Extrusion of Nucleoli From Pronuclei of the Rat

Abstract

Electron microscope observations of osmium tetroxide-fixed rat eggs indicate that small nucleoli are extruded from pronuclei in a sharply demarcated time period after sperm penetration. Approximately 4~ hours after sperm penetration, fine fibrous material aggrcgated in distinct loci along the inner surface of the nuclear envelope and condensed into small, dense bodics. The term tertiary nucleolus or extrusion body is used to designate the forming bodics. The small tertiary nucleoli form distinct protrusions from the pronuclei during the following developmental period and finally bud off into the cytoplasm, carrying with them a small portion of the double nuclear envelope. The extrusion bodies can be observed only in the vicinity of the pronuclei and have not been seen near the cell membrane. The fate of the tertiary nucleoli is not known; apparently they transform or disappear after they have passed into the cytoplasm. Eleven hours after sperm penetration, tertiary nucleoli are not present near the nuclear membrane and the extrusion activity has apparently ceased. Large and small nucleoli react similarly to cytochcmical reagcnts: thcy are Feulgen negative; they are positive to the Millon, Sakaguchi, brom-phenol blue, and PAS reactions. Azure B stain combined with nuclease extraction indicates the presence of small amounts of RNA in the nucleoli.

Wnt Signaling in Neuromuscular Junction Development

“…In addition, these foci are observed in peripheral glial cells in the larva (SD Speese and V Budnik, unpubl.). Notably, granules accumulating between the outer and inner nuclear membrane resembling the DFz2-decorated large RNP granules have been observed in diverse contexts, from plants (Dickinson 1971) to mammals, where they are particularly prevalent at early embryonic stages (Hadek and Swift 1962;Szollosi 1965). Indeed, that such granules might reflect an alternate mode of nucleocytoplasmic export has been previously proposed (Gay 1956;Szollosi and Szollosi 1988), but it had not been experimentally validated until now.…”

Tapetal Ultrastructural Changes During Pollen Development. I. Studies onAntirrhinum Maius

“…Such extrusions wouldn't look like those we described in the perinuclear space of the tapetal cells of Antirrhinum, either for their meaning or origin. Besides, numerous studies on animal tissues (WATSON 1959;CLARK 1960;KESSEL and BEAMS 1963;KESSEL 1964;SzoLLOSI 1965) and particularly on germ cells report the presence of similar bodies in the perinuclear space. The Authors interpret such bodies as extrusions of nucleolar material, which probably transfers ribonucleoproteins or RNA from the nucleus to the cytoplasm.…”

Structures and Functions of the Nuclear Envelope

“…This describes the formation of nuclear outpocketings, followed by membrane breakage and fusion in the neck region of this nuclear bleb, and detachment of a nuclear envelope-surrounded bit of nuclear contents. This seems to be the chief mechanism by which nucleolar material and nucleolar remnants are extruded from the nuclei of various gland cells and oocytes, and from pronuclei (Baud, 1953;Gay, 1955Gay, , 1956Clark, 1960;Berendes and DeBruyn, 1963;Kessel and Beams, 1963;Bell and Miihlethaler, 1964;Szollosi, 1965;Baker and Franchi, 1969;Lima-de-Faria, 1971). After…”