Postnatal Changes in Left Ventricular Performance in Early Neonatal Life

PURPOSE: This study was undertaken to investigate changes in cardiac performance in early neo-natal life by observing the changes of left ventricular(LV) function and volume according to the size of ductus arteriosus. METHODS: The study group consisted of 21 full-term Cesarean section neonates who were admitted to the nursery of Korea University Hospital. We serially investigated the patency and size of the ductus at 2, 24, 120 hours after birth by two-dimensional echocardiography. The standard two-dimensional tracings of LV volume were obtained under the guidance of apical two- and four-chamber views. LV end-diastolic and end-systolic volumes were calculated using a biplanar Simpson's method. RESULTS: LV end-diastolic volume was highest(3.44>0.4mm) at 2 hours of age(P<0.01), being constant from 24 to 120 hours. LV contractility, indicated by the mean normalized systolic ejection rate, remained constant during the whole period of investigation. The size of the ductus arteriosus was maximal at 2 hours after birth, and decreased significantly at 24 hours of age (P<0.01). The size of ductus arteriosus demonstrated a close linear correlation with the left ventricular end-diastolic volume(y=0.17x+2.92, r=0.59: P<0.01). CONCLUSION: Changes in LV end-diastolic volume soon after birth depend on changes in ductus arteriosus flow, which in turn is affected by ductal diameter. Upon patency of the ductus arteriosus, the newborn left ventricle operates at maximal performance with only a limited capacity to increase contractility.

Postnatal changes of myosin light chain patterns and enzyme activities in the extensor digitorum longus and soleus muscles of the rat / 体力科学

Postnatal changes of myosin light chain patterns and enzyme activities were examined in the fast extensor digitorum longus and slow soleus muscles of Wistar strain rats aged 5, 10 and 20 weeks. Sex differences in each parameter were also studied.<BR>The results were summarized as follows:<BR>1) The extensor digitorum longus muscle contained mostly the fast light chains (fLC 1, fLC 2, fLC 3) . However, small amounts of the slow light chains (sLC 1, sLC 2) were also found. There were no postnatal changes in myosin light chain patterns in the extensor digitorum longus muscle.<BR>2) The soleus muscle contained slow and fast light chains (sLC 1, sLC 2, fLC 1, fLC 2, fLC 3) in 5 weeks of age, slow light chains being more predominant than fast light chains. There were an increase in the percentage of slow light chains and a concomitant decrease in the percentage of fast light chains with age. FLC 3 which was found at 5 weeks of age did not be detected in the soleus muscle from the 20-week-old rat.<BR>3) PFK activity decreased significantly with age in the soleus muscle, whereas there was no postnatal changes in PFK activity in the extensor digitorum longus muscle.<BR>4) There was a significant increase in SDH activity during growth in both the extensor digitorum longus and soleus muscles with the exception of the extensor digitorum longus muscle from the male rat.<BR>5) The enzyme activity ratio (PFK/SDH) significantly decreased with age in all muscles with an exception of the extensor digitolum longus muscle from the male rat.<BR>6) In the soleus muscle an increase in the relative amount of slow type myosin light chains and a decrease in the enzyme activity ratio (PFK/SDH) occurred coincidentally during postnatal growth.<BR>7) In most cases no significant sex differences existed in myosin light chain pattern and enzyme activity examined.