The Ultrastructure And Pathobiology Of Urinary Bladder Cancer
George T. Bryan, Samuel M. Cohen in The Pathology of Bladder Cancer, 2017
At the ultrastructural level, all three lines are similar, when grown on either plastic or on collagen-coated Nitex disks (see Figure 59B). Plasma membranes of the tumor cells are 9-nm-thick symmetric unit membranes. AUM-plaques are not observed.296 Lumenal plasma membranes are covered by a sparse glycocalyx and display numerous pleomorphic microvilli at the free surface. Nuclei vary in size and chromatin distribution. The nuclear envelope typically has many shallow infoldings. The tumor cell cytoplasm has a relatively simple cytoarchitecture. It is characterized by the presence of a few clustered mitochondria and numerous free ribosomes. Smooth and rough endoplasmic reticulum are poorly developed. The Golgi apparatus is usually prominent and often multicentric. Secondary lysosomes are plentiful in thin sections in some cells and absent in others. Intracytoplasmic lumina are observed in the cultures. Squamous differentiation is observed in cultures of all three lines, including the development of prominent bundles of tonofilaments.296 On collagen-coated Nitex disks, basal tumor cells lack a basal lamina and grow in direct contact with the collagenous substratum. There are no hemidesmosomes anchoring the basal plama membrane to collagenous fibers.412
Senescent Cells as Drivers of Age-Related Diseases
Shamim I. Ahmad in Aging: Exploring a Complex Phenomenon, 2017
The nuclear envelope is lined by the nuclear lamina, a dense fibrillary network which provides mechanical support and regulates size, shape, and stability of the nucleus [85,86]. Nuclear lamina also partakes in a number of other functions including regulation of DNA synthesis, RNA transcription, and chromatin organization [87]. In mammals, the lamina contains major structural proteins categorized as type A (lamin A and C) and type B (lamin B1 and B2) lamins based on their isoelectric points [85]. Nuclear lamins are dynamic structures that are assembled and disassembled throughout the cell cycle. Lamin A and C are derived from the gene LMNA by alternative splicing and are expressed by non-proliferating and differentiated cells. Lamin B1 and B2 are encoded by separate genes LMNB1 and LMNB2 respectively and are strongly expressed by dividing and undifferentiated cells [88–90]. While there are two types of lamin B, expression of one or the other is sufficient for cell survival [86,91]. Expression of type A and B lamins are differentially regulated in specific tissues during embryogenesis [91,92].
Imaging of Intracellular Targets
George C. Kagadis, Nancy L. Ford, Dimitrios N. Karnabatidis, George K. Loudos in Handbook of Small Animal Imaging, 2018
Intracellular targets also include those situated in the cell nucleus and, in order to reach these, another barrier needs to be overcome: the nuclear envelope, a double membrane that is continuous with the endoplasmic reticulum. All transport across this membrane exclusively occurs via the nuclear pore complexes, which are embedded in the nuclear envelope. Although passive diffusion through these complexes is possible for molecules up to 45 kDa (ions, metabolites, and smaller proteins), active transport is the predominant mechanism to transfer molecules to and from the nucleus (Gorlich and Kutay 1999; van der Aa et al. 2006). This nucleocytoplasmic transport is described well by Conti and Izaurralde (2001).
Systematic alteration of apoptosis: a review with ultrastructural observations on leukemia cells in vivo
Published in Ultrastructural Pathology, 2018
Yong-Xin Ru, Shi-Xuan Zhao, Shu-Xu Dong, Hao-yue Liang, Ying Wang
With chromatin deposition on the inner nuclear membrane around the nuclear periphery, the nuclear center gradually becomes electron-lucent, forming a diffuse domain with low electron density.12 It suggests that most chromatin in a nucleus is deposited on the nuclear membrane during apoptosis. Concurrently, the inner membrane of the nuclear envelope, with its attached deposit of chromatin, becomes disrupted and ill-defined, while the outer membrane degenerates with detachment of ribosomes. At the same time, the inter-space between inner and outer membranes of the nuclear envelope is irregularly expanded. Other regions without chromatin deposits often illustrate a clear image of three layers, with ribosomes detached from the outer surface of the nuclear membrane (Figures 2c and 2d).
Exploiting active nuclear import for efficient delivery of Auger electron emitters into the cell nucleus
Published in International Journal of Radiation Biology, 2023
Andrey A. Rosenkranz, Tatiana A. Slastnikova, Mikhail O. Durymanov, Georgii P. Georgiev, Alexander S. Sobolev
For most of the cellular life, the contents of the cell nucleus are separated from the cytoplasm by the nuclear envelope, which consists of two phospholipidic membranes and intermembrane space that are permeated by numerous NPC (Lin and Hoelz 2019). NPCs are supramolecular protein structures that form rounded holes in the nuclear envelope where both nuclear membranes are fused. NPCs are embedded within these holes and form a stable protein scaffold. On the nuclear side, the scaffold forms eight extended fibers that are connected in a distal ring and form the nuclear basket. Another eight flexible fibers extend into the cytoplasm. Additional fiber-like extensions in a central opening generate the permeability barrier, which controls the import and export of macromolecules (Knockenhauer and Schwartz 2016). The main components of the eukaryotic NPC, called nucleoporins, are a family of approximately 30 proteins that form a part of the scaffolding and transport functions of NPC. The outer diameter, inner diameter of the central transport channel, height, and molecular mass of the human NPC is approximately 120 nm, 42.5 nm, 80 nm, and 110 MDa, respectively (Lin and Hoelz 2019).
Selinexor for the treatment of multiple myeloma
Published in Expert Opinion on Pharmacotherapy, 2020
Klaus Podar, Jatin Shah, Ajai Chari, Paul G Richardson, Sundar Jagannath
The nucleus is an organelle, which encapsulates the genetic material with a double membrane, the nuclear envelope, thereby separating transcription in the nucleus from the translational machinery in the cytoplasm. To allow adequate cell function this spatial compartmentalization in eukaryotic cells requires a finely tuned, selective and efficient bidirectional nuclear-cytoplasmic transport of specific proteins and mRNAs through the nuclear pore complex (NPC) of the nuclear envelope. The passage of macro-molecules (>40 kDa), cargo, through the NPC requires specific transport receptor proteins. The mammalian family of karyopherins, representing the main group of transport receptor proteins, consists of 20 members including karyopherin alpha (KPNA) 1–6, karyopherin beta (KPNB) 1, and exportin-1 (XPO-1), also termed chromosome region maintenance – 1 (CRM-1). Dependent on the presence of precise transport signs in cargo proteins, nuclear localization signals (NLS) or nuclear export signals (NES), karyopherins chaperone them into (importins) or out (exportins) of the nucleus using energy from the RanGTPase complex.
Related Knowledge Centers
- Eukaryote
- Genome
- Intermediate Filament
- Lamin
- Lipid Bilayer
- Nuclear Pore
- Cell Nucleus
- Endoplasmic Reticulum
- Cytosol
- Polarized Membrane