RESUMEN
The Frank-Starling law of the heart is a physiological phenomenon that describes an intrinsic property of heart muscle in which increased cardiac filling leads to enhanced cardiac contractility. Identified more than a century ago, the Frank-Starling relationship is currently known to involve length-dependent enhancement of cardiac myofilament Ca2+ sensitivity. However, the upstream molecular events that link cellular stretch to the length-dependent myofilament Ca2+ sensitivity are poorly understood. Because the angiotensin II type 1 receptor (AT1R) and the multifunctional transducer protein ß-arrestin have been shown to mediate mechanosensitive cellular signaling, we tested the hypothesis that these two proteins are involved in the Frank-Starling mechanism of the heart. Using invasive hemodynamics, we found that mice lacking ß-arrestin 1, ß-arrestin 2, or AT1R were unable to generate a Frank-Starling force in response to changes in cardiac volume. Although wild-type mice pretreated with the conventional AT1R blocker losartan were unable to enhance cardiac contractility with volume loading, treatment with a ß-arrestin-biased AT1R ligand to selectively activate ß-arrestin signaling preserved the Frank-Starling relationship. Importantly, in skinned muscle fiber preparations, we found markedly impaired length-dependent myofilament Ca2+ sensitivity in ß-arrestin 1, ß-arrestin 2, and AT1R knockout mice. Our data reveal ß-arrestin 1, ß-arrestin 2, and AT1R as key regulatory molecules in the Frank-Starling mechanism, which potentially can be targeted therapeutically with ß-arrestin-biased AT1R ligands.
Asunto(s)
Modelos Cardiovasculares , Contracción Miocárdica/fisiología , beta-Arrestina 1/fisiología , Arrestina beta 2/fisiología , Bloqueadores del Receptor Tipo 1 de Angiotensina II/farmacología , Animales , Señalización del Calcio/fisiología , Técnicas In Vitro , Losartán/farmacología , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Contracción Miocárdica/efectos de los fármacos , Receptor de Angiotensina Tipo 1/deficiencia , Receptor de Angiotensina Tipo 1/genética , Receptor de Angiotensina Tipo 1/fisiología , Transducción de Señal/efectos de los fármacos , Transducción de Señal/fisiología , beta-Arrestina 1/deficiencia , beta-Arrestina 1/genética , Arrestina beta 2/deficiencia , Arrestina beta 2/genéticaRESUMEN
α-Tropomyosin (α-TM) has a conserved, charged Asp-137 residue located in the hydrophobic core of its coiled-coil structure, which is unusual in that the residue is found at a position typically occupied by a hydrophobic residue. Asp-137 is thought to destabilize the coiled-coil and so impart structural flexibility to the molecule, which is believed to be crucial for its function in the heart. A previous in vitro study indicated that the conversion of Asp-137 to a more typical canonical Leu alters flexibility of TM and affects its in vitro regulatory functions. However, the physiological importance of the residue Asp-137 and altered TM flexibility is unknown. In this study, we further analyzed structural properties of the α-TM-D137L variant and addressed the physiological importance of TM flexibility in cardiac function in studies with a novel transgenic mouse model expressing α-TM-D137L in the heart. Our NMR spectroscopy data indicated that the presence of D137L introduced long range rearrangements in TM structure. Differential scanning calorimetry measurements demonstrated that α-TM-D137L has higher thermal stability compared with α-TM, which correlated with decreased flexibility. Hearts of transgenic mice expressing α-TM-D137L showed systolic and diastolic dysfunction with decreased myofilament Ca(2+) sensitivity and cardiomyocyte contractility without changes in intracellular Ca(2+) transients or post-translational modifications of major myofilament proteins. We conclude that conversion of the highly conserved Asp-137 to Leu results in loss of flexibility of TM that is important for its regulatory functions in mouse hearts. Thus, our results provide insight into the link between flexibility of TM and its function in ejecting hearts.
Asunto(s)
Mutación Missense , Contracción Miocárdica , Miocardio/metabolismo , Volumen Sistólico , Tropomiosina/biosíntesis , Sustitución de Aminoácidos , Animales , Ratones , Ratones Transgénicos , Miocardio/patología , Resonancia Magnética Nuclear Biomolecular , Estabilidad Proteica , Ratas , Relación Estructura-Actividad , Tropomiosina/química , Tropomiosina/genéticaRESUMEN
Following exposure to microgravity, there is a reduced ability of astronauts to augment peripheral vascular resistance, often resulting in orthostatic hypotension. The purpose of this study was to test the hypothesis that mesenteric arteries and veins will exhibit diminished vasoconstrictor responses after spaceflight. Mesenteric arteries and veins from female mice flown on the Space Transportation System (STS)-131 (n=11), STS-133 (n=6), and STS-135 (n=3) shuttle missions and respective ground-based control mice (n=30) were isolated for in vitro experimentation. Vasoconstrictor responses were evoked in arteries via norepinephrine (NE), potassium chloride (KCl), and caffeine, and in veins through NE across a range of intraluminal pressures (2-12 cmH(2)O). Vasoconstriction to NE was also determined in mesenteric arteries at 1, 5, and 7 d postlanding. In arteries, maximal constriction to NE, KCl, and caffeine were reduced immediately following spaceflight and 1 d postflight. Spaceflight also reduced arterial ryanodine receptor-3 mRNA levels. In mesenteric veins, there was diminished constriction to NE after flight. The results indicate that the impaired vasoconstriction following spaceflight occurs through the ryanodine receptor-mediated intracellular Ca(2+) release mechanism. Such vascular changes in astronauts could compromise the maintenance of arterial pressure during orthostatic stress.
Asunto(s)
Adaptación Fisiológica , Arterias Mesentéricas/fisiología , Venas Mesentéricas/fisiología , Vuelo Espacial , Vasoconstricción , Animales , Femenino , Ratones , Ratones Endogámicos C57BLRESUMEN
Evidence indicates that cerebral blood flow is both increased and diminished in astronauts on return to Earth. Data from ground-based animal models simulating the effects of microgravity have shown that decrements in cerebral perfusion are associated with enhanced vasoconstriction and structural remodeling of cerebral arteries. Based on these results, the purpose of this study was to test the hypothesis that 13 d of spaceflight [Space Transportation System (STS)-135 shuttle mission] enhances myogenic vasoconstriction, increases medial wall thickness, and elicits no change in the mechanical properties of mouse cerebral arteries. Basilar and posterior communicating arteries (PCAs) were isolated from 9-wk-old female C57BL/6 mice for in vitro vascular and mechanical testing. Contrary to that hypothesized, myogenic vasoconstrictor responses were lower and vascular distensibility greater in arteries from spaceflight group (SF) mice (n=7) relative to ground-based control group (GC) mice (n=12). Basilar artery maximal diameter was greater in SF mice (SF: 236±9 µm and GC: 215±5 µm) with no difference in medial wall thickness (SF: 12.4±1.6 µm; GC: 12.2±1.2 µm). Stiffness of the PCA, as characterized via nanoindentation, was lower in SF mice (SF: 3.4±0.3 N/m; GC: 5.4±0.8 N/m). Collectively, spaceflight-induced reductions in myogenic vasoconstriction and stiffness and increases in maximal diameter of cerebral arteries signify that elevations in brain blood flow may occur during spaceflight. Such changes in cerebral vascular control of perfusion could contribute to increases in intracranial pressure and an associated impairment of visual acuity in astronauts during spaceflight.
Asunto(s)
Arterias Cerebrales/patología , Arterias Cerebrales/fisiopatología , Hipertensión Intracraneal/etiología , Ingravidez/efectos adversos , Animales , Astronautas , Circulación Cerebrovascular/fisiología , Femenino , Suspensión Trasera/efectos adversos , Suspensión Trasera/fisiología , Humanos , Hipertensión Intracraneal/fisiopatología , Masculino , Ratones , Ratones Endogámicos C57BL , Ratas , Vuelo Espacial , Vasoconstricción/fisiologíaRESUMEN
OBJECTIVES: Although mechanical ventilation is a life-saving intervention in patients suffering from respiratory failure, prolonged mechanical ventilation is often associated with numerous complications including problematic weaning. In contracting skeletal muscle, inadequate oxygen supply can limit oxidative phosphorylation resulting in muscular fatigue. However, whether prolonged mechanical ventilation results in decreased diaphragmatic blood flow and induces an oxygen supply-demand imbalance in the diaphragm remains unknown. DESIGN: We tested the hypothesis that prolonged controlled mechanical ventilation results in a time-dependent reduction in rat diaphragmatic blood flow and microvascular PO2 and that prolonged mechanical ventilation would diminish the diaphragm's ability to increase blood flow in response to muscular contractions. MEASUREMENTS AND MAIN RESULTS: Compared to 30 mins of mechanical ventilation, 6 hrs of mechanical ventilation resulted in a 75% reduction in diaphragm blood flow (via radiolabeled microspheres), which did not occur in the intercostal muscle or high-oxidative hindlimb muscle (e.g., soleus). There was also a time-dependent decline in diaphragm microvascular PO2 (via phosphorescence quenching). Further, contrary to 30 mins of mechanical ventilation, 6 hrs of mechanical ventilation significantly compromised the diaphragm's ability to increase blood flow during electrically-induced contractions, which resulted in a ~80% reduction in diaphragm oxygen uptake. In contrast, 6 hrs of spontaneous breathing in anesthetized animals did not alter diaphragm blood flow or the ability to augment flow during electrically-induced contractions. CONCLUSIONS: These new and important findings reveal that prolonged mechanical ventilation results in a time-dependent decrease in the ability of the diaphragm to augment blood flow to match oxygen demand in response to contractile activity and could be a key contributing factor to difficult weaning. Although additional experiments are required to confirm, it is tempting to speculate that this ventilator-induced decline in diaphragmatic oxygenation could promote a hypoxia-induced generation of reactive oxygen species in diaphragm muscle fibers and contribute to ventilator-induced diaphragmatic atrophy and contractile dysfunction.
Asunto(s)
Diafragma/irrigación sanguínea , Microcirculación/fisiología , Respiración Artificial/efectos adversos , Animales , Velocidad del Flujo Sanguíneo , Análisis de los Gases de la Sangre , Femenino , Contracción Muscular/fisiología , Ratas , Ratas Sprague-Dawley , Factores de TiempoRESUMEN
Testicular function and associated testosterone concentration decline with advancing age, and an impaired O2 supply may contribute, in part, to this reduction. We hypothesized that there would be a reduced microvascular Po2 (Po2(m)) in the testes from aged rats, and this reduced Po2(m) would be associated with impaired vasomotor control in isolated resistance arterioles. In addition, given the positive effect of exercise on microvascular Po2 and arteriolar function, we further hypothesized that there would be an enhanced Po2(m) in the testes from aged animals after aerobic exercise training. Testicular Po2(m) was measured in vivo via phosphorescence quenching in young and aged sedentary (SED) and exercise-trained (ET; 15 m/min treadmill walking, 15-degree incline, 5 days/wk for 10 wk) male Fischer-344 rats. Vasoconstriction to α-adrenergic [norepinephrine (NE) and phenylephrine (PE)] and myogenic stimuli in testicular arterioles was assessed in vitro. In the SED animals, testicular Po2(m) was reduced by â¼50% with old age (aged SED 11.8 ± 1.9 vs. young SED 22.1 ± 1.1 mmHg; P = 0.0001). Contrary to our hypothesis, exercise training did not alter Po2(m) in the aged group and reduced testicular Po2(m) in the young animals, abolishing age-related differences (young ET, 10.0 ± 0.8 vs. aged ET, 10.7 ± 0.9 mmHg; P = 0.37). Vasoconstrictor responsiveness to NE and PE was diminished in aged compared with young (NE: young SED, 58 ± 2 vs. aged SED, 47 ± 2%; P = 0.001) (PE: young SED, 51 ± 3 vs. aged SED, 36 ± 5%; P = 0.008). Exercise training did not alter maximal vasoconstriction to NE in young or aged groups. In summary, advancing age is associated with a reduced testis Po2(m) and impaired adrenergic vasoconstriction. The diminished testicular microvascular driving pressure of O2 and associated vascular dysfunction provides mechanistic insight into the old age-related decrease in testicular function, and a reduced Po2(m) may contribute, in part, to reduced fertility markers after exercise training.
Asunto(s)
Envejecimiento , Microcirculación , Oxígeno/sangre , Resistencia Física , Testículo/irrigación sanguínea , Vasoconstricción , Agonistas Adrenérgicos/farmacología , Factores de Edad , Análisis de Varianza , Animales , Arteriolas/metabolismo , Relación Dosis-Respuesta a Droga , Fertilidad , Masculino , Microcirculación/efectos de los fármacos , Ratas , Ratas Endogámicas F344 , Vasoconstricción/efectos de los fármacos , Vasoconstrictores/farmacologíaRESUMEN
BACKGROUND: A protein structure can be determined by solving a so-called distance geometry problem whenever a set of inter-atomic distances is available and sufficient. However, the problem is intractable in general and has proved to be a NP hard problem. An updated geometric build-up algorithm (UGB) has been developed recently that controls numerical errors and is efficient in protein structure determination for cases where only sparse exact distance data is available. In this paper, the UGB method has been improved and revised with aims at solving distance geometry problems more efficiently and effectively. METHODS: An efficient algorithm (called the revised updated geometric build-up algorithm (RUGB)) to build up a protein structure from atomic distance data is presented and provides an effective way of determining a protein structure with sparse exact distance data. In the algorithm, the condition to determine an unpositioned atom iteratively is relaxed (when compared with the UGB algorithm) and data structure techniques are used to make the algorithm more efficient and effective. The algorithm is tested on a set of proteins selected randomly from the Protein Structure Database-PDB. RESULTS: We test a set of proteins selected randomly from the Protein Structure Database-PDB. We show that the numerical errors produced by the new RUGB algorithm are smaller when compared with the errors of the UGB algorithm and that the novel RUGB algorithm has a significantly smaller runtime than the UGB algorithm. CONCLUSIONS: The RUGB algorithm relaxes the condition for updating and incorporates the data structure for accessing neighbours of an atom. The revisions result in an improvement over the UGB algorithm in two important areas: a reduction on the overall runtime and decrease of the numeric error.
Asunto(s)
Algoritmos , Proteínas/química , Modelos Moleculares , Conformación ProteicaRESUMEN
The rat model of treadmill running is an invaluable tool for the investigation of experimentally and pathologically induced alterations in exercise performance. Interpretation of such data often presumes knowledge of the within-rat reproducibility of performance measures; however, the literature is bereft of this information. We tested the hypothesis that within-rat exercise endurance capacity and peak O(2) uptake (Vo(2peak)) are highly reproducible across five measurements spanning approximately 5 wk when assessed with treadmill performance protocols. Male Sprague-Dawley rats (n = 13) performed five graded exercise tolerance tests to fatigue and five maximal exercise tests on a motor-driven treadmill for determination of endurance capacity and Vo(2peak), respectively. There were no differences (P = 0.47) in average time to fatigue among any of the five exercise tolerance tests (average range 45.9-52.1 min), and the average within-rat coefficient of variation (CV) over the five runs was 0.13. There were no differences (P > 0.05) among the average CVs from any consecutive weekly exercise tolerance tests (range of 4 CVs 0.06-0.10). As expected with the increase in body mass, relative Vo(2peak) decreased (average range from 80.1 to 75.7 ml x min(-1) x kg(-1), P < 0.05) throughout the five maximal exercise tests. However, there were no differences (P = 0.63) in the average within-rat CVs among any consecutive Vo(2peak) tests (range of 4 CVs 0.03-0.04), and the average within-rat CV for all five tests was 0.06. The present data obtained from the protocols described herein demonstrate that within-rat measurements of endurance capacity and Vo(2peak) are highly reproducible. These results have significant implications for improving and refining exercise testing and experimental designs.
Asunto(s)
Umbral Anaerobio/fisiología , Condicionamiento Físico Animal/fisiología , Resistencia Física/fisiología , Animales , Peso Corporal/fisiología , Masculino , Consumo de Oxígeno/fisiología , Ratas , Ratas Sprague-Dawley , Reproducibilidad de los ResultadosRESUMEN
Mechanical ventilation (MV) is a life-saving intervention, yet with prolonged MV (i.e., ≥6 h) there are time-dependent reductions in diaphragm blood flow and an impaired hyperemic response of unknown origin. Female Sprague-Dawley rats (4-8 mo, n = 118) were randomized into two groups; spontaneous breathing (SB) and 6-h (prolonged) MV. After MV or SB, vasodilation (flow-induced, endothelium-dependent and -independent agonists) and constriction (myogenic and α-adrenergic) responses were measured in first-order (1A) diaphragm resistance arterioles in vitro, and endothelial nitric oxide synthase (eNOS) mRNA expression was quantified. Following prolonged MV, there was a significant reduction in diaphragm arteriolar flow-induced (SB, 34.7 ± 3.8% vs. MV, 22.6 ± 2.0%; P ≤ 0.05), endothelium-dependent (via acetylcholine; SB, 64.3 ± 2.1% vs. MV, 36.4 ± 2.3%; P ≤ 0.05) and -independent (via sodium nitroprusside; SB, 65.0 ± 3.1% vs. MV, 46.0 ± 4.6%; P ≤ 0.05) vasodilation. Compared with SB, there was reduced eNOS mRNA expression (P ≤ 0.05). Prolonged MV diminished phenylephrine-induced vasoconstriction (SB, 37.3 ± 6.7% vs. MV, 19.0 ± 1.9%; P ≤ 0.05) but did not alter myogenic or passive pressure responses. The severe reductions in diaphragmatic blood flow at rest and during contractions, with prolonged MV, are associated with diaphragm vascular dysfunction which occurs through both endothelium-dependent and endothelium-independent mechanisms.NEW & NOTEWORTHY Following prolonged mechanical ventilation, vascular alterations occur through both endothelium-dependent and -independent pathways. This is the first study, to our knowledge, demonstrating that diaphragm arteriolar dysfunction occurs consequent to prolonged mechanical ventilation and likely contributes to the severe reductions in diaphragmatic blood flow and weaning difficulties.
Asunto(s)
Diafragma/fisiología , Resistencia Vascular/fisiología , Vasodilatación/fisiología , Acetilcolina/farmacología , Animales , Arteriolas/efectos de los fármacos , Arteriolas/metabolismo , Arteriolas/fisiología , Diafragma/efectos de los fármacos , Diafragma/metabolismo , Femenino , Contracción Muscular/efectos de los fármacos , Contracción Muscular/fisiología , Óxido Nítrico Sintasa de Tipo III/metabolismo , Nitroprusiato/farmacología , Fenilefrina/farmacología , Ratas , Ratas Sprague-Dawley , Respiración Artificial/métodos , Resistencia Vascular/efectos de los fármacos , Vasoconstricción/efectos de los fármacos , Vasoconstricción/fisiología , Vasodilatación/efectos de los fármacosRESUMEN
BACKGROUND: Hypertrophic cardiomyopathy (HCM) is a genetic cardiovascular disorder, primarily involving mutations in sarcomeric proteins. HCM patients present with hypertrophy, diastolic dysfunction, and fibrosis, but there is no specific treatment. The sphingosine-1-phosphate receptor modulator, FTY720/fingolimod, is approved for treatment of multiple sclerosis. We hypothesize that modulation of the sphingosine-1-phosphate receptor by FTY720 would be of therapeutic benefit in sarcomere-linked HCM. METHODS: We treated mice with an HCM-linked mutation in tropomyosin (Tm-E180G) and nontransgenic littermates with FTY720 or vehicle for 6 weeks. Compared with vehicle-treated, FTY720-treated Tm-E180G mice had a significant reduction in left atrial size (1.99±0.19 [n=7] versus 2.70±0.44 [n=6] mm; P<0.001) and improvement in diastolic function (E/A ratio: 2.69±0.38 [n=7] versus 5.34±1.19 [n=6]; P=0.004) as assessed by echocardiography. RESULTS: Pressure-volume relations revealed significant improvements in the end-diastolic pressure volume relationship, relaxation kinetics, preload recruitable stroke work, and ejection fraction. Detergent-extracted fiber bundles revealed a significant decrease in myofilament Ca2+-responsiveness (pCa50=6.15±0.11 [n=13] versus 6.24±0.06 [n=14]; P=0.041). We attributed these improvements to a downregulation of S-glutathionylation of cardiac myosin binding protein-C in FTY720-treated Tm-E180G mice and reduction in oxidative stress by downregulation of NADPH oxidases with no changes in fibrosis. CONCLUSIONS: This is the first demonstration that modulation of S1PR results in decreased myofilament-Ca2+-responsiveness and improved diastolic function in HCM. We associated these changes with decreased oxidative modification of myofilament proteins via downregulation of NOX2. Our data support the hypothesis that modification of sphingolipid signaling may be a novel therapeutic approach in HCM.
Asunto(s)
Función del Atrio Izquierdo/efectos de los fármacos , Remodelación Atrial/efectos de los fármacos , Cardiomiopatía Hipertrófica/tratamiento farmacológico , Clorhidrato de Fingolimod/farmacología , Miocitos Cardíacos/efectos de los fármacos , Moduladores de los Receptores de fosfatos y esfingosina 1/farmacología , Receptores de Esfingosina-1-Fosfato/efectos de los fármacos , Animales , Señalización del Calcio/efectos de los fármacos , Cardiomiopatía Hipertrófica/genética , Cardiomiopatía Hipertrófica/metabolismo , Cardiomiopatía Hipertrófica/fisiopatología , Diástole , Modelos Animales de Enfermedad , Femenino , Fibrosis , Predisposición Genética a la Enfermedad , Masculino , Ratones Mutantes , Mutación , Miocitos Cardíacos/metabolismo , Miocitos Cardíacos/patología , Miofibrillas/efectos de los fármacos , Miofibrillas/metabolismo , Miofibrillas/patología , Estrés Oxidativo/efectos de los fármacos , Fenotipo , Receptores de Esfingosina-1-Fosfato/metabolismo , Tropomiosina/genéticaRESUMEN
INTRODUCTION: In response to the opioid crisis, the 2016 Vermont legislature commissioned a study to assess acupuncture for patients with chronic pain in the Vermont Medicaid population. OBJECTIVE: To assess the feasibility, acceptability, and effectiveness of acupuncture provided by licensed acupuncturists for Vermont Medicaid patients with chronic pain. METHODS: A total of 156 Medicaid patients with chronic pain were offered up to 12 acupuncture treatments within a 60-day period at the offices of 28 Vermont licensed acupuncturists. PROMIS® questionnaires were administered prior to and at the end of the treatment period to assess changes in pain intensity, pain interference, physical function, fatigue, anxiety, depression, sleep disturbance, and social isolation. Questionnaires also captured patients' overall impressions of treatments as well as self-reported changes in medication use and work function. RESULTS: One hundred eleven women (71%) and 45 men (29%) with a wide range of pain complaints received a mean of 8.2 treatments during the intervention period. Measurements captured prior to and at the end of the treatment period showed significant improvements in group mean pain intensity, pain interference, physical function, fatigue, anxiety, depression, sleep disturbance, and social isolation as assessed by Patient-Reported Outcomes Measurement Information System (PROMIS) measures (paired t tests, P < .01). Fifty-seven percent of patients using analgesic (nonopioid) medication reported reductions in use. Thirty-two percent of patients using opioid medication reported reductions in use of opioid medication following the intervention. Seventy-four percent of employed patients reported improved capacity to work. Ninety-six percent of patients said that they would recommend acupuncture to others with chronic pain, and 91% reported qualitative improvements, including physical (31%), functional/behavioral (29%), and psycho-emotional (24%) improvements. CONCLUSIONS: Our findings demonstrate that acupuncture treatment for chronic pain is feasible and well received by patients in the Vermont Medicaid population. Receiving care from Licensed Acupuncturists was associated with significant improvements in physical, functional, psycho-emotional, and occupational outcomes compared with before receiving acupuncture treatments.
RESUMEN
Research into acupuncture has had ripple effects beyond the field of acupuncture. This paper identifies five exemplars to illustrate that there is tangible evidence of the way insights gleaned from acupuncture research have informed biomedical research, practice, or policy. The first exemplar documents how early research into acupuncture analgesia has expanded into neuroimaging research, broadening physiologic understanding and treatment of chronic pain. The second describes how the acupuncture needle has become a tool to enhance biomedical knowledge of connective tissue. The third exemplar, which illustrates use of a modified acupuncture needle as a sham device, focuses on emergent understanding of placebo effects and, in turn, on insights into therapeutic encounters in treatments unrelated to acupuncture. The fourth exemplar documents that two medical devices now in widespread use were inspired by acupuncture: transcutaneous electrical nerve stimulators for pain control and antinausea wrist bands. The final exemplar describes how pragmatic clinical trial designs applied in acupuncture research have informed current general interest in comparative effectiveness research. In conclusion, these exemplars of unanticipated outcomes of acupuncture research comprise an additional rationale for continued support of basic and clinical research evaluating acupuncture and other under-researched therapies.
Asunto(s)
Terapia por Acupuntura , Acupuntura , Investigación Biomédica , Analgesia por Acupuntura , Dolor Crónico , Investigación sobre la Eficacia Comparativa , Humanos , Manejo del Dolor , Efecto Placebo , Proyectos de Investigación , Estimulación Eléctrica Transcutánea del NervioRESUMEN
AIMS: Therapeutic approaches to treat familial dilated cardiomyopathy (DCM), which is characterized by depressed sarcomeric tension and susceptibility to Ca(2+)-related arrhythmias, have been generally unsuccessful. Our objective in the present work was to determine the effect of the angiotensin II type 1 receptor (AT1R) biased ligand, TRV120023, on contractility of hearts of a transgenic mouse model of familial DCM with mutation in tropomyosin at position 54 (TG-E54K). Our rationale is based on previous studies, which have supported the hypothesis that biased G-protein-coupled receptor ligands, signalling via ß-arrestin, increase cardiac contractility with no effect on Ca(2+) transients. Our previous work demonstrated that the biased ligand TRV120023 is able to block angiotensin-induced hypertrophy, while promoting an increase in sarcomere Ca(2+) response. METHODS AND RESULTS: We tested the hypothesis that the depression in cardiac function associated with DCM can be offset by infusion of the AT1R biased ligand, TRV120023. We intravenously infused saline, TRV120023, or the unbiased ligand, losartan, for 15 min in TG-E54K and non-transgenic mice to obtain left ventricular pressure-volume relations. Hearts were analysed for sarcomeric protein phosphorylation. Results showed that the AT1R biased ligand increases cardiac performance in TG-E54K mice in association with increased myosin light chain-2 phosphorylation. CONCLUSION: Treatment of mice with an AT1R biased ligand, acting via ß-arrestin signalling, is able to induce an increase in cardiac contractility associated with an increase in ventricular myosin light chain-2 phosphorylation. AT1R biased ligands may prove to be a novel inotropic approach in familial DCM.
Asunto(s)
Miosinas Cardíacas/metabolismo , Cardiomiopatía Dilatada/metabolismo , Contracción Miocárdica/fisiología , Cadenas Ligeras de Miosina/metabolismo , Oligopéptidos/metabolismo , Animales , Arrestinas/metabolismo , Modelos Animales de Enfermedad , Femenino , Corazón/fisiopatología , Ligandos , Masculino , Ratones Transgénicos , Fosforilación , beta-ArrestinasRESUMEN
AIMS: Despite its known cardiovascular benefits, the intracellular signalling mechanisms underlying physiological cardiac growth remain poorly understood. Therefore, the purpose of this study was to investigate a novel role of p21-activated kinase-1 (Pak1) in the regulation of exercise-induced cardiac hypertrophy. METHODS AND RESULTS: Wild-type (WT) and Pak1 KO mice were subjected to 6 weeks of treadmill endurance exercise training (ex-training). Cardiac function was assessed via echocardiography, in situ haemodynamics, and the pCa-force relations in skinned fibre preparations at baseline and at the end of the training regimen. Post-translational modifications to the sarcomeric proteins and expression levels of calcium-regulating proteins were also assessed following ex-training. Heart weight/tibia length and echocardiography data revealed that there was marked hypertrophy following ex-training in the WT mice, which was not evident in the KO mice. Additionally, following ex-training, WT mice demonstrated an increase in cardiac contractility, myofilament calcium sensitivity, and phosphorylation of cardiac myosin-binding protein C, cardiac TnT, and tropomyosin compared with KO mice. With ex-training in WT mice, there were also increased protein levels of calcineurin and increased phosphorylation of phospholamban. CONCLUSIONS: Our data suggest that Pak1 is essential for adaptive physiological cardiac remodelling and support previous evidence that demonstrates Pak1 signalling is important for cardiac growth and survival.
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Calcineurina/metabolismo , Cardiomegalia Inducida por el Ejercicio , Cardiomegalia/enzimología , Técnicas de Inactivación de Genes , Miocardio/enzimología , Esfuerzo Físico , Remodelación Ventricular , Quinasas p21 Activadas/deficiencia , Adaptación Fisiológica , Animales , Proteínas de Unión al Calcio/metabolismo , Cardiomegalia/genética , Cardiomegalia/patología , Cardiomegalia/fisiopatología , Proteínas Portadoras/metabolismo , Tolerancia al Ejercicio , Genotipo , Hemodinámica , Ratones Noqueados , Contracción Miocárdica , Miocardio/patología , Miofibrillas/enzimología , Fenotipo , Fosforilación , Carrera , Transducción de Señal , Tropomiosina/metabolismo , Troponina T/metabolismo , Quinasas p21 Activadas/genéticaRESUMEN
OBJECTIVE: To develop and evaluate a method for quantitative evaluation of yin and yang (yin and yang scores) in human subjects for the purposes of research. This method aims to classify subjects into groups allowing future quantitative testing of key research questions such as: do different groups of patients respond differently to acupuncture treatments or Chinese herb formulas? METHODS: In a pilot study of inter-rater reliability, 12 volunteers were each successively interviewed and examined by 6 acupuncturists on the same day. Each acupuncturist gave each volunteer a score for yin and a score for yang on a scale of -10 to +10, zero representing a "balanced" score. Acupuncturists were blinded to each other's scores. RESULTS: Overall mean (+/-standard deviation [SD]) yin and yang scores were -1.86 +/- 0.90 and -0.68 +/- 1.23 respectively. Intraclass correlations (ICCs) associated with a single acupuncturist's ratings were 0.35 (yin) and 0.36 (yang). ICC's for subject's mean scores based on the six acupuncturists were 0.77 (yin) and 0.78 (yang). Significant differences in mean scores across subjects were detected for yin (p < 0.001) and yang (p < 0.001) (repeated-measures analysis of variance [ANOVA]) based on the multiple acupuncturists' ratings. CONCLUSION: These results indicate that (1) yin and yang can be quantified in a reliable manner, but evaluation by multiple acupuncturists is necessary to obtain a reliable score; (2) yin and yang scores can be used to group individuals for the purposes of statistical analysis. Further evaluation of yin and yang scores in a greater number and wider variety of patients will be needed to evaluate the potential usefulness of this measurement tool in acupuncture clinical trials and basic physiologic research.
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Terapia por Acupuntura/normas , Acupuntura/normas , Pautas de la Práctica en Medicina/normas , Yin-Yang , Terapia por Acupuntura/métodos , Adulto , Análisis de Varianza , Diagnóstico Diferencial , Femenino , Humanos , Masculino , Medicina Tradicional China , Persona de Mediana Edad , Variaciones Dependientes del Observador , Proyectos Piloto , Reproducibilidad de los Resultados , Factores de TiempoAsunto(s)
Acupuntura/organización & administración , Dolor Crónico/terapia , Dolor de la Región Lumbar/terapia , Medicare/organización & administración , Terapia por Acupuntura , Investigación Biomédica/métodos , Investigación Biomédica/organización & administración , Humanos , Medicaid/organización & administración , Guías de Práctica Clínica como Asunto , Estados UnidosRESUMEN
BACKGROUND: Hypertrophic cardiomyopathy (HCM) is a common genetic disorder caused mainly by mutations in sarcomeric proteins and is characterized by maladaptive myocardial hypertrophy, diastolic heart failure, increased myofilament Ca(2+) sensitivity, and high susceptibility to sudden death. We tested the following hypothesis: correction of the increased myofilament sensitivity can delay or prevent the development of the HCM phenotype. METHODS AND RESULTS: We used an HCM mouse model with an E180G mutation in α-tropomyosin (Tm180) that demonstrates increased myofilament Ca(2+) sensitivity, severe hypertrophy, and diastolic dysfunction. To test our hypothesis, we reduced myofilament Ca(2+) sensitivity in Tm180 mice by generating a double transgenic mouse line. We crossed Tm180 mice with mice expressing a pseudophosphorylated cardiac troponin I (S23D and S24D; TnI-PP). TnI-PP mice demonstrated a reduced myofilament Ca(2+) sensitivity compared with wild-type mice. The development of pathological hypertrophy did not occur in mice expressing both Tm180 and TnI-PP. Left ventricle performance was improved in double transgenic compared with their Tm180 littermates, which express wild-type cardiac troponin I. Hearts of double transgenic mice demonstrated no changes in expression of phospholamban and sarcoplasmic reticulum Ca(2+) ATPase, increased levels of phospholamban and troponin T phosphorylation, and reduced phosphorylation of TnI compared with Tm180 mice. Moreover, expression of TnI-PP in Tm180 hearts inhibited modifications in the activity of extracellular signal-regulated kinase and zinc finger-containing transcription factor GATA in Tm180 hearts. CONCLUSIONS: Our data strongly indicate that reduction of myofilament sensitivity to Ca(2+) and associated correction of abnormal relaxation can delay or prevent development of HCM and should be considered as a therapeutic target for HCM.
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Calcio/metabolismo , Cardiomiopatía Hipertrófica/genética , Cardiomiopatía Hipertrófica/metabolismo , Miofibrillas/metabolismo , Tropomiosina/genética , Troponina I/genética , Animales , Proteínas de Unión al Calcio/metabolismo , Cardiomiopatía Hipertrófica/terapia , Humanos , Ratones , Ratones Transgénicos , Mutación , Fosforilación , Tropomiosina/metabolismo , Troponina I/metabolismo , Troponina T/metabolismoRESUMEN
Adipose tissue (AT), which typically comprises an increased percentage of body mass with advancing age, receives a large proportion of resting cardiac output. During exercise, an old age-associated inability to increase vascular resistance within the intra-abdominal AT may compromise the ability of the cardiovascular system to redistribute blood flow to the active musculature, contributing to the decline in exercise capacity observed in this population. We tested the hypotheses that 1) there would be an elevated perfusion of AT during exercise with old age that was associated with diminished vasoconstrictor responses of adipose-resistance arteries, and 2) chronic exercise training would mitigate the age-associated alterations in AT blood flow and vascular function. Young (6 mo; n = 40) and old (24 mo; n = 28) male Fischer 344 rats were divided into young sedentary (YSed), old sedentary (OSed), young exercise trained (YET), or old exercise trained (OET) groups, where training consisted of 10-12 wk of treadmill exercise. In vivo blood flow at rest and during exercise and in vitro α-adrenergic and myogenic vasoconstrictor responses in resistance arteries from AT were measured in all groups. In response to exercise, there was a directionally opposite change in AT blood flow in the OSed group (≈ 150% increase) and YSed (≈ 55% decrease) vs. resting values. Both α-adrenergic and myogenic vasoconstriction were diminished in OSed vs. YSed AT-resistance arteries. Exercise training resulted in a similar AT hyperemic response between age groups during exercise (YET, 9.9 ± 0.5 ml · min(-1) · 100(-1) g; OET, 8.1 ± 0.9 ml · min(-1) · 100(-1) g) and was associated with enhanced myogenic and α-adrenergic vasoconstriction of AT-resistance arteries from the OET group relative to OSed. These results indicate that there is an inability to increase vascular resistance in AT during exercise with old age, due, in part, to a diminished vasoconstriction of AT arteries. Furthermore, the results indicate that exercise training can augment vasoconstriction of AT arteries and mitigate age-related alterations in the regulation of AT blood flow during exercise.
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Grasa Abdominal/irrigación sanguínea , Envejecimiento , Esfuerzo Físico , Vasoconstricción , Agonistas alfa-Adrenérgicos/farmacología , Factores de Edad , Animales , Presión Arterial , Arteriolas/fisiología , Velocidad del Flujo Sanguíneo , Peso Corporal , Relación Dosis-Respuesta a Droga , Masculino , Ratas , Ratas Endogámicas F344 , Flujo Sanguíneo Regional , Carrera , Conducta Sedentaria , Resistencia Vascular , Vasoconstricción/efectos de los fármacos , Vasoconstrictores/farmacologíaRESUMEN
OBJECTIVES: The highly variable nature of acupuncture needling creates challenges to systematic research. The goal of this study was to test the feasibility of quantifying acupuncture needle manipulation using motion and force measurements. It was hypothesised that distinct needling styles and techniques would produce different needle motion and force patterns that could be quantified and differentiated from each other. METHODS: A new needling sensor tool (Acusensor) was used to record needling in real time as performed by six New England School of Acupuncture staff from the 'Chinese acupuncture' (style 1) and 'Japanese acupuncture' (style 2) programmes (three from each). Each faculty expert needled 12 points (6 bilateral locations) in 12 healthy human subjects using tonification (technique 1) and dispersal (technique 2). Parameters calculated from the raw needling data were displacement amplitude, displacement frequency, rotation amplitude, rotation frequency, force amplitude and torque amplitude. RESULTS: Data analysis revealed significant differences in the amplitude of displacement and rotation between needling performed by staff from two different acupuncture styles. Significant overall differences in the frequency of displacement between techniques 1 and 2 that were not dependent of the style of acupuncture being performed were also found. The relationships between displacement and rotation frequencies, as well as between displacement and force amplitudes showed considerable variability across individual acupuncturists and subjects. CONCLUSIONS: Needling motion and force parameters can be quantified in a treatment-like setting. Needling data can subsequently be analysed, providing an objective method for characterising needling in basic and clinical acupuncture research.
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Terapia por Acupuntura/instrumentación , Terapia por Acupuntura/métodos , Agujas , Puntos de Acupuntura , Adolescente , Adulto , Niño , Femenino , Humanos , Masculino , Adulto JovenRESUMEN
With old age, blood flow to the high-oxidative red skeletal muscle is reduced and blood flow to the low-oxidative white muscle is elevated during exercise. Changes in the number of feed arteries perforating the muscle are thought to contribute to this altered hyperemic response during exercise. We tested the hypothesis that exercise training would ameliorate age-related differences in blood flow during exercise and feed artery structure in skeletal muscle. Young (6-7 mo old, n = 36) and old (24 mo old, n = 25) male Fischer 344 rats were divided into young sedentary (Sed), old Sed, young exercise-trained (ET), and old ET groups, where training consisted of 10-12 wk of treadmill exercise. In Sed and ET rats, blood flow to the red and white portions of the gastrocnemius muscle (Gast(Red) and Gast(White)) and the number and luminal cross-sectional area (CSA) of all feed arteries perforating the muscle were measured at rest and during exercise. In the old ET group, blood flow was greater to Gast(Red) (264 ± 13 and 195 ± 9 ml · min(-1) · 100 g(-1) in old ET and old Sed, respectively) and lower to Gast(White) (78 ± 5 and 120 ± 6 ml · min(-1) · 100 g(-1) in old ET and old Sed, respectively) than in the old Sed group. There was no difference in the number of feed arteries between the old ET and old Sed group, although the CSA of feed arteries from old ET rats was larger. In young ET rats, there was an increase in the number of feed arteries perforating the muscle. Exercise training mitigated old age-associated differences in blood flow during exercise within gastrocnemius muscle. However, training-induced adaptations in resistance artery morphology differed between young (increase in feed artery number) and old (increase in artery CSA) animals. The altered blood flow pattern induced by exercise training with old age would improve the local matching of O(2) delivery to consumption within the skeletal muscle.