NUCLEAR EXTRUSION AND INTRACISTERNAL INCLUSIONS IN THE RABBIT BLASTOCYST

Abstract

Tro-phoblast cells of 6-day rabbit embryos, as studied with the electron microscope, were observed to contain spherical inclusions up to 0.5/[mu].in diameter inside the cisternae of the endoplasmic reticulum, and also between the membranes of the nuclear envelope. It is suggested that these inclusions arise by extrusion of nuclear material through annular openings in the inner nuclear membrane, and are then distributed to the cisternae as they break off the nuclear envelope.