Death process of primitive erythrocytes and phagocytosis by liver macrophages of the mouse embryo.
Primitive erythrocytes from the yolk sac are nucleated cells which have a short life span of several days in the embryonic circulation of the mouse. The death process of primitive erythrocytes was ultrastructurally investigated in embryonic mice. At 12 days of gestation, primitive erythrocytes accounted for 96.1% of the circulating erythrocytes. The percentages in 13-, 14-, 15- and 18-day-embryos were 43.8%, 15.4%, 7.7% and 0.0%, respectively. Between 13 and 15 days, anucleate primitive erythrocytes made up from 1.5% to 5.9% of circulating erythrocytes. During the gestational period, the nuclei of primitive erythrocytes markedly decreased in volume, and the chromatin underwent condensation and marginated to crescents along the nuclear envelope. Following nuclear fragmentation and dissolution of condensed chromatin, nuclear residues were finally formed in aging primitive erythrocytes. Formation of annulate lamellae was also observed, associated with the nuclear shrinkage. The nuclei had an apoptotic-like appearance, but TUNEL-positive reactions could not be identified in any nuclei of the primitive erythrocytes. Dying erythrocytes with nuclear residues were phagocytosed in toto by hepatic macrophages and disposed of from embryonic circulation without enucleation.
Sasaki
K
K
Department of Anatomy, Kawasaki Medical School, Kurashiki, Japan.
Sonoda
Y
Y
Iwatsuki
H
H
Suda
M
M
Itano
C
C
D000818:Animals; D016923:Cell Death; D004622:Embryo, Mammalian; D004912:Erythrocytes / Q000502:physiology*; D008099:Liver / Q000166:cytology* / Q000196:embryology; D008264:Macrophages / Q000502:physiology*; D051379:Mice; D008813:Mice, Inbred ICR; D010587:Phagocytosis