RESUMEN
The purpose of this paper is to demonstrate that near-infrared (NIR) spectroscopic imaging can provide spatial distribution (maps) of the absolute concentration of hemoglobin + myoglobin, oxygen saturation parameter and optical pathlength, reporting on the biochemico-physiological status of a beating heart in vivo. The method is based on processing the NIR spectroscopic images employing a first-derivative approach. Blood-pressure-controlled gating compensated the effect of heart motion on the imaging. All the maps are available simultaneously and noninvasively at a spatial resolution in the submillimeter range and can be obtained in a couple of minutes. The equipment has no mechanical contact with the tissue, thereby leaving the heart unaffected during the measurement.
Asunto(s)
Hemoglobinas/química , Mioglobina/química , Espectroscopía Infrarroja Corta/métodos , Animales , Presión Sanguínea , Corazón/fisiología , Ventrículos Cardíacos , Luz , Modelos Estadísticos , Modelos Teóricos , Miocardio/citología , Óptica y Fotónica , Oxígeno/química , Dispersión de Radiación , Espectrofotometría/métodos , Estrés Mecánico , PorcinosRESUMEN
A method that provides maps of absolute concentrations of oxygenated and deoxygenated myoglobin (Mb), its oxygenation, and its near-infrared (NIR) optical pathlength in cardiac tissue was developed. These parameters are available simultaneously. The method is based on NIR diffuse reflectance spectroscopic imaging and specific processing of the NIR images, which included a first derivative of the diffuse reflectance spectrum. Mb oxygenation, total Mb concentration, and NIR light pathlength were found to be in the range of 92%, 0.3 mM, and 12.5 mm, respectively, in beating isolated buffer-perfused and arrested pig hearts. The charge-coupled device camera enables sub-millimeter spatial resolution and spectroscopic imaging in 1.5 to 2.0 min. The technique is noninvasive and nondestructive. The equipment has no mechanical contact with the tissue of interest, leaving it undisturbed.
Asunto(s)
Miocardio/química , Mioglobina/química , Mioglobina/metabolismo , Espectroscopía Infrarroja Corta/métodos , Animales , Rayos Infrarrojos , Modelos Teóricos , Miocardio/metabolismo , Oxidación-Reducción , Oxígeno/análisis , Porcinos , Grabación en VideoRESUMEN
This study assessed the potential therapeutic efficacy of adipose-derived stem cells (ASCs) on infarcted hearts. Myocardial infarction was induced in rat hearts by occlusion of the left anterior descending artery (LAD). One week after LAD occlusion, the rats were divided into three groups and subjected to transplantation of ASCs or transplantation of cell culture medium (CCM) or remained untreated. During a 1-mo recovery period, magnetic resonance imaging showed that the ASC-treated hearts had a significantly greater left ventricular (LV) ejection fraction and LV wall thickening than did the CCM-treated and untreated hearts. The capillary density in infarct border zone was significantly higher in the ASC-treated hearts than in the CCM-treated and untreated hearts. However, only 0.5% of the ASCs recovered from the ASC-treated hearts were stained positive for cardiac-specific fibril proteins. It was also found that ASCs under a normal culture condition secreted three cardiac protective growth factors: vascular endothelial growth factor, hepatocyte growth factor, and insulin-like growth factor-1. Results of this study suggest that ASCs were able to improve cardiac function of infarcted rat hearts. Paracrine effect may be the mechanism underlying the improved cardiac function and increased capillary density.
Asunto(s)
Insuficiencia Cardíaca/terapia , Imagen por Resonancia Magnética , Miocitos Cardíacos/citología , Trasplante de Células Madre/métodos , Células Madre/citología , Grasa Subcutánea/citología , Animales , Biomarcadores/metabolismo , Capilares/fisiología , Diferenciación Celular , Circulación Coronaria/fisiología , Modelos Animales de Enfermedad , Femenino , Insuficiencia Cardíaca/patología , Insuficiencia Cardíaca/prevención & control , Factor de Crecimiento de Hepatocito/genética , Factor I del Crecimiento Similar a la Insulina/genética , Proteínas de la Membrana/metabolismo , Infarto del Miocardio/patología , Infarto del Miocardio/terapia , Miocitos Cardíacos/metabolismo , ARN Mensajero/metabolismo , Ratas , Ratas Endogámicas Lew , Células Madre/metabolismo , Factor A de Crecimiento Endotelial Vascular/genética , Función Ventricular Izquierda , Remodelación Ventricular/fisiologíaRESUMEN
Cardiac sarcolemmal K(ATP) channels are crucial in adaptation to stress caused by metabolic inhibition and moderate exercise, which requires not only down-regulation of energy spending, but also up-regulation of mitochondrial ATP synthesis. To investigate sarcolemmal and mitochondrial effects of a Kir6.2 (K(+) ion-selective subunit of the channel) knockout, we used non-invasive techniques ((87)Rb, (31)P NMR and optical spectroscopy) to study (1) K(+) fluxes, (2) high-energy phosphates, (3) the cytochrome c oxidase redox state, (4) myoglobin deoxygenation, and (5) contractile function at the baseline and in response to metabolic uncoupling with 2,4-dintrophenol (DNP) and stimulation with isoproterenol in Langendorff-perfused mouse hearts. Comparison with control C57BL6 hearts demonstrated that the Kir6.2 knockout resulted in: (a) a lack of stimulation of the unidirectional potassium efflux from the hearts when K(ATP) channels were activated metabolically by DNP (50 muM, 20 min); (b) a decrease in ATP, but not phosphocreatine, at the baseline, that became even more pronounced when the hearts were subjected to stress due to metabolic inhibition or increased workload caused by isoproterenol infusion (0.1 microM, 20 min); (c) significantly higher reduction of cytochrome c oxidase in response to DNP uncoupling; (d) a blunted response to isoproterenol stimulation. Thus Kir6.2 knockout is associated with decreased tolerance of mouse hearts to metabolic inhibition and catecholamine stress.
Asunto(s)
Espectroscopía de Resonancia Magnética/métodos , Contracción Miocárdica , Miocardio/metabolismo , Canales de Potasio de Rectificación Interna/fisiología , Canales de Potasio/fisiología , 2,4-Dinitrofenol/farmacología , Animales , Complejo IV de Transporte de Electrones/metabolismo , Técnicas In Vitro , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Mioglobina/metabolismo , Perfusión/métodos , Fosfatos/metabolismo , Canales de Potasio de Rectificación Interna/genética , Análisis Espectral/métodosRESUMEN
We studied the fluxes of a potassium congener (Rb(+)) in mouse hearts by (87)Rb MRS at 8.4T. The hearts were loaded with Rb(+) by perfusion with Krebs-Henseleit buffer, in which 50% of K(+) was substituted with Rb(+). We initiated Rb(+) efflux by changing the perfusion medium to Rb(+)-free buffer. Spectra were acquired every 1.85 min, and the kinetics of Rb(+) transport were analyzed by means of monoexponential fits. The rate constants of Rb(+) uptake and efflux were 0.0680 +/- 0.0028 and 0.0510 +/- 0.0051 min(-1), respectively (approximately 30% faster than in the rat heart). The ATP-sensitive potassium channel opener, P-1075 (5 microM), and mitochondrial uncoupler, 2,4-dintrophenol (50 microM), activated Rb(+) efflux from mouse hearts by approximately 35%. The mechanisms responsible for the differences in Rb(+) uptake and efflux under baseline conditions and stimulation, in comparison with rat hearts, are discussed. These data provide a background for studies of cardiac potassium transport in transgenic mouse strains.
Asunto(s)
Espectroscopía de Resonancia Magnética/métodos , Miocardio/metabolismo , Potasio/metabolismo , Análisis de Varianza , Animales , Circulación Coronaria , Transporte Iónico , Ratones , Fosfocreatina/farmacología , Ratas , Radioisótopos de Rubidio , ATPasa Intercambiadora de Sodio-Potasio/metabolismoRESUMEN
OBJECTIVES: This study was designed to determine if the fatty acid-induced increase in H(+) production from glycolysis uncoupled from glucose oxidation delays the recovery of intracellular pH (pH(i)) during reperfusion of ischemic hearts. BACKGROUND: High rates of fatty acid oxidation inhibit glucose oxidation and impair the recovery of mechanical function and cardiac efficiency during reperfusion of ischemic hearts. METHODS: pH(i) was measured by 31P nuclear magnetic resonance spectroscopy in isolated working rat hearts perfused in the absence (5.5 mmol/l glucose) or presence of 1.2 mmol/l palmitate (glucose+palmitate). Glycolysis and glucose oxidation were measured using [5-3H/U-14C]glucose. RESULTS: When glucose+palmitate hearts were subjected to 20 min of no-flow ischemia, recoveries of mechanical function and cardiac efficiency were significantly impaired compared with glucose hearts. Glucose oxidation rates were significantly lower in glucose+palmitate hearts during reperfusion compared with glucose hearts, whereas glycolysis rates were unchanged. This resulted in an increase in H(+) production from uncoupled glucose metabolism, and a decreased rate of recovery of pH(i) in glucose+palmitate hearts during reperfusion compared with glucose-perfused hearts. Dichloroacetate (3 mmol/l) given at reperfusion to glucose+palmitate hearts resulted in a 3.2-fold increase in glucose oxidation, a 35% +/- 3% decrease in H(+) production from glucose metabolism, a 1.7-fold increase in cardiac efficiency and a 2.2-fold increase in the rate of pH(i) recovery during reperfusion. CONCLUSIONS: A high level of fatty acid delays the recovery of pH(i) during reperfusion of ischemic hearts because of an increased H(+) production from glycolysis uncoupled from glucose oxidation. Improving the coupling of glucose metabolism by stimulating glucose oxidation accelerates the recovery of pH(i) and improves both mechanical function and cardiac efficiency.