RESUMO
OBJECTIVES: The purpose of this study was to determine in preterm newborn infants the effects of ductal ligation on ventricular performance and its determinants: preload, afterload and contractility. BACKGROUND: Neonatal ventricular performance is highly sensitive to afterload. Therefore, the increase in systemic vascular resistance associated with ligation of a patent ductus arteriosus might worsen ventricular performance in the preterm infant. METHODS: All 14 premature infants undergoing patent ductus arteriosus ligation in a 1-year period at our institution underwent echocardiography at three times: before, immediately after and 24 h after ligation. Indexes studied included ventricular performance (fractional area change), preload (left ventricular end-diastolic dimension), afterload (end-systolic wall stress) and contractility (the difference between the measured and predicted velocity of circumferential fiber shortening). Blood pressure was measured; systemic resistance was calculated. These data were compared with those of 14 preterm infants without patent ductus arteriosus. RESULTS: The infants with patent ductus arteriosus had higher values for ventricular performance (mean +/- SD fractional area change 60 +/- 9% vs. 52 +/- 11%, p < 0.05) and lower values for wall stress (22 +/- 6 vs. 44 +/- 17 g/cm2, p < 0.05) before ligation than did the control group. At 24 h after ligation, ventricular performance was not significantly changed (fractional area change 60 +/- 9% to 57 +/- 12%). There were significant increases in blood pressure and systemic vascular resistance but no changes in wall stress or contractility. CONCLUSIONS: Ventricular performance is higher in premature infants with than in those without patent ductus arteriosus because afterload is lower in the former group. Although ductal ligation increases blood pressure and systemic resistance, wall stress and ventricular performance are maintained. Our results suggest that the premature newborn maintains ventricular performance during stress, at least in part, by manipulating afterload.
Assuntos
Permeabilidade do Canal Arterial/cirurgia , Doenças do Prematuro/cirurgia , Recém-Nascido Prematuro/fisiologia , Função Ventricular Esquerda/fisiologia , Pressão Sanguínea/fisiologia , Distribuição de Qui-Quadrado , Permeabilidade do Canal Arterial/diagnóstico , Permeabilidade do Canal Arterial/fisiopatologia , Ecocardiografia , Humanos , Recém-Nascido , Doenças do Prematuro/diagnóstico , Doenças do Prematuro/fisiopatologia , Ligadura , Contração Miocárdica/fisiologia , Estresse Mecânico , Resistência Vascular/fisiologiaRESUMO
Two cDNA clones encoding calcium/calmodulin-dependent (CaM) protein kinase I were isolated. In contrast to the previously reported CaM kinase I cDNA, which encodes a protein with a mass of 37 kDa, the clones identified in this study encode a protein (10-1/CaM kinase I) with a predicted mass of 42 kDa; the size of 10-1/CaM kinase I was verified by hybrid-selected translation.
Assuntos
Proteínas Quinases Dependentes de Cálcio-Calmodulina/genética , DNA Complementar/química , Sequência de Aminoácidos , Animais , Sequência de Bases , Sítios de Ligação , Northern Blotting , Proteína Quinase Tipo 1 Dependente de Cálcio-Calmodulina , DNA Complementar/isolamento & purificação , Biblioteca Gênica , Dados de Sequência Molecular , RNA Mensageiro/análise , RNA Mensageiro/isolamento & purificação , RatosRESUMO
To identify protein kinases that may regulate fetal growth and differentiation, we used an oligonucleotide probe encoding the conserved sequence of serine/threonine kinases to screen a fetal lung cDNA library. Several clones were isolated and sequenced, one of which encodes the rat homolog of the 34 kilodalton cyclin-dependent kinase 4 (p34cdk4). Northern blot analyses of pre- and postnatal rat tissues show that rat cdk4 is expressed in a developmentally regulated pattern in all tissues examined. The mRNA is also significantly decreased in cells that are arrested in the G1 phase of cell cycle. The regulated expression of rat cdk4 is consistent with a proliferation-, rather than a differentiation-, dependent pattern.
