RESUMEN
RATIONALE: Post-myocardial infarction ventricular remodeling is associated with the expression of a variety of factors including S100B that can potentially modulate myocyte apoptosis. OBJECTIVE: This study was undertaken to investigate the expression and function of S100B and its receptor, the receptor for advanced glycation end products (RAGE) in both postinfarction myocardium and in a rat neonatal myocyte culture model. METHODS AND RESULTS: In a rat model of myocardial infarction following coronary artery ligation, we demonstrate in periinfarct myocytes, upregulation of RAGE, induction of S100B, and release into plasma with consequent myocyte apoptosis. Using a coimmunoprecipitation strategy, we demonstrate a direct interaction between S100B and RAGE. In rat neonatal cardiac myocyte cultures, S100B at concentrations > or = 50 nmol/L induced myocyte apoptosis, as evidenced by increased terminal DNA fragmentation, TUNEL, cytochrome c release from mitochondria to cytoplasm, phosphorylation of extracellular signal-regulated kinase (ERK)1/2 and p53, increased expression and activity of proapoptotic caspase-3, and decreased expression of antiapoptotic Bcl-2. Transfection of a full-length cDNA of RAGE or a dominant-negative mutant of RAGE resulted in increased or attenuated S100B-induced myocyte apoptosis, respectively. Inhibition of ERK1/2 by U0126/PD-98059 or overexpression of a dominant negative p53 comparably inhibited S100B-induced myocyte apoptosis. CONCLUSIONS: These results suggest that interaction of RAGE and its ligand S100B after myocardial infarction may play a role in myocyte apoptosis by activating ERK1/2 and p53 signaling. This receptor-mediated mechanism is uniquely amenable to therapeutic intervention.
Asunto(s)
Apoptosis , Proteínas Musculares/metabolismo , Infarto del Miocardio/metabolismo , Miocitos Cardíacos/metabolismo , Factores de Crecimiento Nervioso/metabolismo , Receptores Inmunológicos/metabolismo , Proteínas S100/metabolismo , Animales , Butadienos/farmacología , Caspasa 3/genética , Caspasa 3/metabolismo , Línea Celular , Citocromos c/genética , Citocromos c/metabolismo , Citosol/metabolismo , Fragmentación del ADN/efectos de los fármacos , Modelos Animales de Enfermedad , Inhibidores Enzimáticos/farmacología , Flavonoides/farmacología , Regulación de la Expresión Génica/efectos de los fármacos , Regulación de la Expresión Génica/genética , Humanos , Mitocondrias Cardíacas/genética , Mitocondrias Cardíacas/metabolismo , Proteína Quinasa 3 Activada por Mitógenos/antagonistas & inhibidores , Proteína Quinasa 3 Activada por Mitógenos/genética , Proteína Quinasa 3 Activada por Mitógenos/metabolismo , Proteínas Musculares/antagonistas & inhibidores , Proteínas Musculares/genética , Infarto del Miocardio/genética , Factores de Crecimiento Nervioso/genética , Nitrilos/farmacología , Fosforilación/efectos de los fármacos , Fosforilación/genética , Ratas , Ratas Sprague-Dawley , Receptor para Productos Finales de Glicación Avanzada , Receptores Inmunológicos/genética , Subunidad beta de la Proteína de Unión al Calcio S100 , Proteínas S100/genética , Transducción de Señal/efectos de los fármacos , Transducción de Señal/genética , Proteína p53 Supresora de Tumor/genética , Proteína p53 Supresora de Tumor/metabolismo , Remodelación Ventricular/efectos de los fármacos , Remodelación Ventricular/genéticaRESUMEN
Cardiac-specific gene expression is intricately regulated in response to developmental, hormonal, and hemodynamic stimuli. To test whether cardiac muscle might be a target for regulation by peptide growth factors, the effect of three growth factors on the actin and myosin gene families was investigated by Northern blot analysis in cultured neonatal rat cardiac myocytes. Transforming growth factor-beta 1 (TGF beta 1, 1 ng/ml) and basic fibroblast growth factor (FGF, 25 ng/ml) elicited changes corresponding to those induced by hemodynamic load. The "fetal" beta-myosin heavy chain (MHC) was up-regulated about four-fold, whereas the "adult" alpha MHC was inhibited greater than 50-60%; expression of alpha-skeletal actin increased approximately two-fold, with little or no change in alpha-cardiac actin. Thus, peptide growth factors alter the program of differentiated gene expression in cardiac myocytes, and are sufficient to provoke fetal contractile protein gene expression, characteristic of pressure-overload hypertrophy. Acidic FGF (25 ng/ml) produced seven- to eightfold reciprocal changes in MHC expression but, unlike either TGF-beta 1 or basic FGF, inhibited both striated alpha-actin genes by 70-90%. Expression of vascular smooth muscle alpha-actin, the earliest alpha-actin induced during cardiac myogenesis, was increased by all three growth factors. Thus, three alpha-actin genes demonstrate distinct responses to acidic vs. basic FGF.
Asunto(s)
Actinas/genética , Factores de Crecimiento de Fibroblastos/farmacología , Regulación de la Expresión Génica/efectos de los fármacos , Complejo Mayor de Histocompatibilidad , Miocardio/metabolismo , Miosinas/genética , Factores de Crecimiento Transformadores/farmacología , Animales , Animales Recién Nacidos/metabolismo , Cardiomegalia/etiología , Diferenciación Celular , Células Cultivadas , ARN/análisis , Ratas , Ratas EndogámicasRESUMEN
We have recently reported that the Ca2+-binding protein S100beta was induced in rat heart after infarction and forced expression of S100beta in neonatal rat cardiac myocyte cultures inhibited alpha1-adrenergic induction of beta myosin heavy chain (MHC) and skeletal alpha-actin (skACT). We now extend this work by showing that S100beta is induced in hearts of human subjects after myocardial infarction. Furthermore, to determine whether overexpression of S100beta was sufficient to inhibit in vivo hypertrophy, transgenic mice containing multiple copies of the human gene under the control of its own promoter, and CD1 control mice were treated with norepinephrine (NE) (1.5 mg/kg) or vehicle, intraperitoneally twice daily for 15 d. In CD1, NE produced an increase in left ventricular/body weight ratio, ventricular wall thickness, induction of skACT, atrial natriuretic factor, betaMHC, and downregulation of alphaMHC. In transgenic mice, NE induced S100beta transgene mRNA and protein, but provoked neither hypertrophy nor regulated cardiac-specific gene expression. NE induced hypertrophy in cultured CD1 but not S100beta transgenic myocytes, confirming that the effects of S100beta on cardiac mass reflected myocyte-specific responses. These transgenic studies complement in vitro data and support the hypothesis that S100beta acts as an intrinsic negative regulator of the myocardial hypertrophic response.
Asunto(s)
Proteínas de Unión al Calcio/biosíntesis , Cardiomegalia/metabolismo , Infarto del Miocardio/metabolismo , Factores de Crecimiento Nervioso/biosíntesis , Norepinefrina/farmacología , Proteínas S100 , Actinas/biosíntesis , Animales , Factor Natriurético Atrial/biosíntesis , Proteínas de Unión al Calcio/genética , Proteínas de Unión al Calcio/aislamiento & purificación , Cardiomegalia/inducido químicamente , Cardiomegalia/genética , Células Cultivadas , Ecocardiografía , Regulación de la Expresión Génica , Ventrículos Cardíacos/patología , Humanos , Ratones , Ratones Transgénicos , Miocardio/citología , Cadenas Pesadas de Miosina/biosíntesis , Factores de Crecimiento Nervioso/genética , Factores de Crecimiento Nervioso/aislamiento & purificación , Receptores Adrenérgicos alfa 1/metabolismo , Subunidad beta de la Proteína de Unión al Calcio S100 , Distribución TisularRESUMEN
Cardiac hypertrophy triggered by mechanical load possesses features in common with growth factor signal transduction. A hemodynamic load provokes rapid expression of the growth factor-inducible nuclear oncogene, c-fos, and certain peptide growth factors specifically stimulate the "fetal" cardiac genes associated with hypertrophy, even in the absence of load. These include the gene encoding vascular smooth muscle alpha-actin, the earliest alpha-actin expressed during cardiac myogenesis; however, it is not known whether reactivation of the smooth muscle alpha-actin gene occurs in ventricular hypertrophy. We therefore investigated myocardial expression of the smooth muscle alpha-actin gene after hemodynamic overload. Smooth muscle alpha-actin mRNA was discernible 24 h after coarctation and was persistently expressed for up to 30 d. In hypertrophied hearts, the prevalence of smooth muscle alpha-actin gene induction was 0.909, versus 0.545 for skeletal muscle alpha-actin (P less than 0.05). Ventricular mass after 2 d or more of aortic constriction was more highly correlated with smooth muscle alpha-actin gene activation (r = 0.852; P = 0.0001) than with skeletal muscle alpha-actin (r = 0.532; P = 0.009); P less than 0.0005 for the difference in the correlation coefficients. Thus, smooth muscle alpha-actin is a molecular marker of the presence and extent of pressure-overload hypertrophy, whose correlation with cardiac growth at least equals that of skeletal alpha-actin. Induction of smooth muscle alpha-actin was delayed and sustained after aortic constriction, whereas the nuclear oncogenes c-jun and junB were expressed rapidly and transiently, providing potential dimerization partners for transcriptional control by c-fos.
Asunto(s)
Actinas/genética , Cardiomegalia/metabolismo , Regulación de la Expresión Génica , Músculo Liso Vascular/metabolismo , Animales , Coartación Aórtica/metabolismo , Feto/metabolismo , Genes fos , Genes jun , Masculino , ARN Mensajero/análisis , Ratas , Activación TranscripcionalRESUMEN
Continued adverse remodeling of myocardium after infarction may lead to progressive ventricular dilation and heart failure. We tested the hypothesis that exercise training in a healed myocardial infarction-dysfunction rat model can favorably modify the adverse effects of ventricular remodeling including attenuation of abnormal myosin gene expression. Sprague-Dawley rats were subjected to either proximal LAD ligation or sham operation. At 5 wk after the operation, animals were randomly assigned to sedentary conditions or 6 wk of graduated swim training, creating four experimental groups: infarct sedentary (IS), infarct exercise (IE), sham sedentary (SS), and sham exercise (SE). At 11 wk all rats were sacrificed and analyzed. Compared to sedentary infarct controls, exercise training attenuated left ventricular (LV) dilation and allowed more hypertrophy of the non infarct wall. The exercise-trained hearts also showed a reduction in the estimated peak wall tension. Northern blot analysis showed an increase in beta-myosin heavy chain expression in the hearts of the sedentary infarction group soon after infarction when compared to sham controls. However, with exercise training, there was a significant attenuation of the beta-myosin heavy chain expression in the myocardium. Exercise training in a model of left ventricular dysfunction after healed myocardial infarction can improve the adverse remodeling process by attenuating ventricular dilation and reducing wall tension. The abnormal beta-myosin expression was also attenuated in the exercise trained group. This is evidence that abnormal gene expression following severe myocardial infarction dysfunction can be favorably modified by an intervention.
Asunto(s)
Terapia por Ejercicio , Hipertrofia Ventricular Izquierda/prevención & control , Infarto del Miocardio/fisiopatología , Infarto del Miocardio/rehabilitación , Miosinas/biosíntesis , Regeneración , Función Ventricular , Animales , Convalecencia , Expresión Génica , Ventrículos Cardíacos/patología , Hipertrofia Ventricular Izquierda/etiología , Masculino , Infarto del Miocardio/complicaciones , Infarto del Miocardio/metabolismo , Miocardio/metabolismo , Miocardio/patología , Miosinas/genética , Ratas , Ratas Sprague-Dawley , Natación , Función Ventricular IzquierdaRESUMEN
Uptake and depuration of (131)I into winkles through consumption of the diatom Skeletonema costatum is described. The work follows on from previous studies that investigated the uptake of iodine into winkles from seawater and seaweed. Incorporation of (131)I in S. costatum from labelled seawater followed linear first-order kinetics with an uptake half-time of 0.40 days. Iodine uptake in winkles from labelled S. costatum also followed linear first-order kinetics, with a calculated equilibrium concentration (C(infinity)) of 42Bqkg(-1) and a transfer factor (TF) of 1.1x10(-4) with respect to labelled diatom food. This TF is lower than that observed for uptake of (131)I in winkles from labelled seaweed. For the depuration stage, a biphasic sequence with biological half-lives of 1.3 and 255 days was determined. The first phase is biokinetically important, given that winkles can lose two-thirds of their activity during that period. This study shows that, whilst winkles can obtain radioactive iodine from phytoplankton consumption, they do not retain the majority of that activity for very long. Hence, compared with other exposure pathways, such as uptake from seawater and macroalgae, incorporation from phytoplankton is a relatively minor exposure route.
Asunto(s)
Radioisótopos de Yodo/análisis , Agua de Mar/análisis , Contaminantes Radiactivos del Agua/análisis , Animales , Transporte Biológico , Medios de Cultivo , Diatomeas , Cadena Alimentaria , Contaminación de Alimentos , Cinética , Fitoplancton/metabolismo , Factores de Tiempo , VincaRESUMEN
It is proposed that experimentally observed spectra of proteins and amino acids be fitted with series of Chebychev polynomials. Such fitted curves are particularly useful in generating noise-free first- and second-derivative spectra. Examples of difference spectra produced from a family of spectra are also given.
Asunto(s)
Aminoácidos/análisis , Proteínas/análisis , Espectrofotometría/métodos , Matemática , Modelos TeóricosRESUMEN
The enthalpies of reactions between alpha-s1-casein and Ca2+ in solution were measured using a gradient layer calorimeter. The reactions are exothermic between 0 and 4.3 mM CaCl2. In the region of 4.3 mM CaCl2 there is a change to an endothermic reaction corresponding to micellisation. A calcium-binding curve has been obtained under the same conditions as the calorimetry experiments and this shows two sigmoidal binding phases. Turbidity measurements show that there is an association process corresponding to the second sigmoidal phase. A tentative interpretation of the heat curve in the region before micellisation is given in terms of the site binding of Ca2+, conformational changes in the protein and association. The main thermal processes are taken to be exothermic intramolecular hydrogen bonding induced by calcium binding and endothermic hydrophobic bonding.
Asunto(s)
Cloruro de Calcio , Caseínas , Sitios de Unión , Calorimetría , Electroforesis en Gel de Poliacrilamida , Cinética , Sustancias Macromoleculares , Micelas , Nefelometría y Turbidimetría , Concentración Osmolar , Unión Proteica , Conformación Proteica , Termodinámica , Factores de TiempoRESUMEN
A method of measuring an average particle radius in a highly polydisperse dispersion using the wavelength dependence of turbidity is described. For particles which are no larger than 0.3 of the wavelength of light used, a polynomial representation of the scattering cross-section can be used. For larger particles, more extensive numerical calculations are required. The use of the method is illustrated by determining the average particle radius of casein micelles by both elastic and quasi-elastic light scattering techniques. A polydisperse homogeneous sphere model is found to be a reasonably accurate representation of casein micelles. Several modifications of the model which would improve the agreement between the two techniques are mentioned briefly.
Asunto(s)
Tamaño de la Partícula , Animales , Bovinos , Elasticidad , Femenino , Luz , Matemática , Métodos , Micelas , Leche , Peso Molecular , Nefelometría y Turbidimetría , Dispersión de Radiación , Dióxido de SilicioRESUMEN
Uptake and depuration experiments of (131)I from labelled seaweed (Chondrus crispus) by the edible periwinkle Littorina littorea have been performed. Radioiodine concentrations in winkles during uptake followed first-order kinetics with an uptake half-time of 1 day, and a calculated equilibrium concentration (C(infinity)) of 21 000 Bq kg(-1) resulting in a transfer factor of 0.07 with respect to the labelled seaweed used as food. For depuration, a biphasic sequence with biological half-lives of 1 and 24 days was determined. The results suggest that in general, iodine turnover in periwinkles is slower than observed for other molluscs (monophasic biological half-lives in the order of 2-3 days). Both environmental media, food and seawater, can be significant sources of radioiodine for the winkle.
Asunto(s)
Algas Marinas/química , Caracoles/fisiología , Contaminantes Radiactivos del Agua/farmacocinética , Animales , Dieta , Cadena Alimentaria , Semivida , Radioisótopos de Yodo/farmacocinética , Distribución TisularRESUMEN
Uptake and depuration experiments for the edible periwinkle Littorina littorea have been performed using 131I-labelled seawater. Throughout the experimental phase the winkles were fed on unlabelled Chondrus crispus. 131I concentrations in winkles during uptake followed linear first-order kinetics with an uptake half-time of 11 days, whereas for depuration a triphasic sequence with biological half-lives of 4, 23 and 56 days was determined. In general, iodine turnover in winkles via labelled seawater appears to be slower than observed for other molluscs (2-3 days). Most of the activity prior to and after depuration is found to be in the shell, with indications that shell and soft parts accumulate and depurate 131I at a similar rate. The operculum displays the highest specific activity of all fractions with a concentration factor of 750 l kg(-1). Concentration factors for whole winkle, shell, soft parts and digestive gland are in the order of 40-60 l kg(-1), higher than the IAEA recommended CF value for iodine in molluscs of 10 l kg(-1). The 131I CF in winkles is closer to that of the conservative radionuclides 99Tc and 137Cs than the CF of the particle reactive radionuclides (239,240)Pu and 241Am.
Asunto(s)
Radioisótopos de Yodo/farmacocinética , Agua de Mar/análisis , Caracoles/metabolismo , Animales , Transporte Biológico , Cinética , Factores de Tiempo , Distribución Tisular , Reino UnidoRESUMEN
OBJECTIVE: The aim was to evaluate changes in indices of left ventricular contractility and relaxation in relation to changes in loading conditions in dogs with rapid pacing induced heart failure. METHODS: 14 conscious male mongrel dogs were paced at 250 beats.min-1 to severe heart failure, which occurred at 4.2(SD1.9) weeks. Six sham operated dogs served as controls. Right sided pressures were obtained by a thermodilution catheter. Left ventricular pressure and its derived variables were obtained by a high fidelity manometer tipped catheter. Rate corrected velocity of circumferential fibre shortening--end systolic wall stress relations were obtained by simultaneous haemodynamic and echocardiographic studies. RESULTS: In the paced dogs, baseline right atrial pressure, 6.4(2.0) mm Hg, and pulmonary capillary wedge pressure, 7.1(2.5) mm Hg, increased to 13.3(3.1) mm Hg and 34.5(7.1) mm Hg respectively at severe heart failure (both p less than 0.0001). The peak first derivative of left ventricular pressure dP/dt decreased from 1515(274) mm Hg.s-1 at baseline to 975(321) mm Hg.s-1 at severe heart failure (p less than 0.05) while baseline left ventricular end diastolic pressure, 4.4(3.7) mm Hg, and relaxation time constant tau, 18.0(4.5) ms, increased to 37.2(6.6) mm Hg (p less than 0.01) and 51.9(21.4) ms (p less than 0.05) respectively. The shortening-wall stress relation was markedly displaced downward from baseline. Furthermore, weekly studies revealed a major downward displacement of this relation by one week of pacing with no significant further shift at severe heart failure, whereas both end diastolic diameter (preload) and end systolic wall stress (afterload) increased significantly further from one week. In the sham operated dogs, there was no change over time in any of these study variables. CONCLUSIONS: In pacing induced heart failure, there is impairment of left ventricular contractility and relaxation. The major downward shift of the shortening-wall stress relation at one week suggests that left ventricular contractility is impaired early and may be the initiating mechanism of heart failure in this model.
Asunto(s)
Insuficiencia Cardíaca/fisiopatología , Contracción Miocárdica/fisiología , Función Ventricular Izquierda/fisiología , Animales , Presión Sanguínea/fisiología , Estimulación Cardíaca Artificial , Modelos Animales de Enfermedad , Perros , Electrocardiografía , Frecuencia Cardíaca/fisiología , Masculino , Resistencia Vascular/fisiologíaRESUMEN
Two patients with pulmonary emboli and right heart masses detected on echocardiography are described. One patient underwent successful surgical embolectomy and the other was successfully treated with intravenous thrombolysis. Both were alive and well at six months' follow-up. The presence of a right heart clot in the setting of pulmonary emboli carries a very high mortality rate and warrants urgent therapy, which may include anticoagulation, thrombolysis or surgical embolectomy. Because limited information is available, therapy must be individualized based on patient characteristics, clot location and local expertise. The pertinent literature is reviewed and relevant issues in decision making are discussed.
Asunto(s)
Embolia Pulmonar/terapia , Anciano , Ecocardiografía , Femenino , Humanos , Embolia Pulmonar/diagnóstico por imagen , Embolia Pulmonar/tratamiento farmacológico , Embolia Pulmonar/cirugía , Terapia TrombolíticaAsunto(s)
Caseínas , Leche , Tamaño de la Partícula , Animales , Coloides , Rayos Láser , Sustancias Macromoleculares , Matemática , Dispersión de Radiación , UltracentrifugaciónRESUMEN
A survey of the contribution to external dose from gamma rays originating from intertidal sediments in the vicinity of the British Nuclear Group Sellafield site showed that the major anthropogenic contributions were due to (137)Cs and (60)Co. At some sites, traces of other anthropogenic radionuclides were detected, namely (106)Ru, (125)Sb, and (154)Eu. The proportions of fine grained material (<63 microm) were used to improve model predictions of dose contribution due to external exposure to gamma rays, using the CUMBRIA77/DOSE77 model. Model dose predictions were compared to those directly measured in the field. Using the new proportions of fine grained material (1-17.5%) in conjunction with field gamma-ray spectra, model predictions were improved considerably for most sites. Exceptions were at Drigg Barn Scar and Whitehaven Coal Sands sites, which had their own unique characteristics. The highest (60)Co activity concentrations in this study were detected at Drigg Barn Scar. These relatively high activity concentrations of (60)Co were due to the presence of (60)Co in mussels and barnacles, hence upsetting the fine sediment relationships used in previous dose calculations. Whitehaven Coal Sands was unusual in that it contained higher levels of radionuclides than would be expected in sandy sediment. The mineralogy of these sediments was the controlling factor on (137)Cs binding, rather than the proportion of fine grained material. By adjusting the effective fine grained sediment proportions for calculations involving (60)Co and (137)Cs at Drigg Barn Scar and Whitehaven Coal Sands respectively, the CUMBRIA77/DOSE77 model predictions could be improved upon significantly for these sites. This work highlights the influence of particle size and sediment composition on external dose rate calculations, as well as the potential for external dose contributions from biota.
Asunto(s)
Rayos gamma , Modelos Biológicos , Dosis de Radiación , Contaminantes Radiactivos del Suelo/análisis , Contaminantes Radiactivos del Agua/análisis , Animales , Radioisótopos de Cesio/análisis , Radioisótopos de Cobalto/análisis , Relación Dosis-Respuesta en la Radiación , Inglaterra , Agua de Mar/análisis , Mariscos/análisisRESUMEN
S100A6 (calcyclin), a member of the S100 family of EF-hand Ca2+ binding proteins, has been implicated in the regulation of cell growth and proliferation. We have previously shown that S100B, another member of the S100 family, is induced postinfarction and limits the hypertrophic response of surviving cardiac myocytes. We presently report that S100A6 expression is also increased in the periinfarct zone of rat heart postinfarction and in cultured neonatal rat myocytes by treatment with several trophic agents, including platelet-derived growth factor (PDGF), the alpha1-adrenergic agonist phenylephrine (PE), and angiotensin II (AII). Cotransfection of S100A6 in cultured neonatal rat cardiac myocytes inhibits induction of the cardiac fetal gene promoters skeletal alpha-actin (skACT) and beta-myosin heavy chain (beta-MHC) by PDGF, PE, AII, and the prostaglandin F2alpha (PGF2alpha), induction of the S100B promoter by PE, and induction of the alpha-MHC promoter by triiodothyronine (T3). By contrast, S100B cotransfection selectively inhibited only PE induction of skACT and beta-MHC promoters. Fluorescence microscopy demonstrated overlapping intracellular distribution of S100B and S100A6 in transfected myocytes and in postinfarct myocardium but heterodimerization of the two proteins could not be detected by co-immunoprecipitation. We conclude that S100A6 may function as a global negative modulator of differentiated cardiac gene expression comparable to its putative role in cell cycle progression of dividing cells.
Asunto(s)
Proteínas de Ciclo Celular/metabolismo , Miocitos Cardíacos/metabolismo , Proteínas S100/metabolismo , Actinas/genética , Animales , Secuencia de Bases , Proteínas de Ciclo Celular/genética , Células Cultivadas , ADN/genética , Regulación de la Expresión Génica/efectos de los fármacos , Infarto del Miocardio/genética , Infarto del Miocardio/metabolismo , Miocitos Cardíacos/citología , Miocitos Cardíacos/efectos de los fármacos , Factores de Crecimiento Nervioso , Fenilefrina/farmacología , ARN Mensajero/genética , ARN Mensajero/metabolismo , Ratas , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Proteína A6 de Unión a Calcio de la Familia S100 , Subunidad beta de la Proteína de Unión al Calcio S100 , Proteínas S100/genética , Transfección , Miosinas Ventriculares/genéticaRESUMEN
Pressure-overload cardiac hypertrophy involves not only cellular growth but also reexpression of an extensive "fetal" program of cardiac-specific genes, providing an intriguing system in which to explore molecular signals which transduce altered load. Fibroblast and transforming growth factors are representative of trophic polypeptides produced by myocardium, which are regulated during cardiac morphogenesis and induced by myocardial ischemia, infarction, and load. Growth factors provoke a pattern of gene expression in cultured cardiac myocytes resembling pressure overload in vivo, implying a possible autocrine or paracrine model of cardiac hypertrophy. Growth-factor inducible cellular oncogenes are also expressed in myocardium, upregulated by hemodynamic load, and encode proteins which modulate the cardiac phenotype, in keeping with a possible functional role in growth factor and load-induced intracellular signalling. Demonstration of physiologic implications of growth factor and cellular oncogene expression in the heart awaits application of new technologies in molecular genetics and could herald novel therapeutic interventions for myocardial disease.
Asunto(s)
Cardiomegalia/genética , Sustancias de Crecimiento/genética , Hemodinámica/fisiología , Transducción de Señal/genética , Animales , Regulación de la Expresión Génica/fisiología , Humanos , Proto-Oncogenes/genética , Factores de Transcripción/genéticaRESUMEN
Pressure-overload cardiac hypertrophy is associated with the re-expression of an ensemble of genes representative of embryonic myocardium, whose protein products modulate myocardial function. Regulation of cardiac-specific gene expression in end-stage myocardial disease in humans implies a pathophysiologic role for altered gene expression in the progression from compensatory hypertrophy to decompensated heart failure. The molecular signals that transduce load into a hypertrophic cardiac myocyte phenotype involve mechanical deformation and the local myocardial production of trophic factors, including angiotensin II, and transforming and fibroblast growth factors. Growth factors provoke a pattern of gene expression in cultured cardiac myocytes resembling that seen in pressure overload in vivo, in keeping with an autocrine or paracrine model of hypertrophy. Moreover, growth factor stimulation and pressure-overload hypertrophy share intracellular signaling pathways, including the activation of nuclear proteins encoded by cellular oncogenes. Elucidation of these signaling pathways may provide new therapeutic targets for the treatment of cardiac muscle disease that overcomes the limitations of currently available strategies.
Asunto(s)
Cardiomegalia/genética , Insuficiencia Cardíaca/genética , Angiotensina II/metabolismo , Animales , Calcio/metabolismo , Factores de Crecimiento de Fibroblastos/fisiología , Expresión Génica , Hemodinámica , Humanos , Proteínas Musculares/genética , Proto-Oncogenes , Transducción de Señal , Factores de Transcripción/fisiología , Factores de Crecimiento Transformadores/fisiologíaRESUMEN
The isotherms for Ca++ binding to bovine alpha-casein have been measured at 5 temperatures in the range 4-40 degrees C and at 4 different ionic strengths. The results are interpreted by an interactive-site binding model, and are compared with results previously obtained on alpha s1-casein. The affinity of beta-casein for the first Va2+ to bind is similar to the affinity of alpha s1-casein for the same binding event: however, binding of subsequent Ca2+ to beta-casein is weaker than the binding to alpha s1-casein. The results are discussed in terms of precipitability of the 2 caseins caused by the binding of Ca2+.
Asunto(s)
Calcio/metabolismo , Caseínas/metabolismo , Animales , Bovinos , Femenino , Iones , Leche/metabolismoRESUMEN
The role of polypeptide growth factors in cardiovascular ontogeny, function, and pathologic states is poorly understood. Recent investigations demonstrate that the myocardium produces both known and novel growth factors, which are highly regulated during development and disease, and have suggested that peptide growth factors may direct cardiac organogenesis and adaptation. Aspects of growth factor production, transduction, and action in myocardium are distinct to the cardiac muscle lineage and were not foreseen from results in simpler systems. Transforming growth factor beta 1 and fibroblast growth factors (FGFs) selectively up-regulate an ensemble of tissue-specific genes associated with the fetal myocardium. One of these, encoding the skeletal muscle isoform of alpha-actin, is activated by basic FGF yet is inhibited by acidic FGF. A serum response element of this gene is selectively induced, in cardiac myocytes, by basic FGF but not acidic FGF. Thus, cardiac muscle is an especially intriguing model for the analysis of growth factor signalling pathways that control differentiated gene transcription.