Observations on the ultrastructure of developing myocardium of rat embryos

摘要: Timed pregnancies were obtained in Sprague-Dawley rats and early ultrastructural differentiation of myocardium embryos 10, 11, 12, 13, 14 days was investigated compared with that newborn. Ten-day is characterized by loosely packed cells; the cytoplasm typified a dearth organelles. Both thick (myosin) thin (actin) filaments become identifiable for first time 10-day where heart pulsating but circulation not established. These are visible 9-day-old myocardium. The formation these observed to continue throughout period covered this investigation. Concomitant appearance myofilaments synthesis Z band material. By eleventh day gestation during subsequent there rapid proliferation most organized into fully formed striated fibrils. Intercalated discs appear as. small wavy lines on plicated later stages serve as cell boundaries points attachment There perceptible change number morphology mitochondria from tenth development when becomes functional. Similarly, granular endoplasmic reticulum Golgi bodies. Large quantities free ribosomes dispersed myocardium; however, progressive reduction distribution particles. An intimate association polysomes developing myofibrils discernible. T -system sarcoplasmic begin II-day embryonic displays intense mitotic activity its unique feature myocardial cells simultaneous occurrence myofilament within same cells.