Abstract
The contractile apparatus of left-ventricular cardiomyocytes from from 180-day-old rats that had been born one day preterm was studied using polarization microscopy and transmission electron microscopy. In cardiomyocytes from preterm rats, the myofibrils had non-uniform thickness: along with thinned and disintegrated areas of myofibrils, thickened myofibrils were detected. Myofibril lysis was predominantly focal and less frequently diffuse. Cardiomyocytes with subsegmental contractures were observed. Mitochondria with signs of destruction were detected in cardiomyocytes from premature rats, while numerous small mitochondria that did not form intermitochondrial junctions were found in the dilated intermyofibrillar spaces. Mitochondrial damage leads to structural and functional disturbances of the cardiomyocyte contractile apparatus.