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.

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

Role of nitric oxide in in vitro contractile activity of the third compartment of the stomach in llamas.

PubMed

Van Hoogmoed, L; Rakestraw, P C; Snyder, J R; Harmon, F A

1998-09-01

To determine the role of nitric oxide and an apamin-sensitive nonadrenergic-noncholinergic inhibitory transmitter in in vitro contractile activity of the third compartment in llamas. Isolated strips of third compartment of the stomach from 5 llamas. Strips were mounted in tissue baths containing oxygenated Kreb's buffer solution and connected to a polygraph chart recorder to measure contractile activity. Atropine, guanethidine, and indomethacin were added to tissue baths to inhibit muscarinic receptors, adrenoreceptors, and prostaglandin synthesis. Responses to electrical field stimulation following addition of the nitric oxide antagonist Nwo-nitro-L-arginine methyl ester (L-NAME) and apamin were evaluated. Electrical field stimulation (EFS) resulted in a reduction in the amplitude and frequency of contractile activity, followed by rebound contraction when EFS was stopped. Addition of L-NAME resulted in a significant reduction in inhibition of contractile activity. Addition of apamin also resulted in a significant reduction in inhibitory contractile activity at most stimulation frequencies. The combination of L-NAME and apamin resulted in a significant reduction in inhibition at all frequencies. Nitric oxide and a transmitter acting via an apamin-sensitive mechanism appear to be involved in inhibition of contractile activity of the third compartment in llamas. Results suggest that nitric oxide plays an important role in mediating contractile activity of the third compartment in llamas. Use of nitric oxide synthase inhibitors may have a role in the therapeutic management of llamas with lesions of the third compartment.

Plasticity of TOM complex assembly in skeletal muscle mitochondria in response to chronic contractile activity.

PubMed

Joseph, Anna-Maria; Hood, David A

2012-03-01

We investigated the assembly of the TOM complex within skeletal muscle under conditions of chronic contractile activity-induced mitochondrial biogenesis. Tom40 import into mitochondria was increased by chronic contractile activity, as was its time-dependent assembly into the TOM complex. These changes coincided with contractile activity-induced augmentations in the expression of key protein import machinery components Tim17, Tim23, and Tom22, as well as the cytosolic chaperone Hsp90. These data indicate the adaptability of the TOM protein import complex and suggest a regulatory role for the assembly of this complex in exercise-induced mitochondrial biogenesis. Copyright © 2011 Elsevier B.V. and Mitochondria Research Society. All rights reserved. All rights reserved.

Electrical and contractile activities of the human rectosigmoid.

PubMed Central

Sarna, S; Latimer, P; Campbell, D; Waterfall, W E

1982-01-01

Electrical and mechanical activities were recorded from the rectosigmoid of normal subjects using an intraluminal recording tube with two sets of bipolar electrodes and strain gauges. Four distinct types of electrical activities were recorded. (1) Electrical control activity (ECA). This activity varied in amplitude and frequency over time and the control waves were not phase-locked. The means of dominant frequency components in the lower and higher frequency ranges were 3.86 +/- 0.18 SD and 10.41 +/- 0.46 SD c/min, respectively. The overall dominant frequency component was mostly in the lower frequency range of 2.0-9.0 c/min. (2) Discrete electrical response activity (DERA). This activity appeared as short duration bursts (less than 10 s) of response potentials whose repetition rate was in the total colonic electrical control activity frequency range of 2.0-13.0 c/min. The mean duration of this activity was 2.24 +/- 1.30 SD s. (3) Continuous electrical response activity (CERA). This activity appeared as long duration bursts (greater than 10 s) of response potentials which were not related to electrical control activity. Its mean duration was 14.78 +/- 3.68 SD s. This activity generally did not propagate. (4) Contractile electrical complex (CEC). This activity appeared as oscillations in the frequency range of 25-40 c/min and was also not related to electrical control activity. This activity propagated, sometimes proximally and sometimes distally. Its mean duration was 18.87 +/- 9.22 SD s. The latter three types of electrical activities were all associated with different types of contractions. These contractions, however, did not always occlude the lumen. Colonic electrical control activity controls the appearance of discrete electrical response activity in time and space. The mechanism of generation of continuous electrical response activity and contractile electrical complex is not yet known. PMID:7095566

Compensatory Hypertrophy of Skeletal Muscle: Contractile Characteristics

ERIC Educational Resources Information Center

Ianuzzo, C. D.; Chen, V.

1977-01-01

Describes an experiment using rats that demonstrates contractile characteristics of normal and hypertrophied muscle. Compensatory hypertrophy of the plantaris muscle is induced by surgical removal of the synergistic gastrocnemium muscle. Includes methods for determination of contractile properties of normal and hypertrophied muscle and…

Contractile properties are disrupted in Becker muscular dystrophy, but not in limb girdle type 2I.

PubMed

Løkken, Nicoline; Hedermann, Gitte; Thomsen, Carsten; Vissing, John

2016-09-01

We investigated whether a linear relationship between muscle strength and cross-sectional area (CSA) is preserved in calf muscles of patients with Becker muscular dystrophy (BMD, n = 14) and limb-girdle type 2I muscular dystrophy (LGMD2I, n = 11), before and after correcting for muscle fat infiltration. The Dixon magnetic resonance imaging technique was used to quantify fat and calculate a fat-free contractile CSA. Strength was assessed by dynamometry. Muscle strength/CSA relationships were significantly lower in patients versus controls. The strength/contractile-CSA relationship was still severely lowered in BMD, but was almost normalized in LGMD2I. Our findings suggest close to intact contractile properties in LGMD2I, which are severely disrupted in BMD. Ann Neurol 2016;80:466-471. © 2016 American Neurological Association.

Contractile and mechanical properties of epithelia with perturbed actomyosin dynamics.

PubMed

Fischer, Sabine C; Blanchard, Guy B; Duque, Julia; Adams, Richard J; Arias, Alfonso Martinez; Guest, Simon D; Gorfinkiel, Nicole

2014-01-01

Mechanics has an important role during morphogenesis, both in the generation of forces driving cell shape changes and in determining the effective material properties of cells and tissues. Drosophila dorsal closure has emerged as a reference model system for investigating the interplay between tissue mechanics and cellular activity. During dorsal closure, the amnioserosa generates one of the major forces that drive closure through the apical contraction of its constituent cells. We combined quantitation of live data, genetic and mechanical perturbation and cell biology, to investigate how mechanical properties and contraction rate emerge from cytoskeletal activity. We found that a decrease in Myosin phosphorylation induces a fluidization of amnioserosa cells which become more compliant. Conversely, an increase in Myosin phosphorylation and an increase in actin linear polymerization induce a solidification of cells. Contrary to expectation, these two perturbations have an opposite effect on the strain rate of cells during DC. While an increase in actin polymerization increases the contraction rate of amnioserosa cells, an increase in Myosin phosphorylation gives rise to cells that contract very slowly. The quantification of how the perturbation induced by laser ablation decays throughout the tissue revealed that the tissue in these two mutant backgrounds reacts very differently. We suggest that the differences in the strain rate of cells in situations where Myosin activity or actin polymerization is increased arise from changes in how the contractile forces are transmitted and coordinated across the tissue through ECadherin-mediated adhesion. Altogether, our results show that there is an optimal level of Myosin activity to generate efficient contraction and suggest that the architecture of the actin cytoskeleton and the dynamics of adhesion complexes are important parameters for the emergence of coordinated activity throughout the tissue.

Contractile and Mechanical Properties of Epithelia with Perturbed Actomyosin Dynamics

PubMed Central

Fischer, Sabine C.; Blanchard, Guy B.; Duque, Julia; Adams, Richard J.; Arias, Alfonso Martinez; Guest, Simon D.; Gorfinkiel, Nicole

2014-01-01

Mechanics has an important role during morphogenesis, both in the generation of forces driving cell shape changes and in determining the effective material properties of cells and tissues. Drosophila dorsal closure has emerged as a reference model system for investigating the interplay between tissue mechanics and cellular activity. During dorsal closure, the amnioserosa generates one of the major forces that drive closure through the apical contraction of its constituent cells. We combined quantitation of live data, genetic and mechanical perturbation and cell biology, to investigate how mechanical properties and contraction rate emerge from cytoskeletal activity. We found that a decrease in Myosin phosphorylation induces a fluidization of amnioserosa cells which become more compliant. Conversely, an increase in Myosin phosphorylation and an increase in actin linear polymerization induce a solidification of cells. Contrary to expectation, these two perturbations have an opposite effect on the strain rate of cells during DC. While an increase in actin polymerization increases the contraction rate of amnioserosa cells, an increase in Myosin phosphorylation gives rise to cells that contract very slowly. The quantification of how the perturbation induced by laser ablation decays throughout the tissue revealed that the tissue in these two mutant backgrounds reacts very differently. We suggest that the differences in the strain rate of cells in situations where Myosin activity or actin polymerization is increased arise from changes in how the contractile forces are transmitted and coordinated across the tissue through ECadherin-mediated adhesion. Altogether, our results show that there is an optimal level of Myosin activity to generate efficient contraction and suggest that the architecture of the actin cytoskeleton and the dynamics of adhesion complexes are important parameters for the emergence of coordinated activity throughout the tissue. PMID:24759936

Contractile properties of skinned muscle fibres from young and adult normal and dystrophic (mdx) mice.

PubMed Central

Williams, D A; Head, S I; Lynch, G S; Stephenson, D G

1993-01-01

1. Single muscle fibres were enzymatically isolated from the soleus and extensor digitorum longus (EDL) muscles of genetically dystrophic mdx and normal (C57BL/10) mice aged 3-6 or 17-23 weeks. 2. Fibres of both muscles were chemically skinned with the non-ionic detergent Triton X-100 (2% v/v). Ca(2+)- and Sr(2+)-activated contractile responses were recorded and comparisons were made between several contractile parameters of various fibre types of normal and dystrophic mice of similar age. 3. There were no significant differences in the following contractile parameters of skinned fibres of normal and mdx mice of the same age: sensitivity to activating Ca2+ (pCa50) or Sr2+ (pSr50) and differential sensitivity to the activating ions (pCa50-pSr50). However the maximum isometric tension (Po) and the frequency of myofibrillar force oscillations in EDL fast-twitch fibres of young mdx mice were significantly lower than those of soleus fast-twitch fibres of the same animals, or fast-twitch fibres (EDL or soleus) of normal mice. 4. Age-related differences were apparent in some contractile parameters of both normal and mdx mice. In particular the steepness of force-pCa and force-pSr curves increased with age in normal mice, yet decreased with age in fibres of mdx mice. 5. A fluorescent probe, ethidium bromide, which interchelates with DNA, was used with laser-scanning confocal microscopy to determine the distribution of myonuclei in fibres. Fibres isolated from either muscle type of normal animals displayed a characteristic peripheral spiral of myonuclei. Fibres from muscles of mdx mice displayed three major patterns of nuclear distribution; the normal peripheral spiral, long central strands of nuclei, and a mixture of these two patterns. 6. The contractile characteristics of mdx fibres were not markedly influenced by the nuclear distribution pattern in that there were no discernible differences in the major contractile parameters (the Hill coefficients nCa and nSr, which

Disordered Actomyosin Is Sufficient to Promote Cooperative and Telescopic Contractility

NASA Astrophysics Data System (ADS)

Murrell, Michael; Linsmeier, Ian; Banerjee, Shiladitya; Kim, Tae Yoon; Jung, Wonyeong; Oakes, Patrick

While the molecular interactions between myosin motors and F-actin are well known, the relationship between F-actin organization and myosin-mediated force generation remains poorly understood. Here, we explore the accumulation of myosin-induced stresses within a 2D biomimetic model of the actomyosin cortex, where myosin activity is controlled spatially and temporally using light. By controlling the geometry and the duration of myosin activation, we show that contraction of disordered actomyosin is highly cooperative, telescopic with the activation area and generates a pattern of mechanical stresses consistent with those observed in contractile cells. We quantitatively reproduce these properties using an in vitro isotropic model of the actomyosin cytoskeleton, and explore the physical origins of telescopic contractility in disordered networks using agent-based simulations. NSF CMMI-1525316.

Contractile properties of the pig bladder mucosa in response to neurokinin A: a role for myofibroblasts?

PubMed Central

Sadananda, P; Chess-Williams, R; Burcher, E

2008-01-01

Background and purpose: The bladder urothelium is now known to have active properties. Our aim was to investigate the contractile properties of the urinary mucosa in response to the tachykinin neurokinin A (NKA) and carbachol. Experimental approach: Discrete concentration–response curves for carbachol and NKA were obtained in matched strips of porcine detrusor, mucosa and intact bladder, suspended in organ baths. The effects of inhibitors and tachykinin receptor antagonists were studied on NKA-mediated contractions in mucosal strips. Intact sections of bladder and experimental strips were processed for histology and immunohistochemistry. Key results: All types of strips contracted to both carbachol and NKA. Mucosal responses to NKA (pD2 7.2) were higher than those in intact strips and were inhibited by the NK2 receptor antagonist SR48968 (pKB 9.85) but not the NK1 receptor antagonist SR140333, tetrodotoxin or indomethacin. Immunostaining for smooth muscle actin and vimentin occurred under the urothelium and on blood vessels. Desmin immunostaining and histological studies showed only sparse smooth muscle to be present in the mucosal strips. Removal of smooth muscle remnants from mucosal strips did not alter the responses to NKA. Conclusions and implications: This study has shown both functional and histological evidence for contractile properties of the mucosa, distinct from the detrusor. Mucosal contractions to NKA appear to be directly mediated via NK2 receptors. The main cell type mediating mucosal contractions is suggested to be suburothelial myofibroblasts. Mucosal contractions may be important in vivo for matching the luminal surface area to bladder volume. PMID:18264120

[Effect of acetylcholine and acetylcholinesterase on the activity of contractile vacuole of Amoeba proteus].

PubMed

Bagrov, Ia Iu; Manusova, N B

2011-01-01

Acetylcholine (ACh, 1 microM) stimulates activity of the contractile vacuole of proteus. The effect of ACh is not mimicked by its analogs which are not hydrolyzed by acetylcholinesterase (AChE), i. e., carbacholine and 5-methylfurmethide. The effect of ACh is not sensitive to the blocking action of M-cholinolytics, atropine and mytolone, but is suppressed by N-cholinolytic, tubocurarine. The inhibitors of AChE, eserine (0.01 microM) and armine (0.1 microM), suppress the effect of ACh on amoeba contractile vacuole. ACh does not affect activation of contractile vacuole induced by arginine-vasopressin (1 microM), but it blocks such effect of opiate receptors agonist, dynorphin A1-13 (0.01 microM). This effect of ACh is also suppressed by the inhibitors of AChE. These results suggest that, in the above-described effects of ACh, AChE acts not as an antagonist, but rather as a synergist.

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

Muscular tissues of the squid Doryteuthis pealeii express identical myosin heavy chain isoforms: an alternative mechanism for tuning contractile speed

PubMed Central

Shaffer, Justin F.; Kier, William M.

2012-01-01

SUMMARY The speed of muscle contraction is largely controlled at the sarcomere level by the ATPase activity of the motor protein myosin. Differences in amino acid sequence in catalytically important regions of myosin yield different myosin isoforms with varying ATPase activities and resulting differences in cross-bridge cycling rates and interfilamentary sliding velocities. Modulation of whole-muscle performance by changes in myosin isoform ATPase activity is regarded as a universal mechanism to tune contractile properties, especially in vertebrate muscles. Invertebrates such as squid, however, may exhibit an alternative mechanism to tune contractile properties that is based on differences in muscle ultrastructure, including variable myofilament and sarcomere lengths. To determine definitively whether contractile properties of squid muscles are regulated via different myosin isoforms (i.e. different ATPase activities), the nucleotide and amino acid sequences of the myosin heavy chain from the squid Doryteuthis pealeii were determined from the mantle, arm, tentacle, fin and funnel retractor musculature. We identified three myosin heavy chain isoforms in squid muscular tissues, with differences arising at surface loop 1 and the carboxy terminus. All three isoforms were detected in all five tissues studied. These results suggest that the muscular tissues of D. pealeii express identical myosin isoforms, and it is likely that differences in muscle ultrastructure, not myosin ATPase activity, represent the most important mechanism for tuning contractile speeds. PMID:22189767

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

Differential effects of peroxynitrite on contractile protein properties in fast- and slow-twitch skeletal muscle fibers of rat.

PubMed

Dutka, T L; Mollica, J P; Lamb, G D

2011-03-01

Oxidative modification of contractile proteins is thought to be a key factor in muscle weakness observed in many pathophysiological conditions. In particular, peroxynitrite (ONOO(-)), a potent short-lived oxidant, is a likely candidate responsible for this contractile dysfunction. In this study ONOO(-) or 3-morpholinosydnonimine (Sin-1, a ONOO(-) donor) was applied to rat skinned muscle fibers to characterize the effects on contractile properties. Both ONOO(-) and Sin-1 exposure markedly reduced maximum force in slow-twitch fibers but had much less effect in fast-twitch fibers. The rate of isometric force development was also reduced without change in the number of active cross bridges. Sin-1 exposure caused a disproportionately large decrease in Ca(2+) sensitivity, evidently due to coproduction of superoxide, as it was prevented by Tempol, a superoxide dismutase mimetic. The decline in maximum force with Sin-1 and ONOO(-) treatments could be partially reversed by DTT, provided it was applied before the fiber was activated. Reversal by DTT indicates that the decrease in maximum force was due at least in part to oxidation of cysteine residues. Ascorbate caused similar reversal, further suggesting that the cysteine residues had undergone S-nitrosylation. The reduction in Ca(2+) sensitivity, however, was not reversed by either DTT or ascorbate. Western blot analysis showed cross-linking of myosin heavy chain (MHC) I, appearing as larger protein complexes after ONOO(-) exposure. The findings suggest that ONOO(-) initially decreases maximum force primarily by oxidation of cysteine residues on the myosin heads, and that the accompanying decrease in Ca(2+) sensitivity is likely due to other, less reversible actions of hydroxyl or related radicals.

The effect of exercise hypertrophy and disuse atrophy on muscle contractile properties: a mechanomyographic analysis.

PubMed

Than, Christian; Tosovic, Danijel; Seidl, Laura; Mark Brown, J

2016-12-01

To determine whether mechanomyographic (MMG) determined contractile properties of the biceps brachii change during exercise-induced hypertrophy and subsequent disuse atrophy. Healthy subjects (mean ± SD, 23.7 ± 2.6 years, BMI 21.8 ± 2.4, n = 19) performed unilateral biceps curls (9 sets × 12 repetitions, 5 sessions per week) for 8 weeks (hypertrophic phase) before ceasing exercise (atrophic phase) for the following 8 weeks (non-dominant limb; treatment, dominant limb; control). MMG measures of muscle contractile properties (contraction time; T c , maximum displacement; D max , contraction velocity; V c ), electromyographic (EMG) measures of muscle fatigue (median power frequency; MPF), strength measures (maximum voluntary contraction; MVC) and measures of muscle thickness (ultrasound) were obtained. Two-way repeated measures ANOVA showed significant differences (P < 0.05) between treatment and control limbs. During the hypertrophic phase treatment MVC initially declined (weeks 1-3), due to fatigue (decline in MPF), followed by improvement against control during weeks 6-8. Between weeks 5 and 8 treatment, muscle thickness was greater than control, reflecting gross hypertrophy. MMG variables Dmax (weeks 2, 7) and Vc (weeks 7, 8) declined. During the atrophic phase, MVC (weeks 9-12) and muscle thickness (weeks 9, 10) initially remained high before declining to control levels, reflecting gross atrophy. MMG variables D max (weeks 9, 14) and V c (weeks 9, 14, 15) also declined during the atrophic phase. No change in T c was found throughout the hypertrophic or atrophic phases. MMG detects changes in contractile properties during stages of exercise-induced hypertrophy and disuse atrophy suggesting its applicability as a clinical tool in musculoskeletal rehabilitation.

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.

Effect of season on contractile and metabolic properties of desert camel muscle (Camelus dromedarius).

PubMed

Abdelhadi, O M A; Babiker, S A; Picard, B; Jurie, C; Jailler, R; Hocquette, J F; Faye, B

2012-01-01

Thirty fattened one humped desert camels were used to examine the effect of season on contractile and metabolic properties of Longissimus thoracis (LT) muscle. Ten camels were slaughtered according to seasons of the year (winter, summer and autumn). Season significantly influenced muscle chemical composition, ultimate pH (pHu) and color. Activities of metabolic enzymes were higher during autumn season compared to summer and winter for phosphofructokinase (+64% compared to both seasons) and for isocitrate dehydrogenase (+35% and +145% in autumn vs. summer and winter, respectively). Quantification of muscle myosin heavy chain isoforms by SDS-PAGE electrophoresis showed only presence of type I and type IIa MyHC in camel muscle and indicated high proportion in winter for type I and in autumn for type IIa with respect to other seasons. Several correlations between different MyHC proportions and enzyme activities were reported. These findings indicated that muscle characteristics in camels are influenced by season. Copyright © 2011 Elsevier Ltd. All rights reserved.

Contractile properties of rat, rhesus monkey, and human type I muscle fibers

NASA Technical Reports Server (NTRS)

Widrick, J. J.; Romatowski, J. G.; Karhanek, M.; Fitts, R. H.

1997-01-01

It is well known that skeletal muscle intrinsic maximal shortening velocity is inversely related to species body mass. However, there is uncertainty regarding the relationship between the contractile properties of muscle fibers obtained from commonly studied laboratory animals and those obtained from humans. In this study we determined the contractile properties of single chemically skinned fibers prepared from rat, rhesus monkey, and human soleus and gastrocnemius muscle samples under identical experimental conditions. All fibers used for analysis expressed type I myosin heavy chain as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Allometric coefficients for type I fibers from each muscle indicated that there was little change in peak tension (force/fiber cross-sectional area) across species. In contrast, both soleus and gastrocnemius type I fiber maximal unloaded shortening velocity (Vo), the y-intercept of the force-velocity relationship (Vmax), peak power per unit fiber length, and peak power normalized for fiber length and cross-sectional area were all inversely related to species body mass. The present allometric coefficients for soleus fiber Vo (-0.18) and Vmax (-0.11) are in good agreement with published values for soleus fibers obtained from common laboratory and domesticated mammals. Taken together, these observations suggest that the Vo of slow fibers from quadrupeds and humans scale similarly and can be described by the same quantitative relationships. These findings have implications in the design and interpretation of experiments, especially those that use small laboratory mammals as a model of human muscle function.

Endoplasmic reticulum Chaperon Tauroursodeoxycholic Acid Alleviates Obesity-Induced Myocardial Contractile Dysfunction

PubMed Central

Ceylan-Isik, Asli F.; Sreejayan, Nair; Ren, Jun

2010-01-01

ER stress is involved in the pathophysiology of obesity although little is known about the role of ER stress on obesity-associated cardiac dysfunction. This study was designed to examine the effect of ER chaperone tauroursodeoxycholic acid (TUDCA) on obesity-induced myocardial dysfunction. Adult lean and ob/ob obese mice were treated TUDCA (50 mg/kg/d, p.o.) or vehicle for 5 wks. Oral glucose tolerance test (OGTT) was performed. Echocardiography, cardiomyocyte contractile and intracellular Ca2+ properties were assessed. Sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) activity and protein expression of intracellular Ca2+ regulatory proteins were measured using 45Ca2+ uptake and Western blot analysis, respectively. Insulin signaling, ER stress markers and HSP90 were evaluated. Our results revealed that chronic TUDCA treatment lower systolic blood pressure and lessened glucose intolerance in obese mice. Obesity led to increased diastolic diameter, cardiac hypertrophy, compromised fractional shortening, cardiomyocyte contractile (peak shortening, maximal velocity of shortening/relengthening, and duration of contraction/relaxation) and intracellular Ca2+ properties, all of which were significantly attenuated by TUDCA. TUDCA reconciled obesity-associated decreased in SERCA activity and expression, and increase in serine phosphorylation of IRS, total and phosphorylated cJun, ER stress markers Bip, peIF2α and pPERK. Obesity-induced changes in phospholamban and HSP90 were unaffected by TUDCA. In vitro finding revealed that TUDCA ablated palmitic acid-induced cardiomyocyte contractile dysfunction. In summary, these data depicted a pivotal role of ER stress in obesity-associated cardiac contractile dysfunction, suggesting the therapeutic potential of ER stress as a target in the management of cardiac dysfunction in obesity. PMID:21035453

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.

Recently active contractile deformation in the forearc of southern Peru

NASA Astrophysics Data System (ADS)

Hall, S. R.; Farber, D.; Audin, L.; Finkel, R. C.

2010-12-01

In the Precordillera and Western Cordillera of southern Peru (14°-18°S), vast pediment surfaces have been abandoned through drainage diversion and river incision, with the major drainages carving deep canyons. Within this region, we have identified range-sub-parallel contractile structures that accommodate significant distributed crustal deformation. Young geomorphic features document both the presence and youthfulness of these contractile structures. Here, we determine exposure ages on geomorphic features such as pediment surfaces and fluvial terraces using in situ produced cosmogenic radionuclides, in conjunction with field and remote mapping. This chronologic data reveals that ancient surfaces have been preserved as a result of very low erosion rates. We measure this rate to be <0.5m/Ma on genetically similar surfaces spanning over 4 degrees of latitude throughout this region. While many ancient surfaces are preserved in forearc localities, we also observe young (30ka-1Ma) low-relief pediment surfaces modified by recent processes. Specifically, active structures accommodating compressional stresses locally displace active drainages and offset river terraces leading to their abandonment. Based on our chronology and geomorphic mapping, we calculate a Pleistocene river incision rate of ~0.3mm/yr determined from data collected along exoreic rivers. This rate is consistent with longer-term incision rates measured in other localities along this margin. We suggest that, in this region of southern Peru, the steep western wedge of the Andean margin supports the high topography of the Altiplano through a combination of uplift along steeply dipping contractile west-vergent structures and isostatic responses to the focused removal of large amounts of crustal material through canyon incision. Further, that these range sub-parallel structures are related at depth to a thrust system that plays a role in not only the maintenance of the Andean margin, but potentially in its

In situ assessment of shortening and lengthening contractile properties of hind limb ankle flexors in intact mice.

PubMed

Gorselink, M; Drost, M R; de Louw, J; Willems, P J; Hesselink, M K; Dekkers, E C; Rosielle, N; van der Vusse, G J

2001-05-01

The availability of animal models with disrupted genes has increased the need for small-scale measurement devices. Recently, we developed an experimental device to assess in situ mechanical properties of isometric contractions of intact muscle complexes of the mouse. Although this apparatus provides valuable information on muscle mechanical performance, it is not appropriate for determining contractile properties during shortening and lengthening contractions. In the present study we therefore developed and evaluated an experimental apparatus for assessment of shortening and lengthening contractile properties of intact plantar and dorsal flexors of the mouse. The current through a custom-built, low-inertia servomotor was measured to assess contractile muscular torque ranging from -50 to mN.m. Evaluation of the fixation procedure of the animal to the apparatus via 3-D monitoring of the muscle-tendon complex length showed that the additional shortening in length due to a contraction with maximal torque output has only minor effects on the measured torque. Furthermore, misalignment of the axis of rotation of the apparatus relative to the axis of rotation in the ankle joint, i.e. eccentricity, during a routine experiment was estimated to be less than 1.0 mm and hence did not influence the measured torque output under our experimental conditions. Peak power per unit muscle mass (mean +/- SD) of intact dorsal and plantar flexors was 0.27 +/- 0.02 and 0.19 +/- 0.03 W.g-1, respectively. The angular velocity at maximal peak power generated by the dorsal flexor complex and the plantar flexor complex was 1100 +/- 190 and 700 +/- 90 degrees.s-1, respectively.

Gene transfer of heterologous G protein-coupled receptors to cardiomyocytes: differential effects on contractility.

PubMed

Laugwitz, K L; Weig, H J; Moretti, A; Hoffmann, E; Ueblacker, P; Pragst, I; Rosport, K; Schömig, A; Ungerer, M

2001-04-13

In heart failure, reduced cardiac contractility is accompanied by blunted cAMP responses to beta-adrenergic stimulation. Parathyroid hormone (PTH)-related peptide and arginine vasopressin are released from the myocardium in response to increased wall stress but do not stimulate contractility or adenylyl cyclase at physiological concentrations. To bypass the defective beta-adrenergic signaling cascade, recombinant P1 PTH/PTH-related peptide receptors (rPTH1-Rs) and V(2) vasopressin receptors (rV(2)-Rs), which are normally not expressed in the myocardium and which are both strongly coupled to adenylyl cyclase, and recombinant beta(2)-adrenergic receptors (rbeta(2)-ARs) were overexpressed in cardiomyocytes by viral gene transfer. The capacity of endogenous hormones to increase contractility via the heterologous, recombinant receptors was compared. Whereas V(2)-Rs are uniquely coupled to Gs, PTH1-Rs and beta(2)-ARs are also coupled to other G proteins. Gene transfer of rPTH1-Rs or rbeta(2)-ARs to adult cardiomyocytes resulted in maximally increased basal contractility, which could not be further stimulated by adding receptor agonists. Agonists at rPTH1-Rs induced increased cAMP formation and phospholipase C activity. In contrast, healthy or failing rV(2)-R-expressing cardiomyocytes showed unaltered basal contractility. Their contractility and cAMP formation increased only at agonist exposure, which did not activate phospholipase C. In summary, we found that gene transfer of PTH1-Rs to cardiomyocytes results in constitutive activity of the transgene, as does that of beta(2)-ARS: In the absence of receptor agonists, rPTH1-Rs and rbeta(2)-ARs increase basal contractility, coupling to 2 G proteins simultaneously. In contrast, rV(2)-Rs are uniquely coupled to Gs and are not constitutively active, retaining their property to be activated exclusively on agonist stimulation. Therefore, gene transfer of V(2)-Rs might be more suited to test the effects of c

Mitochondrial fusion dynamics is robust in the heart and depends on calcium oscillations and contractile activity

PubMed Central

Eisner, Verónica; Gao, Erhe; Csordás, György; Slovinsky, William S.; Paillard, Melanie; Cheng, Lan; Ibetti, Jessica; Chen, S. R. Wayne; Chuprun, J. Kurt; Hoek, Jan B.; Koch, Walter J.; Hajnóczky, György

2017-01-01

Mitochondrial fusion is thought to be important for supporting cardiac contractility, but is hardly detectable in cultured cardiomyocytes and is difficult to directly evaluate in the heart. We overcame this obstacle through in vivo adenoviral transduction with matrix-targeted photoactivatable GFP and confocal microscopy. Imaging in whole rat hearts indicated mitochondrial network formation and fusion activity in ventricular cardiomyocytes. Promptly after isolation, cardiomyocytes showed extensive mitochondrial connectivity and fusion, which decayed in culture (at 24–48 h). Fusion manifested both as rapid content mixing events between adjacent organelles and slower events between both neighboring and distant mitochondria. Loss of fusion in culture likely results from the decline in calcium oscillations/contractile activity and mitofusin 1 (Mfn1), because (i) verapamil suppressed both contraction and mitochondrial fusion, (ii) after spontaneous contraction or short-term field stimulation fusion activity increased in cardiomyocytes, and (iii) ryanodine receptor-2–mediated calcium oscillations increased fusion activity in HEK293 cells and complementing changes occurred in Mfn1. Weakened cardiac contractility in vivo in alcoholic animals is also associated with depressed mitochondrial fusion. Thus, attenuated mitochondrial fusion might contribute to the pathogenesis of cardiomyopathy. PMID:28096338

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

Ultraslow myosin molecular motors of placental contractile stem villi in humans.

PubMed

Lecarpentier, Yves; Claes, Victor; Lecarpentier, Edouard; Guerin, Catherine; Hébert, Jean-Louis; Arsalane, Abdelilah; Moumen, Abdelouahab; Krokidis, Xénophon; Michel, Francine; Timbely, Oumar

2014-01-01

Human placental stem villi (PSV) present contractile properties. In vitro mechanics were investigated in 40 human PSV. Contraction of PSV was induced by both KCl exposure (n = 20) and electrical tetanic stimulation (n = 20). Isotonic contractions were registered at several load levels ranging from zero-load up to isometric load. The tension-velocity relationship was found to be hyperbolic. This made it possible to apply the A. Huxley formalism for determining the rate constants for myosin cross-bridge (CB) attachment and detachment, CB single force, catalytic constant, myosin content, and maximum myosin ATPase activity. These molecular characteristics of myosin CBs did not differ under either KCl exposure or tetanus. A comparative approach was established from studies previously published in the literature and driven by mean of a similar method. As compared to that described in mammalian striated muscles, we showed that in human PSV, myosin CB rate constants for attachment and detachment were about 103 times lower whereas myosin ATPase activity was 105 times lower. Up to now, CB kinetics of contractile cells arranged along the long axis of the placental sheath appeared to be the slowest ever observed in any mammalian contractile tissue.

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

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.

Contractile forces originating from Cancer Diskiod regulated by geometrical ECM properties

NASA Astrophysics Data System (ADS)

Alobaidi, Amani; Sun, Bo

Cancer cell migration in three-dimensional extracellular matrix is a major cause of death for cancer patients. Although extensive studies have enlightened detailed mechanism of single cell 3D invasion and cell-ECM interaction, 3D collective cancer invasion is still poorly understood. To capture collective cancer invasion with more realistic, we developed a novel 3D invasion assay, Diskiod In Geometrically Micropatterned ECM (DIGME). DIGME allows us to independently controlling the shape the shape of tumor organoids, microstructure and spatial heterogeneity of the extracellular matrix all at the same time. Here we study the affect of contractile forces originating from different geometrical cancer diskiods. We show that cancer invasion could be regulated by geometrical ECM properties.

Differential effects of targeted tongue exercise and treadmill running on aging tongue muscle structure and contractile properties.

PubMed

Kletzien, Heidi; Russell, John A; Leverson, Glen E; Connor, Nadine P

2013-02-15

Age-associated changes in tongue muscle structure and strength may contribute to dysphagia in elderly people. Tongue exercise is a current treatment option. We hypothesized that targeted tongue exercise and nontargeted exercise that activates tongue muscles as a consequence of increased respiratory drive, such as treadmill running, are associated with different patterns of tongue muscle contraction and genioglossus (GG) muscle biochemistry. Thirty-one young adult, 34 middle-aged, and 37 old Fischer 344/Brown Norway rats received either targeted tongue exercise, treadmill running, or no exercise (5 days/wk for 8 wk). Protrusive tongue muscle contractile properties and myosin heavy chain (MHC) composition in the GG were examined at the end of 8 wk across groups. Significant age effects were found for maximal twitch and tetanic tension (greatest in young adult rats), MHCIIb (highest proportion in young adult rats), MHCIIx (highest proportion in middle-aged and old rats), and MHCI (highest proportion in old rats). The targeted tongue exercise group had the greatest maximal twitch tension and the highest proportion of MHCI. The treadmill running group had the shortest half-decay time, the lowest proportion of MHCIIa, and the highest proportion of MHCIIb. Fatigue was significantly less in the young adult treadmill running group and the old targeted tongue exercise group than in other groups. Thus, tongue muscle structure and contractile properties were affected by both targeted tongue exercise and treadmill running, but in different ways. Studies geared toward optimizing dose and manner of providing targeted and generalized tongue exercise may lead to alternative tongue exercise delivery strategies.

Differential effects of targeted tongue exercise and treadmill running on aging tongue muscle structure and contractile properties

PubMed Central

Kletzien, Heidi; Russell, John A.; Leverson, Glen E.

2013-01-01

Age-associated changes in tongue muscle structure and strength may contribute to dysphagia in elderly people. Tongue exercise is a current treatment option. We hypothesized that targeted tongue exercise and nontargeted exercise that activates tongue muscles as a consequence of increased respiratory drive, such as treadmill running, are associated with different patterns of tongue muscle contraction and genioglossus (GG) muscle biochemistry. Thirty-one young adult, 34 middle-aged, and 37 old Fischer 344/Brown Norway rats received either targeted tongue exercise, treadmill running, or no exercise (5 days/wk for 8 wk). Protrusive tongue muscle contractile properties and myosin heavy chain (MHC) composition in the GG were examined at the end of 8 wk across groups. Significant age effects were found for maximal twitch and tetanic tension (greatest in young adult rats), MHCIIb (highest proportion in young adult rats), MHCIIx (highest proportion in middle-aged and old rats), and MHCI (highest proportion in old rats). The targeted tongue exercise group had the greatest maximal twitch tension and the highest proportion of MHCI. The treadmill running group had the shortest half-decay time, the lowest proportion of MHCIIa, and the highest proportion of MHCIIb. Fatigue was significantly less in the young adult treadmill running group and the old targeted tongue exercise group than in other groups. Thus, tongue muscle structure and contractile properties were affected by both targeted tongue exercise and treadmill running, but in different ways. Studies geared toward optimizing dose and manner of providing targeted and generalized tongue exercise may lead to alternative tongue exercise delivery strategies. PMID:23264540

Adenoviral gene transfer of Akt enhances myocardial contractility and intracellular calcium handling

PubMed Central

Cittadini, A; Monti, MG; Iaccarino, G; Di Rella, F; Tsichlis, PN; Di Gianni, A; Strömer, H; Sorriento, D; Peschle, C; Trimarco, B; Saccà, L; Condorelli, G

2010-01-01

The serine-threonine kinase Akt/PKB mediates stimuli from different classes of cardiomyocyte receptors, including the growth hormone/insulin like growth factor and the β-adrenergic receptors. Whereas the growth-promoting and antiapoptotic properties of Akt activation are well established, little is known about the effects of Akt on myocardial contractility, intracellular calcium (Ca2+) handling, oxygen consumption, and β-adrenergic pathway. To this aim, Sprague–Dawley rats were subjected to a wild-type Akt in vivo adenoviral gene transfer using a catheter-based technique combined with aortopulmonary crossclamping. Left ventricular (LV) contractility and intracellular Ca2+ handling were evaluated in an isolated isovolumic buffer-perfused, aequorin-loaded whole heart preparations 10 days after the surgery. The Ca2+–force relationship was obtained under steady-state conditions in tetanized muscles. No significant hypertrophy was detected in adenovirus with wild-type Akt (Ad.Akt) versus controls rats (LV-to-body weight ratio 2.6±0.2 versus 2.7±0.1 mg/g, controls versus Ad.Akt, P, NS). LV contractility, measured as developed pressure, increased by 41% in Ad.Akt. This was accounted for by both more systolic Ca2+ available to the contractile machinery (+19% versus controls) and by enhanced myofilament Ca2+ responsiveness, documented by an increased maximal Ca2+-activated pressure (+19% versus controls) and a shift to the left of the Ca2+–force relationship. Such increased contractility was paralleled by a slight increase of myocardial oxygen consumption (14%), while titrated dose of dobutamine providing similar inotropic effect augmented oxygen consumption by 39% (P<0.01). Phospholamban, calsequestrin, and ryanodine receptor LV mRNA and protein content were not different among the study groups, while sarcoplasmic reticulum Ca2+ ATPase protein levels were significantly increased in Ad.Akt rats. β-Adrenergic receptor density, affinity, kinase-1 levels, and

Effects of Using Tricaine Methanesulfonate and Metomidate before Euthanasia on the Contractile Properties of Rainbow Trout (Oncorhynchus mykiss) Myocardium

PubMed Central

Roberts, Jordan C; Syme, Douglas A

2016-01-01

Because many anesthetics work through depressing cell excitability, unanesthetized euthanasia has become common for research involving excitable tissues (for example muscle and nerve) to avoid these depressive effects. However, anesthetic use during euthanasia may be indicated for studies involving isolated tissues if the potential depressive effects of brief anesthetic exposure dissipate after subsequent tissue isolation, washout, and saline perfusion. We explore this here by measuring whether, when applied prior to euthanasia, standard immersion doses of 2 fish anesthetics, tricaine methanesulfonate (TMS; 100 mg/L, n = 6) and methyl 1-(1-phenylethyl)-1H-imidazole-5-carboxylate (metomidate, 10 mg/L, n = 6), have residual effects on the contractile properties (force and work output) of isolated and saline-perfused ventricular compact myocardium from rainbow trout (Oncorhynchus mykiss). Results suggest that direct exposure of muscle to immersion doses of TMS—but not metomidate—impairs muscle contractile performance. However, brief exposure (2 to 3 min) to either anesthetic during euthanasia only—providing that the agent is washed out prior to tissue experimentation—does not have an effect on the contractile properties of the myocardium. Therefore, the use of TMS, metomidate, and perhaps other anesthetics that depress cell excitability during euthanasia may be indicated when conducting research on isolated and rinsed tissues. PMID:27657711

Effects of Using Tricaine Methanesulfonate and Metomidate before Euthanasia on the Contractile Properties of Rainbow Trout (Oncorhynchus mykiss) Myocardium.

PubMed

Roberts, Jordan C; Syme, Douglas A

2016-01-01

Because many anesthetics work through depressing cell excitability, unanesthetized euthanasia has become common for research involving excitable tissues (for example muscle and nerve) to avoid these depressive effects. However, anesthetic use during euthanasia may be indicated for studies involving isolated tissues if the potential depressive effects of brief anesthetic exposure dissipate after subsequent tissue isolation, washout, and saline perfusion. We explore this here by measuring whether, when applied prior to euthanasia, standard immersion doses of 2 fish anesthetics, tricaine methanesulfonate (TMS; 100 mg/L, n = 6) and methyl 1-(1-phenylethyl)-1H-imidazole-5-carboxylate (metomidate, 10 mg/L, n = 6), have residual effects on the contractile properties (force and work output) of isolated and saline-perfused ventricular compact myocardium from rainbow trout (Oncorhynchus mykiss). Results suggest that direct exposure of muscle to immersion doses of TMS-but not metomidate-impairs muscle contractile performance. However, brief exposure (2 to 3 min) to either anesthetic during euthanasia only-providing that the agent is washed out prior to tissue experimentation-does not have an effect on the contractile properties of the myocardium. Therefore, the use of TMS, metomidate, and perhaps other anesthetics that depress cell excitability during euthanasia may be indicated when conducting research on isolated and rinsed tissues.

[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.

Local 3D matrix microenvironment regulates cell migration through spatiotemporal dynamics of contractility-dependent adhesions

NASA Astrophysics Data System (ADS)

Doyle, Andrew D.; Carvajal, Nicole; Jin, Albert; Matsumoto, Kazue; Yamada, Kenneth M.

2015-11-01

The physical properties of two-dimensional (2D) extracellular matrices (ECMs) modulate cell adhesion dynamics and motility, but little is known about the roles of local microenvironmental differences in three-dimensional (3D) ECMs. Here we generate 3D collagen gels of varying matrix microarchitectures to characterize their regulation of 3D adhesion dynamics and cell migration. ECMs containing bundled fibrils demonstrate enhanced local adhesion-scale stiffness and increased adhesion stability through balanced ECM/adhesion coupling, whereas highly pliable reticular matrices promote adhesion retraction. 3D adhesion dynamics are locally regulated by ECM rigidity together with integrin/ECM association and myosin II contractility. Unlike 2D migration, abrogating contractility stalls 3D migration regardless of ECM pore size. We find force is not required for clustering of activated integrins on 3D native collagen fibrils. We propose that efficient 3D migration requires local balancing of contractility with ECM stiffness to stabilize adhesions, which facilitates the detachment of activated integrins from ECM fibrils.

Synthesis and contractile activity of the C-terminal heptapeptide of substance P with N5-dimethyl glutamine in the 6-position. Active site studies.

PubMed

Poulos, C P; Pinas, N; Theodoropoulos, D

1980-09-15

The synthesis and testing of [N5-dimethyl-Gln6]-SP5-11 showed 37 +/- 12% contractile activity relative to SP, and intrinsic efficacy 98 +/- 4%. This finding indicates that the carboxamide groups of the dual Gln5-Cln6 moiety are not equally related with the contractile response of the C-terminal heptapeptide of SP.

Cadmium translocation by contractile roots differs from that in regular, non-contractile roots

PubMed Central

Lux, Alexander; Lackovič, Andrej; Van Staden, Johannes; Lišková, Desana; Kohanová, Jana; Martinka, Michal

2015-01-01

Background and Aims Contractile roots are known and studied mainly in connection with the process of shrinkage of their basal parts, which acts to pull the shoot of the plant deeper into the ground. Previous studies have shown that the specific structure of these roots results in more intensive water uptake at the base, which is in contrast to regular root types. The purpose of this study was to find out whether the basal parts of contractile roots are also more active in translocation of cadmium to the shoot. Methods Plants of the South African ornamental species Tritonia gladiolaris were cultivated in vitro for 2 months, at which point they possessed well-developed contractile roots. They were then transferred to Petri dishes with horizontally separated compartments of agar containing 50 µmol Cd(NO3)2 in the region of the root base or the root apex. Seedlings of 4-d-old maize (Zea mays) plants, which do not possess contractile roots, were also transferred to similar Petri dishes. The concentrations of Cd in the leaves of the plants were compared after 10 d of cultivation. Anatomical analyses of Tritonia roots were performed using appropriately stained freehand cross-sections. Key Results The process of contraction required specific anatomical adaptation of the root base in Tritonia, with less lignified and less suberized tissues in comparison with the subapical part of the root. These unusual developmental characteristics were accompanied by more intensive translocation of Cd ions from the basal part of contractile roots to the leaves than from the apical–subapical root parts. The opposite effects were seen in the non-contractile roots of maize, with higher uptake and transport by the apical parts of the root and lower uptake and transport by the basal part. Conclusions The specific characteristics of contractile roots may have a significant impact on the uptake of ions, including toxic metals from the soil surface layers. This may be important for plant

Contractile activity of the bladder urothelium/lamina propria and its regulation by nitric oxide.

PubMed

Moro, Christian; Leeds, Charlotte; Chess-Williams, Russ

2012-01-15

In the bladder, nitric oxide (NO) is released from neuronal and non-neuronal sources, but its actions are unclear. Strips of urothelium plus lamina propria contract in response to agonists and develop spontaneous phasic contractions, and the aim of this study was to investigate the influence of NO on this activity. Isolated strips of urothelium/lamina propria from porcine bladder developed spontaneous contractions (3.5 ± 0.3 cycles/min) and contracted in response to carbachol and electrical field stimulation (EFS). The NO synthase inhibitor N(ω)-nitro-l-arginine (L-NNA, 100 μM) had no effects on the tissues, but the NO donors diethylamine NONOate (DEANO, 100 μM) and nitroprusside (10 μM) caused relaxation, slowed the spontaneous rate of contractions and inhibited responses to carbachol. Maximum tonic contractions to carbachol were reduced by 17 ± 4% (P<0.001) and 35 ± 5% (P<0.001) by DEANO and nitroprusside respectively and the potency of carbachol was also reduced. Carbachol also increased the spontaneous frequency of contraction and these rate responses were again inhibited by DEANO and nitroprusside, but unaffected by L-NNA. Similarly, responses to EFS were significantly depressed (52-70%) by DEANO (P<0.05), but were unaffected by L-NNA. These data demonstrate spontaneous contractile activity and also nerve and agonist-induced tonic contractile activity within the urothelium and lamina propria. This activity is sensitive to depression by NO, but NO does not appear to be spontaneously released to influence this activity, nor does it appear to be released by muscarinic receptor stimulation. However the results suggest that in situations where NO production is increased, NO can influence the contractile activity of this tissue. Copyright © 2011 Elsevier B.V. All rights reserved.

Effects of N-acetylcysteine on isolated skeletal muscle contractile properties after an acute bout of aerobic exercise.

PubMed

Jannig, Paulo R; Alves, Christiano R R; Voltarelli, Vanessa A; Bozi, Luiz H M; Vieira, Janaina S; Brum, Patricia C; Bechara, Luiz R G

2017-12-15

The current study tested the hypotheses that 1) an acute bout of aerobic exercise impairs isolated skeletal muscle contractile properties and 2) N-acetylcysteine (a thiol antioxidant; NAC) administration can restore the impaired muscle contractility after exercise. At rest or immediately after an acute bout of aerobic exercise, extensor digitorum longus (EDL) and soleus muscles from male Wistar rats were harvested for ex vivo skeletal muscle contraction experiments. Muscles from exercised animals were incubated in Krebs Ringer's buffer in absence or presence of 20mM of NAC. Force capacity and fatigue properties were evaluated. Exercised EDL and soleus displayed lower force production across various stimulation frequencies (p<0.001), indicating that skeletal muscle force production was impaired after an acute bout of exercise. However, NAC treatment restored the loss of force production in both EDL and soleus after fatiguing exercise (p<0.05). Additionally, NAC treatment increased relative force production at different time points during a fatigue-induced protocol, suggesting that NAC treatment mitigates fatigue induced by successive contractions. NAC treatment improves force capacity and fatigue properties in ex vivo skeletal muscle from rats submitted to an acute bout of aerobic exercise. Copyright © 2017 Elsevier Inc. All rights reserved.

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.

The Effect of Cleft Palate Repair on Contractile Properties of Single Permeabilized Muscle Fibers From Congenitally Cleft Goats Palates

USDA-ARS?s Scientific Manuscript database

A cleft palate goat model was used to study the contractile properties of the levator veli palatini (LVP) muscle which is responsible for the movement of the soft palate. In 15-25% of patients that undergo palatoplasty, residual velopharyngeal insufficiency (VPI) remains a problem and often require...

Endocrine regulation of airway contractility is overlooked.

PubMed

Bossé, Ynuk

2014-08-01

Asthma is a prevalent respiratory disorder triggered by a variety of inhaled environmental factors, such as allergens, viruses, and pollutants. Asthma is characterized by an elevated activation of the smooth muscle surrounding the airways, as well as a propensity of the airways to narrow excessively in response to a spasmogen (i.e. contractile agonist), a feature called airway hyperresponsiveness. The level of airway smooth muscle (ASM) activation is putatively controlled by mediators released in its vicinity. In asthma, many mediators that affect ASM contractility originate from inflammatory cells that are mobilized into the airways, such as eosinophils. However, mounting evidence indicates that mediators released by remote organs can also influence the level of activation of ASM, as well as its level of responsiveness to spasmogens and relaxant agonists. These remote mediators are transported through circulating blood to act either directly on ASM or indirectly via the nervous system by tuning the level of cholinergic activation of ASM. Indeed, mediators generated from diverse organs, including the adrenals, pancreas, adipose tissue, gonads, heart, intestines, and stomach, affect the contractility of ASM. Together, these results suggest that, apart from a paracrine mode of regulation, ASM is subjected to an endocrine mode of regulation. The results also imply that defects in organs other than the lungs can contribute to asthma symptoms and severity. In this review, I suggest that the endocrine mode of regulation of ASM contractility is overlooked. © 2014 Society for Endocrinology.

Low thermal dependence of the contractile properties of a wing muscle in the bat Carollia perspicillata.

PubMed

Rummel, Andrea D; Swartz, Sharon M; Marsh, Richard L

2018-05-29

Temperature affects contractile rate properties in muscle, which may affect locomotor performance. Endotherms are known to maintain high core body temperatures, but temperatures in the periphery of the body can fluctuate. Such a phenomenon occurs in bats, whose wing musculature is relatively poorly insulated, resulting in substantially depressed temperatures in the distal wing. We examined a wing muscle in the small-bodied tropical bat Carollia perspicillata and a hindlimb muscle in the laboratory mouse at 5°C intervals from 22 to 42°C to determine the thermal dependence of the contractile properties of both muscles. We found that the bat ECRL had low thermal dependence from near body temperature to 10°C lower, with Q 10 values of less than 1.5 for relaxation from contraction and shortening velocities in that interval, and with no significant difference in some rate properties in the interval between 32 and 37°C. In contrast, for all temperature intervals below 37°C, Q 10 values for the mouse EDL were 1.5 or higher, and rate properties differed significantly across successive temperature intervals from 37 to 22°C. An ANCOVA analysis found that the thermal dependencies of all measured isometric and isotonic rate processes were significantly different between the bat and mouse muscles. The relatively low thermal dependence of the bat muscle likely represents a downward shift of its optimal temperature and may be functionally significant in light of the variable operating temperatures of bat wing muscles. © 2018. Published by The Company of Biologists Ltd.

Chronology of UPR activation in skeletal muscle adaptations to chronic contractile activity

PubMed Central

Memme, Jonathan M.; Oliveira, Ashley N.

2016-01-01

The mitochondrial and endoplasmic reticulum unfolded protein responses (UPRmt and UPRER) are important for cellular homeostasis during stimulus-induced increases in protein synthesis. Exercise triggers the synthesis of mitochondrial proteins, regulated in part by peroxisome proliferator activator receptor-γ coactivator 1α (PGC-1α). To investigate the role of the UPR in exercise-induced adaptations, we subjected rats to 3 h of chronic contractile activity (CCA) for 1, 2, 3, 5, or 7 days followed by 3 h of recovery. Mitochondrial biogenesis signaling, through PGC-1α mRNA, increased 14-fold after 1 day of CCA. This resulted in 10–32% increases in cytochrome c oxidase activity, indicative of mitochondrial content, between days 3 and 7, as well as increases in the autophagic degradation of p62 and microtubule-associated proteins 1A/1B light chain 3A (LC3)-II protein. Before these adaptations, the UPRER transcripts activating transcription factor-4, spliced X-box-binding protein 1, and binding immunoglobulin protein were elevated (1.3- to 3.8-fold) at days 1–3, while CCAAT/enhancer-binding protein homologous protein (CHOP) and chaperones binding immunoglobulin protein and heat shock protein (HSP) 70 were elevated at mRNA and protein levels (1.5- to 3.9-fold) at days 1–7 of CCA. The mitochondrial chaperones 10-kDa chaperonin, HSP60, and 75-kDa mitochondrial HSP, the protease ATP-dependent Clp protease proteolytic subunit, and the regulatory protein sirtuin-3 of the UPRmt were concurrently induced 10–80% between days 1 and 7. To test the role of the UPR in CCA-induced remodeling, we treated animals with the endoplasmic reticulum stress suppressor tauroursodeoxycholic acid and subjected them to 2 or 7 days of CCA. Tauroursodeoxycholic acid attenuated CHOP and HSP70 protein induction; however, this failed to impact mitochondrial remodeling. Our data indicate that signaling to the UPR is rapidly activated following acute contractile activity, that this is

[Contractile properties of skeletal muscles of rats after flight on "Kosmos-1887"].

PubMed

Oganov, V S; Skuratova, S A; Murashko, L M

1991-01-01

Contractile properties of skeletal muscles of rats were investigated using glycerinated muscle preparations that were obtained from Cosmos-1887 animals flown for 13 days (plus 2 days on the ground) and from rats that remained hypokinetic for 13 days on the ground. In the flow rats, the absolute mass of postural muscles remained unchanged while their relative mass increased; this may be attributed to their enhanced hydration which developed during the first 2 days after landing. Strength losses of the postural muscles were less significant than after previous flights. Comparison of the Cosmos-1887 and hypokinesia control data has shown that even 2-day exposure to 1 G after 13-day flight can modify drastically flight-induced changes.

Aging alters contractile properties and fiber morphology in pigeon skeletal muscle.

PubMed

Pistilli, Emidio E; Alway, Stephen E; Hollander, John M; Wimsatt, Jeffrey H

2014-12-01

In this study, we tested the hypothesis that skeletal muscle from pigeons would display age-related alterations in isometric force and contractile parameters as well as a shift of the single muscle fiber cross-sectional area (CSA) distribution toward smaller fiber sizes. Maximal force output, twitch contraction durations and the force-frequency relationship were determined in tensor propatagialis pars biceps muscle from young 3-year-old pigeons, middle-aged 18-year-old pigeons, and aged 30-year-old pigeons. The fiber CSA distribution was determined by planimetry from muscle sections stained with hematoxylin and eosin. Maximal force output of twitch and tetanic contractions was greatest in muscles from young pigeons, while the time to peak force of twitch contractions was longest in muscles from aged pigeons. There were no changes in the force-frequency relationship between the age groups. Interestingly, the fiber CSA distribution in aged muscles revealed a greater number of larger sized muscle fibers, which was verified visually in histological images. Middle-aged and aged muscles also displayed a greater amount of slow myosin containing muscle fibers. These data demonstrate that muscles from middle-aged and aged pigeons are susceptible to alterations in contractile properties that are consistent with aging, including lower force production and longer contraction durations. These functional changes were supported by the appearance of slow myosin containing muscle fibers in muscles from middle-aged and aged pigeons. Therefore, the pigeon may represent an appropriate animal model for the study of aging-related alterations in skeletal muscle function and structure.

Prostacyclin primes pregnant human myometrium for an enhanced contractile response in parturition

PubMed Central

Fetalvero, Kristina M.; Zhang, Peisheng; Shyu, Maureen; Young, Benjamin T.; Hwa, John; Young, Roger C.; Martin, Kathleen A.

2008-01-01

An incomplete understanding of the molecular events that regulate the myometrial transition from the quiescent pregnant state to the active contractile state during labor has hindered the development of improved therapies for preterm labor. During myometrial activation, proteins that prime the smooth muscle for contraction are upregulated, allowing maximal responsiveness to contractile agonists and thereby producing strong phasic contractions. Upregulation of one such protein, COX-2, generates PGs that induce contractions. Intriguingly, the predominant myometrial PG produced just prior to labor is prostacyclin (PGI2), a smooth muscle relaxant. However, here we have shown that activation of PGI2 receptor (IP) upregulated the expression of several contractile proteins and the gap junction protein connexin 43 through cAMP/PKA signaling in human myometrial tissue in organ and cell culture. Functionally, these IP-dependent changes in gene expression promoted an enhanced contractile response to oxytocin in pregnant human myometrial tissue strips, which was inhibited by the IP antagonist RO3244794. Furthermore, contractile protein induction was dependent on the concentration and time of exposure to the PGI2 analog iloprost and was blocked by both RO3244794 and PKA knockdown. We therefore propose that PGI2-mediated upregulation of contractile proteins and connexin 43 is a critical step in myometrial activation, allowing for a maximal contractile response. Our observations have important implications regarding activation of the myometrium prior to the onset of labor. PMID:19033666

Contractile properties and sarcoplasmic reticulum calcium content in type I and type II skeletal muscle fibres in active aged humans

PubMed Central

Lamboley, C R; Wyckelsma, V L; Dutka, T L; McKenna, M J; Murphy, R M; Lamb, G D

2015-01-01

This study examined the contractile properties and sarcoplasmic reticulum (SR) Ca2+ content in mechanically skinned vastus lateralis muscle fibres of Old (70 ± 4 years) and Young (22 ± 3 years) humans to investigate whether changes in muscle fibre properties contribute to muscle weakness in old age. In type II fibres of Old subjects, specific force was reduced by ∼17% and Ca2+ sensitivity was also reduced (pCa50 decreased ∼0.05 pCa units) relative to that in Young. S-Glutathionylation of fast troponin I (TnIf) markedly increased Ca2+ sensitivity in type II fibres, but the increase was significantly smaller in Old versus Young (+0.136 and +0.164 pCa unit increases, respectively). Endogenous and maximal SR Ca2+ content were significantly smaller in both type I and type II fibres in Old subjects. In fibres of Young, the SR could be nearly fully depleted of Ca2+ by a combined caffeine and low Mg2+ stimulus, whereas in fibres of Old the amount of non-releasable Ca2+ was significantly increased (by > 12% of endogenous Ca2+ content). Western blotting showed an increased proportion of type I fibres in Old subjects, and increased amounts of calsequestrin-2 and calsequestrin-like protein. The findings suggest that muscle weakness in old age is probably attributable in part to (i) an increased proportion of type I fibres, (ii) a reduction in both maximum specific force and Ca2+ sensitivity in type II fibres, and also a decreased ability of S-glutathionylation of TnIf to counter the fatiguing effects of metabolites on Ca2+ sensitivity, and (iii) a reduction in the amount of releasable SR Ca2+ in both fibre types. Key points Muscle weakness in old age is due in large part to an overall loss of skeletal muscle tissue, but it remains uncertain how much also stems from alterations in the properties of the individual muscle fibres. This study examined the contractile properties and amount of stored intracellular calcium in single muscle fibres of Old (70�

Effects of platelet activating factor on contractile force and 45Ca fluxes in guinea-pig isolated atria.

PubMed Central

Diez, J.; Delpón, E.; Tamargo, J.

1990-01-01

1. The effects of platelet activating factor (PAF) were studied on the electromechanical properties and 45Ca2+ fluxes of guinea-pig isolated atria. 2 Both in spontaneously beating and electrically driven atria, PAF (10(-12)-10(-7) M) increased atrial rate but produced a biphasic effect on contractile force. At low concentrations (up to 10(-10) M) it produced a positive inotropic effect, while at higher concentrations PAF exerted a negative inotropic effect. A similar biphasic effect was observed in the slow contractions elicited by isoprenaline in K(+)-depolarized atrial fibres. 3. The positive inotropic effect of PAF was prevented by verapamil, whereas pretreatment of atria with propranolol, phentolamine, indomethacin or atropine did not modify its positive and negative inotropic actions. BN 52021, a specific PAF antagonist, abolished both the positive and negative inotropic effects. 4. PAF had no effect on the characteristics of the action potentials recorded in either normally polarized or K(+)-depolarized (slow action potential) atrial fibres. 5. At concentrations at which it increased contractile force, PAF potentiated the contractile responses to Ca2+ (0.9-9 mM), whereas at negative inotropic concentrations it inhibited them. The negative inotropic effect of PAF was partially reversed in 70% Na+ medium. 6. At 10(-11) M, PAF increased 45Ca2+ uptake and reduced the rate coefficient (kcm) for the 45Ca2+ efflux. This increase in 45Ca2+ uptake was abolished in atria pretreated with verapamil or BN 52021. However, 10(-7) M PAF modified neither 45Ca2+ uptake nor efflux in atrial muscle.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2379035

Muscle-specific deletion of exons 2 and 3 of the IL15RA gene in mice: effects on contractile properties of fast and slow muscles.

PubMed

O'Connell, Grant; Guo, Ge; Stricker, Janelle; Quinn, LeBris S; Ma, Averil; Pistilli, Emidio E

2015-02-15

Interleukin-15 (IL-15) is a putative myokine hypothesized to induce an oxidative skeletal muscle phenotype. The specific IL-15 receptor alpha subunit (IL-15Rα) has also been implicated in specifying this contractile phenotype. The purposes of this study were to determine the muscle-specific effects of IL-15Rα functional deficiency on skeletal muscle isometric contractile properties, fatigue characteristics, spontaneous cage activity, and circulating IL-15 levels in male and female mice. Muscle creatine kinase (MCK)-driven IL-15Rα knockout mice (mIl15ra(fl/fl)/Cre(+)) were generated using the Cre-loxP system. We tested the hypothesis that IL-15Rα functional deficiency in skeletal muscle would increase resistance to contraction-induced fatigue, cage activity, and circulating IL-15 levels. There was a significant effect of genotype on the fatigue curves obtained in extensor digitorum longus (EDL) muscles from female mIl15ra(fl/fl)/Cre(+) mice, such that force output was greater during the repeated contraction protocol compared with mIl15ra(fl/fl)/Cre(-) control mice. Muscles from female mIl15ra(fl/fl)/Cre(+) mice also had a twofold greater amount of the mitochondrial genome-specific COXII gene compared with muscles from mIl15ra(fl/fl)/Cre(-) control mice, indicating a greater mitochondrial density in these skeletal muscles. There was a significant effect of genotype on the twitch:tetanus ratio in EDL and soleus muscles from mIl15ra(fl/fl)/Cre(+) mice, such that the ratio was lower in these muscles compared with mIl15ra(fl/fl)/Cre(-) control mice, indicating a pro-oxidative shift in muscle phenotype. However, spontaneous cage activity was not different and IL-15 protein levels were lower in male and female mIl15ra(fl/fl)/Cre(+) mice compared with control. Collectively, these data support a direct effect of muscle IL-15Rα deficiency in altering contractile properties and fatigue characteristics in skeletal muscles.

Hindlimb immobilization - Length-tension and contractile properties of skeletal muscle

NASA Technical Reports Server (NTRS)

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

1982-01-01

Casts were placed around rat feet in plantar flexion position to immobilize the soleus muscle in a shortened position, while the other foot was fixed in dorsal flexion to set the extensor digitorum longus in a shortened position. The total muscular atrophy and contractile properties were measured at 1, 2, 4, 7, 14, 21, 28, 35, and 42 days after immobilization, with casts being replaced every two weeks. The slow twitch soleus and the fast-twitch vastus lateralis and longus muscles were excised after termination of the experiment. The muscles were then stretched and subjected to electric shock to elicit peak tetanic tension and peak tetanic tension development. Force velocity features of the three muscles were assayed in a series of afterloaded contractions and fiber lengths were measured from subsequently macerated muscle. All muscles atrophied during immobilization, reaching a new steady state by day 21. Decreases in fiber and sarcomere lengths were also observed.

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.

Increased O-GlcNAcylation of Endothelial Nitric Oxide Synthase Compromises the Anti-contractile Properties of Perivascular Adipose Tissue in Metabolic Syndrome.

PubMed

da Costa, Rafael M; da Silva, Josiane F; Alves, Juliano V; Dias, Thiago B; Rassi, Diane M; Garcia, Luis V; Lobato, Núbia de Souza; Tostes, Rita C

2018-01-01

Under physiological conditions, the perivascular adipose tissue (PVAT) negatively modulates vascular contractility. This property is lost in experimental and human obesity and in the metabolic syndrome, indicating that changes in PVAT function may contribute to vascular dysfunction associated with increased body weight and hyperglycemia. The O -linked β-N-acetylglucosamine ( O -GlcNAc) modification of proteins ( O -GlcNAcylation) is a unique posttranslational process that integrates glucose metabolism with intracellular protein activity. Increased flux of glucose through the hexosamine biosynthetic pathway and the consequent increase in tissue-specific O -GlcNAc modification of proteins have been linked to multiple facets of vascular dysfunction in diabetes and other pathological conditions. We hypothesized that chronic consumption of glucose, a condition that progresses to metabolic syndrome, leads to increased O -GlcNAc modification of proteins in the PVAT, decreasing its anti-contractile effects. Therefore, the current study was devised to determine whether a high-sugar diet increases O -GlcNAcylation in the PVAT and how increased O -GlcNAc interferes with PVAT vasorelaxant function. To assess molecular mechanisms by which O -GlcNAc contributes to PVAT dysfunction, thoracic aortas surrounded by PVAT were isolated from Wistar rats fed either a control or high sugar diet, for 10 and 12 weeks. Rats chronically fed a high sugar diet exhibited metabolic syndrome features, increased O -GlcNAcylated-proteins in the PVAT and loss of PVAT anti-contractile effect. PVAT from high sugar diet-fed rats for 12 weeks exhibited decreased NO formation, reduced expression of endothelial nitric oxide synthase (eNOS) and increased O -GlcNAcylation of eNOS. High sugar diet also decreased OGA activity and increased superoxide anion generation in the PVAT. Visceral adipose tissue samples from hyperglycemic patients showed increased levels of O -GlcNAc-modified proteins, increased ROS

Upregulation of contractile endothelin type B receptors by lipid-soluble cigarette smoking particles in rat cerebral arteries via activation of MAPK

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

Sandhu, Hardip, E-mail: sandhu.hardip@gmail.co; Xu, Cang Bao; Edvinsson, Lars

2010-11-15

Cigarette smoke exposure increases the risk of stroke. However, the underlying molecular mechanisms are poorly understood. Endothelin system plays key roles in the pathogenesis of stroke. The present study was designed to examine if lipid-soluble (dimethyl sulfoxide-soluble) cigarette smoke particles (DSP) induces upregulation of contractile endothelin type B (ET{sub B}) receptors in rat cerebral arteries and if activation of mitogen activated protein kinase (MAPK) and nuclear factor-kappaB (NF-{kappa}B) mediate the upregulation of contractile endothelin receptors in the cerebral arteries. Rat middle cerebral arteries were isolated and organ cultured in serum free medium for 24 h in the presence of DSPmore » with or without specific inhibitors: MEK specific (U0126), p38 specific (SB202190), JNK specific (SP600125), NF-{kappa}B specific (BMS-345541) or (IMD-0354), transcription inhibitor (actinomycin D), or translation blocker (cycloheximide). Contractile responses to the ET{sub B} receptor agonist sarafotoxin 6c were investigated by a sensitive myograph. The expression of the ET{sub B} receptors were studied at mRNA and protein levels using quantitative real time PCR and immunohistochemistry, respectively. Results show that organ culture per se induced transcriptional upregulation of contractile ET{sub B} receptors in the cerebral vascular smooth muscle cells. This upregulation was further increased at the translational level by addition of DSP to the organ culture, but this increase was not seen by addition of nicotine or water-soluble cigarette smoke particles to the organ culture. The increased upregulation of contractile ET{sub B} receptors by DSP was abrogated by U0126, SP600125, actinomycin D, and cycloheximide, suggesting that the underlying molecular mechanisms involved in this process include activation of MEK and JNK MAPK-mediated transcription and translation of new contractile ET{sub B} receptors. Thus, the MAPK-mediated upregulation of contractile ET

Effect of a Periodized Power Training Program on the Functional Performances and Contractile Properties of the Quadriceps in Sprinters

ERIC Educational Resources Information Center

Kamandulis, Sigitas; Skurvydas, Albertas; Brazaitis, Marius; Stanislovaitis, Aleksas; Duchateau, Jacques; Stanislovaitiene, Jurate

2012-01-01

Our purpose was to compare the effect of a periodized preparation consisting of power endurance training and high-intensity power training on the contractile properties of the quadriceps muscle and functional performances in well trained male sprinters (n = 7). After 4 weeks of high-intensity power training, 60-m sprint running time improved by an…

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

Contractile properties and sarcoplasmic reticulum calcium content in type I and type II skeletal muscle fibres in active aged humans.

PubMed

Lamboley, C R; Wyckelsma, V L; Dutka, T L; McKenna, M J; Murphy, R M; Lamb, G D

2015-06-01

Muscle weakness in old age is due in large part to an overall loss of skeletal muscle tissue, but it remains uncertain how much also stems from alterations in the properties of the individual muscle fibres. This study examined the contractile properties and amount of stored intracellular calcium in single muscle fibres of Old (70 ± 4 years) and Young (22 ± 3 years) adults. The maximum level of force production (per unit cross-sectional area) in fast twitch fibres in Old subjects was lower than in Young subjects, and the fibres were also less sensitive to activation by calcium. The amount of calcium stored inside muscle fibres and available to trigger contraction was also lower in both fast- and slow-twitch muscle fibres in the Old subjects. These findings indicate that muscle weakness in old age stems in part from an impaired capacity for force production in the individual muscle fibres. This study examined the contractile properties and sarcoplasmic reticulum (SR) Ca(2+) content in mechanically skinned vastus lateralis muscle fibres of Old (70 ± 4 years) and Young (22 ± 3 years) humans to investigate whether changes in muscle fibre properties contribute to muscle weakness in old age. In type II fibres of Old subjects, specific force was reduced by ∼17% and Ca(2+) sensitivity was also reduced (pCa50 decreased ∼0.05 pCa units) relative to that in Young. S-Glutathionylation of fast troponin I (TnIf ) markedly increased Ca(2+) sensitivity in type II fibres, but the increase was significantly smaller in Old versus Young (+0.136 and +0.164 pCa unit increases, respectively). Endogenous and maximal SR Ca(2+) content were significantly smaller in both type I and type II fibres in Old subjects. In fibres of Young, the SR could be nearly fully depleted of Ca(2+) by a combined caffeine and low Mg(2+) stimulus, whereas in fibres of Old the amount of non-releasable Ca(2+) was significantly increased (by > 12% of endogenous Ca(2+) content). Western

Substrate stiffness regulates cadherin-dependent collective migration through myosin-II contractility

PubMed Central

Ng, Mei Rosa; Besser, Achim

2012-01-01

The mechanical microenvironment is known to influence single-cell migration; however, the extent to which mechanical cues affect collective migration of adherent cells is not well understood. We measured the effects of varying substrate compliance on individual cell migratory properties in an epithelial wound-healing assay. Increasing substrate stiffness increased collective cell migration speed, persistence, and directionality as well as the coordination of cell movements. Dynamic analysis revealed that wounding initiated a wave of motion coordination from the wound edge into the sheet. This was accompanied by a front-to-back gradient of myosin-II activation and establishment of cell polarity. The propagation was faster and farther reaching on stiff substrates, indicating that substrate stiffness affects the transmission of directional cues. Manipulation of myosin-II activity and cadherin–catenin complexes revealed that this transmission is mediated by coupling of contractile forces between neighboring cells. Thus, our findings suggest that the mechanical environment integrates in a feedback with cell contractility and cell–cell adhesion to regulate collective migration. PMID:23091067

Changes of contractile responses due to simulated weightlessness in rat soleus muscle

NASA Astrophysics Data System (ADS)

Elkhammari, A.; Noireaud, J.; Léoty, C.

1994-08-01

Some contractile and electrophysiological properties of muscle fibers isolated from the slow-twitch soleus (SOL) and fast-twitch extensor digitorum longus (EDL) muscles of rats were compared with those measured in SOL muscles from suspended rats. In suspendede SOL (21 days of tail-suspension) membrane potential (Em), intracellular sodium activity (aiNa) and the slope of the relationship between Em and log [K]o were typical of fast-twitch muscles. The relation between the maximal amplitude of K-contractures vs Em was steeper for control SOL than for EDL and suspended SOL muscles. After suspension, in SOL muscles the contractile threshold and the inactivation curves for K-contractures were shifted to more positive Em. Repriming of K-contractures was unaffected by suspencion. The exposure of isolated fibers to perchlorate (ClO4-)-containing (6-40 mM) solutions resulted ina similar concentration-dependent shift to more negative Em of activation curves for EDL and suspended SOL muscles. On exposure to a Na-free TEA solution, SOL from control and suspended rats, in contrast to EDL muscles, generated slow contractile responses. Suspended SOL showed a reduced sensitivity to the contracture-producing effect of caffeine compared to control muscles. These results suggested that the modification observed due to suspension could be encounted by changes in the characteristics of muscle fibers from slow to fast-twitch type.

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.

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

High-definition spatiotemporal mapping of contractile activity in the isolated proximal colon of the rabbit.

PubMed

Lentle, Roger G; Janssen, Patrick W M; Asvarujanon, Patchana; Chambers, Paul; Stafford, Kevin J; Hemar, Yacine

2008-03-01

Four types of contractile activity were identified and characterised in the isolated triple haustrated proximal colon of the rabbit using high-definition spatiotemporal mapping techniques. Mass peristalses were hexamethonium-sensitive deep circular contractions with associated taenial longitudinal contractile activity that occurred irregularly and propagated rapidly aborad, preceded by a zone of local lumen distension. They were sufficiently sustained for each event to occupy the length of the isolated colonic segment and the contraction persisted longer orally than aborally, the difference being more pronounced when lumen contents were viscous. Haustra were bounded by deep even-spaced ring contractions that progressed slowly aborad (haustral progression). Haustral formation and progression were hexamethonium-sensitive and coordinated across intertaenial domains. Ripples were hexamethonium-resistant phasic circular contractions that propagated predominantly orad at varying rates. In the presence of haustra, they were uncoordinated across intertaenial domains but were more coordinated when haustra were absent. Fast phasic contractions were relatively shallow hexamethonium-resistant contractions that propagated rapidly in a predominantly aborad direction. Fast phasic circular contractions were accompanied by taenial longitudinal muscle contractions which increased in amplitude prior to a mass peristaltic event and following the administration of hexamethonium. On the basis of the concurrence and interaction of these contractile activities, we hypothesise that dual pacemakers are present with fast phasic contractions being modulated by the interstitial cells of Cajal in the Auerbach's plexus (ICC-MY) while ripples are due to the submucosal ICC (ICC-SM). Further, that ICC-SM mediate the enteric motor neurons that generate haustral progression, while the intramuscular ICC (ICC-IM) mediate mass peristalsis. The orad movement of watery fluid was possibly due to ripples in

Modelling maternal obesity: the effects of a chronic high-fat, high-cholesterol diet on uterine expression of contractile-associated proteins and ex vivo contractile activity during labour in the rat.

PubMed

Muir, Ronan; Ballan, Jean; Clifford, Bethan; McMullen, Sarah; Khan, Raheela; Shmygol, Anatoly; Quenby, Siobhan; Elmes, Matthew

2016-02-01

Maternal obesity is associated with prolonged and dysfunctional labour and emergency caesarean section, but the mechanisms are unknown. The present study investigated the effects of an adiposity-inducing high-fat, high-cholesterol (HFHC) diet on uterine contractile-associated protein (CAP) expression and ex vivo uterine contractility in term non-labouring (TNL) and term labouring (TL) rats. Female rats were fed either control chow (CON n=20) or HFHC (n=20) diet 6 weeks before conception and during pregnancy. On gestational day 21 (TNL) or day 22 (TL) CON and HFHC (n=10) rats were killed to determine plasma cholesterol, triacylglycerol and progesterone concentrations and collection of myometrium for contractility studies and expression of CAPs caveolin-1 (Cav-1), connexin-43 (CX-43) and it's phosphorylated form (pCX-43), oxytocin receptor (OXTR) and cyclooxygenase-2 (COX-2). HFHC feeding increased visceral fat (P≤0.001), plasma cholesterol (P≤0.001) and triacylglycerol (P=0.039) concentrations. Stage of labour effected uterine expression of CAV-1 (P<0.02), pCX43 and COX-2 (both P<0.03). CAV-1 and pCX43 decreased but COX-2 increased with parturition. Significant diet- and labour-stage interactions were evident for CX-43 and pCX43 (P<0.03 and P<0.004 respectively). CX-43 decreased with TL in HFHC animals but was unaltered in CON. pCX-43 fell with labour in CON but remained high in HFHC. OXTR expression was significantly higher in HFHC compared with CON animals (P<0.03). Progesterone was higher in HFHC rats at term (P<0.014) but fell significantly with labour to similar concentrations as CON. Contractility studies identified synchronous contractions of stable amplitude in lean animals, but unstable asynchronous contractions with obesity. Uterine dose response to oxytocin was blunted during labour in HFHC rats with a log EC50 of -8.84 compared with -10.25 M in CON for integral activity (P<0.05). In conclusion, our adiposity model exhibits adverse effects on

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.

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 �

Nonequilibrium phase transitions, fluctuations and correlations in an active contractile polar fluid.

PubMed

Gowrishankar, Kripa; Rao, Madan

2016-02-21

We study the patterning, fluctuations and correlations of an active polar fluid consisting of contractile polar filaments on a two-dimensional substrate, using a hydrodynamic description. The steady states generically consist of arrays of inward pointing asters and show a continuous transition from a moving lamellar phase, a moving aster street, to a stationary aster lattice with no net polar order. We next study the effect of spatio-temporal athermal noise, parametrized by an active temperature TA, on the stability of the ordered phases. In contrast to its equilibrium counterpart, we find that the active crystal shows true long range order at low TA. On increasing TA, the asters dynamically remodel, concomitantly we find novel phase transitions characterized by bond-orientational and polar order upon "heating".

β2-Adrenergic stimulation enhances Ca2+ release and contractile properties of skeletal muscles, and counteracts exercise-induced reductions in Na+–K+-ATPase Vmax in trained men

PubMed Central

Hostrup, M; Kalsen, A; Ørtenblad, N; Juel, C; Mørch, K; Rzeppa, S; Karlsson, S; Backer, V; Bangsbo, J

2014-01-01

The aim of the present study was to examine the effect of β2-adrenergic stimulation on skeletal muscle contractile properties, sarcoplasmic reticulum (SR) rates of Ca2+ release and uptake, and Na+–K+-ATPase activity before and after fatiguing exercise in trained men. The study consisted of two experiments (EXP1, n = 10 males, EXP2, n = 20 males), where β2-adrenoceptor agonist (terbutaline) or placebo was randomly administered in double-blinded crossover designs. In EXP1, maximal voluntary isometric contraction (MVC) of m. quadriceps was measured, followed by exercise to fatigue at 120% of maximal oxygen uptake (). A muscle biopsy was taken after MVC (non-fatigue) and at time of fatigue. In EXP2, contractile properties of m. quadriceps were measured with electrical stimulations before (non-fatigue) and after two fatiguing 45 s sprints. Non-fatigued MVCs were 6 ± 3 and 6 ± 2% higher (P < 0.05) with terbutaline than placebo in EXP1 and EXP2, respectively. Furthermore, peak twitch force was 11 ± 7% higher (P < 0.01) with terbutaline than placebo at non-fatigue. After sprints, MVC declined (P < 0.05) to the same levels with terbutaline as placebo, whereas peak twitch force was lower (P < 0.05) and half-relaxation time was prolonged (P < 0.05) with terbutaline. Rates of SR Ca2+ release and uptake at 400 nm [Ca2+] were 15 ± 5 and 14 ± 5% (P < 0.05) higher, respectively, with terbutaline than placebo at non-fatigue, but declined (P < 0.05) to similar levels at time of fatigue. Na+–K+-ATPase activity was unaffected by terbutaline compared with placebo at non-fatigue, but terbutaline counteracted exercise-induced reductions in maximum rate of activity (Vmax) at time of fatigue. In conclusion, increased contractile force induced by β2-adrenergic stimulation is associated with enhanced rate of Ca2+ release in humans. While β2-adrenergic stimulation elicits positive inotropic and lusitropic effects on non-fatigued m. quadriceps, these effects are blunted when

A comparison of the contractile properties of smooth muscle from pig urethra and internal anal sphincter.

PubMed

Ramalingam, Thanesan; Durlu-Kandilci, N Tugba; Brading, Alison F

2010-09-01

Smooth muscles from the urethra and internal anal sphincter (IAS) play an essential role in the maintenance of urinary and fecal continence. Any damage in these muscles may cause serious problems. The aim of this study was to directly compare the contractile properties of pig urethra and IAS taken from the same animal. Smooth muscle strips of urethra and IAS dissected from the same pig were transferred to organ baths superfused with Krebs' solution, loaded with 1 g tension and equilibrated for 1 hr. Carbachol and phenylephrine response curves and EFS responses were elicited in the absence and presence of inhibitors. Both tissues developed tone during the 1 hr equilibration period. Carbachol (3 × 10(-6)-10(-3) M) contracted urethra whilst relaxing IAS. Guanethidine (10(-6) M) inhibited the carbachol responses in both tissues. L-NOARG (10(-4) M) decreased carbachol responses in IAS, but not in urethra. Phenylephrine (3 × 10(-6)-10(-2) M) contracted both tissues. EFS (1-40 Hz) induced a contractile response in urethra which was decreased with guanethidine (10(-6) M) and further blocked by atropine (10(-6) M). In the presence of both, a relaxation response was observed that is sensitive to NOS inhibitors especially at low frequencies. EFS induced a relaxation followed by a contraction in IAS strips. This contraction was blocked by guanethidine but not by atropine, and the remaining relaxation at 20 Hz was decreased with L-NOARG and increased with L-arginine. There are differences between urethra and IAS in terms of muscarinic activation and neural innervation, relevant for pharmacotherapy. © 2010 Wiley-Liss, Inc.

Izalpinin from fruits of Alpinia oxyphylla with antagonistic activity against the rat bladder contractility.

PubMed

Yuan, Yuan; Tan, Yin-Feng; Xu, Peng; Li, Hailong; Li, Yong-Hui; Chen, Wen-Ya; Zhang, Jun-Qing; Chen, Feng; Huang, Guo-Jun

2014-01-01

Alpinia oxyphylla (Zingiberaceae), an herbaceous perennial plant, its capsular fruit is commonly used in traditional Chinese medicine for the treatment of different urinary incontinence symptoms including frequency, urgency and nocturia. These symptoms are similar to the overactive bladder syndrome. In our lab, we found that the 95% ethanol extract of the capsular fruits exhibited significant anti-muscarinic activity. Some constituents in capsular fruits including flavonoids (e.g., izalpinin and tectochrysin), diarylheptanoids (e.g., yakuchinone A and yakuchinone B) and sesquiterpenes (e.g., nootkatone), are regarded as representative chemicals with putative pharmacological activities. This study aimed to evaluate the in vitro antagonistic actions of izalpinin on carbachol-induced contraction of the rat detrusor muscle. In vitro inhibition of rat detrusor contractile response to carbachol was used to study the functional activity of izalpinin. The isolated detrusor strips of rats were mounted in organ baths containing oxygenated Krebs' solution. The cumulative consecutive concentration-response curves to carbachol-evoked contractions in strips of rat bladder were obtained. Carbachol induced concentration-dependent contractions of isolated rat bladder detrusor strips. The vehicle DMSO had no impact on the contraction response. The contraction effects were concentration-dependently antagonized by izalpinin, with a mean EC50 value of 0.35 µM. The corresponding cumulative agonist concentration-response curves shifted right-ward. Izalpinin exhibits inhibitory role of muscarinic receptor-related detrusor contractile activity, and it may be a promising lead compound to treat overactive bladder.

Recovery of skeletal muscle mass after extensive injury: positive effects of increased contractile activity.

PubMed

Richard-Bulteau, Hélène; Serrurier, Bernard; Crassous, Brigitte; Banzet, Sébastien; Peinnequin, André; Bigard, Xavier; Koulmann, Nathalie

2008-02-01

The present study was designed to test the hypothesis that increasing physical activity by running exercise could favor the recovery of muscle mass after extensive injury and to determine the main molecular mechanisms involved. Left soleus muscles of female Wistar rats were degenerated by notexin injection before animals were assigned to either a sedentary group or an exercised group. Both regenerating and contralateral intact muscles from active and sedentary rats were removed 5, 7, 14, 21, 28 and 42 days after injury (n = 8 rats/group). Increasing contractile activity through running exercise during muscle regeneration ensured the full recovery of muscle mass and muscle cross-sectional area as soon as 21 days after injury, whereas muscle weight remained lower even 42 days postinjury in sedentary rats. Proliferator cell nuclear antigen and MyoD protein expression went on longer in active rats than in sedentary rats. Myogenin protein expression was higher in active animals than in sedentary animals 21 days postinjury. The Akt-mammalian target of rapamycin (mTOR) pathway was activated early during the regeneration process, with further increases of mTOR phosphorylation and its downstream effectors, eukaryotic initiation factor-4E-binding protein-1 and p70(s6k), in active rats compared with sedentary rats (days 7-14). The exercise-induced increase in mTOR phosphorylation, independently of Akt, was associated with decreased levels of phosphorylated AMP-activated protein kinase. Taken together, these results provided evidence that increasing contractile activity during muscle regeneration ensured early and full recovery of muscle mass and suggested that these beneficial effects may be due to a longer proliferative step of myogenic cells and activation of mTOR signaling, independently of Akt, during the maturation step of muscle regeneration.

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.

Effects of divalent cations and La3+ on contractility and ecto-ATPase activity in the guinea-pig urinary bladder.

PubMed Central

Ziganshin, A U; Ziganshina, L E; Hoyle, C H; Burnstock, G

1995-01-01

1. Several cations (Ba2+, Cd2+, Co2+, Cu2+, Mn2+, Ni2+, Zn2+ and La3+, all as chloride salts, 1-1000 microM) were tested in the guinea-pig urinary bladder for their ability to: (i) modify contractile responses to electrical field stimulation (EFS), ATP, alpha,beta-methylene ATP (alpha,beta-meATP), carbachol (CCh), and KCl; (ii) affect ecto-ATPase activity. 2. Ba2+ (10-1000 microM) concentration-dependently potentiated contractile responses evoked by EFS (4-16 Hz), ATP (100 microM), alpha,beta-meATP (1 microM), CCh (0.5 microM), and KCl (30 mM). Ni2+ at concentrations of 1-100 microM also potentiated contractility of the urinary bladder, but at concentrations tested its effect was not concentration-dependent. Cu2+ at a concentration of 10 microM and Cd2+ at a concentration of 1 microM potentiated responses to all stimuli, except KCl. Ni2+ at a concentration of 1000 microM and Cd2+ at a concentration of 100 microM inhibited contractions evoked by all stimuli, and at a concentration of 1000 microM Cd2+ abolished any contractions. Responses to ATP and alpha,beta-meATP were selectively inhibited by Cu2+, Zn2+ or La3+, each at a concentration of 1 mM. 3. Cu2+, Ni2+, Zn2+ and La3+ (100-1000 microM) concentration-dependently inhibited ecto-ATPase activity in the urinary bladder smooth muscle preparations, while Ba2+ and Mn2+ were without effect, and Cd2+ and Co2+ caused significant inhibition only at a concentration of 1000 microM. 4. There was no correlation between the extent of ecto-ATPase inhibition and the effect on contractile activity of any of the cations.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7735690

Active properties of living tissues lead to size-dependent dewetting

NASA Astrophysics Data System (ADS)

Perez-Gonzalez, Carlos; Alert, Ricard; Blanch-Mercader, Carles; Gomez-Gonzalez, Manuel; Casademunt, Jaume; Trepat, Xavier

Key biological processes such as cancer and development are characterized by drastic transitions from 2D to a 3D geometry. These rearrangements have been classically studied as a wetting problem. According to this theory, wettability of a substrate by an epithelium is determined by the competition between cell-cell and cell-substrate adhesion energies. In contrast, we found that, far from a passive process, tissue dewetting is an active process driven by tissue internal forces. Experimentally, we reproduced epithelial dewetting by promoting a progressive formation of intercellular junctions in a monolayer of epithelial cells. Interestingly, the formation of intercellular junctions produces an increase in cell contractility, with the subsequent increase in traction and intercellular stress. At a certain time, tissue tension overcomes cell-substrate maximum adhesion and the monolayer spontaneously dewets the substrate. We developed an active polar fluid model, finding both theoretically and experimentally that critical contractility to promote wetting-dewetting transition depends on cell-substrate adhesion and, unexpectedly, on tissue size. As a whole, this work generalizes wetting theory to living tissues, unveiling unprecedented properties due to their unique active nature.

Mechanically Induced Chromatin Condensation Requires Cellular Contractility in Mesenchymal Stem Cells.

PubMed

Heo, Su-Jin; Han, Woojin M; Szczesny, Spencer E; Cosgrove, Brian D; Elliott, Dawn M; Lee, David A; Duncan, Randall L; Mauck, Robert L

2016-08-23

Mechanical cues play important roles in directing the lineage commitment of mesenchymal stem cells (MSCs). In this study, we explored the molecular mechanisms by which dynamic tensile loading (DL) regulates chromatin organization in this cell type. Our previous findings indicated that the application of DL elicited a rapid increase in chromatin condensation through purinergic signaling mediated by ATP. Here, we show that the rate and degree of condensation depends on the frequency and duration of mechanical loading, and that ATP release requires actomyosin-based cellular contractility. Increases in baseline cellular contractility via the addition of an activator of G-protein coupled receptors (lysophosphatidic acid) induced rapid ATP release, resulting in chromatin condensation independent of loading. Conversely, inhibition of contractility through pretreatment with either a RhoA/Rock inhibitor (Y27632) or MLCK inhibitor (ML7) abrogated ATP release in response to DL, blocking load-induced chromatin condensation. With loading, ATP release occurred very rapidly (within the first 10-20 s), whereas changes in chromatin occurred at a later time point (∼10 min), suggesting a downstream biochemical pathway mediating this process. When cells were pretreated with blockers of the transforming growth factor (TGF) superfamily, purinergic signaling in response to DL was also eliminated. Further analysis showed that this pretreatment decreased contractility, implicating activity in the TGF pathway in the establishment of the baseline contractile state of MSCs (in the absence of exogenous ligands). These data indicate that chromatin condensation in response to DL is regulated through the interplay between purinergic and RhoA/Rock signaling, and that ligandless activity in the TGF/bone morphogenetic proteins signaling pathway contributes to the establishment of baseline contractility in MSCs. Copyright © 2016 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Contractile function and motor unit firing rates of the human hamstrings.

PubMed

Kirk, Eric A; Rice, Charles L

2017-01-01

Neuromuscular properties of the lower limb in health, aging, and disease are well described for major lower limb muscles comprising the quadriceps, triceps surae, and dorsiflexors, with the notable exception of the posterior thigh (hamstrings). The purpose of this study was to further characterize major muscles of the lower limb by comprehensively exploring contractile properties in relation to spinal motor neuron output expressed as motor unit firing rates (MUFRs) in the hamstrings of 11 (26.5 ± 3.8) young men. Maximal isometric voluntary contraction (MVC), voluntary activation, stimulated contractile properties including a force-frequency relationship, and MUFRs from submaximal to maximal voluntary contractile intensities were assessed in the hamstrings. Strength and MUFRs were assessed at two presumably different muscle lengths by varying the knee joint angles (90° and 160°). Knee flexion MVCs were 60-70% greater in the extended position (160°). The frequency required to elicit 50% of maximum tetanic torque was 16-17 Hz. Mean MUFRs at 25-50% MVC were 9-31% less in the biceps femoris compared with the semimembranosus-semitendinosus group. Knee joint angle (muscle length) influenced MUFRs such that mean MUFRs were greater in the shortened (90°) position at 50% and 100% MVC. Compared with previous reports, mean maximal MUFRs in the hamstrings are greater than those in the quadriceps and triceps surae and somewhat less than those in the tibialis anterior. Mean maximal MUFRs in the hamstrings are influenced by changes in knee joint angle, with lower firing rates in the biceps femoris compared with the semimembranosus-semitendinosus muscle group. We studied motor unit firing rates (MUFRs) at various voluntary contraction intensities in the hamstrings, one of the only major lower limb muscles to have MUFRs affected by muscle length changes. Within the hamstrings muscle-specific differences have greater impact on MUFRs than length changes, with the biceps femoris

β2-adrenergic stimulation enhances Ca2+ release and contractile properties of skeletal muscles, and counteracts exercise-induced reductions in Na+-K+-ATPase Vmax in trained men.

PubMed

Hostrup, M; Kalsen, A; Ortenblad, N; Juel, C; Mørch, K; Rzeppa, S; Karlsson, S; Backer, V; Bangsbo, J

2014-12-15

The aim of the present study was to examine the effect of β2-adrenergic stimulation on skeletal muscle contractile properties, sarcoplasmic reticulum (SR) rates of Ca(2+) release and uptake, and Na(+)-K(+)-ATPase activity before and after fatiguing exercise in trained men. The study consisted of two experiments (EXP1, n = 10 males, EXP2, n = 20 males), where β2-adrenoceptor agonist (terbutaline) or placebo was randomly administered in double-blinded crossover designs. In EXP1, maximal voluntary isometric contraction (MVC) of m. quadriceps was measured, followed by exercise to fatigue at 120% of maximal oxygen uptake (V̇O2, max ). A muscle biopsy was taken after MVC (non-fatigue) and at time of fatigue. In EXP2, contractile properties of m. quadriceps were measured with electrical stimulations before (non-fatigue) and after two fatiguing 45 s sprints. Non-fatigued MVCs were 6 ± 3 and 6 ± 2% higher (P < 0.05) with terbutaline than placebo in EXP1 and EXP2, respectively. Furthermore, peak twitch force was 11 ± 7% higher (P < 0.01) with terbutaline than placebo at non-fatigue. After sprints, MVC declined (P < 0.05) to the same levels with terbutaline as placebo, whereas peak twitch force was lower (P < 0.05) and half-relaxation time was prolonged (P < 0.05) with terbutaline. Rates of SR Ca(2+) release and uptake at 400 nm [Ca(2+)] were 15 ± 5 and 14 ± 5% (P < 0.05) higher, respectively, with terbutaline than placebo at non-fatigue, but declined (P < 0.05) to similar levels at time of fatigue. Na(+)-K(+)-ATPase activity was unaffected by terbutaline compared with placebo at non-fatigue, but terbutaline counteracted exercise-induced reductions in maximum rate of activity (Vmax) at time of fatigue. In conclusion, increased contractile force induced by β2-adrenergic stimulation is associated with enhanced rate of Ca(2+) release in humans. While β2-adrenergic stimulation elicits positive inotropic and lusitropic effects on non-fatigued m. quadriceps, these effects

Changes in contractile properties of muscles receiving repeat injections of botulinum toxin (Botox).

PubMed

Fortuna, Rafael; Vaz, Marco Aurélio; Youssef, Aliaa Rehan; Longino, David; Herzog, Walter

2011-01-04

Botulinum toxin type A (BTX-A) is a frequently used therapeutic tool to denervate muscles in the treatment of neuromuscular disorders. Although considered safe by the US Food and Drug Administration, BTX-A can produce adverse effects in target and non-target muscles. With an increased use of BTX-A for neuromuscular disorders, the effects of repeat injections of BTX-A on strength, muscle mass and structure need to be known. Therefore, the purpose of this study was to investigate the changes in strength, muscle mass and contractile material in New Zealand White (NZW) rabbits. Twenty NZW rabbits were divided into 4 groups: control and 1, 3 and 6 months of unilateral, repeat injections of BTX-A into the quadriceps femoris. Outcome measures included knee extensor torque, muscle mass and the percentage of contractile material in the quadriceps muscles of the target and non-injected contralateral hindlimbs. Strength in the injected muscles was reduced by 88%, 89% and 95% in the 1, 3 and 6 months BTX-A injected hindlimbs compared to controls. Muscle mass was reduced by 50%, 42% and 31% for the vastus lateralis (VL), rectus femoris (RF) and vastus medialis (VM), respectively, at 1 month, by 68%, 51% and 50% at 3 months and by 76%, 44% and 13% at 6 months. The percentage of contractile material was reduced for the 3 and 6 months animals to 80-64%, respectively, and was replaced primarily by fat. Similar, but less pronounced results were also observed for the quadriceps muscles of the contralateral hindlimbs, suggesting that repeat BTX-A injections cause muscle atrophy and loss of contractile tissue in target muscles and also in non-target muscles that are far removed from the injection site. Copyright © 2010 Elsevier Ltd. All rights reserved.

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.

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.

p21-Activated kinase-1 and its role in integrated regulation of cardiac contractility.

PubMed

Sheehan, Katherine A; Ke, Yunbo; Solaro, R John

2007-09-01

We review here a novel concept in the regulation of cardiac contractility involving variations in the activity of the multifunctional enzyme, p21-activated kinase 1 (Pak1), a member of a family of proteins in the small G protein-signaling pathway that is activated by Cdc42 and Rac1. There is a large body of evidence from studies in noncardiac tissue that Pak1 activity is key in regulation of a number of cellular functions, including cytoskeletal dynamics, cell motility, growth, and proliferation. Although of significant potential impact, the role of Pak1 in regulation of the heart has been investigated in only a few laboratories. In this review, we discuss the structure of Pak1 and its sites of posttranslational modification and molecular interactions. We assemble an overview of the current data on Pak1 signaling in noncardiac tissues relative to similar signaling pathways in the heart, and we identify potential roles of Pak1 in cardiac regulation. Finally, we discuss the current state of Pak1 research in the heart in regard to regulation of contractility through functional myofilament and Ca(2+)-flux modification. An important aspect of this regulation is the modulation of kinase and phosphatase activity. We have focused on Pak1 regulation of protein phosphatase 2A (PP2A), which is abundant in cardiac muscle, thereby mediating dephosphorylation of sarcomeric proteins and sensitizing the myofilaments to Ca(2+). We present a model for Pak1 signaling that provides a mechanism for specifically affecting cardiac cellular processes in which regulation of protein phosphorylation states by PP2A dephosphorylation predominates.

Extracellular UDP enhances P2X-mediated bladder smooth muscle contractility via P2Y6 activation of the phospholipase C/inositol trisphosphate pathway

PubMed Central

Yu, Weiqun; Sun, Xiaofeng; Robson, Simon C.; Hill, Warren G.

2013-01-01

Bladder dysfunction characterized by abnormal bladder smooth muscle (BSM) contractions is pivotal to the disease process in overactive bladder, urge incontinence, and spinal cord injury. Purinergic signaling comprises one key pathway in modulating BSM contractility, but molecular mechanisms remain unclear. Here we demonstrate, using myography, that activation of P2Y6 by either UDP or a specific agonist (MRS 2693) induced a sustained increase in BSM tone (up to 2 mN) in a concentration-dependent manner. Notably, activation of P2Y6 enhanced ATP-mediated BSM contractile force by up to 45%, indicating synergistic interactions between P2X and P2Y signaling. P2Y6-activated responses were abolished by phospholipase C (PLC) and inositol trisphosphate (IP3) receptor antagonists U73122 and xestospongin C, demonstrating involvement of the PLC/IP3 signal pathway. Mice null for Entpd1, an ectonucleotidase on BSM, demonstrated increased force generation on P2Y6 activation (150%). Thus, in vivo perturbations to purinergic signaling resulted in altered P2Y6 activity and bladder contractility. We conclude that UDP, acting on P2Y6, regulates BSM tone and in doing so selectively maximizes P2X1-mediated contraction forces. This novel neurotransmitter pathway may play an important role in urinary voiding disorders characterized by abnormal bladder motility.—Yu, W., Sun, X., Robson, S. C., Hill, W. G. Extracellular UDP enhances P2X-mediated bladder smooth muscle contractility via P2Y6 activation of the phospholipase C/inositol trisphosphate pathway. PMID:23362118

Comparison of isometric contractile properties of the tongue muscles in three species of frogs, Litoria caerulea, Dyscophus guinetti, and Bufo marinus.

PubMed

Peters, S E; Nishikawa, K C

1999-11-01

Previous studies show that anurans feed in at least three different ways. Basal frogs have a broad tongue that shortens during protraction and emerges only a short distance from the mouth. Some frogs have long, narrow tongues that elongate dramatically due primarily to inertia from mouth opening, which is transferred to the tongue. A few species have a hydrostatic mechanism that produces tongue elongation during protraction. This functional diversity occurs among frogs that share the same two pairs of tongue muscles. Our study compares the isometric contractile properties of these tongue muscles among three frog species that represent each feeding mechanism. Nerves to the paired protractors and retractors were stimulated electrically in each species to record the force properties, contraction speeds, and fatigabilites of these muscles. Few differences were found in the isometric contractile properties of tongue muscles, and the greatest differences were found in the retractors, not the protractors. We propose that the unique arrangement of the tongue muscles in frogs results in a retractor that may also be coactivated with the protractor in order to produce normal tongue protraction. Inertial effects from body, head, and jaw movements, along with clear differences that we found in passive resistance of the tongues to elongation, may explain much of the behavioral variation in tongue use among species. Copyright 1999 Wiley-Liss, Inc.

Temporal Adaptive Changes in Contractility and Fatigability of Diaphragm Muscles from Streptozotocin-Diabetic Rats

PubMed Central

Brotto, Marco; Brotto, Leticia; Jin, J.-P.; Nosek, Thomas M.; Romani, Andrea

2010-01-01

Diabetes is characterized by ventilatory depression due to decreased diaphragm (DPH) function. This study investigated the changes in contractile properties of rat DPH muscles over a time interval encompassing from 4 days to 14 weeks after the onset of streptozotocin-induced diabetes, with and without insulin treatment for 2 weeks. Maximum tetanic force in intact DPH muscle strips and recovery from fatiguing stimulation were measured. An early (4-day) depression in contractile function in diabetic DPH was followed by gradual improvement in muscle function and fatigue recovery (8 weeks). DPH contractile function deteriorated again at 14 weeks, a process that was completely reversed by insulin treatment. Maximal contractile force and calcium sensitivity assessed in Triton-skinned DPH fibers showed a similar bimodal pattern and the same beneficial effect of insulin treatment. While an extensive analysis of the isoforms of the contractile and regulatory proteins was not conducted, Western blot analysis of tropomyosin suggests that the changes in diabetic DPH response depended, at least in part, on a switch in fiber type. PMID:20467472

Temporal adaptive changes in contractility and fatigability of diaphragm muscles from streptozotocin-diabetic rats.

PubMed

Brotto, Marco; Brotto, Leticia; Jin, J-P; Nosek, Thomas M; Romani, Andrea

2010-01-01

Diabetes is characterized by ventilatory depression due to decreased diaphragm (DPH) function. This study investigated the changes in contractile properties of rat DPH muscles over a time interval encompassing from 4 days to 14 weeks after the onset of streptozotocin-induced diabetes, with and without insulin treatment for 2 weeks. Maximum tetanic force in intact DPH muscle strips and recovery from fatiguing stimulation were measured. An early (4-day) depression in contractile function in diabetic DPH was followed by gradual improvement in muscle function and fatigue recovery (8 weeks). DPH contractile function deteriorated again at 14 weeks, a process that was completely reversed by insulin treatment. Maximal contractile force and calcium sensitivity assessed in Triton-skinned DPH fibers showed a similar bimodal pattern and the same beneficial effect of insulin treatment. While an extensive analysis of the isoforms of the contractile and regulatory proteins was not conducted, Western blot analysis of tropomyosin suggests that the changes in diabetic DPH response depended, at least in part, on a switch in fiber type.

Assembly and positioning of actomyosin rings by contractility and planar cell polarity

PubMed Central

Sehring, Ivonne M; Recho, Pierre; Denker, Elsa; Kourakis, Matthew; Mathiesen, Birthe; Hannezo, Edouard; Dong, Bo; Jiang, Di

2015-01-01

The actomyosin cytoskeleton is a primary force-generating mechanism in morphogenesis, thus a robust spatial control of cytoskeletal positioning is essential. In this report, we demonstrate that actomyosin contractility and planar cell polarity (PCP) interact in post-mitotic Ciona notochord cells to self-assemble and reposition actomyosin rings, which play an essential role for cell elongation. Intriguingly, rings always form at the cells′ anterior edge before migrating towards the center as contractility increases, reflecting a novel dynamical property of the cortex. Our drug and genetic manipulations uncover a tug-of-war between contractility, which localizes cortical flows toward the equator and PCP, which tries to reposition them. We develop a simple model of the physical forces underlying this tug-of-war, which quantitatively reproduces our results. We thus propose a quantitative framework for dissecting the relative contribution of contractility and PCP to the self-assembly and repositioning of cytoskeletal structures, which should be applicable to other morphogenetic events. DOI: http://dx.doi.org/10.7554/eLife.09206.001 PMID:26486861

2-Deoxyadenosine triphosphate restores the contractile function of cardiac myofibril from adult dogs with naturally occurring dilated cardiomyopathy

PubMed Central

Cheng, Yuanhua; Hogarth, Kaley A.; O'Sullivan, M. Lynne; Regnier, Michael

2015-01-01

Dilated cardiomyopathy (DCM) is a major type of heart failure resulting from loss of systolic function. Naturally occurring canine DCM is a widely accepted experimental paradigm for studying human DCM. 2-Deoxyadenosine triphosphate (dATP) can be used by myosin and is a superior energy substrate over ATP for cross-bridge formation and increased systolic function. The objective of this study was to evaluate the beneficial effect of dATP on contractile function of cardiac myofibrils from dogs with naturally occurring DCM. We measured actomyosin NTPase activity and contraction/relaxation properties of isolated myofibrils from nonfailing (NF) and DCM canine hearts. NTPase assays indicated replacement of ATP with dATP significantly increased myofilament activity in both NF and DCM samples. dATP significantly improved maximal tension of DCM myofibrils to the NF sample level. dATP also restored Ca2+ sensitivity of tension that was reduced in DCM samples. Similarly, dATP increased the kinetics of contractile activation (kACT), with no impact on the rate of cross-bridge tension redevelopment (kTR). Thus, the activation kinetics (kACT/kTR) that were reduced in DCM samples were restored for dATP to NF sample levels. dATP had little effect on relaxation. The rate of early slow-phase relaxation was slightly reduced with dATP, but its duration was not, nor was the fast-phase relaxation or times to 50 and 90% relaxation. Our findings suggest that myosin utilization of dATP improves cardiac myofibril contractile properties of naturally occurring DCM canine samples, restoring them to NF levels, without compromising relaxation. This suggests elevation of cardiac dATP is a promising approach for the treatment of DCM. PMID:26497964

2-Deoxyadenosine triphosphate restores the contractile function of cardiac myofibril from adult dogs with naturally occurring dilated cardiomyopathy.

PubMed

Cheng, Yuanhua; Hogarth, Kaley A; O'Sullivan, M Lynne; Regnier, Michael; Pyle, W Glen

2016-01-01

Dilated cardiomyopathy (DCM) is a major type of heart failure resulting from loss of systolic function. Naturally occurring canine DCM is a widely accepted experimental paradigm for studying human DCM. 2-Deoxyadenosine triphosphate (dATP) can be used by myosin and is a superior energy substrate over ATP for cross-bridge formation and increased systolic function. The objective of this study was to evaluate the beneficial effect of dATP on contractile function of cardiac myofibrils from dogs with naturally occurring DCM. We measured actomyosin NTPase activity and contraction/relaxation properties of isolated myofibrils from nonfailing (NF) and DCM canine hearts. NTPase assays indicated replacement of ATP with dATP significantly increased myofilament activity in both NF and DCM samples. dATP significantly improved maximal tension of DCM myofibrils to the NF sample level. dATP also restored Ca(2+) sensitivity of tension that was reduced in DCM samples. Similarly, dATP increased the kinetics of contractile activation (kACT), with no impact on the rate of cross-bridge tension redevelopment (kTR). Thus, the activation kinetics (kACT/kTR) that were reduced in DCM samples were restored for dATP to NF sample levels. dATP had little effect on relaxation. The rate of early slow-phase relaxation was slightly reduced with dATP, but its duration was not, nor was the fast-phase relaxation or times to 50 and 90% relaxation. Our findings suggest that myosin utilization of dATP improves cardiac myofibril contractile properties of naturally occurring DCM canine samples, restoring them to NF levels, without compromising relaxation. This suggests elevation of cardiac dATP is a promising approach for the treatment of DCM. Copyright © 2016 the American Physiological Society.

Repeated stimulation, inter-stimulus interval and inter-electrode distance alters muscle contractile properties as measured by Tensiomyography

PubMed Central

Johnson, Mark I.; Francis, Peter

2018-01-01

Context The influence of methodological parameters on the measurement of muscle contractile properties using Tensiomyography (TMG) has not been published. Objective To investigate the; (1) reliability of stimulus amplitude needed to elicit maximum muscle displacement (Dm), (2) effect of changing inter-stimulus interval on Dm (using a fixed stimulus amplitude) and contraction time (Tc), (3) the effect of changing inter-electrode distance on Dm and Tc. Design Within subject, repeated measures. Participants 10 participants for each objective. Main outcome measures Dm and Tc of the rectus femoris, measured using TMG. Results The coefficient of variance (CV) and the intra-class correlation (ICC) of stimulus amplitude needed to elicit maximum Dm was 5.7% and 0.92 respectively. Dm was higher when using an inter-electrode distance of 7cm compared to 5cm [P = 0.03] and when using an inter-stimulus interval of 10s compared to 30s [P = 0.017]. Further analysis of inter-stimulus interval data, found that during 10 repeated stimuli Tc became faster after the 5th measure when compared to the second measure [P<0.05]. The 30s inter-stimulus interval produced the most stable Tc over 10 measures compared to 10s and 5s respectively. Conclusion Our data suggest that the stimulus amplitude producing maximum Dm of the rectus femoris is reliable. Inter-electrode distance and inter-stimulus interval can significantly influence Dm and/ or Tc. Our results support the use of a 30s inter-stimulus interval over 10s or 5s. Future studies should determine the influence of methodological parameters on muscle contractile properties in a range of muscles. PMID:29451885

Insoluble elastin reduces collagen scaffold stiffness, improves viscoelastic properties, and induces a contractile phenotype in smooth muscle cells.

PubMed

Ryan, Alan J; O'Brien, Fergal J

2015-12-01

Biomaterials with the capacity to innately guide cell behaviour while also displaying suitable mechanical properties remain a challenge in tissue engineering. Our approach to this has been to utilise insoluble elastin in combination with collagen as the basis of a biomimetic scaffold for cardiovascular tissue engineering. Elastin was found to markedly alter the mechanical and biological response of these collagen-based scaffolds. Specifically, during extensive mechanical assessment elastin was found to reduce the specific tensile and compressive moduli of the scaffolds in a concentration dependant manner while having minimal effect on scaffold microarchitecture with both scaffold porosity and pore size still within the ideal ranges for tissue engineering applications. However, the viscoelastic properties were significantly improved with elastin addition with a 3.5-fold decrease in induced creep strain, a 6-fold increase in cyclical strain recovery, and with a four-parameter viscoelastic model confirming the ability of elastin to confer resistance to long term deformation/creep. Furthermore, elastin was found to result in the modulation of SMC phenotype towards a contractile state which was determined via reduced proliferation and significantly enhanced expression of early (α-SMA), mid (calponin), and late stage (SM-MHC) contractile proteins. This allows the ability to utilise extracellular matrix proteins alone to modulate SMC phenotype without any exogenous factors added. Taken together, the ability of elastin to alter the mechanical and biological response of collagen scaffolds has led to the development of a biomimetic biomaterial highly suitable for cardiovascular tissue engineering. Copyright © 2015 Elsevier Ltd. All rights reserved.

Contractile function and motor unit firing rates of the human hamstrings

PubMed Central

Kirk, Eric A.

2016-01-01

Neuromuscular properties of the lower limb in health, aging, and disease are well described for major lower limb muscles comprising the quadriceps, triceps surae, and dorsiflexors, with the notable exception of the posterior thigh (hamstrings). The purpose of this study was to further characterize major muscles of the lower limb by comprehensively exploring contractile properties in relation to spinal motor neuron output expressed as motor unit firing rates (MUFRs) in the hamstrings of 11 (26.5 ± 3.8) young men. Maximal isometric voluntary contraction (MVC), voluntary activation, stimulated contractile properties including a force-frequency relationship, and MUFRs from submaximal to maximal voluntary contractile intensities were assessed in the hamstrings. Strength and MUFRs were assessed at two presumably different muscle lengths by varying the knee joint angles (90° and 160°). Knee flexion MVCs were 60–70% greater in the extended position (160°). The frequency required to elicit 50% of maximum tetanic torque was 16–17 Hz. Mean MUFRs at 25–50% MVC were 9–31% less in the biceps femoris compared with the semimembranosus-semitendinosus group. Knee joint angle (muscle length) influenced MUFRs such that mean MUFRs were greater in the shortened (90°) position at 50% and 100% MVC. Compared with previous reports, mean maximal MUFRs in the hamstrings are greater than those in the quadriceps and triceps surae and somewhat less than those in the tibialis anterior. Mean maximal MUFRs in the hamstrings are influenced by changes in knee joint angle, with lower firing rates in the biceps femoris compared with the semimembranosus-semitendinosus muscle group. NEW & NOTEWORTHY We studied motor unit firing rates (MUFRs) at various voluntary contraction intensities in the hamstrings, one of the only major lower limb muscles to have MUFRs affected by muscle length changes. Within the hamstrings muscle-specific differences have greater impact on MUFRs than length changes

Calcium-responsive contractility during fertilization in sea urchin eggs.

PubMed

Stack, Christianna; Lucero, Amy J; Shuster, Charles B

2006-04-01

Fertilization triggers a reorganization of oocyte cytoskeleton, and in sea urchins, there is a dramatic increase in cortical F-actin. However, the role that myosin II plays during fertilization remains largely unexplored. Myosin II is localized to the cortical cytoskeleton both before and after fertilization and to examine myosin II contractility in living cells, Lytechinus pictus eggs were observed by time-lapse microscopy. Upon sperm binding, a cell surface deflection traversed the egg that was followed by and dependent on the calcium wave. The calcium-dependence of surface contractility could be reproduced in unfertilized eggs, where mobilization of intracellular calcium in unfertilized eggs under compression resulted in a marked contractile response. Lastly, inhibition of myosin II delayed absorption of the fertilization cone, suggesting that myosin II not only responds to the same signals that activate eggs but also participates in the remodeling of the cortical actomyosin cytoskeleton during the first zygotic cell cycle. (c) 2006 Wiley-Liss, Inc.

Calcium-Responsive Contractility During Fertilization in Sea Urchin Eggs

PubMed Central

Stack, Christianna; Lucero, Amy J.; Shuster, Charles B.

2008-01-01

Fertilization triggers a reorganization of oocyte cytoskeleton, and in sea urchins there is a dramatic increase in cortical F-actin. However, the role that myosin II plays during fertilization remains largely unexplored. Myosin II is localized to the cortical cytoskeleton both prior to- and following fertilization, and to examine myosin II contractility in living cells, Lytechinus pictus eggs were observed by time-lapse microscopy. Upon sperm binding, a cell surface deflection traversed the egg that was followed- and dependent on the calcium wave. The calcium-dependence of surface contractility could be reproduced in unfertilized eggs, where mobilization of intracellular calcium in unfertilized eggs under compression resulted in a marked contractile response. Lastly, inhibition of myosin II delayed absorption of the fertilization cone, suggesting that myosin II not only responds to the same signals that activate eggs, but also participates in the remodeling of the cortical actomyosin cytoskeleton during the first zygotic cell cycle. PMID:16470603

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

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).

Blood pressure and the contractility of a human leg muscle.

PubMed

Luu, Billy L; Fitzpatrick, Richard C

2013-11-01

These studies investigate the relationships between perfusion pressure, force output and pressor responses for the contracting human tibialis anterior muscle. Eight healthy adults were studied. Changing the height of tibialis anterior relative to the heart was used to control local perfusion pressure. Electrically stimulated tetanic force output was highly sensitive to physiological variations in perfusion pressure showing a proportionate change in force output of 6.5% per 10 mmHg. This perfusion-dependent change in contractility begins within seconds and is reversible with a 53 s time constant, demonstrating a steady-state equilibrium between contractility and perfusion pressure. These stimulated contractions did not produce significant cardiovascular responses, indicating that the muscle pressor response does not play a major role in cardiovascular regulation at these workloads. Voluntary contractions at forces that would require constant motor drive if perfusion pressure had remained constant generated a central pressor response when perfusion pressure was lowered. This is consistent with a larger cortical drive being required to compensate for the lost contractility with lower perfusion pressure. The relationship between contractility and perfusion for this large postural muscle was not different from that of a small hand muscle (adductor pollicis) and it responded similarly to passive peripheral and active central changes in arterial pressure, but extended over a wider operating range of pressures. If we consider that, in a goal-oriented motor task, muscle contractility determines central motor output and the central pressor response, these results indicate that muscle would fatigue twice as fast without a pressor response. From its extent, timing and reversibility we propose a testable hypothesis that this change in contractility arises through contraction- and perfusion-dependent changes in interstitial K(+) concentration.

PKA catalytic subunit compartmentation regulates contractile and hypertrophic responses to β-adrenergic signaling

PubMed Central

Yang, Jason H.; Polanowska-Grabowska, Renata K.; Smith, Jeffrey S.; Shields, Charles W.; Saucerman, Jeffrey J.

2014-01-01

β-adrenergic signaling is spatiotemporally heterogeneous in the cardiac myocyte, conferring exquisite control to sympathetic stimulation. Such heterogeneity drives the formation of protein kinase A (PKA) signaling microdomains, which regulate Ca2+ handling and contractility. Here, we test the hypothesis that the nucleus independently comprises a PKA signaling microdomain regulating myocyte hypertrophy. Spatially-targeted FRET reporters for PKA activity identified slower PKA activation and lower isoproterenol sensitivity in the nucleus (t50 = 10.60±0.68 min; EC50 = 89.00 nmol/L) than in the cytosol (t50 = 3.71±0.25 min; EC50 = 1.22 nmol/L). These differences were not explained by cAMP or AKAP-based compartmentation. A computational model of cytosolic and nuclear PKA activity was developed and predicted that differences in nuclear PKA dynamics and magnitude are regulated by slow PKA catalytic subunit diffusion, while differences in isoproterenol sensitivity are regulated by nuclear expression of protein kinase inhibitor (PKI). These were validated by FRET and immunofluorescence. The model also predicted differential phosphorylation of PKA substrates regulating cell contractility and hypertrophy. Ca2+ and cell hypertrophy measurements validated these predictions and identified higher isoproterenol sensitivity for contractile enhancements (EC50 = 1.84 nmol/L) over cell hypertrophy (EC50 = 85.88 nmol/L). Over-expression of spatially targeted PKA catalytic subunit to the cytosol or nucleus enhanced contractile and hypertrophic responses, respectively. We conclude that restricted PKA catalytic subunit diffusion is an important PKA compartmentation mechanism and the nucleus comprises a novel PKA signaling microdomain, insulating hypertrophic from contractile β-adrenergic signaling responses. PMID:24225179

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

Robust gap repair in the contractile ring ensures timely completion of cytokinesis

PubMed Central

Maiato, Helder; Pinto, Inês Mendes; Rubinstein, Boris

2016-01-01

Cytokinesis in animal cells requires the constriction of an actomyosin contractile ring, whose architecture and mechanism remain poorly understood. We use laser microsurgery to explore the biophysical properties of constricting rings in Caenorhabditis elegans embryos. Laser cutting causes rings to snap open. However, instead of disintegrating, ring topology recovers and constriction proceeds. In response to severing, a finite gap forms and is repaired by recruitment of new material in an actin polymerization–dependent manner. An open ring is able to constrict, and rings repair from successive cuts. After gap repair, an increase in constriction velocity allows cytokinesis to complete at the same time as controls. Our analysis demonstrates that tension in the ring increases while net cortical tension at the site of ingression decreases throughout constriction and suggests that cytokinesis is accomplished by contractile modules that assemble and contract autonomously, enabling local repair of the actomyosin network. Consequently, cytokinesis is a highly robust process impervious to discontinuities in contractile ring structure. PMID:27974482

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.

Increased CCT-eta expression is a marker of latent and active disease and a modulator of fibroblast contractility in Dupuytren's contracture.

PubMed

Satish, Latha; O'Gorman, David B; Johnson, Sandra; Raykha, Christina; Gan, Bing Siang; Wang, James H-C; Kathju, Sandeep

2013-07-01

Dupuytren's contracture (DC) is a fibroproliferative disorder of unknown etiology characterized by a scar-like contracture that develops in the palm and/or digits. We have previously reported that the eta subunit of the chaperonin containing T-complex polypeptide (CCT-eta) is increased in fibrotic wound healing, and is essential for the accumulation of α-smooth muscle actin (α-SMA) in fibroblasts. The purpose of this study was to determine if CCT-eta is similarly implicated in the aberrant fibrosis seen in DC and to investigate the role of CCT-eta in the behavior of myo/fibroblasts in DC. Fibroblasts were obtained from DC-affected palmar fascia, from adjacent phenotypically normal palmar fascia in the same DC patients (PF), and from non-DC palmar fascial tissues in patients undergoing carpal tunnel (CT) release. Inherent contractility in these three populations was examined using fibroblast-populated collagen lattices (FPCLs) and by cell traction force microscopy. Expression of CCT-eta and α-SMA protein was determined by Western blot. The effect of CCT-eta inhibition on the contractility of DC cells was determined by deploying an siRNA versus CCT-eta. DC cells were significantly more contractile than both matching palmar fascial (PF) cells and CT cells in both assays, with PF cells demonstrating an intermediate contractility in the FPCL assay. Whereas α-SMA protein was significantly increased only in DC cells compared to PF and CT cells, CCT-eta protein was significantly increased in both PF and DC cells compared to CT cells. siRNA-mediated depletion of CCT-eta inhibited the accumulation of both CCT-eta and α-SMA protein in DC cells, and also significantly decreased the contractility of treated DC cells. These observations suggest that increased expression of CCT-eta appears to be a marker for latent and active disease in these patients and to be essential for the increased contractility exhibited by these fibroblasts.

Contractile activity of human skeletal muscle cells prevents insulin resistance by inhibiting pro-inflammatory signalling pathways.

PubMed

Lambernd, S; Taube, A; Schober, A; Platzbecker, B; Görgens, S W; Schlich, R; Jeruschke, K; Weiss, J; Eckardt, K; Eckel, J

2012-04-01

Obesity is closely associated with muscle insulin resistance and is a major risk factor for the pathogenesis of type 2 diabetes. Regular physical activity not only prevents obesity, but also considerably improves insulin sensitivity and skeletal muscle metabolism. We sought to establish and characterise an in vitro model of human skeletal muscle contraction, with a view to directly studying the signalling pathways and mechanisms that are involved in the beneficial effects of muscle activity. Contracting human skeletal muscle cell cultures were established by applying electrical pulse stimulation. To induce insulin resistance, skeletal muscle cells were incubated with human adipocyte-derived conditioned medium, monocyte chemotactic protein (MCP)-1 and chemerin. Similarly to in exercising skeletal muscle in vivo, electrical pulse stimulation induced contractile activity in human skeletal muscle cells, combined with the formation of sarcomeres, activation of AMP-activated protein kinase (AMPK) and increased IL-6 secretion. Insulin-stimulated glucose uptake was substantially elevated in contracting cells compared with control. The incubation of skeletal muscle cells with adipocyte-conditioned media, chemerin and MCP-1 significantly reduced the insulin-stimulated phosphorylation of Akt. This effect was abrogated by concomitant pulse stimulation of the cells. Additionally, pro-inflammatory signalling by adipocyte-derived factors was completely prevented by electrical pulse stimulation of the myotubes. We showed that the effects of electrical pulse stimulation on skeletal muscle cells were similar to the effect of exercise on skeletal muscle in vivo in terms of enhanced AMPK activation and IL-6 secretion. In our model, muscle contractile activity eliminates insulin resistance by blocking pro-inflammatory signalling pathways. This novel model therefore provides a unique tool for investigating the molecular mechanisms that mediate the beneficial effects of muscle

Effects of minoxidil and nitroprusside on reflex increases in myocardial contractility.

PubMed Central

Robie, N W

1978-01-01

1 The effects of nitroprusside and minoxidil on increases in myocardial contractility resulting from carotid artery occlusion were investigated in anaesthetized dogs. The results were compared with those produced by intravenous influsion of noradrenaline. 2 Nitroprusside and minoxidil attenuated the pressor responses produced by carotid artery occlusion. 3 Nitroprusside, but not minoxidil, attenuated the maximal myocardial contractility resulting from carotid occlusion. 4 The pressor and contractility responses to noradrenaline infusion were unaffected by either agent. 5 Nitroprusside failed to alter the myocardial responses produced by dimethylphenylpiperazinium. 6 These results, in conjunction with those of other investigators who have demonstrated that nitroprusside does not affect the release of noradrenaline from adrenergic neurons, suggest that nitroprusside may inhibit sympathetic nervous system reflex activity via an afferent and/or central component. PMID:620094

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

Blood pressure and the contractility of a human leg muscle

PubMed Central

Luu, Billy L; Fitzpatrick, Richard C

2013-01-01

These studies investigate the relationships between perfusion pressure, force output and pressor responses for the contracting human tibialis anterior muscle. Eight healthy adults were studied. Changing the height of tibialis anterior relative to the heart was used to control local perfusion pressure. Electrically stimulated tetanic force output was highly sensitive to physiological variations in perfusion pressure showing a proportionate change in force output of 6.5% per 10 mmHg. This perfusion-dependent change in contractility begins within seconds and is reversible with a 53 s time constant, demonstrating a steady-state equilibrium between contractility and perfusion pressure. These stimulated contractions did not produce significant cardiovascular responses, indicating that the muscle pressor response does not play a major role in cardiovascular regulation at these workloads. Voluntary contractions at forces that would require constant motor drive if perfusion pressure had remained constant generated a central pressor response when perfusion pressure was lowered. This is consistent with a larger cortical drive being required to compensate for the lost contractility with lower perfusion pressure. The relationship between contractility and perfusion for this large postural muscle was not different from that of a small hand muscle (adductor pollicis) and it responded similarly to passive peripheral and active central changes in arterial pressure, but extended over a wider operating range of pressures. If we consider that, in a goal-oriented motor task, muscle contractility determines central motor output and the central pressor response, these results indicate that muscle would fatigue twice as fast without a pressor response. From its extent, timing and reversibility we propose a testable hypothesis that this change in contractility arises through contraction- and perfusion-dependent changes in interstitial K+ concentration. PMID:24018946

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.

CALIX[4]ARENE C-99 INHIBITS MYOSIN ATPase ACTIVITY AND CHANGES THE ORGANIZATION OF CONTRACTILE FILAMENTS OF MYOMETRIUM.

PubMed

Labyntseva, R D; Bevza, A A; Lul'ko, A O; Cherenok, S O; Kalchenko, V I; Kosterin, S O

2015-01-01

Calix[4]arenes are cup-like macrocyclic (polyphenolic) compounds, they are regarded as promising molecular "platforms" for the design of new physiologically active compounds. We have earlier found that calix[4]arene C-99 inhibits the ATPase activity of actomyosin and myosin subfragment-1 of pig uterus in vitro. The aim of this study was to investigate the interaction of calix[4]arene C-99 with myosin from rat uterine myocytes. It was found that the ATPase activity of myosin prepared from pre-incubated with 100 mM of calix[4]arene C-99 myocytes was almost 50% lower than in control. Additionally, we have revealed the effect of calix[4]arene C-99 on the subcellular distribution of actin and myosin in uterus myocytes by the method of confocal microscopy. This effect can be caused by reorganization of the structure of the contractile smooth muscle cell proteins due to their interaction with calix[4]arene. The obtained results demonstrate the ability of calix[4]arene C-99 to penetrate into the uterus muscle cells and affect not only the myosin ATPase activity, but also the structure of the actin and myosin filaments in the myometrial cells. Demonstrated ability of calix[4]arene C-99 can be used for development of new pharmacological agents for efficient normalization of myometrial contractile hyperfunction.

High-fat diet-induced obesity leads to resistance to leptin-induced cardiomyocyte contractile response.

PubMed

Ren, Jun; Zhu, Bang-Hao; Relling, David P; Esberg, Lucy B; Ceylan-Isik, Asli F

2008-11-01

Levels of the obese gene product leptin are often elevated in obesity and may contribute to obesity-induced cardiovascular complications. However, the role of leptin in obesity-associated cardiac abnormalities has not been clearly defined. This study was designed to determine the influence of high-fat diet-induced obesity on cardiac contractile response of leptin. Mechanical and intracellular Ca(2+) properties were evaluated using an IonOptix system in cardiomyocytes from adult rats fed low- and high-fat diets for 12 weeks. Cardiomyocyte contractile and intracellular Ca(2+) properties were examined including peak shortening, duration and maximal velocity of shortening/relengthening (TPS/TR(90), +/-dl/dt), Fura-2-fluorescence intensity change (DeltaFFI), and intracellular Ca(2+) decay rate (tau). Expression of the leptin receptor (Ob-R) was evaluated by western blot analysis. High-fat diet increased systolic blood pressure and plasma leptin levels. PS and +/-dl/dt were depressed whereas TPS and TR(90) were prolonged after high-fat diet feeding. Leptin elicited a concentration-dependent (0-1,000 nmol/l) inhibition of PS, +/-dl/dt, and DeltaFFI in low-fat but not high-fat diet-fed rat cardiomyocytes without affecting TPS and TR(90). The Janus kinase 2 (JAK2) inhibitor AG490, the mitogen-activated protein kinase (MAPK) inhibitor SB203580, and the nitric oxide synthase (NOS) inhibitor L-NAME abrogated leptin-induced cardiomyocyte contractile response in low-fat diet group without affecting the high-fat diet group. High-fat diet significantly downregulated cardiac expression of Ob-R. Elevation of extracellular Ca(2+) concentration nullified obesity-induced cardiomyocyte mechanical dysfunction and leptin-induced depression in PS. These data indicate presence of cardiac leptin resistance in diet-induced obesity possibly associated with impaired leptin receptor signaling.

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.

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.

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

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.

Omecamtiv mercabil and blebbistatin modulate cardiac contractility by perturbing the regulatory state of the myosin filament

PubMed Central

Kampourakis, Thomas; Zhang, Xuemeng; Sun, Yin‐Biao

2017-01-01

Key points Omecamtiv mecarbil and blebbistatin perturb the regulatory state of the thick filament in heart muscle.Omecamtiv mecarbil increases contractility at low levels of activation by stabilizing the ON state of the thick filament.Omecamtiv mecarbil decreases contractility at high levels of activation by disrupting the acto‐myosin ATPase cycle.Blebbistatin reduces contractility by stabilizing the thick filament OFF state and inhibiting acto‐myosin ATPase.Thick filament regulation is a promising target for novel therapeutics in heart disease. Abstract Contraction of heart muscle is triggered by a transient rise in intracellular free calcium concentration linked to a change in the structure of the actin‐containing thin filaments that allows the head or motor domains of myosin from the thick filaments to bind to them and induce filament sliding. It is becoming increasingly clear that cardiac contractility is also regulated through structural changes in the thick filaments, although the molecular mechanisms underlying thick filament regulation are still relatively poorly understood. Here we investigated those mechanisms using small molecules – omecamtiv mecarbil (OM) and blebbistatin (BS) – that bind specifically to myosin and respectively activate or inhibit contractility in demembranated cardiac muscle cells. We measured isometric force and ATP utilization at different calcium and small‐molecule concentrations in parallel with in situ structural changes determined using fluorescent probes on the myosin regulatory light chain in the thick filaments and on troponin C in the thin filaments. The results show that BS inhibits contractility and actin‐myosin ATPase by stabilizing the OFF state of the thick filament in which myosin head domains are more parallel to the filament axis. In contrast, OM stabilizes the ON state of the thick filament, but inhibits contractility at high intracellular calcium concentration by disrupting the actin‐myosin ATPase

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

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.

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.

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.

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

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

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.

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.

Omecamtiv mercabil and blebbistatin modulate cardiac contractility by perturbing the regulatory state of the myosin filament.

PubMed

Kampourakis, Thomas; Zhang, Xuemeng; Sun, Yin-Biao; Irving, Malcolm

2018-01-01

Omecamtiv mecarbil and blebbistatin perturb the regulatory state of the thick filament in heart muscle. Omecamtiv mecarbil increases contractility at low levels of activation by stabilizing the ON state of the thick filament. Omecamtiv mecarbil decreases contractility at high levels of activation by disrupting the acto-myosin ATPase cycle. Blebbistatin reduces contractility by stabilizing the thick filament OFF state and inhibiting acto-myosin ATPase. Thick filament regulation is a promising target for novel therapeutics in heart disease. Contraction of heart muscle is triggered by a transient rise in intracellular free calcium concentration linked to a change in the structure of the actin-containing thin filaments that allows the head or motor domains of myosin from the thick filaments to bind to them and induce filament sliding. It is becoming increasingly clear that cardiac contractility is also regulated through structural changes in the thick filaments, although the molecular mechanisms underlying thick filament regulation are still relatively poorly understood. Here we investigated those mechanisms using small molecules - omecamtiv mecarbil (OM) and blebbistatin (BS) - that bind specifically to myosin and respectively activate or inhibit contractility in demembranated cardiac muscle cells. We measured isometric force and ATP utilization at different calcium and small-molecule concentrations in parallel with in situ structural changes determined using fluorescent probes on the myosin regulatory light chain in the thick filaments and on troponin C in the thin filaments. The results show that BS inhibits contractility and actin-myosin ATPase by stabilizing the OFF state of the thick filament in which myosin head domains are more parallel to the filament axis. In contrast, OM stabilizes the ON state of the thick filament, but inhibits contractility at high intracellular calcium concentration by disrupting the actin-myosin ATPase pathway. The effects of BS and OM

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.

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

Menthol Inhibits Detrusor Contractility Independently of TRPM8 Activation

PubMed Central

Ramos-Filho, Antonio Celso Saragossa; Shah, Ajay; Augusto, Taize Machado; Barbosa, Guilherme Oliveira; Leiria, Luiz Osorio; de Carvalho, Hernandes Faustino; Antunes, Edson; Grant, Andrew Douglas

2014-01-01

Agonists such as icilin and menthol can activate the cool temperature-sensitive ion channel TRPM8. However, biological responses to menthol may occur independently of TRPM8 activation. In the rodent urinary bladder, menthol facilitates the micturition reflex but inhibits muscarinic contractions of the detrusor smooth muscle. The site(s) of TRPM8 expression in the bladder are controversial. In this study we investigated the regulation of bladder contractility in vitro by menthol. Bladder strips from wild type and TRPM8 knockout male mice (25–30 g) were dissected free and mounted in organ baths. Isometric contractions to carbachol (1 nM–30 µM), CaCl2 (1 µM to 100 mM) and electrical field stimulation (EFS; 8, 16, 32 Hz) were measured. Strips from both groups contracted similarly in response to both carbachol and EFS. Menthol (300 µM) or nifedipine (1 µM) inhibited carbachol and EFS-induced contractions in both wild type and TRPM8 knockout bladder strips. Incubation with the sodium channel blocker tetrodotoxin (1 µM), replacement of extracellular sodium with the impermeant cation N-Methyl-D-Glucamine, incubation with a cocktail of potassium channel inhibitors (100 nM charybdotoxin, 1 µM apamin, 10 µM glibenclamide and 1 µM tetraethylammonium) or removal of the urothelium did not affect the inhibitory actions of menthol. Contraction to CaCl2 was markedly inhibited by either menthol or nifedipine. In cultured bladder smooth muscle cells, menthol or nifedipine abrogated the carbachol or KCl-induced increases in [Ca2+]i. Intravesical administration of menthol increased voiding frequency while decreasing peak voiding pressure. We conclude that menthol inhibits muscarinic bladder contractions through blockade of L-type calcium channels, independently of TRPM8 activation. PMID:25375115

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.

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

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.

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

β-Citronellol, an alcoholic monoterpene with inhibitory properties on the contractility of rat trachea

PubMed Central

Vasconcelos, T.B.; Ribeiro-Filho, H.V.; Lucetti, L.T.; Magalhães, P.J.C.

2015-01-01

β-Citronellol is an alcoholic monoterpene found in essential oils such Cymbopogon citratus (a plant with antihypertensive properties). β-Citronellol can act against pathogenic microorganisms that affect airways and, in virtue of the popular use of β-citronellol-enriched essential oils in aromatherapy, we assessed its pharmacologic effects on the contractility of rat trachea. Contractions of isolated tracheal rings were recorded isometrically through a force transducer connected to a data-acquisition device. β-Citronellol relaxed sustained contractions induced by acetylcholine or high extracellular potassium, but half-maximal inhibitory concentrations (IC50) for K+-elicited stimuli were smaller than those for cholinergic contractions. It also inhibited contractions induced by electrical field stimulation or sodium orthovanadate with pharmacologic potency equivalent to that seen against acetylcholine-induced contractions. When contractions were evoked by selective recruitment of Ca2+ from the extracellular medium, β-citronellol preferentially inhibited contractions that involved voltage-operated (but not receptor-operated) pathways. β-Citronellol (but not verapamil) inhibited contractions induced by restoration of external Ca2+ levels after depleting internal Ca2+ stores with the concomitant presence of thapsigargin and recurrent challenge with acetylcholine. Treatment of tracheal rings with L-NAME, indomethacin or tetraethylammonium did not change the relaxing effects of β-citronellol. Inhibition of transient receptor potential vanilloid subtype 1 (TRPV1) or transient receptor potential ankyrin 1 (TRPA1) receptors with selective antagonists caused no change in the effects of β-citronellol. In conclusion, β-citronellol exerted inhibitory effects on rat tracheal rings, with predominant effects on contractions that recruit Ca2+ inflow towards the cytosol by voltage-gated pathways, whereas it appears less active against contractions elicited by receptor

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.

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

Rapid fusion between mesenchymal stem cells and cardiomyocytes yields electrically active, non-contractile hybrid cells.

PubMed

Shadrin, Ilya Y; Yoon, Woohyun; Li, Liqing; Shepherd, Neal; Bursac, Nenad

2015-07-10

Cardiac cell therapies involving bone marrow-derived human mesenchymal stem cells (hMSCs) have shown promising results, although their mechanisms of action are still poorly understood. Here, we investigated direct interactions between hMSCs and cardiomyocytes in vitro. Using a genetic Ca(2+) indicator gCaMP3 to efficiently label hMSCs in co-cultures with neonatal rat ventricular myocytes (NRVMs), we determined that 25-40% of hMSCs (from 4 independent donors) acquired periodic Ca(2+) transients and cardiac markers through spontaneous fusion with NRVMs. Sharp electrode and voltage-clamp recordings in fused cells showed action potential properties and Ca(2+) current amplitudes in between those of non-fused hMSCs and NRVMs. Time-lapse video-microscopy revealed the first direct evidence of active fusion between hMSCs and NRVMs within several hours of co-culture. Application of blebbistatin, nifedipine or verapamil caused complete and reversible inhibition of fusion, suggesting potential roles for actomyosin bridging and Ca(2+) channels in the fusion process. Immunostaining for Cx43, Ki67, and sarcomeric α-actinin showed that fused cells remain strongly coupled to surrounding NRVMs, but downregulate sarcomeric structures over time, acquiring a non-proliferative and non-contractile phenotype. Overall, these results describe the phenotype and mechanisms of hybrid cell formation via fusion of hMSCs and cardiomyocytes with potential implications for cardiac cell therapy.

Diminished contractile responses of isolated conduit arteries in two rat models of hypertension.

PubMed

Zemancíková, Anna; Török, Jozef

2013-08-31

Hypertension is accompanied by thickening of arteries, resulting in marked changes in their passive and active mechanical properties. The aim of this study was to demonstrate that the large conduit arteries from hypertensive individuals may not exhibit enhanced contractions in vitro, as is often claimed. Mechanical responses to vasoconstrictor stimuli were measured under isometric conditions using ring arterial segments isolated from spontaneously hypertensive rats, N(omega)-nitro-L-arginine methyl ester (L-NAME)-treated Wistar rats, and untreated Wistar rats serving as normotensive control. We found that thoracic aortas from both types of hypertensive rats had a greater sensitivity but diminished maximal developed tension in response to noradrenaline, when compared with that from normotensive rats. In superior mesenteric arteries, the sensitivity to noradrenaline was similar in all examined rat groups but in L-NAME-treated rats, these arteries exhibited decreased active force when stimulated with high noradrenaline concentrations, or with 100 mM KCl. These results indicate that hypertension leads to specific biomechanical alterations in diverse arterial types which are reflected in different modifications in their contractile properties.

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.

Geometrical Origins of Contractility in Disordered Actomyosin Networks

NASA Astrophysics Data System (ADS)

Lenz, Martin

2014-10-01

Movement within eukaryotic cells largely originates from localized forces exerted by myosin motors on scaffolds of actin filaments. Although individual motors locally exert both contractile and extensile forces, large actomyosin structures at the cellular scale are overwhelmingly contractile, suggesting that the scaffold serves to favor contraction over extension. While this mechanism is well understood in highly organized striated muscle, its origin in disordered networks such as the cell cortex is unknown. Here, we develop a mathematical model of the actin scaffold's local two- or three-dimensional mechanics and identify four competing contraction mechanisms. We predict that one mechanism dominates, whereby local deformations of the actin break the balance between contraction and extension. In this mechanism, contractile forces result mostly from motors plucking the filaments transversely rather than buckling them longitudinally. These findings shed light on recent in vitro experiments and provide a new geometrical understanding of contractility in the myriad of disordered actomyosin systems found in vivo.

[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.

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.

Effects of Hange-shashin-to (TJ-14) and Keishi-ka-shakuyaku-to (TJ-60) on contractile activity of circular smooth muscle of the rat distal colon.

PubMed

Kito, Yoshihiko; Teramoto, Noriyoshi

2012-11-01

The Japanese Kampo medicines Hange-shashin-to (TJ-14) and Keishi-ka-shakuyaku-to (TJ-60) have been used to treat symptoms of human diarrhea on an empirical basis as Japanese traditional medicines. However, it remains unclear how these drugs affect smooth muscle tissues in the distal colon. The aim of the present study was to investigate the effects of TJ-14 and TJ-60 on the contractile activity of circular smooth muscle from the rat distal colon. TJ-14 and TJ-60 (both 1 mg/ml) inhibited spontaneous contractions of circumferentially cut preparations with the mucosa intact. Blockade of nitric oxide (NO) synthase or soluble guanylate cyclase activity abolished the inhibitory effects of TJ-60 but only attenuated the inhibitory effects of TJ-14. Apamin (1 μM), a blocker of small-conductance Ca(2+)-activated K(+) channels (SK channels), attenuated the inhibitory effects of 5 mg/ml TJ-60 but not those of 5 mg/ml TJ-14. TJ-14 suppressed contractile responses (phasic contractions and off-contractions) evoked by transmural nerve stimulation and increased basal tone, whereas TJ-60 had little effect on these parameters. These results suggest that 1 mg/ml TJ-14 or TJ-60 likely inhibits spontaneous contractions of the rat distal colon through the production of NO. Activation of SK channels seems to be involved in the inhibitory effects of 5 mg/ml TJ-60. Since TJ-14 has potent inhibitory effects on myogenic and neurogenic contractile activity, TJ-14 may be useful in suppressing gastrointestinal motility.

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.

Initial diameter of the polar body contractile ring is minimized by the centralspindlin complex.

PubMed

Fabritius, Amy S; Flynn, Jonathan R; McNally, Francis J

2011-11-01

Polar body formation is an essential step in forming haploid eggs from diploid oocytes. This process involves completion of a highly asymmetric cytokinesis that results in a large egg and two small polar bodies. Unlike mitotic contractile rings, polar body contractile rings assemble over one spindle pole so that the spindle must move through the contractile ring before cytokinesis. During time-lapse imaging of C. elegans meiosis, the contractile ring moved downward along the length of the spindle and completed scission at the midpoint of the spindle, even when spindle length or rate of ring movement was increased. Patches of myosin heavy chain and dynamic furrowing of the plasma membrane over the entire embryo suggested that global cortical contraction forces the meiotic spindle and overlying membrane out through the contractile ring center. Consistent with this model, depletion of myosin phosphatase increased the velocity of ring movement along the length of the spindle. Global dynamic furrowing, which was restricted to anaphase I and II, was dependent on myosin II, the anaphase promoting complex and separase, but did not require cortical contact by the spindle. Large cortical patches of myosin during metaphase I and II indicated that myosin was already in the active form before activation of separase. To identify the signal at the midpoint of the anaphase spindle that induces scission, we depleted two proteins that mark the exact midpoint of the spindle during late anaphase, CYK-4 and ZEN-4. Depletion of either protein resulted in the unexpected phenotype of initial ingression of a polar body ring with twice the diameter of wild type. This phenotype revealed a novel mechanism for minimizing polar body size. Proteins at the spindle midpoint are required for initial ring ingression to occur close to the membrane-proximal spindle pole. 2011 Elsevier Inc. All rights reserved.

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

Effect of fenoterol-induced constitutive beta(2)-adrenoceptor activity on contractile receptor function in airway smooth muscle.

PubMed

de Vries, B; Roffel, A F; Zaagsma, J; Meurs, H

2001-11-23

In the present study, we investigated the effect of fenoterol-induced constitutive beta(2)-adrenoceptor activity on muscarinic receptor agonist- and histamine-induced bovine tracheal smooth muscle contractions. Bovine tracheal smooth muscle strips were incubated with 10 microM fenoterol or vehicle for various periods of time (5, 30 min, 18 h) at 37 degrees C. After extensive washout (3 h, 37 degrees C), isometric contractions were measured to the full muscarinic receptor agonist methacholine, the partial muscarinic receptor agonist 4-(m-chlorophenyl-carbamoyloxy)-2-butynyltrimethylammonium (McN-A-343) and histamine. Fenoterol treatment significantly reduced the sensitivity (pEC(50)) to methacholine in a time-dependent manner, without affecting maximal contraction (E(max)). Fenoterol treatment similarly reduced the pEC(50) of McN-A-343 and histamine; however, E(max) values were also reduced, to approximately 70% of control after 18-h treatment. The inverse agonist timolol, having no effect on control preparations, consistently restored the reduced pEC(50) and E(max) values of the contractile agonists. Remarkably, in the presence of timolol the pEC(50) values of McN-A-343 and histamine in fenoterol-treated airways were significantly enhanced compared to controls. In conclusion, fenoterol-induced constitutive beta(2)-adrenoceptor activity reduces muscarinic receptor agonist- and histamine-induced contractions of bovine tracheal smooth muscle, which can be reversed by the inverse agonist timolol. Moreover, after beta(2)-adrenoceptor agonist treatment, inverse agonism by beta-adrenoceptor antagonists may cause enhanced airway reactivity to contractile mediators.

Stochastic Ratcheting on a Funneled Energy Landscape Is Necessary for Highly Efficient Contractility of Actomyosin Force Dipoles

NASA Astrophysics Data System (ADS)

Komianos, James E.; Papoian, Garegin A.

2018-04-01

Current understanding of how contractility emerges in disordered actomyosin networks of nonmuscle cells is still largely based on the intuition derived from earlier works on muscle contractility. In addition, in disordered networks, passive cross-linkers have been hypothesized to percolate force chains in the network, hence, establishing large-scale connectivity between local contractile clusters. This view, however, largely overlooks the free energy of cross-linker binding at the microscale, which, even in the absence of active fluctuations, provides a thermodynamic drive towards highly overlapping filamentous states. In this work, we use stochastic simulations and mean-field theory to shed light on the dynamics of a single actomyosin force dipole—a pair of antiparallel actin filaments interacting with active myosin II motors and passive cross-linkers. We first show that while passive cross-linking without motor activity can produce significant contraction between a pair of actin filaments, driven by thermodynamic favorability of cross-linker binding, a sharp onset of kinetic arrest exists at large cross-link binding energies, greatly diminishing the effectiveness of this contractility mechanism. Then, when considering an active force dipole containing nonmuscle myosin II, we find that cross-linkers can also serve as a structural ratchet when the motor dissociates stochastically from the actin filaments, resulting in significant force amplification when both molecules are present. Our results provide predictions of how actomyosin force dipoles behave at the molecular level with respect to filament boundary conditions, passive cross-linking, and motor activity, which can explicitly be tested using an optical trapping experiment.

Effect of spaceflight on the isotonic contractile properties of single skeletal muscle fibers in the rhesus monkey

NASA Technical Reports Server (NTRS)

Fitts, R. H.; Romatowski, J. G.; Blaser, C.; De La Cruz, L.; Gettelman, G. J.; Widrick, J. J.

2000-01-01

Experiments from both Cosmos and Space Shuttle missions have shown weightlessness to result in a rapid decline in the mass and force of rat hindlimb extensor muscles. Additionally, despite an increased maximal shortening velocity, peak power was reduced in rat soleus muscle post-flight. In humans, declines in voluntary peak isometric ankle extensor torque ranging from 15-40% have been reported following long- and short-term spaceflight and prolonged bed rest. Complete understanding of the cellular events responsible for the fiber atrophy and the decline in force, as well as the development of effective countermeasures, will require detailed knowledge of how the physiological and biochemical processes of muscle function are altered by spaceflight. The specific purpose of this investigation was to determine the extent to which the isotonic contractile properties of the slow- and fast-twitch fiber types of the soleus and gastrocnemius muscles of rhesus monkeys (Macaca mulatta) were altered by a 14-day spaceflight.

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.

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.

Chronic sustained hypoxia-induced redox remodeling causes contractile dysfunction in mouse sternohyoid muscle

PubMed Central

Lewis, Philip; Sheehan, David; Soares, Renata; Varela Coelho, Ana; O'Halloran, Ken D.

2015-01-01

Chronic sustained hypoxia (CH) induces structural and functional adaptations in respiratory muscles of animal models, however the underlying molecular mechanisms are unclear. This study explores the putative role of CH-induced redox remodeling in a translational mouse model, with a focus on the sternohyoid—a representative upper airway dilator muscle involved in the control of pharyngeal airway caliber. We hypothesized that exposure to CH induces redox disturbance in mouse sternohyoid muscle in a time-dependent manner affecting metabolic capacity and contractile performance. C57Bl6/J mice were exposed to normoxia or normobaric CH (FiO2 = 0.1) for 1, 3, or 6 weeks. A second cohort of animals was exposed to CH for 6 weeks with and without antioxidant supplementation (tempol or N-acetyl cysteine in the drinking water). Following CH exposure, we performed 2D redox proteomics with mass spectrometry, metabolic enzyme activity assays, and cell-signaling assays. Additionally, we assessed isotonic contractile and endurance properties ex vivo. Temporal changes in protein oxidation and glycolytic enzyme activities were observed. Redox modulation of sternohyoid muscle proteins key to contraction, metabolism and cellular homeostasis was identified. There was no change in redox-sensitive proteasome activity or HIF-1α content, but CH decreased phospho-JNK content independent of antioxidant supplementation. CH was detrimental to sternohyoid force- and power-generating capacity and this was prevented by chronic antioxidant supplementation. We conclude that CH causes upper airway dilator muscle dysfunction due to redox modulation of proteins key to function and homeostasis. Such changes could serve to further disrupt respiratory homeostasis in diseases characterized by CH such as chronic obstructive pulmonary disease. Antioxidants may have potential use as an adjunctive therapy in hypoxic respiratory disease. PMID:25941492

The role of skeletal muscle contractile duration throughout the whole day: reducing sedentary time and promoting universal physical activity in all people

PubMed Central

2017-01-01

Abstract A shared goal of many researchers has been to discover how to improve health and prevent disease, through safely replacing a large amount of daily sedentary time with physical activity in everyone, regardless of age and current health status. This involves contrasting how different muscle contractile activity patterns regulate the underlying molecular and physiological responses impacting health‐related processes. It also requires an equal attention to behavioural feasibility studies in extremely unfit and sedentary people. A sound scientific principle is that the body is constantly sensing and responding to changes in skeletal muscle metabolism induced by contractile activity. Because of that, the rapid time course of health‐related responses to physical inactivity/activity patterns are caused in large part directly because of the variable amounts of muscle inactivity/activity throughout the day. However, traditional modes and doses of exercise fall far short of replacing most of the sedentary time in the modern lifestyle, because both the weekly frequency and the weekly duration of exercise time are an order of magnitude less than those for people sitting inactive. This can explain why high amounts of sedentary time produce distinct metabolic and cardiovascular responses through inactivity physiology that are not sufficiently prevented by low doses of exercise. For these reasons, we hypothesize that maintaining a high metabolic rate over the majority of the day, through safe and sustainable types of muscular activity, will be the optimal way to create a healthy active lifestyle over the whole lifespan. PMID:28657123

The Fiber Contractility and Cytoskeleton Losses in Space are Less Pronounced in Mongolian Gerbils

NASA Astrophysics Data System (ADS)

Lipets, E. N.; Ponomareva, E. V.; Ogneva, I. V.; Vikhliantsev, I. M.; Karaduleva, E. V.; Kartashkina, N. L.; Kuznetsov, S. L.; Podlubnaia, Z. A.; Shenkman, B. S.

2008-06-01

This work was purposed on the comparison of space flight effects on m. soleus and m. tibialis anterior of Mongolian gerbils. The animals have been flown onboard biosatellite Foton-M3 for 12 days. Contractile properties of single skinned muscle fibers were studied. It was revealed that diameter of m. soleus skinned fibers and maximal isometric tension were decreased by 19.7% and 21.8% respectively. The Ca-sensitivity reduction wasn't significant, that was in accordance with absence of changes of titin and nebulin relative content in soleus and minor manifestations in slow-to-fast fiber ratio (9%, p<0.05). There weren't observed significant changes of the same parameters in m. tibialis anterior. Ultimately the fiber contractility and cytoskeleton losses in space are less pronounced in Mongolian gerbils than in rats.

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

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

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.

Retosiban Prevents Stretch-Induced Human Myometrial Contractility and Delays Labor in Cynomolgus Monkeys.

PubMed

Aye, Irving L M H; Moraitis, Alexandros A; Stanislaus, Dinesh; Charnock-Jones, D Stephen; Smith, Gordon C S

2018-03-01

Stretch of the myometrium promotes its contractility and is believed to contribute to the control of parturition at term and to the increased risk of preterm birth in multiple pregnancies. To determine the effects of the putative oxytocin receptor (OTR) inverse agonist retosiban on (1) the contractility of human myometrial explants and (2) labor in nonhuman primates. Human myometrial biopsies were obtained at planned term cesarean, and explants were exposed to stretch in the presence and absence of a range of drugs, including retosiban. The in vivo effects of retosiban were determined in cynomolgus monkeys. Prolonged mechanical stretch promoted myometrial extracellular signal-regulated kinase (ERK)1/2 phosphorylation. Moreover, stretch-induced stimulation of myometrial contractility was prevented by ERK1/2 inhibitors. Retosiban (10 nM) prevented stretch-induced stimulation of myometrial contractility and phosphorylation of ERK1/2. Moreover, the inhibitory effect of retosiban on stretch-induced ERK1/2 phosphorylation was prevented by coincubation with a 100-fold excess of a peptide OTR antagonist, atosiban. Compared with vehicle-treated cynomolgus monkeys, treatment with oral retosiban (100 to 150 days of gestational age) reduced the risk of spontaneous delivery (hazard ratio = 0.07, 95% confidence interval 0.01 to 0.60, P = 0.015). The OTR acts as a uterine mechanosensor, whereby stretch increases myometrial contractility through agonist-free activation of the OTR. Retosiban prevents this through inverse agonism of the OTR and, in vivo, reduced the likelihood of spontaneous labor in nonhuman primates. We hypothesize that retosiban may be an effective preventative treatment of preterm birth in high-risk multiple pregnancies, an area of unmet clinical need.

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.

Contractile activity of ATP and diadenosine tetraphosphate on urinary bladder in the rats: role of superoxide anion and urothelium.

PubMed

Khattab, M M; Al-Hrasen, M N

2006-04-01

Both ATP and diadenosine tetraphosphate (AP(4)A) produced a dose-dependent contraction of rat isolated urinary bladder rings. The AP(4)A dose-response curve was to the left of that of ATP, and the maximum response was greater than that produced by ATP. Mechanical removal of the urothelium increased the contractile response to ATP by between 53% and 71%, and that to AP(4)A by 42% (at highest AP(4)A concentration) to 68% at lower concentration. Inhibition of Cu/Zn superoxide dismutase with diethylthiocarbamate (DETCA, 5 mm) significantly reduced the ATP-evoked contraction by 31% (at high ATP concentration) to 40% at low ATP concentration. Similarly, the AP(4)A-induced contractions were significantly decreased by 27% at low AP(4)A level to 38% at higher concentrations. Induction of exogenous superoxide anion stress by the use of the superoxide anion generator, pyrogallol (0.5 mm), significantly decreased both ATP- and AP(4)A-induced contractions of the rat urinary bladder over the whole dose range. Contractile responses to ATP decreased by 36-40%, and those to AP(4)A by 44-49%. In conclusion, the urinary bladder urothelium exerts an inhibitory control over the purinergic contractility produced by adenine mononucleotides and dinucleotides. Superoxide anion stress, whether endogenous or exogenous, attenuates the ATP-induced as well as AP(4)A-induced contractility.

The Role of Rac1 on Carbachol-induced Contractile Activity in Detrusor Smooth Muscle from Streptozotocin-induced Diabetic Rats.

PubMed

Evcim, Atiye Sinem; Micili, Serap Cilaker; Karaman, Meral; Erbil, Guven; Guneli, Ensari; Gidener, Sedef; Gumustekin, Mukaddes

2015-06-01

This study was designed to determine the role of the small GTPase Rac1 on carbachol-induced contractile activity in detrusor smooth muscle using small inhibitor NSC 23766 in diabetic rats. Rac1 expression in bladder tissue was also evaluated. In the streptozotocin (STZ)-induced diabetic rat model, three study groups were composed of control, diabetic and insulin-treated diabetic subjects. The detrusor muscle strips were suspended in organ baths at the end of 8-12 weeks after STZ injection. Carbachol (CCh) (10(-9) -10(-4) M) concentration-response curves were obtained both in the absence and in the presence of Rac1 inhibitor NSC 23766 (0.1, 1 and 10 μM). Diabetes-related histopathological changes and Rac1 expressions were assessed by haematoxylin and eosin staining and immunohistochemical staining, respectively. CCh caused dose-dependent contractile responses in all the study groups. Rac1 inhibitor NSC 23766 inhibited CCh-induced contractile responses in all groups, but this inhibition seen in both diabetes groups was greater than in the control group. Histological examination revealed an increased bladder wall thickness both in the diabetes and in the insulin-treated diabetes groups compared to the control group. In immunohistochemical staining, expression of Rac1 was observed to be increased in all layers of bladder in both diabetic groups compared to the control group. In the diabetic bladders, increased expression of Rac1 and considerable inhibition of CCh-induced responses in the presence of NSC 23766 compared to those of the control group may indicate a specific role of Rac1 in diabetes-related bladder dysfunction, especially associated with cholinergic mediated detrusor overactivity. © 2014 Nordic Association for the Publication of BCPT (former Nordic Pharmacological Society).

Modulation of cardiac contractility by the phospholamban/SERCA2a regulatome.

PubMed

Kranias, Evangelia G; Hajjar, Roger J

2012-06-08

Heart disease remains the leading cause of death and disability in the Western world. Current therapies aim at treating the symptoms rather than the subcellular mechanisms, underlying the etiology and pathological remodeling in heart failure. A universal characteristic, contributing to the decreased contractile performance in human and experimental failing hearts, is impaired calcium sequestration into the sarcoplasmic reticulum (SR). SR calcium uptake is mediated by a Ca(2+)-ATPase (SERCA2), whose activity is reversibly regulated by phospholamban (PLN). Dephosphorylated PLN is an inhibitor of SERCA and phosphorylation of PLN relieves this inhibition. However, the initial simple view of a PLN/SERCA regulatory complex has been modified by our recent identification of SUMO, S100 and the histidine-rich Ca-binding protein as regulators of SERCA activity. In addition, PLN activity is regulated by 2 phosphoproteins, the inhibitor-1 of protein phosphatase 1 and the small heat shock protein 20, which affect the overall SERCA-mediated Ca-transport. This review will highlight the regulatory mechanisms of cardiac contractility by the multimeric SERCA/PLN-ensemble and the potential for new therapeutic avenues targeting this complex by using small molecules and gene transfer methods.

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

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.

Chronic clenbuterol treatment compromises force production without directly altering skeletal muscle contractile machinery

PubMed Central

Py, G; Ramonatxo, C; Sirvent, P; Sanchez, A M J; Philippe, A G; Douillard, A; Galbès, O; Lionne, C; Bonnieu, A; Chopard, A; Cazorla, O; Lacampagne, A; Candau, R B

2015-01-01

Clenbuterol is a β2-adrenergic receptor agonist known to induce skeletal muscle hypertrophy and a slow-to-fast phenotypic shift. The aim of the present study was to test the effects of chronic clenbuterol treatment on contractile efficiency and explore the underlying mechanisms, i.e. the muscle contractile machinery and calcium-handling ability. Forty-three 6-week-old male Wistar rats were randomly allocated to one of six groups that were treated with either subcutaneous equimolar doses of clenbuterol (4 mg kg−1 day−1) or saline solution for 9, 14 or 21 days. In addition to the muscle hypertrophy, although an 89% increase in absolute maximal tetanic force (Po) was noted, specific maximal tetanic force (sPo) was unchanged or even depressed in the slow twitch muscle of the clenbuterol-treated rats (P < 0.05). The fit of muscle contraction and relaxation force kinetics indicated that clenbuterol treatment significantly reduced the rate constant of force development and the slow and fast rate constants of relaxation in extensor digitorum longus muscle (P < 0.05), and only the fast rate constant of relaxation in soleus muscle (P < 0.05). Myofibrillar ATPase activity increased in both relaxed and activated conditions in soleus (P < 0.001), suggesting that the depressed specific tension was not due to the myosin head alteration itself. Moreover, action potential-elicited Ca2+ transients in flexor digitorum brevis fibres (fast twitch fibres) from clenbuterol-treated animals demonstrated decreased amplitude after 14 days (−19%, P < 0.01) and 21 days (−25%, P < 0.01). In conclusion, we showed that chronic clenbuterol treatment reduces contractile efficiency, with altered contraction and relaxation kinetics, but without directly altering the contractile machinery. Lower Ca2+ release during contraction could partially explain these deleterious effects. PMID:25656230

I-Wire Heart-on-a-Chip II: Biomechanical analysis of contractile, three-dimensional cardiomyocyte tissue constructs.

PubMed

Schroer, Alison K; Shotwell, Matthew S; Sidorov, Veniamin Y; Wikswo, John P; Merryman, W David

2017-01-15

This companion study presents the biomechanical analysis of the "I-Wire" platform using a modified Hill model of muscle mechanics that allows for further characterization of construct function and response to perturbation. The I-Wire engineered cardiac tissue construct (ECTC) is a novel experimental platform to investigate cardiac cell mechanics during auxotonic contraction. Whereas passive biomaterials often exhibit nonlinear and dissipative behavior, active tissue equivalents, such as ECTCs, also expend metabolic energy to perform mechanical work that presents additional challenges in quantifying their properties. The I-Wire model uses the passive mechanical response to increasing applied tension to measure the inherent stress and resistance to stretch of the construct before, during, and after treatments. Both blebbistatin and isoproterenol reduced prestress and construct stiffness; however, blebbistatin treatment abolished subsequent force-generating potential while isoproterenol enhanced this property. We demonstrate that the described model can replicate the response of these constructs to intrinsic changes in force-generating potential in response to both increasing frequency of stimulation and decreasing starting length. This analysis provides a useful mathematical model of the I-Wire platform, increases the number of parameters that can be derived from the device, and serves as a demonstration of quantitative characterization of nonlinear, active biomaterials. We anticipate that this quantitative analysis of I-Wire constructs will prove useful for qualifying patient-specific cardiomyocytes and fibroblasts prior to their utilization for cardiac regenerative medicine. Passive biomaterials may have non-linear elasticity and losses, but engineered muscle tissue also exhibits time- and force-dependent contractions. Historically, mathematical muscle models include series-elastic, parallel-elastic, contractile, and viscous elements. While hearts-on-a-chip can

The role of skeletal muscle contractile duration throughout the whole day: reducing sedentary time and promoting universal physical activity in all people.

PubMed

Hamilton, Marc T

2018-04-15

A shared goal of many researchers has been to discover how to improve health and prevent disease, through safely replacing a large amount of daily sedentary time with physical activity in everyone, regardless of age and current health status. This involves contrasting how different muscle contractile activity patterns regulate the underlying molecular and physiological responses impacting health-related processes. It also requires an equal attention to behavioural feasibility studies in extremely unfit and sedentary people. A sound scientific principle is that the body is constantly sensing and responding to changes in skeletal muscle metabolism induced by contractile activity. Because of that, the rapid time course of health-related responses to physical inactivity/activity patterns are caused in large part directly because of the variable amounts of muscle inactivity/activity throughout the day. However, traditional modes and doses of exercise fall far short of replacing most of the sedentary time in the modern lifestyle, because both the weekly frequency and the weekly duration of exercise time are an order of magnitude less than those for people sitting inactive. This can explain why high amounts of sedentary time produce distinct metabolic and cardiovascular responses through inactivity physiology that are not sufficiently prevented by low doses of exercise. For these reasons, we hypothesize that maintaining a high metabolic rate over the majority of the day, through safe and sustainable types of muscular activity, will be the optimal way to create a healthy active lifestyle over the whole lifespan. © 2017 The Authors. The Journal of Physiology published by John Wiley & Sons Ltd on behalf of The Physiological Society.

Pericyte contractility controls endothelial cell cycle progression and sprouting: insights into angiogenic switch mechanics.

PubMed

Durham, Jennifer T; Surks, Howard K; Dulmovits, Brian M; Herman, Ira M

2014-11-01

Microvascular stability and regulation of capillary tonus are regulated by pericytes and their interactions with endothelial cells (EC). While the RhoA/Rho kinase (ROCK) pathway has been implicated in modulation of pericyte contractility, in part via regulation of the myosin light chain phosphatase (MLCP), the mechanisms linking Rho GTPase activity with actomyosin-based contraction and the cytoskeleton are equivocal. Recently, the myosin phosphatase-RhoA-interacting protein (MRIP) was shown to mediate the RhoA/ROCK-directed MLCP inactivation in vascular smooth muscle. Here we report that MRIP directly interacts with the β-actin-specific capping protein βcap73. Furthermore, manipulation of MRIP expression influences pericyte contractility, with MRIP silencing inducing cytoskeletal remodeling and cellular hypertrophy. MRIP knockdown induces a repositioning of βcap73 from the leading edge to stress fibers; thus MRIP-silenced pericytes increase F-actin-driven cell spreading twofold. These hypertrophied and cytoskeleton-enriched pericytes demonstrate a 2.2-fold increase in contractility upon MRIP knockdown when cells are plated on a deformable substrate. In turn, silencing pericyte MRIP significantly affects EC cycle progression and angiogenic activation. When MRIP-silenced pericytes are cocultured with capillary EC, there is a 2.0-fold increase in EC cycle entry. Furthermore, in three-dimensional models of injury and repair, silencing pericyte MRIP results in a 1.6-fold elevation of total tube area due to EC network formation and increased angiogenic sprouting. The pivotal role of MRIP expression in governing pericyte contractile phenotype and endothelial growth should lend important new insights into how chemomechanical signaling pathways control the "angiogenic switch" and pathological angiogenic induction. Copyright © 2014 the American Physiological Society.

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.

Myosin isoforms and contractile properties of single fibers of human Latissimus Dorsi muscle.

PubMed

Paoli, Antonio; Pacelli, Quirico F; Cancellara, Pasqua; Toniolo, Luana; Moro, Tatiana; Canato, Marta; Miotti, Danilo; Reggiani, Carlo

2013-01-01

The aim of our study was to investigate fiber type distribution and contractile characteristics of Latissimus Dorsi muscle (LDM). Samples were collected from 18 young healthy subjects (9 males and 9 females) through percutaneous fine needle muscle biopsy. The results showed a predominance of fast myosin heavy chain isoforms (MyHC) with 42% of MyHC 2A and 25% of MyHC 2X, while MyHC 1 represented only 33%. The unbalance toward fast isoforms was even greater in males (71%) than in females (64%). Fiber type distribution partially reflected MyHC isoform distribution with 28% type 1/slow fibers and 5% hybrid 1/2A fibers, while fast fibers were divided into 30% type 2A, 31% type A/X, 4% type X, and 2% type 1/2X. Type 1/slow fibers were not only less abundant but also smaller in cross-sectional area than fast fibers. During maximal isometric contraction, type 1/slow fibers developed force and tension significantly lower than the two major groups of fast fibers. In conclusion, the predominance of fast fibers and their greater size and strength compared to slow fibers reveal that LDM is a muscle specialized mainly in phasic and powerful activity. Importantly, such specialization is more pronounced in males than in females.

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

Effects of hypoxia and hypercapnia on geniohyoid contractility and endurance.

PubMed

Salmone, R J; Van Lunteren, E

1991-08-01

Sleep apnea and other respiratory diseases produce hypoxemia and hypercapnia, factors that adversely affect skeletal muscle performance. To examine the effects of these chemical alterations on force production by an upper airway dilator muscle, the contractile and endurance characteristics of the geniohyoid muscle were examined in situ during severe hypoxia (arterial PO2 less than 40 Torr), mild hypoxia (PO2 45-65 Torr), and hypercapnia (PCO2 55-80 Torr) and compared with hyperoxic-normocapnic conditions in anesthetized cats. Muscles were studied at optimal length, and contractile force was assessed in response to supramaximal electrical stimulation of the hypoglossal nerve (n = 7 cats) or geniohyoid muscle (n = 2 cats). There were no significant changes in the twitch kinetics or force-frequency curve of the geniohyoid muscle during hypoxia or hypercapnia. However, the endurance of the geniohyoid, as reflected in the fatigue index (ratio of force at 2 min to initial force in response to 40-Hz stimulation at a duty cycle 0.33), was significantly reduced by severe hypoxia but not by hypercapnia or mild hypoxia. In addition, the downward shift in the force-frequency curve after the repetitive stimulation protocol was greater during hypoxia than hyperoxia, especially at higher frequencies. In conclusion, the ability of the geniohyoid muscle to maintain force output during high levels of activation is adversely affected by severe hypoxia but not mild hypoxia or hypercapnia. However, none of these chemical perturbations affected muscle contractility acutely.

Perfusion-induced changes in cardiac contractility depend on capillary perfusion.

PubMed

Dijkman, M A; Heslinga, J W; Sipkema, P; Westerhof, N

1998-02-01

The perfusion-induced increase in cardiac contractility (Gregg phenomenon) is especially found in heart preparations that lack adequate coronary autoregulation and thus protection of changes in capillary pressure. We determined in the isolated perfused papillary muscle of the rat whether cardiac muscle contractility is related to capillary perfusion. Oxygen availability of this muscle is independent of internal perfusion, and perfusion may be varied or even stopped without loss of function. Muscles contracted isometrically at 27 degrees C (n = 7). During the control state stepwise increases in perfusion pressure resulted in all muscles in a significant increase in active tension. Muscle diameter always increased with increased perfusion pressure, but muscle segment length was unaffected. Capillary perfusion was then obstructed by plastic microspheres (15 microns). Flow, at a perfusion pressure of 66.6 +/- 26.2 cmH2O, reduced from 17.6 +/- 5.4 microliters/min in the control state to 3.2 +/- 1.3 microliters/min after microspheres. Active tension developed by the muscle in the unperfused condition before microspheres and after microspheres did not differ significantly (-12.8 +/- 29.4% change). After microspheres similar perfusion pressure steps as in control never resulted in an increase in active tension. Even at the two highest perfusion pressures (89.1 +/- 28.4 and 106.5 +/- 31.7 cmH2O) that were applied a significant decrease in active tension was found. We conclude that the Gregg phenomenon is related to capillary perfusion.

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.

Effects of Hindlimb Unweighting on Arterial Contractile Responses in Mice

NASA Technical Reports Server (NTRS)

Ma, Jia; Ren, Xin-Ling; Purdy, Ralph E.

2003-01-01

The aim of this work was to determine if hindlimb unweighting in mice alters arterial contractile responses. Sixteen male C57B/6 mice and 16 male Chinese Kunming mice were divided into control and 3 weeks hindlimb unweighting groups, respectively. Using isolated arterial rings from different arteries of mouse, effects of 3 weeks hindlimb unweighting on arterial contractile responsiveness were examined in vitro. The results showed that, in arterial rings from both C57B/6 and Chinese Kunming mice, maximum isometric contractile tensions evoked by either KCl or phenylephrine were significantly lower in abdominal aortic, mesenteric arterial and femoral arterial rings from hindlimb unweighting, compared to control mice. However, the maximal contractile responses of common carotid rings to KCl and PE were not significantly different between control and hindlimb unweighting groups. The sensitivity (EC(sub 50)) of all arteries to KCl or PE showed no significant differences between control and hindlimb unweighting mice. These data indicated that 3 weeks hindlimb unweighting results in a reduced capacity of the arterial smooth muscle of the hindquarter to develop tension. In addition, the alterations in arterial contractile responses caused by hindlimb unweighting in mice are similar as those in rats. Our work suggested that hindlimb unweighting mouse model may be used as a model for the study of postflight cardiovascular deconditioning.

Comparison of contractile and extensile pneumatic artificial muscles

NASA Astrophysics Data System (ADS)

Pillsbury, Thomas E.; Wereley, Norman M.; Guan, Qinghua

2017-09-01

Pneumatic artificial muscles (PAMs) are used in robotic and prosthetic applications due to their high power to weight ratio, controllable compliance, and simple design. Contractile PAMs are typically used in traditional hard robotics in place of heavy electric motors. As the field of soft robotics grows, extensile PAMs are beginning to have increased usage. This work experimentally tests, models, and compares contractile and extensile PAMs to demonstrate the advantages and disadvantages of each type of PAM and applications for which they are best suited.

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.

Changes in muscle fiber contractility and extracellular matrix production during skeletal muscle hypertrophy.

PubMed

Mendias, Christopher L; Schwartz, Andrew J; Grekin, Jeremy A; Gumucio, Jonathan P; Sugg, Kristoffer B

2017-03-01

Skeletal muscle can adapt to increased mechanical loads by undergoing hypertrophy. Transient reductions in whole muscle force production have been reported during the onset of hypertrophy, but contractile changes in individual muscle fibers have not been previously studied. Additionally, the extracellular matrix (ECM) stores and transmits forces from muscle fibers to tendons and bones, and determining how the ECM changes during hypertrophy is important in understanding the adaptation of muscle tissue to mechanical loading. Using the synergist ablation model, we sought to measure changes in muscle fiber contractility, collagen content, and cross-linking, and in the expression of several genes and activation of signaling proteins that regulate critical components of myogenesis and ECM synthesis and remodeling during muscle hypertrophy. Tissues were harvested 3, 7, and 28 days after induction of hypertrophy, and nonoverloaded rats served as controls. Muscle fiber specific force (sF o ), which is the maximum isometric force normalized to cross-sectional area, was reduced 3 and 7 days after the onset of mechanical overload, but returned to control levels by 28 days. Collagen abundance displayed a similar pattern of change. Nearly a quarter of the transcriptome changed over the course of overload, as well as the activation of signaling pathways related to hypertrophy and atrophy. Overall, this study provides insight into fundamental mechanisms of muscle and ECM growth, and indicates that although muscle fibers appear to have completed remodeling and regeneration 1 mo after synergist ablation, the ECM continues to be actively remodeling at this time point. NEW & NOTEWORTHY This study utilized a rat synergist ablation model to integrate changes in single muscle fiber contractility, extracellular matrix composition, activation of important signaling pathways in muscle adaption, and corresponding changes in the muscle transcriptome to provide novel insight into the basic

Changes in muscle fiber contractility and extracellular matrix production during skeletal muscle hypertrophy

PubMed Central

Schwartz, Andrew J.; Grekin, Jeremy A.; Gumucio, Jonathan P.; Sugg, Kristoffer B.

2017-01-01

Skeletal muscle can adapt to increased mechanical loads by undergoing hypertrophy. Transient reductions in whole muscle force production have been reported during the onset of hypertrophy, but contractile changes in individual muscle fibers have not been previously studied. Additionally, the extracellular matrix (ECM) stores and transmits forces from muscle fibers to tendons and bones, and determining how the ECM changes during hypertrophy is important in understanding the adaptation of muscle tissue to mechanical loading. Using the synergist ablation model, we sought to measure changes in muscle fiber contractility, collagen content, and cross-linking, and in the expression of several genes and activation of signaling proteins that regulate critical components of myogenesis and ECM synthesis and remodeling during muscle hypertrophy. Tissues were harvested 3, 7, and 28 days after induction of hypertrophy, and nonoverloaded rats served as controls. Muscle fiber specific force (sFo), which is the maximum isometric force normalized to cross-sectional area, was reduced 3 and 7 days after the onset of mechanical overload, but returned to control levels by 28 days. Collagen abundance displayed a similar pattern of change. Nearly a quarter of the transcriptome changed over the course of overload, as well as the activation of signaling pathways related to hypertrophy and atrophy. Overall, this study provides insight into fundamental mechanisms of muscle and ECM growth, and indicates that although muscle fibers appear to have completed remodeling and regeneration 1 mo after synergist ablation, the ECM continues to be actively remodeling at this time point. NEW & NOTEWORTHY This study utilized a rat synergist ablation model to integrate changes in single muscle fiber contractility, extracellular matrix composition, activation of important signaling pathways in muscle adaption, and corresponding changes in the muscle transcriptome to provide novel insight into the basic

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.

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

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.

Stalk-length-dependence of the contractility of Vorticella convallaria

NASA Astrophysics Data System (ADS)

Gul Chung, Eun; Ryu, Sangjin

2017-12-01

Vorticella convallaria is a sessile protozoan of which the spasmoneme contracts on a millisecond timescale. Because this contraction is induced and powered by the binding of calcium ions (Ca2+), the spasmoneme showcases Ca2+-powered cellular motility. Because the isometric tension of V. convallaria increases linearly with its stalk length, it is hypothesized that the contractility of V. convallaria during unhindered contraction depends on the stalk length. In this study, the contractile force and energetics of V. convallaria cells of different stalk lengths were evaluated using a fluid dynamic drag model which accounts for the unsteadiness and finite Reynolds number of the water flow caused by contracting V. convallaria and the wall effect of the no-slip substrate. It was found that the contraction displacement, peak contraction speed, peak contractile force, total mechanical work, and peak power depended on the stalk length. The observed stalk-length-dependencies were simulated using a damped spring model, and the model estimated that the average spring constant of the contracting stalk was 1.34 nN µm-1. These observed length-dependencies of Vorticella’s key contractility parameters reflect the biophysical mechanism of the spasmonemal contraction, and thus they should be considered in developing a theoretical model of the Vorticella spasmoneme.

The effect of cleft palate repair on contractile properties of single permeabilized muscle fibers from congenitally cleft goat palates.

PubMed

Hanes, Michael C; Weinzweig, Jeffrey; Panter, Kip E; McClellan, W Thomas; Caterson, Stefanie A; Buchman, Steven R; Faulkner, John A; Yu, Deborah; Cederna, Paul S; Larkin, Lisa M

2008-02-01

Inherent differences in the levator veli palatini (LVP) muscle of cleft palates before palatoplasty may play a role in persistent postrepair velopharyngeal insufficiency (VPI). Contractile properties of LVP muscle fibers were analyzed from young (2-month) normal (YNP), young congenitally cleft (YCP) and again on the same YCP subjects 6 months after palatoplasty, mature repaired palate (MRP). The cross-sectional area and rate of force development (ktr) were measured. Specific force (sF(0)) and normalized power (nP(max)) were calculated. Using k(tr) to determine fiber type composition, YNP was 44% type 1 and 56% type 2, while YCP was 100% type 2. Two MRP subjects shifted to 100% type 1; 1 demonstrated increased resistance to fatigue. No differences in sF(0) were observed. nP(max) increased with presence of type 2 fibers. The persistent state of type 2 fibers following palatoplasty leads to increased fatigue in the LVP of MRP subjects and may cause VPI symptoms.

Inhibition of isolated human myometrium contractility by minoxidil and reversal by glibenclamide.

PubMed

Prabhakaran, S S; Dhanasekar, K R; Thomas, E; Jose, R; Peedicayil, J; Samuel, P

2010-03-01

This study investigated the ability of the antihypertensive drug minoxidil to inhibit potassium chloride (KCl)-induced contractility of the isolated human myometrium. Twelve strips of myometrium obtained from 12 patients who underwent hysterectomy were triggered to contract with 55 mM KCl before and after incubation with 3 concentrations (1, 3 and 10 microM) of minoxidil. The percent inhibition by minoxidil on the extent of contraction, and the area under the contractile curve of KCl-induced contraction of the myometrial strips was determined. Furthermore, the effect of 10 microM glibenclamide on the inhibition generated by 3 microM minoxidil on KCl-induced contractility was studied. It was found that minoxidil produced a concentration-dependent inhibition of KCl-induced contractility of the myometrium and that glibenclamide reversed this inhibitory effect. These results suggest that the inhibitory effect of minoxidil on isolated human myometrium contractility may prove useful in clinical conditions requiring relaxation of the myometrium. 2010 Prous Science, S.A.U. or its licensors. All rights reserved.

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

MEMS piezoresistive cantilever for the direct measurement of cardiomyocyte contractile force

NASA Astrophysics Data System (ADS)

Matsudaira, Kenei; Nguyen, Thanh-Vinh; Hirayama Shoji, Kayoko; Tsukagoshi, Takuya; Takahata, Tomoyuki; Shimoyama, Isao

2017-10-01

This paper reports on a method to directly measure the contractile forces of cardiomyocytes using MEMS (micro electro mechanical systems)-based force sensors. The fabricated sensor chip consists of piezoresistive cantilevers that can measure contractile forces with high frequency (several tens of kHz) and high sensing resolution (less than 0.1 nN). Moreover, the proposed method does not require a complex observation system or image processing, which are necessary in conventional optical-based methods. This paper describes the design, fabrication, and evaluation of the proposed device and demonstrates the direct measurements of contractile forces of cardiomyocytes using the fabricated device.

Expansion and concatenation of nonmuscle myosin IIA filaments drive cellular contractile system formation during interphase and mitosis

PubMed Central

Fenix, Aidan M.; Taneja, Nilay; Buttler, Carmen A.; Lewis, John; Van Engelenburg, Schuyler B.; Ohi, Ryoma; Burnette, Dylan T.

2016-01-01

Cell movement and cytokinesis are facilitated by contractile forces generated by the molecular motor, nonmuscle myosin II (NMII). NMII molecules form a filament (NMII-F) through interactions of their C-terminal rod domains, positioning groups of N-terminal motor domains on opposite sides. The NMII motors then bind and pull actin filaments toward the NMII-F, thus driving contraction. Inside of crawling cells, NMIIA-Fs form large macromolecular ensembles (i.e., NMIIA-F stacks), but how this occurs is unknown. Here we show NMIIA-F stacks are formed through two non–mutually exclusive mechanisms: expansion and concatenation. During expansion, NMIIA molecules within the NMIIA-F spread out concurrent with addition of new NMIIA molecules. Concatenation occurs when multiple NMIIA-Fs/NMIIA-F stacks move together and align. We found that NMIIA-F stack formation was regulated by both motor activity and the availability of surrounding actin filaments. Furthermore, our data showed expansion and concatenation also formed the contractile ring in dividing cells. Thus interphase and mitotic cells share similar mechanisms for creating large contractile units, and these are likely to underlie how other myosin II–based contractile systems are assembled. PMID:26960797

Using Force to Punch Holes: Mechanics of Contractile Nanomachines.

PubMed

Brackmann, Maximilian; Nazarov, Sergey; Wang, Jing; Basler, Marek

2017-09-01

Using physical force to translocate macromolecules across a membrane has the advantage of being a universal solution independent of the properties of the target membrane. However, physically punching a stiff membrane is not a trivial task and three things are necessary for success: a sharp tip, a source of energy, and the ability to strongly bind to the target. In this review we describe the basic mechanism of membrane puncturing by contractile nanomachines with a focus on the T4 phage, R-type pyocin, and the bacterial Type VI secretion system (T6SS) based on recent studies of the structures and dynamics of their assembly. Copyright © 2017 Elsevier Ltd. All rights reserved.

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.

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

Initial contact guidance during cell spreading is contractility-independent.

PubMed

Sales, Adrià; Holle, Andrew W; Kemkemer, Ralf

2017-08-02

A wide variety of cell types exhibit substrate topography-based behavior, also known as contact guidance. However, the precise cellular mechanisms underlying this process are still unknown. In this study, we investigated contact guidance by studying the reaction of human endothelial cells (ECs) to well-defined microgroove topographies, both during and after initial cell spreading. As the cytoskeleton plays a major role in cellular adaptation to topographical features, two methods were used to perturb cytoskeletal structures. Inhibition of actomyosin contractility with the chemical inhibitor blebbistatatin demonstrated that initial contact guidance events are independent of traction force generation. However, cell alignment to the grooved substrate was altered at later time points, suggesting an initial 'passive' phase of contact guidance, followed by a contractility-dependent 'active' phase that relies on mechanosensitive feedback. The actin cytoskeleton was also perturbed in an indirect manner by culturing cells upside down, resulting in decreased levels of contact guidance and suggesting that a possible loss of contact between the actin cytoskeleton and the substrate could lead to cytoskeleton impairment. The process of contact guidance at the microscale was found to be primarily lamellipodia driven, as no bias in filopodia extension was observed on micron-scale grooves.

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.

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

Cell density and actomyosin contractility control the organization of migrating collectives within an epithelium

PubMed Central

Loza, Andrew J.; Koride, Sarita; Schimizzi, Gregory V.; Li, Bo; Sun, Sean X.; Longmore, Gregory D.

2016-01-01

The mechanisms underlying collective migration are important for understanding development, wound healing, and tumor invasion. Here we focus on cell density to determine its role in collective migration. Our findings show that increasing cell density, as might be seen in cancer, transforms groups from broad collectives to small, narrow streams. Conversely, diminishing cell density, as might occur at a wound front, leads to large, broad collectives with a distinct leader–follower structure. Simulations identify force-sensitive contractility as a mediator of how density affects collectives, and guided by this prediction, we find that the baseline state of contractility can enhance or reduce organization. Finally, we test predictions from these data in an in vivo epithelium by using genetic manipulations to drive collective motion between predicted migratory phases. This work demonstrates how commonly altered cellular properties can prime groups of cells to adopt migration patterns that may be harnessed in health or exploited in disease. PMID:27605707

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.

Lack of muscle contractile property changes at the time of perceived physical exhaustion suggests central mechanisms contributing to early motor task failure in patients with cancer-related fatigue.

PubMed

Kisiel-Sajewicz, Katarzyna; Davis, Mellar P; Siemionow, Vlodek; Seyidova-Khoshknabi, Dilara; Wyant, Alexandria; Walsh, Declan; Hou, Juliet; Yue, Guang H

2012-09-01

Fatigue is one of the most common symptoms reported by cancer survivors, and fatigue worsens when patients are engaged in muscle exertion, which results in early motor task failure. Central fatigue plays a significant role, more than muscle (peripheral) fatigue, in contributing to early task failure in cancer-related fatigue (CRF). The purpose of this study was to determine if muscle contractile property alterations (reflecting muscle fatigue) occurred at the end of a low-intensity muscle contraction to exhaustion and if these properties differed between those with CRF and healthy controls. Ten patients (aged 59.9±10.6 years, seven women) with advanced solid cancer and CRF and 12 age- and gender-matched healthy controls (aged 46.6±12.8 years, nine women) performed a sustained contraction of the right arm elbow flexion at 30% maximal level until exhaustion. Peak twitch force, time to peak twitch force, rate of peak twitch force development, and half relaxation time derived from electrical stimulation-evoked twitches were analyzed pre- and post-sustained contraction. CRF patients reported significantly greater fatigue as measured by the Brief Fatigue Inventory and failed the motor task earlier, 340±140 vs. 503±155 seconds in controls. All contractile property parameters did not change significantly in CRF but did change significantly in controls. CRF patients perceive physical exhaustion sooner during a motor fatigue task with minimal muscular fatigue. The observation supports that central fatigue is a more significant factor than peripheral fatigue in causing fatigue feelings and limits motor function in cancer survivors with fatigue symptoms. Copyright © 2012. Published by Elsevier Inc.

Impact of pregnancy and vaginal delivery on the passive and active mechanics of the rat vagina.

PubMed

Feola, Andrew; Moalli, Pamela; Alperin, Marianna; Duerr, Robbie; Gandley, Robin E; Abramowitch, Steven

2011-01-01

Remodeling of vaginal extracellular matrix and smooth muscle likely plays a critical role in reducing the risk of maternal injury during vaginal delivery by altering the mechanical properties to increase distension and reduce stress. Long-Evans rats were divided into five groups to examine the passive mechanical and active contractile properties throughout pregnancy and postpartum: virgin (n=17), mid-pregnant (Day 14-16, n=12), late-pregnant (Day 20-22, n=14), immediate postpartum (0-2 h after delivery, n=14), and 4 week postpartum (n=15). Longitudinal sections of vaginal tissue were loaded to failure uniaxially for passive mechanical or active contractile properties were examined. For passive mechanics, the tangent modulus decreased 45% by mid-pregnancy and immediately postpartum (p<0.001). The ultimate strain continuously increased up to 43% higher than virgin animals (p=0.007) in the immediate postpartum group. For active mechanics, the maximal contractile force was 36-56% lower through immediate postpartum animals, and was significantly more sensitive to K+ throughout pregnancy and postpartum (p=0.003). The changes observed in the passive and active properties of the rat vagina are consistent with what would be expected from a tissue that is remodeling to maximize its ability to distend at the time of vaginal delivery to facilitate passage of the fetus with minimal injury.

Generation of contractile actomyosin bundles depends on mechanosensitive actin filament assembly and disassembly.

PubMed

Tojkander, Sari; Gateva, Gergana; Husain, Amjad; Krishnan, Ramaswamy; Lappalainen, Pekka

2015-12-10

Adhesion and morphogenesis of many non-muscle cells are guided by contractile actomyosin bundles called ventral stress fibers. While it is well established that stress fibers are mechanosensitive structures, physical mechanisms by which they assemble, align, and mature have remained elusive. Here we show that arcs, which serve as precursors for ventral stress fibers, undergo lateral fusion during their centripetal flow to form thick actomyosin bundles that apply tension to focal adhesions at their ends. Importantly, this myosin II-derived force inhibits vectorial actin polymerization at focal adhesions through AMPK-mediated phosphorylation of VASP, and thereby halts stress fiber elongation and ensures their proper contractility. Stress fiber maturation additionally requires ADF/cofilin-mediated disassembly of non-contractile stress fibers, whereas contractile fibers are protected from severing. Taken together, these data reveal that myosin-derived tension precisely controls both actin filament assembly and disassembly to ensure generation and proper alignment of contractile stress fibers in migrating cells.

[Influence exogenous nicotinamide adenine dinucleotide (NAD+) on contractile and bioelectric activity of the rat heart].

PubMed

Pustovit, K B; Kuz'min, V S; Sukhova, G S

2014-04-01

This study is aimed to the investigation of the nicotinamide adenine dinucleotide (NAD+) effects and mechanisms of action in a heart. NAD+ (mcM) induces multiphase alternation of contractile activity of isolated rat heart: short positive inotropic action is followed by a negative inotropic phase. NAD+ (1-100 mcM) induces decreasing of action potential duration (APD) in rat atrial myocardium (from 45 +/- 0.82 ms in control experiments to 39 +/- 1.05 (n = 8) and 32 +/- 2 (n = 8) during application of 10 and 100 mcM of NAD+, respectively). Significant APD increase (from 45 +/- 0.82 ms to 74 +/- 1.89 (n = 8) ms) was observed during washing out of NAD+ (100 mcM). ATP or adenosine was unable to increase APD both during application or washing out. NAD+ induced APD decrease was not suppressed by P1-antagonist theophylline. P1-purinoreceptor and metabolite independent direct action of NAD+ in rat heart is suggested. Activation of P2X or P2Y receptors, cyclic ADP-ribose accumulation in cardiomyocytes is proposed as a main mechanism of NAD(+)-induced effects in the heart.

Systolic Intrinsic Frequency and Various Measures of Left Ventricle Contractility

NASA Astrophysics Data System (ADS)

Pahlevan, Niema

2017-11-01

There has been growing interest during past six decades to introduce new indices for quantifying left ventricular (LV) contractility. We have recently introduced a new method, called intrinsic frequency (IF), for analyzing the dynamics of systemic circulation. IF method models LV and arterial network as an object rotating around an origin where the angular velocity of the rotation during systole (when LV and arterial network are coupled) and diastole (when arterial network is decoupled) are intrinsic frequencies, ω1 and ω2 respectively. ω1 and ω2 can be extracted from a carotid pulse waveform using IF method. In this study, Huntington Medical Research Institutes heart study data have been used to compare ω1 with various measures of LV contractility such as ejection fraction, mean velocity of circumferential fiber shortening, LV end-systolic meridional wall stress, and maximal LV power corrected for end-diastolic volume. Here, LV contractility indices were computed noninvasively from cardiac MRI and tonometry data. The results indicate that ω1 can be used as a surrogate of LV contractility. This is clinically significant since ω1 can be accurately obtained by a standard iPhone camera.

The regulation of smooth muscle contractility by zipper-interacting protein kinase.

PubMed

Ihara, Eikichi; MacDonald, Justin A

2007-01-01

Smooth muscle contractility is mainly regulated by phosphorylation of the 20 kDa myosin light chains (LC20), a process that is controlled by the opposing activities of myosin light chain kinase (MLCK) and myosin light chain phosphatase (MLCP). Recently, intensive research has revealed that various protein kinase networks including Rho-kinase, integrin-linked kinase, zipper-interacting protein kinase (ZIPK), and protein kinase C (PKC) are involved in the regulation of LC20 phosphorylation and have important roles in modulating smooth muscle contractile responses to Ca2+ (i.e., Ca2+ sensitization and Ca2+ desensitization). Here, we review the general background and structure of ZIPK and summarize our current understanding of its involvement in a number of cell processes including cell death (apoptosis), cell motility, and smooth muscle contraction. ZIPK has been found to induce the diphosphorylation of LC20 at Ser-19 and Thr-18 in a Ca2+-independent manner and to regulate MLCP activity directly through its phosphorylation of the myosin-targeting subunit of MLCP or indirectly through its phosphorylation of the PKC-potentiated inhibitory protein of MLCP. Future investigations of ZIPK function in smooth muscle will undoubtably focus on determining the mechanisms that regulate its cellular activity, including the identification of upstream signaling pathways, the characterization of autoinhibitory domains and regulatory phosphorylation sites, and the development of specific inhibitor compounds.

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.

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.

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

Impact of tamsulosin and nifedipine on contractility of pregnant rat ureters in vitro.

PubMed

Haddad, Lisette; Corriveau, Stéphanie; Rousseau, Eric; Blouin, Simon; Pasquier, Jean-Charles; Ponsot, Yves; Roy-Lacroix, Marie-Ève

2018-01-01

To evaluate the in vitro effect of tamsulosin and nifedipine on the contractility of pregnant rat ureters and to perform quantitative analysis of the pharmacological effects. Medical expulsive therapy (MET) is commonly used to treat urolithiasis. However, this treatment is seldom used in pregnant women since no studies support this practice. This was an in vitro study on animal tissue derived from pregnant Sprague-Dawley rats. A total of 124 ureteral segments were mounted in an organ bath system and contractile response to methacholine (MCh) was assessed. Tamsulosin or nifedipine were added at cumulative concentrations (0.001-1 μM). The area under the curve (AUC) from isometric tension measurements was calculated. The effect of pharmacological agents and the respective controls were assessed by calculating the AUC for each 5-min interval. Statistical analyses were performed using the Mann-Whitney-Wilcoxon nonparametric test. Both drugs displayed statistically significant inhibitory activity at concentrations of 0.1 and 1 μM for tamsulosin and 1 μM for nifedipine when calculated as the AUC as compared to DMSO controls. Tamsulosin and nifedipine directly inhibit MCh-induced contractility of pregnant rat ureters. Further work is needed to determine the clinical efficacy of these medications for MET in pregnancy.

Urothelium-dependent and urothelium-independent detrusor contractility mediated by nitric oxide synthase and cyclooxygenase inhibition.

PubMed

Santoso, Aneira Gracia Hidayat; Lo, Wan Ning; Liang, Willmann

2011-04-01

The urothelium has been implicated in regulating detrusor smooth muscle contractility but the identity of the putative urothelium-derived inhibitory factor remains unconfirmed. There was inconclusive evidence on the role of nitric oxide synthase (NOS) and cyclooxygenase (COX) in mediating detrusor contractions. This study examined varying regulation by NOS and COX in transverse and longitudinal carbachol (CCh)-induced and unstimulated phasic contractions. Rat detrusor strips with the urothelium-intact (+UE) and urothelium-denuded (-UE) were isolated in both transverse and longitudinal directions. Isometric tension of the detrusor strips was recorded both during stimulation with CCh and at the unstimulated state. In the unstimulated state, phasic contractile activity was measured. Tension recordings were made with and without the NOS inhibitor N(ω)-nitro-L-arginine methyl ester (L-NAME) and COX inhibitor indomethacin (Indo). Only transverse +UE strips responded convincingly to L-NAME and Indo treatment, generating larger CCh-induced contractions. In unstimulated tissues, L-NAME treatment increased phasic amplitude in -UE strips only. Indo treatment failed to elicit any change in the amplitude but suppressed frequency of the phasic activity in transverse +UE strips. There was no significant Indo-mediated change in other strips. The data suggested heterogeneity in the regulation of directional detrusor contractility via NOS- and COX-associated mechanisms. Copyright © 2011 Wiley-Liss, Inc.

Multicellular contractility contributes to the emergence of mesothelioma nodules

NASA Astrophysics Data System (ADS)

Czirok, Andras

Malignant pleural mesothelioma (MPM) nodules arise from the mesothelial lining of the pleural cavity by a poorly understood mechanism. We demonstrate that macroscopic multicellular aggregates, reminiscent of the MPM nodules found in patients, develop when MPM cell lines are cultured at high cell densities for several weeks. Surprisingly, the nodule-like aggregates do not arise by excessive local cell proliferation, but by myosin II-driven cell contractility. Contractile nodules contain prominent actin cables that can span several cells. Several features of the in vitro MPM nodule development can be explained by a computational model that assumes uniform and steady intercellular contractile forces within a monolayer of cells, and a mechanical load-dependent lifetime of cell-cell contacts. The model behaves as a self-tensioned Maxwell fluid and exhibits an instability that leads to pattern formation. Altogether, our findings suggest that inhibition of the actomyosin system may provide a hitherto not utilized therapeutic approach to affect MPM growth. NIH R01-GM102801.

[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.

Generation of contractile actomyosin bundles depends on mechanosensitive actin filament assembly and disassembly

PubMed Central

Tojkander, Sari; Gateva, Gergana; Husain, Amjad; Krishnan, Ramaswamy; Lappalainen, Pekka

2015-01-01

Adhesion and morphogenesis of many non-muscle cells are guided by contractile actomyosin bundles called ventral stress fibers. While it is well established that stress fibers are mechanosensitive structures, physical mechanisms by which they assemble, align, and mature have remained elusive. Here we show that arcs, which serve as precursors for ventral stress fibers, undergo lateral fusion during their centripetal flow to form thick actomyosin bundles that apply tension to focal adhesions at their ends. Importantly, this myosin II-derived force inhibits vectorial actin polymerization at focal adhesions through AMPK-mediated phosphorylation of VASP, and thereby halts stress fiber elongation and ensures their proper contractility. Stress fiber maturation additionally requires ADF/cofilin-mediated disassembly of non-contractile stress fibers, whereas contractile fibers are protected from severing. Taken together, these data reveal that myosin-derived tension precisely controls both actin filament assembly and disassembly to ensure generation and proper alignment of contractile stress fibers in migrating cells. DOI: http://dx.doi.org/10.7554/eLife.06126.001 PMID:26652273

Thick Filament Length and Isoform Composition Determine Self-Organized Contractile Units in Actomyosin Bundles

PubMed Central

Thoresen, Todd; Lenz, Martin; Gardel, Margaret L.

2013-01-01

Diverse myosin II isoforms regulate contractility of actomyosin bundles in disparate physiological processes by variations in both motor mechanochemistry and the extent to which motors are clustered into thick filaments. Although the role of mechanochemistry is well appreciated, the extent to which thick filament length regulates actomyosin contractility is unknown. Here, we study the contractility of minimal actomyosin bundles formed in vitro by mixtures of F-actin and thick filaments of nonmuscle, smooth, and skeletal muscle myosin isoforms with varied length. Diverse myosin II isoforms guide the self-organization of distinct contractile units within in vitro bundles with shortening rates similar to those of in vivo myofibrils and stress fibers. The tendency to form contractile units increases with the thick filament length, resulting in a bundle shortening rate proportional to the length of constituent myosin thick filament. We develop a model that describes our data, providing a framework in which to understand how diverse myosin II isoforms regulate the contractile behaviors of disordered actomyosin bundles found in muscle and nonmuscle cells. These experiments provide insight into physiological processes that use dynamic regulation of thick filament length, such as smooth muscle contraction. PMID:23442916

An electron microscope study of the contractile vacuole in Tokophrya infusionum.

PubMed

RUDZINSKA, M A

1958-03-25

Contractile vacuoles are organelles that collect fluid from the cytoplasm and expel it to the outside. After each discharge (systole), they appear again and expand (diastole). They are widely distributed among Protozoa, and have been found also in some fresh water algae, sponges, and recently in some blood cells of the frog, guinea pig, and man. In spite of the extensive work on the contractile vacuole, very little is known concerning its mode of operation. An electron microscope study of a suctorian Tokophrya infusionum provided an opportunity to study thin sections of contractile vacuoles, and in these some structures were found which could be part of a mechanism for the systolic and diastolic motions the organelle displays. In Tokophrya, as in Suctoria and Ciliata in general, the contractile vacuole has a permanent canal connecting it with the outside. The canal appears to have a very elaborate structure and is composed of three parts: (1) a pore; (2) a channel; and (3) a narrow tubule located in a papilla protruding into the cavity of the contractile vacuole. Whereas the pore and channel have fixed dimensions and are permanently widely open, the tubule has a changeable diameter. At diastole it is so narrow (about 25 to 30 mmicro in diameter) that it could be regarded as closed, while at systole it is widely open. It is assumed that the change in diameter is due to the contraction of numerous fine fibrils (about 180 A thick) which are radially disposed around the canal in form of a truncated cone, with its tip at the channel, and its base at the vacuolar membrane. It seems most probable that the broadening of the tubule results in discharge of the content of the contractile vacuole. In the vicinity of the very thin limiting vacuolar membrane, small vesicles and canaliculi of the endoplasmic reticulum, very small dense particles, and mitochondria may be found. In addition, rows of closely packed vesicles are present in this region, and in other parts of the

[Urodynamics foundations: contractile potency and urethral doppler].

PubMed

Benítez Navío, Julio; Caballero Gómez, Pilar; Delgado Elipe, Ildefonso

2002-12-01

To calculate the bladder softening factor, elastic constant and contractile potency. For the analysis we considered bladder behavior like that of a spring. See articles 1 and 2 published in this issue. Using flowmetry, Doppler ultrasound and abdominal pressure (Transrectal pressure register catheter) an analytical solution that permits calculation of factors defining bladder behavior was looked for. Doppler ultrasound allows us to know urine velocity through the prostatic urethra and, therefore, to calculate bladder contractile potency. Equations are solved reaching an analytical solution that allows calculating those factors that define bladder behavior: Bladder contractile potency, detrusor elastic constant, considering it behaves like a spring, and calculation of muscle resistance to movement. All thanks to Doppler ultrasound that allows to know urine speed. The bladder voiding phase is defined with the aforementioned factors; storage phase behavior can be indirectly inferred. Only uroflowmetry curves, Doppler ultrasound and abdominal pressure value are used. We comply with the so called non invasive urodynamics although for us it is just another phase in the biomechanical study of the detrusor muscle. Main conclusion is the addition of Doppler ultrasound to the urodynamist armamentarium as an essential instrument for the comprehension of bladder dynamics and calculation of bladder behavior defining factors. It is not a change in the focus but in the methods, gaining knowledge and diminishing invasion.

Mitosis-Specific Mechanosensing and Contractile Protein Redistribution Control Cell Shape

PubMed Central

Effler, Janet C.; Kee, Yee-Seir; Berk, Jason M.; Tran, Minhchau N.; Iglesias, Pablo A.; Robinson, Douglas N.

2008-01-01

Summary Because cell division failure is deleterious, promoting tumorigenesis in mammals [1], cells utilize numerous mechanisms to control their cell-cycle progression [2–4]. Though cell division is considered a well-ordered sequence of biochemical events [5], cytokinesis, an inherently mechanical process, must also be mechanically controlled to ensure that two equivalent daughter cells are produced with high fidelity. Since cells respond to their mechanical environment [6, 7], we hypothesized that cells utilize mechanosensing and mechanical feedback to sense and correct shape asymmetries during cytokinesis. Because the mitotic spindle and myosin-II are vital to cell division [8, 9], we explored their roles in responding to shape perturbations during cell division. We demonstrate that the contractile proteins, myosin-II and cortexillin-I, redistribute in response to intrinsic and externally induced shape asymmetries. In early cytokinesis, mechanical load overrides spindle cues and slows cytokinesis progression while contractile proteins accumulate and correct shape asymmetries. In late cytokinesis, mechanical perturbation also directs contractile proteins but without apparently disrupting cytokinesis. Significantly, this response only occurs during anaphase through cytokinesis, does not require microtubules, is independent of spindle orientation, but is dependent on myosin-II. Our data provide evidence for a mechanosensory system that directs contractile proteins to regulate cell shape during mitosis. PMID:17027494

Estimation of Bladder Contractility From Intravesical Pressure–Volume Measurements

PubMed Central

Fry, Christopher H.; Gammie, Andrew; Drake, Marcus John; Abrams, Paul; Kitney, Darryl Graham; Vahabi, Bahareh

2017-01-01

Aims To describe parameters from urodynamic pressure recordings that describe urinary bladder contractility through the use of principles of muscle mechanics. Methods Subtracted detrusor pressure and voided flow were recorded from patients undergoing filling cystometry. The isovolumetric increase of detrusor pressure, P, of a voluntary bladder contraction before voiding was used to generate a plot of (dP/dt)/P versus P. Extrapolation of the plot to the y-axis and the x-axis generated a contractility parameter, vCE (the maximum rate of pressure development) and the maximum isovolumetric pressure, P0, respectively. Similar curves were obtained in ex vivo pig bladders with different concentrations of the inotropic agent carbachol and shown in a supplement. Results Values of vCE, but not P0, diminished with age in female subjects. vCE was most significantly associated with the 20–80% duration of isovolumetric contraction t20–80;and a weaker association with maximum flow rate and BCI in women. P0 was not associated with any urodynamic variable in women, but in men was with t20–80 and isovolumetric pressure indices. Conclusions The rate of isovolumetric subtracted detrusor pressure (t20–80) increase shows a very significant association with indices of bladder contractility as derived from a derived force–velocity curve. We propose that t20–80 is a detrusor contractility parameter (DCP). PMID:27265671

Three-dimensional morphogenesis of MDCK cells induced by cellular contractile forces on a viscous substrate

PubMed Central

Imai, Misako; Furusawa, Kazuya; Mizutani, Takeomi; Kawabata, Kazushige; Haga, Hisashi

2015-01-01

Substrate physical properties are essential for many physiological events such as embryonic development and 3D tissue formation. Physical properties of the extracellular matrix such as viscoelasticity and geometrical constraints are understood as factors that affect cell behaviour. In this study, we focused on the relationship between epithelial cell 3D morphogenesis and the substrate viscosity. We observed that Madin-Darby Canine Kidney (MDCK) cells formed 3D structures on a viscous substrate (Matrigel). The structures appear as a tulip hat. We then changed the substrate viscosity by genipin (GP) treatment. GP is a cross-linker of amino groups. Cells cultured on GP-treated-matrigel changed their 3D morphology in a substrate viscosity-dependent manner. Furthermore, to elucidate the spatial distribution of the cellular contractile force, localization of mono-phosphorylated and di-phosphorylated myosin regulatory light chain (P-MRLCs) was visualized by immunofluorescence. P-MRLCs localized along the periphery of epithelial sheets. Treatment with Y-27632, a Rho-kinase inhibitor, blocked the P-MRLCs localization at the edge of epithelial sheets and halted 3D morphogenesis. Our results indicate that the substrate viscosity, the substrate deformation, and the cellular contractile forces induced by P-MRLCs play crucial roles in 3D morphogenesis. PMID:26374384

Three-dimensional morphogenesis of MDCK cells induced by cellular contractile forces on a viscous substrate.

PubMed

Imai, Misako; Furusawa, Kazuya; Mizutani, Takeomi; Kawabata, Kazushige; Haga, Hisashi

2015-09-16

Substrate physical properties are essential for many physiological events such as embryonic development and 3D tissue formation. Physical properties of the extracellular matrix such as viscoelasticity and geometrical constraints are understood as factors that affect cell behaviour. In this study, we focused on the relationship between epithelial cell 3D morphogenesis and the substrate viscosity. We observed that Madin-Darby Canine Kidney (MDCK) cells formed 3D structures on a viscous substrate (Matrigel). The structures appear as a tulip hat. We then changed the substrate viscosity by genipin (GP) treatment. GP is a cross-linker of amino groups. Cells cultured on GP-treated-matrigel changed their 3D morphology in a substrate viscosity-dependent manner. Furthermore, to elucidate the spatial distribution of the cellular contractile force, localization of mono-phosphorylated and di-phosphorylated myosin regulatory light chain (P-MRLCs) was visualized by immunofluorescence. P-MRLCs localized along the periphery of epithelial sheets. Treatment with Y-27632, a Rho-kinase inhibitor, blocked the P-MRLCs localization at the edge of epithelial sheets and halted 3D morphogenesis. Our results indicate that the substrate viscosity, the substrate deformation, and the cellular contractile forces induced by P-MRLCs play crucial roles in 3D morphogenesis.

Differential Activity-Driven Instabilities in Biphasic Active Matter

NASA Astrophysics Data System (ADS)

Weber, Christoph A.; Rycroft, Chris H.; Mahadevan, L.

2018-06-01

Active stresses can cause instabilities in contractile gels and living tissues. Here we provide a generic hydrodynamic theory that treats these systems as a mixture of two phases of varying activity and different mechanical properties. We find that differential activity between the phases causes a uniform mixture to undergo a demixing instability. We follow the nonlinear evolution of the instability and characterize a phase diagram of the resulting patterns. Our study complements other instability mechanisms in mixtures driven by differential adhesion, differential diffusion, differential growth, and differential motion.

Platelets as Contractile Nanomachines for Targeting Drug Delivery in Hemostasis and Thrombosis

DTIC Science & Technology

2015-12-01

capsules were suspended in platelet - rich plasma , which was subsequently exposed to 1 U/mL of thrombin, the capsules successfully targeted target...activated platelets . As thrombi in myocardial infarctions and strokes are platelet - rich , this is an ideal system to achieve high concentrations of...AWARD NUMBER: W81XWH-13-1-0495 TITLE: Platelets as Contractile Nanomachines for Targeting Drug Delivery in Hemostasis and Thrombosis PRINCIPAL

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.

The effect of N-acetylcysteine on cardiac contractility to dobutamine in rats with streptozotocin-induced diabetes.

PubMed

Cheng, Xing; Xia, Zhengyuan; Leo, Joyce M; Pang, Catherine C Y

2005-09-05

We examined if myocardial depression at the acute phase of diabetes (3 weeks after injection of streptozotocin, 60 mg/kg i.v.) is due to activation of inducible nitric oxide synthase and production of peroxynitrite, and if treatment with N-acetylcysteine (1.2 g/day/kg for 3 weeks, antioxidant) improves cardiac function. Four groups of rats were used: control, N-acetylcysteine-treated control, diabetic and N-acetylcysteine-treated diabetic. Pentobarbital-anaesthetized diabetic rats, relative to the controls, had reduced left ventricular contractility to dobutamine (1-57 microg/min/kg). The diabetic rats also had increased myocardial levels of thiobarbituric acid reactive substances, immunostaining of inducible nitric oxide synthase and nitrotyrosine, and similar baseline 15-F2t-isoprostane. N-acetylcysteine did not affect responses in the control rats; but increased cardiac contractility to dobutamine, reduced myocardial immunostaining of inducible nitric oxide synthase and nitrotyrosine and level of 15-F2t-isoprostane, and increased cardiac contractility to dobutamine in the diabetic rats. Antioxidant supplementation in diabetes reduces oxidative stress and improves cardiac function.

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.

Enhanced Uterine Contractility and Stillbirth in Mice Lacking G Protein-Coupled Receptor Kinase 6 (GRK6): Implications for Oxytocin Receptor Desensitization

PubMed Central

Mao, Lan; Pierce, Stephanie L.; Swamy, Geeta K.; Heine, R. Phillips; Murtha, Amy P.

2016-01-01

Oxytocin is a potent uterotonic agent and is used clinically for induction and augmentation of labor, as well as for prevention and treatment of postpartum hemorrhage. Oxytocin increases uterine contractility by activating the oxytocin receptor (OXTR), a member of the G protein-coupled receptor family, which is prone to molecular desensitization. After oxytocin binding, the OXTR is phosphorylated by a member of the G protein-coupled receptor kinase (GRK) family, which allows for recruitment of β-arrestin, receptor internalization, and desensitization. According to previous in vitro analyses, desensitization of calcium signaling by the OXTR is mediated by GRK6. The objective of this study was to determine the role of GRK6 in mediating uterine contractility. Here, we demonstrate that uterine GRK6 levels increase in pregnancy and using a telemetry device to measure changes in uterine contractility in live mice during labor, show that mice lacking GRK6 produce a phenotype of enhanced uterine contractility during both spontaneous and oxytocin-induced labor compared with wild-type or GRK5 knockout mice. In addition, the observed enhanced contractility was associated with high rates of term stillbirth. Lastly, using a heterologous in vitro model, we show that β-arrestin recruitment to the OXTR, which is necessary for homologous OXTR desensitization, is dependent on GRK6. Our findings suggest that GRK6-mediated OXTR desensitization in labor is necessary for normal uterine contractile patterns and optimal fetal outcome. PMID:26886170

Thick filament length and isoform composition determine self-organized contractile units in actomyosin bundles.

PubMed

Thoresen, Todd; Lenz, Martin; Gardel, Margaret L

2013-02-05

Diverse myosin II isoforms regulate contractility of actomyosin bundles in disparate physiological processes by variations in both motor mechanochemistry and the extent to which motors are clustered into thick filaments. Although the role of mechanochemistry is well appreciated, the extent to which thick filament length regulates actomyosin contractility is unknown. Here, we study the contractility of minimal actomyosin bundles formed in vitro by mixtures of F-actin and thick filaments of nonmuscle, smooth, and skeletal muscle myosin isoforms with varied length. Diverse myosin II isoforms guide the self-organization of distinct contractile units within in vitro bundles with shortening rates similar to those of in vivo myofibrils and stress fibers. The tendency to form contractile units increases with the thick filament length, resulting in a bundle shortening rate proportional to the length of constituent myosin thick filament. We develop a model that describes our data, providing a framework in which to understand how diverse myosin II isoforms regulate the contractile behaviors of disordered actomyosin bundles found in muscle and nonmuscle cells. These experiments provide insight into physiological processes that use dynamic regulation of thick filament length, such as smooth muscle contraction. Copyright © 2013 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Effects of sodium metabisulphite on guinea pig contractile airway smooth muscle responses in vitro.

PubMed

Sun, J; Sakamoto, T; Chung, K F

1995-08-01

Sodium metabisulphite (MBS) is known to induce bronchoconstriction in asthmatic patients. The effects of MBS on guinea pig airway smooth muscle and on neurally mediated contraction in vitro have been examined. Tracheal and bronchial airway segments were placed in oxygenated buffer solution and electrical field stimulation was performed in the presence of indomethacin (10(-5) M) and propranolol (10(-6) M) for the measurement of isometric tension. Atropine (10(-6) M) was added to bronchial tissues. Concentrations of MBS up to 10(-3) M had no direct effect on airway smooth muscle contraction and did not alter either tracheal smooth muscle contraction induced by electrical field stimulation at all frequencies or acetylcholine-induced tracheal smooth muscle contraction. There was a similar response in the absence of epithelium, except for potentiation of the response induced by electrical field stimulation at 0.5 Hz (24 (10)% increase). However, MBS (10(-5), 10(-6) and 10(-7) M) augmented neurally-mediated non-adrenergic non-cholinergic contractile responses in the bronchi (13.3 (3.2)%, 23.8 (9.6)%, and 6.4 (1.6)%, respectively). MBS had no effect on the contractile response induced by substance P, but at higher concentrations (10(-3) M and 10(-4) M) it caused a time-dependent attenuation of responses induced by either electrical field stimulation or exogenously applied acetylcholine or substance P. MBS had no direct contractile responses but enhanced bronchoconstriction induced by activation of non-cholinergic neural pathways in the bronchus, probably through increased release of neuropeptides. At high concentrations MBS inhibited contractile responses initiated by receptor or neural stimulation.

Effects of sodium metabisulphite on guinea pig contractile airway smooth muscle responses in vitro.

PubMed Central

Sun, J.; Sakamoto, T.; Chung, K. F.

1995-01-01

BACKGROUND--Sodium metabisulphite (MBS) is known to induce bronchoconstriction in asthmatic patients. The effects of MBS on guinea pig airway smooth muscle and on neurally mediated contraction in vitro have been examined. METHODS--Tracheal and bronchial airway segments were placed in oxygenated buffer solution and electrical field stimulation was performed in the presence of indomethacin (10(-5) M) and propranolol (10(-6) M) for the measurement of isometric tension. Atropine (10(-6) M) was added to bronchial tissues. RESULTS--Concentrations of MBS up to 10(-3) M had no direct effect on airway smooth muscle contraction and did not alter either tracheal smooth muscle contraction induced by electrical field stimulation at all frequencies or acetylcholine-induced tracheal smooth muscle contraction. There was a similar response in the absence of epithelium, except for potentiation of the response induced by electrical field stimulation at 0.5 Hz (24 (10)% increase). However, MBS (10(-5), 10(-6) and 10(-7) M) augmented neurally-mediated non-adrenergic non-cholinergic contractile responses in the bronchi (13.3 (3.2)%, 23.8 (9.6)%, and 6.4 (1.6)%, respectively). MBS had no effect on the contractile response induced by substance P, but at higher concentrations (10(-3) M and 10(-4) M) it caused a time-dependent attenuation of responses induced by either electrical field stimulation or exogenously applied acetylcholine or substance P. CONCLUSIONS--MBS had no direct contractile responses but enhanced bronchoconstriction induced by activation of non-cholinergic neural pathways in the bronchus, probably through increased release of neuropeptides. At high concentrations MBS inhibited contractile responses initiated by receptor or neural stimulation. Images PMID:7570440

Early alterations in vascular contractility associated to changes in fatty acid composition and oxidative stress markers in perivascular adipose tissue.

PubMed

Rebolledo, Alejandro; Rebolledo, Oscar R; Marra, Carlos A; García, María E; Roldán Palomo, Ana R; Rimorini, Laura; Gagliardino, Juan J

2010-10-21

To test the early effect of fructose-induced changes in fatty acid composition and oxidative stress markers in perivascular adipose tissue (PVAT) upon vascular contractility. Adult male Wistar rats were fed a commercial diet without (CD) or with 10% fructose (FRD) in the drinking water for 3 weeks. We measured plasma metabolic parameters, lipid composition and oxidative stress markers in aortic PVAT. Vascular contractility was measured in aortic rings sequentially, stimulated with serotonin (5-HT) and high K+-induced depolarization using intact and thereafter PVAT-deprived rings. Comparable body weights were recorded in both groups. FRD rats had increased plasma triglyceride and fructosamine levels. Their PVAT had an increased saturated to mono- or poly-unsaturated fatty acid ratio, a significant decrease in total superoxide dismutase and glutathione peroxidase activities and in the total content of glutathione. Conversely, lipid peroxidation (TBARS), nitric oxide content, and gluthathione reductase activity were significantly higher, indicating an increase in oxidative stress. In aortic rings, removal of PVAT increased serotonin-induced contractions, but the effect was significantly lower in rings from FRD rats. This effect was no longer observed when the two contractions were performed in PVAT-deprived rings. PVAT did not affect the contractions triggered by high K+-induced depolarization either in CD or FRD rats. FRD induces multiple metabolic and endocrine systemic alterations which also alter PVAT and the vascular relaxant properties of this tissue. The changes in PVAT would affect its paracrine modulation of vascular function.

Metronidazole and 5-aminosalicylic acid enhance the contractile activity of histaminergic agonists on the guinea-pig isolated ileum

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

Winbery, S.L.; Barker, L.A.

1986-03-01

The effects of metronidazole and 5-aminosalicylic acid (5-ASA) on histamine receptor-effector systems in the small intestine and right atrium of the guinea pig were studied. In an apparently all-or-none manner, both caused a sinistral shift in dose-response curves for the phasic component of the contractile response to histamine at H1 receptors on the ileum. In the presence of either, the EC50 value for histamine was reduced from 0.07 to about 0.03 microM. Similarly, in an apparently all-or-none fashion, both produced an elevation in the dose-response curve for the actions of dimaprit at H2-receptors in the ileum; the response to allmore » doses was increased about 30% with no significant change in the EC50 value. Metronidazole and 5-ASA did not alter dose-response curves for the tonic contractile response to histamine or curves generated by the cumulative addition of histamine. Also, neither altered the positive chronotropic response on isolated right atria or the phasic contractile response on isolated segments of jejunum and duodenum to histamine or dimaprit. Likewise, neither altered dose-response curves for the direct action of carbamylcholine at muscarinic receptors or for the indirect actions of dimethylphenylpiperazinium on the ileum. The effects of 5-ASA or metronidazole on the response to histamine could be prevented as well as reversed by scopolamine or tetrodotoxin. The results suggest that metronidazole and 5-ASA enhance the actions of histamine and dimaprit on the ileum by an action on myenteric plexus neurons.« less

Increasing O-GlcNAcylation level on organ culture of soleus modulates the calcium activation parameters of muscle fibers.

PubMed

Cieniewski-Bernard, Caroline; Montel, Valerie; Berthoin, Serge; Bastide, Bruno

2012-01-01

O-N-acetylglucosaminylation is a reversible post-translational modification which presents a dynamic and highly regulated interplay with phosphorylation. New insights suggest that O-GlcNAcylation might be involved in striated muscle physiology, in particular in contractile properties such as the calcium activation parameters. By the inhibition of O-GlcNAcase, we investigated the effect of the increase of soleus O-GlcNAcylation level on the contractile properties by establishing T/pCa relationships. We increased the O-GlcNAcylation level on soleus biopsies performing an organ culture of soleus treated or not with PUGNAc or Thiamet-G, two O-GlcNAcase inhibitors. The enhancement of O-GlcNAcylation pattern was associated with an increase of calcium affinity on slow soleus skinned fibers. Analysis of the glycoproteins pattern showed that this effect is solely due to O-GlcNAcylation of proteins extracted from skinned biopsies. We also characterized the O-GlcNAcylated contractile proteins using a proteomic approach, and identified among others troponin T and I as being O-GlcNAc modified. We quantified the variation of O-GlcNAc level on all these identified proteins, and showed that several regulatory contractile proteins, predominantly fast isoforms, presented a drastic increase in their O-GlcNAc level. Since the only slow isoform of contractile protein presenting an increase of O-GlcNAc level was MLC2, the effect of enhanced O-GlcNAcylation pattern on calcium activation parameters could involve the O-GlcNAcylation of sMLC2, without excluding that an unidentified O-GlcNAc proteins, such as TnC, could be potentially involved in this mechanism. All these data strongly linked O-GlcNAcylation to the modulation of contractile activity of skeletal muscle.

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

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

Bone Morphogenetic Protein 4 Promotes Vascular Smooth Muscle Contractility by Activating MicroRNA-21 (miR-21), which Down-regulates Expression of Family of Dedicator of Cytokinesis (DOCK) Proteins*

PubMed Central

Kang, Hara; Davis-Dusenbery, Brandi N.; Nguyen, Peter H.; Lal, Ashish; Lieberman, Judy; Van Aelst, Linda; Lagna, Giorgio; Hata, Akiko

2012-01-01

The bone morphogenetic protein 4 (BMP4) signaling pathway plays a critical role in the promotion and maintenance of the contractile phenotype in vascular smooth muscle cell (vSMC). Misexpression or inactivating mutations of the BMP receptor gene can lead to dedifferentiation of vSMC characterized by increased migration and proliferation that is linked to vascular proliferative disorders. Previously we demonstrated that vSMCs increase microRNA-21 (miR-21) biogenesis upon BMP4 treatment, which induces contractile gene expression by targeting programmed cell death 4 (PDCD4). To identify novel targets of miR-21 that are critical for induction of the contractile phenotype by BMP4, biotinylated miR-21 was expressed in vSMCs followed by an affinity purification of mRNAs associated with miR-21. Nearly all members of the dedicator of cytokinesis (DOCK) 180-related protein superfamily were identified as targets of miR-21. Down-regulation of DOCK4, -5, and -7 by miR-21 inhibited cell migration and promoted cytoskeletal organization by modulating an activity of small GTPase. Thus, this study uncovers a regulatory mechanism of the vSMC phenotype by the BMP4-miR-21 axis through DOCK family proteins. PMID:22158624

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.

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.

The effects of different durations of static stretching within a comprehensive warm-up on voluntary and evoked contractile properties.

PubMed

Reid, Jonathan C; Greene, Rebecca; Young, James D; Hodgson, Daniel D; Blazevich, Anthony J; Behm, David G

2018-05-02

Evidence for performance decrements following prolonged static stretching (SS) has led to a paradigm shift in stretching routines within a warm-up. Rather than SS, dynamic stretching (DS) and dynamic activity (DA) have replaced SS within warm-up routines. The objective of the present study was to compare the effect of differing lower limb SS durations (30 [SS30s], 60 [SS60s] or 120 s [SS120s] of SS per muscle group or no-stretch control) within a comprehensive warm-up protocol consisting of aerobic activity, DS and DA. Sixteen male participants completed the four stretching conditions in a randomized order, after a 5-min low-intensity (cycle) warm-up and before a DS/DA component on separate days. Tests included passive hip and knee ranges of motion (ROM), maximum voluntary knee extensor/flexor force, force produced at 100 ms (F100), vertical jump height and evoked knee extensor contractile properties. For hip flexion (hamstrings) ROM, SS120s provided the largest increase (5.6-11.7%) followed by SS60s (4.3-11.4%), control (4.4-10.6%) and SS30s (3.6-11.1%). For knee flexion (quadriceps) ROM, SS30s provided the largest increase (9.3-18.2%) followed by SS120s (6.5-16.3%), SS60s (7.2-15.2%) and control (6.3-15.2%). There were decreases in quadriceps F100 following SS in SS120s (29.6%) only. There were increases in vertical jump performance in the control (6.2%), SS60s (4.6%) and SS30s (3.3%). While 120 s SS per muscle increased ROM, even within a comprehensive warm-up routine, it also elicited notable performance decrements. However, moderate durations of SS were observed to improve ROM whilst either having negligible or beneficial (but not detrimental) effects on specific aspects of athletic performance.

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.

The Inhibitory Effect of Botulinum Toxin Type A on Rat Pyloric Smooth Muscle Contractile Response to Substance P In Vitro.

PubMed

Shao, Yu-Feng; Xie, Jun-Fan; Ren, Yin-Xiang; Wang, Can; Kong, Xiang-Pan; Zong, Xiao-Jian; Fan, Lin-Lan; Hou, Yi-Ping

2015-10-15

A decrease in pyloric myoelectrical activity and pyloric substance P (SP) content following intrasphincteric injection of botulinum toxin type A (BTX-A) in free move rats have been demonstrated in our previous studies. The aim of the present study was to investigate the inhibitory effect of BTX-A on rat pyloric muscle contractile response to SP in vitro and the distributions of SP and neurokinin 1 receptor (NK1R) immunoreactive (IR) cells and fibers within pylorus. After treatment with atropine, BTX-A (10 U/mL), similar to [D-Arg¹, D-Phe⁵, D-Trp(7,9), Leu(11)]-SP (APTL-SP, 1 μmol/L) which is an NK1R antagonist, decreased electric field stimulation (EFS)-induced contractile tension and frequency, whereas, subsequent administration of APTL-SP did not act on contractility. Incubation with BTX-A at 4 and 10 U/mL for 4 h respectively decreased SP (1 μmol/L)-induced contractions by 26.64% ± 5.12% and 74.92% ± 3.62%. SP-IR fibers and NK1R-IR cells both located within pylorus including mucosa and circular muscle layer. However, fewer SP-fibers were observed in pylorus treated with BTX-A (10 U/mL). In conclusion, BTX-A inhibits SP release from enteric terminals in pylorus and EFS-induced contractile responses when muscarinic cholinergic receptors are blocked by atropine. In addition, BTX-A concentration- and time-dependently directly inhibits SP-induced pyloric smooth muscle contractility.

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

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

Testosterone deficiency prevents left ventricular contractility dysfunction after myocardial infarction.

PubMed

Ribeiro Júnior, R F; Ronconi, K S; Jesus, I C G; Almeida, P W M; Forechi, L; Vassallo, D V; Guatimosim, S; Stefanon, I; Fernandes, A A

2018-01-15

Testosterone may affect myocardial contractility since its deficiency decreases the contraction and relaxation of the heart. Meanwhile, testosterone replacement therapy has raised concerns because it may worsen cardiac dysfunction and remodeling after myocardial infarction (MI). In this study, we evaluate cardiac contractility 60 days after MI in rats with suppressed testosterone. Male Wistar rats underwent bilateral orchidectomy one week before the ligation of the anterior descending left coronary artery. The animals were divided into orchidectomized (OCT); MI; orchidectomized + MI (OCT + MI); orchidectomized + MI + testosterone (OCT + MI + T) and control (Sham) groups. Eight weeks after MI, papillary muscle contractility was analyzed under increasing calcium (0.62, 1.25, 2.5 and 3.75 mM) and isoproterenol (10 -8 to 10 -2  M) concentrations. Ventricular myocytes were isolated for intracellular calcium measurements and assessment of Ca 2+ handling proteins. Contractility was preserved in the orchidectomized animals after myocardial infarction and was reduced when testosterone was replaced (Ca 2+ 3.75 mM: Sham: 608 ± 70 (n = 11); OCT: 590 ± 37 (n = 16); MI: 311 ± 33* (n = 9); OCT + MI: 594 ± 76 (n = 7); OCT + MI + T: 433 ± 38* (n=4), g/g *p < 0.05 vs Sham). Orchidectomy also increased the Ca 2+ transient amplitude of the ventricular myocytes and SERCA-2a protein expression levels. PLB phosphorylation levels at Thr 17 were not different in the orchidectomized animals compared to the Sham animals but were reduced after testosterone replacement. CAMKII phosphorylation and protein nitrosylation increased in the orchidectomized animals. Our results support the view that testosterone deficiency prevents MI contractility dysfunction by altering the key proteins involved in Ca 2+ handling. Copyright © 2017 Elsevier B.V. All rights reserved.

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.

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

Regulation of contractile protein gene expression in unloaded mouse skeletal muscle

NASA Technical Reports Server (NTRS)

Criswell, D. S.; Carson, J. A.; Booth, F. W.

1996-01-01

Hindlimb unloading was performed on mice in an effort to study the regulation of contractile protein genes. In particular, the regulation of myosin heavy chain IIb was examined. During unloading, muscle fibers undergo a type conversion. Preliminary data from this study does not support the hypothesis that the fiber type conversion is due to an increase in promoter activity of fast isoform genes, such as myosin heavy chain IIb. The consequences of this finding are examined, with particular focus on other factors controlling gene regulation.

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

Modeling beta-adrenergic control of cardiac myocyte contractility in silico.

PubMed

Saucerman, Jeffrey J; Brunton, Laurence L; Michailova, Anushka P; McCulloch, Andrew D

2003-11-28

The beta-adrenergic signaling pathway regulates cardiac myocyte contractility through a combination of feedforward and feedback mechanisms. We used systems analysis to investigate how the components and topology of this signaling network permit neurohormonal control of excitation-contraction coupling in the rat ventricular myocyte. A kinetic model integrating beta-adrenergic signaling with excitation-contraction coupling was formulated, and each subsystem was validated with independent biochemical and physiological measurements. Model analysis was used to investigate quantitatively the effects of specific molecular perturbations. 3-Fold overexpression of adenylyl cyclase in the model allowed an 85% higher rate of cyclic AMP synthesis than an equivalent overexpression of beta 1-adrenergic receptor, and manipulating the affinity of Gs alpha for adenylyl cyclase was a more potent regulator of cyclic AMP production. The model predicted that less than 40% of adenylyl cyclase molecules may be stimulated under maximal receptor activation, and an experimental protocol is suggested for validating this prediction. The model also predicted that the endogenous heat-stable protein kinase inhibitor may enhance basal cyclic AMP buffering by 68% and increasing the apparent Hill coefficient of protein kinase A activation from 1.0 to 2.0. Finally, phosphorylation of the L-type calcium channel and phospholamban were found sufficient to predict the dominant changes in myocyte contractility, including a 2.6x increase in systolic calcium (inotropy) and a 28% decrease in calcium half-relaxation time (lusitropy). By performing systems analysis, the consequences of molecular perturbations in the beta-adrenergic signaling network may be understood within the context of integrative cellular physiology.

Modeling beta-adrenergic control of cardiac myocyte contractility in silico

NASA Technical Reports Server (NTRS)

Saucerman, Jeffrey J.; Brunton, Laurence L.; Michailova, Anushka P.; McCulloch, Andrew D.; McCullough, A. D. (Principal Investigator)

2003-01-01

The beta-adrenergic signaling pathway regulates cardiac myocyte contractility through a combination of feedforward and feedback mechanisms. We used systems analysis to investigate how the components and topology of this signaling network permit neurohormonal control of excitation-contraction coupling in the rat ventricular myocyte. A kinetic model integrating beta-adrenergic signaling with excitation-contraction coupling was formulated, and each subsystem was validated with independent biochemical and physiological measurements. Model analysis was used to investigate quantitatively the effects of specific molecular perturbations. 3-Fold overexpression of adenylyl cyclase in the model allowed an 85% higher rate of cyclic AMP synthesis than an equivalent overexpression of beta 1-adrenergic receptor, and manipulating the affinity of Gs alpha for adenylyl cyclase was a more potent regulator of cyclic AMP production. The model predicted that less than 40% of adenylyl cyclase molecules may be stimulated under maximal receptor activation, and an experimental protocol is suggested for validating this prediction. The model also predicted that the endogenous heat-stable protein kinase inhibitor may enhance basal cyclic AMP buffering by 68% and increasing the apparent Hill coefficient of protein kinase A activation from 1.0 to 2.0. Finally, phosphorylation of the L-type calcium channel and phospholamban were found sufficient to predict the dominant changes in myocyte contractility, including a 2.6x increase in systolic calcium (inotropy) and a 28% decrease in calcium half-relaxation time (lusitropy). By performing systems analysis, the consequences of molecular perturbations in the beta-adrenergic signaling network may be understood within the context of integrative cellular physiology.

Comparative Effects of Urocortins and Stresscopin on Cardiac Myocyte Contractility

PubMed Central

Makarewich, Catherine A.; Troupes, Constantine D.; Schumacher, Sarah M.; Gross, Polina; Koch, Walter J.; Crandall, David L.; Houser, Steven R.

2015-01-01

Rationale There is a current need for development of new therapies for patients with heart failure. Objective To test the effects of members of the Corticotropin-Releasing Factor (CRF) family of peptides on myocyte contractility to validate them as potential heart failure therapeutics. Methods and Results Adult feline left ventricular myocytes (AFMs) were isolated and contractility was assessed in the presence and absence of CRF peptides Urocortin 2 (UCN2), Urocortin 3 (UCN3), Stresscopin (SCP), and the β-adrenergic agonist isoproterenol (Iso). An increase in fractional shortening and peak Ca2+ transient amplitude was seen in the presence of all CRF peptides. A decrease in Ca2+ decay rate (Tau) was also observed at all concentrations tested. cAMP generation was measured by ELISA in isolated AFMs in response to the CRF peptides and Iso and significant production was seen at all concentrations and time points tested. Conclusions The CRF family of peptides effectively increases cardiac contractility and should be evaluated as potential novel therapeutics for heart failure patients. PMID:26231084

American ginseng acutely regulates contractile function of rat heart.

PubMed

Jiang, Mao; Murias, Juan M; Chrones, Tom; Sims, Stephen M; Lui, Edmund; Noble, Earl G

2014-01-01

Chronic ginseng treatments have been purported to improve cardiac performance. However reports of acute administration of ginseng on cardiovascular function remain controversial and potential mechanisms are not clear. In this study, we examined the effects of acute North American ginseng (Panax quinquefolius) administration on rat cardiac contractile function by using electrocardiogram (ECG), non-invasive blood pressure (BP) measurement, and Langendorff isolated, spontaneously beating, perfused heart measurements (LP). Eight-week old male Sprague-Dawley rats (n = 8 per group) were gavaged with a single dose of water-soluble American ginseng at 300 mg/kg body weight. Heart rate (HR) and BP were measured prior to and at 1 and 24 h after gavaging (ECG and BP). Additional groups were used for each time point for Langendorff measurements. HR was significantly decreased (ECG: 1 h: 6 ± 0.2%, 24 h: 8 ± 0.3%; BP: 1 h: 8.8 ± 0.2%, 24 h: 13 ± 0.4% and LP: 1 h: 22 ± 0.4%, 24 h: 19 ± 0.4%) in rats treated with water-soluble ginseng compared with pre or control measures. An initial marked decrease in left ventricular developed pressure was observed in LP hearts but BP changes were not observed in BP group. A direct inhibitory effect of North American ginseng was observed on cardiac contractile function in LP rats and on fluorescence measurement of intracellular calcium transient in freshly isolated cardiac myocytes when exposed to ginseng (1 and 10 μg/ml). Collectively these data present evidence of depressed cardiac contractile function by acute administration of North American ginseng in rat. This acute reduction in cardiac contractile function appears to be intrinsic to the myocardium.

American ginseng acutely regulates contractile function of rat heart

PubMed Central

Jiang, Mao; Murias, Juan M.; Chrones, Tom; Sims, Stephen M.; Lui, Edmund; Noble, Earl G.

2014-01-01

Chronic ginseng treatments have been purported to improve cardiac performance. However reports of acute administration of ginseng on cardiovascular function remain controversial and potential mechanisms are not clear. In this study, we examined the effects of acute North American ginseng (Panax quinquefolius) administration on rat cardiac contractile function by using electrocardiogram (ECG), non-invasive blood pressure (BP) measurement, and Langendorff isolated, spontaneously beating, perfused heart measurements (LP). Eight-week old male Sprague–Dawley rats (n = 8 per group) were gavaged with a single dose of water-soluble American ginseng at 300 mg/kg body weight. Heart rate (HR) and BP were measured prior to and at 1 and 24 h after gavaging (ECG and BP). Additional groups were used for each time point for Langendorff measurements. HR was significantly decreased (ECG: 1 h: 6 ± 0.2%, 24 h: 8 ± 0.3%; BP: 1 h: 8.8 ± 0.2%, 24 h: 13 ± 0.4% and LP: 1 h: 22 ± 0.4%, 24 h: 19 ± 0.4%) in rats treated with water-soluble ginseng compared with pre or control measures. An initial marked decrease in left ventricular developed pressure was observed in LP hearts but BP changes were not observed in BP group. A direct inhibitory effect of North American ginseng was observed on cardiac contractile function in LP rats and on fluorescence measurement of intracellular calcium transient in freshly isolated cardiac myocytes when exposed to ginseng (1 and 10 μg/ml). Collectively these data present evidence of depressed cardiac contractile function by acute administration of North American ginseng in rat. This acute reduction in cardiac contractile function appears to be intrinsic to the myocardium. PMID:24672484

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

Influence of the contractile properties of muscle on motor unit firing rates during a moderate-intensity contraction in vivo.

PubMed

Trevino, Michael A; Herda, Trent J; Fry, Andrew C; Gallagher, Philip M; Vardiman, John P; Mosier, Eric M; Miller, Jonathan D

2016-08-01

It is suggested that firing rate characteristics of motor units (MUs) are influenced by the physical properties of the muscle. However, no study has correlated MU firing rates at recruitment, targeted force, or derecruitment with the contractile properties of the muscle in vivo. Twelve participants (age = 20.67 ± 2.35 yr) performed a 40% isometric maximal voluntary contraction of the leg extensors that included linearly increasing, steady force, and decreasing segments. Muscle biopsies were collected with myosin heavy chain (MHC) content quantified, and surface electromyography (EMG) was recorded from the vastus lateralis. The EMG signal was decomposed into the firing events of single MUs. Slopes and y-intercepts were calculated for 1) firing rates at recruitment vs. recruitment threshold, 2) mean firing rates at steady force vs. recruitment threshold, and 3) firing rates at derecruitment vs. derecruitment threshold relationships for each subject. Correlations among type I %MHC isoform content and the slopes and y-intercepts from the three relationships were examined. Type I %MHC isoform content was correlated with MU firing rates at recruitment (y-intercepts: r = -0.577; slopes: r = 0.741) and targeted force (slopes: r = 0.853) vs. recruitment threshold and MU firing rates at derecruitment (y-intercept: r = -0.597; slopes: r = 0.701) vs. derecruitment threshold relationships. However, the majority of the individual MU firing rates vs. recruitment and derecruitment relationships were not significant (P > 0.05) and, thus, revealed no systematic pattern. In contrast, MU firing rates during the steady force demonstrated a systematic pattern with higher firing rates for the lower- than higher-threshold MUs and were correlated with the physical properties of MUs in vivo. Copyright © 2016 the American Physiological Society.

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

IGF-II and IGFBP-6 regulate cellular contractility and proliferation in Dupuytren's disease.

PubMed

Raykha, Christina; Crawford, Justin; Gan, Bing Siang; Fu, Ping; Bach, Leon A; O'Gorman, David B

2013-10-01

Dupuytren's disease (DD) is a common and heritable fibrosis of the palmar fascia that typically manifests as permanent finger contractures. The molecular interactions that induce the development of hyper-contractile fibroblasts, or myofibroblasts, in DD are poorly understood. We have identified IGF2 and IGFBP6, encoding insulin-like growth factor (IGF)-II and IGF binding protein (IGFBP)-6 respectively, as reciprocally dysregulated genes and proteins in primary cells derived from contracture tissues (DD cells). Recombinant IGFBP-6 inhibited the proliferation of DD cells, patient-matched control (PF) cells and normal palmar fascia (CT) cells. Co-treatments with IGF-II, a high affinity IGFBP-6 ligand, were unable to rescue these effects. A non-IGF-II binding analog of IGFBP-6 also inhibited cellular proliferation, implicating IGF-II-independent roles for IGFBP-6 in this process. IGF-II enhanced the proliferation of CT cells, but not DD or PF cells, and significantly enhanced DD and PF cell contractility in stressed collagen lattices. While IGFBP-6 treatment did not affect cellular contractility, it abrogated the IGF-II-induced contractility of DD and PF cells in stressed collagen lattices. IGF-II also significantly increased the contraction of DD cells in relaxed lattices, however this effect was not evident in relaxed collagen lattices containing PF cells. The disparate effects of IGF-II on DD and PF cells in relaxed and stressed contraction models suggest that IGF-II can enhance lattice contractility through more than one mechanism. This is the first report to implicate IGFBP-6 as a suppressor of cellular proliferation and IGF-II as an inducer of cellular contractility in this connective tissue disease. Copyright © 2013 The Authors. Published by Elsevier B.V. All rights reserved.

Introduction of non-linear elasticity models for characterization of shape and deformation statistics: application to contractility assessment of isolated adult cardiocytes.

PubMed

Bazan, Carlos; Hawkins, Trevor; Torres-Barba, David; Blomgren, Peter; Paolini, Paul

2011-08-22

We are exploring the viability of a novel approach to cardiocyte contractility assessment based on biomechanical properties of the cardiac cells, energy conservation principles, and information content measures. We define our measure of cell contraction as being the distance between the shapes of the contracting cell, assessed by the minimum total energy of the domain deformation (warping) of one cell shape into another. To guarantee a meaningful vis-à-vis correspondence between the two shapes, we employ both a data fidelity term and a regularization term. The data fidelity term is based on nonlinear features of the shapes while the regularization term enforces the compatibility between the shape deformations and that of a hyper-elastic material. We tested the proposed approach by assessing the contractile responses in isolated adult rat cardiocytes and contrasted these measurements against two different methods for contractility assessment in the literature. Our results show good qualitative and quantitative agreements with these methods as far as frequency, pacing, and overall behavior of the contractions are concerned. We hypothesize that the proposed methodology, once appropriately developed and customized, can provide a framework for computational cardiac cell biomechanics that can be used to integrate both theory and experiment. For example, besides giving a good assessment of contractile response of the cardiocyte, since the excitation process of the cell is a closed system, this methodology can be employed in an attempt to infer statistically significant model parameters for the constitutive equations of the cardiocytes.

Early alterations in vascular contractility associated to changes in fatty acid composition and oxidative stress markers in perivascular adipose tissue

PubMed Central

2010-01-01

Aim To test the early effect of fructose-induced changes in fatty acid composition and oxidative stress markers in perivascular adipose tissue (PVAT) upon vascular contractility. Methods Adult male Wistar rats were fed a commercial diet without (CD) or with 10% fructose (FRD) in the drinking water for 3 weeks. We measured plasma metabolic parameters, lipid composition and oxidative stress markers in aortic PVAT. Vascular contractility was measured in aortic rings sequentially, stimulated with serotonin (5-HT) and high K+-induced depolarization using intact and thereafter PVAT-deprived rings. Results Comparable body weights were recorded in both groups. FRD rats had increased plasma triglyceride and fructosamine levels. Their PVAT had an increased saturated to mono- or poly-unsaturated fatty acid ratio, a significant decrease in total superoxide dismutase and glutathione peroxidase activities and in the total content of glutathione. Conversely, lipid peroxidation (TBARS), nitric oxide content, and gluthathione reductase activity were significantly higher, indicating an increase in oxidative stress. In aortic rings, removal of PVAT increased serotonin-induced contractions, but the effect was significantly lower in rings from FRD rats. This effect was no longer observed when the two contractions were performed in PVAT-deprived rings. PVAT did not affect the contractions triggered by high K+-induced depolarization either in CD or FRD rats. Conclusions FRD induces multiple metabolic and endocrine systemic alterations which also alter PVAT and the vascular relaxant properties of this tissue. The changes in PVAT would affect its paracrine modulation of vascular function. PMID:20964827

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.

Exposure to low mercury concentration in vivo impairs myocardial contractile function

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

Furieri, Lorena Barros; Fioresi, Mirian; Junior, Rogerio Faustino Ribeiro

2011-09-01

Increased cardiovascular risk after mercury exposure has been described but cardiac effects resulting from controlled chronic treatment are not yet well explored. We analyzed the effects of chronic exposure to low mercury concentrations on hemodynamic and ventricular function of isolated hearts. Wistar rats were treated with HgCl{sub 2} (1st dose 4.6 {mu}g/kg, subsequent dose 0.07 {mu}g/kg/day, im, 30 days) or vehicle. Mercury treatment did not affect blood pressure (BP) nor produced cardiac hypertrophy or changes of myocyte morphometry and collagen content. This treatment: 1) in vivo increased left ventricle end diastolic pressure (LVEDP) without changing left ventricular systolic pressure (LVSP)more » and heart rate; 2) in isolated hearts reduced LV isovolumic systolic pressure and time derivatives, and {beta}-adrenergic response; 3) increased myosin ATPase activity; 4) reduced Na{sup +}-K{sup +} ATPase (NKA) activity; 5) reduced protein expression of SERCA and phosphorylated phospholamban on serine 16 while phospholamban expression increased; as a consequence SERCA/phospholamban ratio reduced; 6) reduced sodium/calcium exchanger (NCX) protein expression and {alpha}-1 isoform of NKA, whereas {alpha}-2 isoform of NKA did not change. Chronic exposure for 30 days to low concentrations of mercury does not change BP, heart rate or LVSP but produces small but significant increase of LVEDP. However, in isolated hearts mercury treatment promoted contractility dysfunction as a result of the decreased NKA activity, reduction of NCX and SERCA and increased PLB protein expression. These findings offer further evidence that mercury chronic exposure, even at small concentrations, is an environmental risk factor affecting heart function. - Highlights: > Unchanges blood pressure, heart rate, systolic pressure. > Increases end diastolic pressure. > Promotes cardiac contractility dysfunction. > Decreases NKA activity, NCX and SERCA, increases PLB protein expression. > Small

Superoxide anion stress attenuates the contractile response of the Guinea pig vas deferens to ATP and diadenosine tetraphosphate. Possible effect on calcium dysregulation.

PubMed

Al-Rawi, Mahmood B; Aleisa, Abdulaziz M; Khattab, Mahmoud M

2008-01-01

Induction of endogenous superoxide anion stress by the use of the superoxide dismutase inhibitor diethylthiocarbamate (DETCA; 10 mmol/l) produced a potent inhibition of the ATP (0.3-10 mmol/l) and diadenosine tetraphosphate (AP(4)A) contractile activity in the isolated vas deferens by 29-92 and 24-90%, respectively. Pyrogallol (0.1 mmol/l), the exogenous superoxide anion generator, produced a significant inhibition on the contractile activity of the vas deferens induced by ATP and AP(4)A by 33-89 and 25-82%, respectively. DETCA (10 mmol/l) and pyrogallol (0.1 mmol/l) attenuated the contractile response of isolated guinea pig vas deferens strips to the selective P2X agonist alpha,beta-methyleneATP (alpha,beta-meATP; 50 micromol/l) by 25 and 47%, respectively. In Ca(2+)-free high-K(+) (80 mmol/l) Krebs solution, pyrogallol and DETCA produced inhibition of the contractile response to alpha,beta-meATP (50 micromol/l) in similar way to that in normal Krebs solution. The further addition of CaCl(2) (1 mmol/l) abolished the inhibitory effects exerted by pyrogallol and DETCA. The control contractile response to alpha,beta-meATP (50 micromol/l) was not affected in Ca(2+)-free high-K(+) (80 mmol/l) Krebs solution. It may be concluded that superoxide anion stress produces a significant inhibitory effect on both mono- and di-nucleotide purinergic contraction of the vas deferens. Superoxide anion appears to interrupt the P2X(1)-mediated transduction cascade at some step(s) of intracellular calcium handling. Copyright 2008 S. Karger AG, Basel.

Characterization of the adenosine receptor in cultured embryonic chick atrial myocytes: Coupling to modulation of contractility and adenylate cyclase activity and identification by direct radioligand binding

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

Liang, B.T.

1989-06-01

Adenosine receptors in a spontaneously contracting atrial myocyte culture from 14-day chick embryos were characterized by radioligand binding studies and by examining the involvement of G-protein in coupling these receptors to a high-affinity state and to the adenylate cyclase and the myocyte contractility. Binding of the antagonist radioligand (3H)-8-cyclopentyl-1,3-diproylxanthine ((3H)CPX) was rapid, reversible and saturable and was to a homogeneous population of sites with a Kd value of 2.1 +/- 0.2 nM and an apparent maximum binding of 26.2 +/- 3 fmol/mg of protein (n = 10, +/- S.E.). Guanyl-5-yl-(beta, gamma-imido)diphosphate had no effect on either the Kd or themore » maximum binding and CPX reversed the N6-R-phenyl-2-propyladenosine-induced inhibition of adenylate cyclase activity and contractility, indicating that (3H) CPX is an antagonist radioligand. Competition curves for (3H) CPX binding by a series of reference adenosine agonists were consistent with labeling of an A1 adenosine receptor and were better fit by a two-site model than by a one-site model. ADP-ribosylation of the G-protein by the endogenous NAD+ in the presence of pertussis toxin shifted the competition curves from bi to monophasic with Ki values similar to those of the KL observed in the absence of prior pertussis intoxication. The adenosine agonists were capable of inhibiting both the adenylate cyclase activity and myocyte contractility in either the absence or the presence of isoproterenol. The A1 adenosine receptor-selective antagonist CPX reversed these agonist effects. The order of ability of the reference adenosine receptor agonists in causing these inhibitory effects was similar to the order of potency of the same agonists in inhibiting the specific (3H)CPX binding (N6-R-phenyl-2-propyladenosine greater than N6-S-phenyl-2-propyladenosine or N-ethyladenosine-5'-uronic acid).« less

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

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.

The Inhibitory Effect of Botulinum Toxin Type A on Rat Pyloric Smooth Muscle Contractile Response to Substance P In Vitro

PubMed Central

Shao, Yu-Feng; Xie, Jun-Fan; Ren, Yin-Xiang; Wang, Can; Kong, Xiang-Pan; Zong, Xiao-Jian; Fan, Lin-Lan; Hou, Yi-Ping

2015-01-01

A decrease in pyloric myoelectrical activity and pyloric substance P (SP) content following intrasphincteric injection of botulinum toxin type A (BTX-A) in free move rats have been demonstrated in our previous studies. The aim of the present study was to investigate the inhibitory effect of BTX-A on rat pyloric muscle contractile response to SP in vitro and the distributions of SP and neurokinin 1 receptor (NK1R) immunoreactive (IR) cells and fibers within pylorus. After treatment with atropine, BTX-A (10 U/mL), similar to [D-Arg1, D-Phe5, D-Trp7,9, Leu11]-SP (APTL-SP, 1 μmol/L) which is an NK1R antagonist, decreased electric field stimulation (EFS)-induced contractile tension and frequency, whereas, subsequent administration of APTL-SP did not act on contractility. Incubation with BTX-A at 4 and 10 U/mL for 4 h respectively decreased SP (1 μmol/L)-induced contractions by 26.64% ± 5.12% and 74.92% ± 3.62%. SP-IR fibers and NK1R-IR cells both located within pylorus including mucosa and circular muscle layer. However, fewer SP-fibers were observed in pylorus treated with BTX-A (10 U/mL). In conclusion, BTX-A inhibits SP release from enteric terminals in pylorus and EFS-induced contractile responses when muscarinic cholinergic receptors are blocked by atropine. In addition, BTX-A concentration- and time-dependently directly inhibits SP-induced pyloric smooth muscle contractility. PMID:26501321

[Effects of vitamin K3 on the contractile activity of the colonic smooth muscles of guinea pig through the calcium activated potassium channel].

PubMed

Li, Jun; Luo, He-sheng; He, Xiao-gu

2006-07-25

To study the mechanism of relaxation of gastrointestinal smooth muscles by vitamin K(3). Stripes of proximal colon were collected from guinea pigs. Suspension of single cells was created from these stripes. TD-112S transducer was used to measure the contraction of the stripes stimulated by vitamin K(3) of the concentrations of 40, 100, 400, and 800 micromol/L respectively. The Ca(2+)-activated K(+) current [IK(Ca)] of the cytomembrane of the colon smooth muscle was recorded with an EPC 10 amplifier under conventional whole cell patterns. The contraction frequencies of the muscle stripes stimulated by vitamin K(3) of the concentrations of 40, 100, 400, and 800 micromol/L were 79% +/- 4%, 58% +/- 5%, 33% +/- 4%, and 12% +/- 3% respectively of that of the control group (all P < 0.01), and the contraction strength was reduced to 77% +/- 10%, 54% +/- 7%, 30% +/- 6%, and 11% +/- 4% respectively (all P < 0.01). The IK((Ca)) of the cytomembrane of the colon smooth muscle at the voltage of +60 mV was increased to 120% +/- 18%, 149% +/- 12%, 197% +/- 19%, and 223% +/- 14% respectively (all P < 0.01). Vitamin K(3) inhibits the contractile activity of the colonic muscle stripes and increases the IK(Ca) of single myocytes concentration-dependently. The mechanism is activation of the Ca(2+)-activated K(+) channel, thus promoting the potassium efflux.

Suppression of guinea pig ileum induced contractility by plasma albumin of hibernators

USGS Publications Warehouse

Bruce, David S.; Ambler, Douglas L.; Henschel, Timothy M.; Oeltgen, Peter R.; Nilekani, Sita P.; Amstrup, Steven C.

1992-01-01

Previous studies suggest that hibernation may be regulated by internal opioids and that the putative “hibernation induction trigger” (HIT) may itself be an opioid. This study examined the effect of plasma albumin (known to bind HIT) on induced contractility of the guinea pig ileum muscle strip. Morphine (400 nM) depressed contractility and 100 nM naloxone restored it. Ten milligrams of lyophilized plasma albumin fractions from hibernating ground squirrels, woodchucks, black bears, and polar bears produced similar inhibition, with partial reversal by naloxone. Five hundredths mg of d-Ala2-d-Leu5-enkephalin (DADLE) also inhibited contractility and naloxone reversed it. Conclusions are that hibernating individuals of these species contain an HIT substance that is opioid in nature and summer animals do not; an endogenous opioid similar to leu-enkephalin may be the HIT compound or give rise to it.

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.

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

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

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.

[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

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.

The role of microtubules in contractile ring function.

PubMed

Conrad, A H; Paulsen, A Q; Conrad, G W

1992-05-01

During cytokinesis, a cortical contractile ring forms around a cell, constricts to a stable tight neck and terminates in separation of the daughter cells. At first cleavage, Ilyanassa obsoleta embryos form two contractile rings simultaneously. The cleavage furrow (CF), in the animal hemisphere between the spindle poles, constricts to a stable tight neck and separates the daughter cells. The third polar lobe constriction (PLC-3), in the vegetal hemisphere below the spindle, constricts to a transient tight neck, but then relaxes, allowing the polar lobe cytoplasm to merge with one daughter cell. Eggs exposed to taxol, a drug that stabilizes microtubules, before the CF or the PLC-3 develop, fail to form CFs, but form stabilized tight PLCs. Eggs exposed to taxol at the time of PLC-3 formation develop varied numbers of constriction rings in their animal hemispheres and one PLC in their vegetal hemisphere, none of which relax. Eggs exposed to taxol after PLC-3 initiation form stabilized tight CFs and PLCs. At maximum constriction, control embryos display immunolocalization of nonextractable alpha-tubulin in their CFs, but not in their PLCs, and reveal, via electron microscopy, many microtubules extending through their CFs, but not through their PLCs. Embryos which form stabilized tightly constricted CFs and PLCs in the presence of taxol display immunolocalization of nonextractable alpha-tubulin in both constrictions and show many polymerized microtubules extending through both CFs and PLCs. These results suggest that the extension of microtubules through a tight contractile ring may be important for stabilizing that constriction and facilitating subsequent cytokinesis.

The role of microtubules in contractile ring function

NASA Technical Reports Server (NTRS)

Conrad, A. H.; Paulsen, A. Q.; Conrad, G. W.; Spooner, B. S. (Principal Investigator)

1992-01-01

During cytokinesis, a cortical contractile ring forms around a cell, constricts to a stable tight neck and terminates in separation of the daughter cells. At first cleavage, Ilyanassa obsoleta embryos form two contractile rings simultaneously. The cleavage furrow (CF), in the animal hemisphere between the spindle poles, constricts to a stable tight neck and separates the daughter cells. The third polar lobe constriction (PLC-3), in the vegetal hemisphere below the spindle, constricts to a transient tight neck, but then relaxes, allowing the polar lobe cytoplasm to merge with one daughter cell. Eggs exposed to taxol, a drug that stabilizes microtubules, before the CF or the PLC-3 develop, fail to form CFs, but form stabilized tight PLCs. Eggs exposed to taxol at the time of PLC-3 formation develop varied numbers of constriction rings in their animal hemispheres and one PLC in their vegetal hemisphere, none of which relax. Eggs exposed to taxol after PLC-3 initiation form stabilized tight CFs and PLCs. At maximum constriction, control embryos display immunolocalization of nonextractable alpha-tubulin in their CFs, but not in their PLCs, and reveal, via electron microscopy, many microtubules extending through their CFs, but not through their PLCs. Embryos which form stabilized tightly constricted CFs and PLCs in the presence of taxol display immunolocalization of nonextractable alpha-tubulin in both constrictions and show many polymerized microtubules extending through both CFs and PLCs. These results suggest that the extension of microtubules through a tight contractile ring may be important for stabilizing that constriction and facilitating subsequent cytokinesis.

The Functional Lumen Imaging Probe Detects Esophageal Contractility not Observed with Manometry in Patients with Achalasia

PubMed Central

Carlson, Dustin A.; Lin, Zhiyue; Kahrilas, Peter J.; Sternbach, Joel; Donnan, Erica N.; Friesen, Laurel; Listernick, Zoe; Mogni, Benjamin; Pandolfino, John E.

2015-01-01

Background & Aims The functional lumen imaging probe (FLIP) could improve characterization of achalasia subtypes by detecting non-occlusive esophageal contractions not observed with standard manometry. We aimed to evaluate for esophageal contractions during volumetric distention in patients with achalasia using FLIP topography. Methods Fifty one treatment-naïve patients with achalasia, defined and sub-classified by high-resolution esophageal pressure topography, and 10 asymptomatic individuals (controls) were evaluated with the FLIP during endoscopy. During stepwise distension, simultaneous intra-bag pressures and 16 channels of cross-sectional areas were measured; data were exported to software that generated FLIP topography plots. Esophageal contractility was identified by noting periods of reduced luminal diameter. Esophageal contractions were further characterized by propagation direction, repetitiveness, and based on whether they were occluding or non-occluding. Results Esophageal contractility was detected in all 10 controls: 8/10 had repetitive, antegrade, contractions and 9/10 had occluding contractions. Contractility was detected in 27% (4/15) of patients with type I achalasia and 65% (18/26, including 9 with occluding contractions) of patients with type II achalasia. Contractility was detected in all 10 patients with type III achalasia; 8 of these patients had a pattern of contractility not observed in controls (repetitive, retrograde contractions). Conclusions Esophageal contractility not observed with manometry can be detected in patients with achalasia using FLIP topography. The presence and patterns of contractility detected with FLIP topography may represent variations in pathophysiology, such as mechanisms of pan-esophageal pressurization in patients with type II achalasia. These findings could have implications for additional sub-classification to supplement prediction of the achalasia disease course. PMID:26278501

Clinical Characteristics and Associated Systemic Diseases in Patients With Esophageal "Absent Contractility"-A Clinical Algorithm.

PubMed

Laique, Sobia; Singh, Tavankit; Dornblaser, David; Gadre, Abhishek; Rangan, Vikram; Fass, Ronnie; Kirby, Donald; Chatterjee, Soumya; Gabbard, Scott

2018-01-19

This study was carried out to assess the clinical characteristics and associated systemic diseases seen in patients diagnosed with absent contractility as per the Chicago Classification version 3.0, allowing us to propose a diagnostic algorithm for their etiologic testing. The Chicago Classification version 3.0 has redefined major and minor esophageal motility disorders using high-resolution esophageal manometry. There is a dearth of publications based on research on absent contractility, which historically has been associated with myopathic processes such as systemic sclerosis (SSc). We conducted a retrospective, multicenter study. Data of patients diagnosed with absent contractility were pooled from Cleveland Clinic, Cleveland, OH (January 2006 to July 2016) and Metrohealth Medical Center, Cleveland, OH (July 2014 to July 2016) and included: age, gender, associated medical conditions, surgical history, medications, and specific antibody testing. A total of 207 patients, including 57 male individuals and 150 female individuals, with mean age of 56.1 and 60.0 years, respectively, were included. Disease distribution was as follows: SSc (diffuse or limited cutaneous) 132, overlap syndromes 7, systemic lupus erythematosus17, Sjögren syndrome 4, polymyositis 3, and dermatomyositis 3. Various other etiologies including gastroesophageal reflux disease, postradiation esophagitis, neuromuscular disorders, and surgical complications were seen in the remaining cohort. Most practitioners use the term "absent contractility" interchangeably with "scleroderma esophagus"; however, only 63% of patients with absent contractility had SSc. Overall, 20% had another systemic autoimmune rheumatologic disease and 16% had a nonrheumatologic etiology for absent contractility. Therefore, alternate diagnosis must be sought in these patients. We propose an algorithm for their etiologic evaluation.

Decreased contractile response of peripheral arterioles to serotonin after CPB in patients with diabetes.

PubMed

Sabe, Sharif A; Feng, Jun; Liu, Yuhong; Scrimgeour, Laura A; Ehsan, Afshin; Sellke, Frank W

2018-05-11

Regulation of coronary vasomotor tone by serotonin is significantly changed after cardioplegic arrest and reperfusion. The current study investigates whether cardiopulmonary bypass may also affect peripheral arteriolar response to serotonin in patients with or without diabetes. Human peripheral microvessels (90-180 µm diameter) were dissected from harvested skeletal muscle tissues from diabetic and non-diabetic patients before and after cardiopulmonary bypass and cardiac surgery (n = 8/group). In vitro contractile response to serotonin was assessed by videomicroscopy in the presence or absence of serotonin alone (10 -9 -10 -5 M) or combined with the selective serotonin 1B receptor (5-HT1B) antagonist, SB224289 (10 -6 M). 5-HT1A/1B protein expression in the skeletal muscle was measured by Western-blot and immunohistochemistry. There were no significant differences in contractile response of peripheral arterioles to serotonin (10 -5 M) pre-cardiopulmonary bypass between diabetic and non-diabetic patients. After cardiopulmonary bypass, contractile response to serotonin was significantly impaired in both diabetic and non-diabetic patients compared to their pre-cardiopulmonary bypass counterparts (P < .05). This effect was more pronounced in diabetic patients than non-diabetic patients (P < .05 versus non-diabetic). The contractile response to serotonin was significantly inhibited by the 5-HT1B antagonist in both diabetic and non-diabetic vessels (P < .05 versus serotonin alone). There were no significant differences in the expression/distribution of 5-HT1A/1B between non-diabetic and diabetic groups or between pre- versus post- cardiopulmonary bypass vessels. Cardiopulmonary bypass is associated with decreased contractile response of peripheral arterioles to serotonin and this effect was exaggerated in the presence of diabetes. Serotonin-induced contractile response of the peripheral arterioles was via 5-HT1B in both diabetic and non-diabetic patients. Copyright �

Changes in contractile properties and action potentials of motor units in the rat medial gastrocnemius muscle during maturation.

PubMed

Dobrzynska, Z; Celichowski, J

2016-02-01

The early phase of development of muscles stops following the disappearance of embryonic and neonatal myosin and the elimination of polyneuronal innervation of muscle fibres with the formation of motor units (MUs), but later the muscle mass still considerably increases. It is unknown whether the three types are visible among newly formed MUs soon after the early postnatal period and whether their proportion is similar to that in adult muscle. Moreover, the processes responsible for MU-force regulation by changes in motoneuronal firing rate as well as properties of motor unit action potentials (MUAPs) during maturation are unknown. Three groups of Wistar rats were investigated - 1 month old, 2 months old and the adult, 9 months old. The basic contractile properties and action potentials of MUs in the medial gastrocnemius (MG) muscle were analysed. The three types of MUs were distinguishable in all age groups, but higher proportion of slow MUs was noticed in young rats (29%, 18% and 11% in 1, 2 and 9 months rats, respectively). The fatigue index for fast fatigable MUs in 1 month old rats was about 2 times higher than in 9 months old rats. The twitch time parameters of fast MUs were shortened during the maturation; for these units, the force-frequency curves in young rats were shifted towards lower frequencies, which suggested that fast motoneurons of young animals generate lower firing rates. Higher twitch-to-tetanus ratios noted for the three MU types in young rats suggested the smaller role of rate coding in force regulation processes, and the higher role of MU recruitment in young rats. No significant differences in MUAP parameters between two groups of young and adult animals were observed. Concluding, the maturation process evokes deeper changes in fast MUs than in slow ones.

Pharmacological characterization and chemical fractionation of a liposterolic extract of saw palmetto (Serenoa repens): effects on rat prostate contractility.

PubMed

Chua, Thiam; Eise, Nicole T; Simpson, Jamie S; Ventura, Sabatino

2014-03-14

Saw palmetto (Serenoa repens) was first used medicinally by native American Indians to treat urological disorders. Nowadays, saw palmetto extracts are widely used in Europe and North America to treat the urinary symptoms associated with benign prostatic hyperplasia even though its mechanisms of action are poorly understood. This study aimed to characterize the bioactive constituents of a lipid extract of saw palmetto that are able to affect contractility of the rat prostate gland. The mechanism of action will also be investigated. A commercially available lipid extract of saw palmetto was subjected to fractionation using normal phase column chromatography. Composition of fractions was assessed by proton nuclear magnetic resonance spectroscopy ((1)H NMR) and mass spectrometry (MS). Contractile activities of these fractions were evaluated pharmacologically using isolated preparations of rat prostate gland and compared to the activity of the crude extract. Saw palmetto extract inhibited contractions of the rat prostate gland which were consistent with smooth muscle relaxant activity. Only the ethyl acetate fraction resulting from chromatography inhibited contractions of isolated rat prostates similarly to the inhibition produced by the crude lipid extract. Comparison with authentic samples and analysis of NMR data revealed that this bioactivity was due to the fatty acid components present in the ethyl acetate fraction. Bioassay using various pharmacological tools identified multiple contractile mechanisms which were affected by the bioactive constituents. A fatty acid component of saw palmetto extract causes inhibition of prostatic smooth muscle contractions via a non-specific mechanism. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Evaluation of aortic contractility based on analysis of CT images of the heart

NASA Astrophysics Data System (ADS)

DzierŻak, RóŻa; Maciejewski, Ryszard; Uhlig, Sebastian

2017-08-01

The paper presents a method to assess the aortic contractility based on the analysis of CT images of the heart. This is an alternative method that can be used for patients who cannot be examined by using echocardiography. Usage of medical imaging application for DICOM file processing allows to evaluate the aortic cross section during systole and diastole. It makes possible to assess the level of aortic contractility.

A study of ventricular contractility and other parameters possibly related to vasodepressor syncope

NASA Technical Reports Server (NTRS)

Hyatt, K. H.; Sullivan, R. W.; Spears, W. R.; Vetter, W. R.

1973-01-01

The effects of diminished orthostatic and exercise tolerance resulting from prolonged bedrest were studied by noninvasion methods to determine if alterations in myocardial contractility were induced by bedrest. These methods were apexcardiography, systolic time intervals, and echocardiography. It is concluded that bedrest causes detrimental alterations in the contractile state of the myocardium which accounts for the decreases in maximal oxygen uptaken during exercise after bedrest. Tabulated test data are included.

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.

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

Loss of Gα12/13 exacerbates apical area dependence of actomyosin contractility

PubMed Central

Xie, Shicong; Mason, Frank M.; Martin, Adam C.

2016-01-01

During development, coordinated cell shape changes alter tissue shape. In the Drosophila ventral furrow and other epithelia, apical constriction of hundreds of epithelial cells folds the tissue. Genes in the Gα12/13 pathway coordinate collective apical constriction, but the mechanism of coordination is poorly understood. Coupling live-cell imaging with a computational approach to identify contractile events, we discovered that differences in constriction behavior are biased by initial cell shape. Disrupting Gα12/13 exacerbates this relationship. Larger apical area is associated with delayed initiation of contractile pulses, lower apical E-cadherin and F-actin levels, and aberrantly mobile Rho-kinase structures. Our results suggest that loss of Gα12/13 disrupts apical actin cortex organization and pulse initiation in a size-dependent manner. We propose that Gα12/13 robustly organizes the apical cortex despite variation in apical area to ensure the timely initiation of contractile pulses in a tissue with heterogeneity in starting cell shape. PMID:27489340

Modeling the two-way feedback between contractility and matrix realignment reveals a nonlinear mode of cancer cell invasion

PubMed Central

Ahmadzadeh, Hossein; Webster, Marie R.; Behera, Reeti; Jimenez Valencia, Angela M.; Wirtz, Denis; Weeraratna, Ashani T.; Shenoy, Vivek B.

2017-01-01

Cancer cell invasion from primary tumors is mediated by a complex interplay between cellular adhesions, actomyosin-driven contractility, and the physical characteristics of the extracellular matrix (ECM). Here, we incorporate a mechanochemical free-energy–based approach to elucidate how the two-way feedback loop between cell contractility (induced by the activity of chemomechanical interactions such as Ca2+ and Rho signaling pathways) and matrix fiber realignment and strain stiffening enables the cells to polarize and develop contractile forces to break free from the tumor spheroids and invade into the ECM. Interestingly, through this computational model, we are able to identify a critical stiffness that is required by the matrix to break intercellular adhesions and initiate cell invasion. Also, by considering the kinetics of the cell movement, our model predicts a biphasic invasiveness with respect to the stiffness of the matrix. These predictions are validated by analyzing the invasion of melanoma cells in collagen matrices of varying concentration. Our model also predicts a positive correlation between the elongated morphology of the invading cells and the alignment of fibers in the matrix, suggesting that cell polarization is directly proportional to the stiffness and alignment of the matrix. In contrast, cells in nonfibrous matrices are found to be rounded and not polarized, underscoring the key role played by the nonlinear mechanics of fibrous matrices. Importantly, our model shows that mechanical principles mediated by the contractility of the cells and the nonlinearity of the ECM behavior play a crucial role in determining the phenotype of the cell invasion. PMID:28196892

Mechanism of Cytokinetic Contractile Ring Constriction in Fission Yeast

PubMed Central

Stachowiak, Matthew R.; Laplante, Caroline; Chin, Harvey F.; Guirao, Boris; Karatekin, Erdem; Pollard, Thomas D.; O’Shaughnessy, Ben

2014-01-01

SUMMARY Cytokinesis involves constriction of a contractile actomyosin ring. The mechanisms generating ring tension and setting the constriction rate remain unknown, since the organization of the ring is poorly characterized, its tension was rarely measured, and constriction is coupled to other processes. To isolate ring mechanisms we studied fission yeast protoplasts, where constriction occurs without the cell wall. Exploiting the absence of cell wall and actin cortex, we measured ring tension and imaged ring organization, which was dynamic and disordered. Computer simulations based on the amounts and biochemical properties of the key proteins showed that they spontaneously self-organize into a tension-generating bundle. Together with rapid component turnover, the self-organization mechanism continuously reassembles and remodels the constricting ring. Ring constriction depended on cell shape, revealing that the ring operates close to conditions of isometric tension. Thus, the fission yeast ring sets its own tension, but other processes set the constriction rate. PMID:24914559

Effect of lidocaine with and without epinephrine on lymphatic contractile activity in mice in vivo.

PubMed

Kwon, Sunkuk; Sevick-Muraca, Eva M

2016-12-01

A local anesthetic, lidocaine, is known to affect cutaneous blood flow when injected into the skin. However, it is unknown if dermal lymphatic function can also be affected. Therefore, we characterized lymphatic function in response to administration of lidocaine with and without epinephrine. Non-invasive near-infrared fluorescence imaging (NIRFI) with intradermal injection of indocyanine green (ICG) was used to characterize the lymphatic "pumping" function in mice after subcutaneous injection of 2 % lidocaine with and without 1:100,000 epinephrine or saline. NIRFI was performed for 10-20 min immediately after and 1, 3, and 5 h after these interventions. Lymphatic contraction frequencies significantly decreased 10 min after subcutaneous injection of lidocaine and remained plateaued for another 5 min, before returning to baseline. However, addition of 1:100,000 epinephrine to 2 % lidocaine rapidly increased lymphatic contraction frequencies at 5 min post-injection, which returned to baseline levels 15 min later. Injection of saline also increased lymphatic contraction frequency 5 min after injection, which returned to baseline 10 min post-injection. Although lidocaine administration showed a decrease in lymphatic function, the combination of epinephrine with lidocaine resulted in a predominant net effect of increased contractile activity.

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.

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

Tension cost correlates with mechanical and biochemical parameters in different myocardial contractility conditions

PubMed Central

Moreira, Cleci M.; Meira, Eduardo F.; Vestena, Luis; Stefanon, Ivanita; Vassallo, Dalton V.; Padilha, Alessandra S.

2012-01-01

OBJECTIVES: Tension cost, the ratio of myosin ATPase activity to tension, reflects the economy of tension development in the myocardium. To evaluate the mechanical advantage represented by the tension cost, we studied papillary muscle contractility and the activity of myosin ATPase in the left ventricles in normal and pathophysiological conditions. METHODS: Experimental protocols were performed using rat left ventricles from: (1) streptozotocin-induced diabetic and control Wistar rats; (2) N-nitro-L-arginine methyl ester (L-NAME) hypertensive and untreated Wistar rats; (3) deoxycorticosterone acetate (DOCA) salt-treated, nephrectomized and salt- and DOCA-treated rats; (4) spontaneous hypertensive rats (SHR) and Wistar Kyoto (WKY) rats; (5) rats with myocardial infarction and sham-operated rats. The isometric force, tetanic tension, and the activity of myosin ATPase were measured. RESULTS: The results obtained from infarcted, diabetic, and deoxycorticosterone acetate-salt-treated rats showed reductions in twitch and tetanic tension compared to the control and sham-operated groups. Twitch and tetanic tension increased in the N-nitro-L-arginine methyl ester-treated rats compared with the Wistar rats. Myosin ATPase activity was depressed in the infarcted, diabetic, and deoxycorticosterone acetate salt-treated rats compared with control and sham-operated rats and was increased in N-nitro-L-arginine methyl ester-treated rats. These parameters did not differ between SHR and WKY rats. In the studied conditions (e.g., post-myocardial infarction, deoxycorticosterone acetate salt-induced hypertension, chronic N-nitro-L-arginine methyl ester treatment, and streptozotocin-induced diabetes), a positive correlation between force or plateau tetanic tension and myosin ATPase activity was observed. CONCLUSION: Our results suggest that the myocardium adapts to force generation by increasing or reducing the tension cost to maintain myocardial contractility with a better mechanical

Contractile effect of rifaximin on bovine uterus in the presence of steroid hormone antagonists.

PubMed

Sciorsci, R L; Piccinno, M; Rizzo, A

2018-04-01

This in vitro study investigated the modulatory effect of rifaximin on bovine uterus contractility, in both phases of the oestrous cycle, with and without the steroid hormones that are predominant in the respective phases: oestrogen in the follicular phase and progesterone in the luteal phase. The procedures were conducted in an isolated organ bath by using rifaximin alone (10 -4  M) and in association with the steroid hormone antagonists (10 -5  M) tamoxifen (oestrogen antagonist) in the follicular phase and mifepristone (progesterone antagonist) in the luteal phase. The results indicated that rifaximin can stimulate uterine contractility. Indeed, the administration of rifaximin in the presence of tamoxifen or mifepristone increased the tonic activity of the uterus in both phases of the cycle. This result is clinically significant because rifaximin might also enable, in vivo, a simultaneous increase in uterine cleaning and the antimicrobial action against bacteria during the first 14 days postpartum, during the development of acute metritis. Copyright © 2018 Elsevier Inc. All rights reserved.

Evidence for non-adrenergic non-cholinergic contractile responses in bovine and swine trachea.

PubMed

Matera, M G; Amorena, M; Marabese, I; Loffreda, A; D'Agostino, B; Lucisano, A; Rossi, F

1997-01-01

Non-adrenergic non-cholinergic (NANC) contraction of airway smooth muscle has been observed in some but not all animal species. The aim of this study was to investigate the NANC-contractile responses in bovine and swine trachea. Proximal and distal bovine and swine trachea were cut in strips and placed in 10 ml organ baths equilibrated in Krebs Henseleit (KH) solution and electrically stimulated (10 sec, 60 V, 2 ms, 4, 10 and 30 Hz). Contractile frequency response curves performed in the presence of the muscarinic antagonist, atropine (100 mM), the angiotensin converting enzyme inhibitor, captopril (1 microM) and the neutral endopeptidase inhibitor, thiorphan (1 microM), added 30 min prior to electrical field stimulation (EFS). In some tissues, incubated with atropine thiorphan and captopril, were also evaluated the effects of a pretreatment with capsaicin (10 microM) or a selective NK1 receptor antagonist, SR 14033 (100 nM) added to the baths 30 min prior to EFS. Bovine and swine proximal and distal tracheal preparations contracted in a frequency-dependent manner to EFS (4, 10 and 30 Hz). Some experiments were also performed with substance P (0.1 nM to 1 microM) in absence or in presence of SR 14033 (10 nM or 100 nM). At the maximum frequency tested (30 Hz), the contractile response elicited in bovine proximal and distal preparations was 194.5 +/- 17.1% and 229.7 +/- 24.1%, of ACh (100 microM), respectively. Similarly, the contractile response elicited by EFS (30 Hz) in swine proximal and distal preparations was 187.2 +/- 12.1% and 181.6 +/- 9.2% of ACh (100 microM), respectively. In tissues incubated with atropine, a significant decrease in smooth muscle sensitivity to EFS was observed (P < 0.05). When tissues were pretreated with captopril and thiorphan, a significant increase in the contractile response to EFS (30 Hz) was observed in all tested tissue preparations (bovine, proximal 210.1 +/- 14.4%, distal 264.3 +/- 16.2%; swine, proximal 199.3 +/- 14.9%, distal

The Functional Lumen Imaging Probe Detects Esophageal Contractility Not Observed With Manometry in Patients With Achalasia.

PubMed

Carlson, Dustin A; Lin, Zhiyue; Kahrilas, Peter J; Sternbach, Joel; Donnan, Erica N; Friesen, Laurel; Listernick, Zoe; Mogni, Benjamin; Pandolfino, John E

2015-12-01

The functional lumen imaging probe (FLIP) could improve the characterization of achalasia subtypes by detecting nonocclusive esophageal contractions not observed with standard manometry. We aimed to evaluate esophageal contractions during volumetric distention in patients with achalasia using FLIP topography. Fifty-one treatment-naive patients with achalasia, defined and subclassified by high-resolution esophageal pressure topography, and 10 asymptomatic individuals (controls) were evaluated with the FLIP during endoscopy. During stepwise distension, simultaneous intrabag pressures and 16 channels of cross-sectional areas were measured; data were exported to software that generated FLIP topography plots. Esophageal contractility was identified by noting periods of reduced luminal diameter. Esophageal contractions were characterized further by propagation direction, repetitiveness, and based on whether they were occluding or nonoccluding. Esophageal contractility was detected in all 10 controls: 8 of 10 had repetitive antegrade contractions and 9 of 10 had occluding contractions. Contractility was detected in 27% (4 of 15) of patients with type I achalasia and in 65% (18 of 26, including 9 with occluding contractions) of patients with type II achalasia. Contractility was detected in all 10 patients with type III achalasia; 8 of these patients had a pattern of contractility that was not observed in controls (repetitive retrograde contractions). Esophageal contractility not observed with manometry can be detected in patients with achalasia using FLIP topography. The presence and patterns of contractility detected with FLIP topography may represent variations in pathophysiology, such as mechanisms of panesophageal pressurization in patients with type II achalasia. These findings could have implications for additional subclassification to supplement prediction of the achalasia disease course. Copyright © 2015 AGA Institute. Published by Elsevier Inc. All rights

Spatial differences of cellular origins and in vivo hypoxia modify contractile properties of pulmonary artery smooth muscle cells: lessons for arterial tissue engineering.

PubMed

Hall, S M; Soueid, A; Smith, T; Brown, R A; Haworth, S G; Mudera, V

2007-01-01

Tissue engineering of functional arteries is challenging. Within the pulmonary artery wall, smooth muscle cells (PASMCs) have site-specific developmental and functional phenotypes, reflecting differing contractile roles. The force generated by PASMCs isolated from the inner 25% and outer 50% of the media of intrapulmonary elastic arteries from five normal and eight chronically hypoxic (hypertensive) 14 day-old piglets was quantified in a three-dimensional (3D) collagen construct, using a culture force monitor. Outer medial PASMCs from normal piglets exerted more force (528 +/- 50 dynes) than those of hypoxic piglets (177 +/- 42 dynes; p < 0.01). Force generation by inner medial PASMCs from normal and hypoxic piglets was similar (349 +/- 35 and 239 +/- 60 dynes). In response to agonist (thromboxane) stimulation, all PASMCs from normal and hypoxic piglets contracted, but the increase in force generated by outer and inner hypoxic PASMCs (ranges 13-72 and 14-56 dynes) was less than by normal PASMCs (ranges 27-154 and 34-159 dynes, respectively; p < 0.05 for both). All hypoxic PASMCs were unresponsive to antagonist (sodium nitroprusside) stimulation, all normal PASMCs relaxed (range - 87 to - 494 dynes). Myosin heavy chain expression by both hypoxic PASMC phenotypes was less than normal (p < 0.05 for both), as was the activity of focal adhesion kinase, regulating contraction, in hypoxic inner PASMCs (p < 0.01). Chronic hypoxia resulted in the development of abnormal PASMC phenotypes, which in collagen constructs exhibited a reduction in contractile force and reactivity to agonists. Characterization of the mechanical response of spatially distinct cells and modification of their behaviour by hypoxia is critical for successful tissue engineering of major blood vessels.

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.

Dynamics of myosin II organization into cortical contractile networks and fibers

NASA Astrophysics Data System (ADS)

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

2014-03-01

The morphology of adhered cells critically depends on the formation of a contractile meshwork of parallel and cross-linked stress fibers along the contacting surface. The motor activity and mini-filament assembly of non-muscle myosin II is an important component of cell-level cytoskeletal remodeling during mechanosensing. To monitor the dynamics of myosin II, we used confocal microscopy to image cultured HeLa cells that stably express myosin regulatory light chain tagged with GFP (MRLC-GFP). MRLC-GFP was monitored in time-lapse movies at steady state and during the response of cells to varying concentrations of blebbistatin which disrupts actomyosin stress fibers. Using image correlation spectroscopy analysis, we quantified the kinetics of disassembly and reassembly of actomyosin networks and compared them to studies by other groups. This analysis suggested that the following processes contribute to the assembly of cortical actomyosin into fibers: random myosin mini-filament assembly and disassembly along the cortex; myosin mini-filament aligning and contraction; stabilization of cortical myosin upon increasing contractile tension. We developed simple numerical simulations that include those processes. The results of simulations of cells at steady state and in response to blebbistatin capture some of the main features observed in the 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.

Synaptopodin couples epithelial contractility to α-actinin-4–dependent junction maturation

PubMed Central

Kannan, Nivetha

2015-01-01

The epithelial junction experiences mechanical force exerted by endogenous actomyosin activities and from interactions with neighboring cells. We hypothesize that tension generated at cell–cell adhesive contacts contributes to the maturation and assembly of the junctional complex. To test our hypothesis, we used a hydraulic apparatus that can apply mechanical force to intercellular junction in a confluent monolayer of cells. We found that mechanical force induces α-actinin-4 and actin accumulation at the cell junction in a time- and tension-dependent manner during junction development. Intercellular tension also induces α-actinin-4–dependent recruitment of vinculin to the cell junction. In addition, we have identified a tension-sensitive upstream regulator of α-actinin-4 as synaptopodin. Synaptopodin forms a complex containing α-actinin-4 and β-catenin and interacts with myosin II, indicating that it can physically link adhesion molecules to the cellular contractile apparatus. Synaptopodin depletion prevents junctional accumulation of α-actinin-4, vinculin, and actin. Knockdown of synaptopodin and α-actinin-4 decreases the strength of cell–cell adhesion, reduces the monolayer permeability barrier, and compromises cellular contractility. Our findings underscore the complexity of junction development and implicate a control process via tension-induced sequential incorporation of junctional components. PMID:26504173

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

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

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.

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

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.

mTOR-Independent Autophagy Inducer Trehalose Rescues against Insulin Resistance-Induced Myocardial Contractile Anomalies: Role of p38 MAPK and Foxo1

PubMed Central

Wang, Qiurong; Ren, Jun

2016-01-01

Insulin resistance is associated with cardiovascular diseases although the precise mechanisms remain elusive. Akt2, a critical member of the Akt family, plays an essential role in insulin signaling. This study was designed to examine the effect of trehalose, an mTOR-independent autophagy inducer, on myocardial function in an Akt2 knockout-induced insulin resistance model. Adult WT and Akt2 knockout (Akt2−/−) mice were administered trehalose (1 mg/g/day, i.p.) for two days and were then given 2% trehalose in drinking water for two more months. Echocardiographic and myocardial mechanics, intracellular Ca2+ properties, glucose tolerance, and autophagy were assessed. Apoptosis and ER stress were evaluated using TUNEL staining, Caspase 3 assay and Western blot. Autophagy and autophagy flux were examined with a focus on p38 mitogen activated protein kinase (MAPK), Forkhead box O (Foxo1) and Akt. Akt2 ablation impaired glucose tolerance, myocardial geometry and function accompanied with pronounced apoptosis, ER stress and dampened autophagy, the effects of which were ameliorated by trehalose treatment. Inhibition of lysosomal activity using bafilomycin A1 negated trehalose–induced induction of autophagy (LC3B–II and p62). Moreover, phosphorylation of p38 MAPK and Foxo1 were upregulated in Akt2−/− mice, the effect of which was attenuated by trehalose. Phosphorylation of Akt was suppressed in Akt2−/− mice and was unaffected by trehalose. In vitro findings revealed that the p38 MAPK activator anisomycin and the Foxo1 inhibitor (through phosphorylation) AS1842856 effectively masked trehalose-offered beneficial cardiomyocyte contractile response against Akt2 ablation. These data suggest that trehalose may rescue against insulin resistance-induced myocardial contractile defect and apoptosis, via autophagy associated with dephosphorylation of p38 MAPK and Foxo1 without affecting phosphorylation of Akt. PMID:27363949

mTOR-Independent autophagy inducer trehalose rescues against insulin resistance-induced myocardial contractile anomalies: Role of p38 MAPK and Foxo1.

PubMed

Wang, Qiurong; Ren, Jun

2016-09-01

Insulin resistance is associated with cardiovascular diseases although the precise mechanisms remain elusive. Akt2, a critical member of the Akt family, plays an essential role in insulin signaling. This study was designed to examine the effect of trehalose, an mTOR-independent autophagy inducer, on myocardial function in an Akt2 knockout-induced insulin resistance model. Adult WT and Akt2 knockout (Akt2(-/-)) mice were administered trehalose (1mg/g/day, i.p.) for two days and were then given 2% trehalose in drinking water for two more months. Echocardiographic and myocardial mechanics, intracellular Ca(2+) properties, glucose tolerance, and autophagy were assessed. Apoptosis and ER stress were evaluated using TUNEL staining, Caspase 3 assay and Western blot. Autophagy and autophagy flux were examined with a focus on p38 mitogen activated protein kinase (MAPK), Forkhead box O (Foxo1) and Akt. Akt2 ablation impaired glucose tolerance, myocardial geometry and function accompanied with pronounced apoptosis, ER stress and dampened autophagy, the effects of which were ameliorated by trehalose treatment. Inhibition of lysosomal activity using bafilomycin A1 negated trehalose-induced induction of autophagy (LC3B-II and p62). Moreover, phosphorylation of p38 MAPK and Foxo1 were upregulated in Akt2(-/-) mice, the effect of which was attenuated by trehalose. Phosphorylation of Akt was suppressed in Akt2(-/-) mice and was unaffected by trehalose. In vitro findings revealed that the p38 MAPK activator anisomycin and the Foxo1 inhibitor (through phosphorylation) AS1842856 effectively masked trehalose-offered beneficial cardiomyocyte contractile response against Akt2 ablation. These data suggest that trehalose may rescue against insulin resistance-induced myocardial contractile defect and apoptosis, via autophagy associated with dephosphorylation of p38 MAPK and Foxo1 without affecting phosphorylation of Akt. Copyright © 2016 Elsevier Ltd. All rights reserved.

Effects of endothelin, calcium channel blockade and EDRF inhibition on the contractility of human uteroplacental arteries.

PubMed

Fried, G; Liu, Y A

1994-08-01

In order to examine the possibility that endothelin might be important in the regulation of placental blood flow, human uteroplacental vessels were superfused in vitro to study the contractile effect of endothelin as compared with a known strong contractor of placental blood vessels, serotonin (5-HT). The contractile responses were compared in the presence and absence of calcium channel blocking agents, as well as in the presence of L-NMA, an inhibitor of EDRF/nitric oxide. Endothelin (ET, 10(-10)-10(-6) M) and 5-HT (10(-8)-10(-4) M) induced contractions in the vessels. Maximal contractions in the presence of endothelin were elicited at 10(-7) M, whereas 5-HT elicited maximal contractions at 10(-5) M. At 10(-7) M, ET was more potent than 5-HT. The calcium-channel blocking agents nifedipine, diltiazem and NiCl2 relaxed the vessels by 5-15% from baseline. The contractile response to ET in the presence of nifedipine or diltiazem was reduced by 55 and 67%, respectively. The response of 5-HT in the presence of nifedipine was reduced by 58%. The contractile response to 5-HT as well as ET in the presence of both nifedipine and NiCl2 was not significantly lower than in the presence of nifedipine only. The EDRF-inhibiting agent L-NMA caused a small contractile response at concentrations of 10(-6)-10(-5) M. ET as well as 5-HT added after pretreatment with L-NMA produced a larger contractile response than ET or 5-HT alone. The results show that ET has a strong contractile effect on placental blood vessels at concentrations likely to occur during labor and delivery. The mechanism whereby ET as well as 5-HT contracts placental vessel smooth muscle appears to partly involve nifedipine- and diltiazem-sensitive calcium channels, but almost half of the response depends on mobilization of calcium through other means.

Hypothermia Inhibits Endothelium-Independent Vascular Contractility via Rho-kinase Inhibition

PubMed Central

Chung, Yoon Hee; Oh, Keon Woong; Kim, Sung Tae; Park, Eon Sub; Je, Hyun Dong; Yoon, Hyuk-Jun; Sohn, Uy Dong; Jeong, Ji Hoon; La, Hyen-Oh

2018-01-01

The present study was undertaken to investigate the influence of hypothermia on endothelium-independent vascular smooth muscle contractility and to determine the mechanism underlying the relaxation. Denuded aortic rings from male rats were used and isometric contractions were recorded and combined with molecular experiments. Hypothermia significantly inhibited fluoride-, thromboxane A2-, phenylephrine-, and phorbol ester-induced vascular contractions regardless of endothelial nitric oxide synthesis, suggesting that another pathway had a direct effect on vascular smooth muscle. Hypothermia significantly inhibited the fluoride-induced increase in pMYPT1 level and phorbol ester-induced increase in pERK1/2 level, suggesting inhibition of Rho-kinase and MEK activity and subsequent phosphorylation of MYPT1 and ERK1/2. These results suggest that the relaxing effect of moderate hypothermia on agonist-induced vascular contraction regardless of endothelial function involves inhibition of Rho-kinase and MEK activities. PMID:28208012

Bistable front dynamics in a contractile medium: travelling wave and cortical advection define stable zones of RhoA signaling at epithelial adherens junctions

NASA Astrophysics Data System (ADS)

Neufeld, Zoltan

Recent studies have demonstrated that mechanical forces can lead to novel mechanisms of pattern formation such as clustering and oscillations in contractile systems. We investigate how contractile forces in mechanically active media can affect bistable front propagation. We found that contraction regulates the front speed or can fully suppress its propagation in space to create a static localized zone. We demonstrate how the interplay between biochemical signaling through positive feedback, combined with diffusion on the cell membrane and mechanical forces generated in the actomyosin cortex, can determine the spatial distribution of RhoA signaling at cell-cell junctions. The dynamical mechanism relies on the balance between a propagating bistable signal that is opposed by an advective flow generated by an actomyosin stress gradient. Experimental observations on the behaviour of the system when contractility is inhibited are in qualitative agreement with the predictions of the model. In collaboration with: Zoltan Neufeld, Guillermo A. Gomez, and Alpha S. Yap, University of Queensland, Brisbane, Australia

Vascular smooth muscle cell contractile protein expression is increased through protein kinase G-dependent and -independent pathways by glucose-6-phosphate dehydrogenase inhibition and deficiency.

PubMed

Chettimada, Sukrutha; Joshi, Sachindra Raj; Dhagia, Vidhi; Aiezza, Alessandro; Lincoln, Thomas M; Gupte, Rakhee; Miano, Joseph M; Gupte, Sachin A

2016-10-01

Homeostatic control of vascular smooth muscle cell (VSMC) differentiation is critical for contractile activity and regulation of blood flow. Recently, we reported that precontracted blood vessels are relaxed and the phenotype of VSMC is regulated from a synthetic to contractile state by glucose-6-phosphate dehydrogenase (G6PD) inhibition. In the current study, we investigated whether the increase in the expression of VSMC contractile proteins by inhibition and knockdown of G6PD is mediated through a protein kinase G (PKG)-dependent pathway and whether it regulates blood pressure. We found that the expression of VSMC-restricted contractile proteins, myocardin (MYOCD), and miR-1 and miR-143 are increased by G6PD inhibition or knockdown. Importantly, RNA-sequence analysis of aortic tissue from G6PD-deficient mice revealed uniform increases in VSMC-restricted genes, particularly those regulated by the MYOCD-serum response factor (SRF) switch. Conversely, expression of Krüppel-like factor 4 (KLF4) is decreased by G6PD inhibition. Interestingly, the G6PD inhibition-induced expression of miR-1 and contractile proteins was blocked by Rp-β-phenyl-1,N 2 -etheno-8-bromo-guanosine-3',5'-cyclic monophosphorothioate, a PKG inhibitor. On the other hand, MYOCD and miR-143 levels are increased by G6PD inhibition through a PKG-independent manner. Furthermore, blood pressure was lower in the G6PD-deficient compared with wild-type mice. Therefore, our results suggest that the expression of VSMC contractile proteins induced by G6PD inhibition occurs via PKG1α-dependent and -independent pathways. Copyright © 2016 the American Physiological Society.

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.

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.

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.

Recommendations for future development of contractility and obstruction nomograms for women. ICI-RS 2014.

PubMed

Rademakers, Kevin; Apostolidis, Apostolos; Constantinou, Christos; Fry, Christopher; Kirschner-Hermanns, Ruth; Oelke, Matthias; Parsons, Brian; Nelson, Pierre; Valentini, Françoise; Gammie, Andrew

2016-02-01

At present, existing bladder outlet obstruction (BOO) nomograms for women are still not universally accepted. Moreover, only limited information is available regarding bladder contractility in women. The aim is to present the discussions and recommendations from the think tank session "Can we construct and validate contractility and obstruction nomograms for women?" held at the 2014 International Consultation on Incontinence-Research Society (ICI-RS) meeting in Bristol, UK. An overview of clinical significance, bladder mechanics and modelling, lack of existing nomograms for women, and development of new nomograms were presented and discussed in a multidisciplinary think tank session. This think tank session was based on a collaboration between physicians, engineers, and researchers and consensus was achieved on future research initiatives. Based on the think tank discussion, the ICI-RS panel put forward the following recommendations: the need to acquire normative age-matched data in women to define "normal" and "pathological" values of urodynamic parameters; the inclusion of additional clinical data in new nomograms and the use of this extra dimension to develop clinically applicable nomograms for female BOO and contractility; and finally, the need to take into account the variability of BOO in women when developing female bladder contractility nomograms. © 2016 Wiley Periodicals, Inc.

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

Properties of slow- and fast-twitch muscle fibres in a mouse model of amyotrophic lateral sclerosis.

PubMed

Atkin, Julie D; Scott, Rachel L; West, Jan M; Lopes, Elizabeth; Quah, Alvin K J; Cheema, Surindar S

2005-05-01

This investigation was undertaken to determine if there are altered histological, pathological and contractile properties in presymptomatic or endstage diseased muscle fibres from representative slow-twitch and fast-twitch muscles of SOD1 G93A mice in comparison to wildtype mice. In presymptomatic SOD1 G93A mice, there was no detectable peripheral dysfunction, providing evidence that muscle pathology is secondary to motor neuronal dysfunction. At disease endstage however, single muscle fibre contractile analysis demonstrated that fast-twitch muscle fibres and neuromuscular junctions are preferentially affected by amyotrophic lateral sclerosis-induced denervation, being unable to produce the same levels of force when activated by calcium as muscle fibres from their age-matched controls. The levels of transgenic SOD1 expression, aggregation state and activity were also examined in these muscles but there no was no preference for muscle fibre type. Hence, there is no simple correlation between SOD1 protein expression/activity, and muscle fibre type vulnerability in SOD1 G93A mice.

Postextrasystolic potentiation and contractile reserve: requirements and restrictions.

PubMed

Lust, R M; Lutherer, L O; Gardner, M E; Cooper, M W

1982-12-01

These studies were conducted to examine the basic characteristics of postextrasystolic potentiation (PESP) and the relationship of loading effects to PESP. Measurements of left ventricular (LV) and aortic pressures, the rate of pressure rise, and echocardiographically determined LV dimensions were made in anesthetized open-chest dogs. The hearts were paced, and timed extrasystoles were introduced that were followed by postextrasystoles (PES). PES's were elicited after an interval equal to either a full compensatory pause or a time when the diastolic properties of the LV could not be distinguished from control (isolength). Potentiation of contraction for the PES's introduced after an isolength pause was dependent on both the heart rate and the extrasystolic interval, whereas the PES's that occurred after a full pause showed no dependence on either of these intervals. PESP elicited during the isolength period was not dependent on either preload and afterload. It is concluded that PESP depends on the combination of heart rate and extrasystolic and postextrasystolic intervals. Further, PESP may be inaccurate in assessing contractile reserve unless the heart rate and extrasystolic interval are known and the PES is introduced after an isolength pause.

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

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.

Cardiac contractile dysfunction during mild coronary flow reductions is due to an altered calcium-pressure relationship in rat hearts.

PubMed Central

Figueredo, V M; Brandes, R; Weiner, M W; Massie, B M; Camacho, S A

1992-01-01

Coronary artery stenosis or occlusion results in reduced coronary flow and myocardial contractile depression. At severe flow reductions, increased inorganic phosphate (Pi) and intracellular acidosis clearly play a role in contractile depression. However, during milder flow reductions the mechanism(s) underlying contractile depression are less clear. Previous perfused heart studies demonstrated no change of Pi or pH during mild flow reductions, suggesting that changes of intravascular pressure (garden hose effect) may be the mediator of this contractile depression. Others have reported conflicting results regarding another possible mediator of contractility, the cytosolic free calcium (Cai). To examine the respective roles of Cai, Pi, pH, and vascular pressure in regulating contractility during mild flow reductions, Indo-1 calcium fluorescence and 31P magnetic resonance spectroscopy measurements were performed on Langendorff-perfused rat hearts. Cai and diastolic calcium levels did not change during flow reductions to 50% of control. Pi demonstrated a close relationship with developed pressure and significantly increased from 2.5 +/- 0.3 to 4.2 +/- 0.4 mumol/g dry weight during a 25% flow reduction. pH was unchanged until a 50% flow reduction. Increasing vascular pressure to superphysiological levels resulted in further increases of developed pressure, with no change in Cai. These findings are consistent with the hypothesis that during mild coronary flow reductions, contractile depression is mediated by an altered relationship between Cai and pressure, rather than by decreased Cai. Furthermore, increased Pi and decreased intravascular pressure may be responsible for this altered calcium-pressure relationship during mild coronary flow reductions. PMID:1430205

Mediation by SRIF1 receptors of the contractile action of somatostatin in rat isolated distal colon; studies using some novel SRIF analogues.

PubMed Central

McKeen, E S; Feniuk, W; Humphrey, P P

1994-01-01

1. The motor effects of somatostatin-14 (SRIF), and several SRIF peptide analogues were investigated on the rat isolated distal colon. The objective of these studies was to characterize the receptor mediating the contractile action of SRIF by comparing the relative agonist potencies of a range of SRIF analogues. 2. SRIF (1 nM-1 microM) produced concentration-dependent contractions with an EC50 value of approximately 10 nM. Contractile responses induced by SRIF were insensitive to atropine (1 microM) or naloxone (1 microM) but abolished by tetrodotoxin (1 microM). Somatostatin-28 (SRIF28), also induced concentration-dependent contractions and was equipotent with SRIF. Phosphoramidon (1 microM) and amastatin (10 microM) did not increase the potency of either SRIF or SRIF28. 3. The SRIF peptide analogues, octreotide, SRIF25, seglitide, angiopeptin and CGP23996 (1 nM-1 microM) produced contractile responses in the rat distal colon, each having similar potency and maximal activity relative to SRIF. The SSTR2 receptor-selective hexapeptide, BIM23027 (0.1 nM-1 microM), and the SRIF stereoisomer, D-Trp8-SRIF (0.1 nM-1 microM), were the most potent agonists examined being approximately 12 and 7 times more potent than SRIF, respectively. In contrast, the SSTR5 receptor-selective analogue, L362,855, was approximately 120 times weaker than SRIF, whilst the SSTR3 receptor-selective analogue, BIM23056, was inactive at concentrations up to 3 microM. 4. The putative SRIF receptor antagonist, (cyclo(7-aminoheptanoyl Phe-D-Trp-Lys-Thr[Bzl]))(CPP) (1 microM), had no agonist activity and had no effect on contractions induced by SRIF. 5. The contractile actions of BIM23027 and seglitide were subject to pronounced desensitization.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7834217

Metabolic Reprogramming Is Required for Myofibroblast Contractility and Differentiation*

PubMed Central

Bernard, Karen; Logsdon, Naomi J.; Ravi, Saranya; Xie, Na; Persons, Benjamin P.; Rangarajan, Sunad; Zmijewski, Jaroslaw W.; Mitra, Kasturi; Liu, Gang; Darley-Usmar, Victor M.; Thannickal, Victor J.

2015-01-01

Contraction is crucial in maintaining the differentiated phenotype of myofibroblasts. Contraction is an energy-dependent mechanism that relies on the production of ATP by mitochondria and/or glycolysis. Although the role of mitochondrial biogenesis in the adaptive responses of skeletal muscle to exercise is well appreciated, mechanisms governing energetic adaptation of myofibroblasts are not well understood. Our study demonstrates induction of mitochondrial biogenesis and aerobic glycolysis in response to the differentiation-inducing factor transforming growth factor β1 (TGF-β1). This metabolic reprogramming is linked to the activation of the p38 mitogen-activated protein kinase (MAPK) pathway. Inhibition of p38 MAPK decreased accumulation of active peroxisome proliferator-activated receptor γ coactivator 1α in the nucleus and altered the translocation of mitochondrial transcription factor A to the mitochondria. Genetic or pharmacologic approaches that block mitochondrial biogenesis or glycolysis resulted in decreased contraction and reduced expression of TGF-β1-induced α-smooth muscle actin and collagen α-2(I) but not of fibronectin or collagen α-1(I). These data indicate a critical role for TGF-β1-induced metabolic reprogramming in regulating myofibroblast-specific contractile signaling and support the concept of integrating bioenergetics with cellular differentiation. PMID:26318453

Cannabinoid-induced actomyosin contractility shapes neuronal morphology and growth

PubMed Central

Roland, Alexandre B; Ricobaraza, Ana; Carrel, Damien; Jordan, Benjamin M; Rico, Felix; Simon, Anne; Humbert-Claude, Marie; Ferrier, Jeremy; McFadden, Maureen H; Scheuring, Simon; Lenkei, Zsolt

2014-01-01

Endocannabinoids are recently recognized regulators of brain development, but molecular effectors downstream of type-1 cannabinoid receptor (CB1R)-activation remain incompletely understood. We report atypical coupling of neuronal CB1Rs, after activation by endo- or exocannabinoids such as the marijuana component ∆9-tetrahydrocannabinol, to heterotrimeric G12/G13 proteins that triggers rapid and reversible non-muscle myosin II (NM II) dependent contraction of the actomyosin cytoskeleton, through a Rho-GTPase and Rho-associated kinase (ROCK). This induces rapid neuronal remodeling, such as retraction of neurites and axonal growth cones, elevated neuronal rigidity, and reshaping of somatodendritic morphology. Chronic pharmacological inhibition of NM II prevents cannabinoid-induced reduction of dendritic development in vitro and leads, similarly to blockade of endocannabinoid action, to excessive growth of corticofugal axons into the sub-ventricular zone in vivo. Our results suggest that CB1R can rapidly transform the neuronal cytoskeleton through actomyosin contractility, resulting in cellular remodeling events ultimately able to affect the brain architecture and wiring. DOI: http://dx.doi.org/10.7554/eLife.03159.001 PMID:25225054

Effect of noni (Morinda citrifolia Linn.) fruit and its bioactive principles scopoletin and rutin on rat vas deferens contractility: an ex vivo study.

PubMed

Pandy, Vijayapandi; Narasingam, Megala; Kunasegaran, Thubasni; Murugan, Dharmani Devi; Mohamed, Zahurin

2014-01-01

This study examined the effect of methanolic extract of Morinda citrifolia Linn. (MMC) and its bioactive principles, scopoletin and rutin, on dopamine- and noradrenaline-evoked contractility in isolated rat vas deferens preparations. MMC (1-40 mg/mL), scopoletin (1-200 μg/mL), and rutin hydrate (0.6-312.6 μg/mL) dose-dependently inhibited the contractility evoked by submaximal concentrations of both dopamine and noradrenaline, respectively. Haloperidol and prazosin, reference dopamine D2, and α 1-adrenoceptors antagonists significantly reversed the dopamine- and noradrenaline-induced contractions, respectively, in a dose-dependent manner. Interestingly, MMC per se at higher doses (60-100 mg/mL) showed dose-dependent contractile response in rat vas deferens which was partially inhibited by high doses of haloperidol but not by prazosin. These results demonstrated the biphasic effects of MMC on dopaminergic system; that is, antidopaminergic effect at lower concentrations (<40 mg/mL) and dopaminergic agonistic effect at higher concentrations (>60 mg/mL). However, similar contractile response at high doses of scopoletin (0.5-5 mg/mL) and rutin hydrate (0.5-5 mg/mL) per se was not observed. Therefore, it can be concluded that the bioactive principles of MMC, scopoletin, and rutin might be responsible for the antidopaminergic and antiadrenergic activities of MMC.

Right ventricular contractile reserve in mitral stenosis: implications on hemodynamic burden and clinical outcome.

PubMed

Sade, Leyla Elif; Ozin, Bülent; Ulus, Taner; Açikel, Sadik; Pirat, Bahar; Bilgi, Muhammed; Uluçam, Melek; Müderrisoğlu, Haldun

2009-06-26

We investigated whether isovolumic acceleration (IVA) under inotropic stimulation as a means of right ventricular (RV) contractile reserve, is a surrogate for hemodynamic burden and has prognostic value in patients with mitral stenosis (MS). Thirty-one pure MS patients and 20 controls underwent cardiac catheterization, exercise test, and dobutamine stress echocardiography. RV fractional area change (FAC), +dP/dt/P(max), RV tissue Doppler indices (isovolumic contraction [IVC] and systolic [S] velocity, and IVA) were measured. Patients were followed-up for the occurrence of cardiac adverse events. Inotropic modulation unmasked statistically significant differences regarding magnitude of changes in IVA, IVC, S, and +dP/dt/P(max), but not RV FAC. Inability to increase IVA more than 6.5 m/s(2) was the only independent determinant of pulmonary capillary wedge pressure >or=18 mm Hg (P=.004). Although MS severity did not predict the RV contractile reserve and pulmonary artery pressure (PAP) behavior during inotropic stimulation, the RV contractile reserve was related to the degree of systolic PAP. IVA increases of <3.4 m/s(2) had 86% sensitivity and 75% specificity to predict unfavorable outcomes during long-term follow-up (20+/-8 months). RV contractile reserve provides complementary data to the hemodynamic significance of MS severity, may contribute to clinical decision making, and be of prognostic value in these patients.

Emergence of airway smooth muscle mechanical behavior through dynamic reorganization of contractile units and force transmission pathways

PubMed Central

2014-01-01

Airway hyperresponsiveness (AHR) in asthma remains poorly understood despite significant research effort to elucidate relevant underlying mechanisms. In particular, a significant body of experimental work has focused on the effect of tidal fluctuations on airway smooth muscle (ASM) cells, tissues, lung slices, and whole airways to understand the bronchodilating effect of tidal breathing and deep inspirations. These studies have motivated conceptual models that involve dynamic reorganization of both cytoskeletal components as well as contractile machinery. In this article, a biophysical model of the whole ASM cell is presented that combines 1) crossbridge cycling between actin and myosin; 2) actin-myosin disconnectivity, under imposed length changes, to allow dynamic reconfiguration of “force transmission pathways”; and 3) dynamic parallel-to-serial transitions of contractile units within these pathways that occur through a length fluctuation. Results of this theoretical model suggest that behavior characteristic of experimentally observed force-length loops of maximally activated ASM strips can be explained by interactions among the three mechanisms. Crucially, both sustained disconnectivity and parallel-to-serial transitions are necessary to explain the nature of hysteresis and strain stiffening observed experimentally. The results provide strong evidence that dynamic rearrangement of contractile machinery is a likely mechanism underlying many of the phenomena observed at timescales associated with tidal breathing. This theoretical cell-level model captures many of the salient features of mechanical behavior observed experimentally and should provide a useful starting block for a bottom-up approach to understanding tissue-level mechanical behavior. PMID:24481961

Comparative study of spasmolytic properties, antioxidant activity and phenolic content of Arbutus unedo from Montenegro and Greece.

PubMed

Pavlović, Dragana R; Branković, Suzana; Kovačević, Nada; Kitić, Dušanka; Veljković, Slavimir

2011-05-01

Arbutus unedo leaf is used traditionally for gastrointestinal complaints. Ethanol extracts from Arbutus unedo collected in both Montenegro (AuM) and Greece (AuG) were found to decrease the ileal basal tonus, with AuG producing a significantly higher (p < 0.05) reduction in contractile response to acetylcholine. AuM and AuG relaxed 80 mM K(+) induced contractions and shifted the Ca(++) concentration-response curves to the right, similar to that caused by verapamil, suggesting that the spasmolytic effect was induced through calcium channel inhibition. The antioxidant activity of AuM and AuG and the phenolic content of the extracts and dry plant material were studied, and both extracts were found to possess considerable antioxidant properties. AuG showed a stronger in vitro antioxidative activity in the DPPH assay and in the TBA test. Polyphenol, tannin and flavonoid levels were higher in AuG, supporting the more potent spasmolytic and antioxidative effects, whereas the arbutin content was higher in dry plant material collected in Montenegro. Copyright © 2011 John Wiley & Sons, Ltd.

Carboxyl-terminal-dependent recruitment of nonmuscle myosin II to megakaryocyte contractile ring during polyploidization

PubMed Central

Badirou, Idinath; Pan, Jiajia; Legrand, Céline; Wang, Aibing; Lordier, Larissa; Boukour, Siham; Roy, Anita; Vainchenker, William

2014-01-01

Endomitosis is a unique megakaryocyte (MK) differentiation process that is the consequence of a late cytokinesis failure associated with a contractile ring defect. Evidence from in vitro studies has revealed the distinct roles of 2 nonmuscle myosin IIs (NMIIs) on MK endomitosis: only NMII-B (MYH10), but not NMII-A (MYH9), is localized in the MK contractile ring and implicated in mitosis/endomitosis transition. Here, we studied 2 transgenic mouse models in which nonmuscle myosin heavy chain (NMHC) II-A was genetically replaced either by II-B or by a chimeric NMHCII that combined the head domain of II-A with the rod and tail domains of II-B. This study provides in vivo evidence on the specific role of NMII-B on MK polyploidization. It demonstrates that the carboxyl-terminal domain of the heavy chains determines myosin II localization to the MK contractile ring and is responsible for the specific role of NMII-B in MK polyploidization. PMID:25185263

Carboxyl-terminal-dependent recruitment of nonmuscle myosin II to megakaryocyte contractile ring during polyploidization.

PubMed

Badirou, Idinath; Pan, Jiajia; Legrand, Céline; Wang, Aibing; Lordier, Larissa; Boukour, Siham; Roy, Anita; Vainchenker, William; Chang, Yunhua

2014-10-16

Endomitosis is a unique megakaryocyte (MK) differentiation process that is the consequence of a late cytokinesis failure associated with a contractile ring defect. Evidence from in vitro studies has revealed the distinct roles of 2 nonmuscle myosin IIs (NMIIs) on MK endomitosis: only NMII-B (MYH10), but not NMII-A (MYH9), is localized in the MK contractile ring and implicated in mitosis/endomitosis transition. Here, we studied 2 transgenic mouse models in which nonmuscle myosin heavy chain (NMHC) II-A was genetically replaced either by II-B or by a chimeric NMHCII that combined the head domain of II-A with the rod and tail domains of II-B. This study provides in vivo evidence on the specific role of NMII-B on MK polyploidization. It demonstrates that the carboxyl-terminal domain of the heavy chains determines myosin II localization to the MK contractile ring and is responsible for the specific role of NMII-B in MK polyploidization.

A contractile and counterbalancing adhesion system controls the 3D shape of crawling cells.

PubMed

Burnette, Dylan T; Shao, Lin; Ott, Carolyn; Pasapera, Ana M; Fischer, Robert S; Baird, Michelle A; Der Loughian, Christelle; Delanoe-Ayari, Helene; Paszek, Matthew J; Davidson, Michael W; Betzig, Eric; Lippincott-Schwartz, Jennifer

2014-04-14

How adherent and contractile systems coordinate to promote cell shape changes is unclear. Here, we define a counterbalanced adhesion/contraction model for cell shape control. Live-cell microscopy data showed a crucial role for a contractile meshwork at the top of the cell, which is composed of actin arcs and myosin IIA filaments. The contractile actin meshwork is organized like muscle sarcomeres, with repeating myosin II filaments separated by the actin bundling protein α-actinin, and is mechanically coupled to noncontractile dorsal actin fibers that run from top to bottom in the cell. When the meshwork contracts, it pulls the dorsal fibers away from the substrate. This pulling force is counterbalanced by the dorsal fibers' attachment to focal adhesions, causing the fibers to bend downward and flattening the cell. This model is likely to be relevant for understanding how cells configure themselves to complex surfaces, protrude into tight spaces, and generate three-dimensional forces on the growth substrate under both healthy and diseased conditions.

A contractile and counterbalancing adhesion system controls the 3D shape of crawling cells

PubMed Central

Burnette, Dylan T.; Shao, Lin; Ott, Carolyn; Pasapera, Ana M.; Fischer, Robert S.; Baird, Michelle A.; Der Loughian, Christelle; Delanoe-Ayari, Helene; Paszek, Matthew J.; Davidson, Michael W.; Betzig, Eric

2014-01-01

How adherent and contractile systems coordinate to promote cell shape changes is unclear. Here, we define a counterbalanced adhesion/contraction model for cell shape control. Live-cell microscopy data showed a crucial role for a contractile meshwork at the top of the cell, which is composed of actin arcs and myosin IIA filaments. The contractile actin meshwork is organized like muscle sarcomeres, with repeating myosin II filaments separated by the actin bundling protein α-actinin, and is mechanically coupled to noncontractile dorsal actin fibers that run from top to bottom in the cell. When the meshwork contracts, it pulls the dorsal fibers away from the substrate. This pulling force is counterbalanced by the dorsal fibers’ attachment to focal adhesions, causing the fibers to bend downward and flattening the cell. This model is likely to be relevant for understanding how cells configure themselves to complex surfaces, protrude into tight spaces, and generate three-dimensional forces on the growth substrate under both healthy and diseased conditions. PMID:24711500

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.

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.

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 actin cables induced by Bacillus anthracis lethal toxin depend on the histone acetylation machinery.

PubMed

Rolando, Monica; Stefani, Caroline; Doye, Anne; Acosta, Maria I; Visvikis, Orane; Yevick, Hannah G; Buchrieser, Carmen; Mettouchi, Amel; Bassereau, Patricia; Lemichez, Emmanuel

2015-10-01

It remains a challenge to decode the molecular basis of the long-term actin cytoskeleton rearrangements that are governed by the reprogramming of gene expression. Bacillus anthracis lethal toxin (LT) inhibits mitogen-activated protein kinase (MAPK) signaling, thereby modulating gene expression, with major consequences for actin cytoskeleton organization and the loss of endothelial barrier function. Using a laser ablation approach, we characterized the contractile and tensile mechanical properties of LT-induced stress fibers. These actin cables resist pulling forces that are transmitted at cell-matrix interfaces and at cell-cell discontinuous adherens junctions. We report that treating the cells with trichostatin A (TSA), a broad range inhibitor of histone deacetylases (HDACs), or with MS-275, which targets HDAC1, 2 and 3, induces stress fibers. LT decreased the cellular levels of HDAC1, 2 and 3 and reduced the global HDAC activity in the nucleus. Both the LT and TSA treatments induced Rnd3 expression, which is required for the LT-mediated induction of actin stress fibers. Furthermore, we reveal that treating the LT-intoxicated cells with garcinol, an inhibitor of histone acetyl-transferases (HATs), disrupts the stress fibers and limits the monolayer barrier dysfunctions. These data demonstrate the importance of modulating the flux of protein acetylation in order to control actin cytoskeleton organization and the endothelial cell monolayer barrier. © 2015 Wiley Periodicals, Inc.

[The relationship between contractile characteristics and fiber type conversion in hind-limb unloading mice soleus].

PubMed

Li, Li; Liu, Hong-Ju; Yang, Ming-Hao; Li, Jing-Long; Wang, Lu; Chen, Xiao-Ping; Fan, Ming

2012-03-01

To explore the relationship between contractile characteristics and fiber type conversion in hind-limb unloading mice soleus. After 28-day hind-limb unloading and muscle atrophy, we used the method of isolated muscle perfusion with different stimulated protocols to determine the changes in contractile characteristics including the isometric twitch force and tetanus force and fatigue index of slow twitch muscle in mice. The muscle myofibrillar composition and fiber type conversion were detected by immunofluorescence staining and real-time PCR. The isometric twitch force and the tetanus force and fatigue index were decreased progressively in 28-day unloaded mice soleus, with the increase in fast twitch fiber subtype and the decrease in slow twitch fiber subtype. The alteration of contractile characteristics is relevant to the slow-to-fast fiber conversion in mice soleus after 28-day hind-limb unloading.

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

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

Electrically contractile polymers augment right ventricular output in the heart.

PubMed

Ruhparwar, Arjang; Piontek, Patricia; Ungerer, Matthias; Ghodsizad, Ali; Partovi, Sasan; Foroughi, Javad; Szabo, Gabor; Farag, Mina; Karck, Matthias; Spinks, Geoffrey M; Kim, Seon Jeong

2014-12-01

Research into the development of artificial heart muscle has been limited to assembly of stem cell-derived cardiomyocytes seeded around a matrix, while nonbiological approaches to tissue engineering have rarely been explored. The aim of the study was to apply electrically contractile polymer-based actuators as cardiomyoplasty for positive inotropic support of the right ventricle. Complex trilayer polypyrrole (PPy) bending polymers for high-speed applications were generated. Bending motion occurred directly as a result of electrochemically driven charging and discharging of the PPy layers. In a rat model (n = 5), strips of polymers (3 × 20 mm) were attached and wrapped around the right ventricle (RV). RV pressure was continuously monitored invasively by direct RV cannulation. Electrical activation occurred simultaneously with either diastole (in order to evaluate the polymer's stand-alone contraction capacity; group 1) or systole (group 2). In group 1, the pressure generation capacity of the polymers was measured by determining the area under the pressure curve (area under curve, AUC). In group 2, the RV pressure AUC was measured in complexes directly preceding those with polymer contraction and compared to RV pressure complexes with simultaneous polymer contraction. In group 1, the AUC generated by polymer contraction was 2768 ± 875 U. In group 2, concomitant polymer contraction significantly increased AUC compared with complexes without polymer support (5987 ± 1334 U vs. 4318 ± 691 U, P ≤ 0.01). Electrically contractile polymers are able to significantly augment right ventricular contraction. This approach may open new perspectives for myocardial tissue engineering, possibly in combination with fetal or embryonic stem cell-derived cardiomyocytes. Copyright © 2014 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

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.

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.

Cardiac-specific overexpression of metallothionein attenuates myocardial remodeling and contractile dysfunction in l-NAME-induced experimental hypertension: Role of autophagy regulation.

PubMed

Yang, Lifang; Gao, Jian-Yuan; Ma, Jipeng; Xu, Xihui; Wang, Qiurong; Xiong, Lize; Yang, Jian; Ren, Jun

2015-09-02

Hypertension is an independent risk factor for heart disease and is responsible for the increased cardiac morbidity and mortality. Oxidative stress plays a key role in hypertensive heart diseases although the precise mechanism remains unclear. This study was designed to examine the effect of cardiac-specific overexpression of metallothionein, a cysteine-rich antioxidant, on myocardial contractile and intracellular Ca(2+) anomalies in N(G)-nitro-l-arginine methyl ester (l-NAME)-induced experimental hypertension and the mechanism involved with a focus on autophagy. Our results revealed that l-NAME treatment (14 days) led to hypertension and myocardial anomalies evidenced by interstitial fibrosis, cardiomyocyte hypertrophy, increased LV end systolic and diastolic diameters (LVESD and LVEDD) along with suppressed fractional shortening. l-NAME compromised cardiomyocyte contractile and intracellular Ca(2+) properties manifested as depressed peak shortening, maximal velocity of shortening/relengthening, electrically-stimulated rise in intracellular Ca(2+), elevated baseline and peak intracellular Ca(2+). These l-NAME-induced histological and mechanical changes were attenuated or reconciled by metallothionein. Protein levels of autophagy markers LC3B and p62 were decreased and increased, respectively. Autophagy signaling molecules AMPK, TSC2 and ULK1 were inactivated while those of mTOR and p70s6K were activated by l-NAME, the effects of which were ablated by metallothionein. Autophagy induction mimicked whereas autophagy inhibition nullified the beneficial effect of metallothionein against l-NAME. These findings suggested that metallothionein protects against l-NAME-induced myocardial anomalies possibly through restoration of autophagy. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

The guinea pig ileum lacks the direct, high-potency, M(2)-muscarinic, contractile mechanism characteristic of the mouse ileum.

PubMed

Griffin, Michael T; Matsui, Minoru; Ostrom, Rennolds S; Ehlert, Frederick J

2009-10-01

We explored whether the M(2) muscarinic receptor in the guinea pig ileum elicits a highly potent, direct-contractile response, like that from the M(3) muscarinic receptor knockout mouse. First, we characterized the irreversible receptor-blocking activity of 4-DAMP mustard in ileum from muscarinic receptor knockout mice to verify its M(3) selectivity. Then, we used 4-DAMP mustard to inactivate M(3) responses in the guinea pig ileum to attempt to reveal direct, M(2) receptor-mediated contractions. The muscarinic agonist, oxotremorine-M, elicited potent contractions in ileum from wild-type, M(2) receptor knockout, and M(3) receptor knockout mice characterized by negative log EC(50) (pEC (50)) values +/- SEM of 6.75 +/- 0.03, 6.26 +/- 0.05, and 6.99 +/- 0.08, respectively. The corresponding E (max) values in wild-type and M(2) receptor knockout mice were approximately the same, but that in the M(3) receptor knockout mouse was only 36% of wild type. Following 4-DAMP mustard treatment, the concentration-response curve of oxotremorine-M in wild-type ileum resembled that of the M(3) knockout mouse in terms of its pEC (50), E (max), and inhibition by selective muscarinic antagonists. Thus, 4-DAMP mustard treatment appears to inactivate M(3) responses selectively and renders the muscarinic contractile behavior of the wild-type ileum similar to that of the M(3) knockout mouse. Following 4-DAMP mustard treatment, the contractile response of the guinea pig ileum to oxotremorine-M exhibited low potency and a competitive-antagonism profile consistent with an M(3) response. The guinea pig ileum, therefore, lacks a direct, highly potent, M(2)-contractile component but may have a direct, lower potency M(2) component.

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

PubMed Central

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. PMID:25355954

Effect of Bryophyllum pinnatum versus fenoterol on uterine contractility.

PubMed

Gwehenberger, Birgit; Rist, Lukas; Huch, Renate; von Mandach, Ursula

2004-04-15

To characterise the phytotherapeutic tocolytic Bryophyllum pinnatum in vitro versus the conventional betamimetic, fenoterol, in human myometrium. Contractility (endpoints: area under the curve (AUC), amplitude and frequency of isometric force development) was measured in strips of term myometrium biopsied at caesarean section in 14 women and exposed to increasing concentrations of B. pinnatum versus +/- oxytocin 1 U/l. Inhibition of spontaneous contraction by B. pinnatum was concentration-dependent: 16% at maximum concentration (10(4) mg/l), or 53% that with fenoterol 5 x 10(-8)mol/l. B. pinnatum increased contraction frequency by 91% at constant amplitude and inhibited oxytocin-stimulated contractions by 20% (AUC) at constant amplitude with slightly decreased frequency. Fenoterol decreased contraction AUC by 50% with a significant decrease in frequency. Our in vitro data confirm the tocolytic activity of B. pinnatum observed in alternative medicine centres and may justify further clinical studies.

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

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

Urgency of micturition and detrusor contractility in men with prostatic obstruction and overactive bladders.

PubMed

Cucchi, A; Quaglini, S; Giannantoni, A; Guarnaschelli, C; Rovereto, B

2005-01-01

In men with prostatic obstruction and detrusor overactivity (DO), to ascertain whether urgency of micturition affects bladder contractility. We urodynamically assessed five groups of 20 men each who had bladder outflow obstruction (BOO) from benign prostatic enlargement-Groups 1 (with no DO and no urgency), 2 (with DO and no urgency), 3A (with DO and moderate urgency), 3B (with DO and severe urgency), and 4 (with DO, severe urgency and chronic ischemic cerebral lesions). Urgency was graded as moderate or severe by the ability to avert an urgent void at cystometry for > or =2 or <2 min, respectively. BOO was assessed by the "Abrams-Griffiths number" (AG) and bladder contractility by the parameters PIP and WF(max). AG did not differ significantly in Groups 2, 3A, and 3B, proved higher in such groups than in Group 1, and was nearly the same in Groups 1 and 4. PIP and WF(max) were significantly higher in Groups 2, 3A, and 3B than in Groups 1 and 4, had the highest levels in Group 3B, and did not differ significantly in Groups 1-4 and 2-3A. In DO patients with prostatic obstruction there seems to be a DO-related facilitation of bladder contractility. In the same patients, severe urgency of micturition might over-amplify (i.e., enhance a DO-related facilitation of) bladder contractility, provided there are no neurogenic (chronic ischemic cerebral) lesions.

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

The pathophysiological roles of COX-1 and COX-2 in the intestinal smooth muscle contractility under the anaphylactic condition.

PubMed

Kadowaki, Hiroko; Yamamoto, Takeshi; Kageyama-Yahara, Natsuko; Kurokawa, Nobuo; Kadowaki, Makoto

2008-04-01

Various inflammatory mediators released from antigen-activated mast cells are considered to play a key role in the pathogenesis of food allergy. The aim of the present study was to determine the mechanisms underlying the antigen-induced anaphylactic responses in the rat colons. Wistar rats were sensitized by intraperitoneal injection of ovalbumin (OVA). The contractilities of isolated proximal colons of the sensitized rats were studied in the organ bath. OVA challenges of sensitized tissues induced prolonged contractile responses. The antigen-induced contractions were greatly reduced by mast cell stabilizer doxantrazole (10 microM). However, the contractions were resistant to histamine H1 receptor antagonist and prostaglandin D2 receptor antagonist. In contrast, non-selective cyclooxygenase (COX) inhibitor indomethacin (1 microM) significantly reduced the contractions by 61.0%. Furthermore, selective COX-1 inhibitor FR122047 (10 microM) as well as selective COX-2 inhibitor NS-398 (10 microM) significantly inhibited the contractions by 50.1% and 50.3%, respectively. Nevertheless, the transcript levels of COX-2 as well as COX-1 were not upregulated by OVA in the proximal colons of the sensitized rats. The present results indicate that de novo arachidonic acid metabolites synthesis by constitutive COX-1 as well as constitutive COX-2 within mast cells contribute to the altered smooth muscle contractilities in the colons under the anaphylactic condition.

Contractile response of fescue-naive bovine lateral saphenous veins to increasing concentrations of tall fescue alkaloids.

PubMed

Klotz, J L; Kirch, B H; Aiken, G E; Bush, L P; Strickland, J R

2010-01-01

Various alkaloids found in endophyte-infected tall fescue have been shown to elicit different effects in the grazing animal. As part of an ongoing characterization of vascular response generated by different alkaloids, the objective of this study was to examine the vasoconstrictive potentials of ergonovine (a simple lysergic acid derivative) and alpha-ergocryptine, ergocristine, and ergocornine (all ergopeptine alkaloids) using bovine lateral saphenous veins (cranial branch) biopsied from fescue-naïve cattle. Segments (2 to 3 cm) of vein were surgically biopsied from healthy crossbred yearling cattle (n = 18; 274 +/- 8 kg of BW). Veins were trimmed of excess fat and connective tissue, sliced into 2 to 3 mm sections, and suspended in a myograph chamber containing 5 mL of oxygenated Krebs-Henseleit buffer (95% O(2)/5% CO(2); pH = 7.4; 37 degrees C). Tissue was allowed to equilibrate at 1 g of tension for 90 min before initiation of treatment additions. Increasing doses of each alkaloid (1 x 10(-10) to 1 x 10(-4) M) were administered every 15 min after buffer replacement. Data were normalized as a percentage of contractile response induced by a reference dose of norepinephrine (1 x 10(-4) M). Exposure of vein segments to increasing concentrations of ergocryptine, ergocristine, and ergonovine did not result in a contractile response until 1 x 10(-7) M, and ergocornine was even less potent (P < 0.05). Ergonovine had a greater maximal contractile intensity than ergocristine and ergocryptine (P < 0.05), with the 1 x 10(-4) M responses of ergonovine, ergocristine, ergocryptine, and ergocornine reaching maximums of 68.5 +/- 4.1, 45.5 +/- 4.5, 42.9 +/- 4.1%, and 57.2 +/- 9.9% of the norepinephrine maximum, respectively. The contractile response to increasing concentrations of ergonovine vs. ergocryptine, ergocristine, and ergocornine were opposite from previous evaluations of ergoline (e.g., lysergic acid) and ergopeptine (e.g., ergovaline) alkaloids using this bioassay

Contractile properties of single permeabilized muscle fibers from congenital cleft palates and normal palates of Spanish goats.

PubMed

Hanes, Michael C; Weinzweig, Jeffrey; Kuzon, William M; Panter, Kip E; Buchman, Steven R; Faulkner, John A; Yu, Deborah; Cederna, Paul S; Larkin, Lisa M

2007-05-01

Analysis of the composition of muscle fibers constituent to a cleft palate could provide significant insight into the cause of velopharyngeal inadequacy. The authors hypothesized that levator veli palatini muscle dysfunction inherent to cleft palates could affect the timing and outcome of cleft palate repair. Single, permeabilized muscle fibers from levator veli palatini muscles of three normal (n = 19 fibers) and three chemically induced congenital cleft palates (n = 21 fibers) of 14-month-old goats were isolated, and contractile properties were evaluated. The maximum isometric force and rate constants of tension redevelopment (ktr) were measured, and the specific force and normalized power were calculated for each fiber. The ktr measures indicate that cleft fibers are predominantly fast-fatigable; normal fibers are slow fatigue-resistant: after a 10-minute isometric contraction, fibers from cleft palates had a loss of force 16 percent greater than that from normal palates (p = 0.0001). The cross-sectional areas of the fibers from cleft palates (2750 +/- 209 microm2) were greater (p = 0.05) than those from normal palates (2226 +/- 143 microm2). Specific forces did not differ between the two groups. Maximum normalized power of fibers from cleft palates (11.05 +/- 1.82 W/l) was greater (p = 0.0001) than fibers from normal palates (1.60 +/- 0.12 W/l). There are clear physiologic differences in single muscle fibers from cleft palates and normal palates: cleft palate fibers are physiologically fast, have greater fatigability, and have greater power production. Detection of functional and/or fiber type differences in muscles of cleft palates may provide preoperative identification of a patient's susceptibility to velopharyngeal inadequacy and permit early surgical intervention to correct this clinical condition.

The inverted pendulum model of bipedal standing cannot be stabilized through direct feedback of force and contractile element length and velocity at realistic series elastic element stiffness.

PubMed

van Soest, A J Knoek; Rozendaal, Leonard A

2008-07-01

Control of bipedal standing is typically analyzed in the context of a single-segment inverted pendulum model. The stiffness K (SE) of the series elastic element that transmits the force generated by the contractile elements of the ankle plantarflexors to the skeletal system has been reported to be smaller in magnitude than the destabilizing gravitational stiffness K ( g ). In this study, we assess, in case K (SE) + K ( g ) < 0, if bipedal standing can be locally stable under direct feedback of contractile element length, contractile element velocity (both sensed by muscle spindles) and muscle force (sensed by Golgi tendon organs) to alpha-motoneuron activity. A theoretical analysis reveals that even though positive feedback of force may increase the stiffness of the muscle-tendon complex to values well over the destabilizing gravitational stiffness, dynamic instability makes it impossible to obtain locally stable standing under the conditions assumed.

Mechanobiological induction of long-range contractility by diffusing biomolecules and size scaling in cell assemblies

NASA Astrophysics Data System (ADS)

Dasbiswas, K.; Alster, E.; Safran, S. A.

2016-06-01

Mechanobiological studies of cell assemblies have generally focused on cells that are, in principle, identical. Here we predict theoretically the effect on cells in culture of locally introduced biochemical signals that diffuse and locally induce cytoskeletal contractility which is initially small. In steady-state, both the concentration profile of the signaling molecule as well as the contractility profile of the cell assembly are inhomogeneous, with a characteristic length that can be of the order of the system size. The long-range nature of this state originates in the elastic interactions of contractile cells (similar to long-range “macroscopic modes” in non-living elastic inclusions) and the non-linear diffusion of the signaling molecules, here termed mechanogens. We suggest model experiments on cell assemblies on substrates that can test the theory as a prelude to its applicability in embryo development where spatial gradients of morphogens initiate cellular development.

A Conserved RhoGAP Limits M-phase Contractility and Coordinates with Microtubule Asters to Restrict Active RhoA to the Cell Equator During Cytokinesis

PubMed Central

Zanin, Esther; Desai, Arshad; Poser, Ina; Toyoda, Yusuke; Andree, Cordula; Moebius, Claudia; Bickle, Marc; Conradt, Barbara; Piekny, Alisa; Oegema, Karen

2014-01-01

SUMMARY During animal cell cytokinesis, the spindle directs contractile ring assembly by activating RhoA in a narrow equatorial zone. Rapid GTPase activating protein (GAP)-mediated inactivation (RhoA flux) is proposed to limit RhoA zone dimensions. Testing the significance of RhoA flux has been hampered by the fact that the GAP targeting RhoA is not known. Here, we identify M-phase GAP (MP-GAP) as the primary GAP targeting RhoA during mitosis/cytokinesis. MP-GAP inhibition caused excessive RhoA activation in M-phase leading to the uncontrolled formation of large cortical protrusions and late cytokinesis failure. RhoA zone width was broadened by attenuation of the centrosomal asters but was not affected by MP-GAP inhibition alone. Simultaneous aster attenuation and MP-GAP inhibition led to RhoA accumulation around the entire cell periphery. These results identify the major GAP restraining RhoA during cell division and delineate the relative contributions of RhoA flux and centrosomal asters in controlling RhoA zone dimensions. PMID:24012485

Effect of Noni (Morinda citrifolia Linn.) Fruit and Its Bioactive Principles Scopoletin and Rutin on Rat Vas Deferens Contractility: An Ex Vivo Study

PubMed Central

Narasingam, Megala; Murugan, Dharmani Devi; Mohamed, Zahurin

2014-01-01

This study examined the effect of methanolic extract of Morinda citrifolia Linn. (MMC) and its bioactive principles, scopoletin and rutin, on dopamine- and noradrenaline-evoked contractility in isolated rat vas deferens preparations. MMC (1–40 mg/mL), scopoletin (1–200 μg/mL), and rutin hydrate (0.6–312.6 μg/mL) dose-dependently inhibited the contractility evoked by submaximal concentrations of both dopamine and noradrenaline, respectively. Haloperidol and prazosin, reference dopamine D2, and α 1-adrenoceptors antagonists significantly reversed the dopamine- and noradrenaline-induced contractions, respectively, in a dose-dependent manner. Interestingly, MMC per se at higher doses (60–100 mg/mL) showed dose-dependent contractile response in rat vas deferens which was partially inhibited by high doses of haloperidol but not by prazosin. These results demonstrated the biphasic effects of MMC on dopaminergic system; that is, antidopaminergic effect at lower concentrations (<40 mg/mL) and dopaminergic agonistic effect at higher concentrations (>60 mg/mL). However, similar contractile response at high doses of scopoletin (0.5–5 mg/mL) and rutin hydrate (0.5–5 mg/mL) per se was not observed. Therefore, it can be concluded that the bioactive principles of MMC, scopoletin, and rutin might be responsible for the antidopaminergic and antiadrenergic activities of MMC. PMID:25045753

Passive and active ventricular elastances of the left ventricle

PubMed Central

Zhong, Liang; Ghista, Dhanjoo N; Ng, Eddie YK; Lim, Soo T

2005-01-01

Background Description of the heart as a pump has been dominated by models based on elastance and compliance. Here, we are presenting a somewhat new concept of time-varying passive and active elastance. The mathematical basis of time-varying elastance of the ventricle is presented. We have defined elastance in terms of the relationship between ventricular pressure and volume, as: dP = EdV + VdE, where E includes passive (Ep) and active (Ea) elastance. By incorporating this concept in left ventricular (LV) models to simulate filling and systolic phases, we have obtained the time-varying expression for Ea and the LV-volume dependent expression for Ep. Methods and Results Using the patient's catheterization-ventriculogram data, the values of passive and active elastance are computed. Ea is expressed as: ; Epis represented as: . Ea is deemed to represent a measure of LV contractility. Hence, Peak dP/dt and ejection fraction (EF) are computed from the monitored data and used as the traditional measures of LV contractility. When our computed peak active elastance (Ea,max) is compared against these traditional indices by linear regression, a high degree of correlation is obtained. As regards Ep, it constitutes a volume-dependent stiffness property of the LV, and is deemed to represent resistance-to-filling. Conclusions Passive and active ventricular elastance formulae can be evaluated from a single-beat P-V data by means of a simple-to-apply LV model. The active elastance (Ea) can be used to characterize the ventricle's contractile state, while passive elastance (Ep) can represent a measure of resistance-to-filling. PMID:15707494

Urothelial acetylcholine involvement in ATP-induced contractile responses of the rat urinary bladder.

PubMed

Stenqvist, Johanna; Winder, Michael; Carlsson, Thomas; Aronsson, Patrik; Tobin, Gunnar

2017-08-15

Both acetylcholine and adenosine 5'-triphosphate (ATP) are released from the urothelium. In in vivo experiments ATP has been shown to evoke contractile responses that are significantly reduced by atropine. Currently, we aimed to examine the cholinergic part of the ATP-evoked contractile response of normal and inflamed (cyclophosphamide-treated rats) bladders. A whole bladder preparation that enabled drug administration either outside or inside the urinary bladder was used. The responses were examined in bladders from control and cyclophosphamide-treated rats that were either intact or urothelium-denuded. The expression of choline acetyltransferase and carnitine acetyltransferase were examined by Western blotting of normal and inflamed bladders. Methacholine evoked larger contractions when administered to the outside of the bladder in comparison to instillation. For ATP, an opposite trend emerged. While atropine substantially reduced the ATP-induced responses at internal administration (7.4±1.1 and 3.7±0.9 mN at 10 -3 M; n=13; P<0.001), it had no effect when administered outside the bladder. The removal of the urothelium caused a similar reduction of the responses to internal administration of ATP as caused by atropine. In cyclophosphamide-treated rats, neither atropine nor urothelium-denudation had any effect on the ATP-evoked responses. No changes in the expressions of the acetylcholine synthesising enzymes were observed. The current study shows that ATP induces a release of urothelial acetylcholine that contributes to the purinergic contractile response in the rat urinary bladder. This atropine-sensitive part of the purinergic contractile response is absent in the inflamed bladder. This may be one pathological mechanism involved in bladder dysfunction. Copyright © 2017 Elsevier B.V. All rights reserved.

Tumor necrosis factor regulates NMDA receptor-mediated airway smooth muscle contractile function and airway responsiveness.

PubMed

Anaparti, Vidyanand; Pascoe, Christopher D; Jha, Aruni; Mahood, Thomas H; Ilarraza, Ramses; Unruh, Helmut; Moqbel, Redwan; Halayko, Andrew J

2016-08-01

We have shown that N-methyl-d-aspartate receptors (NMDA-Rs) are receptor-operated calcium entry channels in human airway smooth muscle (HASM) during contraction. Tumor necrosis factor (TNF) augments smooth muscle contractility by influencing pathways that regulate intracellular calcium flux and can alter NMDA-R expression and activity in cortical neurons and glial cells. We hypothesized that NMDA-R-mediated Ca(2+) and contractile responses of ASM can be altered by inflammatory mediators, including TNF. In cultured HASM cells, we assessed TNF (10 ng/ml, 48 h) effect on NMDA-R subunit abundance by quantitative PCR, confocal imaging, and immunoblotting. We observed dose- and time-dependent changes in NMDA-R composition: increased obligatory NR1 subunit expression and altered regulatory NR2 and inhibitory NR3 subunits. Measuring intracellular Ca(2+) flux in Fura-2-loaded HASM cultures, we observed that TNF exposure enhanced cytosolic Ca(2+) mobilization and changed the temporal pattern of Ca(2+) flux in individual myocytes induced by NMDA, an NMDA-R selective analog of glutamate. We measured airway responses to NMDA in murine thin-cut lung slices (TCLS) from allergen-naive animals and observed significant airway contraction. However, NMDA acted as a bronchodilator in TCLS from house dust mice-challenged mice and in allergen-naive TCLS subjected to TNF exposure. All contractile or bronchodilator responses were blocked by a selective NMDA-R antagonist, (2R)-amino-5-phosphonopentanoate, and bronchodilator responses were prevented by N(G)-nitro-l-arginine methyl ester (nitric oxide synthase inhibitor) or indomethacin (cyclooxygenase inhibitor). Collectively, we show that TNF augments NMDA-R-mediated Ca(2+) mobilization in HASM cells, whereas in multicellular TCLSs allergic inflammation and TNF exposure leads to NMDA-R-mediated bronchodilation. These findings reveal the unique contribution of ionotrophic NMDA-R to airway hyperreactivity. Copyright © 2016 the American

Comparing contractile apparatus-driven cytokinesis mechanisms across kingdoms.

PubMed

Balasubramanian, Mohan K; Srinivasan, Ramanujam; Huang, Yinyi; Ng, Kian-Hong

2012-11-01

Cytokinesis is the final stage of the cell cycle during which a cell physically divides into two daughters through the assembly of new membranes (and cell wall in some cases) between the forming daughters. New membrane assembly can either proceed centripetally behind a contractile apparatus, as in the case of prokaryotes, archaea, fungi, and animals or expand centrifugally, as in the case of higher plants. In this article, we compare the mechanisms of cytokinesis in diverse organisms dividing through the use of a contractile apparatus. While an actomyosin ring participates in cytokinesis in almost all centripetally dividing eukaryotes, the majority of bacteria and archaea (except Crenarchaea) divide using a ring composed of the tubulin-related protein FtsZ. Curiously, despite molecular conservation of the division machinery components, division site placement and its cell cycle regulation occur by a variety of unrelated mechanisms even among organisms from the same kingdom. While molecular motors and cytoskeletal polymer dynamics contribute to force generation during eukaryotic cytokinesis, cytoskeletal polymer dynamics alone appears to be sufficient for force generation during prokaryotic cytokinesis. Intriguingly, there are life forms on this planet that appear to lack molecules currently known to participate in cytokinesis and how these cells perform cytokinesis remains a mystery waiting to be unravelled. Copyright © 2012 Wiley Periodicals, Inc.

Acute radiation impacts contractility of guinea-pig bladder strips affecting mucosal-detrusor interactions.

PubMed

McDonnell, Bronagh M; Buchanan, Paul J; Prise, Kevin M; McCloskey, Karen D

2018-01-01

Radiation-induced bladder toxicity is associated with radiation therapy for pelvic malignancies, arising from unavoidable irradiation of neighbouring normal bladder tissue. This study aimed to investigate the acute impact of ionizing radiation on the contractility of bladder strips and identify the radiation-sensitivity of the mucosa vs the detrusor. Guinea-pig bladder strips (intact or mucosa-free) received ex vivo sham or 20Gy irradiation and were studied with in vitro myography, electrical field stimulation and Ca2+-fluorescence imaging. Frequency-dependent, neurogenic contractions in intact strips were reduced by irradiation across the force-frequency graph. The radiation-difference persisted in atropine (1μM); subsequent addition of PPADs (100μM) blocked the radiation effect at higher stimulation frequencies and decreased the force-frequency plot. Conversely, neurogenic contractions in mucosa-free strips were radiation-insensitive. Radiation did not affect agonist-evoked contractions (1μM carbachol, 5mM ATP) in intact or mucosa-free strips. Interestingly, agonist-evoked contractions were larger in irradiated mucosa-free strips vs irradiated intact strips suggesting that radiation may have unmasked an inhibitory mucosal element. Spontaneous activity was larger in control intact vs mucosa-free preparations; this difference was absent in irradiated strips. Spontaneous Ca2+-transients in smooth muscle cells within tissue preparations were reduced by radiation. Radiation affected neurogenic and agonist-evoked bladder contractions and also reduced Ca2+-signalling events in smooth muscle cells when the mucosal layer was present. Radiation eliminated a positive modulatory effect on spontaneous activity by the mucosa layer. Overall, the findings suggest that radiation impairs contractility via mucosal regulatory mechanisms independent of the development of radiation cystitis.

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.

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.

Spontaneous myometrial contractility in cows suffering from endometritis-Influence of localisation, smooth muscle layer and cycle phase. An in vitro study.

PubMed

Hirsbrunner, Gaby; Kaufmann, Ch; Keller, Ch; Hüsler, J; Steiner, A

2010-04-01

Contractility of the healthy bovine myometrium depends on the reproductive state. Furthermore, contractility is influenced by localisation and the direction of smooth muscle strips. However, little is known about the contractile behaviour of the uterus when affected by endometritis. In our study, myometrial specimens from the larger horn (near the corpus and near the tip) in cows suffering from endometritis in estrus (n=8) or diestrus (n=8) were collected after slaughter. Two strips were prepared from each region corresponding to the circular and the longitudinal muscle layers, respectively. The spontaneous contractility of these strips was recorded in an organ bath. To analyse the results, the 2.5h recordings were divided into five periods of 30 min each. The variables area under curve (AUC) and maximal (A(max)) and minimal amplitude (A(min)) were calculated separately for each period, and the results were analysed using a non-parametric model regarding the influence of cycle phase (estrus vs. diestrus), region (corpus vs. tip) and muscle layer (circular vs. longitudinal). The values of both AUC and A(max) increased significantly over time. Muscle layer had a significant effect on AUC (corpus, tip) and A(max) (tip): the values of circular layers were increased compared to longitudinal layers. Dividing the data into subgroups allowed us to analyse them additionally according to muscle layer: In longitudinal layers, A(max) was increased at the corpus as compared with the tip. In this model, the factor cycle phase did not produce any significant difference in spontaneous myometrial activity. However, data of all variables showed non-significant higher values in estrus than in diestrus samples. Copyright 2009 Elsevier B.V. All rights reserved.

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.

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.

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

Doppler-derived myocardial systolic strain rate is a strong index of left ventricular contractility

NASA Technical Reports Server (NTRS)

Greenberg, Neil L.; Firstenberg, Michael S.; Castro, Peter L.; Main, Michael; Travaglini, Agnese; Odabashian, Jill A.; Drinko, Jeanne K.; Rodriguez, L. Leonardo; Thomas, James D.; Garcia, Mario J.

2002-01-01

BACKGROUND: Myocardial fiber strain is directly related to left ventricular (LV) contractility. Strain rate can be estimated as the spatial derivative of velocities (dV/ds) obtained by tissue Doppler echocardiography (TDE). The purposes of the study were (1) to determine whether TDE-derived strain rate may be used as a noninvasive, quantitative index of contractility and (2) to compare the relative accuracy of systolic strain rate against TDE velocities alone. METHODS AND RESULTS: TDE color M-mode images of the interventricular septum were recorded from the apical 4-chamber view in 7 closed-chest anesthetized mongrel dogs during 5 different inotropic stages. Simultaneous LV volume and pressure were obtained with a combined conductance-high-fidelity pressure catheter. Peak elastance (Emax) was determined as the slope of end-systolic pressure-volume relationships during caval occlusion and was used as the gold standard of LV contractility. Peak systolic TDE myocardial velocities (Sm) and peak (epsilon'(p)) and mean (epsilon'(m)) strain rates obtained at the basal septum were compared against Emax by linear regression. Emax as well as TDE systolic indices increased during inotropic stimulation with dobutamine and decreased with the infusion of esmolol. A stronger association was found between Emax and epsilon'(p) (r=0.94, P<0.01, y=0.29x+0.46) and epsilon'(m) (r=0.88, P<0.01) than for Sm (r=0.75, P<0.01). CONCLUSIONS: TDE-derived epsilon'(p) and epsilon'(m) are strong noninvasive indices of LV contractility. These indices appear to be more reliable than S(m), perhaps by eliminating translational artifact.

Maturation and long-term hypoxia-induced acclimatization responses in PKC-mediated signaling pathways in ovine cerebral arterial contractility

PubMed Central

Goyal, Ravi; Mittal, Ashwani; Chu, Nina; Arthur, Rebecca Afiba; Zhang, Lubo

2010-01-01

In the developing fetus, cerebral arteries (CA) show striking differences in signal transduction mechanisms compared with the adult, and these differences are magnified in response to high-altitude long-term hypoxia (LTH). In addition, in the mature organism, cerebrovascular acclimatization to LTH may be associated with several clinical problems, the mechanisms of which are unknown. Because PKC plays a key role in regulating CA contractility, in fetal and adult cerebral arteries, we tested the hypothesis that LTH differentially regulates the PKC-mediated Ca2+ sensitization pathways and contractility. In four groups of sheep [fetal normoxic (FN), fetal hypoxic (FH), adult normoxic (AN), and adult hypoxic (AH)], we examined, simultaneously, responses of CA tension and intracellular Ca2+ concentration and measured CA levels of PKC, ERK1/2, RhoA, 20-kDa myosin light chain, and the 17-kDa PKC-potentiated myosin phosphatase inhibitor CPI-17. The PKC activator phorbol 12,13-dibutyrate (PDBu) produced robust contractions in all four groups. However, PDBu-induced contractions were significantly greater in AH CA than in the other groups. In all CA groups except AH, in the presence of MEK inhibitor (U-0126), the PDBu-induced contractions were increased a further 20–30%. Furthermore, in adult CA, PDBu led to increased phosphorylation of ERK1, but not ERK2; in fetal CA, the reverse was the case. PDBu-stimulated ERK2 phosphorylation also was significantly greater in FH than FN CA. Also, although RhoA/Rho kinase played a significant role in PDBu-mediated contractions of FN CA, this was not the case in FH or either adult group. Also, whereas CPI-17 had a significant role in adult CA contractility, this was not the case for the fetus. Overall, in ovine CA, the present study demonstrates several important maturational and LTH acclimatization changes in PKC-induced contractile responses and downstream pathways. The latter may play a key role in the pathophysiologic disorders

Maturation and long-term hypoxia-induced acclimatization responses in PKC-mediated signaling pathways in ovine cerebral arterial contractility.

PubMed

Goyal, Ravi; Mittal, Ashwani; Chu, Nina; Arthur, Rebecca Afiba; Zhang, Lubo; Longo, Lawrence D

2010-11-01

In the developing fetus, cerebral arteries (CA) show striking differences in signal transduction mechanisms compared with the adult, and these differences are magnified in response to high-altitude long-term hypoxia (LTH). In addition, in the mature organism, cerebrovascular acclimatization to LTH may be associated with several clinical problems, the mechanisms of which are unknown. Because PKC plays a key role in regulating CA contractility, in fetal and adult cerebral arteries, we tested the hypothesis that LTH differentially regulates the PKC-mediated Ca(2+) sensitization pathways and contractility. In four groups of sheep [fetal normoxic (FN), fetal hypoxic (FH), adult normoxic (AN), and adult hypoxic (AH)], we examined, simultaneously, responses of CA tension and intracellular Ca(2+) concentration and measured CA levels of PKC, ERK1/2, RhoA, 20-kDa myosin light chain, and the 17-kDa PKC-potentiated myosin phosphatase inhibitor CPI-17. The PKC activator phorbol 12,13-dibutyrate (PDBu) produced robust contractions in all four groups. However, PDBu-induced contractions were significantly greater in AH CA than in the other groups. In all CA groups except AH, in the presence of MEK inhibitor (U-0126), the PDBu-induced contractions were increased a further 20-30%. Furthermore, in adult CA, PDBu led to increased phosphorylation of ERK1, but not ERK2; in fetal CA, the reverse was the case. PDBu-stimulated ERK2 phosphorylation also was significantly greater in FH than FN CA. Also, although RhoA/Rho kinase played a significant role in PDBu-mediated contractions of FN CA, this was not the case in FH or either adult group. Also, whereas CPI-17 had a significant role in adult CA contractility, this was not the case for the fetus. Overall, in ovine CA, the present study demonstrates several important maturational and LTH acclimatization changes in PKC-induced contractile responses and downstream pathways. The latter may play a key role in the pathophysiologic disorders

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

Ndrg2 is a PGC-1α/ERRα target gene that controls protein synthesis and expression of contractile-type genes in C2C12 myotubes.

PubMed

Foletta, Victoria C; Brown, Erin L; Cho, Yoshitake; Snow, Rod J; Kralli, Anastasia; Russell, Aaron P

2013-12-01

The stress-responsive, tumor suppressor N-myc downstream-regulated gene 2 (Ndrg2) is highly expressed in striated muscle. In response to anabolic and catabolic signals, Ndrg2 is suppressed and induced, respectively, in mouse C2C12 myotubes. However, little is known about the mechanisms regulating Ndrg2 expression in muscle, as well as the biological role for Ndrg2 in differentiated myotubes. Here, we show that Ndrg2 is a target of a peroxisome proliferator-activated receptor-gamma coactivator-1α (PGC-1α) and estrogen-related receptor alpha (ERRα) transcriptional program and is induced in response to endurance exercise, a physiological stress known also to increase PGC-1α/ERRα activity. Analyses of global gene and protein expression profiles in C2C12 myotubes with reduced levels of NDRG2, suggest that NDRG2 affects muscle growth, contractile properties, MAPK signaling, ion and vesicle transport and oxidative phosphorylation. Indeed, suppression of NDRG2 in myotubes increased protein synthesis and the expression of fast glycolytic myosin heavy chain isoforms, while reducing the expression of embryonic myosin Myh3, other contractile-associated genes and the MAPK p90 RSK1. Conversely, enhanced expression of NDRG2 reduced protein synthesis, and furthermore, partially blocked the increased protein synthesis rates elicited by a constitutively active form of ERRα. In contrast, suppressing or increasing levels of NDRG2 did not affect mRNA expression of genes involved in mitochondrial biogenesis that are regulated by PGC-1α or ERRα. This study shows that in C2C12 myotubes Ndrg2 is a novel PGC-1α/ERRα transcriptional target, which influences protein turnover and the regulation of genes involved in muscle contraction and function. © 2013 Elsevier B.V. All rights reserved.

Muscle contractility decrement and correlated morphology during the pathogenesis of streptozotocin-diabetic mice.

PubMed

Fahim, M A; el-Sabban, F; Davidson, N

1998-06-01

affects presynaptically the neuromuscular junction as well as muscle itself. Actions at both sites may contribute to the functional alterations seen in muscle contractile properties and may play a role in the pathogenesis of diabetic neuromyopathy.

Alterations in Vasoreactivity of Femoral Artery Induced by Hindlimb Unweighting are Related to the Changes of Contractile Protein in Rats

NASA Technical Reports Server (NTRS)

Ma, Jin; Ren, Xinling; Meng, Qinjun; Zhang, Lifan; Purdy, Ralph E.

2005-01-01

Responses of endothelium removed femoral arterial rings to vasoactive compounds were examined in vitro, and the expression of Myosin and Actin of femoral artery were observed by Western Blotting and Immunohistochemistry in hndlimb unweighting rats and control rats. The results showed that contractile responses of femoral arterial rings evoked by Phenylephrine, Endothelin-1, Vasopressin, KCl, Ca(2+) and Ca(2+) ionophore A23187 were decreased in hindlimb unweighting rats as compared with that of controls. But vasoddatory responses induced by SNPand cGMP were not different between groups. No significant differences have been found in expressions of Calponin, Myosin, Actin, and the ratio of MHC SM1/SM2 between the two groups, but expression of alpha-SM-Actin decreased in hindlimb unweighting rats. The data indicated that the diminished contractile responsiveness probably result from altered contractile apparatus, especially the contractile proteins.

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

Role of STIM1 (Stromal Interaction Molecule 1) in Hypertrophy-Related Contractile Dysfunction.

PubMed

Troupes, Constantine D; Wallner, Markus; Borghetti, Giulia; Zhang, Chen; Mohsin, Sadia; von Lewinski, Dirk; Berretta, Remus M; Kubo, Hajime; Chen, Xiongwen; Soboloff, Jonathan; Houser, Steven

2017-07-07

Pathological increases in cardiac afterload result in myocyte hypertrophy with changes in myocyte electrical and mechanical phenotype. Remodeling of contractile and signaling Ca 2+ occurs in pathological hypertrophy and is central to myocyte remodeling. STIM1 (stromal interaction molecule 1) regulates Ca 2+ signaling in many cell types by sensing low endoplasmic reticular Ca 2+ levels and then coupling to plasma membrane Orai channels to induce a Ca 2+ influx pathway. Previous reports suggest that STIM1 may play a role in cardiac hypertrophy, but its role in electrical and mechanical phenotypic alterations is not well understood. To define the contributions of STIM1-mediated Ca 2+ influx on electrical and mechanical properties of normal and diseased myocytes, and to determine whether Orai channels are obligatory partners for STIM1 in these processes using a clinically relevant large animal model of hypertrophy. Cardiac hypertrophy was induced by slow progressive pressure overload in adult cats. Hypertrophied myocytes had increased STIM1 expression and activity, which correlated with altered Ca 2 + -handling and action potential (AP) prolongation. Exposure of hypertrophied myocytes to the Orai channel blocker BTP2 caused a reduction of AP duration and reduced diastolic Ca 2+ spark rate. BTP2 had no effect on normal myocytes. Forced expression of STIM1 in cultured adult feline ventricular myocytes increased diastolic spark rate and prolonged AP duration. STIM1 expression produced an increase in the amount of Ca 2+ stored within the sarcoplasmic reticulum and activated Ca 2+ /calmodulin-dependent protein kinase II. STIM1 expression also increased spark rates and induced spontaneous APs. STIM1 effects were eliminated by either BTP2 or by coexpression of a dominant negative Orai construct. STIM1 can associate with Orai in cardiac myocytes to produce a Ca 2+ influx pathway that can prolong the AP duration and load the sarcoplasmic reticulum and likely contributes to the

Effect of acute gastric dilatation on gastric myoelectic and motor activity in dogs.

PubMed

Hall, J A; Solie, T N; Seim, H B; Twedt, D C

1999-05-01

To investigate the effects of experimentally induced acute gastric dilatation on electrical and mechanical activities of the stomach in dogs. 7 healthy dogs. Electrodes and strain-gauge force transducers were implanted on the serosal surface of the antrum and pylorus. Eight days later, baseline gastric electrical and contractile activities were recorded. The dogs were anesthetized and mechanically ventilated to maintain normocapnia while the stomach was distended (intragastric pressure, 30 mm Hg) for 180 minutes, using a thin compliant bag. Gastric electrical and contractile activities were recorded again on days 1 and 10 after dilatation. Recordings were analyzed to determine gastric slow-wave frequency, slow-wave dysrhythmia, propagation velocity of slow-waves, coupling of contractions to slow waves, motility index on the basis of relative contractile amplitudes, and onset of contractions after a standardized meal. Electrical or contractile activities were not significantly different 18 hours after acute gastric dilatation (day 1). Arrhythmias were evident before and after gastric dilatation in dogs from which food was withheld and in dogs after consumption of a meal. Variables for assessing gastric electrical and contractile activities were unaffected 18 hours after acute gastric dilatation. Analysis of results of this study indicated that altered electrical and contractile activities in dogs with short-term gastric dilatation are not likely to be secondary to the process of acute gastric dilatation.

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

Serotonin-induced contractile responses of esophageal smooth muscle in the house musk shrew (Suncus murinus).

PubMed

Shiina, T; Naitou, K; Nakamori, H; Suzuki, Y; Horii, K; Sano, Y; Shimaoka, H; Shimizu, Y

2016-11-01

Serotonin (5-hydroxytryptamine, 5-HT) is a regulatory factor in motility of the gastrointestinal tract including the esophagus. Although we proposed that vagal cholinergic and mast cell-derived non-cholinergic components including serotonin coordinately shorten the esophagus, the precise mechanism of serotonin-induced contractions in the suncus esophagus is still unclear. Therefore, the aims of this study were to determine characteristics of contractile responses induced by serotonin and to identify 5-HT receptor subtypes responsible for regulating motility in the suncus esophagus. An isolated segment of the suncus esophagus was placed in an organ bath, and longitudinal or circular mechanical responses were recorded using a force transducer. Serotonin evoked contractile responses of the suncus esophagus in the longitudinal direction but not in the circular direction. Tetrodotoxin did not affect the serotonin-induced contractions. Pretreatment with a non-selective 5-HT receptor antagonist or double application of 5-HT 1 and 5-HT 2 receptor antagonists blocked the serotonin-induced contractions. 5-HT 1 and 5-HT 2 receptor agonists, but not a 5-HT 3 receptor agonist, evoked contractile responses in the suncus esophagus. The findings suggest that serotonin induces contractile responses of the longitudinal smooth muscle in the muscularis mucosae of the suncus esophagus that are mediated via 5-HT 1 and 5-HT 2 receptors on muscle cells. The serotonin-induced contractions might contribute to esophageal peristalsis and emetic response. © 2016 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.

[Inotropic effect of a new probiotic product on myocardial contractility. Comparison with diazoxide].

PubMed

Sobol', K V; Korotkov, S M; Nesterov, V P

2014-01-01

The inotropic effect of a new probiotic product on myocardial contractility of the frog Rana ridibunda and the effect of probiotic product on the rat cardiac mitochondria swelling were studied. In both cases, the comparison with known cardioprotector diazoxide was done. Probiotic product and diazoxide were shown to cause a dual effect on the maximum force induced by the muscle sample during spontaneous atrial contraction. Addition of agents caused a negative impact, while washing out exerted a positive inotropic effect. At the same time probiotic product has virtually no effect on the amplitude of contraction induced by electrical stimulation of the ventricle fragments. Probiotic product decreases both proton passive permeability in the inner mitochondrial membrane, and potassium active transport in mitochondria caused by activation of K(+)-uniporter of cardiomyocytes. A possible mechanism of action of probiotic product is discussed.

Effect of aspirin on the contractility of aortic smooth muscle and the course of blood pressure development in male spontaneously hypertensive rats.

PubMed

Rahmani, M A; David, V; Huang, M; DeGray, G

1998-01-01

The effects of acetylsalicylic acid (ASA) on aortic smooth muscle contractility were studied in aortic rings of male SHR and WKY rats. The rats were administered two intraperitoneal injections of 10 mg/kg of ASA per week for ten weeks. Blood pressure of each rat was monitored twice weekly prior to the i.p. injections. Twenty four hours after the last injection the aortic smooth muscles were evaluated for generation of active tension in response to KCl, Phenylephrine (PE), Clonidine and Norepinephrine (NE). In another set of experiments calcium conductance was evaluated in the presence or absence of endothelium both in ASA treated and non treated animals. We report that aortic rings from ASA-treated SHR animals were more responsive to contractile agents than rings from non-treated SHR male rats. Also, the Ca2+ conductance in vitro was enhanced appreciably in SHR aortic rings denuded of their monolayer of endothelium in response to ASA treatment. No decrease in systolic blood pressure was observed in response to ASA treatment in SHR male rats. These results suggest that acetylsalicylic acid not only may modulate aortic smooth muscle contractility through the metabolites of arachidonic acid but may repair to a great extent the hypertension associated plasma membrane permeability defect of vascular myocytes.

Dependence of Intramyocardial Pressure and Coronary Flow on Ventricular Loading and Contractility: A Model Study

PubMed Central

Borsje, Petra; Arts, Theo; van De Vosse, Frans N.

2006-01-01

The phasic coronary arterial inflow during the normal cardiac cycle has been explained with simple (waterfall, intramyocardial pump) models, emphasizing the role of ventricular pressure. To explain changes in isovolumic and low afterload beats, these models were extended with the effect of three-dimensional wall stress, nonlinear characteristics of the coronary bed, and extravascular fluid exchange. With the associated increase in the number of model parameters, a detailed parameter sensitivity analysis has become difficult. Therefore we investigated the primary relations between ventricular pressure and volume, wall stress, intramyocardial pressure and coronary blood flow, with a mathematical model with a limited number of parameters. The model replicates several experimental observations: the phasic character of coronary inflow is virtually independent of maximum ventricular pressure, the amplitude of the coronary flow signal varies about proportionally with cardiac contractility, and intramyocardial pressure in the ventricular wall may exceed ventricular pressure. A parameter sensitivity analysis shows that the normalized amplitude of coronary inflow is mainly determined by contractility, reflected in ventricular pressure and, at low ventricular volumes, radial wall stress. Normalized flow amplitude is less sensitive to myocardial coronary compliance and resistance, and to the relation between active fiber stress, time, and sarcomere shortening velocity. PMID:17048105

Dynamics of myosin II organization into contractile networks and fibers at the medial cell cortex

NASA Astrophysics Data System (ADS)

Nie, Wei

The cellular morphology of adhered cells depends crucially on the formation of a contractile meshwork of parallel and cross-linked stress fibers along the contacting surface. The motor activity and mini-filament assembly of non-muscle myosin II is an important component of cell-level cytoskeletal remodeling during mechanosensing. To monitor the dynamics of non-muscle myosin II, we used confocal microscopy to image cultured HeLa cells that stably express myosin regulatory light chain tagged with GFP (MRLC-GFP). MRLC-GFP was monitored in time-lapse movies at steady state and during the response of cells to varying concentrations of blebbistatin (which disrupts actomyosin stress fibers). Using image correlation spectroscopy analysis, we quantified the kinetics of disassembly and reassembly of actomyosin networks and compared to studies by other groups. This analysis suggested the following processes: myosin minifilament assembly and disassembly; aligning and contraction; myosin filament stabilization upon increasing contractile tension. Numerical simulations that include those processes capture some of the main features observed in the 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. We discuss methods to monitor myosin reorganization using non-linear imaging methods.

Dependence of intramyocardial pressure and coronary flow on ventricular loading and contractility: a model study.

PubMed

Bovendeerd, Peter H M; Borsje, Petra; Arts, Theo; van De Vosse, Frans N

2006-12-01

The phasic coronary arterial inflow during the normal cardiac cycle has been explained with simple (waterfall, intramyocardial pump) models, emphasizing the role of ventricular pressure. To explain changes in isovolumic and low afterload beats, these models were extended with the effect of three-dimensional wall stress, nonlinear characteristics of the coronary bed, and extravascular fluid exchange. With the associated increase in the number of model parameters, a detailed parameter sensitivity analysis has become difficult. Therefore we investigated the primary relations between ventricular pressure and volume, wall stress, intramyocardial pressure and coronary blood flow, with a mathematical model with a limited number of parameters. The model replicates several experimental observations: the phasic character of coronary inflow is virtually independent of maximum ventricular pressure, the amplitude of the coronary flow signal varies about proportionally with cardiac contractility, and intramyocardial pressure in the ventricular wall may exceed ventricular pressure. A parameter sensitivity analysis shows that the normalized amplitude of coronary inflow is mainly determined by contractility, reflected in ventricular pressure and, at low ventricular volumes, radial wall stress. Normalized flow amplitude is less sensitive to myocardial coronary compliance and resistance, and to the relation between active fiber stress, time, and sarcomere shortening velocity.

Muscle contractile characteristics: relationship to high-intensity exercise.

PubMed

Morris, Martyn G; Dawes, Helen; Howells, Ken; Scott, Oona M; Cramp, Mary; Izadi, Hooshang

2010-09-01

We investigated the relationship between muscle contractile characteristics, collected using percutaneous electrical stimulation, and high-intensity exercise performance. Seventeen participants performed a muscle performance test for the calculation of rate of torque development (RTD), rate of relaxation (RR(1/2)), rate of fatigue and fatigue resistance. On a second visit the participants completed a Wingate cycle ergometer test with peak power, mean power, fatigue index and fatigue rate calculated. The muscle fatigue index related significantly to the WAnT fatigue index and fatigue rate (p < 0.01). The change in rate of torque development (%DeltaRTD) was also related significantly to the fatigue rate (W/s) during the WAnT. Subjects displaying the greatest reduction in RTD had the greatest fatigue rate during the WAnT and greater fatigue during the electrical stimulation protocol. There were no significant relationships between peak (r 0.36; p > 0.01) or mean power (r -0.11, p > 0.01) with any of the muscle performance measures. These findings demonstrate that muscle contractile characteristics, elicited during standardised in vivo electrical stimulation, relate to performance during a Wingate anaerobic test. They suggest that muscle contraction characteristics play an important role in high-intensity exercise performance and indicate that electrical stimulation protocols can be a useful additional tool to explore muscle contraction characteristics in relation to exercise performance and trainability.

The sphingosine analog fingolimod (FTY720) enhances tone and contractility of rat gastric fundus smooth muscle.

PubMed

Kraft, M; Zettl, U K; Noack, T; Patejdl, R

2018-05-08

Sphingosine and its metabolite sphingosine phosphate (S1P) regulate a multitude of biological functions, including the contractile state of smooth. Gastrointestinal side effects have been reported in patients treated with FTY720, a sphingosine analog that is approved for the treatment of multiple sclerosis. The aim of this study was to characterize the effects of FTY720 on rat gastric fundus smooth muscle under basal conditions and during activation induced by high-K + solution. Isometric contractions of isolated circular strips of gastric fundus smooth muscle were recorded using the organ bath method. The effects of FTY720 or vehicle were recorded under control conditions and in the presence of indomethacin, L-NAME, HA-1100, nifedipine, JTE-013, and suramin. Tone and contractions recorded in the presence of FTY720 or vehicle are reported as % of the amplitude of an initial high-K + contraction obtained under control conditions. From a concentration of 10 μmol L -1 onwards, FTY720 increased the tone, reaching 8.9% ± 7.5% at 100 μmol L -1 (P < .05). With indomethacin in the solution, the effects of FTY720 were enhanced (32.1% ± 7.7%; P < .001). The FTY720-induced increase in tone was abolished in the absence of extracellular Ca 2+ and reduced by nifedipine, HA-1100, JTE-013, and suramin. Furthermore, FTY720 increased high-K + contractions in the presence of indomethacin. FTY720 increases tone and contractile responses to depolarization in gastric fundus smooth muscle by triggering calcium entry and calcium sensitization in a S1P receptor-dependent manner. Taken together, the experimental results presented in this work suggest that FTY720 may increase gastric tone and contractility in patients. © 2018 John Wiley & Sons Ltd.

[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.

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

Akt2 Knockout Alleviates Prolonged Caloric Restriction-Induced Change in Cardiac Contractile Function through Regulation of Autophagy

PubMed Central

Zhang, Yingmei; Han, Xuefeng; Hu, Nan; Huff, Anna F.; Gao, Feng; Ren, Jun

2014-01-01

Caloric restriction leads to changes in heart geometry and function although the underlying mechanism remains elusive. Autophagy, a conserved pathway for degradation of intracellular proteins and organelles, preserves energy and nutrient in the face of caloric insufficiency. This study was designed to examine the role of Akt2 in prolonged caloric restriction-induced change in cardiac homeostasis and the underlying mechanism(s) involved. Wild-type (WT) and Akt2 knockout mice were caloric restricted (by 40%) for 30 weeks. Echocardiographic, cardiomyocyte contractile and intracellular Ca2+ properties, autophagy and its regulatory proteins were evaluated. Caloric restriction compromised echocardiographic indices (decreased left ventricular mass, left ventricular diameters and cardiac output), cardiomyocyte contractile and intracellular Ca2+ properties associated with dampened SERCA2a phosphorylation, upregulated phospholamban and autophagy (Beclin-1, Atg7, LC3BII-to-LC3BI ratio), increased autophagy adaptor protein p62, elevated phosphorylation of AMPK, Akt2 and the Akt downstream signal molecule TSC2, the effects of which with the exception of autophagy protein markers (Beclin-1, Atg7, LC3B) and AMPK were mitigated or significantly alleviated by Akt2 knockout. Lysosomal inhibition using bafilomycin A1 negated Akt2 knockout-induced protective effect on p62. Evaluation of downstream signaling molecules of Akt and AMPK including mTOR and ULK1 revealed that caloric restriction suppressed and promoted phosphorylation of mTOR and ULK1, respectively, without affecting total mTOR and ULK1 expression. Akt2 knockout significantly augmented caloric restriction-induced responses on mTOR and ULK1. Taken together, these data suggest a beneficial role of Akt2 knockout in preservation of cardiac homeostasis against prolonged caloric restriction-induced pathological changes possibly through facilitating autophagy. PMID:24368095

Trinitrobenzenesulfonic Acid Colitis Induces Changes in the Contractile Response of Circular Smooth Muscle in the Distal Colon

DTIC Science & Technology

1996-03-27

contractile response of circular smooth muscle in the rat distal colon" Name of Candidate: Jeanette M. Hosseini Doctor of Philosophy Degree 27 March 1996... muscle in the rat distal colon" beyond brief excerpts is with the pennission of the copyright owner, and will save and hold harmless the Unifonned...induces changes in the contractile response of circular smooth muscle 10 the rat colon. Jeanette Marie Hosseini, 1996 Dissertation directed by: Terez

Regulation of adult cardiocyte growth: effects of active and passive mechanical loading

NASA Technical Reports Server (NTRS)

Decker, M. L.; Janes, D. M.; Barclay, M. M.; Harger, L.; Decker, R. S.

1997-01-01

Fluctuations in hemodynamic load have been documented to modulate contractile protein turnover and myofibrillar structure in the heart; however, the relative importance of active and passive loading in regulating adult cardiocyte growth remains unresolved. To address this issue at the cellular level, adult feline cardiocytes were cultured either on Silastic membranes or plastic surfaces. Cardiocyte-laden membranes were stretched 10% of their rest length to enhance passive loading, whereas heart cells cultured on plastic or Silastic were field stimulated at 1 Hz to mimic active loading. Turnover of contractile proteins and structural integrity of the contractile-cytoskeletal apparatus were monitored for periods ranging from 4 to 72 h. Active and passive loading elevated contractile protein synthesis nearly equally (approximately 50%) and promoted the attachment of remodeled myofibrils to vinculin-positive focal contacts and/or costameres during the first 24 h of loading. Thereafter, rates of contractile protein synthesis returned to control values in passively stretched heart cells but remained elevated in field-stimulated cultures. The fractional rate of growth was increased significantly (approximately 8%/day) in electrically paced cells, whereas in passively stretched cardiocytes the growth rate rose only modestly (approximately 2%/day). Changes in the rate of myocyte growth appeared more closely correlated with the development of focal contacts and myofibril remodeling than with changes in myofibrillar protein turnover per se. 2,3-Butanedione monoxime, nifedipine, and, to a lesser extent, ryanodine blocked field-stimulated contractile protein synthesis and myofibrillar remodeling but had no impact on protein turnover or myofibril reassembly in passively loaded cardiocytes. The results of these experiments imply that both active and passive loading stimulate contractile protein turnover and myofibril remodeling, but the generation of active tension accelerates

Regulation of adult cardiocyte growth: effects of active and passive mechanical loading.

PubMed

Decker, M L; Janes, D M; Barclay, M M; Harger, L; Decker, R S

1997-06-01

Fluctuations in hemodynamic load have been documented to modulate contractile protein turnover and myofibrillar structure in the heart; however, the relative importance of active and passive loading in regulating adult cardiocyte growth remains unresolved. To address this issue at the cellular level, adult feline cardiocytes were cultured either on Silastic membranes or plastic surfaces. Cardiocyte-laden membranes were stretched 10% of their rest length to enhance passive loading, whereas heart cells cultured on plastic or Silastic were field stimulated at 1 Hz to mimic active loading. Turnover of contractile proteins and structural integrity of the contractile-cytoskeletal apparatus were monitored for periods ranging from 4 to 72 h. Active and passive loading elevated contractile protein synthesis nearly equally (approximately 50%) and promoted the attachment of remodeled myofibrils to vinculin-positive focal contacts and/or costameres during the first 24 h of loading. Thereafter, rates of contractile protein synthesis returned to control values in passively stretched heart cells but remained elevated in field-stimulated cultures. The fractional rate of growth was increased significantly (approximately 8%/day) in electrically paced cells, whereas in passively stretched cardiocytes the growth rate rose only modestly (approximately 2%/day). Changes in the rate of myocyte growth appeared more closely correlated with the development of focal contacts and myofibril remodeling than with changes in myofibrillar protein turnover per se. 2,3-Butanedione monoxime, nifedipine, and, to a lesser extent, ryanodine blocked field-stimulated contractile protein synthesis and myofibrillar remodeling but had no impact on protein turnover or myofibril reassembly in passively loaded cardiocytes. The results of these experiments imply that both active and passive loading stimulate contractile protein turnover and myofibril remodeling, but the generation of active tension accelerates

A new orthodontic force system for moment control utilizing the flexibility of common wires: Evaluation of the effect of contractile force and hook length.

PubMed

Lai, Wei-Jen; Midorikawa, Yoshiyuki; Kanno, Zuisei; Takemura, Hiroshi; Suga, Kazuhiro; Soga, Kohei; Ono, Takashi; Uo, Motohiro

2018-01-01

The application of an appropriate force system is indispensable for successful orthodontic treatments. Second-order moment control is especially important in many clinical situations, so we developed a new force system composed of a straight orthodontic wire and two crimpable hooks of different lengths to produce the second-order moment. The objective of this study was to evaluate this new force system and determine an optimum condition that could be used in clinics. We built a premolar extraction model with two teeth according to the concept of a modified orthodontic simulator. This system was activated by applying contractile force from two hooks that generated second-order moment and force. The experimental device incorporated two sensors, and forces and moments were measured along six axes. We changed the contractile force and hook length to elucidate their effects. Three types of commercial wires were tested. The second-order moment was greater on the longer hook side of the model. Vertical force balanced the difference in moments between the two teeth. Greater contractile force generated a greater second-order moment, which reached a limit of 150 g. Excessive contractile force induced more undesired reactions in the other direction. Longer hooks induced greater moment generation, reaching their limit at 10 mm in length. The system acted similar to an off-center V-bend and can be applied in clinical practice as an unconventional loop design. We suggest that this force system has the potential for second-order moment control in clinical applications. Copyright © 2017. Published by Elsevier B.V.

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.

Relationship between improvement in left ventricular dyssynchrony and contractile function and clinical outcome with cardiac resynchronization therapy: the MADIT-CRT trial.

PubMed

Pouleur, Anne-Catherine; Knappe, Dorit; Shah, Amil M; Uno, Hajime; Bourgoun, Mikhail; Foster, Elyse; McNitt, Scott; Hall, W Jackson; Zareba, Wojciech; Goldenberg, Ilan; Moss, Arthur J; Pfeffer, Marc A; Solomon, Scott D

2011-07-01

To assess long-term effects of cardiac resynchronization therapy (CRT) on left ventricular (LV) dyssynchrony and contractile function, by two-dimensional speckle-tracking echocardiography, compared with implantable cardioverter defibrillator (ICD) only in MADIT-CRT. We studied 761 patients in New York Heart Association I/II, ejection fraction ≤30%, and QRS ≥130 ms [n = 434, CRT-defibrillator (CRT-D), n = 327, ICD] with echocardiographic studies available at baseline and 12 months. Dyssynchrony was determined as the standard deviation of time to peak transverse strain between 12 segments of apical four- and two-chamber views, and contractile function as global longitudinal strain (GLS) by averaging longitudinal strain over these 12 segments. We compared changes in LV dyssynchrony and contractile function between treatment groups and assessed relationships between these changes over the first year and subsequent outcomes (median post 1-year follow-up = 14.9 months). Mean changes in LV dyssynchrony and contractile function measured by GLS in the overall population were, respectively, -29 ± 83 ms and -1 ± 2.9%. However, both LV dyssynchrony (CRT-D: -47 ± 83 ms vs. ICD: -6 ± 76 ms, P < 0.001) and contractile function (CRT-D: -1.4 ± 3.1% vs. ICD: -0.4 ± 2.5%, P < 0.001) improved to a greater extent in the CRT-D group compared with the ICD-only group. A greater improvement in dyssynchrony and contractile function at 1 year was associated with lower rates of the subsequent primary outcome of death or heart failure, adjusting for baseline dyssynchrony and contractile function, treatment arm, ischaemic status, and change in LV end-systolic volume. Each 20 ms decrease in LV dyssynchrony was associated with a 7% reduction in the primary outcome (P = 0.047); each 1% improvement in GLS over the 12-month period was associated with a 24% reduction in the primary outcome (P < 0.001). Cardiac resynchronization therapy resulted in a significant improvement in both LV

Impaired gut contractility following hemorrhagic shock is accompaied by IL-6 and G-CSF production and neutrophil infiltration.

PubMed

Hierholzer, C; Kalff, J C; Chakraborty, A; Watkins, S C; Billiar, T R; Bauer, A J; Tweardy, D J

2001-02-01

Recovery from hemorrhagic shock (HS) is frequently accompanied by bowel stasis. The aim of this study was to examine whether or not HS initiates an inflammatory response that includes production of cytokines, specifically G-CSF and interleukin-6 (IL-6), and recruitment of leukocytes within the intestinal muscularis which contribute to impaired muscle contractility. Sprague-Dawley rats were subjected to HS (MAP 40 mm Hg for 156 min) followed by resuscitation, and then they were killed at 4 hr. Shock animals demonstrated accumulation of PMNs in the jejunal muscularis and decreased spontaneous and bethanechol-stimulated muscle contractility. Semiquantitative RT-PCR demonstrated elevated levels of IL-6 and G-CSF mRNA in shock animals in full-thickness jejunum and in mucosa and muscularis layers compared to sham controls. Immunostaining demonstrated increased IL-6 protein production within the muscularis externa and submucosa. In situ hybridization studies localized G-CSF mRNA production to the submucosa. Gel shift assays revealed increased NF-kappaB and Stat3 activity in full-thickness jejunum and jejunal layers of shock animals. Activation of Stat3 also was demonstrated in normal muscularis tissue exposed to IL-6 and G-CSF in vitro. IL-6 and G-CSF are produced in the muscularis and mucosa layers of the gut in HS where they may contribute to PMN recruitment and smooth muscle dysfunction.

Myosin IIA-related Actomyosin Contractility Mediates Oxidative Stress-induced Neuronal Apoptosis

PubMed Central

Wang, Yan; Xu, Yingqiong; Liu, Qian; Zhang, Yuanyuan; Gao, Zhen; Yin, Mingzhu; Jiang, Nan; Cao, Guosheng; Yu, Boyang; Cao, Zhengyu; Kou, Junping

2017-01-01

Oxidative stress-induced neuronal apoptosis plays an important role in the progression of central nervous system (CNS) diseases. In our study, when neuronal cells were exposed to hydrogen peroxide (H2O2), an exogenous oxidant, cell apoptosis was observed with typical morphological changes including membrane blebbing, neurite retraction and cell contraction. The actomyosin system is considered to be responsible for the morphological changes, but how exactly it regulates oxidative stress-induced neuronal apoptosis and the distinctive functions of different myosin II isoforms remain unclear. We demonstrate that myosin IIA was required for neuronal contraction, while myosin IIB was required for neuronal outgrowth in normal conditions. During H2O2-induced neuronal apoptosis, myosin IIA, rather than IIB, interacted with actin filaments to generate contractile forces that lead to morphological changes. Moreover, myosin IIA knockout using clustered regularly interspaced short palindromic repeats/CRISPR-associated protein-9 nuclease (CRISPR/Cas9) reduced H2O2-induced neuronal apoptosis and the associated morphological changes. We further demonstrate that caspase-3/Rho-associated kinase 1 (ROCK1) dependent phosphorylation of myosin light chain (MLC) was required for the formation of the myosin IIA-actin complex. Meanwhile, either inhibition of myosin II ATPase with blebbistatin or knockdown of myosin IIA with siRNA reversely attenuated caspase-3 activation, suggesting a positive feedback loop during oxidative stress-induced apoptosis. Based on our observation, myosin IIA-actin complex contributes to actomyosin contractility and is associated with the positive feedback loop of caspase-3/ROCK1/MLC pathway. This study unravels the biochemical and mechanistic mechanisms during oxidative stress-induced neuronal apoptosis and may be applicable for the development of therapies for CNS diseases. PMID:28352215

Toll-like receptors 2 and 4 exert opposite effects on the contractile response induced by serotonin in mouse colon: role of serotonin receptors.

PubMed

Forcén, R; Latorre, E; Pardo, J; Alcalde, A I; Murillo, M D; Grasa, L

2016-08-01

What is the central question of this study? The action of Toll-like receptors (TLRs) 2 and 4 on the motor response to serotonin in mouse colon has not previously been reported. What is the main finding and its importance? Toll-like receptors 2 and 4 modulate the serotonin-induced contractile response in mouse colon by modifying the expression of serotonin (5-HT) receptors. Alterations in 5-HT2A and 5-HT2C receptors explain the increase of the response to serotonin in TLR2(-/-) mice. Alterations in 5-HT2C and 5-HT4 receptors explain the suppression of the response to serotonin in TLR4(-/-) mice. The microbiota, through Toll-like receptors (TLRs), may regulate gastrointestinal motility by activating neuroendocrine mechanisms. We evaluated the influence of TLR2 and TLR4 in spontaneous contractions and in the serotonin (5-HT)-induced motor response in mouse colon, and assessed the 5-HT receptors involved. Muscle contractility studies to evaluate the intestinal spontaneous motility and the response to 5-HT were performed in the colon from wild-type (WT), TLR2(-/-) , TLR4(-/-) and TLR2/4 double knockout (DKO) mice. The 5-HT receptor mRNA expression was determined by real-time PCR. The amplitude and frequency of the spontaneous contractions of the colon were smaller in TLR4(-/-) and TLR2/4 DKO mice with respect to WT mice. In WT, TLR2(-/-) and TLR2/4 DKO mice, 100 μm 5-HT evoked a contractile response. The contractile response induced by 5-HT was significantly higher in TLR2(-/-) than in WT mice. In TLR4(-/-) mice, 5-HT did not evoke any contractile response. The mRNA expression of 5-HT2A was increased in TLR2(-/-) and TLR2/4 DKO mice. The 5-HT2C and 5-HT4 mRNA expressions were increased in TLR4(-/-) and TLR2/4 DKO mice. The 5-HT2C mRNA expression was diminished in TLR2(-/-) mice. The 5-HT3 mRNA expression was increased in TLR2(-/-) , TLR4(-/-) and TLR2/4 DKO mice. The 5-HT7 mRNA expression was diminished in TLR2/4 DKO mice. In WT, TLR2(-/-) and TLR2/4 DKO mice, 5-HT2

A physiological basis for variation in the contractile properties of isolated rat heart.

PubMed Central

Lin, L E; McClellan, G; Weisberg, A; Winegrad, S

1991-01-01

1. The maximum Ca(2+)-activated force, maximum velocity of unloaded shortening and both Ca(2+)- and actin-activated ATPase activities of myosin have been measured in detergent-skinned preparations of isolated bundles of rat right ventricle after exposure of the intact tissue to different conditions of superfusion, mechanical activity and temperature. 2. Maximum Ca(2+)-activated force per unit cross-sectional area decreases with increasing cross-sectional area, and, in the absence of electrical stimulation, with the duration of superfusion. Maximum velocity of unloaded shortening is not influenced by these differences. 3. Actin-activated ATPase activity of myosin decreases as cross-sectional area increases and duration of superfusion increases, but the extent of the decrease in enzymatic activity is less than that of developed force. Ca(2+)-activated ATPase activity is independent of these differences. 4. Actin-activated ATPase activity in cryostatic sections of quickly frozen tissue is not uniform across the transverse section. In thin bundles, it is highest in the centre and lowest at the edge of the section, which correspond, respectively, to the centre and the surface of the tissue bundle. Exposure of the tissue section to 1 microM-cyclic AMP increases the actin-activated ATPase activity of myosin with the largest increase in activity occurring at or near the surface of the bundle. 5. Ca(2+)-activated ATPase activity of myosin is uniform across the transverse section and is not changed by cyclic AMP. 6. Electrical stimulation, elevated Ca2+ concentration in the superfusion medium, or isoprenaline partially or completely reverse the decline in maximum Ca(2+)-activated force produced by prolonged superfusion of the bundle before its skinning. 7. These observations are similar in many ways to those made on frog skeletal muscles by Elzinga, Howarth, Rull, Wilson & Woledge (1989a). An explanation based on the existence of a physiological mechanism for regulating the

Enhanced contractility of the rat stomach during suppression of angiotensin converting enzyme by captopril in vitro.

PubMed

Rani, R; Rao, K S

1991-04-01

1. Intragastric pressure (IGP) was used as an index, of the effect of serosal application of captopril (SQ 14,225; D-3-mercapto-2-methylpropanoyl-L-proline) on the contractility of rat stomach in vitro. 2. Captopril, at concentrations greater than 0.3 microM, enhanced the spontaneous gastric motility (GM) in a concentration-dependent manner whereas concentrations less than 0.3 microM selectively potentiated 4 nM bradykinin (BK)-evoked gastric contractions without significantly affecting the spontaneous GM. 3. The kallikrein inhibitor, aprotinin (100 u ml-1), markedly antagonized the enhanced GM to 1.4 microM captopril and BK (4 nM)-evoked contractions, without affecting the contractions evoked by angiotensin 1 (10 nM) and acetylcholine (0.4 microM). The angiotensin II antagonist, saralasin (50 microM) failed to mimic aprotinin. 4. The enhanced GM to captopril was markedly inhibited by tetrodotoxin (1 microM), and partially inhibited by atropine (1 microM). 5. These results indicate that in vitro, captopril (greater than 0.3 microM) enhances gastric contractility through kininase/ACE inhibitory action, presumably by increasing the concentration of undegraded tissue kinins and substance P. This motor response seems to be predominantly due to activation of the cholinergic neurones but non-cholinergic excitatory neurones are also involved.

Spatial distributions of pericellular stiffness in natural extracellular matrices are dependent on cell-mediated proteolysis and contractility.

PubMed

Keating, M; Kurup, A; Alvarez-Elizondo, M; Levine, A J; Botvinick, E

2017-07-15

Bulk tissue stiffness has been correlated with regulation of cellular processes and conversely cells have been shown to remodel their pericellular tissue according to a complex feedback mechanism critical to development, homeostasis, and disease. However, bulk rheological methods mask the dynamics within a heterogeneous fibrous extracellular matrix (ECM) in the region proximal to a cell (pericellular region). Here, we use optical tweezers active microrheology (AMR) to probe the distribution of the complex material response function (α=α'+α″, in units of µm/nN) within a type I collagen ECM, a biomaterial commonly used in tissue engineering. We discovered cells both elastically and plastically deformed the pericellular material. α' is wildly heterogeneous, with 1/α' values spanning three orders of magnitude around a single cell. This was observed in gels having a cell-free 1/α' of approximately 0.5nN/µm. We also found that inhibition of cell contractility instantaneously softens the pericellular space and reduces stiffness heterogeneity, suggesting the system was strain hardened and not only plastically remodeled. The remaining regions of high stiffness suggest cellular remodeling of the surrounding matrix. To test this hypothesis, cells were incubated within the type I collagen gel for 24-h in a media containing a broad-spectrum matrix metalloproteinase (MMP) inhibitor. While pericellular material maintained stiffness asymmetry, stiffness magnitudes were reduced. Dual inhibition demonstrates that the combination of MMP activity and contractility is necessary to establish the pericellular stiffness landscape. This heterogeneity in stiffness suggests the distribution of pericellular stiffness, and not bulk stiffness alone, must be considered in the study of cell-ECM interactions and design of complex biomaterial scaffolds. Collagen is a fibrous extracellular matrix (ECM) protein widely used to study cell-ECM interactions. Stiffness of ECM has been shown to

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).

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.

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.

Intrinsic increase in lymphangion muscle contractility in response to elevated afterload

PubMed Central

Scallan, Joshua P.; Wolpers, John H.; Muthuchamy, Mariappan; Gashev, Anatoliy A.; Zawieja, David C.

2012-01-01

Collecting lymphatic vessels share functional and biochemical characteristics with cardiac muscle; thus, we hypothesized that the lymphatic vessel pump would exhibit behavior analogous to homeometric regulation of the cardiac pump in its adaptation to elevated afterload, i.e., an increase in contractility. Single lymphangions containing two valves were isolated from the rat mesenteric microcirculation, cannulated, and pressurized for in vitro study. Pressures at either end of the lymphangion [input pressure (Pin), preload; output pressure (Pout), afterload] were set by a servo controller. Intralymphangion pressure (PL) was measured using a servo-null micropipette while internal diameter and valve positions were monitored using video methods. The responses to step- and ramp-wise increases in Pout (at low, constant Pin) were determined. PL and diameter data recorded during single contraction cycles were used to generate pressure-volume (P-V) relationships for the subsequent analysis of lymphangion pump behavior. Ramp-wise Pout elevation led to progressive vessel constriction, a rise in end-systolic diameter, and an increase in contraction frequency. Step-wise Pout elevation produced initial vessel distention followed by time-dependent declines in end-systolic and end-diastolic diameters. Significantly, a 30% leftward shift in the end-systolic P-V relationship accompanied an 84% increase in dP/dt after a step increase in Pout, consistent with an increase in contractility. Calculations of stroke work from the P-V loop area revealed that robust pumps produced net positive work to expel fluid throughout the entire afterload range, whereas weaker pumps exhibited progressively more negative work as gradual afterload elevation led to pump failure. We conclude that lymphatic muscle adapts to output pressure elevation with an intrinsic increase in contractility and that this compensatory mechanism facilitates the maintenance of lymph pump output in the face of edemagenic and

Contractile activity of ATP and diadenosine tetraphosphate on urinary bladder in the rat: role of A1- and P2X-purinoceptors and nitric oxide.

PubMed

Khattab, M M; Al-Hrasen, M N; El-Hadiyah, T M

2007-01-01

1. Both adenosine-5'-triphosphate (ATP) and diadenosine tetraphosphate (AP4A) produced a dose-dependent contraction of the isolated rat urinary bladder rings. AP(4)A dose-response curve was to the left of that of ATP, and maximum response was greater than that produced by ATP. 2. 8-cyclopentyl-1,3-dipropylxanthine (DPCPX), the A1-purinergic receptor blocker (0.01 mm) significantly inhibited the ATP- and AP4A-induced contractions at the whole dose range. The inhibition was between 31-41%, and 15-25% for ATP and AP4A respectively. 3. Pyridoxal phosphate 6-azophenyl-2',4'-disulphonic acid (PPADS), the P2X-purinoceptor antagonist (0.01 mm) potently inhibited the bladder contractions in response to ATP and AP4A by around 75-80%. 4. The nitric oxide (NO) precursor L-arginine reduced the bladder contractile response to ATP by about 22-41% and that of AP4A to a lesser extent by around 20-32%. 5. The nitric oxide synthase inhibitor, N(G)-nitro-L-arginine methyl ester (L-NAME, 0.1 mM), did not produce any significant effect on ATP except for a weak inhibition of about 14% at the lowest dose of ATP. The contractions in response to AP4A were only slightly reduced by L-NAME by about 20%. 6. In conclusion, the contractile response of the bladder to ATP and to the dinucleotide AP4A is mediated mainly through P2X-purinoceptors and A1-purinergic receptors. In the detrusor muscle, NO donation possesses an inhibitory effect on ATP-mediated contractility more than that produced by the dinucleotide AP4A.

Assembly Mechanism of the Contractile Ring for Cytokinesis by Fission Yeast

NASA Astrophysics Data System (ADS)

Vavylonis, Dimitrios; Wu, Jian-Qiu; Huang, Xiaolei; O'Shaughnessy, Ben; Pollard, Thomas

2008-03-01

Animals and fungi assemble a contractile ring of actin filaments and the motor protein myosin to separate into individual daughter cells during cytokinesis. We studied the mechanism of contractile ring assembly in fission yeast with high time resolution confocal microscopy, computational image analysis methods, and numerical simulations. Approximately 63 nodes containing myosin, broadly distributed around the cell equator, assembled into a ring through stochastic motions, making many starts, stops, and changes of direction as they condense into a ring. Estimates of node friction coefficients from the mean square displacement of stationary nodes imply forces for node movement are greater than ˜ 4 pN, similarly to forces by a few molecular motors. Skeletonization and topology analysis of images of cells expressing fluorescent actin filament markers showed transient linear elements extending in all directions from myosin nodes and establishing connections among them. We propose a model with traction between nodes depending on transient connections established by stochastic search and capture (``search, capture, pull and release''). Numerical simulations of the model using parameter values obtained from experiment succesfully condense nodes into a continuous ring.

Increased Ca2+ sensitivity of contractile elements via protein kinase C in alpha-toxin permeabilized SMA from young spontaneously hypertensive rats.

PubMed

Sasajima, H; Shima, H; Toyoda, Y; Kimura, K; Yoshikawa, A; Hano, T; Nishio, I

1997-10-01

The purpose of the present investigation was to examine the Ca2+ sensitivity of the contractile elements via protein kinase C (PKC) in superior mesenteric artery (SMA) from young (5-6 weeks old) spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY). Staphylococcal aureus alpha-toxin, which produces pores in the plasma membrane too small to allow passage of proteins such as PKC, was used to investigate the signal transduction system in vascular smooth muscle cells. We investigated the Ca2+ sensitivity of the contractile apparatus via PKC in intact and alpha-toxin skinned SMA from young SHR and WKY. In intact SMA, high K+ responses were not different between SHR and WKY. However, phorbol 12,13-dibutyrate (PDBu, a PKC activator) augmented high K(+)-evoked contractions and PKC inhibitors, such as 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H-7) and calphostin C, suppressed them more in SHR as compared with WKY. In alpha-toxin skinned SMA, the [Ca2+]i-force relationship curve was not significantly different between SHR and WKY. However, PDBu augmented [Ca2+]i-evoked contractions and PKC inhibitors suppressed them more in SHR than in WKY. These results suggest that the Ca2+ sensitivity of the contractile elements via PKC is significantly greater in prehypertensive SHR than in age-matched WKY. This abnormality in small muscular arteries may be involved in the pathogenesis of hypertension in SHR.

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

Troglitazone stimulates {beta}-arrestin-dependent cardiomyocyte contractility via the angiotensin II type 1{sub A} receptor

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

Tilley, Douglas G., E-mail: douglas.tilley@jefferson.edu; Center for Translational Medicine, Thomas Jefferson University; Nguyen, Anny D.

2010-06-11

Peroxisome proliferator-activated receptor {gamma} (PPAR{gamma}) agonists are commonly used to treat cardiovascular diseases, and are reported to have several effects on cardiovascular function that may be due to PPAR{gamma}-independent signaling events. Select angiotensin receptor blockers (ARBs) interact with and modulate PPAR{gamma} activity, thus we hypothesized that a PPAR{gamma} agonist may exert physiologic effects via the angiotensin II type 1{sub A} receptor (AT1{sub A}R). In AT1{sub A}R-overexpressing HEK 293 cells, both angiotensin II (Ang II) and the PPAR{gamma} agonist troglitazone (Trog) enhanced AT1{sub A}R internalization and recruitment of endogenous {beta}-arrestin1/2 ({beta}arr1/2) to the AT1{sub A}R. A fluorescence assay to measure diacylglycerolmore » (DAG) accumulation showed that although Ang II induced AT1{sub A}R-G{sub q} protein-mediated DAG accumulation, Trog had no impact on DAG generation. Trog-mediated recruitment of {beta}arr1/2 was selective to AT1{sub A}R as the response was prevented by an ARB- and Trog-mediated {beta}arr1/2 recruitment to {beta}1-adrenergic receptor ({beta}1AR) was not observed. In isolated mouse cardiomyocytes, Trog increased both % and rate of cell shortening to a similar extent as Ang II, effects which were blocked with an ARB. Additionally, these effects were found to be {beta}arr2-dependent, as cardiomyocytes isolated from {beta}arr2-KO mice showed blunted contractile responses to Trog. These findings show for the first time that the PPAR{gamma} agonist Trog acts at the AT1{sub A}R to simultaneously block G{sub q} protein activation and induce the recruitment of {beta}arr1/2, which leads to an increase in cardiomyocyte contractility.« less

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

Numerical investigation of perforated polymer microcantilever sensor for contractile behavior of cardiomyocytes

NASA Astrophysics Data System (ADS)

Khoa Nguyen, Trieu; Lee, Dong-Weon; Lee, Bong-Kee

2017-06-01

In this study, a numerical investigation of microcantilever sensors for detecting the contractile behavior of cardiomyocytes (CMs) was performed. Recently, a novel surface-patterned perforated SU-8 microcantilever sensor has been developed for the preliminary screening of cardiac toxicity. From the contractile motion of the CMs cultured on the microcantilever surface, a macroscopic bending of the microcantilever was obtained, which is considered to reflect a physiological change. As a continuation of the previous research, a novel numerical method based on a surface traction model was proposed and verified to further understand the bending behavior of the microcantilevers. Effects of various factors, including surface traction magnitude, focal area of CMs, and stiffness of microcantilever, on the bending displacement were investigated. From static and transient analyses, the focal area was found to be the most crucial factor. In addition, the current result can provide a design guideline for various micromechanical devices based on the same principle.

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

Effects of high- and low-velocity resistance training on the contractile properties of skeletal muscle fibers from young and older humans

PubMed Central

Larkin, Lisa M.; Cederna, Paul S.; Horowitz, Jeffrey F.; Alexander, Neil B.; Cole, Neil M.; Galecki, Andrzej T.; Chen, Shu; Nyquist, Linda V.; Carlson, Bruce M.; Faulkner, John A.; Ashton-Miller, James A.

2011-01-01

A two-arm, prospective, randomized, controlled trial study was conducted to investigate the effects of movement velocity during progressive resistance training (PRT) on the size and contractile properties of individual fibers from human vastus lateralis muscles. The effects of age and sex were examined by a design that included 63 subjects organized into four groups: young (20–30 yr) men and women, and older (65–80 yr) men and women. In each group, one-half of the subjects underwent a traditional PRT protocol that involved shortening contractions at low velocities against high loads, while the other half performed a modified PRT protocol that involved contractions at 3.5 times higher velocity against reduced loads. Muscles were sampled by needle biopsy before and after the 14-wk PRT program, and functional tests were performed on permeabilized individual fiber segments isolated from the biopsies. We tested the hypothesis that, compared with low-velocity PRT, high-velocity PRT results in a greater increase in the cross-sectional area, force, and power of type 2 fibers. Both types of PRT increased the cross-sectional area, force, and power of type 2 fibers by 8–12%, independent of the sex or age of the subject. Contrary to our hypothesis, the velocity at which the PRT was performed did not affect the fiber-level outcomes substantially. We conclude that, compared with low-velocity PRT, resistance training performed at velocities up to 3.5 times higher against reduced loads is equally effective for eliciting an adaptive response in type 2 fibers from human skeletal muscle. PMID:21799130

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).

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

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.

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

3D bioprinted functional and contractile cardiac tissue constructs

PubMed Central

Wang, Zhan; Lee, Sang Jin; Cheng, Heng-Jie; Yoo, James J.; Atala, Anthony

2018-01-01

Bioengineering of a functional cardiac tissue composed of primary cardiomyocytes has great potential for myocardial regeneration and in vitro tissue modeling. However, its applications remain limited because the cardiac tissue is a highly organized structure with unique physiologic, biomechanical, and electrical properties. In this study, we undertook a proof-of-concept study to develop a contractile cardiac tissue with cellular organization, uniformity, and scalability by using three-dimensional (3D) bioprinting strategy. Primary cardiomyocytes were isolated from infant rat hearts and suspended in a fibrin-based bioink to determine the priting capability for cardiac tissue engineering. This cell-laden hydrogel was sequentially printed with a sacrificial hydrogel and a supporting polymeric frame through a 300-μm nozzle by pressured air. Bioprinted cardiac tissue constructs had a spontaneous synchronous contraction in culture, implying in vitro cardiac tissue development and maturation. Progressive cardiac tissue development was confirmed by immunostaining for α-actinin and connexin 43, indicating that cardiac tissues were formed with uniformly aligned, dense, and electromechanically coupled cardiac cells. These constructs exhibited physiologic responses to known cardiac drugs regarding beating frequency and contraction forces. In addition, Notch signaling blockade significantly accelerated development and maturation of bioprinted cardiac tissues. Our results demonstrated the feasibility of bioprinting functional cardiac tissues that could be used for tissue engineering applications and pharmaceutical purposes. PMID:29452273

Intravital imaging of intestinal lacteals unveils lipid drainage through contractility

PubMed Central

Choe, Kibaek; Jang, Jeon Yeob; Park, Intae; Kim, Yeseul; Ahn, Soyeon; Park, Dae-Young; Hong, Young-Kwon; Alitalo, Kari; Koh, Gou Young; Kim, Pilhan

2015-01-01

Lacteals are lymphatic vessels located at the center of each intestinal villus and provide essential transport routes for lipids and other lipophilic molecules. However, it is unclear how absorbed molecules are transported through the lacteal. Here, we used reporter mice that express GFP under the control of the lymphatic-specific promoter Prox1 and a custom-built confocal microscope and performed intravital real-time visualization of the absorption and transport dynamics of fluorescence-tagged fatty acids (FAs) and various exogenous molecules in the intestinal villi in vivo. These analyses clearly revealed transepithelial absorption of these molecules via enterocytes, diffusive distribution over the lamina propria, and subsequent transport through lacteals. Moreover, we observed active contraction of lacteals, which seemed to be directly involved in dietary lipid drainage. Our analysis revealed that the smooth muscles that surround each lacteal are responsible for contractile dynamics and that lacteal contraction is ultimately controlled by the autonomic nervous system. These results indicate that the lacteal is a unique organ-specific lymphatic system and does not merely serve as a passive conduit but as an active pump that transports lipids. Collectively, using this efficient imaging method, we uncovered drainage of absorbed molecules in small intestinal villus lacteals and the involvement of lacteal contractibility. PMID:26436648

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.

Enhanced contractility of the rat stomach during suppression of angiotensin converting enzyme by captopril in vitro.

PubMed Central

Rani, R.; Rao, K. S.

1991-01-01

1. Intragastric pressure (IGP) was used as an index, of the effect of serosal application of captopril (SQ 14,225; D-3-mercapto-2-methylpropanoyl-L-proline) on the contractility of rat stomach in vitro. 2. Captopril, at concentrations greater than 0.3 microM, enhanced the spontaneous gastric motility (GM) in a concentration-dependent manner whereas concentrations less than 0.3 microM selectively potentiated 4 nM bradykinin (BK)-evoked gastric contractions without significantly affecting the spontaneous GM. 3. The kallikrein inhibitor, aprotinin (100 u ml-1), markedly antagonized the enhanced GM to 1.4 microM captopril and BK (4 nM)-evoked contractions, without affecting the contractions evoked by angiotensin 1 (10 nM) and acetylcholine (0.4 microM). The angiotensin II antagonist, saralasin (50 microM) failed to mimic aprotinin. 4. The enhanced GM to captopril was markedly inhibited by tetrodotoxin (1 microM), and partially inhibited by atropine (1 microM). 5. These results indicate that in vitro, captopril (greater than 0.3 microM) enhances gastric contractility through kininase/ACE inhibitory action, presumably by increasing the concentration of undegraded tissue kinins and substance P. This motor response seems to be predominantly due to activation of the cholinergic neurones but non-cholinergic excitatory neurones are also involved. PMID:1713107

Contractile forces at tricellular contacts modulate epithelial organization and monolayer integrity

PubMed Central

Salomon, Julie; Gaston, Cécile; Magescas, Jérémy; Duvauchelle, Boris; Canioni, Danielle; Sengmanivong, Lucie; Mayeux, Adeline; Michaux, Grégoire; Campeotto, Florence; Lemale, Julie; Viala, Jérôme; Poirier, Françoise; Minc, Nicolas; Schmitz, Jacques; Brousse, Nicole; Ladoux, Benoit; Goulet, Olivier; Delacour, Delphine

2017-01-01

Monolayered epithelia are composed of tight cell assemblies that ensure polarized exchanges. EpCAM, an unconventional epithelial-specific cell adhesion molecule, is assumed to modulate epithelial morphogenesis in animal models, but little is known regarding its cellular functions. Inspired by the characterization of cellular defects in a rare EpCAM-related human intestinal disease, we find that the absence of EpCAM in enterocytes results in an aberrant apical domain. In the course of this pathological state, apical translocation towards tricellular contacts (TCs) occurs with striking tight junction belt displacement. These unusual cell organization and intestinal tissue defects are driven by the loss of actomyosin network homoeostasis and contractile activity clustering at TCs, yet is reversed by myosin-II inhibitor treatment. This study reveals that adequate distribution of cortical tension is crucial for individual cell organization, but also for epithelial monolayer maintenance. Our data suggest that EpCAM modulation protects against epithelial dysplasia and stabilizes human tissue architecture. PMID:28084299

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.

Transcellular tunnel dynamics: Control of cellular dewetting by actomyosin contractility and I-BAR proteins.

PubMed

Lemichez, Emmanuel; Gonzalez-Rodriguez, David; Bassereau, Patricia; Brochard-Wyart, Françoise

2013-03-01

Dewetting is the spontaneous withdrawal of a liquid film from a non-wettable surface by nucleation and growth of dry patches. Two recent reports now propose that the principles of dewetting explain the physical phenomena underpinning the opening of transendothelial cell macroaperture (TEM) tunnels, referred to as cellular dewetting. This was discovered by studying a group of bacterial toxins endowed with the property of corrupting actomyosin cytoskeleton contractility. For both liquid and cellular dewetting, the growth of holes is governed by a competition between surface forces and line tension. We also discuss how the dynamics of TEM opening and closure represent remarkable systems to investigate actin cytoskeleton regulation by sensors of plasma membrane curvature and investigate the impact on membrane tension and the role of TEM in vascular dysfunctions. Copyright © 2013 Soçiété Française des Microscopies and Soçiété de Biologie Cellulaire de France.

Akt2 knockout alleviates prolonged caloric restriction-induced change in cardiac contractile function through regulation of autophagy.

PubMed

Zhang, Yingmei; Han, Xuefeng; Hu, Nan; Huff, Anna F; Gao, Feng; Ren, Jun

2014-06-01

Caloric restriction leads to changes in heart geometry and function although the underlying mechanism remains elusive. Autophagy, a conserved pathway for degradation of intracellular proteins and organelles, preserves energy and nutrient in the face of caloric insufficiency. This study was designed to examine the role of Akt2 in prolonged caloric restriction-induced change in cardiac homeostasis and the underlying mechanism(s) involved. Wild-type (WT) and Akt2 knockout mice were calorie restricted (by 40%) for 30weeks. Echocardiographic, cardiomyocyte contractile and intracellular Ca(2+) properties, autophagy and its regulatory proteins were evaluated. Caloric restriction compromised echocardiographic indices (decreased left ventricular mass, left ventricular diameters and cardiac output), cardiomyocyte contractile and intracellular Ca(2+) properties associated with dampened SERCA2a phosphorylation, upregulated phospholamban and autophagy (Beclin-1, Atg7, LC3BII-to-LC3BI ratio), increased autophagy adaptor protein p62, elevated phosphorylation of AMPK, Akt2 and the Akt downstream signal molecule TSC2, the effects of which with the exception of autophagy protein markers (Beclin-1, Atg7, LC3B) and AMPK were mitigated or significantly alleviated by Akt2 knockout. Lysosomal inhibition using bafilomycin A1 negated Akt2 knockout-induced protective effect on p62. Evaluation of downstream signaling molecules of Akt and AMPK including mTOR and ULK1 revealed that caloric restriction suppressed and promoted phosphorylation of mTOR and ULK1, respectively, without affecting total mTOR and ULK1 expression. Akt2 knockout significantly augmented caloric restriction-induced responses on mTOR and ULK1. Taken together, these data suggest a beneficial role of Akt2 knockout in preservation of cardiac homeostasis against prolonged caloric restriction-induced pathological changes possibly through facilitating autophagy. This article is part of a Special Issue entitled "Protein Quality

The fission yeast cytokinetic contractile ring regulates septum shape and closure

PubMed Central

Thiyagarajan, Sathish; Munteanu, Emilia Laura; Arasada, Rajesh; Pollard, Thomas D.; O'Shaughnessy, Ben

2015-01-01

ABSTRACT During cytokinesis, fission yeast and other fungi and bacteria grow a septum that divides the cell in two. In fission yeast closure of the circular septum hole by the β-glucan synthases (Bgs) and other glucan synthases in the plasma membrane is tightly coupled to constriction of an actomyosin contractile ring attached to the membrane. It is unknown how septum growth is coordinated over scales of several microns to maintain septum circularity. Here, we documented the shapes of ingrowing septum edges by measuring the roughness of the edges, a measure of the deviation from circularity. The roughness was small, with spatial correlations indicative of spatially coordinated growth. We hypothesized that Bgs-mediated septum growth is mechanosensitive and coupled to contractile ring tension. A mathematical model showed that ring tension then generates almost circular septum edges by adjusting growth rates in a curvature-dependent fashion. The model reproduced experimental roughness statistics and showed that septum synthesis sets the mean closure rate. Our results suggest that the fission yeast cytokinetic ring tension does not set the constriction rate but regulates septum closure by suppressing roughness produced by inherently stochastic molecular growth processes. PMID:26240178

The fission yeast cytokinetic contractile ring regulates septum shape and closure.

PubMed

Thiyagarajan, Sathish; Munteanu, Emilia Laura; Arasada, Rajesh; Pollard, Thomas D; O'Shaughnessy, Ben

2015-10-01

During cytokinesis, fission yeast and other fungi and bacteria grow a septum that divides the cell in two. In fission yeast closure of the circular septum hole by the β-glucan synthases (Bgs) and other glucan synthases in the plasma membrane is tightly coupled to constriction of an actomyosin contractile ring attached to the membrane. It is unknown how septum growth is coordinated over scales of several microns to maintain septum circularity. Here, we documented the shapes of ingrowing septum edges by measuring the roughness of the edges, a measure of the deviation from circularity. The roughness was small, with spatial correlations indicative of spatially coordinated growth. We hypothesized that Bgs-mediated septum growth is mechanosensitive and coupled to contractile ring tension. A mathematical model showed that ring tension then generates almost circular septum edges by adjusting growth rates in a curvature-dependent fashion. The model reproduced experimental roughness statistics and showed that septum synthesis sets the mean closure rate. Our results suggest that the fission yeast cytokinetic ring tension does not set the constriction rate but regulates septum closure by suppressing roughness produced by inherently stochastic molecular growth processes. © 2015. Published by The Company of Biologists Ltd.

Facilitated ethanol metabolism promotes cardiomyocyte contractile dysfunction through autophagy in murine hearts.

PubMed

Guo, Rui; Hu, Nan; Kandadi, Machender R; Ren, Jun

2012-04-01

Chronic drinking leads to myocardial contractile dysfunction where ethanol metabolism plays an essential role. Acetaldehyde, the main ethanol metabolite, mediates alcohol-induced cell injury although the underlying mechanism is still elusive. This study was designed to examine the mechanism involved in accelerated ethanol metabolism-induced cardiac defect with a focus on autophagy. Wild-type FVB and cardiac-specific overexpression of alcohol dehydrogenase mice were placed on a 4% nutrition-balanced alcohol diet for 8 weeks. Myocardial histology, immunohistochemistry, autophagy markers and signal molecules were examined. Expression of micro RNA miR-30a, a potential target of Beclin 1, was evaluated by real-time PCR. Chronic alcohol intake led to cardiac acetaldehyde accumulation, hypertrophy and overt autophagosome accumulation (LC3-II and Atg7), the effect of which was accentuated by ADH. Signaling molecules governing autophagy initiation including class III PtdIns3K, phosphorylation of mTOR and p70S6K were enhanced and dampened, respectively, following alcohol intake. These alcohol-induced signaling responses were augmented by ADH. ADH accentuated or unmasked alcohol-induced downregulation of Bcl-2, Bcl-xL and MiR-30a. Interestingly, ADH aggravated alcohol-induced p62 accumulation. Autophagy inhibition using 3-MA abolished alcohol-induced cardiomyocyte contractile anomalies. Moreover, acetaldehyde led to cardiomyocyte contractile dysfunction and autophagy induction, which was ablated by 3-MA. Ethanol or acetaldehyde increased GFP-LC3 puncta in H9c2 cells, the effect of which was ablated by 3-MA but unaffected by lysosomal inhibition using bafilomycin A(1), E64D and pepstatin A. In summary, these data suggested that facilitated acetaldehyde production via ADH following alcohol intake triggered cardiac autophagosome formation along with impaired lysosomal degradation, en route to myocardial defect.

Visualization and contractile activity of cochlear pericytes in the capillaries of the spiral ligament.