The fine structure of progressive stages of myocardial mitosis in chick embryos

Abstract

The fine structure of mitosis in myocardial cells possessing myofibrils from embryonic chick hearts (4.5-6 days incubation age) is described. In these cells during prophase, chromosomes appear, but the nuclear membrane, Golgi complexes, and Z bands mostly disappear. In metaphase, lipid droplets and large quantities of membranous cisternae localize around the centrioles, while sarcomeric lengths of myofibrils (largely without Z bands) are found disoriented in the periphery, mainly in the polar zones. In anaphase the cisternae collect near the chromosomes, as reconstruction of the nuclear membrane commences. An intact nuclear envelope and well-formed Golgi complexes characterize telophase, but Z bands still are not present. During all of the mitotic stages, junctional complexes between dividing cells and adjacent resting cells persist.

Features of cardiomyocyte proliferation and its potential for cardiac regeneration

“…Complete myofibril disassembly is only seen in cardiomyocytes in telophase. Importantly, no myocardial cell has been observed in these studies that underwent mitosis without these disruptive changes of the myofibril striation patterns [40, 41, 44].…”

DNA Synthesis and Mitosis in Well-Differentiated Mammalian Cardiocytes

“…Cancer Inst. 36, 717 (1966 Unlike skeletal muscle, embryonic cardiac cells synthesize DNA and divide after myofibrils have appeared (4)(5)(6)(7)(8). With autoradiography, DNA synthesis has been demonstrated in differentiating cardiac cells of chick embryos (4,5).…”

Fetal Myocardial Thickening Measured by Ultrasonic-Based Technique Called ‘Phased-Tracking Method’

“…Because the distribution of blood fl ow in local myocardium is considered to be related to oxygen consumption, contraction of the outer layer of myocardium may be more active in late gestation than after birth. Hay and Low [24] reported that the construction of denser and more regular fi laments and their arrangement in a more fi xed direction were observed in myofi brils in non-dividing myocardial cells as gestation proceeded and that these changes were more marked in the outer myocardial layer. The higher thickness changing rate of the outer layer of myocardium in late gestation may be caused by the high distribution of blood fl ow in the outer layer as well as physiological changes such as more rapid maturity of the myocardial microstructure.…”