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Two to eight days after surgery, we determined biventricular cardiac output with the microsphere-dilution method and individual ventricular output with an electromagnetic flow sensor in 12 fetal lambs. Mean biventricular output was 462 ml.min-1.kg-1. Right ventricular output was 60%, pulmonary blood flow was 6%, blood flow in the ductus arteriosus was 54%,(More)
The generation of new myocytes is an essential process of in utero heart growth. Most, or all, cardiac myocytes lose their capacity for proliferation during the perinatal period through the process of terminal differentiation. An increasing number of studies focus on how experimental interventions affect cardiac myocyte growth in the fetal sheep.(More)
While the fetal heart grows by myocyte enlargement and proliferation, myocytes lose their capacity for proliferation in the perinatal period after terminal differentiation. The relationship between myocyte enlargement, proliferation, and terminal differentiation has not been studied under conditions of combined arterial and venous hypertension, as occurs in(More)
The fetal heart is highly sensitive to changes in mechanical load. We have previously demonstrated that increased cardiac load can stimulate cell cycle activity and maturation of immature cardiomyocytes, but the effects of reduced load are not known. Sixteen fetal sheep were given either continuous intravenous infusion of lactated Ringer solution (LR) or(More)
A proposed convention sets zero pressure at atmospheric pressure at the level of the surface supporting the supine patient and takes the cm of water as the unit of measurement. This ensures that measurements made in different clinics will be comparable. Statements about 'higher' and 'lower' pressures, in different patients or in the same patient in(More)
During fetal life the myocardium expands through replication of cardiomyocytes. In sheep, cardiomyocytes begin the process of becoming terminally differentiated at about 100 gestation days out of 145 days term. In this final step of development, cardiomyocytes become binucleated and stop dividing. The number of cells at birth is important in determining the(More)
Chronic anaemia increases the workload of the growing fetal heart, leading to cardiac enlargement. To determine which cellular process increases cardiac mass, we measured cardiomyocyte sizes, binucleation as an index of terminal differentiation, and tissue volume fractions in hearts from control and anaemic fetal sheep. Fourteen chronically catheterized(More)
Studies in altricial rodents attribute dramatic changes in perinatal cardiomyocyte growth, maturation, and attrition to stimuli associated with birth. Our purpose was to determine whether birth is a critical trigger controlling perinatal cardiomyocyte growth, maturation and attrition in a precocial large mammal, sheep (Ovis aries). Hearts from 0-61 d(More)
We investigated left ventricular (LV) hemodynamics, pressure-volume relations, and morphometry to determine what cardiac changes characterize pregnancy in the guinea pig. Time-bred virgin guinea pigs were paired by weight with unbred controls. Hemodynamic studies and LV pressure-volume relations were obtained on days 59-68 of the 68-day gestation. Weight of(More)