Electron Microscope Studies of Nuclear Extrusions in Pancreatic Acinar Cells of the Rat

Abstract

This paper describes "blebs" protruding from the surface of the nucleus into the cytoplasm. The "blebs" are separated from the cytoplasm by 2 membranes which are continuous with the outer and inner nuclear membranes. The "blebs" contain 3 structurally distinct substances. Two of these substances (13 and 7 substances) are similar to extranucleolar karyoplasm and nucleolar material. The other substance (a substance) is present in every "bleb," but it cannot be readily compared to a recognizable nuclear structure. Cytoplasmic vesicles are described that are apparently different from the Golgi vesicles or the vesicular component of the ergastoplasm. It is suggested that these vesicles may be of nuclear "bleb" origin.A dark karyoplasmic zone extending from the region of the nucleolus into the nuclear "bleb" is shown. This zone may be similar in some respects to the preformed pathway ("Leitbahn") described by Altmann (3) and Hertl (28) and could reflect movement of nuclear material from the nucleolar region into the cytoplasm.The "blebs" are thought to be homologous to structures described by many light microscopists, but they are considerably larger than the nuclear "blebs" described previously by electron microscopists.The transfer of microscopically visible material from the nucleus into the cytoplasm has been described from time to time for many years and has been suggested as one of the possible mechanisms whereby the interphase nucleus could bring its influence to bear on cytoplasmic function. Observations described in this paper of vesicular structures, apparently budding out from the nucleus into the cytoplasm, provide further evidence of possible transfer of nuclear material into the cytoplasm. The size and morphology of these nuclear extrusions indicate that they correspond to the structures described by m a n y light microscopists (3-5, 7, 8, 21, 27, 28, 30, 31, 33, 34, 39, 43, 51), but the extrusions seem to be much larger than those described previously by electron microscopists (1,2,6,17,23,24,37,53).

Neuronal Nuclear Membrane Budding Occurs during a Developmental Window Modulated by Torsin Paralogs

“…Structures similar to neuronal NE buds have been observed in several developmental contexts in diverse wild type organisms (Clark, 1960; Hadek and Swift, 1962; Hochstrasser and Sedat, 1987a; D. Szöllösi, 1965; M.…”

Extrusion of Nucleoli From Pronuclei of the Rat

“…Several electron microscopists have also reported on nuclear "blebbing" (17,23,26) and actual emission of large bodies from the nuclei (1, 2). These processes were interpreted as the microscopically visible elements of nucleocytoplasmic interactions.…”

Nuclear Extrusion and Intracisternal Inclusions in the Rabbit Blastocyst

“…Also a variety of blebs and outpocketings of the nuclear envelope have been observed, and their possible role in the transfer of nuclear material to the cytoplasm has been stressed. These include the outer membrane of the nuclear envelope in a variety of species (5,19,22) or the outpocketing of both layers as in Drosophila (6,20). The possibility that "membrane flow" may carry material from nucleus to cytoplasm has also been suggested (3).…”