Nuclear envelope structure

Schlaich, N and Hurl, E. C. (1995). Analysis of nucleocytoplasmic transport and nuclear envelope structure in yeast disrupted for the gene encoding the nuclear pore protein Nuplp. Eur. J. Cell Biol. 67, 8-14. 

First cytologic alterations of colon adenocarcinoma cells (Fig. 43) manifested 12 h after administration of I and consisted of nuclear changes (Fig. 44) such as chromatin condensation, enlargement of the nuclear envelope, structural aberrations of the nucleoli and formation of segmented nuclei. Cytoplasmic phenomena occurred 12 h later and manifested by the appearance of lipid droplets and inclusion bodies which often contained cellular debris (Figs. 45, 46). These phenomena indicated cytoplasmic degeneration as well as phagocytotic activity of tumor cells. 

The nucleus (37-44) is the most prominent structure within the cytoplasm. It is bounded by a nuclear envelope containing circular pores that are 30-100 nm in diameter. The outer nuclear envelope may be continuous with the er. 

The nucleus is surrounded by the nuclear envelope, which takes on a lumenal structure connected to the endoplasmic reticulum. The transport of proteins into (and out of) the nucleus occurs through the nuclear pore complex (NPC), a large complex composed of more than 100 different proteins (Talcott and Moore, 1999). Because NPC forms an aqueous pore across the two membranes, small proteins less than 9 nm in diameter can pass through it simply by diffusion. However, most of the transports of both proteins and RNAs are mediated by an active transport mechanism. It is now clear that there is heavy traffic through the NPC in both directions. Proteins are not only imported into the nucleus but also actively exported from it as well. There are many reasons for nuclear export. One reason is to send some shuttle proteins back after their import another is for some viral proteins to export their replicated genomes outside the nucleus. 

Nuclear Envelope The membrane system of the cell nucleus that surrounds the nucleoplasm. It consists of two concentric membranes separated by the perinuclear space. The structures of the envelope where it opens to the cytoplasm are called the nuclear pores (nudear pore). [NIH]... 

The nucleus is separated from the cytoplasm by the nuclear envelope, which consists of the outer and inner nuclear membranes. Each of the two nuclear membranes has two layers, and the membranes are separated from each other by the perinuclear space. The outer nuclear membrane is continuous with the rough endoplasmic reticulum and is covered with ribosomes. The inner side of the membrane is covered with a protein layer (the nuclear lamina), in which the nuclear structures are anchored. 

The structure of the nuclear envelope is maintained in part by highly organized meshworks of intermediate filaments composed of the protein laminin. Breakdown of the nuclear envelope before segregation of the sister chromatids in mitosis is partly due to the phosphorylation of laminin by a CDK, which causes laminin filaments to depolymerize. 

Each cell nucleus contains one or more dense nucleoli, regions that are rich in RNA and may contain 10-20% of the total RNA of cells. Nucleoli are sites of synthesis and of temporary storage of ribosomal RNA, which is needed for assembly of ribosomes. The nuclear envelope is a pair of membranes, usually a few tens of nanometers apart, that surround the nucleus. The two membranes of the pair separate off a thin perinuclear space (Fig. 1-7). The membranes contain "pores" -130 ran in diameter with a complex structure (see Fig. 27-8).38/39 There is a central channel -42 ran in diameter, which provides a route for controlled passage of RNA and other large molecules from the nucleus into the cytoplasm and also from the cytoplasm to the nucleus. Smaller -10 nm channels allow passive diffusion of ions and small molecules. 

McKeon, F. D., Kirschner, M. W., and Caput, D. (1986). Homologies in both primary and secondary structure between nuclear envelope and intermediate filament proteins. Nature (London) 319, 463-468. 

The nucleus of eukaryotic cells is a very complex structure, containing various components. It is separated from the rest of the cell by two membranes named the nuclear envelope. At regular intervals, the two membranes of the nuclear envelope form pores with a diameter of around 90 nm. These pores regulate flux of macromolecules to and from the cytoplasm. Inside the nucleus is located the nucleolus, which acts to produce ribonucleic acid (RNA), which is the first step for ribosome synthesis. 

The nucleus of the eukaryotic cell is separated from the cytoplasm by the double-membrane nuclear envelope, which provides a continuous boundary between the nucleoplasm and the cytoplasm, except where it is penetrated by nuclear pores, each of which is surrounded by a disklike structure, the nuclear pore complex. These pores serve an export-import function for an exchange of materials between the nucleus and the cytosol. This is necessary in eukaryotic... 

The ER is a continuous network of membranous tubular and lamellar structures in the cytosol (1, 2). The membranes that build up the organelle can constitute more than 95% of the total cellular membranes, and the total volume of the organelle can compose about 10% of cell volume, e.g., in hepatocytes. Although the ER is a single, spatially continuous compartment, it can be divided structurally and functionally into different subdomains. The ER forms contact sites beside the nuclear envelope with practically all the other organelles and the plasma membrane these junctional regions might have specific composition... 

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