Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 15 de 15
Filtrar
1.
J Physiol ; 597(17): 4521-4531, 2019 09.
Artigo em Inglês | MEDLINE | ID: mdl-31314138

RESUMO

Titin functions as a molecular spring, and cardiomyocytes are able, through splicing, to control the length of titin. We hypothesized that together with diastolic [Ca2+ ], titin-based stretch pre-activates cardiomyocytes during diastole and is a major determinant of force production in the subsequent contraction. Through this mechanism titin would play an important role in active force development and length-dependent activation. Mutations in the splicing factor RNA binding motif protein 20 (RBM20) result in expression of large, highly compliant titin isoforms. We measured single cardiomyocyte work loops that mimic the cardiac cycle in wild-type (WT) and heterozygous (HET) RBM20-deficient rats. In addition, we studied the role of diastolic [Ca2+ ] in membrane-permeabilized WT and HET cardiomyocytes. Intact cardiomyocytes isolated from HET left ventricles were unable to produce normal levels of work (55% of WT) at low pacing frequencies, but this difference disappeared at high pacing frequencies. Length-dependent activation (force-sarcomere length relationship) was blunted in HET cardiomyocytes, but the force-end-diastolic force relationship was not different between HET and WT cardiomyocytes. To delineate the effects of diastolic [Ca2+ ] and titin pre-activation on force generation, measurements were performed in detergent-permeabilized cardiomyocytes. Cardiac twitches were simulated by transiently exposing permeabilized cardiomyocytes to 2 µm Ca2+ . Increasing diastolic [Ca2+ ] from 1 to 80 nm increased force development twofold in WT. Higher diastolic [Ca2+ ] was needed in HET. These findings are consistent with our hypothesis that pre-activation increases active force development. Highly compliant titin allows cells to function at higher diastolic [Ca2+ ].


Assuntos
Cálcio/metabolismo , Conectina/metabolismo , Diástole/fisiologia , Contração Miocárdica/fisiologia , Miócitos Cardíacos/metabolismo , Animais , Feminino , Ventrículos do Coração/metabolismo , Ventrículos do Coração/fisiopatologia , Heterozigoto , Masculino , Proteínas Musculares/metabolismo , Isoformas de Proteínas/metabolismo , Proteínas de Ligação a RNA/metabolismo , Ratos , Ratos Endogâmicos BN , Ratos Sprague-Dawley , Sarcômeros/metabolismo , Sarcômeros/fisiologia
2.
Proc Natl Acad Sci U S A ; 112(50): E7003-12, 2015 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-26621701

RESUMO

Diastolic dysfunction is general to all idiopathic dilated (IDCM) and hypertrophic cardiomyopathy (HCM) patients. Relaxation deficits may result from increased actin-myosin formation during diastole due to altered tropomyosin position, which blocks myosin binding to actin in the absence of Ca(2+). We investigated whether ADP-stimulated force development (without Ca(2+)) can be used to reveal changes in actin-myosin blockade in human cardiomyopathy cardiomyocytes. Cardiac samples from HCM patients, harboring thick-filament (MYH7mut, MYBPC3mut) and thin-filament (TNNT2mut, TNNI3mut) mutations, and IDCM were compared with sarcomere mutation-negative HCM (HCMsmn) and nonfailing donors. Myofilament ADP sensitivity was higher in IDCM and HCM compared with donors, whereas it was lower for MYBPC3. Increased ADP sensitivity in IDCM, HCMsmn, and MYH7mut was caused by low phosphorylation of myofilament proteins, as it was normalized to donors by protein kinase A (PKA) treatment. Troponin exchange experiments in a TNNT2mut sample corrected the abnormal actin-myosin blockade. In MYBPC3trunc samples, ADP sensitivity highly correlated with cardiac myosin-binding protein-C (cMyBP-C) protein level. Incubation of cardiomyocytes with cMyBP-C antibody against the actin-binding N-terminal region reduced ADP sensitivity, indicative of cMyBP-C's role in actin-myosin regulation. In the presence of Ca(2+), ADP increased myofilament force development and sarcomere stiffness. Enhanced sarcomere stiffness in sarcomere mutation-positive HCM samples was irrespective of the phosphorylation background. In conclusion, ADP-stimulated contraction can be used as a tool to study how protein phosphorylation and mutant proteins alter accessibility of myosin binding on actin. In the presence of Ca(2+), pathologic [ADP] and low PKA-phosphorylation, high actin-myosin formation could contribute to the impaired myocardial relaxation observed in cardiomyopathies.


Assuntos
Difosfato de Adenosina/farmacologia , Cardiopatias/metabolismo , Contração Miocárdica/efeitos dos fármacos , Proteínas Quinases Dependentes de AMP Cíclico/metabolismo , Humanos , Fosforilação
3.
J Physiol ; 595(14): 4597-4610, 2017 07 15.
Artigo em Inglês | MEDLINE | ID: mdl-28485491

RESUMO

KEY POINTS: This paper describes a novel model that allows exploration of matrix-induced cardiomyocyte adaptations independent of the passive effect of matrix rigidity on cardiomyocyte function. Detachment of adult cardiomyocytes from the matrix enables the study of matrix effects on cell shortening, Ca2+ handling and myofilament function. Cell shortening and Ca2+ handling are altered in cardiomyocytes cultured for 24 h on a stiff matrix. Matrix stiffness-impaired cardiomyocyte contractility is reversed upon normalization of extracellular stiffness. Matrix stiffness-induced reduction in unloaded shortening is more pronounced in cardiomyocytes isolated from obese ZSF1 rats with heart failure with preserved ejection fraction compared to lean ZSF1 rats. ABSTRACT: Extracellular matrix (ECM) stiffening is a key element of cardiac disease. Increased rigidity of the ECM passively inhibits cardiac contraction, but if and how matrix stiffening also actively alters cardiomyocyte contractility is incompletely understood. In vitro models designed to study cardiomyocyte-matrix interaction lack the possibility to separate passive inhibition by a stiff matrix from active matrix-induced alterations of cardiomyocyte properties. Here we introduce a novel experimental model that allows exploration of cardiomyocyte functional alterations in response to matrix stiffening. Adult rat cardiomyocytes were cultured for 24 h on matrices of tuneable stiffness representing the healthy and the diseased heart and detached from their matrix before functional measurements. We demonstrate that matrix stiffening, independent of passive inhibition, reduces cell shortening and Ca2+ handling but does not alter myofilament-generated force. Additionally, detachment of adult cultured cardiomyocytes allowed the transfer of cells from one matrix to another. This revealed that stiffness-induced cardiomyocyte changes are reversed when matrix stiffness is normalized. These matrix stiffness-induced changes in cardiomyocyte function could not be explained by adaptation in the microtubules. Additionally, cardiomyocytes isolated from stiff hearts of the obese ZSF1 rat model of heart failure with preserved ejection fraction show more pronounced reduction in unloaded shortening in response to matrix stiffening. Taken together, we introduce a method that allows evaluation of the influence of ECM properties on cardiomyocyte function separate from the passive inhibitory component of a stiff matrix. As such, it adds an important and physiologically relevant tool to investigate the functional consequences of cardiomyocyte-matrix interactions.


Assuntos
Cálcio/fisiologia , Matriz Extracelular/fisiologia , Miócitos Cardíacos/fisiologia , Miofibrilas/fisiologia , Animais , Diabetes Mellitus/fisiopatologia , Masculino , Obesidade/fisiopatologia , Ratos Wistar
4.
Eur J Clin Invest ; 46(4): 362-74, 2016 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-26842371

RESUMO

BACKGROUND: To maintain the balance between the demand of the body and supply (cardiac output), cardiac performance is tightly regulated via the parasympathetic and sympathetic nervous systems. In heart failure, cardiac output (supply) is decreased due to pathologic remodelling of the heart. To meet the demands of the body, the sympathetic system is activated and catecholamines stimulate ß-adrenergic receptors (ß-ARs) to increase contractile performance and cardiac output. Although this is beneficial in the acute phase, chronic ß-ARs stimulation initiates a cascade of alterations at the cellular level, resulting in a diminished contractile performance of the heart. MATERIALS AND METHODS: This narrative review includes results from previously published systematic reviews and clinical and basic research publications obtained via PubMed up to May 2015. RESULTS: We discuss the alterations that occur during sustained ß-AR stimulation in diseased myocardium and emphasize the consequences of ß-AR overstimulation for cardiac function. In addition, current treatment options as well as future therapeutic strategies to treat patients with heart failure to normalize consequences of ß-AR overstimulation are discussed. CONCLUSIONS: The heart is able to protect itself from chronic stimulation of the ß-ARs via desensitization and reduced membrane availability of the ß-ARs. However, ultimately this leads to an impaired downstream signalling and decreased protein kinase A (PKA)-mediated protein phosphorylation. ß-blockers are widely used to prevent ß-AR overstimulation and restore ß-ARs in the failing hearts. However, novel and more specific therapeutic treatments are needed to improve treatment of HF in the future.


Assuntos
Cardiomiopatia Hipertrófica/fisiopatologia , Insuficiência Cardíaca/fisiopatologia , Receptores Adrenérgicos beta/fisiologia , Cardiomiopatia Hipertrófica/etiologia , Cardiomiopatia Hipertrófica/terapia , Proteínas Quinases Dependentes de AMP Cíclico/metabolismo , Insuficiência Cardíaca/etiologia , Insuficiência Cardíaca/terapia , Humanos , Fosforilação/fisiologia , Transdução de Sinais/fisiologia
5.
J Physiol ; 593(17): 3899-916, 2015 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-26096258

RESUMO

Diastolic dysfunction in heart failure patients is evident from stiffening of the passive properties of the ventricular wall. Increased actomyosin interactions may significantly limit diastolic capacity, however, direct evidence is absent. From experiments at the cellular and whole organ level, in humans and rats, we show that actomyosin-related force development contributes significantly to high diastolic stiffness in environments where high ADP and increased diastolic [Ca(2+) ] are present, such as the failing myocardium. Our basal study provides a mechanical mechanism which may partly underlie diastolic dysfunction. Heart failure (HF) with diastolic dysfunction has been attributed to increased myocardial stiffness that limits proper filling of the ventricle. Altered cross-bridge interaction may significantly contribute to high diastolic stiffness, but this has not been shown thus far. Cross-bridge interactions are dependent on cytosolic [Ca(2+) ] and the regeneration of ATP from ADP. Depletion of myocardial energy reserve is a hallmark of HF leading to ADP accumulation and disturbed Ca(2+) handling. Here, we investigated if ADP elevation in concert with increased diastolic [Ca(2+) ] promotes diastolic cross-bridge formation and force generation and thereby increases diastolic stiffness. ADP dose-dependently increased force production in the absence of Ca(2+) in membrane-permeabilized cardiomyocytes from human hearts. Moreover, physiological levels of ADP increased actomyosin force generation in the presence of Ca(2+) both in human and rat membrane-permeabilized cardiomyocytes. Diastolic stress measured at physiological lattice spacing and 37°C in the presence of pathological levels of ADP and diastolic [Ca(2+) ] revealed a 76 ± 1% contribution of cross-bridge interaction to total diastolic stress in rat membrane-permeabilized cardiomyocytes. Inhibition of creatine kinase (CK), which increases cytosolic ADP, in enzyme-isolated intact rat cardiomyocytes impaired diastolic re-lengthening associated with diastolic Ca(2+) overload. In isolated Langendorff-perfused rat hearts, CK inhibition increased ventricular stiffness only in the presence of diastolic [Ca(2+) ]. We propose that elevations of intracellular ADP in specific types of cardiac disease, including those where myocardial energy reserve is limited, contribute to diastolic dysfunction by recruiting cross-bridges, even at low Ca(2+) , and thereby increase myocardial stiffness.


Assuntos
Difosfato de Adenosina/fisiologia , Cálcio/fisiologia , Coração/fisiologia , Actomiosina/fisiologia , Animais , Cardiomiopatia Dilatada/fisiopatologia , Creatina Quinase/antagonistas & inibidores , Creatina Quinase/fisiologia , Diástole , Humanos , Iodoacetamida/farmacologia , Contração Isométrica , Masculino , Miócitos Cardíacos/fisiologia , Ratos Wistar
6.
Pflugers Arch ; 467(6): 1303-17, 2015 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-25010737

RESUMO

Hypertrophic cardiomyopathy (HCM), the most common genetic cardiac disorder, is frequently caused by mutations in MYBPC3, encoding cardiac myosin-binding protein C (cMyBP-C). Moreover, HCM is the leading cause of sudden cardiac death (SCD) in young athletes. Interestingly, SCD is more likely to occur in male than in female athletes. However, the pathophysiological mechanisms leading to sex-specific differences are poorly understood. Therefore, we studied the effect of sex and exercise on functional properties of the heart and sarcomeres in mice carrying a MYBPC3 point mutation (G > A transition in exon 6) associated with human HCM. Echocardiography followed by isometric force measurements in left ventricular (LV) membrane-permeabilized cardiomyocytes was performed in wild-type (WT) and heterozygous (HET) knock-in mice of both sex (N = 5 per group) in sedentary mice and mice that underwent an 8-week voluntary wheel-running exercise protocol. Isometric force measurements in single cardiomyocytes revealed a lower maximal force generation (F max) of the sarcomeres in male sedentary HET (13.0 ± 1.1 kN/m(2)) compared to corresponding WT (18.4 ± 1.8 kN/m(2)) male mice. Exercise induced a higher F max in HET male mice, while it did not affect HET females. Interestingly, a low cardiac troponin I bisphosphorylation, increased myofilament Ca(2+)-sensitivity, and LV hypertrophy were particularly observed in exercised HET females. In conclusion, in sedentary animals, contractile differences are seen between male and female HET mice. Male and female HET hearts adapted differently to a voluntary exercise protocol, indicating that physiological stimuli elicit a sexually dimorphic cardiac response in heterozygous MYBPC3-targeted knock-in mice.


Assuntos
Adaptação Fisiológica , Cardiomiopatia Hipertrófica/fisiopatologia , Proteínas de Transporte/genética , Esforço Físico , Animais , Cálcio/metabolismo , Cardiomiopatia Hipertrófica/genética , Cardiomiopatia Hipertrófica/metabolismo , Células Cultivadas , Feminino , Masculino , Camundongos , Mutação , Contração Miocárdica , Miócitos Cardíacos/metabolismo , Miócitos Cardíacos/fisiologia , Fatores Sexuais , Troponina I/metabolismo
7.
Circ Res ; 112(4): 633-9, 2013 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-23277198

RESUMO

RATIONALE: Cardiac myosin-binding protein C (cMyBP-C) regulates cross-bridge cycling kinetics and, thereby, fine-tunes the rate of cardiac muscle contraction and relaxation. Its effects on cardiac kinetics are modified by phosphorylation. Three phosphorylation sites (Ser275, Ser284, and Ser304) have been identified in vivo, all located in the cardiac-specific M-domain of cMyBP-C. However, recent work has shown that up to 4 phosphate groups are present in human cMyBP-C. OBJECTIVE: To identify and characterize additional phosphorylation sites in human cMyBP-C. METHODS AND RESULTS: Cardiac MyBP-C was semipurified from human heart tissue. Tandem mass spectrometry analysis identified a novel phosphorylation site on serine 133 in the proline-alanine-rich linker sequence between the C0 and C1 domains of cMyBP-C. Unlike the known sites, Ser133 was not a target of protein kinase A. In silico kinase prediction revealed glycogen synthase kinase 3ß (GSK3ß) as the most likely kinase to phosphorylate Ser133. In vitro incubation of the C0C2 fragment of cMyBP-C with GSK3ß showed phosphorylation on Ser133. In addition, GSK3ß phosphorylated Ser304, although the degree of phosphorylation was less compared with protein kinase A-induced phosphorylation at Ser304. GSK3ß treatment of single membrane-permeabilized human cardiomyocytes significantly enhanced the maximal rate of tension redevelopment. CONCLUSIONS: GSK3ß phosphorylates cMyBP-C on a novel site, which is positioned in the proline-alanine-rich region and increases kinetics of force development, suggesting a noncanonical role for GSK3ß at the sarcomere level. Phosphorylation of Ser133 in the linker domain of cMyBP-C may be a novel mechanism to regulate sarcomere kinetics.


Assuntos
Proteínas de Transporte/metabolismo , Quinase 3 da Glicogênio Sintase/metabolismo , Contração Miocárdica/fisiologia , Sequência de Aminoácidos , Cardiomiopatia Dilatada/metabolismo , Cardiomiopatia Dilatada/patologia , Proteínas de Transporte/química , Glicogênio Sintase Quinase 3 beta , Ventrículos do Coração/química , Humanos , Dados de Sequência Molecular , Isquemia Miocárdica/metabolismo , Isquemia Miocárdica/patologia , Fragmentos de Peptídeos/metabolismo , Fosforilação , Fosfosserina/metabolismo , Processamento de Proteína Pós-Traducional , Estrutura Terciária de Proteína , Proteínas Recombinantes/metabolismo , Sarcômeros/fisiologia , Espectrometria de Massas em Tandem
8.
Circ Res ; 112(11): 1491-505, 2013 May 24.
Artigo em Inglês | MEDLINE | ID: mdl-23508784

RESUMO

RATIONALE: High-myofilament Ca(2+) sensitivity has been proposed as a trigger of disease pathogenesis in familial hypertrophic cardiomyopathy (HCM) on the basis of in vitro and transgenic mice studies. However, myofilament Ca(2+) sensitivity depends on protein phosphorylation and muscle length, and at present, data in humans are scarce. OBJECTIVE: To investigate whether high myofilament Ca(2+) sensitivity and perturbed length-dependent activation are characteristics for human HCM with mutations in thick and thin filament proteins. METHODS AND RESULTS: Cardiac samples from patients with HCM harboring mutations in genes encoding thick (MYH7, MYBPC3) and thin (TNNT2, TNNI3, TPM1) filament proteins were compared with sarcomere mutation-negative HCM and nonfailing donors. Cardiomyocyte force measurements showed higher myofilament Ca(2+) sensitivity in all HCM samples and low phosphorylation of protein kinase A (PKA) targets compared with donors. After exogenous PKA treatment, myofilament Ca(2+) sensitivity was similar (MYBPC3mut, TPM1mut, sarcomere mutation-negative HCM), higher (MYH7mut, TNNT2mut), or even significantly lower (TNNI3mut) compared with donors. Length-dependent activation was significantly smaller in all HCM than in donor samples. PKA treatment increased phosphorylation of PKA-targets in HCM myocardium and normalized length-dependent activation to donor values in sarcomere mutation-negative HCM and HCM with truncating MYBPC3 mutations but not in HCM with missense mutations. Replacement of mutant by wild-type troponin in TNNT2mut and TNNI3mut corrected length-dependent activation to donor values. CONCLUSIONS: High-myofilament Ca(2+) sensitivity is a common characteristic of human HCM and partly reflects hypophosphorylation of PKA targets compared with donors. Length-dependent sarcomere activation is perturbed by missense mutations, possibly via posttranslational modifications other than PKA hypophosphorylation or altered protein-protein interactions, and represents a common pathomechanism in HCM.


Assuntos
Cardiomiopatia Hipertrófica/genética , Cardiomiopatia Hipertrófica/patologia , Miofibrilas/patologia , Miofibrilas/fisiologia , Sarcômeros/patologia , Sarcômeros/fisiologia , Adolescente , Adulto , Idoso , Animais , Cálcio/metabolismo , Miosinas Cardíacas/genética , Cardiomiopatia Hipertrófica/fisiopatologia , Proteínas de Transporte/genética , Proteínas Quinases Dependentes de AMP Cíclico/metabolismo , Feminino , Humanos , Contração Isométrica/fisiologia , MAP Quinase Quinase Quinases/genética , Masculino , Camundongos , Pessoa de Meia-Idade , Mutação de Sentido Incorreto , Contração Miocárdica/fisiologia , Miocárdio/metabolismo , Miocárdio/patologia , Cadeias Pesadas de Miosina/genética , Fosforilação/fisiologia , Proteínas Serina-Treonina Quinases , Tropomiosina/genética , Troponina T/genética , Adulto Jovem
9.
J Educ Health Promot ; 12: 282, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37849852

RESUMO

BACKGROUND: Since living with a person with a chronic illness in the family can affect the mental state of students, it is necessary to help students by determining and increasing predictors of resilience, followed by increasing their resilience and self-esteem. It protects them from experiencing physical, mental, and educational problems. Aim of this study was determining of predictive level of social support and self-esteem with resilience in students of University of Medical Sciences. MATERIALS AND METHODS: This cross-sectional, descriptive, analytic study was conducted in 2019 on 220 students of University of Medical Sciences, Ardabil, Iran. The statistical population included 3500 students. Purposeful sampling was performed on students who were studying and had a chronic patient in the family. Demographic, social support, resilience, and self-esteem questionnaires were used to collect data. To analyze the results, the mean, standard deviation, Pearson's correlation test, Kolmogorov-Smirnov test, and linear regression test were used. RESULTS: Students had a high mean social support, resilience, and self-esteem. The results showed that the correlation coefficient between resilience and social support was 0.411, and also, the correlation between resilience and self-esteem was 0.396. The results showed that self-esteem had a greater positive effect on resilience than perceived social support. CONCLUSION: The present study concluded that the variables of social support and self-esteem had a direct relationship with students' resilience. Based on this, steps can be taken to strengthen and improve students' resilience by improving the perceived support and self-esteem of students.

10.
Am J Physiol Heart Circ Physiol ; 301(3): H1080-9, 2011 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-21685265

RESUMO

Myocardial infarction (MI) is associated with endothelial dysfunction resulting in an imbalance in endothelium-derived vasodilators and vasoconstrictors. We have previously shown that despite increased endothelin (ET) plasma levels, the coronary vasoconstrictor effect of endogenous ET is abolished after MI. In normal swine, nitric oxide (NO) and prostanoids modulate the vasoconstrictor effect of ET. In light of the interaction among NO, prostanoids, and ET combined with endothelial dysfunction present after MI, we investigated this interaction in control of coronary vasomotor tone in the remote noninfarcted myocardium after MI. Studies were performed in chronically instrumented swine (18 normal swine; 13 swine with MI) at rest and during treadmill exercise. Furthermore, endothelial nitric oxide synthase (eNOS) and cyclooxygenase protein levels were measured in the anterior (noninfarcted) wall of six normal and six swine with MI. eNOS inhibition with N(ω)-nitro-L-arginine (L-NNA) and cyclooxygenase inhibition with indomethacin each resulted in coronary vasoconstriction at rest and during exercise, as evidenced by a decrease in coronary venous oxygen levels. The effect of l-NNA was slightly decreased in swine with MI, although eNOS expression was not altered. Conversely, in accordance with the unaltered expression of cyclooxygenase-1 after MI, the effect of indomethacin was similar in normal and MI swine. L-NNA enhanced the vasodilator effect of the ET(A/B) receptor blocker tezosentan but exclusively during exercise in both normal and MI swine. Interestingly, this effect of L-NNA was blunted in MI compared with normal swine. In contrast, whereas indomethacin increased the vasodilator effect of tezosentan only during exercise in normal swine, indomethacin unmasked a coronary vasodilator effect of tezosentan in MI swine both at rest and during exercise. In conclusion, the present study shows that endothelial control of the coronary vasculature is altered in post-MI remodeled myocardium. Thus the overall vasodilator influences of NO as well as its inhibition of the vasoconstrictor influence of ET on the coronary resistance vessels were reduced after MI. In contrast, while the overall prostanoid vasodilator influence was maintained, its inhibition of ET vasoconstrictor influences was enhanced in post-MI remote myocardium.


Assuntos
Vasos Coronários/metabolismo , Endotelinas/metabolismo , Infarto do Miocárdio/metabolismo , Prostaglandinas/metabolismo , Vasoconstrição , Vasodilatação , Animais , Vasos Coronários/efeitos dos fármacos , Vasos Coronários/fisiopatologia , Ciclo-Oxigenase 1/metabolismo , Ciclo-Oxigenase 2/metabolismo , Inibidores de Ciclo-Oxigenase/farmacologia , Modelos Animais de Doenças , Antagonistas dos Receptores de Endotelina , Inibidores Enzimáticos/farmacologia , Feminino , Masculino , Infarto do Miocárdio/fisiopatologia , Óxido Nítrico/metabolismo , Óxido Nítrico Sintase Tipo III/antagonistas & inibidores , Óxido Nítrico Sintase Tipo III/metabolismo , Consumo de Oxigênio , Esforço Físico , Receptores de Endotelina/metabolismo , Suínos , Vasoconstrição/efeitos dos fármacos , Vasodilatação/efeitos dos fármacos , Vasodilatadores/farmacologia , Disfunção Ventricular Esquerda/metabolismo , Disfunção Ventricular Esquerda/fisiopatologia
11.
J Colloid Interface Sci ; 308(2): 344-50, 2007 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-17257614

RESUMO

Accurate measurement of electrophoretic mobility for gas bubbles is a challenging task as it requires the creation of a desired number of very small air bubbles to ensure negligible rise velocities during the course of the measurement. Here, we report a simple and reliable method for generating stable dispersions of "nano-bubbles." Preparation of such dispersions relies on the nucleation of nano-bubbles in solutions supersaturated with gas. Electrophoretic mobility of these nano-bubbles is determined by the ZetaPALS technique (Brookhaven Instruments) using Uzgiris electrodes coated with palladium. The Smoluchowski limit is assumed in the calculation of zeta potentials. In regard to reproducibility and reliability, this novel method shows a clear advantage over other existing techniques of zeta potential measurement for bubbles.

12.
Cardiovasc Res ; 111(1): 66-73, 2016 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-27037258

RESUMO

AIMS: A single isolated cardiomyocyte is the smallest functional unit of the heart. Yet, all single isolated cardiomyocyte experiments have been limited by the lack of proper methods that could reproduce a physiological cardiac cycle. We aimed to investigate the contractile properties of a single cardiomyocyte that correctly mimic the cardiac cycle. METHODS AND RESULTS: By adjusting the parameters of the feedback loop, using a suitably engineered feedback system and recording the developed force and the length of a single rat cardiomyocyte during contraction and relaxation, we were able to construct force-length (FL) relations analogous to the pressure-volume (PV) relations at the whole heart level. From the cardiac loop graphs, we obtained, for the first time, the power generated by one single cardiomyocyte. CONCLUSION: Here, we introduce a new approach that by combining mechanics, electronics, and a new type optical force transducer can measure the FL relationship of a single isolated cardiomyocyte undergoing a mechanical loop that mimics the PV cycle of a beating heart.


Assuntos
Diástole , Mecanotransdução Celular , Miócitos Cardíacos/fisiologia , Sístole , Transdutores de Pressão , Algoritmos , Animais , Desenho de Equipamento , Retroalimentação Fisiológica , Tecnologia de Fibra Óptica , Interferometria , Miniaturização , Ratos , Processamento de Sinais Assistido por Computador , Fatores de Tempo
13.
Cardiovasc Res ; 110(2): 200-14, 2016 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-26825555

RESUMO

AIMS: Hypertrophic cardiomyopathy (HCM) has been associated with reduced ß-adrenergic receptor (ß-AR) signalling, leading downstream to a low protein kinase A (PKA)-mediated phosphorylation. It remained undefined whether all PKA targets will be affected similarly by diminished ß-AR signalling in HCM. We aimed to investigate the role of ß-AR signalling on regulating myofilament and calcium handling in an HCM mouse model harbouring a gene mutation (G > A transition on the last nucleotide of exon 6) in Mybpc3 encoding cardiac myosin-binding protein C. METHODS AND RESULTS: Cardiomyocyte contractile properties and phosphorylation state were measured in left ventricular permeabilized and intact cardiomyocytes isolated from heterozygous (HET) or homozygous (KI) Mybpc3-targeted knock-in mice. Significantly higher myofilament Ca²âºsensitivity and passive tension were detected in KI mice, which were normalized after PKA treatment. Loaded intact cardiomyocyte force-sarcomere length relation was impaired in both HET and KI mice, suggesting a reduced length-dependent activation. Unloaded cardiomyocyte function revealed an impaired myofilament contractile response to isoprenaline (ISO) in KI, whereas the calcium-handling response to ISO was maintained. This disparity was explained by an attenuated increase in cardiac troponin I (cTnI) phosphorylation in KI, whereas the increase in phospholamban (PLN) phosphorylation was maintained to wild-type values. CONCLUSION: These data provide evidence that in the KI HCM mouse model, ß-AR stimulation leads to preferential PKA phosphorylation of PLN over cTnI, resulting in an impaired inotropic and lusitropic response.


Assuntos
Cardiomiopatia Hipertrófica/genética , Proteínas de Transporte/genética , Proteínas Quinases Dependentes de AMP Cíclico/metabolismo , Contração Miocárdica/genética , Receptores Adrenérgicos beta/genética , Citoesqueleto de Actina/metabolismo , Animais , Proteínas de Ligação ao Cálcio/metabolismo , Cardiomiopatia Hipertrófica/tratamento farmacológico , Cardiomiopatia Hipertrófica/metabolismo , Modelos Animais de Doenças , Feminino , Isoproterenol/farmacologia , Masculino , Camundongos , Contração Miocárdica/fisiologia , Miocárdio/metabolismo , Miócitos Cardíacos/efeitos dos fármacos , Miócitos Cardíacos/metabolismo , Miofibrilas/metabolismo , Fosforilação , Receptores Adrenérgicos beta/efeitos dos fármacos , Receptores Adrenérgicos beta/metabolismo , Sarcômeros/metabolismo
14.
Circ Heart Fail ; 9(7)2016 07.
Artigo em Inglês | MEDLINE | ID: mdl-27370069

RESUMO

BACKGROUND: The purpose of this study was to determine the relative contribution of fibrosis-mediated and myofibril-mediated stiffness in rats with mild and severe right ventricular (RV) dysfunction. METHODS AND RESULTS: By performing pulmonary artery banding of different diameters for 7 weeks, mild RV dysfunction (Ø=0.6 mm) and severe RV dysfunction (Ø=0.5 mm) were induced in rats. The relative contribution of fibrosis- and myofibril-mediated RV stiffness was determined in RV trabecular strips. Total myocardial stiffness was increased in trabeculae from both mild and severe RV dysfunction in comparison to controls. In severe RV dysfunction, increased RV myocardial stiffness was explained by both increased fibrosis-mediated stiffness and increased myofibril-mediated stiffness, whereas in mild RV dysfunction, only myofibril-mediated stiffness was increased in comparison to control. Histological analyses revealed that RV fibrosis gradually increased with severity of RV dysfunction, whereas the ratio of collagen I/III expression was only elevated in severe RV dysfunction. Stiffness measurements in single membrane-permeabilized RV cardiomyocytes demonstrated a gradual increase in RV myofibril stiffness, which was partially restored by protein kinase A in both mild and severe RV dysfunction. Increased expression of compliant titin isoforms was observed only in mild RV dysfunction, whereas titin phosphorylation was reduced in both mild and severe RV dysfunction. CONCLUSIONS: RV myocardial stiffness is increased in rats with mild and severe RV dysfunction. In mild RV dysfunction, stiffness is mainly determined by increased myofibril stiffness. In severe RV dysfunction, both myofibril- and fibrosis-mediated stiffness contribute to increased RV myocardial stiffness.


Assuntos
Pressão Arterial , Hipertensão Pulmonar/complicações , Miocárdio/patologia , Miofibrilas/patologia , Artéria Pulmonar/fisiopatologia , Disfunção Ventricular Direita/fisiopatologia , Função Ventricular Direita , Animais , Colágeno Tipo I/metabolismo , Colágeno Tipo III/metabolismo , Conectina/metabolismo , Constrição , Proteínas Quinases Dependentes de AMP Cíclico/metabolismo , Modelos Animais de Doenças , Elasticidade , Fibrose , Hipertensão Pulmonar/fisiopatologia , Masculino , Miocárdio/metabolismo , Miofibrilas/metabolismo , Fosforilação , Artéria Pulmonar/cirurgia , Ratos Wistar , Índice de Gravidade de Doença , Fatores de Tempo , Disfunção Ventricular Direita/etiologia , Disfunção Ventricular Direita/metabolismo , Disfunção Ventricular Direita/patologia
15.
Circ Heart Fail ; 5(1): 36-46, 2012 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-22178992

RESUMO

BACKGROUND: Hypertrophic cardiomyopathy (HCM), typically characterized by asymmetrical left ventricular hypertrophy, frequently is caused by mutations in sarcomeric proteins. We studied if changes in sarcomeric properties in HCM depend on the underlying protein mutation. METHODS AND RESULTS: Comparisons were made between cardiac samples from patients carrying a MYBPC3 mutation (MYBPC3(mut); n=17), mutation negative HCM patients without an identified sarcomere mutation (HCM(mn); n=11), and nonfailing donors (n=12). All patients had normal systolic function, but impaired diastolic function. Protein expression of myosin binding protein C (cMyBP-C) was significantly lower in MYBPC3(mut) by 33±5%, and similar in HCM(mn) compared with donor. cMyBP-C phosphorylation in MYBPC3(mut) was similar to donor, whereas it was significantly lower in HCM(mn). Troponin I phosphorylation was lower in both patient groups compared with donor. Force measurements in single permeabilized cardiomyocytes demonstrated comparable sarcomeric dysfunction in both patient groups characterized by lower maximal force generating capacity in MYBPC3(mut) and HCM(mn,) compared with donor (26.4±2.9, 28.0±3.7, and 37.2±2.3 kN/m(2), respectively), and higher myofilament Ca(2+)-sensitivity (EC(50)=2.5±0.2, 2.4±0.2, and 3.0±0.2 µmol/L, respectively). The sarcomere length-dependent increase in Ca(2+)-sensitivity was significantly smaller in both patient groups compared with donor (ΔEC(50): 0.46±0.04, 0.37±0.05, and 0.75±0.07 µmol/L, respectively). Protein kinase A treatment restored myofilament Ca(2+)-sensitivity and length-dependent activation in both patient groups to donor values. CONCLUSIONS: Changes in sarcomere function reflect the clinical HCM phenotype rather than the specific MYBPC3 mutation. Hypocontractile sarcomeres are a common deficit in human HCM with normal systolic left ventricular function and may contribute to HCM disease progression.


Assuntos
Cardiomiopatia Hipertrófica/genética , Cardiomiopatia Hipertrófica/fisiopatologia , Proteínas de Transporte/genética , Mutação/genética , Contração Miocárdica/fisiologia , Função Ventricular Esquerda/fisiologia , Adulto , Idoso , Pressão Sanguínea/fisiologia , Cálcio/fisiologia , Cardiomiopatia Hipertrófica/patologia , Proteínas Quinases Dependentes de AMP Cíclico/farmacologia , Diástole/fisiologia , Progressão da Doença , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Fosforilação , Sarcômeros/efeitos dos fármacos , Sarcômeros/fisiologia , Sístole/fisiologia
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA