in Mice

PubMed Central

Kwon, Sunkuk; Agollah, Germaine D.; Wu, Grace; Sevick-Muraca, Eva M.

2014-01-01

Objective To investigate the redirection of lymphatic drainage post-lymphadenectomy using non-invasive near-infrared fluorescence (NIRF) imaging, and to subsequently assess impact on metastasis. Background Cancer-acquired lymphedema arises from dysfunctional fluid transport after lymphadenectomy performed for staging and to disrupt drainage pathways for regional control of disease. However, little is known about the normal regenerative processes of the lymphatics in response to lymphadenectomy and how these responses can be accelerated, delayed, or can impact metastasis. Methods Changes in lymphatic “pumping” function and drainage patterns were non-invasively and longitudinally imaged using NIRF lymphatic imaging after popliteal lymphadenectomy in mice. In a cohort of mice, B16F10 melanoma was inoculated on the dorsal aspect of the paw 27 days after lymphadenectomy to assess how drainage patterns affect metastasis. Results NIRF imaging demonstrates that, although lymphatic function and drainage patterns change significantly in early response to popliteal lymph node (PLN) removal in mice, these changes are transient and regress dramatically due to a high regenerative capacity of the lymphatics and co-opting of collateral lymphatic pathways around the site of obstruction. Metastases followed the pattern of collateral pathways and could be detected proximal to the site of lymphadenectomy. Conclusions Both lymphatic vessel regeneration and co-opting of contralateral vessels occur following lymphadenectomy, with contractile function restored within 13 days, providing a basis for preclinical and clinical investigations to hasten lymphatic repair and restore contractile lymphatic function after surgery to prevent cancer-acquired lymphedema. Patterns of cancer metastasis after lymphadenectomy were altered, consistent with patterns of re-directed lymphatic drainage. PMID:25170770

FAK Is Required for Schwann Cell Spreading on Immature Basal Lamina to Coordinate the Radial Sorting of Peripheral Axons with Myelination

PubMed Central

Grove, Matthew

2014-01-01

Without Focal Adhesion Kinase (FAK), developing murine Schwann cells (SCs) proliferate poorly, sort axons inefficiently, and cannot myelinate peripheral nerves. Here we show that FAK is required for the development of SCs when their basal lamina (BL) is fragmentary, but not when it is mature in vivo. Mutant SCs fail to spread on fragmentary BL during development in vivo, and this is phenocopied by SCs lacking functional FAK on low laminin (LN) in vitro. Furthermore, SCs without functional FAK initiate differentiation prematurely, both in vivo and in vitro. In contrast to their behavior on high levels of LN, SCs lacking functional FAK grown on low LN display reduced spreading, proliferation, and indicators of contractility (i.e., stress fibers, arcs, and focal adhesions) and are primed to differentiate. Growth of SCs lacking functional FAK on increasing LN concentrations in vitro revealed that differentiation is not regulated by G1 arrest but rather by cell spreading and the level of contractile actomyosin. The importance of FAK as a critical regulator of the specific response of developing SCs to fragmentary BL was supported by the ability of adult FAK mutant SCs to remyelinate demyelinated adult nerves on mature BL in vivo. We conclude that FAK promotes the spreading and actomyosin contractility of immature SCs on fragmentary BL, thus maintaining their proliferation, and preventing differentiation until they reach high density, thereby promoting radial sorting. Hence, FAK has a critical role in the response of SCs to limiting BL by promoting proliferation and preventing premature SC differentiation. PMID:25274820

Aqueous two-phase printing of cell-containing contractile collagen microgels.

PubMed

Moraes, Christopher; Simon, Arlyne B; Putnam, Andrew J; Takayama, Shuichi

2013-12-01

This work describes the use of aqueous two-phase systems to print cell-containing contractile collagen microdroplets. The fully aqueous conditions enable convenient formation of sub-microliter 'microgels' that are much smaller than otherwise possible to fabricate while maintaining high cell viability. The produced microgels contract over several days, mimicking the behavior of macroscale contraction assays, which have been valued as an important biological readout for over three decades. Use of microgels not only reduces reagent consumption and increases throughput of the assay, but also improves transport of molecules into and out of the collagen matrix, thereby enabling efficient and more precise studies of timed stimulation profiles. Utility of the technology is demonstrated by analyzing the effects of TGF-β1 on gel contraction, and we demonstrate that brief 'burst' stimulation profiles in microgels prompt contraction of the matrix, a feature not observed in the conventional macroscale assay. The fully aqueous process also enables the integration of contractile collagen microgels within existing cell culture systems, and we demonstrate proof-of-principle experiments in which a contractile collagen droplet is fabricated in situ on an existing epithelial monolayer. The simplicity, versatility and ability to robustly produce collagen microgels should allow effective translation of this microengineering technology into a variety of research environments. Copyright © 2013 Elsevier Ltd. All rights reserved.

Effect of nabumetone treatment on vascular responses of the thoracic aorta in rat experimental arthritis.

PubMed

Ulker, S; Onal, A; Hatip, F B; Sürücü, A; Alkanat, M; Koşay, S; Evinç, A

2000-04-01

Nabumetone is a nonsteroidal anti-inflammatory (NSAI) drug which is known to cause less gastrointestinal damage than other NSAI drugs. This study was performed to evaluate whether nabumetone treatment might alter the vascular aberrations related to inflammation in a rat model of adjuvant-induced arthritis. Nabumetone treatment (120 or 240 mg x kg(-1) x day(-1), orally) was initiated on the 15th day of adjuvant inoculation and continued for 14 days. Arthritic lesions, vascular contractile and relaxant responses and gastroduodenal histopathological preparations were evaluated 29 days after adjuvant inoculation. The contractile responses of aortic rings to phenylephrine and KCl were increased in grade 2 arthritic rats. In grade 3 arthritis only the phenylephrine contractility was decreased. The relaxant responses to acetylcholine and sodium nitroprusside were decreased in grades 2 and 3. In healthy rats, nabumetone did not change the vascular responses. After treatment of arthritic rats with nabumetone, both the contractile and relaxant response of the aortic rings returned to normal, and arthritic score and paw swelling were reduced. Gastroduodenal histopathology did not show erosions or ulcers in any of the groups. In conclusion, nabumetone improved the systemic signs and vascular alterations in experimental arthritis without showing any gastrointestinal side effects. Copyright 2000 S. Karger AG, Basel.

Oxytocin plus antibiotics: A synergism of potentiation to enhance bovine uterine contractility.

PubMed

Piccinno, M; Rizzo, A; Cariello, G; Staffieri, F; Sciorsci, R L

2016-09-15

This in vitro study investigates the modulatory effect of three antibiotics (amoxicillin, enrofloxacin, and rifaximin) on contractility of the bovine uterine tissue, in follicular and luteal phases. The evaluation of the effects of these antibiotics (10(-4) M) was performed on oxytocin-induced contractility. The decision to test these antibiotics with the oxytocin (10(-6) M) comes from the reported ability of these combinations of hinder the antibiotic resistance and the formation of bacterial biofilms. The procedures were carried out in isolated organ bath, and the contractile functionality of the strip throughout the experiment was evaluated after a dose of carbachol (10(-5) M). The results demonstrate the different modulatory activity of these antibiotics, on the plateau of contraction induced by oxytocin, in both phases of the estrus cycle. The differing individual antibiotic effects of our testing made it possible to identify, only in some cases. Rifaximin in the follicular phase and enrofloxacin in both phases of the estrous cycle, induced a synergistic enhancement (potentiation) of uterine strip contraction induced by oxytocin. This result is thought important because these associations might enable, in vivo, a simultaneous increase of uterine cleaning and the antimicrobial action on bacteria in planktonic form and of those organized in biofilms. Copyright © 2016 Elsevier Inc. All rights reserved.

Long-term effects of UV light on contractility of rat arteries in vivo.

PubMed

Morimoto, Yuji; Kohyama, Shinya; Nakai, Kanji; Matsuo, Hirotaka; Karasawa, Fujio; Kikuchi, Makoto

2003-10-01

Several studies have shown that UV irradiation may be effective for preventing vascular restenosis or vasopasm. However, the long-term effects of UV light on the physiological properties of vessels such as arterial tension have not been elucidated. We therefore studied the long-term effects of UV using rat carotid arteries treated with UV-B light (wavelength = 313 nm, total energy = 14 mJ/mm2). The animals were sacrificed at 1, 7 and 14 days after UV light exposure, and the carotid arteries were studied by light microscopy and the contractile responses of isolated arterial rings were recorded under isometric tension. UV treatment had induced a substantial loss of smooth muscle cells (SMC) along the entire circumference of the media on days 7 and 14, whereas loss of SMC on day 1 was negligible. Contractile responses of arteries that had been exposed to UV light were significantly reduced on days, 1, 7 and 14. The susceptibility of UV-treated arteries to phenylephrine and prostaglandin F2 alpha was significantly decreased on days 1 and 7, but decreased susceptibility was not seen on day 14. Acetylcholine-induced relaxations were not altered by UV treatment. These results suggest that the long-term effect of UV light is an attenuation of smooth muscle contractility without impairment of endothelial function.

Contractility of the cell rear drives invasion of breast tumor cells in 3D Matrigel

PubMed Central

Poincloux, Renaud; Collin, Olivier; Lizárraga, Floria; Romao, Maryse; Debray, Marcel; Piel, Matthieu; Chavrier, Philippe

2011-01-01

Cancer cells use different modes of migration, including integrin-dependent mesenchymal migration of elongated cells along elements of the 3D matrix as opposed to low-adhesion-, contraction-based amoeboid motility of rounded cells. We report that MDA-MB-231 human breast adenocarcinoma cells invade 3D Matrigel with a characteristic rounded morphology and with F-actin and myosin-IIa accumulating at the cell rear in a uropod-like structure. MDA-MB-231 cells display neither lamellipodia nor bleb extensions at the leading edge and do not require Arp2/3 complex activity for 3D invasion in Matrigel. Accumulation of phospho-MLC and blebbing activity were restricted to the uropod as reporters of actomyosin contractility, and velocimetric analysis of fluorescent beads embedded within the 3D matrix showed that pulling forces exerted to the matrix are restricted to the side and rear of cells. Inhibition of actomyosin contractility or β1 integrin function interferes with uropod formation, matrix deformation, and invasion through Matrigel. These findings support a model whereby actomyosin-based uropod contractility generates traction forces on the β1 integrin adhesion system to drive cell propulsion within the 3D matrix, with no contribution of lamellipodia extension or blebbing to movement. PMID:21245302

PTP1B triggers integrin-mediated repression of myosin activity and modulates cell contractility

PubMed Central

González Wusener, Ana E.; González, Ángela; Nakamura, Fumihiko; Arregui, Carlos O.

2016-01-01

ABSTRACT Cell contractility and migration by integrins depends on precise regulation of protein tyrosine kinase and Rho-family GTPase activities in specific spatiotemporal patterns. Here we show that protein tyrosine phosphatase PTP1B cooperates with β3 integrin to activate the Src/FAK signalling pathway which represses RhoA-myosin-dependent contractility. Using PTP1B null (KO) cells and PTP1B reconstituted (WT) cells, we determined that some early steps following cell adhesion to fibronectin and vitronectin occurred robustly in WT cells, including aggregation of β3 integrins and adaptor proteins, and activation of Src/FAK-dependent signalling at small puncta in a lamellipodium. However, these events were significantly impaired in KO cells. We established that cytoskeletal strain and cell contractility was highly enhanced at the periphery of KO cells compared to WT cells. Inhibition of the Src/FAK signalling pathway or expression of constitutive active RhoA in WT cells induced a KO cell phenotype. Conversely, expression of constitutive active Src or myosin inhibition in KO cells restored the WT phenotype. We propose that this novel function of PTP1B stimulates permissive conditions for adhesion and lamellipodium assembly at the protruding edge during cell spreading and migration. PMID:26700725

NADPH oxidase-2 inhibition restores contractility and intracellular calcium handling and reduces arrhythmogenicity in dystrophic cardiomyopathy

PubMed Central

Gonzalez, Daniel R.; Treuer, Adriana V.; Lamirault, Guillaume; Mayo, Vera; Cao, Yenong; Dulce, Raul A.

2014-01-01

Duchenne muscular dystrophy may affect cardiac muscle, producing a dystrophic cardiomyopathy in humans and the mdx mouse. We tested the hypothesis that oxidative stress participates in disrupting calcium handling and contractility in the mdx mouse with established cardiomyopathy. We found increased expression (fivefold) of the NADPH oxidase (NOX) 2 in the mdx hearts compared with wild type, along with increased superoxide production. Next, we tested the impact of NOX2 inhibition on contractility and calcium handling in isolated cardiomyocytes. Contractility was decreased in mdx myocytes compared with wild type, and this was restored toward normal by pretreating with apocynin. In addition, the amplitude of evoked intracellular Ca2+ concentration transients that was diminished in mdx myocytes was also restored with NOX2 inhibition. Total sarcoplasmic reticulum (SR) Ca2+ content was reduced in mdx hearts and normalized by apocynin treatment. Additionally, NOX2 inhibition decreased the production of spontaneous diastolic calcium release events and decreased the SR calcium leak in mdx myocytes. In addition, nitric oxide (NO) synthase 1 (NOS-1) expression was increased eightfold in mdx hearts compared with wild type. Nevertheless, cardiac NO production was reduced. To test whether this paradox implied NOS-1 uncoupling, we treated cardiac myocytes with exogenous tetrahydrobioterin, along with the NOX inhibitor VAS2870. These agents restored NO production and phospholamban phosphorylation in mdx toward normal. Together, these results demonstrate that, in mdx hearts, NOX2 inhibition improves the SR calcium handling and contractility, partially by recoupling NOS-1. These findings reveal a new layer of nitroso-redox imbalance in dystrophic cardiomyopathy. PMID:25015966

Myosin phosphorylation improves contractile economy of mouse fast skeletal muscle during staircase potentiation.

PubMed

Bunda, Jordan; Gittings, William; Vandenboom, Rene

2018-01-30

Phosphorylation of the myosin regulatory light chain (RLC) by skeletal myosin light chain kinase (skMLCK) potentiates rodent fast twitch muscle but is an ATP-requiring process. Our objective was to investigate the effect of skMLCK-catalyzed RLC phosphorylation on the energetic cost of contraction and the contractile economy (ratio of mechanical output to metabolic input) of mouse fast twitch muscle in vitro (25°C). To this end, extensor digitorum longus (EDL) muscles from wild-type (WT) and from skMLCK-devoid (skMLCK -/- ) mice were subjected to repetitive low-frequency stimulation (10 Hz for 15 s) to produce staircase potentiation of isometric twitch force, after which muscles were quick frozen for determination of high-energy phosphate consumption (HEPC). During stimulation, WT muscles displayed significant potentiation of isometric twitch force while skMLCK -/- muscles did not (i.e. 23% versus 5% change, respectively). Consistent with this, RLC phosphorylation was increased ∼3.5-fold from the unstimulated control value in WT but not in skMLCK -/- muscles. Despite these differences, the HEPC of WT muscles was not greater than that of skMLCK -/- muscles. As a result of the increased contractile output relative to HEPC, the calculated contractile economy of WT muscles was greater than that of skMLCK -/- muscles. Thus, our results suggest that skMLCK-catalyzed phosphorylation of the myosin RLC increases the contractile economy of WT mouse EDL muscle compared with skMLCK -/- muscles without RLC phosphorylation. © 2018. Published by The Company of Biologists Ltd.

Neuropeptide Y restores non-receptor-mediated vasoconstrictive action in superior mesenteric arteries in portal hypertension.

PubMed

Hartl, Johannes; Dietrich, Peter; Moleda, Lukas; Müller-Schilling, Martina; Wiest, Reiner

2015-12-01

Vascular hyporeactivity to vasoconstrictors contributes to splanchnic arterial vasodilatation and hemodynamic dysregulation in portal hypertension. Neuropeptide Y (NPY), a sympathetic cotransmitter, has been shown to improve adrenergic vascular contractility in portal hypertensive rats and markedly attenuate hyperdynamic circulation. To further characterize the NPY-effects in portal hypertension, we investigated its role for non-receptor-mediated vasoconstriction in the superior mesenteric artery (SMA) of portal vein ligated (PVL) and sham-operated rats. Ex vivo SMA perfusion of PVL and sham rats was used to analyse the effects of NPY on pressure response to non-receptor-mediated vasoconstriction. Dose-response curves to KCl (30-300 mM) were used to bypass G protein-coupled receptor mechanisms. Potential involvement of the cyclooxygenase-pathway was tested by non-selective cyclooxygenase-inhibition using indomethacin. KCl-induced vascular contractility but not vascular sensitivity was significantly attenuated in PVL rats as compared with sham rats. Administration of NPY resulted in an augmentation of KCl-evoked vascular sensitivity being not different between study groups. However, KCl-induced vascular contractility was markedly more enhanced in PVL rats, thus, vascular response was no more significantly different between PVL and sham rats after addition of NPY. Administration of indomethacin abolished the NPY-induced enhancement of vasoconstriction. Receptor-independent vascular contractility is impaired in mesenteric arteries in portal hypertension. NPY improves non-receptor mediated mesenteric vasoconstriction more effective in portal hypertension than in healthy conditions correcting splanchnic vascular hyporesponsiveness. This beneficial vasoactive action of NPY adds to its well known more pronounced effects on adrenergic vasoconstriction in portal hypertension making it a promising therapeutic agent in portal hypertension. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

GSNOR Deficiency Enhances In Situ Skeletal Muscle Strength, Fatigue Resistance, and RyR1 S-Nitrosylation Without Impacting Mitochondrial Content and Activity

PubMed Central

Moon, Younghye; Cao, Yenong; Zhu, Jingjing; Xu, Yuanyuan; Balkan, Wayne; Buys, Emmanuel S.; Diaz, Francisca; Kerrick, W. Glenn; Hare, Joshua M.

2017-01-01

Abstract Aim: Nitric oxide (NO) plays important, but incompletely defined roles in skeletal muscle. NO exerts its regulatory effects partly though S-nitrosylation, which is balanced by denitrosylation by enzymes such as S-nitrosoglutathione reductase (GSNOR), whose functions in skeletal muscle remain to be fully deciphered. Results: GSNOR null (GSNOR−/−) tibialis anterior (TA) muscles showed normal growth and were stronger and more fatigue resistant than controls in situ. However, GSNOR−/− lumbrical muscles showed normal contractility and Ca2+ handling in vitro, suggesting important differences in GSNOR function between muscles or between in vitro and in situ environments. GSNOR−/− TA muscles exhibited normal mitochondrial content, and capillary densities, but reduced type IIA fiber content. GSNOR inhibition did not impact mitochondrial respiratory complex I, III, or IV activities. These findings argue that enhanced GSNOR−/− TA contractility is not driven by changes in mitochondrial content or activity, fiber type, or blood vessel density. However, loss of GSNOR led to RyR1 hypernitrosylation, which is believed to increase muscle force output under physiological conditions. cGMP synthesis by soluble guanylate cyclase (sGC) was decreased in resting GSNOR−/− muscle and was more responsive to agonist (DETANO, BAY 41, and BAY 58) stimulation, suggesting that GSNOR modulates cGMP production in skeletal muscle. Innovation: GSNOR may act as a “brake” on skeletal muscle contractile performance under physiological conditions by modulating nitrosylation/denitrosylation balance. Conclusions: GSNOR may play important roles in skeletal muscle contractility, RyR1 S-nitrosylation, fiber type specification, and sGC activity. Antioxid. Redox Signal. 26, 165–181. PMID:27412893

Pericellular Versican Regulates the Fibroblast-Myofibroblast Transition

PubMed Central

Hattori, Noriko; Carrino, David A.; Lauer, Mark E.; Vasanji, Amit; Wylie, James D.; Nelson, Courtney M.; Apte, Suneel S.

2011-01-01

The cell and its glycosaminoglycan-rich pericellular matrix (PCM) comprise a functional unit. Because modification of PCM influences cell behavior, we investigated molecular mechanisms that regulate PCM volume and composition. In fibroblasts and other cells, aggregates of hyaluronan and versican are found in the PCM. Dermal fibroblasts from Adamts5−/− mice, which lack a versican-degrading protease, ADAMTS5, had reduced versican proteolysis, increased PCM, altered cell shape, enhanced α-smooth muscle actin (SMA) expression and increased contractility within three-dimensional collagen gels. The myofibroblast-like phenotype was associated with activation of TGFβ signaling. We tested the hypothesis that fibroblast-myofibroblast transition in Adamts5−/− cells resulted from versican accumulation in PCM. First, we noted that versican overexpression in human dermal fibroblasts led to increased SMA expression, enhanced contractility, and increased Smad2 phosphorylation. In contrast, dermal fibroblasts from Vcan haploinsufficient (Vcanhdf/+) mice had reduced contractility relative to wild type fibroblasts. Using a genetic approach to directly test if myofibroblast transition in Adamts5−/− cells resulted from increased PCM versican content, we generated Adamts5−/−;Vcanhdf/+ mice and isolated their dermal fibroblasts for comparison with dermal fibroblasts from Adamts5−/− mice. In Adamts5−/− fibroblasts, Vcan haploinsufficiency or exogenous ADAMTS5 restored normal fibroblast contractility. These findings demonstrate that altering PCM versican content through proteolytic activity of ADAMTS5 profoundly influenced the dermal fibroblast phenotype and may regulate a phenotypic continuum between the fibroblast and its alter ego, the myofibroblast. We propose that a physiological function of ADAMTS5 in dermal fibroblasts is to maintain optimal versican content and PCM volume by continually trimming versican in hyaluronan-versican aggregates. PMID:21828051

Differential regulation of myofilament protein isoforms underlying the contractility changes in skeletal muscle unloading

PubMed Central

Yu, Zhi-Bin; Gao, Fang; Feng, Han-Zhong; Jin, J-P

2006-01-01

Weight-bearing skeletal muscles change phenotype rapidly in response to unloading. Using the hind limb-suspension rat model, we investigated the regulation of myofilament protein isoforms in correlation to contractility. Four weeks of continuous hind limb unloading produced progressive atrophy and contractility changes in soleus but not extensor digitorum longus (EDL) muscle. The unloaded soleus muscle also had decreased fatigue resistance. Together with the decrease of myosin heavy chain (MHC) isoform I and IIa and increase of MHC IIb and IIx, coordinated regulation of thin filament regulatory protein isoforms were observed: γ- and β-tropomyosin decreased and α-tropomyosin increased, resulting in an α/β ratio similar to that in normal fast twitch skeletal muscle; troponin I and troponin T (TnT) both showed decrease in the slow isoform and increases in the fast isoform. The TnT isoform switching began after 7 days of unloading and TnI isoform showed detectable changes at 14 days while other protein isoform changes were not significant until 28 days of treatment. Correlating to the early changes in contractility, especially the resistance to fatigue, the early response of TnT isoform regulation may play a unique role in the adaptation of skeletal muscle to unloading. When the fast TnT gene expression was up-regulated in the unloaded soleus muscle, alternative RNA splicing switched to produce more high molecular weight acidic isoforms, reflecting a potential compensation for the decrease of slow TnT that is critical to skeletal muscle function. The results demonstrate that differential regulation of TnT isoforms is a sensitive mechanism in muscle adaptation to functional demands. PMID:17108008

G protein-coupled estrogen receptor 1-mediated effects in the rat myometrium.

PubMed

Tica, Andrei A; Dun, Erica C; Tica, Oana S; Gao, Xin; Arterburn, Jeffrey B; Brailoiu, G Cristina; Oprea, Tudor I; Brailoiu, Eugen

2011-11-01

G protein-coupled estrogen receptor 1 (GPER), also named GPR30, has been previously identified in the female reproductive system. In this study, GPER expression was found in the female rat myometrium by reverse transcriptase-polymerase chain reaction and immunocytochemistry. Using GPER-selective ligands, we assessed the effects of the GPER activation on resting membrane potential and cytosolic Ca(2+) concentration ([Ca(2+)](i)) in rat myometrial cells, as well as on contractility of rat uterine strips. G-1, a specific GPER agonist, induced a concentration-dependent depolarization and increase in [Ca(2+)](i) in myometrial cells. The depolarization was abolished in Na(+)-free saline. G-1-induced [Ca(2+)](i) increase was markedly decreased by nifedipine, a L-type Ca(2+) channel blocker, by Ca(2+)-free or Na(+)-free saline. Intracellular administration of G-1 produced a faster and transitory increase in [Ca(2+)](i), with a higher amplitude than that induced by extracellular application, supporting an intracellular localization of the functional GPER in myometrial cells. Depletion of internal Ca(2+) stores with thapsigargin produced a robust store-activated Ca(2+) entry; the Ca(2+) response to G-1 was similar to the constitutive Ca(2+) entry and did not seem to involve store-operated Ca(2+) entry. In rat uterine strips, administration of G-1 increased the frequency and amplitude of contractions and the area under the contractility curve. The effects of G-1 on membrane potential, [Ca(2+)](i), and uterine contractility were prevented by pretreatment with G-15, a GPER antagonist, further supporting the involvement of GPER in these responses. Taken together, our results indicate that GPER is expressed and functional in rat myometrium. GPER activation produces depolarization, elevates [Ca(2+)](i) and increases contractility in myometrial cells.

Assessment of drug-induced arrhythmic risk using limit cycle and autocorrelation analysis of human iPSC-cardiomyocyte contractility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kirby, R. Jason

2016-08-15

Cardiac safety assays incorporating label-free detection of human stem-cell derived cardiomyocyte contractility provide human relevance and medium throughput screening to assess compound-induced cardiotoxicity. In an effort to provide quantitative analysis of the large kinetic datasets resulting from these real-time studies, we applied bioinformatic approaches based on nonlinear dynamical system analysis, including limit cycle analysis and autocorrelation function, to systematically assess beat irregularity. The algorithms were integrated into a software program to seamlessly generate results for 96-well impedance-based data. Our approach was validated by analyzing dose- and time-dependent changes in beat patterns induced by known proarrhythmic compounds and screening a cardiotoxicitymore » library to rank order compounds based on their proarrhythmic potential. We demonstrate a strong correlation for dose-dependent beat irregularity monitored by electrical impedance and quantified by autocorrelation analysis to traditional manual patch clamp potency values for hERG blockers. In addition, our platform identifies non-hERG blockers known to cause clinical arrhythmia. Our method provides a novel suite of medium-throughput quantitative tools for assessing compound effects on cardiac contractility and predicting compounds with potential proarrhythmia and may be applied to in vitro paradigms for pre-clinical cardiac safety evaluation. - Highlights: • Impedance-based monitoring of human iPSC-derived cardiomyocyte contractility • Limit cycle analysis of impedance data identifies aberrant oscillation patterns. • Nonlinear autocorrelation function quantifies beat irregularity. • Identification of hERG and non-hERG inhibitors with known risk of arrhythmia • Automated software processes limit cycle and autocorrelation analyses of 96w data.« less

LET-99 functions in the astral furrowing pathway, where it is required for myosin enrichment in the contractile ring.

PubMed

Price, Kari L; Rose, Lesilee S

2017-09-01

The anaphase spindle determines the position of the cytokinesis furrow, such that the contractile ring assembles in an equatorial zone between the two spindle poles. Contractile ring formation is mediated by RhoA activation at the equator by the centralspindlin complex and midzone microtubules. Astral microtubules also inhibit RhoA accumulation at the poles. In the Caenorhabditis elegans one-cell embryo, the astral microtubule-dependent pathway requires anillin, NOP-1, and LET-99. LET-99 is well characterized for generating the asymmetric cortical localization of the Gα-dependent force-generating complex that positions the spindle during asymmetric division. However, whether the role of LET-99 in cytokinesis is specific to asymmetric division and whether it acts through Gα to promote furrowing are unclear. Here we show that LET-99 contributes to furrowing in both asymmetrically and symmetrically dividing cells, independent of its function in spindle positioning and Gα regulation. LET-99 acts in a pathway parallel to anillin and is required for myosin enrichment into the contractile ring. These and other results suggest a positive feedback model in which LET-99 localizes to the presumptive cleavage furrow in response to the spindle and myosin. Once positioned there, LET-99 enhances myosin accumulation to promote furrowing in both symmetrically and asymmetrically dividing cells. © 2017 Price and Rose. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).

Impact of scar thickness on the assessment of viability using dobutamine echocardiography and thallium single-photon emission computed tomography: a comparison with contrast-enhanced magnetic resonance imaging.

PubMed

Nelson, Charles; McCrohon, Jane; Khafagi, Frederick; Rose, Stephen; Leano, Rodel; Marwick, Thomas H

2004-04-07

We sought to determine whether the transmural extent of scar (TES) explains discordances between dobutamine echocardiography (DbE) and thallium single-photon emission computed tomography (Tl-SPECT) in the detection of viable myocardium (VM). Discrepancies between DbE and Tl-SPECT are often attributed to differences between contractile reserve and membrane integrity, but may also reflect a disproportionate influence of nontransmural scar on thickening at DbE. Sixty patients (age 62 +/- 12 years; 10 women and 50 men) with postinfarction left ventricular dysfunction underwent standard rest-late redistribution Tl-SPECT and DbE. Viable myocardium was identified when dysfunctional segments showed Tl activity >60% on the late-redistribution image or by low-dose augmentation at DbE. Contrast-enhanced magnetic resonance imaging (ceMRI) was used to divide TES into five groups: 0%, <25%, 26% to 50%, 51% to 75%, and >75% of the wall thickness replaced by scar. As TES increased, both the mean Tl uptake and change in wall motion score decreased significantly (both p < 0.001). However, the presence of subendocardial scar was insufficient to prevent thickening; >50% of segments still showed contractile function with TES of 25% to 75%, although residual function was uncommon with TES >75%. The relationship of both tests to increasing TES was similar, but Tl-SPECT identified VM more frequently than DbE in all groups. Among segments without scar or with small amounts of scar (<25% TES), >50% were viable by SPECT. Both contractile reserve and perfusion are sensitive to the extent of scar. However, contractile reserve may be impaired in the face of no or minor scar, and thickening may still occur with extensive scar.

Mechanisms of TNFalpha-induced cardiac dysfunction in cholestatic bile duct-ligated mice: interaction between TNFalpha and endocannabinoids.

PubMed

Yang, Ying-Ying; Liu, Hongqun; Nam, Soon Woo; Kunos, George; Lee, Samuel S

2010-08-01

Chronic liver disease is associated with endotoxemia, oxidative stress, increased endocannabinoids and decreased cardiac responsiveness. Endocannabinoids activate the tumor necrosis factor-alpha (TNFalpha)-nuclear factor kappaB (NFkappaB) pathway. However, how they interact with each other remains obscure. We therefore aimed to clarify the relationship between the TNFalpha-NFkappaB pathway and endocannabinoids in the pathogenesis of cardiodepression of cholestatic bile duct ligated (BDL) mice. BDL mice with TNFalpha knockout (TNFalpha-/-) and infusion of anti-TNFalpha antibody were used. Cardiac mRNA and protein expression of NFkappaBp65, c-Jun-N-terminal kinases (JNK), p38 mitogen-activated protein kinase (p38MAPK), extracelullar-signal- regulated kinase (ERK), inducible nitric oxide synthase (iNOS), Copper/Zinc and Magnesium-superoxide dismutase (Cu/ Zn- and Mn-SOD), cardiac anandamide, 2-arachidonoylglycerol (2-AG), nitric oxide (NOx) and glutathione, and plasma TNFalpha were measured. The effects of TNFalpha, cannabinoid receptor (CB1) antagonist AM251 and the endocannabinoid reuptake inhibitor UCM707, on the contractility of isolated cardiomyocytes, were assessed. In BDL mice, cardiac mRNA and protein expression of NFkappaBp65, p38MAPK, iNOS, NOx, anandamide, and plasma TNFa were increased, whereas glutathione, Cu/Zn-SOD, and Mn-SOD were decreased. Cardiac contractility was blunted in BDL mice. Anti-TNFa treatment in BDL mice decreased cardiac anandamide and NOx, reduced expression of NFkappaBp65, p38MAPK, and iNOS, enhanced expression of Cu/Zn-SOD and Mn-SOD, increased reductive glutathione and restored cardiomyocyte contractility. TNFa-depressed contractility was worsened by UCM707, whereas AM251 improved contractility. Increased TNFalpha, acting via NFkappaB-iNOS and p38MAPK signaling pathways, plays an important role in the pathogenesis of cardiodepression in BDL mice. TNFalpha also suppressed contractility by increasing oxidative stress and endocannabinoid activity.

MEF2C-MYOCD and Leiomodin1 Suppression by miRNA-214 Promotes Smooth Muscle Cell Phenotype Switching in Pulmonary Arterial Hypertension

PubMed Central

Sahoo, Sanghamitra; Meijles, Daniel N.; Al Ghouleh, Imad; Tandon, Manuj; Cifuentes-Pagano, Eugenia; Sembrat, John; Rojas, Mauricio; Goncharova, Elena; Pagano, Patrick J.

2016-01-01

Background Vascular hyperproliferative disorders are characterized by excessive smooth muscle cell (SMC) proliferation leading to vessel remodeling and occlusion. In pulmonary arterial hypertension (PAH), SMC phenotype switching from a terminally differentiated contractile to synthetic state is gaining traction as our understanding of the disease progression improves. While maintenance of SMC contractile phenotype is reportedly orchestrated by a MEF2C-myocardin (MYOCD) interplay, little is known regarding molecular control at this nexus. Moreover, the burgeoning interest in microRNAs (miRs) provides the basis for exploring their modulation of MEF2C-MYOCD signaling, and in turn, a pro-proliferative, synthetic SMC phenotype. We hypothesized that suppression of SMC contractile phenotype in pulmonary hypertension is mediated by miR-214 via repression of the MEF2C-MYOCD-leiomodin1 (LMOD1) signaling axis. Methods and Results In SMCs isolated from a PAH patient cohort and commercially obtained hPASMCs exposed to hypoxia, miR-214 expression was monitored by qRT-PCR. miR-214 was upregulated in PAH- vs. control subject hPASMCs as well as in commercially obtained hPASMCs exposed to hypoxia. These increases in miR-214 were paralleled by MEF2C, MYOCD and SMC contractile protein downregulation. Of these, LMOD1 and MEF2C were directly targeted by the miR. Mir-214 overexpression mimicked the PAH profile, downregulating MEF2C and LMOD1. AntagomiR-214 abrogated hypoxia-induced suppression of the contractile phenotype and its attendant proliferation. Anti-miR-214 also restored PAH-PASMCs to a contractile phenotype seen during vascular homeostasis. Conclusions Our findings illustrate a key role for miR-214 in modulation of MEF2C-MYOCD-LMOD1 signaling and suggest that an antagonist of miR-214 could mitigate SMC phenotype changes and proliferation in vascular hyperproliferative disorders including PAH. PMID:27144530

A global, myosin light chain kinase-dependent increase in myosin II contractility accompanies the metaphase-anaphase transition in sea urchin eggs.

PubMed

Lucero, Amy; Stack, Christianna; Bresnick, Anne R; Shuster, Charles B

2006-09-01

Myosin II is the force-generating motor for cytokinesis, and although it is accepted that myosin contractility is greatest at the cell equator, the temporal and spatial cues that direct equatorial contractility are not known. Dividing sea urchin eggs were placed under compression to study myosin II-based contractile dynamics, and cells manipulated in this manner underwent an abrupt, global increase in cortical contractility concomitant with the metaphase-anaphase transition, followed by a brief relaxation and the onset of furrowing. Prefurrow cortical contractility both preceded and was independent of astral microtubule elongation, suggesting that the initial activation of myosin II preceded cleavage plane specification. The initial rise in contractility required myosin light chain kinase but not Rho-kinase, but both signaling pathways were required for successful cytokinesis. Last, mobilization of intracellular calcium during metaphase induced a contractile response, suggesting that calcium transients may be partially responsible for the timing of this initial contractile event. Together, these findings suggest that myosin II-based contractility is initiated at the metaphase-anaphase transition by Ca2+-dependent myosin light chain kinase (MLCK) activity and is maintained through cytokinesis by both MLCK- and Rho-dependent signaling. Moreover, the signals that initiate myosin II contractility respond to specific cell cycle transitions independently of the microtubule-dependent cleavage stimulus.

A Global, Myosin Light Chain Kinase-dependent Increase in Myosin II Contractility Accompanies the Metaphase–Anaphase Transition in Sea Urchin Eggs

PubMed Central

Lucero, Amy; Stack, Christianna; Bresnick, Anne R.

2006-01-01

Myosin II is the force-generating motor for cytokinesis, and although it is accepted that myosin contractility is greatest at the cell equator, the temporal and spatial cues that direct equatorial contractility are not known. Dividing sea urchin eggs were placed under compression to study myosin II-based contractile dynamics, and cells manipulated in this manner underwent an abrupt, global increase in cortical contractility concomitant with the metaphase–anaphase transition, followed by a brief relaxation and the onset of furrowing. Prefurrow cortical contractility both preceded and was independent of astral microtubule elongation, suggesting that the initial activation of myosin II preceded cleavage plane specification. The initial rise in contractility required myosin light chain kinase but not Rho-kinase, but both signaling pathways were required for successful cytokinesis. Last, mobilization of intracellular calcium during metaphase induced a contractile response, suggesting that calcium transients may be partially responsible for the timing of this initial contractile event. Together, these findings suggest that myosin II-based contractility is initiated at the metaphase–anaphase transition by Ca2+-dependent myosin light chain kinase (MLCK) activity and is maintained through cytokinesis by both MLCK- and Rho-dependent signaling. Moreover, the signals that initiate myosin II contractility respond to specific cell cycle transitions independently of the microtubule-dependent cleavage stimulus. PMID:16837551

The β3 -adrenoceptor agonist mirabegron increases human atrial force through β1 -adrenoceptors: an indirect mechanism?

PubMed

Mo, Weilan; Michel, Martin C; Lee, Xiang Wen; Kaumann, Alberto J; Molenaar, Peter

2017-08-01

Mirabegron has been classified as a β 3 -adrenoceptor agonist approved for overactive bladder syndrome. We investigated possible cardiac effects of mirabegron in the absence or presence of β-adrenoceptor subtype antagonists. In view of its phenylethanolamine structure, we investigated whether mirabegron has indirect sympathomimetic activity by using neuronal uptake blockers. Right atrial trabeculae, from non-failing hearts, were paced and contractile force measured at 37°C. Single concentrations of mirabegron were added in the absence or presence of the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX), β 3 (L-748,337), β 1 (CGP 20712A), β 2 (ICI 118,551) -adrenoceptor antagonists, neuronal uptake inhibitors desipramine or phenoxybenzamine. Mirabegron significantly increased contractile force in human right atrium (1 μM, 7.6 ± 2.6%, n = 7; 10 μM, 10.2 ± 1.5%, n = 22 compared with (-)-isoprenaline P < 0.05). In the presence of IBMX, mirabegron (10 μM) caused a greater contraction. L-748,337 (100 nM) had no effect on the increase in contractile force caused by mirabegron (10 μM). In contrast, mirabegron (10 μM) reduced contractile force in the presence of CGP 20712A, which was not affected by L-748,337 (100 nM) or ICI 118,551 (50 nM). Mirabegron (10 μM) also reduced contractile force in the presence of desipramine or phenoxybenzamine. Mirabegron increases human atrial force through β 1 - but not β 3 -adrenoceptors. Desipramine and phenoxybenzamine block neuronal uptake and conceivably prevent mirabegron from releasing noradrenaline. A non-specific cardiodepressant effect is not mediated through β 3 (or β 2 )-adrenoceptors, consistent with lack of β 3 -adrenoceptor function on human atrial contractility. © 2017 The British Pharmacological Society.

Fasudil inhibits the proliferation and contractility and induces cell cycle arrest and apoptosis of human endometriotic stromal cells: a promising agent for the treatment of endometriosis.

PubMed

Tsuno, Akitoshi; Nasu, Kaei; Kawano, Yukie; Yuge, Akitoshi; Li, Haili; Abe, Wakana; Narahara, Hisashi

2011-12-01

During the development of endometriotic lesions, excess fibrosis may lead to scarring and to the alterations of tissue function that are the characteristic features of this disease. Enhanced extracellular matrix contractility of endometriotic stromal cells (ECSC) mediated by the mevalonate-Ras homology (Rho)/Rho-associated coiled-coil-forming protein kinase (ROCK) pathway has been shown to contribute to the pathogenesis of endometriosis. To assess the use of fasudil, a selective ROCK inhibitor, for the medical treatment of endometriosis-associated fibrosis, the effects of this agent on the cell proliferation, apoptosis, cell cycle, morphology, cell density, and contractility of ECSC were investigated. The effects of fasudil on the expression of contractility-related, apoptosis-related, and cell cycle-related molecules in ECSC were also evaluated. Fasudil significantly inhibited the proliferation and contractility of ECSC and induced the cell cycle arrest in the G2/M phase and apoptosis of these cells. Morphological observation revealed the suppression of ECSC attachment to collagen fibers and decrease of cell density by fasudil. The expression of α-smooth muscle actin, RhoA, ROCK-I, and ROCK-II proteins was inhibited by fasudil administration. The expression of the antiapoptotic factors, Bcl-2 and Bcl-X(L), in two-dimensional cultured ECSC were down-regulated by the addition of fasudil, whereas, the expression of p16(INK4a) and p21(Waf1/Cip1) was up-regulated by the addition of fasudil. The present findings suggest that fasudil is a promising agent for the treatment of endometriosis. The inhibition of cell proliferation, contractility, and myofibroblastic differentiation, the attenuation of attachment to collagen fibers, the decrease of cell density, and the induction of cell cycle arrest and apoptosis of ECSC are involved in the active mechanisms of fasudil.

FERMT2 links cortical actin structures, plasma membrane tension and focal adhesion function to stabilize podocyte morphology.

PubMed

Yasuda-Yamahara, M; Rogg, M; Frimmel, J; Trachte, P; Helmstaedter, M; Schroder, P; Schiffer, M; Schell, C; Huber, T B

2018-01-11

Simplification and retraction of podocyte protrusions, generally termed as foot process effacement, is a uniform pathological pattern observed in the majority of glomerular disease, including focal segmental glomerulosclerosis. However, it is still incompletely understood how the interaction of cortical actin structures, actomyosin contractility and focal adhesions, is being orchestrated to control foot process morphology in health and disease. By uncovering the functional role of fermitin family member 2 (FERMT2 or kindlin-2) in podocytes, we provide now evidence, how cell-extracellular matrix (ECM) interactions modulate membrane tension and actomyosin contractility. A genetic modeling approach was applied by deleting FERMT2 in a set of in vivo systems as well as in CRISPR/Cas9 modified human podocytes. Loss of FERMT2 results in altered cortical actin composition, cell cortex destabilization associated with plasma membrane blebbing and a remodeling of focal adhesions. We further show that FERMT2 knockout podocytes have high levels of RhoA activation and concomitantly increased actomyosin contractility. Inhibition of actomyosin tension reverses the membrane blebbing phenotype. Thus, our findings establish a direct link between cell-matrix adhesions, cortical actin structures and plasma membrane tension allowing to better explain cell morphological changes in foot process effacement. Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.

Atomic Structure of Type VI Contractile Sheath from Pseudomonas aeruginosa.

PubMed

Salih, Osman; He, Shaoda; Planamente, Sara; Stach, Lasse; MacDonald, James T; Manoli, Eleni; Scheres, Sjors H W; Filloux, Alain; Freemont, Paul S

2018-02-06

Pseudomonas aeruginosa has three type VI secretion systems (T6SSs), H1-, H2-, and H3-T6SS, each belonging to a distinct group. The two T6SS components, TssB/VipA and TssC/VipB, assemble to form tubules that conserve structural/functional homology with tail sheaths of contractile bacteriophages and pyocins. Here, we used cryoelectron microscopy to solve the structure of the H1-T6SS P. aeruginosa TssB1C1 sheath at 3.3 Å resolution. Our structure allowed us to resolve some features of the T6SS sheath that were not resolved in the Vibrio cholerae VipAB and Francisella tularensis IglAB structures. Comparison with sheath structures from other contractile machines, including T4 phage and R-type pyocins, provides a better understanding of how these systems have conserved similar functions/mechanisms despite evolution. We used the P. aeruginosa R2 pyocin as a structural template to build an atomic model of the TssB1C1 sheath in its extended conformation, allowing us to propose a coiled-spring-like mechanism for T6SS sheath contraction. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

Alterations in serotonin receptor-induced contractility of bovine lateral saphenous vein in cattle grazing endophyte-infected tall fescue.

PubMed

Klotz, J L; Brown, K R; Xue, Y; Matthews, J C; Boling, J A; Burris, W R; Bush, L P; Strickland, J R

2012-02-01

As part of a 2-yr study documenting the physiologic impact of grazing endophyte-infected tall fescue on growing cattle, 2 experiments were conducted to characterize and evaluate effects of grazing 2 levels of toxic endophyte-infected tall fescue pastures on vascular contractility and serotonin receptors. Experiment 1 examined vasoconstrictive activities of 5-hydroxytryptamine (5HT), α-methylserotonin (ME5HT; a 5HT(2) receptor agonist), d-lysergic acid (LSA), and ergovaline (ERV) on lateral saphenous veins collected from steers immediately removed from a high-endophyte-infected tall fescue pasture (HE) or a low-endophyte-infected mixed-grass (LE) pasture. Using the same pastures, Exp. 2 evaluated effects of grazing 2 levels of toxic endophyte-infected tall fescue on vasoconstrictive activities of (±)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane hydrochloride (DOI), BW 723C86 (BW7), CGS-12066A (CGS), and 5-carboxamidotryptamine hemiethanolate maleate (5CT), agonists for 5HT(2A),( 2B), 5HT(1B), and 5HT(7) receptors, respectively. One-half of the steers in Exp. 2 were slaughtered immediately after removal from pasture, and the other one-half were fed finishing diets for >91 d before slaughter. For Exp. 1, maximal contractile intensities were greater (P < 0.05) for steers grazing LE pastures than HE pastures for 5HT (73.3 vs. 48.9 ± 2.1%), ME5HT (52.7 vs. 24.9 ± 1.5%), and ERV (65.7 vs. 49.1 ± 2.6%). Onset of contractile response did not differ for 5HT (P = 0.26) and ERV (P = 0.93), but onset of ME5HT contraction was not initiated (P < 0.05) in HE steers until 10(-4) compared with 10(-5) M in LE-grazing steers. For Exp. 2, maximal contractile intensities achieved with DOI were 35% less (P < 0.05), whereas those achieved with 5CT were 37% greater (P < 0.05), in steers grazing HE pastures. Contractile response to CGS did not differ between pasture groups, and there was an absence of contractile response to BW7 in both groups. There were no differences between endophyte content in contractile responses after animals were finished for >91 d. Experiment 1 demonstrated that grazing of HE pastures for 89 to 105 d induces functional alterations in blood vessels, as evidenced by reduced contractile capacity and altered serotonergic receptor activity. Experiment 2 demonstrated that grazing HE pastures alters vascular responses, which may be mediated through altered serotonin receptor activities, and these alterations may be ameliorated by the removal of ergot alkaloid exposure as demonstrated by the absence of differences in finished steers.

Reductions in muscle quality and quantity in CIDP patients assessed by magnetic resonance imaging.

PubMed

Gilmore, Kevin J; Doherty, Timothy J; Kimpinski, Kurt; Rice, Charles L

2018-05-09

Weakness in patients with chronic inflammatory demyelinating polyneuropathy (CIDP) may be caused by decreases in muscle quantity and quality, but these have not been explored. Twelve patients with CIDP (mean 61 years) and ten age- matched (mean 59 years) control subjects were assessed for ankle dorsiflexion strength, and two different MRI scans (T1 and T2) of leg musculature. Isometric strength was lower in CIDP patients by 36% compared with controls. Tibialis anterior muscle volumes of CIDP patients were smaller by ∼17% than controls, and non-contractile tissue volume was ∼58% greater in CIDP patients. When normalized to total muscle or corrected contractile volume, strength was ∼ 29% and ∼18% lower, respectively in CIDP patients DISCUSSION: These results provide insight into structural integrity of muscle contractile proteins and pathological changes to whole-muscle tissue composition that contribute to impaired muscle function in CIDP. This article is protected by copyright. All rights reserved. © 2018 Wiley Periodicals, Inc.

In vitro particulate matter exposure causes direct and lung-mediated indirect effects on cardiomyocyte function.

PubMed

Gorr, Matthew W; Youtz, Dane J; Eichenseer, Clayton M; Smith, Korbin E; Nelin, Timothy D; Cormet-Boyaka, Estelle; Wold, Loren E

2015-07-01

Particulate matter (PM) exposure induces a pathological response from both the lungs and the cardiovascular system. PM is capable of both manifestation into the lung epithelium and entrance into the bloodstream. Therefore, PM has the capacity for both direct and lung-mediated indirect effects on the heart. In the present studies, we exposed isolated rat cardiomyocytes to ultrafine particulate matter (diesel exhaust particles, DEP) and examined their contractile function and calcium handling ability. In another set of experiments, lung epithelial cells (16HBE14o- or Calu-3) were cultured on permeable supports that allowed access to both the basal (serosal) and apical (mucosal) media; the basal media was used to culture cardiomyocytes to model the indirect, lung-mediated effects of PM on the heart. Both the direct and indirect treatments caused a reduction in contractility as evidenced by reduced percent sarcomere shortening and reduced calcium handling ability measured in field-stimulated cardiomyocytes. Treatment of cardiomyocytes with various anti-oxidants before culture with DEP was able to partially prevent the contractile dysfunction. The basal media from lung epithelial cells treated with PM contained several inflammatory cytokines, and we found that monocyte chemotactic protein-1 was a key trigger for cardiomyocyte dysfunction. These results indicate the presence of both direct and indirect effects of PM on cardiomyocyte function in vitro. Future work will focus on elucidating the mechanisms involved in these separate pathways using in vivo models of air pollution exposure. Copyright © 2015 the American Physiological Society.

Cathepsin K knockout alleviates aging-induced cardiac dysfunction

PubMed Central

Hua, Yinan; Robinson, Timothy J; Cao, Yongtao; Shi, Guo-Ping; Ren, Jun; Nair, Sreejayan

2015-01-01

Aging is a major risk factor for cardiovascular disease. It has previously been shown that protein levels of cathepsin K, a lysosomal cysteine protease, are elevated in the failing heart and that genetic ablation of cathepsin K protects against pressure overload-induced cardiac hypertrophy and contractile dysfunction. Here we test the hypothesis that cathepsin K knockout alleviates age-dependent decline in cardiac function. Cardiac geometry, contractile function, intracellular Ca2+ properties, and cardiomyocyte apoptosis were evaluated using echocardiography, fura-2 technique, immunohistochemistry, Western blot and TUNEL staining, respectively. Aged (24-month-old) mice exhibited significant cardiac remodeling (enlarged chamber size, wall thickness, myocyte cross-sectional area, and fibrosis), decreased cardiac contractility, prolonged relengthening along with compromised intracellular Ca2+ release compared to young (6-month-old) mice, which were attenuated in the cathepsin K knockout mice. Cellular markers of senescence, including cardiac lipofuscin, p21 and p16, were lower in the aged-cathepsin K knockout mice compared to their wild-type counterpart. Mechanistically, cathepsin K knockout mice attenuated an age-induced increase in cardiomyocyte apoptosis and nuclear translocation of mitochondrial apoptosis-inducing factor (AIF). In cultured H9c2 cells, doxorubicin stimulated premature senescence and apoptosis. Silencing of cathepsin K blocked the doxorubicin-induced translocation of AIF from the mitochondria to the nuclei. Collectively, these results suggest that cathepsin K knockout attenuates age-related decline in cardiac function via suppressing caspase-dependent and caspase-independent apoptosis. PMID:25692548

Myosin-driven rescue of contractile reserve and energetics in mouse hearts bearing familial hypertrophic cardiomyopathy-associated mutant troponin T is mutation-specific

PubMed Central

He, Huamei; Hoyer, Kirsten; Tao, Hai; Rice, Ronald; Jimenez, Jesus; Tardiff, Jil C; Ingwall, Joanne S

2012-01-01

The thin filament protein troponin T (TnT) is a regulator of sarcomere function. Whole heart energetics and contractile reserve are compromised in transgenic mice bearing missense mutations at R92 within the tropomyosin-binding domain of cTnT, despite being distal to the ATP hydrolysis domain of myosin. These mutations are associated with familial hypertrophic cardiomyopathy (FHC). Here we test the hypothesis that genetically replacing murine αα-MyHC with murine ββ-MyHC in hearts bearing the R92Q cTnT mutation, a particularly lethal FHC-associated mutation, leads to sufficiently large perturbations in sarcomere function to rescue whole heart energetics and decrease the cost of contraction. By comparing R92Q cTnT and R92L cTnT mutant hearts, we also test whether any rescue is mutation-specific. We defined the energetic state of the isolated perfused heart using 31P-NMR spectroscopy while simultaneously measuring contractile performance at four work states. We found that the cost of increasing contraction in intact mouse hearts with R92Q cTnT depends on the type of myosin present in the thick filament. We also found that the salutary effect of this manoeuvre is mutation-specific, demonstrating the major regulatory role of cTnT on sarcomere function at the whole heart level. PMID:22907055

Berberine alleviates the cerebrovascular contractility in streptozotocin-induced diabetic rats through modulation of intracellular Ca²⁺ handling in smooth muscle cells.

PubMed

Ma, Yu-Guang; Zhang, Yin-Bin; Bai, Yun-Gang; Dai, Zhi-Jun; Liang, Liang; Liu, Mei; Xie, Man-Jiang; Guan, Hai-Tao

2016-04-12

Vascular dysfunction is a distinctive phenotype in diabetes mellitus. Current treatments mostly focus on the tight glycemic control and few of these treatments have been designed to directly recover the vascular dysfunction in diabetes. As a classical natural medicine, berberine has been explored as a possible therapy for DM. In addition, it is reported that berberine has an extra-protective effect in diabetic vascular dysfunction. However, little is known whether the berberine treatment could ameliorate the smooth muscle contractility independent of a functional endothelium under hyperglycemia. Furthermore, it remains unknown whether berberine affects the arterial contractility by regulating the intracellular Ca(2+) handling in vascular smooth cells (VSMCs) under hyperglycemia. Sprague-Dawley rats were used to establish the diabetic model with a high-fat diet plus injections of streptozotocin (STZ). Berberine (50, 100, and 200 mg/kg/day) were intragastrically administered to control and diabetic rats for 8 weeks since the injection of STZ. The intracellular Ca(2+) handling of isolated cerebral VSMCs was investigated by recording the whole-cell L-type Ca(2+) channel (CaL) currents, assessing the protein expressions of CaL channel, and measuring the intracellular Ca(2+) in response to caffeine. Our results showed that chronic administration of 100 mg/kg/day berberine not only reduced glucose levels, but also inhibited the augmented contractile function of cerebral artery to KCl and 5-hydroxytryptamine (5-HT) in diabetic rats. Furthermore, chronic administration of 100 mg/kg/day berberine significantly inhibited the CaL channel current densities, reduced the α1C-subunit expressions of CaL channel, decreased the resting intracellular Ca(2+) ([Ca(2+)]i) level, and suppressed the Ca(2+) releases from RyRs in cerebral VSMCs isolated from diabetic rats. Correspondingly, acute application of 10 μM berberine could directly inhibit the hyperglycemia-induced CaL currents and suppress the hyperglycemia-induced Ca(2+) releases from RyRs in cerebral VSMCs isolated from normal control rats. Our study indicated that berberine alleviated the cerebral arterial contractility in the rat model of streptozotocin-induced diabetes via regulating the intracellular Ca(2+) handling of smooth muscle cells.

E258K HCM-causing mutation in cardiac MyBP-C reduces contractile force and accelerates twitch kinetics by disrupting the cMyBP-C and myosin S2 interaction.

PubMed

De Lange, Willem J; Grimes, Adrian C; Hegge, Laura F; Spring, Alexander M; Brost, Taylor M; Ralphe, J Carter

2013-09-01

Mutations in cardiac myosin binding protein C (cMyBP-C) are prevalent causes of hypertrophic cardiomyopathy (HCM). Although HCM-causing truncation mutations in cMyBP-C are well studied, the growing number of disease-related cMyBP-C missense mutations remain poorly understood. Our objective was to define the primary contractile effect and molecular disease mechanisms of the prevalent cMyBP-C E258K HCM-causing mutation in nonremodeled murine engineered cardiac tissue (mECT). Wild-type and human E258K cMyBP-C were expressed in mECT lacking endogenous mouse cMyBP-C through adenoviral-mediated gene transfer. Expression of E258K cMyBP-C did not affect cardiac cell survival and was appropriately incorporated into the cardiac sarcomere. Functionally, expression of E258K cMyBP-C caused accelerated contractile kinetics and severely compromised twitch force amplitude in mECT. Yeast two-hybrid analysis revealed that E258K cMyBP-C abolished interaction between the N terminal of cMyBP-C and myosin heavy chain sub-fragment 2 (S2). Furthermore, this mutation increased the affinity between the N terminal of cMyBP-C and actin. Assessment of phosphorylation of three serine residues in cMyBP-C showed that aberrant phosphorylation of cMyBP-C is unlikely to be responsible for altering these interactions. We show that the E258K mutation in cMyBP-C abolishes interaction between N-terminal cMyBP-C and myosin S2 by directly disrupting the cMyBP-C-S2 interface, independent of cMyBP-C phosphorylation. Similar to cMyBP-C ablation or phosphorylation, abolition of this inhibitory interaction accelerates contractile kinetics. Additionally, the E258K mutation impaired force production of mECT, which suggests that in addition to the loss of physiological function, this mutation disrupts contractility possibly by tethering the thick and thin filament or acting as an internal load.

Continuous Flow Left Ventricular Assist Device Implant Significantly Improves Pulmonary Hypertension, Right Ventricular Contractility, and Tricuspid Valve Competence

PubMed Central

Atluri, Pavan; Fairman, Alexander S.; MacArthur, John W.; Goldstone, Andrew B.; Cohen, Jeffrey E.; Howard, Jessica L.; Zalewski, Christyna M.; Shudo, Yasuhiro; Woo, Y. Joseph

2014-01-01

Background Continuous flow left ventricular assist devices (CF LVAD) are being implanted with increasing frequency for end-stage heart failure. At the time of LVAD implant, a large proportion of patients have pulmonary hypertension, right ventricular (RV) dysfunction, and tricuspid regurgitation (TR). RV dysfunction and TR can exacerbate renal dysfunction, hepatic dysfunction, coagulopathy, edema, and even prohibit isolated LVAD implant. Repairing TR mandates increased cardiopulmonary bypass time and bicaval cannulation, which should be reserved for the time of orthotopic heart transplantation. We hypothesized that CF LVAD implant would improve pulmonary artery pressures, enhance RV function, and minimize TR, obviating need for surgical tricuspid repair. Methods One hundred fourteen continuous flow LVADs implanted from 2005 through 2011 at a single center, with medical management of functional TR, were retrospectively analyzed. Pulmonary artery pressures were measured immediately prior to and following LVAD implant. RV function and TR were graded according to standard echocardiographic criteria, prior to, immediately following, and long-term following LVAD. Results There was a significant improvement in post-VAD mean pulmonary arterial pressures (26.6 ± 4.9 vs. 30.2 ± 7.4 mmHg, p = 0.008) with equivalent loading pressures (CVP = 12.0 ± 4.0 vs. 12.1 ± 5.1 p = NS). RV function significantly improved, as noted by right ventricular stroke work index (7.04 ± 2.60 vs. 6.05 ± 2.54, p = 0.02). There was an immediate improvement in TR grade and RV function following LVAD implant, which was sustained long term. Conclusion Continuous flow LVAD implant improves pulmonary hypertension, RV function, and tricuspid regurgitation. TR may be managed nonoperatively during CF LVAD implant. PMID:24118109

A thermodynamical model for stress-fiber organization in contractile cells.

PubMed

Foucard, Louis; Vernerey, Franck J

2012-01-02

Cell mechanical adaptivity to external stimuli is vital to many of its biological functions. A critical question is therefore to understand the formation and organization of the stress fibers from which emerge the cell's mechanical properties. By accounting for the mechanical aspects and the viscoelastic behavior of stress fibers, we here propose a thermodynamic model to predict the formation and orientation of stress fibers in contractile cells subjected to constant or cyclic stretch and different substrate stiffness. Our results demonstrate that the stress fibers viscoelastic behavior plays a crucial role in their formation and organization and shows good consistency with various experiments.

Tumor Growth Increases Neuroinflammation, Fatigue and Depressive-like Behavior Prior to Alterations in Muscle Function

PubMed Central

Norden, Diana M.; Bicer, Sabahattin; Clark, Yvonne; Jing, Runfeng; Henry, Christopher J.; Wold, Loren E.; Reiser, Peter J.; Godbout, Jonathan P.; McCarthy, Donna O.

2014-01-01

Cancer patients frequently suffer from fatigue, a complex syndrome associated with loss of muscle mass, weakness, and depressed mood. Cancer-related fatigue (CRF) can be present at the time of diagnosis, during treatment, and persists for years after treatment. CRF negatively influences quality of life, limits functional independence, and is associated with decreased survival in patients with incurable disease. Currently there are no effective treatments to reduce CRF. The aim of this study was to use a mouse model of tumor growth and discriminate between two main components of fatigue: loss of muscle mass/function and altered mood/motivation. Here we show that tumor growth increased fatigue- and depressive-like behaviors, and reduced body and muscle mass. Decreased voluntary wheel running activity (VWRA) and increased depressive-like behavior in the forced swim and sucrose preference tests were evident in tumor-bearing mice within the first two weeks of tumor growth and preceded the loss of body and muscle mass. At three weeks, tumor-bearing mice had reduced grip strength but this was not associated with altered expression of myosin isoforms or impaired contractile properties of muscles. These increases in fatigue and depressive-like behaviors were paralleled by increased expression of IL-1β mRNA in the cortex and hippocampus. Minocycline administration reduced tumor-induced expression of IL-1β in the brain, reduced depressive-like behavior, and improved grip strength without altering muscle mass. Taken together, these results indicate that neuroinflammation and depressed mood, rather than muscle wasting, contribute to decreased voluntary activity and precede major changes in muscle contractile properties with tumor growth. PMID:25102452

Pharmacological strategies in lung cancer-induced cachexia: effects on muscle proteolysis, autophagy, structure, and weakness.

PubMed

Chacon-Cabrera, Alba; Fermoselle, Clara; Urtreger, Alejandro J; Mateu-Jimenez, Mercè; Diament, Miriam J; de Kier Joffé, Elisa D Bal; Sandri, Marco; Barreiro, Esther

2014-11-01

Cachexia is a relevant comorbid condition of chronic diseases including cancer. Inflammation, oxidative stress, autophagy, ubiquitin-proteasome system, nuclear factor (NF)-κB, and mitogen-activated protein kinases (MAPK) are involved in the pathophysiology of cancer cachexia. Currently available treatment is limited and data demonstrating effectiveness in in vivo models are lacking. Our objectives were to explore in respiratory and limb muscles of lung cancer (LC) cachectic mice whether proteasome, NF-κB, and MAPK inhibitors improve muscle mass and function loss through several molecular mechanisms. Body and muscle weights, limb muscle force, protein degradation and the ubiquitin-proteasome system, signaling pathways, oxidative stress and inflammation, autophagy, contractile and functional proteins, myostatin and myogenin, and muscle structure were evaluated in the diaphragm and gastrocnemius of LC (LP07 adenocarcinoma) bearing cachectic mice (BALB/c), with and without concomitant treatment with NF-κB (sulfasalazine), MAPK (U0126), and proteasome (bortezomib) inhibitors. Compared to control animals, in both respiratory and limb muscles of LC cachectic mice: muscle proteolysis, ubiquitinated proteins, autophagy, myostatin, protein oxidation, FoxO-1, NF-κB and MAPK signaling pathways, and muscle abnormalities were increased, while myosin, creatine kinase, myogenin, and slow- and fast-twitch muscle fiber size were decreased. Pharmacological inhibition of NF-κB and MAPK, but not the proteasome system, induced in cancer cachectic animals, a substantial restoration of muscle mass and force through a decrease in muscle protein oxidation and catabolism, myostatin, and autophagy, together with a greater content of myogenin, and contractile and functional proteins. Attenuation of MAPK and NF-κB signaling pathway effects on muscles is beneficial in cancer-induced cachexia. © 2014 Wiley Periodicals, Inc.

Tumor growth increases neuroinflammation, fatigue and depressive-like behavior prior to alterations in muscle function.

PubMed

Norden, Diana M; Bicer, Sabahattin; Clark, Yvonne; Jing, Runfeng; Henry, Christopher J; Wold, Loren E; Reiser, Peter J; Godbout, Jonathan P; McCarthy, Donna O

2015-01-01

Cancer patients frequently suffer from fatigue, a complex syndrome associated with loss of muscle mass, weakness, and depressed mood. Cancer-related fatigue (CRF) can be present at the time of diagnosis, during treatment, and persists for years after treatment. CRF negatively influences quality of life, limits functional independence, and is associated with decreased survival in patients with incurable disease. Currently there are no effective treatments to reduce CRF. The aim of this study was to use a mouse model of tumor growth and discriminate between two main components of fatigue: loss of muscle mass/function and altered mood/motivation. Here we show that tumor growth increased fatigue- and depressive-like behaviors, and reduced body and muscle mass. Decreased voluntary wheel running activity (VWRA) and increased depressive-like behavior in the forced swim and sucrose preference tests were evident in tumor-bearing mice within the first two weeks of tumor growth and preceded the loss of body and muscle mass. At three weeks, tumor-bearing mice had reduced grip strength but this was not associated with altered expression of myosin isoforms or impaired contractile properties of muscles. These increases in fatigue and depressive-like behaviors were paralleled by increased expression of IL-1β mRNA in the cortex and hippocampus. Minocycline administration reduced tumor-induced expression of IL-1β in the brain, reduced depressive-like behavior, and improved grip strength without altering muscle mass. Taken together, these results indicate that neuroinflammation and depressed mood, rather than muscle wasting, contribute to decreased voluntary activity and precede major changes in muscle contractile properties with tumor growth. Copyright © 2014 Elsevier Inc. All rights reserved.

The cardiac regenerative potential of myoblasts remains limited despite improving their survival via antioxidant treatment.

PubMed

Beckman, Sarah A; Sekiya, Naosumi; Chen, William C W; Mlakar, Logan; Tobita, Kimimassa; Huard, Johnny

2014-01-01

Since myoblasts have been limited by poor cell survival after cellular myoplasty, the major goal of the current study was to determine whether improving myoblast survival with an antioxidant could improve cardiac function after the transplantation of the myoblasts into an acute myocardial infarction. We previously demonstrated that early myogenic progenitors such as muscle-derived stem cells (MDSCs) exhibited superior cell survival and improved cardiac repair after transplantation into infarcted hearts compared to myoblasts, which we partially attributed to MDSC's higher antioxidant levels. To determine if antioxidant treatment could increase myoblast survival, subsequently improving cardiac function after myoblast transplantation into infarcted hearts. Myoblasts were pre-treated with the antioxidant N-acetylcysteine (NAC) or the glutathione depleter, diethyl maleate (DEM), and injected into infarcted murine hearts. Regenerative potential was monitored by cell survival and cardiac function. At early time points, hearts injected with NAC-treated myoblasts exhibited increased donor cell survival, greater cell proliferation, and decreased cellular apoptosis, compared to untreated myoblasts. NAC-treated myoblasts significantly improved cardiac contractility, reduced fibrosis, and increased vascular density compared to DEM-treated myoblasts, but compared to untreated myoblasts, no difference was noted. While early survival of myoblasts transplanted into infarcted hearts was augmented by NAC pre-treatment, cardiac function remained unchanged compared to non-treated myoblasts. Despite improving cell survival with NAC treated myoblast transplantation in a MI heart, cardiac function remained similar to untreated myoblasts. These results suggest that the reduced cardiac regenerative potential of myoblasts, when compared to MDSCs, is not only attributable to cell survival but is probably also related to the secretion of paracrine factors by the MDSCs.

The cardiac regenerative potential of myoblasts remains limited despite improving their survival via antioxidant treatment

PubMed Central

Beckman, Sarah A.; Sekiya, Naosumi; Chen, William C.W.; Mlakar, Logan; Tobita, Kimimassa; Huard, Johnny

2017-01-01

Introduction Since myoblasts have been limited by poor cell survival after cellular myoplasty, the major goal of the current study was to determine whether improving myoblast survival with an antioxidant could improve cardiac function after the transplantation of the myoblasts into an acute myocardial infarction. Background We previously demonstrated that early myogenic progenitors such as muscle-derived stem cells (MDSCs) exhibited superior cell survival and improved cardiac repair after transplantation into infarcted hearts compared to myoblasts, which we partially attributed to MDSC’s higher antioxidant levels. Aim To determine if antioxidant treatment could increase myoblast survival, subsequently improving cardiac function after myoblast transplantation into infarcted hearts. Materials and Methods Myoblasts were pre-treated with the antioxidant N-acetylcysteine (NAC) or the glutathione depleter, diethyl maleate (DEM), and injected into infarcted murine hearts. Regenerative potential was monitored by cell survival and cardiac function. Results At early time points, hearts injected with NAC-treated myoblasts exhibited increased donor cell survival, greater cell proliferation, and decreased cellular apoptosis, compared to untreated myoblasts. NAC-treated myoblasts significantly improved cardiac contractility, reduced fibrosis, and increased vascular density compared to DEM-treated myoblasts, but compared to untreated myoblasts, no difference was noted. Discussion While early survival of myoblasts transplanted into infarcted hearts was augmented by NAC pre-treatment, cardiac function remained unchanged compared to non-treated myoblasts. Conclusion Despite improving cell survival with NAC treated myoblast transplantation in a MI heart, cardiac function remained similar to untreated myoblasts. These results suggest that the reduced cardiac regenerative potential of myoblasts, when compared to MDSCs, is not only attributable to cell survival but is probably also related to the secretion of paracrine factors by the MDSCs. PMID:28989945

Physical exercise during muscle regeneration improves recovery of the slow/oxidative phenotype.

PubMed

Koulmann, Nathalie; Richard-Bulteau, Hélène; Crassous, Brigitte; Serrurier, Bernard; Pasdeloup, Marielle; Bigard, Xavier; Banzet, Sébastien

2017-01-01

As skeletal muscle mass recovery after extensive injury is improved by contractile activity, we explored whether concomitant exercise accelerates recovery of the contractile and metabolic phenotypes after muscle injury. After notexin-induced degeneration of a soleus muscle, Wistar rats were assigned to active (running exercise) or sedentary groups. Myosin heavy chains (MHC), metabolic enzymes, and calcineurin were studied during muscle regeneration at different time points. The mature MHC profile recovered earlier in active rats (21 days after injury) than in sedentary rats (42 days). Calcineurin was higher in the active degenerated than in the sedentary degenerated muscles at day 14. Citrate synthase and total lactate dehydrogenase (LDH) activity decreased after injury and were similarly recovered in both active and sedentary groups at 14 or 42 days, respectively. H-LDH isozyme activity recovered earlier in the active rats. Exercise improved recovery of the slow/oxidative phenotype after soleus muscle injury. Muscle Nerve 55: 91-100, 2017. © 2016 Wiley Periodicals, Inc.

Use of Dobutamine Stress Echocardiography for Periprocedural Evaluation of a Case of Critical Valvular Pulmonary Stenosis with Delayed Presentation.

PubMed

Barik, Ramachandra; Akula, Siva Prasad; Damera, Sheshagiri Rao

2016-01-01

We report a case illustrating a 39-year-old man with delayed presentation of severe pulmonary valve (PV) stenosis, clinical evidence of congestive right heart failure in the form of enlarged liver, raised jugular venous pressure, and anasarca without cyanosis. Echocardiography (echo) was used both for diagnosis and monitoring this patient as main tool. The contractile reserve of the right ventricle (RV) was evaluated by infusion of dobutamine and diuretic for 4 days before pulmonary balloon valvotomy. Both the tricuspid annular peak systolic excursion and diastolic (diastolic anterograde flow through PV) function of RV improved after percutaneous balloon pulmonary valvotomy. These improvements were clinically apparent by complete resolution of anasarca, pericardial effusion, and normalization albumin-globulin ratio. The periprocedural echo findings were quite unique in this illustration.

Use of Dobutamine Stress Echocardiography for Periprocedural Evaluation of a Case of Critical Valvular Pulmonary Stenosis with Delayed Presentation

PubMed Central

Barik, Ramachandra; Akula, Siva Prasad; Damera, Sheshagiri Rao

2016-01-01

We report a case illustrating a 39-year-old man with delayed presentation of severe pulmonary valve (PV) stenosis, clinical evidence of congestive right heart failure in the form of enlarged liver, raised jugular venous pressure, and anasarca without cyanosis. Echocardiography (echo) was used both for diagnosis and monitoring this patient as main tool. The contractile reserve of the right ventricle (RV) was evaluated by infusion of dobutamine and diuretic for 4 days before pulmonary balloon valvotomy. Both the tricuspid annular peak systolic excursion and diastolic (diastolic anterograde flow through PV) function of RV improved after percutaneous balloon pulmonary valvotomy. These improvements were clinically apparent by complete resolution of anasarca, pericardial effusion, and normalization albumin-globulin ratio. The periprocedural echo findings were quite unique in this illustration. PMID:28465962

Functional myogenic engraftment from mouse iPS cells.

PubMed

Darabi, Radbod; Pan, Weihong; Bosnakovski, Darko; Baik, June; Kyba, Michael; Perlingeiro, Rita C R

2011-11-01

Direct reprogramming of adult fibroblasts to a pluripotent state has opened new possibilities for the generation of patient- and disease-specific stem cells. However the ability of induced pluripotent stem (iPS) cells to generate tissue that mediates functional repair has been demonstrated in very few animal models of disease to date. Here we present the proof of principle that iPS cells may be used effectively for the treatment of muscle disorders. We combine the generation of iPS cells with conditional expression of Pax7, a robust approach to derive myogenic progenitors. Transplantation of Pax7-induced iPS-derived myogenic progenitors into dystrophic mice results in extensive engraftment, which is accompanied by improved contractility of treated muscles. These findings demonstrate the myogenic regenerative potential of iPS cells and provide rationale for their future therapeutic application for muscular dystrophies.

Cardiovascular studies using the chimpanzee (Pan troglodytes)

NASA Technical Reports Server (NTRS)

Hinds, J. E.; Cothran, L. N.; Hawthorne, E. W.

1977-01-01

Despite the phylogenetic similarities between chimpanzees and man, there exists a paucity of reliable data on normal cardiovascular function and the physiological responses of the system to standard interventions. Totally implanted biotelemetry systems or hardwire analog techniques were used to examine the maximum number of cardiovascular variables which could be simultaneously monitored without significantly altering the system's performance. This was performed in order to acquire base-line data not previously obtained in this species, to determine cardiovascular response to specific forcing functions such as ventricular pacing, drug infusions, and lower body negative pressure. A cardiovascular function profile protocol was developed in order to adjust independently the three major factors which modify ventricular performance, namely, left ventricular performance, left ventricular preload, afterload, and contractility. Cardiac pacing at three levels above the ambient rate was used to adjust end diastolic volume (preload). Three concentrations of angiotensin were infused continuously to evaluate afterload in a stepwide fashion. A continuous infusion of dobutamine was administered to raise the manifest contractile state of the heart.

STIM1 signaling controls store operated calcium entry required for development and contractile function in skeletal muscle

PubMed Central

Stiber, Jonathan; Hawkins, April; Zhang, Zhu-Shan; Wang, Sunny; Burch, Jarrett; Graham, Victoria; Ward, Cary C.; Seth, Malini; Finch, Elizabeth; Malouf, Nadia; Williams, R. Sanders; Eu, Jerry P.; Rosenberg, Paul

2009-01-01

It is now well established that stromal interaction molecule 1 (STIM1) is the calcium sensor of endoplasmic reticulum (ER) stores required to activate store-operated calcium entry (SOC) channels at the surface of non-excitable cells. Yet little is known about STIM1 in excitable cells such as striated muscle where the complement of calcium regulatory molecules is rather disparate from that of non-excitable cells. Here, we show that STIM1 is expressed in both myotubes and adult skeletal muscle. Myotubes lacking functional STIM1 fail to exhibit SOC and fatigue rapidly. Moreover, mice lacking functional STIM1 die perinatally from a skeletal myopathy. In addition, STIM1 haploinsufficiency confers a contractile defect only under conditions where rapid refilling of stores would be needed. These findings provide novel insight to the role of STIM1 in skeletal muscle and suggest that STIM1 has a universal role as an ER/SR calcium sensor in both excitable and non-excitable cells. PMID:18488020

Summary of Research Adaptions of Visceral and Cerebral Resistance Arteries to Simulated Microgravity

NASA Technical Reports Server (NTRS)

Delp, Michael

2003-01-01

The proposed studies were designed address the effects of simulated microgravity on vascular smooth muscle and endothelial cell function in resistance arteries isolated from visceral tissues (spleen, mesentery and kidneys) and cerebrum. Alterations in vascular function induced by microgravity are particularly relevant to the problems of orthostatic intolerance and reduced exercise capacity experienced by astronauts upon re-entry into the earth's gravitational field. Decrements in contractile function or enhanced vasodilatory responsiveness of peripheral resistance arteries could lead to decreased peripheral resistance and orthostatic hypotension. Alternatively, augmentation of contractile function in cerebral resistance arteries could lead to increased cerebral vascular resistance and diminished perfusion of the brain. The Specific Aims and hypotheses were proposed in this grant. Following each of the Specific Aims, progress toward addressing that specific aim is presented. With the exception of Specific Aim VI (see aim for details), all aims have been experimentally addressed as proposed. The final six months of the granting period will be used for manuscript preparation; manuscripts in preparation will contain results from Specific Aims I-IV. Results from Specific Aims V and VI have been published.

Role of potassium ion channels in detrusor smooth muscle function and dysfunction

PubMed Central

Petkov, Georgi V.

2013-01-01

Contraction and relaxation of the detrusor smooth muscle (DSM), which makes up the wall of the urinary bladder, facilitates the storage and voiding of urine. Several families of K+ channels, including voltage-gated K+ (KV) channels, Ca2+-activated K+ (KCa) channels, inward-rectifying ATP-sensitive K+ (Kir, KATP) channels, and two-pore-domain K+ (K2P) channels, are expressed and functional in DSM. They control DSM excitability and contractility by maintaining the resting membrane potential and shaping the action potentials that determine the phasic nature of contractility in this tissue. Defects in DSM K+ channel proteins or in the molecules involved in their regulatory pathways may underlie certain forms of bladder dysfunction, such as overactive bladder. K+ channels represent an opportunity for novel pharmacological manipulation and therapeutic intervention in human DSM. Modulation of DSM K+ channels directly or indirectly by targeting their regulatory mechanisms has the potential to control urinary bladder function. This Review summarizes our current state of knowledge of the functional role of K+ channels in DSM in health and disease, with special emphasis on current advancements in the field. PMID:22158596

Correlation of embryonic skeletal muscle myotube physical characteristics with contractile force generation on an atomic force microscope-based bio-microelectromechanical systems device

NASA Astrophysics Data System (ADS)

Pirozzi, K. L.; Long, C. J.; McAleer, C. W.; Smith, A. S. T.; Hickman, J. J.

2013-08-01

Rigorous analysis of muscle function in in vitro systems is needed for both acute and chronic biomedical applications. Forces generated by skeletal myotubes on bio-microelectromechanical cantilevers were calculated using a modified version of Stoney's thin-film equation and finite element analysis (FEA), then analyzed for regression to physical parameters. The Stoney's equation results closely matched the more intensive FEA and the force correlated to cross-sectional area (CSA). Normalizing force to measured CSA significantly improved the statistical sensitivity and now allows for close comparison of in vitro data to in vivo measurements for applications in exercise physiology, robotics, and modeling neuromuscular diseases.

Hypotonic swelling promotes nitric oxide release in cardiac ventricular myocytes: impact on swelling-induced negative inotropic effect

PubMed Central

Gonano, Luis Alberto; Morell, Malena; Burgos, Juan Ignacio; Dulce, Raul Ariel; De Giusti, Verónica Celeste; Aiello, Ernesto Alejandro; Hare, Joshua Michael; Vila Petroff, Martin

2014-01-01

Aims Cardiomyocyte swelling occurs in multiple pathological situations and has been associated with contractile dysfunction, cell death, and enhanced propensity to arrhythmias. We investigate whether hypotonic swelling promotes nitric oxide (NO) release in cardiomyocytes, and whether it impacts on swelling-induced contractile dysfunction. Methods and results Superfusing rat cardiomyocytes with a hypotonic solution (HS; 217 mOsm), increased cell volume, reduced myocyte contraction and Ca2+ transient, and increased NO-sensitive 4-amino-5-methylamino-2′,7′-difluorofluorescein diacetate (DAF-FM) fluorescence. When cells were exposed to HS + 2.5 mM of the NO synthase inhibitor l-NAME, cell swelling occurred in the absence of NO release. Swelling-induced NO release was also prevented by the nitric oxide synthase 1 (NOS1) inhibitor, nitroguanidine, and significantly reduced in NOS1 knockout mice. Additionally, colchicine (inhibitor of microtubule polymerization) prevented the increase in DAF-FM fluorescence induced by HS, indicating that microtubule integrity is necessary for swelling-induced NO release. The swelling-induced negative inotropic effect was exacerbated in the presence of either l-NAME, nitroguandine, the guanylate cyclase inhibitor, ODQ, or the PKG inhibitor, KT5823, suggesting that NOS1-derived NO provides contractile support via a cGMP/PKG-dependent mechanism. Indeed, ODQ reduced Ca2+ wave velocity and both ODQ and KT5823 reduced the HS-induced increment in ryanodine receptor (RyR2, Ser2808) phosphorylation, suggesting that in this context, cGMP/PKG may contribute to preserve contractile function by enhancing sarcoplasmic reticulum Ca2+ release. Conclusions Our findings suggest a novel mechanism for NO release in cardiomyocytes with putative pathophysiological relevance determined, at least in part, by its capability to reduce the extent of contractile dysfunction associated with hypotonic swelling. PMID:25344365

Diadenosine tetra- and pentaphosphates affect contractility and bioelectrical activity in the rat heart via P2 purinergic receptors.

PubMed

Pustovit, Ksenia B; Kuzmin, Vladislav S; Abramochkin, Denis V

2016-03-01

Diadenosine polyphosphates (Ap(n)As) are endogenously produced molecules which have been identified in various tissues of mammalian organism, including myocardium. Ap(n)As contribute to the blood clotting and are also widely accepted as regulators of blood vascular tone. Physiological role of Ap(n)As in cardiac muscle has not been completely elucidated. The present study aimed to investigate the effects of diadenosine tetra- (Ap4A) and penta- (Ap5A) polyphosphates on contractile function and action potential (AP) waveform in rat supraventricular and ventricular myocardium. We have also demonstrated the effects of A4pA and Ap5A in myocardial sleeves of pulmonary veins (PVs), which play a crucial role in genesis of atrial fibrillation. APs were recorded with glass microelectrodes in multicellular myocardial preparations. Contractile activity was measured in isolated Langendorff-perfused rat hearts. Both Ap4A and Ap5A significantly reduced contractility of isolated Langendorff-perfused heart and produced significant reduction of AP duration in left and right auricle, interatrial septum, and especially in right ventricular wall myocardium. Ap(n)As also shortened APs in rat pulmonary veins and therefore may be considered as potential proarrhythmic factors. Cardiotropic effects of Ap4A and Ap5A were strongly antagonized by selective blockers of P2 purine receptors suramin and pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid (PPADS), while P1 blocker DPCPX was not effective. We conclude that Ap(n)As may be considered as new class of endogenous cardioinhibitory compounds. P2 purine receptors play the central role in mediation of Ap4A and Ap5A inhibitory effects on electrical and contractile activity in different regions of the rat heart.

Cardiac-specific knockout of ETA receptor mitigates low ambient temperature-induced cardiac hypertrophy and contractile dysfunction

PubMed Central

Zhang, Yingmei; Li, Linlin; Hua, Yinan; Nunn, Jennifer M.; Dong, Feng; Yanagisawa, Masashi; Ren, Jun

2012-01-01

Cold exposure is associated with oxidative stress and cardiac dysfunction. The endothelin (ET) system, which plays a key role in myocardial homeostasis, may participate in cold exposure-induced cardiovascular dysfunction. This study was designed to examine the role of ET-1 in cold stress-induced cardiac geometric and contractile responses. Wild-type (WT) and ETA receptor knockout (ETAKO) mice were assigned to normal or cold exposure (4°C) environment for 2 and 5 weeks prior to evaluation of cardiac geometry, contractile, and intracellular Ca2+ properties. Levels of the temperature sensor transient receptor potential vanilloid (TRPV1), mitochondrial proteins for biogenesis and oxidative phosphorylation, including UCP2, HSP90, and PGC1α were evaluated. Cold stress triggered cardiac hypertrophy, depressed myocardial contractile capacity, including fractional shortening, peak shortening, and maximal velocity of shortening/relengthening, reduced intracellular Ca2+ release, prolonged intracellular Ca2+ decay and relengthening duration, generation of ROS and superoxide, as well as apoptosis, the effects of which were blunted by ETAKO. Western blotting revealed downregulated TRPV1 and PGC1α as well as upregulated UCP2 and activation of GSK3β, GATA4, and CREB in cold-stressed WT mouse hearts, which were obliterated by ETAKO. Levels of HSP90, an essential regulator for thermotolerance, were unchanged. The TRPV1 agonist SA13353 attenuated whereas TRPV1 antagonist capsazepine mimicked cold stress- or ET-1-induced cardiac anomalies. The GSK3β inhibitor SB216763 ablated cold stress-induced cardiac contractile (but not remodeling) changes and ET-1-induced TRPV1 downregulation. These data suggest that ETAKO protects against cold exposure-induced cardiac remodeling and dysfunction mediated through TRPV1 and mitochondrial function. PMID:22442497

TRPC3 contributes to regulation of cardiac contractility and arrhythmogenesis by dynamic interaction with NCX1

PubMed Central

Doleschal, Bernhard; Primessnig, Uwe; Wölkart, Gerald; Wolf, Stefan; Schernthaner, Michaela; Lichtenegger, Michaela; Glasnov, Toma N.; Kappe, C. Oliver; Mayer, Bernd; Antoons, Gudrun; Heinzel, Frank; Poteser, Michael; Groschner, Klaus

2015-01-01

Aim TRPC3 is a non-selective cation channel, which forms a Ca2+ entry pathway involved in cardiac remodelling. Our aim was to analyse acute electrophysiological and contractile consequences of TRPC3 activation in the heart. Methods and results We used a murine model of cardiac TRPC3 overexpression and a novel TRPC3 agonist, GSK1702934A, to uncover (patho)physiological functions of TRPC3. GSK1702934A induced a transient, non-selective conductance and prolonged action potentials in TRPC3-overexpressing myocytes but lacked significant electrophysiological effects in wild-type myocytes. GSK1702934A transiently enhanced contractility and evoked arrhythmias in isolated Langendorff hearts from TRPC3-overexpressing but not wild-type mice. Interestingly, pro-arrhythmic effects outlasted TRPC3 current activation, were prevented by enhanced intracellular Ca2+ buffering, and suppressed by the NCX inhibitor 3′,4′-dichlorobenzamil hydrochloride. GSK1702934A substantially promoted NCX currents in TRPC3-overexpressing myocytes. The TRPC3-dependent electrophysiologic, pro-arrhythmic, and inotropic actions of GSK1702934A were mimicked by angiotensin II (AngII). Immunocytochemistry demonstrated colocalization of TRPC3 with NCX1 and disruption of local interaction upon channel activation by either GSK1702934A or AngII. Conclusion Cardiac TRPC3 mediates Ca2+ and Na+ entry in proximity of NCX1, thereby elevating cellular Ca2+ levels and contractility. Excessive activation of TRPC3 is associated with transient cellular Ca2+ overload, spatial uncoupling between TRPC3 and NCX1, and arrhythmogenesis. We propose TRPC3-NCX micro/nanodomain communication as determinant of cardiac contractility and susceptibility to arrhythmogenic stimuli. PMID:25631581

The contributions of cardiac myosin binding protein C and troponin I phosphorylation to β‐adrenergic enhancement of in vivo cardiac function

PubMed Central

Gresham, Kenneth S.

2016-01-01

Key points β‐adrenergic stimulation increases cardiac myosin binding protein C (MyBP‐C) and troponin I phosphorylation to accelerate pressure development and relaxation in vivo, although their relative contributions remain unknown.Using a novel mouse model lacking protein kinase A‐phosphorylatable troponin I (TnI) and MyBP‐C, we examined in vivo haemodynamic function before and after infusion of the β‐agonist dobutamine.Mice expressing phospho‐ablated MyBP‐C displayed cardiac hypertrophy and prevented full acceleration of pressure development and relaxation in response to dobutamine, whereas expression of phosphor‐ablated TnI alone had little effect on the acceleration of contractile function in response to dobutamine.Our data demonstrate that MyBP‐C phosphorylation is the principal mediator of the contractile response to increased β‐agonist stimulation in vivo.These results help us understand why MyBP‐C dephosphorylation in the failing heart contributes to contractile dysfunction and decreased adrenergic reserve in response to acute stress. Abstract β‐adrenergic stimulation plays a critical role in accelerating ventricular contraction and speeding relaxation to match cardiac output to changing circulatory demands. Two key myofilaments proteins, troponin I (TnI) and myosin binding protein‐C (MyBP‐C), are phosphorylated following β‐adrenergic stimulation; however, their relative contributions to the enhancement of in vivo cardiac contractility are unknown. To examine the roles of TnI and MyBP‐C phosphorylation in β‐adrenergic‐mediated enhancement of cardiac function, transgenic (TG) mice expressing non‐phosphorylatable TnI protein kinase A (PKA) residues (i.e. serine to alanine substitution at Ser23/24; TnIPKA−) were bred with mice expressing non‐phosphorylatable MyBP‐C PKA residues (i.e. serine to alanine substitution at Ser273, Ser282 and Ser302; MyBPCPKA−) to generate a novel mouse model expressing non‐phosphorylatable PKA residues in TnI and MyBP‐C (DBLPKA−). MyBP‐C dephosphorylation produced cardiac hypertrophy and increased wall thickness in MyBPCPKA− and DBLPKA− mice, and in vivo echocardiography and pressure–volume catheterization studies revealed impaired systolic function and prolonged diastolic relaxation compared to wild‐type and TnIPKA– mice. Infusion of the β‐agonist dobutamine resulted in accelerated rates of pressure development and relaxation in all mice; however, MyBPCPKA− and DBLPKA− mice displayed a blunted contractile response compared to wild‐type and TnIPKA– mice. Furthermore, unanaesthesized MyBPCPKA− and DBLPKA− mice displayed depressed maximum systolic pressure in response to dobutamine as measured using implantable telemetry devices. Taken together, our data show that MyBP‐C phosphorylation is a critical modulator of the in vivo acceleration of pressure development and relaxation as a result of enhanced β‐adrenergic stimulation, and reduced MyBP‐C phosphorylation may underlie depressed adrenergic reserve in heart failure. PMID:26635197

Effects of elevated H+ and Pi on the contractile mechanics of skeletal muscle fibres from young and old men: implications for muscle fatigue in humans.

PubMed

Sundberg, Christopher W; Hunter, Sandra K; Trappe, Scott W; Smith, Carolyn S; Fitts, Robert H

2018-05-28

The mechanisms for the loss in muscle power and increased fatigability with ageing are unresolved. We show that the contractile mechanics of fibres from the vastus lateralis of old men were well-preserved compared to young men, but the selective loss of fast myosin heavy chain (MHC) II muscle was strongly associated with age-related decrements in whole-muscle strength and power. We reveal that the combination of acidosis (H + ) and inorganic phosphate (P i ) is an important mediator of muscle fatigue in humans by inhibiting the low- to high-force state of the cross-bridge cycle and peak power, but the depressive effects of these ions on cross-bridge function were similar in fibres from young and old men. These findings suggest the age-related loss in muscle power is due primarily to the atrophy of fast fibres, but the age-related increased fatigability cannot be explained by an increased sensitivity of the cross-bridge to H + and P i . The purpose of this study was to identify the mechanisms for the loss in muscle power and increased fatigability with ageing by integrating measures of whole-muscle function with single fibre contractile mechanics. After adjusting for the 22% smaller muscle mass in old (73-89 yrs, n = 6) compared with young men (20-29 yrs, n = 6), isometric torque and power output of the knee extensors were, respectively, 38% and 53% lower with age. Fatigability was ∼2.5-fold greater with age and strongly associated with the reductions in the electrically-evoked contractile properties. To test whether cross-bridge mechanisms could explain age-related decrements in knee extensor function, we exposed myofibres (n = 254) from the vastus lateralis to conditions mimicking quiescent muscle and fatiguing levels of H + (pH 6.2) and P i (30 mM). The fatigue-mimicking condition caused marked reductions in force, shortening velocity, and power and inhibited the low- to high-force state of the cross-bridge cycle, confirming non-human studies that these ions act synergistically to impair cross-bridge function. Other than severe age-related atrophy of fast fibres (-55%), contractile function and the depressive effects of the fatigue-mimicking condition did not differ in fibres from young and old men. The selective loss of fast MHC II muscle was strongly associated with the age-related decrease in isometric torque (r = 0.785) and power (r = 0.861). These data suggest that the age-related loss in muscle strength and power is due primarily to the atrophy of fast fibres, but that the age-related increased fatigability cannot be explained by an increased sensitivity of the cross-bridge to H + and P i . This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Dynamic culture yields engineered myocardium with near-adult functional output

PubMed Central

Jackman, Christopher P.; Carlson, Aaron L.; Bursac, Nenad

2016-01-01

Engineered cardiac tissues hold promise for cell therapy and drug development, but exhibit inadequate function and maturity. In this study, we sought to significantly improve the function and maturation of rat and human engineered cardiac tissues. We developed dynamic, free-floating culture conditions for engineering “cardiobundles”, 3-dimensional cylindrical tissues made from neonatal rat cardiomyocytes or human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) embedded in fibrin-based hydrogel. Compared to static culture, 2-week dynamic culture of neonatal rat cardiobundles significantly increased expression of sarcomeric proteins, cardiomyocyte size (~2.1-fold), contractile force (~3.5-fold), and conduction velocity of action potentials (~1.4-fold). The average contractile force per cross-sectional area (59.7 mN/mm2) and conduction velocity (52.5 cm/sec) matched or approached those of adult rat myocardium, respectively. The inferior function of statically cultured cardiobundles was rescued by transfer to dynamic conditions, which was accompanied by an increase in mTORC1 activity and decline in AMPK phosphorylation and was blocked by rapamycin. Furthermore, dynamic culture effects did not stimulate ERK1/2 pathway and were insensitive to blockers of mechanosensitive channels, suggesting increased nutrient availability rather than mechanical stimulation as the upstream activator of mTORC1. Direct comparison with phenylephrine treatment confirmed that dynamic culture promoted physiological cardiomyocyte growth rather than pathological hypertrophy. Optimized dynamic culture conditions also augmented function of human cardiobundles made reproducibly from cardiomyocytes derived from multiple hPSC lines, resulting in significantly increased contraction force (~2.5-fold) and conduction velocity (~1.4-fold). The average specific force of 23.2 mN/mm2 and conduction velocity of 25.8 cm/sec approached the functional metrics of adult human myocardium. In conclusion, we have developed a versatile methodology for engineering cardiac tissues with a near-adult functional output without the need for exogenous electrical or mechanical stimulation, and have identified mTOR signaling as an important mechanism for advancing tissue maturation and function in vitro. PMID:27723557

Dynamic culture yields engineered myocardium with near-adult functional output.

PubMed

Jackman, Christopher P; Carlson, Aaron L; Bursac, Nenad

2016-12-01

Engineered cardiac tissues hold promise for cell therapy and drug development, but exhibit inadequate function and maturity. In this study, we sought to significantly improve the function and maturation of rat and human engineered cardiac tissues. We developed dynamic, free-floating culture conditions for engineering "cardiobundles", 3-dimensional cylindrical tissues made from neonatal rat cardiomyocytes or human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) embedded in fibrin-based hydrogel. Compared to static culture, 2-week dynamic culture of neonatal rat cardiobundles significantly increased expression of sarcomeric proteins, cardiomyocyte size (∼2.1-fold), contractile force (∼3.5-fold), and conduction velocity of action potentials (∼1.4-fold). The average contractile force per cross-sectional area (59.7 mN/mm 2 ) and conduction velocity (52.5 cm/s) matched or approached those of adult rat myocardium, respectively. The inferior function of statically cultured cardiobundles was rescued by transfer to dynamic conditions, which was accompanied by an increase in mTORC1 activity and decline in AMPK phosphorylation and was blocked by rapamycin. Furthermore, dynamic culture effects did not stimulate ERK1/2 pathway and were insensitive to blockers of mechanosensitive channels, suggesting increased nutrient availability rather than mechanical stimulation as the upstream activator of mTORC1. Direct comparison with phenylephrine treatment confirmed that dynamic culture promoted physiological cardiomyocyte growth rather than pathological hypertrophy. Optimized dynamic culture conditions also augmented function of human cardiobundles made reproducibly from cardiomyocytes derived from multiple hPSC lines, resulting in significantly increased contraction force (∼2.5-fold) and conduction velocity (∼1.4-fold). The average specific force of 23.2 mN/mm 2 and conduction velocity of 25.8 cm/s approached the functional metrics of adult human myocardium. In conclusion, we have developed a versatile methodology for engineering cardiac tissues with a near-adult functional output without the need for exogenous electrical or mechanical stimulation, and have identified mTOR signaling as an important mechanism for advancing tissue maturation and function in vitro. Copyright © 2016 Elsevier Ltd. All rights reserved.

Altered myofilament structure and function in dogs with Duchenne muscular dystrophy cardiomyopathy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ait Mou, Younss; Lacampagne, Alain; Irving, Thomas

Aim Duchenne Muscular Dystrophy (DMD) is associated with progressive depressed left ventricular (LV) function. However, DMD effects on myofilament structure and function are poorly understood. Golden Retriever Muscular Dystrophy (GRMD) is a dog model of DMD recapitulating the human form of DMD. Objective The objective of this study is to evaluate myofilament structure and function alterations in GRMD model with spontaneous cardiac failure. Methods and results We have employed synchrotron X-rays diffraction to evaluate myofilament lattice spacing at various sarcomere lengths (SL) on permeabilized LV myocardium. We found a negative correlation between SL and lattice spacing in both sub-epicardium (EPI)more » and sub-endocardium (ENDO) LV layers in control dog hearts. In the ENDO of GRMD hearts this correlation is steeper due to higher lattice spacing at short SL (1.9 μm). Furthermore, cross-bridge cycling indexed by the kinetics of tension redevelopment (ktr) was faster in ENDO GRMD myofilaments at short SL. We measured post-translational modifications of key regulatory contractile proteins. S-glutathionylation of cardiac Myosin Binding Protein-C (cMyBP-C) was unchanged and PKA dependent phosphorylation of the cMyBP-C was significantly reduced in GRMD ENDO tissue and more modestly in EPI tissue. Conclusions We found a gradient of contractility in control dogs' myocardium that spreads across the LV wall, negatively correlated with myofilament lattice spacing. Chronic stress induced by dystrophin deficiency leads to heart failure that is tightly associated with regional structural changes indexed by increased myofilament lattice spacing, reduced phosphorylation of regulatory proteins and altered myofilament contractile properties in GRMD dogs.« less

Deficiency of selenoprotein S, an endoplasmic reticulum resident oxidoreductase, impairs the contractile function of fast twitch hindlimb muscles.

PubMed

Addinsall, Alex Bernard; Wright, Craig Robert; Shaw, Christopher S; McRae, Natasha L; Forgan, Leonard George; Weng, Chia-Heng; Conlan, Xavier A; Francis, Paul S; Smith, Zoe M; Andrikopoulos, Sofianos; Stupka, Nicole

2018-04-18

Selenoprotein S (Seps1) is an endoplasmic reticulum (ER) resident antioxidant implicated in ER stress and inflammation. In human vastus lateralis and mouse hindlimb muscles, Seps1 localization and expression was fiber type specific. In male Seps1 +/- heterozygous mice, spontaneous physical activity was reduced compared to wild type littermates ( d=1.10, P=0.029). A similar trend also observed in Seps1 -/- knockout mice ( d=1.12, P=0.051). Whole body metabolism, body composition, extensor digitorum longus (EDL) and soleus mass, and myofibre diameter were unaffected by genotype. However, in isolated fast EDL muscles from Seps1 -/- knockout mice, the force frequency curve (1-120 Hz; FFC) was shifted downward versus EDL muscles from wild type littermates ( d=0.55, P=0.002), suggestive of reduced strength. During 4 min of intermittent, submaximal (60 Hz) stimulation, the genetic deletion or reduction of Seps1 decreased EDL force production ( d=0.52, P<0.001). Furthermore, at the start of the intermittent stimulation protocol, when compared to the 60 Hz stimulation of the FFC, EDL muscles from Seps1 -/- knockout or Seps1 +/- heterozygous mice produced 10% less force than those from wild type littermates ( d=0.31, P<0.001 and d=0.39, P=0.015). This functional impairment was associated with reduced mRNA transcript abundance of thioredoxin-1 ( Trx1), thioredoxin interacting protein ( Txnip), and the ER stress markers Chop and Grp94. Whereas, in slow soleus muscles, Seps1 deletion did not compromise contractile function and Trx1 ( d=1.38, P=0.012) and Txnip ( d=1.27, P=0.025) gene expression was increased. Seps1 is a novel regulator of contractile function and cellular stress responses in fast twitch muscles.

Impaired cardiac contractile function in arginine:glycine amidinotransferase knockout mice devoid of creatine is rescued by homoarginine but not creatine

PubMed Central

Faller, Kiterie M E; Atzler, Dorothee; McAndrew, Debra J; Zervou, Sevasti; Whittington, Hannah J; Simon, Jillian N; Aksentijevic, Dunja; ten Hove, Michiel; Choe, Chi-un; Isbrandt, Dirk; Casadei, Barbara; Schneider, Jurgen E; Neubauer, Stefan; Lygate, Craig A

2018-01-01

Abstract Aims Creatine buffers cellular adenosine triphosphate (ATP) via the creatine kinase reaction. Creatine levels are reduced in heart failure, but their contribution to pathophysiology is unclear. Arginine:glycine amidinotransferase (AGAT) in the kidney catalyses both the first step in creatine biosynthesis as well as homoarginine (HA) synthesis. AGAT-/- mice fed a creatine-free diet have a whole body creatine-deficiency. We hypothesized that AGAT-/- mice would develop cardiac dysfunction and rescue by dietary creatine would imply causality. Methods and results Withdrawal of dietary creatine in AGAT-/- mice provided an estimate of myocardial creatine efflux of ∼2.7%/day; however, in vivo cardiac function was maintained despite low levels of myocardial creatine. Using AGAT-/- mice naïve to dietary creatine we confirmed absence of phosphocreatine in the heart, but crucially, ATP levels were unchanged. Potential compensatory adaptations were absent, AMPK was not activated and respiration in isolated mitochondria was normal. AGAT-/- mice had rescuable changes in body water and organ weights suggesting a role for creatine as a compatible osmolyte. Creatine-naïve AGAT-/- mice had haemodynamic impairment with low LV systolic pressure and reduced inotropy, lusitropy, and contractile reserve. Creatine supplementation only corrected systolic pressure despite normalization of myocardial creatine. AGAT-/- mice had low plasma HA and supplementation completely rescued all other haemodynamic parameters. Contractile dysfunction in AGAT-/- was confirmed in Langendorff perfused hearts and in creatine-replete isolated cardiomyocytes, indicating that HA is necessary for normal cardiac function. Conclusions Our findings argue against low myocardial creatine per se as a major contributor to cardiac dysfunction. Conversely, we show that HA deficiency can impair cardiac function, which may explain why low HA is an independent risk factor for multiple cardiovascular diseases. PMID:29236952

Thoracic Epidural Anesthesia Reduces Right Ventricular Systolic Function With Maintained Ventricular-Pulmonary Coupling.

PubMed

Wink, Jeroen; de Wilde, Rob B P; Wouters, Patrick F; van Dorp, Eveline L A; Veering, Bernadette Th; Versteegh, Michel I M; Aarts, Leon P H J; Steendijk, Paul

2016-10-18

Blockade of cardiac sympathetic fibers by thoracic epidural anesthesia may affect right ventricular function and interfere with the coupling between right ventricular function and right ventricular afterload. Our main objectives were to study the effects of thoracic epidural anesthesia on right ventricular function and ventricular-pulmonary coupling. In 10 patients scheduled for lung resection, right ventricular function and its response to increased afterload, induced by temporary, unilateral clamping of the pulmonary artery, was tested before and after induction of thoracic epidural anesthesia using combined pressure-conductance catheters. Thoracic epidural anesthesia resulted in a significant decrease in right ventricular contractility (ΔESV 25 : +25.5 mL, P=0.0003; ΔEes: -0.025 mm Hg/mL, P=0.04). Stroke work, dP/dt MAX , and ejection fraction showed a similar decrease in systolic function (all P<0.05). A concomitant decrease in effective arterial elastance (ΔEa: -0.094 mm Hg/mL, P=0.004) yielded unchanged ventricular-pulmonary coupling. Cardiac output, systemic vascular resistance, and mean arterial blood pressure were unchanged. Clamping of the pulmonary artery significantly increased afterload (ΔEa: +0.226 mm Hg/mL, P<0.001). In response, right ventricular contractility increased (ΔESV 25 : -26.6 mL, P=0.0002; ΔEes: +0.034 mm Hg/mL, P=0.008), but ventricular-pulmonary coupling decreased (Δ(Ees/Ea) = -0.153, P<0.0001). None of the measured indices showed significant interactive effects, indicating that the effects of increased afterload were the same before and after thoracic epidural anesthesia. Thoracic epidural anesthesia impairs right ventricular contractility but does not inhibit the native positive inotropic response of the right ventricle to increased afterload. Right ventricular-pulmonary arterial coupling was decreased with increased afterload but not affected by the induction of thoracic epidural anesthesia. URL: http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=2844. Unique identifier: NTR2844. © 2016 American Heart Association, Inc.

A new technique for calculating individual dermal fibroblast contractile forces generated within collagen-GAG scaffolds.

PubMed

Harley, Brendan A; Freyman, Toby M; Wong, Matthew Q; Gibson, Lorna J

2007-10-15

Cell-mediated contraction plays a critical role in many physiological and pathological processes, notably organized contraction during wound healing. Implantation of an appropriately formulated (i.e., mean pore size, chemical composition, degradation rate) three-dimensional scaffold into an in vivo wound site effectively blocks the majority of organized wound contraction and results in induced regeneration rather than scar formation. Improved understanding of cell contraction within three-dimensional constructs therefore represents an important area of study in tissue engineering. Studies of cell contraction within three-dimensional constructs typically calculate an average contractile force from the gross deformation of a macroscopic substrate by a large cell population. In this study, cellular solids theory has been applied to conventional column buckling relationships to quantify the magnitude of individual cell contraction events within a three-dimensional, collagen-glycosaminoglycan scaffold. This new technique can be used for studying cell mechanics with a wide variety of porous scaffolds that resemble low-density, open-cell foams. It extends previous methods for analyzing cell buckling of two-dimensional substrates to three-dimensional constructs. From data available in the literature, the mean contractile force (Fc) generated by individual dermal fibroblasts within the collagen-glycosaminoglycan scaffold was calculated to range between 11 and 41 nN (Fc=26+/-13 nN, mean+/-SD), with an upper bound of cell contractility estimated at 450 nN.

Mechanisms underlying hypothermia-induced cardiac contractile dysfunction.

PubMed

Han, Young-Soo; Tveita, Torkjel; Prakash, Y S; Sieck, Gary C

2010-03-01

Rewarming patients after profound hypothermia may result in acute heart failure and high mortality (50-80%). However, the underlying pathophysiological mechanisms are largely unknown. We characterized cardiac contractile function in the temperature range of 15-30 degrees C by measuring the intracellular Ca(2+) concentration ([Ca(2+)](i)) and twitch force in intact left ventricular rat papillary muscles. Muscle preparations were loaded with fura-2 AM and electrically stimulated during cooling at 15 degrees C for 1.5 h before being rewarmed to the baseline temperature of 30 degrees C. After hypothermia/rewarming, peak twitch force decreased by 30-40%, but [Ca(2+)](i) was not significantly altered. In addition, we assessed the maximal Ca(2+)-activated force (F(max)) and Ca(2+) sensitivity of force in skinned papillary muscle fibers. F(max) was decreased by approximately 30%, whereas the pCa required for 50% of F(max) was reduced by approximately 0.14. In rewarmed papillary muscle, both total cardiac troponin I (cTnI) phosphorylation and PKA-mediated cTnI phosphorylation at Ser23/24 were significantly increased compared with controls. We conclude that after hypothermia/rewarming, myocardial contractility is significantly reduced, as evidenced by reduced twitch force and F(max). The reduced myocardial contractility is attributed to decreased Ca(2+) sensitivity of force rather than [Ca(2+)](i) itself, resulting from increased cTnI phosphorylation.

Osmolality- and Na+ -dependent effects of hyperosmotic NaCl solution on contractile activity and Ca2+ cycling in rat ventricular myocytes.

PubMed

Ricardo, Rafael A; Bassani, Rosana A; Bassani, José W M

2008-01-01

Hypertonic NaCl solutions have been used for small-volume resuscitation from hypovolemic shock. We sought to identify osmolality- and Na(+)-dependent components of the effects of the hyperosmotic NaCl solution (85 mOsm/kg increment) on contraction and cytosolic Ca(2+) concentration ([Ca(2+)](i)) in isolated rat ventricular myocytes. The biphasic change in contraction and Ca(2+) transient amplitude (decrease followed by recovery) was accompanied by qualitatively similar changes in sarcoplasmic reticulum (SR) Ca(2+) content and fractional release and was mimicked by isosmotic, equimolar increase in extracellular [Na(+)] ([Na(+)](o)). Raising osmolality with sucrose, however, augmented systolic [Ca(2+)](i) monotonically without change in SR parameters and markedly decreased contraction amplitude and diastolic cell length. Functional SR inhibition with thapsigargin abolished hyperosmolality effects on [Ca(2+)](i). After 15-min perfusion, both hyperosmotic solutions slowed mechanical relaxation during twitches and [Ca(2+)](i) decline during caffeine-evoked transients, raised diastolic and systolic [Ca(2+)](i), and depressed systolic contractile activity. These effects were greater with sucrose solution, and were not observed after isosmotic [Na(+)](o) increase. We conclude that under the present experimental conditions, transmembrane Na(+) redistribution apparently plays an important role in determining changes in SR Ca(2+) mobilization, which markedly affect contractile response to hyperosmotic NaCl solutions and attenuate the osmotically induced depression of contractile activity.

Cerebral Artery Alpha-1 AR Subtypes: High Altitude Long-Term Acclimatization Responses

PubMed Central

Goyal, Ravi; Goyal, Dipali; Chu, Nina; Van Wickle, Jonathan; Longo, Lawrence D.

2014-01-01

In response to hypoxia and other stress, the sympathetic (adrenergic) nervous system regulates arterial contractility and blood flow, partly through differential activities of the alpha1 (α1) - adrenergic receptor (AR) subtypes (α1A-, α1B-, and α1D-AR). Thus, we tested the hypothesis that with acclimatization to long-term hypoxia (LTH), contractility of middle cerebral arteries (MCA) is regulated by changes in expression and activation of the specific α1-AR subtypes. We conducted experiments in MCA from adult normoxic sheep maintained near sea level (300 m) and those exposed to LTH (110 days at 3801 m). Following acclimatization to LTH, ovine MCA showed a 20% reduction (n = 5; P<0.05) in the maximum tension achieved by 10−5 M phenylephrine (PHE). LTH-acclimatized cerebral arteries also demonstrated a statistically significant (P<0.05) inhibition of PHE-induced contractility in the presence of specific α1-AR subtype antagonists. Importantly, compared to normoxic vessels, there was significantly greater (P<0.05) α1B-AR subtype mRNA and protein levels in LTH acclimatized MCA. Also, our results demonstrate that extracellular regulated kinase 1 and 2 (ERK1/2)-mediated negative feedback regulation of PHE-induced contractility is modulated by α1B-AR subtype. Overall, in ovine MCA, LTH produces profound effects on α1-AR subtype expression and function. PMID:25393740

Substance P activates both contractile and inflammatory pathways in lymphatics through the neurokinin receptors NK1R and NK3R.

PubMed

Chakraborty, Sanjukta; Nepiyushchikh, Zhanna; Davis, Michael J; Zawieja, David C; Muthuchamy, Mariappan

2011-01-01

The aim of this study was to elucidate the molecular signaling mechanisms by which substance P (SP) modulates lymphatic muscle contraction and to determine whether SP stimulates both contractile as well as inflammatory pathways in the lymphatics. A rat mesenteric lymphatic muscle cell culture model (RMLMCs) and known specific pharmacological inhibitors were utilized to delineate SP-mediated signaling pathways in lymphatics. We detected expression of neurokinin receptor 1 (NK1R) and neurokinin receptor 3 (NK3R) in RMLMCs. SP stimulation increased phosphorylation of myosin light chain 20 (MLC₂₀) as well as p38 mitogen associated protein kinase (p38-MAPK) and extracellular signal regulated kinase (ERK1/2) indicating activation of both a contractile and a pro-inflammatory MAPK pathway. Pharmacological inhibition of both NK1R and NK3R significantly affected the downstream SP signaling. We further examined whether there was any crosstalk between the two pathways upon SP stimulation. Inhibition of ERK1/2 decreased levels of p-MLC₂₀ after SP activation, in a PKC dependent manner, indicating a potential crosstalk between these two pathways. These data provide the first evidence that SP-mediated crosstalk between pro-inflammatory and contractile signaling mechanisms exists in the lymphatic system and may be an important bridge between lymphatic function modulation and inflammation. © 2010 John Wiley & Sons Ltd.

Substance P activates both contractile and inflammatory pathways in lymphatics through the neurokinin receptors NK1R and NK3R

PubMed Central

Chakraborty, Sanjukta; Nepiyushchikh, Zhanna; Davis, Michael J.; Zawieja, David C.; Muthuchamy, Mariappan

2010-01-01

Objective The aim of this study was to elucidate the molecular signaling mechanisms by which substance P (SP) modulates lymphatic muscle contraction and to determine whether SP stimulates both contractile as well as inflammatory pathways in the lymphatics. Methods A rat mesenteric lymphatic muscle cell culture model (RMLMCs) and known specific pharmacological inhibitors were utilized to delineate SP mediated signaling pathways in lymphatics. Results We detected expression of neurokinin receptor 1 (NK1R) and neurokinin receptor 3 (NK3R) in RMLMCs. SP stimulation increased phosphorylation of myosin light chain 20 (MLC20) as well as p38 mitogen associated protein kinase (p38-MAPK) and extracellular signal regulated kinase (ERK1/2) indicating activation of both a contractile and a pro-inflammatory MAPK pathway. Pharmacological inhibition of both NK1R and NK3R significantly affected the downstream SP signaling. We further examined whether there was any crosstalk between the two pathways upon SP stimulation. Inhibition of ERK1/2 decreased levels of p-MLC20 after SP activation, in a PKC dependent manner, indicating a potential crosstalk between these two pathways. Conclusions These data provide the first evidence that SP mediated crosstalk between pro-inflammatory and contractile signaling mechanisms exists in the lymphatic system and may be an important bridge between lymphatic function modulation and inflammation. PMID:21166923

Cerebral artery alpha-1 AR subtypes: high altitude long-term acclimatization responses.

PubMed

Goyal, Ravi; Goyal, Dipali; Chu, Nina; Van Wickle, Jonathan; Longo, Lawrence D

2014-01-01

In response to hypoxia and other stress, the sympathetic (adrenergic) nervous system regulates arterial contractility and blood flow, partly through differential activities of the alpha1 (α1) - adrenergic receptor (AR) subtypes (α1A-, α1B-, and α1D-AR). Thus, we tested the hypothesis that with acclimatization to long-term hypoxia (LTH), contractility of middle cerebral arteries (MCA) is regulated by changes in expression and activation of the specific α1-AR subtypes. We conducted experiments in MCA from adult normoxic sheep maintained near sea level (300 m) and those exposed to LTH (110 days at 3801 m). Following acclimatization to LTH, ovine MCA showed a 20% reduction (n = 5; P<0.05) in the maximum tension achieved by 10-5 M phenylephrine (PHE). LTH-acclimatized cerebral arteries also demonstrated a statistically significant (P<0.05) inhibition of PHE-induced contractility in the presence of specific α1-AR subtype antagonists. Importantly, compared to normoxic vessels, there was significantly greater (P<0.05) α1B-AR subtype mRNA and protein levels in LTH acclimatized MCA. Also, our results demonstrate that extracellular regulated kinase 1 and 2 (ERK1/2)-mediated negative feedback regulation of PHE-induced contractility is modulated by α1B-AR subtype. Overall, in ovine MCA, LTH produces profound effects on α1-AR subtype expression and function.

Dynamic denitrosylation via S-nitrosoglutathione reductase regulates cardiovascular function

PubMed Central

Beigi, Farideh; Gonzalez, Daniel R.; Minhas, Khalid M.; Sun, Qi-An; Foster, Matthew W.; Khan, Shakil A.; Treuer, Adriana V.; Dulce, Raul A.; Harrison, Robert W.; Saraiva, Roberto M.; Premer, Courtney; Schulman, Ivonne Hernandez; Stamler, Jonathan S.; Hare, Joshua M.

2012-01-01

Although protein S-nitrosylation is increasingly recognized as mediating nitric oxide (NO) signaling, roles for protein denitrosylation in physiology remain unknown. Here, we show that S-nitrosoglutathione reductase (GSNOR), an enzyme that governs levels of S-nitrosylation by promoting protein denitrosylation, regulates both peripheral vascular tone and β-adrenergic agonist-stimulated cardiac contractility, previously ascribed exclusively to NO/cGMP. GSNOR-deficient mice exhibited reduced peripheral vascular tone and depressed β-adrenergic inotropic responses that were associated with impaired β-agonist–induced denitrosylation of cardiac ryanodine receptor 2 (RyR2), resulting in calcium leak. These results indicate that systemic hemodynamic responses (vascular tone and cardiac contractility), both under basal conditions and after adrenergic activation, are regulated through concerted actions of NO synthase/GSNOR and that aberrant denitrosylation impairs cardiovascular function. Our findings support the notion that dynamic S-nitrosylation/denitrosylation reactions are essential in cardiovascular regulation. PMID:22366318

Continuum mechanical model for cross-linked actin networks with contractile bundles

NASA Astrophysics Data System (ADS)

Ferreira, J. P. S.; Parente, M. P. L.; Natal Jorge, R. M.

2018-01-01

In the context of a mechanical approach to cell biology, there is a close relationship between cellular function and mechanical properties. In recent years, an increasing amount of attention has been given to the coupling between biochemical and mechanical signals by means of constitutive models. In particular, on the active contractility of the actin cytoskeleton. Given the importance of the actin contraction on the physiological functions, this study propose a constitutive model to describe how the filamentous network controls its mechanics actively. Embedded in a soft isotropic ground substance, the network behaves as a viscous mechanical continuum, comprised of isotropically distributed cross-linked actin filaments and actomyosin bundles. Trough virtual rheometry experiments, the present model relates the dynamics of the myosin motors with the network stiffness, which is to a large extent governed by the time-scale of the applied deformations/forces.

A multiplexed chip-based assay system for investigating the functional development of human skeletal myotubes in vitro.

PubMed

Smith, A S T; Long, C J; Pirozzi, K; Najjar, S; McAleer, C; Vandenburgh, H H; Hickman, J J

2014-09-20

This report details the development of a non-invasive in vitro assay system for investigating the functional maturation and performance of human skeletal myotubes. Data is presented demonstrating the survival and differentiation of human myotubes on microscale silicon cantilevers in a defined, serum-free system. These cultures can be stimulated electrically and the resulting contraction quantified using modified atomic force microscopy technology. This system provides a higher degree of sensitivity for investigating contractile waveforms than video-based analysis, and represents the first system capable of measuring the contractile activity of individual human muscle myotubes in a reliable, high-throughput and non-invasive manner. The development of such a technique is critical for the advancement of body-on-a-chip platforms toward application in pre-clinical drug development screens. Copyright © 2014 Elsevier B.V. All rights reserved.

Engineering functional and histological regeneration of vascularized skeletal muscle.

PubMed

Gilbert-Honick, Jordana; Iyer, Shama R; Somers, Sarah M; Lovering, Richard M; Wagner, Kathryn; Mao, Hai-Quan; Grayson, Warren L

2018-05-01

Tissue engineering strategies to treat patients with volumetric muscle loss (VML) aim to recover the structure and contractile function of lost muscle tissue. Here, we assessed the capacity of novel electrospun fibrin hydrogel scaffolds seeded with murine myoblasts to regenerate the structure and function of damaged muscle within VML defects to the mouse tibialis anterior muscle. The electrospun fibrin scaffolds provide pro-myogenic alignment and stiffness cues, myomimetic hierarchical structure, suturability, and scale-up capabilities. Myoblast-seeded scaffolds enabled remarkable muscle regeneration with high myofiber and vascular densities after 2 and 4 weeks, mimicking that of native skeletal muscle, while acellular scaffolds lacked muscle regeneration. Both myoblast-seeded and acellular scaffolds fully recovered muscle contractile function to uninjured values after 2 and 4 weeks. Electrospun scaffolds pre-vascularized with co-cultured human endothelial cells and human adipose-derived stem cells implanted into VML defects for 2 weeks anastomosed with host vasculature and were perfused with host red blood cells. These data demonstrate the significant potential of electrospun fibrin scaffolds seeded with myoblasts to fully regenerate the structure and function of volumetric muscle defects and these scaffolds offer a promising treatment option for patients with VML. Copyright © 2018 Elsevier Ltd. All rights reserved.

Nanowires and Electrical Stimulation Synergistically Improve Functions of hiPSC Cardiac Spheroids.

PubMed

Richards, Dylan J; Tan, Yu; Coyle, Robert; Li, Yang; Xu, Ruoyu; Yeung, Nelson; Parker, Arran; Menick, Donald R; Tian, Bozhi; Mei, Ying

2016-07-13

The advancement of human induced pluripotent stem-cell-derived cardiomyocyte (hiPSC-CM) technology has shown promising potential to provide a patient-specific, regenerative cell therapy strategy to treat cardiovascular disease. Despite the progress, the unspecific, underdeveloped phenotype of hiPSC-CMs has shown arrhythmogenic risk and limited functional improvements after transplantation. To address this, tissue engineering strategies have utilized both exogenous and endogenous stimuli to accelerate the development of hiPSC-CMs. Exogenous electrical stimulation provides a biomimetic pacemaker-like stimuli that has been shown to advance the electrical properties of tissue engineered cardiac constructs. Recently, we demonstrated that the incorporation of electrically conductive silicon nanowires to hiPSC cardiac spheroids led to advanced structural and functional development of hiPSC-CMs by improving the endogenous electrical microenvironment. Here, we reasoned that the enhanced endogenous electrical microenvironment of nanowired hiPSC cardiac spheroids would synergize with exogenous electrical stimulation to further advance the functional development of nanowired hiPSC cardiac spheroids. For the first time, we report that the combination of nanowires and electrical stimulation enhanced cell-cell junction formation, improved development of contractile machinery, and led to a significant decrease in the spontaneous beat rate of hiPSC cardiac spheroids. The advancements made here address critical challenges for the use of hiPSC-CMs in cardiac developmental and translational research and provide an advanced cell delivery vehicle for the next generation of cardiac repair.

Cardiac I-1c overexpression with reengineered AAV improves cardiac function in swine ischemic heart failure.

PubMed

Ishikawa, Kiyotake; Fish, Kenneth M; Tilemann, Lisa; Rapti, Kleopatra; Aguero, Jaume; Santos-Gallego, Carlos G; Lee, Ahyoung; Karakikes, Ioannis; Xie, Chaoqin; Akar, Fadi G; Shimada, Yuichi J; Gwathmey, Judith K; Asokan, Aravind; McPhee, Scott; Samulski, Jade; Samulski, Richard Jude; Sigg, Daniel C; Weber, Thomas; Kranias, Evangelia G; Hajjar, Roger J

2014-12-01

Cardiac gene therapy has emerged as a promising option to treat advanced heart failure (HF). Advances in molecular biology and gene targeting approaches are offering further novel options for genetic manipulation of the cardiovascular system. The aim of this study was to improve cardiac function in chronic HF by overexpressing constitutively active inhibitor-1 (I-1c) using a novel cardiotropic vector generated by capsid reengineering of adeno-associated virus (BNP116). One month after a large anterior myocardial infarction, 20 Yorkshire pigs randomly received intracoronary injection of either high-dose BNP116.I-1c (1.0 × 10(13) vector genomes (vg), n = 7), low-dose BNP116.I-1c (3.0 × 10(12) vg, n = 7), or saline (n = 6). Compared to baseline, mean left ventricular ejection fraction increased by 5.7% in the high-dose group, and by 5.2% in the low-dose group, whereas it decreased by 7% in the saline group. Additionally, preload-recruitable stroke work obtained from pressure-volume analysis demonstrated significantly higher cardiac performance in the high-dose group. Likewise, other hemodynamic parameters, including stroke volume and contractility index indicated improved cardiac function after the I-1c gene transfer. Furthermore, BNP116 showed a favorable gene expression pattern for targeting the heart. In summary, I-1c overexpression using BNP116 improves cardiac function in a clinically relevant model of ischemic HF.

Cardiac I-1c Overexpression With Reengineered AAV Improves Cardiac Function in Swine Ischemic Heart Failure

PubMed Central

Ishikawa, Kiyotake; Fish, Kenneth M; Tilemann, Lisa; Rapti, Kleopatra; Aguero, Jaume; Santos-Gallego, Carlos G; Lee, Ahyoung; Karakikes, Ioannis; Xie, Chaoqin; Akar, Fadi G; Shimada, Yuichi J; Gwathmey, Judith K; Asokan, Aravind; McPhee, Scott; Samulski, Jade; Samulski, Richard Jude; Sigg, Daniel C; Weber, Thomas; Kranias, Evangelia G; Hajjar, Roger J

2014-01-01

Cardiac gene therapy has emerged as a promising option to treat advanced heart failure (HF). Advances in molecular biology and gene targeting approaches are offering further novel options for genetic manipulation of the cardiovascular system. The aim of this study was to improve cardiac function in chronic HF by overexpressing constitutively active inhibitor-1 (I-1c) using a novel cardiotropic vector generated by capsid reengineering of adeno-associated virus (BNP116). One month after a large anterior myocardial infarction, 20 Yorkshire pigs randomly received intracoronary injection of either high-dose BNP116.I-1c (1.0 × 1013 vector genomes (vg), n = 7), low-dose BNP116.I-1c (3.0 × 1012 vg, n = 7), or saline (n = 6). Compared to baseline, mean left ventricular ejection fraction increased by 5.7% in the high-dose group, and by 5.2% in the low-dose group, whereas it decreased by 7% in the saline group. Additionally, preload-recruitable stroke work obtained from pressure–volume analysis demonstrated significantly higher cardiac performance in the high-dose group. Likewise, other hemodynamic parameters, including stroke volume and contractility index indicated improved cardiac function after the I-1c gene transfer. Furthermore, BNP116 showed a favorable gene expression pattern for targeting the heart. In summary, I-1c overexpression using BNP116 improves cardiac function in a clinically relevant model of ischemic HF. PMID:25023328

Transcutaneous electrical nerve stimulation (TENS) improves the diabetic cytopathy (DCP) via up-regulation of CGRP and cAMP.

PubMed

Ding, Liucheng; Song, Tao; Yi, Chaoran; Huang, Yi; Yu, Wen; Ling, Lin; Dai, Yutian; Wei, Zhongqing

2013-01-01

The objective of this study was to investigate the effects and mechanism of Transcutaneous Electrical Nerve Stimulation (TENS) on the diabetic cytopathy (DCP) in the diabetic bladder. A total of 45 rats were randomly divided into diabetes mellitus (DM)/TENS group (n=15), DM group (n=15) and control group (n=15). The rats in the DM/TENS and TENS groups were electronically stimulated (stimulating parameters: intensity-31 V, frequency-31 Hz, and duration of stimulation of 15 min) for three weeks. Bladder histology, urodynamics and contractile responses to field stimulation and carbachol were determined. The expression of calcitonin gene-related peptide (CGRP) was analyzed by RT-PCR and Western blotting. The results showed that contractile responses of the DM rats were ameliorated after 3 weeks of TENS. Furthermore, TENS significantly increased bladder wet weight, volume threshold for micturition and reduced PVR, V% and cAMP content of the bladder. The mRNA and protein levels of CGRP in dorsal root ganglion (DRG) in the DM/TENS group were higher than those in the DM group. TENS also significantly up-regulated the cAMP content in the bladder body and base compared with diabetic rats. We conclude that TENS can significantly improve the urine contractility and ameliorate the feeling of bladder fullness in DM rats possibly via up-regulation of cAMP and CGRP in DRG.

Dose-dependent inhibition of uterine contractility by nitric oxide: A potential mechanism underlying persistent breeding-induced endometritis in the mare.

PubMed

Khan, Firdous A; Chenier, Tracey S; Murrant, Coral L; Foster, Robert A; Hewson, Joanne; Scholtz, Elizabeth L

2017-03-01

Nitric oxide (NO) may have a role in persistent breeding-induced endometritis in mares through an inhibitory effect on uterine contractility. The objectives of this study were to test the effect of NO on spontaneous uterine contractility in-vitro and to evaluate whether this effect varied between the longitudinal and circular muscle layers of the uterus. Reproductive tracts were collected from eight euthanized non-pregnant mares (age 4-19 years; body weight 405-530 kg). Transrectal examination of the reproductive tract was performed before euthanasia to evaluate stage of the estrous cycle and presence of any apparent abnormality. After euthanasia, one uterine tissue sample was collected for histological evaluation and four full-thickness uterine tissue strips (10-12 mm × 2 mm), two parallel to each muscle layer, were excised for in-vitro contractility evaluation. Strips were suspended in tissue chambers containing Krebs-Henseleit solution, with continuous aeration (95% O 2 -5% CO 2 ; pH 7.4) at 37 °C. After equilibration, spontaneous contractility was recorded (pre-treatment) and strips excised in each direction were randomly allocated to each of two groups: 1) SNAP (S-nitroso-N-acetylpenicillamine, an NO donor); or 2) NAP (N-acetyl-d-penicillamine, vehicle and time-matched control). These were treated at 15 min intervals with increasing concentrations (10 -7  M to 10 -3  M) of SNAP and NAP, respectively. Contractility data was recorded throughout the experiment. An interaction effect of group-by-concentration was observed (P < 0.0001). The mean contractility after treatment with 10 -4  M and 10 -3  M SNAP were significantly lower than the pre-treatment contractility and the mean contractility after treatment with lower SNAP concentrations. In contrast, contractility did not change significantly in the NAP treated controls. The effect of treatment on uterine contractility was not influenced by age or weight of the mare, stage of estrous cycle, uterine histology grade, or muscle layer. Secondary findings included significant main effects of stage of estrous cycle (increased contractility in estrus compared to diestrus), uterine histology grade (decreased contractility in grade IIB compared to grade I) and age (decreased contractility in mares aged > 8 years compared to mares aged ≤ 8 years). In conclusion, results of this study indicate that NO has a dose-dependent inhibitory effect on spontaneous uterine contractility irrespective of the muscle layer in the mare. Copyright © 2017 Elsevier Inc. All rights reserved.

Change in the contractile behavior of muscle fibers in subjects with primary muscle dysfunction.

PubMed

Back, Claudio Gregório Nuernberg; Benedini-Elias, Priscila C O; Mattiello, Stela M; Sobreira, Claudia; Martinez, Edson Z; Mattiello-Sverzut, Ana Claudia

2013-01-01

The mechanical and metabolic characteristics of skeletal muscle fibers can interfere with muscle contractile performance in healthy subjects. Few studies have investigated the degree of association between muscle function and muscle fiber morphology in patients with myopathy. A biopsy was obtained from the left biceps brachii muscle of 12 subjects with myopathic disorders. The relative cross-sectional area of type 2 fibers and their subtypes was determined by the ATPase technique. Relative torque (RT) was calculated by dividing isokinetic elbow flexion peak torque (PT) values (90 and 180° s-1) by isometric PT values. Correlations were analyzed using Spearman's coefficient (r). The relative cross-sectional area of type 2b fibers was positively correlated with RT90 (r = 0.71, P = 0.009) and RT180 (r = 0.73, P = 0.007). The relative cross-sectional area of type 2a fibers showed a moderate and negative correlation with RT180 (r = -0.62, P = 0.03) and a low correlation with RT90 (r = -0.57, P = 0.05). In contrast to healthy subjects, patients with myopathy presented changes in the contractile behavior of type 2a fibers and compensatory adaptations in type 2b fibers. The results suggest that RT in combination with morphometric parameters provides data regarding muscle function in patients with myopathic disorders and can contribute to the establishment of therapeutic exercises.

Palmitate-Induced Vacuolar-Type H+-ATPase Inhibition Feeds Forward Into Insulin Resistance and Contractile Dysfunction.

PubMed

Liu, Yilin; Steinbusch, Laura K M; Nabben, Miranda; Kapsokalyvas, Dimitris; van Zandvoort, Marc; Schönleitner, Patrick; Antoons, Gudrun; Simons, Peter J; Coumans, Will A; Geomini, Amber; Chanda, Dipanjan; Glatz, Jan F C; Neumann, Dietbert; Luiken, Joost J F P

2017-06-01

Dietary fat overconsumption leads to myocardial lipid accumulation through mechanisms that are incompletely resolved. Previously, we identified increased translocation of the fatty acid transporter CD36 from its endosomal storage compartment to the sarcolemma as the primary mechanism of excessive myocellular lipid import. Here, we show that increased CD36 translocation is caused by alkalinization of endosomes resulting from inhibition of proton pumping activity of vacuolar-type H + -ATPase (v-ATPase). Endosomal alkalinization was observed in hearts from rats fed a lard-based high-fat diet and in rodent and human cardiomyocytes upon palmitate overexposure, and appeared as an early lipid-induced event preceding the onset of insulin resistance. Either genetic or pharmacological inhibition of v-ATPase in cardiomyocytes exposed to low palmitate concentrations reduced insulin sensitivity and cardiomyocyte contractility, which was rescued by CD36 silencing. The mechanism of palmitate-induced v-ATPase inhibition involved its dissociation into two parts: the cytosolic V 1 and the integral membrane V 0 subcomplex. Interestingly, oleate also inhibits v-ATPase function, yielding triacylglycerol accumulation but not insulin resistance. In conclusion, lipid oversupply increases CD36-mediated lipid uptake that directly impairs v-ATPase function. This feeds forward to enhanced CD36 translocation and further increased lipid uptake. In the case of palmitate, its accelerated uptake ultimately precipitates into cardiac insulin resistance and contractile dysfunction. © 2017 by the American Diabetes Association.

Evaluation of Esophageal Motility Utilizing the Functional Lumen Imaging Probe.

PubMed

Carlson, Dustin A; Kahrilas, Peter J; Lin, Zhiyue; Hirano, Ikuo; Gonsalves, Nirmala; Listernick, Zoe; Ritter, Katherine; Tye, Michael; Ponds, Fraukje A; Wong, Ian; Pandolfino, John E

2016-12-01

Esophagogastric junction (EGJ) distensibility and distension-mediated peristalsis can be assessed with the functional lumen imaging probe (FLIP) during a sedated upper endoscopy. We aimed to describe esophageal motility assessment using FLIP topography in patients presenting with dysphagia. In all, 145 patients (aged 18-85 years, 54% female) with dysphagia that completed upper endoscopy with a 16-cm FLIP assembly and high-resolution manometry (HRM) were included. HRM was analyzed according to the Chicago Classification of esophageal motility disorders; major esophageal motility disorders were considered "abnormal". FLIP studies were analyzed using a customized program to calculate the EGJ-distensibility index (DI) and generate FLIP topography plots to identify esophageal contractility patterns. FLIP topography was considered "abnormal" if EGJ-DI was <2.8 mm 2 /mm Hg or contractility pattern demonstrated absent contractility or repetitive, retrograde contractions. HRM was abnormal in 111 (77%) patients: 70 achalasia (19 type I, 39 type II, and 12 type III), 38 EGJ outflow obstruction, and three jackhammer esophagus. FLIP topography was abnormal in 106 (95%) of these patients, including all 70 achalasia patients. HRM was "normal" in 34 (23%) patients: five ineffective esophageal motility and 29 normal motility. In all, 17 (50%) had abnormal FLIP topography including 13 (37%) with abnormal EGJ-DI. FLIP topography provides a well-tolerated method for esophageal motility assessment (especially to identify achalasia) at the time of upper endoscopy. FLIP topography findings that are discordant with HRM may indicate otherwise undetected abnormalities of esophageal function, thus FLIP provides an alternative and complementary method to HRM for evaluation of non-obstructive dysphagia.

Evaluation of esophageal motility utilizing the functional lumen imaging probe (FLIP)

PubMed Central

Carlson, Dustin A.; Kahrilas, Peter J.; Lin, Zhiyue; Hirano, Ikuo; Gonsalves, Nirmala; Listernick, Zoe; Ritter, Katherine; Tye, Michael; Ponds, Fraukje A.; Wong, Ian; Pandolfino, John E.

2016-01-01

Background Esophagogastric junction (EGJ) distensibility and distension-mediated peristalsis can be assessed with the functional lumen imaging probe (FLIP) during a sedated upper endoscopy. We aimed to describe esophageal motility assessment using FLIP topography in patients presenting with dysphagia. Methods 145 patients (ages 18 – 85, 54% female) with dysphagia that completed upper endoscopy with a 16-cm FLIP assembly and high-resolution manometry (HRM) were included. HRM was analyzed according to the Chicago Classification of esophageal motility disorders; major esophageal motility disorders were considered ‘abnormal’. FLIP studies were analyzed using a customized program to calculate the EGJ-distensibility index (DI) and generate FLIP topography plots to identify esophageal contractility patterns. FLIP topography was considered ‘abnormal’ if EGJ-DI was < 2.8 mm2/mmHg or contractility pattern demonstrated absent contractility or repetitive, retrograde contractions. Results HRM was abnormal in 111 (77%) patients: 70 achalasia (19 type I, 39 type II, 12 type III), 38 EGJ outflow obstruction, and three jackhammer esophagus. FLIP topography was abnormal in 106 (95%) of these patients, including all 70 achalasia patients. HRM was ‘normal’ in 34 (23%) patients: five ineffective esophageal motility and 29 normal motility. 17 (50%) had abnormal FLIP topography including 13 (37%) with abnormal EGJ-DI. Conclusions FLIP topography provides a well-tolerated method for esophageal motility assessment (especially to identify achalasia) at the time of upper endoscopy. FLIP topography findings that are discordant with HRM may indicate otherwise undetected abnormalities of esophageal function, thus FLIP provides an alternative and complementary method to HRM for evaluation of non-obstructive dysphagia. PMID:27725650

Altered expression pattern of molecular factors involved in colonic smooth muscle functions: an immunohistochemical study in patients with diverticular disease.

PubMed

Mattii, Letizia; Ippolito, Chiara; Segnani, Cristina; Battolla, Barbara; Colucci, Rocchina; Dolfi, Amelio; Bassotti, Gabrio; Blandizzi, Corrado; Bernardini, Nunzia

2013-01-01

The pathogenesis of diverticular disease (DD) is thought to result from complex interactions among dietary habits, genetic factors and coexistence of other bowel abnormalities. These conditions lead to alterations in colonic pressure and motility, facilitating the formation of diverticula. Although electrophysiological studies on smooth muscle cells (SMCs) have investigated colonic motor dysfunctions, scarce attention has been paid to their molecular abnormalities, and data on SMCs in DD are lacking. Accordingly, the main purpose of this study was to evaluate the expression patterns of molecular factors involved in the contractile functions of SMCs in the tunica muscularis of colonic specimens from patients with DD. By means of immunohistochemistry and image analysis, we examined the expression of Cx26 and Cx43, which are prominent components of gap junctions in human colonic SMCs, as well as pS368-Cx43, PKCps, RhoA and αSMA, all known to regulate the functions of gap junctions and the contractile activity of SMCs. The immunohistochemical analysis revealed significant abnormalities in DD samples, concerning both the expression and distribution patterns of most of the investigated molecular factors. This study demonstrates, for the first time, that an altered pattern of factors involved in SMC contractility is present at level of the tunica muscularis of DD patients. Moreover, considering that our analysis was conducted on colonic tissues not directly affected by diverticular lesions or inflammatory reactions, it is conceivable that these molecular alterations may precede and predispose to the formation of diverticula, rather than being mere consequences of the disease.

Functional expression of KCNQ (Kv7) channels in guinea pig bladder smooth muscle and their contribution to spontaneous activity

PubMed Central

Anderson, U A; Carson, C; Johnston, L; Joshi, S; Gurney, A M; McCloskey, K D

2013-01-01

Background and Purpose The aim of the study was to determine whether KCNQ channels are functionally expressed in bladder smooth muscle cells (SMC) and to investigate their physiological significance in bladder contractility. Experimental Approach KCNQ channels were examined at the genetic, protein, cellular and tissue level in guinea pig bladder smooth muscle using RT-PCR, immunofluorescence, patch-clamp electrophysiology, calcium imaging, detrusor strip myography, and a panel of KCNQ activators and inhibitors. Key Results KCNQ subtypes 1–5 are expressed in bladder detrusor smooth muscle. Detrusor strips typically displayed TTX-insensitive myogenic spontaneous contractions that were increased in amplitude by the KCNQ channel inhibitors XE991, linopirdine or chromanol 293B. Contractility was inhibited by the KCNQ channel activators flupirtine or meclofenamic acid (MFA). The frequency of Ca2+-oscillations in SMC contained within bladder tissue sheets was increased by XE991. Outward currents in dispersed bladder SMC, recorded under conditions where BK and KATP currents were minimal, were significantly reduced by XE991, linopirdine, or chromanol, and enhanced by flupirtine or MFA. XE991 depolarized the cell membrane and could evoke transient depolarizations in quiescent cells. Flupirtine (20 μM) hyperpolarized the cell membrane with a simultaneous cessation of any spontaneous electrical activity. Conclusions and Implications These novel findings reveal the role of KCNQ currents in the regulation of the resting membrane potential of detrusor SMC and their important physiological function in the control of spontaneous contractility in the guinea pig bladder. PMID:23586426

Passive heating following the prematch warm-up in soccer: examining the time-course of changes in muscle temperature and contractile function.

PubMed

Marshall, Paul W M; Cross, Rebecca; Lovell, Ric

2015-12-01

This study examined changes in muscle temperature, electrically evoked muscle contractile properties, and voluntary power before and after a soccer specific active warm-up and subsequent rest period. Ten amateur soccer players performed two experimental sessions that involved performance of a modified FIFA 11+ soccer specific warm-up, followed by a 12.5-min rest period where participants were required to wear either normal clothing or a passive electrical heating garment was applied to the upper thigh muscles. Assessments around the warm-up and cool-down included measures of maximal torque, rate of torque development, muscle temperature (Tm), and electrically evoked measures of quadriceps contractile function. Tm was increased after the warm-up by 3.2 ± 0.7°C (P < 0.001). Voluntary and evoked rates of torque development increased after the warm-up between 20% and 30% (P < 0.05), despite declines in both maximal voluntary torque and voluntary activation (P < 0.05). Application of a passive heating garment in the cool-down period after the warm-up did not effect variables measured. While Tm was reduced by 1.4 ± 0.4°C after the rest period (P < 0.001), this value was still higher than pre warm-up levels. Voluntary and evoked rate of torque development remained elevated from pre warm-up levels at the end of the cool-down (P < 0.05). The soccer specific warm-up elevated muscle temperature by 3.2°C and was associated with concomitant increases of between 20% and 30% in voluntary rate of torque development, which seems explained by elevations in rate-dependent measures of intrinsic muscle contractile function. Application of a passive heating garment did not attenuate declines in muscle temperature during a 12.5-min rest period. © 2015 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and The Physiological Society.

Detrimental effects of acute hyperglycaemia on the rat heart.

PubMed

Mapanga, R F; Joseph, D; Symington, B; Garson, K-L; Kimar, C; Kelly-Laubscher, R; Essop, M Faadiel

2014-03-01

Hyperglycaemia is an important risk factor for acute myocardial infarction. It can lead to increased induction of non-oxidative glucose pathways (NOGPs) - polyol and hexosamine biosynthetic pathways, advanced glycation end products and protein kinase C - that may contribute to cardiovascular diseases onset. However, the precise underlying mechanisms remain poorly understood. Here we hypothesized that acute hyperglycaemia increases myocardial oxidative stress and NOGP activation resulting in cardiac dysfunction during ischaemia-reperfusion and that inhibition of, and/or shunting flux away from NOGPs [by benfotiamine (BFT) treatment], leads to cardioprotection. We employed several experimental systems: (i) Isolated rat hearts were perfused ex vivo with Krebs-Henseleit buffer containing 33 mm glucose vs. controls (11 mm glucose) ± global ischaemia and reperfusion ± BFT (first 20 min of reperfusion); (ii) Infarct size determination as per the ischaemic protocol, but with regional ischaemia and reperfusion ± BFT treatment; in separate experiments, NOGP inhibitors were also employed for (i) and (ii); and (iii) In vivo coronary ligations performed on streptozotocin-treated rats ± BFT treatment (early reperfusion). Acute hyperglycaemia generated myocardial oxidative stress, NOGP activation and apoptosis, but caused no impairment of cardiac function during pre-ischaemia, thereby priming hearts for later damage. Following ischaemia-reperfusion (under hyperglycaemic conditions), such effects were exacerbated together with cardiac contractile dysfunction. Moreover, inhibition of respective NOGPs and shunting away by BFT treatment (in part) improved cardiac function during ischaemia-reperfusion. Coordinate NOGP activation in response to acute hyperglycaemia results in contractile dysfunction during ischaemia-reperfusion, allowing for the development of novel cardioprotective agents. © 2013 Scandinavian Physiological Society. Published by John Wiley & Sons Ltd.

Randomized placebo controlled blinded study to assess valsartan efficacy in preventing left ventricle remodeling in patients with dual chamber pacemaker--Rationale and design of the trial.

PubMed

Tomasik, Andrzej; Jacheć, Wojciech; Wojciechowska, Celina; Kawecki, Damian; Białkowska, Beata; Romuk, Ewa; Gabrysiak, Artur; Birkner, Ewa; Kalarus, Zbigniew; Nowalany-Kozielska, Ewa

2015-05-01

Dual chamber pacing is known to have detrimental effect on cardiac performance and heart failure occurring eventually is associated with increased mortality. Experimental studies of pacing in dogs have shown contractile dyssynchrony leading to diffuse alterations in extracellular matrix. In parallel, studies on experimental ischemia/reperfusion injury have shown efficacy of valsartan to inhibit activity of matrix metalloproteinase-9, to increase the activity of tissue inhibitor of matrix metalloproteinase-3 and preserve global contractility and left ventricle ejection fraction. To present rationale and design of randomized blinded trial aimed to assess whether 12 month long administration of valsartan will prevent left ventricle remodeling in patients with preserved left ventricle ejection fraction (LVEF ≥ 40%) and first implantation of dual chamber pacemaker. A total of 100 eligible patients will be randomized into three parallel arms: placebo, valsartan 80 mg/daily and valsartan 160 mg/daily added to previously used drugs. The primary endpoint will be assessment of valsartan efficacy to prevent left ventricle remodeling during 12 month follow-up. We assess patients' functional capacity, blood plasma activity of matrix metalloproteinases and their tissue inhibitors, NT-proBNP, tumor necrosis factor alpha, and Troponin T. Left ventricle function and remodeling is assessed echocardiographically: M-mode, B-mode, tissue Doppler imaging. If valsartan proves effective, it will be an attractive measure to improve long term prognosis in aging population and increasing number of pacemaker recipients. ClinicalTrials.org (NCT01805804). Copyright © 2015 Elsevier Inc. All rights reserved.

Role of cardiomyocyte circadian clock in myocardial metabolic adaptation

USDA-ARS?s Scientific Manuscript database

Marked circadian rhythmicities in cardiovascular physiology and pathophysiology exist. The cardiomyocyte circadian clock has recently been linked to circadian rhythms in myocardial gene expression, metabolism, and contractile function. For instance, the cardiomyocyte circadian clock is essential f...

Co-induction of the heat shock response ameliorates disease progression in a mouse model of human spinal and bulbar muscular atrophy: implications for therapy

PubMed Central

Malik, Bilal; Nirmalananthan, Niranjanan; Gray, Anna L.; La Spada, Albert R.; Hanna, Michael G.

2013-01-01

Spinal and bulbar muscular atrophy, also known as Kennedy’s disease, is an adult-onset hereditary neurodegenerative disorder caused by an expansion of the polyglutamine repeat in the first exon in the androgen receptor gene. Pathologically, the disease is defined by selective loss of spinal and bulbar motor neurons causing bulbar, facial and limb weakness. Although the precise disease pathophysiology is largely unknown, it appears to be related to abnormal accumulation of the pathogenic androgen receptor protein within the nucleus, leading to disruption of cellular processes. Using a mouse model of spinal and bulbar muscular atrophy that exhibits many of the characteristic features of the human disease, in vivo physiological assessment of muscle function revealed that mice with the pathogenic expansion of the androgen receptor develop a motor deficit characterized by a reduction in muscle force, abnormal muscle contractile characteristics, loss of functional motor units and motor neuron degeneration. We have previously shown that treatment with arimoclomol, a co-inducer of the heat shock stress response, delays disease progression in the mutant superoxide dismutase 1 mouse model of amyotrophic lateral sclerosis, a fatal motor neuron disease. We therefore evaluated the therapeutic potential of arimoclomol in mice with spinal and bulbar muscular atrophy. Arimoclomol was administered orally, in drinking water, from symptom onset and the effects established at 18 months of age, a late stage of disease. Arimoclomol significantly improved hindlimb muscle force and contractile characteristics, rescued motor units and, importantly, improved motor neuron survival and upregulated the expression of the vascular endothelial growth factor which possess neurotrophic activity. These results provide evidence that upregulation of the heat shock response by treatment with arimoclomol may have therapeutic potential in the treatment of spinal and bulbar muscular atrophy and may also be a possible approach for the treatment of other neurodegenerative diseases. PMID:23393146

Combined atorvastatin and coenzyme Q10 improve the left ventricular function in isoproterenol-induced heart failure in rat.

PubMed

Garjani, Alireza; Andalib, Sina; Biabani, Sajjad; Soraya, Hamid; Doustar, Yousef; Garjani, Afagh; Maleki-Dizaji, Nasrin

2011-09-01

The effect of atorvastatin on cardiac remodeling, function, and homodynamic parameters in isoproterenol-induced heart failure was evaluated in the present study. A subcutaneous injection of isoproterenol (5mg/kg/day) for 10 days was used for the induction of heart failure. Isoproterenol administration produced intensive myocardial necrosis and fibrosis with a significant decrease in the arterial pressure indices, heart rate, contractility (LVdP/dt(max)) and relaxation (LVdP/dt(min)), but an increase in the left ventricular end-diastolic pressure. Rats were randomly assigned to control, treatment with only atorvastatin, and treatment with atorvastatin plus coenzyme Q10. Histopathological analysis showed a marked attenuation of myocyte necrosis and interstitial fibrosis in all atorvastatin treated groups (P<0.001). A low dose of atorvastatin (5mg/kg/day) significantly improved the left ventricular systolic pressure, contractility and relaxation (P<0.01). On the contrary, a high dose of atorvastatin (20mg/kg/day) worsened the isoproterenol-induced left ventricular dysfunction by a further reduction of LVdP/dt(max) from +2780 ± 94 to +1588 ± 248 (mmHg/s; P<0.01) and LVdP/dt(min) from -2007 ± 190 to -2939 ± 291 (mmHg/s; P<0.05). Co-administration of coenzyme Q10 with atorvastatin reversed the hemodynamic depression and the left ventricular dysfunction to a high level (P<0.001). There was a lower level of LVEDPs in the atorvastatin+coenzyme Q10 treated groups (3 ± 1 and 4 ± 1.4 versus 8 ± 3.5 and 14 ± 3.6 mmHg, respectively), thereby suggesting improvement in the myocardial stiffness by the combined coenzyme Q10 and atorvastatin treatment. The atorvastatin therapy attenuated myocardial necrosis and fibrosis in isoproterenol-induced heart failure. However, a high dose of the drug considerably worsened the left ventricular dysfunction and hemodynamic depression, which was reversed by coenzyme Q10 co-administration. Copyright © 2011 Elsevier B.V. All rights reserved.

Roles of Formin Nodes and Myosin Motor Activity in Mid1p-dependent Contractile-Ring Assembly during Fission Yeast Cytokinesis

PubMed Central

Coffman, Valerie C.; Nile, Aaron H.; Lee, I-Ju; Liu, Huayang

2009-01-01

Two prevailing models have emerged to explain the mechanism of contractile-ring assembly during cytokinesis in the fission yeast Schizosaccharomyces pombe: the spot/leading cable model and the search, capture, pull, and release (SCPR) model. We tested some of the basic assumptions of the two models. Monte Carlo simulations of the SCPR model require that the formin Cdc12p is present in >30 nodes from which actin filaments are nucleated and captured by myosin-II in neighboring nodes. The force produced by myosin motors pulls the nodes together to form a compact contractile ring. Live microscopy of cells expressing Cdc12p fluorescent fusion proteins shows for the first time that Cdc12p localizes to a broad band of 30–50 dynamic nodes, where actin filaments are nucleated in random directions. The proposed progenitor spot, essential for the spot/leading cable model, usually disappears without nucleating actin filaments. α-Actinin ain1 deletion cells form a normal contractile ring through nodes in the absence of the spot. Myosin motor activity is required to condense the nodes into a contractile ring, based on slower or absent node condensation in myo2-E1 and UCS rng3-65 mutants. Taken together, these data provide strong support for the SCPR model of contractile-ring formation in cytokinesis. PMID:19864459

[Experimental validation of the efficacy of laser-magnetic therapy for chronic placental insufficiency].

PubMed

Ordzhonikidze, N V; Filimonov, V G; Klimenko, P A; Kondrikov, N I; Akin'shina, V S; Berlin, Iu V

1994-01-01

A new pathogenetically based non-medicamentous method for correction of uteroplacental bloodflow disturbances has been developed on the model of chronic placental insufficiency in rats. A single 5 min laser-magnetic exposure on day 21 of normal pregnancy resulted in a vasodilating effect with reduction of the peripheral resistance in the uterine horn vessels and with improvement of their blood supply. A new LAMA laser magneto-therapeutic device was employed. Daily 5 min sessions of laser magnetic therapy administered to rats with chronic placental insufficiency from pregnancy days 15-16 to 21 normalized uterine horn contractility and resulted in positive morphofunctional changes in the components of the uterine horns and placenta, being associated with a noticeable improvement of fetal functions. Hence, laser magnetic therapy may be regarded as an effective non-drug method for therapy of chronic placental insufficiency.

Cell stiffness, contractile stress and the role of extracellular matrix

DOE Office of Scientific and Technical Information (OSTI.GOV)

An, Steven S., E-mail: san@jhsph.edu; Kim, Jina; Ahn, Kwangmi

Here we have assessed the effects of extracellular matrix (ECM) composition and rigidity on mechanical properties of the human airway smooth muscle (ASM) cell. Cell stiffness and contractile stress showed appreciable changes from the most relaxed state to the most contracted state: we refer to the maximal range of these changes as the cell contractile scope. The contractile scope was least when the cell was adherent upon collagen V, followed by collagen IV, laminin, and collagen I, and greatest for fibronectin. Regardless of ECM composition, upon adherence to increasingly rigid substrates, the ASM cell positively regulated expression of antioxidant genesmore » in the glutathione pathway and heme oxygenase, and disruption of a redox-sensitive transcription factor, nuclear erythroid 2 p45-related factor (Nrf2), culminated in greater contractile scope. These findings provide biophysical evidence that ECM differentially modulates muscle contractility and, for the first time, demonstrate a link between muscle contractility and Nrf2-directed responses.« less

Esophageal motor disorders: how to bridge the gap between advanced diagnostic tools and paucity of therapeutic modalities?

PubMed

Clarke, John O; Pandolfino, John E

2012-07-01

High-resolution manometry has added significantly to our current understanding of esophageal motor function by providing improved detail and a data analysis paradigm that is more akin to an imaging format. Esophageal pressure topography provides a seamless dynamic representation of the pressure profile through the entire esophagus and thus, is able to eliminate movement artifact and also assess intrabolus pressure patterns as a surrogate for bolus transit mechanics. This has led to improved identification of anatomic landmarks and measurement of important physiological parameters (esophagogastric junction relaxation, distal latency, and contractile integrity). This research has bridged the gap into clinical practice by defining physiologically relevant phenotypes that may have prognostic significance and improve treatment decisions in achalasia, spasm, and hypercontractile disorders. However, more work is needed in determining the etiology of symptom generation in the context of normal or trivial motor dysfunction. This research will require new techniques to assess visceral hypersensitivity and alterations in central modulation of pain and discomfort.

Mechanism of valvular regurgitation.

PubMed

Khoo, Nee S; Smallhorn, Jeffery F

2011-10-01

Despite improvements in surgical techniques, valvular regurgitation results in major morbidity in children with heart disease. Functional anatomy, mechanisms of valve closure and adaptation to changing hemodynamic stress in normal mitral and tricuspid valves are complex and only partially understood. As well, pathology of atrioventricular valve regurgitation is further complicated by congenital valve abnormalities involving leaflet tissue, supporting chordal apparatus and displaced papillary muscles. This review provides a current understanding of the mechanisms that result in atrioventricular valve failure. Mitral valve leaflets have contractile elements, in addition to atrial muscle modulation of leaflet tension. When placed under mechanical tethering stress, the mitral valve adapts by leaflet expansion, which increases coaptation surface reserve and chordal thickening. Both pediatric and adult studies are increasingly reporting on the importance of subvalvar apparatus function in maintaining valve competency. The maintenance of efficient valve function is accomplished by a complex series of events involving atrial and annular contraction, annular deformation, active leaflet tension, chordal transmission of papillary muscle contractions and ventricular contraction.

[Effects of ß-alanine supplementation on athletic performance].

PubMed

Domínguez, Raúl; Hernández Lougedo, Juan; Maté-Muñoz, José Luis; Garnacho-Castaño, Manuel Vicente

2014-10-06

Carnosine, dipeptide formed by amino acids ß-alanine and L-histidine, has important physiological functions among which its antioxidant and related memory and learning. However, in connection with the exercise, the most important functions would be associated with muscle contractility, improving calcium sensitivity in muscle fibers, and the regulatory function of pH. Thus, it is proposed that carnosine is the major intracellular buffer, but could contribute to 7-10% in buffer or buffer capacity. Since carnosine synthesis seems to be limited by the availability of ß-alanine supplementation with this compound has been gaining increasing popularity among the athlete population. Therefore, the objective of this study literature review was to examine all those research works have shown the effect of ß-alanine supplementation on athletic performance. Moreover, it also has attempted to establish a specific dosage that maximizing the potential benefits, minimize paresthesia, the main side effect presented in response to supplementation. Copyright AULA MEDICA EDICIONES 2014. Published by AULA MEDICA. All rights reserved.

Respiratory Muscle Plasticity

PubMed Central

Gransee, Heather M.; Mantilla, Carlos B.; Sieck, Gary C.

2014-01-01

Muscle plasticity is defined as the ability of a given muscle to alter its structural and functional properties in accordance with the environmental conditions imposed on it. As such, respiratory muscle is in a constant state of remodeling, and the basis of muscle’s plasticity is its ability to change protein expression and resultant protein balance in response to varying environmental conditions. Here, we will describe the changes of respiratory muscle imposed by extrinsic changes in mechanical load, activity, and innervation. Although there is a large body of literature on the structural and functional plasticity of respiratory muscles, we are only beginning to understand the molecular-scale protein changes that contribute to protein balance. We will give an overview of key mechanisms regulating protein synthesis and protein degradation, as well as the complex interactions between them. We suggest future application of a systems biology approach that would develop a mathematical model of protein balance and greatly improve treatments in a variety of clinical settings related to maintaining both muscle mass and optimal contractile function of respiratory muscles. PMID:23798306

HDAC Inhibition Improves the Sarcoendoplasmic Reticulum Ca2+-ATPase Activity in Cardiac Myocytes.

PubMed

Meraviglia, Viviana; Bocchi, Leonardo; Sacchetto, Roberta; Florio, Maria Cristina; Motta, Benedetta M; Corti, Corrado; Weichenberger, Christian X; Savi, Monia; D'Elia, Yuri; Rosato-Siri, Marcelo D; Suffredini, Silvia; Piubelli, Chiara; Pompilio, Giulio; Pramstaller, Peter P; Domingues, Francisco S; Stilli, Donatella; Rossini, Alessandra

2018-01-31

SERCA2a is the Ca 2+ ATPase playing the major contribution in cardiomyocyte (CM) calcium removal. Its activity can be regulated by both modulatory proteins and several post-translational modifications. The aim of the present work was to investigate whether the function of SERCA2 can be modulated by treating CMs with the histone deacetylase (HDAC) inhibitor suberanilohydroxamic acid (SAHA). The incubation with SAHA (2.5 µM, 90 min) of CMs isolated from rat adult hearts resulted in an increase of SERCA2 acetylation level and improved ATPase activity. This was associated with a significant improvement of calcium transient recovery time and cell contractility. Previous reports have identified K464 as an acetylation site in human SERCA2. Mutants were generated where K464 was substituted with glutamine (Q) or arginine (R), mimicking constitutive acetylation or deacetylation, respectively. The K464Q mutation ameliorated ATPase activity and calcium transient recovery time, thus indicating that constitutive K464 acetylation has a positive impact on human SERCA2a (hSERCA2a) function. In conclusion, SAHA induced deacetylation inhibition had a positive impact on CM calcium handling, that, at least in part, was due to improved SERCA2 activity. This observation can provide the basis for the development of novel pharmacological approaches to ameliorate SERCA2 efficiency.

Rho Kinase (ROCK) collaborates with Pak to Regulate Actin Polymerization and Contraction in Airway Smooth Muscle.

PubMed

Zhang, Wenwu; Bhetwal, Bhupal P; Gunst, Susan J

2018-05-10

The mechanisms by which Rho kinase (ROCK) regulates airway smooth muscle contraction were determined in tracheal smooth muscle tissues. ROCK may mediate smooth muscle contraction by inhibiting myosin regulatory light chain (RLC) phosphatase. ROCK can also regulate F-actin dynamics during cell migration, and actin polymerization is critical for airway smooth muscle contraction. Our results show that ROCK does not regulate airway smooth muscle contraction by inhibiting myosin RLC phosphatase or by stimulating myosin RLC phosphorylation. We find that ROCK regulates airway smooth muscle contraction by activating the serine-threonine kinase Pak, which mediates the activation of Cdc42 and Neuronal-Wiskott-Aldrich Syndrome protein (N-WASp). N-WASP transmits signals from cdc42 to the Arp2/3 complex for the nucleation of actin filaments. These results demonstrate a novel molecular function for ROCK in the regulation of Pak and cdc42 activation that is critical for the processes of actin polymerization and contractility in airway smooth muscle. Rho kinase (ROCK), a RhoA GTPase effector, can regulate the contraction of airway and other smooth muscle tissues. In some tissues, ROCK can inhibit myosin regulatory light chain (RLC) phosphatase, which increases the phosphorylation of myosin RLC and promotes smooth muscle contraction. ROCK can also regulate cell motility and migration by affecting F-actin dynamics. Actin polymerization is stimulated by contractile agonists in airway smooth muscle tissues and is required for contractile tension development in addition to myosin RLC phosphorylation. We investigated the mechanisms by which ROCK regulates the contractility of tracheal smooth muscle tissues by expressing a kinase inactive mutant of ROCK, ROCK-K121G, in the tissues or by treating them with the ROCK inhibitor, H-1152P. Our results show no role for ROCK in the regulation of non-muscle or smooth muscle myosin RLC phosphorylation during contractile stimulation in this tissue. We find that ROCK regulates airway smooth muscle contraction by mediating activation of the serine-threonine kinase, Pak, to promote actin polymerization. Pak catalyzes paxillin phosphorylation on Ser273 and coupling of the GIT1-βPIX-Pak signaling module to paxillin, which activates the GEF activity βPIX towards cdc42. Cdc42 is required for the activation of Neuronal Wiskott-Aldrich Syndrome protein (N-WASp), which transmits signals from cdc42 to the Arp2/3 complex for the nucleation of actin filaments. Our results demonstrate a novel molecular function for ROCK in the regulation of Pak and cdc42 activation that is critical for the processes of actin polymerization and contractility in airway smooth muscle. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Transmural heterogeneity of cellular level power output is reduced in human heart failure.

PubMed

Haynes, Premi; Nava, Kristofer E; Lawson, Benjamin A; Chung, Charles S; Mitov, Mihail I; Campbell, Stuart G; Stromberg, Arnold J; Sadayappan, Sakthivel; Bonnell, Mark R; Hoopes, Charles W; Campbell, Kenneth S

2014-07-01

Heart failure is associated with pump dysfunction and remodeling but it is not yet known if the condition affects different transmural regions of the heart in the same way. We tested the hypotheses that the left ventricles of non-failing human hearts exhibit transmural heterogeneity of cellular level contractile properties, and that heart failure produces transmural region-specific changes in contractile function. Permeabilized samples were prepared from the sub-epicardial, mid-myocardial, and sub-endocardial regions of the left ventricular free wall of non-failing (n=6) and failing (n=10) human hearts. Power, an in vitro index of systolic function, was higher in non-failing mid-myocardial samples (0.59±0.06μWmg(-1)) than in samples from the sub-epicardium (p=0.021) and the sub-endocardium (p=0.015). Non-failing mid-myocardial samples also produced more isometric force (14.3±1.33kNm(-2)) than samples from the sub-epicardium (p=0.008) and the sub-endocardium (p=0.026). Heart failure reduced power (p=0.009) and force (p=0.042) but affected the mid-myocardium more than the other transmural regions. Fibrosis increased with heart failure (p=0.021) and mid-myocardial tissue from failing hearts contained more collagen than matched sub-epicardial (p<0.001) and sub-endocardial (p=0.043) samples. Power output was correlated with the relative content of actin and troponin I, and was also statistically linked to the relative content and phosphorylation of desmin and myosin light chain-1. Non-failing human hearts exhibit transmural heterogeneity of contractile properties. In failing organs, region-specific fibrosis produces the greatest contractile deficits in the mid-myocardium. Targeting fibrosis and sarcomeric proteins in the mid-myocardium may be particularly effective therapies for heart failure. Copyright © 2014 Elsevier Ltd. All rights reserved.

Effects of hindlimb unweighting on the mechanical and structure properties of the rat abdominal aorta

NASA Technical Reports Server (NTRS)

Papadopoulos, Anthony; Delp, Michael D.

2003-01-01

Previous studies have shown that hindlimb unweighting of rats, a model of microgravity, reduces evoked contractile tension of peripheral conduit arteries. It has been hypothesized that this diminished contractile tension is the result of alterations in the mechanical properties of these arteries (e.g., active and passive mechanics). Therefore, the purpose of this study was to determine whether the reduced contractile force of the abdominal aorta from 2-wk hindlimb-unweighted (HU) rats results from a mechanical function deficit resulting from structural vascular alterations or material property changes. Aortas were isolated from control (C) and HU rats, and vasoconstrictor responses to norepinephrine (10(-9)-10(-4) M) and AVP (10(-9)-10(-5) M) were tested in vitro. In a second series of tests, the active and passive Cauchy stress-stretch relations were determined by incrementally increasing the uniaxial displacement of the aortic rings. Maximal Cauchy stress in response to norepinephrine and AVP were less in aortic rings from HU rats. The active Cauchy stress-stretch response indicated that, although maximum stress was lower in aortas from HU rats (C, 8.1 +/- 0.2 kPa; HU, 7.0 +/- 0.4 kPa), it was achieved at a similar hoop stretch. There were also no differences in the passive Cauchy stress-stretch response or the gross vascular morphology (e.g., medial cross-sectional area: C, 0.30 +/- 0.02 mm(2); HU, 0.32 +/- 0.01 mm(2)) between groups and no differences in resting or basal vascular tone at the displacement that elicits peak developed tension between groups (resting tension: C, 1.71 +/- 0.06 g; HU, 1.78 +/- 0.14 g). These results indicate that HU does not alter the functional mechanical properties of conduit arteries. However, the significantly lower active Cauchy stress of aortas from HU rats demonstrates a true contractile deficit in these arteries.

Tachykinin NK2 receptor and functional mechanisms in human colon: changes with indomethacin and in diverticular disease and ulcerative colitis.

PubMed

Burcher, Elizabeth; Shang, Fei; Warner, Fiona J; Du, Qin; Lubowski, David Z; King, Denis W; Liu, Lu

2008-01-01

Neurokinin A (NKA) is an important spasmogen in human colon. We examined inflammatory disease-related changes in the tachykinin NK(2) receptor system in human sigmoid colon circular muscle, using functional, radioligand binding, and quantitative reverse transcription-polymerase chain reaction methods. In circular muscle strips, indomethacin enhanced contractile responses to NKA (p < 0.01) and to the NK(2) receptor-selective agonist [Lys(5),MeLeu(9),Nle(10)]-NKA(4-10) (p < 0.05) in both normal and acute diverticular disease (DD) specimens, indicating NK(2) receptor-mediated release of relaxant prostanoids. Contractile responses to both tachykinins were reduced in strips from DD (p < 0.001) and ulcerative colitis (UC) (p < 0.05) specimens. Responses to acetylcholine were no different in other strips from the same disease patients, demonstrating that the change in responsiveness to tachykinins in disease is specifically mediated by the NK(2) receptor. In membranes from UC specimens, receptor affinity for (125)I-NKA (median K(D) 0.91 nM, n = 16) was lower (p < 0.01) than that in age-matched control specimens (K(D) 0.55 nM, n = 40), whereas K(D) (0.65 nM, n = 28) in DD was no different from control. No disease-related changes in receptor number (B(max)) were found (mean, 2.0-2.5 fmol/mg of wet weight tissue), suggesting that the reduced contractile responses in disease are not due to a loss of receptor number. Different mechanisms may account for the reduced contractility in DD compared with UC. A gender-related difference in receptor density was seen in controls, with B(max) lower in females (1.77 fmol/mg, n = 15) than in males (2.60 fmol/mg, n = 25, p = 0.01). In contrast, no gender-related differences were seen in NK(2) receptor mRNA in control colonic muscle, indicating that the gender difference is a post-translational event.

Isolation and maintenance-free culture of contractile myotubes from Manduca sexta embryos.

PubMed

Baryshyan, Amanda L; Woods, William; Trimmer, Barry A; Kaplan, David L

2012-01-01

Skeletal muscle tissue engineering has the potential to treat tissue loss and degenerative diseases. However, these systems are also applicable for a variety of devices where actuation is needed, such as microelectromechanical systems (MEMS) and robotics. Most current efforts to generate muscle bioactuators are focused on using mammalian cells, which require exacting conditions for survival and function. In contrast, invertebrate cells are more environmentally robust, metabolically adaptable and relatively autonomous. Our hypothesis is that the use of invertebrate muscle cells will obviate many of the limitations encountered when mammalian cells are used for bioactuation. We focus on the tobacco hornworm, Manduca sexta, due to its easy availability, large size and well-characterized muscle contractile properties. Using isolated embryonic cells, we have developed culture conditions to grow and characterize contractile M. sexta muscles. The insect hormone 20-hydroxyecdysone was used to induce differentiation in the system, resulting in cells that stained positive for myosin, contract spontaneously for the duration of the culture, and do not require media changes over periods of more than a month. These cells proliferate under normal conditions, but the application of juvenile hormone induced further proliferation and inhibited differentiation. Cellular metabolism under normal and low glucose conditions was compared for C2C12 mouse and M. sexta myoblast cells. While differentiated C2C12 cells consumed glucose and produced lactate over one week as expected, M. sexta muscle did not consume significant glucose, and lactate production exceeded mammalian muscle production on a per cell basis. Contractile properties were evaluated using index of movement analysis, which demonstrated the potential of these cells to perform mechanical work. The ability of cultured M. sexta muscle to continuously function at ambient conditions without medium replenishment, combined with the interesting metabolic properties, suggests that this cell source is a promising candidate for further investigation toward bioactuator applications.

Cytoskeletal Role in the Contractile Dysfunction of Hypertrophied Myocardium

NASA Astrophysics Data System (ADS)

Tsutsui, Hiroyuki; Ishihara, Kazuaki; Cooper, George

1993-04-01

Cardiac hypertrophy in response to systolic pressure loading frequently results in contractile dysfunction of unknown cause. In the present study, pressure loading increased the microtubule component of the cardiac muscle cell cytoskeleton, which was responsible for the cellular contractile dysfunction observed. The linked microtubule and contractile abnormalities were persistent and thus may have significance for the deterioration of initially compensatory cardiac hypertrophy into congestive heart failure.

Overview of the Muscle Cytoskeleton

PubMed Central

Henderson, Christine A.; Gomez, Christopher G.; Novak, Stefanie M.; Mi-Mi, Lei; Gregorio, Carol C.

2018-01-01

Cardiac and skeletal striated muscles are intricately designed machines responsible for muscle contraction. Coordination of the basic contractile unit, the sarcomere, and the complex cytoskeletal networks are critical for contractile activity. The sarcomere is comprised of precisely organized individual filament systems that include thin (actin), thick (myosin), titin, and nebulin. Connecting the sarcomere to other organelles (e.g., mitochondria and nucleus) and serving as the scaffold to maintain cellular integrity are the intermediate filaments. The costamere, on the other hand, tethers the sarcomere to the cell membrane. Unique structures like the intercalated disc in cardiac muscle and the myotendinous junction in skeletal muscle help synchronize and transmit force. Intense investigation has been done on many of the proteins that make up these cytoskeletal assemblies. Yet the details of their function and how they interconnect have just started to be elucidated. A vast number of human myopathies are contributed to mutations in muscle proteins; thus understanding their basic function provides a mechanistic understanding of muscle disorders. In this review, we highlight the components of striated muscle with respect to their interactions, signaling pathways, functions, and connections to disease. PMID:28640448

Hair Follicle-Derived Smooth Muscle Cells and Small Intestinal Submucosa for Engineering Mechanically Robust and Vasoreactive Vascular Media

PubMed Central

Peng, Hao-Fan; Liu, Jin Yu

2011-01-01

Our laboratory recently reported a new source of smooth muscle cells (SMCs) derived from hair follicle (HF) mesenchymal stem cells. HF-SMCs demonstrated high proliferation and clonogenic potential as well as contractile function. In this study, we aimed at engineering the vascular media using HF-SMCs and a natural biomaterial, namely small intestinal submucosa (SIS). Engineering functional vascular constructs required application of mechanical force, resulting in actin reorganization and cellular alignment. In turn, cell alignment was necessary for development of receptor- and nonreceptor-mediated contractility as soon as 24 h after cell seeding. Within 2 weeks in culture, the cells migrated into SIS and secreted collagen and elastin, the two major extracellular matrix components of the vessel wall. At 2 weeks, vascular reactivity increased significantly up to three- to fivefold and mechanical properties were similar to those of native ovine arteries. Taken together, our data demonstrate that the combination of HF-SMCs with SIS resulted in mechanically strong, biologically functional vascular media with potential for arterial implantation. PMID:21083418

Adiponectin downregulation is associated with volume overload-induced myocyte dysfunction in rats

PubMed Central

Wang, Li-li; Miller, Dori; Wanders, Desiree; Nanayakkara, Gayani; Amin, Rajesh; Judd, Robert; Morrison, Edward E; Zhong, Ju-ming

2016-01-01

Aim: Adiponectin has been reported to exert protective effects during pathological ventricular remodeling, but the role of adiponectin in volume overload-induced heart failure remains unclear. In this study we investigated the effect of adiponectin on cardiac myocyte contractile dysfunction following volume overload in rats. Methods: Volume overload was surgically induced in rats by infrarenal aorta-vena cava fistula. The rats were intravenously administered adenoviral adiponectin at 2-, 6- and 9-weeks following fistula. The protein expression of adiponectin, adiponectin receptors (AdipoR1/R2 and T-cadherin) and AMPK activity were measured using Western blot analyses. Isolated ventricular myocytes were prepared at 12 weeks post-fistula to examine the contractile performance of myocytes and intracellular Ca2+ transient. Results: A-V fistula resulted in significant reductions in serum and myocardial adiponectin levels, myocardial adiponectin receptor (AdipoR1/R2 and T-cadherin) levels, as well as myocardial AMPK activity. Consistent with these changes, the isolated myocytes exhibited significant depression in cell shortening and intracellular Ca2+ transient. Administration of adenoviral adiponectin significantly increased serum adiponectin levels and prevented myocyte contractile dysfunction in fistula rats. Furthermore, pretreatment of isolated myocytes with recombinant adiponectin (2.5 μg/mL) significantly improved their contractile performance in fistula rats, but had no effects in control or adenoviral adiponectin-administered rats. Conclusion: These results demonstrate a positive correlation between adiponectin downregulation and volume overload-induced ventricular remodeling. Adiponectin plays a protective role in volume overload-induced heart failure. PMID:26616727

Atorvastatin calcium inhibits phenotypic modulation of PDGF-BB-induced VSMCs via down-regulation the Akt signaling pathway.

PubMed

Chen, Shuang; Liu, Baoqin; Kong, Dehui; Li, Si; Li, Chao; Wang, Huaqin; Sun, Yingxian

2015-01-01

Plasticity of vascular smooth muscle cells (VSMCs) plays a central role in the onset and progression of proliferative vascular diseases. In adult tissue, VSMCs exist in a physiological contractile-quiescent phenotype, which is defined by lack of the ability of proliferation and migration, while high expression of contractile marker proteins. After injury to the vessel, VSMC shifts from a contractile phenotype to a pathological synthetic phenotype, associated with increased proliferation, migration and matrix secretion. It has been demonstrated that PDGF-BB is a critical mediator of VSMCs phenotypic switch. Atorvastatin calcium, a selective inhibitor of 3-hydroxy-3-methyl-glutaryl l coenzyme A (HMG-CoA) reductase, exhibits various protective effects against VSMCs. In this study, we investigated the effects of atorvastatin calcium on phenotype modulation of PDGF-BB-induced VSMCs and the related intracellular signal transduction pathways. Treatment of VSMCs with atorvastatin calcium showed dose-dependent inhibition of PDGF-BB-induced proliferation. Atorvastatin calcium co-treatment inhibited the phenotype modulation and cytoskeleton rearrangements and improved the expression of contractile phenotype marker proteins such as α-SM actin, SM22α and calponin in comparison with PDGF-BB alone stimulated VSMCs. Although Akt phosphorylation was strongly elicited by PDGF-BB, Akt activation was attenuated when PDGF-BB was co-administrated with atorvastatin calcium. In conclusion, atorvastatin calcium inhibits phenotype modulation of PDGF-BB-induced VSMCs and activation of the Akt signaling pathway, indicating that Akt might play a vital role in the modulation of phenotype.

Increased longitudinal contractility and diastolic function at rest in well-trained amateur Marathon runners: a speckle tracking echocardiography study

PubMed Central

2014-01-01

Background Regular physical activity reduces cardiovascular risk. There is concern that Marathon running might acutely damage the heart. It is unknown to what extent intensive physical endurance activity influences the cardiac mechanics at resting condition. Methods Eighty-four amateur marathon runners (43 women and 41 men) from Berlin-Brandenburg area who had completed at least one marathon previously underwent clinical examination and echocardiography at least 10 days before the Berlin Marathon at rest. Standard transthoracic echocardiography and 2D strain and strain rate analysis were performed. The 2D Strain and strain rate values were compared to previous published data of healthy untrained individuals. Results The average global longitudinal peak systolic strain of the left ventricle was -23 +/- 2% with peak systolic strain rate -1.39 +/- 0.21/s, early diastolic strain rate 2.0 +/- 0.40/s and late diastolic strain rate 1.21 +/- 0.31/s. These values are significantly higher compared to the previous published values of normal age-adjusted individuals. In addition, no age-related decline of longitudinal contractility in well-trained athletes was observed. Conclusions There is increased overall longitudinal myocardial contractility at rest in experienced endurance athletes compared to the published normal values in the literature indicating a preserved and even supra-normal contractility in the athletes. There is no age dependent decline of the longitudinal 2D Strain values. This underlines the beneficial effects of regular physical exercise even in advanced age. PMID:24571726

Alignment of human cardiomyocytes on laser patterned biphasic core/shell nanowire assemblies

NASA Astrophysics Data System (ADS)

Kiefer, Karin; Lee, Juseok; Haidar, Ayman; Martinez Miró, Marina; Akkan, Cagri Kaan; Veith, Michael; Cenk Aktas, Oral; Abdul-Khaliq, Hashim

2014-12-01

The management of end stage heart failure patients is only possible by heart transplantation or by the implantation of artificial hearts as a bridge for later transplantation. However, these therapeutic strategies are limited by a lack of donor hearts and by the associated complications, such as coagulation and infection, due to the used artificial mechanical circulatory assist devices. Therefore, new strategies for myocardial regenerative approaches are under extensive research to produce contractile myocardial tissue in the future to replace non-contractile myocardial ischemic and scarred tissue. Different approaches, such as cell transplantation, have been studied intensively. Although successful approaches have been observed, there are still limitations to the application. It is envisaged that myocardial tissue engineering can be used to help replace infarcted non-contractile tissue. The developed tissue should later mimic the aligned fibrillar structure of the extracellular matrix and provide important guidance cues for the survival, function and the needed orientation of cardiomyocytes. Nanostructured surfaces have been tested to provide a guided direction that cells can follow. In the present study, the cellular adhesion/alignment of human cardiomyocytes and the biocompatibility have been investigated after cultivation on different laser-patterned nanowires compared with unmodified nanowires. As a result, the nanostructured surfaces possessed good biocompatibility before and after laser modification. The laser-induced scalability of the pattern enabled the growth and orientation of the adhered myocardial tissue. Such approaches may be used to modify the surface of potential scaffolds to develop myocardial contractile tissue in the future.

Contractility and Ventricular Systolic Stiffening in Hypertensive Heart Disease: Insights into the Pathogenesis of Heart Failure with Preserved Ejection Fraction

PubMed Central

Borlaug, Barry A.; Lam, Carolyn S.P.; Roger, Véronique L.; Rodeheffer, Richard J.; Redfield, Margaret M.

2009-01-01

Objectives: 1) Compare left ventricular (LV) systolic stiffness and contractility in normal subjects, hypertensives without heart failure, and patients with heart failure and preserved ejection fraction (HFpEF); and 2) Determine whether LV systolic stiffness or myocardial contractility are associated with mortality in HFpEF. Background: Arterial load is increased in hypertension and is matched by increased end-systolic LV stiffness (ventricular-arterial coupling). Increased end-systolic LV stiffness may be mediated by enhanced myocardial contractility or processes which increase passive myocardial stiffness. Methods: Healthy controls (n=617), hypertensives (No HF, n=719) and patients with HFpEF (n=244, 96% hypertensive) underwent echo-Doppler characterization of arterial (Ea) and LV end-systolic (Ees) stiffness (elastance), ventricular-arterial coupling (Ea/Ees ratio), chamber-level and myocardial contractility (stress-corrected midwall shortening). Results: Ea and Ees were similarly elevated in hypertensives with or without HFpEF compared with controls, but ventricular-arterial coupling was similar across groups. In hypertensives, elevated Ees was associated with enhanced chamber-level and myocardial contractility, while in HFpEF, chamber and myocardial contractility were depressed compared with both hypertensives and controls. Group differences persisted after adjusting for geometry. In HFpEF, impaired myocardial contractility (but not Ees) was associated with increased age-adjusted mortality. Conclusions: While arterial load is elevated and matched by increased LV systolic stiffness in hypertension with or without HFpEF, the mechanisms of systolic LV stiffening differ substantially. These data suggest that myocardial contractility increases to match arterial load in asymptomatic hypertensive heart disease, but that progression to HFpEF may be mediated by processes which simultaneously impair myocardial contractility and increase passive myocardial stiffness. PMID:19628115

Cellular and molecular basis of RV hypertrophy in congenital heart disease

PubMed Central

Iacobazzi, D; Suleiman, M-S; Ghorbel, M; George, SJ; Caputo, M; Tulloh, RM

2016-01-01

RV hypertrophy (RVH) is one of the triggers of RV failure in congenital heart disease (CHD). Therefore, improving our understanding of the cellular and molecular basis of this pathology will help in developing strategic therapeutic interventions to enhance patient benefit in the future. This review describes the potential mechanisms that underlie the transition from RVH to RV failure. In particular, it addresses structural and functional remodelling that encompass contractile dysfunction, metabolic changes, shifts in gene expression and extracellular matrix remodelling. Both ischaemic stress and reactive oxygen species production are implicated in triggering these changes and will be discussed. Finally, RV remodelling in response to various CHDs as well as the potential role of biomarkers will be addressed. PMID:26516182

Lifting the nebula: novel insights into skeletal muscle contractility.

PubMed

Ottenheijm, Coen A C; Granzier, Henk

2010-10-01

Nebulin is a giant protein and a constituent of the skeletal muscle sarcomere. The name of this protein refers to its unknown (i.e., nebulous) function. However, recent rapid advances reveal that nebulin plays important roles in the regulation of muscle contraction. When these functions of nebulin are compromised, muscle weakness ensues, as is the case in patients with nemaline myopathy.

Cell biology of sarcomeric protein engineering: disease modeling and therapeutic potential.

PubMed

Thompson, Brian R; Metzger, Joseph M

2014-09-01

The cardiac sarcomere is the functional unit for myocyte contraction. Ordered arrays of sarcomeric proteins, held in stoichiometric balance with each other, respond to calcium to coordinate contraction and relaxation of the heart. Altered sarcomeric structure-function underlies the primary basis of disease in multiple acquired and inherited heart disease states. Hypertrophic and restrictive cardiomyopathies are caused by inherited mutations in sarcomeric genes and result in altered contractility. Ischemia-mediated acidosis directly alters sarcomere function resulting in decreased contractility. In this review, we highlight the use of acute genetic engineering of adult cardiac myocytes through stoichiometric replacement of sarcomeric proteins in these disease states with particular focus on cardiac troponin I. Stoichiometric replacement of disease causing mutations has been instrumental in defining the molecular mechanisms of hypertrophic and restrictive cardiomyopathy in a cellular context. In addition, taking advantage of stoichiometric replacement through gene therapy is discussed, highlighting the ischemia-resistant histidine-button, A164H cTnI. Stoichiometric replacement of sarcomeric proteins offers a potential gene therapy avenue to replace mutant proteins, alter sarcomeric responses to pathophysiologic insults, or neutralize altered sarcomeric function in disease. © 2014 Wiley Periodicals, Inc.

Big-conductance Ca2+-activated K+ channels in physiological and pathophysiological urinary bladder smooth muscle cells

PubMed Central

Parajuli, Shankar P.; Zheng, Yun-Min; Levin, Robert; Wang, Yong-Xiao

2016-01-01

ABSTRACT Contraction and relaxation of urinary bladder smooth muscle cells (UBSMCs) represent the important physiological functions of the bladder. Contractile responses in UBSMCs are regulated by a number of ion channels including big-conductance Ca2+- activated K+ (BK) channels. Great progress has been made in studies of BK channels in UBSMCs. The intent of this review is to summarize recent exciting findings with respect to the functional interactions of BK channels with muscarinic receptors, ryanodine receptors (RyRs) and inositol triphosphate receptors (IP3Rs) as well as their functional importance under normal and pathophysiological conditions. BK channels are highly expressed in UBSMCs. Activation of muscarinic M3 receptors inhibits the BK channel activity, facilitates opening of voltage-dependent Ca2+ (CaV) channels, and thereby enhances excitability and contractility of UBSMCs. Signaling molecules and regulatory mechanisms involving RyRs and IP3Rs have a significant effect on functions of BK channels and thereby regulate cellular responses in UBSMCs under normal and pathophysiological conditions including overactive bladders. Moreover, BK channels may represent a novel target for the treatment of bladder dysfunctions. PMID:27101440

Invited Review: The Myosins: Exploration of the Development of Our Current Understanding of These Mutations in the Motor

PubMed Central

Moore, Jeffrey R.; Leinwand, Leslie; Warshaw, David M.

2013-01-01

Hypertrophic (HCM) and dilated (DCM) cardiomyopathies are inherited diseases with a high incidence of death due to electrical abnormalities or outflow tract obstruction. In many of the families afflicted with either disease, causative mutations have been identified in various sarcomeric proteins. In this review, we focus on mutations in the cardiac muscle molecular motor, myosin and its associated light chains. Despite the >300 identified mutations there is still no clear understanding of how these mutations within the same myosin molecule can lead to the dramatically different clinical phenotypes associated with HCM and DCM. Localizing mutations within myosin’s molecular structure provides insight into the potential consequence of these perturbations to key functional domains of the motor. Review of biochemical and biophysical data that characterize the functional capacities of these mutant myosins suggests that mutant myosins with enhanced contractility lead to HCM while those displaying reduced contractility lead to DCM. With gain and loss of function potentially being the primary consequence of a specific mutation, how these functional changes trigger the hypertrophic response and lead to the distinct HCM and DCM phenotypes will be the future investigative challenge. PMID:22821910

Novel role of transient receptor potential vanilloid 2 in the regulation of cardiac performance

PubMed Central

Lasko, Valerie M.; Koch, Sheryl E.; Singh, Vivek P.; Carreira, Vinicius; Robbins, Nathan; Patel, Amit R.; Jiang, Min; Bidwell, Philip; Kranias, Evangelia G.; Jones, W. Keith; Lorenz, John N.

2013-01-01

Transient receptor potential cation channels have been implicated in the regulation of cardiovascular function, but only recently has our laboratory described the vanilloid-2 subtype (TRPV2) in the cardiomyocyte, though its exact mechanism of action has not yet been established. This study tests the hypothesis that TRPV2 plays an important role in regulating myocyte contractility under physiological conditions. Therefore, we measured cardiac and vascular function in wild-type and TRPV2−/− mice in vitro and in vivo and found that TRPV2 deletion resulted in a decrease in basal systolic and diastolic function without affecting loading conditions or vascular tone. TRPV2 stimulation with probenecid, a relatively selective TRPV2 agonist, caused an increase in both inotropy and lusitropy in wild-type mice that was blunted in TRPV2−/− mice. We examined the mechanism of TRPV2 inotropy/lusitropy in isolated myocytes and found that it modulates Ca2+ transients and sarcoplasmic reticulum Ca2+ loading. We show that the activity of this channel is necessary for normal cardiac function and that there is increased contractility in response to agonism of TRPV2 with probenecid. PMID:24322617

Cell division requires a direct link between microtubule-bound RacGAP and Anillin in the contractile ring.

PubMed

Gregory, Stephen L; Ebrahimi, Saman; Milverton, Joanne; Jones, Whitney M; Bejsovec, Amy; Saint, Robert

2008-01-08

The mitotic microtubule array plays two primary roles in cell division. It acts as a scaffold for the congression and separation of chromosomes, and it specifies and maintains the contractile-ring position. The current model for initiation of Drosophila and mammalian cytokinesis [1-5] postulates that equatorial localization of a RhoGEF (Pbl/Ect2) by a microtubule-associated motor protein complex creates a band of activated RhoA [6], which subsequently recruits contractile-ring components such as actin, myosin, and Anillin [1-3]. Equatorial microtubules are essential for continued constriction, but how they interact with the contractile apparatus is unknown. Here, we report the first direct molecular link between the microtubule spindle and the actomyosin contractile ring. We find that the spindle-associated component, RacGAP50C, which specifies the site of cleavage [1-5], interacts directly with Anillin, an actin and myosin binding protein found in the contractile ring [7-10]. Both proteins depend on this interaction for their localization. In the absence of Anillin, the spindle-associated RacGAP loses its association with the equatorial cortex, and cytokinesis fails. These results account for the long-observed dependence of cytokinesis on the continual presence of microtubules at the cortex.

Variations in carbachol- and ATP-induced contractions of the rat detrusor: effects of gender, mucosa and contractile direction.

PubMed

Liang, Willmann; Leung, Ping Chung

2012-12-01

Contractile characteristics of the bladder may depend on variables such as gender, mucosa (MU) and direction of the contractions. However, definitive information is not yet available despite earlier studies on the effects of one variable or another. Here, we explored the differences in the rat detrusor attributable to gender, mucosa and contractile direction. K+, carbachol (CCh) and ATP were used as contractile stimuli on rat detrusor strips with and without MU. Contractility was monitored using a myograph system. Both tonic and phasic contractile activities were analyzed. MU-independent contractions induced by CCh were more potent in females, an effect specific to the longitudinal direction only. The maximal CCh response was larger also in females when MU was removed, suggesting a stronger MU-independent component in the contraction. The larger area under curves of the females under ATP stimulation showed dependence on MU and contractile direction as well. ATP-induced contractions in the males were affected more by MU in the transverse direction than in the females. Direction- and MU-dependent variability of ATP responses was also observed in the males but not in females. Findings here added new information to the understanding of bladder contractile physiology, providing insights into the quest for better drugs in managing bladder disorders.

A Randomized Controlled Trial to Evaluate the Safety and Efficacy of Cardiac Contractility Modulation.

PubMed

Abraham, William T; Kuck, Karl-Heinz; Goldsmith, Rochelle L; Lindenfeld, JoAnn; Reddy, Vivek Y; Carson, Peter E; Mann, Douglas L; Saville, Benjamin; Parise, Helen; Chan, Rodrigo; Wiegn, Phi; Hastings, Jeffrey L; Kaplan, Andrew J; Edelmann, Frank; Luthje, Lars; Kahwash, Rami; Tomassoni, Gery F; Gutterman, David D; Stagg, Angela; Burkhoff, Daniel; Hasenfuß, Gerd

2018-05-05

The authors sought to confirm a subgroup analysis of the prior FIX-HF-5 (Evaluate Safety and Efficacy of the OPTIMIZER System in Subjects With Moderate-to-Severe Heart Failure) study showing that cardiac contractility modulation (CCM) improved exercise tolerance (ET) and quality of life in patients with ejection fractions between 25% and 45%. CCM therapy for New York Heart Association (NYHA) functional class III and IV heart failure (HF) patients consists of nonexcitatory electrical signals delivered to the heart during the absolute refractory period. A total of 160 patients with NYHA functional class III or IV symptoms, QRS duration <130 ms, and ejection fraction ≥25% and ≤45% were randomized to continued medical therapy (control, n = 86) or CCM (treatment, n = 74, unblinded) for 24 weeks. Peak VO 2 (primary endpoint), Minnesota Living With Heart Failure questionnaire, NYHA functional class, and 6-min hall walk were measured at baseline and at 12 and 24 weeks. Bayesian repeated measures linear modeling was used for the primary endpoint analysis with 30% borrowing from the FIX-HF-5 subgroup. Safety was assessed by the percentage of patients free of device-related adverse events with a pre-specified lower bound of 70%. The difference in peak VO 2 between groups was 0.84 (95% Bayesian credible interval: 0.123 to 1.552) ml O 2 /kg/min, satisfying the primary endpoint. Minnesota Living With Heart Failure questionnaire (p < 0.001), NYHA functional class (p < 0.001), and 6-min hall walk (p = 0.02) were all better in the treatment versus control group. There were 7 device-related events, yielding a lower bound of 80% of patients free of events, satisfying the primary safety endpoint. The composite of cardiovascular death and HF hospitalizations was reduced from 10.8% to 2.9% (p = 0.048). CCM is safe, improves exercise tolerance and quality of life in the specified group of HF patients, and leads to fewer HF hospitalizations. (Evaluate Safety and Efficacy of the OPTIMIZER System in Subjects With Moderate-to-Severe Heart Failure; NCT01381172). Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

Crataegus special extract WS(®)1442 prevents aging-related endothelial dysfunction.

PubMed

Idris-Khodja, N; Auger, C; Koch, E; Schini-Kerth, V B

2012-06-15

Aging is associated with a markedly increased incidence of cardiovascular diseases due, in part, to the development of vascular endothelial dysfunction. The present study has evaluated whether the Crataegus special extract WS(®)1442 prevents the development of aging-related endothelial dysfunction in rats, and, if so, to determine the underlying mechanisms. Wistar rats received either a control diet or the same diet containing 100 or 300 mg/kg/day of WS(®)1442 from week 25 until week 65. Vascular reactivity was assessed in mesenteric artery rings using organ chambers, oxidative stress by dihydroethidine staining and cyclooxygenase-1 (COX-1) and -2 (COX-2) expression by immunohistochemistry. Acetylcholine-induced endothelium-dependent relaxations in mesenteric artery rings were blunted in 65-week-old rats compared to 16-week-old rats. This effect was associated with a marked reduction of the endothelium-derived hyperpolarizing factor (EDHF) component whereas the nitric oxide (NO) component was not affected. Aging was also associated with the induction of endothelium-dependent contractile responses to acetylcholine. Both aging-related impairment of endothelium-dependent relaxations and the induction of endothelium-dependent contractile responses were improved by the Crataegus treatment and by COX inhibitors. An excessive vascular oxidative stress and an upregulation of COX-1 and COX-2 were observed in the mesenteric artery of old rats compared to young rats, and these effects were improved by the Crataegus treatment. In conclusion, chronic intake of Crataegus prevented aging-related endothelial dysfunction by reducing the prostanoid-mediated contractile responses, most likely by improving the increased oxidative stress and the overexpression of COX-1 and COX-2. Copyright © 2012 Elsevier GmbH. All rights reserved.

Potential involvement of dietary advanced glycation end products in impairment of skeletal muscle growth and muscle contractile function in mice.

PubMed

Egawa, Tatsuro; Tsuda, Satoshi; Goto, Ayumi; Ohno, Yoshitaka; Yokoyama, Shingo; Goto, Katsumasa; Hayashi, Tatsuya

2017-01-01

Diets enriched with advanced glycation end products (AGE) have recently been related to muscle dysfunction processes. However, it remains unclear whether long-term exposure to an AGE-enriched diet impacts physiological characteristics of skeletal muscles. Therefore, we explored the differences in skeletal muscle mass, contractile function and molecular responses between mice receiving a diet high in AGE (H-AGE) and low in AGE (L-AGE) for 16 weeks. There were no significant differences between L-AGE and H-AGE mice with regard to body weight, food intake or epididymal fat pad weight. However, extensor digitorum longus (EDL) and plantaris (PLA) muscle weights in H-AGE mice were lower compared with L-AGE mice. Higher levels of N ε -(carboxymethyl)-l-lysine, a marker for AGE, in EDL muscles of H-AGE mice were observed compared with L-AGE mice. H-AGE mice showed lower muscle strength and endurance in vivo and lower muscle force production of PLA muscle in vitro. mRNA expression levels of myogenic factors including myogenic factor 5 and myogenic differentiation in EDL muscle were lower in H-AGE mice compared with L-AGE mice. The phosphorylation status of 70-kDa ribosomal protein S6 kinase Thr389, an indicator of protein synthesis signalling, was lower in EDL muscle of H-AGE mice than that of L-AGE mice. These findings suggest that long-term exposure to an AGE-enriched diet impairs skeletal muscle growth and muscle contractile function, and that these muscle dysfunctions may be attributed to the inhibition of myogenic potential and protein synthesis.

AMP-activated Protein Kinase Phosphorylates Cardiac Troponin I at Ser-150 to Increase Myofilament Calcium Sensitivity and Blunt PKA-dependent Function*

PubMed Central

Nixon, Benjamin R.; Thawornkaiwong, Ariyoporn; Jin, Janel; Brundage, Elizabeth A.; Little, Sean C.; Davis, Jonathan P.; Solaro, R. John; Biesiadecki, Brandon J.

2012-01-01

AMP-activated protein kinase (AMPK) is an energy-sensing enzyme central to the regulation of metabolic homeostasis. In the heart AMPK is activated during cardiac stress-induced ATP depletion and functions to stimulate metabolic pathways that restore the AMP/ATP balance. Recently it was demonstrated that AMPK phosphorylates cardiac troponin I (cTnI) at Ser-150 in vitro. We sought to determine if the metabolic regulatory kinase AMPK phosphorylates cTnI at Ser-150 in vivo to alter cardiac contractile function directly at the level of the myofilament. Rabbit cardiac myofibrils separated by two-dimensional isoelectric focusing subjected to a Western blot with a cTnI phosphorylation-specific antibody demonstrates that cTnI is endogenously phosphorylated at Ser-150 in the heart. Treatment of myofibrils with the AMPK holoenzyme increased cTnI Ser-150 phosphorylation within the constraints of the muscle lattice. Compared with controls, cardiac fiber bundles exchanged with troponin containing cTnI pseudo-phosphorylated at Ser-150 demonstrate increased sensitivity of calcium-dependent force development, blunting of both PKA-dependent calcium desensitization, and PKA-dependent increases in length dependent activation. Thus, in addition to the defined role of AMPK as a cardiac metabolic energy gauge, these data demonstrate AMPK Ser-150 phosphorylation of cTnI directly links the regulation of cardiac metabolic demand to myofilament contractile energetics. Furthermore, the blunting effect of cTnI Ser-150 phosphorylation cross-talk can uncouple the effects of myofilament PKA-dependent phosphorylation from β-adrenergic signaling as a novel thin filament contractile regulatory signaling mechanism. PMID:22493448

Functional and pharmacological consequences of the distribution of voltage-gated calcium channels in the renal blood vessels.

PubMed

Hansen, P B L

2013-04-01

Calcium channel blockers are widely used to treat hypertension because they inhibit voltage-gated calcium channels that mediate transmembrane calcium influx in, for example, vascular smooth muscle and cardiomyocytes. The calcium channel family consists of several subfamilies, of which the L-type is usually associated with vascular contractility. However, the L-, T- and P-/Q-types of calcium channels are present in the renal vasculature and are differentially involved in controlling vascular contractility, thereby contributing to regulation of kidney function and blood pressure. In the preglomerular vascular bed, all the three channel families are present. However, the T-type channel is the only channel in cortical efferent arterioles which is in contrast to the juxtamedullary efferent arteriole, and that leads to diverse functional effects of L- and T-type channel inhibition. Furthermore, by different mechanisms, T-type channels may contribute to both constriction and dilation of the arterioles. Finally, P-/Q-type channels are involved in the regulation of human intrarenal arterial contractility. The calcium blockers used in the clinic affect not only L-type but also P-/Q- and T-type channels. Therefore, the distinct effect obtained by inhibiting a given subtype or set of channels under experimental settings should be considered when choosing a calcium blocker for treatment. T-type channels seem to be crucial for regulating the GFR and the filtration fraction. Use of blockers is expected to lead to preferential efferent vasodilation, reduction of glomerular pressure and proteinuria. Therefore, renovascular T-type channels might provide novel therapeutic targets, and may have superior renoprotective effects compared to conventional calcium blockers. Acta Physiologica © 2013 Scandinavian Physiological Society.

Cardiovascular function in term fetal sheep conceived, gestated and studied in the hypobaric hypoxia of the Andean altiplano.

PubMed

Herrera, Emilio A; Rojas, Rodrigo T; Krause, Bernardo J; Ebensperger, Germán; Reyes, Roberto V; Giussani, Dino A; Parer, Julian T; Llanos, Aníbal J

2016-03-01

High-altitude hypoxia causes intrauterine growth restriction and cardiovascular programming. However, adult humans and animals that have evolved at altitude show certain protection against the effects of chronic hypoxia. Whether the highland fetus shows similar protection against high altitude gestation is unclear. We tested the hypothesis that high-altitude fetal sheep have evolved cardiovascular compensatory mechanisms to withstand chronic hypoxia that are different from lowland sheep. We studied seven high-altitude (HA; 3600 m) and eight low-altitude (LA; 520 m) pregnant sheep at ∼90% gestation. Pregnant ewes and fetuses were instrumented for cardiovascular investigation. A three-period experimental protocol was performed in vivo: 30 min of basal, 1 h of acute superimposed hypoxia (∼10% O2) and 30 min of recovery. Further, we determined ex vivo fetal cerebral and femoral arterial function. HA pregnancy led to chronic fetal hypoxia, growth restriction and altered cardiovascular function. During acute superimposed hypoxia, LA fetuses redistributed blood flow favouring the brain, heart and adrenals, whereas HA fetuses showed a blunted cardiovascular response. Importantly, HA fetuses have a marked reduction in umbilical blood flow versus LA. Isolated cerebral arteries from HA fetuses showed a higher contractile capacity but a diminished response to catecholamines. In contrast, femoral arteries from HA fetuses showed decreased contractile capacity and increased adrenergic contractility. The blunting of the cardiovascular responses to hypoxia in fetuses raised in the Alto Andino may indicate a change in control strategy triggered by chronic hypoxia, switching towards compensatory mechanisms that are more cost-effective in terms of oxygen uptake. © 2015 The Authors. The Journal of Physiology © 2015 The Physiological Society.

Uterine Dysfunction in Biglycan and Decorin Deficient Mice Leads to Dystocia during Parturition

PubMed Central

Wu, Zhiping; Aron, Abraham W.; Macksoud, Elyse E.; Iozzo, Renato V.; Hai, Chi-Ming; Lechner, Beatrice E.

2012-01-01

Cesarean birth rates are rising. Uterine dysfunction, the exact mechanism of which is unknown, is a common indication for Cesarean delivery. Biglycan and decorin are two small leucine-rich proteoglycans expressed in the extracellular matrix of reproductive tissues and muscle. Mice deficient in biglycan display a mild muscular dystrophy, and, along with mice deficient in decorin, are models of Ehlers-Danlos Syndrome, a connective tissue anomaly associated with uterine rupture. As a variant of Ehlers-Danlos Syndrome is caused by a genetic mutation resulting in abnormal biglycan and decorin secretion, we hypothesized that biglycan and decorin play a role in uterine function. Thus, we assessed wild-type, biglycan, decorin and double knockout pregnancies for timing of birth and uterine function. Uteri were harvested at embryonic days 12, 15 and 18. Nonpregnant uterine samples of the same genotypes were assessed for tissue failure rate and spontaneous and oxytocin-induced contractility. We discovered that biglycan/decorin mixed double-knockout dams displayed dystocia, were at increased risk of delayed labor onset, and showed increased tissue failure in a predominantly decorin-dependent manner. In vitro spontaneous uterine contractile amplitude and oxytocin-induced contractile force were decreased in all biglycan and decorin knockout genotypes compared to wild-type. Notably, we found no significant compensation between biglycan and decorin using quantitative real time PCR or immunohistochemistry. We conclude that the biglycan/decorin mixed double knockout mouse is a model of dystocia and delayed labor onset. Moreover, decorin is necessary for uterine function in a dose-dependent manner, while biglycan exhibits partial compensatory mechanisms in vivo. Thus, this model is poised for use as a model for testing novel targets for preventive or therapeutic manipulation of uterine dysfunction. PMID:22253749

Circadian rhythms in myocardial metabolism and contractile function: influence of workload and oleate.

PubMed

Durgan, David J; Moore, Michael W S; Ha, Ngan P; Egbejimi, Oluwaseun; Fields, Anna; Mbawuike, Uchenna; Egbejimi, Anu; Shaw, Chad A; Bray, Molly S; Nannegari, Vijayalakshmi; Hickson-Bick, Diane L; Heird, William C; Dyck, Jason R B; Chandler, Margaret P; Young, Martin E

2007-10-01

Multiple extracardiac stimuli, such as workload and circulating nutrients (e.g., fatty acids), known to influence myocardial metabolism and contractile function exhibit marked circadian rhythms. The aim of the present study was to investigate whether the rat heart exhibits circadian rhythms in its responsiveness to changes in workload and/or fatty acid (oleate) availability. Thus, hearts were isolated from male Wistar rats (housed during a 12:12-h light-dark cycle: lights on at 9 AM) at 9 AM, 3 PM, 9 PM, and 3 AM and perfused in the working mode ex vivo with 5 mM glucose plus either 0.4 or 0.8 mM oleate. Following 20-min perfusion at normal workload (i.e., 100 cm H(2)O afterload), hearts were challenged with increased workload (140 cm H(2)O afterload plus 1 microM epinephrine). In the presence of 0.4 mM oleate, myocardial metabolism exhibited a marked circadian rhythm, with decreased rates of glucose oxidation, increased rates of lactate release, decreased glycogenolysis capacity, and increased channeling of oleate into nonoxidative pathways during the light phase. Rat hearts also exhibited a modest circadian rhythm in responsiveness to the workload challenge when perfused in the presence of 0.4 mM oleate, with increased myocardial oxygen consumption at the dark-to-light phase transition. However, rat hearts perfused in the presence of 0.8 mM oleate exhibited a markedly blunted contractile function response to the workload challenge during the light phase. In conclusion, these studies expose marked circadian rhythmicities in myocardial oxidative and nonoxidative metabolism as well as responsiveness of the rat heart to changes in workload and fatty acid availability.

Relation of murine thoracic aortic structural and cellular changes with aging to passive and active mechanical properties.

PubMed

Wheeler, Jason B; Mukherjee, Rupak; Stroud, Robert E; Jones, Jeffrey A; Ikonomidis, John S

2015-02-25

Maintenance of the structure and mechanical properties of the thoracic aorta contributes to aortic function and is dependent on the composition of the extracellular matrix and the cellular content within the aortic wall. Age-related alterations in the aorta include changes in cellular content and composition of the extracellular matrix; however, the precise roles of these age-related changes in altering aortic mechanical function are not well understood. Thoracic aortic rings from the descending segment were harvested from C57BL/6 mice aged 6 and 21 months. Thoracic aortic diameter and wall thickness were higher in the old mice. Cellular density was reduced in the medial layer of aortas from the old mice; concomitantly, collagen content was higher in old mice, but elastin content was similar between young and old mice. Stress relaxation, an index of compliance, was reduced in aortas from old mice and correlated with collagen fraction. Contractility of the aortic rings following potassium stimulation was reduced in old versus young mice. Furthermore, collagen gel contraction by aortic smooth muscle cells was reduced with age. These results demonstrate that numerous age-related structural changes occurred in the thoracic aorta and were related to alterations in mechanical properties. Aortic contractility decreased with age, likely because of a reduction in medial cell number in addition to a smooth muscle contractile deficit. Together, these unique findings provide evidence that the age-related changes in structure and mechanical function coalesce to provide an aortic substrate that may be predisposed to aortopathies. © 2015 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley Blackwell.

Loss of functional K+ channels encoded by ether-à-go-go-related genes in mouse myometrium prior to labour onset

PubMed Central

Greenwood, I A; Yeung, S Y; Tribe, R M; Ohya, S

2009-01-01

There is a growing appreciation that ion channels encoded by the ether-à-go-go-related gene family have a functional impact in smooth muscle in addition to their accepted role in cardiac myocytes and neurones. This study aimed to assess the expression of ERG1–3 (KCNH1–3) genes in the murine myometrium (smooth muscle layer of the uterus) and determine the functional impact of the ion channels encoded by these genes in pregnant and non-pregnant animals. Quantitative RT-PCR did not detect message for ERG2 and 3 in whole myometrial tissue extracts. In contrast, message for two isoforms of mERG1 were readily detected with mERG1a more abundant than mERG1b. In isometric tension studies of non-pregnant myometrium, the ERG channel blockers dofetilide (1 μm), E4031 (1 μm) and Be-KM1 (100 nm) increased spontaneous contractility and ERG activators (PD118057 and NS1643) inhibited spontaneous contractility. In contrast, neither ERG blockade nor activation had any effect on the inherent contractility in myometrium from late pregnant (19 days gestation) animals. Moreover, dofetilide-sensitive K+ currents with distinctive ‘hooked’ kinetics were considerably smaller in uterine myocytes from late pregnant compared to non-pregnant animals. Expression of mERG1 isoforms did not alter throughout gestation or upon delivery, but the expression of genes encoding auxillary subunits (KCNE) were up-regulated considerably. This study provides the first evidence for a regulation of ERG-encoded K+ channels as a precursor to late pregnancy physiological activity. PMID:19332483

Contractile properties of rat fast-twitch skeletal muscle during reinnervation - Effects of testosterone and castration

NASA Technical Reports Server (NTRS)

Yeagle, S. P.; Mayer, R. F.; Max, S. R.

1983-01-01

The peroneal nerve of subject rats were crushed 1 cm from the muscle in order to examine the isometric contractile properties of skeletal muscle in the recovery sequency during reinnervation of normal, castrated, and testosterone-treated rats. The particular muscle studied was the extensor digitorum longus, with functional reinnervation first observed 8-9 days after nerve crush. No evidence was found that either castration or testosterone injections altered the process of reinnervation after the nerve crush, with the conclusion being valid at the 0.05 p level. The most reliable index of reinnervation was found to be the twitch:tetanus ratio, a factor of use in future studies of the reinnervation of skeletal muscle.

Phenotypic modulation of smooth muscle cells during formation of neointimal thickenings following vascular injury.

PubMed

Thyberg, J

1998-07-01

Smooth muscle cells build up the media of mammalian arteries and constitute one of the principal cell types in atherosclerotic and restenotic lesions. Accordingly, they show a high degree of plasticity and are able to shift from a differentiated, contractile phenotype to a less differentiated, synthetic phenotype, and then back again. This modulation occurs as a response to vascular injury and includes a prominent structural reorganization with loss of myofilaments and formation of an extensive endoplasmic reticulum and a large Golgi complex. At the same time, the expression of cytoskeletal proteins and other gene products is altered. As a result, the cells lose their contractility and become able to migrate from the media to the intima, proliferate, and secrete extracellular matrix components, thereby contributing to the formation of intimal thickenings. The mechanisms behind this change in morphology and function of the smooth muscle cells are still incompletely understood. A crucial role has been ascribed to basement membrane proteins such as laminin and collagen type IV and adhesive proteins such as fibronectin. A significant role is also played by mitogenic proteins such as platelet-derived growth factor (PDGF) and basic fibroblast growth factor (bFGF). An improved knowledge of the regulation of smooth muscle differentiated properties represents an important part in the search for new methods of prevention and treatment of vascular disease.

A short-term statin treatment changes the contractile properties of fast-twitch skeletal muscles.

PubMed

Piette, Antoine Boulanger; Dufresne, Sébastien S; Frenette, Jérôme

2016-10-28

Cumulative evidence indicates that statins induce myotoxicity. However, the lack of understanding of how statins affect skeletal muscles at the structural, functional, and physiological levels hampers proper healthcare management. The purpose of the present study was to investigate the early after-effects of lovastatin on the slow-twitch soleus (Sol) and fast-twitch extensor digitorum longus (EDL) muscles. Adult C57BL/6 mice were orally administrated with placebo or lovastatin [50 mg/kg/d] for 28 days. At the end of the treatment, the isometric ex vivo contractile properties of the Sol and EDL muscles were measured. Subtetanic and tetanic contractions were assessed and contraction kinetics were recorded. The muscles were then frozen for immunohistochemical analyses. Data were analyzed by two-way ANOVA followed by an a posteriori Tukey's test. The short-term lovastatin treatment did not induce muscle mass loss, muscle fiber atrophy, or creatine kinase (CK) release. It had no functional impact on slow-twitch Sol muscles. However, subtetanic stimulations at 10 Hz provoked greater force production in fast-twitch EDL muscles. The treatment also decreased the maximal rate of force development (dP/dT) of twitch contractions and prolonged the half relaxation time (1/2RT) of tetanic contractions of EDL muscles. An early short-term statin treatment induced subtle but significant changes in some parameters of the contractile profile of EDL muscles, providing new insights into the selective initiation of statin-induced myopathy in fast-twitch muscles.

Repeated exposure to methamphetamine induces sex-dependent hypersensitivity to ischemic injury in the adult rat heart

PubMed Central

Seeley, Sarah L.; Stoops, Thorne S.; D’Souza, Manoranjan S.

2017-01-01

Background We previously reported that adult female, but not male rats that were prenatally exposed to methamphetamine exhibit myocardial hypersensitivity to ischemic injury. However, it is unknown whether hypersensitivity to ischemic injury develops when rats are exposed to methamphetamine during adulthood. The goal of this study was to determine whether methamphetamine exposure during adulthood sensitizes the heart to ischemic injury. Methods Adult male and female rats received daily injections of methamphetamine (5 mg/kg) or saline for 10 days. Their hearts were isolated on day 11 and subjected to a 20 min ischemic insult on a Langendorff isolated heart apparatus. Cardiac contractile function was measured by an intraventricular balloon, and infarct size was measured by triphenyltetrazolium chloride staining. Results Hearts from methamphetamine-treated females exhibited significantly larger infarcts and suppressed postischemic recovery of contractile function compared to hearts from saline-treated females. In contrast, methamphetamine had no effect on infarct size or contractile recovery in male hearts. Subsequent experiments demonstrated that hypersensitivity to ischemic injury persisted in female hearts following a 1 month period of abstinence from methamphetamine. Myocardial protein kinase C-ε expression, Akt phosphorylation, and ERK phosphorylation were unaffected by adult exposure to methamphetamine. Conclusions Exposure of adult rats to methamphetamine sex-dependently increases the extent of myocardial injury following an ischemic insult. These data suggest that women who have a heart attack might be at risk of more extensive myocardial injury if they have a recent history of methamphetamine abuse. PMID:28575091

Repeated exposure to methamphetamine induces sex-dependent hypersensitivity to ischemic injury in the adult rat heart.

PubMed

Rorabaugh, Boyd R; Seeley, Sarah L; Stoops, Thorne S; D'Souza, Manoranjan S

2017-01-01

We previously reported that adult female, but not male rats that were prenatally exposed to methamphetamine exhibit myocardial hypersensitivity to ischemic injury. However, it is unknown whether hypersensitivity to ischemic injury develops when rats are exposed to methamphetamine during adulthood. The goal of this study was to determine whether methamphetamine exposure during adulthood sensitizes the heart to ischemic injury. Adult male and female rats received daily injections of methamphetamine (5 mg/kg) or saline for 10 days. Their hearts were isolated on day 11 and subjected to a 20 min ischemic insult on a Langendorff isolated heart apparatus. Cardiac contractile function was measured by an intraventricular balloon, and infarct size was measured by triphenyltetrazolium chloride staining. Hearts from methamphetamine-treated females exhibited significantly larger infarcts and suppressed postischemic recovery of contractile function compared to hearts from saline-treated females. In contrast, methamphetamine had no effect on infarct size or contractile recovery in male hearts. Subsequent experiments demonstrated that hypersensitivity to ischemic injury persisted in female hearts following a 1 month period of abstinence from methamphetamine. Myocardial protein kinase C-ε expression, Akt phosphorylation, and ERK phosphorylation were unaffected by adult exposure to methamphetamine. Exposure of adult rats to methamphetamine sex-dependently increases the extent of myocardial injury following an ischemic insult. These data suggest that women who have a heart attack might be at risk of more extensive myocardial injury if they have a recent history of methamphetamine abuse.

In vitro functional interactions of acetylcholine esterase inhibitors and muscarinic receptor antagonists in the urinary bladder of the rat.

PubMed

Killi, Uday K; Wsol, Vladimir; Soukup, Ondrej; Kuca, Kamil; Winder, Michael; Tobin, Gunnar

2014-02-01

Obidoxime, a weak acetylcholine-esterase (AChE) inhibitor, exerts muscarinic receptor antagonism with a significant muscarinic M2 receptor selective profile. The current examinations aimed to determine the functional significance of muscarinic M2 receptors in the state of AChE inhibition, elucidating muscarinic M2 and M3 receptor interaction. In the in vitro examinations, methacholine evoked concentration-dependent bladder contractile and atrial frequency inhibitory responses. Although atropine abolished both, methoctramine (1 μmol/L) only affected the cholinergic response in the atrial preparations. However, in the presence of methoctramine, physostigmine, an AChE inhibitor, increased the basal tension of the bladder strip preparations (+68%), as well as the contractile responses to low concentrations of methacholine (< 5 μmol/L; +90-290%). In contrast to physostigmine, obidoxime alone raised the basal tension (+58%) and the responses to low concentrations of methacholine (< 5 μmol/L; +80-450%). Physostigmine concentration-dependently increased methacholine-evoked responses, similarly to obidoxime at low concentrations. However, at large concentrations (> 5 μmol/L), obidoxime, because of its unselective muscarinic receptor antagonism, inhibited the methacholine bladder responses. In conclusion, the current results show that muscarinic M2 receptors inhibit muscarinic M3 receptor-evoked contractile responses to low concentrations of acetylcholine in the synaptic cleft. The muscarinic M2 and M3 receptor crosstalk could be a counteracting mechanism in the treatment of AChE inhibition when using reactivators, such as obidoxime. © 2013 Wiley Publishing Asia Pty Ltd.

Ex Vivo Assessment of Contractility, Fatigability and Alternans in Isolated Skeletal Muscles

PubMed Central

Park, Ki Ho; Brotto, Leticia; Lehoang, Oanh; Brotto, Marco; Ma, Jianjie; Zhao, Xiaoli

2012-01-01

Described here is a method to measure contractility of isolated skeletal muscles. Parameters such as muscle force, muscle power, contractile kinetics, fatigability, and recovery after fatigue can be obtained to assess specific aspects of the excitation-contraction coupling (ECC) process such as excitability, contractile machinery and Ca2+ handling ability. This method removes the nerve and blood supply and focuses on the isolated skeletal muscle itself. We routinely use this method to identify genetic components that alter the contractile property of skeletal muscle though modulating Ca2+ signaling pathways. Here, we describe a newly identified skeletal muscle phenotype, i.e., mechanic alternans, as an example of the various and rich information that can be obtained using the in vitro muscle contractility assay. Combination of this assay with single cell assays, genetic approaches and biochemistry assays can provide important insights into the mechanisms of ECC in skeletal muscle. PMID:23149471

Integration of actomyosin contractility with cell-cell adhesion during dorsal closure.

PubMed

Duque, Julia; Gorfinkiel, Nicole

2016-12-15

In this work, we combine genetic perturbation, time-lapse imaging and quantitative image analysis to investigate how pulsatile actomyosin contractility drives cell oscillations, apical cell contraction and tissue closure during morphogenesis of the amnioserosa, the main force-generating tissue during the dorsal closure in Drosophila We show that Myosin activity determines the oscillatory and contractile behaviour of amnioserosa cells. Reducing Myosin activity prevents cell shape oscillations and reduces cell contractility. By contrast, increasing Myosin activity increases the amplitude of cell shape oscillations and the time cells spend in the contracted phase relative to the expanded phase during an oscillatory cycle, promoting cell contractility and tissue closure. Furthermore, we show that in AS cells, Rok controls Myosin foci formation and Mbs regulates not only Myosin phosphorylation but also adhesion dynamics through control of Moesin phosphorylation, showing that Mbs coordinates actomyosin contractility with cell-cell adhesion during amnioserosa morphogenesis. © 2016. Published by The Company of Biologists Ltd.

Effect of melatonin on vascular responses in aortic rings of aging rats.

PubMed

Reyes-Toso, Carlos F; Obaya-Naredo, Daniel; Ricci, Conrado R; Planells, Fernando M; Pinto, Jorge E; Linares, Laura M; Cardinali, Daniel P

2007-04-01

In old animals a marked reduction in endothelium-dependent relaxation occurs. Since there is evidence that the endothelial dysfunction associated with aging may be partly related to the local formation of reactive oxygen species, the purpose of this study was to examine the effect of the natural antioxidant melatonin (10(-5)mol/l) on in vitro contractility of aged aortic rings under conditions of increased oxidative stress (40 m mol/l glucose concentration in medium). Experiments were carried out in 18-20 months old, Wistar male rats, using adult (6-7 months old) animals as controls. A higher plasma lipid peroxidation was found in aged rats as compared to the younger ones. In a first experiment, dose-response curves for acetylcholine-induced relaxation of aortic rings were conducted. Analyzed as a main factor in a factorial ANOVA, age decreased and melatonin augmented the relaxing response to acetylcholine. melatonin's restoring effect on aortic ring relaxation was found in aged aortic rings only and was more pronounced in the presence of a high glucose medium. In a second experiment, the effect of melatonin on the contractility response to phenylephrine of intact or endothelium-denuded aortic rings obtained from aged or control rats was examined in normal or high glucose medium. A main factor analysis in the factorial ANOVA indicated that age and operation augmented, and melatonin decreased, aortic ring contractility response to phenylephrine. Melatonin's restoring effect on aortic contractility was seen in aged aortic rings. The effect of age or a high glucose medium on phenylephrine-induced contractility was more pronounced in the absence of an intact endothelium. Aging did not affect the relaxant response of intact or endothelium-denuded rings to sodium nitroprusside. The results support the improvement by melatonin of vascular response in aging rats, presumably via its antioxidant activity.

Distension-Induced Gastric Contraction is Attenuated in an Experimental Model of Gastric Restraint

PubMed Central

Lu, Xiao; Guo, Xiaomei; Mattar, Samer G.; Navia, Jose A.

2010-01-01

Background Gastric distension has important implications for motility and satiety. The hypothesis of this study was that distension affects the amplitude and duration of gastric contraction and that these parameters are largely mediated by efferent vagus stimulation. Methods A novel isovolumic myograph was introduced to test these hypotheses. The isovolumic myograph isolates the stomach and records the pressure generated by the gastric contraction under isovolumic conditions. Accordingly, the phasic changes of gastric contractility can be documented. A group of 12 rats were used under in vivo conditions and isolated ex vivo conditions and with two different gastric restraints (small and large) to determine the effect of degree of restraint. Results The comparison of the in vivo and ex vivo contractility provided information on the efferent vagus mediation of gastric contraction, i.e., the in vivo amplitude and duration reached maximum of 12.6 ± 2.7 mmHg and 19.8 ± 5.6 s in contrast to maximum of 5.7 ± 0.9 mmHg and 7.3 ± 1.3 s in ex vivo amplitude and duration, respectively. The comparison of gastric restraint and control groups highlights the role of distension on in vivo gastric contractility. The limitation of gastric distension by restraint drastically reduced the maximal amplitude to below 2.9 ± 0.2 mmHg. Conclusions The results show that distension-induced gastric contractility is regulated by both central nervous system and local mechanisms with the former being more substantial. Furthermore, the gastric restraint significantly attenuates gastric contractility (decreased amplitude and shortened duration of contraction) which is mediated by the efferent vagus activation. These findings have important implications for gastric motility and physiology and may improve our understanding of satiety. PMID:20706803

Phosphoinositide 3-Kinase p110β Regulates Integrin αIIbβ3 Avidity and the Cellular Transmission of Contractile Forces*

PubMed Central

Schoenwaelder, Simone M.; Ono, Akiko; Nesbitt, Warwick S.; Lim, Joanna; Jarman, Kate; Jackson, Shaun P.

2010-01-01

Phosphoinositide (PI) 3-kinase (PI3K) signaling processes play an important role in regulating the adhesive function of integrin αIIbβ3, necessary for platelet spreading and sustained platelet aggregation. PI3K inhibitors are effective at reducing platelet aggregation and thrombus formation in vivo and as a consequence are currently being evaluated as novel antithrombotic agents. PI3K regulation of integrin αIIbβ3 activation (affinity modulation) primarily occurs downstream of Gi-coupled and tyrosine kinase-linked receptors linked to the activation of Rap1b, AKT, and phospholipase C. In the present study, we demonstrate an important role for PI3Ks in regulating the avidity (strength of adhesion) of high affinity integrin αIIbβ3 bonds, necessary for the cellular transmission of contractile forces. Using knock-out mouse models and isoform-selective PI3K inhibitors, we demonstrate that the Type Ia p110β isoform plays a major role in regulating thrombin-stimulated fibrin clot retraction in vitro. Reduced clot retraction induced by PI3K inhibitors was not associated with defects in integrin αIIbβ3 activation, actin polymerization, or actomyosin contractility but was associated with a defect in integrin αIIbβ3 association with the contractile cytoskeleton. Analysis of integrin αIIbβ3 adhesion contacts using total internal reflection fluorescence microscopy revealed an important role for PI3Ks in regulating the stability of high affinity integrin αIIbβ3 bonds. These studies demonstrate an important role for PI3K p110β in regulating the avidity of high affinity integrin αIIbβ3 receptors, necessary for the cellular transmission of contractile forces. These findings may provide new insight into the potential antithrombotic properties of PI3K p110β inhibitors. PMID:19940148

Inhibition of CYP2E1 attenuates chronic alcohol intake-induced myocardial contractile dysfunction and apoptosis.

PubMed

Zhang, Rong-Huai; Gao, Jian-Yuan; Guo, Hai-Tao; Scott, Glenda I; Eason, Anna R; Wang, Xiao-Ming; Ren, Jun

2013-01-01

Alcohol intake is associated with myocardial contractile dysfunction and apoptosis although the precise mechanism is unclear. This study was designed to examine the effect of the cytochrome P450 enzyme CYP2E1 inhibition on ethanol-induced cardiac dysfunction. Adult male mice were fed a 4% ethanol liquid or pair-fed control diet for 6weeks. Following 2weeks of diet feeding, a cohort of mice started to receive the CYP2E1 inhibitor diallyl sulfide (100mg/kg/d, i.p.) for the remaining feeding duration. Cardiac function was assessed using echocardiographic and IonOptix systems. Western blot analysis was used to evaluate CYP2E1, heme oxygenase-1 (HO-1), iNOS, the intracellular Ca(2+) regulatory proteins sarco(endo)plasmic reticulum Ca(2+)-ATPase, Na(+)Ca(2+) exchanger and phospholamban, pro-apoptotic protein cleaved caspase-3, Bax, c-Jun-NH(2)-terminal kinase (JNK) and apoptosis signal-regulating kinase (ASK-1). Ethanol led to elevated levels of CYP2E1, iNOS and phospholamban, decreased levels of HO-1 and Na(+)Ca(2+) exchanger, cardiac contractile and intracellular Ca(2+) defects, cardiac fibrosis, overt O(2)(-) production, and apoptosis accompanied with increased phosphorylation of JNK and ASK-1, the effects were significantly attenuated or ablated by diallyl sulfide. Inhibitors of JNK and ASK-1 but not HO-1 inducer or iNOS inhibitor obliterated ethanol-induced cardiomyocyte contractile dysfunction, substantiating a role for JNK and ASK-1 signaling in ethanol-induced myocardial injury. Taken together, these findings suggest that ethanol metabolism through CYP2E1 may contribute to the pathogenesis of alcoholic cardiomyopathy including myocardial contractile dysfunction, oxidative stress and apoptosis, possibly through activation of JNK and ASK-1 signaling. Copyright © 2012 Elsevier B.V. All rights reserved.

Disruption of the circadian clock within the cardiomyocyte influences mycardial contractile function, metabolism, and gene expression

USDA-ARS?s Scientific Manuscript database

Virtually every mammalian cell, including cardiomyocytes, possesses an intrinsic circadian clock. The role of this transcriptionally based molecular mechanism in cardiovascular biology is poorly understood. We hypothesized that the circadian clock within the cardiomyocyte influences diurnal variatio...

Macrophage Migration Inhibitory Factor (MIF) Deficiency Exacerbates Aging-Induced Cardiac Remodeling and Dysfunction Despite Improved Inflammation: Role of Autophagy Regulation.

PubMed

Xu, Xihui; Pang, Jiaojiao; Chen, Yuguo; Bucala, Richard; Zhang, Yingmei; Ren, Jun

2016-03-04

Aging leads to unfavorable geometric and functional sequelae in the heart. The proinflammatory cytokine macrophage migration inhibitory factor (MIF) plays a role in the maintenance of cardiac homeostasis under stress conditions although its impact in cardiac aging remains elusive. This study was designed to evaluate the role of MIF in aging-induced cardiac anomalies and the underlying mechanism involved. Cardiac geometry, contractile and intracellular Ca(2+) properties were examined in young (3-4 mo) or old (24 mo) wild type and MIF knockout (MIF(-/-)) mice. Our data revealed that MIF knockout exacerbated aging-induced unfavorable structural and functional changes in the heart. The detrimental effect of MIF knockout was associated with accentuated loss in cardiac autophagy with aging. Aging promoted cardiac inflammation, the effect was attenuated by MIF knockout. Intriguingly, aging-induced unfavorable responses were reversed by treatment with the autophagy inducer rapamycin, with improved myocardial ATP availability in aged WT and MIF(-/-) mice. Using an in vitro model of senescence, MIF knockdown exacerbated doxorubicin-induced premature senescence in H9C2 myoblasts, the effect was ablated by MIF replenishment. Our data indicated that MIF knockout exacerbates aging-induced cardiac remodeling and functional anomalies despite improved inflammation, probably through attenuating loss of autophagy and ATP availability in the heart.

Alterations in Skeletal Muscle With Disuse Atrophy: The Effects of Countermeasures

NASA Technical Reports Server (NTRS)

Fitts, Robert H.

1996-01-01

The specific aims of this project concerned three general areas: (1) studies on the contractile function of single skinned fibers designed to determine the time course and cellular basis of the Hindlimb Suspension (HS) induced increase in fiber Vo (maximal shortening velocity), and the decrease in peak tension (Po); (2) studies designed to understand the effect of HS on single fiber substrate utilization during contractile activity, and how if at all such changes contribute to the increased muscle fatigue associated with HS; and (3) studies evaluating the effectiveness of standing and ladder climbing as countermeasures to the deleterious effects of HS. We have constructed all of the necessary equipment, and are currently conducting preliminary studies on T-tubular charge movement. A list of publications from this contract is included at the end of this report. The three objectives are (1) Functional Studies on the Single Skinned Fiber; (2) Fiber Substrate Utilization and Muscle Fatugue with Contracting Activity and (3) Exercise Countermeasures.

The Inhibitory Effect of Shikonin on the Agonist-Induced Regulation of Vascular Contractility

PubMed Central

Je, Hyun Dong; Kim, Hyeong-Dong; La, Hyen-Oh

2015-01-01

Shikonin, a natural flavonoid found in the roots of Lithospermum erythrorhizon, has been shown to possess many biological functions. The present study was undertaken to investigate the influence of shikonin on vascular smooth muscle contractility and to determine the mechanism involved. Denuded aortic rings from male rats were used and isometric contractions were recorded and combined with molecular experiments. Shikonin significantly relaxed fluoride-, thromboxane A2- or phorbol ester-induced vascular contraction suggesting as a possible anti-hypertensive on the agonist-induced vascular contraction regardless of endothelial nitric oxide synthesis. Furthermore, shikonin significantly inhibited fluoride-induced increases in pMYPT1 levels and phorbol ester-induced increases in pERK1/2 levels suggesting the mechanism involving the inhibition of Rho-kinase activity and the subsequent phosphorylation of MYPT1 and the inhibition of MEK activity and the subsequent phosphorylation of ERK1/2. This study provides evidence regarding the mechanism underlying the relaxation effect of shikonin on agonist-induced vascular contraction regardless of endothelial function. PMID:25995821

Instrumented cardiac microphysiological devices via multimaterial three-dimensional printing

NASA Astrophysics Data System (ADS)

Lind, Johan U.; Busbee, Travis A.; Valentine, Alexander D.; Pasqualini, Francesco S.; Yuan, Hongyan; Yadid, Moran; Park, Sung-Jin; Kotikian, Arda; Nesmith, Alexander P.; Campbell, Patrick H.; Vlassak, Joost J.; Lewis, Jennifer A.; Parker, Kevin K.

2017-03-01

Biomedical research has relied on animal studies and conventional cell cultures for decades. Recently, microphysiological systems (MPS), also known as organs-on-chips, that recapitulate the structure and function of native tissues in vitro, have emerged as a promising alternative. However, current MPS typically lack integrated sensors and their fabrication requires multi-step lithographic processes. Here, we introduce a facile route for fabricating a new class of instrumented cardiac microphysiological devices via multimaterial three-dimensional (3D) printing. Specifically, we designed six functional inks, based on piezo-resistive, high-conductance, and biocompatible soft materials that enable integration of soft strain gauge sensors within micro-architectures that guide the self-assembly of physio-mimetic laminar cardiac tissues. We validated that these embedded sensors provide non-invasive, electronic readouts of tissue contractile stresses inside cell incubator environments. We further applied these devices to study drug responses, as well as the contractile development of human stem cell-derived laminar cardiac tissues over four weeks.

Detrusor underactivity and the underactive bladder: Symptoms, function, cause-what do we mean? ICI-RS think tank 2014.

PubMed

Smith, Phillip P; Birder, Lori A; Abrams, Paul; Wein, Alan J; Chapple, Chris R

2016-02-01

Impaired bladder emptying is a well-recognized cause of lower urinary tract symptoms. However, the symptoms produced do not always relate to voiding, and may include frequency, urgency and incontinence. Conversely, the etiology of symptoms of disturbed voiding is not necessarily dependent upon objectively impaired voiding. Terms including underactive bladder, detrusor underactivity, and impaired contractility describe aspects of these problems, and have been used somewhat interchangeably. It is possible that the present lack of effective therapy in many cases relates to both etiologic and diagnostic uncertainty stemming from terminologic imprecision. Detrusor underactivity has a standardized definition, unlike underactive bladder and impaired contractility. The relationships of symptoms, function, and cause were the focus of a 2014 ICI-RS Think Tank entitled Does Detrusor Underactivity Exist, and if so it is neurogenic, myogenic, or both? This review presents a summary of the problem and the Think Tank conclusions. A terminologic hierarchy and specific research goals are presented. © 2016 Wiley Periodicals, Inc.

Endothelium-Independent Effect of Fisetin on the Agonist-Induced Regulation of Vascular Contractility

PubMed Central

Je, Hyun Dong; Sohn, Uy Dong; La, Hyen-Oh

2016-01-01

Fisetin, a natural flavonoid found in a variety of vegetables and fruits, has been shown to possess many biological functions. The present study was undertaken to investigate the influence of fisetin on vascular smooth muscle contractility and to determine the mechanism involved. Denuded aortic rings from male rats were used and isometric contractions were recorded and combined with molecular experiments. Fisetin significantly relaxed fluoride-, thromboxane A2- or phorbol ester-induced vascular contraction suggesting as a possible anti-hypertensive on the agonist-induced vascular contraction regardless of endothelial nitric oxide synthesis. Furthermore, fisetin significantly inhibited fluoride-induced increases in pMYPT1 levels and phorbol ester-induced increases in pERK1/2 levels suggesting the mechanism involving the inhibition of Rho-kinase activity and the subsequent phosphorylation of MYPT1 and MEK activity and the subsequent phosphorylation of ERK1/2. This study provides evidence regarding the mechanism underlying the relaxation effect of fisetin on agonist-induced vascular contraction regardless of endothelial function. PMID:26759702

Diagnosis of Swallowing Disorders: How We Interpret Pharyngeal Manometry.

PubMed

Cock, Charles; Omari, Taher

2017-03-01

We provide an overview of the clinical application of novel pharyngeal high-resolution impedance manometry (HRIM) with pressure flow analysis (PFA) in our hands with example cases. In our Centre, we base our interpretation of HRIM recordings upon a qualitative assessment of pressure-impedance waveforms during individual swallows, as well as a quantitative assessment of averaged PFA swallow function variables. We provide a description of two global swallowing efficacy measures, the swallow risk index (SRI), reflecting global swallowing dysfunction (higher SRI = greater aspiration risk) and the post-swallow impedance ratio (PSIR) detecting significant post-swallow bolus residue. We describe a further eight swallow function variables specific to the hypopharynx and upper esophageal sphincter (UES), assessing hypo-pharyngeal distension pressure, contractility, bolus presence and flow timing, and UES basal tone, relaxation, opening and contractility. Pharyngeal HRIM has now come of age, being applicable for routine clinical practice to assess the biomechanics of oropharyngeal swallowing dysfunction. In the future, it may guide treatment strategies and allow more objective longitudinal follow-up on clinical outcomes.

Passive stiffness of pressure-induced hypertrophied cat myocardium.

PubMed

Williams, J F; Potter, R D

1981-07-01

The effect of myocardial hypertrophy on passive stiffness was determined from the stress (sigma)-strain relationship of right ventricular papillary muscles from 18 pulmonary artery-banded and 21 non-banded cats. By use of Lagrangian strain, (1-lo)lo is initial muscle length, and instantaneous stress elastic constants beta and alpha were calculated from the equation sigma = alpha(ebeta epsilon - 1). Elastic stiffness (d sigma/d epsilon) was determined from the formula d sigma/d epsilon = beta alpha + alpha beta. Banding produced an average increase in RV mass of 70%. Beta averaged 14.2 +/- 0.9 (SEM) and 16.0 +/- 0.8 in the non-hypertrophied and hypertrophied muscles, respectively (NS). However, elastic stiffness was significantly greater in hypertrophied muscles over the entire stress range. Contractile function varied widely among hypertrophied muscles but was not related to changes in stiffness. Thus, moderate degrees of pressure-induced hypertrophy are associated with a modest increase in the passive stiffness properties of the muscle, independent of changes in contractile function.

Functional characterization of contractile vacuole isolated from Amoeba proteus.

PubMed

Nishihara, Eri; Shimmen, Teruo; Sonobe, Seiji

2004-12-01

Contractile vacuoles (CVs) released from cells of Amoeba proteus were used to analyze its function in vitro. When CV was transferred to a hypertonic medium, its volume decreased within 10 sec. When it was subsequently returned to its original medium, it quickly started swelling. However, it ruptured before recovering its initial volume. These results suggested that the CV membrane is semi-permeable and that the fluid is collected by the osmotic gradient in vivo. The water permeability of membrane of isolated CV was calculated from the rate of osmotic volume change to be 0.94 microm/sec . OsM. This high value suggested that CV membrane is equipped with water channel. CV contracted (or burst) quickly upon addition of 1 mM ATP. Contraction was induced by ATP, but not by other nucleotides, GTP, ITP, ADP, or the analogues of ATP, AMP-PNP and ATPgammaS. It was suggested that the contraction of isolated CV was caused by increase in the tension of its membrane by ATP.

Self-organization of muscle cell structure and function.

PubMed

Grosberg, Anna; Kuo, Po-Ling; Guo, Chin-Lin; Geisse, Nicholas A; Bray, Mark-Anthony; Adams, William J; Sheehy, Sean P; Parker, Kevin Kit

2011-02-01

The organization of muscle is the product of functional adaptation over several length scales spanning from the sarcomere to the muscle bundle. One possible strategy for solving this multiscale coupling problem is to physically constrain the muscle cells in microenvironments that potentiate the organization of their intracellular space. We hypothesized that boundary conditions in the extracellular space potentiate the organization of cytoskeletal scaffolds for directed sarcomeregenesis. We developed a quantitative model of how the cytoskeleton of neonatal rat ventricular myocytes organizes with respect to geometric cues in the extracellular matrix. Numerical results and in vitro assays to control myocyte shape indicated that distinct cytoskeletal architectures arise from two temporally-ordered, organizational processes: the interaction between actin fibers, premyofibrils and focal adhesions, as well as cooperative alignment and parallel bundling of nascent myofibrils. Our results suggest that a hierarchy of mechanisms regulate the self-organization of the contractile cytoskeleton and that a positive feedback loop is responsible for initiating the break in symmetry, potentiated by extracellular boundary conditions, is required to polarize the contractile cytoskeleton.

Cellular and Physiological Effects of Dietary Supplementation with β-Hydroxy-β-Methylbutyrate (HMB) and β-Alanine in Late Middle-Aged Mice.

PubMed

Vallejo, Julian; Spence, Madoka; Cheng, An-Lin; Brotto, Leticia; Edens, Neile K; Garvey, Sean M; Brotto, Marco

2016-01-01

There is growing evidence that severe decline of skeletal muscle mass and function with age may be mitigated by exercise and dietary supplementation with protein and amino acid ingredient technologies. The purposes of this study were to examine the effects of the leucine catabolite, beta-hydroxy-beta-methylbutyrate (HMB), in C2C12 myoblasts and myotubes, and to investigate the effects of dietary supplementation with HMB, the amino acid β-alanine and the combination thereof, on muscle contractility in a preclinical model of pre-sarcopenia. In C2C12 myotubes, HMB enhanced sarcoplasmic reticulum (SR) calcium release beyond vehicle control in the presence of all SR agonists tested (KCl, P<0.01; caffeine, P = 0.03; ionomycin, P = 0.03). HMB also improved C2C12 myoblast viability (25 μM HMB, P = 0.03) and increased proliferation (25 μM HMB, P = 0.04; 125 μM HMB, P<0.01). Furthermore, an ex vivo muscle contractility study was performed on EDL and soleus muscle from 19 month old, male C57BL/6nTac mice. For 8 weeks, mice were fed control AIN-93M diet, diet with HMB, diet with β-alanine, or diet with HMB and β-alanine. In β-alanine fed mice, EDL muscle showed a 7% increase in maximum absolute force compared to the control diet (202 ± 3vs. 188± 5 mN, P = 0.02). At submaximal frequency of stimulation (20 Hz), EDL from mice fed HMB plus β-alanine showed an 11% increase in absolute force (88.6 ± 2.2 vs. 79.8 ± 2.4 mN, P = 0.025) and a 13% increase in specific force (12.2 ± 0.4 vs. 10.8 ± 0.4 N/cm2, P = 0.021). Also in EDL muscle, β-alanine increased the rate of force development at all frequencies tested (P<0.025), while HMB reduced the time to reach peak contractile force (TTP), with a significant effect at 80 Hz (P = 0.0156). In soleus muscle, all experimental diets were associated with a decrease in TTP, compared to control diet. Our findings highlight beneficial effects of HMB and β-alanine supplementation on skeletal muscle function in aging mice.

Cellular and Physiological Effects of Dietary Supplementation with β-Hydroxy-β-Methylbutyrate (HMB) and β-Alanine in Late Middle-Aged Mice

PubMed Central

Vallejo, Julian; Spence, Madoka; Cheng, An-Lin; Brotto, Leticia; Edens, Neile K.; Garvey, Sean M.; Brotto, Marco

2016-01-01

There is growing evidence that severe decline of skeletal muscle mass and function with age may be mitigated by exercise and dietary supplementation with protein and amino acid ingredient technologies. The purposes of this study were to examine the effects of the leucine catabolite, beta-hydroxy-beta-methylbutyrate (HMB), in C2C12 myoblasts and myotubes, and to investigate the effects of dietary supplementation with HMB, the amino acid β-alanine and the combination thereof, on muscle contractility in a preclinical model of pre-sarcopenia. In C2C12 myotubes, HMB enhanced sarcoplasmic reticulum (SR) calcium release beyond vehicle control in the presence of all SR agonists tested (KCl, P<0.01; caffeine, P = 0.03; ionomycin, P = 0.03). HMB also improved C2C12 myoblast viability (25 μM HMB, P = 0.03) and increased proliferation (25 μM HMB, P = 0.04; 125 μM HMB, P<0.01). Furthermore, an ex vivo muscle contractility study was performed on EDL and soleus muscle from 19 month old, male C57BL/6nTac mice. For 8 weeks, mice were fed control AIN-93M diet, diet with HMB, diet with β-alanine, or diet with HMB and β-alanine. In β-alanine fed mice, EDL muscle showed a 7% increase in maximum absolute force compared to the control diet (202 ± 3vs. 188± 5 mN, P = 0.02). At submaximal frequency of stimulation (20 Hz), EDL from mice fed HMB plus β-alanine showed an 11% increase in absolute force (88.6 ± 2.2 vs. 79.8 ± 2.4 mN, P = 0.025) and a 13% increase in specific force (12.2 ± 0.4 vs. 10.8 ± 0.4 N/cm2, P = 0.021). Also in EDL muscle, β-alanine increased the rate of force development at all frequencies tested (P<0.025), while HMB reduced the time to reach peak contractile force (TTP), with a significant effect at 80 Hz (P = 0.0156). In soleus muscle, all experimental diets were associated with a decrease in TTP, compared to control diet. Our findings highlight beneficial effects of HMB and β-alanine supplementation on skeletal muscle function in aging mice. PMID:26953693

A randomized comparison of 5 versus 12 hours per day of cardiac contractility modulation treatment for heart failure patients: A preliminary report.

PubMed

Kloppe, Axel; Mijic, Dejan; Schiedat, Fabian; Bogossian, Harilaos; Mügge, Andreas; Rousso, Benny; Lemke, Bernd

2016-01-01

Cardiac contractility modulation (CCM) signals are non-excitatory electrical signals delivered during the absolute refractory period intended to improve contraction and cardiac function. Clinical trials have shown that CCM treatment significantly improves exercise tolerance and quality of life in symptomatic heart failure patients. Studies with CCM therapy typically include CCM delivery for 3, 5 or 7 h per day, although other configurations are also commonly used. Each has been associated with improved outcomes in heart failure, but it is not clear whether different application durations are associated with the various degrees of benefit. The purpose of the current pilot evaluation study was to evaluate the quality of life, exercise tolerance, and cardiac function, over a 6-month period when CCM was delivered for 5 h/day vs. 12 h/day. Increasing the daily CCM therapy duration is safe and as good as the standard CCM periods of application per day. This single center pilot evaluation study involved 19 medically refractory symptomatic patients with heart failure and reduced left ventricular function who underwent implantation of an Optimizer™ system (Impulse Dynamics, Orangeburg, NY, USA). Patients were randomized into one of two treatment groups; 5 h/day CCM treatment or 12 h/day CCM treatment. Subjects and evaluating physicians were blinded to the study group. Subjects returned to the hospital after 12 and 24 weeks. Efficacy evaluations included changes from baseline to 24 weeks in Minnesota Living With Heart Failure Questionnaire score (MLWHFQ), maximal oxygen consumption in the cardio-pulmonary stress test (peak VO2), New York Heart Association classification (NYHA), 6-min walk distance (6MWD), and ejection fraction (EF). At the end of 24 weeks, clinical improvement was observed in the entire cohort in all efficacy measures (mean change from baseline of -17.1 in MLWHFQ, -0.86 in NYHA, and improvement trend of 1.48 mL O2/kg/min in peak VO2, 31.3 m in 6MWD, and 2.25% in EF). There were no significant differences, either clinically or statistically, between the groups receiving CCM for 5 h/day vs. 12 h/day. Three subjects were voluntarily withdrawn before completing the study. One subject died from pneumonia after 125 days, and 6 serious adverse events were reported, none of which was classified as related to either the device or the procedure. Together with previously reported experience with CCM, delivery of CCM therapy is equally safe and appears similarly effective over the range of shorter (5 h) to longer (12 h) daily periods of application. Given the small sample size, further studies are warranted.

Progesterone Metabolites Produced by Cytochrome P450 3A Modulate Uterine Contractility in a Murine Model

PubMed Central

Patil, Avinash S.; Swamy, Geeta K.; Murtha, Amy P.; Heine, R. Phillips; Zheng, Xiaomei; Grotegut, Chad A.

2015-01-01

Objective: We seek to characterize the effect of progesterone metabolites on spontaneous and oxytocin-induced uterine contractility. Study Design: Spontaneous contractility was studied in mouse uterine horns after treatment with progesterone, 2α-hydroxyprogesterone, 6β-hydroxyprogesterone (6β-OHP), 16α-hydroxyprogesterone (16α-OHP), or 17-hydroxyprogesterone caproate (17-OHPC) at 10−9 to 10−6 mol/L. Uterine horns were exposed to progestins (10−6 mol/L), followed by increasing concentrations of oxytocin (1-100 nmol/L) to study oxytocin-induced contractility. Contraction parameters were compared for each progestin and matched vehicle control using repeated measures 2-way analysis of variance. In vitro metabolism of progesterone by recombinant cytochrome P450 3A (CYP3A) microsomes (3A5, 3A5, and 3A7) identified major metabolites. Results: Oxytocin-induced contractile frequency was decreased by 16α-OHP (P = .03) and increased by 6β-OHP (P = .05). Progesterone and 17-OHPC decreased oxytocin-induced contractile force (P = .02 and P = .04, respectively) and frequency (P = .02 and P = .03, respectively). Only progesterone decreased spontaneous contractile force (P = .02). Production of 16α-OHP and 6β-OHP metabolites were confirmed in all CYP3A isoforms tested. Conclusion: Progesterone metabolites produced by maternal or fetal CYP3A enzymes influence uterine contractility. PMID:26037300

Endothelin receptor B, a candidate gene from human studies at high altitude, improves cardiac tolerance to hypoxia in genetically engineered heterozygote mice

PubMed Central

Stobdan, Tsering; Zhou, Dan; Ao-Ieong, Eilleen; Ortiz, Daniel; Ronen, Roy; Hartley, Iain; Gan, Zhuohui; McCulloch, Andrew D.; Bafna, Vineet; Cabrales, Pedro; Haddad, Gabriel G.

2015-01-01

To better understand human adaptation to stress, and in particular to hypoxia, we took advantage of one of nature’s experiments at high altitude (HA) and studied Ethiopians, a population that is well-adapted to HA hypoxic stress. Using whole-genome sequencing, we discovered that EDNRB (Endothelin receptor type B) is a candidate gene involved in HA adaptation. To test whether EDNRB plays a critical role in hypoxia tolerance and adaptation, we generated EdnrB knockout mice and found that when EdnrB−/+ heterozygote mice are treated with lower levels of oxygen (O2), they tolerate various levels of hypoxia (even extreme hypoxia, e.g., 5% O2) very well. For example, they maintain ejection fraction, cardiac contractility, and cardiac output in severe hypoxia. Furthermore, O2 delivery to vital organs was significantly higher and blood lactate was lower in EdnrB−/+ compared with wild type in hypoxia. Tissue hypoxia in brain, heart, and kidney was lower in EdnrB−/+ mice as well. These data demonstrate that a lower level of EDNRB significantly improves cardiac performance and tissue perfusion under various levels of hypoxia. Transcriptomic profiling of left ventricles revealed three specific genes [natriuretic peptide type A (Nppa), sarcolipin (Sln), and myosin light polypeptide 4 (Myl4)] that were oppositely expressed (q < 0.05) between EdnrB−/+ and wild type. Functions related to these gene networks were consistent with a better cardiac contractility and performance. We conclude that EDNRB plays a key role in hypoxia tolerance and that a lower level of EDNRB contributes, at least in part, to HA adaptation in humans. PMID:26240367

Thermal acclimation to cold alters myosin content and contractile properties of rainbow smelt, Osmerus mordax, red muscle.

PubMed

Coughlin, David J; Shiels, Lisa P; Nuthakki, Seshuvardhan; Shuman, Jacie L

2016-06-01

Rainbow smelt (Osmerus mordax), a eurythermal fish, live in environments from -1.8 to 20°C, with some populations facing substantial annual variation in environmental temperature. These different temperature regimes pose distinct challenges to locomotion by smelt. Steady swimming performance, red muscle function and muscle myosin content were examined to assess the prediction that cold acclimation by smelt will lead to improved steady swimming performance and that any performance shift will be associated with changes in red muscle function and in its myosin heavy chain composition. Cold acclimated (4°C) smelt had a faster maximum steady swimming speed and swam with a higher tailbeat frequency than warm acclimated (10°C) smelt when tested at the same temperature (10°C). Muscle mechanics experiments demonstrated faster contractile properties in the cold acclimated fish when tested at 10°C. The red muscle of cold acclimated smelt had a shorter twitch times, a shorter relaxation times and a higher maximum shortening velocity. In addition, red muscle from cold acclimated fish displayed reduced thermal sensitivity to cold, maintaining higher force levels at 4°C compared to red muscle from warm acclimated fish. Immunohistochemistry suggests shifts in muscle myosin composition and a decrease in muscle cross-sectional area with cold acclimation. Dot blot analysis confirmed a shift in myosin content. Rainbow smelt do show a significant thermal acclimation response to cold. An examination of published values of maximum muscle shortening velocity in fishes suggests that smelt are particularly well suited to high levels of activity in very cold water. Copyright © 2016 Elsevier Inc. All rights reserved.

Cardio-Metabolic Effects of HIV Protease Inhibitors (Lopinavir/Ritonavir)

PubMed Central

Reyskens, Kathleen M. S. E.; Fisher, Tarryn-Lee; Schisler, Jonathan C.; O'Connor, Wendi G.; Rogers, Arlin B.; Willis, Monte S.; Planesse, Cynthia; Boyer, Florence; Rondeau, Philippe; Bourdon, Emmanuel; Essop, M. Faadiel

2013-01-01

Although antiretroviral treatment decreases HIV-AIDS morbidity/mortality, long-term side effects may include the onset of insulin resistance and cardiovascular diseases. However, the underlying molecular mechanisms responsible for highly active antiretroviral therapy (HAART)-induced cardio-metabolic effects are poorly understood. In light of this, we hypothesized that HIV protease inhibitor (PI) treatment (Lopinavir/Ritonavir) elevates myocardial oxidative stress and concomitantly inhibits the ubiquitin proteasome system (UPS), thereby attenuating cardiac function. Lopinavir/Ritonavir was dissolved in 1% ethanol (vehicle) and injected into mini-osmotic pumps that were surgically implanted into Wistar rats for 8 weeks vs. vehicle and sham controls. We subsequently evaluated metabolic parameters, gene/protein markers and heart function (ex vivo Langendorff perfusions). PI-treated rats exhibited increased serum LDL-cholesterol, higher tissue triglycerides (heart, liver), but no evidence of insulin resistance. In parallel, there was upregulation of hepatic gene expression, i.e. acetyl-CoA carboxylase β and 3-hydroxy-3-methylglutaryl-CoA-reductase, key regulators of fatty acid oxidation and cholesterol synthesis, respectively. PI-treated hearts displayed impaired cardiac contractile function together with attenuated UPS activity. However, there was no significant remodeling of hearts exposed to PIs, i.e. lack of ultrastructural changes, fibrosis, cardiac hypertrophic response, and oxidative stress. Western blot analysis of PI-treated hearts revealed that perturbed calcium handling may contribute to the PI-mediated contractile dysfunction. Here chronic PI administration led to elevated myocardial calcineurin, nuclear factor of activated T-cells 3 (NFAT3), connexin 43, and phosphorylated phospholamban, together with decreased calmodulin expression levels. This study demonstrates that early changes triggered by PI treatment include increased serum LDL-cholesterol levels together with attenuated cardiac function. Furthermore, PI exposure inhibits the myocardial UPS and leads to elevated calcineurin and connexin 43 expression that may be associated with the future onset of cardiac contractile dysfunction. PMID:24098634

Chromium (D-phenylalanine)3 improves obesity-induced cardiac contractile defect in ob/ob mice.

PubMed

Dong, Feng; Yang, Xiaoping; Sreejayan, Nair; Ren, Jun

2007-11-01

Low-molecular weight chromium compounds, such as chromium picolinate [Cr(pic)(3)], improve insulin sensitivity, although toxicity is a concern. We synthesized a novel chromium complex, chromium (d-phenylalanine)(3) [Cr(d-phe)(3)], in an attempt to improve insulin sensitivity with reduced toxicity. The aim of this study was to compare the two chromium compounds on cardiac contractile function in ob/ob obese mice. C57BL lean and ob/ob obese mice were randomly divided into three groups: H(2)O, Cr(d-phe)(3), or Cr(pic)(3) (45 mug/kg per day orally for 6 months). The glucose tolerance test displayed improved glucose clearance by Cr(d-phe)(3) but not Cr(pic)(3). Myocytes from ob/ob mice exhibited depressed peak shortening (PS) and maximal velocity of shortening/relengthening (+/-dL/dt), prolonged time-to-PS and time-to-90% relengthening (TR90), reduced electrically stimulated rise in intracellular Ca(2+) (Deltafura-2 fluorescence intensity), and slowed intracellular Ca(2+) decay. Although a 3-month Cr(d-phe)(3) treatment for a separate group of ob/ob and lean 2-month-old mice only rectified reduced +/-dL/dt in ob/ob mice, all mechanical and intracellular Ca(2+) abnormalities were significantly attenuated or ablated by 6 months of Cr(d-phe)(3) but not Cr(pic)(3) treatment (except TR90). Sarco(endo)plasmic reticulum Ca(2+) ATPase activity and Na(+)-Ca(2+) exchanger expression were depressed in ob/ob mice, which were reversed by both Cr(d-phe)(3) and Cr(pic)(3), with a more pronounced effect from Cr(d-phe)(3). Cr(d-phe)(3) corrected reduced insulin-stimulated glucose uptake and improved basal phosphorylation of Akt and insulin receptor, as well as insulin-stimulated phosphorylation of Akt and insulin receptor in ob/ob myocytes. Heart homogenates from ob/ob mice had enhanced oxidative stress and protein carbonyl formation compared with the lean group, which were attenuated by both Cr(d-phe)(3) and Cr(pic)(3). Our data suggest that the new Cr(d-phe)(3) compound possesses better cardio-protective and insulin-sensitizing properties against obesity.

Microencapsulated krill and tuna oil blend raises plasma long-chain n-3 polyunsaturated fatty acid levels compared to tuna oil with similar increases in ileal contractility in rats.

PubMed

Patten, Glen S; Sanguansri, Luz; Augustin, Mary Ann; Abeywardena, Mahinda Y; Bird, Anthony R; Patch, Craig S; Belobrajdic, Damien P

2017-03-01

Long-chain n-3 polyunsaturated fatty acids (LC n-3 PUFA) may be more bioavailable from krill oil compared to fish oil due to their phospholipid structure. We tested whether a microencapsulated krill and tuna oil blend (ME-TOKO) provided greater LC n-3 PUFA bioavailability, improved blood lipid profiles and increased intestinal contractility compared to microencapsulated tuna oil (ME-TO). Rats were divided into three groups to receive isocaloric diets containing ME-TO, ME-TOKO and microencapsulated olive oil (ME-OO) at 0.3 or 2 g/100 g for 4 weeks. Final body and organ weights, feed intake and waste output were similar. ME-TOKO rats had higher plasma total LC n-3 PUFA levels compared to ME-TO, but liver LC n-3 PUFA levels and plasma triglyceride and cholesterol levels were similar in non-fasted rats. Diets containing 2% ME-TO and ME-TOKO also showed similar increases in ileal contractility. In summary, ME-TO bioavailability of LC n-3 PUFA was similar to ME-TOKO.

Development of a Cyclic Strain Bioreactor for Mechanical Enhancement and Assessment of Bioengineered Myocardial Constructs

PubMed Central

Salazar, Betsy H.; Cashion, Avery T.; Dennis, Robert G.; Birla, Ravi K.

2015-01-01

Purpose The purpose of this study was to develop enabling bioreactor technologies using a novel voice coil actuator system for investigating the effects of periodic strain on cardiac patches fabricated with rat cardiomyocytes. Methods The bioengineered muscle constructs used in this study were formed by culturing rat neonatal primary cardiac cells on a fibrin gel. The physical design of the bioreactor was initially conceived using Solidworks to test clearances and perform structural strain analysis. Once the software design phase was completed the bioreactor was assembled using a combination of commercially available, custom machined, and 3-D printed parts. We utilized the bioreactor to evaluate the effect of a 4-hour stretch protocol on the contractile properties of the tissue after which immunohistological assessment of the tissue was also performed. Results An increase in contractile force was observed after the strain protocol of 10% stretch at 1Hz, with no significant increase observed in the control group. Additionally, an increase in cardiac myofibril alignment, connexin 43 expression, and collagen type I distribution were noted. Conclusion In this study we demonstrated the effectiveness of a new bioreactor design to improve contractility of engineered cardiac muscle tissue. PMID:26577484

Development of a Cyclic Strain Bioreactor for Mechanical Enhancement and Assessment of Bioengineered Myocardial Constructs.

PubMed

Salazar, Betsy H; Cashion, Avery T; Dennis, Robert G; Birla, Ravi K

2015-12-01

The purpose of this study was to develop enabling bioreactor technologies using a novel voice coil actuator system for investigating the effects of periodic strain on cardiac patches fabricated with rat cardiomyocytes. The bioengineered muscle constructs used in this study were formed by culturing rat neonatal primary cardiac cells on a fibrin gel. The physical design of the bioreactor was initially conceived using Solidworks to test clearances and perform structural strain analysis. Once the software design phase was completed the bioreactor was assembled using a combination of commercially available, custom machined, and 3-D printed parts. We utilized the bioreactor to evaluate the effect of a 4-h stretch protocol on the contractile properties of the tissue after which immunohistological assessment of the tissue was also performed. An increase in contractile force was observed after the strain protocol of 10% stretch at 1 Hz, with no significant increase observed in the control group. Additionally, an increase in cardiac myofibril alignment, connexin 43 expression, and collagen type I distribution were noted. In this study we demonstrated the effectiveness of a new bioreactor design to improve contractility of engineered cardiac muscle tissue.

Biventricular structural and functional responses to aortic constriction in a rabbit model of chronic right ventricular pressure overload.

PubMed

Apitz, Christian; Honjo, Osami; Humpl, Tilman; Li, Jing; Assad, Renato S; Cho, Mi Y; Hong, James; Friedberg, Mark K; Redington, Andrew N

2012-12-01

Chronic right ventricular (RV) pressure overload results in pathologic RV hypertrophy and diminished RV function. Although aortic constriction has been shown to improve systolic function in acute RV failure, its effect on RV responses to chronic pressure overload is unknown. Adjustable vascular banding devices were placed on the main pulmonary artery and descending aorta. In 5 animals (sham group), neither band was inflated. In 9 animals (PAB group), only the pulmonary arterial band was inflated, with adjustments on a weekly basis to generate systemic or suprasystemic RV pressure at 28 days. In 9 animals, both pulmonary arterial and aortic devices were inflated (PAB + AO group), the pulmonary arterial band as for the PAB group and the aortic band adjusted to increase proximal systolic blood pressure by approximately 20 mm Hg. Effects on the functional performance were assessed 5 weeks after surgery by conductance catheters, followed by histologic and molecular assessment. Contractile performance was significantly improved in the PAB + AO group versus the PAB group for both ventricles. Relative to sham-operated animals, both banding groups showed significant differences in myocardial histologic and molecular responses. Relative to the PAB group, the PAB + AO group showed significantly decreased RV cardiomyocyte diameter, decreased RV collagen content, and reduced RV expression of endothelin receptor type B, matrix metalloproteinase 9, and transforming growth factor β genes. Aortic constriction in an experimental model of chronic RV pressure overload not only resulted in improved biventricular systolic function but also improved myocardial remodeling. These data suggest that chronically increased left ventricular afterload leads to a more physiologically hypertrophic response in the pressure-overloaded RV. Copyright © 2012 The American Association for Thoracic Surgery. Published by Mosby, Inc. All rights reserved.

Alcohol and Apoptosis: Friends or Foes?

PubMed

Rodriguez, Ana; Chawla, Karan; Umoh, Nsini A; Cousins, Valerie M; Ketegou, Assama; Reddy, Madhumati G; AlRubaiee, Mustafa; Haddad, Georges E; Burke, Mark W

2015-11-19

Alcohol abuse causes 79,000 deaths stemming from severe organ damage in the United States every year. Clinical manifestations of long-term alcohol abuse on the cardiac muscle include defective contractility with the development of dilated cardiomyopathy and low-output heart failure; which has poor prognosis with less than 25% survival for more than three years. In contrast, low alcohol consumption has been associated with reduced risk of cardiovascular disease, however the mechanism of this phenomenon remains elusive. The aim of this study was to determine the significance of apoptosis as a mediating factor in cardiac function following chronic high alcohol versus low alcohol exposure. Adult rats were provided 5 mM (low alcohol), 100 mM (high alcohol) or pair-fed non-alcohol controls for 4-5 months. The hearts were dissected, sectioned and stained with cresyl violet or immunohistochemically for caspase-3, a putative marker for apoptosis. Cardiomyocytes were isolated to determine the effects of alcohol exposure on cell contraction and relaxation. High alcohol animals displayed a marked thinning of the left ventricular wall combined with elevated caspase-3 activity and decreased contractility. In contrast, low alcohol was associated with increased contractility and decreased apoptosis suggesting an overall protective mechanism induced by low levels of alcohol exposure.